Vehicle control device

Abstract

To provide a vehicle controller capable of suppressing hesitation when an engine starts in a vehicle with an engine and an electric motor as a power source.SOLUTION: Value of an upper limit guard value GU is changed to a lower limit guard value GD when an engine torque Te is increased as an engine starts in the case that the lower limit guard value GD is larger than the upper limit guard value GU, so that the upper limit guard value GU is an appropriate value considering surplus power Pexp of an electric motor MG. Thus, even when the surplus power Pexp of the electric motor MG is small, the torque command value Tetgt of the engine torque Te increases to suppress a shortage of the driving torque Tr when the engine starts, so that hesitation is suppressed.SELECTED DRAWING: Figure 1

Description

Technical Field

[0001] The present invention relates to a control device for a vehicle having an engine and an electric motor as power sources.

Background Art

[0002] Vehicles having an engine and an electric motor as power sources are well known. For example, the hybrid vehicle of Patent Document 1 is such a vehicle. Patent Document 1 describes that when the gear stage at the time of starting the engine uses a one-way clutch as an engagement element, the increase in the output of the electric motor at the time of starting the engine is larger than when the gear stage does not use a one-way clutch as an engagement element.

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] By the way, when the output of the electric motor is limited depending on the battery temperature and the state of charge, there is a possibility that the driving force is insufficient at the time of starting the engine, and hesitation occurs, which causes a delay in the acceleration of the vehicle.

[0005] The present invention has been made against the background of the above circumstances, and an object thereof is to provide a vehicle control device that can suppress hesitation at the time of starting an engine in a vehicle having an engine and an electric motor as power sources.

Means for Solving the Problems

[0006] The gist of the present invention is as follows: (a) an engine, an electric motor, and a clutch that disconnects and connects a power transmission path between the engine and the electric motor; (b) when starting the engine during motor driving in which only the electric motor runs as a driving power source with the clutch released, while controlling the clutch toward an engaged state, the rotation of the engine is pulled up by the torque of the electric motor, and when the rotational speed of the engine reaches the synchronous rotational speed, control is executed to increase the engine torque of the engine and decrease the torque of the electric motor. A control device for a vehicle, comprising: (c) an upper limit guard value calculation unit that calculates an upper limit guard value of a change rate of the engine torque at the start of the engine; (d) a lower limit guard value calculation unit that calculates surplus power of the electric motor at the start of the engine and calculates a lower limit guard value of the change rate of the engine torque based on the surplus power; (e) an upper limit guard value change unit that changes the value of the upper limit guard value to the lower limit guard value when the lower limit guard value is larger than the upper limit guard value.

Effect of the Invention

[0007] According to the present invention, when increasing the engine torque and decreasing the torque of the electric motor at the start of the engine, an upper limit guard value of the change rate of the engine torque and a lower limit guard value based on the surplus power of the electric motor are calculated. When the lower limit guard value is larger than the upper limit guard value, the value of the upper limit guard value is changed to the lower limit guard value. Therefore, the upper limit guard value is set to an appropriate value considering the surplus power of the electric motor. Accordingly, when the surplus power of the electric motor is small, the change rate of the engine torque is increased, thereby suppressing a shortage of driving force at the start of the engine and suppressing hesitation.

Brief Description of the Drawings

[0008]

Figure 1

Figure 2

Figure 3

Figure 4

Figure 5

Embodiments for Carrying Out the Invention

[0009] Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings. In the following embodiments, the drawings are appropriately simplified or deformed, and the dimensional ratios, shapes, etc. of each part are not necessarily accurately drawn.

Embodiment

[0010] FIG. 1 is a diagram for explaining the schematic configuration of a vehicle 10 to which the present invention is applied, and is also a diagram for explaining the control functions and main parts of the control system for various controls in the vehicle 10. In FIG. 1, the vehicle 10 is a hybrid vehicle including an engine 12 and an electric motor MG that function as a power source for traveling. Further, the vehicle 10 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] The engine 12 is a well-known internal combustion engine. The engine 12 is controlled by an engine control unit 50 including a throttle actuator, a fuel injection device, an ignition device, etc. provided in the vehicle 10, so that the engine torque Te, which is the output torque of the engine 12, is controlled.

[0012] The electric motor MG is a rotary 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 a power storage device that exchanges electric power with the electric motor MG. The electric motor MG has its MG torque Tm, which is the torque of the electric motor MG, controlled by controlling the inverter 52 by an electronic control device 90 described later. The electric power is also the same as electric energy when not particularly distinguished. The power is also the same as driving force, torque, and force when not particularly distinguished.

[0013] The power transmission device 16 includes a disconnect clutch K0, a start clutch WSC, an automatic transmission 20, a reduction gear mechanism 22, a differential gear 24, etc. inside a case 18. The disconnect clutch K0 is a clutch that disconnects and connects between the engine 12 and the electric motor MG in the power transmission path between the engine 12 and the drive wheels 14. The start clutch WSC is a clutch provided between the engine 12 and the electric motor MG and the automatic transmission 20 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 of the automatic transmission 20. The differential gear 24 is connected to the reduction gear mechanism 22.

[0014] Furthermore, the power transmission device 16 includes a pair of drive shafts 28 connected to the differential gear 24, an engine connecting shaft 30 that connects the engine 12 and the disconnect clutch K0, an electric motor connecting shaft 32 that connects the disconnect clutch K0 and the start clutch WSC, a mechanical oil pump 34, a transmission member 36 that connects the electric motor connecting shaft 32 and the mechanical oil pump 34, etc. The transmission member 36 is composed of, for example, a sprocket and a chain.

[0015] The electric motor MG is connected within the case 18 so as to be capable of transmitting power to the motor connection shaft 32. That is, the electric motor MG is connected so as to be capable of transmitting power to the power transmission path between the engine 12 and the drive wheels 14, particularly to the power transmission path between the disconnect clutch K0 and the launch clutch WSC.

[0016] The disconnect clutch K0 is a wet friction engagement device composed of, for example, a multi-plate or single-plate clutch pressed by an actuator. The disconnect clutch K0 has its operating state, that is, its control state such as the engaged state, slip state, and released state switched by changing the K0 torque Tk0, which is the torque capacity of the disconnect clutch K0, by the regulated hydraulic pressure PRk0 of K0 hydraulic pressure supplied from the hydraulic control circuit 56 provided in the vehicle 10. Note that the disconnect clutch K0 corresponds to the clutch of the present invention.

[0017] The disconnect clutch K0 functions as a clutch that connects or disconnects the engine 12 to / from the electric motor MG, that is, a clutch that disconnects and connects the engine 12 and the electric motor MG.

[0018] The launch clutch WSC is a wet friction engagement device composed of, for example, a multi-plate or single-plate clutch pressed by an actuator. The launch clutch WSC has its control state such as the engaged state, slip state, and released state switched by changing the WSC torque Twsc, which is the torque capacity of the launch clutch WSC, by the regulated hydraulic pressure PRwsc of WSC hydraulic pressure supplied from the hydraulic control circuit 56.

[0019] The input side member of the launch clutch WSC is integrally connected to the motor connection shaft 32. The output side member of the launch clutch WSC is integrally connected to the transmission input shaft 38, which is the input rotating member of the automatic transmission 20. In the engaged state of the launch clutch WSC, the power of the engine 12 and the power of the electric motor MG can be transmitted to the automatic transmission 20. On the other hand, in the released state of the launch clutch WSC, the power transmission from the engine 12 and the electric motor MG to the automatic transmission 20 is interrupted.

[0020] The automatic transmission 20 is a known planetary gear type automatic transmission including, for example, one or a plurality of sets of planetary gear devices (not shown) and an engagement device CB. The engagement device CB includes, for example, a plurality of known hydraulic friction engagement devices. Each of the engagement devices CB has its control state such as an engaged state, a slip state, and a released state switched by changing the CB torque Tcb, which is the respective torque capacity, by the regulated hydraulic pressure CB hydraulic pressure PRcb supplied from the hydraulic control circuit 56.

[0021] The automatic transmission 20 is a stepped transmission in which any one of the engagement devices of the engagement device CB is engaged to form any one of a plurality of gear stages (also referred to as gear steps) having different gear ratios (also referred to as gear ratios) γat (= AT input rotation speed Ni / AT output rotation speed No). For example, the automatic transmission 20 switches the gear stage formed according to the driver's ( = driver) accelerator operation, vehicle speed V, etc. The AT input rotation speed Ni is the rotation speed of the transmission input shaft 38. The AT output rotation speed No is the rotation speed of the transmission output gear 26.

[0022] In the power transmission device 16, the power output from the engine 12 is transmitted to the drive wheels 14 via the automatic transmission 20 and the like when the disconnect clutch K0 and the launch clutch WSC are both engaged. Also, in the power transmission device 16, the power output from the electric motor MG is transmitted to the drive wheels 14 via the automatic transmission 20 and the like when the launch clutch WSC is engaged regardless of the control state of the disconnect clutch K0.

[0023] The vehicle 10 includes a mechanical oil pump 34 connected to the electric motor connection shaft 32 via a transmission member 36. The vehicle 10 further includes an electric oil pump 58, which is an electric oil pump, a pump motor 60, and the like. The electric oil pump 58 is driven by the pump motor 60.

[0024] The hydraulic oil OIL discharged by the mechanical oil pump 34 and the electric oil pump 58 is supplied to the hydraulic control circuit 56. The hydraulic control circuit 56 supplies the regulated K0 hydraulic pressure PRk0, WSC hydraulic pressure PRwsc, CB hydraulic pressure PRcb, etc., based on the hydraulic oil OIL discharged by at least one of the mechanical oil pump 34 and the electric oil pump 58. The hydraulic oil OIL is also used, for example, for lubricating each part of the power transmission device 16.

[0025] The vehicle 10 further includes an electronic control unit 90 as a controller including the control unit of the vehicle 10. The electronic control unit 90 is configured to include various computers for engine control, motor control, hydraulic control, etc., as required.

[0026] Various signals (for example, the engine rotation speed Ne which is the rotation speed of the engine 12, the 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 launch clutch WSC, the AT input rotation speed Ni, the AT output rotation speed No corresponding to the vehicle speed V, the accelerator opening θacc which is the driver's accelerator operation amount representing the magnitude of the driver's acceleration operation, the throttle valve opening θth which is the opening of the electronic throttle valve, the brake on signal Bon which is a signal indicating that the brake pedal for operating the wheel brake (not shown) is being operated by the driver, the brake operation amount Bra, the battery temperature THbat, the battery charge / discharge current Ibat, the battery voltage Vbat of the battery 54, and the working oil temperature THoil which is the temperature of the working oil OIL in the hydraulic control circuit 56, etc.) based on the detection values by various sensors (for example, the engine rotation speed sensor 70, the MG rotation speed sensor 72, the input rotation speed sensor 74, the output rotation speed sensor 76, the accelerator opening sensor 78, the throttle valve opening sensor 80, the brake sensor 82, the battery sensor 84, the oil temperature sensor 86, etc.) provided in the vehicle 10 are respectively supplied to the electronic control unit 90.

[0027] From the electronic control device 90, various command signals (such as an engine control command signal Se for controlling the engine 12, an MG control command signal Sm for controlling the motor MG, a CB hydraulic pressure control command signal Scb for controlling the engagement device CB, a K0 hydraulic pressure control command signal Sk0 for controlling the disconnection clutch K0, a WSC hydraulic pressure control command signal Swsc for controlling the start clutch WSC, an electric oil pump control command signal Seop for controlling the electric oil pump 58, etc.) are output to each device (such as the engine control device 50, the inverter 52, the hydraulic control circuit 56, the pump motor 60, etc.) provided in the vehicle 10, respectively.

[0028] The electronic control device 90 includes a power source control means, that is, a power source control unit 92, and a clutch control means, that is, a clutch control unit 94, in order to realize various controls in the vehicle 10.

[0029] The power source control unit 92 includes a function of controlling the operation of the engine 12 and a function of controlling the operation of the motor MG, and executes hybrid drive control etc. by the engine 12 and the motor MG by these control functions.

[0030] The power source control unit 92 calculates the drive demand amount for the vehicle 10 by the driver, for example, by applying the accelerator opening θacc and the vehicle speed V to a drive demand amount map. The drive demand amount map is a relationship for obtaining the drive demand amount that has been experimentally or designedly obtained and stored in advance, that is, determined in advance. The drive demand amount is, for example, the required drive torque Trdem [Nm] at the drive wheels 14. The required drive torque Trdem is, in other words, the required drive power Prdem [W] at the vehicle speed V at that time. As the drive demand amount, the required driving force Frdem [N] etc. at the drive wheels 14 can also be used. The power source 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 motor MG so as to realize the required drive power Prdem in consideration of transmission losses, accessory loads, the gear ratio γat of the automatic transmission 20, etc.

[0031] When the power source control unit 92 can satisfy the required drive torque Trdem with only the output of the electric motor MG, the drive mode for driving the vehicle 10 is set to the BEV drive mode. The BEV drive mode is a motor drive mode (= BEV running) in which the vehicle can run using only the electric motor MG as the power source in the disengaged state of the disconnect clutch K0. On the other hand, when the power source control unit 92 cannot satisfy the required drive torque Trdem without using at least the output of the engine 12, the drive mode is set to the engine drive mode, that is, the HEV drive mode. The HEV drive mode is a hybrid drive mode (= HEV running) in which the vehicle can run using at least the engine 12 as the power source in the engaged state of the disconnect clutch K0.

[0032] The power source control unit 92 determines whether there is an engine start request to switch the control state of the engine 12 from the stopped state to the operating state. For example, the power source control unit 92 determines whether there is an engine start request based on whether the required drive torque Trdem has increased beyond the range that can be satisfied with only the output of the electric motor MG during the BEV drive mode (i.e., during motor running), whether warm-up of the engine 12 etc. is necessary, whether charging of the battery 54 is necessary, and so on.

[0033] When it is determined by the power source control unit 92 that there is an engine start request, the clutch control unit 94 controls the disconnect clutch K0 to execute the start control of the engine 12. For example, the clutch control unit 94 outputs a K0 hydraulic pressure control command signal Sk0 for controlling the disengaged disconnect clutch K0 toward the engaged state so as to obtain a K0 torque Tk0 for transmitting the cranking torque Tcr to the engine 12 side. The cranking torque Tcr is a predetermined torque required for cranking the engine 12 to raise the engine rotational speed Ne.

[0034] When it is determined that there is an engine start request, the power source control unit 92 controls the engine 12 and the motor MG so as to execute the start control of the engine 12. For example, the power source control unit 92 outputs an MG control command signal Sm for the motor MG to output a cranking torque Tcr in accordance with the switching of the engagement state of the disconnect clutch K0 by the clutch control unit 94. Further, the power source control unit 92 outputs an engine control command signal Se for starting fuel supply, engine ignition, etc. in conjunction with the cranking of the engine 12.

[0035] When the vehicle 10 is in BEV running, the power source control unit 92 executes the start control of the engine 12 in the slip state of the start clutch WSC. Thereby, it is possible to suppress the shock due to the torque fluctuation accompanying the start control of the engine 12.

[0036] Further, when the vehicle 10 starts, the clutch control unit 94 controls to switch the start clutch WSC, which is in the released state or the slip state, to the engaged state while slipping it. Further, when the vehicle 10 is running, the clutch control unit 94 controls to maintain the start clutch WSC in the engaged state. However, when the AT input rotational speed Ni is lower than the operable rotational speed of the engine 12 during HEV running at a low vehicle speed, etc., the clutch control unit 94 controls the start clutch WSC to be in the slip state. Further, when starting the engine 12 during BEV running of the vehicle 10, the clutch control unit 94 controls the start clutch WSC to be in the slip state.

[0037] The clutch control unit 94 makes a shift determination of the automatic transmission 20 using, for example, a shift map which is a predetermined relationship, and outputs a CB hydraulic pressure control command signal Scb for switching the gear stage of the automatic transmission 20 as necessary. The shift map has a predetermined relationship having a shift line for determining the shift of the automatic transmission 20 on a two-dimensional coordinate with, for example, the vehicle speed V and the required drive torque Trdem as variables.

[0038] Hereinafter, the control at engine start described above will be explained in more detail. The power source control unit 92 determines whether or not the engine rotational speed Ne has reached the MG rotational speed Nmg corresponding to the synchronous rotational speed during the rising transient period of the engine rotational speed Ne at engine start. For example, the power source control unit 92 calculates the rotational speed difference ΔN1 (=|Nm - Ne|) between the engine rotational speed Ne and the MG rotational speed Nm of the electric motor MG at any time, and when the rotational speed difference ΔN1 becomes equal to or less than a preset synchronous determination threshold value α, it determines that the engine rotational speed Ne has reached the synchronous rotational speed (i.e., the MG rotational speed), that is, the engine rotational speed Ne has achieved rotational synchronization with the MG rotational speed Nm.

[0039] When the engine rotational speed Ne reaches the synchronous rotational speed (i.e., the MG rotational speed), the power source control unit 92 executes a torque shift to increase the engine torque Te of the engine 12 while decreasing the MG torque Tm of the electric motor MG. Here, if the engine torque rate RT (hereinafter, torque rate RT), which is the change rate of the engine torque Te during the shift transient period of the power source, is large, the engine torque Te increases rapidly, and accordingly, the vehicle acceleration G may fluctuate. In addition, due to the torque fluctuation of the engine 12, shaking due to the twisting of the damper may occur, and this shaking may be transmitted to the drive wheel 14 side, resulting in the occurrence of shocks. Furthermore, when the engine rotational speed Ne is high, the engine noise increases with the rapid change of the engine torque Te, which may give the driver a sense of discomfort. Thus, if the engine torque Te changes rapidly at engine start, it may lead to deterioration of the NV characteristics (noise and vibration characteristics).

[0040] In order to suppress the occurrence of the above shock, the electronic control unit 90 functionally includes an upper limit guard value calculation unit 98 as an upper limit guard value calculation means for calculating an upper limit guard value GU which is the upper limit value of the torque rate RT of the engine torque Te at the start of the engine 12. The upper limit guard value calculation unit 98 calculates the upper limit guard value GU at the start of the engine, for example, by applying the current accelerator opening θacc and the like to a relationship map or relational expression for calculating the upper limit guard value using parameters such as the accelerator opening θacc. The relationship map or relational expression is obtained in advance experimentally or by design, and is configured to obtain an upper limit guard value GU that suppresses the shock generated during the transient period of increasing the engine torque Te within an allowable range.

[0041] When the upper limit guard value GU is calculated, the power source control unit 92 determines the smaller value between the base torque rate RTbs of the engine torque Te and the upper limit guard value GU as the final torque rate RT. When the power source control unit 92 determines the final torque rate RT, it calculates an engine torque command value Tetgt (hereinafter referred to as torque command value Tetgt) based on the torque rate RT, and outputs an engine control command signal Se for controlling the engine torque Te to be the torque command value Tetgt. The base torque rate RTbs is a value set in consideration of the acceleration responsiveness and fuel consumption (power consumption), and is set based on, for example, a target engine torque Teff which is the target value of the engine torque Te after the engine starts. Thus, since the engine torque Te changes rapidly at the start of the engine is suppressed, the shock generated at the start of the engine is suppressed. On the other hand, when the torque rate RT of the engine torque Te is limited by the upper limit guard value GU, there is a possibility that the drive torque Tr transmitted to the drive wheels 14 may be insufficient. In response to this, the power source control unit 92 outputs an MG control command signal Sm for increasing the MG torque Tm so as to compensate for the shortage of the drive torque Tr due to the limitation of the torque rate RT of the engine torque Te. Therefore, even when the torque rate RT of the engine torque Te is limited, the drive torque Tr is ensured.

[0042] However, when starting the engine, if the maximum MG torque Tmmax that can be output from the motor MG is limited due to a decrease in the state of charge value SOC of the battery, heat generation of the motor MG or the battery 54, etc., the MG torque Tm of the motor MG is limited, and there is a possibility that hesitation may occur in acceleration due to a shortage of the actual drive torque Tr with respect to the required drive torque Trdem.

[0043] FIG. 2 is a time chart for explaining one aspect of the control state at the time of engine start. In FIG. 2, the horizontal axis indicates time t [sec], and the vertical axis shows, in order from the top, the accelerator opening θacc, each rotational speed (engine rotational speed Ne, MG rotational speed Nm, AT input rotational speed Ni), and each torque (engine torque command value Tetgt, engine torque Te, converted required drive torque Tidem, MG torque Tm, maximum MG torque Tmmax). Here, the converted required drive torque Tidem is a converted value obtained by converting the required drive torque Trdem at the drive wheels 14 into torque at the motor connection shaft 32.

[0044] At time t1 in FIG. 2, the MG torque Tm (i.e., the cranking torque Tcr) for increasing the engine rotational speed Ne is output from the motor MG. Also, although not shown, the torque capacity Tko of the disconnect clutch K0 is controlled toward the engaged state, and the MG torque Tm of the motor MG is transmitted to the engine side via the disconnect clutch K0, whereby the engine rotational speed Ne increases from time t1. At time t2, when the rotational speed difference ΔN1 between the engine rotational speed Ne and the MG rotational speed Nm becomes equal to or less than the synchronization determination threshold value α, while increasing the engine torque Te, the switching of the torque for decreasing the MG torque Tm is started. From this, after time t2, the torque command value Tetgt of the engine torque Te shown by the solid line gradually increases, and the actual engine torque Te shown by the two-dot chain line increases so as to follow the torque command value Tetgt. Also, after time t2, after the MG torque Tm has decreased to a predetermined value, it is held near that predetermined value. At time t3, as the maximum MG torque Tmmax that can be output from the motor MG decreases, the MG torque Tm decreases together with the maximum MG torque Tmmax. After that, until time t4, as the maximum MG torque Tmmax decreases, the MG torque Tm is limited. As a result, hesitation occurs because it takes time for the sum value of the engine torque Te and the MG torque Tm to reach the converted required drive torque Tidem.

[0045] To suppress the above hesitation, the electronic control device 90 functionally includes a lower guard value calculation unit 100 as a lower guard value calculation means and an upper guard value change unit 102 as an upper guard value change means.

[0046] When the increase in the engine torque Te starts, the lower guard value calculation unit 100 calculates the surplus power Pexp of the motor MG. The surplus power Pexp is calculated from the following formula (1). In formula (1), Pe corresponds to the engine power at the current time, Pmmax corresponds to the MG power (hereinafter, the possible MG power Pmmax) that can be output from the motor MG at the current time, and Pidem is the converted value (hereinafter, the converted required drive power Pidem) obtained by converting the required drive power Prdem of the vehicle 10 into the power at the motor connection shaft 32. In other words, the surplus power Pexp corresponds to the power of the motor MG that can assist at the start of the engine. Pexp = Pe + Pmpos - Pidem ···(1)

[0047] The possible MG power Pmmax is calculated by applying the state of charge value SOC of the battery 54, the MG temperature of the motor MG, etc. to a predefined relationship map or relational expression for calculating the possible MG power Pmmax. The converted drive power Pitgt is calculated by taking into account the gear ratio γm, etc. in the power transmission path from the automatic transmission 20 to the drive wheels 14 for the required drive power Prdem at the drive wheels 14 calculated based on the accelerator opening θacc and the vehicle speed V.

[0048] When the lower guard value calculation unit 100 calculates the surplus power Pexp, it calculates the lower guard value GD based on the surplus power Pexp. The lower guard value calculation unit 100 calculates the lower guard value GD by applying the calculated surplus power Pexp to a relationship map or relational expression for obtaining the lower guard value GD using the surplus power Pexp as a parameter, for example. The relationship map or relational expression is obtained in advance experimentally or by design, and is set to a value that suppresses the hesitation at the start of the engine by ensuring the drive torque Tr transmitted to the drive wheels 14 even when the surplus power Pexp is small.

[0049] FIG. 3 shows one aspect of a relationship map composed of the surplus power Pexp and the lower guard value GD. As shown in FIG. 3, in the region where the surplus power Pexp is equal to or greater than a predetermined value P2, the lower guard value GD is set to zero. The predetermined value P2 is a value at which the assist torque by the motor MG can be sufficiently ensured. Therefore, when the surplus power Pexp is the predetermined value P2, since it is not necessary to set the lower guard value GD, the lower guard value GD is set to zero. Also, when the surplus power Pexp becomes equal to or less than the predetermined value P2, as the surplus power Pexp decreases, the lower guard value GD increases. That is, in the region where the surplus power Pexp is equal to or less than the predetermined value P2, the lower guard value GD increases as the surplus power Pexp becomes smaller so that the drive torque Tr is ensured regardless of the surplus power Pexp. Further, in the region where the surplus power Pexp is equal to or less than a predetermined value P1, it is set to a value with, for example, the base torque rate RTbs as the upper limit. Note that the predetermined value P2 corresponds to the predetermined value of the present invention.

[0050] When the lower guard value GD is obtained, the upper guard value changing unit 102 determines whether the lower guard value GD is greater than the upper guard value GU. When the lower guard value GD is greater than the upper guard value GU, the upper guard value changing unit 102 lower-guards the value of the upper guard value GU with the lower guard value GD. Specifically, when the lower guard value GD is greater than the upper guard value GU, the upper guard value changing unit 102 changes the value of the upper guard value GU to the lower guard value GD. On the other hand, when the lower guard value GD is smaller than the upper guard value GU, the upper guard value changing unit 102 holds the value of the upper guard value GU. That is, the larger side of the upper guard value GU and the lower guard value GD is set as the upper guard value GU. In this way, by restricting the lower limit of the upper guard value GU with the lower guard value GD, when the surplus power Pexp of the motor MG is small, it is possible to prevent the torque rate RT of the engine torque Te from becoming smaller than the lower guard value GD, so that hesitation due to insufficient drive torque Tr at engine start is suppressed.

[0051] FIG. 4 is a flowchart for explaining the control operation of the electronic control unit 90, and is a flowchart for explaining the control operation that can prevent hesitation due to insufficient drive torque Tr at engine start. This flowchart is repeatedly executed during engine start.

[0052] First, in step S10 corresponding to the control function of the power source control unit 92 (hereinafter, steps are omitted), it is determined whether torque switching is in progress, that is, whether the engine torque Te is increased and the MG torque Tm of the motor MG is decreased at engine start. If the determination in S10 is negative, this routine is terminated. If the determination in S10 is affirmative, in S20 corresponding to the control functions of the upper limit guard value calculation unit 98 and the lower limit guard value calculation unit 100, the upper limit guard value GU of the torque rate RT of the engine torque Te is calculated. Further, the lower limit guard value GD is calculated based on the surplus power Pexp. Next, in S30 corresponding to the control function of the upper limit guard value changing unit 102, it is determined whether the lower limit guard value GD is greater than the upper limit guard value GU. If the determination in S30 is negative, in S50 corresponding to the control function of the upper limit guard value changing unit 102, the upper limit guard value GU is held and the process proceeds to S60 described later. If the determination in S30 is affirmative, in S40 corresponding to the control function of the upper limit guard value changing unit 102, the lower limit of the upper limit guard value GU is restricted by the lower limit guard value GD (lower limit guard). Specifically, since the upper limit guard value GU is smaller than the lower limit guard value GD, the value of the upper limit guard value GU is changed to the lower limit guard value GD. Next, in S60 corresponding to the control function of the power source control unit 92, the smaller value of the upper limit guard value GU and the base torque rate RTbs determined in S40 or S50 is set as the final torque rate RT. As a result, by setting the torque command value Tetgt of the engine torque Te based on the torque rate RT set in S60, even when the MG torque Tm of the motor MG is restricted, hesitation due to insufficient drive torque Tr at engine start is suppressed.

[0053] FIG. 5 is a time chart for explaining one aspect of the control state at engine start. In FIG. 5, the horizontal axis represents time t [sec], and the vertical axis represents, in order from the top, the respective rotational speeds (engine rotational speed Ne, MG rotational speed Nm, AT input rotational speed Ni) and the respective engine torques Te (command values).

[0054] At time t1, when engine start is initiated, the disconnect clutch K0 is controlled to engage, and a cranking torque Tcr for cranking the engine 12 is output from the motor MG, causing the engine rotational speed Ne to increase. At time t2, when the engine rotational speed Ne becomes rotationally synchronized with the MG rotational speed Nm, the increase in the engine torque Te starts after time t2. The base engine torque Tebs indicated by the solid line in FIG. 5 is the torque command value of the engine 12 defined based on the base torque rate RTbs. The upper guard torque Tgu indicated by the dashed line in FIG. 5 is the torque command value defined based on the upper guard value GU. Also, the lower guard torque Tgd set between time t3 and time t4 in FIG. 5 is the torque command value of the engine 12 defined based on the lower guard value GD. Between time t3 and time t4, the lower guard value GD calculated as needed during this period is greater than the upper guard value GU, and in relation to this, between time t3 and time t4, the lower guard torque Tgd is greater than the upper guard torque Tgu. At this time, since the lower limit of the upper guard value GU is restricted by the lower guard value GD, the final torque command value Tetgt changes along the lower guard torque Tgd. As a result, the shortage of the drive torque Tr is suppressed, and the hesitation that occurs at engine start is prevented.

[0055] As described above, according to this embodiment, when increasing the engine torque Te and decreasing the MG torque Tm of the motor MG at engine start, the upper limit guard value GU of the engine torque Te and the lower limit guard value GD corresponding to the surplus power Pexp of the motor MG are calculated. When the lower limit guard value GD is larger than the upper limit guard value GU, the value of the upper limit guard value GU is changed to the lower limit guard value GD. Therefore, the upper limit guard value GU is set to an appropriate value considering the surplus power Pexp of the motor MG. Thus, even when the surplus power Pexp of the motor MG is small, by increasing the torque command value Tetgt of the engine torque Te, the shortage of the driving torque Tr at engine start is suppressed, and thus hesitation is suppressed.

[0056] Also, the lower limit guard value GD is set such that when the surplus power Pexp becomes equal to or less than a predetermined value P2, the lower limit guard value GD increases as the surplus power Pexp decreases. Therefore, the lower limit guard value GD becomes an appropriate value corresponding to the surplus power Pexp.

[0057] As described above, the embodiments of the present invention have been described in detail with reference to the drawings. However, the present invention is also applicable to other aspects.

[0058] For example, in the above-described embodiment, the launch clutch WSC is provided between the engine 12, the motor MG, and the automatic transmission 20. However, the launch clutch WSC may be substituted for any of the engagement devices CB of the automatic transmission 20. Also, when a torque converter having a lock-up clutch is interposed between the engine 12, the motor MG, and the automatic transmission 20, the lock-up clutch may be substituted for the launch clutch WSC.

[0059] Note that the above is merely one embodiment, 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 Reference Numerals

[0060] 10: Vehicle 12: Engine 90: Electronic control unit 98: Upper guard value calculation unit 100: Lower guard value calculation unit 102: Upper guard value change unit MG: Motor K0: Disconnect clutch (clutch)

Claims

1. An engine, an electric motor, and a clutch for connecting and disconnecting a power transmission path between the engine and the electric motor, When starting the engine during motor driving in which only the electric motor runs as a driving power source with the clutch released, while controlling the clutch toward the engaged state, the rotation of the engine is pulled up by the torque of the electric motor, and when the rotational speed of the engine reaches the synchronous rotational speed, a control device for a vehicle that executes control to increase the engine torque of the engine and decrease the torque of the electric motor, An upper guard value calculation unit that calculates an upper guard value of a change rate of the engine torque at the start of the engine, A lower guard value calculation unit that calculates the surplus power of the electric motor at the start of the engine and calculates a lower guard value of the change rate of the engine torque based on the surplus power, An upper guard value change unit that, when the lower guard value is larger than the upper guard value, changes the value of the upper guard value to the lower guard value, A control device for a vehicle, characterized by the above.

2. The lower guard value is set so as to increase as the surplus power becomes smaller in a region where the surplus power is equal to or less than a predetermined value. The control device for a vehicle according to claim 1, characterized by the above.

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