DEVICE FOR DETERMINING THE LOCKING STATUS AND METHOD FOR DETERMINING THE AUTOMATIC TRANSMISSION

Abstract

System for determining the locking position of an automatic transmission, which includes: an automatic transmission comprising friction elements and structured in such a way as to determine the gear ratio positions by switching each of the friction elements between an engaged and a disengaged state; and an automatic transmission control unit with a locking determination section configured to determine whether or not a lock is present when the automatic transmission is in a non-shifting state, based on vehicle deceleration and a relationship between a requested gear ratio position and an actual gear ratio; where: the automatic transmission is arranged between a power source and a drive wheel in a hybrid powertrain which uses an EV mode and a HEV mode as drive modes, wherein the power source comprises a machine and a motor; the automatic transmission control includes a determination-activation-evaluation section that is configured to allow or prevent the determination of the locking-determination section, whether or not locking occurs; and The determination-activation-assessment section is configured to prevent the determination of the locking during a period from the start of slippage of a first friction element of the automatic transmission as one of the friction elements until confirmation of the convergence of the slippage of the first friction element in a situation where the first friction element is slipping to start the engine in response to a request to change mode from EV mode to HEV mode.

Description

background

[0001] The present invention relates to a system for determining the locking of an automatic transmission and a method for determining the locking of an automatic transmission in order to ascertain whether a locking mechanism is present in an automatic transmission or not.

[0002] JP 2008-232355, which corresponds to US 7,980,981 B2, discloses an automatic transmission comprising a planetary gear set and friction elements, and is designed to establish a desired gear ratio by switching each of the friction elements between an engaged and a disengaged state based on engagement commands. For such an automatic transmission, it is known in the prior art to calculate a vehicle deceleration and the actual gear ratio of the automatic transmission and, based on the vehicle deceleration and a relationship between the desired gear ratio position and the actual gear ratio, to determine whether or not a lock is present when the automatic transmission is in a non-shifting state.The word "locking" means that between the friction elements of the automatic transmission, one or more of the friction elements to which no engagement command is issued are engaged.

[0003] However, if the locking mechanism described above is applied to a hybrid vehicle where a mode transition from EV mode to HEV mode is achieved by starting the engine while one of the friction elements (second clutch) of the automatic transmission is slipping, there is a possibility of incorrect locking detection. Even if locking detection is prevented during the mode transition from EV mode to HEV mode by setting an engine start flag, there is still a risk that incorrect locking detection could be caused by a reverse transition to EV mode, as described below. Summary

[0004] It is desirable to prevent the erroneous detection of a lock even when a reverse transition to an EV mode is requested, while a friction element for starting a motor in response to a request for a mode transition from EV mode to HEV mode is slipping.

[0005] Patent documents 1 to 3 show further systems for determining the locking of an automatic transmission according to the prior art. Patent document(s) Patent document 1: JP 2010 - 202 151 A Patent document 2: JP 2008 - 44 599 A Patent document 3: JP 2007 - 331 534 A

[0006] According to the present disclosure, a system for determining the locking of an automatic transmission comprises: an automatic transmission comprising friction elements and structured in such a way as to establish gear ratio positions by switching each of the friction elements between an engaged state and a disengaged state; and an automatic transmission control comprising a locking determination section configured to determine, on the basis of vehicle deceleration and a relationship between a requested gear ratio position and an actual gear ratio, whether or not locking occurs when the automatic transmission is in a state where it is not shifted;wherein: the automatic transmission is arranged between a power source and a drive wheel in a hybrid powertrain which uses an EV mode and an HEV mode as drive modes, the power source comprising a machine and a motor; the automatic transmission control includes a determination-activation-assessment section configured to allow or prevent the determination of the interlock determination section, whether or not interlocking occurs;and the determination-activation-assessment section is configured to prevent the determination of the locking mechanism during a period from the start of slippage of a first friction element of the automatic transmission as one of the friction elements until confirmation of the convergence of the slippage of the first friction element in a situation where the first friction element is slipping to start the engine in response to a request to switch from EV mode to HEV mode.

[0007] For example, if, during engine start and vehicle deceleration, a request is made to transition from EV mode to HEV mode, followed by a request to reverse back to EV mode, the engine start flag is reset, causing the first friction element of the automatic transmission to slip. It has been found that if the locking determination is allowed in response to the engine start flag reset, the automatic transmission may be incorrectly determined to be locked. The present disclosure employs a configuration to prevent the locking determination during a period from the onset of friction element slip until confirmation of friction element slip convergence.This is to prevent a false detection of the locking mechanism even when there is a request for the reverse transition to EV mode (that is, a request to transition to EV mode after a request to transition from EV mode to HEV mode), if the friction element for starting the engine is slipping in response to the request to transition from EV mode to HEV mode. Brief description of the drawings Fig. Figure 1 is an overall system diagram showing a rear-wheel-drive FR hybrid vehicle as an example of a hybrid vehicle to which an automatic transmission locking system according to one embodiment is applied. Fig. Figure 2 is an example of an EV-HEV selection map set in a mode selection section of an integrated controller according to the embodiment. Fig. Figure 3 is a skeleton diagram showing an example of an automatic transmission which, depending on the embodiment, is inserted between a motor generator and the drive wheels. Fig. Figure 4 is a table of the engagement processes, showing the engagement state of each friction element and which friction element is a second clutch for each gear ratio position in the automatic transmission according to the embodiment. Fig. Figure 5 is a detailed block diagram showing a locking determination control of an AT controller according to the embodiment. Fig. Figure 6 is a flowchart showing a flow of the interlock determination activation evaluation to be performed by a determination activation evaluation section of the AT control according to the embodiment. Fig. Figure 7 is a timing diagram showing the sequence of an interlock determination to be carried out by an interlock determination part of the AT control according to the embodiment. Fig. Figure 8 is a table showing a friction element that is to be switched off for each transmission ratio position in a provisional emergency running control carried out by an emergency running control part of the AT control unit according to the embodiment after detection of the locking. Fig. Figure 9 is a time diagram showing the properties of the parameters in a normal transition situation as HEV mode -> EV mode -> HEV mode, where the parameters include vehicle speed, HCM state transition control, engine speed, engine speed, output speed, target drive torque, CL2 torque setpoint, engine start flag, and engine stop pre-announcement flag. Fig. Figure 10 is a timing diagram showing the properties of the parameters in a transition situation as HEV mode -> EV mode -> "CL2 in slip readiness with CL1 ON" -> EV mode, where the parameters include vehicle speed, HCM state transition control, engine speed, engine speed, output speed, target drive torque, CL2 torque setpoint, engine start flag, and engine stop pre-announcement flag. Fig. Figure 11 is a time diagram showing the properties of the parameters in a transition situation as HEV mode -> EV mode -> "CL2 turned on" -> EV mode, where the parameters include vehicle speed, HCM state transition control, engine speed, engine speed, output speed, target drive torque, CL2 torque setpoint, engine start flag, and engine stop pre-announcement flag. Fig. Figure 12 is a time diagram showing the properties of the parameters in a transition situation as HEV mode -> EV mode -> HEV mode -> EV mode, where the parameters include vehicle speed, HCM state transition control, engine speed, engine speed, output speed, target drive torque, CL2 torque setpoint, engine start flag, and engine stop pre-announcement flag.

[0008] The following describes a system for determining an automatic transmission lock according to an embodiment shown in the drawings.

[0009] The following describes, firstly, a configuration of a locking determination system for an automatic transmission of an FR hybrid vehicle of the single-engine, two-clutch type (as an example of a hybrid vehicle) according to the embodiment, separately in the sections "Configuration of the overall system", "Schematic configuration of the automatic transmission" and "Configuration of the locking determination system".

[0010] [Overall system configuration] Fig. Figure 1 shows the FR hybrid vehicle to which the automatic transmission locking determination is applied according to the embodiment. Fig. Figure 2 shows an example of an EV-HEV selection map set in a mode selection area of ​​an integrated controller 10. The complete system configuration is described below with reference to... Fig. 1 and Fig. 2 described.

[0011] As in Fig. As shown in Figure 1, the FR hybrid vehicle comprises a powertrain consisting of an engine "Eng", a first clutch CL1, a motor-generator "MG" (motor), a second clutch CL2, an automatic transmission "AT", a transmission input shaft "IN", a driveshaft "PS", a differential "DF", a left driveshaft "DSL", a right driveshaft "DSR", a left rear wheel "RL" (drive wheel), and a right rear wheel "RR" (drive wheel). "FL" stands for left front wheel, "FR" for right front wheel, and "FW" for flywheel.

[0012] The first clutch CL1 is a friction element for switching the operating mode. It is located between the motor Eng and the motor-generator MG and is designed to be disengaged for an EV mode and engaged for an HEV mode. The first clutch CL1 is a so-called normally closed dry clutch. It is engaged by the preload force of a disc spring or similar device when actuated without hydraulic pressure on CL1, and disengaged when hydraulic pressure is applied to resist the preload force.

[0013] The automatic transmission (AT) is a continuously variable transmission (CVT) that automatically shifts between seven forward and one reverse gear ratio, depending on vehicle speed, accelerator pedal position, and other factors. The second clutch, CL2, is integrated into the power transmission path from the engine generator (MG) to the left and right rear wheels (RL and RR). It is not a separate clutch independent of the AT transmission, but rather a friction element (clutch or brake) used to engage the transmission. Specifically, one of the friction elements that must engage in each gear position of the AT transmission is designated as the second clutch, CL2, depending on the engagement state and other parameters. The hydraulic unit for the first clutch, CL1, is integrated into a hydraulic control valve unit (CVU) that is part of the AT transmission system.

[0014] The FR hybrid vehicle uses modes that differ in the type of propulsion, including an electric vehicle mode (hereinafter referred to as "EV mode"), a hybrid vehicle mode (hereinafter referred to as "HEV mode") and a drive torque control mode (hereinafter referred to as "WSC mode").

[0015] EV mode is a mode in which the first clutch CL1 is disengaged and the vehicle is driven solely by the motor-generator MG. EV mode comprises an engine drive mode (engine power running mode) and a generator power generation mode (generator regeneration mode). EV mode is selected, for example, when the required drive power is low and the battery's state of charge (SOC) is sufficient.

[0016] HEV mode is a mode in which the first clutch CL1 is engaged and the vehicle is powered by both the engine Eng and the motor-generator MG. HEV mode includes an engine assistance mode (engine power operation), an engine power generation mode (generator regeneration mode), and a delay regeneration mode (generator regeneration mode). HEV mode is selected, for example, when the required drive power is high or when the battery state of charge (SOC) is insufficient.

[0017] WSC mode is a mode in which the vehicle is driven as in HEV mode, but the motor-generator speed (MG) is controlled to keep the second clutch (CL2) slipping and to manage its torque transmission capacity. This ensures that the drive torque transmitted through CL2 matches the drive torque requested by the driver's accelerator pedal input. WSC mode is selected when the engine speed is below idle, for example, when the vehicle is started in HEV mode.

[0018] As in Fig. As shown in Figure 1, the FR hybrid vehicle has a control system consisting of an engine control unit (ECU) 1, an engine control unit (ECU) 2, an inverter 3, a battery 4, an automatic transmission control unit (ATCU) 7, a brake control unit (BCU) 9, and an integrated control unit 10. The engine control unit 1 is referred to as the "ECU", the automatic transmission control unit 7 as the "ATCU", and the integrated control unit 10 as the "HCM".

[0019] Controllers 1, 2, 7, and 9, as well as the integrated controller 10, are interconnected via a CAN communication line 11 and exchange information with each other. Furthermore, 12 represents a motor speed sensor, 13 a resolver, 19 a wheel speed sensor, and 20 a brake stroke sensor.

[0020] The automatic transmission (AT) control unit 7 receives information from an accelerator pedal opening sensor 16, a vehicle speed sensor 17, a locking switch 18, etc. The locking switch 18 detects a selected range position (N range, D range, R range, P range, etc.). When the vehicle is traveling in the selected D range, an optimal gear ratio position is found based on the position of an operating point in a circuit diagram (not shown), where the operating point is defined by an accelerator pedal opening (APO) and a vehicle speed (VSP). A control command to maintain the found gear ratio position is then sent to the hydraulic valve control unit (CVU).In addition to this shift control, based on a command from the integrated control unit 10, a control operation is performed that sets the first clutch CL1 to a fully engaged state for HEV mode, a slip-dependent state for engine start, and a disengaged state for EV mode. Furthermore, a control operation is performed that sets the second clutch CL2 to a fully engaged state for HEV mode, a micro-slip engagement state for EV mode, a differential-speed-absorbing slip engagement state for WSC mode, and a torque-change-absorbing slip engagement state for engine start and engine stop modes.

[0021] The integrated control unit 10 manages the energy consumed by the entire vehicle and enables the vehicle to operate with optimized efficiency. The integrated control unit 10 receives the necessary information from an engine speed sensor 21 for measuring the engine speed (Nm) and other sensors, switches, etc. 22, and inputs information via the CAN communication line 11. The integrated control unit 10 includes a mode selection section configured to select as its target mode a mode characterized by the fact that the operating point defined by the accelerator pedal opening (APO) and the vehicle speed (VSP) is in the Fig. The integrated control unit 10 is positioned as shown in the EV-HEV selection map 2. In response to a request to switch from EV mode to HEV mode, the integrated control unit 10 performs an engine start control. During the engine start control, the second clutch CL2 is engaged in a slipping state by means of a slip control. Subsequently, the integrated control unit 10 initiates engine starting using the motor generator MG as the starter with the first clutch CL1 in slip. After the engine Eng has entered a state of self-sufficient operation based on fuel injection and ignition, the first clutch CL1 is fully engaged. Furthermore, in response to a request to switch from HEV mode to EV mode, the integrated control unit 10 performs an engine stop control by shutting off the fuel supply, stopping the ignition, and disengaging the first clutch CL1.

[0022] [Schematic configuration of the automatic transmission] Fig. Figure 3 is a skeleton diagram showing an example of an automatic transmission (AT) according to the embodiment. Fig. Figure 4 shows the engagement states of the friction elements in the individual gear ratios of the automatic transmission (AT). The following section describes the schematic structure of the automatic transmission (AT) based on the... Fig. 3 and Fig. 4 described.

[0023] The automatic transmission (AT) is a seven-speed forward and a continuously variable reverse automatic transmission. As in Fig. As shown in Figure 3, the automatic transmission AT receives the drive force from at least the motor Eng and / or the motor generator MG via a transmission input shaft “Input” and changes the speed via four planetary gears and seven friction elements and outputs it via a transmission output shaft “Output”.

[0024] The automatic transmission (AT) comprises a shift mechanism with a first planetary gear set (GS1) and a second planetary gear set (GS2), arranged coaxially. The first planetary gear set (GS1) includes a first planetary gear set (G1) and a second planetary gear set (G2). The second planetary gear set (GS2) includes a third planetary gear set (G3) and a fourth planetary gear set (G4). Hydraulically actuated friction elements include a first clutch (C1), a second clutch (C2), a third clutch (C3), a first brake (B1), a second brake (B2), a third brake (B3), and a fourth brake (B4). Additionally, mechanically actuated detent elements include a first freewheel clutch (F1) and a second freewheel clutch (F2).

[0025] The first planetary gear G1, the second planetary gear G2, the third planetary gear G3 and the fourth planetary gear G4 is each a single-pinion planetary gear with a central pinion S1-S4, a ring gear R1-R4, a pinion P1-P4 and a carrier PC1-PC4, wherein the pinion P1-P4 is meshed with the ring gear R1-R4 and is supported by the carrier PC1-PC4.

[0026] The gearbox input shaft is coupled to the second gear ring R2 and receives the drive torque from at least one of the two motors Eng and motor-generator MG. The gearbox output shaft is coupled to the third support PC3 and transmits output torque via a final drive and other components to the drive wheels (left and right rear wheels RL, RR).

[0027] The first gear ring R1, the second carrier PC2, and the fourth gear ring R4 are integrally coupled via a first coupling element M1. The third gear ring R3 and the fourth carrier PC4 are integrally coupled via a second coupling element M2. The first central pinion S1 and the second central pinion S2 are integrally coupled via a third coupling element M3.

[0028] Fig. 4 is a single-engagement operation table. Fig. 4. Each open circle represents a condition that a corresponding friction element is hydraulically engaged in a drive state, and each open circle in brackets represents a condition that a corresponding friction element is hydraulically engaged in a freewheel state (in a drive state, the one-way clutch functions), and each empty cell represents a condition that a corresponding friction element is disengaged. Each hatched cell represents a condition that a corresponding friction element is engaged and used as a second clutch CL2 for a corresponding gear position.

[0029] As in Fig. As shown in Figure 4, each of the seven forward and one reverse gear position is reached by shifting from an adjacent gear position using an engagement switch, whereby one friction element is switched from an engaged to a disengaged state and another friction element is switched from a disengaged to an engaged state. In the first and second gear positions, the second brake B2 acts as the second clutch CL2. In the third gear position, the second clutch C2 acts as the second clutch CL2. In the fourth and fifth gear positions, the third clutch C3 acts as the second clutch CL2. In the sixth and seventh gear positions, the first clutch C1 acts as the second clutch CL2. In the reverse gear position, the fourth brake B4 acts as the second clutch CL2.

[0030] [Configuration of the locking determination system] Fig. Figure 5 shows a detailed configuration of a locking determination control of the AT control 7 according to the embodiment. The overall configuration of the locking determination system is described below with reference to Fig. 5 described.

[0031] As in Fig. As shown in Figure 5, the control system for determining the locking includes a determination-activation-evaluation section 71, a locking determination section 72 and a limp-home control section 73 in AT control 7.

[0032] Determination-Activation-Assessment Section 71 receives an input of an “ENG-Start-Flag” (ENGSTART) from the integrated control 10, the input of the transmission input speed information from the resolver 13, and the input of the transmission output speed information from the vehicle speed sensor 17. Based on the input information, Determination-Activation-Assessment Section 71 assesses whether the determination by Locking-Determination Section 72 should be allowed or prevented, and whether a lock is present or not.While the second clutch CL2 of the automatic transmission AT is slipping to start the engine Eng in response to a request to change mode from EV mode to HEV mode, the determination-activation-assessment section 71 prevents the determination about the locking during a period from the start of the slip of the second clutch CL2 until the confirmation of the convergence of the slip of the second clutch CL2.

[0033] When the automatic transmission (AT) is in a state outside of the shifting process, section 72 of the Lock Determination determines, based on vehicle deceleration and the ratio between a selected gear ratio position and an actual gear ratio, whether or not a lock occurs in the automatic transmission (AT). Lock Determination section 72 performs the determination of whether or not a lock occurs in the automatic transmission (AT) when the determination is authorized by Determination Activation Assessment section 71.

[0034] When the automatic transmission (AT) is determined to be locked by the Lock Determination Section 72, the Limp Home Control Section 73 performs a limp-home control (emergency avoidance control) to maintain the transmission ratio position of the automatic transmission (AT) unchanged and to keep the drive mode in EV mode. Details of Determination Activation Assessment Section 71, Lock Determination Section 72, and Limp Home Control Section 73 follow.

[0035] <Bestimmungs-Aktivierungs-Beurteilungs-Abschnitt 71> Fig. Figure 6 shows a sequence of the locking determination-activation-evaluation process, which is to be executed by the determination-activation-evaluation section 71 of the AT control 7 according to the embodiment. The steps are described below. Fig. 6 described, which represent the determination-activation-assessment section 71.

[0036] In step S1, after the flowchart has started or after an assessment of the prevention of the interlock determination in step S2, the determination-activation-assessment section 71 determines whether the ENG start flag (ENGSTART) is set or not (ENGSTART = 1). If YES (ENGSTART = 1), the process then proceeds to step S2. If NO (ENGSTART = 0), the process then proceeds to step S3. The ENG start flag (ENGSTART) is set by the integrated controller 10.

[0037] In step S2, after determining ENGSTART = 1 in step S1, determination-activation-assessment section 71 locks the locking determination and returns to step S1.

[0038] In step S3, after the evaluation of ENGSTART = 0 in step S1, the determination activation evaluation section 71 determines whether an input anomaly occurs via a determination condition that requires continuation of the interlock determination inhibition. If YES (an input anomaly via the determination condition occurs), the process then proceeds to step S7. If NO (the input via the determination condition is normal), the process then proceeds to step S4. The "input anomaly via the determination condition" means an input anomaly required to calculate a CL2 differential speed, such as an input anomaly of the transmission input speed from resolver 13 and an input anomaly of the transmission output speed from vehicle speed sensor 17.

[0039] In step S4, after step S3 has determined that the input is normal according to the determination condition, the determination activation evaluation section 71 determines whether the ENG start flag (ENGSTART) has already changed from ON (ENGSTART = 1) to OFF (ENGSTART = 0) during the last execution. If YES (ON -> OFF experienced), the process then proceeds to step S6. If NO (ON -> OFF experienced), the process then proceeds to step S5.

[0040] In step S5, after the determination in step S4 that the transition from ON to OFF is not (for the first time) observed, section 71 determines whether the CL2 differential speed is within a preset value α (set for each gear ratio position). If YES (the CL2 differential speed ≤ preset value α), the process then proceeds to step S7. If NO (the CL2 differential speed > preset value α), the process then proceeds to step S2.

[0041] The preset value α is equal to a slip start determination value (which varies depending on the transmission position, e.g. 8 rpm ∼ 60 rpm) for the slip control of the second clutch CL2 in response to an engine start request.

[0042] In step S6, after the determination in step S4 that the transition from ON to OFF has occurred, the determination-activation-evaluation section 71 determines whether a condition that the CL2 differential speed lies within a preset value β (set for each transmission ratio position) is met for a preset time interval t B (s) was continued or not. In the case of YES (the differential speed CL2 ≤ target value β is for t B (continued), the process then proceeds to step S7. In the case of No (the state of the CL2 differential speed ≤ target value β was set for t B (not continued), the process then proceeds to step S2.

[0043] The preset value β is equal to a differential speed value (which varies depending on the gear ratio setting, for example, 17 rpm ∼ 50 rpm) to prevent incorrect locking. The preset time interval t B is set to a time interval value (for example, approximately 1 s) with which the convergence of the slip can be confirmed under a delay in the motor speed control during rapid braking.

[0044] In step S7, after the determination in step S3 that an anomaly of the input occurs via the determination condition, or after the determination of the CL2 differential speed ≤ preset value α in step S5, or after the determination in step S6 that the condition of the CL2 differential speed ≤ preset value β for t B The determination activation judgment, section 71, allows the locking determination and then proceeds to an end.

[0045] <Verriegelungs-Bestimmungs-Abschnitt 72> Fig. Figure 7 shows an overview of a locking determination to be carried out by the locking determination section 72 of the AT control 7 according to the embodiment. The behavior of the locking determination is described below. Fig. 7 described, which represents the locking determination section 72.

[0046] First, at time t1, when the delay exceeds a predetermined delay value, the interlock determination section 72 begins incrementing a delay determination timer. Then, at time t2, when the delay determination timer reaches a time period (t2 - t1), the interlock determination section 72 begins determining whether the gear ratio is outside a predetermined range. The time period (t2 - t1) is obtained by subtracting a gear ratio determination time period (t3 - t2) from a delay determination time period (t3 - t1). Since the gear ratio is outside the predetermined range, flag A is set to 1. Then, at time t3, when the delay determination timer reaches the delay determination time, the interlock determination section 72 determines that an interlock is active because flag A = 1.

[0047] <Limp-Home-Steuerungs-Abschnitt 73> Fig. Figure 8 shows a friction element that is to be deactivated for each gear ratio position during a temporary limp-home control, which is performed by the limp-home control section 73 of the AT control 7 according to the embodiment after detection of the interlock. The temporary limp-home control by the limp-home control section 73 is described below with reference to Fig. 8 described.

[0048] If the automatic transmission (AT) is determined to be locked by the locking determination in section 72, the Limp Home Control section 73 performs a preliminary limp-home control to resolve a condition that the vehicle is running with a deceleration greater than the specified deceleration value, depending on the currently requested gear ratio position. Specifically, if the currently requested gear ratio position is one of the first through third speed positions, the Limp Home Control section 73 establishes a neutral state by disengaging all friction elements. If the currently requested gear ratio position is one of the fourth through seventh speed positions, a different control is performed for each gear ratio position according to a table in [reference to table]. Fig. 8 carried out.

[0049] If the desired gear ratio position is fourth gear, the Limp Home Control section 73 releases the third brake B3 (2346 brake). This establishes the fifth gear position if the first clutch C1 (input clutch) is mistakenly engaged, and a 2.5-gear position if the first brake B1 (front brake) is mistakenly engaged. The 2.5-gear position is between second and third gear and is established by a different engagement pattern than normal.

[0050] If the desired transmission position is fifth gear, the Limp Home Control section 73 disengages the second clutch C2 (direct clutch). This establishes the sixth speed position if the third brake B3 (2346 brake) is mistakenly applied, and the seventh speed position if the first brake B1 (front brake) is mistakenly applied.

[0051] If the requested gear ratio position is sixth speed, the Limp Home Control section 73 triggers the third brake B3 (2346 brake). This establishes the fifth gear position if the second clutch C2 (direct clutch) is erroneously engaged, and the seventh gear position if the first brake B1 (front brake) is erroneously engaged.

[0052] If the requested gear ratio position is the seventh speed position, the Limp-Home Control Section 73 activates the first brake B1 (front brake). This establishes the sixth gear position if the third brake B3 (2346 brake) is erroneously applied, and the fifth gear position if the second clutch C2 (direct clutch) is erroneously applied.

[0053] The behavior of the embodiment is described below, separately in the sections “Behavior of the determination inhibition in the situation of the normal transition”, “Behavior of the determination inhibition in the situation of the CL2 slip-ready state on EV”, “Behavior of the determination inhibition in the situation of the CL2 switch-on state on EV” and “Behavior of the determination inhibition in the situation of the HEV on EV”.

[0054] [Behavior of the inhibition of determination in the situation of normal transition] Fig. Figure 9 is a time diagram showing the properties of the parameters in a normal transition situation as HEV mode -> EV mode -> HEV mode. The behavior of determination inhibition in the normal transition situation is then discussed with reference to... Fig. 9 described.

[0055] This is a normal transition situation, where a mode change occurs as HEV mode -> EV mode -> HEV mode when the vehicle is traveling at a constant speed maintained by applying the accelerator pedal against a slight incline of the road surface. In this situation, HEV mode is used until time t1. The period from time t1 to time t2 is used to wait for a drop in engine torque. The period from time t2 to time t3 is used to wait for the engine to come to a complete stop. Then, a mode change to EV mode occurs. At time t3, the vehicle switches to EV mode. At time t4, when the integrated control unit 10 issues a request to switch to HEV mode, the ENG start flag (ENGSTART) is simultaneously set.On the other hand, an engine stop warning is set from HCM to ECM (PRESTP) during a period from time t1 to time t6.

[0056] A time interval from time t4 to time t5 is then required to wait for an engagement action. A time interval from time t5 to time t6 is used to wait for an engagement action with CL1 being started. A period from time t6 to time t7 is provided for starting via MG speed control. A time interval from time t7 to time t8 is provided for complete engine ignition with CL2 engaged. Then a mode transition to HEV mode occurs. In this situation, as indicated by arrow "A", the speeds at time t8 have characteristics that satisfy a convergence condition of the CL2 differential speed, provided the CL2 differential speed has remained in a state of convergence for the specified time interval.Simultaneously, the torque parameters, as indicated by arrow "B", have properties that satisfy a condition regarding the CL2 torque: that the CL2 torque follows a target drive torque. In response to the fulfillment of these two conditions, the ENG start flag (ENGSTART) is cleared at time t8. The ENG start flag (ENGSTART) is set during a period from time t4 to time t8.

[0057] Accordingly, the flowchart in Fig. At time t4, the process proceeds as step S1 -> step S2, and the interlock determination inhibition is initiated. During the period from time t4 to time t8, the ENG start flag (ENGSTART) is set so that the sequence from step S1 -> step S2 is repeated to continue inhibiting the interlock determination. At time t8, the ENG start flag (ENGSTART) is cleared, and the process initially proceeds as step S1 -> step S3 -> step S4 -> step S5. However, at time t8, the condition for convergence of the CL2 differential speed is met, and the CL2 differential speed is within the preset value α, so the process proceeds from step S5 to step S7, and the interlock determination is switched from the inhibited state to the allowed state.

[0058] In this way, during the vehicle's journey in such a normal transition situation, the time the ENG start flag (ENGSTART) is set and the time the locking determination is inhibited in a given area are equal to the time from time t4 to time t8. At time t8, the convergence condition of the CL2 differential speed is met, and the second clutch CL2 is engaged. This makes it possible to prevent a false locking detection after time t8, even if the locking determination is permitted.

[0059] [Behavior of the inhibition of determination in the situation of the CL2 readiness state on EV] Fig. Figure 10 is a time diagram showing the properties of the parameters in a transition situation as HEV mode -> EV mode -> CL2 in slip-ready state with CI1 activated -> EV mode. The behavior of the determination inhibit in CL2 in slip-ready state -> EV mode is then described using... Fig. 10 described.

[0060] This is a transition situation in which a mode change occurs as HEV mode → EV mode → CL2 in the slip-ready state with CI1 engaged → EV mode. The mode change includes a reverse transition to EV mode when the vehicle is traveling at a constant speed and then rapidly decelerates to a standstill. In this situation, HEV mode is used until time t1. The period from time t1 to time t2 is used to wait for a drop in engine torque. The period from time t2 to time t3 is used to wait for the engine to be ready to stop. Then, a mode change to EV mode occurs. At time t3, it switches to EV mode. At time t4, when the integrated control 10 issues a request to switch operating modes to HEV mode, the ENG start flag (ENGSTART) is set simultaneously.On the other hand, the engine stop warning is set from HCM to ECM (PRESTP) at and after time t1.

[0061] Then, a time interval from time t4 to time t5 is required to wait for an engagement action. A time interval from time t5 to time t6 is used to wait for an engagement action with the engagement of CL1 to begin. In this situation, a deceleration is initiated immediately after time t4 to reduce the vehicle speed. At time t6, when the integrated control unit 10 issues a request to switch to EV mode, the ENG start flag (ENGSTART) is simultaneously cleared.

[0062] As indicated by arrow "C", the rotational speeds at time t6 have a characteristic that fulfills the condition of convergence of the differential speed CL2, since this time period is designated for waiting for a slip action. Simultaneously, the torque parameters, as indicated by arrow "D", have characteristics that fulfill the condition of CL2 torque recovery, meaning that the CL2 torque command returns to the target drive torque with a constant slope. Without fulfilling these two conditions, it will not switch to any state other than EV mode (e.g., µ slip control). Thus, the ENG start flag (ENGSTART) is set during the period from time t4 to time t6.

[0063] Accordingly, the flowchart in Fig. At time t4, the process proceeds as step S1 -> step S2, and the interlock determination inhibition is initiated. During the period from time t4 to time t6, the ENG start flag (ENGSTART) is set so that the sequence of step S1 -> step S2 is repeated to continue inhibiting the interlock determination. At time t6, the ENG start flag (ENGSTART) is cleared, and the process initially proceeds as step S1 -> step S3 -> step S4 -> step S5. However, at time t6, the condition for convergence of the CL2 differential speed is met, and the CL2 differential speed is within the preset value α, so the process proceeds from step S5 to step S7, and the interlock determination is switched from the inhibited state to the allowed state.

[0064] In this way, during the transition from CL2 in slip-ready state to EV mode, the time the ENG start flag (ENGSTART) is set and the time the locking determination is in the inhibited range are equal to the time from time t4 to time t6. At time t6, the convergence condition of the CL2 differential speed is met, and the second clutch CL2 is engaged. This makes it possible to prevent a false locking detection after time t6, even if the locking determination is allowed.

[0065] [Behavior of the determination inhibition in the situation of the CL2 switch-on state at EV] Fig. Figure 11 is a time diagram showing the characteristics of the parameters in a transition situation as HEV mode -> EV mode -> CL2 in the switched-on state -> EV mode. The behavior of the locking mechanism in the locked CL2 state -> EV mode is then described with reference to... Fig. 11 described.

[0066] This is a transition situation in which a mode change occurs as HEV mode -> EV mode -> CL2 in the engaged state -> EV mode, where the mode change includes a reverse transition to EV mode when the vehicle is traveling at a constant, maintained speed and is then rapidly decelerated by braking. In this situation, HEV mode is used until time t1. The time interval from time t1 to time t2 is used to wait for a drop in engine torque. The time interval from time t2 to time t3 is used to wait for the engine to come to a complete stop. Then, a mode change to EV mode occurs. At time t3, it switches to EV mode. At time t4, when the integrated controller 10 issues a request to switch to HEV mode, the ENG start flag (ENGSTART) is simultaneously set.On the other hand, the pre-announcement of the engine stop from HCM to ECM (PRESTP) is set during a period from time t1 to time t6, as well as at and after time t8.

[0067] A time interval from time t4 to time t5 is then required to wait for an engagement action. A time interval from time t5 to time t6 is used to wait for an engagement action with CL1 being initiated. A period from time t6 to time t7 is reserved for starting via MG speed control. A time interval from time t7 to time t8 is reserved for complete engine ignition with CL2 engaged. In this situation, a delay is initiated immediately after time t4 to reduce the vehicle speed. At time t7, when the integrated control unit 10 issues a request to switch to EV mode, the ENG start flag (ENGSTART) is simultaneously cleared.

[0068] At time t7, when the request to switch to EV mode is issued, the second clutch CL2 is in a slip state with a large differential speed, and engagement of the second clutch CL2 is initiated. As indicated by arrow "E", the speeds at time t8 have characteristics that satisfy the convergence condition of the differential speed CL2. Simultaneously, the torque parameters, as indicated by arrow "F", have characteristics that satisfy a condition regarding the CL2 torque: that the CL2 torque follows and is equal to the target drive torque. Without these two conditions being met, the system will not switch to any state other than EV mode (e.g., µ slip control). Therefore, the ENG start flag (ENGSTART) is set for a period from time t4 to time t7.

[0069] Accordingly, the flowchart in Fig. At time t4, the process proceeds as step S1 -> step S2, and the interlock determination inhibition is initiated. During the period from time t4 to time t7, the ENG start flag (ENGSTART) is set so that the sequence from step S1 -> step S2 is repeated to continue inhibiting the interlock determination. At time t7, the ENG start flag (ENGSTART) is cleared, and the process initially proceeds as step S1 -> step S3 -> step S4 -> step S5. However, at time t7, the convergence condition of the CL2 differential speed is not met, and the CL2 differential speed is above the preset value α, so the process proceeds from step S5 to step S2, and the interlock determination remains inhibited.

[0070] In the next execution and later, the process continues as step S1 -> step S3 -> step S4 -> step S6. In step S6, it is determined whether the condition that the differential speed of CL2 lies within the set value β (set for each gear ratio position) is met for the set time interval t. B (s) has stopped or not. While the convergence condition of the CL2 differential speed is not met in step S6, the process continues from step S6 to step S2 and the interlock determination inhibition continues. However, at time t8, when the convergence condition of the CL2 differential speed is met in step S6, the process transitions from step S6 to step S7. In step S7, the interlock determination is switched from the inhibited state to the allowed state.

[0071] In this way, during the transition from CL2 activation state to EV mode, the time period during which the ENG start flag (ENGSTART) is set (from time t4 to time t7) and the time period during which the locking determination is in the inhibited range (from time t4 to time t8) are not equal. The time period during which the locking determination is in the inhibited range is set by adding a longer time period (from time t7 to time t8) to the time period during which the ENG start flag (ENGSTART) is set (from time t4 to time t7). At time t8, the convergence condition of the CL2 differential speed is met, and the second clutch CL2 is engaged. This makes it possible to prevent a false locking detection after time t8, even if the locking determination is allowed.Furthermore, section 72 of the interlock determination determines, based on the vehicle deceleration and the ratio between the requested and the actual transmission ratio, whether an interlock occurs in the automatic transmission (AT) when the automatic transmission is in a non-shifting state. Therefore, even if the interlock determination is disabled, the CL2 differential speed (slip) remains after the flag is reset, only during the period when the ENG-Start flag (ENGSTART) is set (from time t4 to time t7). This results in the actual transmission ratio being determined as abnormal, leading to an incorrect interlock detection.

[0072] [Behavior of the inhibition of determination in the situation from HEV to EV] Fig. Figure 12 is a time diagram showing the properties of the parameters in a transition situation as HEV mode -> EV mode -> HEV mode -> EV mode. The behavior of the determination inhibition in the HEV to EV transition is then described using... Fig. 12 described.

[0073] This is a transitional situation in which a mode change occurs as HEV mode -> EV mode -> HEV mode -> EV mode, with the mode change including a reverse transition to EV mode when the vehicle is traveling at a constant speed and then decelerates rapidly. In this situation, HEV mode is used until time t1. The period from time t1 to time t2 is used to wait for a drop in engine torque. The period from time t2 to time t3 is used to wait for the engine to come to a complete stop. Then, a mode change to EV mode occurs. At time t3, the vehicle switches to EV mode. At time t4, when the integrated controller 10 issues a request to switch to HEV mode, the ENG start flag (ENGSTART) is simultaneously set.On the other hand, the pre-announcement of the engine stop from HCM to ECM (PRESTP) is set during a period from time t1 to time t6, as well as at and after time t8.

[0074] A time interval from time t4 to time t5 is then required to wait for an engagement action. A time interval from time t5 to time t6 is used to wait for an engagement action with CL1 being initiated. A period from time t6 to time t7 is reserved for starting via MG speed control. A time interval from time t7 to time t8 is reserved for full engine ignition with CL2 engaged. In this situation, a delay is initiated immediately after time t4 to reduce the vehicle speed. At time t8, when the integrated control unit 10 issues a request to switch to EV mode, the ENG start flag (ENGSTART) is simultaneously cleared. During a time interval from time t7 to time t8, HEV mode is used.A time interval from time t8 to time t9 is allocated for waiting for a drop in motor torque. A time interval from time t9 to time t10 is allocated for waiting for a condition that indicates the motor is ready to stop. Then, at time t10, a mode transition to EV mode occurs.

[0075] At time t8, when the request to switch from reverse to EV mode is issued, a failsafe mode is in place, allowing a shock from engine stop during rapid deceleration. Therefore, the determination of CL2 differential speed convergence via the second clutch CL2 is not performed. At time t8, engine stop control is initiated, and at time t10, the mode transition to EV mode occurs. Consequently, after waiting until time t10, the speeds, as indicated by arrow "G", have characteristics that satisfy the CL2 differential speed convergence condition. Conversely, the torque parameters, as indicated by arrow "H", have characteristics that satisfy a CL2 torque recovery condition, namely that the CL2 torque is increased to the target drive torque by a rapid rise of the CL2 torque command.Without these two conditions being met, it will not switch to any states other than EV mode (e.g., µ slip control). Therefore, the ENG start flag (ENGSTART) is set during a period from time t4 to time t8.

[0076] Accordingly, the flowchart in Fig. At time t4, the process proceeds as step S1 -> step S2, and the interlock determination inhibition is initiated. During the period from time t4 to time t8, the ENG start flag (ENGSTART) is set so that the sequence from step S1 -> step S2 is repeated to continue inhibiting the interlock determination. At time t8, the ENG start flag (ENGSTART) is cleared, and the process initially proceeds as step S1 -> step S3 -> step S4 -> step S5. However, at time t8, the convergence condition of the CL2 differential speed is unsatisfied, so the process proceeds from step S5 to step S2, and the interlock determination remains inhibited.

[0077] In the next execution and later, the process continues as step S1 -> step S3 -> step S4 -> step S6. In step S6, it is determined whether the condition that the differential speed of CL2 lies within the set value β (set for each gear ratio position) is met for the set time interval t. B (s) has stopped or not. While the convergence condition of the CL2 differential speed is not met in step S6, the process continues from step S6 to step S2 and the interlock determination inhibition continues. However, at time t10, when the convergence condition of the CL2 differential speed is met in step S6, the process transitions from step S6 to step S7. In step S7, the interlock determination is switched from the inhibited state to the allowed state.

[0078] In this way, during the HEV to EV transition, the time period during which the ENG start flag (ENGSTART) is set (from time t4 to time t8) and the time period during which the locking determination is in the inhibited range (from time t4 to time t10) are not equal. The time period during which the locking determination is in the inhibited range is set by adding a longer time period (from time t8 to time t10) to the time period during which the ENG start marker (ENGSTART) is set (from time t4 to time t8). At time t10, the convergence condition of the CL2 differential speed is met, and the second clutch CL2 is engaged. This makes it possible to prevent a false locking detection after time t10, even if the locking determination is allowed.

[0079] The following describes the effects achieved by the locking determination system for automatic transmissions (AT) according to the embodiment. <1> The system for determining the locking of an automatic transmission comprises: an automatic transmission (AT) comprising friction elements and structured to determine gear ratio positions by switching each of the friction elements between an engaged state and a disengaged state; and an automatic transmission control (AT control 7) comprising a locking determination section (72) configured to determine, based on vehicle deceleration and a relationship between a requested gear ratio position and an actual gear ratio, whether or not locking occurs when the automatic transmission (AT) is in a state outside of gear shifting;wherein: the automatic transmission (AT) is arranged between a power source and a drive wheel (left and right rear wheel RL, RR) in a hybrid powertrain which uses an EV mode and an HEV mode as drive modes, the power source comprising a motor (Eng) and a motor generator (Motor Generator MG); the automatic transmission control (AT control 7) comprises a determination-activation-assessment section (71) configured to allow or prevent the determination of the locking-determination section (72) as to whether or not locking occurs;and the determination-activation-assessment section (71) is configured to prevent the determination of the locking during a period from the start of slip of a first friction element (second clutch CL2) of the automatic transmission (AT) as one of the friction elements until confirmation of the convergence of the slip of the first friction element (second clutch CL2) in a situation where the first friction element (second clutch CL2) is slipping to start the engine (Eng) in response to a request to change mode from EV mode to HEV mode ( ; Fig. 5) This serves to prevent a false detection of the locking mechanism, even in a situation where the friction element (second clutch CL2) is slipped to start the engine in response to a request to transition from EV mode to HEV mode, and a request for the reverse transition to EV mode is received. This prevents the automatic transmission (AT) from being correctly operating but falsely detecting a locking mechanism and being fixed in EV mode as a failsafe function. <2> The system for determining the locking of an automatic transmission further comprises a hybrid control unit (integrated control unit 10), wherein: the hybrid control unit (integrated control unit 10) is configured to: set an engine start flag (ENG start flag) to start the engine (Eng) in response to a request to change mode from EV mode to HEV mode; and reset the engine start flag (ENG start flag) in response to a request to change mode from HEV mode to EV mode; and the determination activation evaluation section (71) is configured to: read the engine start flag (ENG start flag); inhibit the determination about the locking while the engine start flag (ENG start flag) is determined to be set;and further inhibits the determination of the locking until the convergence of the slip of the first friction element (second clutch CL2) is confirmed by monitoring a slip state of the first friction element (second clutch CL2) with respect to a differential speed of the first friction element (second clutch CL2) while the engine start flag (ENG start flag) is determined to be reset (; Fig. 6) In addition to the effect of <1> The feature that it is based on the determination-activation-assessment process using the engine start flag (ENG start flag) as input information serves to prevent, through the simple process, a faulty detection of the locking even when there is a request for reverse mode transition to EV mode. <3> The determination-activation-evaluation section (71) is configured to: continue the determination via the interlock in response to a condition that the differential speed of the first friction element (second clutch CL2) is greater than a slip start determination value (preset value α) via an in-slip control for the slip of the first friction element (second clutch CL2), in a situation where the engine start flag (ENG start flag) changes from a setting state to a resetting state (see S5 -> S2 in Fig. 6); and enables the determination of the locking in response to a condition that the differential speed of the first friction element (second clutch CL2) is less than or equal to the value of the slip start determination (preset α) when the engine start mark (ENG start mark) changes from the setting state to the resetting state (see S5 -> S7 in Fig. 6) In addition to the effect of <2> This serves to enable the locking determination reactively in a situation where the time of resetting the engine start flag (ENG start flag) is identical to the time of convergence of the CL2 differential speed (see Fig. 9 and Fig. 10). <4> The determination-activation-assessment section (71) is configured to: prevent the determination of the interlock in a situation where the engine start flag (ENG start flag) is reset until a first condition is met for a preset time duration (t B ) continues, the first condition being that the differential speed of the first friction element (second clutch CL2) lies within a preset value (β), within which the determination via the locking mechanism is prevented from causing an error (see S6 -> S2 in Fig. 6); and allows the determination of the locking if the first condition is met for the specified time period (t B ) has stopped, in the situation where the engine start flag (ENG start flag) is reset (see S6 -> S7 in Fig. 6) In addition to the effect of <2> or <3> This serves to reliably prevent a faulty detection of the locking mechanism when a request for the reverse mode transition to EV is present, so that the time of resetting the engine start flag (ENG start flag) is not identical to the time of convergence of the CL2 differential speed (see Fig. 11 and Fig. 12).

[0080] Although the system for determining the automatic transmission locking according to the present disclosure is described with reference to the embodiment, the specific configuration is not limited to the embodiment, but can be applied with a design modification or addition, provided that it does not go beyond the subject matter defined by the claims.

[0081] In this embodiment, the determination-activation-evaluation section 71 is based on the evaluation of the determination activation based on the ENG start flag (ENGSTART) from the integrated controller 10 as input information. However, without input of the motor start flag (ENGSTART), the determination-activation-evaluation section can be configured to monitor the CL2 differential speed and inhibit the interlock determination during a period from slip initiation to slip convergence in a situation where there is a request to transition to EV mode.

[0082] In this embodiment, the automatic transmission (AT) is a continuously variable transmission (CVT) with seven forward and one reverse gear ratio. However, the automatic transmission can be configured differently, such that it has gear ratios other than seven forward group positions or reverse group positions other than one reverse group position. Specifically, the automatic transmission can be configured differently if it includes a planetary gear set and friction elements and is designed to determine the gear ratio positions by switching each of the friction elements between an engaged and disengaged state and by the slippage engagement of one of the friction elements.

[0083] In this embodiment, the automatic transmission locking system is applied to the FR hybrid vehicle, including the powertrain with one engine and two clutches. However, the automatic transmission locking system can, of course, also be applied to an FF hybrid vehicle with one engine and a powertrain with two clutches, as well as to a parallel hybrid vehicle with a power-split mechanism for switching between EV and HEV modes.

Claims

[1] System for determining the locking position of an automatic transmission, comprising: an automatic transmission comprising friction elements and structured in such a way as to determine the gear ratio positions by switching each of the friction elements between an engaged and a disengaged state; and an automatic transmission control unit with a locking determination section configured to determine whether or not a lock is present when the automatic transmission is in a non-shifting state, based on vehicle deceleration and a relationship between a requested gear ratio position and an actual gear ratio; where: the automatic transmission is arranged between a power source and a drive wheel in a hybrid powertrain which uses an EV mode and a HEV mode as drive modes, wherein the power source comprises a machine and a motor; the automatic transmission control includes a determination-activation-evaluation section that is configured to allow or prevent the determination of the locking-determination section, whether or not locking occurs; and The determination-activation-assessment section is configured to prevent the determination of the locking during a period from the start of slippage of a first friction element of the automatic transmission as one of the friction elements until confirmation of the convergence of the slippage of the first friction element in a situation where the first friction element is slipping to start the engine in response to a request to change mode from EV mode to HEV mode. [2] System for determining the locking of an automatic transmission according to claim 1, further comprising a hybrid control system, wherein: The hybrid control is configured to: Setting an engine start flag to start the engine in response to a mode transition request from EV mode to HEV mode; and Resetting the engine start flag in response to a request to switch from HEV mode to EV mode, and the determination-activation-assessment section is configured to: Reading the engine start flag; Inhibiting the determination via the interlock while the engine start flag is determined to be set, and Continue to inhibit the determination via the interlock until the convergence of the slip of the first friction element is confirmed by monitoring a slip state of the first friction element with respect to a differential speed of the first friction element while the engine start flag is determined to be reset. [3] System for determining the locking of an automatic transmission according to claim 2, wherein the determination-activation-evaluation section is configured to: furthermore, inhibiting the determination via the interlock in response to a condition that the differential speed of the first friction element is greater than a slip start determination value via an in-slip control for the slip of the first friction element, in a situation where the engine start flag changes from a setting state to a resetting state; and Enabling the determination of the locking in response to a condition that the differential speed of the first friction element is less than or equal to the value of the slip start determination when the engine start flag transitions from the setting state to the resetting state. [4] System for determining the locking of an automatic transmission according to claim 2 or 3, wherein the determination-activation-evaluation section is configured to: Inhibiting the interlock determination in a situation where the engine start flag is reset until a first state has paused for a preset duration, wherein the first state is a state where the differential rotational speed of the first friction element is within a preset value within which the interlock determination is prevented from causing a fault; and Allow the locking to be determined if the first state has been held for the set time period when the engine start flag is reset. [5] Method for determining the locking of an automatic transmission, wherein: the automatic transmission comprises friction elements and is constructed in such a way that the positions of gear ratios are determined by switching each of the friction elements between an engaged and a disengaged state; the automatic transmission is arranged between a power source and a drive wheel in a hybrid powertrain that uses an EV mode and a HEV mode as drive modes, the power source comprising a machine and a motor; and The procedure for determining the automatic transmission lock includes: Determine, based on a vehicle deceleration and a relationship between a requested gear ratio position and an actual gear ratio, regardless of whether a locking occurs or not, when the automatic transmission is in a non-shifting state, and Inhibiting the determination of the locking mechanism during a period from the beginning of the slip of a first friction element of the automatic transmission as one of the friction elements until confirmation of the convergence of the slip of the first friction element in a situation where the first friction element is slipping to start the engine in response to a request to change mode from EV mode to HEV mode.

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