Vehicle control device

Abstract

To provide a control device of a vehicle capable of suppressing a shift shock due to a decrease in an indication pressure in a control device of a vehicle that learns and corrects an indication pressure of a release side engagement device and an engagement side engagement device during coast down shifting of an automatic transmission.SOLUTION: When executing coast down shifting to a first speed gear stage 1st of an automatic transmission 24 when a vehicle speed V is lower than a first predetermined vehicle speed V1, reflection gains K1 and K2 for previously learned learning values ΔPRcb1 and ΔPRcb2 are made small as compared to when the vehicle speed V is the first predetermined vehicle speed V1 or higher so that indication pressures PRcb1 and PRcb2 are inhibited from being excessively decompressed. Consequently, during coast down shifting after the vehicle is stopped, blow-up of a turbine rotation speed Nt (namely, AT input shaft rotation speed Ni) of the automatic transmission 24 is inhibited, and a shift shock attributed to the blow-up can be inhibited.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to a control device for a vehicle equipped with a stepped automatic transmission. [Background technology]

[0002] Patent document 1 describes a system equipped with a stepped automatic transmission in which the command pressures of the release-side engagement device and the engagement-side engagement device are corrected by learning during coast-downshifting of the automatic transmission, and when the change in the learning values of the release-side engagement device and the engagement-side engagement device becomes a negative value (the release-side engagement device disengages slowly and the engagement-side engagement device engages quickly), updating of the learning value of the release-side engagement device is prohibited or updating of the learning value of the engagement-side engagement device is prohibited. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Application Publication No. 2018-17310 Summary of the Invention [Problem to be solved by the invention]

[0004] When a coast-downshift to first gear is performed while the vehicle is traveling at low speed, the turbine rotation speed reaches the synchronous rotation speed early, and the shift control is completed relatively quickly. At this time, the command pressure for at least one of the disengagement side engagement device and the engagement side engagement device is learned to decrease. When a coast-downshift to first gear is then performed after the vehicle has stopped, the input shaft rotation speed of the automatic transmission increases, which can cause a shift shock due to the turbine increase.

[0005] The present invention has been made against the background of the above circumstances, and its purpose is to provide a vehicle control device that learns and corrects the command pressure of the disengagement side engagement device and the engagement side engagement device during coast down shifting of an automatic transmission, and that can suppress shift shock caused by an increase in input shaft rotation speed. [Means for solving the problem]

[0006] The gist of the first invention is (a) An engine, a torque converter, The engagement device includes a plurality of engagement devices. Clutch-to-clutch control for disengaging a disengaging side engaging device and engaging an engaging side engaging device A stepped automatic transmission that shifts between multiple gears by and, and the automatic transmission is adapted to a vehicle equipped with the The aforementioned Indicated pressure for disengagement side engagement device PRcb1 and correcting the automatic transmission. To 1st gear Engaged during coast down shift The aforementioned Indicated pressure of engaging side engaging device PRcb2 A vehicle control device including a learning control unit that learns and corrects (b) When a coast down shift to the first gear of the automatic transmission is performed, the learning control unit updates the command pressure PRcb1 of the disengaging engagement device to a new command pressure (PRcb1+K1×ΔPRcb1) by adding a value obtained by multiplying a learned value ΔPRcb1 calculated so as to reduce an inertia phase start time error, which is the error between an inertia phase start time from the actually measured shift start time until the start of an inertia phase and a target value thereof, by a preset reflection gain K1, to the command pressure PRcb1 of the disengaging engagement device; and updates the command pressure PRcb2 of the engaging side engagement device to a new command pressure (PRcb2+K2×ΔPRcb2) by adding a value obtained by multiplying a learned value ΔPRcb2 calculated so as to suppress a jump in the turbine rotation speed of the torque converter that occurs during the inertia phase, by a preset reflection gain K2, to the command pressure PRcb2 of the engaging side engagement device; (c). The learning control unit controls the automatic transmission when the vehicle speed is less than a predetermined vehicle speed. The aforementioned When coasting down to 1st gear, last time Learning value learned during coast down shift ΔPRcb1 and ΔPRcb2 against The aforementioned Reflection Gain K1 and K2 is made smaller than when the vehicle speed is equal to or higher than the predetermined vehicle speed. [Effects of the Invention]

[0007] According to the first aspect of the present invention, when a coastdown shift to first gear of the automatic transmission is performed when the vehicle speed is less than a predetermined vehicle speed, When coasting down Reflection gain for learned learning value K1 and K2 but , vehicle speedSince the command pressure is smaller than when the vehicle speed is above a predetermined speed, excessive reduction in the command pressure is prevented. As a result, when coasting downshifting after the vehicle has stopped, the increase in the input shaft rotation speed of the automatic transmission can be suppressed, and the shift shock caused by this increase in speed can be suppressed. [Brief explanation of the drawings]

[0008] [Figure 1] 1 is a diagram illustrating a schematic configuration of a vehicle to which the present invention is applied, and is also a diagram illustrating main parts of control functions and control systems for various controls in the vehicle. [Figure 2] 2 is an engagement operation table showing combinations of engagement devices for establishing gear stages of the automatic transmission of FIG. 1. [Figure 3] 6 is a time chart for explaining a control state during coast down from second gear to first gear. [Figure 4] 4 is a flowchart for explaining the main control operations of the electronic control device. DETAILED DESCRIPTION OF THE INVENTION

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

[0010] Fig. 1 is a diagram illustrating the schematic configuration of a vehicle 10 to which the present invention is applied, as well as a diagram illustrating the main parts of the control functions and control systems for various controls in the vehicle 10. In Fig. 1, the vehicle 10 is a hybrid vehicle equipped with an engine 12 and 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.

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

[0012] The electric motor MG is a so-called motor generator that functions as a motor that generates mechanical power from electric power and as 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), thereby controlling 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 when the engine 12 is operating, the MG torque Tm is a powering torque when the positive torque is on the acceleration side, and a regenerative torque when the negative torque is on the deceleration side.

[0013] The electric motor MG generates power for traveling using electric power supplied from a battery 54 via an inverter 52 instead of or in addition to the engine 12. The electric motor 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 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 is synonymous with electrical energy unless otherwise specified. The power is synonymous with torque or force unless otherwise specified.

[0014] 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.

[0015] 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 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 that connects the engine 12 and the K0 clutch 20, an electric motor connecting shaft 36 that connects the K0 clutch 20 and the torque converter 22, etc.

[0016] 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 so as to be able to transmit power. 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.

[0017] The torque converter 22 includes a pump wheel 22a connected to the 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 is also 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 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 and disconnects the pump wheel 22a and the turbine wheel 22b. The LU clutch 40 is a known lock-up clutch.

[0018] 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 without slippage.

[0019] The automatic transmission 24 is a known planetary gear automatic transmission equipped with, for example, one or more planetary gear sets (not shown) and a plurality of engagement devices CB. The engagement devices CB are hydraulic friction engagement devices, such as multi-plate or single-plate clutches or brakes pressed by hydraulic actuators, or band brakes tightened by hydraulic actuators. Each engagement device CB has its torque capacity, or CB torque Tcb, changed by an engagement pressure PRcb regulated by a hydraulic control circuit 56, thereby switching its control state, such as an engaged state or a disengaged state. In this embodiment, the engagement devices CB are composed of, for example, four clutches C1 to C4 and two brakes B1 and B2.

[0020] The automatic transmission 24 is a stepped automatic transmission in which one of a plurality of gear stages (also referred to as "gear stages") with different speed ratios (also referred to as "gear ratios") γat (=AT input 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 shifts to a plurality of gear stages by switching the engagement states of the plurality of engagement devices CB (clutches C1 to C4 and brakes B1, B2). Specifically, the automatic transmission 24 shifts gears based on an engagement operation table shown in FIG. 2 that shows combinations of the engagement devices CB for establishing the gear stages of the automatic transmission 24. In FIG. 2, "◯" indicates the engagement of each engagement device CB (clutches C1 to C4 and brakes B1, B2), and "X" indicates the disengagement of each 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 combination of engagement and disengagement of the engagement devices CB.

[0021] The automatic transmission 24 determines the gear position by an electronic control device 90 (described later) based on the accelerator opening θacc, which is the amount of operation of the accelerator pedal 42 by the driver (=operator), and the vehicle speed V. Note that the decision to shift gears may be made not only based on the accelerator opening θacc but also based on a related value of the accelerator opening θacc that is correlated with the accelerator opening θacc, such as the throttle valve opening θth. Similarly, the decision to shift gears may be made not only based on the vehicle speed V but also based on a related value of the vehicle speed V that is correlated with the vehicle speed V, such as the AT output shaft rotation speed No. The AT input shaft rotation speed Ni is the rotation speed of the transmission input shaft 38. 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, that is, the rotation speed of the output shaft of the automatic transmission 24.

[0022] 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 the K0 oil pressure PRk0 regulated by the hydraulic control circuit 56 and supplies it 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.

[0023] 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. That is, the K0 clutch 20 is an on-off 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.

[0024] 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.

[0025] The vehicle 10 is equipped with a mechanical oil pump 58 (hereinafter referred to as MOP 58), an electric oil pump 60 (hereinafter referred to as EOP 60), 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 (engine 12, 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, a K0 hydraulic pressure PRk0, an LU hydraulic pressure PRlu, etc., which are each adjusted based on the hydraulic oil discharged by at least one of the MOP 58 and the EOP 60.

[0026] 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.

[0027] 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 pedal position sensor 78, throttle valve position 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 pedal position θacc, which is the amount of operation of the accelerator pedal 42 by the driver, which indicates the magnitude of the driver's acceleration operation; throttle valve position θth, which is the opening of the electronic throttle valve; brake-on signal Bon, which is a signal indicating the state in which the brake pedal 44 for operating the wheel brakes is being operated by the driver; battery temperature THbat, battery charge / discharge current Ibat, and battery voltage Vbat of the battery 54; and hydraulic oil temperature THoil, which is the temperature of the hydraulic oil in the hydraulic control circuit 56).

[0028] 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, a CB hydraulic control command signal Sbc for controlling the engagement device CB, a K0 hydraulic control command signal Sko for controlling the K0 clutch 20, an LU hydraulic control command signal Slu for controlling the LU clutch 40, an EOP control command signal Seop for controlling the EOP 60, etc.) to each device provided in the vehicle 10 (e.g., the engine control device 50, the inverter 52, the hydraulic control circuit 56, the pump motor 62, etc.).

[0029] In order to realize various controls in the vehicle 10, the electronic control device 90 is equipped with a hybrid control unit 92 that functions as a hybrid control means, a clutch control unit 94 that functions as a clutch control means, a shift control unit 96 that functions as a shift control means, and a learning control unit 98 that functions as a learning control means.

[0030] 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.

[0031] 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.

[0032] 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.

[0033] 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.

[0034] 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.

[0035] 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.

[0036] The clutch control unit 94 controls the K0 clutch 20 in accordance with the driving mode during driving. For example, when it is determined that the driving mode is to be switched to the HEV driving mode during BEV driving, the clutch control unit 94 performs engagement control of the K0 clutch 20 so as to execute start control of the engine 12. For example, when it is determined that there is a request to start the engine 12 based on the driving state, the clutch control unit 94 outputs a K0 hydraulic control command signal Sko to the hydraulic control circuit 56 to control the K0 clutch 20 from a released state toward an engaged state so as to obtain a K0 torque Tk0 for transmitting to the engine 12 a torque (cranking torque) required for cranking the engine 12, which is a torque that increases the engine rotation speed Ne.

[0037] The shift control unit 96 determines whether to shift the automatic transmission 24 using, for example, a shift map, which is a predetermined relationship, and outputs a CB hydraulic control command signal Sbc to the hydraulic control circuit 56 as needed to execute shift control of the automatic transmission 24. The shift map is a predetermined relationship having shift lines for determining whether to shift the automatic transmission 24 on a two-dimensional coordinate system using, for example, vehicle speed V and accelerator opening θacc as variables. In the shift map, the AT output 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 valve opening θth or the like may be used as a value related to the accelerator opening θacc, instead of the accelerator opening θacc.

[0038] For example, when the shift control unit 96 determines that a downshift should be performed while the vehicle is coasting (inertia running) with the accelerator pedal 42 not depressed (accelerator pedal off), it initiates a coast downshift of the automatic transmission 24 with the accelerator pedal off. At this time, the shift control unit 96 executes clutch-to-clutch control to release the release-side engagement device CB that is released during the shift (hereinafter referred to as release-side engagement device CB1) and to engage the engagement-side engagement device CB that is engaged during the shift (hereinafter referred to as engagement-side engagement device CB2).

[0039] Hereinafter, the shift control during coast downshifting of the automatic transmission 24 will be described using an example of a downshift from second gear (2nd) to first gear (1st). FIG. 3 is a time chart showing the control state during a coast downshift from second gear (2nd) to first gear (1st). Note that the time chart corresponds to a case where the vehicle speed V is extremely low, specifically, a case where the turbine rotation speed Nt (i.e., input shaft rotation speed Nin) is lower than a preset idle rotation speed Needle of the engine 12. During a downshift from second gear (2nd) to first gear (1st), the brake B1 is released and the clutch C2 is engaged. That is, the brake B1 corresponds to the release side engagement device of the present invention, and the clutch C2 corresponds to the engagement side engagement device of the present invention.

[0040] When the shift control unit 96 determines that the vehicle has crossed a downshift line (2-1 downshift line) defined in advance in the shift map as the vehicle speed V decreases during coasting (coasting) with the accelerator pedal released, the shift control unit 96 starts a coast-down shift to first gear position 1st. The start point of the coast-down shift to first gear position 1st of the automatic transmission 24 corresponds to time t1 in FIG. 3.

[0041] When a coastdownshift is initiated at time t1, the command pressure PRb1 of the brake B1, which is the disengaging engagement device CB1, is suddenly reduced to a predetermined pressure, and then the command pressure PRb1 is gradually reduced toward a predetermined standby pressure Pst1 (times t1 to t2). Regarding the clutch C2, which is the engaging engagement device CB2, at time t1, a so-called quick fill is executed, in which the command pressure PRc2 of the clutch C2 is temporarily increased to a predetermined pressure. The quick fill is executed to improve the responsiveness of the engagement oil pressure PRc2 (actual oil pressure) of the clutch C2. When the quick fill is completed, the command pressure PRc2 is maintained at the predetermined standby pressure Pst2 (times t1 to t2).

[0042] When the inertia phase starts at time t2, the turbine rotation speed Nt increases, and at time t3, a racing (a state in which the turbine rotation speed Nt exceeds the first-speed synchronous rotation speed N1 occurs. The first-speed synchronous rotation speed N1 is calculated at any time by multiplying the speed ratio γ1 of the first-speed gear position 1st by the output shaft rotation speed Nout. The reason why the racing of the turbine rotation speed Nt occurs even during a coast downshift is that the turbine rotation speed Nt is lower than the idle rotation speed Needle of the engine 12, and therefore the vehicle is essentially driven by the engine 12 even during coasting (a state in which the turbine rotation speed Nt is increased by the engine 12).

[0043] When a sudden increase in the turbine rotation speed Nt is detected at time t3, the command pressure PRb1 for the brake B1 is reduced toward zero (i.e., complete disengagement). The command pressure PRc2 for the clutch C2 is increased at a preset gradient. When it is determined at time t4 that the turbine rotation speed Nt has synchronized with the first-speed synchronous rotation speed N1, it is determined that the inertia phase has ended, and the command pressure PRc2 for the clutch C2 is increased, causing the clutch C2 to be fully engaged.

[0044] In this embodiment, a target value S* of the turbine speed increase S (hereinafter referred to as the speed increase S) of the turbine rotation speed Nt during a coast downshift of the automatic transmission 24 and a target value Ts* of the inertia phase start time Ts, which is the time from the start of the shift to the start of the inertia phase, are set in advance. Then, during the coast downshift, a command pressure PRcb1 (corresponding to the command pressure PRb1 in FIG. 3 ) of the disengagement side engagement device CB1 (brake B1 in the coast downshift from second gear 2nd to first gear 1st described above) is set so that the inertia phase start time Ts becomes the target value Ts*. Also, a command pressure PRcb2 (corresponding to the command pressure PRc2 in FIG. 3 ) of the engagement side engagement device CB2 (clutch C2 in the downshift from second gear 2nd to first gear 1st described above) is set so that the speed increase S of the turbine rotation speed Nt becomes the target value S*. The command pressure PRcb1 for the disengagement side engagement device CB1 and the command pressure PRcb2 for the engagement side engagement device CB2 are learned and corrected (updated) each time a coast downshift is performed. Note that, because the turbine rotation speed Nt is the same as the input shaft rotation speed Nin of the transmission input shaft 38 of the automatic transmission 24, the amount of racing S of the turbine rotation speed Nt may be read as the amount of racing S of the input shaft rotation speed Nin of the transmission input shaft 38 of the automatic transmission 24.

[0045] The learning control unit 98 has the function of learning and correcting the command pressure PRcb1 for the disengagement side engagement device CB1 that is disengaged during a coast downshift of the automatic transmission 24, and also of learning and correcting the command pressure PRcb2 for the engagement side engagement device CB2 that is engaged during a coast downshift of the automatic transmission 24. When it is determined that a coast downshift of the automatic transmission 24 is to be performed, the learning control unit 98 begins learning the disengagement side engagement device CB1 and learning the engagement side engagement device CB2.

[0046] First, a method for calculating the learned value ΔPRcb1 of the command pressure PRcb1 for the disengaging engagement device CB1 will be described. The learning control unit 98 calculates the learned value ΔPRcb1 of the command pressure PRcb1 for the disengaging engagement device CB1 based on the inertia phase start time Ts. When a coast downshift is started, the learning control unit 98 measures the inertia phase start time Ts (see FIG. 3) from the start of the shift (time t1 in FIG. 3) to the start of the inertia phase. The start of the inertia phase is determined, for example, based on whether the amount of change (here, the amount of increase) per unit time of the turbine rotation speed Nt exceeds a predetermined determination threshold. Furthermore, when the coast downshift is completed, the learning control unit 98 calculates an inertia phase start time error ΔTs (=Ts-Ts*), which is the deviation (error) between the measured inertia phase start time Ts and a target value Ts* of the inertia phase start time Ts.

[0047] The learning control unit 98 calculates a learned value ΔPRcb1 (correction amount) of the command pressure PRcb1 for the disengaging engagement device CB1 based on the calculated inertia phase start time error ΔTs (hereinafter referred to as start time error ΔTs). The learning control unit 98 stores a preset relationship map between the start time error ΔTs and the learned value ΔPRcb1, and calculates the learned value ΔPRcb1 for the disengaging engagement device CB1 by applying the calculated start time error ΔTs to this relationship map.

[0048] Next, a method for calculating the learned value ΔPRcb2 of the command pressure PRcb2 of the on-coming engagement device CB2 will be described. The learning control unit 98 calculates the learned value ΔPRcb2 of the command pressure PRcb2 of the on-coming engagement device CB2. When a coast downshift is started, the learning control unit 98 detects a racing increase in the turbine rotation speed Nt that occurs during the inertia phase. Specifically, when the turbine rotation speed Nt becomes higher than the first speed synchronous rotation speed N1, the learning control unit 98 constantly calculates the difference ΔNt (=Nt-N1) between the turbine rotation speed Nt and the first speed synchronous rotation speed N1, which is a value related to the racing increase in the turbine rotation speed Nt, and calculates a racing increase amount S by integrating the constantly calculated difference ΔNt. When the turbine rotation speed Nt synchronizes with the first speed synchronous rotation speed N1, the learning control unit 98 determines that the racing increase in the turbine rotation speed Nt has converged, and ends calculation of the difference ΔNt and the racing increase amount S. The amount of blow-up S corresponds to the area of the shaded portion in FIG.

[0049] Next, the learning control unit 98 calculates a learned value ΔPRcb2 of the command pressure PRcb2 for the on-coming engagement device CB2 based on the calculated amount of engine racing S. The learning control unit 98 stores, for example, a preset relationship map between the amount of engine racing S and the learned value ΔPRcb2, and calculates the learned value ΔPRcb2 of the command pressure PRcb2 for the on-coming engagement device CB2 by applying the calculated amount of engine racing S to this relationship map.

[0050] After calculating the learned value ΔPRcb1 for the disengaging engagement device CB1 and the learned value ΔPRcb2 for the engaging side engagement device CB2, the learning control unit 98 stores each value. At the time of the next coast downshift, the learning control unit 98 corrects (updates) the command pressure PRcb1 for the disengaging engagement device CB1 by adding (=PRcb1+K1×ΔPRcb1) a value obtained by multiplying the learned value ΔPRcb1 calculated during the previous coast downshift by a preset reflection gain K1 to the command pressure PRcb1 for the disengaging engagement device CB1. Similarly, at the time of the next coast downshift, the learning control unit 98 corrects (updates) the command pressure PRcb2 of the engaging side engagement device CB2 to a new value by adding the value (K2 × ΔPRcb2) obtained by multiplying the learned value ΔPRcb2 calculated during the previous coast downshift by a preset reflection gain K2 (=PRcb2 + K2 × ΔPRcb2).

[0051] Incidentally, in the initial shipping state of the vehicle 10, the command pressure PRcb1 for the disengagement engagement device CB1 and the command pressure PRcb2 for the engagement side engagement device CB2 are both set high to avoid shock associated with an increase in turbine rotation speed Nt during a coast downshift to first gear position 1st. Therefore, as the coast downshift to first gear position 1st progresses, at least one of the command pressure PRcb1 for the disengagement engagement device CB1 and the command pressure PRcb2 for the engagement side engagement device CB2 is corrected to a reduced pressure. Therefore, if a coast downshift to first gear position 1st is performed while the vehicle is stopped with at least one of the command pressures PRcb1 and PRcb2 reduced, the turbine rotation speed Nt may increase during the coast downshift, which could result in a shift shock due to this increase in pressure.

[0052] When the vehicle is stopped, the turbine rotation speed Nt is zero, and therefore, when a coastdown shift is initiated, the turbine rotation speed Nt is synchronized with the synchronous rotation speed (zero rotation) after the shift. Therefore, the torque phase is initiated quickly and the engagement pressure of the on-coming engagement device CB2 is increased, but because the torque phase is initiated before packing of the on-coming engagement device CB2 is complete, a sudden increase in the turbine rotation speed Nt is likely to occur. Furthermore, if at least one of the command pressure PRcb1 for the off-coming engagement device CB1 and the command pressure PRcb2 for the on-coming engagement device CB2 is corrected to a reduced pressure each time a coastdown shift is executed, a sudden increase in the turbine rotation speed Nt will occur due to insufficient oil pressure in the engagement device CB.

[0053] In contrast, when a coast downshift to first gear 1st of the automatic transmission 24 is performed when the vehicle speed V is less than a preset first predetermined vehicle speed V1, the learning control unit 98 reduces the reflection gains K1, K2 for the learned values ΔPRcb1, ΔPRcb2 learned during the previous coast downshift compared to when the vehicle speed V is equal to or greater than the first predetermined vehicle speed V1. The first predetermined vehicle speed V1 is determined in advance experimentally or by design, and is set to an extremely low vehicle speed (for example, approximately 2 to 3 km / h) immediately before the vehicle 10 comes to a stop. The first predetermined vehicle speed V1 corresponds to the predetermined vehicle speed of the present invention.

[0054] The values of the reflection gains K1 and K2 are determined in advance by experiment or design, and are set to values that ensure that the amount of change in the command pressures PRcb1 and PRcb2 corrected based on the learned values ΔPRcb1 and ΔPRcb2 falls within an acceptable range and that prevent the turbine rotation speed Nt from increasing excessively due to a decrease in the command pressures PRcb1 and PRcb2. The values of the reflection gains K1 and K2 may be changed according to the vehicle speed V. For example, the reflection gains K1 and K2 are made smaller as the vehicle speed V decreases. That is, the reflection gains K1 and K2 are set so that the degree to which the learned values ΔPRcb1 and ΔPRcb2 are reflected decreases as the vehicle speed V decreases. The values of the reflection gains K1 and K2 may be zero. That is, the reflection of the learned values ΔPRcb1 and ΔPRcb2 in the command pressures PRcb1 and PRcb2 may be prohibited.

[0055] When the vehicle speed V is extremely low (below the first predetermined vehicle speed V1), the difference in rotation speed between the turbine rotation speed Nt and the first-speed synchronous rotation speed N1 is small, so the turbine rotation speed Nt quickly reaches the first-speed synchronous rotation speed N1 after the coastdown shift begins. Therefore, the torque phase then quickly begins, and the engagement pressure of the on-coming engagement device CB2 is increased. However, because the increase in the engagement pressure of the on-coming engagement device CB2 begins before the on-coming engagement device CB2 is fully packed, the hydraulic pressure of the on-coming engagement device CB2 is insufficient, which can easily cause the turbine rotation speed Nt to increase. In contrast, when the vehicle speed V is below the first predetermined vehicle speed V1, the reflection gains K1 and K2 are smaller than when the vehicle speed V is equal to or greater than the first predetermined vehicle speed V1, reducing the reduction in the command pressures PRcb1 and PRcb2 due to the correction. Therefore, the increase in the turbine rotation speed Nt caused by an excessive reduction in the command pressures PRcb1 and PRcb2 is suppressed. In addition, the gear shift shock caused by the sudden increase in the turbine rotation speed Nt can be suppressed.

[0056] Furthermore, when a coast downshift of the automatic transmission 24 to first gear position 1st is performed in a state where the vehicle speed V is less than a preset second predetermined vehicle speed V2, the learning control unit 98 prohibits learning (hydraulic pressure learning) of the command pressure PRcb1 for the disengagement engagement device CB1 and the command pressure PRcb2 for the engagement side engagement device CB2. In other words, when a coast downshift of the automatic transmission 24 to first gear position 1st is performed in a state where the vehicle speed V is less than a preset second predetermined vehicle speed V2, the learning control unit 98 does not calculate the learned value ΔPRcb1 for the disengagement engagement device CB1 and the learned value ΔPRcb2 for the engagement side engagement device CB2.

[0057] Here, the second predetermined vehicle speed V2 is determined in advance by experiment or design, and is set to a threshold value of the vehicle speed V (for example, approximately 5 km / h) that ensures the accuracy of the learned values ΔPRcb1 and ΔPRcb2 calculated during a coastdown shift. When the vehicle speed V is low, that is, below the second predetermined vehicle speed V2, the differential rotation speed between the turbine rotation speed Nt and the first-speed synchronous rotation speed N1 is small, so the turbine rotation speed Nt quickly reaches the first-speed synchronous rotation speed N1 after the coastdown shift starts. When the turbine rotation speed Nt reaches the first-speed synchronous rotation speed N1, the torque phase is quickly initiated, and the engagement pressure of the disengagement-side engagement device is controlled to decrease and the engagement pressure of the engagement-side engagement device is controlled to increase. However, the start timing of the torque phase is earlier than when the vehicle speed is equal to or higher than the second predetermined vehicle speed V2, and therefore, if learning is performed in this state, erroneous learning may occur. Therefore, when the vehicle speed V is less than the second predetermined vehicle speed V2, learning of the command pressures PRcb1 and PRcb2 is prohibited, thereby avoiding erroneous learning of the command pressures PRcb1 and PRcb2.

[0058] Further, the second predetermined vehicle speed V2 (about 5 km / h) is set to a value higher than the first predetermined vehicle speed V1 (about 2 - 3 km / h). The reason why the second predetermined vehicle speed V2 is higher than the first predetermined vehicle speed V1 is that the reflection of the learning values ΔPRcb1 and ΔPRcb2 is executed based on the learning values ΔPRcb1 and ΔPRcb2 calculated during the previous coast-down shift. Therefore, even if it is difficult to learn the command pressures PRcb1 and PRcb2, there exists a region (i.e., V1 < V < V2) where the reflection of the learning values ΔPRcb1 and ΔPRcb2 is possible. As a result, when the vehicle speed V is less than the second predetermined vehicle speed V2, learning of the command pressures PRcb1 and PRcb2 during coast-down shift to the first gear stage 1st is prohibited, thereby avoiding mislearning caused by learning of the command pressures PRcb1 and PRcb2 in the low vehicle speed range.

[0059] Figure 4 is a flowchart for explaining the main part of the control operation of the electronic control unit 90, and is a flowchart for explaining the control operation for suppressing the surge of the turbine rotational speed Nt due to excessive correction of the command pressures PRcb1 and PRcb2 to the decompression side when performing coast-down shift to the first gear stage 1st of the automatic transmission 24. This flowchart is repeatedly executed during the running of the vehicle 10.

[0060] 4, first, in step S10 (hereinafter, the term "step" will be omitted) corresponding to the control function of the shift control unit 96, it is determined whether a coast downshift of the automatic transmission 24 to first gear (1st) is to be initiated. If the determination in S10 is negative, this routine is terminated. If the determination in S10 is positive, it is determined in S20 corresponding to the control function of the learning control unit 98 whether the vehicle speed V is less than a first predetermined vehicle speed V1. If the determination in S20 is negative, it is permitted in S40 corresponding to the control function of the learning control unit 98 to reflect the learned values ΔPRcb1, ΔPRcb2 calculated during the previous coast downshift to first gear (1st) in the respective command pressures PRcb1, PRcb2. On the other hand, if the determination in S20 is positive, in S30, which corresponds to the control function of the learning control unit 98, the learning values ΔPRcb1, ΔPRcb2 calculated during the previous coast downshift are prohibited from being reflected in the respective command pressures PRcb1, PRcb2. Alternatively, the reflection gains K1, K2 are made smaller than the reflection gains K1, K2 specified in the region where the vehicle speed V is equal to or greater than a first predetermined vehicle speed V1. In other words, the degree to which the learning values ΔPRcb1, ΔPRcb2 are reflected in the command pressures PRcb1, PRcb2 is reduced. In S50, which corresponds to the control function of the learning control unit 98, it is determined whether the vehicle speed V is less than a second predetermined vehicle speed V2. If the determination in S50 is negative, in S70, which corresponds to the control function of the learning control unit 98, the learning of the respective command pressures PRcb1, PRcb2 is permitted during a coast downshift to first gear (1st). That is, calculation of the learned values ΔPRcb1, ΔPRcb2 of the command pressures PRcb1, PRcb2 is permitted. On the other hand, if the determination in S50 is positive, learning of the command pressures PRcb1, PRcb2 is prohibited in S60, which corresponds to the control function of the learning control unit 98, during a coast downshift to first gear (1st). That is, calculation of the learned values ΔPRcb1, ΔPRcb2 of the command pressures PRcb1, PRcb2 is prohibited.

[0061] As described above, according to this embodiment, when a coast downshift to first gear 1st of the automatic transmission 24 is performed when the vehicle speed V is less than the first predetermined vehicle speed V1, the reflection gains K1, K2 for the previously learned learned values ΔPRcb1, ΔPRcb2 are made smaller than when the vehicle speed is equal to or greater than the first predetermined vehicle speed V1, thereby preventing the command pressures PRcb1, PRcb2 from being excessively reduced. As a result, during a coast downshift after the vehicle comes to a stop, it is possible to prevent a racing increase in the turbine rotation speed Nt of the automatic transmission 24 (i.e., the AT input shaft rotation speed Ni), and to suppress gear shift shock caused by this racing increase.

[0062] 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.

[0063] For example, in the above-described embodiment, the vehicle 10 is a hybrid vehicle equipped with the engine 12 and the electric motor MG as a driving force source, but the present invention is not necessarily limited to hybrid vehicles. For example, the vehicle may be one that uses the engine 12 as its only driving force source. In short, the present invention can be applied to any vehicle equipped with a stepped automatic transmission having a plurality of engagement devices.

[0064] Furthermore, the specific values of the first predetermined vehicle speed V1 and the second predetermined vehicle speed V2 given in the above embodiment are merely examples, and may be changed as appropriate depending on the type and structure of the vehicle.

[0065] Furthermore, in the above-described embodiment, when the vehicle speed V is less than the first predetermined vehicle speed V1, the learned values ΔPRcb1, ΔPRcb2 of the command pressure PRcb1 for the disengaging side engagement device CB1 and the command pressure PRcb2 for the engaging side engagement device CB2 are not reflected, or the reflection gains K1, K2 are reduced, but it is also possible that the learned values ΔPRcb1, ΔPRcb2 of either the command pressure PRcb1 or the command pressure PRcb2 are not reflected, or the reflection gains K1, K2 are reduced.

[0066] Furthermore, in the above-described embodiment, when the vehicle speed V is less than the second predetermined vehicle speed V2, the learning of the command pressure PRcb1 of the disengagement side engagement device CB1 and the learning of the command pressure PRcb2 of the engagement side engagement device CB2 are prohibited, but it is also acceptable for either the learning of the command pressure PRcb1 of the disengagement side engagement device CB1 or the learning of the command pressure PRcb2 of the engagement side engagement device CB2 to be prohibited.

[0067] Furthermore, in the above-described embodiment, when the vehicle speed V is less than the first predetermined vehicle speed V1, the reflection of the learned value ΔPRcb1 of the command pressure PRcb1 of the disengagement side engagement device CB1 and the learned value ΔPRcb2 of the command pressure PRcb2 of the engagement side engagement device CB2 is prohibited, and the reflection gains K1 and K2 are reduced. However, the first predetermined vehicle speed V1, which is the judgment threshold for determining whether to reflect the learned values ΔPRcb1 and ΔPRcb2, may be set to a different value for each of the disengagement side engagement device CB1 and the engagement side engagement device CB2.

[0068] Furthermore, in the above-described embodiment, when the vehicle speed V is less than the second predetermined vehicle speed V2, learning of the command pressure PRcb1 for the release side engagement device CB1 and learning of the command pressure PRcb2 for the engagement side engagement device CB2 are prohibited, but the second predetermined vehicle speed V2, which is the judgment threshold for determining whether to perform learning, may be set to a different value for each of the release side engagement device CB1 and the engagement side engagement device CB2.

[0069] 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]

[0070] 10: Vehicle 24: Automatic transmission 90: Electronic control device 98: Learning control unit CB: Engagement device CB1: Release side engagement device CB2: Engagement side engagement device V1: First predetermined vehicle speed (predetermined vehicle speed) PRcb1: Indicated pressure of the disengagement side engagement device PRcb2: Indicated pressure of the engaging device on the engaging side ΔPRcb1, ΔPRcb2: learning values K1, K2: Reflection gain

Claims

[Claim 1] A vehicle control device adapted to a vehicle equipped with an engine, a torque converter, and a stepped automatic transmission comprising a plurality of engagement devices and shifting to a plurality of gear stages by clutch-to-clutch control that disengages a disengagement side engagement device and engages an engagement side engagement device, the vehicle control device comprising a learning control unit that learns and corrects the command pressure PRcb1 of the disengagement side engagement device that is disengaged during a coast down shift of the automatic transmission, and learns and corrects the command pressure PRcb2 of the engagement side engagement device that is engaged during a coast down shift of the automatic transmission to first gear stage, When a coast down shift to the first gear of the automatic transmission is performed, the learning control unit updates the command pressure PRcb1 of the disengaging engagement device to a new command pressure (PRcb1+K1×ΔPRcb1) by adding a value obtained by multiplying a learned value ΔPRcb1 calculated so as to reduce an inertia phase start time error, which is the error between an inertia phase start time from the actually measured shift start time until the start of an inertia phase and a target value thereof, by a preset reflection gain K1, to the command pressure PRcb1 of the disengaging engagement device; and updates the command pressure PRcb2 of the engaging side engagement device to a new command pressure (PRcb2+K2×ΔPRcb2) by adding a value obtained by multiplying a learned value ΔPRcb2 calculated so as to suppress a jump in the turbine rotation speed of the torque converter that occurs during the inertia phase, by a preset reflection gain K2 to the command pressure PRcb2 of the engaging side engagement device. When a coast downshift to the first gear of the automatic transmission is performed when the vehicle speed is less than a predetermined vehicle speed, the learning control unit reduces the reflection gains K1 and K2 for the learned values ΔPRcb1 and ΔPRcb2 learned during the previous coast downshift compared to when the vehicle speed is equal to or greater than the predetermined vehicle speed. A vehicle control device characterized by:

Images