Control device for stepped transmission

Abstract

To provide a control device of a stepped transmission which can make compatible both shock reduction and gear change responsiveness even if one of engagement-side engagement devices is constituted so as to directly connect a prescribed rotation element and an output shaft at the execution of two-element release engagement downshift control.SOLUTION: By releasing clutches C1, C3 at a transition of two-element release engagement downshift control of an automatic transmission 24, the automatic transmission 24 is brought into a neutral state, and after that, a clutch C4 and a brake B2 are engaged with each other; however, by setting the indication pressure PRc4 of the clutch C4 on the basis of differential rotation ΔNc4 between the rotation elements of the clutch C4 after the automatic transmission 24 is brought into the neutral state, the indication pressure PRc4 can be set to a value at which shock reduction and gear change responsiveness can be obtained. As a result, the deterioration of the gear change responsiveness can be suppressed while reducing a shock occurring at a downshift transition.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to a gear shift control for a stepped transmission provided in a vehicle. [Background technology]

[0002] Patent Document 1 describes a stepped transmission that has a plurality of engagement devices and forms a plurality of gear stages by switching the engagement devices. Patent Document 1 also describes a direction in which, when downshifting the stepped transmission, gear stages are formed by disengaging two disengaging side engagement devices that are disengaged during the downshift and engaging two engaging side engagement devices that are engaged during the downshift. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Application Laid-Open No. 2014-137137 Summary of the Invention [Problem to be solved by the invention]

[0004] However, when downshifting a stepped transmission that switches between two disengagement side engagement devices and two engagement side engagement devices, if one of the engagement side engagement devices is an engagement device that directly connects a predetermined rotational element of the stepped transmission to the output shaft, there is a risk that the shock generated when that engagement device is engaged will be transmitted to the output shaft, causing fluctuations in vehicle acceleration.In response to this, extending the engagement time of the engagement device will reduce the shock, but will also worsen gear shift response.

[0005] The present invention was made against the background of the above circumstances, and its purpose is to provide a control device for a stepped transmission that can achieve both shock reduction and gear shift responsiveness when performing a downshift that switches between two disengagement side engagement devices and two engagement side engagement devices, even when one of the engagement side engagement devices directly connects a specified rotating element to the output shaft. [Means for solving the problem]

[0006] The gist of a first invention is a control device for a stepped transmission that (a) is applied to a stepped transmission that has a plurality of engagement devices and establishes a plurality of gear positions according to a combination of the engagement devices that are engaged, and is configured to disengage a first engagement device and a second engagement device among the plurality of engagement devices and engage a third engagement device and a fourth engagement device among the plurality of engagement devices, so that when downshifting from a first gear position to a second gear position, the first engagement device and the second engagement device are disengaged to establish a neutral state, and then engage the third engagement device and the fourth engagement device; and (b) when downshifting from the first gear position to the second gear position, if either the third engagement device or the fourth engagement device is an output shaft direct-coupled engagement device that directly couples a predetermined rotating element to an output shaft, a differential rotation between the rotating elements of the output shaft direct-coupled engagement devices is determined. The smaller The indicated pressure of the output shaft direct-coupled engagement device Increase pressure It is characterized by the following. [Effects of the Invention]

[0007] According to the first aspect of the present invention, during a transitional period of a downshift, the first engagement device and the second engagement device are disengaged to place the stepped transmission in a neutral state, and then the third engagement device and the fourth engagement device are engaged. However, after the stepped transmission has entered the neutral state, the differential rotation between the rotation elements of the output shaft directly coupled engagement device The smaller The indicated pressure of the output shaft direct coupling engagement device Increase pressureBy doing so, the command pressure can be set to an appropriate value that can reduce shock and achieve good shift response, thereby reducing shock that occurs during the downshift transition and preventing deterioration in shift response.

[0008] Preferably, in the first aspect of the present invention, when the differential rotation between the rotational elements of the output shaft direct engagement device is equal to or greater than a preset threshold, the command pressure of the output shaft direct engagement device is maintained at a low pressure, and the command pressure of the output shaft direct engagement device is increased as the differential rotation between the rotational elements of the output shaft direct engagement device decreases. In this way, it is possible to reduce shocks that occur during a downshift transition and to suppress deterioration in gear shift response.

[0009] Preferably, in the first aspect of the present invention, an intermediate gear is set between the first gear and the second gear, and the intermediate gear is established by engaging the output shaft direct engagement device. In this way, it can be estimated that the differential rotation of the output shaft direct engagement device has become zero when the differential rotation between the synchronous rotation speed calculated from the gear ratio and the output shaft rotation speed of the output shaft when the intermediate gear is established and the input shaft rotation speed of the input shaft of the stepped transmission becomes zero. Even if the command pressure of the output shaft direct engagement device is suddenly increased at this point, only a small shock occurs, so the command pressure can be increased quickly to improve gear change response.

[0010] Also, preferably, in the first aspect of the present invention, the command pressure of the output shaft direct engagement device is configured to be changeable depending on whether shock reduction or gear shift response is to be prioritized, and whether shock reduction or gear shift response is to be prioritized is determined based on the accelerator pedal position or a value related to the accelerator pedal position. In this way, whether shock reduction or gear shift response is to be prioritized is determined based on the accelerator pedal position or a value related to the accelerator pedal position, and the command pressure of the output shaft direct engagement device is changed depending on which of shock reduction and gear shift response is to be prioritized, thereby making it possible to control the command pressure more appropriately. [Brief explanation of the drawings]

[0011] [Figure 1] 1 is a diagram illustrating a schematic configuration of a vehicle to which the present invention is applied, and is also a diagram illustrating main parts of control functions and control systems for various controls in the vehicle. [Figure 2] FIG. 2 is a schematic diagram showing the structure of the automatic transmission of FIG. 1 in a simplified manner. [Figure 3] 3 is an engagement operation table showing combinations of engagement devices for establishing gear stages of the automatic transmission of FIG. 2. [Figure 4] FIG. 2 is a collinear diagram showing the rotational states of the rotating elements that constitute the automatic transmission when fourth, fifth, and ninth gears are established. [Figure 5] 3 is a flowchart illustrating a main part of the control operation of the electronic control device. [Figure 6] 4 is a time chart showing one aspect of a control state when two-element release engagement downshift control of an automatic transmission is executed. [Figure 7] 7 is a time chart showing a different aspect of the control state from that shown in FIG. 6 when two-element release engagement downshift control of an automatic transmission is executed. DETAILED DESCRIPTION OF THE INVENTION

[0012] 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]

[0013] 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 an electric motor 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.

[0014] 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.

[0015] The electric motor MG is a rotating electric machine, a so-called motor generator, that functions as both a motor that generates mechanical power from electric power and a generator that generates electric power from mechanical power. The electric motor MG is connected to a battery 54 provided in the vehicle 10 via an inverter 52 provided in the vehicle 10. The inverter 52 is controlled by an electronic control device 90 (described later), which controls the MG torque Tm, which is the output torque of the electric motor MG. For example, when the rotation direction of the electric motor MG is forward, which is the same as the rotation direction of the engine 12 during operation, 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 electric motor 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 electric motor 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 motor 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 electric motor MG. The electric power also refers to electrical energy unless otherwise specified. The power also refers to torque or force unless otherwise specified.

[0016] The power transmission device 16 includes a K0 clutch 20, a torque converter 22, an automatic transmission 24, and the like, housed within a case 18, which is a non-rotating member attached to the vehicle body. The K0 clutch 20 is a clutch provided between the engine 12 and the electric motor MG in 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.

[0017] 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, an electric motor 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.

[0018] The electric motor MG is connected to the electric motor connecting shaft 36 within the case 18 so as to be able to transmit power. The electric motor 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. In other words, the electric motor MG is connected to the torque converter 22 and the automatic transmission 24 so as to be able to transmit power without passing through the K0 clutch 20. In other words, the torque converter 22 and the automatic transmission 24 each constitute part of the power transmission path between the electric motor MG and the drive wheels 14. The torque converter 22 and the automatic transmission 24 transmit the driving power from the driving power sources of the engine 12 and the electric motor MG to the drive wheels 14, respectively.

[0019] The torque converter 22 includes a pump wheel 22a connected to an electric motor connecting shaft 36 and a turbine wheel 22b connected to a transmission input shaft 38, which is an input rotating member of the automatic transmission 24. The pump wheel 22a is connected to the engine 12 via the K0 clutch 20 and directly connected to the electric motor 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 electric motor 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, electric motor 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.

[0020] 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.

[0021] The automatic transmission 24 is a known planetary gear automatic transmission that includes, for example, one or more planetary gear devices and a plurality of engagement devices CB. The engagement devices CB are hydraulic friction engagement devices that include, for example, multi-plate or single-plate clutches or brakes pressed by a hydraulic actuator, or band brakes tightened by a hydraulic actuator. 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 between an engaged state, a disengaged state, and the like.

[0022] 2 is a schematic diagram showing a simplified structure of the automatic transmission 24. The automatic transmission 24 includes a single-pinion first planetary gear set 42 including a sun gear S1, a pinion P1, a carrier CA1, and a ring gear R1, a double-pinion second planetary gear set 44 including a sun gear S2, multiple meshing pairs of pinions P1 and P2, a carrier CA2, and a ring gear R2, a single-pinion third planetary gear set 46 including a sun gear S3, a pinion P3, a carrier CA3, and a ring gear R3, and a single-pinion fourth planetary gear set 48 including a sun gear S4, a pinion P4, a carrier CA4, and a ring gear R4. The automatic transmission 24 changes the speed of rotation of the transmission input shaft 38 and outputs it from the transmission output shaft 26. The first planetary gear set 42 and the second planetary gear set 44 are so-called Ravigneaux type planetary gear trains in which the carrier CA1 and the carrier CA2 are integrally formed, and the ring gear R1 and the ring gear R2 are integrally formed. As shown in Fig. 2, the multiple engagement devices CB are made up of six hydraulic friction engagement devices: clutch C1, clutch C2, clutch C3, clutch C4, brake B1, and brake B2.

[0023] The sun gear S1 of the first planetary gear set 42 is selectively connected to the case 18 via a brake B1. The carrier CA1 of the first planetary gear set 42 and the carrier CA2 of the second planetary gear set 44 are integrally formed and connected to the transmission input shaft 38. The ring gear R1 of the first planetary gear set 42 and the ring gear R2 of the second planetary gear set 44 are integrally formed and connected to the sun gear S3 of the third planetary gear set 46 and the sun gear S4 of the fourth planetary gear set via a clutch C1, and are also connected to the ring gear R3 of the third planetary gear set 46 via a clutch C3. The sun gear S2 of the second planetary gear set 44 is connected to the sun gear S3 of the third planetary gear set 46 and the sun gear S4 of the fourth planetary gear set 48 via a clutch C2.

[0024] The sun gear S3 of the third planetary gear set 46 and the sun gear S4 of the fourth planetary gear set 48, which are coupled to each other, are connected to the ring gear R1 of the first planetary gear set 42 and the ring gear R2 of the second planetary gear set 44 via the clutch C1, and are also connected to the sun gear S2 of the second planetary gear set 44 via the clutch C2. The carrier CA3 of the third planetary gear set 46 is connected to the transmission output shaft 26. The ring gear R3 of the third planetary gear set 46 is connected to the ring gear R1 of the first planetary gear set 42 and the ring gear R2 of the second planetary gear set 44 via the clutch C3, and is also connected to the case 18 via the brake B2. The carrier CA4 of the fourth planetary gear set 48 is connected to the transmission input shaft 38. The ring gear R4 of the fourth planetary gear set 48 is connected to the carrier CA3 of the third planetary gear set 46 and the transmission output shaft 26 via the clutch C4.

[0025] The automatic transmission 24 is a stepped automatic transmission in which one of a plurality of gears (also referred to as "gear stages") with different speed ratios (also referred to as "gear ratios") γat (=AT input shaft rotation speed Ni / AT output shaft rotation speed No) is established by engaging any of the engagement devices CB. That is, the automatic transmission 24 establishes a plurality of gears according to combinations of engagement and disengagement of the plurality of engagement devices CB (clutches C1 to C4 and brakes B1 and B2). Specifically, the automatic transmission 24 shifts gears based on an engagement operation table shown in FIG. 3, which shows combinations of the engagement devices CB for establishing the gears of the automatic transmission 24. In FIG. 3, "◯" indicates engagement of an engagement device CB, and "X" indicates disengagement of an engagement device CB. As shown in FIG. 3, the automatic transmission 24 is configured to be able to switch between ten gears, from 1st gear (1st) to 10th gear (10th), by changing the combinations of engagement and disengagement of the engagement devices CB.

[0026] 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 79 by the driver (=operator), and the vehicle speed V. Note that 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 shaft rotation speed No. The AT input shaft 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 shaft 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. Therefore, the AT input shaft rotation speed Ni can be expressed in terms of the turbine rotation speed Nt. The AT output shaft rotation speed No is the rotation speed of the transmission output shaft 26, and is the output rotation speed of the automatic transmission 24.

[0027] 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.

[0028] 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 electric motor 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 electric motor 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 electric motor MG. That is, the K0 clutch 20 is a connecting / disconnecting clutch that connects the engine 12 and the electric motor MG when engaged and disconnects the connection between the engine 12 and the electric motor MG when disengaged.

[0029] In the power transmission device 16, when the K0 clutch 20 is engaged, the power output from the engine 12 is transmitted from the engine connecting shaft 34 to the drive wheels 14 via the K0 clutch 20, the electric motor connecting shaft 36, the torque converter 22, the automatic transmission 24, the propeller shaft 28, the differential gear 30, the drive shaft 32, etc. in this order. Similarly, the power output from the electric motor MG is transmitted from the electric motor connecting shaft 36 to the drive wheels 14 via the torque converter 22, the automatic transmission 24, the propeller shaft 28, the differential gear 30, the drive shaft 32, etc. in this order, regardless of the control state of the K0 clutch 20.

[0030] The vehicle 10 is equipped with a MOP 58 which is a mechanical oil pump, an EOP 60 which is an electric oil pump, a pump motor 62, etc. The MOP 58 is connected to the pump impeller 22a and is driven to rotate by a driving power source (the engine 12, the electric motor 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 driving 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 the EOP 60 is supplied to a hydraulic control circuit 56. The hydraulic control circuit 56 supplies an engagement pressure PRcb of the engagement device CB, a K0 hydraulic pressure PRk0 of the K0 clutch 20, an LU hydraulic pressure PRlu of the LU clutch 40, etc., which are each adjusted based on the hydraulic oil discharged by at least one of the MOP 58 and the EOP 60.

[0031] The vehicle 10 further includes an electronic control unit 90 including a control unit related to driving control of the vehicle 10. The electronic control unit 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 unit 90 includes computers for engine control, electric motor control, hydraulic control, etc. as necessary. The electronic control unit 90 corresponds to the control device of the present invention.

[0032] 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 shaft 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 the AT input shaft rotation speed Ni; AT output shaft rotation speed No, which corresponds to the vehicle speed V; MG rotation speed Nm, which is the rotation speed of the electric motor MG; accelerator opening θacc, which is the amount of operation of the accelerator pedal 79 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 83 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).

[0033] The electronic control device 90 outputs various command signals (e.g., an engine control command signal Se for controlling the engine 12, an MG control command signal Sm for controlling the electric motor MG, each engagement pressure control command signal Scb for controlling each 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.).

[0034] 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, and a gear shift control unit 96 that functions as a gear shift control means.

[0035] 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 an electric motor control means, i.e., an electric motor control unit 92b, that controls the operation of the electric motor MG via the inverter 52, and performs hybrid drive control using the engine 12 and the electric motor MG using these control functions.

[0036] 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 shaft rotation speed No, or the like, can be used instead of the vehicle speed V.

[0037] The hybrid control unit 92 calculates a target engine torque Tedem for the engine 12 and a target MG torque Tmdem for the electric motor 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 electric motor 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 electric motor MG that outputs the target MG torque Tmdem at a current MG rotation speed Nm.

[0038] 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.

[0039] When the required drive torque Trdem can be satisfied only by the output of the electric motor 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 electric motor 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.

[0040] In the HEV driving mode, the hybrid control unit 92 performs engine driving, i.e., HEV driving, in which the engine 12 and the electric motor 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 electric motor 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.

[0041] 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 should 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 Sk0 to the hydraulic control circuit 56 to control the K0 clutch 20 from a released state toward an engaged state so as to obtain a K0 torque Tk0 for transmitting to the engine 12 a torque required for cranking the engine 12, which is a torque that increases the engine rotation speed Ne.

[0042] 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 an engagement pressure control command signal Scb 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 shaft 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 a value related to the accelerator opening θacc, instead of the accelerator opening θacc.

[0043] For example, when the gear shift control unit 96 determines to perform a jump downshift from 9th gear to 4th gear, it executes downshift control (hereinafter referred to as two-element release-engagement downshift control) to release two engagement devices CB (clutch C1 and clutch C2) and engage two engagement devices CB (clutch C4 and brake B2). Hereinafter, the engagement device CB that is released during a downshift will be referred to as the release-side engagement device CBoff, and the engagement device CB that is engaged during a downshift will be referred to as the engagement-side engagement device CBon. For example, when downshifting from 9th gear to 4th gear, based on the engagement operation table of FIG. 3, two-element release-engagement downshift control is executed to release the clutch C1 and clutch C3 that correspond to the release-side engagement device CBoff, and to engage the clutch C4 and brake B2 that correspond to the engagement-side engagement device CBon.

[0044] In the two-element release engagement downshift control, the gear shift control unit 96 first disengages the two release-side engagement devices CBoff to place the automatic transmission 24 in a neutral state. Next, the gear shift control unit 96 quickly engages one of the two engagement-side engagement devices CBon. Next, the gear shift control unit 96 engages the two engagement-side engagement devices CBon to establish a gear position after the shift (second gear position in the present invention). Furthermore, when the automatic transmission 24 is in a neutral state, the gear shift control unit 96 temporarily increases the engagement pressure PRcb of the engagement device CB that establishes an intermediate gear position set between the gear position before the shift (first gear position in the present invention) and the gear position after the shift (second gear position in the present invention), thereby transmitting torque to the drive wheels 14 and ensuring the acceleration performance of the vehicle 10.

[0045] Here, if the engagement-side engagement device CBon that is engaged first of the two engagement-side engagement devices CBon is an engagement device CB that directly couples a predetermined rotational element of the automatic transmission 24 with the transmission output shaft 26 (hereinafter referred to as the output shaft direct-coupled engagement device CBdc), then even if the automatic transmission 24 is in a neutral state, an engagement shock when the output shaft direct-coupled engagement device CBdc is engaged is transmitted from the transmission output shaft 26 to the drive wheels 14. As a result, the engagement shock appears as a change in vehicle acceleration G (vehicle longitudinal acceleration). One way to suppress this engagement shock that occurs when the output shaft direct-coupled engagement device CBdc is engaged is to lengthen the engagement time of the output shaft direct-coupled engagement device CBdc, but this would result in a problem of poor gear shift response.

[0046] In the automatic transmission 24 of this embodiment, for example, downshift control from 9th gear (9th) to 4th gear (4th) corresponds to the dual-element release-engagement downshift control described above. In a jump downshift from 9th gear (9th) to 4th gear (4th), the clutches C1 and C3 are released, and the clutch C4 and brake B2 are engaged. The clutch C4 is interposed between the ring gear R4 of the fourth planetary gear set 48 and the transmission output shaft 26 so as to be able to connect and disconnect between them. Therefore, the clutch C4 corresponds to the output shaft direct-coupled engagement device CBdc that directly couples the ring gear R4 of the fourth planetary gear set 48, which serves as a predetermined rotating element, to the transmission output shaft 26. In the dual-element release-engagement downshift control from 9th gear (9th) to 4th gear (4th) in the automatic transmission 24, the 9th gear corresponds to the first gear of the present invention, and the 4th gear corresponds to the second gear of the present invention. Furthermore, the clutches C1 and C3 correspond to the first and second engagement devices of the present invention, and the clutch C4 and brake B2 correspond to the third and fourth engagement devices of the present invention. Furthermore, the clutch C4 also corresponds to the output shaft direct-coupled engagement device of the present invention.

[0047] Fig. 4 is a collinear diagram showing the rotational states of the rotating elements constituting the automatic transmission 24 when fourth gear (4th), fifth gear (5th), and ninth gear (9th) are engaged. The vertical lines in Fig. 4 indicate, from left to right, the sun gear S1 of the first planetary gear set 42, the carrier CA1 of the first planetary gear set 42 and the carrier CA2 of the second planetary gear set 44, the ring gear R1 of the first planetary gear set 42 and the ring gear R2 of the second planetary gear set 44, the sun gear S2 of the second planetary gear set 44, the ring gear R3 of the third planetary gear set 46, the carrier CA3 of the third planetary gear set 46, the sun gear S3 of the third planetary gear set 46 and the sun gear S4 of the fourth planetary gear set 48, the carrier CA4 of the fourth planetary gear set 48, and the ring gear R4 of the fourth planetary gear set 48, respectively.

[0048] In addition, in FIG. 4, the solid lines indicate the rotational state in 9th gear (9th), and the intersections of each rotating element with the solid lines indicate the rotational speeds of the corresponding rotating elements. The dashed lines indicate the rotational state in 5th gear (5th), and the intersections of each rotating element with the dashed lines indicate the rotational speeds of the corresponding rotating elements. The dashed lines indicate the rotational state in 4th gear (4th), and the intersections of each rotating element with the dashed lines indicate the rotational speeds of the corresponding rotating elements. When downshifting from 9th gear (9th) to 4th gear (4th), the rotational state in 9th gear (9th), shown by the solid lines, transitionally passes through 5th gear (5th), shown by the dashed lines, and changes to the rotational state in 4th gear (4th), shown by the dashed lines. When downshifting from 9th gear (9th) to 4th gear (4th), 5th gear (5th) corresponds to an intermediate gear.

[0049] Fourth gear (4th) and fifth gear (5th) are established by engaging clutch C4, which is the output shaft direct engagement device CBdc. Immediately after the start of a downshift, a differential rotation speed ΔNc4, as shown in FIG. 4, exists between the rotating elements connected by clutch C4. From this state, the rotation speed of ring gear R4 is increased to the AT output shaft rotation speed No. If clutch C4 is suddenly engaged at this time, the engagement shock of clutch C4 will be transmitted to the drive wheels 14 via transmission output shaft 26, which could cause fluctuations in vehicle acceleration G.

[0050] In contrast, when the shift control unit 96 executes two-element release engagement downshift control, if the engagement side engagement device CBon that establishes the intermediate gear stage is the output shaft direct engagement device CBdc that directly connects a specified rotating element of the automatic transmission 24 to the transmission output shaft 26, it sets the command pressure PRcbdc of the output shaft direct engagement device CBdc according to the differential rotation ΔNcbdc between the rotating elements connected by the output shaft direct engagement device CBdc.

[0051] When the two-element release engagement downshift control is initiated, the shift control unit 96 determines whether one of the engagement-side engagement devices CBon that establish the intermediate gear position corresponds to the output shaft direct engagement device CBdc that directly connects a predetermined rotational element of the automatic transmission 24 to the transmission output shaft 26. If one of the engagement-side engagement devices CBon that establishes the intermediate gear position corresponds to the output shaft direct engagement device CBdc that directly connects the predetermined rotational element to the transmission output shaft 26, the shift control unit 96 constantly calculates the differential rotation ΔNcbdc between the rotational elements connected by the output shaft direct engagement device CBdc.

[0052] Hereinafter, a downshift from 9th gear to 4th gear, which corresponds to the above-described two-element disengagement downshift control, will be described as an example in the automatic transmission 24 of this embodiment. In a downshift from 9th gear to 4th gear, the clutch C4 is engaged in 4th gear and 5th gear, and the clutch C4 directly connects the ring gear R4 of the fourth planetary gear set 48 to the transmission output shaft 26. Furthermore, 5th gear is set as an intermediate gear, the clutch C4 corresponds to the output shaft direct engagement device CBdc, and the differential rotation ΔNc4 between the rotating elements of the clutch C4 corresponds to the differential rotation ΔNcbdc between the rotating elements of the output shaft direct engagement device CBdc.

[0053] When executing dual-element release engagement downshift control, it is necessary to constantly calculate the differential rotation speed ΔNc4 between the rotating elements of clutch C4. However, while the rotational speed of one of the rotating elements connected by clutch C4 (AT output shaft rotation speed No) can be detected by output shaft rotation speed sensor 74, the rotational speed of the other rotating element cannot be detected because no rotational speed sensor is provided. Therefore, the shift control unit 96 estimates the differential rotation speed ΔNc4 of clutch C4 from the differential rotation speed ΔNsyc (Nsyc-Ni) between the AT input shaft rotation speed Ni and the synchronous rotation speed Nsyc (=γ5th×No), which is calculated from the speed ratio γ5th of fifth gear (5th), which is an intermediate gear, and the AT output shaft rotation speed No. For example, if the differential rotation ΔNsyc becomes zero, it is presumptively determined that the differential rotation speed ΔNc4 of clutch C4 has become zero.

[0054] The shift control unit 96 constantly calculates the differential rotation speed ΔNsyc between the AT input shaft rotation speed Ni and the synchronous rotation speed Nsyc and sets the command pressure PRc4 for the clutch C4 based on the calculated differential rotation speed ΔNsyc. When the differential rotation speed ΔNsyc is large, for example, when it is equal to or greater than a preset threshold value α1, the shift control unit 96 maintains the command pressure PRc4 for the clutch C4 at a low hydraulic pressure that maintains the automatic transmission 24 in a neutral or approximately neutral state. When the clutch C4 begins to engage, the release side engagement devices CBoff, i.e., the clutch C1 and the clutch C3, are both controlled to a released or approximately released state. At this time, the automatic transmission 24 is in a neutral or approximately neutral state. In this state, the turbine rotation speed Nt (i.e., the AT input shaft rotation speed Ni) is increased by torque transmitted from at least one of the engine 12 and the electric motor MG, thereby performing downshift control. The threshold value α1 is a value determined in advance through experimentation or design.

[0055] When the differential rotation ΔNsyc becomes equal to or smaller than the threshold value α1, the gear shift control unit 96 increases the command pressure PRc4 for the clutch C4 as the differential rotation ΔNsyc becomes smaller, and when the differential rotation ΔNsyc becomes zero, the command pressure PRc4 is increased to the hydraulic pressure at which the clutch C4 is fully engaged. When the differential rotation ΔNsyc is zero, the differential rotation ΔNc4 of the clutch C4 is also estimated to be zero, so almost no engagement shock occurs even if the increasing gradient of the command pressure PRc4 for the clutch C4 becomes steep.

[0056] The shift control unit 96 can also change the command pressure PRc4 for the clutch C4 depending on whether to prioritize shift response or shock reduction during a downshift transition. Whether to prioritize shift response or shock reduction during shifting is determined based on, for example, whether the accelerator pedal position θacc is equal to or greater than a predetermined threshold value α2. The shift control unit 96 determines to prioritize shift response when the accelerator pedal position θacc at the time of starting engagement of the clutch C4 is equal to or greater than the threshold value α2, whereas it determines to prioritize shock reduction when the accelerator pedal position θacc is less than the threshold value α2. The shift control unit 96 stores different relationship maps for the command pressure PRc4 when prioritizing shift response and when prioritizing shock reduction, and switches between the relationship maps depending on whether to prioritize shift response or shock reduction. The threshold value α2 is a value determined in advance through experimentation or design.

[0057] The relationship map is, for example, a two-dimensional map of differential rotation ΔNsyc and command pressure PRc4 for clutch C4, and is set so that the command pressure PRc4 increases as the differential rotation ΔNsyc decreases. Furthermore, the relationship map for prioritizing shift response sets a higher command pressure PRc4 relative to differential rotation ΔNsyc than the relationship map for prioritizing shock reduction. Therefore, when the relationship map for prioritizing shift response is applied, the clutch C4 is engaged more quickly, improving shift response compared to when the relationship map for prioritizing shock reduction is applied. On the other hand, when the relationship map for prioritizing shock reduction is applied, although the shift time of the clutch C4 is longer, shock generated when the C4 clutch is engaged is reduced compared to when the relationship map for prioritizing shift response is applied. In this way, the command pressure PRc4 for clutch C4 is changed depending on whether shift response or shock reduction is prioritized, thereby enabling downshift control to be performed in accordance with the driver's intentions.

[0058] 5 is a flowchart illustrating the main control operations of the electronic control unit 90. More specifically, the flowchart illustrates the control operations that can achieve both reduced shock and improved gear shift response during dual-element release engagement downshift control, which disengages two release-side engagement devices CBoff and engages two engagement-side engagement devices CBon. This flowchart is executed repeatedly while the vehicle is traveling.

[0059] First, in step S10 (hereinafter, "step" will be omitted) corresponding to the control function of the shift control unit 96, it is determined whether dual-element release-engagement downshift control is being executed, in which two release-side engagement devices CBoff are released and two engagement-side engagement devices CBon are engaged. If the determination in S10 is negative, this routine is terminated. On the other hand, if a downshift from 9th gear (9th) to 4th gear (4th) is determined, for example, the determination in S10 is positive. If the determination in S10 is positive, it is determined in S20, corresponding to the control function of the shift control unit 96, whether an intermediate gear has not yet reached synchronized rotation. For example, in a downshift from 9th gear to 4th gear (4th), it is determined whether 5th gear (5th), which is the intermediate gear, has not yet reached synchronized rotation. In this case, it is determined whether the AT input shaft rotation speed Ni has not yet reached the synchronous rotation speed Nsyc (= No × γ5th), which is calculated from the gear ratio γ5th at 5th gear (5th) and the AT output shaft rotation speed No.

[0060] If the judgment in S20 is negative, the process proceeds to S80, which corresponds to the control function of the shift control unit 96, and the AT input shaft rotation speed Ni is controlled by controlling the engagement pressure PRcb of the release side engagement device CBoff, and conventional control is executed to quickly engage the engagement side engagement device CBon when the release side engagement device CBoff is released.

[0061] If the determination in S20 is positive, then in S30, which corresponds to a control function of the shift control unit 96, it is determined whether the engagement device CB that is engaged when an intermediate gear is established is the output shaft direct-coupled engagement device CBdc that directly couples a predetermined rotational element of the automatic transmission 24 to the transmission output shaft 26. In this embodiment, in a downshift from 9th gear (9th) to 4th gear (4th), the clutch C4 that establishes 5th gear (5th), which is an intermediate gear, is the engagement device CB that directly couples the ring gear R4, which serves as the predetermined rotational element, to the transmission output shaft 26, and therefore the determination in S30 is positive in such a downshift. On the other hand, for example, in a downshift from 9th gear (9th) to 3rd gear (3rd), although two-element release engagement downshift control is executed, the clutch C4 that is directly coupled to the transmission output shaft 26 is not engaged, and therefore the determination in S30 is negative.

[0062] If the determination in S30 is negative, conventional two-element release engagement downshift control is executed in S70, which corresponds to the control function of the shift control unit 96. Specifically, when the two release-side engagement devices CBoff are disengaged and the automatic transmission 24 switches to the neutral state, one engagement-side engagement device CBon is quickly engaged, and then the other engagement-side engagement device CBon is engaged. If the determination in S30 is positive, in S40, which corresponds to the control function of the shift control unit 96, it is determined whether the accelerator pedal 79 is continuously depressed based on whether the accelerator opening θacc is equal to or greater than the threshold value α2. If the determination in S40 is positive, in S50, which corresponds to the control function of the shift control unit 96, the command pressure PRcbdc of the output shaft direct engagement device CBdc is increased in accordance with the differential rotation speed ΔNsyc, which is calculated as needed, based on a relationship map that prioritizes shift response. On the other hand, if the judgment of S40 is negative, in S60, which corresponds to the control function of the shift control unit 96, the command pressure PRcbdc of the output shaft direct-coupled engagement device CBdc is increased in accordance with the differential rotation ΔNsyc calculated at any time based on a relationship map that prioritizes shock reduction.

[0063] Figures 6 and 7 are time charts showing the control state when dual-element release engagement downshift control is executed for the automatic transmission 24. Both Figures 6 and 7 show dual-element release engagement downshift control from ninth gear (9th) to fourth gear (4th). Figure 6 shows the control state when priority is given to gear shift responsiveness by maintaining the accelerator pedal 79 depressed, while Figure 7 shows the control state when priority is given to shock reduction by releasing the accelerator pedal 79 during a downshift.

[0064] First, we will explain the case where priority is given to shift response in two-element release-engagement downshift control, as shown in Figure 6. In Figure 6, the horizontal axis represents time t [msec], and the vertical axis represents, from top to bottom, accelerator opening θacc, turbine rotation speed Nt [rpm] which is the same value as AT input shaft rotation speed Ni, vehicle acceleration G [m / s2], command pressure (engagement pressure) PRc1 [kPa] for clutch C1, command pressure (engagement pressure) PRc2 [kPa] for clutch C2, command pressure (engagement pressure) PRc3 [kPa] for clutch C3, command pressure (engagement pressure) PRc4 [kPa] for clutch C4, command pressure (engagement pressure) PRb1 [kPa] for brake B1, and command pressure (engagement pressure) PRb2 [kPa] for brake B2, respectively. In addition, the hydraulic pressures PRpacc1, PRpacc2, PRpacc3, PRpacc4, and PRpacb2 indicated by dashed lines in Figure 6 represent the pack end pressures at which the respective engagement devices CB are in a state immediately before they begin to deliver torque capacity. The command pressure PRb1max for the brake B1 represents the maximum pressure (maximum pressure PRb1max) at which the brake B1 is fully engaged. In 9th gear (9th), 5th gear (5th), and 4th gear (4th), the brake B1 is engaged, so the command pressure PRb1 for the brake B1 is maintained at the maximum pressure PRb1max during downshifts.

[0065] At time t1 shown in FIG. 6, a determination is made to execute two-element release engagement downshift control from 9th gear (9th) to 4th gear (4th) as the accelerator pedal stroke θacc increases. As a result, release of one clutch C1, one of the two release-side engagement devices CBoff, begins at time t1. At time t2, engagement of clutch C4, which is one of the two engagement-side engagement devices CBon and also the output shaft direct-coupled engagement device CBdc, begins. After a quick apply is performed to temporarily increase the command pressure PRc4, the clutch C4 is maintained at a standby pressure near the pack-end pressure PRpacc4. Therefore, the C4 torque Tc4, which is the torque capacity of the clutch C4, is maintained at zero or a value close to zero. At time t3, release of the other clutch C3, one of the two release-side engagement devices CBoff, begins. Also, at time t3, the command pressure PRc1 for clutch C1 drops sufficiently, and the command pressure PRc3 for clutch C3 also starts to drop. Therefore, after time t3, the automatic transmission 24 switches to a neutral state or a substantially neutral state, and the turbine rotation speed Nt is increased by at least one of the engine torque Te and the MG torque Tm (the inertia phase begins). When the inertia phase begins, the command pressure PRc4 for clutch C4 is set by applying the differential rotation speed ΔNsyc (=Nsyc-Nt) between the turbine rotation speed Nt (i.e., the AT input shaft rotation speed Ni) and the synchronous rotation speed Nsyc in 5th gear to a relationship map that is used when prioritizing shift response. Between time t3 and time t5, the differential rotation speed ΔNsyc is sufficiently large, so the command pressure PRc4 barely increases.

[0066] At time t4, control is initiated to temporarily increase the command pressure PRc2 of the clutch C2, which is engaged when fifth gear 5th, an intermediate gear, is established. By temporarily increasing the command pressure PRc2 of the clutch C2, fifth gear 5th is temporarily established in the automatic transmission 24, making it possible to generate vehicle acceleration G. Next, at time t5, engagement of the brake B2, which is the other of the two on-coming engagement devices CBon, is initiated. Specifically, at time t5, a quick apply is executed in which the command pressure PRb2 of the brake B2 is temporarily increased, and then the hydraulic pressure is maintained at a level close to the pack end pressure PRpacb2.

[0067] After time t5, when the differential rotation ΔNsyc becomes equal to or less than threshold value α1, the command pressure PRc4 is increased as the differential rotation ΔNsyc decreases. Since a relationship map that prioritizes gear shift responsiveness is applied while the accelerator pedal 79 is maintained depressed, the command pressure PRc4 is increased at a relatively steep upward gradient after time t5. When it is determined at time t6 that the differential rotation ΔNsyc becomes equal to or less than threshold value α3, at which the differential rotation ΔNsyc can be determined to be zero, the command pressure PRc4 for the clutch C4 is rapidly increased to the hydraulic pressure at which the clutch C4 is fully engaged after time t6. Although the command pressure PRc4 for the clutch C4 is rapidly increased after time t6, the differential rotation ΔNc4 for the clutch C4 can be estimated to be zero or approximately zero. Therefore, the engagement shock generated at the time of engagement is reduced, and there is almost no fluctuation in the vehicle acceleration G due to the engagement shock being transmitted to the drive wheels 14 via the transmission output shaft 26.

[0068] In Figure 6, the turbine rotation speed Nt and vehicle acceleration G shown by the dashed lines after time t6 represent the behavior when the command pressure PRc4 for clutch C4 is suddenly increased when the clutch C1 and clutch C3, which are the disengaging engagement devices CBoff, enter a disengaged state. In this case, clutch C4 is suddenly engaged while the differential rotation speed ΔNc4 of clutch C4 is large, causing a pull-in of turbine rotation speed Nt as shown by the dashed line. Furthermore, the effect of this pull-in is transmitted to the drive wheels 14 via the transmission output shaft 26, causing the vehicle acceleration G to fluctuate as shown by the dashed line.

[0069] Next, a case where shock reduction is prioritized in the dual-element release engagement downshift control shown in FIG. 7 will be described. In FIG. 7, drive torque Tr is added to the time chart of FIG. 6. At time t1 shown in FIG. 7, a decision is made to execute dual-element release engagement downshift control from 9th gear (9th) to 4th gear (4th) as the accelerator pedal opening θacc increases. At time t1, the release of one clutch C1 of the two on-coming engagement devices CBon begins. At time t2, the engagement of clutch C4, which is one of the two on-coming engagement devices CBon and also the output shaft direct-coupled engagement device CBdc, begins. After a quick apply is performed to temporarily increase the command pressure PRc4, the clutch C4 is maintained at a standby pressure near the pack end pressure PRpacc4. Therefore, the torque capacity of the clutch C4, C4 torque Tc4, is maintained at zero or a value close to zero. At time t3, the release of the other clutch C3 of the two release-side engagement devices CBoff begins. As the clutch C3 starts to be released at time t3, the automatic transmission 24 is in a neutral state or a substantially neutral state from time t3 onwards.

[0070] At time t4, the accelerator pedal 79 is released and the accelerator opening θacc becomes zero. As the accelerator opening θacc decreases, it is determined that shock reduction is to be prioritized. Even when the accelerator opening θacc becomes zero, the synchronization compensation torque Tsyc required to proceed with the downshift, i.e., to increase the turbine rotation speed Nt, is still output. After a predetermined time has elapsed from time t3, the turbine rotation speed Nt begins to increase (i.e., the inertia phase begins). When the inertia phase begins, the command pressure PRc4 for the clutch C4 is set based on the differential rotation ΔNsyc. Between time t3 and time t5, the differential rotation ΔNsyc is sufficiently large that the command pressure PRc4 is hardly increased.

[0071] At time t5, control is started to temporarily increase the command pressure PRc2 of the clutch C2, which is engaged when the intermediate gear position, 5th, is established. At time t6, engagement of the brake B2, which is the other of the two engagement-side engagement devices CBon, is started.

[0072] Furthermore, after time t5, when the differential rotation ΔNsyc, which is calculated as needed, becomes equal to or less than threshold value α1, command pressure PRc4 is increased as differential rotation ΔNsyc decreases. In the example of FIG. 7, command pressure PRc4 is set based on a relationship map that prioritizes shock reduction, so the increase gradient of command pressure PRc4 for clutch C4 after time t5 is gentler than when priority is given to shift response as shown in FIG. 6. Therefore, although the shift time is longer than when priority is given to shift response, the engagement shock that occurs when clutch C4 is engaged is further reduced. At time t7, when it is determined that differential rotation ΔNsyc has become equal to or less than threshold value α3, at which it can be determined that differential rotation ΔNsyc is zero, command pressure PRc4 for clutch C4 is increased to the hydraulic pressure at which clutch C4 is fully engaged. The increasing gradient of the command pressure PRc4 of clutch C4 after time t7 becomes higher than before time t7, but since the differential rotation ΔNc4 of clutch C4 is estimated to be zero or approximately zero, the engagement shock that occurs at the time of engagement becomes small, and the fluctuation in vehicle acceleration G caused by the engagement shock being transmitted to the drive wheels 14 side via the transmission output shaft 26 is reduced.

[0073] Furthermore, even after the time when it is determined that the differential rotation speed ΔNc4 is zero, the gradient of increase in the command pressure PRc4 for clutch C4 can be changed depending on whether priority is given to shift response or shock reduction. For example, the gradient of increase in the command pressure PRc4 from time t7 onwards when priority is given to shock reduction as shown in Figure 7 is gentler than the gradient of increase in the command pressure PRc4 from time t6 onwards when priority is given to shift response as shown in Figure 6. In this way, by changing the gradient of increase in the command pressure PRc4 even after the differential rotation speed ΔNc4 becomes zero depending on whether priority is given to shift response or shock reduction, the effects of shift response and shock reduction can be further improved.

[0074] As described above, according to this embodiment, during a transitional period of two-element release-engagement downshift control of the automatic transmission 24, for example, from ninth gear (9th) to fourth gear (4th), the automatic transmission 24 is placed in a neutral state by disengaging the clutches C1 and C3, and then the clutch C4 and the brake B2 are engaged. However, by setting the command pressure PRc4 for the clutch C4 based on the differential rotation ΔNc4 between the rotating elements of the clutch C4 after the automatic transmission 24 has entered the neutral state, the command pressure PRc4 can be set to an appropriate value that can reduce shock and achieve good gear shift responsiveness. As a result, it is possible to reduce shock that occurs during the downshift transitional period while suppressing deterioration in gear shift responsiveness.

[0075] 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.

[0076] For example, the structure of the automatic transmission 24 in the above-described embodiment is merely one example, and the structure of the automatic transmission can be modified as appropriate. In short, the present invention can be applied as appropriate to a stepped transmission that is capable of executing two-element release engagement downshift control, and in which one of the engagement-side engagement devices CBon that is engaged during execution of the two-element release engagement downshift control is an engagement device CB that forms an intermediate gear and is directly connected to the output shaft.

[0077] In the above embodiment, a downshift from 9th gear (9th) to 4th gear (4th) in the automatic transmission 24 is described as one mode, but the present invention is not necessarily limited to a downshift from 9th gear (9th) to 4th gear (4th). For example, the present invention can also be applied to a downshift from 10th gear (10th) to 4th gear (4th) in the automatic transmission 24.

[0078] Furthermore, in the above-described embodiment, in the two-element release engagement downshift control, even after the differential rotation ΔNc4 of the clutch C4 becomes zero or approximately zero, the increasing gradient of the command pressure PRc4 is changed depending on whether priority is given to shift response or shock reduction, but after the differential rotation ΔNc4 becomes zero or approximately zero, the increasing gradient of the command pressure PRc4 may remain the same.

[0079] Furthermore, in the above-described embodiment, it was determined whether to prioritize shock reduction or gear shift responsiveness based on the accelerator pedal opening θacc, but it would also be acceptable to make the determination based on a related value related to the accelerator pedal opening θacc, such as the required drive torque Tr.

[0080] Furthermore, in the above-described embodiment, the differential rotation ΔNcbdc between the rotating elements of the output shaft direct engagement device CBdc was estimated based on the differential rotation ΔNsyc between the AT input shaft rotation speed Ni and the synchronous rotation speed Nsyc calculated based on the speed ratio γat of the intermediate gear stage. However, it is also possible to provide sensors that detect the rotation speed of each rotating element of the output shaft direct engagement device CBdc, and directly calculate the differential rotation ΔNcbdc of the output shaft direct engagement device CBdc based on the rotation speeds detected by these sensors.

[0081] 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]

[0082] 24: Automatic transmission (stepped transmission) 90: Electronic control device (control device) CB: Engagement device C1: Clutch (first engagement device) C3: Clutch (second engagement device) C4: Clutch (third engagement device, output shaft direct-coupled engagement device) B2: Brake (fourth engagement device)

Claims

[Claim 1] A control device for a stepped transmission that is applied to a stepped transmission that includes a plurality of engagement devices and establishes a plurality of gear stages according to a combination of the engagement devices that are engaged, and that is configured to disengage a first engagement device and a second engagement device among the plurality of engagement devices and engage a third engagement device and a fourth engagement device among the plurality of engagement devices, so that when downshifting from a first gear stage to a second gear stage, the first engagement device and the second engagement device are disengaged to establish a neutral state, and then the third engagement device and the fourth engagement device are engaged, When performing a downshift from the first gear position to the second gear position, if either the third engagement device or the fourth engagement device is an output shaft direct engagement device that directly couples a predetermined rotation element with an output shaft, the smaller the differential rotation between the rotation elements of the output shaft direct engagement device, the greater the command pressure of the output shaft direct engagement device. A control device for a stepped transmission characterized by:

Images