Vehicle control device

Abstract

To suppress the degradation of energy efficiency while securing the original pressure of the hydraulic pressure when braking a vehicle.SOLUTION: When performing regenerative braking, in the case that a rotational speed of a motor is equal to or higher than a prescribed motor rotational speed, a vehicle control device permits the regenerative braking, meanwhile, In the case that the rotational speed of the motor is less than the prescribed motor rotational speed, the vehicle control device makes the motor freely rotatable with respect to rotation of drive wheels while prohibiting the regenerative braking, thereby, enabling the regenerative braking to be performed until the rotational speed of the motor becomes lower than the prescribed motor rotational speed, or enabling the rotational speed of the motor to be controlled such that a rotational speed of an oil pump can be maintained to be equal to or greater than a prescribed oil pump rotational speed regardless of reduction in the vehicle speed, thereby, enabling degradation of energy efficiency to be suppressed while securing the original pressure of the hydraulic pressure when braking the vehicle.SELECTED DRAWING: Figure 2

Description

[Technical Field]

[0001] The present invention relates to a control device for a vehicle equipped with a mechanical oil pump that is rotationally driven by an electric motor. [Background technology]

[0002] There is a well-known vehicle control device that includes an electric motor that functions as a power source, drive wheels to which power from the electric motor is transmitted, a mechanical oil pump that is rotationally driven by the electric motor, and a hydraulic device whose control state is switched by oil pressure adjusted based on the hydraulic oil discharged by the oil pump. For example, a hybrid vehicle control device is described in Patent Document 1. Patent Document 1 discloses a system that performs regenerative braking of the electric motor by converting the drive torque input from the drive wheels into electric power through regeneration and storing the electric power in an electric storage device. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Application Publication No. 2019-202748 Summary of the Invention [Problem to be solved by the invention]

[0004] When performing regenerative braking, constraining the rotation of the electric motor relative to the rotation of the drive wheels makes it easier to transmit the driven torque to the electric motor, improving energy efficiency. However, when braking a vehicle, the rotation speed of the electric motor also decreases as the vehicle speed decreases, which may prevent the mechanical oil pump from delivering a sufficient flow of hydraulic oil to ensure the base pressure of the hydraulic pressure. If regenerative braking is performed while the rotation of the electric motor is free relative to the rotation of the drive wheels in order to ensure the base pressure of the hydraulic pressure when braking a vehicle, or if regenerative braking is not performed at all, energy efficiency may deteriorate.

[0005] The present invention has been made against the background of the above circumstances, and its purpose is to provide a vehicle control device that can suppress deterioration of energy efficiency while ensuring the original hydraulic pressure when braking the vehicle. [Means for solving the problem]

[0006] The gist of a first invention is a control device for a vehicle including: (a) an electric motor that functions as a power source, drive wheels to which power from the electric motor is transmitted, a mechanical oil pump that is rotationally driven by the electric motor, and a hydraulic device whose control state is switched by oil pressure adjusted based on hydraulic oil discharged by the oil pump; (b) a braking control unit that performs regenerative braking of the electric motor when braking the vehicle, by making the electric motor function as a generator in a state in which rotation of the electric motor is constrained relative to rotation of the drive wheels, thereby generating braking torque by regeneration on the drive wheels; and (c) the braking control unit, when performing the regenerative braking, allows the regenerative braking when the rotation speed of the electric motor is equal to or higher than a predetermined electric motor rotation speed that is set based on a predetermined oil pump rotation speed at which the discharge flow rate of the hydraulic oil by the oil pump can ensure the original pressure of the hydraulic oil, while allowing the rotation of the electric motor to be free relative to the rotation of the drive wheels and prohibits the regenerative braking when the rotation speed of the electric motor is less than the predetermined electric motor rotation speed. (d) the braking control unit sets the predetermined electric motor rotation speed to a higher value as the deceleration of the vehicle increases. The reason is that. [Effects of the Invention]

[0007] According to the first aspect of the present invention, when regenerative braking is performed, if the rotational speed of the electric motor is equal to or greater than a predetermined electric motor rotational speed, regenerative braking is permitted, but if the rotational speed of the electric motor is less than the predetermined electric motor rotational speed, the electric motor is allowed to rotate freely relative to the rotation of the drive wheels and regenerative braking is prohibited. Therefore, regenerative braking can be performed until the rotational speed of the electric motor falls below the predetermined electric motor rotational speed, and the rotational speed of the electric motor can be controlled so that the rotational speed of the oil pump can be maintained at or greater than the predetermined oil pump rotational speed regardless of a decrease in vehicle speed. Therefore, when braking the vehicle, it is possible to ensure the source pressure of the hydraulic pressure and suppress a deterioration in energy efficiency. In addition, the greater the deceleration of the vehicle, the higher the predetermined electric motor rotation speed is set. This ensures that the hydraulic oil discharge flow rate from the oil pump required to ensure the hydraulic source pressure can be secured, and energy efficiency can be further improved by continuing regenerative braking of the electric motor according to the deceleration of the vehicle. In other words, it is possible to achieve both improved energy efficiency and the assurance of the hydraulic source pressure at the same time. [Brief explanation of the drawings]

[0008] [Figure 1] 1 is a diagram illustrating a schematic configuration of a vehicle to which the present invention is applied, and is also a diagram illustrating main parts of control functions and control systems for various controls in the vehicle. [Figure 2] 1 is a flowchart illustrating the main control operations of an electronic control device, and is a flowchart illustrating the control operations for suppressing deterioration of energy efficiency while ensuring the original hydraulic pressure when braking the vehicle. DETAILED DESCRIPTION OF THE INVENTION

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

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

[0011] The engine 12 is a known internal combustion engine such as a gasoline engine, a diesel engine, etc. An electronic control device 90 (described later) controls an engine control device 50 including a throttle actuator, a fuel injection device, an ignition device, etc., provided in the vehicle 10, thereby controlling the engine torque Te, which is the output torque of the engine 12.

[0012] The electric motor MG is a rotating electric machine, a so-called motor generator, that functions as both a motor that generates mechanical power from electric power and a generator that generates electric power from mechanical power. The electric motor MG is connected to a battery 54 provided in the vehicle 10 via an inverter 52 provided in the vehicle 10. The battery 54 is an electricity storage device that supplies and receives electric power to the electric motor MG. The inverter 52 is controlled by an electronic control device 90 (described later), thereby controlling the MG torque Tm, which is the output torque of the electric motor MG. For example, when the rotation direction of the electric motor MG is forward, which is the same as the rotation direction of the engine 12 when it is operating, the MG torque Tm is a powering torque Tmp for positive torque on the acceleration side and a regenerative torque Tmr for negative torque on the deceleration side. Specifically, the electric motor MG generates power using electric power supplied from the battery 54. The electric motor MG also generates electric power using the power of the engine 12 and the driven torque input from the drive wheels 14. The battery 54 is charged with the electric power generated by the electric motor MG. The term "electric power" also refers to electrical energy unless otherwise specified. The term "motive power" also refers to driving force, torque, and force unless otherwise specified.

[0013] The power transmission device 16 includes a K0 clutch 20, a torque converter 22, an automatic transmission 24, and other components housed within a case 18, which is a non-rotating member attached to the vehicle body. The K0 clutch 20 is a clutch provided between the engine 12 and the electric motor MG in a power transmission path between the engine 12 and the drive wheels 14. The torque converter 22 is connected to the engine 12 via the K0 clutch 20. The automatic transmission 24 is connected to the torque converter 22 and is disposed 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 part of the power transmission path between the power source SP and the drive wheels 14. The power transmission device 16 also includes a propeller shaft 28 connected to a 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 other components. The power transmission device 16 also includes an engine connecting shaft 34 that connects the engine 12 and the K0 clutch 20, an electric motor connecting shaft 36 that connects the K0 clutch 20 and the torque converter 22, and the like.

[0014] The electric motor MG is connected to the electric motor connecting shaft 36 in the case 18 so as to be able to transmit power. In other words, the electric motor MG is connected 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. In other words, the electric motor MG is connected to the torque converter 22 and the automatic transmission 24 so as to be able to transmit power without passing through the K0 clutch 20.

[0015] The torque converter 22 includes a pump wheel 22a connected to an electric motor connecting shaft 36 and a turbine wheel 22b connected to a transmission input shaft 38, which is an input rotating member of the automatic transmission 24. The torque converter 22 is a fluid transmission device that is provided between the electric motor MG and the drive wheels 14 in a power transmission path between the engine 12 and the drive wheels 14 and transmits power from the power source SP from the electric motor connecting shaft 36 to the transmission input shaft 38 via fluid. The torque converter 22 includes an LU clutch 40 that connects the pump wheel 22a and the turbine wheel 22b, i.e., that connects the electric motor connecting shaft 36 and the transmission input shaft 38. The LU clutch 40 is a direct-coupled clutch that connects the input and output rotating members of the torque converter 22, i.e., a known lock-up clutch.

[0016] The LU clutch 40 is a hydraulic friction engagement device configured, for example, with a multi-plate or single-plate clutch. The LU clutch 40 switches its operating state, i.e., its control state, by changing the LU torque Tlu, which is the torque capacity of the LU clutch 40, using the LU oil pressure PRlu, which is a regulated oil pressure PRcn supplied from a hydraulic control circuit 56 provided in the vehicle 10. The control states of the LU clutch 40 include a release state (also referred to as 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 an engagement state (also referred to as a fully engaged state) in which the LU clutch 40 is engaged. When the LU clutch 40 is in the release state, the torque converter 22 is in a torque converter state in which torque amplification is achieved. When the LU clutch 40 is in the engaged state, the torque converter 22 is in a lock-up state in which the pump wheel 22a and the turbine wheel 22b rotate integrally.

[0017] The automatic transmission 24 is a known planetary gear automatic transmission that includes, for example, one or more 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 engagement device CB has its torque capacity (CB torque Tcb) changed by a CB oil pressure PRcb, which is a regulated oil pressure PRcn supplied from a hydraulic control circuit 56, thereby switching between control states such as an engaged state, a slip state, and a disengaged state.

[0018] The automatic transmission 24 is a stepped transmission in which one of a plurality of gear stages (also referred to as gear stages) with different speed ratios (also referred to as gear ratios) γat (=AT input rotation speed Ni / AT output rotation speed No) is formed by engaging one of the engagement devices CB. The automatic transmission 24 switches between gear stages formed in response to the accelerator operation of the driver (=operator), vehicle speed V, etc. by an electronic control device 90 (described later). The AT input rotation speed Ni is the rotation speed of the transmission input shaft 38, and is the input rotation speed of the automatic transmission 24. The AT input rotation speed Ni is equal to the turbine rotation speed Nt, which is the output rotation speed of the torque converter 22. The AT input rotation speed Ni can be expressed in terms of the turbine rotation speed Nt. The AT output rotation speed No is the rotation speed of the transmission output shaft 26, and is the output rotation speed of the automatic transmission 24.

[0019] The K0 clutch 20 is a hydraulic friction engagement device configured, for example, with a multi-plate or single-plate clutch. The K0 clutch 20 switches between control states such as an engaged state, a slip state, and a released state by changing the K0 torque Tk0, which is the torque capacity of the K0 clutch 20, using the K0 oil pressure PRk0, which is the regulated oil pressure PRcn supplied from the hydraulic control circuit 56.

[0020] In the vehicle 10, when the K0 clutch 20 is engaged, the engine 12 and the torque converter 22 are connected to each other so that power can be transmitted between them. On the other hand, when the K0 clutch 20 is disengaged, power transmission between the engine 12 and the torque converter 22 is interrupted. Because the electric motor MG is connected to the torque converter 22, the K0 clutch 20 functions as a clutch that connects and disconnects the engine 12 from the electric motor MG.

[0021] In the power transmission device 16, when the K0 clutch 20 is engaged, the power output from the engine 12 is transmitted from the engine connecting shaft 34 to the drive wheels 14 via the K0 clutch 20, the electric motor connecting shaft 36, the torque converter 22, the automatic transmission 24, the propeller shaft 28, the differential gear 30, the drive shaft 32, etc. in this order. Furthermore, regardless of the control state of the K0 clutch 20, the power output from the electric motor MG is transmitted from the electric motor connecting shaft 36 to the drive wheels 14 via the torque converter 22, the automatic transmission 24, the propeller shaft 28, the differential gear 30, the drive shaft 32, etc. in this order.

[0022] The vehicle 10 is equipped with a MOP 58 which is a mechanical oil pump, an EOP 60 which is an electric oil pump, a pump motor 62, etc. The MOP 58 is connected to the pump impeller 22a and is driven to rotate by a power source SP to discharge hydraulic oil OIL used in the power transmission device 16. The pump motor 62 is a motor dedicated to the EOP 60 for driving the EOP 60 to rotate. The EOP 60 is driven to rotate by the pump motor 62 to discharge hydraulic oil OIL. The hydraulic oil OIL discharged by the MOP 58 and the EOP 60 is supplied to a hydraulic control circuit 56. The hydraulic control circuit 56 supplies hydraulic pressures PRcn, such as the LU hydraulic pressure PRlu, the CB hydraulic pressure PRcb, and the K0 hydraulic pressure PRk0, which are each adjusted based on the hydraulic oil OIL discharged by the MOP 58 and / or the EOP 60. The LU clutch 40, the engagement device CB, and the K0 clutch 20 are hydraulic devices whose control states are switched by hydraulic pressure PRcn adjusted based on the hydraulic oil OIL discharged by the MOP 58.

[0023] The vehicle 10 is equipped with a wheel brake device 64. The wheel brake device 64 includes a brake master cylinder and a cylinder actuator (not shown) that generate brake hydraulic pressure. Each of the wheels WH, including the drive wheels 14 and non-drive wheels (not shown), is equipped with a wheel brake 66. If the vehicle 10 is an all-wheel drive vehicle, the non-drive wheels are drive wheels. The wheel brake device 64 is a brake device that applies a wheel braking torque TBw, which is a braking torque TB by the wheel brakes 66, to the wheels WH in accordance with a command from an electronic control device 90 (described later). The wheel brake device 64 supplies brake hydraulic pressure to wheel cylinders (not shown) provided in each wheel brake 66 in response to, for example, the driver's depression of the brake pedal. In the wheel brake device 64, under normal conditions, a master cylinder hydraulic pressure corresponding to the brake operation amount Bra generated from the brake master cylinder is supplied to the wheel cylinder as brake hydraulic pressure. On the other hand, in the wheel brake device 64, for example, when the ABS function is activated, skid prevention control is activated, vehicle speed control is activated, automatic driving control is activated, automatic braking function is activated, regeneration control is activated, etc., in order to generate wheel braking torque TBw, brake hydraulic pressure of a magnitude corresponding to the wheel braking torque TBw required for each control is supplied to the wheel cylinder. The brake operation amount Bra is a signal that corresponds to the brake pedal depression force and indicates the magnitude of the brake pedal depression operation by the driver, i.e., the magnitude of the brake operation.

[0024] The vehicle 10 further includes an electronic control device 90 that includes a control device for the vehicle 10. The electronic control device 90 includes a so-called microcomputer equipped with, for example, a CPU, RAM, ROM, an input / output interface, etc., and the CPU executes various controls of the vehicle 10 by performing signal processing in accordance with programs stored in the ROM in advance while utilizing the temporary storage function of the RAM. The electronic control device 90 includes computers for engine control, electric motor control, clutch control, transmission control, etc. as necessary.

[0025] The electronic control device 90 receives various signals based on detected values ​​from various sensors provided in the vehicle 10 (for example, an engine rotation speed sensor 70, a turbine rotation speed sensor 72, an output rotation speed sensor 74, an MG rotation speed sensor 76, an accelerator opening sensor 78, a throttle valve opening sensor 80, a brake sensor 82, a battery sensor 84, an oil temperature sensor 86, etc.) (for example, an engine rotation speed Ne which is the rotation speed of the engine 12, a turbine rotation speed Nt which is the same value as the AT input rotation speed Ni, an AT output rotation speed No which corresponds to the vehicle speed V, a rotation speed of the electric motor MG which is the rotation speed of the electric motor MG, etc.). A certain MG rotation speed Nm, an accelerator opening θacc which is the amount of accelerator operation by the driver which indicates the magnitude of the driver's acceleration operation, a throttle valve opening θth which is the opening of the electronic throttle valve, a brake-on signal Bon which is a signal indicating the state in which the brake pedal for operating the wheel brakes 66 is being operated by the driver, a brake operation amount Bra, a battery temperature THbat, a battery charge / discharge current Ibat and a battery voltage Vbat of the battery 54, a hydraulic oil temperature THoil which is the temperature of the hydraulic oil OIL in the hydraulic control circuit 56, etc. are supplied.

[0026] The electronic control device 90 outputs various command signals (for example, an engine control command signal Se for controlling the engine 12, an MG control command signal Sm for controlling the electric motor MG, a CB hydraulic control command signal Scb for controlling the engagement device CB, a K0 hydraulic control command signal Sk0 for controlling the K0 clutch 20, an LU hydraulic control command signal Slu for controlling the LU clutch 40, an EOP control command signal Seop for controlling the EOP 60, a brake control command signal Sbra for controlling the wheel braking torque TBw, etc.) to each device provided in the vehicle 10 (for example, the engine control device 50, the inverter 52, the hydraulic control circuit 56, the pump motor 62, the wheel brake device 64, etc.).

[0027] In order to realize various controls in the vehicle 10, the electronic control device 90 is equipped with a power source control means, i.e., a power source control unit 92, a K0 clutch control means, i.e., a K0 clutch control unit 94, a transmission control means, i.e., a transmission control unit 96, an LU clutch control means, i.e., an LU clutch control unit 98, and a braking control means, i.e., a braking control unit 99.

[0028] The power source control unit 92 includes a function as engine control means, i.e., engine control unit 92a, that controls the operation of the engine 12, and a function as electric motor control means, i.e., electric motor control unit 92b, that controls the operation of the electric motor MG via the inverter 52, and is a hybrid control means, i.e., a hybrid control unit, that performs hybrid drive control using the engine 12 and the electric motor MG using these control functions.

[0029] The power source control unit 92 calculates the amount of driving demanded by the driver for the vehicle 10, for example, by applying the accelerator opening θacc and the vehicle speed V to a driving demand map. The driving demand map is a relationship that is experimentally or design-based and stored in advance, i.e., a predetermined relationship. The driving demand is, for example, the required driving torque Trdem at the drive wheels 14. In other words, the required driving torque Trdem [Nm] is the required driving power Prdem [W] at the current vehicle speed V. The driving demand may also be the required driving force Frdem [N] at the drive wheels 14 or the required AT output torque at the transmission output shaft 26. In calculating the driving demand, the AT output rotation speed No may be used instead of the vehicle speed V. 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 electric motor MG so as to realize the required driving power Prdem, taking into account transmission loss, auxiliary load, the gear ratio γat of the automatic transmission 24, etc.

[0030] When the required drive torque Trdem can be satisfied by the output of the electric motor MG alone, the power source control unit 92 establishes the motor drive mode, i.e., the BEV drive mode, as the drive mode for driving the vehicle 10. The BEV drive mode is an electric drive mode that enables motor driving, i.e., electric driving (=BEV driving), in which the vehicle runs using only the electric motor MG as the power source SP with the K0 clutch 20 disengaged and the engine 12 stopped. On the other hand, when the required drive torque Trdem cannot be satisfied without using at least the output of the engine 12, the power source control unit 92 establishes the engine drive mode, i.e., the HEV drive mode, as the drive mode. The HEV drive mode is a hybrid drive mode that enables engine driving, i.e., hybrid driving (=HEV driving), in which the vehicle runs using at least the engine 12 as the power source SP with the K0 clutch 20 engaged. On the other hand, even if the required drive torque Trdem can be met by the output of the electric motor MG alone, the power source control unit 92 establishes the HEV drive mode as the drive mode when it is necessary to charge the battery 54 or when it is necessary to warm up the engine 12, etc.

[0031] The power source control unit 92, particularly the engine control unit 92a, determines whether or not there is an engine start request, which is a request to start the engine 12 and switch the control state of the engine 12 from a stopped state to an operating state. For example, in the BEV drive mode, the engine control unit 92a determines whether or not there is an engine start request based on whether or not the required drive torque Trdem has increased beyond a range that can be covered by the output of the electric motor MG alone, whether or not the engine 12 and the like need to be warmed up, or whether or not the battery 54 needs to be charged.

[0032] When the power source control unit 92 determines that there is an engine start request, the K0 clutch control unit 94 controls the K0 clutch 20 to execute start control of the engine 12. For example, the K0 clutch control unit 94 outputs a K0 hydraulic control command signal Sk0 to the hydraulic control circuit 56 to control the K0 clutch 20 from a released state toward an engaged state so as to obtain a K0 torque Tk0 for transmitting the cranking torque Tcr to the engine 12. The cranking torque Tcr is a predetermined torque required for cranking the engine 12 to increase the engine rotation speed Ne.

[0033] When it is determined that there is an engine start request, the power source control unit 92 controls the engine 12 and the electric motor MG to execute start control of the engine 12. For example, in conjunction with switching the K0 clutch 20 to the engaged state, the electric motor control unit 92b outputs an MG control command signal Sm to the inverter 52 for causing the electric motor MG to output cranking torque Tcr. Furthermore, in conjunction with the cranking of the engine 12, the engine control unit 92a outputs an engine control command signal Se to the engine control device 50 for starting fuel supply, engine ignition, and the like.

[0034] The transmission control unit 96 determines whether to shift the automatic transmission 24 using, for example, a shift map, which is a predetermined relationship, and outputs a CB hydraulic control command signal Sbc to the hydraulic control circuit 56 as needed, i.e., depending on the result of the shift determination. In controlling the shift of the automatic transmission 24, the transmission control unit 96 performs shifting of the automatic transmission 24, for example, by switching a disengaging engagement device among the engagement devices CB to a disengaged state and switching an engaging engagement device among the engagement devices CB to an engaged state. The shift map is a predetermined relationship having shift lines on a two-dimensional coordinate system using, for example, vehicle speed V and required drive torque Trdem as variables, for determining whether to shift the automatic transmission 24. In the shift map, the AT output rotation speed No or the like may be used instead of the vehicle speed V, and the required drive force Frdem, accelerator opening θacc, throttle valve opening θth, or the like may be used instead of the required drive torque Trdem.

[0035] The LU clutch control unit 98 is a lock-up clutch control unit that controls the LU clutch 40 to be in one of the control states of released, slipped, and engaged, i.e., controls the control state of the LU clutch 40. Specifically, the LU clutch control unit 98 determines the control region using, for example, a lock-up region diagram, which is a predetermined relationship, and outputs an LU hydraulic control command signal Slu to the hydraulic control circuit 56 to supply the LU clutch 40 with an LU hydraulic pressure PRlu that achieves the control state corresponding to the determined control region. The lock-up region diagram is a predetermined relationship that has a fully released region (i.e., lock-up off region), a slip region, and a fully engaged region (i.e., lock-up region) on a two-dimensional coordinate system with, for example, vehicle speed V and required drive torque Trdem as variables.

[0036] The braking control unit 99 sets the required braking torque TBdem based on, for example, the accelerator operation by the driver (e.g., accelerator opening θacc, the rate of decrease of accelerator opening θacc), the vehicle speed V, the gradient of a downhill road, and the braking operation by the driver to activate the wheel brakes 66 (e.g., the brake operation amount Bra, the rate of increase of the brake operation amount Bra). When the vehicle 10 is decelerating, the braking control unit 99 generates a braking torque TB of the vehicle 10 so as to obtain the required braking torque TBdem. The side where the braking torque TB (<0) is small is the side where the absolute value of the braking torque TB is large, but for convenience, for example, increasing the absolute value of the braking torque TB will be simply expressed as increasing the braking torque TB, i.e., increasing the braking torque TB, and decreasing the absolute value of the braking torque TB will be simply expressed as decreasing the braking torque TB, i.e., decreasing the braking torque TB.

[0037] The required braking torque TBdem is basically a required braking torque for the wheel braking torque TBw by the wheel brake device 64, and is realized by the wheel braking torque TBw. However, from the viewpoint of improving energy efficiency, for example, it is realized preferentially by the regenerative braking torque TBr. The braking torque TB that realizes the required braking torque TBdem is generated by, for example, the regenerative braking torque TBr and the wheel braking torque TBw. The regenerative braking torque TBr is braking torque TB obtained by regenerative braking, which is braking by regeneration of the electric motor MG. In other words, the braking control unit 99 performs regenerative braking of the electric motor MG, i.e., MG regenerative braking, by causing the electric motor MG to function as a generator to generate regenerative braking torque TBr, which is braking torque TB by regeneration, on the drive wheels 14. The regenerative torque Tmr of the electric motor MG is the MG torque Tm during regeneration of the electric motor MG, which is the regenerative braking torque TBr at the drive wheels 14 converted onto the electric motor connecting shaft 36 based on the gear ratio γat of the automatic transmission 24 and the reduction ratio of the differential gear 30, etc. The regeneration of the electric motor MG is a control in which the electric motor MG is rotationally driven by the driven torque input from the drive wheels 14 to operate as a generator, and the electric power generated by the electric motor MG is charged into the battery 54.

[0038] When performing MG regenerative braking, it is necessary for the power transmission path between the electric motor MG and the drive wheels to be in a power transmission enabled state. The power transmission enabled state in the power transmission path between the electric motor MG and the drive wheels is achieved by setting any gear in the automatic transmission 24. Furthermore, when performing MG regenerative braking, a state in which the rotation of the electric motor MG is constrained relative to the rotation of the drive wheels 14 is more likely to transmit the driven torque to the electric motor MG than a state in which the rotation of the electric motor MG is free, thereby improving energy efficiency. Therefore, when braking the vehicle 10, the braking control unit 99 performs MG regenerative braking in a state in which the rotation of the electric motor MG is constrained relative to the rotation of the drive wheels 14. When the power transmission path between the electric motor MG and the drive wheels is in a power transmission enabled state, a state in which the rotation of the electric motor MG is constrained relative to the rotation of the drive wheels 14 can be achieved, for example, by setting the LU clutch 40 in an engaged state or a slip state. When the power transmission path between the electric motor MG and the drive wheels is in a power transmission enabled state, the state in which the electric motor MG is allowed to rotate freely relative to the rotation of the drive wheels 14 is realized, for example, by disengaging the LU clutch 40. When MG regenerative braking is performed, the LU clutch control unit 98 controls the LU clutch 40 to be in a slip state or an engaged state.

[0039] When the required braking torque TBdem can be entirely covered by the regenerative braking torque TBr, the braking control unit 99 sets the required regenerative braking torque TBr as the required braking torque TBdem. When the absolute value of the required braking torque TBdem is greater than the absolute value of the upper limit of the regenerative braking torque TBr and therefore only a portion of the required braking torque TBdem can be covered by the regenerative braking torque TBr, the braking control unit 99 sets the required regenerative braking torque TBr as the upper limit of the regenerative braking torque TBr and sets the remaining portion of the required braking torque TBdem that cannot be covered by the regenerative braking torque TBr as the required wheel braking torque TBw.

[0040] The braking control unit 99 outputs a command to the electric motor control unit 92b to execute regenerative control by the electric motor MG so as to obtain a regenerative torque Tmr for realizing the required regenerative braking torque TBr. The electric motor control unit 92b performs regenerative control of the electric motor MG by outputting an MG control command signal Sm to obtain the regenerative torque Tmr for realizing the required regenerative braking torque TBr. The braking control unit 99 outputs a brake control command signal Sbra to the wheel brake device 64 to operate the wheel brake 66 so as to obtain the required wheel braking torque TBw.

[0041] When braking the vehicle 10, the MG rotational speed Nm is also reduced as the vehicle speed V decreases, that is, the MOP rotational speed Nmop, which is the rotational speed of the MOP 58, is reduced, so there is a possibility that the MOP 58 will not be able to discharge a sufficient flow rate of hydraulic oil OIL to ensure the original pressure of the hydraulic pressure PRcn. In contrast, when braking the vehicle 10, if MG regenerative braking is performed while the rotation of the electric motor MG is free relative to the rotation of the drive wheels 14 in order to ensure the original pressure of the hydraulic pressure PRcn of the hydraulic devices (LU clutch 40, engagement device CB, K0 clutch 20, etc.), or if MG regenerative braking is not performed at all, there is a possibility that energy efficiency will deteriorate.

[0042] Therefore, the braking control unit 99 predicts a decrease in the MG rotation speed Nm and prohibits MG regenerative braking when braking the vehicle 10. However, because the LU clutch 40 is in a slip state or an engaged state during MG regenerative braking, simply prohibiting MG regenerative braking still causes the MG rotation speed Nm to decrease as the vehicle speed V decreases. Therefore, in addition to prohibiting MG regenerative braking, the braking control unit 99 outputs a command to the LU clutch control unit 98 to release the LU clutch 40.

[0043] As a result, the electric motor control unit 92b can control the MG rotation speed Nm by powering the electric motor MG so that the MOP rotation speed Nmop can be maintained at or above a predetermined MOP rotation speed Nmopf regardless of a decrease in vehicle speed V. The predetermined MOP rotation speed Nmopf is, for example, a predetermined oil pump rotation speed that is set in advance as the lower limit value of the MOP rotation speed Nmop at which the discharge flow rate of the hydraulic oil OIL by the MOP 58 can ensure the source pressure of the hydraulic pressure PRcn of the hydraulic device.

[0044] Predicting a decrease in the MG rotation speed Nm means predicting that the MG rotation speed Nm will no longer be able to maintain the MOP rotation speed Nmop at or above the predetermined MOP rotation speed Nmopf. For example, the braking control unit 99 predicts a decrease in the MG rotation speed Nm when the MG rotation speed Nm is less than the predetermined MG rotation speed Nmf. Ensuring the source pressure of the hydraulic PRcn has a higher performance priority than energy efficiency. For this reason, a corresponding margin is ensured for the MG rotation speed Nm at which the source pressure cannot be ensured, i.e., the predetermined MG rotation speed Nmf, at which MG regenerative braking is prohibited. In other words, the predetermined MG rotation speed Nmf is a predetermined motor rotation speed set based on the predetermined MOP rotation speed Nmopf, and is, for example, a threshold value of the MG rotation speed Nm obtained by adding a predetermined margin Nmmgn to the MG rotation speed Nm corresponding to the predetermined MOP rotation speed Nmopf. In this embodiment, the MG rotation speed Nm corresponding to the predetermined MOP rotation speed Nmopf is the lower limit value of the MG rotation speed Nm at which the original pressure can be secured, and is the same value as the predetermined MOP rotation speed Nmopf. However, in a configuration in which, for example, the MOP 58 and the electric motor MG are connected via a gear mechanism, the value differs from the predetermined MOP rotation speed Nmopf by the gear ratio of the gear mechanism.

[0045] In this way, when performing MG regenerative braking, the braking control unit 99 allows MG regenerative braking if the MG rotation speed Nm is equal to or greater than the predetermined MG rotation speed Nmf, but if the MG rotation speed Nm is less than the predetermined MG rotation speed Nmf, the electric motor MG is allowed to rotate freely relative to the rotation of the drive wheels 14 and prohibits MG regenerative braking.

[0046] Here, during strong deceleration when the deceleration of the vehicle 10 is large, that is, when the braking torque TB is large, the MG rotation speed Nm decreases more quickly than during weak deceleration when the deceleration of the vehicle 10 is small, that is, when the braking torque TB is small. If the predetermined margin Nmmgn is set large and the predetermined MG rotation speed Nmf is set to a uniformly high value during strong deceleration in order to ensure a discharge flow rate of the hydraulic oil OIL that can ensure the original pressure of the hydraulic pressure PRcn, then MG regenerative braking will be prohibited as frequently during weak deceleration as during strong deceleration, which may make it difficult to improve energy efficiency.

[0047] For this reason, the braking control unit 99 switches the predetermined MG rotation speed Nmf depending on the deceleration of the vehicle 10. For example, the braking control unit 99 sets the predetermined MG rotation speed Nmf to a high value during strong deceleration, and sets the predetermined MG rotation speed Nmf to a low value during weak deceleration. In other words, the greater the deceleration of the vehicle 10, the higher the value the braking control unit 99 sets the predetermined MG rotation speed Nmf to. This makes it possible to ensure the discharge flow rate of the hydraulic oil OIL necessary to ensure the base pressure of the hydraulic pressure PRcn, and also makes it possible to further improve energy efficiency by continuing MG regenerative braking depending on the deceleration of the vehicle 10. In other words, it is possible to further achieve both improved energy efficiency and ensuring the base pressure of the hydraulic pressure PRcn.

[0048] The predetermined MG rotation speed Nmf is determined in advance according to the deceleration of the vehicle 10. The braking control unit 99 sets the predetermined MG rotation speed Nmf based on the deceleration of the vehicle 10. When setting the predetermined MG rotation speed Nmf, the actual deceleration of the vehicle 10 detected by an acceleration sensor or the like, the required braking torque TBdem, or the braking torque TB (= wheel braking torque TBw + regenerative braking torque TBr) that realizes the required braking torque TBdem may be used. However, if changes in the required braking torque TBdem are reflected directly, the predetermined MG rotation speed Nmf may fluctuate significantly, which may result in erroneous determination. For this reason, in this embodiment, a value that suppresses changes in the braking torque TB, such as a smoothed value obtained by smoothing the braking torque TB, is used as the deceleration of the vehicle 10 when setting the predetermined MG rotation speed Nmf. This smoothed value of the braking torque TB is, for example, a value obtained by performing known first-order delay processing on the braking torque TB calculated based on each command signal for realizing the required braking torque TBdem.

[0049] The predetermined MG rotation speed Nmf corresponding to the deceleration of the vehicle 10 may be predetermined, for example, for each gear position of the automatic transmission 24. Even with the same braking torque TB, the slope of the AT input rotation speed Ni becomes steeper when the gear position is a low gear position with a relatively large gear ratio, and the slope of the AT input rotation speed Ni becomes shallower when the gear position is a high gear position with a relatively small gear ratio. For this reason, the predetermined MG rotation speed Nmf for each gear position is predetermined to be higher for lower gear positions when the deceleration of the vehicle 10 is the same.

[0050] Specifically, the braking control unit 99 determines whether the driver has applied the brakes, that is, whether a braking request is present. If the braking control unit 99 determines that a braking request is present, it determines whether MG regenerative braking is being performed.

[0051] When it is determined that MG regenerative braking is being performed, the braking control unit 99 calculates a predetermined MG rotation speed Nmf according to the deceleration of the vehicle 10. The braking control unit 99 determines whether the MG rotation speed Nm is equal to or greater than the predetermined MG rotation speed Nmf.

[0052] When the braking control unit 99 determines that the MG rotation speed Nm is equal to or greater than the predetermined MG rotation speed Nmf, it permits MG regenerative braking. On the other hand, when the braking control unit 99 determines that the MG rotation speed Nm is less than the predetermined MG rotation speed Nmf, it prohibits MG regenerative braking. When prohibiting MG regenerative braking, the braking control unit 99 outputs a command to the LU clutch control unit 98 to release the LU clutch 40, and at the same time, during the period until the MG rotation speed Nm decreases to the MG rotation speed Nm corresponding to the predetermined MOP rotation speed Nmopf, the braking control unit 99 gradually replaces the regenerative braking torque TBr with the wheel braking torque TBw to achieve the required braking torque TBdem.

[0053] FIG. 2 is a flowchart explaining the main parts of the control operation of the electronic control unit 90, which is a flowchart explaining the control operation for suppressing deterioration of energy efficiency while maintaining the original pressure of the hydraulic pressure PRcn when braking the vehicle 10, and is executed, for example, repeatedly.

[0054] In FIG. 2, each step in the flowchart corresponds to a function of the braking control unit 99. In step (hereinafter, "step" will be omitted) S10, it is determined whether or not a brake request is present. If the determination in S10 is negative, this routine is terminated. If the determination in S10 is positive, it is determined in S20 whether or not MG regenerative braking is being performed. If the determination in S20 is negative, this routine is terminated. If the determination in S20 is positive, a predetermined MG rotation speed Nmf corresponding to the deceleration of the vehicle 10 is calculated in S30. Next, in S40, it is determined whether or not the MG rotation speed Nm is equal to or greater than the predetermined MG rotation speed Nmf. If the determination in S40 is positive, MG regenerative braking is permitted in S50. If the determination in S40 is negative, MG regenerative braking is prohibited in S60. At this time, a command to release the LU clutch 40 is output, and the regenerative braking torque TBr is gradually replaced with the wheel braking torque TBw.

[0055] As described above, according to this embodiment, when MG rotation speed Nm is equal to or greater than the predetermined MG rotation speed Nmf, MG regenerative braking is permitted, whereas when MG rotation speed Nm is less than the predetermined MG rotation speed Nmf, the electric motor MG is allowed to rotate freely relative to the rotation of the drive wheels 14 and MG regenerative braking is prohibited. Therefore, MG regenerative braking can be performed until MG rotation speed Nm becomes less than the predetermined MG rotation speed Nmf, and the MG rotation speed Nm can be controlled so that the MOP rotation speed Nmop can be maintained at or greater than the predetermined MOP rotation speed Nmopf regardless of a decrease in vehicle speed V. Therefore, when braking the vehicle 10, it is possible to suppress a deterioration in energy efficiency while ensuring the source pressure of the hydraulic pressure PRcn.

[0056] Although the embodiments of the present invention have been described in detail above with reference to the drawings, the present invention can also be applied to other embodiments.

[0057] For example, in the above-described embodiment, the required braking torque TBdem is set based on the brake operation by the driver, and the presence or absence of a braking request is determined based on the brake request by the driver's brake operation, but this is not limiting. For example, the braking request may be determined based on a brake request during deceleration with the accelerator released, a brake request in a known automatic driving control, or a brake request in a known automobile speed control, and the required braking torque TBdem may be set based on these brake requests.

[0058] Furthermore, in the above-described embodiment, the predetermined MG rotation speed Nmf is calculated according to the deceleration of the vehicle 10, but this is not limiting. For example, the predetermined MG rotation speed Nmf may be a uniform predetermined MG rotation speed Nmf that is set in advance to suit strong deceleration. In this case, S30 in the flowchart of Fig. 2 is not necessary. Even in this case, a certain effect of suppressing deterioration in energy efficiency while ensuring the source pressure of the hydraulic pressure PRcn when braking the vehicle 10 can be obtained.

[0059] In the above-described embodiment, the smoothed value of the braking torque TB is used as the deceleration of the vehicle 10 when setting the predetermined MG rotation speed Nmf, but this is not limiting. For example, when the majority of the required braking torque TBdem is realized by the regenerative braking torque TBr, the smoothed value of the regenerative braking torque TBr may be used as the deceleration of the vehicle 10 when setting the predetermined MG rotation speed Nmf.

[0060] In the above-described embodiment, a planetary gear automatic transmission is used as the automatic transmission 24, but the present invention is not limited to this. For example, the automatic transmission 24 may be a synchronous mesh parallel two-shaft automatic transmission including a known DCT (Dual Clutch Transmission), a known belt-type continuously variable transmission, or the like. The automatic transmission 24 is not necessarily provided.

[0061] Furthermore, in the above-described embodiment, the torque converter 22 is used as the fluid transmission device, but this is not a limitation. For example, instead of the torque converter 22, another fluid transmission device, such as a fluid coupling that does not have a torque amplification function, may be used as the fluid transmission device. Alternatively, the fluid transmission device does not necessarily have to be provided, and may be replaced with, for example, a starting clutch. In short, the present invention can be applied to any vehicle that includes an electric motor that functions as a power source, a mechanical oil pump that is rotationally driven by the electric motor, and a hydraulic device whose control state is switched by hydraulic pressure adjusted based on the hydraulic oil discharged by the oil pump.

[0062] It should be noted that the above is merely one embodiment, and the present invention can be embodied in various forms with various modifications and improvements based on the knowledge of those skilled in the art. [Explanation of symbols]

[0063] 10: Vehicle 14: Drive wheel 20: K0 clutch (hydraulic device) 40: LU clutch (hydraulic device) 58: MOP (mechanical oil pump) 90: Electronic control device (control device) 99: Braking control unit CB: Engagement device (hydraulic device) MG: Electric motor OIL: Hydraulic oil PRcn: hydraulic pressure SP: Power source

Claims

[Claim 1] A control device for a vehicle including an electric motor that functions as a power source, drive wheels to which power from the electric motor is transmitted, a mechanical oil pump that is rotationally driven by the electric motor, and a hydraulic device whose control state is switched by hydraulic pressure adjusted based on hydraulic oil discharged by the oil pump, a braking control unit that performs regenerative braking of the electric motor, in which, when braking the vehicle, the electric motor functions as a generator in a state in which rotation of the electric motor is constrained relative to rotation of the drive wheels, thereby generating braking torque by regeneration on the drive wheels; The braking control unit, when performing the regenerative braking, allows the regenerative braking if the rotational speed of the electric motor is equal to or higher than a predetermined electric motor rotational speed set based on a predetermined oil pump rotational speed at which the discharge flow rate of the hydraulic oil by the oil pump can ensure the original pressure of the hydraulic pressure, while, when the rotational speed of the electric motor is lower than the predetermined electric motor rotational speed, allows the electric motor to rotate freely relative to the rotation of the drive wheels and prohibits the regenerative braking, The vehicle control device is characterized in that the braking control unit sets the predetermined motor rotation speed to a higher value as the deceleration of the vehicle increases.

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