Air conditioner

Abstract

This air conditioner comprises: a heat source unit having a compressor, a channel switching valve, and a heat source unit-side heat exchanger connected to the channel switching valve; a plurality of indoor units each having an indoor-side heat exchanger and an indoor-side flow rate control device connected to one end of the indoor-side heat exchanger; and a relay unit connecting the heat source unit and the plurality of indoor units, the air conditioner being capable of simultaneous cooling and heating operation enabling each of the plurality of indoor units to selectively perform cooling operation or heating operation. The relay unit comprises: a first branch portion, which is connected to the heat source unit via first connecting ductwork through which refrigerant flowing out to the heat source unit flows and second connecting ductwork through which refrigerant flowing in from the heat source unit flows, and which switchably connects the other end of each of the indoor-side heat exchangers to the first connecting ductwork or the second connecting ductwork; a second branch portion that switchably connects each of the indoor-side flow rate control devices to the first connecting ductwork or the second connecting ductwork; and a first shutoff portion, which is provided between each of the indoor-side flow rate control devices and the second branch portion, and which shuts off the flow of refrigerant between the relay unit and the plurality of indoor units.

Description

air conditioning equipment

[0001] The present disclosure relates to an air conditioner capable of simultaneous cooling and heating operation.

[0002] Conventionally, there has been an air conditioner that includes a heat source unit, multiple indoor units, and a relay unit that connects the heat source unit and the multiple indoor units, and that is capable of simultaneous cooling and heating operation (see, for example, Patent Document 1). In recent years, refrigerant regulations have become stricter, and the use of low GWP refrigerants has progressed. Therefore, the air conditioner of Patent Document 1 also uses a low GWP refrigerant.

[0003] International Publication No. 2011 / 074028

[0004] Many low-GWP refrigerants are slightly flammable or flammable, and air conditioners using these refrigerants require a refrigerant shut-off structure composed of a shut-off valve or the like to prevent refrigerant leakage into the indoor space as a safety measure. However, the air conditioner described in Patent Document 1 does not have such a structure, and requires work to install a refrigerant shut-off structure in the air conditioner on-site (at the installation location), which increases the workload on-site and results in poor installability.

[0005] The present disclosure has been made to solve the above-mentioned problems, and aims to provide an air conditioning apparatus with improved installation ease.

[0006] The air conditioner according to the present disclosure is an air conditioner capable of simultaneous cooling, heating, and cooling operation, comprising: a heat source unit having a compressor, a flow path switching valve, and a heat source unit-side heat exchanger connected to the flow path switching valve; a plurality of indoor units each having an indoor heat exchanger and an indoor flow control device connected to one end of the indoor heat exchanger; and a relay unit connecting the heat source unit and the plurality of indoor units, wherein each of the plurality of indoor units can selectively perform cooling or heating operation, and the relay unit has a first connecting pipe through which refrigerant flowing out to the heat source unit flows, and a second connecting pipe through which refrigerant flowing out to the heat source unit flows. The system comprises a first branch section that is connected to the heat source unit by a second connecting pipe through which the refrigerant flowing in from the heat source unit flows, and that switchably connects the other end of each of the indoor heat exchangers to either the first connecting pipe or the second connecting pipe, a second branch section that switchably connects each of the indoor flow control devices to either the first connecting pipe or the second connecting pipe, and a first blocking section that is provided between each of the indoor flow control devices and the second branch section and blocks the flow of refrigerant between the relay unit and the multiple indoor units.

[0007] According to the air conditioning apparatus of the present disclosure, the relay unit is provided with a first shutoff section between each of the first flow control devices and the second branch section, which shuts off the flow of refrigerant between the relay unit and the multiple indoor units. Because the first shutoff section is provided in advance in the relay unit, there is no need to install a refrigerant shutoff structure in the air conditioning apparatus on site (installation location), which reduces the workload on site and improves ease of installation.

[0008] FIG. 1 is a refrigerant circuit diagram showing an air conditioner according to Embodiment 1. FIG. 2 is an operating state diagram during full cooling operation and full heating operation in an air conditioner according to Embodiment 1. FIG. 3 is an operating state diagram during heating-dominated operation in an air conditioner according to Embodiment 1. FIG. 4 is an operating state diagram during cooling-dominated operation in an air conditioner according to Embodiment 1. FIG. 5 is an operating state diagram during defrosting operation in an air conditioner according to Embodiment 1. A flowchart showing control in the event of a refrigerant leak in an air conditioner according to Embodiment 1. A flowchart showing control during defrosting operation in an air conditioner according to Embodiment 1. A flowchart showing control during heating-dominated operation in an air conditioner according to Embodiment 1. FIG. 6 is a refrigerant circuit diagram showing an air conditioner according to Embodiment 2. A flowchart showing control during defrosting operation in an air conditioner according to Embodiment 2.

[0009] An air conditioning apparatus according to the present disclosure will be described below with reference to the drawings. The present disclosure is not limited to the following embodiments and can be modified in various ways without departing from the spirit and scope of the present disclosure. Furthermore, the present disclosure includes all possible combinations of the configurations shown in the following embodiments. In particular, the combinations of components are not limited to those in the respective embodiments; components described in one embodiment can be applied to another embodiment. The air conditioning apparatus shown in the drawings is an example of an apparatus to which the air conditioning apparatus of the present disclosure can be applied, and the air conditioning apparatus shown in the drawings does not limit the applicable apparatus to which the present disclosure can be applied. In addition, components with the same reference numerals in each drawing represent the same or equivalent components, and this applies throughout the entire specification. Note that the relative dimensions or shapes of the components in each drawing may differ from those in the actual apparatus.

[0010] Embodiment 1. Fig. 1 is a refrigerant circuit diagram showing an air conditioning apparatus 100 according to Embodiment 1. Note that Fig. 1 describes a case where three indoor units and one relay unit are connected to one heat source unit, but similar effects can be obtained when two or more indoor units and two or more relay units are connected to two or more heat source units.

[0011] The air conditioning apparatus 100 according to the first embodiment is an air conditioning apparatus capable of simultaneous cooling and heating operation, i.e., selecting cooling operation in one indoor unit while selecting heating operation in another indoor unit. The air conditioning apparatus 100 comprises a heat source unit A, a relay unit E, and indoor units B, C, and D connected in parallel with each other. The air conditioning apparatus 100 further comprises a control device 70.

[0012] (Heat Source Machine A) The heat source machine A includes a compressor 1, a flow path switching valve 2, a heat source machine side heat exchanger 3, an evaporation temperature detection unit 4, a low pressure detection unit 28, a flow path switching device 30, and the like.

[0013] The discharge side of the compressor 1 is connected to a connection port of a flow path switching valve 2, which is, for example, a four-way valve. The remaining connection ports of the flow path switching valve 2 are connected to the suction side of the compressor 1, one end of the heat source unit heat exchanger 3, and the flow path switching device 30. That is, the flow path switching valve 2 switches the flow path of the refrigerant discharged from the compressor 1 to either the flow path to the heat source unit heat exchanger 3 or the flow path to the flow path switching device 30. The other end of the heat source unit heat exchanger 3 is connected to the flow path switching device 30. The evaporation temperature detection unit 4 is provided in the low-pressure pipe 29 on the suction side of the compressor 1 and is configured to detect the evaporation temperature of the refrigerant flowing through this low-pressure pipe 29. The low-pressure detection unit 28 is provided in the low-pressure pipe 29 on the suction side of the compressor 1 and is configured to detect the pressure (or pipe pressure) of the refrigerant flowing through this low-pressure pipe 29.

[0014] The flow path switching device 30 includes four check valves (check valves 23 to 26), and is connected to the flow path switching valve 2, the heat source unit-side heat exchanger 3, one end of the first connecting pipe 21, and one end of the second connecting pipe 22. The check valve 23 is provided between the heat source unit-side heat exchanger 3 and the second connecting pipe 22, and allows refrigerant to flow only from the heat source unit-side heat exchanger 3 to the second connecting pipe 22. The check valve 24 is provided between the flow path switching valve 2 and the first connecting pipe 21, and allows refrigerant to flow only from the first connecting pipe 21 to the flow path switching valve 2. The check valve 25 is provided between the flow path switching valve 2 and the second connecting pipe 22, and allows refrigerant to flow only from the flow path switching valve 2 to the second connecting pipe 22. The check valve 26 is provided between the heat source unit-side heat exchanger 3 and the first connecting pipe 21, and allows refrigerant to flow only from the first connecting pipe 21 to the heat source unit-side heat exchanger 3. The other end of the second connecting pipe 22 branches off and is connected to a first branch 10 and a second branch 11 of the relay unit E, which will be described later. The other end of the first connecting pipe 21 is connected to the first branch 10 of the relay unit E, which will be described later.

[0015] By providing the flow path switching device 30, the refrigerant discharged from the compressor 1 always flows into the relay unit E through the second connecting pipe 22, and the refrigerant flowing out from the relay unit E always passes through the first connecting pipe 21. This makes it possible to make the diameter of the second connecting pipe 22 smaller than the diameter of the first connecting pipe 21.

[0016] (Indoor Units B, C, D) The indoor units B, C, D each have the same configuration.

[0017] More specifically, the indoor unit B is equipped with an indoor heat exchanger 5B. One end of the indoor heat exchanger 5B is connected to a second branch 11 of the relay unit E (described later) via a second indoor unit connecting pipe 7B. An indoor flow control device 9B is provided on the second indoor unit connecting pipe 7B. The other end of the indoor heat exchanger 5B is connected to a first branch 10 of the relay unit E (described later) via a first indoor unit connecting pipe 6B. The indoor unit B is equipped with a refrigerant leak detection unit 60B that detects refrigerant leaks. The refrigerant leak detection unit 60B may be, for example, a semiconductor gas sensor or a detection unit that detects a sudden drop in refrigerant pressure in the indoor unit B. Note that, while the refrigerant leak detection unit 60B is provided in the indoor unit B in FIG. 1 , this is not limiting and the refrigerant leak detection unit 60B may be provided on a remote control for operating the indoor unit B or in the indoor space that the indoor unit B conditions.

[0018] The indoor unit C also includes an indoor heat exchanger 5C. One end of the indoor heat exchanger 5C is connected to a second branch 11 of the relay unit E (described later) via a second indoor unit connecting pipe 7C. An indoor flow control device 9C is provided on the second indoor unit connecting pipe 7C. The other end of the indoor heat exchanger 5C is connected to a first branch 10 of the relay unit E (described later) via a first indoor unit connecting pipe 6C. The indoor unit C also includes a refrigerant leak detection unit 60C that detects refrigerant leaks. The refrigerant leak detection unit 60C may be, for example, a semiconductor gas sensor or a detector that detects a sudden drop in refrigerant pressure within the indoor unit C. While FIG. 1 shows the refrigerant leak detection unit 60C installed within the indoor unit C, this is not limiting and the refrigerant leak detection unit 60C may be installed on a remote control for operating the indoor unit C, in the indoor space air-conditioned by the indoor unit C, or elsewhere.

[0019] The indoor unit D is also equipped with an indoor heat exchanger 5D. One end of the indoor heat exchanger 5D is connected to a second branch 11 of the relay unit E (described later) via a second indoor unit connecting pipe 7D. An indoor flow control device 9D is provided on the second indoor unit connecting pipe 7D. The other end of the indoor heat exchanger 5D is connected to a first branch 10 of the relay unit E (described later) via a first indoor unit connecting pipe 6D. The indoor unit D is equipped with a refrigerant leak detection unit 60D that detects refrigerant leaks. The refrigerant leak detection unit 60D can be, for example, a semiconductor gas sensor or a detection unit that detects a sudden drop in refrigerant pressure within the indoor unit D. Note that, while the refrigerant leak detection unit 60D is provided within the indoor unit D in FIG. 1 , this is not limited thereto and may be provided on a remote control for operating the indoor unit D or in the indoor space that the indoor unit D air-conditions.

[0020] The opening degrees of the indoor flow control devices 9B to 9D are controlled as follows. When the corresponding indoor units B to D are in cooling operation, the opening degrees of the indoor flow control devices 9B to 9D are controlled based on the degree of superheat on the outlet side of the indoor heat exchangers 5B to 5D. When the corresponding indoor units B to D are in heating operation, the opening degrees of the indoor flow control devices 9B to 9D are controlled based on the degree of subcooling on the outlet side of the indoor heat exchangers 5B to 5D. Note that in the following, when it is not necessary to distinguish between the indoor units and their components, the reference numerals B to D may be omitted in the description.

[0021] (Relay unit E) The relay unit E includes a first branching section 10, a second branching section 11, a gas-liquid separation device 12, a first heat source unit side flow control device 13, a second heat source unit side flow control device 15, a heat exchange section 16, a first blocking section 40, and a second blocking section 50, etc.

[0022] The first branch section 10 is provided with valve devices 8a, 8b (hereinafter also referred to as second on-off valves) in a number corresponding to the number of indoor units. In the first embodiment, three sets of valve devices 8a, 8b (valve devices 8aB, 8bB, valve devices 8aC, 8bC, and valve devices 8aD, 8bD) are provided.

[0023] More specifically, one end of each of the valve devices 8aB and 8bB is connected to the indoor heat exchanger 5B via the first indoor unit connecting pipe 6B. The other end of the valve device 8aB is connected to the first connecting pipe 21, and the other end of the valve device 8bB is connected to the second connecting pipe 22. One end of each of the valve devices 8aC and 8bC is connected to the indoor heat exchanger 5C via the first indoor unit connecting pipe 6C. The other end of the valve device 8aC is connected to the first connecting pipe 21, and the other end of the valve device 8bC is connected to the second connecting pipe 22. One end of each of the valve devices 8aD and 8bD is connected to the indoor heat exchanger 5D via the first indoor unit connecting pipe 6D. The other end of the valve device 8aD is connected to the first connecting pipe 21, and the other end of the valve device 8bD is connected to the second connecting pipe 22.

[0024] That is, the first branch section 10 switches the flow path to which the indoor heat exchangers 5B to 5D are connected to either the first connecting pipe 21 or the second connecting pipe 22 by controlling the opening and closing of the valve device 8a and the valve device 8b.

[0025] The second branch section 11 is provided with check valves 17, 18 arranged in anti-parallel relation according to the number of indoor units. Check valve 17 allows refrigerant to flow only in the direction of flowing into the indoor units. Check valve 18 allows refrigerant to flow only in the direction of flowing out of the indoor units. In the first embodiment, three sets of check valves 17, 18 (check valves 17B, 18B, check valves 17C, 18C, and check valves 17D, 18D) are provided.

[0026] More specifically, one end of each of the check valves 17B and 18B is connected to the indoor heat exchanger 5B via the second indoor unit connecting pipe 7B. The other end of the check valve 17B is connected to the first junction 17A, and the other end of the check valve 18B is connected to the second junction 18A. One end of each of the check valves 17C and 18C is connected to the indoor heat exchanger 5C via the second indoor unit connecting pipe 7C. The other end of the check valve 17C is connected to the first junction 17A, and the other end of the check valve 18C is connected to the second junction 18A. One end of each of the check valves 17D and 18D is connected to the indoor heat exchanger 5D via the second indoor unit connecting pipe 7D. The other end of the check valve 17D is connected to the first meeting portion 17A, and the other end of the check valve 18D is connected to the second meeting portion 18A.

[0027] The first junction 17A is also connected to an end of the second connection pipe 22. The second junction 18A is also connected to the middle of the second connection pipe 22 (the second connection pipe 22 between the first heat source unit-side flow control device 13 and the heat exchange unit 16, which will be described later).

[0028] As described above, the second connection pipe 22 branches and is connected to the first branch portion 10 and the second branch portion 11. This branch portion is provided with the gas-liquid separator 12. In addition, the second connection pipe 22 between the gas-liquid separator 12 and the second branch portion 11 is provided with the first heat source unit-side flow control device 13 and the heat exchanger 16 from the upstream side of the refrigerant flow.

[0029] Furthermore, one end of the bypass pipe 14 is connected to the second connection pipe 22 between the heat exchange unit 16 and the second branch 11. The other end of this bypass pipe 14 is connected to the first connection pipe 21. The bypass pipe 14 is also provided with the heat exchange unit 16 described above. That is, in the heat exchange unit 16, heat is exchanged between the refrigerant flowing through the second connection pipe 22 and the refrigerant flowing through the bypass pipe 14. The bypass pipe 14 is also provided with a second heat source unit-side flow control device 15 on the upstream side of the heat exchange unit 16 in the refrigerant flow direction. Note that the refrigerant flowing out from the second branch 11 passes through this bypass pipe 14 when flowing to the first connection pipe 21. In this case, the bypass pipe 14 constitutes a part of the first connection pipe 21.

[0030] The relay unit E according to the first embodiment is provided with a first shutoff unit 40 that shuts off the flow of refrigerant flowing out from the relay unit E to the indoor units between the indoor-side flow control devices 9B, 9C, 9D and the second branch unit 11. The first shutoff unit 40 includes first shutoff devices 41B, 41C, 41D, the number of which corresponds to the number of indoor units. The first shutoff devices 41B to 41D are flow control devices (hereinafter also referred to as first flow control devices) whose opening degrees can be adjusted.

[0031] More specifically, one end of each of the first shutoff devices 41B, 41C, and 41D is connected to the indoor heat exchangers 5B, 5C, and 5D via the second indoor unit side connecting pipes 7B, 7C, and 7D, respectively, and the other end of each of the first shutoff devices 41B, 41C, and 41D is connected to the first junctions 19B, 19C, and 19D.

[0032] The first shutoff unit 40 controls the opening degree of the first shutoff devices 41B, 41C, 41D, thereby controlling the flow rate of refrigerant flowing from the relay unit E to the indoor heat exchangers 5B, 5C, 5D via the second indoor unit side connecting piping 7B, 7C, 7D.

[0033] Furthermore, the relay unit E according to the first embodiment is provided with a second shutoff section 50 between the indoor heat exchangers 5B, 5C, 5D and the first branch section 10, which shuts off the flow of refrigerant flowing from the relay unit E to the indoor units. The second shutoff section 50 includes second shutoff devices 51B, 51C, 51D in number corresponding to the number of indoor units. The second shutoff devices 51B, 51C, 51D are flow control devices (hereinafter also referred to as second flow control devices) whose opening degrees can be adjusted.

[0034] More specifically, one end of each of the second shutoff devices 51B, 51C, and 51D is connected to the indoor heat exchangers 5B, 5C, and 5D via the first indoor unit side connecting pipes 6B, 6C, and 6D, and the other end of each of the second shutoff devices 51B, 51C, and 51D is connected to the second junctions 20B, 20C, and 20D.

[0035] The second shutoff unit 50 controls the opening degree of the second shutoff devices 51B, 51C, and 51D, thereby controlling the flow rate of refrigerant flowing from the relay unit E to the indoor heat exchangers 5B, 5C, and 5D via the second indoor unit side connecting piping 7B, 7C, and 7D.

[0036] Here, the specifications of the first shutoff devices 41B, 41C, 41D and the second shutoff devices 51B, 51C, 51D are provided in "Facility Guidelines for Ensuring Safety in the Event of Refrigerant Leakage from Commercial Air Conditioners Using Mildly Flammable (A2L) Refrigerant" (JRA GL-16:2017), a guideline issued by the Japan Refrigeration and Air Conditioning Industry Association on September 1, 2017, and the specified specifications must be satisfied. One of the specifications that must be satisfied is the leakage amount when the valve is closed. Specifically, when the fluid is air and the differential pressure before and after the shutoff device is 1 MPa, the leakage amount must be 300 (cm ３ / min) or less is specified as the leakage amount at the time of closing the valve that the shutoff device should satisfy. In other words, the first shutoff devices 41B, 41C, 41D and the second shutoff devices 51B, 51C, 51D have a leakage amount at the time of closing the valve of 300 (cm ３ / min) or less.

[0037] In the first embodiment, the first shut-off devices 41B, 41C, and 41D are flow control devices, but they are not limited to this and may be on-off valves (hereinafter also referred to as first on-off valves) as long as they satisfy the above specifications.

[0038] In addition, in the following, when there is no need to distinguish between the components of the first branch section 10, the second branch section 11, the first interrupting section 40, and the second interrupting section 50, the symbols B to D may be omitted.

[0039] (Control device 70) The control device 70 is configured, for example, by dedicated hardware or a CPU (Central Processing Unit, also called a central processing unit, processing device, arithmetic unit, microprocessor, or processor) that executes a program stored in a memory unit (not shown).

[0040] When the control device 70 is dedicated hardware, the control device 70 may be, for example, a single circuit, a composite circuit, an ASIC (Application Specific Integrated Circuit), an FPGA (Field-Programmable Gate Array), or a combination thereof. Each functional unit realized by the control device 70 may be realized by a separate piece of hardware, or each functional unit may be realized by a single piece of hardware.

[0041] When the control device 70 is a CPU, each function executed by the control device 70 is realized by software, firmware, or a combination of software and firmware. The software and firmware are written as programs and stored in a memory unit. The CPU realizes each function of the control device 70 by reading and executing the programs stored in the memory unit. Here, the memory unit stores various information and includes, for example, a rewritable nonvolatile semiconductor memory such as a flash memory, an EPROM, or an EEPROM.

[0042] It should be noted that some of the functions of the control device 70 may be realized by dedicated hardware, and other functions may be realized by software or firmware.

[0043] The control device 70 controls the operation of the entire air conditioning device 100 based on detection signals from various detection units provided in the air conditioning device 100 and operation signals from an operation unit (not shown). The control device 70 may be provided in the heat source unit A, for example, or may be provided in a location other than the heat source unit A.

[0044] <Explanation of Operation> Next, the operation of the air conditioning apparatus 100 according to Embodiment 1 will be described. The air conditioning apparatus 100 operates in three main modes. That is, the air conditioning apparatus 100 operates in all cooling operation, all heating operation, and simultaneous cooling and heating operation. All cooling operation is an operation in which all of the multiple indoor units operate in cooling mode or are stopped. All heating operation is an operation in which all of the multiple indoor units operate in heating mode or are stopped. Simultaneous cooling and heating operation is an operation mode in which some of the multiple indoor units operate in cooling mode and some operate in heating mode (of course, some indoor units may be stopped). Furthermore, simultaneous cooling and heating operation operates in two modes. That is, heating-dominated operation in which most of the multiple indoor units operate in heating mode, and cooling-dominated operation in which most of the multiple indoor units operate in cooling mode are performed. The operating states for each operation are described below.

[0045] (Cooling only operation) First, the operation of cooling only operation will be described. Fig. 2 is an operational state diagram of the air conditioning apparatus 100 according to Embodiment 1 during cooling only operation and heating only operation. The solid arrows in Fig. 2 indicate the refrigerant flow during cooling only operation. Fig. 2 also illustrates a case where all of the indoor units B, C, and D are in cooling operation. During cooling only operation, the flow path switching valve 2 switches to the state shown by the solid lines in Fig. 2, and the discharge side of the compressor 1 is connected to the heat source unit-side heat exchanger 3.

[0046] The high-temperature, high-pressure gas refrigerant discharged from the compressor 1 passes through the flow path switching valve 2 and flows into the heat source unit-side heat exchanger 3. The refrigerant that flows into the heat source unit-side heat exchanger 3 exchanges heat with the outdoor air and is condensed, and then flows through the check valve 23 and the second connecting pipe 22 and into the relay unit E. The refrigerant that flows into the relay unit E passes through the gas-liquid separator 12 and the first heat source unit-side flow control device 13 in this order, and flows into the heat exchange unit 16. The refrigerant that flows into the heat exchange unit 16 is cooled by the refrigerant flowing through the bypass pipe 14, and flows into the second branch unit 11 with a sufficient degree of subcooling. The refrigerant that flows into the second branch section 11 passes through check valves 17B, 17C, and 17D at the first junction section 17A and is diverted to the second indoor unit side connecting pipes 7B, 7C, and 7D, and flows into each indoor side flow control device 9B, 9C, and 9D via the first shut-off devices 41B, 41C, and 41D.

[0047] The refrigerant flowing into the indoor flow control devices 9B, 9C, and 9D is decompressed to a predetermined low pressure based on the superheat degree at the outlet of each indoor heat exchanger 5B, 5C, and 5D, and then flows into the indoor heat exchangers 5B, 5C, and 5D of each indoor unit B, C, and D. The refrigerant flowing into each indoor heat exchanger 5B, 5C, and 5D exchanges heat with the indoor air in the indoor heat exchangers 5B, 5C, and 5D, evaporating and gasifying, thereby cooling the room. The gaseous refrigerant then passes through the first indoor unit connecting pipes 6B, 6C, and 6D, the second shutoff devices 51B, 51C, and 51D, the valve devices 8aB, 8aC, and 8aD of the first branch section 10, and the first connecting pipe 21, and flows into the heat source unit A. The refrigerant flowing into the heat source unit A passes through the check valve 24 and the flow path switching valve 2 and is drawn into the compressor 1. At this time, the valve devices 8aB, 8aC, and 8aD are in an open state, and the valve devices 8bB, 8bC, and 8bD are in a closed state. In addition, the first shutoff devices 41B, 41C, and 41D are in an open state, and the second shutoff devices 51B, 51C, and 51D are in an open state.

[0048] Furthermore, at this time, because the first connecting pipe 21 is at low pressure and the second connecting pipe 22 is at high pressure, the refrigerant inevitably flows through the check valves 23 and 24. Furthermore, in the cooling only operation shown in Fig. 2, part of the refrigerant that has passed through the first heat source unit-side flow control device 13 flows into the bypass pipe 14. This refrigerant is depressurized to low pressure by the second heat source unit-side flow control device 15 and flows into the heat exchanger 16. The refrigerant depressurized by the second heat source unit-side flow control device 15 then cools and evaporates the refrigerant flowing through the second connecting pipe 22, and merges with the refrigerant flowing through the first connecting pipe 21.

[0049] (Heating only operation) Next, the operation of heating only operation will be described using Fig. 2. The dashed arrows in Fig. 2 indicate the refrigerant flow during heating only operation. Fig. 2 also shows a case where indoor units B, C, and D are all in heating operation. During heating only operation, the flow path switching valve 2 switches to the state shown by the dashed lines in Fig. 2, and the discharge side of the compressor 1 is connected to the flow path switching device 30.

[0050] High-temperature, high-pressure refrigerant gas discharged from compressor 1 passes through flow path switching valve 2, check valve 25, and second connecting pipe 22 and flows into relay unit E. The refrigerant that flows into relay unit E passes through gas-liquid separator 12 and flows into first branch section 10. The refrigerant that flows into first branch section 10 passes through valve devices 8bB, 8bC, 8bD, second shutoff devices 51B, 51C, 51D, and first indoor unit connecting pipes 6B, 6C, 6D, and flows into indoor heat exchangers 5B, 5C, 5D of indoor units B, C, D. The refrigerant that flows into each indoor heat exchanger 5B, 5C, 5D exchanges heat with indoor air in indoor heat exchangers 5B, 5C, 5D, condenses and liquefies, and heats the room. The liquid refrigerant then passes through indoor flow control devices 9B, 9C, and 9D, which are controlled by the degree of subcooling at the outlets of the indoor heat exchangers 5B, 5C, and 5D, and second indoor unit connection pipes 7B, 7C, and 7D, and then through first shutoff devices 41B, 41C, and 41D, and flows into the second branch section 11. The refrigerant that flows into the second branch section 11 passes through check valves 18B, 18C, and 18D and then merges at the second junction section 18A. This merged refrigerant flows through the second connection pipe 22 and bypass pipe 14 into the second heat source unit flow control device 15, where it is decompressed to a low-pressure gas-liquid two-phase state. The refrigerant decompressed to low pressure flows through the bypass pipe 14, heat exchange section 16, and first connection pipe 21, and flows into the heat source unit A. The refrigerant that flows into the heat source unit A passes through the check valve 26 and flows into the heat source unit-side heat exchanger 3. The refrigerant that flows into the heat source unit-side heat exchanger 3 exchanges heat with the outdoor air, evaporates into a gaseous state, and is then drawn into the compressor 1 through the flow path switching valve 2. At this time, the valve devices 8aB, 8aC, and 8aD are closed, and the valve devices 8bB, 8bC, and 8bD are open. Furthermore, the first shutoff devices 41B, 41C, and 41D are open, and the second shutoff devices 51B, 51C, and 51D are open. Furthermore, because the first connecting pipe 21 is at low pressure and the second connecting pipe 22 is at high pressure, the refrigerant inevitably flows through the check valves 25 and 26.

[0051] (Heating-dominant operation) Next, the operation of heating-dominant operation, which is one form of simultaneous heating and cooling operation, will be described. Fig. 3 is an operational state diagram of the air conditioning apparatus 100 according to Embodiment 1 during heating-dominant operation. The solid arrows shown in Fig. 3 indicate the refrigerant flow during heating-dominant operation. Fig. 3 also shows a case where indoor units B and C perform heating operation and indoor unit D performs cooling operation. During heating-dominant operation, the flow path switching valve 2 switches to the state shown by the dashed line in Fig. 3, and the discharge side of the compressor 1 is connected to the flow path switching device 30.

[0052] High-temperature, high-pressure refrigerant gas discharged from compressor 1 passes through flow switching valve 2, check valve 25, and second connecting pipe 22 before flowing into relay unit E. The refrigerant flowing into relay unit E passes through gas-liquid separator 12 and then flows into first branch 10. The refrigerant flowing into first branch 10 passes through valve devices 8bB and 8bC, second shutoff devices 51B and 51C, and first indoor-unit connecting pipes 6B and 6C before flowing into indoor heat exchangers 5B and 5C of indoor units B and C that are being heated. The refrigerant flowing into indoor heat exchangers 5B and 5C exchanges heat with the indoor air and condenses to heat the room. The liquid refrigerant then passes through indoor flow control devices 9B and 9C, which are controlled by the degree of subcooling at the outlets of indoor heat exchangers 5B and 5C and are fully open, slightly reducing the pressure to an intermediate pressure between high and low pressures (intermediate pressure). The intermediate-pressure refrigerant passes through the second indoor unit side connecting pipes 7B, 7C, the first shutoff devices 41B, 41C, and the check valves 18B, 18C, and joins at the second junction 18A.

[0053] The refrigerant that joins at the second junction 18A of the second branch 11 flows into the heat exchanger 16. The refrigerant that flows into the heat exchanger 16 is cooled by the refrigerant flowing through the bypass piping 14, and flows out of the heat exchanger 16 with a sufficient degree of subcooling. A portion of the refrigerant that flows out of the heat exchanger 16 flows into the second branch 11. The refrigerant that flows into the second branch 11 passes through the first junction 17A, the check valve 17D, the first shutoff device 41D, and the second indoor unit connecting piping 7D, and flows into the indoor flow control device 9D. The refrigerant that flows into the indoor flow control device 9D is decompressed to a predetermined low pressure based on the superheat degree at the outlet of the indoor heat exchanger 5D, and then flows into the indoor heat exchanger 5D of the indoor unit D. The refrigerant that flows into the indoor heat exchanger 5D exchanges heat with the indoor air, evaporates, and gasifies, cooling the room. The refrigerant that has become gas passes through the first indoor unit side connecting pipe 6D, the second shutoff device 51D, the valve device 8aD of the first branch section 10, and the first connecting pipe 21, and flows into the heat source unit A. The refrigerant that has flowed into the heat source unit A passes through the check valve 26 and flows into the heat source unit side heat exchanger 3. The refrigerant that has flowed into the heat source unit side heat exchanger 3 exchanges heat with the outdoor air, evaporates, and becomes gaseous, and is then sucked into the compressor 1 via the flow path switching valve 2.

[0054] Meanwhile, a remaining portion of the refrigerant that has flowed out of the heat exchange unit 16 flows into the bypass pipe 14. This refrigerant is depressurized to a predetermined pressure by the second heat source unit-side flow control device 15 and flows into the heat exchange unit 16. The refrigerant depressurized by the second heat source unit-side flow control device 15 then cools and evaporates the refrigerant flowing through the second connecting pipe 22, and merges with the refrigerant flowing through the first connecting pipe 21. The opening degree of the second heat source unit-side flow control device 15 is controlled so that the difference between the high pressure of the second connecting pipe 22 and the intermediate pressure of the second branch unit 11 is constant.

[0055] At this time, the valve devices 8a and 8b connected to indoor units B and C that are attempting to heat have valve devices 8aB and 8aC in a closed state, and valve devices 8bB and 8bC in an open state. Furthermore, the valve device 8a and valve device 8b connected to indoor unit D that is attempting to cool have valve device 8aD in an open state, and valve device 8bD in a closed state. Furthermore, the first shutoff devices 41B, 41C, and 41D are in an open state, and the second shutoff devices 51B, 51C, and 51D are in an open state. Furthermore, because the first connecting pipe 21 is at low pressure and the second connecting pipe 22 is at high pressure, refrigerant inevitably flows through check valves 25 and 26.

[0056] During heating-dominant operation, the evaporation temperature of the indoor unit D performing cooling operation is affected by the ambient temperature of the indoor heat exchanger 5D. Because evaporation and gasification occur at the ambient temperature, the evaporation temperature is lower than the ambient temperature. For example, if the ambient temperature is minus 5°C, the evaporation temperature will be lower than minus 5°C, such as approximately minus 11°C. Assuming there is no throttle circuit in the path from the indoor heat exchanger 5D to the heat source unit heat exchanger 3, the piping length is sufficiently short for illustrative purposes, and pressure loss due to the first branch 10 is negligible, the evaporation temperature of the indoor heat exchanger 5D will be equal to that of the heat source unit heat exchanger 3. In other words, the evaporation temperature of the indoor heat exchanger 5D decreases as the outdoor temperature decreases, triggering anti-freeze control. Anti-freeze control refers to a control that forcibly stops operation of the indoor unit when the piping temperature of the indoor unit drops below a predetermined temperature. By performing anti-freeze control, it is possible to prevent situations such as deformation and breakage of pipes due to ice generated by freezing caused by a drop in the evaporating temperature of the indoor unit during cooling operation, and water leakage caused by the drain pan being unable to contain the frost that has formed on the fins of the indoor heat exchanger installed in the indoor unit when it melts.

[0057] (Cooling-dominated operation) Next, the operation of cooling-dominated operation, which is one form of simultaneous cooling and heating operation, will be described. Fig. 4 is an operational state diagram of the air conditioning apparatus 100 according to Embodiment 1 during cooling-dominated operation. The solid arrows shown in Fig. 4 indicate the refrigerant flow during cooling-dominated operation. Fig. 4 also shows a case where indoor units B and C perform cooling operation and indoor unit D performs heating operation. During cooling-dominated operation, the flow path switching valve 2 switches to the state shown by the solid lines in Fig. 4, and the discharge side of the compressor 1 is connected to the heat source unit-side heat exchanger 3.

[0058] The high-temperature, high-pressure refrigerant gas discharged from the compressor 1 passes through the flow path switching valve 2 and undergoes a desired amount of heat exchange in the heat source unit side heat exchanger 3 to become a gas-liquid two-phase high-temperature, high-pressure refrigerant, which passes through the check valve 23 and the second connecting pipe 22 and flows into the relay unit E. The refrigerant that has flowed into the relay unit E flows into the gas-liquid separator 12 and is separated into gas refrigerant and liquid refrigerant.

[0059] Meanwhile, the gas refrigerant separated by the gas-liquid separator 12 passes through the valve device 8bD of the first branch section 10, the second shutoff device 51D, and the first indoor-unit-side connecting pipe 6D, in that order, before flowing into the indoor-side heat exchanger 5D of the indoor unit D that is being heated. The refrigerant that flows into the indoor-side heat exchanger 5D of the indoor unit D exchanges heat with the indoor air and condenses to liquefy, heating the room. The liquid refrigerant then passes through the indoor-side flow control device 9D, which is controlled by the degree of subcooling at the outlet of the indoor-side heat exchanger 5D and is almost fully open, where it is slightly depressurized to an intermediate pressure. The intermediate-pressure refrigerant passes through the second indoor-unit-side connecting pipe 7D, the first shutoff device 41D, the check valve 18D, and the second junction 18A, before merging with the liquid refrigerant (liquid refrigerant separated by the gas-liquid separator 12) flowing through the second connecting pipe 22.

[0060] The liquid refrigerant separated in the gas-liquid separator 12 of the relay unit E flows into the heat exchange unit 16. The refrigerant that flows into the heat exchange unit 16 is cooled by the refrigerant flowing through the bypass piping 14 to a sufficient degree of subcooling, and then flows into the first heat source unit-side flow control device 13 where it is reduced in pressure to a predetermined level. At this time, the opening degree of the first heat source unit-side flow control device 13 is controlled so that the difference between the high pressure of the second connecting piping 22 upstream of the first heat source unit-side flow control device 13 and the intermediate pressure of the second branch unit 11 is constant.

[0061] A portion of the refrigerant that has flowed out of the first heat source unit-side flow control device 13 passes through the first junction 17A of the second branch unit 11, the check valves 17B, 17C, the first shutoff devices 41B, 41C, and the second indoor unit-side connecting pipes 7B, 7C, and flows into the indoor unit-side flow control devices 9B, 9C. The refrigerant that has flowed into the indoor unit-side flow control devices 9B, 9C is reduced in pressure to a predetermined low pressure based on the degree of superheat at the outlets of the indoor unit-side heat exchangers 5B, 5C, and then flows into the indoor unit-side heat exchangers 5B, 5C of the indoor units B, C. The refrigerant that has flowed into the indoor unit-side heat exchangers 5B, 5C exchanges heat with the indoor air, evaporates, and gasifies, thereby cooling the room. The gaseous refrigerant passes through the first indoor unit side connecting pipes 6B, 6C, the second shutoff devices 51B, 51C, the valve devices 8aB, 8aC of the first branch section 10, and the first connecting pipe 21, and flows into the heat source unit A. The refrigerant that has flowed into the heat source unit A passes through the check valve 24 and the flow path switching valve 2, and is sucked into the compressor 1.

[0062] Meanwhile, a remaining portion of the refrigerant that has flowed out of the first heat source unit-side flow control device 13 flows into the bypass piping 14. This refrigerant is depressurized to a low pressure by the second heat source unit-side flow control device 15 and flows into the heat exchanger 16. Then, the refrigerant depressurized by the second heat source unit-side flow control device 15 cools and evaporates the refrigerant flowing through the second connecting piping 22, and merges with the refrigerant flowing through the first connecting piping 21.

[0063] At this time, the valve devices 8a and 8b connected to indoor units B and C that are to perform cooling have valve devices 8aB and 8aC in the open state, and valve devices 8bB and 8bC in the closed state. Furthermore, the valve device 8a and valve device 8b connected to indoor unit D that is to perform heating have valve device 8aD in the closed state, and valve device 8bD in the open state. Furthermore, the first shutoff devices 41B, 41C, and 41D are in the open state, and the second shutoff devices 51B, 51C, and 51D are in the open state. Furthermore, because the first connecting pipe 21 is at low pressure and the second connecting pipe 22 is at high pressure, refrigerant inevitably flows through check valves 23 and 24.

[0064] (Defrosting operation) Next, the operation of the defrosting operation will be described using Fig. 5. Fig. 5 is an operational state diagram during the defrosting operation in the air conditioning apparatus 100 according to Embodiment 1. Note that the solid line arrows shown in Fig. 5 indicate the refrigerant flow during the defrosting operation. Furthermore, during the defrosting operation, the flow path switching valve 2 switches to the state shown by the solid line in Fig. 5, and the discharge side of the compressor 1 and the heat source unit side heat exchanger 3 are connected.

[0065] In the air conditioning apparatus 100, when heating only operation or heating-dominated operation is performed, the heat source unit-side heat exchanger 3 of the heat source unit A functions as an evaporator and exchanges heat with the outside air. Therefore, when the outside air temperature is low, the evaporation temperature of the heat source unit-side heat exchanger 3 becomes lower, and moisture from the outside air frosts on the surface of the heat source unit-side heat exchanger 3, which may result in a decrease in heat exchange performance. Therefore, in the air conditioning apparatus 100, for example, an evaporation temperature detection unit 4 provided in the heat source unit A detects the evaporation temperature, and when the detected evaporation temperature falls below a predetermined threshold, a defrosting operation is performed to remove frost from the surface of the heat source unit-side heat exchanger 3. The defrosting operation is performed during heating only operation or heating-dominated operation.

[0066] The high-temperature, high-pressure gas refrigerant discharged from the compressor 1 passes through the flow path switching valve 2 and flows into the heat source unit-side heat exchanger 3. This defrosts the heat source unit-side heat exchanger 3. After defrosting the heat source unit-side heat exchanger 3, the refrigerant exchanges heat with outdoor air and condenses, then passes through the check valve 23 and the second connecting pipe 22 and flows into the relay unit E. The refrigerant that flows into the relay unit E passes through the gas-liquid separator 12 and the first heat source unit-side flow control device 13 in this order, and flows into the heat exchange unit 16. The refrigerant that flows into the heat exchange unit 16 is cooled by the refrigerant flowing through the bypass pipe 14 and is sufficiently subcooled. The refrigerant is then depressurized to a low pressure by the second heat source unit-side flow control device 15 and flows into the heat exchange unit 16. The refrigerant depressurized by the second heat source unit-side flow control device 15 cools the refrigerant flowing through the second connecting pipe 22, evaporates, and flows into the first connecting pipe 21. This refrigerant passes through the check valve 24 and the flow path switching valve 2 and is sucked into the compressor 1 .

[0067] At this time, the first shutoff devices 41B, 41C, and 41D are in a closed state, and the second shutoff devices 51B, 51C, and 51D are in a closed state.

[0068] 6 is a flowchart showing control when a refrigerant leaks in the air conditioning apparatus 100 according to Embodiment 1. Next, control when a refrigerant leaks in the air conditioning apparatus 100 according to Embodiment 1 will be described using FIG.

[0069] (Step S101) The control device 70 determines whether a refrigerant leak has been detected based on the refrigerant leak detection unit 60. If the control device 70 determines that a refrigerant leak has been detected (YES), the process proceeds to step S102. On the other hand, if the control device 70 determines that a refrigerant leak has not been detected (NO), the process repeats step S101.

[0070] (Step S102) The control device 70 closes all of the first shutoff devices 41 and closes the second shutoff device 51 of the target indoor unit. Here, the second shutoff device 51 of the target indoor unit refers to the second shutoff device 51 connected to the first indoor-unit-side connecting piping 6 that is connected to the indoor unit equipped with the refrigerant leak detection unit 60 that detected the refrigerant leak. For example, if the refrigerant leak detection units 60B, 60C detect a refrigerant leak, the second shutoff devices 51B, 51C are closed.

[0071] As described above, when a refrigerant leak occurs, all first shut-off devices 41 and the second shut-off devices 51 of the target indoor units can be closed to prevent the refrigerant from leaking into the indoor space.

[0072] 7 is a flowchart showing control during defrosting operation in the air conditioning apparatus 100 according to Embodiment 1. Next, control during defrosting operation in the air conditioning apparatus 100 according to Embodiment 1 will be described using FIG.

[0073] (Step S201) When the defrosting operation is started, the control device 70 closes all of the first shutoff devices 41 and all of the second shutoff devices 51.

[0074] (Step S202) The control device 70 determines whether the defrosting operation should be terminated. Here, the determination of whether the defrosting operation should be terminated is made, for example, when the evaporating temperature detected by the evaporating temperature detection unit 4 provided in the heat source unit A becomes equal to or higher than a predetermined threshold. Alternatively, for example, the control device 70 determines that the defrosting operation should be terminated when a predetermined time has elapsed since the start of the defrosting operation. If the control device 70 determines that the defrosting operation should be terminated (YES), the process proceeds to step S203. On the other hand, if the control device 70 determines that the defrosting operation should not be terminated (NO), the process repeats step S202.

[0075] (Step S203) The control device 70 returns the first shutoff devices 41 and the second shutoff devices 51 to the state they were in during the original operation (full heating operation or heating-dominant operation) before the start of the defrosting operation. Specifically, all of the first shutoff devices 41 are set to the open state, and all of the second shutoff devices 51 are set to the open state.

[0076] As described above, by closing all of the first shutoff devices 41 and all of the second shutoff devices 51 during defrosting operation, the refrigerant can be confined in the first indoor unit side connecting pipe 6 and the second indoor unit side connecting pipe 7 between the first shutoff devices 41 and the second shutoff devices 51. This makes it possible to prevent the refrigerant from moving from the indoor units to the heat source unit A during defrosting operation, causing a decrease in the amount of refrigerant in the indoor units. As a result, after the defrosting operation ends, it is possible to shorten the time it takes to return to the original operation (heating-only operation or heating-dominated operation) before the defrosting operation started.

[0077] 8 is a flowchart showing control during heating-dominated operation in the air conditioning apparatus 100 according to Embodiment 1. Next, control during heating-dominated operation in the air conditioning apparatus 100 according to Embodiment 1 will be described using FIG.

[0078] (Step S301) During heating-dominant operation, the control device 70 throttles (controls to intermediate opening) the second shutoff device 51 connected to the first indoor-unit-side connecting pipe 6 connected to the indoor unit performing cooling operation. For example, when indoor unit B is performing cooling operation, the second shutoff device 51B is throttled (controlled to intermediate opening).

[0079] As described above, during heating-dominant operation, the second shutoff device 51 connected to the first indoor unit-side connecting piping 6 connected to the indoor unit performing cooling operation is throttled. By doing so, the refrigerant pressure flowing through the first indoor unit-side connecting piping 6 between the indoor-side flow control device 9 of the indoor unit performing cooling operation and the second shutoff device 51 of the second shutoff section 50 rises relatively higher than the refrigerant pressure flowing through the low-pressure piping, and the refrigerant temperature also rises. As a result, it is possible to avoid anti-freeze control, which is activated when the evaporating temperature of the indoor unit during cooling operation drops, and it is possible to extend the duration of continuous operation.

[0080] As described above, the air conditioning apparatus 100 according to the first embodiment is an air conditioning apparatus 100 that is capable of simultaneous cooling and heating operation and includes a heat source unit A having a compressor 1, a flow path switching valve 2, and a heat source unit side heat exchanger 3 connected to the flow path switching valve 2, a plurality of indoor units each having an indoor heat exchanger 5 and an indoor side flow control device 9 connected to one end of the indoor side heat exchanger 5, and a relay unit E that connects the heat source unit A and the plurality of indoor units, and in which each of the plurality of indoor units can selectively perform cooling operation or heating operation, and the relay unit E is an air conditioning apparatus 100 that is capable of simultaneous cooling and heating operation and in which the plurality of indoor units can selectively perform cooling operation or heating operation, and the relay unit E is 1, and a first branch section 10 connected to the heat source unit A by a second connecting pipe 22 through which the refrigerant flowing in from the heat source unit A flows, and which switchably connects the other end of each of the indoor heat exchangers 5 to the first connecting pipe 21 or the second connecting pipe 22, a second branch section 11 which switchably connects each of the indoor flow control devices 9 to the first connecting pipe 21 or the second connecting pipe 22, and a first blocking section 40 provided between each of the indoor flow control devices 9 and the second branch section 11 and which blocks the flow of refrigerant between the relay unit E and the multiple indoor units.

[0081] According to the air conditioning apparatus 100 pertaining to embodiment 1, the relay unit E is provided with a first shutoff section 40 that shuts off the flow of refrigerant between the relay unit E and the multiple indoor units, between each of the indoor flow control devices 9 and the second branch section 11. Because the first shutoff section 40 is provided in advance in the relay unit E, there is no need to perform work to provide a refrigerant shutoff structure in the air conditioning apparatus 100 on site (installation location), which reduces the workload on site and improves ease of installation.

[0082] Furthermore, in the air conditioning apparatus 100 according to embodiment 1, each of the multiple indoor units is equipped with a refrigerant leakage detection unit 60 that detects refrigerant leakage, and when the leakage detection unit 60 detects refrigerant leakage, the control unit 70 closes all of the multiple first on-off valves or multiple first flow control devices of the first shut-off unit 40, and also closes the second flow control device, among the multiple second flow control devices of the second shut-off unit 50, that is connected to the indoor unit equipped with the leakage detection unit 60 that detected the leakage among the multiple indoor units.

[0083] According to the air conditioning apparatus 100 of embodiment 1, in the event of a refrigerant leak, all of the multiple first on-off valves or multiple first flow control devices are closed, and the second flow control device connected to the indoor unit equipped with the leak detection unit 60 that detected the leak among the multiple indoor units is closed, thereby preventing refrigerant from leaking into the indoor space.

[0084] Furthermore, in the air conditioning apparatus 100 according to embodiment 1, when defrosting operation starts, the control device 70 closes all of the multiple first on-off valves or multiple first flow control devices of the first shut-off section 40, and also closes all of the multiple second flow control devices of the second shut-off section 50.

[0085] According to the air conditioning apparatus 100 of Embodiment 1, by closing all of the first shutoff devices 41 and all of the second shutoff devices 51 during defrosting operation, it is possible to confine the refrigerant in the first indoor unit side connecting pipe 6 and the second indoor unit side connecting pipe 7 between the first shutoff devices 41 and the second shutoff devices 51. Therefore, it is possible to prevent the refrigerant from moving from the indoor units to the heat source unit A during defrosting operation, causing a decrease in the refrigerant in the indoor units. As a result, it is possible to shorten the time to return to the original operation (heating-only operation or heating-dominated operation) before the start of the defrosting operation after the defrosting operation ends.

[0086] Furthermore, in the air conditioning apparatus 100 according to embodiment 1, during heating-dominated operation, the control device 70 throttles down the second flow control device connected to the indoor unit that is performing cooling operation among the multiple indoor units, out of the multiple second flow control devices of the second shutoff section 50.

[0087] According to the air conditioning apparatus 100 of Embodiment 1, during heating-dominant operation, the second shutoff device 51 connected to the first indoor unit-side connecting piping 6 connected to the indoor unit performing cooling operation is throttled. By doing so, the refrigerant pressure flowing through the first indoor unit-side connecting piping 6 between the indoor-side flow control device 9 of the indoor unit performing cooling operation and the second shutoff device 51 of the second shutoff section 50 increases relatively compared to the refrigerant pressure flowing through the low-pressure piping, and the refrigerant temperature also increases. As a result, it is possible to avoid anti-freeze control that is activated when the evaporating temperature of the indoor unit during cooling operation drops, and the operation time can be extended.

[0088] Second Embodiment A second embodiment will be described below, but explanations of parts that overlap with those of the first embodiment will be omitted, and parts that are the same as or equivalent to those of the first embodiment will be given the same reference numerals.

[0089] FIG. 9 is a refrigerant circuit diagram showing an air conditioning apparatus 100 according to embodiment 2. As shown in FIG. 9 , the air conditioning apparatus 100 according to embodiment 2 has a first branch section 10 provided with a second shutoff section 50. Specifically, the first branch section 10 does not have valve devices 8a and 8b, but instead has second shutoff devices 51a and 51b in a number corresponding to the number of indoor units. In embodiment 2, three sets of second shutoff devices 51a and 51b (second shutoff devices 51aB and 51bB, second shutoff devices 51aC and 51bC, and second shutoff devices 51aD and 51bD) are provided. In other words, the first branch section 10 is composed of the second shutoff section 50. Note that the other configurations are the same as those in embodiment 1.

[0090] With the above configuration, the second shutoff devices 51a, 51b not only function as the second shutoff section 50 but also as the first branch section 10, so the number of parts in the air conditioning apparatus 100 can be reduced compared to the air conditioning apparatus 100 of embodiment 1.

[0091] 10 is a flowchart showing control during defrosting operation in the air conditioning apparatus 100 according to Embodiment 2. Next, control during defrosting operation in the air conditioning apparatus 100 according to Embodiment 2 will be described using FIG.

[0092] (Step S401) When the defrosting operation is started, the control device 70 closes all of the first shutoff devices 41 and all of the second shutoff devices 51.

[0093] (Step S402) The control device 70 determines, based on the low-pressure detection unit 28, whether the pressure of the refrigerant flowing through the low-pressure pipe 29 on the suction side of the compressor 1 is equal to or lower than a predetermined threshold. If the control device 70 determines that the pressure of the refrigerant flowing through the low-pressure pipe 29 on the suction side of the compressor 1 is equal to or lower than the predetermined threshold (YES), the process proceeds to step S403. On the other hand, if the control device 70 determines that the pressure of the refrigerant flowing through the low-pressure pipe 29 on the suction side of the compressor 1 is not equal to or lower than the predetermined threshold (NO), the process proceeds to step S405. (Step S403) The control device 70 determines whether all of the second shutoff devices 51 are in the open state. If the control device 70 determines that all of the second shutoff devices 51 are in the open state (YES), the process proceeds to step S405. On the other hand, if the control device 70 determines that all of the second shutoff devices 51 are not in the open state (NO), the process proceeds to step S404.

[0094] (Step S404) The control device 70 opens all of the second shutoff devices 51.

[0095] (Step S405) The control device 70 determines whether the defrosting operation should be terminated. Here, the determination of whether the defrosting operation should be terminated is made, for example, when the evaporating temperature detected by the evaporating temperature detection unit 4 provided in the heat source unit A becomes equal to or higher than a predetermined threshold. If the control device 70 determines that the defrosting operation should be terminated (YES), the process proceeds to step S406. On the other hand, if the control device 70 determines that the defrosting operation should not be terminated (NO), the process returns to step S402.

[0096] (Step S406) The control device 70 returns the first shutoff devices 41 and the second shutoff devices 51 to the states they were in during the original operation (heating only operation or heating-dominated operation) before the start of the defrosting operation. Specifically, when the operation returns from the defrosting operation to heating only operation, all of the first shutoff devices 41 are opened, the second shutoff devices 51bB, 51bC, and 51bD are opened, and the second shutoff devices 51aB, 51aC, and 51aD are closed. When the operation returns from the defrosting operation to heating-dominated operation, all of the first shutoff devices 41 are opened, and the second shutoff devices 51 are controlled so that refrigerant from the heat source unit A flows to the indoor units performing heating operation and so that refrigerant flows from the indoor units performing cooling operation to the heat source unit A. Regarding the second shut-off device 51, for example, when indoor units B and C are performing heating operation and indoor unit D is performing cooling operation, the second shut-off devices 51bB, 51bC, and 51aD are in the open state, and the second shut-off devices 51aB, 51aC, and 51bD are in the closed state.

[0097] As described above, when the pressure of the refrigerant flowing through the low-pressure pipe 29 on the suction side of the compressor 1 falls below the threshold during defrosting operation, by opening all of the second shutoff devices 51, the low-pressure pipe 29 on the suction side of the compressor 1 is connected to the pipe through which the high-pressure refrigerant flows, thereby increasing the pressure of the refrigerant flowing through the low-pressure pipe 29 on the suction side of the compressor 1. As a result, the time required for the defrosting operation can be shortened.

[0098] As described above, in the air conditioning apparatus 100 according to embodiment 2, the first branching section 10 is composed of a second shutoff section 50 that shuts off the flow of refrigerant between the relay unit E and multiple indoor units, the first shutoff section 40 is composed of multiple first on-off valves or multiple first flow control devices, and the second shutoff section 50 is composed of multiple second flow control devices.

[0099] According to the air conditioning device 100 of embodiment 2, multiple second flow control devices serve as the first branch section 10 in addition to the second blocking section 50, thereby reducing the number of parts in the air conditioning device 100.

[0100] Furthermore, in the air conditioning apparatus 100 according to embodiment 2, the heat source unit A is provided with a low-pressure detection unit 28 that is provided in the low-pressure piping 29 on the suction side of the compressor 1 and detects the pressure of the refrigerant flowing through the low-pressure piping 29, and the control device 70 opens all of the multiple second flow control devices of the second shut-off unit 50 when the pressure detected by the low-pressure detection unit 28 is below a predetermined threshold during defrosting operation.

[0101] According to the air conditioning apparatus 100 of the second embodiment, when the pressure of the refrigerant flowing through the low-pressure pipe 29 on the suction side of the compressor 1 falls below a threshold during defrosting operation, all of the second shutoff devices 51 are opened, so that the low-pressure pipe 29 on the suction side of the compressor 1 is connected to the pipe through which the high-pressure refrigerant flows, thereby increasing the pressure of the refrigerant flowing through the low-pressure pipe 29 on the suction side of the compressor 1. As a result, the time required for the defrosting operation can be shortened.

[0102] 1 Compressor, 2 Flow switching valve, 3 Heat source unit side heat exchanger, 4 Evaporation temperature detection unit, 5 Indoor side heat exchanger, 5B Indoor side heat exchanger, 5C Indoor side heat exchanger, 5D Indoor side heat exchanger, 6 First indoor unit side connecting pipe, 6B First indoor unit side connecting pipe, 6C First indoor unit side connecting pipe, 6D First indoor unit side connecting pipe, 7 Second indoor unit side connecting pipe, 7B Second indoor unit side connecting pipe, 7C Second indoor unit side connecting pipe, 7D Second indoor unit side connecting pipe, 8a Valve device, 8aB Valve device, 8aC Valve device, 8aD Valve device, 8b Valve device, 8bB Valve device, 8bC Valve device, 8bD Valve device, 9 Indoor side flow control device, 9B Indoor side flow control device, 9C Indoor side flow control device, 9D Indoor side flow control device, 10 First branch section, 11 Second branch section, 12 Gas-liquid separator, 13 First heat source unit side flow control device, 14 Bypass piping, 15 Second heat source unit side flow control device, 16 Heat exchange section, 17 Check valve, 17A First junction section, 17B Check valve, 17C Check valve, 17D Check valve, 18 Check valve, 18A Second junction section, 18B Check valve, 18C Check valve, 18D Check valve, 19B First junction section, 19C First junction section, 19D First junction section, 20B Second junction section, 20C Second junction section, 20D Second junction section, 21 First connecting piping, 22 Second connecting piping, 23 Check valve, 24 Check valve, 25 Check valve, 26 Check valve, 28 Low pressure detection section, 29 Low pressure piping, 30 flow path switching device, 40 first shutoff section, 41 first shutoff device, 41B first shutoff device, 41C first shutoff device, 41D first shutoff device, 50 second shutoff section, 51 second shutoff device, 51B second shutoff device, 51C second shutoff device, 51D second shutoff device, 51a second shutoff device, 51aB second shutoff device, 51aC second shutoff device, 51aD second shutoff device, 51b second shutoff device, 51bB second shutoff device, 51bC second shutoff device, 51bD second shutoff device, 60 refrigerant leak detection section, 60B refrigerant leak detection section, 60C refrigerant leak detection section, 60D refrigerant leak detection section, 70 control device, 100 air conditioning device, A heat source unit, B indoor unit, C Indoor unit, D indoor unit, E repeater unit.

Claims

1. An air conditioning system capable of simultaneous cooling and heating operation, comprising: a heat source unit having a compressor, a flow path switching valve, and a heat source unit-side heat exchanger connected to the flow path switching valve; a plurality of indoor units each having an indoor heat exchanger and an indoor flow control device connected to one end of the indoor heat exchanger; and a relay unit connecting the heat source unit and the plurality of indoor units, wherein each of the plurality of indoor units can selectively operate in cooling or heating mode, wherein the relay unit is connected to the heat source unit by a first connecting pipe through which refrigerant flowing out to the heat source unit flows and a second connecting pipe through which refrigerant flowing in from the heat source unit flows, and has a first branching section that can switchably connect the other end of each of the indoor heat exchangers to either the first connecting pipe or the second connecting pipe, and a second branching section that can switchably connect each of the indoor flow control devices to either the first connecting pipe or the second connecting pipe, a first blocking section that is provided between each of the indoor flow rate control devices and the second branch section and that blocks the flow of refrigerant between the relay unit and the plurality of indoor units.

2. An air conditioning apparatus as described in claim 1, further comprising a second shutoff section provided between each of the indoor heat exchangers and the first branch section, for shutting off the flow of refrigerant between the relay unit and the plurality of indoor units, wherein the first shutoff section is composed of a plurality of first on-off valves or a plurality of first flow control devices, the second shutoff section is composed of a plurality of second flow control devices, and the first branch section is composed of a plurality of second on-off valves.

3. The air conditioning apparatus of claim 1, wherein the first branching section is composed of a second blocking section that blocks the flow of refrigerant between the relay unit and the plurality of indoor units, the first blocking section is composed of a plurality of first on-off valves or a plurality of first flow control devices, and the second blocking section is composed of a plurality of second flow control devices.

4. An air conditioning apparatus according to claim 2 or 3, comprising a control device that controls the first shutoff section and the second shutoff section.

5. The air conditioning apparatus according to claim 4, wherein each of the plurality of indoor units is equipped with a refrigerant leak detection unit that detects refrigerant leaks, and wherein the control unit, when the leak detection unit detects a refrigerant leak, closes all of the plurality of first on-off valves or the plurality of first flow control devices of the first shut-off unit, and closes the second flow control device, of the plurality of second flow control devices of the second shut-off unit, that is connected to the indoor unit equipped with the leak detection unit that detected the leak among the plurality of indoor units.

6. An air conditioning apparatus as described in claim 4 or 5, wherein the control device closes all of the plurality of first on-off valves or the plurality of first flow control devices of the first shut-off section when defrosting operation starts, and closes all of the plurality of second flow control devices of the second shut-off section.

7. The air conditioning apparatus according to claim 6, wherein, after completion of the defrosting operation, the control device returns the plurality of first on-off valves or the plurality of first flow control devices of the first shut-off unit and the plurality of second flow control devices of the second shut-off unit to the state they were in before the defrosting operation started.

8. The air conditioning apparatus according to any one of claims 4 to 7, wherein the control device throttles down the second flow control device connected to the indoor unit performing cooling operation among the plurality of indoor units, out of the plurality of second flow control devices of the second shutoff section, during heating-dominated operation.

9. An air conditioning apparatus according to any one of claims 4 to 8 dependent on claim 3, wherein the heat source machine comprises a low-pressure detection unit provided in the low-pressure piping on the suction side of the compressor and detecting the pressure of the refrigerant flowing through the low-pressure piping, and the control device opens all of the plurality of second flow control devices of the second shutoff unit when the pressure detected by the low-pressure detection unit is equal to or lower than a preset threshold during defrosting operation.

Images