Patent Description:
Conventionally, as an electric vehicle having a plurality of electric motors, there is an electric vehicle in which four wheels (front wheels and rear wheels) are rotationally driven using a plurality of electric motors. For example, <CIT> discloses a hybrid vehicle that determines torque distributions for a plurality of motor generators in a manner that the loss while driving in the 4WD mode becomes minimized. In this hybrid vehicle, the torque distribution for each motor generator is set on the basis of the torque required by the vehicle in a manner that the electric power loss becomes minimized, and the drive of each motor generator is controlled on the basis of the set torque distribution. <CIT> discloses a method for controlling an electric vehicle driven by a plurality of electric motors including a first electric motor, in which a lubricant, which is used for lubricating the electric motors and power transmission systems therefor, is used for cooling the electric motors; setting torque distributions for the plurality of electric motors on the basis of a driving force required by the electric vehicle; controlling the drive of the plurality of electric motors on the basis of the set torque distributions. <CIT> discloses a method for controlling an electric vehicle driven by a plurality of electric motors, the method comprising setting torque distributions for the plurality of electric motors on the basis of a driving force required by the electric vehicle; and controlling the drive of the plurality of electric motors on the basis of the set torque distributions. <CIT> discloses method for controlling an electric vehicle, driven by an electric motor , in which a lubricant, which is used for lubricating the electric motor and power transmission system therefor, is used for cooling the electric motor.

In the prior art described above, the torque distribution of one motor generator may be set to <NUM> in order to minimize power loss. In this case, the drive of the motor generator whose torque distribution is set to <NUM> is stopped. Here, in the electric vehicle in which a lubricant works for both lubrication and cooling of the motor generator, once the drive of the motor generator is stopped and the circulation of the lubricant is stopped, the lubrication might not be performed properly. On the other hand, when the lubricant continues to circulate as usual during the stop of the drive of the motor generator, the electric power consumption of the cooling system cannot be suppressed, the energy loss increases, and the electric power consumption of the vehicle might increase.

An object of the present invention is to properly lubricate electric motors and power transmission systems therefor and to suppress the electric power consumption of the cooling system.

According to an aspect of the present invention, a method for controlling an electric vehicle is provided. The method for controlling the electric vehicle driven by a plurality of electric motors including a first electric motor, in which a lubricant, which is used for lubricating the electric motors and power transmission systems therefor, is used for cooling the electric motors; the electric vehicle includes a plurality of pumps that cool the electric motors by circulating the lubricant and that are provided for each of the plurality of electric motors. The method includes; setting torque distributions for the plurality of electric motors on the basis of a driving force required by the electric vehicle; controlling the drive of the plurality of electric motors on the basis of the set torque distributions; and circulating intermittently the lubricant used for cooling the first electric motor when the torque distribution set for the first electric motor is smaller than a predetermined value which is regarded as a reference value.

Embodiments of the present disclosure will be described below with reference to the accompanying drawings.

<FIG> is a diagram showing a schematic configuration of a vehicle cooling system <NUM> according to a first embodiment of the present invention. Notably, the vehicle according to the first embodiment is an electric vehicle of a four-wheel drive vehicle (4WD vehicle) in which motors <NUM>, <NUM> are provided as drive sources for the drive wheels of front wheels and rear wheels, respectively. That is, the vehicle according to the first embodiment is an electric vehicle in which the front wheels are driven by the motor <NUM> and the rear wheels are driven by the motor <NUM>.

<FIG> shows a cooling system <NUM> in which a first cooling system <NUM> is realized by two pumps <NUM> and <NUM>. Notably, the first cooling system <NUM> is a water cooling system that cools each unit of the vehicle using cooling water. For example, the first cooling system <NUM> adjusts the flow rate of cooling water according to the temperature of the cooling water (water temperature). Notably, in the first embodiment, an example in which the first cooling system <NUM> uses one refrigerant (cooling water) is shown, but each unit may be cooled by the first cooling system <NUM> using a plurality of refrigerants.

As shown in <FIG>, the cooling system <NUM> includes a controller <NUM>, a cooler <NUM>, pumps <NUM>, <NUM>, <NUM>, <NUM>, supply channels <NUM> to <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, inverters <NUM>, <NUM>, heat exchangers <NUM>, <NUM>, and motors <NUM>, <NUM>. Notably, the first cooling system <NUM> includes the cooler <NUM>, the pumps <NUM>, <NUM>, and the supply channels <NUM> to <NUM>. A second cooling system <NUM> of the front wheel motor <NUM> includes the heat exchanger <NUM>, the pump <NUM>, and the supply channels <NUM>, <NUM>. A second cooling system <NUM> of the rear wheel motor <NUM> includes the heat exchanger <NUM>, the pump <NUM>, and the supply channels <NUM>, <NUM>. Notably, the pumps <NUM> and <NUM> are circulation pumps for circulating (pumping) the refrigerant (cooling water) in the first cooling system <NUM>. The pumps <NUM>, <NUM> are circulation pumps for circulating (pumping) the refrigerant (cooling oil) in the second cooling systems <NUM>, <NUM>. In addition, the pumps <NUM>, <NUM>, <NUM>, <NUM> can not only be driven or stopped but can also be operated intermittently under the control of the controller <NUM>.

The controller <NUM> includes a microprocessor, an input / output interface, a ROM (Read Only Memory), a RAM (Random Access Memory), etc., and controls each unit of the vehicle. In the example shown in <FIG>, the controller <NUM> controls pumps <NUM>, <NUM>, <NUM>, <NUM>, and inverters <NUM>, <NUM>.

Further, the controller <NUM> acquires vehicle information (e.g., accelerator pedal depression amount, the speed of the vehicle (vehicle speed)) from each unit of the vehicle, and calculates a driving force (torque command value for the entire vehicle, torque command request for the entire vehicle) required by the vehicle on the basis of the vehicle information. Then, the controller <NUM> sets torque distributions for the plurality of motors <NUM>, <NUM> on the basis of the calculated driving force. That is, a driving force required for the front wheels (torque command value) and a driving force required for the rear wheels (torque command value) are set. In this way, the torque distributions for the plurality of motors <NUM>, <NUM> are determined on the basis of the vehicle information (accelerator pedal depression amount, and the vehicle speed) acquired from each unit of the vehicle. In other words, the torque distributions (e.g., equal division, predetermined ratio) for the plurality of motors <NUM>, <NUM> are determined in a manner that the behavior of the vehicle becomes desirably. Further, the controller <NUM> outputs torque command values corresponding to the set torque distributions to the inverters <NUM>, <NUM>. That is, the controller <NUM> controls the inverters <NUM>, <NUM> to drive the front wheel motor <NUM> and the rear wheel motor <NUM> in a manner that torque distributions become the set torque distributions. In this way, the controller <NUM> controls the plurality of motors <NUM>, <NUM> on the basis of the set torque distributions.

Notably, when the torque distribution for the rear wheel motor <NUM> is set to <NUM>, the controller <NUM> controls the inverter <NUM> to stop driving the rear wheel motor <NUM>. That is, when the torque distribution for the rear wheel motor <NUM> is set to <NUM>, the controller <NUM> stops the switching operation of the inverter <NUM> that drives the rear wheel motor <NUM>. For example, the torque distribution for the rear wheels may be <NUM> in a state where the vehicle is travelling at a somewhat low vehicle speed and in a somewhat constant traffic flow. Further, for example, the torque distribution for the rear wheels may also be <NUM> when the vehicle speed is low and accelerator pedal depression amount is small. Further, for example, the torque distribution for the rear wheels may also be <NUM> when there are few torque command requests for the entire vehicle (when the torque command value is small). As described above, the vehicle according to the first embodiment has a function of driving only a part of the front wheels and the rear wheels (front wheels) and stopping the other (rear wheels) when the required torque is small.

The cooler <NUM> is a radiator attached to the front portion of the vehicle, and is an apparatus for transferring the heat of cooling water to the air outside the vehicle. Further, the cooler <NUM> is connected to the supply channels <NUM> to <NUM> through which cooling water flows. Further, in the example shown in <FIG>, the supply channel <NUM> is provided with the pump <NUM> for circulating cooling water, and the supply channel <NUM> is provided with the pump <NUM> for circulating cooling water. Specifically, wind passes through the cooler <NUM> as the vehicle travels, and the wind cools cooling water inside the cooler <NUM>. Further, the cooling water cooled in the cooler <NUM> is pumped by the pumps <NUM>, <NUM> to circulate in the supply channels <NUM> to <NUM>, thereby cooling the inverters <NUM>, <NUM> and the heat exchangers <NUM>, <NUM>.

The inverter <NUM> is a power converter that is connected to the motor <NUM> and a battery (not shown) and controls the exchange of electricity between the motor <NUM> and the battery according to an instruction from the controller <NUM>. Further, the inverter <NUM> is a power converter that is connected to the motor <NUM> and a battery (not shown) and controls the exchange of electricity between the motor <NUM> and the battery according to an instruction from the controller <NUM>. Further, the inverter <NUM> and the heat exchanger <NUM> are cooled by cooling water flowing through the supply channel <NUM>, and the inverter41 and the heat exchanger <NUM> are cooled by cooling water flowing through the supply channel <NUM>.

The heat exchanger <NUM> is a heat exchanger that lowers the temperature of the front wheel motor <NUM> by using cooling water flowing through the supply channel <NUM> and cooling oil flowing through the supply channels <NUM>, <NUM>. Specifically, the heat exchanger <NUM> is cooled by the cooling water cooled inside the cooler <NUM> flowing through the supply channel <NUM>. Further, the cooling oil cooled inside the heat exchanger <NUM> is pumped by the pump <NUM> to circulate in the supply channels <NUM>, <NUM>, thereby cooling the motor <NUM>.

Further, the heat exchanger <NUM> is a heat exchanger that lowers the temperature of the rear wheel motor <NUM> by using cooling water flowing through the supply channel <NUM> and cooling oil flowing through the supply channels <NUM>, <NUM>. Specifically, the heat exchanger <NUM> is cooled by the cooling water cooled inside the cooler <NUM> flowing through the supply channel <NUM>. Further, the cooling oil cooled inside the heat exchanger <NUM> is pumped by the pump <NUM> to circulate in the supply channels <NUM>, <NUM>, thereby cooling the motor <NUM>.

As described above, the first cooling system <NUM> also functions as a cooling system for cooling cooling oil in the second cooling systems <NUM>, <NUM>.

The motor <NUM> is an electric motor for driving the front wheels of the vehicle and is connected to the battery via the inverter <NUM>. The motor <NUM> is an electric motor for driving the rear wheels of the vehicle and is connected to the battery via the inverter <NUM>. Notably, as the motors <NUM>, <NUM>, for example, a winding field type synchronous electric motor (EESM) can be used. However, another electric motor (e.g., an induction electric motor or a magnet synchronous electric motor) capable of stopping the switching of the inverter when the required torque is small may be used.

Further, a passage through which cooling oil flows is provided inside or around the motors <NUM>, <NUM>. Then, the cooling oil pumped by the pump <NUM> circulates in the heat exchanger <NUM>, the motor <NUM>, and the supply channels <NUM>, <NUM>, thereby cooling the motor <NUM>. The cooling oil pumped by the pump <NUM> also functions as a lubricant for the motor <NUM> and the power transmission system therefor. Similarly, the cooling oil pumped by the pump <NUM> circulates in the heat exchanger <NUM>, the motor <NUM>, and the supply channels <NUM>, <NUM>, thereby cooling the motor <NUM>. The cooling oil pumped by the pump <NUM> also functions as a lubricant for the motor <NUM> and the power transmission system therefor.

Notably, an oil temperature sensor is mounted on the motor <NUM>, and the inverter <NUM> detects the oil temperature of the motor <NUM> on the basis of a signal output from the oil temperature sensor, and outputs the detected result to the controller <NUM>. Similarly, an oil temperature sensor is mounted on the motor <NUM>, and the inverter <NUM> detects the oil temperature of the motor <NUM> on the basis of a signal output from the oil temperature sensor, and outputs the detected result to the controller <NUM>.

As described above, the cooling oil used in the second cooling system <NUM> is used for cooling the motor <NUM> and also functions as a lubricant (refrigerant lubricating oil) for the motor <NUM> and the power transmission system therefor. Similarly, the cooling oil used in the second cooling system <NUM> is used for cooling the motor <NUM> and also functions as a lubricant (refrigerant lubricating oil) for the motor <NUM> and the power transmission system therefor. As described above, the second cooling systems <NUM>, <NUM> are oil lubrication circuits for an electric motor including an apparatus such as a pump for pumping cooling oil and a supply channel for supplying the cooling oil. Also, in the second cooling systems <NUM>, <NUM>, by operating the apparatus such as a pump and the oil supply channel in a state where they are combined, the cooling oil is supplied to each unit to be lubricated. In addition, the action of the second cooling systems <NUM>, <NUM> can prevent seizure of the lubricated part. In addition, the second cooling systems <NUM>, <NUM> are provided with apparatuses for cooling the cooling oil (heat exchangers <NUM> and <NUM>), and this apparatus can prevent the temperature of the cooling oil from rising. Notably, since the second cooling systems <NUM>, <NUM> use cooling oil, they can also be referred to as an oil cooling system. The second cooling systems <NUM>, <NUM> can also be referred to as a lubrication cooling apparatus.

Also, during normal operation, the circulation of cooling oil in the second cooling system <NUM> is controlled on the basis of at least one of the vehicle speed of the electric vehicle, the rotation speed of the front wheel motor <NUM>, and the cooling oil temperature (oil temperature) of the second cooling system <NUM>. Similarly, during normal operation, the circulation of cooling oil in the second cooling system <NUM> is controlled on the basis of at least one of the vehicle speed of the electric vehicle, the rotation speed of the rear wheel motor <NUM>, and the cooling oil temperature (oil temperature) of the second cooling system <NUM>.

As described above, in the first embodiment, when the torque distribution for the rear wheel motor <NUM> is set to <NUM>, the drive of the rear wheel motor <NUM> is stopped. In this way, in a case where the drive of the rear wheel motor <NUM> is stopped, once the cooling oil used for cooling the motor <NUM> is circulated as usual, the energy loss may increase due to the circulation of the cooling oil. On the other hand, it is conceivable that when the drive of the rear wheel motor <NUM> is stopped, the circulation of the cooling oil used for cooling the motor <NUM> is completely stopped. However, since the cooling oil used for cooling the motor <NUM> is also used as a lubricant for the motor <NUM> and the power transmission system therefor, once the circulation of the cooling oil used for cooling the motor <NUM> is completely stopped, the lubrication of the motor <NUM> and the power transmission system therefor may be insufficient. In other words, in a case where the torque distribution for the rear wheel motor <NUM> is set to <NUM> and the switching operation of the inverter <NUM> is stopped, since the rear wheel motor <NUM> and the inverter <NUM> do not generate heat, there is often no problem in terms of heat. However, even the switching operation of the inverter <NUM> and the drive of rear wheel motor <NUM> are stopped, the motor <NUM> whose drive has been stopped may be rotated by the drive wheels as the vehicle travels. Therefore, since some sliding parts of the motor <NUM> need to be lubricated, it is necessary to supply cooling oil to the motor <NUM>.

Therefore, in the first embodiment, an example is shown in which when the torque distribution for the rear wheel motor <NUM> is set to <NUM>, the drive of the rear wheel motor <NUM> is stopped and cooling oil used for cooling the motor <NUM> is intermittently circulated (at least temporarily stopped). Note that "intermittently" means performing at regular intervals, but in the present embodiment, the "intermittently" also means that the circulation is performed at a timing (regular timing, irregular timing) satisfying a predetermined condition after a temporarily stop.

That is, when the torque distribution for the rear wheel motor <NUM> is set to <NUM>, the controller <NUM> performs control to stop driving the rear wheel motor <NUM> and to intermittently drive the pump <NUM> that circulates the cooling oil used for cooling the motor <NUM>. This intermittent drive will be described in detail with reference to <FIG> and <FIG>.

<FIG> are diagrams showing the relation between the pump flow rate (vertical axis) of cooling oil when the second cooling system <NUM> for the rear wheel motor <NUM> is driven intermittently and the elapsed time (horizontal axis) from the start of intermittent drive. <FIG> show examples of cases where a threshold value (parameter) used when determining the intermittent drive has been changed. Note that <FIG> will be described in detail with reference to <FIG>.

<FIG> is a flowchart showing an example of a processing procedure of the drive control processing of the second cooling system <NUM> for the rear wheel motor <NUM>, which is executed by the controller <NUM>. Note that this processing procedure is a processing programmed in the controller <NUM> and is repeatedly executed at predetermined intervals (e.g., about several milliseconds).

In step S101, the controller <NUM> acquires vehicle information (accelerator pedal depression amount, vehicle speed) from each unit of the vehicle, and calculates a driving force (torque command value for the entire vehicle) required by the vehicle on the basis of the vehicle information. Then, the controller <NUM> sets torque distributions for the plurality of motors <NUM>, <NUM> on the basis of the calculated driving force. That is, the controller <NUM> sets torque distributions for the plurality of motors <NUM>, <NUM> on the basis of the driving force required by the electric vehicle.

In step S102, the controller <NUM> determines whether or not the torque distribution for the rear wheels is <NUM>. When the torque distribution for the rear wheels is not <NUM>, in step S103, the controller <NUM> outputs torque command values corresponding to the set torque distributions to the inverters <NUM>, <NUM>. That is, the controller <NUM> controls the inverters <NUM>, <NUM> to drive the front wheel motor <NUM> and the rear wheel motor <NUM> in a manner that torque distributions become the set torque distributions.

In step S104, the controller <NUM> normally drives the second cooling system <NUM> for the front wheel motor <NUM> and the second cooling system <NUM> for the rear wheel motor <NUM>. That is, the controller <NUM> controls the drive of the pumps <NUM> and <NUM>.

Also, when it is determined in step S102 that the torque distribution for the rear wheels is <NUM>, in step S105, the controller <NUM> determines whether or not the torque distribution for the rear wheels is also <NUM> in the last setting. When the torque distribution for the rear wheels is not <NUM> in the last setting, in step S106, the controller <NUM> starts counting the rotation speed of the rear wheel motor <NUM> on the basis of the information from the inverter <NUM>.

In step S107, the controller <NUM> controls the inverter <NUM> to drive the front wheel motor <NUM> in a manner that a torque becomes the set torque in step S101. Also, the controller <NUM> controls the inverter <NUM> to stop driving the rear wheel motor <NUM>.

In step S108, the controller <NUM> normally drives the second cooling system <NUM> for the front wheel motor <NUM> and stops the second cooling system <NUM> for the rear wheel motor <NUM>. That is, the drive of the pump <NUM> of the second cooling system <NUM> is stopped.

When it is determined in step S105 that the torque distribution for the rear wheels is also <NUM> in the last setting, in step S109, the controller <NUM> controls the inverter <NUM> to drive the front wheel motor <NUM> in a manner that a torque becomes the set torque in step S101. Also, the controller <NUM> controls the inverter <NUM> to continuously stop the drive of the rear wheel motor <NUM>.

In step S110, the controller <NUM> determines whether or not a cumulative rotation speed of the rear wheel motor <NUM>, which started counting in step S106, has become equal to or higher than the threshold value TH1. When the cumulative rotation speed of the rear wheel motor <NUM> is less than the threshold value TH1, the operation of this processing procedure is ended.

When the cumulative rotation speed of the rear wheel motor <NUM> becomes equal to or higher than the threshold value TH1, in step <NUM>, the controller <NUM> resets the cumulative rotation speed of the rear wheel motor <NUM> and starts counting the rotation speed of the rear wheel motor <NUM>.

In step S112, the controller <NUM> sets the second cooling system <NUM> for the rear wheel motor <NUM> to be driven for a predetermined time. That is, the pump <NUM> of the second cooling system <NUM> is driven for a predetermined time. Note that, as a predetermined time, a fixed value (e.g., several seconds) may be used, or a value determined from a plurality of values (e.g., <NUM> seconds, <NUM> seconds, <NUM> seconds) on the basis of some rules may be used. For example, a predetermined value may be determined on the basis of the cooling oil temperature (oil temperature) of the second cooling system <NUM>. For example, when the cooling oil temperature is low, it is assumed that the cooling oil stays on the slider for a long time because the viscosity of the cooling oil is high. Therefore, when the cooling oil temperature is low, a relatively short time can be set as a predetermined time. On the other hand, when the cooling oil temperature is high, it is assumed that the cooling oil stays on the slider for a short time because the viscosity of the cooling oil is low. Therefore, when the cooling oil temperature is high, a relatively long time can be set as a predetermined time.

For example, when the vehicle speed is constant, the cumulative rotation speed of the rear wheel motor <NUM> becomes equal to or higher than the threshold value TH1 at regular intervals. Therefore, as shown in <FIG>, the drive timing is periodically generated according to the vehicle speed, and the pump <NUM> of the second cooling system <NUM> is intermittently driven. Note that <FIG> is an example of a case where the threshold value TH1 is set relatively high, and <FIG> is an example of a case where the threshold value TH1 is set relatively low.

In this way, when the torque distribution for the rear wheels is <NUM>, the second cooling system <NUM> is intermittently driven. In this intermittent drive, the drive of the pump <NUM> is first stopped, and then, the pump <NUM> is sequentially driven at the timing when the cumulative rotation speed of the rear wheel motor <NUM> becomes the threshold value TH1.

Notably, the above shows an example in which when the pump <NUM> is intermittently driven, the drive timing of the pump <NUM> is determined on the basis of the cumulative rotation speed of the rear wheel motor <NUM>, but the drive timing of the pump <NUM> may be also determined on the basis of other conditions. For example, the drive timing of the pump <NUM> may be determined on the basis of the vehicle speed. As described above, the vehicle speed and the rotation speed of the rear wheel motor <NUM> are in a proportional relation. Therefore, the rotation speed of the rear wheel motor <NUM> can be sequentially calculated on the basis of the vehicle speed, and the drive timing of the pump <NUM> can be determined on the basis of the cumulative value of the rotation speed. Also, when the pump <NUM> is intermittently driven, the drive timing of the pump <NUM> may be determined on the basis that whether or not the vehicle speed is equal to or higher than a predetermined value. In this case, since the arithmetic processing for calculating the rotation speed of the motor on the basis of the vehicle speed is not required, the processing load of the second cooling system drive control can be reduced.

It is also assumed that the rotation speed of the rear wheel motor <NUM> cannot be obtained for some reasons after the intermittent drive of the pump <NUM> is set. In this case, the pump <NUM> may be intermittently driven at preset intervals (e.g., at intervals of several seconds). Alternatively, a plurality of intermittent drive intervals and the cooling oil temperature (oil temperature) of the second cooling system <NUM> are registered in association with each other, and on the basis of the cooling oil temperature (oil temperature) of the second cooling system <NUM>, one interval may be determined from the plurality of intermittent drive intervals to execute the intermittent drive of the pump <NUM>. For example, a setting is possible that the frequency of intermittent drive increases when the oil temperature is higher than the reference threshold value (e.g., the frequency shown in <FIG>) and the frequency of intermittent drive decreases when the oil temperature is lower than the reference threshold value (e.g., the frequency shown in <FIG>). In this way, a control is possible that the circulation of cooling oil in the second cooling system <NUM> is intermittently performed on the basis of the oil temperature.

As shown above, the vehicle speed of the electric vehicle, the rotation speed of the rear wheel motor <NUM>, and the cooling oil temperature (oil temperature) of the second cooling system <NUM> can be used as independent parameters. That is, a control is possible that the circulation of cooling oil in the second cooling system <NUM> is intermittently performed on the basis of at least one of the vehicle speed of the electric vehicle, the rotation speed of the rear wheel motor <NUM>, and the cooling oil temperature (oil temperature) of the second cooling system <NUM>.

Note that although <FIG> shows an example in which the threshold value TH1 is set to a constant value, the threshold value TH1 may be changed according to a predetermined rule. For example, the threshold value TH1 may be changed on the basis of the cooling oil temperature (oil temperature) of the second cooling system <NUM>.

As described above, when the oil temperature of cooling oil is low, it is assumed that the cooling oil stays on the slider for a long time because the viscosity of the cooling oil is high. Therefore, it is desirable to decrease the frequency of intermittent drive when the cooling oil temperature is low. On the other hand, when the cooling oil temperature is high, it is assumed that the cooling oil stays on the slider for a short time because the viscosity of the cooling oil is low. Therefore, it is desirable to increase the frequency of intermittent drive when the cooling oil temperature is high.

Therefore, since the frequency of intermittent drive decreases when the cooling oil temperature (oil temperature) of the second cooling system <NUM> is lower than the reference threshold TH2 (e.g., the threshold value TH2 ≥ oil temperature), a relatively high value is set as the threshold TH1. And, since the frequency of intermittent drive increases when the cooling oil temperature (oil temperature) of the second cooling system <NUM> is higher than the reference threshold value TH2 (e.g., the threshold value TH2 < oil temperature), a relatively low value is set as the threshold TH <NUM>.

With reference to <FIG> can be grasped as an example of a drive timing when the cooling oil temperature (oil temperature) of the second cooling system <NUM> is lower than the reference threshold TH2. On the other hand, <FIG> can be grasped as an example of a drive timing when the cooling oil temperature (oil temperature) of the second cooling system <NUM> is higher than the reference threshold value TH2. In this way, the threshold TH1 can be changed on the basis of the oil temperature. That is, the drive timing of the pump <NUM> can be changed on the basis of the oil temperature. In addition, in this example, two values are set as the threshold value TH1 on the basis of the oil temperature, but three or more values may be set.

Further, an example of using cooling oil as a refrigerant (lubricant, refrigerant lubricating oil) used for cooling and lubricating the motors <NUM>, <NUM> is shown, but a fluid other than oil (e.g., an inert refrigerant) suitable for lubricating motors may be used. Further, the cooling oil used for cooling and lubricating the motors <NUM> and <NUM> may be shared as the oil used for lubricating other units.

As described above, according to the first embodiment, when the torque distribution for the rear wheels is set to <NUM>, the circulation of cooling oil in the second cooling system <NUM> for the rear wheel motor <NUM> is temporarily stopped. In this way, by temporarily stopping the circulation of cooling oil in the second cooling system <NUM>, it is possible to suppress the electric power consumption of the cooling system of the vehicle and to reduce the electric power consumption of the vehicle. As a result, the cruising distance of the vehicle can be extended. After the torque distribution for the rear wheels is set to <NUM> and the circulation of cooling oil in the second cooling system <NUM> is temporarily stopped, the cooling oil is circulated at a timing satisfying a predetermined condition (e.g., an intermittent timing). As a result, even after the circulation of cooling oil in the second cooling system <NUM> is temporarily stopped, since the cooling oil is supplied to the rear wheel motor <NUM> and the power transmission system therefor at a timing satisfying a predetermined condition, it is possible to prevent seizure of each unit (sliding parts that require lubrication, etc.). Thus, according to the first embodiment, the electric motors (motors <NUM> and <NUM>) and the power transmission systems therefor can be properly lubricated, and the electric power consumption of the cooling system (second cooling system <NUM>) can be suppressed.

Notably, although <FIG> shows the cooling system <NUM> in which the first cooling system <NUM> is realized by two pumps <NUM> and <NUM>, the first embodiment can also be applied to a case where the number of pumps is <NUM> or <NUM> or more. Therefore, <FIG> shows a cooling system <NUM> that realizes a first cooling system <NUM> with one pump <NUM>. That is, <FIG> shows a schematic configuration of the cooling system <NUM> of the vehicle.

Note that the configuration of the first cooling system <NUM> is almost the same as that of the first cooling system <NUM> except that the number of pumps to be provided is different, and therefore the units common to the first cooling system <NUM> are designated by the same reference numerals and the description thereof is omitted. Further, the pump <NUM> is a circulation pump for circulating (pumping) the refrigerant (cooling water) in the first cooling system <NUM>, and is provided in the supply channel <NUM>. The cooling water cooled in the cooler <NUM> is pumped by the pump <NUM> to circulate in the supply channels <NUM> to <NUM>, thereby cooling the inverters <NUM>, <NUM> and the heat exchangers <NUM>, <NUM>. In addition, the pump <NUM> can not only be driven or stopped but can also be operated intermittently under the control of the controller <NUM>. That is, in the example shown in <FIG>, the controller <NUM> controls the pumps <NUM>, <NUM>, <NUM>, and the inverters <NUM>, <NUM>.

The method for controlling the electric vehicle according to the first embodiment uses the lubricant, which is used for lubricating the electric motors (motors <NUM> and <NUM>) and the power transmission systems therefor, for cooling the electric motors, and drives the electric vehicle by a plurality of electric motors including the first electric motor (motor <NUM>). According to this control method, in step S101, the torque distributions for the plurality of electric motors are set on the basis of the driving force required by the electric vehicle. Further, in steps S103, S107, S109, the drive of a plurality of electric motors is controlled on the basis of the torque distributions set in step S101. Further, in steps S108, S112, when the torque distribution set for the first electric motor is smaller than the predetermined value which is regarded as a reference value, the lubricant used for cooling the first electric motor is circulated intermittently.

According to such a method for controlling the electric vehicle, the electric power consumption of the vehicle cooling system can be suppressed and the electric power consumption of the vehicle can be reduced by intermittently circulating the lubricant used for cooling the first electric motor. As a result, the cruising distance of the vehicle can be extended. Also, since the cooling oil is intermittently supplied to the first electric motor and the power transmission system therefor (e.g., at the timing when a predetermined condition is satisfied), it is possible to prevent seizure of each unit (sliding parts that require lubrication, etc.). That is, the electric motors (motors <NUM> and <NUM>) and the power transmission systems therefor can be properly lubricated, and the electric power consumption of the cooling system (second cooling system <NUM>) can be suppressed.

In addition, according to the method for controlling the electric vehicle according to the first embodiment, when the state continues, in which the torque distribution set for the first electric motor (motor <NUM>) is smaller than the predetermined value which is regarded as the reference value, the timing of circulating the lubricant used for the first electric motor is determined on the basis of at least one of the vehicle speed of the electric vehicle, the rotation speed of the first electric motor, and the temperature of the lubricant used for the first electric motor.

According to such a method for controlling the electric vehicle, it is possible to properly circulate the lubricant used for the first electric motor at a timing determined on the basis of at least one of the vehicle speed of the electric vehicle, the rotation speed of the first electric motor, and the temperature of the lubricant used for the first electric motor. Also, since it is possible to properly circulate the lubricant used for the first electric motor at an appropriate timing in consideration of these three factors, it is possible to prevent seizure of each unit (sliding parts that require lubrication, etc.).

In addition, in the method for controlling the electric vehicle according to the first embodiment, when the torque distribution set for the first electric motor (motor <NUM>) is <NUM>, the lubricant used for the first electric motor is circulated intermittently.

According to such a method for controlling the electric vehicle, the electric power consumption of the vehicle cooling system can be suppressed and the electric power consumption of the vehicle can be reduced by intermittently circulating the lubricant used for cooling the first electric motor when the torque distribution set for the first electric motor (motor <NUM>) is <NUM>. As a result, the cruising distance of the vehicle can be extended.

The electric vehicle according to the first embodiment includes a plurality of electric motors (motors <NUM>, <NUM>), a plurality of pumps (pumps <NUM>, <NUM>), and a controller <NUM>. The plurality of electric motors (motor33, <NUM>) drive the electric vehicle. The plurality of pumps (pumps <NUM>, <NUM>) are pumps for cooling the electric motors by circulating the lubricant used for lubricating the electric motors and the power transmission systems therefor and for cooling the electric motors, and are provided for each of the plurality of electric motors. The controller <NUM> controls in a manner of setting torque distributions for the plurality of electric motors on the basis of the driving force required by the electric vehicle, driving the plurality of electric motors on the basis of the set torque distributions, and intermittently driving the pump (pump <NUM>) that cools the first electric motor when the torque distribution set for the first electric motor (motor <NUM>) is smaller than the predetermined value which is regarded as the reference value.

According to such an electric vehicle, the electric power consumption of the vehicle cooling system can be suppressed and the electric power consumption of the vehicle can be reduced by intermittently circulating the lubricant used for cooling the first electric motor. As a result, the cruising distance of the vehicle can be extended. Also, since the cooling oil is intermittently supplied to the first electric motor and the power transmission system therefor (e.g., at the timing when a predetermined condition is satisfied), it is possible to prevent seizure of each unit (sliding parts that require lubrication, etc.). That is, the electric motors (motors <NUM> and <NUM>) and the power transmission systems therefor can be properly lubricated, and the electric power consumption of the cooling system (second cooling system <NUM>) can be suppressed.

In the first embodiment, an example is shown in which the second cooling system <NUM> for the rear wheel motor <NUM> is temporarily stopped and then intermittently driven in order to reduce the electric power consumption. In the second embodiment, an example is shown in which the electric power consumption is further reduced by temporarily stopping a part of cooling water in the first cooling system <NUM>. In addition, in the second embodiment, an example of a case where the first cooling system <NUM> includes two pumps <NUM> and <NUM> (shown in <FIG>) is shown. The second embodiment is an example in which a part of the first embodiment is modified, and the illustration and a part of the description thereof are omitted for the parts common to the first embodiment.

<FIG> is a flowchart showing an example of a processing procedure of drive control process, which is executed by the controller <NUM>, between the first cooling system <NUM> and the second cooling system <NUM> for the rear wheel motor <NUM>. Note that this processing procedure is a processing programmed in the controller <NUM> and is repeatedly executed at predetermined intervals (e.g., about several milliseconds). Further, this processing procedure is a modification of a part of the processing procedure shown in <FIG>, and the parts common to the processing procedure shown in <FIG> are designated by the same reference numerals, and a part of the description thereof is omitted.

In this processing procedure, an example is shown in which the pump <NUM> of the first cooling system <NUM> is stopped when the torque distribution for the rear wheels is <NUM>.

When it is determined in step S102 that the torque distribution for the rear wheels is not <NUM>, in step S103, the front wheel motor <NUM> and the rear wheel motor <NUM> are driven. In step S104, the second cooling system <NUM> for the front wheel motor <NUM> and the second cooling system <NUM> for the rear wheel motor <NUM> are normally driven.

In step S201, the controller <NUM> normally drives the two pumps <NUM> and <NUM> of the first cooling system <NUM>.

When it is determined in step S102 that the torque distribution for the rear wheels is <NUM> and it is determined in step S105 that the torque distribution for the rear wheels is not <NUM> in the last setting, in step S106, the counting of the rotation speed of the rear wheel motor <NUM> is started. In step S107, the front wheel motor <NUM> is driven and the rear wheel motor <NUM> is stopped. In step S108, the second cooling system <NUM> for the front wheel motor <NUM> is normally driven, and the second cooling system <NUM> for the rear wheel motor <NUM> is temporarily stopped.

In step S202, the controller <NUM> normally drives the pump <NUM> on the front wheel side and stops the pump <NUM> on the rear wheel side of the first cooling system <NUM>.

As described above, according to the second embodiment, when the torque distribution for the rear wheels is set to <NUM>, the circulation of cooling oil in the second cooling system <NUM> for the rear wheel motor <NUM> is intermittently driven (temporarily stopped), and a part of circulation of cooling water in the first cooling system <NUM> is stopped. In this way, the electric power consumption of the vehicle cooling system can be suppressed and the electric power consumption of the vehicle can be further reduced by at least temporarily stopping the circulation of cooling oil in the second cooling system <NUM> and a part of circulation of cooling water in the first cooling system <NUM>. As a result, the cruising distance of the vehicle can be further extended. As described above, according to the second embodiment, the electric motors (motors <NUM> and <NUM>) and the power transmission systems therefor can be properly lubricated, and the electric power consumption of the cooling systems (first cooling system <NUM> and second cooling system <NUM>) can be suppressed.

In the method for controlling the electric vehicle according to the second embodiment, when the torque distribution set for the first electric motor (motor <NUM>) is smaller than the predetermined value which is regarded as the reference value, in the cooling system (first cooling system <NUM>) that cools the lubricant (cooling oil) using a refrigerant (cooling water) different from the lubricant, the circulation of the refrigerant in the cooling system that cools the lubricant used for the first electric motor is at least temporarily stopped (the pump <NUM> on the rear wheel side of the first cooling system <NUM> is stopped).

According to such a method for controlling the electric vehicle, the electric power consumption of the vehicle cooling system can be suppressed and the electric power consumption of the vehicle can be further reduced by at least temporarily stopping a part of circulation of cooling water in the first cooling system <NUM>. As a result, the cruising distance of the vehicle can be further extended.

In the above, an example is shown in which a part of the first cooling system (pump <NUM> on the rear wheel side) is stopped. Next, an example is shown in which a part of the first cooling system (pump <NUM> on the rear wheel side) is intermittently driven for the purpose of reducing the electric power consumption. Note that in the modified example of the second embodiment, an example is shown in which the pump <NUM> on the rear wheel side is intermittently driven on the basis of the temperature of the cooling oil (oil temperature) for lowering the temperature of the rear wheel motor <NUM>. The drive timing will be described in detail with reference to <FIG> and <FIG>.

<FIG> shows the relation between the pump flow rate (vertical axis) of cooling water in the first cooling system <NUM> when the first cooling system <NUM> is normally driven and the cooling oil temperature (oil temperature) (horizontal axis) of the second cooling system <NUM>. Here, the inverter (particularly, a high-power conversion element (e.g., IGPT, power module)) temperature may rise sharply. For example, even when the water temperature is low because the inverter temperature is low, the inverter temperature may rise sharply thereafter. Therefore, when the pump flow rate of cooling water is set to <NUM> under a state where the inverter temperature and the water temperature are low, once the inverter temperature rises sharply thereafter, there is a risk that the rate at which the cooling water temperature of the first cooling system <NUM> decreases cannot keep up with the rate at which the inverter temperature increases. Therefore, it is necessary to always supply cooling water when the inverter is driving. Specifically, the pump flow rate of cooling water in the first cooling system <NUM> is a constant value F1 until the cooling oil temperature (oil temperature) of the second cooling system <NUM> reaches the predetermined temperature <NUM>.

Then, when the cooling oil temperature (oil temperature) of the second cooling system <NUM> is equal to or higher than the predetermined temperature O2 and lower than the predetermined temperature O3, the value of the pump flow rate of cooling water in the first cooling system <NUM> changes from F1 to F2 as the oil temperature rises. When the cooling oil temperature (oil temperature) of the second cooling system <NUM> is equal to or higher than the predetermined temperature O3, the pump flow rate of cooling water in the first cooling system <NUM> is a constant value F2 (wherein, F1 <F2).

<FIG> shows the relation between the pump flow rate (vertical axis) of cooling water in the first cooling system <NUM> when the first cooling system <NUM> is intermittently driven and the cooling oil temperature (oil temperature) (horizontal axis) of the second cooling system <NUM>. That is, the pump flow rate of cooling water in the first cooling system <NUM> is stopped until the cooling oil temperature (oil temperature) of the second cooling system <NUM> reaches the predetermined temperature O1. Then, when the cooling oil temperature (oil temperature) of the second cooling system <NUM> is equal to or higher than the predetermined temperature O1 and lower than the predetermined temperature O3, the value of the pump flow rate of cooling water in the first cooling system <NUM> changes from <NUM> to F2 as the oil temperature rises. When the cooling oil temperature (oil temperature) of the second cooling system <NUM> is equal to or higher than the predetermined temperature O3, the pump flow rate of cooling water in the first cooling system <NUM> is a constant value F2 (wherein, F1 <F2).

Thus, the normal and intermittent drives of the first cooling system <NUM> are different before the cooling oil temperature (oil temperature) of the second cooling system <NUM> reaches the predetermined temperature O2, and are common when the cooling oil temperature is equal to or higher than the predetermined value O2.

<FIG> briefly shows an example of the relation between the pump flow rate of cooling water (vertical axis) in the first cooling system <NUM> when the first cooling system <NUM> is temporarily stopped, and the elapsed time from the temporary stop (horizontal axis). As shown in <FIG>, after temporarily stopping the first cooling system <NUM>, the pump flow rate of the cooling water is <NUM> when the cooling oil temperature (oil temperature) is less than the predetermined temperature O1 (the period up to t11 shown in <FIG>). In addition, once the cooling oil temperature (oil temperature) is equal to or higher than the predetermined temperature O1 (the period from t11 to t12 shown in <FIG>), the pump flow rate of the cooling water (wherein, <NUM> <pump flow rate ≤ F2) is determined according to the relation shown in <FIG>. Once the cooling oil temperature (oil temperature) is less than the predetermined temperature O1 (the period after t12 shown in <FIG>), the pump flow rate of the cooling water becomes <NUM>. Note that <FIG> briefly shows an example of the drive timing of the cooling water pump <NUM> in order to facilitate the explanation, and the drive timing is not limited to this.

<FIG> is a flowchart showing an example of a processing procedure of drive control process, which is executed by the controller <NUM>, between the first cooling system <NUM> and the second cooling system <NUM> for the rear wheel motor <NUM>. This processing procedure is a processing programmed in the controller <NUM> and is repeatedly executed at predetermined intervals (e.g., about several milliseconds). Further, this processing procedure is a modification of a part of the processing procedure shown in <FIG>, and the parts common to the processing procedure shown in <FIG> are designated by the same reference numerals, and a part of the description thereof is omitted. Note that the threshold value TH3 shown in this example corresponds to O1 shown in <FIG>.

In step S112, it is set to drive the second cooling system <NUM> for the rear wheel motor <NUM> for a predetermined time, and then in step S301, the controller <NUM> determines whether the cooling oil temperature (oil temperature) of the second cooling system <NUM> for the rear wheel motor <NUM> is equal to or higher than the threshold value TH3.

When it is determined in step S301 that the oil temperature is less than the threshold value TH3, the process returns to step S202, and the controller <NUM> stops the pump <NUM> on the rear wheel side of the first cooling system <NUM>. Note that during the stop of the pump <NUM> on the rear wheel side, the stop continues. On the other hand, when it is determined in step S301 that the oil temperature is equal to or higher than the threshold value TH3, in step <NUM>, the controller <NUM> drives the pump <NUM> on the rear wheel side of the first cooling system <NUM>. In this case, the drive of the pump <NUM> is controlled according to the relation shown in <FIG>. Note that during the drive of the pump <NUM> on the rear wheel side, the drive continues.

Note that <FIG> shows an example in which the pump <NUM> of the first cooling system <NUM> is driven on the basis that whether or not the cooling oil temperature (oil temperature) of the second cooling system <NUM> is equal to or higher than the threshold value TH3. However, the pump <NUM> of the first cooling system <NUM> may be driven on the basis of other conditions. For example, the pump <NUM> of the first cooling system <NUM> may be driven on condition that the circulation of cooling oil in the second cooling system <NUM> for the rear wheel motor <NUM> is restarted. Also, for example, the pump <NUM> of the first cooling system <NUM> may be driven at a timing when the circulation of cooling oil in the second cooling system <NUM> for the rear wheel motor <NUM> is about to be restarted. That is, the pump <NUM> of the first cooling system <NUM> may be driven on the basis of the timing of driving the circulation of cooling oil in the second cooling system <NUM> for the rear wheel motor <NUM> or before and after the driving. In other words, the pump <NUM> of the first cooling system <NUM> may be driven on the basis of the drive timing of the circulation of cooling oil in the second cooling system <NUM> for the rear wheel motor <NUM>.

Thus, according to the modified example of the second embodiment, when the torque distribution for the rear wheels is set to <NUM>, the circulation of cooling oil in the second cooling system <NUM> for the rear wheel motor <NUM> is intermittently driven (temporarily stopped), and a part of circulation of cooling water in the first cooling system <NUM> is intermittently driven (temporarily stopped). In this way, the electric power consumption of the vehicle cooling system can be suppressed and the electric power consumption of the vehicle can be further reduced by temporarily stopping the circulation of cooling oil in the second cooling system <NUM> and a part of circulation of cooling water in the first cooling system <NUM>. As a result, the cruising distance of the vehicle can be further extended. After the torque distribution for the rear wheels is set to <NUM> and a part of circulation of cooling water in the first cooling system <NUM> is temporarily stopped, the cooling water is circulated at a timing satisfying a predetermined condition (oil temperature is equal to or higher than the threshold TH3). As a result, even after a part of circulation of cooling water in the first cooling system <NUM> is temporarily stopped, the circulation of the cooling water is restarted at the timing when a predetermined condition is satisfied, so that proper cooling of the entire vehicle can be realized. As described above, according to the second embodiment, the electric motors (motors <NUM> and <NUM>) and the power transmission systems therefor can be properly lubricated, and the electric power consumption of the cooling systems (first cooling system <NUM> and second cooling system <NUM>) can be suppressed.

In the method for controlling the electric vehicle according to modified example of the second embodiment, when the state continues, in which the torque distribution set for the first electric motor (motor <NUM>) is smaller than the predetermined value which is regarded as the reference value, the refrigerant is intermittently circulated in the cooling system (first cooling system <NUM>) for cooling the lubricant used for the first electric motor (the pump <NUM> on the rear wheel side of the first cooling system <NUM> is intermittently driven).

According to such a method for controlling the electric vehicle, by intermittently driving a part of circulation of cooling water in the first cooling system <NUM>, the electric power consumption of the vehicle cooling system can be suppressed and the electric power consumption of the vehicle can be reduced. Further, since a part of circulation of cooling water in the first cooling system <NUM> is intermittently driven, proper cooling of the entire vehicle can be realized.

In the method for controlling the electric vehicle according to modified example of the second embodiment, when the state continues, in which the torque distribution set for the first electric motor (motor <NUM>) is smaller than the predetermined value which is regarded as the reference value, the timing of circulating the refrigerant in the cooling system (first cooling system <NUM>) that cools the lubricant used for the first electric motor is determined on the basis of the temperature (oil temperature) of the lubricant (cooling oil) used for the first electric motor (the timing of driving the pump <NUM> on the rear wheel side of the first cooling system <NUM> is determined).

According to such a method for controlling the electric vehicle, it is possible to properly circulate the refrigerant in the cooling system (first cooling system <NUM>) at an appropriate timing in consideration of the temperature (oil temperature) of the lubricant (cooling oil) used for the first electric motor.

In the first and second embodiments, in order to facilitate the explanation, an example is shown in which the drive of the rear wheel motor <NUM> is stopped when the torque distribution for the rear wheels is set to <NUM>. However, the present invention is not limited to this. For example, when the torque distribution for the rear wheels is smaller than the predetermined value (predetermined lower limit torque) which is regarded as the reference value (for example, when the torque distribution for the rear wheels is smaller than or equal to the predetermined value, when the torque distribution for the rear wheels is smaller than the predetermined value), the drive of the rear wheel motor <NUM> may be stopped. In this way, when the drive of the rear wheel motor <NUM> is stopped, as shown in the first and second embodiments, the pump <NUM> of the second cooling system <NUM> can be temporarily stopped and intermittently driven, and the pump <NUM> of the first cooling system <NUM> can be temporarily stopped and intermittently driven. As the predetermined value shown here, for example, ± <NUM> Newton (N) can be used.

Claim 1:
A method for controlling an electric vehicle, wherein:
- the electric vehicle is driven by a plurality of electric motors (<NUM>, <NUM>) including a first electric motor (<NUM>), in which a lubricant, which is used for lubricating the electric motors (<NUM>, <NUM>) and power transmission systems therefor, is used for cooling the electric motors (<NUM>, <NUM>),
- the electric vehicle includes a plurality of pumps (<NUM>, <NUM>) that cool the electric motors (<NUM>, <NUM>) by circulating the lubricant and that are provided for each of the plurality of electric motors (<NUM>, <NUM>), and
- the method comprises:
- setting torque distributions for the plurality of electric motors (<NUM>, <NUM>) on the basis of a driving force required by the electric vehicle;
- controlling the drive of the plurality of electric motors (<NUM>, <NUM>) on the basis of the set torque distributions; and
- circulating intermittently the lubricant used for cooling the first electric motor (<NUM>) when the torque distribution set for the first electric motor (<NUM>) is smaller than a predetermined value which is regarded as a reference value.