Air conditioner and air conditioner control method

Abstract

One embodiment of an air conditioner according to the present disclosure comprises: a compressor; an outdoor heat exchanger; an indoor heat exchanger; a first temperature sensor; a second temperature sensor; an outdoor fan; and a control device. The rotation speed of the outdoor fan can be set within a range from a first speed to a second speed that is faster than the first speed. The control device executes defrosting operation, and after execution of the defrosting operation, the control device executes outdoor fan control to set the rotation speed of the outdoor fan to the first speed and rotate the outdoor fan. During the execution of the outdoor fan control, the control device maintains the operation frequency of the compressor at the same operation frequency as the operation frequency of the compressor in the defrosting operation.

Description

Air conditioner and method for controlling air conditioner

[0001] The present disclosure relates to an air conditioner and a method for controlling an air conditioner.

[0002] When an air conditioner such as a heat pump air conditioner performs heating operation in a low-temperature, high-humidity environment, frost forms on the heat exchanger of the outdoor unit. The air conditioner performs a defrosting operation to remove the frost from the heat exchanger. Hereinafter, conventional defrosting operation will be referred to as a normal defrosting operation. In normal defrosting operation, it is difficult to remove frost that has formed on equipment and components located downstream of the airflow that mediates heat exchange. Hereinafter, the equipment and components will be referred to as the outdoor unit shell.

[0003] Patent Document 1 describes a technique for removing frost that has adhered to the exterior of an outdoor unit. In this technique, the compressor operates with the refrigerant flowing in the same direction as in normal defrosting operation, and the outdoor fan rotates. This allows heat generated in the heat exchanger during defrosting operation to be transferred to the exterior of the outdoor unit. Hereinafter, the control performed in this technique will be referred to as conventional control.

[0004] JP 2010-121789 A JP 57-174641 A

[0005] In ultra-low temperature and high humidity environments where the outdoor temperature is below -10°C and the humidity is above 70%, conventional control may not be able to provide enough heat. As a result, it may not be possible to remove the frost that has built up on the outdoor unit's outer casing. In such environments, additional heat is required to remove the frost that has built up on the outdoor unit's outer casing.

[0006] In view of the above circumstances, an object of the present disclosure is to provide an air conditioner and a method for controlling an air conditioner that can remove frost that has adhered to the outer casing of an outdoor unit.

[0007] One aspect of the present disclosure is an air conditioner comprising a compressor, an outdoor heat exchanger, an indoor heat exchanger, a first temperature sensor that measures an outdoor air temperature, a second temperature sensor that measures the temperature of a refrigerant flowing through the outdoor heat exchanger, an outdoor fan that sends air to the outdoor heat exchanger, and a control device, wherein the rotation speed of the outdoor fan can be set within a range from a first speed to a second speed that is faster than the first speed, and the control device performs a defrosting operation, and after performing the defrosting operation, performs outdoor fan control that sets the rotation speed of the outdoor fan to the first speed and rotates the outdoor fan, and while the outdoor fan control is being performed, maintains the operating frequency of the compressor at the same operating frequency as the operating frequency of the compressor in the defrosting operation.

[0008] One aspect of the present disclosure is a control method for an air conditioner comprising a compressor, an outdoor heat exchanger, an indoor heat exchanger, a first temperature sensor that measures an outdoor air temperature, a second temperature sensor that measures the temperature of a refrigerant flowing through the outdoor heat exchanger, and an outdoor fan that sends air to the outdoor heat exchanger, wherein the rotation speed of the outdoor fan is settable within a range from a first speed to a second speed that is faster than the first speed, the control method comprising: performing a defrosting operation; and, after performing the defrosting operation, performing outdoor fan control that sets the rotation speed of the outdoor fan to the first speed and rotates the outdoor fan; and, while the outdoor fan control is being performed, maintaining the operating frequency of the compressor at the same operating frequency as the operating frequency of the compressor in the defrosting operation.

[0009] According to the present disclosure, frost adhering to the outer casing of the outdoor unit can be removed.

[0010] Fig. 1 is a diagram showing the configuration of an air conditioner in an embodiment. Fig. 2 is a block diagram showing the hardware configuration of a control device in an embodiment. Fig. 3 is an exploded perspective view of an outdoor unit in an embodiment. Fig. 4 is a flowchart showing the operation of an air conditioner in an embodiment. Fig. 5 is a flowchart showing the operation of an air conditioner in an embodiment. Fig. 6 is a diagram showing an example of the operating frequency of a compressor and the rotation speed of an outdoor fan in an embodiment.

[0011] Hereinafter, embodiments of the present disclosure will be described with reference to the drawings. Note that the scope of the present disclosure is not limited to the following embodiments and can be modified as desired within the scope of the technical concept of the present disclosure.

[0012] Fig. 1 shows the configuration of an air conditioner 1 according to an embodiment. The air conditioner 1 shown in Fig. 1 includes an outdoor unit 2 and an indoor unit 3. The outdoor unit 2 includes a compressor 10, a four-way switching valve 11, a heat exchanger 12 (outdoor heat exchanger), a defrost temperature thermistor 13 (second temperature sensor), an expansion valve 14, an outdoor air temperature thermistor 15 (first temperature sensor), an outdoor fan 16, a fan motor 17, and a control device 18. The indoor unit 3 includes a heat exchanger 19 (indoor heat exchanger).

[0013] The air conditioner 1 performs cooling operation, heating operation, or normal defrosting operation. After performing normal defrosting operation in a low-temperature and high-humidity environment, the air conditioner 1 performs an additional defrosting operation, which will be described later. Hereinafter, the additional defrosting operation may also be referred to as outdoor fan control.

[0014] The compressor 10 draws in a refrigerant at a low temperature and pressure and compresses it. The compressor 10 discharges the compressed refrigerant at a high temperature and high pressure. The four-way switching valve 11 switches the refrigerant flow direction. The heat exchanger 12 exchanges heat between the refrigerant and the outdoor air. The heat exchanger 12 functions as a condenser during cooling operation and as an evaporator during heating operation.

[0015] The defrost temperature thermistor 13 is a temperature sensor and is disposed in the pipe connecting the heat exchanger 12 and the expansion valve 14. The defrost temperature thermistor 13 is in close contact with the pipe. The defrost temperature thermistor 13 measures the temperature of the refrigerant flowing into the heat exchanger 12 during heating operation, and measures the temperature of the refrigerant passing through the heat exchanger 12 during cooling operation. Hereinafter, the temperature measured by the defrost temperature thermistor 13 will be referred to as the defrost temperature. The expansion valve 14 decompresses the refrigerant to expand it.

[0016] The outdoor air temperature thermistor 15 is a temperature sensor, and is disposed in a position inside the housing of the outdoor unit 2 where it comes into contact with the outdoor air. The outdoor air temperature thermistor 15 measures the temperature of the outdoor air, i.e., the outdoor air temperature. Below, the defrost temperature and the outdoor air temperature are expressed in degrees Celsius. The outdoor fan 16 sends the outdoor air to the heat exchanger 12. The fan motor 17 rotates the outdoor fan 16. The air volume of the outdoor fan 16 changes depending on the rotation speed of the fan motor 17. The control device 18 controls the entire outdoor unit 2.

[0017] The heat exchanger 19 exchanges heat between the indoor air and the refrigerant. The heat exchanger 19 functions as an evaporator during cooling operation and as a condenser during heating operation. The indoor unit 3 may have an indoor fan that sends indoor air to the heat exchanger 19.

[0018] Fig. 2 shows the hardware configuration of the control device 18. The control device 18 shown in Fig. 2 includes a processor 20 and a memory 21. The functions of the control device 18 are realized by software, firmware, or a combination of software and firmware. The software and firmware are written as programs and stored in the memory 21. The processor 20 realizes the functions of the control device 18 by reading and executing the programs stored in the memory 21.

[0019] The processor 20 may be an application-specific integrated circuit (ASIC), a field programmable gate array (FPGA), or a combination thereof. The memory 21 is, for example, a non-volatile semiconductor memory such as a read-only memory (ROM), a flash memory, an erasable programmable read-only memory (EPROM), or an electrically erasable programmable read-only memory (EEPROM). The memory 21 may also be a volatile semiconductor memory such as a random access memory (RAM). The memory 21 may also be a removable recording medium.

[0020] The operation of the air conditioner 1 during cooling operation will be described. During cooling operation, the four-way selector valve 11 is in the connected state shown by the solid line in Figure 1. The compressor 10 compresses the refrigerant drawn into the compressor 10 and discharges the refrigerant in a high-temperature, high-pressure gas state. The refrigerant discharged from the compressor 10 passes through the four-way selector valve 11 and flows into the heat exchanger 12. The heat exchanger 12 functions as a condenser. The refrigerant that flows into the heat exchanger 12 releases heat to the outdoor ambient air and liquefies. At this time, the fan motor 17 rotates the outdoor fan 16, which blows air toward the heat exchanger 12. This promotes heat exchange between the refrigerant and the outdoor air.

[0021] The liquid refrigerant flows into the expansion valve 14. The expansion valve 14 reduces the pressure of the refrigerant and expands it. The low-temperature, low-pressure refrigerant that has passed through the expansion valve 14 flows into the heat exchanger 19. The heat exchanger 19 functions as an evaporator. The refrigerant that has flowed into the heat exchanger 19 absorbs heat from the indoor air and vaporizes. At this time, the indoor air is cooled. The low-temperature, low-pressure gas refrigerant passes through the four-way switching valve 11 and flows into the compressor 10.

[0022] The operation of the air conditioner 1 during heating operation will be described. During heating operation, the four-way switching valve 11 is in the connected state indicated by the dashed line in Figure 1. The compressor 10 compresses the refrigerant drawn into the compressor 10 and discharges the refrigerant in a high-temperature, high-pressure gas state. The refrigerant discharged from the compressor 10 passes through the four-way switching valve 11 and flows into the heat exchanger 19. The heat exchanger 19 functions as a condenser. The refrigerant that flows into the heat exchanger 19 releases heat into the room and liquefies. At this time, the indoor air is heated.

[0023] The liquid refrigerant flows into the expansion valve 14. The expansion valve 14 reduces the pressure of the refrigerant and expands it. The low-temperature, low-pressure refrigerant that has passed through the expansion valve 14 flows into the heat exchanger 12. The heat exchanger 12 functions as an evaporator. The refrigerant that has flowed into the heat exchanger 12 absorbs heat from the outdoor air and vaporizes. At this time, the fan motor 17 rotates the outdoor fan 16, which sends air to the heat exchanger 12. This promotes heat exchange between the refrigerant and the outdoor air. The low-temperature, low-pressure gas refrigerant passes through the four-way switching valve 11 and flows into the compressor 10.

[0024] The direction of refrigerant flow during normal defrosting operation and additional defrosting operation is the same as the direction of refrigerant flow during cooling operation. Compressor 10 compresses the refrigerant drawn into compressor 10 and discharges the refrigerant in a high-temperature, high-pressure gas state. The refrigerant discharged from compressor 10 passes through four-way switching valve 11 and flows into heat exchanger 12. The refrigerant that flows into heat exchanger 12 releases heat to the frost adhering to heat exchanger 12 and is liquefied. Unlike normal defrosting operation, when additional defrosting operation is performed, fan motor 17 rotates outdoor fan 16, which blows air toward heat exchanger 12. Frost that has adhered to heat exchanger 12 during heating operation is removed by the heat released from the refrigerant.

[0025] Fig. 3 shows the internal configuration of the outdoor unit 2. As shown in Fig. 3, the compressor 10, outdoor fan 16, fan motor 17, etc. are arranged inside the housing of the outdoor unit 2. The housing of the outdoor unit 2 forms the outer shell of the outdoor unit and includes a bottom plate 40, a front panel 41, side portions 42, a back portion 43, and a top panel 44.

[0026] The bottom plate 40 forms the bottom of the housing. The compressor 10, outdoor fan 16, fan motor 17, etc. are arranged on the bottom plate 40. The front panel 41 forms the front and side of the housing. An opening is formed in the front panel 41 in the portion facing the outdoor fan 16. The front panel 41 also has a lattice-shaped fan cover 41a that covers the opening. The side portion 42 is made up of a combination of multiple parts and forms the side of the housing. The rear portion 43 is made up of a combination of multiple parts and forms the rear of the housing. The parts that make up the rear portion 43 have multiple ventilation holes formed through which air sent to the heat exchanger 12 passes. The top panel 44 forms the top of the housing.

[0027] The outdoor temperature thermistor 15 is disposed within the housing of the outdoor unit 2. The position of the outdoor temperature thermistor 15 satisfies the following conditions 1 to 5. Condition 1: To avoid heat conduction from the top panel 44, the outdoor temperature thermistor 15 is not in close contact with the top panel 44. Condition 2: To prevent the outdoor temperature thermistor 15 from measuring the outdoor temperature when snow is attached to the outdoor temperature thermistor 15, the outdoor temperature thermistor 15 is disposed in a location covered by the top panel 44. Condition 3: To avoid being affected by radiant heat from the heat exchanger 12, the outdoor temperature thermistor 15 is disposed as far away as possible from the heat exchanger 12. Condition 4: To avoid being affected by geothermal heat, the outdoor temperature thermistor 15 is disposed high above the ground. Condition 5: To avoid being affected by the temperature of the air after heat exchange, the outdoor temperature thermistor 15 is disposed upwind of the heat exchanger 12.

[0028] 4 shows the operation of the air conditioner 1. The operation of the air conditioner 1 relating to the heating operation, normal defrosting operation, and additional defrosting operation will be described.

[0029] The control device 18 sets the connection state of the four-way switching valve 11 to the state shown by the dashed line in Fig. 1. Thereafter, the control device 18 sets the operating frequency of the compressor 10 and the rotation speed of the outdoor fan 16, and starts the heating operation (step S10).

[0030] The operating frequency of the compressor 10 can be set within a range from a first frequency to a second frequency higher than the first frequency. The first frequency is the lowest frequency, and the second frequency is the highest frequency. The operating frequency of the compressor 10 in heating operation is stored in advance in the memory 21. That is, the operating frequency is set in advance in the control device 18. The processor 20 of the control device 18 reads the operating frequency from the memory 21 and sets the operating frequency in the heat exchanger 12.

[0031] The rotation speed of the outdoor fan 16 can be set within a range from a first speed to a second speed that is faster than the first speed. The first speed is the lowest speed, and the second speed is the highest speed. The rotation speed of the outdoor fan 16 during heating operation is pre-stored in the memory 21. That is, the rotation speed is pre-set in the control device 18. For example, the rotation speed is the second speed. The processor 20 of the control device 18 reads the second speed from the memory 21 and causes the fan motor 17 to rotate the outdoor fan 16 at the second speed.

[0032] After the heating operation starts, the rotation of the outdoor fan 16 creates an air flow around the outdoor temperature thermistor 15. The control device 18 periodically acquires information on the outdoor temperature from the outdoor temperature thermistor 15. After several minutes have passed since the start of the heating operation, the control device 18 calculates the average temperature of the outdoor air temperature over a preset reference time. This average temperature is the initial outdoor temperature. The control device 18 first uses the initial outdoor temperature. Thereafter, the control device 18 uses the outdoor temperature indicated by the information acquired from the outdoor temperature thermistor 15.

[0033] After the heating operation is started, the control device 18 receives a normal defrosting operation command (step S10a). The control device 18 determines whether the outdoor air temperature acquired as described above is equal to or lower than X degrees (step S11). The threshold value X is a value for determining whether the outdoor unit 2 is in a low-temperature environment. The threshold value X is pre-stored in the memory 21. That is, the threshold value X is pre-set in the control device 18. For example, the threshold value X is 0 or -1. If the outdoor air temperature is equal to or lower than X degrees, step S12 is executed. If the outdoor air temperature is higher than X degrees, step S19 is executed.

[0034] If the outdoor air temperature is equal to or lower than X degrees, the control device 18 acquires information on the defrost temperature from the defrost temperature thermistor 13. The control device 18 calculates the difference between the outdoor air temperature and the defrost temperature by subtracting the defrost temperature indicated by the acquired information from the outdoor air temperature. The control device 18 determines whether the difference is equal to or greater than Y (step S12). The threshold value Y is a value for determining whether the outdoor unit 2 is in a humid environment. The threshold value Y is pre-stored in the memory 21. That is, the threshold value Y is pre-set in the control device 18. For example, the threshold value Y is 8. If the difference between the outdoor air temperature and the defrost temperature is equal to or lower than Y, step S13 is executed. If the difference between the outdoor air temperature and the defrost temperature is greater than Y, step S19 is executed.

[0035] If the difference between the outdoor air temperature and the defrost temperature is equal to or less than Y, the control device 18 sets the connection state of the four-way switching valve 11 to the state indicated by the solid line in Fig. 1. This causes the control device 18 to switch the refrigerant flow direction (step S13). Thereafter, the control device 18 causes the fan motor 17 to stop the rotation of the outdoor fan 16. The control device 18 also sets the operating frequency of the compressor 10 and starts a normal defrosting operation (step S14).

[0036] The operating frequency of the compressor 10 in the normal defrosting operation is stored in advance in the memory 21. That is, the operating frequency is set in advance in the control device 18. For example, the operating frequency is the second frequency. The processor 20 of the control device 18 reads the second frequency from the memory 21 and sets the second frequency in the heat exchanger 12.

[0037] After the normal defrosting operation is started, the control device 18 acquires information on the defrost temperature from the defrost temperature thermistor 13. The control device 18 determines whether the defrost temperature indicated by the acquired information is higher than F degrees (step S15). The threshold value F indicates the temperature at which it is no longer necessary to remove frost from the heat exchanger 12. The threshold value F is pre-stored in the memory 21. That is, the threshold value F is pre-set in the control device 18. For example, the threshold value F is 10. If the defrost temperature is higher than F degrees, step S16 is executed. If the defrost temperature is equal to or lower than F degrees, step S15 is executed. Step S15 is repeated until the defrost temperature becomes higher than F degrees.

[0038] If the defrost temperature is higher than F degrees, the control device 18 starts the additional defrosting operation (steps S16 and S17). That is, the control device 18 starts the additional defrosting operation immediately after the normal defrosting operation has completed removing frost from the heat exchanger 12. The direction in which the refrigerant flows in the additional defrosting operation is the same as the direction in which the refrigerant flows in the normal defrosting operation.

[0039] First, the control device 18 sets the operation frequency of the compressor 10. The operation frequency of the compressor 10 in the additional defrosting operation is stored in advance in the memory 21. That is, the operation frequency is set in advance in the control device 18. The processor 20 of the control device 18 reads out the operation frequency from the memory 21 and sets the operation frequency in the heat exchanger 12 (step S16). The operation frequency of the compressor 10 in the additional defrosting operation is the same as the operation frequency of the compressor 10 in the normal defrosting operation.

[0040] After step S16 is executed, the control device 18 sets the rotation speed of the outdoor fan 16. The rotation speed of the outdoor fan 16 in the additional defrosting operation is stored in advance in the memory 21. In other words, the rotation speed is set in advance in the control device 18. The processor 20 of the control device 18 reads out the first speed, which is the lowest speed, from the memory 21, and causes the fan motor 17 to rotate the outdoor fan 16 at the first speed (step S17).

[0041] The order in which steps S16 and S17 are executed may be reversed from the above order, i.e., step S16 may be executed after step S17 is executed.

[0042] After the additional defrosting operation is started, the control device 18 determines whether a reference time has elapsed since the start of the additional defrosting operation (step S18). For example, the reference time is 10 minutes. If the reference time has elapsed, the control device 18 stops the additional defrosting operation and starts the heating operation.

[0043] If the reference time has not elapsed, the control device 18 acquires information on the defrost temperature from the defrost temperature thermistor 13. The control device 18 determines whether the defrost temperature indicated by the acquired information is higher than H degrees (step S23). The threshold value H indicates the temperature at which it is no longer necessary to remove frost from the outdoor unit outer casing. The threshold value H is pre-stored in the memory 21. That is, the threshold value H is pre-set in the control device 18. The threshold value H is greater than F, for example, 10. If the defrost temperature is higher than H degrees, the control device 18 stops the additional defrosting operation and starts heating operation. If the defrost temperature is equal to or lower than H degrees, step S18 is executed. Steps S18 and S23 are repeated until the reference time has elapsed or the defrost temperature becomes higher than H degrees.

[0044] If the outdoor air temperature is higher than X degrees, or if the difference between the outdoor air temperature and the defrost temperature is greater than Y, the control device 18 acquires information on the defrost temperature from the defrost temperature thermistor 13. The control device 18 determines whether the defrost temperature indicated by the acquired information is equal to or lower than Z degrees (step S19). The threshold value Z is a value for determining whether the outdoor unit 2 is in an ultra-low temperature environment. The threshold value Z is pre-stored in the memory 21. That is, the threshold value Z is pre-set in the control device 18. The threshold value Z is smaller than the threshold value X, and is, for example, equal to or higher than -25 and equal to or lower than -20. If the defrost temperature is equal to or lower than Z degrees, step S20 is executed. If the defrost temperature is higher than Z degrees, step S21 is executed.

[0045] If the defrosting temperature is Z degrees or lower, the control device 18 determines whether or not the normal defrosting operation has been performed a reference number of times without performing the additional defrosting operation (step S20). The reference number of times is pre-stored in the memory 21. That is, the reference number of times is pre-set in the control device 18. For example, the reference number of times is 1 or more. The control device 18 determines whether or not step S22 has been performed a reference number of times without performing steps S16 and S17. Step S22 will be described later.

[0046] If a normal defrosting operation has been performed a reference number of times without a single additional defrosting operation being performed, step S15 is executed. If a normal defrosting operation has been performed a reference number of times after an additional defrosting operation has been performed and before the next additional defrosting operation is performed, step S15 is executed. If the defrost temperature is Z degrees or lower, the control device 18 performs an additional defrosting operation every time a normal defrosting operation has been performed a reference number of times. If an additional defrosting operation has been performed before a normal defrosting operation has been performed a reference number of times, step S21 is executed.

[0047] If the defrosting temperature is higher than Z degrees, the control device 18 performs the following process. Alternatively, if the number of times the normal defrosting operation has been performed does not satisfy the condition in step S20, the control device 18 performs the following process. The control device 18 sets the connection state of the four-way switching valve 11 to the state shown by the solid line in Figure 1. As a result, the control device 18 switches the direction of refrigerant flow (step S21). Step S21 is the same as step S13.

[0048] After step S21 is executed, the control device 18 causes the fan motor 17 to stop the rotation of the outdoor fan 16. The control device 18 also sets the operating frequency of the compressor 10 and starts a normal defrosting operation (step S22). Step S22 is the same as step S14.

[0049] After the normal defrosting operation is started, the control device 18 acquires information on the defrosting temperature from the defrosting temperature thermistor 13. The control device 18 determines whether the defrosting temperature indicated by the acquired information is higher than F degrees (step S24). If the defrosting temperature is higher than F degrees, the control device 18 stops the additional defrosting operation and starts heating operation. If the defrosting temperature is equal to or lower than F degrees, step S24 is executed. Step S24 is repeated until the defrosting temperature becomes higher than F degrees.

[0050] 5 shows the operation of the air conditioner 1 for managing the number of times the normal defrosting operation is performed. The operation of the air conditioner 1 for managing the number of times the normal defrosting operation is performed will be described.

[0051] The memory 21 stores the number of times the normal defrosting operation has been performed. The control device 18 resets the number of times the normal defrosting operation has been performed stored in the memory 21. For example, the number of times the normal defrosting operation has been performed is reset to 0 (step S30).

[0052] After step S30 is executed, the control device 18 determines whether or not the normal defrosting operation has started (step S31). If the normal defrosting operation has started, step S32 is executed. If the normal defrosting operation has not started, step S31 is executed. Step S31 is repeated until the normal defrosting operation is started.

[0053] When the normal defrosting operation is started, the control device 18 increments the number of times of execution stored in the memory 21 by 1 (step S32). After step S32 is executed, the control device 18 determines whether the additional defrosting operation is started (step S33). When the additional defrosting operation is started, step S34 is executed. When the additional defrosting operation is not started, step S31 is executed.

[0054] When the additional defrosting operation is started, the control device 18 resets the number of times the additional defrosting operation has been performed stored in the memory 21. For example, the number of times the additional defrosting operation has been performed is reset to 0 (step S34). After step S34 is performed, step S31 is performed.

[0055] Each time an additional defrosting operation is performed without starting a normal defrosting operation, the number of times the normal defrosting operation is performed is incremented by 1. The control device 18 acquires the number of times the normal defrosting operation has been performed from the memory 21 in step S20 shown in FIG. 4. The control device 18 also determines in step S20 whether the number of times the normal defrosting operation has been performed is the same as a reference number of times. If the number of times the normal defrosting operation has been performed is the same as the reference number of times, step S15 is executed. If the number of times the normal defrosting operation has been performed is less than the reference number of times, step S21 is executed.

[0056] 6 shows an example of the operating frequency of the compressor 10 and the rotation speed of the outdoor fan 16. For example, at the start of a normal defrosting operation, the operating frequency of the compressor 10 is set to F1. This operating frequency F1 is the highest frequency that can be set for the compressor 10. Furthermore, at the start of a normal defrosting operation, the rotation of the outdoor fan 16 stops. The control device 18 performs a normal defrosting operation in this state.

[0057] Thereafter, the control device 18 stops the normal defrosting operation and performs the additional defrosting operation. During the additional defrosting operation, the operating frequency of the compressor 10 is maintained at F1. Furthermore, at the start of the additional defrosting operation, the rotation speed of the outdoor fan 16 is set to V1. This speed V1 is the lowest speed that can be set for the outdoor fan 16.

[0058] 4 is satisfied, the control device 18 stops the additional defrosting operation and starts the heating operation. At the start of the heating operation, the operating frequency of the compressor 10 is set to F2, which is lower than F1. Also, at the start of the heating operation, the rotation speed of the outdoor fan 16 is set to V2, which is higher than V1.

[0059] As described above, the air conditioner 1 includes the compressor 10, the heat exchanger 12, the heat exchanger 19, the outdoor air temperature thermistor 15, the defrost temperature thermistor 13, the outdoor fan 16, and the control device 18. The outdoor air temperature thermistor 15 measures the outdoor air temperature. The defrost temperature thermistor 13 measures the temperature of the refrigerant flowing through the heat exchanger 12. The outdoor fan 16 sends air to the heat exchanger 12. The rotation speed of the outdoor fan 16 can be set within a range from a first speed to a second speed that is faster than the first speed. The control device 18 performs a defrosting operation (normal defrosting operation). After performing the defrosting operation, the control device 18 performs outdoor fan control (additional defrosting operation) in which the rotation speed of the outdoor fan 16 is set to the first speed and the outdoor fan is rotated. During the outdoor fan control, the control device 18 maintains the operating frequency of the compressor 10 at the same operating frequency as the operating frequency of the compressor 10 during the defrosting operation.

[0060] In order to reduce the amount of heat used to change the state of the refrigerant during outdoor fan control, the control device 18 rotates the outdoor fan 16 at a first speed, which is the lowest speed. Furthermore, in order to increase the amount of refrigerant circulating and to compensate for the lack of energy, the control device 18 maintains the operating frequency of the compressor 10 at the same operating frequency as the operating frequency of the compressor 10 during defrosting operation. This allows the air conditioner 1 to remove frost that has adhered to the exterior casing of the outdoor unit.

[0061] If the heating operation is not performed for a long period of time, the comfort of the user of the air conditioner 1 will be impaired. Therefore, when the outdoor air temperature is below a preset temperature and the value obtained by subtracting the refrigerant temperature from the outdoor air temperature is equal to or greater than a preset value, the control device 18 performs outdoor fan control. For example, the preset temperature is X degrees as described above. For example, the preset value is Y as described above. Outdoor fan control is performed in situations where outdoor fan control is necessary, and execution of outdoor fan control is suppressed in situations where outdoor fan control is not necessary. Therefore, comfort is less likely to be impaired.

[0062] If the refrigerant temperature during outdoor fan control is higher than a preset temperature, the control device 18 stops outdoor fan control. For example, the preset temperature is the aforementioned H degree. Because outdoor fan control is stopped in a situation where outdoor fan control is not necessary, comfort is less likely to be impaired.

[0063] In an ultra-low temperature environment such as -20 degrees, the temperature detection accuracy of the thermistor is low. Therefore, it may be difficult to set detailed temperature conditions. If the refrigerant temperature is below a preset temperature, the control device 18 controls the outdoor fan each time a defrosting operation is performed a preset number of times. For example, the preset temperature is the aforementioned Z degrees. The air conditioner 1 can control the outdoor fan even in an ultra-low temperature environment.

[0064] The configurations and methods described in this specification can be combined as appropriate within the scope of not contradicting each other.

[0065] 1 Air conditioner, 2 Outdoor unit, 3 Indoor unit, 10 Compressor, 11 Four-way switching valve, 12, 19 Heat exchanger, 13 Defrost temperature thermistor, 14 Expansion valve, 15 Outdoor temperature thermistor, 16 Outdoor fan, 17 Fan motor, 18 Control device, 20 Processor, 21 Memory, 40 Bottom plate, 41 Front panel, 41a Fan cover, 42 Side portion, 43 Rear portion, 44 Top panel

Claims

1. Compressor and, Outdoor heat exchanger, Indoor heat exchanger, A first temperature sensor that measures the outside air temperature, A second temperature sensor for measuring the temperature of the outdoor heat exchanger, An outdoor fan that supplies air to the aforementioned outdoor heat exchanger, Control device and Equipped with, The rotation speed of the outdoor fan can be set within a range from a first speed to a second speed that is faster than the first speed. The control device is Defrosting operation will be performed. After performing the defrosting operation, the outdoor fan control is performed to rotate the outdoor fan by setting the rotation speed of the outdoor fan to the first speed according to the outside air temperature and the temperature of the outdoor heat exchanger. During the implementation of the outdoor fan control, the operating frequency of the compressor is maintained at the same operating frequency as the operating frequency of the compressor during the defrosting operation. Air conditioner.

2. If the outside air temperature is below a preset temperature, and the value obtained by subtracting the temperature of the outdoor heat exchanger from the outside air temperature is equal to or greater than a preset value, the control device performs the outdoor fan control. The air conditioner according to claim 1.

3. If the temperature of the outdoor heat exchanger is higher than a preset temperature while the outdoor fan control is being performed, the control device stops the outdoor fan control. An air conditioner according to claim 1 or claim 2.

4. If the temperature of the outdoor heat exchanger is below a preset temperature, the control device will perform the outdoor fan control each time the defrosting operation is performed a preset number of times. An air conditioner according to claim 1 or claim 2.

5. A control method for an air conditioner comprising a compressor, an outdoor heat exchanger, an indoor heat exchanger, a first temperature sensor for measuring the outside air temperature, a second temperature sensor for measuring the temperature of the outdoor heat exchanger, and an outdoor fan for supplying air to the outdoor heat exchanger, wherein the rotation speed of the outdoor fan can be set within a range from a first speed to a second speed that is faster than the first speed, Defrosting operation will be performed. After performing the defrosting operation, the outdoor fan control is performed to rotate the outdoor fan by setting the rotation speed of the outdoor fan to the first speed according to the outside air temperature and the temperature of the outdoor heat exchanger. During the implementation of the outdoor fan control, the operating frequency of the compressor is maintained at the same operating frequency as the operating frequency of the compressor during the defrosting operation. Control methods for air conditioners.