Refrigerant container and refrigeration cycle device

Abstract

Provided are a refrigerant container and a refrigeration cycle device capable of suppressing the accumulation of refrigeration oil inside. A secondary side receiver (45) stores refrigerant in a secondary side refrigerant circuit (10) for circulating refrigerant and refrigeration oil, comprising: a container body (90), a first refrigerant pipe (96) connected to the container body (90), and a second refrigerant pipe (97) connected to the container body (90), wherein the refrigeration oil is immiscible with the refrigerant and has a density greater than that of the refrigerant, and the second refrigerant pipe (97) extends downward from the bottom (93) of the container body (90).

Description

Technical Field

[0001] The invention relates to a refrigerant container and a refrigeration cycle device. Background Art

[0002] Conventionally, a receiver for storing refrigerant is used in a refrigerant circuit included in a refrigeration cycle apparatus.

[0003] As such a refrigeration cycle device, for example, in the refrigeration cycle device described in Patent Document 1 (Japanese Patent Laid-Open No. 2008-164225), carbon dioxide refrigerant is used as refrigerant, and immiscible PAG oil is used as refrigeration oil. In this refrigeration cycle device, in order to prevent the refrigeration oil from accumulating at the bottom of a refrigerant container such as a receiver, it is proposed that the outlet pipe connected to the side circumference of the refrigerant container is cut obliquely near the front end located inside the refrigerant container, and arranged in such a way that the front end contacts the bottom of the refrigerant container. Summary of the invention

[0004] Technical problem to be solved by the invention

[0005] The above arrangement can suppress the refrigeration oil from remaining in the refrigerator container. However, since the opening at the front end of the outlet pipe is inclined, the refrigeration oil may continue to accumulate at a position lower than the upper end of the outlet pipe opening in the refrigerant container.

[0006] Technical solutions adopted to solve technical problems

[0007] The refrigerant container of the first viewpoint is a refrigerant container for storing refrigerant in a refrigerant circuit. In the refrigerant circuit, refrigerant and refrigerating machine oil circulate. The refrigerant container includes a container body, a first refrigerant pipe, and a second refrigerant pipe. The first refrigerant pipe is connected to the container body. The second refrigerant pipe is connected to the container body. The refrigerating machine oil is immiscible with the refrigerant. The density of the refrigerating machine oil is greater than the density of the refrigerant. The second refrigerant pipe extends downward from the bottom of the container body.

[0008] Furthermore, the first refrigerant pipe may introduce the refrigerant into the container body, and the second refrigerant pipe may lead the refrigerant out of the container body.

[0009] In addition, the refrigerating machine oil and the refrigerant are immiscible, which means that the refrigerant and the refrigerating machine oil are separated and do not form a uniform layer of liquid in a refrigerant container under the use environment of the refrigerant and the refrigerating machine oil.

[0010] In addition, the fact that the density of the refrigeration oil is greater than the density of the refrigerant means that, in the use environment of the refrigerant and the refrigeration oil, the density of the refrigeration oil is greater than the density of the liquid refrigerant.

[0011] In this refrigerant container, the refrigeration oil is suppressed from accumulating on the bottom portion in the refrigerant container.

[0012] The refrigerant container according to the second aspect is the refrigerant container according to the first aspect, wherein the height position of the upper end of the second refrigerant tube is lower than a position 15 mm higher than the lowest end of the inner peripheral surface of the bottom of the container body.

[0013] In addition, it is preferable that the height position of the upper end of the second refrigerant pipe is 10 mm or less higher than the lowermost end of the inner peripheral surface of the bottom of the container body.

[0014] In this refrigerant container, the refrigerating machine oil in the refrigerant container can be easily guided to the second refrigerant pipe.

[0015] The refrigerant container according to the third aspect is the refrigerant container according to the first aspect or the second aspect, wherein the bottom of the container body has a curved portion convex downward, and the second refrigerant pipe extends downward from a lower end of the curved portion.

[0016] In this refrigerant container, the refrigeration oil in the refrigerant container is easily guided to the second refrigerant pipe by its own weight due to the bent shape of the bottom.

[0017] The refrigerant container of the fourth aspect is the refrigerant container of any one of the first to third aspects, wherein the refrigerant container is a high-pressure receiver which is provided at a location in the refrigerant circuit where the high-pressure refrigerant flows and stores the high-pressure refrigerant therein.

[0018] In this refrigerant container, accumulation of refrigeration oil when used as a high-pressure receiver is suppressed.

[0019] The refrigerant container of the fifth aspect is the refrigerant container of any one of the first to third aspects, wherein the refrigerant circuit has a portion through which the high-pressure refrigerant, the low-pressure refrigerant, and the intermediate-pressure refrigerant flow. The refrigerant container is an intermediate-pressure receiver. The intermediate-pressure receiver is provided at a portion through which the intermediate-pressure refrigerant flows in the refrigerant circuit and stores the intermediate-pressure refrigerant therein.

[0020] In this refrigerant container, accumulation of refrigeration oil when used as an intermediate pressure receiver is suppressed.

[0021] The refrigerant container of the sixth aspect is based on the refrigerant container of any one of the first to fifth aspects, and the refrigerant container further includes a third refrigerant pipe. The refrigerant circuit has a compressor. The third refrigerant pipe is connected to the container body and guides the refrigerant in the container body to the suction side of the compressor.

[0022] In this refrigerant container, even if the third refrigerant pipe is a pipe mainly used to extract the gas refrigerant in the refrigerant container, it is possible to suppress the accumulation of refrigeration oil in the refrigerant container.

[0023] A refrigerant container according to a seventh aspect is the refrigerant container according to any one of the first to sixth aspects, wherein the refrigerant is a refrigerant containing carbon dioxide refrigerant.

[0024] In this refrigerant container, when a carbon dioxide refrigerant and a refrigeration oil that is incompatible with the carbon dioxide refrigerant are used, accumulation of the refrigeration oil in the refrigerant container is suppressed.

[0025] A refrigerant container according to an eighth aspect is the refrigerant container according to any one of the first to seventh aspects, wherein the refrigeration oil is PAG oil (polyalkylene glycol oil).

[0026] In this refrigerant container, accumulation of the PAG oil in the refrigerant container is suppressed.

[0027] A refrigeration cycle device according to a ninth aspect includes the refrigerant container according to any one of the first to eighth aspects.

[0028] In this refrigeration cycle device, the refrigeration cycle can be performed while suppressing the accumulation of refrigeration oil in the refrigerant container.

[0029] The refrigeration cycle device of the tenth viewpoint is based on the refrigeration cycle device of the ninth viewpoint, and the refrigeration cycle device includes a first refrigerant circuit, a second refrigerant circuit and a cascade heat exchanger. The first refrigerant circuit is for refrigerant to flow. The second refrigerant circuit is the refrigerant circuit of the refrigeration cycle device of the eighth viewpoint, and is a refrigerant circuit independent of the first refrigerant circuit. In the cascade heat exchanger, heat exchange is performed between the refrigerant flowing in the first refrigerant circuit and the refrigerant flowing in the second refrigerant circuit. The refrigerant of the second refrigerant circuit that is cooled by the refrigerant of the first refrigerant circuit in the cascade heat exchanger and becomes a liquid refrigerant is stored in a refrigerant container.

[0030] In this refrigeration cycle device, the refrigerant flowing in the second refrigerant circuit exchanges heat with the refrigerant flowing in the first refrigerant circuit in the cascade heat exchanger, thereby adjusting the state of the refrigerant sent to the refrigerant container through the cascade heat exchanger. BRIEF DESCRIPTION OF THE DRAWINGS

[0031] Figure 1 This is a schematic diagram of the refrigeration cycle device.

[0032] Figure 2 This is a schematic functional block diagram of a refrigeration cycle device.

[0033] Figure 3 It is a diagram showing the operation (flow of refrigerant) of the refrigeration cycle device during cooling operation.

[0034] Figure 4 It is a diagram showing the operation (flow of refrigerant) of the refrigeration cycle device during the heating operation.

[0035] Figure 5 This is a diagram showing the operation (flow of refrigerant) of the refrigeration cycle device in the simultaneous cooling and heating operation (cooling main operation).

[0036] Figure 6 This is a diagram showing the operation (flow of refrigerant) of the refrigeration cycle device in the simultaneous cooling and heating operation (heating main operation).

[0037] Figure 7 This is a schematic diagram of the secondary side receiver.

[0038] Figure 8 This is a schematic diagram of the secondary side receiver of another embodiment A.

[0039] Fig. 9 This is a schematic structural diagram of a secondary side receiver according to another embodiment B.

[0040] Fig.10 This is a schematic structural diagram of a secondary side receiver of another embodiment C.

[0041] Fig.11 This is a schematic structural diagram of a secondary side receiver according to another embodiment D.

[0042] Fig.12 This is a schematic structural diagram of a refrigerant circuit including an intermediate pressure receiver according to another embodiment E.

[0043] Fig.13 This is a schematic structural diagram of a refrigeration cycle device according to another embodiment F. DETAILED DESCRIPTION

[0044] (1) Structure of Refrigeration Cycle Device

[0045] Figure 1 It is a schematic structural diagram of the refrigeration cycle device 1. Figure 2 This is a schematic functional block diagram of the refrigeration cycle device 1.

[0046] The refrigeration cycle device 1 is a device used for cooling and heating indoors in a building or the like by performing a vapor compression refrigeration cycle operation.

[0047] The refrigeration cycle device 1 has a binary refrigerant circuit composed of a vapor compression type primary refrigerant circuit 5a (equivalent to the first refrigerant circuit) and a vapor compression type secondary refrigerant circuit 10 (equivalent to the second refrigerant circuit), and performs a binary refrigeration cycle. In the present embodiment, as a refrigerant, R32 or R410A, etc. are sealed in the primary refrigerant circuit 5a. As a refrigerant, carbon dioxide, for example, is sealed in the secondary refrigerant circuit 10. In addition, in the secondary refrigerant circuit 10, a refrigeration oil that is incompatible with the refrigerant is used as a refrigeration oil that circulates in the circuit together with the refrigerant and improves the lubricity of sliding parts, etc. In the use state, the density of the refrigeration oil is greater than the density of the refrigerant and the specific gravity is large, so it is often located below the refrigerant. In the present embodiment, PAG oil (polyhydroxyethylene glycol oil) that is incompatible with carbon dioxide as a refrigerant and has a density greater than that of carbon dioxide is used.

[0048] The primary refrigerant circuit 5 a and the secondary refrigerant circuit 10 are thermally connected via a cascade heat exchanger 35 to be described later.

[0049] The refrigeration cycle device 1 is configured in such a manner that a primary side unit 5, a cascade unit 2, a plurality of branch units 6a, 6b, 6c, and a plurality of utilization units 3a, 3b, 3c are connected to each other via pipes. The primary side unit 5 and the cascade unit 2 are connected by a primary side first communication pipe 111 and a primary side second communication pipe 112. The cascade unit 2 and the plurality of branch units 6a, 6b, 6c are connected by three refrigerant communication pipes: a secondary side second communication pipe 9, a secondary side first communication pipe 8, and a secondary side third communication pipe 7. The plurality of branch units 6a, 6b, 6c and the plurality of utilization units 3a, 3b, 3c are connected by first connection pipes 15a, 15b, 15c and second connection pipes 16a, 16b, 16c. In the present embodiment, the primary side unit 5 is one. In the present embodiment, the cascade unit 2 is one. In the present embodiment, the plurality of utilization units 3a, 3b, 3c are three, namely, the first utilization unit 3a, the second utilization unit 3b, and the third utilization unit 3c. In the present embodiment, the plurality of branching units 6a, 6b, and 6c are three units of a first branching unit 6a, a second branching unit 6b, and a third branching unit 6c.

[0050] Furthermore, in the refrigeration cycle device 1, each utilization unit 3a, 3b, 3c is configured to be able to perform cooling operation or heating operation independently, and to be able to perform heat recovery between the utilization units by transferring refrigerant from the utilization unit performing heating operation to the utilization unit performing cooling operation. Specifically, in the present embodiment, heat recovery is performed by executing cooling main operation and heating main operation in which cooling operation and heating operation are performed simultaneously. Furthermore, in the refrigeration cycle device 1, it is configured to balance the heat load of the cascade unit 2 based on the overall heat load of the plurality of utilization units 3a, 3b, 3c in which the above-mentioned heat recovery (cooling main operation, heating main operation) is also considered.

[0051] (2) Primary refrigerant circuit

[0052] The primary refrigerant circuit 5a includes a primary compressor 71, a primary switching mechanism 72, a primary heat exchanger 74, a primary first expansion valve 76, a primary subcooling heat exchanger 103, a primary subcooling circuit 104, a primary subcooling expansion valve 104a, a first liquid stop valve 108, a primary first connecting pipe 111, a second liquid stop valve 106, a second refrigerant pipe 114, a primary second expansion valve 102, a cascade heat exchanger 35 common to the secondary refrigerant circuit 10, a first refrigerant pipe 113, a second gas stop valve 107, a primary second connecting pipe 112, a first gas stop valve 109, and a primary accumulator 105. Specifically, the primary refrigerant circuit 5a includes a primary flow path 35b of the cascade heat exchanger 35.

[0053] The primary-side compressor 71 is a device for compressing the primary-side refrigerant, and is constituted by, for example, a positive displacement compressor such as a scroll type whose operating capacity can be varied by performing inverter control on the compressor motor 71 a.

[0054] The primary-side accumulator 105 is provided in the middle of the suction flow path connecting the primary-side switching mechanism 72 and the suction side of the primary-side compressor 71 .

[0055] When the cascade heat exchanger 35 functions as an evaporator of the primary-side refrigerant, the primary-side switching mechanism 72 is in a fifth connection state (see Figure 1 In addition, when the cascade heat exchanger 35 is used as a heat sink for the primary refrigerant, the primary switching mechanism 72 is changed to a sixth connection state (see FIG. 1 ) that connects the discharge side of the primary compressor 71 and the gas side of the primary flow path 35b of the cascade heat exchanger 35. Figure 1In this way, the primary side switching mechanism 72 is a device capable of switching the flow path of the refrigerant in the primary side refrigerant circuit 5a, and is composed of, for example, a four-way switching valve. And, by changing the switching state of the primary side switching mechanism 72, the cascade heat exchanger 35 can function as an evaporator or radiator of the primary side refrigerant.

[0056] The cascade heat exchanger 35 is a device for performing heat exchange between a refrigerant such as R32 as a primary refrigerant and a refrigerant such as carbon dioxide as a secondary refrigerant without mixing with each other. The cascade heat exchanger 35 is composed of, for example, a plate heat exchanger. The cascade heat exchanger 35 has a secondary side flow path 35a belonging to the secondary side refrigerant circuit 10 and a primary side flow path 35b belonging to the primary side refrigerant circuit 5a. The gas side of the secondary side flow path 35a is connected to the secondary side switching mechanism 22 via the third pipe 25, and the liquid side of the secondary side flow path 35a is connected to the cascade expansion valve 36 via the fourth pipe 26. The gas side of the primary side flow path 35b is connected to the primary side compressor 71 via the first refrigerant piping 113, the second gas stop valve 107, the primary side second connecting pipe 112, the first gas stop valve 109, and the primary side switching mechanism 72, and the liquid side of the primary side flow path 35b is connected via the second refrigerant piping 114 provided with the primary side second expansion valve 102.

[0057] The primary side heat exchanger 74 is a device for performing heat exchange between the primary side refrigerant and the outdoor air. The gas side of the primary side heat exchanger 74 is connected to the pipe extending from the primary side switching mechanism 72. The primary side heat exchanger 74 is composed of, for example, a fin-tube heat exchanger composed of a plurality of heat transfer tubes and fins.

[0058] The first primary expansion valve 76 is provided in the liquid piping extending from the liquid side of the primary heat exchanger 74 to the primary subcooling heat exchanger 103. The first primary expansion valve 76 is an electric expansion valve capable of adjusting the opening degree, and performs the adjustment of the flow rate of the primary refrigerant flowing in the liquid side portion of the primary refrigerant circuit 5a.

[0059] The primary side subcooling circuit 104 branches from between the primary side first expansion valve 76 and the primary side subcooling heat exchanger 103, and is connected to the portion of the suction flow path between the primary side switching mechanism 72 and the primary side accumulator 105. The primary side subcooling expansion valve 104a is an electric expansion valve capable of adjusting the opening degree, and is provided at the upstream side of the primary side subcooling heat exchanger 103 in the primary side subcooling circuit 104 to adjust the flow rate of the primary side refrigerant, etc.

[0060] The primary subcooling heat exchanger 103 is a heat exchanger that exchanges heat between the refrigerant flowing from the primary first expansion valve 76 toward the first liquid stop valve 108 and the refrigerant decompressed in the primary subcooling expansion valve 104 a in the primary subcooling circuit 104 .

[0061] The primary-side first communication pipe 111 is a pipe that connects the first liquid stop valve 108 and the second liquid stop valve 106 , and connects the primary-side unit 5 and the cascade unit 2 .

[0062] The primary-side second communication pipe 112 is a pipe that connects the first gas shutoff valve 109 and the second gas shutoff valve 107 , and connects the primary-side unit 5 and the cascade unit 2 .

[0063] The second refrigerant pipe 114 is a pipe extending from the liquid side of the primary-side flow path 35 b of the cascade heat exchanger 35 to the second liquid stop valve 106 .

[0064] The second primary expansion valve 102 is provided in the second refrigerant pipe 114. The second primary expansion valve 102 is an electric expansion valve capable of adjusting the opening degree for adjusting the flow rate of the primary refrigerant flowing in the primary flow path 35b of the cascade heat exchanger 35.

[0065] The first refrigerant pipe 113 is a pipe extending from the gas side of the primary-side flow path 35 b of the cascade heat exchanger 35 to the second gas shutoff valve 107 .

[0066] The first gas shutoff valve 109 is provided between the primary-side second communication pipe 112 and the primary-side switching mechanism 72 .

[0067] (3) Secondary refrigerant circuit

[0068] The secondary refrigerant circuit 10 is constructed in a manner that a plurality of utilization units 3a, 3b, 3c, a plurality of branch units 6a, 6b, 6c and a cascade unit 2 are connected to each other. Each utilization unit 3a, 3b, 3c is connected one-to-one with the corresponding branch unit 6a, 6b, 6c. Specifically, the utilization unit 3a and the branch unit 6a are connected via the first connecting pipe 15a and the second connecting pipe 16a, the utilization unit 3b and the branch unit 6b are connected via the first connecting pipe 15b and the second connecting pipe 16b, and the utilization unit 3c and the branch unit 6c are connected via the first connecting pipe 15c and the second connecting pipe 16c. In addition, each branch unit 6a, 6b, 6c is connected to the cascade unit 2 via three connecting pipes, namely, the secondary side third connecting pipe 7, the secondary side first connecting pipe 8 and the secondary side second connecting pipe 9. Specifically, the secondary side third communicating pipe 7, the secondary side first communicating pipe 8, and the secondary side second communicating pipe 9 extending from the cascade unit 2 are respectively branched into a plurality of pipes and connected to the branching units 6a, 6b, 6c.

[0069] Depending on the operating state, either the refrigerant in the gas-liquid two-phase state or the refrigerant in the gas state flows in the secondary-side first connecting tube 8. Also, depending on the operating state, the refrigerant in the supercritical state flows in the secondary-side first connecting tube 8. Depending on the operating state, either the refrigerant in the gas-liquid two-phase state or the refrigerant in the gas state flows in the secondary-side second connecting tube 9. Depending on the operating state, either the refrigerant in the gas-liquid two-phase state or the refrigerant in the liquid state flows in the secondary-side third connecting tube 7. Also, depending on the operating state, the refrigerant in the supercritical state flows in the secondary-side third connecting tube 7.

[0070] The secondary refrigerant circuit 10 is configured such that a cascade circuit 12 , branch circuits 14 a , 14 b , 14 c , and utilization circuits 13 a , 13 b , 13 c are connected to one another.

[0071] The cascade circuit 12 mainly includes a secondary compressor 21, a secondary switching mechanism 22, a first pipe 28, a second pipe 29, a suction flow path 23, a discharge flow path 24, a third pipe 25, a fourth pipe 26, a fifth pipe 27, a cascade heat exchanger 35, a cascade expansion valve 36, a third stop valve 31, a first stop valve 32, a second stop valve 33, a secondary accumulator 30, an oil separator 34, an oil return circuit 40, a secondary receiver 45 (equivalent to a refrigerant container), a bypass circuit 46, a bypass expansion valve 46a, a secondary subcooling heat exchanger 47, a secondary subcooling circuit 48, and a secondary subcooling expansion valve 48a. Specifically, the cascade circuit 12 of the secondary refrigerant circuit 10 includes a secondary flow path 35a of the cascade heat exchanger 35.

[0072] The secondary compressor 21 is a device for compressing the secondary refrigerant, and is composed of a positive displacement compressor such as a scroll type that can make the operating capacity variable by inverter control of the compressor motor 21a. In addition, the secondary compressor 21 is controlled so that the operating capacity increases as the load increases according to the load during operation.

[0073] The secondary side switching mechanism 22 is a mechanism capable of switching the connection state of the secondary side refrigerant circuit 10, especially the flow path of the refrigerant in the cascade circuit 12. In the present embodiment, the secondary side switching mechanism 22 has a discharge side communication portion 22x, a suction side communication portion 22y, a first switching valve 22a, and a second switching valve 22b. The discharge side communication portion 22x is connected to the end of the discharge flow path 24 on the side opposite to the secondary side compressor 21. The suction side communication portion 22y is connected to the end of the suction flow path 23 on the side opposite to the secondary side compressor 21. The first switching valve 22a and the second switching valve 22b are arranged in parallel with each other between the discharge flow path 24 and the suction flow path 23 of the secondary side compressor 21. The first switching valve 22a is connected to one end of the discharge side communication portion 22x and one end of the suction side communication portion 22y. The second switching valve 22b is connected to the other end of the discharge side communication portion 22x and the other end of the suction side communication portion 22y. In the present embodiment, the first switching valve 22a and the second switching valve 22b are both composed of four-way reversing valves. The first switching valve 22a and the second switching valve 22b respectively have four connection ports, namely, a first connection port, a second connection port, a third connection port and a fourth connection port. In the first switching valve 22a and the second switching valve 22b of the present embodiment, each fourth port is a connection port that is closed and not connected to the flow path of the secondary refrigerant circuit 10. In the first switching valve 22a, the first connection port is connected to one end of the discharge side communication part 22x, the second connection port is connected to the third pipe 25 extending from the secondary side flow path 35a of the cascade heat exchanger 35, and the third connection port is connected to one end of the suction side communication part 22y. The first switching valve 22a switches the switching state in which the first connection port is connected to the second connection port and the third connection port is connected to the fourth connection port and the switching state in which the third connection port is connected to the second connection port and the first connection port is connected to the fourth connection port. In the second switching valve 22b, the first connection port is connected to the other end of the discharge-side communication portion 22x, the second connection port is connected to the first pipe 28, and the third connection port is connected to the other end of the suction-side communication portion 22y. The second switching valve 22b switches between a switching state in which the first connection port is connected to the second connection port and the third connection port is connected to the fourth connection port, and a switching state in which the third connection port is connected to the second connection port and the first connection port is connected to the fourth connection port.

[0074] When the cascade heat exchanger 35 functions as a radiator of the secondary refrigerant and the secondary refrigerant discharged from the secondary compressor 21 is prevented from being transported to the secondary first connecting pipe 8, the secondary switching mechanism 22 is switched to a first connection state in which the discharge flow path 24 and the third pipe 25 are connected through the first switching valve 22 and the first pipe 28 and the suction flow path 23 are connected through the second switching valve 22b. The first connection state of the secondary switching mechanism 22 is a connection state adopted in the cooling operation described later. In addition, when the cascade heat exchanger 35 functions as an evaporator of the secondary refrigerant, the secondary switching mechanism 22 is switched to a second connection state in which the discharge flow path 24 and the first pipe 28 are connected through the second switching valve 22b and the third pipe 25 and the suction flow path 23 are connected through the first switching valve 22a. The second connection state of the secondary switching mechanism 22 is a connection state adopted in the heating operation described later and the heating main operation. Furthermore, when the cascade heat exchanger 35 functions as a radiator of the secondary refrigerant and the secondary refrigerant discharged from the secondary compressor 21 is delivered to the secondary first connecting pipe 8, the secondary switching mechanism 22 is switched to a third connection state in which the discharge flow path 24 and the third piping 25 are connected via the first switching valve 22a and the discharge flow path 24 and the first piping 28 are connected via the second switching valve 22b. The third connection state of the secondary switching mechanism 22 is a connection state adopted during the refrigeration main operation described later.

[0075] As described above, the cascade heat exchanger 35 is a device for performing heat exchange between a refrigerant such as R32 as a primary refrigerant and a refrigerant such as carbon dioxide as a secondary refrigerant without mixing with each other. In addition, the cascade heat exchanger 35 has a secondary side flow path 35a for the secondary side refrigerant of the secondary side refrigerant circuit 10 to flow and a primary side flow path 35b for the primary side refrigerant of the primary side refrigerant circuit 5a to flow, and is thus shared by the primary side unit 5 and the cascade unit 2. In addition, in the present embodiment, the cascade heat exchanger 35 is arranged inside the cascade shell (not shown) of the cascade unit 2. The gas side of the primary side flow path 35b of the cascade heat exchanger 35 passes through the first refrigerant piping 113 and the second gas stop valve 107, and extends to the primary side second connecting pipe 112 outside the cascade shell. The liquid side of the primary flow path 35b of the cascade heat exchanger 35 passes through the second refrigerant pipe 114 provided with the primary second expansion valve 102 and the second liquid stop valve 106, and extends to the primary first communication pipe 111 outside the cascade shell.

[0076] The cascade expansion valve 36 is an expansion valve for adjusting the flow rate of the secondary side refrigerant flowing in the cascade heat exchanger 35. The cascade expansion valve 36 is an electric expansion valve connected to the liquid side of the cascade heat exchanger 35 and capable of adjusting the opening degree. The cascade expansion valve 36 is provided in the fourth pipe 26.

[0077] The third stop valve 31, the first stop valve 32, and the second stop valve 33 are valves provided at the connection ports with external equipment and piping (specifically, the connecting pipes 7, 8, and 9). Specifically, the third stop valve 31 is connected to the secondary side third connecting pipe 7 drawn out from the cascade unit 2. The first stop valve 32 is connected to the secondary side first connecting pipe 8 drawn out from the cascade unit 2. The second stop valve 33 is connected to the secondary side second connecting pipe 9 drawn out from the cascade unit 2.

[0078] The first pipe 28 is a refrigerant pipe that connects the first stop valve 32 and the secondary-side switching mechanism 22. Specifically, the first pipe 28 connects the first stop valve 32 and the second connection port of the second switching valve 22b in the secondary-side switching mechanism 22.

[0079] The suction flow path 23 is a flow path that connects the secondary side switching mechanism 22 and the suction side of the secondary side compressor 21. Specifically, the suction flow path 23 connects the suction side communication portion 22y in the secondary side switching mechanism 22 and the suction side of the secondary side compressor 21. A secondary side accumulator 30 is provided in the middle of the suction flow path 23.

[0080] The second pipe 29 is a refrigerant pipe that connects the second stop valve 33 and the middle of the suction flow path 23. In addition, in the present embodiment, the second pipe 29 is connected to the suction flow path 23 at a connection portion between the suction side communication portion 22y of the secondary side switching mechanism 22 and the secondary side accumulator 30 in the suction flow path 23.

[0081] The discharge flow path 24 is a refrigerant pipe that connects the discharge side of the secondary compressor 21 to the secondary switching mechanism 22. Specifically, the discharge flow path 24 connects the discharge side of the secondary compressor 21 to the discharge-side communication portion 22x in the secondary switching mechanism 22.

[0082] The third pipe 25 is a refrigerant pipe that connects the secondary switching mechanism 22 and the gas side of the cascade heat exchanger 35. Specifically, the third pipe 25 connects the second connection port of the first switching valve 22a in the secondary switching mechanism 22 and the gas side end of the secondary flow path 35a in the cascade heat exchanger 35.

[0083] The fourth pipe 26 is a refrigerant pipe that connects the liquid side (the side opposite to the gas side, the side opposite to the side where the secondary side switching mechanism 22 is provided) of the cascade heat exchanger 35 and the secondary side receiver 45. Specifically, the fourth pipe 26 connects the liquid side end (the end on the side opposite to the gas side) of the secondary side flow path 35a in the cascade heat exchanger 35 and the secondary side receiver 45.

[0084] The secondary-side receiver 45 is a refrigerant container that stores excess refrigerant in the secondary-side refrigerant circuit 10. The fourth pipe 26, the fifth pipe 27, and the bypass circuit 46 extend from the secondary-side receiver 45.

[0085] The bypass circuit 46 is a refrigerant pipe that connects the gas phase region, which is the upper region inside the secondary side receiver 45, and the suction flow path 23. Specifically, the bypass circuit 46 is connected between the secondary side switching mechanism 22 and the secondary side accumulator 30 in the suction flow path 23. A bypass expansion valve 46a is provided in the bypass circuit 46. The bypass expansion valve 46a is an electric expansion valve that can adjust the amount of refrigerant guided from the secondary side receiver 45 to the suction side of the secondary side compressor 21 by adjusting the opening degree.

[0086] The fifth pipe 27 is a refrigerant pipe that connects the secondary-side receiver 45 and the third stop valve 31 .

[0087] The secondary side subcooling circuit 48 is a refrigerant pipe that connects a portion of the fifth pipe 27 and the suction flow path 23. Specifically, the secondary side subcooling circuit 48 is connected between the secondary side switching mechanism 22 and the secondary side storage tank 30 in the suction flow path 23. In addition, in the present embodiment, the secondary side subcooling circuit 48 extends in a branched manner from between the secondary side receiver 45 and the secondary side subcooling heat exchanger 47.

[0088] The secondary side subcooling heat exchanger 47 is a heat exchanger that performs heat exchange using the refrigerant flowing in the flow path belonging to the fifth pipe 27 and the refrigerant flowing in the flow path belonging to the secondary side subcooling circuit 48. In the present embodiment, it is provided between the portion of the fifth pipe 27 where the secondary side subcooling circuit 48 branches and the third stop valve 31. The secondary side subcooling expansion valve 48a is provided between the portion of the secondary side subcooling circuit 48 branching from the fifth pipe 27 and the secondary side subcooling heat exchanger 47. The secondary side subcooling expansion valve 48a is an electric expansion valve capable of adjusting the opening, and supplies the decompressed refrigerant to the secondary side subcooling heat exchanger 47.

[0089] The secondary-side accumulator 30 is a container capable of storing the secondary-side refrigerant, and is provided on the suction side of the secondary-side compressor 21 .

[0090] The oil separator 34 is provided in the middle of the discharge flow path 24. The oil separator 34 is a device for separating the refrigeration oil discharged from the secondary compressor 21 along with the secondary refrigerant from the secondary refrigerant and returning the refrigeration oil to the secondary compressor 21.

[0091] The oil return circuit 40 is provided to connect the oil separator 34 and the suction flow path 23. The flow path of the oil return circuit 40 extending from the oil separator 34 has an oil return flow path 41, and the oil return flow path 41 extends in a manner of merging with a portion of the suction flow path 23 between the secondary side accumulator 30 and the suction side of the secondary side compressor 21. An oil return capillary tube 42 and an oil return on-off valve 44 are provided in the middle of the oil return flow path 41. By controlling the oil return on-off valve 44 to an open state, the refrigeration oil separated in the oil separator 34 passes through the oil return capillary tube 42 of the oil return flow path 41 and returns to the suction side of the secondary side compressor 21. Here, in the present embodiment, when the secondary side compressor 21 is in the operating state in the secondary side refrigerant circuit 10, the oil return on-off valve 44 controls the amount of refrigeration oil returned through the oil return circuit 40 by repeatedly maintaining the open state for a predetermined time and maintaining the closed state for a predetermined time. In the present embodiment, the oil return on-off valve 44 is an electromagnetic valve whose on-off control is performed, but it may be an electric expansion valve whose opening degree can be adjusted and the oil return capillary tube 42 may be omitted.

[0092] The following describes the utilization loops 13a, 13b, and 13c. Since the utilization loops 13b and 13c have the same structure as the utilization loop 13a, the symbols "b" or "c" are marked on the utilization loops 13b and 13c instead of "a" representing the various parts of the utilization loop 13a, and the description of each part is omitted.

[0093] The utilization circuit 13a mainly includes a utilization-side heat exchanger 52a, a first utilization pipe 57a, a second utilization pipe 56a, and a utilization-side expansion valve 51a.

[0094] The utilization side heat exchanger 52a is a device for performing heat exchange between the refrigerant and the indoor air, and is composed of, for example, a fin-tube heat exchanger, which is composed of a plurality of heat transfer tubes and fins. In addition, the plurality of utilization side heat exchangers 52a, 52b, 52c are connected in parallel with respect to the secondary side switching mechanism 22, the suction flow path 23, and the cascade heat exchanger 35.

[0095] One end of the second utilization pipe 56a is connected to the liquid side (the side opposite to the gas side) of the utilization side heat exchanger 52a of the first utilization unit 3a. The other end of the second utilization pipe 56a is connected to the second connecting pipe 16a. The utilization side expansion valve 51a is provided in the middle of the second utilization pipe 56a.

[0096] The usage-side expansion valve 51a is an electric expansion valve whose opening degree can be adjusted, and performs adjustment of the flow rate of the refrigerant flowing through the usage-side heat exchanger 52a, etc. The usage-side expansion valve 51a is provided in the second usage pipe 56a.

[0097] One end of the first utilization pipe 57a is connected to the gas side of the utilization side heat exchanger 52a of the first utilization unit 3a. In the present embodiment, the first utilization pipe 57a is connected to the side of the utilization side heat exchanger 52a opposite to the utilization side expansion valve 51a side. The other end of the first utilization pipe 57a is connected to the first connecting pipe 15a.

[0098] The following describes the branching circuits 14a, 14b, and 14c. Since the branching circuits 14b and 14c have the same structure as the branching circuit 14a, the branching circuits 14b and 14c are marked with "b" or "c" instead of the symbol "a" representing the various parts of the branching circuit 14a, and the description of each part is omitted.

[0099] The branch circuit 14a mainly includes a joining pipe 62a, a first branch pipe 63a, a second branch pipe 64a, a first regulating valve 66a, a second regulating valve 67a, a bypass pipe 69a, a check valve 68a, and a third branch pipe 61a.

[0100] One end of the merging pipe 62a is connected to the first connecting pipe 15a. The first branch pipe 63a and the second branch pipe 64a are branched and connected to the other end of the merging pipe 62a.

[0101] The side of the first branch pipe 63a opposite to the joining pipe 62a is connected to the secondary side first communicating pipe 8. The first branch pipe 63a is provided with an openable and closable first regulating valve 66a.

[0102] The side of the second branch pipe 64a opposite to the merging pipe 62a is connected to the secondary-side second communicating pipe 9. The second branch pipe 64a is provided with an openable and closable second regulating valve 67a.

[0103] The bypass pipe 69a is a refrigerant pipe that connects a portion of the first branch pipe 63a that is closer to the secondary side first communicating pipe 8 than the first regulating valve 66a and a portion of the second branch pipe 64a that is closer to the secondary side second communicating pipe 9 than the second regulating valve 67a. A check valve 68a is provided in the middle of the bypass pipe 69a. The check valve 68a allows only the refrigerant to flow from the second branch pipe 64a side to the first branch pipe 63a side, and does not allow the refrigerant to flow from the first branch pipe 63a side to the second branch pipe 64a side.

[0104] One end of the third branch pipe 61 a is connected to the second connection pipe 16 a , and the other end of the third branch pipe 61 a is connected to the secondary-side third communication pipe 7 .

[0105] Furthermore, when the first branch unit 6a performs the cooling operation described later, by setting the first regulating valve 66a to the closed state and the second regulating valve 67a to the open state, it can play the following role. The first branch unit 6a transports the refrigerant that passes through the secondary side third connecting pipe 7 and flows into the third branch pipe 61a to the second connecting pipe 16a. In addition, the refrigerant that passes through the second connecting pipe 16a and flows in the second utilization pipe 56a of the first utilization unit 3a passes through the utilization side expansion valve 51a and is transported to the utilization side heat exchanger 52a of the first utilization unit 3a. Furthermore, the refrigerant transported to the utilization side heat exchanger 52a evaporates due to heat exchange with the indoor air and flows in the first connecting pipe 15a through the first utilization pipe 57a. The refrigerant flowing in the first connecting pipe 15a is transported to the confluence pipe 62a of the first branch unit 6a. The refrigerant flowing in the confluence pipe 62a does not flow to the first branch pipe 63a, but flows to the second branch pipe 64a. The refrigerant flowing in the second branch pipe 64a passes through the second regulating valve 67a. A portion of the refrigerant after passing through the second regulating valve 67a is delivered to the secondary side second communicating pipe 9. In addition, the remaining portion of the refrigerant after passing through the second regulating valve 67a flows in a manner branched at the bypass pipe 69a provided with a check valve 68a, and is delivered to the secondary side first communicating pipe 8 after flowing through a portion of the first branch pipe 63a. As a result, the total flow path cross-sectional area when the gaseous refrigerant on the secondary side evaporated in the utilization side heat exchanger 52a is delivered to the secondary side compressor 21 can be increased, and thus the pressure loss can be reduced.

[0106] In addition, when the first branch unit 6a performs the cooling main operation described later and the heating main operation, when the room is cooled in the first utilization unit 3a, by setting the first regulating valve 66a to the closed state and the second regulating valve 67a to the open state, it can play the following role. The first branch unit 6a conveys the refrigerant that passes through the secondary side third connecting pipe 7 and flows into the third branch pipe 61a to the second connecting pipe 16a. In addition, the refrigerant that passes through the second connecting pipe 16a and flows in the second utilization pipe 56a of the first utilization unit 3a passes through the utilization side expansion valve 51a and is conveyed to the utilization side heat exchanger 52a of the first utilization unit 3a. And, the refrigerant conveyed to the utilization side heat exchanger 52a evaporates due to heat exchange with the indoor air, and then flows in the first connection pipe 15a via the first utilization pipe 57a. The refrigerant flowing in the first connection pipe 15a is conveyed to the confluence pipe 62a of the first branch unit 6a. The refrigerant flowing through the merging pipe 62 a flows toward the second branch pipe 64 a , passes through the second regulating valve 67 a , and is then sent to the secondary-side second communicating pipe 9 .

[0107] In addition, when the first branch unit 6a performs the heating operation described later, by setting the second regulating valve 67a to the closed state and the first regulating valve 66a to the open state, the following effects can be achieved. In the first branch unit 6a, the refrigerant that passes through the secondary side first connecting pipe 8 and flows into the first branch pipe 63a passes through the first regulating valve 66a and is transported to the junction pipe 62a. The refrigerant that flows through the junction pipe 62a flows in the first utilization pipe 57a of the utilization unit 3a via the first connecting pipe 15a and is transported to the utilization side heat exchanger 52a. Then, the refrigerant transported to the utilization side heat exchanger 52a passes through the utilization side expansion valve 51a provided in the second utilization pipe 56a after heat is dissipated due to heat exchange with the indoor air. The refrigerant that passes through the second utilization pipe 56a flows in the third branch pipe 61a of the first branch unit 6a via the second connecting pipe 16a and is transported to the secondary side third connecting pipe 7.

[0108] In addition, when the first branch unit 6a performs the cooling main operation described later and the heating main operation, when the room is heated in the first utilization unit 3a, by setting the second regulating valve 67a to a closed state and the first regulating valve 66a to an open state, the following effect can be achieved. In the first branch unit 6a, the refrigerant that passes through the secondary side first connecting pipe 8 and flows into the first branch pipe 63a passes through the first regulating valve 66a and is transported to the confluence pipe 62a. The refrigerant that flows through the confluence pipe 62a flows in the first utilization pipe 57a of the utilization unit 3a via the first connecting pipe 15a and is transported to the utilization side heat exchanger 52a. Then, the refrigerant transported to the utilization side heat exchanger 52a passes through the utilization side expansion valve 51a provided in the second utilization pipe 56a after heat is dissipated due to heat exchange with the indoor air. The refrigerant that has passed through the second utilization pipe 56 a flows through the second connection pipe 16 a and the third branch pipe 61 a of the first branch unit 6 a , and is then sent to the secondary-side third communication pipe 7 .

[0109] Not only the first branching unit 6a has the above function, but the second branching unit 6b and the third branching unit 6c also have the above function. Therefore, the first branching unit 6a, the second branching unit 6b, and the third branching unit 6c can individually switch each utilization side heat exchanger 52a, 52b, and 52c to function as an evaporator of the refrigerant or as a radiator of the refrigerant.

[0110] (4) Primary side unit

[0111] The primary unit 5 is installed in a space different from the space where the utilization units 3a, 3b, 3c and the branching units 6a, 6b, 6c are arranged, on the roof, or the like.

[0112] The primary unit 5 includes a part of the primary refrigerant circuit 5 a , a primary fan 75 , various sensors, a primary control unit 70 , and a primary casing (not shown).

[0113] The primary side unit 5 has a primary side compressor 71, a primary side switching mechanism 72, a primary side heat exchanger 74, a primary side first expansion valve 76, a primary side subcooling heat exchanger 103, a primary side subcooling circuit 104, a primary side subcooling expansion valve 104a, a first liquid stop valve 108, a first gas stop valve 109 and a primary side storage tank 105 in the primary side shell as a part of the primary side refrigerant circuit 5a.

[0114] The primary fan 75 is provided in the primary unit 5, and generates air flow that guides outdoor air to the primary heat exchanger 74, exchanges heat with the primary refrigerant flowing in the primary heat exchanger 74, and then discharges the air to the outside. The primary fan 75 is driven by a primary fan motor 75a.

[0115] In addition, various sensors are provided in the primary side unit 5. Specifically, there are provided: an outside air temperature sensor 77, which detects the temperature of the outdoor air before passing through the primary side heat exchanger 74; a primary side discharge pressure sensor 78, which detects the pressure of the primary side refrigerant discharged from the primary side compressor 71; a primary side suction pressure sensor 79, which detects the pressure of the primary side refrigerant sucked into the primary side compressor 71; a primary side suction temperature sensor 81, which detects the temperature of the primary side refrigerant sucked into the primary side compressor 71; and a primary side heat exchange temperature sensor 82, which detects the temperature of the refrigerant flowing in the primary side heat exchanger 74.

[0116] The primary-side control unit 70 controls the operation of each part 71 (71a), 72, 75 (75a), 76, 104a provided in the primary-side unit 5. The primary-side control unit 70 has a processor such as a CPU or a microcomputer and a memory provided for controlling the primary-side unit 5, and can exchange control signals and the like with a remote controller (not shown), and can exchange control signals and the like with the cascade-side control unit 20 of the cascade unit 2, the branching unit control units 60a, 60b, 60c, and the utilization-side control units 50a, 50b, 50c.

[0117] (5) Cascade unit

[0118] The cascade unit 2 is installed in a space different from the space where the utilization units 3a, 3b, 3c and the branching units 6a, 6b, 6c are arranged, on the roof, or the like.

[0119] The cascade unit 2 is connected to the branch units 6a, 6b, 6c via the connecting pipes 7, 8, 9, and constitutes a part of the secondary refrigerant circuit 10. In addition, the cascade unit 2 is connected to the primary unit 5 via the primary first connecting pipe 111 and the primary second connecting pipe 112, and constitutes a part of the primary refrigerant circuit 5a.

[0120] The cascade unit 2 mainly includes the above-mentioned cascade circuit 12, various sensors, a cascade side control unit 20, a second liquid stop valve 106 constituting a part of the primary side refrigerant circuit 5a, a second refrigerant piping 114, a primary side second expansion valve 102, a first refrigerant piping 113 and a second gas stop valve 107, a cascade shell not shown, etc.

[0121] The cascade unit 2 is provided with: a secondary side suction pressure sensor 37, which detects the pressure of the secondary side refrigerant on the suction side of the secondary side compressor 21; a secondary side discharge pressure sensor 38, which detects the pressure of the secondary side refrigerant on the discharge side of the secondary side compressor 21; a secondary side discharge temperature sensor 39, which detects the temperature of the secondary side refrigerant on the discharge side of the secondary side compressor 21; a secondary side suction temperature sensor 88, which detects the temperature of the secondary side refrigerant on the suction side of the secondary side compressor 21; a secondary side cascade temperature sensor 83, which detects the secondary side refrigerant flowing between the secondary side flow path 35a of the cascade heat exchanger 35 and the cascade expansion valve 36. The receiver outlet temperature sensor 84 detects the temperature of the secondary refrigerant flowing between the secondary receiver 45 and the secondary subcooling heat exchanger 47; the bypass circuit temperature sensor 85 detects the temperature of the secondary refrigerant flowing on the downstream side of the bypass expansion valve 46a in the bypass circuit 46; the subcooling outlet temperature sensor 86 detects the temperature of the secondary refrigerant flowing between the secondary subcooling heat exchanger 47 and the third stop valve 31; and the subcooling circuit temperature sensor 87 detects the temperature of the secondary refrigerant flowing at the outlet of the secondary subcooling heat exchanger 47 in the secondary subcooling circuit 48.

[0122] The cascade side control unit 20 controls the operation of each part 21 (21a), 22, 36, 44, 46a, 48a, 102 provided inside the cascade housing of the cascade unit 2. The cascade side control unit 20 has a processor such as a CPU or a microcomputer and a memory provided for controlling the cascade unit 2, and is configured to be able to exchange control signals and the like with the primary side control unit 70 of the primary side unit 5, the utilization side control units 50a, 50b, 50c of the utilization units 3a, 3b, 3c, and the branch unit control units 60a, 60b, 60c.

[0123] In addition, in this way, the cascade side control unit 20 can control not only the various parts of the cascade circuit 12 constituting the secondary side refrigerant circuit 10, but also the primary side second expansion valve 102 constituting a part of the primary side refrigerant circuit 5a. Therefore, the cascade side control unit 20 can make the condition of the cascade circuit 12 close to the desired condition by controlling the valve opening of the primary side second expansion valve 102 based on the condition of the cascade circuit 12 controlled by itself. Specifically, the secondary side refrigerant flowing in the secondary side flow path 35a of the cascade heat exchanger 35 in the cascade circuit 12 can control the heat received from the primary side refrigerant flowing in the primary side flow path 35b of the cascade heat exchanger 35 or the heat provided to the primary side refrigerant.

[0124] (6) Utilization unit

[0125] The utilization units 3a, 3b, and 3c are installed by being embedded in, suspended from, or hung on a ceiling in a room of a building or the like, or by being hung on a wall in a room or the like.

[0126] The utilization units 3 a , 3 b , and 3 c are connected to the cascade unit 2 via communication pipes 7 , 8 , and 9 .

[0127] The utilization units 3 a , 3 b , and 3 c include utilization circuits 13 a , 13 b , and 13 c that constitute a part of the secondary refrigerant circuit 10 .

[0128] The following describes the structures of the side units 3a, 3b, and 3c. In addition, since the second utilization unit 3b and the third utilization unit 3c have the same structure as the first utilization unit 3a, only the structure of the first utilization unit 3a is described here, and the structures of the second utilization unit 3b and the third utilization unit 3c are respectively marked with symbols "b" or "c" instead of the symbol "a" representing each part of the first utilization unit 3a, and the description of each part is omitted.

[0129] The first usage unit 3a mainly includes the above-mentioned usage circuit 13a, the indoor fan 53a, the usage-side control unit 50a, and various sensors. In addition, the indoor fan 53a includes an indoor fan motor 54a.

[0130] The indoor fan 53a draws indoor air into the unit, exchanges heat with the refrigerant flowing in the utilization side heat exchanger 52a, and then generates an air flow supplied to the room as supply air. The indoor fan 53a is driven by an indoor fan motor 54a.

[0131] The utilization unit 3a is provided with a liquid side temperature sensor 58a, which detects the temperature of the refrigerant on the liquid side of the utilization side heat exchanger 52a. In addition, the utilization unit 3a is provided with an indoor temperature sensor 55a, which detects the indoor temperature, which is the temperature of the air introduced from the room before passing through the utilization side heat exchanger 52a.

[0132] The utilization side control unit 50a controls the operation of each part 51a, 53a (54a) constituting the utilization unit 3a. The utilization side control unit 50a has a processor such as a CPU or a microcomputer and a memory provided for controlling the utilization unit 3a, and can exchange control signals and the like with a remote controller (not shown), and can exchange control signals and the like with the cascade side control unit 20 of the cascade unit 2, the branch unit control units 60a, 60b, 60c, and the primary side control unit 70 of the primary side unit 5.

[0133] The second usage unit 3b includes a usage circuit 13b, an indoor fan 53b, a usage-side control unit 50b, and an indoor fan motor 54b. The third usage unit 3c includes a usage circuit 13c, an indoor fan 53c, a usage-side control unit 50c, and an indoor fan motor 54c.

[0134] (7) Bifurcation unit

[0135] The branching units 6a, 6b, and 6c are installed in a space behind a ceiling in a building or the like.

[0136] The branching units 6a, 6b, 6c are connected to the utilization units 3a, 3b, 3c in a one-to-one correspondence. The branching units 6a, 6b, 6c are connected to the cascade unit 2 via the connecting pipes 7, 8, 9.

[0137] Next, the structures of the branching units 6a, 6b, and 6c are described. In addition, since the second branching unit 6b and the third branching unit 6c have the same structure as the first branching unit 6a, only the structure of the first branching unit 6a is described here, and the structures of the second branching unit 6b and the third branching unit 6c are respectively marked with the symbol "b" or "c" instead of the symbol "a" representing each part of the first branching unit 6a, and the description of each part is omitted.

[0138] The first branching unit 6a mainly includes the above-mentioned branching circuit 14a and a branching unit control unit 60a.

[0139] The branch unit control unit 60a controls the operation of each part 66a, 67a constituting the branch unit 6a. The branch unit control unit 60a has a processor such as a CPU, a microcomputer, and a memory provided for controlling the branch unit 6a, and can exchange control signals and the like with a remote controller (not shown), and can exchange control signals and the like with the cascade side control unit 20 of the cascade unit 2, the utilization units 3a, 3b, 3c, and the primary side control unit 70 of the primary side unit 5.

[0140] In addition, the second branch unit 6b includes a branch circuit 14b and a branch unit control unit 60b. The third branch unit 6c includes a branch circuit 14c and a branch unit control unit 60c.

[0141] (8) Control unit

[0142] In the refrigeration cycle device 1, the cascade side control unit 20, the utilization side control units 50a, 50b, 50c, the branch unit control units 60a, 60b, 60c, and the primary side control unit 70 are connected to each other via wires or wirelessly so as to be able to communicate with each other, thereby constituting a control unit 80. Therefore, the control unit 80 controls the actions of the parts 21 (21a), 22, 36, 44, 46a, 48a, 51a, 51b, 51c, 53a, 53b, 53c (54a, 54b, 54c), 66a, 66b, 66c, 67a, 67b, 67c, 71 (71a), 72, 75 (75a), 76, 104a based on the detection information of various sensors 37, 38, 39, 83, 84, 85, 86, 87, 88, 77, 78, 79, 81, 82, 58a, 58b, 58c, etc. and the instruction information received from the remote control not shown in the figure.

[0143] (9) Operation of refrigeration cycle device

[0144] Next, use Figure 3 to Figure 6 The operation of the refrigeration cycle apparatus 1 will be described.

[0145] The refrigeration cycle operation of the refrigeration cycle device 1 can be mainly divided into a cooling operation, a heating operation, a cooling-dominant operation, and a heating-dominant operation.

[0146] Here, the cooling operation is a refrigeration cycle operation in which only the utilization unit in which the utilization side heat exchanger functions as an evaporator of the refrigerant exists, and the cascade heat exchanger 35 functions as a radiator of the secondary side refrigerant for the evaporation load of the entire utilization unit.

[0147] The heating operation is a refrigeration cycle operation in which only the utilization unit in which the utilization side heat exchanger functions as a radiator of the refrigerant exists and the cascade heat exchanger 35 functions as an evaporator of the secondary side refrigerant for the heat dissipation load of the entire utilization unit.

[0148] The cooling-main operation is an operation in which a utilization unit performs an operation in which the utilization-side heat exchanger functions as an evaporator of the refrigerant and a utilization unit performs an operation in which the utilization-side heat exchanger functions as a radiator of the refrigerant. The cooling-main operation is a refrigeration cycle operation in which, when the evaporation load is the main load in the heat load of the entire utilization unit, the cascade heat exchanger 35 functions as a radiator of the secondary-side refrigerant in order to handle the evaporation load of the entire utilization unit.

[0149] The heating-main operation is an operation in which a utilization unit performs an operation in which the utilization-side heat exchanger functions as an evaporator of the refrigerant and a utilization unit performs an operation in which the utilization-side heat exchanger functions as a radiator of the refrigerant. The heating-main operation is a refrigeration cycle operation in which, when the heat dissipation load is the main part of the heat load of the entire utilization unit, the cascade heat exchanger 35 functions as an evaporator of the secondary-side refrigerant in order to handle the heat dissipation load of the entire utilization unit.

[0150] In addition, the operation of the refrigeration cycle device 1 including the refrigeration cycle operation is performed by the control unit 80 .

[0151] (9-1) Refrigeration operation

[0152] In the cooling operation, for example, the utilization side heat exchangers 52a, 52b, 52c of the utilization units 3a, 3b, 3c all function as evaporators of the refrigerant, and the cascade heat exchanger 35 functions as a radiator of the secondary side refrigerant. In this cooling operation, the primary side refrigerant circuit 5a and the secondary side refrigerant circuit 10 of the refrigeration cycle device 1 are operated as follows. Figure 3 In addition, Figure 3 The arrows indicated in the primary-side refrigerant circuit 5a and the arrows indicated in the secondary-side refrigerant circuit 10 indicate the flow of the refrigerant during the cooling operation.

[0153] Specifically, in the primary unit 5, the primary switching mechanism 72 is switched to the fifth connection state, so that the cascade heat exchanger 35 functions as an evaporator of the primary refrigerant. Figure 3The primary side switching mechanism 72 of the primary side switching mechanism 72 is connected in a state shown by a solid line. Thus, in the primary side unit 5, the primary side refrigerant discharged from the primary side compressor 71 passes through the primary side switching mechanism 72, and is heat-exchanged with the external air supplied from the primary side fan 75 in the primary side heat exchanger 74, thereby condensing. The primary side refrigerant condensed in the primary side heat exchanger 74 passes through the primary side first expansion valve 76 controlled to be fully open, and a part of the refrigerant passes through the primary side subcooling heat exchanger 103 and flows to the first liquid stop valve 108, and the other part of the refrigerant branches and flows to the primary side subcooling circuit 104. The refrigerant flowing in the primary side subcooling circuit 104 is decompressed when passing through the primary side subcooling expansion valve 104a. The refrigerant flowing from the primary side first expansion valve 76 to the first liquid stop valve 108 is heat-exchanged with the refrigerant decompressed by the primary side subcooling expansion valve 104a and flowing in the primary side subcooling circuit 104 in the primary side subcooling heat exchanger 103, and is cooled to a subcooled state. The refrigerant in the supercooled state flows in the order of the primary-side first connecting pipe 111, the second liquid stop valve 106, and the second refrigerant piping 114, and is decompressed when passing through the primary-side second expansion valve 102. Here, the valve opening of the primary-side second expansion valve 102 is controlled so that the superheat of the primary-side refrigerant sucked into the primary-side compressor 71 satisfies a predetermined condition. When the primary-side refrigerant decompressed in the primary-side second expansion valve 102 flows in the primary-side flow path 35b of the cascade heat exchanger 35, it exchanges heat with the secondary-side refrigerant flowing in the secondary-side flow path 35a to evaporate, passes through the first refrigerant piping 113, and flows toward the second gas stop valve 107. The refrigerant that has passed through the second gas stop valve 107 reaches the primary-side switching mechanism 72 after passing through the primary-side second connecting pipe 112 and the first gas stop valve 109. The refrigerant that has passed through the primary-side switching mechanism 72 merges with the refrigerant flowing in the primary-side subcooling circuit 104 , and is then sucked into the primary-side compressor 71 via the primary-side accumulator 105 .

[0154] In addition, in the cascade unit 2, the secondary side switching mechanism 22 is switched to the first connection state, so that the cascade heat exchanger 35 functions as a radiator of the secondary side refrigerant. In addition, in the first connection state of the secondary side switching mechanism 22, the discharge flow path 24 and the third pipe 25 are connected through the first switching valve 22a, and the first pipe 28 and the suction flow path 23 are connected through the second switching valve 22b. In the first to third utilization units 3a, 3b, 3c, the second regulating valves 67a, 67b, 67c are controlled to be in the open state. As a result, the utilization side heat exchangers 52a, 52b, 52c of the utilization units 3a, 3b, 3c all function as evaporators of the refrigerant. In addition, all the utilization side heat exchangers 52a, 52b, 52c of the utilization units 3a, 3b, 3c and the suction side of the secondary side compressor 21 of the cascade unit 2 are connected via the first utilization pipes 57a, 57b, 57c, the first connecting pipes 15a, 15b, 15c, the converging pipes 62a, 62b, 62c, the second branch pipes 64a, 64b, 64c, the bypass pipes 69a, 69b, 69c, a part of the first branch pipes 63a, 63b, 63c, the secondary side first communicating pipe 8 and the secondary side second communicating pipe 9. In addition, the opening degree of the secondary side subcooling expansion valve 48a is controlled so that the subcooling degree of the secondary side refrigerant flowing toward the secondary side third communicating pipe 7 at the outlet of the secondary side subcooling heat exchanger 47 satisfies a predetermined condition. The bypass expansion valve 46a is controlled to be in a closed state. In the utilization units 3a, 3b, and 3c, the opening degrees of the utilization-side expansion valves 51a, 51b, and 51c are adjusted.

[0155] Furthermore, in the cooling operation, in the secondary refrigerant circuit 10, for example, the frequency of the secondary compressor 21 is controlled so that the evaporation temperature of the secondary refrigerant in the utilization side heat exchangers 52a, 52b, and 52c reaches a predetermined secondary evaporation target temperature, thereby performing capacity control. The opening of the cascade expansion valve 36 is adjusted so that the secondary refrigerant flowing in the cascade heat exchanger 35 reaches a critical pressure or less. Furthermore, in the primary refrigerant circuit 5a, for example, the frequency of the primary compressor 71 is controlled so that the evaporation temperature of the primary refrigerant in the primary side flow path 35b of the cascade heat exchanger 35 reaches a predetermined primary evaporation target temperature, thereby performing capacity control. In this way, in the cooling operation, by executing either or both of the control of increasing the valve opening of the cascade expansion valve 36 and the control of increasing the frequency of the primary compressor 71 in the primary refrigerant circuit 5a, the carbon dioxide refrigerant flowing in the cascade heat exchanger 35 is controlled so as not to exceed the critical point.

[0156] In the secondary refrigerant circuit 10, the secondary high-pressure refrigerant compressed and discharged by the secondary compressor 21 is delivered to the secondary flow path 35a of the cascade heat exchanger 35 through the first switching valve 22a of the secondary switching mechanism 22. In the cascade heat exchanger 35, the secondary high-pressure refrigerant flowing in the secondary flow path 35a dissipates heat, and the primary refrigerant flowing in the primary flow path 35b of the cascade heat exchanger 35 evaporates. The secondary refrigerant after dissipating heat in the cascade heat exchanger 35 flows into the secondary receiver 45 after passing through the cascade expansion valve 36 whose opening is adjusted, and a part of the refrigerant flowing out of the secondary receiver 45 flows in a branched manner to the secondary subcooling circuit 48, and merges with the suction flow path 23 after being decompressed in the secondary subcooling expansion valve 48a. In the secondary-side subcooling heat exchanger 47 , another portion of the refrigerant flowing out of the secondary-side receiver 45 is cooled by the refrigerant flowing in the secondary-side subcooling circuit 48 , passes through the third stop valve 31 , and is delivered to the secondary-side third communicating pipe 7 .

[0157] Next, the refrigerant delivered to the secondary side third connecting pipe 7 is branched into three and passes through the third branch pipes 61a, 61b, 61c of the first to third branch units 6a, 6b, 6c. Then, the refrigerant flowing in the second connecting pipes 16a, 16b, 16c is delivered to the second utilization pipes 56a, 56b, 56c of the first to third utilization units 3a, 3b, 3c. The refrigerant delivered to the second utilization pipes 56a, 56b, 56c is delivered to the utilization side expansion valves 51a, 51b, 51c of the utilization units 3a, 3b, 3c.

[0158] Next, the refrigerant that has passed through the utilization side expansion valves 51a, 51b, 51c whose openings have been adjusted exchanges heat with the indoor air supplied by the indoor fans 53a, 53b, 53c in the utilization side heat exchangers 52a, 52b, 52c. As a result, the refrigerant flowing through the utilization side heat exchangers 52a, 52b, 52c evaporates and becomes a low-pressure gas refrigerant. The indoor air is cooled and supplied to the room. As a result, the indoor space is cooled. The low-pressure gas refrigerant evaporated in the utilization side heat exchangers 52a, 52b, 52c flows through the first utilization pipes 57a, 57b, 57c, and after flowing through the first connecting pipes 15a, 15b, 15c, is transported to the converging pipes 62a, 62b, 62c of the first to third branching units 6a, 6b, 6c.

[0159] The low-pressure gas refrigerant delivered to the converging pipes 62a, 62b, 62c flows to the second branch pipes 64a, 64b, 64c. A portion of the refrigerant that has passed through the second regulating valves 67a, 67b, 67c in the second branch pipes 64a, 64b, 64c is delivered to the secondary-side second communicating pipe 9. The remaining portion of the refrigerant that has passed through the second regulating valves 67a, 67b, 67c passes through the bypass pipes 69a, 69b, 69c, flows through a portion of the first branch pipes 63a, 63b, 63c, and is then delivered to the secondary-side first communicating pipe 8.

[0160] Next, the low-pressure gas refrigerant delivered to the first secondary-side connecting pipe 8 and the second secondary-side connecting pipe 9 passes through the first stop valve 32, the second stop valve 33, the first pipe 28, the second pipe 29, the second switching valve 22b of the secondary-side switching mechanism 22, the suction flow path 23 and the secondary-side storage tank 30, and returns to the suction side of the secondary-side compressor 21.

[0161] In this way, the cooling operation is performed.

[0162] (9-2) Heating operation

[0163] In the heating operation, for example, the utilization side heat exchangers 52a, 52b, 52c of the utilization units 3a, 3b, 3c all function as radiators of the refrigerant. In addition, in the heating operation, the cascade heat exchanger 35 functions as an evaporator of the secondary side refrigerant. In the heating operation, the primary side refrigerant circuit 5a and the secondary side refrigerant circuit 10 of the refrigeration cycle device 1 are operated as follows: Figure 4 As shown. Figure 4 The arrows indicated in the primary-side refrigerant circuit 5a and the arrows indicated in the secondary-side refrigerant circuit 10 indicate the flow of the refrigerant during the heating operation.

[0164] Specifically, in the primary unit 5, the primary switching mechanism 72 is switched to the sixth connection state, so that the cascade heat exchanger 35 functions as a heat sink for the primary refrigerant. The sixth connection state of the primary switching mechanism 72 is Figure 4The primary-side switching mechanism 72 of the primary unit 5 is connected in a state shown by a dotted line. Thus, in the primary unit 5, the primary refrigerant discharged from the primary compressor 71, passing through the primary switching mechanism 72 and passing through the first gas stop valve 109 passes through the primary second connecting pipe 112 and the second gas stop valve 107, and is transported to the primary flow path 35b of the cascade heat exchanger 35. The refrigerant flowing in the primary flow path 35b of the cascade heat exchanger 35 is condensed by heat exchange with the secondary refrigerant flowing in the secondary flow path 35a. When the primary refrigerant condensed in the cascade heat exchanger 35 flows in the second refrigerant piping 114, it passes through the primary second expansion valve 102 controlled to be fully open. The refrigerant after passing through the primary second expansion valve 102 flows in the order of the second liquid stop valve 106, the primary first connecting pipe 111, the first liquid stop valve 108, and the primary subcooling heat exchanger 103, and is decompressed in the primary first expansion valve 76. In addition, during the heating operation, the primary side subcooling expansion valve 104a is controlled to be in a closed state, whereby the refrigerant does not flow in the primary side subcooling circuit 104, and therefore, heat exchange is not performed in the primary side subcooling heat exchanger 103. In addition, the valve opening of the primary side first expansion valve 76 is controlled, for example, so that the superheat of the refrigerant sucked into the primary side compressor 71 satisfies a prescribed condition. The refrigerant decompressed in the primary side first expansion valve 76 is evaporated by heat exchange with the external air supplied from the primary side fan 75 in the primary side heat exchanger 74, passes through the primary side switching mechanism 72 and the primary side accumulator 105, and is sucked into the primary side compressor 71.

[0165] In addition, in the cascade unit 2, the secondary side switching mechanism 22 is switched to the second connection state. As a result, the cascade heat exchanger 35 functions as an evaporator of the secondary side refrigerant. In the second connection state of the secondary side switching mechanism 22, the discharge flow path 24 is connected to the first pipe 28 through the second switching valve 22b, and the third pipe 25 is connected to the suction flow path 23 through the first switching valve 22a. In addition, the opening of the cascade expansion valve 36 is adjusted. In the first to third branching units 6a, 6b, 6c, the first regulating valves 66a, 66b, 66c are controlled to be in the open state, and the second regulating valves 67a, 67b, 67c are controlled to be in the closed state. As a result, the utilization side heat exchangers 52a, 52b, 52c of the utilization units 3a, 3b, 3c all function as radiators of the refrigerant. Furthermore, the discharge side of the utilization side heat exchangers 52a, 52b, 52c of the utilization units 3a, 3b, 3c and the secondary side compressor 21 of the cascade unit 2 are connected via the discharge flow path 24, the first piping 28, the secondary side first connecting pipe 8, the first branch piping 63a, 63b, 63c, the converging piping 62a, 62b, 62c, the first connecting pipes 15a, 15b, 15c and the first utilization piping 57a, 57b, 57c. In addition, the secondary side subcooling expansion valve 48a and the bypass expansion valve 46a are controlled to be closed. In the utilization units 3a, 3b, 3c, the opening of the utilization side expansion valves 51a, 51b, 51c is adjusted.

[0166] In addition, during the heating operation, in the secondary refrigerant circuit 10, the capacity of the secondary compressor 21 is controlled so that it becomes a frequency that can handle the load in the utilization side heat exchangers 52a, 52b, and 52c. Thus, during the heating operation, control is performed so that the secondary refrigerant discharged from the secondary compressor 21 can become a critical state exceeding the critical pressure. In addition, in the primary refrigerant circuit 5a, for example, the frequency of the primary compressor 71 is controlled so that the condensation temperature of the primary refrigerant in the primary side flow path 35b of the cascade heat exchanger 35 reaches a predetermined primary side condensation target temperature, thereby performing capacity control.

[0167] In the secondary refrigerant circuit 10, the high-pressure refrigerant compressed and discharged by the secondary compressor 21 passes through the second switching valve 22b of the secondary switching mechanism 22 and is delivered to the first pipe 28. The refrigerant delivered to the first pipe 28 passes through the first stop valve 32 and is delivered to the secondary first communication pipe 8.

[0168] Then, the high-pressure refrigerant delivered to the secondary side first connecting pipe 8 is branched into three and delivered to the first branch pipes 63a, 63b, 63c of each utilization unit 3a, 3b, 3c in operation. The high-pressure refrigerant delivered to the first branch pipes 63a, 63b, 63c passes through the first regulating valves 66a, 66b, 66c and flows in the converging pipes 62a, 62b, 62c. Then, the refrigerant flowing through the first connecting pipes 15a, 15b, 15c and the first utilization pipes 57a, 57b, 57c is delivered to the utilization side heat exchangers 52a, 52b, 52c.

[0169] Next, the high-pressure refrigerant delivered to the utilization side heat exchangers 52a, 52b, 52c exchanges heat with the indoor air supplied by the indoor fans 53a, 53b, 53c in the utilization side heat exchangers 52a, 52b, 52c. Thus, the refrigerant flowing through the utilization side heat exchangers 52a, 52b, 52c dissipates heat. The indoor air is heated and supplied to the room. Thus, the indoor space is heated. The refrigerant after dissipating heat in the utilization side heat exchangers 52a, 52b, 52c flows through the second utilization pipes 56a, 56b, 56c and passes through the utilization side expansion valves 51a, 51b, 51c whose openings are adjusted. In addition, the secondary side refrigerant after passing through the utilization side expansion valves 51a, 51b, 51c becomes below the critical pressure. Then, the refrigerant flowing through the second connection pipes 16a, 16b, and 16c flows through the third branch pipes 61a, 61b, and 61c of the branch units 6a, 6b, and 6c.

[0170] Next, the refrigerant sent to the third branch pipes 61a, 61b, and 61c is sent to the secondary-side third communication pipe 7 and merges there.

[0171] Next, the refrigerant delivered to the secondary side third connecting pipe 7 passes through the third stop valve 31 and is delivered to the cascade expansion valve 36. The refrigerant delivered to the cascade expansion valve 36 is flow-regulated in the cascade expansion valve 36 and then delivered to the cascade heat exchanger 35. In the cascade heat exchanger 35, the secondary side refrigerant flowing in the secondary side flow path 35a evaporates and becomes a low-pressure gas refrigerant and is delivered to the secondary side switching mechanism 22, and the primary side refrigerant flowing in the primary side flow path 35b of the cascade heat exchanger 35 is condensed. Next, the secondary side low-pressure gas refrigerant delivered to the first switching valve 22a of the secondary side switching mechanism 22 passes through the suction flow path 23 and the secondary side accumulator 30 and returns to the suction side of the secondary side compressor 21.

[0172] In this way, the operation during the heating operation is performed.

[0173] (9-3) Refrigeration main operation

[0174] In the cooling-main operation, for example, the following operation is performed: the utilization-side heat exchangers 52a and 52b of the utilization units 3a and 3b function as evaporators of the refrigerant, and the utilization-side heat exchanger 52c of the utilization unit 3c functions as a radiator of the refrigerant. In the cooling-main operation, the cascade heat exchanger 35 functions as a radiator of the secondary-side refrigerant. In the cooling-main operation, the primary-side refrigerant circuit 5a and the secondary-side refrigerant circuit 10 of the refrigeration cycle device 1 function as evaporators of the refrigerant. Figure 5 As shown. Figure 5 The arrows indicated in the primary-side refrigerant circuit 5a and the arrows indicated in the secondary-side refrigerant circuit 10 indicate the flow of the refrigerant during the cooling main operation.

[0175] Specifically, in the primary unit 5, by switching the primary switching mechanism 72 to the fifth connection state ( Figure 5The cascade heat exchanger 35 functions as an evaporator of the primary-side refrigerant (the state shown by the solid line of the primary-side switching mechanism 72 of the primary-side switching mechanism 72). As a result, in the primary-side unit 5, the primary-side refrigerant discharged from the primary-side compressor 71 passes through the primary-side switching mechanism 72, and exchanges heat with the external air supplied from the primary-side fan 75 in the primary-side heat exchanger 74, thereby condensing. The primary-side refrigerant condensed in the primary-side heat exchanger 74 passes through the primary-side first expansion valve 76 controlled to be fully open, and a part of the refrigerant passes through the primary-side subcooling heat exchanger 103 and flows to the first liquid stop valve 108, and the other part of the refrigerant branches and flows to the primary-side subcooling circuit 104. The refrigerant flowing in the primary-side subcooling circuit 104 is decompressed when passing through the primary-side subcooling expansion valve 104a. The refrigerant flowing from the primary side first expansion valve 76 to the first liquid stop valve 108 exchanges heat with the refrigerant that is decompressed by the primary side subcooling expansion valve 104a and flows in the primary side subcooling circuit 104 in the primary side subcooling heat exchanger 103, and is cooled to a subcooled state. The refrigerant in the subcooled state flows in the order of the primary side first communication pipe 111, the second liquid stop valve 106, and the second refrigerant piping 114, and is decompressed in the primary side second expansion valve 102. In addition, at this time, the valve opening of the primary side second expansion valve 102 is controlled, for example, so that the superheat of the refrigerant sucked into the primary side compressor 71 satisfies a predetermined condition. When the primary side refrigerant that has been decompressed in the primary side second expansion valve 102 flows in the primary side flow path 35b of the cascade heat exchanger 35, it exchanges heat with the secondary side refrigerant that flows in the secondary side flow path 35a to evaporate, passes through the first refrigerant piping 113, and flows toward the second gas stop valve 107. The refrigerant passing through the second gas shut-off valve 107 reaches the primary-side switching mechanism 72 after passing through the primary-side second connecting pipe 112 and the first gas shut-off valve 109. The refrigerant passing through the primary-side switching mechanism 72 merges with the refrigerant flowing in the primary-side subcooling circuit 104, and is then sucked into the primary-side compressor 71 via the primary-side storage tank 105.

[0176] In addition, in the cascade unit 2, the secondary side switching mechanism 22 is switched to the third connection state in which the discharge flow path 24 is connected to the third pipe 25 through the first switching valve 22a and the discharge flow path 24 is connected to the first pipe 28 through the second switching valve 22b, so that the cascade heat exchanger 35 functions as a radiator of the refrigerant on the secondary side. In addition, the opening degree of the cascade expansion valve 36 is adjusted. In the first to third branch units 6a, 6b, 6c, the first regulating valve 66c and the second regulating valves 67a, 67b are controlled to be in an open state, and the first regulating valves 66a, 66b and the second regulating valve 67c are controlled to be in a closed state. As a result, the utilization side heat exchangers 52a, 52b of the utilization units 3a, 3b function as evaporators of the refrigerant, and the utilization side heat exchanger 52c of the utilization unit 3c functions as a radiator of the refrigerant. In addition, the utilization side heat exchangers 52a, 52b of the utilization units 3a, 3b and the suction side of the secondary side compressor 21 of the cascade unit 2 are connected via the secondary side second connecting pipe 9, and the utilization side heat exchanger 52c of the utilization unit 3c and the discharge side of the secondary side compressor 21 of the cascade unit 2 are connected via the secondary side first connecting pipe 8. In addition, the opening of the secondary side subcooling expansion valve 48a is controlled so that the subcooling degree of the secondary side refrigerant flowing toward the secondary side third connecting pipe 7 at the outlet of the secondary side subcooling heat exchanger 47 satisfies the specified conditions. The bypass expansion valve 46a is controlled to be closed. In the utilization units 3a, 3b, 3c, the opening of the utilization side expansion valves 51a, 51b, 51c is adjusted.

[0177] In addition, in the cooling main operation, in the secondary refrigerant circuit 10, for example, the frequency of the secondary compressor 21 is controlled so that the evaporation temperature in the heat exchanger that functions as the evaporator of the secondary refrigerant among the utilization side heat exchangers 52a, 52b, and 52c reaches a predetermined secondary evaporation target temperature, thereby performing capacity control. The opening of the cascade expansion valve 36 is adjusted so that the secondary refrigerant flowing in the cascade heat exchanger 35 reaches a critical pressure or less. In addition, in the primary refrigerant circuit 5a, for example, the frequency of the primary compressor 71 is controlled so that the evaporation temperature of the primary refrigerant in the primary side flow path 35b of the cascade heat exchanger 35 reaches a predetermined primary evaporation target temperature, thereby performing capacity control. In this way, in the cooling operation, by executing either or both of the control of increasing the valve opening of the cascade expansion valve 36 and the control of increasing the frequency of the primary compressor 71 in the primary refrigerant circuit 5a, the carbon dioxide refrigerant flowing in the cascade heat exchanger 35 is controlled so that it does not exceed the critical point.

[0178] In the above-mentioned secondary side refrigerant circuit 10, a portion of the secondary side high-pressure refrigerant compressed and discharged by the secondary side compressor 21 is delivered to the secondary side first connecting pipe 8 through the second switching valve 22b of the secondary side switching mechanism 22, the first piping 28 and the first stop valve 32, and the rest is delivered to the secondary side flow path 35a of the cascade heat exchanger 35 through the first switching valve 22a of the secondary side switching mechanism 22 and the third piping 25.

[0179] Next, the high-pressure refrigerant sent to the secondary side first communication pipe 8 is sent to the first branch pipe 63c. The high-pressure refrigerant sent to the first branch pipe 63c passes through the first regulating valve 66c and the converging pipe 62c and is sent to the utilization side heat exchanger 52c of the utilization unit 3c.

[0180] Next, the high-pressure refrigerant delivered to the utilization side heat exchanger 52c exchanges heat with the indoor air supplied by the indoor fan 53c in the utilization side heat exchanger 52c. As a result, the refrigerant flowing in the utilization side heat exchanger 52c dissipates heat. The indoor air is heated and supplied to the room, and the heating operation of the utilization unit 3c is performed. The refrigerant after dissipating heat in the utilization side heat exchanger 52c flows through the second utilization pipe 56c, and the flow rate is adjusted in the utilization side expansion valve 51c. Then, the refrigerant flowing through the second connecting pipe 16c is delivered to the third branch pipe 61c of the branch unit 6c.

[0181] Next, the refrigerant sent to the third branch pipe 61 c is sent to the secondary-side third communication pipe 7 .

[0182] In addition, the high-pressure refrigerant delivered to the secondary side flow path 35a of the cascade heat exchanger 35 exchanges heat with the primary side refrigerant flowing in the primary side flow path 35b in the cascade heat exchanger 35, thereby dissipating heat. The secondary side refrigerant that has dissipated heat in the cascade heat exchanger 35 is flow-regulated in the cascade expansion valve 36 and then flows into the secondary side receiver 45. A portion of the refrigerant that has flowed out of the secondary side receiver 45 flows in a branched manner to the secondary side subcooling circuit 48, is decompressed in the secondary side subcooling expansion valve 48a, and then merges with the suction flow path 23. In the secondary side subcooling heat exchanger 47, another portion of the refrigerant that has flowed out of the secondary side receiver 45 is cooled by the refrigerant flowing in the secondary side subcooling circuit 48, passes through the third stop valve 31, and is delivered to the secondary side third connecting pipe 7, and merges with the refrigerant that has dissipated heat in the utilization side heat exchanger 52c.

[0183] Next, the refrigerant that has merged in the secondary side third connecting pipe 7 is branched into two and delivered to the third branch pipes 61a and 61b of the second branch units 6a and 6b. Then, the refrigerant flowing in the second connecting pipes 16a and 16b is delivered to the second utilization pipes 56a and 56b of the first and second utilization units 3a and 3b. The refrigerant flowing in the second utilization pipes 56a and 56b passes through the utilization side expansion valves 51a and 51b of the utilization units 3a and 3b.

[0184] Next, the refrigerant that has passed through the utilization side expansion valves 51a and 51b whose openings have been adjusted exchanges heat with the indoor air supplied by the indoor fans 53a and 53b in the utilization side heat exchangers 52a and 52b. As a result, the refrigerant flowing in the utilization side heat exchangers 52a and 52b evaporates and becomes a low-pressure gas refrigerant. The indoor air is cooled and supplied to the room. As a result, the indoor space is cooled. The low-pressure gas refrigerant evaporated in the utilization side heat exchangers 52a and 52b is transported to the converging pipes 62a and 62b of the first and second branching units 6a and 6b.

[0185] Then, the low-pressure refrigerant sent to the merging pipes 62a and 62b passes through the second regulating valves 67a and 67b and the second branch pipes 64a and 64b, and is sent to the secondary-side second communicating pipe 9 and merges there.

[0186] Next, the low-pressure gas refrigerant sent to the secondary-side second communication pipe 9 passes through the second stop valve 33 , the second pipe 29 , the suction flow path 23 , and the secondary-side accumulator 30 , and returns to the suction side of the secondary-side compressor 21 .

[0187] In this way, the operation in the cooling main operation is performed.

[0188] (9-4) Heating main operation

[0189] In the heating-main operation, for example, the following operation is performed: the utilization-side heat exchangers 52a and 52b of the utilization units 3a and 3b function as radiators of the refrigerant, and the utilization-side heat exchanger 52c functions as an evaporator of the refrigerant. In the heating-main operation, the cascade heat exchanger 35 functions as an evaporator of the secondary-side refrigerant. In the heating-main operation, the primary-side refrigerant circuit 5a and the secondary-side refrigerant circuit 10 of the refrigeration cycle device 1 are operated as follows. Figure 6 As shown. Figure 6 The arrows indicated in the primary-side refrigerant circuit 5a and the arrows indicated in the secondary-side refrigerant circuit 10 indicate the flow of the refrigerant during the heating main operation.

[0190] Specifically, in the primary unit 5, the primary switching mechanism 72 is switched to the sixth connection state, so that the cascade heat exchanger 35 functions as a heat sink for the primary refrigerant. The sixth connection state of the primary switching mechanism 72 is Figure 6 The primary side switching mechanism 72 of the primary side switching mechanism 72 is connected in a state shown by a dotted line. Thus, in the primary side unit 5, the primary side refrigerant discharged from the primary side compressor 71, passing through the primary side switching mechanism 72 and passing through the first gas stop valve 109 passes through the primary side second connecting pipe 112 and the second gas stop valve 107, and is transported to the primary side flow path 35b of the cascade heat exchanger 35. The refrigerant flowing in the primary side flow path 35b of the cascade heat exchanger 35 is condensed by heat exchange with the secondary side refrigerant flowing in the secondary side flow path 35a. When the primary side refrigerant condensed in the cascade heat exchanger 35 flows in the second refrigerant piping 114, after passing through the primary side second expansion valve 102 controlled to be fully open, it flows in the order of the second liquid stop valve 105, the primary side first connecting pipe 111, the first liquid stop valve 108, and the primary side subcooling heat exchanger 103, and is decompressed in the primary side first expansion valve 76. In addition, when the heating main operation is performed, the primary side subcooling expansion valve 104a is controlled to be in a closed state, whereby the refrigerant does not flow in the primary side subcooling circuit 104, and therefore, the heat exchange in the primary side subcooling heat exchanger 103 is not performed. In addition, the valve opening of the primary side first expansion valve 76 is controlled, for example, so that the superheat of the refrigerant sucked into the primary side compressor 71 satisfies a prescribed condition. The refrigerant decompressed in the primary side first expansion valve 76 is evaporated by heat exchange with the external air supplied from the primary side fan 75 in the primary side heat exchanger 74, passes through the primary side switching mechanism 72 and the primary side accumulator 105, and is sucked into the primary side compressor 71.

[0191] In the cascade unit 2, the secondary side switching mechanism 22 is switched to the second connection state. In the second connection state of the secondary side switching mechanism 22, the discharge flow path 24 is connected to the first pipe 28 through the second switching valve 22b, and the third pipe 25 is connected to the suction flow path 23 through the first switching valve 22a. Thus, the cascade heat exchanger 35 functions as an evaporator of the secondary side refrigerant. In addition, the opening degree of the cascade expansion valve 36 is adjusted. In the first to third branch units 6a, 6b, 6c, the first regulating valve 66a, 66b and the second regulating valve 67c are controlled to be in the open state, and the first regulating valve 66c and the second regulating valve 67a, 67b are controlled to be in the closed state. Thus, the utilization side heat exchangers 52a, 52b of the utilization units 3a, 3b function as radiators of the refrigerant, and the utilization side heat exchanger 52c of the utilization unit 3c functions as an evaporator of the refrigerant. And, the utilization side heat exchanger 52c of the utilization unit 3c and the suction side of the secondary side compressor 21 of the cascade unit 2 are connected via the first utilization pipe 57a, the first connecting pipe 15c, the converging pipe 62c, the second branching pipe 64c, and the secondary side second connecting pipe 9. In addition, the utilization side heat exchangers 52a, 52b of the utilization units 3a, 3b and the discharge side of the secondary side compressor 21 of the cascade unit 2 are connected via the discharge flow path 24, the first pipe 28, the secondary side first connecting pipe 8, the first branching pipes 63a, 63b, the converging pipes 62a, 62b, the first connecting pipes 15a, 15b, and the first utilization pipes 57a, 57b. In addition, the secondary side subcooling expansion valve 48a and the bypass expansion valve 46a are controlled to be closed. In the utilization units 3a, 3b, 3c, the opening of the utilization side expansion valves 51a, 51b, 51c is adjusted.

[0192] Furthermore, in the heating-main operation, in the secondary-side refrigerant circuit 10, for example, the frequency of the secondary-side compressor 21 is controlled so that the load in the heat exchangers that function as radiators of the secondary-side refrigerant among the utilization-side heat exchangers 52a, 52b, and 52c is processed, thereby performing capacity control. Thus, in the heating-main operation, control is performed so that the secondary-side refrigerant discharged from the secondary-side compressor 21 can reach a critical state exceeding the critical pressure. Furthermore, in the primary-side refrigerant circuit 5a, for example, the frequency of the primary-side compressor 71 is controlled so that the condensation temperature of the primary-side refrigerant in the primary-side flow path 35b of the cascade heat exchanger 35 reaches a predetermined primary-side condensation target temperature, thereby performing capacity control.

[0193] In the secondary refrigerant circuit 10 , the secondary high-pressure refrigerant compressed and discharged by the secondary compressor 21 is delivered to the secondary first communication pipe 8 through the second switching valve 22 b of the secondary switching mechanism 22 , the first pipe 28 and the first stop valve 32 .

[0194] Next, the high-pressure refrigerant delivered to the secondary side first connecting pipe 8 is branched into two and delivered to the first branch pipes 63a and 63b of the first branch unit 6a and the second branch unit 6b respectively connected to the first utilization unit 3a and the second utilization unit 3b in operation. The high-pressure refrigerant delivered to the first branch pipes 63a and 63b passes through the first regulating valves 66a and 66b, the converging pipes 62a and 62b, and the first connecting pipes 15a and 15b, and is delivered to the utilization side heat exchangers 52a and 52b of the first utilization unit 3a and the second utilization unit 3b.

[0195] Next, the high-pressure refrigerant delivered to the utilization side heat exchangers 52a and 52b exchanges heat with the indoor air supplied by the indoor fans 53a and 53b in the utilization side heat exchangers 52a and 52b. Thus, the refrigerant flowing in the utilization side heat exchangers 52a and 52b dissipates heat. The indoor air is heated and supplied to the room. Thus, the indoor space is heated. The refrigerant dissipating heat in the utilization side heat exchangers 52a and 52b flows in the second utilization pipes 56a and 56b and passes through the utilization side expansion valves 51a and 51b whose opening is adjusted. In addition, the secondary side refrigerant after passing through the utilization side expansion valves 51a and 51b becomes below the critical pressure. Then, the refrigerant flowing in the second connecting pipes 16a and 16b is delivered to the secondary side third connecting pipe 7 via the third branching pipes 61a and 61b of the branching units 6a and 6b.

[0196] Next, part of the refrigerant sent to the third secondary-side communication pipe 7 is sent to the third branch pipe 61 c of the branch unit 6 c , and the rest flows to the third stop valve 31 .

[0197] Next, the refrigerant sent to the third branch pipe 61c flows through the second connection pipe 16c, flows through the second usage pipe 56c of the usage unit 3c, and is sent to the usage-side expansion valve 51c.

[0198] Next, the refrigerant that has passed through the utilization side expansion valve 51c whose opening is adjusted exchanges heat with the indoor air supplied by the indoor fan 53c in the utilization side heat exchanger 52c. As a result, the refrigerant flowing in the utilization side heat exchanger 52c evaporates and becomes a low-pressure gas refrigerant. The indoor air is cooled and supplied to the room. As a result, the indoor space is cooled. The low-pressure gas refrigerant evaporated in the utilization side heat exchanger 52c passes through the first utilization pipe 57c and the first connecting pipe 15c and is transported to the confluence pipe 62c.

[0199] Next, the low-pressure gas refrigerant sent to the joining pipe 62 c passes through the second regulating valve 67 c and the second branching pipe 64 c and is sent to the secondary-side second communication pipe 9 .

[0200] Next, the low-pressure gas refrigerant sent to the secondary-side second communication pipe 9 passes through the second stop valve 33 , the second pipe 29 , the suction flow path 23 , and the secondary-side accumulator 30 , and returns to the suction side of the secondary-side compressor 21 .

[0201] In addition, the refrigerant flowing to the third stop valve 31 is delivered to the cascade expansion valve 36. After passing through the cascade expansion valve 36 whose opening is adjusted, the refrigerant delivered to the cascade expansion valve 36 exchanges heat with the primary refrigerant flowing in the primary flow path 35b in the secondary flow path 35a of the cascade heat exchanger 35. As a result, the refrigerant flowing in the secondary flow path 35a of the cascade heat exchanger 35 evaporates and becomes a low-pressure gas refrigerant, and is delivered to the first switching valve 22a of the secondary switching mechanism 22. The low-pressure gas refrigerant delivered to the first switching valve 22a of the secondary switching mechanism 22 merges with the low-pressure gas refrigerant evaporated in the utilization side heat exchanger 52c in the suction flow path 23. The merged refrigerant returns to the suction side of the secondary compressor 21 via the secondary accumulator 30.

[0202] In this way, the operation in the heating main operation is performed.

[0203] (9-5) Oil return operation

[0204] During the heating operation and the heating-main operation, when the predetermined oil return condition is satisfied, the connection state of the secondary refrigerant circuit 10 is temporarily changed to the connection state during the cooling operation and the operation is performed, thereby performing the oil return operation. As a result, the refrigeration oil accumulated at the lower end of the container body 90 of the secondary receiver 45 can be extracted from the secondary receiver 45 via the second refrigerant pipe 97 in the fifth pipe 27 extending from the lower end of the secondary receiver 45.

[0205] The predetermined oil return condition is not particularly limited, and for example, the heating operation and the heating main operation may be performed for a predetermined time. In addition, the end of the oil return operation is also not particularly limited, and for example, the oil return operation may be performed for a predetermined time.

[0206] (10) Secondary side receiver

[0207] Figure 7 A schematic structural diagram of the secondary side receiver 45 is shown.

[0208] The secondary side receiver 45 has a container body 90 , a first refrigerant tube 96 , a second refrigerant tube 97 , and a third refrigerant tube 98 .

[0209] The container body 90 is a substantially cylindrical container having an internal volume corresponding to the amount of refrigerant filled in the secondary refrigerant circuit 10, and temporarily stores the refrigerant flowing in the secondary refrigerant circuit 10. The container body 90 has an upper portion 91, a lower peripheral surface portion 92, and a bottom portion 93, which are welded and fixed to each other. The upper portion 91 has a cylindrical shape in which an internal space is formed in a manner opening downward. The lower peripheral surface portion 92 is arranged below the upper portion 91 and has a cylindrical shape penetrating in the vertical direction. The bottom portion 93 is a cylindrical member with the vertical direction as the thickness direction. The bottom portion 93 has an upper surface 93a facing the space side inside the secondary receiver 45, that is, the upper side, and a lower surface 93b facing the space side outside the secondary receiver 45, that is, the lower side. In this embodiment, both the upper surface 93a and the lower surface 93b extend in a horizontal plane. The bottom portion 93 has a portion penetrating in the vertical direction at the center when viewed from above, and the end of the second refrigerant pipe 97 on the side connected to the secondary receiver 45 is inserted from below. The bottom portion 93 and the second refrigerant pipe 97 are welded to each other.

[0210] In the present embodiment, the first refrigerant pipe 96 is, for example, a pipe extending laterally from a portion of the circumferential surface of the container body 90, and constitutes a portion of the fourth pipe 26 in the secondary refrigerant circuit 10. The first refrigerant pipe 96 is welded to the upper portion 91 of the container body 90. The first refrigerant pipe 96 has a portion extending downward inside the secondary receiver 45, and the end portion located inside the secondary receiver 45 has an opening portion 96a formed by being inclined relative to the axial direction in which the pipe extends. The end portion of the first refrigerant pipe 96 inside the secondary receiver 45 is in contact with the upper surface 93a of the bottom portion 93, or extends to the front of the upper surface 93a of the bottom portion 93.

[0211] The second refrigerant pipe 97 is a pipe extending downward from the bottom 93 of the container body 90, and constitutes a part of the fifth pipe 27 in the secondary refrigerant circuit 10. The second refrigerant pipe 97 is welded to the bottom 93 in a state where it is inserted into a through portion formed in the up-down direction of the bottom 93. In the present embodiment, the height position of the upper end 97a of the second refrigerant pipe 97 is arranged to be lower than the height position of the portion connected to the second refrigerant pipe 97 in the upper surface 93a of the bottom 93. Specifically, in the present embodiment, the upper end 97a of the second refrigerant pipe 97 and the upper surface 93a of the bottom 93 are arranged on the same horizontal plane.

[0212] The third refrigerant pipe 98 is a pipe extending laterally from a portion of the peripheral surface of the container body 90 and constitutes a portion of the bypass circuit 46 in the secondary refrigerant circuit 10. The third refrigerant pipe 98 is welded to the upper portion 91 of the container body 90.

[0213] (11) Features of the embodiments

[0214] In the secondary refrigerant circuit 10 of the refrigeration cycle device 1 of the present embodiment, carbon dioxide refrigerant and PAG oil, which are in a mutually immiscible relationship, are used. Here, under the use condition in the secondary refrigerant circuit 10, the density of the PAG oil is greater than the density of the carbon dioxide refrigerant. Therefore, in the secondary receiver 45, the PAG oil is easily located below the carbon dioxide refrigerant.

[0215] In contrast, in the secondary receiver 45 of the present embodiment, the second refrigerant pipe 97 is provided so as to penetrate the bottom 93 in the up-down direction. In addition, the upper end 97a of the second refrigerant pipe 97 is arranged at the same height position as the upper surface 93a of the bottom 93, or at a height position lower than the upper surface 93a of the bottom 93. Thus, the PAG oil that flows into the secondary receiver 45 through the first refrigerant pipe 96 and is located below the carbon dioxide refrigerant is efficiently sent out of the secondary receiver 45 through the second refrigerant pipe 97. Therefore, the refrigeration oil is prevented from being continuously stored in the secondary receiver 45.

[0216] In the refrigeration cycle device 1 of the present embodiment, the carbon dioxide refrigerant discharged from the secondary compressor 21 of the secondary refrigerant circuit 10 is changed to a state that is not a supercritical state by heat exchange with the primary refrigerant flowing in the primary refrigerant circuit 5a in the cascade heat exchanger 35 or by controlling the valve opening of the cascade expansion valve 36, and is sent to the secondary receiver 45. Therefore, it is possible to avoid the state being changed to a supercritical state, which is often unstable, and even if the carbon dioxide refrigerant and the refrigeration oil are phase-separated in the secondary receiver 45, it is possible to avoid the refrigeration oil from being continuously accumulated in the secondary receiver 45.

[0217] (12) Other Implementation Methods

[0218] (12-1) Other Implementation Methods A

[0219] In the above embodiment, the case where the upper surface 93 a of the bottom portion 93 of the secondary side receiver 45 is a horizontal surface is described as an example.

[0220] In contrast, for example, Figure 8 As shown, instead of the upper surface 93a of the above-mentioned embodiment, the bottom 93 of the secondary side receiver 45 may also have an upper curved surface 193a that is gently curved downward in a convex shape and constitutes the bottom surface of the inner side of the secondary side receiver 45. The upper curved surface 193a has a curved shape that gently descends as it approaches the upper end 97a of the second refrigerant tube 97. In addition, the upper end 97a of the second refrigerant tube 97 is located at the lowermost end of the upper curved surface 193a.

[0221] In this case, the refrigeration oil on the upper curved surface 193 a is guided to the upper end 97 a of the second refrigerant pipe 97 by its own weight, so the refrigeration oil can be efficiently discharged from the secondary receiver 45 .

[0222] (12-2) Other Implementation Methods B

[0223] In the above-mentioned other embodiment A, the case where the bottom 93 of the secondary side receiver 45 has the upper curved surface 193 a is described as an example.

[0224] In contrast, for example, Fig. 9 As shown, instead of the lower surface 93 b , the bottom 93 of the secondary receiver 45 may have a lower curved surface 193 b that is curved convexly downward like the upper curved surface 193 a and constitutes the outer bottom surface of the secondary receiver 45 .

[0225] In this case, not only can the effects of the above-described embodiment and other embodiment A be obtained, but also the thickness of the bottom portion 93 in the vertical direction can be constant, thereby making it easier to ensure the pressure resistance of the secondary side receiver 45 .

[0226] (12-3) Other Implementation Methods C

[0227] In the above embodiment, the case where the height position of the upper end 97a of the second refrigerant pipe 97 is lower than the height position of the portion connected to the second refrigerant pipe 97 on the upper surface 93a of the bottom 93 is described as an example.

[0228] On the other hand, the height position of the upper end 97a of the second refrigerant pipe 97 is not limited thereto.

[0229] For example, Fig.10 As shown, the upper end 197a of the second refrigerant tube 197 may also be located slightly above the portion of the upper surface 93a of the bottom 93 connected to the second refrigerant tube 197. For example, the height position of the upper end 197a of the second refrigerant tube 197 may be higher than the portion of the upper surface 93a of the bottom 93 connected to the second refrigerant tube 197 and lower than the height position 15 mm higher than the portion. In addition, the height position of the upper end 197a of the second refrigerant tube 197 may also be lower than the height position 10 mm higher than the portion of the upper surface 93a of the bottom 93 connected to the second refrigerant tube 197. In addition, the difference in height direction between the upper end 197a of the second refrigerant tube 197 and the portion of the upper surface 93a of the bottom 93 connected to the second refrigerant tube 197 may also be less than 1 / 100 of the height of the container body 90 of the secondary side receiver 45. In this way, the upper end 197a of the second refrigerant pipe 197 protrudes further upward from the upper surface 93a of the bottom portion 93, thereby ensuring pipe replacement and facilitating manufacturing.

[0230] In addition, a portion of the second refrigerant pipe 197 above the upper surface 93a of the bottom portion 93 near the upper end 197a may be expanded so that the flow path area increases upward.

[0231] (12-4) Other Implementation Methods D

[0232] In the above embodiment, the case where the first refrigerant pipe 96 is provided so as to extend laterally from a part of the peripheral surface of the secondary-side receiver 45 is described as an example.

[0233] On the other hand, the connection method between the first refrigerant pipe 96 and the secondary-side receiver 45 is not limited to this.

[0234] For example, Fig.11 As shown, the first refrigerant pipe 196 may also be provided to extend downward from the bottom 93 of the secondary side receiver 45. In this case, the upper end 196a of the first refrigerant pipe 196 may also be configured similarly to the upper end 97a of the second refrigerant pipe 97 of the above-mentioned embodiment, or similarly to the upper end 197a of the second refrigerant pipe 197 of the above-mentioned other embodiment C.

[0235] (12-5) Other Implementation Methods E

[0236] In the above embodiment, the second refrigerant pipe 97 is arranged to penetrate the bottom 93 vertically in the secondary receiver 45 as a high-pressure receiver provided in the secondary refrigerant circuit 10 where the high-pressure refrigerant flows.

[0237] In contrast, for example, Fig.12 Like the intermediate pressure receiver 18 in the refrigerant circuit 210 of the air conditioning device 201 shown in the figure, the second refrigerant pipe 19 is provided so as to penetrate the bottom edge up and down.

[0238] The air conditioner 201 is a device that adjusts the air of a target space by performing a vapor compression refrigeration cycle. The air conditioner 201 mainly includes an outdoor unit 202, an indoor unit 203, a liquid-side refrigerant communication pipe 207 and a gas-side refrigerant communication pipe 208 that connect the outdoor unit 202 and the indoor unit 203, and a controller 4 that controls the operation of the air conditioner 201. In the air conditioner 201, the refrigerant sealed in the refrigerant circuit 210 is compressed, radiates heat, is decompressed, evaporates, and is compressed again. The air conditioner 201 is filled with a refrigerant and a refrigeration oil that is immiscible with the refrigerant and has a higher density than the refrigerant. Specifically, the refrigerant is a carbon dioxide refrigerant, and the refrigeration oil is a PAG oil.

[0239] The outdoor unit 202 is connected to the indoor unit 203 via a liquid-side refrigerant communication pipe 207 and a gas-side refrigerant communication pipe 208, and constitutes a part of the refrigerant circuit 210. The outdoor unit 202 mainly includes a compressor 221, a four-way reversing valve 222, an outdoor heat exchanger 235, a first refrigerant pipe 17, a first outdoor expansion valve 17a, an intermediate pressure receiver 18, a second refrigerant pipe 19, a second outdoor expansion valve 19a, an outdoor fan 11, a liquid-side stop valve 231, and a gas-side stop valve 232.

[0240] The compressor 221 is a device that compresses the low-pressure refrigerant in the refrigeration cycle to a high pressure. Here, a closed-type compressor in which a positive displacement compression element such as a rotary type or a scroll type is driven to rotate by a compressor motor is used as the compressor 221. The compressor motor is used to change the capacity, and the operating frequency can be controlled by an inverter.

[0241] The four-way reversing valve 222 can switch the connection state between a connection state in which the discharge side of the compressor 221 is connected to the outdoor heat exchanger 235 and the suction side of the compressor 221 is connected to the gas side stop valve 232 for cooling operation and a connection state in which the discharge side of the compressor 221 is connected to the gas side stop valve 232 and the suction side of the compressor 221 is connected to the outdoor heat exchanger 235 for heating operation.

[0242] The outdoor heat exchanger 235 is a heat exchanger that functions as a radiator of high-pressure refrigerant in the refrigeration cycle during cooling operation and functions as an evaporator of low-pressure refrigerant in the refrigeration cycle during heating operation. The outdoor heat exchanger 235 has a plurality of heat transfer fins and a plurality of heat transfer pipes that penetrate and are fixed thereto. The outdoor heat exchanger 235 is an air heat exchanger that performs heat exchange between the refrigerant and the air flowing outside.

[0243] The outdoor fan 11 generates an air flow for sucking outdoor air into the outdoor unit 202, exchanging heat with the refrigerant in the outdoor heat exchanger 235, and then exhausting the air to the outside. The outdoor fan 11 is driven to rotate by an outdoor fan motor.

[0244] The first refrigerant pipe 17 connects the end of the outdoor heat exchanger 235 on the opposite side of the compressor 221 to the intermediate pressure receiver 18. The first refrigerant pipe 17 is provided with a first outdoor expansion valve 17a capable of controlling the valve opening. The opening of the first outdoor expansion valve 17a is controlled during cooling operation to deliver the intermediate pressure refrigerant obtained by decompressing the high pressure refrigerant to the intermediate pressure receiver 18. In addition, the opening of the first outdoor expansion valve 17a is controlled during heating operation to deliver the low pressure refrigerant obtained by decompressing the intermediate pressure refrigerant to the outdoor heat exchanger 235.

[0245] The intermediate pressure receiver 18 is provided between the first outdoor expansion valve 17a and the second outdoor expansion valve 19a in the refrigerant circuit 210. The specific structural details of the intermediate pressure receiver 18 are the same as those of the secondary side receiver 45 of the above-described embodiment.

[0246] The second refrigerant pipe 19 connects the bottom of the intermediate pressure receiver 18 to the liquid side stop valve 231. The second refrigerant pipe 19 is provided with a second outdoor expansion valve 19a capable of controlling the valve opening. The opening of the second outdoor expansion valve 19a is controlled during the heating operation to deliver the intermediate pressure refrigerant obtained by decompressing the high pressure refrigerant to the intermediate pressure receiver 18. In addition, the opening of the second outdoor expansion valve 19a is controlled during the cooling operation to deliver the low pressure refrigerant obtained by decompressing the intermediate pressure refrigerant to the indoor heat exchanger 252.

[0247] The liquid-side stop valve 231 is a manual valve disposed at a portion of the outdoor unit 202 connected to the liquid-side refrigerant communication pipe 207. The gas-side stop valve 232 is a manual valve disposed at a portion of the outdoor unit 202 connected to the gas-side refrigerant communication pipe 208.

[0248] The outdoor unit 202 has an outdoor unit control unit 4a that controls the operation of each part constituting the outdoor unit 202. The indoor unit 203 is installed on a wall surface of a room as a target space, etc. The indoor unit 203 is connected to the outdoor unit 202 through a liquid-side refrigerant communication pipe 207 and a gas-side refrigerant communication pipe 208, and constitutes a part of the refrigerant circuit 210. The indoor unit 203 has an indoor heat exchanger 252, an indoor fan 253, etc.

[0249] The liquid side of the indoor heat exchanger 252 is connected to the liquid side refrigerant communication pipe 207, and the gas side end thereof is connected to the gas side refrigerant communication pipe 208. The indoor heat exchanger 252 is a heat exchanger that functions as an evaporator of low-pressure refrigerant in the refrigeration cycle during cooling operation and functions as a condenser of high-pressure refrigerant in the refrigeration cycle during heating operation. The indoor heat exchanger 252 has a plurality of heat transfer fins and a plurality of heat transfer pipes that penetrate and are fixed thereto.

[0250] The indoor fan 253 generates an air flow for sucking indoor air into the indoor unit 203 , exchanging heat with the refrigerant in the indoor heat exchanger 252 , and then exhausting the air to the outside.

[0251] Furthermore, the indoor unit 203 includes an indoor unit control unit 4 b that controls the operation of each portion constituting the indoor unit 203 .

[0252] In the intermediate pressure receiver 18 described above, as in the above embodiment, the refrigeration oil which is incompatible with the carbon dioxide refrigerant, has a higher density than the carbon dioxide refrigerant and is often located below the carbon dioxide refrigerant can be efficiently discharged through the second refrigerant pipe 19 .

[0253] (12-6) Other Implementation Methods F

[0254] In the above-described embodiment, the refrigeration cycle apparatus 1 in which one cascade unit 2 is connected to one primary-side unit 5 is described as an example.

[0255] In contrast, Fig.13 As shown, as a refrigeration cycle device 1, for example, a plurality of cascade units, namely, a first cascade unit 2a, a second cascade unit 2b, and a third cascade unit 2c, are connected in parallel with respect to one primary side unit 5, thereby including a first secondary side refrigerant circuit 10a having a first cascade circuit 12a, a second secondary side refrigerant circuit 10b having a second cascade circuit 12b, and a third secondary side refrigerant circuit 10c having a third cascade circuit 12c. In addition, in Fig.13 In the figure, the internal structures of the first cascade unit 2a, the second cascade unit 2b, and the third cascade unit 2c are the same as those of the cascade unit 2 of the above-mentioned embodiment, and therefore, only a part thereof is shown to be omitted.

[0256] Here, although the first cascade unit 2a, the second cascade unit 2b, and the third cascade unit 2c are omitted from the illustration, they are connected to a plurality of branching units 6a, 6b, 6c, and a plurality of utilization units 3a, 3b, and 3c, as in the above-mentioned embodiment. Specifically, the first cascade unit 2a is connected to a plurality of branching units and a plurality of utilization units via the secondary side third communicating tube 7a, the secondary side first communicating tube 8a, and the secondary side second communicating tube 9a. The second cascade unit 2b is connected to a plurality of branching units and a plurality of utilization units other than the branching units and utilization units connected to the first cascade unit 2a via the secondary side third communicating tube 7b, the secondary side first communicating tube 8b, and the secondary side second communicating tube 9b. The third cascade unit 2c is connected to a plurality of branching units and utilization units other than the branching units and utilization units connected to the first cascade unit 2a and also different from the branching units and utilization units connected to the second cascade unit 2b via the secondary side third communicating tube 7c, the secondary side first communicating tube 8c, and the secondary side second communicating tube 9c.

[0257] Here, the primary unit 5 and the first cascade unit 2a are connected via the primary first communicating tube 111a and the primary second communicating tube 112a. The primary unit 5 and the second cascade unit 2b are connected via the primary first communicating tube 111b branched from the primary first communicating tube 111a and the primary second communicating tube 112b branched from the primary second communicating tube 112a. The primary unit 5 and the third cascade unit 2c are connected via the primary first communicating tube 111c branched from the primary first communicating tube 111a and the primary second communicating tube 112c branched from the primary second communicating tube 112a.

[0258] Here, the first cascade unit 2a, the second cascade unit 2b, and the third cascade unit 2c each have a primary-side second expansion valve 102 that performs opening control by itself. In addition, the first cascade-side control unit 20a of the first cascade unit 2a, the second cascade-side control unit 20b of the second cascade unit 2b, and the third cascade-side control unit 20c of the third cascade unit 2c each perform opening control of the corresponding primary-side second expansion valve 102. In addition, similarly to the above-mentioned embodiment, the first cascade-side control unit 20a, the second cascade-side control unit 20b, and the third cascade-side control unit 20c each control the valve opening of the corresponding primary-side second expansion valve 102 based on the conditions of the first cascade circuit 12a, the second cascade circuit 12b, and the third cascade circuit 12c that they control by themselves. Thus, among the primary refrigerant flowing in the primary refrigerant circuit 5a, the flow rates of the primary refrigerant in the first primary connecting tube 111a and the second primary connecting tube 112a, the flow rates of the primary refrigerant in the first primary connecting tube 111b and the second primary connecting tube 112b, and the flow rates of the primary refrigerant in the first primary connecting tube 111c and the second primary connecting tube 112c are controlled to correspond to the differences in loads in the first secondary refrigerant circuit 10a, the second secondary refrigerant circuit 10b, and the third secondary refrigerant circuit 10c.

[0259] (12-7) Other Implementation Methods G

[0260] In the above-described embodiment, R32 or R410A is exemplified as the refrigerant used in the primary-side refrigerant circuit 5 a , and carbon dioxide is exemplified as the refrigerant used in the secondary-side refrigerant circuit 10 .

[0261] The refrigerant used in the primary refrigerant circuit 5 a is not particularly limited, and HFC-32, HFO-based refrigerants, mixed refrigerants of HFC-32 and HFO-based refrigerants, carbon dioxide, ammonia, propane, and the like can be used.

[0262] In addition, instead of the primary refrigerant circuit 5a through which the refrigerant flows, a heat medium circuit through which a heat medium such as water or salt water flows may be used. In this case, the heat medium circuit may include a heat source that functions as a heat source or a cold source and a pump for circulating the heat medium. In this case, the flow rate can be adjusted by the pump, and the amount of heat can be controlled by the heat source or the cold source.

[0263] The refrigerant used in the secondary refrigerant circuit 10 is not particularly limited, and HFC-32, HFO-based refrigerants, mixed refrigerants of HFC-32 and HFO-based refrigerants, carbon dioxide, ammonia, propane, and the like can be used.

[0264] Moreover, as an HFO-type refrigerant, for example, HFO-1234yf, HFO-1234ze, etc. can be used.

[0265] In addition, the same refrigerant may be used in the primary refrigerant circuit 5a and the secondary refrigerant circuit 10, or different refrigerants may be used. However, it is preferred that the refrigerant used in the secondary refrigerant circuit 10 satisfies at least one of low global warming potential (GWP: Global Warming Potential), low ozone depletion potential (ODP: Ozone Depletion Potential), low flammability, and low toxicity compared with the refrigerant used in the primary refrigerant circuit 5a. Here, the flammability can be compared, for example, based on the classification related to the flammability of ASHRAE34. Here, the toxicity can be compared, for example, based on the classification related to the safety level of ASHRAE34. In particular, when the total content volume of the secondary refrigerant circuit 10 is larger than the total content volume of the primary refrigerant circuit 5a, by using a refrigerant with at least one of a lower global warming potential (GWP), an ozone depletion potential (OPD), flammability, and toxicity than the refrigerant in the primary refrigerant circuit 5a in the secondary refrigerant circuit 10, the adverse effect when leakage occurs can be suppressed to a small extent.

[0266] (Note)

[0267] As mentioned above, although embodiment of this disclosure is described, it should be understood that various changes in form and details can be made without departing from the spirit and scope of this disclosure described in the claims.

[0268] Explanation of symbols

[0269] 1. Refrigeration cycle device;

[0270] 2 cascade units;

[0271] 2x cascade housing;

[0272] 3a first utilization unit;

[0273] 3b second utilization unit;

[0274] 3c third utilization unit;

[0275] 5 primary side unit;

[0276] 5a primary refrigerant circuit (first refrigerant circuit);

[0277] 10 secondary refrigerant circuit (refrigerant circuit, second refrigerant circuit);

[0278] 12 cascade circuits;

[0279] 13a, 13b, 13c utilize loops;

[0280] 18 Intermediate pressure receiver (refrigerant container);

[0281] 20 cascade side control unit;

[0282] 21 secondary side compressor (compressor);

[0283] 21a compressor motor;

[0284] 22 secondary side switching mechanism;

[0285] 22a first switching valve;

[0286] 22b second switching valve;

[0287] 22x discharge side communication portion;

[0288] 22y suction side communication portion;

[0289] 23 suction flow path (refrigerant flow path);

[0290] 24 discharge flow path;

[0291] 25 third piping;

[0292] 26 fourth pipe;

[0293] 27 fifth pipe;

[0294] 28 first piping;

[0295] 29 second piping;

[0296] 30 secondary side storage tank;

[0297] 34 oil separator;

[0298] 35 cascade heat exchanger;

[0299] 35a secondary side flow path;

[0300] 35b primary side flow path;

[0301] 36 cascade expansion valve;

[0302] 45 secondary side receiver (refrigerant container);

[0303] 46 bypass circuit (refrigerant flow path);

[0304] 46a bypass expansion valve;

[0305] 47 secondary side subcooling heat exchanger;

[0306] 48 secondary side subcooling circuit;

[0307] 48a secondary side subcooling expansion valve;

[0308] 50a-c: a side control unit;

[0309] 51a-c: expansion valve on the utilization side;

[0310] 52a-c: heat exchanger on the utilization side;

[0311] 53a-c indoor fan;

[0312] 60a, 60b, 60c branch unit control unit;

[0313] 66a, 66b, 66c first regulating valve;

[0314] 67a, 67b, 67c second regulating valve;

[0315] 68a, 68b, 68c check valves;

[0316] 69a, 69b, 69c bypass pipe;

[0317] 70 primary side control unit;

[0318] 71 primary side compressor;

[0319] 72 primary side switching mechanism;

[0320] 74 primary side heat exchanger;

[0321] 76: a first expansion valve on the primary side;

[0322] 80 Control Department;

[0323] 90 container body;

[0324] 91 upper part;

[0325] 92 next week face;

[0326] 93 bottom;

[0327] 93a upper surface;

[0328] 93b lower surface;

[0329] 96 first refrigerant pipe;

[0330] 97 second refrigerant pipe;

[0331] 97a upper end;

[0332] 98 third refrigerant pipe;

[0333] 102 a second expansion valve on the primary side;

[0334] 103 primary side subcooling heat exchanger;

[0335] 104 primary side subcooling circuit;

[0336] 104a primary side subcooling expansion valve;

[0337] 105 primary side storage tank;

[0338] 111 a first connecting pipe on the primary side;

[0339] 112 a second primary side connecting pipe;

[0340] 113 first refrigerant pipe;

[0341] 114 second refrigerant pipe;

[0342] 193a upper curved surface (curved shape portion);

[0343] 193b lower curved surface;

[0344] 196 first refrigerant pipe;

[0345] 197 second refrigerant pipe;

[0346] 197a upper end;

[0347] 210 Refrigerant circuit.

[0348] Prior art literature

[0349] Patent Literature

[0350] Patent Document 1: Japanese Patent Application Publication No. 2008-164225.

Claims

1. A refrigeration cycle device (1), comprising a refrigerant circuit (10, 210) for circulating a refrigerant containing a carbon dioxide refrigerant and refrigeration oil, characterized in that: The refrigerant circuit has: Compressor (21); a first heat exchanger (35); A refrigerant container (45, 18) for storing the refrigerant; as well as The second heat exchanger (52a, 52b, 52c), The refrigerant container comprises: A container body (90), the container body having cylindrical members (91, 92) and a bottom member (93), the bottom member being welded and fixed to the cylindrical member, with the vertical direction being the thickness direction; a first refrigerant pipe (96, 196) connected to the container body; and a second refrigerant pipe (97, 197) connected to the container body, The bottom member (93) has a surface facing the space inside the cylindrical refrigerant container that is a downwardly convex curved surface (193a). The refrigeration oil is immiscible with the refrigerant, and the density of the refrigeration oil is greater than the density of the refrigerant. The second refrigerant pipe extends downward from the bottom member, The first refrigerant pipe is connected to the first heat exchanger, The second refrigerant pipe is connected to the second heat exchanger.

2. The refrigeration cycle device according to claim 1, characterized in that: The height position of the upper end of the second refrigerant pipe is lower than the lowermost end of the inner peripheral surface of the bottom member of the container body.

3. The refrigeration cycle device according to claim 1 or 2, characterized in that: The refrigerant container is a high-pressure receiver that is provided at a location in the refrigerant circuit where the high-pressure refrigerant flows and stores the high-pressure refrigerant therein.

4. The refrigeration cycle device according to claim 1 or 2, characterized in that: The refrigerant circuit has a portion for high-pressure refrigerant, low-pressure refrigerant and intermediate-pressure refrigerant to flow. The refrigerant container is an intermediate-pressure receiver that is provided at a location in the refrigerant circuit where the intermediate-pressure refrigerant flows and stores the intermediate-pressure refrigerant therein.

5. The refrigeration cycle device according to claim 1 or 2, characterized in that: The refrigerant container further includes a third refrigerant pipe (98) connected to the container body and guiding the refrigerant in the container body to the suction side of the compressor.

6. The refrigeration cycle device according to claim 1 or 2, characterized in that: The refrigeration oil is PAG oil.

7. The refrigeration cycle device according to claim 1 or 2, characterized in that: include: A first refrigerant circuit (5a) for the flow of refrigerant; as well as a cascade heat exchanger (35) as said first heat exchanger, The refrigeration cycle device includes the refrigerant circuit as a second refrigerant circuit (10) independent of the first refrigerant circuit. In the cascade heat exchanger, heat exchange is performed between the refrigerant flowing in the first refrigerant circuit and the refrigerant flowing in the second refrigerant circuit. The refrigerant of the second refrigerant circuit, which is cooled by the refrigerant of the first refrigerant circuit in the cascade heat exchanger and becomes liquid refrigerant, is stored in the refrigerant container.

8. A refrigeration cycle device, characterized in that: include: A primary refrigerant circuit (5a) through which a first refrigerant flows; A secondary refrigerant circuit (10, 210), which is independent of the primary refrigerant circuit and is used for circulation of a second refrigerant containing carbon dioxide refrigerant and refrigeration oil; and a cascade heat exchanger (35) for performing heat exchange between the first refrigerant flowing in the primary refrigerant circuit and the second refrigerant flowing in the secondary refrigerant circuit, The primary refrigerant circuit includes a compressor (71) that sucks the first refrigerant that has passed through the cascade heat exchanger. The secondary refrigerant circuit includes a refrigerant container (45, 18) storing the second refrigerant and an expansion valve (36) provided between the cascade heat exchanger and the refrigerant container. The refrigerant container comprises a container body (90), a first refrigerant pipe (96, 196) connected to the container body, and a second refrigerant pipe (97, 197) connected to the container body. The refrigeration oil is immiscible with the second refrigerant, the density of the refrigeration oil is greater than the density of the second refrigerant, The second refrigerant pipe extends downward from the bottom of the container body. The second refrigerant cooled by the first refrigerant in the cascade heat exchanger to become liquid refrigerant is stored in the refrigerant container. Either or both of the compressor and the expansion valve are controlled so that the second refrigerant flowing from the cascade heat exchanger toward the refrigerant container does not exceed a critical point.

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