GB2578372A

GB2578372A - Relay device and air conditioning device

Info

Publication number: GB2578372A
Application number: GB1913868.4A
Authority: GB
Inventors: Azuma Koji; Morimoto Osamu; Kawagoe Tomokazu; Takahashi Hiroki
Original assignee: Mitsubishi Electric Corp
Current assignee: Mitsubishi Electric Corp
Priority date: 2017-06-01
Filing date: 2017-06-01
Publication date: 2020-05-06
Anticipated expiration: 2037-06-01
Also published as: JPWO2018220804A1; WO2018220804A1; GB2578372B; JP6704520B2; GB2578372B8; GB201913868D0

Abstract

A relay device and an air conditioning device, in which a first relay device and a heat source device are connected by a first connection pipe and a second connection pipe, are provided with a first cooling electromagnetic valve, a first heating electromagnetic valve, a first check valve, a second check valve, a first low-pressure gas pipe, a first high-pressure gas pipe, a first liquid pipe, a first control valve, and a second control valve. The first control valve is provided to the first low-pressure gas pipe. The first control valve allows the flow of a refrigerant from the first cooling electromagnetic valve to the first connection pipe, and when power is not being supplied, blocks the flow of the refrigerant from the first connection pipe to the first cooling electromagnetic valve. The second control valve is provided to the first liquid pipe. The second control valve is open when power is being supplied, and when power is not being supplied, the second control valve blocks a flow of the refrigerant towards the first check valve.

Description

DESCRIPTION Title of Invention

RELAY UNITAND AIR-CONDITIONING APPARATUS

Technical Field

[0001] The present invention relates to a relay unit that distributes refrigerant supplied from a heat source unit to a plurality of indoor units, and an air-conditioning apparatus including the relay unit.

Background Art

[0002] An air-conditioning apparatus provided with a plurality of indoor units which individually perform a heating operation or a cooling operation has a refrigerant circuit and a structure in which heating energy, cooling energy, or both heating energy and cooling energy generated, for example, in a heat source unit are efficiently supplied to a plurality of loads. Such an air-conditioning apparatus is applied to, for example, a variable refrigerant flow system. In an existing air-conditioning apparatus such as a variable refrigerant flow system, refrigerant is circulated between an outdoor unit provided outdoors that is, for example, a heat source unit and indoor units provided in indoor spaces, thereby performing a cooling operation or a heating operation. To be more specific, an air-conditioned space is heated or cooled by air that is cooled when the refrigerant removes heat from the air or air that is heated when the refrigerant transfers heat to the air. As the refrigerant for use in such an air-conditioning apparatus, for example, a HFC refrigerant, that is, a hydrofluorocarbon refrigerant, is used in many cases. Furthermore, an air-conditioning apparatus using natural refrigerant such as carbon dioxide (CO2) has been proposed.

[0003] An air-conditioning apparatus that simultaneously performs cooling and heating has been proposed (see, for example, Patent Literature 1). The air-conditioning apparatus disclosed in Patent Literature 1 includes a heat source unit and a plurality of indoor units, and the heat source unit and a plurality of indoor units are connected in parallel by a first connection pipe and a second connection pipe. Also, the air-conditioning apparatus of Patent Literature 1 includes a relay unit provided with a first branch unit and a second branch unit. The first branch unit connects one side of each of the indoor units to the first connection pipe or the second connection pipe in a switchable manner, and the second branch unit connects the other side of each indoor unit to the second connection pipe. Whether to allow refrigerant to flow into an indoor unit being in a heating operation or allow passage of refrigerant from an indoor unit being in a cooling operation is determined using a cooling solenoid valve and a heating solenoid valve in the first branch unit. Furthermore, the second branch unit includes check valves connected in antiparallel, and causes the refrigerant to flow in one direction in accordance with the flow of the refrigerant that is determined by a switching operation of the first branch unit.

Citation List Patent Literature [0004] Patent Literature 1: Japanese Unexamined Patent Application Publication No. H09-042804

Summary of Invention

Technical Problem [0005] The air-conditioning apparatus disclosed in Patent Literature 1 includes a cooling solenoid valve and a heating solenoid valve for each of the indoor units, and opens and closes these solenoid valves to simultaneously perform the cooling operation and the heating operation. As such a solenoid valve, a one-way solenoid valve having a simple structure is used, for example, in order that a product be made more compact.

When supplied with power, the one-way solenoid valve is opened, and when supplied with no power, the one-way solenoid valve blocks the flow of refrigerant in one direction and allows the refrigerant to flow in the opposite direction to the above one direction. In the second branch unit, one of the check valves allow the refrigerant to flow from the relay unit to the indoor unit side at all times.

[0006] After the air-conditioning apparatus stops an air-conditioning operation, the pressure of the refrigerant pressure in pipes is uniformized, and the pressure in a low-pressure pipe becomes higher than the pressure on an indoor unit side, and as a result the refrigerant may transfer through the first branch unit and the second branch unit to the indoor unit side. However, in the case where refrigerant leakage occurs in an indoor unit, in order to reduce the amount of refrigerant leakage, the configuration of the air-conditioning apparatus needs to be capable of blocking the flow of the refrigerant between the relay unit and the indoor unit even when power is not supplied to the air-conditioning apparatus.

[0007] In general, in air-conditioning apparatuses, evacuation is performed in order to release air in a pipe. Since the evacuation is first performed from an outdoor unit, it is necessary to secure a flow passage such that the flow of air from an indoor unit to the outdoor unit is not blocked in the evacuation.

[0008] The present invention has been made to solve the above problems, and an object of the invention is to provide a relay unit and an air-conditioning apparatus which can cope with refrigerant leakage and it is ensured that work in maintenance and construction can be easily conducted.

Solution to Problem [0009] In a relay unit and an air-conditioning apparatus according to an embodiment of the present invention, a first relay unit is connected to a heat source unit by a first connection pipe and a second connection pipe, connected to a plurality of indoor units by respective first gas branch pipes and respective first liquid branch pipes, and configured to distribute refrigerant supplied from the heat source unit to the plurality of indoor units. The first relay unit includes: first cooling solenoid valves connected to the first gas branch pipes at one side of each of the first cooling solenoid valves, and configured to be opened in a cooling operation and closed in a heating operation; first heating solenoid valves connected to the first gas branch pipes at one side of each of the first heating solenoid valve, and configured to be opened in the heating operation and closed in the cooling operation; first check valves connected to the first liquid branch pipes at one side of each of the first check valves, and each configured to allow the refrigerant to flow into an associated one of the first liquid branch pipes through the first check valve, second check valves connected to the first liquid branch pipes at one side of each of the second check valves, and each configured to allow the refrigerant from an associated one of the first liquid branch pipes to pass through the second check valve; a first low-pressure gas pipe connecting the first connection pipe and an other side of each of the first cooling solenoid valves to each other; a first high-pressure gas pipe connecting the second connection pipe and an other side of each of the first heating solenoid valves to each other; a first liquid pipe connecting the second connection pipe and an other side of each of the first check valves and an other side of each of the second checks valve to each other; a first control valve provided at the first low-pressure gas pipe, and configured to allow a flow of the refrigerant from the first cooling solenoid valve toward the first connection pipe, and block a flow of the refrigerant from the first connection pipe toward the first cooling solenoid valve when the first control valve is not supplied with power; and a second control valve provided at the first liquid pipe, and configured to be opened when the second control valve is supplied with power, and block a flow of the refrigerant toward the first check valve when the second control valve is not supplied with power.

Advantageous Effects of Invention [0010] According to the embodiment of the present invention, the first low-pressure gas pipe is provided with the first control valve, and the first liquid pipe is provided with the second control valve. Therefore, the first control valve and the second control valve allow the flow of the refrigerant flow in operation and the flow of air in the evacuation, and block the transfer of the refrigerant from the first relay unit to the indoor units while the operation is stopped. Not only when power is supplied to the air-conditioning apparatus but even when power cannot be supplied to the air-conditioning apparatus, for example, before a power supply construction or during a power outage, the first control valve and the second control valve can block the flow of the refrigerant to the indoor unit side. Therefore, in the relay unit and the air-conditioning apparatus, the refrigerant leakage in the indoor units and indoor pipes such as the first gas branch pipe and the first liquid branch pipe can be reduced, and at the same time the work in construction and maintenance such as the evacuation can be easily conducted. Brief Description of Drawings [0011] [Fig. 1] Fig. 1 is a circuit diagram illustrating a circuit configuration of an air-conditioning apparatus according to Embodiment 1 of the present invention.

[Fig. 2] Fig. 2 is a block diagram illustrating functions of a controller in Embodiment 1 of the present invention.

[Fig. 3] Fig. 3 is a circuit diagram illustrating a state of the air-conditioning apparatus in a cooling only operation in Embodiment 1 of the present invention.

[Fig. 4] Fig. 4 is a circuit diagram illustrating a state of the air-conditioning apparatus in a heating only operation in Embodiment 1 of the present invention.

[Fig. 5] Fig. 5 is a circuit diagram illustrating a state of the air-conditioning apparatus in a cooling main operation in Embodiment 1 of the present invention.

[Fig. 6] Fig. 6 is a circuit diagram illustrating a state of the air-conditioning apparatus in a heating main operation in Embodiment 1 of the present invention.

[Fig. 7] Fig. 7 is a diagram indicating flows of refrigerant at branch units and the vicinity in operation according to Embodiment 1 of the present invention.

[Fig. 8A] Fig. 8A is a diagram illustrating the state of the refrigerant in the branch units and the vicinity thereof during a power outage in Embodiment 1 of the present invention.

[Fig. 8B] Fig. 8B is a diagram indicating flows of air in evacuation in the branch units and the vicinity thereof in Embodiment 1 of the present invention.

[Fig. 9A] Fig. 9A is a diagram illustrating the state of the refrigerant during a power outage in a modification of a first control valve.

[Fig. 9B] Fig. 9B is a diagram indicating flows of air in evacuation in the modification example of the first control valve.

[Fig. 10A] Fig. 10A is a diagram illustrating the state of the refrigerant during a power outage in a modification of a second control valve.

[Fig. 10B] Fig. 10B is a diagram indicating flows of air in evacuation in the modification of the second control valve.

[Fig. 11] Fig. 11 is a schematic diagram illustrating a schematic circuit configuration of an air-conditioning apparatus according to Embodiment 2 of the present invention.

[Fig. 12] Fig. 12 is a circuit diagram illustrating a circuit configuration of a first relay unit in the air-conditioning apparatus according to Embodiment 2 of the present invention.

[Fig. 13] Fig. 13 is a circuit diagram illustrating a circuit configuration of a second relay unit in the air-conditioning apparatus according to Embodiment 2 of the present invention.

[Fig. 14] Fig. 14 is a diagram illustrating a configuration of branch units and the vicinity thereof in Embodiment 3 of the present invention.

[Fig. 15] Fig. 15 is a diagram indicating flows of the refrigerant in the branch units and the vicinity thereof in a separate operation mode in Embodiment 3 of the present invention.

[Fig. 16] Fig. 16 is a flowchart indicating control by a controller in an air-conditioning apparatus according to Embodiment 3 of the present invention. Description of Embodiments [0012] An air-conditioning apparatus according to each of the embodiments of the present invention will be described with reference to the drawings. It should be noted that "one-way solenoid valve" which will be described later is a solenoid valve that is opened when supplied with power, and blocks, when supplied with no power, the flow of refrigerant only in one direction and allows the flow of refrigerant in the opposite direction to the above one direction.

[0013] Embodiment 1 Fig. 1 is a circuit diagram illustrating a circuit configuration of an air-conditioning apparatus according to Embodiment 1 of the present invention. As illustrated in Fig. 1, an air-conditioning apparatus 100 includes a heat source unit A, a plurality of indoor units B, C, and D, a first relay unit E, and a controller 80. Embodiment 1 will be described by referring to by way of example the case where a single source apparatus A is connected to three indoor units B, C, and D. However, the number of heat source unites A and the number of indoor units are not limited to the above numbers.

[0014] As illustrated in Fig. 1, in the air-conditioning apparatus 100, the heat source unit A, a plurality of indoor units B, C, and D, and the first relay unit E are connected. The heat source unit A has a function of supplying heating energy or cooling energy to the indoor units B, C, and D. The indoor units B, C, and D are connected in parallel with each other, and have the same configuration. Each of the indoor units B, C, and D has a function of cooling or heating an air-conditioned space such as an indoor space with the cooling energy or the heating energy supplied from the heat source unit A. The first relay unit E is located between the heat source unit A and the indoor units B, C, and D, and changes the flow of refrigerant which is supplied from the heat source unit A in response to a request from each of the indoor units B, C, and D. The air-conditioning apparatus 100 includes a plurality of sensors such as a pressure sensor and a temperature sensor that each detect a state of the refrigerant (which will be referred to as a sensor group 60), and a plurality of first refrigerant detection sensors 85b, 85c, and 85d that detect the refrigerant. The sensor group 60 includes, for example, a discharge pressure detection sensor 61, a liquid outflow-pressure detection sensor 62, a downstream-side liquid outflow-pressure detection sensor 63, and other sensors.

Although it is not illustrated, the sensor group 60 also includes a plurality of temperature sensors provided at pipes for the first relay unit E, and temperature sensors provided at respective indoor units, that is, the indoor units B, C, and D. [0015] (Heat source unit A) The heat source unit A includes a compressor 1 having a variable capacity, a flow-passage switching device 2, a heat-source-side heat exchanger 3 that operates as an evaporator or a condenser, an accumulator 4, a heat-source-side flow-passage adjustment unit 20 that restricts the flow direction of refrigerant, and other units. The flow-passage switching device 2 changes the flow direction of refrigerant at the heat source unit A in a switching manner, and the accumulator 4 is connected to a suction side of the compressor 1 via the flow-passage switching device 2. Although it is illustrated by way of example that the flow-passage switching device 2 is a four-way valve, the flow-passage switching device 2 may be formed of a combination of, for example, two-way valves or three-way valves.

[0016] The heat-source-side heat exchanger 3 is, for example, a plate-fin-and-tube heat exchanger. Although it is not illustrated, an outdoor fan is provided close to the heatsource-side heat exchanger 3, and the heat-source-side heat exchanger 3 transfers heat between air sent from the outdoor fan and refrigerant in the pipe. One of ends of the heat-source-side heat exchanger 3 is connected to a second connection pipe 7 and the other is connected to a suction side of the accumulator 4 in a heating operation mode or to a discharge side of the compressor 1 in a cooling operation mode, by a switching operation of the flow-passage switching device 2.

[0017] The heat-source-side flow-passage adjustment unit 20 includes a heat-sourceside first check valve 21, a heat-source-side second check valve 22, a heat-source-side third check valve 23, and a heat-source-side fourth check valve 24. The heat-sourceside first check valve 21 is provided at a pipe connecting the heat-source-side heat exchanger 3 and the second connection pipe 7, and allows the refrigerant to flow from the heat-source-side heat exchanger 3 toward the second connection pipe 7. The heat-source-side second check valve 22 is provided at a pipe connecting the flow-passage switching device 2 in the heat source unit A and a first connection pipe 6, and allows the refrigerant to flow from the first connection pipe 6 toward the flow-passage switching device 2. The heat-source-side third check valve 23 is provided at a pipe connecting the flow-passage switching device 2 and the second connection pipe 7, and allows the refrigerant to flow from the flow-passage switching device 2 toward the second connection pipe 7. The heat-source-side fourth check valve 24 is provided at a pipe connecting the heat-source-side heat exchanger 3 and the first connection pipe 6, and allows the refrigerant to flow from the first connection pipe 6 toward the heat-source-side heat exchanger 3.

[0018] The heat source unit A includes the discharge pressure detection sensor 61. The discharge pressure detection sensor 61 is provided at a pipe connecting the flow-passage switching device 2 and a discharge side of the compressor 1, and detects a discharge pressure at the compressor 1.

[0019] (Indoor units B, C, and D) The indoor unit B includes an indoor-side heat exchanger 5b that operates as a condenser or an evaporator, and a first flow-rate control device 9b. The indoor unit C includes an indoor-side heat exchanger 5c and a first flow-rate control device 9c, and the indoor unit D includes an indoor-side heat exchanger 5d and a first flow-rate control device 9d.

[0020] During a cooling operation, the first flow-rate control device 9b is controlled based on the amount of superheat on an outlet side of the indoor-side heat exchanger 5b. During a heating operation, the first flow-rate control device 9b is controlled based on the amount of sub-cooling on the outlet side of the indoor-side heat exchanger 5b. The indoor unit B is provided with the first refrigerant detection sensor 85b that detects the refrigerant in the indoor space, a temperature sensor not illustrated, etc. The first refrigerant detection sensor 85b detects refrigerant leakage into the indoor space from the indoor unit B or the pipe connecting the indoor unit B and the first relay unit E such as a first gas branch pipe 6b and a first liquid branch pipe 7b. The first refrigerant detection sensor 85b may be of any type so long as it can detect leakage of refrigerant for use in the air-conditioning apparatus 100. The first refrigerant detection sensor 85b may be, for example, of a semiconductor type or an infrared type, and detect the refrigerant leakage based on, for example, a change in the concentration of a refrigerant gas at its location or a change in the temperature of ambient air. It is appropriate that the first refrigerant detection sensor 85b is provided at a position where it can easily detect refrigerant leakage, in view of the property of the refrigerant, a convection in the indoor space, etc. Although the above description is made regarding the indoor unit B, the same is true of the indoor unit C and the indoor unit D, that is, the indoor unit C and the indoor unit D have the same configuration as the indoor unit B. [0021] (First relay unit E) The first relay unit E includes a first branch unit 10, a second branch unit 11, a gas-liquid separation device 12, a second flow-rate control device 13, a third flow-rate control device 15, a first heat exchange unit 19, a second heat exchange unit 16, and other units. The first relay unit E is located between the heat source unit A and the indoor units B, C, and D, and has a function of changing the flow of the refrigerant that is supplied from the heat source unit A in a switching manner in response to a request from each of the indoor units B, C, and D to distribute the refrigerant supplied from the heat source unit A to the indoor units B, C, and D. [0022] It should be noted that the flow-passage switching device 2 in the heat source unit A and the first relay unit E are connected to each other by the first connection pipe 6. The indoor-side heat exchangers 5b, 5c, and 5d in the indoor units B, C, and D are connected to the first relay unit E by first gas branch pipes 6b, 6c, and 6d that correspond to the first connection pipe 6 and are associated the indoor units B, C, and D, respectively. The heat-source-side heat exchanger 3 in the heat source unit A and the first relay unit E are connected to each other by the second connection pipe 7 that is smaller in diameter than the first connection pipe 6. The indoor-side heat exchangers 5b, 5c, and 5d in the indoor units B, C, and D and the first relay unit E are connected by the first connection pipe 6, and are connected by a plurality of first liquid branch pipes 7b, 7c, and 7d that correspond to the second connection pipe 7 and are associated with the indoor units B, C, and D, respectively.

[0023] The first relay unit E includes a first low-pressure gas pipe 6g, a first high-pressure gas pipe 7g, a first liquid pipe 71, etc., and the first connection pipe 6 is connected to the first low-pressure gas pipe 6g. The second connection pipe 7 is connected via the gas-liquid separation device 12 to the first high-pressure gas pipe 7g and the first liquid pipe 71.

[0024] The gas-liquid separation device 12 separates gas refrigerant and liquid refrigerant from each other. An inflow side of the gas-liquid separation device 12 is connected to the second connection pipe 7, a gas outflow side of the gas-liquid separation device 12 is connected via the first high-pressure gas pipe 7g to the first branch unit 10, and a liquid outflow side of the gas-liquid separation device 12 is connected via the first liquid pipe 71 to the second branch unit 11.

[0025] One of sides of the first branch unit 10 is connected to the first gas branch pipes 6b, 6c, and 6d and the other is connected to the first low-pressure gas pipe 6g and the first high-pressure gas pipe 7g, and in the first branch unit 10, the flowing direction of the refrigerant in the cooling operation is different from that in in the heating operation.

The first branch unit 10 includes first cooling solenoid valves 32b, 32c, and 32d associated with the indoor units B, C, and D, respectively, and the first heating solenoid valves 30b, 30c, and 30d associated with the indoor units B, C, and D, respectively. [0026] One of sides of the first cooling solenoid valve 32b is connected to the first gas branch pipe 6b and the other is connected to the first low-pressure gas pipe 6g.

Similarly, one of sides of the first cooling solenoid valve 32c is connected to the first gas branch pipe 6c and the other is connected to the first low-pressure gas pipe 6g. One of sides of the first cooling solenoid valve 32d is connected to the first gas branch pipe 6d and the other is connected to the first low-pressure gas pipe 6g. The first cooling solenoid valves 32b, 32c, and 32d are opened in the cooling operations of the indoor units B, C, and D, respectively, and are closed in the heating operations of the indoor units B, C, and D, respectively.

[0027] One of sides of the first heating solenoid valve 30b is connected to the first gas branch pipe 6b and the other is connected to the first high-pressure gas pipe 7g.

Similarly, one of sides of the first heating solenoid valve 30c is connected to the first gas branch pipe 6c and the other is connected to the first high-pressure gas pipe 7g. One of sides of the first heating solenoid valve 30d is connected to the first gas branch pipe 6d and the other is connected to the first high-pressure gas pipe 7g. The first heating solenoid valves 30b, 30c, and 30d are opened in the heating operations of the indoor units B, C, and D, respectively, and are closed in the cooling operations of the indoor units B, C, and D, respectively.

[0028] In such a manner, the first branch unit 10 connects the indoor units B, C, and D to the first connection pipe 6 or the second connection pipe 7 such that connection of each of the indoor units B, C, and D can be switched between the connection of each indoor unit to the first connection pipe 6 and the connection of each indoor unit to the second connection pipe 7. Each of a plurality of first cooling solenoid valves 32b, 32c, and 32d and each of a plurality of first heating solenoid valves 30b, 30c, and 30d is, for example, a one-way solenoid valve. Referring to Fig. 1, in each of the first cooling solenoid valves 32b, 32c, and 32d, two solenoid valves are connected in parallel with each other, but the number of the solenoid valves is not limited to two, that is, a single solenoid valve or three or more solenoid valves may be provided.

[0029] One of sides of the second branch unit 11 is connected to the first liquid branch pipes 7b, 7c, and 7d and the other is connected to the first liquid pipe 71, and the flowing direction of the refrigerant in the cooling operation is different from that in the heating operation. The second branch unit 11 includes a plurality of first check valves 50b, 50c, and 50d, and a plurality of second check valves 52b, 52c, and 52d. The number of the first check valves and the number of the second check valves are the same as the number of the indoor units B, C, and D. A plurality of first check valves 50b, 50c, and 50d are connected to the first liquid branch pipes 7b, 7c, and 7d, respectively, and allow the refrigerant to flow from the first liquid pipe 71 toward the first liquid branch pipes 7b, 7c, and 7d, respectively. A plurality of second check valves 52b, 52c, and 52d are connected to the first liquid branch pipes 7b, 7c, and 7d in parallel with the first check valves 50b, 50c, and 50d, respectively. The second check valves 52b, 52c, and 52d allow the refrigerant to flow from the first liquid branch pipes 7b, 7c, and 7d toward the first liquid pipe 71, respectively.

[0030] A side of the first liquid pipe 71 that is located upstream of the second branch unit 11 is connected to downstream sides of the first check valves 50b, 50c, and 50d at the first liquid branch pipes 7b, 7c, and 7d by a first liquid branch pipe 17 serving as a bypass. A plurality of pipes in the first liquid branch pipe 17 that are each connected to an associated one the first liquid branch pipes 7b, 7c, and 7d join a pipe connected to the first liquid pipe 71 in the first liquid branch pipe 17. The first liquid pipe 71 is connected to the first low-pressure gas pipe 6g by a first bypass pipe 14 serving as a bypass.

[0031] The second check valves 52b, 52c, and 52d are provided at the pipes in the first liquid branch pipe 17 that are each connected to an associated one of the first liquid branch pipes 7b, 7c, and 7d. Then, flow passages are provided to extend from the first liquid pipe 71 via the first check valves 50b, 50c, and 50d to the first flow-rate control devices 9b, 9c, and 9d in the indoor units B, C, and D. Also, flow passages are provided to extend from the first flow-rate control devices 9b, 9c, and 9d in the indoor units B, C, and D via the second check valves 52b, 52c, and 52d to the first liquid pipe 71.

[0032] The first relay unit E includes a direction control device 90 that controls the flow of refrigerant toward the indoor units B, C, and D (see Fig. 2). The direction control device 90 includes a first control valve 91 provided at the first low-pressure gas pipe 6g and a second control valve 92 provided at the first liquid pipe 71.

[0033] The first control valve 91 allows the refrigerant to flow from the first cooling solenoid valves 32b, 32c, and 32d toward the first connection pipe 6, and blocks the flow of the refrigerant from the first connection pipe 6 toward the first cooling solenoid valves 32b, 32c, and 32d. The first control valve 91 is, for example, a check valve. [0034] The second control valve 92 is opened when supplied with power, and blocks the flow of refrigerant toward the first check valves 50b, 50c, and 50d when supplied with no power. The second control valve 92 is, for example, a one-way solenoid valve.

[0035] The second flow-rate control device 13 includes, for example, an openable/closable electric expansion valve 13a, an open/close solenoid valve 13b, etc., and the third flow-rate control device 15 also includes an electric expansion valve 15a, an open/close solenoid valve 15b, etc. Each of the first heat exchange unit 19 and the second heat exchange unit 16 transfer heat between the pipes.

[0036] The gas-liquid separation device 12 and the second branch unit 11 are connected to each other via the first heat exchange unit 19, the second flow-rate control device 13, and the second heat exchange unit 16. The first bypass pipe 14 is provided with the third flow-rate control device 15, and the second branch unit 11 and the first low-pressure gas pipe 6g are connected to each other via the third flow-rate control device 15, the second heat exchange unit 16, and the first heat exchange unit 19.

[0037] The first heat exchange unit 19 transfers heat between a side of the first liquid pipe 71 that is located upstream of the second flow-rate control device 13 and a side of the first bypass pipe 14 that is located downstream of the second heat exchange unit 16. The second heat exchange unit 16 transfers heat between a side of the first liquid pipe 71 that is located downstream of the second flow-rate control device 13 and a side of the first bypass pipe 14 that is located downstream of the third flow-rate control device 15.

[0038] The first relay unit E is provided with the liquid outflow-pressure detection sensor 62, the downstream-side liquid outflow-pressure detection sensor 63, and other sensors. The liquid outflow-pressure detection sensor 62 provided at pad of the first liquid pipe 71 that is located between the first heat exchange unit 19 and the second flow-rate control device 13, and detects a pressure of the refrigerant on the liquid outflow side of the gas-liquid separation device 12. The downstream-side liquid outflow-pressure detection sensor 63 is provided at part of the first liquid pipe 71 that is located between the second flow-rate control device 13 and the second heat exchange unit 16, and detects a pressure of the refrigerant between the second flow-rate control device 13 and the second heat exchange unit 16. To be more specific, the downstream-side liquid outflow-pressure detection sensor 63 detects a pressure of the refrigerant that flows through a region where the first liquid branch pipes 7b, 7c, and 7d join each other.

[0039] As the refrigerant, for example, carbon dioxide (CO2), carbon hydride, natural refrigerant such as helium, chlorofluorocarbon alternative refrigerant not containing chlorine, such as HFC410A, HFC407C, and HFC404A, chlorofluorocarbon refrigerant for use in an existing product, such as R22 and R134a, is used. HFC407C is a zeotropic refrigerant mixture containing 23 wt% of R32 of HFC, 25 wt% of R125 of HFC, and 52 wt% of R134a of HFC. The pipes of the air-conditioning apparatus 100 may be filled with heat medium, not the refrigerant. The heat medium is, for example, water or brine.

[0040] (Controller 80) The controller 80 is, for example, a microcomputer, and is intended to control the entire air-conditioning apparatus 100. To be more specific, the controller 80 controls the air-conditioning apparatus 100 based on, for example, detection information received from the sensor group 60, a plurality of first refrigerant detection sensors 85b, 85c, and 85d, etc., and an instruction from a remote control unit (not illustrated). [0041] The controller 80 may be mounted on any of the heat source unit A, the indoor unit B, the indoor unit C, the indoor unit D, and the first relay unit E, or functions of the controller 80 may be divided and allocated to the above units. The controller 80 may be located separate from the heat source unit A, the indoor units B, C, and D, and the first relay unit E. In the case that the air-conditioning apparatus 100 includes a plurality of controllers 80, the controllers 80 are connected to each other wirelessly or by signal lines.

[0042] Fig. 2 is a block diagram indicating functions of the controller in Embodiment 1 of the present invention. As illustrated in Fig. 2, the controller 80 includes an operation control unit 81 and a leakage detection unit 82.

[0043] The operation control unit 81 acquires detection information from the sensor group 60, and controls each of devices and units based on the acquired detection information. To be more specific, the operation control unit 81 controls, for example, the driving frequency of the compressor 1, the rotation speed of the outdoor fan, and the switching operation of the flow-passage switching device 2. The operation control unit 81 controls, concerning the indoor units B, C, and D, for example, the opening degrees of the first flow-rate control devices 9b, 9c, and 9d, the rotation speeds of indoor fans not illustrated. The operation control unit 81 controls, concerning the first relay unit E, opening and closing of the first cooling solenoid valves 32b, 32c, and 32d, opening and closing of the first heating solenoid valves 30b, 30c, and 30d, the opening degree of the second flow-rate control device 13, and the opening degree of the third flow-rate control device 15. The operation control unit 81 further controls, for example, the opening degree of the first control valve 91, opening and closing of the second control valve 92, etc. The operation control unit 81 controls the supply of power to each of units such as the heat source unit A, the indoor units B, C, and D, and the first relay unit E. In the case that the first control valve 91 is a check valve, it does not need to be controlled.

[0044] The leakage detection unit 82 acquires detection information from the first refrigerant detection sensors 85b, 85c, and 85d, and determines whether refrigerant leakage is detected or not based on the acquired detection information. Then, if refrigerant leakage is detected, the leakage detection unit 82 notifies the operation control unit 81 of it.

[0045] Next, an operation of the air-conditioning apparatus 100 will be described. The air-conditioning apparatus 100 can perform a cooling only operation, a heating only operation, a cooling main operation, and a heating main operation, as normal operations. The cooling only operation is an operation in which the indoor units B, C, and D all perform the cooling operation. The heating only operation is an operation in which the indoor units B, C, and D all perform the heating operation. The cooling main operation is an operation in which the cooling operation and the heating operation are simultaneously performed such that the capacity for the cooling operation is larger than that for the heating operation. The heating main operation is an operation in which the cooling operation and the heating operation are simultaneously performed such that the capacity for the heating operation is larger than that for the cooling operation.

[0046] (Cooling only operation) Fig. 3 is a circuit diagram illustrating a state of the air-conditioning apparatus in the cooling only operation according to Embodiment 1 of the present invention. First of all, the cooling only operation will be described. In the air-conditioning apparatus 100, the indoor units B, C, and D all perform the cooling operation. As illustrated in Fig. 3, high temperature and high pressure gas refrigerant discharged from the compressor 1 flows through the flow-passage switching device 2, and exchanges heat with air sent by an outdoor fan that sends air at a variable rate and is provided in the heat-source-side heat exchanger 3, and as a result the refrigerant condenses and liquefies. The liquefied refrigerant flows through the heat-source-side first check valve 21, the second connection pipe 7, the gas-liquid separation device 12, and the first liquid pipe 71 in this order, and further flows through the second branch unit 11 and the first liquid branch pipes 7b, 7c, and 7d, and then flows into the indoor units B, C, and D. When flowing through the first liquid pipe 71, the refrigerant flows through the second flow-rate control device 13 and the second control valve 92.

[0047] The pressure of the refrigerant having flowed into the indoor units B, C, and D is reduced to a low pressure by the first flow-rate control devices 9b, 9c, and 9d whose opening degrees are controlled in accordance with the amounts of superheat on the outlet sides of the indoor-side heat exchangers 5b, 5c, and 5d, respectively. The refrigerant reduced in pressure flows into each of the indoor-side heat exchangers 5b, 5c, and 5d, exchanges heat with indoor air at each of the indoor-side heat exchangers 5b, 5c, and 5d, and thus evaporates and gasifies into gas refrigerant to cool an associated one of the indoor spaces. The gas refrigerant flows through the first gas branch pipes 6b, 6c, and 6d, the first cooling solenoid valves 32b, 32c, and 32d in the first branch unit 10, the first low-pressure gas pipe 6g, and the first connection pipe 6.

After flowing through the first connection pipe 6, the gas refrigerant flows through the heat-source-side second check valve 22, and the flow-passage switching device 2 and the accumulator 4 in the heat source unit A, and is sucked into the compressor 1. [0048] In the cooling only operation, the first heating solenoid valves 30b, 30c, and 30d are all closed, and the first cooling solenoid valves 32b, 32c, and 32d are all opened. Since the first connection pipe 6 is set at a low pressure and the second connection pipe 7 is set at a high pressure, the refrigerant flows through the heat-source-side first check valve 21 and the heat-source-side second check valve 22.

[0049] Part of the refrigerant having flowed through the second flow-rate control device 13 in the first liquid pipe 71 flows into the first bypass pipe 14. The pressure of the refrigerant having flowed into the first bypass pipe 14 is reduced to a low pressure at the third flow-rate control device 15. The refrigerant reduced in pressure exchanges heat with the refrigerant having flowed through the second flow-rate control device 13, at the second heat exchange unit 16, and further exchanges heat with refrigerant which is to flow into the second flow-rate control device 13, in the first heat exchange unit 19, and as a result evaporates. The evaporated refrigerant flows into the first connection pipe 6 and the heat-source-side second check valve 22, then flows through the flow-passage switching device 2 and the accumulator 4 in the heat source unit A, and is sucked into the compressor 1.

[0050] On the other hand, the refrigerant that flows through the first liquid pipe 71 and is subcooled in the first heat exchange unit 19 and the second heat exchange unit 16 flows through the first check valves 50b, 50c, and 50d into each of the indoor units B, C, and D that is to perform the cooling operation. It should be noted that the controller 80 adjusts the capacity of the variable capacity compressor 1 and the flow rate of air from the outdoor fan such that evaporating temperatures of the indoor units B, C, and D and a condensing temperature of the heat-source-side heat exchanger 3 reach respective predetermined target temperatures. Therefore, in each of the indoor units B, C, and D, a target cooling capacity can be obtained. The condensing temperature of the heatsource-side heat exchanger 3 is determined as a saturation temperature for the pressure detected by the discharge pressure detection sensor 61.

[0051] (Heating only operation) Fig. 4 is a circuit diagram illustrating a state of the air-conditioning apparatus in the heating only operation in Embodiment 1 of the present invention. Next, the heating only operation will be described. In the air-conditioning apparatus 100, the indoor units B, C, and D all perform the heating operation. The high-temperature and high- pressure gas refrigerant discharged from the compressor 1 flows through the flow-passage switching device 2, the heat-source-side third check valve 23, the second connection pipe 7, the gas-liquid separation device 12, the first high-pressure gas pipe 7g, the first heating solenoid valves 30b, 30c, and 30d, and the first gas branch pipes 6b, 6c, and 6d, in this order. Then, the refrigerant having flowed through the first gas branch pipes 6b, 6c, and 6d flows into the indoor units B, C, and D. The refrigerant having flowed into the indoor units B, C, and D exchange heat with indoor air, and condenses and liquefies to cool the indoor spaces. The liquefied refrigerant flows through the first flow-rate control devices 9b, 9c, and 9d whose opening degrees are controlled in accordance with the amounts of subcooling on the outlet sides of the indoor-side heat exchangers 5b, 5c, and 5d.

[0052] The refrigerant having flowed out of the first flow-rate control devices 9b, 9c, and 9d flows from the first liquid branch pipes 7b, 7c, and 7d into the second branch unit 11, then flows through the second check valves 52b, 52c, and 52d, and join each other in the first liquid branch pipe 17. After joining each other in the second branch unit 11, the refrigerant is guided to part of the first liquid pipe 71 that is located between the second flow-rate control device 13 and the second heat exchange unit 16, then flows into the first bypass pipe 14, and flows through the third flow-rate control device 15. The refrigerant is reduced in pressure in the first flow-rate control devices 9b, 9c, and 9d and the third flow-rate control device 15 to change into low-pressure two-phase gas-liquid refrigerant.

[0053] The refrigerant whose pressure is reduced to a low pressure flows through the first connection pipe 6, and flows through the heat-source-side fourth check valve 24 in the heat source unit A. Then, the refrigerant flows into the heat-source-side heat exchanger 3, exchanges heat with air sent by the outdoor fan that is variable in flow rate of air, and then evaporates to change into gas refrigerant. The gas refrigerant flows through the flow-passage switching device 2 and the accumulator 4, and is sucked into the compressor 1.

[0054] In the heating only operation, the first heating solenoid valves 30b, 30c, and 30d are all opened, and the first cooling solenoid valves 32b, 32c, and 32d are all closed. [0055] Since the first connection pipe 6 is set at a low pressure and the second connection pipe 7 is set at a high pressure, the refrigerant flows through the heat-source-side third check valve 23 and the heat-source-side fourth check valve 24. Since each of the first liquid branch pipes 7b, 7c, and 7d is set at a pressure higher than at the second connection pipe 7, the refrigerant does not flow through any of the first check valves 50b, 50c, and 50d. It should be noted that the controller 80 adjusts the capacity of the compressor 1 that is variable in capacity and the flow rate of air that is sent from the outdoor fan such that condensing temperatures of the indoor units B, C, and D, and an evaporating temperature of the heat-source-side heat exchanger 3 reach respective predetermined target temperatures. Therefore, in the indoor units B, C, and D, target heating capacities can be obtained.

[0056] (Cooling main operation) Fig. 5 is a circuit diagram illustrating a state of the air-conditioning apparatus in the cooling main operation in Embodiment 1 of the present invention. The cooling main operation will be described. It is assumed that in the air-conditioning apparatus 100, the indoor unit B and the indoor unit C make a request for cooling, and the indoor unit D makes a request for heating. In the cooling main operation, the first heating solenoid valve 30b and the first heating solenoid valve 30c connected to the indoor units B and C, respectively, are closed, and the first heating solenoid valve 30d connected to the indoor unit D is opened. The first cooling solenoid valve 32b and the first cooling solenoid valve 32c connected to the indoor units B and C, respectively, are opened, and the first cooling solenoid valve 32d connected to the indoor unit D is closed.

[0057] As illustrated in Fig. 5, high-temperature and high-pressure gas refrigerant discharged from the compressor 1 flows into the heat-source-side heat exchanger 3 via the flow-passage switching device 2, and exchanges heat with air sent by the outdoor fan which is variable in flow rate of sending air to change into high-temperature and high-pressure two-phase refrigerant.

[0058] Here, the controller 80 adjusts the capacity of the variable capacity compressor 1 and the flow rate of air that is sent from the outdoor fan such that evaporating temperatures and condensing temperatures of the indoor units B, C, and D reach respective predetermined target temperatures. In each of the indoor units B, C, and D, a target heating capacity or a target cooling capacity can be obtained.

[0059] The high-temperature and high-pressure two-phase refrigerant is sent via the heat-source-side first check valve 21 and the second connection pipe 7 to the gas-liquid separation device 12 in the first relay unit E, and is separated into gas refrigerant and liquid refrigerant. The gas refrigerant separated by the gas-liquid separation device 12 flows through the first high-pressure gas pipe 7g, the first heating solenoid valve 30d in the first branch unit 10, and the first gas branch pipe 6d in this order, and flows into the indoor unit D which is to perform the heating operation. The gas refrigerant having flowed into the indoor unit D exchanges heat with indoor air at the indoor-side heat exchanger 5d, and condenses and liquefies. At that time, the indoor space is heated by the indoor unit D. Furthermore, the refrigerant having flowed out of the indoor-side heat exchanger 5d flows through the first flow-rate control device 9d whose opening degree is controlled in accordance with the amount of subcooling on the outlet side of the indoor-side heat exchanger 5d in the indoor unit D, is reduced in pressure, and flows into the second branch unit 11. The refrigerant having flowed into the second branch unit 11 flows through the first liquid branch pipe 17 including the second check valve 52d into part of the first liquid pipe 71 that is located downstream of the second flow-rate control device 13.

[0060] On the other hand, the liquid refrigerant separated by the gas-liquid separation device 12 flows through the second flow-rate control device 13 that is controlled based on a pressure detected by the liquid outflow-pressure detection sensor 62 and a pressure detected by the downstream-side liquid outflow-pressure detection sensor 63, and joins the refrigerant having flowed through the indoor unit D described above. The refrigerant obtained by the above joining flows into the second heat exchange unit 16, and is cooled by the second heat exchange unit 16.

[0061] Then, part of the refrigerant cooled by the second heat exchange unit 16 flows into the first check valves 50b and 50c, and flows through the first liquid branch pipes 7b and 7c into the indoor units B and C which are to perform the cooling operation. The pressure of the refrigerant having flowed into each of the indoor units B and C is reduced to a low pressure by an associated one of the first flow-rate control devices 9b and 9c whose opening degrees are controlled in accordance with the amounts of superheating on the outlet sides of the indoor-side heat exchangers 5b and 5c. Thereafter, the refrigerant reduced in pressure flows into each of the indoor-side heat exchangers 5b and 5c, and is then subjected to heat exchange to evaporate and gasify into gas refrigerant. At that time, the indoor spaces are cooled by the indoor units B and C. The gas refrigerant flows into the first connection pipe 6 via the first cooling solenoid valves 32b and 32c and the first low-pressure gas pipe 6g.

[0062] On the other hand, remaining part of the refrigerant cooled by the second heat exchange unit 16 flows through the third flow-rate control device 15 whose opening degree is controlled such that a difference between a pressure detected by the liquid outflow-pressure detection sensor 62 and a pressure detected by the downstream-side liquid outflow-pressure detection sensor 63 falls within a set range. Then, the remaining part of the refrigerant is subjected to heat exchange at the second heat exchange unit 16 and the first heat exchange unit 19 to evaporate, and then joins, in the first connection pipe 6, the refrigerant having flowed through the indoor units B and C. The refrigerant obtained by the above joining in the first connection pipe 6 flows through the heat-source-side second check valve 22, the flow-passage switching device 2, and the accumulator 4 in the heat source unit A, and is sucked into the compressor 1.

[0063] Since the first connection pipe 6 is set at a low pressure and the second connection pipe 7 is set at a high pressure, the refrigerant flows through the heatsource-side first check valve 21 and the heat-source-side second check valve 22. Since the first liquid branch pipes 7b and 7c are lower in pressure than the first liquid pipe 71, the refrigerant does not flow through the second check valves 52b and 52c.

Since the first liquid branch pipe 7d is higher in pressure than the first liquid pipe 71, the refrigerant does not flow through the first check valve 50d. The first check valves 50b, 50c, and 50d and the second check valves 52b, 52c, and 52d prevent the refrigerant having flowed through the indoor unit D from flowing into the indoor units B and C that are in the cooling operation, without flowing through the second heat exchange unit 16 and also without being sufficiently subcooled.

[0064] (Heating main operation) Fig. 6 is a circuit diagram illustrating a state of the air-conditioning apparatus in the heating main operation in Embodiment 1 of the present invention. The heating main operation will be described. It is assumed that in the air-conditioning apparatus 100, the indoor unit B and the indoor unit C make a request for heating, and the indoor unit D makes a request for cooling. In the heating main operation, the first heating solenoid valves 30b and 30c connected to the indoor units B and C, respectively, are opened, and the first heating solenoid valve 30d connected to the indoor unit D is closed. The first cooling solenoid valves 32b and 32c connected to the indoor units B and C, respectively, are closed, and the first cooling solenoid valve 32d connected to the indoor unit D is opened.

[0065] As illustrated in Fig. 6, high-temperature and high-pressure gas refrigerant discharged from the compressor 1 is sent to the first relay unit E through the flow-passage switching device 2, the heat-source-side third check valve 23, and the second connection pipe 7, and then flows through the gas-liquid separation device 12. The refrigerant having flowed through the gas-liquid separation device 12 flows through the first high-pressure gas pipe 7g into the first heating solenoid valves 30b and 30c in the first branch unit 10. The refrigerant having flowed into the first heating solenoid valves 30b and 30c flows through the first gas branch pipes 6b and 6c into the indoor units B and C, respectively. The refrigerant having flowed into each of the indoor units B and C exchanges heat with indoor air at an associated one of the indoor-side heat exchangers 5b and 5c to condense and liquefy. At that time, the indoor spaces are heated by the indoor units B and C. The liquefied refrigerant flows through the first flow-rate control devices 9b and 9c whose opening degrees are controlled in accordance with the amounts of subcooling on the outlet sides of the indoor-side heat exchangers 5b and 5c, respectively, and is then reduced in pressure, and further flows into the second branch unit 11.

[0066] The refrigerant having flowed into the second branch unit 11 flows through the first liquid branch pipe 17 including the second check valves 52b and 52c, joins the refrigerant that flows through the first liquid pipe 71, and is cooled by the second heat exchange unit 16. Part of the refrigerant cooled by the second heat exchange unit 16 flows through the first check valve 50d and the first liquid branch pipe 7d into the indoor unit D which is to perform the cooling operation. The refrigerant having flowed into the indoor unit D flows into the first flow-rate control device 9d whose opening degree is controlled in accordance with the amount of superheat on the outlet side of the indoor-side heat exchanger 5d, and is reduced in pressure. The refrigerant reduced in pressure flows into the indoor-side heat exchanger 5d, and is subjected to heat exchange to evaporate and gasify into gas refrigerant. At that time, the indoor space is cooled by the indoor unit D. Then, the gas refrigerant flows into the first connection pipe 6 via the first cooling solenoid valve 32d and the first low-pressure gas pipe 6g.

[0067] On the other hand, remaining part of the refrigerant cooled by the second heat exchange unit 16 flows through the third flow-rate control device 15 that is controlled such that a difference between a pressure detected by the liquid outflow-pressure detection sensor 62 and a pressure detected by the downstream-side liquid outflow-pressure detection sensor 63 falls within a set range. The refrigerant having flowed through the third flow-rate control device 15 exchanges heat with the refrigerant having flowed out of the indoor units B and C, at the second heat exchange unit 16 to evaporate. After that, the evaporated refrigerant joins, in the first low-pressure gas pipe 6g, the refrigerant having flowed through the indoor unit D, and flows via the first connection pipe 6 into the heat-source-side fourth check valve 24 and the heat-source-side heat exchanger 3 in the heat source unit A. The refrigerant having flowed into the heat-source-side heat exchanger 3 exchanges heat with air sent from the outdoor fan to evaporate and gasify.

[0068] It should be noted that the controller 80 adjusts the capacity of the compressor 1 and the flow rate of air from the outdoor fan based on the information acquired from the sensor group 60 such that an evaporating temperature of the indoor unit D which makes a request for cooling and condensing temperatures of the indoor units B and C which make a request for heating reach respective predetermined target temperatures.

Thereby, the indoor unit B and the indoor unit C can operate with the target heating capacity, and the indoor unit D can obtain a cooling capacity. The refrigerant flows through the flow-passage switching device 2 and the accumulator 4 in the heat source unit A, and is sucked into the compressor 1.

[0069] Since the first connection pipe 6 is set at a low pressure and the second connection pipe 7 is set at a high pressure, the refrigerant flows through the heatsource-side third check valve 23 and the heat-source-side fourth check valve 24. The second flow-rate control device 13 is closed. Since the first liquid branch pipes 7b and 7c are higher in pressure than the first liquid pipe 71, the refrigerant does not flow through the first check valves 50b and 50c. Since the first liquid branch pipe 7d is lower in pressure than the first liquid pipe 71, the refrigerant does not flow through the second check valve 52d. The first check valves 50b, 50c, and 50d and the second check valves 52b, 52c, and 52d prevent the refrigerant having flowed through the indoor units B and C that are in the heating operation from flowing into the indoor unit D without flowing through the second heat exchange unit 16 and without being sufficiently subcooled.

[0070] Fig. 7 is a diagram indicating flows of the refrigerant in branch units and the vicinity thereof during an operation in Embodiment 1 of the present invention. Fig. 7 indicating flows of refrigerant in the branch units and the vicinity thereof during the cooling main operation as illustrated in Fig. 5. An operation and a function of the direction control device 90 will be described.

[0071] As described above, when the air-conditioning apparatus 100 is in operation, the controller 80 controls, concerning the indoor units B, C, and D, opening and closing of the first cooling solenoid valves 32b, 32c, and 32d and the first heating solenoid valves 30b, 30c, and 30d by controlling whether or not to supply power. For example, in the first branch unit 10, the first cooling solenoid valve 32b for the indoor unit B that is in the cooling operation is opened, and the first heating solenoid valve 30b for the indoor unit B is closed. The refrigerant having flowed from the first gas branch pipe 6b and flowed through the first cooling solenoid valve 32b toward the first low-pressure gas pipe 6g flows through the first control valve 91 in a forward direction. On the other hand, the first cooling solenoid valve 32d for the indoor unit D that is in the heating operation is closed, and the first heating solenoid valve 30d for the indoor unit D is opened. Then, the refrigerant flows from the first high-pressure gas pipe 7g and flows through the first heating solenoid valve 30d toward the first gas branch pipe 6d. When the air-conditioning apparatus 100 is in operation, the controller 80 causes the second control valve 92 to be opened. Because of control of the first branch unit 1, in the second branch unit 11, for the indoor unit B that is in the cooling operation, the first check valve 50b allows the refrigerant to flow from the first liquid pipe 71 toward the first liquid branch pipe 7b. On the other hand, for the indoor unit D that is in the heating operation, the second check valve 52b allows the refrigerant to flow from the first liquid branch pipe 7d toward the first liquid branch pipe 17. At this time, since the second control valve 92 is opened, the refrigerant flow at the first check valve 50b is not obstructed.

[0072] Fig. 8A is a diagram illustrating a state of the refrigerant in the branch units and the vicinity thereof during a power outage in Embodiment 1 of the present invention. Fig. 8A illustrates a state of a circuit in the case where the air-conditioning apparatus 100 stops the air-conditioning operation and power is not supplied to the first relay unit E. When the operation of the air-conditioning apparatus 100 is stopped, the pressure in each of pipes changes. In Fig. 8A, arrows indicate the flow of the refrigerant in the case where a refrigerant pressure is applied from the first relay unit E to an indoor unit side. The first cooling solenoid valves 32b, 32c, and 32d and the first heating solenoid valves 30b, 30c, and 30d are each a one-way solenoid valve as descried above. Thus, when not supplied with power, each of these solenoid valves blocks the flow of the refrigerant flow in one direction, but allows the flow of the refrigerant in an opposite direction to the above one direction.

[0073] In the first branch unit 10, while the operation is stopped, the flow of the refrigerant from the first high-pressure gas pipe 7g to the indoor unit side is blocked by the first heating solenoid valves 30b, 30c, and 30d. On the other hand, while the operation is stopped, the first cooling solenoid valves 32b, 32c, and 32d are located in such positions as to allow the refrigerant to flow from the first low-pressure gas pipe 6g to the indoor unit side, but the refrigerant flow to the indoor unit side is blocked by the first control valve 91 provided at the first low-pressure gas pipe 6g.

[0074] In the second branch unit 11, while the operation is stopped, the flow of the refrigerant from the first liquid branch pipe 17 to the indoor unit side is blocked by the second check valves 52b, 52c, and 52d. On the other hand, the first check valves 50b, 50c, and 50d are set to allow the refrigerant to flow from the first liquid pipe 71 to the indoor unit side, but the second control valve 92 provided at the first liquid pipe 71 blocks the flow of the refrigerant toward the indoor unit side while the operation is stopped. In such a manner, when power is not supplied to the first relay unit E, transfer of the refrigerant from the first relay unit E to an indoor pipe is prevented.

[0075] The controller 80 may be configured to stop, for example, when refrigerant leakage is detected, the air-conditioning operation of the air-conditioning apparatus 100 to stop the supply of power to the first relay unit E. In such a configuration, it is possible to reduce the amount of refrigerant that transfers to the indoor space, and thus reduce the amount of leakage refrigerant.

[0076] Fig. 8B is a diagram indicating flows of air in evacuation at the branch units and the vicinity thereof in Embodiment 1 of the present invention. The evacuation is carried out from the heat source unit A, and power is not supplied to the first relay unit E. Arrows in the figure indicate the flows of air. The first control valve 91 and the second control valve 92 both allow air to flow from the indoor unit side toward the heat source unit.

[0077] It should be noted that as the first control valve 91, a check valve is used, and as the second control valve 92, a one-way solenoid valve is used, in order that the flow of air in the evacuation should not be obstructed, and the transfer of the refrigerant toward the indoor unit side should be reduced; however, the configuration of the direction control device 90 is not limited to such a configuration.

[0078] (Modification 1) Fig. 9A is a diagram indicating flows of the refrigerant during a power outage in a modification of the first control valve. Fig. 9B is a diagram indicating flows of air in evacuation in the modification of the first control valve. It is illustrated by way of example that a one-way solenoid valve is used as a first control valve 97 instead of a check valve. In this case, when the air-conditioning apparatus 100 is in operation, the first control valve 97 is supplied with power, and is thereby opened. In the case where a one-way solenoid valve is used, the flow of the refrigerant during the operation and the flow of air in the evacuation are not obstructed, and the flow of the refrigerant toward the indoor unit side during a power outage can be blocked, as in the case where the check valve is used. The check valve is inexpensive as compared with the one-way solenoid valve, whereas the one-way solenoid valve can maintain a blocking function even in the case that a pressure difference at a set position is small, unlike the check valve.

[0079] (Modification 2) Fig. 10A is a diagram illustrating a state of the refrigerant during a power outage in a modification of the second control valve. Fig. 10B is a diagram indicating flows of air in evacuation in the modification of the second control valve. It is illustrated by way of example that a combination of a plurality of valves is used as a second control valve 98 instead of the one-way solenoid valve. The second control valve 98 can be configured such that a solenoid valve 98a and a check valve 98b are connected in parallel with each other. The solenoid valve 98a as illustrated in the figure is a valve that is opened when supplied with power. However, unlike the above one-way solenoid valve, when not supplied with power, the solenoid valve 98a blocks bidirectional flows of the refrigerant. When the air-conditioning apparatus 100 is in the normal operation, the solenoid valve 98a is supplied with power and is opened; however, when the solenoid valve 98a is not conductive or it is not supplied with power, the solenoid valve 98a is closed. In the second control valve 98 having the above configuration, during the operation, the solenoid valve 98a allows the refrigerant to flow from the heat source unit side toward the indoor unit side, and when not supplied with power, the solenoid valve 98a is closed to block the transfer of the refrigerant. Furthermore, when the evacuation is carried out, the second control valve 98 can secure a flow passage of air using the check valve.

[0080] As described above, in Embodiment 1, the relay unit (the first relay unit E) includes the first check valves 50b, 50c, and 50d, the second check valves 52b, 52c, and 52d, the first control valve 91, and the second control valve 92. The first check valves 50b, 50c, and 50d allow the refrigerant to flow therefrom into the first liquid branch pipes 7b, 7c, and 7d, respectively, and the second check valves 52b, 52c, and 52d allow the refrigerant from the first liquid branch pipes 7b, 7c, and 7d to pass through the second check valves 52b, 52c, and 52d, respectively. The first control valve 91 is provided at the first low-pressure gas pipe 6g and allows the refrigerant to flow from the first cooling solenoid valves 32b, 32c, and 32d toward the first connection pipe 6.

When not supplied with power, the first control valve 91 blocks the flow of the refrigerant from the first connection pipe 6 toward the first cooling solenoid valves 32b, 32c, and 32d. On the other hand, the second control valve 92 is provided at the first liquid pipe 71, and is opened when supplied with power, and blocks the flow of the refrigerant toward the first check valves 50b, 50c, and 50d when not supplied with power.

[0081] Thereby, in the first relay unit E, the first control valve 91 provided at the first low-pressure gas pipe 6g and the second control valve 92 provided at the first liquid pipe 71 allow the flow of the refrigerant during the operation and that of the refrigerant during the evacuation. The first control valve 91 and the second control valve 92 block the transfer of the refrigerant from the first relay unit E to the indoor units B, C, and D while the operation is stopped. Therefore, in the first relay unit E, it is possible to reduce the refrigerant leakage in the indoor units B, C, and D, and the indoor pipes such as the first gas branch pipes 6b, 6c, and 6d, the first liquid branch pipes 7b, 7c, and 7d, and easily perform the evacuation.

[0082] The first control valve 91 is a check valve. Therefore, the control of the refrigerant flow as described above can be controlled by the first control valve 91, which is inexpensive.

[0083] The first control valve 91 is a one-way solenoid valve that blocks the flow of the refrigerant only in one direction when not supplied with power, and allows the flow of the refrigerant when a pressure is applied in the opposite direction to the above one flow direction. Thereby, even in the case where the internal pressure in a pipe is uniform ized to reduce the pressure difference, the first control valve 97 can maintain the blocking function between the first relay unit E and the indoor units B, C, and D. [0084] The second control valve 92 is also a one-way solenoid valve that blocks the flow of the refrigerant only in one direction when not supplied with power, and allows the flow of the refrigerant when a pressure is applied in the opposite direction to the above one direction. Therefore, the above control of the flow of the refrigerant can be achieved with a smaller number of components.

[0085] The second control valve 92 may include the solenoid valve 98a which blocks bidirectional flows when not supplied with power, and the check valve 98b provided in parallel with the solenoid valve 98a. Thereby, with a combination of the solenoid valve 98a and the check valve 98b, the second control valve 98 can obtain the same advantage as in the case where the second control valve 98 is a one-way solenoid valve. The versatility of components is improved.

[0086] The first relay unit E further includes the first bypass pipe 14 that bypasses the first low-pressure gas pipe 6g and the first liquid pipe 71. The first control valve 91 is provided between the junction of the first low-pressure gas pipe 6g and the first bypass pipe 14 and the first cooling solenoid valves 32b, 32c, and 32d. The second control valve 92 is provided between the junction of the first liquid pipe 71 and the first bypass pipe 14 and the first check valves 50b, 50c, and 50d.

[0087] Thereby, while the operation of the air-conditioning apparatus 100 is stopped, the second control valve 92 blocks the flow of the refrigerant from the first liquid pipe 71 toward the first check valves 50b, 50c, and 50d. The first control valve 91 blocks the flow of the refrigerant that flows from the first bypass pipe 14 via the junction into the first low-pressure gas pipe 6g and toward the first cooling solenoid valves 32b, 32c, and 32d. Therefore, the air-conditioning apparatus 100 can prevent the refrigerant from flowing out of the first relay unit E into the indoor unit side.

[0088] The air-conditioning apparatus 100 includes the heat source unit A, the indoor units B, C, and D, and the first relay unit E. Thereby, in the air-conditioning apparatus 100, the first control valve 91 and the second control valve 92 can allow the flow of the refrigerant during the operation and the flow of air during the evacuation, and block the transfer of the refrigerant from the first relay unit E to the indoor units B, C, and D while the operation is stopped. Particularly, not only when power is supplied to a system of the air-conditioning apparatus, but even when power cannot be supplied to the system, for example, before a power supply construction or during a power outage, it is possible to block the transfer of the refrigerant to the indoor units B, C, and D. It is therefore possible to provide an air-conditioning apparatus 100 which can cope with the refrigerant leakage, and enables work in maintenance and construction such as the evacuation to be easily conducted.

[0089] Embodiment 2 Fig. 11 is a schematic diagram illustrating a schematic circuit configuration of an air-conditioning apparatus according to Embodiment 2 of the present invention.

Embodiment 1 is described above by referring to the case where the first relay unit E is connected to the heat source unit A and the plurality of indoor units B, C, and D. In Embodiment 2, an air-conditioning apparatus 200 includes a second relay unit E2 in addition to the heat source unit A, a first relay unit E1, and the indoor units B, C, and D. In the air-conditioning apparatus 200, the entire system thereof is controlled by a controller 280. Regarding Embodiment 2, configurations and components which are different from those in Embodiment 1 will be described; and configurations and components which are the same as those in Embodiment 1 will be denoted by the same reference signs, and their descriptions will be omitted.

[0090] The first relay unit El is connected to the heat source unit A and the indoor units B, C, and D as in Embodiment 1. The first relay unit El is connected to the second relay unit E2 by a third connection pipe 106g, a fourth connection pipe 107g, and a fifth connection pipe 1071. The third connection pipe 106g is connected to the first low-pressure gas pipe 6g, the fourth connection pipe 107g is connected to the first high-pressure gas pipe 7g, and the fifth connection pipe 1071 is connected to the first liquid pipe 71. The second relay unit E2 is connected to a plurality of indoor units H, I, and J, and provided with a second refrigerant detection sensor 285 that detects the refrigerant. The second relay unit E2 is connected to the indoor units H, I, and J by second gas branch pipes 106h, 106i, and 106h, and second liquid branch pipes 107h, 107i, and 107j, which are associated with the indoor units H, I, and J, respectively. It should be noted that Fig. 11 illustrates the case that the second relay unit E2 is connected to three indoor units, that is, the indoor units H, I, and J, but the number of indoor units may be one or more. Each the indoor units H, I, and J has the same configuration as the indoor unit B, etc. described above.

[0091] Fig. 12 is a circuit diagram illustrating a circuit configuration of the first relay unit in the air-conditioning apparatus according to Embodiment 2 of the present invention. In Embodiment 2, the first relay unit El includes a third control valve 93 and a fourth control valve 94 in addition to the first control valve 91 and the second control valve 92.

[0092] The third control valve 93 is provided at the first high-pressure gas pipe 7g to control the flow of the refrigerant between the first relay unit El and the second relay unit E2. The third control valve 93 is, for example, a one-way solenoid valve. For example, when the air-conditioning apparatus 200 is in operation and receives an operation request from any of the indoor units H, I and J connected to the second relay unit E2, the controller 280 causes the third control valve 93 to be opened to allow the refrigerant to flow from the first high-pressure gas pipe 7g to the second relay unit E2. Furthermore, when the air-conditioning apparatus 200 is in operation and does not receive an operation request from any of the indoor units H, I, and J, the controller 280 causes the third control valve 93 to be closed. When not supplied with power, the third control valve 93 allows only the flow of the refrigerant into the first relay unit El and blocks the flow of the refrigerant from the first relay unit El, when not supplied with power.

[0093] The fourth control valve 94 is provided at the first liquid pipe 71 to control the flow of the refrigerant between the first relay unit El and the second relay unit E2. The fourth control valve 94 is, for example, a one-way solenoid valve. For example, when the air-conditioning apparatus 200 is in operation and receives an operation request from any of the indoor units H, I, and J connected to the second relay unit E2, the controller 280 causes the fourth control valve 94 to be opened to allow the refrigerant to flow between the first relay unit El and the second relay unit E2. Furthermore, when the air-conditioning apparatus 200 is in operation and does not receive an operation request from any of the indoor units H, I, and J, the controller 280 causes the fourth control valve 94 to be closed. When not supplied with power, the fourth control valve 94 allows only the flow of the refrigerant into the first relay unit El and blocks the flow of the refrigerant from the first relay unit E1.

[0094] The second refrigerant detection sensor 285 may be provided at the third connection pipe 106g, the fourth connection pipe 107g, the fifth connection pipe 1071, or the second relay unit E2. The controller 280 may be configured to close the third control valve 93 and the fourth control valve 94 when the second refrigerant detection sensor 285 detects leakage. In such a configuration, even if refrigerant leakage occurs in space in which the second relay unit E2, the third connection pipe 106g, the fourth connection pipe 107g, the fifth connection pipe 1071 or another pipe is provided, it is possible to reduce the amount of leak refrigerant in the space.

[0095] Fig. 13 is a circuit diagram illustrating a circuit configuration of the second relay unit in the air-conditioning apparatus according to Embodiment 2 of the present invention. The second relay unit E2 includes a third branch unit 210, a fourth branch unit 211, a fourth flow-rate control device 215, a third heat exchange unit 216, and other units. The second relay unit E2 has a function of changing the flow of the refrigerant in a switching manner in response to an operation request from any of the indoor units H, I, and J, and distributing the refrigerant supplied from the first relay unit El to the indoor units H, I, and J. [0096] The second relay unit E2 includes a second low-pressure gas pipe 206g, a second high-pressure gas pipe 207g, a second liquid pipe 2071, and other pipes. The third connection pipe 106g is connected to the second low-pressure gas pipe 206g, the fourth connection pipe 107g is connected to the second high-pressure gas pipe 207g, and the fifth connection pipe 1071 is connected to the second liquid pipe 2071.

[0097] In the third branch unit 210, the flow direction of the refrigerant in the cooling operation is different from that in the heating operation. The third branch unit 210 includes second cooling solenoid valves 232h, 232i, and 232j, and second heating solenoid valves 230h, 230i, and 230j for the indoor units H, I, and J, respectively. The second cooling solenoid valves 232h, 232i, and 232j are connected to the second gas branch pipes 106h, 106i, and 106j, respectively, at one side of each of the second cooling solenoid valves 232h, 232i, and 232j, and the second cooling solenoid valves 232h, 232i, and 232j are also connected to the second low-pressure gas pipe 206g at the other side of each of the second cooling solenoid valves 232h, 232i, and 232j. The second cooling solenoid valves 232h, 232i, and 232j are opened when the indoor units H, I, and J connected thereto are in the cooling operation, and are closed when the indoor units H, I, and J are in the heating operation. The second heating solenoid valves 230h, 230i, and 230j are connected to the second gas branch pipes 106h, 106i, and 106j, respectively, at one side of each of the second heating solenoid valves 230h, 230i, and 230j, and the second heating solenoid valves 230h, 230i, and 230j are also connected to the second high-pressure gas pipe 207g at the other side of each of second heating solenoid valves 230h, 230i, and 230j. The second heating solenoid valves 230h, 230i, and 230j are opened when the indoor units H, I, and J connected thereto are in the heating operation, and are closed when the indoor units H, I, and J are in the cooling operation.

[0098] In the fourth branch unit 211, the flowing direction of the refrigerant in the cooling operation is different from that in the heating operation. The fourth branch unit 211 includes a plurality of third check valves 250h, 250i, and 250j, and a plurality of fourth check valves 252h, 252i, and 252j. The number of the third check valves 250h, 250i, and 250j is the same as the number of the indoor units H, 1, and J. The third check valves 250h, 250i, and 250j are connected to the second liquid branch pipes 107h, 107i, and 107j, respectively, to allow the refrigerant to flow from the second liquid pipe 2071 toward the second liquid branch pipes 107h, 107i, and 107j. The number of the fourth check valves 252h, 252i, and 252j is the same as the number of the indoor units B, C, and D. The fourth check valves 252h, 252i, and 252j are connected parallel to the third check valves 250h, 250i, and 250j in the second liquid branch pipes 107h, 107i, and 107j, respectively. The fourth check valves 252h, 252i, and 252j allow the refrigerant to flow from the second liquid branch pipes 107h, 107i, and 107j, respectively, toward the second liquid pipe 2071. Part of the second liquid pipe 2071 that is located upstream of the fourth branch unit 211 is bypassed by part of a second liquid branch pipe 217 and part of a plurality of second liquid branch pipes 107h, 107i, and 107j that is downstream of the third check valves 250h, 250i, and 250j. A plurality of pipes in the second liquid branch pipe 217 that are connected to the second liquid branch pipes 107h, 107i, and 107j, respectively, join a pipe in the second liquid branch pipe 217 that is connected to the second liquid pipe 2071, at a middle location. The second liquid pipe 2071 is connected to the second low-pressure gas pipe 206g by the second bypass pipe 214.

[0099] The second relay unit E2 includes a fifth control valve 295 and a sixth control valve 296. The fifth control valve 295 is, for example, a check valve, and is provided at the second low-pressure gas pipe 206g. The fifth control valve 295 allows the refrigerant to flow from the second gas branch pipes 106h, 106i, and 106j toward the first relay unit El. The sixth control valve 296 is, for example, a one-way solenoid valve, and is provided at the second liquid pipe 2071. The sixth control valve 296 is opened by the controller 80 when supplied with power, and blocks the flow of the refrigerant toward the third check valves 250h, 250i, and 250j when not supplied with power.

[0100] In such a manner, in the second relay unit E2, when power is not supplied, the transfer of the refrigerant from the third branch unit 210 and the fourth branch unit 211 to the indoor units H, I, and J is blocked. In the air-conditioning apparatus 200, when the evacuation is performed, the flow of air from the indoor unit side toward the first relay unit El side is not obstructed [0101] As described, in Embodiment 2, the air-conditioning apparatus 200 further includes the second relay unit E2 connected to the heat source unit A, with the first relay unit El interposed between the second relay unit E2 and the heat source unit A, and the first relay unit El includes the third control valve 93 and the fourth control valve 94.

The third control valve 93 is provided at the first high-pressure gas pipe 7g, and blocks the flow of the refrigerant toward the second relay unit E2 when not supplied with power. The fourth control valve 94 is provided at the first liquid pipe 71, and blocks the flow of the refrigerant toward the second relay unit E2 when not supplied with power.

[0102] Thereby, when the air-conditioning apparatus 200 stops the air-conditioning operation, and power is not supplied to any of the first control valve 91, the second control valve 92, the third control valve 93, and the fourth control valve 94, the transfer of the refrigerant from the first relay unit El to the downstream side is reduced. To be more specific, the transfer of the refrigerant toward the indoor units B, C, and D connected to the first relay unit El and also toward the second relay unit E2 is reduced. When the evacuation is performed, the flow of air from the indoor units B, C, and D and the second relay unit E2 toward the heat source unit A is allowed, and the air-conditioning apparatus 200 can easily perform the evacuation. In such a manner, in the air-conditioning apparatus 200, even when power is not supplied, it is possible to reduce the transfer of the refrigerant from the first relay unit El to a load side, cope with leakage, and improve the workability in construction and maintenance.

[0103] The second relay unit E2 is connected to one or more indoor units (for example, the indoor units H, I, and J) by the second gas branch pipes 106h, 106i, and 106j and the second liquid branch pipes 107h, 107i, and 107j. The second relay unit E2 includes the third check valves 250h, 250i, and 250j, the fourth check valves 252h, 252i, and 252j, the fifth control valve 295, and the sixth control valve 296. The third check valves 250h, 250i, and 250j allow the refrigerant to flow out into the second liquid branch pipes 107h, 107i, and 107j, respectively. The fourth check valves 252h, 252i, and 252j allow the refrigerant to flow into the second liquid branch pipes 107h, 107i, and 107j, respectively. The fifth control valve 295 is provided at the second low-pressure gas pipe 206g, and allows the refrigerant to flow from the second cooling solenoid valves 232h, 232i, and 232j toward the first low-pressure gas pipe 6g. The fifth control valve 295 blocks, when not supplied with power, the flow of the refrigerant from the first low-pressure gas pipe 6g toward the second cooling solenoid valves 232h, 232i, and 232j. The sixth control valve 296 is provided at the second liquid pipe 2071, and is opened when supplied with power, and blocks the flow of the refrigerant toward the third check valves 250h, 250i, and 250j when not supplied with power.

[0104] Thereby, in the second relay unit E2, when power is not supplied to the system, the flow of the refrigerant toward the indoor units H, I, and J is blocked by the fifth control valve 295 and the sixth control valve 296. Therefore, the air-conditioning apparatus 200 can cope with the refrigerant leakage even when the system cannot be supplied with power. The air-conditioning apparatus can perform the evacuation on the first relay unit El, the second relay unit E2, and the indoor units B, C, D, H, I, and J, and the workability in construction and in a maintenance is satisfactory.

[0105] Embodiment 3 Fig. 14 is a diagram illustrating a configuration of branch units and the vicinity thereof in Embodiment 3 of the present invention. In Embodiments 1 and 2, the second control valve 92 is provided at part of the first liquid pipe 71 that is upstream of branching positions in the second branch unit 11 in the flow of the refrigerant, and a single second control valve, that is, only the second control valve 92, reduces the transfer of the refrigerant to all the indoor units B, C, and D. Furthermore, in Embodiments 1 and 2, the first control valve 91 is provided at part of the first low-pressure gas pipe 6g that is located downstream of branching positions in the first branch unit 10 in the flow of the refrigerant, and a single first control valve, that is, only the first control valve 91, reduces the transfer of the refrigerant to all the indoor units B, C, and D. In Embodiment 3, a plurality of second control valves 392b, 392c, and 392d are provided and paired with the first check valves 50b, 50c, and 50d for the indoor units B, C, and D, respectively. A plurality of first control valves 397b, 397c, and 397d are provided and paired with the first cooling solenoid valves 32b, 32c, and 32d for the indoor units B, C, and D, respectively. It should be noted that regarding Embodiment 3, descriptions of configurations and components which are the same as those in the air-conditioning apparatus 100 in Embodiment 1 will be omitted, and configurations and components which are different from those of Embodiment 1 will be described.

[0106] As illustrate in Fig. 14, the first control valves 397b, 397c, and 397d are provided at a first branch unit 310, and are each, for example, a one-way solenoid valve. The first control valves 397b, 397c, and 397d are provided at respective pipes that branch off from the first low-pressure gas pipe 6g and are associated with the indoor units B, C, and D, respectively. The second control valves 392b, 392c, and 392d are provided at the second branch unit 311, and are each, for example, a one-way solenoid valve. The second control valves 392b, 392c, and 392d are provided at respective pipes that branch off from the first liquid pipe 71 and are associated with the indoor units B, C, and D, respectively. In the normal operation mode, the controller 80 performs control to supply current to the first control valves 397b, 397c, and 397d and the second control valves 392b, 392c, and 392d and to open the first control valves 397b, 397c, and 397d and the second control valves 392b, 392c, and 392d. Also, the controller 80 can causes the air-conditioning apparatus to enter a separate operation mode in which an operation of a given one or ones of the indoor units is stopped and an operation of another one or ones of the indoor units is continued. The first control valves 397b, 397c, and 397d and the plurality of second control valves 392b, 392c, and 392d may be provided in respective indoor units in the case where the number of the provided indoor units is large. Fig. 14 illustrates the case where each of the first control valves 397b, 397c, and 397d is a one-way solenoid valve; however, each first control valve may be a check valve.

[0107] Fig. 15 is a diagram indicating flows of the refrigerant in the branch units and the vicinity thereof in the separate operation mode in Embodiment 3 of the present invention. Referring to Fig. 15, the indoor unit B is in the cooling operation, and the indoor unit D is in the heating operation. Furthermore, the operation of the indoor unit C is stopped, and the first cooling solenoid valve 32c, the first heating solenoid valve 30c, the first control valve 397c, and the second control valve 392c for the indoor unit C are closed. Therefore, the transfer of the refrigerant from the first branch unit 310 to the first gas branch pipe 6c and the indoor unit C and the transfer of the refrigerant from the second branch unit 311 to the first liquid branch pipe 7c and the indoor unit C are blocked.

[0108] Fig. 16 is a flowchart indicating control by the controller in the air-conditioning apparatus according to Embodiment 3 of the present invention. An operation control by the controller 80 will be described. When the air-conditioning apparatus 100 is in operation, the controller 80 monitors whether refrigerant leakage occurs or not based on information obtained by detection by the first refrigerant detection sensors 85b, 85c, and 85d provided in the indoor units B, C, and D, respectively.

[0109] The operation control unit 81 in the controller 80 causes the air-conditioning apparatus 100 to operate in the normal operation mode in response to an operation request for from each of the indoor units B, C, and D (step ST201). The controller 80 determines at set intervals whether refrigerant leakage is detected or not (step ST202). To be more specific, the leakage detection unit 82 determines whether refrigerant leakage occurs or not in each of the indoor units B, C, and D based on the detection information acquired from first refrigerant detection sensors 85b, 85c, and 85d. When refrigerant leakage is not detected (NO in step ST202), the operation control unit 81 causes the normal operation mode to continue (step ST201). By contrast, when detecting refrigerant leakage (YES in step ST202), the leakage detection unit 82 determines which of the indoor units the refrigerant leakage occurs in, and notifies the operation control unit 81 of the indoor unit in which the refrigerant leakage occurs. The operation control unit 81 indicates the refrigerant leakage with sound information or other information (step ST203), and stops the air-conditioning operation of the air-conditioning apparatus 100 (step ST204). Next, the operation control unit 81 determines whether an operation continuation instruction is input from, for example, a remote control unit or not (step ST205). When determining that an operation continuation instruction is not input (NO in step ST205), the operation control unit 81 further determines whether or not an ending instruction to end a state in which the leakage is detected is input (step ST206). When the ending instruction is input (YES in step ST206), the operation control unit 81 causes the air-conditioning apparatus 100 to operate in the normal operation mode (step ST201), and when the ending instruction is not input (No in step ST206), the operation control unit 81 keeps the air-conditioning operation stopped (step ST204). On the other hand, when the operation continuation instruction is input (YES in step ST205), the operation control unit 81 causes the air-conditioning apparatus 100 to operate in the separate operation mode (step ST207). To be more specific, the operation control unit 81 stops the operation of an indoor unit determined by the leakage detection unit 82 as an indoor unit in which the refrigerant leakage occur, and causes each of the other indoor units to continue the normal operation in response to an operation request. With respect to the above determined indoor unit, for example, in the case where it is the indoor unit C, the operation control unit 81 closes the first cooling solenoid valve 32c, the first heating solenoid valve 30c, the first control valve 397c, and the second control valve 392c. Furthermore, the operation control unit 81 determines whether an operation stop instruction is input or not (step ST208), and when the operation stop instruction is not input (NO in step ST208), the operation control unit 81 further determines whether the ending instruction is input or not (step ST209). When the ending instruction is input (YES in step ST209), the operation control unit 81 changes the mode to the normal operation mode (step ST201).

On the other hand, when the ending instruction is not input (NO in step ST209), the operation control unit 81 causes the separate operation mode to continue (step ST207). On the other hand, in step ST 298, when the operation stop instruction is input (YES in step ST208), the operation control unit 81 stops the air-conditioning operation of the air-conditioning apparatus 100 (step ST210).

[0110] Fig. 16 illustrates the control in which the separate operation mode is started based on the detection information from the first refrigerant detection sensors 85b, 85c, and 85d, but the control flow is not limited to the above one. For example, in the air-conditioning apparatus 200 according to Embodiment 2 that includes the first relay unit E1, the second relay unit E2, the second refrigerant detection sensor 285, etc., detection information from the second refrigerant detection sensor 285 may be further used in determination in step ST 202 regarding whether refrigerant leakage occurs or not. In this case, it is appropriate that if leakage is detected by the second refrigerant detection sensor 285, when the separate operation mode is applied, the controller 280 closes the third control valve 93 and the fourth control valve 94.

[0111] As described above, in Embodiment 3, the second control valves 392b, 392c, and 392d are paired with the first check valves 50b, 50c, and 50d for the indoor units B, C, and D, respectively. The first control valves 397b, 397c, and 397d are paired with the first cooling solenoid valves 32b, 32c, and 32d for the indoor units B, C, and D, respectively. Thereby, the air-conditioning apparatus 100 can obtain the same advantages as in Embodiment 1, and the operations of the indoor units or the operations of the systems of the indoor units can be performed separately from each other.

[0112] The air-conditioning apparatus 100 further includes the controller 80 and the first refrigerant detection sensors 85b, 85c, and 85d that are respectively provided in at least two of the indoor units B, C, and D and detect refrigerant leakage. The controller 80 stops the operation of an indoor unit in which any of the first refrigerant sensors, 85b, 85c, and 85d that detects refrigerant leakage is provided. For example, in the case where the first refrigerant sensor 85c detects refrigerant leakage, the controller 80 stops the operation of the indoor unit C in which the first refrigerant sensor 85c is provided. To be more specific, the controller 80 closes the first cooling solenoid valve 32c, the first heating solenoid valve 30c, the first control valve 397c, and the second control valve 392c for the indoor unit C. [0113] Thereby, when refrigerant leakage in a given indoor unit, for example, the indoor unit C, is detected, the air-conditioning apparatus 100 can stop the operation of the given indoor unit and continue the operations of the indoor units other than the given indoor unit, that is, the indoor units B and D in the case where the given indoor unit is the indoor unit C. In the case where refrigerant leakage in the indoor unit C is detected, in the indoor unit C, the first control valve 397c and the second control valve 392c reduce the transfer of the refrigerant from the first relay unit E to the indoor unit C, and allows the flow of air in the evacuation. Such an advantage can be obtained even in the case where the system cannot be supplied with power, for example, during a power outage. Therefore, the air-conditioning apparatus 100 can cope with the refrigerant leakage, and achieve satisfactory workability in construction and maintenance.

[0114] The air-conditioning apparatus 200 further includes the second refrigerant detection sensor 285 that detects the refrigerant leakage, and the controller 280 that controls the third control valve 93 and the fourth control valve 94. The second refrigerant detection sensor 285 is provided at the pipe between the second relay unit E2 and the first relay unit El (for example, at the third connection pipe 106g, the fourth connection pipe 107g or the fifth connection pipe 1071), or the second relay unit E2. The controller 280 may close the third control valve 93 and the fourth control valve 94 when refrigerant leakage is detected by the second refrigerant detection sensor 285. [0115] In such a configuration, when refrigerant leakage occurs in the third connection pipe 106g, the fourth connection pipe 107g, the fifth connection pipe 1071, or other pipes, the second relay unit E2 can block the flow of refrigerant from the first relay unit El toward the second relay unit E2 to reduce the refrigerant leakage. In addition, the first relay unit El in which refrigerant leakage does not occur can be operated independently.

[0116] The embodiments of the present invention are not limited to the above embodiments, and can be variously modified. For example, the circuit configuration of the air-conditioning apparatus 100 is not limited to those described regarding the embodiments. Each of the first control valve 91, the second control valve 92, the third control valve 93, the fourth control valve 94, the fifth control valve 295 and the sixth control valve 296 may be a combination of a plurality of valves.

Reference Signs List [0117] 1 compressor 2 flow-passage switching device 3 heat-source-side heat exchanger 4 accumulator 5b, 5c, 5d indoor-side heat exchanger 6 first connection pipe 6b, 6c, 6d first gas branch pipe 6g first low-pressure gas pipe 7 second connection pipe 7b, 7c, 7d first liquid branch pipe 7g first high-pressure gas pipe 71 first liquid pipe 9b, 9c, 9d first flow-rate control device 10 first branch unit 11, 311 second branch unit 12 gas-liquid separation device 13 second flow-rate control device 13a electric expansion valve 13b open/close solenoid valvel4 first bypass pipe 15 third flow-rate control device 15a electric expansion valve 15b open/close solenoid valve 16 second heat exchange unit17 first liquid branch pipe 19 first heat exchange unit 20 heat-source-side flow-passage adjustment unit 21 heat- source-side first check valve 22 heat-source-side second check valve 23 heat-source-side third check valve 24 heat-source-side fourth check valve 30b, 30c, 30d first heating solenoid valve 32b, 32c, 32d first cooling solenoid valve 50b, 50c, 50d first check valve 52b, 52c, 52d second check valve 60 sensor group 61 discharge pressure detection sensor 62 liquid outflow-pressure detection sensor 63 downstream-side liquid outflow-pressure detection sensor 80, 280 controller 81 operation control unit 82 leakage detection unit 85b, 85c, 85d first refrigerant detection sensor 90 direction control device 91, 97, 397b, 397c, 397d first control valve 92, 98, 392b, 392c, 392d second control valve 93 third control valve 94 fourth control valve 100, 200 air-conditioning apparatus 106g third connection pipe 106h, 106i, 106j second gas branch pipe 107g fourth connection pipe 1071 fifth connection pipe 107h, 107i, 107j second liquid branch pipe 206g second low-pressure gas pipe 207g second high-pressure gas pipe 2071 second liquid pipe 210 third branch unit 211 fourth branch unit 214 second bypass pipe 215 fourth flow-rate control device 216 third heat exchange unit 230h, 230i, 230j second heating solenoid valve 232h, 232i, 232j second cooling solenoid valve 250h, 250i, 250j third check valve 252h, 252i, 252j fourth check valve 285 second refrigerant detection sensor 295 fifth control valve 296 sixth control valve A heat source unit B, C, D, H, 1 J indoor unit E, El first relay unit E2 second relay unit