Air conditioning device

Abstract

An air conditioning device according to one embodiment of the present invention is provided with: an outdoor unit having a plurality of outdoor heat exchangers and an outdoor fan for blowing air to the plurality of outdoor heat exchangers; at least one indoor unit connected to the outdoor unit via a refrigerant pipe; and a control device for controlling the rotation speed of the outdoor fan. When the number of outdoor heat exchangers used is increased, the control device determines the rotation speed of the outdoor fan so that the heat exchange amount in the outdoor heat exchanger after the number of outdoor heat exchangers is increased is less than or equal to the heat exchange amount in the outdoor heat exchanger before the number of outdoor heat exchangers is increased, and when the number of outdoor heat exchangers used is decreased, the rotation speed of the outdoor fan is determined so that the heat exchange amount in the outdoor heat exchanger before the number of outdoor heat exchangers is decreased. The rotation speed of the outdoor fan is determined so that the heat exchange amount in the outdoor heat exchanger after the number of the outdoor fans is reduced is greater than or equal to the heat exchange amount in the outdoor heat exchanger before the number of the outdoor fans is reduced.

Description

Technical Field

[0001] The present invention relates to an air conditioning apparatus, and more particularly, to an air conditioning apparatus including an outdoor unit having a plurality of outdoor heat exchangers. Background Art

[0002] There is known an air conditioning apparatus including an outdoor unit having a plurality of outdoor heat exchangers (see, for example, Patent Document 1). Such an air conditioning apparatus switches the number of outdoor heat exchangers to be used and the rotational speed of an outdoor fan according to the air conditioning capacity required by an indoor unit.

[0003] Prior Art Documents Patent Documents Patent Document 1: International Publication No. 2015 / 11141 Summary of the Invention Technical Problem to be Solved by the Invention However, when increasing the number of outdoor heat exchangers to be used in response to an increase in the air conditioning load caused by an increase in the required capacity from the indoor unit and a change in the external gas temperature, there is a case where the condensation capacity or evaporation capacity of the outdoor heat exchanger is greatly exceeded the required capacity due to the increase in the number. On the other hand, when decreasing the number of outdoor heat exchangers to be used in response to a decrease in the air conditioning load caused by a decrease in the required capacity from the indoor unit and a change in the external gas temperature, there is a case where the condensation capacity or evaporation capacity of the outdoor heat exchanger is much lower than the required capacity due to the decrease in the number. Thus, if the capacity becomes too large or too small when increasing or decreasing the number of outdoor heat exchangers to be used, the air conditioning apparatus decreases the number of outdoor heat exchangers to be used when the capacity is too large, and increases the number of outdoor heat exchangers to be used when the capacity is too small. Therefore, it is possible that the number of outdoor heat exchangers to be used is frequently and repeatedly increased and decreased.

[0004] In the case of having a plurality of outdoor heat exchangers, a flow path switching valve for switching the flow direction of the refrigerant in each outdoor heat exchanger is provided. As described above, during the operation of the air conditioning apparatus, due to a change in the required capacity from the indoor unit and a change in the air conditioning load caused by a change in the external gas temperature, the number of outdoor heat exchangers to be used is frequently and repeatedly increased and decreased. In this case, the flow path switching valve is switched according to the increase and decrease in the number of outdoor heat exchangers to be used, so that its operation sound is generated as noise. In addition, due to the frequent switching operation of the flow path switching valve, there is a problem of premature deterioration. Further, due to the frequent and repeated change in the capacity of the outdoor heat exchanger, there are problems of unstable temperature in the air conditioning space and deteriorated comfort.

[0005] In view of the above circumstances, an object of the present invention is to provide an air conditioning apparatus that can suppress noise, reduction in reliability, and deterioration in comfort caused by frequent increase and decrease in the number of operating outdoor heat exchangers.

[0006] Technical solution for solving technical problems An air conditioning apparatus according to an aspect of the present invention includes: a compressor; an outdoor unit having a plurality of outdoor heat exchangers, a plurality of flow path switching valves provided for each of the plurality of outdoor heat exchangers, and an outdoor fan, the plurality of flow path switching valves switching the connection of one refrigerant inlet / outlet of each outdoor heat exchanger to the refrigerant discharge port or the refrigerant suction port of the compressor, the outdoor fan blowing air to the plurality of outdoor heat exchangers; at least one indoor unit connected to the outdoor unit through a refrigerant pipe; and a control device that controls the rotational speed of the outdoor fan.

[0007] The control device determines whether to increase the number of operating outdoor heat exchangers based on the required air conditioning capacity. When it is determined to increase the number of operating outdoor heat exchangers, the control device determines the rotational speed of the outdoor fan so that the heat exchange amount in the outdoor heat exchanger after the number increase is less than or equal to the heat exchange amount in the outdoor heat exchanger before the number increase. The control device determines whether to decrease the number of operating outdoor heat exchangers based on the required air conditioning capacity. When it is determined to decrease the number of operating outdoor heat exchangers, the control device determines the rotational speed of the outdoor fan so that the heat exchange amount in the outdoor heat exchanger after the number decrease is greater than or equal to the heat exchange amount in the outdoor heat exchanger before the number decrease.

[0008] Alternatively, when the maximum value of the heat exchange amount in the outdoor heat exchanger before the number increase is set as the first heat exchange amount and the minimum value of the heat exchange amount in the outdoor heat exchanger after the number increase is set as the second heat exchange amount, when the control device determines to increase the number of operating outdoor heat exchangers, the control device determines the rotational speed of the outdoor fan so that the first heat exchange amount is greater than or equal to the second heat exchange amount.

[0009] Alternatively, when the maximum value of the heat exchange amount in the outdoor heat exchanger after the number decrease is set as the first heat exchange amount and the minimum value of the heat exchange amount in the outdoor heat exchanger before the number decrease is set as the second heat exchange amount, when the control device determines to decrease the number of operating outdoor heat exchangers, the control device determines the rotational speed of the outdoor fan so that the first heat exchange amount is greater than or equal to the second heat exchange amount.

[0010] Alternatively, when the value obtained by dividing the second heat exchange amount by the first heat exchange amount is used as the heat exchange amount change rate, the control device determines the rotation speed of the outdoor fan so that the heat exchange amount change rate is equal to or less than a given first threshold value.

[0011] Alternatively, the control device determines the rotation speed of the outdoor fan so that the heat exchange amount change rate is equal to or greater than a given second threshold value, where the second threshold value is less than the first threshold value.

[0012] Alternatively, the control device uses an evaluation index determined based on the volume of each outdoor heat exchanger, the air volume delivered by the outdoor fan, and the ratio of the air volume flowing through each outdoor heat exchanger to the air volume delivered as the heat exchange amount.

[0013] Advantageous Effects of the Invention According to the present invention, it is possible to suppress noise, a decrease in reliability, and deterioration of comfort caused by frequent increases and decreases in the number of operating outdoor heat exchangers. BRIEF DESCRIPTION OF THE DRAWINGS

[0014] Figure 1 It is a refrigerant circuit diagram showing a structural example of an air conditioner according to an embodiment of the present invention.

[0015] Figure 2 It is a block diagram showing the structure of a control device in the air conditioner.

[0016] Figure 3 It is a graph showing the relationship between the number of operating outdoor heat exchangers for main refrigeration operation, the heat exchange amount (condensing capacity) of the outdoor heat exchanger before and after the increase in the number of operating units, and the condensing temperature of the refrigerant in the outdoor heat exchanger.

[0017] Figure 4 It is a schematic diagram showing the relationship between the number of operating outdoor heat exchangers in the air conditioner and the control range of the rotation speed of the outdoor fan.

[0018] Figure 5 It is a flowchart showing an example of a processing procedure executed by the control device.

[0019] Figure 6 It is a diagram for explaining an operation of the air conditioner, showing the relationship between the number of operating outdoor heat exchangers for main refrigeration operation, the heat exchange amount (condensing capacity) of the outdoor heat exchanger before and after the increase in the number of operating units, and the condensing temperature of the refrigerant in the outdoor heat exchanger.

[0020] Figure 7 It is a graph showing the relationship between the first heat exchange amount and the second heat exchange amount of an outdoor heat exchanger functioning as a condenser in the air conditioner.

[0021] Figure 8 This is a diagram for explaining one function of the above air conditioner, showing the relationship between the number of outdoor heat exchangers used for the main heating operation, the heat exchange amount (evaporation capacity) of the outdoor heat exchanger before and after the increase in the number of used outdoor heat exchangers, and the evaporation temperature of the refrigerant in the outdoor heat exchanger.

[0022] Figure 9 This is a diagram showing the relationship between the first heat exchange amount and the second heat exchange amount of the outdoor heat exchanger that functions as an evaporator in the above air conditioner.

[0023] Figure 10 This is a refrigerant circuit diagram of an air conditioner according to another embodiment of the present invention. Detailed Embodiment

[0024] Hereinafter, embodiments of the present invention will be described with reference to the drawings.

[0025] Figure 1 This is a refrigerant circuit diagram showing a structural example of an air conditioner 10 according to an embodiment of the present invention. The air conditioner 10 includes a plurality of indoor units, and either cooling or heating can be selectively performed in each indoor unit (free cooling and heating mode). In the present embodiment, an air conditioner in which three indoor units 8a, 8b, and 8c are connected in parallel to one outdoor unit 2a will be described as an example.

[0026] [Air conditioner] First, with reference to Figure 1 , the structure and operation example of the air conditioner 10 will be described.

[0027] As Figure 1 shown, the air conditioner 10 includes: an outdoor unit 2a; three indoor units 8a, 8b, and 8c; and three flow dividing units 6a, 6b, and 6c. These outdoor unit 2a, indoor units 8a to 8c, and flow dividing units 6a to 6c are connected to each other through a high-pressure gas pipe 30, a low-pressure gas pipe 31, and a liquid pipe 32, thereby forming a refrigerant circuit of the air conditioner 10.

[0028] In this air conditioner 10, according to the opening and closing states of various valves provided in the outdoor unit 2a and the flow dividing units 6a to 6c, various operations such as heating operation (all indoor units perform heating operation), main heating operation (when the total value of the capacities required by the indoor units performing heating operation exceeds the total value of the capacities required by the indoor units performing cooling operation), cooling operation (all indoor units perform cooling operation), and main cooling operation (when the total value of the capacities required by the indoor units performing cooling operation exceeds the total value of the capacities required by the indoor units performing heating operation) can be performed.

[0029] (Outdoor unit) The outdoor unit 2a includes: a compressor 21, a first four-way valve 22 and a second four-way valve 23, a first outdoor heat exchanger 24, a second outdoor heat exchanger 25, an outdoor fan 26, a liquid receiver 27, a first outdoor expansion valve 40 connected to the first outdoor heat exchanger 24, and a second outdoor expansion valve 41 connected to the second outdoor heat exchanger 25.

[0030] The compressor 21 is a capacity variable type compressor capable of changing the operating capacity by being driven by a motor (not shown) whose speed is controlled by an inverter. The discharge side of the compressor 21 is connected to the port a of the first four-way valve 22 and the port e of the second four-way valve 23 through a discharge pipe 28, and is connected to a stop valve 44 through the discharge pipe 28 and an outdoor unit high-pressure gas pipe 33. The discharge pipe 28 is a refrigerant pipe connecting the discharge side of the compressor 21 and the connection point A, and the outdoor unit high-pressure gas pipe 33 is a refrigerant pipe connecting the connection point A and the stop valve 44. In addition, the suction side of the compressor 21 is connected to the outflow side of the liquid receiver 27 through a suction pipe 42, and the inflow side of the liquid receiver 27 is connected to a stop valve 45 through an outdoor unit low-pressure gas pipe 34.

[0031] The first four-way valve 22 and the second four-way valve 23 are equivalent to a plurality of flow path switching valves provided for each of a plurality of outdoor heat exchangers (the first outdoor heat exchanger 24, the second outdoor heat exchanger 25). The first four-way valve 22 and the second four-way valve 23 are valves for switching the flow direction of the refrigerant in the refrigerant circuit. The first four-way valve 22 switches the connection of one refrigerant inlet / outlet of the first outdoor heat exchanger 24 to be connected to the refrigerant discharge port or the refrigerant suction port of the compressor 21, and the second four-way valve 23 switches the connection of one refrigerant inlet / outlet of the second outdoor heat exchanger 25 to be connected to the refrigerant discharge port or the refrigerant suction port of the compressor 21.

[0032] The first four-way valve 22 has four ports a, b, c, and d. In the first four-way valve 22, the refrigerant pipe connected to the port a is connected to the discharge pipe 28 and the outdoor unit high-pressure gas pipe 33 at the connection point A. In addition, the port b and one end (one refrigerant inlet / outlet) of the first outdoor heat exchanger 24 are connected by a refrigerant pipe, the refrigerant pipe connected to the port c is connected to the outdoor unit low-pressure gas pipe 34 at the connection point D, and the port d is closed.

[0033] The second four-way valve 23 has four ports, namely e, f, g, and h. In the second four-way valve 23, the refrigerant pipe connected to port e is connected at connection point A to the refrigerant pipe connected to the discharge pipe 28 and the outdoor unit high-pressure gas pipe 33. In addition, port f and one end (one refrigerant inlet / outlet) of the second outdoor heat exchanger 25 are connected by a refrigerant pipe, the refrigerant pipe connected to port g is connected at connection point C to the refrigerant pipe connected to port c of the first three-way valve 22, and port h is closed.

[0034] As described above, one end (one refrigerant inlet / outlet) of the first outdoor heat exchanger 24 is connected to port b of the first four-way valve 22 via a refrigerant pipe, and the other end (the other refrigerant inlet / outlet) is connected to one port of the first outdoor expansion valve 40 via a refrigerant pipe. The other port of the first outdoor expansion valve 40 is connected to the stop valve 46 through the outdoor unit liquid pipe 35. In addition, as described above, one end (one refrigerant inlet / outlet) of the second outdoor heat exchanger 25 is connected to port f of the second four-way valve 23 via a refrigerant pipe, and the other end (the other refrigerant inlet / outlet) is connected to one port of the second outdoor expansion valve 41 via a refrigerant pipe. The other port of the second outdoor expansion valve 41 is connected to connection point B of the outdoor unit liquid pipe 35 through a refrigerant pipe.

[0035] The inflow side of the accumulator 27 is connected to the outdoor unit low-pressure gas pipe 34, and the outflow side is connected to the suction side of the compressor 21 through the suction pipe 42. The accumulator 27 separates the incoming refrigerant into gaseous refrigerant and liquid refrigerant, and allows only the gaseous refrigerant to be sucked into the compressor 21. The outdoor fan 26 rotates through a fan motor (not shown), thereby taking in external air into the outdoor unit 2a. After the refrigerant exchanges heat with the external air in the first outdoor heat exchanger 24 and the second outdoor heat exchanger 25, the heat-exchanged external air is discharged to the outside of the outdoor unit 2a.

[0036] In addition to the structure described above, various sensors are provided in the outdoor unit 2a. As Figure 1 shown, a high-pressure sensor 50 for detecting the pressure of the refrigerant discharged from the compressor 21 and a discharge temperature sensor 53 for detecting the temperature of the refrigerant discharged from the compressor 21 are provided in the discharge pipe 28. In addition, between connection point D of the outdoor unit low-pressure gas pipe 34 and the inflow side of the accumulator 27, a low-pressure sensor 51 for detecting the pressure of the refrigerant sucked into the compressor 21 and an intake temperature sensor 54 for detecting the temperature of the refrigerant sucked into the compressor 21 are provided.

[0037] In the first outdoor heat exchanger 24, a first heat exchange temperature sensor 56 is provided to detect the temperature of the refrigerant flowing in the first outdoor heat exchanger 24. In addition, in the second outdoor heat exchanger 25, a second heat exchange temperature sensor 57 is provided to detect the temperature of the refrigerant flowing in the second outdoor heat exchanger 25. Further, an outside air temperature sensor 58 is provided to detect the temperature of the outside air flowing into the outdoor unit 2a, that is, the outside air temperature.

[0038] (Indoor unit) The three indoor units 8a to 8c are equipped with an indoor heat exchanger 81, an indoor expansion valve 82, and an indoor fan 83. It should be noted that the structures of the indoor units 8a to 8c are all the same. Therefore, in the following description, only the structure of the indoor unit 8a will be described, and the descriptions of the other indoor units 8b and 8c will be omitted.

[0039] One end (one refrigerant inlet and outlet) of the indoor heat exchanger 81 is connected to one port of the indoor expansion valve 82 through a refrigerant pipe, and the other end (the other refrigerant inlet and outlet) is connected to a later-described flow splitting unit 6a through a refrigerant pipe 87. The indoor heat exchanger 81 functions as an evaporator when the indoor unit 8a performs a cooling operation, and functions as a condenser when the indoor unit 8a performs a heating operation.

[0040] As described above, one port of the indoor expansion valve 82 is connected to the indoor heat exchanger 81, and the other port is connected to the liquid pipe 32. The indoor expansion valve 82 adjusts its opening degree according to the required cooling capacity when the indoor heat exchanger 81 functions as an evaporator, and adjusts its opening degree according to the required heating capacity when the indoor heat exchanger 81 functions as a condenser.

[0041] The indoor fan 83 rotates through a fan motor (not shown), thereby taking in indoor air into the indoor unit 8a. After the refrigerant exchanges heat with the indoor air in the indoor heat exchanger 81, the heat-exchanged air is supplied to the room.

[0042] In addition to the structures described above, various sensors are provided in the indoor unit 8a. A refrigerant temperature sensor 84 for detecting the temperature of the refrigerant is provided in the refrigerant pipe on the indoor expansion valve 82 side of the indoor heat exchanger 81, and a refrigerant temperature sensor 85 for detecting the temperature of the refrigerant is provided in the refrigerant pipe on the flow splitting unit 6a side of the indoor heat exchanger 81. In addition, near the suction port of the indoor air (not shown) of the indoor unit 8a, a room temperature sensor 86 for detecting the temperature of the indoor air flowing into the indoor unit 8a, that is, the room temperature, is provided.

[0043] (Flow splitting unit) The air conditioner 10 is provided with three flow dividing units 6a to 6c corresponding to three indoor units 8a to 8c. The flow dividing units 6a to 6c include first solenoid valves 61a to 61c, second solenoid valves 62a to 62c, first flow dividing pipes 63a to 63c, and second flow dividing pipes 64a to 64c. It should be noted that since the structures of the flow dividing units 6a to 6c are all the same, in the following description, only the structure of the flow dividing unit 6a will be described, and the descriptions of the other flow dividing units 6b and 6c will be omitted.

[0044] One end of the first flow dividing pipe 63a is connected to the high-pressure gas pipe 30, and one end of the second flow dividing pipe 64a is connected to the low-pressure gas pipe 31. In addition, the other end of the first flow dividing pipe 63a and the other end of the second flow dividing pipe 64a are connected to each other, and this connection part is connected to the indoor heat exchanger 81 through the refrigerant pipe 87. A first solenoid valve 61a is provided in the first flow dividing pipe 63a, and a second solenoid valve 62a is provided in the second flow dividing pipe 64a. By opening and closing the first solenoid valve 61a and the second solenoid valve 62a respectively, the flow path of the refrigerant in the refrigerant circuit can be switched so that the indoor heat exchanger 81 of the indoor unit 8a corresponding to the flow dividing unit 6a is connected to the discharge side (high-pressure gas pipe 30 side) or the suction side (low-pressure gas pipe 31 side) of the compressor 21.

[0045] Through the connections described above, the refrigerant circuit of the air conditioner 10 is constituted, and by making the refrigerant flow in the refrigerant circuit, the refrigeration cycle is established.

[0046] (Control device) The outdoor unit 2a is provided with a control device 90. Figure 2 It is a block diagram showing the structure of the control device 90. As shown in this figure, the control device 90 has a CPU 91, a storage unit 92, a communication unit 93, a sensor input unit 94, and a rotation speed detection unit 95.

[0047] The storage unit 92 is a non-volatile memory such as a flash memory, and stores the control program of the outdoor unit 2a, control parameters, detection values corresponding to detection signals from various sensors, control states of the compressor 21, the outdoor fan 26, etc.

[0048] The communication unit 93 is an interface for communicating with the indoor units 8a to 8c. The sensor input unit 94 takes in the detection results of various sensors in the outdoor unit 2a and outputs them to the CPU 91. The rotation speed detection unit 95 detects the rotation speed of the motor of the compressor 21 and outputs it to the CPU 91. The rotation speed detection unit 95 can be configured to directly detect the rotation speed of the motor through an encoder or the like installed on the drive shaft of the motor, or can be configured to detect the rotation speed of the motor according to the drive current supplied to the motor.

[0049] The CPU 91 is a control unit that controls each device of the outdoor unit 2a including the compressor 21 by executing a program stored in the storage unit 92. The program is, for example, pre-installed in the control device 90. Alternatively, the installation and update of the program can also be executed via the Internet or the like.

[0050] The CPU 91 takes in the detection results of the respective sensors of the outdoor unit 2a via the sensor input unit 94. In addition, the CPU 91 takes in the control signals sent from the indoor units 8a to 8c via the communication unit 93. Further, as described above, the CPU 91 takes in the rotational speed of the motor of the compressor 21 from the rotational speed detection unit 95. The CPU 91 performs drive control of the compressor 21 and the outdoor fan 26 based on the taken-in detection results and control signals. In addition, the CPU 91 performs switching control of the first four-way valve 22, the second four-way valve 23, the first expansion valve 40, the second expansion valve 41, etc. based on the taken-in detection results and control signals.

[0051] It should be noted that the opening and closing control of the first solenoid valves 61a to 61c and the second solenoid valves 62a to 62c in the flow dividing units 6a to 6c is performed by a control device (not shown) of the indoor units 8a to 8c corresponding to the flow dividing units 6a to 6c.

[0052] [Basic operating actions of the air conditioning device] Next, the basic operating actions of the air conditioning device 10 will be described. It should be noted that in the description of the operating actions, both the first outdoor heat exchanger 24 and the second outdoor heat exchanger 25 are used simultaneously.

[0053] (Full heating operation) As Figure 1 shown, when heating operation is performed in all of the indoor units 8a to 8c, the first four-way valve 22 of the outdoor unit 2a is switched so that port b and port c are connected (shown by a solid line in Figure 1 ), whereby the first outdoor heat exchanger 24 functions as an evaporator, and the second four-way valve 23 is switched so that port f and port g are connected (shown by a solid line in Figure 1 ), whereby the second outdoor heat exchanger 25 functions as an evaporator.

[0054] In the indoor units 8a to 8c, the first solenoid valves 61a to 61c of the corresponding flow dividing units 6a to 6c are opened so that the refrigerant flows in the first flow dividing pipes 63a to 63c, and the second solenoid valves 62a to 62c are closed to cut off the second flow dividing pipes 64a to 64c. Thus, all of the indoor heat exchangers 81 of the indoor units 8a to 8c function as condensers.

[0055] The high-pressure refrigerant discharged from the compressor 21 of the outdoor unit 2a flows in the discharge pipe 28 and the outdoor unit high-pressure gas pipe 33, and flows into the high-pressure gas pipe 30 via the stop valve 44. The high-pressure refrigerant flowing into the high-pressure gas pipe 30 separately flows into the flow dividing units 6a to 6c. The high-pressure refrigerant flowing into the flow dividing units 6a to 6c flows in the first flow dividing pipes 63a to 63c provided with the opened first solenoid valves 61a to 61c, flows out from the flow dividing units 6a to 6c, and flows into the corresponding indoor units 8a to 8c via the refrigerant pipes 87.

[0056] The high-pressure refrigerant flowing into each of the indoor units 8a to 8c flows into the indoor heat exchanger 81, exchanges heat with the indoor air and condenses. As a result, the indoor air is heated, and heating of the room where the indoor units 8a to 8c are provided is performed. The high-pressure refrigerant flowing out from the indoor heat exchanger 81 is decompressed by the indoor expansion valve 82. The opening degree of the indoor expansion valve 82 is determined according to the supercooling degree of the refrigerant at the refrigerant outlet of the indoor heat exchanger 81. The supercooling degree of the refrigerant is obtained, for example, by subtracting the refrigerant temperature at the refrigerant outlet of the indoor heat exchanger 81 detected by the refrigerant temperature sensor 84 from the high-pressure saturation temperature (equivalent to the condensation temperature in the indoor heat exchanger 81) calculated from the pressure detected by the high-pressure sensor 50 of the outdoor unit 2a.

[0057] The intermediate-pressure refrigerant flowing out from each of the indoor units 8a to 8c flows into the liquid pipe 32, and flows into the outdoor unit 2a via the stop valve 46. The intermediate-pressure refrigerant flowing into the outdoor unit 2a flows in the outdoor unit liquid pipe 35, is divided at the connection point B, and is decompressed by the first outdoor expansion valve 40 and the second outdoor expansion valve 41 to become a low-pressure refrigerant.

[0058] The opening degree of the first outdoor expansion valve 40 is determined according to the superheat degree of the refrigerant at the refrigerant outlet of the first outdoor heat exchanger 24. In addition, the opening degree of the second outdoor expansion valve 41 is determined according to the superheat degree of the refrigerant at the refrigerant outlet of the second outdoor heat exchanger 25. The superheat degree of the refrigerant is obtained, for example, by subtracting the low-pressure saturation temperature (equivalent to the evaporation temperature in the first outdoor heat exchanger 24 and the second outdoor heat exchanger 25) calculated from the pressure detected by the low-pressure sensor 51 of the outdoor unit 2a from the refrigerant temperatures in the first outdoor heat exchanger 24 and the second outdoor heat exchanger 25 detected by the first heat exchange temperature sensor 56 and the second heat exchange temperature sensor 57.

[0059] The low-pressure refrigerant decompressed by the first outdoor expansion valve 40 and the second outdoor expansion valve 41 flows into the first outdoor heat exchanger 24 and the second outdoor heat exchanger 25, exchanges heat with the external gas and evaporates. Then, the low-pressure refrigerant flowing out of the first outdoor heat exchanger 24 and the second outdoor heat exchanger 25 converges at the connection point C via the first four-way valve 22 and the second four-way valve 23, and is sucked into the compressor 21 via the connection point D and the accumulator 27 and compressed again.

[0060] (Full cooling operation) Next, the case where all the indoor units 8a to 8c perform cooling operation will be described. When all the indoor units 8a to 8c perform cooling operation, the first four-way valve 22 of the outdoor unit 2a is switched so that the port a and the port b are connected (indicated by a dotted line in Figure 1 ), thereby causing the first outdoor heat exchanger 24 to function as a condenser. By switching so that the port e and the port f of the second four-way valve 23 are connected (indicated by a dotted line in Figure 1 ), thereby causing the second outdoor heat exchanger 25 to function as a condenser.

[0061] In the indoor units 8a to 8c, the first solenoid valves 61a to 61c of the corresponding flow dividing units 6a to 6c are closed, the first flow dividing pipes 63a to 63c are cut off, and the second solenoid valves 62a to 62c are opened so that the refrigerant flows in the second flow dividing pipes 64a to 64c. Thus, all the indoor heat exchangers 81 of the indoor units 8a to 8c function as evaporators.

[0062] The high-pressure refrigerant discharged from the compressor 21 of the outdoor unit 2a is divided into the first four-way valve 22 side, the second four-way valve 23 side, and the high-pressure gas pipe 30 side. The refrigerant flowing on the first four-way valve 22 and the second four-way valve 23 sides flows into the first outdoor heat exchanger 24 and the second outdoor heat exchanger 25, exchanges heat with the external gas and condenses. Since the first solenoid valves 61a to 61c of the respective flow dividing units 6a to 6c are closed, the refrigerant flowing toward the high-pressure gas pipe 30 side does not flow into the indoor units 8a to 8c, but stays in the outdoor unit high-pressure gas pipe 33 and the high-pressure gas pipe 30.

[0063] The refrigerant condensed in the first outdoor heat exchanger 24 and the second outdoor heat exchanger 25 of the outdoor unit 2a flows into the liquid pipe 32 via the first outdoor expansion valve 40 and the second outdoor expansion valve 41 that are set to the fully open state by the control device 90 and the stop valve 46. The intermediate-pressure refrigerant flowing into the liquid pipe 32 separately flows into each of the indoor units 8a to 8c.

[0064] The refrigerant at intermediate pressure flowing into each of the indoor units 8a to 8c is decompressed by the indoor expansion valve 82 to become a low-pressure refrigerant, and flows into the indoor heat exchanger 81. The low-pressure refrigerant flowing into the indoor heat exchanger 81 exchanges heat with the indoor air and evaporates, thereby performing cooling in the room where the indoor units 8a to 8c are provided. Here, based on the refrigerant temperature detected by the refrigerant temperature sensors 84 and 85, the refrigerant superheat at the outlet of the indoor heat exchanger 81 serving as an evaporator is obtained, and the opening degree of the indoor expansion valve 82 is determined based on this refrigerant superheat.

[0065] The low-pressure refrigerant flowing out of the indoor heat exchanger 81 flows into the flow dividing units 6a to 6e via the refrigerant pipe 87, and flows in the second flow dividing pipes 64a to 64b having the open second solenoid valves 62a to 62c and flows into the low-pressure gas pipe 31. Then, the low-pressure refrigerant flowing into the low-pressure gas pipe 31 from each of the flow dividing units 6a to 6c and merging in the low-pressure gas pipe 31 flows into the outdoor unit 2a. The low-pressure refrigerant flowing into the outdoor unit 2a passes through the outdoor unit low-pressure gas pipe 34, is sucked into the compressor 21 via the accumulator 27, and is compressed again.

[0066] Next, the heating main operation and the cooling main operation (hereinafter also referred to as the cooling and heating mixed operation) in which the cooling operation and the heating operation coexist in the indoor units 8a to 8c will be described.

[0067] When the cooling operation and the heating operation coexist in the indoor units 8a to 8c, the state of the refrigerant circuit is determined based on the comparison result between the total value of the cooling capacities required by the indoor units performing the cooling operation and the total value of the heating capacities required by the indoor units performing the heating operation. In the present embodiment, as an example, the indoor units 8a and 8b perform the heating operation / the indoor unit 8c performs the cooling operation. When the heating capacities required by the two indoor units 8a and 8b performing the heating operation are greater than the cooling capacity required by the one indoor unit 8c performing the cooling operation, the heating main operation is performed in which the first outdoor heat exchanger 24 and the second outdoor heat exchanger 25 function as evaporators, respectively. In addition, the indoor units 8a and 8b perform the cooling operation / the indoor unit 8c performs the heating operation. When the cooling capacities required by the two indoor units 8a and 8b performing the cooling operation are greater than the heating capacity required by the one indoor unit 8c performing the heating operation, the cooling main operation is performed in which the first outdoor heat exchanger 24 and the second outdoor heat exchanger 25 function as condensers, respectively.

[0068] (Heating main operation) In the heating main operation, in the outdoor unit 2a, the first four-way valve 22 is switched so that the port b communicates with the port c (indicated by a solid line in Figure 1 ), and the second four-way valve 23 is switched so that the port f communicates with the port g (inFigure 1 It is indicated by a solid line. Thus, both the first outdoor heat exchanger 24 and the second outdoor heat exchanger 25 function as evaporators.

[0069] In addition, the first solenoid valves 61a and 61b of the two flow dividing units 6a and 6b corresponding to the two indoor units 8a and 8b that are in heating operation are opened to connect the first flow dividing pipes 63a and 63b, and the second solenoid valves 62a and 62b are closed to cut off the second flow dividing pipes 64a and 64b. Thus, the indoor heat exchangers 81 of the two indoor units 8a and 8b become condensers. On the other hand, the first solenoid valve 61c of the flow dividing unit 6c corresponding to the indoor unit 8c that is in cooling operation is closed to cut off the first flow dividing pipe 63c, and the second solenoid valve 62c is opened to connect the second flow dividing pipe 64c. Thus, the indoor heat exchanger 81 of the indoor unit 8c becomes an evaporator.

[0070] The high-pressure refrigerant discharged from the compressor 21 of the outdoor unit 2a flows in the high-pressure gas pipe 30 and separately flows into the flow dividing units 6a and 6b. The high-pressure refrigerant flowing into the flow dividing units 6a and 6b flows in the first flow dividing pipes 63a and 63b with the opened first solenoid valves 61a and 61b, flows out of the flow dividing units 6a and 6b, and flows into the corresponding indoor units 8a and 8b via the refrigerant pipes 87.

[0071] The high-pressure refrigerant flowing into the indoor units 8a and 8b flows into the indoor heat exchanger 81, exchanges heat with the indoor air and condenses, thereby heating the interior of the room where the indoor units 8a and 8b are installed. The high-pressure refrigerant condensed in the indoor heat exchanger 81 is decompressed by the indoor expansion valve 82 and becomes a medium-pressure refrigerant. Here, the control unit of the indoor units 8a and 8b calculates the refrigerant subcooling degree in the indoor heat exchanger 81 as a condenser based on the refrigerant temperature detected by the refrigerant temperature sensor 84 and the high-pressure saturation temperature obtained from the outdoor unit 2a, and determines the opening degree of the indoor expansion valve 82 based on this refrigerant subcooling degree.

[0072] The medium-pressure refrigerant flowing out of the indoor units 8a and 8b flows into the liquid pipe 32. Then, a part of the medium-pressure refrigerant that converges in the liquid pipe 32 flows into the outdoor unit 2a, and the remaining part flows in the liquid pipe 32 and flows into the indoor unit 8c.

[0073] The intermediate-pressure refrigerant flowing into the outdoor unit 2a is decompressed when passing through the first outdoor expansion valve 40 and the second outdoor expansion valve 41 set to an opening corresponding to the superheat degree of the first outdoor heat exchanger 24 and the second outdoor heat exchanger 25, and becomes a low-pressure refrigerant, and flows into the first outdoor heat exchanger 24 and the second outdoor heat exchanger 25. The low-pressure refrigerant flowing into the first outdoor heat exchanger 24 and the second outdoor heat exchanger 25 exchanges heat with the external air and evaporates. Then, the low-pressure refrigerant flowing out of the first outdoor heat exchanger 24 and the second outdoor heat exchanger 25 passes through the first four-way valve 22 and the second four-way valve 23, and is sucked into the compressor 21 through the accumulator 27 and compressed again.

[0074] On the other hand, the intermediate-pressure refrigerant flowing into the indoor unit 8c is decompressed by the indoor expansion valve 82 to become a low-pressure refrigerant, and flows into the indoor heat exchanger 81. The low-pressure refrigerant flowing into the indoor heat exchanger 81 exchanges heat with the indoor air and evaporates, thereby cooling the room in which the indoor unit 8c is installed. Here, the refrigerant superheat in the indoor heat exchanger 81 as an evaporator is obtained based on the refrigerant temperature detected by the refrigerant temperature sensors 84 and 85, and the opening degree of the indoor expansion valve 82 of the indoor unit 8c is determined based on the refrigerant superheat.

[0075] The low-pressure refrigerant flowing out of the indoor heat exchanger 8c flows into the flow divider unit 6c via the refrigerant pipe 87, flows through the second flow divider pipe 64c having the opened second solenoid valve 62c, and flows into the low-pressure gas pipe 31. The low-pressure refrigerant flowing into the low-pressure gas pipe 31 flows into the outdoor unit 2a via the branch pipe 71 and the low-pressure gas branch pipes 31a and 31b, and is sucked into the compressor 21 via the accumulator 27 to be compressed again.

[0076] (Refrigeration main operation) In the cooling main operation, in the outdoor unit 2a, the first four-way valve 22 is switched so that the port a communicates with the port b (in Figure 1 The second four-way valve 23 is switched so that port e is connected to port f (indicated by dotted lines in FIG. Figure 1 Thus, both the first outdoor heat exchanger 24 and the second outdoor heat exchanger 25 function as condensers.

[0077] In addition, the first solenoid valves 61a and 61b of the two flow dividing units 6a and 6b corresponding to the two indoor units 8a and 8b operating in the cooling mode are closed to cut off the first flow dividing pipes 63a and 63b, and the second solenoid valves 62a and 62b are closed to connect the second flow dividing pipes 64a and 64b. Thus, the indoor heat exchangers 81 of the two indoor units 8a and 8b become evaporators. On the other hand, the solenoid valve 61c of the flow dividing unit 6c corresponding to the indoor unit 8c operating in the heating mode is opened to connect the first flow dividing pipe 63c, and the second solenoid valve 62c is closed to cut off the second flow dividing pipe 64c. Thus, the indoor heat exchanger 81 of the indoor unit 8c becomes a condenser.

[0078] The high-pressure refrigerant discharged from the compressor 21 of the outdoor unit 2a is divided into the first four-way valve 22 side, the second four-way valve 23 side, and the high-pressure gas pipe 30 side. The high-pressure refrigerant passing through the first four-way valve 22 and the second four-way valve 23 flows into the first outdoor heat exchanger 24 and the second outdoor heat exchanger 25, and exchanges heat with the external gas to condense. The refrigerant condensed in the first outdoor heat exchanger 24 and the second outdoor heat exchanger 25 becomes an intermediate-pressure refrigerant through the first outdoor expansion valve 40 and the second outdoor expansion valve 41 whose opening degrees are set corresponding to the difference between the discharge pressure of the compressor 21 and the hydraulic pressure by using the control device 90, flows in the liquid pipe 32, and separately flows into the indoor units 8a and 8b.

[0079] The intermediate-pressure refrigerant flowing into the indoor units 8a and 8b is decompressed by the indoor expansion valves 82 to become a low-pressure refrigerant and flows into the indoor heat exchangers 81. The low-pressure refrigerant flowing into the indoor heat exchangers 81 exchanges heat with the indoor air and evaporates, thereby performing cooling in the room where the indoor units 8a and 8b are installed. Here, based on the refrigerant temperatures detected by the refrigerant temperature sensors 84 and 85, the refrigerant superheat degree in the indoor heat exchanger 81 serving as an evaporator is obtained, and the opening degree of the indoor expansion valve 82 is determined based on this refrigerant superheat degree.

[0080] The low-pressure refrigerant flowing out from the indoor heat exchangers 81 of the indoor units 8a and 8b flows into the flow dividing units 6a and 6b via the refrigerant pipes 87, flows in the second flow dividing pipes 64a and 64b with the open second solenoid valves 62a and 62b, and flows into the low-pressure gas pipe 31. Then, the low-pressure refrigerants flowing into the low-pressure gas pipe 31 from the respective flow dividing units 6a and 6b merge in the low-pressure gas pipe 31, flow into the outdoor unit 2a, are sucked into the compressor 21 through the accumulator 27, and are compressed again.

[0081] On the other hand, the high-pressure refrigerant flowing in the high-pressure gas pipe 30 and flowing into the flow dividing unit 6c flows in the first flow dividing pipe 63c with the solenoid valve 61c opened and flows into the indoor unit 8c. The high-pressure refrigerant flowing into the indoor unit 8c from the flow dividing unit 6c via the refrigerant pipe 87 flows into the indoor heat exchanger 81, exchanges heat with the indoor air and condenses, thereby performing heating in the room where the indoor unit 8c is installed. The high-pressure refrigerant flowing out of the indoor heat exchanger 81 is decompressed by the indoor expansion valve 82 and becomes a refrigerant at an intermediate pressure. Here, the degree of subcooling of the refrigerant in the indoor heat exchanger 81 as a condenser is obtained based on the refrigerant temperature detected by the refrigerant temperature sensor 84 and the high-pressure saturation temperature obtained from the outdoor units 2a and 2b, and the opening degree of the indoor expansion valve 82 of the indoor unit 8c is determined based on this degree of subcooling of the refrigerant.

[0082] Then, the refrigerant at an intermediate pressure flowing out of the indoor unit 8c and flowing out into the liquid pipe 32 flows into the outdoor unit 2a. The refrigerant at an intermediate pressure flowing into the outdoor unit 2a is decompressed when passing through the first outdoor expansion valve 40 and the second outdoor expansion valve 41 whose opening degrees are set corresponding to the superheat degrees of the first outdoor heat exchanger 24 and the second outdoor heat exchanger 25, and becomes a low-pressure refrigerant, and flows into the first outdoor heat exchanger 24 and the second outdoor heat exchanger 25. The low-pressure refrigerant flowing into the first outdoor heat exchanger 24 and the second outdoor heat exchanger 25 exchanges heat with the external gas and evaporates. Then, the low-pressure refrigerant flowing out of the first outdoor heat exchanger 24 and the second outdoor heat exchanger 25 passes through the first four-way valve 22 and the second four-way valve 23, and is sucked into the compressor 21 through the accumulator 27 and is compressed again.

[0083] It should be noted that in the full heating operation and the main heating operation, if the heating capacity required by the indoor unit is small, the number of outdoor heat exchangers used can be one. When the number of outdoor heat exchangers used is one, in the outdoor unit 2a, the first four-way valve 22 is switched so that the port b is communicated with the port c ( Figure 1 shown by the solid line in the figure), the second four-way valve 23 is switched so that the port e is communicated with the port f ( Figure 1 shown by the dotted line in the figure), and the second outdoor expansion valve 41 is fully closed. Thus, only the first outdoor heat exchanger 24 is used as an evaporator, and the use of the second outdoor heat exchanger 25 is stopped. As described later, the number of outdoor heat exchangers used is switched according to the increase or decrease of the required capacity from the indoor unit performing the heating operation and the increase or decrease of the air-conditioning load caused by the change of the external gas temperature.

[0084] Similarly, in full cooling operation and cooling main unit operation, if the required cooling capacity of the indoor unit is small, the number of outdoor heat exchangers used can be one. When the number of outdoor heat exchangers used is one, in the outdoor unit 2a, the first four-way valve 22 is switched so that port a is connected to port b ( Figure 1 shown by a solid line in), the second four-way valve 23 is switched so that port f is connected to port g ( Figure 1 shown by a solid line in), and the first outdoor expansion valve 40 is fully closed. Thus, only the first outdoor heat exchanger 24 is used as a condenser, and the use of the second outdoor heat exchanger 25 is stopped. As described later, the number of outdoor heat exchangers used is switched according to the increase or decrease in the required capacity from the indoor unit performing the cooling operation and the increase or decrease in the air-conditioning load caused by the change in the outside air temperature.

[0085] (Problems when switching the number of heat exchangers used) In an air-conditioning apparatus having a plurality of outdoor heat exchangers, when the required capacity from the indoor unit increases or the air-conditioning load increases due to a change in the outside air temperature, the number of outdoor heat exchangers used increases, and when the required capacity from the indoor unit decreases or the air-conditioning load decreases due to a change in the outside air temperature, the number of outdoor heat exchangers used decreases. For example, in cooling operation, the number of outdoor heat exchangers functioning as condensers increases or decreases according to the increase or decrease in the number of indoor units performing the cooling operation, etc., and in heating operation, the number of outdoor heat exchangers functioning as evaporators increases or decreases according to the increase or decrease in the number of indoor units performing the heating operation, etc. Further, in cooling main unit operation or heating main unit operation, the number of outdoor heat exchangers functioning as condensers or evaporators increases or decreases according to the increase or decrease in both the number of indoor units performing the cooling operation and the number of indoor units performing the heating operation.

[0086] Here, when increasing the number of outdoor heat exchangers used, there is a case where the condensation capacity or evaporation capacity of the outdoor heat exchangers significantly exceeds the required capacity due to the increase in the number. Further, when decreasing the number of outdoor heat exchangers used, there is a case where the condensation capacity or evaporation capacity of the outdoor heat exchangers significantly falls below the required capacity due to the decrease in the number. Thus, if the capacity becomes too large or too small when increasing or decreasing the number of outdoor heat exchangers used, the air-conditioning apparatus decreases the number of outdoor heat exchangers used when the capacity is too large and increases the number of outdoor heat exchangers used when the capacity is too small, and thus it is possible that the number of outdoor heat exchangers used frequently and repeatedly increases and decreases.

[0087] For example, if referring to Figure 1To explain, when the air conditioner 10 performs cooling operation using one outdoor heat exchanger, the flow path switching valve (the first four-way valve 22) of the used outdoor heat exchanger (the first outdoor heat exchanger 24) is switched to connect the inlet of the first outdoor heat exchanger 24 to the refrigerant discharge side of the compressor 21 (port a is in communication with port b), and the flow path switching valve (the second four-way valve 23) of the unused outdoor heat exchanger (the second outdoor heat exchanger 25) is switched to connect the outlet of the second outdoor heat exchanger to the refrigerant suction side of the compressor 21 (port f is in communication with port g). Therefore, if the number of used outdoor heat exchangers frequently increases and decreases repeatedly, the flow path switching valve on the side of the outdoor heat exchanger to be used or not used (in this example, the second four-way valve 23 of the second outdoor heat exchanger 25) is frequently switched. As a result, the generation of noise associated with the operation of the flow path switching valve and the premature deterioration of the flow path switching valve may lead to a reduction in reliability.

[0088] When the outdoor heat exchanger functions as a condenser, the condensation capacity of the outdoor heat exchanger increases and decreases with the increase and decrease in the number of used outdoor heat exchangers, and the condensation temperature varies with the increase and decrease in the condensation capacity of the outdoor heat exchanger. More specifically, if the condensation capacity increases, the condensation temperature decreases, and if the condensation capacity decreases, the condensation temperature rises. For example, when the air conditioner performs the main cooling operation, the indoor heat exchanger of the indoor unit performing the heating operation functions as a condenser. Therefore, if the condensation capacity of the outdoor heat exchanger is repeatedly increased and decreased by repeatedly increasing and decreasing the number of used outdoor heat exchangers, the condensation temperature in the indoor heat exchanger of this indoor unit changes, and thus the heating capacity of this indoor unit is repeatedly reduced and increased. Therefore, stable heating operation cannot be continued.

[0089] On the other hand, when the outdoor heat exchanger functions as an evaporator, the evaporation capacity of the outdoor heat exchanger increases and decreases with the increase and decrease in the number of used outdoor heat exchangers, and the evaporation temperature varies with the increase and decrease in the evaporation capacity of the outdoor heat exchanger. More specifically, if the evaporation capacity increases, the evaporation temperature rises, and if the evaporation capacity decreases, the evaporation temperature decreases. For example, when the air conditioner performs the main heating operation, the indoor heat exchanger of the indoor unit performing the cooling operation functions as an evaporator. Therefore, if the evaporation capacity of the outdoor heat exchanger is repeatedly increased and decreased by repeatedly increasing and decreasing the number of used outdoor heat exchangers, the evaporation temperature in the indoor heat exchanger of this indoor unit changes, and thus the cooling capacity of this indoor unit is repeatedly reduced and increased. Therefore, stable cooling operation cannot be continued.

[0090] As an example, Figure 3Represents the relationship between the number of outdoor heat exchangers used for the operation of the refrigeration main body, the heat exchange amount (condensation capacity) of the outdoor heat exchangers before and after the increase in the number of used outdoor heat exchangers, and the condensation temperature of the refrigerant in the outdoor heat exchangers. (A) is a schematic diagram when the number of outdoor heat exchangers used is increased from 1 to 2. The used outdoor heat exchangers are shaded in the figure. (B) is a diagram showing an example of the relationship between the number of outdoor heat exchangers used and their heat exchange amount. Then, (C) is a diagram showing an example of the change in the condensation temperature of the refrigerant flowing in the outdoor heat exchangers when the number of outdoor heat exchangers used is increased from 1 to 2.

[0091] The heat exchange amount of the outdoor heat exchanger can generally be obtained based on the refrigerant flow rate in the outdoor heat exchanger, the volume of each outdoor heat exchanger, the air volume delivered by the outdoor fan (the product of the number and rotation speed of the outdoor fans), and the ratio of the air volume flowing into each outdoor heat exchanger to the above-mentioned air volume delivered.

[0092] Here, the ratio of the air volume flowing into each outdoor heat exchanger varies depending on the number and layout of the outdoor fans relative to the two outdoor heat exchangers. In the present embodiment, as shown in (A) of Figure 3 , relative to one outdoor fan 26, two outdoor heat exchangers 24 and 25 are respectively arranged on the upwind side or the downwind side, and the air volume sent out from the outdoor fan 26 is distributed to each of the outdoor heat exchangers 24 and 25 at a given ratio. In this example, the air volume ratio between the first outdoor heat exchanger 24 located on the upwind side and the second outdoor heat exchanger 25 located on the downwind side is 3:1 (0.75:0.25). It should be noted that in the case where two outdoor fans are provided corresponding to each outdoor heat exchanger, the above-mentioned air volume ratio is 1:1 (0.5:0.5). As shown in (B) of Figure 3 , the higher the rotation speed of the outdoor fan, the greater the heat exchange amount of the outdoor heat exchanger.

[0093] In this way, the heat exchange amount of the outdoor heat exchanger mainly increases or decreases according to the number of outdoor heat exchangers used and the air volume of the outdoor fan. In the following description, the product of the number of these outdoor heat exchangers used and the rotation speed of the outdoor fan is also referred to as the number of units · rotation speed cumulative value [unit · rpm] for evaluating the magnitude of the heat exchange amount.

[0094] The rotation speed of the outdoor fan can be different when the outdoor heat exchanger functions as a condenser and when it functions as an evaporator, and can also be set to different values according to the number of outdoor heat exchangers used. The rotation speed of the outdoor fan is not limited to the case of a fixed value, and can also be variably controlled within an arbitrary rotation speed range.

[0095] As an example, the following case will be described: when the number of outdoor heat exchangers functioning as condensers is 1, the control range of the rotational speed of the outdoor fan is 0 rpmm to 500 rpmm; when the number of outdoor heat exchangers is 2, the control range of the rotational speed of the outdoor fan is 500 rpm to the maximum value of the rotational speed of the outdoor fan.

[0096] Figure 3 (C) is an explanatory diagram showing an example of the time change of the condensation temperature of the refrigerant in the outdoor heat exchanger functioning as a condenser, and shows the situation when the number of outdoor heat exchangers is switched from 1 to 2 at time T1 while the rotational speed of the compressor is maintained constant. In this figure, the control upper limit is the temperature used as a reference when determining whether the control device 90 needs to increase the number of outdoor heat exchangers. The control upper limit is set to a temperature lower than a given temperature compared to the protection control start temperature, so as not to cause a protection control in which the condensation temperature reaches the protection control start temperature and the compressor stops. In addition, the control lower limit is the temperature used as a reference when determining whether the control device 90 needs to reduce the number of outdoor heat exchangers. The control device 90 controls the rotational speed of the outdoor fan 23 so that the temperature of the refrigerant detected by the first heat exchange temperature sensor 56 and the second heat exchange temperature sensor 57 becomes a temperature between the control lower limit and the control upper limit.

[0097] When the condensation capacity in one outdoor heat exchanger is insufficient to maintain the condensation temperature below the control upper limit, the control device 90 increases the number of outdoor heat exchangers from 1 to 2 ( Figure 3 at time T1 in (C)). At this time, as shown in Figure 3 (B), when the maximum heat exchange amount of the outdoor heat exchanger before the increase when there is 1 outdoor heat exchanger is set as HE1max, and the minimum heat exchange amount of the outdoor heat exchanger just after the increase when there are 2 outdoor heat exchangers is set as HE2min, the number·rotational speed cumulative value of the heat exchange amount HE1max of the outdoor heat exchanger before the increase is 500 [unit·rpm] (1 unit × 500 rpm). In contrast, the number·rotational speed cumulative value of the heat exchange amount HE2min of the outdoor heat exchanger just after the increase is 1000 [unit·rpm] (2 units × 500 rpm). Therefore, as shown in Figure 3 (B), the heat exchange amount of the outdoor heat exchanger rises sharply just after the number of units is increased, greatly exceeding the required condensation capacity.

[0098] If the heat exchange amount (condensation capacity) of the outdoor heat exchanger just after the number of units is increased is too large compared to the required condensation capacity, then if the rotational speed of the outdoor fan is the same before and after the increase in the number of units, the condensation temperature of the refrigerant in the outdoor heat exchanger is likely to decrease sharply. For example, asFigure 3 As shown in (C) of FIG. , when the number of outdoor heat exchangers in use is increased from one to two, if the heat exchange capacity of the outdoor heat exchanger after the increase in the number of units is too large, there is a case where the condensation temperature of the refrigerant in the outdoor heat exchanger drops sharply from the control upper limit (for example, 54.5°C) to below the control lower limit (for example, 42°C). If the state where the condensation temperature is below the control lower limit continues for a given time, in order to increase the condensation temperature of the refrigerant, it is necessary to switch the number of outdoor heat exchangers in use back to one again. On the other hand, when the number of outdoor heat exchangers in use is one, the heat exchange capacity is originally too small, so even after switching the number of units in use to one, the condensation temperature immediately reaches the stable upper limit, and it is necessary to switch the number of units in use back to two again.

[0099] In this way, when the condensation capacity of the outdoor heat exchanger greatly exceeds the required capacity due to an increase in the number of outdoor heat exchangers in use, the increase and decrease of the number of outdoor heat exchangers in use are sometimes frequently repeated. In this case, the four-way valve is switched according to the increase and decrease of the number of outdoor heat exchangers in use, so its operating sound becomes noise. In addition, due to the frequent operation of this four-way valve, there is a problem of premature deterioration. Further, due to the frequent repetition of changes in the capacity of the outdoor heat exchanger, there are problems of unstable temperature in the air-conditioned space and deteriorated comfort. For example, if the condensation capacity of the outdoor heat exchanger that functions as a condenser during the operation of the refrigeration main body changes, it will affect the air-conditioning control of the heating machine.

[0100] Such problems occur not only when increasing the number of outdoor heat exchangers in use but also when decreasing the number of outdoor heat exchangers in use. That is, if the number of outdoor heat exchangers in use is reduced from two to one, the condensation capacity of the outdoor heat exchanger is greatly reduced, so the condensation temperature of the refrigerant rises significantly, and there is a case where the condensation temperature exceeds the stable upper limit. In this case, if the number of outdoor heat exchangers in use is increased again, the heat exchange capacity is too large when the number of outdoor heat exchangers in use is two, so even after switching the number of units in use to two, the condensation temperature reaches the stable lower limit, and it is necessary to switch the number of units in use back to one again.

[0101] It should be noted that the above problems occur not only during the operation of the refrigeration main body but also during the operation of the heating main body.

[0102] Therefore, the air conditioner 10 of the present embodiment suppresses noise, reduction in reliability, and deterioration in comfort caused by frequent increase and decrease in the number of multiple outdoor heat exchangers by optimizing the rotation speed of the outdoor fan 26. Hereinafter, the details of the control device 90 that controls the drive of the outdoor fan 26 will be described.

[0103] [Details of the control device according to this embodiment] Figure 4 It is a schematic diagram showing the relationship between the number of operating outdoor heat exchangers (the first outdoor heat exchanger 24 and the second outdoor heat exchanger 25) and the control range of the rotational speed of the outdoor fan 26.

[0104] It should be noted that in Figure 4 , on the right side of the thick line C in the center, it represents the control range of the rotational speed of the outdoor fan 26 when switching the number of outdoor heat exchangers functioning as condensers, and on the left side of the thick line C, it represents the relationship between the number of operating outdoor heat exchangers functioning as evaporators and the control range of the rotational speed of the outdoor fan 26. Hereinafter, the rotational speed of the compressor 21 is assumed to be constant for the following description.

[0105] When the outdoor heat exchanger functions as a condenser, the rotational speed of the outdoor fan 26 is controlled within the above control range so that the condensation temperature is maintained between the control upper limit and the control lower limit shown in (C) of Figure 3 . In the example shown in Figure 4 , when the number of operating outdoor heat exchangers increases, the control range of the rotational speed of the outdoor fan 26 is 0 rpm to 720 rpm for one outdoor heat exchanger, and 360 rpm to the maximum rotational speed (max) for two outdoor heat exchangers. In addition, when the number of operating outdoor heat exchangers decreases, the control range of the rotational speed of the outdoor fan 26 is 300 rpm to the maximum rotational speed (max) for two outdoor heat exchangers, and 0 rpm to 600 rpm for one outdoor heat exchanger. That is, when the condensation temperature cannot be made below the control upper limit due to insufficient condensation capacity even when the rotational speed of the outdoor fan 26 reaches the upper limit value, when the number of operating outdoor heat exchangers is increased from one to two to improve the condensation capacity, the rotational speed of the outdoor fan 26 just before the increase is set to 720 rpm, and the rotational speed of the outdoor fan 26 just after the increase is set to 360 rpm. In addition, even when the rotational speed of the outdoor fan 26 reaches the lower limit value, the condensation temperature is not between the control upper limit and the control lower limit. Therefore, when the number of operating outdoor heat exchangers is decreased from two to one, the rotational speed of the outdoor fan 26 just before the decrease is set to 300 rpm, and the rotational speed of the outdoor fan 26 just after the decrease is set to 600 rpm.

[0106] On the other hand, the same applies to the case where the outdoor heat exchanger functions as an evaporator. In Figure 4In the example shown, when the number of outdoor heat exchangers in use increases, the control range of the rotational speed of the outdoor fan 26 is 300 rpm to 680 rpm when there is 1 outdoor heat exchanger, and 340 rpm to the maximum rotational speed (max) when there are 2 outdoor heat exchangers. Additionally, when the number of outdoor heat exchangers in use decreases, the control range of the rotational speed of the outdoor fan 26 is 300 rpm to the maximum rotational speed (max) when there are 2 outdoor heat exchangers, and 300 rpm to 600 rpm when there is 1 outdoor heat exchanger. That is, the rotational speed of the outdoor fan 26 before increasing the number of units in use from 1 to 2 is set to 680 rpm, and the rotational speed of the outdoor fan 26 immediately after the increase is set to 340 rpm. The rotational speed of the outdoor fan 26 before decreasing the number of units in use from 2 to 1 is set to 300 rpm, and the rotational speed of the outdoor fan 26 immediately after the decrease is set to 600 rpm.

[0107] Regarding the rotational speed of the outdoor fan 26 before and after increasing or decreasing the number of outdoor heat exchangers in use, the rotational speed before the change in the number of units is set to be twice the rotational speed after the change in the number of units. However, this is not limited to this, and as will be described later, the rotational speed before the change in the number of units can also be set to be less than twice the rotational speed after the change in the number of units. It should be noted that when the outdoor heat exchanger functions as an evaporator, the lower limit value of the controlled rotational speed of the outdoor fan 26 is not set to 0 rpm to prevent the refrigerant from being incompletely evaporated in the outdoor heat exchanger and being sucked into the compressor 21 in a liquid phase state (liquid return).

[0108] Figure 5 It is a flowchart showing an example of the processing procedure executed by the control device 90 in the air conditioner 10 of the present embodiment. First, an example where the outdoor heat exchanger functions as a condenser will be described.

[0109] (Case where the outdoor heat exchanger functions as a condenser) If the air conditioner 10 starts operating, the control device 90 acquires the operation information of each indoor unit 8a to 8c via the communication unit 93 (step 101). As the information of the indoor units 8a to 8c, it is information related to the air conditioning state of the indoor units 8a to 8c. For example, the operation modes such as "cooling" and "heating" of the indoor units 8a to 8c, and the air conditioning capabilities such as the required cooling capacity and heating capacity of the indoor units 8a to 8c can be cited. As the operation modes of the air conditioner 10 in which the outdoor heat exchanger (the first outdoor heat exchanger 24, the second outdoor heat exchanger 25) functions as a condenser, full cooling operation or cooling main operation can be cited.

[0110] Next, the control device 90 determines the number of outdoor heat exchangers to be used based on the operation information of the indoor units 8a to 8c obtained in step 101 (step 102). In the present embodiment, when the air-conditioning capacity required by the indoor units 8a to 8c can be provided by the heat exchange amount (condensation capacity) of one outdoor heat exchanger, only the first outdoor heat exchanger 24 is used. When it cannot be provided by the heat exchange amount (condensation capacity) of one outdoor heat exchanger, both the first outdoor heat exchanger 24 and the second outdoor heat exchanger 25 are used.

[0111] When the number of outdoor heat exchangers to be used is one, the first four-way valve 22 is switched so that port a communicates with port b, and the second four-way valve 23 is switched so that port f communicates with port g (the second outdoor expansion valve 41 is fully closed). Thus, only the first outdoor heat exchanger 24 functions as a condenser, and the second outdoor heat exchanger 25 is in a state of being stopped from use. The rotation speed of the outdoor fan 26 is controlled so that the condensation temperature of the refrigerant in the first outdoor heat exchanger 24 becomes Figure 3 the temperature between the control lower limit and the control upper limit shown in (C) of

[0112] On the other hand, when the number of outdoor heat exchangers to be used is two, the first four-way valve 22 is switched so that port a communicates with port b, and the second four-way valve 23 is switched so that port e communicates with port f. Thus, both the first outdoor heat exchanger 24 and the second outdoor heat exchanger 25 function as condensers. The rotation speed of the outdoor fan 26 is controlled so that the condensation temperature of the refrigerant in the first outdoor heat exchanger 24 and the second outdoor heat exchanger 25 becomes Figure 3 the temperature between the control lower limit and the control upper limit shown in (C) of

[0113] The control device 90 determines, for example, based on the change in the air-conditioning capacity required by the indoor unit, whether it is necessary to change the number of outdoor heat exchangers to be used (step 103). When the control device 90 determines that it is not necessary to change the number of outdoor heat exchangers to be used (No in step 103), it continues to operate with the current number of outdoor heat exchangers. On the other hand, when the control device 90 determines that it is necessary to change the number of outdoor heat exchangers to be used (Yes in step 103), it determines whether to increase the number of outdoor heat exchangers to be used according to the required air-conditioning capacity (step 104).

[0114] As described above, the rotation speed of the outdoor fan 26 is controlled within the control range determined for each number of outdoor heat exchangers to be used so that the condensation temperature is maintained at Figure 3between the upper control limit and the lower control limit shown in (C) thereof. For example, when the number of outdoor heat exchangers in use is 1, the condensation temperature of the refrigerant in the first outdoor heat exchanger 24 is maintained between the upper control limit and the lower control limit. In this case, the operation is continued with the current number of outdoor heat exchangers in use (1) without increasing the number of outdoor heat exchangers in use. On the other hand, when the rise in the condensation temperature of the refrigerant cannot be suppressed below the upper control limit even when the rotational speed of the outdoor fan 26 is at the upper limit value (720 rpm), it is determined that it is necessary to increase the number of outdoor heat exchangers in use (improve the condensation capacity) (Yes in step 104).

[0115] On the other hand, when the number of outdoor heat exchangers in use is 2, the condensation temperatures of the refrigerants in the first outdoor heat exchanger 24 and the second outdoor heat exchanger 25 are maintained between the upper control limit and the lower control limit. In this case, the operation is continued with the current number of outdoor heat exchangers in use (2) without reducing the number of outdoor heat exchangers in use. On the other hand, when the decrease in the condensation temperature of the refrigerant cannot be suppressed above the lower control limit even when the rotational speed of the outdoor fan 26 is at the lower limit value (300 rpm), it is determined that it is necessary to reduce the number of outdoor heat exchangers in use (reduce the condensation capacity) (No in step 104).

[0116] When it is determined to increase the number of outdoor heat exchangers in use (Yes in step 104), the control device 90 determines the rotational speed of the outdoor fan 26 so that the heat exchange amount in the outdoor heat exchanger after the number of units is increased is equal to or less than the heat exchange amount in the outdoor heat exchanger before the number of units is increased (step 105a). Thereby, it is possible to suppress a sharp decrease in the condensation temperature of the refrigerant in the outdoor heat exchanger immediately after the number of units is increased.

[0117] Figure 6 is a diagram for explaining one operation of the air conditioner 10 obtained by setting the rotational speed of the outdoor fan 26 within the control range shown in Figure 4 and shows the relationship between the number of outdoor heat exchangers in use and the heat exchange amount (condensation capacity) of the outdoor heat exchanger before and after the increase in the number of units and the condensation temperature of the refrigerant in the outdoor heat exchanger. (A) is a diagram showing an example of the relationship between the number of outdoor heat exchangers in use and their heat exchange amount. The higher the rotational speed of the outdoor fan 26, the greater the heat exchange amount of the outdoor heat exchanger. Then, (B) is a diagram showing an example of the change in the condensation temperature of the refrigerant flowing in the outdoor heat exchanger. In this example, at time T1, the number of outdoor heat exchangers in use is changed from 1 to 2.

[0118] In step 105a, as shown in Figure 6As shown in (A) below, when the maximum heat exchange amount (HE1max) in the outdoor heat exchanger before the number of units is increased is set as the first heat exchange amount and the minimum heat exchange amount (HE2min) in the outdoor heat exchanger after the number of units is increased is set as the second heat exchange amount, the control device 90 determines the rotational speed of the outdoor fan 26 so that the first heat exchange amount is equal to or greater than the second heat exchange amount (HE1max≥HE2min). In Figure 6 In (A) below, the dashed line indicates the case where the first heat exchange amount is the same as the second heat exchange amount (HE1max = HE2min), and the double-dashed line indicates the case where the first heat exchange amount is greater than the second heat exchange amount (HE1max>HE2min).

[0119] As Figure 6 shown in (B) below, in the case where the first heat exchange amount is the same as the second heat exchange amount (HE1max = HE2min), it is possible to maintain a constant condensation temperature without changing the condensation temperature before and after the number of outdoor heat exchangers is increased. In addition, in the case where the first heat exchange amount is greater than the second heat exchange amount (HE1max>HE2min), the condensation temperature of the refrigerant in the outdoor heat exchanger is as Figure 6 shown by the double-dashed line in (B) below, it temporarily rises and then converges to the original condensation temperature. In this way, by controlling the rotational speed of the outdoor fan 26 to obtain a heat exchange amount that satisfies the relationship of HE1max≥HE2min, it is possible to prevent Figure 3 as shown in (C) below, a sharp decrease in the condensation temperature of the refrigerant in the outdoor heat exchanger due to excessive condensation capacity.

[0120] Regarding the relationship between the number of outdoor heat exchangers used and their heat exchange amount, as Figure 7 shown below, when the difference between the first heat exchange amount (HE1max) and the second heat exchange amount (HE2min) is set as A and the magnitude of the first heat exchange amount (the total change amount of the heat exchange amount when the number of outdoor heat exchangers used is 1) is set as B, the second heat exchange amount is expressed as (B - A). Then, when the value obtained by dividing the second heat exchange amount by the first heat exchange amount is used as the heat exchange amount change rate ((B - A) / B), the control device 90 determines the rotational speed of the outdoor fan 26 so that the heat exchange amount change rate is equal to or less than a given first threshold value.

[0121] In the case where the first threshold value is greater than 1, the second heat exchange amount is greater than the first heat exchange amount (HE1max<HE2min), as Figure 3As shown in (B) and (C) of , the heat exchange amount of the outdoor heat exchanger increases sharply immediately after the number of operating units is increased, and may greatly exceed the required condensation capacity, resulting in a sharp decrease in the condensation temperature. Therefore, the first threshold value is preferably 1 or less. Further, the first threshold value is more preferably 1 (HE1max = HE2min). In this case, since the heat exchange amount does not change before and after the increase or decrease in the number of operating units of the outdoor heat exchanger, the air-conditioning capacity exhibited remains stable without change.

[0122] In addition, the control device 90 determines the rotation speed of the outdoor fan 26 so that the heat exchange amount change rate ((B - A) / B) is equal to or greater than a given second threshold value, and the second threshold value is a value smaller than the first threshold value. When the first threshold value is less than 1, the second heat exchange amount is smaller than the first heat exchange amount ( Figure 6 the double-dot dash line in (A) of ), and therefore, the condensation temperature of the refrigerant in the outdoor heat exchanger immediately after the number of units is increased rises compared to before the increase in the number of units ( Figure 6 the double-dot dash line in (B) of ). The larger the difference A between the first heat exchange amount and the second heat exchange amount, the greater the increase in the condensation temperature at this time. If the condensation temperature reaches Figure 3 the given high-pressure protection control start temperature shown in (C) of Figure 6 and (B) of , in order to protect the compressor 21, the compressor 21 is stopped, and the operation of the air-conditioning device 10 also stops accordingly. Therefore, the second threshold value is set to any value that suppresses the condensation temperature below the high-pressure protection control start temperature (for example, 57.6°C), and is preferably 0.5 or more, for example.

[0123] In addition, in the present embodiment, when increasing the outdoor heat exchanger that functions as a condenser, the upper limit value of the rotation speed of the outdoor fan 26 when the number of operating units is 1 is 720 rpm, and the lower limit value of the rotation speed of the outdoor fan 26 when the number of operating units is 2 is 360 rpm (see Figure 4 ). Therefore, the cumulative value of the number of units and rotation speed of the heat exchange amount when the number of operating units is 1 is 720 [unit·rpm] (1 unit × 720 rpm), and the cumulative value of the number of units and rotation speed of the heat exchange amount when the number of operating units is 2 is also 720 [unit·rpm] (2 units × 360 rpm). Therefore, even when the number of operating units of the outdoor heat exchanger is increased from 1 unit to 2 units, the first heat exchange amount and the second heat exchange amount can be set to the same value (HE1max = HE2min, heat exchange amount change rate: (B - A) / B = 1).

[0124] It should be noted that the first heat exchange amount (HE1max) and the second heat exchange amount (HE2min), Figure 4The rotation speed of the outdoor fan 26 and the second threshold value shown are respectively values determined in advance through tests or the like. These measured values are stored in the storage unit 92 of the control device 90 and are referred to when changing the number of outdoor heat exchangers in use.

[0125] In addition, in addition to the method of obtaining the heat exchange amount of the outdoor heat exchanger through the above-mentioned test, the control device 90 can also use an evaluation index determined based on the volume of each outdoor heat exchanger (the first outdoor heat exchanger 24, the second outdoor heat exchanger 25), the air volume delivered by the outdoor fan 26, and the ratio of the air volume flowing into each outdoor heat exchanger to the above-mentioned air volume delivered. In this case, if information related to the volume of the outdoor heat exchanger and the ratio of the above-mentioned air volume is stored in the storage unit 92 in advance, the heat exchange amount of the outdoor heat exchanger can be estimated based on the number of outdoor heat exchangers in use and the rotation speed of the outdoor fan 26. Therefore, the heat exchange amount change rate ((B - A) / B) can also be calculated based on this estimated value, and the rotation speed of the outdoor fan 26 can be determined so that this value is 1 (the first threshold) or less.

[0126] Furthermore, the increase in the number of outdoor heat exchangers in use can also be carried out before the heat exchange amount of the outdoor heat exchanger reaches its maximum value (HE1max). In this case, the heat exchange amount change rate ((B' - A) / B' (B' is the heat exchange amount just before the number of units is increased)) can also be calculated based on the heat exchange amount estimated as described above, and the rotation speed of the outdoor fan 26 before and after the increase in the number of units can be controlled separately so that the change rate is, for example, 0.5 or more and 1 or less.

[0127] In addition, by selecting the first heat exchange amount B that can select the rotation speed of the outdoor fan 26 to be exactly 1 / 2 times (when the number of outdoor heat exchangers increases), the heat exchange amount ratio can be set to 1. Therefore, when such a rotation speed can be selected, the number of outdoor heat exchangers in use can also be increased before the first heat exchange amount reaches its maximum value (HE1max). In addition, when the rotation speed of the outdoor fan 26 can only be selected in predetermined steps, the number of outdoor heat exchangers in use can also be increased in the step (rotation speed) where the heat exchange amount ratio is the value closest to 1.

[0128] As described above, after determining the rotational speed of the outdoor fan 26 in step 105a, the control device 90 switches the second four-way valve 23 so that port e is in communication with port f (step 106), and adjusts the opening degree of the second outdoor expansion valve 41 to the same opening degree as that of the first outdoor expansion valve 40. In addition, the control device 90 adjusts the rotational speed of the outdoor fan 26 to the lower limit value (360 rpm) of the rotational speed when the number of outdoor heat exchangers in use is two (step 107). Thus, the number of outdoor heat exchangers in use is changed to two. After that, the control device 90 controls the rotational speed of the outdoor fan 26 between 360 rpm and the maximum value so that the condensation temperature becomes a temperature between the control upper limit and the control lower limit (step 108).

[0129] On the other hand, in the case of performing full refrigeration operation or main refrigeration operation using two outdoor heat exchangers as condensers, for example, when it is determined that the number of indoor units performing heating operation increases and it is necessary to reduce the number of outdoor heat exchangers in use according to the required air-conditioning capacity (in step 104, "no"), the control device 90 determines the rotational speed of the outdoor fan 26 so that the heat exchange amount in the outdoor heat exchanger after the number reduction is equal to or greater than the heat exchange amount in the outdoor heat exchanger before the number reduction (step 105b).

[0130] In step 105b, as Figure 7 shown, when setting the maximum value (HE1max) of the heat exchange amount in the outdoor heat exchanger after the number reduction as the first heat exchange amount and the minimum value (HE2min) of the heat exchange amount in the outdoor heat exchanger before the number reduction as the second heat exchange amount, when the control device 90 determines that the number of outdoor heat exchangers in use is reduced, it determines the rotational speed of the outdoor fan 26 so that the first heat exchange amount is equal to or greater than the second heat exchange amount (HE1max≥HE2min). Thus, it is possible to maintain the condensation temperature of the refrigerant in the outdoor heat exchanger constant when the number is reduced.

[0131] When reducing the number of outdoor heat exchangers in use, similar to when increasing the number of them in use, when taking the value obtained by dividing the second heat exchange amount by the first heat exchange amount as the heat exchange amount change rate ((B - A) / B), the control device 90 determines the rotational speed of the outdoor fan 26 so that the heat exchange amount change rate is equal to or greater than the second threshold value and equal to or less than the first threshold value (in this embodiment, 0.5 or more and 1 or less). Thus, it is possible to prevent a sharp drop in the condensation temperature of the refrigerant in the outdoor heat exchanger when the number is reduced, and it is possible to maintain the high pressure of the outdoor heat exchanger functioning as a condenser.

[0132] In this embodiment, when reducing the number of outdoor heat exchangers functioning as condensers, the lower limit of the rotational speed of the outdoor fan 26 when the number of units in use is two is 300 rpm, and the upper limit of the rotational speed of the outdoor fan 26 when the number of units in use is one is 600 rpm (refer to Figure 5 ). Therefore, the cumulative value of the number of units and rotational speed of the heat exchange amount when the number of units in use is two is 600 [unit·rpm] (2 units × 300 rpm), and the cumulative value of the number of units and rotational speed of the heat exchange amount when the number of units in use is one is also 600 [unit·rpm] (1 unit × 600 rpm). Therefore, when switching the number of outdoor heat exchangers in use from two to one, the first heat exchange amount and the second heat exchange amount can be set to the same value (HE1max = HE2min, (B - A) / B = 1).

[0133] As described above, after determining the rotational speed of the outdoor fan 26 in step 105b, the control device 90 switches the second four-way valve 23 so that port f communicates with port g, and fully closes the second outdoor expansion valve 41 (step 106). In addition, the control device 90 adjusts the rotational speed of the outdoor fan 26 to the upper limit value of the rotational speed when the number of outdoor heat exchangers in use is one (600 rpm) (step 107). Thereby, the number of outdoor heat exchangers in use is changed to one. After that, the control device 90 controls the rotational speed of the outdoor fan 26 between 0 rpm and 600 rpm so that the condensation temperature becomes a temperature between the control upper limit and the control lower limit (step 108). By repeatedly executing the above processing, the air conditioner 10 continues full cooling operation or cooling main body operation.

[0134] (When the outdoor heat exchanger functions as an evaporator) Next, the case where the outdoor heat exchanger functions as an evaporator will be described. As the operation modes of the air conditioner 10 in which the outdoor heat exchanger (the first outdoor heat exchanger 24, the second outdoor heat exchanger 25) functions as an evaporator, full heating operation or heating main body operation can be cited. In full heating operation or heating main body operation, the control device 90 also executes processing according to the Figure 5 flowchart shown. Hereinafter, the description will be centered on the parts different from the above.

[0135] When the number of outdoor heat exchangers in use is one, the first four-way valve 22 is switched so that port b communicates with port c, and the second four-way valve 23 is switched so that port f communicates with port g (the second outdoor expansion valve 41 is fully closed). Thereby, only the first outdoor heat exchanger 24 functions as an evaporator, and the second outdoor heat exchanger 25 is in a state of being out of use. The rotational speed of the outdoor fan 26 is controlled so that the evaporation temperature of the refrigerant in the outdoor heat exchanger becomes a temperature between the control lower limit and the control upper limit.

[0136] On the other hand, when the number of outdoor heat exchangers in use is two, the first four-way valve 22 is switched so that port b communicates with port c, and the second four-way valve 23 is switched so that port f communicates with port g. Thus, both the first outdoor heat exchanger 24 and the second outdoor heat exchanger 25 function as evaporators. The rotational speed of the outdoor fan 26 is controlled so that the condensation temperature of the refrigerant in the first outdoor heat exchanger 24 and the second outdoor heat exchanger 25 becomes a temperature between the control lower limit and the control upper limit.

[0137] The control device 90 determines, for example, based on the change in the air-conditioning capacity required by the indoor unit, whether it is necessary to change the number of outdoor heat exchangers in use (step 103). When the control device 90 determines that it is not necessary to change the number of outdoor heat exchangers in use (No in step 103), it continues to operate with the current number of outdoor heat exchangers. On the other hand, when the control device 90 determines that it is necessary to change the number of outdoor heat exchangers in use (Yes in step 103), it determines whether to increase the number of outdoor heat exchangers in use according to the required air-conditioning capacity (step 104).

[0138] The rotational speed of the outdoor fan 26 is controlled within the control range determined for each number of outdoor heat exchangers in use so that the evaporation temperature is maintained between the control upper limit and the control lower limit (refer to (B) described later). Figure 8 For example, when the number of outdoor heat exchangers in use is one, the evaporation temperature of the refrigerant in the first outdoor heat exchanger 24 is maintained between the control upper limit and the control lower limit. In this case, the operation continues with the current number of outdoor heat exchangers in use (one) without increasing the number. In contrast, when the evaporation temperature of the refrigerant cannot be suppressed above the control lower limit even when the rotational speed of the outdoor fan 26 is the upper limit value (680 rpm), it is determined that it is necessary to increase the number of outdoor heat exchangers in use (increase the evaporation capacity) (Yes in step 104).

[0139] On the other hand, when the number of outdoor heat exchangers in use is two, the evaporation temperatures of the refrigerant in the first outdoor heat exchanger 24 and the second outdoor heat exchanger 25 are maintained between the control upper limit and the control lower limit. In this case, the operation continues with the current number of outdoor heat exchangers in use (two) without reducing the number. In contrast, when the evaporation temperature of the refrigerant cannot be suppressed below the control upper limit even when the rotational speed of the outdoor fan 26 is the lower limit value (300 rpm), it is determined that it is necessary to reduce the number of outdoor heat exchangers in use (reduce the evaporation capacity) (No in step 104).

[0140] When it is determined that the number of outdoor heat exchangers to be increased (Yes in step 104), the control device 90 determines the rotation speed of the outdoor fan 26 so that the heat exchange amount in the outdoor heat exchanger after the number increase is equal to or less than the heat exchange amount in the outdoor heat exchanger before the number increase (step 105a). Thereby, it is possible to suppress a sharp rise in the evaporation temperature of the refrigerant in the outdoor heat exchanger immediately after the number increase.

[0141] Figure 8 This is a diagram for explaining one operation of the air conditioner 10 obtained by setting the rotation speed of the outdoor fan 26 within the control range shown in Figure 4 It shows the relationship between the number of outdoor heat exchangers used and the heat exchange amount (evaporation capacity) of the outdoor heat exchanger before and after the increase in the number of used units, and the evaporation temperature of the refrigerant in the outdoor heat exchanger. (A) is a diagram showing an example of the relationship between the number of outdoor heat exchangers used and their heat exchange amount. The higher the rotation speed of the outdoor fan 26, the greater the heat exchange amount of the outdoor heat exchanger. Then, (B) is a diagram showing an example of the change in the evaporation temperature of the refrigerant flowing in the outdoor heat exchanger. In this example, at time T2, the number of outdoor heat exchangers used changes from 1 to 2.

[0142] In step 105a, as shown in (A) of Figure 8 when the maximum value (HE1max) of the heat exchange amount in the outdoor heat exchanger before the number increase is set as the first heat exchange amount and the minimum value (HE2min) of the heat exchange amount in the outdoor heat exchanger after the number increase is set as the second heat exchange amount, the control device 90 determines the rotation speed of the outdoor fan 26 so that the first heat exchange amount is equal to or greater than the second heat exchange amount (HE1max≥HE2min). In Figure 8 In (A) of

[0143] As shown in (B) of Figure 8 when the first heat exchange amount is the same as the second heat exchange amount (HE1max = HE2min), it is possible to maintain the evaporation temperature constant without change before and after the increase in the number of outdoor heat exchangers. In addition, when the first heat exchange amount is the same as the second heat exchange amount (HE1max = HE2min), the evaporation temperature of the refrigerant in the outdoor heat exchanger temporarily decreases and then converges to the original evaporation temperature. Thus, by controlling the rotation speed of the outdoor fan 26 to obtain a heat exchange amount that satisfies the relationship of HE1max≥HE2min, it is possible to prevent a sharp rise in the evaporation temperature of the refrigerant in the outdoor heat exchanger due to excessive evaporation capacity.

[0144] Regarding the relationship between the number of outdoor heat exchangers in use and their heat exchange capacity, as Figure 9 shown, when the difference between the first heat exchange capacity (HE1max) and the second heat exchange capacity (HE2min) is set as C, and the magnitude of the first heat exchange capacity (the total change amount of the heat exchange capacity when the number of outdoor heat exchangers in use is 1) is set as D, the second heat exchange capacity is expressed as (D - C). Then, when the value obtained by dividing the second heat exchange capacity by the first heat exchange capacity is used as the heat exchange capacity change rate ((D - C) / D), the control device 90 determines the rotational speed of the outdoor fan 26 so that the heat exchange capacity change rate is below a given first threshold value.

[0145] When the first threshold value is greater than 1, the second heat exchange capacity is greater than the first heat exchange capacity (HE1max < HE2min), and the heat exchange capacity of the outdoor heat exchanger rises sharply just after the number of units in use increases, and it may greatly exceed the required evaporation capacity, resulting in a sharp rise in the evaporation temperature. Therefore, the first threshold value is preferably 1 or less, and most preferably 1.

[0146] In addition, the control device 90 determines the rotational speed of the outdoor fan 26 so that the heat exchange capacity change rate ((D - C) / D) is above a given second threshold value, and the second threshold value is a value smaller than the first threshold value. When the first threshold value is less than 1, since the second heat exchange capacity is smaller than the first heat exchange capacity ( Figure 8 in (A)), the evaporation temperature of the refrigerant in the outdoor heat exchanger just after the number of units increases decreases compared with before the number of units increases ( Figure 6 in (B)). The larger the difference C between the first heat exchange capacity and the second heat exchange capacity, the greater the decrease in the evaporation temperature at this time. If the evaporation temperature reaches a given low-pressure protection control start temperature, the operation of the air conditioner 10 stops from the viewpoint of the low-pressure protection of the outdoor heat exchanger functioning as an evaporator. Therefore, the second threshold value is set to any value that suppresses the evaporation temperature below a given low-pressure protection control start temperature (for example, -30°C), and is preferably 0.5 or more, for example.

[0147] On the one hand, in the present embodiment, when increasing the outdoor heat exchanger functioning as an evaporator, the upper limit value of the rotational speed of the outdoor fan 26 when the number of units in use is 1 is 680 rpm, and the lower limit value of the rotational speed of the outdoor fan 26 when the number of units in use is 2 is 340 rpm (refer to Figure 5). Therefore, the cumulative value of the number of units and rotational speed of the heat exchange amount when the number of units used is 2 is 680 [unit·rpm] (1 unit × 680 rpm), and the cumulative value of the number of units and rotational speed of the heat exchange amount when the number of units used is 2 is also 680 [unit·rpm] (2 units × 340 rpm). Therefore, when switching the number of outdoor heat exchangers used from 1 unit to 2 units, the first heat exchange amount and the second heat exchange amount can be set to the same value (HE1max = HE2min, (D - C) / D = 1).

[0148] As described above, after determining the rotational speed of the outdoor fan 26 in step 105a, the control device 90 maintains the second four-way valve 23 in a state where port f and port g are connected, and gradually increases the opening degree of the second outdoor expansion valve 41 from the closed state (step 106). In addition, the control device 90 adjusts the rotational speed of the outdoor fan 26 to the lower limit value of the rotational speed when the number of outdoor heat exchangers used is 2 (340 rpm) (step 107). Thus, the number of outdoor heat exchangers used is changed to 2 units. After that, the rotational speed of the outdoor fan 26 is controlled between 340 rpm and the maximum value according to the air-conditioning state so that the evaporation temperature becomes a temperature between the control upper limit and the control lower limit (step 108).

[0149] On the other hand, in the case of performing full heating operation or heating main operation using 2 outdoor heat exchangers as evaporators, for example, when it is determined that the number of indoor units performing cooling operation has decreased and it is necessary to reduce the number of outdoor heat exchangers used according to the required air-conditioning capacity (in step 104, "no"), the control device 90 determines the rotational speed of the outdoor fan 26 so that the heat exchange amount in the outdoor heat exchanger after the number of units is reduced is not less than the heat exchange amount in the outdoor heat exchanger before the number of units is reduced (step 105b).

[0150] In step 105b, as Figure 9 shown, when setting the maximum value (HE1max) of the heat exchange amount in the outdoor heat exchanger after the number of units is reduced as the first heat exchange amount and the minimum value (HE2min) of the heat exchange amount in the outdoor heat exchanger before the number of units is reduced as the second heat exchange amount, when the control device 90 determines that the number of outdoor heat exchangers used is reduced, it determines the rotational speed of the outdoor fan 26 so that the first heat exchange amount is not less than the second heat exchange amount (HE1max ≥ HE2min). Thus, the evaporation temperature of the refrigerant in the outdoor heat exchanger can be maintained constant when the number of units is reduced.

[0151] When reducing the number of outdoor heat exchangers in use, similar to when increasing the number of outdoor heat exchangers in use, when the value obtained by dividing the second heat exchange amount by the first heat exchange amount is used as the heat exchange amount change rate ((D - C) / D), the control device 90 determines the rotational speed of the outdoor fan 26 so that the heat exchange amount change rate is equal to or greater than the second threshold value and equal to or less than the first threshold value (in this embodiment, 0.5 or more and 1 or less). Thereby, it is possible to prevent a sharp drop in the evaporation temperature of the refrigerant in the outdoor heat exchanger when the number of units is reduced, and it is possible to maintain the low pressure of the outdoor heat exchanger functioning as an evaporator.

[0152] In this embodiment, when reducing the outdoor heat exchanger functioning as an evaporator, the lower limit value of the rotational speed of the outdoor fan 26 when the number of units in use is 2 is 300 rpm, and the upper limit value of the rotational speed of the outdoor fan 26 when the number of units in use is 1 is 600 rpm (refer to Figure 5 ). Therefore, the cumulative value of the number of units · rotational speed of the heat exchange amount when the number of units in use is 2 is 600 [unit · rpm] (2 units × 300 rpm), and the cumulative value of the number of units · rotational speed of the heat exchange amount when the number of units in use is 1 is also 600 [unit · rpm] (1 unit × 600 rpm). Therefore, when switching the number of outdoor heat exchangers in use from 2 units to 1 unit, it is possible to make the first heat exchange amount and the second heat exchange amount the same value (HE1max = HE2min, (D - C) / D = 1).

[0153] As described above, after determining the rotational speed of the outdoor fan 26 in step 105b, the control device 90 maintains the state where the port e and the port f of the second four-way valve 23 are in communication, and fully closes the second outdoor expansion valve 41 (step 106). In addition, the control device 90 adjusts the rotational speed of the outdoor fan 26 to the upper limit value of the rotational speed when the number of outdoor heat exchangers in use is 1 (600 rpm) (step 107). Thereby, the number of outdoor heat exchangers in use is changed to 1 unit. After that, the control device 90 controls the rotational speed of the outdoor fan 26 between 300 rpm and 600 rpm according to the air-conditioning state so that the evaporation temperature becomes a temperature between the control upper limit and the control lower limit (step 108). By repeatedly performing the above processing, the air-conditioning device 10 continues to perform full heating operation or heating main body operation.

[0154] As described above, according to the present embodiment, when increasing the number of outdoor heat exchangers in use, the rotational speed of the outdoor fan is determined so that the heat exchange amount in the outdoor heat exchanger after the number of units is increased is equal to or less than the heat exchange amount in the outdoor heat exchanger before the number of units is increased. When decreasing the number of outdoor heat exchangers in use, the rotational speed of the outdoor fan is determined so that the heat exchange amount in the outdoor heat exchanger after the number of units is decreased is equal to or greater than the heat exchange amount in the outdoor heat exchanger before the number of units is decreased. Therefore, it is possible to prevent a sudden change in the condensation temperature or evaporation temperature of the refrigerant when increasing or decreasing the number of outdoor heat exchangers in use.

[0155] Thereby, it is possible to prevent deterioration of the comfort of the occupants due to a decrease in the heating performance or cooling performance of each indoor unit. In addition, since it is possible to prevent a sudden change in the condensation temperature or evaporation temperature when increasing or decreasing the number of outdoor heat exchangers in use, it is possible to prevent frequent switching operations of the number of outdoor heat exchangers in use. Thereby, it is possible to prevent noise of the operation sound of the flow path switching valve and a decrease in reliability due to deterioration.

[0156] The embodiments of the present invention have been described above, but the present invention is not limited to the above-described embodiments, and it goes without saying that various modifications can be made.

[0157] For example, in the above embodiment, the air conditioner 10 having one outdoor unit 2a has been described as an example, but the present invention can also be applied to an air conditioner having two or more outdoor units.

[0158] Figure 10 FIG. is a refrigerant circuit diagram of an air conditioner 20 having two outdoor units 2a and 2b and three indoor units 8a to 8c. In this figure, the outdoor units 2a and 2b have the same structure, and the outdoor high-pressure gas pipes 33 of the respective outdoor units 2a and 2b are connected to the high-pressure gas pipe via the stop valves 44, the high-pressure gas branch pipes 30a and 30b, and the flow dividing unit 70. In addition, the outdoor low-pressure gas pipes 34 of the respective outdoor units 2a and 2b are connected to the low-pressure gas pipe 31 via the stop valves 45, the low-pressure gas branch pipes 31a and 31b, and the flow dividing unit 71. Further, the outdoor liquid pipes 35 of the respective outdoor units 2a and 2b are connected to the liquid pipe 32 via the stop valves 46, the liquid branch pipes 32a and 32b, and the flow dividing unit 72.

[0159] Regarding Figure 10The air conditioner 20 shown has a total of four outdoor heat exchangers since each of the outdoor units 2a and 2b has two outdoor heat exchangers. The air conditioner 20 switches the number of outdoor heat exchangers in use between one and four according to, for example, an increase or decrease in the required capacity from the indoor units 8a to 8c, or an increase or decrease in the air-conditioning load caused by a change in the external air temperature. At this time, when the number of units in use increases, the rotational speed of the outdoor fan 26 is determined so that the heat exchange amount in the outdoor heat exchanger after the increase in the number of units is equal to or less than the heat exchange amount in the outdoor heat exchanger before the increase in the number of units. When the number of units in use decreases, the rotational speed of the outdoor fan is determined so that the heat exchange amount in the outdoor heat exchanger after the decrease in the number of units is equal to or greater than the heat exchange amount in the outdoor heat exchanger before the decrease in the number of units. Thus, the same operational effects as those of the above-described embodiment can be obtained.

[0160] In addition, in the above embodiment, an air conditioner in a free cooling and heating mode capable of performing cooling and heating mixed operation has been described as an example, but the present invention is not limited thereto, and the present invention can also be applied to an air conditioner using an operation mode (cooling and heating switching mode) in which any one of cooling or heating is performed in all indoor units.

[0161] In addition, in the above embodiment, a four-way valve (the first four-way valve 22 and the second four-way valve 23) is used as the flow path switching valve that is switched when the number of outdoor heat exchangers in use is increased or decreased, but a three-way valve can also be used as the flow path switching valve.

[0162] Explanation of reference numerals 2a, 2b Outdoor units 8a, 8b, 8c Indoor units 10, 20 Air conditioners 21 Compressor 22 First four-way valve 23 Second four-way valve 24 First outdoor heat exchanger 25 Second outdoor heat exchanger 30 High-pressure gas pipe 31 Low-pressure gas pipe 32 Liquid pipe 81 Indoor heat exchanger 90 Control device.

Claims

1. An air conditioning apparatus, comprising: A compressor; An outdoor unit having a plurality of outdoor heat exchangers, a plurality of flow path switching valves provided for each of the plurality of outdoor heat exchangers, and an outdoor fan, wherein the plurality of flow path switching valves switch the connection of one refrigerant inlet / outlet of each outdoor heat exchanger to be connected to the refrigerant discharge port or the refrigerant suction port of the compressor, and the outdoor fan blows air to the plurality of outdoor heat exchangers; At least one indoor unit connected to the outdoor unit through a refrigerant pipe; And A control device that controls the rotational speed of the outdoor fan, The control device determines whether to increase the number of outdoor heat exchangers used according to the required air conditioning capacity. When it is determined to increase the number of outdoor heat exchangers used, the control device determines the rotational speed of the outdoor fan so that the heat exchange amount in the outdoor heat exchangers after the number increase is less than or equal to the heat exchange amount in the outdoor heat exchangers before the number increase. The control device determines whether to reduce the number of outdoor heat exchangers used according to the required air conditioning capacity. When it is determined to reduce the number of outdoor heat exchangers used, the control device determines the rotational speed of the outdoor fan so that the heat exchange amount in the outdoor heat exchangers after the number decrease is greater than or equal to the heat exchange amount in the outdoor heat exchangers before the number decrease.

2. The air conditioning apparatus according to claim 1, Wherein, When the maximum value of the heat exchange amount in the outdoor heat exchangers before the number increase is set as the first heat exchange amount, and the minimum value of the heat exchange amount in the outdoor heat exchangers after the number increase is set as the second heat exchange amount, when the control device determines to increase the number of outdoor heat exchangers used, the control device determines the rotational speed of the outdoor fan so that the first heat exchange amount is greater than or equal to the second heat exchange amount.

3. The air conditioning apparatus according to claim 1, Wherein, When the maximum value of the heat exchange amount in the outdoor heat exchangers after the number decrease is set as the first heat exchange amount, and the minimum value of the heat exchange amount in the outdoor heat exchangers before the number decrease is set as the second heat exchange amount, when the control device determines to reduce the number of outdoor heat exchangers used, the control device determines the rotational speed of the outdoor fan so that the first heat exchange amount is greater than or equal to the second heat exchange amount.

4. The air conditioning apparatus according to claim 2 or 3, Wherein, When the value obtained by dividing the second heat exchange amount by the first heat exchange amount is used as the heat exchange amount change rate, the control device determines the rotational speed of the outdoor fan so that the heat exchange amount change rate is less than or equal to a given first threshold value.

5. The air conditioning apparatus according to claim 4, Wherein, The control device determines the rotational speed of the outdoor fan so that the heat exchange amount change rate is greater than or equal to a given second threshold value, and the second threshold value is a value less than the first threshold value.

6. The air conditioning apparatus according to any one of claims 1 to 3, Wherein, The control device uses an evaluation index determined based on the volume of each outdoor heat exchanger, the air volume delivered by the outdoor fan, and the ratio of the air volume flowing in each outdoor heat exchanger to the air volume delivered as the heat exchange amount.

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