Control device of electric vehicle

Abstract

To appropriately protect a motor for vehicle driving and an electric oil pump for cooling, without complicating control of a four-wheel drive electric vehicle.SOLUTION: There is provided a control device of an electric vehicle, which includes four motors for each independently driving front / rear and right / left wheels, and four electric oil pumps for supplying oil for cooling to each of the motors, and independently controls driving forces of the four wheels. The control device executes oil pump protection control of restricting continuous operation of the electric oil pumps reaching a continuous operation limit when the operation state of any electric oil pump reaches a continuous operation switching time and the electric vehicle travels straight, increasing / decreasing the output of the motor on the front wheel side and the output of the motor on the rear wheel side, and changing a driving torque distribution of the front / rear wheels (steps S4 and S5).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 that drives four wheels, front, rear, left, and right, with independent motors respectively.

Background Art

[0002] Patent Document 1 describes a four-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 this Patent Document 1, the mutual relationship of the thermal ratings of the front motor and the rear motor is set in a specific state (for example, a state where the thermal rating of the front motor is higher than the thermal rating of the rear motor). Further, when the operation of the rear motor is restricted (during driving operation restriction or regeneration operation restriction), the operation (driving operation or regeneration operation) of the front motor 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 make the driving force distribution ratio between the front and rear wheels the target distribution ratio. Thereby, the front-rear driving force balance is maintained and the running stability of the electric vehicle is ensured.

[0003] Further, Patent Document 2 describes an electric oil pump control device including a mechanical oil pump that is mechanically connected to a drive source (engine or motor) and driven, an electric oil pump that is operated by electric energy (power of the motor), and pump control means for operating the electric oil pump while the mechanical oil pump is stopped. In the electric oil pump control device described in this Patent Document 2, the electric oil pump is operated on the condition that the continuous operation time of the electric oil pump does not exceed a predetermined allowable operation time. When the continuous operation time of the electric oil pump exceeds the predetermined allowable operation time, the drive source is started and the mechanical oil pump is operated. That is, in order to protect the electric oil pump, the hydraulic pressure generation source is switched from the electric oil pump that is restricted in continuous operation time to another oil pump that is not restricted.

Prior Art Documents

Patent Document

[0004]

Patent Document 1

Patent Document 2

Summary of the Invention

Problems to be Solved by the Invention

[0005] In the electric vehicle described in the above Patent Document 1, by controlling the front motor and the rear motor individually, the driving force of the front wheels and the driving force of the rear wheels can be controlled independently. Also, electric vehicles have been developed in which motors for vehicle driving (driving motors) are provided on all four wheels, front, rear, left, and right, and by controlling these four driving motors individually, it is possible to control all the driving forces of the four wheels independently. Then, in order to cool and lubricate each driving motor that drives the front and rear wheels or the four wheels independently, and the transmission mechanism between the driving motor and the wheels, for example, an electric oil pump as described in Patent Document 2 is used. Since each driving motor that drives the front and rear wheels or the four wheels is controlled individually, an electric oil pump is also provided for each driving motor, and the operation of each electric oil pump is controlled individually. Therefore, for example, when the electric oil pump of the driving motor that drives either the front wheels or the rear wheels is restricted in its continuous operation time as in the electric oil pump control device described in Patent Document 2, in order to protect the electric oil pump and the driving motor, it is conceivable to perform control (switching control of the electric oil pump and the driving motor) such as switching to the driving motor provided with the other electric oil pump that is not restricted to drive the wheels.

[0006] On the one hand, in an electric vehicle that independently drives the front and rear wheels or four wheels as described above, in order to stabilize straight running performance or improve turning performance, control is performed to change the driving force distribution or torque distribution of the front and rear wheels or four wheels. In particular, when an electric vehicle that independently drives all four wheels on the front, rear, left, and right turns, a rotational difference between the left and right wheels, a torque difference between the front and rear wheels, etc. occur, so the control content of the driving force becomes complicated. When such an electric vehicle that independently drives four wheels turns, if the switching control of the electric oil pump and the driving motor as described above is involved, the control of the electric vehicle becomes even more complicated.

[0007] This invention was conceived by paying attention to the above technical problems, and an object thereof is to provide a control device for an electric vehicle that can appropriately protect an electric oil pump and a motor for vehicle driving without complicating the control of an electric vehicle that independently drives all four wheels on the front, rear, left, and right.

Means for Solving the Problems

[0008] In order to achieve the above object, the present invention provides a first motor and a second motor that respectively drive the left and right front wheels, a third motor and a fourth motor that respectively drive the left and right rear wheels, and a first electric oil pump, a second electric oil pump, a third electric oil pump, and a fourth electric oil pump that respectively discharge and supply oil for cooling and lubrication to the first motor, the second motor, the third motor, and the fourth motor. The present invention is a control device for an electric vehicle that independently controls the driving forces of the front, rear, left, and right wheels, and includes a controller that controls each of the motors and each of the electric oil pumps. When the operating state of any one of the electric oil pumps meets a predetermined continuous operation limit condition and the electric vehicle is traveling straight, the controller restricts the continuous operation of the electric oil pump that meets the continuous operation limit condition, and reduces the output of each of the motors on either the front wheels or the rear wheels to which the oil is supplied from the electric oil pump that restricts the continuous operation, and increases the output of each of the other motors, and executes oil pump protection control.

[0009] Further, the controller in the present invention may be configured to execute the oil pump protection control in a four-wheel drive state in which the driving force is generated by all the front, rear, left, and right wheels.

[0010] Furthermore, the present invention further includes a notification device that causes a predetermined information to be recognized by an occupant (driver, passenger) of the electric vehicle. The controller in the present invention may be configured to cause the occupant to recognize, by the notification device, that the oil pump protection control is executed and the four-wheel drive state is restricted.

[0011] Moreover, the present invention further includes a motor cooling device that cools each of the motors with a coolant. The controller in the present invention may be configured to cool each of the motors whose output is increased with the coolant when executing the oil pump protection control.

[0012] And, after starting the execution of the oil pump protection control, the controller in the present invention may be configured to increase the coolant.

Advantages of the Invention

[0013] The vehicle to be controlled in this invention is at least an electric vehicle having a motor as a driving force source, and in particular, is a four-wheel drive electric vehicle in which the four wheels on the front, rear, left, and right are each driven by an independent motor. Each motor for vehicle driving is provided with an electric oil pump for supplying cooling oil (lubricating oil) to each motor. Since the electric oil pump is driven by a dedicated (pump driving) motor, predetermined continuous operation limit conditions are set to protect the pump driving motor. And in the control device of the electric vehicle of this invention, when the operating state of the electric oil pump meets the continuous operation limit conditions, the continuous operation of the electric oil pump is restricted. For example, when the continuous operation time of the electric oil pump exceeds a predetermined continuous operation allowable time, the operation of the electric oil pump is stopped, or the rotational speed of the pump driving motor is reduced. At the same time, the output (output torque) of the vehicle driving motor supplied with oil from the electric oil pump whose operation is restricted, and another vehicle driving motor that forms a pair (is arranged opposite) in the left-right direction with the vehicle driving motor is reduced. Also, in this way, for each of the pair of motors on the left and right of either the front wheels or the rear wheels whose output is reduced, the output of each of the pair of vehicle driving motors on the other of the front wheels or the rear wheels is increased respectively. That is, the torque distribution between the front and rear wheels by the output of the vehicle driving motors is changed. Thereby, the electric oil pump and the vehicle driving motors are appropriately protected.

[0014] Furthermore, in the control device for an electric vehicle of the present invention, the control that relates the limitation of the continuous operation of the electric oil pump and the change in the torque distribution between the front and rear wheels as described above, that is, the oil pump protection control in the present invention, is executed during the straight running of the electric vehicle. During the turning running of the electric vehicle, the oil pump protection control is not executed. The four-wheel drive electric vehicle targeted for control in the present invention, when turning in the four-wheel drive state, is controlled considering, for example, the rotational difference between the left and right wheels and the torque difference between the front and rear wheels, etc. Compared with straight running, the control content of the driving force becomes more complex. If, during such turning running, the above-described oil pump protection control is executed concurrently, the control of the electric vehicle will become even more complicated. Therefore, the control device for an electric vehicle of the present invention executes the oil pump protection control only during the straight running of the electric vehicle as described above, thereby avoiding the superposition of complex controls and simplifying the control content of the electric vehicle.

[0015] Therefore, according to the control device for an electric vehicle of the present invention, it is possible to appropriately protect the electric oil pump and the motor for vehicle driving without complicating the control content of the electric vehicle.

Brief Description of the Drawings

[0016]

Figure 1

Figure 2

Figure 3

Figure 4

Figure 5

BEST MODE FOR CARRYING OUT THE INVENTION

[0017] Embodiments of the present invention will be described with reference to the drawings. Note that the embodiments shown below are merely examples of the present invention when embodied, and do not limit the present invention.

[0018] The vehicle to be controlled in the embodiments of the present invention is an electric vehicle with four-wheel drive that is equipped with at least a motor as a driving force source and can drive four wheels on the front, rear, left, and right. The motor of the driving force source can independently control at least the driving torque of the front wheels and the driving torque of the rear wheels. Therefore, at least two motors, namely, a front-wheel drive motor for driving the left and right front wheels and a rear-wheel drive motor for driving the left and right rear wheels, are mounted. In the following examples, an example is shown in which four motors (first motor 1, second motor 2, third motor 3, and fourth motor 4) capable of independently controlling the driving torques of the four wheels on the front, rear, left, and right are mounted.

[0019] The electric vehicle (hereinafter referred to as vehicle) Ve shown in FIG. 1 includes a driving force source, that is, a first motor (MG1) 1, a second motor (MG2) 2, a third motor (MG3) 3, and a fourth motor (MG4) 4 as 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 above motors 1, 2, 3, 4. The vehicle Ve includes a detection unit 9 and a controller (ECU) 10 for executing various controls.

[0020] Each of the motors 1, 2, 3, and 4 is constituted by, for example, a permanent magnet synchronous motor or an induction motor. Each of the motors 1, 2, 3, and 4 has at least a function as a prime mover that is driven by being supplied with power to output torque. Further, each of the motors 1, 2, 3, and 4 may function as a generator that generates electric power by being driven by receiving torque from the outside. That is, each of the motors 1, 2, 3, and 4 may be a so-called motor - generator having both a function as a prime mover and a function as a generator. A battery (not shown) is connected to each of the motors 1, 2, 3, and 4 via an inverter (not shown). Therefore, the electric power stored in the battery can be supplied to each of the motors 1, 2, 3, and 4, and each of the motors 1, 2, 3, and 4 can be made to function as a prime mover to output driving torque. Also, each of the motors 1, 2, 3, and 4 can be driven by the torque transmitted from the wheels 11, 12, 13, and 14 described later, and at that time, each of the motors 1, 2, 3, and 4 can be made to function as a generator to charge the battery with the generated electric power.

[0021] The first motor 1 drives the left front wheel 11. For example, the first motor 1 and the front wheel 11 are connected so as to be able to transmit power via a predetermined transmission mechanism such as a reduction gear (not shown). Alternatively, as a so - called "in - wheel motor", the first motor 1 may be disposed inside the wheel (not shown) of the front wheel 11, and the first motor 1 and the front wheel 11 may be directly connected.

[0022] The second motor 2 drives the right front wheel 12. For example, the second motor 2 and the front wheel 12 are connected so as to be able to transmit power via a predetermined transmission mechanism such as a reduction gear (not shown). Alternatively, as a so - called "in - wheel motor", the second motor 2 may be disposed inside the wheel (not shown) of the front wheel 12, and the second motor 2 and the front wheel 12 may be directly connected.

[0023] The third motor 3 drives the left rear wheel 13. For example, the third motor 3 and the rear wheel 13 are connected so that power can be transmitted therebetween via a predetermined transmission mechanism such as a reduction gear (not shown). Alternatively, as a so-called "in-wheel motor", the third motor 3 may be disposed inside a wheel (not shown) of the rear wheel 13, and the third motor 3 and the rear wheel 13 may be directly connected.

[0024] The fourth motor 4 drives the right rear wheel 14. For example, the fourth motor 4 and the rear wheel 14 are connected so that power can be transmitted therebetween via a predetermined transmission mechanism such as a reduction gear (not shown). Alternatively, as a so-called "in-wheel motor", the fourth motor 4 may be disposed inside a wheel (not shown) of the rear wheel 14, and the fourth motor 4 and the rear wheel 14 may be directly connected.

[0025] 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. Note that the oil discharged by the first electric oil pump 5 may lubricate and cool the transmission mechanism between the first motor 1 and the front wheel 11. In the example shown in FIG. 1, in addition to the cooling system for the first motor 1 by the first electric oil pump 5, for example, a motor cooling device 15 that circulates a coolant (not shown) for cooling to cool the first motor 1 is provided in parallel.

[0026] 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. Note that 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. Further, in the example shown in FIG. 1, in addition to the cooling system of the second motor 2 by this second electric oil pump 6, for example, a motor cooling device 16 that circulates a coolant (not shown) for cooling to cool the second motor 2 is provided together.

[0027] 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. Note that the oil discharged by the third electric oil pump 7 may lubricate and cool the transmission mechanism between the third motor 3 and the rear wheels 13. Further, in the example shown in FIG. 1, in addition to the cooling system of the third motor 3 by this third electric oil pump 7, for example, a motor cooling device 17 that circulates a coolant (not shown) for cooling to cool the third motor 3 is provided together.

[0028] 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. Note that 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. Further, in the example shown in FIG. 1, in addition to the cooling system of the fourth motor 4 by this fourth electric oil pump 8, for example, a motor cooling device 18 that circulates a coolant (not shown) for cooling to cool the fourth motor 4 is provided together.

[0029] The drive unit 21 for the front wheel 11 is constituted by the above-described first motor 1, first electric oil pump 5, motor cooling device 15, etc. Similarly, the drive unit 22 for the front wheel 12 is constituted by the above-described second motor 2, second electric oil pump 6, motor cooling device 16, etc. And the front wheel drive unit 31 is constituted by these drive units 21 and 22 on the front wheel 11, 12 sides.

[0030] Fig. 2 shows an example of the drive system (gear transmission mechanism) of the above-described front wheel drive unit 31. The front wheel drive unit 31 shown in this Fig. 2 includes a gear transmission mechanism 41 that transmits power between the first motor 1 and the front wheel 11, and a gear transmission mechanism 42 that transmits power between the second motor 2 and the front wheel 12.

[0031] 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 drive gear 41c via an idler gear 41b. Since the counter drive gear 41c has a larger diameter than the drive gear 41a, a reduction mechanism is constituted by the gear pair of these drive gear 41a and counter drive gear 41c. Further, a counter drive gear 41d that rotates integrally with the counter drive gear 41c meshes with a driven gear 41e attached to a drive shaft 11a integral with the front wheel 11. Since the driven gear 41e has a larger diameter than the counter drive gear 41d, a reduction mechanism is constituted by the gear pair of these counter drive gear 41d and driven gear 41e.

[0032] 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 drive gear 42c via an idle gear 42b. Since the counter drive gear 42c has a larger diameter than the drive gear 42a, a reduction mechanism is constituted by the gear pair of the drive gear 42a and the counter drive gear 42c. Further, a counter drive gear 42d that rotates integrally with the counter drive gear 42c meshes with a driven gear 42e attached to a drive shaft 12a integral with the front wheel 12. Since the driven gear 42e has a larger diameter than the counter drive gear 42d, a reduction mechanism is constituted by the gear pair of the counter drive gear 42d and the driven gear 42e.

[0033] On the other hand, a drive unit 23 for the rear wheel 13 is constituted by the above-described third motor 3, third electric oil pump 7, motor cooling device 17, etc. Similarly, a drive unit 24 for the rear wheel 14 is constituted by the above-described fourth motor 4, fourth electric oil pump 8, motor cooling device 18, etc. And a rear wheel drive unit 32 is constituted by these drive units 23 and 24 on the rear wheel 13, 14 sides.

[0034] FIG. 3 shows an example of a drive system (gear transmission mechanism) of the above-described rear wheel drive unit 32. The rear wheel drive unit 32 shown in this 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.

[0035] 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 drive gear 43b. Since the counter drive gear 43b has a larger diameter than the drive gear 43a, a speed reduction mechanism is constituted by the gear pair of the drive gear 43a and the counter drive gear 43b. Further, a counter drive gear 43c that rotates integrally with the counter drive gear 43b meshes, as a hypoid gear, with a driven gear 43d attached to a drive shaft 13a integral with the rear wheel 13. Since the driven gear 43d has a larger diameter than the counter drive gear 43c, a speed reduction mechanism is constituted by the gear pair of the counter drive gear 43c and the driven gear 43d.

[0036] 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 drive gear 44b. Since the counter drive gear 44b has a larger diameter than the drive gear 44a, a speed reduction mechanism is constituted by the gear pair of the drive gear 41a and the counter drive gear 44b. Further, a counter drive gear 44c that rotates integrally with the counter drive gear 44b meshes, as a hypoid gear, with a driven gear 44d attached to a drive shaft 14a integral with the rear wheel 14. Since the driven gear 44d has a larger diameter than the counter drive gear 44c, a speed reduction mechanism is constituted by the gear pair of the counter drive gear 44c and the driven gear 44d.

[0037] The detection unit 9 is a device or apparatus for acquiring various types of data and information necessary for controlling the vehicle Ve. For example, it includes a power supply unit, a microcomputer, sensors, an input / output interface, and the like. 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, respectively. At the same time, for controlling the motors 1, 2, 3, 4 for driving the vehicle and the electric oil pumps 5, 6, 7, 8, and for detecting various types of data for executing the oil pump protection control in the embodiment of the present invention.

[0038] Specifically, the detection unit 9 includes a wheel speed sensor 9a that detects the rotational speed of each wheel 11, 12, 13, 14, a motor rotation speed sensor (or resolver) 9b that detects the rotational speed of each motor 1, 2, 3, 4, a motor torque sensor 9c that detects the torque of each motor 1, 2, 3, 4, a pump rotation speed sensor 9d that detects the rotational speed of each electric oil pump 5, 6, 7, 8 (the rotational speed of the pump drive motor that drives each electric oil pump 5, 6, 7, 8), a timer 9e that measures the operating time of each electric oil pump 5, 6, 7, 8, and a steering angle sensor 9f that detects the steering angle of the steering wheel (front wheels 11, 12 or rear wheels 13, 14) or the steering angle of a steering device (not shown), etc. In addition, the detection unit 9 has, for example, a motor temperature sensor (not shown) that detects the temperature of each motor 1, 2, 3, 4, a SOC sensor (not shown) that detects the state of charge (SOC) of a 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 for cooling each motor 1, 2, 3, 4. And the detection unit 9 is electrically connected to a controller 10 described later, and outputs an electrical signal corresponding to the detection values or calculated values of the various sensors, devices, and apparatuses as described above to the controller 10 as detection data.

[0039] The controller 10 is an electronic control device mainly composed of, for example, a microcomputer. 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 vehicle driving and each of the electric oil pumps 5, 6, 7, 8 to execute the oil pump protection control in the embodiment of the present invention. Various data detected or calculated by the detection unit 9 described above are input to the controller 10. The controller 10 performs calculations using the input various data and the data and calculation formulas stored in advance. Then, the controller 10 outputs the calculation result as a control command signal, and as described above, is configured to control each of the motors 1, 2, 3, 4 for vehicle driving and each of the electric oil pumps 5, 6, 7, 8, and execute the oil pump protection control in the embodiment of the present invention.

[0040] In the example shown in FIG. 1, the vehicle Ve is provided with a display 19. The display 19 corresponds to the "notification device" in the embodiment of the present invention, and enables the passengers (driver or passengers) of the vehicle Ve to recognize predetermined information. Therefore, the controller 10 outputs a predetermined control signal to the display 19 to cause the display 19 to display predetermined information for the passengers of the vehicle Ve. Further, FIG. 1 shows an example in which one controller 10 is provided, but 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 vehicle Ve to be controlled in the embodiment of the present invention can independently control the driving torque on the front wheel 11, 12 side and the driving torque on the rear wheel 13, 14 side by controlling the front wheel drive unit 31 and the rear wheel drive unit 32 respectively. Further, 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, and by controlling each of the drive units 21, 22, 23, 24 respectively, the driving torques of the front, rear, left, and right wheels 11, 12, 13, 14 can be independently controlled.

[0042] Note that the control device for an electric vehicle in the embodiment of the present invention can target at least an "electric vehicle" capable of independently controlling the drive torque on the front wheel 11, 12 side and the drive torque on the rear wheel 13, 14 side for control. For example, as described in the aforementioned Patent Document 1, an "electric vehicle" configured to independently drive "left and right front wheels" and "left and right rear wheels" with a "front motor" and a "rear motor", respectively, can also be targeted for control. Further, a "hybrid vehicle" equipped with an engine (not shown) as a drive power source in any of the front wheel drive unit 31 and the rear wheel drive unit 32 as described above can also be targeted for control.

[0043] As described above, the control device for an electric vehicle in the embodiment of the present invention is configured to execute oil pump protection control for the purpose of appropriately protecting each electric oil pump 5, 6, 7, 8 and each motor 1, 2, 3, 4 for vehicle drive without complicating the control of the vehicle Ve. For this purpose, an example of the control executed by the controller 10 is shown in the flowchart of FIG. 4.

[0044] The control shown in the flowchart of FIG. 4 is executed when the vehicle Ve is running. Also, as shown in the control content of the next step S1, it may be executed only when the vehicle Ve is running in a four-wheel drive state. Alternatively, it may be executed without being limited to the four-wheel drive state of the vehicle Ve.

[0045] In the flowchart of FIG. 4, first, in step S1, it is determined whether the vehicle Ve is running in a four-wheel drive state, that is, a state in which driving forces are generated by all the wheels 11, 12, 13, 14 on the front, rear, left, and right. For example, based on the vehicle speed and the detected values of the rotational speeds and torques of each motor 1, 2, 3, 4 for vehicle drive, it is possible to determine whether the vehicle Ve is in a four-wheel drive state. Note that, as described above, the control shown in the flowchart of FIG. 4 may be executed without being limited to the four-wheel drive state of the vehicle Ve. Therefore, this step S1 may be skipped and the control may be started from the next step S2.

[0046] If the vehicle Ve is not running in a four-wheel drive state, that is, if at least one of the vehicle Ve is not in a four-wheel drive state or the vehicle Ve is not running, and it is determined as "No" in this step S1, then without executing the control of each subsequent step, the routine shown in this flowchart of FIG. 4 is terminated once.

[0047] On the contrary, if the vehicle Ve is running in a four-wheel drive state, that is, if the vehicle Ve is running and the vehicle Ve is in a four-wheel drive state, and it is determined as "Yes" in step S1, then proceed to step S2.

[0048] In step S2, it is determined whether the operating states of the electric oil pumps 5, 6, 7, and 8 correspond to predetermined continuous operation limit conditions. For example, it is determined whether the continuous operation time of any of the electric oil pumps 5, 6, 7, and 8 has reached the continuous operation switching time. The continuous operation switching time is a threshold value predetermined as a continuous operation limit condition for protecting the pump drive motors that drive the electric oil pumps 5, 6, 7, and 8.

[0049] Note that the continuous operation limit conditions in the embodiments of the present invention are not limited to the continuous operation switching time as described above. For example, based on the temperature of the oil that cools each of the motors 1, 2, 3, and 4, it may be determined whether the pump drive motors can operate continuously. Alternatively, based on the load factor of each of the motors 1, 2, 3, and 4 that are supplied with oil from the electric oil pumps 5, 6, 7, and 8, it may be determined whether the pump drive motors can operate continuously.

[0050] If the continuous operation time of the electric oil pumps 5, 6, 7, and 8 has not yet reached the continuous operation switching time, that is, if the operating states of the electric oil pumps 5, 6, 7, and 8 do not correspond to the predetermined continuous operation limit conditions and it is determined as "No" in this step S2, then without executing the control of each subsequent step, the routine shown in this flowchart of FIG. 4 is terminated once.

[0051] On the other hand, if the operating states of the electric oil pumps 5, 6, 7, and 8 meet the predetermined continuous operation limit conditions, for example, as shown at time t1 in the time chart of FIG. 5, when any of the continuous operation times of the electric oil pumps 5, 6, 7, and 8 reaches the continuous operation switching time (the dashed-dotted line in FIG. 5) and it is determined "Yes" in step S2, the process proceeds to step S3.

[0052] In step S3, it is determined whether the vehicle Ve is in a straight-ahead driving state. For example, based on the rotational speeds of the respective wheels 11, 12, 13, 14, the rotational speed differences between the left and right wheels 11, 13 and the wheels 12, 14, and the detection value of the steering angle sensor 9f, etc., it can be determined whether the vehicle Ve is in a straight-ahead driving state.

[0053] If it is determined "No" in this step S3 because the vehicle Ve is not in a straight-ahead driving state, the control of this step S3 is executed again. For example, if it is determined "No" in step S3 because the vehicle Ve is in a turning driving, the control of this step S3 is repeated until the vehicle Ve finishes its turning driving and enters a straight-ahead driving state.

[0054] On the other hand, for example, as shown at time t2 in the time chart of FIG. 5, if it is determined "Yes" in step S3 because the vehicle Ve is in a straight-ahead driving state, the process proceeds to step S4.

[0055] In the following steps S4 and S5, the oil pump protection control in the embodiment of the present invention is executed. That is, the control for restricting the continuous operation of each electric oil pump 5, 6, 7, 8 and the control for changing the torque distribution between the front wheels 11, 12 and the rear wheels 13, 14 are executed in linkage.

[0056] In step S4, the drive torque distribution (distribution ratio) at the front and rear wheels (front wheels 11, 12 and rear wheels 13, 14) of the vehicle Ve is changed. Specifically, in step S2 above, oil is supplied from any one of the electric oil pumps 5 (or 6, 7, 8) whose continuous operation is restricted due to meeting the continuous operation restriction conditions. The output of any one of the motors 1 (or 2, 3, 4) and the motor 2 (or 1, 4, 3) located opposite in the left - right direction of the vehicle Ve to any one of those motors 1 (or 2, 3, 4) is reduced together. Additionally, the output of the motors 3, 4 (or 1, 2) located opposite to the motors 1, 2 (or 3, 4) whose output is reduced in the front - rear direction of the vehicle Ve is increased. For example, the output of the other motor 3, 4 (or 1, 2) is increased so as to compensate for the reduction in the output reduced by one of the motors 1, 2 (or 3, 4). Thereby, while maintaining the magnitude of the overall driving force of the vehicle Ve, the drive torque distribution of the front and rear wheels 11, 12, 13, 14 is changed.

[0057] In step S5, the operation of any one of the electric oil pumps 5 (or 6, 7, 8) that met the continuous operation restriction conditions in step S2 above is stopped. Or, the rotational speed of the pump drive motor that drives any one of the electric oil pumps 5 (or 6, 7, 8) that met the continuous operation restriction conditions is reduced. Thereby, any one of the electric oil pumps 5 (or 6, 7, 8) and the pump drive motor, which may have had their durability reduced due to continuous operation, are protected.

[0058] Note that the order of execution of steps S4 and S5 above is different. For example, from step S3 above, the control may be executed in the order of step S5, step S4. Or, the controls of step S4 and step S5 may be executed in parallel.

[0059] Also, as shown in the time chart of FIG. 5, in addition to the continuous operation switching time set as a continuous operation restriction condition in the control shown in step S5 above, a continuous operation prohibition time (two-dot chain line in FIG. 5) may be set. The continuous operation prohibition time is set to a continuous operation time longer than the continuous operation switching time. In the time chart of FIG. 5, in the period from when the continuous operation time of the electric oil pump 5 (or 6, 7, 8) reaches the continuous operation switching time at time t1 until the straight-ahead state of the vehicle Ve is determined at time t2, if by chance the continuous operation time of the electric oil pump 5 (or 6, 7, 8) reaches the continuous operation prohibition time first, the operation of the electric oil pump 5 (or 6, 7, 8) is stopped. That is, in this case, the protection of the electric oil pump 5 (or 6, 7, 8) is prioritized over the execution of the oil pump protection control, and the operation of the electric oil pump 5 (or 6, 7, 8) is stopped. Thereby, it is possible to reliably protect any of the electric oil pumps 5 (or 6, 7, 8) whose durability may be reduced due to continuous operation, and the pump drive motor that drives it.

[0060] Then, when the oil pump protection control in the embodiment of the present invention is executed in steps S4 and S5 above, thereafter, the routine shown in the flowchart of FIG. 4 is once terminated.

[0061] Furthermore, when the control device for an electric vehicle in the embodiment of the present invention executes oil pump protection control, it displays on the display 19 that the oil pump protection control is executed and the four-wheel drive state of the vehicle Ve is restricted, so that the passengers of the vehicle Ve can recognize it. By executing the oil pump protection control as described above, although the magnitude of the overall driving force of the vehicle Ve is maintained, the drive torque distribution between the front and rear wheels 11, 12, 13, 14 is changed. As a result, the four-wheel drive state of the vehicle Ve is restricted. Therefore, when the magnitudes of the drive torques of the front and rear wheels 11, 12, 13, 14 increase or decrease respectively, the passengers of the vehicle Ve may feel discomfort. On the other hand, as described above, by displaying on the display 19 that the four-wheel drive state of the vehicle Ve is restricted and making the passengers recognize it, it is possible to avoid giving discomfort to the passengers.

[0062] Note that, as described above, the display 19 corresponds to the "notification device" in the embodiment of the present invention, but such a "notification device" is not limited to the display 19. For example, a simpler display lamp (not shown) or warning lamp (not shown) than the display 19 may be used to make the passengers recognize the above information. Alternatively, the audio device (not shown) of the vehicle Ve may be used as the "notification device" to make the passengers recognize the above information by means of sound, warning sound, etc.

[0063] Also, when the control device for an electric vehicle in the embodiment of the present invention executes oil pump protection control, any one of the motors 1 (or 2, 3, 4) whose output will be increased by changing the drive torque distribution between the front and rear wheels 11, 12, 13, 14 as described above may be cooled by the coolant of the motor cooling device 15 (or 16, 17, 18). Furthermore, after starting the execution of the oil pump protection control, the amount of the coolant circulated by the motor cooling device 15 (or 16, 17, 18) may be increased. For example, the coolant preliminarily stored in a reservoir tank (not shown) etc. may be added to the coolant circulation path (not shown) in the motor cooling device 15 (or 16, 17, 18).

[0064] The motor cooling devices 15, 16, 17, 18 as described above each include, for example, a mechanical fluid pump (not shown) that is driven by receiving torque from the rotating shafts 1a, 2a, 3a, 4a of the motors 1, 2, 3, 4, or from the drive shafts 11a, 12a, 13a, 14a, and are configured to circulate a coolant with the mechanical fluid pump. Alternatively, the motor cooling devices 15, 16, 17, 18 may each include an electric fluid pump (not shown) separately from the electric oil pumps 5, 6, 7, 8 as described above, and may be configured to circulate a coolant with such an electric fluid pump. Therefore, for example, by increasing the output of any one of the motors 1 (or 2, 3, 4), for any one of the motors 1 (or 2, 3, 4) whose heat generation amount increases, in addition to the cooling by the oil of the electric oil pump 5 (or 6, 7, 8), cooling by the coolant of the motor cooling device 15 (or 16, 17, 18) can be performed assistively. Therefore, the cooling performance of each of the motors 1, 2, 3, 4 can be ensured, and each of the motors 1, 2, 3, 4 can be appropriately protected.

[0065] As described above, in the control device for an electric vehicle according to the embodiment of the present invention, when the operating state of any one of the electric oil pumps 5 (or 6, 7, 8) meets the continuous operation limit conditions set to protect the pump drive motor, the continuous operation of the electric oil pump 5 (or 6, 7, 8) is restricted. For example, when the continuous operation time of the electric oil pump 5 (or 6, 7, 8) exceeds a predetermined continuous operation switching time or continuous operation allowable time, the operation of the electric oil pump 5 (or 6, 7, 8) is stopped, or the rotational speed of the pump drive motor is reduced. At the same time, the output (output torque) of the vehicle drive motor 1 (or 2, 3, 4) supplied with oil from any one of the electric oil pumps 5 (or 6, 7, 8) whose operation is restricted, and another vehicle drive motor 2 (or 1, 4, 3) that is paired (oppositely arranged) with the vehicle drive motor 1 (or 2, 3, 4) in the left-right direction is reduced. Also, for each of the left and right pair of motors 1, 2 (or 3, 4) on either the front wheels 11, 12 or the rear wheels 13, 14, as the output of each is reduced, the output of each of the left and right pair of vehicle drive motors 3, 4 (or 1, 2) on the other of the rear wheels 13, 14 or the front wheels 11, 12 is increased respectively. That is, the torque distribution of the front and rear wheels 11, 12, 13, 14 by the output of each of the vehicle drive motors 1, 2, 3, 4 is changed. Thereby, each of the electric oil pumps 5, 6, 7, 8 and each of the vehicle drive motors 1, 2, 3, 4 are appropriately protected.

[0066] Furthermore, in the control device for an electric vehicle according to an embodiment of the present invention, the control that relates the restriction of continuous operation of the electric oil pump 5 (or 6, 7, 8) and the change of torque distribution between the front and rear wheels 11, 12, 13, 14 as described above, that is, the oil pump protection control in the embodiment of the present invention, is executed during straight running of the vehicle Ve. In short, during turning of the vehicle Ve, the oil pump protection control is not executed. When the four-wheel drive vehicle Ve targeted for control in the embodiment of the present invention turns in a four-wheel drive state, for example, control takes into account the rotational difference between the left and right wheels (wheel 11 and wheel 12, or wheel 13 and wheel 14) and the torque difference between the front and rear wheels (front wheels 11, 12 and rear wheels 13, 14), etc., and the control content of the driving force becomes more complicated compared to straight running. On the other hand, the control device for an electric vehicle according to an embodiment of the present invention executes the oil pump protection control only during straight running of the vehicle Ve as described above. Therefore, it is possible to avoid the superposition of complicated control of the vehicle Ve and simplify the control content of the vehicle Ve.

[0067] Therefore, according to the control device for an electric vehicle according to an embodiment of the present invention, each electric oil pump 5, 6, 7, 8 and each motor 1, 2, 3, 4 for vehicle drive can be appropriately protected without complicating the control content of the vehicle Ve, and their durability can be improved.

Description of Signs

[0068] 1 First motor (driving force source) 1a Rotating shaft (of the first motor) 2 Second motor (driving force source) 2a Rotating shaft (of the second motor) 3 Third motor (driving force source) 3a Rotating shaft (of the third motor) 4 Fourth motor (driving force source) 4a Rotating shaft (of the fourth motor) 5 First electric oil pump 6 Second electric oil pump 7 Third electric oil pump 8 Fourth electric oil pump 9 Detection unit 9a Wheel speed sensor (of the detection unit) 9b Motor rotation speed sensor (or resolver) (of the detection unit) 9c Motor torque sensor (of the detection unit) 9d Pump rotation speed sensor (of the detection unit) 9e Timer (of the detection unit) 9f Steering angle sensor (of the detection unit) 10 Controller (ECU) 11 Front wheel (left side) 11a Drive shaft (of the left front wheel) 12 Front wheel (right side) 12a Drive shaft (of the right front wheel) 13 Rear wheel (left side) 13a Drive shaft (of the left rear wheel) 14 Rear wheel (right side) 14a Drive shaft (of the right rear wheel) 15, 16, 17, 18 Motor cooling device 19 Display (notification 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 (of the front wheel drive unit) 41a, 42a Drive gear (of the front wheel drive unit) 41b, 42b Idle gear (of the front wheel drive unit) 41c, 42c Counter driven gear (of the front wheel drive unit) 41d, 42d Counter drive gear (of the front wheel drive unit) 41e, 42e Driven gear (of the front wheel drive unit) 43, 44 Gear transmission mechanism (of the rear wheel drive unit) 43a, 44a Drive gear (of the rear wheel drive unit) 43b, 44b Counter driven gear (of the rear wheel drive unit) 43c, 44c Counter drive gear (of the rear wheel drive unit) Driven gear (of the rear wheel drive unit) 43d, 44d Ve vehicle (electric vehicle)

Claims

1. A control device for an electric vehicle comprising a first motor and a second motor which drive left and right front wheels, respectively, a third motor and a fourth motor which drive left and right rear wheels, respectively, and a first electric oil pump, a second electric oil pump, a third electric oil pump and a fourth electric oil pump which supply oil for cooling and lubrication to the first motor, the second motor, the third motor and the fourth motor, respectively, and which controls driving forces of the front, rear, left and right wheels independently, a controller for controlling each of the motors and each of the electric oil pumps, When the operation state of any one of the electric oil pumps satisfies a predetermined continuous operation limiting condition and the electric vehicle is traveling straight, The continuous operation of the electric oil pump that satisfies the continuous operation limiting condition is limited, and an oil pump protection control is executed to reduce the output of each of the motors of either the front wheels or the rear wheels to which the oil is supplied from the electric oil pump that limits the continuous operation, and to increase the output of each of the motors of the other of the front wheels or the rear wheels. A control device for an electric vehicle.

2. The control device for an electric vehicle according to claim 1, The controller: The oil pump protection control is executed in a four-wheel drive state in which the driving force is generated by all of the front, rear, left, and right wheels. A control device for an electric vehicle.

3. The control device for an electric vehicle according to claim 2, The vehicle further includes a notification device that notifies a passenger of the electric vehicle of predetermined information. The controller: The notification device notifies the occupant that the oil pump protection control is executed and the four-wheel drive state is restricted. A control device for an electric vehicle.

4. The control device for an electric vehicle according to any one of claims 1 to 3, The vehicle further includes a motor cooling device that cools each of the motors with a coolant, The controller: When the oil pump protection control is executed, the motors that increase the output are cooled by the coolant. A control device for an electric vehicle.

5. The control device for an electric vehicle according to claim 4, The controller: After starting execution of the oil pump protection control, the amount of the coolant is increased. A control device for an electric vehicle.

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