Refrigerator, refrigerator control device, refrigerator control method, and program

Abstract

This refrigerator comprises a low-stage compressor for compressing a low-pressure refrigerant to a medium-pressure refrigerant, a high-stage compressor for compressing the medium-pressure refrigerant

Description

TITLE OF INVENTION: REFRIGERATOR, REFRIGERATOR CONTROL DEVICE, REFRIGERATOR CONTROL METHOD, AND PROGRAM TECHNIC AL FIELD

[0001] The present disclosure relates to a refrigerator, a control device of a refrigerator, a control method of a refrigerator, and a program. Priority is claimed on Japanese Patent Application No. 2022-112320, filed July 13, 2022, the content of which is incorporated herein by reference. BACKGROUND ART

[0002] Patent Document 1 discloses a configuration in which, in a refrigerator including a plurality of outdoor units each of which includes a compressor and arranged in parallel, a pressure of the oil to be supplied to the compressor together with a refrigerant is adjusted by an oil equalization pipe between the plurality of outdoor units. Citation List Patent Document

[0003] Patent Document 1: Japanese Unexamined Patent Application, First Publication No. 2000-146324 SUMMARY OF INVENTION Technical Problem

[0004] In the refrigerator, a plurality of compressors may be provided in series. In this case, the refrigerator includes a low-stage compressor that compresses a low-pressure refrigerant into a medium-pressure refrigerant, and a high-stage compressor that compresses the medium-pressure refrigerant into a high-pressure refrigerant. In such a refrigerator, the low-pressure refrigerant flows through a pipe on an upstream side in a flow direction of the refrigerant with respect to the low-stage compressor. The medium-pressure refrigerant compressed by the low-stage compressor flows through a pipe between the low-stage compressor and the high-stage compressor. The high-pressure refrigerant flows through a pipe on a downstream side in the flow direction of the refrigerant with respect to the high-stage compressor. Therefore, during the operation of the refrigerator, a difference in pressure of the refrigerant is generated between a low-pressure pipe on an upstream side with respect to the low-stage compressor, a medium-pressure pipe between the low-stage compressor and the high-stage compressor, and a high-pressure pipe on a downstream side with respect to the high-stage compressor. In a case where the refrigerator stops operating, it may be desirable to equalize the pressure among the low-pressure pipe, the medium-pressure pipe, and the high-pressure pipe in order to stably stop the refrigerator. However, in a configuration in which the plurality of compressors are provided, the configuration is likely to be complicated in order to equalize the pressure among the low-pressure pipe, the medium-pressure pipe, and the high-pressure pipe.

[0005] The present disclosure has been made in order to achieve the above-described object, and an object of the present disclosure is to provide a refrigerator in which a pressure is easily equalized, a control device of a refrigerator, a control method of a refrigerator, and a program. Solution to Problem In order to achieve the above-described object, the present disclosure provides a refrigerator including: a low-stage compressor configured to compress a low-pressure refrigerant into a medium-pressure refrigerant; a high-stage compressor configured to compress the medium-pressure refrigerant into a high-pressure refrigerant; a low-pressure pipe connected to the low-stage compressor and through which the low-pressure refrigerant flows; a medium-pressure pipe connected between the low-stage compressor and the high-stage compressor and through which the medium-pressure refrigerant flows; a high-pressure pipe connected to the high-stage compressor and through which the high-pressure refrigerant flows; a first circuit extending from the high-pressure pipe to the low-pressure pipe; and a pressure equalization circuit configured to equalize a pressure between the first circuit and the medium-pressure pipe, in which the first circuit includes a first valve configured to open and close a flow channel in the first circuit, and the pressure equalization circuit includes a pressure equalization valve configured to open and close a flow channel in the pressure equalization circuit.

[0007] The present disclosure provides a control device of a refrigerator configured to control a refrigerator including a low-stage compressor configured to compress a low-pressure refrigerant into a medium-pressure refrigerant, a high-stage compressor configured to compress the medium-pressure refrigerant into a high-pressure refrigerant, a low-pressure pipe connected to the low-stage compressor and through which the low-pressure refrigerant flows, a medium-pressure pipe connected between the low-stage compressor and the high-stage compressor and through which the medium-pressure refrigerant flows, and a high-pressure pipe connected to the high-stage compressor and through which the high-pressure refrigerant flows, the control device of the refrigerator including: a first valve control unit configured to open a first valve of a first circuit extending to the high-pressure pipe and the low-pressure pipe; and a pressure equalization valve control unit configured to open a pressure equalization valve of a pressure equalization circuit configured to equalize a pressure between the first circuit and the medium-pressure pipe.

[0008] The present disclosure provides a control method of a refrigerator including a low-stage compressor configured to compress a low-pressure refrigerant into a mediumpressure refrigerant, a high-stage compressor configured to compress the medium-pressure refrigerant into a high-pressure refrigerant, a low-pressure pipe connected to the low-stage compressor and through which the low-pressure refrigerant flows, a mediumpressure pipe connected between the low-stage compressor and the high-stage compressor and through which the medium-pressure refrigerant flows, and a high-pressure pipe connected to the high-stage compressor and through which the high-pressure refrigerant flows, the control method including: in a case where operations of the low-stage compressor and the high-stage compressor are stopped, a step of opening a first valve of a first circuit extending to the high-pressure pipe and the low-pressure pipe; and a step of opening a pressure equalization valve of a pressure equalization circuit configured to equalize a pressure between the first circuit and the medium-pressure pipe.

[0009] The present disclosure provides a program causing a control device of a refrigerator including a low-stage compressor configured to compress a low-pressure refrigerant into a medium-pressure refrigerant, a high-stage compressor configured to compress the medium-pressure refrigerant into a high-pressure refrigerant, a low-pressure pipe connected to the low-stage compressor and through which the low-pressure refrigerant flows, a medium-pressure pipe connected between the low-stage compressor and the high-stage compressor and through which the medium-pressure refrigerant flows, and a high-pressure pipe connected to the high-stage compressor and through which the high-pressure refrigerant flows, to execute control including: in a case where operations of the low-stage compressor and the high-stage compressor are stopped, a step of opening a first valve of a first circuit extending to the high-pressure pipe and the low-pressure pipe; and a step of opening a pressure equalization valve of a pressure equalization circuit configured to equalize a pressure between the first circuit and the medium-pressure pipe. Advantageous Effects of Invention

[0010] With the refrigerator, the control device of the refrigerator, the control method of the refrigerator, and the program according to the present disclosure, it is possible to provide the refrigerator in which the pressure is easily equalized. BRIEF DESCRIPTION OF DRAWINGS

[0011] [FIG. 1] A diagram showing a configuration of a refrigerator according to an embodiment of the present disclosure. [FIG. 2] A diagram showing a configuration of a first circuit and a pressure equalization circuit provided in the refrigerator according to the embodiment of the present disclosure. [FIG. 3] A functional block diagram of a control device of the refrigerator according to the embodiment of the present disclosure. [FIG. 4] A flowchart showing a procedure of a control method of the refrigerator according to the embodiment of the present disclosure. [FIG. 5] A diagram showing a flow of a refrigerant in a case where a normal operation is performed in the refrigerator according to the embodiment of the present disclosure. [FIG. 6] A diagram showing a flow of the refrigerant in a case where the operation is stopped in the refrigerator according to the embodiment of the present disclosure. [FIG. 7] A diagram showing a hardware configuration of a control device of the refrigerator according to the embodiment of the present disclosure. DESCRIPTION OF EMBODIMENTS

[0012] Hereinafter, a refrigerator, a control device of a refrigerator, a control method of a refrigerator, and a program according to an embodiment of the present disclosure will be described with reference to FIGS. 1 to 7. (Configuration of Refrigerator) As shown in FIG. 1, the refrigerator 1 mainly includes a compression unit 2, a condenser 3, an expansion valve 4, and a receiver 5. The refrigerator 1 is an outdoor unit constituting a refrigeration cycle system. The refrigerator 1 circulates a refrigerant between the refrigerator 1 and an indoor unit (not shown) constituting the refrigeration cycle system. The refrigerator 1 cools the refrigerant to generate a liquid refrigerant. The refrigerator 1 supplies the generated liquid refrigerant to the indoor unit (not shown). The refrigerator 1 suctions the refrigerant of which the temperature has risen by performing heat exchange in the indoor unit from the indoor unit. In the present embodiment, the refrigerant is, for example, carbon dioxide (CO2). The refrigerant other than carbon dioxide may be used.

[0013] The compression unit 2 compresses the refrigerant circulated from the indoor unit. The compression unit 2 mainly includes an inlet accumulator (accumulator) 21, a sub-accumulator 22, a low-stage compressor 23, an intercooler 24, an intermediate accumulator 25, a high-stage compressor 26, and an oil separator 27.

[0014] The inlet accumulator 21 suctions the refrigerant from the indoor unit through a first pipe 101. The inlet accumulator 21 separates the refrigerant suctioned from the indoor unit (not shown) into a gas refrigerant and a liquid refrigerant. The refrigerant discharged from the indoor unit (not shown) flows into the inlet accumulator 21 through the first pipe 101. The inlet accumulator 21 supplies the gas refrigerant, which is separated in the inlet accumulator 21, to the sub-accumulator 22 through the second pipe 102. The second pipe 102 connects the inlet accumulator 21 and the sub-accumulator 22.

[0015] The oil contained in the liquid refrigerant separated in the inlet accumulator 21 is delivered to the sub-accumulator 22 through a first oil return pipe 401. The first oil return pipe 401 connects a bottom portion of the inlet accumulator 21 and a second pipe 102. The oil supplied into the second pipe 102 through the first oil return pipe 401 is mixed with the gas refrigerant flowing in the second pipe 102, and is delivered to the sub-accumulator 22.

[0016] The gas refrigerant separated in the inlet accumulator 21 flows into the sub-accumulator 22 through the second pipe 102. The sub-accumulator 22 separates the gas refrigerant and the liquid refrigerant. The sub-accumulator 22 separates the liquid refrigerant contained in the gas refrigerant separated in the inlet accumulator 21. The sub-accumulator 22 supplies the gas refrigerant, which is separated in the sub-accumulator 22, to the low-stage compressor 23 through the third pipe 103. The third pipe 103 connects the sub-accumulator 22 and the low-stage compressor 23.

[0017] The low-stage compressor 23 suctions the gas refrigerant, which is separated in the sub-accumulator 22, through the third pipe 103 by a negative pressure generated by the operation of the low-stage compressor 23. The low-stage compressor 23 compresses the suctioned gas refrigerant. In the present embodiment, the low-stage compressor 23 is a two-stage compressor including a first rotary compression unit (compression unit) 231 and a first scroll compression unit (compression unit) 232 in series. The first rotary compression unit 231 compresses the gas refrigerant suctioned through the third pipe 103. The first scroll compression unit 232 further compresses the refrigerant compressed by the first rotary compression unit 231. The refrigerant compressed by the first scroll compression unit 232 is discharged to the intercooler 24 through a fourth pipe 104. The fourth pipe 104 connects the low-stage compressor 23 and the intercooler 24.

[0018] The intercooler 24 and the intermediate accumulator 25 are disposed between the low-stage compressor 23 and the high-stage compressor 26. The refrigerant compressed by the low-stage compressor 23 is delivered through the fourth pipe 104 in the intercooler 24. The intercooler 24 cools the delivered refrigerant. The intercooler 24 is, for example, an air-cooled type in the present embodiment. The intercooler 24 includes an intercooler body 241 and a fan 242. The intercooler body 241 has a flow channel (not shown) of the refrigerant compressed by the low-stage compressor 23. The intercooler body 241 exchanges heat between the refrigerant flowing in the flow pipe and the outside air outside the flow pipe. The fan 242 delivers air to the intercooler body 241, to improve the efficiency of heat exchange in the intercooler body 241. The refrigerant cooled by the intercooler 24 is delivered to the intermediate accumulator 25 through a fifth pipe 105. The fifth pipe 105 connects the intercooler 24 and the intermediate accumulator 25.

[0019] The intermediate accumulator 25 separates the refrigerant, which is cooled by the intercooler 24 and delivered through the fifth pipe 105, into the gas refrigerant and the liquid refrigerant. The gas refrigerant separated in the intermediate accumulator 25 is supplied to the high-stage compressor 26 through a sixth pipe 106. The sixth pipe 106 connects the intermediate accumulator 25 and the high-stage compressor 26.

[0020] The oil contained in the liquid refrigerant separated in the intermediate accumulator 25 is delivered to the high-stage compressor 26 through a second oil return pipe 402. The second oil return pipe 402 connects a bottom portion of the intermediate accumulator 25 and the sixth pipe 106. The oil supplied into the sixth pipe 106 through the second oil return pipe 402 is mixed with the refrigerant flowing in the sixth pipe 106, and is delivered to the high-stage compressor 26.

[0021] The high-stage compressor 26 suctions the gas refrigerant, which is separated in the intermediate accumulator 25, through the sixth pipe 106 by the negative pressure generated by an operation of the high-stage compressor 26. The high-stage compressor 26 compresses the suctioned gas refrigerant. In the present embodiment, the high-stage compressor 26 is a two-stage compressor including a second rotary compression unit (compression unit) 261 and a second scroll compression unit (compression unit) 262 in series. The second rotary compression unit 261 compresses the gas refrigerant suctioned through the sixth pipe 106. The second scroll compression unit 262 further compresses a high-temperature and high-pressure refrigerant compressed by the second rotary compression unit 261. The refrigerant compressed by the high-stage compressor 26 is delivered to the oil separator 27 through a seventh pipe 107. The seventh pipe 107 connects the high-stage compressor 26 and the oil separator 27.

[0022] The oil separator 27 separates the oil contained in the refrigerant from the refrigerant compressed by the high-stage compressor 26 and delivered through the seventh pipe 107. The refrigerant from which the oil has been separated in the oil separator T1 is delivered to the condenser 3 through an eighth pipe 108. The eighth pipe 108 connects the oil separator 27 and the condenser 3.

[0023] The oil separated in the oil separator 27 is discharged to the oil tank 28 through a third oil return pipe 403. The third oil return pipe 403 connects the oil separator 27 and the oil tank 28. The oil tank 28 stores the oil discharged from the oil separator 27 through the third oil return pipe 403.

[0024] The oil stored in the oil tank 28 is returned to the low-stage compressor 23 and the high-stage compressor 26 through a fourth oil return pipe 404 and a fifth oil return pipe 405. An oil cooler 29 is provided in the intermediate part of the fourth oil return pipe 404 and the fifth oil return pipe 405. The oil cooler 29 cools the oil passing through the fourth oil return pipe 404 and 12 the fifth oil return pipe 405.

[0025] The condenser 3 cools and condenses the refrigerant delivered through the eighth pipe 108. The condenser 3 is, for example, an air-cooled type in the present embodiment. The condenser 3 includes a condenser body 31 and a fan 32. The condenser body 31 has a flow channel (not shown) of the refrigerant delivered through the eighth pipe 108. The heat is exchanged between the refrigerant flowing in the flow pipe and the outside air of the flow pipe through the eighth pipe 108. The fan 32 delivers air to the condenser body 31, to improve the efficiency of heat exchange in the condenser body 31. The refrigerant cooled by the condenser 3 is delivered to the expansion valve 4 through a ninth pipe 109. The ninth pipe 109 connects the condenser 3 and the expansion valve 4.

[0026] The expansion valve 4 expands the refrigerant condensed in the condenser 3 and delivered through the ninth pipe 109. The expansion valve 4 delivers the expanded refrigerant to the receiver 5 through a tenth pipe 110. The tenth pipe 110 connects the expansion valve 4 and the receiver 5.

[0027] The receiver 5 separates the refrigerant, which is expanded by the expansion valve 4 and delivered through the tenth pipe 110, into the gas refrigerant and the liquid refrigerant. The receiver 5 supplies the separated liquid refrigerant to the indoor unit (not shown) through an eleventh pipe 111.

[0028] In the present embodiment, a subcooling heat exchanger 6 is provided in the intermediate part of the eleventh pipe 111. The subcooling heat exchanger 6 further cools (subcools) the liquid refrigerant, which is supplied to the indoor unit through the eleventh pipe 111. The subcooling heat exchanger 6 has a first flow channel (not shown) of the liquid refrigerant delivered through the eleventh pipe 111 and a second flow channel (not shown) of the liquid refrigerant delivered through a twelfth pipe 112.

[0029] The twelfth pipe 112 branches off from the eleventh pipe 111. One end of the twelfth pipe 112 branches off from the eleventh pipe 111 on the upstream side in the eleventh pipe 111 in the flow direction of the refrigerant in the eleventh pipe 111 with respect to the subcooling heat exchanger 6. The other end of the twelfth pipe 112 is connected to the second flow channel of the subcooling heat exchanger 6. The twelfth pipe 112 is provided with an injection valve 61 and an expansion valve 62 for a subcooling heat exchanger.

[0030] The injection valve 61 opens and closes the flow channel of the liquid refrigerant in the twelfth pipe 112. The opening / closing operation of the injection valve 61 is controlled by a control device 300. In a case where the injection valve 61 is opened, the liquid refrigerant is supplied to the subcooling heat exchanger 6 through the twelfth pipe 112. In a case where the injection valve 61 is closed, the liquid refrigerant is not supplied to the subcooling heat exchanger 6 through the twelfth pipe 112.

[0031] The expansion valve 62 for a subcooling heat exchanger expands the liquid refrigerant passing through the twelfth pipe 112. The subcooling heat exchanger 6 is configured such that the first flow channel (not shown) of the liquid refrigerant delivered through the eleventh pipe 111 and the second flow channel of the liquid refrigerant delivered through the twelfth pipe 112 have opposite flow directions of the liquid refrigerant. The subcooling heat exchanger 6 exchanges heat between the liquid refrigerant in the first flow channel and the liquid refrigerant in the second flow channel, which flow in opposite directions to each other. In the subcooling heat exchanger 6, the liquid refrigerant in the first flow channel is cooled by heat exchange with the liquid refrigerant in the second flow channel expanded by the expansion valve 62 for a subcooling heat exchanger. The liquid refrigerant cooled in the first flow channel of the subcooling heat exchanger 6 is supplied to the indoor unit through the eleventh pipe 111.

[0032] In the subcooling heat exchanger 6, the temperature of the liquid refrigerant in the second flow channel rises due to heat exchange with the liquid refrigerant in the first flow channel. The liquid refrigerant heated in the second flow channel of the subcooling heat exchanger 6 is supplied to the high-stage compressor 26 through an injection circuit 120.

[0033] The injection circuit 120 connects the subcooling heat exchanger 6 and the sixth pipe 106. The injection circuit 120 is connected to the sixth pipe 106 disposed on a downstream side in the flow direction of the refrigerant with respect to the intermediate accumulator 25. The injection circuit 120 is connected to the sixth pipe 106 between the intercooler 24 and the high-stage compressor 26. The injection circuit 120 delivers the liquid refrigerant heated in the subcooling heat exchanger 6 to the high-stage compressor 26 through the sixth pipe 106. The sixth pipe 106 is connected to the high-stage compressor 26 between the second rotary compression unit 261 and the second scroll compression unit 262. The injection circuit 120 delivers the liquid refrigerant to the high-stage compressor 26 on a rear stage side of the second rotary compression unit 261.

[0034] In a case where the injection valve 61 is opened by the control of the control device 300, the injection circuit 120 injects the liquid refrigerant into the high-stage compressor 26 through the sixth pipe 106. In a case where the injection valve 61 is closed by the control of the control device 300, the injection circuit 120 does not inject the liquid refrigerant into the high-stage compressor 26.

[0035] Such a refrigerator 1 includes a low-pressure pipe 100L, a medium-pressure pipe 100M, and a high-pressure pipe 100H. A low-pressure refrigerant flows through the low-pressure pipe 100L before being compressed by the low-stage compressor 23. The low-pressure refrigerant flowing through the low-pressure pipe 100L has the lowest pressure in the refrigerator 1. The low-pressure pipe 100L is connected to the low-stage compressor 23. The low-pressure pipe 100L includes a first pipe 101, a second pipe 102, and a third pipe 103 that are disposed on the upstream side in the flow direction of the refrigerant with respect to the low-stage compressor 23.

[0036] The low-stage compressor 23 compresses the low-pressure refrigerant into a medium-pressure refrigerant. The medium-pressure refrigerant compressed by the low-stage compressor 23 flows through the medium-pressure pipe 100M. The medium-pressure pipe 100M is connected between the low-stage compressor 23 and the high-stage compressor 26. The medium-pressure pipe 100M includes a fourth pipe 104, a fifth pipe 105, and a sixth pipe 106.

[0037] The high-stage compressor 26 compresses the medium-pressure refrigerant into a high-pressure refrigerant. The high-pressure refrigerant compressed by the high-stage compressor 26 flows through the high-pressure pipe 100H. The high-pressure refrigerant flowing through the high-pressure pipe 100H has the highest pressure in the refrigerator 1. The high-pressure pipe 100H is connected to the high-stage compressor 26. The high-pressure pipe 100H is disposed between the high-stage compressor 26 and the expansion valve 4. The high-pressure pipe 100H includes a seventh pipe 107, an eighth pipe 108, and a ninth pipe 109.

[0038] The refrigerator 1 includes a pressure equalization mechanism 500. The pressure equalization mechanism 500 equalizes the pressure among the low-pressure pipe 100L, the medium-pressure pipe 100M, and the high-pressure pipe 100H when the operation is stopped. As shown in FIGS. 1 and 2, the pressure equalization mechanism 500 includes a first circuit 510 and a pressure equalization circuit 520.

[0039] The first circuit 510 extends from the high-pressure pipe 100H to the low-pressure pipe 100L. The first circuit 510 connects the downstream side in the high-pressure pipe 100H in the flow direction of the high-pressure refrigerant with respect to the oil separator 27 and the downstream side in the low-pressure pipe 100L in the flow direction of the low-pressure refrigerant with respect to the inlet accumulator 21. One end 510a of the first circuit 510 is connected to the eighth pipe 108 on the downstream side in the flow direction of the high-pressure refrigerant with respect to the oil separator 27 in the high-pressure pipe 100H. The other end 510b of the first circuit 510 is connected to the second pipe 102 on the downstream side in the flow direction of the low-pressure refrigerant with respect to the inlet accumulator 21 in the low-pressure pipe 100L.

[0040] The first circuit 510 includes a first valve 511 and a flow rate adjustment mechanism 512. The first valve 511 opens and closes the flow channel in the first circuit 510. In a case where the first valve 511 is opened, the first circuit 510 supplies the high-pressure refrigerant, which flows through the high-pressure pipe 100H and has a higher pressure and a higher temperature than the low-pressure refrigerant, to the low-pressure pipe 100L. The opening / closing operation of the first valve 511 is controlled by the control device 300. In a case where the first valve 511 is opened, the high-pressure refrigerant is supplied to the low-pressure pipe 100L through the first circuit 510 and then through the high-pressure pipe 10OH. As a result, the pressure equalization between the high-pressure pipe 100H and the low-pressure pipe 100L is achieved. In a case where the first valve 511 is closed, the pressure equalization is not performed via the first circuit 510.

[0041] The flow rate adjustment mechanism 512 is disposed on the downstream side in the first circuit 510 in the flow direction of the refrigerant in the first circuit 510 with respect to the first valve 511. The flow rate adjustment mechanism 512 is, for example, a capillary pipe. The refrigerant flowing through the first circuit 510 receives the flow channel resistance by the flow rate adjustment mechanism 512 formed of the capillary pipe, and the flow rate thereof is reduced. The flow rate adjustment mechanism 512 may have a configuration other than the capillary pipe.

[0042] The pressure equalization circuit 520 is connectable to the first circuit 510 and the injection circuit 120. The pressure equalization circuit 520 connects the injection circuit 120 and a position 513 on the downstream side in the first circuit 510 in the flow direction of the high-pressure refrigerant in the first circuit 510. One end 520a of the pressure equalization circuit 520 is connected to the injection circuit 120. The one end 520a of the pressure equalization circuit 520 is connected to the injection circuit 120 between the subcooling heat exchanger 6 and the sixth pipe 106. The other end 520b of the pressure equalization circuit 520 is connected to the first circuit 510. The other end 520b of the pressure equalization circuit 520 is connected to the position 513 on the downstream side in the first circuit 510 in the flow direction of the high-pressure refrigerant with respect to the first valve 511.

[0043] The pressure equalization circuit 520 includes a pressure equalization valve 521. The pressure equalization valve 521 opens and closes the flow channel in the pressure equalization circuit 520. In a case where the pressure equalization valve 521 is opened, the pressure equalization circuit 520 connects the first circuit 510 and the injection circuit 120. In a case where the pressure equalization valve 521 is opened, the first circuit 510 and the injection circuit 120 communicate with each other via the pressure equalization circuit 520. In a case where the pressure equalization valve 521 is opened, the high-pressure pipe 100H and the low-pressure pipe 100L, which communicate with each other via the first circuit 510, and the medium-pressure pipe 100M communicate with each other via the pressure equalization circuit 520 and the injection circuit 120. In a case where the pressure equalization valve 521 is opened, the pressure is equalized among the high-pressure pipe 10011. the medium-pressure pipe 100M, and the low-pressure pipe 100L. The opening / closing operation of the pressure equalization valve 521 is controlled by the control device 300.

[0044] (Configuration of Control Device) The control device 300 can control the refrigerator 1. The control device 300 controls at least the opening / closing operations of the low-stage compressor 23, the high-stage compressor 26, the injection valve 61, the first valve 511, and the pressure equalization valve 521. As shown in FIG. 3, the control device 300 includes a central processing unit (hereinafter, referred to as a "CPU") 310 and a memory 320.

[0045] The CPU 310 functionally includes an operation control unit 311, an injection valve control unit 312, a first valve control unit 313, and a pressure equalization valve control unit 314. That is, the CPU 310 operates based on a predetermined program to exhibit functions as the operation control unit 311, the injection valve control unit 312, the first valve control unit 313, and the pressure equalization valve control unit 314. The memory 320 stores various types of data acquired by the control device 300.

[0046] The operation control unit 311 controls the operation of the refrigerator 1 based on a control command output from the indoor unit in response to the operation performed on the indoor unit side. The operation control unit 311 controls the low-stage compressor 23 and the high-stage compressor 26 based on the control command output from the indoor unit. The operation control unit 311 controls the operation of each unit of the refrigerator 1, such as the fans 242 and 32, based on the control command output from the indoor unit.

[0047] The injection valve control unit 312 controls the opening / closing operation of the injection valve 61 of the injection circuit 120. For example, in a case where the temperature in the high-stage compressor 26 detected by a temperature sensor (not shown) is equal to or higher than a predetermined reference, the injection valve control unit 312 opens the injection valve 61 and executes the injection of the refrigerant into the high-stage compressor 26 via the injection circuit 120.

[0048] The first valve control unit 313 controls the opening / closing operation of the first valve 511 of the first circuit 510. The first valve control unit 313 opens the first valve 511 to equalize the pressure between the high-pressure pipe 100H and the low-pressure pipe 100L via the first circuit 510. The pressure equalization valve control unit 314 controls the opening / closing operation of the pressure equalization valve 521 of the pressure equalization circuit 520. The pressure equalization valve control unit 314 opens the pressure equalization valve 521 to equalize the pressure between the first circuit 510 and the medium-pressure pipe 100M via the pressure equalization circuit 520. (Procedure of Control Method of Refrigerator) As shown in FIG. 4, a control method S10 of the refrigerator 1 according to the embodiment of the present disclosure includes a step S11 of opening the first valve 511 of the first circuit 510 and a step S12 of opening the pressure equalization valve 521 of the pressure equalization circuit 520. As shown in FIG. 5, in the refrigerator 1, during the normal operation, the refrigerant is delivered from the low-pressure pipe 100L to the indoor unit through the low-stage compressor 23, the medium-pressure pipe 100M, the high-stage compressor 26, the high-pressure pipe 10OH, and then through the eleventh pipe 111. In the present embodiment, the control method S10 of the refrigerator 1 is automatically executed in a case where the operations of the low-stage compressor 23 and the high-stage compressor 26 are stopped. In the step SI 1 of opening the first valve 511 of the first circuit 510, the first valve 511 of the first circuit 510 is opened by the control of the first valve control unit 313. In this case, as shown in FIG. 6, the high-pressure pipe 10OH and the low-pressure pipe 100L communicate with each other via the first circuit 510 extending from the high-pressure pipe 100H to the low-pressure pipe 100L. As a result, the pressure is equalized between the high-pressure pipe 100H and the low-pressure pipe 100L. In the step S12 of opening the pressure equalization valve 521 of the pressure equalization circuit 520, the pressure equalization valve 521 of the pressure equalization circuit 520 is opened by the control of the pressure equalization valve control unit 314. In this case, in a case where the injection valve 61 is not opened, the injection valve 61 is opened by the control of the injection valve control unit 312. Asa result, the first circuit 510 and the medium-pressure pipe 100M communicate with each other via the pressure equalization circuit 520. As a result, the pressure is equalized among the high-pressure pipe 100H, the medium-pressure pipe 100M, and the low-pressure pipe 100L.

[0050] (Operations and Effects) In the present embodiment, the refrigerator 1 includes the pressure equalization circuit 520 that can equalize the pressure between the first circuit 510 extending from the high-pressure pipe 1 OOH to the low-pressure pipe 100L, and the medium-pressure pipe 100M. In a case where the operations of the low-stage compressor 23 and the high-stage compressor 26 are stopped and the first valve 511 provided in the first circuit 510 is opened, the pressure is equalized between the high-pressure pipe 100H and the low-pressure pipe 100L. In addition, in a case where the pressure equalization valve 521 provided in the pressure equalization circuit 520 is opened, the pressure is equalized between the first circuit 510 and the medium-pressure pipe WOM. As a result, the pressure is equalized among the high-pressure pipe 100H, the medium-pressure pipe 100M, and the low-pressure pipe 100L. In this manner, in order to equalize the pressure among the high-pressure pipe 100H, the medium-pressure pipe I OOM, and the low-pressure pipe 100L, the first circuit 510 including the first valve 511 and the pressure equalization circuit 520 including the pressure equalization valve 521 need only be provided. Therefore, it is possible to provide the refrigerator 1 in which the pressure is easily equalized with a simple configuration.

[0051] In addition, in a case where the first circuit 510 is opened, the refrigerator 1 supplies the high-pressure refrigerant, which has a higher temperature than the low-pressure refrigerant, to the low-pressure pipe 100L via the first circuit 510. Asa result, in such a case where the temperature of the refrigerant supplied from the low-pressure pipe 100L to the low-stage compressor 23 is excessively lowered, the temperature of the refrigerant can be raised. Therefore, it is possible to improve the efficiency in a case where the refrigerant is compressed by the low-stage compressor 23.

[0052] In addition, in the refrigerator 1, the efficiency of compressing the refrigerant by the high-stage compressor 26 is improved by injecting the refrigerant having a low temperature into the high-stage compressor 26 via the injection circuit 120. The pressure equalization circuit 520 can connect the first circuit 510 and the injection circuit 120 to equalize the pressure between the first circuit 510, which equalizes the pressure between the high-pressure pipe 100H and the low-pressure pipe 100L, and the mediumpressure pipe 100M via the injection circuit 120. In this manner, by using the injection circuit 120 for the pressure equalization, the number of pipes to be newly installed can be reduced.

[0053] In addition, the pressure equalization circuit 520 connects the injection circuit 120 and the position 513 on the downstream side in the first circuit 510 in the flow direction of the high-pressure refrigerant. The position 513 on the downstream side in the first circuit 510 in the flow direction of the high-pressure refrigerant is a position close to the low-pressure pipe 100L. Therefore, the pressure can be equalized between the medium-pressure pipe 100M and the low-pressure pipe 100L, at a position close to the low-pressure pipe 100L in the first circuit 510 via the injection circuit 120.

[0054] In addition, the refrigerator 1 can raise the temperature of the refrigerant, for example, in a case where the refrigerant is cooled by the intercooler 24 and the temperature of the refrigerant is excessively lowered, by delivering the refrigerant via the injection circuit 120 to the refrigerant cooled by the intercooler 24 provided in the medium-pressure pipe 100M. Therefore, the efficiency in compressing the refrigerant in the high-stage compressor 26 is improved.

[0055] In addition, since the first circuit 510 includes the flow rate adjustment mechanism 512, the refrigerator 1 can adjust the flow rate of the high-pressure refrigerant flowing from the high-pressure pipe 100H side to the low-pressure pipe 100L side in a case where the first valve 511 is opened.

[0056] In addition, in the refrigerator 1, the downstream side in the high-pressure pipe 100H in the flow direction of the high-pressure refrigerant with respect to the oil separator Z1 is a position at which the pressure of the high-pressure refrigerant compressed by the high-stage compressor 26 is the highest. The downstream side in the low-pressure pipe 100L in the flow direction of the low-pressure refrigerant with respect to the inlet accumulator 21 is a position at which the pressure of the low-pressure refrigerant is the lowest, immediately before the low-stage compressor 23. The first circuit 510 connects the downstream side in the flow direction of the high-pressure refrigerant with respect to the oil separator 27 and the downstream side in the low-pressure pipe 100L in the flow direction of the low-pressure refrigerant with respect to the inlet accumulator 21. Asa result, it is possible to efficiently equalize the pressure between a position in the high-pressure pipe 100H at which the pressure of the high-pressure refrigerant is the highest and a position in the low-pressure pipe 100L at which the pressure of the low-pressure refrigerant is the lowest, via the first circuit 510.

[0057] In addition, the high-stage compressor 26 includes the two compression units 261 and 262 in series, and the low-stage compressor 23 includes the two compression units 231 and 232 in series. That is, the high-stage compressor 26 and the low-stage compressor 23 include a total of four stages of the compression units 231, 232, 261, and 262. In such a configuration, the pressure can be equalized among the high-pressure pipe 100H, the medium-pressure pipe 100M, and the low-pressure pipe 100L.

[0058] In addition, in the control device 300 of the refrigerator 1, in a case where the operations of the low-stage compressor 23 and the high-stage compressor 26 are stopped, and the first valve 511 provided in the first circuit 510 is opened, the pressure is equalized between the high-pressure pipe 10OH and the low-pressure pipe 100L. In addition, in a case where the pressure equalization valve 521 provided in the pressure equalization circuit 520 is opened, the pressure is equalized between the first circuit 510 and the medium-pressure pipe 1 OOM. As a result, the pressure is equalized among the high-pressure pipe 100H, the medium-pressure pipe 100M, and the low-pressure pipe 100L. In this manner, in order to equalize the pressure among the high-pressure pipe 1 OOH, the medium-pressure pipe 1 OOM, and the low-pressure pipe 100L, the first circuit 510 including the first valve 511 and the pressure equalization circuit 520 including the pressure equalization valve 521 need only be provided. Therefore, it is possible to provide the refrigerator 1 in which the pressure is easily equalized with a simple configuration.

[0059] In addition, in the control method S10 of the refrigerator 1, in a case where the operations of the low-stage compressor 23 and the high-stage compressor 26 are stopped, and the first valve 511 provided in the first circuit 510 is opened, the pressure is equalized between the high-pressure pipe 100H and the low-pressure pipe 100L. In addition, in a case where the pressure equalization valve 521 provided in the pressure equalization circuit 520 is opened, the pressure is equalized between the first circuit 510 and the medium-pressure pipe 100M. As a result, the pressure is equalized among the high-pressure pipe I OOH, the medium-pressure pipe I OOM, and the low-pressure pipe 100L. In this manner, in order to equalize the pressure among the high-pressure pipe 100H, the medium-pressure pipe 100M, and the low-pressure pipe 100L, the first circuit 510 including the first valve 511 and the pressure equalization circuit 520 including the pressure equalization valve 521 need only be provided. Therefore, it is possible to provide the refrigerator 1 in which the pressure is easily equalized with a simple configuration.

[0060] In addition, with this program, in a case where the operations of the low-stage compressor 23 and the high-stage compressor 26 are stopped, and the first valve 511 provided in the first circuit 510 is opened, the pressure is equalized between the high-pressure pipe 100H and the low-pressure pipe 100L. In addition, in a case where the pressure equalization valve 521 provided in the pressure equalization circuit 520 is opened, the pressure is equalized between the first circuit 510 and the medium-pressure pipe 100M. As a result, the pressure is equalized among the high-pressure pipe 100H, the medium-pressure pipe 100M, and the low-pressure pipe 100L. In this manner, in order to equalize the pressure among the high-pressure pipe 100H, the medium-pressure pipe 100M, and the low-pressure pipe 100L, the first circuit 510 including the first valve 511 and the pressure equalization circuit 520 including the pressure equalization valve 521 need only be provided. Therefore, it is possible to provide the refrigerator 1 in which the pressure is easily equalized with a simple configuration. In the above-described embodiment, the various types of processing are performed by recording a program for implementing various functions of the control device 300 on a computer-readable recording medium, reading the program recorded on the recording medium into a computer system such as a microcomputer, and executing the program. Here, a process of various types of processing of the CPU of the computer system is stored in the computer-readable recording medium in a form of the program, and the various types of processing are performed by reading and executing the program via the computer. The computer-readable recording medium refers to a magnetic disk, a magneto-optical disk, a CD-ROM, a DVD-ROM, a semiconductor memory, or the like. In addition, this computer program may be distributed to the computer via a communication line, and the computer that receives the distribution may execute the program.

[0062] In the above-described embodiment, an example of a hardware configuration of the computer that executes the program for implementing various functions of the control device 300 will be described.

[0063] As shown in FIG. 7, the computer provided in the control device 300 includes the CPU 310, the memory 320, a storage / reproduction device 330, an input output interface (hereinafter, referred to as an "IO 1 / F") 340, and a communication interface (hereinafter, referred to as a "communication I / F") 350.

[0064] The memory 320 is a medium such as a random access memory (hereinafter, referred to as a "RAM") that temporarily stores data and the like used in the program executed by the control device 300. The storage / reproduction device 330 is a device that stores data and the like in an external medium such as the CD-ROM, the DVD, and the flash memory, or reproduces data and the like of the external medium. The IO I / F 340 is an interface for inputting and outputting information or the like between the control device 300 and another device. The communication I / F 350 is an interface for performing communication with another device via a communication line such as the Internet or a dedicated communication line.

[0065] (Other Embodiments) Although the embodiment of the present disclosure has been described above, the embodiment is merely an example and is not intended to limit the scope of the present disclosure. The embodiment can be carried out in various other forms, and various omissions, replacements, and changes can be made without departing from the gist of the present disclosure. The embodiment and the modification thereof are included in the scope or the gist of the present disclosure, and are also included in the scope or the gist of equivalents of the present disclosure.

[0066] Supplementary Noto The refrigerator 1, the control device 300 of the refrigerator 1, the control method S10 of the refrigerator 1, and the program according to the embodiment are understood, for example, as follows.

[0067] (1) A first aspect relates to a refrigerator 1 including: a low-stage compressor 23 configured to compress a low-pressure refrigerant into a medium-pressure refrigerant; a high-stage compressor 26 configured to compress the medium-pressure refrigerant into a high-pressure refrigerant; a low-pressure pipe 100L connected to the low-stage compressor 23 and through which the low-pressure refrigerant flows; a medium-pressure pipe 100M connected between the low-stage compressor 23 and the high-stage compressor 26 and through which the medium-pressure refrigerant flows; a high-pressure pipe 100H connected to the high-stage compressor 26 and through which the high-pressure refrigerant flows; a first circuit 510 extending from the high-pressure pipe 100H to the low-pressure pipe 100L; and a pressure equalization circuit 520 configured to equalize a pressure between the first circuit 510 and the medium-pressure pipe 100M, in which the first circuit 510 includes a first valve 511 configured to open and close a flow channel in the first circuit 510, and the pressure equalization circuit 520 includes a pressure equalization valve 521 configured to open and close a flow channel in the pressure equalization circuit 520.

[0068] The refrigerator 1 includes the pressure equalization circuit 520 that can equalize the pressure between the first circuit 510 extending from the high-pressure pipe 100H to the low-pressure pipe 100L, and the medium-pressure pipe 100M. In a case where the operations of the low-stage compressor 23 and the high-stage compressor 26 are stopped and the first valve 511 provided in the first circuit 510 is opened, the pressure is equalized between the high-pressure pipe 100H and the low-pressure pipe 100L. In addition, in a case where the pressure equalization valve 521 provided in the pressure equalization circuit 520 is opened, the pressure is equalized between the first circuit 510 and the medium-pressure pipe 100M. As a result, the pressure is equalized among the high-pressure pipe 100H, the medium-pressure pipe 100M, and the low-pressure pipe 100L. In this manner, in order to equalize the pressure among the high-pressure pipe 100H, the medium-pressure pipe 100M, and the low-pressure pipe 100L, the first circuit 510 including the first valve 511 and the pressure equalization circuit 520 including the pressure equalization valve 521 need only be provided. Therefore, it is possible to provide the refrigerator 1 in which the pressure is easily equalized with a simple configuration.

[0069] (2) A second aspect relates to the refrigerator 1 according to (1), in which, in a case where the first valve 511 is opened, the first circuit 510 supplies the high-pressure refrigerant, which flows through the high-pressure pipe 10OH and has a higher temperature than the low-pressure refrigerant, to the low-pressure pipe 100L.

[0070] As a result, in a case where the first circuit 510 is opened, the first circuit 510 supplies the high-pressure refrigerant having a higher temperature than the low-pressure refrigerant to the low-pressure pipe 100L. As a result, in such a case where the temperature of the refrigerant supplied from the low-pressure pipe 100L to the low-stage compressor 23 is excessively lowered, the temperature of the refrigerant can be raised. Therefore, it is possible to improve the efficiency in a case where the refrigerant is compressed by the low-stage compressor 23.

[0071] (3) A third aspect relates to the refrigerator 1 according to (1) or (2), further including: an injection circuit 120 connected to the medium-pressure pipe 100M and configured to inject a refrigerant, which has a lower temperature than a refrigerant in the high-stage compressor 26, into the high-stage compressor 26, in which the pressure equalization circuit 520 is configured to connect the first circuit 510 and the injection circuit 120.

[0072] As a result, the efficiency in compressing the refrigerant by the high-stage compressor 26 is improved by injecting the refrigerant having a low temperature into the high-stage compressor 26 via the injection circuit 120. The pressure equalization circuit 520 can connect the first circuit 510 and the injection circuit 120 to equalize the pressure between the first circuit 510, which equalizes the pressure between the high-pressure pipe 100H and the low-pressure pipe 100L, and the medium-pressure pipe 100M via the injection circuit 120. In this manner, by using the injection circuit 120 for the pressure equalization, the number of pipes to be newly installed can be reduced.

[0073] (4) A fourth aspect relates to the refrigerator 1 according to (3), in which the pressure equalization circuit 520 connects the injection circuit 120 and a position 513 on a downstream side in the first circuit 510 in a flow direction of the high-pressure refrigerant in the first circuit 510.

[0074] In this manner, the pressure equalization circuit 520 connects the injection circuit 120 and the position 513 on the downstream side in the first circuit 510 in the flow direction of the high-pressure refrigerant. The position 513 on the downstream side in the first circuit 510 in the flow direction of the high-pressure refrigerant is a position close to the low-pressure pipe 100L. Therefore, the pressure can be equalized between the medium-pressure pipe 100M and the low-pressure pipe 100L, at a position close to the low-pressure pipe 100L in the first circuit 510 via the injection circuit 120.

[0075] (5) A fifth aspect relates to the refrigerator 1 according to (3) or (4), further including: an intercooler 24 disposed in an intermediate part of the medium-pressure pipe 100M and configured to cool the medium-pressure refrigerant compressed by the low-stage compressor 23, in which the injection circuit 120 is connected to the mediumpressure pipe 100M between the intercooler 24 and the high-stage compressor 26.

[0076] As a result, it is possible to raise the temperature of the refrigerant, for example, in a case where the refrigerant is cooled by the intercooler 24 and the temperature of the refrigerant is excessively lowered, by delivering the refrigerant via the injection circuit 120 to the refrigerant cooled by the intercooler 24 provided in the medium-pressure pipe 10OM. Therefore, the efficiency in compressing the refrigerant in the high-stage compressor 26 is improved.

[0077] (6) A sixth aspect relates to the refrigerator 1 according to any one of (1) to (5), in which the first circuit 510 includes a flow rate adjustment mechanism 512 configured to adjust a flow rate of the high-pressure refrigerant in a case where the first valve 511 is opened.

[0078] As a result, since the first circuit 510 includes the flow rate adjustment mechanism 512, it is possible to adjust the flow rate of the high-pressure refrigerant flowing from the high-pressure pipe 100H side to the low-pressure pipe 100L side in a case where the first valve 511 is opened.

[0079] (7) A seventh aspect relates to the refrigerator 1 according to any one of (1) to (6), further including: an accumulator 21 configured to separate the low-pressure refrigerant supplied to the low-stage compressor 23 into a gas refrigerant and a liquid refrigerant; and an oil separator 27 configured to separate oil contained in the high-pressure refrigerant discharged from the high-stage compressor 26, in which the first circuit 510 connects a downstream side in the high-pressure pipe 100H with respect to the oil separator 27 in a flow direction of the high-pressure refrigerant and a downstream side in the low-pressure pipe 100L with respect to the accumulator 21 in a flow direction of the low-pressure refrigerant.

[0080] The downstream side in the high-pressure pipe 100H in the flow direction of the high-pressure refrigerant with respect to the oil separator 27 is a position at which the pressure of the high-pressure refrigerant compressed by the high-stage compressor 26 is the highest. The downstream side in the low-pressure pipe 100L in the flow direction of the low-pressure refrigerant with respect to the accumulator 21 is a position at which the pressure of the low-pressure refrigerant is the lowest, immediately before the low-stage compressor 23. The first circuit 510 connects the downstream side in the flow direction of the high-pressure refrigerant with respect to the oil separator 27 and the downstream side in the low-pressure pipe 100L in the flow direction of the low-pressure refrigerant with respect to the accumulator 21. Asa result, it is possible to efficiently equalize the pressure between a position in the high-pressure pipe 100H at which the pressure of the high-pressure refrigerant is the highest and a position in the low-pressure pipe 100L at which the pressure of the low-pressure refrigerant is the lowest, via the first circuit 510.

[0081] (8) An eighth aspect relates to the refrigerator 1 according to any one of (1) to (7), in which the high-stage compressor 26 and the low-stage compressor 23 are each a two-stage compressor including two compression units 231, 232, 261, 262 arranged in series. As a result, the high-stage compressor 26 includes the two compression units 261 and 262 in series, and the low-stage compressor 23 includes the two compression units 231 and 232 in series. That is, the high-stage compressor 26 and the low-stage compressor 23 include a total of four stages of the compression units 231, 232, 261, and 262. In such a configuration, the pressure can be equalized among the high-pressure pipe 100H, the medium-pressure pipe 100M, and the low-pressure pipe 100L.

[0083] (9) A ninth aspect relates to a control device 300 configured to control a refrigerator 1 including a low-stage compressor 23 configured to compress a low-pressure refrigerant into a medium-pressure refrigerant, a high-stage compressor 26 configured to compress the medium-pressure refrigerant into a high-pressure refrigerant, a low-pressure pipe 100L connected to the low-stage compressor 23 and through which the low-pressure refrigerant flows, a medium-pressure pipe 100M connected between the low-stage compressor 23 and the high-stage compressor 26 and through which the medium-pressure refrigerant flows, and a high-pressure pipe 100H connected to the high-stage compressor 26 and through which the high-pressure refrigerant flows, the control device 300 including: a first valve control unit 313 configured to open a first valve 511 of a first circuit 510 extending to the high-pressure pipe 100H and the low-pressure pipe 100L; and a pressure equalization valve control unit 314 configured to open a pressure equalization valve 521 of a pressure equalization circuit 520 configured to equalize a pressure between the first circuit 510 and the medium-pressure pipe 100M.

[0084] As a result, in a case where the operations of the low-stage compressor 23 and the high-stage compressor 26 are stopped and the first valve 511 provided in the first circuit 510 is opened, the pressure is equalized between the high-pressure pipe 100H and the low-pressure pipe 100L. In addition, in a case where the pressure equalization valve 521 provided in the pressure equalization circuit 520 is opened, the pressure is equalized between the first circuit 510 and the medium-pressure pipe 1 OOM. As a result, the pressure is equalized among the high-pressure pipe 100H, the medium-pressure pipe 100M, and the low-pressure pipe 100L. In this manner, in order to equalize the pressure among the high-pressure pipe 100H, the medium-pressure pipe 100M, and the low-pressure pipe 100L, the first circuit 510 including the first valve 511 and the pressure equalization circuit 520 including the pressure equalization valve 521 need only be provided. Therefore, it is possible to provide the refrigerator 1 in which the pressure is easily equalized with a simple configuration.

[0085] (10) A tenth aspect relates to a control method S10 of a refrigerator 1 including a low-stage compressor 23 configured to compress a low-pressure refrigerant into a medium-pressure refrigerant, a high-stage compressor 26 configured to compress the medium-pressure refrigerant into a high-pressure refrigerant, a low-pressure pipe 100L connected to the low-stage compressor 23 and through which the low-pressure refrigerant flows, a medium-pressure pipe 100M connected between the low-stage compressor 23 and the high-stage compressor 26 and through which the medium-pressure refrigerant flows, and a high-pressure pipe 100H connected to the high-stage compressor 26 and through which the high-pressure refrigerant flows, the control method S10 including: in a case where operations of the low-stage compressor 23 and the high-stage compressor 26 are stopped, a step SI 1 of opening a first valve 511 of a first circuit 510 extending to the high-pressure pipe 100H and the low-pressure pipe 100L; and a step S12 of opening a pressure equalization valve 521 of a pressure equalization circuit 520 configured to equalize a pressure between the first circuit 510 and the medium-pressure pipe 100M.

[0086] As a result, in a case where the operations of the low-stage compressor 23 and the high-stage compressor 26 are stopped and the first valve 511 provided in the first circuit 510 is opened, the pressure is equalized between the high-pressure pipe 100H and the low-pressure pipe 100L. In addition, in a case where the pressure equalization valve 521 provided in the pressure equalization circuit 520 is opened, the pressure is equalized between the first circuit 510 and the medium-pressure pipe 1 OOM. As a result, the pressure is equalized among the high-pressure pipe 100H, the medium-pressure pipe 10OM, and the low-pressure pipe 100L. Tn this manner, in order to equalize the pressure among the high-pressure pipe 100H, the medium-pressure pipe 100M, and the low-pressure pipe 100L, the first circuit 510 including the first valve 511 and the pressure equalization circuit 520 including the pressure equalization valve 521 need only be provided. Therefore, it is possible to provide the refrigerator 1 in which the pressure is easily equalized with a simple configuration.

[0087] (11) An eleventh aspect relates to a program causing a control device 300 of a refrigerator 1 including a low-stage compressor 23 configured to compress a low-pressure refrigerant into a medium-pressure refrigerant, a high-stage compressor 26 configured to compress the medium-pressure refrigerant into a high-pressure refrigerant, a low-pressure pipe 100L connected to the low-stage compressor 23 and through which the low-pressure refrigerant flows, a medium-pressure pipe 100M connected between the low-stage compressor 23 and the high-stage compressor 26 and through which the medium-pressure refrigerant flows, and a high-pressure pipe 100H connected to the high-stage compressor 26 and through which the high-pressure refrigerant flows, to execute control including: in a case where operations of the low-stage compressor 23 and the high-stage compressor 26 are stopped, a step of opening a first valve 511 of a first circuit 510 extending to the high-pressure pipe 10011 and the low-pressure pipe 100L; and a step of opening a pressure equalization valve 521 of a pressure equalization circuit 520 configured to equalize a pressure between the first circuit 510 and the medium-pressure pipe 100M.

[0088] With this program, in a case where the operations of the low-stage compressor 23 and the high-stage compressor 26 are stopped, and the first valve 511 provided in the first circuit 510 is opened, the pressure is equalized between the high-pressure pipe 100H and the low-pressure pipe 100L. In addition, in a case where the pressure equalization valve 521 provided in the pressure equalization circuit 520 is opened, the pressure is equalized between the first circuit 510 and the medium-pressure pipe 1 OOM. As a result, the pressure is equalized among the high-pressure pipe 100H, the mediumpressure pipe 100M, and the low-pressure pipe 100L. In this manner, in order to equalize the pressure among the high-pressure pipe 100H, the medium-pressure pipe 100M, and the low-pressure pipe 100L, the first circuit 510 including the first valve 511 and the pressure equalization circuit 520 including the pressure equalization valve 521 need only be provided. Therefore, it is possible to provide the refrigerator 1 in which the pressure is easily equalized with a simple configuration. INDUSTRIAL APPLICABILITY

[0089] With the refrigerator, the control device of the refrigerator, the control method of the refrigerator, and the program according to the present disclosure, it is possible to provide the refrigerator in which the pressure is easily equalized. REFERENCE SIGNS LIST

[0090] 1 Refrigerator 2 Compression unit 3 Condenser 4 Expansion valve 5 Receiver 6 Subcooling heat exchanger 21 Inlet accumulator (accumulator) 22 Sub-accumulator 23 Low-stage compressor 24 Intercooler 25 Intermediate accumulator 26 High-stage compressor 27 Oil separator 28 Oil tank 29 Oil cooler 31 Condenser body 32 Fan 61 Injection valve 62 Expansion valve for subcooling heat exchanger 100L Low-pressure pipe 100M Medium-pressure pipe 100H High-pressure pipe 101 First pipe 102 Second pipe 103 Third pipe 104 Fourth pipe 105 Fifth pipe 106 Sixth pipe 107 Seventh pipe 108 Eighth pipe 109 Ninth pipe 110 Tenth pipe 111 Eleventh pipe 112 Twelfth pipe 120 Injection circuit 231 First rotary compression unit (compression unit) 232 First scroll compression unit (compression unit) 241 Intercooler body 242 Fan 261 Second rotary compression unit (compression unit) 262 Second scroll compression unit (compression unit) 300 Control device 310 CPU 311 Operation control unit 312 Injection valve control unit 313 First valve control unit 314 Pressure equalization valve control unit 320 Memory 330 Storage / reproduction device 340 IO I / F 350 Communication I / F 401 First oil return pipe 402 Second oil return pipe 403 Third oil return pipe 404 Fourth oil return pipe 405 Fifth oil return pipe 500 Pressure equalization mechanism 510 First circuit 510a One end 510b Other end 511 First valve 512 Flow rate adjustment mechanism 520 Pressure equalization circuit 520a One end 520b Other end 521 Pressure equalization valve S10 Control method of refrigerator S11 Step of opening first valve of first circuit S12 Step of opening pressure equalization valve of pressure equalization circuit

Claims

1. A refrigerator comprising:a low-stage compressor configured to compress a low-pressure refrigerant into a medium-pressure refrigerant;a high-stage compressor configured to compress the medium-pressure refrigerant into a high-pressure refrigerant;a low-pressure pipe connected to the low-stage compressor and through which the low-pressure refrigerant flows;a medium-pressure pipe connected between the low-stage compressor and the high-stage compressor and through which the medium-pressure refrigerant flows;a high-pressure pipe connected to the high-stage compressor and through which the high-pressure refrigerant flows;a first circuit extending from the high-pressure pipe to the low-pressure pipe; anda pressure equalization circuit configured to equalize a pressure between the first circuit and the medium-pressure pipe,wherein the first circuit includes a first valve configured to open and close a flow channel in the first circuit, andthe pressure equalization circuit includes a pressure equalization valve configured to open and close a flow channel in the pressure equalization circuit.

2. The refrigerator according to Claim 1,wherein, in a case where the first valve is opened, the first circuit supplies the high-pressure refrigerant, which flows through the high-pressure pipe and has a higher temperature than the low-pressure refrigerant, to the low-pressure pipe.

3. The refrigerator according to Claim 1 or 2, further comprising:an injection circuit connected to the medium-pressure pipe and configured to inject a refrigerant, which has a lower temperature than a refrigerant in the high-stage compressor, into the high-stage compressor,wherein the pressure equalization circuit is configured to connect the first circuit and the injection circuit.

4. The refrigerator according to Claim 3,wherein the pressure equalization circuit connects the injection circuit and a position on a downstream side in the first circuit in a flow direction of the high-pressure refrigerant in the first circuit.

5. The refrigerator according to Claim 3, further comprising:an intercooler disposed in an intermediate part of the medium-pressure pipe and configured to cool the medium-pressure refrigerant compressed by the low-stage compressor,wherein the injection circuit is connected to the medium-pressure pipe between the intercooler and the high-stage compressor.

6. The refrigerator according to Claim 1 or 2,wherein the first circuit includes a flow rate adjustment mechanism configured to adjust a flow rate of the high-pressure refrigerant in a case where the first valve is opened.

7. The refrigerator according to Claim 1 or 2, further comprising:an accumulator configured to separate the low-pressure refrigerant supplied to the low-stage compressor into a gas refrigerant and a liquid refrigerant; andan oil separator configured to separate oil contained in the high-pressure refrigerant discharged from the high-stage compressor,wherein the first circuit connects a downstream side in the high-pressure pipewith respect to the oil separator in a flow direction of the high-pressure refrigerant and a downstream side in the low-pressure pipe with respect to the accumulator in a flow direction of the low-pressure refrigerant.

8. The refrigerator according to Claim 1 or 2,wherein the high-stage compressor and the low-stage compressor are each a two-stage compressor including two compression units arranged in series.

9. A control device configured to control a refrigerator including a low-stage compressor configured to compress a low-pressure refrigerant into a medium-pressure refrigerant, a high-stage compressor configured to compress the medium-pressure refrigerant into a high-pressure refrigerant, a low-pressure pipe connected to the low-stage compressor and through which the low-pressure refrigerant flows, a mediumpressure pipe connected between the low-stage compressor and the high-stage compressor and through which the medium-pressure refrigerant flows, and a high-pressure pipe connected to the high-stage compressor and through which the high-pressure refrigerant flows, the control device comprising:a first valve control unit configured to open a first valve of a first circuit extending to the high-pressure pipe and the low-pressure pipe; anda pressure equalization valve control unit configured to open a pressure equalization valve of a pressure equalization circuit configured to equalize a pressure between the first circuit and the medium-pressure pipe.

10. A control method of a refrigerator including a low-stage compressor configured to compress a low-pressure refrigerant into a medium-pressure refrigerant, a high-stage compressor configured to compress the medium-pressure refrigerant into a high-pressure refrigerant, a low-pressure pipe connected to the low-stage compressor and through which the low-pressure refrigerant flows, a medium-pressure pipe connectedbetween the low-stage compressor and the high-stage compressor and through which the medium-pressure refrigerant flows, and a high-pressure pipe connected to the high-stage compressor and through which the high-pressure refrigerant flows, the control method comprising:in a case where operations of the low-stage compressor and the high-stage compressor are stopped,a step of opening a first valve of a first circuit extending to the high-pressure pipe and the low-pressure pipe; anda step of opening a pressure equalization valve of a pressure equalization circuit configured to equalize a pressure between the first circuit and the medium-pressure pipe.

11. A program causing a control device of a refrigerator including a low-stage compressor configured to compress a low-pressure refrigerant into a medium-pressure refrigerant, a high-stage compressor configured to compress the medium-pressure refrigerant into a high-pressure refrigerant, a low-pressure pipe connected to the low-stage compressor and through which the low-pressure refrigerant flows, a mediumpressure pipe connected between the low-stage compressor and the high-stage compressor and through which the medium-pressure refrigerant flows, and a high-pressure pipe connected to the high-stage compressor and through which the high-pressure refrigerant flows, to execute control comprising:in a case where operations of the low-stage compressor and the high-stage compressor are stopped,a step of opening a first valve of a first circuit extending to the high-pressure pipe and the low-pressure pipe; anda step of opening a pressure equalization valve of a pressure equalization circuit configured to equalize a pressure between the first circuit and the medium-pressure pipe.INTERNATIONAL SEARCH REPORT International application No. PCT / JP2023 / 005771A. CLASSIFICATION OF SUBJECT MATTERF25B l / 00(2006.01)i;F2SB 1 / 10(2006.01)1FI: F25B1 / 00 351E; F25B1 / 10 E; F25B1 / 10 CAccording to International Patent Classification (IPC) or to both national classification and IPCB. FIELDS SEARCHED Minimum documentation searched (classification system followed by classification symbols) F25B1 / 00-49 / 04 Documentation searched other than minimum documentation to the extent that such documents are included in the fields searched Published examined utility model applications of Japan 1922-1996 Published unexamined utility model applications of Japan 1971-2023 Registered utility model specifications of Japan 1996-2023 Published registered utility model applications of Japan 1994-2023 Electronic data base consulted during the international search (name of data base and, where practicable, search terms used) C. DOCUMENTS CONSIDERED TO BE RELEVANT Category* Citation of document, with indication, where appropriate, of the relevant passages Relevant to claim No. Y WO 2018 / 025935 Al (MITSUBISHI HEAVY INDUSTRIES THERMAL SYSTEMS, LTD.) 08 February 2018 (2018-02-08) paragraphs [0014]-[0017], [0022], fig. 1-2 1-11 Y JP 2010-117072 A (MITSUBISHI HEAVY IND LTD) 27 May 2010 (2010-05-27) paragraphs [0021]-[0023], [0037]-[0038], [0041]-[0043], fig. 6-7 1-11 Y WO 2021 / 039087 Al (DAIKIN INDUSTRIES, LTD.) 04 March 2021 (2021-03-04) paragraphs [0042], [0044], fig. 1 5 Y JP 56-12959 A (MATSUSHITA ELECTRIC IND CO LTD) 07 February 1981 (1981-02-07) p. 2, upper right column, lines 9-15, p. 3, lower right column, lines 3-8, fig. 1 6 Y A A WO 2019 / 186647 Al (MITSUBISHI ELECTRIC CORP) 03 October 2019 (2019-10-03) paragraphs [0014]-[0016], fig. 1 paragraphs [0012]-[0016], [0029], [0050]-[0063], fig. 1 JP 2004-28492 A (SANYO ELECTRIC CO LTD) 29 January 2004 (2004-01-29) paragraphs [0003]-[0006], [0030]-[0034], fig. 2 8 1-2,9-11 1-2, 7, 9-11 | | Further documents are listed in the continuation of Box C. | V | See patent family annex. * Special categories of cited documents: “A” document defining the general state of the art which is not considered to be of particular relevance “E” earlier application or patent but published on or after the international filing date “L” document which may throw doubts on priority claim(s) or which is cited to establish the publication date of another citation or other special reason (as specified) “O” document referring to an oral disclosure, use, exhibition or other means “P” document published prior to the international filing date but later than the priority date claimed “T” later document published after the international filing date or priority date and not in conflict with the application but cited to understand the principle or theory underlying the invention “X” document of particular relevance; the claimed invention cannot be considered novel or cannot be considered to involve an inventive step when the document is taken alone “Y” document of particular relevance; the claimed invention cannot be considered to involve an inventive step when the document is combined with one or more other such documents, such combination being obvious to a person skilled in the ait document member of the same patent family Date of the actual completion of the international search 12 April 2023 Date of mailing of the international search report 25 April 2023 Name and mailing address of the ISA / JP Japan Patent Office (ISA / JP) 3-4-3 Kasumigaseki, Chiyoda-ku, Tokyo 100-8915 Japan Authorized officer Telephone No.INTERNATIONAL SEARCH REPORT Information on patent family members International application No. PCT / JP2023 / 005771Patent document cited in search report Publication date (day / month / year) Patent family member)s) Publication date (day / month / year) WO 2018 / 025935 Al 08 February 2018 EP 3453986 Al paragraphs [0020]-[0023], [0031], fig. 1-2 JP 2018-21732 A JP 2010-117072 A 27 May 2010 (Family: none) WO 2021 / 039087 Al 04 March 2021 US 2022 / 0146172 Al paragraphs [0035], [0037], fig. 1 EP 3995757 Al CN 114174732 A JP 2021-32512 A JP 56-12959 A 07 February 1981 (Family: none) WO 2019 / 186647 Al 03 October 2019 GB 2585594 A paragraphs [0012]-[0016], [0029], [0050]-[0063], fig. 1 JP 2004-28492 A 29 January 2004 (Family: none)

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