electric vehicles

Abstract

To provide a technique that can reduce electric charges remaining in a smoothing capacitor for charging.SOLUTION: A motor car comprises: a first motor; a battery that supplies power to the first motor; a first inverter that is provided between the battery and the first motor, and converts DC power from the battery into AC power to be supplied to the first motor; a charging inlet that is removably connected to an external charger, and receives charging power for charging the battery; a charging circuit that connects the charging inlet to the first inverter through a neutral point of the first motor; and a control unit that controls the operation of the first inverter. The charging circuit has a smoothing capacitor for charging provided between the charging inlet and the first motor. The control unit causes the first inverter to execute step-up operations after the charger completes charging the battery, thereby discharging electric charges accumulated in the smoothing capacitor for charging from the first inverter toward the battery.SELECTED DRAWING: Figure 2

Description

[Technical Field]

[0001] The technology disclosed in this specification relates to an electric vehicle. [Background technology]

[0002] Patent Document 1 discloses an electric vehicle that includes a motor that drives the wheels of the electric vehicle, a battery that supplies power to the traction motor, an inverter provided between the battery and the motor that converts DC power from the battery into AC power that is supplied to the motor, a charging inlet that is detachably connected to an external charging device and receives charging power for charging the battery, a charging circuit that connects the charging inlet to the inverter via the neutral point of the motor, and a control device that controls the operation of the inverter. The charging circuit has a charging smoothing capacitor provided between the charging inlet and the motor. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] U.S. Patent No. 11,171,504 Summary of the Invention [Problem to be solved by the invention]

[0004] In Patent Document 1, an electric vehicle receives charging power from a charging device to charge the battery. When the battery is being charged, charge accumulates in the charging smoothing capacitor. Therefore, when the battery charging is completed, charge still accumulates in the charging smoothing capacitor. There is a possibility that the charge accumulated in the charging smoothing capacitor may flow to an unintended path. Therefore, it is undesirable for charge to remain in the charging smoothing capacitor.

[0005] This specification provides a technique that can reduce the charge remaining in a charging smoothing capacitor. [Means for solving the problem]

[0006] In a first aspect disclosed in this specification, an electric vehicle includes a first motor that drives a first wheel of the electric vehicle, a battery that supplies power to the first motor, a first inverter disposed between the battery and the first motor and that converts DC power from the battery to AC power that is supplied to the first motor, a charging inlet that is detachably connected to an external charging device and that receives charging power for charging the battery, a charging circuit that connects the charging inlet to the first inverter via a neutral point of the first motor, and a control device that controls operation of the first inverter. The charging circuit has a charging smoothing capacitor disposed between the charging inlet and the first motor, and the control device causes the first inverter to perform a boost operation after charging of the battery by the charging device is completed, thereby discharging the charge accumulated in the charging smoothing capacitor from the first inverter to the battery.

[0007] According to the above configuration, the charge stored in the charging smoothing capacitor during battery charging is discharged from the first inverter to the battery side by the boost operation performed by the first inverter, thereby reducing the charge remaining in the charging smoothing capacitor.

[0008] In a second aspect, in the first aspect, the charging circuit may further include a first relay provided between the charging inlet and the charging smoothing capacitor, and the control device may electrically open the first relay before performing the voltage boosting operation.

[0009] When the first relay is electrically connected, charge accumulates in the charging smoothing capacitor and the charge cannot be discharged. With the above configuration, the charge accumulated in the charging smoothing capacitor can be discharged.

[0010] In a third aspect, in the first or second aspect, the electric vehicle may further include a second relay provided between the battery and the first inverter. The control device may electrically open the second relay before starting the voltage boost operation.

[0011] According to the above configuration, it is possible to prevent the charge stored in the charging smoothing capacitor from flowing to the battery, thereby preventing the battery from being unintentionally charged.

[0012] In a fourth aspect, the electric vehicle according to the third aspect may further include a running smoothing capacitor provided between the battery and the first inverter. The charging circuit may further include a third relay provided between the charging smoothing capacitor and the neutral point of the first motor. After completing the voltage step-up operation, the control device may electrically open the third relay, and after opening the third relay, control the first inverter to electrically connect the running smoothing capacitor and the first motor.

[0013] According to the above configuration, the charge stored in the charging smoothing capacitor flows to the traction smoothing capacitor due to the boost operation performed by the first inverter, and charge accumulates in the traction smoothing capacitor. After the boost operation is completed, the third relay is electrically opened, electrically connecting the traction smoothing capacitor to the first motor, and the charge stored in the traction smoothing capacitor flows to the first motor and is discharged. This prevents the charge stored in the traction smoothing capacitor from flowing to an unintended path.

[0014] In a fifth aspect, the electric vehicle includes a first motor that drives a first wheel of the electric vehicle, a battery that supplies power to the first motor, a first inverter that is provided between the battery and the first motor and converts DC power from the battery into AC power that is supplied to the first motor, a charging inlet that is detachably connected to an external charging device and receives charging power for charging the battery, a charging circuit that connects the charging inlet to the first inverter via the neutral point of the first motor, a second motor that drives a second wheel of the electric vehicle, second inverters that are provided between the battery and the second motor and between the battery and the first inverter and convert DC power from the battery into AC power that is supplied to the second motor, a specific relay that is provided between the battery and the second inverter, and a control device that controls operation of the first inverter and the second inverter. The charging circuit has a charging smoothing capacitor arranged between the charging inlet and the first motor, and the control device opens the specific relay after charging of the battery by the charging device is completed, and after opening the specific relay, controls the second inverter to electrically connect between the second inverter and the second motor, thereby discharging the charge stored in the charging smoothing capacitor from the second inverter.

[0015] According to the above configuration, the second inverter and the second motor are electrically connected, so that the charge stored in the charging smoothing capacitor flows through the first inverter and the second inverter to the second motor and is discharged, thereby reducing the charge remaining in the charging smoothing capacitor. [Brief explanation of the drawings]

[0016] [Figure 1] 1 shows a circuit diagram of a charging system 2 according to a first embodiment. [Figure 2] 3 shows a flowchart of a discharge process executed by the electric vehicle 10 of the first embodiment. [Figure 3]1 shows a circuit diagram of a charging system 2 when a voltage boosting operation is performed in a first embodiment. [Figure 4] 1 shows a circuit diagram of the charging system 2 when a first motor discharging operation is performed in the first embodiment. [Figure 5] 1 shows a circuit diagram of a charging system 202 according to a second embodiment. [Figure 6] 10 shows a flowchart of a discharge process executed by an electric vehicle 210 of a second embodiment. [Figure 7] 10 shows a circuit diagram of the charging system 202 when a second motor discharging operation is performed in the second embodiment. DETAILED DESCRIPTION OF THE INVENTION

[0017] (First Example) 1, the charging system 2 includes an electric vehicle 10 and a charging device 100. The electric vehicle 10 includes a battery 12, a system main relay 14, a running smoothing capacitor 16, a first inverter 20, a first motor 30, a charging circuit 40, a charging inlet 50, and a control device 70. The charging inlet 50 is detachably connected to the charging device 100 and receives charging power for charging the battery 12.

[0018] The battery 12 is a rechargeable secondary battery, typically a lithium ion battery, that has multiple built-in secondary battery cells (not shown), such as lithium ion cells, and is configured to be repeatedly charged and discharged. The battery 12 is connected to the first inverter 20 via a system main relay 14. The operation of the system main relay 14 is controlled by a control device 70.

[0019] The running smoothing capacitor 16 is provided between the battery 12 and the first inverter 20. The running smoothing capacitor 16 is provided to stabilize the voltage of the circuits of the electric vehicle 10.

[0020] The first inverter 20 is provided between the running smoothing capacitor 16 and the first motor 30. The first inverter 20 is a device that converts DC power from the battery 12 into AC power. The first inverter 20 includes three upper switching elements 22UH, 22VH, and 22WH and three lower switching elements 22UL, 22VL, and 22WL. Hereinafter, the "switching elements" will be referred to as "SW elements." The upper SW elements 22UH, 22VH, and 22WH are connected in series with the lower SW elements 22UL, 22VL, and 22WL, respectively.

[0021] The midpoint between the upper SW element 22UH and the lower SW element 22UL connected in series is electrically connected to the U-phase terminal 32 of the first motor 30. As a result, the upper SW element 22UH and the lower SW element 22UL form a pair of upper and lower U-phase arms that connect the U-phase terminal 32 of the first motor 30 to the positive or negative electrode of the battery 12. Similarly, the upper SW element 22VH and the lower SW element 22VL connected in series form a pair of upper and lower V-phase arms, the midpoint between which is electrically connected to the V-phase terminal 34 of the first motor 30. Furthermore, the upper SW element 22WH and the lower SW element 22WL connected in series form a pair of upper and lower W-phase arms, the midpoint between which is electrically connected to the W-phase terminal 36 of the first motor 30. The operation of the three lower SW elements 22UL, 22VL, and 22WL and the operation of the three lower SW elements 22UL, 22VL, and 22WL are controlled by a control device 70.

[0022] First motor 30 is a three-phase AC motor that drives the front wheels of electric vehicle 10 using power supplied from battery 12. First motor 30 includes a U-phase coil 32A, a W-phase coil 36B, and a W-phase coil 36C. One end of U-phase coil 32A, W-phase coil 36B, and W-phase coil 36C is connected to U-phase terminal 32, V-phase terminal 34, and W-phase terminal 36, respectively. The other ends of U-phase coil 32A, W-phase coil 36B, and W-phase coil 36C are connected to one another at neutral point 30A.

[0023] The charging circuit 40 is a circuit for supplying power from the charging device 100 to the battery 12. The charging circuit 40 includes a first charging relay 42, a charging smoothing capacitor 44, and a second charging relay 46. The charging smoothing capacitor 44 is provided between the first motor 30 and the charging inlet 50. The charging smoothing capacitor 44 is provided to stabilize the voltage of the charging circuit 40. The first charging relay 42 is provided between the neutral point 30A of the first motor 30 and the first charging relay 42. The second charging relay 46 is provided between the charging inlet 50 and the charging smoothing capacitor 44. The operation of the first charging relay 42 and the second charging relay 46 is controlled by the control device 70.

[0024] The control device 70 is a computer including a CPU. The control device 70 controls the operation of the system main relay 14, the upper switching elements 22UH, 22VH, and 22WH, the lower switching elements 22UL, 22VL, and 22WL, the first charging relay 42, and the second charging relay 46.

[0025] The charging process executed by the control device 70 will be described. The control device 70 starts the charging process when the charging device 100 is connected to the charging inlet 50. First, as shown in FIG. 1 , the control device 70 electrically connects the system main relay 14, the first charging relay 42, and the second charging relay 46. In this embodiment, the voltage of the charging power received by the electric vehicle 10 from the charging device 100 via the charging inlet 50 is lower than the rated voltage of the battery 12. Therefore, the control device 70 performs a voltage boost operation to charge the battery 12. Specifically, the control device 70 repeatedly turns on and off at least one of the lower switching devices 22UL, VL, and WL while keeping the upper switching devices 22UH, 22VH, and 22WH off. The control device 70 controls the duty ratio of the lower switching devices to be turned on and off. The control device 70 may symmetrically turn on and off the upper switching elements 22UH, 22VH, and 22WH in synchronization with the repeatedly turned on and off lower switching elements 22UL, VL, and WL. For example, a case where the lower switching element 22UL is turned on and off will be described. When the lower switching element 22UL is turned on, a current flows through the U-phase coil 32A and the lower switching element 22UL. Energy is stored in the U-phase coil 32A. When the lower switching element 22UL is turned off in this state, the energy stored in the U-phase coil 32A is superimposed on the power from the battery. As a result, the voltage of the power supplied from the first inverter 20 to the battery 12 is boosted. This charges the battery 12. At this time, charge is also stored in the charging smoothing capacitor 44.

[0026] (Discharge treatment; Figure 2) The discharge process executed by the control device 70 of the electric vehicle 10 will be described with reference to Fig. 2. When the charging process is completed, the control device 70 starts the process of Fig. 2. As a result, after the charging process is completed, the charge accumulated in the charging smoothing capacitor 44 is discharged.

[0027] The control device 70 electrically opens the system main relay 14 in S10, and electrically opens the second charging relay 46 in S12 (see FIG. 3).

[0028] In S14, the control device 70 causes the first inverter 20 to perform a boost operation. The boost operation in S14 is the same as the boost operation performed during the charging process. As a result, the charge accumulated in the charging smoothing capacitor 44 during the charging process flows toward the battery 12. The charge that has flowed toward the battery 12 is then accumulated in the running smoothing capacitor 16.

[0029] In S16, the control device 70 monitors whether the voltage of the charging smoothing capacitor 44 has become equal to or lower than the first threshold. In this embodiment, when the time elapsed since the start of the voltage boosting operation is equal to or greater than a first predetermined time, the control device 70 determines that the voltage of the charging smoothing capacitor 44 has become equal to or lower than the first threshold, determines YES in S16, and proceeds to S18. The first predetermined time is a time sufficient for the voltage of the charging smoothing capacitor 44 to become equal to or lower than the first threshold. In a modified example, the control device 70 may use a voltage sensor that detects the voltage of the charging smoothing capacitor 44 to determine that the voltage of the charging smoothing capacitor 44 has become equal to or lower than the first threshold.

[0030] In S18, the control device 70 causes the first inverter 20 to end the voltage step-up operation.

[0031] In S20, the control device 70 electrically opens the first charging relay 42 (see FIG. 4).

[0032] In S22, the control device 70 executes a first motor discharging operation using the first motor 30. The first motor discharging operation is executed to discharge the charge accumulated in the running smoothing capacitor 16 by energizing the first motor 30 so as not to generate torque. For example, the control device 70 turns on the upper SW element 22UH of the U-phase arm and the lower SW element 22VL of the V-phase arm. This electrically connects the running smoothing capacitor 16 to the first motor 30 via the first inverter 20. As a result, the charge accumulated in the running smoothing capacitor 16 is discharged.

[0033] In S24, the control device 70 monitors whether the voltage of the running smoothing capacitor 16 has become equal to or lower than the second threshold. In this embodiment, when the time elapsed since the start of the motor discharging operation is equal to or greater than a second predetermined time, the control device 70 determines that the voltage of the running smoothing capacitor 16 has become equal to or lower than the second threshold, determines YES in S24, and proceeds to S26. The second predetermined time is a time sufficient for the voltage of the running smoothing capacitor 16 to become equal to or lower than the second threshold. In a modified example, the control device 70 may use a voltage sensor that detects the voltage of the running smoothing capacitor 16 to determine that the voltage of the running smoothing capacitor 16 has become equal to or lower than the second threshold.

[0034] In S26, the control device 70 ends the motor discharging operation. After S26 is completed, the control device 70 ends the processing of FIG.

[0035] As described above, the electric vehicle 10 includes a first motor 30 that drives the front wheels (an example of a "first wheel") of the electric vehicle 10, a battery 12 that supplies power to the first motor 30, a first inverter 20 that is provided between the battery 12 and the first motor 30 and converts DC power from the battery 12 into AC power that is supplied to the first motor 30, a charging inlet 50 that is detachably connected to an external charging device 100 and receives charging power for charging the battery 12, a charging circuit 40 that connects the charging inlet 50 to the first inverter 20 via the neutral point 30A of the first motor 30, and a control device 70 that controls the operation of the first inverter 20. The charging circuit 40 has a charging smoothing capacitor 44 arranged between the charging inlet 50 and the first motor 30, and after charging of the battery 12 by the charging device 100 is completed, the control device 70 causes the first inverter 20 to perform a boost operation, thereby discharging the charge accumulated in the charging smoothing capacitor 44 from the first inverter 20 to the battery 12 side (S14 in Figure 2).

[0036] According to the above configuration, the charge stored in the charging smoothing capacitor 44 during charging of the battery 12 is discharged from the first inverter 20 to the battery 12 by the boost operation performed by the first inverter 20. Therefore, after charging of the battery 12 is completed, the charge stored in the charging smoothing capacitor 44 can be quickly discharged.

[0037] The charging circuit 40 also includes an example of a second charging relay 46 ("first relay") provided between the charging inlet 50 and the charging smoothing capacitor 44. Before performing the boost operation, the control device 70 electrically opens the second charging relay 46 (S12 in FIG. 2).

[0038] According to the above configuration, the charge stored in the charging smoothing capacitor 44 can be discharged.

[0039] The electric vehicle 10 further includes a system main relay 14 (an example of a "second relay") provided between the battery 12 and the first inverter 20. Before starting the voltage boosting operation, the control device 70 electrically opens the system main relay 14 (S10 in FIG. 2).

[0040] According to the above configuration, the charge stored in the charging smoothing capacitor 44 flows to the battery 12, and it is possible to prevent the battery 12 from being unintentionally charged.

[0041] The electric vehicle 10 also includes a running smoothing capacitor 16 provided between the battery 12 and the first inverter 20. The charging circuit 40 also includes a first charging relay 42 (an example of a "third relay") provided between the charging smoothing capacitor 44 and the neutral point 30A of the first motor 30. After completing the voltage step-up operation, the control device 70 electrically opens the first charging relay 42 (S20 in FIG. 2), and after opening the first charging relay 42, controls the first inverter 20 to electrically connect the running smoothing capacitor 16 and the first motor 30 (S22).

[0042] According to the above configuration, the charge stored in the charging smoothing capacitor 44 flows to the running smoothing capacitor 16 due to the voltage boost operation performed by the first inverter 20, and charge accumulates in the running smoothing capacitor 16. After the voltage boost operation is completed, the first charging relay 42 is electrically opened, and the running smoothing capacitor 16 and the first motor 30 are electrically connected, so that the charge stored in the running smoothing capacitor 16 flows to the first motor 30 and is discharged. This makes it possible to prevent the charge stored in the running smoothing capacitor 16 from flowing to an unintended path.

[0043] (Second Example) A charging system 202 of the second embodiment will be described. In this embodiment, the configuration of an electric vehicle 210 differs from the configuration of the electric vehicle 10 of the first embodiment. Note that components common to the embodiments are given the same reference numerals and descriptions thereof will be omitted.

[0044] The electric vehicle 210 includes a second inverter 220 and a second motor 230. The configuration of the second inverter 220 is similar to that of the first inverter 20. The second inverter 220 is provided between the battery 12 and the running smoothing capacitor 16. The configuration of the second motor 230 is similar to that of the first motor 30. The second motor 230 is a three-phase AC motor that drives the rear wheels of the electric vehicle 10 using power supplied from the battery 12. The second motor 230 is connected to the second inverter 220.

[0045] (Discharge treatment; Figure 6) The discharge process executed by the control device 70 of the electric vehicle 210 will be described with reference to Fig. 6. S110 and S112 in Fig. 6 are the same as S10 and S112 in Fig. 2, respectively.

[0046] In S114, the control device 70 executes a second motor discharging operation using the second motor 230. In the second motor discharging operation, the control device 70 controls the second inverter 220 to electrically connect the charging smoothing capacitor 44 to the second motor 230 via the first inverter 20 and the second inverter 220. As a result, the charge stored in the charging smoothing capacitor 44 is discharged through the second motor 230 via the first inverter 20 (more specifically, the freewheeling diodes of the upper switching elements 22UH, 22VH, 22WH and the lower switching elements 22UL, 22VL, 22WL) and the second inverter 220.

[0047] S116 is the same as S16 in Fig. 2. In S118, the control device 70 ends the second motor discharging operation. When S118 ends, the control device 70 ends the processing in Fig. 6. In a modified example, the control device 70 may execute the processing of S114 while executing the voltage boosting operation of S14 in Fig. 2.

[0048] As described above, the electric vehicle 210 includes the first motor 30, the battery 12, the first inverter 20, the charging inlet 50, the charging circuit 40, the second motor 230 that drives the rear wheels (an example of a "second wheel") of the electric vehicle 210, the second inverter 220 that is provided between the battery 12 and the second motor 230 and between the battery 12 and the first inverter 20 and that converts DC power from the battery 12 into AC power that is supplied to the second motor 230, the system main relay 14 (an example of a "specific relay") that is provided between the battery 12 and the second inverter 220, and the control device 70 that controls the operation of the first inverter 20 and the second inverter 220. The charging circuit 40 has a charging smoothing capacitor 44 arranged between the charging inlet 50 and the first motor 30, and after charging of the battery 12 by the charging device 100 is completed, the control device 70 opens the system main relay 14 (S110 in FIG. 6), and after opening the system main relay 14, controls the second inverter 220 to electrically connect the second inverter 220 and the second motor 230, thereby discharging the charge accumulated in the charging smoothing capacitor 44 from the second inverter 220 (S114 in FIG. 6).

[0049] According to the above configuration, the second inverter 220 and the second motor 230 are electrically connected, so that the charge stored in the charging smoothing capacitor 44 flows to the second motor 230 via the first inverter 20 and the second inverter 220 and is discharged. Therefore, the charge remaining in the charging smoothing capacitor 44 can be reduced.

[0050] Although specific examples of the technology disclosed in this specification have been described in detail above, these are merely examples and do not limit the scope of the claims. The technology described in the claims includes various modifications and variations of the specific examples exemplified above. Modifications of the above examples are listed below.

[0051] (First Modification) The control device 70 may electrically open the system main relay 14 after S14 in FIG.

[0052] (Second Modification) S12 in FIG. 2 can be omitted.

[0053] The technical elements described in this specification or drawings may exhibit technical utility either alone or in various combinations, and are not limited to the combinations described in the claims at the time of filing. Furthermore, the technologies illustrated in this specification or drawings may achieve multiple objectives simultaneously, and achieving one of those objectives alone is technically useful. [Explanation of symbols]

[0054] 2: Charging system, 10: electric vehicle, 12: battery, 14: system main relay, 16: running smoothing capacitor, 20: first inverter, 22UH: upper switch element, 22UL: lower switch element, 22VH: upper switch element, 22VL: lower switch element, 22WH: upper switch element, 22WL: lower switch element, 30: first motor, 30A: neutral point, 32: U-phase terminal, 32A: U-phase coil, 34: V-phase terminal, 36: W-phase terminal, 36B: W-phase coil, 36C: W-phase coil, 40: charging circuit, 42: first charging relay, 44: charging smoothing capacitor, 46: second charging relay, 50: charging inlet, 70: control device, 100: charging device, 202: charging system, 210: electric vehicle, 220: second inverter, 230: second motor

Claims

[Claim 1] An electric vehicle, a first motor that drives a first wheel of the electric vehicle; a battery that supplies power to the first motor; a first inverter provided between the battery and the first motor, the first inverter converting DC power from the battery into AC power to be supplied to the first motor; a charging inlet that is detachably connected to an external charging device and that receives charging power for charging the battery; a charging circuit connecting the charging inlet to the first inverter via a neutral point of the first motor; a second motor that drives a second wheel of the electric vehicle; a second inverter provided between the battery and the second motor and between the battery and the first inverter, and configured to convert DC power from the battery into AC power to be supplied to the second motor; a specific relay provided between the battery and the second inverter; a control device that controls operations of the first inverter and the second inverter; Equipped with the charging circuit includes a charging smoothing capacitor provided between the charging inlet and the first motor, The control device After the charging device has finished charging the battery, the specific relay is opened; and after opening the specific relay, controlling the second inverter to electrically connect the second inverter and the second motor, thereby discharging the charge stored in the charging smoothing capacitor from the second inverter.

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