Hybrid vehicle

Abstract

To provide a hybrid vehicle having a frictional engagement device arranged between an internal combustion engine and an electric motor, which enables the frictional engagement device to engage with quickly when starting the internal combustion engine.SOLUTION: At the time of starting an engine 12, when a predetermined condition for engaging a K0 clutch 20 quickly is satisfied, hydraulic oil that is supplied to a hydraulic actuator 42 of the K0 clutch 20 is switched from control pressure Pslu that is outputted from a linear solenoid valve 116 to line pressure PL, so that the K0 clutch 20 can be engaged with quickly.SELECTED DRAWING: Figure 1

Description

Technical Field

[0001] The present invention relates to the control at the start of an internal combustion engine provided in a hybrid vehicle.

Background Art

[0002] Patent Document 1 describes that in a hybrid vehicle equipped with a friction engagement device between an internal combustion engine and an electric motor, when the rotational speed of the electric motor deviates from a reference rotational speed at the start of the internal combustion engine, the torque capacity of the friction engagement device is increased to suppress the overshoot of the rotational speed.

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] By the way, at the start of the internal combustion engine, the rotational speed of the internal combustion engine is increased by engaging the friction engagement device. However, under a predetermined state, it may be desirable to engage the friction engagement device promptly, prioritizing responsiveness over the shock generated during the engagement of the friction engagement device. Conventionally, the torque capacity of the friction engagement device is controlled by the hydraulic pressure output from a linear solenoid valve that adjusts the pressure with, for example, the line pressure as the source pressure. However, there is a possibility that the friction engagement device cannot be engaged promptly due to the responsiveness of the linear solenoid valve.

[0005] The present invention has been made in view of the above circumstances, and an object thereof is to provide a hybrid vehicle capable of promptly engaging a friction engagement device at the start of an internal combustion engine in a hybrid vehicle equipped with a friction engagement device between the internal combustion engine and the electric motor.

Means for Solving the Problems

[0006] The gist of the first invention is as follows: (a) a hydraulic friction engagement device provided between an internal combustion engine and an electric motor, An automatic transmission provided between the internal combustion engine and the drive wheels, and a control device, wherein the control device starts the internal combustion engine by increasing the rotational speed of the internal combustion engine by engaging the friction engagement device at the start of the internal combustion engine. The hybrid vehicle is characterized in that (b) the hydraulic pressure of the hydraulic oil supplied to the hydraulic actuator of the friction engagement device can be switched to either a line pressure capable of switching the friction engagement device to an engaged state or a control pressure regulated by a linear solenoid valve using the line pressure as the source pressure, and (c) when a predetermined condition for quickly engaging the friction engagement device is satisfied during the start-up transient period of the internal combustion engine, the control device switches the hydraulic pressure supplied to the hydraulic actuator of the friction engagement device from the control pressure output from the linear solenoid valve to the line pressure. and as a predetermined condition for quickly engaging the friction engagement device, at least one of the following conditions is defined: whether the accelerator opening during downshifting of the automatic transmission in the vehicle driving state is equal to or greater than a predetermined value defined in advance, whether the inertia phase of the automatic transmission has started during downshifting of the automatic transmission in the vehicle driving state, whether the rotational speed difference between the rotating elements constituting the friction engagement device is equal to or greater than a predetermined value defined in advance, and whether the rising gradient of the rotational speed of the electric motor is equal to or greater than a predetermined value defined in advance. This is the gist of the invention.

Effect of the Invention

[0007] According to the first invention, when a predetermined condition for quickly engaging the friction engagement device is satisfied at the start of the internal combustion engine, the hydraulic pressure supplied to the hydraulic actuator of the friction engagement device is switched from the control pressure output from the linear solenoid valve to the line pressure, so that the friction engagement device can be quickly engaged. As such, at least one of the following conditions: whether the accelerator opening during downshifting of the automatic transmission in the vehicle driving state is equal to or greater than a predetermined value defined in advance, whether the inertia phase of the automatic transmission has started during downshifting of the automatic transmission in the vehicle driving state, whether the rotational speed difference between the rotating elements constituting the friction engagement device is equal to or greater than a predetermined value defined in advance, and whether the rising gradient of the rotational speed of the electric motor is equal to or greater than a predetermined value defined in advance.

Brief Description of the Drawings

Brief Description of the Drawings

[0008]

Figure 1

Figure 2

Figure 3

Figure 4

Embodiment for Carrying Out the Invention

[0009] Here, preferably, in the hydraulic control circuit that controls the hydraulic pressure of the hydraulic oil supplied to the hydraulic actuator of the friction engagement device, a switching valve is provided that switches the hydraulic pressure of the hydraulic oil supplied to the hydraulic actuator to either the control pressure or the line pressure output from the linear solenoid valve.

[0011] 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 and shapes of each part are not necessarily accurately drawn.

Embodiment

[0012] FIG. 1 is a diagram for explaining the schematic configuration of a hybrid vehicle 10 (hereinafter, vehicle 10) to which the present invention is applied, and is a diagram for explaining the main parts of the control functions and control systems for various controls in vehicle 10. In FIG. 1, vehicle 10 is a hybrid-type vehicle equipped with an engine 12 and an electric motor MG, which are driving power sources for traveling. Further, vehicle 10 is provided with drive wheels 14 and a power transmission device 16 provided in the power transmission path between engine 12 and drive wheels 14.

[0013] The engine 12 is a known internal combustion engine such as a gasoline engine or a diesel engine. The engine 12 is controlled by an engine control device 50 including a throttle actuator, a fuel injection device, an ignition device, etc. provided in the vehicle 10 by an electronic control device 90 described later, so that the engine torque Te, which is the output torque of the engine 12, is controlled.

[0014] The electric motor MG is a rotary electric machine having a function as an engine 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 electric motor MG is controlled by controlling the inverter 52 by an electronic control device 90 described later, so that the MG torque Tm, which is the output torque of the electric motor MG, is controlled. The MG torque Tm is, for example, a driving torque on the positive torque side for acceleration and a regenerative torque on the negative torque side for deceleration when the rotation direction of the electric motor MG is the same as the rotation direction during the operation of the engine 12, i.e., a positive rotation. Specifically, the electric motor MG generates driving power for traveling by the electric power supplied from the battery 54 via the inverter 52 instead of or in addition to the engine 12. Further, the electric motor MG generates electric power by the power of the engine 12 or the driven power input from the drive wheel 14 side. The electric power generated by the power generation of the electric motor MG is stored in the battery 54 via the inverter 52. The battery 54 is a power storage device that exchanges electric power with the electric motor MG. The electric power is also the same as electrical energy unless otherwise distinguished. The power is also the same as torque or force unless otherwise distinguished.

[0015] The power transmission device 16 includes a K0 clutch 20, a torque converter 22, an automatic transmission 24, etc. in a case 18 which is a non-rotating member attached to the vehicle body. The K0 clutch 20 is a hydraulic friction engagement device provided between the engine 12 and the electric motor MG in the 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.

[0016] 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 torque converter 22 and the automatic transmission 24 each constitute a part of the power transmission path between the engine 12 and the drive wheels 14. Further, the power transmission device 16 includes a propeller shaft 28 connected to the transmission output shaft 26 which 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. Further, the power transmission device 16 includes an engine connection shaft 34 connecting the engine 12 and the K0 clutch 20, a motor connection shaft 36 connecting the K0 clutch 20 and the torque converter 22, and the like.

[0017] The motor MG is connected to the motor connection shaft 36 so as to be power-transmittable within the case 18. The motor MG is connected to be power-transmittable to the power transmission path between the engine 12 and the drive wheels 14, particularly to the power transmission path between the K0 clutch 20 and the torque converter 22. That is, the motor MG is connected to be power-transmittable to the torque converter 22 and the automatic transmission 24 without passing through the K0 clutch 20. In other words, the torque converter 22 and the automatic transmission 24 each constitute a part of the power transmission path between the motor MG and the drive wheels 14. The torque converter 22 and the automatic transmission 24 each transmit the driving force from each of the driving force sources of the engine 12 and the motor MG to the drive wheels 14.

[0018] The torque converter 22 includes an impeller 22a connected to the motor connection shaft 36 and a turbine 22b connected to the transmission input shaft 38 which is an input rotating member of the automatic transmission 24. The impeller 22a is connected to the engine 12 via the K0 clutch 20 and is directly connected to the motor MG. The impeller 22a is an input member of the torque converter 22, and the turbine 22b is an output member of the torque converter 22. The motor connection shaft 36 is also an input rotating member of the torque converter 22. The transmission input shaft 38 is also an output rotating member of the torque converter 22 which is integrally formed with a turbine shaft rotated by the turbine 22b. The torque converter 22 is a fluid transmission device that transmits the driving force from each of the driving force sources (engine 12, motor MG) to the transmission input shaft 38 via a fluid. The torque converter 22 includes a lock-up clutch 40 (hereinafter, LU clutch 40) that connects the impeller 22a and the turbine 22b. The LU clutch 40 is a known engagement / disengagement clutch that engages and disengages the input and output rotating members of the torque converter 22.

[0019] The LU clutch 40 has its operating state, that is, its control state switched by changing the LU clutch torque Tlu which is the torque capacity of the LU clutch 40 by the regulated LU hydraulic pressure PRlu supplied from the hydraulic control circuit 56 provided in the vehicle 10. As the control state of the LU clutch 40, there are a fully released state in which the LU clutch 40 is released, a slip state in which the LU clutch 40 is engaged with slippage, and a fully engaged state in which the LU clutch 40 is engaged.

[0020] The automatic transmission 24 is a known planetary gear type automatic transmission that includes, for example, one or more sets of planetary gear devices (not shown) and a plurality of engagement devices CB. The engagement device CB is a hydraulic friction engagement device configured by, for example, a multi-plate or single-plate clutch or brake pressed by a hydraulic actuator, a band brake tightened by a hydraulic actuator, etc. Each engagement device CB has its control state, such as an engaged state or a released state, switched by changing the CB torque Tcb, which is the respective torque capacity, by the regulated CB hydraulic pressure PRcb supplied from the hydraulic control circuit 56.

[0021] The automatic transmission 24 is a stepped transmission in which any one of the engagement devices among the engagement devices CB is engaged to form any one of a plurality of gear stages (also referred to as gear ratios) with different gear ratios (also referred to as gear ratios) γat (= AT input rotational speed Ni / AT output rotational speed No). The automatic transmission 24 has the gear stage formed according to the driver's ( = driver) accelerator operation, vehicle speed V, etc. switched by an electronic control device 90 described later, that is, a plurality of gear stages are selectively formed. The AT input rotational speed Ni is the rotational speed of the transmission input shaft 38 and is the input rotational speed of the automatic transmission 24. Further, the AT input rotational speed Ni is also the rotational speed of the output rotating member of the torque converter 22 and is the same value as the turbine rotational speed Nt, which is the output rotational speed of the torque converter 22. The AT input rotational speed Ni can be represented by the turbine rotational speed Nt. The AT output rotational speed No is the rotational speed of the transmission output shaft 26 and is the output rotational speed of the automatic transmission 24.

[0022] The K0 clutch 20 is a wet or dry friction engagement device composed of a multi-plate or single-plate clutch pressed by a hydraulic actuator 42 (see FIG. 2). The operating state of the hydraulic actuator 42 is controlled by an electronic control device 90 described later, so that the control states such as the engaged state and the released state of the K0 clutch 20 can be switched. In the K0 clutch 20, when the K0 hydraulic pressure PRk0 regulated from the hydraulic control circuit 56 is supplied to the hydraulic actuator 42, the K0 torque Tk0, which is the torque capacity of the K0 clutch 20, is changed, thereby switching the control state (engaged state) of the K0 clutch 20. Note that the K0 clutch 20 corresponds to the friction engagement device of the present invention.

[0023] In the engaged state of the K0 clutch 20, the pump impeller 22a and the engine 12 are integrally rotated via the engine connecting shaft 34. That is, when the K0 clutch 20 is engaged, the engine 12 and the drive wheels 14 are connected so that power can be transmitted therebetween. On the other hand, in the released state of the K0 clutch 20, the power transmission between the engine 12 and the pump impeller 22a is interrupted. That is, when the K0 clutch 20 is released, the connection between the engine 12 and the drive wheels 14 is disconnected. Since the motor MG is connected to the pump impeller 22a, the K0 clutch 20 is provided in the power transmission path between the engine 12 and the motor MG and functions as a clutch that disconnects and connects the power transmission path, that is, a clutch that disconnects and connects the engine 12 and the motor MG. That is, the K0 clutch 20 is a disconnecting and connecting clutch that connects the engine 12 and the motor MG when engaged and disconnects the connection between the engine 12 and the motor MG when released.

[0024] 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 connection shaft 34 to the drive wheels 14 through the K0 clutch 20, the motor connection shaft 36, the torque converter 22, the automatic transmission 24, the propeller shaft 28, the differential gear 30, the drive shaft 32, and the like in sequence. Further, the power output from the motor MG is transmitted from the motor connection shaft 36 to the drive wheels 14 through the torque converter 22, the automatic transmission 24, the propeller shaft 28, the differential gear 30, the drive shaft 32, and the like in sequence regardless of the control state of the K0 clutch 20.

[0025] The vehicle 10 includes a mechanical oil pump MOP58, an electric oil pump EOP60, a pump motor 62, and the like. The MOP58 is connected to the pump impeller 22a and is rotationally driven by a driving power source (engine 12, motor MG) to discharge hydraulic oil used in the power transmission device 16. The pump motor 62 is a dedicated motor for the EOP60 to rotationally drive the EOP60. The EOP60 is rotationally driven by the pump motor 62 to discharge hydraulic oil. The hydraulic oil discharged by the MOP58 and the EOP60 is supplied to the hydraulic control circuit 56. The hydraulic control circuit 56 supplies the regulated CB hydraulic pressure PRcb, K0 hydraulic pressure PRk0, LU hydraulic pressure PRlu, etc. based on the hydraulic oil discharged by at least one of the MOP58 and the EOP60.

[0026] The vehicle 10 further includes an electronic control device 90 including a control device related to the running control of the vehicle 10 and the like. The electronic control device 90 is configured to include a so-called microcomputer including, for example, a CPU, a RAM, a ROM, an input / output interface, and the like. The CPU performs signal processing according to a program stored in the ROM in advance while using the temporary storage function of the RAM to execute various controls of the vehicle 10. The electronic control device 90 is configured to include each computer for engine control, motor control, hydraulic control, etc. as necessary. Note that the electronic control device 90 corresponds to the control device of the present invention.

[0027] The electronic control unit 90 is supplied with various signals (e.g., the engine rotational speed Ne which is the rotational speed of the engine 12, the turbine rotational speed Nt which is the same value as the AT input rotational speed Ni, the AT output rotational speed No corresponding to the vehicle speed V, the MG rotational speed Nm which is the rotational speed of the electric motor MG, 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 is being operated by the driver, the battery temperature THbat, the battery charge / discharge current Ibat, and the battery voltage Vbat of the battery 54, the operating oil temperature THoil which is the temperature of the operating oil in the hydraulic control circuit 56, and the K0 hydraulic pressure PRk0 of the operating oil supplied to the hydraulic actuator 42 (see FIG. 2) of the K0 clutch 20) based on the detection values from various sensors etc. (e.g., the engine rotational speed sensor 70, the turbine rotational speed sensor 72, the output rotational speed sensor 74, the MG rotational speed sensor 76, the accelerator opening sensor 78, the throttle valve opening sensor 80, the brake switch 82, the battery sensor 84, the oil temperature sensor 86, the hydraulic pressure sensor 88) provided in the vehicle 10.

[0028] The electronic control unit 90 outputs various command signals (e.g., the engine control command signal Se for controlling the engine 12, the MG control command signal Sm for controlling the electric motor MG, the CB hydraulic pressure control command signal Scb for controlling the engagement device CB, the K0 hydraulic pressure control command signal Sk0 for controlling the K0 clutch 20, the LU hydraulic pressure control command signal Slu for controlling the LU clutch 40, the EOP control command signal Seop for controlling the EOP 60 etc.) to each device (e.g., the engine control unit 50, the inverter 52, the hydraulic control circuit 56, the pump motor 62 etc.) provided in the vehicle 10.

[0029] The electronic control unit 90 includes a hybrid control means i.e., a hybrid control section 92, a clutch control means i.e., a clutch control section 94, and a shift control means i.e., a shift control section 96 etc. in order to realize various controls in the vehicle 10.

[0030] The hybrid control unit 92 includes a function as engine control means for controlling the operation of the engine 12, that is, the engine control unit 92a, and a function as motor control means for controlling the operation of the motor MG via the inverter 52, that is, the motor control unit 92b, and executes hybrid drive control and the like by the engine 12 and the motor MG with these control functions.

[0031] The hybrid control unit 92 calculates the drive request amount for the vehicle 10 by the driver, for example, by applying the accelerator opening θacc and the vehicle speed V to a drive request amount map. The drive request amount map is a relationship obtained experimentally or designed in advance and stored, that is, a predetermined relationship. The drive request amount is, for example, the required drive torque Trdem at the drive wheels 14. The required drive torque Trdem [Nm] is, in other words, the required drive power Prdem [W] at the vehicle speed V at that time. As the drive request amount, the required drive force Frdem [N] at the drive wheels 14, the required AT output torque at the output shaft 26 of the transmission, etc. can also be used. In the calculation of the drive request amount, the AT output rotational speed No or the like may be used instead of the vehicle speed V.

[0032] 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 motor MG so as to realize the required drive power Prdem in consideration of transmission loss, accessory load, the gear ratio γat of the automatic transmission 24, the chargeable power Win and the dischargeable power Wout of the battery 54, etc. The engine control command signal Se is a command value of the engine power Pe, which is the power of the engine 12 that outputs the engine torque Te at the engine rotational speed Ne at that time, for example. The MG control command signal Sm is a command value of the power consumption Wm of the motor MG that outputs the MG torque Tm at the MG rotational speed Nm at that time, for example.

[0033] The chargeable power Win of the battery 54 is the maximum input power that can be input, which defines the input power limit of the battery 54 and indicates the input limit of the battery 54. The dischargeable power Wout of the battery 54 is the maximum output power that can be output, which defines the output power limit of the battery 54 and indicates the output limit of the battery 54. The chargeable power Win and the dischargeable power Wout of the battery 54 are calculated by the electronic control device 90 based on, for example, the battery temperature THbat and the state of charge value SOC[%] of the battery 54. The state of charge value SOC of the battery 54 is a value indicating the state of charge of the battery 54 and is calculated by the electronic control device 90 based on, for example, the battery charge and discharge current Ibat and the battery voltage Vbat, etc.

[0034] When the output of the electric motor MG alone can cover the required driving torque Trdem, the hybrid control unit 92 sets the driving mode to the motor driving (= BEV driving) mode. In the BEV driving mode, the hybrid control unit 92 performs BEV driving in which only the electric motor MG is used as the driving power source with the K0 clutch 20 disengaged. On the other hand, when the required driving torque Trdem cannot be covered without using at least the output of the engine 12, the hybrid control unit 92 sets the driving mode to the engine driving mode, that is, the hybrid driving (= HEV driving) mode. In the HEV driving mode, the hybrid control unit 92 performs engine driving, that is, HEV driving, with at least the engine 12 as the driving power source with the K0 clutch 20 engaged. On the other hand, even when the output of the electric motor MG alone can cover the required driving torque Trdem, the hybrid control unit 92 establishes the HEV driving mode when the state of charge value SOC of the battery 54 is less than a predetermined engine start threshold value or when warm-up of the engine 12 etc. is necessary. The engine start threshold value is a predetermined threshold value for determining that it is the state of charge value SOC at which it is necessary to forcibly start the engine 12 to charge the battery 54. Thus, the hybrid control unit 92 automatically stops the engine 12 during HEV driving, restarts the engine 12 after the engine stop, or starts the engine 12 during BEV driving based on the required driving torque Trdem etc., and appropriately switches between the BEV driving mode and the HEV driving mode.

[0035] The hybrid control unit 92 further has a function as a starting control means for starting the engine 12, that is, the starting control unit 92c.

[0036] The starting control unit 92c determines whether there is a starting request for the engine 12. For example, when in the BEV driving mode, the starting control unit 92c determines whether the required drive torque Trdem has increased beyond the range that can be covered only by the output of the motor MG, or whether warm-up of the engine 12 etc. is necessary, or whether the state of charge value SOC of the battery 54 is less than the engine starting threshold value, etc., to determine whether there is a starting request for the engine 12. Also, the starting control unit 92c determines whether the starting control of the engine 12 has been completed.

[0037] The clutch control unit 94 controls the K0 clutch 20 to execute the starting control of the engine 12. For example, when the starting control unit 92c determines that there is a starting request for the engine 12, the clutch control unit 94 outputs a K0 hydraulic pressure control command signal Sk0 to the hydraulic pressure control circuit 56 to control the released K0 clutch 20 toward the engaged state so as to obtain a K0 torque Tk0 for transmitting the torque required for cranking the engine 12 (hereinafter, the required cranking torque Tcrn), which is the torque for raising the engine rotation speed Ne, to the engine 12 side. That is, when starting the engine 12, the clutch control unit 94 outputs a K0 hydraulic pressure control command signal Sk0 to the hydraulic pressure control circuit 56 to control the hydraulic actuator 42 of the K0 clutch 20 so as to switch the control state of the K0 clutch 20 from the released state to the engaged state. As a result, as the K0 clutch 20 is engaged, the engine rotation speed Ne is raised to a rotation speed at which self-sustained operation is possible, thereby starting the engine 12.

[0038] The starting control unit 92c controls the engine 12 and the motor MG so as to execute the starting control of the engine 12. For example, when it is determined that there is a starting request for the engine 12, the starting control unit 92c outputs an MG control command signal Sm for causing the motor MG to output a required cranking torque Tcrn to the inverter 52 in accordance with the switching of the engagement state of the K0 clutch 20 by the clutch control unit 94. That is, when starting the engine 12, the starting control unit 92c outputs an MG control command signal Sm for controlling the motor MG so that the motor MG outputs the required cranking torque Tcrn, that is, so that the MG torque Tm increases by the amount of the required cranking torque Tcrn.

[0039] Also, when it is determined that there is a starting request for the engine 12, the starting control unit 92c outputs an engine control command signal Se for starting fuel supply, engine ignition, etc. to the engine control device 50 in conjunction with the cranking of the engine 12 by the K0 clutch 20 and the motor MG. That is, when starting the engine 12, the starting control unit 92c outputs an engine control command signal Se for controlling the engine 12 so that the engine 12 starts operating to the engine control device 50.

[0040] Incidentally, during the start-up transient period of the engine 12, when in a predetermined state, it may be desirable to force the K0 clutch 20 to engage promptly with priority given to responsiveness over the shock generated during the engagement transient period of the K0 clutch 20. For example, when the accelerator opening θacc is at a high opening when the vehicle 10 is in a driving state and the automatic transmission 24 is downshifted, since the driver's acceleration demand is high, it is desirable to promptly engage the K0 clutch 20 to start the engine 12 and transmit the power of the engine 12 to the automatic transmission 24 side. Also, when the vehicle 10 is in a driving state and the automatic transmission 24 is downshifted, if the inertia phase of the automatic transmission 24 has started before the K0 clutch 20 is engaged, it is desirable to promptly engage the K0 clutch 20. Further, when the rotational speed difference between the rotating elements engaged by the K0 clutch 20 exceeds the allowable range, for the purpose of protecting the components of the K0 clutch 20, it is desirable to promptly engage the K0 clutch 20. Also, when the MG rotational speed Nm of the motor MG is rising rapidly, to suppress the overshoot of the MG rotational speed Nm of the motor MG, it is desirable to promptly engage the K0 clutch 20. In contrast, when in the state as described above during the start-up transient period of the engine 12, the clutch control unit 94 executes control described later to force the K0 clutch 20 to engage promptly.

[0041] Figures 2 and 3 show circuit diagrams for controlling the K0 hydraulic pressure PRk0, which is the hydraulic pressure of the hydraulic oil supplied to the hydraulic actuator 42 of the K0 clutch 20, in the hydraulic control circuit 56 provided in the vehicle 10. Figure 2 shows a state in which the hydraulic actuator 42 is controlled by the control pressure Pslu output from a linear solenoid valve 116 described later, and Figure 3 shows a state in which the hydraulic actuator 42 is controlled by the line pressure PL.

[0042] The hydraulic control circuit 56 is configured to include a regulator valve 110, a modulator valve 112, an on-off solenoid valve 114, a linear solenoid valve 116, and a switching valve 118.

[0043] The regulator valve 110 is a pressure regulating valve that regulates the line pressure PL using the hydraulic pressure of the working oil discharged from the MOP 58 or the EOP 60 as the original pressure. The line pressure PL is a high-pressure hydraulic pressure used as the original pressure for a linear solenoid valve 116, a linear solenoid valve (not shown) that controls the hydraulic actuator of the engagement device CB provided in the automatic transmission 24, and the like. The line pressure PL is set to a value at which the K0 clutch 20 is quickly engaged when supplied to the hydraulic actuator 42 of the K0 clutch 20, that is, a value at which the K0 clutch 20 is quickly switched to an engaged state (fully engaged state) without slippage.

[0044] The modulator valve 112 is configured to output a modulator pressure Pm, which is a predetermined constant pressure, using the line pressure PL as the original pressure. The modulator valve 112 includes an input port 112a to which the line pressure PL is input, an output port 112b from which the modulator pressure Pm is output, an oil chamber 112c, a spool valve element 112d, and a spring 112e. In the modulator valve 112, the spool valve element 112d is moved to a position where the biasing force generated by the hydraulic pressure in the oil chamber 112c and the biasing force of the spring 112e are balanced, thereby regulating the line pressure PL to the modulator pressure Pm. The modulator pressure Pm output from the output port 112b is supplied to an input port 114a (described later) of the on-off solenoid valve 114 via the oil passage 120.

[0045] The on-off solenoid valve 114 (hereinafter referred to as the solenoid valve 114) is configured to output a switching pressure Psw with the modulated pressure Pm output from the modulator valve 112 as the source pressure. The solenoid valve 114 includes an input port 114a to which the modulated pressure Pm is supplied and an output port 114b from which the switching pressure Psw is output. When a command signal for outputting the switching pressure Psw is input from the electronic control unit 90 to the solenoid valve 114, the input port 114a and the output port 114b are communicated, and the switching pressure Psw is output from the output port 114b. On the other hand, when a command signal for outputting the switching pressure Psw is not input from the electronic control unit 90 to the solenoid valve 114, the connection between the input port 114a and the output port 114b is blocked, and the switching pressure Psw is not output from the output port 114b. The switching pressure Psw output from the output port 114b is supplied to an oil chamber 118c (described later) of the switching valve 118 via an oil passage 122.

[0046] The linear solenoid valve 116 outputs a regulated control pressure Pslu with the line pressure PL as the source pressure. The linear solenoid valve 116 includes an input port 116a to which the line pressure PL is input, an output port 116b from which the regulated control pressure Pslu is output, and a feedback port 116c. The linear solenoid valve 116 is an electromagnetic valve capable of regulating the pressure to the control pressure Pslu according to an electric signal (current value) output from the electronic control unit 90. The control pressure Pslu output from the output port 116b is supplied to a first input port 118a (described later) of the switching valve 118 via an oil passage 124.

[0047] The switching valve 118 is configured to be switchable between the K0 hydraulic pressure PRk0, which is the hydraulic pressure supplied to the hydraulic actuator 42 of the K0 clutch 20, and either the control pressure Pslu or the line pressure PL output from the linear solenoid valve 116. The switching valve 118 includes a first input port 118a into which the control pressure Pslu regulated by the linear solenoid valve 116 is input, a second input port 118b into which the line pressure PL is input, an oil chamber 118c to which the switching pressure Psw output from the solenoid valve 114 is supplied, an output port 118d connected to the hydraulic actuator 42 of the K0 clutch 20 via an oil passage 126, a spool valve element 118e, and a spring 118f.

[0048] By switching the position of the spool valve element 118e, the switching valve 118 switches the communication destination of the output port 118d to either the first input port 118a or the second input port 118b. The switching valve 118 shown in FIG. 2 shows a state in which the first input port 118a and the output port 118d are in communication. At this time, the control pressure Pslu output from the linear solenoid valve 116 is supplied to the hydraulic actuator 42 of the K0 clutch 20 via the switching valve 118 and the oil passage 126. On the other hand, the switching valve 118 shown in FIG. 3 shows a state in which the second input port 118b and the output port 118d are in communication. At this time, the line pressure PL is supplied to the hydraulic actuator 42 of the K0 clutch 20 via the switching valve 118 and the oil passage 126.

[0049] The spool valve element 118e of the switching valve 118 is moved based on the biasing force according to the switching pressure Psw supplied to the oil chamber 118c and the biasing force of the spring 118f. For example, when the switching pressure Psw is not output from the solenoid valve 114, since the switching pressure Psw is not supplied to the oil chamber 118c, the spool valve element 118e is moved upward in the drawing by the biasing force of the spring 118f. At this time, the state shown in FIG. 2 is obtained, and the first input port 118a and the output port 118d are communicated. On the other hand, when the switching pressure Psw is output from the solenoid valve 114, the switching pressure Psw is supplied to the oil chamber 118c, so that the spool valve element 118e is moved downward in the drawing against the biasing force of the spring 118f. At this time, the state shown in FIG. 3 is obtained, and the second input port 118b and the output port 118d are communicated. As described above, the switching valve 118 switches the communication state according to whether or not the switching pressure Psw is output from the solenoid valve 114. When the switching pressure Psw is not output, the control pressure Pslu of the linear solenoid valve 116 is supplied to the hydraulic actuator 42 of the K0 clutch 20 via the switching valve 118 and the oil passage 126. When the switching pressure Psw is output, the line pressure PL is supplied to the hydraulic actuator 42 via the switching valve 118 and the oil passage 126. That is, when the switching pressure Psw is not output, the control pressure Pslu is supplied to the hydraulic actuator 42 as the K0 hydraulic pressure PRk0, and when the switching pressure Psw is output, the line pressure PL is supplied to the hydraulic actuator 42 as the K0 hydraulic pressure PRk0. As described above, in the hydraulic control circuit 56, the K0 hydraulic pressure PRk0 supplied to the hydraulic actuator 42 of the K0 clutch 20 can be switched to either the control pressure Pslu regulated by the linear solenoid valve 116 or the line pressure PL.

[0050] Returning to FIG. 1, the clutch control unit 94 determines whether or not a predetermined condition that it is desirable to quickly engage the K0 clutch 20 is satisfied during the engagement transition period of the K0 clutch 20 at the start of the engine 12.

[0051] In this embodiment, a plurality of conditions (Condition a to Condition d) are defined as predetermined conditions. As Condition a, for example, it is defined that the accelerator opening θacc during downshifting of the automatic transmission 24 while the vehicle 10 is in a driving state is equal to or greater than a predetermined value α1 that is predefined. The predetermined value α1 is obtained in advance experimentally or by design, and is set, for example, as a threshold value of a value at which it is determined that the driver's acceleration demand is high.

[0052] Also, as Condition b, for example, it is defined that the inertia phase of the automatic transmission 24 is started during downshifting of the automatic transmission 24 while the vehicle 10 is in a driving state.

[0053] Also, as Condition c, for example, it is defined that the rotational speed difference ΔNk0 between the rotating elements constituting the K0 clutch 20 is equal to or greater than a predetermined value α2 that is predefined. The predetermined value α2 is obtained in advance experimentally or by design, and is set, for example, as a threshold value of a value at which it is determined that it is necessary to protect the components from heat and wear due to friction generated between the rotating elements of the K0 clutch 20. Note that the rotational speed difference ΔNk0 is calculated from the difference between the engine rotational speed Ne and the MG rotational speed Nm (=|Ne - Nm|).

[0054] Also, as Condition d, for example, it is defined that the gradient of increase ΔNm of the MG rotational speed Nm of the electric motor MG is equal to or greater than a predetermined value α3 that is predefined. The predetermined value α3 is obtained in advance experimentally or by design, and is set as the threshold value of the gradient of increase ΔNm at which it is determined that the overshoot of the MG rotational speed Nm of the electric motor MG exceeds the allowable value. Note that the gradient of increase ΔNm is the amount of change in the MG rotational speed Nm per unit time, and is calculated based on the MG rotational speed Nm detected at any time by the MG rotational speed sensor 76.

[0055] When any one of the above conditions (a) to (d) is satisfied, the clutch control unit 94 determines that a predetermined condition for forcibly and promptly engaging the K0 clutch 20 is satisfied. When the above predetermined condition is satisfied, the clutch control unit 94 switches the linear solenoid valve 116 to the non-operating state and outputs a command signal to the hydraulic control circuit 56 not to output the control pressure Pslu from the linear solenoid valve 116. Further, the clutch control unit 94 outputs a command signal to the hydraulic control circuit 56 to output the switching pressure Psw from the solenoid valve 114. At this time, since the switching pressure Psw is supplied to the oil chamber 118c of the switching valve 118, the switching valve 118 is switched to the state shown in FIG. 3, and the second input port 118b and the output port 118d are communicated with each other. As a result, the line pressure PL is supplied to the hydraulic actuator 42 of the K0 clutch 20 via the switching valve 118 and the oil passage 126, and the K0 clutch 20 is forcibly and promptly engaged. In this way, when the above predetermined condition is satisfied during the starting transient period of the engine 12, the clutch control unit 94 switches the K0 hydraulic pressure PRk0 supplied to the hydraulic actuator 42 of the K0 clutch 20 from the control pressure Pslu output from the linear solenoid valve 116 to the line pressure PL, so that the K0 clutch 20 is promptly engaged (fully engaged). Here, immediately after switching the linear solenoid valve 116 to the non-operating state and outputting the switching pressure Psw from the solenoid valve 114, since the flow rate of the working oil may change in the hydraulic control circuit 56, quick apply (also called quick fill) for temporarily increasing the indicated pressure in the shift control of the automatic transmission 24 is prohibited for a predetermined time from this point.

[0056] On the other hand, when the above-described predetermined conditions are not satisfied, the clutch control unit 94 outputs a command signal for activating the linear solenoid valve 116 to the hydraulic control circuit 56, causing the linear solenoid valve 116 to output the control pressure Pslu. Further, the clutch control unit 94 outputs a command signal for not outputting the switching pressure Psw from the solenoid valve 114 to the hydraulic control circuit 56. As a result, the switching valve 118 is switched to the state shown in FIG. 2, and the first input port 118a and the output port 118d are brought into communication. Consequently, the control pressure Pslu regulated by the linear solenoid valve 116 is supplied as the K0 hydraulic pressure PRk0 to the hydraulic actuator 42 of the K0 clutch 20 via the switching valve 118 and the oil passage 126, and the state during the engagement transition period of the K0 clutch 20 can be precisely controlled by the control pressure Pslu.

[0057] FIG. 4 is a flowchart for explaining the main part of the control operation of the electronic control device 90, and is a flowchart for explaining the control operation of quickly engaging the K0 clutch 20 when it is desirable to quickly engage the K0 clutch 20 during the starting transient period of the engine 12. This flowchart is repeatedly executed during the operation of the vehicle 10.

[0058] First, in step S10 corresponding to the control function of the start control unit 92c (hereinafter, steps are omitted), it is determined whether it is the time of engine start, that is, the start transient period of the engine 12. If the determination in S10 is negative, the process returns. If the determination in S10 is positive, in S20 corresponding to the control function of the clutch control unit 94, the K0 hydraulic pressure PRk0 of the K0 clutch 20 required at the start of the engine 12 is calculated. In S30 corresponding to the control function of the clutch control unit 94, it is determined whether a predetermined condition (forced engagement condition) for forcibly and promptly engaging the K0 clutch 20 is satisfied during the start transient period of the engine 12. If the determination in S30 is negative, in S40 corresponding to the control function of the clutch control unit 94, the K0 hydraulic pressure PRk0 supplied to the hydraulic actuator 42 of the K0 clutch 20 is controlled by the control pressure Pslu output from the linear solenoid valve 116. On the other hand, if the determination in S30 is positive, in S50 corresponding to the control function of the clutch control unit 94, the line pressure PL is supplied to the hydraulic actuator 42 of the K0 clutch 20, so that the K0 clutch 20 is promptly engaged.

[0059] As described above, according to this embodiment, when a predetermined condition for promptly engaging the K0 clutch 20 is satisfied at the start of the engine 12, the hydraulic pressure supplied to the hydraulic actuator 42 of the K0 clutch 20 is switched from the control pressure Pslu output from the linear solenoid valve 116 to the line pressure PL, so that the K0 clutch 20 can be promptly engaged.

[0060] As described above, the embodiments of the present invention have been described in detail based on the drawings, but the present invention is also applicable in other aspects.

[0061] For example, in the foregoing embodiment, whether to promptly engage the K0 clutch 20 or not is determined based on whether the accelerator opening θacc during downshifting of the automatic transmission 24 when the vehicle 10 is in a driving state is equal to or greater than a predetermined value α1 (condition a), whether the inertia phase of the automatic transmission 24 has started during downshifting of the automatic transmission 24 when the vehicle 10 is in a driving state (condition b), whether the rotational speed difference ΔNk0 between the rotating elements constituting the K0 clutch 20 is equal to or greater than a predetermined value α2 (condition c), and whether the rising gradient ΔNm of the MG rotational speed Nm of the motor MG is equal to or greater than a predetermined value α3 (condition d). However, it is not necessary to determine all of these conditions. For example, it may be determined whether to promptly engage the K0 clutch 20 based on any one of these conditions a to d. That is, it suffices if it is determined whether to promptly engage the K0 clutch 20 based on at least one of conditions a to d. Also, it may be determined whether to promptly engage the K0 clutch 20 based on other conditions other than the above.

[0062] Further, in the foregoing embodiment, the automatic transmission 24 is a known planetary gear type automatic transmission including one or more sets of planetary gear devices and a plurality of engagement devices CB. However, the present invention is not necessarily limited to the above aspect. For example, the automatic transmission 24 may be a known synchronized meshing type parallel two-shaft automatic transmission including a known DCT (Dual Clutch Transmission), a known belt type continuously variable transmission, or the like.

[0063] 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

[0064] 10: Hybrid vehicle 12: Engine (internal combustion engine) 20: K0 clutch (friction engagement device) 42: Hydraulic actuator 90: Electronic control unit (control unit) 116: Linear solenoid valve MG: Electric motor PL: Line pressure Pslu: Control pressure

Claims

【Claim 1】 A hybrid vehicle comprising a hydraulic friction engagement device provided between an internal combustion engine and an electric motor, an automatic transmission provided between the internal combustion engine and drive wheels, and a control device, wherein the control device starts the internal combustion engine by increasing the rotational speed of the internal combustion engine by engaging the friction engagement device at the start of the internal combustion engine. The hydraulic pressure of the hydraulic oil supplied to the hydraulic actuator of the friction engagement device is configured to be switchable to either a line pressure capable of switching the friction engagement device to an engaged state or a control pressure regulated by a linear solenoid valve using the line pressure as the original pressure. When a predetermined condition for quickly engaging the friction engagement device is satisfied during the start-up transient period of the internal combustion engine, the control device switches the hydraulic pressure supplied to the hydraulic actuator of the friction engagement device from the control pressure output from the linear solenoid valve to the line pressure. As the predetermined condition for quickly engaging the friction engagement device, at least one of the following conditions is defined: whether the accelerator opening during downshifting of the automatic transmission in the vehicle driving state is equal to or greater than a predetermined value defined in advance, whether the inertia phase of the automatic transmission has started during downshifting of the automatic transmission in the vehicle driving state, whether the rotational speed difference between the rotating elements constituting the friction engagement device is equal to or greater than a predetermined value defined in advance, and whether the rising gradient of the rotational speed of the electric motor is equal to or greater than a predetermined value defined in advance. A hybrid vehicle characterized by the above.

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