Control device for electric vehicles

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 particularly to a control device for an electric vehicle that drives four wheels, namely 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 to 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). Also, 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 set the driving force distribution ratio between the front and rear wheels to the target distribution ratio. Thereby, the balance of the driving force between the front and rear is maintained, and the running stability of the electric vehicle is ensured.

[0003] [[ID=1,6]]Moreover, Patent Document 2 describes an electric oil pump control device provided with a mechanical oil pump that is mechanically connected to and driven by a driving source (engine or motor), an electric oil pump that is operated by electric energy (the power of the motor), and pump control means for operating the electric oil pump during the stop of the mechanical oil pump. 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, and when the continuous operation time of the electric oil pump exceeds the predetermined allowable operation time, the driving 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 by the continuous operation time to another oil pump that is not restricted.

Prior Art Documents

[0004] [Patent Document 1] Japanese Patent Publication No. 2001-112114 [Patent Document 2] Patent No. 3867521 [Overview of the project] [Problems that the invention aims to solve]

[0005] In the electric vehicle described in Patent Document 1 above, the driving force of the front wheels and the driving force of the rear wheels can be controlled independently by individually controlling the front motor and the rear motor. Furthermore, electric vehicles have been developed in which the driving force of all four wheels can be controlled independently by providing a motor for driving the vehicle (drive motor) on all four wheels (front, rear, left, and right) and individually controlling these four drive motors. To cool and lubricate each drive motor that independently drives the front and rear wheels or all four wheels, and the transmission mechanism between the drive motor and the wheel, for example, an electric oil pump such as the one described in Patent Document 2 is used. Since each drive motor that drives the front and rear wheels or all four wheels is controlled individually, an electric oil pump is also provided for each drive motor, and the operation of each electric oil pump is controlled individually. Therefore, for example, as in the electric oil pump control device described in Patent Document 2, if the electric oil pump of a drive motor that drives either the front wheel or the rear wheel is subject to a limit on continuous operating time, it is conceivable to implement control (switching control of electric oil pump and drive motor) that switches to the other drive motor equipped with an unlimited electric oil pump to drive the wheel in order to protect the electric oil pump and drive motor.

[0006] On the other hand, in electric vehicles with independently driven front and rear wheels or all four wheels, control is performed to change the distribution of driving force or torque to the front and rear wheels or all four wheels in order to stabilize straight-line driving performance or to improve cornering performance. In particular, when an electric vehicle with independently driven front, rear, left, and right wheels turns, differences in rotation between the left and right wheels and torque differences between the front and rear wheels occur, making the control of the driving force complex. When such an electric vehicle with independently driven four wheels turns, the switching control of the electric oil pump and drive motor as described above becomes even more complicated to control.

[0007] This invention was conceived in response to the above-mentioned technical problems, and aims to provide a control device for an electric vehicle that can properly protect the electric oil pump and the motor for driving the vehicle without complicating the control of an electric vehicle that independently drives all four wheels (front, rear, left, and right). [Means for solving the problem]

[0008] To achieve the above objective, this invention provides a control device for an electric vehicle that independently controls the driving force of the front, rear, left, and right wheels, comprising: a first motor and a second motor that drive the left and right front wheels, respectively; a third motor and a fourth motor that drive the 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 that discharge and supply oil for cooling and lubrication to the first motor, the second motor, the third motor, and the fourth motor, respectively, and further comprising a controller that controls each of the motors and each of the electric oil pumps, wherein the controller, when the operating state of any of the electric oil pumps falls under a predetermined continuous operation limit condition and the electric vehicle is traveling in a straight line, restricts the continuous operation of the electric oil pump that falls under the continuous operation limit condition, and performs oil pump protection control by reducing the output of each motor on either the left or right side of the front wheel or the rear wheel to which the oil is supplied from the electric oil pump whose continuous operation is restricted, and increasing the output of each motor on the other side of the vehicle.

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

[0010] Furthermore, this invention further includes a notification device that causes the occupants (driver, passengers) of the electric vehicle to recognize predetermined information, and the controller in this invention may be configured to allow the occupants to recognize through the notification device that the oil pump protection control is being executed and the four-wheel drive state is being restricted.

[0011] Furthermore, this invention further includes a motor cooling device that cools each of the motors with coolant, and the controller in this invention may be configured to cool each of the motors that increase the output with the coolant when performing the oil pump protection control.

[0012] Furthermore, the controller in this invention may be configured to increase the amount of coolant after the execution of the oil pump protection control has started. [Effects of the Invention]

[0013] The vehicle to be controlled by this invention is an electric vehicle that uses at least a motor as a driving force source, and in particular, a four-wheel drive electric vehicle in which each of the four wheels (front, rear, left, and right) is driven by an independent motor. Each motor for driving the vehicle is provided with an electric oil pump to supply cooling oil (lubricating oil) to the motor. Since the electric oil pump is driven by a dedicated (pump drive) motor, a predetermined continuous operation limit condition is set to protect the pump drive motor. In the electric vehicle control device of this invention, if the operating state of the electric oil pump falls under the continuous operation limit condition, the continuous operation of the electric oil pump is limited. For example, if the continuous operating 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 drive motor is reduced. At the same time, the output (output torque) of the vehicle drive motor to which oil is supplied from the electric oil pump whose operation is limited, and the output of another vehicle drive motor that is paired with (arranged opposite) that vehicle drive motor in the left-right direction are reduced. Furthermore, by reducing the output of each of the left and right motors on either the front or rear wheels, the output of each of the left and right motors for vehicle drive on the other side of the front or rear wheels is increased. In other words, the torque distribution between the front and rear wheels is altered by the output of the vehicle drive motors. This ensures proper protection of the electric oil pump and the vehicle drive motors.

[0014] Furthermore, in the electric vehicle control device of this invention, the control that links the limitation of continuous operation of the electric oil pump with the change in torque distribution between the front and rear wheels, that is, the oil pump protection control in this invention, is executed when the electric vehicle is traveling in a straight line. The oil pump protection control is not executed when the electric vehicle is traveling in a turn. In the case of a four-wheel drive electric vehicle controlled by this invention, when traveling in a turn in four-wheel drive mode, the control takes into account, for example, the difference in rotation between the left and right wheels and the difference in torque between the front and rear wheels, and the content of the driving force control becomes more complex compared to when traveling in a straight line. If the oil pump protection control described above were to be executed in parallel during such travel in a turn, the control of the electric vehicle would become even more complicated. Therefore, the electric vehicle control device of this invention, as described above, avoids the superposition of complex control and simplifies the control content of the electric vehicle by executing the oil pump protection control only when the electric vehicle is traveling in a straight line.

[0015] Therefore, according to the electric vehicle control device of this invention, the electric oil pump and the motor for driving the vehicle can be properly protected without complicating the control of the electric vehicle. [Brief explanation of the drawing]

[0016] [Figure 1] Figure 1 is a schematic diagram showing the configuration (drive system and control system) of the electric vehicle to be controlled in this invention. [Figure 2] Figure 2 is a diagram showing an example of a specific configuration of an electric vehicle to be controlled by this invention, and is a gear train diagram showing the drive system (gear transmission mechanism) of the front wheel drive unit that drives the left and right front wheels of the electric vehicle, respectively. [Figure 3] Figure 3 is a diagram showing an example of a specific configuration of an electric vehicle to be controlled by this invention, and is a gear train diagram showing the drive system (gear transmission mechanism) of the rear wheel drive unit that drives the left and right rear wheels of the electric vehicle, respectively. [Figure 4] Figure 4 is a flowchart illustrating an example of the control performed by the control device for the electric vehicle of this invention. [Figure 5]FIG. 5 is a time chart showing an image of the continuous operation switching time (continuous operation limit condition) when executing the control shown in the flowchart of FIG. 4.

Embodiments for Carrying Out the Invention

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

[0018] The vehicle to be controlled in the embodiments of this 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 the four wheels on the front, rear, left, and right. The motor of the driving force source can at least independently control 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 vehicle driving. Further, the vehicle Ve 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. And 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 type 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 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 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 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 capable of power transmission 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 capable of power transmission 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 in a way that allows power transmission via a predetermined transmission mechanism such as a reduction gear (not shown). Alternatively, the third motor 3 may be positioned 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.

[0024] The fourth motor 4 drives the right rear wheel 14. For example, the fourth motor 4 and the rear wheel 14 are connected in a way that allows power transmission via a predetermined transmission mechanism such as a reduction gear (not shown). Alternatively, the fourth motor 4 may be positioned 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.

[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 located close to the first motor 1 and supplies the discharged oil to the first motor 1 to cool it. The oil discharged by the first electric oil pump 5 may also be used to lubricate and cool the transmission mechanism between the first motor 1 and the front wheel 11. In the example shown in Figure 1, in addition to the cooling system for the first motor 1 by the first electric oil pump 5, a motor cooling device 15 is also provided, which cools the first motor 1 by circulating a cooling coolant (not shown).

[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 located close to the second motor 2 and supplies the discharged oil to the second motor 2 to cool it. The oil discharged by the second electric oil pump 6 may also be used to lubricate and cool the transmission mechanism between the second motor 2 and the front wheel 12. In addition, in the example shown in Figure 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 cools the second motor 2 by circulating, for example, a cooling coolant (not shown).

[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 located close to the third motor 3 and supplies the discharged oil to the third motor 3 to cool it. The oil discharged by the third electric oil pump 7 may also be used to lubricate and cool the transmission mechanism between the third motor 3 and the rear wheel 13. In addition, in the example shown in Figure 1, in addition to the cooling system for the third motor 3 by the third electric oil pump 7, a motor cooling device 17 is also provided, which cools the third motor 3 by circulating, for example, a cooling coolant (not shown).

[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 located close to the fourth motor 4 and supplies the discharged oil to the fourth motor 4 to cool it. The oil discharged by the fourth electric oil pump 8 may also be used to lubricate and cool the transmission mechanism between the fourth motor 4 and the rear wheel 14. In addition, in the example shown in Figure 1, in addition to the cooling system for the fourth motor 4 by the fourth electric oil pump 8, a motor cooling device 18 is also provided, which cools the fourth motor 4 by circulating, for example, a cooling coolant (not shown).

[0029] The drive unit 21 for the front wheel 11 is composed of the first motor 1, the first electric oil pump 5, the motor cooling device 15, etc. Similarly, the drive unit 22 for the front wheel 12 is composed of the second motor 2, the second electric oil pump 6, the motor cooling device 16, etc. These drive units 21 and 22 for the front wheels 11 and 12 constitute the front wheel drive unit 31.

[0030] Figure 2 shows an example of the drive system (gear transmission mechanism) of the front wheel drive unit 31 described above. The front wheel drive unit 31 shown in Figure 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-driven gear 41c via an idler gear 41b. Because 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 integrated with the front wheel 11. Because 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.

[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-driven gear 42c via an idler gear 42b. Because the counter-driven gear 42c has a larger diameter than the drive gear 42a, the gear pair of these drive gears 42a and counter-driven gear 42c constitutes 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 integrated with the front wheel 12. Because the driven gear 42e has a larger diameter than the counter-drive gear 42d, the gear pair of these counter-drive gears 42d and driven gear 42e constitutes a reduction mechanism.

[0033] Meanwhile, the drive unit 23 for the rear wheel 13 is composed of the third motor 3, the third electric oil pump 7, the motor cooling device 17, etc. Similarly, the drive unit 24 for the rear wheel 14 is composed of the fourth motor 4, the fourth electric oil pump 8, the motor cooling device 18, etc. These drive units 23 and 24 for the rear wheels 13 and 14 constitute the rear wheel drive unit 32.

[0034] Figure 3 shows an example of the drive system (gear transmission mechanism) of the rear-wheel drive unit 32 described above. The rear-wheel drive unit 32 shown in Figure 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-driven gear 43b. Because the counter-driven gear 43b has a larger diameter than the drive gear 43a, the gear pair of these drive gears 43a and counter-driven gear 43b constitutes a reduction mechanism. In addition, a counter-drive gear 43c, which rotates integrally with the counter-driven gear 43b, meshes as a hypoid gear with a driven gear 43d attached to the drive shaft 13a, which is integrated with the rear wheel 13. Because the driven gear 43d has a larger diameter than the counter-drive gear 43c, the gear pair of these counter-drive gears 43c and driven gear 43d constitutes a reduction mechanism.

[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-driven gear 44b. Because the counter-driven gear 44b has a larger diameter than the drive gear 44a, the gear pair of these drive gears 41a and counter-driven gear 44b constitutes a reduction mechanism. In addition, a counter-drive gear 44c, which rotates integrally with the counter-driven gear 44b, meshes as a hypoid gear with a driven gear 44d attached to the drive shaft 14a, which is integrated with the rear wheel 14. Because the driven gear 44d has a larger diameter than the counter-drive gear 44c, the gear pair of these counter-drive gears 44c and driven gear 44d constitutes a reduction mechanism.

[0037] The detection unit 9 is a device or apparatus for acquiring various data and information necessary for controlling the vehicle Ve, and includes, for example, a power supply unit, a microcomputer, sensors, and an input / output interface. In particular, the detection unit 9 in this embodiment of the invention detects the driving state of the vehicle Ve, the operating state of each of the vehicle drive motors 1, 2, 3, and 4, and the operating state of each of the electric oil pumps 5, 6, 7, and 8, respectively, and also detects various data for controlling each of the vehicle drive motors 1, 2, 3, and 4, and each of the electric oil pumps 5, 6, 7, and 8, as well as for performing the oil pump protection control in this embodiment of the invention.

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

[0039] The controller 10 is an electronic control device mainly composed of a microcomputer, and in this embodiment of the invention, the controller 10 controls the vehicle Ve and, in particular, controls each of the vehicle drive motors 1, 2, 3, 4 and each of the electric oil pumps 5, 6, 7, 8 to perform the oil pump protection control in this embodiment of the invention. Various data detected or calculated by the detection unit 9 are input to the controller 10. The controller 10 performs calculations using the input data and pre-stored data and calculation formulas. The controller 10 then outputs the calculation result as a control command signal and is configured to control each of the vehicle drive motors 1, 2, 3, 4 and each of the electric oil pumps 5, 6, 7, 8, as well as to perform the oil pump protection control in this embodiment of the invention, as described above.

[0040] In the example shown in Figure 1, the vehicle Ve is equipped with a display 19. The display 19 corresponds to the “notification device” in this embodiment of the invention, and makes the occupants of the vehicle Ve (driver or passenger) aware of predetermined information. Therefore, the controller 10 outputs a predetermined control signal to the display 19, causing the predetermined information to be displayed on the display 19 for the occupants of the vehicle Ve. Although Figure 1 shows an example in which one controller 10 is provided, multiple controllers 10 may be provided for each device or equipment to be controlled, or for each control content.

[0041] As described above, in this embodiment of the invention, the vehicle Ve to be controlled can have its driving torque on the front wheels 11 and 12 and the driving torque on the rear wheels 13 and 14 controlled independently 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 left and right drive units 21 and 22 and left and right drive units 23 and 24, respectively, and by controlling each of the drive units 21, 22, 23, and 24, the driving torque of each of the front and rear wheels 11, 12, 13, and 14 can be controlled independently.

[0042] Furthermore, the control device for electric vehicles in this embodiment of the invention can control electric vehicles that are capable of independently controlling the drive torque of the front wheels 11 and 12 and the drive torque of the rear wheels 13 and 14. For example, as described in the aforementioned Patent Document 1, electric vehicles configured to independently drive the left and right front wheels and the left and right rear wheels with a front motor and a rear motor, respectively, can also be controlled. In addition, hybrid vehicles equipped with an engine (not shown) as a driving force source in either the front wheel drive unit 31 or the rear wheel drive unit 32 can also be controlled.

[0043] As described above, the control device for the electric vehicle in this embodiment of the invention is configured to perform oil pump protection control aimed at 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. An example of the control performed by the controller 10 for this purpose is shown in the flowchart of Figure 4.

[0044] The control shown in the flowchart of Figure 4 is executed when the vehicle Ve is in motion. Alternatively, as shown in the control details of the next step S1, it may be executed only when the vehicle Ve is in four-wheel drive mode. Or, it may be executed without being limited to the vehicle Ve being in four-wheel drive mode.

[0045] In the flowchart of Figure 4, first, in step S1, it is determined whether the vehicle Ve is in a four-wheel drive state, that is, in a state where driving force is generated in all four wheels 11, 12, 13, and 14 on the front, rear, left, and right sides. For example, it can be determined whether the vehicle Ve is in a four-wheel drive state based on the vehicle speed and the detected rotational speed and torque values ​​of each motor 1, 2, 3, and 4 for driving the vehicle. As mentioned above, the control shown in the flowchart of Figure 4 may be performed without being limited to the four-wheel drive state of the vehicle Ve. Therefore, it is possible to skip step S1 and start the control from the next step S2.

[0046] If the result in step S1 is "No" because vehicle Ve is not in four-wheel drive mode, that is, vehicle Ve is not in four-wheel drive mode, or vehicle Ve is not moving, the routine shown in the flowchart of Figure 4 is terminated without executing the control of the subsequent steps.

[0047] On the other hand, if the vehicle Ve is running in four-wheel drive mode, that is, if the vehicle Ve is running and the vehicle Ve is in four-wheel drive mode, and the result in "Yes" is determined in step S1, then proceed to step S2.

[0048] In step S2, it is determined whether the operating state of each electric oil pump 5, 6, 7, and 8 meets a predetermined continuous operation limit condition. 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 predetermined threshold value set as a continuous operation limit condition for the purpose of protecting the pump drive motors that drive each electric oil pump 5, 6, 7, and 8.

[0049] It should be noted that the continuous operation limiting conditions in this embodiment of the invention are not limited to the continuous operation switching time as described above. For example, the feasibility of continuous operation of the pump drive motors may be determined based on the temperature of the oil that cools each of the motors 1, 2, 3, and 4. Alternatively, the feasibility of continuous operation of the pump drive motors may be determined based on the load ratio of each of the motors 1, 2, 3, and 4 that receive oil from each of the electric oil pumps 5, 6, 7, and 8.

[0050] If the continuous operating time of each electric oil pump 5, 6, 7, and 8 has not yet reached the continuous operation switching time, that is, if the operating state of each electric oil pump 5, 6, 7, and 8 does not meet the predetermined continuous operation limit conditions, and therefore "No" is determined in step S2, the routine shown in the flowchart of Figure 4 is terminated without executing the control of the subsequent steps.

[0051] On the other hand, if the operating state of each electric oil pump 5, 6, 7, 8 meets a predetermined continuous operation limit condition, for example, as shown at time t1 in the time chart of Figure 5, the continuous operation time of any of the electric oil pumps 5, 6, 7, or 8 reaches the continuous operation switching time (dotted line in Figure 5), and the result is determined to be "Yes" in step S2, then proceed to step S3.

[0052] In step S3, it is determined whether the vehicle Ve is traveling in a straight line. For example, it can be determined whether the vehicle Ve is traveling in a straight line based on the rotational speed of each wheel 11, 12, 13, and 14, the difference in rotational speed between the left and right wheels 11, 13 and the wheels 12, 14, and the detected value of the steering angle sensor 9f.

[0053] If the result in step S3 is determined to be "No" because vehicle Ve is not traveling in a straight line, the control in step S3 is executed again. For example, if the result in step S3 is determined to be "No" because vehicle Ve is turning, the control in step S3 is repeated until vehicle Ve finishes turning and is traveling in a straight line.

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

[0055] In steps S4 and S5 below, the oil pump protection control according to this embodiment of the invention is performed. Specifically, control to limit the continuous operation of each electric oil pump 5, 6, 7, 8 and control to change the torque distribution between the front wheels 11, 12 and the rear wheels 13, 14 are performed in conjunction.

[0056] In step S4, the drive torque distribution (distribution ratio) between the front and rear wheels (front wheels 11, 12 and rear wheels 13, 14) of the vehicle Ve is changed. Specifically, the output of one of the motors 1 (or 2, 3, 4) that receives oil from one of the electric oil pumps 5 (or 6, 7, 8) whose continuous operation is restricted in step S2 due to meeting the continuous operation restriction conditions, and the output of motor 2 (or 1, 4, 3) located opposite that motor 1 (or 2, 3, 4) in the left-right direction of the vehicle Ve are both reduced. At the same time, the output of motors 3, 4 (or 1, 2) located opposite the motors 1, 2 (or 3, 4) whose output is reduced in the front-rear direction of the vehicle Ve are increased. For example, the output of the other motor 3, 4 (or 1, 2) is increased to compensate for the reduction in output of one of the motors 1, 2 (or 3, 4). This changes the torque distribution between the front and rear wheels 11, 12, 13, and 14 while maintaining the overall driving force of the vehicle Ve.

[0057] In step S5, the operation of any of the electric oil pumps 5 (or 6, 7, 8) that met the continuous operation limit condition in step S2 is stopped. Alternatively, the rotational speed of the pump drive motor that drives any of the electric oil pumps 5 (or 6, 7, 8) that met the continuous operation limit condition is reduced. This protects any of the electric oil pumps 5 (or 6, 7, 8) and pump drive motors that might have had their durability reduced by continuous operation.

[0058] Note that the order in which steps S4 and S5 are executed does not matter. For example, the controls may be executed in the order of step S3, then step S5, then step S4. Alternatively, the controls in steps S4 and S5 may be executed in parallel.

[0059] Furthermore, as shown in the time chart of Figure 5, in addition to the continuous operation switching time set as the continuous operation limiting condition in the control shown in step S5 above, a continuous operation prohibition time (double-dotted line in Figure 5) may also be set. The continuous operation prohibition time is set to a continuous operation time that is longer than the continuous operation switching time. In the time chart of Figure 5, if, between time t1, when the continuous operation time of the electric oil pump 5 (or 6, 7, 8) reaches the continuous operation switching time, and time t2, when the straight-ahead state of the vehicle Ve is determined, the continuous operation 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) will be stopped. In other words, in this case, the protection of the electric oil pump 5 (or 6, 7, 8) takes precedence over the execution of oil pump protection control, and the operation of the electric oil pump 5 (or 6, 7, 8) is stopped. This ensures that any of the electric oil pumps 5 (or 6, 7, 8) and the pump drive motors that drive them, which could potentially suffer reduced durability due to continuous operation, are protected.

[0060] Then, after the oil pump protection control in this embodiment of the invention is performed in steps S4 and S5 described above, the routine shown in the flowchart of Figure 4 is terminated.

[0061] Furthermore, in this embodiment of the invention, when the control device for the electric vehicle performs oil pump protection control, it displays on the display 19 that the oil pump protection control is being performed and that the four-wheel drive state of the vehicle Ve is being restricted, thereby making the occupants of the vehicle Ve aware of this. By performing the oil pump protection control as described above, the overall driving force of the vehicle Ve is maintained, but the drive torque distribution of the front and rear wheels 11, 12, 13, and 14 is changed, and as a result, the four-wheel drive state of the vehicle Ve is restricted. Therefore, when the magnitude of the drive torque of the front and rear wheels 11, 12, 13, and 14 increases or decreases, the occupants of the vehicle Ve may feel uncomfortable. However, by displaying on the display 19 that the four-wheel drive state of the vehicle Ve is being restricted, as described above, and making the occupants aware of this, it is possible to avoid making the occupants feel uncomfortable.

[0062] As mentioned above, the display 19 corresponds to the “notification device” in this embodiment of the invention, but such “notification devices” are not limited to the display 19. For example, the above information may be made known to the occupants by simpler indicator lamps (not shown) or warning lights (not shown) than the display 19. Alternatively, the sound equipment (not shown) of the vehicle Ve may be used as the “notification device” to make the above information known to the occupants by voice or warning sounds.

[0063] Furthermore, in the embodiment of this invention, when the control device for the electric vehicle performs oil pump protection control, it may cool any of the motors 1 (or 2, 3, 4) whose output is increased by changing the drive torque distribution of the front and rear wheels 11, 12, 13, 14 as described above, with the coolant of the motor cooling device 15 (or 16, 17, 18). Moreover, after starting the execution of oil pump protection control, the amount of coolant circulating in the motor cooling device 15 (or 16, 17, 18) may be increased. For example, coolant that has been temporarily stored in a reservoir tank (not shown) or the like may be added to the coolant circulation path (not shown) in the motor cooling device 15 (or 16, 17, 18).

[0064] Each of the motor cooling devices 15, 16, 17, and 18 described above is equipped with a mechanical fluid pump (not shown) that is driven by torque received from, for example, the rotating shafts 1a, 2a, 3a, 4a of motors 1, 2, 3, and 4, or the drive shafts 11a, 12a, 13a, and 14a, and is configured to circulate coolant with this mechanical fluid pump. Alternatively, each of the motor cooling devices 15, 16, 17, and 18 may be equipped with an electric fluid pump (not shown) in addition to the electric oil pumps 5, 6, 7, and 8 described above, and is configured to circulate coolant with such an electric fluid pump. Therefore, for example, by increasing the output of any of the motors 1 (or 2, 3, and 4), the amount of heat generated by any of the motors 1 (or 2, 3, and 4) increases, and in addition to the oil cooling by the electric oil pump 5 (or 6, 7, and 8), the motor cooling device 15 (or 16, 17, and 18) can be used to provide supplementary cooling with coolant. Therefore, the cooling performance of each motor 1, 2, 3, and 4 can be ensured, and each motor 1, 2, 3, and 4 can be properly protected.

[0065] Thus, in the control device for an electric vehicle according to this embodiment of the invention, if the operating state of any of the electric oil pumps 5 (or 6, 7, 8) falls under a continuous operation limit condition set to protect the pump drive motor, the continuous operation of the electric oil pump 5 (or 6, 7, 8) is limited. For example, if the continuous operating time of an electric oil pump 5 (or 6, 7, 8) exceeds a predetermined continuous operation switching time or a continuous operation allowable time, the operation of that 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) to which oil is supplied from any of the electric oil pumps 5 (or 6, 7, 8) whose operation is limited, and of the other vehicle drive motor 2 (or 1, 4, 3) which is paired with (arranged opposite) the vehicle drive motor 1 (or 2, 3, 4) in the left-right direction, are reduced. Furthermore, the output of each pair of motors 1,2 (or 3,4) on either the front wheels 11,12 or the rear wheels 13,14 is reduced, while the output of each pair of vehicle drive motors 3,4 (or 1,2) on the other side of the rear wheels 13,14 or front wheels 11,12 is increased. In other words, the torque distribution between the front and rear wheels 11,12,13,14 is changed by the output of each vehicle drive motor 1,2,3,4. This ensures proper protection of each electric oil pump 5,6,7,8 and each vehicle drive motor 1,2,3,4.

[0066] Furthermore, in the control device for the electric vehicle in this embodiment of the invention, the control that links the limitation of continuous operation of the electric oil pump 5 (or 6, 7, 8) with the change in torque distribution of the front and rear wheels 11, 12, 13, 14, that is, the oil pump protection control in this embodiment of the invention, is executed while the vehicle Ve is traveling in a straight line. In short, the oil pump protection control is not executed while the vehicle Ve is turning. When the four-wheel drive vehicle Ve, which is the target of control in this embodiment of the invention, is turning in four-wheel drive mode, the control takes into account, for example, the rotational difference between the left and right wheels (wheels 11 and 12, or wheels 13 and 14) and the torque difference between the front and rear wheels (front wheels 11, 12 and rear wheels 13, 14), and the content of the driving force control becomes more complex compared to when traveling in a straight line. In contrast, the control device for the electric vehicle in this embodiment of the invention, as described above, executes the oil pump protection control only when the vehicle Ve is traveling in a straight line. Therefore, it is possible to avoid the superposition of complex control of vehicle Ve and simplify the control content of vehicle Ve.

[0067] Therefore, according to the control device for an electric vehicle in this embodiment of the invention, it is possible to properly protect each electric oil pump 5, 6, 7, 8 and each motor 1, 2, 3, 4 for driving the vehicle without complicating the control of the vehicle Ve, and to improve their durability. [Explanation of symbols]

[0068] 1. First motor (driving force source) 1a Rotation shaft (of the first motor) 2. Second motor (driving power source) 2a Rotation shaft (of the second motor) 3. Third motor (driving power source) 3a Rotation shaft (of the third motor) 4. Fourth motor (driving power source) 4a Rotation 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 (Detection unit) Motor torque sensor 9d Pump rotation speed sensor (detection unit) 9e (Detection unit) timer 9f (Detection unit) Rudder angle sensor 10 Controller (ECU) 11 Front wheel (left side) 11a Drive shaft (for the left front wheel) 12 Front wheel (right side) 12a Drive shaft (for the right front wheel) 13 Rear wheel (left side) 13a Drive shaft (left rear wheel) 14. Rear wheel (right side) 14a Drive shaft (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 Idler gear (for front-wheel drive unit) 41c, 42c (for front-wheel drive units) counter-driven gear 41d, 42d (front-wheel drive unit) counter drive gear 41e, 42e Driven gear (for 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 (rear-wheel drive unit) counter drive gear 43d, 44d (Driven gear of rear-wheel drive unit) Vehicles (electric vehicles)

Claims

1. A control device for an electric vehicle comprising: a first motor and a second motor that drive the left and right front wheels respectively; a third motor and a fourth motor that drive the 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 that supply oil for cooling and lubrication to the first motor, the second motor, the third motor, and the fourth motor, respectively, and independently controlling the driving force of the front, rear, left, and right wheels, Each of the motors and each of the electric oil pumps is controlled by a controller, and the controller is If the operating state of any of the aforementioned electric oil pumps meets a predetermined continuous operation limit condition, and the electric vehicle is traveling in a straight line, The continuous operation of the electric oil pump that meets the continuous operation limitation conditions is restricted, and the oil pump protection control is performed to reduce the output of the motors of either the front wheel or the rear wheel to which the oil is supplied from the electric oil pump that restricts continuous operation, and to increase the output of the motor of the other wheel. A control device for electric vehicles characterized by the following features.

2. A control device for an electric vehicle according to claim 1, The aforementioned controller, In the four-wheel drive state where the driving force is generated in all four wheels (front, rear, left, and right), the oil pump protection control is executed. A control device for electric vehicles characterized by the following features.

3. A control device for an electric vehicle according to claim 2, The electric vehicle is further equipped with a notification device that causes the occupants to recognize predetermined information. The aforementioned controller, The notification device informs the occupant that the oil pump protection control is being executed and that the four-wheel drive state is being restricted. A control device for electric vehicles characterized by the following features.

4. A control device for an electric vehicle according to any one of claims 1 to 3, The motor cooling system further comprises cooling each of the aforementioned motors with coolant. The aforementioned controller, When the oil pump protection control is performed, the motors that increase the output are cooled with the coolant. A control device for electric vehicles characterized by the following features.

5. A control device for an electric vehicle according to claim 4, The aforementioned controller, After the execution of the oil pump protection control is started, the amount of coolant is increased. A control device for electric vehicles characterized by the following features.

Images