electric vehicles

Abstract

To provide an electric vehicle that directly drives drive wheels via a synchronous electric motor and that can improve run-through performance (e.g., step riding-over performance) without hindering, for example, overheat protection (output limit) on a motor locked state during riding over of a step and the like.SOLUTION: When it is determined that motor generators 21, 22 are in a locked state, an EV-CU 60 of an electric all-wheel drive vehicle (electric vehicle 1) sets a retrieval target torque which is higher than a required torque of a driver as a target torque of the motor generators 21, 22, and increases a motor torque to the target torque. When it is determined that the locked states have been cancelled within a prescribed time after the start of increase of the motor torque, the EV-CU 60 lowers the target torque after storing the target torque at that time. Subsequently, when the required torque of the driver has reached the stored target torque or higher, the EV-CU 60 sets the target torque according to the required torque and drives the motor generators 21, 22.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to an electric vehicle that uses an electric motor as a driving force source. [Background technology]

[0002] In recent years, electric vehicles (BEVs) that use electric motors as a driving force source and emit no exhaust gases have been put into practical use. For example, Patent Document 1 discloses an electric all-wheel drive vehicle in which the front wheels are driven by a front motor and the rear wheels are driven by a rear motor.

[0003] In such electric vehicles, for example, when going over a step, if an attempt is made to output torque when the wheels (tires) hit the step and are unable to move, i.e., when the motor is locked, in the case of a synchronous motor (three-phase AC motor) that uses a rotating magnetic field of three-phase AC, current may concentrate in a specific phase (one phase) of the three phases, which may cause the electric motor, three-phase wires, inverter, etc. (particularly the parts and components corresponding to the specific phase) to overheat. Therefore, in such cases, the output of the synchronous motor (electric motor) is usually limited to prevent overheating of the components, etc. and protect the components, etc. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Japanese Patent Application Laid-Open No. 2012-105482 Summary of the Invention [Problem to be solved by the invention]

[0005] For example, in an electric vehicle that uses a synchronous motor as a driving force source with no clutch or the like interposed between it and the drive wheels (i.e., in an electric vehicle in which the drive wheels are directly driven by a synchronous electric motor), if the accelerator pedal is gradually depressed while the synchronous motor is locked (the wheels are stuck on the step and cannot move) when going over a bump, the above-mentioned protection function (protective operation) may determine that the synchronous motor is in an overheated state (locked state) before it can fully utilize its performance (output torque), and the output torque may be throttled (limited), making it impossible to go over a bump that the motor specifications (vehicle specifications) allow it to go over.

[0006] The present invention has been made to solve the above-mentioned problems, and aims to provide an electric vehicle in which the drive wheels are directly driven by a synchronous electric motor, and which is capable of improving driving performance (e.g., bump-going performance) without interfering with overheat protection (output limitation) against a motor lock state, for example, when going over bumps. [Means for solving the problem]

[0007] An electric vehicle according to one aspect of the present invention includes a synchronous electric motor that directly drives drive wheels, and a control unit that controls the drive of the electric motor. The control unit determines whether the electric motor is in a locked state based on the motor torque and motor rotation speed of the electric motor, and if it determines that the electric motor is in a locked state, sets a search target torque for the electric motor that is higher than a driver's requested torque determined according to an accelerator pedal position, and increases the motor torque of the electric motor up to the target torque. If it determines that the locked state has been resolved within a predetermined time after the motor torque of the electric motor starts to increase, it stores the target torque at that time and then reduces the target torque. If the requested torque thereafter becomes equal to or greater than the stored target torque, it sets a target torque according to the requested torque and drives the electric motor according to the target torque. [Effects of the Invention]

[0008] According to the present invention, in an electric vehicle in which the drive wheels are directly driven by a synchronous electric motor, it is possible to improve driving performance (e.g., bump-going performance) without interfering with overheat protection (output limitation) against a motor lock state, for example, when going over bumps. [Brief explanation of the drawings]

[0009] [Figure 1] 1 is a diagram showing the overall configuration of an electric all-wheel drive vehicle according to an embodiment; [Figure 2] 4 is a flowchart showing the procedure of a lock-up release control (step-over control) performed by an electric all-wheel drive vehicle according to an embodiment. [Figure 3] 10 is a timing chart showing changes in accelerator opening, target torque, lock determination flag, actual motor torque, and motor rotation speed during lock-up release control (bump climbing control) performed by an electric all-wheel drive vehicle according to an embodiment. DETAILED DESCRIPTION OF THE INVENTION

[0010] A preferred embodiment of the present invention will be described in detail below with reference to the drawings. In the drawings, the same or corresponding parts will be designated by the same reference numerals. In each drawing, the same elements will be designated by the same reference numerals, and redundant explanations will be omitted. In this embodiment, an electric all-wheel drive vehicle (AWD EV) will be described as an example of an electric vehicle.

[0011] First, the configuration of an electric all-wheel drive vehicle (AWD EV) 1 according to an embodiment will be described with reference to Fig. 1. Fig. 1 is a diagram showing the overall configuration of the electric all-wheel drive vehicle 1.

[0012] The front motor generator 21 (corresponding to the electric motor described in the claims) is connected to the left front wheel 10FL via the left front wheel drive shaft 45L so as to be able to transmit torque, and is also connected to the right front wheel 10FR via the right front wheel drive shaft 45R so as to be able to transmit torque. In other words, the front motor generator 21 is directly connected to the front wheels 10FL, 10FR and directly drives the front wheels 10FL, 10FR.

[0013] The term "directly" means that the rotation speed (vehicle speed) of the front wheels 10FL, 10FR is determined uniquely (one-to-one) with respect to the rotation speed of the front motor generator 21, without the intervention of a torque converter, a clutch, etc. Therefore, in addition to the configuration (this embodiment) in which the front motor generator 21 directly drives the left front wheel drive shaft 45L and the right front wheel drive shaft 45R, it also includes a configuration in which the left front wheel drive shaft 45L and the right front wheel drive shaft 45R are driven via a pair of gears (reduction gears) with a fixed gear ratio, and a configuration in which the left front wheel drive shaft 45L and the right front wheel drive shaft 45R are driven via gears (reduction gears) and a front differential.

[0014] Similarly, the rear motor generator 22 (corresponding to the electric motor described in the claims) is connected to the left rear wheel 10RL via the left rear wheel drive shaft 48L so as to be able to transmit torque, and is also connected to the right rear wheel 10RR via the right rear wheel drive shaft 48R so as to be able to transmit torque. In other words, the rear motor generator 22 is directly connected to the rear wheels 10RL and 10RR, and directly drives the rear wheels 10RL and 10RR. The meaning of the word "directly" is the same as in the case of the front motor generator 21 described above.

[0015] The front motor generator 21 and the rear motor generator 22 are configured as synchronous generator motors that combine the function of a synchronous motor that converts supplied electric power (three-phase AC) into mechanical power and the function of a generator that converts input mechanical power into electric power. That is, the front motor generator 21 and the rear motor generator 22 each operate as a synchronous motor that generates drive torque when driving the vehicle, and operate as a generator when regenerating power.

[0016] Each of the wheels 10FL-10RR (hereinafter, all of the wheels 10FL-10RR may be collectively referred to as wheels 10) is fitted with a brake 11FL-11RR (hereinafter, all of the brakes 11FL-11RR may be collectively referred to as brake 11) that brakes the wheels 10FL-10RR. Also, each of the wheels 10FL-10RR is fitted with a wheel speed sensor 12FL-12RR (hereinafter, all of the wheel speed sensors 12FL-12RR may be collectively referred to as wheel speed sensor 12) that detects the wheel rotation speed.

[0017] The wheel speed sensor 12 is a non-contact sensor that detects changes in the magnetic field caused by a rotor (gear rotor or magnetic rotor) that rotates together with the wheel 10. For example, a method of detecting rotor rotation using a magnetic pickup, a Hall element, an MR element, or the like is preferably used. The wheel speed sensor 12 is connected to the EV-CU 60, which will be described later.

[0018] As a result of this configuration, in the electric all-wheel drive vehicle 1 (hereinafter also referred to simply as "vehicle 1"), the front wheels 10FL, 10FR are directly driven by the front motor generator 21, and the rear wheels 10RL, 10RR are directly driven by the rear motor generator 22. The balance between the driving force of the front motor generator 21 and the driving force of the rear motor generator 22 is controlled, and the driving force of the front and rear wheels 10 is variably distributed as desired. Furthermore, regeneration can also be performed by the front motor generator 21 and the rear motor generator 22 during braking, etc.

[0019] The drive of the front motor generator 21 and the rear motor generator 22 is comprehensively controlled by the EV-CU 60. The EV-CU 60 is connected via a CAN (Controller Area Network) 100 to be able to communicate with a vehicle dynamics control unit (hereinafter referred to as "VDCU") 50 and the like, which improves driving stability by suppressing skidding of the vehicle 1.

[0020] The EV-CU60 and VDCU50 are configured with a microprocessor that performs calculations, an EEPROM that stores programs and the like for causing the microprocessor to execute each process, a RAM that stores various data such as calculation results, a backup RAM in which the stored contents are retained, and an input / output I / F, etc.

[0021] Connected to the VDCU 50 are, for example, a steering angle sensor 16, a longitudinal acceleration (longitudinal G) sensor 55, a lateral acceleration (lateral G) sensor 56, a yaw rate sensor 57, and a brake switch 58. The longitudinal acceleration sensor 55 detects longitudinal acceleration acting on the vehicle 1, and the lateral acceleration sensor 56 detects lateral acceleration acting on the vehicle 1. The steering angle sensor 16 detects the turning angle of the front wheels 10FL, 10FR, which are steered wheels (i.e., the steering angle of the steering wheel 15), by detecting the rotation angle of the pinion shaft. The yaw rate sensor 57 detects the yaw rate of the vehicle 1.

[0022] The VDCU 50 brakes the vehicle 1 by driving a brake actuator in accordance with the amount of operation (depression) of the brake pedal, and detects vehicle behavior using various sensors (e.g., wheel speed sensor 12, steering angle sensor 16, longitudinal acceleration sensor 55, lateral acceleration sensor 56, yaw rate sensor 57, etc.), and suppresses skidding through brake control by automatic pressure application and motor torque control, thereby ensuring vehicle stability during cornering. In other words, the VDCU 50 prevents skidding and ensures excellent driving stability, for example, when the vehicle enters a corner at an excessive speed or when the vehicle posture (behavior) becomes unstable due to a sudden steering operation. The VDCU 50 also drives a brake actuator to brake the vehicle 1 in accordance with a braking request from the EV-CU 60 (details of which will be described later).

[0023] The VDCU 50 transmits the detected steering angle, longitudinal acceleration, lateral acceleration, yaw rate, braking information, etc. to the EV-CU 60 via the CAN 100. On the other hand, the VDCU 50 receives braking request information, etc. from the EV-CU 60 via the CAN 100.

[0024] Various sensors are connected to the EV-CU 60, including, for example, an accelerator opening sensor 61 that detects the amount of depression of the accelerator pedal (accelerator opening), a resolver 62 that detects the rotational position (rotation speed) of the front motor generator 21, a resolver 63 that detects the rotational position (rotation speed) of the rear motor generator 22, and a wheel speed sensor 12 that detects the speed of the wheels 10 mentioned above.

[0025] Furthermore, the EV-CU 60 receives various information from the VDCU 50 via the CAN 100, such as the steering angle, longitudinal acceleration, lateral acceleration, yaw rate, and braking information.

[0026] Based on the various types of information acquired, EV-CU 60 comprehensively controls the drive of front motor generator 21 and rear motor generator 22. EV-CU 60 calculates and outputs target torques (torque command values) for front motor generator 21 and rear motor generator 22 based on, for example, accelerator pedal opening (driver's required driving force), the driving state of vehicle 1 (vehicle speed, etc.), and the state of charge (SOC) of high-voltage battery 71. In other words, EV-CU 60 functions as a control unit as recited in the claims.

[0027] At this time, EV-CU 60 adjusts (controls) the output torque of front motor generator 21 and rear motor generator 22 so that the front and rear driving force distribution is in accordance with the frictional force between the front wheels 10FL, 10FR and the rear wheels 10RL, 10RR and the road surface. Note that EV-CU 60 calculates the ground contact loads of the front wheels 10FL, 10FR and the rear wheels 10RL, 10RR from the longitudinal acceleration and lateral acceleration of vehicle 1, and estimates the frictional force between the front wheels 10FL, 10FR and the rear wheels 10RL, 10RR and the road surface based on the ground contact loads.

[0028] A power control unit (hereinafter referred to as "PCU") 70 drives the front motor generator 21 and the rear motor generator 22 via an inverter 70a based on the target torque (torque command value). Here, the inverter 70a includes a front inverter and a rear inverter, and converts DC power from the high-voltage battery 71 into three-phase AC power, which is supplied to the front motor generator 21 and the rear motor generator 22. Meanwhile, during regeneration, the inverter 70a converts AC voltage generated by the front motor generator 21 and / or the rear motor generator 22 into DC voltage to charge the high-voltage battery 71.

[0029] In particular, the EV-CU 60 has a function to improve driving performance (e.g., bump-going performance) without interfering with overheat protection (output limitation) against motor lock when going over bumps, etc. The EV-CU 60 realizes this function by having a microprocessor execute a program stored in an EEPROM or the like.

[0030] EV-CU 60 determines whether front motor generator 21 and / or rear motor generator 22 (hereinafter referred to as "motor generators 21, 22") are in a locked state based on the motor torque and motor rotation speed of the motor generators 21, 22. If EV-CU 60 determines that the motor generators 21, 22 are in a locked state, more specifically, if the motor torque of the motor generators 21, 22 is equal to or greater than a predetermined threshold (lock determination threshold) and the rotation speed (motor rotation speed) of the motor generators 21, 22 remains below a predetermined rotation speed (rotation speed at which continuous current cannot be applied) for a predetermined time (e.g., several seconds) or more, EV-CU 60 sets a search target torque that is higher (i.e., added by a predetermined value) than the driver's requested torque determined according to the accelerator pedal position as the target torque of the motor generators 21, 22. Then, EV-CU 60 gradually increases the motor torque of the motor generators 21, 22 up to the target torque.

[0031] Here, the lock determination threshold is set to a current value (current value that allows cooling in time) that will not cause overheating of the inverter 70a, etc., even if one phase is concentrated, from the viewpoint of thermal protection of the inverter 70a, etc. Also, the continuous non-energizable rotation speed is set to a rotation speed (rotation speed that allows cooling in time) that will not cause overheating of the motor generators 21, 22, etc., even if one phase is concentrated, from the viewpoint of thermal protection of the motor generators 21, 22, etc.

[0032] When EV-CU 60 determines that the locked state has been resolved within a predetermined time after the motor torque (target torque) of motor generators 21, 22 starts to increase, more specifically, when the rotation speed (motor rotation speed) of motor generators 21, 22 (which may be the rotation speed of wheels 10) reaches or exceeds a predetermined rotation speed (when rotation occurs), EV-CU 60 stores the target torque at that time. Then, EV-CU 60 reduces the target torque thereafter.

[0033] In order to prevent overheating of the motor generators 21 and 22, the EV-CU 60 stores the target torque when the locked state is released, and then when lowering the target torque, lowers the target torque to a value below the torque that allows continuous operation (continuous current supply) (for example, zero).

[0034] If the driver's requested torque subsequently becomes equal to or greater than the stored target torque, EV-CU 60 sets the target torque according to the requested torque and drives (controls) motor generators 21 and 22 according to the target torque (i.e., returns to normal control).

[0035] On the other hand, when EV-CU60 determines that the locked state has not been resolved within a predetermined time after the motor torque (target torque) of motor generators 21, 22 starts to increase, more specifically, when the motor rotation speed of motor generators 21, 22 does not exceed a predetermined rotation speed (does not rotate), EV-CU60 stores the target torque at that time (maximum value within the predetermined time) and then reduces the target torque to a value below the torque that allows continuous operation (continuous current supply) (for example, zero).

[0036] When the torque required by the driver subsequently becomes equal to or greater than the stored target torque, the EV-CU 60 sets a search target torque that is higher than the required torque by a predetermined value (adding a predetermined value) as the target torque, and gradually increases the motor torque of the motor generators 21, 22 up to the target torque.

[0037] When EV-CU60 determines that the locked state has been resolved within a predetermined time after the motor torque (target torque) of motor generators 21, 22 starts to increase, more specifically, when the motor rotation speed of motor generators 21, 22 reaches or exceeds a predetermined rotation speed (when they rotate), EV-CU60 stores the target torque at that time and then reduces the target torque to a value below the torque that allows continuous operation (continuous current supply) (for example, zero).

[0038] If the driver's requested torque subsequently becomes equal to or greater than the stored target torque, EV-CU 60 sets the target torque according to the requested torque and drives (controls) motor generators 21 and 22 according to the target torque (i.e., returns to normal control).

[0039] On the other hand, when EV-CU60 determines that the locked state has not been resolved within a predetermined time after the motor torque (target torque) of motor generators 21, 22 starts to increase, more specifically, when the motor rotation speed of motor generators 21, 22 does not reach or exceed a predetermined rotation speed (when the motor does not rotate), EV-CU60 repeats the above-mentioned series of processes (motor lock resolution process (step climbing process)) that were executed when it was determined that the locked state had not been resolved until the locked state is resolved.

[0040] Furthermore, in order to prevent swing back (backward movement of vehicle 1) when the target torque is lowered, EV-CU 60 cooperates with VDCU 50 (corresponding to a braking device described in the claims) that brakes vehicle 1 to automatically brake vehicle 1 while the target torque is being lowered (while the target torque is being lowered). That is, EV-CU 60 transmits a braking request to VDCU 50 requesting braking of vehicle 1 (wheels 10), and VDCU 50 drives a brake actuator to brake vehicle 1 (wheels 10) in response to the braking request from EV-CU 60.

[0041] In this case, when the accelerator pedal opening degree falls below a predetermined lock determination threshold, EV-CU 60 releases the braking of vehicle 1. In other words, EV-CU 60 stops transmitting a braking request to VDCU 50.

[0042] Next, the operation of the electric all-wheel drive vehicle 1 will be described with reference to Figures 2 and 3. Figure 2 is a flowchart showing the processing procedure for lock-up release control (step-over control) by the electric all-wheel drive vehicle 1. This processing is executed repeatedly at predetermined timing, mainly by the EV-CU 60. Figure 3 is a timing chart showing changes in accelerator opening, target torque, lock-up determination flag, actual motor torque, and motor rotation speed during lock-up release control (step-over control) by the electric all-wheel drive vehicle 1. The horizontal axis of Figure 3 represents time, and the vertical axis represents, from top to bottom, accelerator opening (deg), target torque (Nm), lock-up determination flag, actual motor torque (Nm), and motor rotation speed (rpm).

[0043] In step S100, a determination is made as to whether or not the motor generators 21, 22 are in a locked state based on the motor torque and motor rotation speed of the motor generators 21, 22. More specifically, for example, a determination is made as to whether or not the motor torque of the motor generators 21, 22 is equal to or greater than a predetermined threshold (lock determination threshold) and the rotation speed (motor rotation speed) of the motor generators 21, 22 is less than a predetermined rotation speed (rotation speed at which continuous power cannot be supplied). If it is determined that the motor generators 21, 22 are in a locked state, the process proceeds to step S102 (see time t1 in FIG. 3). On the other hand, if it is determined that the motor generators 21, 22 are not in a locked state, the process temporarily exits.

[0044] In step S102, it is determined whether or not the above state (locked state) has continued for a predetermined time (for example, several seconds) or more (whether or not the locked state has been established). If the state has continued for the predetermined time or more (if the locked state has been established), the process proceeds to step S104 (see time t2 in FIG. 3). On the other hand, if the predetermined time or more has not passed (if the locked state has not been established), the process proceeds to step S100, and the processes of steps S100 to S102 described above are repeatedly executed.

[0045] In step S104, a search target torque that is higher (i.e., added by a predetermined value) than the driver's requested torque determined according to the accelerator opening by a predetermined value (for example, about 10% to 20%) is set as the target torque (motor torque requested value) of motor generators 21, 22, and the motor torque (target torque) of motor generators 21, 22 is gradually increased up to this target torque (see times t2 to t3 (, t6 to t7) in Figure 3).

[0046] Next, in step S106, a determination is made as to whether the locked state has been resolved within a predetermined time after the motor torque (target torque) of motor generators 21, 22 has started to increase. More specifically, a determination is made as to whether the rotation speed (motor rotation speed) of motor generators 21, 22 has reached or exceeded a predetermined rotation speed (whether the motors have rotated). If the locked state has been resolved, the process proceeds to step S108. On the other hand, if the locked state has not been resolved, the process proceeds to step S110.

[0047] In step S108, the target torque (motor torque) at that time (when it is determined that the motor lock state has been resolved) is stored (the target torque is substituted for the motor torque threshold value). Thereafter, the process proceeds to step S112.

[0048] On the other hand, in step S110, the target torque (maximum value within a predetermined time) at that time (when it is determined that the motor lock state has not been resolved) is stored (the maximum value of the target torque within the predetermined time is substituted for the motor torque threshold value). Thereafter, the process proceeds to step S112.

[0049] In step S112, it is determined whether the torque required by the driver is equal to or greater than the stored target torque (motor torque threshold value). If the required torque is equal to or greater than the stored target torque (motor torque threshold value), the process proceeds to step S116. On the other hand, if the required torque is not equal to or greater than the stored target torque (motor torque threshold value), the process proceeds to step S114.

[0050] In step S114, the target torque is reduced to a torque (for example, zero) that allows continuous operation (continuous energization) or less (see times t4 to t5 (and t8 to t9) in FIG. 3). When the target torque is being reduced (while it is being reduced), the vehicle 1 is automatically braked by cooperative control with the VDCU 50. Thereafter, the process proceeds to step S112, and the processes of steps S112 to S114 described above are repeatedly executed until the torque requested by the driver becomes equal to or greater than the stored target torque (motor torque threshold value).

[0051] In step S116, a target torque is set according to the torque required by the driver, and the motor generators 21 and 22 are driven (controlled) according to the target torque (see times t5 to t6 (and t9 and after) in FIG. 3).

[0052] Next, in step S118, it is determined whether the locked state has been released within a predetermined time. The method for determining whether the locked state has been released is as described above, and therefore a detailed description thereof will be omitted here. If the locked state has been released (see time t9 onward in FIG. 3), the process ends. On the other hand, if the locked state has not been released, the process proceeds to step S104, and the processes of steps S104 to S118 described above are repeatedly executed.

[0053] As described above in detail, according to this embodiment, when it is determined that the motor generators 21, 22 are in a locked state, a target torque higher than the torque requested by the driver is first set and the motor generators 21, 22 are driven, so that it is possible to search for a torque (minimum necessary torque) that will allow the motor generators 21, 22 to rotate (to release the locked state). Note that if the torque cannot be searched (obtained) in one go, the search is repeated multiple times as necessary, so that it is possible to more reliably search for a torque (minimum necessary torque) that will allow the motor generators 21, 22 to rotate (to release the locked state).

[0054] Then, the target torque (motor torque) is lowered until the driver's requested torque reaches the torque at which the acquired (searched) motor generators 21, 22 can rotate (the locked state can be released). This prevents the motor generators 21, 22, etc. from overheating. In other words, it is possible to prevent the motor generators 21, 22 from continuing to be energized (a large current being applied) in a locked state (for example, a state in which they have come to a stop after hitting a bump).

[0055] Then, when the required torque reaches a torque at which the motor can rotate (the locked state can be released), motor generators 21, 22 are driven at that torque (target torque), and the locked state can be released (for example, to go over a bump). As a result, it is possible to improve the vehicle's running performance (for example, ability to go over a bump) without interfering with overheat protection (output limitation) against a motor locked state when going over a bump, for example.

[0056] Furthermore, according to this embodiment, it is possible to search for the torque (minimum required torque) required to release the locked state (for example, to go over a step), thereby preventing the motor torque from becoming excessively large when the locked state is released and the vehicle 1 starts to move, and preventing the vehicle 1 from jumping out after the lock is released (after going over a step).

[0057] Furthermore, according to this embodiment, without providing (adding) a clutch, torque converter, or the like between the motor generators 21, 22 and the drive wheels 10, the traveling performance (for example, ability to overcome obstacles) can be improved.

[0058] According to this embodiment, after the target torque when the locked state is released is stored, when the target torque is lowered, the target torque is lowered to a value below the torque that allows continuous operation (continuous current supply) (for example, zero), thereby effectively preventing overheating of the motor generators 21 and 22.

[0059] Furthermore, according to this embodiment, when the target torque is being reduced (while being reduced), the vehicle 1 (wheels 10) is automatically braked through cooperative control with the VDCU 50, thereby making it possible to appropriately prevent backward movement (swinging back) of the vehicle 1. Note that, according to this embodiment, when the accelerator pedal opening degree falls below a predetermined lock determination threshold, the braking of the vehicle 1 can be appropriately released.

[0060] Although the embodiments of the present invention have been described above, the present invention is not limited to the above embodiments and various modifications are possible. For example, in the above embodiments, the present invention is applied to an electric all-wheel drive vehicle 1 configured such that the left and right front wheels 10FL, 10FR are driven by a front motor generator 21 and the left and right rear wheels 10RL, 10RR are driven by a rear motor generator 22. However, the present invention can also be applied to, for example, an electric all-wheel drive vehicle in which an in-wheel motor is attached to each of the four wheels. Furthermore, in the above embodiments, a two-motor electric vehicle (BEV) has been described as an example of an electric vehicle, but the present invention can also be applied to, for example, a single-motor electric vehicle (BEV), a hybrid vehicle (HEV, P-HEV), a fuel cell vehicle (FCV), etc.

[0061] In addition, in the above embodiment, when it is determined that a locked state exists, the process of setting the target torque to a value obtained by adding a predetermined value to the torque requested by the driver is repeatedly executed until the locked state is resolved. However, for example, the target torque may be gradually increased (continue to be increased) until the locked state is resolved.

[0062] Furthermore, the system configuration of the controllers such as the EV-CU 60 and the VDCU 50, and the allocation of functions among the controllers, are not limited to the above-described embodiments. For example, in the above-described embodiments, the wheel speed sensor 12 is connected to the EV-CU 60, but it may be connected to the VDCU 50 and transmit the information to the EV-CU 60 via the CAN 100. Furthermore, in the above-described embodiments, the EV-CU 60, the PCU 70, and the VDCU 50 are connected to each other via the CAN 100 so that they can communicate with each other, but the system configuration is not limited to this, and can be arbitrarily changed (integrated, etc.) in consideration of, for example, functional requirements, costs, etc. [Explanation of symbols]

[0063] 1 Electric all-wheel drive vehicle (electric vehicle) 10FL,10FR,10RL,10RR wheels 11FL, 11FR, 11RL, 11RR Brake 12FL, 12FR, 12RL, 12RR wheel speed sensor 16 Steering angle sensor 21 Front motor generator (front electric motor) 22 Rear motor generator (rear electric motor) 45L left front wheel drive shaft 45R right front wheel drive shaft 48L Left rear wheel drive shaft 48R right rear wheel drive shaft 50 VDCU 55 Front and rear acceleration sensor 56 Lateral acceleration sensor 57 Yaw rate sensor 58 Brake switch 60 EV-CU (Control Unit) 61 Accelerator opening sensor 62, 63 Resolver 70 PCU 70a inverter 71 High Voltage Battery 100 CAN

Claims

1. a synchronous electric motor that directly drives the drive wheels; a control unit that controls the driving of the electric motor, The control unit determining whether the electric motor is in a locked state based on the motor torque and motor rotation speed of the electric motor, and if it is determined that the electric motor is in a locked state, setting a search target torque that is higher than a driver's requested torque determined according to an accelerator opening as a target torque of the electric motor, and increasing the motor torque of the electric motor up to the target torque; When it is determined that the locked state has been resolved within a predetermined time after the motor torque of the electric motor has started to increase, the target torque at that time is stored and then the target torque is reduced; Thereafter, when the torque required by the driver becomes equal to or greater than the stored target torque, the target torque is set in accordance with the required torque, and the electric motor is driven in accordance with the target torque. An electric vehicle characterized by:

2. The control unit determining whether the electric motor is in a locked state based on the motor torque and motor rotation speed of the electric motor, and if it is determined that the electric motor is in a locked state, setting a search target torque that is higher by a predetermined value than a torque required by a driver that is determined according to an accelerator opening as a target torque of the electric motor, and increasing the motor torque of the electric motor up to the target torque; When it is determined that the locked state has not been resolved within a predetermined time after the motor torque of the electric motor starts to increase, the target torque at that time is stored and then the target torque is reduced; Thereafter, when the torque required by the driver becomes equal to or greater than the stored target torque, a search target torque that is higher than the required torque by a predetermined value is set as the target torque, and the motor torque of the electric motor is increased up to the target torque; When it is determined that the locked state has been resolved within a predetermined time after the motor torque of the electric motor has started to increase, the target torque at that time is stored and then the target torque is reduced; Thereafter, when the torque required by the driver becomes equal to or greater than the stored target torque, the target torque is set in accordance with the required torque, and the electric motor is driven in accordance with the target torque; If it is determined that the locked state has not been released within a predetermined time after the motor torque of the electric motor starts to increase, the series of processes that were executed when it was determined that the locked state has not been released are repeated until the locked state is released.

2. The electric vehicle according to claim 1 .

3. 3. The electric vehicle according to claim 2, wherein the control unit stores the target torque when it is determined that the locked state has been released, and then, when lowering the target torque, lowers the target torque to a continuous operation torque or less.

4. 4. The electric vehicle according to claim 1, wherein the control unit automatically brakes the electric vehicle by controlling in cooperation with a braking device that brakes the electric vehicle while the target torque is being reduced.

5. 5. The electric vehicle according to claim 4, wherein the control unit releases braking of the electric vehicle when the accelerator pedal opening degree falls below a predetermined lock determination threshold value.

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