JP7806743B2 - electric car - Google Patents

Description

This disclosure relates to an electric vehicle, and more particularly to an electric vehicle equipped with a battery, a three-phase AC motor, and a DC charger that charges the battery using external DC power.

Conventionally, one proposed electric vehicle of this type includes a battery, a three-phase AC motor, an inverter connected to the battery via a power line and using power from the battery to drive the three-phase AC motor, and a charger connected to the neutral point of the three-phase AC motor via a relay and using external power to charge the battery (see, for example, Patent Document 1). In this electric vehicle, the charger is equipped with a leakage detection circuit that detects ground faults and a breaker that cuts off the power when a ground fault is detected, as well as a ground fault circuit interrupter that includes a ground fault test relay and a ground fault resistor. During charging, the ground fault test relay is closed to forcibly short-circuit the circuit, and the function of the breaker relay is confirmed.

Japanese Patent Application Publication No. 11-205909

However, in the electric vehicles mentioned above, the earth leakage breaker needs to be equipped with an additional earth leakage test relay and earth leakage resistor to determine if the cut-off relay has failed, which makes the configuration more complex and increases the size of the earth leakage breaker.

The primary purpose of the electric vehicle disclosed herein is to determine a continuity fault in the interrupter circuit without adding any additional components.

The electric vehicle disclosed herein employs the following measures to achieve the above-mentioned primary objective.

The electric vehicle of the present disclosure includes:
An electric vehicle including: a battery; a three-phase AC motor; an inverter that drives the three-phase AC motor using power from the battery; a system main relay with a pre-charge function that is provided in a power line that connects the battery and the inverter; a DC charger that charges the battery using external DC power supplied from an external charging connector; and a control device,
The DC charger includes a charging power line connected between the external charging connector and the inverter on the power line, a bypass relay attached to a positive side line of the charging power line, a neutral point charging line connecting a neutral point of the three-phase AC motor to the external charging connector on the positive side line of the charging power line and the bypass relay, a neutral point relay attached to the neutral point charging line, and a power line connected from the neutral point relay on the neutral point charging line to the external charging connector. a neutral point side interrupting circuit connected to the external charging connector side of the charging power line, a negative side interrupting circuit attached to the negative side line of the charging power line, a capacitor connected to the power line side of the negative side line of the charging power line from the negative side interrupting circuit and between the neutral point relay and the neutral point side interrupting circuit of the neutral point charging line, and a voltage sensor connected to the external charging connector side of the neutral point side interrupting circuit of the neutral point charging line and to the external charging connector side of the negative side line of the charging power line,
the control device determines that a continuity fault has occurred in the negative side shutoff circuit when a voltage rise is detected by the voltage sensor while the inverter is controlled so that the voltage of the capacitor becomes a first predetermined voltage with the system main relay and the neutral point relay turned on and the neutral point side shutoff circuit and the negative side shutoff circuit turned off (shut off),
It is characterized by:

In the electric vehicle disclosed herein, the inverter is controlled to maintain the capacitor voltage at a first predetermined voltage with the system main relay and neutral relay turned on and the neutral-side shutoff circuit and negative-side shutoff circuit turned off (shut off). When a voltage rise is detected by voltage sensors connected to the neutral-side shutoff circuit on the external charging connector side of the neutral charging line and the negative-side shutoff circuit on the negative side of the charging power line on the external charging connector side, a continuity fault is determined to have occurred in the negative-side shutoff circuit. This is based on the fact that when there is no continuity fault in the negative-side shutoff circuit, the voltage detected by the voltage sensor does not change. As a result, a continuity fault in the negative-side shutoff circuit can be determined without the need for additional configuration.

In the electric vehicle disclosed herein, the control device may turn on the neutral point side interrupting circuit (release interruption) when it determines that no continuity fault has occurred in the negative pole side interrupting circuit, and determine that a continuity fault has occurred in the neutral point side interrupting circuit when a voltage drop is detected by the voltage sensor after controlling the inverter to make the capacitor voltage the first predetermined voltage and then controlling the inverter to make the capacitor voltage a second predetermined voltage that is lower than the first predetermined voltage. This is based on the fact that when no continuity fault has occurred in the neutral point side interrupting circuit, the voltage detected by the voltage sensor does not change. As a result, a continuity fault in the neutral point side interrupting circuit can be determined without the need for additional configuration.

In the electric vehicle disclosed herein, the control device may prohibit charging of the battery using the external DC power when it determines that a continuity fault has occurred in the negative pole side interrupting circuit and/or the neutral point side interrupting circuit.

1 is a diagram showing an outline of the configuration of an electric vehicle 20 according to an embodiment of the present disclosure. 4 is a flowchart showing an example of a boost charging start process executed by an electronic control unit 60.

Next, a mode (embodiment) for carrying out the present disclosure will be described. FIG. 1 is a diagram showing an outline of the configuration of an electric vehicle 20 according to an embodiment of the present disclosure. The electric vehicle 20 of the embodiment includes a traction motor 22, an inverter 24 that drives the motor 22, a battery 26, a charger 40, and an electronic control unit 60.

The motor 22 is configured as a well-known synchronous generator-motor, for example, with a rotor with a permanent magnet attached to its outer surface and a stator around which a three-phase coil is wound. The inverter 24 is configured with six transistors T1-T6 and six diodes D1-D6 connected in parallel in the opposite direction to the transistors T1-T6. The transistors T1-T6 are arranged in pairs, two on the source side and two on the sink side of the positive and negative busbars that the inverter 24 shares as power line 30. Each of the three-phase coils (U-phase, V-phase, and W-phase) of the motor 22 is connected to each of the junctions between the paired transistors. Therefore, by controlling the proportion of on-time of the paired transistors T1-T6 when voltage is applied between the positive and negative busbars, a rotating magnetic field can be generated in the three-phase coils, thereby driving the motor 22 to rotate. A smoothing capacitor 34 is connected to the power line 30.

The battery 26 is configured as, for example, a lithium-ion secondary battery or a nickel-metal hydride secondary battery and is connected to the power line 30. A system main relay 28 is attached to the power line 30. The system main relay 28 has a positive relay SMRB provided on the positive side of the power line 30, a negative relay SMRG provided on the negative side of the power line 30, and a precharge circuit in which a precharge resistor R and a precharge relay SMRP are connected in series to bypass the negative relay SMRG. A filter 32 that removes noise is also attached to the power line 30.

The charger 40 includes an external charging connector 42 that connects to an external power source, a charging power line 43 (positive line 44 and negative line 45) that is connected to the external charging connector 42 and is connected to the power line 30 between the system main relay 28 and the inverter 24 (between the filter 32 and the inverter 24 in Figure 1), and a neutral point charging line 50 that is connected to the positive line 44 of the charging power line 43 and the neutral point of the motor 22.

Attached to the charging power line 43, in order from the external charging connector 42 side, are a charging relay 48 and a noise filter 49 including a smoothing capacitor. The charging relay 48 has a positive relay CHRB attached to the positive line 44 of the charging power line 43 and a negative relay CHRG attached to the negative line 45 of the charging power line 43. A bypass relay 46 is attached to the positive line 44 of the charging power line 43. A negative cutoff circuit 47 is attached to the negative line 45 of the charging power line 43. The negative cutoff circuit 47 is configured to connect in parallel a diode with its forward direction running from the battery 26 to the external charging connector 42, a transistor as a switching element, and a varistor.

Attached to the neutral point charging line 50, in order from the motor 22 side, are a neutral point relay 51 and a neutral point side shutoff circuit 52. Similar to the negative side shutoff circuit 47, the neutral point side shutoff circuit 52 is configured to connect in parallel a diode with its forward direction running from the battery 26 to the external charging connector 42, a transistor as a switching element, and a varistor.

The terminals of a capacitor 53 are connected between the neutral point relay 51 and the neutral point shutoff circuit 52 of the neutral point charging line 50, and to the battery 26 side of the negative side shutoff circuit 47 of the negative side line 45 of the charging power line 43. A voltage sensor 54 that detects the voltage between the neutral point charging line 50 and the negative side line 45 is connected between the neutral point shutoff circuit 52 of the neutral point charging line 50 and the external charging connector 42 side, and between the negative side shutoff circuit 47 of the negative side line 45 of the charging power line 43 and the external charging connector 42 side. A leakage detection circuit 55 that detects leakage current is also installed between the neutral point charging line 50 and the negative side line 45.

Although not shown, the electronic control unit 60 is configured as a microprocessor centered around a CPU. In addition to the CPU, it also includes a ROM for storing processing programs, a RAM for temporarily storing data, flash memory, input/output ports, and communication ports. Signals from various sensors are input to the electronic control unit 60 via input ports. Examples of signals input to the electronic control unit 60 include the rotational position θm from a rotational position detection sensor (e.g., a resolver) 23 that detects the rotational position of the rotor of the motor 22, phase currents flowing through the three-phase coils (U-phase, V-phase, and W-phase) of the motor 22, the voltage VL from a voltage sensor 54 provided in the charger 40, and detection signals from a leakage detection circuit 55. The electronic control unit 60 is also connected to a communication line for communicating with an external DC power supply via the external charging connector 42. The electronic control unit 60 also functions as a control device for the electric vehicle 20, and therefore also receives inputs such as the shift position, accelerator position, and brake position.

Various control signals are output from the electronic control unit 60 via the output port. Examples of signals output from the electronic control unit 60 include a switching control signal to transistors T1 to T6 of the inverter 24, a drive control signal to the system main relay 28, a drive control signal to the charging relay 48, a drive control signal to the bypass relay 46, a drive control signal to the neutral point relay 51, a drive control signal to the negative side shutoff circuit 47, and a drive control signal to the neutral point side shutoff circuit 52.

When an external DC power supply is connected to the external charging connector 42 of the charger 40, the electronic control unit 60 inputs the DC power voltage Vd (external DC voltage Vd) supplied by the external DC power supply. When the external DC voltage Vd is higher than the voltage Vb of the battery 26, the electronic control unit 60 charges the battery 26 using normal charging with the charger 40. When the external DC voltage Vd is lower than the voltage Vb of the battery 26, the electronic control unit 60 charges the battery 26 using boost charging with the charger 40. During normal charging, the bypass relay 46 is turned on, the neutral point relay 51 is turned off, and the system main relay 28 is turned on, and the battery 26 is charged using the positive line 44 and negative line 45 of the charging power line 43. During boost charging, the bypass relay 46 is turned off, the neutral point relay 51 is turned on, and the system main relay 28 is turned on, and the battery 26 is charged using the neutral point charging line 50 and the negative line 45 of the charging power line 43. In this boost charging, the combination of the three-phase coils (U-phase, V-phase, W-phase) of the motor 22 and each phase of the inverter 24 functions as a boost circuit by switching on and off transistors T1 to T6 of the inverter 24, thereby boosting the voltage of the external DC power and charging the battery 26.

Next, we will explain the operation of the electric vehicle 20 configured in this manner, particularly the operation when starting boost charging using the charger 40. Figure 2 is a flowchart showing an example of the boost charging start process executed by the electronic control unit 60.

When the boost charging start process is executed, the electronic control unit 60 first turns on the system main relay 28 (step S100) and the neutral relay 51 (step S110) while both the neutral point side shutoff circuit 52 and the negative pole side shutoff circuit 47 are off (shut down). Then, it controls the switching of transistors T1-T6 of the inverter 24 to cause each phase of the motor 22 and each phase of the inverter 24 to function as a boost circuit, charging the capacitor 53 until its voltage reaches a first predetermined voltage (e.g., 400 V) (step S120). It then determines whether the sensor voltage of the voltage sensor 54 is rising (step S130). Because both the neutral point side shutoff circuit 52 and the negative pole side shutoff circuit 47 are off (shut down), the sensor voltage does not rise when the negative pole side shutoff circuit 47 is normal, but rises when a continuity fault occurs in the negative pole side shutoff circuit 47. Therefore, if it is determined that the sensor voltage of the voltage sensor 54 is rising, a continuity failure of the negative electrode side shutoff circuit 47 is determined (step S140), and this process ends without starting boost charging. On the other hand, if it is determined that the sensor voltage of the voltage sensor 54 is not rising, it is determined that the negative electrode side shutoff circuit 47 is normal (step S150).

If the negative-side shutoff circuit 47 is determined to be normal, the inverter 24 is switched to charge the capacitor 53 so that its voltage is maintained at a first predetermined voltage (step S160), and the negative-side shutoff circuit 47 is turned on (released from shutoff) (step S170). The inverter 24 is then switched to discharge the capacitor 53 so that its voltage becomes a second predetermined voltage (e.g., 300 V) lower than the first predetermined voltage (step S170). It is then determined whether the sensor voltage of the voltage sensor 54 has dropped (step S180). Because the neutral-side shutoff circuit 52 is off (shutoff) and the negative-side shutoff circuit 47 is on (released from shutoff), the sensor voltage does not drop when the neutral-side shutoff circuit 52 is normal, but drops when a continuity fault occurs in the neutral-side shutoff circuit 52. Therefore, if it is determined that the sensor voltage of the voltage sensor 54 has dropped, it determines that there is a continuity fault in the neutral point side interruption circuit 52 (step S200), and this process ends without starting boost charging. On the other hand, if it is determined that the sensor voltage of the voltage sensor 54 has not dropped, it determines that the neutral point side interruption circuit 52 is normal (step S210).

If it is determined that the neutral point side shutoff circuit 52 is normal, the neutral point side shutoff circuit 52 is turned on (shutoff is released) (step S220), boost charging is initiated (step S230), and this process ends.

In the electric vehicle 20 of the embodiment described above, when charging of the battery 26 by boost charging using the charger 40 begins, the neutral point side shutoff circuit 52 and the negative pole side shutoff circuit 47 are both turned off (shut down), the system main relay 28 is turned on, and the neutral point relay 51 is turned on. Then, each phase of the motor 22 and each phase of the inverter 24 function as a boost circuit to charge the capacitor 53 until its voltage reaches a first predetermined voltage, and when the sensor voltage of the voltage sensor 54 rises, it is determined that a continuity fault has occurred in the negative pole side shutoff circuit 47. This makes it possible to determine a continuity fault in the negative pole side shutoff circuit 47 without adding any additional components.

In the electric vehicle 20 of this embodiment, when it is determined that the negative-side interrupting circuit 47 is normal, the negative-side interrupting circuit 47 is turned on (disconnected) while the voltage of the capacitor 53 is maintained at a first predetermined voltage, and the charge in the capacitor 53 is discharged so that the voltage of the capacitor 53 becomes a second predetermined voltage that is lower than the first predetermined voltage. When the sensor voltage of the voltage sensor 54 drops, it is determined that a continuity fault has occurred in the neutral-side interrupting circuit 52. This makes it possible to determine a continuity fault in the neutral-side interrupting circuit 52 without providing any additional components.

In the electric vehicle 20 of this embodiment, boost charging begins when it is determined that both the negative pole side shutoff circuit 47 and the neutral point side shutoff circuit 52 are normal, allowing for more appropriate boost charging.

The correspondence between the main elements of the embodiment and the main elements of the invention described in the "Means for Solving the Problem" section will be explained below. In the embodiment, the battery 26 corresponds to the "battery," the motor 22 corresponds to the "three-phase AC motor," the inverter 24 corresponds to the "inverter," the system main relay 28 corresponds to the "system main relay," the external charging connector 42 corresponds to the "external charging connector," the charger 40 corresponds to the "DC charger," and the electronic control unit 60 corresponds to the "control device." Furthermore, the power line 30 corresponds to the "power line", the charging power line 43 corresponds to the "charging power line", the bypass relay 46 corresponds to the "bypass relay", the neutral point charging line 50 corresponds to the "neutral point charging line", the neutral point relay 51 corresponds to the "neutral point relay", the neutral point side shutoff circuit 52 corresponds to the "neutral point side shutoff circuit", the negative side shutoff circuit 47 corresponds to the "negative side shutoff circuit", the capacitor 53 corresponds to the "capacitor", and the voltage sensor 54 corresponds to the "voltage sensor".

The correspondence between the main elements of the embodiments and the main elements of the invention described in the "Means for Solving the Problem" section does not limit the elements of the invention described in the "Means for Solving the Problem" section, as the embodiments are examples used to specifically explain the invention described in the "Means for Solving the Problem" section. In other words, the interpretation of the invention described in the "Means for Solving the Problem" section should be based on the description in that section, and the embodiments are merely a specific example of the invention described in the "Means for Solving the Problem" section.

The above describes embodiments of the present disclosure, but the present disclosure is not limited to these embodiments and can, of course, be embodied in various forms without departing from the spirit of the present disclosure.

This disclosure can be used in the electric vehicle manufacturing industry, etc.

20 Electric vehicle, 22 Motor, 24 Inverter, 26 Battery, 28 System main relay, 30 Power line, 32 Filter, 34 Capacitor, 40 Charger, 42 External charging connector, 43 Charging power line, 44 Positive side line, 45 Negative side line, 46 Bypass relay, 47 Negative side cutoff circuit, 48 Charging relay, 49 Filter, 50 Neutral point charging line, 51 Neutral point relay, 52 Neutral point side cutoff circuit, 53 Capacitor, 54 Voltage sensor, 55 Leak detection circuit, 60 Electronic control unit, CHRB Positive side relay, CHRG Negative side relay, SMRB Positive side relay, SMRG Negative side relay, SMRP Precharge relay, R Precharge resistor.

Claims (3)

An electric vehicle including: a battery; a three-phase AC motor; an inverter that drives the three-phase AC motor using power from the battery; a system main relay with a pre-charge function that is provided in a power line that connects the battery and the inverter; a DC charger that charges the battery using external DC power supplied from an external charging connector; and a control device,
The DC charger includes a charging power line connected between the external charging connector and the inverter on the power line, a bypass relay attached to a positive side line of the charging power line, a neutral point charging line connecting a neutral point of the three-phase AC motor to the external charging connector on the positive side line of the charging power line and the bypass relay, a neutral point relay attached to the neutral point charging line, and a power line connected from the neutral point relay on the neutral point charging line to the external charging connector. a neutral point side interrupting circuit connected to the external charging connector side of the charging power line, a negative side interrupting circuit attached to the negative side line of the charging power line, a capacitor connected to the power line side of the negative side line of the charging power line from the negative side interrupting circuit and between the neutral point relay and the neutral point side interrupting circuit of the neutral point charging line, and a voltage sensor connected to the external charging connector side of the neutral point side interrupting circuit of the neutral point charging line and to the external charging connector side of the negative side line of the charging power line,
the control device determines that a continuity fault has occurred in the negative side shutoff circuit when a voltage rise is detected by the voltage sensor while the inverter is controlled so that the voltage of the capacitor becomes a first predetermined voltage with the system main relay and the neutral point relay turned on and the neutral point side shutoff circuit and the negative side shutoff circuit turned off;
An electric vehicle characterized by: The electric vehicle according to claim 1,
the control device turns on the neutral point side interrupting circuit when it determines that no continuity fault has occurred in the negative pole side interrupting circuit, and determines that a continuity fault has occurred in the neutral point side interrupting circuit when a voltage drop is detected by the voltage sensor when the control device controls the inverter so that the capacitor voltage becomes the first predetermined voltage and then controls the inverter so that the capacitor voltage becomes a second predetermined voltage that is lower than the first predetermined voltage.
Electric car. 3. The electric vehicle according to claim 2,
When the control device determines that a continuity fault has occurred in the negative pole side interrupting circuit or/and the neutral point side interrupting circuit, the control device prohibits charging of the battery using the external DC power.
Electric car.