JP7373113B2 - Vehicle power control device - Google Patents

Description

The present invention relates to a power supply control device for a vehicle, and particularly to a control device for a power supply installed in a vehicle.

Japanese Unexamined Patent Publication No. 2016-118126 (Patent Document 1) describes an engine stop control device. This engine stop control device is equipped with a first power storage unit and a second power storage unit, and when the second power storage unit does not store electric power equal to or greater than the amount of starting power required to start the engine, The generator is caused to store electricity in the second power storage unit, and after the required power is stored, the engine is stopped. In addition, in this engine stop control device, the DC-DC converter is operated according to the state of charge of the first power storage unit and the second power storage unit, and the electric power stored in the high voltage second power storage unit is reduced to a low voltage. The first power storage unit is configured to be charged.

As in the invention described in Patent Document 1, two power storage units operating at different voltages are provided, and a DC-DC converter is operated according to their charging states to transfer the electric power stored in each power storage unit. 2. Description of the Related Art Power control devices for vehicles that attempt to use power efficiently are known. For example, there are known power supply devices for vehicles that include a high-voltage battery and a low-voltage battery as the first and second power storage units, and power supply devices for vehicles that include a capacitor and a lead battery that is a low-voltage battery. There is. In these power supply devices, part of the power stored in the high-voltage power storage unit or the power generated by the motor generator can be stepped down by a DC-DC converter and then supplied to a lead-acid battery or various electrical loads. It is being said.

Japanese Patent Application Publication No. 2016-118126

However, it is difficult to accurately grasp the state of charge of the plurality of power storage units, and there is a problem in that a part of the electric power generated by the generator or the like is wasted. For example, it is possible to detect the state of charge of each power storage unit by providing a dedicated current sensor for each power storage unit, but providing a dedicated current sensor for each power storage unit would be costly. There's a problem. For this reason, when a lead-acid battery is used as a low-voltage power storage unit, charging is always continued from the high-voltage side via the DC-DC converter regardless of the state of charge, and a portion of the power is wasted. This is the current situation.

Therefore, the present invention provides a vehicle power supply control device that can accurately determine the state of charge of a low-voltage power storage unit without providing a dedicated sensor for detecting the current flowing into the low-voltage power storage unit. is intended to provide.

In order to solve the above-mentioned problems, the present invention is a control device for a power supply installed in a vehicle, which includes: a generator that generates electric power; a high-voltage battery that stores the electric power generated by the generator; A low-voltage battery whose nominal voltage is lower than this high-voltage battery, a voltage converter to step down the output voltage from the high-voltage battery, a current output from this voltage converter and flowing to the low-voltage battery, and a low-voltage battery. It has a current sensor for detecting the output current, which is the sum of the current flowing through the electrical load, and a control unit for controlling the voltage converter, and the voltage converter steps down the output voltage from the high voltage battery. The control unit is configured to charge the low-voltage battery and power a low-voltage electrical load connected to the low-voltage battery and the voltage converter, and the control unit detects the usage status of the low-voltage electrical load and the current sensor. The low voltage battery is configured to determine the state of charge of the low voltage battery based only on the output current, and does not determine whether the low voltage battery is fully charged when the engine mounted on the vehicle is operating. When the engine installed in the vehicle is stopped, if the output current detected by the current sensor drops below a predetermined first current, it is determined that the low voltage battery is fully charged , and the low voltage battery The fact that the battery is no longer fully charged is determined based on the output current detected by the current sensor even while the engine is running.

In the present invention configured in this way, the electric power generated by the generator is stored in the high voltage battery. The voltage converter also steps down the output voltage from the high-voltage battery to charge the low-voltage battery, which has a nominal voltage lower than the high-voltage battery, and also connects the low-voltage battery and the voltage converter to the low-voltage battery. Provides power to the load. The control unit determines when the engine is stopped that the low voltage battery is fully charged based on the current detected by the current sensor that detects the output current of the voltage converter.

The state of charge of a low-voltage battery can be determined by using a current sensor that detects the output current of a voltage converter connected to the low-voltage battery and low-voltage electrical load, instead of using a dedicated current sensor that detects the current flowing into the low-voltage battery. It is also conceivable to estimate based on the detected current. However, when the engine installed in a vehicle is running, pulsed current is constantly supplied to the engine's injectors and spark plugs, which introduces a large amount of noise into the electrical system and reduces the The inventor has discovered that the state of charge of a voltage battery cannot be accurately estimated. According to the present invention configured as described above, when the output current detected by the current sensor decreases to a predetermined first current or less while the engine is stopped, the control unit causes the low voltage battery to become fully charged. Determine whether it has been done. Therefore, electrical noise generated by the engine can be avoided, and it is possible to accurately determine whether the low voltage battery is fully charged by the current sensor that detects the output current of the voltage converter.
Furthermore, if the power stored in the low-voltage battery decreases significantly, it may become impossible to supply sufficient power to the engine or on-vehicle electrical equipment, which may impede their operation. According to the present invention configured as described above, it is determined that the low voltage battery is no longer in a fully charged state based on the output current detected by the current sensor while the engine is operating. A decrease in the amount of electricity stored in the battery can be determined before the amount of electricity stored in the battery decreases significantly. Thereby, it is possible to reliably avoid an excessive decrease in the amount of electricity stored in the low voltage battery.

In the present invention, preferably, the control unit reduces the target output voltage of the voltage converter when determining that the low voltage battery is fully charged.
In the present invention configured in this manner, when it is determined that the low voltage battery is fully charged, the target output voltage of the voltage converter is lowered, so that the voltage flows from the voltage converter to the low voltage battery. The current becomes essentially zero. Thereby, the current supplied to the fully charged low voltage battery can be suppressed, and the electric power stored in the high voltage battery can be efficiently utilized.

In the present invention, preferably, the control unit is configured to execute idling stop when a predetermined idling stop condition is satisfied, and the control unit is configured to perform idling stop when the engine is stopped due to idling stop, and the control unit is configured to Determine whether the battery is fully charged.

Generally, the low voltage battery is often fully charged in the idling stop state while the vehicle is running, and sufficient time can be secured to determine whether the low voltage battery is fully charged. According to the present invention configured as described above, when the engine is stopped due to idling stop, it is determined whether or not the low voltage battery is fully charged, so that the low voltage battery can be reliably and effectively charged. It is possible to determine whether the battery is fully charged.

According to the vehicle power supply control device of the present invention, the state of charge of the low voltage battery can be accurately determined without providing a dedicated sensor for detecting the current flowing into the low voltage battery.

1 is a block diagram schematically showing the overall configuration of a hybrid vehicle to which a vehicle power control device according to an embodiment of the present invention is applied. 1 is a block diagram schematically showing the electrical configuration of a vehicle power supply control device according to an embodiment of the present invention. 3 is a flowchart showing the operation of the vehicle power supply control device according to the embodiment of the present invention. FIG. 3 is a diagram showing the relationship between the current output from the DC-DC converter and the current flowing through the low-voltage battery and the low-voltage electric load in the vehicle power supply control device according to the embodiment of the present invention. FIG. 3 is a diagram schematically showing the relationship between the charging state of a low-voltage battery and the output current from a DC-DC converter in a vehicle power supply control device according to an embodiment of the present invention.

Next, a vehicle power supply control device according to an embodiment of the present invention will be described with reference to the accompanying drawings.

[Device configuration]
First, the configuration of a vehicle power supply control device according to an embodiment of the present invention will be described. FIG. 1 is a block diagram schematically showing the overall configuration of a hybrid vehicle to which a vehicle power control device according to an embodiment of the present invention is applied. As shown in FIG. 1, the hybrid vehicle 1 mainly includes an engine 11, a gear-driven starter 12, an ISG (Integrated Starter Generator) 13, a lithium-ion battery 14, and a DC-DC converter that is a voltage converter. 17, a lead acid battery 19, a high voltage electrical load 20, and a low voltage electrical load 21. In the following, since the voltage (nominal voltage) of the lithium ion battery 14 is higher than the voltage (nominal voltage) of the lead acid battery 19, the lithium ion battery 14 will be appropriately referred to as the "high voltage battery 14", and the lead acid battery 19 will be appropriately referred to as "the high voltage battery 14". low voltage battery 19.

The engine 11 is an internal combustion engine (gasoline engine or diesel engine) that generates driving force for the hybrid vehicle 1. The driving force of the engine 11 is transmitted to the wheels 5 via the output shaft 9, the transmission 2, the reduction gear 3, and the drive shaft 4. A gear-driven starter 12 is connected to the output shaft 9 of the engine 11 via a gear. The gear-driven starter 12 starts the engine 11 using electric power supplied from the low-voltage battery 19 when an ignition switch (not shown) is turned on by the user. Further, the hybrid vehicle 1 includes a brake system 7 for applying a braking force to the vehicle 1 according to the operation of the brake pedal by the driver. This brake system 7 is constituted by, for example, an electric brake.

ISG 13 is a motor generator that is driven by engine 11 and has a power generation function to generate electricity, and an electric function to generate driving force for hybrid vehicle 1 . ISG 13 is connected to output shaft 9 of engine 11 via belt 8 . Further, the ISG 13 is electrically connected to a high voltage battery 14 via a resistor 6a and switch elements 6b and 6c. These switch elements 6b and 6c function as a relay device that switches between connecting and disconnecting the high voltage battery 14 and the DC-DC converter 17. When the ISG 13 and the high voltage battery 14 are connected for the first time, the switch element 6b on the side where the resistor 6a is provided is turned on to prevent damage to electronic components etc. due to rush current. Thereafter, the switch element 6c is turned on to maintain the connection between the ISG 13 and the high voltage battery 14.

Furthermore, when the ISG 13 operates with a power generation function, it functions as a generator that generates power by rotating a rotor that rotates in conjunction with the output shaft 9 of the engine 11 in a magnetic field. The ISG 13 has a built-in rectifier (not shown), and uses this rectifier to convert the generated AC power into DC power. The electric power generated by the ISG 13 is supplied to the high voltage battery 14 for charging, or is supplied to the high voltage electric load 20. On the other hand, when the ISG 13 operates by electric function, it drives the output shaft 9 of the engine 11 via the belt 8 using the electric power charged in the high voltage battery 14 . In addition, in order to adjust the tension of the belt 8 when switching between operation using the power generation function and operation using the electric function in the ISG 13, it is recommended to apply a pendulum type variable tension tensioner (decoupling alternator tensioner) to the belt 8. good.

High voltage battery 14 includes a plurality of lithium ion batteries connected in series, and low voltage battery 19 includes a plurality of lead acid batteries connected in series. For example, the nominal voltage of the high voltage battery 14 is 24V DC, and the nominal voltage of the low voltage battery 19 is 12V DC. These high-voltage batteries 14 and low-voltage batteries 19 store electrical energy through chemical reactions, so they are not suitable for rapid charging and discharging, but they can store a relatively large amount of electric power because it is easy to secure a charging capacity. It has the characteristic of being able to

DC-DC converter 17 is provided between high voltage battery 14 and low voltage battery 19. The DC-DC converter 17 changes the input voltage by, for example, turning on and off a built-in switching element and outputs the input voltage. Specifically, the DC-DC converter 17 steps down the output voltage of the high voltage battery 14 and supplies it to the low voltage battery 19 side, thereby charging the low voltage battery 19. For example, the DC-DC converter 17 steps down a voltage of approximately 24 V DC supplied from the high voltage battery 14 side to approximately 12 V DC, and outputs the voltage to the low voltage battery 19 side. Further, a converter output current sensor 18, which is a current sensor for detecting the output current from the DC-DC converter 17, is connected to the output side of the DC-DC converter 17. Current supplied from the DC-DC converter 17 to the low voltage battery 19, low voltage electrical load 21, etc. flows through the converter output current sensor 18, and the total value of these currents can be measured.

The high-voltage electrical load 20 is an electrical load that operates at a voltage of, for example, about 24 VDC, and the low-voltage electrical load 21 is an electrical load that operates at a voltage lower than the high-voltage electrical load 20, for example, about 12 VDC. The high voltage electrical load 20 is supplied with at least one of the power generated by the ISG 13 and the power charged in the high voltage battery 14 . Furthermore, the low voltage electrical load 21 includes at least one of the power generated by the power generation of the ISG 13, charged to the high voltage battery 14, and stepped down by the DC-DC converter 17, and the power charged to the low voltage battery 19. is supplied. In one example, the high voltage electrical load 20 includes a heater (such as a seat heater), and the low voltage electrical load 21 includes an electric power steering mechanism (EAPS), an air conditioner, audio equipment, and the like.

Next, with reference to FIG. 2, the electrical configuration of the vehicle power supply control device according to the embodiment of the present invention will be described. FIG. 2 is a block diagram schematically showing the electrical configuration of the vehicle power supply control device according to the embodiment of the present invention.

In this embodiment, the hybrid vehicle 1 is controlled by a controller 10, which is a control unit as shown in FIG. This controller 10 includes one or more processors, various programs that are interpreted and executed on the processor (including basic control programs such as an OS, and application programs that are started on the OS and realize specific functions), and programs. The computer is equipped with an internal memory such as ROM or RAM for storing information and various data.

Specifically, as shown in FIG. 2, the controller 10 mainly includes a converter input voltage sensor 30, a battery voltage sensor 34, a battery temperature sensor 35, an ISG temperature sensor 36, a converter output current sensor 18, and a bonnet sensor. Detection signals corresponding to the parameters detected by each of 38 are input. Converter input voltage sensor 30 detects the input voltage of DC-DC converter 17. Battery voltage sensor 34 detects the terminal voltage of low voltage battery 19 . Battery temperature sensor 35 detects the temperature of low voltage battery 19 . The ISG temperature sensor 36 detects the temperature of the ISG 13.

Converter output current sensor 18 detects the current output from DC-DC converter 17. Current supplied from the DC-DC converter 17 to the low voltage battery 19, low voltage electrical load 21, etc. flows through the converter output current sensor 18, and the total value of these currents can be measured. The hood sensor 38 is configured to output a detection signal indicating whether the hood of the vehicle 1 is in an open state or a closed state.

The controller 10 also controls the ISG 13, the DC-DC converter 17, the gear drive starter 12, the switch elements 6b, 6c, and the A control signal is output to each of the voltage electrical load 20 and the low voltage electrical load 21. In this way, the controller 10 controls the power generation operation and electric operation of the ISG 13, the step-down operation of the DC-DC converter 17, the driving and stopping of the high-voltage electrical load 20, the low-voltage electrical load 21, and the gear-driven starter 12, and the switching Controls on/off of elements 6b and 6c.

Typically, the controller 10 is configured to use at least the ISG 13 to execute a plurality of controls prescribed according to the operating state of the hybrid vehicle 1 for the purpose of improving fuel efficiency and the like. These multiple controls include an acceleration assist control for generating power from the ISG 13 to assist acceleration by the engine 11 when the hybrid vehicle 1 accelerates, and an acceleration assist control for causing the ISG 13 to generate regenerative power when the hybrid vehicle 1 decelerates. deceleration regeneration control and supplying power to the high voltage electrical load 20 and the low voltage electrical load 21 when a predetermined condition is satisfied (for example, a situation in which an increase in the load on the engine 11 due to power generation by the ISG 13 should be suppressed). Non-power generation control that prohibits the ISG 13 from generating electricity, and idling that automatically stops the engine 11 when the hybrid vehicle 1 stops and then restarts the engine 11 by generating power from the ISG 13 when the hybrid vehicle 1 starts. and a stop control.

Furthermore, the controller 10 performs control to operate each of the high voltage electrical load 20 and the low voltage electrical load 21. Specifically, when operating the high-voltage electric load 20, the controller 10 supplies at least one of the electric power generated by the power generation of the ISG 13 and the electric power charged in the high-voltage battery 14 to the high-voltage electric load 20. control to supply the Further, when operating the low voltage electrical load 21, the controller 10 uses at least the power charged in the high voltage battery 14 and stepped down by the DC-DC converter 17, and the power charged in the low voltage battery 19. Control is performed to supply either one to the low voltage electrical load 21.

The "vehicle power supply control device" according to the embodiment of the present invention mainly includes an ISG 13 as a "generator," a high voltage battery 14, a low voltage battery 19, and a DC-DC as a "voltage converter." It is composed of a DC converter 17, a converter output current sensor 18 as a "current sensor", and a controller 10 as a "control unit".

Next, the operation of the vehicle power supply control device according to the embodiment of the present invention will be described with reference to FIGS. 3 to 5.
FIG. 3 is a flowchart showing the operation of the vehicle power control device according to the embodiment of the present invention. FIG. 4 is a diagram showing the relationship between the current output from the DC-DC converter and the current flowing through the low voltage battery and the low voltage electrical load. FIG. 5 is a diagram schematically showing the relationship between the charging state of the low voltage battery and the output current from the DC-DC converter.

FIG. 3 is a flowchart showing the process executed by the controller 10 in order to set the target output voltage of the DC-DC converter 17.
First, in step S1 of FIG. 3, detection signals from each sensor are read into the controller 10. Specifically, in step S1, the input voltage of the DC-DC converter 17 detected by the converter input voltage sensor 30, the terminal voltage of the low voltage battery 19 detected by the battery voltage sensor 34, and the terminal voltage of the low voltage battery 19 detected by the battery temperature sensor 35 are determined. The temperature of the low voltage battery 19 and the temperature of the ISG 13 detected by the ISG temperature sensor 36 are read into the controller 10. Further, in step S1, the current output from the DC-DC converter 17 detected by the converter output current sensor 18 is also read into the controller 10.

Next, in step S2, it is determined whether or not the engine 11 is under idling stop. In this embodiment, the controller 10 is configured to transmit a control signal to the engine 11 and execute the idling stop when a predetermined idling stop condition is satisfied. Therefore, the process in the flowchart of FIG. 3 proceeds to step S3 if the controller 10 is executing the idling stop, and returns to step S1 if the idling stop is not being executed.

That is, when the engine 11 is operating, current is supplied to the injector, spark plug, etc. (not shown), so a large pulsed current flows through the power system of the hybrid vehicle 1. As a result, the current value detected by converter output current sensor 18 includes large noise. As described above, when the engine 11 is being operated, the detection value by the converter output current sensor 18 is not stable, so the determination of full charge in step S3 and subsequent steps is not executed. If the idling stop is not in progress in step S2, the process in the flowchart returns to step S1, and thereafter, the processes in steps S1 and S2 are repeated until the idling stop is executed.

Next, if the idling stop is in progress, the process advances to step S3, and in step S3, it is determined whether or not the low voltage electrical load 21 with large current consumption is being used. If the low voltage electrical load 21 with large current consumption is not in use, the process proceeds to step S4, and if the low voltage electrical load 21 with large current consumption is in use, the process returns to step S1.

That is, as shown in FIG. 4, the current supplied from the high voltage battery 14 and stepped down by the DC-DC converter 17 is supplied to the low voltage electrical load 21 and is also used to charge the low voltage battery 19. Ru. Here, the current I _dcout [A] detected by the converter output current sensor 18 is the current I _car [A] supplied to the low voltage electrical load 21 and the charging current I _bat [A] to the low voltage battery 19 is the total current of Therefore, depending on the converter output current sensor 18, it is not possible to directly measure the charging current I _bat to the low voltage battery 19, but when the current I _car supplied to the low voltage electrical load 21 is small, the low voltage battery The charging current I _bat to 19 can be estimated. Therefore, if the electrical component (low-voltage electrical load 21) with large current consumption is not in use, the process advances to step S4, and if it is in use, it is determined whether the low-voltage battery 19 is fully charged or not. No determination is made and the process returns to step S1.

Next, in step S4, it is determined whether the output current I _dcout from the DC-DC converter 17 detected by the converter output current sensor 18 is less than or equal to a predetermined first current. If the output current I _dcout from the DC-DC converter 17 is less than or equal to the predetermined first current, it is determined that the low voltage battery 19 is "fully charged" and the process proceeds to step S5, where the predetermined first current If the current is less than 1 current, it is determined that the battery is not fully charged, and the process returns to step S1.

That is, when the low voltage battery 19 is fully charged, the charging current I _bat flowing to the low voltage battery 19 is small and is mainly consumed for gassing, and this current is stored in the low voltage battery 19 as electrical energy. It never happens. Furthermore, when the low voltage electrical load 21, which consumes a large amount of current, is not in use, the current I _car supplied to the low voltage electrical load 21 is also relatively small and has a substantially constant value. Therefore, if the output current I _dcout from the DC-DC converter 17 is less than or equal to the predetermined first current while the low-voltage electrical load 21 with a large current consumption is not in use, the low-voltage battery 19 is It can be determined that the battery is fully charged. In this embodiment, when the output current from the DC-DC converter 17 is 12.5 [A] or less, it is determined that the low voltage battery 19 is "fully charged."

FIG. 5 schematically illustrates this relationship. FIG. 5 is a diagram in which the vertical axis represents the output current I _dcout from the DC-DC converter 17 when the low-voltage electric load 21 with large current consumption is not used, and the horizontal axis represents the state of charge of the low-voltage battery 19. It is. Further, in FIG. 5, the output current I _dcout when the engine 11 is not operating is shown by a solid line, and the output current I _dcout when the engine 11 is not operating is shown by a dashed-dotted line.

As shown by the solid line in FIG. 5, when the low voltage battery 19 is not fully charged (insufficient charge), a relatively large charging current I _bat flows, so the output current I _dcout from the DC-DC converter 17 is relatively large. , the output current I _dcout becomes smaller as the fully charged state approaches. When the low voltage battery 19 is fully charged, the charging current I _bat of the low voltage battery 19 becomes very small, so the output current I _dcout from the DC-DC converter 17 is equal to the current supplied to the low voltage electrical load 21. It is almost equal to I _car . In this embodiment, this current is approximately 12.5 [A], and when the output current I _dcout becomes 12.5 [A] or less, it is determined that the battery is in a fully charged state. In other words, when the low voltage battery 19 is not fully charged and the charging current I _bat is substantially flowing, the output current I _dcout from the DC-DC converter 17 decreases to about 12.5 [A] or less. There's nothing to do.

In this way, in step S4 of FIG. 3, when it is determined that the output current I _dcout is equal to or less than the predetermined first current (12.5 [A]) and the low voltage battery 19 is determined to be "fully charged" In step S5, the target output voltage of the DC-DC converter 17 is lowered. That is, the controller 10 sends a control signal to the DC-DC converter 17, and the DC-DC converter 17 steps down the voltage of the high voltage battery 14 to lower the target value of the output voltage. In this embodiment, the target output voltage of the DC-DC converter 17 is reduced from 13.85 [V] to 13.5 [V].

By lowering the target output voltage of the DC-DC converter 17 in this way, the charging current I _bat that flows from the DC-DC converter 17 to the low-voltage battery 19 and was consumed for gassing becomes almost zero, reducing wasted current. Can be suppressed. Note that the above target output voltage is a value when the temperature of the battery fluid of the low voltage battery 19 detected by the battery temperature sensor 35 is 30°C, and the target output voltage is determined based on a preset map (not shown). ) etc. and preferably change based on temperature.

Next, in step S6, the detection signals of each sensor are read into the controller 10 again. The processing in step S6 is the same as step S1 described above, so the explanation will be omitted.

Furthermore, in step S7, it is determined whether the output current I _dcout of the DC-DC converter 17 is greater than zero. Under normal conditions, the output current I _dcout of the DC-DC converter 17 is greater than zero (current flows out from the DC-DC converter 17), but if the output voltage of the DC-DC converter 17 drops for some reason. In this case, the output current I _dcout becomes smaller than zero (current flows into the DC-DC converter 17). If the output current I _dcout is greater than zero, the process advances to step S8, and if the output current I _dcout is zero or less than zero, the process advances to step S10 to set the target output voltage of the DC-DC converter 17. raise.

Next, in step S8, it is determined whether the voltage between the terminals of the low voltage battery 19 detected by the battery voltage sensor 34 is higher than a predetermined voltage. That is, when the low voltage battery 19 becomes over-discharged, the voltage between the terminals drops significantly, so in this case, the process proceeds to step S10, and the output voltage of the DC-DC converter 17 is increased. In this embodiment, when the voltage between the terminals of the low voltage battery 19 becomes lower than about 11 [V], it is determined that over-discharge has occurred, and the output voltage of the DC-DC converter 17 is increased. Note that at the time when step S8 is executed, the target output voltage of the DC-DC converter 17 is set to 13.5 [V] (step S5), but in the case of overdischarge, etc., the low voltage battery The voltage across terminals 19 is significantly lower than the target output voltage. On the other hand, if the inter-terminal voltage of the low voltage battery 19 is higher than the predetermined voltage, the process proceeds to step S9.

Next, in step S9, it is determined whether the output current I _dcout of the DC-DC converter 17 is equal to or higher than a predetermined second current. In the present embodiment, the determination of the output current I _dcout in step S9 is performed while the engine 11 is being operated, and the output current I _dcout of the DC-DC converter 17 is 22.0 [A] or more. In some cases, it is determined that the low voltage battery 19 is "no longer fully charged."

This state is shown by the dashed line in FIG. That is, when the engine 11 is in operation, power is consumed by the attached equipment of the engine 11, so even if the low voltage battery 19 is fully charged, the output current I _dcout of the DC-DC converter 17 is It is approximately 19.5 [A]. On the other hand, when the low voltage battery 19 is no longer fully charged (undercharged), the charging current I _bat begins to flow to the low voltage battery 19, so the output current I _dcout of the DC-DC converter 17 increases. In this embodiment, the output current I _dcout increases by about 2.5 [A] to 22.0 [A] compared to the average output current I _dcout of about 19.5 [A] during operation of the engine 11. When the voltage exceeds [A], it is determined that the low voltage battery 19 is not fully charged.

As described above, in the present embodiment, it is determined that the low voltage battery 19 is "no longer in a fully charged state" while the engine 11 is operating, so whether or not the low voltage battery 19 is no longer in a fully charged state is determined. judgments can be performed frequently. Therefore, it is possible to prevent the hybrid vehicle 1 from being driven for a long time in a state where the determination is not performed and the low voltage battery 19 from being over-discharged. Further, as described above, since large noise is generated while the engine 11 is operating, it is difficult to accurately detect the current. However, even if it is erroneously determined that the low voltage battery 19 is no longer in a fully charged state due to noise, it is possible to reliably prevent the low voltage battery 19 from falling into overdischarge, which is on the safe side.

Furthermore, in the present embodiment, the determination as to whether the low voltage battery 19 is no longer fully charged is performed while the engine 11 is running; however, as a modification, this determination may also be performed while the engine 11 is stopped. can be executed. In this case, it is preferable to set the predetermined second current that determines that the low-voltage battery 19 is "no longer fully charged" to be higher than the first current that determines that it is "fully charged." . For example, the second current is set approximately 2.5 [A] more than the first current (12.5 [A]), and the output current I _dcout of the DC-DC converter 17 becomes 15 [A] or more. When the battery is no longer fully charged, it can be determined that the battery is no longer fully charged.

Next, in step S10, the target output voltage of the DC-DC converter 17 is increased from 13.5 [V] to 13.85 [V]. That is, if it is determined in step S9 that the battery is no longer fully charged, or if it is determined that it is over-discharged in step S8, the low voltage battery 19 is increased by increasing the target output voltage. A sufficient charging current I _bat can be passed through the battery, and insufficient charging can be resolved at an early stage. Furthermore, even if it is determined in step S7 that the output current I _dcout of the DC-DC converter 17 is negative, the output voltage of the DC-DC converter 17 is increased by increasing the target output voltage, and the current Backflow can be avoided. Note that the setting of the target output voltage in step S10 is also preferably changed in accordance with the liquid temperature of the low voltage battery 19, similar to the process in step S5.

After increasing the target output voltage of the DC-DC converter 17 in step S10, the process in the flowchart of FIG. The processes from S4 to S4 are repeatedly executed.

According to the vehicle power supply control device of the embodiment of the present invention, when the engine 11 is stopped (steps S2→S3 in FIG. 3), the controller 10 detects the output current I detected by the converter output current sensor 18. When _dcout falls below a predetermined first current (12.5 [A]), it is determined that the low voltage battery 19 is fully charged (steps S4→S5 in FIG. 3). Therefore, electrical noise generated by the engine 11 can be avoided, and the converter output current sensor 18 that detects the output current of the DC-DC converter 17 can accurately detect that the low voltage battery 19 is fully charged. can be determined.

Further, according to the vehicle power supply control device of the present embodiment, when it is determined that the low voltage battery 19 is fully charged, the target output voltage of the DC-DC converter 17 is reduced (step S5), the current flowing from the DC-DC converter 17 to the low voltage battery 19 becomes substantially zero. Thereby, the current supplied to the fully charged low voltage battery 19 can be suppressed, and the electric power stored in the high voltage battery 14 can be efficiently utilized.

Further, according to the vehicle power supply control device of the present embodiment, it is determined that the low voltage battery 19 is no longer in a fully charged state based on the output current I _dcout detected by the converter output current sensor 18 . It is determined in the middle (steps S9→S10 in FIG. 3). Therefore, it is determined frequently that the amount of stored power in the low voltage battery 19 has decreased, and it can be determined that the low voltage battery 19 is no longer in a fully charged state before the amount of stored power decreases significantly. Thereby, an excessive decrease in the amount of electricity stored in the low voltage battery 19 (over-discharge) can be reliably avoided.

Further, according to the vehicle power control device of this embodiment, when the engine is stopped due to idling stop, it is determined whether the low voltage battery 19 is fully charged (step S2 in FIG. 3→ S3). Therefore, the converter output current sensor 18 can detect the output current of the DC-DC converter 17 with less noise, and it is possible to reliably and effectively determine whether the low voltage battery 19 is fully charged.

Although preferred embodiments of the present invention have been described above, various changes can be made to the embodiments described above. In particular, in the embodiments described above, the vehicle power control device of the present invention is applied to a hybrid vehicle, but the present invention can also be applied to vehicles other than hybrid vehicles. Furthermore, in the embodiment described above, it is determined that "the low voltage battery is fully charged" when the engine is in idling stop mode, but the determination can also be made in other cases. . For example, as a modification, it is determined that the low voltage battery is fully charged after the ignition switch of the vehicle is turned on and before cranking is performed (before the engine starts operating). The present invention can also be configured in such a way that

1 Hybrid vehicle 2 Transmission 3 Reducer 4 Drive shaft 5 Wheel 6a Resistor 6b, 6c Switch element (relay device)
7 Brake system 8 Belt 9 Output shaft 10 Controller (control unit)
11 Engine 12 Gear-driven starter 13 ISG (generator)
14 High voltage battery 17 DC-DC converter (voltage converter)
18 Converter output current sensor (current sensor)
19 Low voltage battery 20 High voltage electrical load 21 Low voltage electrical load 30 Converter input voltage sensor 34 Battery voltage sensor 35 Battery temperature sensor 36 ISG temperature sensor 38 Bonnet sensor

Claims (3)

A control device for a power source installed in a vehicle,
a generator that generates electricity;
a high-voltage battery that stores the power generated by this generator;
A low voltage battery whose nominal voltage is lower than this high voltage battery,
a voltage converter for stepping down the output voltage from the high voltage battery;
a current sensor for detecting an output current that is the sum of the current output from the voltage converter and flowing to the low-voltage battery and the current flowing to the low-voltage electric load;
a control unit that controls the voltage converter;
has
The voltage converter steps down the output voltage from the high voltage battery to charge the low voltage battery, and supplies power to the low voltage electrical load connected to the low voltage battery and the voltage converter. It is configured as follows,
The control unit is configured to determine the state of charge of the low voltage battery based only on the usage state of the low voltage electrical load and the output current detected by the current sensor, and is configured to When the engine is running, the determination of whether the low voltage battery is fully charged is not performed;
When the engine mounted on the vehicle is stopped and the output current detected by the current sensor drops below a predetermined first current, it is determined that the low voltage battery is fully charged ;
A power supply control device for a vehicle, characterized in that whether the low voltage battery is no longer in a fully charged state is determined based on an output current detected by the current sensor even while the engine is operating. The vehicle power supply control device according to claim 1, wherein the control unit reduces the target output voltage of the voltage converter when determining that the low voltage battery is fully charged. The control unit is configured to perform idling stop when a predetermined idling stop condition is satisfied, and the control unit is configured to perform idling stop when the engine is stopped due to idling stop, and the low voltage battery is in a fully charged state. The vehicle power supply control device according to claim 1 or 2, wherein the vehicle power control device determines whether or not.

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