JP2018062870A - Vehicular cooling system - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a technique for suppressing an increase in the flow amount of a cooling medium.SOLUTION: A vehicular cooling system includes a circuit in which the cooling medium flows for cooling a cooled object, two motor pumps arranged in series in the circuit for forcibly feeding the cooling medium, a rotational frequency sensor for detecting the rotational frequency of at least one of the two motor pumps, and a controller for controlling the rotational frequency of each motor pump. When the rotational frequency of the one motor pump detected by the rotational frequency sensor is lower than a predetermined lower limit value, the controller increases/reduces the rotational frequency of the one motor pump and increases/reduces the rotational frequency of the other motor pump so that the flow amount of the cooling medium forcibly fed by the two motor pumps becomes a predetermined flow amount.SELECTED DRAWING: Figure 5

Description

  The technology disclosed in the present specification relates to a vehicle cooling system.

  A vehicle cooling system disclosed in Patent Document 1 includes a circulation path through which a cooling medium for cooling a cooling target flows, an electric pump that pumps the cooling medium to the circulation path, and a rotation speed sensor that detects the rotation speed of the electric pump. And a controller for controlling the rotational speed of the electric pump. When the rotation of the electric pump stops, the controller performs an intermittent operation that increases or decreases the rotation speed of the electric pump in a low range.

JP, 2014-047660, A

  In a vehicle cooling system, two electric pumps may be provided in a circulation path through which a cooling medium flows, and the cooling medium may be pumped by the two electric pumps. In such a vehicle cooling system, when the rotational speed of one of the two electric pumps is reduced, the rotational speed of the other electric pump may be increased. Thereby, even if the flow rate of the cooling medium by one electric pump is reduced, the flow rate of the cooling medium by the two electric pumps is not reduced by increasing the flow rate of the cooling medium by the other electric pump. . At this time, if one of the electric pumps whose rotational speed is reduced is configured to increase or decrease the rotational speed as described in Patent Document 1, the flow rate of the cooling medium by the two electric pumps may increase excessively. That is, since the rotation speed of the other electric pump is increased, the flow rate of the cooling medium does not increase excessively when the rotation speed of one of the electric pumps is decreased. When it is increased, the flow rate of the cooling medium by the two electric pumps may increase excessively. If the flow rate of the cooling medium flowing through the circulation path increases too much, it may cause air jamming in which air is mixed into the cooling medium. Therefore, the present specification provides a technique capable of suppressing an increase in the flow rate of the cooling medium.

  The vehicle cooling system disclosed in the present specification includes a circulation path through which a cooling medium for cooling an object to be cooled flows, two electric pumps arranged in series in the circulation path to pump the cooling medium, and the two A rotation speed sensor that detects the rotation speed of at least one of the electric pumps; and a controller that controls the rotation speed of each of the electric pumps. The controller increases or decreases the rotational speed of one of the electric pumps when the rotational speed of one of the electric pumps detected by the rotational speed sensor is lower than a predetermined lower limit value, and the two electric pumps The number of rotations of the other electric pump is increased / decreased so that the flow rate of the cooling medium to be pumped becomes a predetermined flow rate.

  In such a configuration, when the rotational speed of one of the electric pumps decreases, the flow rate of the cooling medium flowing through the circulation path decreases. Further, when the rotational speed of one electric pump becomes lower than a predetermined lower limit value, the controller increases / decreases the rotational speed of one electric pump, so that the flow rate of the cooling medium flowing through the circulation path increases / decreases within a low range. At the same time, the controller increases or decreases the rotational speed of the other electric pump. At this time, the controller increases or decreases the rotational speed of the other electric pump so that the flow rate of the cooling medium pumped by the two electric pumps becomes a predetermined flow rate. As described above, the controller increases or decreases the rotation speed of the other electric pump in accordance with the increase or decrease of the rotation speed of one electric pump, so that the flow rate of the cooling medium pumped by the two electric pumps does not increase excessively. Therefore, according to said structure, the increase in the flow volume of a cooling medium can be suppressed. Further, it is possible to suppress air biting in which air is mixed into the cooling medium.

It is a block diagram which shows the structural example of the drive system of a hybrid vehicle. It is a block diagram which shows the structural example of the cooling system of an Example. It is a figure which shows the relationship between the rotation speed of a 1st water pump, and the flow volume of a cooling fluid. It is a figure which shows the relationship between the rotation speed of a 2nd water pump, and the flow volume of a cooling fluid. It is a flowchart of the process which a cooling controller performs. It is a figure which shows the relationship between the rotation speed of two water pumps in intermittent operation, and the flow volume of a cooling fluid.

  A vehicle cooling system according to an embodiment will be described with reference to the drawings. Hereinafter, an example of a cooling system for a hybrid vehicle will be described as an example of a cooling system for a vehicle. First, the configuration of the hybrid vehicle 2 will be described with reference to FIG. FIG. 1 is a block diagram illustrating a configuration example of a drive system of the hybrid vehicle 2.

  The hybrid vehicle 2 includes a motor 8 and an engine 6 as a driving source for traveling. The output torque of the motor 8 and the output torque of the engine 6 are appropriately distributed or synthesized by the power distribution mechanism 7 and output. The power distribution mechanism 7 is a planetary gear, for example. The power distribution mechanism 7 distributes or inputs power transmitted from the output shaft 6a of the engine 6 and the motor shaft 8a of the motor 8 at a predetermined ratio or outputs the power to the output shaft 7a. The output of the power distribution mechanism 7 is further transmitted to the drive wheels 10a and 10b via the transmission 9. The transmission 9 shifts the rotation input from the output shaft 7a of the power distribution mechanism 7 at a gear ratio corresponding to the selected shift speed, and outputs the rotation to the propeller shaft 9a. Through the differential gear 10, the drive wheels 10a 10b are driven. It should be noted that FIG. 1 shows only parts necessary for the description of the present specification, and parts not related to the description are not shown.

  Electric power for driving the motor 8 is supplied from the main battery 3. The output voltage of the main battery 3 is, for example, 300 volts. Although not shown, the hybrid vehicle 2 is a device group (commonly called “auxiliary machine”) driven by a voltage lower than the output voltage of the main battery 3, such as a car navigation device and a room lamp, in addition to the main battery 3. Auxiliary battery for supplying electric power is also provided. Two water pumps 13 and 14 and a cooling controller 20 constituting the cooling system 11 described later are also a kind of auxiliary machine. The name “main battery” is used for convenience to distinguish from “auxiliary battery”.

  The main battery 3 is connected to a power control unit 5 (hereinafter referred to as “PCU 5”) via a system main relay 4. The system main relay 4 is a switch for connecting or disconnecting the main battery 3 and the drive system of the vehicle. The system main relay 4 is switched by the HV controller 50 of the host system.

  The PCU 5 is a power conversion device that is interposed between the main battery 3 and the motor 8. The PCU 5 includes a voltage converter (not shown) that boosts the voltage of the main battery 3 to a voltage suitable for driving the motor 8 (for example, 600 volts), an inverter (not shown) that converts the boosted DC power into AC, and A power controller 30 for controlling them is included. The output of the inverter corresponds to the power supplied to the motor 8. In the PCU 5, electronic components constituting a voltage converter and an inverter are constantly cooled by a cooling system 11 described later.

  The hybrid vehicle 2 can also use the driving force of the engine 6 or the deceleration energy of the vehicle, that is, at the time of braking, to generate electric power with the motor 8 using the kinetic energy of the vehicle. Such power generation is called “regeneration”. When the motor 8 generates electric power, the inverter converts alternating current into direct current, and the voltage converter further steps down the voltage to a voltage slightly higher than the main battery 3 and supplies it to the main battery 3.

  The voltage converter includes a switching element such as a reactor or an IGBT. The inverter is configured by a switching element that performs a switching operation corresponding to each phase of U, V, and W of the motor 8. These are controlled by the power controller 30 to perform a predetermined switching operation to increase or decrease the voltage, convert direct current to alternating current, or convert alternating current to direct current.

  The power controller 30 is an information processing apparatus that includes electronic components such as a microcomputer, a memory, and an input / output interface. The power controller 30 is connected to a voltage converter, an inverter, and an HV controller 50 to control the switching operation as described above. For example, accelerator opening information and brake pedal force information are input to the HV controller 50 connected to the power controller 30 as operation information by the driver. Therefore, the operation of each switching element is performed according to control information corresponding to the accelerator opening degree input from the HV controller 50.

  Each switching element of the voltage converter or inverter controlled in this way generates a large amount of heat. Further, the motor 8 generates a large amount of heat when a load is applied suddenly at the time of starting or on an uphill. Therefore, the PCU 5 including the voltage converter and the inverter and the motor 8 that generates the driving force are always cooled by the cooling system 11 described below.

  The configuration of the cooling system 11 for cooling the PCU 5 and the motor 8 will be described with reference to FIG. In FIG. 2, the block diagram showing the structural example of the cooling system 11 of an Example is shown. The cooling system 11 includes two water pumps 13 and 14, a reserve tank 15, a radiator 16, a PCU cooler 17, a motor cooler 18, and a cooling pipe 12 that goes around them. A coolant 19 is circulated through the cooling pipe 12 to cool the PCU 5 by the PCU cooler 17 and the motor 8 by the motor cooler 18. The main cooling objects of the cooling system 11 are the PCU 5 and the motor 8.

  In FIG. 2, it should be noted that only parts necessary for the description of this specification are shown, and parts not related to the description are not shown. Further, the arrangement of the water pumps 13 and 14 and the PCU cooler 17 in FIG. 2 is for convenience of drawing, and is arranged at a position suitable for the characteristics of the object to be cooled, such as the difference in heat resistance between the semiconductor and the motor. Is done.

  The cooling liquid 19 is, for example, LLC (Long Life Coolant). The cooling liquid 19 is stored in the reserve tank 15 and is a cooling medium that is pumped by the water pumps 13 and 14 and circulates in the cooling pipe 12.

  The two water pumps 13 and 14 are centrifugal pumps that rotate an internal impeller by a motor, generate a lift pressure by the centrifugal force, pump the coolant 19 from the reserve tank 15 and send it out. In the embodiment, the water pump 13 is disposed on the upstream side and the water pump 14 is disposed on the downstream side with the PCU cooler 17 interposed therebetween. Hereinafter, when these water pumps 13 and 14 are particularly distinguished, the upstream pump is referred to as a first water pump 13 and the downstream pump is referred to as a second water pump 14. The two water pumps 13 and 14 are arranged in series with the cooling pipe 12.

  The driving amount of the water pumps 13 and 14 is normally controlled by a rotation speed command value for the motor of the water pumps 13 and 14 output from the cooling controller 20. For example, the drive amounts of the water pumps 13 and 14 are controlled by the voltage of the PWM signal whose duty ratio is controlled according to the rotational speed command value.

  In the embodiment, the cooling system 11 includes a temperature sensor 21 that detects the temperature of the switching element of the PCU 5 that is cooled by the PCU cooler 17, and a temperature sensor 23 that detects the temperature of the cooling liquid 19 flowing through the cooling pipe 12, that is, the liquid temperature. I have. The cooling system 11 also includes a rotation speed sensor 24 that detects the rotation speed of the first water pump 13 and a rotation speed sensor 25 that detects the rotation speed of the second water pump 14. The rotation speed sensors 24 and 25 detect the rotation speed of the motors or impellers of the water pumps 13 and 14.

  The rotation speed data output from the rotation speed sensors 24 and 25 is input to the cooling controller 20. The rotation speed data is used for operation control of the first water pump 13 and the second water pump 14.

  Similar to the power controller 30, the cooling controller 20 that controls the water pumps 13 and 14 is an information processing apparatus that includes electronic components such as a microcomputer, a memory, and an input / output interface. The cooling controller 20 has a clock function. In addition to the water pumps 13 and 14, the cooling controller 20 is connected to the sensors 21 and 23 described above and the HV controller 50 of the host system. Thereby, the cooling controller 20 performs operation control of the first water pump 13 and the second water pump 14 as described later. The memory of the cooling controller 20 stores programs and data tables for each process described later.

  For example, vehicle information such as vehicle speed is input to the HV controller 50 connected to the cooling controller 20 as driving information of the hybrid vehicle 2. These are input to the HV controller 50 via in-vehicle LAN, for example. The cooling controller 20 obtains information from the HV controller 50 that the hybrid vehicle 2 has started traveling by inputting information on the vehicle speed and the accelerator opening.

  Next, the relationship between the number of rotations of the two water pumps 13 and 14 and the flow rate of the coolant 19 flowing through the cooling pipe 12 will be described. The flow rate of the coolant 19 flowing through the cooling pipe 12 changes according to the number of rotations of the two water pumps 13 and 14. The flow rate of the coolant 19 flowing through the cooling pipe 12 is the sum of the flow rate by the first water pump 13 and the flow rate by the second water pump 14. Therefore, when the rotational speed of one of the two water pumps 13 and 14 increases, the flow rate of the coolant 19 increases. Similarly, when the rotation speed of one water pump is reduced, the flow rate of the coolant 19 is reduced. For example, when the rotational speed of the first water pump 13 increases, the flow rate of the coolant 19 increases, and when the rotational speed of the first water pump 13 decreases, the flow rate of the coolant 19 decreases. The second water pump 14 is the same as the first water pump 13.

  The relationship between the rotational speed of each water pump 13 and 14 and the flow rate of the coolant 19 flowing through the cooling pipe 12 is obtained in advance by experiments and simulations, and a data table indicating the relationship is stored in the memory of the cooling controller 20 in advance. Has been. FIG. 3 shows the relationship between the rotational speed of the first water pump 13 and the flow rate of the coolant 19 flowing through the cooling pipe 12. FIG. 4 shows the relationship between the rotational speed of the second water pump 14 and the flow rate of the coolant 19 flowing through the cooling pipe 12. The rotational speed of each water pump 13 and 14 and the flow rate of the cooling liquid 19 correspond one-to-one. In this embodiment, the first water pump 13 and the second water pump 14 are pumps having the same performance. In addition, when the flow rate changes in accordance with the temperature of the coolant 19, the temperature of the coolant 19 may be taken into consideration.

  There are a normal upper limit value and a normal lower limit value, and a diagnosis upper limit value and a diagnosis lower limit value for the rotation speed of each water pump 13, 14. The normal upper limit value and the normal lower limit value are threshold values for distinguishing whether or not the water pumps 13 and 14 are operating normally. When the rotational speed of the water pumps 13 and 14 is not less than the normal lower limit value and not more than the normal upper limit value, the water pumps 13 and 14 are operating normally. Hereinafter, the water pumps 13 and 14 in such a state are referred to as “normal pumps”.

  The diagnosis upper limit value and the diagnosis lower limit value are threshold values for distinguishing whether or not the water pumps 13 and 14 are out of order. When the rotation speed of the water pumps 13 and 14 is not more than the diagnosis lower limit value, it can be said that the water pumps 13 and 14 are out of order. Hereinafter, the water pumps 13 and 14 in such a state are referred to as “failure pumps”. With this failure pump, it becomes difficult to achieve the cooling performance assumed in advance in the cooling system. Moreover, it can be said that the water pumps 13 and 14 are out of order also when the rotational speed of the water pumps 13 and 14 is equal to or greater than the diagnosis upper limit value.

  Moreover, when the rotation speed of the water pumps 13 and 14 is lower than the normal lower limit value and higher than the diagnosis lower limit value, the rotation speed of the water pumps 13 and 14 is lower than usual. Hereinafter, the water pumps 13 and 14 in such a state are referred to as “rotational reduction pumps”. In the rotation reduction pump, it becomes difficult to achieve the cooling performance assumed in advance in the cooling system. Moreover, when the rotation speed of the water pumps 13 and 14 is higher than the normal upper limit value and lower than the diagnosis upper limit value, the rotation speeds of the water pumps 13 and 14 are higher than usual.

  Next, processing executed by the cooling controller 20 will be described with reference to FIG. This process is realized by the microcomputer of the cooling controller 20 appropriately executing the corresponding program stored (stored) in the memory of the cooling controller 20 in advance. This process is performed immediately after the cooling system 11 starts operating. That is, this process is executed after the power switch (start switch) of the hybrid vehicle 2 is turned on until the switch is turned off.

  First, it is assumed that the two water pumps 13 and 14 are operating normally at the start point shown in FIG. The two water pumps 13 and 14 are normal pumps. A coolant 19 having a flow rate corresponding to the number of rotations of the two water pumps 13 and 14 flows through the cooling pipe 12. The number of rotations of the two water pumps 13 and 14 is a value between the normal lower limit value and the normal upper limit value.

  Subsequently, in step S10, the cooling controller 20 monitors whether the rotational speed of any of the water pumps 13 and 14 is lower than the normal lower limit value. Specifically, the cooling controller 20 acquires the rotation speeds of the water pumps 13 and 14 from the rotation speed sensors 24 and 25, respectively. When the rotational speed of any one of the water pumps 13 and 14 is lower than the normal lower limit value, the cooling controller 20 determines Yes in step S10 and proceeds to step S11. For example, when the rotational speed of the first water pump 13 decreases and becomes lower than the normal lower limit value due to foreign matter biting into the impeller of the first water pump 13, it is determined Yes in step S10. In the present embodiment, description will be made on the assumption that the rotation speed of the first water pump 13 is lower than the normal lower limit value. The description will be made assuming that the rotation speed of the second water pump 14 is normal. That is, of the two water pumps 13 and 14, the rotation speed of one water pump (first water pump 13) is lower than the normal lower limit value, and the rotation speed of the other water pump (second water pump 14). The case where is normal will be described. In Step S10, when both the rotation speeds of the water pumps 13 and 14 are normal, the cooling controller 20 determines No and stands by.

  Subsequently, in step S11, the cooling controller 20 determines that the rotational speed of the water pump (first water pump 13) determined in step S10 to be lower than the normal lower limit value is lower than the diagnosis lower limit value. Determine whether or not. When the rotation speed of the first water pump 13 is lower than the diagnosis lower limit value, the cooling controller 20 determines Yes in step S11 and proceeds to step S12. A water pump whose rotational speed is lower than the diagnosis lower limit value is a failure pump. Therefore, when it is determined Yes in step S11, the water pump is a fault pump. On the other hand, when the rotation speed of the first water pump 13 is equal to or greater than the diagnosis lower limit value, the cooling controller 20 determines No in step S11 and proceeds to step S20. A water pump whose rotational speed is lower than the normal lower limit value and higher than the diagnosis lower limit value is a rotation lowering pump. Therefore, when it is determined No in step S11, the water pump is a rotation reduction pump. In this embodiment, the first water pump 13 will be described on the assumption that it is a failure pump or a rotation reduction pump.

  In step S12 after it is determined Yes in step S11, the cooling controller 20 reduces the rotational speed of the failure pump (first water pump 13). Specifically, the cooling controller 20 sets the rotation speed of the failed pump to 0 (zero). The cooling controller 20 outputs 0 as the rotational speed command value for the motor of the failed pump and stops the failed pump. When the failure pump (first water pump 13) stops, the flow rate of the coolant 19 flowing through the cooling pipe 12 decreases.

  Subsequent to step S12, in step S13, the cooling controller 20 increases the rotation speed of the normal pump (second water pump 14) that has not failed. Specifically, the cooling controller 20 maximizes the rotation speed of the normal pump. The cooling controller 20 maximizes the rotational speed command value for the motor of the failed pump. When the rotation speed of the normal pump (second water pump 14) increases, the flow rate of the coolant 19 flowing through the cooling pipe 12 increases. Therefore, even if the flow rate of the cooling liquid 19 by the failure pump (first water pump 13) decreases as described above, the flow rate of the cooling liquid 19 by the normal pump (second water pump 14) increases. The flow rate of the coolant 19 pumped by the water pumps 13 and 14 can be maintained. Thereby, the flow rate of the coolant 19 before the failure of the first water pump 13 can be maintained.

  On the other hand, in step S20 after it is determined No in step S11, the cooling controller 20 performs an intermittent operation for increasing or decreasing the rotational speed of the rotation lowering pump (first water pump 13). The cooling controller 20 increases or decreases the rotation speed of the rotation lowering pump (first water pump 13) in a range lower than the normal lower limit value and higher than the diagnosis lower limit value. As shown in FIG. 6, the rotation speed of the rotation reducing pump (first water pump 13) increases or decreases at predetermined time intervals. For example, the cooling controller 20 repeats the operation of rotating the motor of the rotation reducing pump at 150 rpm for 0.5 seconds and rotating at 100 rpm for 0.5 seconds. By the intermittent operation of the rotation lowering pump (first water pump 13), the foreign matter biting into the impeller is removed.

  When the rotation speed of the first water pump 13 decreases, the flow rate of the coolant 19 by the first water pump 13 decreases. Therefore, the flow rate of the coolant 19 flowing through the cooling pipe 12 is reduced as it is. Therefore, it is preferable to increase the rotational speed of the second water pump 14. As a result, the flow rate of the coolant 19 by the second water pump 14 increases, so that the flow rate of the coolant 19 pumped by the two water pumps 13 and 14 can be maintained. The decrease in the flow rate of the coolant 19 by the rotation lowering pump (first water pump 13) is compensated by increasing the number of rotations of the normal pump (second water pump 14).

  However, when the cooling controller 20 increases or decreases the rotation speed of the rotation lowering pump (first water pump 13) (step S20), if the rotation speed of the normal pump (second water pump 14) is increased, it flows through the cooling pipe 12. It is conceivable that the flow rate of the coolant 19 increases excessively. That is, there is no problem when the cooling controller 20 increases the rotation speed of the normal pump (second water pump 14) when the rotation speed of the rotation reduction pump (first water pump 13) is reduced. If the rotational speed of the normal pump (second water pump 14) is also increased when the rotational speed of the 1 water pump 13) is increased, the rotational speeds of the rotation-lowering pump and the normal pump overlap, and the cooling that flows through the cooling pipe 12 is performed. It is conceivable that the flow rate of the liquid 19 increases too much. Therefore, the cooling controller 20 executes the following process.

  In step S21 following step S20, the cooling controller 20 performs an intermittent operation for increasing or decreasing the rotational speed of the normal pump (second water pump 14). The cooling controller 20 increases or decreases the rotation speed of the normal pump (second water pump 14) in a range higher than the normal upper limit value and lower than the diagnosis upper limit value. As shown in FIG. 6, the number of rotations of the normal pump (second water pump 14) increases or decreases at predetermined time intervals. For example, the cooling controller 20 repeats the operation of rotating the motor of the rotation reducing pump at 150 rpm for 0.5 seconds and rotating at 100 rpm for 0.5 seconds.

  At this time, the cooling controller 20 executes the intermittent operation of the normal pump (second water pump 14) in accordance with the intermittent operation of the rotation reduction pump (first water pump 13). More specifically, the cooling controller 20 increases the number of rotations of the normal pump (second water pump 14) when the number of rotations of the rotation reduction pump (first water pump 13) is reduced, and the rotation reduction pump (first water pump 14). When the rotational speed of the 1 water pump 13) is increased, the rotational speed of the normal pump (second water pump 14) is reduced. The decrease in the rotation speed of the rotation reduction pump (first water pump 13) and the increase in the rotation speed of the normal pump (second water pump 14) overlap, and the increase in the rotation speed of the rotation reduction pump (first water pump 13) and normality. Reduction of the rotation speed of the pump (second water pump 14) overlaps.

  In addition, the cooling controller 20 increases or decreases the rotational speed of the normal pump (second water pump 14) so that the flow rate of the coolant 19 pumped by the two water pumps 13 and 14 becomes a predetermined flow rate. The predetermined flow rate is not particularly limited. For example, the predetermined flow rate is the flow rate of the coolant 19 that was pumped by the two water pumps 13 and 14 before the rotation speed of the first water pump 13 is decreased. As shown in FIG. 6, the predetermined flow rate is a value lower than the maximum flow rate threshold value. The maximum flow rate threshold is the maximum value of the flow rate of the coolant 19 that can flow through the cooling pipe 12. The cooling controller 20 performs intermittent operation so that the flow rate of the coolant 19 by the rotation lowering pump (first water pump 13) and the normal pump (second water pump 14) becomes a predetermined flow rate.

  In step S21, the rotational speed command value for the normal pump (second water pump 14) is calculated as follows, for example. That is, first, the cooling controller 20 calculates the flow rate of the coolant 19 by the rotation reduction pump based on the relationship shown in FIG. 3 from the current rotation speed of the rotation reduction pump (first water pump 13). Next, the cooling controller 20 subtracts the calculated flow rate of the coolant 19 from the rotation lowering pump (first water pump 13) from the predetermined flow rate, and the coolant 19 from the normal pump (second water pump 14) is subtracted. Calculate the required flow rate. Next, the cooling controller 20 calculates the rotation speed of the normal pump from the calculated required flow rate of the coolant 19 by the normal pump (second water pump 14) based on the relationship shown in FIG.

  As described above, when the rotational speed of one of the two water pumps 13 and 14 (the first water pump 13) becomes lower than the normal lower limit value, the cooling controller 20 The intermittent operation of the first water pump 13) and the normal pump (second water pump 14) is executed.

  As described above, the cooling system 11 according to the embodiment includes the cooling pipe 12 through which the cooling liquid 19 for cooling the cooling target (for example, the PCU 5 and the motor 8) flows, and the cooling liquid 19 arranged in series with the cooling pipe 12. Are provided with two water pumps 13 and 14 and a rotation speed sensor 24 for detecting the rotation speed of at least one of the two water pumps 13 and 14 (first water pump 13). . The cooling system 11 includes a cooling controller 20 that controls the rotational speeds of the two water pumps 13 and 14. The cooling controller 20 increases or decreases the number of rotations of the first water pump 13 when the number of rotations of the first water pump 13 detected by the rotation number sensor 24 is lower than a predetermined normal lower limit value. Processing is performed to increase or decrease the rotational speed of the other water pump (second water pump 14) so that the flow rate of the coolant 19 pumped by the pumps 13 and 14 becomes a predetermined flow rate.

  According to such a configuration, the cooling controller 20 increases / decreases the rotation speed of the normal pump (second water pump 14) in accordance with the increase / decrease of the rotation speed of the rotation reduction pump (first water pump 13). The flow rate of the coolant 19 pumped by the water pumps 13 and 14 does not increase excessively. Therefore, according to said structure, the increase in the flow volume of the cooling fluid 19 which flows through the cooling pipe 12 can be suppressed. Further, it is possible to suppress the air biting in which air is mixed into the coolant 19.

  Points to be noted regarding the example technology will be described. The PCU 5 corresponds to an example of a cooling target. The cooling liquid 19 corresponds to an example of a cooling medium. The cooling pipe 12 corresponds to an example of a circulation path. The water pumps 13 and 14 correspond to an example of two electric pumps. The first water pump 13 corresponds to an example of one electric pump. The second water pump 14 corresponds to an example of the other electric pump. The cooling controller 20 corresponds to an example of a controller. The normal lower limit value corresponds to an example of a lower limit value.

  In the above embodiment, the first water pump 13 is a rotation lowering pump and the second water pump 14 is a normal pump. On the contrary, the first water pump 13 is a normal pump, and the second water pump 14 is a normal pump. The water pump 14 may be a rotation reduction pump.

  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: Hybrid vehicle 3: Main battery 5: PCU
6: Engine 8: Motor 11: Cooling system 12: Cooling pipe 13: First water pump 14: Second water pump 15: Reserve tank 16: Radiator 17: PCU cooler 18: Motor cooler 19: Coolant 20: Cooling controller 24: Rotational speed sensor 25: Rotational speed sensor 30: Power controller 50: HV controller

Claims (1)

A circulation path through which a cooling medium for cooling the object to be cooled flows;
Two electric pumps arranged in series in the circulation path to pump the cooling medium;
A rotational speed sensor for detecting the rotational speed of at least one of the two electric pumps;
A controller for controlling the rotational speed of each electric pump,
The controller increases or decreases the rotational speed of one of the electric pumps when the rotational speed of one of the electric pumps detected by the rotational speed sensor is lower than a predetermined lower limit value, and the two electric pumps A cooling system for a vehicle, wherein the number of rotations of the other electric pump is increased or decreased so that the flow rate of the cooling medium pumped by the air pump becomes a predetermined flow rate.

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