JP7697349B2 - Vehicle control device - Google Patents

Description

The present invention relates to a control device for a vehicle equipped with an automatic transmission in which gear stages are formed by engaging an engagement device.

Vehicle control devices that include a power source and an automatic transmission that constitutes part of the power transmission path between the power source and the drive wheels and that forms one of a number of gear stages by engaging one of a number of hydraulic engagement devices are well known. For example, there is a gear shift control device for a vehicle automatic transmission described in Patent Document 1. Patent Document 1 discloses that the automatic transmission is shifted by controlling the operating state of the hydraulic engagement device so that a gear stage determined based on the vehicle speed and the accelerator opening is obtained.

Japanese Patent Application Publication No. 5-44830

Meanwhile, when decelerating at low vehicle speeds, it is possible to hasten the downshift of the automatic transmission in preparation for re-accelerating at low vehicle speeds, i.e., to shift to a lower vehicle speed at a relatively high vehicle speed. This could make shift shock more likely to occur. On the other hand, in order to suppress the occurrence of shift shock, it is possible to delay the start of the downshift, i.e., to start the downshift at a relatively low vehicle speed or after the vehicle has come to a stop. This could reduce the flow rate of hydraulic oil discharged from the oil pump, which is driven by the power source, and could result in a shortage of the flow rate of hydraulic oil required to control the engagement of the engagement device, leading to a drop in the hydraulic pressure of the engagement device.

The present invention was made against the background of the above circumstances, and its purpose is to provide a vehicle control device that can ensure oil pressure in the engagement device while suppressing the occurrence of shift shock when downshifting an automatic transmission while decelerating at low vehicle speeds.

The gist of a first aspect of the present invention is a control device for a vehicle including: (a) a power source; and an automatic transmission that constitutes a part of a power transmission path between the power source and drive wheels, and that forms one of a plurality of gear stages by engaging one of a plurality of hydraulic engagement devices, (b) a shift control unit that performs gear shifting of the automatic transmission by switching a release-side engagement device of the engagement devices to a release state and switching an engagement-side engagement device of the engagement devices to an engagement state, (c) when the shift control unit determines a downshift of the automatic transmission during deceleration traveling in a predetermined low vehicle speed range, the shift control unit determines a progression stage of the downshift by inputting the release-side engagement device to the automatic transmission. The downshift is initiated so that the engaging side engagement device waits with a torque capacity capable of handling the torque and is in a preparatory stage to bring the engaging side engagement device into a packing completion state in which pack clearance has been reduced, and a shift delay control is executed to maintain the progression stage in a state in which the preparatory stage has been completed until the vehicle stops, and after the vehicle stops , the next progression stage after the preparatory stage is started to progress the downshift; (d) when the shift control unit determines to downshift during deceleration traveling, if the driving mode of the vehicle is a predetermined driving mode that emphasizes power performance, the downshift is progressed without executing the shift delay control .

According to the first invention, when a downshift of the automatic transmission is determined during deceleration driving in a predetermined low vehicle speed range, the downshift is started so that the downshift progress stage is a preparation stage in which the disengagement side engagement device waits with a torque capacity capable of handling the input torque to the automatic transmission and the engagement side engagement device is in a packing complete state. A shift delay control is executed to maintain the progress stage in a preparation stage completed state until the vehicle stops, and after the vehicle stops, the next progress stage of the preparation stage is started and the downshift progresses. Therefore, the downshift during driving is performed until packing is completed, and even if the start of the downshift is accelerated, the occurrence of shift shock is suppressed, and the downshift after stopping starts from a packing complete state, suppressing a shortage of the flow rate of hydraulic oil required for engagement control of the engagement device. Therefore, when the automatic transmission is downshifted during deceleration driving in a low vehicle speed range, the occurrence of shift shock is suppressed while the hydraulic pressure of the engagement device can be secured.

Furthermore, according to the first aspect of the invention, when a downshift is determined during deceleration driving, if the vehicle's driving mode is a predetermined driving mode that emphasizes power performance, the downshift is allowed to proceed without executing gear shift delay control, making it easier to achieve the desired drive torque and suppressing a decrease in rough road performance.

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 a control system for various controls in the vehicle. This is a flowchart explaining the main control operations of the electronic control device, and is a flowchart explaining the control operations for ensuring oil pressure in the engagement device while suppressing the occurrence of shift shock when downshifting an automatic transmission during deceleration driving in a low vehicle speed range. FIG. 3 is a diagram showing an example of a time chart when the control operation shown in the flowchart of FIG. 2 is executed, in the case where the brake is on and the vehicle is stopped. FIG. 3 is a diagram showing an example of a time chart when the control operation shown in the flowchart of FIG. 2 is executed, in which the brake is released during a gear shift. 11 is a table summarizing whether or not a downshift to first gear is delayed for each driving mode. This is a flowchart explaining the main control operations of the electronic control device, and explains the control operations for ensuring oil pressure in the engagement device while suppressing the occurrence of shift shock when downshifting the automatic transmission during deceleration driving in a low vehicle speed range, and is a different embodiment from the flowchart of Figure 2.

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 of the automatic transmission is the gear on the high vehicle speed side where the gear ratio is small. The low-side gear of the automatic transmission is the gear on the low vehicle speed side where the gear ratio is large. For example, the lowest-side gear is the gear on the lowest vehicle speed side where the vehicle speed is the lowest, and is the gear with the maximum gear ratio where the gear ratio is the largest.

The following describes in detail an embodiment of the present invention with reference to the drawings.

Figure 1 is a diagram illustrating the general configuration of a vehicle 10 to which the present invention is applied, as well as a diagram illustrating the main parts of the control functions and control system for various controls in the vehicle 10. In Figure 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 the power transmission path between the engine 12 and the drive wheels 14.

The engine 12 is a known internal combustion engine such as a gasoline engine or a diesel engine. The engine 12 has an engine control device 50, which includes a throttle actuator, a fuel injection device, an ignition device, and the like, provided on the vehicle 10, controlled by an electronic control device 90 (described later), thereby controlling the engine torque Te, which is the output torque of the engine 12.

The electric motor MG is a rotating electric machine that functions as a motor to generate mechanical power from electric power and as a generator to generate 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 an electric storage device that supplies electric power to the electric motor MG. The electric motor MG controls the MG torque Tm, which is the output torque of the electric motor MG, by controlling the inverter 52 by an electronic control device 90 described later. For example, when the rotation direction of the electric motor MG is the same as the rotation direction when the engine 12 is operating, the MG torque Tm is a power torque when it is a positive torque on the acceleration side, and a regenerative torque when it is a negative torque on the deceleration side. When there is no particular distinction between the electric power and electric energy, the same is also true. When there is no particular distinction between the power and driving force, torque, and force, the same is also true.

The power transmission device 16 includes a K0 clutch 20, a torque converter 22, an automatic transmission 24, and the like, in 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 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. 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, and an electric motor connecting shaft 36 that connects the K0 clutch 20 and the torque converter 22.

The electric motor MG is connected to the electric motor connecting shaft 36 inside the case 18 so as to be capable of transmitting power. In other words, the electric motor MG is connected to the power transmission path between the engine 12 and the drive wheels 14, and in particular to the power transmission path between the K0 clutch 20 and the torque converter 22 so as to be capable of transmitting power. In other words, the electric motor MG is connected to the torque converter 22 and the automatic transmission 24 so as to be capable of transmitting power without passing through the K0 clutch 20.

The torque converter 22 includes a pump wheel 22a connected to the motor connecting shaft 36, and a turbine wheel 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-type power transmission device that transmits power from the power source SP from the motor connecting shaft 36 to the transmission input shaft 38 via a 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, that is, that connects the motor connecting shaft 36 and the transmission input shaft 38. The LU clutch 40 is a known lock-up clutch.

The automatic transmission 24 is a known planetary gear type 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. The engagement devices CB have their respective torque capacities, or CB torques Tcb, changed by the 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, a released state, and the like.

The automatic transmission 24 is a stepped transmission in which one of a plurality of gear stages (also called gear stages) with different gear ratios (also called 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 the formed gear stages by switching the control state of the engagement devices CB involved in the shifting of the automatic transmission 24 in response to the driver's (=operator's) accelerator operation and the vehicle speed V, etc., by the electronic control device 90 described later. In other words, in the shift control of the automatic transmission 24, for example, the shift is performed by switching the engagement of the engagement devices involved in the shift, that is, the shift is performed by disengaging the release side engagement device and engaging the engagement side engagement device, so-called clutch-to-clutch shifting is performed. The disengagement side engagement device is an engagement device that is in an engaged state before the automatic transmission 24 is shifted among the engagement devices involved in the shift, and is an engagement device that is controlled from an engaged state to a released state during the shift transition of the automatic transmission 24. The engagement side engagement device is an engagement device that is in a disengaged state before the automatic transmission 24 is shifted among the engagement devices involved in the shift, and is an engagement device that is controlled from a released state to an engaged state during the 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 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 expressed as 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.

The K0 clutch 20 is a hydraulic friction engagement device that is composed of, for example, 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 torque capacity of the K0 clutch 20, K0 torque Tk0, using the regulated hydraulic pressure, K0 hydraulic pressure PRk0, supplied from the hydraulic control circuit 56.

In the vehicle 10, when the K0 clutch 20 is engaged, the engine 12 and the torque converter 22 are connected so that power can be transmitted. On the other hand, when the K0 clutch 20 is disengaged, power transmission between the engine 12 and the torque converter 22 is interrupted. Since 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.

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 addition, 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., regardless of the control state of the K0 clutch 20.

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, and the like. The MOP 58 is connected to the pump impeller 22a, and is rotated and driven by the 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 rotating and driving the EOP 60. The EOP 60 is rotated and driven by the pump motor 62 to discharge hydraulic oil OIL. The hydraulic oil OIL discharged by the MOP 58 and EOP 60 is supplied to the hydraulic control circuit 56. The hydraulic control circuit 56 supplies the CB hydraulic pressure PRcb, the K0 hydraulic pressure PRk0, and the like, which are adjusted based on the hydraulic oil OIL discharged by the MOP 58 and/or the EOP 60.

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 according to a program previously stored in the ROM while utilizing the temporary storage function of the RAM. The electronic control device 90 includes computers for engine control, electric motor control, gear change control, etc. as necessary.

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

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

Each hydraulic control command signal S will be described by taking the CB hydraulic control command signal Scb as an example. The electronic control device 90 calculates the command pressure of the engagement device CB for supplying the CB hydraulic pressure PRcb adjusted from the hydraulic control circuit 56 as each command value of the CB hydraulic pressure PRcb corresponding to each engagement device CB. The command pressure is a target hydraulic pressure commanded by the electronic control device 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 according to this command pressure. The electronic control device 90 converts the command pressure of the engagement device CB into a CB command current value for driving the solenoid SLcb provided in the hydraulic 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 engagement device CB. The CB command current value is a command current for a drive circuit provided in the electronic control device 90 that drives the solenoid SLcb. The CB hydraulic control command signal Scb is a drive current or drive voltage for the drive circuit to drive the solenoid SLcb based on the CB command current value. In other words, the command pressure of the engagement device CB is converted to the CB hydraulic control command signal Scb and output to the hydraulic control circuit 56. In this embodiment, for convenience, the command pressure of the engagement device CB and the CB hydraulic control command signal Scb are treated as the same thing.

The electronic control device 90 includes a power source control means, i.e., a power source control unit 92, a clutch control means, i.e., a clutch control unit 94, and a gear shift control means, i.e., a gear shift control unit 96, in order to realize various controls in the vehicle 10.

The power source control unit 92 includes a function as an engine control means, i.e., an engine control unit 92a, that controls the operation of the engine 12, and a function as an electric motor control means, i.e., an 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 by the engine 12 and the electric motor MG through these control functions.

The power source control unit 92 calculates the amount of driving required 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-wise determined and stored in advance, i.e., a predetermined relationship. The driving demand is, for example, the required driving torque Trdem at the driving wheels 14. In other words, the required driving torque Trdem [Nm] is the required driving power Prdem [W] at the vehicle speed V at that time. The driving demand can also be the required driving force Frdem [N] at the driving wheels 14, the required AT output torque at the transmission output shaft 26, etc. In calculating the driving demand, the AT output rotation speed No, etc. may be used instead of the vehicle speed V. The power source control unit 92 outputs an engine control command signal Se that controls the engine 12 and an MG control command signal Sm that controls the electric motor MG to realize the required driving power Prdem, taking into account the transmission loss, the auxiliary load, the gear ratio γat of the automatic transmission 24, etc.

When the required drive torque Trdem can be satisfied only by the output of the electric motor MG, the power source control unit 92 sets the drive mode for driving the vehicle 10 to the BEV drive mode. The BEV drive mode is a motor drive mode that allows motor driving (=BEV driving) using only the electric motor MG as the power source SP when the K0 clutch 20 is in the released state. 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 sets the drive mode to the engine drive mode, i.e., the HEV drive mode. The HEV drive mode is a hybrid drive mode that allows engine driving (=HEV driving) using at least the engine 12 as the power source SP when the K0 clutch 20 is in the engaged state. On the other hand, even if the required drive torque Trdem can be satisfied only by the output of the electric motor MG, the power source control unit 92 establishes the HEV drive mode when it is necessary to charge the battery 54 or when it is necessary to warm up the engine 12, etc.

The motor control unit 92b executes MG idling control, which is idling control of the motor MG, for example, when the engine 12 is stopped. The MG idling control is a control in which, for example, a target MG rotation speed Nmtgt, which is a target value of the MG rotation speed Nm, is set to an idling rotation speed of the 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 put the motor MG in an idling state. The MG idling control is a control in which, for example, when the engine 12 is stopped and the accelerator is off, the brake is off during a temporary stop, and a predetermined creep torque Tcpf is output from the motor MG to cause a creep phenomenon in which the vehicle 10 moves slowly with the accelerator off. The specified creep torque Tcpf is a predetermined torque that is determined in advance to allow the vehicle 10 to run in a so-called creep mode, for example, when the vehicle is stopped and the brake is released and the accelerator remains released.

The power source control unit 92, particularly the engine control unit 92a, determines whether there is an engine start request 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 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 by the output of the electric motor MG alone, whether the engine 12, etc. needs to be warmed up, or whether the battery 54 needs to be charged.

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 command value Spk0 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 side. The cranking torque Tcr is the torque required for cranking the engine 12 to increase the engine rotation speed Ne.

When the power source control unit 92 determines that there is an engine start request, it controls the engine 12 and the electric motor MG to execute start control of the engine 12. For example, the electric motor control unit 92b outputs an MG control command signal Sm to the inverter 52 in response to switching of the K0 clutch 20 to the engaged state, so that the electric motor MG outputs a cranking torque Tcr. In addition, the engine control unit 92a outputs an engine control command signal Se to the engine control device 50 in conjunction with the cranking of the engine 12, so as to start fuel supply, engine ignition, and the like.

The shift control unit 96 uses, for example, a shift map, which is a predetermined relationship, to determine whether or not to shift the automatic transmission 24, and outputs a CB hydraulic 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 shifting of the automatic transmission 24, for example, by switching the disengagement side engagement device of the engagement device CB to a disengaged state and switching the engagement side engagement device of the engagement device CB to an engaged state. The shift map is a predetermined relationship having a shift line for determining whether or not to shift the automatic transmission 24, for example, on a two-dimensional coordinate system with the vehicle speed V and the required driving torque Trdem as variables. In the shift map, the AT output rotation speed No may be used instead of the vehicle speed V, and the required driving force Frdem, the accelerator opening θacc, the throttle valve opening θth, etc. may be used instead of the required driving torque Trdem.

The shift progress stage, i.e., phase, of the automatic transmission 24 will be described by taking a downshift during deceleration as an example. When the shift control unit 96 determines that the automatic transmission 24 is to be downshifted, the shift control unit 96 outputs a CB hydraulic control command signal Scb to the hydraulic control circuit 56 to set the downshift phase to a preparation stage, i.e., a preparation phase, in which the disengagement side engagement device waits with a torque capacity capable of handling the input torque Tin to the automatic transmission 24 and the engagement side engagement device is in a packing completion state in which the pack clearance is reduced, thereby starting the downshift. The packing completion state of the engagement device CB is a state in which the engagement device CB begins to have a torque capacity if the CB hydraulic pressure PRcb is increased from the packing completion state. The shift control unit 96 determines whether the preparation phase is completed based on whether a predetermined preparation time TMpk has elapsed from the start of the preparation phase. The predetermined preparation time TMpk is, for example, a predetermined time at which the engagement side engagement device is in a packing completion state. When the shift control unit 96 determines that the preparation phase is completed, it outputs a CB hydraulic control command signal Scb to the hydraulic control circuit 56 to gradually decrease the torque capacity of the disengagement 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 brings out the 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) is increased toward the post-downshift synchronous rotation speed (=No x γat after downshift) during the downshift transition, the downshift phase is transitioned from the torque phase to the inertia phase. In the inertia phase, the shift control unit 96 outputs a CB hydraulic control command signal Scb 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 the shift shock. The shift control unit 96 determines whether the downshift is completed based on whether the turbine rotation speed Nt coincides with the post-downshift synchronous rotation speed. When the shift control unit 96 determines that the downshift is complete, it outputs a CB hydraulic 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 engagement device to the CB hydraulic pressure PRcb that maintains the engaging engagement device in a fully engaged state, completing the series of shift control operations related to the downshift.

Here, when the vehicle speed V is decelerating in a predetermined low vehicle speed range, a downshift between low-side gear stages is determined. The downshift between low-side gear stages is, for example, a 2→1 downshift in which the gear stage of the automatic transmission 24 is switched 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 engagement device CB1 and the third engagement device CB3 of the engagement devices CB are both engaged to form the first gear stage. Also, in the automatic transmission 24, for example, the second engagement device CB2 and the third engagement device CB3 of the engagement devices CB are both engaged to form the second gear stage. When the shift control unit 96 determines that the automatic transmission 24 is to downshift from 2 to 1 while decelerating in a predetermined low vehicle speed range, it switches the second engagement device CB2, which is the disengagement side engagement device, to a disengaged state and switches the first engagement device CB1, which is the engagement side engagement device, to an engaged state. This causes the automatic transmission 24 to shift from second gear to first gear.

However, re-acceleration is considered to be frequent in the low vehicle speed range near a stop. When re-acceleration is requested by accelerator operation, etc., if the vehicle is in the transition of downshifting, the generation of the drive torque Tr is delayed, and acceleration responsiveness may decrease. For this reason, it is considered that the automatic transmission 24 performs a 2 → 1 downshift at a relatively high vehicle speed in preparation for re-acceleration during deceleration driving at a low vehicle speed range. This may make shift shock more likely to occur. On the other hand, in order to suppress the occurrence of shift shock, it is considered that the 2 → 1 downshift is started at a relatively low vehicle speed or after the vehicle is stopped. In this case, the MOP 58 is rotated and driven when the rotation speed of the electric motor connecting shaft 36 is low, and the discharge flow rate of the hydraulic oil OIL from the MOP 58 decreases, so that the flow rate of the hydraulic oil OIL required for engagement control of the first engagement device CB1 is insufficient, which may lead to a drop in the hydraulic pressure of the first engagement device CB1 supplied from the hydraulic control circuit 56.

Therefore, when the shift control unit 96 judges that the automatic transmission 24 is to be downshifted, for example, 2→1 downshifted, during deceleration driving in a predetermined low vehicle speed range, it starts the 2→1 downshift so that the 2→1 downshift phase becomes the preparation phase. Furthermore, even if the preparation phase is completed, the shift control unit 96 executes the shift delay control CTsd to maintain the 2→1 downshift phase in a state in which 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 control command signal Scb to the hydraulic control circuit 56 to gradually decrease the torque capacity of the disengagement side engagement device and gradually increase the torque capacity of the engagement side engagement device. In other words, the shift control unit 96 starts the torque phase, which is the next phase of the preparation phase, after the vehicle 10 stops, and proceeds with the 2→1 downshift, that is, it switches the engagement devices involved in the downshift.

During deceleration in a predetermined low vehicle speed range, when the driver is not braking, i.e., the brake is off, it is considered that the frequency of re-acceleration is higher than when the driver is braking, i.e., the brake is on. For this reason, the shift control unit 96 executes the shift delay control CTsd, for example, when the brake is on. If the driver performs a brake-off operation while the shift delay control CTsd is being executed, the shift control unit 96 releases the shift delay control CTsd and outputs a CB hydraulic control command signal Scb to the hydraulic control circuit 56 to quickly increase the hydraulic pressure of the disengagement side engagement device and quickly decrease the hydraulic pressure of the engagement side engagement device. This causes the automatic transmission 24 to return to second gear and maintain second gear.

Figure 2 is a flowchart that explains the main control operations of the electronic control unit 90, and is a flowchart that explains the control operations for ensuring the CB hydraulic pressure PRcb while suppressing the occurrence of shift shock when the automatic transmission 24 is downshifted during deceleration driving in the low vehicle speed range, and is executed repeatedly, for example. Figures 3 and 4 each show an example of a time chart when the control operations shown in the flowchart of Figure 2 are executed.

2, each step of the flow chart corresponds to a function of the shift control unit 96. In step (hereinafter, step is omitted) S10, 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, it is determined in S20 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 make the 2→1 downshift phase a state in which the preparation phase is completed, that is, clutch preparation for 1st gear engagement is performed. Next, in S40, it is determined whether the brake is on and the vehicle is stopped. If the determination in S40 is negative, it is determined in S50 whether a brake-off operation has been performed. If the determination in S50 is negative, the process returns to S40. If the determination in S40 is positive, in S60, a downshift to the 1st gear stage is performed following clutch preparation for 1st gear engagement. On the other hand, if the determination in S50 is positive, in S70 the clutch preparation for first gear engagement is released and the gear is returned to second gear, and second gear is maintained.

Figure 3 shows an example of a case where a 2→1 downshift is initiated during deceleration driving at a predetermined low vehicle speed, followed by brake application and a stop. In Figure 3, time t1a indicates the time when clutch preparation for 1st gear engagement is initiated at a predetermined low vehicle speed in a 2→1 downshift determined during deceleration driving. When clutch preparation for 1st gear engagement is initiated, each command pressure is output to put the second engagement device CB2, which is the release side engagement device, into standby with a torque capacity capable of handling the input torque Tin to the automatic transmission 24, and to put the first engagement device CB1, which is the engagement side engagement device, into a packing completion state in which the pack clearance has been reduced (see time t1a-t2a). When the vehicle is stopped while the shift delay control CTsd is being executed to maintain the state in which the clutch preparation for first gear engagement is complete (see time t2a), command pressures are output to gradually decrease the torque capacity of the second engagement device CB2 and gradually increase the torque capacity of the first engagement device CB1, and the downshift to first gear following the clutch preparation for first gear engagement is progressed (see time t2a and onward). In this way, when the brake is on and the vehicle is stopped, the 2→1 downshift is executed until it is completed.

Figure 4 shows an example of a case where a 2 → 1 downshift is started during deceleration driving at a predetermined low vehicle speed, and then the brake is released before the vehicle is stopped. In Figure 4, time t1b indicates the time when the clutch preparation for 1st gear engagement is started at a predetermined low vehicle speed in a 2 → 1 downshift determined during deceleration driving. After the start of clutch preparation for 1st gear engagement, during the execution transition of clutch preparation for 1st gear engagement (see time t1b-time t2b), if the brake is released before the vehicle is stopped (see time t2b), each command pressure is output to quickly increase the hydraulic pressure of the second engagement device CB2 and quickly decrease the hydraulic pressure of the first engagement device CB1, and the gear is returned to the second gear (see time t2b and after). In this way, when the brake is released during the shift delay control CTsd, the gear is returned to the second gear and the second gear is maintained.

As described above, according to this embodiment, when a downshift of the automatic transmission 24 is determined during deceleration driving in a predetermined low vehicle speed range, the downshift is started so that the downshift phase is the preparation phase, and the shift delay control CTsd is executed to maintain the phase in a state where the preparation phase is completed until the vehicle is stopped, and the next phase of the preparation phase is started after the vehicle is stopped and the downshift proceeds. Therefore, the downshift while driving is only performed until packing is completed, and even if the start of the downshift is accelerated, the occurrence of a shift shock is reduced, and the downshift after the vehicle is stopped is started from a state where packing is completed, suppressing a shortage of the flow rate of the hydraulic oil OIL required for engagement control of the engagement device CB. Therefore, when the automatic transmission 24 is downshifted while decelerating driving in a low vehicle speed range, the occurrence of a shift shock is suppressed while the CB hydraulic pressure PRcb can be secured.

Next, other embodiments of the present invention will be described. In the following description, parts common to the embodiments will be given the same reference numerals and will not be described.

The vehicle 10 may be provided with a power performance-oriented mode MRpwr, which is a predetermined driving mode that emphasizes power performance over suppression of shift shock, such as a towing mode, an AWD mode, and a manual mode. The towing mode is a predetermined driving mode suitable for driving while towing a towed vehicle, and is selected, for example, by the driver operating a towing mode selection switch (not shown). The AWD mode is a driving mode in which the driving state of the vehicle 10 is an AWD (= all-wheel drive) state in which power from the power source SP is transmitted to the driving wheels 14 (e.g., rear wheels) and to driving wheels (e.g., front wheels) other than the driving wheels 14 (not shown), and is selected, for example, by the driver operating an AWD mode selection switch (not shown). If the vehicle 10 is provided with a transfer (not shown) in the power transmission path between the automatic transmission 24 and the differential gear 30, for example, the transfer transmits the power transmitted from the automatic transmission 24 only to the driving wheels 14, or distributes it to each of the front and rear wheels. Furthermore, when the transfer includes an auxiliary 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 the auxiliary transmission, the AWD mode can be selected by operating the AWD mode selection switch between a high gear AWD mode in which the auxiliary transmission is in an AWD state in a high gear stage and a low gear AWD mode in which the auxiliary transmission is in an AWD state in a low gear stage. The manual mode is a predetermined driving mode that allows 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 to select the manual mode is, for example, a shift operation in which a shift operation position of a shift lever (not shown) is set to a manual shift operation position, or a shift operation by operating a paddle switch (not shown) provided on a steering wheel. The vehicle 10 further includes, for example, a sports mode and a normal mode as driving modes in addition to the power performance-oriented mode MRpwr. The sports mode is a predetermined driving mode for improving driving performance, and is selected, for example, by the driver operating a sports mode selection switch (not shown). The normal mode is a predetermined driving mode that balances fuel efficiency and power performance, and is selected, for example, when the sports mode is not selected by the driver.

However, when the driving mode is the power performance-oriented mode MRpwr, if the shift delay control CTsd is executed during a 2→1 downshift and the shift to first gear is delayed, the desired drive torque Tr and rough road performance in first gear may be impaired.

Therefore, when the gear shift control unit 96 determines a downshift of the automatic transmission 24, for example a 2→1 downshift, during deceleration driving in a predetermined low vehicle speed range, if the driving mode of the vehicle 10 is the power performance focused mode MRpwr, it prohibits the gear shift delay control CTsd and allows the 2→1 downshift to proceed without executing the gear shift delay control CTsd. On the other hand, when the gear shift control unit 96 determines a downshift of the automatic transmission 24 during deceleration driving in a predetermined low vehicle speed range, if the driving mode of the vehicle 10 is a driving mode other than the power performance focused mode MRpwr, it permits the gear shift delay control CTsd and executes the gear shift delay control CTsd.

Figure 5 is a chart summarizing whether or not to execute the shift delay control CTsd for 2→1 downshifts for each driving mode, i.e., whether or not to delay the downshift to 1st gear. In Figure 5, when the driving mode is, for example, sports mode or normal mode, the shift delay control CTsd is permitted. On the other hand, when the driving mode is, for example, a power performance-oriented mode MRpwr such as high gear AWD mode, low gear AWD mode, towing mode, or manual mode, the shift delay control CTsd is prohibited.

In the power performance focused mode MRpwr, which requires rough road performance and drive torque Tr in first gear, it is considered that at the same time, the engine 12 is often kept in operation, i.e., intermittent operation of the engine 12 is often prohibited. Therefore, the engine operating state may be linked to whether or not to delay the downshift to first gear. For example, when intermittent operation of the engine 12 is prohibited, the shift delay control CTsd is prohibited.

Figure 6 is a flowchart explaining the main control operations of the electronic control unit 90, and is a flowchart explaining the control operations for ensuring the CB hydraulic pressure PRcb while suppressing the occurrence of shift shock when the automatic transmission 24 is downshifted during deceleration driving in the low vehicle speed range, and is executed repeatedly, for example. Figure 6 is an embodiment different from the flowchart in Figure 2. In Figure 6, the differences from Figure 2 will be mainly explained.

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

As described above, according to this embodiment, when a downshift of the automatic transmission 24 is determined while the vehicle 10 is decelerating at a predetermined low vehicle speed range, if the vehicle's driving mode is the power performance-oriented mode MRpwr, the downshift is performed without executing the shift delay control CTsd, which makes it easier to achieve the desired drive torque Tr and suppresses a decrease in rough road performance.

The above describes in detail an embodiment of the present invention based on the drawings, but the present invention can also be applied in other aspects.

For example, in the above-mentioned second embodiment, the high gear AWD mode, low gear AWD mode, towing mode, and manual mode are exemplified as the power performance-oriented mode MRpwr, but this is not limited to the above. For example, the power performance-oriented mode MRpwr may be an off-road mode, a circuit mode, or the like. The off-road mode is a predetermined driving mode for improving the running performance on off-roads, etc., and is selected, for example, by the driver operating an off-road mode selection switch (not shown). The circuit mode is a predetermined driving mode for improving the running performance on a closed course such as a circuit, and is selected, for example, by the driver operating a circuit mode selection switch (not shown). Alternatively, the sports mode may be included in the power performance-oriented mode MRpwr. In short, the power performance-oriented mode MRpwr may be a driving mode in which rough road running performance and a drive torque Tr in the first gear stage are required.

In the above embodiment, the vehicle 10 having the engine 12, the electric motor MG, and the automatic transmission 24 is exemplified as a vehicle to which the present invention is applied, but the present invention is not limited to this embodiment. For example, the present invention can be applied to an engine vehicle that uses at least an engine as a power source, an electric vehicle that does not have an engine and uses only an electric motor as a power source, a hybrid vehicle that has an automatic transmission in series after a known electric continuously variable transmission, and the like. The automatic transmission 24 may also be a known DCT (Dual Clutch Transmission). In the case of a DCT, the multiple engagement devices are engagement devices that are respectively connected to the input shafts of the two systems, one of the multiple engagement devices corresponds to a release side engagement device, and the other of the multiple engagement devices corresponds to an engagement side engagement device. In short, the present invention can be applied to any vehicle that has an automatic transmission that forms a part of the power transmission path between the power source and the drive wheels and that forms one of multiple gear stages by engaging one of the multiple hydraulic engagement devices.

In addition, in the above-mentioned embodiment, the torque converter 22 is used as the fluid transmission device, but this is not limited to the embodiment. For example, instead of the torque converter 22, other fluid transmission devices 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.

The above is merely one embodiment, and the present invention can be implemented in various forms with various modifications and improvements based on the knowledge of those skilled in the art.

10: vehicle 14: drive wheels 24: automatic transmission 90: electronic control device (control device)
96: Transmission control unit CB: Engagement device CB1: First engagement device (engagement side engagement device)
CB2: Second engagement device (release side engagement device)
SP: Power source

Claims (1)

A control device for a vehicle including a power source and an automatic transmission that constitutes a part of a power transmission path between the power source and a drive wheel and that forms one of a plurality of gear stages by engaging one of a plurality of hydraulic engagement devices,
a shift control unit that performs shifting of the automatic transmission by switching a release-side engagement device among the engagement devices to a release state and switching an engagement-side engagement device among the engagement devices to an engagement state,
When the shift control unit determines to downshift the automatic transmission while the vehicle is decelerating in a predetermined low vehicle speed range, the shift control unit starts the downshift so that the downshift progress stage is a preparatory stage in which the disengagement side engagement device waits at a torque capacity capable of handling an input torque to the automatic transmission and the engagement side engagement device is in a packing completion state in which pack clearance is reduced, executes shift delay control to maintain the progress stage in a state in which the preparatory stage is completed until the vehicle stops, and starts the next progress stage of the preparatory stage after the vehicle stops to progress the downshift ,
The vehicle control device is characterized in that, when the gear shift control unit determines the downshift during the deceleration driving, if the driving mode of the vehicle is a predetermined driving mode that emphasizes power performance, the gear shift control unit proceeds with the downshift without executing the gear shift delay control .