Air conditioner

Abstract

To suppress loss of capacity of an air conditioner.SOLUTION: An air conditioner 1 includes: a refrigerant circuit 4 in which a compressor 11, an indoor heat exchanger 12 and an outdoor heat exchanger 15 are connected by refrigerant piping 40; a liquid side regulating valve 13 for regulating a flow rate of a refrigerant flowing in the liquid state in liquid side piping 40e located between the indoor heat exchanger 12 and the outdoor heat exchanger 15 of the refrigerant piping 40; a gas side regulating valve 61 for regulating a flow rate of a refrigerant flowing in the gaseous state in gas side piping 40b located between the indoor heat exchanger 12 and the compressor 11 of the refrigerant piping 40; and a control section 5 executing first closing control for closing the liquid side regulating valve 13 to a predetermined first opening or smaller, stop control for stopping the compressor 11 and second closing control for closing the gas side regulating valve 61 to a predetermined second opening or smaller when a predetermined first condition is satisfied.SELECTED DRAWING: Figure 1

Description

Technical Field

[0001] The present disclosure relates to an air conditioner.

Background Art

[0002] An air conditioner that performs air conditioning by a refrigerant circulating in a refrigerant circuit has been conventionally known. The refrigerant circuit includes a compressor for circulating the refrigerant. A technique is known in which when the indoor temperature reaches a predetermined target temperature, the circulation of the refrigerant is stopped by stopping the compressor (for example, Patent Document 1).

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] In the refrigerant circuit in a state where the compressor is stopped (thermo-off state), the refrigerant does not actively circulate. However, due to the influence of a temperature difference or the like, the refrigerant may naturally move in the refrigerant circuit even in the thermo-off state. When the refrigerant naturally moves, phenomena such as a heat reverse flow in which heat contained in the refrigerant flows backward from the normal flow direction may occur, which may cause a loss of capacity in the air conditioner.

[0005] An object of the present disclosure is to suppress a loss of capacity of an air conditioner.

Means for Solving the Problems

[0006] (1) The air conditioner according to the present disclosure includes a refrigerant circuit in which a compressor, an indoor heat exchanger, and an outdoor heat exchanger are connected by refrigerant pipes, a liquid-side adjustment valve that adjusts the flow rate of the refrigerant flowing in a liquid state in the liquid-side pipe located between the indoor heat exchanger and the outdoor heat exchanger among the refrigerant pipes, a gas-side adjustment valve that adjusts the flow rate of the refrigerant flowing in a gas state in the gas-side pipe located between the indoor heat exchanger and the compressor among the refrigerant pipes, a first closing control that closes the liquid-side adjustment valve to a predetermined first opening or less when a predetermined first condition is satisfied, a stop control that stops the compressor, and a second closing control that closes the gas-side adjustment valve to a predetermined second opening or less, and a control unit that executes the above.

[0007] When closing the liquid-side adjustment valve and stopping the compressor, by closing the gas-side adjustment valve by the control unit, the natural movement of the refrigerant in the gas-side pipe can be restricted. Thereby, the circulation of the refrigerant during the stop of the compressor can be suppressed, so that the capacity loss of the air conditioner can be suppressed.

[0008] (2) Preferably, after executing the first closing control, the control unit executes the second closing control and the stop control.

[0009] After restricting the circulation of the refrigerant in the liquid-side pipe by the first closing control, until the second closing control and the stop control are executed, the compressor can accumulate the refrigerant in a liquid state in the liquid-side pipe. Thereby, since the amount of refrigerant that can circulate during the stop of the compressor can be reduced, the capacity loss of the air conditioner can be suppressed.

[0010] (3) Preferably, after executing the first closing control, when a predetermined closing condition is satisfied, the control unit executes the second closing control, and after executing the second closing control, the control unit executes the stop control.

[0011] When the rotational speed of the compressor decreases and the force of the compressor to circulate the refrigerant weakens, natural movement of the refrigerant in the gas-side piping may occur even before the compressor completely stops. Therefore, preferably, after a predetermined closing condition is satisfied and before the execution of the stop control, the second closing control is executed to more reliably restrict the flow of the refrigerant in the gas-side piping. Thereby, since the flow of the refrigerant during the stop of the compressor can be suppressed, the capacity loss of the air conditioner can be suppressed.

[0012] (4) Preferably, the predetermined closing condition includes that a predetermined time has elapsed since the start of execution of the first closing control, the refrigerant pressure in the pressure sensor provided on the suction side of the compressor has become equal to or lower than a predetermined pressure, or the degree of superheat on the suction side of the compressor calculated based on the temperature sensor and the pressure sensor provided on the suction side of the compressor has become equal to or higher than a predetermined temperature.

[0013] The predetermined closing condition indicates that the pump-down operation of the compressor has been completed to a certain extent. By making it possible to determine the predetermined closing condition based on time, pressure, or superheat degree, the control unit can execute the second closing control in a timely manner.

[0014] (5) Preferably, after the execution of the first closing control, the stop control, and the second closing control, when a predetermined second condition is satisfied, the control unit executes a first opening control for opening the liquid-side regulating valve wider than the predetermined first opening degree, a starting control for rotating the compressor, and a second opening control for opening the gas-side regulating valve wider than the predetermined second opening degree.

[0015] By configuring in this way, the circulation of the refrigerant can be restarted.

[0016] (6) Preferably, when the predetermined second condition is satisfied, the control unit executes the second opening control, and after executing the second opening control, executes the starting control.

[0017] When restarting the refrigerant cycle, by first performing the second opening control, the rotation of the compressor is started with a wide range of the refrigerant piping being in communication, so that the refrigerant cycle can be restarted more quickly.

[0018] (7) Preferably, when the predetermined second condition is satisfied, the control unit executes the start control, and after the execution of the start control, the control unit executes the second opening control.

[0019] During the stop of the compressor, for example, due to the temperature difference in the refrigerant piping or the like, refrigerant may condense in a part of the refrigerant circuit (for example, the gas-side piping), and there is a possibility that liquid refrigerant may accumulate. If the accumulated liquid refrigerant is directly sucked into the compressor, there is a possibility that a problem may occur in the compressor. By executing the start control before the second opening control, the suction pressure can be lowered with the rotational speed of the compressor having increased to a certain extent, and the accumulated liquid refrigerant can be evaporated, so that the accumulation of the refrigerant can be eliminated. Thereby, the occurrence of problems in the compressor can be suppressed.

[0020] (8) Preferably, when the predetermined second condition is satisfied and a predetermined opening condition is satisfied, the control unit executes the second opening control after the execution of the start control, and when the predetermined opening condition is not satisfied, the control unit executes the start control after the execution of the second opening control.

[0021] By determining the control order of the start control and the second opening control according to the situation, the refrigerant cycle can be restarted more suitably.

[0022] (9) Preferably, the predetermined release condition includes that the detected temperature of the first detection unit that detects the outdoor temperature has decreased by more than a predetermined temperature from the detected temperature detected by the first detection unit at the time of execution of the stop control, the detected temperature of the second detection unit that detects the indoor temperature has decreased by more than a predetermined temperature from the detected temperature detected by the second detection unit at the time of execution of the stop control, the detected temperature of the temperature sensor provided on the suction side of the compressor has decreased by more than a predetermined temperature from the detected temperature detected by the temperature sensor at the time of execution of the stop control, or the compressor has been stopped without going through the stop control of the control unit.

[0023] The predetermined release condition indicates a condition in which there is a high possibility of refrigerant retention in a part of the refrigerant circuit. Specifically, the predetermined release condition includes a case where at least one of various temperatures that cause refrigerant retention during the stop of the compressor has decreased, or a case where the compressor has stopped abnormally. By configuring in this way, when there is a high possibility of refrigerant retention, the control unit performs the start control prior to the second release control to suppress the occurrence of malfunctions of the compressor, and when there is a low possibility of refrigerant retention, the control unit performs the second release control prior to the start control, so that the refrigerant circulation can be restarted more quickly.

[0024] (10) Preferably, the air conditioner further includes a second detection unit that detects the indoor temperature, the predetermined first condition includes that the temperature difference between the detected temperature of the second detection unit and the target temperature is equal to or less than a predetermined value, and the predetermined second condition includes that the temperature difference is equal to or greater than a second predetermined value smaller than the predetermined value.

[0025] By configuring in this way, based on the temperature difference between the detected temperature (indoor temperature) of the second detection unit and the target temperature, the timing of the operation and stop of the compressor can be determined in a timely manner.

[0026] (11) Preferably, the air conditioner further includes an indoor unit that houses the indoor heat exchanger, and an outdoor unit that houses the compressor and the outdoor heat exchanger, and the gas-side regulating valve is located in an external area of the indoor unit and the outdoor unit, or an internal area of the indoor unit, among the gas-side piping.

[0027] By configuring in this way, the length of the gas-side piping from the indoor heat exchanger to the gas-side regulating valve can be shortened, so that the amount of refrigerant that can freely move from the gas-side piping to the indoor heat exchanger after the execution of the second shut-off control can be reduced. Thereby, the circulation of the refrigerant during the stop of the compressor can be more suppressed, and thus the capacity loss of the air conditioner can be suppressed.

Brief Description of the Drawings

[0028]

Figure 1

Figure 2

Figure 3

Figure 4

Figure 5

Figure 6

Figure 7

Embodiments for Carrying Out the Invention

[0029] Hereinafter, embodiments of the present disclosure will be described with reference to the accompanying drawings.

[0030] [Embodiment] [Regarding Conventional Problems] FIG. 6 and FIG. 7 are diagrams for explaining the problems of the present disclosure. With reference to FIGS. 6 and 7, the natural movement of the refrigerant when the compressor stops will be specifically described.

[0031] FIGS. 6 and 7 are diagrams schematically showing a conventional air conditioner 9. The air conditioner 9 includes an indoor unit 902 that houses an indoor fan 921, an outdoor unit 903 that houses an outdoor fan 931, and a refrigerant circuit 904. The refrigerant circuit 904 includes a refrigerant pipe 940 including a gas-side pipe 940b and a liquid-side pipe 940b, and a compressor 911, an indoor heat exchanger 912, a liquid-side regulating valve 913 (expansion valve), a liquid-side regulating valve 914 (expansion valve), an outdoor heat exchanger 915, a switching mechanism 916 (four-way switching valve), and an accumulator 917 connected by the refrigerant pipe 940.

[0032] The indoor heat exchanger 912 and the liquid-side regulating valve 913 are housed in the indoor unit 902. The compressor 911, the liquid-side regulating valve 914, the outdoor heat exchanger 915, the switching mechanism 916, and the accumulator 917 are housed in the outdoor unit 903. The liquid-side regulating valves 913 and 914 adjust the flow rate of the refrigerant flowing in a liquid state in the liquid-side pipe 940e located between the indoor heat exchanger 912 and the outdoor heat exchanger 915 in the refrigerant pipe 940.

[0033] FIG. 6 schematically shows the state of the air conditioner 9 when the compressor 911 is stopped during the cooling operation. During the cooling operation, the high-pressure refrigerant discharged from the compressor 911 passes through the switching mechanism 916 and enters the outdoor heat exchanger 915, where it exchanges heat with the outdoor air and condenses. The condensed refrigerant is depressurized when passing through the liquid-side regulating valve 913, and then enters the indoor heat exchanger 912, where it exchanges heat with the indoor air and evaporates. The conditioned air cooled by the refrigerant is blown into the room by the indoor fan 921. The gaseous refrigerant that exits the indoor heat exchanger 912 passes through the gas-side pipe 940b and the switching mechanism 916 and enters the accumulator 917, where gas-liquid separation is performed and then is inhaled by the compressor 911.

[0034] During the cooling operation, when the indoor temperature reaches the target temperature, for example, the compressor 911 is operated with the liquid-side regulating valve 913 closed, so that the refrigerant in a liquid state is stored in the region of the liquid-side pipe 940e from the outdoor heat exchanger 915 to the liquid-side regulating valve 913 (the thick-line region in FIG. 6). Then, after a predetermined time has elapsed since the liquid-side regulating valve 913 was closed and a certain amount of refrigerant has been stored in the region, the compressor 911 is stopped. As a result, the active refrigerant circulation in the refrigerant circuit 904 stops.

[0035] During the cooling operation, the indoor unit 902 is at a lower temperature than the outdoor unit 903. In particular, when the outside air temperature is high, the temperature difference between the indoor unit 902 and the outdoor unit 903 becomes large. The refrigerant in the refrigerant pipe 940 becomes a higher pressure under high temperature. Therefore, in the gas-side pipe 940b, the refrigerant on the outdoor unit 903 side becomes a higher pressure than the refrigerant on the indoor unit 902 side, and a pressure difference of the refrigerant is generated in the gas-side pipe 940b. Then, due to this pressure difference, a refrigerant flow F1 is generated in which the refrigerant on the outdoor unit 903 side naturally moves to the indoor unit 902 side.

[0036] The refrigerant flow F1 is in the opposite direction to the flow direction of the refrigerant during the cooling operation. For example, when the gaseous refrigerant flows into the indoor heat exchanger 912 due to the refrigerant flow F1 and the refrigerant condenses in the indoor heat exchanger 912, the indoor air may be heated by the condensation heat. Thus, when the reverse flow of the refrigerant occurs, when the air conditioner 9 performs the cooling operation, the indoor air is unintentionally heated, so there is a possibility that a capacity loss occurs in the air conditioner 9.

[0037] Referring to FIG. 7, the problems of the air conditioner 9 in the heating operation will be described. FIG. 7 schematically shows the state of the air conditioner 9 when the compressor 911 is stopped during the heating operation. In the heating operation, the high-pressure refrigerant discharged from the compressor 911 passes through the switching mechanism 916 and the gas-side pipe 940b and enters the indoor heat exchanger 912, where it exchanges heat with the indoor air and condenses. The conditioned air heated by the refrigerant is blown into the room by the indoor fan 921. The condensed refrigerant is depressurized when passing through the liquid-side regulating valve 914, and then enters the outdoor heat exchanger 915, where it exchanges heat with the outdoor air and evaporates. The gaseous refrigerant that exits the outdoor heat exchanger 915 passes through the switching mechanism 916 and enters the accumulator 917. After gas-liquid separation, it is sucked into the compressor 911.

[0038] During the heating operation, for example, when the indoor temperature reaches the target temperature, the compressor 911 is operated with the liquid-side regulating valve 914 closed, so that the refrigerant in a liquid state is stored in the region of the liquid-side pipe 940e from the indoor heat exchanger 912 to the liquid-side regulating valve 914 (the thick-line region in FIG. 7). Then, after a predetermined time has elapsed since the liquid-side regulating valve 914 was closed and a certain amount of refrigerant has been stored in this region, the compressor 911 is stopped. As a result, the active refrigerant circulation in the refrigerant circuit 904 stops.

[0039] Due to the heating operation, the indoor unit 902 is at a higher temperature than the outdoor unit 903. In particular, when the outside air temperature is low, the temperature difference between the indoor unit 902 and the outdoor unit 903 becomes large. The refrigerant in the refrigerant pipe 940 becomes a higher pressure under high temperature. Therefore, in the gas-side pipe 940b, the refrigerant on the indoor unit 902 side becomes a higher pressure than the refrigerant on the outdoor unit 903 side, and a pressure difference of the refrigerant is generated in the gas-side pipe 940b. Then, due to this pressure difference, a refrigerant flow F2 is generated in which the refrigerant on the indoor unit 902 side naturally moves to the outdoor unit 903 side.

[0040] The refrigerant flow F2 is in the direction opposite to the flow direction of the refrigerant during the heating operation. For example, when the gaseous refrigerant flows into the outdoor unit 903 due to the refrigerant flow F2 and the refrigerant condenses in the outdoor unit 903, the refrigerant pressure in the gas-side pipe 940b decreases. In this case, when the compressor 911 is started next, it takes time to increase the pressure of the refrigerant. Therefore, compared with the case where the refrigerant does not condense, the starting performance deteriorates, and there is a possibility that the air conditioner 9 may suffer a capacity loss.

[0041] Note that when the indoor unit 2 becomes hotter than the outdoor unit 3 during the cooling operation, there is a possibility that the refrigerant flow F2 may occur in the gas-side pipe 940b while the compressor 911 is stopped. In this case, similar to the description during the heating operation in FIG. 4 above, there is a possibility that the air conditioner 9 may suffer a capacity loss due to the deterioration of the starting performance of the compressor 911.

[0042] In the present disclosure, in order to suppress the refrigerant flows F1 and F2 that cause the capacity loss in the air conditioner 9, it is proposed to provide a gas-side regulating valve for adjusting the flow rate of the refrigerant in the gas-side pipe and to devise the closing timing of the gas-side regulating valve. Hereinafter, the specific configuration will be described.

[0043] [Configuration of the air conditioner 1] FIG. 1 is a diagram schematically showing the configuration of the air conditioner 1 according to the embodiment. FIG. 2 is a functional block diagram of the air conditioner 1 according to the embodiment. Hereinafter, with reference to FIGS. 1 and 2, the configuration of the air conditioner 1 will be described.

[0044] The air conditioner 1 has a function of cooling and heating the room R1. The air conditioner 1 includes an indoor unit 2 installed in the room R1, an outdoor unit 3 installed outdoors, a refrigerant circuit 4 in which a refrigerant circulates inside, and a control unit 5. The refrigerant is, for example, R32. The use of the room R1 is not particularly limited, and it may be, for example, a living space for humans (e.g., a house, a store, an office, a factory), a warehouse for storing foodstuffs, or a space where mechanical equipment (e.g., a server) is installed.

[0045] The refrigerant circuit 4 has a refrigerant pipe 40, a compressor 11, an indoor heat exchanger 12, a liquid-side regulating valve 13, a liquid-side regulating valve 14, an outdoor heat exchanger 15, a switching mechanism 16, and an accumulator 17. In the refrigerant circuit 4, when the indoor heat exchanger 12 functions as a condenser (i.e., when the air conditioner 1 is in heating operation), the refrigerant discharged from the compressor 11 flows in the order of the switching mechanism 16, the indoor heat exchanger 12, the liquid-side regulating valve 13, the liquid-side regulating valve 14, the outdoor heat exchanger 15, the switching mechanism 16, and the accumulator 17 and returns to the compressor 11, and each part 11 to 17 is connected by the refrigerant pipe 40.

[0046] The refrigerant pipe 40 includes five regions 40a to 40e. The region 40a is the region from the discharge side of the compressor 11 to the switching mechanism 16. The region 40b is the region from the switching mechanism 16 to the indoor heat exchanger 12. The region 40c is the region from the switching mechanism 16, passing through the accumulator 17, to the suction side of the compressor 11. The region 40d is the region from the switching mechanism 16 to the outdoor heat exchanger 15. The region 40e is the region from the indoor heat exchanger 12, passing through the liquid-side regulating valves 13 and 14, to the outdoor heat exchanger 15. Since mainly gaseous refrigerant flows through the region 40b, it is appropriately referred to as the "gas-side pipe 40b". Since mainly liquid refrigerant flows through the region 40e, it is appropriately referred to as the "liquid-side pipe 40e".

[0047] The control unit 5 includes an indoor control unit 5a and an outdoor control unit 5b that are connected to each other by a communication line. As shown in FIG. 2, the indoor control unit 5a includes a processor 52a and a memory 53a. Based on the programs included in the memory 53a, the processor 52a performs various operations and controls, whereby the indoor control unit 5a controls each part included in the indoor unit 2. The outdoor control unit 5b includes a processor 52b and a memory 53b. Based on the programs included in the memory 53b, the processor 52b performs various operations and controls, whereby the outdoor control unit 5b controls each part included in the outdoor unit 3.

[0048] The outdoor unit 3 has a housing 31 in which a suction port (not shown) and an exhaust port (not shown) are formed. The housing 31 houses a part of the refrigerant pipe 40 in the refrigerant circuit 4, a compressor 11, a liquid-side regulating valve 14, an outdoor heat exchanger 15, a switching mechanism 16, and an accumulator 17. The housing 31 further houses the outdoor control unit 5b, an outdoor fan 32, a pressure sensor 33, a temperature sensor 34, and a first detection unit 35.

[0049] The compressor 11 is, for example, a variable-capacity compressor, and its rotational frequency is controlled by an inverter based on an operation command from the control unit 5.

[0050] The liquid-side regulating valve 14 is a valve provided in the liquid-side pipe 40e in the outdoor unit 3 and is, for example, an expansion valve (pressure-reducing mechanism). Based on an operation command from the control unit 5, the opening degree of the liquid-side regulating valve 14 is controlled, whereby the pressure and flow rate of the refrigerant flowing in a liquid state in the liquid-side pipe 40e are adjusted.

[0051] The outdoor heat exchanger 15 is, for example, a cross-finned tube type heat exchanger.

[0052] The switching mechanism 16 is a mechanism for switching the flow direction of the refrigerant in the refrigerant circuit 4, and is, for example, a four-way switching valve. The switching mechanism 16 is switched, under the control of the control unit 5, between a first connection state (solid line in FIG. 1) in which the refrigerant discharged from the compressor 11 is sent to the outdoor heat exchanger 15 and a second connection state (broken line in FIG. 1) in which the refrigerant discharged from the compressor 11 is sent to the indoor heat exchanger 12.

[0053] The accumulator 17 is a device that separates the gas and liquid of the refrigerant for the protection of the compressor 11.

[0054] The outdoor fan 32 is, for example, a propeller fan. When the outdoor fan 32 operates, outdoor air is sucked in from the suction port (not shown) of the housing 31, and the air that has exchanged heat with the refrigerant in the outdoor heat exchanger 15 is discharged to the outdoor space from the exhaust port (not shown) of the housing 31.

[0055] The pressure sensor 33 is provided on the suction side (low-pressure side) of the compressor 11 and is a sensor that measures the pressure of the refrigerant. More specifically, the pressure sensor 33 is provided in the middle of the pipeline in the region 40c and measures the pressure of the refrigerant flowing through the region 40c. The measurement signal of the pressure sensor 33 is input to the control unit 5.

[0056] The temperature sensor 34 is provided on the suction side (low-pressure side) of the compressor 11 and is a sensor that measures the temperature of the refrigerant. More specifically, the temperature sensor 34 is installed in the region 40c close to the position between the accumulator 17 and the compressor 11 and measures the temperature of the refrigerant flowing through the region 40c. The measurement signal of the temperature sensor 34 is input to the control unit 5.

[0057] The first detection unit 35 detects the outdoor temperature and inputs the detection signal to the control unit 5. The first detection unit 35 is, for example, a temperature sensor. The first detection unit 35 is installed, for example, near the suction port (not shown) of the housing 31.

[0058] The indoor unit 2 is, for example, a wall-mounted unit installed on the side wall of the room R1. Note that the installation method of the indoor unit 2 in the room R1 is not particularly limited, and the indoor unit 2 may be a ceiling-embedded unit embedded in the ceiling space of the room R1, or a ceiling-suspended unit suspended from the ceiling of the room R1, or a floor-standing unit installed on the floor of the room R1.

[0059] The indoor unit 2 has a housing 21 in which a suction port (not shown) and a blowout port (not shown) are formed. The housing 21 houses a part of the refrigerant piping 40 in the refrigerant circuit 4, the indoor heat exchanger 12, and the liquid-side regulating valve 13. The housing 21 further houses the indoor control unit 5a, the indoor fan 22, and the second detection unit 23.

[0060] The indoor heat exchanger 12 is, for example, a cross fin tube type heat exchanger.

[0061] The liquid-side regulating valve 13 is a valve provided in the liquid-side piping 40e in the indoor unit 2, and is, for example, an expansion valve (pressure reducing mechanism). Based on the operation command of the control unit 5, by controlling the opening degree of the liquid-side regulating valve 13, the pressure and flow rate of the refrigerant flowing in a liquid state in the liquid-side piping 40e are adjusted.

[0062] The indoor fan 22 is, for example, a cross flow fan. When the indoor fan 22 operates, the air in the room R1 is sucked in from the suction port (not shown) of the housing 21, and the conditioned air that has exchanged heat with the refrigerant in the indoor heat exchanger 12 is supplied into the room R1 from the blowout port (not shown) of the housing 21.

[0063] The second detection unit 23 detects the temperature of the room R1 and inputs the detection signal to the control unit 5. The second detection unit 23 is, for example, a temperature sensor. The second detection unit 23 is installed, for example, near the suction port (not shown) of the housing 21.

[0064] The indoor unit 2 is equipped with a remote control unit 51 (hereinafter referred to as the "remote controller 51"). The remote controller 51 is provided in the room R1 in a state where it can communicate with the indoor control unit 5a by wire or wirelessly, and transmits a control signal to the indoor control unit 5a according to the user's operation.

[0065] The remote controller 51 includes a plurality of switches 70. As shown in FIG. 2, the plurality of switches 70 include an operation switch 71, an operation mode changeover switch 72, and a temperature setting switch 73. Each time the operation switch 71 is operated, the operation and stop of the air conditioner 1 are switched. Each time the operation mode changeover switch 72 is operated, the operation mode of the air conditioner 1 is alternately switched between cooling operation and heating operation. The temperature setting switch 73 includes an up button and a down button. Each time the up button is operated, the target temperature (set temperature) rises, and each time the down button is operated, the target temperature drops. Note that each of the above switches 71 to 73 and their operation contents are examples, and the remote controller 51 may include other switches, or there may be switches that are not included among the switches 71 to 73.

[0066] The gas-side regulating valve 61 is a valve provided in the gas-side pipe 40b, for example, an electromagnetic valve. Based on the operation command of the control unit 5, by controlling the opening degree of the gas-side regulating valve 61, the flow rate of the refrigerant flowing in the gas state in the gas-side pipe 40b is adjusted. Note that the gas-side regulating valve 61 may be a valve that can be controlled only in two states of an opening degree of 100% (fully open state) and an opening degree of 0% (fully closed state), or in addition to the fully open state and the fully closed state, for example, a valve that can be controlled stepwise such as an opening degree of 25%, 50%, 75%, or a valve that can arbitrarily control the opening degree between 100% and 0% of the opening degree. In any valve, by controlling the opening degree of the gas-side regulating valve 61, the flow rate of the refrigerant flowing in the gas state in the gas-side pipe 40b is adjusted.

[0067] The gas-side pipe 40b includes an internal area 41 located inside the indoor unit 2, an external area 42 located outside the indoor unit 2 and the outdoor unit 3, and an internal area 43 located inside the outdoor unit 3. The gas-side regulating valve 61 is provided, for example, in the external area 42. More specifically, the gas-side regulating valve 61 is provided at a position closer to the indoor unit 2 than the outdoor unit 3 in the external area 42 (for example, within 10 meters from the indoor unit 2). The gas-side regulating valve 61 is installed, for example, in the ceiling space of the room R1 and receives power supply from the indoor unit 2.

[0068] [Regarding the operation mode] Based on the instruction received by the remote controller 51, the control unit 5 operates the air conditioner 1 in a cooling operation or a heating operation. In the cooling operation, the control unit 5 sets the switching mechanism 16 to the first connection state (solid line in FIG. 1). When the control unit 5 operates the compressor 11 in this state, a refrigeration cycle is performed in which the indoor heat exchanger 12 becomes an evaporator and the outdoor heat exchanger 15 becomes a condenser.

[0069] In this cycle, the high-pressure refrigerant discharged from the compressor 11 to the area 40a passes through the switching mechanism 16 and the area 40d and enters the outdoor heat exchanger 15, where it exchanges heat with the outdoor air and condenses. The condensed refrigerant passes through the liquid-side regulating valve 14 and the liquid-side pipe 40e, and then is depressurized when passing through the liquid-side regulating valve 13. The depressurized refrigerant then enters the indoor heat exchanger 12, where it exchanges heat with the air in the room R1 and evaporates. The conditioned air cooled by the refrigerant is blown into the room R1 by the indoor fan 22. The refrigerant that has exited the indoor heat exchanger 12 passes through the gas-side pipe 40b and the gas-side regulating valve 61, then passes through the switching mechanism 16 and enters the accumulator 17. After gas-liquid separation, it is inhaled by the compressor 11.

[0070] In the heating operation, the control unit 5 sets the switching mechanism 16 to the second connection state (dashed line in FIG. 1). When the control unit 5 operates the compressor 11 in this state, a refrigeration cycle is performed in which the outdoor heat exchanger 15 becomes an evaporator and the indoor heat exchanger 12 becomes a condenser.

[0071] In this cycle, the high-pressure refrigerant discharged from the compressor 11 to the region 40a passes through the switching mechanism 16, the gas-side pipe 40b, and the gas-side regulating valve 61 and enters the indoor heat exchanger 12, where it exchanges heat with the air in the room R1 and condenses. The conditioned air heated by the refrigerant is blown into the room R1 by the indoor fan 22. The condensed refrigerant passes through the liquid-side regulating valve 13 and the liquid-side pipe 40e, and then is depressurized when passing through the liquid-side regulating valve 14. The depressurized refrigerant enters the outdoor heat exchanger 15, where it exchanges heat with the outdoor air and evaporates. The refrigerant that exits the outdoor heat exchanger 15 passes through the region 40d and the switching mechanism 16 and enters the accumulator 17. After gas-liquid separation, it is sucked into the compressor 11.

[0072] [Control Example of the Air Conditioner 1] FIGS. 3 and 4 are flowcharts showing control examples of the air conditioner 1. In the cooling operation and the heating operation, when the temperature difference ΔT between the detected temperature (indoor temperature) of the second detection unit 23 and the target temperature (for example, the temperature set by the temperature setting switch 73) becomes equal to or less than a predetermined value Th1, the control unit 5 issues an operation command to the compressor 11, and the operation of the compressor 11 is stopped (stop control). The stop control is also referred to as "thermo-off control".

[0073] In this control example, when the circulation of the refrigerant in the refrigerant pipe 40 is stopped by the stop control of the compressor 11, the gas-side regulating valve 61 is closed in order to suppress the natural movement of the refrigerant. Hereinafter, the control in the "cooling operation" will be taken as an example to explain this control example in detail.

[0074] Referring to FIG. 3. In the cooling operation, the control unit 5 monitors whether a predetermined first condition is satisfied (step ST11). The predetermined first condition is a condition for performing the stop control (thermo-off control) of the compressor 11, and is also referred to as the "thermo-off condition". The predetermined first condition is, for example, that the temperature difference ΔT is equal to or less than a predetermined value Th1 (ΔT ≦ Th1).

[0075] The temperature difference ΔT is, for example, a value obtained by subtracting the target temperature T2 from the detected temperature T1 of the second detection unit 23 (ΔT = T1 - T2). The temperature difference ΔT may be a value obtained by further subtracting a predetermined margin value A1 (where A1 > 0) from the value obtained by subtracting the target temperature T2 from the detected temperature T1 (ΔT = T1 - T2 - A1). The predetermined value Th1 is a value also referred to as the "thermo-off temperature" and is, for example, a value of 0 or less.

[0076] When a predetermined first condition is not satisfied (the NO route in step ST11, for example, ΔT > Th1), the control unit 5 maintains the operation of the compressor 11, opens the opening degree of the liquid-side regulating valve 13 wider than a predetermined first opening degree, and opens the opening degree of the gas-side regulating valve 61 wider than a predetermined second opening degree. The opening degree of the gas-side regulating valve 61 is, for example, set to 100% (fully open). Thereby, the refrigerant circulates through the refrigerant piping 40.

[0077] When a predetermined first condition is satisfied (the YES route in step ST11, for example, ΔT ≤ Th1), the control unit 5 executes a first closing control to close the opening degree of the liquid-side regulating valve 13 to be equal to or less than a predetermined first opening degree (step ST12). The opening degree of the liquid-side regulating valve 13 is, for example, set to 0% (fully closed), and the flow of the refrigerant in the liquid-side regulating valve 13 is blocked. Note that the opening degree of the liquid-side regulating valve 13 after the first closing control only needs to be smaller than the opening degree of the liquid-side regulating valve 13 before the first closing control and may be larger than 0%. As long as the flow of the refrigerant in the liquid-side regulating valve 13 is restricted more than before the first closing control by the first closing control, it does not need to be completely blocked.

[0078] Next, the control unit 5 monitors whether or not a predetermined closing condition is satisfied (step ST13). The predetermined closing condition is a condition indicating that the pump-down operation (operation of storing the refrigerant) of the compressor 11 has been completed to a certain extent. When the predetermined closing condition is not satisfied (the NO route in step ST13), the control unit 5 maintains the operation of the compressor 11 with the liquid-side regulating valve 13 closed. Thereby, a high-pressure refrigerant in a liquid state can be stored in the region from the liquid-side regulating valve 13 to the outdoor heat exchanger 15 in the liquid-side piping 40e.

[0079] The predetermined closing condition includes, for example, the following Condition 1 (time condition), Condition 2 (pressure condition), or Condition 3 (superheat degree condition). The control unit 5 monitors at least one of Conditions 1 to 3. The predetermined closing condition may be that one of Conditions 1 to 3 is satisfied (Condition 1, Condition 2 or Condition 3), or two or more of Conditions 1 to 3 are satisfied (for example, Condition 1 and (Condition 2 or Condition 3)).

[0080] 《Predetermined Closing Condition》 Condition 1: The elapse of a predetermined time X1 from the start of execution of the first closing control Condition 2: The pressure of the refrigerant measured by the pressure sensor 33 has become equal to or lower than a predetermined pressure P1 Condition 3: The superheat degree SH1 on the suction side of the compressor 11 has become equal to or higher than a predetermined temperature SH2

[0081] Condition 1 means that a predetermined time X1 has elapsed since the liquid-side regulating valve 13 was closed. The control unit 5 counts the elapsed time from the start of execution of the first closing control based on, for example, a timer (not shown) built in the control unit 5, and determines whether or not the count exceeds the predetermined time X1. During the predetermined time X1, the refrigerant is stored in the above region by the operation of the compressor 11. Therefore, the control unit 5 determines that the pump-down operation of the compressor 11 has been completed to a certain extent based on the elapse of the predetermined time X1.

[0082] Condition 2 means that the pressure of the refrigerant measured by the pressure sensor 33 has become equal to or lower than a predetermined pressure P1. When the refrigerant storage is started by the first closing control, the pressure of the gaseous refrigerant flowing through the gas-side pipe 40b and the region 40c (that is, the suction side of the compressor 11) gradually decreases. Therefore, the control unit 5 determines that the pump-down operation of the compressor 11 has been completed to a certain extent based on the measured pressure of the pressure sensor 33.

[0083] Condition 3 is that the superheat degree SH1 on the suction side of the compressor 11 has reached a predetermined temperature SH2 or higher. When the refrigerant accumulation is started by the first shut-off control, as a result of the pressure of the gaseous refrigerant flowing through the suction side of the compressor 11 gradually decreasing, the superheat degree SH1 on the suction side of the compressor 11 increases. The superheat degree SH1 is calculated by a known method based on, for example, the refrigerant pressure measured by the pressure sensor 33 and the refrigerant temperature measured by the temperature sensor 34. The control unit 5 determines, based on the superheat degree SH1, that the pump-down operation of the compressor 11 has been completed to a certain extent.

[0084] When a predetermined shut-off condition is satisfied (the YES route in step ST13), the control unit 5 executes a second shut-off control to close the opening degree of the gas-side regulating valve 61 to a predetermined second opening degree or less (step ST14). The opening degree of the gas-side regulating valve 61 is set to, for example, 0% (fully closed), and the flow of the refrigerant through the gas-side regulating valve 61 is blocked. Note that the opening degree of the gas-side regulating valve 61 after the second shut-off control only needs to be smaller than the opening degree of the gas-side regulating valve 61 before the second shut-off control, and may be larger than 0%. By the second shut-off control, the flow of the refrigerant through the gas-side regulating valve 61 only needs to be more restricted than before the second shut-off control, and does not need to be completely blocked.

[0085] The control unit 5 can execute the second shut-off control in a timely manner by determining a predetermined shut-off condition based on time, pressure, or superheat degree in step ST13.

[0086] Next, the control unit 5 monitors whether a predetermined time X2 has elapsed since the start of the execution of the second shut-off control (step ST15). If the predetermined time X2 has not elapsed (the NO route in step ST15), the control unit 5 maintains the operation of the compressor 11 with the liquid-side regulating valve 13 and the gas-side regulating valve 61 closed. Thereby, the refrigerant on the compressor 11 side rather than the gas-side regulating valve 61 can be sucked, and more refrigerant can be accumulated in the region between the liquid-side regulating valve 13 and the outdoor heat exchanger 15 in the liquid-side pipe 40e.

[0087] When the specified time X2 has elapsed (the YES route in step ST15), the control unit 5 executes stop control to stop the compressor 11 (step ST16). By the stop control, the rotation speed of the compressor 11 becomes 0.

[0088] In this control example, during the first closing control and the stop control, the control unit 5 executes second closing control to close the gas-side regulating valve 61, thereby restricting the natural movement of the refrigerant in the gas-side pipe 40b. As a result, unintended refrigerant flow such as backflow of the refrigerant in the refrigerant circuit 4 can be suppressed, and thus the capacity loss of the air conditioner 1 can be suppressed.

[0089] In particular, after executing the first closing control, the control unit 5 executes the second closing control and the stop control, thereby allowing the refrigerant in a liquid state to be stored in the liquid-side pipe 40e. As a result, since the amount of refrigerant in the gas-side pipe 40b is reduced, the amount of refrigerant that can naturally move in the refrigerant circuit 4 can be reduced, and thus the capacity loss of the air conditioner 1 can be suppressed.

[0090] Also, after executing the second closing control, the control unit 5 executes stop control, thereby further reducing the amount of refrigerant in the gas-side pipe 40b.

[0091] Further, when the rotation speed of the compressor 11 decreases and the force of the compressor 11 to circulate the refrigerant weakens, backflow of the refrigerant in the gas-side pipe 40b may occur even before the compressor 11 completely stops. By the control unit 5 executing the stop control after executing the second closing control, the backflow of the refrigerant in the gas-side pipe 40b can be more reliably suppressed.

[0092] As shown in FIG. 1, the gas-side regulating valve 61 is located in the external region 42. By configuring it in this way, the length of the gas-side pipe 40b from the indoor heat exchanger 12 to the gas-side regulating valve 61 can be shortened, so that the amount of refrigerant that can freely move from the gas-side pipe 40b to the indoor heat exchanger 12 after the execution of the second shut-off control can be reduced. As a result, the amount of refrigerant that can flow backward in the refrigerant circuit 4 can be reduced, so that the capacity loss of the air conditioner 1 can be suppressed.

[0093] In the example of FIG. 3, the first shut-off control, the second shut-off control, and the stop control are executed in this order, but the order of these controls is not particularly limited. For example, the control unit 5 may execute the first shut-off control, the second shut-off control, and the stop control simultaneously.

[0094] Next, with reference to FIG. 4, a control example when restarting the circulation of the refrigerant will be described. After executing the first shut-off control, the second shut-off control, and the stop control, the control unit 5 monitors whether a predetermined second condition is satisfied (step ST21). The predetermined second condition is a condition for performing the start control (thermo-on control) of the compressor 11 and is also referred to as the "thermo-on condition". The predetermined second condition includes, for example, that the temperature difference ΔT becomes equal to or greater than a second predetermined value Th2 (ΔT≧Th2).

[0095] The second predetermined value Th2 is a value also referred to as the "thermo-on temperature" and is, for example, a value smaller than the predetermined value Th1 (Th2<Th1). The predetermined second condition may be that the temperature difference ΔT becomes equal to or greater than the second predetermined value Th2, or the temperature difference ΔT becomes equal to or greater than the predetermined value Th1.

[0096] When the predetermined second condition is not satisfied (the NO route in step ST21, for example, ΔT<Th2), the control unit 5 maintains the compressor 11 in a stopped state and maintains the liquid-side regulating valve 13 and the gas-side regulating valve 61 in a closed state.

[0097] When a predetermined second condition is satisfied (the YES route in step ST21, for example, ΔT ≧ Th2), the control unit 5 executes control to rotate the compressor 11 (start-up control), control to open the liquid-side regulating valve 13 wider than a predetermined first opening degree (first opening control), and control to open the gas-side regulating valve 61 wider than a predetermined second opening degree (second opening control).

[0098] More specifically, when a predetermined second condition is satisfied, the control unit 5 monitors whether a predetermined opening condition is satisfied (step ST22). The predetermined opening condition is a condition for determining the control order of the start-up control and the second opening control, and is a condition in which there is a relatively high possibility that refrigerant accumulates (also referred to as "refrigerant pooling" or "refrigerant slumber") in a part of the refrigerant circuit 4.

[0099] During the stop of the compressor 11, for example, due to the temperature difference of the refrigerant pipe 40 or the like, there is a possibility that refrigerant accumulates in a part of the refrigerant circuit 4 (for example, the gas-side pipe 40b). If the refrigerant circulation is restarted in a state where refrigerant has accumulated, the refrigerant liquefied due to the accumulation may be directly sucked into the compressor 11, which may cause a problem in the compressor 11.

[0100] Therefore, when there is a relatively high possibility that refrigerant accumulates in a part of the refrigerant circuit 4, that is, when a predetermined opening condition is satisfied (the YES route in step ST22), the control unit 5 executes the start-up control (step ST23), waits for the elapse of a predetermined time X3 (step ST25), and then executes the second opening control (step ST25). As a result, by starting the refrigerant flow in the gas-side pipe 40b in a state where the rotational speed of the compressor 11 has increased to a certain extent, the suction pressure can be lowered, so that the accumulated liquid refrigerant can be evaporated and the refrigerant accumulation can be eliminated. Thereby, the occurrence of problems in the compressor 11 can be suppressed.

[0101] On the other hand, when there is a relatively low possibility that refrigerant stagnation has occurred in a part of the refrigerant circuit 4, that is, when a predetermined release condition is not satisfied (the NO route in step ST22), the control unit 5 executes second release control (step ST26), and then executes startup control (step ST27). Steps ST26 and ST27 may be executed simultaneously. By performing the second release control prior to (or simultaneously with) the startup control when restarting the refrigerant circulation, the rotation of the compressor 11 is started in a state where a wide range of the refrigerant piping 40 is communicated, so that the refrigerant circulation can be restarted more quickly.

[0102] The predetermined release condition includes, for example, the following condition 1 (outdoor air temperature decrease condition), condition 2 (room temperature decrease condition), condition 3 (piping temperature decrease condition), or condition 4 (abnormal stop condition). The control unit 5 monitors at least one of the conditions 1 to 4. The predetermined release condition may be that one of the conditions 1 to 4 is satisfied (condition 1, condition 2, condition 3 or condition 4), or may include that a plurality of the conditions 1 to 4 are satisfied (for example, {(condition 1 and condition 2) or condition 3 or condition 4}).

[0103] 《Predetermined Release Condition》 Condition 1: The detected temperature T11 of the first detection unit 35 has decreased by more than a predetermined temperature Th11 from the detected temperature T12 of the first detection unit 35 detected at the time of execution of the stop control. Condition 2: The detected temperature T21 of the second detection unit 23 has decreased by more than a predetermined temperature Th21 from the detected temperature T22 of the second detection unit 23 detected at the time of execution of the stop control. Condition 3: The detected temperature T31 of the temperature sensor 34 has decreased by more than a predetermined temperature Th31 from the detected temperature T32 of the temperature sensor 34 detected at the time of execution of the stop control. Condition 4: The compressor 11 has been stopped without going through the stop control of the control unit 5.

[0104] Condition 1 means a condition where the outside air temperature has dropped while the compressor 11 is stopped. When the outside air temperature drops, the temperature of the refrigerant pipe 40 can drop. When the temperature of the refrigerant pipe 40 drops while the compressor 11 is stopped, the gaseous refrigerant contained in the refrigerant pipe 40 may condense in the refrigerant pipe 40 (for example, the gas-side pipe 40b or the region 40c) or the accumulator 17, and there is a risk of refrigerant stagnation.

[0105] The control unit 5 calculates the difference (T11 - T12) between the detected temperature T11 of the first detection unit 35 at the time of executing step ST22 and the detected temperature T12 of the first detection unit 35 detected at the time of executing the stop control, and compares the difference (T11 - T12) with a predetermined temperature Th11. Then, when the difference (T11 - T12) is greater than the predetermined temperature Th11 (T11 - T12 > Th11), the control unit 5 determines that there is a high risk of refrigerant stagnation (that is, it determines that condition 1 is satisfied).

[0106] Condition 2 means a condition where the temperature (room temperature) of the room R1 has dropped while the compressor 11 is stopped. When the room temperature drops while the compressor 11 is stopped, the temperature of the refrigerant pipe 40 drops, and there is a risk of refrigerant stagnation.

[0107] The control unit 5 calculates the difference (T21 - T22) between the detected temperature T21 of the second detection unit 23 at the time of executing step ST22 and the detected temperature T22 of the second detection unit 23 detected at the time of executing the stop control, and compares the difference (T21 - T22) with a predetermined temperature Th21. Then, when the difference (T21 - T22) is greater than the predetermined temperature Th21 (T21 - T22 > Th21), the control unit 5 determines that there is a high risk of refrigerant stagnation (that is, it determines that condition 2 is satisfied).

[0108] Condition 3 means that the temperature of the refrigerant pipe 40 has dropped while the compressor 11 is stopped. When the temperature of the refrigerant pipe 40 drops while the compressor 11 is stopped, there is a risk of refrigerant stagnation.

[0109] During the execution of step ST22, the control unit 5 calculates the difference (T31 - T32) between the detected temperature T31 of the temperature sensor 34 and the detected temperature T32 of the temperature sensor 34 during the execution of the stop control, and compares the difference (T31 - T32) with a predetermined temperature Th31. Then, when the difference (T31 - T32) is greater than the predetermined temperature Th31 (T31 - T32 > Th31), the control unit 5 determines that there is a high possibility that refrigerant has accumulated (that is, it determines that condition 3 is satisfied).

[0110] Condition 4 means that the compressor 11 has stopped unintentionally due to an abnormality such as a power failure. When the compressor 11 stops unintentionally, if the compressor 11 stops while the gas-side pipe 40b is not sufficiently low in pressure, there is a high possibility that refrigerant has accumulated in the gas-side pipe 40b. For example, during the execution of step ST22, the control unit 5 reads the control record of the control unit 5. Then, when the compressor 11 has stopped without going through the stop control of step ST16, the control unit 5 determines that condition 4 is satisfied.

[0111] Note that the control unit 5 may determine that condition 4 is satisfied when the compressor 11 has stopped in a state where none of the controls from step ST11 to step ST16 has been executed. Also, the control unit 5 may determine that condition 4 is satisfied when the compressor 11 has stopped in a state where the control includes a control executed in an order different from the order planned by the control unit 5 for any of the controls from step ST11 to step ST16.

[0112] After the execution of the start control and the second opening control, the control unit 5 executes the first opening control (step ST28). As a result, the circulation of the refrigerant in the refrigerant circuit 4 restarts.

[0113] Note that the control unit 5 may execute the first opening control prior to the start control and the second opening control. Also, the control unit 5 may execute the first opening control simultaneously with the second opening control in step ST25, or may execute the first opening control simultaneously with the start control in step ST27.

[0114] [In the case of heating operation] In the above control example, the control in the case of cooling operation was described. However, the control unit 5 controls each part of the air conditioner 1 in the same manner also in the case of heating operation. Hereinafter, the parts different from the cooling operation will be described.

[0115] In the heating operation, the temperature difference ΔT in step S11 is, for example, a value obtained by subtracting the detected temperature T1 of the second detection unit 23 from the target temperature T2 (ΔT = T2 - T1). The temperature difference ΔT may be a value obtained by further subtracting a predetermined margin value A1 (where A1 > 0) from the value obtained by subtracting the detected temperature T1 from the target temperature T2 (ΔT = T2 - T1 - A1).

[0116] In the first closing control (step ST12) of the heating operation, the control unit 5 closes the opening degree of the liquid-side adjustment valve 14 to a predetermined first opening degree or less without closing the liquid-side adjustment valve 13. Further, in the first opening control (step ST28) of the heating operation, the control unit 5 opens the opening degree of the liquid-side adjustment valve 14 to be larger than the predetermined first opening degree while keeping the opening degree of the liquid-side adjustment valve 13 as it is.

[0117] [Modification example] The present disclosure is not limited to the above-described embodiments, and various modifications are possible. In the following modification examples, the same components as those in the above-described embodiments are denoted by the same reference numerals, and the description thereof will be omitted as appropriate.

[0118] [Modification example of the gas-side adjustment valve] FIG. 5 is a schematic diagram showing the internal structure of the indoor unit 2a according to the modification example. The gas-side adjustment valve 61 in the above-described embodiment is provided in the external region 42. However, the gas-side adjustment valve 61a according to the modification example may be provided in the internal region 41 as shown in FIG. 5, or may be provided in the internal region 43 (FIG. 1) on the outdoor unit 3 side. Further, the gas-side adjustment valve 61a may receive power supply from the indoor unit 2a or may receive power supply from the outdoor unit 3.

[0119] In particular, by providing the gas-side regulating valve 61a in the internal region 41, the control line from the indoor control unit 5a to the gas-side regulating valve 61a can be shortened, so that the gas-side regulating valve 61a can be installed more easily in a controllable manner. Further, by providing the gas-side regulating valve 61a in the internal region 41, the length of the gas-side pipe 40b from the indoor heat exchanger 12 to the gas-side regulating valve 61a can be shortened, so that the amount of refrigerant that can freely move from the gas-side pipe 40b to the indoor heat exchanger 12 after the execution of the second closing control (FIG. 3: step ST14) can be reduced.

[0120] [Modification example of the liquid-side regulating valve] Referring to FIG. 5. The liquid-side regulating valve 13 of the above-described embodiment has both a function as a shut-off valve for adjusting the flow rate of the refrigerant in the liquid-side pipe 40e and a function as an expansion valve for adjusting the pressure of the refrigerant. However, the liquid-side regulating valve of the present disclosure only needs to be able to adjust the flow rate of the refrigerant in the liquid-side pipe 40e, and does not necessarily have a function as an expansion valve for adjusting the pressure of the refrigerant.

[0121] The liquid-side regulating valve 62 according to the modification example is, for example, an electric shut-off valve and is provided in the liquid-side pipe 40e. The liquid-side regulating valve 62 is electrically connected to the control unit 5. Based on the operation command of the control unit 5, the opening degree of the liquid-side regulating valve 62 is controlled, so that the flow rate of the refrigerant flowing through the liquid-side pipe 40e in the liquid state is adjusted.

[0122] An expansion valve 13a is provided between the liquid-side regulating valve 62 and the indoor heat exchanger 12. The expansion valve 13a is electrically connected to the control unit 5. Based on the operation command of the control unit 5, the opening degree of the expansion valve 13a is controlled, so that the pressure of the refrigerant flowing through the liquid-side pipe 40e in the liquid state is adjusted.

[0123] [Others] Regarding the above-described embodiments and modification examples, at least a part of them may be arbitrarily combined with each other.

[0124] [Operational effects of the embodiment] (1) The air conditioner 1 according to the embodiment includes a refrigerant circuit 4 in which a compressor 11, an indoor heat exchanger 12, and an outdoor heat exchanger 15 are connected by a refrigerant pipe 40, liquid-side regulating valves 13, 14, 62 that adjust the flow rate of the refrigerant flowing in a liquid state in a liquid-side pipe 40e located between the indoor heat exchanger 12 and the outdoor heat exchanger 15 in the refrigerant pipe 40, gas-side regulating valves 61, 61a that adjust the flow rate of the refrigerant flowing in a gaseous state in a gas-side pipe 40b located between the indoor heat exchanger 12 and the compressor 11 in the refrigerant pipe 40, a first closing control that closes the liquid-side regulating valves 13, 14, 62 to a predetermined first opening or less when a predetermined first condition is satisfied, a stop control that stops the compressor 11, and a second closing control that closes the gas-side regulating valves 61, 61a to a predetermined second opening or less, and a control unit 5 that executes the above.

[0125] When closing the liquid-side regulating valves 13, 14, 62 and stopping the compressor 11, by closing the gas-side regulating valves 61, 61a by the control unit 5, the natural movement of the refrigerant in the gas-side pipe 40b can be restricted. Thereby, the reverse flow of the refrigerant in the refrigerant circuit 4 can be suppressed, so that the capacity loss of the air conditioner 1 can be suppressed.

[0126] (2) The control unit 5 according to the embodiment executes the second closing control and the stop control after executing the first closing control.

[0127] After restricting the flow of the refrigerant in the liquid-side pipe 40e by the first closing control, until the second closing control and the stop control are executed, the compressor 11 can store the refrigerant in a liquid state in the liquid-side pipe 40e. Thereby, the amount of refrigerant that can flow backward in the refrigerant circuit 4 can be reduced, so that the capacity loss of the air conditioner 1 can be suppressed.

[0128] (3) The control unit 5 according to the embodiment executes the second closing control when a predetermined closing condition is satisfied after executing the first closing control, and executes the stop control after executing the second closing control.

[0129] When the rotational speed of the compressor 11 decreases and the force of the compressor 11 to circulate the refrigerant weakens, natural movement of the refrigerant in the gas-side pipe 40b may occur even before the compressor 11 completely stops. Therefore, preferably, after a predetermined closing condition is satisfied and before the execution of the stop control, by executing the second closing control, the flow of the refrigerant in the gas-side pipe 40b can be more reliably restricted. Thereby, the reverse flow of the refrigerant in the refrigerant circuit 4 can be suppressed, and thus the capacity loss of the air conditioner 1 can be suppressed.

[0130] (4) The predetermined closing condition according to the embodiment includes that a predetermined time has elapsed since the start of execution of the first closing control, that the refrigerant pressure in the pressure sensor 33 provided on the suction side of the compressor 11 has become equal to or lower than a predetermined pressure, or that the degree of superheat on the suction side of the compressor 11 calculated based on the temperature sensor 34 and the pressure sensor 33 provided on the suction side of the compressor 11 has become equal to or higher than a predetermined temperature.

[0131] The predetermined closing condition indicates that the pump-down operation of the compressor 11 has been completed to a certain extent. By making it possible to determine the predetermined closing condition based on time, pressure, or degree of superheat, the control unit 5 can execute the second closing control in a timely manner.

[0132] (5) When a predetermined second condition is satisfied after the execution of the first closing control, the stop control, and the second closing control, the control unit 5 according to the embodiment executes a first opening control for opening the liquid-side regulating valves 13, 14, 62 wider than the predetermined first opening degree, a starting control for rotating the compressor 11, and a second opening control for opening the gas-side regulating valves 61, 61a wider than the predetermined second opening degree.

[0133] By configuring in this way, the circulation of the refrigerant can be restarted.

[0134] (6) When the predetermined second condition is satisfied, the control unit 5 according to the embodiment executes the second opening control, and after executing the second opening control, executes the starting control.

[0135] When restarting the refrigerant circulation, by first performing the second opening control, the rotation of the compressor 11 is started with a wide range of the refrigerant piping 40 being in communication, so that the refrigerant circulation can be restarted more quickly.

[0136] (7) When the predetermined second condition is satisfied, the control unit 5 according to the embodiment executes the startup control, and after the execution of the startup control, executes the second opening control.

[0137] During the stop of the compressor 11, for example, due to the temperature difference of the refrigerant piping 40 or the like, there is a possibility that refrigerant may accumulate in a part of the refrigerant circuit 4 (for example, the gas-side piping 40b). Condensation of the refrigerant may occur due to the accumulation, and there is a possibility that a problem may occur in the compressor 11 if the liquefied refrigerant is directly sucked into the compressor 11. By executing the startup control prior to the second opening control, the suction pressure can be lowered while the rotational speed of the compressor 11 has increased to a certain extent, and the accumulated liquid refrigerant can be evaporated, so that the accumulation of the refrigerant can be eliminated. Thereby, the occurrence of problems in the compressor 11 can be suppressed.

[0138] (8) When the predetermined second condition is satisfied, if a predetermined opening condition is satisfied, the control unit 5 according to the embodiment executes the second opening control after the execution of the startup control, and if the predetermined opening condition is not satisfied, executes the startup control after the execution of the second opening control.

[0139] By determining the control order of the startup control and the second opening control according to the situation, the refrigerant circulation can be restarted more preferably.

[0140] (9) The predetermined release conditions according to the embodiment include that the detected temperature of the first detection unit 35 that detects the outdoor temperature has decreased by more than a predetermined temperature from the detected temperature detected by the first detection unit 35 at the time of execution of the stop control, the detected temperature of the second detection unit 23 that detects the indoor temperature has decreased by more than a predetermined temperature from the detected temperature detected by the second detection unit 23 at the time of execution of the stop control, the detected temperature of the temperature sensor 34 provided on the suction side of the compressor 11 has decreased by more than a predetermined temperature from the detected temperature detected by the temperature sensor 34 at the time of execution of the stop control, or the compressor 11 has been stopped without going through the stop control of the control unit 5.

[0141] The predetermined release conditions indicate conditions where there is a high possibility of refrigerant retention in a part of the refrigerant circuit 4. Specifically, the predetermined release conditions include the case where at least one of various temperatures that cause refrigerant retention during the stop of the compressor 11 has decreased, or the case where the compressor 11 has stopped abnormally. By configuring in this way, when there is a high possibility of refrigerant retention, the control unit 5 performs the start control prior to the second release control to suppress the occurrence of malfunctions of the compressor 11, and when there is a low possibility of refrigerant retention, the control unit 5 performs the second release control prior to the start control, so that the refrigerant circulation can be restarted more quickly.

[0142] (10) The air conditioner 1 according to the embodiment further includes a second detection unit 23 that detects the indoor temperature. The predetermined first condition includes that the temperature difference between the detected temperature of the second detection unit 23 and the target temperature is equal to or less than a predetermined value. The predetermined second condition includes that the temperature difference is equal to or greater than a second predetermined value that is smaller than the predetermined value.

[0143] By configuring in this way, based on the temperature difference between the detected temperature (indoor temperature) of the second detection unit 23 and the target temperature, the timing of the operation and stop of the compressor 11 can be determined in a timely manner.

[0144] (11) The air conditioner 1 according to the embodiment further includes an indoor unit 2 that houses an indoor heat exchanger 12, and an outdoor unit 3 that houses a compressor 11 and an outdoor heat exchanger 15. The gas-side regulating valves 61, 61a are located in the external region 42 of the indoor unit 2 and the outdoor unit 3, or the internal region 41 of the indoor unit 2, in the gas-side pipe 40b.

[0145] By configuring in this way, the length of the gas-side pipe 40b from the indoor heat exchanger 12 to the gas-side regulating valves 61, 61a can be shortened. Therefore, the amount of refrigerant that can freely move from the gas-side pipe 40b to the indoor heat exchanger 12 after the execution of the second shut-off control can be reduced. As a result, the circulation of the refrigerant during the stop of the compressor 11 can be more suppressed, and thus the capacity loss of the air conditioner 1 can be suppressed.

[0146] [Supplementary Note] Although the embodiments have been described above, it will be understood that various changes in form and details are possible without departing from the spirit and scope of the claims.

Explanation of Reference Numerals

[0147] 1: Air conditioner, 11: Compressor, 12: Indoor heat exchanger, 13: Liquid-side regulating valve (expansion valve), 13a: Expansion valve, 14: Liquid-side regulating valve (expansion valve), 15: Outdoor heat exchanger, 16: Switching mechanism, 17: Accumulator, 2: Indoor unit, 2a: Indoor unit, 21: Housing, 22: Indoor fan, 23: Second detection unit, 3: Outdoor unit, 31: Housing, 32: Outdoor fan, 33: Pressure sensor, 34: Temperature sensor, 35: First detection unit, 4: Refrigerant circuit, 40: Refrigerant pipe, 40a: Region, 40b: Region (gas-side pipe), 40c: Region, 40d: Region, 40e: Region (liquid-side pipe), 41: Internal region, 42: External region, 43: Internal region, 5: Control unit, 5a: Indoor control unit, 5b: Outdoor control unit, 51: Remote control unit (remote controller), 52a: Processor, 52b: Processor, 53a: Memory, 53b: Memory, 61: Gas-side regulating valve, 61a: Gas-side regulating valve, 62: Liquid-side regulating valve, 70: Switch, 71: Operation switch, 72: Operation switching switch, 73: Temperature setting switch, 9: Air conditioner, 902: Indoor unit, 903: Outdoor unit, 904: Refrigerant circuit, 911: Compressor, 912: Indoor heat exchanger, 913: Liquid-side regulating valve, 914: Liquid-side regulating valve, 915: Outdoor heat exchanger, 916: Switching mechanism, 917: Accumulator, 921: Indoor fan, 931: Outdoor fan, 940: Refrigerant pipe, 940b: Gas-side pipe, 940e: Liquid-side pipe, R1: Room, T1: Detected temperature, T2: Target temperature, T11: Detected temperature, T12: Detected temperature, T21: Detected temperature, T22: Detected temperature, T31: Detected temperature, T32: Detected temperature, ΔT: Temperature difference, A1: Margin value, Th1: Predetermined value, Th2: Second predetermined value, Th11: Predetermined temperature, Th21: Predetermined temperature, Th31: Predetermined temperature, X1: Predetermined time, X2: Predetermined time, X3: Predetermined time, P1: Predetermined pressure, SH1: Superheat degree, SH2: Predetermined temperature

Claims

1. A refrigerant circuit (4) in which a compressor (11), an indoor heat exchanger (12), and an outdoor heat exchanger (15) are connected by refrigerant pipes (40), In a liquid-side pipe (40e) located between the indoor heat exchanger (12) and the outdoor heat exchanger (15) among the refrigerant pipes (40), a liquid-side regulating valve (13, 14, 62) for adjusting the flow rate of the refrigerant flowing in a liquid state, In a gas-side pipe (40b) located between the indoor heat exchanger (12) and the compressor (11) among the refrigerant pipes (40), a gas-side regulating valve (61, 61a) for adjusting the flow rate of the refrigerant flowing in a gaseous state, When a predetermined first condition is satisfied, a first closing control for closing the liquid-side regulating valve (13, 14, 62) to a predetermined first opening or less, a stop control for stopping the compressor (11), and a second closing control for closing the gas-side regulating valve (61, 61a) to a predetermined second opening or less are executed by a control unit (5), comprising After the execution of the first closing control, the stop control, and the second closing control, when a predetermined second condition is satisfied, the control unit (5) performs a first opening control for opening the liquid-side regulating valve (13, 14, 62) wider than the predetermined first opening, a start control for rotating the compressor (11), and a second opening control for opening the gas-side regulating valve (61, 61a) wider than the predetermined second opening, When the predetermined second condition is satisfied, the control unit (5) When a predetermined opening condition is satisfied, the second opening control is executed after the execution of the start control, When the predetermined opening condition is not satisfied, the start control is executed after the execution of the second opening control, The predetermined opening condition is that the detected temperature of a first detection unit (35) for detecting the outdoor temperature has dropped by more than a predetermined temperature from the detected temperature detected by the first detection unit (35) at the time of execution of the stop control, The detected temperature of the second detection unit (23) that detects the indoor temperature has dropped below a predetermined temperature from the detected temperature detected by the second detection unit (23) when the stop control is executed. The detected temperature of the temperature sensor (34) provided on the suction side of the compressor (11) has dropped below a predetermined temperature from the detected temperature detected by the temperature sensor (34) when the stop control is executed, or The compressor (11) has been stopped without going through the stop control by the control unit (5), including the air conditioner (1).

2. After executing the first closing control, the control unit (5) executes the second closing control and the stop control. The air conditioner (1) according to claim 1.

3. The control unit (5) After executing the first closing control, when a predetermined closing condition is satisfied, the second closing control is executed. After executing the second closing control, the stop control is executed. The predetermined closing condition is A predetermined time has elapsed since the start of execution of the first closing control. The refrigerant pressure in the pressure sensor (33) provided on the suction side of the compressor (11) has become equal to or lower than a predetermined pressure, or The degree of superheat on the suction side of the compressor (11) calculated based on the temperature sensor (34) and the pressure sensor (33) provided on the suction side of the compressor (11) has become equal to or higher than a predetermined temperature. The air conditioner (1) according to claim 2, including the above.

4. The control unit (5) When the predetermined second condition is satisfied, the second opening control is executed. After executing the second opening control, the start control is executed. The air conditioner (1) according to claim 1.

5. The control unit (5) When the predetermined second condition is satisfied, execute the startup control, After the execution of the startup control, execute the second opening control, The air conditioner (1) according to claim 1.

6. Further comprising a second detection unit (23) for detecting the indoor temperature, The predetermined first condition includes that the temperature difference between the detected temperature by the second detection unit (23) and the target temperature is equal to or less than a predetermined value, The predetermined second condition includes that the temperature difference is equal to or greater than a second predetermined value smaller than the predetermined value, The air conditioner (1) according to any one of claims 1 to 5.

7. An indoor unit (2) housing the indoor heat exchanger (12), An outdoor unit (3) housing the compressor (11) and the outdoor heat exchanger (15), Further comprising, The gas-side regulating valves (61, 61a) are located in, The external region (42) of the indoor unit (2) and the outdoor unit (3), or, The internal region (41) of the indoor unit (2), The air conditioner (1) according to any one of claims 1 to 6.

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