Air conditioning device

Abstract

An air conditioning device comprises: an outdoor unit having a compressor configured to compress a refrigerant, an accumulator configured to store the refrigerant, and an outdoor heat exchanger configured to cause heat exchange to be performed between the refrigerant and air; at least one indoor unit having an indoor heat exchanger configured to cause heat exchange to be performed between the refrigerant and air; and a relay unit configured to allow or block the flow of the refrigerant between the outdoor unit and the at least one indoor unit. The outdoor unit and the relay unit are connected by means of a low-pressure gas main pipe, a high-pressure gas main pipe, and a liquid main pipe.wherein the low-pressure gas main pipe is configured as a pipe through which gaseous refrigerant flows, wherein the high-pressure gas main pipe is configured as a pipe through which gaseous refrigerant flows at a higher pressure than the gaseous refrigerant flowing through the low-pressure gas main pipe, wherein the liquid main pipe is configured as a pipe through which liquid refrigerant flows. The relay unit and the at least one indoor unit are connected by means of a gas branch pipe and a liquid branch pipe, wherein the gas branch pipe is configured as a pipe through which gaseous refrigerant flows, wherein the liquid branch pipe is configured as a pipe through which liquid refrigerant flows. The relay unit comprises: a relay gas pipe connecting the gas branch pipe, the high-pressure gas main pipe, and the low-pressure gas main pipe,wherein the relay gas pipe includes a high-pressure gas branch pipe connected to the high-pressure gas main pipe and a low-pressure gas branch pipe connected to the low-pressure gas main pipe; a relay liquid pipe connecting the liquid main pipe and the liquid branch pipe; a bypass pipe connecting the high-pressure gas branch pipe and the relay liquid pipe; and a bypass valve arranged on the bypass pipe and having the function of switching such that the state of the bypass valve is switched between an open state in which the bypass valve allows the refrigerant to flow through the bypass pipe and a closed state in which the bypass valve blocks the refrigerant flow through the bypass pipe.

Description

Technical area

[0001] The present invention relates to an air conditioning device having an accumulator. State of the art

[0002] When a heat pump-type air conditioner performs heating operation at low outdoor air temperatures, frost or ice forms on the outdoor heat exchanger. Therefore, periodic defrosting is necessary. Generally, when the operation switches from heating operation to defrosting operation, liquid refrigerant accumulated in the heat exchanger and piping during heating operation flows into an accumulator in the outdoor unit (liquid backflow). If the amount of liquid refrigerant flowing into the accumulator as liquid backflow exceeds the accumulator's capacity, the overflow refrigerant flows into the compressor and dilutes the lubricating oil, causing the compressor to malfunction.

[0003] Patent Literature 1 discloses a configuration of a three-pipe type simultaneous cooling and heating operation system in which the opening and closing or orientation of the valves is controlled so that liquid refrigerant flowing toward an accumulator in the defrosting operation flows through a pipe heated in the heating operation. Consequently, in the air conditioning device disclosed in Patent Literature 1, the liquid refrigerant in the defrosting operation is caused to absorb heat from the pipe heated by high-temperature gaseous refrigerant in the heating operation and subsequently evaporates, resulting in a reduction in the occurrence of liquid backflow to the accumulator. BibliographyPatent literature

[0004] Patent Literature 1: Japanese Unexamined Patent Application Publication JP 2017 - 26 171 A Summary of the inventionTechnical problem

[0005] However, the tubes are gradually cooled during defrosting. Therefore, according to Patent Literature 1, during defrosting, if the amount of frost formed is large and the defrosting operation must be performed for a long period of time, the effect of reducing the occurrence of liquid backflow may be reduced.

[0006] The present invention is used to solve the above problem, and relates to an air conditioning device in which the occurrence of liquid backflow in the defrosting operation can be continuously reduced even in a case where the amount of frost formed is large and the defrosting operation must be performed for a long period of time. Solution to the problem

[0007] An air conditioning device according to an embodiment of the present invention includes: an outdoor unit including a compressor configured to compress a refrigerant, an accumulator configured to store the refrigerant, and an outdoor heat exchanger configured to cause heat exchange to be performed between the refrigerant and air; at least one indoor unit including an indoor heat exchanger configured to cause heat exchange to be performed between the refrigerant and air; and a relay unit configured to allow or block the flow of the refrigerant between the outdoor unit and the at least one indoor unit.

[0008] The outdoor unit and the relay unit are connected by means of a low-pressure gas main pipe, a high-pressure gas main pipe, and a liquid main pipe, wherein the low-pressure gas main pipe is configured as a pipe through which gaseous refrigerant flows, wherein the high-pressure gas main pipe is configured as a pipe through which gaseous refrigerant flows at a higher pressure than the gaseous refrigerant flowing through the low-pressure gas main pipe, wherein the liquid main pipe is configured as a pipe through which liquid refrigerant flows. The relay unit and the at least one indoor unit are connected by means of a gas branch pipe and a liquid branch pipe, wherein the gas branch pipe is configured as a pipe through which gaseous refrigerant flows, wherein the liquid branch pipe is configured as a pipe through which liquid refrigerant flows.

[0009] The relay unit includes: a relay gas pipe connecting the gas branch pipe, the high-pressure gas main pipe, and the low-pressure gas main pipe, the relay gas pipe including a high-pressure gas branch pipe connected to the high-pressure gas main pipe and a low-pressure gas branch pipe connected to the low-pressure gas main pipe; a relay liquid pipe connecting the liquid main pipe and the liquid branch pipe; a bypass pipe connecting the high-pressure gas branch pipe and the relay liquid pipe;and a bypass valve arranged on the bypass pipe, the bypass valve having a function of switching such that the state of the bypass valve is switched between an open state in which the bypass valve allows the refrigerant to flow through the bypass pipe and a closed state in which the bypass valve blocks the flow of refrigerant through the bypass pipe. Advantageous effects of the invention

[0010] The air conditioning device according to the embodiment of the present invention has the bypass valve arranged on the bypass pipe. Therefore, in the air conditioning device according to the embodiment of the present invention, during a defrosting operation, by causing the bypass valve to be in the open state and blocking the flow of refrigerant to the indoor unit, it is possible to cause high-temperature refrigerant to flow into the outdoor heat exchanger while liquid refrigerant is stored in the indoor unit. That is, in the defrosting operation of the air conditioning device according to the embodiment of the present invention, the occurrence of liquid backflow is reduced without utilizing heat from a pipe heated by high-temperature gas refrigerant in the heating operation.Therefore, the air conditioning device according to the embodiment of the present invention can continuously reduce the occurrence of liquid backflow to the accumulator in the defrosting operation. Short description of the drawings Fig. 1 is a refrigerant cycle diagram of an air conditioning device according to Embodiment 1. Fig. 2 is a hardware configuration diagram illustrating a configuration example of a control device according to Embodiment 1. Fig. 3 is a hardware configuration diagram illustrating another configuration example of the control device according to Embodiment 1. Fig. 4 is a functional block diagram illustrating the air conditioning device according to Embodiment 1. Fig. 5 is an explanatory view for the heating operation of the air conditioning device according to Embodiment 1. Fig. 6 is an explanatory view for a defrosting operation of the air conditioning device according to Embodiment 1. Fig. 7 is an explanatory view for explaining a cooling operation of the air conditioning device according to Embodiment 1. Fig. 8 is an explanatory view for a liquid removing operation of the air conditioning device according to Embodiment 1. Fig. 9 is a flowchart of the operation of the control device in the air conditioning device according to Embodiment 1. Fig. 10 is a flowchart of another operation of the control device in the air conditioning device according to Embodiment 1. Fig. 11 is a refrigerant cycle diagram of an air conditioning device according to Embodiment 2. Fig. 12 is a functional block diagram illustrating the air conditioning device according to Embodiment 2. Fig. 13 is an explanatory view for a heating operation of the air conditioning device according to Embodiment 2. Fig. 14 is an explanatory view for a defrosting operation of the air conditioning device according to Embodiment 2. Fig. 15 is an explanatory view for a cooling operation of the air conditioning device according to Embodiment 2. Fig. 16 is an explanatory view for a liquid removing operation of the air conditioning device according to Embodiment 2. Fig. 17 is a refrigerant cycle diagram of an air conditioning device according to Embodiment 3. Fig. 18 is a functional block diagram illustrating the air conditioning device according to Embodiment 3. Fig. 19 is an explanatory view for a heating operation of the air conditioning device according to Embodiment 3. Fig. 20 is an explanatory view for a defrosting operation of the air conditioning device according to Embodiment 3. Fig. 21 is a refrigerant cycle diagram of an air conditioning device according to Embodiment 4. Fig. 22 is a functional block diagram illustrating the air conditioning device according to Embodiment 4. Fig. 23 is an explanatory view for a heating operation of the air conditioning device according to Embodiment 4. Fig. 24 is an explanatory view for a defrosting operation of the air conditioning device according to Embodiment 4. Fig. 25 is a refrigerant cycle diagram of an air conditioning device according to Embodiment 5. Fig. 26 is an explanatory view for a heating operation of the air conditioning device according to Embodiment 5. Fig. 27 is an explanatory view for a defrosting operation of the air conditioning device according to Embodiment 5. Fig. 28 is an explanatory view for a cooling operation of the air conditioning device according to Embodiment 5. Fig. 29 is an explanatory view for a liquid removing operation of the air conditioning device according to Embodiment 5. Fig. 30 is a refrigerant cycle diagram of an air conditioning device according to Embodiment 6. Fig. 31 is an explanatory view for a heating operation of the air conditioning device 1E according to Embodiment 6. Fig. 32 is an explanatory view for a defrosting operation of the air conditioning device according to Embodiment 6. Fig. 33 is an explanatory view for a cooling operation of the air conditioning device according to Embodiment 6. Fig. 34 is an explanatory view for a liquid removing operation of the air conditioning device according to Embodiment 6. Fig. 35 is a refrigerant cycle diagram of an air conditioning device according to Embodiment 7. Fig. 36 is an explanatory view for a heating operation of the air conditioning device according to Embodiment 7. Fig. 37 is an explanatory view for a defrosting operation of the air conditioning device according to Embodiment 7. Fig. 38 is a refrigerant cycle diagram of an air conditioning device according to Embodiment 8. Fig. 39 is an explanatory view for a heating operation of the air conditioning device according to Embodiment 8. Fig. 40 is an explanatory view for a defrosting operation of the air conditioning device according to Embodiment 8. Description of embodiments

[0011] An air conditioning device according to each of the embodiments will be described below with reference to the drawings. Note that in each of the drawings, components that are the same as those in one or more previous drawings are denoted by the same reference numerals, and after each of the components has been described once, the description thereof will not be repeated unless necessary. The present invention can encompass all combinations of the combinable configurations described with regard to the following embodiments.

[0012] It should be noted that the configurations of the components described throughout the specification are merely examples; that is, the configurations of the components are not limited to those described in the specification. In particular, combinations of the components are not limited merely to those described with respect to the same embodiment. A component or components in one embodiment may be applied to another embodiment. Embodiment 1

[0013] Fig. 1 is a refrigerant cycle diagram of an air conditioning device 1 according to Embodiment 1. As shown in Fig. 1, the air conditioning device 1 comprises: an outdoor unit 2, a forwarding unit 3, a first indoor unit 4a and a second indoor unit 4b.

[0014] The outdoor unit 2 and the relay unit 3 are connected by three pipes: a low-pressure gas main pipe 101, a high-pressure gas main pipe 102, and a liquid main pipe 103. The low-pressure gas main pipe 101 is a pipe through which gaseous refrigerant flows from the relay unit 3 to the outdoor unit 2 during cooling operation. The high-pressure gas main pipe 102 is a pipe through which gaseous refrigerant flows from the outdoor unit 2 to the relay unit 3 during heating operation. The gaseous refrigerant flowing through the high-pressure gas main pipe 102 has a higher pressure than the gaseous refrigerant flowing through the low-pressure gas main pipe 101. The liquid main pipe 103 is a pipe through which refrigerant flows from the relay unit 3 to the outdoor unit 2 in the heating operation and flows from the outdoor unit 2 to the relay unit 3 in the cooling operation.

[0015] The low-pressure gas main pipe 101, the high-pressure gas main pipe 102, and the low-pressure liquid main pipe 103 connecting the outdoor unit 2 and the relay unit 3 each branch independently. A pipe branching from the low-pressure gas main pipe 101, a pipe branching from the high-pressure gas main pipe 102, and a pipe branching from the liquid main pipe 103 may be connected to a relay unit other than the relay unit 3 or an indoor unit.

[0016] The relay unit 3 and the first indoor unit 4a are connected by a first gas branch pipe 104a and a first liquid branch pipe 105a. The relay unit 3 and the second indoor unit 4b are connected by a second gas branch pipe 104b and a second liquid branch pipe 105b. The first gas branch pipe 104a and the second gas branch pipe 104b allow a gaseous refrigerant to flow therethrough. The first liquid branch pipe 105a and the second liquid branch pipe 105b allow a liquid refrigerant to flow therethrough.

[0017] The outdoor unit 2 is a device that supplies heating or cooling energy to the first indoor unit 4a and the second indoor unit 4b. The outdoor unit 2 includes outdoor pipes 201 to 204, a suction pipe 206, and an exhaust pipe 207. The outdoor unit 2 includes a compressor 10, a flow switching device 21 on the heat exchanger side, an outdoor heat exchanger 30, an outdoor expansion valve 40, and an accumulator 50.

[0018] The outdoor pipe 201 is a pipe connecting the flow switching device 21 on the heat exchanger side and the low-pressure gas main pipe 101. The outdoor pipe 202 is a pipe connecting the flow switching device 21 on the heat exchanger side, the outdoor heat exchanger 30, the outdoor expansion valve 40, and the liquid main pipe 103. The outdoor pipe 203 is a pipe branching from the outdoor pipe 201 and connecting to the accumulator 50. The outdoor pipe 204 is a pipe connecting the outlet pipe 207 and the high-pressure gas main pipe 102. The suction pipe 206 is a pipe connecting the accumulator 50 and the compressor 10. The outlet pipe 207 is a pipe connecting the compressor 10 and the flow switching device 21 on the heat exchanger side.

[0019] The compressor 10 draws in low-temperature and low-pressure refrigerant, compresses the drawn-in refrigerant, and discharges the high-temperature and high-pressure refrigerant. The flow switching device 21 on the heat exchanger side is, for example, a four-way valve. The state of the flow switching device 21 on the heat exchanger side is switched between a state in which the flow switching device 21 on the heat exchanger side connects the outdoor heat exchanger 30 to the compressor 10 and a state in which the flow switching device 21 on the heat exchanger side connects the outdoor heat exchanger 30 to the accumulator 50, so that the flow direction of the refrigerant in a refrigerant cycle is switched among multiple flow directions.

[0020] The outdoor heat exchanger 30 enables heat exchange between the refrigerant and the outdoor air. The outdoor heat exchanger 30 serves as a condenser during cooling operation and as an evaporator during heating operation. The outdoor expansion valve 40 decompresses the pressure of the refrigerant, causing it to expand. It is, for example, an electronic expansion valve whose opening degree is adjustable. The accumulator 50 is a device that stores excess refrigerant circulating in the outdoor unit 2.

[0021] The transfer unit 3 is a device that allows or blocks the flow of refrigerant between the outdoor unit 2 and the first and second indoor units 4a and 4b. The transfer unit 3 includes a transfer gas pipe 301, a transfer liquid pipe 304, and a bypass pipe 305. The transfer unit 3 includes a bypass valve 60, a first low-pressure valve 71a, a second low-pressure valve 71b, a first high-pressure valve 72a, and a second high-pressure valve 72b.

[0022] The relay gas pipe 301 connects the first gas branch pipe 104a and the second gas branch pipe 104b to the high-pressure gas main pipe 102 and the low-pressure gas main pipe 101. The relay gas pipe 301 is a pipe that branches into a high-pressure side part and a low-pressure side part, and it includes a high-pressure gas branch pipe 302 and a low-pressure gas branch pipe 303. The high-pressure gas branch pipe 302 is a pipe that connects the high-pressure gas main pipe 102 to a bifurcation of the relay gas pipe 301. The low-pressure gas branch pipe 303 is a pipe that connects the low-pressure gas main pipe 101 to a bifurcation of the relay gas pipe 301.

[0023] The high-pressure gas branch pipe 302 branches out to correspond to the first indoor unit 4a and the second indoor unit 4b. Similarly, the low-pressure gas branch pipe 303 branches out to correspond to the first indoor unit 4a and the second indoor unit 4b. The relay liquid pipe 304 branches out to correspond to the first indoor unit 4a and the second indoor unit 4b, and connects the liquid main pipe 103 to the first and second liquid branch pipes 105a and 105b. The bypass pipe 305 connects the high-pressure gas branch pipe 302 to the relay liquid pipe 304.

[0024] The bypass valve 60 is arranged on the bypass pipe 305, and the state of the bypass valve 60 is switched between an open state in which the bypass pipe 305 allows the refrigerant to flow through the bypass pipe 305 and a closed state in which the bypass pipe 305 blocks the flow of the refrigerant through the bypass pipe 305.

[0025] The first low-pressure valve 71a is arranged at a position associated with the first indoor unit 4a in the low-pressure gas branch pipe 303, which branches to correspond to the first indoor unit 4a and the second indoor unit 4b. The state of the first low-pressure valve 71a is switched between an open state in which the first low-pressure valve 71a allows refrigerant to flow through a region associated with the first indoor unit 4a in the low-pressure gas branch pipe 303, and a closed state in which the first low-pressure valve 71a blocks the flow of refrigerant through the region associated with the first indoor unit 4a in the low-pressure gas branch pipe 303.

[0026] The second low-pressure valve 71b is arranged at a position associated with the second indoor unit 4b in the low-pressure gas branch pipe 303, which branches in association with the first indoor unit 4a and the second indoor unit 4b. The state of the second low-pressure valve 71b is switched between an open state in which the second low-pressure valve 71b allows refrigerant to flow through a region associated with the second indoor unit 4b in the low-pressure gas branch pipe 303, and a closed state in which the second low-pressure valve 71b blocks the flow of refrigerant through the region associated with the second indoor unit 4b in the low-pressure gas branch pipe 303.

[0027] The first high-pressure valve 72a is arranged at a position associated with the first indoor unit 4a in the high-pressure gas branch pipe 302, which branches to correspond to the first indoor unit 4a and the second indoor unit 4b. The state of the first high-pressure valve 72a is switched between an open state in which the first high-pressure valve 72a allows the refrigerant to flow through a region associated with the first indoor unit 4a in the high-pressure gas branch pipe 302, and a closed state in which the first high-pressure valve 72a blocks the refrigerant from flowing through the region associated with the first indoor unit 4a in the high-pressure gas branch pipe 302.

[0028] The second high-pressure valve 72b is arranged at a position associated with the second indoor unit 4b in the high-pressure gas branch pipe 302, which branches in association with the first indoor unit 4a and the second indoor unit 4b.

[0029] The state of the second low-pressure valve 72b is switched between an open state in which the second high-pressure valve 72b allows the refrigerant to flow through a region connected to the second indoor unit 4b in the high-pressure gas branch pipe 302, and a closed state in which the second high-pressure valve 72b blocks the flow of the refrigerant through the region connected to the second indoor unit 4b in the high-pressure gas branch pipe 302.

[0030] Note that the types of the bypass valve 60, the first low-pressure valve 71a, the second low-pressure valve 71b, the first high-pressure valve 72a, and the second high-pressure valve 72b are not limited; that is, each of these valves may have any type of mechanism, as long as the mechanism is capable of switching the state of the valve between a state where the valve allows the flow of refrigerant and a state where the valve blocks the flow of refrigerant. Therefore, the above valves may be, for example, on / off valves or expansion valves.

[0031] The first indoor unit 4a and the second indoor unit 4b are devices that supply heating energy or cooling energy to an associated indoor space. The first indoor unit 4a has a first indoor tube 401a. The first indoor unit 4a has a first indoor heat exchanger 80a and a first indoor expansion valve 90a. The second indoor unit 4b has a second indoor tube 401b. The second indoor unit 4b has a second indoor heat exchanger 80b and a second indoor expansion valve 90b. The first indoor tube 401a is a tube that connects the first gas branch pipe 104a, the first indoor heat exchanger 80a, the first indoor expansion valve 90a, and the first liquid branch pipe 105a.

[0032] The second indoor pipe 401b is a pipe connecting the second gas branch pipe 104b, the second indoor heat exchanger 80b, the second indoor expansion valve 90b, and the second liquid branch pipe 105b. The first indoor heat exchanger 80a and the second indoor heat exchanger 80b cause heat exchange to be performed between the refrigerant and the indoor air. Each of the first indoor heat exchanger 80a and the second indoor heat exchanger 80b serves as an evaporator during the cooling operation and as a condenser during the heating operation. Each of the first indoor expansion valve 90a and the second indoor expansion valve 90b decompresses the refrigerant to expand, and is, for example, an electronic expansion valve whose opening degree is adjustable, for example.

[0033] The number of indoor units in the air conditioning device 1 is not limited to two. The air conditioning device 1 may also include one or three or more indoor units. In the following description, in the case where the indoor units and components associated with the respective indoor units are not particularly distinguished from each other, the indoor units and components may be referred to as follows. Namely, the first indoor unit 4a and the second indoor unit 4b are referred to as indoor units 4 when they are not distinguished from each other. The first gas branch pipe 104a and the second gas branch pipe 104b are referred to as gas branch pipes 104 when they are not distinguished from each other.The first liquid branch pipe 105a and the second liquid branch pipe 105b are referred to as liquid branch pipes 105 when they are not distinguished from each other.

[0034] The first low-pressure valve 71a and the second low-pressure valve 71b are referred to as low-pressure valves 71 when they are not distinguished from each other. The first high-pressure valve 72a and the second high-pressure valve 72b are referred to as high-pressure valves 72 when they are not distinguished from each other. The first indoor tube 401a and the second indoor tube 401b are referred to as indoor tubes 401 when they are not distinguished from each other. The first indoor heat exchanger 80a and the second indoor heat exchanger 80b are referred to as indoor heat exchanger 80 when they are not distinguished from each other. The first indoor expansion valve 90a and the second indoor expansion valve 90b are referred to as indoor expansion valves 90 when they are not distinguished from each other.

[0035] The air conditioning device 1 includes a controller 5 that controls the components included in the outdoor unit 2, the relay unit 3, and the indoor units 4. The controller 5 controls switching between different operation modes and the execution of each of the operation modes. The operations performed in the respective modes by the air conditioning device 1 according to Embodiment 1 are the heating operation, a defrosting operation, the cooling operation, and a defrosting operation. For the heating operation and the cooling operation, a user gives an instruction to execute the operation using, for example, a remote controller (not shown). The defrosting operation is an operation performed in a mode for removing frost that forms on the outdoor heat exchanger 30 in the heating operation.The liquid removal operation is an operation performed in a mode for removing liquid accumulated in the high-pressure gas main pipe 102 in the cooling operation.

[0036] An example of the hardware of the control device 5 is described. Fig. 2 is a hardware configuration diagram illustrating a configuration example of the control device 5 in Embodiment 1. In the case where the functions of the control device 5 are performed by hardware, the control device 5 is a processing circuit 501 as shown in Fig. 2. Processing circuitry 501 is, for example, a single circuit, a composite circuit, a programmed processor 502, a parallel programmed processor 502, an application-specific integrated circuit (ASIC), a field-programmable gate array (FPGA), or a combination of these circuits. The functions performed by processing circuitry 501 may be performed by individual hardware or may be performed by individual hardware.

[0037] Another example of hardware of the control device 5 is described. Fig. 3 is a hardware configuration diagram illustrating another configuration example of the control device 5 in Embodiment 1. In the case where the functions of the control device 5 are performed by software, the control device 5 includes the processor 502, such as a central processing unit (CPU), and a memory 503, as shown in Fig. 3 illustrates. Fig. Figure 3 illustrates processor 502 and memory 503, which are connected to a bus 504 so that they can communicate with each other. The functions of control device 5 are performed by software, firmware, or a combination of software and firmware. The software and firmware are written as programs and stored in memory 503. Processor 502 reads programs from memory 503 and executes the programs, thus performing the respective functions.

[0038] For example, a non-volatile semiconductor memory such as a read-only memory (ROM), a flash memory, an erasable and programmable ROM (EPROM), or an electrically erasable and programmable ROM (EEPROM) is used as the memory 503. Alternatively, a volatile semiconductor memory such as a random access memory (RAM) may be used as the memory 503. Furthermore, a removable recording medium such as a magnetic disk, a flexible disk, an optical disk, a compact disc (CD), a mini disc (MD), or a digital versatile disc (DVD) may be used as the memory 503. One or more of the functions of the processing circuit 501 may be performed by dedicated hardware, and one or more of the other functions may be performed by software or firmware.

[0039] Fig. 4 is a functional block diagram illustrating the air conditioning device 1 according to Embodiment 1. As in Fig. 4, the controller 5 controls the compressor 10, the flow switching device 21 on the heat exchanger side, and the outdoor expansion valve 40 in the outdoor unit 2 based on the operation mode. In addition, the controller 5 controls the bypass valve 60, the low-pressure valves 71, and the high-pressure valves 72 in the relay unit 3 based on the operation mode. The controller 5 controls the first indoor expansion valve 90a in the indoor units 4 based on the operation mode.

[0040] The control device 5 controls the execution of the defrosting operation and the liquid removal process based on the measurement results of a frost detection device 6, a defrost detection device 7, and a liquid accumulation detection device 8. The frost detection device 6 is a sensor that detects frost on the outdoor heat exchanger 30 and is, for example, a pressure sensor. The frost detection device 6 is arranged, for example, on a pipe located between the outdoor heat exchanger 30 and the compressor 10, although its position is not limited to such a specific position. The frost detection device 6 transmits the measurement result of the frost detection device 6 to the control device 5.

[0041] The control device 5 changes the operation performed in the predetermined operation mode from the heating operation to the defrosting operation when it determines, based on the measurement result of the frost formation detection device 27, that an amount of frost that needs to be removed has formed on the outdoor heat exchanger 23. For example, if the refrigerant pressure measured by the frost formation detection device 27 is less than a predetermined threshold, the control device 5 determines that an amount of frost that needs to be removed has formed on the outdoor heat exchanger 23. The defrosting detection device is a sensor that detects the defrosting of the outdoor heat exchanger 30 and is, for example, a temperature sensor.

[0042] The defrost detection device 7 is arranged on a pipe located between the outdoor heat exchanger 30 and the compressor 10. The defrost detection device 7 transmits the measurement result by the defrost detection device 7 to the control device 5. The control device 5 changes the operation performed in the predetermined mode from the defrost operation to the heating operation when it determines, based on the measurement result by the defrost detection device 28, that defrosting of the outdoor heat exchanger 23 is complete. For example, if the refrigerant temperature measured by the defrost detection device 28 exceeds a predetermined threshold, the control device 5 determines that defrosting of the outdoor heat exchanger 23 is complete.

[0043] The liquid accumulation detection device 8 is a sensor or a timer that detects the occurrence or removal of liquid accumulation, whereby liquid refrigerant accumulates in the high-pressure gas main pipe 102. The liquid accumulation detection device 8 is, for example, a temperature sensor, a pressure sensor, a total time timer, or a combination of the temperature sensor, the pressure sensor, and the total time timer. Note that the liquid accumulation occurs due to condensation of the gaseous refrigerant accumulated in the high-pressure gas main pipe 102 during cooling operation. The gaseous refrigerant has a pressure equivalent to the outlet pressure of the compressor 10, has a saturation temperature higher than the ambient air temperature, and thus gradually condenses as the cooling operation continues.

[0044] Liquid accumulation during cooling operation can cause a refrigerant shortage. The liquid accumulation detection device 8 is arranged, for example, on the high-pressure gas main pipe 102, although its position is not limited to such a specific position. The liquid accumulation detection device 8 transmits the measurement result by the liquid accumulation detection device 8 to the control device 5. The control device 5 changes the operation performed in the predetermined mode from the cooling operation to the liquid removal operation when it determines—based on the measurement result by the liquid accumulation detection device 8—that liquid accumulation that needs to be removed has occurred on the high-pressure gas main pipe 102.

[0045] For example, if each parameter of the temperature and pressure of the refrigerant measured by the liquid accumulation detection device 8 is less than a predetermined threshold, the control device 5 determines that liquid accumulation that needs to be eliminated is occurring in the high-pressure gas main pipe 102. Furthermore, the control device 5 changes the operation performed in the predetermined mode from the liquid removal operation to the cooling operation when it determines, based on the measurement result by the liquid accumulation detection device 8, that the elimination of the liquid accumulation in the high-pressure gas main pipe 102 is complete.For example, when the duration of the liquid removal operation measured by the total time timer exceeds a predetermined threshold, the controller 5 determines that the liquid accumulation in the high-pressure gas main pipe 102 is eliminated.

[0046] The states of the components and the refrigerant flow in each of the operating modes are described. Heating mode is described first. Fig. 5 is an explanatory view for the heating operation of the air conditioning device 1 according to Embodiment 1.

[0047] In Fig. 5, the arrows indicate the flow directions of the refrigerant. To perform the heating operation, the control device 5 switches the state of the flow switching device 21 on the heat exchanger side to the state in which the outdoor heat exchanger 30 and the accumulator 50 are connected through the flow switching device 21 on the heat exchanger side. Furthermore, the control device 5 causes the bypass valve 60 to be in the closed state, causes the low-pressure valve 71 to be in the closed state, and causes the high-pressure valve 72 to be in the open state. Furthermore, the control device 5 opens the indoor expansion valve 90 and opens the outdoor expansion valve 40.

[0048] In the heating operation, the refrigerant drawn in by the compressor 10 is compressed by the compressor 10 to become a high-temperature, high-pressure gas refrigerant, and the high-temperature, high-pressure gas refrigerant is then discharged from the compressor 10. The high-temperature, high-pressure gas refrigerant discharged from the compressor 10 passes through the high-pressure gas main pipe 102 and then flows into the relay unit 3. The refrigerant that has flowed into the relay unit 3 passes through the high-pressure gas branch pipe 302, where the high-pressure valve 72 is arranged, and the gas branch pipe 104, and then flows into the indoor unit 4.

[0049] The refrigerant that has flowed into the indoor unit 4 passes through the indoor heat exchanger 80, which serves as a condenser or condenser. The refrigerant that has passed through the indoor heat exchangers 80 exchanges heat with the indoor air and consequently condenses and liquefies. At this time, the indoor air is heated, thus heating the indoor space. The liquid refrigerant passes through the indoor expansion valve 90 and is decompressed and expanded, transforming into a low-temperature, low-pressure, two-phase gas-liquid refrigerant. The two-phase gas-liquid refrigerant passes through the liquid branch pipe 105, the relay liquid pipe 304, and the liquid main pipe 103, and then flows into the outdoor unit 2.

[0050] The refrigerant that has flowed into the outdoor unit 2 passes through the outdoor expansion valve 40, is further decompressed and expanded, and then passes through the outdoor heat exchanger 30, which serves as an evaporator. The refrigerant passing through the outdoor heat exchanger 30 exchanges heat with the outdoor air and thus evaporates and becomes a gas. The evaporated gaseous, low-temperature and low-pressure refrigerant then passes through the flow switching device 21 on the heat exchanger side and the accumulator 50. The refrigerant is then sucked into the compressor 10 again and circulated.

[0051] Next, the de-icing operation is described. Fig. 6 is an explanatory view for the defrosting operation of the air conditioning device 1 according to Embodiment 1. In Fig. 6, the arrows indicate the flow directions of the refrigerant. To perform the defrosting operation, the control device 5 switches the state of the heat exchanger-side flow switching device 21 to a state in which the heat exchanger-side flow switching device 21 connects the outdoor heat exchanger 30 and the accumulator 50. Furthermore, the control device 5 causes the bypass valve 60 to be in the open state, causes the low-pressure valve 71 to be in the closed state, and causes the high-pressure valve 72 to be in the open state. Furthermore, the control device 5 closes the indoor expansion valve 90 and opens the outdoor expansion valve 40.

[0052] In defrosting operation, the refrigerant drawn in by the compressor 10 is compressed by the compressor 10 to become a high-temperature, high-pressure gas refrigerant, and the high-temperature, high-pressure gas refrigerant is then discharged from the compressor 10. The high-temperature, high-pressure gas refrigerant discharged from the compressor 10 passes through the high-pressure gas main pipe 102 and then flows into the relay unit 3. The refrigerant that has flowed into the relay unit 3 passes through a part of the high-pressure gas branch pipe 302, the bypass pipe 305 where the bypass valve 60 is arranged, a part of the relay liquid pipe 304, and the liquid main pipe 103, and then flows back into the outdoor unit 2.

[0053] The high-temperature, high-pressure gas refrigerant that flows into the outdoor unit 2 passes through the outdoor expansion valve 40 and then passes through the outdoor heat exchanger 30, which serves as an evaporator. The high-temperature, low-pressure gas refrigerant that passes through the outdoor heat exchanger 30 exchanges heat with the frost that forms on the outdoor heat exchanger 30 and subsequently condenses, turning into a low-temperature, low-pressure gas refrigerant. At this time, the outdoor heat exchanger 30 is defrosted. Afterward, the low-temperature, low-pressure gas refrigerant passes through the flow switching device 21 on the heat exchanger side and the accumulator 50. The refrigerant is then sucked into the compressor 10 again and circulated. In defrosting operation, the low pressure valve 71 is caused to be in the closed state and the interior expansion valve 90 is closed.As a result, the flow of refrigerant to the indoor unit 4 is blocked, and liquid refrigerant is stored in the indoor unit 4.

[0054] The cooling operation is described. Fig. 7 is an explanatory view for explaining the cooling operation of the air conditioning device 1 according to Embodiment 1. In Fig. 7, the arrows indicate the flow directions of the refrigerant. To perform the cooling operation, the control device 5 switches the state of the heat exchanger-side flow switching device 21 to a state in which the heat exchanger-side flow switching device 21 connects the compressor 10 to the outdoor heat exchanger 30. Furthermore, the control device 5 causes the bypass valve 60 to be in the closed state, causes the high-pressure valve 72 to be in the closed state, and causes the low-pressure valve 71 to be in the open state. Furthermore, the control device 5 opens the indoor expansion valve 90 and opens the outdoor expansion valve 40.

[0055] In cooling operation, the refrigerant drawn in by the compressor 10 is compressed by the compressor 10 to become a high-temperature, high-pressure gas refrigerant, and the high-temperature, high-pressure gas refrigerant is then discharged from the compressor 10. The high-temperature, high-pressure gas refrigerant discharged from the compressor 10 passes through the flow switching device 21 on the heat exchanger side and then passes through the outdoor heat exchanger 30. The refrigerant passing through the outdoor heat exchanger 30 exchanges heat with the outdoor air and thus condenses and becomes liquid. The liquid refrigerant passes through the outdoor expansion valve 40 and is decompressed and expanded. The liquid refrigerant passes through the liquid main pipe 103 and then flows into the relay unit 3.

[0056] The refrigerant that has flowed into the relay unit 3 passes through the relay liquid pipe 304 and the liquid branch pipes 105, and then flows into the indoor unit 4. The refrigerant that has flowed into the indoor unit 4 is further decompressed and expanded to become a low-temperature, low-pressure, two-phase gas-liquid refrigerant through the indoor expansion valve 90. The low-temperature, low-pressure, two-phase gas-liquid refrigerant passes through the indoor heat exchanger 80, exchanges heat with the indoor air, and subsequently evaporates and becomes gaseous. At this time, the indoor air is cooled, thus cooling the indoor space. The gaseous refrigerant passes through the gas branch pipe 104 and then flows into the transfer unit 3.The refrigerant that has flowed into the relay unit 3 passes through the low-pressure gas branch pipe 303, on which the low-pressure valve 71 of the relay gas pipe 301 is arranged, and the low-pressure gas main pipe 101, and then flows into the outdoor unit 2. The refrigerant that has flowed into the outdoor unit 2 passes through the accumulator 50, is sucked into the compressor 10 again, and circulates.

[0057] Next, the fluid removal process is described. Fig. Fig. 8 is an explanatory view for the liquid removal process of the air conditioning device 1 according to Embodiment 1. In Fig. 8, the arrows indicate the flow directions of the refrigerant. To perform the liquid removal process, the control device 5 switches the state of the flow switching device 21 on the heat exchanger side to the state in which the flow switching device 21 on the heat exchanger side connects the compressor 10 to the outdoor heat exchanger 30. Furthermore, the control device 5 causes the bypass valve 60 to be in the open state, causes the high-pressure valve 72 to be in the closed state, and causes the low-pressure valve 71 to be in the open state. Furthermore, the control device 5 opens the indoor expansion valve 90 and opens the outdoor expansion valve 40.

[0058] In the liquid removal process, a main circuit and a bypass circuit are formed. In the main circuit, the refrigerant flows in a manner similar to that during cooling operation. In the bypass circuit, the high-temperature and high-pressure gas refrigerant discharged from the compressor 10 passes through the high-pressure gas main pipe 102 and then flows into the relay unit 3. The refrigerant that has flowed into the relay unit 3 passes through a portion of the high-pressure gas branch pipe 302 and the bypass pipe 305, where the bypass valve 60 is arranged, and then flows into the relay liquid pipe 304 and joins the refrigerant flowing through the main circuit.

[0059] As the refrigerant flows through the bypass circuit, the liquid refrigerant accumulated in the high-pressure gas main pipe 102 flows and combines with the refrigerant flowing through the main circuit. As a result, the liquid accumulation in the high-pressure gas main pipe 102 is eliminated. The flow of refrigerant to the indoor unit 4 is blocked, and liquid refrigerant is stored in the indoor unit 4. After combining with the refrigerant flowing through the main circuit, the liquid refrigerant becomes gaseous through the indoor expansion valve 90 and the indoor heat exchanger 80. This reduces the occurrence of liquid backflow to the accumulator 50.

[0060] The operation of the control device 5 is described. Fig. 9 and Fig. 10 are flowcharts showing the respective operations of the control device 5 in the air conditioning device 1 according to Embodiment 1. First, the execution of the defrosting operation will be explained with reference to Fig. 9. During the heating operation, the controller 5 determines, based on the measurement result by the frost detection device 6, whether the outdoor heat exchanger 30 needs to be defrosted or not (step S1). If it is determined that the outdoor heat exchanger 30 does not need to be defrosted (NO in step S1), the controller 5 repeats the process from step S1 until it determines that the outdoor heat exchanger 30 needs to be defrosted. If it is determined that the outdoor heat exchanger 30 needs to be defrosted (YES in step S1), the controller 5 changes the operation performed in the predetermined mode from the heating operation to the defrosting operation (step S2).

[0061] During the defrosting operation, the controller 5 determines whether the defrosting of the outdoor heat exchanger 30 is complete or not based on the measurement result of the defrosting detection device 7 (step S3). If it is determined that the defrosting of the outdoor heat exchanger 30 is not complete (NO in step S3), the controller 5 repeats the process in step S3 until it determines that the defrosting of the outdoor heat exchanger 30 is complete. If it determines that the defrosting of the outdoor heat exchanger 30 is complete (YES in step S3), the controller 5 changes the operation performed in the predetermined mode from the defrosting operation to the heating operation (step S4).

[0062] The execution of the liquid removal process is described with reference to Fig. 10. During the cooling operation, the controller 5 determines, based on the measurement result by the liquid accumulation detection device 8, whether or not liquid accumulation in the high-pressure gas main pipe 102 needs to be removed (step S11). If it is determined that the liquid accumulation in the high-pressure gas main pipe 102 does not need to be removed (NO in step S11), the controller 5 repeats the process in step S11 until it determines that the liquid accumulation in the high-pressure gas main pipe 102 needs to be removed. If it is determined that the liquid accumulation in the high-pressure gas main pipe 102 needs to be removed (YES in step S11), the controller 5 changes the operation performed in the predetermined mode from the cooling operation to the liquid removal operation (step S12).

[0063] During the liquid removal process, the controller 5 determines, based on the measurement result of the liquid accumulation detection device 8, whether the removal of the liquid accumulation in the high-pressure gas main pipe 102 is complete (step S13). If it is determined that the removal of the liquid accumulation in the high-pressure gas main pipe 102 is not complete (NO in step S13), the controller 5 repeats the process in step S13 until it determines that the removal of the liquid accumulation in the high-pressure gas main pipe 102 is complete. If it is determined that the removal of the liquid accumulation in the high-pressure gas main pipe 102 is complete (YES in step S13), the controller 5 changes the operation performed in the predetermined mode from the liquid removal process to the cooling operation (step S14).

[0064] As described above, according to Embodiment 1, the bypass valve 60 is disposed on the bypass pipe 305. Therefore, in the air conditioning device 1 according to Embodiment 1, during the defrosting operation, by causing the bypass valve 60 to be in the open state and blocking the refrigerant flow to the indoor unit 4, it is possible to cause high-temperature refrigerant to flow into the outdoor heat exchanger 30 while liquid refrigerant is stored in the indoor unit 4. That is, in the defrosting operation of the air conditioning device 1, the occurrence of liquid backflow is reduced without using heat from a pipe heated by high-temperature gaseous refrigerant in the heating operation. Therefore, the air conditioning device 1 according to Embodiment 1 can continuously reduce the occurrence of liquid backflow to the accumulator 50 in the defrosting operation.In addition, in the air conditioning device 1 according to Embodiment 1, in the defrosting operation, neither the high-pressure gas main pipe 102 nor the liquid main pipe 103 cools, so that the operation can be switched back to the heating operation early from the defrosting operation. Embodiment 2

[0065] Fig. 11 is a refrigerant cycle diagram of an air conditioning device 1A according to Embodiment 2. As shown in Fig. As illustrated in Figure 11, in Embodiment 2, the outdoor unit 2 includes a flow switching device 22 on the high-pressure pipe side. In this respect, Embodiment 2 differs from Embodiment 1. Regarding Embodiment 2, components that are the same as those in Embodiment 1 are denoted by the same reference numerals, and their descriptions are thus omitted. The following description will be made by mainly referring to the differences between Embodiments 1 and 2.

[0066] The outdoor unit 2 further includes an outdoor pipe 205. Furthermore, the outdoor unit 2 includes the high-pressure pipe-side flow switching device 22. The outdoor pipe 205 connects the high-pressure pipe-side flow switching device 22 to the outdoor pipe 201. The high-pressure pipe-side flow switching device 22 is disposed on the outdoor pipe 204. The state of the high-pressure pipe-side flow switching device 22 is switched between a state in which the high-pressure pipe-side flow switching device 22 connects the high-pressure gas main pipe 102 to the compressor 10 and a state in which the high-pressure pipe-side flow switching device 22 connects the high-pressure gas main pipe 102 to the accumulator 50.

[0067] Fig. 12 is a functional block diagram illustrating the air conditioning device 1A according to Embodiment 2. As in Fig. 12, the controller 5 controls the compressor 10, the heat exchanger-side flow switching device 21, the high-pressure pipe-side flow switching device 22, and the outdoor expansion valve 40 in the outdoor unit 2 based on the operation mode. In addition, the controller 5 controls the bypass valve 60, the low-pressure valves 71, and the high-pressure valves 72 in the relay unit 3 based on the operation mode. The controller 5 controls the first indoor expansion valve 90a in the indoor unit 4 based on the operation mode.

[0068] The states of the components and the refrigerant flow in each operating mode are described. Heating mode is described first. Fig. 13 is an explanatory view for the heating operation of the air conditioning device 1A according to Embodiment 2. In Fig. 13, the arrows indicate the flow directions of the refrigerant. To perform the heating operation, the control device 5 switches the state of the flow switching device 21 on the heat exchanger side to the state in which the flow switching device 21 on the heat exchanger side connects the outdoor heat exchanger 30 to the accumulator 50, and switches the state of the flow switching device 22 on the high-pressure pipe side to the state in which the flow switching device 22 on the high-pressure pipe side connects the compressor 10 to the high-pressure gas main pipe 102. Furthermore, the control device 5 causes the bypass valve 60 to be in the closed state, causes the low-pressure valve 71 to be in the closed state, and causes the high-pressure valve 72 to be in the open state. Furthermore, the control device 5 opens the indoor expansion valve 90 and opens the outdoor expansion valve 40.

[0069] In the heating operation, refrigerant sucked in by the compressor 10 is compressed by the compressor 10 to be changed into a high-temperature and high-pressure gaseous refrigerant, and the high-temperature and high-pressure gaseous refrigerant is then discharged from the compressor 10. The high-temperature and high-pressure gas refrigerant discharged from the compressor 10 flows through the flow switching device 22 on the high-pressure pipe side, passes through the high-pressure gas main pipe 102, and then flows into the relay unit 3. The refrigerant that has flowed into the relay unit 3 passes through the high-pressure gas branch pipe 302, on which the high-pressure valve 72 is arranged, and the gas branch pipe 104, and then flows into the indoor unit 4. The refrigerant that has flowed into the indoor unit 4 passes through the indoor heat exchanger 80, which serves as a condenser.The refrigerant passing through the indoor heat exchanger 80 exchanges heat with the indoor air and consequently condenses and becomes liquid.

[0070] At this time, the indoor air is heated, thus heating the indoor space. The liquid refrigerant passes through the indoor expansion valve 90 and is decompressed and expanded, transforming into a low-temperature, low-pressure, two-phase gas-liquid refrigerant. The two-phase gas-liquid refrigerant passes through the liquid branch pipe 105, the relay liquid pipe 304, and the liquid main pipe 103, and then flows into the outdoor unit 2. The refrigerant that has flowed into the outdoor unit 2 passes through the outdoor expansion valve 40, is further decompressed and expanded, and then passes through the outdoor heat exchanger 30, which serves as an evaporator. The refrigerant passing through the outdoor heat exchanger 30 exchanges heat with the outdoor air and consequently evaporates and becomes gaseous.Thereafter, the evaporated gaseous low-temperature and low-pressure refrigerant passes through the flow switching device 21 on the heat exchanger side and the accumulator 50, is sucked into the compressor 10 again and circulates.

[0071] Next, the de-icing operation is described. Fig. 14 is an explanatory view for the defrosting operation of the air conditioning device 1A according to Embodiment 2. In Fig. 14, the arrows indicate the flow directions of the refrigerant. To perform the defrosting operation, the control device 5 switches the state of the heat exchanger-side flow switching device 21 to the state where the heat exchanger-side flow switching device 21 connects the outdoor heat exchanger 30 to the accumulator 50, and switches the state of the high-pressure pipe-side flow switching device 22 to the state where the high-pressure pipe-side flow switching device 22 connects the compressor 10 to the high-pressure gas main pipe 102. Furthermore, the control device 5 causes the bypass valve 60 to be in the open state, causes the low-pressure valve 71 to be closed, and causes the high-pressure valve 72 to be in the open state.Furthermore, the control device 5 closes the indoor expansion valve 90 and opens the outdoor expansion valve 40.

[0072] In defrosting operation, refrigerant sucked in by the compressor 10 is compressed by the compressor 10 to change into a high-temperature and high-pressure gaseous refrigerant, and the high-temperature and high-pressure gaseous refrigerant is then discharged from the compressor 10. The high-temperature and high-pressure gas refrigerant discharged from the compressor 10 flows through the flow switching device 22 on the high-pressure pipe side, passes through the high-pressure gas main pipe 102, and then flows into the relay unit 3. The refrigerant flowing into the relay unit 3 passes through a part of the high-pressure gas branch pipe 302, the bypass pipe 305 on which the bypass valve 60 is arranged, a part of the relay liquid pipe 304, and the liquid main pipe 103, and then flows back into the outdoor unit 2.

[0073] The high-temperature, high-pressure gas refrigerant that flows into the outdoor unit 2 passes through the outdoor expansion valve 40 and then passes through the outdoor heat exchanger 30, which serves as an evaporator. The high-temperature, low-pressure gas refrigerant that passes through the outdoor heat exchanger 30 exchanges heat with the frost that forms on the outdoor heat exchanger 30 and subsequently condenses, turning into a low-temperature, low-pressure gas refrigerant. At this time, the outdoor heat exchanger 30 is defrosted. Afterward, the low-temperature, low-pressure gas refrigerant passes through the flow switching device 21 on the heat exchanger side and the accumulator 50, is sucked into the compressor 10, and circulates. In defrosting mode, the low pressure valve 71 is closed.Furthermore, the indoor expansion valve 90 is caused to be in the closed state. As a result, the flow of refrigerant to the indoor unit 4 is blocked, and liquid refrigerant is stored in the indoor unit 4.

[0074] The cooling operation is described. Fig. 15 is an explanatory view for the cooling operation of the air conditioning device 1A according to Embodiment 2. In Fig. 15, the arrows indicate the flow directions of the refrigerant. To perform the cooling operation, the control device 5 switches the state of the heat exchanger-side flow switching device 21 to the state where the heat exchanger-side flow switching device 21 connects the compressor 10 to the outdoor heat exchanger 30, and switches the state of the high-pressure pipe-side flow switching device 22 to the state where the high-pressure pipe-side flow switching device 22 connects the accumulator 50 to the high-pressure gas main pipe 102. Furthermore, the control device 5 causes the bypass valve 60 to be in the closed state, causes the high-pressure valve 72 to be in the closed state, and causes the low-pressure valve 71 to be in the open state. Furthermore, the control device 5 opens the indoor expansion valve 90 and opens the outdoor expansion valve 40.

[0075] In cooling operation, the refrigerant drawn in by the compressor 10 is compressed by the compressor 10 to become a high-temperature, high-pressure gas refrigerant, and the high-temperature, high-pressure gas refrigerant is then discharged from the compressor 10. The high-temperature, high-pressure gas refrigerant discharged from the compressor 10 passes through the flow switching device 21 on the heat exchanger side and then passes through the outdoor heat exchanger 30. The refrigerant passing through the outdoor heat exchanger 30 exchanges heat with the outdoor air and thus condenses and becomes liquid. The liquid refrigerant passes through the outdoor expansion valve 40 and is decompressed and expanded. The liquid refrigerant passes through the liquid main pipe 103 and then flows into the relay unit 3.

[0076] The refrigerant that flows into the relay unit 3 passes through the relay liquid pipe 304 and the liquid branch pipes 105 and then flows into the indoor unit 4. The refrigerant that flows into the indoor unit 4 is further decompressed and expanded at the indoor expansion valve 90, transforming into a low-temperature, low-pressure, two-phase gas-liquid refrigerant. The low-temperature, low-pressure, two-phase gas-liquid refrigerant passes through the indoor heat exchanger 80, exchanges heat with the indoor air, and evaporates and becomes gaseous. At this time, the indoor air is cooled, thus cooling the indoor space. The gaseous refrigerant passes through the gas branch pipe 104 and then flows into the relay unit 3.The refrigerant that has flowed into the relay unit 3 passes through the low-pressure gas branch pipe 303, on which the low-pressure valve 71 of the relay gas pipe 301 is arranged, and the low-pressure gas main pipe 101, and then flows into the outdoor unit 2. The refrigerant that has flowed into the outdoor unit 2 passes through the accumulator 50, is sucked into the compressor 10 again, and circulates.

[0077] Next, the fluid removal process is described. Fig. 16 is an explanatory view for the liquid removal process of the air conditioning device 1A according to Embodiment 2. In Fig. 16, the arrows indicate the flow directions of the refrigerant. To perform the liquid removal process, the control device 5 switches the state of the heat exchanger-side flow switching device 21 to the state where the heat exchanger-side flow switching device 21 connects the compressor 10 to the outdoor heat exchanger 30, and switches the state of the high-pressure pipe-side flow switching device 22 to the state where the high-pressure pipe-side flow switching device 22 connects the accumulator 50 to the high-pressure gas main pipe 102. Furthermore, the control device 5 causes the bypass valve 60 to be in the open state, causes the high-pressure valves 72 to be in the closed state, and causes the low-pressure valves 71 to be in the open state.Furthermore, the control device 5 opens the indoor expansion valve 90 and opens the outdoor expansion valve 40.

[0078] In the liquid removal process, a main circuit and a bypass circuit are formed. In the main circuit, the refrigerant flows in a manner similar to that during cooling operation. In the bypass circuit, the high-temperature and high-pressure gas refrigerant discharged from the compressor 10 passes through the high-pressure gas main pipe 102 and then flows into the relay unit 3. The refrigerant that has flowed into the relay unit 3 passes through a portion of the high-pressure gas branch pipe 302 and the bypass pipe 305, where the bypass valve 60 is arranged, and then flows into the relay liquid pipe 304 and joins the refrigerant flowing through the main circuit. As the refrigerant flows through the bypass circuit, the liquid refrigerant accumulated in the high-pressure gas main pipe 102 flows and combines with the refrigerant flowing through the main circuit.As a result, the liquid accumulation in the high-pressure gas main pipe 102 is eliminated. The flow of refrigerant to the indoor units 4 is blocked, and liquid refrigerant is stored in the indoor unit 4. After combining with the refrigerant flowing through the main circuit, the liquid refrigerant becomes gaseous through the indoor expansion valve 90 and the indoor heat exchanger 80. Consequently, the occurrence of liquid backflow to the accumulator 50 is reduced.

[0079] As described above, the air conditioning device 1A according to Embodiment 2 has the bypass valve 60 arranged on the bypass pipe 305, as in Embodiment 1. Therefore, in the air conditioning device 1A according to Embodiment 2, during the defrosting operation, by causing the bypass valve 60 to be in the open state and blocking the flow of refrigerant to the indoor unit 4, it is possible to cause high-temperature refrigerant to flow into the outdoor heat exchanger 30 while liquid refrigerant is stored in the indoor unit 4. That is, in the defrosting operation of the air conditioning device 1A, the occurrence of liquid backflow is reduced without using heat from a pipe heated by high-temperature gas refrigerant in the heating operation.Therefore, the air conditioning device 1A according to Embodiment 2 can continuously reduce the occurrence of liquid backflow to the accumulator 50 during the defrosting operation. In addition, in the air conditioning device 1A according to Embodiment 2, during the defrosting operation, neither the high-pressure gas main pipe 102 nor the liquid main pipe 103 cools, and the operation can be switched from the defrosting operation back to the heating operation early. Embodiment 3

[0080] Fig. 17 is a refrigerant cycle diagram of an air conditioning device 1B according to Embodiment 3. As in Fig. As illustrated in Figure 17, in Embodiment 3, the relay unit 3 includes a first medium-pressure valve 73a and a second medium-pressure valve 73b. In this respect, Embodiment 3 differs from Embodiment 1. Regarding Embodiment 3, components that are the same as those in Embodiment 1 are denoted by the same reference numerals, and their descriptions are thus omitted. The following description will be made by mainly referring to the differences between Embodiments 1 and 3.

[0081] The relay unit 3 includes the first medium-pressure valve 73a and the second medium-pressure valve 73b. The first medium-pressure valve 73a and the second medium-pressure valve 73b are arranged between a portion of the relay liquid pipe 304 connected to the bypass pipe 305 and portions of the relay liquid pipe 304 connected to the liquid branch pipes 105. The first medium-pressure valve 73a is arranged at a position associated with the first indoor unit 4a in the relay liquid pipe 304, which branches to correspond to the first indoor unit 4a and the second indoor unit 4b.The state of the first medium-pressure valve 73a can be switched between an open state in which the first medium-pressure valve 73a allows the refrigerant to flow through a region connected to the first indoor unit 4a in the relay liquid pipe 304, and a closed state in which the first medium-pressure valve 73a blocks the flow of the refrigerant through the region connected to the first indoor unit 4a in the relay liquid pipe 304.

[0082] The second medium-pressure valve 73b is arranged at a position associated with the second indoor unit 4b in the relay liquid pipe 304, which branches to correspond to the first indoor unit 4a and the second indoor unit 4b. The state of the second medium-pressure valve 73b can be switched between an open state in which the second medium-pressure valve 73b allows the refrigerant to flow through a region associated with the second indoor unit 4b in the relay liquid pipe 304, and a closed state in which the second medium-pressure valve 73b blocks the refrigerant from flowing through the region associated with the second indoor unit 4b in the relay liquid pipe 304.In the following description, the first medium-pressure valve 73a and the second medium-pressure valve 73b may be referred to as medium-pressure valves 73 in the case where they are not distinguished from each other. The type of each of the medium-pressure valves 73 is not limited as long as the medium-pressure valve 73 has a mechanism capable of switching the state of the medium-pressure valve 73 between a state in which the medium-pressure valve 73 allows the flow of refrigerant and a state in which the medium-pressure valve 73 blocks the flow of refrigerant. Therefore, the medium-pressure valve 73 may be, for example, an on / off valve or an expansion valve.

[0083] Fig. 18 is a functional block diagram illustrating the air conditioning device 1B according to Embodiment 3. As in Fig. 18, the controller 5 controls the compressor 10, the flow switching device 21 on the heat exchanger side, and the outdoor expansion valve 40 in the outdoor unit 2 based on the operation mode. In addition, the controller 5 controls the bypass valve 60, the low-pressure valves 71, the high-pressure valves 72, and the medium-pressure valves 73 in the relay unit 3 based on the operation mode. The controller 5 controls the first indoor expansion valve 90a in the indoor unit 4 based on the operation mode.

[0084] The states of the components and the refrigerant flow in each operating mode will be described. The cooling operation and the liquid removal process are the same as those in Embodiment 1, and their description will therefore be omitted. The heating operation will be described first. Fig. 19 is an explanatory view for the heating operation of the air conditioning device 1B according to Embodiment 3. In Fig. 19, the arrows indicate the flow directions of the refrigerant. To perform the heating operation, the control device 5 switches the state of the flow switching device 21 on the heat exchanger side to the state in which the flow switching device 21 on the heat exchanger side connects the outdoor heat exchanger 30 and the accumulator 50.

[0085] Furthermore, the control device 5 causes the bypass valve 60 to be closed, causes the low-pressure valve 71 to be closed, causes the high-pressure valve 72 to be open, and causes the medium-pressure valve 73 to be open. Furthermore, the control device 5 opens the indoor expansion valve 90 and opens the outdoor expansion valve 40.

[0086] In the heating operation, refrigerant sucked in by the compressor 10 is compressed by the compressor 10 to change it into a high-temperature and high-pressure gas refrigerant, and the high-temperature and high-pressure gas refrigerant is then discharged from the compressor 10. The high-temperature and high-pressure gas refrigerant discharged from the compressor 10 passes through the high-pressure gas main pipe 102 and then flows into the relay unit 3. The refrigerant that has flowed into the relay unit 3 passes through the high-pressure gas branch pipe 302, on which the high-pressure valve 72 is arranged, and the gas branch pipe 104, and then flows into the indoor unit 4. The refrigerant that has flowed into the indoor unit 4 passes through the indoor heat exchanger 80, which serves as a condenser.The refrigerant passing through the interior heat exchanger 80 exchanges heat with the interior air and subsequently condenses and becomes liquid. At this time, the interior air is heated, thus heating the interior.

[0087] The liquid refrigerant passes through the indoor expansion valve 90 and is decompressed and expanded, transforming into a low-temperature, low-pressure, two-phase gas-liquid refrigerant. The two-phase gas-liquid refrigerant passes through the liquid branch pipes 105, the relay liquid pipe 304, where the medium-pressure valve 73 is located, and the liquid main pipe 103, and then flows into the outdoor unit 2.

[0088] The refrigerant that has flowed into the outdoor unit 2 passes through the outdoor expansion valve 40, is further decompressed and expanded, and then passes through the outdoor heat exchanger 30, which serves as an evaporator. The refrigerant passing through the outdoor heat exchanger 30 exchanges heat with the outdoor air and thus evaporates and becomes a gas. The evaporated gaseous, low-temperature and low-pressure refrigerant then passes through the flow switching device 21 on the heat exchanger side and the accumulator 50. The refrigerant is sucked into the compressor 10 again and circulates.

[0089] Next, the de-icing operation is described. Fig. 20 is an explanatory view for the defrosting operation of the air conditioning device 1B according to Embodiment 3. In Fig. 20, the arrows indicate the flow directions of the refrigerant. To perform the defrosting operation, the control device 5 switches the state of the flow switching device 21 on the heat exchanger side to a state in which the flow switching device 21 on the heat exchanger side connects the outdoor heat exchanger 30 and the accumulator 50. Furthermore, the control device 5 causes the bypass valve 60 to be in the open state, causes the low-pressure valve 71 to be in the closed state, causes the high-pressure valve 72 to be in the open state, and causes the medium-pressure valve 73 to be in the closed state. Furthermore, the control device 5 opens the indoor expansion valve 90 and opens the outdoor expansion valve 40. The indoor expansion valve 90 can be closed.

[0090] In defrosting operation, the refrigerant drawn in by the compressor 10 is compressed by the compressor 10 to become a high-temperature, high-pressure gas refrigerant, and the high-temperature, high-pressure gas refrigerant is then discharged from the compressor 10. The high-temperature, high-pressure gas refrigerant discharged from the compressor 10 passes through the high-pressure gas main pipe 102 and then flows into the relay unit 3. The refrigerant that has flowed into the relay unit 3 passes through a part of the high-pressure gas branch pipe 302, the bypass pipe 305 where the bypass valve 60 is arranged, a part of the relay liquid pipe 304, and the liquid main pipe 103, and then flows back into the outdoor unit 2.

[0091] The high-temperature, high-pressure gas refrigerant that flows into the outdoor unit 2 passes through the outdoor expansion valve 40 and then passes through the outdoor heat exchanger 30, which serves as an evaporator. The high-temperature, low-pressure gas refrigerant that passes through the outdoor heat exchanger 30 exchanges heat with the frost that forms on the outdoor heat exchanger 30 and subsequently condenses, turning into a low-temperature, low-pressure gas refrigerant. At this time, the outdoor heat exchanger 30 is defrosted. Afterward, the low-temperature, low-pressure gas refrigerant passes through the flow switching device 21 on the heat exchanger side and the accumulator 50, is sucked into the compressor 10, and circulates. During defrosting operation, the low-pressure valve 71 is closed. In addition, the interior expansion valve 90 is closed.Consequently, the flow of refrigerant to the indoor unit 4 is blocked, and liquid refrigerant is stored in the indoor unit 4.

[0092] As described above, the air conditioning device 1B according to Embodiment 3 has the bypass valve 60 arranged on the bypass pipe 305, as in Embodiment 1. Therefore, in the air conditioning device 1B according to Embodiment 3, during the defrosting operation, by causing the bypass valve 60 to be in the open state and blocking the refrigerant flow to the indoor unit 4, it is possible to cause the high-temperature refrigerant to flow into the outdoor heat exchanger 30 while liquid refrigerant is stored in the indoor unit 4. That is, in the defrosting operation of the air conditioning device 1B, the occurrence of liquid backflow is reduced without using heat from a pipe heated by high-temperature gas refrigerant in the heating operation.Therefore, the air conditioning device 1B according to Embodiment 3 can continuously reduce the occurrence of liquid backflow to the accumulator 50 during the defrosting operation. Furthermore, in the air conditioning device 1B according to Embodiment 3, neither the high-pressure gas main pipe 102 nor the liquid main pipe 103 cools during the defrosting operation, and thus the operation can easily return to the heating operation. Embodiment 4

[0093] Fig. 21 is a refrigerant cycle diagram of an air conditioning device 1C according to Embodiment 4. As in Fig. As illustrated in Fig. 21, in Embodiment 4, the outdoor unit 2 includes the flow switching device 22 on the high-pressure pipe side, and the relay unit 3 includes the first medium-pressure valve 73a and the second medium-pressure valve 73b. In this respect, Embodiment 4 differs from Embodiment 1. That is, Embodiment 4 corresponds to a combination of Embodiments 2 and 3. Regarding Embodiment 4, components that are the same as those in Embodiment 1 are denoted by the same reference numerals, and thus, their repeated description will be omitted. The following description will be made by mainly referring to the differences between Embodiments 1 and 4.

[0094] The outdoor unit 2 further includes the outdoor pipe 205. Furthermore, the outdoor unit 2 includes the high-pressure pipe-side flow switching device 22. The outdoor pipe 205 connects the high-pressure pipe-side flow switching device 22 to the outdoor pipe 201. The high-pressure pipe-side flow switching device 22 is disposed on the outdoor pipe 204. The state of the high-pressure pipe-side flow switching device 22 is switched between a state in which the high-pressure pipe-side flow switching device 22 connects the high-pressure gas main pipe 102 to the compressor 10 and a state in which the high-pressure pipe-side flow switching device 22 connects the high-pressure gas main pipe 102 to the accumulator 50.

[0095] The relay unit 3 includes the first medium-pressure valve 73a and the second medium-pressure valve 73b. The first medium-pressure valve 73a and the second medium-pressure valve 73b are arranged between a part of the relay liquid pipe 304 connected to the bypass pipe 305 and parts of the relay liquid pipe 304 connected to the liquid branch pipes 105. The first medium-pressure valve 73a is arranged at the position associated with the first indoor unit 4a in the relay liquid pipe 304, which branches to correspond to the first indoor unit 4a and the second indoor unit 4b.The state of the first medium-pressure valve 73a can be switched between the open state in which the first medium-pressure valve 73a allows the flow of the refrigerant through the area connected to the first indoor unit 4a in the relay liquid pipe 304 and the closed state in which the first medium-pressure valve 73a blocks the flow of the refrigerant through the area connected to the first indoor unit 4a in the relay liquid pipe 304.

[0096] The second medium-pressure valve 73b is arranged at the position associated with the second indoor unit 4b in the relay liquid pipe 304, which branches to correspond to the first indoor unit 4a and the second indoor unit 4b. The state of the second medium-pressure valve 73b can be switched between the open state in which the second medium-pressure valve 73b allows the flow of refrigerant through the area associated with the second indoor unit 4b in the relay liquid pipe 304, and the closed state in which the second medium-pressure valve 73b blocks the flow of refrigerant through the area associated with the second indoor unit 4b in the relay liquid pipe 304.In the following description, the first medium pressure valve 73a and the second medium pressure valve 73b may be referred to as medium pressure valves 73 in the case where they are not distinguished from each other.

[0097] The type of each of the medium-pressure valves 73 is not limited, as long as the medium-pressure valve 73 has a mechanism capable of switching the state of the medium-pressure valve 73 between a state in which the medium-pressure valve 73 allows refrigerant flow and a state in which the medium-pressure valve 73 blocks refrigerant flow. Therefore, the medium-pressure valve 73 can be, for example, an on / off valve or an expansion valve.

[0098] Fig. 22 is a functional block diagram illustrating the air conditioning device 1C according to Embodiment 4. As in Fig. 22, the controller 5 controls the compressor 10, the heat exchanger-side flow switching device 21, the high-pressure pipe-side flow switching device 22, and the outdoor expansion valve 40 in the outdoor unit 2 based on the operation mode. In addition, the controller 5 controls the bypass valve 60, the low-pressure valves 71, the high-pressure valves 72, and the medium-pressure valve 73 in the relay unit 3 based on the operation mode. The controller 5 controls the first indoor expansion valve 90a in the indoor unit 4 based on the operation mode.

[0099] The states of the components and the refrigerant flow in each operating mode will be described. The cooling operation and the liquid removal process are the same as those in Embodiment 1, and their descriptions will therefore be omitted. The heating operation will be described first. Fig. 23 is an explanatory view for the heating operation of the air conditioning device 1C according to Embodiment 4. In Fig. 23, the arrows indicate the flow directions of the refrigerant. To perform the heating operation, the control device 5 switches the state of the flow switching device 21 on the heat exchanger side to the state in which the flow switching device 21 on the heat exchanger side connects the outdoor heat exchanger 30 to the accumulator 50, and switches the state of the flow switching device 22 on the high-pressure pipe side to the state in which the flow switching device 22 on the high-pressure pipe side connects the compressor 10 to the high-pressure gas main pipe 102.

[0100] Furthermore, the control device 5 causes the bypass valve 60 to be closed, causes the low-pressure valve 71 to be closed, causes the high-pressure valve 72 to be open, and causes the medium-pressure valve 73 to be open. Furthermore, the control device 5 opens the indoor expansion valve 90 and opens the outdoor expansion valve 40.

[0101] In the heating operation, refrigerant sucked in by the compressor 10 is compressed by the compressor 10 to be changed into a high-temperature and high-pressure gaseous refrigerant, and the high-temperature and high-pressure gaseous refrigerant is then discharged from the compressor 10. The high-temperature and high-pressure gas refrigerant discharged from the compressor 10 flows through the flow switching device 22 on the high-pressure pipe side, passes through the high-pressure gas main pipe 102, and then flows into the relay unit 3. The refrigerant that has flowed into the relay unit 3 passes through the high-pressure gas branch pipe 302, on which the high-pressure valve 72 is arranged, and the gas branch pipe 104, and then flows into the indoor unit 4. The refrigerant that has flowed into the indoor unit 4 passes through the indoor heat exchanger 80, which serves as a condenser.The refrigerant passing through the indoor heat exchanger 80 exchanges heat with the indoor air and consequently condenses and becomes liquid.

[0102] At this time, the indoor air is heated, thus heating the indoor space. The liquid refrigerant passes through the indoor expansion valve 90 and is decompressed and expanded, transforming into a low-temperature, low-pressure gas-liquid two-phase refrigerant. The two-phase gas-liquid refrigerant passes through the liquid branch pipes 105, the relay liquid pipe 304, where the medium-pressure valve 73 is arranged, and the liquid main pipe 103, and then flows into the outdoor unit 2. The refrigerant that has flowed into the outdoor unit 2 passes through the outdoor expansion valve 40, is further decompressed and expanded, and then passes through the outdoor heat exchanger 30, which serves as an evaporator. The refrigerant passing through the outdoor heat exchanger 30 exchanges heat with the outdoor air and consequently evaporates and becomes gaseous.Thereafter, the evaporated gaseous low-temperature and low-pressure refrigerant passes through the flow switching device 21 on the heat exchanger side and the accumulator 50, is sucked into the compressor 10 again and circulates.

[0103] Next, the de-icing operation is described. Fig. 24 is an explanatory view for the defrosting operation of the air conditioning device 1C according to Embodiment 4. In Fig. 24, the arrows indicate the flow directions of the refrigerant. To perform the defrosting operation, the control device 5 switches the state of the flow switching device 21 on the heat exchanger side to the state in which the flow switching device 21 on the heat exchanger side connects the outdoor heat exchanger 30 to the accumulator 50, and switches the state of the flow switching device 22 on the high-pressure pipe side to the state in which the flow switching device 21 on the heat exchanger side connects the compressor 10 to the high-pressure gas main pipe 102. Furthermore, the control device 5 causes the bypass valve 60 to be in the open state, causes the low-pressure valve 71 to be in the closed state, causes the high-pressure valve 72 to be in the open state, and causes the medium-pressure valve 73 to be in the closed state.Furthermore, the control device 5 opens the indoor expansion valve 90 and opens the outdoor expansion valve 40. The indoor expansion valves 90 can be closed.

[0104] In defrosting operation, refrigerant sucked in by the compressor 10 is compressed by the compressor 10 to change into a high-temperature and high-pressure gaseous refrigerant, and the high-temperature and high-pressure gaseous refrigerant is then discharged from the compressor 10. The high-temperature and high-pressure gas refrigerant discharged from the compressor 10 flows through the flow switching device 22 on the high-pressure pipe side, passes through the high-pressure gas main pipe 102, and then flows into the relay unit 3. The refrigerant flowing into the relay unit 3 passes through a part of the high-pressure gas branch pipe 302, the bypass pipe 305 on which the bypass valve 60 is arranged, a part of the relay liquid pipe 304, and the liquid main pipe 103, and then flows back into the outdoor unit 2.

[0105] The high-temperature, high-pressure gas refrigerant that flows into the outdoor unit 2 passes through the outdoor expansion valve 40 and then passes through the outdoor heat exchanger 30, which serves as an evaporator. The high-temperature, low-pressure gas refrigerant that passes through the outdoor heat exchanger 30 exchanges heat with the frost that forms on the outdoor heat exchanger 30 and subsequently condenses, turning into a low-temperature, low-pressure gas refrigerant. At this time, the outdoor heat exchanger 30 is defrosted. Afterward, the low-temperature, low-pressure gas refrigerant passes through the flow switching device 21 on the heat exchanger side and the accumulator 50, is sucked into the compressor 10, and circulates. During defrosting operation, the low-pressure valve 71 is closed. The medium-pressure valve 73 is also closed.Consequently, the flow of refrigerant to the indoor units 4 is blocked, and liquid refrigerant is stored in the indoor units 4.

[0106] As described above, the air conditioning device 1C according to Embodiment 4 has the bypass valve 60 arranged on the bypass pipe 305, as in Embodiment 1. Therefore, in the air conditioning device 1C according to Embodiment 4, during the defrosting operation, by causing the bypass valve 60 to be in the open state and blocking the flow of refrigerant to the indoor unit 4, it is possible to cause the high-temperature refrigerant to flow into the outdoor heat exchanger 30 while liquid refrigerant is stored in the indoor unit 4. That is, in the defrosting operation of the air conditioning device 1C, the occurrence of liquid backflow is reduced without using heat from a pipe heated by high-temperature gas refrigerant in the heating operation.Therefore, the air conditioning device 1C according to Embodiment 4 can continuously reduce the occurrence of liquid backflow to the accumulator 50 during the defrosting operation. Furthermore, in the air conditioning device 1C according to Embodiment 4, neither the high-pressure gas main pipe 102 nor the liquid main pipe 103 cools during the defrosting operation, and thus the operation can easily return to the heating operation. Embodiment 5

[0107] Fig. 25 is a refrigerant cycle diagram of an air conditioning device 1D according to Embodiment 5. As in Fig. As illustrated in Figure 25, in Embodiment 5, the air conditioning device includes a first outdoor unit 2a and a second outdoor unit 2b. In this respect, Embodiment 5 differs from Embodiment 1. Regarding Embodiment 5, components that are the same as those in Embodiment 1 are denoted by the same reference numerals, and their descriptions are thus omitted. The following description will be made by mainly referring to the differences between Embodiments 1 and 5.

[0108] The first outdoor unit 2a and the second outdoor unit 2b have a configuration similar to that of the outdoor unit 2 described in Embodiment 1. Specifically, the first outdoor unit 2a includes a first compressor 10a, a first heat exchanger-side flow switching device 21a, a first outdoor heat exchanger 30a, a first outdoor expansion valve 40a, and a first accumulator 50a. The first compressor 10a draws in low-temperature and low-pressure refrigerant, compresses the drawn refrigerant to change it into high-temperature and high-pressure refrigerant, and discharges the high-temperature and high-pressure refrigerant. The first heat exchanger-side flow switching device 21a is, for example, a four-way valve.

[0109] The state of the first flow switching device 21a on the heat exchanger side is switched between a state in which the first flow switching device 21a on the heat exchanger side connects the first outdoor heat exchanger 30a to the first compressor 10a and a state in which the first flow switching device 21a on the heat exchanger side connects the first outdoor heat exchanger 30a to the first accumulator 50a, so that the flow direction of the refrigerant in a refrigerant cycle is switched between multiple flow directions. The first outdoor heat exchanger 30a causes heat exchange to be performed between the refrigerant and the outdoor air. The first outdoor expansion valve 40a decompresses the refrigerant so that the refrigerant expands, and is, for example, an electronic expansion valve whose opening degree can be adjusted.The first accumulator 50a is a device for storing excess refrigerant circulating in the first outdoor unit 2a.

[0110] Similarly, the second outdoor unit 2b includes a second compressor 10b, a second flow switching device 21b on the heat exchanger side, a second outdoor heat exchanger 30b, a second outdoor expansion valve 40, and a second accumulator 50b. The second compressor 10b draws in low-temperature and low-pressure refrigerant, compresses the drawn-in refrigerant, thus changing it into high-temperature and high-pressure refrigerant, and discharges the high-temperature and high-pressure refrigerant. The second flow switching device 21b on the heat exchanger side is, for example, a four-way valve.

[0111] The state of the second heat exchanger-side flow switching device 21b is switched between a state in which the second heat exchanger-side flow switching device 21b connects the second outdoor heat exchanger 30b to the second compressor 10b and a state in which the second heat exchanger-side flow switching device 21b connects the second outdoor heat exchanger 30b to the second accumulator 50b, so that the flow direction of the refrigerant in a refrigerant cycle is switched between multiple flow directions. The second outdoor heat exchanger 30b causes heat exchange to be performed between the refrigerant and the outdoor air. The second outdoor expansion valve 40b decompresses the refrigerant to expand the refrigerant, and is, for example, an electronic expansion valve whose opening degree can be adjusted.The second accumulator 50b is a device for storing excess refrigerant circulating in the second outdoor unit 2b.

[0112] The number of outdoor units 2 in the air conditioning device 1D is not limited to one or two. The air conditioning device 1D may also include three or more outdoor units. In the following description, in the case where the outdoor units and components related to the respective outdoor units are not particularly distinguished from each other, the outdoor units and the components may be referred to as follows, as in Embodiment 1. The first outdoor unit 2a and the second outdoor unit 2b may be referred to as outdoor units 2 in the case where they are not distinguished from each other. The first compressor 10a and the second compressor 10b may be referred to as compressors 10 in the case where they are not distinguished from each other.

[0113] The first heat exchanger-side flow switching device 21a and the second heat exchanger-side flow switching device 21b may be referred to as heat exchanger-side flow switching devices 21 when they are not distinguished from each other. The first outdoor heat exchanger 30a and the second outdoor heat exchanger 30b may be referred to as outdoor heat exchanger 30 when they are not distinguished from each other. The first outdoor expansion valve 40a and the second outdoor expansion valve 40b may be referred to as outdoor expansion valves 40 when they are not distinguished from each other. The first accumulator 50a and the second accumulator 50b may be referred to as accumulators 50 when they are not distinguished from each other.

[0114] As in Fig. 4 with respect to Embodiment 1, the controller 5 controls the compressors 10, the flow switching devices 21 on the heat exchanger side, and the outdoor expansion valves 40 in the outdoor units 2 based on the operation mode. In addition, the controller 5 controls the bypass valve 60, the low-pressure valves 71, and the high-pressure valves 72 in the relay unit 3 based on the operation mode. The controller 5 controls the first indoor expansion valve 90a in the indoor units 4 based on the operation mode.

[0115] The states of the components and the refrigerant flow in each operating mode are described. Heating operation is described first. Fig. 26 is an explanatory view for the heating operation of the air conditioning device 1D according to Embodiment 5. In Fig. 26, the arrows indicate the flow directions of the refrigerant. To perform the heating operation, the control device 5 switches the state of each of the heat exchanger-side flow switching devices 21 to the state in which the heat exchanger-side flow switching device 21 connects the outdoor heat exchanger 30 and the accumulator 50. Furthermore, the control device 5 causes the bypass valve 60 to be in the closed state, causes the low-pressure valve 71 to be in the closed state, and causes the high-pressure valve 72 to be in the open state. Furthermore, the control device 5 opens the indoor expansion valve 90 and opens the outdoor expansion valve 40.

[0116] In the heating operation, refrigerant drawn in by the first compressor 10a is compressed by the first compressor 10a to become a high-temperature, high-pressure refrigerant gas, and the high-temperature, high-pressure refrigerant gas is then discharged from the first compressor 10a. The high-temperature, high-pressure refrigerant gas discharged from the first compressor 10a passes through the high-pressure gas main pipe 102 and then flows into the relay unit 3. The refrigerant that has flowed into the relay unit 3 passes through the high-pressure gas branch pipe 302, where the high-pressure valve 72 is disposed, and the gas branch pipe 104, and then flows into the indoor unit 4. The refrigerant that has flowed into the indoor unit 4 passes through the indoor heat exchanger 80, which serves as a condenser.

[0117] The refrigerant passing through the indoor heat exchanger 80 exchanges heat with the indoor air and thus condenses and becomes liquid. At this time, the indoor air is heated, thus heating the indoor space. The liquid refrigerant passes through the indoor expansion valves 90 and is decompressed and expanded, transforming into a low-temperature, low-pressure, two-phase gas-liquid refrigerant. The two-phase gas-liquid refrigerant passes through the liquid branch pipes 105, the relay liquid pipe 304, and the liquid main pipe 103, and then flows into the first outdoor unit 2a. The refrigerant that has flowed into the first outdoor unit 2a passes through the outdoor expansion valve 40, is further decompressed and expanded, and then passes through the first outdoor heat exchanger 30a serving as an evaporator.The refrigerant passing through the first outdoor heat exchanger 30a exchanges heat with the outdoor air and thus evaporates and becomes gaseous. The evaporated gaseous low-temperature and low-pressure refrigerant then passes through the first flow switching device 21a on the heat exchanger side and the accumulator 50 and is sucked into the first compressor 10a again.

[0118] Furthermore, the refrigerant drawn in by the second compressor 10b is compressed by the second compressor 10b to become a high-temperature, high-pressure gas refrigerant, and the high-temperature, high-pressure gas refrigerant is then discharged from the second compressor 10b. The high-temperature, high-pressure gas refrigerant discharged from the second compressor 10b flows into the high-pressure gas main pipe 102 and joins the refrigerant flowing between the first outdoor unit 2a and the relay unit 3. Furthermore, the two-phase gas-liquid refrigerant flowing through the liquid main pipe 103 branches off from the refrigerant flowing between the first outdoor unit 2a and the relay unit 3 and then flows into the second outdoor unit 2b.

[0119] The refrigerant that has flowed into the second outdoor unit 2b passes through the outdoor expansion valve 40, is further decompressed and expanded, and then passes through the second outdoor heat exchanger 30b, which serves as an evaporator. The refrigerant passing through the second outdoor heat exchanger 30b exchanges heat with the outdoor air and thus evaporates and becomes a gas. Afterward, the evaporated, low-temperature, low-pressure gaseous refrigerant passes through the second flow switching device 21b on the heat exchanger side and the accumulator 50, and is then sucked into the second compressor 10b again.

[0120] Next, the de-icing operation is described. Fig. 27 is an explanatory view for the defrosting operation of the air conditioning device 1D according to Embodiment 5. In Fig. 27, the arrows indicate the flow directions of the refrigerant. To perform the defrosting operation, the control device 5 switches the state of each of the heat exchanger-side flow switching devices 21 to the state in which the heat exchanger-side flow switching device 21 connects the outdoor heat exchanger 30 and the accumulator 50. Furthermore, the control device 5 causes the bypass valve 60 to be in the open state, causes the low-pressure valves 71 to be in the closed state, and causes the high-pressure valve 72 to be in the open state. Furthermore, the control device 5 closes the indoor expansion valve 90 and opens the outdoor expansion valve 40.

[0121] In the defrosting operation, refrigerant drawn in by the first compressor 10a is compressed by the first compressor 10a to become a high-temperature, high-pressure gas refrigerant, and the high-temperature, high-pressure gas refrigerant is then discharged from the first compressor 10a. The high-temperature, high-pressure gas refrigerant discharged from the first compressor 10a passes through the high-pressure gas main pipe 102 and then flows into the relay unit 3. The refrigerant that has flowed into the relay unit 3 passes through a part of the high-pressure gas branch pipe 302, the bypass pipe 305 where the bypass valve 60 is disposed, a part of the relay liquid pipe 304, and the liquid main pipe 103, and then flows back into the first outdoor unit 2a.The high-temperature and high-pressure gaseous refrigerant that has flowed into the first outdoor unit 2a passes through the outdoor expansion valve 40 and then passes through the first outdoor heat exchanger 30a serving as an evaporator.

[0122] The high-temperature, low-pressure gaseous refrigerant passing through the first outdoor heat exchanger 30a exchanges heat with the frost formed on the first outdoor heat exchanger 30a and subsequently condenses to become a low-temperature, low-pressure gaseous refrigerant. At this time, the first outdoor heat exchanger 30a is defrosted. Afterward, the low-temperature, low-pressure gaseous refrigerant passes through the first flow switching device 21a on the heat exchanger side and the accumulator 50 and is sucked into the first compressor 10a again. In the defrosting operation, the low-pressure valve 71 is caused to be closed. Furthermore, the indoor expansion valve 90 is closed. Consequently, the flow of refrigerant to the indoor unit 4 is blocked, and liquid refrigerant is stored in the indoor units 4.

[0123] Furthermore, the refrigerant drawn in by the second compressor 10b is compressed by the second compressor 10b to become a high-temperature, high-pressure refrigerant gas, and the high-temperature, high-pressure refrigerant gas is then discharged from the second compressor 10b. The high-temperature, high-pressure refrigerant gas discharged from the second compressor 10b flows into the high-pressure gas main pipe 102 and joins the refrigerant flowing between the first outdoor unit 2a and the relay unit 3.

[0124] The two-phase gas-liquid refrigerant flowing through the liquid main pipe 103 branches off from the refrigerant flowing between the first outdoor unit 2a and the relay unit 3, and then flows into the second outdoor unit 2b. The refrigerant flowing into the second outdoor unit 2b passes through the outdoor expansion valve 40, is decompressed and expanded, and then passes through the second outdoor heat exchanger 30b, which serves as an evaporator. The refrigerant passing through the second outdoor heat exchanger 30b exchanges heat with the outdoor air and thus evaporates and becomes gaseous. Thereafter, the evaporated gaseous low-temperature and low-pressure refrigerant passes through the second flow switching device 21b on the heat exchanger side and the accumulator 50 and is then sucked into the second compressor 10b again.

[0125] The cooling operation is described. Fig. 28 is an explanatory view for the cooling operation of the air conditioning device 1D according to Embodiment 5. In Fig. 28, the arrows indicate the flow directions of the refrigerant. To perform the cooling operation, the control device 5 switches the state of each of the heat exchanger-side flow switching devices 21 to a state in which the heat exchanger-side flow switching device connects the compressor 10 to the outdoor heat exchanger 30. Furthermore, the control device 5 causes the bypass valve 60 to be in the closed state, causes the high-pressure valves 72 to be in the closed state, and causes the low-pressure valves 71 to be in the open state. Furthermore, the control device 5 opens the indoor expansion valve 90 and opens the outdoor expansion valve 40.

[0126] In cooling operation, the refrigerant drawn in by the first compressor 10a is compressed by the first compressor 10a to become a high-temperature, high-pressure gas refrigerant, and the high-temperature, high-pressure gas refrigerant is then discharged from the first compressor 10a. The high-temperature, high-pressure gas refrigerant discharged from the first compressor 10a passes through the first flow switching device 21a on the heat exchanger side and then passes through the first outdoor heat exchanger 30a. The refrigerant passing through the first outdoor heat exchanger 30a exchanges heat with the outdoor air and condenses and becomes a liquid. The liquid refrigerant passes through the outdoor expansion valve 40 and is decompressed and expanded. The liquid refrigerant passes through the liquid main pipe 103 and then flows into the transfer unit 3.The refrigerant that has flowed into the relay unit 3 passes through the relay liquid pipe 304 and the liquid branch pipe 105 and then flows into the indoor unit 4.

[0127] The refrigerant that has flowed into the indoor unit 4 is further decompressed and expanded to become a two-phase, low-temperature, low-pressure gas-liquid refrigerant through the indoor expansion valve 90. The two-phase, low-temperature, low-pressure gas-liquid refrigerant passes through the indoor heat exchanger 80, exchanges heat with the indoor air, and evaporates and becomes gaseous. At this time, the indoor air is cooled, thus cooling the indoor space. The gaseous refrigerant passes through the gas branch pipes 104 and then flows into the relay unit 3. The refrigerant that has flowed into the relay unit 3 passes through the low-pressure gas branch pipe 303, on which the low-pressure valve 71 of the relay gas pipe 301 is arranged, and the low-pressure gas main pipe 101, and then flows into the first outdoor unit 2a.The refrigerant that has flowed into the first outdoor unit 2a passes through the accumulator 50 and is then sucked into the first compressor 10a again.

[0128] Furthermore, the refrigerant drawn in by the second compressor 10b is compressed by the second compressor 10b to become a high-temperature, high-pressure gas refrigerant, and the high-temperature, high-pressure gas refrigerant is then discharged from the second compressor 10b. The high-temperature, high-pressure gas refrigerant discharged from the second compressor 10b passes through the second flow switching device 21b on the heat exchanger side and then passes through the second outdoor heat exchanger 30b. The refrigerant passing through the second outdoor heat exchanger 30b exchanges heat with the outdoor air and condenses and becomes liquid. The liquid refrigerant passes through the outdoor expansion valve 40 and is decompressed and expanded.

[0129] The liquid refrigerant flows into the liquid main pipe 103 and joins the refrigerant flowing between the first outdoor unit 2a and the relay unit 3. The refrigerant flowing through the low-pressure gas main pipe 101 branches off from the refrigerant flowing between the first outdoor unit 2a and the relay unit 3 and then flows into the second outdoor unit 2b. The refrigerant flowing into the second outdoor unit 2b passes through the accumulator 50 and is then sucked into the second compressor 10b again.

[0130] Next, the fluid removal process is described. Fig. 29 is an explanatory view for the liquid removal process of the air conditioning device 1D according to Embodiment 5. In Fig. 29, the arrows indicate the flow directions of the refrigerant. To perform the liquid removal process, the control device 5 switches the state of the flow switching devices 21 on the heat exchanger side to the state in which the flow switching device 21 on the heat exchanger side connects the compressor 10 to the outdoor heat exchanger 30. Furthermore, the control device 5 causes the bypass valve 60 to be in the open state, causes the high-pressure valve 72 to be in the closed state, and causes the low-pressure valve 71 to be in the open state. Furthermore, the control device 5 opens the indoor expansion valve 90 and opens the outdoor expansion valve 40.

[0131] In the liquid removal process, a main circuit and a bypass circuit are formed. In the main circuit, the refrigerant flows in a manner similar to that in the cooling operation. In the bypass circuit, the high-temperature and high-pressure gas refrigerant discharged from the first compressor 10a passes through the high-pressure gas main pipe 102 and then flows into the relay unit 3. The refrigerant that has flowed into the relay unit 3 passes through a part of the high-pressure gas branch pipe 302 and the bypass pipe 305, where the bypass valve 60 is arranged, and then flows into the relay liquid pipe 304 and joins the refrigerant flowing in the main circuit.

[0132] As the refrigerant flows through the bypass circuit, the liquid refrigerant accumulated in the high-pressure gas main pipe 102 flows and combines with the refrigerant flowing through the main circuit. As a result, the liquid accumulation in the high-pressure gas main pipe 102 is eliminated. The flow of refrigerant to the indoor unit 4 is blocked, and liquid refrigerant is stored in the indoor unit 4. The liquid refrigerant that has combined with the refrigerant flowing through the main circuit is gasified by the indoor expansion valve 90 and the indoor heat exchanger 80, thus reducing the occurrence of liquid backflow to the accumulator 50.

[0133] Furthermore, the refrigerant drawn in by the second compressor 10b is compressed by the second compressor 10b to become a high-temperature, high-pressure gas refrigerant, and the high-temperature, high-pressure gas refrigerant is then discharged from the second compressor 10b. The high-temperature, high-pressure gas refrigerant discharged from the second compressor 10b passes through the second flow switching device 21b on the heat exchanger side, and then passes through the second outdoor heat exchanger 30b. The refrigerant passing through the second outdoor heat exchanger 30b exchanges heat with the outdoor air and condenses to become a liquid.

[0134] The liquid refrigerant passes through the outdoor expansion valve 40 and is decompressed and expanded. The liquid refrigerant flows into the liquid main pipe 103 and joins the refrigerant flowing between the first outdoor unit 2a and the relay unit 3. The refrigerant flowing through the low-pressure gas main pipe 101 branches off from the refrigerant flowing between the first outdoor unit 2a and the relay unit 3 and then flows into the second outdoor unit 2b. The refrigerant flowing into the second outdoor unit 2b passes through the accumulator 50 and is then sucked into the second compressor 10b again.

[0135] As described above, the air conditioning device 1D according to Embodiment 5 includes the bypass valve 60 disposed on the bypass pipe 305, as in Embodiment 1. Therefore, in the air conditioning device 1D according to Embodiment 5, during the defrosting operation, by causing the bypass valve 60 to be in the open state and blocking the refrigerant flow to the indoor unit 4, it is possible to cause high-temperature refrigerant to flow into the outdoor heat exchangers 30 while liquid refrigerant is stored in the indoor units 4. That is, in the defrosting operation of the air conditioning device 1D, the occurrence of liquid backflow is reduced without using heat from a pipe heated by high-temperature gas refrigerant in the heating operation.Therefore, the air conditioning device 1D according to Embodiment 5 can continuously reduce the occurrence of liquid backflow to the accumulators 50 during the defrosting operation. Furthermore, in the air conditioning device 1D according to Embodiment 5, neither the high-pressure gas main pipe 102 nor the liquid main pipe 103 cools during the defrosting operation, and the operation can return to the warming operation early. Embodiment 6

[0136] Fig. 30 is a refrigerant cycle diagram of an air conditioning device 1E according to Embodiment 6. As in Fig. As illustrated in Fig. 30, in Embodiment 6, the air conditioning device includes the first outdoor unit 2a and the second outdoor unit 2b as described in Embodiment 5. In this respect, Embodiment 6 differs from Embodiment 2. Regarding Embodiment 6, components that are the same as those in Embodiment 2 are denoted by the same reference numerals, and their repeated descriptions will be omitted. The following description will be made by mainly referring to the differences between Embodiments 2 and 6.

[0137] The second outdoor unit 2b includes a second high-pressure pipe-side flow switching device 22b. The state of the second high-pressure pipe-side flow switching device 22b is switched between a state in which the second high-pressure pipe-side flow switching device 22b connects the high-pressure gas main pipe 102 and the second compressor 10b, and a state in which the second high-pressure pipe-side flow switching device 22b connects the high-pressure gas main pipe 102 and the second accumulator 50b. In the following description, a first high-pressure pipe-side flow switching device 22a and the second high-pressure pipe-side flow switching device 22b may be referred to as high-pressure pipe-side flow switching devices 22, in the case where they are not distinguished from each other.

[0138] The states of the components in each operating mode will be described. The description regarding the refrigerant flow in Embodiment 6 will be omitted because Embodiment 6 differs from Embodiment 2 only in that, as described with respect to Embodiment 5, the refrigerant flow between the first compressor 10a and the relay unit 3 is parallel to the refrigerant flow between the second compressor 10b and the relay unit 3. First, the heating operation will be described. Fig. 31 is an explanatory view for the heating operation of the air conditioning device 1E according to Embodiment 6.

[0139] In Fig. 31, the arrows indicate the flow directions of the refrigerant. To perform the heating operation, the controller 5 switches the state of each of the flow switching devices 21 on the heat exchanger side to the state where the flow switching device 21 on the heat exchanger side connects the outdoor heat exchanger 30 to the accumulator 50, and switches the state of the flow switching devices 22 on the high-pressure pipe side to the state where the flow switching device 22 on the high-pressure pipe side connects the compressor 10 to the high-pressure gas main pipe 102. Furthermore, the controller 5 causes the bypass valve 60 to be in the closed state, causes the low-pressure valve 71 to be in the closed state, and causes the high-pressure valve 72 to be in the open state.Furthermore, the control device 5 opens the indoor expansion valve 90 and opens the outdoor expansion valve 40.

[0140] Next, the de-icing operation is described. Fig. 32 is an explanatory view for the defrosting operation of the air conditioning device 1E according to Embodiment 6. In Fig. 32, the arrows indicate the flow directions of the refrigerant. To perform the defrosting operation, the controller 5 switches the state of each of the flow switching devices 21 on the heat exchanger side to the state where the flow switching device 21 on the heat exchanger side connects the outdoor heat exchanger 30 to the accumulator 50, and switches the state of the flow switching devices 22 on the high-pressure pipe side to the state where the flow switching device 22 on the high-pressure pipe side connects the compressor 10 to the high-pressure gas main pipe 102. Furthermore, the controller 5 causes the bypass valve 60 to be in the open state, causes the low-pressure valve 71 to be in the closed state, and causes the high-pressure valve 72 to be in the open state.Furthermore, the control device 5 closes the indoor expansion valve 90 and opens the outdoor expansion valve 40.

[0141] Then the cooling operation is described. Fig. 33 is an explanatory view for the cooling operation of the air conditioning device 1E according to Embodiment 6. In Fig. 33, the arrows indicate the flow directions of the refrigerant. To perform the cooling operation, the control device 5 switches the state of each of the flow switching devices 21 on the heat exchanger side to the state where the flow switching device 21 on the heat exchanger side connects the compressor 10 to the outdoor heat exchanger 30, and switches the state of each of the flow switching devices 22 on the high-pressure pipe side to the state where the flow switching device 22 on the high-pressure pipe side connects the accumulator 50 to the high-pressure gas main pipe 102. Furthermore, the control device 5 causes the bypass valve 60 to be in the closed state, causes the high-pressure valve 72 to be in the closed state, and causes the low-pressure valve 71 to be in the open state.Furthermore, the control device 5 opens the indoor expansion valve 90 and opens the outdoor expansion valve 40.

[0142] Next, the fluid removal process is described. Fig. 34 is an explanatory view for the liquid removal process of the air conditioning device 1E according to Embodiment 6. In Fig. 34, the arrows indicate the flow directions of the refrigerant. To perform the liquid removal process, the control device 5 switches the state of each of the flow switching devices 21 on the heat exchanger side to the state in which the flow switching device 21 on the heat exchanger side connects the compressor 10 to the outdoor heat exchanger 30, and switches the state of each of the flow switching devices 22 on the high-pressure pipe side to the state in which the flow switching device 22 on the high-pressure pipe side connects the accumulator 50 to the high-pressure gas main pipe 102. Furthermore, the control device 5 causes the bypass valve 60 to be in the open state, causes the high-pressure valve 72 to be in the closed state, and causes the low-pressure valve 71 to be in the open state.Furthermore, the control device 5 opens the indoor expansion valve 90 and opens the outdoor expansion valve 40.

[0143] As described above, the air conditioning device 1E according to Embodiment 6 has the bypass valve 60 arranged on the bypass pipe 305 as in Embodiment 2. Therefore, in the air conditioning device 1E according to Embodiment 6 of the present invention, during a defrosting operation, by causing the bypass valve 60 to be in the open state and blocking the flow of refrigerant to the indoor unit 4, it is possible to cause high-temperature refrigerant to flow into the outdoor heat exchanger 30 while liquid refrigerant is stored in the indoor unit 4.

[0144] That is, in the defrosting operation of the air conditioning device 1E, the occurrence of liquid backflow is reduced without using heat from a pipe heated by high-temperature gas refrigerant in the heating operation. Therefore, the air conditioning device 1E according to Embodiment 6 can continuously reduce the occurrence of liquid backflow to the accumulators 50 in the defrosting operation. Furthermore, in the air conditioning device 1E according to Embodiment 6, neither the high-pressure gas main pipe 102 nor the liquid main pipe 103 cools during the defrosting operation, and the operation can return to the heating operation early. Embodiment 7

[0145] Fig. 35 is a refrigerant cycle diagram of an air conditioning device 1F according to Embodiment 7. As in Fig. As illustrated in Fig. 35, in Embodiment 7, the air conditioning device includes the first outdoor unit 2a and the second outdoor unit 2b as described in Embodiment 5. In this respect, Embodiment 7 differs from Embodiment 3. Regarding Embodiment 7, components that are the same as those in Embodiment 3 are denoted by the same reference numerals, and descriptions thereof will be omitted. The following description will be made by mainly referring to the differences between Embodiments 3 and 7.

[0146] The states of the components in each operation mode will be described. The description of the refrigerant flow in Embodiment 7 will be omitted because Embodiment 7 differs from Embodiment 3 only in that, as described with respect to Embodiment 5, the refrigerant flow between the first compressor 10a and the relay unit 3 is parallel to the refrigerant flow between the second compressor 10b and the relay unit 3. The cooling operation and the liquid removal operation are also the same as those in Embodiment 5, and their descriptions will therefore be omitted. First, the heating operation will be described. Fig. 36 is an explanatory view for the heating operation of the air conditioning device 1F according to Embodiment 7. In Fig. 36 the arrows indicate the flow directions of the refrigerant.

[0147] To perform the heating operation, the control device 5 switches the state of each of the heat exchanger-side flow switching devices 21 to the state where the heat exchanger-side flow switching device 21 connects the outdoor heat exchanger 30 and the accumulator 50. Furthermore, the control device 5 causes the bypass valve 60 to be closed, causes the low-pressure valve 71 to be closed, causes the high-pressure valve 72 to be open, and causes the medium-pressure valve 73 to be open. Furthermore, the control device 5 opens the indoor expansion valve 90 and opens the outdoor expansion valve 40.

[0148] Next, the de-icing operation is described. Fig. 37 is an explanatory view for the defrosting operation of the air conditioning device 1F according to Embodiment 7. In Fig. 37, the arrows indicate the flow directions of the refrigerant. To perform the defrosting operation, the controller 5 switches the state of each of the heat exchanger-side flow switching devices 21 to the state where the heat exchanger-side flow switching device 21 connects the outdoor heat exchanger 30 and the accumulator 50. Furthermore, the controller 5 causes the bypass valve 60 to be in the open state, causes the low-pressure valves 71 to be in the closed state, causes the high-pressure valves 72 to be in the open state, and causes the medium-pressure valves 73 to be in the closed state. Furthermore, the controller 5 opens the indoor expansion valve 90 and opens the outdoor expansion valve 40. The indoor expansion valve 90 may be closed.

[0149] As described above, the air conditioning device 1F according to Embodiment 7 has the bypass valve 60 arranged on the bypass pipe 305 as in Embodiment 3. Therefore, in the air conditioning device 1F according to Embodiment 7 of the present invention, during a defrosting operation, by causing the bypass valve 60 to be in the open state and blocking the flow of refrigerant to the indoor unit 4, it is possible to cause high-temperature refrigerant to flow into the outdoor heat exchanger 30 while liquid refrigerant is stored in the indoor unit 4.

[0150] That is, in the defrosting operation of the air conditioning device 1F, the occurrence of liquid backflow is reduced without using heat from a pipe heated by high-temperature gas refrigerant in the heating operation. Therefore, the air conditioning device 1F according to Embodiment 7 can continuously reduce the occurrence of liquid backflow to the accumulators 50 in the defrosting operation. Furthermore, in the air conditioning device 1F according to Embodiment 7, neither the high-pressure gas main pipe 102 nor the liquid main pipe 103 cools during the defrosting operation, and the operation can return to the heating operation early. Embodiment 8

[0151] Fig. 38 is a refrigerant cycle diagram of an air conditioning device 1G according to Embodiment 8. As in Fig. As illustrated in Fig. 38, in Embodiment 8, the air conditioning device includes the first outdoor unit 2a and the second outdoor unit 2b as described in Embodiment 5. In this respect, Embodiment 8 differs from Embodiment 1. Regarding Embodiment 8, components that are the same as those in Embodiment 4 are denoted by the same reference numerals, and their descriptions are thus omitted. The following description will be made by mainly referring to Embodiments 1 and 4.

[0152] The states of the components in each operation mode will be described. The description of the refrigerant flow in Embodiment 8 will be omitted because Embodiment 8 differs from Embodiment 4 only in that, as described with respect to Embodiment 5, the refrigerant flow between the first compressor 10a and the relay unit 3 is parallel to the refrigerant flow between the second compressor 10b and the relay unit 3. The cooling operation and the liquid removal operation are also the same as those in Embodiment 5, and their descriptions will therefore be omitted. First, the heating operation will be described. Fig. 39 is an explanatory view for the heating operation of the air conditioning device 1G according to Embodiment 8. In Fig. 39 the arrows indicate the flow directions of the refrigerant.

[0153] To perform the heating operation, the control device 5 switches the state of each of the flow switching devices 21 on the heat exchanger side to the state where the flow switching device 21 on the heat exchanger side connects the outdoor heat exchanger 30 to the accumulator 50, and switches the state of the flow switching devices 22 on the high-pressure pipe side to the state where the flow switching device 22 on the high-pressure pipe side connects the compressor 10 to the high-pressure gas main pipe 102. Furthermore, the control device 5 causes the bypass valve 60 to be in the closed state, causes the low-pressure valve 71 to be in the closed state, causes the high-pressure valve 72 to be in the open state, and causes the medium-pressure valve 73 to be in the open state.Furthermore, the control device 5 opens the indoor expansion valve 90 and opens the outdoor expansion valve 40.

[0154] Next, the de-icing operation is described. Fig. 40 is an explanatory view for the defrosting operation of the air conditioning device 1G according to Embodiment 8. In Fig. 40, the arrows indicate the flow directions of the refrigerant. To perform the defrosting operation, the control device 5 switches the state of each of the flow switching devices 21 on the heat exchanger side to the state in which the flow switching device 21 on the heat exchanger side connects the outdoor heat exchanger 30 to the accumulator 50, and switches the state of the flow switching devices 22 on the high-pressure pipe side to the state in which the flow switching device 22 on the high-pressure pipe side connects the compressor 10 to the high-pressure gas main pipe 102.

[0155] In addition, the control device 5 causes the bypass valve 60 to be in the open state, causes the low-pressure valve 71 to be in the closed state, causes the high-pressure valve 72 to be in the open state, and causes the medium-pressure valve 73 to be in the closed state. Furthermore, the control device 5 opens the indoor expansion valve 90 and opens the outdoor expansion valve 40. The indoor expansion valve 90 can be closed.

[0156] As described above, the air conditioning device 1G according to Embodiment 8 has the bypass valve 60 arranged on the bypass pipe 305 as in Embodiment 4. Therefore, in the air conditioning device 1G according to Embodiment 8 of the present invention, during a defrosting operation, by causing the bypass valve 60 to be in the open state and blocking the flow of refrigerant to the indoor unit 4, it is possible to cause high-temperature refrigerant to flow into the outdoor heat exchanger 30 while liquid refrigerant is stored in the indoor unit 4.

[0157] That is, in the defrosting operation of the air conditioning device 1G, the occurrence of liquid backflow is reduced without using heat from a pipe heated by high-temperature gas refrigerant in the heating operation. Therefore, the air conditioning device 1G according to Embodiment 8 can continuously reduce the occurrence of liquid backflow to the accumulators 50 in the defrosting operation. Furthermore, in the air conditioning device 1G according to Embodiment 8, neither the high-pressure gas main pipe 102 nor the liquid main pipe 103 cools during the defrosting operation, and the operation can return to the heating operation early.

[0158] Although the embodiments of the present invention are described above, the present invention is not limited to the configurations of the embodiments. Various modifications or combinations of the configurations can be made within the technical concept of the present invention. For example, the liquid removal process may be performed not only based on the measurement result by the liquid accumulation detection device 8, but also at predetermined time intervals. Alternatively, the liquid removal process may be performed at predetermined time intervals instead of based on the measurement result by the liquid accumulation detection device 8.

[0159] In addition, although the above description is made by referring to the example case where the heating operation and the cooling operation are performed in both or all of the indoor units 4, a simultaneous cooling and heating operation may also be performed in which one of the indoor units 4 performs the cooling operation and the other indoor unit 4 performs the heating operation. In addition, although the above description is made by referring to the example case where the defrosting operation is performed after the heating operation and the liquid removal operation is performed after the cooling operation, the order in which each operation is performed is not limited to that in the above case. List of reference symbols 1 air conditioning device 1A air conditioning device 1B Air conditioning device 1C Air conditioning device 1D air conditioning device 1E Air conditioning device 1F Air conditioning device 1G Air conditioning device 2 outdoor units 2a first outdoor unit 2b second outdoor unit 3 forwarding unit 4 indoor unit 4a first indoor unit 4b second indoor unit 5 Control device 6 Frost detection device 7 De-icing detection device 8 Liquid accumulation detection device 10 Compressor 10a first compressor 10b second compressor 21 Flow switching device on the heat exchanger side 21a first flow switching device on the heat exchanger side 21b second flow switching device on the heat exchanger side 22 Flow switching device on the high-pressure pipe side 22a first flow switching device on the high-pressure pipe side 22b second flow switching device on the high-pressure pipe side 30 outdoor heat exchangers 30a first outdoor heat exchanger 30b second outdoor heat exchanger 40 Outdoor expansion valve 40a first outdoor expansion valve 40b second outdoor expansion valve 50 accumulator 50a first accumulator 50b second accumulator 60 Bypass valve 71 Low pressure valve 71a first low-pressure valve 71b second low-pressure valve 72 High pressure valve 72a first high-pressure valve 72b second high-pressure valve 73 Medium pressure valve 73a first medium pressure valve 73b second medium pressure valve 80 interior heat exchangers 80a first interior heat exchanger 80b second interior heat exchanger 90 Interior expansion valve 90a first interior expansion valve 90b second interior expansion valve 101 Low-pressure gas main pipe 102 High-pressure gas main pipe 103 Liquid main pipe 104 Gas branch pipe 104a first gas branch pipe 104b second gas branch pipe 105 Liquid branch pipe 105a first liquid branch pipe 105b second liquid branch pipe 201 Outdoor pipe 202 outdoor pipe 203 Outdoor pipe 204 Outdoor pipe 205 Outdoor pipe 206 intake manifold 207 Outlet pipe 301 forwarding gas pipe 302 High pressure gas branch pipe 303 Low-pressure gas branch pipe 304 Transfer Fluid Pipe 305 bypass pipe 401a first interior tube 401b second interior pipe 501 processing circuit 502 processor 503 memory 504 Bus QUOTES CONTAINED IN THE DESCRIPTION

[0000] This list of documents submitted by the applicant was generated automatically and is included solely for the convenience of the reader. This list is not part of the German patent or utility model application. The DPMA assumes no liability for any errors or omissions. Cited patent literature

[0000] JP 2017 - 26 171 A

[0004]

Claims

[1] Air conditioning device comprising: an outdoor unit comprising a compressor configured to compress a refrigerant, an accumulator configured to store the refrigerant, and an outdoor heat exchanger configured to cause heat exchange to be performed between the refrigerant and air; at least one indoor unit having an indoor heat exchanger configured to cause heat exchange to be performed between the refrigerant and air; and a transfer unit configured to allow or block the flow of refrigerant between the outdoor unit and the at least one indoor unit, wherein the outdoor unit and the transfer unit are connected by means of a low-pressure gas main pipe, a high-pressure gas main pipe and a liquid main pipe, wherein the low-pressure gas main pipe is configured as a pipe through which gaseous refrigerant flows, wherein the high-pressure gas main pipe is configured as a pipe through which gaseous refrigerant flows at a higher pressure than the gaseous refrigerant flowing through the low-pressure gas main pipe, wherein the liquid main pipe is configured as a pipe through which liquid refrigerant flows, wherein the transfer unit and the at least one indoor unit are connected by means of a gas branch pipe and a liquid branch pipe, wherein the gas branch pipe is configured as a pipe through which gaseous refrigerant flows, wherein the liquid branch pipe is configured as a pipe through which liquid refrigerant flows, and wherein the forwarding unit comprises: a forwarding gas pipe connecting the gas branch pipe, the high-pressure gas main pipe, and the low-pressure gas main pipe, the forwarding gas pipe comprising a high-pressure gas branch pipe connected to the high-pressure gas main pipe and a low-pressure gas branch pipe connected to the low-pressure gas main pipe, a transfer liquid pipe connecting the liquid main pipe and the liquid branch pipe, a bypass pipe connecting the high-pressure gas branch pipe and the forwarding liquid pipe, and a bypass valve arranged on the bypass pipe, the bypass valve having a function of performing switching so that the state of the bypass valve is switched between an open state in which the bypass valve allows the refrigerant to flow through the bypass pipe and a closed state in which the bypass valve blocks the flow of refrigerant through the bypass pipe. [2] Air conditioning device according to claim 1, further comprising a control device configured to control the execution of a cooling operation and a heating operation, wherein the outdoor unit further comprises: an outdoor expansion valve which is continuous to expand the refrigerant, and a flow switching device on the heat exchanger side configured to perform switching so that the state of the flow switching device on the heat exchanger side is switched between a state in which the flow switching device on the heat exchanger side connects the outdoor heat exchanger and the compressor and a state in which the flow switching device on the heat exchanger side connects the outdoor heat exchanger and the accumulator, wherein the forwarding unit further comprises: a high-pressure valve arranged on the high-pressure gas branch pipe, the high-pressure valve having the function of performing a switching operation so that the state of the high-pressure valve is switched between an open state in which the high-pressure valve allows the refrigerant to flow through the high-pressure gas branch pipe and a closed state in which the high-pressure valve blocks the flow of refrigerant through the high-pressure gas branch pipe, and a low-pressure valve arranged on the low-pressure gas branch pipe, the low-pressure valve having the function of performing a switching operation so that the state of the low-pressure valve is switched between an open state in which the low-pressure valve allows the refrigerant to flow through the low-pressure gas branch pipe and a closed state in which the low-pressure valve blocks the flow of the refrigerant through the low-pressure gas branch pipe, and wherein the at least one indoor unit further comprises an indoor expansion valve configured to expand the refrigerant. [3] Air conditioning device according to claim 2, wherein the at least one indoor unit is configured as a plurality of indoor units, wherein, when all of the plurality of indoor units are in heating operation, the refrigerant circulates through the compressor, the high-pressure valve, the indoor heat exchanger, the indoor expansion valve, the outdoor expansion valve, the outdoor heat exchanger, the flow switching device on the heat exchanger side, and the accumulator in this order, and wherein, when all of the plurality of indoor units are in the cooling operation, the refrigerant circulates through the compressor, the heat exchanger side flow switching device, the outdoor heat exchanger, the outdoor expansion valve, the indoor expansion valve, the indoor heat exchanger, the low pressure valve, and the accumulator in this order. [4] Air conditioning device according to claim 2 or 3, wherein the control device is configured to control the execution of a defrosting operation for removing frost that forms on the outdoor heat exchanger in the heating operation, and wherein the control device is configured to perform the following control in defrosting mode: Switching the state of the flow switching device on the heat exchanger side to the position where the flow switching device on the heat exchanger side connects the outdoor heat exchanger and the accumulator, Ensure that the bypass valve is in the open state, Opening the outdoor expansion valve, Closing the interior expansion valve, and Ensure that the low pressure valve is in the closed position. [5] The air conditioning device according to claim 2, wherein the outdoor unit further comprises a high-pressure pipe side flow switching device configured to perform switching such that the state of the high-pressure pipe side flow switching device is switched between a state in which the high-pressure pipe side flow switching device connects the high-pressure gas main pipe and the compressor and a state in which the high-pressure pipe side flow switching device connects the high-pressure gas main pipe and the accumulator. [6] Air conditioning device according to claim 5, wherein the at least one indoor unit is configured as a plurality of indoor units, wherein, when all of the plurality of indoor units are in heating operation, the refrigerant circulates through the compressor, the high-pressure pipe-side flow switching device, the high-pressure valve, the indoor heat exchanger, the indoor expansion valve, the outdoor expansion valve, the outdoor heat exchanger, the heat exchanger-side flow switching device, and the accumulator in this order, and wherein, when all of the plurality of indoor units are in the cooling operation, the refrigerant circulates through the compressor, the heat exchanger side flow switching device, the outdoor heat exchanger, the outdoor expansion valve, the indoor expansion valve, the indoor heat exchanger, the low pressure valve, and the accumulator in this order. [7] Air conditioning device according to claim 5 or 6, wherein the control device is configured to control the execution of a defrosting operation for removing frost that forms on the outdoor heat exchanger in the heating operation, and wherein the control device is configured to perform the following control in defrosting mode: Switching the state of the flow switching device on the heat exchanger side to the state in which the flow switching device on the heat exchanger side connects the outdoor heat exchanger and the accumulator, Causing the state of the flow switching device on the high-pressure pipe side to be in the state where the flow switching device on the high-pressure pipe side connects the high-pressure gas main pipe and the compressor, Ensure that the bypass valve is in the open state, Opening the outdoor expansion valve, Closing the interior expansion valve, and Ensure that the low pressure valve is in the closed position. [8] The air conditioning device according to any one of claims 2 to 7, wherein the relay unit includes a medium-pressure valve disposed between a part of the relay liquid pipe connected to the bypass pipe and a part of the relay liquid pipe connected to the liquid branch pipe, the medium-pressure valve having a function of switching such that the state of the medium-pressure valve is switched between an open state in which the medium-pressure valve allows refrigerant to flow through the relay liquid pipe and a closed state in which the medium-pressure valve blocks the refrigerant to flow through the relay liquid pipe. [9] An air conditioning device according to claim 8 when dependent on claim 2 or 3, wherein the control device is configured to control the execution of a defrosting operation for removing frost that forms on the outdoor heat exchanger in the heating operation, and wherein the control device is configured to perform the following control in defrosting mode: Switching the state of the flow switching device on the heat exchanger side to the state in which the flow switching device on the heat exchanger side connects the outdoor heat exchanger and the accumulator, Ensure that the bypass valve is in the open state, Opening the outdoor expansion valve, Ensure that the medium pressure valve is in the closed state, and Ensure that the low pressure valve is in the closed position. [10] An air conditioning device according to claim 8 when dependent on claim 5 or 6, wherein the control device is configured to control the execution of a defrosting operation for removing frost that forms on the outdoor heat exchanger in the heating operation, and wherein the control device is configured to perform the following control in defrosting mode: Switching the state of the flow switching device on the heat exchanger side to the state in which the flow switching device on the heat exchanger side connects the outdoor heat exchanger and the accumulator, Causing the state of the flow switching device on the high-pressure pipe side to be in the state where the flow switching device on the high-pressure pipe side connects the high-pressure gas main pipe and the compressor, Ensure that the bypass valve is in the open state, Opening the outdoor expansion valve, Ensure that the medium pressure valve is in the closed state, and Ensure that the low pressure valve is in the closed position. [11] The air conditioning device according to any one of claims 2 to 7, wherein the control means is configured to close the high pressure valve in the cooling operation. [12] The air conditioning device according to claim 11, wherein the control means is configured to cause the bypass valve to be in the open state and to perform a liquid removal operation so that liquid refrigerant accumulated in the high-pressure gas main pipe is removed when, in the cooling operation, accumulation of liquid in the high-pressure gas main pipe is detected. [13] The air conditioning device according to claim 11, wherein the control means is configured to, in the cooling operation, cause the bypass valve to be in the open state at predetermined time intervals and perform a liquid removal operation for removing liquid refrigerant accumulated in the high-pressure gas main pipe.

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