Vehicle control device

Abstract

To secure hydraulic pressure of an engagement device while suppressing a speed change shock from being generated in down-shifting of an automatic transmission during a speed reduced travel in a low vehicle speed range.SOLUTION: If a down shift is determined during a speed reduced travel in a low vehicle speed range, speed change delay control is executed in which down-shift is started so that a progress stage of the down-shift is a preparation stage in which a release-side engagement device stands by with torque capacity large enough to accept input torque to an automatic transmission, and an engagement-side engagement device is placed in a packing completion state, and maintained in a state in which the preparation stage is completed until the vehicle stops, a preparation stage right after the preparation stage is started after the vehicle stops, to advance the down-shift, so the down-shift in a travel lasts until packing is completed, a speed change shock is hardly generated even if the down-shift is started earlier, and a down-shift after the vehicle stop starts from the packing completion state, thereby suppressing a deficiency in a flow rate of working oil needed for engagement control of the engagement devices.SELECTED DRAWING: Figure 2

Description

Technical Field

[0001] The present invention relates to a control device for a vehicle equipped with an automatic transmission in which a gear stage is formed by engagement of an engagement device.

Background Art

[0002] A control device for a vehicle including a power source and an automatic transmission that forms part of a power transmission path between the power source and drive wheels and forms any one of a plurality of gear stages by engagement of any one of a plurality of hydraulic engagement devices is well known. For example, the shift control device for a vehicle automatic transmission described in Patent Document 1 is such a device. Patent Document 1 discloses that shifting of the automatic transmission is performed by controlling the operating state of a hydraulic engagement device so as to obtain a gear stage determined based on the vehicle speed and the accelerator opening.

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] By the way, during deceleration driving in a low vehicle speed range, in preparation for re-acceleration in the low vehicle speed range, it is conceivable to advance the execution of downshifting of the automatic transmission, that is, to perform a shift from a relatively high vehicle speed side to a low vehicle speed side. Then, there is a risk that a shift shock is likely to occur. On the other hand, in order to suppress the occurrence of a shift shock, it is conceivable to delay the start of downshifting, that is, to start downshifting on the relatively low vehicle speed side or after stopping. Then, since the discharge flow rate of the working oil from the oil pump that is rotationally driven by the power source decreases, there is a risk that the flow rate of the working oil required for the engagement control of the engagement device becomes insufficient, leading to a pressure drop in the oil pressure of the engagement device.

[0005] The present invention has been made in view of the above circumstances, and an object thereof is to provide a vehicle control device capable of suppressing the occurrence of shift shock and ensuring the hydraulic pressure of an engagement device when downshifting an automatic transmission during decelerating travel in a low vehicle speed range.

Means for Solving the Problems

[0006] The gist of the first invention is a control device for a vehicle including: (a) a power source; and an automatic transmission that forms part of a power transmission path between the power source and drive wheels and forms any one of a plurality of shift stages by engaging any one of a plurality of hydraulic engagement devices, the control device including: (b) a shift control unit that performs a shift of the automatic transmission by switching a release-side engagement device among the engagement devices to a released state and switching an engagement-side engagement device among the engagement devices to an engaged state; and (c) when the shift control unit determines a downshift of the automatic transmission during decelerating travel in a predetermined low vehicle speed range, the shift control unit starts the downshift so that the progress stage of the downshift is a preparation stage in which the release-side engagement device is made to standby with a torque capacity capable of receiving the input torque to the automatic transmission and the engagement-side engagement device is made to a packed state with the pack clearance filled, executes a shift delay control for maintaining the progress stage in a state where the preparation stage is completed until the vehicle stops, and starts the next progress stage of the preparation stage after the vehicle stops to advance the downshift. wherein (d) when the shift control unit determines the downshift during the decelerating travel, if the driving mode of the vehicle is a predetermined driving mode that emphasizes power performance, the downshift is advanced without executing the shift delay control This is the case.

Effects of the Invention

[0008] According to the first invention, when a downshift of the automatic transmission is determined during decelerating travel in a predetermined low vehicle speed range, if the progress stage of the downshift is such that the release-side engaging device waits with a torque capacity capable of receiving the input torque to the automatic transmission and the engaging-side engaging device is in a state where packing is completed, the downshift is started, and until the vehicle stops, a shift delay control is executed to maintain the progress stage in a state where the preparation stage is completed. After the vehicle stops, the next progress stage of the preparation stage is started and the downshift is advanced. Therefore, during a downshift while driving, the packing is completed, and even if the start of the downshift is advanced, it is difficult for a shift shock to occur. Also, the downshift after stopping starts from a state where the packing is completed, and a shortage of the flow rate of the hydraulic oil required for the engagement control of the engaging device is suppressed. Thus, when performing a downshift of the automatic transmission during decelerating travel in a low vehicle speed range, it is possible to suppress the occurrence of a shift shock and secure the hydraulic pressure of the engaging device.

[0009] Also, according to the 1 invention, when a downshift is determined during decelerating travel, if the driving mode of the vehicle is a predetermined driving mode that emphasizes power performance, the downshift is advanced without executing the shift delay control. Therefore, it becomes easier to realize a desired driving torque, or a decrease in rough road running performance is suppressed.

Brief Description of the Drawings

[0010]

Figure 1

Figure 2

Figure 3

Figure 4

Figure 5

Figure 6

DETAILED DESCRIPTION OF THE INVENTION

[0011] In an embodiment of the present invention, the gear ratio in the automatic transmission is "rotation speed of the input rotating member / rotation speed of the output rotating member". The high-side gear stage of the automatic transmission is the high vehicle speed side gear stage where the gear ratio becomes smaller. The low-side gear stage of the automatic transmission is the low vehicle speed side gear stage where the gear ratio becomes larger. For example, the lowest gear stage is the lowest vehicle speed side gear stage on the lowest vehicle speed side, and it is the gear stage with the largest gear ratio having the largest value.

[0012] Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.

EXAMPLE

[0013] FIG. 1 is a diagram for explaining the schematic configuration of a vehicle 10 to which the present invention is applied, and is also a diagram for explaining the 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 including an engine 12 and an electric motor MG that function as a power source SP. Further, the vehicle 10 includes drive wheels 14 and a power transmission device 16 provided in the power transmission path between the engine 12 and the drive wheels 14.

[0014] The engine 12 is a known internal combustion engine such as a gasoline engine or a diesel engine. The engine 12 is controlled by an engine control device 50 including a throttle actuator, a fuel injection device, an ignition device, etc. provided in the vehicle 10 by an electronic control device 90 described later, whereby the engine torque Te, which is the output torque of the engine 12, is controlled.

[0015] The electric motor MG is a rotary electric machine having a function as an engine that generates mechanical power from electric power and a function as a generator that generates electric power from mechanical power, and is a so-called motor generator. The electric motor MG is connected to a battery 54 provided in the vehicle 10 via an inverter 52 provided in the vehicle 10. The battery 54 is a power storage device that exchanges electric power with the electric motor MG. The electric motor MG is controlled by controlling the inverter 52 by an electronic control device 90 described later, whereby the MG torque Tm, which is the output torque of the electric motor MG, is controlled. The MG torque Tm is, for example, a power running torque as a positive torque on the acceleration side and a regenerative torque as a negative torque on the deceleration side when the rotation direction of the electric motor MG is the same as the rotation direction during the operation of the engine 12, i.e., a normal rotation. The electric power is also the same as electric energy unless otherwise specified. The power is also the same as driving force, torque, and force unless otherwise specified.

[0016] The power transmission device 16 includes a K0 clutch 20, a torque converter 22, an automatic transmission 24, etc. 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 motor MG in the power transmission path between the engine 12 and the drive wheels 14. The torque converter 22 is connected to the engine 12 via the K0 clutch 20. The automatic transmission 24 is connected to the torque converter 22 and is interposed in the power transmission path between the torque converter 22 and the drive wheels 14. The torque converter 22 and the automatic transmission 24 each constitute a part of the power transmission path between the power source SP and the drive wheels 14. Also, the power transmission device 16 includes a propeller shaft 28 connected to the transmission output shaft 26 which is the 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, etc. Also, the power transmission device 16 includes an engine connecting shaft 34 connecting the engine 12 and the K0 clutch 20, a motor connecting shaft 36 connecting the K0 clutch 20 and the torque converter 22, etc.

[0017] The motor MG is connected within the case 18 so as to be capable of power transmission to the motor connecting shaft 36. That is, the motor MG is connected so as to be capable of power transmission to the power transmission path between the engine 12 and the drive wheels 14, particularly the power transmission path between the K0 clutch 20 and the torque converter 22. Put another way, the motor MG is connected so as to be capable of power transmission to the torque converter 22 and the automatic transmission 24 without passing through the K0 clutch 20.

[0018] The torque converter 22 includes an impeller 22a connected to the motor connecting shaft 36 and a turbine 22b connected to the transmission input shaft 38 which is an input rotating member of the automatic transmission 24. The torque converter 22 is a fluid transmission device that transmits power from the power source SP to the transmission input shaft 38 from the motor connecting shaft 36 via a fluid. The torque converter 22 includes an LU clutch 40 as a direct clutch that connects the impeller 22a and the turbine 22b, that is, connects the motor connecting shaft 36 and the transmission input shaft 38. The LU clutch 40 is a known lock-up clutch.

[0019] The automatic transmission 24 is a known planetary gear type automatic transmission including, for example, one or more sets of planetary gear devices (not shown) and an engagement device CB. The engagement device CB includes, for example, a plurality of hydraulic engagement devices, for example, known friction engagement devices. The engagement device CB is respectively changed in the engagement state, the slip state, the release state, etc., that is, the operating state or the control state is switched by changing the CB torque Tcb which is the respective torque capacity by the regulated hydraulic pressure CB hydraulic pressure PRcb supplied from the hydraulic control circuit 56 provided in the vehicle 10.

[0020] The automatic transmission 24 is a stepped transmission in which any one of the engagement devices of the engagement device CB forms any one of a plurality of shift stages (also referred to as gear stages) with different gear ratios (also referred to as gear ratios) γat (= AT input rotation speed Ni / AT output rotation speed No). The automatic transmission 24 is controlled by an electronic control unit 90 described later. According to the driver's (i.e., the operator's) accelerator operation, vehicle speed V, etc., the control state of the engagement device involved in the shifting of the automatic transmission 24 among the engagement devices CB is switched, so that the formed shift stage is switched. That is, in the shift control of the automatic transmission 24, for example, shifting is executed by changing the engagement of the engagement devices involved in shifting, that is, so-called clutch-to-clutch shifting is executed, in which shifting is executed by releasing the release-side engagement device and engaging the engagement-side engagement device. The release-side engagement device is an engagement device that was in an engaged state before the shift of the automatic transmission 24 among the engagement devices involved in shifting, and is an engagement device that is controlled from the engaged state to the released state during the shift transient of the automatic transmission 24. The engagement-side engagement device is an engagement device that was in a released state before the shift of the automatic transmission 24 among the engagement devices involved in shifting, and is an engagement device that is controlled from the released state to the engaged state during the shift transient 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 the same value as the turbine rotation speed Nt, which is the output rotation speed of the torque converter 22. The AT input rotation speed Ni can be represented by 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.

[0021] The K0 clutch 20 is a hydraulic friction engagement device constituted by, for example, a multi-plate or single-plate clutch. The K0 clutch 20 has its control state, such as the engaged state, slip state, and released state, switched by changing the K0 torque Tk0, which is the torque capacity of the K0 clutch 20, by the regulated hydraulic pressure K0 hydraulic pressure PRk0 supplied from the hydraulic control circuit 56.

[0022] In the vehicle 10, in the engaged state of the K0 clutch 20, the engine 12 and the torque converter 22 are connected so that power can be transmitted therebetween. On the other hand, in the released state of the K0 clutch 20, the power transmission between the engine 12 and the torque converter 22 is interrupted. Since the 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 motor MG.

[0023] In the power transmission device 16, when the K0 clutch 20 is engaged, the power output from the engine 12 is transmitted from the engine connection shaft 34, through the K0 clutch 20, the motor connection shaft 36, the torque converter 22, the automatic transmission 24, the propeller shaft 28, the differential gear 30, and the drive shaft 32, etc., to the drive wheels 14 in sequence. Also, the power output from the motor MG is transmitted from the motor connection shaft 36, through the torque converter 22, the automatic transmission 24, the propeller shaft 28, the differential gear 30, and the drive shaft 32, etc., to the drive wheels 14 in sequence regardless of the control state of the K0 clutch 20.

[0024] The vehicle 10 includes a mechanical oil pump MOP58, an electric oil pump EOP60, a pump motor 62, etc. The MOP58 is connected to the pump impeller 22a and is rotationally driven by the power source SP to discharge the hydraulic oil OIL used in the power transmission device 16. The pump motor 62 is a dedicated motor for the EOP60 to rotationally drive the EOP60. The EOP60 is rotationally driven by the pump motor 62 to discharge the hydraulic oil OIL. The hydraulic oil OIL discharged by the MOP58 and the EOP60 is supplied to the hydraulic control circuit 56. The hydraulic control circuit 56 supplies the regulated CB hydraulic pressure PRcb, K0 hydraulic pressure PRk0, etc., based on the hydraulic oil OIL discharged by the MOP58 and / or the EOP60.

[0025] The vehicle 10 further includes an electronic control unit 90 that includes a control unit of the vehicle 10. The electronic control unit 90 is configured to include a so-called microcomputer including, for example, a CPU, a RAM, a ROM, an input / output interface, etc. The CPU performs signal processing according to a program stored in advance in the ROM while using the temporary storage function of the RAM, thereby executing various controls of the vehicle 10. The electronic control unit 90 is configured to include each computer for engine control, motor control, shift control, etc. as necessary.

[0026] Various signals (for example, the engine rotational speed Ne which is the rotational speed of the engine 12, the turbine rotational speed Nt which is the same value as the AT input rotational speed Ni, the AT output rotational speed No corresponding to the vehicle speed V, the MG rotational speed Nm which is the rotational speed of the electric motor MG, the accelerator opening θacc which is the driver's accelerator operation amount representing the magnitude of the driver's acceleration operation, the throttle valve opening θth which is the opening of the electronic throttle valve, the brake-on signal Bon which is a signal indicating that the brake pedal for operating the wheel brake is being operated by the driver, the battery temperature THbat, the battery charge / discharge current Ibat, the battery voltage Vbat of the battery 54, the operating oil temperature THoil which is the temperature of the operating oil OIL in the hydraulic control circuit 56, etc.) based on the detection values by various sensors (for example, the engine rotational speed sensor 70, the turbine rotational speed sensor 72, the output rotational speed sensor 74, the MG rotational speed sensor 76, the accelerator opening sensor 78, the throttle valve opening sensor 80, the brake switch 82, the battery sensor 84, the oil temperature sensor 86, etc.) provided in the vehicle 10 are respectively supplied to the electronic control unit 90.

[0027] From the electronic control device 90, various command signals (for example, engine control command signal Se for controlling the engine 12, MG control command signal Sm for controlling the motor MG, CB hydraulic pressure control command signal Scb for controlling the engagement device CB, K0 hydraulic pressure control command signal Sk0 for controlling the K0 clutch 20, LU hydraulic pressure control command signal Slu for controlling the LU clutch 40, EOP control command signal Seop for controlling the EOP 60, etc.) are output to each device (for example, engine control device 50, inverter 52, hydraulic pressure control circuit 56, pump motor 62, etc.) provided in the vehicle 10, respectively.

[0028] Regarding each hydraulic pressure control command signal S, the CB hydraulic pressure control command signal Scb will be exemplified and explained. The electronic control device 90 calculates an indicated pressure of the engagement device CB for supplying the CB hydraulic pressure PRcb regulated from the hydraulic pressure control circuit 56 as each command value of the CB hydraulic pressure PRcb corresponding to each of the engagement devices CB. The indicated pressure is the target hydraulic pressure indicated from the electronic control device 90 with respect to the hydraulic oil OIL supplied to the engagement device, and the actual hydraulic pressure (actual oil pressure) supplied to the engagement device changes according to this indicated pressure. The electronic control device 90 converts the indicated pressure of the engagement device CB into a CB indicated current value for driving the solenoid SLcb provided in the hydraulic pressure control circuit 56. The solenoid SLcb is each solenoid valve for the engagement device CB that outputs the CB hydraulic pressure PRcb corresponding to each of the engagement devices CB. The CB indicated current value is the indicated current for the drive circuit provided in the electronic control device 90 that drives the solenoid SLcb. The CB hydraulic pressure control command signal Scb is a drive current or drive voltage for the drive circuit to drive the solenoid SLcb based on the CB indicated current value. That is, the indicated pressure of the engagement device CB is converted into the CB hydraulic pressure control command signal Scb and output to the hydraulic pressure control circuit 56. In this embodiment, for the sake of convenience, the indicated pressure of the engagement device CB and the CB hydraulic pressure control command signal Scb are handled synonymously.

[0029] The electronic control device 90 includes a power source control means, that is, a power source control unit 92, a clutch control means, that is, a clutch control unit 94, and a shift control means, that is, a shift control unit 96, in order to realize various controls in the vehicle 10.

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

[0031] The power source control unit 92 calculates the drive request amount for the vehicle 10 by the driver, for example, by applying the accelerator opening θacc and the vehicle speed V to a drive request amount map. The drive request amount map is a relationship obtained experimentally or designedly in advance, that is, a predetermined relationship. The drive request amount is, for example, the required drive torque Trdem at the drive wheels 14. The required drive torque Trdem [Nm] is, in other words, the required drive power Prdem [W] at the vehicle speed V at that time. As the drive request amount, the required drive force Frdem [N] at the drive wheels 14, the required AT output torque at the transmission output shaft 26, and the like can also be used. In the calculation of the drive request amount, the AT output rotational speed No or the like may be used instead of the vehicle speed V. The power source control unit 92 outputs an engine control command signal Se for controlling the engine 12 and an MG control command signal Sm for controlling the motor MG so as to realize the required drive power Prdem in consideration of transmission losses, accessory loads, the gear ratio γat of the automatic transmission 24, and the like.

[0032] When the power source control unit 92 can cover the required drive torque Trdem only with the output of the electric motor MG, the drive mode for driving the vehicle 10 is set to the BEV drive mode. The BEV drive mode is a motor drive mode (=BEV driving) in which the vehicle can travel using only the electric motor MG as the power source SP in the released state of the K0 clutch 20. On the other hand, when the power source control unit 92 cannot cover the required drive torque Trdem without using at least the output of the engine 12, the drive mode is set to the engine drive mode, that is, the HEV drive mode. The HEV drive mode is a hybrid drive mode in which the vehicle can travel using at least the engine 12 as the power source SP in the engaged state of the K0 clutch 20, that is, engine driving or hybrid driving (=HEV driving). On the other hand, even when the power source control unit 92 can cover the required drive torque Trdem only with the output of the electric motor MG, if the battery 54 needs to be charged or the engine 12 needs to be warmed up, etc., the HEV drive mode is established.

[0033] When the engine 12 is in a stopped state, for example, the electric motor control unit 92b executes MG idling control, which is idling control of the electric motor MG. The MG idling control is, for example, a control in which the target MG rotation speed Nmtgt, which is the target value of the MG rotation speed Nm, is set to an idling rotation speed of the electric motor MG that is equal to or higher than a predetermined MG idling rotation speed Nmidlf, and the MG rotation speed Nm is controlled to the target MG rotation speed Nmtgt to make the electric motor MG in an idling state. The MG idling control is, for example, a control for outputting a predetermined creep torque Tcpf from the electric motor MG to cause a creep phenomenon in which the vehicle 10 slowly moves while remaining in the accelerator-off state when the brake is released during a temporary stop in a situation where the engine 12 is stopped and the accelerator is off. The predetermined creep torque Tcpf is a predetermined torque for driving the vehicle 10 in so-called creep running when the brake-off operation is performed in the vehicle stopped state and the accelerator remains off.

[0034] The power source control unit 92, particularly the engine control unit 92a, determines whether there is an engine start request for switching the control state of the engine 12 from the stopped state to the operating state. For example, when in the BEV drive mode, the engine control unit 92a determines whether there is an engine start request based on whether the required drive torque Trdem has increased beyond the range that can be covered only by the output of the motor MG, whether warm-up of the engine 12 etc. is necessary, whether charging of the battery 54 is necessary, and the like.

[0035] When the clutch control unit 94 determines that there is an engine start request by the power source control unit 92, it controls the K0 clutch 20 to execute the start control of the engine 12. For example, the clutch control unit 94 outputs a K0 hydraulic pressure command value Spk0 for controlling the released K0 clutch 20 to the engaged state so as to obtain a K0 torque Tk0 for transmitting the cranking torque Tcr to the engine 12 side. The cranking torque Tcr is the torque required for cranking the engine 12 to raise the engine rotational speed Ne.

[0036] When the power source control unit 92 determines that there is an engine start request, it controls the engine 12 and the motor MG to execute the start control of the engine 12. For example, the motor control unit 92b outputs an MG control command signal Sm for the motor MG to output the cranking torque Tcr to the inverter 52 in accordance with the switching of the K0 clutch 20 to the engaged state. Also, the engine control unit 92a outputs an engine control command signal Se for starting fuel supply, engine ignition, etc. to the engine control device 50 in conjunction with the cranking of the engine 12.

[0037] The shift control unit 96 performs shift determination of the automatic transmission 24 using, for example, a shift map that is a predetermined relationship, and outputs a CB hydraulic pressure control command signal Scb to the hydraulic control circuit 56 to execute shift control of the automatic transmission 24 as necessary. In the shift control of the automatic transmission 24, the shift control unit 96 performs a shift of the automatic transmission 24, for example, by switching the release side engaging device of the engaging device CB to the released state and switching the engaging side engaging device of the engaging device CB to the engaged state. The shift map is a predetermined relationship having shift lines for determining shifts of the automatic transmission 24 on a two-dimensional coordinate with, for example, the vehicle speed V and the required driving torque Trdem as variables. In the shift map, instead of the vehicle speed V, the AT output rotational speed No or the like may be used, or instead of the required driving torque Trdem, the required driving force Frdem, the accelerator opening θacc, the throttle valve opening θth, or the like may be used.

[0038] The progress stage, i.e., the phase, of the shift of the automatic transmission 24 during deceleration will be exemplified and described by taking downshifting as an example. When the shift control unit 96 determines a downshift of the automatic transmission 24, it causes the release-side engagement device to wait with a torque capacity capable of receiving the input torque Tin to the automatic transmission 24, and at the same time, outputs a CB hydraulic pressure control command signal Scb to the hydraulic control circuit 56 to start the downshift, setting the engagement-side engagement device to the ready stage, i.e., the ready phase, where the pack clearance is filled and the pack filling is completed. The state where the pack filling of the engagement device CB is completed is a state where the engagement device CB starts to have a torque capacity when the CB hydraulic pressure PRcb is increased from this state. The shift control unit 96 determines whether the ready phase is completed based on whether a predetermined ready time TMpk has elapsed since the start of the ready phase. The predetermined ready time TMpk is, for example, a predetermined time when the engagement-side engagement device reaches the state where the pack filling is completed. When the shift control unit 96 determines that the ready phase is completed, it outputs a CB hydraulic pressure control command signal Scb to the hydraulic control circuit 56 to gradually decrease the torque capacity of the release-side engagement device and gradually increase the torque capacity of the engagement-side engagement device, thereby starting the torque phase. In the case of a downshift, this torque phase is a phase in which the engagement-side engagement device takes out the torque capacity and the output torque of the automatic transmission 24 changes. During the transition of the downshift, when the turbine rotational speed Nt (= AT input rotational speed Ni) is increased toward the post-downshift synchronous rotational speed (= No × post-downshift γat), the phase of the downshift is shifted from the torque phase to the inertia phase. In the inertia phase, the shift control unit 96 outputs a CB hydraulic pressure control command signal Scb to the hydraulic control circuit 56 to change the turbine rotational speed Nt at a predetermined rising gradient in consideration of, for example, the shift time and the shift shock. The shift control unit 96 determines whether the downshift is completed based on whether the turbine rotational speed Nt matches the post-downshift synchronous rotational speed.When the shift control unit 96 determines that the downshift has ended, it sets the CB hydraulic pressure PRcb of the release-side engagement device to zero and outputs a CB hydraulic pressure control command signal Scb for setting the CB hydraulic pressure PRcb of the engagement-side engagement device to the CB hydraulic pressure PRcb for maintaining the engagement-side engagement device in a fully engaged state to the hydraulic control circuit 56, thereby completing a series of shift controls related to the downshift.

[0039] Here, during deceleration driving in a predetermined low vehicle speed range, a downshift between the low-side shift stages is determined. The downshift between the low-side shift stages is, for example, a 2→1 downshift that switches the shift stage of the automatic transmission 24 from the second gear stage to the first gear stage. The predetermined low vehicle speed range is, for example, a vehicle speed range close to a stop, and is a low vehicle speed range in which a shift line for determining a 2→1 downshift is predetermined in the shift map. In the automatic transmission 24, for example, the first gear stage is formed by both the first engagement device CB1 and the third engagement device CB3 of the engagement device CB being in an engaged state. Also, in the automatic transmission 24, for example, the second gear stage is formed by both the second engagement device CB2 and the third engagement device CB3 of the engagement device CB being in an engaged state. When the shift control unit 96 determines a 2→1 downshift of the automatic transmission 24 during deceleration driving in a predetermined low vehicle speed range, it switches the second engagement device CB2, which becomes the release-side engagement device, to the released state and switches the first engagement device CB1, which becomes the engagement-side engagement device, to the engaged state. Thereby, the automatic transmission 24 is switched from the second gear stage to the first gear stage.

[0040] Incidentally, it is considered that the re-acceleration frequency is high in the low vehicle speed range near a stop. When re-acceleration is required by an accelerator operation or the like, if it is during the transition of downshifting, the generation of the driving torque Tr may be delayed, and the acceleration responsiveness may decrease. Therefore, in preparation for re-acceleration during decelerating travel in the low vehicle speed range, it is conceivable to perform the 2→1 downshift of the automatic transmission 24 on the relatively high vehicle speed side. Then, there is a risk that shift shock is likely to occur. On the other hand, in order to suppress the occurrence of shift shock, it is conceivable to start the 2→1 downshift on the relatively low vehicle speed side or after stopping. Then, since the MOP 58 is rotationally driven in a state where the rotational speed of the motor coupling shaft 36 is low and the discharge flow rate of the working oil OIL from the MOP 58 decreases, there is a risk that the flow rate of the working oil OIL required for the engagement control of the first engagement device CB1 becomes insufficient, leading to a pressure drop in the hydraulic pressure of the first engagement device CB1 supplied from the hydraulic control circuit 56.

[0041] Therefore, when the shift control unit 96 determines a downshift of the automatic transmission 24, for example, a 2→1 downshift, during decelerating travel in a predetermined low vehicle speed range, the shift control unit 96 starts the 2→1 downshift so that the phase of the 2→1 downshift is a preparation phase. Further, even after the preparation phase is completed, the shift control unit 96 executes a shift delay control CTsd that maintains the phase of the 2→1 downshift in a state where the preparation phase is completed until the vehicle 10 stops. Next, when the vehicle 10 stops, the shift control unit 96 releases the shift delay control CTsd and outputs a CB hydraulic pressure control command signal Scb to the hydraulic control circuit 56 to gradually decrease the torque capacity of the release-side engagement device and gradually increase the torque capacity of the engagement-side engagement device. That is, the shift control unit 96 starts the torque phase, which is the next phase of the preparation phase, after the vehicle 10 stops and advances the 2→1 downshift, that is, performs the switching of the engagement of the engagement devices involved in the downshift.

[0042] When decelerating in a specified low vehicle speed range and the driver is not performing a braking operation (i.e., brake-off), the re-acceleration frequency is considered to be higher than when the driver is performing a braking operation (i.e., brake-on). Therefore, the shift control unit 96 executes, for example, shift delay control CTsd when the brake is on. When the driver performs a brake-off operation during the execution of the shift delay control CTsd, the shift control unit 96 releases the shift delay control CTsd and outputs a CB hydraulic pressure control command signal Scb to the hydraulic control circuit 56 to rapidly increase the hydraulic pressure of the release-side engaging device and rapidly decrease the hydraulic pressure of the engaging-side engaging device. As a result, the automatic transmission 24 is returned to the second gear stage and the second gear stage is maintained.

[0043] Figure 2 is a flowchart for explaining the main part of the control operation of the electronic control device 90, and is a flowchart for explaining the control operation for ensuring the CB hydraulic pressure PRcb while suppressing the occurrence of a shift shock during downshifting of the automatic transmission 24 during decelerating travel in a low vehicle speed range, and is executed repeatedly, for example. Figures 3 and 4 are diagrams each showing an example of a time chart when the control operation shown in the flowchart of Figure 2 is executed.

[0044] In FIG. 2, each step of the flowchart corresponds to the function of the shift control unit 96. In step S10 (hereinafter, steps are omitted), it is determined whether the brake is on. If the determination in S10 is negative, this routine is terminated. If the determination in S10 is positive, in S20, it is determined whether a 2→1 downshift has been determined. If the determination in S20 is negative, this routine is terminated. If the determination in S20 is positive, in S30, control is performed to set the phase of the 2→1 downshift to a state where the preparation phase is completed, that is, clutch preparation for the first gear is carried out. Next, in S40, it is determined whether the brake is on and the vehicle has stopped. If the determination in S40 is negative, in S50, it is determined whether a brake-off operation has been performed. If the determination in S50 is negative, the process returns to the aforementioned S40. If the determination in S40 is positive, in S60, a downshift to the first gear following the clutch preparation for the first gear is advanced. On the other hand, if the determination in S50 is positive, in S70, the clutch preparation for the first gear is released and the vehicle returns to the second gear, and the second gear is maintained.

[0045] FIG. 3 is a diagram showing an example when braking is applied and the vehicle comes to a stop after the 2→1 downshift is started during decelerated driving in a predetermined low vehicle speed range. In FIG. 3, the time point t1a indicates the time when the clutch preparation for the first gear is started at a predetermined low vehicle speed in the 2→1 downshift determined during decelerated driving. When the clutch preparation for the first gear is started, the second engaging device CB2, which becomes the releasing-side engaging device, is made to standby with a torque capacity capable of receiving the input torque Tin to the automatic transmission 24, and at the same time, respective command pressures for bringing the first engaging device CB1, which becomes the engaging-side engaging device, into a completely packed state with the pack clearance filled are output (refer to the time point t1a - the time point t2a). When stopping during the execution of the shift delay control CTsd that maintains the state where the clutch preparation for the first gear is completed (refer to the time point t2a), respective command pressures for gradually decreasing the torque capacity of the second engaging device CB2 and gradually increasing the torque capacity of the first engaging device CB1 are output, and the downshift to the first gear following the clutch preparation for the first gear is advanced (refer to after the time point t2a). Thus, when braking is applied and the vehicle comes to a stop, the 2→1 downshift is allowed to be executed until it is completed.

[0046] FIG. 4 is a diagram showing an example when a brake-off operation is performed before stopping after the 2→1 downshift is started during decelerated driving in a predetermined low vehicle speed range. In FIG. 4, the time point t1b indicates the time when the clutch preparation for the first gear is started at a predetermined low vehicle speed in the 2→1 downshift determined during decelerated driving. After the start of the clutch preparation for the first gear, when a brake-off operation is performed before stopping during the transitional period of the execution of the clutch preparation for the first gear (refer to the time point t1b - the time point t2b) (refer to the time point t2b), respective command pressures for quickly increasing the hydraulic pressure of the second engaging device CB2 and quickly decreasing the hydraulic pressure of the first engaging device CB1 are output, and the vehicle returns to the second gear (refer to after the time point t2b). Thus, when the brake is released during the shift delay control CTsd, the vehicle returns to the second gear and the second gear is maintained.

[0047] As described above, according to this embodiment, when a downshift of the automatic transmission 24 is determined during decelerating travel in a predetermined low vehicle speed range, the downshift is started such that the phase of the downshift is set to the preparation phase, and a shift delay control CTsd is executed to maintain the phase in a state where the preparation phase is completed until the vehicle stops. After the vehicle stops, the next phase of the preparation phase is started and the downshift is advanced. Therefore, the downshift during travel is until the packing is completed, and even if the start of the downshift is advanced, it is difficult for a shift shock to occur. The downshift after stopping starts from a state where the packing is completed, and a shortage of the flow rate of the operating oil OIL required for the engagement control of the engagement device CB is suppressed. Therefore, when the automatic transmission 24 downshifts during decelerating travel in the low vehicle speed range, it is possible to secure the CB hydraulic pressure PRcb while suppressing the occurrence of a shift shock.

[0048] Next, another embodiment of the present invention will be described. In the following description, parts common to the embodiments are denoted by the same reference numerals and the description thereof is omitted.

Embodiment

[0049] The vehicle 10 may be equipped with a power performance - focused driving mode MRpwr, which is a predetermined driving mode that emphasizes power performance rather than suppressing shift shocks, such as a towing mode, an AWD mode, a manual mode, etc. The towing mode is a predetermined driving mode suitable for towing a towed vehicle, and is selected, for example, by an operation of a towing - mode selection switch (not shown) by the driver. The AWD mode is a driving mode that sets the driving state of the vehicle 10 to an AWD (= all - wheel drive) state in which power from the power source SP is transmitted to the drive wheels 14 (for example, the rear wheels) and another drive wheel (for example, the front wheels) not shown that is different from the drive wheels 14, and is selected, for example, by an operation of an AWD - mode selection switch (not shown) by the driver. When the vehicle 10 is equipped with a transfer (not shown) in the power transmission path between, for example, the automatic transmission 24 and the differential gear 30, the power transmitted from the automatic transmission 24 is transmitted, for example, only to the drive wheels 14 or distributed to each of the front and rear wheels by that transfer. Further, when the transfer is equipped with a sub - transmission that can be switched between a high - gear stage, which is a high - speed gear stage, and a low - gear stage, which is a low - speed gear stage, and power is transmitted through this sub - transmission, as the AWD mode, there are a high - gear AWD mode in which the sub - transmission is set to the high - gear stage and an AWD state, and a low - gear AWD mode in which the sub - transmission is set to the low - gear stage and an AWD state, and these can be selected by an operation of the AWD - mode selection switch. The manual mode is a predetermined driving mode that enables manual shifting of the automatic transmission 24 by a shift operation by the driver, and is selected, for example, by a shift operation by the driver. The shift operation by the driver for selecting the manual mode is, for example, a shift operation in which the shift operation position of a shift lever (not shown) is set to the manual - shift operation position, or a shift operation by operating paddle switches (not shown) provided on the steering wheel. The vehicle 10 further has, as driving modes, for example, a sports mode and a normal mode, separate from the power performance - focused driving mode MRpwr. The sports mode is a predetermined driving mode for improving driving performance and is selected, for example, by an operation of a sports - mode selection switch (not shown) by the driver.The normal mode is a predetermined driving mode in which fuel efficiency performance and power performance are balanced, and is selected, for example, when the sports mode is not selected by the driver.

[0050] By the way, when the driving mode is the power performance priority mode MRpwr, if the shift delay control CTsd is executed during the 2→1 downshift and the shift to the first gear stage is delayed, there is a possibility that the desired drive torque Tr and rough road running performance in the first gear stage may be impaired.

[0051] Therefore, when the shift control unit 96 determines a downshift of the automatic transmission 24, for example, a 2→1 downshift, during decelerating travel in a predetermined low vehicle speed range, if the driving mode of the vehicle 10 is the power performance priority mode MRpwr, the shift delay control CTsd is prohibited, and the 2→1 downshift is advanced without executing the shift delay control CTsd. On the other hand, when the shift control unit 96 determines a downshift of the automatic transmission 24 during decelerating travel in a predetermined low vehicle speed range, if the driving mode of the vehicle 10 is a driving mode other than the power performance priority mode MRpwr, the shift delay control CTsd is permitted and the shift delay control CTsd is executed.

[0052] FIG. 5 is a chart summarizing whether or not to execute the shift delay control CTsd in the 2→1 downshift, that is, whether or not to delay the downshift to the first gear stage, for each driving mode. In FIG. 5, when the driving mode is, for example, the sports mode or the normal mode, the shift delay control CTsd is permitted. On the other hand, when the driving mode is, for example, the high gear AWD mode, the low gear AWD mode, the towing mode, the manual mode, or other power performance priority modes MRpwr, the shift delay control CTsd is prohibited.

[0053] In the power performance - focused mode MRpwr that requires rough - road driving performance and drive torque Tr in the first - speed gear range, it is considered that the operation of the engine 12 often continues, that is, the intermittent operation of the engine 12 is often prohibited. Therefore, it may be possible to interlock the operating state of the engine and whether to delay the downshift to the first - speed gear range. For example, when the intermittent operation of the engine 12 is prohibited, the shift - delay control CTsd is prohibited.

[0054] FIG. 6 is a flowchart for explaining the main part of the control operation of the electronic control unit 90, and is a flowchart for explaining the control operation for ensuring the CB hydraulic pressure PRcb while suppressing the occurrence of shift shock during the downshift of the automatic transmission 24 during decelerating driving in a low vehicle - speed range, and is executed repeatedly, for example. FIG. 6 is an embodiment different from the flowchart of FIG. 2. In FIG. 6, the differences from FIG. 2 will be mainly described.

[0055] In FIG. 6, following S30, at S35, it is determined whether the driving mode of the vehicle 10 is the power performance - focused mode MRpwr. If the determination at S35 is negative, S40 is executed. If the determination at S35 is positive, or if the determination at S40 is positive, S60 is executed.

[0056] As described above, according to this embodiment, when it is determined that the automatic transmission 24 is to downshift during decelerating driving in a predetermined low vehicle - speed range, if the driving mode of the vehicle 10 is the power performance - focused mode MRpwr, the downshift is allowed to proceed without executing the shift - delay control CTsd, so that it is easier to achieve the desired drive torque Tr and the reduction in rough - road driving performance is suppressed.

[0057] As described above, the embodiments of the present invention have been described in detail based on the drawings, but the present invention is also applicable in other aspects.

[0058] For example, in the aforementioned Second Embodiment, as the power performance - focused mode MRpwr, the high - gear AWD mode, the low - gear AWD mode, the towing mode, and the manual mode were exemplified, but it is not limited to this mode. For example, the power performance - focused mode MRpwr may be an off - road mode, a circuit mode, etc. The off - road mode is a predefined driving mode for improving the traversability on off - road areas and is selected, for example, by the driver's operation of an off - road mode selection switch (not shown). The circuit mode is a predefined driving mode for improving the driving performance on closed courses such as circuits and is selected, for example, by the driver's operation of a circuit mode selection switch (not shown). Or, the sports mode may be included in the power performance - focused mode MRpwr. In short, the power performance - focused mode MRpwr may be any driving mode that requires poor - road traversability or driving torque Tr in the first - speed gear stage.

[0059] Also, in the aforementioned embodiments, as the vehicle to which the present invention is applied, the vehicle 10 including the engine 12, the motor MG, and the automatic transmission 24 was exemplified, but it is not limited to this mode. For example, the present invention can be applied to an engine vehicle that uses at least the engine as a power source, an electric vehicle that does not include an engine and uses only a motor as a power source, a hybrid vehicle that includes an automatic transmission in series after a known electric continuously variable transmission, etc. Also, the automatic transmission 24 may be a known DCT (Dual Clutch Transmission), etc. In the case of a DCT, the plurality of engaging devices are engaging devices respectively connected to each of the two input shafts, one of the plurality of engaging devices corresponds to the disengaging - side engaging device, and the other of the plurality of engaging devices corresponds to the engaging - side engaging device. In short, the present invention can be applied to a vehicle equipped with an automatic transmission that constitutes a part of the power transmission path between the power source and the drive wheels and forms any one of the plurality of gear stages by the engagement of any one of the plurality of hydraulic engaging devices.

[0060] In addition, 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 mode. For example, as the fluid transmission device, instead of the torque converter 22, other fluid transmission devices such as a fluid coupling without a torque amplification function may be used. Or, the fluid transmission device does not necessarily have to be provided, and for example, it may be replaced with a clutch for starting.

[0061] Note that the above is merely one embodiment, and the present invention can be implemented in various modified and improved forms based on the knowledge of those skilled in the art.

Explanation of Reference Numerals

[0062] 10: Vehicle 14: Driving wheel 24: Automatic transmission 90: Electronic control device (control device) 96: Shift control unit CB: Engaging device CB1: First engaging device (engaging side engaging device) CB2: Second engaging device (releasing side engaging device) SP: Power source

Claims

【Claim 1】 A control device for a vehicle, comprising: a power source; and an automatic transmission that forms part of a power transmission path between the power source and drive wheels and forms any one of a plurality of gear stages by engagement of any one of a plurality of hydraulic engagement devices. The control device includes a shift control unit that shifts the automatic transmission by switching a release-side engagement device among the engagement devices to a released state and switching an engagement-side engagement device among the engagement devices to an engaged state. When determining a downshift of the automatic transmission during decelerating travel in a predetermined low vehicle speed range, the shift control unit starts the downshift so that the progress stage of the downshift is a preparation stage in which the release-side engagement device is made to wait with a torque capacity capable of receiving the input torque to the automatic transmission and the engagement-side engagement device is brought into a packed state with the pack clearance filled. The shift delay control is executed to maintain the progress stage in a state where the preparation stage is completed until the vehicle stops, and the next progress stage of the preparation stage is started after the vehicle stops to advance the downshift. When determining the downshift during the decelerating travel, if the driving mode of the vehicle is a predetermined driving mode that emphasizes power performance, the shift control unit advances the downshift without executing the shift delay control. A control device for a vehicle, characterized by this.

Images