JP2012125051A - Power supply control device of electric automobile - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a power supply control device of an electric automobile, which efficiently uses an electric motor while preventing a degradation of a battery.SOLUTION: The electric automobile includes the battery 18 and a capacitor 20 as power supplies of the motor 6 driving a vehicle 1. When the battery 18 becomes in an over-loading state (S2), charging and discharging in the battery 18 is restricted (S4), and an insufficient or excessive power (S5) generated by the restriction is distributed to the capacitor 20 (S7).

Description

  The present invention relates to a power supply control device for an electric vehicle, and more particularly to a power distribution control technique for an electric vehicle having a motor (motor) as a drive source and a battery and a capacitor as a power supply for the motor.

In recent years, a hybrid electric vehicle (HEV) including an electric motor together with an engine as a drive source of the vehicle, an electric vehicle (EV) using only the electric motor as a drive source, and the like. And although the battery is mainly used as the power supply of the said electric motor, a capacitor can also be used.
In general, the power source of the motor is required to have both a large charge capacity and a light weight / small volume, that is, high energy density and charge / discharge characteristics that can cope with various acceleration / deceleration patterns. A battery has good characteristics in terms of energy density, but generates heat during charging and discharging. For this reason, depending on the conditions, there is a need to add a power output limitation by a protection circuit against self-heating, or the battery itself may be deteriorated. Such an influence is caused by, for example, charging / discharging of a large current or continuous repeated charging / discharging. On the other hand, the capacitor is suitable for charge / discharge of a large current and repeated charge / discharge, and has good charge / discharge characteristics. On the other hand, it does not reach the battery in terms of energy density, and as a result, the charge capacity that can be mounted on the electric vehicle is smaller than that of the battery.

  Paying attention to such characteristics, there is a technique in which charging of a capacitor is performed at the time of braking when a large current is generated, and charging to the battery is performed at the time of non-braking to avoid rapid charging (see Patent Document 1).

JP 2010-202189 A

In Patent Document 1, switching between the battery and the capacitor is performed in accordance with the driver's accelerator operation and brake operation, and the capacitor is charged during braking when the accelerator operation is not performed and the brake operation is performed.
However, for example, when there is no braking operation on an expressway or the like and the driving is continuously performed only by turning the accelerator on and off, in Patent Document 1, a load is applied only to the battery. Furthermore, when the above Patent Document 1 is applied to a vehicle (for example, a large commercial vehicle) set to generate a strong deceleration driving force by an accelerator OFF operation, and further assuming the driving conditions shown in the above example, the vehicle characteristics and As a result of the control characteristics, a large load is applied to the battery. In this way, when the battery is subjected to a long-term or strong load, the temperature of the battery rises, and it is forced to limit power output by the battery protection circuit, and as a result, generation of the expected motor driving force becomes impossible. Alternatively, there is a problem that deterioration of the battery itself is promoted.

  The present invention has been made to solve such a problem, and an object of the present invention is to provide a power supply control device for an electric vehicle that can efficiently use an electric motor while preventing deterioration of the battery. It is in.

  In order to achieve the above object, the power control apparatus for an electric vehicle according to claim 1 is a power control apparatus for an electric vehicle provided with a battery and a capacitor as a power source of an electric motor for driving the vehicle, the battery and the capacitor, Between the power supply distribution means for distributing the power supplied to the motor and the charging power from the motor, the battery state detection means for detecting the state of the battery, and the battery state detected by the battery state detection means Battery charging / discharging limiting means for limiting charging / discharging in the battery and charging / discharging to the battery by the battery charging / discharging limiting means when the battery is in a predetermined state indicating an overload state, The power distribution means causes insufficient power supply to the electric motor due to restriction of charging / discharging to the battery or It is characterized by and a power distribution control means for distributing the capacitor surplus charging power from the electric motor.

  The power control apparatus for an electric vehicle according to claim 2, wherein the battery state detection unit detects a battery state based on a temperature of the battery, and the battery charge / discharge restriction unit includes the battery state detection unit. When the temperature of the battery detected by the detection means is equal to or higher than a predetermined temperature, it is determined that the battery is overloaded, and charging / discharging in the battery is limited.

  According to the electric vehicle power supply control apparatus of the first aspect of the present invention using the above means, in an electric vehicle including a battery and a capacitor as a power source of an electric motor for driving the vehicle, when the battery is overloaded. The charging / discharging in the battery is limited, and the insufficient supply power or surplus charging power generated by the limitation is distributed to the capacitors.

As described above, during the charging / discharging limitation of the battery, the capacitor can supplementally support the limitation, so that the power supply to the motor can be maintained while preventing the battery from being deteriorated, and at the time of charging. Can recover the charging power without waste, and can efficiently use the electric motor.
According to the power control device for an electric vehicle of the second aspect, the battery state can be detected easily and accurately by detecting the battery state based on the battery temperature that affects the deterioration of the battery. And by restrict | limiting a battery based on such a battery temperature, it can restrict | limit a battery appropriately and can prevent deterioration of a battery more reliably.

BRIEF DESCRIPTION OF THE DRAWINGS It is the schematic block diagram which showed the whole structure in one Embodiment of the power supply control apparatus of the electric vehicle concerning this invention. It is a flowchart showing the control routine which vehicle ECU in one Embodiment of the power supply control apparatus of the electric vehicle which concerns on this invention performs.

Hereinafter, embodiments of the present invention will be described with reference to the drawings.
Referring to FIG. 1, there is shown a schematic configuration diagram of a power supply control device for an electric vehicle according to an embodiment of the present invention.
A vehicle 1 shown in FIG. 1 is a parallel hybrid electric vehicle, and an input shaft of a clutch 4 is connected to an output shaft of a diesel engine (hereinafter referred to as an engine) 2. An input shaft of the transmission 8 is connected via a rotating shaft of an electric motor 6 that can generate electric power, such as a synchronous motor. The output shaft of the transmission 8 is connected to the left and right drive wheels 16 via a propeller shaft 10, a differential device 12 and a drive shaft 14.

The engine 2 is a prime mover that is generally used for automobiles, and may be a gasoline engine other than a diesel engine.
In the vehicle 1 having the configuration, when the clutch 4 is connected, both the output shaft of the engine 2 and the rotating shaft of the electric motor 6 are mechanically connected to the drive wheels 16 via the transmission 8, and the clutch 4 is disconnected. When this is done, only the rotating shaft of the electric motor 6 is mechanically connected to the drive wheels 16 via the transmission 8.

In addition, a battery 18 and a capacitor 20 are mounted on the vehicle 1 as a power source for the electric motor 6. The battery 18 is a secondary battery such as lithium ion or nickel metal hydride, and the capacitor 20 is an electric double layer capacitor.
The battery 18 and the capacitor 20 are electrically connected to a power distribution unit 22 (power distribution unit, battery charge / discharge limiting unit), and the power distribution unit 22 is electrically connected to the electric motor 6 via an inverter 24. ing.

The power distribution unit 22 distributes the power supplied to the motor 6 and the charging power from the motor 6 between the battery 18 and the capacitor 20.
When power is supplied to the electric motor 6 to be driven by the electric motor 6 at the time of vehicle acceleration or the like, the battery 18 and the capacitor 20 discharge DC power at a rate distributed by the power distribution unit 22, respectively, and AC power is supplied by the inverter 24. And is supplied to the electric motor 6. The electric motor 6 operates as a motor when electric power is supplied, and the driving force is changed to an appropriate speed by the transmission 8 and then transmitted to the driving wheels 16.

  Further, when the vehicle decelerates, the electric motor 6 functions as a generator, and the electric motor 6 generates AC power by the driving force transmitted in reverse from the driving wheels 16 and is driven by the regenerative torque generated by the electric motor 6 at this time. A deceleration resistance is applied to the wheel 16. Then, the AC power is converted into DC power by the inverter 24, and then charged to the battery 18 and the capacitor 20 at the distribution ratio distributed in the power distribution unit 22, and the kinetic energy due to the rotation of the drive wheels 16 is recovered as electric energy. Is done.

  On the other hand, the driving force of the engine 2 is transmitted to the transmission 8 via the rotating shaft of the electric motor 6 when the clutch 4 is connected, and is transmitted to the drive wheels 16 after being shifted to an appropriate speed. Therefore, when the electric motor 6 operates as a motor when the driving force of the engine 2 is transmitted to the driving wheels 16, the driving force of the engine 2 and the driving force of the electric motor 6 are respectively driven via the transmission 8. It will be transmitted to the wheel 16. That is, a part of the driving force to be transmitted to the driving wheels 16 for driving the vehicle 1 is supplied from the engine 2 and the shortage is supplied from the electric motor 6 and assisted.

  Further, when the state of charge (SOC) of the battery 18 or the capacitor 20 decreases and the battery 18 or the capacitor 20 needs to be charged, the electric motor 6 is used as a generator even when the vehicle 1 is traveling. The power is generated by operating the electric motor 6 using a part of the driving force of the engine 2 and converting the generated AC power into DC power by the inverter 20 and distributing it in the power distribution unit 22. The battery 18 and the capacitor 20 can be charged.

The battery 18 and the capacitor 20 are provided with a corresponding battery ECU 26 (battery state detecting means) and a capacitor ECU 28, respectively.
The battery ECU 26 detects the battery state such as the temperature of the battery 18, the voltage of the battery 18, and the current flowing between the battery 24 and the battery 18, and calculates the charging rate of the battery 18.

Capacitor ECU 28 detects a capacitor state such as a voltage of capacitor 20 and a current flowing between inverter 24 and calculates a charging rate of capacitor 20.
The vehicle 1 is provided with a vehicle ECU 30 to which information from the battery ECU 26 and the capacitor ECU 28 and other information from various sensors and devices (not shown) are input. The vehicle ECU 30 controls various devices based on the input information.

For example, the vehicle ECU 30 has a function of distributing the driving force necessary for driving the vehicle to the engine 2 and the electric motor 6 according to conditions and controlling each driving force. Further, the vehicle ECU 30 performs power distribution control on the battery 18 and the capacitor 20 by the power distribution unit 22 based on the battery state detected by the battery ECU 26.
Hereinafter, the power distribution control executed in the vehicle ECU 30 will be described in detail.

FIGS. 2 and 3 show flowcharts showing a power distribution control routine executed in the vehicle ECU, which will be described below.
As shown in step S <b> 1 of FIG. 2, the vehicle ECU 30 first acquires battery information from the battery ECU 26.
In subsequent step S2, it is determined whether or not the battery 18 is in an overload state from the acquired battery information. Specifically, the determination is made based on whether or not the battery temperature is higher than a predetermined temperature at which battery deterioration is promoted. If it is determined that the battery temperature is equal to or lower than the predetermined temperature and the battery 18 is not in an overload state, the determination result is false (No), and the process proceeds to step S3.

In step S <b> 3, the vehicle ECU 30 normally controls the power distribution unit 22. The normal control is to control the power distribution unit 22 so that the battery 18 is mainly used as a power source for the electric motor 6, and is a control conventionally performed, and detailed description thereof is omitted.
On the other hand, if the battery temperature is higher than the predetermined temperature and it can be determined that the battery 18 is in an overload state in step S2, the determination result is true (Yes), and the process proceeds to step S4.

In step S <b> 4, the vehicle ECU 30 limits the charging / discharging rate of the battery 18 according to the overload state of the battery 18 by the power distribution unit 22. As the limitation, for example, the charging / discharging ratio of the battery 18 is decreased as the temperature of the battery 18 increases.
In the next step S5, the power shortage due to the shortage of the power supplied to the motor 6 caused by limiting the charge / discharge ratio of the battery 18 in the above step S4 or the surplus power in the surplus of the charging power regenerated by the motor 6 is calculated. To do.

In step S6, it is determined whether or not the charging rate of the capacitor 20 is within a predetermined range (for example, 10 to 90%) based on information from the capacitor ECU 28. When the capacitor charging rate is within the predetermined range, the determination result is true (Yes), and the process proceeds to the next step S7.
In step S7, the distribution ratio to the capacitor 20 is increased in the power distribution unit 22 so as to assist the capacitor 20 with the insufficient power or surplus power calculated in step S5 (capacitor assist).

On the other hand, if the capacitor charging rate is outside the predetermined range in step S6, the determination result is false (No), and the process proceeds to step S8.
In step S8, when the electric power supplied to the electric motor 6 is insufficient, the vehicle ECU 30 stops the distribution of the driving force to the electric motor 6, and the engine 2 compensates for the driving torque shortage caused by the electric motor 6 caused by the electric power shortage ( Engine assist). When the charging power is surplus, the vehicle ECU 30 stops the surplus charging by stopping or reducing the request for the regenerative driving force for the electric motor 6, or discharging the surplus charging to the outside.

  By repeating the control routine as described above, the vehicle ECU 30 distributes insufficient supply power or excess charge power generated by the restriction to the capacitor 20 while restricting charging / discharging of the battery 18 when the battery 18 is overloaded. . Since the capacitor 20 can efficiently charge and discharge in a shorter time than the battery 18, such insufficient power or surplus power can be allowed immediately.

In this way, during the charging / discharging limitation of the battery 18, the capacitor 20 supplementarily bears the limitation, so that it is possible to maintain the power supply to the electric motor 6 while preventing the deterioration of the battery 18. Further, at the time of charging, the charging power can be recovered without waste, and the electric motor 6 can be used efficiently.
Further, the battery state can be easily and accurately detected by detecting the battery state based on the battery temperature that affects the deterioration of the battery 18. And by restrict | limiting the battery 18 based on such battery temperature, the restriction | limiting of the battery 18 can be performed appropriately and deterioration of the battery 18 can be prevented more reliably.

Although the description of the embodiment of the power control device for an electric vehicle according to the present invention is finished above, the embodiment is not limited to the above embodiment.
For example, in the above embodiment, the vehicle 1 is a hybrid vehicle including the engine 2 and the electric motor 6 as drive sources, but the present invention can also be applied to an electric vehicle using only the electric motor as a drive source.

Moreover, in the said embodiment, although the overload state of the battery 18 is detected based on the temperature of the battery 18 in the battery ECU26, the said battery state detection means is not restricted to battery temperature. For example, the current integrated value of the battery during a predetermined period may be calculated, and it may be determined that the battery is in an overload state when the current integrated value exceeds a predetermined threshold.
Moreover, in the said embodiment, when it determines with the battery 18 being an overload state, the charging / discharging rate to the battery 18 is reduced so that the temperature of the battery 18 becomes high, and the charging / discharging rate of the battery 18 is restrict | limited. However, the charging / discharging itself by the battery 18 may be stopped and switched to the capacitor 20 as a power source of the electric motor.

DESCRIPTION OF SYMBOLS 1 Vehicle 2 Engine 6 Electric motor 18 Battery 20 Capacitor 22 Power distribution part (Power distribution means, battery charge / discharge restriction means)
26 battery ECU (battery state detection means)
28 Capacitor ECU
30 vehicle ECU (power distribution control means)

Claims (2)

A power control device for an electric vehicle including a battery and a capacitor as a power source for an electric motor that drives the vehicle,
Power distribution means for distributing supply power to the motor and charging power from the motor between the battery and the capacitor;
The battery state detecting means for detecting the state of the battery;
Battery charge / discharge restriction means for restricting charge / discharge in the battery when the battery state detected by the battery state detection means is in a predetermined state indicating an overload state;
When charging / discharging of the battery is restricted by the battery charging / discharging limiting means, the power distribution means causes insufficient power supply to the electric motor due to restriction of charging / discharging to the battery or surplus charging from the electric motor. Power distribution control means for distributing power to the capacitors;
An electric vehicle power supply control device comprising: The battery state detection means detects a battery state based on the temperature of the battery,
The battery charge / discharge limiting unit determines that the battery is overloaded when the temperature of the battery detected by the battery state detection unit is equal to or higher than a predetermined temperature, and limits charge / discharge in the battery. The power control apparatus for an electric vehicle according to claim 1.

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