Vehicle control device

Abstract

To suppress deterioration of durability of a friction engagement device when switching to an engagement state of the friction engagement device.SOLUTION: While traveling in an electric driving mode, a transmission ratio of a limit on a low vehicle speed side restricting a transmission ratio that can be used by a transmission is set so that the rotation speed of an input rotary member of the transmission becomes a predetermined rotation speed or less, so that increase in a differential rotation speed of a friction engagement device is suppressed, and heating of a friction material when the friction engagement device is switched to an engagement state is suppressed. When switching to the engagement state of the friction engagement state, deterioration of durability of the friction engagement device can be suppressed.SELECTED DRAWING: Figure 3

Description

[Technical Field]

[0001] The present invention relates to a control device for a vehicle that includes a friction engagement device provided between an engine and an electric motor, and a transmission that transmits power from a power source including the engine and the electric motor. [Background technology]

[0002] There is a well-known control device for a vehicle that includes an engine, an electric motor connected to a power transmission path between the engine and drive wheels so as to transmit power, a friction engagement device provided in the power transmission path between the engine and the electric motor, and a transmission provided in the power transmission path between the electric motor and the drive wheels. For example, Patent Document 1 discloses a control device for a hybrid vehicle. Patent Document 1 discloses establishing an electric drive mode as a drive mode for driving the vehicle, in which the friction engagement device is disengaged and the engine is stopped, and the vehicle can run using only the electric motor as a power source, and also discloses controlling the gear ratio of the transmission. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Application Laid-Open No. 2014-151909 Summary of the Invention [Problem to be solved by the invention]

[0004] When the rotational speed of the input rotary member of the transmission is increased during driving in the electric drive mode, the differential rotational speed of the friction engagement device is increased. When the friction engagement device is switched to an engaged state, for example, to start the engine, during driving in the electric drive mode, depending on the magnitude of the differential rotational speed of the friction engagement device, there is a concern that the durability of the friction engagement device may be reduced due to heat generation in the friction material of the friction engagement device.

[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 a decrease in the durability of a friction engagement device when switching the friction engagement device to an engaged state. [Means for solving the problem]

[0006] The gist of a first aspect of the present invention is a control device for a vehicle including: (a) an engine; an electric motor connected to a power transmission path between the engine and drive wheels so as to be able to transmit power; a friction engagement device provided in the power transmission path between the engine and the electric motor; and a transmission provided in the power transmission path between the electric motor and the drive wheels, (b) a power source control unit that establishes, as a drive mode for driving the vehicle, an electric drive mode in which, with the friction engagement device in a disengaged state, the vehicle can travel using only the electric motor as a power source with the engine stopped; and (c) a transmission control unit that controls the gear ratio of the transmission to establish a required gear ratio, and (d) the transmission control unit sets a limit gear ratio on the low vehicle speed side that limits the usable gear ratio of the transmission so that the rotational speed of an input rotary member of the transmission is equal to or lower than a predetermined rotational speed when traveling in the electric drive mode. (e) the transmission control unit cancels the setting of the limit speed ratio on the low vehicle speed side when the speed change state is before the start of an inertia phase and when it is predicted that the friction engagement device will be switched to an engaged state during a power-on downshift transition of the transmission. The reason is that. [Effects of the Invention]

[0007] According to the first aspect of the present invention, when traveling in electric drive mode, a limit gear ratio on the low vehicle speed side that limits the usable gear ratio of the transmission is set so that the rotational speed of the input rotary member of the transmission is equal to or lower than a predetermined rotational speed, thereby preventing the differential rotational speed of the friction engagement devices from increasing and suppressing heat generation in the friction material when the friction engagement devices are switched to an engaged state. Therefore, it is possible to prevent a decrease in the durability of the friction engagement devices when they are switched to an engaged state. In addition, during a power-on downshift transition of the transmission, if the gear shift state has not yet begun the inertia phase and it is predicted that the friction engagement devices will be fully engaged, the setting of the limit gear ratio on the low vehicle speed side is canceled. This makes it possible to suppress a decrease in the durability of the friction engagement devices while also suppressing a delay in acceleration response caused by an inability to downshift to the target gear ratio. [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] FIG. 4 is a diagram showing an example of a time chart when engine start control is executed. [Figure 3] 1 is a flowchart illustrating the main control operations of the electronic control device, and is a flowchart illustrating the control operations for suppressing a decrease in the durability of the K0 clutch when the K0 clutch is switched to an engaged state. [Figure 4] FIG. 4 is a diagram showing an example of a time chart when the control operation shown in the flowchart of FIG. 3 is executed, in which the BEV gear position restriction is released before the start of the inertia phase. [Figure 5] FIG. 4 is a diagram showing an example of a time chart when the control operation shown in the flowchart of FIG. 3 is executed, in which the BEV gear position restriction is released during the execution of the inertia phase. DETAILED DESCRIPTION OF THE INVENTION

[0009] In an embodiment of the present invention, the gear ratio of the transmission is "rotational speed of the input rotating member / rotational speed of the output rotating member." The high-side gear ratio of the transmission is the gear ratio on the high vehicle speed side where the gear ratio is small. The low-side gear ratio of the transmission is the gear ratio on the low vehicle speed side where the gear ratio is large. For example, the lowest-side gear ratio is the gear ratio on the lowest vehicle speed side where the gear ratio is the largest.

[0010] Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings. [Example]

[0011] 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.

[0012] 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.

[0013] The electric motor MG is a rotating electric machine, a so-called motor generator, that functions as a motor that generates mechanical power from electric power and as 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 when the engine 12 is operating, the MG torque Tm is a power torque when the positive torque is on the acceleration side, and a regenerative torque when the negative torque is on the deceleration side. The electric power also refers to electric energy unless otherwise specified. The power also refers to driving force, torque, and force unless otherwise specified.

[0014] The power transmission device 16 includes a K0 clutch 20, a torque converter 22, an automatic transmission 24, and the like, 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 interposed in the power transmission path between the torque converter 22 and the drive wheels 14. The automatic transmission 24 is a transmission provided between the electric motor MG and the drive wheels 14 in the power transmission path between the engine 12 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 the like. The power transmission device 16 also includes an engine connecting shaft 34 that connects the engine 12 and the K0 clutch 20, an electric motor connecting shaft 36 that connects the K0 clutch 20 and the torque converter 22, and the like.

[0015] 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.

[0016] The torque converter 22 includes a pump wheel 22a connected to the 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 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 as a direct-coupled clutch 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 known lock-up clutch.

[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 hydraulic engagement devices, such as known friction engagement devices. Each engagement device CB has its torque capacity, or CB torque Tcb, changed by a CB hydraulic pressure PRcb, which is a regulated hydraulic pressure supplied from a hydraulic control circuit 56 provided in the vehicle 10, thereby switching between operating states, i.e., 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 the formed gear stages by an electronic control device 90 (described later) switching the control state of the engagement devices CB involved in the shifting of the automatic transmission 24 in accordance with the accelerator operation of the driver (=operator), the vehicle speed V, etc. In other words, in the shift control of the automatic transmission 24, a shift is performed, for example, by switching the engagement of the engagement devices involved in the shift, that is, a so-called clutch-to-clutch shift is performed in which a shift is performed by disengaging a release-side engagement device and engaging an engagement-side engagement device. The disengagement-side engagement device is an engagement device that, among the engagement devices involved in the shift, was in an engaged state before the automatic transmission 24 was shifted, and is an engagement device that is controlled from an engaged state to a disengaged state during a shift transition of the automatic transmission 24. The engagement-side engagement device is an engagement device that, among the engagement devices involved in the shift, was in a disengaged state before the automatic transmission 24 was shifted, and is an engagement device that is controlled from a disengaged state to an engaged state during a shift transition of the automatic transmission 24. 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 equivalent 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 adjusted oil pressure 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 a CB hydraulic pressure PRcb, a K0 hydraulic pressure PRk0, etc., which are adjusted based on the hydraulic oil OIL discharged by the MOP 58 and / or the EOP 60.

[0023] 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.

[0024] The electronic control device 90 is supplied with various signals based on detection values ​​from various sensors provided on 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 switch 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 corresponding to the vehicle speed V, an MG rotation speed Nm which is the rotation speed of the electric motor MG, 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 is being operated by the driver, a battery temperature THbat, a battery charge / discharge current Ibat, a battery voltage Vbat of the battery 54, and a hydraulic oil temperature THoil which is the temperature of the hydraulic oil in the hydraulic control circuit 56).

[0025] The electronic control device 90 outputs various command signals (e.g., an engine control command signal Se for controlling the engine 12, an MG control command signal Sm for controlling the electric motor MG, a CB hydraulic control command signal 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, etc.) to each device provided in the vehicle 10 (e.g., the engine control device 50, the inverter 52, the hydraulic control circuit 56, the pump motor 62, etc.).

[0026] Each hydraulic control command signal S will be described using the K0 hydraulic control command signal Sk0 as an example. The electronic control unit 90 calculates a K0 clutch command pressure Spk0, which is a command pressure for the K0 clutch 20 to supply the adjusted K0 hydraulic pressure PRk0 from the hydraulic control circuit 56, as a command value for the K0 hydraulic pressure PRk0. The command pressure is a target hydraulic pressure commanded by the electronic control unit 90 for the hydraulic oil OIL supplied to the engagement device, and the actual hydraulic pressure, which is the actual hydraulic pressure supplied to the engagement device, changes depending on this command pressure. The electronic control unit 90 converts the K0 clutch command pressure Spk0 into a K0 command current value Sik0 for driving a K0 solenoid SLk0 provided in the hydraulic control circuit 56. The K0 solenoid SLk0 is a solenoid valve for the K0 clutch 20 that outputs the K0 hydraulic pressure PRk0. The K0 command current value Sik0 is a command current for a solenoid driver, which is a drive circuit provided in the electronic control unit 90 that drives the K0 solenoid SLk0. The K0 hydraulic control command signal Sk0 is a drive current or drive voltage for the solenoid driver to drive the K0 solenoid SLk0 based on the K0 command current value Sik0. In other words, the K0 clutch command pressure Spk0 is converted into the K0 hydraulic control command signal Sk0 and output to the hydraulic control circuit 56. In this embodiment, for convenience, the K0 clutch command pressure Spk0 and the K0 hydraulic control command signal Sk0 are treated as the same.

[0027] The electronic control unit 90 includes a power source control means, i.e., a power source control section 92, a clutch control means, i.e., a clutch control section 94, and a transmission control means, i.e., a transmission control section 96, in order to realize various controls in the vehicle 10.

[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 determines whether there is an engine start request, which is a request to start the engine 12 to switch the control state of the engine 12 from a stopped state to an operating state. For example, in the BEV drive mode, the power source control unit 92 determines whether there is an engine start request based on whether the required drive torque Trdem has increased beyond a range that can be covered by the output of the electric motor MG alone, whether the engine 12 or the like needs to be warmed up, or whether the battery 54 needs to be charged.

[0032] When the power source control unit 92 determines that there is an engine start request, the clutch control unit 94 controls the K0 clutch 20 to execute start control of the engine 12. For example, the 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 power source control unit 92 outputs an MG control command signal Sm to the inverter 52 for causing the electric motor MG to output cranking torque Tcr. In addition, in conjunction with the cranking of the engine 12, the power source control unit 92 outputs an engine control command signal Se to the engine control device 50 for starting fuel supply, engine ignition, and the like.

[0034] FIG. 2 is a diagram showing an example of a time chart when start control of the engine 12 is executed. In FIG. 2, time t1a indicates the time when engine start control is started, for example, when the driver further depresses the accelerator pedal during BEV driving, and it is determined that there is an engine start request. After the engine start control is started, packing control of the K0 clutch 20, i.e., K0 packing control, is executed (see time t1a-t2a). The packing control is a control that brings the friction engagement device into a packing-completed state, in which pack clearances in the friction plates of the friction engagement device, etc., are reduced. The packing-completed state of the friction engagement device is a state in which the friction engagement device begins to have torque capacity if the hydraulic pressure supplied to the friction engagement device is increased from the packing-completed state. In the K0 packing control, first, a quick apply is executed to temporarily output a high K0 clutch command pressure Spk0 to improve the initial response of the K0 oil pressure PRk0 (see section a). Next, a constant pressure standby for packing is executed to wait at a constant pressure to complete packing of the K0 clutch 20 (see section b). The K0 clutch command pressure Spk0 shown by the dashed line is the K0 oil pressure PRk0 required to maintain the K0 clutch 20 in a packing-completed state. The K0 clutch command pressure Spk0 shown by the solid line is the total K0 oil pressure PRk0, which is the K0 oil pressure PRk0 required to maintain the packing-completed state plus the K0 oil pressure PRk0 corresponding to the cranking torque Tcr. The K0 clutch command pressure Spk0 shown by the dashed line and the K0 clutch command pressure Spk0 shown by the solid line actually have different K0 packing control periods, but for convenience, they are shown as the same length in FIG. 2. After the K0 packing control is completed, cranking is performed by the K0 clutch 20, which transmits the cranking torque Tcr to the engine 12, in order to crank the engine 12 (see time t2a-t3a). During K0 cranking, when the engine rotation speed Ne is increased, engine ignition and the like are started, and the engine 12 is first fired.

[0035] After the K0 cranking is completed, a post-cranking constant-pressure standby is executed to wait for the K0 clutch 20 to be switched to the engaged state, in which the K0 torque Tk0 is reduced below the cranking torque Tcr and maintained at a predetermined torque Tk0f (see time points t3a-t4a). The K0 clutch command pressure Spk0 during the post-cranking constant-pressure standby is, for example, equal to or greater than the K0 oil pressure PRk0 that maintains the K0 clutch 20 in a packing-completed state, and is the K0 clutch command pressure Spk0 that achieves the K0 torque Tk0 that does not disturb the complete combustion of the engine 12. During the post-cranking constant-pressure standby, the engine speed Ne is increased solely by the combustion torque of the engine 12, not by the K0 torque Tk0. In this embodiment, prior to the post-cranking constant-pressure standby, a quick drain is executed to temporarily output a low K0 clutch command pressure Spk0 in order to improve the initial responsiveness of the K0 oil pressure PRk0 (see part c). During constant pressure standby after cranking, when the engine 12 reaches a stable state of self-sustaining rotation due to combustion, i.e., when the engine 12 reaches a complete combustion state, rotation synchronization control between the engine 12 and the electric motor MG, i.e., synchronization control by the K0 clutch 20 to synchronize the engine rotation speed Ne and the MG rotation speed Nm, i.e., K0 synchronization control, is executed (see time t4a and onwards). The engine rotation speed Ne is the rotation speed of the engine connecting shaft 34 and is equal to the input rotation speed of the K0 clutch 20. The MG rotation speed Nm is the rotation speed of the electric motor connecting shaft 36 and is equal to the output rotation speed of the K0 clutch 20. In other words, synchronizing the engine rotation speed Ne and the MG rotation speed Nm is the same as synchronizing the input rotation speed and output rotation speed of the K0 clutch 20. After the synchronization of the input rotation speed and the output rotation speed of the K0 clutch 20, i.e., K0 synchronization, is completed, that is, after the switching of the K0 clutch 20 to the engaged state, i.e., K0 engagement, is completed, K0 engagement sweep control (=K0 engagement SW control) is executed to transition the K0 clutch 20 to a fully engaged state (see time t4a-t5a). After the K0 clutch 20 is placed in the fully engaged state by the K0 engagement SW control, the start control of the engine 12 is completed (see time t5a), and K0 full engagement control is executed to maintain the fully engaged state of the K0 clutch 20 (see time t5a and onwards).In this embodiment, the starting type of the engine 12 is a starting type in which constant pressure standby after cranking is performed to increase the engine rotation speed Ne through the independent rotation of the engine 12. However, a starting type may also be employed in which constant pressure standby after cranking is not performed, and a K0 clutch command pressure Spk0 is output so as to increase the engine rotation speed Ne until it is synchronized with the MG rotation speed Nm by performing K0 cranking or K0 synchronization control, and ignition of the engine 12 is started after the engine rotation speed Ne has been increased to near K0 synchronization or up to K0 synchronization.

[0036] The transmission control unit 96 determines whether to perform a gear shift in the automatic transmission 24, for example, using a gear shift map having a predetermined relationship, and outputs a CB hydraulic control command signal Sbc to the hydraulic control circuit 56 as needed, i.e., in accordance with the result of the gear shift determination. That is, the transmission control unit 96 determines the gear position of the automatic transmission 24 to be established, for example, using the gear shift map, and outputs a CB hydraulic control command signal Sbc to the hydraulic control circuit 56 for controlling the control state of the engagement devices CB so that the determined gear position is established. In the gear shift control of the automatic transmission 24, the transmission control unit 96 performs gear shifts in the automatic transmission 24, for example, by switching a disengagement-side engagement device among the engagement devices CB to a disengaged state and switching an engagement-side engagement device among the engagement devices CB to an engaged state. In this way, the transmission control unit 96 controls the gear ratio of the automatic transmission 24 to establish a requested gear ratio. The shift map is a predetermined relationship having shift lines on a two-dimensional coordinate system with vehicle speed V and required drive torque Trdem as variables, for example, to determine shifts in the automatic transmission 24. In the shift map, the AT output rotation speed No may be used instead of the vehicle speed V, and the required drive force Frdem, accelerator opening θacc, throttle valve opening θth, etc. may be used instead of the required drive torque Trdem.

[0037] The progression stages, or phases, of the shifting of the automatic transmission 24 will be described using a downshift as an example. When the transmission control unit 96 determines that the automatic transmission 24 should downshift, the transmission control unit 96 outputs a CB hydraulic control command signal Scb to the hydraulic control circuit 56 to initiate the downshift. This signal sets the downshift phase to a preparation phase, i.e., a preparation phase in which the disengagement engagement device waits at a torque capacity capable of handling the input torque Tin to the automatic transmission 24 and the on-coming engagement device is in a packing-completed state. The preparation phase is clutch preparation control that prepares the disengagement engagement device to be switched to a released state and the on-coming engagement device to have torque capacity. The transmission control unit 96 determines whether the preparation phase is complete based on whether a predetermined preparation time has elapsed since the start of the preparation phase. This predetermined preparation time is, for example, a predetermined time required for the on-coming engagement device to be in a packing-completed state. When the transmission control unit 96 determines that the preparation phase is complete, it outputs a CB hydraulic control command signal Sbc to the hydraulic control circuit 56 to gradually decrease the torque capacity of the disengagement engagement device and gradually increase the torque capacity of the engagement engagement device, thereby starting the torque phase. In the case of a downshift, this torque phase is the phase in which the engagement engagement device generates torque capacity, causing a change in the output torque of the automatic transmission 24. When the turbine rotation speed Nt (= AT input rotation speed Ni) increases toward the post-downshift synchronous rotation speed (= No × γat after downshift) during the downshift transition, the downshift phase transitions from the torque phase to the inertia phase. During the inertia phase, the transmission control unit 96 outputs a CB hydraulic control command signal Sbc to the hydraulic control circuit 56 to change the turbine rotation speed Nt at a predetermined increasing gradient, taking into account, for example, the shift time and shift shock. The transmission control unit 96 determines whether the downshift is complete based on whether the turbine rotation speed Nt matches the post-downshift synchronous rotation speed.When the transmission control unit 96 determines that the downshift has ended, it outputs a CB hydraulic pressure control command signal Scb to the hydraulic control circuit 56 to set the CB hydraulic pressure PRcb of the disengaging engagement device to zero and to set the CB hydraulic pressure PRcb of the engaging side engagement device to the CB hydraulic pressure PRcb that maintains the engaging side engagement device in a fully engaged state, thereby completing a series of gear change controls related to the downshift.

[0038] Meanwhile, if the synchronous rotation speed (= No × γat) of the turbine rotation speed Nt is increased during BEV driving or engine start control, thereby increasing the K0 differential rotation speed ΔNk0 (= Nm - Ne) of the K0 clutch 20, there is a concern that the durability of the K0 clutch 20 may be reduced due to heat generated by the friction material of the K0 clutch 20 when cranking the engine 12 using the K0 clutch 20. The synchronous rotation speed of the turbine rotation speed Nt is increased, for example, by downshifting the automatic transmission 24 or by increasing the AT output rotation speed No. At this time, if the K0 clutch 20 is in a disengaged state, for example, during BEV driving, the K0 differential rotation speed ΔNk0 is increased.

[0039] Therefore, during BEV driving, the electronic control device 90 prohibits the use of a gear stage of the automatic transmission 24 in which the synchronous rotation speed of the turbine rotation speed Nt is relatively high, in other words, limits the usable gear stages of the automatic transmission 24, so that the K0 difference rotation speed ΔNk0 does not become so large that there is a concern about a decrease in durability of the K0 clutch 20. Prohibiting the use of a gear stage of the automatic transmission 24 in which the synchronous rotation speed of the turbine rotation speed Nt is, for example, prohibiting a downshift to a gear stage of the automatic transmission 24 in which the synchronous rotation speed of the turbine rotation speed Nt is relatively high. Limiting the usable gear stages of the automatic transmission 24 is limiting the gear stages to which the automatic transmission 24 can be downshifted. That is, when traveling in the BEV drive mode, the transmission control unit 96 implements BEV gear limiting, which sets a lower vehicle speed limit gear ratio, e.g., a gear, that limits the usable gear ratio, e.g., gear, of the automatic transmission 24 so that the turbine rotation speed Nt is equal to or less than a predetermined rotation speed Ntf. The usable gear ratio of the automatic transmission 24 is, for example, a gear ratio at which the automatic transmission 24 can be downshifted. The predetermined rotation speed Ntf is, for example, a predetermined threshold value at which the K0 difference rotation speed ΔNk0 becomes a K0 permissible difference rotation speed ΔNk0p. The K0 permissible difference rotation speed ΔNk0p is, for example, a predetermined upper limit of the K0 difference rotation speed ΔNk0 that is permissible with respect to a decrease in durability of the K0 clutch 20. The low vehicle speed limit gear in the BEV gear limit is the lowest gear that can be used during BEV driving, and is the limit of the low-side gear where the turbine rotation speed Nt is equal to or lower than a predetermined rotation speed Ntf, that is, the lowest gear, depending on the AT output rotation speed No. The lowest gear that can be used during BEV driving is, for example, the lowest gear that can be downshifted to during BEV driving.

[0040] The transmission control unit 96 releases the BEV gear limit based on the control state of the K0 clutch 20 and / or the shift state of the automatic transmission 24, e.g., the state of the shift phase. Releasing the BEV gear limit at the appropriate time reduces the occurrence of a delayed acceleration response, which occurs when, for example, a downshift to the desired gear is not possible due to the gear limit still being in effect at the start of a power-on downshift. In a normal power-on downshift, the downshift destination gear and the intermediate gear during a jump shift are selected to be optimal, taking into account the acceleration conditions and responsiveness during the shift transition. Releasing the BEV gear limit at the appropriate time appropriately prevents the BEV gear limit from becoming a disturbance during a power-on downshift, resulting in the selection of an undesired gear. This allows for both hardware protection performance and drivability, such as response, e.g., acceleration responsiveness.

[0041] Specifically, the power source control unit 92 determines whether the drive mode is the HEV drive mode or not, and also determines whether the engine start control is in transition or not.

[0042] If the power source control unit 92 determines that the drive mode is not the HEV drive mode, for example, if it determines that the drive mode is the BEV drive mode, the transmission control unit 96 implements the BEV gear position restriction.

[0043] If the power source control unit 92 determines that the engine start control is in transition while the BEV gear stage restriction is being implemented, the clutch control unit 94 determines whether the control of the K0 clutch 20 has reached the K0 engagement SW control.

[0044] When the power source control unit 92 determines that engine start control is in transition while the BEV gear position restriction is being implemented, and the clutch control unit 94 determines that control of the K0 clutch 20 has reached K0 engagement SW control, the transmission control unit 96 releases the BEV gear position restriction. As a result, the BEV gear position restriction continues until the K0 clutch 20 is engaged. In particular, when the automatic transmission 24 is in the inertia phase of shifting, the turbine rotation speed Nt is likely to change, so the transmission control unit 96 continues the BEV gear position restriction until the K0 clutch 20 is engaged, prioritizing hardware protection over acceleration responsiveness.

[0045] However, even before the K0 clutch 20 is engaged, the transmission control unit 96 releases the BEV gear stage restriction if the gear shifting state of the automatic transmission 24 is in a steady state, i.e., before the inertia phase starts, for example, in the preparatory phase, and if it is predicted that the K0 clutch 20 will have been switched to the engaged state. As a result, during a power-on downshift of the automatic transmission 24, the BEV gear stage restriction is released before the inertia phase starts, so the inertia phase starts when the lower limit gear stage is not set, and acceleration responsiveness can be prioritized.

[0046] When the power source control unit 92 determines that the engine start control is in transition during BEV gear position restriction and determines that the control of the K0 clutch 20 has not yet reached K0 engagement SW control, the clutch control unit 94 determines whether the power-on downshift state of the automatic transmission 24 is in the preparation phase and whether a K0 clutch engagement prediction determination is established. The K0 clutch engagement prediction determination is a determination that completion of switching of the K0 clutch 20 to the engaged state is predicted. The clutch control unit 94 determines whether the K0 clutch engagement prediction determination is established based on whether the K0 differential rotation speed ΔNk0 is less than a predetermined differential rotation speed ΔNk0f and whether the engine rotation speed Ne is a predetermined engine rotation speed Nef. The predetermined differential rotation speed ΔNk0f is, for example, a predetermined threshold value for determining whether the K0 differential rotation speed ΔNk0 has become small enough to prevent a decrease in the durability of the K0 clutch 20. The predetermined engine rotation speed Nef is a predetermined threshold value for determining, for example, that the engine rotation speed Ne is small enough to reduce the cranking K0 torque Tk0 to a level that does not reduce the durability of the K0 clutch 20. The preparatory phase in determining whether the power-on downshift state of the automatic transmission 24 is in the preparatory phase may be any phase before the start of the inertia phase, and may include the torque phase.

[0047] When the power source control unit 92 determines that engine start control is in transition while the BEV gear stage restriction is being implemented and the clutch control unit 94 determines that control of the K0 clutch 20 has not yet reached K0 engagement SW control, the transmission control unit 96 releases the BEV gear stage restriction if the clutch control unit 94 determines that the power-on downshift state of the automatic transmission 24 is in the preparation phase and that the K0 clutch engagement prediction determination is established. As a result, during a power-on downshift, the BEV gear stage restriction can be released earlier by an engagement determination, i.e., a K0 clutch engagement prediction determination, which is different from the normal engagement determination that control of the K0 clutch 20 has reached K0 engagement SW control.

[0048] Fig. 3 is a flowchart illustrating the main control operations of the electronic control device 90, and is a flowchart illustrating the control operations for suppressing a decrease in the durability of the K0 clutch 20 when the K0 clutch 20 is switched to an engaged state, and is executed, for example, repeatedly. Fig. 4 and Fig. 5 each show an example of a time chart when the control operations shown in the flowchart of Fig. 3 are executed.

[0049] 3, first, in step S10 (hereinafter, the step will be omitted) corresponding to the function of the power source control unit 92, it is determined whether the drive mode is the HEV drive mode. If the determination in S10 is affirmative, the routine is terminated. If the determination in S10 is negative, BEV gear position restriction is implemented in S20, corresponding to the function of the transmission control unit 96. Next, in S30, corresponding to the function of the power source control unit 92, it is determined whether the engine start control is in transition. If the determination in S30 is negative, this S30 is repeatedly executed. If the determination in S30 is affirmative, it is determined in S40, corresponding to the function of the clutch control unit 94, whether control of the K0 clutch 20 has reached K0 engagement SW control. If the determination in S40 is negative, it is determined in S50, corresponding to the function of the clutch control unit 94, whether the power-on downshift state of the automatic transmission 24 is clutch preparation control, i.e., the preparation phase, and whether the K0 clutch engagement prediction determination is established. If the determination in S50 is negative, the process returns to S40. If the determination in S40 is positive, or if the determination in S50 is positive, the BEV gear position restriction is released in S60, which corresponds to the function of the transmission control unit 96.

[0050] FIG. 4 illustrates an example in which the BEV gear position restriction is released before the inertia phase begins. In FIG. 4, time t1b indicates the time when a power-on downshift is initiated during BEV driving, for example, by the driver further depressing the accelerator pedal. At time t1b, an engine start request is made, for example, by further depressing the accelerator pedal, and the BEV gear position restriction is in effect. When engine start control is initiated in response to the engine start request, the engine speed Ne is increased, and when the power-on downshift state of the automatic transmission 24 is in the clutch preparation control, i.e., preparation phase, the K0 clutch engagement prediction determination is established, and the BEV gear position restriction is released (see time t2b). Thereafter, the K0 clutch 20 is engaged, and the inertia phase begins during the power-on downshift of the automatic transmission 24 (see time t3b). When the inertia phase ends during the power-on downshift of the automatic transmission 24, the shift ends (see time t4b). In this way, the BEV gear stage restriction is released before the inertia phase begins and before the normal engagement determination that the control of the K0 clutch 20 has reached the K0 engagement switch control is made because the K0 clutch engagement prediction determination is established, thereby improving acceleration response, i.e., response.

[0051] FIG. 5 illustrates an example in which the BEV gear limit is released during the inertia phase. In FIG. 5, time t1c indicates the time when a power-on downshift is initiated, for example, by the driver further depressing the accelerator pedal during deceleration in the BEV drive mode. This power-on downshift, for example, requests a jump shift from the current nth gear to n-3rd gear, which is three steps lower. At time t1c, an engine start request is made, for example, by further depressing the accelerator pedal, and the BEV gear limit is in effect. In this BEV gear limit, n-2nd gear, which is two steps lower than nth gear, is set as the lowest gear. Time t2c indicates the time when the inertia phase is initiated during the power-on downshift of the automatic transmission 24. In this power-on downshift, a jump shift to n-2nd gear, which is the lowest gear, is executed. During this inertia phase, engine start control is initiated in response to an engine start request, the engine rotation speed Ne is increased, and when a normal engagement determination is established that the control of the K0 clutch 20 has reached the K0 engagement SW control, the BEV gear position restriction is released (see time t3c). Therefore, after the n-2nd gear position is once established, a downshift to the n-3rd gear position, which is the originally intended gear position, is executed (from time t3c). When the inertia phase ends during the downshift to the n-3rd gear position, the gear change is ended (see time t4c). In this way, the engagement determination is established that the control of the K0 clutch 20 has reached the K0 engagement SW control, and the BEV gear position restriction is released. This prevents or suppresses the BEV gear stage restriction from being released early, causing the turbine rotation speed Nt to rise above the specified rotation speed Ntf, i.e., the MG rotation speed Nm to exceed the threshold value and the K0 difference rotation speed ΔNk0 to exceed the K0 allowable difference rotation speed ΔNk0p.

[0052] As described above, according to this embodiment, when traveling in the BEV drive mode, a lower limit gear stage that limits the usable gear stages of the automatic transmission 24 is set so that the turbine rotation speed Nt is equal to or lower than the predetermined rotation speed Ntf, thereby preventing the K0 differential rotation speed ΔNk0 from increasing and suppressing heat generation in the friction material when the K0 clutch 20 is switched to the engaged state. Therefore, it is possible to suppress a decrease in the durability of the K0 clutch 20 when the K0 clutch 20 is switched to the engaged state.

[0053] 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.

[0054] For example, in the above-described embodiment, the requested gear ratio is a gear ratio requested based on the accelerator operation by the driver or the vehicle speed V, but this is not limiting. For example, the requested gear ratio may be a gear ratio requested by an automatic driving control including a known cruise control.

[0055] In addition, in the above-described embodiment, a planetary gear automatic transmission is exemplified 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. In short, the present invention can be applied to any vehicle that includes a power source including an engine and an electric motor, a friction engagement device provided between the engine and the electric motor, and a transmission that transmits power from the power source to the drive wheels, and that can run using only the electric motor as a power source.

[0056] In the above-described embodiment, the torque converter 22 is used as the fluid transmission device, but the present invention is not limited to this. For example, instead of the torque converter 22, another fluid transmission device, such as a fluid coupling that does not have a torque amplifying effect, 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.

[0057] 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]

[0058] 10: Vehicle 12: Engine 14: Drive wheel 20: K0 clutch (friction engagement device) 24: Automatic transmission (transmission) 38: Transmission input shaft (input rotating member) 90: Electronic control device (control device) 92: Power source control unit 96: Transmission control unit MG: Electric motor

Claims

[Claim 1] A control device for a vehicle including an engine, an electric motor connected to a power transmission path between the engine and drive wheels so as to be able to transmit power, a friction engagement device provided between the engine and the electric motor in the power transmission path, and a transmission provided between the electric motor and the drive wheels in the power transmission path, a power source control unit that establishes an electric drive mode as a drive mode for driving the vehicle, in which the friction engagement device is in a disengaged state and the engine is stopped, and the vehicle can travel using only the electric motor as a power source; a transmission control unit that controls the gear ratio of the transmission so as to establish a required gear ratio; It contains the transmission control unit sets a limit gear ratio on the low vehicle speed side that limits the usable gear ratio of the transmission so that the rotation speed of the input rotation member of the transmission is equal to or less than a predetermined rotation speed when traveling in the electric drive mode, the transmission control unit cancels the setting of the limit gear ratio on the low vehicle speed side when, during a power-on downshift transition of the transmission, the gear shift state is before the start of an inertia phase and it is predicted that the friction engagement device will be switched to an engaged state.

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