JP3757602B2 - Battery temperature protection control device - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a battery temperature protection control device that can be applied to a device equipped with a secondary battery as a power source.
[0002]
[Prior art]
It is known that a battery mounted on an electric vehicle or the like generates heat to some extent along with the discharge when the discharge is continued to supply electric power to a device such as a motor. For example, when an overcurrent exceeding the battery capacity is discharged, the battery is excessively heated, causing premature deterioration.
[0003]
Conventionally, in order to avoid such a situation, a method of mounting a battery with a large capacity with some margin than the power consumption of the device has been taken, but this has caused new problems such as enlargement of the device and cost increase .
Accordingly, it is desired to prevent early deterioration of the battery due to excessive heat generation without using an unnecessarily large capacity battery and without increasing the size and cost of the device.
[0004]
As one of countermeasures, there is known a method of determining output power that can be supplied from a battery using the battery temperature as a parameter. That is, the output power may be narrowed toward the upper limit temperature for use of the battery and controlled so as not to exceed the upper limit temperature.
[0005]
Usually, the heat-resistant upper limit temperature of the battery is about 60 ° C., and when the battery is used exceeding this temperature, the battery life may be reduced due to significant deterioration or breakage of the battery cell. Therefore, in the conventional battery temperature protection control device, as shown in FIG. 8, an output restriction region (su) is provided when the battery temperature is between 55 ° C. and 60 ° C., for example, and the output restriction region (su) is reached. When the battery temperature rises, the output power supplied from the battery is controlled to decrease, and the driver may be warned that the battery needs to be charged. Furthermore, when the battery temperature becomes 60 ° C. or higher, the battery is prohibited from being used, and the output power of the motor may be stopped. However, it is not preferable to suddenly stop the battery output at 0% when the battery temperature reaches 60 ° C.
[0006]
[Problems to be solved by the invention]
In the conventional battery temperature protection control device, the absolute value of the battery output is determined in accordance with the battery temperature. Therefore, as shown in FIG. Therefore, the output is limited, the temperature rise of the battery can be suppressed, and the conventional battery temperature protection control device is sufficient.
[0007]
However, as shown in FIG. 10, in the state where the remaining capacity of the battery does not remain so much, it is not necessary to limit the output even when the battery temperature reaches 50 ° C. That is, even if the battery continues to output as it is, DOD = 100% before reaching the temperature (60 ° C.) at which the battery output needs to be prohibited, and the battery cannot be output and covers the battery. There is no need to do it.
It is not preferable to limit the output until there is no need for it.
[0008]
The present invention has been made in view of the above, and as its purpose, the battery output performance can be utilized to the maximum extent within a range where the battery temperature does not exceed the upper limit of use temperature without reducing the battery life. The object is to provide a battery temperature protection control device.
[0009]
[Means for Solving the Problems]
In order to solve the above problem, the invention according to claim 1 is a discharge depth calculation means for obtaining a discharge depth representing the current discharge degree with respect to the output power when the battery is fully charged, and the calculated discharge depth. Accordingly, output limit start temperature calculating means for obtaining an output limit start temperature representing a temperature at which the battery output power limit is started, battery temperature detection means for detecting the battery temperature, and the detected battery temperature is output. When the temperature is higher than the limit start temperature, the gist is to include output limit value calculation means for obtaining an output limit value for limiting the output power of the battery according to the battery temperature.
[0010]
In order to solve the above problem, the invention according to claim 2 is characterized in that the output restriction start temperature calculation means has an output restriction start temperature table that records in advance the output restriction start temperature corresponding to the discharge depth of the battery. To do.
[0011]
In order to solve the above-mentioned problem, the output restriction start temperature table corrects the output restriction start temperature corresponding to the discharge depth based on the heat generation characteristic of the battery according to the battery discharge depth. The gist of this is
[0012]
In order to solve the above-mentioned problem, the invention according to claim 4 is a discharge depth calculation means for obtaining a discharge depth representing a current discharge degree with respect to output power at the time of full charge of the battery, and according to the battery temperature. Output limit value recording means having an output limit value table for prerecording output limit values for limiting output power corresponding to a plurality of different discharge depths, battery temperature detection means for detecting battery temperature, and current discharge The gist of the invention is to include an output limit value calculating means for obtaining an output limit value corresponding to the detected battery temperature with reference to the output limit value table corresponding to the depth.
[0013]
In order to solve the above-mentioned problem, the output limit value table of the output limit value recording means includes a limit start temperature at which the output power of the battery is limited to an output stop temperature at which the output power is stopped. The gist is to record the output limit value in advance.
[0014]
【The invention's effect】
According to the first aspect of the present invention, the discharge depth representing the current degree of discharge is obtained with respect to the output power when the battery is fully charged, and the output power of the battery is determined according to the calculated discharge depth. An output restriction start temperature representing a temperature at which the restriction starts is obtained. Here, when the battery temperature is larger than the output limit start temperature, the battery is determined based on the output limit value by obtaining an output limit value for limiting the output power of the battery according to the battery temperature. Therefore, the output performance of the battery can be utilized to the maximum extent that the battery temperature does not exceed the upper limit temperature of use without reducing the battery life.
[0015]
According to the second aspect of the present invention, there is provided an output restriction start temperature table that records in advance the output restriction start temperature corresponding to the discharge depth of the battery, so that the output restriction start temperature according to the calculated discharge depth. The output limit start temperature can be obtained by referring to the table.
[0016]
According to the third aspect of the present invention, the output restriction start temperature table is obtained by correcting the output restriction start temperature corresponding to the discharge depth based on the heat generation characteristic of the battery according to the battery discharge depth. The output power of the battery can be limited based on the output limit start temperature adapted to the heat generation characteristics of the battery.
[0017]
According to the fourth aspect of the present invention, the depth of discharge representing the current degree of discharge is obtained with respect to the output power when the battery is fully charged. In addition, an output limit value table that records in advance an output limit value for limiting the output power of the battery according to the battery temperature is prepared corresponding to a plurality of different discharge depths. Here, by referring to the output limit value table corresponding to the current depth of discharge, the output limit value corresponding to the detected battery temperature is obtained, so that the output power of the battery is limited based on this output limit value. Therefore, the output performance of the battery can be utilized to the maximum extent within the range where the battery temperature does not exceed the use upper limit temperature without reducing the battery life.
[0018]
According to the invention of claim 5, the output limit value table records in advance the output limit value from the limit start temperature at which the output power of the battery is limited to the output stop temperature at which the output power is stopped. Thus, the output limit value corresponding to the detected battery temperature can be obtained with reference to the output limit value table corresponding to the current discharge depth.
[0019]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, embodiments of the present invention will be described with reference to the drawings.
FIG. 1 is a diagram showing a system configuration of a battery power calculation device 1 suitable for a battery temperature protection control device according to an embodiment of the present invention.
[0020]
In the figure, a motor 7 is connected to the battery 3 via an inverter 5, and a direct current from the battery 3 is converted into a desired three-phase alternating current by the inverter 5 to drive the motor 7.
[0021]
The inverter 5 has a plurality of switching elements inside, and the switching elements are ON / OFF controlled according to the PWM signal output from the motor control unit 9 to thereby convert the DC current from the battery 3 into the three-phase AC current. The output torque of the motor 7 can be controlled by driving control of the switching element. A motor control unit 9 is connected to the inverter 5, and a switching element in the inverter 5 is ON / OFF controlled in accordance with a PWM signal from the motor control unit 9, and a desired three-phase alternating current is supplied to the motor 7. Supplied. The motor 7 drives the vehicle according to the three-phase alternating current supplied from the inverter 5.
[0022]
The motor control unit 9 generates a PWM signal according to a torque command value corresponding to an accelerator opening from the accelerator 11 and a shift position from the shift lever 13 as an operation amount of the driver, and performs PWM (pulse width modulation) control. Do. Further, the motor control unit 9 performs limiter control so as to limit the output power of the battery 3 in accordance with the output limit value PL that changes in the range of 0 to 100% set by the battery control unit 21.
[0023]
The current detector 15 detects a direct current I supplied from the battery 3 to the inverter 5. The temperature detector 17 includes a temperature sensor and detects the battery temperature T of the battery 3 that generates heat during power supply. The voltage detector 19 detects the DC voltage V supplied from the battery 3 to the inverter 5.
[0024]
The battery control unit 21 includes a CPU, a ROM, a RAM (memory unit), a timer, and the like. The direct current I of the battery 3 detected by the current detector 15 and the battery temperature of the battery 3 detected by the temperature detector 17. T, based on the DC voltage V across the battery 3 detected by the voltage detector 19, an output limit value PL for limiting the output power from the battery 3 is calculated and set in the motor controller 9 at predetermined intervals. To do.
[0025]
Here, the discharge characteristics of the battery 3 will be described.
The power value P that can be output when the battery 3 is fully charged is set to 100%, and normally the output power is gradually limited from about 55 ° C., for example. However, in actuality, while the vehicle is running, the battery 3 generates heat, so that the battery temperature T gradually rises and the battery temperature T is 55 ° C., for example, even though the output power value P is sufficient. If it exceeds, the output power will be limited. Ideally, it is not necessary to limit the output power from the battery 3 when the battery temperature T does not exceed 60 ° C. before the output power of the battery 3 runs out.
[0026]
In general, the amount of heat generated by the battery 3 depends on a discharge depth DOD (Depth of Discharge) representing the current degree of discharge with respect to the output power when the battery 3 is fully charged. For example, after an electric vehicle equipped with a fully charged battery is started, when the heat generation amount of the battery 3 is large due to continuous operation and the battery temperature T is also high, the discharge depth DOD is deep and the remaining output power in the battery 3 When there is little, there exists a tendency for battery temperature to approach upper limit temperature (60 degreeC) by the end of discharge of the battery 3. FIG.
[0027]
Therefore, the present embodiment is characterized in that the output limit value PL is controlled so as to limit the output power supplied from the battery according to the discharge depth DOD and the battery temperature T.
The battery discharge depth DOD is a value calculated according to a known calculation processing method. That is, the integration calculation is performed based on the direct current I, the direct current voltage V, and the discharge time t when the battery 3 is discharged, and the output power value P ( I, V, t) is obtained. Next, the discharge depth DOD is calculated based on DOD = {P (I, V, t) from the output power value PMAX stored in the battery 3 at the time of full charge and the output power value P (I, V, t). ) / PMAX} * 100
Asking.
[0028]
In the present embodiment, the battery control unit 21 obtains the discharge depth DOD by performing integration calculation every predetermined time, and stores it in a RAM (memory unit). Needless to say, the depth of discharge DOD thus determined is 0% when fully charged and 100% when fully discharged.
[0029]
Next, the operation of the battery control unit 21 provided in the battery temperature protection control device 1 will be described using the flowchart shown in FIG. 2 with reference to FIGS. The control program shown in this flowchart is stored in a ROM provided in the battery control unit 21 and is processed every predetermined time.
[0030]
First, in step S10, the current discharge depth DOD stored in the RAM (memory unit) inside the battery control unit 21 is read and referenced.
Here, as shown in FIG. 3, an output limit start temperature TS table corresponding to the discharge depth DOD is stored in advance in the ROM inside the battery control unit 21 as a discharge depth DOD-output limit start temperature TS table. .
[0031]
In step S20, the output limit start temperature TS corresponding to the discharge depth DOD is read out and obtained from the discharge depth DOD-output limit start temperature TS table stored in the ROM inside the battery control unit 21.
[0032]
Next, in step S <b> 30, the temperature detector 17 detects the battery temperature T of the battery 3. Next, in step S40, the battery temperature T is compared with the output restriction start temperature TS, and it is determined whether or not the battery temperature T is higher than the output restriction start temperature TS. If the battery temperature T is higher than the output limit start temperature TS, the process proceeds to step S60. On the other hand, if the battery temperature T is lower than the output restriction start temperature TS, the process proceeds to step S50.
[0033]
Here, in step S50, the battery temperature T is smaller than the output restriction start temperature TS, and as shown in FIG. 4, the battery temperature T does not need to limit the output power supplied from the battery. Since it is in the limit region (c), the battery control unit 21 sets the output limit value PL to 100% and sets it in the motor control unit 9.
[0034]
As a result, the PWM signal output from the motor control unit 9 to the inverter 5 is output without being restricted. That is, the motor control unit 9 outputs the PWM signal generated according to the accelerator opening from the accelerator 11 and the torque command value corresponding to the shift position from the shift lever 13 to the inverter 5 as it is.
[0035]
On the other hand, in step S60, the battery temperature T is larger than the output restriction start temperature TS, and as shown in FIG. 4, the battery temperature T falls within a restricted region (d) where the output power supplied from the battery should be restricted. Therefore, the output limit value PL corresponding to the battery temperature T is obtained.
[0036]
Here, as shown in FIG. 4, the output limit value PL corresponding to the battery temperature T is stored in advance in the ROM inside the battery control unit 21 as a battery temperature T-output limit value PL table. In step S60, the output limit value PL corresponding to the battery temperature T is read out from the battery temperature T-output limit value PL table stored in the ROM inside the battery control unit 21, and the output limit value PL is obtained. Set to 9.
[0037]
As a result, the PWM signal output from the motor control unit 9 to the inverter 5 is output with limitation. That is, in the motor control unit 9, the PWM signal generated according to the accelerator opening from the accelerator 11 and the torque command value corresponding to the shift position from the shift lever 13 is multiplied by the output limit value PL and corrected. The PWM signal is output to the inverter 5.
[0038]
As described above, the battery control unit 21 obtains the discharge depth DOD representing the current discharge degree with respect to the output power when the battery 3 is fully charged, and according to the calculated discharge depth DOD, An output restriction start temperature TS for starting output power restriction is obtained. Here, when the battery temperature detected by the temperature detector 17 is larger than the output restriction start temperature, an output limit value PL for limiting the output power of the battery 3 according to the battery temperature is obtained. Since the output power of the battery 3 is limited based on the output limit value PL, the battery output performance is maximized within the range where the battery temperature does not exceed the upper limit temperature of use without reducing the battery life. Can be used.
[0039]
In the present embodiment, after obtaining the output restriction start temperature TS corresponding to the discharge depth DOD from the discharge depth DOD-output restriction start temperature TS table in step S20, the battery temperature T-output restriction is obtained in step S60. The output limit value PL corresponding to the battery temperature T is obtained from the value PL characteristic table. However, the present invention is not limited to such a case. As shown in FIG. 5, the battery temperature T-output limit value PL table corresponding to each different discharge depth DOD is stored in the ROM inside the battery control unit 21. After storing in advance and specifying the current discharge depth DOD to determine only one battery temperature T-output limit value PL table, the output limit value PL corresponding to the battery temperature T is read from this table and obtained. Also good. In this case, since the battery temperature T-output limit value PL table corresponding to the discharge depth DOD is determined, smooth continuity from the non-limit region to the limit region of the output limit value PL according to the battery temperature T. As a result, there is no change in the front and rear G applied to the vehicle due to the fluctuation of the motor torque that is expected to occur when the output limit value PL is switched from the non-limit region to the limit region. It can contribute to improvement.
[0040]
Further, the calorific value QP of the battery 3 generally varies depending on the depth of discharge DOD as shown in FIG. Further, the output restriction start temperature TS needs to be set lower as the heat generation amount QP increases. In this case, it is desired to control so as to limit the heat generation amount QP by setting the output limit value PL to be lower as the heat generation amount QP becomes larger. That is, the output limit value PL may be set so that the heat generation amount QP of the battery 3 is equal to the previous amount.
[0041]
Specifically, as shown in FIG. 7, a discharge depth DOD-output restriction start temperature TS characteristic table is created. When the depth of discharge DOD is in the middle region (G), as shown in FIG. 6, the amount of heat generation QP is the smallest, so as shown in FIG. 7, if the limit start temperature TS is set higher than the reference line (A). Good. As a result, when the discharge depth DOD is in the intermediate region (G), the heat generation amount QP is maintained at a constant level, so that the limit start temperature can be set high and the output power can be increased.
[0042]
On the other hand, in the region (h) where the discharge depth DOD is deeper, as shown in FIG. 6, the calorific value QP becomes larger. do it. As a result, in the region (h) where the depth of discharge DOD is deep, the heat generation amount QP increases rapidly, so the restriction start temperature TS can be set low to limit the heat generation amount QP. The reference line (A) shown in FIG. 7 is a general discharge depth DOD-output limit start temperature TS characteristic graph shown in FIG.
[Brief description of the drawings]
FIG. 1 is a diagram showing a system configuration of a battery power calculation device 1 suitable for a battery temperature protection control device according to an embodiment of the present invention.
FIG. 2 is a flowchart for explaining the operation of a battery control unit 21 provided in the battery temperature protection control device 1;
FIG. 3 is a graph showing a discharge depth DOD-output limit start temperature TS characteristic graph;
FIG. 4 is a graph showing a characteristic graph of output limit value PL corresponding to battery temperature T;
FIG. 5 is a graph showing a characteristic graph of a battery temperature T-output limit value PL table.
FIG. 6 is a graph showing a characteristic graph of a discharge depth DOD and a calorific value QP of a battery.
FIG. 7 is a diagram showing that a discharge depth DOD-output restriction start temperature TS characteristic graph is corrected using a calorific value QP.
FIG. 8 is a diagram showing that an output restriction region is provided when the battery temperature is between 55 ° C. and 60 ° C.
FIG. 9 is a diagram showing a state in which a sufficient remaining capacity of the battery remains.
FIG. 10 is a diagram showing a state where the remaining capacity of the battery does not remain much.
[Explanation of symbols]
3 Battery 5 Inverter 7 Motor 9 Motor controller 15 Current detector 17 Temperature detector 19 Voltage detector 21 Battery controller

Claims (5)

A discharge depth calculation means for obtaining a discharge depth representing the current discharge degree with respect to the output power when the battery is fully charged,
According to the calculated depth of discharge, output limit start temperature calculating means for obtaining an output limit start temperature representing a temperature at which the limit of the output power of the battery starts, and
Battery temperature detecting means for detecting the battery temperature;
When the detected battery temperature is higher than the output restriction start temperature, the battery has an output limit value calculation means for obtaining an output limit value for limiting the output power of the battery according to the battery temperature. Battery temperature protection control device. The output restriction start temperature calculating means includes
2. The battery temperature protection control device according to claim 1, further comprising an output limit start temperature table that records in advance an output limit start temperature corresponding to the depth of discharge of the battery. The output limit start temperature table is:
3. The battery temperature protection control device according to claim 2, wherein an output restriction start temperature corresponding to the depth of discharge is corrected based on a heat generation characteristic of the battery corresponding to the depth of discharge of the battery. A discharge depth calculation means for obtaining a discharge depth representing the current discharge degree with respect to the output power when the battery is fully charged,
An output limit value recording means having an output limit value table for previously recording an output limit value for limiting the output power of the battery according to the battery temperature, corresponding to a plurality of different discharge depths;
Battery temperature detecting means for detecting the battery temperature;
A battery temperature protection control device comprising: an output limit value calculating means for obtaining an output limit value corresponding to the detected battery temperature with reference to an output limit value table corresponding to a current discharge depth. The output limit value table of the output limit value recording means is:
5. The battery temperature protection control device according to claim 4, wherein an output limit value from a limit start temperature at which the output power of the battery is started to an output stop temperature at which the output power is stopped is recorded in advance.

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