Electric vehicles

Abstract

To provide an electric vehicle that can continue to operate regardless of a drop in power supply voltage. [Solution] The electric vehicle comprises a first travel motor and a second travel motor, a drive circuit for driving the first travel motor and the second travel motor, and a DC power supply device capable of supplying power to the drive circuit. The power supply device is capable of outputting a first voltage and a second voltage lower than the first voltage. When the power of the first voltage is supplied, the drive circuit drives the first travel motor and the second travel motor with the power of the first voltage. When the power of the second voltage is supplied, the drive circuit uses the coil of the first travel motor to boost the power of the second voltage and drives the second travel motor with the boosted power.

Description

Technical Field

[0001] The present invention relates to an electric vehicle.

Background Art

[0002] An electric vehicle that drives the driving wheels of a vehicle by the power of a driving motor generally includes, as a power source, a high-voltage battery that stores electric power supplied to the driving motor, and a low-voltage battery. The electric power stored in the low-voltage battery is supplied to, for example, various in-vehicle auxiliary machines.

[0003] When an abnormality occurs in the high-voltage battery, there is a risk that electric power cannot be appropriately supplied from the high-voltage battery to the driving motor, and the electric vehicle may become inoperable. In an automated driving system with a driving automation level of 4 or higher that is progressing towards practical use, that is, an automated driving system in which the system executes all of the vehicle's driving under specific conditions or unconditionally, a situation where the driver is absent is expected, and redundancy against abnormalities in the high-voltage battery is required.

[0004] The drive device described in Patent Document 1 and the power supply system described in Patent Document 2 boost the electric power stored in the low-voltage battery when an abnormality occurs in the high-voltage battery, and supply the boosted electric power to the driving motor to continue the running of the electric vehicle. Thereby, for example, it becomes possible to evacuate the vehicle to a safe place.

Prior Art Documents

Patent Documents

[0005]

Patent Document 1

Patent Document 2

Summary of the Invention

Problems to be Solved by the Invention

[0006] The drive device described in Patent Document 1 and the power supply system described in Patent Document 2 require a booster device to increase the voltage of the power stored in the low-voltage battery, which raises concerns about increased cost and weight.

[0007] This invention provides an electric vehicle that can continue to operate regardless of a drop in power supply voltage. [Means for solving the problem]

[0008] An electric vehicle according to one aspect of the present invention comprises a first drive motor and a second drive motor, A drive circuit that drives the first travel motor and the second travel motor, A DC power supply capable of supplying power to the aforementioned drive circuit, Equipped with, The power supply device is capable of outputting a first voltage and a second voltage lower than the first voltage. The aforementioned drive circuit is When the power of the first voltage is supplied, the first travel motor and the second travel motor are driven by the power of the first voltage. When the power of the second voltage is supplied, the coil of the first travel motor is used to boost the power of the second voltage, and the boosted power drives the second travel motor. [Effects of the Invention]

[0009] According to the present invention, it is possible to provide an electric vehicle that can continue to run regardless of a decrease in power supply voltage, while suppressing increases in cost and weight. [Brief explanation of the drawing]

[0010] [Figure 1] This is a block diagram of an example of an electric vehicle for illustrating embodiments of the present invention. [Figure 2] This is a circuit diagram of the drive circuit for an electric vehicle. [Figure 3] This is a circuit diagram of the drive circuit for the first drive configuration. [Figure 4] This is a circuit diagram of the drive circuit for the second drive configuration. [Figure 5] It is a circuit diagram of a drive circuit of the second drive configuration. [Figure 6] It is a circuit diagram of a drive circuit of the second drive configuration. [Figure 7] It is a block diagram of a modification example of an electric vehicle. [Figure 8] It is a block diagram of a power supply device of an electric vehicle. [Figure 9] It is a circuit diagram of an output circuit of the first output configuration. [Figure 10] It is a circuit diagram of an output circuit of the second output configuration. [Figure 11] It is a circuit diagram of an output circuit of the second output configuration. [Figure 12] It is a block diagram of a modification example of a power supply device.

Embodiments for Carrying Out the Invention

[0011] FIG. 1 shows an example of an electric vehicle.

[0012] The electric vehicle 1 shown in FIG. 1 is a four-wheel vehicle having a pair of left and right front wheels and a pair of left and right rear wheels. The electric vehicle 1 includes a first traveling motor 10, a second traveling motor 11, a drive circuit 12 that drives the first traveling motor 10 and the second traveling motor 11, and a DC power supply device 13 that can supply power to the drive circuit 12.

[0013] The power output from the first traveling motor 10 is transmitted to one of the front or rear wheels 2. The power output from the second traveling motor 11 is transmitted to the other of the front or rear wheels 3. Although illustration is omitted, differential devices are provided in the power transmission paths 4 between the first traveling motor 10 and the wheel 2, and the power transmission paths 5 between the second traveling motor 11 and the wheel 3, respectively. A speed reducer may be provided between the first traveling motor 10 and the differential device, and between the second traveling motor 11 and the differential device, respectively.

[0014] In addition, the electric vehicle 1 further includes an ECU (Electronic Control Unit) 14, other auxiliary machines 15 (such as lights, navigation systems, etc.), and an auxiliary machine battery 16 capable of supplying power to the ECU 14 and the auxiliary machines 15. The ECU 14 is mainly composed of a processor and controls the operations of each part of the electric vehicle 1 including the drive circuit 12 and the power supply device 13.

[0015] The power supply device 13 includes a main battery and outputs a high voltage required for driving the first traveling motor 10 and the second traveling motor 11. The auxiliary machine battery 16 outputs a low voltage required for the operations of the ECU 14 and the auxiliary machines 15. The auxiliary machine battery 16 is charged by the power supplied from the power supply device 13. A DC-DC converter 17 for converting the high voltage output of the power supply device 13 into a low voltage is provided between the power supply device 13 and the auxiliary machine battery 16.

[0016] The power supply device 13 is capable of outputting a first voltage (for example, 800 volts) and a second voltage lower than the first voltage (for example, 400 volts). During normal times, the power supply device 13 outputs the first voltage. On the other hand, when an abnormality occurs in a part of the main battery of the power supply device 13 or when the SOC (State of Charge) of the main battery decreases, etc., the power supply device 13 outputs the second voltage. The abnormality of the main battery and the decrease in SOC are detected by sensors. When the abnormality of the main battery and the decrease in SOC are detected, the ECU 14 controls the power supply device 13 to output the second voltage.

[0017] FIG. 2 shows the drive circuit 12.

[0018] When the power of the first voltage is supplied from the power supply device 13, the drive circuit 12 drives the first traveling motor 10 and the second traveling motor 11 with the power of the first voltage. Also, when the power of the second voltage is supplied from the power supply device 13, the drive circuit 12 boosts the power of the second voltage using the coil of the first traveling motor 10. Then, the drive circuit 12 drives the second traveling motor 11 with the boosted power.

[0019] In the example shown in Figure 2, the first travel motor 10 is a three-phase AC motor, and the coils of the first travel motor 10 have a U-phase winding U, a V-phase winding V, and a W-phase winding W. The drive circuit 12 has a first drive circuit 20 that drives the first travel motor 10, and the first drive circuit 20 includes an inverter 30. The inverter 30 generates three-phase alternating current with a phase difference of 120°. The U-phase winding U, V-phase winding V, and W-phase winding W of the first travel motor 10 are excited to form a rotating magnetic field by the three-phase alternating current generated by the inverter 30. The rotor of the first travel motor 10 rotates in accordance with the rotation of the magnetic field, thereby generating power in the first travel motor 10.

[0020] The inverter 30 has three-phase switch circuits 31U, 31V, and 31W. One end of each switch circuit 31U, 31V, and 31W is connected to the positive input line PL of the first drive circuit 20, and the other end of each switch circuit 31U, 31V, and 31W is connected to the negative input line NL of the first drive circuit 20. The first drive circuit 20 also has a capacitor 32 that stabilizes the line voltage between the positive input line PL and the negative input line NL. One end of the capacitor 32 is connected to the positive input line PL, and the other end of the capacitor 32 is connected to the negative input line NL.

[0021] Switch circuit 31U has a high-side switch 33H and a low-side switch 33L, which are connected in series with each other. Switch circuits 31V and 31W also similarly have a high-side switch 33H and a low-side switch 33L. The high-side switch 33H and the low-side switch 33L are made of semiconductor switching elements such as IGBTs (Insulated Gate Bipolar Transistors) and MOSFETs (Metal Oxide Semiconductor Field Effect Transistors), and their ON / OFF state is controlled by the ECU 14.

[0022] One end of the U-phase winding U of the first travel motor 10 is connected to switch circuit 31U between the high-side switch 33H and the low-side switch 33L of switch circuit 31U. One end of the V-phase winding V is connected to switch circuit 31V between the high-side switch 33H and the low-side switch 33L of switch circuit 31V. One end of the W-phase winding W is connected to switch circuit 31W between the high-side switch 33H and the low-side switch 33L of switch circuit 31W. As the high-side switches 33H and low-side switches 33L of switch circuits 31U, 31V, and 31W are periodically switched ON / OFF, a three-phase alternating current is generated and supplied to the U-phase winding U, the V-phase winding V, and the W-phase winding W of the first travel motor 10.

[0023] The second travel motor 11 is also a three-phase AC motor, and the coils of the second travel motor have a U-phase winding U, a V-phase winding V, and a W-phase winding W. The drive circuit 12 has a second drive circuit 21 that drives the second travel motor 11, and the second drive circuit 21 is configured in the same way as the first drive circuit 20.

[0024] The first travel motor 10 and the second travel motor 11 are not limited to three-phase AC motors, but may also be multi-phase AC motors with four or more phases. The inverters 30 of the first drive circuit 20 and the second drive circuit 21 are configured appropriately to match the number of phases of the first travel motor 10 and the second travel motor 11.

[0025] When power of the first voltage is supplied from the power supply unit 13 to the drive circuit 12, the first drive circuit 20 and the second drive circuit 21 are connected to the power supply unit 13 in parallel with each other. The first drive circuit 20 and the second drive circuit 21 each generate three-phase alternating current from the power supplied from the power supply unit 13 and drive the first travel motor 10 and the second travel motor 11.

[0026] On the other hand, when the second voltage power is supplied from the power supply unit 13 to the drive circuit 12, the direct power supply from the power supply unit 13 to the second drive circuit 21 is interrupted. Then, a boost circuit is formed by the U-phase winding U, V-phase winding V, and W-phase winding W of the first travel motor 10 and the switch circuits 31U, 31V, and 31W included in the inverter 30 of the first drive circuit 20. The second voltage power is supplied from the power supply unit 13 to the boost circuit, and the power boosted by the boost circuit is supplied to the second drive circuit 21. The second drive circuit 21 generates a three-phase alternating current from the boosted power and drives the second travel motor 11.

[0027] Furthermore, since the first travel motor 10 and the first drive circuit 20 and the second travel motor 11 and the second drive circuit 21 have the same configuration as described above, a boost circuit may be formed by the U-phase winding U, V-phase winding V, and W-phase winding W of the second travel motor 11 and the switch circuits 31U, 31V, and 31W included in the inverter 30 of the second drive circuit 21. In this case, the direct power supply from the power supply device 13 to the first drive circuit 20 is interrupted, and a boost circuit is formed between the power supply device 13 and the first drive circuit 20. The first drive circuit 20 then generates a three-phase alternating current from the boosted power and drives the first travel motor 10.

[0028] The drive circuit 12 further includes a drive circuit switching unit 40, which switches the configuration of the drive circuit 12 between a first drive configuration in which the first drive circuit 20 and the second drive circuit 21 are connected to the power supply unit 13 in parallel with each other, and a second drive configuration in which the direct power supply from the power supply unit 13 to the first drive circuit 20 or the second drive circuit 21 is cut off, and a boost circuit is formed between the power supply unit 13 and the first drive circuit 20 or the second drive circuit 21.

[0029] The drive circuit switching unit 40 has switches 41-45. Switch 41 connects the positive input line PL of the first drive circuit 20 to the positive terminal PT of the power supply unit 13. Switch 42 connects the positive input line PL of the second drive circuit 21 to the positive terminal PT of the power supply unit 13. Switch 43 connects the positive input line PL of the first drive circuit 20 to the positive input line PL of the second drive circuit 21. Switch 44 connects the neutral point N where the U-phase winding U, V-phase winding V, and W-phase winding W of the first travel motor 10 are joined to the positive terminal PT of the power supply unit 13. Switch 45 connects the neutral point N where the U-phase winding U, V-phase winding V, and W-phase winding W of the second travel motor 11 are joined to the positive terminal PT of the power supply unit 13. Switches 41-45 consist of semiconductor switching elements such as IGBTs and MOSFETs, or mechanical switches such as relays, and the ON / OFF state of switches 41-45 is controlled by the ECU 14.

[0030] Figure 3 shows the drive circuit 12 of the first drive configuration.

[0031] In the first drive configuration, switches 41 and 42 are turned ON, and switches 43-45 are turned OFF. The first drive circuit 20 and the second drive circuit 21 are connected in parallel to the power supply unit 13. The first drive circuit 20 and the second drive circuit 21 each generate three-phase alternating current from the power of the first voltage supplied from the power supply unit 13, and drive the first travel motor 10 and the second travel motor 11.

[0032] Figures 4 and 5 show the drive circuit 12 of the second drive configuration.

[0033] In the second drive configuration, switches 43 and 44 are turned ON, and switches 41, 42, and 45 are turned OFF. When switches 41 and 42 are turned OFF, the connection between the positive input lines PL of the first drive circuit 20 and the second drive circuit 21 and the positive terminal PT of the power supply unit 13 is disconnected. The positive input lines PL of the first drive circuit 20 and the second drive circuit 21 are then connected in series with each other via the ON switch 43. Furthermore, the neutral point N of the first travel motor 10 is connected to the positive terminal PT of the power supply unit 13 via the ON switch 44. In this second drive configuration, the boost circuit formed by the U-phase winding U, V-phase winding V, and W-phase winding W of the first travel motor 10 and the switch circuits 31U, 31V, and 31W of the first drive circuit 20 will be described below.

[0034] First, the high-side switch 33H of the switch circuit 31U is turned OFF, and the low-side switch 33L is turned ON. As shown by the dashed arrow in Figure 4, current flows from the power supply 13 through the ON switch 44 and the low-side switch 33L of the switch circuit 31U to the U-phase winding U, and energy is stored in the U-phase winding U.

[0035] Next, the low-side switch 33L of the switch circuit 31U is turned OFF. When the low-side switch 33L is turned OFF, the U-phase winding U releases the energy it has stored. As shown by the dashed arrow in Figure 5, current flows from the power supply 13 through the ON switch 44, the freewheeling diode D of the high-side switch 33H of the switch circuit 31U, and the ON switch 43 to the positive input line PL of the second drive circuit 21. The voltage induced in the U-phase winding U is superimposed on the second voltage output from the power supply 13, and the boosted voltage is input to the second drive circuit 21. The V-phase winding V and switch circuit 31V, and the W-phase winding W and switch circuit 31W also perform the same boosting operation as the U-phase winding U and switch circuit 31U. The second drive circuit 21 generates a three-phase AC current from the boosted power and drives the second travel motor 11.

[0036] The boosted voltage changes depending on the time that the low-side switches 33L of each switch circuit 31U, 31V, and 31W are ON, with the boosted voltage being higher the longer the time. By switching the low-side switches 33L of each switch circuit 31U, 31V, and 31W ON / OFF at different phases, the pulsation of the boosted voltage input to the second drive circuit 21 can be suppressed.

[0037] In the drive circuit 12 of the second drive configuration shown in Figures 4 and 5, a boost circuit is formed by the U-phase winding U, V-phase winding V, and W-phase winding W of the first travel motor 10 and the switch circuits 31U, 31V, and 31W of the first drive circuit 20. However, as shown in Figure 6, a boost circuit may also be formed by the U-phase winding U, V-phase winding V, and W-phase winding W of the second travel motor 11 and the switch circuits 31U, 31V, and 31W of the second drive circuit 21.

[0038] In the second drive configuration shown in Figure 6, switches 43 and 45 are turned ON, and switches 41, 42, and 44 are turned OFF. When switches 41 and 42 are turned OFF, the connection between the positive input lines PL of the first drive circuit 20 and the second drive circuit 21 and the positive terminal PT of the power supply unit 13 is disconnected. Then, the positive input lines PL of the first drive circuit 20 and the second drive circuit 21 are connected in series with each other via the ON switch 43. Furthermore, the neutral point N of the second travel motor 11 is connected to the positive terminal PT of the power supply unit 13 via the ON switch 45.

[0039] Focusing on the U-phase winding U of the second drive motor 11 and the switch circuit 31U of the second drive circuit 21, first, the high-side switch 33H of the switch circuit 31U is turned OFF and the low-side switch 33L is turned ON. Current flows from the power supply unit 13 through the ON switch 45 and the low-side switch 33L to the U-phase winding U, and energy is stored in the U-phase winding U.

[0040] Next, the low-side switch 33L of the switch circuit 31U is turned OFF. When the low-side switch 33L is turned OFF, the U-phase winding U releases the stored energy. As shown by the dashed arrow in Figure 6, current flows from the power supply 13 through the ON switch 45, the freewheeling diode D of the high-side switch 33H, and the ON switch 43 to the positive input line PL of the first drive circuit 20. The voltage induced in the U-phase winding U is superimposed on the second voltage output from the power supply 13, and the boosted voltage is input to the first drive circuit 20. The first drive circuit 20 generates a three-phase alternating current from the boosted power and drives the first travel motor 10.

[0041] As a result, even if the voltage output from the power supply unit 13 drops to the second voltage due to a malfunction of the main battery or a decrease in the State of Charge (SOC), the voltage required to drive the first drive motor 10 can be secured, and the electric vehicle 1 can continue to run.

[0042] As described above, the electric vehicle 1 boosts the second voltage output from the power supply unit 13 using the coil of one of the motors, the first motor 10 and the second motor 11, and uses the boosted power to drive the other motor of the first motor 10 and the second motor 11. Even if the voltage output from the power supply unit 13 drops to the second voltage due to a malfunction of the main battery or a decrease in the State of Charge (SOC), the voltage required to drive either the first motor 10 or the second motor 11 can be secured, and the electric vehicle 1 can continue to run. Furthermore, by boosting the voltage using the coil of one of the motors, the cost and weight increase can be suppressed.

[0043] In particular, in the electric vehicle 1, a boost circuit can be formed by the multi-phase windings U, V, W that form the coil of the first travel motor 10 and the semiconductor switching elements high-side switch 33H and low-side switch 33L of the first drive circuit 20, or by the multi-phase windings U, V, W that form the coil of the second travel motor 11 and the semiconductor switching elements high-side switch 33H and low-side switch 33L of the second drive circuit 21, thereby further suppressing increases in cost and weight.

[0044] Preferably, as shown in Figure 7, disconnecting devices 18 are provided in the power transmission path 4 between the first travel motor 10 and the wheel 2 to which power output from the first travel motor 10 is transmitted, and in the power transmission path 5 between the second travel motor 11 and the wheel 3 to which power output from the second travel motor 11 is transmitted. For example, when the coil of the first travel motor 10 is used for voltage boosting, the disconnecting device 18 in the power transmission path 4 can disconnect the first travel motor 10 from the wheel 2. This stops the rotation of the rotor of the first travel motor 10, enabling stable voltage boosting operation. Similarly, when the coil of the second travel motor 11 is used for voltage boosting, the disconnecting device 18 in the power transmission path 5 can disconnect the second travel motor 11 from the wheel 3. This stops the rotation of the rotor of the second travel motor 11, enabling stable voltage boosting operation.

[0045] Preferably, as described above, the power output from the first drive motor 10 is transmitted to one of the front or rear wheels 2, and the power output from the second drive motor 11 is transmitted to the other of the front or rear wheels 3, so that the drive wheels of each drive motor are positioned at the front and rear of the electric vehicle 1. This allows the electric vehicle 1 to continue running with minimal impact on its operation even if the voltage output from the power supply unit 13 drops to the second voltage. However, for example, the power from both the first drive motor 10 and the second drive motor 11 may be input to a common differential, and one of the front or rear wheels may be driven by both the first drive motor 10 and the second drive motor 11.

[0046] Figure 8 shows the power supply unit 13.

[0047] The power supply unit 13 includes a first battery 50 and a second battery 51, which are the main batteries, and an output circuit 52.

[0048] The first battery 50 has multiple battery cells, such as lithium-ion battery cells and nickel-metal hydride battery cells. Multiple battery cells are connected in series and parallel to ensure the required voltage and capacity. The second battery 51 is also configured similarly to the first battery 50, with multiple battery cells connected in series and parallel to ensure the required voltage and capacity.

[0049] For example, if the output voltage required for the power supply unit 13 is 800 volts at its rated value, the first battery 50 and the second battery 51 are configured to output a voltage of 400 volts at their rated value. By connecting the first battery 50 and the second battery 51 in series with each other to the output circuit 52, the power supply unit 13 can output a voltage of 800 volts as the first voltage. Alternatively, by connecting the first battery 50 and the second battery 51 in parallel with each other to the output circuit 52, or by connecting only one of the batteries (the first battery 50 or the second battery 51) to the output circuit 52, the power supply unit 13 can output a voltage of 400 volts as the second voltage.

[0050] In addition, the output voltages of the first battery 50 and the second battery 51 may be set to different voltages, as long as the required output voltage can be obtained from the power supply 13 when the first battery 50 and the second battery 51 are connected in series. However, from the viewpoint of reducing costs by using the same components for the first battery 50 and the second battery 51, and simplifying the control of the drive circuit 12 and the charging circuit, it is preferable that the output voltages of the first battery 50 and the second battery 51 be set to the same voltage.

[0051] The output circuit 52 has an output circuit switching unit 53, which switches the configuration of the output circuit 52 between a first output configuration that outputs a first voltage and a second output configuration that outputs a second voltage. The output circuit switching unit 53 has a switch circuit 54 that spans between the high-potential line HL and the low-potential line LL of the output circuit 52, and the switch circuit 54 has a first switch 55, a second switch 56, and a third switch 57. The first switch 55, the second switch 56, and the third switch 57 are connected in series from the high-potential line HL side of the output circuit 52 in the order of the first switch 55, the second switch 56, and the third switch 57. The first switch 55, the second switch 56, and the third switch 57 consist of semiconductor switching elements such as IGBTs and MOSFETs, or mechanical switches such as relays, and their ON / OFF status is controlled by the ECU 14.

[0052] The positive terminal PT of the first battery 50 is connected to the switch circuit 54 on the high-potential line HL side of the first switch 55, and the negative terminal NT of the first battery 50 is connected to the switch circuit 54 between the second switch 56 and the third switch 57. The positive terminal PT of the second battery 51 is connected to the switch circuit 54 between the first switch 55 and the second switch 56, and the negative terminal NT of the second battery 51 is connected to the switch circuit 54 on the low-potential line LL side of the third switch 57.

[0053] Figure 9 shows the output circuit 52 of the first output configuration.

[0054] In the first output configuration, of the three switches 57 (first switch 55, second switch 56, and third switch 57), only the second switch 56 is turned ON, while the first switch 55 and the third switch 57 are turned OFF. As shown by the dashed arrow in Figure 9, the negative terminal NT of the first battery 50 and the positive terminal PT of the second battery 51 are connected via the ON second switch 56, and the first battery 50 and the second battery 51 are connected in series to the output circuit 52. As a result, a first voltage (for example, 800 volts) is output from the power supply 13.

[0055] When the power supply 13 outputs a first voltage, the drive circuit 12 is configured as a first drive configuration, as described above, and the first drive circuit 20 and the second drive circuit 21 are connected to the power supply 13 in parallel. The first drive circuit 20 and the second drive circuit 21 each generate a three-phase alternating current from the power of the first voltage supplied from the power supply 13, and drive the first travel motor 10 and the second travel motor 11.

[0056] Figures 10 and 11 show the output circuit 52 of the second output configuration.

[0057] If an abnormality occurs in either the first battery 50 or the second battery 51, the ECU 14 controls the first switch 55, the second switch 56, and the third switch 57 to disconnect the abnormal battery from the output circuit 52. Examples of abnormalities in the first battery 50 and the second battery 51 include an increase in battery temperature and an increase in internal battery pressure. These abnormalities are detected by sensors such as a temperature sensor and a pressure sensor and transmitted to the ECU 14.

[0058] Figure 10 shows the second output configuration when an abnormality occurs in the first battery 50. Of the first switch 55, second switch 56, and third switch 57, only the first switch 55 is ON, while the second switch 56 and third switch 57 are OFF. The negative terminal NT of the first battery 50 is disconnected from the low-potential line LL of the output circuit 52 by the OFF state of the third switch 57, and the first battery 50 is disconnected from the output circuit 52.

[0059] On the other hand, as shown by the dashed arrow in Figure 10, the positive terminal PT of the second battery 51 is connected to the high-potential line HL of the output circuit 52 via the first switch 55, which is in the ON state, and the negative terminal NT of the second battery 51 is connected to the low-potential line LL of the output circuit 52. Therefore, the output voltage of the second battery 51 is output from the power supply unit 13 as a second voltage (for example, 400 volts).

[0060] Figure 11 shows the second output configuration when an abnormality occurs in the second battery 51. Of the first switch 55, second switch 56, and third switch 57, only the third switch 57 is ON, while the first switch 55 and second switch 56 are OFF. The positive terminal PT of the second battery 51 is disconnected from the high-potential line HL of the output circuit 52 by the OFF state of the first switch 55, and the second battery 51 is disconnected from the output circuit 52.

[0061] On the other hand, as shown by the dashed arrow in Figure 11, the positive terminal PT of the first battery 50 is connected to the high-potential line HL of the output circuit 52, and the negative terminal NT of the second battery 51 is connected to the low-potential line LL of the output circuit 52 via the third switch 57, which is in the ON state. Therefore, the output voltage of the first battery 50 is output from the power supply unit 13 as the second voltage (for example, 400 volts).

[0062] When the second voltage is output from the power supply 13, the drive circuit 12 is configured as a second drive circuit, as described above. Direct power supply from the power supply 13 to the second drive circuit 21 is cut off, and a boost circuit is formed by the U-phase winding U, V-phase winding V, and W-phase winding W of the first travel motor 10 and the switch circuits 31U, 31V, and 31W of the first drive circuit 20. Power of the second voltage is supplied from the power supply 13 to the boost circuit, and the power boosted by the boost circuit is supplied to the second drive circuit 21. The second drive circuit 21 then generates a three-phase alternating current from the boosted power and drives the second travel motor 11. Alternatively, the direct power supply from the power supply unit 13 to the first drive circuit 20 is interrupted, and a boost circuit is formed by the U-phase winding U, V-phase winding V, and W-phase winding W of the second travel motor 11 and the switch circuits 31U, 31V, and 31W of the second drive circuit 21. Power of the second voltage is supplied from the power supply unit 13 to the boost circuit, and the power boosted by the boost circuit is supplied to the first drive circuit 20. The first drive circuit 20 then generates a three-phase alternating current from the boosted power and drives the first travel motor 10.

[0063] Figure 12 shows a modified example of the power supply unit 13.

[0064] In the modified power supply unit 13 shown in Figure 12, the first switch 55, the second switch 56, and the third switch 57 of the switch circuit 54 are made of semiconductor switching elements. Semiconductor switching elements generally have superior operating speed compared to mechanical switches. The output circuit switching unit 53 further includes a first mechanical switch 58 and a second mechanical switch 59. Mechanical switches generally have superior insulation in the OFF state compared to semiconductor switching elements.

[0065] The first mechanical switch 58 is provided between the positive terminal PT of the first battery 50 and the switch circuit 54, and can disconnect the connection between the positive terminal PT of the first battery 50 and the switch circuit 54. The second mechanical switch 59 is provided between the negative terminal NT of the second battery 51 and the switch circuit 54, and can disconnect the connection between the negative terminal NT of the second battery 51 and the switch circuit 54.

[0066] In the first output configuration, the first mechanical switch 58 and the second mechanical switch 59 are turned ON in addition to the second switch 56, while the first switch 55 and the third switch 57 are turned OFF. The first battery 50 and the second battery 51 are connected in series to the output circuit 52, and a first voltage (for example, 800 volts) is output from the power supply unit 13.

[0067] In the second output configuration, where the first battery 50 is disconnected from the output circuit 52, the first switch 55 and the second mechanical switch 59 are turned ON, while the second switch 56, the third switch 57, and the first mechanical switch 58 are turned OFF. The negative terminal NT of the first battery 50 is disconnected from the low-potential line LL of the output circuit 52 by the OFF state of the third switch 57, and furthermore, the positive terminal PT of the first battery 50 is also disconnected from the high-potential line HL of the output circuit 52 by the OFF state of the first mechanical switch 58. This makes it possible to more reliably disconnect the first battery 50, which has experienced an abnormality, from the output circuit 52.

[0068] In the second output configuration, where the second battery 51 is disconnected from the output circuit 52, the third switch 57 and the first mechanical switch 58 are turned ON, while the first switch 55, the second switch 56, and the second mechanical switch 59 are turned OFF. The positive terminal PT of the second battery 51 is disconnected from the high-potential line HL of the output circuit 52 by the OFF state of the first switch 55, and furthermore, the negative terminal NT of the second battery 51 is also disconnected from the low-potential line LL of the output circuit 52 by the OFF state of the second mechanical switch 59. This makes it possible to more reliably disconnect the abnormal second battery 51 from the output circuit 52.

[0069] Assuming that the output voltages of the first battery 50 and the second battery 51 are the same and both the first battery 50 and the second battery 51 are functioning correctly, the power supply device 13, in which the first switch 55, the second switch 56, and the third switch 57 are semiconductor switching elements, can also output an intermediate voltage (e.g., 600 volts) between the output voltage obtained by connecting the first battery 50 and the second battery 51 in series (e.g., 800 volts) and the output voltage of either the first battery 50 or the second battery 51 (e.g., 400 volts).

[0070] When the second switch 56, the first mechanical switch 58, and the second mechanical switch 59 are turned ON, and the first switch 55 and the third switch 57 are turned OFF, the first battery 50 and the second battery 51 are connected in series to the output circuit 52. When the first mechanical switch 58 and the second mechanical switch 59 remain ON, and the first switch 55 and the third switch 57 are turned ON, and the second switch 56 is turned OFF, the first battery 50 and the second battery 51 are connected in parallel to the output circuit 52.

[0071] The connection of the first battery 50 and the second battery 51 to the output circuit 52 is rapidly switched between series and parallel by the ON / OFF control of the first switch 55, the second switch 56, and the third switch 57, which are made of semiconductor switching elements. This provides an intermediate voltage (e.g., 600 volts) between the output voltage when connected in series (e.g., 800 volts) and the output voltage when connected in parallel (e.g., 400 volts). This intermediate voltage can also be used as the second voltage of the power supply unit 13.

[0072] This specification contains at least the following information. Note that the components etc. in parentheses indicate those corresponding to the embodiments described above, but are not limited thereto.

[0073] (1) A first travel motor (first travel motor 10) and a second travel motor (second travel motor 11), A drive circuit (drive circuit 12) that drives the first travel motor and the second travel motor, A DC power supply (power supply 13) capable of supplying power to the aforementioned drive circuit, Equipped with, The power supply device is capable of outputting a first voltage and a second voltage lower than the first voltage. The aforementioned drive circuit is When the power of the first voltage is supplied, the first travel motor and the second travel motor are driven by the power of the first voltage. An electric vehicle (electric vehicle 1) that, when the power of the second voltage is supplied, uses the coil of the first travel motor to boost the power of the second voltage, and drives the second travel motor with the boosted power.

[0074] (2) The electric vehicle described in (1) above, The coil of the first travel motor has multiple phase windings (U-phase winding U, V-phase winding V, W-phase winding W) which are excited to form a rotating magnetic field by multiple phase alternating currents with different phases. The drive circuit has an inverter (inverter 30) that uses a plurality of semiconductor switching elements (high-side switch 33H, low-side switch 33L) to generate the multi-phase AC current from the power supplied from the power supply device. An electric vehicle in which a boost circuit is formed by the multiple phase windings and the multiple semiconductor switching elements to boost the power of the second voltage.

[0075] (3) The electric vehicle described in (2) above, The aforementioned drive circuit is The first drive circuit (first drive circuit 20) includes the inverter and drives the first travel motor, A second drive circuit (second drive circuit 21) that drives the second travel motor, A drive circuit switching unit (drive circuit switching unit 40) that switches the configuration of the drive circuit between a first drive configuration and a second drive configuration, Equipped with, In the first drive configuration, the drive circuit switching unit connects the first drive circuit and the second drive circuit to the power supply in parallel with each other. In the second drive configuration, the drive circuit switching unit disconnects the connection between the positive terminal (positive terminal PT) of the power supply and the positive input lines (positive input lines PL) of the first drive circuit and the second drive circuit, respectively, and connects the positive input lines of the first drive circuit and the second drive circuit in series with each other, and connects the neutral point (neutral point N) of the first travel motor, to which the windings of the multiple phases are combined, to the positive terminal of the power supply.

[0076] (4) Any one of the electric vehicles described in (1) to (3) above, An electric vehicle further comprising a disconnection device (connection device 18) for disconnecting / connecting the power transmission path between the first travel motor and the drive wheel (wheel 2) to which power output from the first travel motor is transmitted.

[0077] (5) Any one of the electric vehicles described in (1) to (4) above, The first drive motor drives either the front wheel or the rear wheel (wheel 2) of the electric vehicle. The second drive motor is an electric vehicle that drives the other of the front wheel and the rear wheel (wheel 3).

[0078] (6) Any one of the electric vehicles described in (1) to (5) above, The aforementioned power supply device is The first battery (first battery 50), The second battery (second battery 51), Output circuit (output circuit 52), Equipped with, The output circuit has an output circuit switching unit (output circuit switching unit 53) that switches the configuration of the output circuit between a first output configuration and a second output configuration. In the first output configuration, the output circuit switching unit connects the first battery and the second battery in series with the output circuit, thereby causing the output circuit to output the first voltage. In the second output configuration, the output circuit switching unit disconnects one of the first battery and the second battery from the output circuit, thereby causing the output circuit to output the second voltage.

[0079] (7) The electric vehicle described in (6) above, The output circuit switching unit includes a switch circuit (switch circuit 54) that spans between the high-potential line (high-potential line HL) and the low-potential line (low-potential line LL) of the output circuit. The switch circuit includes a first switch (first switch 55), a second switch (second switch 56), and a third switch (third switch 57) connected in series in order from the high-potential line side. The positive terminal (positive terminal PT) of the first battery is connected to the switch circuit on the high-potential line side of the first switch. The negative terminal (negative terminal NT) of the first battery is connected to the switch circuit between the second switch and the third switch. The positive terminal (positive terminal PT) of the second battery is connected to the switch circuit between the first switch and the second switch. The negative terminal (negative terminal NT) of the second battery is connected to the switch circuit on the low-potential line side of the third switch in this electric vehicle.

[0080] (8) The electric vehicle described in (7) above, The first switch, the second switch, and the third switch are made of semiconductor switching elements. The output circuit switching unit is A first mechanical switch (first mechanical switch 58) capable of disconnecting the connection between the positive terminal of the first battery and the switch circuit, An electric vehicle further comprising a second mechanical switch (second mechanical switch 59) capable of disconnecting the connection between the negative terminal of the second battery and the switch circuit. [Explanation of Symbols]

[0081] 1. Electric Vehicle 2 wheels 3 wheels 4. Power transmission path 5 Power transmission path 10. First travel motor 11. Second travel motor 12 Drive Circuit 13 Power supply 14 ECU 15 Auxiliary equipment 16. Auxiliary battery 17 DC-DC Converters 18 Disconnecting device 20 First drive circuit 21 Second drive circuit 30 Inverters 31U, 31V, 31W Switch Circuit 32 Capacitors 33H High-Side Switch 33L Low-side switch 40 Drive circuit switching section 41-45 Switch 50 First Battery 51 Second Battery 52 Output Circuit 53 Output circuit switching section 54 Switch Circuits 55 First switch 56 Second switch 57 Third switch 58. First Mechanical Switch 59. Second mechanical switch D freewheel diode N neutral point UU phase winding VV phase winding WW phase winding HL High Potential Line LL Low-Potential Line PL positive input line NL Negative Input Line PT positive terminal NT negative terminal

Claims

1. First travel motor and second travel motor, A drive circuit that drives the first travel motor and the second travel motor, A DC power supply capable of supplying power to the aforementioned drive circuit, Equipped with, The power supply device is capable of outputting a first voltage and a second voltage lower than the first voltage. The aforementioned drive circuit is When the power of the first voltage is supplied, the first travel motor and the second travel motor are driven by the power of the first voltage. An electric vehicle that, when the power of the second voltage is supplied, uses the coil of the first travel motor to boost the power of the second voltage, and drives the second travel motor with the boosted power.

2. The electric vehicle according to claim 1, The coil of the first travel motor has multiple phase windings that are excited to form a rotating magnetic field by multiple phase alternating currents with different phases. The drive circuit has an inverter that uses a plurality of semiconductor switching elements to generate the plurality of phase alternating currents from the power supplied from the power supply device. An electric vehicle in which a boost circuit is formed by the multiple phase windings and the multiple semiconductor switching elements to boost the power of the second voltage.

3. The electric vehicle according to claim 2, The aforementioned drive circuit is A first drive circuit that includes the inverter and drives the first travel motor, The second drive circuit drives the second travel motor, A drive circuit switching unit that switches the configuration of the drive circuit between a first drive configuration and a second drive configuration, Equipped with, In the first drive configuration, the drive circuit switching unit connects the first drive circuit and the second drive circuit to the power supply in parallel with each other. In the second drive configuration, the drive circuit switching unit disconnects the connection between the positive terminal of the power supply and the positive input lines of the first drive circuit and the second drive circuit, respectively, connects the positive input lines of the first drive circuit and the second drive circuit in series with each other, and connects the neutral point of the first drive motor, to which the multiple phase windings are combined, to the positive terminal of the power supply.

4. An electric vehicle according to any one of claims 1 to 3, An electric vehicle further comprising a disconnection device for disconnecting / connecting a power transmission path between the first travel motor and the drive wheel to which power output from the first travel motor is transmitted.

5. An electric vehicle according to any one of claims 1 to 3, The first drive motor drives either the front wheel or the rear wheel of the electric vehicle. The second drive motor is an electric vehicle that drives the other of the front wheel and the rear wheel.

6. An electric vehicle according to any one of claims 1 to 3, The aforementioned power supply device is First battery and The second battery, Output circuit and, Equipped with, The output circuit has an output circuit switching unit that switches the configuration of the output circuit between a first output configuration and a second output configuration. In the first output configuration, the output circuit switching unit connects the first battery and the second battery in series with the output circuit, thereby causing the output circuit to output the first voltage. In the second output configuration, the output circuit switching unit disconnects one of the first battery and the second battery from the output circuit, thereby causing the output circuit to output the second voltage in the electric vehicle.

7. The electric vehicle according to claim 6, The output circuit switching unit includes a switch circuit that spans between the high-potential line and the low-potential line of the output circuit. The switch circuit includes a first switch, a second switch, and a third switch connected in series in order from the high-potential line side, The positive terminal of the first battery is connected to the switch circuit on the high-potential line side of the first switch. The negative terminal of the first battery is connected to the switch circuit between the second switch and the third switch. The positive terminal of the second battery is connected to the switch circuit between the first switch and the second switch. The negative terminal of the second battery is connected to the switch circuit on the low-potential line side of the third switch in this electric vehicle.

8. The electric vehicle according to claim 7, The first switch, the second switch, and the third switch are made of semiconductor switching elements. The output circuit switching unit is A first mechanical switch capable of disconnecting the connection between the positive terminal of the first battery and the switch circuit, An electric vehicle further comprising a second mechanical switch capable of disconnecting the connection between the negative terminal of the second battery and the switch circuit.

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