Drive device

Abstract

To provide a technique capable of raising temperature of coils of a plurality of phases of an electric motor.SOLUTION: A drive device mounted on a vehicle includes: a first electric motor having coils of a plurality of phases and configured to rotate a drive wheel of the vehicle; a rotation prohibition device configured to prohibit rotation of the drive wheel by the first electric motor; and a control device configured to control a current supplied to the first electric motor. The control unit is configured to execute temperature raising processing of raising temperature of the coils of the plurality of phases of the first electric motor by applying a current to the coils of the plurality of phases. In the temperature raising processing, the rotation prohibition device prohibits rotation of the drive wheel, and the current supplied to the coils of the plurality of phases includes a q-axis current.SELECTED DRAWING: Figure 4

Description

[Technical Field]

[0001] The technology disclosed in this specification relates to a drive device, and more particularly to a drive device including an electric motor having a multi-phase coil. [Background technology]

[0002] Patent Document 1 discloses a vehicle equipped with a motor generator having a three-phase coil. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Application Laid-Open No. 2009-118659 Summary of the Invention [Problem to be solved by the invention]

[0004] In motor generators such as those described in Patent Document 1, the coils are sometimes heated. However, when heating the coils of multiple phases, if a temperature difference occurs between the coils of each phase, the motor generator may not be able to exhibit the intended magnetic characteristics. This specification provides a technology that can reduce the temperature difference between the coils of each phase when heating the coils of multiple phases of an electric motor. [Means for solving the problem]

[0005] The technology disclosed in this specification is embodied in a drive unit mounted on a vehicle. The drive unit includes a first electric motor having multiple phase coils and rotating drive wheels of the vehicle, a rotation prohibiting device that prohibits the first electric motor from rotating the drive wheels, and a control device that controls current flowing through the first electric motor. The control device is capable of executing a temperature rise process that raises the temperature of the multiple phase coils of the first electric motor by passing current through the multiple phase coils. In the temperature rise process, the rotation prohibiting device prohibits rotation of the drive wheels, and the current flowing through the multiple phase coils includes a q-axis current.

[0006] In the drive device described above, while the rotation prohibition device prohibits rotation of the drive wheels, a current including a q-axis current is passed through the coils of multiple phases of the first electric motor. This prevents the drive wheels from rotating even when the first electric motor generates torque due to the q-axis current, and allows the coils of multiple phases to generate heat. By allowing the q-axis current to pass through, the coils of multiple phases of the first electric motor can be heated independently, regardless of the rotational position of the rotor. This allows the temperature difference between the coils of each phase to be reduced when heating the coils of multiple phases.

[0007] Another example is a comparative example in which the temperature of the multiple phase coils of the first electric motor is increased by passing a current including only a d-axis current through the multiple phase coils of the first electric motor. According to this comparative example, the temperature of the multiple phase coils of the first electric motor can be increased while preventing torque from being generated in the first electric motor. However, in this comparative example, currents of different magnitudes may be continuously passed through the multiple phase coils. In this case, the amount of current passed through the multiple phase coils may differ. As a result, the amount of heat generated in the multiple phase coils may not be uniform, resulting in temperature differences between the multiple phase coils. Temperature differences between the multiple phase coils may prevent the first electric motor from achieving the intended magnetic characteristics. In the drive device disclosed in this specification, a current including a q-axis current is passed through the multiple phase coils of the first electric motor. This allows the magnitude of the current passed through the multiple phase coils to be more uniform than in the comparative example. This allows the temperature of the multiple phase coils of the first electric motor to be appropriately increased.

[0008] Details and further improvements of the technology disclosed in this specification are described in the following "Description of Embodiments of the Invention." [Brief explanation of the drawings]

[0009] [Figure 1] 1 shows a block diagram of an electric vehicle 10 equipped with a drive unit 20 of a first embodiment. [Figure 2] 2 shows a cross-sectional view taken along line II-II in FIG. [Figure 3] 1 shows a circuit diagram of a driving device 20. [Figure 4] 1 shows a flow diagram of processing executed by a control device 90 of the drive device 20. DETAILED DESCRIPTION OF THE INVENTION

[0010] In one embodiment of the present technology, the multi-phase coil may include a three-phase coil, but in another embodiment, the multi-phase coil may include a two-phase coil.

[0011] In one embodiment of the present technology, the rotation prevention device may include a locking component that mechanically locks an axle connected to the drive wheel.

[0012] With this configuration, the temperature raising process can be carried out with the rotation of the drive wheels reliably prohibited by the locking component.

[0013] In one embodiment of the present technology, the control device may execute the temperature increase process while the vehicle is stopped.

[0014] With this configuration, the rotation prohibition device prohibits the rotation of the drive wheels while the vehicle is stopped, so that the temperature increase process can be performed without affecting the running of the vehicle.

[0015] In one embodiment of the present technology, the drive device may further include a second electric motor having a multi-phase coil and rotating drive wheels of the vehicle. However, in another embodiment, the drive device does not need to include a second electric motor. Note that the second electric motor may drive the same drive wheels as the first electric motor, or may drive drive wheels different from the first electric motor.

[0016] In one embodiment of the present technology, the first electric motor and the second electric motor may rotate a common drive shaft. However, in another embodiment, for example, the first electric motor may rotate a drive shaft connected to front wheels of a vehicle, and the second electric motor may rotate a drive shaft connected to rear wheels of the vehicle. That is, the first electric motor and the second electric motor may rotate different drive shafts.

[0017] In one embodiment of the present technology, the vehicle may further include a second power conversion device electrically connected to the second electric motor. In this case, the second electric motor and the second power conversion device may form a charging circuit that supplies electric power from an external power supply to a battery of the vehicle via a neutral point of the second electric motor, and the control device may perform the temperature increase process in response to charging of the battery by the charging circuit.

[0018] When the battery is charged by the charging circuit, the temperature of the second electric motor rises. With this configuration, the temperature of the first electric motor is raised by the temperature raising process in response to the charging of the battery by the charging circuit, so that the temperature difference between the second electric motor and the first electric motor can be reduced.

[0019] In one embodiment of the present technology, the control device may execute the temperature increase process during at least a portion of a period during which the charging circuit charges the battery.

[0020] The temperature of the second electric motor rises while the battery is being charged by the charging circuit. With this configuration, the temperature of the first electric motor is raised by the temperature raising process during at least a part of the battery charging period, thereby reducing the temperature difference between the second electric motor and the first electric motor.

[0021] In one embodiment of the present technology, the control device may determine the timing to start execution of the temperature increase process according to a scheduled start time of use of the vehicle.

[0022] For example, if the heating process is started regardless of the start time of use, the heating process may be carried out for an unnecessarily long time, which may result in excessive current flowing through the coils of multiple phases.With this configuration, it is possible to prevent excessive current from flowing through the coils of multiple phases, thereby enabling the heating process to be carried out with energy efficiency.

[0023] In one embodiment of the present technology, the control device may determine the timing to end the execution of the temperature increase process according to a scheduled start time of use of the vehicle.

[0024] For example, if the heating process is terminated regardless of the end time of use, the heating process may be executed for an unnecessarily long time, which may result in excessive current flowing through the coils of multiple phases. With this configuration, it is possible to prevent excessive current from flowing through the coils of multiple phases, thereby enabling the heating process to be executed with energy efficiency.

[0025] In one embodiment of the present technology, the control device may change the magnitude of the current flowing through the multiple phase coils of the first electric motor according to a temperature difference between the first electric motor and the second electric motor.

[0026] With this configuration, for example, when the temperature difference between the first electric motor and the second electric motor is small, the magnitude of the current flowing through the coils of the multiple phases can be reduced, thereby enabling the temperature rise process to be performed with energy efficiency.

[0027] In one embodiment of the present technology, the electric vehicle may further include a heat medium circuit that circulates a heat medium. In this case, in the temperature increase process, the heat medium circuit may circulate the heat medium at least between the first electric motor and a battery of the electric vehicle.

[0028] With this configuration, the heat generated by the temperature raising process in the first electric motor can be used to raise the temperature of the battery of the electric vehicle.

[0029] (Example) FIG. 1 shows a block diagram of an electric vehicle 10 equipped with a drive unit 20 of a first embodiment, as seen from above. In this specification, the front of the electric vehicle 10 (i.e., the top of the paper in FIG. 1) may be simply referred to as the "front," and the opposite side may be simply referred to as the "rear." Furthermore, the left side of the electric vehicle 10 (i.e., the left side of the paper in FIG. 1) may be simply referred to as the "left," and the opposite side may be simply referred to as the "right." Furthermore, the top of the electric vehicle 10 (i.e., the front side of the paper in FIG. 1) may be simply referred to as the "top," and the opposite side may be simply referred to as the "bottom." Note that in this specification, the term "electric vehicle" includes, for example, rechargeable electric vehicles that are charged by an external power source, fuel cell vehicles that use fuel cells as a power source, and hybrid vehicles that also have an engine.

[0030] In addition to a drive unit 20, an electric vehicle 10 further includes a vehicle body 2, a battery pack 3, a pair of left and right front wheels 4L, 4R, a pair of left and right rear wheels 5L, 5R, a charging inlet 6, a parking brake 9, a radiator 12, and a radiator thermal circuit 16. The drive unit 20 includes a first electric motor 30L, a second electric motor 30R, a first inverter 40L, a second inverter 40R, a first power transmission mechanism 50L, and a second power transmission mechanism 50R. Hereinafter, the expression "a pair of left and right wheels" may be simply referred to as "a pair."

[0031] The drive unit 20 drives the pair of front wheels 4L, 4R by supplying electric power from the battery pack 3 to the electric motors 30L, 30R, thereby driving the electric vehicle 10. In other words, the pair of front wheels 4L, 4R are the drive wheels of the electric vehicle 10. In a modified example, the pair of rear wheels 5L, 5R may be the drive wheels of the electric vehicle 10, or the pair of front wheels 4L, 4R and the pair of rear wheels 5L, 5R may be the drive wheels of the electric vehicle 10.

[0032] The first electric motor 30L and the second electric motor 30R are disposed symmetrically with respect to the center line C1 in the left-right direction of the electric vehicle 10 and have the same structure. The first electric motor 30L is located to the left of the center line C1, and the second electric motor 30R is located to the right of the center line C1. The first inverter 40L is disposed above the first electric motor 30L, and the second inverter 40R is disposed above the second electric motor 30R. The first electric motor 30L and the first inverter 40L are electrically connected to each other, and the second electric motor 30R and the second inverter 40R are electrically connected to each other. The power transmission mechanisms 50L and 50R are mechanically connected to the electric motors 30L and 30R, respectively. The structure of each power transmission mechanism 50L and 50R will be described in detail below with reference to FIG. 2.

[0033] The charging inlet 6 is disposed on the right side of the vehicle body 2. The charging inlet 6 is configured to be connected to an external power source 7 (e.g., a charging stand) via a power cable 8. When the charging inlet 6 is connected to the external power source 7, charging power from the external power source 7 is supplied to the battery pack 3.

[0034] The radiator 12 is disposed at the front end of the body of the electric vehicle 10. The radiator 12 is a device that exchanges heat between a heat medium (for example, antifreeze or water) circulating in a radiator thermal circuit 16 and outside air. The radiator 12 cools the heat medium, for example, by airflow that flows into the body 2 while the electric vehicle 10 is running. When the electric vehicle 10 is running, the heat medium functions, for example, as a refrigerant that cools the electric motors 30L, 30R. Furthermore, as will be described in detail later, the heat medium also functions, for example, as a heat medium that heats the battery pack 3 at low temperatures.

[0035] The radiator thermal circuit 16 includes a radiator pump 17, a first pipe 18L, a second pipe 19L, a third pipe 18R, and a fourth pipe 19R. The first pipe 18L connects the radiator 12 and the first electric motor 30L. The second pipe 19L connects the first electric motor 30L and the battery pack 3. Similarly, the third pipe 18R connects the radiator 12 and the second electric motor 30R, and the fourth pipe 19R connects the second electric motor 30R and the battery pack 3. The radiator pump 17 pumps the heat medium in the radiator thermal circuit 16. In this embodiment, the radiator pump 17 circulates the heat medium through the first pipe 18L, the first electric motor 30L, the second pipe 19L, the battery pack 3, the third pipe 18R, the second electric motor 30R, the fourth pipe 19R, and the radiator 12 in this order.

[0036] The detailed structure of the drive device 20 will be described with reference to Fig. 2. In addition to the electric motors 30L, 30R, etc. described above, the drive device 20 further includes a control device 90. The control device 90 is a computer equipped with a CPU, and is configured to be able to communicate with, for example, the electric motors 30L, 30R, the parking brake 9, and the radiator pump 17, and controls the operation of these devices.

[0037] The first electric motor 30L of the drive unit 20 includes a first motor case 32L, a first motor bearing 33L, a first rotor 34L, a first stator 35L, and a first temperature sensor 39L. The first motor case 32L accommodates the first rotor 34L, the first stator 35L, and the first temperature sensor 39L. The first rotor 34L has a first permanent magnet 36L. The first stator 35L faces the first rotor 34L from the radially outer side. The outer periphery of the first stator 35L is covered by a U-phase coil 35U, a V-phase coil 35V, and a W-phase coil 35W (see FIG. 3). The coils 35U, 35V, and 35W of each phase are arranged along the circumferential direction of the first stator 35L. The first temperature sensor 39L is fixed to the left end face of the first stator 35L. The first temperature sensor 39L detects the temperature T1 of the first electric motor 30L and transmits it to the control device 90. In a modified example, the first temperature sensor 39L may be fixed to, for example, the inner wall of the first motor case 32L. The first motor bearing 33L is, for example, a ball bearing. The first motor bearing 33L rotates the first motor shaft 51L by rolling balls along an inner raceway. The other bearings are also ball bearings. In a modified example, each bearing may be a roller bearing instead of a ball bearing.

[0038] As described above, the second electric motor 30R has a similar configuration to the first electric motor 30L. Therefore, like the first electric motor 30L, the second electric motor 30R includes a second motor case 32R, a second motor bearing 33R, a second rotor 34R having a second permanent magnet 36R, a second stator 35R, and a second temperature sensor 39R. The second motor bearing 33R rotates the second motor shaft 51R. The second temperature sensor 39R detects the temperature T2 of the second electric motor 30R and transmits it to the control device 90.

[0039] The first power transmission mechanism 50L transmits the power of the first electric motor 30L to the drive shaft 14. The drive shaft 14 connects the pair of front wheels 4L, 4R to each other. The first power transmission mechanism 50L includes a plurality of bearings 53L, 56L, 58L, a plurality of gears 54L, 57L, 61L, 62L, and a plurality of shafts 55L, 59L. The first power transmission mechanism 50L reduces the rotation speed of the first electric motor 30L by using, for example, the plurality of gears 54L, 57L, 61L, 62L to drive the drive shaft 14. The first power transmission mechanism 50L also includes a parking gear 70. When the parking brake 9 (see FIG. 1) is operated, the parking gear 70 engages with a parking lock (not shown) to stop the rotation of the first motor shaft 51L. That is, the parking gear 70 prohibits the rotation of the front wheels 4L by locking the drive shaft 14 connected to the front wheels 4L. When operated by the user, the parking brake 9 transmits an ON signal S1 to the control device 90, indicating that the parking brake is being applied.

[0040] The second power transmission mechanism 50R transmits the power of the second electric motor 30R to the drive shaft 14. The second power transmission mechanism 50R has a bilaterally symmetrical structure to the first power transmission mechanism 50L described above. Therefore, the second power transmission mechanism 50R includes a plurality of bearings 53R, 56R, 58R, a plurality of gears 54R, 57R, 61R, 62R, and a plurality of shafts 55R, 59R. The second power transmission mechanism 50R reduces the rotation speed of the second electric motor 30R by using, for example, the plurality of gears 54R, 57R, 61R, 62R, etc., to rotate the drive shaft 14.

[0041] As shown in Fig. 1, in this embodiment, the drive shaft 14 connects the pair of front wheels 4L, 4R. Therefore, the pair of front wheels 4L, 4R are driven by two electric motors 30L, 30R. In a modified example, the drive shaft 14 may be separated at the center in the left-right direction of the electric vehicle 10. In other words, the pair of front wheels 4L, 4R may be driven independently by the electric motors 30L, 30R, respectively.

[0042] The electric circuit of the drive device 20 will be described with reference to FIG. 3. The first electric motor 30L is a three-phase motor including a U-phase coil 35U, a V-phase coil 35V, and a W-phase coil 35W. One ends of the U-phase coil 35U, the V-phase coil 35V, and the W-phase coil 35W are connected to a neutral point NP1. The other end of the U-phase coil 35U of the first electric motor 30L is connected to a U-phase arm 42U of the first inverter 40L. Similarly, the other end of the V-phase coil 35V of the first electric motor 30L is connected to a V-phase arm 42V of the first inverter 40L, and the other end of the W-phase coil 35W is connected to a W-phase arm 42W. In this manner, the first inverter 40L is electrically connected to the first electric motor 30L.

[0043] Similarly, the second electric motor 30R is also a three-phase motor. One ends of the U-phase coil 35U, V-phase coil 35V, and W-phase coil 35W of the second electric motor 30R are connected to the neutral point NP2. The other end of the U-phase coil 35U of the second electric motor 30R is connected to a U-phase arm 42U of the second inverter 40R. Similarly, the other end of the V-phase coil 35V of the second electric motor 30R is connected to a V-phase arm 42V of the second inverter 40R, and the other end of the W-phase coil 35W is connected to a W-phase arm 42W. In this manner, the second inverter 40R is electrically connected to the second electric motor 30R.

[0044] As shown in FIG. 3 , the drive device 20 further includes a charging circuit 11. The charging circuit 11 is a circuit for supplying DC charging power supplied from the external power source 7 to the battery pack 3. In the charging circuit 11, one terminal of the charging inlet 6 is connected to the positive electrode of the battery pack 3 via the neutral point NP2 of the second electric motor 30R and the second inverter 40R. That is, the charging circuit 11 supplies the charging power supplied from the external power source 7 to the neutral point NP2 of the second electric motor 30R. The other terminal of the charging inlet 6 is connected to the negative electrode of the battery pack 3 via the second inverter 40R. The charging circuit 11 supplies the charging power to the battery pack 3 via the neutral point NP2 of the second electric motor 30R. As a result, the second electric motor 30R and the second inverter 40R can function as three boost circuits connected in parallel between the charging inlet 6 and the battery pack 3. As a result, the drive unit 20 can boost the output voltage of the external power source 7 using the second electric motor 30R and the second inverter 40R. This allows rapid charging even if the output voltage of the external power source 7 is lower than the voltage of the battery pack 3. One terminal of the charging inlet 6 is directly connected to the positive electrode of the battery pack 3 via a switch 13. When the output voltage of the external power source 7 is equal to the voltage of the battery pack 3, the charging circuit 11 turns on the switch 13 to allow the output voltage of the external power source 7 to bypass the neutral point NP2 of the second electric motor 30R. Although not shown, the charging circuit 11 also includes a charging unit including a relay, a capacitor, and the like. The charging unit is connected to the neutral point NP2 and the second inverter 40R.

[0045] In this embodiment, while the charging inlet 6 is connected to the external power source 7 and charging power from the external power source 7 is supplied to the neutral point NP2 of the second electric motor 30R, current flows through the coils 35U, 35V, and 35W of each phase of the second electric motor 30R. As a result, the coils 35U, 35V, and 35W of each phase generate heat, causing the temperature T2 of the second electric motor 30R to rise. On the other hand, even when the charging inlet 6 is connected to the external power source 7, no current flows through the coils 35U, 35V, and 35W of each phase of the first electric motor 30L, so the temperature T1 of the first electric motor 30L does not rise. Therefore, while charging power from the external power source 7 is supplied to the neutral point NP2 of the second electric motor 30R, the temperature difference between the electric motors 30L and 30R increases. In this case, the output torques of the electric motors 30L and 30R become unbalanced, which may reduce the running stability of the electric vehicle 10.

[0046] Referring to FIG. 4, the temperature rise setting process executed by the control device 90 of the drive device 20 will be described. The temperature rise setting process is a process for executing a temperature rise process in which currents including a q-axis current are passed through the coils 35U, 35V, and 35W of each phase of the first electric motor 30L, thereby causing the coils 35U, 35V, and 35W of each phase to generate heat. The control device 90 starts the temperature rise setting process in response to connection of the charging inlet 6 to the external power supply 7. That is, the control device 90 executes the temperature rise process in response to charging of the battery pack 3 by the charging circuit 11. This makes it possible to prevent the temperature difference between the electric motors 30L and 30R from becoming large due to charging of the battery pack 3.

[0047] In the temperature acquisition process S2, the control device 90 acquires the temperature T1 of the first electric motor 30L from the first temperature sensor 39L, and acquires the temperature T2 of the second electric motor 30R from the second temperature sensor 39R.

[0048] In the temperature rise determination process S4, the control device 90 calculates a temperature difference T2-T1 from the temperatures T1 and T2 acquired in the temperature acquisition process S2 and compares this temperature difference with a pre-stored threshold temperature difference Tth. The threshold temperature difference Tth is a threshold for determining whether the temperature difference T2-T1 will cause a decrease in stability during operation of the drive unit 20. The threshold temperature difference Tth is determined based on the size, output torque, etc. of each electric motor 30L, 30R, but can be changed by the user afterward. If the temperature difference T2-T1 is smaller than the threshold temperature difference Tth (NO in the temperature rise determination process S4), the output torque of each electric motor 30L, 30R is maintained relatively uniform even if the temperature rise process is not performed on the coils 35U, 35V, and 35W of each phase of the first electric motor 30L. This allows the drive unit 20 to operate stably. If the control device 90 determines NO in the temperature rise determination process S4, it terminates the process shown in FIG. 4. This prevents unnecessary execution of temperature increase processing even when the temperature difference T2-T1 is smaller than the threshold temperature difference Tth and the electric motors 30L, 30R can be driven in a balanced manner. On the other hand, if the temperature difference T2-T1 is equal to or greater than the threshold temperature difference Tth (YES in the temperature increase determination processing S4), the control device 90 determines that temperature increase processing is necessary because the output torques of the electric motors 30L, 30R will become unbalanced and the stability of the electric motors 30L, 30R when driven may decrease, and proceeds to the current adjustment processing S6.

[0049] In the current adjustment process S6, the control device 90 adjusts the magnitude of the current supplied to the coils 35U, 35V, and 35W of each phase of the first electric motor 30L during the temperature increase process, based on the temperature difference T2-T1 calculated in the temperature increase determination process S4. Specifically, the control device 90 calculates the value of the current supplied by multiplying the temperature difference T2-T1 by a predetermined conversion value. Therefore, the larger the temperature difference T2-T1, the larger the value of the current supplied. In other words, the value of the current supplied is proportional to the temperature difference T2-T1. For example, when the temperature difference T2-T1 is small, the magnitude of the current supplied can be reduced compared to when the temperature difference T2-T1 is large. This allows the temperature increase process to be performed with greater energy efficiency. Hereinafter, the current supplied by the current adjustment process S6 may be referred to as the "adjusted current."

[0050] In the time calculation process S10, the control device 90 calculates the use start time. The use start time is the time when, after the start of charging of the battery pack 3, it is predicted that charging of the battery pack 3 will be completed and the electric vehicle 10 will start traveling again. The control device 90 stores, for example, the charge amount per unit time and an actual value of the time from completion of charging to start of traveling. Therefore, the control device 90 first calculates the charging time required to complete charging from the current remaining power level of the battery pack 3. The control device 90 calculates the use start time by adding the predicted time from completion of charging to restart of traveling to the calculated charging time. The predicted time from completion of charging to restart of traveling may be, for example, the average of the actual values ​​or the shortest actual value. In another variation, the predicted time may be any time input by the user.

[0051] In the first monitoring process S12, the control device 90 monitors whether the temperature rise start time has arrived. The temperature rise start time indicates the timing to start supplying current to the coils 35U, 35V, and 35W of each phase of the first electric motor 30L. The temperature rise start time is determined based on the use start time calculated in the time calculation process S10 and the adjusted current calculated in the current adjustment process S6. Specifically, the temperature rise start time is calculated by subtracting from the use start time calculated in the time calculation process S10 the time required for the temperature to rise until the current temperature difference T2 - T1 becomes smaller than the threshold temperature difference Tth when the adjusted current is supplied to the coils 35U, 35V, and 35W of each phase of the first electric motor 30L. For example, if the difference between the temperature difference T2 - T1 and the threshold temperature difference Tth is large, a relatively early temperature rise start time is set. Therefore, the temperature T1 rises relatively quickly, and the temperature difference T2-T1 can be reliably made smaller than the threshold temperature difference Tth by the time the use start time arrives.

[0052] On the other hand, when the difference between the temperature difference T2-T1 and the threshold temperature difference Tth is small, a later temperature rise start time is set compared to when the difference between the temperature difference T2-T1 and the threshold temperature difference Tth is large. The control device 90 repeats the first monitoring process S12 until the temperature rise start time is reached. This prevents the temperature rise process from being started before the temperature rise start time, thereby preventing the first electric motor 30L from being energized for an unnecessarily long period of time. In this way, by determining the timing to start energizing the coils 35U, 35V, and 35W of each phase of the first electric motor 30L according to the start time of use of the electric vehicle 10, the temperature of the first electric motor 30L can be increased with energy efficiency. When the start time of use is reached, the control device 90 determines YES in the first monitoring process S12 and proceeds to the brake determination process S20.

[0053] In the brake determination process S20, the control device 90 determines whether the parking brake 9 is in operation. Specifically, the control device 90 determines whether an ON signal S1 is received from the parking brake 9. If the control device 90 has not received the ON signal S1 (NO in S20), the control device 90 proceeds to brake operation process S22, and if the control device 90 has received the ON signal S1 (YES in S20), the control device 90 proceeds to energization process S24.

[0054] In the brake application process S22, the control device 90 turns on and activates the parking brake 9. This locks the drive shaft 14, preventing the electric vehicle 10 from running during the temperature increase process. When the brake application process S22 ends, the control device 90 proceeds to the power application process S24.

[0055] In the current application process S24, the control device 90 applies the adjusted current calculated in the current adjustment process S6 to the first electric motor 30L. As a result, the coils 35U, 35V, and 35W of each phase of the first electric motor 30L generate heat, and the temperature T1 of the first electric motor 30L rises.

[0056] Furthermore, in the pump operation process S26, the control device 90 turns on the radiator pump 17 to operate it. As a result, the radiator pump 17 circulates the heat medium in the radiator thermal circuit 16. As a result, the heat medium circulates, for example, between the first electric motor 30L and the battery pack 3. As a result, heat generated in the coils 35U, 35V, and 35W of each phase of the first electric motor 30L can be supplied to the battery pack 3 via the heat medium. As a result, the temperature of the battery pack 3 can be increased.

[0057] In the second monitoring process S30, the control device 90 monitors whether the temperature rise end time has been reached. The temperature rise end time indicates the timing to end the supply of current to the coils 35U, 35V, and 35W of each phase of the first electric motor 30L. The temperature rise end time is the time when the temperature rise start time is reached (YES in the first monitoring process S12) and the temperature difference T2-T1 is estimated to be smaller than the threshold temperature difference Tth after the supply of current to the first electric motor 30L is started in the current supply process S24. The temperature rise end time is determined based on the use start time calculated in the time calculation process S10. The control device 90 repeats the second monitoring process S30 until the temperature rise end time is reached, and when the temperature rise end time has been reached (YES in the second monitoring process S30), the control device 90 proceeds to the current supply end process S32.

[0058] In the power distribution termination process S32, the control device 90 terminates power distribution to the first electric motor 30L. By terminating power distribution at the temperature rise start time corresponding to the use start time and the corresponding temperature rise end time in this manner, it is possible to prevent power being distributed to the first electric motor 30L for an unnecessarily long period of time. When the power distribution termination process S32 ends, the control device 90 terminates the temperature rise setting process of FIG. 4.

[0059] (Effects of this embodiment) In the drive unit 20 of this embodiment, when the parking gear 70 prohibits rotation of the pair of front wheels 4L and 4R, currents including a q-axis current are applied to the coils 35U, 35V, and 35W of each phase of the first electric motor 30L (energization process S24 in FIG. 4). As a result, even if the first electric motor 30L generates torque due to the q-axis current, the rotation of the pair of front wheels 4L and 4R is prevented and the three-phase coils 35U, 35V, and 35W can generate heat. Because not only the d-axis current but also the q-axis current is allowed to flow, the temperatures of the multiple phase coils 35U, 35V, and 35W of the first electric motor 30L can be raised independently of the rotational position of the first rotor 34L. As a result, when raising the temperatures of the coils 35U, 35V, and 35W of each phase, the temperature difference between the coils 35U, 35V, and 35W of each phase can be reduced.

[0060] (Correspondence) The parking gear 70 is an example of a "rotation inhibiting device" or a "locking component." The energization process S24 in Fig. 4 is an example of a "temperature increasing process." The second inverter 40R is an example of a "second power conversion device."

[0061] Although specific examples of the technology disclosed in this specification have been described in detail above, these are merely examples and do not limit the scope of the claims. The technology described in the claims includes various modifications and variations of the specific examples exemplified above. Modifications of the above examples are listed below.

[0062] (Modification 1) The first electric motor 30L and the second electric motor 30R may each have a two-phase coil. In another modification, the first electric motor 30L and the second electric motor 30R may each have a four- or more-phase coil.

[0063] (Variation 2) The gear 62L of the first power transmission mechanism 50L may be configured to be able to disconnect the drive shaft 14. In this case, the control device 90 may disconnect the gear 62L from the drive shaft 14 instead of turning on the parking brake 9 in the brake activation process S22 of FIG. 4. This prevents the drive shaft 14 from rotating. In this variation, the gear 62L is an example of a "rotation prohibiting device."

[0064] (Variation 3) The control device 90 does not have to execute the temperature increase setting process in Figure 4 when the connection of the charging inlet 6 to the external power supply 7 is used as a trigger. The control device 90 may execute the process in Figure 4 in response to, for example, a user instruction. In that case, the control device 90 may execute the process in Figure 4 while the electric vehicle 10 is traveling.

[0065] (Variation 4) The drive device 20 may not include the second electric motor 30R. The drive device 20 may include only the first electric motor 30L. In this case, the control device 90 may acquire the temperatures of the coils 35U, 35V, and 35W of each phase of the first electric motor 30L in the temperature acquisition process S2 of FIG. 4. In this variation, in the temperature increase determination process S4, the control device 90 may execute the temperature increase process if the temperature difference between the coils 35U, 35V, and 35W of each phase exceeds a threshold value. In this case, in the current adjustment process S6, the control device 90 may adjust the magnitude of the current flowing through the coil in the phase with the lowest temperature so that the coil generates the most heat.

[0066] (Variation 5) The second electric motor 30R and the second inverter 40R do not have to constitute the charging circuit 11. In this case, the control device 90 may execute the processing of FIG. 4 for both the first electric motor 30L and the second electric motor 30R.

[0067] (Variation 6) The control device 90 does not have to execute the time calculation process S10 and the first monitoring process S12 in Fig. 4. In this variation, for example, the supply of electricity to the first electric motor 30L may start after a predetermined time has elapsed since the charging inlet 6 was connected to the external power supply 7.

[0068] (Variation 7) The control device 90 does not have to execute the second monitoring process S30 of Fig. 4. In this variation, for example, the control device 90 may execute the power distribution termination process S32 when the temperature difference T2-T1 becomes smaller than the threshold temperature difference Tth.

[0069] (Variation 8) The control device 90 does not have to execute the pump operation process S26 of Fig. 4. In this case, the radiator thermal circuit 16 of the electric vehicle 10 does not have to include the second pipe 19L and the fourth pipe 19R.

[0070] The technical elements described in this specification or drawings may exhibit technical utility either alone or in various combinations, and are not limited to the combinations described in the claims at the time of filing. Furthermore, the technologies illustrated in this specification or drawings may achieve multiple objectives simultaneously, and achieving one of those objectives alone is technically useful. [Explanation of symbols]

[0071] 2: Body, 3: Battery pack, 4L, 4R: Front wheels, 5L, 5R: Rear wheels, 6: Charging inlet, 7: External power supply, 8: Power cable, 9: Parking brake, 10: Electric vehicle, 11: Charging circuit, 12: Radiator, 13: Switch, 14: Drive shaft, 16: Radiator thermal circuit, 17: Radiator pump, 18L: First pipe, 18R: Third pipe, 19L: Second pipe, 19R: Fourth pipe, 20: Drive unit, 30L: First electric motor, 30R: Second electric motor, 32L: First motor case, 32R: Second motor case, 33L: First motor bearing, 33R: Second motor bearing, 34L: First rotor, 34R: Second rotor, 35L: First stator, 35R: Second stator, 35U: U-phase coil, 35V: V-phase coil, 35W: W-phase coil, 36L: first permanent magnet, 36R: second permanent magnet, 39L: first temperature sensor, 39R: second temperature sensor, 40L: first inverter, 40R: second inverter, 42U: U-phase arm, 42V: V-phase arm, 42W: W-phase arm, 50L: first power transmission mechanism, 50R: second power transmission mechanism, 51L: first motor shaft, 5 1R: second motor shaft, 53L, 53R, 56L, 56R, 58L, 58R: bearings, 54L, 54R, 57L, 57R, 61L, 61R, 62L, 62R: gears, 55L, 55R, 59L, 59R: shafts, 70: parking gear, 90: control device, NP1, NP2: neutral point, S1: on signal, T1: temperature, T2: temperature, Tth: threshold temperature difference

Claims

1. A drive device mounted on a vehicle, a first electric motor having coils of multiple phases and rotating drive wheels of the vehicle; a rotation prohibiting device that prohibits the first electric motor from rotating the drive wheels; a control device for controlling a current supplied to the first electric motor; Equipped with the control device is capable of executing a temperature raising process of raising temperatures of the coils of the multiple phases of the first electric motor by passing current through the coils of the multiple phases, In the temperature increase process, the rotation prohibition device prohibits rotation of the drive wheels, and the currents flowing through the coils of the multiple phases include a q-axis current. Drive unit.

2. The drive device according to claim 1 , wherein the multi-phase coils include three-phase coils.

3. The drive unit according to claim 1 , wherein the rotation inhibiting device includes a locking component that mechanically locks an axle connected to the drive wheel.

4. The drive device according to claim 1 , wherein the control device executes the temperature increase process while the vehicle is stopped.

5. The drive device according to claim 1 , further comprising a second electric motor having a multi-phase coil and rotating drive wheels of the vehicle.

6. The drive device according to claim 5 , wherein the first electric motor and the second electric motor rotate a common drive shaft.

7. a second power converter electrically connected to the second electric motor; the second electric motor and the second power conversion device form a charging circuit that supplies electric power from an external power supply to a battery of the vehicle via a neutral point of the second electric motor, the control device executes the temperature increase process in response to charging of the battery by the charging circuit. The drive device according to claim 5.

8. The drive device according to claim 7 , wherein the control device executes the temperature increase process during at least a portion of a period during which the charging circuit is charging the battery.

9. The drive device according to claim 7 , wherein the control device determines a timing to start the execution of the temperature raising process in accordance with a scheduled start time of use of the vehicle.

10. The drive device according to claim 7 , wherein the control device determines a timing to end the execution of the temperature increase process in accordance with a scheduled start time of use of the vehicle.

11. 6. The drive device according to claim 5, wherein the control device changes the magnitude of the currents applied to the coils of the multiple phases of the first electric motor in accordance with a temperature difference between the first electric motor and the second electric motor.

12. The electric vehicle further includes a heat medium circuit for circulating a heat medium, The drive device according to claim 1 , wherein in the temperature increase process, the heat medium circuit circulates the heat medium at least between the first electric motor and a battery of the vehicle.

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