CN112771320B

CN112771320B - Air conditioner

Info

Publication number: CN112771320B
Application number: CN201880098056.1A
Authority: CN
Inventors: 永井宏幸; 三浦贤; 今任尚希
Original assignee: Toshiba Carrier Corp
Current assignee: Toshiba Carrier Corp
Priority date: 2018-09-25
Filing date: 2018-09-25
Publication date: 2022-08-02
Anticipated expiration: 2038-09-25
Also published as: EP3859231A1; JP7047120B2; JPWO2020065730A1; CN112771320A; EP3859231A4; WO2020065730A1

Abstract

The air conditioner of the present invention opens the 2 nd electric expansion valve of one or more indoor units in an operating state among the indoor units, and completely closes the 2 nd electric expansion valve of one or more indoor units in an operation stop state. And gradually increasing the opening degree of the 2 nd electric expansion valve in the one or more indoor units in the operation stop state when the refrigerant circulation amount in the refrigeration cycle is insufficient.

Description

Air conditioner

Technical Field

Embodiments of the present invention relate to a multi-type air conditioner having at least one outdoor unit and a plurality of indoor units.

Background

A multi-type air conditioner having at least one outdoor unit and a plurality of indoor units is provided with a heat pump refrigeration cycle for returning refrigerant discharged from a compressor to the compressor through a four-way valve, an outdoor heat exchanger, a decompressor, and each indoor heat exchanger.

Disclosure of Invention

Technical problem to be solved by the invention

In the above air conditioning apparatus, during the heating operation, a part of the refrigerant accumulates in the indoor heat exchanger of the stopped indoor unit, and the refrigerant circulation amount in the refrigeration cycle may be insufficient.

An object of an embodiment of the present invention is to provide an air conditioner capable of solving a shortage of a refrigerant circulation amount in a refrigeration cycle.

Technical solution for solving technical problem

The air conditioning unit of claim 1 comprising: an outdoor unit including a compressor, an outdoor heat exchanger, and a 1 st motor-operated expansion valve; a plurality of indoor units including a 2 nd electric expansion valve and an indoor heat exchanger, respectively; a refrigeration cycle in which, during a heating operation, a refrigerant discharged from the compressor is caused to flow into each of the indoor heat exchangers, the refrigerant flowing out of each of the indoor heat exchangers is caused to flow into the outdoor heat exchanger through each of the 2 nd electric expansion valve and the 1 st electric expansion valve, and the refrigerant flowing out of the outdoor heat exchanger is caused to return to the compressor; and a controller controlling operations of the outdoor unit and each of the indoor units. The controller opens the 2 nd electric expansion valve of one or more indoor units in an operating state among the indoor units, and completely closes the 2 nd electric expansion valve of one or more indoor units in an operation stop state. Further, the controller may gradually increase the opening degree of the 2 nd electric expansion valve in the one or more indoor units in the operation stop state when the refrigerant circulation amount in the refrigeration cycle is insufficient.

Drawings

Fig. 1 is a diagram showing a configuration of an embodiment.

Fig. 2 is a flowchart showing control according to an embodiment.

Fig. 3 is a mollier chart showing changes in the refrigerant temperature TL in one embodiment.

Detailed Description

An embodiment of the present invention will be described below with reference to the drawings.

As shown in fig. 1, a four-way valve 3 is connected to a discharge port of a compressor 1 via a high-pressure side pipe 2, and one end of an outdoor heat exchanger 5 is connected to the four-way valve 3 via a gas side pipe 4. One end of a pressure reducer, for example, an electric expansion valve (1 st electric expansion valve) 7 is connected to the other end of the outdoor heat exchanger 5 via a liquid-side pipe 6, and a sealing valve 9 is connected to the other end of the electric expansion valve 7 via a liquid-side pipe 8. The motor-operated expansion valve 7 is a Pulse Motor Valve (PMV) whose opening Qo changes in accordance with the number of input drive pulse signals. The opening degree Qo may be continuously changed from a minimum opening degree Qomin (fully closed) corresponding to "0" drive pulse signals pls to a maximum opening degree Qomax (fully open) corresponding to "3000" drive pulse signals pls.

One ends of the plurality of indoor heat exchangers 42 are connected to the sealing valve 9 via a liquid-side transfer pipe 31 and a plurality of electric expansion valves (2 nd electric expansion valve) 41, and the other ends of the indoor heat exchangers 42 are connected to the sealing valve 10 via a gas-side transfer pipe 32. Each of the motor-operated expansion valves 41 is a Pulse Motor Valve (PMV) whose opening degree Qi changes in accordance with the number of input drive pulse signals. The opening degree Qi may be continuously changed from a minimum opening degree Qimin (fully closed) corresponding to "0" drive pulse signals pls to a maximum opening degree Qimax (fully open) corresponding to "1500" drive pulse signals pls.

The four-way valve 3 is connected to a sealing valve 10 via a gas-side pipe 11, and an inlet of an accumulator 13 is connected to the four-way valve 3 via a low-pressure-side pipe 12. The suction pad 15 of the compressor 1 is connected to the outlet of the accumulator via a low-pressure-side pipe 14.

These piping connections constitute a heat pump refrigeration cycle.

The compressor 1 is a hermetic compressor in which a motor 1M operated by an output of an inverter 18 is housed in a hermetic case, and sucks a refrigerant flowing out of an accumulator 13, compresses the sucked refrigerant, and discharges the compressed refrigerant. The inverter 18 converts the voltage of the ac power supply 19 into a dc voltage, converts the dc voltage into a frequency F (referred to as an output frequency F) corresponding to a command from the outdoor controller 20, and outputs the ac voltage at a level corresponding to the output frequency F. The speed of the motor 1M, i.e., the capacity of the compressor 1, varies according to the value of the output frequency F.

During the cooling operation, as indicated by solid arrows, the refrigerant discharged from the compressor 1 flows into the indoor heat exchangers 42 through the four-way valve 3, the outdoor heat exchanger 5, the motor-operated expansion valve 7, and the motor-operated expansion valves 41. The refrigerant flowing out of each indoor heat exchanger 42 is sucked into the compressor 1 through the four-way valve 3 and the accumulator 13. The outdoor heat exchanger 5 functions as a condenser, and each of the indoor heat exchangers 42 functions as an evaporator.

During the heating operation, by switching the flow path of the four-way valve 2, the refrigerant discharged from the compressor 1 flows into each indoor heat exchanger 42 through the four-way valve 3 as indicated by the broken-line arrows. The refrigerant flowing out of each indoor heat exchanger 42 passes through the motor-operated expansion valve 7, the outdoor heat exchanger 5, the four-way valve 3, and the accumulator 13, and is sucked into the compressor 1. Each indoor heat exchanger 42 functions as a condenser, and the outdoor heat exchanger 5 functions as an evaporator.

An outdoor fan 16 that sucks in outside air and supplies the air to the outdoor heat exchanger 5 is disposed near the outdoor heat exchanger 5. An outside air temperature sensor 17 that detects an outside air temperature To is disposed in a flow path of the outside air taken in by the outdoor fan 16. A temperature sensor 21 for detecting a high-pressure-side refrigerant temperature TD and a pressure sensor 22 for detecting a high-pressure-side refrigerant pressure PD are attached to the high-pressure-side pipe 2 between the discharge port of the compressor 1 and the four-way valve 3. A temperature sensor 23 for detecting the refrigerant temperature TL is attached to the liquid-side pipe 8 between the electric expansion valve 7 and the sealing valve 9. A temperature sensor 24 for detecting the refrigerant temperature TS on the low pressure side and a pressure sensor 25 for detecting the refrigerant pressure PS on the low pressure side are attached to the low pressure side pipe 12 between the four-way valve 3 and the accumulator 13.

An indoor fan 43 for sucking indoor air and supplying the air to each indoor heat exchanger 42 is disposed in the vicinity of each indoor heat exchanger 42. An indoor temperature sensor 44 for detecting an indoor temperature Ta is disposed in a flow path of the indoor air taken in by the indoor fan 43.

A temperature sensor 47 is attached to the other end side of each indoor heat exchanger 42, and this temperature sensor 47 detects the temperature TC2 of the refrigerant flowing out of each indoor heat exchanger 42 during heating. A temperature sensor 48 is attached to one end side of each indoor heat exchanger 42, and the temperature sensor 48 detects a temperature TC1 of the refrigerant flowing into each indoor heat exchanger 42 during heating. Detection signals of these temperature sensors 47 and 48 are sent to the respective indoor controllers 45. Each of the indoor controllers 45 is connected to a remote controller type operator (so-called remote controller) 46 for allowing a user to set various operation conditions such as a cooling operation, a dehumidifying operation, a heating operation, an air blowing operation, a target indoor temperature Tas, an operation start, and an operation stop.

The compressor 1, the four-way valve 3, the outdoor heat exchanger 5, the motor-operated expansion valve 7, the

sealing valves

9 and 10, the accumulator 13, the outdoor fan 16, the inverter 18, the outdoor controller 20, the pipes, and the sensors are housed in the outdoor unit a. The indoor heat exchangers 42, the outdoor fans 43, the indoor controllers 45, the operators 46, the pipes, and the sensors are housed in the N indoor units B1, B2, and … Bn, respectively. A multi-type air conditioner is configured by these outdoor unit a and indoor units B1, B2, … Bn. The outdoor controller 20 and the indoor controllers 45 are connected to each other via a signal line 50 for data transmission.

The outdoor controller 20 controls the operations of the outdoor unit a and the indoor units B1 to Bn in cooperation with the respective indoor controllers 45, and includes, as main functions, a 1 st control section 20a, a 2 nd control section 20B, a detection section 20c, and a 3 rd control section 20 d.

The 1 st control section 20a performs superheat degree control that controls the opening degree Qo of the motor-operated expansion valve 7 in such a manner that the degree of superheat (superheat) SH of the refrigerant in the outdoor heat exchanger (evaporator) 5 becomes the target value SHs during the heating operation. The degree of superheat SH of the refrigerant corresponds to the difference between the detected temperature TL of the temperature sensor 23 and the detected temperature TS of the temperature sensor 24.

The 2 nd control part 20b performs the supercooling degree control that operates the opening degree Qi of the electric expansion valve 41 of the indoor unit in such a manner that the supercooling degree (supercooling) SC of the refrigerant in the indoor heat exchanger (condenser) 42 of the indoor unit or units in the operation state becomes the target value SCs at the time of the heating operation, and completely closes the electric expansion valve 41 of the indoor unit or units in the operation stop state. The difference between the condensation temperature TG of the refrigerant in each indoor heat exchanger 42 and the detection temperature TC2 of each temperature sensor 47 can be determined as the degree of subcooling SC of the refrigerant in each indoor heat exchanger 42. The condensation temperature TG can be obtained by conversion from the refrigerant pressure PD detected by the pressure sensor 22 of the high-pressure-side pipe 2. In addition, when the difference between the target indoor temperature Tas of the operator 46 and the detected temperature Ta of the indoor temperature sensor 44 in the indoor unit in the operating state increases with the execution of the degree of subcooling control and the heating load increases, the 2 nd control unit 20b decreases the target value SCs for the degree of subcooling SC to change the opening degree Qo of the electric expansion valve 7 in the increasing direction, thereby increasing the refrigerant flow rate to the indoor heat exchanger 42 and increasing the heating capacity. In addition, when the difference between the target indoor temperature Tas of the operator 46 and the detected temperature Ta of the indoor temperature sensor 44 in the indoor unit in the operating state is decreased as the degree of subcooling control is executed and the heating load is decreased, the 2 nd control unit 20b increases the target value SCs for the degree of subcooling SC to change the opening Qo of the electric expansion valve 7 in the decreasing direction, thereby decreasing the refrigerant flow rate to the indoor heat exchanger 42 and decreasing the heating capacity.

The detecting portion 20c detects the refrigerant circulation amount in the heat pump type refrigeration cycle at the time of the heating operation, specifically, detects the shortage X (%) of the refrigerant circulation amount.

The 3 rd control portion 20d gradually increases the opening degree Qi of the motor-operated expansion valve 41 in the indoor unit or units in the operation stop state from the fully closed state when the refrigerant circulation amount detected by the detecting portion 20c is insufficient, specifically, when the shortage rate X detected by the detecting portion 20c is in a non-negligible condition of the threshold value Xs (e.g., 30%) or more. In detail, the 3 rd control portion 20d gradually increases the opening degree Qi of the electric expansion valve 41 in the indoor unit or units in the operation stop state from the fully closed state by the fixed opening degree Δ Q with the predetermined opening degree Qis (for example, 10% of the maximum opening degree Qimax) as the upper limit when the deficiency rate X detected by the detection portion 20c is the threshold value Xs or more and the opening degree Qo of the electric expansion valve 7 operated by the superheat degree control of the 1 st control portion 20a is the set value Qos or more (that is, when it is difficult to suppress the increase in the superheat degree SH accompanying the shortage of the refrigerant circulation amount by the superheat degree control). The set value Qos corresponds to an opening degree such as 2/3 of the maximum opening degree Qomax. The prescribed opening degree Qis determined as the upper limit is used to prevent excessive inflow of the refrigerant due to excessive opening of the electric expansion valve 41.

The shortage X of the refrigerant circulation amount can be detected by using one or more elements of the condensation temperature TG of the refrigerant in the condenser, the evaporation temperature TU of the refrigerant in the evaporator (indoor heat exchanger 42), the temperature TC2 of the refrigerant flowing out of the evaporator (the detection temperature of the temperature sensor 47), and the temperature TL of the refrigerant flowing into the condenser (the detection temperature of the temperature sensor 23). The evaporation temperature TU can be obtained by converting the detected pressure PS of the pressure sensor 25 in the low-pressure side pipe 12.

For example, when the refrigerant in the heat pump refrigeration cycle is appropriately circulated without being accumulated in all of the indoor units B1 to Bn and the refrigerant circulation amount is not insufficient, the liquid-side transfer pipe 31 and the liquid-side pipes 8 and 7 are in a state of being filled with the liquid refrigerant, and the liquid refrigerant flows into the outdoor heat exchanger (evaporator) 5. When the refrigerant accumulates in any of the indoor units B1 to Bn and the amount of refrigerant circulation in the heat pump refrigeration cycle becomes insufficient, the liquid refrigerant and the gas refrigerant flow through the liquid-side transmission pipe 31 and the liquid-side pipes 8 and 7 together, and the refrigerant in a so-called gas-liquid two-phase state flows into the outdoor heat exchanger 5.

When the refrigerant in the gas-liquid two-phase state flows into the outdoor heat exchanger 5, the degree of superheat SH of the refrigerant in the outdoor heat exchanger 5 increases, and the degree of superheat control is effected to suppress the increase in the degree of superheat SH, so that the opening Qo of the motor-operated expansion valve 7 changes in the increasing direction. However, when the increase in the opening degree Qo of the motor-operated expansion valve 7 continues and the opening degree Qo reaches the maximum opening degree Qomax of the motor-operated expansion valve 7, it becomes impossible to suppress the increase in the superheat SH, and the temperature TS of the refrigerant sucked into the compressor 1 increases. When the refrigerant temperature TS increases, the temperature TD (and the pressure PD) of the refrigerant discharged from the compressor 1 increases, and the output frequency F of the inverter 18 is lowered by the high-pressure protection control of the indoor controller 20 for the increase in the refrigerant temperature TD. When the output frequency F decreases, the capacity of the compressor 1 decreases, and the heating capacity of the indoor unit in the operating state decreases accordingly.

The solid line in the mollier diagram of fig. 3 indicates a state of the heat pump refrigeration cycle when the liquid refrigerant flows into the outdoor heat exchanger 5, and the broken line in the mollier diagram indicates a state of the heat pump refrigeration cycle when the gas-liquid two-phase refrigerant flows into the outdoor heat exchanger 5. When the liquid refrigerant flows in, the refrigerant temperature TL is present on the side near the condensation temperature TG, but when the gas-liquid two-phase refrigerant flows in, the refrigerant temperature TL deviates from the condensation temperature TG and becomes a value TL' closer to the evaporation temperature TU side.

Therefore, the detecting portion 20c detects at which position between the refrigerant temperature TL and the refrigerant temperature TL' on the above mollier chart the actual refrigerant temperature TL detected by the temperature sensor 23 exists as the shortage rate X (%) of the refrigerant circulation amount. That is, the shortage rate X is 0% when the actual refrigerant temperature TL is at the same position as the refrigerant temperature TL on the mollier chart, 50% when the actual refrigerant temperature TL is at an intermediate position between the refrigerant temperature TL and the refrigerant temperature TL 'on the mollier chart, and 100 (%) when the actual refrigerant temperature TL is at the same position as the refrigerant temperature TL' on the mollier chart.

Next, the control performed by the outdoor controller 20 is described with reference to the flowchart of fig. 3. Steps S1, S2 … in the flowchart are simply referred to as S1, S2 ….

During the heating operation, the outdoor controller 20 controls the opening degree of the motor-operated expansion valve 7 so that the degree of superheat SH of the refrigerant in the outdoor heat exchanger (evaporator) 5 becomes the target value SHs (S1). At the same time, the outdoor controller 20 controls the opening degrees of the electric expansion valves 41 of the indoor units B1 and B2 so that the degrees of subcooling SC of the refrigerant in the indoor heat exchangers 42 of the one or more indoor units in the operating state, for example, the indoor units B1 and B2, respectively, become the target values SCs, and completely closes the electric expansion valves 41 of the one or more indoor units in the operation-stopped state, for example, the indoor units B3 to Bn (S2).

Then, the outdoor controller 20 detects the shortage X of the refrigerant circulation amount in the heat pump refrigeration cycle (S3), and determines whether or not the detected shortage X is equal to or greater than the threshold Xs (S4). When the detected shortage rate X is not the threshold value Xs or more (no at S4), the outdoor controller 20 repeats the processing from S1 described above.

When the detected shortage X is equal to or greater than the threshold value Xs (yes at S4), the outdoor controller 20 determines whether or not the opening Qo of the motor-operated expansion valve 7 adjusted by superheat degree control is equal to or greater than a set value Qos (S5). When the opening degree Qo is not equal to or greater than the set value Qos (no at S5), the outdoor controller 20 repeats the processing from S1 described above.

When the opening degree Qo is equal to or greater than the set value Qos (yes at S5), the outdoor controller 20 increases the opening degrees Qi of the motor-operated expansion valves 41 of the indoor units B3 to Bn by the predetermined opening degree Δ Q, on condition that the opening degrees Qi of the motor-operated expansion valves 41 of the indoor units B3 to Bn in the operation stop state are smaller than the predetermined opening degree Qis (yes at S6) (S7). When each of the fully closed motor-operated expansion valves 41 is opened, the dormant refrigerant that has been accumulated in the indoor heat exchangers 42 of the indoor units B3 to Bn and liquefied flows out to the liquid-side transfer pipe 31 and the liquid-side pipe 8.

As the opening degree increases, the outdoor controller 20 starts a time count t (S8), and determines whether the time count t reaches a fixed time ts (e.g., 300 seconds) (S9). When the time count t is less than the fixed time ts (no at S9), the outdoor controller 20 keeps the opening degree Qi of the motor-operated expansion valve 41 increased as described above (S10), and continues the time count t (S8). When the time count t reaches the fixed time ts (yes at S9), the outdoor controller 20 detects the shortage X of the refrigerant circulation amount again through the processing at S1 and S2 (S3).

When the detected deficiency rate X is equal to or greater than the threshold value Xs despite the increase in the opening degree (yes at S4) and the opening degree Qo of the motor-operated expansion valve 7 is equal to or greater than the set value Qos (yes at S5), the outdoor controller 20 increases the opening degrees Qi of the motor-operated expansion valves 41 of the indoor units B1 to Bn by the predetermined opening degree Δ Q again (S7) on condition that the opening degrees Qi of the motor-operated expansion valves 41 of the indoor units B3 to Bn in the operation stop state are smaller than the predetermined opening degree Qis (yes at S6). By further increasing the opening degree Qi of each of the motor-operated expansion valves 41 that are completely closed, the dormant refrigerant that has been accumulated in the indoor heat exchangers 42 of the indoor units B3 through Bn and liquefied flows out to the liquid-side transfer pipe 31 and the liquid-side pipe 8.

As the opening degree increases, the outdoor controller 20 starts the time count t from the beginning (S8), and determines whether the time count t reaches the fixed time ts (S9). When the time count t is less than the fixed time ts (no at S9), the outdoor controller 20 maintains the increased opening degree Qi of the motor-operated expansion valve 41 (S10), and continues the time count t (S8). When the time count t reaches the fixed time ts (yes at S9), the outdoor controller 20 repeats the detection of the shortage X of the refrigerant circulation amount by the above-described processing at S1 and S2 (S3).

When the opening degree Qi of the motor-operated expansion valve 41 in the indoor units B3 to Bn in the operation stop state in S6 described above reaches the set value Qis (yes in S6), the outdoor controller 20 starts the time count t from the beginning without performing the process of increasing the opening degree in S7 (S8).

As described above, when the refrigerant circulation amount is insufficient, the motor-operated expansion valves 41 of the indoor units B3 to Bn in the operation stop state are opened from the fully closed state, and the opening degrees Qi thereof are gradually increased at regular time ts intervals, thereby gradually promoting the outflow of the dormant refrigerant accumulated in the indoor heat exchangers 42 of the indoor units B3 to Bn. By this outflow, the gas-liquid two-phase state of the refrigerant in the liquid-side delivery pipe 31 and the liquid-side pipes 8 and 7 is gradually eliminated.

When the refrigerant in the gas-liquid two-phase state does not flow into the outdoor heat exchanger 5, an unnecessary increase in the degree of superheat SH of the refrigerant in the outdoor heat exchanger 5 can be prevented, and an unnecessary increase in the opening degree Qo of the motor-operated expansion valve 7 due to the degree of superheat control can be prevented. Accordingly, an unnecessary increase in the temperature TS of the refrigerant sucked into the compressor 1, and further an unnecessary increase in the temperature TD (and the pressure PD) of the refrigerant discharged from the compressor 1 can be avoided, so that an unnecessary decrease in the output frequency F of the inverter 18 due to the high-pressure protection control can be avoided. As a result, unnecessary reduction in heating capacity in the operating indoor unit can be prevented.

When the opening degree Qi of the motor-operated expansion valve 41 is greatly increased at once, a large amount of refrigerant flows into the indoor units B3 to Bn in the operation stop state at once, but since the opening degree Qi of the motor-operated expansion valve 41 is gradually increased at fixed time ts, a large amount of refrigerant does not flow into the indoor units B3 to Bn in the operation stop state at once, and therefore, stable and efficient energy saving operation of the heat pump refrigeration cycle can be achieved.

[ modified examples ]

In the above embodiment, the ratio of the value of the refrigerant temperature TL with respect to the value of the condensation temperature TG is detected as the shortage rate X (%) of the refrigerant circulation amount, but the present invention is not limited to this, and in short, any one or more elements of the condensation temperature TG, the evaporation temperature TU, the refrigerant temperature TC2, and the refrigerant temperature TL may be used for detection.

Since the deficiency rate X (%) can be regarded as the deficiency rate Y (%) which is an inverse concept, the deficiency rate Y (%) which is an inverse concept to the deficiency rate X (%) can also be detected. The shortage of the refrigerant circulation amount indicates a value of the sufficiency rate Y (%) closer to 0%, and the shortage of the refrigerant circulation amount indicates a value of the sufficiency rate Y (%) closer to 100%. That is, the deficiency rate X is 0% to the sufficiency rate Y is 100%, the deficiency rate X is 50% to the sufficiency rate Y is 50%, and the deficiency rate X is 100% to the sufficiency rate Y is 0%.

In the above embodiment, the control of gradually increasing the opening degree Qi of the electric expansion valve 41 is started when the deficiency rate X of the refrigerant circulation amount is equal to or greater than the threshold value Xs and the opening degree Qo of the electric expansion valve 7 is equal to or greater than the set value Qos, but the condition that the opening degree Qo of the electric expansion valve 7 is equal to or greater than the set value Qos may be omitted, and the control of gradually increasing the opening degree Qi of the electric expansion valve 41 may be started immediately when the deficiency rate X of the refrigerant circulation amount is equal to or greater than the threshold value Xs.

The above embodiments and modifications are presented as examples, and are not intended to limit the scope of the invention. These new embodiments and modifications can be implemented in other various ways, and various omissions, rewrites, and changes can be made without departing from the scope of the invention. These embodiments and modifications are included in the scope and gist of the invention, and are included in the invention described in the patent claims and the equivalent scope thereof.

Description of the reference symbols

A … outdoor unit, B1 to Bn … indoor units, 1 … compressor, 3 … four-way valve, 5 … outdoor heat exchanger, 7 … electric expansion valve, 16 … outdoor fan, 18 … inverter, 20 … outdoor controller, 41 … electric expansion valve, 42 … indoor heat exchanger, 43 … indoor fan, 45 … indoor controller, 46 … operator.

Claims

1. An air conditioning apparatus, comprising:

an outdoor unit including a compressor, an outdoor heat exchanger, and a 1 st motor-operated expansion valve;

a plurality of indoor units including a 2 nd electric expansion valve and an indoor heat exchanger, respectively;

a refrigeration cycle in which, during a heating operation, a refrigerant discharged from the compressor is caused to flow into each of the indoor heat exchangers, the refrigerant flowing out of each of the indoor heat exchangers is caused to flow into the outdoor heat exchanger through each of the 2 nd electric expansion valve and the 1 st electric expansion valve, and the refrigerant flowing out of the outdoor heat exchanger is caused to return to the compressor;

a temperature sensor that is provided in a liquid-side pipe of the outdoor unit between the 1 st electric expansion valve and each of the 2 nd electric expansion valves and detects a refrigerant temperature; and

a controller controlling operations of the outdoor unit and each of the indoor units,

the controller opens the 2 nd electric expansion valve in one or more indoor units in an operation state among the indoor units, completely closes the 2 nd electric expansion valve in one or more indoor units in an operation stop state,

the controller controls the opening degree of the 1 st electric expansion valve so that the degree of superheat of the refrigerant in the outdoor heat exchanger becomes a target value,

the controller controls the opening degree of the 2 nd electric expansion valve of the indoor units such that the degree of supercooling of the refrigerant in the indoor heat exchanger of one or more indoor units in an operating state among the indoor units becomes a target value,

the controller detects a shortage rate of the refrigerant circulation amount in the refrigeration cycle based on which position between the refrigerant temperature at which the shortage rate on the mollier chart is 0% and the refrigerant temperature at which the shortage rate is 100% the actual refrigerant temperature detected by the temperature sensor exists, and gradually increases the opening degree of the 2 nd electric expansion valve in the one or more indoor units in the operation stop state when the detected shortage rate is equal to or greater than a threshold value and the opening degree of the 1 st electric expansion valve is equal to or greater than a set value.

2. The air conditioner according to claim 1,

the controller gradually increases the opening degree of the 2 nd motor-operated expansion valve with a predetermined opening degree as an upper limit.