WO2006115053A1

WO2006115053A1 - Air conditioner

Info

Publication number: WO2006115053A1
Application number: PCT/JP2006/307712
Authority: WO
Inventors: Hideki Sangenya; Takeshi Kitagawa
Original assignee: Daikin Industries, Ltd.
Priority date: 2005-04-18
Filing date: 2006-04-12
Publication date: 2006-11-02
Also published as: JP4001149B2; JP2006300374A

Abstract

There is provided an air conditioner capable of suppressing a coolant sound when the operation of cooling cycle is switched to operation of warming cycle. The air conditioner (100) includes a coolant circuit having a compressor (10), an outdoor heat exchanger (14), a first indoor expansion valve (5a), and a first indoor heat exchanger (3a). The air conditioner (100) further includes a switching mechanism (11) and a control unit (60). The switching mechanism (11) switches between the cooling cycle and the warming cycle by switching the coolant circulation direction. When a defrost operation control by cooling cycle or oil collection operation control is switched to normal warming/cooling operation control, the control unit (60) closes the first indoor expansion valve (5a) and performs pump down operation control for driving the compressor (10) while the switching mechanism (11) in the cooling cycle side. After this, the control unit (60) opens the first indoor expansion valve (5a) to start normal warming/cooling operation control.

Description

Specification

Air conditioner

Technical field

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

Background art

[0002] Conventionally, an air conditioner that can switch between a cooling cycle and a heating cycle by switching the flow direction of refrigerant can be switched from a state to an operation based on the heating cycle. There is a case. For example, in order to perform defrosting of outdoor diplomacy during heating operation, a so-called defrost operation in which the expansion valve is opened and the outdoor heat exchange functions as a condenser in a cooling cycle may be performed. When the defrosting of the outdoor heat exchanger is completed, the heating cycle is switched to the heating operation (see Patent Document 1).

Patent Document 1: Japanese Patent Laid-Open No. 2002-22306

Disclosure of the invention

Problems to be solved by the invention

[0003] However, when the operation is performed in the cooling cycle as in the above-described defrost operation, the temperature on the indoor heat exchanger side is lowered, so that the liquid refrigerant is easily accumulated on the indoor heat exchange side. If operation with a heating cycle is started in a state where liquid refrigerant has accumulated on the indoor heat exchange side, the sound of the refrigerant being discharged when the expansion valve is opened may propagate in the liquid, causing discomfort to the user. There is.

The subject of this invention is providing the air conditioner which can suppress the refrigerant | coolant sound at the time of switching from the driving | operation by a cooling cycle to the driving | operation by a heating cycle.

Means for solving the problem

[0004] An air conditioner according to a first aspect of the present invention is an air conditioner including a refrigerant circuit including a compressor, an outdoor heat exchanger, a first expansion valve, and a first indoor heat exchanger. Department. The mechanism switches between the cooling cycle and the heating cycle by switching the refrigerant circulation direction. The control unit performs the second operation by the heating cycle from the first operation control by the cooling cycle. When switching to rotation control, the first expansion valve is closed, and after the pump down operation control is performed to drive the compressor while the mechanism is on the cooling cycle side, the first expansion valve is opened and the second operation control is started. To do.

In this air conditioner, the first operation control force by the cooling cycle is switched to the second operation control by the heating cycle, and the pump down operation control is performed. As a result, it is possible to prevent the refrigerant from being collected on the outdoor heat exchange side and the liquid refrigerant from accumulating on the first indoor heat exchange side. For this reason, the refrigerant | coolant sound at the time of a 1st expansion valve being opened can be suppressed.

[0005] An air conditioner according to a second invention is the air conditioner according to the first invention, wherein a discharge-side pressure sensor for detecting a pressure on a discharge side of the compressor and a pressure on a suction side of the compressor are detected. And a suction side pressure sensor. The mechanism is a four-way selector valve. Then, after performing the pump down operation control, the control unit determines that the difference between the discharge side pressure detected by the discharge side pressure sensor and the suction side pressure detected by the suction side pressure sensor reaches the minimum operating pressure of the four-way switching valve. After that, open the first expansion valve.

In this air conditioner, the first expansion valve is opened after the difference between the discharge-side pressure and the suction-side pressure reaches the minimum operating pressure of the four-way switching valve, so the first expansion until the four-way switching valve switches reliably. The valve does not open. For this reason, it is possible to prevent the refrigerant from flowing backward when the first expansion valve is opened, and it is possible to suppress the refrigerant noise due to the refrigerant backward flow.

[0006] An air conditioner according to a third aspect of the present invention is the air conditioner of the first aspect or the second aspect, further comprising an outdoor fan that generates an air flow through the outdoor heat exchanger. The first operation control is defrost operation control in which the outdoor blower is stopped or driven with a low air volume, and the cooling medium is circulated in the cooling cycle.

In this air conditioner, pump down operation control is performed when switching from defrost operation control, which is an operation by a cooling cycle, to second operation control by a heating cycle. As a result, the defrost operation control force is easily generated when the refrigerant circulation direction is switched, and the refrigerant noise can be suppressed.

[0007] An air conditioner according to a fourth invention is the air conditioner of the first invention or the second invention, and further comprises an oil separator, an oil recovery circuit, and an oil recovery circuit opening / closing part. The oil separator is provided on the discharge side of the compressor and separates oil in the refrigerant. The oil recovery circuit consists of an oil separator and a compressor. Connect the suction side. The oil recovery circuit opening / closing part is provided on the oil recovery circuit and opens and closes the oil recovery circuit. The first operation control is oil recovery operation control in which the oil recovery circuit opening / closing part is opened and the refrigerant is circulated in the cooling cycle.

In this air conditioner, pump down operation control is performed when switching to the second operation control by the oil recovery operation control force heating heating that is the operation by the cooling cycle. Thereby, the oil recovery operation control force It is possible to suppress the refrigerant noise that is likely to occur when the refrigerant circulation direction is switched.

[0008] An air conditioner according to a fifth aspect of the present invention is the air conditioner according to the fourth aspect of the present invention, further comprising a receiver, a degas circuit, and a degas circuit opening / closing section. The receiver 1 is located upstream of the first expansion valve and downstream of the outdoor heat exchanger in the cooling cycle, and can store liquid refrigerant. The degassing circuit is connected from the receiver to the suction side of the compressor, and sends the refrigerant in the gaseous state in the receiver to the suction side of the compressor. The degassing circuit opening / closing part is provided on the degassing circuit and opens and closes the degassing circuit. Then, after the pump down operation control, the control unit performs the refrigerant recovery control for opening the gas vent circuit opening / closing unit, and then opens the first expansion valve and starts the second operation control.

When the pump down operation is performed in the cooling cycle, the refrigerant circuit! If the refrigerant is in an excessive state, the refrigerant is stored between the receiver and the first expansion valve, and the pressure of the refrigerant is likely to be higher than the other parts. For this reason, if the first expansion valve is opened when the second operation control is displayed, the refrigerant may flow backward and a refrigerant noise may be generated. However, with this air conditioner, even if a refrigerant with a relatively high pressure is stored between the receiver and the first expansion valve, the receiver and the first expansion valve are opened by opening the venting circuit. The refrigerant between the valves can be collected in the receiver. For this reason, it is possible to prevent the refrigerant from flowing backward when the first expansion valve is opened, and to suppress the generation of refrigerant noise.

[0009] An air conditioner according to a sixth invention is the air conditioner according to the first invention and the fifth invention, wherein the refrigerant circuit is arranged in parallel with the first expansion valve and the first indoor heat exchanger. It further includes a second indoor heat exchanger and a second expansion valve.

This air conditioner is equipped with a plurality of indoor heat exchangers, so-called multi-type air conditioners. In such a multi-type air conditioner, the refrigerant tends to be excessive. Therefore, an environment in which the liquid refrigerant is likely to stay as soon as the above-mentioned liquid refrigerant stays is obtained. Therefore, the present invention that can suppress refrigerant noise is more effective.

[0010] An air conditioner according to a seventh aspect of the present invention includes a compressor, an outdoor heat exchanger, a first expansion valve, a first indoor heat exchanger, and a cooling cycle and a heating by switching a refrigerant circulation direction. A control method for an air conditioner including a refrigerant circuit including a switching mechanism for switching between cycles, comprising a first operation control execution step, a pump down operation step, and a second operation control start step. In the first operation control execution step, the first operation control by the cooling cycle is executed. In the pump down operation step, after the first operation control execution step, pump down operation control is performed in which the first expansion valve is closed and the compressor is driven in a state where the mechanism is on the cooling cycle side. In the second operation control start step, after the pump down operation step, the first expansion valve is closed and the second operation control by the heating cycle is started.

In this air conditioner control method, pump down operation control is performed when switching from the first operation control by the cooling cycle to the second operation control by the heating cycle. As a result, it is possible to prevent the refrigerant from being collected on the outdoor heat exchanger side and the liquid refrigerant from accumulating on the first indoor heat exchanger side. For this reason, it is possible to suppress refrigerant noise when the first expansion valve is opened.

The invention's effect

[0011] In the air conditioner according to the first invention, when the first operation control by the cooling cycle is switched to the second operation control by the heating cycle, the refrigerant is recovered to the outdoor heat exchange side, and the first indoor heat exchange is performed. It can suppress that a liquid refrigerant accumulates on the side. For this reason, the refrigerant | coolant sound at the time of a 1st expansion valve being opened can be suppressed.

In the air conditioner according to the second aspect of the invention, the first expansion valve is not opened until the four-way switching valve is reliably switched, so that it is possible to prevent the refrigerant from flowing backward when the first expansion valve is opened. .

In the air conditioner according to the third aspect of the invention, the defrosting operation control force is easily generated when the refrigerant circulation direction is switched, and the refrigerant noise can be suppressed.

In the air conditioner according to the fourth aspect of the invention, the refrigerant circulation direction is switched from the oil recovery operation control. It is easy to generate the refrigerant noise when it is obtained.

[0012] In the air conditioner pertaining to the fifth aspect of the invention, even when refrigerant having a relatively high pressure is stored between the receiver and the first expansion valve, the refrigerant when the first expansion valve is opened. Can be prevented from flowing backward, and the generation of refrigerant noise can be suppressed.

The air conditioner pertaining to the sixth aspect of the invention is a multi-type air conditioner, and the present invention that can suppress refrigerant noise is more effective.

In the air conditioner pertaining to the seventh aspect of the invention, when the first operation control based on the cooling cycle is switched to the second operation control based on the heating cycle, the refrigerant is collected on the outdoor heat exchange side and the liquid is transferred to the first indoor heat exchange side. It can suppress that a refrigerant | coolant accumulates. For this reason, the refrigerant | coolant sound at the time of a 1st expansion valve being opened can be suppressed.

Brief Description of Drawings

FIG. 1 is a refrigerant circuit diagram showing a configuration of an air conditioner.

FIG. 2 is a control block diagram of the air conditioner.

FIG. 3 is a diagram showing a control flow at the start of heating operation.

FIG. 4 is a diagram showing a control flow at the time of transition from defrost operation control to normal heating operation control.

FIG. 5 is a diagram showing a control flow at the time of shifting to normal heating operation control. Explanation of symbols

[0014] 3a First indoor heat exchanger

3b Second indoor heat exchanger

5a 1st expansion valve (1st indoor expansion valve)

5b Second expansion valve (second indoor expansion valve)

10 Compressor

11 Switching mechanism

12 Oil separator

13 Hot gas bypass circuit (oil recovery circuit)

14 Outdoor heat exchange

16 receiver

20 Degassing circuit 25 Hot gas bypass circuit switching part (oil recovery circuit switching part)

27 Outdoor blower

30 Degassing circuit opening / closing part

40 Suction pressure sensor

41 Discharge pressure sensor

60 Control unit

100 air conditioner

BEST MODE FOR CARRYING OUT THE INVENTION

[0015] <Configuration>

FIG. 1 shows a refrigerant circuit diagram showing a configuration of an air conditioner 100 that is effective in one embodiment of the present invention. This air conditioner 100 is an air conditioner that heats and cools a house, and a plurality of indoor units 2a-2c are connected to one outdoor unit 1. V, a so-called multi-type air conditioner. It is. The indoor units 2a-2c are connected to the outdoor unit 1 via the branch unit BP1. In this embodiment, a total of three indoor units 2a-2c including the first indoor unit 2a, the second indoor unit 2b, and the third indoor unit 2c are connected to one outdoor unit 1 via the branch unit BP1. ing.

The refrigerant circuit on the outdoor unit 1 side includes the compressor 10, the switching mechanism 11, the oil separator 12, the hot gas bypass circuit 13, the outdoor heat exchanger 14, the outdoor expansion valve 15, the receiver 16, the bridge circuit 17, and the cooler 18 In addition, a supercooling bypass circuit 19, a gas vent circuit 20, a pressure equalizing circuit 21 and the like are included.

[0016] The compressor 10 is an electric motor driven scroll compressor, and is a device for compressing the sucked gas refrigerant. The compressor 10 can variably control the operation frequency by an inverter.

The mechanism 11 is a mechanism that switches the direction of the refrigerant flow when switching between the cooling cycle operation and the heating cycle operation. The gas side of the discharge pipe 22, the suction pipe 23, and the outdoor heat exchanger 14 of the compressor 10 is used. _And a four-way switching valve connected to the gas side of the indoor heat exchanger 3 _& — 3c. The mechanism 11 connects the discharge side of the compressor 10 and the gas side of the outdoor heat exchange 14 and operates the suction of the compressor 10 during operation by the cooling cycle. And the gas shut-off valve 24 are connected (see the solid line of the shelf structure 11 in FIG. 1; this state is hereinafter referred to as “cooling cycle side state”). In addition, the switching mechanism 11 can connect the discharge side of the compressor 10 and the gas shut-off valve 24 and can connect the suction side of the compressor 10 and the gas side of the outdoor heat exchanger 14 during operation by the heating cycle. Yes (Refer to the broken line in Structure 11 in Fig. 1. This state is referred to as the “heating cycle side state”.)

The oil separator 12 is a mechanism for separating the lubricating oil contained in the refrigerant on the discharge side of the compressor 10 and returning it to the suction side of the compressor 10, and is provided in the middle of the discharge pipe 22. Yes.

The hot gas bypass circuit 13 is a circuit that connects the discharge pipe 22 and the suction pipe 23 of the compressor 10, and connects the suction side and the discharge side of the compressor 10. The hot gas bypass circuit 13 has one end connected to the oil separator 12 and the other end connected to the suction pipe 23. Therefore, the hot gas bypass circuit 13 also serves as an oil recovery circuit for returning the refrigerant discharged from the compressor 10 to the suction side and returning the oil separated by the oil separator 12 to the suction side of the compressor 10. Can function. On the hot gas bypass circuit 13, a hot gas bypass circuit opening / closing part 25 (oil recovery circuit opening / closing part) and a firefly 26 for reducing the pressure of the refrigerant passing therethrough are provided. The hot gas bypass circuit opening / closing unit 25 is an electromagnetic valve that opens and closes the hot gas bypass circuit 13, and can close and open the flow of refrigerant flowing through the hot gas bypass circuit 13.

[0018] The outdoor heat exchanger 14 is a cross-fin tube type heat exchanger, and is a device for exchanging heat with a refrigerant using air as a heat source. The outdoor unit 1 includes an outdoor blower 27 that generates an air flow through the outdoor heat exchanger 14 in order to take outdoor air into the outdoor unit 1 and send it out. The outdoor fan 27 exchanges heat between outdoor air and the refrigerant flowing through the outdoor heat exchanger 14 by passing air through the outdoor heat exchanger 14.

The outdoor expansion valve 15 is connected to the liquid side of the outdoor heat exchanger 14 and is positioned between a bridge circuit 17 and an outdoor heat exchanger 14 described later. The outdoor expansion valve 15 is a motor-operated valve that can depressurize the refrigerant passing therethrough, and the flow rate of the refrigerant passing therethrough can be adjusted by controlling the opening degree of the valve.

Receiver 16, the outdoor heat exchange with the indoor heat exchange 3 _a - a container for storing the refrigerant flowing between the 3c temporarily, it is capable of storing a refrigerant in a liquid state. receiver 16 has an inlet at the top of the container and an outlet at the bottom of the container. The inlet of the receiver 16 is connected to the outdoor expansion valve 15 and the liquid closing valve 28 via the bridge circuit 17. The outlet of the receiver 16 is connected to an outdoor expansion valve 15 and a liquid closing valve 28 via a cooler 18 and a bridge circuit 17. The receiver 16 is located between the outdoor heat exchanger ^^ 14 and the indoor heat exchanger 3 _a — 3c, on the opposite side of the compressor 10, and is connected to the indoor expansion valve 5 a — 5 c and the outdoor heat exchanger 14. Located between. The receiver 16 is located upstream of the indoor expansion valves 5a-5c and downstream of the outdoor heat exchanger 14 in the refrigerant flow direction in the cooling cycle.

[0019] The bridge circuit 17 is composed of four check valves 17a_17d connected between the outdoor expansion valve 15 and the receiver 16, and includes an outdoor heat exchange 14 and an indoor heat exchange 3 _& — 3c-3c side force when the refrigerant flowing between 3c flows into the receiver 16 from the outdoor heat exchange side and when flowing into the receiver 16, the inlet of the receiver 16 force also allowed to flow into the refrigerant in the receiver 16, and the outlet force is also the outdoor heat exchange with the indoor heat exchange 3 _a receiver 16 - has the function of returning the refrigerant between 3c. Specifically, the check valve 17a is connected to guide the refrigerant flowing from the indoor heat exchangers 3a-3c toward the outdoor heat exchanger 14 to the inlet of the receiver 16. The check valve 17b is connected to guide the refrigerant flowing from the outdoor heat exchanger 14 toward the indoor heat exchanger 3a-3c to the inlet of the receiver 16. Check valve 17c is connected to the outlet of receiver 16.

It is connected. The check valve 17d is connected so that the outlet force of the receiver 16 can also flow the refrigerant flowing through the cooler 18 to the outdoor heat exchange side. As a result, the refrigerant flowing between the outdoor heat exchanger ^^ 14 and the indoor heat exchanger 3 _a -3c always flows in the inlet force of the receiver 16 and also flows out of the outlet force of the receiver 16 ^^ 14 And indoor heat exchange

[0020] The cooler 18 is a double-pipe heat exchanger and is provided to cool the refrigerant condensed in the outdoor heat exchanger 14 and sent to the indoor heat exchanger-3c. The cooler 18 is connected between the receiver 16 and the bridge circuit 17.

Subcooling Bruno Ipasu circuit 19 from the outdoor heat exchange indoor heat exchange 3 _a - is sent to 3c A part of the refrigerant is branched and returned to the suction side of the compressor 10. Specifically, the supercooling bypass circuit 19 is branched from the circuit portion connecting the outlet of the receiver 16 and the check valve 17d of the bridge circuit 17 and passes through the cooler 18 to the suction pipe 23 of the compressor 10. Connected to join. The supercooling bypass circuit 19 is provided with a supercooling bypass expansion valve 29 for adjusting the flow rate of the refrigerant flowing through the supercooling bypass circuit 19. The supercooling bypass expansion valve 29 is an electric valve for adjusting the flow rate of the refrigerant flowing through the cooler 18. As a result, the refrigerant flowing through the refrigerant circuit 10 is cooled in the cooler 18 by the refrigerant returned to the suction pipe 23 of the compressor 10 by the outlet force of the expansion valve 29 for the supercooling no-pass! /, The

The degassing circuit 20 has one end connected to the upper end of the receiver 16 and the other end connected to the supercooling bypass circuit 19 and joined to the suction pipe 23 of the compressor 10. The degassing circuit 20 is a circuit for sending the gaseous refrigerant in the receiver 16 to the suction side of the compressor 10. Further, a degas circuit opening / closing section 30 is provided on the degas circuit 20. The degassing circuit opening / closing unit 30 is an electromagnetic valve that opens and closes the degassing circuit 20 and can close and open the flow of refrigerant flowing through the degassing circuit 20.

One end of the pressure equalizing circuit 21 is connected between the degassing circuit opening / closing portion 30 and the receiver 16 in the degassing circuit 20, and the other end is connected to the discharge pipe 22. In addition, the pressure equalizing circuit 21 is provided with a pressure equalizing check valve 31 that allows only one refrigerant to flow toward the other end. This pressure equalization circuit 21 prevents the receiver 16 from bursting by allowing the gas refrigerant to escape if the outside air temperature rises abnormally while the air conditioner 100 is stopped and the pressure in the receiver 16 becomes too high. Is.

The plurality of indoor units 2a-2c are arranged on the indoor wall and the ceiling, respectively, and blow out conditioned air into the room. The indoor units 2a-2c may be arranged in different rooms or at different positions in the same room. Each of the indoor units 2a-2c can be independently thermo-on / off and start / stop operation, and the operation state can be switched for each of the indoor units 2a-2c. The plurality of indoor units 2a-2c are connected to the outdoor unit 1 via the branch unit BP1, and the refrigerant sent from the outdoor unit 1 branches. It is branched at unit BP1 and sent to the indoor heat exchangers ^^ 3a-3c. In addition, the refrigerant that has flowed through each of the indoor heat exchangers 3a to 3c merges again in the branch unit BP1, and is sent to the outdoor unit 1.

[0023] The first indoor unit 2a includes a first indoor heat exchange 3 _& and a first indoor blower 4a. In the first indoor heat exchange, heat is exchanged between the refrigerant flowing inside and the air. The first indoor fan 4a generates a flow of air blown from the first indoor unit 2a, and sends the air that has exchanged heat with the refrigerant flowing through the first indoor heat exchanger 3a to the room.

The second indoor unit 2b includes a second indoor heat exchanger 3b and a second indoor blower 4b. In the second indoor heat exchange, heat is exchanged between the refrigerant flowing inside and the air. The second indoor fan 4b generates an air flow that also blows the internal force of the second indoor unit 2b, and sends the air that has exchanged heat with the refrigerant flowing through the second indoor heat exchanger 3b to the room.

The third indoor unit 2c includes a third indoor heat exchanger 3c and a third indoor fan 4c. The third indoor heat exchange exchanges heat between the refrigerant flowing inside and the air. The third indoor fan 4c generates a flow of air blown out from the third indoor unit 2c, and sends the air that has exchanged heat with the refrigerant flowing through the third indoor heat exchanger 3c to the room.

[0024] The first indoor heat exchanger 3a, the second indoor heat exchanger 3b, and the third indoor heat exchanger 3c are provided in parallel with the refrigerant circuit, and are connected to the branch unit BP1. .

The branch unit BP1 branches the refrigerant sent from one outdoor unit 1 and distributes it to the plurality of indoor units 2a 2c, and also merges the refrigerant sent from the plurality of indoor units 2a-2c into one outdoor unit. Unit to send to 1. In this air conditioner 100, three indoor units 2a-2c are connected to one branch unit BP1! However, even if more indoor units or fewer indoor units are connected to one branch unit BP1 Good. Also, multiple branch units may be connected to one outdoor unit 1.

The branch unit BP1 has a liquid branch pipe 32 branched into three and a gas branch pipe 33 branched into three. The liquid branch pipe 32 is connected to the liquid shut-off valve 28 of the outdoor unit 1 and the first indoor heat exchange 3 _&

The In addition, the gas branch pipe 33 includes the gas shut-off valve 24 of the outdoor unit 1, the first indoor heat exchanger 3a, and the second indoor heat exchanger 3 It is connected to b and the gas side of the third indoor heat exchanger. Between the branch point of the liquid branch pipe 32 and each indoor heat exchanger 3a-3c, the first indoor expansion valve 5a (first indoor expansion valve), the second indoor expansion valve 5b (second indoor expansion valve) and A third indoor expansion valve 5c is provided, and the indoor expansion valves 5a-5c are provided in parallel in the refrigerant circuit. Therefore, a refrigerant circuit on the first indoor unit 2a side composed of the first indoor heat exchanger 3a and the first indoor expansion valve 5a, and a second room composed of the second indoor heat exchanger 3b and the second indoor expansion valve 5b. The refrigerant circuit on the side of the unit 2b and the refrigerant circuit on the side of the third indoor unit 2c consisting of the third indoor heat exchanger 3c and the third indoor expansion valve 5c are connected in parallel to each other via the branch unit BP1. Connected to the refrigerant circuit. The first indoor expansion valve 5a, the second indoor expansion valve 5b, and the third indoor expansion valve 5c are motor-operated valves that can depressurize the refrigerant that passes through them, respectively. The amount can be controlled. The first indoor expansion valve 5a, the second indoor expansion valve 5b, and the third indoor expansion valve 5c can be independently controlled.

[0025] Note that an electric valve 6 for pressure adjustment is provided between the liquid branch pipe 32 and the first gas-liquid branch pipe.

The air conditioner 100 includes various sensors 40-51 such as a pressure sensor and a temperature sensor provided in each part. Hereinafter, various sensors 40-51 will be described with reference to FIG. The suction pipe 23 of the compressor 10 is provided with a suction side pressure sensor 40 for detecting the pressure of the low-pressure gas refrigerant flowing on the suction side of the compressor 10 (hereinafter referred to as “suction side pressure Pe”). ing. The discharge pipe 22 of the compressor 10 is provided with a discharge side pressure sensor 41 for detecting the pressure of the high-pressure gas refrigerant flowing on the discharge side of the compressor 10 (hereinafter referred to as “discharge side pressure Pc”). It has been. Further, the discharge pipe 22 of the compressor 10 is provided with a high-pressure switch 42 for detecting an excessive increase in the pressure of the high-pressure gas refrigerant. The discharge pipe 22 of the compressor 10 is provided with a discharge temperature sensor 43 for detecting the discharge temperature Td of the refrigerant on the discharge side of the compressor 10, and the suction pipe 23 of the compressor 10 is provided with the compressor 10 An intake temperature sensor 44 is provided for detecting the intake temperature Ts of the refrigerant on the intake side.

[0026] In addition, an outdoor air temperature sensor 45 for detecting the temperature Ta of the outdoor air is provided at the air inlet of the outdoor fan 27 of the outdoor unit 1. The outdoor heat exchanger 14 is used for cooling operation. Is provided with an outdoor heat exchange temperature sensor 46 for detecting a refrigerant temperature Tb corresponding to the refrigerant condensation temperature and corresponding to the refrigerant evaporation temperature during heating operation.

Further, at the junction of the supercooling bypass circuit 19 with the suction side of the compressor 10, the temperature Tsh of the refrigerant flowing through the supercooling bypass circuit 19 on the outlet side of the cooler 18 is detected to detect the degree of superheat. A supercooling no-pass circuit temperature sensor 47 is provided. The supercooling bypass circuit temperature sensor 47 can detect the degree of superheat on the suction side of the compressor 10. The air blower of the indoor unit 2a-2c indoor fan 4a-4c has the indoor air temperature Tr Each room temperature sensor 48 is provided for detection. The indoor temperature sensor 48 can detect the temperature of the room subject to air conditioning by the indoor units 2a-2c. Each of the indoor heat exchangers 3a to 3c is provided with an indoor heat exchanger temperature sensor 49 for detecting a refrigerant temperature Tn corresponding to the evaporation temperature during the cooling operation and corresponding to the condensation temperature during the heating operation. Speak.

[0027] Each branch of the gas branch pipe 33 in the branch unit BP1 is provided with a gas pipe temperature sensor 50 for detecting the temperature of the refrigerant passing through the inside. Gas pipe temperature sensor 50, the chamber expansion valve 5a-5c and the indoor heat exchange 3 _a - is provided between the 3c. Each branch of the liquid branch pipe 32 is provided with a liquid pipe temperature sensor 51 for detecting the temperature of the refrigerant passing through the inside. The liquid pipe temperature sensor 51 is provided between the indoor heat exchangers 3a-3c and the branch point of the liquid branch pipe.

In addition, for the various sensors 48-51 provided in each indoor unit 2a-2c and branch unit BP1, sensors having the same function are denoted by the same reference numerals for simplicity.

As shown in FIG. 2, the air conditioner 100 controls each device such as the compressor 10 and the switching mechanism 11 based on the signals detected by the various sensors 40-51, and performs cooling operation and heating. A control unit 60 for performing air conditioning operation such as operation is provided.

[0028] The control unit 60 mainly includes a microcomputer and a memory, and is connected so that it can receive input signals of the various sensors 40-51 described above, as well as commands input to the operation terminal 61. Can receive a signal. The control unit 60 receives these input signals and commands. Various devices 4a-4c, 10, 11, 27, valves 5a-5c, 15, 29, and various opening / closing sections 25, 30 are connected so as to be controlled based on the signal. The control unit 60 controls the various devices 4a-4c, 10, 11, 27, the valves 5a-5c, 15, 29, and the various opening / closing units 25, 30 to perform air conditioning operations such as cooling operation and heating operation. It can be carried out. In FIG. 2, a plurality of components such as valves 5a-5c, various opening / closing sections 25, 30, indoor blowers 4a-4c, and indoor expansion valves 5a-5c are displayed together in one block. However, each component can be controlled individually.

Hereinafter, various controls performed by the control unit 60 will be described.

The control unit 60 can switch between the operation by the cooling cycle and the operation by the heating cycle. The cooling cycle operation includes cooling operation, defrost operation, and oil recovery operation. There is a heating operation as an operation by the heating cycle.

In the state where the air conditioner 100 is stopped, the Kiriura structure 11 maintains the previous operation state! /. For example, if the operation by the cooling cycle was performed during the previous operation, the state is the cooling cycle side state. The compressor 10, the outdoor blower 27, and the indoor blowers 4a-4c are stopped, and the outdoor expansion valve 15, the indoor expansion valves 5a-5c, and the supercooling bypass expansion valve 29 are fully closed. Further, the hot gas bypass circuit opening / closing section 25 and the gas vent circuit opening / closing section 30 are closed. When the start of the heating operation is instructed from the operation terminal 61 or the like in such a stopped state of the air conditioner 100, first, as shown in FIG. 3, after the refrigerant recovery control is started in the first step S1, 2Normal heating operation control is started in step S2. In addition, when the normal heating operation control is performed and the air conditioner 100 stops, the pump down operation control is performed in the third step S3, and then the air conditioner 100 stops the operation.

[0030] (Refrigerant recovery control)

Refrigerant recovery control is performed at the start of activation of the heating operation. In the refrigerant recovery control, the gas vent circuit opening / closing part 30 is opened with the indoor expansion valves 5a-5c closed. As a result, the gas refrigerant in the receiver 16 is sent to the suction side of the compressor 10 through the gas vent circuit 20. The liquid refrigerant staying between the receiver 16 and the indoor expansion valves 5a-5c is recovered by the receiver 16. The degassing circuit opening / closing part 30 is closed when the time T1 has elapsed since being opened, and when the condition of Tsh-Teg is satisfied. Teg is the saturated gas temperature corresponding to the pressure of the suction side gas refrigerant, and a is a predetermined constant. That is, when the degree of superheat of the refrigerant sent from the gas vent circuit 20 to the suction side of the compressor 10 becomes smaller than a predetermined value, the gas vent circuit opening / closing part 30 is closed.

At the start of heating operation start, refrigerant recovery control is performed, and an ON signal is input to the mechanism 11 so that the switching mechanism 11 is switched to the heating cycle side state. Further, the compressor 10 starts to be driven at a low frequency, for example, the lowest operating frequency, and the outdoor blower 27 is driven at a predetermined number of rotations. At this time, the outdoor expansion valve 15, the subcooling bypass expansion valve 29, and the indoor expansion valves 5a to 5c are in a fully closed state.

The compressor 10 is controlled so that the frequency increases stepwise after startup, and the outdoor expansion valve 15 is opened to a predetermined opening.

(Normal heating operation control)

After the start control of the heating operation is performed as described above, when the normal heating operation start condition is satisfied, the indoor expansion valves 5a-5c of the indoor units 2a-2c to which the thermo-on command is issued are opened at a predetermined opening degree. As a result, the normal heating operation control is started. Note that the normal heating operation start condition is a condition that allows the switching mechanism 11 to be considered to have reliably switched from the cooling cycle side state to the heating cycle side state, and the start control of the heating operation is started. This is the case when either the force time T2 has passed or the condition Pc—Pe> b is satisfied. Where b is the minimum operating pressure of mechanism 11. In other words, even if the ON signal is input, the switching mechanism 11 does not immediately switch due to the effect of the high / low pressure differential pressure, so the switching mechanism when the high / low pressure differential pressure exceeds the minimum operating pressure of the switching mechanism 11 Assuming that 11 has changed, the indoor expansion valves 5a to 5c are opened. Therefore, in the normal heating operation control, the switching mechanism 11 is switched to the state indicated by the wavy line in FIG. The hot gas bypass circuit opening / closing part 25 is closed, and the supercooling bypass expansion valve 29 is fully closed. In addition, the outdoor expansion valve 15, the outdoor blower 27, the indoor expansion valve 5a-5c of the indoor unit 2a-2c in operation, and the indoor blower 4a-4c are used for operating conditions of the indoor unit 2a-2c. Is controlled accordingly. In this state, the refrigerant circulates through the refrigerant circuit, so that the indoor heat exchangers 3a-3c of the indoor units 2a-2c in the operating state function as a condenser and the outdoor heat exchanger 14 functions as an evaporator. As a result, the heated air is blown into the room, and the normal heating operation is performed.

[0032] In the operation by the heating cycle including the normal heating operation as described above, the refrigerant circulates in the refrigerant circuit as follows. Note that. Here, it is assumed that the first indoor unit 2a is in the thermo-on state, and the second indoor unit 2b and the third indoor unit 2c are in the thermo-off state or the operation stopped state.

First, the refrigerant discharged from the compressor 10 is sent from the mechanism 11 to the first indoor heat exchanger 3a through the gas shut-off valve 24 and the branch unit BP1. In the first indoor heat exchanger 3a, the refrigerant dissipates heat to the room air and condenses. The refrigerant condensed in the first indoor heat exchanger 3a flows into the receiver 16 through the first indoor expansion valve 5a, the liquid closing valve 28, and the bridge circuit 17. The refrigerant flowing out from the receiver 16 is decompressed by the outdoor expansion valve 15 and sent to the outdoor heat exchanger 14 through the bridge circuit 17. In the outdoor heat exchanger 14, the refrigerant absorbs heat from the outdoor air and evaporates. The refrigerant evaporated in the outdoor heat exchanger 14 is sucked into the compressor 10 through the switching mechanism 11. The compressor 10 compresses the sucked refrigerant and discharges it again.

[0033] In the second indoor unit 2b and the third indoor unit 2c that are stopped among the indoor units 2a-2c, the corresponding second indoor expansion valve 5b and third indoor expansion valve 5c have a slight opening degree. Open and restricted inflow of refrigerant.

The control unit 60 controls the frequency of the compressor 10, the opening degree of the outdoor expansion valve 15, and the like according to the change in the operating state of each indoor unit 2a-2c.

(Pump down operation control)

When the normal heating operation is stopped, the indoor fans 4a-4c are stopped, the indoor expansion valves 5a-5c are fully closed, and the operations of the indoor units 2a-2c are stopped. Then, after the operation of the indoor units 2a-2c is stopped, the pump-down operation control for recovering the refrigerant to the high pressure side is performed in order to prevent the liquid back at the next start-up.

[0034] In the pump down operation control, the compressor 10 is driven while the switching mechanism 11 is in the cooling cycle side state and the indoor expansion valves 5a-5c are fully closed. The outdoor expansion valve 15 The supercooling bypass expansion valve 29 is fully closed and the hot gas bypass circuit opening / closing part 25 is closed. The outdoor blower 27 is stopped or driven at a predetermined rotational speed. Thereafter, the compressor 10 and the outdoor blower 27 are stopped, the outdoor expansion valve 15 is fully closed, and the operation of the outdoor unit 1 is stopped.

(Defrost operation control)

When the outdoor temperature is low, such as in winter, the outdoor heat exchanger 14 of the outdoor unit 1 may freeze. In this case, the outdoor heat exchanger 14 can be defrosted by performing a defrost operation (first operation control) according to the refrigerant operation.

In this air conditioner 100, as shown in FIG. 4, after defrost operation control is performed in the eleventh step S11 (first operation control execution step), the twelfth step S12 (pump down) is performed. In the operation step), pump down operation control is performed. Next, refrigerant recovery control is performed in the thirteenth step S13, and then normal heating operation control (second operation control) is performed in the fourteenth step S14 (second operation control start step). In other words, after the differential opening operation control is performed, the pump down operation control is performed before switching to the normal heating operation control. Further, after the pump down operation control is performed, the refrigerant recovery control is performed before switching to the normal heating operation.

In the defrost operation control, the compressor 11 is driven in a state where the switch 11 is switched to the cooling cycle side state and the outdoor blower 27 and the indoor blowers 4a-4c are stopped. At this time, the outdoor expansion valve 15 is opened at a predetermined opening, and the supercooling bypass expansion valve 29 is fully closed. The hot gas bypass circuit opening / closing section 25 is opened, and the indoor expansion valves 5a-5c of the indoor units 2a-2c in the operating state are opened to a predetermined opening. The degassing circuit opening / closing part 30 is also opened after a predetermined time T4 has elapsed, and then closed again.

[0036] Such defrost operation control is performed under the condition that either the defrost operation control start force predetermined time T5 has passed, Tb> c is satisfied, or Pc> d is satisfied. Is finished, and then pump down operation control is performed. Here, c and d are predetermined constants and are determined so that the defrosting is sufficiently performed in the outdoor heat exchanger 14. Following the completion of defrost operation control, pump down operation control is performed. In the pump down operation control, the compressor 10 is driven while the switching mechanism 11 is in the cooling cycle side state and the indoor expansion valves 5a-5c are closed. Further, the hot gas no-pass circuit opening / closing part 25 is closed. The pump-down operation control is performed when the pump-down operation start time T3 has elapsed, Pe <e is satisfied, Td> f is satisfied, or Pc> g is satisfied. The process is terminated when the condition is satisfied, and then the refrigerant recovery control is performed. Note that e, f, and g are predetermined constants. When the refrigerant recovery control is completed, the normal heating operation control is started. The refrigerant recovery control and the normal heating operation control are the same controls as described above, but different conditions are used for the judgment at the end of each power control.

[0037] (Oil recovery operation control)

In the air conditioner 100, when a predetermined condition is satisfied during normal heating operation control, oil recovery operation control (first operation control) is performed, and the oil content in the refrigerant is collected in the compressor 10. can do. In this case, as shown in FIG. 5, first, oil recovery operation control is performed in the 21st step S21 (first operation control execution step), and then pump down operation is performed in the 22nd step S22 (pump down operation step). Control is performed. Thereafter, refrigerant recovery control is performed in the 23rd step S23, and then normal heating operation control (second operation control) is performed in the 24th step S24 (second operation control start step). In other words, when switching to oil recovery operation control force normal heating operation control, normal heating operation control is performed after pump down operation control is performed. Further, after the pump down operation control is performed, the refrigerant recovery control is performed before the normal heating operation control is performed.

[0038] In the oil recovery operation control, the mechanism 11 is switched to the cooling cycle side state, the outdoor fan 27 is driven at a predetermined rotational speed, and the compressor 10 is driven with the indoor fans 4a-4c stopped. The At this time, the outdoor expansion valve 15 is opened at a predetermined opening, and the subcooling bypass expansion valve 29 is fully closed. The hot gas bypass circuit opening / closing section 25 is opened, and the indoor expansion valves 5a-5c of the indoor units 2a-2c in the operating state are opened to a predetermined opening. The degassing circuit opening / closing part 30 is also opened after a predetermined time has elapsed and then closed again. Such oil recovery operation control is continued until either a predetermined time elapses when the oil recovery operation control start force is satisfied or Th-Teg <h is satisfied, and then Pump down operation control is performed. Note that h is a predetermined constant and is determined so that oil recovery can be performed sufficiently.

[0039] Following the oil recovery operation control, pump down operation control is performed. In the pump down operation control, the compressor 10 is driven while the mechanism 11 is in the cooling cycle side state and the indoor expansion valves 5a-5c are closed. Further, the hot gas bypass circuit opening / closing part 25 is closed. The pump down operation control is performed when the pump down operation is started and the force has exceeded the specified time T3, when Pe e is satisfied, when Td> f is satisfied, or when Pc> g is satisfied. Is finished, and then refrigerant recovery control is performed. When the refrigerant recovery control is finished, the normal heating operation control is started. The pump-down operation control, the refrigerant recovery control, and the normal heating operation control may be different conditions with respect to the determination of the end of each power control, which is the same control as described above.

(1)

In the air conditioner 100, after the operation of the indoor units 2a-2c is stopped, a pump-down operation for recovering the refrigerant to the high pressure side is performed in order to prevent generation of a liquid back at the next start-up. If the pump-down operation is performed when the indoor units 2a-2c are stopped, a refrigerant with a relatively high pressure may remain between the receiver 16 and the indoor expansion valves 5a-5c in a situation where the refrigerant is excessive. When the heating operation is restarted, the indoor expansion valve 5a-5c is opened with a predetermined opening, so that the refrigerant is accumulated as described above, and if the indoor expansion valve 5a-5c is opened with the refrigerant accumulated, the receiver 16 and the indoor High-pressure refrigerant between the expansion valves 5a-5c may flow backward to the indoor units 2a-2c, generating refrigerant noise. In particular, air conditioners used for homes may be uncomfortable for residents.

[0040] However, in the air conditioner 100, the refrigerant recovery control for opening the indoor expansion valves 5a-5c when starting the heating operation and recovering the refrigerant remaining between the receiver 16 and the indoor expansion valves 5a-5c to the receiver 16 After that, the indoor expansion valves 5a-5c are opened and the normal heating operation is started. Therefore, when the indoor expansion valves 5a-5c are opened, the refrigerant flows backward. It is possible to suppress the occurrence of refrigerant noise.

Further, in the air conditioner 100, in the refrigerant recovery control, when the difference between the discharge side pressure Pc and the suction side pressure Pe exceeds the minimum operating pressure of the switching mechanism 11, or when the refrigerant recovery control is started and the force is sufficient. When a long time elapses, the operation shifts to normal heating operation. For this reason, the indoor expansion valves 5a to 5c are not opened until the mechanism 11 is reliably switched to the cooling cycle side power heating cycle side. For this reason, the reverse flow of the refrigerant can be suppressed more reliably, and the generation of refrigerant noise can be suppressed.

[0041] Further, since the back flow of the refrigerant can be suppressed when the heating operation is started, it is possible to improve the start-up performance when the heating operation is started.

(2)

In the air conditioner 100, the defrost operation and the oil recovery operation during heating are performed by circulating the refrigerant in the cooling cycle. When such a defrosting operation or an oil recovery operation during heating is performed, the pressure on the receiver 16 side becomes high. Therefore, when the heating operation is restarted in this state, the indoor expansion valves 5a-5c are opened. As a result, the refrigerant flows back to the suction side and the amount of refrigerant on the suction side tends to increase. Alternatively, in the defrosting operation and the oil recovery operation during heating, the refrigerant circulates in the cooling cycle, so the temperature on the indoor unit 2a-2c side decreases, and the ratio of liquid refrigerant on the indoor unit 2a-2c side increases. . Therefore, when the mechanism 11 is switched to the cooling cycle side state force heating cycle side state in the above state, the inlets of the indoor expansion valves 5a-5c are liquid-sealed, and if a differential pressure exceeding a certain pressure is applied, There is a risk that the sound from the air will propagate to the indoor units 2a-2c in the liquid. In this case, the air conditioner used for residential use may be uncomfortable for residents.

However, in this air conditioner 100, the pump down operation control is performed after completion of the defrost operation control and the oil recovery operation control during heating, and the refrigerant in the refrigerant circuit is recovered by the receiver 16. For this reason, the amount of refrigerant on the suction side at the time of startup is reduced, and the generation of refrigerant noise can be suppressed.

Also, in this air conditioner 100, when the pump down operation control is performed after the defrost operation control and the oil recovery operation control during heating are performed, the refrigerant recovery control is performed before the transition to the normal heating operation control. Is called. Therefore, mechanism 11 is The indoor expansion valves 5a-5c are not opened until the switching to the heating cycle side is ensured, and the refrigerant backflow can be more reliably suppressed. Thereby, generation | occurrence | production of a refrigerant | coolant sound can be suppressed. Furthermore, since the amount of low-temperature liquid refrigerant is reduced, the refrigerant temperature can be increased more quickly when the heating operation is started.

[0043] (3)

In this air conditioner 100, it is possible to temporarily store the refrigerant in the receiver 16, and it is easy to occur when the refrigerant is excessive as described above, and the generation of refrigerant noise can be suppressed. For this reason, an accumulator generally used for storing the refrigerant can be omitted. Therefore, the manufacturing cost can be reduced by reducing the number of parts.

(1)

The number of indoor units 2a-2c connected to one outdoor unit 1 is not limited to the above, but one or more indoor units may be connected. However, the problem of refrigerant noise is that the refrigerant is excessive in the refrigerant circuit. Therefore, the present invention is particularly effective for a multi-type air conditioner including a plurality of indoor units 2a-2c as described above. .

[0044] (2)

In the above embodiment, the refrigerant circuit is provided with the supercooling bypass circuit 19, the pressure equalization circuit 21, and the hot gas binos circuit 13, but this is not always necessary from the viewpoint of performing the above control to suppress the refrigerant noise. It is not a thing.

Further, the indoor units 2a-2c each including the indoor expansion valves 5a-5c without the branch unit BP1 may be directly connected to the outdoor unit 1.

Further, the outlet of the gas vent circuit 20 may be connected to the suction pipe 23 of the compressor 10 instead of being connected to the supercooling bypass circuit 19.

(3)

In the above embodiment, the condition for shifting from the refrigerant recovery control to the normal heating operation control is determined by the minimum operating pressure b of the mechanism 11, but the mechanism 11 is changed from the cooling cycle side state to the heating cycle side state. Even if the conditions can be considered to have switched reliably For example, it may be determined based on a pressure value other than the minimum operating pressure b of the Kiriura structure 11. For example, a pressure value above the minimum operating pressure b of the switching mechanism 11 may be considered.

[0045] (4)

From the viewpoint of collecting the refrigerant that has accumulated between the receiver 16 and the indoor expansion valves 5a to 5c in the receiver 16 by the pump-down operation control, the refrigerant recovery control described above is performed after the pump-down operation control is performed. Although it may be performed only at the start of operation, it may always be performed at the start of heating operation.

(Five)

In the above-described embodiment, the pump down operation is performed at the time of transition from the defrost operation control to the normal heating operation control and at the time of transition to the oil recovery operation control force normal heating operation control. From the standpoint of reducing the occurrence of heat generation, it may be performed at the time of transition to operating power normal heating operation control by a cooling cycle other than defrost operation control and oil recovery operation. Further, the pump-down operation may be performed at the time of shifting to the operation by the heating cycle other than the normal heating operation control.

[0046] (6)

In the above defrost operation control, the outdoor blower 27 and the indoor blowers 4a to 4c do not stop completely, but operate with a low air flow!

(7)

Regarding the above defrost operation control, the normal heating operation control, the defrost operation control, the pump down operation control, the refrigerant recovery control, and the normal heating operation control may be sequentially performed in order.

Similarly for the oil recovery operation control described above, the normal heating operation control, the oil recovery operation control, the pump down operation control, the refrigerant recovery control, and the normal heating operation control may be performed successively in this order.

Industrial applicability

[0047] The present invention is effective as an air conditioner because it has the effect of suppressing refrigerant noise when switching from operation by a cooling cycle to operation by a heating cycle.

Claims

The scope of the claims

[1] An air conditioner (100) including a refrigerant circuit including a compressor (10), an outdoor heat exchanger (14), a first expansion valve (5a), and a first indoor heat exchanger (3a),

A switch (11) that switches between the cooling cycle and the heating cycle by switching the refrigerant circulation direction;

When the first operation control force by the cooling cycle is switched to the second operation control by the heating cycle, the first expansion valve (5a) is closed and the switching mechanism (11) is in the state on the cooling cycle side. A control unit (60) that opens the first expansion valve (5a) after the pump down operation control for driving the compressor (10) and starts the second operation control, and an air conditioner (100 ).

[2] A discharge-side pressure sensor (41) for detecting a pressure on the discharge side of the compressor (10),

A suction side pressure sensor (40) for detecting the pressure on the suction side of the compressor (10), and

The switching mechanism (11) is a four-way switching valve,

The control unit (60), after performing the pump down operation control, difference between the discharge side pressure detected by the discharge side pressure sensor (41) and the suction side pressure detected by the suction side pressure sensor (40). Opens the first expansion valve (5a) after reaching the minimum operating pressure of the four-way selector valve

The air conditioner (100) according to claim 1.

[3] The outdoor fan (27) that generates an air flow passing through the outdoor heat exchanger (14) is further provided, and the first operation control stops the outdoor fan (27) or drives it with a low air volume, and The air conditioner (100) according to claim 1 or 2, wherein the air conditioner (100) is defrost operation control for circulating the refrigerant in the cooling cycle.

[4] An oil separator (12) provided on the discharge side of the compressor (10) for separating oil in the refrigerant;

An oil recovery circuit (13) connecting the oil separator (12) and the suction side of the compressor (10), and provided on the oil recovery circuit (13) to open and close the oil recovery circuit (13) Oil recovery circuit opening and closing part (25), Further comprising

The first operation control is oil recovery operation control in which the oil recovery circuit opening / closing part (25) is opened and the refrigerant is circulated in the cooling unit.

The air conditioner (100) according to claim 1 or 2.

[5] A receiver (16) located upstream of the first expansion valve (5a) in the cooling cycle and downstream of the outdoor heat exchanger (14) and capable of storing the liquid refrigerant. And a gas vent circuit (20) connected from the receiver (16) to the suction side of the compressor (10) and sending the refrigerant in the gas state in the receiver (16) to the suction side of the compressor (10). )When,

A degassing circuit opening / closing section (30) provided on the degassing circuit (20) for opening and closing the degassing circuit (20);

Further comprising

After the pump down operation control, the control unit (60) performs refrigerant recovery control for opening the gas vent circuit opening / closing unit (30), and then opens the first expansion valve (5a) to perform the second operation control. To start the

The air conditioner (100) according to any one of claims 1 to 4.

[6] The refrigerant circuit includes a second indoor heat exchanger (3b) and a second expansion valve (5b) arranged in parallel with the first expansion valve (5a) and the first indoor heat exchanger (3a). The air conditioner (100) according to any one of claims 1 to 5, further comprising:

[7] Compressor (10), outdoor heat exchanger (14), first expansion valve (5a), first indoor heat exchanger (3a), cooling cycle and heating by switching refrigerant circulation direction A control method of an air conditioner (100) including a refrigerant circuit including a mechanism (11) for switching between cycles, wherein a first operation control execution step (S1) in which the first operation control by the cooling cycle is executed

1, S21)

After the first operation control execution step (Sll, S21), the first expansion valve (5a) is closed, and the switching mechanism (11) drives the compressor (10) in a state of the cooling cycle side. Pump down operation step (S 12, S22) in which pump down operation control is performed, A second operation control start step (S14, S24) in which, after the pump down operation step (SI 2, S22), the first expansion valve (5a) is closed and the second operation control by the heating cycle is started;

A method for controlling an air conditioner (100) comprising: