JP2020022261A - Cooling system - Google Patents

Abstract

To achieve both the suppression of excessive pump output and the suppression of sudden temperature change of a power conversion circuit in a cooling system of the power conversion circuit.SOLUTION: A cooling system is provided with: a cooler for cooling a power conversion circuit; a coolant circuit connected to the cooler; a pump for pressure-feeding the coolant in the coolant circuit; and a controller for providing the pump with a command value for controlling an output of the pump. The controller provides the pump with a first command value based on an output when an output variation of the power conversion circuit exceeds a predetermined value, and provides the pump with a second command value based on a coolant temperature in the coolant circuit when the variation is less than the predetermined value.SELECTED DRAWING: Figure 3

Description

  The technology disclosed in the present specification relates to a cooling system for cooling a power conversion circuit.

  Patent Literature 1 discloses a cooling system that cools a transistor in a vehicle-mounted inverter. The cooling system includes a refrigerant path connected to the inverter and a pump for circulating the refrigerant in the refrigerant path. The cooling system controls the pump based on the temperature of the refrigerant. Specifically, the rotation speed of the pump is increased in accordance with the rise in the temperature of the refrigerant.

  Further, Patent Document 2 discloses a transistor arranged on a heat sink via silicon grease.

JP 2007-166804 A JP 2008-253098 A

  The cooling system of Patent Literature 1 increases the rotation speed of the pump when the temperature of the refrigerant increases, and is advantageous in that the rotation speed of the pump can be prevented from excessively increasing when the temperature of the refrigerant is low. However, in this system, even when the output of the inverter suddenly rises due to sudden acceleration of the vehicle, if the temperature of the refrigerant has not risen, the rotation speed of the pump is maintained, so that the temperature of the transistor in the inverter rises sharply. There are cases. A sudden change in the temperature of the transistor is not preferable. For example, when a transistor is arranged on a heat sink via silicon grease as in Patent Document 2, when the transistor repeatedly changes abruptly, the gap between the transistor and the heat sink repeats expansion and contraction. Degradation of the sandwiched silicon grease may be accelerated.

  For example, if the rotation speed of the pump is increased in advance in anticipation of a situation in which the temperature of the transistor suddenly rises due to a rapid rise in the output of the inverter, the rise in the temperature of the transistor can be suppressed. As a result, a sudden change in temperature of the transistor can be suppressed. However, if the number of revolutions of the pump is increased in advance, the number of revolutions of the pump becomes excessively large, and the advantages of the cooling system of Patent Document 1 are lost.

  The present specification discloses a technique for achieving both suppression of an excessive output of a pump and suppression of a rapid temperature change of a power conversion circuit in a cooling system for a power conversion circuit.

  The cooling system disclosed in this specification controls a cooler for cooling a power conversion circuit, a refrigerant circuit connected to the cooler, a pump for pumping refrigerant in the refrigerant circuit, and an output of the pump. For supplying a command value for the pump to the pump. The controller acquires the output of the power conversion circuit and the temperature of the refrigerant in the refrigerant circuit, and supplies a first command value based on the output to the pump when the amount of change in the output exceeds a predetermined value. The controller supplies a second command value based on the temperature to the pump when the amount of change in the output is less than the predetermined value.

  When the output of the power conversion circuit rises sharply, there is a high possibility that the temperature of the power conversion circuit also rises sharply. According to the above configuration, when the amount of change in the output of the power conversion circuit exceeds a predetermined value, the controller supplies the first command value based on the output to the pump. Thus, the first command value in anticipation of a rapid rise in the temperature of the power conversion circuit can be supplied to the pump. As a result, a rise in temperature of the power conversion circuit is suppressed, and a sudden change in temperature of the power conversion circuit can be suppressed. On the other hand, when the amount of change in the output of the power conversion circuit is less than the predetermined value, the controller supplies a second command value based on the temperature of the refrigerant to the pump. Accordingly, when the possibility that the temperature of the power conversion circuit rapidly rises is small, the second command value based on the temperature of the refrigerant can be supplied to the pump, and the output of the pump can be prevented from becoming excessive. it can. Therefore, it is possible to achieve both suppression of an excessive output of the pump and suppression of a sudden temperature change of the power conversion circuit. The details and further improvements of the technology disclosed in this specification will be described in the following “Detailed description of the invention”.

1 is a block diagram of a drive system of an electric vehicle equipped with a cooling system according to an embodiment. It is a figure showing a 1st map. It is a figure showing a 2nd map. It is a flowchart of the process which a controller performs.

The features of the embodiment described below will be summarized.
(Feature 1) The output of the power conversion circuit is a measured value of the output current of the power conversion circuit.
(Feature 2) The electronic components in the power conversion circuit are in contact with the heat transfer member. The cooler faces the electronic component and is in contact with the heat transfer member. The electronic component is, for example, a power card containing a transistor.

(First embodiment)
A cooling system 10 according to a first embodiment will be described with reference to the drawings. The cooling system 10 is mounted on the vehicle 100. The vehicle 100 is an electric vehicle that can run using only the driving force of a motor, or a hybrid vehicle that can run using at least one of an engine and a motor. FIG. 1 shows a block diagram of a drive system of a vehicle 100 including a cooling system 10. The cooling system 10 of the embodiment cools the power conversion circuit 20. The power conversion circuit 20 is connected to the vehicle-mounted battery 21 via a system main relay 21a. The power conversion circuit 20 includes an inverter circuit that converts the DC power of the vehicle-mounted battery 21 into AC power and supplies the AC power to the traveling motor 22, and a boost converter circuit that boosts the DC power of the vehicle-mounted battery 21 and supplies the DC power to the inverter circuit. Including. The output torque of the traveling motor 22 is transmitted to the drive wheels 24 via the axle 23. Since the power conversion circuit 20 handles a large power of 10 kilowatts or more, the amount of heat generated by electronic components (eg, transistors) in the power conversion circuit 20 is large. Therefore, vehicle 100 includes cooling system 10 that cools power conversion circuit 20.

  The cooling system 10 includes a refrigerant circuit 11, a radiator 12, a pump 13, a temperature sensor 14, and a cooler 15. The refrigerant circuit 11 is a flow path of the refrigerant, and passes through the radiator 12 and the cooler 15. The pump 13 pumps the refrigerant in the refrigerant circuit 11. Thereby, the refrigerant circulates between the radiator 12 and the cooler 15. The refrigerant is, for example, water or LLC (Long Life Coolant). The temperature sensor 14 measures the temperature of the refrigerant that has passed through the cooler 15.

  The cooler 15 cools the power conversion circuit 20. In FIG. 1, the power conversion circuit 20 and the cooler 15 are schematically illustrated. The power conversion circuit 20 is mainly configured by a plurality of transistors (not shown). Each transistor is housed in a power card (not shown). A heat transfer member (not shown) is in contact with a side surface of each power card. The cooler 15 is in contact with the heat transfer member facing the side surface of the power card. In other words, a heat transfer member is sandwiched between the power card and the cooler 15. The heat transfer member is, for example, a heat transfer grease or a heat transfer sheet.

  The controller 16 supplies a command value for controlling the output of the pump 13 to the pump 13. The pump 13 is of an electric type whose rotation speed is controlled by a duty ratio, and a command value to the pump 13 is specifically given by a duty ratio. If the duty ratio is large, the pump 13 operates at high rotation (that is, high output).

  The broken lines in the figure indicate signal lines. The controller 16 acquires a temperature measurement value of the temperature sensor 14 and a current measurement value of a current sensor 20a that measures an output current flowing from the power conversion circuit 20 to the motor 22 via a signal line. Further, the controller 16 stores a first map 17 and a second map 18. The controller 16 specifies the command value by using the temperature measurement value, the current measurement value, the first map 17 and the second map, and supplies the specified command value to the pump 13 (see FIG. 4).

  The first map 17 shown in FIG. 2 shows a relationship between an output current flowing from the power conversion circuit 20 to the motor 22 and a command value to the pump 13. As the output current of the power conversion circuit 20 increases, the amount of heat generated by the transistors in the power conversion circuit 20 also increases. In the first map 17, the relationship between the output current and the command value is designed so that the temperature of the transistor becomes constant with respect to the change in the amount of heat generated by the transistor. As shown in FIG. 2, the output current and the command value show a proportional relationship. The command value to the pump 13 can be specified as a value corresponding to the current measurement value of the current sensor 20a using the first map 17.

  The second map 18 shown in FIG. 3 shows the relationship between the temperature of the refrigerant flowing through the refrigerant circuit 11 and the command value to the pump 13. In the second map 18, the relationship between the temperature of the refrigerant and the command value is designed based on the flow rate of the refrigerant for keeping the temperature of the transistor below the allowable temperature with respect to the temperature of the refrigerant. As shown in FIG. 3, the refrigerant temperature and the command value show a positive correlation, and the slope of the positive correlation becomes larger in a range where the refrigerant temperature is high than in a range where the refrigerant temperature is low. The command value to the pump 13 can be specified as a value corresponding to the temperature measurement value of the temperature sensor 14 using the second map 18.

  With reference to FIG. 4, the process of the controller 16 for specifying the command value using the first map 17 or the second map 18 will be described. The process of FIG. 4 is started when the system main relay 21a changes from the cut-off state to the conductive state. The process of FIG. 4 is repeatedly executed until the system main relay 21a is turned off.

  In S10, the controller 16 acquires a current measurement value of the current sensor 20a. The controller 16 stores the measured current value each time the measured current value is acquired. That is, the controller 16 stores the history of the current measurement values. In S12, the controller 16 acquires a temperature measurement value of the temperature sensor 14.

  In S20, the controller 16 determines whether the amount of change in the measured current value is equal to or greater than a predetermined value. The change amount of the current measurement value is, for example, a first-order differentiation amount calculated using the history of the stored current measurement values. Further, in the modified example, the amount of change in the current measurement value may be a second-order differential amount calculated using the history of the stored current measurement value, or may be a predetermined period in the history of the stored current measurement value. May be a fluctuation range between the maximum value and the minimum value, or an evaluation amount obtained by combining the first-order differential amount, the second-order differential amount, and the fluctuation range. The fact that the amount of change in the measured current value is equal to or larger than the predetermined value means that there is a high possibility that a sudden temperature rise of the transistor in the power conversion circuit 20 will occur. This means that there is a high possibility that a rapid temperature rise and a temperature drop (that is, a rapid temperature change) of the transistor will occur. When the process of FIG. 4 is first executed, the history of the stored current measurement values includes only one current measurement value. Since the amount of change cannot be calculated using only one current measurement value, in this case, the controller 16 estimates that the amount of change in the current measurement value is less than a predetermined value. In the present embodiment, the controller 16 compares the absolute value of the amount of change in the measured current value with a predetermined value. That is, also in the case where the output current decreases rapidly, the determination in step S20 becomes YES.

  If the controller 16 determines that the amount of change in the current measurement value is equal to or greater than the predetermined value (YES in S20), the controller 16 determines in S22 the first command value corresponding to the current measurement value acquired in S10 from the first map 17. Identify. Then, in S30, the controller 16 supplies the specified first command value to the pump 13.

  If the controller 16 determines that the amount of change in the measured current value is smaller than the predetermined value (NO in S20), the controller 16 determines in S28 the second command corresponding to the measured temperature value acquired from the second map 18 in S12. Specify a value. Then, in S40, the controller 16 supplies the specified second command value to the pump 13. When S30 or S40 ends, the process returns to S10, and the processing in FIG. 4 is repeated.

(Effects of the present embodiment)
For example, a first comparative example in which a command value corresponding to a temperature measurement value is always specified from the second map 18 without performing the determination in S20 of FIG. In the first comparative example using the second map 18, since the output of the pump 13 is increased when the temperature of the refrigerant is high, it is possible to suppress the output of the pump 13 from excessively increasing when the temperature of the refrigerant is low. It is advantageous. However, in the first comparative example, even when the output of the power conversion circuit 20 sharply increases due to rapid acceleration of the vehicle 100 or the like, the output of the pump 13 is maintained unless the temperature of the refrigerant increases. In some cases, the temperature of the transistor inside 20 may rise rapidly. Conversely, even when the temperature of the refrigerant is high and the output of the pump 13 is large, if the output of the power conversion circuit 20 sharply drops, the pump output becomes excessive with respect to the calorific value of the transistor, and the temperature of the transistor increases. There is a danger of a sudden descent. That is, the temperature of the transistor may change suddenly. In this embodiment, a heat transfer member is interposed between the power card containing the transistor and the cooler 15. In this case, if the power card repeatedly expands and contracts due to a sudden change in the temperature of the transistor, the heat transfer member between the power card and the cooler 15 repeatedly compresses and restores, and as a result, the heat transfer member may deteriorate faster. There is.

  Further, for example, a second comparative example in which a command value corresponding to a current measurement value is always specified from the first map 17 without performing the determination in S20 of FIG. In the second comparative example using the first map 17, the output of the pump 13 is increased in advance in anticipation of a situation in which the temperature of the transistor in the power conversion circuit 20 increases due to the increase in the output of the power conversion circuit 20. Therefore, a rise in the temperature of the transistor can be suppressed. As a result, a sudden change in temperature of the transistor can be suppressed. However, if the output of the pump 13 is raised in advance by employing the second comparative example, the output of the pump 13 becomes excessive, and the advantage of the first comparative example cannot be obtained.

  On the other hand, according to the present embodiment, when the amount of change in the current measurement value is equal to or larger than the predetermined value (YES in S20 of FIG. 4), that is, when the transistor in the power conversion circuit 20 When there is a high possibility that a temperature rise will occur, a first command value based on the measured current value is supplied to the pump using the first map 17 (S30). As a result, the first command value in anticipation of a sudden rise in the temperature of the transistor can be supplied to the pump 13, and as a result, a rise in the temperature of the transistor is suppressed, and a sudden change in the temperature of the transistor can be suppressed. it can. On the other hand, when the amount of change in the measured current value is smaller than the predetermined value (NO in S20 of FIG. 4), that is, when there is a low possibility that a sudden temperature increase of the transistor occurs, the controller 16 sets the second map 18 The second command value based on the temperature measurement value is supplied to the pump by using (S40). Thereby, when the temperature of the transistor does not rise rapidly, the second command value based on the temperature of the refrigerant can be supplied to the pump 13, and as a result, the output of the pump 13 can be suppressed from becoming excessive. . Therefore, it is possible to achieve both suppression of an excessive output of the pump and suppression of a sudden change in temperature of the transistor. Then, by suppressing a sudden temperature change of the power conversion circuit 20, it is possible to suppress an excessive load on the heat transfer member.

(Correspondence)
The power conversion circuit 20, the cooler 15, the refrigerant circuit 11, the pump 13, and the controller 16 are examples of a “power conversion circuit”, a “cooler”, a “refrigerant circuit”, a “pump”, and a “controller”, respectively. The measured current value and the measured temperature value are examples of the “output of the power conversion circuit” and the “temperature of the refrigerant”, respectively.

(Second embodiment)
This embodiment is the same as the first embodiment except that S24 and S26 are executed in the processing of FIG. That is, instead of the transition from step S22 to step S30 (solid line), the portion indicated by the broken line indicating the transition between steps indicates the processing added in the second embodiment. Hereinafter, S24 and S26 in FIG. 4 will be described.

  The controller 16 executes S24 following S22. S24 is the same as S28. Then, in S26, the controller 16 determines whether the first command value specified in S22 is greater than or equal to the second command value specified in S24. When the controller 16 determines that the first command value is equal to or larger than the second command value (YES in S26), the process proceeds to S30. On the other hand, when the controller 16 determines that the first command value is smaller than the second command value (NO in S26), the process proceeds to S40.

  If the amount of change in the current measurement value is equal to or greater than the predetermined value and the first command value is less than the second command value (that is, NO in S26), for example, the power conversion circuit 20 may be operated in a state where the temperature of the refrigerant is high. Means a situation where the output of the power supply rises sharply. In such a situation, the output of the pump 13 is increased so as to increase the cooling efficiency of the cooler 15 in a state where the temperature of the refrigerant is high. When the first command value is supplied to the pump 13, the cooling efficiency of the cooler 15 is reduced. In this embodiment, in such a situation, it is possible to suppress a decrease in the cooling efficiency of the cooler 15 by supplying the second command value to the pump 13 instead of the first command value. Sudden temperature change of the transistor can be suppressed.

  Hereinafter, points to be noted regarding the technology shown in the embodiments will be described. The “output of the power conversion circuit” in the technology disclosed in this specification is not limited to the current measurement value, and may be, for example, a measurement value of the output power of the power conversion circuit 20 or a value having a correlation with the output power. Good. This is because a value having a correlation with the output of the power conversion circuit can be used as an estimated value of the output of the power conversion circuit. The value having the correlation is, for example, a duty ratio of a signal supplied to the gate terminal of the transistor in the power conversion circuit 20, a target value for the output power of the power conversion circuit 20, and information for determining the target value (eg, , Accelerator opening), a measured value of input power (or input current) input to the power conversion circuit 20, an output torque of the motor 22, and the like.

  The controller 16 according to the embodiment supplies the first command value based on the output current when the absolute value of the amount of change in the output current is equal to or greater than a predetermined value. That is, even when the output current drops sharply, the first command value based on the output current is supplied. When the absolute value of the change amount is large, the pump output is quickly adjusted according to the temperature change tendency of the power conversion circuit by determining the command value to the pump based on the output current rather than based on the refrigerant temperature. it can.

  The controller 16 may output the first command value based on the output current when the amount of change in the positive value of the output current is equal to or more than a predetermined value. In this case, the cooling system can realize the pump output in anticipation of the temperature rise of the power conversion circuit.

  When the controller 16 detects that the amount of change in the positive value of the output current of the power conversion circuit 20 is equal to or more than a predetermined value, the controller 16 may supply the first command value based on the output current for a certain period thereafter. Good. With such a configuration, when the large output current is maintained after the output current changes from a small value to a large value, that is, even when the amount of change temporarily increases and then falls below a predetermined amount, The supply of the first command value is maintained for a certain period. The certain period is, for example, 60 seconds. After a period of about 60 seconds during which the output current is large, the temperature of the refrigerant also increases. After the temperature of the refrigerant increases, a command value depending on the temperature may be supplied.

  Further, when the controller 16 detects that the amount of change in the negative value is smaller than the second predetermined amount of the negative value during the above-mentioned fixed period, the controller 16 may supply a temperature-dependent command value. When the amount of change in the output current becomes smaller than the second predetermined amount, which is a negative value, it means that the amount of heat generated by the power conversion circuit thereafter becomes smaller. If the amount of heat generated by the power conversion circuit is small, the output of the pump 13 can be suppressed by supplying a temperature-dependent command value.

  The controller 16 of the embodiment outputs a first command value when the amount of change in the output current is equal to a predetermined value. The controller may be configured to output the second command value when the amount of change is equal to the predetermined value.

  As described above, the specific examples of the present invention have been described in detail, 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 the present 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 illustrated in the present specification or the drawings can simultaneously achieve a plurality of objects, and has technical utility by achieving one of the objects.

10: Cooling system 11: Refrigerant circuit 12: Radiator 13: Pump 14: Temperature sensor 15: Cooler 16: Controller 17: First map 18: Second map 20: Power conversion circuit 20a: Current sensor 21: In-vehicle battery 21a: System main relay 22: Motor 23: Axle 24: Drive wheel 100: Vehicle

Claims (3)

A cooler for cooling the power conversion circuit;
A refrigerant circuit connected to the cooler,
A pump for pumping the refrigerant in the refrigerant circuit,
A controller that supplies a command value for controlling the output of the pump to the pump,
With
The controller is
When the change amount of the output of the power conversion circuit exceeds a predetermined value, supplying a first command value based on the output of the power conversion circuit to the pump,
When the amount of change is less than the predetermined value, supplying a second command value based on the temperature of the refrigerant in the refrigerant circuit to the pump,
Cooling system. The controller stores a first map indicating a relationship between an output of the power conversion circuit and the command value, and a second map indicating a relationship between the temperature and the command value.
The controller is
When the amount of change exceeds the predetermined value, the first command value corresponding to the output of the power conversion circuit is specified from the first map,
The cooling system according to claim 1, wherein when the amount of change is less than the predetermined value, the second command value corresponding to the temperature is specified from the second map. The controller is
When the change amount exceeds the predetermined value, and the first command value exceeds the second command value, supplies the first command value to the pump;
The second command value is supplied to the pump when it is determined that the amount of change exceeds the predetermined value and the first command value is less than the second command value. A cooling system according to claim 1.

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