Electric vehicles

Abstract

While the electric vehicle is stopped, the three-phase coils of the three-phase AC motor are protected, while the three-phase AC motor generates more heat. [Solution] The electric vehicle of this disclosure includes a three-phase AC motor having three-phase coils connected at a neutral point and capable of outputting power for driving, a battery, a power control device that adjusts the power from the battery and supplies it to the three-phase AC motor, a heat exchange system capable of transferring heat generated by the three-phase AC motor to the battery, and a control device that performs heat generation control while the electric vehicle is stopped, controlling the power control device so that a DC current flows through each of the three-phase coils in accordance with predetermined conditions, and during the execution of heat generation control, controls the power control device so that the maximum current flows through the coil of the three-phase coils that is most immersed in the cooling medium of the three-phase AC motor, and increases the maximum current.

Description

Technical Field

[0001] The present disclosure relates to an electric vehicle including a three-phase AC motor having three-phase coils connected at a neutral point and capable of outputting driving power.

Background Art

[0002] Conventionally, a motor control device for controlling an AC motor having m stator coils wound around each of m teeth, with one end of each stator coil connected to an inverter and the other end connected as a neutral point, is known (see, for example, Patent Document 1). When the temperature of p stator coils is lower than the temperature of the remaining (m - p) stator coils, this motor control device supplies alternating current with equal amplitude to the p stator coils with a current phase shift of 360° / p each, and supplies alternating current with equal amplitude to the remaining (m - p) coils with a current phase shift of 360° / (m - p). As a result, more current flows through the stator coils with a lower temperature than through those with a higher temperature, thereby equalizing the coil temperature and improving the torque of the entire motor.

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] In a vehicle powered by an AC motor controlled by the conventional motor control device described above, the AC motor can be heated and the battery warmed up by applying DC current to each stator coil so that the total current flowing through the m stator coils is zero while the vehicle is stopped. However, in this case, if the current flowing to the lower-temperature stator coils is increased to increase the heat generated by the AC motor, the increased current will also flow to the higher-temperature stator coils. Therefore, the increase in current in the lower-temperature stators must be set to prevent burnout of the higher-temperature coils, making it difficult to generate a large amount of heat in the AC motor. In addition, there is a risk of demagnetization due to heat conduction near the higher-temperature stator coils.

[0005] Therefore, the primary objective of this disclosure is to generate more heat in a three-phase AC motor while protecting the three-phase coils of the motor when the electric vehicle is stopped. [Means for solving the problem]

[0006] The electric vehicle of this disclosure includes a three-phase AC motor, a battery, a power control device, a heat exchange system, and a control device. The three-phase AC motor has three-phase coils connected at a neutral point and is capable of outputting power for driving. The power control device adjusts the power from the battery and supplies it to the three-phase AC motor. The heat exchange system is capable of transferring the heat generated by the three-phase AC motor to the battery. The control device performs thermal generation control when the electric vehicle is stopped, controlling the power control device so that a DC current flows through each of the three-phase coils when predetermined conditions are met. Furthermore, while performing thermal generation control, the control device controls the power control device so that the maximum current flows through the coil of the three-phase coils that is most immersed in the cooling medium of the three-phase AC motor, and so that this maximum current increases.

[0007] This allows the coil carrying the largest current among the three-phase coils to be cooled by the cooling medium of the three-phase AC motor to prevent burnout, while simultaneously preventing burnout of the remaining coils that do not carry the largest current, and increasing the current flowing through each coil to promote heat generation in the three-phase AC motor. As a result, while the electric vehicle is stopped, it becomes possible to generate more heat in the three-phase AC motor while protecting the three-phase coils of the motor. The heat generated in the three-phase AC motor can then be transferred to the battery via a heat exchange system to warm up the battery.

[0008] Furthermore, the predetermined conditions may be met when the battery temperature is at least below a predetermined temperature. In addition, the battery may be rechargeable by power from an external charging device. Furthermore, the control device may, after the start of the heat generation control, correct the electrical angle of the three-phase AC motor so that the maximum current flows to the coil with the highest degree of immersion, if the maximum current is not flowing to the coil with the highest degree of immersion. Furthermore, the control device may, when the maximum current is flowing to the coil with the highest degree of immersion, control the power control device so that the maximum current is an upper limit current that does not burn out the coils other than the coil with the highest degree of immersion. [Brief explanation of the drawing]

[0009] [Figure 1] This is a schematic diagram illustrating the electric vehicle disclosed herein. [Figure 2] This is a schematic diagram showing the stator of a three-phase AC motor of the electric vehicle disclosed herein. [Figure 3] This diagram illustrates the heat generation control in the electric vehicle described herein. [Figure 4] This flowchart shows the routines executed by the control device of the electric vehicle of this disclosure. [Modes for carrying out the invention]

[0010] Next, with reference to the drawings, embodiments for carrying out the invention of this disclosure will be described.

[0011] Figure 1 is a schematic diagram showing the electric vehicle 1 of this disclosure. The electric vehicle 1 shown in the figure is an electric vehicle (BEV) that includes a motor generator MG that drives a pair of drive wheels DW, a battery (energy storage device) 2, a power control unit (hereinafter referred to as "PCU") 3, and an electronic control unit (hereinafter referred to as "ECU") 20. However, the electric vehicle 1 may also be a plug-in or non-plug-in hybrid vehicle (PHEV, HEV) that includes an internal combustion engine in addition to the battery 2 and motor generator MG.

[0012] The motor generator MG is a three-phase AC motor (synchronous regenerative motor) including a stator S and a rotor R, and exchanges power with the battery 2 via the PCU 3. The stator S of the motor generator MG includes an annular stator core SC and stator coils Cu (U-phase coil), stator coil Cv (V-phase coil), and stator coil Cw (W-phase coil) as shown in Figure 2 (however, only one of the stator coils Cu, Cv, and Cw is shown in Figure 2).

[0013] The stator core SC of the stator S is formed in an annular shape by, for example, stacking multiple electromagnetic steel sheets formed in a substantially annular shape by press working and connecting them in the stacking direction, or by, for example, press-molding and sintering ferromagnetic powder. The stator core SC includes a central hole SO in which the rotor R is arranged, a plurality of teeth ST extending radially from the annular outer circumference (yoke portion) toward the axis and adjacent to each other at a certain interval in the circumferential direction, and a plurality of slots SS (for example, 48 in this embodiment) formed between adjacent teeth ST. Each of the plurality of slots SS extends radially from the stator core SC and is arranged circumferentially at a certain interval, and opens at the central hole SO in which the rotor R is arranged.

[0014] The stator coils Cu, Cv, and Cw are wound around the stator core SC by passing the coil wire through a plurality of corresponding slots SS on the stator core SC, with the wires offset in the circumferential direction. One end (leader wire) of the stator coils Cu, Cv, and Cw is connected to a corresponding power line (not shown), and the other ends of the stator coils Cu, Cv, and Cw are connected by a star connection (Y connection) to form a neutral point NP. In this embodiment, the coil wires forming each of the stator coils Cu, Cv, and Cw are, for example, conductors with an enamel resin insulating coating on their surface.

[0015] Battery 2 is, for example, a lithium-ion secondary battery or nickel-metal hydride secondary battery having a rated output voltage of approximately 200-800V. PCU3 includes an inverter and a boost converter, and is connected to battery 2 via a positive power line, a negative power line, and a system main relay SMR. The inverter of PCU3 includes, for example, six transistors (switching elements) and six diodes connected in parallel in opposite directions to each transistor, and converts DC power from battery 2 to three-phase AC power and supplies it to the motor generator MG, and also converts three-phase AC power from the motor generator MG to DC power and supplies it to battery 2.

[0016] Furthermore, the electric vehicle 1 includes a charging relay DCR and a charging inlet CI. The charging relay DCR is connected to the neutral point NP of the motor generator MG via a power line and is also connected to the negative side power line between the system main relay SMR and the PCU 3 via a power line. The charging inlet CI is located inside a charging lid (not shown) of the electric vehicle 1 and is connected to the charging relay DCR via a power line. As a result, when both the system main relay SMR and the charging relay DCR are closed, the battery 2 is electrically connected to the charging inlet CI via the motor generator MG and the PCU 3.

[0017] When the charging connector 101 of an external charging device 100, such as a DC type, installed on an external charging facility such as a charging station, is plugged into (connected to) the charging inlet CI, the battery 2 can be charged by power from the external charging device 100. However, the charging relay DCR may be connected to the positive and negative power lines between the system main relay SMR and the PCU 3 via a power line, and the electric vehicle 1 may be equipped with an on-board charging device.

[0018] As shown in Figure 1, the rotor R of the motor generator MG is connected to a pair of drive wheels DW via a reduction mechanism 4, a differential gear DF, and a drive shaft DS. The motor generator MG, the reduction mechanism 4, the differential gear DF, and a portion of each drive shaft DS are housed in a transaxle case 5, forming the transaxle of the electric vehicle 1. An oil reservoir 50 for storing lubricating and cooling oil (lubricating and cooling medium) O is defined in the lower part of the transaxle case 5, and the lubricating and cooling oil O, which is scraped up by the gears included in the reduction mechanism 4 and the differential gear DF, is supplied to the gears and bearings inside the transaxle case 5 via oil passages and oil guides (not shown).

[0019] Furthermore, in the electric vehicle 1, a strainer 6, a heat exchanger (cooler) 7, and an electric oil pump 8 are arranged inside the transaxle case 5. The strainer 6 is fixed inside the oil reservoir 50, for example, with a suction port located at the bottom that opens downwards. The suction port of the electric oil pump 8 is connected to the oil outlet of the strainer 6 via the heat exchanger 7. The lubricating and cooling oil O discharged from the outlet of the electric oil pump 8 is supplied to the inside of the rotor R of the motor generator MG via oil passages and oil guides (not shown), and from inside the rotor R it is also supplied to the stator S (coil end) and bearings around the motor generator MG. After passing through the objects to be lubricated and cooled, such as the motor generator MG, the lubricating and cooling oil O flows down into the oil reservoir 50.

[0020] In this embodiment, a part of the stator S of the motor generator MG, that is, a part (lower part) of the stator core SC and a part of the stator coils Cu, Cv, Cw are immersed (oil-immersed) in the lubricating and cooling oil O stored in the oil storage part 50 as shown in FIG. 2. The oil immersion rate (the number of slots SS through which the conductors are inserted) indicating the degree of immersion of the stator coils Cu, Cv, Cw in the lubricating and cooling oil O stored in the oil storage part 50 is determined according to the mounting state of the stator S (motor generator MG) to the transaxle case 5. And the oil immersion rate of any one of the stator coils Cu, Cv, Cw (for example, the stator coil Cu in this embodiment) becomes higher than the other two.

[0021] Further, the electric vehicle 1 includes a heat exchange system 10 capable of transferring the heat generated by the motor generator MG or the like in the transaxle case 5 to the battery 2. The heat exchange system 10 includes a heat exchanger 7 in the transaxle case 5, a heat exchanger 11 provided in the PCU 3 (inside the PCU case), a heat exchanger 12 provided in the battery 2 (inside the battery case), and an electric circulation pump 14 for circulating a heat medium (coolant) among the heat exchangers 7, 11, 12. By operating the circulation pump 14, the heat medium that has taken heat from the motor generator MG and the PCU 3 in the heat exchangers 7, 11 can be supplied to the heat exchanger 12, and the heat can be released from the heat medium to the battery 2 in the heat exchanger 12.

[0022] <于 The ECU 20 includes a computer having a CPU, ROM, RAM, input / output interfaces, etc., various drive circuits, various logic ICs, etc., and controls (switching control) the inverter and boost converter of the PCU 3. Further, the ECU 20 obtains the accelerator opening Acc indicating the depression amount of the accelerator pedal detected by an accelerator pedal position sensor (not shown), the vehicle speed V detected by a vehicle speed sensor (not shown), the rotational position of the rotor R of the motor generator MG detected by a rotational position sensor (resolver) 21, the phase currents Iu, Iv, Iw flowing through the stator coils Cu, Cv, Cw detected by current sensors 22u, 22v, 22w, etc. Furthermore, the ECU 20 obtains from a battery electronic control unit (hereinafter referred to as "battery ECU") 25 that manages the battery 2, the SOC (charge rate) of the battery 2 calculated by the battery ECU 25, the allowable charging power Win (negative value) and the allowable discharging power Wout (positive value), the temperature (representative temperature) Tb of the battery 2 detected by a temperature sensor not shown, etc.

[0023] When the electric vehicle 1 is running, the ECU 20 calculates the electrical angle θe and the rotational speed Nm of the motor generator MG (rotor R) based on the rotational position of the rotor R. Further, the ECU 20 sets a torque command Tm* to the motor generator MG corresponding to the required torque for the running of the electric vehicle 1 based on the accelerator opening Acc and the vehicle speed V within the ranges of the allowable charging power Win and the allowable discharging power Wout of the battery 2, and performs switching control of the inverter (a plurality of transistors) etc. of the PCU 3 based on the torque command Tm*. Controls the PCU 3. Also, when the electric vehicle 1 is braking, the ECU 20 controls the PCU 3 so that the motor generator MG outputs a regenerative braking torque (torque command Tm*) of the share within the ranges of the allowable charging power Win and the allowable discharging power Wout of the battery 2 to the pair of drive wheels DW.

[0024] When switching control the inverter (multiple transistors) of PCU3, ECU20 performs a coordinate transformation (3-phase to 2-phase transformation) on the phase currents Iu, Iv, and Iw based on the separately calculated electrical angle θe to calculate the d-axis and q-axis currents Id and Iq. Next, ECU20 sets the d-axis and q-axis current commands Id* and Iq* based on the torque command Tm*, and calculates the d-axis and q-axis voltage commands Vd* and Vq* so that the difference between the current commands Id* and Iq* and the currents Id and Iq is canceled out by current feedback control. Furthermore, ECU20 performs a coordinate transformation (2-phase to 3-phase transformation) on the d-axis and q-axis voltage commands Vd* and Vq* based on the electrical angle θe to three-phase voltage commands Vu*, Vv*, and Vw*. Then, by comparing the voltage commands Vu*, Vv*, Vw* with the carrier wave (triangular wave), PWM signals are generated for multiple transistors in the inverter, and these multiple transistors are switched on using the generated PWM signals.

[0025] Furthermore, when charging the battery 2 with power (DC power) from the external charging device 100, the ECU 20 controls the opening and closing of the charging relay DCR, and also causes each phase of the three-phase stator coils Cu, Cv, and Cw of the motor generator MG and the inverter of the PCU 3 to function as a multi-phase boost converter. As a result, by switching control of multiple transistors in the inverter, the power (DC power) supplied to the charging inlet CI is boosted by the multi-phase boost converter, and the battery 2 is charged with the boosted power.

[0026] Furthermore, the ECU 20 controls the electric oil pump 8 and the circulation pump 14 of the heat exchange system 10 located within the transaxle case 5. In addition, the ECU 20 performs thermal control to warm up the battery 2 as needed while the electric vehicle 1 is stopped, and also controls the electric oil pump 8 in the transaxle case 5 and the circulation pump 14 of the heat exchange system 10. As shown in Figure 4, the thermal control involves flowing a DC current through each stator coil Cu, Cv, and Cw of the motor generator MG, and controlling the inverter of the PCU 3 so that the total current flowing through the three-phase stator coils Cu, Cv, and Cw becomes zero. By performing this thermal control, each stator coil Cu, Cv, and Cw of the motor generator MG generates heat, and the heat from the motor generator MG is transferred to the battery 2 via the lubricating cooling oil O and the heat transfer medium of the heat exchange system 10, thereby warming up the battery 2. Furthermore, a thermal switch 23 is connected to the ECU 20, and the driver of the electric vehicle 1 can operate the thermal switch 23 to allow or prohibit the execution of thermal control. The ECU 20 sets the heat generation flag to "1" when the heat generation switch 23 is ON, and sets the heat generation flag to "0" when the heat generation switch 23 is OFF. Note that the functions of the ECU 20 may be distributed among multiple electronic control units.

[0027] Next, with reference to Figure 5, the operation related to the heat generation control of the electric vehicle 1 will be explained. Figure 5 is a flowchart showing a routine that is started by the ECU 20 at predetermined time intervals while the electric vehicle 1 is running.

[0028] When the execution timing for the routine in Figure 5 arrives, the ECU 20 acquires the rotational speed Nm of the motor generator MG, the temperature Tb of the battery 2, and the value of the heat generation flag (step S100). Next, the ECU 20 determines whether the electric vehicle 1 is stopped or not based on the rotational speed Nm of the motor generator MG acquired in step S100 (step S110). In step S110, the ECU 20 determines that the electric vehicle 1 is stopped when the rotational speed Nm is zero, and determines that the electric vehicle 1 is not stopped when the rotational speed Nm is not zero. If the rotational speed Nm is not zero and the electric vehicle 1 is not stopped (step S110: NO), the ECU 20 terminates the routine in Figure 5 at that point. Note that the processing in step S110 may also determine whether the electric vehicle 1 is stopped or not based on the vehicle speed V, the detected value of the rotational position sensor 21, or the slope of the U-phase, V-phase, and W-phase carrier waves, etc.

[0029] If the electric vehicle 1 is stopped (step S110: YES), the ECU 20 determines whether the execution conditions for the heat generation control are met based on the temperature Tb of the battery 2 and the value of the heat generation flag obtained in step S100 (step S120). In step S120, the ECU 20 determines that the execution conditions for the heat generation control are met if the temperature Tb of the battery 2 is less than or equal to a predetermined heat generation execution temperature (for example, 0°C) and the heat generation switch 23 is turned on and the heat generation flag is set to "1". Also in step S120, the ECU 20 determines that the execution conditions for the heat generation control are not met if the temperature Tb of the battery 2 is above the heat generation execution temperature or if the heat generation switch 23 is turned off and the heat generation flag is set to "0". If the execution conditions for the heat generation control are not met (step S120: NO), the ECU 20 terminates the routine in Figure 5 at that point.

[0030] If the conditions for executing heat generation control are met (step S120: YES), the ECU 20 controls the PCU 3 (inverter) to flow a predetermined relatively low DC current Iref (Arms) through one of the stator coils Cu, Cv, and Cw, thereby starting heat generation control (step S130). The DC current Iref is a constant value smaller than the upper limit current Ilim (Arms), which is a current that is acquired in advance as a current that will not burn out the stator coils Cu, Cv, and Cw (conductors). This upper limit current Ilim (positive value) is the current that will not burn out the stator coils Cu, Cv, and Cw when they are not cooled by the lubricating cooling oil O stored in the oil reservoir 50 or from the electric oil pump 8. When the DC current Iref flows through one of the stator coils Cu, Cv, and Cw, as shown in Figure 4, approximately equal currents will flow through the remaining two so that the total current of the three phases becomes zero.

[0031] After starting the heat generation control in step S130, the ECU 20 acquires the phase currents Iu, Iv, and Iw detected by the current sensors 22u, 22v, and 22w, and identifies the stator coil Cu, Cv, and Cw through which the current with the largest absolute value flows based on the acquired phase currents Iu, Iv, and Iw (step S140). Note that the process in step S140 may instead identify the stator coil Cu, Cv, and Cw through which the current with the largest absolute value flows based on the amplitude of the carrier waves of the U-phase, V-phase, and W-phase, instead of the phase currents Iu, Iv, and Iw.

[0032] Next, the ECU 20 determines whether the stator coil Cu, Cv, or Cw, which has the largest absolute value current identified in step S140, is the one with the highest oil immersion rate in the lubricating cooling oil O stored in the oil reservoir 50 (in this embodiment, the stator coil Cu) (step S150). If the stator coil Cu, Cv, or Cw identified in step S140 is not the one with the highest oil immersion rate (step S150: NO), the ECU 20 corrects the electrical angle of the motor generator MG at the stopping position of the rotor R, which was calculated when the motor generator MG stopped rotating, so that the largest current flows through the stator coil Cu, Cv, or Cw with the highest oil immersion rate (step S155). In step S155, the ECU 20 uses the difference between the electrical angle θref, which is determined according to the mounting state of the stator S to the transaxle case 5 and is the point in time when the maximum current flows through the stator coil Cu, Cv, or Cw with the highest oil immersion rate, and the electrical angle θ0 of the motor generator MG at the stopping position of the rotor R, as a correction amount, and sets the electrical angle θref to the electrical angle θe of the motor generator MG. After the processing in step S155, the ECU 20 repeats the processing in steps S130 and S140.

[0033] Furthermore, if the stator coil Cu, Cv, or Cw identified in step S140 has the highest oil immersion rate (step S150: YES), the ECU 20 activates the electric oil pump 8 in the transaxle case 5 and the circulation pump 14 of the heat exchange system 10, and controls the PCU 3 (inverter) to match the absolute value of the current flowing through the stator coil Cu, Cv, or Cw, which has the largest absolute value current, to the upper limit current Ilim mentioned above, thereby continuing the heat generation control (step S160).

[0034] In other words, in step S160, the ECU20 increases the d-axis and q-axis current commands Id* and Iq* according to the difference between the DC current Iref and the upper limit current Ilim, and controls the PCU3 (inverter) based on these current commands Id* and Iq*. This allows the motor generator MG, i.e., the three-phase stator coils Cu, Cv, and Cw, to generate more heat. Furthermore, the heat generated in the motor generator MG is recovered by the lubricating coolant O discharged from the electric oil pump 8, and transferred from the lubricating coolant O to the coolant in the heat exchange system 10 in the heat exchanger 7. Furthermore, the coolant passes through the heat exchanger 11 of the PCU3 and is pressurized and sent to the heat exchanger 12 of the battery 2. As a result, the heat generated in the motor generator MG and PCU3 is transferred to the battery 2 via the coolant, making it possible to warm up the battery 2 properly.

[0035] After the processing in step S160, the ECU 20 obtains the rotational speed Nm of the motor generator MG, the temperature Tb of the battery 2, and the value of the heat generation flag (step S170), and determines whether or not to stop the heat generation control based on the obtained values ​​of rotational speed Nm, temperature Tb, and heat generation flag (step S180). The ECU 20 determines that the heat generation control should be continued if the rotational speed Nm is zero and the electric vehicle 1 is stopped, the temperature Tb of the battery 2 is slightly higher than the heat generation execution temperature but below the heat generation stop temperature, and the heat generation switch 23 is ON and the heat generation flag is set to "1" (step S180: NO). In this case, the ECU 20 executes the processing in steps S160-S180 again. Note that the processing in step S180 may also determine whether or not the vehicle is stopped based on the vehicle speed V, the detected value of the rotational position sensor 21, or the slope of the U-phase, V-phase, and W-phase carrier waves.

[0036] Furthermore, the ECU 20 determines that the heat generation control should be stopped if the rotational speed Nm is not zero and the electric vehicle 1 is starting, if the temperature Tb of the battery 2 is above the heat generation stop temperature, or if the heat generation switch 23 is off and the heat generation flag is set to "0" (step S180: YES). In these cases, the ECU 20 stops the electric oil pump 8 and the circulation pump 14 and also stops the heat generation control (step S190), and terminates the routine in Figure 5.

[0037] As described above, the electric vehicle 1 includes a motor generator MG, a battery 2, a PCU 3 (inverter), a heat exchange system 10, and an ECU 20 as a control device. The motor generator MG has three phase stator coils Cu, Cv, and Cw connected at a neutral point NP and is capable of outputting power for driving. The PCU 3 (inverter) adjusts the power from the battery 2 and supplies it to the motor generator MG. The heat exchange system 10 is capable of transferring the heat generated by the motor generator MG to the battery 2. When the electric vehicle 1 is stopped (step S110: YES), the ECU 20 performs heat generation control, controlling the PCU 3 (inverter) so that a DC current flows through each of the three phase stator coils Cu, Cv, and Cw in accordance with the fulfillment of the heat generation execution conditions (predetermined conditions) (step S120: YES, S130). Furthermore, during the execution of heat generation control, the ECU20 controls the PCU3 (inverter) so that the current with the largest absolute value flows to the stator coil Cu, Cv, and Cw of the three phases that has the highest degree of immersion in the lubricating cooling oil O of the motor generator MG stored in the oil reservoir 50, and so that this maximum current increases (its absolute value becomes larger) (steps S150-S170, S180: NO).

[0038] This allows the stator coil Cu, Cv, or Cw carrying the current with the largest absolute value among the three-phase stator coils Cu, Cv, and Cw to be cooled by the lubricating cooling oil O in the oil reservoir 50, preventing burnout of the stator coil Cu, etc., while also preventing burnout of the remaining stator coils Cv, Cw, etc. that do not carry the current with the largest absolute value, and increasing the current flowing through each stator coil Cu, Cv, and Cw to promote heat generation in the motor generator MG. As a result, while the electric vehicle 1 is stopped, it becomes possible to generate more heat in the motor generator MG while protecting the three-phase stator coils Cu, Cv, and Cw of the motor generator MG. Then, in the electric vehicle 1, the heat generated in the motor generator MG can be transferred to the battery 2 by the heat exchange system 10 to warm up the battery 2.

[0039] Furthermore, in the electric vehicle 1, the heat generation execution condition is met when the temperature Tb of the battery 2 is at least below a predetermined heat generation execution temperature (specified temperature) (step S120). This makes it possible to warm up the battery 2 using the time the electric vehicle 1 is stopped, thereby protecting the battery 2 and suppressing the prolonged charging time of the battery 2.

[0040] Furthermore, the battery 2 can be charged using power from the external charging device 100 of the external charging facility. This allows the battery 2 to be heated up before charging by the external charging device 100 begins, using the time the electric vehicle 1 is stopped before arriving at the external charging facility, thereby suppressing the prolonged charging time at the external charging facility.

[0041] Furthermore, after the start of the heat generation control, if the ECU 20 is not receiving the maximum absolute current from the stator coil Cu, Cv, or Cw with the highest degree of immersion (step S150: NO), it corrects the electrical angle θe of the motor generator MG so that the maximum absolute current flows through the stator coil Cu, Cv, or Cw with the highest degree of immersion (step S155). This makes it possible to receive the maximum absolute current from the stator coil Cu, Cv, or Cw with the highest degree of immersion in the lubricating coolant O immediately after the electric vehicle 1 stops, even if the maximum absolute current does not flow through it afterward.

[0042] Furthermore, the ECU20 controls the PCU3 (inverter) so that the absolute value of the maximum current is set to an upper limit current Ilim that prevents burnout of stator coils Cu, Cv, and Cw that are not cooled by the lubricating cooling oil O stored in the oil reservoir 50 or from the electric oil pump 8, i.e., stator coils Cv, Cw, etc., other than the stator coil Cu, etc., which has the highest oil immersion rate (step S150). This makes it possible to increase the maximum current (increase the absolute value) while more reliably preventing burnout of all three-phase stator coils Cu, Cv, and Cw.

[0043] Furthermore, the invention disclosed herein is not limited in any way to the embodiments described above, and it goes without saying that various modifications can be made within the scope of this disclosure. Moreover, the embodiments described above are merely one specific form of the invention described in the summary of the invention, and do not limit the elements of the invention described in the summary of the invention. [Industrial applicability]

[0044] The invention disclosed herein can be used in industries such as the electric vehicle manufacturing industry. [Explanation of Symbols]

[0045] 1 Electric vehicle, 2 Battery, 3 Power control unit (PCU), 4 Reduction mechanism, 5 Transaxle case, 50 Oil reservoir, 6 Strainer, 7, 11, 12 Heat exchanger, 8 Electric oil pump, 10 Heat exchange system, 14 Circulation pump, 20 Electronic control unit (ECU), 21 Rotational position sensor, 22u Current sensor, 23 Heat generation switch, 100 External charging device, Cu, Cv, Cw Stator coil, MG Motor generator, NP Neutral point, O Lubricating coolant, R Rotor, S Stator.

Claims

1. An electric vehicle comprising a three-phase AC motor having three-phase coils connected at a neutral point and capable of outputting power for driving, a battery, and a power control device that adjusts the power from the battery and supplies it to the three-phase AC motor, A heat exchange system capable of transferring heat generated by the three-phase AC motor to the battery, A control device that, while the electric vehicle is stopped, performs thermal control by controlling the power control device so that a direct current flows through each of the three-phase coils in accordance with predetermined conditions, and during the execution of the thermal control, controls the power control device so that the maximum current flows through the coil among the three-phase coils that is most immersed in the cooling medium of the three-phase AC motor, and so that the maximum current increases. An electric vehicle equipped with [a specific feature / equipment].

2. In the electric vehicle according to claim 1, The aforementioned predetermined condition is met when the temperature of the battery is at least below a predetermined temperature in an electric vehicle.

3. In the electric vehicle according to claim 1 or 2, The aforementioned battery is an electric vehicle that can be charged by power from an external charging facility.

4. In the electric vehicle according to claim 1 or 2, The control device corrects the electrical angle of the three-phase AC motor so that, after the start of the heat generation control, the coil with the highest degree of immersion among the three-phase coils does not receive the maximum current, so that the maximum current flows through the coil with the highest degree of immersion.

5. In the electric vehicle according to claim 4, The control device controls the power control device so that, when the maximum current flows through the coil with the highest degree of immersion, the maximum current becomes an upper limit current that does not burn out the coils other than the coil with the highest degree of immersion.

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