JP4479123B2 - Vehicle battery control apparatus and method - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a vehicle battery control apparatus and method, and more particularly to battery state of charge (SOC) control.
[0002]
[Prior art]
A hybrid vehicle equipped with a motor generator and a battery in addition to the engine is known.
[0003]
In a hybrid vehicle (or widely an electric vehicle), the state of charge (SOC) of the battery (or battery) is detected, and when the SOC drops below a predetermined value, the motor generator functions as a generator to charge the battery. Charging is stopped when the SOC reaches a predetermined target value.
[0004]
Normally, the SOC is controlled with a target value of about 50% in order to start the engine and perform torque assist and to efficiently perform regenerative braking.
[0005]
[Problems to be solved by the invention]
However, the output and regeneration of the battery are temperature-dependent, and generally the output or regeneration characteristics rapidly decrease at low temperatures. Therefore, the output characteristics at low temperatures are factors that determine the battery capacity in order to supply the power necessary to start the engine reliably (ie, start the motor) in cold regions. If the battery is designed to be secured, the battery capacity becomes very large, which is disadvantageous in terms of weight or cost.
[0006]
In addition, if the design is based on the characteristics at low temperature, the output characteristics are excessive and more wasteful than the originally required output characteristics at room temperature or high temperature.
[0007]
A configuration in which a plurality of batteries having different SOCs are provided in parallel for sharing the output / regeneration function has been proposed, but there is a problem in that the cost increases.
[0008]
The present invention has been made in view of the above-described problems of the prior art, and an object of the present invention is to stably operate a battery even under various temperature conditions without increasing the battery capacity. A control device and method are provided.
[0009]
[Means for Solving the Problems]
In order to achieve the above object, the present invention is an apparatus for controlling the state of charge of a battery mounted on a vehicle, and changes the state of charge according to the temperature of the battery so that output characteristics are substantially constant. And a charging state adjusting means.
[0010]
Here, it is preferable that the state of charge adjustment means increase the state of charge as the temperature of the battery decreases.
[0011]
The apparatus further includes means for detecting an outside air temperature of the battery, and the charge state adjusting means preferably changes the lower limit value of the state of charge according to the outside air temperature, It is preferable that the charging state adjusting unit increases the lower limit value of the charging state as the outside air temperature is lower.
[0012]
The present invention also provides a method for controlling the state of charge of a battery mounted on a vehicle. The method includes a step of detecting a temperature of the battery, and a step of controlling charging / discharging of the battery by changing a control target value of the state of charge of the battery according to the temperature of the battery. .
[0013]
In this method, it is preferable that the control target value is set to be lower as the temperature of the battery is higher.
[0014]
The method further includes detecting an outside air temperature of the battery, and it is preferable that the lower limit value of the control target value is changed according to the outside air temperature, and the lower limit value of the control target value is It is preferable to set the temperature lower as the outside air temperature is higher.
[0015]
Thus, in the present invention, the SOC is not controlled to a constant value, but is changed according to the temperature of the battery and the outside air temperature. The battery output decreases as the battery temperature decreases. Therefore, the lower the battery temperature, the larger the SOC is set (the higher the battery temperature is, the smaller the SOC is set), thereby suppressing both the shortage of output at low temperature and the excessive output at high temperature, and the required output regardless of temperature. Can be obtained. In addition, when the outside air temperature is low, the battery temperature may drop suddenly when the battery is not operating, and in some cases, the required output may not be obtained at the time of restarting. By setting the lower limit value, the required output can be secured.
[0016]
Since the outside air temperature can change variously, the lower limit value of the SOC may be adjusted using the minimum value of the outside air temperature within a certain period.
[0017]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, embodiments of the present invention will be described with reference to the drawings.
[0018]
<First Embodiment>
FIG. 1 shows a system conceptual diagram of the present embodiment. A battery 10 is mounted on the vehicle and cooled by a cooling system 20 to prevent overheating. A motor generator 14 is connected to the battery 10 via a relay 12. The battery 10 is supplied to a battery ECU 16 that monitors the current and voltage of the battery 10 and the state of the battery temperature battery.
[0019]
On the other hand, an ECU 18 that controls the operation of the motor generator 14 is provided, and the battery ECU 16 detects the SOC of the battery 10 based on the input current and voltage and outputs the detected SOC to the ECU 18. The battery ECU 16 also outputs the detected battery temperature to the ECU 18.
[0020]
The ECU 18 controls the operation of the motor generator 14 based on the supplied SOC and battery temperature. That is, the SOC of the battery 10 is compared with a control target value, and the motor generator 14 is charged as a generator so as to match the control target value.
[0021]
Conventionally, the SOC control target value is constant regardless of the temperature, for example, approximately 50%. However, in this embodiment, the SOC control target value is changed according to the detected battery temperature, and the SOC is set. Dynamically controlled according to temperature.
[0022]
FIG. 2 shows the relationship between the SOC of the battery 10 controlled by the ECU 18 in this embodiment and the battery output at that time. In the figure, the horizontal axis is the battery temperature, the vertical axis (left) is the control center SOC value, and the right axis is the battery output. The SOC of the battery 10 is set so as to have a negative correlation with the battery temperature as indicated by reference numeral 100, that is, the SOC decreases as the battery temperature increases (or the SOC increases as the battery temperature decreases). The
[0023]
As described above, the output of the battery 10 decreases at a low temperature and increases at a high temperature. Therefore, by controlling the SOC so that it is large at a low temperature and small at a high temperature as indicated by reference numeral 100, the output of the battery 10 becomes substantially constant regardless of the temperature as indicated by reference numeral 102. As a result, the engine can be reliably started even at low temperatures without significantly increasing the battery capacity, and the output can be ensured as necessary and sufficient even at high temperatures, and waste can be eliminated.
[0024]
In FIG. 2, the SOC is linearly related to the battery temperature. However, the present invention is not limited to this, and an arbitrary relationship in which the SOC decreases as the battery temperature increases (non-linear is also possible). Including).
[0025]
<Second Embodiment>
FIG. 3 is a block diagram showing a configuration according to another embodiment of the present invention. A battery 10 is mounted as in FIG. 1, and a motor generator 14 is connected to the battery 10 via a relay 12. The battery 10 is supplied to a battery ECU 16 that monitors the current and voltage of the battery 10 and the state of the battery temperature battery. The motor generator 14 is controlled by the ECU 18. Specifically, the motor generator 14 is controlled so that the SOC of the battery 10 matches the control target value. The control target value is set to be smaller as the battery temperature is higher.
[0026]
On the other hand, in this embodiment, the detection part 22 which detects the external temperature of the battery 10 (or vehicle in which the battery 10 is mounted) is further provided, and the detected external temperature data is supplied to the battery ECU 16 or the ECU 18.
[0027]
The ECU 18 changes the lower limit value of the SOC of the battery 10 according to the outside air temperature data. Specifically, when the outside air temperature is low, the SOC lower limit value is set large, and when the outside air temperature is high, the lower limit value is set small.
[0028]
FIG. 4 shows the relationship between the battery temperature and the control center SOC in the present embodiment. The horizontal axis is the battery temperature, and the vertical axis is the control center SOC. Further, the SOC indicated by reference numeral 104 is when the outside air temperature is high, and the reference numeral 106 is the SOC when the outside air temperature is low. The SOC of the battery 10 is basically small when the battery temperature is high, but if it is set too small, it may be considered that the engine restart may be hindered when the outside air temperature is low. For example, it is assumed that the battery temperature is 40 ° C. and the outside air temperature is 0 ° C. and 20 ° C. When the vehicle is stopped, the ignition is turned off, and the battery 10 shifts from the operating state to the non-operating state, the battery temperature rapidly decreases when the outside air temperature is 0 ° C. compared to 20 ° C. Accordingly, if the SOC when the battery temperature is 40 ° C. is uniquely set, the SOC is sufficient to obtain a sufficient output when the outside air temperature is 20 ° C., but the outside temperature is 0 ° C. May not be an SOC that provides sufficient output upon restart.
[0029]
Therefore, the lower limit value of the SOC is raised particularly when the outside air temperature is low in a high temperature range where the SOC is small (correcting the SOC upward), so that the engine can be reliably restarted even when the outside air temperature is low. it can. In FIG. 4, it should be noted that the lower limit raising amount (upward correction amount) is larger as the outside air temperature is lower.
[0030]
When setting the lower limit based on the outside air temperature data, it is desirable to extract the lowest temperature from the outside air temperature data for the past several days and set it according to this lowest temperature (minimum outside air temperature). This is because the engine restart is guaranteed at the lowest temperature, so that the engine can be reliably restarted at other temperatures.
[0031]
Of course, the lower limit value can also be set based on the future minimum outside air temperature data instead of the minimum temperature data of the past several days. For example, the vehicle is equipped with an information terminal for Internet connection, and the minimum temperature data of the next day is acquired by this information terminal and a lower limit value is set.
[0032]
Alternatively, it is possible to determine the current season from date data and the like, and indirectly set the lower limit value by estimating the minimum temperature from the season.
[0033]
【The invention's effect】
As described above, according to the present invention, the required output can be secured even under various temperature conditions by controlling the state of charge of the battery without increasing the battery capacity.
[Brief description of the drawings]
FIG. 1 is a configuration block diagram of an embodiment.
FIG. 2 is a graph showing the relationship between battery temperature, SOC, and output according to the embodiment.
FIG. 3 is a configuration block diagram of another embodiment.
FIG. 4 is a graph showing the relationship between battery temperature, SOC, and outside air temperature according to another embodiment.
[Explanation of symbols]
10 battery, 12 relay, 14 motor generator, 16 battery ECU, 18 ECU, 20 cooling system.

Claims (8)

A device for controlling the state of charge of a battery mounted on a vehicle,
Charge state adjusting means for changing the state of charge according to the temperature of the battery so that the output characteristics are substantially constant, the charge state adjusting means for increasing the state of charge as the temperature of the battery decreases;
Means for detecting the outside temperature of the battery;
Have
The vehicle battery control device according to claim 1, wherein the charging state adjusting means increases the lower limit value of the charging state as the outside air temperature is lower . The apparatus of claim 1.
The means for detecting the outside temperature extracts the minimum temperature from the outside temperature data of the past several days,
The vehicular battery control device, wherein the charging state adjusting means sets a lower limit value of the charging state according to the extracted minimum temperature . The apparatus of claim 1 .
The means for detecting the outside air temperature predicts the future minimum outside air temperature data,
The vehicle state battery control apparatus, wherein the state of charge adjusting means sets a lower limit value of the state of charge according to the predicted minimum temperature . The apparatus of claim 1 .
The means for detecting the outside temperature estimates a minimum temperature from the current season,
The vehicle battery control device, wherein the charging state adjusting means sets a lower limit value of the charging state according to the estimated minimum temperature . A method for controlling the state of charge of a battery mounted on a vehicle,
Detecting the temperature of the battery;
The step of controlling the charging / discharging of the battery by changing the control target value of the state of charge of the battery according to the temperature of the battery , wherein the control target value is set lower as the temperature of the battery is higher When,
Detecting the outside temperature of the battery;
Have
In the charging / discharging control step, the lower limit value of the control target value is set lower as the outside air temperature is higher . The method of claim 5, wherein
In the step of detecting the outside air temperature, the lowest temperature is extracted from the outside air temperature data of the past several days,
The vehicle battery control method characterized in that, in the step of controlling the charge / discharge, a lower limit value of the state of charge is set according to the extracted minimum temperature . The method of claim 5 , wherein
In the step of detecting the outside air temperature, predicting future minimum outside air temperature data,
In the step of controlling the charging / discharging, a vehicle battery control method is characterized in that a lower limit value of the state of charge is set according to the predicted minimum temperature . The method of claim 5 , wherein
In the step of detecting the outside air temperature, the minimum temperature is estimated from the current season,
In the step of controlling the charging / discharging, the vehicle battery control method is characterized in that a lower limit value of the state of charge is set according to the estimated minimum temperature .

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