air conditioner

Abstract

Improves compressor reliability. [Solution] The air conditioner includes a compressor that circulates refrigerant through a refrigerant circuit, an outdoor fan that blows outside air to an outdoor heat exchanger provided in the refrigerant circuit, and a control device that controls the outdoor fan, and the control device controls the outdoor fan so that the outdoor fan frequency changes by an manipulated variable when the compressor frequency that drives the compressor changes, and the compressor frequency is included in either a fluctuation region 41 or a constant region 42, and the constant region 42 is a region where a target differential pressure change rate, which is the rate of change of a target differential pressure that is a target value for the differential pressure between the pressure of refrigerant sucked into the compressor and the pressure of refrigerant discharged from the compressor, is smaller than that in the fluctuation region 41. The manipulated variable is calculated according to the target differential pressure and the rate of change of the compressor frequency, and the manipulated variable is smaller when the compressor frequency is included in the fluctuation region 41 than when it is included in the constant region 42.

Description

[Technical Field]

[0001] The technology of the present disclosure relates to an air conditioner. [Background technology]

[0002] There is known an air conditioner that performs feedback control of the outdoor fan rotation speed based on the differential pressure, so that the differential pressure, which is the difference between the pressure of the refrigerant discharged from the compressor and the pressure of the refrigerant drawn into the compressor, is equal to a target differential pressure (Patent Document 1). This type of air conditioner can prevent compressor problems, such as vane wear and poor lubrication of refrigerating machine oil, caused by a drop in differential pressure, particularly during cooling operation under low outdoor temperatures, thereby improving compressor reliability. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Publication No. 2020-122626 Summary of the Invention [Problem to be solved by the invention]

[0004] However, in such air conditioners, when the compressor rotation speed drops significantly, the differential pressure drops rapidly, and therefore feedback control of the outdoor fan rotation speed alone may result in the differential pressure dropping more than the target differential pressure.

[0005] The disclosed technology has been made in consideration of the above points, and aims to provide an air conditioner that improves the reliability of the compressor. [Means for solving the problem]

[0006] An air conditioner according to one aspect of the present disclosure includes a compressor that circulates refrigerant through a refrigerant circuit, an outdoor fan that blows outside air to a condenser provided in the refrigerant circuit, and a control device that controls the outdoor fan, wherein the control device controls the outdoor fan such that when a compressor frequency that drives the compressor changes, the outdoor fan frequency changes by an manipulated variable, the compressor frequency being included in either a fluctuation region or a constant region, the constant region being a region where a target differential pressure change rate, which is the rate of change of a target differential pressure that is a target value for the differential pressure between the pressure of suction refrigerant sucked into the compressor and the pressure of discharge refrigerant discharged from the compressor, with respect to the compressor frequency, is smaller than that in the fluctuation region, the manipulated variable is calculated according to the target differential pressure and the rate of change of the compressor frequency, and the manipulated variable is smaller when the compressor frequency is included in the fluctuation region than when it is included in the constant region. [Effects of the Invention]

[0007] The disclosed air conditioner can improve the reliability of the compressor. [Brief explanation of the drawings]

[0008] [Figure 1] FIG. 1 is a refrigerant circuit diagram showing an air conditioner according to a first embodiment. [Figure 2] FIG. 2 is a block diagram showing the control device. [Figure 3] FIG. 3 is a graph showing the relationship between the compressor frequency of the compressor and the target differential pressure. [Figure 4] FIG. 4 is a flowchart showing outdoor fan frequency control. [Figure 5] FIG. 5 is a flowchart showing feedback control of the outdoor fan. [Figure 6] FIG. 6 is a time chart showing the changes in the target differential pressure, differential pressure, compressor frequency, and outdoor fan frequency in the air conditioner of Example 1 when the compressor frequency is within a certain range and the compressor frequency is reduced. [Figure 7]FIG. 7 is a time chart showing other changes in the target differential pressure, differential pressure, compressor frequency, and outdoor fan frequency in the air conditioner of Example 1 when the compressor frequency is within a certain range and the compressor frequency is reduced. [Figure 8] FIG. 8 is a time chart showing the changes in the target differential pressure, differential pressure, compressor frequency, and outdoor fan frequency in the air conditioner of Example 1 when the compressor frequency is included in the fluctuation range and the compressor frequency decreases. [Figure 9] FIG. 9 is a time chart showing other changes in the target differential pressure, differential pressure, compressor frequency, and outdoor fan frequency in the air conditioner of Example 1 when the compressor frequency is included in the fluctuation range and the compressor frequency becomes smaller. [Figure 10] FIG. 10 is a time chart showing the changes in the target differential pressure, differential pressure, compressor frequency, and outdoor fan frequency in an air conditioner of a comparative example when the compressor frequency is within a certain range and the compressor frequency decreases. [Figure 11] FIG. 11 is a time chart showing the changes in the target differential pressure, differential pressure, compressor frequency, and outdoor fan frequency in an air conditioner of a comparative example when the compressor frequency is included in the fluctuation range and the compressor frequency decreases. DETAILED DESCRIPTION OF THE INVENTION

[0009] An air conditioner according to an embodiment of the present disclosure will be described in detail below with reference to the drawings. Note that the following description does not limit the technology of the present disclosure. In addition, in the following description, the same components are given the same reference numerals, and duplicated descriptions will be omitted. [Example]

[0010] As shown in Fig. 1, the air conditioner 1 of the first embodiment includes an outdoor unit 2 and an indoor unit 3. Fig. 1 is a refrigerant circuit diagram showing the air conditioner 1 of the first embodiment. The outdoor unit 2 is installed outside a room to be cooled or heated by the air conditioner 1. The indoor unit 3 is installed inside a room to be cooled or heated by the air conditioner 1. The air conditioner 1 further includes a refrigerant circuit 5. The refrigerant circuit 5 includes a compressor 6, a four-way valve 7, an outdoor heat exchanger 8, an expansion valve 11, and an indoor heat exchanger 12. The refrigerant circuit 5 further includes a suction pipe 14, a discharge pipe 15, an outdoor gas pipe 16, an outdoor liquid pipe 17, an indoor liquid pipe 18, and an indoor gas pipe 19.

[0011] Compressor 6 is disposed inside outdoor unit 2. Compressor 6 is connected to four-way valve 7 via suction pipe 14 and discharge pipe 15. Compressor 6 has a main body and a rotor, and as the rotor rotates relative to the main body, it compresses the refrigerant drawn into compressor 6 via suction pipe 14 and discharges the compressed refrigerant to discharge pipe 15. The flow rate at which refrigerant is discharged from compressor 6 per unit time increases as the compressor frequency, which indicates the number of rotations at which the rotor rotates relative to the main body per unit time, increases.

[0012] The four-way valve 7 is disposed inside the outdoor unit 2. The four-way valve 7 is connected to the outdoor heat exchanger 8 via an outdoor gas pipe 16 and to the indoor heat exchanger 12 via an indoor gas pipe 19. The four-way valve 7 switches the refrigerant circuit 5 to a heating cycle or to a cooling cycle. When the refrigerant circuit 5 is switched to the heating cycle, the discharge pipe 15 is connected to the indoor gas pipe 19 via the four-way valve 7, and the outdoor gas pipe 16 is connected to the suction pipe 14 via the four-way valve 7. When the refrigerant circuit 5 is switched to the cooling cycle, the discharge pipe 15 is connected to the outdoor gas pipe 16 via the four-way valve 7, and the indoor gas pipe 19 is connected to the suction pipe 14 via the four-way valve 7.

[0013] The outdoor heat exchanger 8 is disposed inside the outdoor unit 2. The outdoor heat exchanger 8 is connected to the expansion valve 11 via an outdoor liquid pipe 17. The outdoor heat exchanger 8 exchanges heat between the refrigerant flowing through the outdoor heat exchanger 8 and the air passing through the outdoor heat exchanger 8. The outdoor unit 2 is equipped with an outdoor fan 21. The outdoor fan 21 has blades that rotate relative to the outdoor unit 2, causing outdoor air from outside where the outdoor unit 2 is installed to pass through the outdoor heat exchanger 8. The volume of air that the outdoor fan 21 passes through the outdoor heat exchanger 8 per unit time increases as the outdoor fan frequency, which indicates the number of rotations of the blades relative to the outdoor unit 2 per unit time, increases.

[0014] The expansion valve 11 is disposed inside the outdoor unit 2. The expansion valve 11 is connected to the indoor heat exchanger 12 via an indoor liquid pipe 18. The expansion valve 11 reduces the pressure of the refrigerant flowing through the expansion valve 11. The indoor heat exchanger 12 is disposed inside the indoor unit 3. The indoor heat exchanger 12 exchanges heat between the refrigerant flowing through the indoor heat exchanger 12 and the air passing through the indoor heat exchanger 12. The indoor unit 3 is equipped with an indoor fan 22. The indoor fan 22 passes air from the room in which the indoor unit 3 is installed through the indoor heat exchanger 12, and blows the air that has exchanged heat with the refrigerant by the indoor heat exchanger 12 into the room.

[0015] The air conditioner 1 further comprises a differential pressure detection means 24, a room temperature sensor 25, and a remote control 26. The differential pressure detection means 24 is disposed inside the outdoor unit 2, and comprises a suction pressure sensor 28 and a discharge pressure sensor 29. The suction pressure sensor 28 measures the pressure of the refrigerant flowing through the suction pipe 14. The discharge pressure sensor 29 measures the pressure of the refrigerant flowing through the discharge pipe 15. The room temperature sensor 25 is provided in the indoor unit 3. The room temperature sensor 25 measures the room temperature of the room in which the indoor unit 3 is installed. The remote control 26 is an input device that is operated by the user to determine cooling or heating operation and set the set temperature. The air conditioner 1 further comprises a control device 31.

[0016] 2 is a block diagram showing the control device 31. The control device 31 is a computer and includes a storage device 32 and a CPU (Central Processing Unit) 33. The storage device 32 stores computer programs installed in the control device 31 and stores information used by the CPU 33. The CPU 33 executes the computer programs installed in the control device 31. The control device 31 is connected to the compressor 6, the four-way valve 7, and the outdoor fan 21, and is also connected to the room temperature sensor 25, the remote control 26, the suction pressure sensor 28, and the discharge pressure sensor 29.

[0017] The control device 31 performs multiple functions by executing a computer program. The control device 31 has, as its multiple functions, a four-way valve control unit 34, a compressor control unit 35, a compressor frequency change rate calculation unit 36, a target differential pressure calculation unit 37, an outdoor fan feedforward control unit 38, and an outdoor fan feedback control unit 39. The four-way valve control unit 34 controls the four-way valve 7 so that the refrigerant circuit 5 switches to either the heating cycle or the cooling cycle, selected based on information acquired from the remote control 26. The compressor control unit 35 controls the compressor 6 to adjust the compressor frequency based on the room temperature measured by the room temperature sensor 25 and the set temperature set by the remote control 26.

[0018] The compressor frequency change rate calculation unit 36 ​​stores the compressor frequency adjusted by the compressor control unit 35 in the storage device 32 at predetermined control intervals. The compressor frequency change rate calculation unit 36 ​​calculates the compressor frequency change rate based on the current compressor frequency to be adjusted by the compressor control unit 35 and the previous compressor frequency stored in the storage device 32. The compressor frequency change rate is equal to a value calculated by dividing the current compressor frequency by the previous compressor frequency. The target differential pressure calculation unit 37 determines a frequency range that includes the current compressor frequency adjusted by the compressor control unit 35. The target differential pressure calculation unit 37 further calculates a target differential pressure based on the current compressor frequency adjusted by the compressor control unit 35. The frequency range and the target differential pressure are set according to the specifications of the compressor 6.

[0019] The outdoor fan feedforward control unit 38 calculates the manipulated variable based on the compressor frequency change rate calculated by the compressor frequency change rate calculation unit 36 ​​and the frequency range determined by the target differential pressure calculation unit 37. The outdoor fan feedforward control unit 38 controls the outdoor fan 21 to adjust the outdoor fan frequency so that the outdoor fan frequency changes by the calculated manipulated variable.

[0020] The outdoor fan feedback control unit 39 acquires the differential pressure from the differential pressure detection means 24. The differential pressure is equal to a value calculated by subtracting the suction pressure measured by the suction pressure sensor 28 from the discharge pressure measured by the discharge pressure sensor 29. When the differential pressure is greater than the target differential pressure calculated by the target differential pressure calculation unit 37, the outdoor fan feedback control unit 39 controls the outdoor fan 21 to adjust the outdoor fan frequency so that the outdoor fan frequency becomes higher. Furthermore, when the differential pressure is smaller than the target differential pressure calculated by the target differential pressure calculation unit 37, the outdoor fan feedback control unit 39 controls the outdoor fan 21 to adjust the outdoor fan frequency so that the outdoor fan frequency becomes lower.

[0021] 3 is a graph showing the relationship between the compressor frequency of the compressor 6 and the target differential pressure. The compressor frequency of the compressor 6 is included in either a fluctuation region 41 or a constant region 42. The fluctuation region 41 has a first fluctuation region 43 and a second fluctuation region 44. The compressor frequency included in the first fluctuation region 43 is smaller than a first threshold value 45. The compressor frequency included in the constant region 42 is larger than the first threshold value 45 and smaller than a second threshold value 46 that is larger than the first threshold value 45. The compressor frequency included in the second fluctuation region 44 is larger than the second threshold value 46. The first threshold value 45 and the second threshold value 46 are set according to the specifications of the compressor 6.

[0022] The broken line 47 in the graph of FIG. 3 represents the target differential pressure calculated by the target differential pressure calculation unit 37. When the compressor frequency is within the first fluctuation region 43, the target differential pressure is smaller than the constant C and increases monotonically with the compressor frequency. That is, the target differential pressure change rate, calculated by dividing the change in the target differential pressure by the change in the compressor frequency, is equal to a first change rate 48 greater than 0 when the compressor frequency is within the first fluctuation region 43. When the compressor frequency is within the constant region 42, the target differential pressure is equal to the constant C and is constant with respect to the compressor frequency. That is, the target differential pressure change rate is equal to 0 when the compressor frequency is within the constant region 42. When the compressor frequency is within the second fluctuation region 44, the target differential pressure is greater than the constant C and increases monotonically with the compressor frequency. When the compressor frequency is within the second fluctuation region 44, the target differential pressure change rate is equal to a second change rate 49 greater than the first change rate 48. The constant C is a value that is determined in advance in accordance with the specifications of the compressor 6 so as to ensure the reliability of the compressor 6.

[0023] [Operation of Air Conditioner 1] The operations performed by the air conditioner 1 include heating operation, cooling operation, compressor frequency control, and outdoor fan frequency control. [Heating operation] The heating operation is executed, for example, when the user operates the remote control 26 to select the heating operation. When the heating operation is executed, the control device 31 controls the four-way valve 7 to switch the refrigerant circuit 5 to the heating cycle and start the compressor 6. The compressor 6 compresses the low-pressure gas-phase refrigerant that is sucked into the compressor 6 from the four-way valve 7 through the suction pipe 14. The low-pressure gas-phase refrigerant is compressed by the compressor 6 to become high-pressure gas-phase refrigerant. The high-pressure gas-phase refrigerant is discharged from the compressor 6 to the discharge pipe 15, and because the refrigerant circuit 5 has switched to the heating cycle, it flows into the indoor heat exchanger 12 through the four-way valve 7 and the indoor gas pipe 19.

[0024] The indoor fan 22 of the indoor unit 3 passes air from the room in which the indoor unit 3 is installed through the indoor heat exchanger 12. The indoor heat exchanger 12 exchanges heat between the high-pressure gas-phase refrigerant and the air passing through the indoor heat exchanger 12, heating the air and cooling the high-pressure gas-phase refrigerant. The indoor fan 22 then blows the air heated by the indoor heat exchanger 12 into the room. The room in which the indoor unit 3 is installed is heated by blowing the air heated by the indoor heat exchanger 12 into the room. The high-pressure gas-phase refrigerant is cooled and condensed by the indoor heat exchanger 12 to become a high-pressure liquid-phase refrigerant. That is, the indoor heat exchanger 12 functions as a condenser when heating operation is performed.

[0025] The high-pressure liquid-phase refrigerant flows from the indoor heat exchanger 12 through the indoor liquid pipe 18 into the expansion valve 11. The expansion valve 11 reduces the pressure of the high-pressure liquid-phase refrigerant. The high-pressure liquid-phase refrigerant is reduced in pressure by the expansion valve 11 and becomes a low-pressure gas-liquid two-phase refrigerant. The low-pressure gas-liquid two-phase refrigerant flows from the expansion valve 11 through the outdoor liquid pipe 17 into the outdoor heat exchanger 8.

[0026] The outdoor fan 21 of the outdoor unit 2 passes outdoor air from the outdoor area where the outdoor unit 2 is installed through the outdoor heat exchanger 8. The outdoor heat exchanger 8 exchanges heat between the outdoor air passing through the outdoor heat exchanger 8 and low-pressure gas-liquid two-phase refrigerant, heating the low-pressure gas-liquid two-phase refrigerant. The low-pressure gas-liquid two-phase refrigerant is heated by the outdoor heat exchanger 8, causing it to evaporate and become low-pressure gas-phase refrigerant. In other words, the outdoor heat exchanger 8 functions as an evaporator when heating operation is performed. The low-pressure gas-phase refrigerant flows from the outdoor heat exchanger 8 through the outdoor gas pipe 16 into the four-way valve 7, and because the refrigerant circuit 5 is switched to the heating cycle, it is drawn into the compressor 6 through the four-way valve 7 and the suction pipe 14.

[0027] [Cooling operation] Cooling operation is performed, for example, when the user operates the remote control 26 to select cooling operation. When the air conditioner 1 performs cooling operation, the control device 31 controls the four-way valve 7 to switch the refrigerant circuit 5 to the cooling cycle and start the compressor 6. The compressor 6 compresses the low-pressure gas-phase refrigerant that has been sucked into the compressor 6 from the four-way valve 7 via the suction pipe 14. The low-pressure gas-phase refrigerant is compressed by the compressor 6 to become high-pressure gas-phase refrigerant. The high-pressure gas-phase refrigerant is discharged from the compressor 6 to the discharge pipe 15, and because the refrigerant circuit 5 has switched to the cooling cycle, it flows into the outdoor heat exchanger 8 via the four-way valve 7 and the outdoor gas pipe 16.

[0028] The outdoor fan 21 of the outdoor unit 2 passes outdoor air through the outdoor heat exchanger 8. The outdoor heat exchanger 8 exchanges heat between the high-pressure gas-phase refrigerant and the outdoor air, cooling the high-pressure gas-phase refrigerant. The high-pressure gas-phase refrigerant is cooled and condensed by the outdoor heat exchanger 8 to become a high-pressure liquid-phase refrigerant. In other words, the outdoor heat exchanger 8 functions as a condenser when cooling operation is performed. The high-pressure liquid-phase refrigerant flows from the outdoor heat exchanger 8 through the outdoor liquid pipe 17 into the expansion valve 11. The expansion valve 11 reduces the pressure of the high-pressure liquid-phase refrigerant. The high-pressure liquid-phase refrigerant is reduced in pressure by the expansion valve 11 to become a low-pressure two-phase gas-liquid refrigerant. The low-pressure two-phase gas-liquid refrigerant flows from the expansion valve 11 through the indoor liquid pipe 18 into the indoor heat exchanger 12.

[0029] The indoor fan 22 of the indoor unit 3 passes air from the room where the indoor unit 3 is installed through the indoor heat exchanger 12. The indoor heat exchanger 12 exchanges heat between the low-pressure gas-liquid two-phase refrigerant and the air, cooling the air and heating the low-pressure gas-liquid two-phase refrigerant. The indoor fan 22 then blows the air cooled by the indoor heat exchanger 12 into the room. The room where the indoor unit 3 is installed is cooled by blowing the air cooled by the indoor heat exchanger 12 into the room. The low-pressure gas-liquid two-phase refrigerant is heated by the indoor heat exchanger 12 and evaporates, becoming low-pressure gas-phase refrigerant. In other words, the indoor heat exchanger 12 functions as an evaporator when cooling operation is performed. The low-pressure gas-phase refrigerant flows from the indoor heat exchanger 12 into the four-way valve 7 via the indoor gas pipe 19. Because the refrigerant circuit 5 is switched to the cooling cycle, it is drawn into the compressor 6 via the four-way valve 7 and the suction pipe 14.

[0030] [Compressor frequency control] Compressor frequency control is performed in parallel with heating or cooling operation while the heating or cooling operation is being performed. During heating or cooling operation, the user may operate the remote control 26 to set a set temperature in the air conditioner 1. During compressor frequency control, the control device 31 acquires the set temperature set in the air conditioner 1 and intermittently acquires the room temperature measured by the room temperature sensor 25 from the room temperature sensor 25. The control device 31 calculates the temperature difference between the room temperature and the set temperature.

[0031] The control device 31 calculates a target compressor frequency based on the temperature difference, and controls the compressor 6 to adjust the compressor frequency so that it is equal to the target compressor frequency. As a result of compressor frequency control being executed, the compressor frequency of the compressor 6 fluctuates in accordance with the air conditioning load applied to the air conditioner 1 when heating operation or cooling operation is performed, increasing as the air conditioning load increases and decreasing as the air conditioning load decreases.

[0032] [Outdoor fan frequency control] The outdoor fan frequency control is repeatedly executed at predetermined control intervals in parallel with the cooling operation while the cooling operation is being performed. FIG. 4 is a flowchart showing the outdoor fan frequency control. In the outdoor fan frequency control, feedforward control of the outdoor fan 21 is executed. In the feedforward control of the outdoor fan 21, the control device 31 acquires the previous compressor frequency (step S1) and stores the previous compressor frequency in the storage device 32. The previous compressor frequency indicates the compressor frequency adjusted by the compressor frequency control immediately before the processing of step S1 is executed. The control device 31 determines whether the current compressor frequency to be adjusted by the compressor control unit 35 has changed from the previous compressor frequency (step S2).

[0033] When the current compressor frequency has changed from the previous compressor frequency (step S2-Yes), the control device 31 calculates a compressor frequency change rate based on the current compressor frequency and the previous compressor frequency, and calculates a target differential pressure based on the current compressor frequency (step S3). The compressor frequency change rate is equal to a value calculated by dividing the current compressor frequency by the previous compressor frequency. The target differential pressure is equal to the target differential pressure corresponding to the current compressor frequency in the graph of FIG. 3.

[0034] The control device 31 sets the manipulated variable based on the current compressor frequency and the compressor frequency change rate (steps S4 to S8). The manipulated variable is equal to a value calculated by multiplying the compressor frequency change rate by the control parameter. When the current compressor frequency is within the constant range 42 (step S4-Yes), the control parameter is set to a first value (step S5). The first value is, for example, a value that is determined in advance by predicting a change in differential pressure caused by a change in the compressor frequency when the compressor frequency is within the constant range 42.

[0035] The control parameter is set to a second value (step S7) when the current compressor frequency is not within the constant region 42 (step S4-No) and when the current compressor frequency is within the first fluctuation region 43 (step S6-Yes). The second value is smaller than the first value, and is, for example, 50% of the first value when the first value is 100%. The second value is, for example, a value that is determined in advance by predicting a change in differential pressure caused by a change in the compressor frequency when the compressor frequency is within the first fluctuation region 43.

[0036] The control parameter is set to a third value (step S8) when the current compressor frequency is not within the first fluctuation region 43 (step S6-No), that is, when the current compressor frequency is within the second fluctuation region 44. The third value is smaller than the second value, and is, for example, a value that is 25% of the first value when the first value is 100%. The third value is, for example, a value that is determined in advance by predicting a change in differential pressure caused by a change in the compressor frequency when the compressor frequency is within the second fluctuation region 44. Therefore, the manipulated variable when the compressor frequency is within the fluctuation region 41 is smaller than the manipulated variable when the compressor frequency is within the constant region 42 when the compressor frequency change rate is the same value.

[0037] The control device 31 controls the outdoor fan 21 and adjusts the outdoor fan frequency so that the outdoor fan frequency changes by the manipulated variable set in the processing of steps S4 to S8 (step S9). The volume of outdoor air passing through the outdoor heat exchanger 8 increases as the outdoor fan frequency increases, and decreases as the outdoor fan frequency decreases. The amount of heat exchanged between the refrigerant and the outdoor air by the outdoor heat exchanger 8 increases as the volume of outdoor air passing through the outdoor heat exchanger 8 increases, and decreases as the volume of outdoor air passing through the outdoor heat exchanger 8 decreases. The control device 31 executes feedback control of the outdoor fan 21 (step S10) when the current compressor frequency is equal to the previous compressor frequency (step S2-No) or after the outdoor fan frequency has been adjusted in the processing of step S9.

[0038] 5 is a flowchart showing the feedback control of the outdoor fan 21. The control device 31 acquires the differential pressure from the differential pressure detection means 24 (step S11). That is, the control device 31 acquires the suction pressure measured by the suction pressure sensor 28 from the suction pressure sensor 28, and acquires the discharge pressure measured by the discharge pressure sensor 29 from the discharge pressure sensor 29. The control device 31 calculates the differential pressure based on the suction pressure and the discharge pressure. The differential pressure is equal to a value calculated by subtracting the suction pressure from the discharge pressure.

[0039] The control device 31 determines whether the differential pressure is larger or smaller than the target differential pressure calculated in the processing of step S3. When the control device 31 determines that the differential pressure is equal to the target differential pressure (step S12-Yes), it controls the outdoor fan 21 and maintains the outdoor fan frequency so that the outdoor fan frequency does not change (step S13). Here, "equal" does not only mean a state of being strictly equal, but also a state where there is a tolerance or a difference to the extent that the same function is obtained. When the control device 31 determines that the differential pressure is not equal to the target differential pressure (step S12-No) or that the differential pressure is smaller than the target differential pressure (step S14-Yes), it controls the outdoor fan 21 and adjusts the outdoor fan frequency so that the outdoor fan frequency is lower (step S15). When it is determined that the differential pressure is not smaller than the target differential pressure (step S14-No), that is, when it is determined that the differential pressure is larger than the target differential pressure, the control device 31 controls the outdoor fan 21 and adjusts the outdoor fan frequency so that the outdoor fan frequency increases (step S16). Here, the manipulated variable in the feedback control of the outdoor fan 21 is set by, for example, PID control.

[0040] After the process of step S15 or step S16 is completed, the control device 31 again acquires the differential pressure from the differential pressure detection means 24 (step S11). The control device 31 repeatedly executes the processes of steps S11 to S16 until the differential pressure becomes equal to the target differential pressure (step S12-Yes).

[0041] In the air conditioner 1, for example, when the differential pressure falls far below the target differential pressure, causing vanes (not shown) inside the compressor 6 to skip, a malfunction such as wear on the sliding parts of the compressor 6 can occur. Here, the vanes are pressed against rollers (not shown) inside the compressor 6 by the biasing force of a vane spring (not shown) inside the compressor 6 and the pressure of the compressed, high-pressure discharge gas acting as back pressure. Vane skipping is a phenomenon in which the vanes separate from the rollers due to reduced compliance with the rollers caused by insufficient back pressure. When the differential pressure exceeds the target differential pressure to the extent that the air conditioning capacity exceeds the air conditioning load, the air conditioner 1 can experience a malfunction in which power consumption increases and operating efficiency deteriorates. By executing feedforward control of the outdoor fan 21, the air conditioner 1 can prevent the differential pressure from deviating so far from the target differential pressure that the malfunction described above occurs. When the target differential pressure change rate differs, the amount of outdoor fan frequency control required to maintain the differential pressure may change in response to changes in the compressor frequency. The air conditioner 1 can more appropriately perform feedforward control of the outdoor fan 21 by changing the manipulated variable in accordance with the target differential pressure change rate, and can more appropriately prevent the differential pressure from significantly deviating from the target differential pressure because the outdoor fan frequency changes in advance in accordance with changes in the compressor frequency. Furthermore, the air conditioner 1 executes feedback control of the outdoor fan 21, so that even when the differential pressure deviates from the target differential pressure, the outdoor fan frequency changes so that the differential pressure becomes equal to the target differential pressure, thereby shortening the period during which the differential pressure deviates from the target differential pressure.

[0042] Fig. 6 is a time chart showing changes in the target differential pressure, differential pressure, compressor frequency, and outdoor fan frequency in the air conditioner 1 of Example 1 when the compressor frequency is within constant region 42 and when the compressor frequency is controlled to be reduced. Curve 51 in the time chart of Fig. 6 shows changes in the compressor frequency of compressor 6. Curve 51 shows that as a result of compressor frequency control being executed, the compressor frequency is reduced during period 55 between time t1 and time t2, and that the compressor frequency remains constant during the period after time t2.

[0043] Curve 52 in the time chart of Fig. 6 shows changes in the target differential pressure. Curve 52 shows that, because the compressor frequency is included in constant region 42, the target differential pressure remains constant during period 55 even when the compressor frequency decreases. Curve 53 in the time chart of Fig. 6 shows changes in the outdoor fan frequency of outdoor fan 21. Curve 53 shows that, because feedforward control of outdoor fan 21 is executed, the outdoor fan frequency is adjusted when the compressor frequency decreases, and the outdoor fan frequency decreases during period 55 when the compressor frequency decreases.

[0044] Curve 54 in the time chart of Fig. 6 shows changes in the differential pressure. When the outdoor fan frequency is constant and the compressor frequency is reduced, the differential pressure decreases and may become smaller than the target differential pressure. Curve 54 shows that, as the outdoor fan frequency decreases during period 55, the differential pressure does not decrease during period 55, and the differential pressure remains approximately equal to the target differential pressure during period 55. In other words, the time chart of Fig. 6 shows that, by performing feedforward control on the outdoor fan 21, the air conditioner 1 can prevent the differential pressure from significantly deviating from the target differential pressure when the compressor frequency is within the constant region 42.

[0045] Fig. 7 is a time chart showing other changes in the target differential pressure, differential pressure, compressor frequency, and outdoor fan frequency in the air conditioner 1 of Example 1 when the compressor frequency is within the constant region 42 and when the compressor frequency is controlled to be reduced. Curve 61 in the time chart of Fig. 7 shows changes in the compressor frequency of the compressor 6. Curve 61 shows that the compressor frequency is reduced during a period 65 between time t11 and time t12 as a result of compressor frequency control being executed, and that the compressor frequency remains constant during the period after time t12.

[0046] Curve 62 in the time chart of Fig. 7 shows changes in the target differential pressure. Curve 62 shows that, because the compressor frequency is included in constant region 42, the target differential pressure remains constant without change during period 65, even when the compressor frequency decreases. Curve 63 in the time chart of Fig. 7 shows changes in the outdoor fan frequency of outdoor fan 21. Curve 63 shows that, because feedforward control of outdoor fan 21 is executed, the outdoor fan frequency is adjusted when the compressor frequency decreases, and the outdoor fan frequency decreases during period 65 when the compressor frequency decreases. Curve 63 further shows that the outdoor fan frequency remains constant without change during the period from time t12 onwards, when the compressor frequency becomes constant.

[0047] Curve 64 in the time chart of Fig. 7 shows changes in the differential pressure. Curve 64 shows that the differential pressure may decrease during period 65 due to a decrease in the compressor frequency, and that the differential pressure may become smaller than the target differential pressure during period 65. In other words, curve 64 shows that when the compressor frequency is within the constant region 42 and feedforward control of the outdoor fan 21 is insufficient, the differential pressure may become smaller than the target differential pressure.

[0048] The air conditioner 1 executes feedback control of the outdoor fan 21 after a period 65 in which feedforward control of the outdoor fan 21 is executed to adjust the outdoor fan frequency. Curve 63 shows that when it is determined that the differential pressure is smaller than the target differential pressure as a result of the execution of feedback control of the outdoor fan 21, the outdoor fan frequency decreases after time t13. Curve 64 shows that the differential pressure increases after time t13 as a result of the outdoor fan frequency decreasing after time t13.

[0049] Curve 63 further indicates that, as a result of feedback control of the outdoor fan 21 being executed, the outdoor fan frequency does not decrease but remains constant after time t14, when the differential pressure becomes approximately equal to the target differential pressure. Curve 64 indicates that, as the outdoor fan frequency becomes constant after time t14, the differential pressure does not increase after time t14 and is maintained approximately at the target differential pressure. In other words, the time chart in Fig. 7 indicates that the air conditioner 1 can prevent the differential pressure from significantly deviating from the target differential pressure, even when feedforward control of the outdoor fan 21 is insufficient.

[0050] Fig. 8 is a time chart showing changes in the target differential pressure, differential pressure, compressor frequency, and outdoor fan frequency in the air conditioner 1 of Example 1 when the compressor frequency is within fluctuation region 41 and is controlled to be lower. Curve 71 in the time chart of Fig. 8 shows changes in the compressor frequency of compressor 6. Curve 71 shows that as a result of compressor frequency control being executed, the compressor frequency is lowered during period 75 between time t21 and time t22, and that the compressor frequency remains constant during the period after time t22.

[0051] Curve 72 in the time chart of Fig. 8 shows changes in the target differential pressure. Curve 72 shows that, because the compressor frequency is included in fluctuation region 41, when the compressor frequency decreases, the target differential pressure decreases along with the compressor frequency. Curve 73 in the time chart of Fig. 8 shows changes in the outdoor fan frequency of the outdoor fan 21. Curve 73 shows that, because feedforward control of the outdoor fan 21 is executed, the outdoor fan frequency is adjusted when the compressor frequency decreases, and the outdoor fan frequency decreases in period 75 when the compressor frequency decreases.

[0052] Curve 74 in the time chart of Fig. 8 shows the change in the differential pressure. Curve 74 shows that the outdoor fan frequency decreases during period 75 when the compressor frequency decreases, thereby reducing the differential pressure and maintaining a state in which the differential pressure is approximately equal to the target differential pressure. In other words, the time chart of Fig. 8 shows that by performing feedforward control on the outdoor fan 21, the air conditioner 1 can prevent the differential pressure from significantly deviating from the target differential pressure, even when the compressor frequency is within fluctuation region 41.

[0053] Fig. 9 is a time chart showing other changes in the target differential pressure, differential pressure, compressor frequency, and outdoor fan frequency in the air conditioner 1 of Example 1 when the compressor frequency is within fluctuation region 41 and is controlled to be lower. Curve 81 in the time chart of Fig. 9 shows changes in the compressor frequency of compressor 6. Curve 81 shows that as a result of compressor frequency control being executed, the compressor frequency is lowered during period 85 between time t31 and time t32, and that the compressor frequency remains constant during the period after time t32.

[0054] Curve 82 in the time chart of Fig. 9 shows changes in the target differential pressure. Curve 82 shows that, because the compressor frequency is included in fluctuation region 41, when the compressor frequency decreases, the target differential pressure decreases along with the compressor frequency. Curve 83 in the time chart of Fig. 9 shows changes in the outdoor fan frequency of the outdoor fan 21. Curve 83 shows that, because feedforward control of the outdoor fan 21 is executed, the outdoor fan frequency is adjusted when the compressor frequency decreases, and the outdoor fan frequency decreases in period 85 when the compressor frequency decreases. Curve 83 further shows that the outdoor fan frequency remains constant without change in the period after time t32 when the compressor frequency becomes constant.

[0055] Curve 84 in the time chart of FIG. 9 indicates changes in the differential pressure. Curve 84 indicates that the differential pressure decreases as the outdoor fan frequency decreases during period 85 when the compressor frequency decreases, and that the differential pressure may become smaller than the target differential pressure during period 85. In other words, curve 84 indicates that even when the compressor frequency is within fluctuation range 41, the differential pressure may become smaller than the target differential pressure if feedforward control of the outdoor fan 21 is insufficient. The air conditioner 1 executes feedback control of the outdoor fan 21 after period 85, when feedforward control of the outdoor fan 21 is executed to adjust the outdoor fan frequency. Curve 83 indicates that the outdoor fan frequency decreases after time t33, when it is determined that the differential pressure is smaller than the target differential pressure, due to the execution of feedback control of the outdoor fan 21. Curve 84 indicates that the outdoor fan frequency decreases after time t33, causing the differential pressure to increase after time t33.

[0056] Curve 83 further indicates that, as a result of feedback control of the outdoor fan 21 being executed, the outdoor fan frequency does not decrease but remains constant after time t34, when the differential pressure becomes approximately equal to the target differential pressure. Curve 84 indicates that, as the outdoor fan frequency becomes constant after time t34, the differential pressure does not increase after time t34 and is maintained at approximately the target differential pressure. In other words, the time chart in Fig. 9 indicates that the air conditioner 1 can prevent the differential pressure from significantly deviating from the target differential pressure, even when the compressor frequency is within the fluctuation region 41 and feedforward control of the outdoor fan 21 is insufficient.

[0057] The air conditioner of the comparative example is configured similarly to the air conditioner 1 of the above-described embodiment 1. In the operation of the air conditioner of the comparative example, the feedforward control of the outdoor fan 21 in steps S4 to S9 of the operation of the above-described air conditioner 1 is not performed, but the above-described feedback control of the outdoor fan 21 is performed.

[0058] Fig. 10 is a time chart showing changes in the target differential pressure, differential pressure, compressor frequency, and outdoor fan frequency in an air conditioner of a comparative example when the compressor frequency is within constant region 42 and is controlled to be lower. Curve 101 in the time chart of Fig. 10 shows changes in the compressor frequency of compressor 6 in the air conditioner of the comparative example. Curve 101 shows that as a result of compressor frequency control being executed, the compressor frequency is lowered during period 105 between time t101 and time t102, and that the compressor frequency becomes constant after time t102.

[0059] Curve 102 in the time chart of Fig. 10 shows the change in the target differential pressure. Curve 102 shows that the target differential pressure remains constant even when the compressor frequency decreases because the compressor frequency is included in constant region 42. Curve 103 in the time chart of Fig. 10 shows the change in the outdoor fan frequency of outdoor fan 21 in the air conditioner of the comparative example. Curve 103 shows that the outdoor fan frequency remains constant even when the compressor frequency decreases because feedforward control of outdoor fan 21 is not executed in the air conditioner of the comparative example.

[0060] Curve 104 in the time chart of Figure 10 shows the change in differential pressure in the air conditioner of the comparative example. Curve 104 shows that when the compressor frequency decreases, the differential pressure decreases because the outdoor fan frequency is constant, and that the differential pressure may fall significantly below the target differential pressure. Curve 103 shows that feedback control of the outdoor fan 21 is executed, causing the outdoor fan frequency to decrease after time t103 after period 105. Curve 104 shows that the differential pressure increases after time t103 as the outdoor fan frequency decreases.

[0061] Curve 103 shows that, as a result of feedback control of the outdoor fan 21 being executed, the outdoor fan frequency does not decrease but remains constant after time t104 when the differential pressure becomes approximately equal to the target differential pressure. Curve 104 shows that, as a result of the outdoor fan frequency becoming constant, the differential pressure does not increase after time t104 and is maintained approximately at the target differential pressure.

[0062] The time charts of Fig. 6, 8, and 10 show that the air conditioner 1 of Example 1 is more able to prevent the differential pressure from falling significantly below the target differential pressure than the air conditioner of the comparative example when the compressor frequency is within the constant region 42. The time charts of Fig. 8 and 10 show that even when the differential pressure falls below the target differential pressure when the compressor frequency is within the constant region 42, the air conditioner 1 of Example 1 can shorten the period during which the differential pressure is below the target differential pressure than the air conditioner of the comparative example. Therefore, the time charts of Fig. 6, 8, and 10 show that the air conditioner 1 of Example 1 is more able to prevent malfunctions in the compressor 6 caused by a small differential pressure than the air conditioner of the comparative example.

[0063] Fig. 11 is a time chart showing changes in the target differential pressure, differential pressure, compressor frequency, and outdoor fan frequency in an air conditioner of a comparative example when the compressor frequency is within fluctuation range 41 and is controlled to be lower. Curve 111 in the time chart of Fig. 11 shows changes in the compressor frequency of compressor 6 in the air conditioner of the comparative example. Curve 111 shows that as a result of compressor frequency control being executed, the compressor frequency decreases during period 115 between time t111 and time t112, and that the compressor frequency becomes constant after time t112.

[0064] Curve 112 in the time chart of Fig. 11 shows the change in the target differential pressure. Curve 112 shows that, because the compressor frequency is included in fluctuation region 41, the target differential pressure decreases along with the compressor frequency as the compressor frequency decreases. Curve 113 in the time chart of Fig. 11 shows the change in the outdoor fan frequency of the outdoor fan 21 of the air conditioner of the comparative example. Curve 113 shows that, because feedforward control of the outdoor fan 21 is not executed in the air conditioner of the comparative example, the outdoor fan frequency remains constant even as the compressor frequency decreases.

[0065] Curve 114 in the time chart of Figure 11 shows the change in differential pressure in the air conditioner of the comparative example. Curve 114 shows that when the compressor frequency decreases, the differential pressure decreases because the outdoor fan frequency is constant, and that the differential pressure may fall significantly below the target differential pressure. Curve 113 shows that feedback control of the outdoor fan 21 is performed, causing the outdoor fan frequency to decrease after time t113 after period 115. Curve 114 shows that the differential pressure increases after time t113 as the outdoor fan frequency decreases.

[0066] Curve 113 shows that the outdoor fan frequency does not decrease but remains constant after time t114 when the differential pressure becomes approximately equal to the target differential pressure due to the execution of feedback control of the outdoor fan 21. Curve 114 shows that the outdoor fan frequency becomes constant, so that the differential pressure does not increase after time t114 and is maintained approximately at the target differential pressure.

[0067] The time charts of Fig. 7, 9, and 11 show that the air conditioner 1 of Example 1 is more able to prevent the differential pressure from falling below the target differential pressure than the air conditioner of the comparative example when the compressor frequency is within fluctuation region 41. The time charts of Fig. 9 and 11 show that even when the differential pressure falls below the target differential pressure when the compressor frequency is within fluctuation region 41, the air conditioner 1 of Example 1 can shorten the period during which the differential pressure is below the target differential pressure than the air conditioner of the comparative example. Therefore, the time charts of Fig. 7, 9, and 11 show that the air conditioner 1 of Example 1 is more able to prevent malfunctions in the compressor 6 caused by the differential pressure falling below the target differential pressure than the air conditioner of the comparative example.

[0068] [Summary of the air conditioner 1 of Example 1] The air conditioner 1 of the first embodiment includes a compressor 6 that circulates refrigerant through a refrigerant circuit 5, an outdoor fan 21 that blows outdoor air to an outdoor heat exchanger 8 provided in the refrigerant circuit 5, and a control device 31 that controls the outdoor fan 21. The control device 31 controls the outdoor fan 21 so that the outdoor fan frequency changes by an amount of manipulated variable when the compressor frequency that drives the compressor 6 changes. The compressor frequency is included in either a fluctuation region 41 or a constant region 42. The constant region 42 is a region where a target differential pressure change rate, which is a rate of change of a target differential pressure that is a target value of the differential pressure between the pressure of refrigerant drawn into the compressor 6 and the pressure of refrigerant discharged from the compressor 6, is smaller than that in the fluctuation region 41. The manipulated variable is calculated based on the target differential pressure and the rate of change of the compressor frequency. The manipulated variable is smaller when the compressor frequency is included in the fluctuation region 41 than when it is included in the constant region 42. The air conditioner 1 of Example 1 can suppress deviation of the differential pressure from the target differential pressure by subjecting the outdoor fan 21 to feedforward control, and can prevent malfunctions caused by the differential pressure deviating significantly from the target differential pressure. Furthermore, the air conditioner 1 of Example 1 can appropriately feedforward control the outdoor fan 21 so that the differential pressure does not deviate significantly from the target differential pressure by changing the manipulated variable in accordance with the target differential pressure change rate.

[0069] The air conditioner 1 of Example 1 further includes differential pressure detection means 24 that detects the differential pressure. The control device 31 also feedback-controls the outdoor fan 21 so that the differential pressure is equal to the target differential pressure. In this case, by feedback-controlling the outdoor fan 21, the air conditioner 1 of Example 1 can shorten the period during which the differential pressure significantly deviates from the target differential pressure even when feedforward control of the outdoor fan 21 is insufficient.

[0070] In addition, in the constant region 42 of the air conditioner 1 of Example 1, the target differential pressure is constant with respect to the compressor frequency. In the fluctuation region 41, the target differential pressure monotonically increases with respect to the compressor frequency. The fluctuation region 41 includes a first fluctuation region 43 and a second fluctuation region 44. The target differential pressure change rate is equal to a first change rate 48 when the compressor frequency is within the first fluctuation region 43, and equal to a second change rate 49 when the compressor frequency is within the second fluctuation region 44. The second change rate 49 is greater than the first change rate 48. The manipulated variable is calculated based on a first value when the compressor frequency is within the constant region 42. The manipulated variable is calculated based on a second value smaller than the first value when the compressor frequency is within the first fluctuation region 43. The manipulated variable is calculated based on a third value smaller than the second value when the compressor frequency is within the second fluctuation region 44. In this case, the air conditioner 1 of Example 1 can appropriately feedforward control the outdoor fan 21 so that the differential pressure does not deviate significantly from the target differential pressure, even when the fluctuation region 41 includes a first fluctuation region 43 and a second fluctuation region 44 which have different target differential pressure change rates.

[0071] Incidentally, the third value of the air conditioner 1 described above is smaller than the second value, but may be equal to the second value. Even in this case, the air conditioner 1 of the first embodiment can appropriately perform feedforward control of the outdoor fan 21 based on the compressor frequency, thereby improving the reliability of the compressor 6.

[0072] Incidentally, the target differential pressure change rate in the second fluctuation region 44 of the air conditioner 1 described above is greater than the target differential pressure change rate in the first fluctuation region 43, but may be smaller than the target differential pressure change rate in the first fluctuation region 43 and greater than the target differential pressure change rate in the constant region 42. In this case, the third value is greater than the first value and smaller than the second value. Alternatively, the third value may be equal to the second value. Even in this case, the air conditioner 1 of the first embodiment can appropriately feedforward control the outdoor fan 21 based on the compressor frequency, thereby improving the reliability of the compressor 6.

[0073] Incidentally, the target differential pressure of the air conditioner 1 of the first embodiment described above is constant relative to the compressor frequency when the target differential pressure is within the constant region 42, but may also increase monotonically relative to the compressor frequency. In this case, the rate of change of the target differential pressure in the constant region 42 is smaller than the rate of change of the target differential pressure in the first fluctuation region 43 and is also smaller than the rate of change of the target differential pressure in the second fluctuation region 44. Even in this case, the air conditioner 1 of the first embodiment can appropriately feedforward control the outdoor fan 21 based on the compressor frequency, thereby improving the reliability of the compressor 6.

[0074] Incidentally, although the fluctuation range 41 of the air conditioner 1 of the first embodiment described above includes the second fluctuation range 44, it does not have to include the second fluctuation range 44. Even in this case, the air conditioner 1 of the first embodiment can appropriately perform feedforward control of the outdoor fan 21 based on the compressor frequency, thereby improving the reliability of the compressor 6.

[0075] Although the embodiments have been described above, the embodiments are not limited to the above content. Furthermore, the above-described components include those that can be easily imagined by a person skilled in the art, those that are substantially the same, and those that are within the so-called equivalent range. Furthermore, the above-described components can be combined as appropriate. Furthermore, at least one of various omissions, substitutions, and modifications of the components can be made without departing from the spirit of the embodiments. [Explanation of symbols]

[0076] 1: Air conditioner 5: Refrigerant circuit 6: Compressor 8:Outdoor heat exchanger 21: Outdoor fan 24: Differential pressure detection means 31: Control device 41: Variable area 42: Fixed area 43: First variable area 44: Second variable area 45: First threshold 46: Second threshold 48: First rate of change 49: Second rate of change

Claims

1. a compressor that circulates a refrigerant through a refrigerant circuit; an outdoor fan that blows outside air to a condenser provided in the refrigerant circuit; a control device for controlling the outdoor fan, the control device controls the outdoor fan so that the outdoor fan frequency changes by an amount of operation when a compressor frequency that drives the compressor changes; the compressor frequency is in either a variable domain or a constant domain; the constant region is a region in which a target differential pressure change rate, which is a change rate of a target differential pressure, which is a target value of a differential pressure between a pressure of suction refrigerant sucked into the compressor and a pressure of discharge refrigerant discharged from the compressor, with respect to the compressor frequency, is smaller than that of the variable region; the manipulated variable is calculated in accordance with the target differential pressure and the rate of change of the compressor frequency, The manipulated variable is smaller when the compressor frequency is in the variable region than when it is in the constant region. Air conditioner.

2. Further, a differential pressure detection means for detecting the differential pressure is provided, The control device further feedback controls the outdoor fan so that the differential pressure becomes equal to the target differential pressure. The air conditioner according to claim 1.

3. The variable region includes a region in which the compressor frequency is lower than the constant region, but does not include the compressor frequency of the constant region. The air conditioner according to claim 1.

4. In the constant region, the target differential pressure with respect to the compressor frequency becomes constant, In the fluctuation region, the target differential pressure increases monotonically with respect to the compressor frequency, the variable region includes a first variable region and a second variable region, The target differential pressure change rate is when the compressor frequency is within a first fluctuation region, the first rate of change is equal to a first rate of change; when the compressor frequency is within a second variation range, the second rate of change is equal to a second rate of change that is greater than the first rate of change; The manipulated variable is When the compressor frequency is within the certain range, the calculated value is based on a first value; When the compressor frequency is included in the first fluctuation range, the calculated value is based on a second value that is smaller than the first value, When the compressor frequency is included in the second fluctuation range, the frequency is calculated based on a third value that is smaller than the second value. The air conditioner according to claim 3.

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