Control device of electric vehicle

Abstract

To properly control a vehicle driving motor without complicating control of a four-wheel-drive electric vehicle.SOLUTION: A control device of an electric vehicle includes four motors for independently driving each of front, rear, right and left wheels and independently controls driving force of the four wheels. When a possibility of the occurrence of an output limit or a load factor limit of any one motor is predicted, there is a limit prediction motor in which the possibility of the occurrence of the output limit or the load factor limit is a prescribed value or more and the electric vehicle travels straight, drive torque distribution change control is executed to reduce an output of the limit prediction motor and outputs of other motors at positions facing the limit prediction motor in a right and left direction of the electric vehicle and increase outputs of each motor of any one of a front wheel or a rear wheel for reducing the outputs and each motor on each of other motors facing in a longitudinal direction of the electric vehicle (step S6).SELECTED DRAWING: Figure 4

Description

[Technical field]

[0001] The present invention relates to a control device for an electric vehicle equipped with at least a motor as a driving force source, and more particularly to a control device for an electric vehicle in which each of the four wheels (front, rear, left and right) is driven by an independent motor. [Background technology]

[0002] Patent Document 1 describes a front-and-rear-wheel drive vehicle (electric vehicle) equipped with a front motor for driving the front wheels and a rear motor for driving the rear wheels. In the electric vehicle described in Patent Document 1, the relationship between the thermal ratings of the front motor and the rear motor is set to a specific state (for example, a state in which the thermal rating of the front motor is higher than that of the rear motor). Furthermore, when the operation of the rear motor is restricted (when the driving operation is restricted or when the regenerative operation is restricted), the operation of the front motor (driving operation or regenerative operation) is increased. On the other hand, when the operation of the front motor is restricted, the operation of the rear motor is reduced in order to set the driving force distribution ratio of the front and rear wheels to a target distribution ratio. This maintains the balance of the driving forces between the front and rear wheels, and ensures the running stability of the electric vehicle.

[0003] Patent Document 2 describes a driving force control device for an electric vehicle equipped with a motor that drives left and right wheels independently. The driving force control device for an electric vehicle described in Patent Document 2 detects the centrifugal force acting on the electric vehicle when turning and the required value of driving force, sets the driving forces of the left and right wheels based on the centrifugal force and the required value of driving force, and controls the motor. When traveling straight ahead where centrifugal force is not detected, the required value of driving force is distributed equally to each of the left and right wheels, and when turning, the required value of driving force is distributed to each of the left and right wheels so that the driving force of the wheel on the inside of the turn is reduced and the driving force of the wheel on the outside of the turn is increased according to the centrifugal force, and the driving forces of the left and right wheels are set. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] JP 2001-112114 A [Patent Document 2] Patent No. 2660992 Summary of the Invention [Problem to be solved by the invention]

[0005] In the electric vehicle described in the above Patent Document 1, the front motor and the rear motor are controlled separately, thereby making it possible to control the driving force of the front wheels and the driving force of the rear wheels independently. Also, an electric vehicle has been developed in which a motor for driving the vehicle (driving motor) is provided for each of the four wheels (front, rear, left and right), and the driving force of all four wheels can be controlled independently by controlling the four driving motors individually.

[0006] In the electric vehicle in which the front and rear wheels or the four wheels are driven independently as described above, in order to stabilize straight running performance or improve cornering performance, a control is performed to change the driving force distribution or torque distribution of the front and rear wheels or the four wheels. Also, as in the electric vehicle described in Patent Document 2, a control is performed to change the driving force distribution or torque distribution of each of the left and right wheels when turning. When the electric vehicle in which all four wheels are driven independently as described above turns, a rotation difference between the left and right wheels and a torque difference between the front and rear wheels occur, so the control of the driving force becomes complicated. If a limit is imposed on the load rate or output of the drive motor during such turning, it may be necessary to switch the control of the driving force, which may make the control of the electric vehicle even more complicated.

[0007] The present invention has been devised with an eye on the technical problems described above, and aims to provide a control device for an electric vehicle that is capable of appropriately controlling a motor for driving the vehicle without complicating the control of an electric vehicle that drives all four wheels independently (front, rear, left and right). [Means for solving the problem]

[0008] In order to achieve the above-mentioned object, the present invention provides a control device for an electric vehicle which includes a first motor and a second motor which drive the left and right front wheels, respectively, and a third motor and a fourth motor which drive the left and right rear wheels, respectively, and which independently controls the driving forces of the front, rear, left and right wheels, and which further includes a controller which controls each of the motors, and which predicts the possibility that a restriction on the output or load rate of any of the motors will occur, and when there is a restriction prediction motor for which the possibility of the restriction occurring has reached a predetermined value or above, and the electric vehicle is traveling straight, the controller executes front and rear wheel driving torque distribution change control which reduces the output of the restriction prediction motor and the output of another motor located opposite the restriction prediction motor in the left-right direction of the electric vehicle, on both the left and right, thereby increasing the output of either the motor of the front or rear wheels which reduces the output, and the output of the other motor located opposite the limit prediction motor in the front-to-rear direction of the electric vehicle, on both the left and right.

[0009] The controller in the present invention may be configured to predict the possibility that the restriction will occur based on the temperature of each of the motors.

[0010] The controller in the present invention may be configured to predict the possibility that the restriction will occur based on the temperature of oil that cools each of the motors.

[0011] In the present invention, each motor is provided with an electric oil pump that discharges and supplies the oil, and the controller in the present invention may be configured to predict the possibility of the restriction occurring based on the oil supply capacity of each electric oil pump. Effect of the Invention

[0012] The vehicle to be controlled in this invention is an electric vehicle using at least a motor as a driving force source, and in particular, a four-wheel drive electric vehicle in which the front, rear, left and right four wheels are driven by independent motors. In the control device for the electric vehicle of this invention, which is a control target for such a four-wheel drive electric vehicle, the possibility or probability that the output limit or the load rate limit of the motor for driving the vehicle will occur is estimated based on, for example, the temperature of the motor and the rate of change of the temperature of the motor, or the temperature of the oil cooling the motor and the rate of change of the temperature of the oil. If the possibility or probability that such a limit will occur is equal to or greater than a predetermined value, before the output or load rate of the motor is actually limited, the output (output torque) of the limit prediction motor predicted to have the possibility of the limit occurring and the output of another motor paired with the limit prediction motor (disposed opposite to the limit prediction motor) in the left-right direction is reduced. In this way, the output of each of the pair of left and right motors of either the front wheels or the rear wheels is reduced, and the output of each of the pair of left and right motors of the other of the front wheels or the rear wheels is increased. That is, the torque distribution to the front and rear wheels due to the output of each motor for driving the vehicle is changed. This makes it possible to avoid or suppress the above-mentioned motor output limit or load factor limit from actually being implemented.

[0013] Furthermore, in the control device for an electric vehicle of the present invention, the control for predicting the occurrence of the output limit or load rate limit as described above and changing the torque distribution between the front and rear wheels in advance, that is, the drive torque distribution change control of the present invention, is executed while the electric vehicle is traveling straight. The drive torque distribution change control is not executed while the electric vehicle is traveling in a turn. When the four-wheel drive electric vehicle that is the subject of control in the present invention turns in a four-wheel drive state, for example, the control is performed taking into account the rotation difference between the left and right wheels and the torque difference between the front and rear wheels, and the like, and the control content of the drive force becomes more complicated compared to when traveling straight. If the drive torque distribution change control as described above is executed in parallel during such turning, the control of the electric vehicle becomes more complicated. Therefore, the control device for an electric vehicle of the present invention executes the drive torque distribution change control only while the electric vehicle is traveling straight when the occurrence of the motor output limit or load rate limit is predicted as described above, thereby avoiding the overlapping of complicated controls and simplifying the control content of the electric vehicle.

[0014] Therefore, according to the control device for an electric vehicle of the present invention, it is possible to appropriately control the motor for driving the vehicle without complicating the control content of the electric vehicle. [Brief description of the drawings]

[0015] [Figure 1] FIG. 1 is a diagram showing a schematic configuration (drive system and control system) of an electric vehicle to be controlled in the present invention. [Diagram 2] FIG. 2 is a diagram showing an example of a specific configuration of an electric vehicle to be controlled in this invention, and is a gear train diagram showing the drive system (gear transmission mechanism) of a front wheel drive unit that drives each of the left and right front wheels of the electric vehicle. [Diagram 3] FIG. 3 is a diagram showing an example of a specific configuration of an electric vehicle to be controlled in this invention, and is a gear train diagram showing the drive system (gear transmission mechanism) of a rear wheel drive unit that drives each of the left and right rear wheels of the electric vehicle. [Figure 4]FIG. 4 is a flowchart for explaining an example of control executed by the control device for an electric vehicle of the present invention (an example of executing drive torque distribution change control when traveling straight ahead). [Diagram 5] FIG. 5 is a time chart showing an image of the transition of the distribution ratio of the driving torque between the front and rear wheels and the transition of the motor temperature when the driving torque distribution change control of the present invention is executed. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0016] DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described with reference to the accompanying drawings. Note that the following embodiment is merely an example of a specific embodiment of the present invention, and is not intended to limit the present invention.

[0017] The vehicle to be controlled in the embodiment of the present invention is a four-wheel drive electric vehicle equipped with at least a motor as a driving force source and capable of driving four wheels (front, rear, left and right). The motor as the driving force source is capable of independently controlling at least the driving torque of the front wheels and the driving torque of the rear wheels. For this reason, at least two motors are equipped: a front-wheel drive motor that drives the left and right front wheels, and a rear-wheel drive motor that drives the left and right rear wheels. In the following embodiment, an example is shown in which four motors (a first motor 1, a second motor 2, a third motor 3, and a fourth motor 4) are equipped that are capable of independently controlling the driving torque of the four wheels (front, rear, left and right).

[0018] 1 includes a first motor (MG1) 1, a second motor (MG2) 2, a third motor (MG3) 3, and a fourth motor (MG4) 4 as driving force sources, i.e., motors for driving the vehicle. The vehicle Ve also includes a first electric oil pump 5, a second electric oil pump 6, a third electric oil pump 7, and a fourth electric oil pump 8 provided in each of the motors 1, 2, 3, and 4, respectively. The vehicle Ve also includes a detection unit 9 and a controller (ECU) 10 in order to execute various controls.

[0019] Each of the motors 1, 2, 3, 4 is, for example, a permanent magnet synchronous motor or an induction motor. Each of the motors 1, 2, 3, 4 has at least a function as a prime mover that is driven by power supply and outputs torque. Each of the motors 1, 2, 3, 4 may also function as a generator that generates power by receiving torque from the outside and being driven. That is, each of the motors 1, 2, 3, 4 may be a so-called motor generator that combines a function as a prime mover and a function as a generator. Each of the motors 1, 2, 3, 4 is connected to a battery (not shown) via an inverter (not shown). Therefore, the power stored in the battery can be supplied to each of the motors 1, 2, 3, 4, and each of the motors 1, 2, 3, 4 can function as a prime mover to output a drive torque. In addition, each of the motors 1, 2, 3, and 4 is driven by torque transmitted from wheels 11, 12, 13, and 14, which will be described later, and at that time, each of the motors 1, 2, 3, and 4 can function as a generator and the generated electricity can be used to charge the battery.

[0020] The first motor 1 drives the left front wheel 11. For example, the first motor 1 and the front wheel 11 are connected to be capable of transmitting power via a predetermined transmission mechanism such as a reduction gear (not shown). Alternatively, the first motor 1 may be disposed inside the wheel (not shown) of the front wheel 11 as a so-called "in-wheel motor," and the first motor 1 and the front wheel 11 may be directly connected.

[0021] The second motor 2 drives the right front wheel 12. For example, the second motor 2 and the front wheel 12 are connected to be capable of transmitting power via a predetermined transmission mechanism such as a reduction gear (not shown). Alternatively, the second motor 2 may be disposed inside the wheel (not shown) of the front wheel 12 as a so-called "in-wheel motor," and the second motor 2 and the front wheel 12 may be directly connected.

[0022] The third motor 3 drives the left rear wheel 13. For example, the third motor 3 and the rear wheel 13 are connected to be capable of transmitting power via a predetermined transmission mechanism such as a reduction gear (not shown). Alternatively, the third motor 3 may be disposed inside the wheel (not shown) of the rear wheel 13 as a so-called "in-wheel motor," and the third motor 3 and the rear wheel 13 may be directly connected.

[0023] The fourth motor 4 drives the right rear wheel 14. For example, the fourth motor 4 and the rear wheel 14 are connected to be capable of transmitting power via a predetermined transmission mechanism such as a reduction gear (not shown). Alternatively, the fourth motor 4 may be disposed inside the wheel (not shown) of the rear wheel 14 as a so-called "in-wheel motor," and the fourth motor 4 and the rear wheel 14 may be directly connected.

[0024] The first electric oil pump 5 is driven by a dedicated pump drive motor (not shown) and discharges oil (not shown) for cooling and lubrication. The first electric oil pump 5 is provided close to the first motor 1 and supplies the discharged oil to the first motor 1 to cool the first motor 1. The oil discharged by the first electric oil pump 5 may lubricate and cool a transmission mechanism between the first motor 1 and the front wheels 11. In the example shown in FIG. 1, in addition to the cooling system for the first motor 1 using the first electric oil pump 5, a motor cooling device 15 is also provided that circulates a cooling coolant (not shown) to cool the first motor 1.

[0025] The second electric oil pump 6 is driven by a dedicated pump drive motor (not shown) and discharges oil (not shown) for cooling and lubrication. The second electric oil pump 6 is provided close to the second motor 2 and supplies the discharged oil to the second motor 2 to cool the second motor 2. The oil discharged by the second electric oil pump 6 may lubricate and cool the transmission mechanism between the second motor 2 and the front wheels 12. In the example shown in FIG. 1, in addition to the cooling system for the second motor 2 by the second electric oil pump 6, a motor cooling device 16 is also provided which circulates a cooling coolant (not shown) to cool the second motor 2.

[0026] The third electric oil pump 7 is driven by a dedicated pump drive motor (not shown) and discharges oil (not shown) for cooling and lubrication. The third electric oil pump 7 is provided close to the third motor 3 and supplies the discharged oil to the third motor 3 to cool the third motor 3. The oil discharged by the third electric oil pump 7 may lubricate and cool a transmission mechanism between the third motor 3 and the rear wheels 13. In the example shown in FIG. 1, in addition to the cooling system for the third motor 3 using the third electric oil pump 7, a motor cooling device 17 is also provided that circulates a cooling coolant (not shown) to cool the third motor 3.

[0027] The fourth electric oil pump 8 is driven by a dedicated pump drive motor (not shown) and discharges oil (not shown) for cooling and lubrication. The fourth electric oil pump 8 is provided close to the fourth motor 4 and supplies the discharged oil to the fourth motor 4 to cool the fourth motor 4. The oil discharged by the fourth electric oil pump 8 may lubricate and cool the transmission mechanism between the fourth motor 4 and the rear wheels 14. In the example shown in FIG. 1, in addition to the cooling system for the fourth motor 4 by the fourth electric oil pump 8, a motor cooling device 18 that circulates a cooling coolant (not shown) to cool the fourth motor 4 is also provided.

[0028] The first motor 1, first electric oil pump 5, motor cooling device 15, etc., constitute a drive unit 21 for the front wheels 11. Similarly, the second motor 2, second electric oil pump 6, motor cooling device 16, etc., constitute a drive unit 22 for the front wheels 12. The drive units 21 and 22 on the front wheels 11, 12 side constitute a front wheel drive unit 31.

[0029] Fig. 2 shows an example of a drive system (gear transmission mechanism) of the above-mentioned front wheel drive unit 31. The front wheel drive unit 31 shown in Fig. 2 includes a gear transmission mechanism 41 that transmits power between the first motor 1 and the front wheels 11, and a gear transmission mechanism 42 that transmits power between the second motor 2 and the front wheels 12.

[0030] In the gear transmission mechanism 41, a drive gear 41a attached to the rotating shaft 1a of the first motor 1 meshes with a counter driven gear 41c via an idle gear 41b. Since the counter driven gear 41c has a larger diameter than the drive gear 41a, the gear pair of the drive gear 41a and the counter driven gear 41c constitutes a reduction mechanism. In addition, a counter drive gear 41d that rotates integrally with the counter driven gear 41c meshes with a driven gear 41e attached to a drive shaft 11a that is integral with the front wheel 11. Since the driven gear 41e has a larger diameter than the counter drive gear 41d, the gear pair of the counter drive gear 41d and the driven gear 41e constitutes a reduction mechanism.

[0031] Similarly, in the gear transmission mechanism 42, a drive gear 42a attached to the rotating shaft 2a of the second motor 2 meshes with a counter driven gear 42c via an idle gear 42b. Since the counter driven gear 42c has a larger diameter than the drive gear 42a, the gear pair of the drive gear 42a and the counter driven gear 42c constitute a reduction mechanism. In addition, a counter drive gear 42d that rotates integrally with the counter driven gear 42c meshes with a driven gear 42e attached to a drive shaft 12a that is integral with the front wheel 12. Since the driven gear 42e has a larger diameter than the counter drive gear 42d, the gear pair of the counter drive gear 42d and the driven gear 42e constitute a reduction mechanism.

[0032] Meanwhile, the third motor 3, the third electric oil pump 7, the motor cooling device 17, etc. constitute a drive unit 23 for the rear wheels 13. Similarly, the fourth motor 4, the fourth electric oil pump 8, the motor cooling device 18, etc. constitute a drive unit 24 for the rear wheels 14. The drive units 23 and 24 on the rear wheels 13, 14 side constitute a rear wheel drive unit 32.

[0033] Fig. 3 shows an example of a drive system (gear transmission mechanism) of the rear wheel drive unit 32. The rear wheel drive unit 32 shown in Fig. 3 includes a gear transmission mechanism 43 that transmits power between the third motor 3 and the rear wheel 13, and a gear transmission mechanism 44 that transmits power between the fourth motor 4 and the rear wheel 14.

[0034] In the gear transmission mechanism 43, a drive gear 43a attached to the rotating shaft 3a of the third motor 3 meshes with a counter driven gear 43b. Since the counter driven gear 43b has a larger diameter than the drive gear 43a, the gear pair of the drive gear 43a and the counter driven gear 43b constitutes a reduction mechanism. In addition, a counter drive gear 43c that rotates integrally with the counter driven gear 43b meshes with a driven gear 43d attached to the drive shaft 13a integral with the rear wheel 13 as a hypoid gear. Since the driven gear 43d has a larger diameter than the counter drive gear 43c, the gear pair of the counter drive gear 43c and the driven gear 43d constitutes a reduction mechanism.

[0035] Similarly, in the gear transmission mechanism 44, a drive gear 44a attached to the rotating shaft 4a of the fourth motor 4 meshes with a counter driven gear 44b. Since the counter driven gear 44b has a larger diameter than the drive gear 44a, the gear pair of the drive gear 44a and the counter driven gear 44b constitutes a reduction mechanism. In addition, a counter drive gear 44c that rotates integrally with the counter driven gear 44b meshes with a driven gear 44d attached to the drive shaft 14a integral with the rear wheel 14 as a hypoid gear. Since the driven gear 44d has a larger diameter than the counter drive gear 44c, the gear pair of the counter drive gear 44c and the driven gear 44d constitutes a reduction mechanism.

[0036] The detection unit 9 is a device or apparatus for acquiring various data and information required to control the vehicle Ve, and includes, for example, a power supply unit, a microcomputer, a sensor, an input / output interface, etc. In particular, the detection unit 9 in the embodiment of the present invention detects the running state of the vehicle Ve, the operating states of the motors 1, 2, 3, 4 for driving the vehicle, and the operating states of the electric oil pumps 5, 6, 7, 8, etc., and mainly detects various data for controlling the motors 1, 2, 3, 4 for driving the vehicle and for executing the drive torque distribution change control in the embodiment of the present invention.

[0037] Specifically, the detection unit 9 includes a wheel speed sensor 9a that detects the rotational speed of each of the wheels 11, 12, 13, 14, a motor rotation speed sensor (or resolver) 9b that detects the rotation speed of each of the motors 1, 2, 3, 4, a motor torque sensor 9c that detects the torque of each of the motors 1, 2, 3, 4, a pump rotation speed sensor 9d that detects the rotation speed of each of the electric oil pumps 5, 6, 7, 8 (the rotation speed of the pump drive motor that drives each of the electric oil pumps 5, 6, 7, 8), a timer 9e that measures the operating time of each of the electric oil pumps 5, 6, 7, 8, and a steering angle sensor 9f that detects the steering angle of the steered wheels (front wheels 11, 12 or rear wheels 13, 14) or the steering angle of the steering device (not shown). The detection unit 9 also includes an accelerator pedal sensor 9g that detects the amount of accelerator pedal operation (depression amount, depressing angle, etc.) by the driver, and a shift position sensor 9h that detects the operation position of a shift device (not shown) by the driver. In addition, the detection unit 9 also includes, for example, a motor temperature sensor (not shown) that detects the temperature of each of the motors 1, 2, 3, and 4, a SOC sensor (not shown) that detects the state of charge (SOC) of the battery (not shown), a battery temperature sensor (not shown) that detects the temperature of the battery, and an oil temperature sensor (not shown) that detects the temperature of the oil that cools the motors 1, 2, 3, and 4. The detection unit 9 is electrically connected to a controller 10 (described later) and outputs an electric signal corresponding to the detected value or calculated value of the various sensors, devices, and equipment as described above to the controller 10 as detection data.

[0038] The controller 10 is an electronic control device mainly composed of, for example, a microcomputer, and the controller 10 in the embodiment of the present invention controls the vehicle Ve, and in particular, controls each of the motors 1, 2, 3, 4 for driving the vehicle and each of the electric oil pumps 5, 6, 7, 8, to execute the drive torque distribution change control in the embodiment of the present invention. The controller 10 receives various data detected or calculated by the above-mentioned detection unit 9. The controller 10 performs calculations using the various input data, pre-stored data, calculation formulas, and the like. The controller 10 then outputs the calculation results as a control command signal, and is configured to mainly control each of the motors 1, 2, 3, 4 for driving the vehicle, as well as execute the drive torque distribution change control in the embodiment of the present invention, as described above.

[0039] As described above, the vehicle Ve that is the subject of control in this embodiment of the present invention can independently control the drive torque on the front wheels 11, 12 side and the drive torque on the rear wheels 13, 14 side by controlling the front wheel drive unit 31 and the rear wheel drive unit 32, respectively. Furthermore, the front wheel drive unit 31 and the rear wheel drive unit 32 are each composed of the left and right drive units 21, 22 and the left and right drive units 23, 24, respectively, and by controlling each drive unit 21, 22, 23, 24, respectively, the drive torque of each of the front, rear, left and right wheels 11, 12, 13, 14 can be independently controlled.

[0040] The control device for an electric vehicle according to the embodiment of the present invention can control at least an "electric vehicle" capable of independently controlling the drive torque of the front wheels 11, 12 and the drive torque of the rear wheels 13, 14. For example, as described in the above-mentioned Patent Document 1, an "electric vehicle" configured to drive the "left and right front wheels" and the "left and right rear wheels" independently by a "front motor" and a "rear motor", respectively, can also be controlled. In addition, a "hybrid vehicle" in which either the front wheel drive unit 31 or the rear wheel drive unit 32 is provided with an engine (not shown) as a drive source can also be controlled. Although FIG. 1 shows an example in which one controller 10 is provided, a plurality of controllers 10 may be provided for each device or equipment to be controlled, or for each control content.

[0041] As described above, the control device for an electric vehicle in the embodiment of the present invention is configured to execute drive torque distribution change control for the purpose of appropriately controlling the operating states of the vehicle driving motors 1, 2, 3, 4 without complicating the control of the vehicle Ve. An example of the control executed by the controller 10 for this purpose is shown in the flowchart of FIG.

[0042] The control shown in the flowchart of Fig. 4 is executed when the vehicle Ve is traveling. First, in step S1, in order to grasp the traveling state of the vehicle Ve, the detection unit 9 reads in the detection values ​​of various sensors, etc. For example, the accelerator opening (the amount of operation of the accelerator pedal), the vehicle speed, the shift range (the shift position), the steering angle, etc. are read.

[0043] Next, in step S2, it is determined whether the vehicle Ve is traveling straight ahead. For example, whether the vehicle Ve is traveling straight ahead can be determined based on the rotation speed of each wheel 11, 12, 13, 14, the rotation speed difference between the left and right wheels 11, 13 and 12, 14, the detection value of the steering angle sensor 9f, etc.

[0044] If the vehicle Ve is not traveling straight ahead and therefore the determination in step S2 is "No," the routine shown in the flowchart of FIG. 4 is temporarily terminated without executing the controls in the subsequent steps.

[0045] On the other hand, if the vehicle Ve is traveling straight and therefore the answer is "Yes" in step S2, the process proceeds to step S3.

[0046] In step S3, a prediction is made as to whether a load rate limit or output limit will occur for each of the motors 1, 2, 3, and 4. Specifically, the temperature (motor temperature) of each of the motors 1, 2, 3, and 4 is detected, and when the motor temperature of any of the motors 1 (or 2, 3, and 4) reaches a predetermined temperature that is set as a threshold, it is predicted that there is a possibility that a load rate limit or output limit will be performed for that motor 1 (or 2, 3, and 4). In other words, it is determined that there is a motor 1 (or 2, 3, and 4) for which the possibility or probability of a load rate limit or output limit occurring is equal to or greater than a predetermined value, that is, a "restriction predicted motor" in the embodiment of the present invention.

[0047] For example, as shown in the time chart of FIG. 5, when the actual motor temperature (solid line) of any of the motors 1 (or 2, 3, 4) reaches the load rate caution temperature (dashed line) at time t1, the actual motor temperature (dashed line) estimated from the actual motor temperature is predicted to reach the load rate limit temperature at time t3 in the future. The load rate limit temperature is determined in advance as a threshold value for determining whether to implement the load rate limit of each of the motors 1, 2, 3, 4. When the motor temperature (actual value) of any of the motors 1 (or 2, 3, 4) reaches this load rate limit temperature, the load rate limit of the motor 1 (or 2, 3, 4) is started. The load rate caution temperature is a temperature lower than the load rate limit temperature, and the magnitudes of the load rate caution temperature and the load rate limit temperature, as well as the magnitude relationship, are determined in advance in order to predict the possibility or probability of the occurrence of the load rate limit of each of the motors 1, 2, 3, 4. Therefore, when the motor temperature (actual measured value) of any of the motors 1 (or 2, 3, 4) reaches the load factor caution temperature, it is determined that there is a possibility or probability that the motor temperature of that motor 1 (or 2, 3, 4) will rise to the load factor limit temperature with a predetermined value (e.g., 60%, 80%, etc.) or more. In other words, it is determined that the possibility or probability that a load factor limit will occur is a predetermined value or more.

[0048] In addition, the time chart of Figure 5 above shows an example in which the possibility or probability that a load rate limit will occur for each motor 1, 2, 3, 4 is determined based on the motor temperature (actual measured value) of each motor 1, 2, 3, 4, but the possibility or probability that a load rate limit will occur for each motor 1, 2, 3, 4 may also be determined based on the rate of change of the motor temperature of each motor 1, 2, 3, 4 (i.e., the slope of the solid line indicating the motor temperature in the time chart of Figure 5).

[0049] Alternatively, the possibility or probability that the load factor limit of each of the motors 1, 2, 3, 4 will occur may be determined based on the temperature (oil temperature) of the oil (not shown) that cools each of the motors 1, 2, 3, 4. Alternatively, the possibility or probability that the load factor limit of each of the motors 1, 2, 3, 4 will occur may be determined based on the rate of change of the oil temperature of each of the motors 1, 2, 3, 4. As in the example shown in FIG. 5 above, when the oil temperature of any of the motors 1 (or 2, 3, 4) reaches a load factor caution temperature (not shown) set for the oil temperature, it is determined that the possibility or probability that the load factor limit of any of the motors 1 (or 2, 3, 4) will occur is equal to or greater than a predetermined value. Alternatively, when the rate of change of the oil temperature of any of the motors 1 (or 2, 3, 4) is greater than a predetermined rate of change, it is determined that the possibility or probability that the load factor limit of any of the motors 1 (or 2, 3, 4) will occur is equal to or greater than a predetermined value.

[0050] Furthermore, the possibility or probability that the load factor limit of each of the motors 1, 2, 3, 4 will occur may be determined based on the oil supply capacity of each of the electric oil pumps 5, 6, 7, 8 for supplying the cooling oil for each of the motors 1, 2, 3, 4 as described above to each of the motors 1, 2, 3, 4. The oil supply capacity of each of the electric oil pumps 5, 6, 7, 8 varies depending on, for example, the temperature, continuous operation time, or oil temperature of each of the electric oil pumps 5, 6, 7, 8. Therefore, the current oil supply capacity of each of the electric oil pumps 5, 6, 7, 8 is determined based on the temperature, continuous operation time, or oil temperature of each of the electric oil pumps 5, 6, 7, 8, and the possibility or probability that the load factor limit of each of the motors 1, 2, 3, 4 will occur is determined based on the determined oil supply capacity. For example, if the oil supply capacity of the electric oil pump 5 (or 6, 7, or 8) that cools any of the motors 1 (or 2, 3, or 4) is greater than a predetermined capacity value that has been set in advance, it is determined that the possibility or probability that a load factor limit will occur for any of the motors 1 (or 2, 3, or 4) is greater than a predetermined value.

[0051] In addition, the time chart of FIG. 5 above shows an example of limiting the load factor (i.e., the ratio of the actual load to the rated load) of each of the motors 1, 2, 3, 4. However, in the control device for an electric vehicle in an embodiment of the present invention, instead of limiting the load factor, the output of each of the motors 1, 2, 3, 4 may be controlled to be limited.

[0052] Next, in step S4, it is determined whether or not there is a prediction of a load rate limit or output limit for each of the motors 1, 2, 3, 4, i.e., whether or not the possibility (or probability) of the load rate limit or output limit for each of the motors 1, 2, 3, 4 is equal to or greater than a predetermined value. As described above, it is determined whether or not there is a prediction of a load rate limit or output limit for each of the motors 1, 2, 3, 4, based on the motor temperature or the rate of change of the motor temperature for each of the motors 1, 2, 3, 4, the oil temperature or the rate of change of the oil temperature for each of the motors 1, 2, 3, 4, and further the oil supply capacity of each of the electric oil pumps 5, 6, 7, 8, etc.

[0053] If the answer to step S4 is "No" because the possibility (or probability) of load rate limiting or output limiting occurring for each motor 1, 2, 3, 4 is less than a predetermined value, that is, it is predicted that there is no (or a low) possibility that load rate limiting or output limiting will occur for each motor 1, 2, 3, 4, proceed to step S5.

[0054] In step S5, normal drive torque distribution control of the front and rear wheels (front wheels 11, 12 and rear wheels 13, 14) is executed. In this case, since it is predicted that there is no possibility (or the possibility is low) of the load factor limit or output limit of each of the motors 1, 2, 3, 4 occurring, the drive torque distribution change control in the embodiment of the present invention is not executed, so that the control contents of the vehicle Ve are not complicated due to overlapping of controls. Therefore, drive torque distribution control of the front and rear wheels 11, 12, 13, 14 is executed as normal. For example, the distribution ratio of the drive torque of the front and rear wheels 11, 12, 13, 14 is set according to the magnitude of the required drive force of the vehicle Ve, and the drive force of the vehicle Ve is controlled based on the distribution ratio.

[0055] Then, in step S5, normal drive torque distribution control for the front and rear wheels 11, 12, 13, 14 is executed, and then the routine shown in the flowchart of FIG. 4 is temporarily ended.

[0056] On the other hand, if the possibility (or probability) of a load rate limit or output limit occurring for any of motors 1 (or 2, 3, 4) is equal to or greater than a predetermined value, that is, if it is predicted that there is a possibility (or a high probability) that a load rate limit or output limit will occur for any of motors 1 (or 2, 3, 4), and therefore the answer to step S4 is "Yes," proceed to step S6.

[0057] In step S6, control for changing the distribution rate (or distribution ratio) of the drive torque of the front and rear wheels (front wheels 11, 12 and rear wheels 13, 14), that is, drive torque distribution change control in the embodiment of the present invention, is executed. Specifically, the output of any of the motors 1 (or 2, 3, 4) predicted to have a possibility (or high possibility) of load rate restriction or output restriction, that is, the "restriction prediction motor" in the embodiment of the present invention, and the motor 2 (or 1, 4, 3) located opposite the "restriction prediction motor" in the left-right direction of the vehicle Ve are both reduced. In addition, the output of the motors 3, 4 (or 1, 2) located opposite the motors 1, 2 (or 3, 4) whose output is reduced, is increased. For example, the output of the motors 3, 4 (or 1, 2) is increased so as to compensate for the reduction in the output of one of the motors 1, 2 (or 3, 4) to be reduced. As a result, the distribution of drive torque among the front and rear wheels 11, 12, 13, and 14 is changed while maintaining the magnitude of the overall drive force of the vehicle Ve.

[0058] For example, as shown in the time chart of FIG. 5, when it is predicted at time t1 that there is a possibility that a load factor limit or output limit of any of the motors 1 (or 2, 3, 4) will occur, that is, when it is determined that there is a "restriction predicted motor" in the embodiment of the present invention, the above-mentioned drive torque distribution change control is started. Then, from time t1 to time t2, the drive torque distribution of the front and rear wheels 11, 12, 13, 14 is changed. In the example shown in FIG. 5, the output of the motors 3, 4 on the rear wheels 13, 14 side is reduced, and the output of the motors 1, 2 on the front wheels 11, 12 side is increased, thereby changing the drive torque distribution of the front and rear wheels 11, 12, 13, 14 from "5:5" to "7:3", for example.

[0059] Then, when the drive torque distribution change control in the embodiment of the present invention is executed in step S6, the routine shown in the flowchart of FIG. 4 is temporarily ended.

[0060] In this way, the control device for an electric vehicle in the embodiment of the present invention estimates the possibility or probability that output restriction or load rate restriction of each of the motors 1, 2, 3, 4 will occur based on the motor temperature of each of the motors 1, 2, 3, 4, the rate of change of that motor temperature, or the oil temperature of the oil cooling each of the motors 1, 2, 3, 4, and the rate of change of that oil temperature. Then, if the possibility or probability that such restriction will occur is equal to or greater than a predetermined value, before the output or load rate of the motor 1 (or 2, 3, 4) is actually restricted, the output (output torque) of the "restriction prediction motor" predicted to have the possibility of restriction and the other motor 2 (or 1, 4, 3) paired with (disposed opposite) the "restriction prediction motor" in the left-right direction is reduced. In this way, the output of each of the pair of left and right motors 1, 2 (or 3, 4) for either the front wheels 11, 12 or the rear wheels 13, 14 is reduced, and the output of each of the pair of left and right motors 3, 4 (or 1, 2) for the other of the front wheels 11, 12 or the rear wheels 13, 14 is increased accordingly. In other words, the torque distribution to the front and rear wheels 11, 12, 13, 14 by the output of each of the motors 1, 2, 3, 4 for driving the vehicle is changed. This makes it possible to avoid or suppress the output restriction or load rate restriction of the motor 1 (or 2, 3, 4) as described above from actually being implemented.

[0061] Furthermore, in the control device for an electric vehicle in the embodiment of the present invention, the occurrence of the output limit or load factor limit as described above is predicted, and the control for changing the torque distribution between the front and rear wheels 11, 12, 13, and 14 in advance, that is, the drive torque distribution change control in the embodiment of the present invention, is executed while the vehicle Ve is traveling straight. The drive torque distribution change control is not executed while the vehicle Ve is traveling in a turn. Therefore, it is possible to avoid the overlapping of complicated controls and simplify the control content of the vehicle Ve.

[0062] Therefore, according to the control device for an electric vehicle in the embodiment of the present invention, it is possible to appropriately control the motors 1, 2, 3, 4 for driving the vehicle without complicating the control content of the vehicle Ve. [Explanation of symbols]

[0063] 1. First motor (driving force source) 1a Rotating shaft (of first motor) 2 Second motor (driving force source) 2a (Second motor) rotating shaft 3. Third motor (driving force source) 3a (3rd motor) rotating shaft 4. Fourth motor (driving force source) 4a (4th motor) rotating shaft 5. First electric oil pump 6. No. 2 electric oil pump 7. 3rd electric oil pump 8. 4th electric oil pump 9. Detection Unit 9a (Detection section) Wheel speed sensor 9b (Detection section) Motor revolution sensor (or resolver) 9c (detection section) motor torque sensor 9d (Detection section) Pump speed sensor 9e (detector) timer 9f (Detection section) steering angle sensor 9g (Detection part) Accelerator pedal sensor 9h Shift position sensor (detection part) 10 Controller (ECU) 11 Front wheel (left side) 11a (Front left wheel) drive shaft 12 Front wheel (right side) 12a (Right front wheel) drive shaft 13 Rear wheel (left side) 13a (left rear wheel) drive shaft 14 Rear wheel (right side) 14a (Right rear wheel) drive shaft 15,16,17,18 Motor cooling device 21,22 Drive unit (front wheel side) 23,24 Drive unit (rear wheel side) 31 Front wheel drive unit 32 Rear wheel drive unit 41,42 Gear transmission mechanism (for front wheel drive unit) 41a, 42a (Front wheel drive unit) drive gear 41b, 42b (Front wheel drive unit) idle gear 41c, 42c (front wheel drive unit) counter driven gear 41d, 42d (Front wheel drive unit) counter drive gear 41e, 42e (Front wheel drive unit) Driven gear 43,44 Gear transmission mechanism (for rear wheel drive unit) 43a, 44a Drive gear (for rear wheel drive unit) 43b, 44b Counter driven gear (for rear wheel drive unit) 43c, 44c (rear wheel drive unit) counter drive gear 43d, 44d (Rear wheel drive unit) driven gear Ve vehicle (electric vehicle)

Claims

1. A control device for an electric vehicle including a first motor and a second motor for driving left and right front wheels, respectively, and a third motor and a fourth motor for driving left and right rear wheels, respectively, and configured to independently control driving forces of the front, rear, left and right wheels, A controller is provided to control each of the motors, The controller: predicting the possibility of limiting the output or load factor of any of said motors; When there is a restriction prediction motor in which the possibility of the restriction occurring has reached a predetermined value or more, and the electric vehicle is traveling straight, and executing a drive torque distribution change control for increasing the output of each of the motors of either the front wheels or the rear wheels, which reduces the output of the limit prediction motor and the output of the motor at a position opposite to the limit prediction motor in the left-right direction of the electric vehicle, and increasing the output of each of the motors of the other of the motors opposite to the limit prediction motor in the front-rear direction of the electric vehicle. A control device for an electric vehicle.

2. The control device for an electric vehicle according to claim 1, The controller: Predicting the likelihood that the restriction will occur based on the temperature of each of the motors. A control device for an electric vehicle.

3. The control device for an electric vehicle according to claim 2, The controller: Predicting the likelihood of the restriction occurring based on the temperature of the oil cooling each of the motors A control device for an electric vehicle.

4. The control device for an electric vehicle according to claim 3, Each of the motors is provided with an electric oil pump that supplies the oil, The controller: Predicting the possibility of the restriction occurring based on the oil supply capacity of each of the electric oil pumps A control device for an electric vehicle.

Images