Cooling device for electrically driven vehicle

Abstract

The invention provides a cooling device for an electrically driven vehicle, which suppresses reduction of cooling capability as much as possible and suppresses noise during cooling. When at least one of a first condition in which the compressor rotation speed is set to be less than or equal to a limited compressor rotation speed preset on the basis of the predetermined noise limit value and a second condition in which the fan rotation speed is set to be less than or equal to a limited fan rotation speed preset on the basis of the predetermined noise limit value is not satisfied. The cooling device (1) sets the corrected compressor rotation speed and sets the corrected fan rotation speed on the basis of the corrected compressor rotation speed such that the noise when the compressor (3) and the fan (41) are operating is equal to or less than a predetermined noise limit value. The cooling device (1) sets the corrected fan rotation speed to a lower value as the corrected compressor rotation speed is higher.

Description

Technical Field

[0001] The technology disclosed herein belongs to the technical field related to cooling devices for electric drive vehicles. Background Art

[0002] Conventionally, in cooling devices mounted on vehicles, methods for suppressing noise generated when cooling refrigerant have been studied.

[0003] For example, Patent Document 1 discloses a cooling fan control device, which sets a refrigerant pressure reference fan speed based on the current refrigerant pressure of the air-conditioning device, sets an upper limit protection speed of the fan corresponding to the required outlet temperature, and sets the fan speed to the upper limit protection speed when the vehicle is currently stopped, the current engine speed is the idle speed, and the refrigerant pressure reference fan speed is greater than the upper limit protection speed. In all other cases, the fan speed is set to the refrigerant pressure reference fan speed.

[0004] Prior art literature

[0005] Patent Literature

[0006] Patent Document 1: Japanese Patent Application Laid-Open No. 10-196364

[0007] Technical problem to be solved by the invention

[0008] However, the higher the speed of the booster and the higher the speed of the fan, the louder the noise becomes. The speed of the booster and the speed of the fan are basically set to be higher as the required cooling capacity is higher. Scenarios that require a high cooling capacity from the cooling device include rapid battery charging while the vehicle is parked, high-load driving such as hill climbing and towing, and the like. Therefore, in such scenarios, the noise becomes louder. In particular, when the vehicle is an electric drive vehicle that uses a drive motor as the main drive source, no engine sound is generated, so even when driving, the noise generated from the cooling device may cause annoyance not only to people around the vehicle but also to the occupants of the vehicle.

[0009] In the cooling fan control device described in Patent Document 1, it is expected that noise can be suppressed by reducing the fan speed to the upper limit protection speed, but the cooling capacity is reduced. Therefore, there is room for improvement in achieving both high cooling capacity and noise suppression. Summary of the invention

[0010] The technology disclosed herein has been made in view of this point, and an object of the technology is to suppress a decrease in cooling capacity as much as possible and to suppress noise during cooling.

[0011] Technical means for solving technical problems

[0012] In order to solve the above-mentioned technical problems, a first mode of the technology disclosed herein is a cooling device for an electric drive vehicle that uses a refrigerant to cool an electric drive component mounted on the vehicle, and is the following structure, comprising: a pressurizer that pressurizes the refrigerant; a fan that allows a condenser to draw in external air, and the condenser cools and condenses the refrigerant pressurized by the pressurizer; an electric drive component temperature detection unit that detects the temperature of the electric drive component; a refrigerant pressure detection unit that detects the pressure of the refrigerant compressed by the pressurizer; and a controller that controls the pressurizer and the fan, the controller calculates a required cooling capacity based at least on a detection result of the electric drive component temperature detection unit, the controller calculates a set pressurizer speed, the set pressurizer speed is based on the speed of the pressurizer with the required cooling capacity, the controller calculates a set fan speed, The set fan speed is the speed of the fan based on the detection result of the refrigerant pressure detection unit. When both a first condition that the set compressor speed is below the limited compressor speed pre-set based on a specified noise limit value and a second condition that the set fan speed is below the limited fan speed pre-set based on the specified noise limit value are satisfied, the controller causes the compressor and the fan to operate at the set compressor speed and the set fan speed, respectively. On the other hand, when at least one of the first condition and the second condition is not satisfied, the controller sets a corrected compressor speed and sets a corrected fan speed based on the corrected compressor speed, and causes the compressor and the fan to operate at the corrected compressor speed and the corrected fan speed, respectively, so that the noise of the compressor and the fan during operation is below the specified noise limit value. The higher the corrected compressor speed, the lower the corrected fan speed is set to.

[0013] That is, when the fan speed is set based on the refrigerant pressure, the higher the speed of the booster is, the higher the fan speed is set. Therefore, when a high cooling capacity is required in normal control, the noise is likely to be higher than the noise limit value. Therefore, when the noise is about to be higher than the noise limit value, the fan speed is set based on the speed of the booster instead of the refrigerant pressure. In particular, the higher the speed of the booster is, the lower the fan speed is set.

[0014] The higher the speed of the compressor, the higher the speed of the fan, and the higher the cooling capacity. Therefore, if one of the speed of the compressor and the speed of the fan is increased and the other is decreased, the reduction in cooling capacity can be suppressed. Thus, the combination of the corrected compressor speed and the corrected fan speed can be set to a combination that suppresses the reduction in cooling capacity as much as possible within a range where the noise is below the noise limit value. As a result, the reduction in cooling capacity is suppressed as much as possible and the noise during cooling is suppressed.

[0015] A second aspect of the technology disclosed herein is, in the first aspect, further comprising an outside air temperature detection unit that detects the outside air temperature, and the controller sets the corrected pressurizer rotation speed and the corrected fan rotation speed in consideration of the outside air temperature.

[0016] According to this configuration, the outside air temperature is equivalent to the temperature of the air taken in by the fan, so by considering the outside air temperature, the corrected fan speed can be set more appropriately to minimize the reduction in cooling capacity. This can more effectively suppress the reduction in cooling capacity and reduce noise during cooling.

[0017] A third aspect of the technology disclosed herein is that, in the first or second aspect, the controller sets the corrected pressurizer rotation speed and the corrected fan rotation speed so that the generated noise reaches the noise limit value.

[0018] According to this configuration, the corrected compressor rotation speed and the corrected fan rotation speed can be set to values ​​as high as possible, thereby more effectively suppressing a decrease in cooling capacity and suppressing noise during cooling.

[0019] In a fourth mode of the technology disclosed herein, in the above-mentioned third mode, the controller calculates the cooling capacity for a plurality of combinations of the rotational speed of the compressor and the rotational speed of the fan, respectively, in which the noise generated is the noise limit value, and sets the combination among the plurality of combinations whose cooling capacity is closest to the required cooling capacity as the corrected compressor rotational speed and the corrected fan rotational speed, respectively.

[0020] According to this configuration, it is possible to set an appropriate corrected compressor rotation speed and a corrected fan rotation speed within a range that can suppress noise, thereby more effectively suppressing a decrease in cooling capacity and suppressing noise during cooling.

[0021] Furthermore, by selecting a combination of the rotation speed of the compressor and the rotation speed of the fan that has the cooling capacity closest to the required cooling capacity, it is possible to suppress the excessive cooling capacity. Thus, the power consumption can be suppressed as much as possible.

[0022] According to a fifth mode of the technology disclosed herein, in the fourth mode, when there are multiple combinations whose cooling capacity is closest to the required cooling capacity, the controller sets the combination with the lowest speed of the compressor among these combinations as the corrected compressor speed and the corrected fan speed, respectively.

[0023] According to this configuration, the rotation speed of the compressor can be reduced as much as possible. Since the amount of refrigerant to be cooled is smaller when the rotation speed of the compressor is lower, the refrigerant can be cooled efficiently. Therefore, the cooling efficiency can be improved.

[0024] The sixth mode of the technology disclosed herein is that in the above-mentioned third mode, the controller calculates a first compressor speed candidate and a first fan speed candidate based on the first compressor speed candidate, the speed of the first compressor speed candidate is higher than the limiting compressor speed by a constant number, the controller calculates a second compressor speed candidate and a second fan speed candidate based on the second compressor speed candidate, the speed of the second compressor speed candidate is lower than the limiting compressor speed by a constant number, the controller respectively calculates the cooling capacity for the combination of the limiting compressor speed and the limiting fan speed, the combination of the first compressor speed candidate and the first fan speed candidate, and the combination of the second compressor speed candidate and the second fan speed candidate, and sets the combinations whose cooling capacities are closest to the required cooling capacity among these combinations as the corrected compressor speed and the corrected fan speed, respectively.

[0025] According to this configuration, the amount of calculation of the controller can be reduced as much as possible. As a result, it is possible to more effectively suppress a decrease in cooling capacity and noise during cooling, thereby suppressing power consumption as much as possible.

[0026] Effects of the Invention

[0027] As described above, according to the technology disclosed herein, in a cooling device for an electrically driven vehicle, it is possible to suppress a decrease in cooling capacity as much as possible and suppress noise during cooling. BRIEF DESCRIPTION OF THE DRAWINGS

[0028] Figure 1 This is a structural diagram of a vehicle according to the first embodiment.

[0029] Figure 2 It is a structural diagram of the cooling device.

[0030] Figure 3 This is a block diagram showing a control system of a cooling device.

[0031] Figure 4 This is a map showing the relationship between the rotation speed of the compressor and the rotation speed of the fan and the cooling capacity, and indicates when the outside air temperature is relatively low.

[0032] Figure 5 This is a map showing the relationship between the rotation speed of the compressor and the rotation speed of the fan and the cooling capacity, and indicates when the outside air temperature is relatively high.

[0033] Figure 6 This is a graph showing the relationship between the noise limit value and the cooling capacity. The upper graph shows the noise limit line in the cooling capacity map, and the lower graph shows the relationship between the operating point on the noise limit line and the cooling capacity.

[0034] Figure 7 This is a flowchart showing the processing operation of the cooling system ECM.

[0035] Figure 8 This is a diagram schematically showing a calculation method of a correction compressor rotation speed and a correction fan rotation speed in the cooling device according to the second embodiment.

[0036] Fig. 9 This is a part of a flowchart showing the processing operation of the cooling system ECM of the cooling device according to the second embodiment.

[0037] Fig.10 This is the remaining part of the flowchart showing the processing operation of the cooling system ECM of the cooling device according to the second embodiment.

[0038] Explanation of symbols

[0039] 1Cooling device

[0040] 2Heat exchanger

[0041] 3Compressor (booster)

[0042] 4 Condenser

[0043] 41 Fan

[0044] 70 battery assembly (electric drive component)

[0045] 80 Cooling system ECM (controller)

[0046] 100 vehicles

[0047] 102 drive motor (electric drive component)

[0048] 103 Inverter (electric drive component)

[0049] 104 Converter (electric drive component)

[0050] SW1 Battery temperature sensor (electric drive component temperature detection unit)

[0051] SW3 Second refrigerant pressure sensor (refrigerant pressure detection unit)

[0052] SW4 outside air temperature sensor (outside air temperature detection unit)

[0053] SW5 motor water temperature sensor (electric drive component temperature detection unit). DETAILED DESCRIPTION

[0054] Hereinafter, exemplary embodiments will be described in detail with reference to the accompanying drawings.

[0055] (Implementation Method 1)

[0056] 〈Overall structure of vehicle〉

[0057] Figure 1 A vehicle 100 is shown that includes the cooling device 1 according to Embodiment 1. The vehicle 100 is an electrically driven vehicle that can travel mainly using a drive motor 102 that rotates using electric power. The vehicle 100 is, for example, an electric vehicle or a hybrid vehicle.

[0058] The vehicle 100 has a drive motor 102. The rotation of the drive motor 102 is transmitted to the two front wheels of the four wheels 101 via the shaft. Thus, the vehicle 100 moves (runs). The drive motor 102 is an electric generator, and operates as a generator when the vehicle 100 decelerates (when recovering energy).

[0059] The drive motor 102 is connected to the battery assembly 70 via an inverter 103 and a converter 104 .

[0060] A plurality of rectangular box-shaped battery cells (not shown) are stacked to form a battery assembly 70. The battery assembly 70 is disposed under the floor of the vehicle 100. The battery cells are formed of, for example, lithium-ion batteries or nickel-metal hydride batteries.

[0061] The inverter 103 performs conversion between direct current and alternating current. When the vehicle 100 is running, the inverter 103 converts the direct current supplied via the converter 104 into three-phase alternating current with different phases and supplies it to the drive motor 102. When the vehicle 100 recovers energy, the inverter 103 converts the alternating current generated by the drive motor 102 into direct current and supplies it to the converter 104.

[0062] When the vehicle 100 is running, the converter 104 steps down the DC power output from the battery pack 70 to the driving voltage of the driving motor 102 and supplies it to the inverter 103. When the vehicle 100 is recovering energy, the converter 104 steps up the DC power from the inverter 103 and charges the battery pack 70.

[0063] The drive motor 102 , the inverter 103 , the converter 104 , and the battery assembly 70 are examples of electric drive components mounted on the vehicle 100 .

[0064] 〈Overall structure of cooling device〉

[0065] Figure 2 1 shows a cooling device 1 mounted on a vehicle 100. The cooling device 1 can cool an electric drive component. The cooling device 1 can, for example, directly cool the battery assembly 70 by utilizing an endothermic reaction when a liquid refrigerant changes phase into a gas. The cooling device 1 can indirectly cool the drive motor 102 by utilizing a refrigerant via a cooling water cooling mechanism 21 described later. The refrigerant is, for example, an HFO (hydrofluoroolefin) refrigerant, specifically R1234yf.

[0066] The cooling device 1 includes: a battery heat exchanger 2 for exchanging heat between the refrigerant and the battery assembly 70, a compressor 3 for pressurizing the refrigerant flowing out of the battery heat exchanger 2, and a condenser 4 for cooling and condensing the refrigerant pressurized by the compressor 3. The cooling device 1 includes a cooling water cooling mechanism 21 for cooling the cooling water for cooling the drive motor 102, and an air conditioning device 22 used for air conditioning in the vehicle interior. The cooling device 1 includes: a main inflow path 11, which is a refrigerant path from the condenser 4 to the battery heat exchanger 2; a first branch inflow path 11a, which branches from the main inflow path 11 to the cooling water cooling mechanism 21; and a second branch inflow path 11b, which branches from the main inflow path 11 to the air conditioning device 22. The cooling device 1 has a main outflow path 12, which is a refrigerant path from the battery heat exchanger 2 to the compressor 3; a first branch outflow path 12a, which is a first branch outflow path 12a from the cooling water cooling mechanism 21 to the main outflow path 12; and a second branch outflow path 12b, which is a second branch outflow path 12b from the air conditioning device 22 to the main outflow path 12. In addition, the cooling device 1 has an expansion valve 5, which is provided in the main inflow path 11 and reduces the pressure of the refrigerant condensed by the condenser 4.

[0067] The compressor 3 pressurizes the refrigerant after heat exchange with the battery assembly 70. The compressor 3 is, for example, a scroll compressor, and can adjust the pressure of the refrigerant flowing out by adjusting the rotation speed. Specifically, the higher the compressor rotation speed, the higher the pressure of the refrigerant flowing out of the compressor 3. In other words, the higher the compressor rotation speed, the more the amount of refrigerant flowing out of the compressor 3. When the refrigerant is pressurized by the compressor 3, the temperature of the refrigerant rises due to adiabatic compression.

[0068] The condenser 4 is disposed at the front side of the vehicle 100. A fan 41 is provided at the vehicle rear side of the condenser 4. The condenser 4 cools the refrigerant using the running wind or a combination of the running wind and the air sucked in by the rotation of the fan 41 when the vehicle 100 is running. On the other hand, when the vehicle 100 is stopped, the refrigerant is cooled using the air sucked in by the rotation of the fan 41. In the condenser 4, the refrigerant is condensed and liquefied by reducing the temperature without reducing the pressure.

[0069] In the first embodiment, the fan 41 is an electric fan. The fan 41 has a small electric motor (not shown) and rotates by the rotation of the electric motor. The higher the speed of the fan 41, the more air is sucked in. Specifically, the air volume of the fan 41 is proportional to the speed of the fan.

[0070] A receiving tank 42 is provided on the downstream side of the condenser 4. The receiving tank 42 temporarily stores the refrigerant liquefied by the condenser 4. The receiving tank 42 is connected to the main inlet path 11. When the refrigerant liquefied by the condenser 4 flows into the receiving tank 42, an amount of refrigerant corresponding to the amount of the inflowing refrigerant flows out from the receiving tank 42 to the main inlet path 11.

[0071] The expansion valve 5 reduces the pressure of the refrigerant in the main inflow path 11 and causes the refrigerant to flow into the battery heat exchanger 2. The refrigerant that has passed through the expansion valve 5 is adiabatically expanded and its temperature is reduced. In addition, by reducing the pressure using the expansion valve 5, the saturation temperature (equivalent to the boiling point) is reduced. In addition, by reducing the pressure using the expansion valve 5, the flow of the refrigerant in the heat exchanger 2 is slowed down, so that the refrigerant in the heat exchanger 2 and the battery assembly 70 are thoroughly heat exchanged.

[0072] The expansion valve 5 is also used to adjust the flow rate of the refrigerant flowing into the battery heat exchanger 2. Specifically, the larger the opening of the expansion valve 5, the larger the flow rate of the refrigerant flowing into the battery heat exchanger 2, and on the other hand, the smaller the opening of the expansion valve 5, the smaller the flow rate of the refrigerant flowing into the battery heat exchanger 2.

[0073] The cooling water cooling mechanism 21 includes an expansion valve and a heat exchanger. The expansion valve is provided in the first branch inflow path 11 a.

[0074] The air conditioner 22 includes an expansion valve, a heat exchanger, and a fan. The expansion valve is provided in the second branch inflow path 11b. The rotation speed of the fan is set based on the target temperature in the vehicle interior.

[0075] 〈Control system for cooling device〉

[0076] Next, the control system of cooling device 1 will be described.

[0077] like Figure 3 As shown, the vehicle 100 has a cooling system ECM (Electric Control Module) 80. The cooling system ECM 80 is a controller that mainly controls the cooling device 1. The cooling system ECM 80 includes: one or more processors 80a having a CPU; and a memory 80b having a ROM and a RAM and storing various programs. The memory 80b is, for example, a non-volatile memory. Programs related to the control performed by the cooling system ECM 80 are respectively stored in the memory 80b. The cooling system ECM 80 performs control by the processor 80a reading the program stored in the memory 80b.

[0078] The cooling system ECM 80 receives input signals from a battery temperature sensor SW1 for detecting the temperature of the battery cell, a first refrigerant pressure sensor SW2 for detecting the pressure of the refrigerant flowing into the compressor 3, a second refrigerant pressure sensor SW3 for detecting the pressure of the refrigerant before being pressurized by the compressor 3 and flowing into the condenser 4, an outside air temperature sensor SW4 for detecting the outside air temperature, a motor water temperature sensor SW5 for detecting the water temperature of the cooling water of the drive motor 102, a vehicle interior temperature sensor SW6 for detecting the temperature of the vehicle interior, and an air conditioning control panel SW7 for controlling the air conditioning in the vehicle interior. In addition, the cooling system ECM receives input signals from a PCM (Powertrain Control Module) 81, which is a controller for controlling the overall power system of the vehicle 100, and a BECM (Battery Energy Control Module) 82, which is a controller for controlling the charge and discharge of the battery assembly 70. The PCM 81 receives input signals from a vehicle speed sensor SW8. Although not shown in the figure, the PCM 81 and the BECM 82 each have a processor and a memory.

[0079] The battery temperature sensor SW1 is, for example, arranged near the outlet of the refrigerant in the battery assembly 70. The first refrigerant pressure sensor SW2 is arranged at a position upstream of the compressor 3 in the main outflow path 12. The second refrigerant pressure sensor SW3 is arranged downstream of the compressor 3 and upstream of the condenser 4. The outside air temperature sensor SW4 is arranged on the vehicle front side of the condenser 4. The outside air temperature detected by the outside air temperature sensor SW4 is equivalent to the temperature of the air sucked by the fan 41. The motor water temperature sensor SW5 faces the cooling water passage of the drive motor 102. The water temperature detected by the motor water temperature sensor SW5 is regarded as the temperature of the drive motor 102. The air conditioning control panel SW7 is a panel operated by the occupants of the vehicle 100, and is provided with a switch for controlling the on and off of the air conditioning, a switch for setting the air volume, a switch for setting the target temperature in the vehicle interior, etc. In addition, a plurality of battery temperature sensors SW1 can be provided, for example, in addition to being arranged near the outlet of the refrigerant in the battery assembly 70, it can also be arranged in the center of the battery assembly 70 when viewed from above. The battery temperature sensor SW1 and the motor water temperature sensor SW5 are examples of a temperature detection unit for an electric drive component.

[0080] The cooling system ECM80 controls the fan 41, the compressor 3, the expansion valve 5, the cooling water cooling mechanism 21, and the air conditioning device 22 based on the signals from the sensors SW1 to SW7, the signals from the PCM81, and the signals from the BECM82. Specifically, the cooling system ECM80 obtains information about the vehicle speed from the PCM81, obtains information about the target temperature of the cooling object (drive motor 102, battery assembly 70) from the BECM82, and obtains information about the target temperature in the vehicle cabin from the air conditioning control panel SW7. The cooling system ECM80 compares the detection results of the battery temperature sensor SW1, the motor water temperature sensor SW5, and the vehicle cabin temperature sensor SW6 with the target temperatures, and calculates the required cooling capacity Qr of the cooling device 1. The cooling system ECM80 sets the compressor speed based on the required cooling capacity Qr. The cooling system ECM80 calculates the air volume to be supplied to the condenser 4 based on the detection result of the second refrigerant pressure sensor SW3, and sets the fan speed based on the air volume. Then, the cooling system ECM 80 rotates the compressor 3 and the fan 41 at the respective set rotation speeds, and adjusts the respective openings of the expansion valve 5, the expansion valve of the coolant cooling mechanism 21, and the expansion valve of the air conditioning device 22 so that the necessary flow of refrigerant flows in. In addition, the rotation speed of the fan of the air conditioning device 22 is adjusted according to the target temperature in the vehicle interior. In addition, the cooling capacity is, for example, the amount of heat that the refrigerant can absorb per unit time.

[0081] In addition, the cooling system ECM80 calculates the air volume of the running wind based on the information about the vehicle speed obtained from the PCM81. The cooling system ECM80 considers the air volume of the running wind when setting the fan speed. Specifically, the cooling system ECM80 subtracts the air volume obtained by the running wind from the amount to be supplied to the condenser 4, and sets the fan speed so that the remaining air volume is obtained by the fan 41. When the air volume to be supplied to the condenser 4 is all obtained by the running wind, the cooling system ECM80 may set the fan speed to 0 so that the fan 41 does not rotate.

[0082] 〈Cooling capacity map〉

[0083] Next, the cooling capacity of the cooling device 1 will be described.

[0084] As described above, condenser 4 cools the refrigerant using at least one of the traveling wind and the air sucked by fan 41. That is, condenser 4 cools the refrigerant using the outside air. Therefore, the cooling capacity of cooling device 1 depends on the outside air temperature.

[0085] Figure 4 and Figure 5 A cooling capacity map of the cooling device 1 is shown. Figure 4 is a low temperature cooling capacity map 300 when the outside air temperature is relatively low, Figure 5This is a high temperature cooling capacity map 400 when the outside air temperature is relatively high. The low temperature cooling capacity map 300 and the high temperature cooling capacity map 400 are stored in the memory 80b, respectively. Here, only two cooling capacity maps are illustrated, but in fact, for each outside air temperature, three or more cooling capacity maps are stored in the memory 80b.

[0086] In the low-temperature cooling capacity map 300 and the high-temperature cooling capacity map 400, the horizontal axis is the compressor speed and the vertical axis is the fan speed. Regions Z1 to Z8 are regions with similar cooling capacities, respectively. Region Z1 has the lowest cooling capacity, and region Z8 has the highest cooling capacity. The closer regions Z2 to Z7 are to region Z8, the higher the cooling capacity. The boundary line between each region Z1 to Z8 is a line of equal cooling capacity. Basically, the higher the compressor speed and the higher the fan speed, the greater the cooling capacity. Therefore, in each region Z1 to Z8, the farther away from the boundary line on the lower side is to the upper right, the higher the cooling capacity.

[0087] Comparing the low-temperature cooling capacity map 300 with the high-temperature cooling capacity map 400, it can be seen that the area Z8 of the low-temperature cooling capacity map 300 is greatly expanded compared to the high-temperature cooling capacity map 400. This means that the cooling efficiency is high on the side where the outside air temperature is low. That is, the compressor 3 is restricted due to abnormal operation such as blockage and restrictions related to noise described later. The large expansion of the area with high cooling capacity can be said to mean that a high cooling capacity can be exerted even at a restricted rotation speed, and the cooling efficiency can be improved.

[0088] 〈Noise suppression control〉

[0089] Here, when the cooling device 1 is operated, noise is generated. The noise is mainly generated by the operation of the compressor 3 and the fan 41. The higher the compressor speed and the fan speed, the louder the noise. As described above, the higher the speed of each of the compressor 3 and the fan 41, the greater the cooling capacity of the cooling device 1. Therefore, if a high cooling capacity is to be exerted, the noise becomes louder. That is, the cooling capacity and the noise are in a trade-off relationship.

[0090] As scenes requiring high cooling capacity for the cooling device 1, there are scenes of rapidly charging the battery assembly 70 while the vehicle 100 is parked, scenes of high-load driving such as hill climbing and towing, etc. Therefore, in such scenes, the noise becomes louder. In particular, as in the first embodiment, when the vehicle 100 is an electric drive vehicle capable of driving with the drive motor 102 as the main drive source, no engine sound is generated, so even during driving, the noise generated from the cooling device 1 may cause annoyance not only to people around the vehicle 100, but also to the occupants of the vehicle 100.

[0091] In this regard, conventionally, a limited compressor speed NCL and a limited fan speed NFL are set in advance based on a prescribed noise limit value, and when at least one of the set compressor speed and the set fan speed, which are the compressor speed and the fan speed set based on the required cooling capacity, is greater than the limited compressor speed NCL and the limited fan speed NFL, the compressor 3 and the fan 41 are operated at the limited compressor speed NCL and the limited fan speed NFL. Figure 6 As shown in the above figure, the combination of the set compressor speed and the set fan speed (hereinafter referred to as the required operating point P0) is located at the upper right position than the combination of the limited compressor speed NCL and the limited fan speed NFL (hereinafter referred to as the limited operating point PL). In the conventional control, the required operating point P0 is corrected to the limited operating point PL, so that the compressor 3 and the fan 41 are operated at the limited compressor speed NCL and the limited fan speed NFL.

[0092] However, if Figure 6 As shown in the figure above, in the previous control, the working point moves from area Z7 to area Z6, and the cooling capacity decreases. If the cooling capacity decreases, the charging efficiency of the battery assembly 70 deteriorates, the deterioration of the drive motor 102 is promoted, and the cooling efficiency of the air conditioner in the vehicle interior deteriorates.

[0093] Therefore, in the present first embodiment, a noise level indicating the magnitude of noise is calculated to be below the noise level of the limit operating point PL (i.e., the noise limit value) and an operating point at which the reduction in cooling capacity can be suppressed. Specifically, when at least one of the first condition of setting the compressor speed to be below the limit compressor speed NCL and the second condition of setting the fan speed to be below the limit fan speed NFL is not satisfied, the cooling system ECM 80 performs noise suppression control of setting a modified compressor speed and setting a modified fan speed based on the modified compressor speed so that the noise level is below the above-mentioned noise limit value. In particular, in the noise suppression control, the higher the modified compressor speed is, the lower the modified fan speed becomes.

[0094] As described above, the fan speed is basically set based on the detection result of the second refrigerant pressure sensor SW3. The higher the compressor speed, the higher the detection result (refrigerant pressure). Therefore, the fan speed is basically set to be higher as the compressor speed increases. That is, in normal control, such as Figure 6 As shown by the dotted line in the upper figure of FIG. , the combination of the compressor speed and the fan speed is set in the range from the lower left to the upper right of the cooling capacity map. Figure 4 , Figure 5 and Figure 6As shown in the figure above, there are actually combinations with the same cooling capacity that are outside the normal control range. Therefore, if the fan speed is set to be independent of the refrigerant pressure, it is possible to set an operating point that maintains a high cooling capacity and suppresses the noise level.

[0095] In the first embodiment, in particular, for a combination of the compressor speed and the fan speed (hereinafter referred to as a candidate operating point) at which the noise level is the above-mentioned noise limit value, the cooling system ECM 80 respectively obtains the cooling capacity when the compressor 3 and the fan 41 are operated at each candidate operating point, selects the candidate operating point whose cooling capacity is closest to the required cooling capacity among the candidate operating points as the correction operating point, and sets the compressor speed and the fan speed of the selected correction operating point as the correction compressor speed and the correction fan speed, respectively. If the correction operating point is selected in such a way that the noise level becomes the above-mentioned noise limit value, the compressor speed and the fan speed can be set as high as possible. Therefore, it is easy to maintain a high cooling capacity. In addition, the cooling capacity of the candidate operating point and each candidate operating point can be calculated by the cooling system ECM 80, or can be pre-stored in the memory 80b in the form of a mapping map 500 described later according to each cooling capacity map, and the cooling system ECM 80 reads an appropriate mapping map based on the outside air temperature to calculate. Furthermore, “the cooling capacity is closest to the required cooling capacity” includes the case where the cooling capacity is the same as the required cooling capacity. When there is a candidate operating point with the same cooling capacity as the required cooling capacity, the candidate operating point is the candidate operating point with the cooling capacity closest to the required cooling capacity.

[0096] The higher the compressor speed and the higher the fan speed, the greater the noise level. Figure 6 As shown in the figure above, the operating point where the noise level is the above noise limit value is located on a straight line (hereinafter referred to as the noise limit line SL) that descends to the right, where the higher the compressor speed, the lower the fan speed. The noise limit line SL is not based on the refrigerant pressure, but is based on the compressor speed to set the fan speed so that the noise level becomes the above noise limit value. Figure 6 In the above figure, the upper left part and the lower right part of the noise limit line SL are interrupted, which is mainly caused by the working limit of the compressor 3. The upper limit value of the compressor speed is set based on the upper limit pressure of the compressor 3, and the lower limit value of the compressor speed is set based on the speed at which abnormal operations such as blockage do not occur. In addition, the noise limit line SL is set based on the above noise limit value. For example, if the noise limit value is 20 decibels, the noise limit line with a noise level of 20 decibels is set. The noise limit value can be set arbitrarily.

[0097] Figure 6The figure below is a map 500 showing the cooling capacity in the noise limit line SL. In the map 500, the horizontal axis represents the position of the operating point, and the vertical axis represents the cooling capacity. The left side of the horizontal axis is the operating point where the compressor speed is low and the fan speed is high, and the right side is the operating point where the compressor speed is high and the fan speed is low. The limit operating point PL, the candidate operating point P1, and the candidate operating point P2 are respectively Figure 6 Corresponding to PL, P1 and P2 in the above figure.

[0098] As shown in the map 500, on the noise limit line SL, at the candidate operating point P1, the cooling capacity and the required cooling capacity ( Figure 6 In addition, on the noise limit line SL, the cooling capacity at the candidate operating point P2 is the maximum cooling capacity ( Figure 6 Qm in the figure below). When there is a candidate operating point with the same cooling capacity as the required cooling capacity, the cooling system ECM80 sets the candidate operating point as the corrected operating point. Here, the cooling system ECM80 sets the candidate operating point P1 as the corrected operating point, and sets the compressor speed and fan speed of the candidate operating point P1 to the corrected compressor speed and the corrected fan speed, respectively. This is because, although the cooling capacity candidate operating point P2 is higher, if an operating point with a cooling capacity higher than the required cooling capacity is selected, the cooling efficiency may be deteriorated.

[0099] When the required cooling capacity is greater than the maximum cooling capacity and there is no candidate operating point with the same cooling capacity as the required cooling capacity, the cooling system ECM 80 sets the candidate operating point with the cooling capacity closest to the required cooling capacity, that is, the candidate operating point with the maximum cooling capacity (here, the candidate operating point P2) as the correction operating point. In addition, when there are multiple correction operating points with the cooling capacity equal to the required cooling capacity, the cooling system ECM 80 selects the candidate operating point with a lower compressor speed as the correction operating point. This is because, from the perspective of cooling efficiency, the lower the compressor speed and the higher the fan speed, the higher the cooling efficiency.

[0100] Figure 7 1 is a flowchart showing the processing operation of the cooling system ECM 80 when the noise suppression control is executed. This flowchart is executed at every predetermined cycle.

[0101] First, in step S101 , the cooling system ECM 80 receives and reads signals from various sensors SW1 to SW7 , the PCM 81 , and the BECM 82 .

[0102] Next, in step S102 , the cooling system ECM 80 calculates a required cooling capacity.

[0103] Next, in step S103, the cooling system ECM 80 calculates the set compressor speed NC based on the required cooling capacity. Next, in step S104, the cooling system ECM 80 calculates the set fan speed NF based on the detection result of the second refrigerant pressure sensor SW3.

[0104] Next, in step S105, the cooling system ECM80 determines whether the vehicle speed is less than the prescribed speed. When the vehicle speed is high, the road noise is large, so even if noise of a magnitude exceeding the noise limit value is generated from the cooling device 1, it is difficult for the occupants of the vehicle 100 to feel annoyed. Therefore, the cooling system ECM80 does not perform noise suppression control when the vehicle speed is high. When the vehicle speed is less than the prescribed speed, that is, "Yes", the cooling system ECM80 proceeds to step S106. On the other hand, when the vehicle speed is greater than the prescribed speed, that is, "No", the cooling system ECM80 proceeds to step S111. In addition, the prescribed vehicle speed is a speed at which road noise of a magnitude exceeding the noise limit value is generated, and can be set to 20 km / h, for example.

[0105] Next, in step S106, the cooling system ECM80 determines whether the set compressor speed NC is greater than the limit compressor speed NCL. When the set compressor speed NC is greater than the limit compressor speed NCL, that is, "Yes", the cooling system ECM80 proceeds to step S108. On the other hand, when the set compressor speed NC is less than the limit compressor speed NCL, that is, "No", the cooling system ECM80 proceeds to step S107.

[0106] In the above step S107, the cooling system ECM80 determines whether the set fan speed NF is greater than the limit fan speed NFL. If the set fan speed NF is greater than the limit fan speed NFL, that is, "Yes", the cooling system ECM80 proceeds to step S108. On the other hand, if the set fan speed NF is less than the limit fan speed NFL, that is, "No", the cooling system ECM80 proceeds to step S111.

[0107] In the above-mentioned step S108, the cooling system ECM 80 obtains the cooling capacity at each candidate operating point on the noise limit line SL.

[0108] Next, in step S109, the cooling system ECM 80 sets the candidate operating point whose cooling capacity is closest to the required cooling capacity as the corrected operating point, and sets the compressor speed and the fan speed of the corrected operating point as the corrected compressor speed and the corrected fan speed. When there is a candidate operating point whose cooling capacity is the same as the required cooling capacity, the cooling system ECM 80 sets the candidate operating point as the corrected operating point. In addition, when there are multiple candidate operating points whose cooling capacity is closest to the required cooling capacity, the cooling system ECM 80 sets the candidate operating point with the lowest compressor speed as the corrected operating point.

[0109] Next, in step S110, the cooling system ECM 80 operates the cooling device 1 at the corrected compressor speed and the corrected fan speed. The process returns after step S110.

[0110] On the other hand, in the above-mentioned step S111, the cooling system ECM 80 operates the cooling device 1 at the set compressor speed and the set fan speed.

[0111] <Effects of Implementation Method 1>

[0112] Therefore, in the present embodiment 1, there are: a compressor 3, which pressurizes the refrigerant; a fan 41, which is used to allow the condenser 4 to suck in external air, and the condenser 4 cools the refrigerant pressurized by the compressor 3 and condenses it; a battery temperature sensor SW1, which detects the temperature of the battery assembly 70; a motor water temperature sensor SW5, which detects the temperature of the drive motor 102; a second refrigerant pressure sensor SW3, which detects the pressure of the refrigerant compressed by the compressor 3; and a cooling system ECM80, which controls the compressor 3 and the fan 41, and the cooling system ECM80 calculates the required cooling capacity, calculates the set compressor speed, and calculates the set fan speed based on at least the detection results of the battery temperature sensor SW1 and the motor water temperature sensor SW5. The set compressor speed is based on The set fan speed is the speed of the fan 41 based on the detection result of the second refrigerant pressure sensor SW3. When both the first condition that the set compressor speed is less than the limited compressor speed NCL pre-set based on the prescribed noise limit value and the second condition that the set fan speed is less than the limited fan speed NFL pre-set based on the prescribed noise limit value are satisfied, the compressor 3 and the fan 41 are operated at the set compressor speed and the set fan speed, respectively. On the other hand, when at least one of the first condition and the second condition is not satisfied, a modified compressor speed is set and a modified fan speed is set based on the modified compressor speed so that the noise of the compressor 3 and the fan 41 when operating is less than the prescribed noise limit value, and the compressor 3 and the fan 41 are operated at the modified compressor speed and the modified fan speed, respectively. The higher the modified compressor speed, the lower the modified fan speed. In this way, the fan speed is set in such a way that the higher the compressor speed, the lower the fan speed, not based on the refrigerant pressure, based on the compressor speed, thereby suppressing the reduction in cooling capacity as much as possible and suppressing the noise during cooling.

[0113] In addition, in the first embodiment, an outside air temperature sensor SW4 for detecting the outside air temperature is further provided, and the cooling system ECM 80 sets the corrected compressor speed and the corrected fan speed in consideration of the outside air temperature. Thus, the temperature of the air sucked by the fan can be considered, and therefore, the corrected fan speed can be set more appropriately to suppress the reduction in cooling capacity as much as possible. Thus, the reduction in cooling capacity can be suppressed more effectively.

[0114] In addition, in the first embodiment, the cooling system ECM 80 sets the modified compressor speed and the modified fan speed so that the generated noise is at the noise limit value. Thus, the modified compressor speed and the modified fan speed can be set to the highest possible value. Therefore, the reduction in cooling capacity can be more effectively suppressed.

[0115] In addition, in the first embodiment, the cooling system ECM 80 obtains the cooling capacity for each of the plurality of combinations of compressor speed and fan speed that generate noise at the noise limit value, and sets the combination whose cooling capacity is closest to the required cooling capacity as the corrected compressor speed and the corrected fan speed. Thus, it is possible to set appropriate corrected compressor speed and corrected fan speed within the range that can suppress noise. Thus, it is possible to more effectively suppress the reduction in cooling capacity and suppress noise during cooling.

[0116] In addition, in the first embodiment, when there are multiple combinations whose cooling capacity is the same as or closest to the required cooling capacity, the cooling system ECM 80 sets the combination with the lowest compressor speed as the corrected compressor speed and the corrected fan speed. In this way, the compressor speed can be reduced as much as possible. Since the amount of refrigerant to be cooled is small on the side with the lower compressor speed, the refrigerant can be cooled effectively. Therefore, the cooling efficiency can be improved.

[0117] (Implementation Method 2)

[0118] Hereinafter, Embodiment 2 will be described in detail with reference to the drawings. In the following description, the same reference numerals are given to the parts common to Embodiment 1, and detailed description thereof will be omitted.

[0119] Figure 8The calculation method of the correction operating point in the cooling device according to the second embodiment is schematically shown. In the second embodiment, when at least one of the first condition of setting the compressor speed to be lower than the limit compressor speed NCL and the second condition of setting the fan speed to be lower than the limit fan speed NFL is not satisfied, the cooling system ECM 80 calculates a first compressor speed candidate whose speed is higher than the limit compressor speed NCL by a constant number, a first fan speed candidate based on the first compressor speed candidate, a second compressor speed candidate whose speed is lower than the limit compressor speed NCL by a constant number, and a second fan speed candidate based on the second compressor speed candidate. Next, the cooling system ECM 80 calculates the cooling capacity when the compressor 3 and the fan 41 are operated at each operating point for the limit operating point PL which is a combination of the limit compressor speed NCL and the limit fan speed NFL, the first candidate operating point P4 which is a combination of the first compressor speed candidate and the first fan speed candidate, and the second candidate operating point P5 which is a combination of the second compressor speed candidate and the second fan speed candidate. Then, the cooling system ECM 80 selects the operating point whose cooling capacity is closest to the required cooling capacity among the operating points as the corrected operating point, and sets the compressor speed and fan speed of the corrected operating point as the corrected compressor speed and the corrected fan speed, respectively. That is, the limit operating point PL is also one of the candidate operating points.

[0120] like Figure 8 As shown, in the present second embodiment, the cooling system ECM80 calculates the first candidate operating point P4 and the second candidate operating point P5 from the noise limit line SL. That is, the first fan speed candidate is lower than the limit fan speed NFL, and the second fan speed candidate is higher than the limit fan speed NFL. In addition, the absolute value of the difference between the first compressor speed candidate and the limit compressor speed NCL and the absolute value of the difference between the second compressor speed candidate and the limit compressor speed NCL are the same as the above-mentioned constant number, so the absolute value of the difference between the first fan speed candidate and the limit fan speed NFL and the absolute value of the difference between the second fan speed candidate and the limit fan speed NFL are the same. In addition, the above-mentioned constant number is preset.

[0121] In this Figure 8 In the example shown, the cooling capacity of the first candidate operating point P4 is closest to the required cooling capacity, so the first candidate operating point P4 is selected as the correction operating point. In addition, when there are two candidate operating points whose cooling capacity is closest to the required cooling capacity, and the cooling capacity of one candidate operating point is lower than the required cooling capacity, and the cooling capacity of the other candidate operating point is higher than the required cooling capacity, the cooling system ECM 80 selects the candidate operating point whose cooling capacity is higher than the required cooling capacity as the correction operating point.

[0122] Fig. 9 and Fig.10 This is a flowchart showing the processing operation of the cooling system ECM 80 when executing the noise suppression control according to the present Embodiment 2. This flowchart is executed at every predetermined cycle.

[0123] First, in step S201 , the cooling system ECM 80 receives and reads signals from various sensors SW1 to SW7 , the PCM 81 , and the BECM 82 .

[0124] Next, in step S202 , the cooling system ECM 80 calculates a required cooling capacity.

[0125] Next, in step S203 , the cooling system ECM 80 calculates the set compressor speed NC based on the required cooling capacity.

[0126] Next, in step S204 , the cooling system ECM 80 calculates the set fan speed NF based on the detection result of the second refrigerant pressure sensor SW3 .

[0127] Next, in step S205, the cooling system ECM 80 determines whether the vehicle speed is less than a predetermined speed. If the vehicle speed is less than the predetermined speed, the cooling system ECM 80 proceeds to step S206. On the other hand, if the vehicle speed is greater than the predetermined speed, the cooling system ECM 80 proceeds to step S215.

[0128] Next, in step S206, the cooling system ECM80 determines whether the set compressor speed NC is greater than the limit compressor speed NCL. When the set compressor speed NC is greater than the limit compressor speed NCL, that is, "Yes", the cooling system ECM80 proceeds to step S208. On the other hand, when the set compressor speed NC is less than the limit compressor speed NCL, that is, "No", the cooling system ECM80 proceeds to step S207.

[0129] In the above step S207, the cooling system ECM80 determines whether the set fan speed NF is greater than the limit fan speed NFL. When the set fan speed NF is greater than the limit fan speed NFL, that is, "Yes", the cooling system ECM80 proceeds to step S208. On the other hand, when the set fan speed NF is less than the limit fan speed NFL, that is, "No", the cooling system ECM80 proceeds to step S215.

[0130] In the above-mentioned step S208 , the cooling system ECM 80 calculates the first compressor speed candidate.

[0131] Next, in step S209 , the cooling system ECM 80 calculates a first fan speed candidate based on the first compressor speed candidate.

[0132] Next, in step S210 , the cooling system ECM 80 calculates a second compressor speed candidate.

[0133] Next, in step S211 , the cooling system ECM 80 calculates a second fan speed candidate based on the second compressor speed candidate.

[0134] Next, in step S212 , the cooling system ECM 80 calculates the cooling capacities at the limit operating point PL, the first candidate operating point P4 , and the second candidate operating point P5 .

[0135] Next, in step S213 , the cooling system ECM 80 sets the operating point closest to the required cooling capacity as the corrected operating point, and sets the compressor speed and the fan speed of the operating point as the corrected compressor speed and the corrected fan speed.

[0136] Next, in step S214, the cooling system ECM 80 operates the cooling device 1 at the corrected compressor speed and the corrected fan speed. The process returns after step S214.

[0137] On the other hand, in step S215, the cooling system ECM 80 operates the cooling device 1 at the set compressor speed and the set fan speed. The process returns after step S215.

[0138] In the configuration of the second embodiment, the fan speed is set based on the compressor speed, thereby minimizing the reduction in cooling capacity and noise. In addition, the amount of calculation of the cooling system ECM 80 can be reduced as much as possible. Thus, power consumption can be minimized.

[0139] (Other embodiments)

[0140] The technology disclosed herein is not limited to the above-described embodiments, and can be replaced within the scope of the gist of the claims.

[0141] For example, in the above-mentioned embodiments 1 and 2, the correction operating point is set from the noise limit line SL. However, the present invention is not limited to this, and the correction operating point may be set in an area below the noise limit line SL in the cooling capacity map even if it is not on the noise limit line SL.

[0142] In addition, in the above-mentioned embodiments 1 and 2, when at least one of the above-mentioned first condition and the above-mentioned second condition is not satisfied, the compressor speed and the fan speed are respectively set to the set compressor speed and the set fan speed until the correction operating point is selected. Without being limited to this, when at least one of the above-mentioned first condition and the above-mentioned second condition is not satisfied, the compressor speed and the fan speed may be temporarily set to the limited compressor speed NCL and the limited fan speed NFL, respectively, until the correction operating point is selected.

[0143] In the above-mentioned second embodiment, only three candidate operating points including the limit operating point PL are calculated, but the present invention is not limited thereto, and the number of candidate operating points may be four or more.

[0144] In the above-mentioned first and second embodiments, cooling device 1 cools battery module 70 by circulating refrigerant through heat exchanger 2. Without being limited thereto, cooling device 1 may further include a heat exchanger (cooler) for circulating cooling water through heat exchanger 2 that has exchanged heat with the refrigerant.

[0145] The above embodiments are merely examples and should not be interpreted as limiting the scope of the present invention. The scope of the present invention is defined by the scope of the claims, and all modifications and changes within the scope of the claims and equivalents are within the scope of the present invention.

[0146] Industrial Applicability

[0147] The technology disclosed herein is useful as a cooling device for an electrically driven vehicle that uses a refrigerant to cool electrically driven components mounted on the vehicle.

Claims

1. A cooling device for an electric drive vehicle, using a refrigerant to cool an electric drive component mounted on the vehicle, characterized in that: have: a pressurizer that pressurizes the refrigerant; a fan for causing a condenser to draw in outside air, and the condenser cools and condenses the refrigerant pressurized by the pressurizer; an electric drive component temperature detection unit, the electric drive component temperature detection unit detecting the temperature of the electric drive component; a refrigerant pressure detection unit configured to detect the pressure of the refrigerant compressed by the pressurizer; as well as a controller, the controller controlling the pressurizer and the fan, The controller calculates a required cooling capacity based on at least a detection result of the electric drive component temperature detection unit, The controller calculates a set compressor speed based on the compressor speed of the required cooling capacity. The controller calculates a set fan speed, which is a speed of the fan based on a detection result of the refrigerant pressure detection unit. When both a first condition that the set compressor speed is below a limited compressor speed pre-set based on a prescribed noise limit value and a second condition that the set fan speed is below a limited fan speed pre-set based on the prescribed noise limit value are satisfied, the controller causes the compressor and the fan to operate at the set compressor speed and the set fan speed, respectively. On the other hand, when at least one of the first condition and the second condition is not satisfied, the controller sets a corrected compressor speed and sets a corrected fan speed based on the corrected compressor speed, and causes the compressor and the fan to operate at the corrected compressor speed and the corrected fan speed, respectively, so that the noise generated by the compressor and the fan during operation is below the prescribed noise limit value. The corrected fan speed is set to a lower value as the corrected pressure device speed is higher.

2. The cooling device for an electric vehicle according to claim 1, characterized in that: further comprising an outside air temperature detection unit for detecting the outside air temperature, The controller also sets the corrected pressurizer rotation speed and the corrected fan rotation speed in consideration of the outside air temperature.

3. The cooling device for an electric vehicle according to claim 1 or 2, characterized in that: The controller sets the modified pressure device rotation speed and the modified fan rotation speed so that the generated noise is the noise limit value.

4. The cooling device for an electric vehicle according to claim 3, characterized in that: The controller calculates the cooling capacity for multiple combinations of the speed of the compressor and the speed of the fan whose noise generated is the noise limit value, and sets the combination whose cooling capacity is closest to the required cooling capacity among the multiple combinations as the corrected compressor speed and the corrected fan speed.

5. The cooling device for an electric vehicle according to claim 4, characterized in that: When there are a plurality of combinations whose cooling capabilities are closest to the required cooling capability, the controller sets the combination having the lowest rotation speed of the compressor among the combinations as the corrected compressor rotation speed and the corrected fan rotation speed.

6. The cooling device for an electric vehicle according to claim 3, characterized in that: The controller calculates a first booster speed candidate and a first fan speed candidate based on the first booster speed candidate, wherein the speed of the first booster speed candidate is higher than the limit booster speed by a constant number, The controller calculates a second booster speed candidate and a second fan speed candidate based on the second booster speed candidate, wherein the speed of the second booster speed candidate is lower than the limit booster speed by a constant number, The controller calculates the cooling capacity for the combination of the limiting compressor speed and the limiting fan speed, the combination of the first compressor speed candidate and the first fan speed candidate, and the combination of the second compressor speed candidate and the second fan speed candidate, respectively, and sets the combination among these combinations whose cooling capacity is closest to the required cooling capacity as the corrected compressor speed and the corrected fan speed, respectively.

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