JP2018019527A - Power system for electric vehicle - Google Patents

Abstract

PROBLEM TO BE SOLVED: To further reliably discharge a smoothing capacitor when a vehicle collides.SOLUTION: A power system 8 for an electric vehicle includes: a main battery 4 mounted on the rear part of a vehicle; a power control unit 12 provided with a pair of input terminals; a switch 20 connected between the main battery and the power control unit; a smoothing capacitor 14 connected between the pair of input terminals; a sub-battery 22 mounted on the front part of the vehicle; a first DDC 28 applying voltage obtained by stepping down the voltage between both ends of the smoothing capacitor to the sub-battery; a second DDC 30 applying voltage obtained by pressure-rising the voltage of the sub-battery to the main battery; and a control device 60 supplying power to the main battery from the smoothing capacitor via the first DDC and the second DDC when the collision of the front part of the vehicle is detected, and supplying power to the sub-battery from the smoothing capacitor via the first DDC when the collision of the rear part of the vehicle is detected.SELECTED DRAWING: Figure 2

Description

  The present specification discloses a power supply system for an electric vehicle. The “electric vehicle” in this specification includes a hybrid vehicle including both a traveling motor and an engine.

  Patent Document 1 discloses an example of a power supply system for an electric vehicle. The power supply system includes a main battery, a sub battery, an inverter, and a DC-DC converter. The inverter includes a pair of input terminals connected to the main battery, and converts DC power supplied between the pair of input terminals into AC power. AC power is supplied from the inverter to the traveling motor. A smoothing capacitor is connected between the input terminals of the inverter. A switch is provided between the inverter and the main battery. The DC-DC converter can step down the voltage across the smoothing capacitor and apply the stepped down voltage to the sub-battery. The smoothing capacitor can be discharged and the sub-battery can be charged simultaneously by the DC-DC converter.

JP 10-248263 A

  In an electric vehicle, in order to ensure safety after a collision, it is required to discharge a smoothing capacitor when the vehicle collides. In the power supply system of patent document 1, a smoothing capacitor can be discharged by sending electric power from a smoothing capacitor to a sub-battery by a DC-DC converter. However, if the sub-battery or its wiring member is damaged due to a vehicle collision, the sub-battery cannot be charged, and therefore the smoothing capacitor cannot be discharged. For this reason, in this specification, the power supply system which can discharge a smoothing capacitor more reliably when a vehicle collides is provided.

  A power supply system for an electric vehicle disclosed in this specification includes a main battery, a power control unit, a travel motor, a switch, a smoothing capacitor, a sub-battery, a collision detection device, a first DC-DC converter, a second DC-DC converter, and It has a control device. The main battery is mounted at the rear of the vehicle. The power control unit includes a pair of input terminals connected to the main battery, and converts power supplied between the pair of input terminals. The traveling motor receives electric power converted by the electric power control unit. The switch switches between the main battery and the power control unit between a connected state and a disconnected state. The smoothing capacitor is connected between the pair of input terminals. The sub-battery is mounted on the front of the vehicle. The collision detection device detects a collision at the front of the vehicle and a collision at the rear of the vehicle. The first DC-DC converter steps down the voltage across the smoothing capacitor and applies the stepped down voltage to the sub-battery. The second DC-DC converter boosts the voltage of the sub-battery and applies the boosted voltage to the main battery. The control device turns off the switch when a collision in the front part of the vehicle is detected, and supplies power to the main battery from the smoothing capacitor via the first DC-DC converter and the second DC-DC converter. When a collision at the rear of the vehicle is detected, the switch is turned off and power is supplied from the smoothing capacitor to the sub-battery via the first DC-DC converter.

  The “power control unit” means a unit that converts power supplied to the input terminal into power having a different voltage waveform or current waveform. Examples of the power control unit include an inverter that converts a direct current into an alternating current, a DC-DC converter that converts the magnitude of a direct current voltage, and a unit that combines a DC-DC converter and an inverter.

  In this power supply system, when the vehicle collides at the rear part, the switch is turned off to stop the application of voltage from the main battery to the input terminals of the power control unit (that is, between both ends of the smoothing capacitor). Is done. Furthermore, the voltage across the smoothing capacitor is stepped down by the first DC-DC converter, and the stepped down voltage is applied to the sub-battery. For this reason, electric power is supplied from the smoothing capacitor to the sub-battery. As a result, the smoothing capacitor is discharged at the same time as the sub-battery is charged. Since the sub-battery is mounted on the front part of the vehicle, it is unlikely that charging of the sub-battery is impossible even if a collision occurs at the rear part of the vehicle. Therefore, the smoothing capacitor can be discharged almost reliably when a collision occurs at the rear of the vehicle.

  Also, in this power supply system, when the vehicle collides at the front part, the switch is turned off, so that the voltage from the main battery to the input terminals of the power control unit (that is, between both ends of the smoothing capacitor) is reduced. Application is stopped. Further, power is supplied from the smoothing capacitor to the main battery by the first DC-DC converter and the second DC-DC converter. More specifically, the voltage between both ends of the smoothing capacitor is stepped down by the first DC-DC converter. The voltage stepped down by the first DC-DC converter (voltage applied to the sub-battery) is boosted by the second DC-DC converter, and the boosted voltage is applied to the main battery. Therefore, a voltage higher than that of the sub battery is applied to the main battery. For this reason, the main battery is charged. At the same time as the main battery is charged, the smoothing capacitor is discharged. Since the main battery is mounted in the rear part of the vehicle, it is unlikely that the main battery cannot be charged even if a collision occurs in the front part of the vehicle. Therefore, when a collision occurs in the front part of the vehicle, the smoothing capacitor can be discharged almost reliably.

  As described above, according to this power supply system, the smoothing capacitor can be discharged almost reliably even when a collision occurs at the front part of the vehicle and when a collision occurs at the rear part of the vehicle.

The block diagram of the power supply system 8. FIG. The circuit diagram of the power supply system 8. FIG. The flowchart which shows the process at the time of a collision.

  As shown in FIG. 1, the power supply system 8 of the embodiment is mounted on a hybrid vehicle 100. The hybrid vehicle 100 includes an engine 61, a motor 1, and a motor 2, and can travel using these powers. When using a motor, the hybrid vehicle 100 drives the motor 2 with the electric power supplied from the main battery 4, and rotates driving wheels (not shown) with the power of the motor 2. When traveling using the engine 61, the hybrid vehicle 100 starts the engine 61 using the motor 1 as a cell motor. The hybrid vehicle 100 transmits a part of the power generated by the engine 61 to the drive wheels by the power distribution mechanism 62, while transmitting the remaining power to the motor 1 to generate power by the motor 1. The electric power generated by the motor 1 can be supplied to the motor 2 to be used for rotating the drive wheels, or the main battery 4 can be charged.

  When the traveling hybrid vehicle 100 decelerates, regenerative power generation can be performed by the motor 1 or the motor 2, and the main battery 4 can be charged with the generated power. Thus, the motor 1 and the motor 2 also function as a generator. In that sense, the motor 1 and the motor 2 can be referred to as “motor generators”. 1 and 2, “MG1” represents the motor 1 (motor generator 1), and “MG2” represents the motor 2 (motor generator 2).

  As shown in FIGS. 1 and 2, the power supply system 8 includes a main battery 4, a sub battery 22, a power control unit (PCU) 12, a system main relay (SMR) 20, a first DC-DC converter (first DDC) 28, A 2DC-DC converter (second DDC) 30 is provided. Hereinafter, the power control unit 12 is represented as PCU 12, the system main relay 20 is represented as SMR 20, the first DC-DC converter 28 is represented as first DDC 28, and the second DC-DC converter 30 is represented as second DDC 30.

  The upper side of FIG. 1 corresponds to the front part of the vehicle, and the lower side corresponds to the rear part of the vehicle. As shown in FIG. 1, the main battery 4 is mounted on the rear of the vehicle (more specifically, around the trunk room). The main battery 4 is a secondary battery (rechargeable battery) such as a nickel metal hydride battery or a lithium ion battery. In the present embodiment, the voltage of the main battery 4 is about 300 V (volts). As shown in FIG. 2, the main battery 4 is connected to the PCU 12 through a pair of main power lines 10a and 10b. The positive electrode of the main battery 4 is connected to the main power line 10a, and the negative electrode of the main battery 4 is connected to the main power line 10b.

  As shown in FIGS. 1 and 2, the PCU 12 is connected between the main battery 4 and the MGs 1 and 2. The PCU 12 has a pair of input terminals 12a and 12b. The main power line 10a is connected to the input terminal 12a, and the main power line 10b is connected to the input terminal 12b. The PCU 12 converts DC power between the main power lines 10a and 10b (DC power supplied from the main battery 4) into three-phase AC power, and supplies the three-phase AC power to the MGs 1 and 2. The PCU 12 can also convert the three-phase AC power supplied from the MGs 1 and 2 into DC power and supply the DC power between the main power lines 10a and 10b. The PCU 12 includes a converter (CNV) 16 and an inverter (INV) 17.

  The converter 16 boosts the voltage of the DC power between the pair of input terminals 12 a and 12 b and supplies the boosted voltage to the inverter 17. Inverter 17 converts the DC power supplied from converter 16 into three-phase AC power, and supplies the converted three-phase AC power to MG1 and MG2. The inverter 17 can also convert the three-phase AC power generated by the MG1 and MG2 into DC power and supply the DC power to the converter 16. The converter 16 can step down the voltage of the DC power supplied from the inverter 17 and apply the stepped down voltage between the pair of input terminals 12a and 12b.

  The smoothing capacitor 14 is connected between the pair of input terminals 12 a and 12 b of the PCU 12. The smoothing capacitor 14 smoothes the voltage between the pair of input terminals 12a and 12b (that is, between the main power lines 10a and 10b).

  The SMR 20 is provided on the main power lines 10a and 10b. The SMR 20 includes switches interposed in the main power line 10a and the main power line 10b. The SMR 20 switches between the main battery 4 and the PCU 12 between a connected state and a disconnected state. When the SMR 20 is turned on, the main battery 4 is electrically connected to the PCU 12. When the SMR 20 is turned off, the main battery 4 is disconnected from the PCU 12. While the vehicle main switch (ignition switch) (not shown) is off, the SMR 20 is off. When the vehicle main switch is switched from off to on, the SMR 20 is turned on, and the main battery 4 and the PCU 12 are connected. When the main battery 4 and the PCU 12 are connected, the motor 1 and the motor 2 can be supplied with power, that is, the vehicle can run. In addition, when the SMR 20 is on, the voltage of the main battery 4 is applied to the smoothing capacitor 14, so that charges are stored in the smoothing capacitor 14.

  As shown in FIG. 1, the sub-battery 22 is mounted on the front portion of the vehicle (more specifically, in the engine room). The output voltage of the sub battery 22 is lower than the output voltage of the main battery 4. The sub-battery 22 is typically a secondary battery (a rechargeable battery) configured by a lead storage battery. In this embodiment, the voltage of the sub battery 22 is about 13V. As shown in FIG. 2, the sub battery 22 is connected to an auxiliary machine (AUX) 26 through a pair of sub power lines 24. In FIG. 2, the symbol “AUX” means an auxiliary machine. The auxiliary machine 26 is a generic name for devices (low voltage devices) that operate with the voltage of the sub-battery 22. In FIG. 2, the auxiliary machine 26 is represented by one rectangle, but the auxiliary machine 26 includes a plurality of low-voltage devices such as a room lamp, a navigation system, and a car audio. The conductive body of the vehicle may also serve as the negative electrode line of the sub power line 24. The potential of the negative electrode line of the sub power line 24 may be referred to as a ground potential (reference potential).

  As shown in FIGS. 1 and 2, the first DDC 28 is connected between the input terminals 12 a and 12 b of the PCU 12 (that is, between the main power lines 10 a and 10 b closer to the PCU 12 than the SMR 20). The first DDC 28 is also connected to the pair of sub power lines 24. The first DDC 28 can perform a step-down operation in which the voltage between the pair of input terminals 12 a and 12 b is stepped down and the stepped-down voltage is applied between the pair of sub power lines 24. In the hybrid vehicle 100, the first DDC 28 performs the step-down operation, so that the sub-battery 22 can be charged with the electric power generated by the motor 1 and the motor 2 even when the SMR 20 is off.

  A second DDC 30 (second DC-DC converter) is connected between the positive electrode and the negative electrode of the main battery 4 (that is, between the main power lines 10a and 10b closer to the main battery 4 than the SMR 20). The second DDC 30 is also connected to the pair of sub power lines 24. The second DDC 30 can step down the voltage between the positive electrode and the negative electrode of the main battery 4 and apply the stepped down voltage between the pair of sub power lines 24. When the second DDC 30 performs the step-down operation, the sub battery 22 can be charged with the power of the main battery 4. The second DDC 30 can also perform a boosting operation in which the voltage between the pair of sub power lines 24 is boosted and the boosted voltage is applied between the positive electrode and the negative electrode of the main battery 4. When the second DDC 30 performs the boosting operation, the main battery 4 can be charged with the power of the sub-battery 22.

  The power supply system 8 further includes an MG-ECU 60 (Motor Generator Electronic Control Unit), an A / B-ECU 70 (Airbag Electronic Control Unit), and a sensor group 72. The MG-ECU 60 is connected to the SMR 20, the first DDC 28, the second DDC 30, the PCU 12, and the like via a communication line, but the communication line is not drawn in FIG.

  The MG-ECU 60 controls each component constituting the electric system of the hybrid vehicle 100 such as the PCU 12, the SMR 20, the first DDC 28, and the second DDC 30. The MG-ECU 60 controls operations of an ignition mechanism, a fuel injection mechanism, a supply / exhaust mechanism, and the like of the engine 61. In FIGS. 1 and 2, the MG-ECU 60 is drawn as one rectangle, but the function of the MG-ECU 60 may be realized by cooperation of a plurality of processors.

  The sensor group 72 has a plurality of sensors (for example, acceleration sensors) for detecting a vehicle collision. As shown in FIG. 1, some sensors of the sensor group 72 are provided in the front part of the vehicle. A sensor at the front of the vehicle can detect a collision at the front of the vehicle. In addition, some sensors of the sensor group 72 are provided at the rear of the vehicle. A sensor at the rear of the vehicle can detect a collision at the rear of the vehicle. A detection signal of each sensor in the sensor group 72 is transmitted to the A / B-ECU 70.

  The A / B-ECU 70 receives detection signals from the sensors of the sensor group 72 and determines whether the vehicle is colliding. The A / B-ECU 70 operates an airbag (not shown) when the vehicle collides. Further, the A / B-ECU 70 determines whether a collision has occurred at the front part of the vehicle or a collision has occurred at the rear part of the vehicle, based on detection signals from the sensors of the sensor group 72. The determination result of the A / B-ECU 70 is transmitted to the MG-ECU 60.

  FIG. 3 shows processing executed by the power supply system 8 at the time of a vehicle collision. While the vehicle is traveling, the MG-ECU 60 constantly monitors signals from the A / B-ECU 70. When a vehicle collision occurs, the A / B-ECU 70 determines that the vehicle has collided based on a signal from the sensor group 72. Further, the A / B-ECU 70 determines whether a collision has occurred in the front part of the vehicle or a collision has occurred in the rear part of the vehicle based on the signal from the sensor group 72. The determination result of the A / B-ECU 70 is transmitted to the MG-ECU 60. When MG-ECU 60 receives a determination result indicating a vehicle collision from A / B-ECU 70, the process of FIG. 3 is disclosed.

  In step S2, the MG-ECU 60 turns off the SMR 20. Thereby, the supply of power from the main battery 4 to the PCU 12 is stopped. Accordingly, the supply of power from the main battery 4 to the smoothing capacitor 14 is stopped.

  In step S4, the MG-ECU 60 determines whether the determination result received from the A / B-ECU 70 indicates a collision at the front of the vehicle or a collision at the rear of the vehicle.

  If it is determined in step S4 that a collision has occurred at the front of the vehicle, MG-ECU 60 executes step S6. In step S6, the MG-ECU 60 causes the first DDC 28 to perform a step-down operation. That is, the first DDC 28 steps down the voltage between the pair of input terminals 12 a and 12 b and applies the stepped down voltage between the pair of sub power lines 24.

  Step S8 is executed substantially simultaneously with step S6. In step S8, the MG-ECU 60 causes the second DDC 30 to perform a boost operation. That is, the second DDC 30 boosts the voltage between the pair of sub power lines 24 and applies the boosted voltage between the positive electrode and the negative electrode of the main battery 4.

  Accordingly, in steps S6 and S8, the step-down operation of the first DDC 28 and the step-up operation of the second DDC 30 are performed simultaneously. Power is sent from the smoothing capacitor 14 to the sub power line 24 by the step-down operation of the first DDC 28, and power is sent from the sub power line 24 to the main battery 4 by the step-up operation of the second DDC 30. The voltage obtained by stepping down the voltage of the smoothing capacitor 14 is applied to the sub power line 24 by the step-down operation of the first DDC 28, but the voltage obtained by stepping up the voltage of the sub power line 24 by the step-up operation of the second DDC 30 is applied to the main battery 4. . For this reason, a voltage that is high enough to charge the main battery 4 is applied to the main battery 4. Therefore, the smoothing capacitor 14 is discharged and the main battery 4 is charged. That is, by sending electric power from the smoothing capacitor 14 to the main battery 4, the smoothing capacitor 14 is discharged. As described above, since the main battery 4 is mounted in the rear part of the vehicle, when a collision occurs in the front part of the vehicle, the possibility that the main battery 4 and its wiring are damaged is low. Therefore, when a collision occurs in the front part of the vehicle, the smoothing capacitor 14 can be discharged almost certainly by sending electric power from the smoothing capacitor 14 to the main battery 4 as described above. Steps S6 and S8 are executed until the voltage across the smoothing capacitor 14 falls below 60V in step S10. When the voltage between both ends of the smoothing capacitor 14 falls below 60V, the MG-ECU 60 stops the operations of the first DDC 28 and the second DDC 30 in step S18.

  On the other hand, if it determines with the collision having arisen in the vehicle rear part in step S4, MG-ECU60 will perform step S12. In step S12, the MG-ECU 60 stops the second DDC 30.

  Step S14 is executed substantially simultaneously with step S12. In step S14, the MG-ECU 60 causes the first DDC 28 to perform a step-down operation. That is, the first DDC 28 steps down the voltage between the pair of input terminals 12 a and 12 b and applies the stepped down voltage between the pair of sub power lines 24.

  Accordingly, in steps S12 and S14, the step-down operation of the first DDC 28 is performed with the second DDC 30 stopped. Power is sent from the smoothing capacitor 14 to the sub power line 24 by the step-down operation of the first DDC 28. Therefore, the smoothing capacitor 14 is discharged and the sub-battery 22 is charged. That is, the smoothing capacitor 14 is discharged by sending electric power from the smoothing capacitor 14 to the sub-battery 22. As described above, since the sub-battery 22 is mounted in the front part of the vehicle, when a collision occurs in the rear part of the vehicle, the possibility that the sub-battery 22 and its wiring are damaged is low. Therefore, when a collision occurs at the rear of the vehicle, the smoothing capacitor 14 can be discharged almost certainly by sending electric power from the smoothing capacitor 14 to the sub-battery 22 as described above. Steps S12 and S14 are executed until the voltage across the smoothing capacitor 14 falls below 60V in step S16. When the voltage between both ends of the smoothing capacitor 14 falls below 60V, the MG-ECU 60 stops the operation of the first DDC 28 in step S18.

  As described above, in this power supply system, when a collision occurs at the front part of the vehicle, smoothing is performed by sending power from the smoothing capacitor 14 to the main battery 4 (battery mounted at the rear part of the vehicle). When the capacitor 14 is discharged and a collision occurs at the rear of the vehicle, the smoothing capacitor 14 is discharged by sending electric power from the smoothing capacitor 14 to the sub-battery 22 (battery mounted on the front of the vehicle). Therefore, the smoothing capacitor 14 can be discharged almost reliably even when a collision occurs in either the front part or the rear part of the vehicle.

  The power supply system 8 of the embodiment is applied to a hybrid vehicle that includes both an engine and a motor for traveling. The power supply system disclosed in this specification can also be applied to an electric vehicle that does not include an engine.

  Specific examples of the present invention have been described in detail above, but these are merely examples and do not limit the scope of the claims. The technology described in the claims includes various modifications and changes of the specific examples illustrated above. The technical elements described in this specification or the drawings exhibit technical usefulness alone or in various combinations, and are not limited to the combinations described in the claims at the time of filing. In addition, the technology exemplified in this specification or the drawings can achieve a plurality of objects at the same time, and has technical usefulness by achieving one of the objects.

1: Motor 2: Motor 4: Main battery 8: Power supply system 10a, 10b: Main power line 12: Power control unit 14: Smoothing capacitor 16: Converter 17: Inverter 20: System main relay 22: Sub battery 24: Sub power line 26 : Auxiliary machine 28: 1st DC-DC converter 30: 2nd DC-DC converter 60: MG-ECU
61: Engine 62: Power distribution mechanism 70: A / B-ECU
72: Sensor group 100: Hybrid vehicle

Claims (1)

A power supply system for an electric vehicle,
A main battery mounted at the rear of the vehicle;
A power control unit that includes a pair of input terminals connected to the main battery, and that converts power supplied between the pair of input terminals;
A traveling motor that receives the power converted by the power control unit;
A switch for switching between a connected state and a disconnected state between the main battery and the power control unit;
A smoothing capacitor connected between the pair of input terminals;
A sub-battery mounted on the front of the vehicle;
A collision detection device for detecting a collision at the front of the vehicle and a collision at the rear of the vehicle;
A first DC-DC converter that steps down the voltage across the smoothing capacitor and applies the stepped down voltage to the sub-battery;
A second DC-DC converter that boosts the voltage of the sub-battery and applies the boosted voltage to the main battery;
When a collision at the front of the vehicle is detected, the switch is turned off and power is supplied from the smoothing capacitor to the main battery via the first DC-DC converter and the second DC-DC converter. A control device for turning off the switch and supplying power from the smoothing capacitor to the sub-battery via the first DC-DC converter when a collision is detected;
Having a power system.

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