Control device for stepped transmission

Abstract

To provide a controller capable of suppressing wrong learning of engagement pressure of an engagement side hydraulic frictional engagement device, in a stepped transmission comprising a plurality of hydraulic frictional engagement devices.SOLUTION: When an inertia phase is started in a state in which an engagement pressure PRcb1 of an engagement side engagement device CB1 is a standby pressure PRconst, and a post-correction engagement pressure PRcb1 calculated based on a learning value S calculated after downshift changes to a pressure reduction side with respect to a pre-learning engagement pressure PRcb1, an electronic controller 90 prohibits correction of the engagement pressure PRcb1, so that it is possible to prevent the engagement pressure PRcb1 from being continuously corrected toward the pressure reduction side by the learning value S calculated under a condition that is not suitable for learning.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to learning control of engagement pressure in a stepped transmission equipped with a plurality of hydraulic friction engagement devices. [Background technology]

[0002] Patent document 1 describes that in a stepped transmission comprising a plurality of hydraulic friction engagement devices, the engagement pressure (indicated pressure) of the disengagement side hydraulic friction engagement device is corrected by learning control so that the slip period of the disengagement side hydraulic friction engagement device during clutch-to-clutch shifting is a preset period. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Application Laid-Open No. 2003-42281 Summary of the Invention [Problem to be solved by the invention]

[0004] However, there are cases where the inertia phase is initiated while the engagement pressure of the engagement-side hydraulic friction engagement device that is engaged during gear shifting remains at the standby pressure after quick apply. In this case, if the learned value calculated by learning control is a value that would correct the engagement pressure to a reduced value, the engagement pressure will be corrected to a reduced value even under conditions that are not suitable for learning. If this type of learning is repeated, there is a risk that the engagement pressure will continue to be erroneously learned until it reaches a predetermined lower limit guard value.

[0005] The present invention has been made against the background of the above circumstances, and its purpose is to provide a control device that can suppress erroneous learning of the engagement pressure of the engaging side hydraulic friction engagement device in a stepped transmission configured with multiple hydraulic friction engagement devices. [Means for solving the problem]

[0006] The gist of the first invention is that (a) a hydraulic friction engagement device is provided ,before The hydraulic friction engagement device The release of the hydraulic friction engagement device on the release side that is released and the engagement of the hydraulic friction engagement device on the engagement side that is engaged are Multiple depending on the combination kinds Shifting gears will be carried out Applied to stepped transmissions, when downshifting In this case, the torque is transferred by gradually increasing the engagement pressure of the engagement-side hydraulic friction engagement device while gradually decreasing the engagement pressure of the release-side hydraulic friction engagement device to allow the release-side hydraulic friction engagement device to slip, and the like. Meanwhile, pack learning is performed to learn and correct a constant standby pressure of the engagement pressure of the engagement-side hydraulic friction engagement device, which is maintained in a packed state, which is a state immediately before the engagement-side hydraulic friction engagement device has a torque capacity, so as to maintain a constant differential pressure between the engagement pressure at the start of the torque phase of the shift and the engagement pressure at the start of the inertia phase of the shift; and torque learning is performed to determine a learning value so that the period from the start of the target inertia phase of the engagement-side hydraulic friction engagement device to the start of the actual inertia phase is a predetermined target period, and to correct the engagement pressure after the torque phase using the learning value. A control device for a stepped transmission, wherein (b) the engagement pressure of the engagement-side hydraulic friction engagement device is The aforementioned At standby pressure The aforementioned The inertia phase begins, and In the torque learning, Calculated based on the learned value calculated after the downshift After the torque phase Engagement pressure The torque When the engagement pressure changes to the decreasing side compared to the engagement pressure before learning, After the torque phase due to torque learning The present invention is characterized in that correction of the engagement pressure is prohibited. [Effects of the Invention]

[0007] According to the first aspect of the present invention, the inertia phase is initiated when the engagement pressure of the engagement-side hydraulic friction engagement device is at a predetermined standby pressure, and In torque learning, Calculated based on the learned value calculated after downshifting After the torque phase Engagement pressure torque If the engagement pressure changes to the pressure reducing side compared to before learning, After the torque phase due to torque learning Since correction of the engagement pressure is prohibited, it is possible to prevent the engagement pressure from being continually corrected to a lower pressure using a learned value calculated under conditions that are not suitable for learning. [Brief explanation of the drawings]

[0008] [Figure 1] 1 is a diagram illustrating a schematic configuration of a vehicle to which the present invention is applied, and is also a diagram illustrating main parts of control functions and control systems for various controls in the vehicle. [Figure 2] 3 is an engagement operation table showing combinations of engagement devices for establishing gear stages of an automatic transmission. [Figure 3] 10 is a time chart illustrating pack learning of the standby pressure of the engagement-side engagement device, which is performed after a downshift of the automatic transmission. [Figure 4]10 is a time chart illustrating torque learning of the engagement pressure of the engagement-side engagement device in the torque phase and thereafter, which is executed after a downshift of the automatic transmission. [Figure 5] 4 is a time chart showing the engagement pressure of an engagement-side engagement device during a downshift of the automatic transmission. [Figure 6] 10 is a flowchart illustrating the control operation of the electric control device, and is a flowchart illustrating the control operation of torque learning that is executed after a downshift of the automatic transmission. DETAILED DESCRIPTION OF THE INVENTION

[0009] Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings. Note that in the following embodiments, the drawings are appropriately simplified or modified, and the dimensional ratios and shapes of the various parts are not necessarily drawn accurately. [Example]

[0010] Fig. 1 is a diagram illustrating the schematic 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 systems for various controls in the vehicle 10. In Fig. 1, the vehicle 10 is a hybrid vehicle equipped with an engine 12 and a rotary machine MG, which are driving power sources for traveling. The vehicle 10 also has drive wheels 14 and a power transmission device 16 provided in a power transmission path between the engine 12 and the drive wheels 14.

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

[0012] The rotating machine MG is a rotating electric machine that functions as a motor that generates mechanical power from electric power and as a generator that generates electric power from mechanical power, and is a so-called motor generator. The rotating machine MG is connected to a battery 54 provided in the vehicle 10 via an inverter 52 provided in the vehicle 10. The inverter 52 is controlled by an electronic control device 90 (described later), thereby controlling the MG torque Tm, which is the output torque of the rotating machine MG. For example, when the rotating machine MG rotates in the forward direction, which is the same direction as the rotation of the engine 12, the MG torque Tm is a powering 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. Specifically, the rotating machine MG generates power for traveling using electric power supplied from the battery 54 via the inverter 52 instead of or in addition to the engine 12. The rotating machine MG also generates electric power using the power of the engine 12 and the driven force input from the drive wheels 14. The electric power generated by the electric power generation of the rotating machine MG is stored in the battery 54 via the inverter 52. The battery 54 is an electricity storage device that supplies and receives electric power to the rotary machine MG. The electric power also refers to electrical energy unless otherwise specified. The power also refers to torque or force unless otherwise specified.

[0013] The power transmission device 16 includes a K0 clutch 20, a torque converter 22, an automatic transmission 24, and the like, housed within a case 18, which is a non-rotating member attached to the vehicle body. The K0 clutch 20 is a clutch provided between the engine 12 and a rotary machine MG in a power transmission path between the engine 12 and the drive wheels 14. The torque converter 22 is connected to the engine 12 via the K0 clutch 20.

[0014] The automatic transmission 24 is connected to the torque converter 22 and is interposed in a power transmission path between the torque converter 22 and the drive wheels 14. The torque converter 22 and the automatic transmission 24 each constitute a part of the power transmission path between the engine 12 and the drive wheels 14. 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, etc. The power transmission device 16 also includes an engine connecting shaft 34 connecting the engine 12 and the K0 clutch 20, and a rotating machine connecting shaft 36 connecting the K0 clutch 20 and the torque converter 22, etc. The automatic transmission 24 corresponds to the stepped transmission of the present invention.

[0015] The rotary machine MG is connected to a rotary machine connecting shaft 36 within the case 18 so as to be able to transmit power. The rotary machine MG is connected to a power transmission path between the engine 12 and the drive wheels 14, particularly to a power transmission path between the K0 clutch 20 and the torque converter 22 so as to be able to transmit power. In other words, the rotary machine MG is connected to the torque converter 22 and the automatic transmission 24 so as to be able to transmit power without passing through the K0 clutch 20. In other words, the torque converter 22 and the automatic transmission 24 each constitute part of the power transmission path between the rotary machine MG and the drive wheels 14. The torque converter 22 and the automatic transmission 24 transmit driving power from the driving power sources of the engine 12 and the rotary machine MG to the drive wheels 14, respectively.

[0016] The torque converter 22 includes a pump wheel 22a connected to a rotary machine connecting shaft 36 and a turbine wheel 22b connected to a transmission input shaft 38, which is an input rotating member of the automatic transmission 24. The pump wheel 22a is connected to the engine 12 via the K0 clutch 20 and is also directly connected to the rotary machine MG. The pump wheel 22a is the input member of the torque converter 22, and the turbine wheel 22b is the output member of the torque converter 22. The rotary machine connecting shaft 36 also serves as the input rotating member of the torque converter 22. The transmission input shaft 38 is also the output rotating member of the torque converter 22, formed integrally with a turbine shaft that is rotationally driven by the turbine wheel 22b. The torque converter 22 is a fluid-type power transmission that transmits driving force from each of the driving force sources (engine 12, rotary machine MG) to the transmission input shaft 38 via fluid. The torque converter 22 includes an LU clutch 40 that connects the pump wheel 22a and the turbine wheel 22b. The LU clutch 40 is a direct coupling clutch that connects the input and output rotary members of the torque converter 22, that is, a known lock-up clutch.

[0017] The operating state, i.e., the control state, of the LU clutch 40 is switched by changing the LU clutch torque Tlu, which is the torque capacity of the LU clutch 40, using the regulated LU oil pressure PRlu supplied from a hydraulic control circuit 56 provided in the vehicle 10. The control states of the LU clutch 40 include a fully released state in which the LU clutch 40 is released, a slip state in which the LU clutch 40 is engaged with slippage, and a fully engaged state in which the LU clutch 40 is engaged.

[0018] The automatic transmission 24 is a known planetary gear automatic transmission equipped with, for example, one or more planetary gear sets (not shown) and a plurality of engagement devices CB. The engagement devices CB are hydraulic friction engagement devices, such as multi-plate or single-plate clutches or brakes pressed by hydraulic actuators, or band brakes tightened by hydraulic actuators. Each engagement device CB has its torque capacity, or CB torque Tcb, changed by an engagement pressure PRcb regulated by a hydraulic control circuit 56, thereby switching its control state, such as an engaged state or a disengaged state. In this embodiment, the engagement devices CB are composed of, for example, four clutches C1 to C4 and two brakes B1 and B2.

[0019] The automatic transmission 24 is a stepped automatic transmission in which one of a plurality of gear stages (also referred to as "gear stages") with different speed ratios (also referred to as "gear ratios") γat (=AT input rotation speed Ni / AT output rotation speed No) is established by engaging one of the engagement devices CB. That is, the automatic transmission 24 establishes a plurality of gear stages according to combinations of engagement and disengagement of the plurality of engagement devices CB (clutches C1 to C4 and brakes B1, B2). Specifically, the automatic transmission 24 shifts gears based on an engagement operation table shown in FIG. 2, which shows combinations of the engagement devices CB for establishing the gear stages of the automatic transmission 24. In FIG. 2, "◯" indicates engagement of an engagement device CB, and "X" indicates disengagement of an engagement device CB. As shown in FIG. 2, the automatic transmission 24 is configured to be able to switch between 10 gear stages by changing the combinations of engagement and disengagement of the engagement devices CB.

[0020] The automatic transmission 24 determines the gear position by an electronic control device 90 (described later) based on the accelerator opening θacc, which is the amount of operation of the accelerator pedal 42 by the driver (=operator), and the vehicle speed V. Note that the decision to shift gears may be made not only based on the accelerator opening θacc, but also based on a related value of the accelerator opening θacc that is correlated with the accelerator opening θacc, such as the throttle opening θth. Similarly, the decision to shift gears may be made not only based on the vehicle speed V, but also based on a related value of the vehicle speed V that is correlated with the vehicle speed V, such as the AT output rotation speed No. 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 also the rotation speed of the output rotating member of the torque converter 22 and is equivalent to the turbine rotation speed Nt, which is the output rotation speed of the torque converter 22. The AT input rotation speed Ni can be expressed in terms of the turbine rotation speed Nt. The AT output rotation speed No is the rotation speed of the transmission output shaft 26, and is the output rotation speed of the automatic transmission 24.

[0021] The K0 clutch 20 is a wet or dry friction engagement device configured with a multi-plate or single-plate clutch pressed by a hydraulic actuator (not shown). The control state of the K0 clutch 20, such as an engaged state or a disengaged state, is switched by an electronic control device 90 (described later) controlling the operating state of the hydraulic actuator. When the K0 clutch 20 receives a K0 oil pressure PRk0 regulated by the hydraulic control circuit 56 and supplied to the hydraulic actuator, the K0 torque Tk0, which is the torque capacity of the K0 clutch 20, is changed, thereby switching the control state of the K0 clutch 20.

[0022] When the K0 clutch 20 is engaged, the pump wheel 22a and the engine 12 are rotated integrally via the engine connecting shaft 34. That is, when engaged, the K0 clutch 20 connects the engine 12 and the drive wheels 14 so that power can be transmitted between them. On the other hand, when the K0 clutch 20 is disengaged, power transmission between the engine 12 and the pump wheel 22a is interrupted. That is, when disengaged, the K0 clutch 20 disconnects the engine 12 and the drive wheels 14. Because the rotary machine MG is connected to the pump wheel 22a, the K0 clutch 20 is provided in the power transmission path between the engine 12 and the rotary machine MG and functions as a clutch that connects and disconnects the power transmission path, i.e., a clutch that connects and disconnects the engine 12 and the rotary machine MG. That is, the K0 clutch 20 is a connecting / disconnecting clutch that connects the engine 12 and the rotary machine MG when engaged and disconnects the connection between the engine 12 and the rotary machine MG when disengaged.

[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 connecting shaft 34 to the drive wheels 14 via the K0 clutch 20, the rotating machine connecting shaft 36, the torque converter 22, the automatic transmission 24, the propeller shaft 28, the differential gear 30, the drive shaft 32, etc. in this order. In addition, regardless of the control state of the K0 clutch 20, the power output from the rotating machine MG is transmitted from the rotating machine connecting shaft 36 to the drive wheels 14 via the torque converter 22, the automatic transmission 24, the propeller shaft 28, the differential gear 30, the drive shaft 32, etc. in this order.

[0024] The vehicle 10 is equipped with a MOP 58 which is a mechanical oil pump, an EOP 60 which is an electric oil pump, a pump motor 62, etc. The MOP 58 is connected to the pump impeller 22a and is rotationally driven by a driving power source (the engine 12, the rotary machine MG) to discharge hydraulic oil used in the power transmission device 16. The pump motor 62 is a motor dedicated to the EOP 60 for rotationally driving the EOP 60. The EOP 60 is rotationally driven by the pump motor 62 to discharge hydraulic oil. The hydraulic oil discharged by the MOP 58 and the EOP 60 is supplied to a hydraulic control circuit 56. The hydraulic control circuit 56 supplies an engagement pressure PRcb, a K0 hydraulic pressure PRk0, an LU hydraulic pressure PRlu, etc., which are each adjusted based on the hydraulic oil discharged by at least one of the MOP 58 and the EOP 60.

[0025] The vehicle 10 further includes an electronic control device 90 including a control device related to driving control of 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. The CPU executes various controls of the vehicle 10 by performing signal processing in accordance with programs stored in the ROM in advance while utilizing the temporary storage function of the RAM. The electronic control device 90 includes computers for engine control, rotating machine control, hydraulic control, etc. as needed. The electronic control device 90 corresponds to the control device of the present invention.

[0026] The electronic control device 90 is supplied with various signals based on detection values ​​from various sensors provided on 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 opening sensor 80, brake switch 82, battery sensor 84, oil temperature sensor 86) (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, which corresponds to vehicle speed V; MG rotation speed Nm, which is the rotation speed of the rotating machine MG; accelerator opening θacc, which is the amount of operation of the accelerator pedal 42 by the driver, which indicates the magnitude of the driver's acceleration operation; throttle opening θth, which is the opening of the electronic throttle valve; brake-on signal Bon, which is a signal indicating the state in which the brake pedal 44 for operating the wheel brakes is being operated by the driver; battery temperature THbat, battery charge / discharge current Ibat, and battery voltage Vbat of the battery 54; and hydraulic oil temperature THoil, which is the temperature of the hydraulic oil in the hydraulic control circuit 56).

[0027] The electronic control device 90 outputs various command signals (e.g., an engine control command signal Se for controlling the engine 12, an MG control command signal Sm for controlling the rotating machine MG, a CB hydraulic control command signal Sbc for controlling the engagement device CB, a K0 hydraulic control command signal Sko for controlling the K0 clutch 20, an LU hydraulic control command signal Slu for controlling the LU clutch 40, an EOP control command signal Seop for controlling the EOP 60, etc.) to each device provided in the vehicle 10 (e.g., the engine control device 50, the inverter 52, the hydraulic control circuit 56, the pump motor 62, etc.).

[0028] In order to realize various controls in the vehicle 10, the electronic control device 90 is equipped with a hybrid control unit 92 that functions as a hybrid control means, a clutch control unit 94 that functions as a clutch control means, a shift control unit 96 that functions as a shift control means, and a learning control unit 98 that functions as a learning control means.

[0029] The hybrid control unit 92 has 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 a rotating machine control means, i.e., a rotating machine control unit 92b, that controls the operation of the rotating machine MG via the inverter 52, and performs hybrid drive control using the engine 12 and the rotating machine MG, etc., using these control functions.

[0030] The hybrid control unit 92 calculates the drive amount required by the driver for the vehicle 10, for example, by applying the accelerator opening θacc and the vehicle speed V to a required drive amount map. The required drive amount map is a relationship that is experimentally or design-based and stored in advance, i.e., a predetermined relationship. The required drive amount is, for example, the required drive torque Trdem at the drive wheels 14. In other words, the required drive torque Trdem [Nm] is the required drive power Prdem [W] at the current vehicle speed V. The required drive amount can also be the required drive force Frdem [N] at the drive wheels 14, the required AT output torque at the transmission output shaft 26, or the like. When calculating the required drive amount, the AT output rotation speed No, or the like, can be used instead of the vehicle speed V.

[0031] The hybrid control unit 92 calculates a target engine torque Tedem for the engine 12 and a target MG torque Tmdem for the rotating machine MG that realize the required drive torque Trdem, taking into consideration transmission loss, the auxiliary load, the gear ratio γat of the automatic transmission 24, the chargeable power Win and dischargeable power Wout of the battery 54, etc. The hybrid control unit 92 outputs an engine control command signal Se for the engine 12 that outputs the calculated target engine torque Tedem to the engine control device 50. The hybrid control unit 92 also outputs an MG control command signal Sm for the rotating machine MG that outputs the calculated target MG torque Tmdem to the inverter 52. The engine control command signal Se is, for example, a command value for engine power Pe, which is the power of the engine 12 that outputs the target engine torque Tedem at a current engine rotation speed Ne. The MG control command signal Sm is, for example, a command value for power consumption Wm of the rotating machine MG that outputs the target MG torque Tmdem at a current MG rotation speed Nm.

[0032] The chargeable power Win of the battery 54 is the maximum power that can be input, which defines a limit on the input power of the battery 54, and indicates the input limit of the battery 54. The dischargeable power Wout of the battery 54 is the maximum power that can be output, which defines a limit on the output power of the battery 54, and indicates the output limit of the battery 54. The chargeable power Win and dischargeable power Wout of the battery 54 are calculated by the electronic control device 90 based on, for example, the battery temperature THbat and the state-of-charge value SOC [%] of the battery 54. The state-of-charge value SOC of the battery 54 is a value that indicates the state of charge (charge amount, remaining charge) of the battery 54, and is calculated by the electronic control device 90 based on, for example, the battery charge / discharge current Ibat and the battery voltage Vbat.

[0033] When the required drive torque Trdem can be satisfied only by the output of the rotary machine MG, the hybrid control unit 92 sets the drive mode to motor drive (hereinafter referred to as BEV drive) mode. In the BEV drive mode, the hybrid control unit 92 performs BEV drive, in which the vehicle runs using only the rotary machine MG as a drive power source with the K0 clutch 20 in a disengaged 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 hybrid control unit 92 sets the drive mode to engine drive mode, i.e., hybrid drive (hereinafter referred to as HEV drive) mode.

[0034] In the HEV driving mode, the hybrid control unit 92 performs engine driving, i.e., HEV driving, in which the engine 12 and the rotary machine MG are used as driving power sources with the K0 clutch 20 engaged. On the other hand, even if the required driving torque Trdem can be satisfied solely by the output of the rotary machine MG, the hybrid control unit 92 establishes the HEV driving mode when the state of charge value SOC of the battery 54 falls below a predetermined engine start threshold or when warming up of the engine 12, etc. is required. The engine start threshold is a predetermined threshold for determining that the state of charge value SOC is such that the engine 12 must be forcibly started to charge the battery 54. In this way, the hybrid control unit 92 automatically stops the engine 12 during HEV driving, restarts the engine 12 after the engine stop, or starts the engine 12 during BEV driving, appropriately switching between the BEV driving mode and the HEV driving mode, based on the required driving torque Trdem, etc.

[0035] The clutch control unit 94 controls the K0 clutch 20 in accordance with the driving mode during driving. For example, when it is determined that the driving mode is to be switched to the HEV driving mode during BEV driving, the clutch control unit 94 controls the engagement of the K0 clutch 20 so as to execute start control of the engine 12. For example, when it is determined that there is a request to start the engine 12 based on the driving state, the clutch control unit 94 outputs a K0 hydraulic control command signal Sko to the hydraulic control circuit 56 to control the K0 clutch 20 from a released state toward an engaged state so as to obtain a K0 torque Tk0 for transmitting to the engine 12 a torque required for cranking the engine 12, which is a torque that increases the engine rotation speed Ne.

[0036] The shift control unit 96 determines whether to shift the automatic transmission 24 using, for example, a shift map, which is a predetermined relationship, and outputs a CB hydraulic control command signal Sbc to the hydraulic control circuit 56 as needed to execute shift control of the automatic transmission 24. The shift map is a predetermined relationship having shift lines for determining whether to shift the automatic transmission 24 on a two-dimensional coordinate system using, for example, vehicle speed V and accelerator opening θacc as variables. In the shift map, the AT output rotation speed No or the like may be used as a value related to the vehicle speed V, instead of the vehicle speed V, and the required drive torque Trdem, required drive force Frdem, throttle opening θth or the like may be used as values ​​related to the accelerator opening θacc, instead of the accelerator opening θacc.

[0037] The learning control unit 98 performs multiple types of learning control, including learning of the engagement pressure PRcb1, which is the command pressure during an engagement transition period for the engagement-side engagement device CB (hereinafter referred to as the engagement-side engagement device CB1) that is engaged when the automatic transmission 24 is shifted. For example, after a downshift of the automatic transmission 24 is performed, the learning control unit 98 performs pack learning, which corrects the standby pressure PRconst of the engagement-side engagement device CB1, which is the hydraulic pressure (constant pressure) that is maintained in a packed state, which is the state immediately before the engagement-side engagement device CB1 produces the CB1 torque Tcb1 (torque capacity), and torque learning, which corrects the engagement pressure PRcb1 of the engagement-side engagement device CB1 after the start of the torque phase. Note that pack learning and torque learning correspond to the predetermined learning controls when performing a downshift of the present invention.

[0038] First, pack learning will be described. The learning control unit 98 learns the standby pressure PRconst so as to maintain a constant differential pressure ΔPRcb1 (PRcb1i-PRcb1t), which is the difference between the engagement pressure PRcb1 at the start of the torque phase (hereinafter referred to as torque phase start pressure PRcb1t) and the engagement pressure PRcb1 at the start of the inertia phase (hereinafter referred to as inertia phase start pressure PRcb1i).

[0039] When the downshift of the automatic transmission 24 is completed, the learning control unit 98 calculates a differential pressure ΔPRcb1 (=PRcb1t-PRcb1i) between the torque phase start pressure PRcb1t at the start of the torque phase of the automatic transmission 24 and the inertia phase start pressure PRcb1i when the inertia phase is detected. Here, when a downshift is started, a quick apply is executed to temporarily increase the engagement pressure PRcb1 to improve the responsiveness of the hydraulic pressure (actual pressure), and then the engagement pressure PRcb1 (command pressure) of the engagement side engagement device CB1 is maintained at a constant standby pressure PRconst until the torque phase starts. Therefore, the torque phase start pressure PRcb1t has the same value as the standby pressure PRconst. In addition, the inertia phase start pressure PRcb1i when the inertia phase is detected is set to the engagement pressure PRcb1 when the increase in the AT input rotation speed Ni, based on the rotation speed when the AT input rotation speed Ni switches from decreasing to increasing, reaches a predetermined value α (see Figure 3).

[0040] Next, the learning control unit 98 calculates a deviation D (K-ΔPRcb1) between the calculated differential pressure ΔPRcb1 and a preset target value K of the differential pressure ΔPRcb1, and calculates a learning value M based on the deviation D. The learning value M is a correction value to be added to the standby pressure PRconst before learning, and is calculated, for example, by multiplying the deviation D by a preset coefficient K1 (=K1×D). As a result, the learning value M increases in proportion to the deviation D. Furthermore, the learning value M changes to either a positive value or a negative value depending on whether the deviation D is positive or negative. The learning control unit 98 adds the calculated learning value M to the standby pressure PRconst before learning (Pconst+M) to calculate and correct (update) a new standby pressure PRconst based on the learning value M.

[0041] 3 is a time chart illustrating pack learning of the standby pressure PRconst of the engagement side engagement device CB1 that is executed after a downshift of the automatic transmission 24. In FIG. 3, the upper part shows the turbine rotation speed Nt, i.e., the AT input rotation speed Ni of the automatic transmission 24, and the lower part shows the engagement pressure PRcb1 (command pressure) of the engagement side engagement device CB1 that is engaged during a downshift of the automatic transmission 24.

[0042] When a downshift of the automatic transmission 24 is initiated at time t1 in FIG. 3, a quick apply is executed between time t1 and time t2, temporarily increasing the engagement pressure PRcb1 (command pressure) of the on-coming engagement device CB1 to improve the responsiveness of the hydraulic pressure (actual pressure). From time t2 onward, the engagement pressure PRcb1 is maintained at standby pressure PRconst, which is the packed state immediately before the on-coming engagement device CB1 produces the CB1 torque Tcb1. A predetermined time has elapsed since time t2, and the torque phase begins, and at time t3, the engagement pressure PRcb1 begins to increase. Just before time t4, the inertia phase begins, and the turbine rotation speed Nt begins to increase. At time t4, the increase in the rotation speed from the time when the turbine rotation speed Nt began to increase reaches a predetermined value α, and the start of the inertia phase is detected.

[0043] In pack learning, after a downshift, a differential pressure ΔPRcb1 is calculated between the torque phase start pressure PRcb1t (=PRconst) at time t3 and the inertia phase start pressure PRcb1i at time t4, when the start of the inertia phase is detected. Next, a learned value M is calculated so that the differential pressure ΔPRcb1 becomes constant (target value K). Specifically, a deviation D between the target value K and the differential pressure ΔPRcb1 is calculated, and a learned value M corresponding to the deviation D is calculated. Next, the learned value M is added to the standby pressure PRconst before learning, thereby updating it to a new standby pressure PRconst. From time t2 to time t3 in FIG. 3, the standby pressure PRconst indicated by the dashed line and the dash-dot line represents the standby pressure PRconst after correction by pack learning. If the learned value M is a positive value M1, the standby pressure PRconst is corrected to the increased side. If the learned value M is a negative value M2, the standby pressure PRconst is corrected to the decreased side.

[0044] Next, torque learning of the engagement pressure PRcb1 (command pressure) of the engagement-side engagement device CB1 after the start of the torque phase will be described. The learning control unit 98 learns the engagement pressure PRcb1 (command pressure) after the torque phase so that the period Term (= tiner2 - tiner1) from a preset target inertia phase start time tiner1, which is based on the start time of a downshift, to an actual inertia phase start time tiner2, when the start of the inertia phase is actually detected, is maintained at a preset target period Terma.

[0045] When the automatic transmission 24 completes a downshift, the learning control unit 98 detects an actual inertia phase start time tiner2, which is the time when the start of the inertia phase is actually detected, relative to the start of the downshift. In this embodiment, the actual inertia phase start time tiner2 is set to the time when the increase in the turbine rotation speed Nt reaches a predetermined value α at the time when the turbine rotation speed Nt starts to increase (see FIG. 4). Upon detecting the actual inertia phase start time tiner2, the learning control unit 98 calculates a period Term (= tiner2 - tiner1) between the actual inertia phase start time tiner2 and a preset target inertia phase start time tiner1, relative to the start of the downshift. Furthermore, the learning control unit 98 calculates a time error ΔTerm (= Term - Terma), which is the difference between this period Term and a preset target period Terma.

[0046] After calculating the time error ΔTerm, the learning control unit 98 calculates a learning value S based on the calculated time error ΔTerm. In this embodiment, the learning value S is a correction value to be added to the engagement pressure PRcb1 before learning, for example, after the start of the torque phase. The learning value S is calculated, for example, by multiplying the time error ΔTerm by a preset coefficient K2 (=K2×ΔTerm). As a result, the learning value S increases in proportion to the time error ΔTerm. The learning value S changes to either a positive value or a negative value depending on whether the time error ΔTerm is positive or negative. The learning control unit 98 calculates and corrects (updates) a new engagement pressure PRcb1 based on the learning value S by adding the calculated learning value S to the engagement pressure PRcb1 before learning (PRcb1+S).

[0047] Fig. 4 is a time chart illustrating torque learning of the engagement pressure PRcb1 of the engagement-side engagement device CB1 from the torque phase onwards, which is performed after a downshift of the automatic transmission 24. In Fig. 4, the upper part shows the turbine rotation speed Nt, i.e., the AT input rotation speed Ni of the automatic transmission 24, and the lower part shows the engagement pressure PRcb1 (command pressure) of the engagement-side engagement device CB1 that is engaged during a downshift of the automatic transmission 24.

[0048] When a downshift of the automatic transmission 24 is initiated at time t1 in FIG. 4, a quick apply is executed between time t1 and time t2, temporarily increasing the engagement pressure PRcb1 (command pressure) of the on-coming engagement device CB1 to improve the responsiveness of the actual hydraulic pressure. From time t2 onward, the engagement pressure PRcb1 is maintained at standby pressure PRconst, which is the packed state immediately before the on-coming engagement device CB1 produces the CB1 torque Tcb1. A predetermined time after time t2, the torque phase begins, and at time t3, the engagement pressure PRcb1 begins to increase. Just before time t4, the inertia phase begins, and the turbine rotation speed Nt begins to increase. At time t4, the increase in the rotation speed from the time when the turbine rotation speed Nt began to increase reaches a predetermined value α, and the start of the inertia phase is detected.

[0049] In torque learning, after a downshift, the period Term between the time t4 when the start of the inertia phase is actually detected, i.e., the actual inertia phase start time tiner2, and the preset target inertia phase start time tiner1 is calculated, and the learning value S of the engagement pressure PRcb1 from the torque phase onwards is calculated based on the time error ΔTerm (=Term-Terma), which is the difference between the period Term and the target period Terma.

[0050] For example, if the calculated learning value S is a positive value S1, i.e., if the period Term is longer than the target period Terma, or if the inertia phase starts later than the target time, the learned engagement pressure PRcb1 will be corrected (updated) to an increased pressure side as shown by the dashed line relative to the pre-learning engagement pressure PRcb1 shown by the solid line after time t3 when the engagement pressure PRcb1 starts to increase. Also, if the calculated learning value S is a negative value S2, i.e., if the period Term is shorter than the target period Terma, or if the inertia phase starts earlier than the target time, the learned engagement pressure PRcb1 will be corrected (updated) to a decreased pressure side as shown by the dashed line relative to the pre-learning engagement pressure PRcb1 shown by the solid line after time t3 when the engagement pressure PRcb1 starts to increase.

[0051] As described above, when the downshift of the automatic transmission 24 is completed, pack learning is performed to correct the standby pressure PRconst of the engagement pressure PRcb1 of the engagement side engagement device CB1 based on the learning value M, and torque learning is performed to correct the engagement pressure PRcb1 from the torque phase onwards based on the learning value S.

[0052] Incidentally, when the hydraulic response of the engagement side engagement device CB1 is poor, the standby pressure PRconst is set high in order to keep the shift time of the automatic transmission 24 within the target value. In this case, it is conceivable that the inertia phase will start in the state of the standby pressure PRconst due to the standby pressure PRconst being set high.

[0053] Fig. 5 is a time chart showing the engagement pressure PRcb1 of the engagement-side engagement device CB1 during a downshift of the automatic transmission 24. In Fig. 5, the vertical axes represent, from top to bottom, the AT input rotation speed Ni, the engagement pressure PRcb1 of the engagement-side engagement device CB1 (at high torque), and the engagement pressure PRcb1 of the engagement-side engagement device CB1 (at low torque). Here, "at high torque" refers to a case where the input torque input to the automatic transmission 24, or the MG torque Tm of the rotary machine MG during BEV driving, is high, and "at low torque" refers to a case where the input torque input to the automatic transmission 24, or the MG torque Tm of the rotary machine MG during BEV driving, is low.

[0054] Normally, as shown during high torque, after quick apply is performed at time t1, the standby pressure PRconst is maintained. After a predetermined time has elapsed since time t2 when the torque phase starts, the engagement pressure PRcb1 begins to increase, and the inertia phase starts at time t3. On the other hand, during low torque, the inertia phase starts at time t3 when the engagement pressure PRcb1 is maintained at the standby pressure PRconst. As a result, during low torque, the engagement pressure PRcb1 becomes equal to the standby pressure PRconst at time t3 when the inertia phase starts.

[0055] When the inertia phase starts while the standby pressure PRconst is maintained as described above, if the period Term becomes shorter than the target period Terma (i.e., the actual inertia phase start time tiner2 becomes earlier than the target time), the learning value S becomes a negative value even though the conditions are not suitable for learning, and the engagement pressure PRcb1 is corrected to a reduced value. If this occurs repeatedly, there is a risk that the engagement pressure PRcb1 will be erroneously learned until it reaches a preset lower limit guard value, even though the conditions are not suitable for learning. The lower limit guard value is set to, for example, the standby pressure PRconst.

[0056] In contrast, when the automatic transmission 24 is downshifted, if the inertia phase begins with the engagement pressure PRcb1 of the engagement side engagement device CB1 at standby pressure PRconst, and the learning value S calculated after the downshift is a negative value, i.e., if the engagement pressure PRcb1 calculated based on the learning value S changes to a reduced value compared to the engagement pressure PRcb1 before learning, the learning control unit 98 prohibits correction (updating) of the engagement pressure PRcb1 through torque learning.

[0057] When the start of the inertia phase is detected, the learning control unit 98 determines whether the inertia phase has started in a state of standby pressure PRconst based on whether the engagement pressure PRcb1 at that time is equal to standby pressure PRconst. The learning control unit 98 also calculates a learning value S and determines whether the calculated learning value S is a negative value. In this embodiment, since the learning value S is added to the engagement pressure PRcb1, a positive value of the learning value S indicates that the engagement pressure PRcb1 is to be corrected toward an increased pressure, and a negative value of the learning value S indicates that the engagement pressure PRcb1 is to be corrected toward a decreased pressure.

[0058] When the inertia phase starts with the standby pressure PRconst and the learning value S is a negative value, the learning control unit 98 prohibits the correction (updating) of the engagement pressure PRcb1 through torque learning. Here, when the learning value S is a negative value, this indicates that the engagement pressure PRcb1 is corrected to a reduced pressure. Therefore, when the learning value S is a negative value, the correction (updating) of the engagement pressure PRcb1 is prohibited, thereby preventing the engagement pressure PRcb1 from being erroneously learned to a reduced pressure.

[0059] 6 is a flowchart for explaining the control operation of the electronic control unit 90, and is a flowchart for explaining the control operation of torque learning that is executed after a downshift of the automatic transmission 24. This flowchart is executed every time a downshift of the automatic transmission 24 is executed.

[0060] First, in a step (hereinafter, the term "step" will be omitted) corresponding to the control function of the learning control unit 98, it is determined whether a downshift of the automatic transmission 24 has been completed. If the determination in S10 is negative, this routine is terminated. If the determination in S10 is positive, it is determined in S20, corresponding to the control function of the learning control unit 98, whether a permission condition for learning control is satisfied. As the permission condition for learning control, multiple permission conditions for permitting learning control are set, such as vehicle speed V being equal to or lower than a predetermined vehicle speed. Furthermore, if all of the permission conditions are satisfied, it is determined that the permission condition for learning control is satisfied. If the determination in S20 is negative, this routine is terminated. If the determination in S20 is positive, in S30, corresponding to the control function of the learning control unit 98, a time error ΔTerm (=Term - Terma) between the period Term (tiner2 - tiner1) and the target period Terma is calculated. Next, in S40, corresponding to the control function of the learning control unit 98, a learning value S is calculated based on the time error ΔTerm.

[0061] In S50, which corresponds to the control function of the learning control unit 98, it is determined whether the inertia phase has started with the engagement pressure PRcb1 at the standby pressure PRconst and whether the learning value S is a negative value. If the determination in S50 is negative, in S60, which corresponds to the control function of the learning control unit 98, the engagement pressure PRcb1 from the torque phase onwards is corrected (updated) based on the calculated learning value S. On the other hand, if the determination in S50 is positive, the process returns. Therefore, if the determination in S50 is positive, i.e., if the inertia phase has started at the standby pressure PRconst and the learning value S is a negative value, i.e., if the inertia phase has started earlier than the target time (if the period Term is shorter than the target period Terma), the correction (updating) of the engagement pressure PRcb1 is not executed, and the engagement pressure PRcb1 is prevented from being erroneously learned to be reduced.

[0062] As described above, according to this embodiment, when the inertia phase begins with the engagement pressure PRcb1 of the engagement side engagement device CB1 at standby pressure PRconst, and the corrected engagement pressure PRcb1 calculated based on the learning value S calculated after the downshift changes to a reduced pressure side compared to the engagement pressure PRcb1 before learning, correction of the engagement pressure PRcb1 is prohibited, thereby preventing the engagement pressure PRcb1 from continuing to be corrected to a reduced pressure side due to the learning value S calculated under conditions that are not suitable for learning.

[0063] Although the embodiments of the present invention have been described in detail above with reference to the drawings, the present invention can also be applied to other embodiments.

[0064] For example, in the above-described embodiment, when the inertia phase starts with the engagement pressure PRcb1 at the standby pressure PRconst and the learning value S is a negative value, correction (updating) of the engagement pressure PRcb1 is prohibited. However, instead of the learning value S, correction (updating) of the engagement pressure PRcb1 may be prohibited when the period Term, which is the difference (tiner2-tiner1) between the actual inertia phase start time tiner2 and the target inertia phase start time tiner1, is shorter than the preset target period Terma (i.e., when the time error ΔTerm is a negative value), or when the actual inertia phase start time tiner2 is earlier than the target time. In other words, any requirement that can determine whether the engagement pressure PRcb1 after learning will decrease relative to the engagement pressure PRcb1 before learning can be applied as appropriate.

[0065] In the above-described embodiment, the vehicle 10 is a hybrid vehicle using the engine 12 and the rotary machine MG as a driving force source, but the present invention is not limited to this. For example, the present invention can be applied to a vehicle using only the engine 12 as a driving force source, or to an electric vehicle using only the rotary machine MG as a driving force source.

[0066] Furthermore, in the above-described embodiment, the torque learning involves calculating the learning value S to be added to the engagement pressure PRcb1 based on the time error ΔTerm. However, instead, the gradient β of the engagement pressure PRcb1 after the start of the torque phase may be calculated based on the time error Δ.

[0067] It should be noted that 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. [Explanation of symbols]

[0068] 24: Automatic transmission (stepped transmission) 90: Electronic control device (control device) CB: Engagement device (hydraulic friction engagement device) S: Learning value PRcb, PRcb1: Engagement pressure

Claims

[Claim 1] This invention is applied to a stepped transmission that includes a plurality of hydraulic friction engagement devices, and performs a plurality of types of gear changes according to a combination of the release of a release-side hydraulic friction engagement device that is released and the engagement of an engagement-side hydraulic friction engagement device that is engaged, and when performing a downshift, the engagement pressure of the engagement-side hydraulic friction engagement device is gradually increased while the engagement pressure of the release-side hydraulic friction engagement device is gradually decreased to allow the release-side hydraulic friction engagement device to slip, thereby transferring torque. A control device for a stepped transmission that performs pack learning, which learns and corrects a constant standby pressure that is maintained in a packed state, which is a state immediately before an engaging side hydraulic friction engagement device has a torque capacity, so as to maintain a constant differential pressure between the engaging pressure at the start of a torque phase of the shift and the engaging pressure at the start of an inertia phase of the shift, and torque learning, which determines a learned value so that a period from the start of a target inertia phase of the engaging side hydraulic friction engagement device to the start of an actual inertia phase is a predetermined target period, and corrects the engaging pressure after the torque phase using the learned value, When the inertia phase is initiated with the engagement pressure of the engagement-side hydraulic friction engagement device at the standby pressure, and when, in the torque learning, the engagement pressure after the torque phase calculated based on the learned value calculated after the downshift changes to a reduced pressure side compared to the engagement pressure before the torque learning, correction of the engagement pressure after the torque phase by the torque learning is prohibited. A control device for a stepped transmission characterized by:

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