JP2012044805A - Vehicular power supply system - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a vehicular power supply system capable of suppressing consumption of electric power charged into a high-voltage battery, and performing charging without burdening an auxiliary equipment battery for long service life of the auxiliary equipment battery.SOLUTION: The vehicular power supply system comprises: a motor that drives wheels; a high-voltage battery that supplies electric power to the motor; an auxiliary equipment battery that supplies electric power to auxiliary equipment; a DC-DC converter that steps down a voltage of the high-voltage battery and charges the auxiliary equipment battery by the voltage stepped down by the DC-DC converter, and further includes voltage control means that changes an output voltage of the DC-DC converter according to power consumption of the auxiliary equipment.

Description

  The present invention relates to a vehicle power supply system, and in particular, a high voltage battery for a motor that drives wheels, an auxiliary battery for driving an auxiliary system that supplies electric power to auxiliary devices, and electric power of the high voltage battery are predetermined. The present invention relates to a power supply system for a vehicle that controls charging of an auxiliary battery of a hybrid vehicle or an electric vehicle equipped with a DC / DC converter that converts the voltage of the auxiliary battery and charges the auxiliary battery.

  A vehicle power supply system such as a high-lid vehicle or an electric vehicle has a high-voltage battery that supplies electric power to a motor that drives wheels, and, like a gasoline vehicle, an auxiliary machine as a power source for wipers, blower fans for air conditioners and various controllers. It has a battery. In addition, a motor cooling pump, which is a unique component of a hybrid vehicle or an electric vehicle, is also supplied with power from an auxiliary battery. In the vehicle power supply system, the auxiliary battery is configured to be charged by a DC / DC converter located between the direct current source of the high voltage battery for the motor that drives the wheel and the auxiliary battery. The auxiliary battery constantly supplies power to the auxiliary load of the vehicle and plays a role similar to an alternator in a gasoline vehicle.

  As a vehicle power supply system for a high-lid vehicle or an electric vehicle, a charging voltage supplied from the main battery to the auxiliary battery is increased according to the charging state of the auxiliary battery when an insufficient charging of the auxiliary battery is detected. (Patent Document 1), when reducing the torque of the generator for charging the high voltage battery, the power voltage of the low voltage battery is decreased (Patent Document 2), the operation of the DC / DC converter is stopped when the vehicle is accelerated, There is one (Patent Document 3) that increases the output voltage of the DC / DC converter during deceleration.

JP 2007-302129 A JP 2002-281601 A JP-A-7-99706

However, in the conventional vehicle power supply system using the DC / DC converter, since the output voltage of the DC / DC converter is constant regardless of the power consumption of the auxiliary system, the maximum load of the auxiliary system is reduced. Since the voltage is set in consideration, there is a problem that fuel consumption is deteriorated as a result of incurring more electric power than necessary at times other than the maximum load.
Moreover, since the said patent document 1 charges a battery after the voltage of an auxiliary machine battery falls, a burden will be applied to a battery and the lifetime of a battery will become short. In addition, it is necessary to increase the output voltage of the DC / DC converter to some extent so that the terminal voltage of the auxiliary system does not decrease at high loads. However, at low loads, even if the output voltage of the DC / DC converter is low, Since the terminal voltage does not decrease, the output voltage of the DC / DC converter increases more than necessary, and the consumption of power charged in the high voltage battery increases.
The above-mentioned patent document 2 lowers the power supply voltage of the low-voltage battery according to the operating state such as the torque of the generator that charges the high-voltage battery is applied to the assist side, and can improve fuel efficiency. Therefore, the operation of the auxiliary machine may be hindered by a decrease in the terminal voltage of the auxiliary battery.
Patent Document 3 stops the DC / DC converter when accelerating the vehicle and raises the output voltage of the DC / DC converter when decelerating, and does not take into account the power consumption of the auxiliary system. In some cases, the output voltage of the DC / DC converter rises to increase the consumption of power charged in the high-voltage battery, or the terminal voltage of the auxiliary battery decreases, which may hinder the operation of the auxiliary machine.

  The present invention realizes a vehicle power supply system that can suppress the consumption of electric power charged in a high-voltage battery, can charge the auxiliary battery without imposing a burden, and can extend the life of the auxiliary battery. With the goal.

  The present invention relates to a motor for driving wheels, a high voltage battery for supplying electric power to the motor, an auxiliary battery for supplying electric power to auxiliary machines, and a DC / DC converter for stepping down the voltage of the high voltage battery, A power supply system for a vehicle that charges the auxiliary battery with a voltage stepped down by the DC / DC converter, the voltage changing the output voltage of the DC / DC converter according to the power consumption of the auxiliary equipment Control means is provided.

In a vehicle power supply system including a high voltage battery, an auxiliary battery, and a DC / DC converter, it is necessary to increase the output voltage of the DC / DC converter to some extent so that the terminal voltage of the auxiliary system does not decrease at a high load. is there. However, when the load is low, the terminal voltage of the auxiliary system does not decrease even if the output voltage of the DC / DC converter is low.
The power supply system for a vehicle according to the present invention changes the output voltage of the DC / DC converter according to the power consumption of the auxiliary machinery, and prevents the output voltage of the DC / DC converter from being increased more than necessary. Consumption of power charged in the battery can be suppressed. In addition, even when the output voltage of the DC / DC converter is low at the time of low load, the amount of decrease in the terminal voltage of the auxiliary system is small, so that the driver does not feel uncomfortable such as the light becoming dark.
Further, the vehicle power supply system of the present invention charges the auxiliary battery as appropriate according to the power consumption of the auxiliary machines as needed, rather than charging the battery after the voltage of the auxiliary battery drops. Since it is not necessary to place a burden on the battery by appropriately charging the necessary power, the life of the auxiliary battery can be extended.

FIG. 1 is a control flowchart of the vehicle power supply system. (Example) FIG. 2 is a diagram showing the setting of the output voltage of the DC / DC converter in the running state. (Example) FIG. 3 is a block diagram of the vehicle power supply system. (Example)

  Embodiments of the present invention will be described below with reference to the drawings.

1 to 3 show an embodiment of the present invention. In FIG. 3, reference numeral 1 denotes a vehicle made up of a high-lid vehicle or an electric vehicle, 2 denotes wheels, and 3 denotes a vehicle power supply system. A vehicle power supply system 3 for a vehicle 1 including a high-lid vehicle or an electric vehicle includes a high-voltage battery 6 that supplies power to a motor 4 that drives wheels 2 via an inverter 5, a wiper, a blower fan for an air conditioner, and the like. An auxiliary battery 8 that supplies power to the auxiliary machinery 7 and a DC / DC converter 9 that steps down the voltage of the high voltage battery 6 are provided, and a power supply control device 10 that controls the output voltage of the DC / DC converter 9 is provided. ing.
The high voltage battery 6 drives a motor 4 that is a driving force of the vehicle 1. The auxiliary battery 8 supplies power to auxiliary systems such as a headlamp, an air conditioner blower fan, and various controllers. The auxiliary battery 8 is charged via a DC / DC converter 9 provided between the high voltage battery 6 that drives the motor 4 and the auxiliary battery 8. The DC / DC converter 9 steps down the voltage of the high voltage battery 6, outputs it, supplies it to the auxiliary battery 8, and charges the auxiliary battery 8.
The output voltage of the DC / DC converter 9 can be adjusted in proportion to the auxiliary battery charge voltage command Duty of the signal input from the external power supply control device 10. Therefore, the power supply control device 10 can arbitrarily adjust the output voltage of the DC / DC converter 9 by controlling the auxiliary battery charge voltage command Duty input to the DC / DC converter 9.

The vehicle power supply system 3 includes a current sensor 11 for detecting a current value of a current input from the DC / DC converter 9 to the auxiliary battery 8 between the DC / DC converter 9 and the auxiliary battery 8. The power supply control device 10 is provided with power consumption calculation means 12 for calculating the power consumption of the auxiliary battery 8 from the current value detected by the current sensor 11. The vehicle power supply system 3 uses the power consumption calculated by the power consumption calculation means 12 as the power consumption of the auxiliary machinery 7, and according to the power consumption of the auxiliary machinery 7, the DC / DC converter 9 The power supply control device 10 includes voltage control means 13 that changes the output voltage. The voltage control means 13 adjusts the output voltage of the DC / DC converter 9 to change in accordance with the power consumption of the auxiliary machinery 7 by controlling the auxiliary battery charging voltage command Duty.
The vehicle power supply system 3 is connected to the voltage control means 13 of the power supply control device 10 with an air conditioner device 14 of the vehicle 1 that inputs a signal indicating an operating state of an air conditioner blower fan that is an auxiliary machine. The voltage power supply means 13 lowers the output voltage of the DC / DC converter 9 when the air conditioner blower fan is not operating by a signal indicating the operating state of the air conditioner blower fan input from the air conditioner device 14. The voltage power supply means 13 adjusts the output voltage of the DC / DC converter 9 to be lowered by controlling the auxiliary battery charge voltage command Duty so that the air conditioner blower fan is not operating.
In the vehicle power supply system 3, a vehicle speed sensor 15 that detects and inputs a vehicle speed that is the traveling state of the vehicle 1 is connected to the voltage control means 13 of the power supply control device 10. The voltage power supply means 13 increases the output voltage of the DC / DC converter 9 when the vehicle 1 is decelerated by the vehicle speed signal input from the vehicle speed sensor 15. The voltage power supply means 13 adjusts the output voltage of the DC / DC converter 9 to increase when the vehicle 1 is decelerating by controlling the auxiliary battery charge voltage command Duty.

Next, the operation of the vehicle power supply system 3 will be described with reference to FIGS.
When the control program starts (S01), the vehicle power supply system 3 reads an air conditioner blower fan operating state signal from the air conditioner 14 (S02), and determines whether the air conditioner blower fan is stopped (S03). .
If this determination (S03) is YES, it is determined to lower the output voltage of the DC / DC converter 9 (S04), and the output voltage of the DC / DC converter 9 is lowered by controlling the auxiliary battery charge voltage command Duty. Then, the process returns to the reading of the operation state signal of the air conditioner blower fan (S02) (S05).
If the determination (S03) is NO, a vehicle speed signal is read from the vehicle speed sensor 15 (S06), and it is determined whether the vehicle 1 is in a decelerating state (S07). If this determination (S07) is YES, it is determined to increase the output voltage of the DC / DC converter 9 (S08), and the output voltage of the DC / DC converter 9 is increased by controlling the auxiliary battery charge voltage command Duty. Then, the process returns to the reading of the operation state signal of the air conditioner blower fan (S02) (S05).
If the determination (S07) is NO, the current value detected by the current sensor 11 is read into the power consumption calculation means 12, the power consumption of the auxiliary battery 8 is calculated (A09), and the calculated current consumption is calculated. A decision is made to change the output voltage of the DC / DC converter 9 according to the amount (S10), and the output voltage of the DC / DC converter 9 is adjusted by controlling the auxiliary battery charge voltage command Duty, for the air conditioner The process returns to the reading of the blower fan operating state signal (S02) (S05).

In the vehicular power supply system 3 including the high voltage battery 6, the auxiliary battery 8, and the DC / DC converter 9, the output voltage of the DC / DC converter 9 is set so that the terminal voltage of the auxiliary system does not decrease when the load is high. It is necessary to raise it to some extent. However, when the load is low, the terminal voltage of the auxiliary system does not decrease even if the output voltage of the DC / DC converter 9 is low.
The vehicle power supply system 3 includes voltage control means 13 that changes the output voltage of the DC / DC converter 9 in accordance with the power consumption of the auxiliary machinery 7, and does not increase the output voltage of the DC / DC converter 9 more than necessary. By doing so, consumption of the electric power charged in the high voltage battery 6 can be suppressed. In addition, when the load is low, even if the output voltage of the DC / DC converter 9 is low, the amount of decrease in the terminal voltage of the auxiliary system is small, so that the driver does not feel uncomfortable such as the light becoming dark.
In addition, the vehicle power supply system 3 charges the auxiliary battery 8 as necessary according to the power consumption of the auxiliary machines 7 and charges the battery after the voltage of the auxiliary battery 8 is lowered. Rather than imposing a burden on the battery, it is possible to extend the life of the auxiliary battery 8 because it is not necessary to charge the battery more appropriately.

The vehicle power supply system 3 includes a power consumption calculation means 12 for calculating the power consumption of the auxiliary battery 8 from the current value detected by the current sensor 11 in the power supply control device 10, and the power consumption calculation means 12 Since the calculated power consumption is used as the power consumption of the auxiliary machinery 7, the power consumption of the auxiliary machinery 7 necessary for changing the output voltage of the DC / DC converter 9 can be easily detected.
Further, since the power supply system 3 for a vehicle consumes less power when the air conditioner blower fan as an auxiliary machine is stopped, the vehicle power supply system 3 is set to lower the output voltage of the DC / DC converter 9 when the air conditioner blower fan is stopped. Therefore, the fuel consumption can be improved without adding a circuit for monitoring the output voltage of the DC / DC converter 9.
Therefore, the vehicle power supply system 3 does not output the output voltage of the DC / DC converter 9 according to the power consumption of the auxiliary system such as ON / OFF of the air conditioner 14 and ON / OFF of the headlamps, not the vehicle running state. By lowering, it is possible to reduce power consumption and improve fuel efficiency. In other words, the vehicle power supply system 3 does not apply an unnecessarily large voltage to the auxiliary battery 8, so that it is possible to reduce power consumption and improve fuel efficiency.

The vehicle power supply system 3 includes a power consumption calculation means 12 that detects the amount of power used from the vehicle running state and the power consumption of the auxiliary system, and a voltage control means 13 that changes the output voltage of the DC / DC converter 9. The output voltage of the DC / DC converter 9 is changed according to the vehicle running state, such as when the vehicle is decelerated or when the air-conditioning blower fan is stopped, and the power consumption used in the auxiliary system.
While the blower fan for air conditioner is stopped, the power consumption of the auxiliary system is always low and the power consumption is approximately constant. Therefore, increase the output voltage (square line in FIG. 2), and change the power consumption by reducing the output voltage of the DC / DC converter 9 according to the power consumption in the auxiliary system during normal driving other than during deceleration. If the power consumption in the auxiliary system is low, the fuel efficiency can be improved by lowering the output voltage of the DC / DC converter 9.
Note that, unlike an electric vehicle, a hybrid vehicle has an engine and may consume fuel even during deceleration. When a large regenerative torque is applied to a hybrid vehicle equipped with an engine during deceleration, energy is recovered by regenerating the torque generated by increasing the fuel consumption, and the fuel efficiency deteriorates. Therefore, in the case of a hybrid vehicle, the condition for increasing the output voltage of the DC / DC converter 9 (S07 in FIG. 1) is not limited to the deceleration state, but limited to the deceleration state and the fuel cut state.

  The present invention can suppress the consumption of electric power charged in a high voltage battery and extend the life of an auxiliary battery, and can be applied to a vehicle power supply system for a high lid vehicle equipped with an engine as well as an electric motor vehicle. Can also be applied.

DESCRIPTION OF SYMBOLS 1 Vehicle 2 Wheel 3 Vehicle power supply system 4 Motor 5 Inverter 6 High voltage battery 7 Auxiliary machinery 8 Auxiliary battery 9 DC / DC converter 10 Power supply control device 11 Current sensor 12 Power consumption calculation means 13 Voltage control means 14 Air-conditioner apparatus 15 Vehicle speed sensor

Claims (3)

A motor that drives the wheels;
A high voltage battery that supplies power to the motor;
An auxiliary battery that supplies power to the auxiliary equipment, and
A DC / DC converter for stepping down the voltage of the high-voltage battery,
In the vehicle power supply system for charging the auxiliary battery with the voltage stepped down by the DC / DC converter,
A vehicle power supply system comprising voltage control means for changing an output voltage of the DC / DC converter according to the power consumption of the auxiliary machinery. A current sensor for detecting a current value of a current input to the auxiliary battery;
Power consumption calculating means for calculating the power consumption of the auxiliary battery from the current value detected by the current sensor,
2. The vehicle power supply system according to claim 1, wherein the power consumption calculated by the power consumption calculation means is used as the power consumption of the auxiliary equipment. A motor that drives the wheels;
A high-voltage battery that supplies power to the motor, an auxiliary battery that supplies power to the accessories,
A DC / DC converter for stepping down the voltage of the high-voltage battery,
In the vehicle power supply system for charging the auxiliary battery with the voltage stepped down by the DC / DC converter,
A vehicle power supply system comprising voltage control means for reducing an output voltage of the DC / DC converter when an air conditioner blower fan is not operating.

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