JP2013069470A - Battery cooling device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a battery cooling device capable of finely adjusting the cooling capacity in accordance with temporal change.SOLUTION: A cooling device 100 has: a fan 2 for cooling a battery 3; a temperature sensor 8 measuring a battery temperature; and a controller 12 controlling the fan 2 on the basis of a detection temperature by the temperature sensor 8. The controller 12 calculates a cooling capacity of the fan 2 and a battery calorific value by using a predefined arithmetic expression, and further calculates an estimation temperature of the battery 3 from those calculated values. The controller 12 further derives a correction coefficient for making the estimation temperature accord with the detection temperature and for use in an expression for calculating the cooling capacity. The controller 12 determines a target rotation number of the fan 2 depending on the derived correction coefficient.

Description

  The present invention relates to a battery cooling device.

  A battery having a large output current, for example, a battery for supplying electric power to a wheel driving motor of an electric vehicle, generates a large amount of heat. Therefore, a cooling device for cooling the battery is required. If the cooling device does not operate properly, the temperature of the battery may increase excessively and the performance of the battery may be impaired. Patent Document 1 proposes a technique for detecting an abnormality of the cooling device, and Patent Document 2 proposes a technique for detecting an abnormality of the cooling device and maintaining the battery in an appropriate temperature range. In both technologies, the cooling capacity of the cooling device and the amount of heat generated by the battery are determined using predetermined formulas, the estimated temperature of the battery is determined from the cooling capacity and the amount of heat generated, and the estimated temperature and the actual temperature of the battery (detection) The abnormality of the cooling device is determined from the difference in temperature. If the expected cooling capacity is achieved, the estimated temperature and the detected temperature are almost the same, but if the cooling capacity is below the expected value (i.e., if an abnormality has occurred), the detected temperature exceeds the estimated temperature (i.e. , The battery does not cool as expected). Therefore, it is determined that an abnormality has occurred when the estimated temperature is significantly higher than the detected temperature.

JP 2001-86601 A JP 2001-313092 A

  The technique of Patent Document 2 controls the cooling device in a direction in which the cooling effect increases when it is determined that an abnormality has occurred. Such countermeasures are effective when an abnormality occurs. However, if the cooling device is used for a long period of time, the cooling capacity gradually decreases with time. In addition to the technique for dealing with abnormal situations such as the technique of Patent Document 2, a technique for finely adjusting the cooling capacity in response to changes with time is desired.

  Similarly to Patent Document 1 and Patent Document 2, the cooling device disclosed in the present specification calculates the battery heat generation amount and the cooling capacity of the cooling device using predetermined mathematical formulas, and estimates the battery temperature from those calculated values. Is calculated. Then, the cooling capacity is adjusted based on the difference between the estimated temperature and the detected temperature. The technology disclosed in the present specification introduces a parameter called a correction coefficient into an equation for calculating the cooling capacity so as to cope with a gradual change of the cooling device with time. Since the correction coefficient represents the change over time of the cooling device, the cooling performance considering the change over time is realized by determining the target rotational speed of the fan according to the correction coefficient.

  One embodiment of a cooling device disclosed in the present specification includes a fan for cooling a battery, a temperature sensor that measures a battery temperature, and a controller that controls the fan based on a temperature detected by the temperature sensor. The controller calculates the cooling capacity of the fan and the amount of heat generated by the battery using a predetermined arithmetic expression, and further calculates the estimated temperature of the battery from these calculated values. The controller further obtains a correction coefficient for making the estimated temperature coincide with the detected temperature and in a formula for calculating the cooling capacity. Then, the controller determines the target rotational speed of the fan according to the obtained correction coefficient. The controller executes the above processing every predetermined control cycle. That is, the controller updates the correction coefficient every predetermined control cycle.

  The correction coefficient is introduced so that the cooling capacity theoretically determined by the cooling capacity calculation formula accurately represents the actual cooling capacity. Therefore, the initial value of the correction coefficient is set to 1.0. When the actual cooling capacity decreases due to the change over time, the actual temperature (detected temperature) of the battery becomes higher than the estimated temperature. In such a case, that is, when the estimated temperature is lower than the detected temperature, the controller decreases the correction coefficient by a predetermined correction amount. This reduces the theoretical cooling capacity and accurately represents the actual cooling capacity. Conversely, when the estimated temperature is higher than the detected temperature, the controller increases the correction coefficient by a predetermined correction amount. The upper limit of the correction coefficient is 1.0.

  As described above, if the correction coefficient is smaller than 1.0, it indicates that the actual cooling capacity has decreased. Therefore, as the correction coefficient becomes smaller, the controller increases the target rotational speed of the fan to reduce the actual cooling capacity. Increase and suppress battery temperature rise.

  An example of an arithmetic method such as cooling capacity is as follows. The controller calculates the amount of heat generated from the battery output current and the battery internal resistance, and the theoretical (ie, expected) cooling capacity from the fan speed and fan intake temperature (temperature of air passing through the fan). Is calculated. More specifically, the controller calculates the cooling capacity by multiplying the difference between the detected temperature and the intake air temperature by the fan rotation speed, a predetermined constant, and a correction coefficient. That is, an example of an expression for calculating the cooling capacity is to multiply the difference between the detected temperature and the intake air temperature by the fan rotation speed, a predetermined constant, and a correction coefficient. Here, the predetermined constant is a proportionality constant representing the relationship between the rotational speed of the fan and the cooling capacity, and is determined by the structure of the cooling device.

  An example of a method for calculating the estimated battery temperature is to multiply the difference between the battery heat generation amount and the cooling capacity (the cooling capacity obtained by the above arithmetic expression) by the reciprocal of the battery heat capacity, and further to calculate the control period (temperature estimation period). Obtained by adding the estimated temperature in the previous cycle to the multiplied value.

  If the above algorithm is adopted, the abnormality of the cooling device can be detected. For example, the controller may output a signal indicating an abnormality of the cooling device when the correction coefficient is outside a predetermined correction coefficient allowable range. An example of an output destination of a signal indicating an abnormality is a display or a memory for diagnosis during maintenance.

  Details and further improvements of the technology disclosed in this specification will be described in the section of the embodiments of the invention.

It is a block diagram of a cooling device. It is a flowchart figure of a correction coefficient calculation process. It is the graph which shows an example of the change of detected temperature and estimated temperature, and the graph which shows an example of the change of a correction coefficient. It is an example of a base air volume map (a graph which defines the relationship between a vehicle speed and a fan target air volume). It is an example of a fan rotation speed map (a graph that defines the relationship between fan air volume and target rotation speed). 4 is an example of a map of a rotation speed correction coefficient F (a graph that defines the relationship between the correction coefficient β and the rotation speed correction coefficient F).

  A cooling device 100 according to an embodiment will be described with reference to the drawings. FIG. 1 shows a block diagram of the cooling device 100. 1, the fan 2 that sends air to the battery 3 for cooling, the rotation speed sensor 7 that detects the rotation speed of the fan 2, and the intake air temperature of the fan 2 (the temperature of the air that passes through the fan 2) An intake air temperature sensor 6 that detects the temperature of the battery 3, a battery temperature sensor 8 that detects the temperature of the battery 3, a current sensor 9 that detects the output current of the battery 3, and a controller 12 that controls the fan 2 based on the sensor data. The cooling device 100 is configured.

  The cooling device 100 is a device for cooling the battery 3 that is mounted on an electric vehicle and stores electric power supplied to the wheel driving motor 5. The output (DC power) of the battery 3 is sent to the inverter 4. The inverter 4 converts the DC power of the battery 3 into AC power suitable for driving the motor and outputs the AC power to the motor 5. The inverter 4 also converts regenerative power (AC) generated by the motor using the kinetic energy of the vehicle during braking into DC power suitable for charging the battery 3. The battery 3 is charged by the regenerative power of the motor. In addition, although illustration is abbreviate | omitted, the battery 3 may receive charge from an external power supply (for example, household commercial alternating current 100V power supply). Therefore, although not shown, the electric vehicle also includes an ACDC converter that converts AC 100V power into DC power suitable for battery charging.

  The output voltage of the battery 3 is approximately 300 [V], and generates heat during power output or charging. The purpose of the cooling device 100 is to suppress the heat generation of the battery 3 and maintain the performance of the battery 3. Although depicted in a simplified manner in FIG. 1, a duct that guides the air blown by the fan 2 to the battery 3 is provided between the fan 2 and the battery 3.

  The cooling capacity here means not the maximum capacity of the cooling device 100 but the cooling capacity at that time, which depends mainly on the rotational speed of the fan 2 and the intake air temperature. Therefore, if the rotational speed of the fan 2 is increased, the cooling capacity is increased, and if the rotational speed is decreased, the cooling capacity is decreased. Further, if the intake air temperature is high, the cooling capacity decreases, and if the intake air temperature is low, the cooling capacity increases. The cooling capacity will be described in detail later.

  The rotational speed N of the fan 2 is controlled by the controller 12. The controller 12 outputs the target rotational speed Nt as a command value to the fan 2 based on some sensor data. The controller 12 outputs the output current I of the battery 3 (detected by the current sensor 9), the temperature TB of the battery 3 (detected by the battery temperature sensor 8), the fan rotational speed N (detected by the rotational speed sensor 7), and Sensor data of the intake air temperature TC (detected by the intake air temperature sensor 6) is received. Hereinafter, the temperature of the battery detected by the battery temperature sensor 8 is referred to as “detected temperature” in order to distinguish it from an estimated temperature (described later) calculated by the controller 12.

  The controller 12 includes a CPU 13 and a memory 14 that stores a program executed by the CPU 13. The program is divided into a plurality of modules. The module is actually a program, but in this specification, it means a function realized by the CPU 13 as a result of executing the program. The modules stored in the memory 14 include an internal resistance calculation module 14a, a calorific value calculation module 14b, a cooling capacity calculation module 14c, an estimated temperature calculation module 14d, a correction coefficient calculation module 14e, an abnormality determination module 14f, and a fan control module. There is 14g. The character string “MDL” in FIG. 1 means “module”.

  An outline of processing executed by the controller 12 will be described. The controller 12 calculates the heat generation amount HW [W] of the battery 3, the cooling capacity CW [W] of the cooling device 100, and the estimated temperature TS [° C.] of the battery 3 based on the sensor data described above. That is, the cooling capacity CW is the “estimated cooling capacity CW” of the cooling device 100 when expressed strictly. Here, the calculation coefficient of the cooling capacity CW includes the correction coefficient β, and the controller 12 corrects the correction coefficient β based on the magnitude relationship between the estimated temperature TS of the battery 3 and the detected temperature TB [° C.]. (A new correction coefficient β is obtained). The correction coefficient β represents a decrease in cooling capacity. Note that the decrease in cooling capacity is mainly due to the deterioration of the cooling device over time, and gradually proceeds with the passage of time (the cooling capacity gradually decreases). The controller 12 determines the target rotational speed Nt of the fan based on the new correction coefficient β, and outputs the target rotational speed Nt to the fan 2 as a command value. Furthermore, when the magnitude of the correction coefficient β is out of a predetermined range (correction coefficient allowable range), the controller 12 determines that an abnormality has occurred and outputs a signal indicating the occurrence of the abnormality. The controller 12 executes the above processing every predetermined control cycle dT. That is, the controller 12 updates the correction coefficient β every period dT.

  Processing performed by the controller 12 will be described in detail. First, the calculation process of the correction coefficient β will be described. FIG. 2 shows a flowchart of the correction coefficient calculation process. First, the controller 12 calculates the internal resistance R of the battery 3 based on the detected temperature TB of the battery 3 (S2). This processing is performed by the internal resistance calculation module 14a. Specifically, values of internal resistance R for various battery temperatures (detected temperatures) are stored in advance in the memory 14 of the controller 12 as a map, and the internal resistance calculation module 14a refers to the map to The internal resistance R corresponding to the detected temperature TB is obtained.

  Next, the controller 12 calculates the heat generation amount HW [W] of the battery 3 (S3). This process is performed by the calorific value calculation module 14b. Specifically, the calorific value calculation module 14b calculates the calorific value HW based on the following equation (1).

Calorific value HW = I ² × Internal resistance R (Equation 1)

  In the formula (1), “I” is the output current of the battery 3 detected by the current sensor 9. Next, the controller 12 calculates the cooling capacity CW [W] (more precisely, the estimated cooling capacity CW) of the cooling device 100 (S4). This processing is performed by the cooling capacity calculation module 14c. Specifically, the cooling capacity calculation module 14c calculates the cooling capacity CW based on the following equation (2).

  Cooling capacity CW = (detected temperature TB−intake air temperature TC) × K × fan air volume (Equation 2)

In Equation (2), K is a predetermined constant and is stored in the memory 14 in advance. The fan air volume [m ³ / h] is obtained by the following (Equation 3).

  Fan air volume = α x fan speed N x β (Equation 3)

  In the equation (3), α is a predetermined coefficient and is stored in the memory 14 in advance. The fan speed N is detected by the speed sensor 7. β is a correction coefficient, and the initial value is 1.0. The correction coefficient β will be described in detail later. After all, from (Equation 2) and (Equation 3), the cooling capacity CW is obtained by the following (Equation 4).

Cooling capacity CW = (detected temperature TB−intake air temperature TC) × K × α × fan rotational speed N × β
(Equation 4)

  As shown in the equation (4), the controller 12 multiplies the difference between the detected temperature TB of the battery 3 and the intake air temperature TC by a predetermined constant (K × α), the fan rotational speed N, and the correction coefficient β to provide a cooling capacity. Get CW.

  Next, the controller 12 calculates the estimated temperature TS of the battery 3 (S5). This process is performed by the estimated temperature calculation module 14d. Specifically, the estimated temperature calculation module 14d calculates the estimated temperature TS based on the following equation (5).

Estimated temperature TS = previous estimated temperature TS + γ × (heat generation amount HW−cooling capacity CW) × dT
(Equation 5)

  In the equation (5), the “previous estimated temperature TS” is an estimated temperature calculated in the previous control cycle (however, as will be described later, the previous estimated temperature TS is the previous estimated temperature TS). Of the detected temperature TB). Γ is the reciprocal of the heat capacity of the battery. dT is a control period (temperature estimation period).

  The controller 12 compares the estimated temperature TS obtained by the equation (5) with the detected temperature TB (actual temperature of the battery 3), and corrects the correction coefficient β according to the magnitude relationship between them. When the estimated temperature TS is higher than the detected temperature TB (S6: YES), the controller 12 increases the correction coefficient β by a predetermined amount (for example, 0.1) (S8). Conversely, when the estimated temperature TS is equal to or lower than the detected temperature TB (S6: NO), the controller 12 decreases the correction coefficient β by a predetermined amount (for example, 0.1) (S7). When the correction coefficient β exceeds 1.0 (S9: YES), the controller 12 sets the correction coefficient β to 1.0 (S10). That is, when the estimated temperature TS is higher than the detected temperature TB, the controller 12 increases the correction coefficient β by a predetermined number with 1.0 as an upper limit. Finally, the controller 12 assigns the detected temperature TB to the estimated temperature TS and ends the process (S12). The processing of steps S6 to S12 described above is performed by the correction coefficient calculation module 14e.

  An example of changes in the estimated temperature TS and the correction coefficient β by the correction coefficient calculation process described above is shown in FIG. The upper graph in FIG. 3 shows changes in the detected temperature TB and the estimated temperature TS, and the lower graph shows changes in the correction coefficient β. In the first control cycle (time T1), the detected temperature TB is the temperature Q1, and the estimated temperature TS is the temperature P1 (Q1> P1). That is, the estimated temperature TS (P1) is smaller than the detected temperature TB (Q1). This means that the actual cooling capacity is smaller than the calculated cooling capacity CW, so that the actual battery temperature (detected temperature TB) is higher than the calculated battery temperature (estimated temperature TS). Represent. In this case, the controller 12 decreases the correction coefficient β by 0.1 (S6: NO, S7 in FIG. 2). As shown in the lower graph of FIG. 3, at time T1, the correction coefficient β decreases by 0.1. Further, the controller 12 replaces the estimated temperature TS value (P1) with the detected temperature TB value (Q1) for the next estimated temperature calculation. The arrow from P1 to Q1 in FIG. 3 indicates value replacement.

  Further, in the second control cycle (time T2), the detected temperature TB is the temperature Q2, and the estimated temperature TS is the temperature P2 (Q2> P2). Also at this time, the estimated temperature TS (P2) is smaller than the detected temperature TB (Q2). Therefore, the controller 12 further reduces the correction coefficient β by 0.1 (S6: NO, S7 in FIG. 2). As shown in the lower graph of FIG. 3, at time T2, the correction coefficient β is further decreased by 0.1. Further, the controller 12 replaces the estimated temperature TS value (P2) with the detected temperature TB value (Q2) for the next estimated temperature calculation. The arrow from P2 to Q2 in FIG. 3 indicates value replacement.

  Further, in the third control cycle (time T3), the detected temperature TB is the temperature Q3, and the estimated temperature TS is the temperature P3 (Q3> P3). Also at this time, the estimated temperature TS (P3) is lower than the detected temperature TB (Q3). Therefore, the controller 12 further reduces the correction coefficient β by 0.1 (S6: NO, S7 in FIG. 2). As shown in the lower graph of FIG. 3, at time T3, the correction coefficient β is further decreased by 0.1. Furthermore, the controller 12 replaces the value (P3) of the estimated temperature TS with the value (Q3) of the detected temperature TB for the next estimated temperature calculation. The arrow from P3 to Q3 in FIG. 3 indicates value replacement. Thereafter, similarly, the controller 12 corrects the correction coefficient β every control cycle dT.

  In this way, the controller 12 updates the correction coefficient β so that the estimated temperature TS of the battery 3 matches the actual temperature (detected temperature TB) at each control cycle. That is, the controller 12 learns the correction coefficient β so that the estimated temperature TS of the battery 3 matches the actual temperature (detected temperature TB).

  Next, the determination process of the fan target rotation speed Nt using the updated value of the correction coefficient β will be described. This process is performed by the fan control module 14g. In summary, the controller 12 (the fan control module 14g) increases the target rotational speed Nt of the fan to increase the cooling capacity when the correction coefficient β is smaller than 1.0, that is, when the actual cooling capacity is reduced. Increase.

  The memory 14 of the controller 12 stores a base air volume map (a graph that defines the relationship between the vehicle speed and the fan target air volume) shown in FIG. 4 and a fan speed map (a relationship between the fan target air volume and the target speed Nt) shown in FIG. And a map of the rotational speed correction coefficient F shown in FIG. 6 (a graph that defines the relationship between the correction coefficient β and the rotational speed correction coefficient F). As shown in FIG. 4, the base air volume map defines two types of graphs when the battery is at room temperature and when the battery is hot. Here, normal temperature is, for example, a temperature range of 60 [° C.] or less, and high temperature is a temperature range exceeding 60 [° C.]. First, the controller 12 refers to the base air volume map and specifies an air volume (target air volume) corresponding to the current vehicle speed. Next, the controller 12 refers to the fan rotation speed map and specifies the target rotation speed Nt corresponding to the target air volume.

  The controller 12 outputs a value obtained by multiplying the target rotational speed Nt obtained using FIGS. 4 and 5 by the rotational speed correction coefficient F as a command (final target rotational speed Nt) to the fan 2. The rotation speed correction coefficient F will be described. FIG. 6 shows a map of the rotation speed correction coefficient F (a graph defining the relationship between the rotation speed correction coefficient F and the correction coefficient β). The map of the rotational speed correction coefficient F is a graph that defines the rotational speed correction coefficient F (a coefficient for correcting the target rotational speed of the fan) corresponding to the value of the correction coefficient β described above. In the graph of FIG. 6, the vertical axis represents the rotation speed correction coefficient F, and the horizontal axis represents the reciprocal of the correction coefficient β. Therefore, in the graph of FIG. 6, when 1 / β is larger than 1.0 (that is, when β is smaller than 1.0), it indicates that the cooling capacity is lowered. In that case, 1 / β is set as the rotation speed correction coefficient F to increase the target rotation speed Nt of the fan (F> 1.0 because β <1.0). However, in order to provide a dead zone, the rotational speed correction coefficient F is fixed to 1.0 when 1 / β is between 1.0 and Dp. As described above, since the upper limit of β is 1.0, the lower limit of 1 / β is 1.0, and the lower limit of the rotation speed correction coefficient F is 1.0. This means that when the actual cooling capacity exceeds the calculated cooling capacity CW and the actual temperature (detected temperature TB) of the battery 3 is lower than the estimated temperature TS, the cooling capacity is intentionally lowered. It means not.

  Next, processing in which the controller 12 detects an abnormality based on the value of the correction coefficient β will be described. This process is performed by the abnormality determination module 14f. When the correction coefficient β is outside the predetermined range (correction coefficient allowable range), the controller 12 determines that some abnormality has occurred and outputs a signal indicating the occurrence of the abnormality. For example, the correction coefficient allowable range is set to a range of correction coefficient β ≧ 0.5. In this case, when the correction coefficient β is less than 0.5, the controller 12 outputs a signal indicating that an abnormality has occurred. That the correction coefficient β is less than 0.5 indicates that the cooling capacity has become less than half of the initial value. The output destination of the signal indicating the occurrence of abnormality is, for example, the vehicle display 16 or the memory 18 (see FIG. 1). The memory 18 is a memory that stores a history of the state of the vehicle, and is read out during vehicle maintenance.

  It is also preferable that the controller 12 executes the correction coefficient calculation process and the target rotation speed determination process using the rotation speed correction coefficient F only when the detected temperature TB of the battery 3 exceeds a predetermined temperature threshold value. . The predetermined temperature threshold is set to 60 [° C.], for example. That is, it is also preferable to perform the correction coefficient calculation process and the target rotation speed determination process described above only when the battery 3 is at a high temperature.

  Points to be noted regarding the cooling device 100 shown in the embodiment will be described. The battery to be cooled by the cooling device 100 is, for example, a lithium ion battery, but is not limited thereto. The battery to be cooled may be a fuel cell. The battery may be a battery of a type in which a plurality of cells are connected in series. When the battery is composed of a plurality of cells, it is also preferable that the controller calculates the internal resistance R of the battery for each block in which several cells are grouped. In that case, the controller may calculate the cooling capacity of the cooling device 100 for each block. Further, the constant K introduced by the equation (2) may be determined for each block. This is because the battery characteristics may vary from block to block and this variation is accommodated.

  Further, the internal resistance R of the battery increases as the battery deteriorates. Therefore, it is also preferable to introduce a deterioration coefficient indicating a change in the internal resistance R due to deterioration. Specifically, first, the initial value of the internal resistance is specified by the least square method from the output voltage and current of the battery, and then the value obtained by multiplying the initial value by the deterioration coefficient is used as the internal resistance R in the equation (1). It is also suitable to use as. The deterioration coefficient is mapped and stored in advance in the controller.

  In the embodiment, the increase / decrease width per correction coefficient β is set to 0.1. The increase / decrease width per time may be a small value such as 0.01. Furthermore, it is also preferable to store the correction coefficient β in the nonvolatile memory so that the correction coefficient β is maintained even when the ignition of the vehicle is turned off. By storing the correction coefficient β in the nonvolatile memory, the previous correction coefficient β can be used the next time the ignition is turned on.

In addition, when any of the following conditions is satisfied, it is also preferable to stop updating the correction coefficient β (that is, fix the value of the correction coefficient β), assuming that the accuracy of the battery temperature estimation is reduced. is there.
Condition 1: When the fluctuation width per predetermined time of the state of charge (SOC) of the battery exceeds a predetermined threshold.
Condition 2: When gas is generated in the battery.
Condition 3: When the difference between the estimated temperature TS and the detected temperature TB becomes small.

  The update of the correction coefficient β does not require a high-band response compared to the control of the actuator or the like. That is, it is preferable that the period for updating the correction coefficient β is longer than the control period (for example, 10 [msec]) of the fan speed control. The period (control period dT) for updating the correction coefficient β may be, for example, about 5 seconds.

  It is also preferable to stop updating the correction coefficient β for a predetermined time immediately after driving the cooling fan, that is, until the cooling performance is stabilized.

  In addition, in places where the altitude is high, the density of air is reduced, and there is a possibility that the learning accuracy of the correction coefficient β by the above mathematical formula group may be reduced. Therefore, it is also preferable to stop updating the correction coefficient β when the atmospheric pressure is lower than a predetermined threshold value. The atmospheric pressure may be detected by, for example, an atmospheric pressure sensor.

  Specific examples of the present invention have been described in detail above, but these are merely examples and do not limit the scope of the claims. The technology described in the claims includes various modifications and changes of the specific examples illustrated above. The technical elements described in this specification or the drawings exhibit technical usefulness alone or in various combinations, and are not limited to the combinations described in the claims at the time of filing. In addition, the technology exemplified in this specification or the drawings can achieve a plurality of objects at the same time, and has technical usefulness by achieving one of the objects.

2: Fan 3: Battery 4: Inverter 5: Motor 6: Intake air temperature sensor 7: Speed sensor 8: Battery temperature sensor 9: Current sensor 12: Controller 13: CPU
14: Memory 16: Display 18: Memory 100: Cooling device

Claims (7)

A fan for cooling the battery;
A temperature sensor that measures the battery temperature;
And a controller that controls the fan based on the temperature detected by the temperature sensor.
Calculate the estimated battery temperature from the cooling capacity of the fan and the amount of heat generated by the battery,
A correction coefficient for matching the estimated temperature with the detected temperature and calculating the correction coefficient in the formula for calculating the cooling capacity,
Determine the target rotational speed of the fan according to the calculated correction coefficient.
A battery cooling device.   The battery cooling device according to claim 1, wherein the controller calculates the amount of heat generated by the battery from the values of the battery output current and the battery internal resistance, and calculates the cooling capacity from the rotational speed of the fan and the intake air temperature of the fan.   The battery cooling device according to claim 2, wherein the controller calculates the cooling capacity by multiplying a difference between the detected temperature and the intake air temperature by a fan rotation speed, a predetermined constant, and a correction coefficient.   The controller is characterized by decreasing the correction coefficient by a predetermined correction amount when the estimated temperature is lower than the detected temperature, and increasing the correction coefficient by the predetermined correction amount when the estimated temperature is higher than the detected temperature. The battery cooling device according to any one of claims 1 to 3.   5. The battery cooling device according to claim 1, wherein the controller increases the target rotation speed as the correction coefficient decreases. 6.   6. The cooling according to claim 1, wherein the controller determines the target rotational speed of the fan according to the correction coefficient only when the detected temperature exceeds a predetermined temperature threshold. apparatus.   The battery cooling according to any one of claims 1 to 6, wherein the controller outputs a signal indicating an abnormality of the cooling device when the correction coefficient is out of a predetermined correction coefficient allowable range. apparatus.

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