GB2555258A

GB2555258A - Air conditioning device

Info

Publication number: GB2555258A
Application number: GB1718085.2A
Authority: GB
Inventors: Ariyama Tadashi; Tamura Naomichi; Takenaka Naofumi; Watanabe Kazuya
Original assignee: Mitsubishi Electric Corp
Current assignee: Mitsubishi Electric Corp
Priority date: 2015-05-28
Filing date: 2015-05-28
Publication date: 2018-04-25
Anticipated expiration: 2035-05-28
Also published as: WO2016189739A1; GB201718085D0; JPWO2016189739A1; JP6448780B2; GB2555258B

Abstract

In this air conditioning device, a heat source machine and an indoor machine including an indoor-side flow rate control device and an indoor-side heat exchanger are coupled to one another by means of refrigerant piping. The heat source machine is provided with: an outdoor-side heat exchanging unit including a plurality of outdoor-side heat exchangers coupled in parallel with one another to a compressor; first heat-source-side bypass piping one end of which is coupled to a discharge side of the compressor and the other end of which is coupled to each of the plurality of outdoor-side heat exchangers; a first pressure reducing device which is provided in the first heat-source-side bypass piping and which reduces the pressure of refrigerant discharged from the compressor; a bypass opening and closing unit which is provided in the first heat-source-side bypass piping and which either allows refrigerant discharged from the compressor to pass through to each of the outdoor-side heat exchangers, or shuts off the flow of refrigerant to each of the outdoor-side heat exchangers; second heat-source-side bypass piping which couples the plurality of outdoor-side heat exchangers to one another, and which causes refrigerant that has flowed out from one outdoor-side heat exchanger to flow into another outdoor-side heat exchanger; and a second pressure reducing device which is provided in the second heat-source-side bypass piping and which reduces the pressure of refrigerant passing through the second heat-source-side bypass piping.

Description

(54) Title of the Invention: Air conditioning device Abstract Title: Air conditioning device (57) In this air conditioning device, a heat source machine and an indoor machine including an indoor-side flow rate control device and an indoor-side heat exchanger are coupled to one another by means of refrigerant piping. The heat source machine is provided with: an outdoor-side heat exchanging unit including a plurality of outdoor-side heat exchangers coupled in parallel with one another to a compressor; first heat-source-side bypass piping one end of which is coupled to a discharge side of the compressor and the other end of which is coupled to each of the plurality of outdoor-side heat exchangers; a first pressure reducing device which is provided in the first heat-sourceside bypass piping and which reduces the pressure of refrigerant discharged from the compressor; a bypass opening and closing unit which is provided in the first heat-source-side bypass piping and which either allows refrigerant discharged from the compressor to pass through to each of the outdoor-side heat exchangers, or shuts off the flow of refrigerant to each of the outdoor-side heat exchangers; second heat-source-side bypass piping which couples the plurality of outdoor-side heat exchangers to one another, and which causes refrigerant that has flowed out from one outdoor-side heat exchanger to flow into another outdoor-side heat exchanger; and a second pressure reducing device which is provided in the second heat-source-side bypass piping and which reduces the pressure of refrigerant passing through the second heat-source-side bypass piping.

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DESCRIPTION

Title of Invention

AIR-CONDITIONING APPARATUS

Technical Field [0001]

The present invention relates to an air-conditioning apparatus configured to perform air conditioning by cooling and heating using a refrigeration cycle, and to an air-conditioning apparatus for suppressing a reduction of heating capacity while maintaining defrosting capacity.

Background Art [0002]

For example, in an air-conditioning apparatus using a refrigeration cycle (heat pump cycle), a refrigerant circuit configured to cause refrigerant to circulate through the refrigerant circuit is provided in which an outdoor unit (heat-source-unit-side unit) including a compressor, an outdoor-side heat exchange unit, and other units, and an indoor unit including a flow rate control device, an indoor-side heat exchanger, and other units are connected to each other by refrigerant pipes. In the indoor-side heat exchanger, by using heat transfer or heat removal from air in an air-conditioned space as a heat exchange target when refrigerant evaporates or condenses, air conditioning is performed while pressure, temperature, or other parameters regarding refrigerant in the refrigerant circuit being changed.

[0003]

Further, an air-conditioning apparatus has been proposed in which a plurality of indoor units are installed and a cooling and heating simultaneous operation (cooling and heating mixed operation) that implements cooling or heating for each of the indoor units may be performed by automatically determining cooling or heating in each of the indoor units corresponding to, for example, a set temperature of a remote controller and the temperature around the indoor unit.

[0004]

When an air-conditioning apparatus performs a heating operation at a low outside air temperature, frost is deposited on a fin surface of an outdoor-side heat exchange unit acting as an evaporator. Such deposition of frost increases air duct pressure loss of the outdoor-side heat exchange unit, and heat transmission capacity gradually decreases. Consequently, a regular defrosting operation is required. Defrosting operation methods include a method of performing defrosting by switching from the flow of refrigerant for a heating operation to the flow of refrigerant for a cooling operation. However, during a defrosting operation, indoor heating is stopped, and consequently, comfortability decreases.

[0005]

To address the above-mentioned problem, a method for continuing a heating operation even during a defrosting operation has been proposed (for example, see Patent Literature 1 and Patent Literature 2). In Patent Literature 1, a method is suggested in which an outdoor-side heat exchange unit is divided into a plurality of parts, a part of the outdoor-side heat exchange unit performs defrosting while another part of the outdoor-side heat exchange unit is operating as an evaporator, which receives heat from air, and heating is thus performed. In this method, part of refrigerant at high temperature discharged from a compressor is caused to flow directly into a heat exchanger to be defrosted via a bypass pipe. After defrosting for one heat exchanger is completed, defrosting for another heat exchanger is performed.

[0006]

In Patent Literature 2, a method is proposed in which a plurality of heat source units and at least one indoor unit are provided, and during a defrosting operation, connection of a four-way valve of a heat source unit to be defrosted is switched from a heating flow passage to a cooling flow passage, and refrigerant discharged from a compressor is caused to flow directly into an outdoor-side heat exchange unit to be defrosted. In this method, defrosting is performed under a state in which the pressure of refrigerant inside the outdoor-side heat exchange unit to be defrosted is equivalent to the discharge pressure of the compressor.

Citation List

Patent Literature [0007]

Patent Literature 1: Japanese Unexamined Patent Application Publication No. 2009-085484

Patent Literature 2: Japanese Unexamined Patent Application Publication No. 2007-271094

Summary of Invention

Technical Problem [0008]

However, in Patent Literatures 1 and 2, when the pressure of a heat exchanger to be defrosted is low, the refrigerant saturation temperature of refrigerant at the heat exchanger is lower than the outside air temperature. Consequently, latent heat of refrigerant cannot be used, and the defrosting capacity is thus small. In contrast, when the pressure of a heat exchanger to be defrosted is high, the amount of condensation of refrigerant at an outdoor-side heat exchange unit to be defrosted is large. Consequently, refrigerant at an indoor unit that is performing a heating operation may be insufficient, and a sufficient heating capacity cannot be exhibited. [0009]

The present invention has been designed in light of the above problems, and therefore has an object to provide an air-conditioning apparatus that is capable of preventing heating capacity from decreasing while exhibiting a sufficient defrosting capacity even when defrosting is performed for a part of an outdoor-side heat exchange unit while continuing a heating operation.

Solution to Problem [0010]

According to one embodiment of the present invention, there is provided an airconditioning apparatus including a heat source unit and an indoor unit that are connected by a refrigerant pipe, the indoor unit including an indoor-side flow rate control device and an indoor-side heat exchanger. The heat source unit includes a compressor configured to compress refrigerant and discharge the refrigerant, an outdoor-side heat exchange unit including a plurality of outdoor-side heat exchangers connected to the compressor in parallel to one another, a first heat-source-side bypass pipe having one end connected to a discharge side of the compressor and another end connected to each of the plurality of outdoor-side heat exchangers, a first decompression device provided at the first heat-source-side bypass pipe, and configured to reduce a pressure of the refrigerant discharged from the compressor, a bypass opening and closing portion provided at the first heat-source-side bypass pipe, and configured to allow passage and block of the refrigerant discharged from the compressor to each of the plurality of outdoor-side heat exchangers, a second heat-source-side bypass pipe configured to connect the plurality of outdoor-side heat exchangers to one another, and to allow the refrigerant flowing out of one of the plurality of outdoor-side heat exchangers to flow into another one of the plurality of outdoor-side heat exchangers, and a second decompression device provided at the second heat-source-side bypass pipe, and configured to reduce a pressure of refrigerant passing through the second heat-source-side bypass pipe.

Advantageous Effects of Invention [0011]

According to one embodiment of the present invention, the air-conditioning apparatus may have a circuit configuration in which refrigerant that has flowed out of the outdoor-side heat exchanger to be defrosted is decompressed by the second decompression device and then flows into the outdoor-side heat exchanger acting as the evaporator via the second heat-source-side bypass pipe. Consequently, when defrosting for a part ofthe outdoor-side heat exchange unit is performed, a reduction in heating capacity may be prevented while a sufficient defrosting capacity being exhibited.

Brief Description of Drawings 5 [0012] [Fig. 1] Fig. 1 is a refrigerant circuit diagram for illustrating an air-conditioning apparatus according to an embodiment of the present invention.

[Fig. 2] Fig. 2 is a refrigerant circuit diagram for illustrating the flow of refrigerant during a heating only operation in the air-conditioning apparatus illustrated in Fig. 1.

[Fig. 3] Fig. 3 is a refrigerant circuit diagram for illustrating the flow of refrigerant during a heating main operation in the air-conditioning apparatus illustrated in Fig. 1.

[Fig. 4] Fig. 4 is a refrigerant circuit diagram for illustrating the flow of 15 refrigerant during a cooling main operation in the air-conditioning apparatus illustrated in Fig. 1.

[Fig. 5] Fig. 5 is a refrigerant circuit diagram for illustrating the flow of refrigerant during a defrosting operation in the air-conditioning apparatus illustrated in Fig. 1.

Description of Embodiments [0013]

Hereinafter, an air-conditioning apparatus according to one embodiment of the present invention is described with reference to the drawings. Fig. 1 is a refrigerant circuit diagram for illustrating an air-conditioning apparatus according to Embodiment 1 of the present invention. A circuit configuration of an air-conditioning apparatus 1 is described with reference to Fig. 1. The air-conditioning apparatus 1 illustrated in Fig. 1 is configured to perform a cooling and heating operation using a refrigeration cycle (heat pump cycle) based on refrigerant circulation. In particular, the air30 conditioning apparatus according to Embodiment 1 is capable of performing a cooling and heating simultaneous operation in which cooling and heating are performed at the same time in a mixed manner in a plurality of indoor units.

[0014]

The air-conditioning apparatus 1 includes a heat source unit 10, a relay unit 20, and a plurality of indoor units 30A and 30B. Those units are connected by refrigerant pipes. That is, the relay unit 20 is provided between the heat source unit and the indoor units 30Aand 30B to control the flow of refrigerant, and the plurality of indoor units 30A and 30B are connected to the relay unit 20 such that the plurality of indoor units 30A and 30B are arranged in parallel to each other.

[0015]

The heat source unit 10 and the relay unit 20 are connected by a first main pipe 2 and a second main pipe 3 having a pipe diameter larger than that of the first main pipe 2. In the first main pipe 2, refrigerant at high pressure flows from the heat source unit 10 side to the relay unit 20 side. In the second main pipe 3, refrigerant at a pressure lower than that of the refrigerant flowing in the first main pipe 2 flows from the relay unit 20 side to the heat source unit 10 side. The level of pressure is not determined on the basis of the relationship with a reference pressure (numerical value) but is represented on the basis of being relatively high and low (including medium) in a refrigerant circuit depending on pressurization of a compressor 11, control of the opening and closing state (opening degree) of each flow rate control device, or other condition. The pressure of refrigerant discharged from the compressor 11 is highest, and pressure is reduced by a flow rate control device and other devices. Consequently, the pressure of refrigerant sucked into the compressor is lowest.

[0016]

The relay unit 20 and the indoor units 30A and 30B are connected by first branch pipes 4A and 4B and second branch pipes 5A and 5B. Pipe connection made by the first main pipe 2, the second main pipe 3, the first branch pipes 4A and

4B, and the second branch pipes 5A and 5B forms a refrigerant circuit in which refrigerant circulates among the heat source unit 10, the relay unit 20, and the indoor units 30Aand 30B.

[0017] [Heat Source Unit 10]

The heat source unit 10 includes the compressor 11, a flow switching device 12, an outdoor-side heat exchange unit 13, an accumulator 15, and a flow passage forming portion 16. The compressor 11 is configured to add pressure to sucked refrigerant and then discharge the refrigerant. The compressor 11 is, for example, an inverter compressor capable of varying a discharge capacity, which is the whole amount of discharge of refrigerant per time, and capability corresponding to the amount of discharge. The compressor 11 is capable of varying, with use of an inverter circuit (not shown), driving frequency in a desired manner in accordance with an instruction from a controller 60.

[0018]

The flow switching device 12 is connected to a discharge side of the compressor 11, is configured to perform switching of a flow passage corresponding to the mode of heating or cooling, in accordance with an instruction from the controller 60, and includes, for example, a four-way valve. The flow switching device 12 is configured to switch a flow passage depending on whether the air-conditioning apparatus 1 is performing a cooling only operation in which all the indoor units are performing a cooling operation and a cooling main operation in which cooling is mainly performed in the cooling and heating simultaneous operation, or a heating only operation in which all the indoor units are performing heating and a heating main operation in which heating is mainly performed in the cooling and heating simultaneous operation.

[0019]

The outdoor-side heat exchange unit 13 includes a heat transfer pipe through which refrigerant flows and a fin (not shown) for increasing a heat transfer area between the refrigerant passing through the heat transfer pipe and outside air, and is configured to exchange heat between the refrigerant and air (outside air). For example, the outdoor-side heat exchange unit 13 acting as an evaporator to evaporate and gasify refrigerant during the heating only operation and the heating main operation. In contrast, the outdoor-side heat exchange unit 13 acts as a condenser to condense and liquefy refrigerant during the cooling only operation and the cooling main operation. The outdoor-side heat exchange unit 13 may perform adjustments, such as condensing refrigerant up to a two-phase mixture (two-phase gas-liquid refrigerant) state of liquid and gas instead of totally gasifying or liquefying refrigerant, as in the cooling main operation, for example.

[0020]

A heat-source-unit-side air-sending device 14 for sending air to the outdoorside heat exchange unit 13 so that heat exchange between refrigerant and air may be performed efficiently is provided in the heat source unit 10. The heat-source-unitside air-sending device 14 may vary the airflow rate in accordance with an instruction from the controller 60, and may also vary the capacity of heat exchange in the outdoor-side heat exchange unit 13 with use of the variation in the airflow rate.

[0021]

The accumulator 15 is connected to a suction side of the compressor 11, and is configured to store excess refrigerant in the refrigerant circuit. The flow passage forming portion 16 allows refrigerant to flow out through the first main pipe 2 and flow in through the second main pipe 3 in a circulation path, irrespective of switching of a flow passage by the flow switching device 12, and includes check valves 16a to 16d. The check valve 16a is located at a pipe between the outdoor-side heat exchange unit 13 and the first main pipe 2, and allows refrigerant to flow in a direction from the outdoor-side heat exchange unit 13 to the first main pipe 2. The check valve 16b is located at a pipe between the flow switching device 12 and the second main pipe 3, and allows refrigerant to flow in a direction from the second main pipe 3 to the flow switching device 12. The check valve 16c is located at a pipe between the flow switching device 12 and the first main pipe 2, and allows refrigerant to flow in a direction from the flow switching device 12 to the second main pipe 3. The check valve 16d is located at a pipe between the outdoor-side heat exchange unit 13 and the second main pipe 3, and allows refrigerant to flow in a direction from the second main pipe 3 to the outdoor-side heat exchange unit 13.

[0022]

The outdoor-side heat exchange unit 13 includes a plurality of outdoor-side heat exchangers 13A and 13B that are connected in parallel to each other. That is, one ends of the plurality of outdoor-side heat exchangers 13Aand 13B are connected to the flow switching device 12 in parallel, and the other ends of the plurality of outdoor-side heat exchangers 13Aand 13B are connected to the first main pipe 2 in parallel. The plurality of outdoor-side heat exchangers 13A and 13B may be formed by dividing one heat exchanger into a plurality of regions or may be formed by a plurality of heat exchangers. As described above, the heat source unit 10 has a circuit configuration that is capable of continuing a heating operation by causing one of the plurality of outdoor-side heat exchangers 13A and 13B to act as an evaporator while defrosting another one of the plurality of outdoor-side heat exchangers 13A and 13B using refrigerant discharged from the compressor 11.

[0023]

The heat source unit 10 includes a first heat-source-side bypass pipe 41, a first decompression device 42, a bypass opening and closing portion 43, a second heatsource-side bypass pipe 44, and a second decompression device 45. One end of the first heat-source-side bypass pipe 41 is connected to a discharge side of the compressor 11, and the other end of the first heat-source-side bypass pipe 41 is connected to each of the plurality of outdoor-side heat exchangers 13Aand 13B.

The first heat-source-side bypass pipe 41 forms a flow passage through which refrigerant discharged from the compressor 11 is allowed to flow into each of the outdoor-side heat exchangers 13Aand 13B.

[0024]

The first decompression device 42 is provided at the first heat-source-side bypass pipe 41, and is configured to reduce the pressure of refrigerant discharged from the compressor 11 and allow the refrigerant to flow into each of the outdoor-side heat exchangers 13A and 13B. The first decompression device 42 may be, for example, a capillary tube or an electronic expansion valve having an opening degree that is controlled by the controller 60.

[0025]

The bypass opening and closing portion 43 is provided at the first heat-sourceside bypass pipe 41 to allow passage and block of refrigerant discharged from the compressor 11 to each of the outdoor-side heat exchangers 13A and 131B. The bypass opening and closing portion 43 allows refrigerant discharged from the compressor 11 to flow into an outdoor-side heat exchanger to be defrosted, and prevents refrigerant discharged from the compressor 11 from flowing to an outdoorside heat exchanger acting as an evaporator. The bypass opening and closing portion 43 includes a plurality of bypass opening and closing valves 43Aand 43B corresponding to the outdoor-side heat exchangers 13A and 13B, respectively. The bypass opening and closing valve 43A is configured to control inflow of refrigerant to the outdoor-side heat exchanger 13Aside, and the bypass opening and closing valve 43B is configured to control inflow of refrigerant to the outdoor-side heat exchanger 13B side. An operation of the bypass opening and closing portion 43 is controlled by the controller 60. For example, when defrosting is performed for the outdoor-side heat exchanger 13A, the bypass opening and closing valve 43A is opened and the bypass opening and closing valve 43B is closed. In contrast, when the outdoor-side heat exchanger 13B is to be defrosted, the bypass opening and closing valve 43B is opened and the bypass opening and closing valve 43A is closed.

[0026]

The second heat-source-side bypass pipe 44 connects between the plurality of outdoor-side heat exchangers 13Aand 13B to each other on the second main pipe 3 side, and allows refrigerant that has flowed out of an outdoor-side heat exchanger to be defrosted to flow into an outdoor-side heat exchanger acting as an evaporator.

For example, when defrosting is performed for the outdoor-side heat exchanger 13A, the second heat-source-side bypass pipe 44 allows refrigerant that has flowed out of the outdoor-side heat exchanger 13A to flow into the outdoor-side heat exchanger

13B. In contrast, when the outdoor-side heat exchanger 13B is to be defrosted, the second heat-source-side bypass pipe 44 allows refrigerant that has flowed out of the outdoor-side heat exchanger 13B to flow into the outdoor-side heat exchanger 13A. [0027]

The second decompression device 45 is provided at the second heat-sourceside bypass pipe 44, and is configured to reduce the pressure of refrigerant passing through the second heat-source-side bypass pipe 44. The second decompression device 45 is configured to reduce the pressure of two-phase gas-liquid or liquid refrigerant that has flowed out of an outdoor-side heat exchanger to be defrosted, and allow the refrigerant to flow into the outdoor-side heat exchanger 13B. The second decompression device 45 is, for example, an electronic expansion valve, and has an opening degree that is controlled by the controller 60.

[0028]

Further, the heat source unit 10 includes a first flow restriction portion 46 and a second flow restriction portion 47 configured to prevent refrigerant that has flowed out ofthe indoor units 30Aand 30B from flowing into an outdoor-side heat exchanger to be defrosted. The first flow restriction portion 46 includes first opening and closing valves 46Aand 46B that are provided between the first main pipe 2 and the plurality of outdoor-side heat exchangers 13Aand 13B, and the second flow restriction portion 47 includes second opening and closing valves 47Aand 47B that are provided between the flow switching device 12 and the plurality of outdoor-side heat exchangers 13A and 13B. Operations of the first opening and closing valves 46A and 46B and the second opening and closing valves 47A and 47B are controlled by the controller 60. When the outdoor-side heat exchanger 13A is to be defrosted, the first opening and closing valve 46A and the second opening and closing valve 47A that are connected to the outdoor-side heat exchanger 13B side are closed, and the first opening and closing valve 46B and the second opening and closing valve 47B that are connected to the outdoor-side heat exchanger 13B side are opened. In contrast, when the outdoor-side heat exchanger 13B is to be defrosted, the first opening and closing valve 46B and the second opening and closing valve 47B that are connected to the outdoor-side heat exchanger 13B side are closed, and the first opening and closing valve 46Aand the second opening and closing valve 47Athat are connected to the outdoor-side heat exchanger 13Aside are opened.

[0029] [Relay Unit 20]

The relay unit 20 includes a gas-liquid separation device 21, a first intermediate heat exchanger 22, a first relay-side flow rate control device 23, a second intermediate heat exchanger 24, a second relay-side flow rate control device 25, a first distribution portion 26, and a second distribution portion 27. The gas-liquid separation device 21 is configured to separate refrigerant flowing from the first main pipe 2 into gas refrigerant and liquid refrigerant. The gas-liquid separation device 21 is connected to a gas-phase pipe 21a from which gas refrigerant flows and a liquidphase pipe 21 b from which liquid refrigerant flows. The gas-phase pipe 21a is connected to the first distribution portion 26, and the liquid-phase pipe 21b is connected to the first intermediate heat exchanger 22.

[0030]

The first intermediate heat exchanger 22 is an intermediate heat exchanger configured to subcool liquid refrigerant to supply the resultant refrigerant to the indoor units 30A and 30B side during the cooling only operation. The first intermediate heat exchanger 22 is configured to exchange heat between refrigerant flowing from the gas-liquid separation device 21 to the first relay-side flow rate control device 23 and refrigerant flowing from the second intermediate heat exchanger 24 to the second main pipe 3.

[0031]

The first relay-side flow rate control device 23 is, for example, an electronic expansion valve, and is provided between the first intermediate heat exchanger 22 and the second intermediate heat exchanger 24. The first relay-side flow rate control device 23 is configured to adjust the flow rate and pressure of refrigerant flowing from the first intermediate heat exchanger 22 to the second intermediate heat exchanger 24, and has an opening degree that is controlled by the controller 60. [0032]

The second intermediate heat exchanger 24 is configured to exchange heat between refrigerant flowing from the first relay-side flow rate control device 23 to the second distribution portion 27 and refrigerant flowing through a first relay-side bypass pipe 28 in a downstream part of the second relay-side flow rate control device 25 (refrigerant that has passed through the second relay-side flow rate control device 25). The first relay-side bypass pipe 28 connects the second intermediate heat exchanger 24 and the second distribution portion 27 to each other, such that part of refrigerant flowing between the second intermediate heat exchanger 24 and the second distribution portion 27 flows through the first relay-side bypass pipe 28 into the second intermediate heat exchanger 24. Further, refrigerant that has flowed out from the first relay-side bypass pipe 28 through the second intermediate heat exchanger 24 flows into the first intermediate heat exchanger 22. As described above, the first intermediate heat exchanger 22 and the second intermediate heat exchanger 24 subcool liquid refrigerant and supply the resultant refrigerant to the indoor units 30Aand 30B side during the cooling only operation.

[0033]

The second relay-side flow rate control device 25 is, for example, an electronic expansion valve, and is configured to adjust the flow rate and pressure of refrigerant passing through the first relay-side bypass pipe 28. The opening degree of the second relay-side flow rate control device 25 is controlled by the controller 60.

[0034]

During the cooling only operation or the cooling main operation, refrigerant that has flowed out of the gas-liquid separation device 21 flows into the second distribution portion 27 via the first intermediate heat exchanger 22, the first relay-side flow rate control device 23, and the second intermediate heat exchanger 24. In contrast, refrigerant that has passed through the second relay-side flow rate control device 25 and the first relay-side bypass pipe 28 subcools refrigerant at the second intermediate heat exchanger 24 and the first intermediate heat exchanger 22, and flows to the second main pipe 3.

[0035]

The first distribution portion 26 and the second distribution portion 27 are configured to distribute refrigerant supplied from the heat source unit 10 to the plurality of indoor units 30A and 30B. The first distribution portion 26 includes a heating opening and closing valve 26a and a cooling opening and closing valve 26b that are connected to the indoor unit 30A, and a heating opening and closing valve 26c and a cooling opening and closing valve 26d that are connected to the indoor unit 30B side. The heating opening and closing valves 26a and 26c are connected to the gas-phase pipe 21a, and the cooling opening and closing valves 26b and 26d are connected to the second main pipe 3. When the indoor units 30A and 30B perform a cooling operation, the cooling opening and closing valves 26b and 26d are opened, and refrigerant flows from the indoor units 30A and 30B through the second main pipe 3 to the heat source unit 10. During this operation, the heating opening and closing valves 26a and 26c are closed. In contrast, when the indoor units 30A and 30B perform a heating operation, the heating opening and closing valves 26a and 26c are opened, and refrigerant flows from the gas-phase pipe 21a to the indoor units 30A and 30B. During this operation, the cooling opening and closing valves 26b and 26d are closed.

[0036]

The case in which the first distribution portion 26 includes the heating opening and closing valves 26a and 26c and the cooling opening and closing valves 26b and 26d is illustrated as an example. However, for example, a three-way switching valve may be provided for each of the indoor units 30A and 30B so that switching between connection to the second main pipe 3 and connection to a gas-phase pipe may be performed.

[0037]

The second distribution portion 27 includes a heating check valve 27a and a cooling check valve 27b that are connected to the indoor unit 30A, and a heating check valve 27c and a cooling check valve 27d that are connected to the indoor unit 30B side. When the indoor units 30A and 30B perform a cooling operation, refrigerant that has been subcooled at the second intermediate heat exchanger 24 flows via the cooling check valves 27b and 27d to the indoor units 30A and 30B. In contrast, when the indoor units 30Aand 30B perform a heating operation, refrigerant that has flowed out of the indoor units 30Aand 30B flows via the heating check valves 27a and 27c to a second relay-side bypass pipe 29. The second relay-side bypass pipe 29 connects the heating check valves 27a and 27c, the first relay-side flow rate control device 23, and the second intermediate heat exchanger 24 to one another. [0038]

Further, during the cooling main operation or the heating main operation, refrigerant that has flowed out of the indoor unit 30A or 30B that is performing a heating operation through the second distribution portion 27 flows to the second relay-side bypass pipe 29. Part or the entire refrigerant that has passed through the second relay-side bypass pipe 29 passes through the second intermediate heat exchanger 24 and the second distribution portion 27, and then flows to the indoor unit 30A or 30B that is performing a cooling operation. In contrast, during the heating only operation, the entire refrigerant that has flowed out of the indoor units 30A and 30B that are performing a heating operation through the second distribution portion 27 passes through the second relay-side flow rate control device 25 and the first relay-side bypass pipe 28, and flows to the second main pipe 3.

[0039]

The two indoor units 30A and 30B are connected to the first distribution portion 26 and the second distribution portion 27, and consequently, two pairs of opening and closing valves and check valves are installed at the first distribution portion 26. The number of pairs of opening and closing valves and check valves installed at the first distribution portion 26 corresponds to the number of installed indoor units 30Aand 30B, accordingly.

[0040] [Indoor Units 30Aand 30B]

The plurality of indoor units 30A and 30B are connected to the relay unit 20 in parallel to each other via the first branch pipes 4A and 4B and the second branch pipes 5A and 5B. The plurality of indoor units 30A and 30B each include an indoor15 side expansion device 31 and an indoor-side heat exchanger 32, which is connected in series to the indoor-side expansion device 31. The indoor-side expansion device 31 is, for example, an electronic expansion valve, and has the opening degree that may be variably controlled. During a cooling operation, the indoor-side expansion device 31 is configured to decompress and expand refrigerant supplied from the relay unit 20 to supply the resultant refrigerant to the indoor-side heat exchanger 32. The opening degree of the indoor-side expansion device 31 is controlled by the controller 60. The indoor-side heat exchanger 32 is configured to exchange heat between air sent from an indoor air-sending device 33, for example, a fan, and refrigerant supplied from the relay unit 20 to generate heating air or cooling air to be supplied to an indoor space.

[0041] [Controller 60]

An operation of the air-conditioning apparatus 1 described above is controlled by the controller 60. The controller 60 is, for example, a microcomputer or a computer, and is configured to perform, for example, determination processing and other types of processing in accordance with signals transmitted from various types of detectors (sensors) provided inside or outside the air-conditioning apparatus and each device (unit) of the air-conditioning apparatus. The controller 60 causes each device to operate on the basis of a determination result, and comprehensively controls the entire operation of the air-conditioning apparatus. For example, the controller 60 performs driving frequency control of the compressor 11, opening degree control of flow rate control devices, such as the first decompression device 42 and the second decompression device 45, control of the flow switching device 12 and the first distribution portion 26, and control of other units.

[0042]

Specifically, the air-conditioning apparatus 1 includes a discharge pressure detection unit 51 that is provided at a pipe connected to the discharge side of the compressor 11 and is configured to measure the pressure of refrigerant regarding discharge, and an outside air temperature sensor 52 for measuring the temperature of outside air (outside air temperature). For example, the controller 60 measures the pressure, temperature, and other parameters of refrigerant discharged from the compressor 11 and calculates a condensing temperature Tc on the basis of pressure Pd and other parameters, in accordance with, for example, signals from the discharge pressure detection unit 51. The air-conditioning apparatus 1 also includes refrigerant temperature detection units 53Aand 53B configured to measure the temperature of refrigerant flowing out of or flowing into the outdoor-side heat exchangers 13Aand 13B during a defrosting operation, and a pressure detection unit 54 configured to measure the pressure of refrigerant at the outdoor-side heat exchangers 13Aand 13B during the defrosting operation. The pressure detection unit 54 may be a pressure detection sensor configured to directly measure the pressure of refrigerant, or may be a temperature sensor configured to measure the temperature of refrigerant flowing into the outdoor-side heat exchangers 13A and 13B to calculate the pressure of the refrigerant on the basis of the measured temperature of the refrigerant.

[0043]

Further, a first relay-side pressure detector 55 is provided on the inflow side of the second relay-side flow rate control device 25, and a second relay-side pressure detector 56 is provided on the outflow side of the second relay-side flow rate control device 25. The controller 60 performs control such that the difference between a first relay-side pressure measured by the first relay-side pressure detector 55 and a second relay-side pressure measured by the second relay-side pressure detector 56 is equal to a target relay-side pressure.

[0044]

A memory 61 stores, on a temporary or long-term basis, various data, programs, and other items required for the controller 60 to perform processing. In Fig. 1, the controller 60 and the memory 61 are provided separately from the heat source unit 10. However, the controller 60 and the memory 61 may be provided, for example, in the heat source unit 10. Further, the controller 60 and the memory 61 are provided close to the apparatus. However, for example, by signal communication using a public electric communication network, remote control may be performed.

[0045]

As described above, the air-conditioning apparatus 1 may perform an operation in any of the four modes the cooling only operation, the heating only operation, the cooling main operation, and the heating main operation. The outdoor-side heat exchange unit 13 of the heat source unit 10 acts as a condenser during the cooling only operation and the cooling main operation, and acts as an evaporator during the heating only operation and the heating main operation. Next, an operation example of the air-conditioning apparatus 1 and the flow of refrigerant in each of the operation modes are explained.

[0046] [Cooling Only Operation]

An operation example of the air-conditioning apparatus 1 and the flow of refrigerant in the cooling only operation are explained with reference to Fig. 1. In Fig. 1, a case in which all the indoor units 30Aand 30B are performing cooling without stopping is described. Further, regarding check valves and opening and closing valves in Fig. 1, an opened state is represented by black, and a closed state is represented by white. During the cooling only operation, control is performed by the controller 60 such that the bypass opening and closing portion 43 is in the closed state, each of the first flow restriction portion 46 and the second flow restriction portion 47 is in the opened state, the heating opening and closing valves 26a and 26c of the first distribution portion 26 are in the closed state, and the cooling opening and closing valves 26b and 26d are in the opened state.

[0047]

First, refrigerant that has been sucked from the accumulator 15 is compressed by the compressor 11, and high-pressure gas refrigerant is discharged. The refrigerant that has been discharged from the compressor 11 passes through the flow switching device 12, and flows to the outdoor-side heat exchange unit 13. At this time, refrigerant flows into each of the outdoor-side heat exchangers 13Aand 13B.

The high-pressure gas refrigerant is condensed by heat exchange with outside air while passing through the outdoor-side heat exchange unit 13, turns into highpressure liquid refrigerant, and flows through the check valve 16a. By virtue of the pressure of the refrigerant, the refrigerant does not flow to the check valves 16c and 16d side. Then, the high-pressure liquid refrigerant passes through the first main pipe 2 and flows into the relay unit 20.

[0048]

The refrigerant that has flowed into the relay unit 20 is separated into gas refrigerant and liquid refrigerant by the gas-liquid separation device 21. The refrigerant flowing into the relay unit 20 during the cooling only operation is liquid refrigerant, and gas refrigerant does not flow to the indoor units 30A and 30B side from the gas-liquid separation device 21. The liquid refrigerant passes through the first intermediate heat exchanger 22, the first relay-side flow rate control device 23, and the second intermediate heat exchanger 24, and is divided to flow to the second distribution portion 27 and the first relay-side bypass pipe 28. The refrigerant that has flowed into the second distribution portion 27 flows into the indoor units 30A and 30B through the cooling check valves 27b and 27d and the first branch pipes 4A and 4B.

[0049]

The pressure of the liquid refrigerant that has flowed into the indoor units 30A and 30B is adjusted at the indoor-side expansion devices 31. As described above, adjustment of the opening degree of the indoor-side expansion device 31 is performed on the basis of the degree of superheat on a refrigerant outlet side of each of the indoor-side heat exchangers 32. The low-pressure liquid refrigerant or twophase gas-liquid refrigerant obtained by the adjustment of the opening degree of the indoor-side expansion devices 31 flows to the indoor-side heat exchangers 32.

[0050]

The low-pressure liquid refrigerant or two-phase gas-liquid refrigerant is evaporated by heat exchange with indoor air as an air-conditioned space while passing through the indoor-side heat exchangers 32, and turns into low-pressure gas refrigerant. At this time, the indoor air is cooled by heat exchange, so that indoor cooling is performed. For example, in the case where the air conditioning load (amount of heat required for an indoor unit, hereinafter referred to as load) at the indoor unit 30B is small, a case where the indoor unit 30B is in a transient state, for example, a state immediately after the indoor unit 30B starts, or other cases, refrigerant may not be completely gasified at the indoor-side heat exchanger 32, and two-phase gas-liquid refrigerant may flow.

[0051]

The low-pressure gas refrigerant or two-phase gas-liquid refrigerant (lowpressure refrigerant) flows in the second branch pipes 5Aand 5B, and flows to the second main pipe 3 via the cooling opening and closing valves 26b and 26d of the first distribution portion 26. The refrigerant that has passed through the second main pipe 3 and flowed to the heat source unit 10 completes a round of circulation by passing through the check valve 16b, the flow switching device 12, and the accumulator 15 and returning again to the compressor 11.

[0052]

The flow of refrigerant at the first intermediate heat exchanger 22 and the second intermediate heat exchanger 24 is described below. The refrigerant that has been divided by the second intermediate heat exchanger 24 and has flowed to the first relay-side bypass pipe 28 passes through the second relay-side flow rate control device 25, subcools the refrigerant flowing from the gas-liquid separation device 21 at the second intermediate heat exchanger 24 and the first intermediate heat exchanger 22, and flows to the second main pipe 3. At this time, when the opening degree of the second relay-side flow rate control device 25 is large and the flow rate of refrigerant (refrigerant used for subcooling) flowing in the first relay-side bypass pipe 28 is large, the flow rate of non-vaporized refrigerant is too large. Consequently, the controller 60 controls, with the second relay-side flow rate control device 25, the degree of superheat of the refrigerant at the outlet of the first relay-side flow rate control device 23 such that the difference in pressure between the first relay-side pressure detector 55 and the second relay-side pressure detector 56 is equal to a predetermined value. As described above, the subcooled refrigerant flows to the second distribution portion 27 side, and consequently, enthalpy on the refrigerant inlet side (in this example, the first branch pipe 4B side) is decreased, and the amount of heat exchange with air at the indoor-side heat exchanger 32 may be increased.

[0053] [Heating Only Operation]

Fig. 2 is a refrigerant circuit diagram for illustrating the flow of refrigerant during the heating only operation in the air-conditioning apparatus illustrated in Fig. 1. An operation example of the air-conditioning apparatus 1 and the flow of refrigerant during the heating only operation are explained with reference to Fig. 2. In Fig. 2, a case in which all the indoor units 30Aand 30B are performing heating without stopping is described. During the heating only operation, control is performed by the controller 60 such that the bypass opening and closing portion 43 is in the closed state, each of the first flow restriction portion 46 and the second flow restriction portion 47 is in the opened state, the heating opening and closing valves 26a and 26c of the first distribution portion 26 are in the opened state, and the cooling opening and closing valves 26b and 26d are in the closed state.

[0054]

Refrigerant that has been sucked from the accumulator 15 is compressed by the compressor 11, and high-pressure gas refrigerant is discharged. The refrigerant that has been discharged from the compressor 11 flows through the flow switching device 12 and the check valve 16c, passes through the first main pipe 2, and flows into the relay unit 20. By virtue of the pressure of the refrigerant, the refrigerant does not flow to the check valves 16b and 16a side.

[0055]

The refrigerant that has flowed into the relay unit 20 is separated into gas refrigerant and liquid refrigerant by the gas-liquid separation device 21, passes through the gas-phase pipe 21a, and flows to the first distribution portion 26. The gas refrigerant flows via the heating opening and closing valves 26a and 26c of the first distribution portion 26, passes through the second branch pipes 5A and 5B, and flows to the plurality of indoor units 30A and 30B.

[0056]

In the indoor units 30Aand 30B, the high-pressure gas refrigerant is condensed by heat exchange while passing through the indoor-side heat exchangers 32, turns into liquid refrigerant, and passes through the indoor-side expansion devices 31. At this time, the indoor air is heated by heat exchange, so that heating for the air-conditioned space (indoor space) is performed. Adjustment of the opening degree of each of the indoor-side expansion devices 31 is controlled by the controller 60 on the basis of the degree of subcooling on the refrigerant outlet side of each of the indoor-side heat exchangers 32. Specifically, the controller 60 performs control such that the condensing temperature of the refrigerant at the indoor-side heat exchangers 32 in the indoor units 30Aand 30B is equal to a predetermined target temperature, and such that the evaporating temperature of the refrigerant at the outdoor-side heat exchange unit 13 is equal to a predetermined target temperature. Consequently, the controller 60 controls the discharge capacity of the compressor 11 and the airflow rate in the heat-source-unit-side air-sending device 14, and supplies capacity corresponding to the loads of the indoor units 30A and 30B.

[0057]

The refrigerant that has passed through the indoor-side expansion devices 31 turns into low-pressure liquid refrigerant or two-phase gas-liquid refrigerant, and flows into the second distribution portion 27 of the relay unit 20 through the first branch pipes 4A and 4B. Subsequently, the refrigerant flows in the second relay-side bypass pipe 29 via the heating check valves 27a and 27c of the second distribution portion 27. Then, the refrigerant passes through the second relay-side flow rate control device 25 and the first relay-side bypass pipe 28, and flows to the second main pipe 3. At this time, the opening degree of the second relay-side flow rate control device 25 is controlled by the controller 60 such that the low-pressure twophase gas-liquid refrigerant flows in the second main pipe 3.

[0058]

The refrigerant that has flowed into the heat source unit 10 from the second main pipe 3 passes through the check valve 16d of the heat source unit 10, and flows into the outdoor-side heat exchange unit 13. While passing through the outdoor-side heat exchange unit 13, the refrigerant evaporates by heat exchange with air and turns into gas refrigerant. Then, the gas refrigerant passes through the flow switching device 12 and the accumulator 15, and returns again to the compressor 11.

[0059] [Heating Main Operation]

Fig. 3 is a refrigerant circuit diagram for illustrating the flow of refrigerant during the heating main operation in the air-conditioning apparatus illustrated in Fig. 1. The heating main operation is explained with reference to Fig. 3. In Fig. 3, a case in which the indoor unit 30A performs a heating operation and the indoor unit 30B performs a cooling operation is illustrated as an example. In this case, control is performed by the controller 60 such that the bypass opening and closing portion 43 is in the closed state and each of the first flow restriction portion 46 and the second flow restriction portion 47 is in the opened state. Further, the heating opening and closing valve 26a on the indoor unit 30A side of the first distribution portion 26 is opened, and the cooling opening and closing valve 26b is closed. In contrast, the cooling opening and closing valve 26d on the indoor unit 30B side is opened, and the heating opening and closing valve 26c is closed. Further, the controller 60 blocks the flow of refrigerant between the first relay-side flow rate control device 23 and the gas-liquid separation device 21 by closing the first relay-side flow rate control device 23.

[0060]

In Fig. 3, an operation of each device of the heat source unit 10 and the flow of refrigerant are the same as those during the heating only operation illustrated in Fig.

2, and the flow of refrigerant during a heating operation at the indoor unit 30A is the same as that during the heating only operation illustrated in Fig. 2. In contrast, during the heating main operation illustrated in Fig. 3, refrigerant that has been subjected to heat exchange at the indoor unit 30A flows into the indoor unit 30B that is performing a cooling operation.

[0061]

That is, refrigerant that has been condensed by heat exchange while passing through the indoor-side heat exchanger 32 of the indoor unit 30A passes through the indoor-side expansion device 31 and the heating check valve 27c, and flows to the second relay-side bypass pipe 29. Subsequently, the condensed refrigerant passes through the second intermediate heat exchanger 24, and flows into the second distribution portion 27. Then, the refrigerant passes through the cooling check valve 27d and the first branch pipe 4B, flows into the indoor unit 30B, and serves as a refrigerant to be used for cooling. At this time, the controller 60 adjusts the second relay-side flow rate control device 25, controls heat exchange at the first intermediate heat exchanger 22, and supplies refrigerant required for the indoor unit 30B, while causing the remaining refrigerant to flow to the second main pipe 3 through the first relay-side bypass pipe 28.

[0062]

As described above, during the heating main operation, refrigerant that has flowed out of the indoor unit 30Athat is performing a heating operation flows to the indoor unit 30B that is performing a cooling operation. Consequently, when the indoor unit 30B that is performing a cooling operation stops, the flow rate of twophase gas-liquid refrigerant flowing in the first relay-side bypass pipe 28 increases.

In contrast, when the load in the indoor unit 30B that is performing a cooling operation increases, the flow rate of two-phase gas-liquid refrigerant flowing in the first relayside bypass pipe 28 decreases. Consequently, the load of the indoor-side heat exchanger 32 (evaporator) in the indoor unit 30B that is performing a cooling operation changes while the amount of refrigerant required for the indoor unit 30A that is performing a heating operation being unchanged. Also during the heating main operation described above, the controller 60 controls the discharge capacity of the compressor 11 and the airflow rate in the heat-source-unit-side air-sending device 14, and supplies capacity corresponding to the load of each of the indoor units 30A and 30B.

[0063] [Cooling Main Operation]

Fig. 4 is a refrigerant circuit diagram for illustrating the flow of refrigerant during the cooling main operation in the air-conditioning apparatus illustrated in Fig. 1. An operation of each device during the cooling main operation is explained with reference to Fig. 4. In Fig. 4, a case in which the indoor unit 30A is performing a cooling operation and the indoor unit 30B is performing a heating operation is described. In this case, control is performed by the controller 60 such that the bypass opening and closing portion 43 is in the closed state, and each of the first flow restriction portion 46 and the second flow restriction portion 47 is in the opened state. Further, the heating opening and closing valve 26a of the first distribution portion 26 that is connected to the indoor unit 30A is closed, and the cooling opening and closing valve 26b is opened. In contrast, the cooling opening and closing valve 26d of the first distribution portion 26 that is connected to the indoor unit 30B is closed, and the heating opening and closing valve 26c is opened.

[0064]

An operation of the heat source unit 10 and the flow of refrigerant illustrated in Fig. 4 are the same as those for the cooling only operation illustrated in Fig. 1. However, condensation of refrigerant in the outdoor-side heat exchange unit 13 is controlled, and consequently, refrigerant that passes through the first main pipe 2 and flows into the relay unit 20 turns into two-phase gas-liquid refrigerant. Further, the flow of refrigerant that reaches the indoor unit 30Athat is performing a cooling operation, passes through the second main pipe 3, and then flows into the heat source unit 10 is similar to the flow of refrigerant during the cooling only operation illustrated in Fig. 1. In contrast, the flow of refrigerant regarding the indoor unit 30B that is performing heating during the cooling main operation illustrated in Fig. 4 is different from the flow of refrigerant regarding the indoor unit 30Athat is performing cooling.

[0065]

That is, two-phase gas-liquid refrigerant that has flowed into the relay unit 20 is separated into gas refrigerant and liquid refrigerant by the gas-liquid separation device 21. In the indoor unit 30B, the opening degree of the indoor-side expansion device 31 is adjusted, and consequently, the flow rate of refrigerant flowing into the indoor-side heat exchanger 32 from the first branch pipe 4B is adjusted. Then, the high-pressure gas refrigerant is condensed by heat exchange while passing through the indoor-side heat exchanger 32 on the indoor unit 30B side and turns into liquid refrigerant, and the liquid refrigerant passes through the indoor-side expansion device 31. At this time, indoor air is heated by heat exchange, so that indoor heating is performed. The refrigerant that has passed through the indoor-side expansion device 31 turns into liquid refrigerant having a pressure that is slightly reduced, and flows in the second relay-side bypass pipe 29 through the first branch pipe 4B and the heating check valve 27c. Then, the refrigerant flowing through the second relay-side bypass pipe 29 merges with the liquid refrigerant flowing from the gas-liquid separation device 21, flows to the indoor unit 30A through the second intermediate heat exchanger 24 and the cooling check valve 27b, and is used as a refrigerant for a cooling operation of the indoor unit 30A.

[0066]

As described above, during the cooling main operation, the outdoor-side heat exchange unit 13 of the heat source unit 10 acts as a condenser. Further, the refrigerant that has passed through the indoor unit 30B that is performing heating is used as a refrigerant for the indoor unit 30A that is performing cooling. When the load of the indoor unit 30A is small and refrigerant flowing in the indoor unit 30A is to be suppressed or other cases, the controller 60 increases the opening degree of the second relay-side flow rate control device 25. Refrigerant may be allowed to flow to the second main pipe 3 through the first relay-side bypass pipe 28 without more than necessary amount of refrigerant being supplied to the indoor unit 30Athat is performing cooling, accordingly. Also during the cooling main operation described above, the controller 60 controls the discharge capacity of the compressor 11 and the airflow rate in the heat-source-unit-side air-sending device 14, and supplies capacity corresponding to the load of each of the indoor units 30A and 30B.

[0067] [Defrosting Operation]

Fig. 5 is a refrigerant circuit diagram for illustrating the flow of refrigerant during the defrosting operation in the air-conditioning apparatus illustrated in Fig. 1. An operation during the defrosting operation in the air-conditioning apparatus 1 is explained. In Fig. 5, a heating only operation during which all the indoor units 30A and 30B perform heating without stopping is illustrated as an example. Further, a case in which defrosting for the outdoor-side heat exchanger 13A of the outdoor-side heat exchange unit 13 is performed is described.

[0068]

In this case, the controller 60 performs opening and closing operations as described below. In the bypass opening and closing portion 43 at the first heatsource-side bypass pipe 41, the bypass opening and closing valve 43Athat is connected to the outdoor-side heat exchanger 13A side is opened, and the bypass opening and closing valve 43B that is connected to the outdoor-side heat exchanger 13B side is closed. Further, in the first flow restriction portion 46, the first opening and closing valve 46Athat is connected to the outdoor-side heat exchanger 13A side is closed, and the first opening and closing valve 46B that is connected to the outdoor-side heat exchanger 13B side is opened. Further, in the second flow restriction portion 47, the second opening and closing valve 47Athat is connected to the outdoor-side heat exchanger 13Aside is closed, and the second opening and closing valve 47B that is connected to the outdoor-side heat exchanger 13B side is opened.

[0069]

In the heat source unit 10, sucked refrigerant is compressed into high-pressure gas refrigerant by the compressor 11, and is discharged. Part of the refrigerant discharged from the compressor 11 flows in the flow switching device 12 and the check valve 16c. By virtue of the pressure of the refrigerant, the refrigerant does not flow to the check valve 16b side and the check valve 16a side. Then, the refrigerant passes through the first main pipe 2 and flows into the relay unit 20. Subsequently, in a manner similar to the flow of refrigerant during the heating only operation illustrated in Fig. 2, the refrigerant passes through the indoor units 30Aand 30B, flows again through the relay unit 20, and returns to the heat source unit 10. This flow of refrigerant is defined as a main flow during the defrosting operation.

[0070]

Meanwhile, part of the refrigerant that has been discharged from the compressor 11 passes through the first heat-source-side bypass pipe 41, is decompressed by the first decompression device 42, and then flows into the outdoorside heat exchanger 13A. The refrigerant that has flowed into the outdoor-side heat exchanger 13A passes through the outdoor-side heat exchanger 13A in a state of high-temperature, medium-pressure gas refrigerant. Consequently, frost deposited on the outdoor-side heat exchanger 13A is removed. The refrigerant having heat removed by defrosting turns into refrigerant in a two-phase gas-liquid state or liquid refrigerant in a subcooled state, and flows out of the outdoor-side heat exchanger 13A.

[0071]

The two-phase gas-liquid refrigerant or liquid refrigerant that has flowed out of the outdoor-side heat exchanger 13A passes through the second heat-source-side bypass pipe 44, and is decompressed by the second decompression device 45.

Then, the decompressed refrigerant merges with the refrigerant that has returned to the heat source unit 10, and the resultant refrigerant flows into the outdoor-side heat exchanger 13B. In the outdoor-side heat exchanger 13B, the refrigerant that has passed through the indoor units 30Aand 30B and the outdoor-side heat exchanger 13A evaporates and turns into gas refrigerant. Then, the gas refrigerant passes through the flow switching device 12 and the accumulator 15, and returns again to the compressor 11.

[0072]

In Fig. 5, the defrosting operation during the heating only operation is illustrated as an example. However, such a defrosting operation may also be performed during the heating main operation. Further, although the defrosting operation for the outdoor-side heat exchanger 13A is illustrated as an example, defrosting may also be performed for the outdoor-side heat exchanger 13B. For the defrosting operation for the outdoor-side heat exchanger 13B, in the bypass opening and closing portion 43, the bypass opening and closing valve 43Athat is connected to the outdoor-side heat exchanger 13Aside is closed, and the bypass opening and closing valve 43B that is connected to the outdoor-side heat exchanger 13B side is opened. Further, in the first flow restriction portion 46, the first opening and closing valve 46Athat is connected to the outdoor-side heat exchanger 13A side is opened, and the first opening and closing valve 46B that is connected to the outdoor-side heat exchanger 13B side is closed. Further, in the second flow restriction portion 47, the second opening and closing valve 47Athat is connected to the outdoor-side heat exchanger 13A side is opened, and the second opening and closing valve 47B that is connected to the outdoor-side heat exchanger 13B side is closed.

[0073]

When the first decompression device 42 is an electronic expansion valve, during the defrosting operation, the controller 60 controls an operation of the first decompression device 42 such that the gas refrigerant discharged from the compressor 11 is decompressed into medium-pressure refrigerant. Further, the controller 60 controls the opening degree of the second decompression device such that the pressure of the refrigerant in the outdoor-side heat exchanger 13A to be defrosted is equal to a target refrigerant pressure. The pressure of the refrigerant in the outdoor-side heat exchanger 13Ato be defrosted is measured by the pressure detection unit 54 that is provided at the first heat-source-side bypass pipe 41.

[0074]

The pressure of the refrigerant in the outdoor-side heat exchanger 13A to be defrosted affects defrosting capacity and heating capacity during the defrosting operation. When the pressure of the refrigerant in the outdoor-side heat exchanger 13Ato be defrosted is low, the refrigerant saturation temperature at the time of defrosting is lower than the outside air temperature, and the defrosting capacity decreases because latent heat of the refrigerant cannot be used. In contrast, as the pressure of the refrigerant in the outdoor-side heat exchanger 13A to be defrosted increases, the refrigerant saturation temperature at the heat exchanger to be defrosted increases, and the defrosting capacity thus increases because latent heat of the refrigerant can be used for defrosting. However, more refrigerant is condensed at the outdoor-side heat exchanger 13Ato be defrosted, and a shortage of refrigerant thus occurs. Consequently, heating capacity cannot be exhibited. That is, the most efficient operation state in terms of defrosting capacity and heating capacity is that the pressure of the refrigerant in the outdoor-side heat exchanger 13A to be defrosted is equal to a pressure at which an appropriate amount of refrigerant in the system can be used. The pressure of the refrigerant at which an appropriate amount of refrigerant in the system can be used represents a state in which excess refrigerant inside the refrigerant circuit stays inside the outdoor-side heat exchanger 13A to be defrosted.

[0075]

When the defrosting operation is performed during the heating only operation or the heating main operation, an operation configuration of the indoor units 30A and 30B is a factor relating to the excess amount of refrigerant. During the heating only operation, as the number of indoor units 30Aand 30B that are performing a heating operation decreases, the number of indoor-side heat exchangers operating as condensers decreases, and the excess amount of refrigerant inside the refrigerant circuit thus increases. Further, during the heating main operation, as the ratio of a cooling operation in the plurality of indoor units 30Aand 30B increases, the gas ratio of refrigerant in the second main pipe 3 increases, and the amount of refrigerant inside the second main pipe 3 thus decreases. Consequently, the excess amount of refrigerant inside the refrigerant circuit increases.

[0076]

The controller 60 performs control such that, under the above-described condition in which the excess amount of refrigerant increases, the pressure of the refrigerant in the outdoor-side heat exchanger 13A to be defrosted increases. By prompting a change in the latent heat of the refrigerant in the outdoor-side heat exchanger 13Ato be defrosted, the defrosting capacity may be increased. In contrast, the controller 60 performs control such that, under an operation condition in which the excess amount of refrigerant decreases, the pressure of the refrigerant in the outdoor-side heat exchanger 13A to be defrosted decreases. Consequently, a situation in which excess refrigerant condenses in a heat exchanger to be defrosted may be avoided, and a reduction in heating capacity caused by a shortage of refrigerant may thus be avoided.

[0077]

Specifically, the controller 60 has a function of changing a target refrigerant pressure corresponding to the operation configuration of the plurality of indoor units 30A and 30B. The memory 61 stores a reference value PdmO for medium pressure, a correction value A for the ratio of the all of the indoor units that perform a heating operation to all of the plurality of indoor units 30A and 30B, and a correction value B based on the ratio of the indoor units that perform a heating operation to the all of the plurality of indoor units that operate. The correction value A decreases as the ratio of the all of the indoor units that perform a heating operation to all of the plurality of indoor units 30Aand 30B during the heating only operation increases, and the correction value A is set to 1 for the heating main operation. Further, the correction value B increases as the ratio of the indoor units that perform a cooling operation to the all of the plurality of indoor units that operate during the heating main operation increases, and the correction value B is set to 1 for the heating only operation.

[0078]

The controller 60 calculates a target refrigerant pressure Pdm on the basis of Equation (1) below.

[0079]

Target refrigerant pressure Pdm = PdmO χ A χ B (1) [0080]

In Equation (1), for the case of a condition in which the ratio of the all of the indoor units that perform a heating operation to all of the plurality of indoor units 30A and 30B during the heating only operation is small and the excess amount of refrigerant is large, the correction value A is large, and the target refrigerant pressure

Pdm is set to be high. In contrast, for the case of a condition in which the ratio of the all of the indoor units that perform a heating operation to all of the plurality of indoor units 30Aand 30B during the heating only operation is large and the excess amount of refrigerant is small, the correction value A is small, and the target refrigerant pressure Pdm is set to be low.

[0081]

Further, in the operation configuration during the heating main operation, for the case of a condition in which the ratio of a cooling operation in the plurality of indoor units 30Aand 30B is high and the excess amount of refrigerant is large, the correction value B is large, and the target refrigerant pressure Pdm is set to be high.

In contrast, for the case of a condition in which the ratio of a cooling operation during the heating main operation is small and the excess amount of refrigerant is small, the correction value B is small, and the target refrigerant pressure Pdm is set to be low. [0082]

According to the embodiment described above, during the defrosting operation, the bypass opening and closing portion 43 allows refrigerant that has been discharged from the compressor to pass through the outdoor-side heat exchanger 13Ato be defrosted after being decompressed by the first decompression device 42 through the first heat-source-side bypass pipe 41, and the second heat-source-side bypass pipe 44 allows the refrigerant that has flowed out of the outdoor-side heat exchanger 13A to be defrosted to flow into the outdoor-side heat exchanger 13B acting as an evaporator. Consequently, when defrosting is performed for a part of the outdoor-side heat exchange unit 13, the heating capacity may be prevented from being reduced while the defrosting capacity being maintained.

[0083]

Further, when the controller 60 controls the opening degree of the second decompression device 45 such that the pressure of the refrigerant at the outdoor-side heat exchanger 13Ato be defrosted is equal to the target refrigerant pressure Pdm, the second heat-source-side bypass pipe 44 and the second decompression device 45 may control the pressure of the refrigerant at the outdoor-side heat exchanger 13A to be defrosted to the target refrigerant pressure. Consequently, avoidance of a situation in which the refrigerant pressure is low and the defrosting capacity is thus reduced, or in which the refrigerant pressure is high and sufficient heating capacity cannot be exhibited may be ensured.

[0084]

Further, when the controller 60 has a function of changing the target refrigerant pressure Pdm corresponding to the operation state of the plurality of indoor units 30A and 30B, when the excess amount of refrigerant inside the refrigerant circuit changes corresponding to the operation state, the amount of refrigerant used for defrosting may be adjusted corresponding to the excess amount of refrigerant, and reductions in defrosting capacity and heating capacity may be suppressed.

[0085]

In particular, during the heating only operation in which all the operating indoor units 30Aand 30B perform a heating operation, when the controller 60 changes the target refrigerant pressure Pdm corresponding to the ratio of the all of the indoor units that perform a heating operation to all of the plurality of indoor units 30A and 30B, a reduction in heating capacity may be suppressed while defrosting is being performed by effectively using excess refrigerant inside the refrigerant circuit.

[0086]

Further, during the heating main operation with a high heating load in which the indoor unit 30B performs a cooling operation and the indoor unit 30A performs a heating operation in a mixed manner, when the controller 60 changes the target refrigerant pressure corresponding to the ratio of the indoor unit 30A that is performing a heating operation to the plurality of indoor units 30A and 30B that are operating, a reduction in heating capacity may be suppressed while defrosting is being performed by effectively using excess refrigerant inside the refrigerant circuit. [0087]

The embodiments of the present invention are not limited to the embodiment described above. For example, explanation has been provided on the assumption that all the indoor units 30Aand 30B are operating during the cooling only operation and the heating only operation. However, for example, a part of the indoor units 30A and 30B may stop.

Reference Signs List [0088] air-conditioning apparatus 2 first main pipe (refrigerant pipe) 3 second main pipe (refrigerant pipe) 4Aand4B first branch pipe 5Aand5B second branch pipe 10 heat source unit 11 compressor 12 flow switching device 13 outdoor-side heat exchange unit 13Aand13B outdoor-side heat exchanger 14 heat-source-unit-side air-sending device 15 accumulator 16 flow passage forming portion 16a to 16d check valve 20 relay unit 21 gas-liquid separation device 21a gas-phase pipe 21b liquid-phase pipe 22 first intermediate heat exchanger 23 first relay-side flow rate control device 24 second intermediate heat exchanger 25 second relayside flow rate control device 26 first distribution portion 26a and 26c heating opening and closing valve 26b and 26d cooling opening and closing valve 27 second distribution portion 27a and 27c heating checkvalve 27b and 27d cooling check valve 28 first relay-side bypass pipe 29 second relayside bypass pipe 30A and 30B indoor unit 31 indoor-side expansion device indoor-side heat exchanger 33 indoor air-sending device 41 first heat-source-side bypass pipe 42 first decompression device 43 bypass opening and closing portion43A and 43B bypass opening and closing valve 44 second heat-source-side bypass pipe 45 second decompression device 46 first flow restriction portion 46A and 46B first opening and closing valve 47 second flow restriction portion 47Aand47B second opening and closing valve 51 discharge pressure detection unit 52 outside air temperature sensor 53Aand 53B refrigerant temperature detection unit 54 pressure detection unit relay-side pressure detector 56 second relay-side pressure detector first controller 61 memory

A correction value

B correction value

Pd pressure Pdm target refrigerant pressure value

PdmO reference

Claims

CLAIMS [Claim 1]

An air-conditioning apparatus, comprising a heat source unit and an indoor unit that are connected by a refrigerant pipe, the indoor unit including an indoor-side flow rate control device and an indoorside heat exchanger, the heat source unit including a compressor configured to compress refrigerant and discharge the refrigerant, an outdoor-side heat exchange unit including a plurality of outdoor-side heat exchangers connected to the compressor in parallel to one another, a first heat-source-side bypass pipe having one end connected to a discharge side of the compressor and an other end connected to each of the plurality of outdoor-side heat exchangers, a first decompression device provided at the first heat-source-side bypass pipe, and configured to reduce a pressure of the refrigerant discharged from the compressor, a bypass opening and closing portion provided at the first heat-sourceside bypass pipe, and configured to allow passage and block of the refrigerant discharged from the compressor to each of the plurality of outdoor-side heat exchangers, a second heat-source-side bypass pipe configured to connect the plurality of outdoor-side heat exchangers to one another, and to allow the refrigerant flowing out of one of the plurality of outdoor-side heat exchangers to flow into an other one of the plurality of outdoor-side heat exchangers, and a second decompression device provided at the second heat-sourceside bypass pipe, and configured to reduce a pressure of refrigerant passing through the second heat-source-side bypass pipe.
[Claim 2]

The air-conditioning apparatus of claim 1, wherein, during a defrosting operation, in the outdoor-side heat exchange unit, defrosting is performed in one of the plurality of outdoor-side heat exchangers to be defrosted, and an other one of the plurality of outdoor-side heat exchangers acts as an evaporator, wherein, during the defrosting operation, the bypass opening and closing portion is configured to allow the refrigerant discharged from the compressor to pass through the one of the plurality of outdoor-side heat exchangers to be defrosted, and to prevent the refrigerant discharged from the compressor from flowing into the other one of the plurality of outdoor-side heat exchangers acting as the evaporator, and wherein the second heat-source-side bypass pipe is configured to allow the refrigerant flowing out of the one of the plurality of outdoor-side heat exchangers to be defrosted to flow into the other one of the plurality of outdoor-side heat exchangers acting as the evaporator.
[Claim 3]

The air-conditioning apparatus of claim 2, wherein the heat source unit further includes a first flow restriction portion provided between the indoor unit and the plurality of outdoor-side heat exchangers, and configured to prevent the refrigerant flowing out of the indoor unit during the defrosting operation from flowing into the other one of the plurality of outdoor-side heat exchangers acting as the evaporator, and a second flow restriction portion provided between the compressor and the plurality of outdoor-side heat exchangers, and configured to prevent the refrigerant flowing out of the other one of the plurality of outdoor-side heat exchangers acting as the evaporator during the defrosting operation from flowing into the one of the plurality of outdoor-side heat exchangers to be defrosted.
[Claim 4]

The air-conditioning apparatus of claim 2 or 3, further comprising a controller configured to control an opening degree of the second decompression device such that a pressure of refrigerant at the one of the plurality of outdoor-side heat exchangers to be defrosted is equal to a target refrigerant pressure.
[Claim 5]

The air-conditioning apparatus of claim 4, further comprising:

a plurality of indoor units including the indoor unit; and a relay unit provided between the heat source unit and the plurality of indoor units, and configured to distribute refrigerant supplied from the heat source unit to the plurality of indoor units such that each of the plurality of indoor units performs a cooling operation or a heating operation in an independent manner, wherein the controller has a function of changing the target refrigerant pressure corresponding to an operation state of the plurality of indoor units.
[Claim 6]

The air-conditioning apparatus of claim 5, wherein the controller is configured to change, during a heating only operation in which all of the plurality of indoor units that operate perform a heating operation, the target refrigerant pressure corresponding to a ratio of the all of the plurality of indoor units that operate to all of the plurality of indoor units in the air-conditioning apparatus.
[Claim 7]

The air-conditioning apparatus of claim 5, wherein the controller is configured to change, during a heating main operation with a high heating load in which at least one of the plurality of indoor units performs a cooling operation and at least one of the plurality of indoor units performs a heating operation in a mixed manner, the target refrigerant pressure corresponding to a ratio of the at least one of the plurality of indoor units that performs the heating operation to the all of the plurality of indoor units that operate.