Refrigeration cycle device

Abstract

This refrigeration cycle device (1) comprises a load device (3) and an outdoor unit (2). The outdoor unit (2) includes: a first flow path (F1) from a refrigerant inlet port (PI2) to a refrigerant outl

Description

Refrigeration cycle equipment

[0001] The present invention relates to a refrigeration cycle device.

[0002] Some refrigeration cycle systems use two-stage compression to reduce the compression ratio per compressor stage. In such systems, the refrigerant flow rate in the low-stage cycle is kept to a minimum, minimizing the compression power required in the low-stage cycle, and improving efficiency compared to a single-stage cycle.

[0003] However, the temperature of the refrigerant supplied to the high-stage compressor may rise, and the refrigerant discharged from the high-stage compressor may become excessively superheated. As a countermeasure against this, a refrigeration cycle device disclosed in JP 2020-24046 A includes an intermediate pipe that supplies the refrigerant discharged from the intermediate receiver to a suction port of the high-stage compressor, an internal heat exchanger that heats the refrigerant circulating through the intermediate pipe, a bypass pipe that supplies the liquid-phase refrigerant separated in the gas-liquid separator to the intermediate pipe upstream of the internal heat exchanger, and a control valve provided in the bypass pipe.

[0004] By injecting refrigerant into the compressor through the bypass piping, it is possible to prevent problems in the high-stage compressor caused by the refrigerant being discharged from the high-stage compressor being over-superheated.

[0005] Japanese Patent Application Laid-Open No. 2020-24046

[0006] In recent years, the use of natural refrigerants in refrigeration cycle equipment has been considered as a measure against global warming. ２ In a refrigeration cycle device using a refrigerant, a refrigerant liquid is stored, so it is possible to place an intermediate pressure receiver with a pressure below the critical pressure on an intermediate pipe (hereinafter also referred to as an injection flow path) that supplies the refrigerant to the suction port (intermediate pressure port) of a high-stage compressor.

[0007] However, there is a demand for refrigeration cycle systems with a wide range of capacities, from small to large. For example, if multiple compressors are installed in parallel to increase capacity, multiple injection flow paths are also required. The intermediate-pressure receiver is located on the injection flow path, but because it is a pressure-resistant container, it is expensive to manufacture, and it is difficult to install multiple intermediate-pressure receivers due to total cost and space constraints.

[0008] The present disclosure aims to provide a refrigeration cycle device that solves these problems and that can achieve a large capacity while suppressing costs and size.

[0009] The refrigeration cycle apparatus of the present disclosure includes a load device including a first expansion valve and an evaporator, and an outdoor unit having a refrigerant inlet port and a refrigerant outlet port for connection to the load device. The outdoor unit includes a first flow path from the refrigerant inlet port to the refrigerant outlet port, which forms a circulation flow path through which the refrigerant circulates together with the load device, a condenser disposed in the first flow path, a plurality of compressors disposed in parallel in the first flow path between the refrigerant inlet port and the condenser, a receiver, a second flow path branching from a portion of the first flow path between the condenser and the refrigerant outlet port and connected to the receiver, a second expansion valve disposed in the second flow path, a plurality of third flow paths branching downstream of the receiver and sending refrigerant to the plurality of compressors, and a plurality of third expansion valves disposed in each of the third flow paths.

[0010] According to the refrigeration cycle device of the present disclosure, the number of intermediate-pressure receivers is not increased, so that a large capacity can be achieved while suppressing costs and size.

[0011] Fig. 1 is an overall configuration diagram of a refrigeration cycle device according to embodiment 1. Fig. 2 is a flowchart for explaining control of the opening degree of expansion valve 71. Fig. 3 is a flowchart for explaining control of the opening degree of expansion valve 72A. Fig. 4 is a flowchart for explaining control of the opening degree of expansion valve 72B. Fig. 5 is an overall configuration diagram of a refrigeration cycle device according to embodiment 2.

[0012] Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings. While several embodiments will be described below, it was originally intended that the configurations described in each embodiment be combined as appropriate. Note that identical or corresponding parts in the drawings will be designated by the same reference numerals, and their description will not be repeated.

[0013] Embodiment 1. Fig. 1 is an overall configuration diagram of a refrigeration cycle apparatus according to embodiment 1. Note that Fig. 1 functionally illustrates the connection relationships and arrangement of devices in the refrigeration cycle apparatus, and does not necessarily illustrate the physical spatial arrangement.

[0014] 1 includes an outdoor unit 2 and a load device 3. The outdoor unit 2 has a refrigerant outlet port PO2 and a refrigerant inlet port PI2 for connection to the load device 3. The load device 3 has a refrigerant outlet port PO3 and a refrigerant inlet port PI3 for connection to the outdoor unit 2.

[0015] The outdoor unit 2 of the refrigeration cycle apparatus 1 is configured so as to be connectable to the load device 3 via an extension pipe or the like. The outdoor unit 2 includes an accumulator 60, compressors 10A and 10B, a condenser 20, and heat exchangers 30A and 30B.

[0016] Each of the compressors 10A and 10B is a single-stage compressor having a suction port, a discharge port, and an injection port. Each of the heat exchangers 30A and 30B has a first passage and a second passage, and is configured to exchange heat between the refrigerant flowing through the first passage and the refrigerant flowing through the second passage.

[0017] The load device 3 includes a first expansion valve 40 and an evaporator 50. The evaporator 50 is configured to perform heat exchange between air and a refrigerant. In the refrigeration cycle device 1, the evaporator 50 evaporates the refrigerant by absorbing heat from the air in the space to be cooled. The first expansion valve 40 is, for example, a temperature expansion valve that is controlled independently of the outdoor unit 2. Note that the first expansion valve 40 may also be an electronic expansion valve that can reduce the pressure of the refrigerant.

[0018] Compressor 10A compresses refrigerant drawn from accumulator 60 via pipe 86A and discharges the compressed refrigerant to pipe 80A. Compressor 10B compresses refrigerant drawn from accumulator 60 via pipe 86B and discharges the compressed refrigerant to pipe 80B. Pipes 80A and 80B merge to form pipe 80, which is connected to condenser 20. Each of compressors 10A and 10B is configured to change its operating frequency within a predetermined range through inverter control. Each of compressors 10A and 10B is also provided with an injection port, allowing refrigerant from the injection port to flow into the middle of the compression process. Compressors 10A and 10B are configured to adjust their rotational speeds in accordance with control signals from control device 100. Adjusting the rotational speeds of compressors 10A and 10B adjusts the amount of refrigerant circulating, thereby adjusting the capacity of refrigeration cycle system 1. Various types of compressors can be used for compressors 10A and 10B, including scroll types.

[0019] Condenser 20 is configured so that high-temperature, high-pressure gas refrigerant discharged from compressors 10A and 10B exchanges heat (radiates heat) with outside air. This heat exchange condenses the refrigerant and changes it to a liquid phase. The refrigerant discharged from compressors 10A and 10B to pipe 80 is condensed and liquefied in condenser 20 and flows out to pipe 81. A fan (not shown) that blows outside air is attached to condenser 20 to increase the efficiency of heat exchange.

[0020] Here, the refrigerant used in the refrigerant circuit of the refrigeration cycle device 1 is CO ２ However, if it becomes difficult to ensure the degree of supercooling, other refrigerants may be used.

[0021] In this specification, for ease of explanation, CO in a supercritical state is used. ２ In this specification, for ease of explanation, the amount of temperature drop from the reference temperature of a refrigerant in a supercritical state is also referred to as the degree of subcooling.

[0022] The pipe 81 branches into pipes 81A and 81B. The refrigerant that has passed through the pipes 81A and 81B passes through the first flow paths of the heat exchangers 30A and 30B, respectively, and then flows out into pipes 82A and 82B. The pipes 82A and 82B merge to form the pipe 82.

[0023] A first flow path F1 extending from the refrigerant inlet port PI2 to the refrigerant outlet port PO2 via the first passages of the compressors 10A, 10B, the condenser 20, and the heat exchangers 30A, 30B forms a circulation flow path through which the refrigerant circulates, together with a flow path in which the first expansion valve 40 and the evaporator 50 of the load device 3 are disposed. Hereinafter, this circulation flow path will also be referred to as the "main refrigerant circuit" of the refrigeration cycle.

[0024] The outdoor unit 2 further includes a second expansion valve 71, an intermediate receiver (liquid receiver) 73, on-off valves 70A and 70B, and third expansion valves 72A and 72B.

[0025] A pipe 91 branches off from the boundary between the pipes 82 and 83 and is connected to the second expansion valve 71. The second expansion valve 71 and the intermediate pressure receiver 73 are connected by a pipe 92. The pipes 91 and 92 form a second flow path F2. A pipe 93 that discharges liquid refrigerant is connected to the bottom of the intermediate pressure receiver 73. The pipe 93 branches off into pipes 93A and 93B. The liquid refrigerant stored in the bottom of the intermediate pressure receiver 73 passes through pipes 93A and 93B, respectively, and is depressurized in the third expansion valves 72A and 72B. The refrigerant depressurized in the third expansion valves 72A and 72B passes through pipes 94A and 94B, respectively, and is sent to the second passages of the heat exchangers 30A and 30B. The refrigerant that has passed through the second passages of the heat exchangers 30A and 30B further passes through pipes 95A and 95B, respectively, and is sent to the injection ports of the compressors 10A and 10B.

[0026] The pipes 91 and 92 form a second flow path F2, the pipes 93A, 94A, and 95A form a third flow path F3A, and the pipes 93B, 94B, and 95B form a third flow path F3B.

[0027] Hereinafter, the flow paths F2, F3A, and F3B that branch off from the main refrigerant circuit and send refrigerant to each injection port of the compressors 10A and 10B via each second passage of the heat exchangers 30A and 30B are also referred to as "injection flow paths."

[0028] The intermediate-pressure receiver 73 is disposed in common with the flow paths F3A and F3B and stores the refrigerant. The on-off valve 70A opens and closes a gas vent passage that connects the gas outlet of the intermediate-pressure receiver 73 to the connection between the pipe 94A and the pipe 95A. The on-off valve 70B opens and closes a gas vent passage that connects the gas outlet of the intermediate-pressure receiver 73 to the connection between the pipe 94B and the pipe 95B. The expansion valve 72A adjusts the refrigerant flow rate in the flow path F3A. The expansion valve 72B adjusts the refrigerant flow rate in the flow path F3B.

[0029] The second expansion valve 71 is an electronic expansion valve that can reduce the refrigerant in the high-pressure section of the main refrigerant circuit to intermediate pressure. The intermediate-pressure receiver 73 is a container that separates the reduced-pressure refrigerant into gas and liquid phases, stores the liquid refrigerant, and adjusts the amount of refrigerant circulating in the main refrigerant circuit. A gas vent pipe connected to the top of the intermediate-pressure receiver 73 and a pipe 93 connected to the bottom of the intermediate-pressure receiver 73 are pipes for removing the refrigerant separated into gas and liquid refrigerant in the intermediate-pressure receiver 73 in a separated state. The amount of refrigerant in the intermediate-pressure receiver 73 can be adjusted by adjusting the amount of liquid refrigerant discharged from the pipe 93 using the third expansion valves 72A and 72B.

[0030] By providing the intermediate-pressure receiver 73 in the injection flow path in this way, it becomes easy to ensure the degree of subcooling of the refrigerant in the liquid pipe 83. Generally, gas refrigerant is present in the intermediate-pressure receiver 73, and the refrigerant temperature becomes the saturation temperature. Therefore, if the intermediate-pressure receiver 73 is placed in the pipes 82 and 83 without the second expansion valve 71 interposed therebetween, the degree of subcooling of the refrigerant cannot be ensured.

[0031] Furthermore, by providing the intermediate pressure receiver 73 in the intermediate pressure section, even when the pressure in the high pressure section of the main refrigerant circuit is high and the refrigerant is in a supercritical state, it becomes possible to store intermediate pressure liquid refrigerant inside the intermediate pressure receiver 73. Therefore, the design pressure of the container of the intermediate pressure receiver 73 can be lower than that of the high pressure section.

[0032] The outdoor unit 2 further includes a pressure sensor 111, temperature sensors 120A, 120B, and 121, and a control device 100. The control device 100 is configured to control the compressors 10A and 10B, the second expansion valve 71, and the third expansion valves 72A and 72B.

[0033] The pressure sensor 111 detects the pressure PH of the refrigerant discharged from the compressors 10A and 10B and flowing through the pipe 80 where the refrigerant joins, and outputs the detected value to the control device 100.

[0034] Temperature sensor 120A detects a discharge temperature TdA of compressor 10A and outputs the detected value to control device 100. Temperature sensor 120B detects a discharge temperature TdB of compressor 10B and outputs the detected value to control device 100. Temperature sensor 121 detects a refrigerant temperature T1 in pipe 81 at the outlet of condenser 20 and outputs the detected value to control device 100.

[0035] In this embodiment, the flow path F2 controls the discharge temperatures TdA and TdB of the compressors 10A and 10B by flowing the reduced-pressure two-phase refrigerant into the compressors 10A and 10B. In addition, the amount of refrigerant in the main refrigerant circuit can be adjusted by the intermediate-pressure receiver 73 installed on the flow path F2. Furthermore, the second flow path F2 also ensures that the refrigerant in the main refrigerant circuit is subcooled by heat exchange in the heat exchangers 30A and 30B.

[0036] The control device 100 is configured to include a CPU (Central Processing Unit) 102, memory 104 (ROM (Read Only Memory) and RAM (Random Access Memory)), an input / output buffer (not shown) for inputting and outputting various signals, etc. The CPU 102 loads a program stored in the ROM into the RAM, etc., and executes it. The program stored in the ROM is a program in which the processing procedures of the control device 100 are written. The control device 100 controls each device in the outdoor unit 2 in accordance with these programs. This control is not limited to processing by software, but can also be processed by dedicated hardware (electronic circuitry).

[0037] 1, in a refrigeration cycle apparatus 1 in which compressors 10A, 10B are arranged in parallel, an intermediate pressure receiver 73 is installed in the injection flow path, and the liquid refrigerant separated from the gas refrigerant in the common intermediate pressure receiver 73 is branched and circulated through flow paths F3A, F3B of each compressor 10A, 10B. With this configuration, the branched portions to the injection flow paths F3A, F3B to each compressor are reliably liquid single-phase, thereby preventing uneven distribution of the liquid refrigerant and the gas refrigerant.

[0038] Next, the control executed by the control device 100 will be described using a flowchart. Fig. 2 is a flowchart for explaining the control of the opening degree of the expansion valve 71. First, in step S1, the control device 100 detects the degree of subcooling SC of the refrigerant by referring to a table prepared in advance based on the refrigerant temperature T1 at the outlet of the condenser 20 and the pressure of the condenser 20 (approximated by PH).

[0039] Next, in step S2, the control device 100 compares the degree of subcooling SC with the target degree of subcooling SC*. If the degree of subcooling SC is greater than the target degree of subcooling SC* (YES in S2), the control device 100 reduces the opening of the expansion valve 71 (S3). This reduces the amount of liquid refrigerant flowing into the intermediate pressure receiver 73, and the amount of liquid refrigerant in the intermediate pressure receiver 73 decreases, so the amount of refrigerant circulating in the main refrigerant circuit increases. As a result, if the amount of heat radiation from the condenser 20 is constant, the degree of subcooling SC decreases.

[0040] On the other hand, if the degree of subcooling SC is equal to or lower than the target degree of subcooling SC* (NO in S2), the control device 100 increases the opening of the expansion valve 71 (S4). This increases the amount of liquid refrigerant flowing into the intermediate pressure receiver 73, increasing the amount of liquid refrigerant stored in the intermediate pressure receiver 73 and decreasing the amount of refrigerant circulating in the main refrigerant circuit. This increases the degree of subcooling SC when the amount of heat radiation from the condenser 20 is constant.

[0041] In this way, the control device 100 controls the opening degree of the second expansion valve 72 so that the degree of subcooling SC of the refrigerant at the outlet of the condenser 20 approaches the target degree of subcooling SC*.

[0042] 3 is a flowchart for explaining the control of the opening degree of the expansion valve 72A. First, in step S11, the control device 100 detects the temperature TdA of the refrigerant discharged from the compressor 10A using the temperature sensor 120A.

[0043] Next, in step S12, the control device 100 compares the temperature TdA with the target temperature TdA*. If the temperature TdA is higher than the target temperature TdA* (YES in S12), the control device 100 increases the opening of the expansion valve 72A (S13). This increases the amount of intermediate-pressure refrigerant introduced into the compressor 100A, and reduces the discharge temperature TdA of the compressor 100A.

[0044] On the other hand, if the temperature TdA is equal to or lower than the target temperature TdA* (NO in S12), the control device 100 decreases the opening of the expansion valve 72A (S14), thereby decreasing the amount of intermediate-pressure refrigerant introduced into the compressor 100A and increasing the discharge temperature TdA of the compressor 100A.

[0045] In this way, the control device 100 controls the opening degree of the expansion valve 72A so that the discharge temperature TdA of the compressor 10A approaches the target temperature TdA*.

[0046] 4 is a flowchart for explaining the control of the opening degree of the expansion valve 72B. First, in step S21, the control device 100 detects the temperature TdB of the refrigerant discharged from the compressor 10B using the temperature sensor 120B.

[0047] Next, in step S22, the control device 100 compares the temperature TdB with the target temperature TdB*. If the temperature TdB is higher than the target temperature TdB* (YES in S22), the control device 100 increases the opening of the expansion valve 72B (S23). This increases the amount of intermediate-pressure refrigerant introduced into the compressor 100B, and the discharge temperature TdB of the compressor 100B decreases.

[0048] On the other hand, if the temperature TdB is equal to or lower than the target temperature TdB* (NO in S22), the control device 100 decreases the opening of the expansion valve 72B (S24), thereby decreasing the amount of intermediate-pressure refrigerant introduced into the compressor 100B and increasing the discharge temperature TdB of the compressor 100B.

[0049] In this way, the control device 100 controls the opening degree of the expansion valve 72B so that the discharge temperature TdB of the compressor 10B approaches the target temperature TdB*.

[0050] By repeatedly executing the processes of FIGS. 2 to 4, the amount of refrigerant circulating in the main refrigerant circuit and the discharge temperatures TdA and TdB of the compressors 10A and 10B can be set to appropriate values.

[0051] (Control During Low Capacity Operation) The refrigeration cycle device 1 shown in FIG. 1 has a plurality of compressors connected in parallel to increase the capacity.

[0052] When the load is heavy, it is sufficient to operate multiple compressors simultaneously, but depending on the season, the load may decrease and operation at a lower capacity may be necessary. In such cases, operating multiple compressors simultaneously would increase the frequency of on / off switching, so some of the multiple compressors are stopped and only one compressor is operated at a low capacity for continuous operation.

[0053] However, if the same compressor is always stopped during this type of operation, the operating time will be uneven, shortening the overall product life. Therefore, when switching to low-capacity operation, the operating time is averaged by looking at the shutdown history so that the compressor to be stopped is not fixed among the multiple compressors.

[0054] 5 is a flowchart for explaining the compressor stop control during low-capacity operation. First, in step S31, the control device 100 determines whether to transition to low-capacity operation. For example, in the case of a refrigeration system, the control device 100 determines to transition to low-capacity operation when the internal temperature of the refrigeration system drops too much below the set temperature.

[0055] If the system is not to be switched to low capacity operation (NO in S31), the control of the flowchart in Fig. 5 is terminated. On the other hand, if the system is to be switched to low capacity operation (YES in S31), the control device 100 reads out the previous compressor stop history information from a non-volatile memory or the like in step S32. For example, if there are two compressors as shown in Fig. 1, storing which compressor was stopped during the previous low capacity operation can be used as a reference for determining which compressor to stop this time.

[0056] Next, in step S33, the control device 100 determines which compressor to stop. Specifically, the compressor that was stopped during the previous low-capacity operation is operated this time, and the compressor that was operating during the previous low-capacity operation is stopped this time. This alternate stopping of the compressors averages the total operating time of each of the two compressors. When a compressor is stopped, the expansion valves 72A, 72B and on-off valves 70A, 70B corresponding to the stopped compressor are closed, thereby blocking the injection flow path.

[0057] Then, in step S34, the control device 100 updates the stop history information to reflect the result determined in step S33, and stores the updated information in a non-volatile memory or the like.

[0058] In this way, the compressor to be stopped when switching to low capacity operation is determined. When there are two compressors, they are stopped alternately, but when there are three or more compressors, the compressor that has been stopped the least number of times should be stopped so that the number of times the compressors are stopped is averaged out.

[0059] Furthermore, by storing the total operating time in the stop history information and stopping the compressor with the longest total operating time in step S33, it is possible to accurately optimize the lifespan even when the operating time of low-capacity operation varies.

[0060] Embodiment 2. Fig. 6 is an overall configuration diagram of a refrigeration cycle apparatus according to embodiment 2. Note that Fig. 6 functionally illustrates the connection relationships and arrangement of the devices in the refrigeration cycle apparatus, and does not necessarily illustrate the physical spatial arrangement.

[0061] The refrigeration cycle apparatus 201 shown in Fig. 6 includes an outdoor unit 202 and a load device 3. The outdoor unit 202 has a refrigerant outlet port PO2 and a refrigerant inlet port PI2 for connection to the load device 3. The load device 3 has a refrigerant outlet port PO3 and a refrigerant inlet port PI3 for connection to the outdoor unit 2. The configuration of the load device 3 is the same as that of the load device shown in Fig. 1.

[0062] Outdoor unit 202 includes compressors 210A and 210B instead of compressors 10A and 10B in the configuration of outdoor unit 2 shown in Fig. 1. The configuration of other parts of outdoor unit 202 is similar to the configuration of outdoor unit 2, and therefore description thereof will not be repeated here.

[0063] The compressors 10A and 10B are single-stage compressors having an injection port, but the compressors 210A and 210B are two-stage compressors having an intermediate pressure port.

[0064] The compressor 210A includes a first-stage compressor 211A, an intercooler 121A, and a second-stage compressor 213A. The compressor 210B includes a first-stage compressor 211B, an intercooler 121B, and a second-stage compressor 213B.

[0065] In the second embodiment, various types of compressors can be used for the compressors 210A and 210B, such as a scroll type, a rotary type, a screw type, and the like.

[0066] 6 is similar to the configuration in FIG. 1 in that multiple compressors 210A, 210B operate in parallel in a flow path F1 of a main refrigerant circuit. In the flow path F1, refrigerant flows in the order of first-stage compressors 211A, 211B, intercoolers 212A, 212B, and second-stage compressors 213A, 213B. The merged refrigerant then flows in the order of condenser 20, heat exchangers 30A, 30B, expansion valve 40, evaporator 50, and accumulator 60, before returning to the first-stage compressors 211A, 211B.

[0067] By cooling the refrigerant in the economizers 212A and 212B and merging the injection flow path therein, the compression power of the downstream compressors 213A and 213B can be reduced, resulting in an energy saving effect. The economizers 212A and 212B may be integrated with the condenser 20.

[0068] In the injection flow path F2, the refrigerant that has passed through the expansion valve 71 and the intermediate pressure receiver 73 branches, the flow rate is adjusted by the expansion valves 72A and 72B, and after flowing through the second flow paths of the heat exchangers 30A and 30B, it is sucked into the second stage compressors 213A and 213B.

[0069] In the second embodiment, similarly to the first embodiment, a large-capacity refrigeration cycle device can be realized by operating a plurality of existing compressors in parallel without increasing the number of intermediate-pressure receivers 73, which are pressure-resistant containers. This makes it possible to reduce manufacturing costs and development man-hours.

[0070] (Summary) Hereinafter, the first and second embodiments will be summarized again with reference to the drawings.

[0071] (1) The refrigeration cycle apparatus 1, 201 shown in Figures 1 and 6 includes a load device 3 including a first expansion valve 40 and an evaporator 50, and an outdoor unit 2 having a refrigerant outlet port PO2 and a refrigerant inlet port PI2 for connection to the load device 3. The outdoor unit 2 includes a first flow path F1 that is a flow path from a refrigerant inlet port PI2 to a refrigerant outlet port PO2 and forms a circulation flow path through which the refrigerant circulates together with the load device 3, a condenser 20 arranged in the first flow path F1, a plurality of compressors 10A, 10B or 210A, 210B arranged in parallel in the first flow path F1 between the refrigerant inlet port PI2 and the condenser 20, an intermediate pressure receiver 73, a second flow path F2 that branches off from a portion of the first flow path F1 between the condenser 20 and the refrigerant outlet port PO2 and is connected to the intermediate pressure receiver 73, a second expansion valve 71 arranged in the second flow path F2, a plurality of third flow paths F3A, F3B that branch off downstream of the intermediate pressure receiver 73 and send refrigerant to the plurality of compressors 10A, 10B or 210A, 210B, respectively, and a plurality of third expansion valves 72A, 72B that are arranged in the plurality of third flow paths F3A, F3B, respectively.

[0072] (2) In paragraph (1), the outdoor unit 2 further includes a plurality of heat exchangers 30A, 30B that are respectively arranged in the plurality of third flow paths F3A, F3B between the plurality of third expansion valves 72A, 72B and the plurality of compressors 10A, 10B or 210A, 210B. Each of the plurality of heat exchangers 30A, 30B is configured to exchange heat between the refrigerant flowing through the corresponding third flow path F3A, F3B and the refrigerant that passes through the condenser 20 in the first flow path F1 and then flows toward the branch point where the second flow path F2 branches off.

[0073] (3) In the configuration described in (1) or (2), the outdoor unit 2 further includes a control device 100 configured to control the second expansion valve 71 and the plurality of third expansion valves 72A, 72B. The control device 100 is configured to control the opening degree of the second expansion valve 71 based on the degree of subcooling SC of the refrigerant at the outlet of the condenser 20, and to control the opening degree of each of the plurality of third expansion valves 72A, 72B based on the discharge temperature of the compressors 10A, 10B or 210A, 210B corresponding to each of the plurality of third expansion valves 72A, 72B.

[0074] (4) In item (1), as shown in FIG. 1, each of the plurality of compressors 10A, 10B is a single-stage compressor having an injection port, and each of the plurality of third flow paths F3A, F3B is connected to a corresponding injection port.

[0075] (5) In section (1), as shown in FIG. 6, each of the plurality of compressors 210A, 210B has two-stage compressors 211A and 213A, 211B and 213B connected in series, and an intermediate pressure port communicating with an intermediate portion of the two-stage compressors 211A and 213A, 211B and 213B, and each of the plurality of third flow paths F3A, F3B is connected to a corresponding intermediate pressure port.

[0076] (6) In the above-mentioned item (1), the outdoor unit 2 further includes a control device 100 configured to control the plurality of compressors 10A, 10B or 210A, 210B. As shown in Fig. 5, when the refrigeration load is lower than the determination value (YES in S31), the control device 100 is configured to perform low-load operation by stopping some of the plurality of compressors 10A, 10B or 210A, 210B and operating the remaining compressors. The control device is configured to determine which compressors to stop each time low-load operation occurs so as to prevent bias in the operation times of the plurality of compressors 10A, 10B or 210A, 210B (S33).

[0077] The refrigeration cycle devices of the first and second embodiments described above have the following advantages.

[0078] Increasing the capacity of a single compressor requires new development and new parts, which requires a lot of man-hours and costs. In contrast, in the refrigeration cycle devices of the first and second embodiments, the capacity can be freely expanded by adding the number of existing compressors, and no new parts are required for the compressors.

[0079] The refrigerant is CO ２ The intermediate pressure receiver 73 is effective when using supercritical fluid such as the above. The intermediate pressure receiver 73 is shared by multiple compressors, making it possible to realize a compact outdoor unit. Furthermore, having a single receiver, which is a pressure vessel, reduces costs.

[0080] Furthermore, by providing heat exchangers 30A and 30B that exchange heat between the refrigerant at the outlet of the condenser 20 and the refrigerant passing through the injection flow paths F3A and F3B, the performance of the refrigeration cycle device can be improved.

[0081] Furthermore, by branching the single-phase liquid stored in the intermediate pressure receiver 73 into two injection flow paths F3A and F3B, it is possible to avoid the uneven liquid / gas distribution that may occur when branching into two phases. This ensures that the heat exchange amounts of the heat exchangers 30A and 30B are obtained, and stabilizes the controllability of the discharge temperature in each compressor.

[0082] Furthermore, since a gas vent pipe is provided in the intermediate pressure receiver 73, the controllability of the amount of refrigerant stored is improved.

[0083] Furthermore, since the suction portions of the compressors are branched at the common accumulator 60, the refrigerant liquid and refrigerating machine oil are distributed evenly to the plurality of compressors 10A, 10B or 210A, 210B, which is preferable.

[0084] Although the present embodiment has been described above by exemplifying the case where the refrigeration cycle apparatus 1, 201 is mainly applied to a refrigerator, the refrigeration cycle apparatus 1, 201 may also be used in an air conditioner or the like.

[0085] The embodiments disclosed herein should be considered to be illustrative in all respects and not restrictive. The scope of the present invention is defined by the claims, not by the description of the above embodiments, and is intended to include all modifications within the meaning and scope of the claims.

[0086] 1,201 Refrigeration cycle device, 2,202 Outdoor unit, 3 Load device, 10A, 10B, 100A, 100B, 210A, 210B, 211A, 211B, 213A, 213B Compressor, 20 Condenser, 30A, 30B Heat exchanger, 40, 71, 72A, 72B Expansion valve, 50 Evaporator, 60 Accumulator, 70A, 70B Opening / closing valve, 73 Intermediate pressure receiver, 100 Control device, 102 CPU, 104 Memory, 111 Pressure sensor, 120A, 120B, 121 Temperature sensor, 121A, 121B, 212A, 212B Intermediate cooler, F1, F2, F3B, F3A Flow path, PI2, PI3 Refrigerant inlet port, PO2, PO3 Refrigerant outlet port.

Claims

1. A refrigeration cycle device comprising: a load device including a first expansion valve and an evaporator; and an outdoor unit having a refrigerant inlet port and a refrigerant outlet port for connection to the load device, wherein the outdoor unit comprises: a first flow path from the refrigerant inlet port to the refrigerant outlet port, which forms a circulation flow path along which the refrigerant circulates together with the load device; a condenser disposed in the first flow path; a plurality of compressors disposed in parallel in the first flow path between the refrigerant inlet port and the condenser; a receiver; a second flow path branching from a portion of the first flow path between the condenser and the refrigerant outlet port and connected to the receiver; a second expansion valve disposed in the second flow path; a plurality of third flow paths branching downstream of the receiver and sending refrigerant to each of the plurality of compressors; and a plurality of third expansion valves disposed in each of the third flow paths.

2. The refrigeration cycle device according to claim 1, wherein the outdoor unit further comprises a plurality of heat exchangers respectively arranged in the plurality of third flow paths between the plurality of third expansion valves and the plurality of compressors, and each of the plurality of heat exchangers is configured to exchange heat between refrigerant flowing through the corresponding third flow path and refrigerant that passes through the condenser in the first flow path and then heads toward a branch point where the second flow path branches off.

3. The refrigeration cycle device according to claim 1 or 2, wherein the outdoor unit further comprises a control device configured to control the second expansion valve and the plurality of third expansion valves, and the control device is configured to control the opening degree of the second expansion valve based on the degree of subcooling of the refrigerant at the outlet of the condenser, and to control the opening degree of each of the plurality of third expansion valves based on the discharge temperature of the compressor corresponding to each of the plurality of third expansion valves.

4. The refrigeration cycle device according to claim 1, wherein each of the plurality of compressors is a single-stage compressor having an injection port, and each of the plurality of third flow paths is connected to a corresponding injection port.

5. A refrigeration cycle device as described in claim 1, wherein each of the plurality of compressors has a two-stage compressor connected in series and an intermediate pressure port communicating with an intermediate portion of the two-stage compressor, and each of the plurality of third flow paths is connected to a corresponding intermediate pressure port.

6. The refrigeration cycle apparatus of claim 1, wherein the outdoor unit further comprises a control device configured to control the plurality of compressors, the control device being configured to perform low-load operation in which some of the plurality of compressors are stopped and the remaining compressors are operated when the refrigeration load is lower than a judgment value, and the control device being configured to determine which compressor to stop each time the low-load operation occurs so as not to cause a bias in the operating times of the plurality of compressors.

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