Electric vehicle

Abstract

To provide an electric vehicle capable of turning on a system main relay while preventing exposure of a high voltage to an inlet even when a charging relay is welded.SOLUTION: In an electric vehicle in which electric power supplied from an external power supply via an inlet during external charging of a battery is supplied to the battery via a path of electric power, a control device performs welding diagnosis of a charging relay and a neutral point relay after completion of the external charging of the battery and, when it is diagnosed that the charging relay and the neutral point relay are welded, the control device turns on a system main relay while the path of electric power is cut off by a component other than the charging relay and the neutral point relay.SELECTED DRAWING: Figure 3

Description

Technical Field

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

Background Art

[0002] Patent Document 1 discloses an electric vehicle capable of external charging. In the configuration described in Patent Document 1, when the external connector is unexpectedly disconnected from the vehicle-side inlet or when charging is forcibly terminated by removing the external connector from the vehicle-side inlet, the charging relay is turned off, and the charging relay is diagnosed for welding abnormality with the system main relay turned on.

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] In the configuration described in Patent Document 1, when diagnosing the welding of the charging relay, the charging relay is turned off and the system main relay is turned on. Therefore, when the charging relay is welded, a high voltage is exposed at the inlet during the diagnosis.

[0005] The present invention has been made in view of the above circumstances, and an object thereof is to provide an electric vehicle capable of turning on the system main relay while preventing the exposure of a high voltage to the inlet even when the charging relay is welded.

Means for Solving the Problems

[0006] The present invention relates to an electric vehicle comprising a three-phase AC rotating electric machine, an inverter for driving the three-phase AC rotating electric machine, a battery for storing electric power to be supplied to the three-phase AC rotating electric machine, a system main relay provided between the battery and the inverter, an inlet to which a connector on the power supply equipment side connected to an external power supply is connected, a charging relay for connecting or disconnecting a power path from the inlet to the battery, and a control device. When externally charging the battery, electric power supplied from the external power supply via the inlet is supplied to the battery via the power path. The electric vehicle is characterized in that a neutral point relay provided in the power path and connected to a neutral point to which one end of a three-phase coil of the three-phase AC rotating electric machine is connected. The control device executes welding diagnosis of the charging relay and the neutral point relay after completion of external charging of the battery. When it is diagnosed that the charging relay and the neutral point relay are welded, the system main relay is turned on while the power path is blocked by a component different from the charging relay and the neutral point relay provided in the power path.

Effects of the Invention

[0007] In the present invention, even when the charging relay and the neutral point relay are welded, the system main relay can be turned on while preventing exposure of high voltage to the inlet.

Brief Description of the Drawings

[0008]

Figure 1

Figure 2

Figure 3

Figure 4

Embodiments for Carrying Out the Invention

[0009] Hereinafter, the electric vehicle according to the embodiment of the present invention will be specifically described. Note that the present invention is not limited to the embodiments described below.

[0010] FIG. 1 is a diagram schematically showing an electric vehicle according to an embodiment. The electric vehicle 1 is configured to be rechargeable with electric power supplied from outside the vehicle. The electric vehicle 1 includes a motor 2, a battery 3, an inverter 4, a DC inlet 5, a system main relay 6, a charging relay 7, a neutral point relay 8, a drive device (MG+INV) 9, and a control device (ECU) 10.

[0011] The motor 2 is a three-phase AC rotating electric machine and is a motor generator having the functions of an electric motor and a generator. In the electric vehicle 1, the wheels are driven by the power output from the motor 2. The motor 2 is a synchronous motor including a rotor in which permanent magnets are embedded and a stator around which a three-phase coil is wound. The three-phase coils (U-phase, V-phase, W-phase) wound around the stator of the motor 2 are electrically connected to the inverter 4. One end of the three-phase coils is commonly connected to the neutral point. The other end of the three-phase coils is connected to the inverter 4. When a three-phase voltage is applied to the motor 2 by the inverter 4, a three-phase current flows through the three-phase coils of the motor 2, and torque is generated in the motor 2. The motor 2 can generate electricity by regenerative braking. The electric power generated by the motor 2 is stored in the battery 3.

[0012] The battery 3 is a DC power source and is a storage battery capable of charging and discharging. The battery 3 is composed of a secondary battery such as a lithium ion battery or a nickel metal hydride battery, for example. The battery 3 stores the electric power used for the running of the electric vehicle 1. When the electric vehicle 1 is running, the battery 3 supplies the electric power for generating the driving force of the electric vehicle 1 to the inverter 4. When the electric vehicle 1 is performing regenerative braking, the battery 3 stores the electric power generated by the motor 2.

[0013] The inverter 4 is a power conversion device that drives the motor 2. The inverter 4 converts the DC power supplied from the battery 3 into AC power and outputs it to the motor 2. The inverter 4 converts the power supplied from the motor 2 side into power suitable for charging and supplies it to the battery 3. When power is supplied to the inverter 4 from the motor 2 side, it includes the case where regenerative power generation is performed by the motor 2 and the case where external charging using the DC inlet 5 is performed. When storing the power generated by the motor 2 in the battery 3, the inverter 4 converts the AC power supplied from the motor 2 into DC power and outputs it to the battery 3. When performing external charging, the inverter 4 boosts the voltage of the DC power supplied from the external power source via the DC inlet 5 and supplies it to the battery 3. During external charging, the inverter 4 converts the DC power supplied from the DC inlet 5 into DC power suitable for the battery 3.

[0014] The inverter 4 is composed of an inverter circuit provided with a plurality of switching elements so as to be able to energize three-phase currents to the three-phase coils of the motor 2. The inverter 4 includes first to sixth switching elements SW1 to SW6. Diodes are connected in anti-parallel to each of the switching elements SW1 to SW6. Each of the switching elements SW1 to SW6 is composed of an IGBT or an MOFET.

[0015] In the inverter 4, the U-phase arm, the V-phase arm, and the W-phase arm are connected in parallel. The U-phase arm is an upper and lower arm in which the first switching element SW1 and the second switching element SW2 are connected in series. The first switching element SW1 is the upper arm, and the second switching element SW2 is the lower arm. The V-phase arm is an upper and lower arm in which the third switching element SW3 and the fourth switching element SW4 are connected in series. The third switching element SW3 is the upper arm, and the fourth switching element SW4 is the lower arm. The W-phase arm is an upper and lower arm in which the fifth switching element SW5 and the sixth switching element SW6 are connected in series. The fifth switching element SW5 is the upper arm, and the sixth switching element SW6 is the lower arm. In the inverter 4, each of the three-phase coils of the motor 2 is connected to each of the connection points of the paired switching elements. The other end of the U-phase coil is connected to the connection point between the first switching element SW1 and the second switching element SW2. The other end of the V-phase coil is connected to the connection point between the third switching element SW3 and the fourth switching element SW4. The other end of the W-phase coil is connected to the connection point between the fifth switching element SW5 and the sixth switching element SW6. Each switching element of the inverter 4 performs a switching operation according to a control signal from the control device 10. The inverter 4 includes a capacitor C1 connected in parallel with each upper and lower arm.

[0016] The DC inlet 5 is an inlet to which a connector on the power supply equipment side connected to an external power supply is connected. A DC connector provided in the power supply equipment can be connected to the DC inlet 5. For example, a DC connector connected to a DC charging cable of a charging stand is connected to the DC inlet 5. When performing external charging, the DC inlet 5 is electrically connected to the battery 3 via the motor 2 and the inverter 4. The motor 2 and the inverter 4 function as a charger during external charging using the DC inlet 5.

[0017] The system main relay 6 is a relay used for the running of the electric vehicle 1 etc. The system main relay 6 is provided between the battery 3 and the inverter 4. The inverter 4 is electrically connected to the battery 3 via the system main relay 6. The system main relay 6 is provided between the battery 3 and the drive device 9. The inverter of the drive device 9 is electrically connected to the battery 3 via the system main relay 6. The system main relay 6 includes a positive-side relay 6A provided on the power line connected to the positive terminal of the battery 3, and a negative-side relay 6B provided on the power line connected to the negative terminal of the battery 3. The system main relay 6 is opened (OFF) or closed (ON) according to the control signal from the control device 10. When the electric vehicle 1 runs, the power of the battery 3 is supplied to the driving motor with the system main relay 6 being in the ON state.

[0018] When the system main relay 6 is turned on, the battery 3 and the inverter 4 become conductive, and power can be transferred between the battery 3 and the inverter 4. In the state where the system main relay 6 is turned on, the battery 3 and the drive device 9 become conductive, and power can be transferred between the battery 3 and the drive device 9. When the system main relay 6 is turned off, the battery 3 and the inverter 4 are in an electrically disconnected state, and the battery 3 and the drive device 9 are in an electrically disconnected state.

[0019] The charging relay 7 connects or disconnects the power path from the DC inlet 5 to the battery 3. The charging relay 7 is provided between the DC inlet 5 and the battery 3. The charging relay 7 includes a positive-side relay 7A connected to the positive terminal of the DC inlet 5, and a negative-side relay 7B connected to the negative terminal of the DC inlet 5. The opening (OFF) and closing (ON) of the charging relay 7 are controlled according to the control signal from the control device 10. When the charging relay 7 is turned on, external charging of the battery 3 using the DC inlet 5 becomes possible. When the charging relay 7 is turned off, the DC inlet 5 and the battery 3 are electrically disconnected.

[0020] The neutral point relay 8 is a relay connected to the neutral point of the three-phase coil of the motor 2. The neutral point relay 8 is provided in the power path from the DC inlet 5 to the battery 3. The neutral point relay 8 is provided between the neutral point of the three-phase coil of the motor 2 and the positive-side relay 7A of the charging relay 7. A capacitor C2 is connected to the power line between the neutral point relay 8 and the charging relay 7. The opening (OFF) and closing (ON) of the neutral point relay 8 are controlled according to a control signal from the control device 10. When the neutral point relay 8 is turned on, the capacitor C2 is electrically connected to the motor 2 and the inverter 4. When the neutral point relay 8 is turned off, the capacitor C2 is disconnected from the motor 2 and the inverter 4. The neutral point relay 8 disconnects the capacitor C2 during the running of the electric vehicle 1. During the running of the electric vehicle 1, the neutral point relay 8 is turned off.

[0021] The drive device 9 includes a motor generator (MG) having the functions of a motor and a generator, and an inverter (INV) that drives this motor generator. The drive device 9 can only be used for the running of the electric vehicle 1. The inverter of the drive device 9 converts the DC power supplied from the battery 3 into AC power and outputs it to the motor generator. On the other hand, the drive device including the motor 2 and the inverter 4 can be used for the running of the electric vehicle 1 and can also be used for external charging. During external charging using the DC inlet 5, the motor 2 and the inverter 4 boost the voltage of the charging stand to charge the battery 3.

[0022] The control device 10 is configured to include a microcomputer having a CPU, a RAM, a ROM, and an input / output interface. The control device 10 performs signal processing according to a program pre-stored in the ROM. Signals from various sensors mounted on the electric vehicle 1 are input to the control device 10. For example, signals from a voltage sensor 21 that detects the voltage of the DC inlet 5 and the like are input to the control device 10. The control device 10 executes various controls based on the signals input from the various sensors. Control signals for controlling the system main relay 6, control signals for controlling the inverter 4, control signals for controlling the neutral point relay 8, control signals for controlling the charging relay 7, control signals for controlling the drive device 9, and the like are output from the control device 10.

[0023] In the electric vehicle 1 configured as described above, since boost charging via the neutral point of the motor 2 is employed during external charging using the DC inlet 5, if the charging relay 7 and the neutral point relay 8 are welded, as shown in FIG. 2, there is a possibility that a high voltage is exposed at the terminals of the DC inlet 5, and thus the system main relay 6 cannot be turned on. If the system main relay 6 cannot be turned on, the electric vehicle 1 cannot run. Therefore, in the electric vehicle 1, even when the charging relay 7 and the neutral point relay 8 are welded, it is configured to be able to turn on the system main relay 6 while preventing the exposure of a high voltage to the terminals of the DC inlet 5.

[0024] The control device 10 executes welding diagnosis control for diagnosing the welding of the charging relay 7 and the neutral point relay 8. The control device 10 performs welding diagnosis of the charging relay 7 and the neutral point relay 8 based on the voltage value input from the voltage sensor 21. The control device 10 determines whether the voltage value of the voltage sensor 21 is greater than a threshold value with the system main relay 6 turned on and the charging relay 7 and the neutral point relay 8 turned off. When the voltage value of the voltage sensor 21 is greater than the threshold value, the control device 10 determines that the charging relay 7 and the neutral point relay 8 are welded. When the voltage value of the voltage sensor 21 is equal to or less than the threshold value, the control device 10 determines that the charging relay 7 and the neutral point relay 8 are not welded.

[0025] When the control device 10 determines that the charging relay 7 and the neutral point relay 8 are welded, as shown in FIG. 2, in order to cut off the power path from the DC inlet 5 to the battery 3, the upper arm of the inverter 4 to which the charging relay 7 is connected is turned off. With the upper arm of the inverter 4 turned off, the control device 10 uses the drive device 9 to drive the electric vehicle 1.

[0026] FIG. 3 is a flowchart showing welding diagnosis control. The control shown in FIG. 3 is implemented by the control device 10.

[0027] The control device 10 detects that the charging has ended (step S1). In step S1, it is detected that the external charging of the battery 3 using the DC inlet 5 has ended.

[0028] The control device 10 performs welding diagnosis on the charging relay 7 (DC relay) and the neutral point relay 8 (step S2). In step S2, the welding diagnosis control by the control device 10 is executed. The control device 10 determines whether the result of the welding diagnosis is normal (step S3).

[0029] If it is determined in the determination process of step S3 that the result of the welding diagnosis is normal, the control device 10 determines that the electric vehicle 1 can run normally (step S4). When the process of step S4 is performed, this control routine ends.

[0030] If it is determined in the determination process of step S3 that the result of the welding diagnosis is abnormal, the control device 10 turns off the upper arm of the inverter 4 to which the charging relay 7 is connected (step S5). In step S5, the first switching element SW1, the third switching element SW3, and the fifth switching element SW5 of the inverter 4 are turned off. When the upper arm of the inverter 4 is turned off, the power path from the DC inlet 5 to the battery 3 shown by the thick line in FIG. 2 is cut off. The upper arm of the inverter 4 is a component different from the charging relay 7 and the neutral point relay 8 provided in the power path from the DC inlet 5 to the battery 3.

[0031] The control device 10 travels using the remaining inverter and motor generator (step S6). In step S6, it travels using the drive device 9. The control device 10 causes the electric vehicle 1 to travel using the drive device 9 with the system main relay 6 turned on. When the process of step S6 is executed, this control routine ends.

[0032] As described above, according to the embodiment, even when the charging relay 7 and the neutral point relay 8 are welded, by turning off the upper arm of the inverter 4 connected to the charging relay 7, it is possible to prevent a high voltage from being exposed at the terminals of the DC inlet 5. Therefore, it is possible to turn on the system main relay 6. It is possible to turn on the system main relay 6 and travel using the drive device 9 which is the remaining motor generator and inverter.

[0033] Note that the electric circuit provided in the electric vehicle 1 is not limited to the example shown in FIG. 1. For example, as shown in FIG. 4, it is possible to configure a modified example of the electric vehicle 1.

[0034] The modified example of the electric vehicle 1 does not include the drive device 9 and includes a pilot fuse 22. The pilot fuse 22 shuts off the path of DC charging. The pilot fuse 22 is provided between the charging relay 7 and the capacitor C2. The pilot fuse 22 includes a positive electrode side pilot fuse 22A provided between the positive electrode side relay 7A of the charging relay 7 and the capacitor C2, and a negative electrode side pilot fuse 22B provided between the negative electrode side relay 7B of the charging relay 7 and the capacitor C2.

[0035] When the control device 10 determines that the charging relay 7 and the neutral point relay 8 are welded, it shuts off the pilot fuse 22. That is, in the electric vehicle 1 of the modified example, the control device 10 can execute welding diagnosis control by changing a part of the processing flow shown in FIG. 3. The control device 10 of the modified example executes a process of shutting off the pilot fuse 22 instead of step S5 in FIG. 3, and can drive the electric vehicle 1 using the motor 2 and the inverter 4 instead of step S6 in FIG. 3.

[0036] According to the electric vehicle 1 of the modified example, even when the charging relay 7 and the neutral point relay 8 are welded, by shutting off the pilot fuse 22, it is possible to prevent the exposure of high voltage to the terminals of the DC inlet 5.

[0037] Also, in the electric vehicle 1 of the modified example, it is not limited to the configuration shown in FIG. 4, and a drive device 9 may be provided. In this case, in a state where the pilot fuse 22 is shut off, the vehicle may be driven using either the drive device including the motor 2 and the inverter 4 or the drive device 9.

Description of Reference Numerals

[0038] 1 Electric vehicle 2 Motor (Three-phase AC rotating electric machine) 3 Battery 4 Inverter 5 DC Inlet (Inlet) 6 System Main Relay 7 Charging Relay 8 Neutral Point Relay 10 Control Device (ECU)

Claims

【Claim 1】 A three-phase AC rotating electric machine, an inverter that drives the three-phase AC rotating electric machine, a battery that stores electric power to be supplied to the three-phase AC rotating electric machine, a system main relay provided between the battery and the inverter, an inlet to which a connector on the power supply equipment side connected to an external power supply is connected, a charging relay that connects or disconnects the power path from the inlet to the battery, a control device, comprising: an electric vehicle in which, when externally charging the battery, electric power supplied from the external power supply through the inlet is supplied to the battery via the power path, a neutral point relay provided in the power path and connected to a neutral point to which one end of a three-phase coil of the three-phase AC rotating electric machine is connected, wherein the control device: performs welding diagnosis of the charging relay and the neutral point relay after completion of external charging of the battery, and when it is diagnosed that the charging relay and the neutral point relay are welded, turns on the system main relay with the power path blocked by a component other than the charging relay and the neutral point relay provided in the power path characterized in that it is an electric vehicle.

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