JP6965608B2 - Power converter - Google Patents

Description

The present invention relates to a power converter.

In a vehicle such as a hybrid vehicle, there is a technique of stepping down the electric power supplied from the high voltage first battery by a voltage converter to charge the second battery. The charge control device described in Patent Document 1 is known as a conventional technique of this type. The charge control device described in Patent Document 1 includes a charge current calculating means for calculating the charge current of the second battery based on the output current of the voltage converter and the load current on the electric component, and the charge current exceeds a specified value. It is provided with a charge control means for controlling the output voltage of the voltage converter so as not to be present.

Japanese Unexamined Patent Publication No. 2010-200529

However, as in the charging control device described in Patent Document 1, simply controlling the output voltage of the voltage conversion unit so that the charging current does not exceed the specified value is sufficient for the voltage conversion unit as long as the charging current is equal to or less than the specified value . The output voltage keeps rising .

Therefore, in the charge control device described in Patent Document 1, the charge state of the first battery that supplies electric power to the voltage conversion unit may be significantly lowered. Further, in the charge control device described in Patent Document 1, the motor generates electric power to supply electric power to the voltage conversion unit, which may reduce the running performance and acceleration responsiveness of the vehicle and the fuel efficiency. was there.

Therefore, an object of the present invention is to provide a power conversion device capable of improving the acceleration response and fuel efficiency of a vehicle.

In order to solve the above problems, the present invention is a power conversion device including a motor, a first battery, and a second battery, and the motor is mounted on a vehicle connected to the first battery. A voltage converter connected between the first battery and the second battery, transforming the power generated by the motor and the power supplied from the first battery and supplying the second battery, and the voltage conversion. The output voltage control unit includes an output voltage control unit that controls the output voltage of the device, and the output voltage control unit is said to be the voltage converter from the voltage converter while power is being supplied from the motor or the first battery to the voltage converter. The charging current is smaller than the first predetermined current, provided that power is always supplied to the second battery and the charging current charged in the second battery is less than the first predetermined current. It is characterized in that charging current reduction control for controlling the output voltage is performed so as to reduce the current to less than the second predetermined current.

As described above, according to the present invention, it is possible to improve the acceleration responsiveness and fuel efficiency of the vehicle.

FIG. 1 is a block diagram showing a schematic configuration of a vehicle equipped with a power conversion device according to an embodiment of the present invention. FIG. 2 is a flowchart illustrating the operation of the power conversion device according to the embodiment of the present invention. FIG. 3 is a timing chart illustrating the operation of the power conversion device according to the embodiment of the present invention.

The power conversion device according to the embodiment of the present invention is a power conversion device including a motor, a first battery, and a second battery, and the motor is mounted on a vehicle connected to the first battery. , A voltage converter connected between the first battery and the second battery, transforming the power generated by the motor and the power supplied from the first battery and supplying it to the second battery, and the output voltage of the voltage converter. The output voltage control unit includes an output voltage control unit that controls the above, and the output voltage control unit has a charging current that is greater than the first predetermined current, provided that the charging current charged in the second battery is less than the first predetermined current. It is characterized in that charging current reduction control for controlling the output voltage so as to reduce the current to less than a small second predetermined current is performed. Thereby, the power conversion device according to the embodiment of the present invention can improve the acceleration response and the fuel consumption of the vehicle.

Hereinafter, the power conversion device according to the embodiment of the present invention will be described in detail with reference to the drawings.

In FIG. 1, the vehicle 1 according to an embodiment of the present invention includes an engine 2, a starter 3, a motor 4, a main battery 5 as a first battery, a sub battery 6 as a second battery, and voltage conversion. It includes a DC (direct current) DC converter 11 as a device and a control unit 12 as an output voltage control unit. The DCDC converter 11 and the control unit 12 constitute a power conversion device 10.

A plurality of cylinders are formed in the engine 2. In this embodiment, the engine 2 is configured to perform a series of four strokes including an intake stroke, a compression stroke, an expansion stroke, and an exhaust stroke for each cylinder.

The starter 3 is connected to a crankshaft (not shown) of the engine 2, and the engine 2 is started by being rotated by being supplied with electric power from the DCDC converter 11 or the sub-battery 6.

The motor 4 is connected to the crankshaft of the engine 2 via a belt or the like (not shown). The motor 4 has a function of an electric motor that generates motor torque by being supplied with electric power and a function of a generator that converts the rotational force transmitted from the engine 2 into electric power.

By functioning as an electric motor, the motor 4 can assist the power of the engine 2 by the motor torque, or can drive the vehicle 1 only by the motor torque. As described above, the vehicle 1 is configured as a hybrid vehicle capable of traveling by the engine 2 and the motor 4.

The main battery 5 is composed of, for example, a lithium ion storage battery. The main battery 5 is electrically connected to the motor 4 and the DCDC converter 11. The output voltage of the main battery 5 is, for example, about 48V. The main battery 5 is charged with electric power from the motor 4 at a voltage larger than about 48 V.

The sub-battery 6 is composed of, for example, a lead storage battery. The sub-battery 6 is electrically connected to the starter 3, the vehicle load 14, which is an electric load, and the DCDC converter 11. The output voltage of the sub-battery 6 is, for example, about 12V. A current sensor 6A is connected to the sub-battery 6. The current sensor 6A detects the charging current (accepting current) and the discharging current of the sub-battery 6. The current sensor 6A is connected to the control unit 12.

The DCDC converter 11 is connected between the sub-battery 6 and the main battery 5. The DCDC converter 11 transforms the electric power generated by the motor 4 and the electric power supplied from the main battery 5, and can supply the transformed electric power to the sub battery 6. More specifically, the DCDC converter 11 steps down the 48V power generated by the motor 4 or supplied from the main battery 5 to 12V, and supplies the stepped down power to the sub-battery 6.

The control unit 12 includes a CPU (Central Processing Unit), a RAM (Random Access Memory), a ROM (Read Only Memory), a flash memory for storing backup data, an input port, and an output port. It is composed of computer units. That is, the control unit 12 is an ECU (Electronic Control Unit) that electrically controls the control target.

In the ROM of these computer units, various constants, various maps, and the like, as well as programs for causing the computer unit to function as the control unit 12, are stored. When the CPU executes a program stored in the ROM using the RAM as a work area, each of these computer units functions as a control unit 12 in this embodiment. The above-mentioned current sensor 6A is connected to the input port of the control unit 12. Various control objects including the DCDC converter 11 are connected to the output port of the control unit 12.

The control unit 12 controls the output voltage of the DCDC converter 11. Specifically, the control unit 12 sets the output voltage of the DCDC converter 11 as normal control so that the sub-battery 6 is charged with a charging current according to the state of charge (SOC) and performance of the sub-battery 6. It is designed to be controlled.

Therefore, in such a normal control of the DCDC converter 11, when the charging state of the sub-battery 6 is large, the charging current to the sub-battery 6 is controlled to be small.

Here, generally, as a charging method for a battery such as a lead storage battery, a method of continuing charging even when the charged state is sufficiently large and the state is close to full charge is used.

However, when the sub-battery 6 is constantly charged, it is necessary to constantly supply power to the DCDC converter 11 from at least one of the motor 4 and the main battery 5.

Therefore, a part of the engine torque is used for the motor 4 to generate electric power, which causes deterioration of the acceleration responsiveness of the vehicle 1 and deterioration of fuel consumption. Further, by supplying electric power from the main battery 5 to the DCDC converter 11, the state of charge of the main battery 5 is lowered, and the frequency of running in which the motor 4 assists the engine 2 and the frequency of running by the motor 4 alone are reduced. However, there is a possibility that the superiority of the hybrid vehicle cannot be exhibited or the fuel efficiency deteriorates.

Therefore, in order to suppress deterioration of acceleration responsiveness and fuel efficiency of the vehicle 1, the control unit 12 increases the output voltage of the DCDC converter 11 so as to further reduce the charging current when the charging current to the sub-battery 6 is small. Is designed to control.

Specifically, the control unit 12 outputs the DCDC converter 11 so that the charging current I drops below the predetermined current I2, provided that the charging current I charged in the sub-battery 6 is less than the predetermined current I1. Charging current reduction control that controls the voltage is being implemented. The predetermined current I1 corresponds to the first predetermined current in the present invention, and the predetermined current I2 corresponds to the second predetermined current in the present invention.

Further, the control unit 12 executes the charging current reduction control from the time when the execution condition of the charging current reduction control is satisfied until the predetermined time T2 elapses. The predetermined time T2 corresponds to the predetermined time in the present invention.

Further, in the control unit 12, the charging current I is less than the predetermined current I1 before the first charge current reduction control is executed after the engine 2 is started by the starter 3, or the engine 2 is first started. The execution condition of the charge current reduction control is satisfied, provided that the charge current reduction control is executed and the charge current I is larger than the predetermined current I1 and less than the predetermined current I3. The charging current reduction control is performed from the time until the predetermined time T1 elapses. The predetermined current I3 corresponds to the third predetermined current in the present invention.

The output voltage control operation by the control unit 12 of the power conversion device according to the present embodiment configured as described above will be described with reference to FIG. This output voltage control operation is an operation of controlling the output voltage of the DCDC converter 11, and is executed at preset time intervals while the control unit 12 is activated.

The flag f used in the output voltage control operation is set to either 0 or 1. If it is not between the start of the engine 2 and the completion of the first charge current reduction control after the start, and it is not desirable that the charge current reduction control is executed, the flag f is set to 1 and the engine 2 is set. The flag f is set to 0 between the start of the start and the completion of the first charge current reduction control after the start, or when the charge current reduction control may be executed. Here, the case where it is not desirable to execute the charging current reduction control is specifically a case where the execution time of the charging current reduction control exceeds a predetermined time (Ta).

The reason for managing the flag f will be described below. The charge current threshold value I1 used for determining whether or not to execute the charge current reduction control immediately after the engine 2 is started (first after the start) is such that the charge current reduction control is executed when the charge current is not immediately after the engine 2 is started. It is smaller than the threshold value I3 of the charging current used for determining whether or not. Therefore, when the flag f is not used, the charging current becomes less than the threshold value I3 before the charging current becomes less than the threshold value I1 after the engine 2 is started, and the charging current reduction control is started. In this embodiment, the first charge current reduction control after the start of the engine 2 is executed on the condition that the charge current becomes less than the threshold value I1, so that the flag is set until the first charge current reduction control is completed. F is set to 0, and the flag conditions are different depending on whether the charging current reduction control is performed first after the engine 2 is started or not. As a result, since the flag is f = 0 until the charging current reduction control is first executed after the engine 2 is started, step S8 described later becomes NO, and even if the charging current becomes less than I3, it is not less than I1. The charging current reduction control is not executed.

In step S1, the control unit 12 has passed a predetermined time T1 from the start of the engine 2 (denoted as ENG in the figure) by the starter 3, the charging current I is I <I1, and the flag f is f = 0. It is determined whether or not it is. If all three conditions are satisfied in step S1, the determination in step S1 is YES, and if any of the conditions is not satisfied, the determination in step S1 is NO.

If the determination in step S1 is NO, the control unit 12 proceeds to step S7, which will be described later. If the determination in step S1 is YES, the control unit 12 starts counting the timer Ta (counting up from 0) in step S2, and whether the timer Ta is less than T2 (Ta <T2) for a predetermined time in step S3. Judge whether or not.

When Ta <T2 is established in step S3, the control unit 12 performs charge current reduction control for controlling the DCDC converter 11 so that the charge current I drops to I <I2 in step S4, and performs this operation. finish.

If Ta <T2 is not established in step S3, the control unit 12 sets the flag f to 1 in step S5 and resets the timer Ta to 0 in step S6.

Next, the control unit 12 starts counting the timer Tb (counting up from 0) in step S7, and in step S8, Tb is T3 or more (Tb ≧ T3) for a predetermined time, the charging current I is I <I3, and the flag f. Determines whether or not f = 1. If all of these three conditions are satisfied, the determination in step S8 is YES, and if any of the three conditions is not satisfied, the determination in step S8 is NO.

If the determination in step S8 is NO, the control unit 12 performs normal control on the DCDC converter 11 in step S9, and ends the current operation. In the normal control of step S9, the control unit 12 controls the output voltage of the DCDC converter 11 so that the sub-battery 6 is charged with a charging current according to the charging state and performance of the sub-battery 6.

If the determination in step S8 is YES, the control unit 12 sets the flag f to 0 in step S10, resets the timer Tb to 0 in step S11, and proceeds to step S4.

In the output voltage control operation of FIG. 2, immediately after the engine 2 is started by the starter 3, steps S1 and S8 become NO, and steps S1, S7, S8, and S9 change.

After that, while the timer Ta is Ta <T2, steps S1 and S3 become YES, and the process changes to steps S1, S2, S3, and S4.

After that, since the timer Ta becomes Ta ≧ T2, step S1 becomes YES, steps S3 and S8 become NO, and steps S1, S2, S3, S5, S6, S7, S8, and S9.

After that, while the timer Tb is Tb <T3, steps S1 and S8 become NO, and the process changes to step S1, step S7, S8, and S9.

After that, since the timer Tb becomes Tb ≧ T3, step S1 becomes NO, step S8 becomes YES, and the transitions to steps S1, S7, S8, S10, S11, and S4.

When the output voltage control operation is performed by the control unit 12, the charging current of the sub-battery 6 (hereinafter, simply referred to as charging current) and the output voltage of the DCDC converter 11 (hereinafter, simply referred to as output voltage) are as shown in FIG. Transition to.

In FIG. 3, when the starter 3 is driven to start the engine 2 at time t0, electric power is taken out from the sub-battery 6 and the charge amount is reduced. At this time, since the charge amount of the sub-battery 6 decreases, charging is started when the charging current I is larger than I3. After that, as the charging progresses, the charging amount of the sub-battery 6 increases, and the charging current I starts to decrease. Then, at time t1, the charging current I becomes I <I1. After that, at time t2, since the predetermined time T1 has elapsed from the start of the engine 2 (time t0), the charging current reduction control is executed. In this charge current reduction control, the output voltage of the DCDC converter 11 is reduced so that the charge current I is reduced to I <I2. The timing chart of FIG. 3 is an example. When the charging current I becomes I <I1 after a predetermined time T1 has elapsed from the start of the engine 2 (time t0), the charging current I becomes I <I1. The charging current reduction control is executed at the timing when it becomes.

After that, the charging current reduction control is performed from the time t2 until the predetermined time T2 elapses. Then, at time t3 after the elapse of the predetermined time T2, the charging current reduction control is switched to the normal control, so that the charging current I rises to the predetermined threshold value I3 or higher.

After that, at time t4, the charging current I becomes I <I3. After that, at time t5, since the predetermined time T3 has elapsed from time t3, the charging current reduction control is executed, and the output voltage of the DCDC converter 11 is reduced so that the charging current I is reduced to I <I2. The timing chart of FIG. 3 is an example, and when the charging current I becomes I <I3 after the elapse of the predetermined time T3, the charging current reduction control is executed at that timing.

As described above, in the above-described embodiment, the control unit 12 reduces the charging current I to less than the predetermined current I2 on the condition that the charging current I charged to the sub-battery 6 is less than the predetermined current I1. Charge current reduction control that controls the output voltage is performed.

As a result, when the charging current I to the sub-battery 6 is less than the predetermined current I1, the sub-battery 6 does not need to be charged immediately, so that the output voltage of the DCDC converter 11 is set so that the charging current I becomes smaller. Since it is controlled, the power supply from the motor 4 or the main battery 5 to the sub battery 6 is suppressed. Therefore, the acceleration responsiveness and fuel efficiency of the vehicle 1 can be improved.

Further, in the above-described embodiment, the control unit 12 performs the charging current reduction control from the time when the execution condition of the charging current reduction control is satisfied until the elapse of the predetermined time T2.

As a result, when the charging current to the sub-battery 6 is less than the predetermined current I1, the output voltage of the DCDC converter 11 is controlled so that the charging current I becomes even smaller until the predetermined time T2 elapses. The power supply from the motor 4 or the main battery 5 to the sub-battery 6 is suppressed only during the predetermined time T2.

Therefore, it is possible to improve the acceleration responsiveness and fuel efficiency of the vehicle 1 while preventing the state of charge of the sub-battery 6 from being significantly lowered.

Further, in the above-described embodiment, the vehicle 1 includes an engine 2 and a starter that starts the engine 2 by supplying electric power from the sub-battery 6. Then, the control unit 12 is that the charge current I is less than the predetermined current I1 before the first charge current reduction control is executed after the engine 2 is started by the starter 3, or the engine 2 is first after the start. The execution condition of the charge current reduction control is satisfied, provided that the charge current reduction control is executed and the charge current I is larger than the predetermined current I1 and less than the predetermined current I3. The charging current reduction control is performed from the time until the predetermined time T2 elapses.

As described above, when the engine 2 is started, the voltage of the sub-battery 6 drops by supplying electric power to the starter 3, and the charging current I temporarily increases. Therefore, the charging current reduction control is performed with the predetermined current I1 as a threshold value. Will be implemented.

On the other hand, when the engine 2 is not started, the charging current reduction control is performed with a predetermined current I3 larger than the predetermined current I1 as a threshold value.

That is, a small threshold value (predetermined current I1) is used when the engine 2 in which a large amount of electric power is taken out from the sub-battery 6 to the starter 3 is used, whereas a large threshold value (predetermined current I3) is used when the engine 2 is not started. I am using it. Therefore, when the engine 2 is started, it can be charged without limiting the charging current until the charging current becomes smaller than when the engine 2 is not started, so that a large amount of electric power is taken out when the engine 2 is started. The sub-battery 6 can be fully charged.

In this way, by making the threshold value of the charging current for performing the charging current reduction control different depending on whether the engine 2 is started or not, the vehicle can be prevented from significantly deteriorating the charged state of the sub-battery 6. It is possible to improve the acceleration responsiveness and fuel efficiency of 1.

In the above-described embodiment, in step S1, whether or not the charging current I is less than I1 is satisfied as one of the determination conditions, but instead of this determination condition, the charging current I is less than I1. Whether or not I2 or more is satisfied or whether the charging current reduction control is being executed may be used as a determination condition. According to this configuration, when a predetermined time T1 has elapsed from the ENG start by the starter, the flag f = 0, and the charging current I drops to less than I1, the charging current reduction control is started. Can be done. Further, when the charging current reduction control has already been executed, step S1 is YES even if the charging current I is less than I2, so that the charging current reduction control can be continued.

Further, in the above-described embodiment, in step S8, whether or not the charging current I is less than I3 is satisfied as one of the determination conditions, but instead of this determination condition, the charging current I is less than I3. Whether or not I2 or more is satisfied or whether the charging current reduction control is being executed may be used as a determination condition. According to this configuration, when the timer Tb is T3 or more and the flag f = 1, the charging current reduction control can be started when the charging current I drops to less than I3. Further, when the charging current reduction control has already been executed, step S8 is YES even if the charging current I is less than I2, so that the charging current reduction control can be continued.

Although the embodiments of the present invention have been disclosed, it is clear that some skilled in the art can make changes without departing from the scope of the present invention. All such modifications and equivalents are intended to be included in the following claims.

1 Vehicle 2 Engine 3 Starter 4 Motor 5 Main battery (1st battery)
6 Sub-battery (second battery)
10 Power converter 11 DCDC converter (voltage converter)
12 Control unit (output voltage control unit)

Claims (3)

A power conversion device including a motor, a first battery, and a second battery, wherein the motor is mounted on a vehicle connected to the first battery.
A voltage converter connected between the first battery and the second battery, which transforms the electric power generated by the motor and the electric power supplied from the first battery and supplies the second battery.
An output voltage control unit that controls the output voltage of the voltage converter is provided.
The output voltage control unit
While power is being supplied from the motor or the first battery to the voltage converter, control is performed so that power is always supplied from the voltage converter to the second battery.
The implementation condition is that the charging current charged in the second battery is less than the first predetermined current.
A power conversion device characterized in that charging current reduction control for controlling the output voltage is performed so that the charging current is reduced to less than the second predetermined current, which is smaller than the first predetermined current. The output voltage control unit
The power conversion device according to claim 1, wherein the charging current reduction control is performed from the time when the execution conditions are satisfied until a predetermined time elapses. The vehicle includes an engine and a starter that starts the engine by being supplied with electric power from the second battery.
The output voltage control unit
Before the first charging current reduction control is executed after the engine is started by the starter, and the charging current is less than the first predetermined current, or.
The implementation condition is that the charging current is greater than the first predetermined current and less than the third predetermined current after the first charging current reduction control is executed after the engine is started.
The power conversion device according to claim 2, wherein the charging current reduction control is performed from the time when the execution conditions are satisfied until the predetermined time elapses.

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