Air conditioner

Abstract

This air conditioning device comprises: a heat source machine having a compressor, a flow path switching valve, and a heat source-side heat exchanger; an indoor unit that has a load-side flow rate adjustment valve and a load-side heat exchanger, and performs a cooling operation or a heating operation; a relay that is connected to the heat source machine by a low-pressure tube and a high-pressure tube, is connected to the indoor unit by a gas branch tube and a liquid branch tube, and supplies, to the indoor unit, a refrigerant supplied from the heat source machine; and a control device, wherein the relay comprises a branch part that allows communication between the gas branch tube and the low-pressure tube when the indoor unit performs the cooling operation, and allows communication between the gas branch tube and the high-pressure tube when the indoor unit performs the heating operation, the branch part has an expansion valve which is connected to the gas branch tube and the low-pressure tube and of which the opening degree is adjustable, and the control device controls the expansion valve such that communication is allowed between the gas branch tube and the low-pressure tube when the heat source machine is stopped.

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] An air conditioner using a refrigeration cycle includes a heat source unit having a compressor and a heat source side heat exchanger, an indoor unit having an expansion valve and a load side heat exchanger, and a refrigerant circuit through which refrigerant flows, which are connected by piping. When the refrigerant evaporates or condenses in the load side heat exchanger, the air conditioner performs air conditioning while changing the pressure and temperature of the refrigerant flowing through the refrigerant circuit by absorbing or releasing heat to the air in the air conditioning target space that is the heat exchange target.

[0003] In addition, an air conditioner including a heat source unit, a plurality of indoor units, and a relay unit that distributes the refrigerant supplied from the heat source unit to the plurality of indoor units is also known. In such an air conditioner, according to the set temperature and indoor temperature set by a remote controller, etc., in each of the plurality of indoor units, the necessity of cooling operation or heating operation is automatically determined, and a simultaneous cooling and heating operation in which each indoor unit performs a cooling operation or a heating operation is carried out. As an air conditioner that performs a simultaneous cooling and heating operation, Patent Document 1 discloses a configuration in which, in a relay unit between a heat source unit and an indoor unit, the flow of refrigerant during cooling operation and the flow of refrigerant during heating operation are switched by two electromagnetic valves.

Prior Art Documents

Patent Documents

[0004]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0005] In the configuration of Patent Document 1, when the power supply to the air conditioner is stopped to perform evacuation or the like, the solenoid valve of the relay unit closes. Therefore, in order to enable evacuation of the gas branch pipe connecting the relay unit and the indoor unit, it is necessary to provide, for example, an orifice in the solenoid valve for cooling switching. However, when an orifice is provided in the solenoid valve for cooling switching, a part of the refrigerant supplied from the compressor during heating operation flows through the orifice of the solenoid valve for cooling switching to the low-pressure pipe without passing through the indoor unit, resulting in a decrease in the heating capacity of the indoor unit. On the other hand, if the diameter of the orifice is reduced to suppress the decrease in heating capacity, the air flow rate flowing through the orifice during evacuation of the entire air conditioner decreases, and it takes time for evacuation. Therefore, in the conventional high-back type, there is a problem that improvement in heating capacity and reduction in evacuation time are in a trade-off relationship, and it is difficult to achieve both of them.

[0006] The present disclosure solves the above problems, and provides an air conditioner that can suppress a decrease in heating capacity and reduce evacuation time.

Means for Solving the Problems

[0007] The air conditioner according to the present disclosure includes a heat source unit having a compressor, a flow path switching valve, and a heat source side heat exchanger, an indoor unit having a load side flow rate adjustment valve and a load side heat exchanger and performing cooling operation or heating operation, a relay unit connected to the heat source unit by a low-pressure pipe and a high-pressure pipe and connected to the indoor unit by a gas branch pipe and a liquid branch pipe and supplying the refrigerant supplied from the heat source unit to the indoor unit, and a control device. The relay unit includes a branch portion that communicates the gas branch pipe and the low-pressure pipe when the indoor unit performs a cooling operation, and communicates the gas branch pipe and the high-pressure pipe when the indoor unit performs a heating operation. The branch portion , open has an expansion valve whose degree can be adjusted, The expansion valve is connected to the gas branch pipe and the low-pressure pipe, The control device controls the expansion valve so that the gas branch pipe and the low-pressure pipe communicate with each other when the heat source unit stops.

Effects of the Invention

[0008] According to the air conditioner of the present disclosure, by providing an expansion valve with an adjustable opening degree at the branch portion of the relay machine, the low-pressure pipe can be closed during the heating operation, and the gas branch pipe and the low-pressure pipe can be communicated to open the low-pressure pipe during the stop. Thereby, it is possible to suppress a decrease in heating capacity and reduce the evacuation time.

Brief Description of the Drawings

[0009]

Figure 1

Figure 2

Figure 3

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Figure 8

Figure 9

Modes for Carrying Out the Invention

[0010] Hereinafter, embodiments will be described with reference to the drawings. In each figure, those denoted by the same reference numerals are the same or corresponding ones, which is common throughout the entire specification. Also, the forms of the constituent elements shown throughout the entire specification are merely examples and are not limited to these descriptions. Furthermore, in the following drawings, the relationship of the sizes of the respective constituent members may be different from the actual ones.

[0011] Embodiment 1. FIG. 1 is a refrigerant circuit diagram of the air conditioner 1 according to Embodiment 1. As shown in FIG. 1, the air conditioner 1 includes a heat source unit 100, a plurality of indoor units 300a and 300b, a relay unit 200, and a control device 10. In Embodiment 1, a configuration in which two indoor units 300a and 300b are connected to one heat source unit 100 will be described, but the number of the heat source unit 100 and the relay unit 200 may be two or more. Also, the number of indoor units may be one or three or more.

[0012] (Configuration of the air conditioner) As shown in FIG. 1, the air conditioner 1 is configured by connecting a heat source unit 100, indoor units 300a and 300b, and a relay unit 200. The heat source unit 100 has a function of supplying heat to two indoor units 300a and 300b. The indoor units 300a and 300b are connected in parallel with each other and have the same configuration. The indoor units 300a and 300b have a function of cooling or heating an air-conditioning target 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 and 300b, 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 and 300b and supplying it to the indoor units 300a and 300b.

[0013] The heat source unit 100 and the relay unit 200 are connected on the high-pressure side by a high-pressure pipe 402 through which high-pressure refrigerant flows, and on the low-pressure side by a low-pressure pipe 401 through which low-pressure refrigerant flows. Also, the relay unit 200 and the indoor units 300a and 300b are connected by gas branch pipes 403a and 403b, and liquid branch pipes 404a and 404b, respectively. The gas branch pipes 403a and 403b mainly carry refrigerant in a gaseous state. The liquid branch pipes 404a and 404b mainly carry refrigerant in a liquid state.

[0014] (Heat source unit 100) The heat source unit 100 includes a compressor 101, a flow path switching valve 102, a heat source side heat exchange unit 120, an accumulator 104, and a heat source side flow path adjustment unit 140. The compressor 101 is a fluid machine that sucks in and compresses low-pressure gas refrigerant and discharges it as high-pressure gas refrigerant. The compressor 101 is, for example, an inverter-driven compressor whose operating frequency can be adjusted. The flow path switching valve 102 is a four-way valve that switches the flow path of the refrigerant discharged from the compressor 101. Note that the flow path switching valve 102 may be configured by combining a two-way valve or a three-way valve, etc.

[0015] The heat source side heat exchange unit 120 includes a main pipe 114, a heat source side heat exchanger 103, a heat source side blower 111, a bypass pipe 113, a heat source side flow rate adjustment valve 109, and a bypass flow rate adjustment valve 110. The heat source side heat exchanger 103 is a heat exchanger that performs heat exchange between the refrigerant flowing inside and the air blown by the heat source side blower 111. The heat source side heat exchanger 103 functions as an evaporator or a condenser. Note that the heat source side heat exchanger 103 may be a water-cooled heat exchanger that performs heat exchange between, for example, water or brine and the refrigerant.

[0016] The heat source side blower 111 is a propeller fan, a cross-flow fan, or a multi-wing centrifugal fan that supplies air to the heat source side heat exchanger 103. By controlling the rotation speed of the heat source side blower 111, the heat exchange capacity is controlled. Note that when the heat source side heat exchanger 103 is water-cooled, the heat source side blower 111 is omitted, and instead, a pump for circulating the heat medium is provided.

[0017] The main pipe 114 is connected to the flow path switching valve 102 on one side and to the high-pressure pipe 402 on the other side, and the heat source side heat exchanger 103 and the heat source side flow rate adjustment valve 109 are provided. The bypass pipe 113 is connected to the flow path switching valve 102 on one side and to the high-pressure pipe 402 on the other side, and is connected in parallel to the main pipe 114. The refrigerant flowing through the bypass pipe 113 does not pass through the heat source side heat exchanger 103 and is not heat-exchanged.

[0018] The heat source side flow rate adjustment valve 109 is connected in series to the heat source side heat exchanger 103 in the main pipe 114, and adjusts and reduces the pressure of the refrigerant flowing through the main pipe 114. The heat source side flow rate adjustment valve 109 is composed of, for example, a two-way electric expansion valve whose opening degree can be adjusted. The bypass flow rate adjustment valve 110 is provided in the bypass pipe 113, and adjusts and reduces the pressure of the refrigerant flowing through the bypass pipe 113. The bypass flow rate adjustment valve 110 is composed of, for example, an electric expansion valve whose opening degree can be adjusted.

[0019] The accumulator 104 is provided between the flow path switching valve 102 and the suction port of the compressor 101. The accumulator 104 has a refrigerant storage function for storing surplus refrigerant and a gas-liquid separation function for separating the gas-liquid two-phase refrigerant flowing into the accumulator 104, discharging the gas refrigerant to the compressor 101, and retaining the liquid refrigerant.

[0020] The heat source side flow path adjustment unit 140 has a third check valve 105, a fourth check valve 106, a fifth check valve 107, and a sixth check valve 108. The third check valve 105 is provided in a pipe connecting the heat source side heat exchange unit 120 and the high-pressure pipe 402, and allows the flow of refrigerant from the heat source side heat exchange unit 120 toward the high-pressure pipe 402. The fourth check valve 106 is provided in a pipe connecting the flow path switching valve 102 of the heat source machine 100 and the low-pressure pipe 401, and allows the flow of refrigerant from the low-pressure pipe 401 toward the flow path switching valve 102. The fifth check valve 107 is provided in a pipe connecting the flow path switching valve 102 of the heat source machine 100 and the high-pressure pipe 402, and allows the flow of refrigerant from the flow path switching valve 102 toward the high-pressure pipe 402. The sixth check valve 108 is provided in a pipe connecting the heat source side heat exchange unit 120 and the low-pressure pipe 401, and allows the flow of refrigerant from the low-pressure pipe 401 toward the heat source side heat exchange unit 120.

[0021] Also, a discharge pressure sensor 126 is provided in the heat source machine 100. The discharge pressure sensor 126 is provided in a pipe connecting the flow path switching valve 102 and the discharge side of the compressor 101, and detects the pressure of the refrigerant discharged from the compressor 101. The discharge pressure sensor 126 transmits a signal of the detected discharge pressure to the control device 10.

[0022] Also, a suction pressure sensor 127 is provided in the heat source machine 100. The suction pressure sensor 127 is provided in a pipe connecting the flow path switching valve 102 and the accumulator 104, and detects the pressure of the refrigerant sucked into the compressor 101. The suction pressure sensor 127 transmits a signal of the detected suction pressure to the control device 10.

[0023] Note that the discharge pressure sensor 126 and the suction pressure sensor 127 may each have a storage device or the like. In this case, each pressure sensor accumulates the detected pressure data in a storage device or the like for a predetermined period, and transmits a signal including the pressure data accumulated every predetermined cycle to the control device 10.

[0024] In addition, the heat source machine 100 is provided with refrigerant charging parts 131 and 132. The refrigerant charging part 131 is provided in a pipe connecting the flow path switching valve 102 and the discharge side of the compressor 101, and enables refrigerant charging or evacuation from the discharge side of the compressor 101. The refrigerant charging part 132 is provided in a pipe connecting the flow path switching valve 102 and the accumulator 104, and enables refrigerant charging or evacuation from the suction side of the compressor 101. The refrigerant charging parts 131 and 132 are composed of, for example, check joints or the like.

[0025] (Indoor units 300a and 300b) The indoor units 300a and 300b each include load side heat exchangers 301a and 301b that function as condensers or evaporators, and load side flow control valves 302a and 302b that adjust the flow rate of the refrigerant flowing through the indoor units 300a and 300b. The load side heat exchangers 301a and 301b are heat exchangers that perform heat exchange between the refrigerant flowing inside and the air blown by an indoor blower (not shown). Note that the load side heat exchangers 301a and 301b may be water-cooled heat exchangers that perform heat exchange, for example, between water or brine and the refrigerant.

[0026] The load side flow control valves 302a and 302b adjust and depressurize the flow rate of the refrigerant flowing into or flowing out of the load side heat exchangers 301a and 301b. The load side flow control valves 302a and 302b are composed of, for example, two-way electric expansion valves whose opening degrees can be adjusted. The opening degrees of the load side flow control valves 302a and 302b during cooling are respectively controlled by the control device 10 based on the superheat degree on the outlet side of the load side heat exchangers 301a and 301b. Also, the opening degrees of the load side flow control valves 302a and 302b during heating are respectively controlled by the control device 10 based on the subcooling degree on the outlet side of the load side heat exchangers 301a and 301b.

[0027] The indoor units 300a and 300b are respectively provided with gas pipe temperature sensors 304a and 304b, and liquid pipe temperature sensors 303a and 303b. The gas pipe temperature sensors 304a and 304b are respectively provided between the load side heat exchangers 301a and 301b and the relay unit 200. The gas pipe temperature sensors 304a and 304b detect the temperature of the refrigerant flowing through the gas branch pipes 403a and 403b that connect the load side heat exchangers 301a and 301b and the relay unit 200. The gas pipe temperature sensors 304a and 304b are composed of, for example, thermistors, etc., and transmit the detected temperature signal to the control device 10.

[0028] The liquid pipe temperature sensors 303a and 303b are respectively provided between the load side heat exchangers 301a and 301b and the load side flow control valves 302a and 302b. The liquid pipe temperature sensors 303a and 303b detect the temperature of the refrigerant flowing through the pipes that connect the load side heat exchangers 301a and 301b and the load side flow control valves 302a and 302b. The liquid pipe temperature sensors 303a and 303b are composed of, for example, thermistors, etc., and transmit the detected temperature signal to the control device 10.

[0029] The gas pipe temperature sensors 304a and 304b, and the liquid pipe temperature sensors 303a and 303b may each have a storage device or the like. In this case, each temperature sensor accumulates the detected temperature data in a storage device or the like for a predetermined period, and transmits a signal including the temperature data accumulated every predetermined cycle to the control device 10.

[0030] (Relay unit 200) The relay unit 200 includes a first branch portion 240, a second branch portion 250, a gas-liquid separator 201, a relay bypass pipe 209, a first flow control valve 204, a second flow control valve 205, a first heat exchange portion 206, and a second heat exchange portion 207.

[0031] The first branch portion 240 has one side connected to the gas branch pipes 403a and 403b, and the other side connected to the low-pressure pipe 401 and the high-pressure pipe 402. The first branch portion 240 connects the gas branch pipes 403a and 403b to the low-pressure pipe 401 or the high-pressure pipe 402, and makes the refrigerant flow direction during the cooling operation different from the refrigerant flow direction during the heating operation. The first branch portion 240 is provided with three-way electric expansion valves 202a and 202b whose opening degrees can be adjusted.

[0032] The three-way electric expansion valve 202a is connected to the gas branch pipe 403a, the high-pressure pipe 402, and the low-pressure pipe 401. The three-way electric expansion valve 202b is connected to the gas branch pipe 403b, the high-pressure pipe 402, and the low-pressure pipe 401. The three-way electric expansion valves 202a and 202b have the function of switching the refrigerant flow direction and the function of adjusting the refrigerant flow rate. Specifically, the three-way electric expansion valve 202a has a first flow path that connects the gas branch pipe 403a and the low-pressure pipe 401, and a second flow path that connects the gas branch pipe 403a and the high-pressure pipe 402. Similarly, the three-way electric expansion valve 202b has a first flow path that connects the gas branch pipe 403b and the low-pressure pipe 401, and a second flow path that connects the gas branch pipe 403b and the high-pressure pipe 402. Then, by controlling the opening degrees of the three-way electric expansion valves 202a and 202b by the control device 10, the first flow path and the second flow path are opened and closed, and the flow rate of the refrigerant flowing through the first flow path and the second flow path is adjusted.

[0033] When the indoor unit 300a performs a cooling operation, the three-way electric expansion valve 202a controls the opening degree so as to open the first flow path that communicates the gas branch pipe 403a and the low-pressure pipe 401 and close the second flow path. Also, when the indoor unit 300a performs a heating operation, the three-way electric expansion valve 202a controls the opening degree so as to open the second flow path that communicates the gas branch pipe 403a and the high-pressure pipe 402 and close the first flow path. Similarly, when the indoor unit 300b performs a cooling operation, the three-way electric expansion valve 202b controls to open the first flow path that communicates the gas branch pipe 403b and the low-pressure pipe 401 and close the second flow path. Also, when the indoor unit 300b performs a heating operation, the three-way electric expansion valve 202b controls to open the second flow path that communicates the gas branch pipe 403b and the high-pressure pipe 402 and close the first flow path.

[0034] One side of the second branch portion 250 is connected to the liquid branch pipes 404a and 404b, and the other side is connected to the low-pressure pipe 401 and the high-pressure pipe 402. The second branch portion 250 connects the liquid branch pipes 404a and 404b to the low-pressure pipe 401 or the high-pressure pipe 402, and makes the refrigerant flow direction during the cooling operation different from the refrigerant flow direction during the heating operation. The second branch portion 250 has the first check valves 210a and 210b and the second check valves 211a and 211b.

[0035] One side of each of the first check valves 210a and 210b is connected to the liquid branch pipes 404a and 404b, and the other side of each is connected to the high-pressure pipe 402, allowing the refrigerant to flow from the high-pressure pipe 402 toward the liquid branch pipes 404a and 404b.

[0036] One side of each of the second check valves 211a and 211b is connected to the liquid branch pipes 404a and 404b, and the other side of each is connected to the low-pressure pipe 401, allowing the refrigerant to flow from the liquid branch pipes 404a and 404b toward the low-pressure pipe 401.

[0037] The gas-liquid separator 201 separates the refrigerant in a gaseous state from the refrigerant in a liquid state. The inflow side is connected to the high-pressure pipe 402, the gas outflow side is connected to the first branch portion 240, and the liquid outflow side is connected to the second branch portion 250. The relay bypass pipe 209 connects the second branch portion 250 and the low-pressure pipe 401. The first flow rate adjustment valve 204 is connected to the liquid outflow side of the gas-liquid separator 201 and is composed of, for example, a two-way electric expansion valve capable of adjusting the opening degree. The first flow rate adjustment valve 204 adjusts the flow rate of the refrigerant in a liquid state flowing out from the gas-liquid separator 201 and reduces the pressure.

[0038] The first heat exchange portion 206 is provided between the liquid outflow side of the gas-liquid separator 201 and the first flow rate adjustment valve 204, and in the relay bypass pipe 209. The first heat exchange portion 206 exchanges heat between the refrigerant in a liquid state flowing out from the gas-liquid separator 201 and the refrigerant flowing in the relay bypass pipe 209. The second heat exchange portion 207 is provided on the downstream side of the first flow rate adjustment valve 204 and in the relay bypass pipe 209. The second heat exchange portion 207 exchanges heat between the refrigerant flowing out from the first flow rate adjustment valve 204 and the refrigerant flowing in the relay bypass pipe 209.

[0039] The second flow rate adjustment valve 205 is connected to the upstream side of the second heat exchange portion 207 in the relay bypass pipe 209 and is composed of, for example, a two-way electric expansion valve capable of adjusting the opening degree. The second flow rate adjustment valve 205 adjusts the flow rate of the refrigerant flowing into the relay bypass pipe 209 among the refrigerant flowing out from the second heat exchange portion 207 and reduces the pressure.

[0040] Here, the upstream sides of the first check valves 210a and 210b are connected to the downstream side of the second heat exchanger 207 and the relay bypass pipe 209. Therefore, the refrigerant flowing out from the second heat exchanger 207 is divided into the refrigerant flowing toward the first check valves 210a and 210b and the refrigerant flowing into the relay bypass pipe 209. Also, the downstream sides of the second check valves 211a and 211b are connected between the first flow control valve 204 and the upstream side of the second heat exchanger 207. That is, the refrigerant flowing out from the second check valves 211a and 211b flows into the second heat exchanger 207 for heat exchange and then is divided into the refrigerant flowing toward the first check valves 210a and 210b and the refrigerant flowing into the relay bypass pipe 209.

[0041] In addition, the relay unit 200 is provided with a first pressure sensor 231, a second pressure sensor 232, and a relay bypass temperature sensor 208. The first pressure sensor 231 is provided between the first heat exchanger 206 and the upstream side of the first flow control valve 204, and detects the pressure of the refrigerant on the liquid outflow side of the gas-liquid separator 201. The first pressure sensor 231 transmits the detected pressure signal to the control device 10.

[0042] The second pressure sensor 232 is provided between the downstream side of the first flow control valve 204 and the second heat exchanger 207, and detects the pressure of the refrigerant flowing out from the first flow control valve 204. The second pressure sensor 232 transmits the detected pressure signal to the control device 10. The opening degree of the first flow control valve 204 is adjusted by the control device 10 so that the difference between the pressure detected by the first pressure sensor 231 and the pressure detected by the second pressure sensor 232 becomes constant.

[0043] The relay bypass temperature sensor 208 is provided in the relay bypass pipe 209 and detects the temperature of the refrigerant flowing through the relay bypass pipe 209. The relay bypass temperature sensor 208 is composed of, for example, a thermistor, etc., and transmits the detected temperature signal to the control device 10. The second flow rate adjustment valve 205 has its opening degree adjusted by the control device 10 based on at least one or more of the pressure detected by the first pressure sensor 231, the pressure detected by the second pressure sensor 232, and the temperature detected by the relay bypass temperature sensor 208.

[0044] Note that the first pressure sensor 231, the second pressure sensor 232, and the relay bypass temperature sensor 208 may have a storage device or the like. In this case, each pressure sensor and temperature sensor accumulates the detected pressure or temperature data in a storage device or the like for a predetermined period, and transmits a signal including the pressure or temperature data accumulated every predetermined cycle to the control device 10.

[0045] (Refrigerant) The air conditioner 1 has a refrigerant filled inside the piping. The refrigerant is, for example, a natural refrigerant such as carbon dioxide (CO2), hydrocarbon, helium, etc., a chlorine-free refrigerant substitute such as HFC410A, HFC407C, HFC404A, etc., or a fluorocarbon refrigerant such as R22, R134a, etc. used in existing products. Note that HFC407C is a zeotropic mixture refrigerant in which R32, R125, and R134a of HFC are mixed at ratios of 23 wt%, 25 wt%, and 52 wt% respectively. Also, the inside of the piping of the air conditioner 1 may be filled with a heat medium instead of a refrigerant. The heat medium is, for example, water or brine.

[0046] (Control device 10) The control device 10 controls the operation of the entire air conditioner 1. The control device 10 is composed of a computer, dedicated hardware such as an ASIC or FPGA, or both, which includes a memory for storing data and programs necessary for control, and a CPU for executing programs. The control device 10 controls the drive frequency of the compressor 101, the rotation speeds of the heat source side blower 111 and the indoor blowers (not shown) provided in the indoor units 300a and 300b, the switching of the flow path switching valve 102, the opening degrees of the three-way electric expansion valves 202a and 202b, the heat source side flow rate adjustment valve 109, the bypass flow rate adjustment valve 110, the load side flow rate adjustment valves 302a and 302b, and the opening degrees of the first flow rate adjustment valve 204 and the second flow rate adjustment valve 205, based on the detection information received from the gas pipe temperature sensors 304a and 304b, the liquid pipe temperature sensors 303a and 303b, the first pressure sensor 231, the second pressure sensor 232, the relay bypass temperature sensor 208, the discharge pressure sensor 126, and the suction pressure sensor 127, and instructions from a remote controller (not shown).

[0047] Further, the control device 10 may calculate the cooling capacity or heating capacity in the cooling main operation and heating main operation from the discharge pressure detected by the discharge pressure sensor 126 or the suction pressure detected by the suction pressure sensor 127. Alternatively, the control device 10 may calculate the cooling capacity or heating capacity in the cooling main operation and heating main operation using the evaporation temperature and condensation temperature obtained from the temperatures detected by the gas pipe temperature sensors 304a and 304b and the liquid pipe temperature sensors 303a and 303b.

[0048] Note that in FIG. 1, the control device 10 is mounted on the heat source unit 100, but it is not limited thereto, and it may be mounted on any of the relay unit 200, the indoor unit 300a, or 300b, or may be provided separately from the heat source unit 100, the relay unit 200, the indoor unit 300a, or 300b. Alternatively, the heat source unit 100, the relay unit 200, the indoor units 300a and 300b may each be provided with a control device and be communicably connected to each other wirelessly or by wire to transmit and receive various data and the like.

[0049] Next, the operations of the three-way electric expansion valves 202a and 202b in the first branch section 240 will be described. FIG. 2 is a graph showing the relationship between the control amount and the opening degree of the three-way electric expansion valve 202a according to the first embodiment. The relationship between the control amount and the opening degree of the three-way electric expansion valve 202b is the same as the relationship between the control amount and the opening degree of the three-way electric expansion valve 202a shown in FIG. 2. In FIG. 2, the vertical axis represents the opening degree of the three-way electric expansion valve 202a, and the horizontal axis represents the control amount transmitted from the control device 10 to the three-way electric expansion valve 202a. The "control amount" here corresponds to the number of pulses of the pulse signal transmitted from the control device 10 to the three-way electric expansion valve 202a.

[0050] In FIG. 2, in the three-way electric expansion valve 202a, when the control amount is less than P1, the first flow path that connects the gas branch pipe 403a and the low-pressure pipe 401 is opened, and the second flow path that connects the gas branch pipe 403a and the high-pressure pipe 402 is closed. Also, when the control amount is the minimum control amount Pmin, the opening degree of the first flow path of the three-way electric expansion valve 202a becomes the maximum opening degree A1, and as the control amount increases, the opening degree of the first flow path of the three-way electric expansion valve 202a decreases.

[0051] Next, when the control amount is equal to or greater than P1 and less than P2, regardless of the control amount, both the first flow path and the second flow path of the three-way electric expansion valve 202a are closed. Further, when the control amount is equal to or greater than P2, the second flow path that connects the gas branch pipe 403a and the high-pressure pipe 402 is opened, and the first flow path that connects the gas branch pipe 403a and the low-pressure pipe 401 is closed. Also, when the control amount is the maximum control amount Pmax, the opening degree of the second flow path of the three-way electric expansion valve 202a becomes the maximum opening degree A1, and as the control amount decreases, the opening degree of the second flow path of the three-way electric expansion valve 202a decreases.

[0052] (Operation of the air conditioner) Next, the operation of the air conditioner 1 will be described. The air conditioner 1 has, as operation modes, full cooling operation, full heating operation, cooling-dominant operation, and heating-dominant operation. The full cooling operation is a mode in which all of the indoor units 300a and 300b perform cooling operation. The full heating operation is a mode in which all of the indoor units 300a and 300b perform heating operation. The cooling-dominant operation is a mode in which, among the simultaneous cooling and heating operations, the capacity of the cooling operation is larger than the capacity of the heating operation. The heating-dominant operation is a mode in which, among the simultaneous cooling and heating operations, the capacity of the heating operation is larger than the capacity of the cooling operation. The control device 10 performs full cooling operation, full heating operation, cooling-dominant operation, or heating-dominant operation according to the operation requests for the indoor units 300a and 300b. Each operation will be described with reference to FIGS. 3 to 6. In FIGS. 3 to 6, the high-pressure refrigerant is indicated by a solid line arrow, and the low-pressure refrigerant is indicated by a broken line arrow. Also, in FIGS. 3 to 6, among the check valves, the check valve through which the refrigerant does not flow is shown in black.

[0053] (Full cooling operation) First, the full cooling operation will be described. FIG. 3 is a refrigerant circuit diagram showing the state during the full cooling operation of the air conditioner 1 according to the first embodiment. In the full cooling operation, all of the indoor units 300a and 300b perform cooling operation. As shown in FIG. 3, the high-temperature and high-pressure gas refrigerant discharged from the compressor 101 passes through the flow path switching valve 102 and is heat-exchanged with the outdoor air blown by the heat source side blower 111 in the heat source side heat exchanger 103 and condenses and liquefies. The condensed and liquefied refrigerant then reaches the gas-liquid separator 201 through the heat source side flow rate adjustment valve 109, the third check valve 105, and the high-pressure pipe 402. Here, since the bypass flow rate adjustment valve 110 is fully closed, no refrigerant flows through the bypass pipe 113.

[0054] Then, the refrigerant is separated into a gaseous refrigerant and a liquid refrigerant by the gas-liquid separator 201. The liquid refrigerant flows out from the liquid outlet side and flows in the order of the first heat exchanger 206, the first flow control valve 204, and the second heat exchanger 207, and branches at the second branch portion 250. The branched refrigerants flow into the indoor units 300a and 300b through the first check valves 210a and 210b, and the liquid branch pipes 404a and 404b, respectively. In the full cooling operation, since the liquid branch pipes 404a and 404b are at a lower pressure than the high-pressure pipe 402, no refrigerant flows through the second check valves 211a and 211b.

[0055] Then, the refrigerants flowing into the indoor units 300a and 300b are decompressed to a low pressure by the load-side flow control valves 302a and 302b controlled based on the superheat degrees at the outlet sides of the load-side heat exchangers 301a and 301b, respectively. The decompressed refrigerants flow into the load-side heat exchangers 301a and 301b, and are heat-exchanged with the indoor air in the load-side heat exchangers 301a and 301b to evaporate and gasify. At this time, the room where the indoor units 300a and 300b are installed is cooled. Then, the refrigerants in the gaseous state flow into the first branch portion 240 of the relay unit 200 through the gas branch pipes 403a and 403b, respectively.

[0056] During the full cooling operation, the control device 10 controls the opening degrees of the three-way electric expansion valves 202a and 202b so that the first flow path communicating with the low-pressure pipe 401 is opened and the second flow path communicating with the high-pressure pipe 402 is closed. Therefore, the refrigerants flowing into the first branch portion 240 pass through the first flow paths of the three-way electric expansion valves 202a and 202b, then merge, and pass through the low-pressure pipe 401.

[0057] Also, a part of the refrigerant that has passed through the second heat exchanger 207 flows into the relay bypass pipe 209. Then, the refrigerant that has flowed into the relay bypass pipe 209 is depressurized to a low pressure by the second flow rate adjustment valve 205, and then, in the second heat exchanger 207, it exchanges heat with the refrigerant that has passed through the first flow rate adjustment valve 204, that is, the refrigerant before branching into the relay bypass pipe 209, and evaporates. Further, the refrigerant evaporates by exchanging heat with the refrigerant before flowing into the first flow rate adjustment valve 204 in the first heat exchanger 206. The evaporated refrigerant flows into the low-pressure pipe 401 and merges with the refrigerant that has passed through the three-way electric expansion valves 202a and 202b. Then, the merged refrigerant is sucked into the compressor 101 through the fourth check valve 106, the flow path switching valve 102, and the accumulator 104.

[0058] (Full heating operation) Next, the full heating operation will be described. FIG. 4 is a refrigerant circuit diagram showing the state during the full heating operation of the air conditioner 1 according to Embodiment 1. In the full heating operation, all of the indoor units 300a and 300b perform heating operations. As shown in FIG. 4, the high-temperature and high-pressure gas refrigerant discharged from the compressor 101 passes through the flow path switching valve 102, passes through the fifth check valve 107 and the high-pressure pipe 402, and reaches the gas-liquid separator 201.

[0059] The refrigerant is separated into a gaseous refrigerant and a liquid refrigerant by the gas-liquid separator 201, and the gaseous refrigerant flows out from the gas outflow side of the gas-liquid separator 201 and flows into the first branch portion 240. During the full heating operation, the control device 10 controls the opening degrees of the three-way electric expansion valves 202a and 202b so that the second flow path communicating with the high-pressure pipe 402 is opened and the first flow path communicating with the low-pressure pipe 401 is closed. Therefore, the refrigerant that has flowed into the first branch portion 240 passes through the second flow paths of the three-way electric expansion valves 202a and 202b, passes through the gas branch pipes 403a and 403b, and flows into the indoor units 300a and 300b, respectively.

[0060] The refrigerant flowing into the indoor units 300a and 300b is respectively heat-exchanged with the indoor air in the load-side heat exchangers 301a and 301b and condensed and liquefied. At this time, the room where the indoor units 300a and 300b are installed is heated. Then, the condensed and liquefied refrigerant is depressurized through the load-side flow control valves 302a and 302b controlled based on the degree of subcooling on the outlet side of the load-side heat exchangers 301a and 301b respectively.

[0061] The refrigerant depressurized by the load-side flow control valves 302a and 302b respectively passes through the liquid branch pipes 404a and 404b and the check valves 211a and 211b of the second branch section 250, and then merges. At this time, no refrigerant flows through the check valves 210a and 210b. The merged refrigerant passes through the second heat exchange section 207, flows into the relay bypass pipe 209, and is depressurized to a low pressure by the second flow control valve 205. Then, the depressurized refrigerant flows out from the second branch section 250 and is heat-exchanged with the refrigerant before branching into the relay bypass pipe 209 and evaporates.

[0062] Furthermore, the refrigerant passes through the first heat exchange section 206. In all heating operations, the first flow control valve 204 is closed. The refrigerant passing through the first heat exchange section 206 flows into the low-pressure pipe 401, passes through the check valve 108, is depressurized by the heat source-side flow control valve 109, and is heat-exchanged with the outdoor air blown by the heat source-side blower 111 in the heat source-side heat exchanger 103 and evaporates and gasifies. The gasified refrigerant is sucked into the compressor 101 through the flow path switching valve 102 and the accumulator 104. Since the bypass flow control valve 110 is fully closed, no refrigerant flows through the bypass pipe 113.

[0063] (Cooling main unit operation) Next, the main cooling operation will be described. FIG. 5 is a refrigerant circuit diagram showing the state during the main cooling operation of the air conditioner 1 according to Embodiment 1. Hereinafter, a case where the indoor unit 300a performs a cooling operation and the indoor unit 300b performs a heating operation, and the cooling capacity is larger will be described. As shown in FIG. 5, the high-temperature and high-pressure gas refrigerant discharged from the compressor 101 passes through the flow path switching valve 102 and branches into the refrigerant flowing into the main pipe 114 and the refrigerant flowing into the bypass pipe 113. In the main cooling operation, the bypass flow rate adjustment valve 110 is open.

[0064] The refrigerant flowing into the main pipe 114 exchanges heat with the outdoor air blown by the heat source side blower 111 in the heat source side heat exchanger 103 and condenses and liquefies. The condensed and liquefied refrigerant is then decompressed by the heat source side flow rate adjustment valve 109. On the other hand, the refrigerant flowing into the bypass pipe 113 is decompressed by the bypass flow rate adjustment valve 110. The refrigerant flowing into the heat source side heat exchanger 103 and the refrigerant flowing into the bypass pipe 113 merge in front of the third check valve 105 and reach the gas-liquid separator 201 through the third check valve 105 and the high-pressure pipe 402.

[0065] The refrigerant is separated into a gaseous refrigerant and a liquid refrigerant by the gas-liquid separator 201. The liquid refrigerant flowing out from the liquid outflow side of the gas-liquid separator 201 reaches the second branch portion 250 through the first heat exchange portion 206, the first flow rate adjustment valve 204, and the second heat exchange portion 207. The refrigerant flows into the indoor unit 300a through the first check valve 210a and the liquid branch pipe 404a of the second branch portion 250. Since the liquid branch pipe 404a is at a lower pressure than the high-pressure pipe 402, no refrigerant flows through the second check valve 211a.

[0066] Then, the refrigerant flowing into the indoor unit 300a is decompressed to a low pressure by the load side flow rate adjustment valve 302a controlled based on the superheat degree at the outlet side of the load side heat exchanger 301a. The decompressed refrigerant flows into the load side heat exchanger 301a, exchanges heat with the indoor air in the load side heat exchanger 301a, and evaporates and gasifies. At this time, the room where the indoor unit 300a is installed is cooled. Then, the refrigerant in the gaseous state flows into the first branch portion 240 of the relay unit 200 through the gas branch pipe 403a.

[0067] In the operation of the cooling main body, the three-way electric expansion valve 202a connected to the indoor unit 300a that performs the cooling operation is controlled by the control device 10 such that the first flow path communicating with the low-pressure pipe 401 is opened and the second flow path communicating with the high-pressure pipe 402 is closed. Therefore, the refrigerant flowing into the first branch portion 240 flows into the low-pressure pipe 401 through the first flow path of the three-way electric expansion valve 202a.

[0068] On the other hand, the gaseous refrigerant flowing out from the gas outflow side of the gas-liquid separator 201 flows into the first branch portion 240. The three-way electric expansion valve 202b connected to the indoor unit 300b that performs the heating operation in the operation of the cooling main body is controlled by the control device 10 such that the second flow path communicating with the high-pressure pipe 402 is opened and the first flow path communicating with the low-pressure pipe 401 is closed. Therefore, the refrigerant flowing into the first branch portion 240 flows into the indoor unit 300b through the second flow path of the three-way electric expansion valve 202b and the gas branch pipe 403b.

[0069] The refrigerant flowing into the indoor unit 300b exchanges heat with the indoor air in the load-side heat exchanger 301b and condenses and liquefies. At this time, the room where the indoor unit 300b is installed is heated. Then, the condensed and liquefied refrigerant passes through the load-side flow rate adjustment valve 302b controlled based on the degree of subcooling on the outlet side of the load-side heat exchanger 301b and becomes a liquid state at an intermediate pressure, which is the intermediate pressure between the high pressure and the low pressure. The refrigerant in the liquid state at the intermediate pressure flows into the second heat exchange portion 207 through the liquid branch pipe 404b and the second check valve 211b of the second branch portion 250. At this time, no refrigerant flows through the first check valve 210b.

[0070] Thereafter, the refrigerant flows into the relay bypass pipe 209, is decompressed to a low pressure by the second flow rate adjustment valve 205, and then, in the second heat exchanger 207, exchanges heat with the refrigerant that has passed through the first flow rate adjustment valve 204, that is, the refrigerant before branching into the relay bypass pipe 209, and evaporates. Further, the refrigerant exchanges heat with the refrigerant before flowing into the first flow rate adjustment valve 204 in the first heat exchanger 206 and evaporates. The evaporated refrigerant flows into the low pressure pipe 401 and merges with the refrigerant that has passed through the three-way electric expansion valve 202a. Thereafter, the merged refrigerant is sucked into the compressor 101 through the fourth check valve 106, the flow path switching valve 102, and the accumulator 104.

[0071] (Heating main operation) Next, the heating main operation will be described. FIG. 6 is a refrigerant circuit diagram showing the state during the heating main operation of the air conditioner 1 according to the first embodiment. Hereinafter, the case where the indoor unit 300a performs a cooling operation and the indoor unit 300b performs a heating operation, and the heating capacity is larger will be described. As shown in FIG. 6, the high-temperature and high-pressure gas refrigerant discharged from the compressor 101 passes through the flow path switching valve 102, passes through the fifth check valve 107 and the high-pressure pipe 402, and reaches the gas-liquid separator 201.

[0072] The refrigerant is separated into a gaseous refrigerant and a liquid refrigerant by the gas-liquid separator 201. The gaseous refrigerant flowing out from the gas outflow side of the gas-liquid separator 201 flows into the first branch portion 240. The three-way electric expansion valve 202b connected to the indoor unit 300b that performs the heating operation in the heating main operation is controlled by the control device 10 so that the second flow path communicating with the high-pressure pipe 402 is opened and the first flow path communicating with the low-pressure pipe 401 is closed. Therefore, the refrigerant flowing into the first branch portion 240 flows into the indoor unit 300b through the second flow path of the three-way electric expansion valve 202b and the gas branch pipe 403b.

[0073] The refrigerant flowing into the indoor unit 300b exchanges heat with the indoor air in the load-side heat exchanger 301b and condenses and liquefies. At this time, the room where the indoor unit 300b is installed is heated. Then, the condensed and liquefied refrigerant passes through the load-side flow control valve 302b controlled based on the degree of subcooling on the outlet side of the load-side heat exchanger 301b and becomes a liquid state at an intermediate pressure, which is a pressure between high pressure and low pressure. The refrigerant in the liquid state at the intermediate pressure passes through the liquid branch pipe 404b and the second check valve 211b of the second branch portion 250 and flows into the second heat exchange portion 207. At this time, no refrigerant flows through the first check valve 210b. Then, the refrigerant passing through the second check valve 211b flows out from the liquid outflow side of the gas-liquid separator 201 and merges with the liquid-state refrigerant that has passed through the first heat exchange portion 206 and the first flow control valve 204. The merged refrigerant branches into the refrigerant flowing into the second branch portion 250 and the refrigerant flowing into the relay bypass pipe 209.

[0074] The refrigerant flowing into the second branch portion 250 passes through the first check valve 210a and the liquid branch pipe 404a of the second branch portion 250 and flows into the indoor unit 300a. Since the liquid branch pipe 404a is at a lower pressure than the high-pressure pipe 402, no refrigerant flows through the second check valve 211a. Then, the refrigerant flowing into the indoor unit 300a is depressurized to a low pressure by the load-side flow control valve 302a controlled based on the degree of superheat on the outlet side of the load-side heat exchanger 301a. The depressurized refrigerant flows into the load-side heat exchanger 301a, exchanges heat with the indoor air in the load-side heat exchanger 301a, and evaporates and gasifies. At this time, the room where the indoor unit 300a is installed is cooled. Then, the refrigerant in the gas state passes through the gas branch pipe 403a and flows into the first branch portion 240 of the relay unit 200.

[0075] The three-way electric expansion valve 202a connected to the indoor unit 300a that performs a cooling operation during the heating main operation is controlled by the control device 10 such that the first flow path communicating with the low-pressure pipe 401 is opened and the second flow path communicating with the high-pressure pipe 402 is closed. Therefore, the refrigerant flowing into the first branch portion 240 passes through the first flow path of the three-way electric expansion valve 202a and flows into the low-pressure pipe 401.

[0076] On one hand, the refrigerant flowing into the relay bypass pipe 209 is depressurized to a low pressure by the second flow rate adjustment valve 205, and then in the second heat exchange section 207, it exchanges heat with the refrigerant flowing out from the second branch section 250, that is, the refrigerant before branching into the relay bypass pipe 209, and evaporates. Further, the refrigerant exchanges heat with the refrigerant before flowing into the first flow rate adjustment valve 204 in the first heat exchange section 206 and evaporates. The evaporated refrigerant flows into the low-pressure pipe 401 and merges with the refrigerant that has passed through the three-way electric expansion valve 202a. Then, the merged refrigerant passes through the sixth check valve 108 and flows into the main pipe 114 and the bypass pipe 113. In the main heating operation, the bypass flow rate adjustment valve 110 is open.

[0077] The refrigerant flowing into the main pipe 114 is depressurized by the heat source side flow rate adjustment valve 109 and exchanges heat with the outdoor air blown by the heat source side blower 111 in the heat source side heat exchanger 103 to evaporate and gasify. On the other hand, the refrigerant flowing into the bypass pipe 113 is depressurized by the bypass flow rate adjustment valve 110 and then merges with the refrigerant flowing out from the main pipe 114. The merged refrigerant is sucked into the compressor 101 through the flow path switching valve 102 and the accumulator 104.

[0078] (Stopped state) Next, the case where the air conditioner 1 is stopped will be described. The refrigerant circuit diagram when the air conditioner 1 is stopped is the same as the refrigerant circuit diagram during full cooling operation in FIG. 3. When the air conditioner 1 is stopped, there is no operation request from the indoor units 300a and 300b, the compressor 101 is stopped, and the flow path switching valve 102 is switched so that the discharge pipe of the compressor 101 and the main pipe 114 communicate with each other. Also, the heat source side flow rate adjustment valve 109, the bypass flow rate adjustment valve 110, the first flow rate adjustment valve 204, and the second flow rate adjustment valve 205 are opened at a preset opening degree. The load side flow rate adjustment valves 302a and 302b are closed.

[0079] Also, when the air conditioner 1 is stopped, the three-way electric expansion valves 202a and 202b are controlled with a control amount of Pmin. That is, when the air conditioner 1 is stopped, the three-way electric expansion valves 202a and 202b are controlled such that the first flow path communicating with the low-pressure pipe 401 is opened and the second flow path communicating with the high-pressure pipe 402 is closed. In this state, for example, a vacuum pump can be connected to the refrigerant enclosures 131 and 132, and the air conditioner 1 can be evacuated by starting the vacuum pump.

[0080] FIG. 7 is a flowchart showing the control operation of the three-way electric expansion valve 202a according to Embodiment 1. The control operation of the three-way electric expansion valve 202b is the same as that of the three-way electric expansion valve 202a. The control device 10 determines the control amount of the three-way electric expansion valve 202a according to the required operation mode for the indoor unit 300a connected to the three-way electric expansion valve 202a. First, the control device 10 determines whether the heat source unit 100 is in operation (S1). Here, when the compressor 101 is in operation, the control device 10 determines that the heat source unit 100 is in operation. When the heat source unit 100 is in operation (S1: YES), the control device 10 determines the state of the indoor unit 300a (S2). Here, the control device 10 determines whether the indoor unit 300a is requesting stop, cooling operation, or heating operation.

[0081] When the indoor unit 300a is requesting stop (S2: stop), the control device 10 transmits a pulse signal with a control amount of P1 to the three-way electric expansion valve 202a (S3). As a result, both the first flow path and the second flow path of the three-way electric expansion valve 202a are closed. That is, when the heat source unit 100 is in operation and the indoor unit 300a is stopped, the gas branch pipe 403a of the indoor unit 300a is closed.

[0082] When the indoor unit 300a requests heating operation (S2: Heating), the control device 10 transmits a pulse signal with a control amount of Pmax to the three-way electric expansion valve 202a (S4). As a result, the second flow path of the three-way electric expansion valve 202a is opened, and the first flow path is closed. That is, when the heat source unit 100 is in operation and the indoor unit 300a performs heating operation, the gas manifold 403a of the indoor unit 300a and the high-pressure pipe 402 are communicated with each other.

[0083] When the indoor unit 300a requests cooling operation (S2: Cooling), or when the heat source unit 100 is not in operation (S1: NO), the control device 10 transmits a pulse signal with a control amount of Pmin to the three-way electric expansion valve 202a (S5). As a result, the first flow path of the three-way electric expansion valve 202a is opened, and the second flow path is closed. That is, when the heat source unit 100 is in operation and the indoor unit 300a performs cooling operation, or when the heat source unit 100 is stopped, the gas manifold 403a of the indoor unit 300a and the low-pressure pipe 401 are communicated with each other.

[0084] As described above, in the present embodiment, when the indoor units 300a and 300b request heating operation, the three-way electric expansion valves 202a and 202b of the relay unit 200 communicate the gas manifolds 403a and 403b with the high-pressure pipe 402, and block the flow of the refrigerant to the low-pressure pipe 401. As a result, the refrigerant flowing from the high-pressure pipe 402 is not bypassed from the three-way electric expansion valves 202a and 202b to the low-pressure pipe 401, and it is possible to suppress a decrease in heating capacity as compared with the conventional air conditioner.

[0085] Further, when it is determined that the heat source unit 100 is stopped, the three-way electric expansion valves 202a and 202b communicate the gas manifolds 403a and 403b with the low-pressure pipe 401 at the maximum opening degree. By performing evacuation in such a state, it is possible to ensure a larger flow rate of air flowing through the gas manifolds 403a and 403b and the low-pressure pipe 401 than in the conventional case, and it is possible to reduce the time required for evacuation of the air conditioner 1.

[0086] Also, by using the three-way electric expansion valves 202a and 202b to switch the refrigerant flow during cooling operation and heating operation, the number of components in the first branch portion 240 can be reduced, and the occupied space in the relay unit 200 can also be reduced. Further, when switching the refrigerant flow during cooling operation and heating operation with a plurality of valves for one indoor unit 300a, it is actually difficult to operate the plurality of valves simultaneously, and a time lag of several seconds will occur. In contrast, by performing the switching with one three-way electric expansion valve 202a for one indoor unit 300a, since the control target becomes one, it is not necessary to consider the occurrence of a time lag.

[0087] Embodiment 2. FIG. 8 is a refrigerant circuit diagram of the air conditioner 1A according to Embodiment 2. As shown in FIG. 8, the air conditioner 1A of Embodiment 2 is different from Embodiment 1 in the configuration of the first branch portion 240A of the relay unit 200A. Other configurations of the air conditioner 1A are the same as those in Embodiment 1.

[0088] As shown in FIG. 8, the first branch portion 240A of the relay unit 200A of the present embodiment includes heating on-off valves 213a and 213b, and cooling expansion valves 214a and 214b. One of each of the heating on-off valves 213a and 213b is connected to the gas branch pipes 403a and 403b, and the other of each is connected to the high-pressure pipe 402. One of each of the cooling expansion valves 214a and 214b is connected to the gas branch pipes 403a and 403b, and the other of each is connected to the low-pressure pipe 401. The heating on-off valves 213a and 213b are, for example, electromagnetic valves. The cooling expansion valves 214a and 214b are configured by, for example, two-way electric expansion valves whose opening degrees can be adjusted.

[0089] FIG. 9 is a flowchart showing the control operations of the heating on-off valve 213a and the cooling expansion valve 214a according to Embodiment 2. The control operations of the heating on-off valve 213b and the cooling expansion valve 214b are the same as those of the heating on-off valve 213a and the cooling expansion valve 214a. The control device 10 determines the opening and closing of the heating on-off valve 213a and the opening degree of the cooling expansion valve 214a according to the required operation mode for the indoor unit 300a connected to the heating on-off valve 213a and the cooling expansion valve 214a.

[0090] First, the control device 10 determines whether the heat source unit 100 is in operation (S21). Here, when the compressor 101 is in operation, it is determined that the heat source unit 100 is in operation. When the heat source unit 100 is in operation (S21: YES), the control device 10 determines the state of the indoor unit 300a (S22). Here, the control device 10 determines whether the indoor unit 300a is requesting stop, cooling operation, or heating operation.

[0091] When the indoor unit 300a requests stop (S22: stop), the control device 10 closes both the heating on-off valve 213a and the cooling expansion valve 214a (S23). That is, when the heat source unit 100 is in operation and the indoor unit 300a is stopped, the gas branch pipe 403a of the indoor unit 300a is closed.

[0092] When the indoor unit 300a requests heating operation (S22: heating), the control device 10 opens the heating on-off valve 213a and closes the cooling expansion valve 214a (S24). Thereby, when the heat source unit 100 is in operation and the indoor unit 300a performs heating operation, the gas branch pipe 403a of the indoor unit 300a and the high-pressure pipe 402 are communicated.

[0093] When the indoor unit 300a requests a cooling operation (S22: Cooling), or when the heat source unit 100 is not in operation (S21: NO), the control device 10 closes the heating on-off valve 213a and opens the cooling expansion valve 214a (S25). Here, the control device 10 fully opens the cooling expansion valve 214a. As a result, when the heat source unit 100 is in operation and the indoor unit 300a performs a cooling operation, or when the heat source unit 100 is stopped, the gas branch pipe 403a of the indoor unit 300a and the low-pressure pipe 401 are communicated with each other.

[0094] As described above, also in this embodiment, when it is determined that the indoor units 300a and 300b request a heating operation, the gas branch pipes 403a and 403b and the high-pressure pipe 402 can be communicated with each other, and the flow of the refrigerant to the low-pressure pipe 401 can be blocked. For this reason, since the refrigerant flowing from the high-pressure pipe 402 does not bypass from the cooling expansion valves 214a and 214b to the low-pressure pipe 401, it is possible to suppress a decrease in heating capacity as compared with a conventional air conditioner.

[0095] Further, when it is determined that the heat source unit 100 is stopped, the gas branch pipes 403a and 403b and the low-pressure pipe 401 can be communicated with each other at the maximum opening degree. By performing evacuation in such a state, it is possible to ensure a larger flow rate of air flowing through the gas branch pipes 403a and 403b and the low-pressure pipe 401 than in the conventional case, and it is possible to reduce the time required for evacuation of the air conditioner 1.

[0096] The above is the description of the embodiment. However, the present disclosure is not limited to the above-described embodiment, and various modifications or combinations can be made without departing from the gist of the present disclosure. For example, in Embodiment 1, when the indoor unit 300a requests a stop (S2: Stop), the control device 10 is configured to transmit a pulse signal of a control amount P1 to the three-way electric expansion valve 202a, but a pulse signal of an arbitrary control amount between P1 and P2 or more may be transmitted.

[0097] Also, in Embodiment 1, when the heat source machine 100 is not in operation (S1: NO), the control device 10 is configured to transmit a pulse signal with a control amount of Pmin to the three-way electric expansion valve 202a. However, a pulse signal with an arbitrary control amount equal to or greater than Pmin and less than P1 may be transmitted. For example, when refrigerant pooling in the load-side heat exchanger 301a through the gas branch pipe 403a of the indoor unit 300a from the relay unit 200 is assumed while the heat source machine 100 is stopped, the control amount may be set larger than Pmin. Thereby, the opening degree of the three-way electric expansion valve 202a can be reduced, and the amount of refrigerant pooling can be suppressed.

[0098] Also, in Embodiment 2, instead of the heating on-off valves 213a and 213b, a heating expansion valve composed of a two-way electric expansion valve with an adjustable opening degree may be used. In this case, when the indoor unit 300a requests a stop (S22: stop), the control device 10 closes both the heating expansion valve and the cooling expansion valve 214a. Also, when the indoor unit 300a requests a heating operation (S22: heating), the control device 10 fully opens the heating expansion valve and closes the cooling expansion valve 214a. Further, when the indoor unit 300a requests a cooling operation (S22: cooling), or when the heat source machine 100 is not in operation (S21: NO), the control device 10 closes the heating expansion valve and opens the cooling expansion valve 214a. In this case, the same effects as in Embodiment 2 can be obtained.

Explanation of Reference Numerals

[0099] 1. 1A air conditioner, 10 control device, 100 heat source machine, 101 compressor, 102 flow path switching valve, 103 heat source side heat exchanger, 104 accumulator, 105 third check valve, 106 fourth check valve, 107 fifth check valve, 108 sixth check valve, 109 heat source side flow rate adjustment valve, 110 bypass flow rate adjustment valve, 111 heat source side blower, 113 bypass pipe, 114 main pipe, 120 heat source side heat exchange unit, 126 discharge pressure sensor, 127 suction pressure sensor, 131, 132 refrigerant enclosure part, 140 heat source side flow path adjustment unit, 200, 200A relay machine, 201 gas-liquid separator, 202a, 202b three-way electric expansion valve, 204 first flow rate adjustment valve, 205 second flow rate adjustment valve, 206 first heat exchange part, 207 second heat exchange part, 208 relay bypass temperature sensor, 209 relay bypass pipe, 210a, 210b first check valve, 211a, 211b second check valve, 213a, 213b heating on-off valve, 214a, 214b cooling expansion valve, 231 first pressure sensor, 232 second pressure sensor, 240, 240A first branch part, 250 second branch part, 300a, 300b indoor unit, 301a, 301b load side heat exchanger, 302a, 302b load side flow rate adjustment valve, 303a, 303b liquid pipe temperature sensor, 304a, 304b gas pipe temperature sensor, 401 low pressure pipe, 402 high pressure pipe, 403a, 403b gas branch pipe, 404a, 404b liquid branch pipe.

Claims

1. A heat source unit having a compressor, a flow path switching valve, and a heat source side heat exchanger, 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 relay unit connected to the heat source unit by a low pressure pipe and a high pressure pipe, and connected to the indoor unit by a gas branch pipe and a liquid branch pipe, for supplying the refrigerant supplied from the heat source unit to the indoor unit, A control device, and is provided with, When the indoor unit performs the cooling operation, the relay unit includes a branch portion that communicates the gas branch pipe with the low pressure pipe, and when the indoor unit performs the heating operation, communicates the gas branch pipe with the high pressure pipe, The branch portion has an expansion valve whose opening degree can be adjusted, The expansion valve is connected to the gas branch pipe and the low pressure pipe, The control device is an air conditioner that controls the expansion valve so that the gas branch pipe and the low pressure pipe communicate with each other when the heat source unit stops.

2. The air conditioner according to claim 1, wherein the expansion valve is a three-way electric expansion valve having a first flow path that communicates the gas branch pipe with the low pressure pipe and a second flow path that communicates the gas branch pipe with the high pressure pipe.

3. The control device is, The air conditioner according to claim 2, wherein when the heat source unit is stopped, the three-way electric expansion valve is controlled so as to open the first flow path and close the second flow path.

4. The control device is, The air conditioner according to claim 3, wherein when the heat source unit is operating and the indoor unit is stopped, the three-way electric expansion valve is controlled so as to close the first flow path and the second flow path.

5. The control device is, The air conditioner according to claim 3 or 4, wherein when the heat source unit is operating and the indoor unit is performing a cooling operation, the three-way electric expansion valve is controlled so as to open the first flow path and close the second flow path.

6. The control device is configured to: control the three-way electric expansion valve to open the second flow path and close the first flow path when the heat source machine is operating and the indoor unit is performing heating operation, according to any one of claims 3 to 5 of the air conditioner.

7. The expansion valve is an expansion valve for cooling composed of a two-way electric expansion valve, The air conditioner according to claim 1, wherein the branch portion further includes an on-off valve for heating connected to the gas branch pipe and the high-pressure pipe.

8. The control device is configured to: control the cooling expansion valve so that the gas branch pipe and the low-pressure pipe communicate with each other, and control the heating on-off valve so that the gas branch pipe and the high-pressure pipe are closed, when the heat source machine is stopped, according to claim 7 of the air conditioner.

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