JP7827464B2 - Control device for stepped transmission - Google Patents

Description

The present invention relates to learning control of engagement pressure in a stepped transmission equipped with multiple hydraulic friction engagement devices.

Patent Document 1 describes a step-variable transmission equipped with multiple hydraulic friction engagement devices, in which the engagement pressure (indicated pressure) of the disengagement hydraulic friction engagement device is corrected through learning control so that the slip-out period of the disengagement hydraulic friction engagement device during clutch-to-clutch shifting is a preset period.

Japanese Patent Application Laid-Open No. 2003-42281

However, there are cases where the inertia phase begins 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 the reduced side, the engagement pressure will be corrected to the reduced side even though the conditions are not suitable for learning. If this type of learning is repeated, there is a risk that the engagement pressure will continue to be incorrectly learned until it reaches a specified lower limit guard value.

The present invention was made against the backdrop of the above circumstances, and its purpose is to provide a control device that can suppress erroneous learning of the engagement pressure of an engaging hydraulic friction engagement device in a stepped transmission equipped with multiple hydraulic friction engagement devices.

The gist of the first invention is that (a) the invention is applied to a stepped transmission that includes a plurality of hydraulic friction engagement devices, and that 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, among the hydraulic friction engagement devices, and when performing a downshift , the engagement pressure of the release-side hydraulic friction engagement device is gradually reduced to allow the release-side hydraulic friction engagement device to slip while the engagement pressure of the engagement-side hydraulic friction engagement device is gradually increased to transfer torque, while a constant standby pressure of the engagement pressure of the engagement-side hydraulic friction engagement device that is kept in a packed state, which is a state immediately before the engagement-side hydraulic friction engagement device has a torque capacity, is calculated by dividing the engagement pressure at the start of the torque phase of the gear shift by the engagement pressure at the start of the torque phase of the gear shift and the inner load of the gear shift. a control device for a stepped transmission that performs pack learning, which learns and corrects the differential pressure between the engagement pressure at the start of the inertia phase and the standby pressure so as to maintain a constant differential pressure between the engagement pressure at the start of the inertia phase and the standby pressure at the start of the inertia phase; and torque learning, which determines 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 corrects the engagement pressure after the torque phase using the learning value; and (b) when the inertia phase starts 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, the correction of the engagement pressure after the torque phase by the torque learning is prohibited.

According to the first invention, when the inertia phase is initiated with the engagement pressure of the engagement side hydraulic friction engagement device at a predetermined standby pressure, and when, during torque learning, the engagement pressure after the torque phase calculated based on the learning value calculated after the downshift changes to a reduced pressure compared to the engagement pressure before torque learning, correction of the engagement pressure after the torque phase by torque learning is prohibited, thereby preventing the engagement pressure from being continuously corrected to a reduced pressure by a learning value calculated under conditions that are not suitable for learning.

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. 3 is an engagement operation table showing combinations of engagement devices for establishing gear stages of an automatic transmission. 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. 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. 4 is a time chart showing the engagement pressure of an engagement-side engagement device during a downshift of the automatic transmission. 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.

Embodiments of the present invention will now be described in detail with reference to the drawings. Please note that the drawings in the following embodiments have been simplified or modified as appropriate, and the dimensional proportions and shapes of each part are not necessarily drawn accurately.

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 control functions and main parts of the 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 a rotary machine MG, which are sources of driving power for traveling. 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 controls the engine torque Te, which is the output torque of the engine 12, by an electronic control unit 90 (described below) controlling an engine control unit 50, which includes a throttle actuator, fuel injection system, ignition system, and other devices provided on the vehicle 10.

The rotating machine MG is a rotating electric machine that functions as both a motor that generates mechanical power from electrical power and a generator that generates electrical power from mechanical power, and is a so-called motor generator. The rotating machine MG is connected to a battery 54 provided on the vehicle 10 via an inverter 52 provided on the vehicle 10. The inverter 52 is controlled by an electronic control device 90 (described below), which controls the MG torque Tm, 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 engine 12 when it is operating, the MG torque Tm is a powering torque when it rotates in the forward direction, which is the same direction as the engine 12 when it is operating, and a regenerative torque when it rotates in the negative direction, which is the acceleration torque. Specifically, the rotating machine MG generates power for traveling using the 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 electricity using the power of the engine 12 and the driven force input from the drive wheels 14. The electric power generated by the rotating machine MG is stored in the battery 54 via the inverter 52. The battery 54 is an electric storage device that supplies and receives electric power to the rotating machine MG. The term "electric power" also refers to electrical energy unless otherwise specified. The term "motive power" also refers to torque or force unless otherwise specified.

The power transmission device 16 includes a K0 clutch 20, a torque converter 22, an automatic transmission 24, and other components housed within a case 18, which is a non-rotating member attached to the vehicle body. The K0 clutch 20 is a clutch provided between the engine 12 and the rotary machine 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 located in the power transmission path between the torque converter 22 and the drive wheels 14. The torque converter 22 and the automatic transmission 24 each constitute part of the power transmission path between the 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 the output rotating member of the automatic transmission 24, a differential gear 30 connected to the propeller shaft 28, and a pair of drive shafts 32 connected to the differential gear 30. 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. The automatic transmission 24 corresponds to the stepped transmission of the present invention.

The rotary machine MG is power-transmittably connected to the rotary machine connecting shaft 36 within the case 18. The rotary machine MG is power-transmittably connected to the power transmission path between the engine 12 and the drive wheels 14, particularly to the power transmission path between the K0 clutch 20 and the torque converter 22. In other words, the rotary machine MG is power-transmittably connected to the torque converter 22 and the automatic transmission 24 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 force from the driving force sources of the engine 12 and the rotary machine MG to the drive wheels 14, respectively.

The torque converter 22 includes a pump wheel 22a connected to the rotary machine connecting shaft 36 and a turbine wheel 22b connected to the transmission input shaft 38, which is the input rotating member of the automatic transmission 24. The pump wheel 22a is connected to the engine 12 via the K0 clutch 20 and directly 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 is also 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 the turbine shaft that is rotationally driven by the turbine wheel 22b. The torque converter 22 is a fluid transmission device 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 is equipped with an LU clutch 40 that connects the pump impeller 22a and the turbine impeller 22b. The LU clutch 40 is a direct-coupled clutch that connects the input and output rotating members of the torque converter 22, i.e., a well-known lock-up clutch.

The LU clutch 40 switches its operating state, or control state, by changing the LU clutch torque Tlu, which is the torque capacity of the LU clutch 40, using the regulated LU hydraulic pressure PRlu supplied from the hydraulic control circuit 56 provided on 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.

The automatic transmission 24 is a known planetary gear automatic transmission equipped with, for example, one or more planetary gear sets (not shown) and multiple 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 switches between control states such as engaged and disengaged states by changing its respective torque capacity, or CB torque Tcb, using the regulated engagement pressure PRcb supplied from the hydraulic control circuit 56. In this embodiment, the engagement devices CB are composed of, for example, four clutches C1 to C4 and two brakes B1 and B2.

The automatic transmission 24 is a stepped automatic transmission that establishes 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) by engaging one of the engagement devices CB. That is, the automatic transmission 24 establishes a plurality of gear stages according to the combinations of engagement and disengagement of the plurality of engagement devices CB (clutches C1-C4 and brakes B1, B2). Specifically, the automatic transmission 24 shifts gears based on an engagement operation table shown in FIG. 2, which represents the combinations of each engagement device CB required to establish 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 each engagement device CB.

The automatic transmission 24 determines the gear position by the electronic control unit 90 (described later) based on the accelerator opening θacc, which is the amount of accelerator pedal 42 operation by the driver, and the vehicle speed V. The decision to shift gears may be based not only on the accelerator opening θacc but also 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 based not only on the vehicle speed V but also 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 rotational speed of the transmission input shaft 38 and is the input rotational speed of the automatic transmission 24. The AT input rotation speed Ni is also the rotational speed of the output rotating member of the torque converter 22 and is equivalent to the turbine rotation speed Nt, which is the output rotational 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.

The K0 clutch 20 is a wet or dry friction engagement device composed of a multi-plate or single-plate clutch pressed by a hydraulic actuator (not shown). The electronic control unit 90 (described below) controls the operating state of the hydraulic actuator, thereby switching the control state of the K0 clutch 20 between engaged and disengaged states. When the K0 oil pressure PRk0 regulated by the hydraulic control circuit 56 is supplied to the hydraulic actuator in the K0 clutch 20, 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.

When the K0 clutch 20 is engaged, the pump impeller 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. On the other hand, when the K0 clutch 20 is disengaged, power transmission between the engine 12 and the pump impeller 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 impeller 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. In other words, 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.

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, rotating machine connecting shaft 36, torque converter 22, automatic transmission 24, propeller shaft 28, differential gear 30, drive shaft 32, etc. in that order. Furthermore, 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, automatic transmission 24, propeller shaft 28, differential gear 30, drive shaft 32, etc. in that order.

The vehicle 10 is equipped with a mechanical oil pump MOP 58, an electric oil pump EOP 60, a pump motor 62, and other components. The MOP 58 is connected to the pump impeller 22a and is driven to rotate by a driving force source (engine 12, 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 that drives the EOP 60 to rotate. The EOP 60 is driven to rotate by the pump motor 62 to discharge hydraulic oil. The hydraulic oil discharged by the MOP 58 and EOP 60 is supplied to the hydraulic control circuit 56. The hydraulic control circuit 56 supplies the engagement pressure PRcb, K0 hydraulic pressure PRk0, LU hydraulic pressure PRlu, and other pressures adjusted based on the hydraulic oil discharged by at least one of the MOP 58 and EOP 60.

The vehicle 10 is further equipped with an electronic control unit 90, which includes control devices related to vehicle 10 driving control, etc. The electronic control unit 90 is configured to include 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 utilizing the temporary storage function of the RAM and performing signal processing according to programs pre-stored in the ROM. The electronic control unit 90 is configured to include computers for engine control, rotating machine control, hydraulic control, etc. as needed. The electronic control unit 90 corresponds to the control device of the present invention.

The electronic control unit 90 receives various signals (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 the AT input rotation speed Ni; AT output rotation speed O, which corresponds to the vehicle speed V; rotation speed of the rotating machine MG, etc.) based on detected 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 opening sensor 80, brake switch 82, battery sensor 84, oil temperature sensor 86). The signals supplied include the MG rotation speed Nm, which is the rotation speed; the accelerator opening θacc, which is the amount of operation of the accelerator pedal 42 by the driver and indicates the magnitude of the driver's acceleration operation; the throttle opening θth, which is the opening of the electronic throttle valve; the brake-on signal Bon, which is a signal indicating that the brake pedal 44 for operating the wheel brakes is being operated by the driver; the battery temperature THbat, battery charge/discharge current Ibat, and battery voltage Vbat of the battery 54; and the hydraulic oil temperature THoil, which is the temperature of the hydraulic oil in the hydraulic control circuit 56.

The electronic control unit 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 rotating machine MG, CB hydraulic control command signal Scb for controlling the engagement device CB, K0 hydraulic control command signal Sko 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 provided in the vehicle 10 (e.g., engine control unit 50, inverter 52, hydraulic control circuit 56, pump motor 62, etc.).

To realize various controls in the vehicle 10, the electronic control unit 90 is equipped with a hybrid control unit 92 that functions as hybrid control means, a clutch control unit 94 that functions as clutch control means, a gear shift control unit 96 that functions as gear shift control means, and a learning control unit 98 that functions as learning control means.

The hybrid control unit 92 functions as an engine control means, i.e., engine control unit 92a, that controls the operation of the engine 12, and as a rotating machine control means, i.e., rotating machine control unit 92b, that controls the operation of the rotating machine MG via the inverter 52. These control functions are used to perform hybrid drive control using the engine 12 and rotating machine MG, etc.

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 vehicle speed V to a drive amount map. The drive amount map is a relationship that is experimentally or design-based and stored in advance, i.e., a predetermined relationship. The drive amount required is, for example, the drive torque required Trdem at the drive wheels 14. The drive torque required Trdem [Nm] can be viewed as the drive power required Prdem [W] at the current vehicle speed V. The drive amount required can also be the drive force required Frdem [N] at the drive wheels 14, the AT output torque required at the transmission output shaft 26, or the like. When calculating the drive amount required, the AT output rotation speed No, or the like, can be used instead of the vehicle speed V.

The hybrid control unit 92 calculates the target engine torque Tedem for the engine 12 and the target MG torque Tmdem for the rotating machine MG to achieve the required drive torque Trdem, taking into account transmission loss, 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 the engine power Pe, which is the power of the engine 12 that outputs the target engine torque Tedem at the current engine rotation speed Ne. The MG control command signal Sm is, for example, a command value for the power consumption Wm of the rotating machine MG that outputs the target MG torque Tmdem at the current MG rotation speed Nm.

The chargeable power Win of the battery 54 is the maximum power that can be input, which defines the 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 the 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 unit 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 unit 90 based on, for example, the battery charge/discharge current Ibat and the battery voltage Vbat.

When the required drive torque Trdem can be met using only the output of the rotary machine MG, the hybrid control unit 92 sets the driving mode to motor driving (hereinafter referred to as BEV driving). In BEV driving mode, the hybrid control unit 92 performs BEV driving, using only the rotary machine MG as a driving force source with the K0 clutch 20 in a disengaged state. On the other hand, when the required drive torque Trdem cannot be met without using at least the output of the engine 12, the hybrid control unit 92 sets the driving mode to engine driving mode, i.e., hybrid driving (hereinafter referred to as HEV driving) mode.

In HEV driving mode, the hybrid control unit 92 performs engine driving, i.e., HEV driving, using the engine 12 and rotary machine MG as driving power sources with the K0 clutch 20 engaged. On the other hand, even if the required driving torque Trdem can be met solely by the output of the rotary machine MG, the hybrid control unit 92 establishes 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 BEV driving mode and HEV driving mode, based on the required driving torque Trdem, etc.

The clutch control unit 94 controls the K0 clutch 20 according to the driving mode during driving. For example, when a switch to HEV driving mode is determined during BEV driving, the clutch control unit 94 controls the engagement of the K0 clutch 20 to execute start control of the engine 12. For example, when the clutch control unit 94 determines that there is a request to start the engine 12 based on the driving state, it outputs a K0 hydraulic control command signal Sko to the hydraulic control circuit 56 to control the K0 clutch 20 from a disengaged state toward an engaged state so as to obtain a K0 torque Tk0 to transmit to the engine 12 the torque required to crank the engine 12, which is the torque that increases the engine rotation speed Ne.

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 Scb to the hydraulic control circuit 56 as needed to control the shift 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 may be used instead of the vehicle speed V as a related value of the vehicle speed V, and the required drive torque Trdem, required drive force Frdem, throttle opening θth, or the like may be used instead of the accelerator opening θacc as a related value of the accelerator opening θacc.

The learning control unit 98 performs multiple types of learning control, including learning of the engagement pressure PRcb1, which is the command pressure during the engagement transition period of 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. The learning control unit 98 performs, for example, pack learning, which corrects the standby pressure PRconst of the engagement-side engagement device CB1, which is the hydraulic pressure (constant pressure) maintained in a packed state, which is the state immediately before the engagement-side engagement device CB1 produces the CB1 torque Tcb1 (torque capacity), after the automatic transmission 24 has downshifted, and torque learning, which corrects the engagement pressure PRcb1 of the engagement-side engagement device CB1 after the start of the torque phase. Pack learning and torque learning correspond to the predetermined learning controls used when performing a downshift in the present invention.

First, we will explain pack learning. 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 the torque phase start pressure PRcb1t) and the engagement pressure PRcb1 when the start of the inertia phase is detected (hereinafter referred to as the inertia phase start pressure PRcb1i).

When the automatic transmission 24 completes a downshift, the learning control unit 98 calculates the 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 at the time the inertia phase is detected. Here, when a downshift is initiated, a quick apply is performed to temporarily increase the engagement pressure PRcb1 to improve the responsiveness of the hydraulic pressure (actual pressure), and then the engagement pressure PRcb1 (indicated pressure) of the on-coming engagement device CB1 is maintained at a constant standby pressure PRconst until the torque phase is initiated. Therefore, the torque phase start pressure PRcb1t is equal to the standby pressure PRconst. Furthermore, 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).

The learning control unit 98 then calculates the deviation D (K - ΔPRcb1) between the calculated differential pressure ΔPRcb1 and a preset target value K for 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 x D). As a result, the learning value M increases in proportion to the deviation D. Furthermore, the learning value M can take either a positive or 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.

Figure 3 is a time chart that explains the pack learning of the standby pressure PRconst of the on-coming engagement device CB1 that is performed after a downshift of the automatic transmission 24. In Figure 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 on-coming engagement device CB1 that is engaged during a downshift of the automatic transmission 24.

When a downshift of the automatic transmission 24 is initiated at time t1 in Figure 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 hydraulic pressure (actual pressure) responsiveness. From time t2 onwards, the engagement pressure PRcb1 is maintained at standby pressure PRconst, which represents a packed state just before the on-coming engagement device CB1 produces CB1 torque Tcb1. A predetermined time after time t2 has elapsed, the torque phase begins, and at time t3, the engagement pressure PRcb1 begins to increase. Just before time t4, the inertia phase begins, causing the turbine rotation speed Nt to begin to increase. At time t4, the increase in rotation speed from the time the turbine rotation speed Nt began to increase reaches a predetermined value α, and the start of the inertia phase is detected.

In pack learning, after a downshift, the 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, the 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 Figure 3, the standby pressure PRconst indicated by the dashed and dashed lines represents the standby pressure PRconst after being corrected by pack learning. If the learning value M is a positive value M1, the standby pressure PRconst is corrected to the increased side, and if the learning value M is a negative value M2, the standby pressure PRconst is corrected to the decreased side.

Next, we will explain torque learning of the engagement pressure PRcb1 (command pressure) of the on-coming engagement device CB1 after the start of the torque phase. 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 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 the preset target period Term.

When the automatic transmission 24 completes a downshift, the learning control unit 98 detects the actual inertia phase start time tiner2, 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 point at which the increase in turbine rotation speed Nt reaches a predetermined value α when the turbine rotation speed Nt begins to increase (see Figure 4). Upon detecting the actual inertia phase start time tiner2, the learning control unit 98 calculates the period Term (= tiner2 - tiner1) between this 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 - Term), which is the difference between this period Term and a preset target period Term.

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 that is 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 can take either a positive or 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).

Figure 4 is a time chart that explains the 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 Figure 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 (indicated pressure) of the engagement-side engagement device CB1 that is engaged during a downshift of the automatic transmission 24.

When a downshift of the automatic transmission 24 is initiated at time t1 in Figure 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 onwards, the engagement pressure PRcb1 is maintained at the 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, causing the turbine rotation speed Nt to begin to increase. At time t4, the increase in rotation speed from the time the turbine rotation speed Nt began to increase reaches a predetermined value α, and the start of the inertia phase is detected.

In torque learning, after a downshift, the period Term between 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 learned value S of the engagement pressure PRcb1 from the torque phase onwards is calculated based on the time error ΔTerm (= Term - Term), which is the difference between this period Term and the target period Term.

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

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.

However, if the hydraulic response of the engaging-side engagement device CB1 is poor, the standby pressure PRconst will be 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 at the standby pressure PRconst state due to the standby pressure PRconst being set high.

Figure 5 is a time chart showing the engagement pressure PRcb1 of the on-coming engagement device CB1 during a downshift of the automatic transmission 24. In Figure 5, the vertical axes represent, from top to bottom, the AT input rotation speed Ni, the engagement pressure PRcb1 of the on-coming engagement device CB1 (at high torque), and the engagement pressure PRcb1 of the on-coming engagement device CB1 (at low torque). Here, "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 "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.

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

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 Term (i.e., the actual inertia phase start time tiner2 becomes earlier than the target time), the learning value S becomes negative 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 the standby pressure PRconst, for example.

In response to this, the learning control unit 98 prohibits correction (updating) of the engagement pressure PRcb1 through torque learning when the inertia phase is initiated during a downshift of the automatic transmission 24 with the engagement pressure PRcb1 of the engagement-side engagement device CB1 at standby pressure PRconst, and the learned value S calculated after the downshift is a negative value, i.e., when the engagement pressure PRcb1 calculated based on the learned value S changes to a reduced value compared to the engagement pressure PRcb1 before learning.

When the start of the inertia phase is detected, the learning control unit 98 determines whether the inertia phase has started at 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, the learning value S is added to the engagement pressure PRcb1, so a positive value for learning value S indicates that the engagement pressure PRcb1 is to be corrected toward an increased pressure, and a negative value for learning value S indicates that the engagement pressure PRcb1 is to be corrected toward a decreased pressure.

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

Figure 6 is a flowchart illustrating the control operation of the electronic control unit 90, and is a flowchart illustrating the control operation of torque learning executed after a downshift of the automatic transmission 24. This flowchart is executed each time a downshift of the automatic transmission 24 is executed.

First, in a step (hereinafter, "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, then in S20, corresponding to the control function of the learning control unit 98, it is determined whether the permission conditions for learning control are met. As permission conditions for learning control, multiple permission conditions are set for permitting learning control, such as vehicle speed V being equal to or less than a predetermined vehicle speed. Furthermore, if all of the permission conditions are met, it is determined that the permission conditions for learning control are met. If the determination in S20 is negative, this routine is terminated. If the determination in S20 is positive, then in S30, corresponding to the control function of the learning control unit 98, the time error ΔTerm (=Term - Term) between the period Term (tiner2 - tiner1) and the target period Term is calculated. Next, in S40, which corresponds to the control function of the learning control unit 98, the learning value S is calculated based on the time error ΔTerm.

In S50, which corresponds to the control function of the learning control unit 98, it is determined whether the inertia phase begins when the engagement pressure PRcb1 is at 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 begins at standby pressure PRconst and the learning value S is negative, i.e., if the inertia phase begins earlier than the target time (i.e., if the period Term is shorter than the target period Term), the engagement pressure PRcb1 is not corrected (updated), and erroneous learning of a reduced engagement pressure PRcb1 is prevented.

As described above, according to this embodiment, if the inertia phase is initiated when the engagement pressure PRcb1 of the on-coming engagement device CB1 is at standby pressure PRconst, and the corrected engagement pressure PRcb1 calculated based on the learning value S calculated after a downshift changes to a reduced pressure relative to the engagement pressure PRcb1 before learning, correction of the engagement pressure PRcb1 is prohibited, thereby preventing the engagement pressure PRcb1 from being continually corrected to a reduced pressure due to the learning value S calculated under conditions unsuitable for learning.

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-described embodiment, when the inertia phase started with the engagement pressure PRcb1 at standby pressure PRconst and the learning value S was a negative value, correction (updating) of the engagement pressure PRcb1 was 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 Term (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 period. In other words, any requirement that can determine whether the engagement pressure PRcb1 after learning will decrease compared to the engagement pressure PRcb1 before learning can be applied as appropriate.

Furthermore, in the above-described embodiment, the vehicle 10 is a hybrid vehicle using the engine 12 and the rotary machine MG as its driving force source, but the present invention is not limited to hybrid vehicles. For example, the present invention can be applied to a vehicle using only the engine 12 as its driving force source, or even to an electric vehicle using only the rotary machine MG as its driving force source.

Furthermore, in the above-described embodiment, torque learning involves calculating the learning value S to be added to the engagement pressure PRcb1 based on the time error ΔTerm, but 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.

Please note 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.

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 (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,
a control device for a stepped transmission, characterized in that, when the inertia phase is started 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 learning 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.