Drive device

Abstract

To provide a drive device which can reduce a temperature difference between two electric motors during charging of a power storage device.SOLUTION: A drive device comprises: a first electric motor; a second electric motor; a first power control device; a power supply circuit which is electrically connected with a neutral point of the first electric motor and supplies charging power supplied from an external power source to the neutral point; a first heat circuit which performs heat exchange with the first electric motor; a second heat circuit which performs heat exchange with the second electric motor and at least a part of a segment of which is in common with the first heat circuit; at least one pump which circulates heating medium in the first heat circuit and the second heat circuit; and a pump control device which controls the pump. The pump control device activates the pump during at least a part of charging period where the charging power is supplied through the power supply circuit to the neutral point of the first electric motor to circulate the heating medium in both of the first heat circuit and the second heat circuit.SELECTED DRAWING: Figure 4

Description

Technical Field

[0001] The technology disclosed in this specification relates to a drive device for a vehicle.

Background Art

[0002] Patent Document 1 describes a drive device for a vehicle. This drive device includes two electric motors that drive the left and right drive wheels.

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] When charging a power storage device of a vehicle, a technique is known in which charging power is supplied to the neutral point of an electric motor, and the electric motor and a power control device (typically an inverter) function as a boost circuit. When this technique is applied to a drive device including two electric motors, only one of the electric motors is used for charging, and charging power is supplied only to the one electric motor. As a result, when the charging of the power storage device is completed, a temperature difference may occur between the one electric motor used for charging and the other electric motor not used for charging. The temperature of the electric motor affects the characteristics of the electric motor. Therefore, if a large temperature difference occurs between the two electric motors, the running stability of the vehicle may decrease after charging is completed. In this specification, a technique is provided that can reduce the temperature difference between two electric motors even when heat generation occurs in one of the two electric motors during charging of the power storage device.

Means for Solving the Problems

[0005] The drive device disclosed in this specification drives a pair of left and right drive wheels of a vehicle. The drive device includes a first electric motor that drives at least one of the pair of left and right drive wheels, a second electric motor that drives at least the other of the pair of left and right drive wheels, a first power control device that controls power between the power storage device of the vehicle and at least the first electric motor, a power supply circuit that is electrically connected to the neutral point of the first electric motor and supplies charging power supplied from an external power source to the neutral point, a first heat circuit that performs heat exchange with the first electric motor, a second heat circuit that performs heat exchange with the second electric motor and at least a part of which is common to the first heat circuit, at least one pump that circulates a heat medium through the first heat circuit and the second heat circuit, and a pump control device that controls the at least one pump. The pump control device operates the at least one pump during at least a part of a charging period in which the power supply circuit supplies the charging power to the neutral point of the first electric motor, thereby circulating the heat medium in both the first heat circuit and the second heat circuit.

[0006] In the drive device described above, during charging of the power storage device, the heat medium circulates in both the first heat circuit and the second heat circuit. The first heat circuit and the second heat circuit have a section common to each other and are configured to share the heat medium. For this reason, the heat generated in the first electric motor is transmitted to the second electric motor via the shared heat medium. Thereby, even when only the first electric motor generates heat during charging of the power storage device, the temperature difference between the first electric motor and the second electric motor is reduced.

[0007] Details and further improvements of the technology disclosed in this specification will be described in the following "Mode for Carrying Out the Invention".

Brief Description of the Drawings

[0008]

Figure 1

Figure 2

Figure 3

Figure 4

Figure 5

Embodiments for Carrying Out the Invention

[0009] In one embodiment of the present technology, the at least one pump may include a first pump that circulates the heat medium in the first heat circuit and a second pump that circulates the heat medium in the second heat circuit. In that case, the pump control device may circulate the heat medium in both the first heat circuit and the second heat circuit by operating both the first pump and the second pump during at least a part of the charging period.

[0010] According to such a configuration, compared with a configuration in which one pump circulates the heat medium in both the first heat circuit and the second heat circuit, relatively small pumps can be adopted for the first pump and the second pump. Thereby, for example, when it is sufficient to circulate the heat medium only in the first heat circuit, the power consumption related to the circulation of the heat medium can be suppressed by operating only the first pump.

[0011] In one embodiment of the present technology, the pump control device may stop the operation of the second pump even during the charging period when the temperature difference between the first electric motor and the second electric motor is below a predetermined threshold value.

[0012] According to such a configuration, when there is no significant temperature difference between the two electric motors and there is no need to transfer the heat of the first electric motor to the second electric motor, the power consumption related to the circulation of the heat medium can be suppressed by prohibiting the operation of the second pump.

[0013] In one embodiment of the present technology, when the temperature of the second electric motor is higher than the temperature of the heat medium, the pump control device may stop the operation of the second pump even during the charging period.

[0014] According to such a configuration, when the temperature of the second electric motor is relatively high and there is no need to transfer the heat of the first electric motor to the second electric motor, by prohibiting the operation of the second pump, the power consumption related to the circulation of the heat medium can be suppressed.

[0015] In one embodiment of the present technology, the pump control device may change the output of the second pump according to the temperature difference between the first electric motor and the second electric motor during the charging period.

[0016] According to such a configuration, for example, when the temperature difference between the first electric motor and the second electric motor is large, the pump control device can increase the output of the second pump. Thereby, compared with the configuration of controlling the second pump at a constant output, the temperature difference between the first electric motor and the second electric motor can be quickly reduced.

[0017] In one embodiment of the present technology, the drive device may further include a casing that houses at least the first electric motor and the second electric motor. In that case, at least a part of the section common to the first heat circuit and the second heat circuit may be located within the casing.

[0018] According to such a configuration, for example, a heat medium reservoir formed at the lower part of the casing can be used as a section common to the first heat circuit and the second heat circuit.

[0019] In one embodiment of the present technology, the drive device may further include a first heat exchanger located between the at least one pump and the first electric motor in the first heat circuit, a second heat exchanger located between the at least one pump and the second electric motor in the second heat circuit, and a third heat circuit connecting the first heat exchanger and the second heat exchanger. The third heat circuit may circulate a different heat medium from the heat medium that has passed through the radiator of the vehicle.

[0020] According to such a configuration, it is possible to cool the heat medium circulating in the first heat circuit and the second heat circuit by using a different heat medium cooled by the radiator of the vehicle. Thereby, while suppressing the temperature difference between the first electric motor and the second electric motor, the heat generated by the first electric motor can be released to the outside.

[0021] In one embodiment of the present technology, the heat medium may be lubricating oil for the first electric motor and the second electric motor.

[0022] Thereby, it is possible to reduce the temperature difference between the first electric motor and the second electric motor and reduce the frictional force generated in each electric motor.

[0023] In one embodiment of the present technology, the first electric motor may drive one of the pair of left and right drive wheels, and the second electric motor may drive the other of the pair of left and right drive wheels. However, in another embodiment, the first electric motor and the second electric motor may drive both of the pair of left and right drive wheels.

[0024] (First Embodiment) FIG. 1 shows a block diagram of an electric vehicle 10 including a drive device 20 according to the first embodiment as viewed from above. FIG. 2 shows a cross-sectional view taken along line II-II in FIG. 1. In this specification, the front of the electric vehicle 10 (i.e., above the paper surface in FIG. 1) may be simply referred to as "front", and the opposite side may be simply referred to as "rear". Further, the left side of the electric vehicle 10 (i.e., the left side of the paper surface in FIG. 1) may be simply referred to as "left", and the opposite side may be simply referred to as "right". Also, the upper side of the electric vehicle 10 (i.e., the front direction of the paper surface in FIG. 1) may be simply referred to as "up", and the opposite side may be simply referred to as "down".

[0025] The electric vehicle 10 includes a vehicle body 2, a pair of left and right front wheels 4R and 4L, a pair of left and right rear wheels 5R and 5L, a charging inlet 6, a radiator 12, a radiator pump 16, a radiator thermal circuit 18, and a drive device 20. The drive device 20 includes a casing 21, a pair of left and right electric motors 30R and 30L, a pair of left and right power transmission mechanisms 50R and 50L, a pair of left and right oil coolers 22R and 22L, and a pair of left and right inverters 40R and 40L. Hereinafter, the description of "a pair of left and right" may be simply described as "a pair".

[0026] The drive device 20 drives a pair of front wheels 4R and 4L by supplying the power of the battery pack 3 to the pair of electric motors 30R and 30L. Thereby, the electric vehicle 10 is driven. That is, the pair of front wheels 4R and 4L are the drive wheels of the electric vehicle 10. In a modified example, the pair of rear wheels 5R and 5L may be the drive wheels of the electric vehicle 10, or the pair of front wheels 4R and 4L and the pair of rear wheels 5R and 5L may be the drive wheels of the electric vehicle 10. Note that the "electric vehicle" in this specification includes, for example, a rechargeable electric vehicle charged by an external power source, a fuel cell vehicle using a fuel cell as a power source, and a hybrid vehicle having an engine.

[0027] The casing 21 houses a pair of electric motors 30R and 30L and a pair of power transmission mechanisms 50R and 50L. A pair of inverters 40R and 40L are arranged on the upper surface of the casing 21. The right power transmission mechanism 50R transmits the power of the right electric motor 30R to the right drive shaft 14R connected to the right front wheel 4R. The right power transmission mechanism 50R has a plurality of gears, bearings, etc. The right power transmission mechanism 50R functions as a speed reducer that decelerates the rotational speed of the right electric motor 30R, for example, and rotates the right drive shaft 14R. Similarly, the left power transmission mechanism 50L transmits the power of the left electric motor 30L to the left drive shaft 14L connected to the left front wheel 4L. As shown in FIG. 1, the right drive shaft 14R and the left drive shaft 14L are separated at the center in the left-right direction of the electric vehicle 10. Therefore, the pair of front wheels 4R and 4L are independently driven by the pair of electric motors 30R and 30L. In a modified example, the drive shafts 14R and 14L may be connected at the center. In that case, the two electric motors 30R and 30L may drive the pair of front wheels 4R and 4L.

[0028] The charging inlet 6 is arranged on the right side surface of the vehicle body 2. The charging inlet 6 is configured to be connected to an external power source 7 (for example, a charging stand) via a power cable 8. When the charging inlet 6 is connected to the external power source 7, the charging power of the external power source 7 is supplied to the battery pack 3.

[0029] The radiator 12 is disposed at the front end of the vehicle body of the electric vehicle 10. The radiator 22 is a device that performs heat exchange between the heat medium M1 (for example, antifreeze) circulating in the radiator heat circuit 18 and the outside air. The radiator 12 cools the heat medium M1, for example, by the traveling wind that enters the vehicle body 2 when the electric vehicle 10 is traveling. The radiator pump 16 circulates the heat medium M1 through the radiator heat circuit 18. As shown by the arrows in FIG. 1, the heat medium M1 pumped by the radiator pump 16 passes through the right oil cooler 22R and the left oil cooler 22L and returns to the radiator 12. Thus, the radiator heat circuit 18 is a circuit that connects the oil coolers 22R and 22L and circulates the heat medium M1 through the oil coolers 22R and 22L. Further, behind the radiator pump 16, a temperature sensor 19 for acquiring the temperature of the heat medium M1 in the radiator heat circuit 18 is provided.

[0030] The detailed structure of the drive device 20 will be described with reference to FIG. 2. In addition to the pair of electric motors 30R and 30L described above, the drive device 20 further includes a pair of oil pumps 36R and 36L housed in the casing 21, a pair of motor heat circuits 60R and 60L, a temperature sensor 29, and a pump control device 70. The drive device 20 is configured symmetrically about the center line CL1. For this reason, hereinafter, the configuration located on the right side of the center line CL1 of the drive device 20 will be mainly described.

[0031] The right electric motor 30R includes a motor shaft 33R, a rotor 34R, a stator 35R, and a temperature sensor 39R. The motor shaft 33R passes through the rotor 34R and extends in the left-right direction. The motor shaft 33R extends leftward beyond the left end of the rotor 34R and is connected to the gear 51R of the right power transmission mechanism 50R. When the rotor 34R rotates and the motor shaft 33R rotates accordingly, the gear 51R rotates. Although not shown in the figure, the gear 51R rotates the right drive shaft 14R (see FIG. 1) via a plurality of gears. That is, the right power transmission mechanism 50R transmits the power of the right electric motor 30R to the right drive shaft 14R. The motor shaft 33R has a hollow structure. A plurality of through holes 64R are formed on the side surface of the motor shaft 33R. The plurality of through holes 64R communicate the internal space of the motor shaft 33R with the internal space of the casing 21. In FIG. 1, only two through holes 64R located at the right end among the plurality of through holes 64R are labeled, and the labels of the other through holes 64R are omitted. Similarly, the left power transmission mechanism 50L transmits the power of the left electric motor 30L to the left drive shaft 14L via gears such as the gear 51L connected to the motor shaft 33L of the left electric motor 30L.

[0032] The right oil pump 36R is fixedly mounted from the inside on the right side wall of the casing 21. The right oil pump 36R is a pump that pumps the heat medium M2 to the right motor heat circuit 60R. The right motor heat circuit 60R includes a right pipe 62R, a motor shaft 33R, a space 66R, and a storage portion 68R. The right pipe 62R includes an upstream portion that extends upward from the storage portion 68R, bends to the right and is connected to the right oil pump 36R, and a downstream portion that is connected to the discharge port of the right oil pump 36R and extends upward outside the right side wall of the casing 21. The other upper end of the downstream portion of the right pipe 62R passes through the right oil cooler 22R and is connected to the motor shaft 33R. The storage portion 68R is located at the lower part of the casing 21 and is a space for storing the heat medium M2. The storage portion 68R is a so-called heat medium reservoir. The right oil pump 36R sucks up the heat medium M2 stored in the storage portion 68R and pumps it toward the motor shaft 33R via the right pipe 62R. The heat medium M2 falls into the space 66R of the casing 21 through the internal space of the motor shaft 33R and the through-hole 64R and reaches the storage portion 68R again. In this way, the right motor heat circuit 60R circulates the heat medium M2. Similarly, the left motor heat circuit 60L also circulates the heat medium M2 through a left pipe 62L that extends upward along the outer surface of the left side wall of the casing 21, a motor shaft 33L, a through-hole 64L, and a space 66L.

[0033] The heat medium M2 discharged from the through-hole 64R of the motor shaft 33R adheres to the surface of the rotor 34R of the right electric motor 30R and the gear 51R of the right power transmission mechanism 50R. The heat medium M2 is a lubricating oil for the right electric motor 30R and the gear (e.g., 51R) of the right power transmission mechanism 50R. Therefore, the heat medium M2 reduces the frictional force generated on the surfaces of the rotor 34R and the gear 51R. Further, the heat medium M2 absorbs heat from the right electric motor 30R particularly when circulating through the right motor heat circuit 60R. That is, the heat medium M2 cools the right electric motor 30R. In this way, the right motor heat circuit 60R performs heat exchange with the right electric motor 30R by circulating the heat medium M2.

[0034] As described above, the right pipe 62R passes through the right oil cooler 22R and is connected to the motor shaft 33R. That is, it can be said that the right oil cooler 22R is provided in the right motor heat circuit 60R. Further, the heat medium M1 that has passed through the radiator 12 (see FIG. 1) circulates in the right oil cooler 22R. Therefore, the right oil cooler 22R performs heat exchange between the right pipe 62R of the right motor heat circuit 60R and the radiator heat circuit 18. In other words, the right oil cooler 22R transfers the heat of the heat medium M2 in the right pipe 62R to the heat medium M1. As a result, the heat medium M2 is cooled by the heat medium M1. Thereby, the temperature rise of the heat medium M2 that has absorbed heat from the right electric motor 30R is suppressed. Therefore, the heat generated by the right electric motor 30R can be released to the outside of the electric vehicle 10.

[0035] Similarly, the left oil pump 36L circulates the heat medium M2 by the left motor heat circuit 60L. That is, the heat medium M2 is lubricating oil for the left electric motor 30L and the gears (for example, 51L) of the left power transmission mechanism 50L. Here, the storage portion 68L of the left motor heat circuit 60L communicates with the storage portion 68R of the right motor heat circuit 60R. That is, the storage portions 68R and 68L are common sections in the right motor heat circuit 60R and the left motor heat circuit 60L. Therefore, the heat medium M2 that has circulated in the right motor heat circuit 60R and the heat medium M2 that has circulated in the left motor heat circuit 60L are mixed in the storage portions 68R and 68L. Therefore, the heat medium M2 in the right pipe 62R and the heat medium M2 in the left pipe 62L have substantially the same temperature. Thus, in this embodiment, the storage portions 68R and 68L formed at the lower part of the casing 21 can be made into a common section of the right motor heat circuit 60R and the left motor heat circuit 60L. Further, compared with a configuration in which another pipe common to each motor heat circuit 60R and 60L is located outside the casing 21, the right motor heat circuit 60R and the left motor heat circuit 60L can be shortened.

[0036] The temperature sensor 39R is disposed on the right side surface of the stator 35R of the right electric motor 30R. The temperature sensor 39R acquires the temperature of the right electric motor 30R (for example, the stator 35R). Further, the lower end of the temperature sensor 29 disposed at the lower center in the left-right direction of the casing 21 is disposed in the heat medium M2 stored in the storage portion 68R. The temperature sensor 29 acquires the temperature of the heat medium M2 stored in the storage portion 68R.

[0037] The pump control device 70 is disposed above the right inverter 40R. The pump control device 70 is a computer having a CPU and a memory, and is communicable with, for example, each of the temperature sensors 19, 29, 39R, 39L and each of the pumps 16, 36R, 36L. The pump control device 70 acquires the temperature T1 of the heat medium M1 from the temperature sensor 19. Similarly, the pump control device 70 acquires the temperature T2 of the heat medium M2 from the temperature sensor 29, acquires the temperature TR of the right electric motor 30R from the temperature sensor 39R, and acquires the temperature TL of the left electric motor 30L from the temperature sensor 39L. The pump control device 70 controls the operations of the pumps 16, 36R, 36L based on the respective temperatures T1, T2, TR, TL acquired from, for example, each of the temperature sensors 19, 29, 39R, 39L. In a modified example, the pump control device 70 may be disposed on any one of the right side, left side, front side, and rear side of the right inverter 40R. Further, the pump control device 70 is not limited to one, and may be disposed on both the left and right side surfaces of the right inverter 40R, for example.

[0038] Referring to FIG. 3, the electric circuit of the drive device 20 will be described. As shown in FIG. 3, the drive device 20 further includes a power supply circuit 11. The power supply circuit 11 is a circuit for supplying the DC charging power supplied from the external power supply 7 to the battery pack 3. The electric motor 30R is a three-phase motor including a U-phase coil 35U, a V-phase coil 35V, and a W-phase coil 35W. One end of each of the U-phase coil 35U, the V-phase coil 35V, and the W-phase coil 35W is connected to the neutral point NP. The other end of the U-phase coil 35U is connected to the U-phase arm 42U, the other end of the V-phase coil 35V is connected to the V-phase arm 42V, and the other end of the W-phase coil 35W is connected to the W-phase arm 42W.

[0039] In the power supply circuit 11 of the present embodiment, one terminal of the charging inlet 6 is connected to the positive electrode of the battery pack 3 via the neutral point NP of the right electric motor 30R and the right inverter 40R. That is, the power supply circuit 11 supplies the charging power supplied from the external power supply 7 to the neutral point NP of the right electric motor 30R. The other terminal of the charging inlet 6 is connected to the negative electrode of the battery pack 3 via the right inverter 40R. The power supply circuit 11 supplies the charging power to the battery pack 3 via the neutral point NP of the right electric motor 30R. Thereby, the right electric motor 30R and the right inverter 40R can function as three boost circuits connected in parallel between the charging inlet 6 and the battery pack 3. Thereby, the drive device 20 can boost the output voltage of the external power supply 7 by using the right electric motor 30R and the right inverter 40R. Thereby, even if the output voltage of the external power supply 7 is lower than the voltage of the battery pack 3, rapid charging can be performed. One terminal of the charging inlet 6 is directly connected to the positive electrode of the battery pack 3 via the switch 13. When the output voltage of the external power supply 7 is equal to the voltage of the battery pack 3, the power supply circuit 11 can bypass the neutral point NP of the right electric motor 30R to the output voltage of the external power supply 7 by turning on the switch 13. Although not shown, the power supply circuit 11 further includes a charging unit including a relay, a capacitor, etc. The charging unit is connected to the neutral point NP and the right inverter 40.

[0040] While the charging inlet 6 is connected to the external power source 7 and the charging power of the external power source 7 is supplied to the neutral point NP of the right electric motor 30R, current flows through the coils 35U, 35V, and 35W of each phase of the right electric motor 30R. As a result, the coils 35U, 35V, and 35W of each phase generate heat, and the temperature TR of the right electric motor 30R rises. 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 left electric motor 30L, so the temperature TL of the left electric motor 30L does not rise. That is, while the charging power of the external power source 7 is supplied to the neutral point NP of the right electric motor 30R, the temperature difference between the electric motors 30R and 30L increases. The temperatures TR and TL of the electric motors 30R and 30L affect the characteristics of the electric motors 30R and 30L. Therefore, if the temperature difference between the electric motors 30R and 30L becomes too large exceeding a predetermined value, the running stability of the electric vehicle 10 after charging power supply may decrease.

[0041] Referring to FIG. 4, the process executed by the pump control device 70 of the drive device 20 will be described. The process of FIG. 4 is started triggered by the charging inlet 6 being connected to the external power source 7 and the switch 13 (see FIG. 3) being turned off. The pump control device 70 repeats the process of FIG. 4 while the charging inlet 6 is connected to the external power source 7. Hereinafter, the period during which the charging inlet 6 is connected to the external power source 7 and the switch 13 (see FIG. 3) is turned off may be described as the "charging period".

[0042] In S10, the pump control device 70 compares the temperature TL of the left electric motor 30L acquired from the temperature sensor 39L with the temperature T2 of the heat medium M2 acquired from the temperature sensor 29, and determines whether the temperature TL is less than or equal to the temperature T2. When the temperature TL is less than or equal to the temperature T2 (YES in S10), the pump control device 70 proceeds to S20, and when the temperature TL is greater than the temperature T2 (NO in S10), the pump control device 70 proceeds to S40.

[0043] In S20, the pump control device 70 compares the temperature difference between the two electric motors 30R and 30L (i.e., the difference between temperature TR and temperature TL) with the threshold temperature Tth. Here, the threshold temperature Tth is a value for determining whether the temperature difference between the two electric motors 30R and 30L affects the running stability of the electric vehicle 10, and is pre-stored in a memory (not shown) of the pump control device 70. In a modification, the threshold temperature Tth may be a value automatically specified by the pump control device 70 according to the specifications of the two electric motors 30R and 30L, or may be a value that can be changed retrospectively by an operator during maintenance of the electric vehicle 10.

[0044] When the temperature difference exceeds the threshold temperature Tth (YES in S20), the pump control device 70 proceeds to S30; when the temperature difference is less than or equal to the threshold temperature Tth (NO in S20), the pump control device 70 proceeds to S40.

[0045] In S30, the pump control device 70 determines the output of the left oil pump 36L during the charging period. Here, in S30, the pump control device 70 determines the output of the left oil pump 36L according to the temperature difference calculated in S20. Although not shown, the pump control device 70 stores, for example, a table associating the temperature difference between the two electric motors 30R and 30L with the output of the left electric motor 30L. In this table, the values of the temperature difference and the output are stored in a substantially proportional relationship. The pump control device 70 uses the temperature difference calculated in S20 based on this table to determine the output of the left oil pump 36L. In a modification, the pump control device 70 may store a calculation formula for calculating the output of the left oil pump 36L based on the temperature difference. In this modification example, the pump control device 70 may determine the output of the left oil pump 36L during the charging period based on this calculation formula in S30.

[0046] In S32, the pump control device 70 drives both electric motors 30R and 30L. Here, the pump control device 70 drives the right oil pump 36R at a predetermined output stored in advance. On the other hand, the pump control device 70 drives the left oil pump 36L at the output determined in S30. In this way, the pump control device 70 determines the output of the left oil pump 36L based on the temperature difference between both electric motors 30R and 30L. For example, when the temperature difference is large, the pump control device 70 drives the left oil pump 36L at a large output. Therefore, compared with a configuration in which the left oil pump 36L is driven at a constant output, the temperature difference between both electric motors 30R and 30L can be quickly reduced. Further, when the temperature difference is small, the pump control device 70 drives the left oil pump 36L at a small output. Therefore, it is possible to prevent the left oil pump 36L from being driven at an excessive output for a small temperature difference. Thereby, the power consumption of the drive device 20 can be suppressed.

[0047] In S40, the pump control device 70 drives only the right oil pump 36R at a predetermined output stored in advance. In S40, the pump control device 70 stops the operation of the left oil pump 36L. When the temperature TL of the left electric motor 30L is higher than the temperature T2 of the heat medium M2 (NO in S10), even if the heat medium M2 is circulated through the left motor heat circuit 60L, the temperature TL of the left motor heat circuit 60L does not rise. That is, in this case, even if the left oil pump 36L is driven, the temperature difference between both electric motors 30R and 30L does not decrease. That is, in this case, it is not necessary to transfer the heat of the right electric motor 30R to the left electric motor 30L. In the drive device 20 of the present embodiment, when the temperature TL of the left electric motor 30L is higher than the temperature T2 of the heat medium M2 (NO in S10), by prohibiting the operation of the left electric motor 30L, the power consumption related to the circulation of the heat medium M2 can be suppressed.

[0048] Furthermore, when the temperature difference between the two electric motors 30R and 30L is smaller than the threshold temperature Tth (NO in S20), the pump control device 70 also stops the operation of the left oil pump 36L. When the temperature difference between the two electric motors 30R and 30L is smaller than the threshold temperature Tth, even if circulated in the left motor heat circuit 60L, the temperature difference between the two electric motors 30R and 30L is unlikely to become smaller. That is, in this case, there is no significant temperature difference between the two electric motors 30R and 30L, and there is no need to transfer the heat of the right electric motor 30R to the left electric motor 30L. In the drive device 20 of the present embodiment, when the temperature difference between the two electric motors 30R and 30L is smaller than the threshold temperature Tth (NO in S20), by stopping the operation of the left electric motor 30L, the power consumption related to the circulation of the heat medium M2 can be suppressed.

[0049] As described above, in the drive device 20 of the present embodiment, during the charging period of the battery pack 3, the heat medium M2 circulates in both the right motor heat circuit 60R and the left motor heat circuit 60L. The right motor heat circuit 60R and the left motor heat circuit 60L have storage portions 68R and 68L that are common to each other and share the heat medium M2. Therefore, the heat generated in the right motor heat circuit 60R by the charging power is transmitted to the left motor heat circuit 60L through the shared heat medium M2. Thereby, even when only the right electric motor 30R generates heat during the charging period, the temperature difference between the two electric motors 30R and 30L is reduced. Thereby, it is possible to suppress a decrease in the running stability of the electric vehicle 10 after charging is completed.

[0050] (Corresponding relationship) The right electric motor 30R is an example of the "first electric motor". The left electric motor 30L is an example of the "second electric motor". The battery pack 3 is an example of the "power storage device". The right inverter 40R is an example of the "first power control device". The right motor heat circuit 60R is an example of the "first heat circuit". The left motor heat circuit 60L is an example of the "second heat circuit". The radiator heat circuit 18 is an example of the "third heat circuit". The right oil pump 36R is an example of the "first pump". The left oil pump 36L is an example of the "second pump". The right oil cooler 22R is an example of the "first heat exchanger". The left oil cooler 22L is an example of the "second heat exchanger". The right power transmission mechanism 50 is an example of the "first power transmission mechanism". The left power transmission mechanism 50L is an example of the "second power transmission mechanism".

[0051] (Second Embodiment) Referring to FIG. 5, the detailed structure of the drive device 120 of the second embodiment will be described. In the drive device 120 of this embodiment, the path for circulating the heat medium M2 is different from that of the drive device 20 of the first embodiment described above. In the drive device 120 of this embodiment, one oil pump 136 circulates the heat medium M2. However, in other respects, the drive device 120 of this embodiment has the same configuration as the drive device 20 of the first embodiment.

[0052] In the drive device 120 of this embodiment, a pair of electric motors 130R and 130L are housed in the motor casing 121M adjacent to each other in the left-right direction. Also, a pair of power transmission mechanisms 150R and 150L are arranged outside the vehicle of the pair of electric motors 130R and 130L. The motor shaft 133R of the right electric motor 130R penetrates the right side wall of the motor casing 121M and is connected to the gear 151R of the right power transmission mechanism 150R. Similarly, the motor shaft 133L of the left electric motor 130L penetrates the left side wall of the motor casing 121M and is connected to the gear 151L of the left power transmission mechanism 150L. The pair of power transmission mechanisms 150R and 150L are housed in the pump casing 121P. The pump casing 121P supports the motor casing 121M from below. As shown in FIG. 5, a heat medium M2 is stored at the bottom of the pump casing 121P. That is, the bottom of the pump casing 121P defines storage portions 168R and 168L.

[0053] In the drive device 120 of this embodiment, one oil pump 136 is arranged at the center in the left-right direction of the pump casing 121P. The oil pump 136 pumps the heat medium M2 accumulated in the storage portions 168R and 168L to a pipe 162 extending upward from the center of the pump casing 121P. The pipe 162 branches to the left and right at the upper end and is connected to each of the motor shafts 133R and 133L. In this embodiment, one oil pump 136 supplies the heat medium M2 accumulated at the bottom of the pump casing 121P to both the motor shaft 133R of the right electric motor 130R and the motor shaft 133L of the left electric motor 130L via the pipe 162. Similar to the motor shaft 33R of the first embodiment, a plurality of through holes 164R and 164L are formed on the side surfaces of each of the motor shafts 133R and 133L.

[0054] In the right motor heat circuit 160R of this embodiment, the heat medium M2 stored in the storage portion 168R is supplied to the right electric motor 130R and the right power transmission mechanism 150R by the oil pump 136 through the pipe 162 and the motor shaft 133R of the right electric motor 130R. A communication hole is formed at the right end of the lower surface of the motor casing 121M to communicate the space inside the motor casing 121M with the space 166R inside the pump casing 121P. Therefore, after the heat medium M2 supplied to the right electric motor 130R drops from the right electric motor 130R, it drops into the space 166R through the communication hole and reaches the storage portion 168R again. Further, the heat medium M2 supplied to the right power transmission mechanism 150R through the plurality of through holes 164R of the motor shaft 133R drops through the space 166R of the pump casing 121P and reaches the storage portion 168R again. In this way, the right motor heat circuit 160R circulates the heat medium M2. In the left motor heat circuit 160L, the heat medium M2 stored in the storage portion 168L is supplied to the left electric motor 130L and the left power transmission mechanism 150L by the oil pump 136 through the pipe 162 and the motor shaft 133L of the left electric motor 130L. A communication hole is formed at the left end of the lower surface of the motor casing 121M to communicate the space inside the motor casing 121M with the space 166L inside the pump casing 121P. Therefore, also in the left motor heat circuit 160L, the heat medium M2 circulates in the same manner as in the right motor heat circuit 160R.

[0055] Further, the storage portions 168R and 168L communicate with each other within the motor casing 121M. Furthermore, each motor heat circuit 160R, 160L has the same pipe 162. That is, each motor heat circuit 160R, 160L has a common section with each other (that is, the pipe 162 and the storage portions 168R, 168L). In the drive device 120 of the present embodiment, the pump control device 70 drives the oil pump 136 during the charging period of the battery pack 3. Thereby, the heat medium M2 circulates in both the right motor heat circuit 160R and the left motor heat circuit 160L during the charging period of the battery pack 3. For this reason, the heat generated in the right motor heat circuit 160R by the charging power is transmitted to the left motor heat circuit 160L via the shared heat medium M2. Thereby, even when only the right electric motor 130R generates heat during the charging period, the temperature difference between the two electric motors 130R, 130L is reduced. Thereby, it is possible to suppress a decrease in the running stability of the electric vehicle 10 after charging is completed. In the present embodiment, the pipe 162 and the storage portions 168R, 168L are an example of "at least a part of the section". Also, unlike the first embodiment, in the present embodiment, regardless of whether the temperature of the left electric motor 130L is lower than the temperature T2 of the heat medium M2 and whether the temperature difference between the two electric motors 130R, 130L is higher than the threshold temperature Tth, the oil pump 136 is driven during the charging period. That is, in the present embodiment, the processes of S10 to S20 in FIG. 4 can be omitted. However, in a modified example, the pump control device 70 may change whether to pump the heat medium M2 to the left motor heat circuit 160L by controlling a valve provided in the discharge portion of the oil pump 136. In this modified example, at least one of the processes of S10 to S30 in FIG. 4 may be executed.

[0056] As described above, specific examples of the technology disclosed in this specification have been described in detail, but these are merely examples and do not limit the scope of the claims. The technology described in the claims includes various modifications and changes of the specific examples illustrated above. Modifications of the above embodiments are listed below.

[0057] Points to note in the embodiments are described below. The drive device 20 does not necessarily have to include the left inverter 40L. In that case, for example, one inverter 40R may be connected to both electric motors 30R and 30L.

[0058] The pump control device 70 does not necessarily have to execute the process of S10 in FIG. 4. That is, the pump control device 70 may drive the left oil pump 36L regardless of whether the temperature TL of the left motor heat circuit 60L is less than or equal to the temperature T2 of the heat medium M2.

[0059] The pump control device 70 does not necessarily have to execute the process of S20 in FIG. 4. That is, the pump control device 70 may drive the left oil pump 36L regardless of whether the temperature difference between both electric motors 30R and 30L is greater than or equal to the threshold temperature Tth.

[0060] The pump control device 70 does not necessarily have to execute the process of S30 in FIG. 4. That is, it is not necessary to determine the output of the left oil pump 36L according to the temperature difference between both electric motors 30R and 30L. In this case, the pump control device 70 may drive the left oil pump 36L with the same output as, for example, the right oil pump 36R in S32.

[0061] Both electric motors 30R and 30L may be cooled by the heat medium M1. In that case, for example, a first heat circuit and a second heat circuit through which the heat medium M1 circulates may be arranged around the stators 35R and 35L of both electric motors 30R and 30L. That is, both electric motors 30R and 30L may be water-cooled, and in that case, the drive device 20 may include a first water-cooling circuit for cooling the right electric motor 30R and a second water-cooling circuit for cooling the left electric motor 30L. In this modification, the pump control device 70 may control the radiator pump 16 instead of the oil pump 36L. That is, in this modification, the first water-cooling circuit is an example of the "first heat circuit", and the second water-cooling circuit is an example of the "second heat circuit". Further, the radiator heat circuit 18 is an example of the "at least a part of the section", and the radiator pump 16 is an example of the "at least one pump".

[0062] The technical elements described in this specification or the drawings exhibit technical utility either individually or in various combinations, and are not limited to the combinations described in the claims at the time of filing. In addition, the technologies exemplified in this specification or the drawings can achieve multiple objectives simultaneously, and achieving one of those objectives itself has technical utility.

Description of Reference Numerals

[0063] 2: Vehicle body, 3: Battery pack, 4L: Left front wheel, 4R: Right front wheel, 5L, 5R: Rear wheels, 6: Charging inlet, 7: External power source, 8: Power cable, 10: Electric vehicle, 11: Power supply circuit, 12: Radiator, 14L: Left drive shaft, 14R: Right drive shaft, 16: Radiator pump, 18: Radiator heat circuit, 19, 29, 39L, 39R: Temperature sensors, 20, 120: Drive devices, 21: Casing, 22: Radiator, 22L: Left oil cooler, 22R: Right oil cooler, 30L, 130L: Left electric motor, 30R, 130R: Right electric motor, 33L, 33R, 133L, 133R: Motor shafts, 34R: Rotor, 35L, 35R: Stators, 35U: U-phase coil, 35V: V-phase coil, 35W: W-phase coil, 36L: Left oil pump, 36R: Right oil pump, 40L: Left inverter, 40R: Right inverter, 42U: U-phase arm, 42V: V-phase arm, 42W: W-phase arm, 50L, 150L: Left power transmission mechanism, 50R, 150R: Right power transmission mechanism, 51L, 51R, 151L, 151R: Gears, 60L, 160L: Left motor heat circuit, 60R, 160R: Right motor heat circuit, 62L: Left pipe, 62R: Right pipe, 64L, 64R, 164L, 164R: Through holes, 66L, 66R, 166L, 166R: Spaces, 68L, 68R, 168L, 168R: Reservations, 70: Pump control device, M1, M2: Heat medium, NP: Neutral point

Claims

1. A drive device for driving a pair of left and right drive wheels of a vehicle, a first electric motor for driving at least one of the pair of left and right drive wheels, a second electric motor for driving at least the other of the pair of left and right drive wheels, a first power control device for controlling power between the power storage device of the vehicle and at least the first electric motor, a power supply circuit that is electrically connected to the neutral point of the first electric motor and supplies charging power supplied from an external power source to the neutral point, a first heat circuit that performs heat exchange with the first electric motor, a second heat circuit that performs heat exchange with the second electric motor and at least a part of which is common to the first heat circuit, at least one pump for circulating a heat medium through the first heat circuit and the second heat circuit, a pump control device for controlling the at least one pump, comprising The pump control device circulates the heat medium through both the first heat circuit and the second heat circuit by operating the at least one pump at least in part of a charging period during which the power supply circuit supplies the charging power to the neutral point of the first electric motor. Drive device.

2. The at least one pump a first pump for circulating the heat medium through the first heat circuit, a second pump for circulating the heat medium through the second heat circuit, comprising The pump control device circulates the heat medium through both the first heat circuit and the second heat circuit by operating both the first pump and the second pump at least in part of the charging period. The drive device according to claim 1.

3. The pump control device stops the operation of the second pump even during the charging period when the temperature difference between the first electric motor and the second electric motor is less than a predetermined threshold value. The drive device according to claim 2.

4. The pump control device stops the operation of the second pump even during the charging period when the temperature of the second electric motor is higher than the temperature of the heat medium. The drive device according to claim 2.

5. The pump control device changes the output of the second pump according to the temperature difference between the first electric motor and the second electric motor during the charging period. The drive device according to claim 2.

6. The drive device further includes a casing that houses at least the first electric motor and the second electric motor. At least a part of the section is located within the casing. The drive device according to claim 1.

7. The drive device further includes A first heat exchanger provided in the first heat circuit and performing heat exchange between the first heat circuit and a third heat circuit provided in the vehicle. A second heat exchanger disposed in the second heat circuit and performing heat exchange between the second heat circuit and the third heat circuit. And includes The third heat circuit is configured to pass through a radiator of the vehicle. The drive device according to claim 6.

8. The drive device further includes A first power transmission mechanism that transmits the power of the first electric motor to at least one of the pair of left and right drive wheels. A second power transmission mechanism that transmits the power of the second electric motor to at least the other of the pair of left and right drive wheels. And includes The drive device according to claim 6, wherein the heat medium is lubricating oil for a first gear of the first power transmission mechanism and a second gear of the second power transmission mechanism.

9. The first electric motor drives one of the pair of left and right drive wheels. The second electric motor drives the other of the pair of left and right drive wheels. The drive device according to claim 1.

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