Air conditioning apparatus and control method

Abstract

The present application provides an air conditioning device and a control method, which can inhibit intermittent operation of indoor units and maintain comfort in the case where multiple indoor units with different air conditioning loads or rated capacities are operating. The air conditioning device is provided with multiple indoor units (11a-11c) and an outdoor unit (12), each indoor unit (11a-11c) comprising an indoor heat exchanger (20a-20c), a room temperature sensor (21a-21c) for detecting the indoor temperature, and an indoor expansion valve (22a-22c) for adjusting the flow rate of refrigerant flowing in the indoor unit, and the outdoor unit (12) comprises an outdoor heat exchanger (32) and a compressor (30), and the air conditioning device comprises a controller (34) for calculating the difference between the load of the indoor unit (11a-11c) and the air conditioning capacity based on the deviation of the room temperature detected by the room temperature sensor (21a-21c) from the set temperature and the variation of the room temperature within a predetermined time, and controlling the opening degree of the indoor expansion valve (22a-22c) based on the obtained difference.

Description

Technical Field

[0001] This invention relates to an air conditioning device and a method for controlling the operation of the air conditioning device. Background Technology

[0002] Existing air conditioning systems adjust the indoor temperature (hereinafter referred to as room temperature) by controlling the frequency of the compressor in the outdoor unit according to the indoor air conditioning load. Air conditioning systems may include those with multiple indoor units. In such systems, the following situations exist: each indoor unit is installed in a different room and used under different air conditioning loads; or different rated capacities of indoor units are installed based on the room's spaciousness (air conditioning volume), etc.

[0003] When multiple indoor units with different air conditioning loads and rated capacities are operating, even with compressor frequency control, only the refrigerant flow circulating within the system can be controlled, not the refrigerant flow to each individual indoor unit. Therefore, sometimes an indoor unit may fail to maintain a stable room temperature. Currently, room temperature is stabilized by repeatedly stopping (thermal shutdown) and starting (thermal on) the indoor unit.

[0004] However, compared to continuous operation, the intermittent operation of repeatedly turning the equipment on and off with heat results in reduced efficiency and reliability, and greater fluctuations in room temperature, which can compromise comfort.

[0005] To avoid intermittent operation, an air conditioning device is known that, when the compressor is operating near its lowest operating frequency, forces the opening of the expansion valve of the outdoor unit to be smaller than the opening under normal control to reduce the refrigerant flow, thereby reducing the capacity (for example, see Patent Document 1).

[0006] However, in the aforementioned prior art, when multiple indoor units with different air conditioning loads and rated capacities are operating, even if the opening of the expansion valve of the outdoor unit is controlled, it is impossible to adjust the production capacity of each indoor unit. Therefore, there is a problem that the intermittent operation of the indoor units cannot be suppressed, and comfort cannot be obtained.

[0007] Patent Document 1: Japanese Patent Application Publication No. 10-141740 Summary of the Invention

[0008] In view of the above-mentioned problems, the present invention provides an air conditioning device comprising multiple indoor units and outdoor units.

[0009] Each indoor unit includes:

[0010] Indoor heat exchanger;

[0011] Indoor temperature detection unit, which detects indoor temperature; and

[0012] The indoor expansion valve is used to regulate the flow rate of refrigerant within the indoor unit.

[0013] The outdoor unit includes:

[0014] Outdoor heat exchangers; and

[0015] compressor,

[0016] The air conditioning unit includes a control unit that, for each indoor unit, calculates the difference between the load of the indoor unit and the air conditioning capacity of the indoor unit based on the deviation between the indoor temperature detected by the indoor temperature detection unit and the set temperature, as well as the change in indoor temperature over a predetermined time. Based on the obtained difference, the control unit controls the opening degree of the indoor expansion valve.

[0017] According to the present invention, when multiple indoor units with different air conditioning loads and rated capacities are operating, the intermittent operation of the indoor units can be suppressed, thereby maintaining comfort. Attached Figure Description

[0018] Figure 1 Example of the structure of an air conditioning unit.

[0019] Figure 2 This is an example of the hardware structure of the control device in an air conditioning unit.

[0020] Figure 3 The room temperature changes under the existing control system with intermittent operation of indoor units in each room are compared with those under this control system.

[0021] Figure 4 This is a flowchart representing the first control process for adjusting the air conditioning capacity of the indoor unit.

[0022] Figure 5 This is a flowchart representing the second control process for adjusting the air conditioning capacity of the indoor unit.

[0023] Figure 6 This is a flowchart representing the third control process for adjusting the air conditioning capacity of the indoor unit.

[0024] Figure 7 This is a flowchart representing the fourth control process for adjusting the air conditioning capacity of the indoor unit. Detailed Implementation

[0025] Figure 1This section illustrates a structural example of the air conditioning unit according to this embodiment. The air conditioning unit 10 is configured to include: multiple indoor units 11a-11c installed in multiple rooms such as residences or buildings; an outdoor unit 12 installed outdoors; a control device; and multiple operating devices (remote controllers) installed in each room for operating each indoor unit 11a-11c individually. The control device can be installed inside the indoor units 11a-11c or the outdoor unit 12, or it can be installed separately from the multiple indoor units 11a-11c and the outdoor unit 12. The number of indoor units 11a-11c can be as many as desired. Here, the control device is installed inside the outdoor unit 12, and three indoor units 11a-11c will be used for explanation.

[0026] Multiple indoor units 11a-11c are connected to outdoor unit 12 via piping 13, forming a system in which refrigerant circulates between the indoor units 11a-11c and outdoor unit 12 via piping 13. Hydrofluorocarbons such as R410a and R32 are used as the refrigerant. Furthermore, each indoor unit 11a-11c and outdoor unit 12 is connected to a communication cable or similar device for communication. The connection between the indoor units 11a-11c and outdoor unit 12 is not limited to a communication cable; it can also be configured to communicate wirelessly using devices such as WiFi (registered trademark).

[0027] Each indoor unit 11a-11c communicates wirelessly with the remote control located in each unit using infrared or similar methods. For example, the user operates the indoor unit 11a using the remote control. The user uses the remote control to start, stop, change the set temperature, and switch operating modes of the indoor unit 11a. These commands are sent to the indoor unit 11a wirelessly. The indoor unit 11a starts upon receiving a start command, and instructs the outdoor unit 12 to start if it is not already running. The indoor unit 11a notifies the outdoor unit 12 of any changes to the set temperature and operating mode. The indoor unit 11a stops upon receiving a stop command and notifies the user that it has stopped.

[0028] During operation, the indoor unit 11a draws in indoor air, exchanges heat between the drawn-in air and the refrigerant supplied from the outdoor unit 12, and blows out cooled or heated air to cool or heat the room to bring it to a set temperature. Therefore, the indoor unit 11a includes an indoor heat exchanger 20a that exchanges heat between indoor air and refrigerant, and an indoor fan that draws in indoor air and blows out the heat-exchanged air.

[0029] In order to notify the outdoor unit 12 of the room temperature, the indoor unit 11a is equipped with a room temperature sensor 21a, which serves as an indoor temperature detection unit for detecting the room temperature. In addition, the indoor unit 11a is equipped with an indoor expansion valve 22a, which is used to expand the refrigerant and adjust the flow rate of the refrigerant flowing in the indoor heat exchanger 20a.

[0030] When indoor unit 11a is used for heating, indoor heat exchanger 20a functions as a condenser, with refrigerant flowing into it in a gaseous state. The gaseous refrigerant flowing into indoor heat exchanger 20a exchanges heat with air drawn in by the indoor fan, condensing and discharging as a liquid from indoor heat exchanger 20a, then being sent to outdoor unit 12 via indoor expansion valve 22a. Only indoor unit 11a has been described here; indoor units 11b and 11c also have indoor heat exchangers 20b and 20c, room temperature sensors 21b and 21c, and indoor expansion valves 22b and 22c, and perform the same operations.

[0031] Outdoor unit 12 starts upon receiving a start command from one of the indoor units 11a-11c, and begins operation in a set operating mode or an operating mode notified by the indoor unit that issued the start command. Operating modes include cooling mode, heating mode, and fan mode. Outdoor unit 12 controls the temperature, pressure, and flow rate of the refrigerant based on the set temperature or room temperature notified by the indoor unit. Additionally, outdoor unit 12 receives a stop notification from indoor units 11a-11c, determines whether all indoor units 11a-11c have stopped, and stops operating if all have stopped.

[0032] The outdoor unit 12 includes a compressor 30 for circulating refrigerant within the system. The outdoor unit 12 also includes an outdoor expansion valve 31, which expands the refrigerant flowing within the system to adjust its flow rate. The compressor 30 includes an outdoor heat exchanger 32 for drawing in refrigerant in a gaseous state and discharging it while maintaining that state. This outdoor heat exchanger 32 is used to evaporate the refrigerant that is discharged from each indoor unit 11a-11c during heating operation and supplied via the outdoor expansion valve 31 in a two-phase state of gas and liquid mixture.

[0033] The outdoor unit 12 has an outdoor fan that draws in outside air, exchanges heat between the drawn-in outside air and the refrigerant, and then blows out the heat-exchanged outside air. In addition, in order to enable the air conditioning unit to operate in either cooling or heating mode, the outdoor unit 12 has a four-way valve 33 for switching the direction of refrigerant flow.

[0034] The outdoor unit 12 is equipped with a controller 34 as a control device. The controller 34 controls the operating frequency of the compressor 30, the opening degree of the outdoor expansion valve 31, and the opening degree of the indoor expansion valves 22a-22c based on the room temperature detected by the room temperature sensors 21a-21c, the set temperature of each indoor unit, and the operating mode. The controller 34 switches the four-way valve 33 according to the set operating mode.

[0035] The compressor 30 controls its operating frequency based on the total air conditioning load calculated from the loads of each indoor unit 11a-11c, adjusting the refrigerant flow rate circulating in the system, thereby adjusting the air conditioning capacity. The air conditioning capacity is calculated as the sum of the cooling or heating capabilities produced by each indoor unit 11a-11c. When the air conditioning load varies among indoor units, there may be indoor units with a larger air conditioning capacity than their air conditioning load; these indoor units may be unable to maintain the room temperature at the set temperature.

[0036] Therefore, the indoor unit is currently operating intermittently, repeatedly switching between hot shut-off and hot start-up, and is controlled to maintain each room temperature at its set temperature.

[0037] The intermittent operation of the indoor unit, with repeated starting and stopping, causes significant fluctuations in the compressor's operating frequency, resulting in higher energy consumption and lower energy efficiency. Furthermore, it increases the likelihood of equipment malfunction and reduces reliability. During intermittent operation, for example, it enters thermal shutdown when the room temperature is below the lower limit of the set temperature (cooling) or above the upper limit of the set temperature (heating), and thermal on when the room temperature exceeds the upper limit of the set temperature (cooling) or falls below the lower limit of the set temperature (heating). Therefore, the room temperature fluctuates within the upper and lower limits, causing people to feel either too hot or too cold, thus failing to provide comfort.

[0038] Therefore, the controller 34 is configured to control each indoor expansion valve 22a-22c separately. Before describing its details, please refer to... Figure 2 The hardware structure of controller 34 is described.

[0039] The controller 34 includes a CPU 40, flash memory 41, RAM (Random Access Memory) 42, communication I / F 43, and control I / F 44. The CPU 40 and other components are connected to the bus 45, and information is exchanged via the bus 45.

[0040] CPU 40 controls the entire air conditioning unit 10. Flash memory 41 stores the programs and various data used in the control of CPU 40. RAM 42 provides the operating area for CPU 40. Communication I / F 43 receives information from each indoor unit 11a-11c, frequency sensor, and other sensors. Control I / F 44 connects to compressor 30, each indoor fan, each indoor expansion valve 22a-22c, outdoor fan, outdoor expansion valve 31, and four-way valve 33 to control each unit.

[0041] Here, the controller 34 implements the above control by having the CPU 40 read the program from the flash memory 41 and execute the program, but it is not limited to this and can also implement the above control using dedicated hardware such as circuits.

[0042] The following section will explain the specific control measures in detail, assuming the operation is in heating mode. First, refer to... Figure 1 This section briefly explains the refrigerant flow during heating operation. Compressor 30 draws in low-pressure gaseous refrigerant, pressurizes it to a predetermined pressure, and then discharges it. The discharged refrigerant is supplied to each indoor unit 11a-11c in a high-temperature gaseous state through piping 13. In each indoor unit 11a-11c, air is drawn in by each indoor fan, and the drawn-in air exchanges heat with the supplied high-temperature gaseous refrigerant in each indoor heat exchanger 20a-20c.

[0043] The high-temperature, high-pressure gaseous refrigerant condenses due to heat exchange, losing heat and discharging as a liquid from each indoor heat exchanger 20a-20c. The liquid refrigerant discharged from the indoor heat exchangers 20a-20c expands through indoor expansion valves 22a-22c and outdoor expansion valve 31, partially vaporizing and being sent to the outdoor heat exchanger 32 in a low-pressure two-phase flow. In the outdoor heat exchanger 32, the refrigerant exchanges heat with the outside air drawn in by the outdoor fan, gaining heat from the outside gas and completely vaporizing into a gaseous state. The low-pressure gaseous refrigerant returns to the compressor 30 through the four-way valve 33. This cycle is repeated, allowing the refrigerant to circulate within the system.

[0044] By controlling the operating frequency and the opening degree of the outdoor expansion valve 31, the flow rate of refrigerant circulating in the system can be increased or decreased, thereby adjusting the air conditioning capacity of the indoor units 11a-11c.

[0045] If the air conditioning load and rated capacity of indoor units 11a-11c are the same, they can operate continuously.

[0046] However, due to differences in air conditioning volume, room purpose and location, and set temperature, the air conditioning load of indoor units 11a-11c generally varies. Furthermore, the rated capacity of indoor units 11a-11c also varies depending on the air conditioning volume. In this case, the capacity adjustment achieved by controlling the operating frequency and the opening of the outdoor expansion valve 31 is insufficient, resulting in intermittent operation of the indoor units.

[0047] In this case, based on the difference RL between the air conditioning load and the air conditioning capacity of the indoor units 11a-11c, the opening of the indoor expansion valves 22a-22c is controlled to increase or decrease the flow rate of refrigerant flowing in the indoor units 11a-11c, thereby adjusting the air conditioning capacity to enable the indoor units to operate continuously.

[0048] Therefore, the controller 34 detects the difference RL for each indoor unit 11a-11c and controls the opening degree of each indoor expansion valve 22a-22c based on the detected difference RL. Since the opening degree control of each indoor expansion valve 22a-22c is the same for all indoor units 11a-11c, only indoor unit 11a will be described below.

[0049] The difference RL between the indoor air conditioning load and the air conditioning capacity depends on the change in room temperature over a predetermined time. Furthermore, since the air conditioning unit needs to adjust the room temperature to the set temperature, the difference RL can be detected using the difference between the set temperature and the room temperature detected by the room temperature sensor 21a, and the change in room temperature over a predetermined time. The change is detected as the difference between the room temperature detected by the room temperature sensor 21a at any given time and the room temperature detected by the room temperature sensor 21a after a predetermined time has elapsed from that given time.

[0050] Regarding the preset time, in a short period of time such as a few seconds when controlling the indoor expansion valve 22a, the change is too small to be detected. In a longer period of time such as tens of minutes, intermittent operation may occur. Therefore, the preset time is set to a period of tens of seconds to several minutes. The preset time can be measured using a timer or the like.

[0051] Based on the detected difference RL, the controller 34 generates a control signal for controlling the opening degree of the indoor expansion valve 22a and sends the control signal to the indoor expansion valve 22a. The indoor expansion valve 22a adjusts its opening degree based on the control signal. Through this control, the refrigerant flow can be adjusted to balance the air conditioning capacity with the air conditioning load, thus enabling the air conditioning unit 10 to operate without intermittent operation of the indoor unit 11a.

[0052] Figure 3 This refers to the existing control system, which operates intermittently, and the room temperature variation under this control. Figure 3 (a) represents the room temperature change under existing control. Figure 3(b) represents the room temperature change under this control. Figure 3 In (a) and (b), the vertical axis represents room temperature and the horizontal axis represents time elapsed.

[0053] exist Figure 3 In the existing control shown in (a), the indoor unit of room 1 repeatedly operates intermittently, switching between thermal shutdown and thermal startup. When the indoor unit of room 1 thermally shuts down, the room temperature of room 1 decreases. As the number of indoor units operating decreases, the compressor's operating frequency decreases, thus the room temperature of room 2 also decreases. When the room temperature of room 1 decreases to a certain level, the indoor unit of room 1 thermally starts up, and the room temperature of room 1 rises. As the number of indoor units operating increases, the compressor's operating frequency increases, and the room temperature of room 2 also rises.

[0054] exist Figure 3 In the control shown in (b), the refrigerant flow rate is increased or decreased via the indoor expansion valve, thereby adjusting the air conditioning capacity to balance with the air conditioning load and thus maintaining continuous operation. Therefore, compared with Figure 3 Unlike the existing control shown in (a), the room temperatures of rooms 1 and 2 do not fluctuate but are controlled to a roughly constant temperature close to the set temperature. In this way, a roughly constant temperature close to the set temperature can be maintained, thus maintaining indoor comfort.

[0055] Figure 4 This is a flowchart illustrating the first example of this control. Control begins from step 100 upon user start-up. In step 101, controller 34 calculates the difference RL between the air conditioning load and the air conditioning capacity of the target room. The difference RL is calculated using the room temperature detected by the room temperature sensor 21a of the indoor unit 11a, the set temperature set for the indoor unit 11a, and the amount of room temperature change within a predetermined time period measured by a timer.

[0056] In step 102, the controller 34 calculates the change in the opening degree of the indoor expansion valve 22a based on the calculated difference RL. For example, the controller 34 can calculate how much the refrigerant flow rate should increase or decrease based on the difference RL, and can calculate the change in the opening degree of the indoor expansion valve 22a based on the increase or decrease in the refrigerant flow rate. This is just an example; a table that maps the difference RL to the change in opening degree can also be used for the calculation.

[0057] In step 103, the controller 34 sends the calculated change in opening degree as a control signal to the indoor expansion valve 22a, controlling the opening degree of the indoor expansion valve 22a. In step 104, it is determined whether a stop command has been received. If no stop command has been received, the process returns to step 101 and continues control. On the other hand, if a command has been received, the process proceeds to step 105 and ends control. Here, only indoor unit 11a is described, but the same control is performed on indoor units 11b and 11c. The following examples are the same.

[0058] Figure 5 This is a flowchart illustrating a second example of this control. Control begins from step 200 upon user startup. In step 201, controller 34 calculates the difference RL between the air conditioning load and the air conditioning capacity of the target room. In step 202, controller 34 uses the set threshold RL... th Determine whether the calculated difference RL is less than the threshold RL. th .

[0059] By setting the threshold RL th It is easy to determine whether the opening changes in the direction of decreasing or increasing.

[0060] In step 202, it is determined that the difference RL is less than the threshold RL. th In this case, proceed to step 203 to calculate the change in opening in the direction of tightening the indoor expansion valve 22a. On the other hand, in step 202, it is determined that the difference RL is equal to the threshold RL. th Upon reaching the above, proceed to step 204 to calculate the change in opening degree in the direction of opening the indoor expansion valve 22a.

[0061] In step 205, the controller 34 sends the calculated opening change as a control signal to the indoor expansion valve 22a to control the opening of the indoor expansion valve 22a. In step 206, it is determined whether a stop command has been received. If no stop command has been received, the process returns to step 201 to continue control. On the other hand, if a command has been received, the process proceeds to step 207 to end control.

[0062] Figure 6 This is a flowchart illustrating the third example of this control. Control begins from step 300 upon user startup. In step 301, controller 34 calculates the difference RL between the air conditioning load and air conditioning capacity in the target room. In step 302, controller 34 also calculates the differences RL in all other rooms and calculates the average RL of these differences. ave Then, in step 303, the controller 34 calculates the difference RL and the average RL within the target room. ave The difference (RL - RL)ave ).

[0063] In step 304, the controller 34 calculates the difference (RL - RL) based on the calculated difference. ave The opening change of the indoor expansion valve 22a is calculated using this method.

[0064] In the first example described above, which only uses the difference RL, when the difference RL is large across all indoor units in the system, it will cause the indoor expansion valves of all indoor units to close significantly. This poses a risk of excessive increase in the discharge pressure and temperature of the compressor 30.

[0065] However, by using the average RL ave To calculate the difference (RL - RL) ave ), and based on the difference (RL-RL) ave The calculation is performed to determine the change in the opening of the indoor expansion valve. Even if the difference RL increases across all indoor units in the system, the average value RL remains constant. ave It also becomes a large value when the difference (RL - RL) is calculated. ave When the value is small, even if it is turned off together, it is only a small shutdown action, thus suppressing the excessive rise in discharge pressure and discharge temperature of the compressor 30.

[0066] In step 305, the controller 34 sends the calculated change in opening degree as a control signal to the indoor expansion valve 22a to control the opening degree of the indoor expansion valve 22a. In step 306, it is determined whether a stop command has been received. If no stop command has been received, the process returns to step 301 to continue control. On the other hand, if a stop command has been received, the process proceeds to step 307 to end control.

[0067] Figure 7 This is a flowchart illustrating the fourth example of this control. Control begins at step 400 upon user start-up. In step 401, controller 34 calculates the difference RL between the air conditioning load and air conditioning capacity in the target room. In step 402, controller 34 also calculates the differences RL in all other rooms and calculates the average RL of these differences. ave Then, in step 403, the controller 34 calculates the difference RL and the average RL within the target room. ave The difference (RL - RL) ave ).

[0068] In step 404, the controller 34 uses the set threshold RL th Determine the difference calculated (RL - RL) ave Is it less than RL? th In step 404, the difference is determined to be (RL - RL).ave ) <RL th In this case, proceed to step 405 to calculate the change in opening in the direction of tightening the indoor expansion valve 22a. On the other hand, in step 404, the difference (RL - RL) is determined... ave ) is RL th In the above case, proceed to step 406 to calculate the change in opening degree in the direction of opening the indoor expansion valve 22a.

[0069] In step 407, the controller 34 sends the calculated opening change as a control signal to the indoor expansion valve 22a to control the opening of the indoor expansion valve 22a. In step 408, it is determined whether a stop command has been received. If no stop command has been received, the process returns to step 401 to continue control. On the other hand, if a stop command has been received, the process proceeds to step 409 to end control.

[0070] As explained above, this control can suppress intermittent operation of indoor units and maintain comfort when multiple indoor units with different air conditioning loads and rated capacities are operating.

[0071] Thus far, the air conditioning device and control method of the present invention have been described in detail through the above embodiments. However, the present invention is not limited to the above embodiments. It can be modified in other embodiments or by adding, changing, deleting, etc., within the scope that can be thought of by those skilled in the art. Any method that achieves the function and effect of the present invention is included in the scope of the present invention.

[0072] Explanation of reference numerals in the attached figures

[0073] 10 Air conditioning units

[0074] 11. Indoor units 11a-11c

[0075] 12 outdoor units

[0076] 13Piping

[0077] 20a-20c Indoor Heat Exchanger

[0078] 21a-21c room temperature sensor

[0079] 22a-22c Indoor Expansion Valve

[0080] 30 compressor

[0081] 31 Outdoor expansion valve

[0082] 32 Outdoor heat exchangers

[0083] 33 Four-way Valve

[0084] 34 controllers

[0085] 40 CPUs

[0086] 41 flash memory

[0087] 42 RAM

[0088] 43 Communication I / F

[0089] 44 Control I / F

[0090] 45 bus.

Claims

1. An air conditioning unit comprising an outdoor unit and multiple indoor units, characterized in that, Each of the indoor units includes: Indoor heat exchanger; Indoor temperature detection unit, which detects indoor temperature; and An indoor expansion valve is used to regulate the flow rate of refrigerant flowing within the indoor unit. The outdoor unit includes: Outdoor heat exchanger; as well as compressor, The air conditioning device includes a control unit that, for each of the indoor units, calculates the difference between the load of the indoor unit and the air conditioning capacity of the indoor unit based on the deviation between the indoor temperature detected by the indoor temperature detection unit and the set temperature, as well as the change in the indoor temperature over a predetermined time period, and calculates the average value of the difference obtained for each of the indoor units. Based on the difference obtained for each of the indoor units and the average value, the control unit controls the opening degree of the indoor expansion valve.

2. The air conditioning device according to claim 1, characterized in that, The control unit determines whether to reduce the opening of each indoor expansion valve based on whether the difference between the difference obtained for each indoor unit and the average value is less than a threshold.

3. The air conditioning device according to claim 1 or 2, characterized in that, At least one of the multiple indoor units has a different air conditioning load or rated capacity.

4. A control method executed by the control unit of an air conditioning unit, The air conditioning unit includes: Multiple indoor units, among which, Each indoor unit includes an indoor heat exchanger, an indoor temperature detection unit for detecting indoor temperature, and an indoor expansion valve for adjusting the flow rate of refrigerant flowing within the indoor unit. The outdoor unit includes an outdoor heat exchanger and a compressor; and The control unit Its features are, The control method includes the following steps: For each indoor unit, the difference between the load of the indoor unit and the air conditioning capacity of the indoor unit is calculated based on the deviation between the indoor temperature detected by the indoor temperature detection unit and the set temperature and the change in the indoor temperature within a predetermined time. Calculate the average of the differences obtained for each of the indoor units; and Based on the difference and the average value obtained for each of the indoor units, the opening degree of each of the indoor expansion valves of each of the indoor units is controlled.

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