JP2017110622A - Cooling system - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a cooling system including a plurality of pumps, for avoiding an increase in the vibration of a structure system for a circuit and the plurality of pumps.SOLUTION: The cooling system includes the circuit in which cooling medium flows for cooling cooled objects, the plurality of pumps for forcibly feeding the cooling medium into the circuit, and a controller. The controller determines the output of each of the plurality of pumps and controls each pump to actualize the determined output. The controller stores a corresponding relationship between the output of each of the plurality of pumps and the peak vibration frequency of the pump when the pump operates with its output, and determines the output of each pump so that the peak frequencies of the plurality of pumps do not overlap one another.SELECTED DRAWING: Figure 3

Description

  The present invention relates to a cooling system including a plurality of pumps in one circulation path for circulating a refrigerant.

  A cooling system having a plurality of pumps in one circulation path for circulating a refrigerant is known. For example, Patent Document 1 discloses a cooling system including two pumps. When a plurality of pumps are provided in one circulation path and the flow rate of the refrigerant flowing through the circulation path is determined using the plurality of pumps, a rule for determining the output of each of the plurality of pumps is required. For example, the flow rate (required flow rate) of the refrigerant that should flow through the circulation path is determined from the temperature of the cooling target or the temperature of the refrigerant. For example, the controller that controls each of the two pumps must determine what percentage of the required flow is to be covered by the output of the first pump and the rest is covered by the second pump. For example, one method is to operate only the first pump while the required flow rate can be covered only by the output of the first pump, and to supplement the flow rate that cannot be covered by the output of the first pump with the second pump. is there.

Japanese Patent Laid-Open No. 11-200858

  By the way, since the pump includes a rotating impeller (impeller), the peak frequency of vibration changes when the output (number of rotations) changes. When a plurality of pumps are provided in one circulation path and the peak frequencies of these pumps are close, a large vibration may be generated in a structural system composed of the plurality of pumps and the circulation path due to a resonance phenomenon. Vibration causes noise. This specification pays attention to the vibration of a cooling system including a plurality of pumps, and provides a technique for preventing the vibration (and noise due to the vibration) of the circulation path and the structure system of the plurality of pumps from increasing.

  The cooling system disclosed in the present specification determines the output for each of a circulation path through which a refrigerant that cools a cooling target flows, a plurality of pumps that pump the refrigerant into the circulation path, and each of the plurality of pumps. A controller for controlling each pump is provided. The controller stores, for each pump, a correspondence relationship between the pump output and the peak frequency of vibration of the pump when the pump is operated at the output. Note that “pump vibration” refers to vibration of the pump in a state of being incorporated in the cooling system. The controller determines the output of each pump so that the peak frequencies of the plurality of pumps do not overlap. The cooling system disclosed in this specification pays attention to the correspondence between the pump output and the peak frequency of vibration of the pump, and determines the output of each pump so that the peak frequencies of a plurality of pumps do not overlap. The vibration of the structural system of the cooling system including the circulation path and the cooling pump (and the noise due to the vibration) should not be increased.

  Note that “determining the output of each pump so that the peak frequencies of a plurality of pumps do not overlap” actually means that the difference between the peak frequencies of a plurality of pumps does not become smaller than a predetermined threshold difference. Can be determined. The correspondence between the pump output and the vibration peak frequency is obtained in advance by analysis, experiment, or simulation. The predetermined threshold difference is a frequency difference necessary for preventing resonance, and is determined in advance through experiments and simulations.

  When the cooling system has three or more pumps, the output may be determined so that the peak frequencies do not overlap for all the pumps, or some of the pumps having a large influence on vibration among the plurality of pumps. However, the output may be determined so that the peak frequencies do not overlap. Details and further improvements of the technology disclosed in this specification will be described in the following “DETAILED DESCRIPTION”.

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 flowchart of the pump control which a cooling controller performs. It is a table | surface which shows an example of the correspondence of a pump output (duty ratio) and a peak frequency. FIG. 5 is a graph of the table in FIG. 4.

  A cooling system according to an embodiment will be described with reference to the drawings. Hereinafter, as an example of the cooling system, an example mounted as a cooling system of a hybrid vehicle will be described. 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 motor 8 may function as a generator. The output torque of the motor 8 and the output torque of the engine 6 are combined by the power distribution mechanism 7 and output to the output shaft 7a. Alternatively, the power distribution mechanism 7 may distribute the output torque of the engine 6 to the output shaft 7a and the motor shaft 8a. At this time, the motor 8 generates power with a part of the driving force of the engine 6. The power distribution mechanism 7 is a planetary gear, for example. The power distribution mechanism 7 combines the motive power transmitted and input from the output shaft 6a of the engine 6 and the motor shaft 8a of the motor 8 and outputs the combined power to the output shaft 7a. Alternatively, as described above, the power distribution mechanism 7 distributes the power transmitted from the output shaft 6a of the engine 6 to the output shaft 7a and the motor shaft 8a at a predetermined ratio. The motor 8 is reversely driven by the power distributed to the motor shaft 8a to generate electric power. 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. Is also provided with an auxiliary battery for supplying power. 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. In FIG. 1, the PCU 5 and the power controller 30 are drawn separately to help understanding. 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 generate electric power with the motor 8 using the driving force of the engine 6 or the deceleration energy of the vehicle, that is, using the kinetic energy of the vehicle during braking. Such power generation is called “regeneration”. When the motor 8 generates power, the inverter converts the AC power generated by the motor 8 into DC power, and the voltage converter steps down to a voltage slightly higher than the main battery 3 and supplies the voltage 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 based on the 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 also generates a large amount of heat when a load is applied suddenly, such as when starting or when going 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 that cools 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. That is, 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 refrigerant 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.

  As described above, the water pumps 13 and 14 pump the refrigerant by the rotation of the impeller. As the impeller rotates, the water pumps 13 and 14 vibrate. The vibration frequency depends on the mechanical characteristics of the structures such as the water pumps 13 and 14 and the cooling pipe 12 connected thereto, and the rotation speed of the impeller. That is, the peak frequency of the vibrations of the water pumps 13 and 14 and the structural system connected to them varies depending on the rotational speed. Hereinafter, for convenience of explanation, “the peak frequency of vibration of each water pump 13, 14 and the structural system connected thereto” is referred to as “the peak frequency of vibration of each water pump”.

  Since the two water pumps 13 and 14 are both connected to the cooling pipe 12 that circulates the refrigerant, if the peak frequency of vibration of the two water pumps 13 and 14 is close, a resonance phenomenon occurs, and the water pump The structure including 13, 14 and the cooling pipe 12 vibrates greatly. Therefore, in the cooling system 11, the water pumps 13 and 14 are controlled so that the vibration peak frequencies of the two water pumps 13 and 14 do not overlap.

  The water pumps 13 and 14 are controlled by a cooling controller 20. Specifically, the cooling controller 20 controls the water pumps 13 and 14 such that each of the two water pumps 13 and 14 rotates at a desired rotational speed. More specifically, the water pumps 13 and 14 are pumps of a type controlled by the duty ratio of the PWM signal, and rotate at a rotational speed corresponding to the duty ratio. The cooling controller 20 commands a PWM signal having a duty ratio corresponding to the rotation speed target value to each of the water pumps 13 and 14. The rotation speed of each water pump corresponds to the output of the water pump. Since the rotation speed and the duty ratio of the water pump uniquely correspond to each other, the duty ratio of the PWM signal given to each water pump is equivalent to the output (rotation speed) of each water pump. Hereinafter, the duty ratio of the PWM signal before being output to each water pump may be referred to as an output target value (rotation speed target value).

  The cooling system 11 includes several sensors. The cooling system 11 includes temperature sensors 21 and 23 and rotation speed sensors 24 and 25. The temperature sensor 21 detects the temperature of the switching element of the PCU 5 cooled by the PCU cooler 17 (hereinafter referred to as “the temperature of the PCU 5”). The temperature sensor 23 detects the temperature of the coolant 19 flowing through the cooling pipe 12, that is, the refrigerant temperature. The rotation speed sensors 24 and 25 detect the rotation speed of the motor or impeller of the first water pump 13 or 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. In addition to the water pumps 13 and 14, the above-described sensors 21 and 23 and the HV controller 50 of the host system are connected to the cooling controller 20.

  The pump control process will be described with reference to FIG. FIG. 3 is a flowchart of pump control executed by the cooling controller 20. In FIG. 3, the symbol “W / P” means “water pump”. The cooling controller 20 determines the flow rate of the coolant 19 to be circulated through the cooling pipe 12 based on the measurement data of the temperature sensors 21 and 23 (S2). Hereinafter, the flow rate to be circulated through the cooling pipe 12 is referred to as a target total flow rate. The cooling controller 20 determines the duty ratio (rotation speed target value) of the PWM signal for each of the water pumps 13 and 14 based on the target total flow rate (S3). The cooling controller 20 has map data describing the relationship between the duty ratio (number of rotations) and the flow rate for each water pump. Such map data is obtained in advance by experiments and simulations. In step S3, the cooling controller 20 sets the rotational speed target value of each water pump 13, 14 so that the sum of the flow rate of the first water pump 13 and the flow rate of the second water pump 14 becomes the target total flow rate described above, that is, Determine the duty ratio. For example, the cooling controller 20 has pump efficiency data at each duty ratio in addition to the map data described above, the sum of the flow rates of the two water pumps 13 and 14 is equal to or greater than the target total flow rate, and 2 The rotation speed target value, that is, the duty ratio of each of the water pumps 13 and 14 is determined so that the pump efficiency of the water pumps 13 and 14 of the machine is minimized.

  Next, the cooling controller 20 determines whether or not the difference in peak frequency is greater than a predetermined threshold difference with respect to the peak frequency of vibration in the main orders of the two water pumps 13 and 14 (S4). For each of the two water pumps 13, 14, the cooling controller 20 has a correspondence relationship between the rotation speed (duty ratio) of the pump and the peak frequency of pump vibration when the water pump operates at the rotation speed. Is remembered. The cooling controller 20 stores the correspondence between the rotation speed (duty ratio) and the peak frequency for a plurality of main orders. The major orders of vibration are orders that have a particularly great influence on the structure among the vibration orders of the structural system including the water pumps 13 and 14 and the cooling pipe 12. For example, the first order vibration is excluded from the main order because it does not have a large amplitude because its energy is absorbed by other structures of the cooling system 11.

  FIG. 4 shows an example of the correspondence relationship between the rotation speed (duty ratio) and the peak frequency. In the present embodiment, since the first water pump 13 and the second water pump 14 have the same vibration characteristics, the correspondence relationship in FIG. 4 is common to the first and second water pumps 13 and 14. In the example of FIG. 4, the sixth, seventh, ninth, and eighteenth vibration modes are structurally important. Therefore, these orders are selected as the main orders, and the respective orders. The peak frequency corresponding to is stored.

  FIG. 5 shows a graph of the table of FIG. Using FIG. 5 as an example, the processing up to steps S3 to S5 will be specifically described. For example, it is assumed that the cooling controller 20 determines the duty ratio of the first water pump 13 to 48 [%] and the duty ratio of the second water pump 14 to 60 [%] in step S3. In FIG. 5, the peak frequency of each order when the duty ratio is 48 [%] is shown in the range indicated by the symbol G <b> 1. Further, the peak frequencies of the respective orders when the duty ratio is 60 [%] are shown in the range indicated by the symbol G2. In step S4, the cooling controller 20 determines the peak frequency of each order in the duty ratio assigned to the first water pump 13 (= 48 [%]) and the duty ratio assigned to the second water pump 14 (= 60 [ %]) And the difference between each order and the peak frequency is calculated, and it is checked whether the difference is larger than a predetermined threshold difference. In this embodiment, the threshold difference is set to 20 [Hz]. The difference between the ninth peak frequency (= 466 [Hz]) at a duty ratio of 48 [%] and the seventh peak frequency (= 480 [Hz]) at a duty ratio of 60 [%] is 14 [Hz]. It is found that the difference is smaller than the threshold difference (= 20 [Hz]) (step S4: NO). In FIG. 5, the part indicated by reference sign P1 indicates the ninth peak frequency (= 466 [Hz]) at a duty ratio of 48 [%], and the part indicated by reference sign P2 indicates a duty ratio of 60 [%]. 7 shows the seventh-order peak frequency (= 480 [Hz]).

  If the first water pump 13 is driven with a duty ratio of 48 [%] and the second water pump 14 is driven with a duty ratio of 60 [%], the peak frequencies of the vibrations of both are close to each other. The second water pump 14 resonates, and the structural system including both the water pumps 13 and 14 and the cooling pipe 12 connecting them is vibrated greatly. Large vibrations cause noise. Therefore, the cooling controller 20 changes the duty ratio of the second water pump 14 so that the difference between the peak frequencies of the water pumps 13 and 14 is larger than the threshold difference (S5). At this time, the cooling controller 20 changes the duty ratio of the second water pump 14 so as to satisfy the condition that the total flow rate of the water pumps 13 and 14 exceeds the target total flow rate. Specifically, the cooling controller 20 makes the duty ratio of the second water pump 14 larger than the duty ratio determined in step S3. In the example of FIG. 5, the cooling controller 20 changes the duty ratio for the second water pump 14 from 60 [%] to 62.5 [%]. In FIG. 5, the range indicated by the symbol G3 is the peak frequency of each order when the duty ratio is 62.5 [%].

  Next, the cooling controller 20 returns to step S4, and the difference between the peak frequency of each order corresponding to the new duty ratio determined in step S5 and the peak frequency of each order of the first water pump 13 is greater than the threshold difference. Check again if it is larger. If the determination in step S4 is NO, the cooling controller 20 further increases the duty ratio of the second water pump 14 (S5), and checks the step S4 again. If the determination in step S4 is YES, that is, if the difference between the peak frequencies of the orders of the water pumps 13 and 14 is greater than the threshold difference, the cooling controller 20 sets the duty ratio assigned to each water pump. Output (S6). That is, the cooling controller 20 controls the water pumps 13 and 14 based on the duty ratio determined through the processing of steps S3 to S5.

  Note that the seventh peak frequency at a duty ratio of 62.5 [%] is 506 [Hz]. In FIG. 5, the portion indicated by the symbol P <b> 3 indicates the seventh peak frequency at a duty ratio of 62.5 [%]. At this time, the difference from the ninth peak frequency (= 466 [Hz]) in the duty ratio 48 [%] of the first water pump 13 is 40 [Hz], which is larger than the threshold difference (= 20). The difference between the peak frequency of any order at the duty ratio 62.5 [%] of the second water pump 14 and the peak frequency of any order at the duty ratio 48 [%] of the first water pump 13 is the threshold difference (= 20 [Hz]) or more. Therefore, the determination in step S4 is YES. The cooling controller 20 changes the duty ratio of the second water pump 14 to 62.5 [%] in step S5, and then proceeds to the next step S6 through the determination in step S4. In step S6, the cooling controller 20 supplies a command (PWM signal) with a duty ratio of 48% to the first water pump 13, and a duty ratio of 62.5 [%] to the second water pump 14. Command (PWM signal) is supplied. Each of the water pumps 13 and 14 operates according to the command value. At this time, since the peak frequencies of the water pumps 13 and 14 are not close, resonance does not occur (that is, no large vibration occurs). Since the cooling system 11 does not generate large vibrations, noise caused by the vibrations can be suppressed.

  Since the duty ratio for each of the water pumps 13 and 14 corresponds to the number of rotations, that is, the output of each of the water pumps 13 and 14, the processing in steps S3 to S6 can be stated in the following manner. That is, the cooling controller 20 determines the output of each water pump so that the peak frequency of each water pump 13 and 14 does not overlap, and controls each water pump 13 and 14 so that the output may be implement | achieved.

  As described above, the cooling system 11 according to the embodiment determines the outputs (duty ratio corresponding to the number of rotations) of the two water pumps 13 and 14 so that the peak frequencies of vibration do not overlap, and the two water pumps. The pumps 13 and 14 are prevented from causing resonance.

  Points to be noted regarding the technology described in the embodiments will be described. In step S <b> 2 of the flowchart of FIG. 3, the cooling controller 20 determines a target total flow rate that should flow through the cooling pipe 12. The rule for determining the target total flow rate is not limited to the rule of the embodiment. For example, the cooling controller 20 may determine the target total flow rate based on, for example, the output of the motor 8 (or the output of the PCU 5) in addition to the sensor data of the temperature sensors 21 and 23.

  In the cooling system 11 of the embodiment, the cooling targets are the PCU 5 and the motor 8. The cooling target of the cooling system disclosed in this specification is not limited to a PCU or a motor. The cooling system 11 of the example was provided with two pumps (water pumps 13 and 14). The technology disclosed in this specification is also preferably applied to a cooling system including three or more pumps. In the case of a cooling system including a plurality of pumps of three or more, the outputs of at least two pumps are determined so that the peak frequencies do not overlap with respect to at least two of the plurality of pumps. Also good.

  In the cooling system of the example, the unit system of the pump output was the rotation speed of the pump. In the technology disclosed in this specification, the unit system of the output of the pump may be a unit system other than the rotational speed, for example, electric power. Since the pump power also correlates with the rotation speed, the peak frequency of the pump vibration also changes depending on the power. Therefore, the technology disclosed in this specification can be applied to a cooling system in which the output of the pump is expressed in units of electric power.

  The cooling pipe 12 according to the embodiment corresponds to an example of a “circulation path” in the claims.

  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 4: System main relay 5: Power control unit 6: Engine 7: Power distribution mechanism 8: Motor 9: Transmission 10: Differential gear 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 21, 23: Temperature sensor 24, 25: Revolution sensor 30: Power controller 50: HV controller

Claims (1)

A circulation path through which a coolant for cooling the object to be cooled flows;
A plurality of pumps for pumping the refrigerant into the circulation path;
A controller that determines an output for each of the plurality of pumps, and controls each pump so that the determined output is realized;
With
The controller is
For each of the plurality of pumps, the correspondence between the output of the pump and the peak frequency of vibration of the pump when the pump is operated at the output is stored.
A cooling system that determines an output of each pump so that peak frequencies of the plurality of pumps do not overlap.

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