JP2014091426A - Cooling device - Google Patents

Abstract

The present invention provides a technique capable of properly eliminating a gas retention phenomenon in a cooling device in which a coolant circulates in a circulation path.
A cooling system 30 disclosed in this specification includes a cooling pipe 31 that surrounds a heating element and a radiator, an electric pump 32 that circulates a coolant through the cooling pipe 31, and a drive current that is supplied to the electric pump 32. The reverse drive detection circuit 60 that detects that an electromotive force is generated by the motor of the electric pump 32 while the electric pump 32 is running, and the rotation when the electric pump 32 is activated when the reverse drive detection circuit 60 detects the occurrence of the electromotive force And a cooling controller 39 that makes the number higher than the number of revolutions when the electric pump 32 is activated when the occurrence of electromotive force is not detected.
[Selection] Figure 2

Description

  The technology disclosed in this specification relates to a cooling device in which a coolant circulates in a cooling path.

  In a cooling device in which the cooling liquid circulates in the circulation path, when the cooling liquid is injected into the circulation path for maintenance or the like, a phenomenon in which gas is trapped in the circulation path (gas retention phenomenon) may occur. When the gas retention phenomenon occurs, the cooling efficiency of the cooling device may decrease. For this reason, a technique has been proposed that aims to discharge gas confined in the circulation path out of the circulation path.

  For example, Patent Document 1 discloses a cooling device mounted on a vehicle. This cooling device includes a circulation path, a pump that circulates coolant through the circulation path, a vehicle battery that supplies power to the cooling apparatus, a connection state of the battery, and a control device that controls the operation of the pump. Prepare. The control device determines that the coolant has been injected (replaced) when the history that the battery has been disconnected is stored, and increases the flow rate of the coolant by increasing the pump rotation speed when the pump is activated. By circulating the coolant at high speed, the gas confined in the circulation path is discharged out of the circulation path.

JP 2005-57953 A

  However, depending on the structure of the cooling device, when injecting the coolant into the circulation path for maintenance, the connection between the battery and the cooling device may not be released (if the battery need not be removed to improve workability). That is preferred). In such a case, the technique disclosed in Patent Document 1 cannot recognize that the cooling liquid has been injected into the circulation path, and may not readily eliminate the generated gas retention phenomenon. In the cooling device in which the coolant circulates in the circulation path, the present specification detects that the coolant has been directly injected into the circulation path, rather than an indirect method such as battery attachment / detachment, Provided is a technique capable of appropriately eliminating the gas retention phenomenon.

  The cooling device disclosed in this specification includes a circulation path around a heating element and a heat dissipation body, a pump that circulates a coolant in the circulation path, and an electromotive force generated by a pump motor while no driving current is supplied to the pump. Pump reverse drive detection means for detecting the occurrence and a control device for controlling the operation of the pump. The control device makes the rotational speed at the time of starting the pump when the pump reverse drive detecting means detects the occurrence of the electromotive force higher than the rotational speed at the time of starting the pump when the occurrence of the electromotive force is not detected.

  When injecting the coolant into the circulation path for maintenance or the like, the drive current is not supplied and the pump is in a stopped state. When the coolant is injected into the circulation path in such a state, the impeller of the pump is rotated by the injected coolant. When the pump impeller rotates, the pump motor rotates in conjunction with it, and an electromotive force is generated by the motor. That is, when no drive current is supplied to the pump, an electromotive force generated by the pump motor means that the pump has been rotated from the impeller side by the flow of the cooling liquid, and the cooling path is cooled. It means that liquid has been injected.

  When the pump motor generates a back electromotive force while no drive current is supplied to the pump, the control device drives the pump at a higher rotational speed than usual when the pump is started. The pump is driven at a high speed, the flow rate of the coolant in the circulation path is increased, the gas trapped in the circulation path is discharged out of the circulation path, and the gas retention phenomenon is eliminated. As described above, the technology disclosed in this specification detects that the cooling liquid is injected into the circulation path by the counter electromotive force of the pump motor in the cooling device in which the cooling liquid circulates in the circulation path. A gas retention phenomenon can be eliminated appropriately.

  When the above cooling device is applied to a vehicle, the coolant is exchanged while the main switch of the vehicle is OFF. Therefore, it is desirable that the pump reverse drive detection means can detect the generation of the counter electromotive force of the motor without a power source. As a specific example, the pump reverse drive detection means includes a capacitor connected between both terminals of the pump motor and a circuit that detects whether or not the capacitor is charged. When the main switch (ignition switch) of the vehicle is turned off, the control device discharges the capacitor so that the electric charge is zero. When the pump motor is driven in reverse to generate electromotive force, the capacitor is charged. The control device checks the capacity accumulated in the capacitor when the main switch of the vehicle is turned on again. If the capacity is larger than a predetermined threshold, the pump motor is reversely driven while the main switch is off. That is, it is detected that the coolant has been injected. A circuit for confirming the capacitance of the capacitor can be simply realized by a single comparator that compares the electrode potential on the high voltage side of the capacitor with a predetermined potential (threshold potential).

  As described above, when the pump reverse drive detection means has detected the occurrence of electromotive force, the control device does not detect the number of rotations at the time of starting the pump ("normal case"). Higher than the number of revolutions when the pump is started. Here, in a specific case, the control device may have an exceptional case in which the rotational speed at the time of starting the pump is high regardless of whether or not the starting force is generated. The exceptional case is when the coolant temperature at the start of the pump is higher than the normal temperature. Typically, when starting the vehicle again immediately after stopping the vehicle, the coolant temperature may remain high. In such a case, immediately after starting, the engine and electronic circuits of the vehicle should be cooled. Even so, it is common practice to rotate the pump at high speed. Until such a case, it is not necessary to determine the rotational speed at the time of starting the pump based on the detection result of the pump reverse drive detection means. When the coolant temperature is room temperature, the control device determines the rotation speed at the pump startup when the pump reverse drive detection means has detected the occurrence of electromotive force. What is necessary is just to make it higher than rotation speed.

  Details and further improvements of the technology disclosed in this specification will be described in detail in the section of Detailed Description.

The block diagram which shows the drive system of a hybrid vehicle. The block diagram of the cooling system of a hybrid vehicle. The graph which shows the relationship between cooling water temperature and pump rotation speed. The flowchart which shows the process which a cooling controller performs.

  The main features of the embodiments described below are listed. The technical elements described below are independent technical elements and exhibit technical usefulness alone or in various combinations, and are not limited to the combinations described in the claims at the time of filing. Absent.

(Characteristic 1) When the pump reverse drive detection means detects the occurrence of electromotive force, the number of revolutions when starting the pump is the gas staying in the circulation path when the coolant is low temperature and highly viscous The pump speed is sufficient to obtain a flow rate sufficient to discharge the gas out of the circulation path. By driving the pump at such a pump speed, the gas retention phenomenon is eliminated.

(Characteristic 2) The cooling device cools the traveling electric device of the hybrid vehicle.

(Example)
A cooling system according to an embodiment will be described with reference to the drawings. The cooling system of this embodiment cools an inverter of a hybrid vehicle. First, the outline of this cooling system will be described with reference to FIGS. 1 and 2. FIG. 1 shows a block diagram of a drive system of hybrid vehicle 100, and FIG. 2 shows a block diagram of cooling system 30.

  The hybrid vehicle 100 includes a first motor 2, a second motor 3, and an engine 4 as drive sources. The first motor 2 functions as a cell motor or a generator of the engine 4, and the second motor 3 drives a wheel in the same manner as the engine 4 as a traveling motor. The first motor 2 may generate power by the torque of the engine 4 during steady running. During braking, the second motor 3 functions as a generator. The power distribution mechanism 5 synthesizes / distributes outputs from the first motor 2, the second motor 3, and the engine 4 and outputs them to the axle 6. The drive train 7 includes a first motor 2, a second motor 3, and a power distribution mechanism 5. Driving power is supplied to the first motor 2 and the second motor 3 from the main battery 11 via the voltage converter 15 and the inverters 17 and 18. Hereinafter, the first motor 2 and the second motor 3 are simply referred to as “motors 2 and 3”. The drive train 7 (the motors 2 and 3 and the power distribution mechanism 5) generates heat during operation.

  The output voltage of the main battery 11 is 100 volts or more, and after being boosted by the voltage converter 15, it is converted into AC power by the inverters 17 and 18 and supplied to the motors 2 and 3. A system main relay 13 is interposed between the main battery 11 and the voltage converter 15. The voltage converter 15 increases the voltage of the main battery 11 to a voltage suitable for driving the motors 2 and 3, and reduces the regenerative power generated by the motors 2 and 3 to a voltage suitable for charging the main battery 11. Have The voltage converter 15 and the inverters 17 and 18 have switching elements such as IGBTs, and these are controlled by a PWM signal output from the power controller 21. The HV controller 22 calculates a running torque to be output by the drive system based on the vehicle speed, the accelerator opening, the remaining amount of the main battery 11, and outputs an appropriate command to the power controller 21. Based on this command, the power controller 21 generates the previous PWM signal and outputs it to the voltage converter 15 and the inverters 17 and 18. The switching elements of the voltage converter 15 and the inverters 17 and 18 that are controlled as described above generate heat when switching a large current.

  Next, the cooling system 30 will be described with reference to FIG. The cooling system 30 circulates the coolant in the cooling pipe 31 that goes around the radiator 35, the inverter cooler 36, the reserve tank 37, and the oil cooler 38, and each of the switching elements (voltage converter 15, inverters 17 and 18), and Then, the drive train 7 is cooled. An electric pump 32 for circulating the coolant is interposed in the cooling pipe 31. The cooling liquid is, for example, LLC (Long Life Coolant), and is pumped by the electric pump 32 and circulates in the cooling pipe 31. The viscosity of the cooling liquid increases at low temperatures.

  The radiator 35 releases the heat of the coolant in the cooling pipe 31 to the outside air. The inverter cooler 36 cools each of the switching elements (the voltage converter 15 and the inverters 17 and 18), which are heating elements. The oil cooler 38 cools the drive train 7 (the motors 2 and 3 and the power distribution mechanism 5), which is a heating element, with the oil circulating in the cooling pipe 52 by the pumping of the oil pump 51. In the oil cooler 38, the oil after cooling the drive train 7 is cooled by the coolant that passes through the cooling pipe 31.

  The reserve tank 37 is a tank that stores the coolant that circulates in the cooling pipe 31. In the upper part and the lower part of the reserve tank 37, an inlet 37a and a drain outlet 37b are provided, respectively. When replacing the coolant in the reserve tank 37 and the cooling pipe 31 during maintenance or the like, the user first opens the drainage port 37b and supplies the coolant in the reserve tank 37 and the cooling pipe 31. Discharge. Next, the user closes the drainage port 37 b and opens the injection port 37 a to inject new coolant into the reserve tank 37 from the injection port 37 a. New coolant injected into the reserve tank 37 also flows into the cooling pipe 31. At this time, a phenomenon (gas retention phenomenon) in which gas (mainly air) is confined in the cooling pipe 31 is likely to occur. A detailed method for eliminating the gas retention phenomenon will be described later.

  The electric pump 32 includes a motor and an impeller (impeller). When a drive current is supplied to the motor, the motor rotates and the impeller rotates accordingly. Due to the centrifugal force accompanying the rotation of the impeller, the coolant in the cooling pipe 31 is pumped and circulated. On the other hand, for example, during maintenance of the hybrid vehicle 100, while the main switch of the hybrid vehicle 100 is OFF, the drive current is not supplied to the motor, and the electric pump 32 is stopped. In this case, as described above, when the coolant is exchanged and a new coolant is injected into the cooling pipe 31, the impeller of the electric pump 32 is rotated by the injected coolant. When the impeller of the electric pump 32 rotates, the motor rotates in conjunction with each other, and an electromotive force is generated by the motor. That is, when the drive current is not supplied to the electric pump 32, the fact that the electromotive force is generated by the motor of the electric pump 32 means that the pump is rotated from the impeller side by the flow of the cooling liquid. This means that the coolant has been injected into the pipe 31.

  The electric pump 32 is provided with a rotation speed sensor 41 that detects the rotation speed of the electric pump 32. Further, the cooling pipe 31 is provided with a temperature sensor 42 that detects the temperature of the coolant flowing through the cooling pipe 31 and a flow rate sensor 43 that detects the flow rate of the coolant flowing through the cooling pipe 31.

  The cooling system 30 further includes a cooling controller 39, an HV controller 20, and a reverse drive detection circuit 60. The HV controller 20 is as described above. As shown in FIG. 2, the HV controller 20 includes an ignition switch 22a. The ignition switch 22a is a main switch of the hybrid vehicle 100.

  The cooling controller 39 controls the operation of each element of the cooling system 30. The cooling controller 39 receives detection values of the rotation speed sensor 41, the temperature sensor 42, and the flow rate sensor 43. The cooling controller 39 is electrically connected to the HV controller 20 and operates when the ignition switch 22a of the HV controller 20 is turned on. The cooling controller 39 is also electrically connected to the electric pump 32 and supplies a driving current to the electric pump 32. The cooling controller 39 controls the rotation speed of the electric pump 32 by PWM control. Details of the processing executed by the cooling controller 39 will be described later.

  The reverse drive detection circuit 60 includes a changeover switch 61, a capacitor 62, a comparator 63, and a constant voltage terminal 64. The capacitor 62 is connected between both terminals of the motor of the electric pump 32. The changeover switch 61 can switch between a state in which the motor of the electric pump 32 and the capacitor 62 are disconnected (state a: see FIG. 2) and a state in which the motor of the electric pump 32 and the capacitor 62 are connected (state b). Switch. The changeover switch 61 operates in conjunction with the ignition switch 22a. When the ignition switch 22a is turned on, the changeover switch 61 is switched to the state a after the cooling controller 39 compares the voltage across the capacitor 62 with a predetermined threshold voltage (the potential of the constant voltage terminal 64). That is, while the main switch of the hybrid vehicle 100 is ON, the changeover switch 61 is in the state a. During this time, the capacitor 62 is discharged and no charge is charged. When the ignition switch 22a (the main switch of the hybrid vehicle 100) is turned off, the changeover switch 61 is switched to the state b. In this case, when the motor of the electric pump 32 is reversely driven as described above and the electromotive force is generated while the main switch of the hybrid vehicle 100 is OFF, the capacitor 62 is charged.

  The input side of the comparator 63 is connected to the constant voltage terminal 64 and the capacitor 62, and the output side is connected to the cooling controller 39. The comparator 63 compares the potential of the constant voltage terminal 64 (predetermined threshold potential) with the electrode potential on the high voltage side of the capacitor 62 when the main switch of the hybrid vehicle 100 is turned on. The comparator 63 outputs a signal to the cooling controller 39 when the difference between the potential of the constant voltage terminal 64 and the electrode potential on the high voltage side of the capacitor 62 is smaller than a predetermined threshold value. In this case, it means that an electromotive force is generated by the motor of the electric pump 32 while the main switch of the hybrid vehicle 100 is OFF.

  With reference to FIG. 3, control of the rotation speed (hereinafter referred to as “pump rotation speed”) of the electric pump 32 by the cooling controller 39 will be described. When no main electromotive force is generated by the motor of the electric pump 32 while the main switch of the hybrid vehicle 100 is OFF (hereinafter referred to as “normal case”), the cooling controller 39 performs pump rotation speed according to the graph of FIG. The first control for controlling is executed. That is, the cooling controller 39 decreases the pump speed when the coolant temperature detected by the temperature sensor 42 is low, and increases the pump speed when the coolant temperature is high. In FIG. 3, T <b> 1 is the lowest temperature assumed for the coolant, and R <b> 1 is the lowest rotation speed of the electric pump 32. T3 is the highest temperature assumed for the coolant, and R3 is the highest rotational speed of the electric pump 32. As described above, when the cooling controller 39 performs the first control for determining the pump rotation speed based on the coolant temperature, the cooling system 30 reduces the energy consumption by the electric pump 32 while ensuring the necessary cooling capacity. Can be suppressed.

  When the electric pump 32 is driven at a high pump speed, even if a gas stagnation phenomenon occurs in the cooling pipe 31, the air staying in the cooling pipe 31 is pushed away by the flow of the cooling liquid, It can be discharged from the cooling pipe 31 to the reserve tank 37. That is, the gas retention phenomenon can be eliminated. In FIG. 3, the coolant temperature T <b> 2 and the pump rotational speed R <b> 2 indicate the temperature and rotational speed that are threshold values at which air can be discharged from the cooling pipe 31.

  It should be noted that the cooling controller 39 is used when the coolant temperature is equal to or higher than T2 even if an electromotive force is generated by the motor of the electric pump 32 while the main switch of the hybrid vehicle 100 is OFF (hereinafter referred to as “exceptional case”). In this case, the electric pump 32 can be driven at a pump rotational speed R2 or more by executing the first control described above. Therefore, even if the coolant is exchanged and the gas stagnation phenomenon occurs in the cooling pipe 31, the gas stagnation phenomenon is eliminated by driving the electric pump 32 at the pump rotational speed R2 or higher. be able to. The exceptional case is a case where the coolant temperature is already high at the time of starting the vehicle, for example, when the vehicle is started again immediately after the vehicle stops. In such a case, even immediately after startup, the pump may be rotated at a high speed to cool each component.

  On the other hand, when an electromotive force is generated by the motor of the electric pump 32 while the main switch of the hybrid vehicle 100 is OFF, and the coolant temperature is lower than T2 (hereinafter referred to as a “specific case”). However, depending on the first control, since the electric pump 32 is driven only at a pump speed smaller than R2, the air in the cooling pipe 31 cannot be discharged, and the gas retention phenomenon cannot be eliminated. Therefore, in the above specific case, the cooling controller 39 executes the second control for driving the electric pump 32 at the maximum rotational speed R3 as shown by the arrow 40 in FIG. 3 instead of the first control. As a result, even if the cooling liquid is low temperature and highly viscous, the air in the cooling pipe 31 can be swept away by the cooling liquid, and the gas retention phenomenon can be eliminated by discharging the air in the cooling pipe 31. it can. The above specific case is, for example, a case where the coolant in the reserve tank 37 and the cooling pipe 31 is replaced while the main switch of the hybrid vehicle 100 is OFF.

  With reference to the flowchart of FIG. 4, the process which the cooling controller 39 performs is further demonstrated. The process of FIG. 4 is started when the main switch (ignition switch 22a of FIG. 2) of the hybrid vehicle 100 is turned on.

  In S <b> 10, the cooling controller 39 determines whether an electromotive force is generated by the motor of the electric pump 32 while the main switch of the hybrid vehicle 100 is OFF. Specifically, in S <b> 10, the cooling controller 39 monitors whether a signal is output from the comparator 63 in the reverse drive detection circuit 60. When receiving the signal from the comparator 63, the cooling controller 39 determines YES in S10, and proceeds to S12. On the other hand, when the cooling controller 39 does not receive a signal from the comparator 63 (that is, in a normal case), the cooling controller 39 determines NO in S10 and proceeds to S16.

  In S12, the cooling controller 39 determines whether or not the coolant temperature in the cooling pipe 31 is lower than T2 (see FIG. 3). When the coolant temperature detected by the temperature sensor 42 is lower than T2 (that is, in a specific case), the cooling controller 39 determines YES in S12, and proceeds to S14. On the other hand, when the coolant temperature detected by the temperature sensor 42 is equal to or higher than T2 (that is, in an exceptional case), the cooling controller 39 determines NO in S12, and proceeds to S16.

  In S14, the cooling controller 39 drives the electric pump 32 at the maximum rotational speed R3 (second control). As a result, even if the cooling liquid is low temperature and highly viscous, the air in the cooling pipe 31 can be swept away by the cooling liquid, and the gas retention phenomenon can be eliminated by discharging the air in the cooling pipe 31. it can.

  In S16, the cooling controller 39 determines the pump speed based on the temperature of the coolant, and drives the electric pump 32 at the pump speed (first control). Specifically, the cooling controller 39 determines the pump rotation speed according to the graph of FIG. 3 and drives the electric pump 32. In a normal case (NO in S10), the cooling system 30 can suppress the energy consumption by the electric pump 32 while ensuring the necessary cooling capacity by the operation of S16. Even in exceptional cases (NO in S12), even if a gas retention phenomenon occurs in the cooling pipe 31 by the operation of S16, the gas retention phenomenon can be eliminated. .

  When the operation of S14 or S16 is continued for a predetermined time, the cooling controller 39 returns to S10 again and repeatedly executes the process of FIG.

  The hybrid vehicle 100 and the cooling system 30 according to the present embodiment have been described above. As described above, in the cooling system 30 of the present embodiment, the motor of the electric pump 32 generates a counter electromotive force while the drive current is not supplied to the electric pump 32, and the coolant temperature is lower than T2. In the case (YES in S10 and S12 in FIG. 4), the cooling controller 39 drives the electric pump 32 at a rotational speed R3 higher than normal. The electric pump 32 is driven at a high speed, the flow rate of the coolant in the cooling pipe 31 is increased, the air trapped in the cooling pipe 31 is discharged, and the gas retention phenomenon is eliminated. Thus, according to the present embodiment, in the cooling system 30 in which the coolant circulates in the cooling pipe 31, it is detected by the back electromotive force of the motor of the electric pump 32 that the coolant has been injected into the cooling pipe 31. Thus, the gas retention phenomenon can be appropriately eliminated.

  Further, the cooling system 30 of this embodiment includes a capacitor 62 connected between both terminals of the motor of the electric pump 32 and a reverse drive detection having a comparator 63 that can determine whether or not the capacitor 62 is charged. A circuit 60 is provided. The capacitor 62 of the reverse drive detection circuit 60 can be charged when an electromotive force is generated by the electric pump 32 even when there is no power source (that is, when the vehicle main switch is turned off). Therefore, in the cooling system 30 of the present embodiment, it is possible to detect that an electromotive force is generated in the motor without power supply, that is, that the coolant has been injected.

  The correspondence between this embodiment and the description of the claims will be described. The drive train 7, the voltage converter 15, and the inverters 17 and 18 are examples of “heating elements”. The radiator 35 is an example of a “heat radiator”. The cooling pipe 31 is an example of a “circulation path”. The reverse drive detection circuit 60 is an example of “pump reverse drive detection means”. The cooling controller 39 and the HV controller 22 are examples of the “control device”.

  Although the present embodiment has been described in detail above, 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. For example, the following modifications may be included.

  (Modification 1) Instead of the reverse drive detection circuit 60, the cooling controller 39 detects the electromotive force generated by the motor while the drive current is not supplied to the electric pump 32, and the electromotive force You may provide the memory | storage means to memorize | store the information which shows having generate | occur | produced. In this case, the cooling system 30 may include a standby power source for operating the cooling controller 39 and storing information indicating that an electromotive force has been generated while the main switch of the vehicle is turned off. preferable. When the main switch of the vehicle is turned on, the cooling controller 39 determines whether or not information indicating that an electromotive force has been stored in the storage unit.

  (Modification 2) In the above embodiment, the cooling controller 39 has a coolant temperature equal to or higher than T2 even if an electromotive force is generated by the motor of the electric pump 32 while the main switch of the hybrid vehicle 100 is OFF. In the case (YES in S10 of FIG. 4, NO in S12), the first control is executed. Instead, the cooling controller 39 determines whether or not the coolant temperature is equal to or higher than T2 when an electromotive force is generated by the motor of the electric pump 32 while the main switch of the hybrid vehicle 100 is OFF. Regardless of this, the second control may be executed. Also in this case, the gas retention phenomenon can be appropriately eliminated.

  (Modification 3) Although the example in which the cooling system 30 is mounted on the hybrid vehicle 100 has been described in the embodiment, the cooling system 30 may be mounted on an electric vehicle or a fuel cell vehicle.

  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 illustrated in the present specification or the drawings achieves a plurality of objects at the same time, and has technical utility by achieving one of the objects.

2: First motor 3: Second motor 4: Engine 5: Power distribution mechanism 6: Axle 7: Drive train 11: Main battery 13: System main relay 15: Voltage converter 17: Inverter 20: Controller 21: Power controller 22: HV controller 22a: ignition switch 30: cooling system 31: cooling pipe 32: electric pump 35: radiator 36: inverter cooler 37: reserve tank 37a: inlet 37b: drainage port 38: oil cooler 39: cooling controller 41: number of revolutions Sensor 42: Temperature sensor 43: Flow rate sensor 51: Oil pump 52: Cooling pipe 60: Reverse drive detection circuit 61: Changeover switch 62: Capacitor 63: Comparator 64: Constant voltage terminal 100: Hybrid vehicle

Claims (2)

A circulation path around the heating element and the radiator,
A pump for circulating the coolant in the circulation path;
A pump reverse drive detection means for detecting that an electromotive force is generated in the pump motor while no drive current is supplied to the pump;
A control device for making the rotational speed at the time of starting the pump when the pump reverse drive detecting means has detected the occurrence of the electromotive force higher than the rotational speed at the time of starting the pump when not detecting the occurrence of the electromotive force;
A cooling device comprising:   2. The pump reverse drive detection means comprises a capacitor connected between both terminals of a pump motor and a circuit for detecting whether or not the capacitor is charged. The cooling device as described.

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