JP2007237856A - Vehicle power supply system - Google Patents

Abstract

An object of the present invention is to provide a vehicular power supply system capable of appropriately executing power transfer between power storage devices.
A low-voltage battery 10 that is a power source of a low-voltage load 50, a high-voltage battery 60 that is a power source of a high-voltage load 60, a generator 21 that can charge power generated by the low-voltage battery 10, and a high voltage A power supply system for a vehicle having a DC / DC converter 30 that performs power transfer from the low-voltage battery 50 to the low-voltage battery 50, wherein the state of the low-voltage battery 10 satisfies a predetermined condition indicating a decrease in power supply capability In this case, the amount of power generated by the generator 21 increases when the high-voltage system load 60 is in an operating state, and power transfer by the DC / DC converter 30 is executed when the high-voltage system load 60 is in an inoperative state. A power supply system for a vehicle.
[Selection] Figure 1

Description

  The present invention relates to a vehicle power supply system that uses a plurality of power storage devices in combination.

2. Description of the Related Art Conventionally, a power supply control device for a vehicle that uses two different voltage systems of batteries is known (see, for example, Patent Document 1). The power supply control device described in Patent Document 1 and other power supply control devices that use a plurality of such power storage devices together use the power supply voltage of one power storage device via the voltage conversion means such as a DC / DC converter. In some cases, the power storage device has a power transfer function of converting the power supply voltage of the other power storage device to charge the other power storage device or supplying power to an electric load that uses the other power storage device as a power source.
JP 2002-171691 A

  By the way, in the transitional situation in which the power transfer as described above is started or the direction of the power transfer is switched, the voltage of the power storage device is constantly affected by the operating state of the electric load, the state of the power storage device, and the like. Often fluctuates more than normal situations. Therefore, there is a concern that if the power transfer is not performed properly, the operation of the electric load connected to the power storage device becomes unstable due to such a transient voltage fluctuation.

  In this regard, the power supply control device described in Patent Document 1 described above only discloses that whether or not power transfer can be performed is determined based on a decrease in battery voltage. Therefore, since power transfer is executed only by detecting a decrease in battery voltage, it is considered difficult to eliminate the above-mentioned concerns depending on the operating state of the electric load and the state of the battery.

  Therefore, an object of the present invention is to provide a vehicle power supply system that can appropriately execute power transfer between power storage devices.

In order to solve the above problems, as a first invention,
First power storage means that is a power source of the first electrical load;
A second power storage means that is a power source of the second electrical load;
Power generation means capable of charging power generated by the first power storage means;
A power supply system for a vehicle having power transfer means for executing power transfer from the second power storage means to the first power storage means,
An operating state detecting means for detecting an operating state of the second electric load;
When the state of the first power storage unit satisfies a predetermined condition indicating a decrease in power supply capacity, and the second electrical load is detected as an operating state by the operating state detecting unit, the power generating unit The power transfer by the power transfer means is executed when the power generation amount by the power transfer means increases and the second electrical load is detected to be inactive by the operation state detection means. Provide a power system.

In order to solve the above problem, as a second invention,
First power storage means that is a power source of the first electrical load;
A second power storage means that is a power source of the second electrical load;
Power generation means capable of charging power generated by the first power storage means;
A power supply system for a vehicle having power transfer means for executing power transfer from the second power storage means to the first power storage means,
An internal resistance detecting means for detecting an internal resistance of the second power storage means;
When the internal resistance of the second power storage unit is detected by the internal resistance detection unit when the state of the first power storage unit satisfies a predetermined condition indicating a decrease in power supply capability, When the amount of power generated by the power generation means increases and the internal resistance detection means detects that the internal resistance of the second power storage means is smaller than a predetermined value, the power transfer by the power transfer means is executed. A vehicle power supply system is provided.

In order to solve the above problem, as a third invention,
First power storage means that is a power source of the first electrical load;
A second power storage means that is a power source of the second electrical load;
A power supply system for a vehicle having power transfer means for executing power transfer from the second power storage means to the first power storage means,
The vehicle is characterized in that the power transfer means increases the transfer power at an output change rate equal to or less than a predetermined value when the state of the first power storage means satisfies a predetermined condition indicating a decrease in power supply capability. A power supply system is provided.

  Here, the fourth invention is a vehicular power supply system according to the third invention, wherein the power transfer means adjusts a current of the transfer power.

  The fifth invention is a vehicle power supply system according to any one of the first to third inventions, wherein, as the predetermined condition, the first power storage means is set to a predetermined voltage or less. According to a sixth aspect of the present invention, there is provided a vehicle power supply system according to any one of the first to third aspects, wherein, as the predetermined condition, the first power storage means has a predetermined remaining capacity or less. Features.

  The seventh invention is a vehicle power supply system according to the first or second invention, wherein the power generation means generates power based on rotation of an engine.

  The eighth invention is a vehicle power supply system according to the seventh invention, characterized in that the amount of power generated by the power generation means increases as the idle speed of the engine increases.

  According to a ninth aspect of the present invention, there is provided the vehicle power supply system according to the eighth aspect of the present invention, wherein when the power transfer by the power transfer means is executed, the idle speed of the engine is reduced. .

  The power transfer by the power transfer means is preferably executed when the remaining capacity of the second power storage means is a predetermined value or more. The second power storage means is a higher voltage power supply than the first power storage means, and the second power storage means includes a lithium ion battery, and the second electric load includes an electric power steering device. Can be mentioned.

  ADVANTAGE OF THE INVENTION According to this invention, the electric power transfer between electrical storage apparatuses can be performed appropriately.

  The best mode for carrying out the present invention will be described below with reference to the drawings. FIG. 1 is a configuration diagram showing an embodiment of a vehicle power supply system of the present invention. The vehicle on which the vehicle power supply system is mounted includes a high-voltage battery 20 that is a high-voltage (for example, 42V) power storage means, a low-voltage battery 10 that is a low-voltage (for example, 14V) power storage means, Step-down mode that converts the voltage of the high-voltage system to a voltage of the low-voltage system and supplies power from the high-voltage system to the low-voltage system and the voltage from the low-voltage system to the high-voltage system by converting the voltage of the low-voltage system to the voltage of the high-voltage system A DC / DC converter 30 having a boosting mode in which power is supplied and a stop mode in which voltage conversion is stopped and power is not supplied, and an electronic control unit 40 (hereinafter referred to as “ECU 40”) that controls the DC / DC converter 30 It has. Note that the DC / DC converter 30 and the ECU 40 may be integrated.

  There are cases where a plurality of electric loads exist on the vehicle and electric loads of different voltage systems are mixed, and the high voltage battery 20 mainly corresponds to the power supply to the high voltage system load 60 that operates with the voltage of the high voltage system, The low-voltage battery 10 mainly corresponds to power supply to the low-voltage load 50 that operates with a low-voltage voltage. A specific example of the high voltage battery 20 is a lithium ion battery, and a specific example of the low voltage battery 10 is a lead battery. Lithium ion batteries have higher power density (unit: W / kg or W / l), lower internal resistance, and less energy loss due to charging / discharging than lead batteries. The low-voltage battery 10 or the high-voltage battery 20 may be a nickel metal hydride battery or an electric double layer capacitor, or a combination of any of a lead battery, a lithium ion battery, a nickel metal hydride battery, and an electric double layer capacitor. Good.

  As the low-voltage load 50 on the low-voltage battery 10 side, for example, an engine control device, a brake control device, an air conditioner, a headlight, a rear defogger, a rear wiper, a mirror heater, a seat heater, an audio, a lamp, a cigar socket, various ECUs (Electronic Control Unit) and solenoid valves.

  As the high-voltage system load 60 on the high-voltage system battery 20 side, for example, an electric power steering device (EPS) that assists the steering operation of the driver by generating an assist force by an electric motor according to the steering state or the lateral acceleration of the vehicle An electric stability control device (electric STB) that adjusts the roll angle of the vehicle by an electric motor is provided. The EPS has an EPS motor that is an electric motor and an inverter that drives the EPS motor. The electric STB has an electric STB motor that is an electric motor and an inverter that drives the electric STB motor.

  The DC / DC converter 30 performs step-down conversion of the voltage on the high-voltage battery 20 side by a voltage conversion mechanism inside the DC / DC converter 30 such as a transformer, a switching regulator, or a series regulator, and outputs the voltage to the low-voltage battery 10 side. Alternatively, the voltage on the low-voltage battery 10 side is boosted and converted and output to the high-voltage battery 20 side. The converted output voltage is monitored by the ECU 40 or a converter control circuit inside the DC / DC converter 30 and controlled so that the output voltage becomes constant. The DC / DC converter 30 step-down converts the voltage on the high-voltage battery 20 side and outputs it to the low-voltage battery 10 side, and step-up converts the voltage on the low-voltage battery 10 side and outputs the voltage to the high-voltage battery 20 side. Among the boost mode and the stop mode in which voltage conversion is stopped and voltage output is not performed, the mode is set to any mode during operation. By using the voltage conversion function of the DC / DC converter 30, it is possible to step down the voltage on the high voltage system battery 20 to supply power to the low voltage system load 50 or charge the low voltage system battery 10. Thus, the voltage on the low-voltage system battery 10 side can be boosted to supply power to the high-voltage system load 60 or to charge the high-voltage system battery 20, and the voltage conversion is stopped to supply power. It becomes possible not to.

  The low voltage battery 10 is connected via a low voltage power supply line 19 to a generator 21 that generates electric power by converting kinetic energy into electric energy. The generator 21 generates power using the output of the engine 22 for running the vehicle. The electric power generated by the generator 21 is supplied to the low-voltage load 50 or the low-voltage battery 10 is charged. In the step-up mode, supply to the high-voltage system load 60 can be performed via the DC / DC converter 30. A specific example of the generator 21 is an alternator. As the rotational speed of the engine 22 increases, the power generation amount of the alternator also increases. In addition, since charging to the low-voltage system battery 10 and the like can be performed by regenerating the motor (electric motor), the generator 21 may be a motor capable of regenerative control. For example, in order to secure the braking force of the vehicle, the low-voltage system battery 10 can be charged via the inverter or the low-voltage system load 50 can be charged by regeneratively controlling the motor connected to the wheel drive shaft. You can supply power.

  In addition, when the generator 21 is stopped, power can be supplied from the low-voltage battery 10 to the low-voltage load 50. For example, the electric power required in the parking state where the engine 22 is stopped and the alternator is inoperative can be supplied from the low-voltage battery 10.

  The ECU 40 calculates the charge / discharge current value of the low-voltage battery 10 based on the output value of the current sensor 4a that detects the charge / discharge current (battery current) of the low-voltage battery 10, and the charge / discharge current (battery of the high-voltage battery 20) The charge / discharge current value of the high-voltage battery 20 is calculated based on the output value of the current sensor 4b that detects the current. Further, the ECU 40 calculates the voltage value of the low-voltage battery 10 based on the output value of the voltage sensor 5 a that detects the voltage of the low-voltage battery 10, and sets the output value of the voltage sensor 5 b that detects the voltage of the high-voltage battery 20. Based on this, the voltage value of the high voltage battery 20 is calculated. The voltage of the low voltage system battery 10 or the voltage of the high voltage system battery 20 is the voltage of the low voltage system power supply line 19 or the high voltage system power supply line 29, as is clear from FIG. This corresponds to the voltage applied to 60.

  The ECU 40 detects whether the low pressure system load 50 or the high pressure system load 60 is operating by detecting the operating state of the low pressure system load 50 or the high pressure system load 60. For example, the ECU 40 detects the operation information of the low-voltage load 50 and the high-voltage load 60 through the communication line, or detects the consumption current of the low-voltage load 50 and the high-voltage load 60, thereby detecting the low-voltage load. 50 and the operating state of the high-voltage system load 60 can be determined.

  The ECU 40 detects a current value and a voltage value of the high-voltage battery 20 and the low-voltage battery 10 to obtain a “battery remaining capacity” indicating how much capacity of the high-voltage battery 20 and the low-voltage battery 10 remains. You may make it calculate. The ECU 40 calculates the remaining battery capacity of the high-voltage battery 20 by, for example, integrating (integrating) the charge / discharge current of the high-voltage battery 20, and the low-voltage battery 10 by integrating (integrating) the charge / discharge current of the low-voltage battery 10. Calculate the remaining battery capacity. This is because the rate of change over time in the amount of electricity (battery capacity) corresponds to the current. Since the remaining battery capacity corresponds to a value obtained by subtracting the amount of discharge discharged from the battery from the capacity when the battery is fully charged, the ECU 40 monitors the charging / discharging current of the high-voltage battery 20 using the current sensor 4b and the like, and its history. Is recorded in the memory, the remaining battery capacity of the high-voltage battery 20 can be calculated, the charge / discharge current of the low-voltage battery 10 is monitored by the current sensor 4a and the like, and the history is recorded in the memory. The remaining battery capacity of the low-voltage battery 10 can be calculated. In addition, the capacity | capacitance at the time of a full charge is memorize | stored in the memory as an initial value.

  Moreover, ECU40 may estimate each battery remaining capacity by measuring the minimum value of the voltage at the time of the discharge initial stage of the low voltage system battery 10 or the high voltage system battery 20. FIG. Since it is known that there is a correlation between the minimum value caused by the voltage drop at the initial stage of discharge and the remaining battery capacity, the ECU 40 may estimate the remaining battery capacity based on the correlation (for example, map data). it can.

  If the high-voltage battery 20 or the low-voltage battery 10 can be replaced with an electric double layer capacitor and its capacitance is known, the ECU 40 determines the voltage value and capacitance of the high-voltage electric double layer capacitor. The remaining capacity of the high voltage electric double layer capacitor can be calculated based on the voltage, and the remaining capacity of the low voltage electric double layer capacitor can be calculated based on the voltage value and capacitance of the low voltage electric double layer capacitor. .

  Further, the ECU 40 may calculate the internal resistances of the low voltage battery 10 and the high voltage battery 20 based on the output value of the current sensor 4 and the output value of the voltage sensor 5. For example, the ECU 40 samples the output value of the current sensor 4 and the output value of the voltage sensor 5 at a predetermined timing, thereby calculating the internal resistances of the low-voltage battery 10 and the high-voltage battery 20 based on the least square method or the like. be able to. The internal resistance can also be calculated by detecting the initial discharge current and the initial discharge voltage.

  Although details will be described later, the ECU 40 outputs a control signal for controlling the mode switching of the DC / DC converter 30 and the output voltage and output current based on predetermined conditions.

  The ECU 40 includes a plurality of ROMs such as a ROM for storing control programs and control data, a RAM for temporarily storing control program processing data, a CPU for processing control programs, and an input / output interface for exchanging information with the outside. It is composed of circuit elements. The ECU 40 is not limited to one control unit, and may be a plurality of control units so that control is shared.

  Now, the operation of the vehicle power supply system of this embodiment will be described. When the engine 22 is idling, a specific low-voltage load 50 (for example, an electric load with large power consumption, more specifically, an air conditioner or a headlight) is activated, or the power supply capability of the low-voltage battery 10 is insufficient. In order to suppress the discharge from the low-voltage battery 10, the idle speed of the engine 22 is increased (that is, idled up) for the purpose of increasing the power generation amount of the generator 21. Here, the idle speed is based on the idle speed when the specific low-pressure system load 50 is not operating, and raising the engine speed from the standard idle speed is called idle-up. Lowering the engine speed than the idling engine speed is called idle down.

  As shown in FIG. 1, if there are a plurality of batteries, if there is a margin in the remaining capacity of the high-voltage battery 20, power is actively transferred from the high-voltage battery 20 side to the low-voltage battery 10 side. , The discharge from the low-voltage battery 10 can be suppressed without performing the above-described idle-up. If the high-voltage system load 60 connected to the high-voltage system battery 20 is an electric load in which a dark current (current consumed when the ignition is turned off) hardly flows, the capacity reduction factor of the high-voltage system battery 20 when the ignition is off is only self-discharge. Therefore, power can be more positively transferred from the high voltage system battery 20 side to the low voltage system battery 10 side.

  However, in a transient situation such as when the operation of power transfer by the DC / DC converter 30 is started or when the direction of power transfer is switched, the high-voltage battery 20 depends on the operating state of the high-voltage load 60 and the internal state of the high-voltage battery 20. The voltage on the side may fluctuate.

  FIG. 2 is a diagram showing voltage fluctuation and current fluctuation of the high voltage battery 20 when the operation mode of the DC / DC converter 30 is switched between the boost mode and the stop mode. The high voltage load 60 is EPS and the high voltage It is a simulation result in case the system battery 20 is a lithium ion battery. (A) Current consumption (load current) of EPS, (b) Charge / discharge current (Li battery current) of a lithium ion battery, (c) Output current (DDC current) of DC / DC converter 30, (d) Represents the voltage of the lithium ion battery when the DC / DC converter 30 switches the power transfer, and (e) represents the voltage of the lithium ion battery when the DC / DC converter 30 does not switch the power transfer. (A) is a positive value in the direction of flowing into the EPS, (b) is in the direction of discharging, and (c) is in the direction of transferring power from the low pressure system side to the high pressure system side.

  As shown in FIG. 2, when the operation mode of the DC / DC converter 30 is switched from the step-up mode to the stop mode, the DDC current becomes almost zero (period of “DDC switching”). Accordingly, when the operation mode of the DC / DC converter 30 is switched from the boost mode to the stop mode while the EPS connected to the lithium ion battery is in operation, the discharge current from the lithium ion battery increases rapidly, and therefore (d) of FIG. ), The voltage of the lithium ion battery tends to drop. The voltage of the lithium ion battery tends to drop as the current consumption of the EPS increases, and also tends to drop as the internal resistance of the lithium ion battery increases. If such a rapid voltage fluctuation occurs while the high-voltage system load 60 is operating, the operation of the high-voltage system load 60 tends to become unstable. It is also conceivable that the voltage is lower than the minimum operating voltage of the high-voltage load 60 due to voltage fluctuation. For example, in the case of EPS, the assist amount may change due to a rapid voltage fluctuation (for example, 3 V or more), and the steering steering feeling may change. Although FIG. 2 shows a case where the boost mode is switched to the stop mode, a phenomenon similar to that of FIG. 2 may occur when the boost mode is switched to the step-down mode.

  Therefore, the vehicle power supply system according to the present embodiment is a DC / DC converter when the state of the low-voltage system battery 10 satisfies a predetermined condition indicating a decrease in power supply capacity and the high-voltage system load 60 is in an operating state. When the high-voltage load 60 is in an inoperative state, the DC / DC converter 30 compensates for the shortage of power required on the low-voltage system side by increasing the amount of power generated by the generator 21 without executing the power transfer by the generator 21. The shortage of power required on the low-voltage system side is compensated by executing power transfer from the high-voltage system side to the low-voltage system side. Alternatively, the vehicular power supply system according to the present embodiment, when the state of the low voltage battery 10 satisfies a predetermined condition indicating a decrease in power supply capacity, and the internal resistance of the high voltage battery 20 is greater than a predetermined value. When the shortage of power required on the low-voltage system side is compensated by the increase in the amount of power generated by the generator 21 without executing the power transfer by the DC / DC converter 30, and the internal resistance of the high-voltage battery 20 is smaller than a predetermined value. Compensates for the shortage of power required on the low-voltage system side by transferring power from the high-voltage system side to the low-voltage system side by the DC / DC converter 30.

  FIG. 3 is an operation flow of the vehicle power supply system of the present embodiment. The ECU 40 monitors the voltage of the low voltage system battery 10 and monitors whether or not a voltage equal to or lower than a predetermined value is detected (step 10). When the voltage of the low-voltage battery 10 is detected to be equal to or lower than a predetermined value, it is considered that the power supply capability of the low-voltage battery 10 is reduced. In addition, when the battery remaining capacity of the low voltage system battery 10 is detected to be equal to or less than a predetermined value, it may be considered that the power supply capability of the low voltage system battery 10 is reduced. When the voltage of the low-voltage battery 10 is equal to or lower than the predetermined value (step 10; Yes), the ECU 40 determines whether or not the high-voltage load 60 is in operation (step 12). When the high-voltage system load 60 is in operation (step 12; Yes), the power generation amount by the generator 21 is increased to increase the power supply capability on the low-voltage system battery 10 side (step 14). In order to increase the power generation amount of the generator 21, the idle rotation speed of the engine 22 may be increased to a rotation speed that generates a necessary power generation amount. On the other hand, when the high-voltage system load 60 is inactive (step 12; No), the operation mode of the DCDC converter 30 is set to the step-down mode without increasing the power generation amount by the generator 21, and the low-voltage system battery 10 In order to increase the power supply capability on the side, execution of power transfer is started (step 16).

  Of course, in step 12, it is determined whether or not the internal resistance of the high-voltage battery 20 is greater than or equal to a predetermined value. If it is greater than or equal to the predetermined value, the process proceeds to step 14, and if smaller than the predetermined value, the process proceeds to step 16. .

  It is desirable that the power transfer to the low-voltage system side be executed only when the remaining capacity of the high-voltage system battery 20 is greater than or equal to a predetermined value. This is to prevent the power supply capability on the high voltage system side from being reduced by executing the power transfer to the low voltage system side when the remaining capacity of the high voltage system battery 20 is small. Moreover, it is desirable that the power transfer to the low-voltage system side be executed only when the current sensor 4 and other devices in the system are not abnormal.

  Therefore, according to the vehicle power supply system of the present embodiment, when the high voltage system load 60 is in an operating state or when the internal resistance of the high voltage system battery 20 is large, power transfer to the low voltage system battery 20 side is not performed. Can prevent the operation of the high-voltage system load 60 (especially, an electric load such as EPS with high power consumption) from becoming unstable, and can increase the amount of power generated by the generator 21 to increase the amount of power generated by the generator 21. It is possible to suppress a decrease in power capability. When the power generation amount by the generator 21 is increased and the pulley ratio of the alternator that is the generator 21 is variable, the pulley ratio is changed within the allowable range of the engine torque without idling up. The amount of power generation can be increased. The speed of the alternator is equal to the product of the engine speed and the pulley ratio.

  Moreover, according to the vehicle power supply system of the present embodiment, the frequency of idle-up can be suppressed by executing the power transfer from the high voltage system side to the low voltage system side. As a result, it is possible to suppress deterioration in fuel consumption due to idle-up and to reduce NV (noise and vibration) due to an increase in engine speed. In addition, by performing power transfer from the high voltage system side to the low voltage system side, it is possible to idle down by that amount of power, so when performing power transfer from the high voltage system side to the low voltage system side, by idling down Suppression of fuel consumption deterioration and NV can be reduced.

  By the way, as the voltage fluctuation on the low voltage system side increases, the low voltage system load 50 may become unstable. In particular, the unstable operation of the lamps appears as a phenomenon that is easily perceived by the user as a change in luminance (illuminance) such as blinking of light. The blinking of the lamps causes the brightness of the lamps to fluctuate instantaneously due to a voltage drop instantaneously, and the user feels as if the lamps are blinking. However, when the luminance of the lamps changes gradually, that is, when the voltage changes gradually, the user becomes difficult to recognize the luminance change.

FIG. 4 is a diagram illustrating a case where the voltage of the low-voltage battery 10 rapidly increases due to power transfer of the DC / DC converter. When the voltage of the low-voltage battery 10 drops because the low-voltage battery 10 is in a discharged state and a specific low-voltage load 50 (for example, an air conditioner or a headlight) is turned on (operated), Power transfer to the low-pressure system side is executed. When the state of the low-voltage battery 10 is switched from the discharged state to the charged state by the electric power transfer, as shown in FIG. 4, the voltage of the low-voltage battery 10 has a large fluctuation range (ΔV ₁ ). As a result, the operation of the low-pressure load 50 tends to become unstable.

  Therefore, the vehicle power supply system according to the present embodiment has a case where the state of the low-voltage battery 10 satisfies a predetermined condition indicating a decrease in power supply capacity (for example, when the low-voltage battery 10 is equal to or lower than a predetermined voltage, When the system battery 10 is below a predetermined remaining capacity, or when the low voltage system battery 10 is in a discharged state and a specific electric load is turned on, the rate of increase in the output value of the transfer power of the DC / DC converter 30 is reduced. . FIG. 5 is a diagram showing a case where the increase rate of the output current of the DC / DC converter 30 is changed to a predetermined value or less. As shown in FIG. 5, the current increases gradually by reducing the increase rate of the output current of the DCDC converter 30, so that instantaneous voltage fluctuations are suppressed and a rapid brightness change of the lamps is caused. Can be prevented.

On the other hand, FIG. 6 is a diagram showing a case where the voltage of the low-voltage battery 10 suddenly drops due to the power transfer of the DC / DC converter. When the voltage of the low voltage battery 10 rises due to a specific low voltage system load 50 (for example, an air conditioner or a headlight) being turned off (inactive) while the low voltage system battery 10 is charged, the high voltage system side by the DC / DC converter The power transfer from the power source to the low-pressure system side is stopped. When the state of the low voltage battery 10 is switched from the charged state to the discharged state due to the stop of the power transfer, as shown in FIG. 6, the voltage range of the voltage of the low voltage battery 10 increases (ΔV ₃ ). As a result, the operation of the low-pressure load 50 tends to become unstable.

  Therefore, in the vehicle power supply system of the present embodiment, the reduction rate of the output value of the transfer power of the DC / DC converter 30 in the process of stopping the execution of the power transfer from the high voltage system side to the low voltage system side of the DC / DC converter 30. Make it smaller. FIG. 7 is a diagram showing a case where the output current reduction rate of the DC / DC converter 30 is changed to a predetermined value or less. As shown in FIG. 7, the current decreases gradually by reducing the decrease rate of the output current of the DC / DC converter 30, so that instantaneous voltage fluctuations are suppressed and the lamps have a sharp brightness. Changes can be prevented.

  The preferred embodiments of the present invention have been described in detail above. However, the present invention is not limited to the above-described embodiments, and various modifications and substitutions can be made to the above-described embodiments without departing from the scope of the present invention. Can be added.

  For example, when the temperature of the high-voltage battery 20 (lithium ion battery) is high, the internal resistance is small and the instantaneous voltage fluctuation is low. Therefore, when the temperature of the high-voltage system battery 20 is equal to or higher than a predetermined value, it is possible to permit execution of power transfer from the high-voltage system side to the low-voltage system side, assuming that the influence of voltage fluctuation is small.

  In the embodiment of the above-described vehicle power supply system, the high-voltage system side and the low-voltage system side are divided through the DC / DC converter 30. However, even in the same voltage system embodiment, the high-voltage system and the low-voltage system are used. The present invention can also be implemented in embodiments in which are mutually replaced.

It is a block diagram which shows one Embodiment of the power supply system for vehicles of this invention. It is the figure which showed the voltage fluctuation | variation and electric current fluctuation | variation of the high voltage | pressure system battery 20 when the operation mode of the DC / DC converter 30 is switched between a pressure | voltage rise mode and a stop mode. It is an operation | movement flow of the vehicle power supply system of this embodiment. It is the figure which showed the case where the voltage of the low voltage | pressure system battery 10 raised rapidly by the electric power transfer of a DC / DC converter. It is the figure which showed the case where the increase rate of the output current of the DC / DC converter 30 was changed into below predetermined value. It is the figure which showed the case where the voltage of the low voltage | pressure system battery 10 fell rapidly by the electric power transfer of a DC / DC converter. It is the figure which showed the case where the decreasing rate of the output current of the DC / DC converter 30 was changed into below predetermined value.

Explanation of symbols

4 Current Sensor 5 Voltage Sensor 10 Low Voltage Battery 20 High Voltage Battery 21 Generator 22 Engine 30 DC / DC Converter 40 ECU
50 Low pressure system load 60 High pressure system load

Claims (13)

First power storage means that is a power source of the first electrical load;
A second power storage means that is a power source of the second electrical load;
Power generation means capable of charging power generated by the first power storage means;
A power supply system for a vehicle having power transfer means for executing power transfer from the second power storage means to the first power storage means,
An operating state detecting means for detecting an operating state of the second electric load;
When the state of the first power storage unit satisfies a predetermined condition indicating a decrease in power supply capacity, and the second electrical load is detected as an operating state by the operating state detecting unit, the power generating unit The power transfer by the power transfer means is executed when the power generation amount by the power transfer means increases and the second electrical load is detected to be inactive by the operation state detection means. Power system. First power storage means that is a power source of the first electrical load;
A second power storage means that is a power source of the second electrical load;
Power generation means capable of charging power generated by the first power storage means;
A power supply system for a vehicle having power transfer means for executing power transfer from the second power storage means to the first power storage means,
An internal resistance detecting means for detecting an internal resistance of the second power storage means;
When the internal resistance of the second power storage unit is detected by the internal resistance detection unit when the state of the first power storage unit satisfies a predetermined condition indicating a decrease in power supply capability, When the amount of power generated by the power generation means increases and the internal resistance detection means detects that the internal resistance of the second power storage means is smaller than a predetermined value, the power transfer by the power transfer means is executed. A power supply system for a vehicle. First power storage means that is a power source of the first electrical load;
A second power storage means that is a power source of the second electrical load;
A power supply system for a vehicle having power transfer means for executing power transfer from the second power storage means to the first power storage means,
The vehicle is characterized in that the power transfer means increases the transfer power at an output change rate equal to or less than a predetermined value when the state of the first power storage means satisfies a predetermined condition indicating a decrease in power supply capability. Power system.   The vehicle power supply system according to claim 3, wherein the power transfer unit adjusts a current of the transfer power.   The vehicular power supply system according to any one of claims 1 to 3, wherein, as the predetermined condition, the first power storage unit is set to a predetermined voltage or less.   The vehicular power supply system according to any one of claims 1 to 3, wherein the first power storage unit has a predetermined remaining capacity or less as the predetermined condition.   The vehicle power supply system according to claim 1, wherein the power generation means generates power based on rotation of an engine.   The vehicle power supply system according to claim 7, wherein the amount of power generated by the power generation means increases as the idle speed of the engine increases.   The vehicular power supply system according to claim 8, wherein when the power transfer by the power transfer means is executed, the idle speed of the engine is reduced.   The vehicle power supply system according to any one of claims 1 to 9, wherein the power transfer by the power transfer means is executed when a remaining capacity of the second power storage means is a predetermined value or more.   The vehicle power supply system according to any one of claims 1 to 10, wherein the second power storage unit is a voltage system power supply higher than the first power storage unit.   The vehicle power supply system according to any one of claims 1 to 11, wherein the second power storage means is a lithium ion battery.   The vehicle power supply system according to any one of claims 1 to 12, wherein the second electric load is an electric power steering device.

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