Driving device for vehicle

Abstract

To provide a driving device for vehicle which implements a technique usable for a heat source warming up at least one side of a rotation dynamo-electric machine and an inverter even when an input current to a battery is restricted, in a travel state decelerating a vehicle in a low-temperature environment.SOLUTION: A driving device for vehicle includes a rotation dynamo-electric machine and an inverter which is electrically connected with a battery and is used for driving and controlling the rotation dynamo-electric machine, a heat medium circuit 71 through which a heat transfer medium is circulated and an inverter control part which controls the inverter. The heat medium circuit 71 includes a first heat exchange part 81 in which heat exchange with at least one side of the rotation dynamo-electric machine and the inverter is performed, and a second heat exchange part 82 in which heat exchange with at least one side of the battery and a cabin of the vehicle is performed. The inverter control part conducts an active short circuit control when a temperature of the battery is a predetermined threshold value or less and causes the rotation dynamo-electric machine to generate negative torque.SELECTED DRAWING: Figure 3

Description

Technical Field

[0001] The present invention relates to a vehicle drive device including a rotating electrical machine, an inverter electrically connected to a battery and for driving and controlling the rotating electrical machine, and an inverter control unit for controlling the inverter.

Background Art

[0002] An example of the vehicle drive device as described above is disclosed in Japanese Patent Application Laid-Open No. 2012-165526 (Patent Document 1). Hereinafter, the reference numerals shown in parentheses in the description of the background art are those of Patent Document 1. The vehicle drive device of Patent Document 1 includes a drive motor (10), an inverter (11) electrically connected to a battery (20) and for driving and controlling the drive motor (10), and a motor ECU (12) for controlling the inverter (11). And Patent Document 1 describes warming up the battery (20) by self-heating due to discharge of the battery (20) (paragraph 0023), and warming up the battery (20) by using the heat generated in the drive motor (10) and the inverter (11) in addition to the above self-heating (paragraph 0044).

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] Although not described in Patent Document 1, the heat generated in a rotating electrical machine (a drive motor in Patent Document 1) or an inverter can be used not only as a heat source for warming the battery but also as a heat source for warming the cabin of a vehicle. And it is desirable that the heat generation of the rotating electrical machine or the inverter for use as a heat source can be performed particularly in a driving situation where the vehicle is driven in a low-temperature environment. For example, in a driving situation where the vehicle is decelerated in a low-temperature environment, it is conceivable to execute a regeneration operation of converting the deceleration energy of the vehicle into a regenerative current by the rotating electrical machine and supplying it to the battery to generate heat in the rotating electrical machine and the inverter. However, when the input current (charging current) to the battery is limited because the temperature of the battery is low, the execution of the regeneration operation is also limited, so it becomes difficult to generate heat in the rotating electrical machine and the inverter as described above and use them as a heat source. Note that Patent Document 1 has no description about this point.

[0005] Therefore, in a driving situation where the vehicle is decelerated in a low-temperature environment, even when the input current to the battery is limited, it is desired to realize a technology that can use at least one of the rotating electrical machine and the inverter as a heat source for warming at least one of the battery and the cabin.

Means for Solving the Problem

[0006] The vehicle drive device according to the present disclosure includes a rotating electric machine, a power transmission mechanism that transmits driving force between the rotating electric machine and a wheel, an inverter that is electrically connected to a battery and controls the driving of the rotating electric machine, a heat medium circuit through which a heat medium circulates, and an inverter control unit that controls the inverter. The heat medium circuit includes a first heat exchange unit that exchanges heat with at least one of the rotating electric machine and the inverter, and a second heat exchange unit that exchanges heat with at least one of the battery and the cabin of the vehicle. The inverter has an arm for one-phase alternating current configured by a series circuit of an upper-stage switching element and a lower-stage switching element. When the temperature of the battery is equal to or lower than a predetermined threshold value and a negative torque is generated in the rotating electric machine, the inverter control unit turns off all the upper-stage switching elements of the inverter and turns on all the lower-stage switching elements, or turns on all the upper-stage switching elements of the inverter and turns off all the lower-stage switching elements to execute active short circuit control.

[0007] According to this configuration, in a driving situation where the vehicle is decelerated in a low-temperature environment, even when the input current to the battery is limited because the temperature of the battery is low, by executing the active short circuit control of the inverter, while generating a negative torque (deceleration torque) in the rotating electric machine, the regenerative current can be consumed by the rotating electric machine and the inverter to generate heat in them. Then, the heat generated in at least one of the rotating electric machine and the inverter can be transmitted to at least one of the battery and the cabin of the vehicle by the heat medium circuit to warm at least one of them. Thus, according to this configuration, in a driving situation where the vehicle is decelerated in a low-temperature environment, even when the input current to the battery is limited, at least one of the rotating electric machine and the inverter can be used as a heat source for warming at least one of the battery and the cabin.

[0008] Further features and advantages of the vehicle drive device will become clear from the following description of the embodiments described with reference to the drawings.

Brief Description of the Drawings

[0009]

Figure 1

Figure 2

Figure 3

Figure 4

Mode for Carrying Out the Invention

[0010] An embodiment of a vehicle drive device will be described with reference to the drawings. As shown in FIG. 1, the vehicle drive device 1 includes a first rotating electric machine 11, a first power transmission mechanism 51, and a first inverter 21 for driving and controlling the first rotating electric machine 11. In the present embodiment, the vehicle drive device 1 further includes a second rotating electric machine 12, a second power transmission mechanism 52, and a second inverter 22 for driving and controlling the second rotating electric machine 12. In the present embodiment, the first rotating electric machine 11 corresponds to the "rotating electric machine", the first power transmission mechanism 51 corresponds to the "power transmission mechanism", and the first inverter 21 corresponds to the "inverter".

[0011] The battery 40 is a battery (secondary battery) such as a lithium ion battery that can be charged and discharged by a chemical reaction. The first inverter 21 is electrically connected to the battery 40. In the present embodiment, the battery 40 is also electrically connected to the second inverter 22. Note that the battery 40 may be a collection of a first battery electrically connected to the first inverter 21 and a second battery electrically connected to the second inverter 22. In this case, a configuration that allows power to be transferred between the first battery and the second battery can also be adopted. Further, a configuration can also be adopted in which the battery 40 is not electrically connected to the second inverter 22 and the second inverter 22 is electrically connected to a power storage device different from the battery 40 (for example, a capacitor such as an electric double layer capacitor).

[0012] The vehicle V on which the vehicle drive device 1 is mounted is an electric vehicle equipped with a rotating electric machine as a driving force source for wheels, such as a battery electric vehicle (BEV). The vehicle V includes a first wheel W1 driven by a first rotating electric machine 11. In the present embodiment, the vehicle V further includes a second wheel W2 driven by a second rotating electric machine 12. As shown in FIG. 1, the first wheel W1 is one of the front and rear wheels (in the example shown in FIG. 1, the front wheel), and the second wheel W2 is the other of the front and rear wheels (in the example shown in FIG. 1, the rear wheel). In the present embodiment, the vehicle V includes two first wheels W1 and two second wheels W2. In the present embodiment, the first wheel W1 corresponds to the "wheel".

[0013] The first rotating electric machine 11 and the second rotating electric machine 12 have a function as a motor (electric motor) that generates power upon receiving power supply, and a function as a generator (electric generator) that generates power upon receiving power supply. Specifically, the first rotating electric machine 11 travels by the power stored in the battery 40 to generate a driving force, and also generates electricity by the driving force transmitted from the side of the first wheel W1 to charge the battery 40. Further, the second rotating electric machine 12 travels by the power stored in the power storage device (in the present embodiment, the battery 40) to generate a driving force, and also generates electricity by the driving force transmitted from the side of the second wheel W2 to charge the power storage device. In the present embodiment, the vehicle V is configured such that the battery 40 can be charged not only by the power generated by the rotating electric machines (11, 12) but also by the power supplied from an external power source (for example, an AC commercial power source) of the vehicle V.

[0014] The first power transmission mechanism 51 transmits driving force between the first rotating electric machine 11 and the first wheels W1. In the present embodiment, the first power transmission mechanism 51 transmits driving force between the first rotating electric machine 11 and the two first wheels W1. Therefore, the first power transmission mechanism 51 includes an output differential gear mechanism that transmits the torque input from the side of the first rotating electric machine 11 to the two first wheels W1 via the two first drive shafts 61. The first power transmission mechanism 51 may be configured to include a transmission (a transmission with a fixed gear ratio or a variable gear ratio) that shifts the rotation input from the side of the first rotating electric machine 11 and outputs it to the side of the first wheels W1.

[0015] The second power transmission mechanism 52 transmits driving force between the second rotating electric machine 12 and the second wheels W2. In the present embodiment, the second power transmission mechanism 52 transmits driving force between the second rotating electric machine 12 and the two second wheels W2. Therefore, the second power transmission mechanism 52 includes an output differential gear mechanism that transmits the torque input from the side of the second rotating electric machine 12 to the two second wheels W2 via the two second drive shafts 62. The second power transmission mechanism 52 may be configured to include a transmission (a transmission with a fixed gear ratio or a variable gear ratio) that shifts the rotation input from the side of the second rotating electric machine 12 and outputs it to the side of the second wheels W2.

[0016] The first power transmission mechanism 51 may be configured to transmit driving force between the first rotating electric machine 11 and one first wheel W1. In this case, the first power transmission mechanism 51 may be configured to include only a transmission shaft that transmits power. Also, the second power transmission mechanism 52 may be configured to transmit driving force between the second rotating electric machine 12 and one second wheel W2. In this case, the second power transmission mechanism 52 may be configured to include only a transmission shaft that transmits power.

[0017] As shown in FIG. 2, the vehicle drive device 1 includes an inverter control unit 91 that controls the first inverter 21. In the present embodiment, the inverter control unit 91 is configured to also control the second inverter 22. The inverter control unit 91 includes an arithmetic processing device such as a CPU (Central Processing Unit) as a core member, and also includes a storage device such as a RAM (Random Access Memory) and a ROM (Read Only Memory) that can be referenced by the arithmetic processing device. Then, each function of the inverter control unit 91 is realized by software (program) stored in a storage device such as a ROM, hardware such as a separately provided arithmetic circuit, or both of them.

[0018] Based on a command from a vehicle control unit 90 (see FIG. 1) that controls the entire vehicle V, the inverter control unit 91 controls the first inverter 21 and the second inverter 22. The inverter control unit 91 performs switching control of the first inverter 21 and the second inverter 22, for example, by pulse width modulation control. Note that the inverter control unit 91 is at least logically or conceptually distinguishable from the vehicle control unit 90, and physically does not necessarily need to be distinguishable. That is, the functions of the inverter control unit 91 and the vehicle control unit 90 may be realized in separate control devices or in a common control device. The control device is, for example, an ECU (Electronic Control Unit).

[0019] The first inverter 21 and the second inverter 22 include an inverter circuit that converts power between direct current and alternating current of a plurality of phases (in the present embodiment, three phases). The inverter circuit is configured using switching elements. The circuit configuration of the inverter is well known, and the scope of application of the present disclosure is not limited to the circuit configurations of the first inverter 21 and the second inverter 22. Therefore, hereinafter, only an example of the circuit configuration of the first inverter 21 will be described with reference to the circuit configuration shown in FIG. 2, and a detailed description of the circuit configuration of the second inverter 22 will be omitted.

[0020] As shown in Fig. 2, the first inverter 21 is configured such that an arm 30 for single-phase alternating current is composed of a series circuit of an upper switching element 31 and a lower switching element 32. The first inverter 21 includes a plurality of arms 30, and the plurality of arms 30 are connected in parallel to each other to form a bridge circuit. In the present embodiment, the first rotating electrical machine 11 is a rotating electrical machine driven by three-phase alternating current, and the first inverter 21 includes one arm 30 for each of the three phases. That is, the first inverter 21 includes three arms 30.

[0021] In the present embodiment, the first rotating electrical machine 11 is a rotating electrical machine with a rotating magnetic field. A permanent magnet is fixed to the rotor core of the first rotating electrical machine 11, and a stator coil is wound around the stator core of the first rotating electrical machine 11. The midpoint of each arm 30 (connection point between the upper switching element 31 and the lower switching element 32) is connected to the corresponding phase stator coil in the first rotating electrical machine 11, and the first inverter 21 supplies alternating current power of a plurality of phases (three phases in the present embodiment) to the stator coils of the first rotating electrical machine 11. A smoothing capacitor 34 for smoothing the voltage on the DC side of the first inverter 21 is provided between the DC side of the first inverter 21, that is, between the first inverter 21 and the battery 40.

[0022] As the switching elements (31, 32), an IGBT (Insulated Gate Bipolar Transistor), a power MOSFET (Metal Oxide Semiconductor Field Effect Transistor), a HEMT (High Electron Mobility Transistor), etc. are used. As shown in FIG. 2, for each switching element (31, 32), a freewheel diode 33 is provided in parallel with the direction from the negative electrode to the positive electrode (the direction from the lower stage side to the upper stage side) defined as the forward direction. Note that in the case of using a body diode or in the case of using reverse conduction in a transistor of a wide bandgap semiconductor composed of enhancement-mode gallium nitride (E-GaN), etc., such a freewheel diode 33 may not be provided.

[0023] The inverter control unit 91 performs current feedback control based on, for example, a target torque, the rotational position of the rotor (magnetic pole position of the permanent magnet), the rotational speed of the rotor, and the current flowing through each phase of the stator coil, and controls the first rotating electrical machine 11 via the first inverter 21. The current flowing through the stator coil is detected by a current sensor 37. The rotational position and rotational speed of the rotor are detected by a rotation sensor 36 such as a resolver or an inductive position sensor, for example. Between the inverter control unit 91 and the first inverter 21, a driver is provided that amplifies the voltage amplitude of the switching control signal output from the inverter control unit 91, increases the driving force, and supplies it to the first inverter 21, for example.

[0024] The vehicle V is provided with various sensors, and the detection information of the various sensors is appropriately used in the inverter control unit 91 and the vehicle control unit 90. As shown in FIGS. 1 and 2, in the present embodiment, in addition to the rotation sensor 36 and the current sensor 37 described above, a battery temperature sensor 41, a driving operation sensor 42, a vehicle state sensor 43, and a temperature sensor 35 are provided in the vehicle V. The battery temperature sensor 41 detects the temperature of the battery 40. The driving operation sensor 42 detects information related to driving operations such as an accelerator operation, a brake operation, and a steering operation. The vehicle state sensor 43 detects information related to the vehicle state such as the speed of the vehicle V and the acceleration of the vehicle V. The temperature sensor 35 detects the temperature of the switching elements (31, 32) constituting the first inverter 21. The temperature sensor 35 is configured to detect, for example, the forward voltage of a temperature detection diode that changes according to the temperature of the switching elements (31, 32).

[0025] Based on the information related to the driving operation and the information related to the vehicle state, the vehicle control unit 90 determines the torque to be generated in the first rotating electrical machine 11 (hereinafter referred to as "first target torque") and the torque to be generated in the second rotating electrical machine 12 (hereinafter referred to as "second target torque"). Then, the inverter control unit 91 controls the first inverter 21 so that the first rotating electrical machine 11 outputs the first target torque, and controls the second inverter 22 so that the second rotating electrical machine 12 outputs the second target torque. Note that the first target torque and the second target torque are positive torque (torque in the same direction as the rotation direction) or negative torque (torque in the direction opposite to the rotation direction). The negative torque is a deceleration torque that decelerates the vehicle V both when the vehicle V is moving forward and when it is moving backward.

[0026] The first target torque and the second target torque are determined such that the sum of these two torques (the sum considering the positive and negative of the torque) becomes the torque required for the running of the vehicle V. Specifically, the torque required to be transmitted from the side of the first rotating electric machine 11 to the first wheel W1 for the running of the vehicle V is defined as the first wheel required torque, and the torque required to be transmitted from the side of the second rotating electric machine 12 to the second wheel W2 for the running of the vehicle V is defined as the second wheel required torque. The first target torque converted to the torque at the first wheel W1 and the second target torque converted to the torque at the second wheel W2 are determined such that their sum is equal to the sum of the first wheel required torque and the second wheel required torque.

[0027] As schematically shown in FIG. 3, the vehicle drive device 1 includes a first heat medium circuit 71 through which a heat medium (heat exchange medium) circulates. In the present embodiment, the heat medium is an aqueous heat medium. For example, an antifreeze liquid (cooling water) called LLC (Long Life Coolant) can be used as the heat medium. Note that the heat medium is not limited to an aqueous heat medium, and may be a non-aqueous heat medium such as a fluorine-based heat medium, for example. In the present embodiment, the first heat medium circuit 71 corresponds to the "heat medium circuit".

[0028] The first heat medium circuit 71 includes a first heat exchange portion 81 where heat exchange is performed with at least one of the first rotating electric machine 11 and the first inverter 21, and a second heat exchange portion 82 where heat exchange is performed with at least one of the battery 40 and the cabin C of the vehicle V. The heat exchange between the heat medium and the heat exchange object in the first heat exchange portion 81 and the second heat exchange portion 82 may be performed directly or indirectly (for example, via another heat medium such as gas or oil). The first heat medium circuit 71 includes a pump 85 (for example, an electric pump), and the heat medium is circulated in the first heat medium circuit 71 by driving the pump 85. In FIG. 3, the direction in which the heat medium flows is indicated by an arrow.

[0029] In this embodiment, the first heat medium circuit 71 further includes a radiator 80 that exchanges heat between the heat medium and the outside air. The radiator 80 cools the heat medium, for example, by transferring the heat of the heat medium to the outside air. The radiator 80 is disposed, for example, in front of the vehicle V. As shown in FIG. 3, the first heat exchange portion 81 is disposed on the downstream side of the radiator 80, and the second heat exchange portion 82 is disposed on the downstream side of the first heat exchange portion 81. And the radiator 80 is disposed on the downstream side of the second heat exchange portion 82. Therefore, the heat medium flowing out from the radiator 80 flows through the first heat exchange portion 81 and the second heat exchange portion 82 in sequence and then flows into the radiator 80. Although details are omitted, the first heat medium circuit 71 may be configured to include a bypass passage for circulating the heat medium without passing through the radiator 80, and when heat dissipation from the heat medium by the radiator 80 is not necessary, the heat medium can be circulated without passing through the radiator 80.

[0030] When at least one of the first rotating electric machine 11 and the first inverter 21 is used as a heat source for heating at least one of the battery 40 and the cabin C, the heat medium is heated by the heat exchange in the first heat exchange portion 81, and the heat medium is cooled by the heat exchange in the second heat exchange portion 82. That is, heat moves from at least one of the first rotating electric machine 11 and the first inverter 21 to the heat medium by the heat exchange in the first heat exchange portion 81, and heat moves from the heat medium to at least one of the battery 40 and the cabin C by the heat exchange in the second heat exchange portion 82. Thus, since at least one of the first rotating electric machine 11 and the first inverter 21 can be used as a heat source for heating at least one of the battery 40 and the cabin C, there is no need to provide another heat source such as an electric heater, or even when another heat source such as an electric heater is used in combination, the energy consumption (for example, power consumption) of the other heat source can be reduced.

[0031] When configured such that heat exchange between the heat medium and the first rotating electric machine 11 is performed in the first heat exchange section 81, this heat exchange is performed, for example, directly in the vicinity of the first rotating electric machine 11 (for example, near the stator core), or is performed via oil circulating in the vicinity of the first rotating electric machine 11. This oil is, for example, oil for cooling and lubricating the first rotating electric machine 11 and the first power transmission mechanism 51, and the heat exchange between the heat medium and the oil is performed in an oil cooler. When configured such that heat exchange between the heat medium and the first inverter 21 is performed in the first heat exchange section 81, this heat exchange is performed, for example, directly in the vicinity of the first inverter 21 (for example, a heat sink for discharging heat generated in the first inverter 21). When configured such that heat exchange between the heat medium and both the first rotating electric machine 11 and the first inverter 21 is performed in the first heat exchange section 81, the first heat exchange section 81 is configured such that, for example, the heat exchange section between the heat medium and the first rotating electric machine 11 is arranged on the downstream side of the heat exchange section between the heat medium and the first inverter 21.

[0032] When configured such that heat exchange between the heat medium (hereinafter referred to as "first heat medium") in the second heat exchange section 82 and at least one of the battery 40 and the cabin C is performed indirectly via another heat medium (hereinafter referred to as "second heat medium"), this heat exchange is performed, for example, in a chiller or a water-cooled condenser that transfers heat between the first heat medium and the second heat medium (for example, transfers heat from the first heat medium to the second heat medium).

[0033] As shown in FIG. 3, in the present embodiment, the vehicle drive device 1 further includes a second heat medium circuit 72 through which the heat medium circulates. The second heat medium circuit 72 includes a third heat exchange section 83 in which heat exchange is performed with at least one of the second rotating electric machine 12 and the second inverter 22, and a fourth heat exchange section 84 in which heat exchange is performed with at least one of the battery 40 and the cabin C. The heat exchange between the heat medium and the heat exchange object in the third heat exchange section 83 and the fourth heat exchange section 84 may be performed directly or indirectly. The third heat exchange section 83 is configured in the same manner as the first heat exchange section 81, for example, except that the first rotating electric machine 11 is replaced with the second rotating electric machine 12. Also, the fourth heat exchange section 84 is configured in the same manner as the second heat exchange section 82, for example.

[0034] When at least one of the second rotating electric machine 12 and the second inverter 22 is used as a heat source for heating at least one of the battery 40 and the cabin C, the heat medium is heated by heat exchange in the third heat exchange section 83, and the heat medium is cooled by heat exchange in the fourth heat exchange section 84. That is, heat moves from at least one of the second rotating electric machine 12 and the second inverter 22 to the heat medium by heat exchange in the third heat exchange section 83, and heat moves from the heat medium to at least one of the battery 40 and the cabin C by heat exchange in the fourth heat exchange section 84.

[0035] The second heat medium circuit 72 may be connected to or separated from the first heat medium circuit 71. As shown in FIG. 3, in the present embodiment, the second heat medium circuit 72 is connected to the first heat medium circuit 71. Specifically, the second heat medium circuit 72 is formed to branch from the first heat medium circuit 71 at the branch section 73 and merge into the first heat medium circuit 71 at the merge section 74. In the example shown in FIG. 3, the branch section 73 is disposed on the downstream side of the radiator 80 and on the upstream side of the first heat exchange section 81. Also, in the example shown in FIG. 3, the merge section 74 is disposed on the downstream side of the second heat exchange section 82 and on the upstream side of the radiator 80. The second heat exchange section 82 and the fourth heat exchange section 84 are at least conceptually distinguished, and these two heat exchange sections (82, 84) may be configured as a common heat exchange section. In this case, the merge section 74 is disposed on the downstream side of the first heat exchange section 81 and on the upstream side of the second heat exchange section 82, different from the example shown in FIG. 3.

[0036] Incidentally, in a driving situation where the vehicle V is decelerated in a low-temperature environment, even when the input current to the battery 40 is restricted, it is desirable that at least one of the rotating electric machines (11, 12) and the inverters (21, 22) can be utilized as a heat source for warming at least one of the battery 40 and the cabin C. To achieve this, when the temperature of the battery 40 is equal to or lower than a predetermined threshold value and a negative torque is generated in the first rotating electric machine 11, the inverter control unit 91 is configured to execute active short circuit control (active short circuit control of the first inverter 21). The active short circuit control is control for turning off all the upper-side switching elements 31 of the first inverter 21 and turning on all the lower-side switching elements 32 (hereinafter referred to as "lower-side active short circuit control"), or control for turning on all the upper-side switching elements 31 of the first inverter 21 and turning off all the lower-side switching elements 32 (hereinafter referred to as "upper-side active short circuit control").

[0037] The above-mentioned threshold value (hereinafter referred to as "judgment threshold value") is set to a temperature at which the input current to the battery 40 is restricted (for example, a temperature of 0 degrees or lower). For example, the judgment threshold value is set to the upper limit temperature of the temperature range in which the input current to the battery 40 is restricted, in other words, the lower limit temperature of the temperature range in which the input current to the battery 40 is not restricted. Here, the "restriction of the input current" means, for example, that the input of the normal current (normal charging current) is restricted, or that the input of a low current lower than the normal current is restricted. Further, the judgment threshold value is set to a temperature higher than, for example, a temperature at which a failure may occur when the battery 40 is charged.

[0038] During the execution of the active short circuit control of the first inverter 21, a negative torque (deceleration torque) is generated in the first rotating electrical machine 11. The vehicle control unit 90 controls the braking device, for example, so that the sum of the braking force due to the negative torque of the first rotating electrical machine 11 and the braking force due to the braking device of the wheels (W1, W2) (for example, a disc brake) becomes the braking force required for the running of the vehicle V.

[0039] The inverter control unit 91 may be configured to execute the active short circuit control of the second inverter 22 in addition to the active short circuit control of the first inverter 21. In this case, the vehicle control unit 90 controls the braking device, for example, so that the sum of the braking force due to the negative torque of the first rotating electrical machine 11, the braking force due to the negative torque of the second rotating electrical machine 12, and the braking force due to the braking device becomes the braking force required for the running of the vehicle V. Here, the active short circuit control for the second inverter 22 is control in which all the upper side switching elements of the second inverter 22 are turned off and all the lower side switching elements are turned on, or control in which all the upper side switching elements of the second inverter 22 are turned on and all the lower side switching elements are turned off.

[0040] Note that the inverter control unit 91 does not necessarily have to execute the active short circuit control when the temperature of the battery 40 is equal to or lower than a predetermined threshold value and a negative torque is generated in the first rotating electrical machine 11. That is, in addition to the condition that the temperature of the battery 40 is equal to or lower than a predetermined threshold value and a negative torque is generated in the first rotating electrical machine 11, another condition may be included in the condition for executing the active short circuit control. For example, it can be included in the condition for executing the active short circuit control that the torque of the first rotating electrical machine 11 generated by the active short circuit control is not smaller than the torque required for the running of the vehicle V. Here, the magnitude relationship of the torques is a magnitude relationship considering the signs (positive and negative), not the absolute values. Therefore, when the torque required for the running of the vehicle V is a negative torque, "the torque of the first rotating electrical machine 11 generated by the active short circuit control is not smaller than the torque required for the running of the vehicle V" means that the absolute value of the negative torque of the first rotating electrical machine 11 generated by the active short circuit control is equal to or less than the absolute value of the negative torque required for the running of the vehicle V.

[0041] In the present embodiment, the vehicle drive device 1 includes a second rotating electrical machine 12 in addition to the first rotating electrical machine 11 as a driving force source for the wheels (W1, W2). Therefore, even when the torque of the first rotating electrical machine 11 generated by the active short circuit control is smaller than the torque required for the running of the vehicle V, by outputting a positive torque to the second rotating electrical machine 12, the sum of the torque of the first rotating electrical machine 11 and the torque of the second rotating electrical machine 12 (the sum considering the positive and negative of the torques) can be adjusted to the torque required for the running of the vehicle V.

[0042] In view of the above points, as an example, when the inverter control unit 91 executes the active short circuit control of the first inverter 21, the second inverter 22 is controlled such that the sum of the torque of the first rotating electric machine 11 generated by the active short circuit control and the torque generated in the second rotating electric machine 12 becomes the torque required for the running of the vehicle V. The torque required for the running of the vehicle V here may be negative torque or positive torque. When the torque required for the running of the vehicle V is positive torque, the second rotating electric machine 12 is controlled to output a positive torque having an absolute value larger than the negative torque of the first rotating electric machine 11. Note that the above control is executed on the condition that, for example, the temperature of the battery 40 is within the temperature range in which discharge from the battery 40 is permitted.

[0043] FIG. 4 shows an example of a control flow executed by the inverter control unit 91. In FIG. 4, the active short circuit control is denoted as “ASC”. As shown in FIG. 4, the inverter control unit 91 determines whether or not the start condition of the active short circuit is satisfied (step #01). The start condition of the active short circuit is satisfied, for example, when the temperature of the battery 40 is equal to or lower than a determination threshold value and a negative torque is generated in the first rotating electric machine 11.

[0044] In the present embodiment, the inverter control unit 91 determines whether or not the temperature of the battery 40 is equal to or lower than a determination threshold value based on the detection information of the battery temperature sensor 41. Note that the inverter control unit 91 may be configured to perform the above determination based on an index correlated with the temperature of the battery 40 (for example, detection information of a temperature correlated with the temperature of the battery 40) instead of the detection information of the battery temperature sensor 41. Further, the inverter control unit 91 determines that a negative torque is generated in the first rotating electric machine 11 when the target torque (the first target torque described above) of the first rotating electric machine 11 is negative torque. For example, when the accelerator is off or when a one-pedal operation for decelerating the vehicle V is performed, the target torque of the first rotating electric machine 11 is set as negative torque.

[0045] When the start condition of the active short circuit is satisfied (step #01: Yes), the inverter control unit 91 starts the active short circuit control of the first inverter 21 (step #02). The inverter control unit 91 continues the active short circuit control of the first inverter 21 until the end condition of the active short circuit control is satisfied (step #05: No). Then, when the end condition of the active short circuit control is satisfied (step #05: Yes), the inverter control unit 91 ends the active short circuit control of the first inverter 21 (step #06). The end condition of the active short circuit is, for example, that the temperature of the battery 40 exceeds the determined threshold value, or that the torque generated in the first rotating electrical machine 11 becomes zero or positive torque.

[0046] By the way, during the execution of the active short circuit of the first inverter 21, the switching element in the on state between the upper stage switching element 31 and the lower stage switching element 32 generates heat. In view of this point, as an example, when the inverter control unit 91 determines that the temperature of the target switching element, which is the switching element in the on state between the upper stage switching element 31 and the lower stage switching element 32, has reached or exceeded a predetermined switching temperature during the execution of the active short circuit control of the first inverter 21, a switching process can be configured to turn on the switching element in the off state between the upper stage switching element 31 and the lower stage switching element 32 and turn off the target switching element. By executing the switching process, the upper stage active short circuit control and the lower stage active short circuit control are switched.

[0047] In FIG. 4, as an example, it is assumed that the inverter control unit 91 is configured to execute the above switching process. Therefore, during the execution of the active short circuit of the first inverter 21, the inverter control unit 91 determines whether or not the switching condition, which is the execution condition of the switching process, is satisfied (step #03). If the switching condition is satisfied (step #03: Yes), the switching process is executed (step #04). The switching condition is satisfied when the temperature of the target switching element becomes equal to or higher than the above switching temperature. In the present embodiment, the inverter control unit 91 determines whether or not the temperature of the target switching element has become equal to or higher than the switching temperature based on the detection information of the temperature sensor 35.

[0048] The inverter control unit 91 may be configured to determine whether or not the temperature of the target switching element has become equal to or higher than the switching temperature based on an index correlated with the temperature of the target switching element instead of the detection information of the temperature sensor 35. This index can be, for example, the duration of the on-state of the target switching element. In this case, when the duration of the on-state of the target switching element reaches a predetermined switching time, the inverter control unit 91 determines that the temperature of the target switching element has become equal to or higher than the switching temperature. Generally, the magnitude of the negative torque generated in the first electric rotating machine 11 by the active short circuit control changes according to the vehicle speed (specifically, according to the rotational speed of the first electric rotating machine 11). Considering this point, the above switching time may be set to different values according to the vehicle speed or the rotational speed of the first electric rotating machine 11.

[0049] [Other Embodiments] (1) In the above embodiment, the configuration in which the vehicle drive device 1 includes the second heat medium circuit 72 has been described as an example. However, the present disclosure is not limited to such a configuration, and the vehicle drive device 1 may be configured not to include the second heat medium circuit 72.

[0050] (2) In the above-described embodiment, the vehicle drive device 1 has been described by taking as an example the configuration including the first rotating electric machine 11 and the second rotating electric machine 12 as the drive power sources of the wheels (W1, W2). However, the present disclosure is not limited to such a configuration, and the vehicle V may be configured to further include another device (for example, an internal combustion engine) as the drive power source of the wheels (W1, W2). Further, the vehicle drive device 1 may be configured not to include the second rotating electric machine 12, the second power transmission mechanism 52, and the second inverter 22. In this case, for example, the second wheel W2 may be a non-driving wheel, or in addition to the first wheel W1, the second wheel W2 may also be driven by the first rotating electric machine 11. Further, the vehicle V may be configured not to include the second wheel W2.

[0051] (3) Note that the configurations disclosed in the above-described embodiments can be applied in combination with the configurations disclosed in other embodiments (including combinations of the embodiments described as other embodiments) as long as no contradiction occurs. Regarding other configurations as well, all the embodiments disclosed in this specification are merely examples in all respects. Therefore, various modifications can be appropriately made within the scope not departing from the gist of the present disclosure.

[0052] Summary of the present embodiment Hereinafter, a summary of the embodiment related to the vehicle drive device described above will be described.

[0053] The vehicle drive device (1) includes a rotating electric machine (11), a power transmission mechanism (51) that transmits driving force between the rotating electric machine (11) and a wheel (W1), an inverter (21) that is electrically connected to a battery (40) and drives and controls the rotating electric machine (11), a heat medium circuit (71) through which a heat medium circulates, and an inverter control unit (91) that controls the inverter (21). The heat medium circuit (71) includes a first heat exchange unit (81) that performs heat exchange with at least one of the rotating electric machine (11) and the inverter (21), and a second heat exchange unit (82) that performs heat exchange with at least one of the battery (40) and a cabin (C) of the vehicle (V). The inverter (21) is configured such that an arm (30) for single-phase alternating current is formed by a series circuit of an upper-stage switching element (31) and a lower-stage switching element (32). When the temperature of the battery (40) is equal to or lower than a predetermined threshold value and a negative torque is generated in the rotating electric machine (11), the inverter control unit (91) turns off all the upper-stage switching elements (31) of the inverter (21) and turns on all the lower-stage switching elements (32), or executes active short-circuit control in which all the upper-stage switching elements (31) of the inverter (21) are turned on and all the lower-stage switching elements (32) are turned off.

[0054] According to this configuration, in a driving situation where the vehicle (V) is decelerated in a low-temperature environment, even when the input current to the battery (40) is limited because the temperature of the battery (40) is low, by executing the active short-circuit control of the inverter (21), a negative torque (deceleration torque) can be generated in the rotating electric machine (11), and the regenerative current can be consumed by the rotating electric machine (11) and the inverter (21) to generate heat in them. Then, the heat generated in at least one of the rotating electric machine (11) and the inverter (21) can be transmitted to at least one of the battery (40) and the cabin (C) of the vehicle (V) by the heat medium circuit (71) to warm at least one of them. Thus, according to this configuration, in a driving situation where the vehicle (V) is decelerated in a low-temperature environment, even when the input current to the battery (40) is limited, at least one of the rotating electric machine (11) and the inverter (21) can be used as a heat source for warming at least one of the battery (40) and the cabin (C).

[0055] Here, it is preferable that the heat medium circuit (71) further includes a radiator (80) that exchanges heat between the heat medium and the outside air, the first heat exchange part (81) is arranged on the downstream side of the radiator (80), and the second heat exchange part (82) is arranged on the downstream side of the first heat exchange part (81).

[0056] According to this configuration, the heat of the heat medium obtained by the heat exchange in the first heat exchange part (81) can be efficiently transmitted to at least one of the battery (40) and the cabin (C) of the vehicle (V).

[0057] Further, the wheel (W1) is a first wheel (W1) which is either the front wheel or the rear wheel of the vehicle (V), the rotary electric machine (11) is a first rotary electric machine (11), the power transmission mechanism (51) is a first power transmission mechanism (51), the inverter (21) is a first inverter (21), the heat medium circuit (71) is a first heat medium circuit (71), and the vehicle drive device (1) further includes a second rotary electric machine (12), a second power transmission mechanism (52) that transmits driving force between the second rotary electric machine (12) and a second wheel (W2) which is the other of the front wheel and the rear wheel, a second inverter (22) for driving and controlling the second rotary electric machine (12), and a second heat medium circuit (72) through which a heat medium circulates. The battery (40) is also electrically connected to the second inverter (22), the inverter control unit (91) is configured to also control the second inverter (22), the second heat medium circuit (72) includes a third heat exchange unit (83) that performs heat exchange with at least one of the second rotary electric machine (12) and the second inverter (22), and a fourth heat exchange unit (84) that performs heat exchange with at least one of the battery (40) and the cabin (C). When the inverter control unit (91) executes the active short circuit control of the first inverter (21), it is preferable to control the second inverter (22) such that the sum of the torque of the first rotary electric machine (11) generated by the active short circuit control and the torque generated in the second rotary electric machine (12) becomes the torque required for the running of the vehicle (V).

[0058] According to this configuration, even when the first rotating electric machine (11) generates a negative torque due to the active short circuit control of the first inverter (21), by combining the torques of both the first rotating electric machine (11) and the second rotating electric machine (12), the torque required for the running of the vehicle (V) can be appropriately transmitted to the wheels (W1, W2). Also, according to this configuration, both the heat generated in the first rotating electric machine (11) and the first inverter (21) due to the active short circuit control of the first inverter (21) and the heat generated in the second rotating electric machine (12) and the second inverter (22) due to the control of the second inverter (22) can be transmitted to at least one of the battery (40) and the cabin (C) of the vehicle (V) via the heat medium to warm at least one of them. Therefore, at least one of the battery (40) and the cabin (C) of the vehicle (V) can be efficiently warmed.

[0059] Further, during the execution of the active short circuit control, when the inverter control unit (91) determines that the temperature of the target switching element, which is either the upper stage side switching element (31) or the lower stage side switching element (32) that is in the on state, has reached or exceeded a predetermined switching temperature, it is preferable to execute a switching process of turning on the switching element that is in the off state between the upper stage side switching element (31) and the lower stage side switching element (32) and turning off the target switching element.

[0060] According to this configuration, it is possible to avoid the temperature of the target switching element becoming too high during the execution of the active short circuit control. Therefore, the switching elements of the inverter (21) can be protected.

[0061] The vehicle drive device according to the present disclosure only needs to be able to achieve at least one of the above-described various effects.

Explanation of Reference Numerals

[0062] 1: Vehicle drive device, 11: First rotating electric machine (rotating electric machine), 12: Second rotating electric machine, 21: First inverter (inverter), 22: Second inverter, 30: Arm, 31: Upper-stage switching element, 32: Lower-stage switching element, 40: Battery, 51: First power transmission mechanism (power transmission mechanism), 52: Second power transmission mechanism, 71: First heat medium circuit (heat medium circuit), 72: Second heat medium circuit, 80: Radiator, 81: First heat exchange section, 82: Second heat exchange section, 83: Third heat exchange section, 84: Fourth heat exchange section, 91: Inverter control unit, C: Cabin, V: Vehicle, W1: First wheel (wheel), W2: Second wheel

Claims

1. A vehicle drive device comprising: a rotating electric machine; a power transmission mechanism that transmits driving force between the rotating electric machine and a wheel; an inverter that is electrically connected to a battery and controls driving of the rotating electric machine; a heat medium circuit in which a heat medium circulates; and an inverter control unit that controls the inverter, wherein: the heat medium circuit includes a first heat exchange unit that performs heat exchange with at least one of the rotating electric machine and the inverter, and a second heat exchange unit that performs heat exchange with at least one of the battery and a cabin of the vehicle; the inverter is configured such that an arm for one phase of alternating current is constituted by a series circuit of an upper-stage switching element and a lower-stage switching element; when the temperature of the battery is equal to or lower than a predetermined threshold value and a negative torque is generated in the rotating electric machine, the inverter control unit turns off all the upper-stage switching elements of the inverter and turns on all the lower-stage switching elements, or executes active short circuit control in which all the upper-stage switching elements of the inverter are turned on and all the lower-stage switching elements of the inverter are turned off.

2. The heat medium circuit further includes a radiator that performs heat exchange between the heat medium and outside air, the first heat exchange unit is disposed downstream of the radiator, and the second heat exchange unit is disposed downstream of the first heat exchange unit. The vehicle drive device according to claim 1.

3. The wheel is a first wheel that is either a front wheel or a rear wheel of the vehicle, the rotating electric machine is a first rotating electric machine, the power transmission mechanism is a first power transmission mechanism, the inverter is a first inverter, and the heat medium circuit is a first heat medium circuit. The vehicle drive device further includes: a second rotating electric machine; a second power transmission mechanism that transmits driving force between the second rotating electric machine and a second wheel that is the other of the front wheel and the rear wheel; a second inverter that controls driving of the second rotating electric machine; and a second heat medium circuit in which a heat medium circulates. The battery is also electrically connected to the second inverter. The inverter control unit is configured to also control the second inverter. The second heat medium circuit includes a third heat exchange unit that performs heat exchange with at least one of the second rotating electric machine and the second inverter, and a fourth heat exchange unit that performs heat exchange with at least one of the battery and the cabin. When the inverter control unit executes the active short circuit control of the first inverter, the total of the torque of the first rotating electrical machine generated by the active short circuit control and the torque generated in the second rotating electrical machine is the torque required for the running of the vehicle. The vehicle drive device according to claim 1 or 2, which controls the second inverter so as to be

4. During the execution of the active short circuit control, when it is determined that the temperature of the target switching element, which is either the upper-stage switching element or the lower-stage switching element and is in the on state, has reached or exceeded a predetermined switching temperature, the vehicle drive device according to claim 1 or 2 executes a switching process of turning on the switching element that is in the off state among the upper-stage switching element and the lower-stage switching element and turning off the target switching element.

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