Control Method for Electric Vehicle and Electric Vehicle

Abstract

A control method for an electric vehicle, wherein a lubricant used for lubricating a motor and a power transmission system thereof in the electric vehicle is used for cooling the motor, and the electric vehicle is driven by a plurality of motors including a first motor. In this control method, torque distribution of the plurality of motors is set based on a driving force required by the electric vehicle, and driving of the plurality of motors is controlled based on the set torque distribution. When the torque distribution set for the first motor is small with respect to a prescribed value, circulation of the lubricant for cooling the first motor is intermittently implemented.

Description

Technical Field

[0001] The present invention relates to an electric vehicle having a plurality of electric motors and a control method therefor. Background Art

[0002] Conventionally, as an electric vehicle having a plurality of electric motors, there is an electric vehicle that rotationally drives four wheels (front wheels and rear wheels) using a plurality of electric motors. For example, in Japanese Patent Laid-Open No. 2015-136980, a hybrid vehicle is proposed in which the torque distribution of a plurality of motor generators is determined during traveling in 4WD mode to minimize losses. In this hybrid vehicle, the torque distribution of each motor generator is set based on the torque required by the vehicle to minimize the loss power, and the driving of each motor generator is controlled based on the set torque distribution.

[0003] In the above prior art, in order to minimize the loss power, the torque distribution of one motor generator is sometimes set to 0. In this case, the driving of the motor generator whose torque distribution is set to 0 is stopped. Here, in the case where the lubricant for lubricating and cooling the motor generator is shared in the electric vehicle, if the circulation of the lubricant is stopped while the driving of the motor generator is stopped, proper lubrication may not be possible. On the other hand, if the lubricant continues to circulate as usual during the stop of the driving of the motor generator, the power consumption of the cooling system cannot be suppressed, the energy loss becomes large, and the power consumption rate of the vehicle may deteriorate. Summary of the Invention

[0004] An object of the present invention is to properly lubricate an electric motor and its power transmission system and suppress the power consumption of a cooling system.

[0005] One aspect of the present invention is a control method for an electric vehicle, in which a lubricant used for lubricating an electric motor and its power transmission system of the electric vehicle is used for cooling the electric motor, and the electric vehicle is driven by a plurality of electric motors including a first electric motor. The control method sets the torque distribution of the plurality of electric motors based on the driving force required by the electric vehicle, controls the driving of the plurality of electric motors based on the set torque distribution, and intermittently performs the circulation of the lubricant for cooling the first electric motor when the torque distribution set for a part (first electric motor) of the plurality of electric motors is small based on a specified value. Brief Description of the Drawings

[0006] Figure 1 It is a diagram showing a schematic configuration of a cooling system of a vehicle according to a first embodiment of the present invention.

[0007] Figure 2A It is a diagram showing the relationship between the pump flow rate of the cooling oil during intermittent driving of a second cooling system of a rear-wheel electric motor and the elapsed time since the start of intermittent driving.

[0008] Figure 2B It is a graph showing the relationship between the pump flow rate of the cooling oil during the intermittent driving of the second cooling system of the motor for the rear wheels and the elapsed time since the start of the intermittent driving.

[0009] Figure 3 It is a flowchart showing an example of the processing sequence of the drive control process of the second cooling system of the motor for the rear wheels executed by the controller.

[0010] Figure 4 It is a diagram showing the schematic structure of the cooling system of the vehicle according to the first embodiment of the present invention.

[0011] Figure 5 It is a flowchart showing an example of the processing sequence of the drive control process of the first cooling system and the second cooling system of the motor for the rear wheels executed by the controller.

[0012] Figure 6A It is a graph showing the relationship between the pump flow rate of the cooling water of the first cooling system and the temperature (oil temperature) of the cooling oil of the second cooling system when the first cooling system is driving normally.

[0013] Figure 6B It is a graph showing the relationship between the pump flow rate of the cooling water of the first cooling system and the temperature (oil temperature) of the cooling oil of the second cooling system when the first cooling system is driven intermittently.

[0014] Figure 6C It is a diagram simplifying and showing an example of the relationship between the pump flow rate of the cooling water of the first cooling system and the elapsed time since the temporary stop when the first cooling system is temporarily stopped.

[0015] Figure 7 It is a flowchart showing an example of the processing sequence of the drive control process of the first cooling system and the second cooling system of the motor for the rear wheels executed by the controller. Detailed Embodiment

[0016] Hereinafter, embodiments of the present invention will be described with reference to the drawings.

[0017] [First Embodiment]

[0018] (System Structure Diagram)

[0019] Figure 1 It is a diagram showing the schematic structure of the cooling system 1 of the vehicle according to the first embodiment of the present invention. In addition, the vehicle in the first embodiment is an electric vehicle (4WD vehicle) with electric motors 33 and 43 as drive sources on the drive wheels of the front and rear wheels respectively. That is, the vehicle in the first embodiment is an electric vehicle in which the front wheels are driven by the motor 33 and the rear wheels are driven by the motor 43.

[0020] Figure 1 A cooling system 1 implemented by two pumps 22 and 23 for a first cooling system 20. Additionally, the first cooling system 20 is a water-cooled cooling system that uses cooling water to cool various parts of the vehicle. For example, the flow rate of the cooling water is adjusted according to the temperature of the cooling water (water temperature). Additionally, in the first embodiment, an example where the first cooling system 20 uses one refrigerant (cooling water) is shown, but the first cooling system 20 may also use multiple refrigerants to cool various parts.

[0021] As Figure 1 shown, the cooling system 1 includes a controller 10, a cooler 21, pumps 22, 23, 34, 44, supply flow paths 24 - 26, 35, 36, 45, 46, inverters 31, 41, heat exchangers 32, 42, and motors 33, 43. Additionally, the cooler 21, pumps 22, 23, and supply flow paths 24 - 26 constitute the first cooling system 20. Additionally, the heat exchanger 32, pump 34, and supply flow paths 35, 36 constitute a second cooling system 30 for the motor 33 of the front wheels. Additionally, the heat exchanger 42, pump 44, and supply flow paths 45, 46 constitute a second cooling system 40 for the motor 43 of the rear wheels. Additionally, pumps 22, 23 are circulation pump devices for circulating (pressurizing) the refrigerant (cooling water) in the first cooling system 20. Additionally, pumps 34, 44 are circulation pump devices for circulating (pressurizing) the refrigerant (cooling oil) in the second cooling systems 30, 40. Additionally, pumps 22, 23, 34, 44 can be driven or stopped based on the control of the controller 10, and can also operate intermittently.

[0022] The controller 10 is composed of a microprocessor, an input / output interface, a ROM (Read Only Memory), a RAM (Random Access Memory), etc., and controls various parts of the vehicle. In Figure 1 the example shown, the controller 10 controls pumps 22, 23, 34, 44, inverters 31, 41.

[0023] In addition, the controller 10 obtains vehicle information (e.g., the depression amount of the accelerator pedal, the speed of the vehicle (vehicle speed), etc.) from various parts of the vehicle, and calculates the driving force required for the vehicle (the torque command value for the entire vehicle, the torque command request for the entire vehicle) based on this vehicle information. And, the controller 10 sets the torque distribution of the plurality of electric motors 33, 43 based on the calculated driving force. That is, it sets the driving force (torque command value) requested for the front wheels and the driving force (torque command value) requested for the rear wheels. In this way, the torque distribution of the plurality of electric motors 33, 43 is determined based on the vehicle information (the depression amount of the accelerator pedal, the vehicle speed) obtained from various parts of the vehicle. In other words, the torque distribution of the plurality of electric motors 33, 43 (e.g., equal division, a specified ratio) is determined to achieve a preferable vehicle behavior. In addition, the controller 10 outputs a torque command value corresponding to the set torque distribution to the inverters 31, 41. That is, the controller 10 controls the inverters 31, 41 to drive the electric motor 33 for the front wheels and the electric motor 43 for the rear wheels so as to achieve the set torque distribution. In this way, the controller 10 controls the driving of the plurality of electric motors 33, 43 based on the set torque distribution.

[0024] In addition, when the torque distribution of the electric motor 43 for the rear wheels is set to 0, the controller 10 controls the inverter 41 to stop the driving of the electric motor 43 for the rear wheels. That is, when the torque distribution of the electric motor 43 for the rear wheels is set to 0, the controller 10 stops the switching operation of the inverter 41 that drives the electric motor 43 for the rear wheels. For example, in a state where the vehicle is traveling at a relatively low speed (low vehicle speed) and following the traffic flow, the torque distribution for the rear wheels is sometimes 0. In addition, for example, when the vehicle speed is low and the depression amount of the accelerator pedal is small, the torque distribution for the rear wheels is sometimes also 0. In addition, for example, when the torque command request for the entire vehicle is small (when the torque command value is small), the torque distribution for the rear wheels is sometimes also 0. In this way, the vehicle in the first embodiment has a function of driving only a part (front wheels) of the front and rear wheels and stopping the other (rear wheels) when the requested torque is small.

[0025] The cooler 21 is a radiator installed at the front of the vehicle and is a device for dissipating the heat of the cooling water to the outside air. In addition, the cooler 21 is connected to the supply flow paths 24 to 26 through which the cooling water flows. In addition, in Figure 1 the example shown, a pump 22 for circulating the cooling water is provided on the supply flow path 26, and a pump 23 for circulating the cooling water is provided on the supply flow path 25. Specifically, according to the running of the vehicle, the wind passes through the cooler 21, and the cooling water in the cooler 21 is cooled by this wind. In addition, the cooling water cooled in the cooler 21 circulates in the supply flow paths 24 to 26 by the pressure of the pumps 22, 23, whereby the inverters 31, 41, and the heat exchangers 32, 42 are cooled.

[0026] The inverter 31 is a power converter that is connected to the motor 33 and a storage battery (not shown), and controls the power exchange between the motor 33 and the storage battery based on an instruction from the controller 10. Further, the inverter 41 is a power converter that is connected to the motor 43 and a storage battery (not shown), and controls the power exchange between the motor 43 and the storage battery based on an instruction from the controller 10. Further, the inverter 31 and the heat exchanger 32 are cooled by the cooling water flowing in the supply flow path 26, and the inverter 41 and the heat exchanger 42 are cooled by the cooling water flowing in the supply flow path 25.

[0027] The heat exchanger 32 is a heat exchanger that uses the cooling water flowing in the supply flow path 26 and the cooling oil flowing in the supply flow paths 35 and 36 to lower the temperature of the motor 33 for the front wheels. Specifically, the cooling water cooled in the cooler 21 flows in the supply flow path 26, whereby the heat exchanger 32 is cooled. Further, the cooling oil cooled in the heat exchanger 32 is circulated in the supply flow paths 35 and 36 by the pressure of the pump 34, whereby the motor 33 is cooled.

[0028] Further, the heat exchanger 42 is a heat exchanger that uses the cooling water flowing in the supply flow path 25 and the cooling oil flowing in the supply flow paths 45 and 46 to lower the temperature of the motor 43 for the rear wheels. Specifically, the cooling water cooled in the cooler 21 flows in the supply flow path 25, whereby the heat exchanger 42 is cooled. Further, the cooling oil cooled in the heat exchanger 42 is circulated in the supply flow paths 45 and 46 by the pressure of the pump 44, whereby the motor 43 is cooled.

[0029] Thus, the first cooling system 20 also functions as a cooling system for cooling the cooling oil of the second cooling systems 30 and 40.

[0030] The motor 33 is a motor for driving the front wheels of the vehicle and is connected to the storage battery via the inverter 31. Further, the motor 43 is a motor for driving the rear wheels of the vehicle and is connected to the storage battery via the inverter 41. Further, the motors 33 and 43 can use, for example, a wound-field synchronous motor (EESM). However, other motors (e.g., an induction motor or a magnet-type synchronous motor) that can stop the switching of the inverter in the case of a small required torque can also be used.

[0031] In addition, passages for the circulation of cooling oil are provided inside or around the electric motors 33 and 43. Moreover, the cooling oil pumped by the pumps 34 circulates in the heat exchangers 32, the electric motors 33, and the supply flow paths 35 and 36, and the electric motor 33 is cooled. In addition, the cooling oil pumped by the pump 34 also functions as a lubricant for the electric motor 33 and its power transmission system. Similarly, the cooling oil pumped by the pump 44 circulates in the heat exchanger 42, the electric motor 43, and the supply flow paths 45 and 46, and the electric motor 43 is cooled. In addition, the cooling oil pumped by the pump 44 also acts as a lubricant for the electric motor 43 and its power transmission system.

[0032] In addition, an oil temperature sensor is installed on the electric motor 33. The inverter 31 detects the oil temperature of the electric motor 33 based on the signal output from the oil temperature sensor and outputs the detection result to the controller 10. Similarly, an oil temperature sensor is installed on the electric motor 43. The inverter 41 detects the oil temperature of the electric motor 43 based on the signal output from the oil temperature sensor and outputs the detection result to the controller 10.

[0033] In this way, the cooling oil for the second cooling system 30 is used for cooling the electric motor 33 and also functions as a lubricant (refrigerant lubricating oil) for the electric motor 33 and its power transmission system. Similarly, the cooling oil for the second cooling system 40 is used for cooling the electric motor 43 and also functions as a lubricant (refrigerant lubricating oil) for the electric motor 43 and its power transmission system. In this way, the second cooling systems 30 and 40 are oil lubrication circuits for electric motors that include devices such as pumps for pumping cooling oil and supply flow paths for supplying cooling oil. In addition, in the second cooling systems 30 and 40, the cooling oil is supplied to each part of the lubrication target by operating in a state where devices such as pumps are combined with the oil supply flow path. In addition, by the action of the second cooling systems 30 and 40, sintering of the lubricated parts can be prevented. In addition, the second cooling systems 30 and 40 are equipped with devices (heat exchangers 32 and 42) for cooling the cooling oil, and the temperature of the cooling oil can be prevented from rising by this device. In addition, since the second cooling systems 30 and 40 use cooling oil, they can also be called oil cooling systems. In addition, the second cooling systems 30 and 40 can also be called lubrication cooling devices.

[0034] In addition, during normal operation, the circulation of the cooling oil in the second cooling system 30 is controlled based on at least one of the vehicle speed of the electric vehicle, the rotational speed of the electric motor 33 of the front wheels, and the temperature (oil temperature) of the cooling oil in the second cooling system 30. Similarly, during normal operation, the circulation of the cooling oil in the second cooling system 40 is controlled based on at least one of the vehicle speed of the electric vehicle, the rotational speed of the electric motor 43 of the rear wheels, and the temperature (oil temperature) of the cooling oil in the second cooling system 40.

[0035] As described above, in the first embodiment, when the torque distribution of the rear-wheel motor 43 is set to 0, the driving of the rear-wheel motor 43 is stopped. Thus, when the driving of the rear-wheel motor 43 is stopped, if the cooling oil used for cooling the motor 43 circulates as usual, the energy loss may increase due to the circulation of the cooling oil. On the other hand, when the driving of the rear-wheel motor 43 is stopped, it is also considered to completely stop the circulation of the cooling oil used for cooling the motor 43. However, since the cooling oil used to cool the motor 43 is also used as a lubricant for the motor 43 and its power transmission system, if the circulation of the cooling oil used to cool the motor 43 is completely stopped, the lubrication of the motor 43 and its power transmission system may become insufficient. In other words, when the torque distribution of the rear-wheel motor 43 is set to 0 and the switching operation of the inverter 41 is stopped, since the rear-wheel motor 43 and the inverter 41 do not generate heat, there are mostly no problems in terms of heat. However, even when the switching operation of the inverter 41 and the driving of the rear-wheel motor 43 are stopped, the motor 43 during the driving stop sometimes rotates with the driving wheels due to the vehicle running. Therefore, it is necessary to lubricate some sliding parts in the motor 43, and thus it is necessary to supply cooling oil to the motor 43.

[0036] Then, in the first embodiment, an example (an example of at least temporarily stopping) is shown in which when the torque distribution of the rear-wheel motor 43 is set to 0, the driving of the rear-wheel motor 43 is stopped and the circulation of the cooling oil used for cooling the motor 43 is intermittently performed. In addition, the so-called intermittent performance means performing at regular intervals, but in this embodiment, it also means performing at a moment (regular moment, irregular moment) that satisfies a specified condition after temporarily stopping.

[0037] That is, when the torque distribution of the rear-wheel motor 43 is set to 0, the controller 10 performs control to stop the driving of the rear-wheel motor 43 and to intermittently drive the pump 44 that circulates the cooling oil used for cooling the motor 43. Regarding this intermittent driving, refer to Figure 2A 、 Figure 2B and Figure 3 for a detailed description.

[0038] [Examples of driving times of pump flow rate of cooling oil during intermittent driving]

[0039] Figure 2A and Figure 2B are graphs showing the relationship between the pump flow rate (vertical axis) of the cooling oil during the intermittent driving of the second cooling system 40 of the rear-wheel motor 43 and the elapsed time (horizontal axis) since the start of the intermittent driving. Figure 2A and Figure 2BThis shows an example of a case where the threshold value (parameter) used for intermittent drive determination of changes is shown. Additionally, refer to Figure 3 for details Figure 2A and Figure 2B .

[0040] [Example of Second Cooling System Drive Control]

[0041] Figure 3 This is a flowchart showing an example of the processing sequence of the drive control process of the second cooling system 40 of the rear-wheel motor 43 executed by the controller 10. Additionally, this processing sequence is a process programmed by the controller 10 and is repeatedly executed at a specified interval (for example, about several milliseconds).

[0042] In step S101, the controller 10 acquires vehicle information (the depression amount of the accelerator pedal, vehicle speed) from various parts of the vehicle, and calculates the driving force required for the vehicle (the torque command value for the entire vehicle) based on this vehicle information. And the controller 10 sets the torque distribution of the plurality of motors 33 and 43 based on the calculated driving force. That is, the controller 10 sets the torque distribution of the plurality of motors 33 and 43 based on the driving force required for the electric vehicle.

[0043] In step S102, the controller 10 determines whether the torque distribution of the rear wheels is 0. When the torque distribution of the rear wheels is not 0, in step S103, the controller 10 outputs a torque command value corresponding to the set torque distribution to the inverters 31 and 41. That is, the controller 10 controls the inverters 31 and 41 to drive the front-wheel motor 33 and the rear-wheel motor 43 to achieve the set torque distribution.

[0044] In step S104, the controller 10 normally drives the second cooling system 30 of the front-wheel motor 33 and the second cooling system 40 of the rear-wheel motor 43. That is, the controller 10 performs drive control of the pumps 34 and 44.

[0045] Additionally, when it is determined in step S102 that the torque distribution of the rear wheels is 0, in step S105, the controller 10 determines whether the torque distribution of the rear wheels was 0 in the previous setting. When the torque distribution of the rear wheels was not 0 in the previous setting, in step S106, the controller 10 starts counting the rotational speed of the rear-wheel motor 43 based on the information from the inverter 41.

[0046] In step S107, the controller 10 controls the inverter 31 to drive the front-wheel motor 33 so that it becomes the torque set in step S101. Additionally, the controller 10 controls the inverter 41 to stop the drive of the rear-wheel motor 43.

[0047] In step S108, the controller 10 normally drives the second cooling system 30 of the front-wheel motor 33 and stops the second cooling system 40 of the rear-wheel motor 43. That is, the driving of the pump 44 of the second cooling system 40 is stopped.

[0048] In addition, when it is determined in step S105 that the torque distribution of the rear wheels was also 0 in the previous setting, in step S109, the controller 10 controls the inverter 31 to drive the front-wheel motor 33 to achieve the torque set in step S101. In addition, the controller 10 controls the inverter 41 to keep the driving of the rear-wheel motor 43 stopped.

[0049] In step S110, the controller 10 determines whether the cumulative rotation speed of the rear-wheel motor 43 started to be counted in step S106 is equal to or higher than the threshold value TH1. When the cumulative rotation speed of the rear-wheel motor 43 is less than the threshold value TH1, the operation of this processing sequence ends.

[0050] When the cumulative rotation speed of the rear-wheel motor 43 is equal to or higher than the threshold value TH1, in step S111, the controller 10 resets the cumulative rotation speed of the rear-wheel motor 43 and starts counting the rotation speed of the rear-wheel motor 43.

[0051] In step S112, the controller 10 sets a specified time for driving the second cooling system 40 of the rear-wheel motor 43. That is, the pump 44 of the second cooling system 40 is driven for a specified time. In addition, as the specified time, a fixed value (for example, several seconds) can be used, or a value determined from multiple values based on a certain rule (for example, 2 seconds, 4 seconds, 6 seconds) can be used. For example, the specified value can also be determined based on the temperature of the cooling oil (oil temperature) of the second cooling system 40. For example, when the oil temperature of the cooling oil is low, since the viscosity of the cooling oil is high, it is assumed that the cooling oil stays in the sliding part for a long time. Therefore, when the oil temperature of the cooling oil is low, a relatively short time can be set as the specified time. On the other hand, when the oil temperature of the cooling oil is high, since the viscosity of the cooling oil is low, it is assumed that the cooling oil stays in the sliding part for a short time. Therefore, when the oil temperature of the cooling oil is high, a relatively long time can be set as the specified time.

[0052] For example, when the vehicle speed is constant, the cumulative rotation speed of the rear-wheel motor 43 becomes equal to or higher than the threshold value TH1 at regular intervals. Therefore, as Figure 2A and Figure 2B shown, drive times are periodically generated according to the vehicle speed, and the pump 44 of the second cooling system 40 is intermittently driven. In addition, Figure 2A is an example of a case where the threshold value TH1 is set relatively high, Figure 2B is an example of a case where the threshold value TH1 is set relatively low.

[0053] In this way, when the torque distribution to the rear wheels is 0, the second cooling system 40 is intermittently driven. In this intermittent driving, the driving of the pump 44 is initially stopped, and after this stop, the pump 44 is driven in sequence when the cumulative rotation speed of the motor 43 of the rear wheels reaches the threshold value TH1.

[0054] In addition, the above shows an example in which when the pump 44 is intermittently driven, the driving time of the pump 44 is determined based on the cumulative rotation speed of the motor 43 of the rear wheels, but the driving time of the pump 44 can also be determined based on other conditions. For example, the driving time of the pump 44 can be determined based on the vehicle speed. As described above, the vehicle speed is in a proportional relationship with the rotation speed of the motor 43 of the rear wheels. Therefore, the rotation speed of the motor 43 of the rear wheels can be calculated in sequence based on the vehicle speed, and the cumulative value of this rotation speed can be used to determine the driving time of the pump 44. In addition, when the pump 44 is intermittently driven, the driving time of the pump 44 can also be determined based on whether the vehicle speed is above a specified value. In this case, since there is no need for arithmetic processing for calculating the rotation speed of the motor based on the vehicle speed, the processing load of the driving control of the second cooling system can be reduced.

[0055] In addition, after setting the intermittent driving of the pump 44, it is also assumed that the rotation speed of the motor 43 of the rear wheels cannot be obtained for some reason. In this case, the pump 44 can also be intermittently driven at a preset interval (for example, at intervals of several seconds). Or, the intervals of multiple intermittent drivings can be registered in association with the temperature (oil temperature) of the cooling oil of the second cooling system 40, and based on the temperature (oil temperature) of the cooling oil of the second cooling system 40, one interval can be determined from the intervals of multiple intermittent drivings, and the intermittent driving of the pump 44 can be executed. For example, it can be set that when the oil temperature is high based on the threshold value, the frequency of intermittent driving is increased (for example, the frequency shown in Figure 2B ), and when the oil temperature is low based on the threshold value, the frequency of intermittent driving is decreased (for example, the frequency shown in Figure 2A ). In this way, the control can be performed in such a manner that the circulation of the cooling oil of the second cooling system 40 is intermittently implemented based on the oil temperature.

[0056] As described above, the vehicle speed of the electric vehicle, the rotation speed of the motor 43 of the rear wheels, and the temperature (oil temperature) of the cooling oil of the second cooling system 40 can be used as independent parameters respectively. That is, based on at least one of the vehicle speed of the electric vehicle, the rotation speed of the motor 43 of the rear wheels, and the temperature (oil temperature) of the cooling oil of the second cooling system 40, the control can be performed in such a manner that the circulation of the cooling oil of the second cooling system 40 is intermittently implemented.

[0057] In addition, in Figure 3In [the figure], an example is shown in which the threshold value TH1 is set to a certain value, but the threshold value TH1 can also be changed based on a specified rule. For example, the threshold value TH1 can also be changed based on the temperature (oil temperature) of the cooling oil of the second cooling system 40.

[0058] As described above, when the oil temperature of the cooling oil is low, since the viscosity of the cooling oil is high, it is assumed that the cooling oil stays at the sliding part for a long time. Therefore, when the oil temperature of the cooling oil is low, it is preferable to reduce the frequency of the intermittent drive. On the other hand, when the oil temperature of the cooling oil is high, since the viscosity of the cooling oil is low, it is assumed that the cooling oil stays at the sliding part for a short time. Therefore, when the oil temperature of the cooling oil is high, it is preferable to increase the frequency of the intermittent drive.

[0059] Then, when the temperature (oil temperature) of the cooling oil of the second cooling system 40 is low based on the threshold value TH2 (for example, threshold value TH2 ≥ oil temperature), in order to reduce the frequency of the intermittent drive, a relatively high value is set as the threshold value TH1. In addition, when the temperature (oil temperature) of the cooling oil of the second cooling system 40 is high based on the threshold value TH2 (for example, threshold value TH2 < oil temperature), in order to increase the frequency of the intermittent drive, a relatively low value is set as the threshold value TH1.

[0060] Refer to Figure 2A 、 Figure 2B When Figure 2A it can be grasped as an example of the drive timing when the temperature (oil temperature) of the cooling oil of the second cooling system 40 is low based on the threshold value TH2. In contrast, Figure 2B it can be grasped as an example of the drive timing when the temperature (oil temperature) of the cooling oil of the second cooling system 40 is high based on the threshold value TH2. In this way, the threshold value TH1 can be changed based on the oil temperature. That is, the drive timing of the pump 44 can be changed based on the oil temperature. In addition, in this example, an example is shown in which two values are set as the threshold value TH1 based on the oil temperature, but three or more values can also be set.

[0061] In addition, an example is shown in which cooling oil is used as a refrigerant (lubricant, refrigerant lubricating oil) for cooling and lubricating the motors 33 and 43, but other fluids other than oil (for example, inert refrigerant) suitable for lubricating the motors can also be used. In addition, the cooling oil for cooling and lubricating the motors 33 and 43 can also be shared with the oil for lubricating other components.

[0062] Thus, according to the first embodiment, when the torque distribution to the rear wheels is set to 0, the circulation of the cooling oil in the second cooling system 40 of the rear-wheel motor 43 is temporarily stopped. In this way, by temporarily stopping the circulation of the cooling oil in the second cooling system 40, the power consumption of the vehicle's cooling system can be suppressed, and the power consumption rate of the vehicle can be improved. Thereby, the cruising range of the vehicle can be extended. In addition, after the torque distribution to the rear wheels is set to 0 and the circulation of the cooling oil in the second cooling system 40 is temporarily stopped, the cooling oil is circulated at a moment (for example, intermittently) when a specified condition is satisfied. Thus, even after the circulation of the cooling oil in the second cooling system 40 is temporarily stopped, the cooling oil can be supplied to the rear-wheel motor 43 and its power transmission system at a moment when the specified condition is satisfied, so that sintering of each part (such as sliding parts that require lubrication) can be prevented. In this way, according to the first embodiment, the lubrication of the motor (motors 33 and 43) and its power transmission system can be appropriately performed, and the power consumption of the cooling system (second cooling system 40) can be suppressed.

[0063] In addition, in Figure 1 , the cooling system 1 of the first cooling system 20 is implemented by two pumps 22 and 23, but the first embodiment can also be applied to the case where the number of pumps is one or three or more. Then, Figure 4 shows the cooling system 2 of the first cooling system 50 implemented by one pump 51. That is, Figure 4 shows the schematic structure of the cooling system 2 of the vehicle.

[0064] In addition, regarding the structure of the first cooling system 50, except for the difference in the number of pumps provided, it is substantially the same as the first cooling system 20. Therefore, the same reference numerals are assigned to the parts common to the first cooling system 20 and their description is omitted. In addition, the pump 51 is a circulation pump device for circulating (pressurizing) the refrigerant (cooling water) in the first cooling system 50 and is provided in the supply flow path 24. In addition, the cooling water cooled in the cooler 21 is circulated in the supply flow paths 24 to 26 by the pressurization of the pump 51, whereby the inverters 31, 41, the heat exchangers 32, 42 are cooled. In addition, the pump 51 can be driven or stopped based on the control of the controller 10 and can also operate intermittently. That is, in Figure 4 the example shown, the controller 10 controls the pumps 51, 34, 44, the inverters 31, 41.

[0065] [Advantages and effects of the first embodiment]

[0066] The control method of the electric vehicle according to the first embodiment is a control method in which the lubricant for lubricating the motor (motors 33 and 43) and its power transmission system is used for cooling the motor, and the electric vehicle is driven by a plurality of motors including the first motor (motor 43). In this control method, in step S101, the torque distribution of the plurality of motors is set based on the driving force required by the electric vehicle. In addition, in steps S103, S107, and S109, the driving of the plurality of motors is controlled based on the torque distribution set in step S101. In addition, in steps S108 and S112, when the torque distribution set for the first motor based on a specified value is small, the circulation of the lubricant for cooling the first motor is intermittently implemented.

[0067] According to such a control method of the electric vehicle, by intermittently implementing the circulation of the lubricant for cooling the first motor, the power consumption of the vehicle's cooling system can be suppressed, and the power consumption rate of the vehicle can be improved. As a result, the cruising range of the vehicle can be extended. In addition, since the cooling oil is intermittently supplied to the first motor and its power transmission system (for example, at a moment when specified conditions are satisfied), sintering of each part (such as sliding members that require lubrication) can be prevented. That is, the lubrication of the motor (motors 33 and 43) and its power transmission system can be appropriately performed, and the power consumption of the cooling system (second cooling system 40) can be suppressed.

[0068] In addition, in the control method of the electric vehicle according to the first embodiment, when the state in which the torque distribution set for the first motor (motor 43) based on a specified value is small continues, the timing for implementing the circulation of the lubricant of the first motor is determined based on at least one of the vehicle speed of the electric vehicle, the rotational speed of the first motor, and the temperature of the lubricant of the first motor.

[0069] According to such a control method of the electric vehicle, the circulation of the lubricant of the first motor can be appropriately implemented at a timing determined based on at least one of the vehicle speed of the electric vehicle, the rotational speed of the first motor, and the temperature of the lubricant of the first motor. In addition, since the circulation of the lubricant of the first motor can be appropriately implemented at an appropriate timing considering these three factors, sintering of each part (such as sliding members that require lubrication) can be prevented.

[0070] In addition, in the control method of the electric vehicle according to the first embodiment, when the torque distribution set for the first motor (motor 43) is 0, the circulation of the lubricant of the first motor is intermittently implemented.

[0071] According to the control method of such an electric vehicle, when the torque distribution set for the first motor (motor 43) is 0, by intermittently implementing the circulation of the lubricant for cooling the first motor, the power consumption of the vehicle's cooling system can be suppressed, and the power consumption rate of the vehicle can be improved. Thereby, the cruising range of the vehicle can be extended.

[0072] In addition, the electric vehicle of the first embodiment includes a plurality of motors (motors 33, 43), a plurality of pumps (pumps 34, 44), and a controller 10. The plurality of motors (motors 33, 43) drive the electric vehicle. In addition, the plurality of pumps (pumps 34, 44) are pumps that are used for lubricating the motors and their power transmission systems and for cooling the motors by circulating the lubricant for cooling the motors, and are provided for each of the plurality of motors. In addition, the controller 10 sets the torque distribution of the plurality of motors based on the driving force required by the electric vehicle, and controls the driving of the plurality of motors based on the set torque distribution. When the torque distribution set for the first motor (motor 43) is small with respect to a specified value, it is controlled to intermittently drive the pump (pump 44) for cooling the first motor.

[0073] According to such an electric vehicle, by intermittently implementing the circulation of the lubricant for cooling the first motor, the power consumption of the vehicle's cooling system can be suppressed, and the power consumption rate of the vehicle can be improved. Thereby, the cruising range of the vehicle can be extended. In addition, since the cooling oil is intermittently supplied to the first motor and its power transmission system (for example, at a moment when a specified condition is satisfied), sintering of each part (such as sliding members that require lubrication) can be prevented. That is, the lubrication of the motors (motors 33, 43) and their power transmission systems can be appropriately performed, and the power consumption of the cooling system (second cooling system 40) can be suppressed.

[0074] [Second Embodiment]

[0075] In the first embodiment, in order to improve the power consumption rate, an example is shown in which the second cooling system 40 of the rear-wheel motor 43 is temporarily stopped and then intermittently driven. In the second embodiment, an example is shown in which the power consumption rate is further improved by temporarily stopping a part of the cooling water of the first cooling system 20. In addition, in the second embodiment, an example is shown in which the first cooling system 20 includes two pumps 22, 23 ( Figure 1 as shown). In addition, the second embodiment is an example in which a part of the first embodiment is changed, and for the parts common to the first embodiment, a part of the illustration and description thereof is omitted.

[0076] Figure 5This is a flowchart showing an example of the processing sequence for the drive control process of the first cooling system 20 and the second cooling system 40 of the motor 43 of the rear wheels, which is executed by the controller 10. Additionally, this processing sequence is a process programmed by the controller 10 and is repeatedly executed at a specified interval (for example, about several milliseconds). Also, this processing sequence is a processed sequence obtained by modifying a part of the processing sequence shown in Figure 3 and the parts common to the processing sequence shown in Figure 3 are marked with the same symbols and part of the description is omitted.

[0077] Moreover, in this processing sequence, an example is shown where the pump 23 of the first cooling system 20 is stopped when the torque distribution to the rear wheels is 0.

[0078] When it is determined in step S102 that the torque distribution to the rear wheels is not 0, the motor 33 of the front wheels and the motor 43 of the rear wheels are driven in step S103. In step S104, the second cooling system 30 of the motor 33 of the front wheels and the second cooling system 40 of the motor 43 of the rear wheels are driven normally.

[0079] In step S201, the controller 10 drives the two pumps 22 and 23 of the first cooling system 20 normally.

[0080] Also, when it is determined in step S102 that the torque distribution to the rear wheels is 0 and it is determined in step S105 that the torque distribution to the rear wheels was not 0 in the previous setting, in step S106, counting of the rotational speed of the motor 43 of the rear wheels is started. In step S107, the motor 33 of the front wheels is driven and the drive of the motor 43 of the rear wheels is stopped. In step S108, the second cooling system 30 of the motor 33 of the front wheels is driven normally, and the second cooling system 40 of the motor 43 of the rear wheels is temporarily stopped.

[0081] In step S202, the controller 10 drives the pump 22 on the front wheel side of the first cooling system 20 normally and stops the pump 23 on the rear wheel side.

[0082] Thus, according to the second embodiment, when the torque distribution to the rear wheels is set to 0, the circulation of the cooling oil in the second cooling system 40 of the motor 43 that intermittently drives (temporarily stops) the rear wheels is stopped, and a part of the circulation of the cooling water in the first cooling system 20 is stopped. In this way, by at least temporarily stopping the circulation of the cooling oil in the second cooling system 40 and a part of the circulation of the cooling water in the first cooling system 20, the power consumption of the vehicle's cooling system can be suppressed, and the power consumption rate of the vehicle can be further improved. As a result, the cruising range of the vehicle can be further extended. Thus, according to the second embodiment, the lubrication of the motors (motors 33 and 43) and their power transmission systems can be appropriately performed, and the power consumption of the cooling systems (first cooling system 20 and second cooling system 40) can be suppressed.

[0083] [Operation and Effect of the Second Embodiment]

[0084] In the control method of the electric vehicle according to the second embodiment, when the torque distribution set for the first motor (motor 43) is small with respect to a specified value, for the cooling system (first cooling system 20) 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 of the first motor is at least temporarily stopped (the pump 23 on the rear wheel side of the first cooling system 20 is stopped).

[0085] According to such a control method of the electric vehicle, by at least temporarily stopping a part of the circulation of the cooling water in the first cooling system 20, the power consumption of the vehicle's cooling system can be suppressed, and the power consumption rate of the vehicle can be further improved. As a result, the cruising range of the vehicle can be further extended.

[0086] [Modification Example of the Second Embodiment]

[0087] The above shows an example of stopping a part (the pump 23 on the rear wheel side) of the first cooling system. Next, an example of intermittently driving a part (the pump 23 on the rear wheel side) of the first cooling system for the purpose of improving the power consumption rate is shown. In addition, in the modification example of the second embodiment, an example of intermittently driving the pump 23 on the rear wheel side based on the temperature of the cooling oil (oil temperature) for reducing the temperature of the motor 43 of the rear wheels is shown. In addition, regarding the driving timing, refer to Figures 6A - 6C 、 Figure 7 for a detailed description.

[0088] [Example of Relationship between Cooling Water Pump Flow Rate and Cooling Oil of Motor]

[0089] Figure 6AThe figure shows the relationship between the pump flow rate of the cooling water of the first cooling system 20 (vertical axis) and the temperature of the cooling oil (oil temperature) of the second cooling system 40 (horizontal axis) when the first cooling system 20 is normally driven. Here, the inverter (especially the high-power conversion element (such as IGPT, power module)) sometimes experiences a sharp temperature rise. For example, even when the temperature of the inverter is low and the water temperature is low, there is a possibility that the temperature of the inverter will rise sharply later. Therefore, when the pump flow rate of the cooling water is 0 in a state where the temperature of the inverter is low and the water temperature is low, if the temperature of the inverter rises sharply later, it may not be possible to catch up with the rate of temperature rise of the inverter when reducing the temperature of the cooling water of the first cooling system 20. Thus, it is necessary to always supply cooling water when driving the inverter. Specifically, during the period before the temperature of the cooling oil (oil temperature) of the second cooling system 40 reaches the specified temperature O2, the pump flow rate of the cooling water of the first cooling system 20 is a constant value F1.

[0090] In addition, when the temperature of the cooling oil (oil temperature) of the second cooling system 40 is equal to or higher than the specified temperature O2 and lower than the specified temperature O3, the value of the pump flow rate of the cooling water of the first cooling system 20 is changed from F1 to F2 according to the oil temperature. In addition, when the temperature of the cooling oil (oil temperature) of the second cooling system 40 is equal to or higher than the specified temperature O3, the pump flow rate of the cooling water of the first cooling system 20 is a constant value F2 (where F1 < F2).

[0091] Figure 6B The figure shows the relationship between the pump flow rate of the cooling water of the first cooling system 20 (vertical axis) and the temperature of the cooling oil (oil temperature) of the second cooling system 40 (horizontal axis) when the first cooling system 20 is driven intermittently. That is, during the period before the temperature of the cooling oil (oil temperature) of the second cooling system 40 reaches the specified temperature O1, the pump flow rate of the cooling water of the first cooling system 20 is stopped. In addition, when the temperature of the cooling oil (oil temperature) of the second cooling system 40 is equal to or higher than the specified temperature O1 and less than the specified temperature O3, the value of the pump flow rate of the cooling water of the first cooling system 20 is changed from 0 to F2 according to the oil temperature. In addition, when the temperature of the cooling oil (oil temperature) of the second cooling system 40 is equal to or higher than the specified temperature O3, the pump flow rate of the cooling water of the first cooling system 20 is a constant value F2 (where F1 < F2).

[0092] In this way, in the case of normally driving the first cooling system 20 and the case of driving the first cooling system 20 intermittently, it is different when the temperature of the cooling oil (oil temperature) of the second cooling system 40 is less than the specified temperature O2, but the same when it is equal to or higher than the specified value O2.

[0093] Figure 6CAn example of the relationship between the pump flow rate of the cooling water of the first cooling system 20 (vertical axis) and the elapsed time since the temporary stop (horizontal axis) when the first cooling system 20 is temporarily stopped. As Figure 6C shown, after the first cooling system 20 is temporarily stopped, when the temperature of the cooling oil (oil temperature) is less than the specified temperature O1 (during the period up to Figure 6C t11 shown), the pump flow rate of the cooling water is 0. In addition, when the temperature of the cooling oil (oil temperature) becomes equal to or higher than the specified temperature O1 ( Figure 6C during the period from t11 to t12 shown), the pump flow rate of the cooling water is determined according to the relationship shown in Figure 6B (where 0 < pump flow rate ≤ F2). In addition, when the temperature of the cooling oil (oil temperature) is less than the specified temperature O1 ( Figure 6C during the period after t12 shown), the pump flow rate of the cooling water is 0. In addition, Figure 6C the example shown simplifies an example of the driving time of the cooling water pump 23 for easy explanation and is not limited thereto.

[0094] [Example of Cooling System Driving Control]

[0095] Figure 7 is a flowchart showing an example of the processing sequence of the driving control process of the first cooling system 20 and the second cooling system 40 of the rear wheel motor 43 executed by the controller 10. In addition, this processing sequence is a process programmed by the controller 10 and is repeatedly executed at a specified interval (for example, about several milliseconds). In addition, this processing sequence is a modified processing sequence of a part of the processing sequence shown in Figure 5 , and the same symbols are marked for the parts common to the processing sequence shown in Figure 5 and a part of the description is omitted. In addition, the threshold value TH3 shown in this example corresponds to the value of O1 shown in Figure 6B .

[0096] After driving the second cooling system 40 of the rear wheel motor 43 for a specified time in step S112, in step S301, the controller 10 determines whether the temperature of the cooling oil (oil temperature) of the second cooling system 40 of the rear wheel motor 43 is equal to or higher than the threshold value TH3.

[0097] If 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 10 stops the pump 23 on the rear wheel side of the first cooling system 20. In addition, when the pump 23 on the rear wheel side is stopped, it remains stopped. On the other hand, if it is determined in step S301 that the oil temperature is equal to or higher than the threshold value TH3, in step S302, the controller 10 drives the pump 23 on the rear wheel side of the first cooling system 20. In this case, based on Figure 6BControl the drive of the pump 23 according to the relationship shown. Additionally, when the pump 23 on the rear wheel side is in a driving state, continue driving.

[0098] Additionally, in Figure 7 an example is shown where the pump 23 of the first cooling system 20 is driven based on whether the temperature of the cooling oil (oil temperature) of the second cooling system 40 is equal to or higher than the threshold value TH3. However, the pump 23 of the first cooling system 20 can also be driven based on other conditions. For example, the pump 23 of the first cooling system 20 can be driven on the condition that the circulation of the cooling oil of the second cooling system 40 of the rear wheel motor 43 is restarted. Additionally, for example, the pump 23 of the first cooling system 20 can be driven at the moment when the circulation of the cooling oil of the second cooling system 40 of the rear wheel motor 43 is to be restarted again. That is, the pump 23 of the first cooling system 20 can also be driven based on the driving time of the cooling oil circulation of the second cooling system 40 of the rear wheel motor 43 or the moments before and after it. In other words, the pump 23 of the first cooling system 20 can also be driven based on the driving time of the cooling oil circulation of the second cooling system 40 of the rear wheel motor 43.

[0099] In this way, according to the modified example of the second embodiment, when the torque distribution of the rear wheels is set to 0, the circulation of the cooling oil of the second cooling system 40 of the rear wheel motor 43 is intermittently driven (temporarily stopped), and a part of the circulation of the cooling water of the first cooling system 20 is intermittently driven (temporarily stopped). In this way, by temporarily stopping the circulation of the cooling oil of the second cooling system 40 and a part of the circulation of the cooling water of the first cooling system 20, the power consumption of the vehicle's cooling system can be suppressed, and the power consumption rate of the vehicle can be further improved. As a result, the cruising range of the vehicle can be further extended. Additionally, after the torque distribution of the rear wheels is set to 0 and a part of the circulation of the cooling water of the first cooling system 20 is temporarily stopped, the cooling water circulation is restarted at a moment when a specified condition is met (the oil temperature is equal to or higher than the threshold value TH3). Thus, even after a part of the circulation of the cooling water of the first cooling system 20 is temporarily stopped, the cooling water circulation is restarted again at a moment when the specified condition is met, so that appropriate cooling of the entire vehicle can be achieved. In this way, according to the second embodiment, proper lubrication of the motor (motors 33 and 43) and its power transmission system can be performed, and the power consumption of the cooling system (first cooling system 20, second cooling system 40) can be suppressed.

[0100] [Effects of the Modified Example of the Second Embodiment]

[0101] In the control method of the electric vehicle according to the modified example of the second embodiment, when the state where the torque distribution set for the first motor (motor 43) is small based on a prescribed value continues, the circulation of the refrigerant in the cooling system (first cooling system 20) that cools the lubricant of the first motor is intermittently performed (the pump 23 on the rear wheel side of the first cooling system 20 is intermittently driven).

[0102] According to such a control method of the electric vehicle, by intermittently driving the circulation of a part of the cooling water of the first cooling system 20, the power consumption of the vehicle's cooling system can be suppressed, and the power consumption rate of the vehicle can be improved. In addition, since the circulation of a part of the cooling water of the first cooling system 20 is intermittently driven, appropriate cooling of the entire vehicle can be achieved.

[0103] In addition, in the control method of the electric vehicle according to the modified example of the second embodiment, when the state where the torque distribution set for the first motor (motor 43) is small based on a prescribed value continues, based on the temperature (oil temperature) of the lubricant (cooling oil) of the first motor, the timing for performing the circulation of the refrigerant in the cooling system (first cooling system 20) that cools the lubricant of the first motor is determined (the timing for driving the pump 23 on the rear wheel side of the first cooling system 20 is determined).

[0104] According to such a control method of the electric vehicle, the circulation of the refrigerant in the cooling system (first cooling system 20) can be appropriately performed at an appropriate timing considering the temperature (oil temperature) of the lubricant (cooling oil) of the first motor.

[0105] In addition, in the first and second embodiments, for the sake of easy explanation, an example is shown where when the torque distribution to the rear wheels is set to 0, the driving of the motor 43 of the rear wheels is stopped. However, the present invention is not limited to this. For example, when the torque distribution to the rear wheels is small based on a prescribed value (prescribed lower limit torque) (for example, when the torque distribution to the rear wheels is equal to or less than the prescribed value, when the torque distribution to the rear wheels is smaller than the prescribed value), the driving of the motor 43 of the rear wheels can be stopped. In this way, when the driving of the motor 43 of the rear wheels is stopped, as shown in the first and second embodiments, the temporary stop and intermittent driving of the pump 44 of the second cooling system 40 and the temporary stop and intermittent driving of the pump 23 of the first cooling system 20 can be performed. As the prescribed value shown here, for example, ±0.5 Newton (N) can be used.

[0106] The embodiments of the present invention have been described above, but the above embodiments only show a part of the application examples of the present invention, and it is not intended to limit the technical scope of the present invention to the specific structures of the above embodiments.

Claims

1. A control method for an electric vehicle, wherein a lubricant used for lubricating a motor and a power transmission system of the electric vehicle is used for cooling the motor, and the electric vehicle is driven by a plurality of the motors including a first motor, wherein, Based on a driving force required by the electric vehicle, a torque distribution of the plurality of motors is set. Based on the set torque distribution, driving of the plurality of motors is controlled. When a torque distribution set for the first motor based on a prescribed value is small, circulation of the lubricant for cooling the first motor is intermittently performed.

2. The control method for an electric vehicle according to claim 1, wherein, When a state where a torque distribution set for the first motor based on the prescribed value is small continues, a timing for performing circulation of the lubricant for the first motor is determined based on at least one of a vehicle speed of the electric vehicle, a rotational speed of the first motor, and a temperature of the lubricant for the first motor.

3. The control method for an electric vehicle according to claim 1, wherein, When a torque distribution set for the first motor based on the prescribed value is small, for a cooling system that cools the lubricant using a refrigerant different from the lubricant, circulation of the refrigerant in the cooling system for cooling the lubricant for the first motor is at least temporarily stopped.

4. The control method for an electric vehicle according to claim 3, wherein, When a state where a torque distribution set for the first motor based on the prescribed value is small continues, circulation of the refrigerant in the cooling system for cooling the lubricant for the first motor is intermittently performed.

5. The control method for an electric vehicle according to claim 4, wherein, When a state where a torque distribution set for the first motor based on the prescribed value is small continues, a timing for performing circulation of the refrigerant in the cooling system for cooling the lubricant for the first motor is determined based on the temperature of the lubricant for the first motor.

6. The control method for an electric vehicle according to any one of claims 1 to 5, wherein, The prescribed value is 0, and When a torque distribution set for the first motor is 0, circulation of the lubricant for the first motor is intermittently performed.

7. An electric vehicle, comprising: A plurality of motors that drive the electric vehicle; A plurality of pumps that circulate a lubricant used for lubricating the motors and a power transmission system and for cooling the motors, and are provided for each of the plurality of motors to cool the motors; A controller that sets a torque distribution of the plurality of motors based on a driving force required by the electric vehicle, and controls driving of the plurality of motors based on the set torque distribution, and When a torque distribution set for a first motor constituting the plurality of motors based on a prescribed value is small, the controller controls in a manner of intermittently driving the pump for cooling the first motor.

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