Air conditioner

Abstract

This air conditioning device comprises a heat source machine including a compressor, a flow passage switching valve, and a heat source side heat exchanger, one or more indoor units which include a load side flow rate adjusting valve and a load side heat exchanger, and which carry out a space cooling operation or a space heating operation, and a relay unit which is connected to the heat source machine by means of a gas main pipe through which a gas refrigerant flows when the space cooling operation and the space heating operation are carried out, and a liquid main pipe through which a liquid refrigerant or a gas-liquid two-phase refrigerant flows when the space cooling operation and the space heating operation are carried out, the relay unit being connected to each of the one or more indoor units by means of a gas branch pipe and a liquid branch pipe, and supplying a refrigerant supplied from the heat source machine to the one or more indoor machines, wherein: the relay unit comprises a gas-liquid separator for separating the refrigerant into the gas refrigerant and the liquid refrigerant, and one or more flow passage opening and closing devices for respectively opening and closing a refrigerant flow passage from the heat source machine toward the one or more indoor units and a refrigerant flow passage from the one or more indoor units toward the heat source machine; and the relay unit includes a refrigerant route through which, when the space heating operation is being carried out, the refrigerant flowing from the heat source machine through the gas main pipe into the relay unit flows into the one or more flow passage opening and closing devices without passing through the gas-liquid separator.

Description

Technical Field

[0001] The present disclosure relates to an air conditioner having a relay unit that supplies refrigerant supplied from a heat source unit to an indoor unit.

Background Art

[0002] Conventionally, in air conditioners such as multi-split air conditioners for buildings, for example, an outdoor unit which is a heat source unit disposed outside the building and an indoor unit disposed inside the building are connected by piping to form a refrigerant circuit, and refrigerant is circulated through the refrigerant circuit. Then, by heating or cooling air using heat radiation and heat absorption of the refrigerant, heating or cooling of the air-conditioned space is performed.

[0003] In such an air conditioner, in order to reduce the amount of refrigerant in the piping connecting the outdoor unit and the relay unit or the indoor unit, there is one that adopts a liquid-gas pipe method for the two pipes connecting the outdoor unit and the relay unit or the indoor unit. The liquid-gas pipe method is a method in which, regardless of the operation status of cooling or heating, the refrigerant flowing through one of the two pipes connecting the outdoor unit and the relay unit or the indoor unit is in a gaseous state, and the refrigerant flowing through the other is in a liquid state or a gas-liquid two-phase state.

[0004] As such an air conditioner using the liquid-gas pipe method, in Patent Document 1, an air conditioner having a gas-liquid separation unit including a gas-liquid separator and a refrigerant flow path switching circuit for switching the flow of liquid refrigerant and gas refrigerant is proposed. This gas-liquid separation unit is connected to the outdoor unit by two refrigerant pipes. The air conditioner of Patent Document 1 is capable of performing cooling operation and heating operation. When the heating operation is performed, the high-pressure gas refrigerant discharged from the compressor has a circuit configuration such that it flows to the indoor unit after passing through the refrigerant flow path switching circuit and the gas-liquid separator.

Prior Art Documents

Patent Documents

[0005]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0006] In the circuit configuration of Patent Document 1, when the heating operation is performed, the refrigerant passes through the gas-liquid separator in addition to the refrigerant flow path switching circuit, so that a pressure loss occurs in the refrigerant in the gas-liquid separator. When a pressure loss occurs in the refrigerant, the capacity of the air conditioner decreases. Therefore, in order to increase the capacity, it becomes necessary to increase the size of the compressor or operate the compressor at high speed, but these lead to an increase in the manufacturing cost and operating cost of the air conditioner.

[0007] The present disclosure is based on the above problems, and provides an air conditioner that does not cause a pressure loss in the refrigerant in the gas-liquid separator when the heating operation is performed.

Means for Solving the Problems

[0008] The air conditioner according to the present disclosure includes a heat source machine having a compressor, a flow path switching valve, and a heat source side heat exchanger, and an indoor unit having a load side flow rate adjustment valve and a load side heat exchanger, and performing a cooling operation or a heating operation a plurality An indoor unit, a gas main pipe through which a gas refrigerant flows when the cooling operation and the heating operation are performed, and a liquid main pipe through which a liquid refrigerant or a gas-liquid two-phase refrigerant flows when the cooling operation and the heating operation are performed, are connected to the heat source machine, and are connected to the indoor unit of a plurality by a gas branch pipe and a liquid branch pipe, and the refrigerant supplied from the heat source machine is supplied to the indoor unit of a plurality An indoor unit, and a relay machine, wherein the relay machine includes a gas-liquid separator that separates the refrigerant into a gas refrigerant and a liquid refrigerant, and a flow path of the refrigerant flowing from the heat source machine to the indoor unit of a plurality An indoor unit and a flow path opening / closing device that opens and closes the flow path of the refrigerant flowing from the indoor unit of a plurality An indoor unit to the heat source machine, respectively, and when the heating operation is performed on the relay machine, the refrigerant flowing into the relay machine from the heat source machine through the gas main pipe does not pass through the gas-liquid separator and , a plurality equal in number to the plurality of indoor units The refrigerant flows into the relay machine from the heat source machine through the gas main pipe and does not pass through the gas-liquid separator when the heating operation is performed, and a pluralityThe flow path of the refrigerant flowing into the flow path opening and closing device is and the plurality of flow path opening / closing devices are controlled such that the cooling operation by any one or more of the plurality of indoor units and the heating operation by any other one or more of the plurality of indoor units are simultaneously performed. The relay unit is provided in a pipe connected to the gas main pipe, allows the refrigerant to flow from the indoor unit to the heat source unit, and includes a first check valve that blocks the flow of the refrigerant from the heat source unit to the indoor unit. A second check valve is provided in parallel with the first check valve in a pipe connected to the gas main pipe, allows the refrigerant to flow from the heat source unit to the indoor unit, and blocks the flow of the refrigerant from the indoor unit to the heat source unit. A pipe communicating with the refrigerant outlet of the second check valve is connected to a pipe connecting each of the plurality of flow path opening / closing devices and the gas outlet through which the gas refrigerant of the gas-liquid separator flows out It is something. Effect of the Invention

[0009] In the relay unit of the air conditioner of the present disclosure, when heating operation is performed, the refrigerant that flows from the heat source unit through the gas main pipe into the relay unit has a refrigerant path that flows into the flow path opening and closing device without passing through the gas-liquid separator. Therefore, no pressure loss occurs in the refrigerant in the gas-liquid separator, and it is possible to avoid a decrease in the capacity of the air conditioner due to pressure loss of the refrigerant in the gas-liquid separator. [Brief description of the drawings]

[0010]

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Embodiments for Carrying Out the Invention

[0011] Hereinafter, embodiments of the present disclosure will be described with reference to the drawings. The present disclosure is not limited to the following embodiments, and various modifications can be made without departing from the gist of the present disclosure. Also, the present disclosure includes all possible combinations of the configurations shown in the following embodiments that can be combined. Also, regarding the high and low of temperature, pressure, etc., it is not determined in relation to absolute values in particular, but is determined relatively in the states and operations of systems, devices, etc. Also, in each figure, those with the same reference numerals are the same or corresponding ones, which is common throughout the entire specification. Furthermore, in the following drawings, the relationship of the sizes of each component may be different from the actual ones.

[0012] Embodiment 1. FIG. 1 is a refrigerant circuit diagram showing the state of the air conditioner 1000 according to Embodiment 1 during full cooling operation. The air conditioner 1000 circulates refrigerant in a refrigerant circuit and performs air conditioning of an air-conditioned space using a refrigeration cycle. The air conditioner 1000 includes a heat source unit 100, a plurality of indoor units 300a, 300b, and 300c, and a relay unit 200. The air conditioner 1000 according to the present embodiment can perform cooling operation or heating operation for each of the plurality of indoor units 300a, 300b, and 300c. The air conditioner 1000 can execute a full cooling operation in which cooling operation is performed for all of the plurality of indoor units 300a, 300b, and 300c, and a full heating operation in which heating operation is performed for all of the plurality of indoor units 300a, 300b, and 300c. Further, the air conditioner 1000 according to the present embodiment can execute a simultaneous cooling and heating operation in which cooling operation is performed for any one of the plurality of indoor units 300a, 300b, and 300c and heating operation is performed for any one of the others. Among the simultaneous cooling and heating operations, an operation in which the load of the cooling operation is larger than the load of the heating operation is referred to as a cooling-dominant operation, and an operation in which the load of the heating operation is larger than the load of the cooling operation is referred to as a heating-dominant operation. In Embodiment 1, a configuration in which three indoor units 300a, 300b, and 300c are connected to one heat source unit 100 will be described, but the number of heat source units 100 and relay units 200 may be two or more. Also, the number of indoor units may be one, two, or four or more.

[0013] (Configuration of Air Conditioner) The air conditioner 1000 is configured by connecting a heat source unit 100, indoor units 300a to 300c, and a relay unit 200. The heat source unit 100 has a function of supplying heat to each of the indoor units 300a to 300c. The indoor units 300a to 300c are connected to the heat source unit 100 and the relay unit 200 in parallel with each other. The indoor units 300a to 300c have a function of cooling or heating an air-conditioned space such as a room by the heat supplied from the heat source unit 100. The relay unit 200 is interposed between the heat source unit 100 and the indoor units 300a to 300c, and has a function of switching the flow of the refrigerant supplied from the heat source unit 100 in response to requests from the indoor units 300a to 300c and supplying it to the indoor units 300a to 300c.

[0014] The heat source unit 100 and the relay unit 200 are connected by a total of two refrigerant pipes, namely the gas main pipe 41 and the liquid main pipe 42, and are connected in a so-called liquid-gas pipe connection mode. The gas main pipe 41 is a pipe through which gas refrigerant flows in both the cooling operation and the heating operation. The liquid main pipe 42 is a pipe through which liquid refrigerant or gas-liquid two-phase refrigerant flows in both the cooling operation and the heating operation. The relay unit 200 and the indoor units 300a to 300c are each connected by a total of two refrigerant pipes. Specifically, the relay unit 200 and the indoor unit 300a are connected by a gas branch pipe 43a and a liquid branch pipe 44a. The relay unit 200 and the indoor unit 300b are connected by a gas branch pipe 43b and a liquid branch pipe 44b. The relay unit 200 and the indoor unit 300c are connected by a gas branch pipe 43c and a liquid branch pipe 44c. Mainly gaseous refrigerant flows through the gas branch pipes 43a to 43c. Mainly liquid-state or gas-liquid two-phase state refrigerant flows through the liquid branch pipes 44a to 44c.

[0015] (Heat source unit 100) The heat source unit 100 includes a compressor 1, a flow path switching valve 2, a heat source side heat exchanger 3, a heat source side flow control valve 4, and a heat source unit control device 5. The compressor 1, the flow path switching valve 2, the heat source side heat exchanger 3, and the heat source side flow control valve 4 are connected by the refrigerant pipes shown by solid lines in FIG. 1.

[0016] The compressor 1 is a fluid machine that sucks in and compresses low-pressure gas refrigerant and discharges it as high-pressure gas refrigerant. The compressor 1 is, for example, an inverter-driven compressor whose operating frequency can be adjusted. The operating frequency or capacity of the compressor 1 is controlled by the heat source unit control device 5.

[0017] The flow path switching valve 2 is a valve that switches the flow direction of the refrigerant. Depending on which of the full cooling operation, the main cooling operation, the full heating operation, and the main heating operation is implemented, the flow path switching valve 2 switches the flow direction of the refrigerant discharged from the compressor 1. The flow path switching valve 2 is composed of a four-way valve, or a combination of a two-way valve or a three-way valve, etc. The operation of the flow path switching valve 2 is controlled by the heat source unit control device 5.

[0018] The heat source side heat exchanger 3 exchanges heat between the refrigerant flowing inside and another fluid. The heat source side heat exchanger 3 functions as an evaporator or a condenser. The heat source side heat exchanger 3 is, for example, an air-cooled heat exchanger, and exchanges heat between the air from a blower disposed around the heat source side heat exchanger 3 and the refrigerant. The heat source side heat exchanger 3 may be, for example, a water-cooled heat exchanger that performs heat exchange between water or brine and the refrigerant.

[0019] The heat source side flow control valve 4 is connected in series to the heat source side heat exchanger 3 and adjusts the flow rate of the refrigerant flowing through the refrigerant pipe. The heat source side flow control valve 4 has functions as a pressure reducing valve for reducing the pressure of the refrigerant and an expansion valve for expanding the refrigerant. The heat source side flow control valve 4 is composed of, for example, an electric expansion valve whose opening degree can be adjusted. The operation of the heat source side flow control valve 4 is controlled by the heat source control device 5.

[0020] The heat source control device 5 controls the overall operation of the heat source unit 100. Further, the heat source control device 5 cooperates with the relay control device 201 and the indoor unit control device 33, which will be described later, to control the overall operation of the air conditioner 1000. The heat source control device 5, the relay control device 201, and the indoor unit control device 33 are connected to each other by control lines (not shown). The heat source control device 5 is composed of a computer, an ASIC (Application Specific Integrated Circuit), an FPGA (Field Programmable Gate Array), or the like, which includes a memory for storing data and programs necessary for control, and a CPU (Central Processing Unit) for executing the programs, or both dedicated hardware.

[0021] (Indoor units 300a to 300c) The indoor unit 300a includes a load-side heat exchanger 31a, a load-side flow rate adjustment valve 32a, and an indoor unit control device 33a. The indoor unit 300b includes a load-side heat exchanger 31b, a load-side flow rate adjustment valve 32b, and an indoor unit control device 33b. The indoor unit 300c includes a load-side heat exchanger 31c, a load-side flow rate adjustment valve 32c, and an indoor unit control device 33c. In the following description, when describing matters common to the indoor units 300a to 300c, the indoor units 300a to 300c are referred to as the indoor unit 300. When referring to the indoor unit 300, it includes both singular and plural. Also, when describing matters common to the load-side heat exchangers 31a to 31c, the load-side heat exchangers 31a to 31c are referred to as the load-side heat exchanger 31. When referring to the load-side heat exchanger 31, it includes both singular and plural. Also, when describing matters common to the load-side flow rate adjustment valves 32a to 32c, the load-side flow rate adjustment valves 32a to 32c are referred to as the load-side flow rate adjustment valve 32. When referring to the load-side flow rate adjustment valve 32, it includes both singular and plural. Also, when describing matters common to the indoor unit control devices 33a to 33c, the indoor unit control devices 33a to 33c are referred to as the indoor unit control device 33. When referring to the indoor unit control device 33, it includes both singular and plural.

[0022] The load-side heat exchanger 31 exchanges heat between the refrigerant flowing inside and another fluid. The load-side heat exchanger 31 functions as a condenser or an evaporator. The load-side heat exchanger 31 is, for example, an air-cooled heat exchanger, and exchanges heat between the air from a blower disposed around the load-side heat exchanger 31 and the refrigerant. The load-side heat exchanger 31 may be, for example, a water-cooled heat exchanger that exchanges heat between water or brine and the refrigerant.

[0023] The load-side flow control valve 32 adjusts the flow rate of the refrigerant flowing into or out of the load-side heat exchanger 31. The load-side flow control valve 32 has functions as a pressure-reducing valve for reducing the pressure of the refrigerant and an expansion valve for expanding the refrigerant. The load-side flow control valve 32 is composed of, for example, an electric expansion valve that can adjust the opening degree continuously or in multiple steps. The opening degree of the load-side flow control valve 32 is controlled by the indoor unit control device 33. The load-side flow control valve 32 is arranged upstream of the load-side heat exchanger 31 in the flow direction of the refrigerant during full cooling operation.

[0024] Based on the control signal from the heat source unit control device 5, the indoor unit control device 33 controls the opening degree of the load-side flow control valve 32. The indoor unit control device 33 is composed of a computer equipped with a CPU (Central Processing Unit) that executes a program, dedicated hardware such as an ASIC (Application Specific Integrated Circuit) or an FPGA (Field Programmable Gate Array), or both.

[0025] (Relay unit 200) The relay unit 200 includes a relay unit control device 201, a gas-liquid separator 202, and flow path opening / closing devices 206a to 206c. The flow path opening / closing devices 206a to 206c are provided in one-to-one correspondence with the indoor units 300a to 300c, and a total of three flow path opening / closing devices 206a to 206c are provided in this embodiment. Further, the relay unit 200 of this embodiment includes a first check valve 209, a second check valve 210, check valves 211 and 212, an opening / closing valve 213, and an opening / closing valve 214.

[0026] The relay mechanism control device 201 controls the operations of the flow path opening / closing devices 206a to 206c, the first check valve 209, the second check valve 210, the check valve 211, the check valve 212, the on-off valve 213, and the on-off valve 214 based on the control signal from the heat source machine control device 5. The relay mechanism control device 201 is composed of a computer including a CPU (Central Processing Unit) that executes a program, a dedicated hardware such as an ASIC (Application Specific Integrated Circuit) or an FPGA (Field Programmable Gate Array), or both.

[0027] The gas-liquid separator 202 separates the refrigerant into a gas refrigerant and a liquid refrigerant. The gas-liquid separator 202 in the present embodiment separates the high-pressure gas-liquid two-phase refrigerant generated by the heat source machine 100 into a liquid refrigerant and a gas refrigerant when the cooling main operation is performed. The gas-liquid separator 202 is a container capable of storing the refrigerant, and has an inlet 203, a gas outlet 204, and a liquid outlet 205. The inlet 203 is connected to a pipe connected to the liquid main pipe 42, and allows the refrigerant flowing into the relay machine 200 through the liquid main pipe 42 to flow into the gas-liquid separator 202. The gas outlet 204 is provided on the upper side in the gravity direction of the gas-liquid separator 202, and allows the gas refrigerant separated in the gas-liquid separator 202 to flow out from the gas-liquid separator 202 to the pipe. The liquid outlet 205 is provided on the lower side in the gravity direction of the gas-liquid separator 202, and allows the liquid refrigerant separated in the gas-liquid separator 202 to flow out from the gas-liquid separator 202 to the pipe. Here, an example where the gas-liquid separator 202 is a container capable of storing the refrigerant is described, but instead of the container, a pipe can also be used as the gas-liquid separator 202. In this case, the pipe serving as the gas-liquid separator 202 may be branched to provide the inlet 203, the gas outlet 204, and the liquid outlet 205.

[0028] The flow path opening / closing devices 206a to 206c are devices that open and close the flow path of the refrigerant from the heat source unit 100 to the indoor units 300a to 300c and the flow path of the refrigerant from the indoor units 300a to 300c to the heat source unit 100, respectively. The flow path opening / closing device 206a includes a first valve 207a and a second valve 208a, the flow path opening / closing device 206b includes a first valve 207b and a second valve 208b, and the flow path opening / closing device 206c includes a first valve 207c and a second valve 208c. In the following description, when explaining matters common to the flow path opening / closing devices 206a to 206c, the flow path opening / closing devices 206a to 206c are referred to as the flow path opening / closing device 206. When referring to the flow path opening / closing devices 206a to 206c, it includes both singular and plural. Also, when explaining matters common to the first valves 207a to 207c, the first valves 207a to 207c are referred to as the first valve 207. When referring to the first valve 207, it includes both singular and plural. Further, when explaining matters common to the second valves 208a to 208c, the second valves 208a to 208c are referred to as the second valve 208. When referring to the second valve 208, it includes both singular and plural.

[0029] The flow path opening / closing device 206 has a first valve 207 and a second valve 208 connected in parallel to the indoor unit 300. The first valve 207 opens and closes the flow path between the first backflow prevention valve 209 and the gas branch pipe 43. Specifically, the first valve 207 is provided in a pipe connecting a pipe connected to the gas main pipe 41 and provided with the first backflow prevention valve 209 and a pipe connected to the gas branch pipe 43. The first valve 207 is an opening / closing valve that opens and closes the flow path of the refrigerant flowing from the indoor unit 300 toward the heat source unit 100. The second valve 208 opens and closes the flow path between the second backflow prevention valve 210 and the gas branch pipe 43. The second valve 208 is provided in a pipe connecting a pipe connected to the gas main pipe 41 and provided with the second backflow prevention valve 210 and a pipe connected to the gas branch pipe 43. The second valve 208 is an opening / closing valve that opens and closes the flow path of the refrigerant flowing from the heat source unit 100 toward the indoor unit 300. The first valve 207 and the second valve 208 are, for example, electromagnetic valves or throttle valves with adjustable opening degrees having a fully closed function, but the specific valve structure is not limited as long as the flow path can be opened and closed. When one of the first valve 207 and the second valve 208 is in the open state, the other is in the closed state, and both are not in the open state at the same time.

[0030] The first backflow prevention valve 209 is provided in a pipe connected to the gas main pipe 41, allows the flow of the refrigerant from the indoor unit 300 to the heat source unit 100, and blocks the flow of the refrigerant from the heat source unit 100 to the indoor unit 300. The first backflow prevention valve 209 prevents the high-temperature and high-pressure gas refrigerant from flowing backward from the discharge side flow path of the compressor 1 to the flow path opening / closing device 206 when the full heating operation and the main heating operation are carried out.

[0031] The second backflow prevention valve 210 is provided in parallel with the first backflow prevention valve 209 in a pipe connected to the gas main pipe 41, allows the flow of the refrigerant from the heat source unit 100 to the indoor unit 300, and blocks the flow of the refrigerant from the indoor unit 300 to the heat source unit 100. The second backflow prevention valve 210 prevents the high-pressure liquid state or gas-liquid two-phase state refrigerant that has passed through the gas-liquid separator 202 from flowing backward to the refrigerant pipe on the outlet side of the first backflow prevention valve 209, that is, the gas main pipe 41, when the full cooling operation and the main cooling operation are carried out.

[0032] The check valve 211 is provided in a pipe connecting the inlet side of the first check valve 209 and the liquid main pipe 42, allows the refrigerant to flow from the indoor unit 300 to the heat source unit 100, and blocks the flow of the refrigerant from the heat source unit 100 to the indoor unit 300. The check valve 211 prevents the refrigerant in a high-pressure liquid state or a gas-liquid two-phase state from flowing from the liquid main pipe 42 into the outdoor unit 101 when all-cooling operation and cooling-main operation are performed.

[0033] The check valve 212 is provided in a pipe connecting the inlet 203 of the gas-liquid separator 202 and the liquid main pipe 42, allows the refrigerant to flow from the heat source unit 100 to the indoor unit 300, and blocks the flow of the refrigerant from the indoor unit 300 to the heat source unit 100. The check valve 212 prevents the high-temperature and high-pressure gas refrigerant from flowing into the heat source-side heat exchanger 3 when all-heating operation and heating-main operation are performed.

[0034] The on-off valve 213 is provided in a pipe 241 connected to the liquid outlet 205 of the gas-liquid separator 202, and opens and closes the refrigerant flow path. The on-off valve 213 is, for example, an electromagnetic valve.

[0035] The on-off valve 214 is provided in a pipe through which the liquid refrigerant flowing out from the liquid branch pipe 44 flows when all-heating operation or heating-main operation is performed, and opens and closes the refrigerant flow path. Specifically, in the present embodiment, the on-off valve 214 is provided in a pipe 240 connecting the inlet side of the first check valve 209 and the liquid branch pipe 44. The pipe 240 is a single pipe connected to a plurality of liquid branch pipes 44 via pipes 243 and 244.

[0036] The pipe 240 and the pipe 241 intersect at an intersection 242. The refrigerant in the pipe 240 and the refrigerant in the pipe 241 merge or branch and flow at the intersection 242 according to the open / closed states of the on-off valve 213 and the on-off valve 214.

[0037] The operations of the second valve 208, the first valve 207, the first check valve 209, the second check valve 210, the check valve 211, the check valve 212, the on-off valve 213, and the on-off valve 214 of the flow path opening / closing device 206 are controlled by the relay control device 201.

[0038] The piping configuration within the relay 200 will be described. The pipe connected to the main gas pipe 41 is branched into two. A first check valve 209 is provided in one pipe, and a second check valve 210 is provided in the other pipe. To the pipe 240 on the inlet side of the first check valve 209 of the pipe to which the first check valve 209 is connected, a pipe connected to the check valve 211 and a pipe connected to the first valve 207 are connected. To the outlet side of the second check valve 210 of the pipe to which the second check valve 210 is connected, a pipe 245 connected to the gas outlet 204 of the gas-liquid separator 202 and a pipe connected to the second valve 208 are connected.

[0039] The pipe 240 and the pipe 241 intersect at the intersection 242 and further branch into a pipe 243 and a pipe 244. All the liquid branch pipes 44 are connected to the pipe 243, and all the liquid branch pipes 44 are also connected to the pipe 244.

[0040] (Refrigerant) The air conditioner 1000 has its pipes filled with refrigerant. The refrigerant is not particularly limited and can be, for example, natural refrigerants such as carbon dioxide, hydrocarbons, helium, chlorine-free refrigerant substitutes such as HFC410A, HFC407C, HFC404A, or fluorocarbon refrigerants such as R22, R134a used in existing products.

[0041] (Operation of the air conditioner) The operation of the air conditioner 1000 will be described with reference to FIGS. 1 to 4. In FIGS. 1 to 4, the flow of the refrigerant is indicated by arrows. Also, among the on-off valves shown in FIGS. 1 to 4, the on-off valves through which the refrigerant does not flow are shown in black.

[0042] (Full cooling operation) In full cooling operation, all of the indoor units 300a to 300c perform cooling operation. The flow path switching valve 2 is set such that the discharge side of the compressor 1 is connected to the heat source side heat exchanger 3 with respect to the refrigerant flow path.

[0043] As shown in FIG. 1, a low-temperature and low-pressure refrigerant is sucked into the compressor 1 and compressed, and is discharged from the compressor 1 as a high-temperature and high-pressure gas refrigerant. The high-temperature and high-pressure gas refrigerant discharged from the compressor 1 passes through the flow path switching valve 2 and exchanges heat with a fluid such as air in the heat source side heat exchanger 3 functioning as a condenser or radiator, and condenses and liquefies. The high-pressure liquid refrigerant then flows through the heat source side flow control valve 4, flows through the liquid main pipe 42, and flows into the relay unit 200. The refrigerant that has flowed into the relay unit 200 passes through the check valve 212 and reaches the inside of the gas-liquid separator 202 from the inlet 203.

[0044] The high-pressure liquid refrigerant that has flowed into the gas-liquid separator 202 flows out from the liquid outlet 205 and passes through the open on-off valve 213 provided in the pipe 241. The refrigerant that has flowed through the pipe 241 branches and flows into each of the liquid branch pipes 44a to 44c through the pipes 243 and 244. The refrigerant flowing through each of the liquid branch pipes 44a to 44c flows into each of the indoor units 300a to 300c.

[0045] The refrigerant that has flowed into the indoor units 300a to 300c is decompressed by the load side flow control valves 32a to 32c, respectively. The refrigerant that has been decompressed to a low-temperature and low-pressure gas-liquid two-phase state flows into the load side heat exchangers 31a to 31c functioning as evaporators, and exchanges heat with the indoor air in the load side heat exchangers 31a to 31c and evaporates and gasifies. At this time, the air-conditioning target space such as the indoor space where the indoor units 300a to 300c are installed is cooled. Then, the refrigerant that has become a low-temperature and low-pressure gas state flows into the flow path opening and closing devices 206a to 206c of the relay unit 200 through the gas branch pipes 43a to 43c, respectively.

[0046] The first valves 207a - 207c are in the open state, and the second valves 208a - 208c are in the closed state. The refrigerant flowing into each of the flow path opening / closing devices 206a - 206c passes through each of the first valves 207a - 207c, further passes through the first check valve 209, and then flows out from the relay unit 200. The gaseous refrigerant flowing out from the relay unit 200 flows into the heat source unit 100 through the main gas pipe 41. The refrigerant flowing into the heat source unit 100 is sucked into the compressor 1 through the flow path switching valve 2.

[0047] (Cooling main operation) FIG. 2 is a refrigerant circuit diagram showing the state during the cooling main operation of the air conditioner 1000 according to Embodiment 1. Here, a case will be described as an example where heating operation is performed in the indoor unit 300a, and cooling operations are performed in the indoor units 300b and 300c. The load of the cooling operation is for two indoor units 300b and 300c, while the load of the heating operation is for one indoor unit 300a. Therefore, the load of the cooling operation is larger than the load of the heating operation. The flow path switching valve 2 is set such that the discharge side of the compressor 1 is connected to the heat source side heat exchanger 3.

[0048] As shown in FIG. 2, the low-temperature and low-pressure refrigerant is sucked into the compressor 1 and compressed, and then discharged from the compressor 1 as a high-temperature and high-pressure gaseous refrigerant. The high-temperature and high-pressure gaseous refrigerant discharged from the compressor 1 passes through the flow path switching valve 2 and exchanges heat with a fluid such as air in the heat source side heat exchanger 3 functioning as a condenser or radiator, and becomes a gas-liquid two-phase state. The high-pressure gas-liquid two-phase state refrigerant then flows through the heat source side flow control valve 4, flows through the liquid main pipe 42, and flows into the relay unit 200. The refrigerant flowing into the relay unit 200 passes through the check valve 212 and reaches the inside of the gas-liquid separator 202 from the inlet 203. In the gas-liquid separator 202, the gas-liquid two-phase state refrigerant is separated into gaseous refrigerant and liquid refrigerant.

[0049] The gaseous refrigerant flowing out from the gas outlet 204 of the gas-liquid separator 202 passes through the second valve 208a and flows into the indoor unit 300a through the gas branch pipe 43a. The refrigerant flowing into the indoor unit 300a exchanges heat with the indoor air in the load-side heat exchanger 31a that functions as a condenser or radiator, and condenses and liquefies. At this time, the air-conditioned target space such as the indoor space where the indoor unit 300a is installed is heated. The high-pressure liquid refrigerant flows out from the load-side heat exchanger 31a and passes through the load-side flow control valve 32a. Although the load-side flow control valve 32a is in the fully open state, the refrigerant is slightly depressurized when passing through the load-side flow control valve 32a. The refrigerant passing through the load-side flow control valve 32a flows into the relay unit 200 through the liquid branch pipe 44a and flows through the pipes 243 and 244.

[0050] The liquid refrigerant flowing out from the liquid outlet 205 of the gas-liquid separator 202 passes through the open on-off valve 213 provided in the pipe 241, passes through the intersection 242, and flows into the pipes 243 and 244. In the pipes 243 and 244, the liquid refrigerant from the liquid branch pipe 44a and the liquid refrigerant from the pipe 241 merge, and this liquid refrigerant flows into the indoor units 300b or 300c through the liquid branch pipes 44b or 44c.

[0051] The refrigerant flowing into the indoor unit 300b or 300c is depressurized by the load-side flow control valve 32b or 32c respectively to become a gas-liquid two-phase state. The depressurized gas-liquid two-phase refrigerant flows into the load-side heat exchanger 31b or 31c that functions as an evaporator, exchanges heat with the indoor air in the load-side heat exchanger 31b or 31c, and evaporates and gasifies. At this time, the air-conditioned target space such as the indoor space where the indoor units 300b and 300c are installed is cooled. Then, the refrigerant that has become a low-temperature and low-pressure gaseous state flows into the flow path opening / closing devices 206b or 206c of the relay unit 200 through the gas branch pipes 43b or 43c respectively.

[0052] The gas refrigerant flowing into the flow path opening / closing device 206b or 206c merges after passing through the first valve 207b or 207c respectively, passes through the first check valve 209, and flows out of the relay unit 200. The gas refrigerant flowing out of the relay unit 200 flows into the heat source unit 100 through the main gas pipe 41. The refrigerant flowing into the heat source unit 100 is sucked into the compressor 1 through the flow path switching valve 2.

[0053] In the cooling main body operation, the adjustment of the amount of refrigerant flowing into the indoor unit 300 performing the cooling operation and the amount of refrigerant flowing into the indoor unit 300 performing the heating operation is realized by adjusting the heat exchange amount in the heat source side heat exchanger 3. When the required heating load increases, the capacity of the compressor 1 increases, the amount of gas refrigerant flowing out of the heat source side heat exchanger 3 increases, and the amount of gas refrigerant flowing from the gas-liquid separator 202 into the indoor unit 300 performing the heating operation also increases. On the other hand, when the required heating load decreases, the capacity of the compressor 1 is reduced, the amount of gas refrigerant flowing out of the heat source side heat exchanger 3 decreases, and the amount of gas refrigerant flowing from the gas-liquid separator 202 into the indoor unit 300 performing the heating operation decreases.

[0054] (Full heating operation) FIG. 3 is a refrigerant circuit diagram showing the state during the full heating operation of the air conditioner 1000 according to Embodiment 1. In the full heating operation, all of the indoor units 300a to 300c perform heating operation. The flow path switching valve 2 is set with the refrigerant flow path so that the discharge side of the compressor 1 is connected to the main gas pipe 41.

[0055] As shown in FIG. 3, the low-temperature and low-pressure refrigerant is sucked into the compressor 1 and compressed, and is discharged from the compressor 1 as a high-temperature and high-pressure gas refrigerant. The high-temperature and high-pressure gas refrigerant discharged from the compressor 1 passes through the flow path switching valve 2, flows through the main gas pipe 41, and flows into the relay unit 200.

[0056] The high-temperature and high-pressure gas refrigerant flowing into the relay unit 200 passes through the second backflow prevention valve 210 and flows into each of the flow path opening / closing devices 206a to 206c. Here, the second valves 208a to 208c are in the open state, and the first valves 207a to 207c are in the closed state. The refrigerant flowing into each of the flow path opening / closing devices 206a to 206c passes through each of the second valves 208a to 208c, further passes through each of the gas branch pipes 43a to 43c, and flows into each of the indoor units 300a to 300c.

[0057] The gas refrigerant flowing into each of the indoor units 300a to 300c exchanges heat with the indoor air in the load-side heat exchangers 31a to 31c functioning as condensers or radiators, and condenses and liquefies. At this time, the air-conditioning target space such as the indoor space where the indoor units 300a to 300c are installed is heated. The liquid refrigerant flowing out from each of the indoor units 300a to 300c is depressurized by each of the load-side flow control valves 32a to 32c. Then, the low-pressure liquid refrigerant flows through each of the liquid branch pipes 44a to 44c and into the relay unit 200.

[0058] The low-pressure liquid refrigerant flowing into the relay unit 200 through the liquid branch pipes 44a to 44c flows through the pipes 243 or 244, merges at the intersection 242, and flows through the pipe 240. Here, in the flow direction of the refrigerant during all heating operations, the downstream side of the on-off valve 214 and the downstream side of the first backflow prevention valve 209 are in communication, but the downstream side of the first backflow prevention valve 209 communicating with the discharge side of the compressor 1 is at a high pressure, while the refrigerant flowing through the on-off valve 214 is at a low pressure. For this reason, other refrigerant does not pass through the first backflow prevention valve 209 when flowing through the on-off valve 214. Then, the low-pressure liquid refrigerant passes through the open on-off valve 214 and the backflow prevention valve 211 and flows out from the relay unit 200.

[0059] The liquid refrigerant flowing out from the relay unit 200 flows into the heat source unit 100 through the liquid main pipe 42. The refrigerant flowing into the heat source unit 100 passes through the heat source-side flow control valve 4 and flows into the heat source-side heat exchanger 3 functioning as an evaporator. The low-pressure liquid refrigerant exchanges heat with a fluid such as air in the heat source-side heat exchanger 3, absorbs heat, and evaporates and gasifies. The low-pressure gas refrigerant flowing out from the heat source-side heat exchanger 3 is sucked into the compressor 1 through the flow path switching valve 2.

[0060] As described here, when the full heating operation is carried out, in the relay unit 200, a path for the high-temperature and high-pressure gas refrigerant to flow into each indoor unit 300a to 300c is formed without passing through the gas-liquid separator 202. Since the gas refrigerant does not pass through the gas-liquid separator 202, no pressure loss of the gas refrigerant occurs in the gas-liquid separator 202. Therefore, it is possible to avoid the reduction in the capacity of the air conditioner 1000 due to the pressure loss of the refrigerant in the gas-liquid separator 202.

[0061] (Heating main operation) FIG. 4 is a refrigerant circuit diagram showing the state during the heating main operation of the air conditioner 1000 according to the first embodiment. Here, a case where the cooling operation is carried out in the indoor unit 300a and the heating operation is carried out in the indoor units 300b and 300c will be described as an example. Since the heating operation load is for two indoor units 300b and 300c, while the cooling operation load is for one indoor unit 300a, the heating operation load is larger than the cooling operation load. The flow path switching valve 2 is set such that the discharge side of the compressor 1 is connected to the gas main pipe 41.

[0062] As shown in FIG. 4, the low-temperature and low-pressure refrigerant is sucked into the compressor 1 and compressed, and then discharged from the compressor 1 as a high-temperature and high-pressure gas refrigerant. The high-temperature and high-pressure gas refrigerant discharged from the compressor 1 passes through the flow path switching valve 2, flows through the gas main pipe 41, and flows into the relay unit 200.

[0063] The high-temperature and high-pressure gas refrigerant flowing into the relay unit 200 passes through the second backflow prevention valve 210 and flows into each of the flow path opening / closing devices 206a to 206c. Here, the second valves 208b and 208c are in the open state, and the second valve 208a is in the closed state. Also, the first valve 207a is in the open state, and the first valves 207b and 207c are in the closed state. The gas refrigerant flowing into the flow path opening / closing device 206b or 206c passes through the second valve 208b or 208c respectively, and flows into the indoor unit 300b or 300c through the gas branch pipe 43b or 43c.

[0064] The high-pressure gas refrigerant flowing into the indoor unit 300b or 300c exchanges heat with the indoor air in the load-side heat exchanger 31b or 31c that functions as a condenser or radiator, respectively, and condenses and liquefies. At this time, the air-conditioned target space such as the indoor space where the indoor unit 300b or 300c is installed is heated. The high-pressure liquid refrigerant flows out from the load-side heat exchanger 31b or 31c and is depressurized to a low pressure by the load-side flow control valves 32b or 32c, respectively, to become a refrigerant in a low-temperature and low-pressure gas-liquid two-phase state. The refrigerant in the gas-liquid two-phase state that has passed through the load-side flow control valves 32b or 32c flows into the relay unit 200 through the liquid branch pipes 44b or 44c and flows through the pipe 243 or the pipe 244.

[0065] Most of the refrigerant in the gas-liquid two-phase state flowing into the pipe 243 or the pipe 244 flows into the indoor unit 300a through the liquid branch pipe 44a, and the remaining refrigerant flows through the pipe 240 from the intersection 242 and further passes through the open on-off valve 214. The refrigerant in the gas-liquid two-phase state flowing into the indoor unit 300a is depressurized at the load-side flow control valve 32a and exchanges heat with the indoor air in the load-side heat exchanger 31a that functions as an evaporator, and evaporates and gasifies. At this time, the air-conditioned target space such as the indoor space where the indoor unit 300a is installed is cooled. The gas refrigerant flowing out from the load-side heat exchanger 31a flows into the flow path opening / closing device 206a through the gas branch pipe 43a. The gas refrigerant flowing into the flow path opening / closing device 206a passes through the first valve 207a, merges with the refrigerant in the gas-liquid two-phase state that has passed through the on-off valve 214, and passes through the check valve 211 as a gas-liquid two-phase refrigerant. The refrigerant in the gas-liquid two-phase state that has passed through the check valve 211 flows out from the relay unit 200.

[0066] The refrigerant in the gas-liquid two-phase state flowing out from the relay unit 200 flows into the heat source unit 100 through the liquid main pipe 42. The refrigerant flowing into the heat source unit 100 passes through the heat source-side flow control valve 4 and flows into the heat source-side heat exchanger 3 that functions as an evaporator. The refrigerant flowing into the heat source-side heat exchanger 3 exchanges heat with a fluid such as air in the heat source-side heat exchanger 3 and absorbs heat to become a low-temperature and low-pressure gas refrigerant. The low-temperature and low-pressure gas refrigerant flowing out from the heat source-side heat exchanger 3 is sucked into the compressor 1 through the flow path switching valve 2.

[0067] As described herein, when the heating main operation is performed, in the relay unit 200, a path for the high-temperature and high-pressure gas refrigerant to flow into any one of the indoor units 300a to 300c without passing through the gas-liquid separator 202 is formed. Since the gas refrigerant does not pass through the gas-liquid separator 202, no pressure loss of the gas refrigerant occurs in the gas-liquid separator 202. Therefore, it is possible to avoid a reduction in the capacity of the air conditioner 1000 due to the pressure loss of the refrigerant in the gas-liquid separator 202.

[0068] As described above, the air conditioner 1000 according to the present embodiment includes a heat source unit 100 having a compressor 1, a flow path switching valve 2, and a heat source side heat exchanger 3, one or more indoor units 300, and a relay unit 200. The one or more indoor units 300 have a load side flow rate adjustment valve 32 and a load side heat exchanger 31, and perform a cooling operation or a heating operation. The relay unit 200 is connected to the heat source unit 100 by a gas main pipe 41 through which the gas refrigerant flows in the cooling operation and the heating operation and a liquid main pipe 42 through which the liquid refrigerant or the gas-liquid two-phase refrigerant flows in the cooling operation and the heating operation. The relay unit 200 is also connected to the indoor unit 300 by a gas branch pipe 43 and a liquid branch pipe 44, and supplies the refrigerant supplied from the heat source unit 100 to the indoor unit 300. Further, the relay unit 200 includes a gas-liquid separator 202 that separates the refrigerant into a gas refrigerant and a liquid refrigerant, and one or more flow path opening / closing devices 206 that open and close the flow path of the refrigerant from the heat source unit 100 to the indoor unit 300 and the flow path of the refrigerant from the indoor unit 300 to the heat source unit 100, respectively. In the relay unit 200, when the heating operation is performed in the indoor unit 300, a path for the refrigerant flowing into the relay unit 200 from the heat source unit 100 through the gas main pipe 41 to flow into the flow path opening / closing device 206 without passing through the gas-liquid separator 202 is provided.

[0069] Thus, in the air conditioner 1000 of the present embodiment, when the heating operation is performed, the high-temperature and high-pressure gas refrigerant flows into the indoor unit 300 without passing through the gas-liquid separator 202. Since the gas refrigerant does not pass through the gas-liquid separator 202, no pressure loss of the gas refrigerant occurs in the gas-liquid separator 202. Therefore, it is possible to avoid a reduction in the capacity of the air conditioner 1000 due to the pressure loss of the refrigerant in the gas-liquid separator 202.

[0070] In addition, in the air conditioner 1000 of the present embodiment, one or more indoor units 300 are a plurality of indoor units 300a to 300c, and the flow path opening / closing devices 206 are a plurality of flow path opening / closing devices 206a to 206c having the same number as the plurality of indoor units 300. Then, the plurality of flow path opening / closing devices 206a to 206c are controlled so that cooling operation by any one or more of the plurality of indoor units 300a to 300c and heating operation by any other one or more of the plurality of indoor units 300a to 300c are simultaneously performed.

[0071] According to such a configuration of the air conditioner 1000 of the present embodiment, simultaneous heating and cooling operation in which cooling operation and heating operation are simultaneously performed becomes possible, so that the convenience of the user in the building where the air conditioner 1000 is installed can be improved.

[0072] Further, the relay unit 200 of the air conditioner 1000 of the present embodiment is provided in a pipe connected to the main gas pipe 41, and includes a first check valve 209 that allows the refrigerant to flow from the indoor unit 300 to the heat source unit 100 and blocks the flow of the refrigerant from the heat source unit 100 to the indoor unit 300. In addition, the relay unit 200 is provided in parallel with the first check valve 209 in a pipe connected to the main gas pipe 41, and includes a second check valve 210 that allows the refrigerant to flow from the heat source unit 100 to the indoor unit 300 and blocks the flow of the refrigerant from the indoor unit 300 to the heat source unit 100. And a pipe 245 communicating with the refrigerant outlet of the second check valve 210 is connected to a pipe connecting each of the plurality of flow path opening / closing devices 206a to 206c and the gas outlet 204 for discharging the gas refrigerant of the gas-liquid separator 202.

[0073] The air conditioner 1000 of the present embodiment includes the first check valve 209 as described above. Therefore, when all heating operation or heating main operation is performed, it is possible to prevent the high-temperature and high-pressure gas refrigerant from flowing backward from the flow path on the discharge side of the compressor 1 to the flow path opening / closing device 206.

[0074] In addition, the air conditioner 1000 of the embodiment includes the second check valve 210 as described above. Therefore, when the full cooling operation and the main cooling operation are performed, even if the high-pressure liquid-state or gas-liquid two-phase refrigerant that has passed through the gas-liquid separator 202 flows into the pipe 245, the flow is blocked by the second check valve 210. For this reason, it is possible to prevent the high-pressure liquid-state or gas-liquid two-phase refrigerant that has passed through the gas-liquid separator 202 from flowing backward into the refrigerant pipe on the outlet side of the first check valve 209, that is, the gas main pipe 41.

[0075] Embodiment 2. In this embodiment, in addition to the circuit configuration shown in Embodiment 1, a configuration including a pressure relief valve 215 will be described. In this embodiment, the description will focus on the differences from Embodiment 1, and the description of matters common to Embodiment 1 will be omitted as appropriate.

[0076] FIG. 5 is a refrigerant circuit diagram showing the state during the full cooling operation of the air conditioner 1000A according to Embodiment 2. The air conditioner 1000A includes a pressure relief valve 215 provided in a pipe connecting a pipe connected to the gas outlet 204 of the gas-liquid separator 202 and a pipe connected to the gas main pipe 41 inside the relay machine 200. The pressure relief valve 215 is an on-off valve whose opening and closing state is controlled by the relay controller 201. The pressure relief valve 215 is connected to a pipe 250 which is a high-pressure line connected to the second valves 208a to 208c. The pressure relief valve 215 is in an open state when the pressure of the refrigerant in the pipe 250 connecting the gas-liquid separator 202 and the second valves 208a to 208c becomes equal to or higher than the saturation pressure of the refrigerant. The pressure relief valve 215 is in a closed state if the pressure of the refrigerant in the pipe 250 is less than the saturation pressure of the refrigerant. The opening and closing state of the pressure relief valve 215 is controlled by the relay controller 201.

[0077] (Operation of the air conditioner) The operation of the air conditioner 1000A will be described with reference to FIGS. 5 to 8. In FIGS. 5 to 8, the flow of the refrigerant is indicated by arrows. Also, among the on-off valves shown in FIGS. 5 to 8, the on-off valves through which the refrigerant does not flow are shown in black.

[0078] (Full cooling operation) FIG. 5 is a refrigerant circuit diagram showing the state of the full cooling operation of the air conditioner 1000A according to the second embodiment. In the full cooling operation, all of the indoor units 300a to 300c perform the cooling operation. In the full cooling operation of the air conditioner 1000A shown in FIG. 5, in addition to the operations shown in the first embodiment, the pressure relief valve 215 operates as follows. That is, the pressure relief valve 215 opens when the pressure of the refrigerant in the pipe 250 connecting the gas-liquid separator 202 and the second valves 208a to 208c becomes equal to or higher than the saturation pressure of the refrigerant. The pressure relief valve 215 closes if the pressure of the refrigerant in the pipe 250 is less than the saturation pressure of the refrigerant.

[0079] As described above, in the relay unit 200 of the air conditioner 1000A, when the full cooling operation is performed, the pressure relief valve 215 is provided such that the pressure in the pipe 250, which is the high-pressure line, opens when it becomes equal to or higher than the saturation pressure of the refrigerant. Therefore, the refrigerant circuit of the air conditioner 1000A does not exceed the saturation pressure of the refrigerant. Therefore, the safety of the air conditioner 1000A can be improved.

[0080] Even when the pressure of the refrigerant in the pipe 250 is less than the saturation pressure, the pressure relief valve 215 may be periodically opened. By doing so, the refrigerant circuit of the air conditioner 1000A does not exceed the saturation pressure of the refrigerant. Therefore, the safety of the air conditioner 1000A can be improved.

[0081] (Main cooling operation) FIG. 6 is a refrigerant circuit diagram showing the state during the main cooling operation of the air conditioner 1000A according to the second embodiment. Here, as in FIG. 2, the case where the heating operation is performed by the indoor unit 300a and the cooling operation is performed by the indoor units 300b and 300c will be described as an example. Since the load of the cooling operation is for two indoor units 300b and 300c, while the load of the heating operation is for one indoor unit 300a, the load of the cooling operation is greater than the load of the heating operation.

[0082] In the cooling main operation shown in FIG. 6 of the present embodiment, in addition to the operations shown in the first embodiment, the pressure relief valve 215 operates as follows. That is, the pressure relief valve 215 is in an open state when the pressure of the refrigerant in the pipe 250 connecting the gas-liquid separator 202 and the second valves 208a to 208c becomes equal to or higher than the saturation pressure of the refrigerant. The pressure relief valve 215 is in a closed state if the pressure of the refrigerant in the pipe 250 is less than the saturation pressure of the refrigerant.

[0083] In this way, in the relay unit 200 of the air conditioner 1000A, when the cooling main operation is performed, a pressure relief valve 215 is provided such that the pressure in the pipe 250, which is the high-pressure line, becomes open when the pressure becomes equal to or higher than the saturation pressure of the refrigerant. Therefore, the refrigerant circuit of the air conditioner 1000A does not exceed the saturation pressure of the refrigerant. Accordingly, the safety of the air conditioner 1000A can be enhanced.

[0084] (Full heating operation) FIG. 7 is a refrigerant circuit diagram showing the state of the full heating operation of the air conditioner 1000A according to the second embodiment. In the full cooling and heating operation, all of the indoor units 300a to 300c perform heating operations. The air conditioner 1000A shown in FIG. 7 performs the operations shown in the first embodiment during the full heating operation. The pressure relief valve 215 of the relay unit 200 is always in a fully closed state.

[0085] (Heating main operation) FIG. 8 is a refrigerant circuit diagram showing the state of the air conditioner 1000A according to the second embodiment during the heating main operation. In the heating main operation, a cooling operation is performed by the indoor unit 300a, and heating operations are performed by the indoor units 300b and 300c. The air conditioner 1000A shown in FIG. 8 performs the operations shown in the first embodiment during the heating main operation. The pressure relief valve 215 of the relay unit 200 is always in a fully closed state.

[0086] As described above, the air conditioner 1000A of the present embodiment includes a pressure relief valve 215 provided in a pipe that connects the main gas pipe 41 and the gas outlet 204 of the gas-liquid separator 202. When the cooling operation is being performed in one or more of the plurality of indoor units 300, the pressure relief valve 215 opens when the refrigerant pressure in the pipe 250 connecting each of the flow path opening / closing devices 206a to 206c and the gas outlet 204 for discharging the gas refrigerant of the gas-liquid separator 202 becomes equal to or higher than the saturation pressure of the refrigerant. For this reason, the refrigerant circuit of the air conditioner 1000A does not exceed the saturation pressure of the refrigerant. Therefore, the safety of the air conditioner 1000A can be enhanced.

[0087] Note that the pressure relief valve 215 of the air conditioner 1000A may be periodically opened when the pressure of the refrigerant in the pipe connecting each of the plurality of flow path opening / closing devices 206a to 206c and the gas outlet 204 for discharging the gas refrigerant of the gas-liquid separator 202 is less than the saturation pressure of the refrigerant when all cooling operations or cooling-dominant operations are performed. By doing so, the refrigerant circuit of the air conditioner 1000A does not exceed the saturation pressure of the refrigerant. Therefore, the safety of the air conditioner 1000A can be enhanced.

[0088] Embodiment 3. In the present embodiment, an air conditioner 1000B provided with a flow path opening / closing device 223 different from those in Embodiments 1 and 2 will be described. The air conditioner 1000B of the present embodiment further includes a refrigerant intermediate heat exchanger 226. In the present embodiment, the description will focus on the differences from Embodiments 1 and 2, and the description of matters common to Embodiments 1 and 2 will be omitted as appropriate.

[0089] (Configuration of the air conditioner) FIG. 9 is a refrigerant circuit diagram showing the state during full cooling operation of the air conditioner 1000B according to Embodiment 3. The air conditioner 1000B is configured by connecting a heat source unit 100, indoor units 300a to 300c, and a relay unit 200. The heat source unit 100 has a function of supplying heat to each of the indoor units 300a to 300c. The indoor units 300a to 300c are connected in parallel with each other. The indoor units 300a to 300c have a function of cooling or heating an air-conditioned space such as a room by the heat supplied from the heat source unit 100. The relay unit 200 is interposed between the heat source unit 100 and the indoor units 300a to 300c, and has a function of switching the flow of the refrigerant supplied from the heat source unit 100 according to a request from the indoor units 300a to 300c and supplying it to the indoor units 300a to 300c.

[0090] The heat source unit 100 and the relay unit 200 are connected by a total of two refrigerant pipes, namely a gas main pipe 41 and a liquid main pipe 42, and are connected in a so-called liquid-gas pipe connection mode. The gas main pipe 41 is a pipe through which gas refrigerant flows in both cooling operation and heating operation. The liquid main pipe 42 is a pipe through which liquid refrigerant or gas-liquid two-phase refrigerant flows in both cooling operation and heating operation. The relay unit 200 and the indoor units 300a to 300c are each connected by a total of two refrigerant pipes. Specifically, the relay unit 200 and the indoor unit 300a are connected by a gas branch pipe 43a and a liquid branch pipe 44a. The relay unit 200 and the indoor unit 300b are connected by a gas branch pipe 43b and a liquid branch pipe 44b. The relay unit 200 and the indoor unit 300c are connected by a gas branch pipe 43c and a liquid branch pipe 44c. Gas refrigerant mainly flows through the gas branch pipes 43a to 43c. Liquid refrigerant or gas-liquid two-phase refrigerant mainly flows through the liquid branch pipes 44a to 44c.

[0091] The configurations of the heat source unit 100 and the indoor unit 300 are the same as those in Embodiments 1 and 2.

[0092] (Relay unit 200) The relay unit 200 includes a relay unit control device 201, a gas-liquid separator 202, and flow path opening / closing devices 223a to 223c. The flow path opening / closing devices 223a to 223c are provided in a one-to-one correspondence with the indoor units 300a to 300c, and a total of three flow path opening / closing devices 223a to 223c are provided in this embodiment. Further, the relay unit 200 of this embodiment includes a low-pressure pipe 220, a high-pressure pipe 221, return pipes 222a and 222b, a refrigerant intermediate heat exchanger 226, a first check valve 229, a second check valve 230, and a third check valve 231.

[0093] The low-pressure pipe 220 is a pipe connected to the pipe connected to the gas main pipe 41 via the first check valve 229. The low-pressure pipe 220 is connected to each of the indoor units 300a to 300c via first valves 224a to 224b provided in each of the flow path opening / closing devices 223a to 223c.

[0094] The high-pressure pipe 221 is a pipe connected to the pipe connected to the gas main pipe 41 via the second check valve 230. The high-pressure pipe 221 is connected to each of the indoor units 300a to 300c via second valves 225a to 225b provided in each of the flow path opening / closing devices 223a to 223c.

[0095] The return pipes 222a and 222b are pipes connected to each of the indoor units 300a to 300c. The return pipe 222a is connected to each of the liquid branch pipes 44a to 44c via first check valves 236a to 236c for indoor units. The first check valves 236a to 236c for indoor units allow the flow of refrigerant from the return pipe 222a to each of the indoor units 300a to 300c and block the flow of refrigerant in the reverse direction. The return pipe 222a is connected to the return pipe 222b and the refrigerant intermediate heat exchanger 226 via a pipe. The return pipe 222b is connected to each of the liquid branch pipes 44a to 44c via second check valves 237a to 237c for indoor units. The second check valves 237a to 237c for indoor units allow the flow of refrigerant from each of the indoor units 300a to 300c to the return pipe 222b and block the flow of refrigerant in the reverse direction.

[0096] The first backflow prevention valve 229 is provided in a pipe connected to the main gas pipe 41, allows the refrigerant to flow from the indoor unit 300 to the heat source unit 100, and blocks the flow of the refrigerant from the heat source unit 100 to the indoor unit 300. When all heating operations and the main heating operation are carried out, the first backflow prevention valve 229 prevents the high-temperature and high-pressure gas refrigerant from flowing back from the discharge-side flow path of the compressor 1 to the flow path opening / closing device 206.

[0097] The second backflow prevention valve 230 is provided in parallel with the first backflow prevention valve 229 in a pipe connected to the main gas pipe 41, allows the refrigerant to flow from the heat source unit 100 to the indoor unit 300, and blocks the flow of the refrigerant from the indoor unit 300 to the heat source unit 100. When all cooling operations and the main cooling operation are carried out, the second backflow prevention valve 230 prevents the high-pressure liquid-state or gas-liquid two-phase state refrigerant that has passed through the gas-liquid separator 202 from flowing back to the refrigerant pipe on the outlet side of the first backflow prevention valve 229, that is, the main gas pipe 41.

[0098] The flow path opening / closing devices 223a to 223c are devices that respectively open and close the flow path of the refrigerant flowing from the heat source unit 100 to the indoor units 300a to 300c and the flow path of the refrigerant flowing from the indoor units 300a to 300c to the heat source unit 100. The flow path opening / closing device 223a includes a first valve 224a and a second valve 225a, the flow path opening / closing device 223b includes a first valve 224b and a second valve 225b, and the flow path opening / closing device 223c includes a first valve 224c and a second valve 225c. In the following description, when describing matters common to the flow path opening / closing devices 223a to 223c, the flow path opening / closing devices 223a to 223c are referred to as the flow path opening / closing device 223. When referring to the flow path opening / closing devices 223a to 223c, it includes both singular and plural. Also, when describing matters common to the first valves 224a to 224c, the first valves 224a to 224c are referred to as the first valve 224. When referring to the first valve 224, it includes both singular and plural. Also, when describing matters common to the second valves 225a to 225c, the second valves 225a to 225c are referred to as the second valve 225. When referring to the second valve 225, it includes both singular and plural.

[0099] The flow path opening / closing device 223 has a first valve 224 and a second valve 225 connected in parallel to the indoor unit 300. The first valve 224 is connected to the low-pressure pipe 220. The first valve 224 opens and closes the flow path between the first backflow prevention valve 229 and the gas branch pipe 43. The first valve 224 is an opening / closing valve that opens and closes the flow path of the refrigerant flowing from the indoor unit 300 toward the heat source unit 100. The second valve 225 is connected to the high-pressure pipe 221. The second valve 225 opens and closes the flow path between the second backflow prevention valve 230 and the gas branch pipe 43. The second valve 225 is an opening / closing valve that opens and closes the flow path of the refrigerant flowing from the heat source unit 100 toward the indoor unit 300. The first valve 224 and the second valve 225 are, for example, electromagnetic valves or throttle valves with adjustable opening degrees having a fully closed function, but the specific valve structure is not limited as long as the flow path can be opened and closed. When one of the first valve 224 and the second valve 225 is in the open state, the other is in the closed state, and both are not in the open state at the same time.

[0100] The refrigerant-to-refrigerant heat exchanger 226 exchanges heat between the refrigerant flowing in the relay unit 200 and the refrigerant. Specifically, the refrigerant-to-refrigerant heat exchanger 226 is provided in the pipe connecting the liquid flow outlet 205 of the gas-liquid separator 202 and the return pipes 222a and 222b. A branch pipe 227 branches from a branch portion 228 between the refrigerant-to-refrigerant heat exchanger 226 and the return pipes 222a and 222b and serves as the flow path of the refrigerant in the refrigerant-to-refrigerant heat exchanger 226. A third opening / closing valve 234 is provided between the branch portion 228 and the refrigerant-to-refrigerant heat exchanger 226 in the branch pipe 227. The branch pipe 227 that has exited the refrigerant-to-refrigerant heat exchanger 226 is connected to the high-pressure pipe 221. Specifically, the end of the branch pipe 227 is connected to the high-pressure pipe 221 on the outlet side of the second backflow prevention valve 230. In the branch pipe 227, a pipe 262 branches from between the connection portion of the refrigerant-to-refrigerant heat exchanger 226 and the high-pressure pipe 221. The pipe 262 is connected to the pipe connecting the low-pressure pipe 220 and the first backflow prevention valve 229. In the refrigerant-to-refrigerant heat exchanger 226, heat exchange is performed between the refrigerant flowing through the pipe 260 and the refrigerant flowing through the branch pipe 227.

[0101] The third on-off valve 234 is constituted by, for example, an electric expansion valve whose opening degree can be adjusted. The operation of the third on-off valve 234 is controlled by the relay control device 201.

[0102] A first on-off valve 232 is provided in a pipe 260 that connects the return pipes 222a and 222b and the liquid main pipe 42 via the gas-liquid separator 202 and the refrigerant intermediate heat exchanger 226. The first on-off valve 232 opens and closes the refrigerant flow path in the pipe 260. The first on-off valve 232 is constituted by, for example, an electric expansion valve or the like whose opening degree can be adjusted. The operation of the first on-off valve 232 is controlled by the relay control device 201.

[0103] A portion between the position where the pipe 262 branches from the branch pipe 227 and the end connected to the high-pressure pipe 221 in the branch pipe 227 is referred to as a pipe 261. A third backflow prevention valve 231 is provided in the pipe 261. The third backflow prevention valve 231 allows the refrigerant to flow from the branch pipe 227 of the refrigerant intermediate heat exchanger 226 to the high-pressure pipe 221, and blocks the refrigerant from flowing in the reverse direction.

[0104] A valve pressure control on-off valve 235 is provided in the pipe 262. During full cooling operation, the high-pressure refrigerant attempting to flow into the indoor unit 300 pushes the closed third on-off valve 234 and passes through it, and can flow into the high-pressure pipe 221 through the pipe 261. However, the refrigerant flowing into the high-pressure pipe 221 loses its flow direction due to the second backflow prevention valve 230, is pressurized, and may become liquid refrigerant when it exceeds the condensation pressure. Therefore, a valve pressure control on-off valve 235 is provided in the pipe 262 provided in parallel with the pipe 261 on the downstream side of the third on-off valve 234. Then, the valve pressure control on-off valve 235 is opened and closed so that the pressure of the refrigerant flowing through the pipe 261 does not exceed the condensation pressure. Thereby, the accumulation of liquid refrigerant in the high-pressure pipe 221 can be suppressed. The opening degree of the valve pressure control on-off valve 235 is controlled by the relay control device 201.

[0105] The pipe 263 connected to the gas outlet 204 of the gas-liquid separator 202 is connected between the first check valve 229 and the on-off valve 235 for valve pressure control in the pipe 262. A second on-off valve 233 is provided in the pipe 263. The second on-off valve 233 opens and closes the refrigerant flow path in the pipe 263. The second on-off valve 233 is composed of, for example, an electric expansion valve whose opening degree can be adjusted. The operation of the second on-off valve 233 is controlled by the relay control device 201.

[0106] The third check valve 231 is provided in the pipe 261, allows the flow of refrigerant from the branch pipe 227 of the refrigerant intermediate heat exchanger 226 toward the high-pressure pipe 221, and blocks the reverse flow of the refrigerant.

[0107] (Operation of the air conditioner) The operation of the air conditioner 1000B will be described with reference to FIGS. 9 to 12. In FIGS. 9 to 12, the flow of the refrigerant is indicated by arrows. Also, among the on-off valves shown in FIGS. 9 to 12, the on-off valves through which the refrigerant does not flow are shown in black.

[0108] (Full cooling operation) In the full cooling operation, all of the indoor units 300a to 300c perform the cooling operation. The flow path switching valve 2 is set such that the discharge side of the compressor 1 is connected to the heat source side heat exchanger 3. As shown in FIG. 9, the low-temperature and low-pressure refrigerant is sucked into the compressor 1 and compressed, and is discharged from the compressor 1 as a high-temperature and high-pressure gas refrigerant. The high-temperature and high-pressure gas refrigerant discharged from the compressor 1 passes through the flow path switching valve 2 and exchanges heat with a fluid such as air in the heat source side heat exchanger 3 that functions as a condenser or radiator, and condenses and liquefies. The high-pressure liquid refrigerant then flows through the heat source side flow control valve 4, flows through the liquid main pipe 42, and flows into the relay unit 200. The refrigerant that has flowed into the relay unit 200 reaches the inside of the gas-liquid separator 202 from the inlet 203.

[0109] The high-pressure liquid refrigerant flowing into the gas-liquid separator 202 flows out from the liquid outlet 205 and passes through the refrigerant intermediate heat exchanger 226. The third on-off valve 234 is in a closed state, and the refrigerant does not flow into the branch pipe 227. The on-off valve 235 for valve pressure control has its opening degree controlled as described above so that the refrigerant in the pipe 261 does not exceed the condensation pressure. The refrigerant flowing out from the refrigerant intermediate heat exchanger 226 passes through the open first on-off valve 232 provided in the pipe 260 and flows into the return pipe 222a. The refrigerant flowing into the return pipe 222a passes through any one of the first backflow prevention valves 236a to 236c for the indoor unit and flows through any one of the liquid branch pipes 44a to 44c. The refrigerant flowing through each of the liquid branch pipes 44a to 44c flows into each of the indoor units 300a to 300c.

[0110] The refrigerant flowing into the indoor units 300a to 300c is decompressed by the load-side flow control valves 32a to 32c respectively. The decompressed refrigerant flows into the load-side heat exchangers 31a to 31c that function as evaporators, and exchanges heat with the indoor air in the load-side heat exchangers 31a to 31c and evaporates and gasifies. At this time, the air-conditioning target space such as the indoor space where the indoor units 300a to 300c are installed is cooled. Then, the refrigerant in the gaseous state flows into the flow path opening and closing devices 223a to 223c of the relay unit 200 through the gas branch pipes 43a to 43c respectively.

[0111] The first valves 224a to 224b are in an open state, and the second valves 225a to 225b are in a closed state. The refrigerant flowing into each of the flow path opening and closing devices 223a to 223c passes through each of the first valves 224a to 224b, further passes through the first backflow prevention valve 229, and flows out from the relay unit 200. The gaseous refrigerant flowing out from the relay unit 200 flows into the heat source unit 100 through the main gas pipe 41. The refrigerant flowing into the heat source unit 100 is sucked into the compressor 1 through the flow path switching valve 2.

[0112] (Cooling main operation) FIG. 10 is a refrigerant circuit diagram showing the state during the cooling main body operation of the air conditioner 1000B according to Embodiment 3. Here, a case will be described as an example where heating operation is performed in the indoor unit 300a, and cooling operation is performed in the indoor units 300b and 300c. The load of the cooling operation is for two indoor units 300b and 300c, while the load of the heating operation is for one indoor unit 300a. Therefore, the load of the cooling operation is larger than the load of the heating operation. The flow path switching valve 2 is set such that the discharge side of the compressor 1 is connected to the heat source side heat exchanger 3.

[0113] As shown in FIG. 10, a low-temperature and low-pressure refrigerant is sucked into the compressor 1 and compressed, and is discharged from the compressor 1 as a high-temperature and high-pressure gas refrigerant. The high-temperature and high-pressure gas refrigerant discharged from the compressor 1 passes through the flow path switching valve 2 and exchanges heat with a fluid such as air in the heat source side heat exchanger 3 that functions as a condenser or radiator, and becomes a gas-liquid two-phase state. The high-pressure gas-liquid two-phase refrigerant then flows through the heat source side flow control valve 4, flows through the liquid main pipe 42, and flows into the relay unit 200. The liquid refrigerant that has flowed into the relay unit 200 reaches the gas-liquid separator 202 from the inlet 203. In the gas-liquid separator 202, the refrigerant is separated into a gaseous refrigerant and a liquid refrigerant.

[0114] The liquid refrigerant flowing out from the liquid outlet 205 of the gas-liquid separator 202 passes through the refrigerant-to-refrigerant heat exchanger 226. A part of the refrigerant that has passed through the refrigerant-to-refrigerant heat exchanger 226 flows from the branch portion 228 to the branch pipe 227, and the remaining refrigerant flows toward the first on-off valve 232 provided in the pipe 260. The amount of the refrigerant flowing from the downstream side of the refrigerant-to-refrigerant heat exchanger 226 to the branch pipe 227 is adjusted by the opening degree of the third on-off valve 234. The on-off valve 235 for valve pressure control is in a closed state.

[0115] The refrigerant flowing through the branch pipe 227 and the pipe 261 passes through the third check valve 231 and flows into the high-pressure pipe 221. The refrigerant flowing into the high-pressure pipe 221 passes through the open first valve 224a, further passes through the gas branch pipe 43a, and flows into the indoor unit 103a. The refrigerant flowing into the indoor unit 103a exchanges heat with the indoor air in the load-side heat exchanger 31a that functions as a condenser or radiator, and condenses and liquefies. At this time, the air-conditioned target space such as the indoor space where the indoor unit 300a is installed is heated. The high-pressure liquid refrigerant flows out from the load-side heat exchanger 31a and passes through the load-side flow control valve 32a. Although the load-side flow control valve 32a is in the fully open state, the refrigerant is slightly depressurized when passing through the load-side flow control valve 32a. The refrigerant passing through the load-side flow control valve 32a flows through the liquid branch pipe 44a and into the relay unit 200.

[0116] The refrigerant flowing into the relay unit 200 passes through the second check valve 237a for the indoor unit and flows into the return pipe 222b, and merges with the refrigerant that has passed through the first on-off valve 232 of the pipe 260. The merged refrigerant flows into the return pipe 222a.

[0117] The refrigerant flowing into the return pipe 222a passes through the first check valve 236b or 236c for the indoor unit and flows through the liquid branch pipe 44b or 44c. The refrigerant flowing through each of the liquid branch pipes 44b or 44c flows into the indoor units 300b or 300c.

[0118] The refrigerant flowing into the indoor units 300b or 300c is depressurized by the load-side flow control valves 32b or 32c respectively. The depressurized refrigerant flows into the load-side heat exchangers 31b and 31c that function as evaporators, and exchanges heat with the indoor air in the load-side heat exchangers 31b and 31c to evaporate and gasify. At this time, the air-conditioned target spaces such as the indoor spaces where the indoor units 300b and 300c are installed are cooled. Then, the refrigerant in the gaseous state flows into the flow path opening / closing devices 223b or 223c of the relay unit 200 through the gas branch pipes 43b or 43c respectively.

[0119] The gas refrigerant flowing into the flow path opening / closing device 223b or 223c merges in the low-pressure pipe 220 after passing through the first valve 224b or 224c respectively, passes through the first check valve 229, and then flows out from the relay unit 200. The gas refrigerant flowing out from the relay unit 200 flows into the heat source unit 100 through the main gas pipe 41. The refrigerant flowing into the heat source unit 100 is sucked into the compressor 1 through the flow path switching valve 2.

[0120] In the cooling main body operation, the adjustment of the amount of refrigerant flowing into the indoor unit 300 performing the cooling operation and the amount of refrigerant flowing into the indoor unit 300 performing the heating operation is adjusted by the heat exchange amount in the heat source side heat exchanger 3. When the required heating load increases, the capacity of the compressor 1 is increased, and the amount of gas refrigerant flowing from the gas-liquid separator 202 into the indoor unit 300 performing the heating operation increases. On the other hand, when the required heating load decreases, the capacity of the compressor 1 is reduced, and the amount of gas refrigerant flowing from the gas-liquid separator 202 into the indoor unit 300 performing the heating operation decreases.

[0121] (Full heating operation) FIG. 11 is a refrigerant circuit diagram showing the state during the full heating operation of the air conditioner 1000B according to Embodiment 3. In the full heating operation, all of the indoor units 300a to 300c perform the heating operation. The flow path switching valve 2 is set so that the discharge side of the compressor 1 is connected to the main gas pipe 41.

[0122] As shown in FIG. 11, the low-temperature and low-pressure refrigerant is sucked into the compressor 1 and compressed, and then discharged from the compressor 1 as a high-temperature and high-pressure gas refrigerant. The high-temperature and high-pressure gas refrigerant discharged from the compressor 1 passes through the flow path switching valve 2, flows through the main gas pipe 41, and then flows into the relay unit 200.

[0123] The high-temperature and high-pressure gas refrigerant flowing into the relay unit 200 passes through the second backflow prevention valve 230 and flows into the high-pressure pipe 221. The refrigerant flowing into the high-pressure pipe 221 flows into each of the flow path opening / closing devices 223a to 223c. Here, the second valves 225a to 225c are in the open state, and the first valves 224a to 224c are in the closed state. The refrigerant flowing into each of the flow path opening / closing devices 223a to 223c passes through each of the first valves 224a to 224c, further passes through each of the gas branch pipes 43a to 43c, and flows into each of the indoor units 300a to 300c.

[0124] The gas refrigerant flowing into each of the indoor units 300a to 300c exchanges heat with the indoor air in the load-side heat exchangers 31a to 31c that function as condensers or radiators, respectively, and condenses and liquefies. At this time, the air-conditioning target space such as the indoor space where the indoor units 300a to 300c are installed is heated. The liquid refrigerant flowing out from each of the indoor units 300a to 300c is depressurized by each of the load-side flow control valves 32a to 32c. Then, the low-pressure liquid refrigerant flows into the relay unit 200 through the liquid branch pipes 44a to 44c, respectively.

[0125] The low-pressure liquid refrigerant flowing into the relay unit 200 through the liquid branch pipes 44a to 44c passes through the second backflow prevention valves 237a to 237c for the indoor unit and flows into the return pipe 222b. The refrigerant flowing into the return pipe 222b passes through the first on-off valve 232, passes through the refrigerant-to-refrigerant heat exchanger 226, and reaches the inside of the gas-liquid separator 202 from the liquid outlet 205. The third on-off valve 234 and the on-off valve 235 for valve pressure control are in the closed state. The low-pressure liquid refrigerant flowing into the gas-liquid separator 202 flows out from the relay unit 200.

[0126] The liquid refrigerant flowing out from the relay unit 200 flows into the heat source unit 100 through the liquid main pipe 42. The refrigerant flowing into the heat source unit 100 passes through the heat source-side flow control valve 4 and flows into the heat source-side heat exchanger 3 that functions as an evaporator. The low-pressure liquid refrigerant exchanges heat with a fluid such as air in the heat source-side heat exchanger 3, absorbs heat, and evaporates and gasifies. The low-pressure gas refrigerant flowing out from the heat source-side heat exchanger 3 is sucked into the compressor 1 through the flow path switching valve 2.

[0127] As described here, when the full heating operation is performed, the high-temperature and high-pressure gas refrigerant flows into each indoor unit 300a to 300c without passing through the gas-liquid separator 202. Since the gas refrigerant does not pass through the gas-liquid separator 202, no pressure loss of the gas refrigerant occurs in the gas-liquid separator 202. Therefore, it is possible to avoid a reduction in the capacity of the air conditioner 1000B due to the pressure loss of the refrigerant in the gas-liquid separator 202.

[0128] (Heating main operation) FIG. 12 is a refrigerant circuit diagram showing the state during the heating main operation of the air conditioner 1000B according to Embodiment 3. Here, a case where the cooling operation is performed in the indoor unit 300a and the heating operations are performed in the indoor units 300b and 300c will be described as an example. Since the load of the heating operation is for two units of the indoor units 300b and 300c, while the load of the cooling operation is for one unit of the indoor unit 300a, the load of the heating operation is larger than the load of the cooling operation. The flow path switching valve 2 is set such that the discharge side of the compressor 1 is connected to the gas main pipe 41.

[0129] As shown in FIG. 12, the low-temperature and low-pressure refrigerant is sucked into the compressor 1 and compressed, and is discharged from the compressor 1 as a high-temperature and high-pressure gas refrigerant. The high-temperature and high-pressure gas refrigerant discharged from the compressor 1 passes through the flow path switching valve 2, flows through the gas main pipe 41, and flows into the relay unit 200.

[0130] The high-temperature and high-pressure gas refrigerant flowing into the relay unit 200 passes through the second backflow prevention valve 230 and flows into each of the flow path opening / closing devices 223a to 223c. Here, the first valves 224b and 224c are in the closed state, and the first valve 224a is in the open state. Also, the second valve 225a is in the closed state, and the second valves 225b and 225c are in the open state. The gas refrigerant flowing into the flow path opening / closing device 223b or 223c passes through the second valves 225b or 225c, respectively, and flows into the indoor unit 300b or 300c through the gas branch pipes 43b or 43c.

[0131] The high-pressure gas refrigerant flowing into the indoor unit 300b or 300c exchanges heat with the indoor air in the load-side heat exchanger 31b or 31c that functions as a condenser or radiator, respectively, and condenses and liquefies. At this time, the air-conditioned target space such as the indoor space where the indoor unit 300b or 300c is installed is heated. The high-pressure liquid refrigerant flows out from the load-side heat exchanger 31b or 31c and is depressurized to a low pressure by the load-side flow control valves 32b or 32c, respectively, to become a refrigerant in a low-temperature and low-pressure gas-liquid two-phase state. The refrigerant in the two-phase state that has passed through the load-side flow control valves 32b or 32c flows into the relay unit 200 through the liquid branch pipes 44b or 44c.

[0132] The low-pressure liquid refrigerant flowing into the relay unit 200 through the liquid branch pipes 44b or 44c passes through the second backflow prevention valve 237b or 237c for the indoor unit and flows into the return pipe 222b. A part of the refrigerant flowing into the return pipe 222b passes through the first on-off valve 232, passes through the refrigerant-to-refrigerant heat exchanger 226, and reaches the inside of the gas-liquid separator 202 from the liquid outlet 205. The third on-off valve 234 and the on-off valve 235 for valve pressure control are in the closed state. The remainder of the refrigerant flowing into the return pipe 222b passes through the return pipe 222a and the first backflow prevention valve 236a for the indoor unit.

[0133] The gas-liquid two-phase state refrigerant that has passed through the first backflow prevention valve 236a for the indoor unit flows into the indoor unit 300a through the liquid branch pipe 44a. The gas-liquid two-phase state refrigerant flowing into the indoor unit 300a is depressurized at the load-side flow control valve 32a and exchanges heat with the indoor air in the load-side heat exchanger 31a that functions as an evaporator, and evaporates and gasifies. At this time, the air-conditioned target space such as the indoor space where the indoor unit 300a is installed is cooled. The gas refrigerant flowing out from the load-side heat exchanger 31a flows into the flow path opening / closing device 223a through the gas branch pipe 43a. The gas refrigerant flowing into the flow path opening / closing device 223a passes through the first valve 224a and flows through the low-pressure pipe 220. The refrigerant flowing through the low-pressure pipe 220 passes through the second on-off valve 233 of the pipe 262 and flows into the inside of the gas-liquid separator 202 through the gas outlet 204. The refrigerant in the gas-liquid separator 202 flows out from the relay unit 200.

[0134] The two-phase refrigerant flowing out of the relay unit 200 flows into the heat source unit 100 through the liquid main pipe 42. The refrigerant flowing into the heat source unit 100 passes through the heat source side flow control valve 4 and flows into the heat source side heat exchanger 3 that functions as an evaporator. The low-pressure gas refrigerant exchanges heat with a fluid such as air in the heat source side heat exchanger 3 and absorbs heat to become a low-temperature and low-pressure gas refrigerant. The low-temperature and low-pressure gas refrigerant flowing out of the heat source side heat exchanger 3 is sucked into the compressor 1 through the flow path switching valve 2.

[0135] As described here, when the main heating operation is carried out, the high-temperature and high-pressure gas refrigerant flows into any one of the indoor units 300a to 300c without passing through the gas-liquid separator 202. Since the gas refrigerant does not pass through the gas-liquid separator 202, no pressure loss of the gas refrigerant occurs in the gas-liquid separator 202. Therefore, it is possible to avoid a reduction in the capacity of the air conditioner 1000 due to the pressure loss of the refrigerant in the gas-liquid separator 202.

[0136] In Embodiments 1 to 3, examples in which the constituent members of the air conditioners 1000 to 1000B are controlled by the heat source unit control device 5, the relay unit control device 201, and the indoor unit control device 33, respectively, have been shown. The physical arrangement of the control devices for controlling the constituent members of the air conditioners 1000 to 1000B is not limited to the examples illustrated in Embodiments 1 to 3. For example, the constituent members of the heat source unit 100, the relay unit 200, and the indoor unit 300 may be controlled by a control device provided in the heat source unit 100.

Explanation of Reference Numerals

[0137] 1 Compressor, 2 Flow path switching valve, 3 Heat source side heat exchanger, 4 Heat source side flow control valve, 5 Heat source machine control device, 31 Load side heat exchanger, 31a Load side heat exchanger, 31b Load side heat exchanger, 31c Load side heat exchanger, 32 Load side flow adjustment valve, 32a Load side flow adjustment valve, 32b Load side flow adjustment valve, 32c Load side flow adjustment valve, 33 Indoor unit control device, 33a Indoor unit control device, 33b Indoor unit control device, 33c Indoor unit control device, 41 Gas main pipe, 42 Liquid main pipe, 43 Gas branch pipe, 43a Gas branch pipe, 43b Gas branch pipe, 43c Gas branch pipe, 44 Liquid branch pipe, 44a Liquid branch pipe, 44b Liquid branch pipe, 44c Liquid branch pipe, 100 Heat source machine, 101 Outdoor unit, 103a Indoor unit, 107 First valve, 107a First valve, 107b First valve, 107c First valve, 200 Relay machine, 201 Relay machine control device, 202 Gas-liquid separator, 203 Inlet, 204 Gas outlet, 205 Liquid outlet, 206 Flow path opening / closing device, 206a Flow path opening / closing device, 206b Flow path opening / closing device, 206c Flow path opening / closing device, 208 Second valve, 208a Second valve, 208b Second valve, 208c Second valve, 209 First backflow prevention valve, 210 Second backflow prevention valve, 211 Backflow prevention valve, 212 Backflow prevention valve, 213 On-off valve, 214 On-off valve, 215 Pressure relief valve, 220 Low pressure pipe, 221 High pressure pipe, 222a Return pipe, 222b Return pipe, 223 Flow path opening / closing device, 223a Flow path opening / closing device, 223b Flow path opening / closing device, 223c Flow path opening / closing device, 224 First valve, 224a First valve, 224b First valve, 224c First valve, 225 Second valve, 225a Second valve, 225b Second valve, 225c Second valve, 226 Refrigerant intermediate heat exchanger, 227 Branch pipe, 228 Branch section, 229 First backflow prevention valve, 230 Second backflow prevention valve, 231 Third backflow prevention valve, 232 First on-off valve, 233 Second on-off valve, 234 Third on-off valve, 235 Valve pressure control on-off valve, 236a First backflow prevention valve for indoor unit, 236b First backflow prevention valve for indoor unit, 236c First backflow prevention valve for indoor unit, 237a Second backflow prevention valve for indoor unit, 237b Second backflow prevention valve for indoor unit, 237c Second backflow prevention valve for indoor unit, 240 Pipe, 241 Pipe, 242 Intersection, 243 Pipe, 244 Pipe, 250 Pipe, 260 Pipe, 261 Pipe, 262 Pipe, 263 Pipe, 300 Indoor unit, 300a Indoor unit, 300bIndoor unit, 300c indoor unit, 1000 air conditioner, 1000A air conditioner, 1000B air conditioner.

Claims

1. A heat source machine having a compressor, a flow path switching valve, and a heat source side heat exchanger; A plurality of indoor units having a load side flow rate adjustment valve and a load side heat exchanger, and performing cooling operation or heating operation; A relay machine that is connected to the heat source machine by a gas main pipe through which a gas refrigerant flows when the cooling operation and the heating operation are performed, and a liquid main pipe through which a liquid refrigerant or a gas-liquid two-phase refrigerant flows when the cooling operation and the heating operation are performed, and is connected to the plurality of indoor units by a gas branch pipe and a liquid branch pipe, and supplies the refrigerant supplied from the heat source machine to the plurality of indoor units; The relay machine includes: A gas-liquid separator that separates the refrigerant into a gas refrigerant and a liquid refrigerant; A plurality of flow path opening and closing devices equal in number to the plurality of indoor units, which open and close the flow path of the refrigerant from the heat source machine to the plurality of indoor units and the flow path of the refrigerant from the plurality of indoor units to the heat source machine respectively; When the heating operation is performed, the relay machine has a path for the refrigerant flowing into the relay machine from the heat source machine through the gas main pipe to flow into the plurality of flow path opening and closing devices without passing through the gas-liquid separator; The plurality of flow path opening and closing devices are controlled so that the cooling operation by any one or more of the plurality of indoor units and the heating operation by any other one or more of the plurality of indoor units are performed simultaneously; The relay machine includes: A first check valve provided in a pipe connected to the gas main pipe, allowing the refrigerant to flow from the indoor unit to the heat source machine and blocking the flow of the refrigerant from the heat source machine to the indoor unit; A second check valve provided in parallel with the first check valve in a pipe connected to the gas main pipe, allowing the refrigerant to flow from the heat source machine to the indoor unit and blocking the flow of the refrigerant from the indoor unit to the heat source machine; A pipe connecting the second check valve's refrigerant outlet is connected to a pipe connecting each of the plurality of flow path opening and closing devices and the gas outlet of the gas-liquid separator for discharging the gas refrigerant; An air conditioner.

2. Comprising a pressure relief valve provided in a pipe communicating the gas main pipe and the gas outlet, When the cooling operation is being performed in any one or more of the plurality of indoor units, the pressure relief valve is in an open state when the pressure of the refrigerant in the pipe connecting each of the plurality of flow path opening and closing devices and the gas outlet of the gas-liquid separator becomes equal to or higher than the saturation pressure of the refrigerant; The air conditioner according to Claim 1.

3. It is provided with a pressure relief valve provided in a pipe that connects the main gas pipe and the gas outlet, When the pressure of the refrigerant in the pipe connecting each of the plurality of flow path opening / closing devices and the gas outlet of the gas-liquid separator is less than the saturation pressure of the refrigerant, the pressure relief valve periodically becomes open. The air conditioner according to claim 1.

4. A heat source machine having a compressor, a flow path switching valve, and a heat source side heat exchanger, A plurality of indoor units having a load side flow rate adjustment valve and a load side heat exchanger, and performing a cooling operation or a heating operation, Connected to the heat source machine by a main gas pipe through which a gas refrigerant flows when the cooling operation and the heating operation are performed, and a main liquid pipe through which a liquid refrigerant or a gas-liquid two-phase refrigerant flows when the cooling operation and the heating operation are performed, and connected to the plurality of indoor units by a gas branch pipe and a liquid branch pipe, and a relay machine that supplies the refrigerant supplied from the heat source machine to the plurality of indoor units, The relay machine, A gas-liquid separator that separates the refrigerant into a gas refrigerant and a liquid refrigerant, It is provided with a plurality of flow path opening / closing devices equal in number to the plurality of indoor units, which open and close the flow path of the refrigerant from the heat source machine to the plurality of indoor units and the flow path of the refrigerant from the plurality of indoor units to the heat source machine respectively, When the heating operation is performed, the relay machine has a path for the refrigerant that has flowed into the relay machine from the heat source machine through the main gas pipe to flow into the plurality of flow path opening / closing devices without passing through the gas-liquid separator, The plurality of flow path opening / closing devices are controlled so that the cooling operation by any one or more of the plurality of indoor units and the heating operation by any other one or more of the plurality of indoor units are simultaneously performed, Each of the plurality of flow path opening / closing devices includes a first valve and a second valve, A low-pressure pipe that connects the main gas pipe and the first valve and through which the low-pressure refrigerant flows, A high-pressure pipe that connects the main gas pipe and the second valve and through which the high-pressure refrigerant flows, When the cooling operation by any one or more of the plurality of indoor units and the heating operation by any other one or more of the plurality of indoor units are simultaneously performed, a return pipe that allows the refrigerant flowing out from the one or more indoor units performing the heating operation to flow into the one or more indoor units performing the cooling operation, A first on-off valve provided in a pipe that connects the return pipe and the main liquid pipe, A first check valve connected to the low-pressure pipe, allowing the refrigerant to flow from the indoor unit to the heat source unit and blocking the refrigerant from flowing from the heat source unit to the indoor unit. A second check valve connected to the high-pressure pipe, allowing the refrigerant to flow from the heat source unit to the indoor unit and blocking the refrigerant from flowing from the indoor unit to the heat source unit, and An air conditioner.

5. A second on-off valve provided in a pipe connecting the gas outlet for discharging the gaseous refrigerant of the gas-liquid separator and the low-pressure pipe. A refrigerant intermediate heat exchanger provided between the liquid outlet for discharging the liquid refrigerant of the gas-liquid separator and the return pipe. A branch pipe branched from a branch portion between the refrigerant intermediate heat exchanger and the return pipe and connected to the high-pressure pipe via the refrigerant intermediate heat exchanger. A third on-off valve provided in the branch pipe between the branch portion and the refrigerant intermediate heat exchanger. A third check valve provided in the branch pipe between the refrigerant intermediate heat exchanger and the high-pressure pipe, allowing the refrigerant to flow from the refrigerant intermediate heat exchanger to the high-pressure pipe and blocking the refrigerant from flowing from the high-pressure pipe to the refrigerant intermediate heat exchanger. When the cooling operation by any one or more of the plurality of indoor units and the heating operation by any other one or more of the plurality of indoor units are simultaneously performed, and when the load of the cooling operation is greater than the load of the heating operation, the refrigerant branched from the branch portion passes through the third on-off valve, the refrigerant intermediate heat exchanger, and the third check valve and flows into the high-pressure pipe. The air conditioner according to claim 4.

6. The second on-off valve is in an open state when the cooling operation by any one or more of the plurality of indoor units and the heating operation by any other one or more of the plurality of indoor units are simultaneously performed, and when the load of the heating operation is greater than the load of the cooling operation, allowing the refrigerant to flow from the low-pressure pipe to the gas outlet. The air conditioner according to claim 5.

7. An air conditioner provided with an on-off valve for valve pressure control provided in a pipe connecting a pipe connecting the second on-off valve and the low-pressure pipe and a pipe connecting the refrigerant intermediate heat exchanger and the third check valve. The air conditioner according to claim 5 or claim 6.

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