Refrigeration unit, control device for refrigeration unit, control method for refrigeration unit, and program

Abstract

To provide a refrigerator that easily equalizes pressure.SOLUTION: A refrigerator comprises: a low-stage compressor for compressing a low-pressure refrigerant into an intermediate-pressure refrigerant; a high-stage compressor for compressing the intermediate-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; an intermediate-pressure pipe connected between the low-stage compressor and the high-stage compressor, and through which the intermediate-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 capable of equalizing pressure between the first circuit and the intermediate-pressure pipe. The first circuit comprises a first valve for opening / closing a flow passage in the first circuit. The pressure equalization circuit comprises a pressure equalization valve for opening / closing a flow passage in the pressure equalization circuit.SELECTED DRAWING: Figure 1

Description

Technical Field

[0001] The present disclosure relates to a refrigerator, a control device for the refrigerator, a control method for the refrigerator, and a program.

Background Art

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

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] By the way, in a 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, low-pressure refrigerant flows through the pipe on the upstream side in the refrigerant flow direction with respect to the low-stage compressor. Medium-pressure refrigerant compressed by the low-stage compressor flows through the pipe between the low-stage compressor and the high-stage compressor. High-pressure refrigerant flows through the pipe on the downstream side in the refrigerant flow direction with respect to the high-stage compressor. Therefore, during operation of the refrigerator, a pressure difference of the refrigerant occurs between the low-pressure pipe on the upstream side of the low-stage compressor, the medium-pressure pipe between the low-stage compressor and the high-stage compressor, and the high-pressure pipe on the downstream side of the high-stage compressor. When the operation of the refrigerator is stopped, equalization of pressure among the low-pressure pipe, the medium-pressure pipe, and the high-pressure pipe may be desired for stable stopping of the refrigerator or the like. However, in a configuration including a plurality of compressors, the configuration tends to become complicated in order to equalize the pressure among the low-pressure pipe, the medium-pressure pipe, and the high-pressure pipe. Note: The patent number in Japanese Unexamined Patent Application Publication No. ********-**** is masked as it contains specific numbers which are not provided in the original text. You can replace it with the actual patent number if available.

[0005] This disclosure was made to solve the above-mentioned problems and aims to provide a refrigerator that facilitates pressure equalization, a control device for the refrigerator, a control method for the refrigerator, and a program. [Means for solving the problem]

[0006] To solve the above problems, the refrigerator according to the present disclosure comprises a low-stage compressor for compressing a low-pressure refrigerant to an intermediate-pressure refrigerant, a high-stage compressor for compressing the intermediate-pressure refrigerant to a high-pressure refrigerant, a low-pressure pipe connected to the low-stage compressor through which the low-pressure refrigerant flows, an intermediate-pressure pipe connected between the low-stage compressor and the high-stage compressor through which the intermediate-pressure refrigerant flows, a high-pressure pipe connected to the high-stage compressor 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 capable of equalizing the pressure between the first circuit and the intermediate-pressure pipe, wherein the first circuit includes a first valve for opening and closing the flow path within the first circuit, and the pressure equalization circuit includes a pressure equalization valve for opening and closing the flow path within the pressure equalization circuit.

[0007] The control device for a refrigerator according to this disclosure is capable of controlling a refrigerator comprising: a low-stage compressor for compressing a low-pressure refrigerant to an intermediate-pressure refrigerant; a high-stage compressor for compressing the intermediate-pressure refrigerant to a high-pressure refrigerant; a low-pressure pipe connected to the low-stage compressor through which the low-pressure refrigerant flows; an intermediate-pressure pipe connected between the low-stage compressor and the high-stage compressor through which the intermediate-pressure refrigerant flows; and a high-pressure pipe connected to the high-stage compressor through which the high-pressure refrigerant flows. The control device comprises: a first valve control unit that opens a first valve of a first circuit extending to the high-pressure pipe and the low-pressure pipe; and a pressure equalizing valve control unit that opens a pressure equalizing valve of a pressure equalizing circuit capable of equalizing the pressure between the first circuit and the intermediate-pressure pipe.

[0008] A control method for a refrigerator according to the present disclosure comprises: a low-stage compressor for compressing a low-pressure refrigerant to an intermediate-pressure refrigerant; a high-stage compressor for compressing the intermediate-pressure refrigerant to a high-pressure refrigerant; a low-pressure pipe connected to the low-stage compressor through which the low-pressure refrigerant flows; an intermediate-pressure pipe connected between the low-stage compressor and the high-stage compressor through which the intermediate-pressure refrigerant flows; and a high-pressure pipe connected to the high-stage compressor through which the high-pressure refrigerant flows, the control method for a refrigerator comprising: when the operation of the low-stage compressor and the high-stage compressor is stopped, opening a first valve of a first circuit extending to the high-pressure pipe and the low-pressure pipe; and opening a pressure equalizing valve of a pressure equalizing circuit capable of equalizing the pressure between the first circuit and the intermediate-pressure pipe.

[0009] The program relating to this disclosure causes a control device for a refrigerator, which includes a low-stage compressor for compressing a low-pressure refrigerant to an intermediate-pressure refrigerant, a high-stage compressor for compressing the intermediate-pressure refrigerant to a high-pressure refrigerant, a low-pressure pipe connected to the low-stage compressor through which the low-pressure refrigerant flows, an intermediate-pressure pipe connected between the low-stage compressor and the high-stage compressor through which the intermediate-pressure refrigerant flows, to execute control including the steps of opening a first valve of a first circuit extending to the high-pressure pipe and the low-pressure pipe, and opening a pressure equalizing valve of a pressure equalizing circuit capable of equalizing the pressure between the first circuit and the intermediate-pressure pipe, when the operation of the low-stage compressor and the high-stage compressor is stopped. [Effects of the Invention]

[0010] According to the refrigerator, refrigerator control device, refrigerator control method, and program of this disclosure, it is possible to provide a refrigerator that facilitates pressure equalization. [Brief explanation of the drawing]

[0011] [Figure 1] This figure shows the configuration of a refrigerator according to an embodiment of the present disclosure. [Figure 2] This figure shows the configuration of the first circuit and the pressure equalization circuit provided in the refrigerator according to the embodiment of this disclosure. [Figure 3] This is a functional block diagram of the control device for a refrigerator according to the present disclosure. [Figure 4]This flowchart shows the procedure for a control method of a refrigerator according to an embodiment of the present disclosure. [Figure 5] This diagram shows the flow of refrigerant during normal operation in a refrigerator according to an embodiment of this disclosure. [Figure 6] This diagram shows the flow of refrigerant when the operation of a refrigerator according to an embodiment of this disclosure is stopped. [Figure 7] This figure shows the hardware configuration of the control device for a refrigerator according to the embodiment of this disclosure. [Modes for carrying out the invention]

[0012] Hereinafter, a refrigerator, a control device for the refrigerator, a control method for the refrigerator, and a program according to the embodiments of this disclosure will be described with reference to Figures 1 to 7. (Refrigeration unit configuration) As shown in Figure 1, the refrigerator 1 mainly comprises a compression unit 2, a condenser 3, an expansion valve 4, and a receiver 5. Refrigeration unit 1 is an outdoor unit that constitutes a refrigeration cycle system. The refrigerator 1 circulates refrigerant between itself and the indoor unit (not shown) that constitutes the refrigeration cycle system. Refrigeration unit 1 cools the refrigerant and produces liquid refrigerant. Refrigeration unit 1 supplies the generated liquid refrigerant to the indoor unit (not shown). Refrigeration unit 1 draws in refrigerant from the indoor unit, which has been heated by heat exchange in the indoor unit. In this embodiment, the refrigerant is, for example, carbon dioxide (CO2). The refrigerant may be something other than carbon dioxide.

[0013] The compression unit 2 compresses the refrigerant circulated from the indoor unit. The compression section 2 mainly comprises 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 sucks in refrigerant from the indoor unit through the first pipe 101. The inlet accumulator 21 separates the refrigerant sucked in from an indoor unit (not shown) into gaseous refrigerant and liquid refrigerant. Refrigerant discharged from an indoor unit (not shown) flows into the inlet accumulator 21 through the first pipe 101. The inlet accumulator 21 supplies the gaseous refrigerant separated within 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 by the inlet accumulator 21 is sent to the sub-accumulator 22 through the first oil return pipe 401. The first oil return pipe 401 connects the bottom of the inlet accumulator 21 and the second pipe 102. The oil supplied into the second pipe 102 through the first oil return pipe 401 mixes with the gaseous refrigerant flowing in the second pipe 102 and is sent to the sub-accumulator 22.

[0016] The sub-accumulator 22 receives the gaseous refrigerant separated by the inlet accumulator 21 through the second pipe 102. The sub-accumulator 22 separates gaseous refrigerant and liquid refrigerant. The sub-accumulator 22 separates the liquid refrigerant contained in the gaseous refrigerant separated by the inlet accumulator 21. The sub-accumulator 22 supplies the gaseous refrigerant separated within 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 sucks in the gaseous refrigerant separated by the sub-accumulator 22 through the third pipe 103 due to the negative pressure generated by the operation of the low-stage compressor 23. The low-stage compressor 23 compresses the sucked-in gaseous refrigerant. In this embodiment, the low-stage compressor 23 is a two-stage compressor equipped with 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 gaseous refrigerant drawn in through the third pipe 103. The first scroll compression section 232 further compresses the refrigerant that has been compressed in the first rotary compression section 231. The refrigerant compressed in the first scroll compression section 232 is discharged to the intercooler 24 through the fourth pipe 104. The fourth pipe 104 connects the low-stage compressor 23 and the intercooler 24.

[0018] The intercooler 24 and intermediate accumulator 25 are located between the low-stage compressor 23 and the high-stage compressor 26. The intercooler 24 receives refrigerant compressed by the low-stage compressor 23 through the fourth pipe 104. Intercooler 24 cools the refrigerant that is supplied to it. In this embodiment, the intercooler 24 is, for example, air-cooled. The intercooler 24 consists of an intercooler body 241 and a fan 242. The intercooler body 241 has a flow passage (not shown) for the refrigerant compressed by the low-stage compressor 23. The intercooler unit 241 performs heat exchange between the refrigerant flowing through the circulation pipe and the outside air outside the circulation pipe. The fan 242 blows air onto the intercooler body 241, improving the efficiency of heat exchange within the intercooler body 241. The refrigerant cooled by the intercooler 24 is sent to the intermediate accumulator 25 through the fifth pipe 105. The fifth pipe 105 connects the intercooler 24 and the intermediate accumulator 25.

[0019] The intermediate accumulator 25 is cooled by the intercooler 24 and separates the refrigerant supplied through the fifth pipe 105 into gaseous refrigerant and liquid refrigerant. The gaseous refrigerant separated in the intermediate accumulator 25 is supplied to the high-stage compressor 26 through the 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 sent to the high-stage compressor 26 through the second oil return pipe 402. The second oil return pipe 402 connects the bottom of the intermediate accumulator 25 to the sixth pipe 106. The oil supplied to the sixth pipe 106 through the second oil return pipe 402 mixes with the refrigerant flowing through the sixth pipe 106 and is sent to the high-stage compressor 26.

[0021] The high-stage compressor 26 draws in the gaseous refrigerant separated by the intermediate accumulator 25 through the sixth pipe 106 due to the negative pressure generated when the high-stage compressor 26 is operating. The high-stage compressor 26 compresses the gaseous refrigerant that has been drawn in. In this embodiment, the high-stage compressor 26 is a two-stage compressor equipped with 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 gaseous refrigerant drawn in through the sixth pipe 106. The second scroll compression section 262 further compresses the high-temperature, high-pressure refrigerant that has been compressed in the second rotary compression section 261. The refrigerant compressed by the high-stage compressor 26 is sent to the oil separator 27 through the 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 that has been compressed by the high-stage compressor 26 and sent through the seventh pipe 107. The refrigerant, from which the oil has been separated by the oil separator 27, is sent to the condenser 3 through the eighth pipe 108. The eighth pipe 108 connects the oil separator 27 and the capacitor 3.

[0023] The oil separated by the oil separator 27 is discharged to the oil tank 28 through the 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 the fourth oil return pipe 404 and the fifth oil return pipe 405. An oil cooler 29 is provided in the middle 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 the fifth oil return pipe 405.

[0025] Condenser 3 cools and condenses the refrigerant sent through the eighth pipe 108. In this embodiment, capacitor 3 is, for example, air-cooled. Capacitor 3 comprises a capacitor body 31 and a fan 32. The condenser body 31 has a flow passage (not shown) for the refrigerant supplied through the eighth pipe 108. Through the eighth pipe 108, heat exchange takes place between the refrigerant flowing inside the pipe and the outside air outside the pipe. The fan 32 blows air onto the capacitor body 31, thereby improving the efficiency of heat exchange within the capacitor body 31. The refrigerant cooled in condenser 3 is sent to expansion valve 4 through ninth pipe 109. The ninth pipe, 109, connects the capacitor 3 and the expansion valve 4.

[0026] The expansion valve 4 expands the refrigerant that has been condensed in the condenser 3 and sent through the ninth pipe 109. The expansion valve 4 sends the expanded refrigerant to the receiver 5 through the tenth pipe 110. The tenth pipe 110 connects the expansion valve 4 and the receiver 5.

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

[0028] In this embodiment, a supercooled heat exchanger 6 is provided in the middle of the eleventh pipe 111. The subcooled heat exchanger 6 further cools (subcools) the liquid refrigerant supplied to the indoor unit through the eleventh pipe 111. The subcooled heat exchanger 6 has a first flow passage (not shown) for liquid refrigerant supplied through the eleventh pipe 111 and a second flow passage (not shown) for liquid refrigerant supplied through the 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, upstream of the refrigerant flow direction in the eleventh pipe 111 to the subcooled heat exchanger 6. The other end of the twelfth pipe 112 is connected to the second flow passage of the supercooled heat exchanger 6. The twelfth pipe 112 is equipped with an injection valve 61 and an expansion valve 62 for the subcooled heat exchanger.

[0030] The injection valve 61 opens and closes the flow path of liquid refrigerant in the twelfth pipe 112. The opening and closing operation of the injection valve 61 is controlled by the control device 300. When the injection valve 61 is opened, liquid refrigerant is supplied to the subcooled heat exchanger 6 through the twelfth pipe 112. When the injection valve 61 is closed, liquid refrigerant is not supplied to the subcooled heat exchanger 6 through the twelfth pipe 112.

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

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

[0033] The injection circuit 120 connects the supercooled heat exchanger 6 and the sixth pipe 106. The injection circuit 120 is connected to the sixth pipe 106, which is located downstream of the intermediate accumulator 25 in the direction of refrigerant flow. 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 sends the liquid refrigerant heated in the subcooled 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 section 261 and the second scroll compression section 262. The injection circuit 120 is located downstream of the second rotary compression unit 261 and supplies liquid refrigerant to the high-stage compressor 26.

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

[0035] Such a refrigerator 1 has a low-pressure pipe 100L, a medium-pressure pipe 100M, and a high-pressure pipe 100H. The low-pressure piping 100L carries the low-pressure refrigerant before it is compressed by the low-stage compressor 23. The low-pressure refrigerant flowing through the 100L low-pressure piping has the lowest pressure in refrigeration unit 1. The low-pressure piping 100L is connected to the low-stage compressor 23. The low-pressure piping 100L includes a first pipe 101, a second pipe 102, and a third pipe 103, which are located upstream of the low-stage compressor 23 in the direction of refrigerant flow.

[0036] The low-stage compressor 23 compresses the low-pressure refrigerant to an intermediate-pressure refrigerant. The 100M medium-pressure piping carries the medium-pressure refrigerant, which has been compressed by the low-stage compressor 23. The medium-pressure piping 100M is connected between the low-stage compressor 23 and the high-stage compressor 26. The medium-pressure piping 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. High-pressure refrigerant, compressed by the high-stage compressor 26, flows through the high-pressure piping 100H. The high-pressure refrigerant flowing through high-pressure piping 100H has the highest pressure in refrigerator 1. The high-pressure piping 100H is connected to the high-stage compressor 26. The high-pressure piping 100H is located between the high-stage compressor 26 and the expansion valve 4. The high-pressure piping 100H includes the seventh piping 107, the eighth piping 108, and the ninth piping 109.

[0038] Refrigeration unit 1 is equipped with a pressure equalization mechanism 500. The pressure equalization mechanism 500 equalizes the pressure between the low-pressure pipe 100L, the medium-pressure pipe 100M, and the high-pressure pipe 100H when the system is stopped. As shown in Figures 1 and 2, the equalizing mechanism 500 includes a first circuit 510 and a equalizing circuit 520.

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

[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 path in the first circuit 510. When the first valve 511 is opened, the first circuit 510 flows through the high-pressure pipe 100H and supplies high-pressure refrigerant, which has a higher pressure and temperature than the low-pressure refrigerant, to the low-pressure pipe 100L. The opening and closing operation of the first valve 511 is controlled by the control device 300. When the first valve 511 is opened, high-pressure refrigerant is supplied to the low-pressure pipe 100L through the first circuit 510 and the high-pressure pipe 100H. This equalizes the pressure between the high-pressure pipe 100H and the low-pressure pipe 100L. When the first valve 511 is closed, voltage equalization is not performed through the first circuit 510.

[0041] The flow rate adjustment mechanism 512 is located in the first circuit 510, downstream of the first valve 511 in the direction of refrigerant flow in the first circuit 510. The flow rate adjustment mechanism 512 is, for example, a capillary tube. The refrigerant flowing through the first circuit 510 is subjected to flow resistance by the flow rate adjustment mechanism 512, which consists of capillary piping, and its flow rate is reduced. The flow rate adjustment mechanism 512 may have a configuration other than capillary piping.

[0042] The equalizing circuit 520 is designed to be connectable to the first circuit 510 and the injection circuit 120. The pressure equalization circuit 520 connects the injection circuit 120 to the first circuit 510, specifically to the downstream position 513 in the flow direction of the high-pressure refrigerant in the first circuit 510. One end 520a of the equalizing circuit 520 is connected to the injection circuit 120. One end 520a of the pressure equalization circuit 520 is connected to the injection circuit 120 between the supercooled heat exchanger 6 and the sixth pipe 106. The other end 520b of the equalizing circuit 520 is connected to the first circuit 510. The other end 520b of the pressure equalization circuit 520 is connected to a position 513 in the first circuit 510 that is downstream of the first valve 511 in the flow direction of the high-pressure refrigerant.

[0043] The pressure equalization circuit 520 is equipped with a pressure equalization valve 521. The pressure equalizing valve 521 opens and closes the flow path within the pressure equalizing circuit 520. When the pressure equalization valve 521 is opened, the pressure equalization circuit 520 connects the first circuit 510 and the injection circuit 120. When the pressure equalization valve 521 is opened, the first circuit 510 and the injection circuit 120 are connected through the pressure equalization circuit 520. When the pressure equalization valve 521 is opened, the high-pressure pipe 100H and low-pressure pipe 100L, which are connected by the first circuit 510, are connected to the medium-pressure pipe 100M via the pressure equalization circuit 520 and the injection circuit 120. When the pressure equalization valve 521 is opened, the high-pressure piping 100H, the medium-pressure piping 100M, and the low-pressure piping 100L are all equalized in pressure. The opening and closing operation of the pressure equalizing valve 521 is controlled by the control device 300.

[0044] (Control device configuration) The control device 300 is capable of controlling the refrigerator 1. The control device 300 controls the opening and closing operations of at least the low-stage compressor 23, the high-stage compressor 26, the injection valve 61, the first valve 511, and the pressure equalizing valve 521. As shown in Figure 3, the control device 300 includes a Central Processing Unit (hereinafter referred to as "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. In other words, the CPU 310 operates based on a predetermined program, performing the functions of 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 data acquired by the control device 300.

[0046] The operation control unit 311 controls the operation of the chiller 1 based on control commands output from the indoor unit in response to operations 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 commands output from the indoor unit. The operation control unit 311 controls the operation of each part of the refrigerator 1, such as the fans 242 and 32, based on the control commands output from the indoor unit.

[0047] The injection valve control unit 312 controls the opening and closing operation of the injection valve 61 of the injection circuit 120. The injection valve control unit 312 opens the injection valve 61 and injects refrigerant into the high-stage compressor 26 through the injection circuit 120 when the temperature inside the high-stage compressor 26, detected by a temperature sensor (not shown), exceeds a predetermined standard.

[0048] The first valve control unit 313 controls the opening and closing operation of the first valve 511 of the first circuit 510. The first valve control unit 313 equalizes the pressure between the high-pressure pipe 100H and the low-pressure pipe 100L via the first circuit 510 by opening the first valve 511. The pressure equalization valve control unit 314 controls the opening and closing operation of the pressure equalization valve 521 of the pressure equalization circuit 520. The pressure equalization valve control unit 314 equalizes the pressure between the first circuit 510 and the medium-pressure piping 100M via the pressure equalization circuit 520 by opening the pressure equalization valve 521.

[0049] (Procedure for controlling the refrigerator) As shown in Figure 4, the 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 equalizing valve 521 of the pressure equalizing circuit 520. As shown in Figure 5, during normal operation, the refrigerant in the chiller 1 is sent from the low-pressure piping 100L through the low-stage compressor 23, the medium-pressure piping 100M, the high-stage compressor 26, the high-pressure piping 100H, and then through the eleventh piping 111 to the indoor unit. In this embodiment, the control method S10 for the refrigerator 1 is automatically executed when the operation of the low-stage compressor 23 and the high-stage compressor 26 is stopped. In step S11, which involves opening the first valve 511 of the first circuit 510, the first valve 511 of the first circuit 510 is opened under the control of the first valve control unit 313. As a result, as shown in Figure 6, the first circuit 510, which extends from the high-pressure pipe 100H to the low-pressure pipe 100L, connects the high-pressure pipe 100H and the low-pressure pipe 100L. This equalizes the pressure in the high-pressure pipe 100H and the low-pressure pipe 100L. In step S12, which involves 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 under the control of the pressure equalization valve control unit 314. At this time, if the injection valve 61 is not open, the injection valve control unit 312 opens the injection valve 61. As a result, the first circuit 510 and the intermediate pressure piping 100M are connected via the pressure equalization circuit 520. This equalizes the pressure in the high-pressure piping 100H, the intermediate pressure piping 100M, and the low-pressure piping 100L.

[0050] (Effects and Benefits) In this embodiment, the chiller 1 includes a first circuit 510 extending from the high-pressure pipe 100H to the low-pressure pipe 100L, and a pressure equalization circuit 520 capable of equalizing the pressure between the first circuit 510 and the medium-pressure pipe 100M. When the operation of the low-stage compressor 23 and the high-stage compressor 26 is stopped, opening the first valve 511 in the first circuit 510 equalizes the pressure between the high-pressure pipe 100H and the low-pressure pipe 100L. Also, opening the pressure equalization valve 521 in the pressure equalization circuit 520 equalizes the pressure between the first circuit 510 and the medium-pressure pipe 100M. As a result, the high-pressure pipe 100H, the medium-pressure pipe 100M, and the low-pressure pipe 100L are all equalized. Thus, to equalize the pressure of the high-pressure piping 100H, the medium-pressure piping 100M, and the low-pressure piping 100L, it is sufficient to provide a first circuit 510 equipped with a first valve 511 and a pressure equalization circuit 520 equipped with a pressure equalization valve 521. Therefore, it is possible to provide a refrigerator 1 with a simple configuration that makes pressure equalization easy.

[0051] Furthermore, when the first circuit 510 of the refrigerator 1 is opened, the first circuit 510 supplies high-pressure refrigerant, which is at a higher temperature than the low-pressure refrigerant, to the low-pressure piping 100L. This allows the temperature of the refrigerant to be raised if the temperature of the refrigerant supplied from the low-pressure piping 100L to the low-stage compressor 23 drops too low. Therefore, the efficiency of compressing the refrigerant in the low-stage compressor 23 can be increased.

[0052] Furthermore, the refrigerator 1 can improve the efficiency of compressing the refrigerant in the high-stage compressor 26 by injecting a low-temperature refrigerant into the high-stage compressor 26 via the injection circuit 120. The pressure equalization circuit 520 connects the first circuit 510 and the injection circuit 120, allowing 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 to be equalized via the injection circuit 120. In this way, by using the injection circuit 120 for pressure equalization as well, the amount of new piping to be installed can be reduced.

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

[0054] Furthermore, the refrigerator 1 can increase the temperature of the refrigerant if, for example, the temperature of the refrigerant drops too low due to cooling by the intercooler 24, by supplying refrigerant to the refrigerant cooled by the intercooler 24, which is located in the medium-pressure piping 100M, via the injection circuit 120. Therefore, the efficiency of compressing the refrigerant by the high-stage compressor 26 is increased.

[0055] Furthermore, the refrigerator 1 has a first circuit 510 equipped with a flow rate adjustment mechanism 512, which allows the flow rate of high-pressure refrigerant flowing from the high-pressure piping 100H side to the low-pressure piping 100L side to be adjusted when the first valve 511 is opened.

[0056] Furthermore, in the refrigerator 1, the pressure of the high-pressure refrigerant compressed by the high-stage compressor 26 is highest on the downstream side of the high-pressure refrigerant flow direction relative to the oil separator 27 in the high-pressure piping 100H. In the low-pressure piping 100L, the pressure of the low-pressure refrigerant is lowest immediately before the low-stage compressor 23 on the downstream side of the low-pressure refrigerant flow direction relative to the inlet accumulator 21 in the low-pressure piping 100L. The first circuit 510 connects the downstream side of the high-pressure refrigerant flow direction relative to the oil separator 27 and the downstream side of the low-pressure refrigerant flow direction relative to the inlet accumulator 21 in the low-pressure piping 100L. This allows for efficient pressure equalization between the position with the highest pressure of the high-pressure refrigerant in the high-pressure piping 100H and the position with the lowest pressure of the low-pressure refrigerant in the low-pressure piping 100L via the first circuit 510.

[0057] Furthermore, the high-stage compressor 26 and the low-stage compressor 23 are each equipped with two compression sections 231, 232, 261, and 262 in series. In other words, the high-stage compressor 26 and the low-stage compressor 23 are equipped with a total of four compression sections 231, 232, 261, and 262. With this configuration, it is possible to equalize the pressure in the high-pressure piping 100H, the medium-pressure piping 100M, and the low-pressure piping 100L.

[0058] Furthermore, when the operation of the low-stage compressor 23 and the high-stage compressor 26 is stopped, the control device 300 of the chiller 1 opens the first valve 511 in the first circuit 510, equalizing the pressure in the high-pressure piping 100H and the low-pressure piping 100L. Also, when the pressure equalizing valve 521 in the pressure equalizing circuit 520 is opened, the pressure equalizes in the first circuit 510 and the intermediate-pressure piping 100M. As a result, the pressure equalizes in the high-pressure piping 100H, the intermediate-pressure piping 100M, and the low-pressure piping 100L. Thus, to equalize the pressure in the high-pressure piping 100H, the intermediate-pressure piping 100M, and the low-pressure piping 100L, it is sufficient to provide the first circuit 510 equipped with the first valve 511 and the pressure equalizing circuit 520 equipped with the pressure equalizing valve 521. Therefore, it is possible to provide a chiller 1 that is easy to equalize with a simple configuration.

[0059] Furthermore, in the control method S10 of the chiller 1, when the operation of the low-stage compressor 23 and the high-stage compressor 26 is stopped, opening the first valve 511 provided in the first circuit 510 equalizes the pressure of the high-pressure piping 100H and the low-pressure piping 100L. Also, opening the pressure equalizing valve 521 provided in the pressure equalizing circuit 520 equalizes the pressure of the first circuit 510 and the intermediate-pressure piping 100M. As a result, the high-pressure piping 100H, the intermediate-pressure piping 100M, and the low-pressure piping 100L are equalized. Thus, to equalize the pressure of the high-pressure piping 100H, the intermediate-pressure piping 100M, and the low-pressure piping 100L, it is sufficient to provide the first circuit 510 equipped with the first valve 511 and the pressure equalizing circuit 520 equipped with the pressure equalizing valve 521. Therefore, it is possible to provide a chiller 1 that is easy to equalize with a simple configuration.

[0060] Furthermore, if the operation of the low-stage compressor 23 and the high-stage compressor 26 is stopped, the program opens the first valve 511 in the first circuit 510, equalizing the pressure in the high-pressure piping 100H and the low-pressure piping 100L. Also, if the pressure equalizing valve 521 in the pressure equalizing circuit 520 is opened, the pressure equalizes in the first circuit 510 and the intermediate-pressure piping 100M. As a result, the pressure equalizes in the high-pressure piping 100H, the intermediate-pressure piping 100M, and the low-pressure piping 100L. Thus, to equalize the pressure in the high-pressure piping 100H, the intermediate-pressure piping 100M, and the low-pressure piping 100L, it is sufficient to provide the first circuit 510 equipped with the first valve 511 and the pressure equalizing circuit 520 equipped with the pressure equalizing valve 521. Therefore, it is possible to provide a refrigerator 1 that is easy to equalize with a simple configuration.

[0061] In the above-described embodiment, a program for realizing the various functions of the control device 300 is recorded on a computer-readable recording medium, and the program recorded on this recording medium is read by a computer system such as a microcontroller and executed to perform various processes. Here, the processes of various operations of the CPU of the computer system are stored in the form of a program on a computer-readable recording medium, and the above-mentioned operations are performed when the computer reads and executes this program. The computer-readable recording medium refers to magnetic disks, magneto-optical disks, CD-ROMs, DVD-ROMs, semiconductor memory, etc. Alternatively, this computer program may be distributed to a computer via a communication line, and the computer that receives this distribution may execute the program.

[0062] In the above-described embodiment, an example of a computer hardware configuration for executing a program to realize various functions of the control device 300 will be explained.

[0063] As shown in Figure 7, the computer included in the control device 300 comprises a CPU 310, memory 320, storage / playback device 330, input output interface (hereinafter referred to as "IO I / F") 340, and communication interface (hereinafter referred to as "communication I / F") 350.

[0064] The memory 320 is a medium such as Random Access Memory (hereinafter referred to as "RAM") that temporarily stores data used by programs executed by the control device 300. The storage / playback device 330 is a device for storing data on external media such as CD-ROMs, DVDs, and flash memory, and for playing back data from external media. The IO I / F340 is an interface for inputting and outputting information between the control device 300 and other devices. The Communication I / F350 is an interface that enables communication with other devices via communication lines such as the Internet or dedicated communication lines.

[0065] <Note> The refrigerator 1, the control device 300 for the refrigerator 1, the control method S10 for the refrigerator 1, and the program described in the embodiment can be understood, for example, as follows.

[0066] (1) The refrigerator 1 according to the first embodiment comprises a low-stage compressor 23 that compresses low-pressure refrigerant to medium-pressure refrigerant, a high-stage compressor 26 that compresses the medium-pressure refrigerant to 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-pressure 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 capable of equalizing the pressure between the first circuit 510 and the medium-pressure pipe 100M, wherein the first circuit 510 comprises a first valve 511 that opens and closes the flow path within the first circuit 510, and the pressure equalization circuit 520 comprises a pressure equalization valve 521 that opens and closes the flow path within the pressure equalization circuit 520.

[0067] This chiller 1 is equipped with a first circuit 510 extending from a high-pressure pipe 100H to a low-pressure pipe 100L, and a pressure equalization circuit 520 capable of equalizing the pressure between the first circuit 510 and the medium-pressure pipe 100M. When the operation of the low-stage compressor 23 and the high-stage compressor 26 is stopped, opening the first valve 511 in the first circuit 510 equalizes the pressure between the high-pressure pipe 100H and the low-pressure pipe 100L. Also, opening the pressure equalization valve 521 in the pressure equalization circuit 520 equalizes the pressure between the first circuit 510 and the medium-pressure pipe 100M. As a result, the high-pressure pipe 100H, the medium-pressure pipe 100M, and the low-pressure pipe 100L are equalized. Thus, to equalize the pressure between the high-pressure pipe 100H, the medium-pressure pipe 100M, and the low-pressure pipe 100L, it is sufficient to provide a first circuit 510 equipped with a first valve 511 and a pressure equalization circuit 520 equipped with a pressure equalization valve 521. Therefore, it becomes possible to provide a refrigerator 1 with a simple configuration that facilitates pressure equalization.

[0068] (2) The refrigerator 1 according to the second embodiment is the refrigerator 1 of (1), wherein when the first valve 511 is opened, the first circuit 510 flows through the high-pressure pipe 100H and supplies the high-pressure refrigerant, which is at a higher temperature than the low-pressure refrigerant, to the low-pressure pipe 100L.

[0069] As a result, when the first circuit 510 is opened, the first circuit 510 supplies high-pressure refrigerant, which is at a higher temperature than the low-pressure refrigerant, to the low-pressure piping 100L. This allows the temperature of the refrigerant to be raised if the temperature of the refrigerant supplied from the low-pressure piping 100L to the low-stage compressor 23 drops too low. Therefore, the efficiency of compressing the refrigerant in the low-stage compressor 23 can be increased.

[0070] (3) The refrigerator 1 according to the third embodiment is the refrigerator 1 according to (1) or (2), and is connected to the intermediate pressure piping 100M and includes an injection circuit 120 that injects a refrigerant at a lower temperature than the refrigerant in the high-stage compressor 26 into the high-stage compressor 26, and the pressure equalization circuit 520 is capable of connecting the first circuit 510 and the injection circuit 120.

[0071] This allows for the injection of a lower-temperature refrigerant into the high-stage compressor 26 via the injection circuit 120, thereby increasing the efficiency of refrigerant compression in the high-stage compressor 26. The pressure equalization circuit 520 connects the first circuit 510 and the injection circuit 120, allowing 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 to be equalized via the injection circuit 120. In this way, using the injection circuit 120 for pressure equalization also reduces the amount of new piping that needs to be installed.

[0072] (4) The refrigerator 1 according to the fourth embodiment is the refrigerator 1 of (3), wherein the equalizing circuit 520 connects the injection circuit 120 to the first circuit 510, specifically to the downstream position 513 in the flow direction of the high-pressure refrigerant in the first circuit 510.

[0073] Thus, the pressure equalization circuit 520 connects the injection circuit 120 to a position 513 in the first circuit 510 that is downstream in the flow direction of the high-pressure refrigerant. The position 513 in the first circuit 510 that is downstream in the flow direction of the high-pressure refrigerant is close to the low-pressure piping 100L. Therefore, the medium-pressure piping 100M and the low-pressure piping 100L can be equalized via the injection circuit 120 at a position close to the low-pressure piping 100L in the first circuit 510.

[0074] (5) The refrigerator 1 according to the fifth embodiment is the refrigerator 1 of (3) or (4), and is equipped with an intercooler 24 located in the middle of the intermediate pressure piping 100M and cooling the intermediate pressure refrigerant compressed by the low-stage compressor 23, and the injection circuit 120 is connected to the intermediate pressure piping 100M between the intercooler 24 and the high-stage compressor 26.

[0075] This allows the refrigerant temperature to be raised, for example, if the refrigerant temperature drops too low due to cooling by the intercooler 24, by supplying refrigerant to the intercooler 24 located in the medium-pressure piping 100M via the injection circuit 120. Consequently, the efficiency of compressing the refrigerant in the high-stage compressor 26 is improved.

[0076] (6) The refrigerator 1 according to the sixth embodiment is any one of the refrigerators 1 from (1) to (5), and includes a flow rate adjustment mechanism 512 that adjusts the flow rate of the high-pressure refrigerant when the first circuit 510 opens the first valve 511.

[0077] As a result, the first circuit 510 is equipped with a flow rate adjustment mechanism 512, which allows the flow rate of high-pressure refrigerant flowing from the high-pressure piping 100H to the low-pressure piping 100L to be adjusted when the first valve 511 is opened.

[0078] (7) The refrigerator 1 according to the seventh embodiment is any one of the refrigerators 1 from (1) to (6), comprising an accumulator 21 that separates the low-pressure refrigerant supplied to the low-stage compressor 23 into gaseous refrigerant and liquid refrigerant, and an oil separator 27 that separates the oil contained in the high-pressure refrigerant discharged from the high-stage compressor 26, wherein the first circuit 510 connects the oil separator 27 downstream in the flow direction of the high-pressure refrigerant in the high-pressure piping 100H, and the accumulator 21 downstream in the flow direction of the low-pressure refrigerant in the low-pressure piping 100L.

[0079] In the high-pressure piping 100H, the downstream side of the high-pressure refrigerant flow direction relative to the oil separator 27 is where the pressure of the high-pressure refrigerant compressed by the high-stage compressor 26 is highest. In the low-pressure piping 100L, the downstream side of the low-pressure refrigerant flow direction relative to the accumulator 21 is where the pressure of the low-pressure refrigerant is lowest, just before the low-stage compressor 23. The first circuit 510 connects the downstream side of the high-pressure refrigerant flow direction relative to the oil separator 27 and the downstream side of the low-pressure refrigerant flow direction relative to the accumulator 21 in the low-pressure piping 100L. This allows for efficient pressure equalization between the position where the high-pressure refrigerant pressure is highest in the high-pressure piping 100H and the position where the low-pressure refrigerant pressure is lowest in the low-pressure piping 100L via the first circuit 510.

[0080] (8) The refrigerator 1 according to the eighth embodiment is any one of the refrigerators 1 from (1) to (7), wherein the high-stage compressor 26 and the low-stage compressor 23 are two-stage compressors each comprising two compression units 231, 232, 261, and 262 in series.

[0081] As a result, the high-stage compressor 26 and the low-stage compressor 23 each have two compression sections 231, 232, 261, and 262 in series. In other words, the high-stage compressor 26 and the low-stage compressor 23 have a total of four compression sections 231, 232, 261, and 262. With this configuration, it is possible to equalize the pressure in the high-pressure piping 100H, the medium-pressure piping 100M, and the low-pressure piping 100L.

[0082] (9) The control device 300 for the refrigerator 1 according to the ninth embodiment is capable of controlling a refrigerator 1 comprising: a low-stage compressor 23 for compressing low-pressure refrigerant to medium-pressure refrigerant; a high-stage compressor 26 for compressing the medium-pressure refrigerant to high-pressure refrigerant; a low-pressure pipe 100L connected to the low-stage compressor 23 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 through which the medium-pressure refrigerant flows; and a high-pressure pipe 100H connected to the high-stage compressor 26 through which the high-pressure refrigerant flows, and comprises: a first valve control unit 313 that opens the 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 that opens the pressure equalization valve 521 of a pressure equalization circuit 520 capable of equalizing the pressure between the first circuit 510 and the medium-pressure pipe 100M.

[0083] As a result, when the operation of the low-stage compressor 23 and the high-stage compressor 26 is stopped, opening the first valve 511 in the first circuit 510 equalizes the pressure in the high-pressure piping 100H and the low-pressure piping 100L. Also, opening the pressure equalizing valve 521 in the pressure equalizing circuit 520 equalizes the pressure in the first circuit 510 and the intermediate-pressure piping 100M. This equalizes the pressure in the high-pressure piping 100H, the intermediate-pressure piping 100M, and the low-pressure piping 100L. Thus, to equalize the pressure in the high-pressure piping 100H, the intermediate-pressure piping 100M, and the low-pressure piping 100L, it is sufficient to provide the first circuit 510 equipped with the first valve 511 and the pressure equalizing circuit 520 equipped with the pressure equalizing valve 521. Therefore, it is possible to provide a refrigerator 1 that is easy to equalize with a simple configuration.

[0084] (10) The control method S10 of the refrigerator 1 according to the tenth embodiment includes a low-stage compressor 23 that compresses low-pressure refrigerant to medium-pressure refrigerant, a high-stage compressor 26 that compresses the medium-pressure refrigerant to 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 refrigerant A control method S10 for a refrigerator 1 comprising a high-pressure pipe 100H through which gas flows, the method comprising: step S11 opening a first valve 511 of a first circuit 510 extending from the high-pressure pipe 100H to the low-pressure pipe 100L when the operation of the low-stage compressor 23 and the high-stage compressor 26 is stopped; and step S12 opening a pressure equalizing valve 521 of a pressure equalizing circuit 520 capable of equalizing the pressure between the first circuit 510 and the medium-pressure pipe 100M.

[0085] As a result, when the operation of the low-stage compressor 23 and the high-stage compressor 26 is stopped, opening the first valve 511 in the first circuit 510 equalizes the pressure in the high-pressure piping 100H and the low-pressure piping 100L. Also, opening the pressure equalizing valve 521 in the pressure equalizing circuit 520 equalizes the pressure in the first circuit 510 and the intermediate-pressure piping 100M. This equalizes the pressure in the high-pressure piping 100H, the intermediate-pressure piping 100M, and the low-pressure piping 100L. Thus, to equalize the pressure in the high-pressure piping 100H, the intermediate-pressure piping 100M, and the low-pressure piping 100L, it is sufficient to provide the first circuit 510 equipped with the first valve 511 and the pressure equalizing circuit 520 equipped with the pressure equalizing valve 521. Therefore, it is possible to provide a refrigerator 1 that is easy to equalize with a simple configuration.

[0086] (11) The program according to the eleventh embodiment causes the control device 300 of a refrigerator 1, which includes a low-stage compressor 23 for compressing low-pressure refrigerant to medium-pressure refrigerant, a high-stage compressor 26 for compressing the medium-pressure refrigerant to 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, to execute control including the steps of opening the first valve 511 of the first circuit 510 extending to the high-pressure pipe 100H and the low-pressure pipe 100L when the operation of the low-stage compressor 23 and the high-stage compressor 26 is stopped, and opening the pressure equalizing valve 521 of the pressure equalizing circuit 520 capable of equalizing the pressure between the first circuit 510 and the medium-pressure pipe 100M.

[0087] This program equalizes the pressure in the high-pressure piping 100H and the low-pressure piping 100L when the operation of the low-stage compressor 23 and the high-stage compressor 26 is stopped. Furthermore, when the pressure equalizing valve 521 in the pressure equalizing circuit 520 is opened, the pressure in the first circuit 510 and the intermediate-pressure piping 100M is equalized. This equalizes the pressure in the high-pressure piping 100H, the intermediate-pressure piping 100M, and the low-pressure piping 100L. Thus, to equalize the pressure in the high-pressure piping 100H, the intermediate-pressure piping 100M, and the low-pressure piping 100L, it is sufficient to provide a first circuit 510 equipped with the first valve 511 and a pressure equalizing circuit 520 equipped with the pressure equalizing valve 521. Therefore, it is possible to provide a refrigerator 1 with a simple configuration that facilitates pressure equalization. [Explanation of Symbols]

[0088] 1…Refrigeration unit 2... Compression section 3…Capacitor 4…Expansion valve 5…Receiver 6…Supercooling 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...Capacitor body 32...fan 61…Injection valve 62... Expansion valve for supercooled heat exchanger 100L... Low-pressure piping 100M…Medium-pressure piping 100H... High-pressure piping 101…First piping 102…Second piping 103…Third piping 104…Fourth piping 105...Fifth piping 106…Sixth piping 107...Seventh piping 108…Eighth piping 109…Ninth Piping 110…10th piping 111…Eleventh Piping 112...Twelfth piping 120... Injection circuit 231...First rotary compression section (compression section) 232...First scroll compression section (compression section) 241...Intercooler unit 242...fan 261...Second rotary compression section (compression section) 262...Second scroll compression section (compression section) 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 / playback 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... Voltage equalization circuit 520a…one end 520b...other end 521...Pressure equalization valve S10... Control method for the refrigerator S11... Step to open the first valve of the first circuit. S12...Step to open the pressure equalizing valve of the pressure equalizing circuit.

Claims

1. A low-stage compressor that compresses low-pressure refrigerant to medium-pressure refrigerant, A high-stage compressor for compressing the aforementioned medium-pressure refrigerant into a high-pressure refrigerant, A low-pressure pipe connected to the aforementioned low-stage compressor, through which the low-pressure refrigerant flows, A medium-pressure pipe is connected between the low-stage compressor and the high-stage compressor, through which the medium-pressure refrigerant flows, A high-pressure piping connected to the aforementioned high-stage compressor, through which the high-pressure refrigerant flows, A first circuit extending from the high-pressure piping to the low-pressure piping, A pressure equalizing circuit capable of equalizing the pressure between the first circuit and the medium-pressure piping, An accumulator that separates the low-pressure refrigerant supplied to the aforementioned low-stage compressor into gaseous refrigerant and liquid refrigerant, An oil separator for separating oil contained in the high-pressure refrigerant discharged from the high-stage compressor, Equipped with, The first circuit includes a first valve that opens and closes the flow path within the first circuit. The pressure equalization circuit includes a pressure equalization valve that opens and closes the flow path within the pressure equalization circuit. The first circuit connects the high-pressure piping to the oil separator on the downstream side in the flow direction of the high-pressure refrigerant, and the low-pressure piping to the accumulator on the downstream side in the flow direction of the low-pressure refrigerant. Refrigeration unit.

2. When the first valve is opened, the first circuit supplies the high-pressure refrigerant, which flows through the high-pressure piping and is at a higher temperature than the low-pressure refrigerant, to the low-pressure piping. The refrigerator according to claim 1.

3. It is connected to the aforementioned intermediate pressure piping and includes an injection circuit that injects a refrigerant at a lower temperature than the refrigerant in the aforementioned high-stage compressor into the aforementioned high-stage compressor, The voltage equalization circuit is configured to be connectable to the first circuit and the injection circuit. A refrigerator according to claim 1 or 2.

4. The pressure equalization circuit connects the injection circuit to the first circuit, specifically to a position downstream in the flow direction of the high-pressure refrigerant in the first circuit. The refrigerator according to claim 3.

5. The intermediate pressure piping is equipped with an intercooler that is positioned in the middle of the intermediate pressure piping and cools the intermediate pressure refrigerant compressed by the low-stage compressor, The injection circuit is connected to the intermediate pressure piping between the intercooler and the high-stage compressor. The refrigerator according to claim 3.

6. The first circuit includes a flow rate adjustment mechanism that adjusts the flow rate of the high-pressure refrigerant when the first valve is opened. A refrigerator according to claim 1 or 2.

7. The aforementioned high-stage compressor and the aforementioned low-stage compressor are each two-stage compressors equipped with two compression sections in series. A refrigerator according to claim 1 or 2.

8. A low-stage compressor that compresses low-pressure refrigerant to medium-pressure refrigerant, A high-stage compressor for compressing the aforementioned medium-pressure refrigerant into a high-pressure refrigerant, A low-pressure pipe connected to the aforementioned low-stage compressor, through which the low-pressure refrigerant flows, A medium-pressure pipe is connected between the low-stage compressor and the high-stage compressor, through which the medium-pressure refrigerant flows, A high-pressure piping connected to the aforementioned high-stage compressor, through which the high-pressure refrigerant flows, An accumulator that separates the low-pressure refrigerant supplied to the aforementioned low-stage compressor into gaseous refrigerant and liquid refrigerant, An oil separator for separating oil contained in the high-pressure refrigerant discharged from the high-stage compressor, A refrigerator equipped with the following features is controllable: A first valve control unit that opens the first valve of the first circuit extending to the high-pressure piping and the low-pressure piping, A pressure equalization valve control unit that opens the pressure equalization valve of a pressure equalization circuit capable of equalizing the pressure between the first circuit and the medium-pressure piping, Equipped with, The first circuit connects the high-pressure piping to the oil separator on the downstream side in the flow direction of the high-pressure refrigerant, and the low-pressure piping to the accumulator on the downstream side in the flow direction of the low-pressure refrigerant. Control unit for a refrigerator.

9. A low-stage compressor that compresses low-pressure refrigerant to medium-pressure refrigerant, A high-stage compressor for compressing the aforementioned medium-pressure refrigerant into a high-pressure refrigerant, A low-pressure pipe connected to the aforementioned low-stage compressor, through which the low-pressure refrigerant flows, A medium-pressure pipe is connected between the low-stage compressor and the high-stage compressor, through which the medium-pressure refrigerant flows, A high-pressure piping connected to the aforementioned high-stage compressor, through which the high-pressure refrigerant flows, An accumulator that separates the low-pressure refrigerant supplied to the aforementioned low-stage compressor into gaseous refrigerant and liquid refrigerant, An oil separator for separating oil contained in the high-pressure refrigerant discharged from the high-stage compressor, A control method for a refrigerator equipped with, When the operation of the low-stage compressor and the high-stage compressor is stopped, the first valve of the first circuit extending to the high-pressure piping and the low-pressure piping is opened. The steps include opening the pressure equalizing valve of a pressure equalizing circuit capable of equalizing the pressure between the first circuit and the medium-pressure piping, Includes, The first circuit connects the high-pressure piping to the oil separator on the downstream side in the flow direction of the high-pressure refrigerant, and the low-pressure piping to the accumulator on the downstream side in the flow direction of the low-pressure refrigerant. Control methods for refrigerators.

10. A low-stage compressor that compresses low-pressure refrigerant to medium-pressure refrigerant, A high-stage compressor for compressing the aforementioned medium-pressure refrigerant into a high-pressure refrigerant, A low-pressure pipe connected to the aforementioned low-stage compressor, through which the low-pressure refrigerant flows, A medium-pressure pipe is connected between the low-stage compressor and the high-stage compressor, through which the medium-pressure refrigerant flows, A high-pressure piping connected to the aforementioned high-stage compressor, through which the high-pressure refrigerant flows, An accumulator that separates the low-pressure refrigerant supplied to the aforementioned low-stage compressor into gaseous refrigerant and liquid refrigerant, An oil separator for separating oil contained in the high-pressure refrigerant discharged from the high-stage compressor, A control device for a refrigerator equipped with: When the operation of the low-stage compressor and the high-stage compressor is stopped, the first valve of the first circuit extending to the high-pressure piping and the low-pressure piping is opened. The steps include opening the pressure equalizing valve of a pressure equalizing circuit capable of equalizing the pressure between the first circuit and the medium-pressure piping, Perform a control that includes this, The first circuit connects the high-pressure piping to the oil separator on the downstream side in the flow direction of the high-pressure refrigerant, and the low-pressure piping to the accumulator on the downstream side in the flow direction of the low-pressure refrigerant. program.

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