Compressor unit and refrigeration system

Abstract

This compressor unit comprises: a compressor which compresses a refrigerant; an accumulator which separates a gas refrigerant and a liquid refrigerant contained in the refrigerant; an intake pipe whic

Description

TITLE OF INVENTION: COMPRESSOR UNIT AND REFRIGERATION SYSTEM TECHNICAL FIELD

[0001] The present disclosure relates to a compressor unit and a refrigeration system. Priority is claimed on Japanese Patent Application No. 2022-112976, filed July 14, 2022, the content of which is incorporated herein by reference. BACKGROUND ART

[0002] Patent Document 1 discloses a configuration including a compressor that compresses a refrigerant, an accumulator that separates the refrigerant guided to the compressor into gas and liquid, a suction pipe that guides a gas refrigerant separated in the accumulator to the compressor, and an oil return pipe that is connected between a bottom portion of the accumulator and the suction pipe. Citation List Patent Document

[0003] Patent Document 1: Japanese Unexamined Patent Application, First Publication No. 2018-96608 SUMMARY OF INVENTION Technical Problem

[0004] However, in the configuration described in Patent Document 1, the oil return pipe extends upward from an upstream end connected to a lower end of the bottom portion of the accumulator toward the suction pipe in order to return oil contained in the refrigerant to the compressor. However, the oil or a liquid refrigerant contained in the refrigerant may be accumulated in the suction pipe or the oil return pipe while the compressor is not operating. Thereafter, in a case where the inner portion of the accumulator is filled with the liquid refrigerant due to a reason such as a power failure, the oil or the liquid refrigerant accumulated in the accumulator or the oil return pipe may flow into the compressor at the time of restart to damage the compressor.

[0005] The present disclosure provides a compressor unit and a refrigeration system that can suppress inflow of a liquid refrigerant into a compressor at the time of restart. Solution to Problem

[0006] The present disclosure provides a compressor unit including: a compressor configured to compress a refrigerant; an accumulator disposed on an upstream side in a flow direction of the refrigerant with respect to the compressor and configured to separate a gas refrigerant and a liquid refrigerant that are contained in the refrigerant; a suction pipe connected to the accumulator and the compressor and configured to supply the gas refrigerant in the accumulator to the compressor; and an oil return pipe having a first end connected to a bottom portion of the accumulator and a second end connected to an intermediate part of the suction pipe between the accumulator and the compressor, the oil return pipe being configured to discharge oil accumulated in the accumulator, in which, in the oil return pipe, the first end is disposed on an upper side in a vertical direction with respect to the second end, and the oil return pipe extends from the first end toward the second end such that an inclined angle of a downward slope with respect to a horizontal plane is 0° or more. The present disclosure provides a refrigeration system including the compressor unit described above. Advantageous Effects of Invention

[0008] With the compressor unit and the refrigeration system according to the present disclosure, the inflow of the liquid refrigerant into the compressor at the time of restart can be suppressed. BRIEF DESCRIPTION OF DRAWINGS

[0009] [FIG. 1] A diagram showing the configuration of a compressor unit and a refrigeration system according to an embodiment of the present disclosure. [FIG. 2] A diagram showing the configuration of a first suction pipe and a first oil return pipe of the compressor unit. [FIG. 3] A diagram showing the configuration of a second suction pipe and a second oil return pipe of the compressor unit. [FIG. 4] A diagram showing the configuration of a compressor unit according to a modification example of the embodiment of the present disclosure. DESCRIPTION OF EMBODIMENTS

[0010] Hereinafter, an embodiment for carrying out a compressor unit and a refrigeration system according to the present disclosure will be described with reference to the accompanying drawings. However, the present disclosure is not limited only to the embodiment. (Configuration of Refrigeration System) As shown in FIG. 1, a refrigeration system 1 includes a compressor unit 10 that compresses a refrigerant. The refrigeration system 1 allows the refrigerant compressed by the compressor unit 10 to circulate, for example, between the refrigeration system 1 and a cooling supply target such as an indoor unit. In the present embodiment, the refrigerant is, for example, carbon dioxide (CO2). In addition, a refrigerant other than carbon dioxide may be used.

[0012] The refrigeration system 1 includes a condenser (not shown) that condenses the refrigerant compressed by the compressor unit 10, a receiver (not shown) that recovers a liquid refrigerant from the condensed refrigerant, and the like, in addition to the compressor unit 10. The refrigeration system 1 supplies the liquid refrigerant recovered by the receiver to the refrigerant supply target. The refrigerant that has exchanged heat with the refrigerant supply target is circulated to the compressor unit 10. In the refrigeration system 1, the configuration other than the compressor unit 10 is not limited, and the configuration can be changed as appropriate.

[0013] The compressor unit 10 mainly includes an inlet accumulator (accumulator) 20, a first compressor (compressor) 30, an intercooler 40, an intermediate accumulator (accumulator) 50, a second compressor (compressor) 60, an oil separator 70, an oil tank 71, an inlet pipe 101, a first suction pipe (suction pipe) 102, a first discharge pipe 103, a connection pipe 104, a second suction pipe (suction pipe) 105, a second discharge pipe 106, a refrigerant supply pipe 107, an oil discharge pipe 201, an oil return portion 200, a first oil return pipe (oil return pipe) 150, and a second oil return pipe (oil return pipe) In the compressor unit 10, the refrigerant flows from the inlet accumulator 20 (indoor unit side) toward the oil separator 70. Hereinafter, in a flow direction Df of the refrigerant and the oil in the compressor unit 10, a side on which the inlet accumulator 20 is disposed will be referred to as an upstream side Dfl, and a side on which the oil separator 70 is disposed will be referred to as a downstream side Df2.

[0015] The inlet accumulator 20 separates the refrigerant supplied from the refrigerant supply target into a gas refrigerant and a liquid refrigerant. The refrigerant supplied from the refrigerant supply target flows into the inlet accumulator 20 through the inlet pipe 101. The inlet accumulator 20 supplies the gas refrigerant separated in the inlet accumulator 20 to the first compressor 30 through the first suction pipe (suction pipe) 102. The first suction pipe 102 connects the inlet accumulator 20 and the first compressor 30. A sub-accumulator (second accumulator) 25 is disposed in the intermediate part of the first suction pipe 102. The sub-accumulator 25 further separates the refrigerant that has passed through the first suction pipe 102 and the first oil return pipe 150, which will be described below, into the gas refrigerant and the liquid refrigerant. The sub-accumulator 25 supplies the gas refrigerant separated in the subaccumulator 25 to the first compressor 30 through the first suction pipe 102.

[0016] The first compressor 30 is disposed on the downstream side Df2 in the flow direction Df of the refrigerant with respect to the inlet accumulator 20. The first compressor 30 compresses the gas refrigerant supplied from the inlet accumulator 20 through the first suction pipe 102 in multiple stages (two stages in the present embodiment). In the present embodiment, the first compressor 30 is a two-stage compressor including a first rotary compression mechanism 31 and a first scroll compression mechanism 32 in series. The first rotary compression mechanism 31 compresses the gas refrigerant supplied from the outside. The first scroll compression mechanism 32 further compresses the refrigerant that is compressed by the first rotary compression mechanism 31. The refrigerant, which is compressed by the first scroll compression mechanism 32, is delivered to the intercooler 40 through the first discharge pipe 103. The first discharge pipe 103 connects the first compressor 30 and the intercooler 40.

[0017] The intercooler 40 is disposed between the first compressor 30 and the second compressor 60. The intercooler 40 is disposed on the downstream side Df2 in the flow direction Df of the refrigerant with respect to the first compressor 30. The intercooler 40 cools the refrigerant that is compressed by the first compressor 30 and that is delivered through the first discharge pipe 103. In the present embodiment, the intercooler 40 is an air-cooled type. The intercooler 40 according to the present embodiment includes an intercooler body 41 and a fan 42. The intercooler body 41 includes a flow pipe (not shown) through which the refrigerant compressed by the first compressor 30 flows. The intercooler body 41 exchanges heat between the refrigerant flowing in the flow pipe and the outside air outside the flow pipe. The fan 42 delivers air to the intercooler body 41, to improve the efficiency of heat exchange in the intercooler body 41. The refrigerant cooled by the intercooler 40 is delivered to the intermediate accumulator 50 through the connection pipe 104. The connection pipe 104 connects the intercooler 40 and the intermediate accumulator 50.

[0018] The intermediate accumulator 50 is disposed between the intercooler 40 and the second compressor 60. The intermediate accumulator 50 is disposed on the downstream side Df2 in the flow direction Df of the refrigerant with respect to the intercooler 40. The intermediate accumulator 50 separates the refrigerant delivered from the intercooler 40 through the connection pipe 104 into the gas refrigerant and the liquid refrigerant. The gas refrigerant, which is separated in the intermediate accumulator 50, is delivered to the second compressor 60 through the second suction pipe (suction pipe) 105. The second suction pipe 105 connects the intermediate accumulator 50 and the second compressor 60.

[0019] The second compressor 60 is disposed on the downstream side Df2 in the flow direction Df of the refrigerant with respect to the intermediate accumulator 50. The second compressor 60 further compresses the gas refrigerant delivered through the second suction pipe 105 after being compressed and cooled by the first compressor 30, in multiple stages (two stages in the present embodiment). In the present embodiment, the second compressor 60 is a two-stage compressor including a second rotary compression mechanism 61 and a second scroll compression mechanism 62 in series. The second rotary compression mechanism 61 compresses the supplied gas refrigerant. The second scroll compression mechanism 62 further compresses the refrigerant that is compressed by the second rotary compression mechanism 61. The refrigerant, which is compressed by the second rotary compression mechanism 61, is delivered to the oil separator 70 through the second discharge pipe 106. The second discharge pipe 106 connects the second compressor 60 and the oil separator 70.

[0020] The oil separator 70 is disposed on the downstream side Df2 in the flow direction Df of the refrigerant with respect to the second compressor 60. The oil separator 70 separates oil (refrigeration oil) contained in the refrigerant from the refrigerant delivered through the second discharge pipe 106. The refrigerant that has passed through the oil separator 70 is delivered to the condenser (not shown), which is disposed on the downstream side D12 in the flow direction Df with respect to the compressor unit 10, through the refrigerant supply pipe 107.

[0021] Further, the oil separated in the oil separator 70 is discharged to the oil tank 71 through the oil discharge pipe 201. The oil tank 71 stores the oil separated in the oil separator 70. The oil discharge pipe 201 connects the oil separator 70 and the oil tank 71.

[0022] The oil, which is stored in the oil tank 71, is delivered to the oil return portion 200. The oil return portion 200 returns the oil, which is compressed together with the refrigerant by the first compressor 30 and the second compressor 60, to each of the first compressor 30 and the second compressor 60. Specifically, the oil return portion 200 returns the oil, which is stored in the oil tank 71, to the first compressor 30 and the second compressor 60. The oil return portion 200 includes a main oil supply pipe 210, a first oil supply pipe 211, and a second oil supply pipe 212.

[0023] The oil, which is stored in the oil tank 71, flows into the main oil supply pipe 210. An upstream end of the main oil supply pipe 210 is connected to the oil tank 71. A downstream end of the main oil supply pipe 210 is connected to branch off into the first oil supply pipe 211 and the second oil supply pipe 212. That is, the oil, which has flowed into the main oil supply pipe 210 from the oil tank 71, branches off to flow into the first oil supply pipe 211 and the second oil supply pipe 212. The first oil supply pipe 211 is connected to the first compressor 30. The second oil supply pipe 212 is connected to the second compressor 60. Therefore, a part of the oil stored in the oil tank 71 is returned to the first compressor 30 through the main oil supply pipe 210 and the first oil supply pipe 211. In addition, a part of the oil stored in the oil tank 71 is returned to the second compressor 60 through the main oil supply pipe 210 and the second oil supply pipe 212.

[0024] (Configuration of First Suction Pipe) Further, the first suction pipe 102 will be described in more detail. As shown in FIG. 2, a first suction pipe first end 102a of the first suction pipe 102 is connected to the inlet accumulator 20. In the present embodiment, the first suction pipe first end 102a is connected to a top portion of the inlet accumulator 20 in a vertical direction Dv. A first suction pipe second end 102b of the first suction pipe 102, which is an end portion on an opposite side to the first suction pipe first end 102a, is connected to the first compressor 30.

[0025] The first suction pipe 102 according to the present embodiment has a first suction pipe upstream portion 102P disposed between the inlet accumulator 20 and the sub-accumulator 25, and a first suction pipe downstream portion 102Q disposed between the sub-accumulator 25 and the first compressor 30.

[0026] The first suction pipe upstream portion 102P suctions the gas refrigerant, which is separated in the inlet accumulator 20, from the upper portion (top portion) in the inlet accumulator 20 and delivers the gas refrigerant to the sub-accumulator 25. The first suction pipe upstream portion 102P according to the present embodiment includes a first vertical pipe portion 1021, a first folded-back portion 1022, a second vertical pipe portion 1023, a second folded-back portion 1024, a third vertical pipe portion 1025, a third folded-back portion 1026, and an accumulator connection portion 1027 in order from a position close to the first suction pipe first end 102a in the flow direction Df.

[0027] The first vertical pipe portion 1021 extends to an upper side Dvu in the vertical direction Dv from the top portion of the inlet accumulator 20. Therefore, an end portion of the first vertical pipe portion 1021, which is connected to the inlet accumulator 20, is the first suction pipe first end 102a.

[0028] The first folded-back portion 1022 is connected to the first vertical pipe portion 1021. The first folded-back portion 1022 extends from an upper end of the first vertical pipe portion 1021 in a horizontal direction Dh. The first folded-back portion 1022 is disposed at a higher position than the first suction pipe first end 102a in the vertical direction Dv.

[0029] The second vertical pipe portion 1023 is connected to the first folded-back portion 1022. The second vertical pipe portion 1023 extends to a lower side Dvd in the vertical direction Dv from an end portion of the first folded-back portion 1022.

[0030] The second folded-back portion 1024 is connected to the second vertical pipe portion 1023. The second folded-back portion 1024 extends from a lower end of the second vertical pipe portion 1023 in the horizontal direction Dh. The second folded-back portion 1024 is disposed at a lower position than the first suction pipe first end 102a, the first folded-back portion 1022, and a first oil return pipe second end (second end) 150b, which will be described below, in the vertical direction Dv.

[0031] The third vertical pipe portion 1025 is connected to the second folded-back portion 1024. The third vertical pipe portion 1025 extends to the upper side Dvu in the vertical direction Dv from the second folded-back portion 1024,

[0032] The third folded-back portion 1026 is connected to the third vertical pipe portion 1025. The third folded-back portion 1026 extends from an upper end of the third vertical pipe portion 1025 in the horizontal direction Dh. The third folded-back portion 1026 is disposed at a position between the first suction pipe first end 102a and the second folded-back portion 1024 in the vertical direction Dv.

[0033] The accumulator connection portion 1027 is connected to the third folded-back portion 1026. The accumulator connection portion 1027 extends from an end portion of the third folded-back portion 1026 to the sub-accumulator 25 in the horizontal direction Dh.

[0034] With these configurations, a first low region (low region) 102L and a first high region (high region) 102H, which are located at different positions in the vertical direction Dv, are formed in the first suction pipe upstream portion 102P disposed between the inlet accumulator 20 and the first compressor 30.

[0035] Specifically, the first low region 102L is a region that is located on the lower side Dvd in the vertical direction Dv with respect to a first oil return pipe first end 150a of the first oil return pipe 150, which will be described below. The first low region 102L according to the present embodiment is a region that is located at the most lower side Dvd in the vertical direction Dv in the first suction pipe upstream portion 102P. The first low region 102L is a region that is located on the downstream side Df2 in the flow direction Df with respect to the first oil return pipe second end 150b of the first oil return pipe 150, which will be described below. The first low region 102L is formed between the inlet accumulator 20 and the sub-accumulator 25. The first low region 102L is formed on the lower side Dvd in the vertical direction Dv with respect to the first folded-back portion 1022 and the third folded-back portion 1026. The first low region 102L according to the present embodiment is a region including the second folded-back portion 1024, a lower portion of the second vertical pipe portion 1023, and a lower portion of the third vertical pipe portion 1025. In the present embodiment, the first low region 102L is formed on the lower side Dvd in the vertical direction Dv with respect to the first oil return pipe second end 150b.

[0036] The first high region 102H is a region that is located on the upper side Dvu in the vertical direction Dv with respect to the first low region 102L and the first oil return pipe first end 150a of the first oil return pipe 150, which will be described below. The first high region 102H is a region that is located on the upper side Dvu in the vertical direction Dv and on the downstream side Df2 in the flow direction Df with respect to the first low region 102L. The first high region 102H is formed between the inlet accumulator 20 and the sub-accumulator 25. The first high region 102H is formed on the upper side Dvu in the vertical direction Dv with respect to the second folded-back portion 1024, the third vertical pipe portion 1025, and the accumulator connection portion 1027. The first high region 102H according to the present embodiment is a region including the third folded-back portion 1026, an upper portion of the third vertical pipe portion 1025, and an upper portion of the accumulator connection portion 1027. Therefore, the first high region 102H according to the present embodiment is formed on the lower side Dvd in the vertical direction Dv with respect to the first low region 102L and the first oil return pipe second end 150b.

[0037] The first suction pipe downstream portion 102Q suctions the gas refrigerant, which is separated in the sub-accumulator 25, from the upper portion in the subaccumulator 25 and delivers the gas refrigerant to the first compressor 30. The first suction pipe downstream portion 102Q according to the present embodiment includes a fourth vertical pipe portion 1028, a fourth folded-back portion 1029, a fifth vertical pipe portion 1030, a fifth folded-back portion 1031, a sixth vertical pipe portion 1032, and a first compressor connection portion 1033 between the sub-accumulator 25 and the first suction pipe second end 102b.

[0038] The fourth vertical pipe portion 1028 extends to the lower side Dvd in the vertical direction Dv from the sub-accumulator 25 to penetrate a bottom portion of the sub-accumulator 25. An upper end 1028t of the fourth vertical pipe portion 1028 is open to the upper side Dvu in the vertical direction Dv at a position close to the top portion in the sub-accumulator 25. A lower end of the fourth vertical pipe portion 1028 is located outside the sub-accumulator 25. The fourth folded-back portion 1029 is connected to the fourth vertical pipe portion 1028.

[0039] The fourth folded-back portion 1029 extends from the lower end of the fourth vertical pipe portion 1028 in the horizontal direction Dh. The fourth folded-back portion 1029 is disposed on the lower side Dvd in the vertical direction Dv with respect to the bottom portion of the sub-accumulator 25.

[0040] The fifth vertical pipe portion 1030 is connected to the fourth folded-back portion 1029. The fifth vertical pipe portion 1030 extends to the upper side Dvu in the vertical direction Dv from an end portion of the fourth folded-back portion 1029.

[0041] The fifth folded-back portion 1031 is connected to the fifth vertical pipe portion 1030. The fifth folded-back portion 1031 extends from an upper end of the fifth vertical pipe portion 1030 in the horizontal direction Dh. The fifth folded-back portion 1031 is located on the upper side Dvu in the vertical direction Dv with respect to the sub-accumulator 25 and the fourth folded-back portion 1029.

[0042] The sixth vertical pipe portion 1032 is connected to the fifth folded-back portion 1031. The sixth vertical pipe portion 1032 extends to the lower side Dvd in the vertical direction Dv from an end portion of the fifth folded-back portion 1031.

[0043] The first compressor connection portion 1033 is connected to the sixth vertical pipe portion 1032. The first compressor connection portion 1033 extends from the sixth vertical pipe portion 1032 in the horizontal direction Dh, and is connected to the first compressor 30. Therefore, an end portion of the first compressor connection portion 1033, which is connected to the first compressor 30, is the first suction pipe second end 102b.

[0044] (Configuration of First Oil Return Pipe) The first oil return pipe (oil return pipe) 150 is also connected to the inlet accumulator 20 disposed on the upstream side Dfl in the flow direction Df of the refrigerant with respect to the first compressor 30, in addition to the first suction pipe 102. The first oil return pipe 150 discharges the oil accumulated in the inlet accumulator 20. The first oil return pipe 150 allows the oil accumulated in the bottom portion of the inlet accumulator 20 to flow into the intermediate part of the first suction pipe 102. The first oil return pipe first end (first end) 150a of the first oil return pipe 150 is connected to the bottom portion of the inlet accumulator 20. The first oil return pipe second end (second end) 150b, which is an end portion of the first oil return pipe 150 on an opposite side to the first oil return pipe first end 150a, is connected in the intermediate part of the first suction pipe 102 between the inlet accumulator 20 and the first compressor 30. The fust oil return pipe first end 150a is disposed on the upper side Dvu in the vertical direction Dv with respect to the first oil return pipe second end 150b. The first oil return pipe 150 extends over the entire region such that an inclined angle of a downward slope with respect to a horizontal plane is 0° or more. That is, in the first oil return pipe 150, there is no region having an upward slope, with respect to the horizontal plane from the first oil return pipe first end 150a toward the first oil return pipe second end 150b. Here, the downward slope is a slope in which the fluid flows from the upstream side Dfl to the downstream side Df2 in the flow direction Df. In addition, the upward slope is a slope in which the fluid flows back from the downstream side Df2 to the upstream side Dfl in the flow direction Df. Therefore, the first oil return pipe 150 is formed with a slope in which the oil does not flow back over the entire region.

[0045] The first oil return pipe 150 according to the present embodiment includes a first downward extension portion (downward extension portion) 151 and a first horizontal extension portion (horizontal extension portion) 152. The first downward extension portion 151 extends to the lower side Dvd in the vertical direction Dv from the bottom portion of the inlet accumulator 20. Therefore, an end portion of the first downward extension portion 151, which is connected to the inlet accumulator 20, is the first oil return pipe first end 150a. The first downward extension portion 151 extends straight in the vertical direction Dv to have an angle of 90° with respect to the horizontal plane. The first horizontal extension portion 152 is connected to the first downward extension portion 151. The first horizontal extension portion 152 extends from a lower end of the first downward extension portion 151 in the horizontal direction Dh. The first horizontal extension portion 152 extends such that the inclined angle of the downward slope with respect to the horizontal plane is 0° or more. Specifically, the first horizontal extension portion 152 according to the present embodiment extends with the inclined angle of the downward slope of 0° (horizontal) or slightly (for example, about 1 / 25) inclined with respect to the horizontal plane. The first horizontal extension portion 152 is connected to the intermediate part of the second vertical pipe portion 1023. Therefore, an end portion of the first horizontal extension portion 152, which is connected to the second vertical pipe portion 1023, is the first oil return pipe second end 150b.

[0047] The first oil return pipe 150 further includes a first flow rate adjustment portion (flow rate adjustment portion) 155 that adjusts a flow rate of the oil in the first oil return pipe 150. In the present embodiment, the first flow rate adjustment portion 155 is a capillary pipe. The first flow rate adjustment portion 155 formed of the capillary pipe adds flow channel resistance to the oil flowing through the first oil return pipe 150. As a result, the flow rate of the oil in the first oil return pipe 150 is reduced. The first flow rate adjustment portion 155 according to the present embodiment is disposed in the intermediate part of the first horizontal extension portion 152.

[0048] (Configuration of Second Suction Pipe) Further, the second suction pipe 105 will be described in more detail. As shown in FIG. 3, the second suction pipe 105 suctions the gas refrigerant, which is separated in the intermediate accumulator 50, from the upper portion in the intermediate accumulator 50 and delivers the gas refrigerant to the second compressor 60. A second suction pipe first end 105a of the second suction pipe 105 is disposed inside the intermediate accumulator 50. The second suction pipe second end 105b, which is an end portion on an opposite side to the second suction pipe first end 105a, is connected to the second compressor 60.

[0049] The second suction pipe 105 according to the present embodiment includes a seventh vertical pipe portion 1051, a sixth folded-back portion 1052, an eighth vertical pipe portion 1053, a seventh folded-back portion 1054, a ninth vertical pipe portion 1055, and a second compressor connection portion 1056 in order from a position close to the second suction pipe first end 105a in the flow direction Df.

[0050] The seventh vertical pipe portion 1051 extends to the lower side Dvd in the vertical direction Dv from the inner portion of the intermediate accumulator 50 to penetrate the bottom portion of the intermediate accumulator 50. The second suction pipe first end 105a, which is an upper end of the seventh vertical pipe portion 1051, is open to the upper side Dvu in the vertical direction Dv at a position close to the top portion in the intermediate accumulator 50. A lower end of the seventh vertical pipe portion 1051 is located outside the intermediate accumulator 50.

[0051] The sixth folded-back portion 1052 is connected to the seventh vertical pipe portion 1051. The sixth folded-back portion 1052 extends from the lower end of the seventh vertical pipe portion 1051 in the horizontal direction Dh, The sixth folded-back portion 1052 is disposed at a lower position than the second suction pipe first end 105a or a second oil return pipe first end (first end) 160a, which will be described below, in the vertical direction Dv.

[0052] The eighth vertical pipe portion 1053 is connected to the sixth folded-back portion 1052. The eighth vertical pipe portion 1053 extends to the upper side Dvu in the vertical direction Dv from an end portion of the sixth folded-back portion 1052.

[0053] The seventh folded-back portion 1054 is connected to the eighth vertical pipe portion 1053. The seventh folded-back portion 1054, which extends from an upper end of the eighth vertical pipe portion 1053 in the horizontal direction Dh, is disposed at a higher position than the second suction pipe first end 105a and the sixth folded-back portion 1052 in the vertical direction Dv.

[0054] The ninth vertical pipe portion 1055 is connected to the seventh folded-back portion 1054. The ninth vertical pipe portion 1055 extends to the lower side Dvd in the vertical direction Dv from an end portion of the seventh folded-back portion 1054.

[0055] The second compressor connection portion 1056 is connected to the ninth vertical pipe portion 1055. The second compressor connection portion 1056 extends from a lower end of the ninth vertical pipe portion 1055 in the horizontal direction, and is connected to the second compressor 60. Therefore, an end portion of the second compressor connection portion 1056, which is connected to the second compressor 60, is the second suction pipe second end 105b. The second compressor connection portion 1056 is disposed at a lower position than the second suction pipe first end 105a and a second oil return pipe second end (second end) 160b, which will be described below, in the vertical direction Dv.

[0056] With these configurations, a second low region (low region) 105L and a second high region (high region) 105H, which are located at different positions in the vertical direction Dv, are formed in the second suction pipe 105 disposed between the intermediate accumulator 50 and the second compressor 60.

[0057] Specifically, the second low region 105L is a region that is located on the lower side Dvd in the vertical direction Dv with respect to the second oil return pipe first end 160a of the second oil return pipe 160, which will be described below. The second low region 105L according to the present embodiment is a region including the sixth folded-back portion 1052, a lower portion of the seventh vertical pipe portion 1051, and a lower portion of the eighth vertical pipe portion 1053.

[0058] The second high region 105H is a region that is located on the upper side Dvu in the vertical direction Dv with respect to the second low region 105L and the second oil return pipe first end 160a of the second oil return pipe 160, which will be described below. The second high region 105H is a region that is located on the upper side Dvu in the vertical direction Dv and on the downstream side Df2 in the flow direction Df with respect to the second low region 105L. The second high region 105H is formed on the upper side Dvu in the vertical direction Dv with respect to the lower ends of the sixth folded-back portion 1052 and the ninth vertical pipe portion 1055. The second high region 105H is a region including the seventh folded-back portion 1054, an upper portion of the eighth vertical pipe portion 1053, and an upper portion of the ninth vertical pipe portion 1055. The second high region 105H according to the present embodiment is a region that is located on the upper side Dvu in the vertical direction Dv and on the upstream side Dfl in the flow direction Df with respect to the second oil return pipe second end (second end) 160b of the second oil return pipe 160, which will be described below.

[0059] (Configuration of Second Oil Return Pipe) The second oil return pipe (oil return pipe) 160 is also connected to the intermediate accumulator 50 disposed on the upstream side Dfl in the flow direction Df of the refrigerant with respect to the second compressor 60, in addition to the second suction pipe 105. The second oil return pipe 160 discharges the oil accumulated in the intermediate accumulator 50. The first oil return pipe 150 allows the oil accumulated in the bottom portion of the intermediate accumulator 50 to flow into the intermediate part of the second suction pipe 105. The second oil return pipe first end (first end) 160a of the second oil return pipe 160 is connected to the bottom portion of the intermediate accumulator 50. The second oil return pipe second end (second end) 160b, which is an end portion of the second oil return pipe 160 on the opposite side to the second oil return pipe first end 160a, is connected in the intermediate part of the second suction pipe 105 between the intermediate accumulator 50 and the second compressor 60. The second oil return pipe first end 160a is disposed on the upper side Dvu in the vertical direction Dv with respect to the second oil return pipe second end 160b. The second oil return pipe 160 extends over the entire region such that the inclined angle of the downward slope with respect to the horizontal plane is 0° or more. That is, in the second oil return pipe 160, there is no region having an upward slope, with respect to the horizontal plane from the second oil return pipe first end 160a toward the second oil return pipe second end 160b. Therefore, the second oil return pipe 160 is formed with a slope in which the oil does not flow back over the entire region.

[0060] The second oil return pipe 160 according to the present embodiment includes a second downward extension portion (downward extension portion) 161 and a second horizontal extension portion (horizontal extension portion) 162.

[0061] The second downward extension portion 161 extends to the lower side Dvd in the vertical direction Dv from the bottom portion of the intermediate accumulator 50. Therefore, an end portion of the second downward extension portion 161, which is connected to the intermediate accumulator 50, is the second oil return pipe first end 160a. The second downward extension portion 161 extends straight in the vertical direction Dv to have an angle of 90° with respect to the horizontal plane. The second horizontal extension portion 162 is connected to the second downward extension portion 161. The second horizontal extension portion 162 extends straight from a lower end of the second downward extension portion 161 in the horizontal direction Dh. The second horizontal extension portion 162 extends such that the inclined angle of the downward slope with respect to the horizontal plane is 0° or more. Specifically, the second horizontal extension portion 162 according to the present embodiment extends with the inclined angle of the downward slope of 0° (horizontal) or slightly (for example, about 1 / 25) inclined with respect to the horizontal plane. The second horizontal extension portion 162 is connected to the intermediate part of the ninth vertical pipe portion 1055. Therefore, an end portion of the second horizontal extension portion 162, which is connected to the ninth vertical pipe portion 1055, is the second oil return pipe second end 160b.

[0062] The second oil return pipe 160 further includes a second flow rate adjustment portion (flow rate adjustment portion) 165 that adjusts a flow rate of the oil in the second oil return pipe 160. In the present embodiment, the second flow rate adjustment portion 165 is a capillary pipe. The second flow rate adjustment portion 165 formed of the capillary pipe adds flow channel resistance to the oil flowing through the second oil return pipe 160. As a result, the flow rate of the oil in the second oil return pipe 160 is reduced. The second flow rate adjustment portion 165 according to the present embodiment is disposed in the intermediate part of the second downward extension portion 161.

[0063] In the compressor unit 10 of the refrigeration system 1 as described above, as shown in FIG. 2, the refrigerant supplied from the refrigerant supply target flows into the inlet accumulator 20 through the inlet pipe 101. The inlet accumulator 20 separates the inflow refrigerant into the liquid refrigerant and the gas refrigerant. The gas refrigerant is suctioned out from the inlet accumulator 20 through the first suction pipe upstream portion 102P. The gas refrigerant is delivered from the first suction pipe upstream portion 102P to the sub-accumulator 25.

[0064] In addition, the oil contained in the liquid refrigerant separated in the inlet accumulator 20 is suctioned out through the first oil return pipe 150 by a negative pressure generated by the first compressor 30 during the operation. The suctioned-out oil is delivered to the intermediate part of the first suction pipe upstream portion 102P, is mixed with the gas refrigerant, and is delivered to the sub-accumulator 25. An amount of the oil suctioned out from the inlet accumulator 20 is determined in accordance with the rotation speed of the first compressor 30. The amount of the oil suctioned out from the inlet accumulator 20 is adjusted by the capillary pipe that is the first flow rate adjustment portion 155 disposed in the first oil return pipe 150. In addition, the liquid refrigerant suctioned out from the inlet accumulator 20 together with the oil is captured in the first low region 102L. Further, the liquid refrigerant that has reached the sub-accumulator 25 is further separated into the liquid refrigerant and the gas refrigerant in the sub-accumulator 25 together with the gas refrigerant that has passed through the first suction pipe upstream portion 102P. Then, only the separated gas refrigerant is suctioned out from the sub-accumulator 25 through the first suction pipe downstream portion 102Q. The gas refrigerant separated in the sub-accumulator 25 is delivered from the first suction pipe downstream portion 102Q to the first compressor 30. In the first compressor 30, the gas refrigerant is compressed in two stages in an order of the first rotary compression mechanism 31 and the first scroll compression mechanism 32.

[0065] The gas refrigerant, which is compressed in two stages by the first compressor 30, is discharged to the intercooler 40 through the first discharge pipe 103. The refrigerant cooled by the intercooler 40 is delivered to the intermediate accumulator 50 through the connection pipe 104. The cooled refrigerant is separated into the gas refrigerant and the liquid refrigerant in the intermediate accumulator 50.

[0066] In addition, the oil contained in the liquid refrigerant, which is separated in the intermediate accumulator 50, is suctioned out through the second oil return pipe 160 by a negative pressure generated by the second compressor 60 during the operation. The suctioned-out oil is delivered to the intermediate part of the second suction pipe 105, is mixed with the gas refrigerant, and is delivered to the second compressor 60. An amount of the oil suctioned out from the intermediate accumulator 50 is determined in accordance with the rotation speed of the second compressor 60. The amount of the oil suctioned out from the intermediate accumulator 50 is adjusted by the capillary pipe that is the second flow rate adjustment portion 165 disposed in the second oil return pipe 160. In the first compressor 30, the gas refrigerant is compressed in two stages in an order of the first rotary compression mechanism 31 and the first scroll compression mechanism 32. The gas refrigerant is delivered to the second compressor 60 through the second suction pipe 105. The gas refrigerant is compressed by the second compressor 60 in two stages in an order of the second rotary compression mechanism 61 and the second scroll compression mechanism 62. The refrigerant compressed in two stages is delivered to the condenser (not shown) or the like through the second discharge pipe 106 and then through the oil separator 70. In addition, the refrigerant delivered to the condenser is delivered again to the first compressor 30 or the second compressor 60 via the receiver (not shown), the expansion valve (not shown), or an economizer (not shown).

[0067] (Operations and Effects) In the compressor unit 10 and the refrigeration system 1 having the abovedescribed configuration, the first oil return pipe first end 150a, which is an end portion on one side of the first oil return pipe 150, is connected to the bottom portion of the inlet accumulator 20. Further, the first oil return pipe second end 150b, which is the opposite end portion of the first oil return pipe 150, is connected to the intermediate part of the first suction pipe 102. Therefore, the oil or the liquid refrigerant accumulated in the bottom portion of the inlet accumulator 20 flows into the intermediate part of the first suction pipe 102 through the first oil return pipe 150.

[0068] During the operation of the compressor unit 10, the oil contained in the liquid refrigerant, which is separated in the inlet accumulator 20 by separating the gas refrigerant and the liquid refrigerant, is accumulated in the bottom portion of the inlet accumulator 20. This accumulated oil continues to flow in the first oil return pipe 150 due to the negative pressure generated by the first compressor 30 during the operation of the compressor unit 10, so that the accumulated oil flows into the first suction pipe 102 regardless of the shape of the oil return pipe. Thereafter, in a case where the operation of the compressor unit 10 is stopped and the negative pressure generated by the first compressor 30 is eliminated, the oil or the liquid refrigerant may be accumulated in the oil return pipe or the inlet accumulator 20 depending on the shape of the oil return pipe. Thereafter, in a case where a time during which the compressor unit 10 is stopped is increased due to a reason such as a power failure, the inner portion of the inlet accumulator 20 may be filled with the liquid refrigerant. As a result, the oil or the liquid refrigerant, which is accumulated in the oil return pipe, flows into the first compressor 30 collectively at the time of restart, and the first compressor 30 may be damaged.

[0069] However, in the first oil return pipe 150 according to the present embodiment, the first oil return pipe first end 150a is disposed on the upper side Dvu in the vertical direction Dv with respect to the first oil return pipe second end 150b. Further, the first oil return pipe 150 is composed only of the first downward extension portion 151 that extends straight to the lower side Dvd in the vertical direction Dv from the first oil return pipe first end 150a and the first horizontal extension portion 152 that extends straight from the end portion of the first downward extension portion 151 in the horizontal direction Dh toward the first oil return pipe second end 150b. That is, the first oil return pipe 150 extends from the first oil return pipe first end 150a toward the first oil return pipe second end 150b such that the inclined angle of the downward slope with respect to the horizontal plane is always 0° or more. As a result, the oil or the liquid refrigerant, which has flowed into the first oil return pipe 150, is naturally dropped due to gravity and returned to the first suction pipe 102 without being accumulated inside the inlet accumulator 20 and the first oil return pipe 150. Therefore, the oil or the liquid refrigerant accumulated in the bottom portion of the inlet accumulator 20 during the operation of the first compressor 30 can be returned to the first compressor 30 through the first oil return pipe 150 without using power while the first compressor 30 is being stopped. As a result, it is possible to suppress the inflow of the oil or the liquid refrigerant, which is accumulated in the first oil return pipe 150, into the first compressor 30 collectively at the time of restart, and to suppress the damage to the first compressor 30.

[0070] Similarly, the second oil return pipe first end 160a, which is an end portion on one side of the second oil return pipe 160, is connected to the bottom portion of the intermediate accumulator 50. Further, the second oil return pipe second end 160b, which is the end portion on the opposite side to the second oil return pipe 160, is connected to the intermediate part of the second suction pipe 105. Therefore, the oil or the liquid refrigerant accumulated in the bottom portion of the intermediate accumulator 50 flows into the intermediate part of the second suction pipe 105 through the second oil return pipe 160.

[0071] In the second oil return pipe 160, the second oil return pipe first end 160a is disposed on the upper side Dvu in the vertical direction Dv with respect to the second oil return pipe second end 160b. Further, the second oil return pipe 160 is composed only of the second downward extension portion 161 that extends straight to the lower side Dvd in the vertical direction Dv from the second oil return pipe first end 160a, and the second horizontal extension portion 162 that extends straight from the end portion of the second downward extension portion 161 in the horizontal direction Dh toward the second oil return pipe second end 160b. That is, the second oil return pipe 160 extends from the second oil return pipe first end 160a toward the second oil return pipe second end 160b such that the inclined angle of the downward slope with respect to the horizontal plane is always 0° or more. As a result, the oil or liquid refrigerant, which has flowed into the second oil return pipe 160, is naturally dropped due to gravity and flows into the second suction pipe 105 from the second oil return pipe second end 160b. The oil or liquid refrigerant, which has flowed into the second suction pipe 105 through the second oil return pipe 160, is returned to the second compressor 60. Therefore, the oil or the liquid refrigerant, which is accumulated in the bottom portion of the intermediate accumulator 50 during the operation of the second compressor 60, can be returned to the second compressor 60 through the second oil return pipe 160 without using power while the second compressor 60 is being stopped. As a result, it is possible to suppress the inflow of the oil or the liquid refrigerant, which is accumulated in the second oil return pipe 160, into the second compressor 60 collectively at the time of restart, and to suppress the damage to the second compressor 60.

[0072] Accordingly, it is possible to provide the compressor unit 10 that can suppress the inflow of the liquid refrigerant into the first compressor 30 or the second compressor 60 at the time of restart.

[0073] Tn addition, the first oil return pipe 150 includes the first downward extension portion 151 extending in the vertical direction Dv and the first horizontal extension portion 152 extending in the horizontal direction Dh. Therefore, the oil or the liquid refrigerant, which is accumulated at the bottom portion of the inlet accumulator 20, can be naturally dropped due to gravity and flow into the first suction pipe 102. That is, it is possible to form, with a simple structure, the oil return pipe, which allows the oil or the liquid refrigerant to naturally flow into the first suction pipe 102 without using the power.

[0074] Similarly, the second oil return pipe 160 includes the second downward extension portion 161 extending in the vertical direction Dv and the second horizontal extension portion 162 extending in the horizontal direction Dh. Therefore, it is possible to form, with a simple structure, the oil return pipe that allows the oil or the liquid refrigerant to naturally flow into the second suction pipe 105 without using power even using the second oil return pipe 160.

[0075] The intermediate accumulator 50 is disposed on the downstream side Df2 in the flow direction Df with respect to the intercooler 40. Therefore, even in a case where the gas refrigerant in the intercooler 40 is liquefied to be the liquid refrigerant and then accumulated in the intermediate accumulator 50 while the compressor unit 10 is being stopped, the inflow of the liquid refrigerant, which is accumulated in the intermediate accumulator 50, into the second compressor 60 at the time of restart can be suppressed. As a result, it is possible to suppress the damage to the second compressor 60.

[0076] The refrigerant compressed by the first compressor 30 is cooled by the intercooler 40, and then further compressed by the second compressor 60 through the intermediate accumulator 50. The liquid refrigerant generated by cooling the refrigerant in the intercooler 40 is recovered in the intermediate accumulator 50, and only the gas refrigerant is supplied to the second compressor 60. The second oil return pipe 160 is connected to the intermediate accumulator 50. Therefore, the oil or the liquid refrigerant accumulated in the bottom portion of the intermediate accumulator 50 during the operation can flow into the second suction pipe 105 even in a case where the second compressor 60 is stopped. As a result, the inflow of the oil or the liquid refrigerant, which is accumulated in the intermediate accumulator 50, into the second compressor 60 at the time of restart is suppressed, and the damage to the second compressor 60 can be suppressed.

[0077] The first flow rate adjustment portion 155 is disposed in the first oil return pipe 150, and the second flow rate adjustment portion 165 is disposed in the second oil return pipe 160. Therefore, it is possible to suppress the flow rate of the oil or the liquid refrigerant that has flowed into the first oil return pipe 150 or the second oil return pipe 160. As a result, the inflow of a large amount of the oil or the liquid refrigerant into the first suction pipe 102 or the second suction pipe 105 can be suppressed.

[0078] In addition, the capillary pipes are disposed as the first flow rate adjustment portion 155 and the second flow rate adjustment portion 165. Therefore, it is possible to easily install, with a simple configuration, a structure for adjusting the flow rates in the first oil return pipe 150 and the second oil return pipe 160.

[0079] In addition, the sub-accumulator 25 is disposed on the downstream side Df2 in the flow direction Df with respect to the first oil return pipe second end 150b in the intermediate part of the first suction pipe 102. As a result, even in a case where the liquid refrigerant slightly flows into the first suction pipe 102 through the first oil return pipe 150 from the bottom portion of the inlet accumulator 20 while the first compressor 30 is being stopped, the liquid refrigerant can be recovered by the sub-accumulator 25. Therefore, it is possible to make it more difficult for the liquid refrigerant to flow into the first compressor 30.

[0080] In addition, the first suction pipe 102 includes, between the first oil return pipe first end 150a and the first oil return pipe second end 150b, the first low region 102L and the first high region 102H disposed at a higher position than the first low region 102L. Similarly, the second suction pipe 105 includes, between the second oil return pipe first end 160a and the second oil return pipe second end 160b, the second low region 105L and the second high region 105H disposed at a higher position than the second low region 105L. In this manner, in the first suction pipe 102 and the second suction pipe 105, the high region is formed on the downstream side Df2 in the flow direction Df with respect to the low region. Therefore, in the first suction pipe 102 and the second suction pipe 105, the liquid refrigerant first flows down to the low region. Then, the liquid refrigerant, which has flowed into the low region, flows toward the high region disposed at a higher position than the low region. Since the high region is disposed at a higher position than the low region, the liquid refrigerant in the low region is less likely to flow into the high region. In this manner, a so-called trap is formed in the first suction pipe 102 and the second suction pipe 105 by the low region and the high region. As a result, the inflow of the liquid refrigerant into the first compressor 30 or the second compressor 60 through the first suction pipe 102 or the second suction pipe 105 can be suppressed.

[0081] The first suction pipe 102 communicates with the inner portion of the inlet accumulator 20 at a higher position than the first oil return pipe first end 150a. As a result, only the gas refrigerant inside the inlet accumulator 20 is supplied to the first compressor 30 through the first suction pipe 102. Therefore, the inflow of the liquid refrigerant into the first compressor 30 through the first suction pipe 102 can be suppressed.

[0082] Similarly, the second suction pipe 105 communicates with the inner portion of the intermediate accumulator 50 at a higher position than the second oil return pipe first end 160a. As a result, only the gas refrigerant inside the intermediate accumulator 50 is supplied to the second compressor 60 through the second suction pipe 105. Therefore, the inflow of the liquid refrigerant into the second compressor 60 through the second suction pipe 105 can be suppressed.

[0083] (Modification Example of Embodiment) Although the embodiment of the present disclosure has been described in detail above with reference to the drawings, the specific configuration is not limited to this embodiment, and design changes and the like that do not depart from the gist of the present disclosure are also included.

[0084] In the embodiment described above, the compressor unit 10 includes the sub-accumulator 25 in the intermediate part of the first suction pipe 102, but the present disclosure is not limited to such a structure. That is, the present disclosure is not limited to a structure in which the liquid refrigerant or oil that has flowed into the first suction pipe 102 from the first oil return pipe 150 during the first compressor 30 is being stopped is recovered.

[0085] For example, as shown in FIG. 4, the sub-accumulator 25 need not be disposed in the first suction pipe 102. An on-off valve 158, such as a solenoid valve, may be disposed as a flow rate adjustment mechanism in the first oil return pipe 150. With such a configuration, in a case where the operation of the first compressor 30 is stopped, the on-off valve 158 is closed, so that the inflow of the liquid refrigerant or the oil into the first compressor 30 from the bottom portion of the inlet accumulator 20 through the first oil return pipe 150 while the first compressor 30 is being stopped can be reliably suppressed.

[0086] An expansion valve may be provided as the flow rate adjustment mechanism instead of the on-off valve 158 shown in FIG. 4. Even in such a configuration, the amount of the liquid refrigerant or the oil flowing into the first compressor 30 through the first oil return pipe 150 can be suppressed by the expansion valve. In this case, during the operation, the amount of the oil to be supplied to the first compressor 30 through the first oil return pipe 150 can be adjusted to an appropriate amount in accordance with the rotation speed of the first compressor 30. In the refrigeration system 1, the configuration other than the compressor unit 10 is not limited, and the configuration can be changed as appropriate.

[0088] In addition, in the embodiment described above, the compressor unit 10 includes the first compressor 30 and the second compressor 60, but the present disclosure is not limited to such a configuration. The compressor unit 10 may have, for example, a configuration in which only one compressor is provided.

[0089] The first compressor 30 and the second compressor 60 are not limited to the two-stage compressor. The first compressor 30 and the second compressor 60 may be a multi-stage compressor having three or more stages, or may be a single-stage compressor having only one stage. The first compressor 30 and the second compressor 60 are not limited to having a structure including a rotary compression mechanism and a scroll compression mechanism. For example, in the first compressor 30 and the second compressor 60, only the rotary compression mechanism may have a plurality of stages, or only the scroll compression mechanism may have a plurality of stages.

[0090] Supplementary Noto The compressor unit 10 and the refrigeration system 1 according to the embodiment are understood, for example, as follows.

[0091] (1) A first aspect relates to a compressor unit 10 including: a compressor 30, 60 configured to compress a refrigerant; an accumulator 20, 50 disposed on an upstream side Dfl in a flow direction Df of the refrigerant with respect to the compressor 30, 60 and configured to separate a gas refrigerant and a liquid refrigerant that are contained in the refrigerant; 102, 105 connected to the accumulator 20, 50 and the compressor 30, 60 and configured to supply the gas refrigerant in the accumulator 20, 50 to the compressor 30, 60; and an oil return pipe 150, 160 having a first end 150a, 160a connected to a bottom portion of the accumulator 20, 50 and a second end 150b, 160b connected to an intermediate part of the suction pipe 102, 105 between the accumulator 20, 50 and the compressor 30, 60, the oil return pipe 150, 160 being configured to discharge oil accumulated in the accumulator 20, 50, in which, in the oil return pipe 150, 160, the first end 150a, 160a is disposed on an upper side Dvu in a vertical direction Dv with respect to the second end 150b, 160b, and the oil return pipe 150, 160 extends from the first end 150a, 160a toward the second end 150b, 160b such that an inclined angle of a downward slope with respect to a horizontal plane is 0° or more.

[0092] As a result, the first end 150a, 160a, which is an end portion on one side of the oil return pipe 150, 160, is connected to the bottom portion of the accumulator 20, 50. Further, the second end 150b, 160b, which is the opposite end portion of the oil return pipe 150, 160, is connected to the intermediate part of the suction pipe 102, 105. Therefore, the oil or the liquid refrigerant, which is accumulated in the bottom portion of the accumulator 20, 50, flows into the intermediate part of the suction pipe 102, 105 through the oil return pipe 150, 160.

[0093] In the oil return pipe 150, 160, the first end 150a, 160a is disposed on the upper side Dvu in the vertical direction Dv with respect to the second end 150b, 160b. Further, the oil return pipe 150,160 extends from the first end 150a, 160a toward the second end 150b, 160b such that the inclined angle of the downward slope with respect to the horizontal plane is 0° or more. As a result, the oil or the liquid refrigerant, which has flowed into the oil return pipe 150, 160, is naturally dropped due to gravity and is returned to the suction pipe 102, 105 without being accumulated inside the accumulator 20, 50 and the oil return pipe 150, 160. Therefore, the oil or the liquid refrigerant, which is accumulated in the bottom portion of the accumulator 20, 50 during the operation of the compressor 30, 60, can be returned to the compressor 30, 60 through the oil return pipe 150, 160 without using power while the compressor 30, 60 is being stopped. As a result, it is possible to suppress the inflow of the oil or the liquid refrigerant, which is accumulated in the oil return pipe 150, 160, into the compressor 30, 60 collectively at the time of restart, and to suppress the damage to the compressor 30, 60.

[0094] (2) A second aspect relates to the compressor unit 10 according to (1), in which the oil return pipe 150, 160 includes a downward extension portion 151, 161 extending toward a lower side in the vertical direction Dv and a horizontal extension portion 152, 162 connected to the downward extension portion 151, 161 and extending in a horizontal direction Dh.

[0095] As a result, the oil or the liquid refrigerant, which is accumulated in the bottom portion of the accumulator 20, 50, can be naturally dropped due to gravity and flow into the suction pipe 102, 105. That is, it is possible to form, with a simple structure, the oil return pipe, which allows the oil or the liquid refrigerant to naturally flow into the suction pipe 102, 105 without using the power.

[0096] (3) A third aspect relates to the compressor unit 10 according to (1) or (2), further including: an intercooler 40 configured to cool the refrigerant, in which the accumulator 50 is disposed on a downstream side Df2 in the vertical direction Dv with respect to the intercooler 40.

[0097] As a result, even in a case where the gas refrigerant in the intercooler 40 is liquefied to be the liquid refrigerant and then accumulated in the accumulator 50 while the compressor unit 10 is being stopped, the inflow of the liquid refrigerant, which is accumulated in the accumulator 50, into the compressor 60 at the time of restart can be suppressed. As a result, it is possible to suppress the damage to the compressor 60.

[0098] (4) A fourth aspect relates to the compressor unit 10 according to (3), in which the compressor 30, 60 includes a first compressor 30, and a second compressor 60 disposed on the downstream side Df2 in the flow direction Df with respect to the first compressor 30 and configured to further compress the refrigerant compressed by the first compressor 30, and the intercooler 40 and the accumulator 50 are disposed between the first compressor 30 and the second compressor 60.

[0099] As a result, the refrigerant compressed by the first compressor 30 is cooled by the intercooler 40, and then further compressed by the second compressor 60. The liquid refrigerant generated by cooling the refrigerant in the intercooler 40 is recovered in the accumulator 50, and only the gas refrigerant is supplied to the second compressor 60. In the accumulator 50 disposed between the first compressor 30 and the second compressor 60, the oil accumulated at the bottom portion of the accumulator 50 during operation can be returned to the compressor 60 through the oil return pipe 160 while the compressor 60 is being stopped. As a result, the inflow of the oil or the liquid refrigerant, which is accumulated in the accumulator 50, into the compressor 60 at the time of restart is suppressed, and the damage to the second compressor 60 can be suppressed.

[0100] (5) A fifth aspect relates to the compressor unit 10 according to any one of (1) to (4), in which the oil return pipe 150, 160 further includes a flow rate adjustment portion 155, 165 configured to adjust a flow rate of the oil in the oil return pipe 150, 160.

[0101] As a result, it is possible to suppress the flow rate of the oil or the liquid refrigerant that has flowed into the oil return pipe 150, 160. As a result, the inflow of a large amount of the oil or the liquid refrigerant into the suction pipe 102, 105 can be suppressed.

[0102] (6) A sixth aspect relates to the compressor unit 10 according to (5), in which the flow rate adjustment portion 155, 165 is a capillary pipe.

[0103] As a result, a structure for adjusting the flow rate in the oil return pipe 150, 160 can be easily installed with a simple configuration.

[0104] (7) A seventh aspect relates to the compressor unit 10 according to any one of (1) to (6), further including: an on-off valve 158 disposed in an intermediate part of the oil return pipe 150 and configured to open and close a flow channel through which the oil flows in the oil return pipe 150.

[0105] With such a configuration, in a case where the operation of the compressor 30 is stopped, an on-off valve 158 is closed, so that the inflow of the liquid refrigerant or the oil into the compressor 30 from the bottom portion of the accumulator 20 through the oil return pipe 150 while the compressor 30 is being stopped can be reliably suppressed.

[0106] (8) An eighth aspect relates to the compressor unit 10 according to any one of (1) to (7), further including: a second accumulator 25 disposed in an intermediate part of the suction pipe 102 on a downstream side Df2 in the flow direction Df with respect to the second end 150b.

[0107] As a result, even in a case where the liquid refrigerant slightly flows into the suction pipe 102 through the oil return pipe 150 from the bottom portion of the accumulator 20 while the compressor 30 is being stopped, the liquid refrigerant can be recovered by the sub-accumulator 25. Therefore, it is possible to make it more difficult for the liquid refrigerant to flow into the compressor 30.

[0108] (9) A ninth aspect relates to the compressor unit 10 according to any one of (1) to (8), in which the suction pipe 102, 105 includes, between the first end 150a, 160a and the second end 150bm 160b, a low region 102L, 105L disposed at a lower position than the first end 150a, 160a and a high region 102H, 105H disposed at a higher position than the first end 150a, 160a and the low region 102L, 105L.

[0109] In this manner, in the suction pipe 102, 105, the high region is formed on the downstream side Df2 in the flow direction Df with respect to the low region. Therefore, in the suction pipe 102,105, the liquid refrigerant first flows down to the low region. Then, the liquid refrigerant, which has flowed into the low region, flows toward the high region disposed at a higher position than the low region. Since the high region is disposed at a higher position than the low region, the liquid refrigerant in the low region is less likely to flow into the high region. In this manner, a so-called trap is formed in the suction pipe 102, 105 by the low region and the high region. As a result, the inflow of the liquid refrigerant into the compressor 30, 60 through the suction pipe 102, 105 is suppressed.

[0110] (10) A tenth aspect relates to the compressor unit 10 according to any one of (1) to (9), in which the suction pipe 102, 105 communicates with an inner portion of the accumulator 20, 50 at a higher position than the first end 150a, 160a.

[0111] As a result, only the gas refrigerant inside the accumulator 20, 50 is supplied to the compressor 30, 60 through the suction pipe 102, 105. Therefore, the inflow of the liquid refrigerant into the compressor 30, 60 through the suction pipe 102, 105 can be suppressed.

[0112] (11) An eleventh aspect relates to a refrigeration system including the compressor unit 10 according to any one of (1) to (10).

[0113] Since the refrigeration system 1 includes the compressor unit 10 as described above, the inflow of the liquid refrigerant into the compressor 30, 60 at the time of restart can be suppressed. INDUSTRIAL APPLIC ABILITY

[0114] With the compressor unit and the refrigeration system according to the present disclosure, the inflow of the liquid refrigerant into the compressor at the time of restart can be suppressed. REFERENCE SIGNS LIST

[0115] 1 Refrigeration system 10 Compressor unit 20 Inlet accumulator (accumulator) 25 Sub-accumulator (second accumulator) 30 First compressor (compressor) 31 First rotary compression mechanism 32 First scroll compression mechanism 40 Intercooler 41 Intercooler body 42 Fan 50 Intermediate accumulator (accumulator) 60 Second compressor (compressor) 61 Second rotary compression mechanism 62 Second scroll compression mechanism 70 Oil separator 71 Oil tank 101 Inlet pipe 102 First suction pipe (suction pipe) 102H First high region (high region) 102L First low region (low region) 102Q First suction pipe downstream portion 102a First suction pipe first end 102b First suction pipe second end 1021 First vertical pipe portion 1022 First folded-back portion 1023 Second vertical pipe portion 1024 Second folded-back portion 1025 Third vertical pipe portion 1026 Third folded-back portion 1027 Accumulator connection portion 1028 Fourth vertical pipe portion 1028t Upper end 1029 Fourth folded-back portion 1030 Fifth vertical pipe portion 1031 Fifth folded-back portion 1032 Sixth vertical pipe portion 1033 First compressor connection portion 103 First discharge pipe 104 Connection pipe 105 Second suction pipe (suction pipe) 105H Second high region (high region) 105L Second low region (low region) 105a Second suction pipe first end 105b Second suction pipe second end 1052 Sixth folded-back portion 1053 Eighth vertical pipe portion 1054 Seventh folded-back portion 1055 Ninth vertical pipe portion 1056 Second compressor connection portion 106 Second discharge pipe 107 Refrigerant supply pipe 150 First oil return pipe (oil return pipe) 150a First oil return pipe first end (first end) 150b First oil return pipe second end (second end) 151 First downward extension portion (downward extension portion) 152 First horizontal extension portion (horizontal extension portion) 155 First flow rate adjustment portion (flow rate adjustment portion) 158 On-off valve 160 Second oil return pipe (oil return pipe) 160a Second oil return pipe first end (first end) 160b Second oil return pipe second end (second end) 161 Second downward extension portion (downward extension portion) 162 Second horizontal extension portion (horizontal extension portion) 165 Second flow rate adjustment portion (flow rate adjustment portion) 201 Oil discharge pipe 200 Oil return portion 210 Main oil supply pipe 211 First oil supply pipe 212 Second oil supply pipe Df Flow direction Dfl Upstream side Df2 Downstream side Dh Horizontal direction 5 Dv Vertical direction

Claims

1. A compressor unit comprising:a compressor configured to compress a refrigerant;an accumulator disposed on an upstream side in a flow direction of the refrigerant with respect to the compressor and configured to separate a gas refrigerant and a liquid refrigerant that are contained in the refrigerant;a suction pipe connected to the accumulator and the compressor and configured to supply the gas refrigerant in the accumulator to the compressor; andan oil return pipe having a first end connected to a bottom portion of the accumulator and a second end connected to an intermediate part of the suction pipe between the accumulator and the compressor, the oil return pipe being configured to discharge oil accumulated in the accumulator,wherein, in the oil return pipe, the first end is disposed on an upper side in a vertical direction with respect to the second end, andthe oil return pipe extends from the first end toward the second end such that an inclined angle of a downward slope with respect to a horizontal plane is 0° or more.

2. The compressor unit according to Claim 1,wherein the oil return pipe includes a downward extension portion extending toward a lower side in the vertical direction and a horizontal extension portion connected to the downward extension portion and extending in a horizontal direction.

3. The compressor unit according to Claim 1 or 2, further comprising:an intercooler configured to cool the refrigerant,wherein the accumulator is disposed on a downstream side in the flow direction with respect to the intercooler.

4. The compressor unit according to Claim 3,wherein the compressor includes a first compressor, and a second compressordisposed on the downstream side in the flow direction with respect to the first compressor and configured to further compress the refrigerant compressed by the first compressor, andthe intercooler and the accumulator are disposed between the first compressor and the second compressor.

5. The compressor unit according to Claim 1 or 2,wherein the oil return pipe further includes a flow rate adjustment portionconfigured to adjust a flow rate of the oil in the oil return pipe.

6. The compressor unit according to Claim 5,wherein the flow rate adjustment portion is a capillary pipe.

7. The compressor unit according to Claim 1 or 2, further comprising:an on-off valve disposed in an intermediate part of the oil return pipe andconfigured to open and close a flow channel through which the oil flows in the oil return pipe.

8. The compressor unit according to Claim 1 or 2, further comprising:a second accumulator disposed in an intermediate part of the suction pipe on a downstream side in the flow direction with respect to the second end.

9. The compressor unit according to Claim 1 or 2,wherein the suction pipe includes, between the accumulator and the compressor,a low region disposed at a lower position than the first end and a high region disposed at a higher position than the first end and the low region.

10. The compressor unit according to Claim 1 or 2,wherein the suction pipe communicates with an inner portion of the accumulatorat a higher position than the first end.

11. A refrigeration system comprising:the compressor unit according to Claim 1 or 2.INTERNATIONAL SEARCH REPORT International application No. PCT / JP2023 / 005958A. CLASSIFICATION OF SUBJECT MATTER F25B l / 00(2006.01)i;F25B 43 / 00(2006.01)1 FI: F25B1 / 00 387G; F25B43 / 00 C; F25B1 / 00 387K; F25B1 / 00 387L; F25B43 / 00 E According to International Patent Classification (IPC) or to both national classification and IPC B. FIELDS SEARCHED Minimum documentation searched (classification system followed by classification symbols) F25B1 / 00; F25B43 / 00 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. X Y Y Y JP 2010-236829 A (MITSUBISHI HEAVY IND LTD) 21 October 2010 (2010-10-21) paragraphs [0018]-[0036], fig. 1-2 paragraphs [0018]-[0036], fig. 1-2 JP 2020-056508 A (DAIKIN INDUSTRIES, LTD.) 09 April 2020 (2020-04-09) paragraphs [0025]-[0041], fig. 1 JP 2014-181869 A (FUJITSU GENERAL LTD) 29 September 2014 (2014-09-29) paragraphs [0004]-[0008], fig. 2 1-2, 7, 10-11 1-11 1-11 Y JP 2018-096608 A (MITSUBISHI HEAVY INDUSTRIES THERMAL SYSTEMS, LTD.) 21 June 2018 (2018-06-21) paragraph [0023], fig. 1 1-11 Y Y JP 05-322323 A (DAIKIN INDUSTRIES, LTD.) 07 December 1993 (1993-12-07) paragraphs [0023]-[0024], fig. 1 Microfilm of the specification and drawings annexed to the request of Japanese Utility Model Application No. 065017 / 1977 (Laid-open No. 158974 / 1978) (DAIKIN INDUSTRIES, LTD.) 13 December 1978 (1978-12-13), specification, p. 5, lines 5-8, fig. 3(A) 1-11 1-11 | | Further documents are listed in the continuation of Box C. | | See patent family annex. * Special categories of cited documents: “T” later document published after the international filing date or priority “A” document defining the general state of the art which is not considered date and not in conflict with the application but cited to understand the to be of particular relevance principle or theory underlying the invention “E" earlier application or patent but published on or after the international -‘X” document of particular relevance; the claimed invention cannot be filing date considered novel or cannot be considered to involve an inventive step “L” document which may throw doubts on priority claim(s) or which is when the document is taken alone cited to establish the publication date of another citation or other “y document of particular- relevance; the claimed invention cannot be special reason (as specified) considered to involve an inventive step when the document is “O” document referring to an oral disclosure, use, exhibition or other combined with one or more other such documents, such combination means being obvious to a person skilled in the ait “P” document published prior to the international filing date but later than document member of the same patent family the priority date claimed Date of the actual completion of the international search 19 April 2023 Date of mailing of the international search report 09 May 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 International application No. PCT / JP2023 / 005958c.DOCUMENTS CONSIDERED TO BE RELEVANTCategory* Citation of document, with indication, where appropriate, of the relevant passages Relevant to claim No. Y JP 2001-280759 A (MITSUBISHI HEAVY IND LTD) 10 October 2001 (2001-10-10) paragraph [0006], fig. 3 8 A US 2016 / 0238293 Al (HEATCRAFT REFRIGERATION PRODUCTS LLC) 18 August 2016 (2016-08-18) entire text, all drawings 1-11INTERNATIONAL SEARCH REPORT Information on patent family membersInternational application No.PCT / JP2023 / 005958Patent document cited in search report Publication date (day / month / year) Patent family member)s) Publication date (day / month / year) JP 2010-236829 A 21 October 2010 (Family: none) JP 2020-056508 A 09 April 2020 US 2021 / 0310701 Al paragraphs [0029]-[0045], fig. WO 2020 / 067194 Al EP 3835685 Al CN 112752934 A JP 2014-181869 A 29 September 2014 (Family: none) JP 2018-096608 A 21 June 2018 EP 3495746 Al paragraph [0028], fig. 1 WO 2018 / 110331 Al JP 05-322323 A 07 December 1993 (Family: none) JP 53-158974 UI 13 December 1978 (Family: none) JP 2001-280759 A 10 October 2001 (Family: none) US 2016 / 0238293 Al 18 August 2016 EP 3059523 Al

Images