Usage as refrigerant in refrigeration cycle device

Abstract

To provide usage as a refrigerant in a refrigeration cycle device that can suppress degradation of the refrigerant.SOLUTION: There is provided usage of a mixed refrigerant as a refrigerant in a refrigeration cycle device (1). The refrigeration cycle device comprises a refrigerant circuit (10) with a compressor (11). The compressor (11) includes a compression element (21) that compresses the refrigerant, and an oil reservoir section (37) in which a refrigerator oil is stored. An air pressure in an interior of the refrigerant circuit (10) is 667 Pa or less. The refrigerator oil contains an acid capture agent in an amount from 3.0 wt.% to 5.0 wt.% inclusive. A temperature of the refrigerator oil in the oil reservoir section (37) is maintained at 120°C or less. The mixed refrigerant is at least one of mixed refrigerants that include 1,2-difluoroethylene and one or more types of hydrofluorocarbon, mixed refrigerants that include 1,2-difluoroethylene and one or more types of hydrofluoroolefin, and mixed refrigerants that include one or more types of hydrofluorocarbon and one or more types of hydrofluoroolefin.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] Use as a refrigerant in a refrigeration cycle device. [Background technology]

[0002] Hydrofluoroolefins (HFO refrigerants), which have a lower global warming potential (hereinafter sometimes simply referred to as GWP) than HFC refrigerants, have traditionally attracted attention for refrigeration equipment. For example, 1,2-difluoroethylene (HFO-1132) is also considered as a refrigerant with a low GWP in Patent Document 1 (JP 2019-196312 A). Summary of the Invention [Problem to be solved by the invention]

[0003] Although such HFO refrigerants have a low GWP, they are unstable and may decompose under certain conditions to produce highly corrosive hydrogen fluoride. [Means for solving the problem]

[0004] The use as a refrigerant in a refrigeration cycle device according to a first aspect is the use as a refrigerant in a refrigeration cycle device of at least one of a mixed refrigerant containing 1,2-difluoroethylene and one or more hydrofluorocarbons, a mixed refrigerant containing 1,2-difluoroethylene and one or more hydrofluoroolefins, and a mixed refrigerant containing one or more hydrofluorocarbons and one or more hydrofluoroolefins. The refrigeration cycle device includes a refrigerant circuit having a compressor. The compressor has a compression element that compresses the refrigerant and an oil reservoir in which refrigeration oil is stored. The air pressure inside the refrigerant circuit is 667 Pa or less. The refrigeration oil contains 3.0 wt % or more and 5.0 wt % or less of an acid scavenger. The temperature of the refrigeration oil in the oil reservoir is maintained at 120°C or less.

[0005] The content of the acid scavenger in the refrigerating machine oil is the ratio when the refrigerating machine oil is taken as 100 parts by weight.

[0006] When used as a refrigerant in this refrigeration cycle device, decomposition of the refrigerant can be suppressed, and corrosion in the refrigerant circuit can be suppressed.

[0007] The use as a refrigerant in a refrigeration cycle device according to a second aspect is the use as a refrigerant in a refrigeration cycle device of at least one of a mixed refrigerant containing 1,2-difluoroethylene and one or more hydrofluorocarbons, a mixed refrigerant containing 1,2-difluoroethylene and one or more hydrofluoroolefins, and a mixed refrigerant containing one or more hydrofluorocarbons and one or more hydrofluoroolefins. The refrigeration cycle device includes a refrigerant circuit having a compressor. The compressor has a compression element that compresses the refrigerant and an oil reservoir in which refrigerating machine oil is stored. The air pressure inside the refrigerant circuit is 1333 Pa or less. The refrigerating machine oil does not contain an acid scavenger or contains less than 3.0 wt% of an acid scavenger. The temperature of the refrigerating machine oil in the oil reservoir is maintained at 100°C or less.

[0008] The content of the acid scavenger in the refrigerating machine oil is the ratio when the refrigerating machine oil is taken as 100 parts by weight.

[0009] When used as a refrigerant in this refrigeration cycle device, decomposition of the refrigerant can be suppressed, and corrosion in the refrigerant circuit can be suppressed.

[0010] The use as a refrigerant in a refrigeration cycle apparatus according to a third aspect is the use as a refrigerant in a refrigeration cycle apparatus of at least one of a mixed refrigerant containing 1,2-difluoroethylene and one or more hydrofluorocarbons, a mixed refrigerant containing 1,2-difluoroethylene and one or more hydrofluoroolefins, and a mixed refrigerant containing one or more hydrofluorocarbons and one or more hydrofluoroolefins. The refrigeration cycle apparatus comprises a refrigerant circuit having a compressor. The compressor has a compression element that compresses the refrigerant and an oil reservoir in which refrigeration oil is stored. The air pressure inside the refrigerant circuit is 2000 Pa or less. The refrigeration oil contains 3.0 wt % or more and 5.0 wt % or less of an acid scavenger. The temperature of the refrigeration oil in the oil reservoir is maintained at 100°C or less.

[0011] The content of the acid scavenger in the refrigerating machine oil is the ratio when the refrigerating machine oil is taken as 100 parts by weight.

[0012] When used as a refrigerant in this refrigeration cycle device, decomposition of the refrigerant can be suppressed, and corrosion in the refrigerant circuit can be suppressed.

[0013] A fourth aspect of the present invention relates to use of a refrigerant in a refrigeration cycle apparatus as at least one of a mixed refrigerant containing 1,2-difluoroethylene and one or more hydrofluorocarbons, a mixed refrigerant containing 1,2-difluoroethylene and one or more hydrofluoroolefins, and a mixed refrigerant containing one or more hydrofluorocarbons and one or more hydrofluoroolefins. The refrigeration cycle apparatus includes a refrigerant circuit having a compressor. The compressor has a compression element that compresses the refrigerant and an oil reservoir in which refrigerating machine oil is stored. The air pressure inside the refrigerant circuit is 2000 Pa or less. The refrigerating machine oil does not contain an acid scavenger or contains less than 3.0 wt% of an acid scavenger. The temperature of the refrigerating machine oil in the oil reservoir is maintained at 80°C or less.

[0014] The content of the acid scavenger in the refrigerating machine oil is the ratio when the refrigerating machine oil is taken as 100 parts by weight.

[0015] When used as a refrigerant in this refrigeration cycle device, decomposition of the refrigerant can be suppressed, and corrosion in the refrigerant circuit can be suppressed.

[0016] A fifth aspect of the present invention relates to a use of a refrigerant in a refrigeration cycle apparatus as at least one of a mixed refrigerant containing 1,2-difluoroethylene and one or more hydrofluorocarbons, a mixed refrigerant containing 1,2-difluoroethylene and one or more hydrofluoroolefins, and a mixed refrigerant containing one or more hydrofluorocarbons and one or more hydrofluoroolefins. The refrigeration cycle apparatus includes a refrigerant circuit having a compressor. The compressor has a compression element that compresses the refrigerant and an oil reservoir in which refrigerating machine oil is stored. The air pressure inside the refrigerant circuit is 4000 Pa or less. The refrigerating machine oil contains 3.0 wt % or more and 5.0 wt % or less of an acid scavenger. The temperature of the refrigerating machine oil in the oil reservoir is maintained at 80°C or less.

[0017] The content of the acid scavenger in the refrigerating machine oil is the ratio when the refrigerating machine oil is taken as 100 parts by weight.

[0018] When used as a refrigerant in this refrigeration cycle device, decomposition of the refrigerant can be suppressed, and corrosion in the refrigerant circuit can be suppressed.

[0019] When used as a refrigerant in a refrigeration cycle device according to the sixth aspect, the temperature of the refrigeration oil in the oil reservoir is maintained at or below the value obtained by substituting the air pressure inside the refrigerant circuit into the following equation: 0.1=((8×10 -5× 133.322 × air pressure (Pa)) + 0.0017) × (refrigerant oil temperature (℃)) + (-0.0032 × 133.322 × air pressure (Pa) - 0.15)

[0020] When used as a refrigerant in this refrigeration cycle device, decomposition of the refrigerant can be further suppressed, and corrosion in the refrigerant circuit can be sufficiently suppressed.

[0021] In the use as a refrigerant in a refrigeration cycle device according to a seventh aspect, in the use as a refrigerant in a refrigeration cycle device according to any one of the first aspect to the sixth aspect, the refrigeration oil contains at least one of polyvinyl ether and polyol ester.

[0022] When used as a refrigerant in a refrigeration cycle device according to an eighth aspect, the amount of moisture inside the refrigerant circuit is 300 ppm or less relative to the amount of refrigerant sealed in the refrigerant circuit when used as a refrigerant in a refrigeration cycle device according to any one of the first aspect to the seventh aspect.

[0023] When used as a refrigerant in this refrigeration cycle device, corrosion due to the presence of moisture in the refrigerant circuit is suppressed.

[0024] In a ninth aspect, the refrigerant is used as a refrigerant in a refrigeration cycle apparatus according to any one of the first to eighth aspects, wherein the refrigerant circuit includes an expansion valve having a needle portion, and the needle portion is made of SUS or brass.

[0025] The SUS may be, for example, stainless steel having a chromium content of 10.5 mass % or more and a carbon content of 1.2 mass % or less.

[0026] The brass may be, for example, an alloy of copper and zinc, with the zinc content being 20 mass % or more.

[0027] When used as a refrigerant in this refrigeration cycle device, corrosion of the needle portion made of SUS or brass is suppressed even if such a needle portion is used.

[0028] The use as a refrigerant in a refrigeration cycle apparatus according to a tenth aspect is the use as a refrigerant in a refrigeration cycle apparatus according to any one of the first aspect to the ninth aspect, wherein the refrigerant is any one of a refrigerant consisting of 1,2-difluoroethylene and R32, a refrigerant consisting of 1,2-difluoroethylene and R1234yf, a refrigerant consisting of 1,2-difluoroethylene, R32 and R1234yf, and a refrigerant consisting of R1234yf, R1234ze, R1233zd and a hydrofluorocarbon.

[0029] In the use as a refrigerant in a refrigeration cycle apparatus according to an eleventh aspect, in the use as a refrigerant in the refrigeration cycle apparatus according to any one of the first to tenth aspects, the refrigeration cycle apparatus includes a temperature detection unit that detects the temperature of refrigeration oil in an oil reservoir. In the refrigeration cycle apparatus, the rotation speed of the compressor is controlled based on the detection result of the temperature detection unit.

[0030] The refrigeration cycle device may include a control unit having a processor or the like that grasps the detection result of the temperature detection unit and controls the rotation speed of the compressor based on the detection result.

[0031] When used as a refrigerant in this refrigeration cycle device, decomposition of the refrigerant can be easily suppressed. [Brief explanation of the drawings]

[0032] [Figure 1] FIG. 1 is a schematic diagram of an air conditioning device. [Figure 2] FIG. 1 is a schematic block diagram of an air conditioning apparatus. [Figure 3] FIG. 2 is a schematic cross-sectional view of a compressor. [Figure 4] FIG. 2 is a schematic cross-sectional view of an expansion valve. [Figure 5]10 is a graph showing the relationship between the discharge gas temperature and the acid value for each air pressure when an acid scavenger is blended at 3 wt %. [Figure 6] 10 is a graph showing the relationship between the discharge gas temperature and the acid value for each air pressure when an acid scavenger is blended at 2 wt %. [Figure 7] FIG. 10 is a schematic configuration diagram of an air conditioning apparatus according to another embodiment J. [Figure 8] FIG. 10 is a schematic cross-sectional view of a compressor according to another embodiment J. [Figure 9] FIG. 10 is an enlarged view of the periphery of a floating member of a compressor according to another embodiment J. [Figure 10] 10 is a graph showing the relationship between the discharge gas temperature and the acid value when the air pressure for the refrigerant circuit according to another embodiment J is different. DETAILED DESCRIPTION OF THE INVENTION

[0033] An air conditioner 1 as a refrigeration cycle device according to this embodiment will be described below with reference to FIG. 1, which is a schematic configuration diagram of a refrigerant circuit, and FIG. 2, which is a schematic control block configuration diagram.

[0034] (1) Overview of the air conditioning device 1 The air conditioner 1 is a device that conditions the air in a target space by performing a vapor compression refrigeration cycle.

[0035] The air conditioning device 1 mainly has an outdoor unit 2, an indoor unit 3, a liquid refrigerant connection pipe 6 and a gas refrigerant connection pipe 5 that connect the outdoor unit 2 and the indoor unit 3, and a controller 7 that controls the operation of the air conditioning device 1.

[0036] In the air conditioner 1, a refrigeration cycle is performed in which the refrigerant sealed in the refrigerant circuit 10 is compressed, condensed or releases heat, decompresses, evaporates, and then compressed again. In this embodiment, the refrigerant circuit 10 is filled with a refrigerant for performing a vapor compression refrigeration cycle.

[0037] (refrigerant) The refrigerant filled in the refrigerant circuit 10 is at least one of a mixed refrigerant containing 1,2-difluoroethylene and one or more hydrofluorocarbons, a mixed refrigerant containing 1,2-difluoroethylene and one or more hydrofluoroolefins, and a mixed refrigerant containing one or more hydrofluorocarbons and one or more hydrofluoroolefins. 1,2-Difluoroethylene or other hydrofluoroolefins have a low GWP, which helps to mitigate global warming. Furthermore, 1,2-difluoroethylene and other hydrofluoroolefins have low stability and are prone to decomposition due to disproportionation reactions and other factors. Decomposition and degradation are particularly likely when present together with high-temperature refrigerating machine oil. However, in the air conditioner 1 of this embodiment, the pressure of the air inside the refrigerant circuit 10 is 667 Pa or less, the refrigerating machine oil contains 3.0 wt % to 5.0 wt % of an acid scavenger, and the temperature of the refrigerating machine oil in the oil reservoir (described below) is maintained at 120°C or less, thereby preventing refrigerant degradation and decomposition.

[0038] Examples of mixed refrigerants containing 1,2-difluoroethylene and one or more hydrofluorocarbons include mixed refrigerants containing 1,2-difluoroethylene and R32, mixed refrigerants consisting only of 1,2-difluoroethylene and R32, mixed refrigerants containing 1,2-difluoroethylene, R32, and R1234yf, and mixed refrigerants consisting only of 1,2-difluoroethylene, R32, and R1234yf.

[0039] Furthermore, examples of mixed refrigerants containing 1,2-difluoroethylene and one or more hydrofluoroolefins include mixed refrigerants containing 1,2-difluoroethylene and R1234yf, mixed refrigerants consisting only of 1,2-difluoroethylene and R1234yf, mixed refrigerants containing 1,2-difluoroethylene, R32, and R1234yf, and mixed refrigerants consisting only of 1,2-difluoroethylene, R32, and R1234yf.

[0040] Examples of mixed refrigerants containing one or more hydrofluorocarbons and one or more hydrofluoroolefins include mixed refrigerants containing R1234yf, R1234ze, R1233zd, and hydrofluorocarbons, mixed refrigerants consisting only of R1234yf, R1234ze, R1233zd, and hydrofluorocarbons, mixed refrigerants containing 1,2-difluoroethylene, R32, and R1234yf, and mixed refrigerants consisting only of 1,2-difluoroethylene, R32, and R1234yf. Examples include:

[0041] Examples of hydrofluorocarbons include R32, R134a, and R410A, with R32 being particularly preferred.

[0042] (Refrigerating machine oil) The refrigerant circuit 10 is filled with a refrigerant oil together with the refrigerant. The refrigerant oil used together with the refrigerant is preferably an ether oil or an ester oil. Examples of the ether oil include polyvinyl ether oil (PVE) and polyoxyalkylene oil. Examples of the ester oil include dibasic acid ester oil of a dibasic acid and a monohydric alcohol, polyol ester oil of a polyol and a fatty acid, complex ester oil of a polyol, a polybasic acid, and a monohydric alcohol (or fatty acid), and polyol carbonate ester oil. One type of refrigerant oil may be used alone, or two or more types may be used in combination.

[0043] In this embodiment, 3.0 wt % to 5.0 wt % of an acid scavenger is blended into the refrigerant oil. This suppresses corrosion of the refrigerant circuit 10 due to acids that may be generated by decomposition of the refrigerant. The blending amount of the acid scavenger can be, for example, a value obtained by measuring the refrigerant oil stored in the oil reservoir 37 of the compressor 11 in the refrigerant circuit 10 of the air conditioner 1 while the air conditioner 1 is not operating. Examples of such acid scavengers that can be used include phenyl glycidyl ether, alkyl glycidyl ether, alkylene glycol glycidyl ether, cyclohexene oxide, α-olefin oxide, epoxy compounds such as epoxidized soybean oil, and carbodiimides. Among these, phenyl glycidyl ether, alkyl glycidyl ether, alkylene glycol glycidyl ether, cyclohexene oxide, and α-olefin oxide are preferred from the viewpoint of compatibility. The number of carbon atoms in these compounds may be 3 to 30, and more preferably 4 to 24. The α-olefin oxide may have a total carbon number of 4 or more and 50 or less, and more preferably 4 or more and 24 or less. The acid scavenger may be used alone or in combination of two or more types.

[0044] The refrigerating machine oil may further contain at least one additive selected from the group consisting of an extreme pressure agent and an antioxidant. These additives are preferably blended into the refrigerating machine oil in an amount of, for example, 3 wt% or less. By adjusting the blending amount of the antioxidant and acid scavenger, it becomes easier to adjust the water content in the fluid containing the refrigerant and the refrigerating machine oil.

[0045] Examples of extreme pressure agents include organic sulfur compound-based extreme pressure agents such as those containing phosphate esters, monosulfides, polysulfides, sulfoxides, sulfones, thiosulfinates, sulfurized oils and fats, thiocarbonates, thiophenes, thiazoles, and methanesulfonate esters; thiophosphate ester-based extreme pressure agents such as thiophosphate triesters; ester-based extreme pressure agents such as higher fatty acids, hydroxyaryl fatty acids, polyhydric alcohol esters, and acrylic esters; chlorinated hydrocarbons such as chlorinated paraffins; Examples of the extreme pressure agent include organic chlorine-based extreme pressure agents such as chlorinated carboxylic acid derivatives, organic fluorinated extreme pressure agents such as fluorinated aliphatic carboxylic acids, fluorinated ethylene resins, fluorinated alkylpolysiloxanes, and fluorinated graphite, alcohol-based extreme pressure agents such as higher alcohols, and metal compound-based extreme pressure agents such as naphthenates (lead naphthenate, etc.), fatty acid salts (lead fatty acid, etc.), thiophosphates (zinc dialkyldithiophosphate, etc.), thiocarbamates, organic molybdenum compounds, organic tin compounds, organic germanium compounds, and borate esters.

[0046] Examples of antioxidants that can be used include phenol-based antioxidants and amine-based antioxidants. Phenol-based antioxidants include 2,6-di-tert-butyl-4-methylphenol (DBPC), 2,6-di-tert-butyl-4-ethylphenol, 2,2'-methylenebis(4-methyl-6-tert-butylphenol), 2,4-dimethyl-6-tert-butylphenol, 2,6-di-tert-butylphenol, di-tert-butyl-p-cresol, and bisphenol A. Amine-based antioxidants include N,N'-diisopropyl-p-phenylenediamine, N,N'-di-sec-butyl-p-phenylenediamine, phenyl-α-naphthylamine, N,N'-di-phenyl-p-phenylenediamine, and N,N-di(2-naphthyl)-p-phenylenediamine.

[0047] The moisture content inside the refrigerant circuit 10 is preferably 300 ppm or less, from the viewpoint of suppressing decomposition of 1,2-difluoroethylene and other hydrofluoroolefins.

[0048] The pressure of the air inside the refrigerant circuit 10 is 667 Pa (5 Torr) or less, from the viewpoint of suppressing decomposition of 1,2-difluoroethylene and other hydrofluoroolefins.

[0049] The moisture content and air pressure inside the refrigerant circuit 10 can be values ​​that are taken for, for example, the fluid at the outlet of a heat exchanger (indoor heat exchanger 18 or outdoor heat exchanger 13) that functions as a refrigerant condenser in the refrigerant circuit 10 of the air conditioning unit 1 that is not operating, or the fluid at the outlet of the high-pressure receiver 8 described below.

[0050] (1-1) Outdoor unit 2 The outdoor unit 2 is connected to the indoor unit 3 via a liquid refrigerant connection pipe 6 and a gas refrigerant connection pipe 5, and constitutes part of a refrigerant circuit 10. The outdoor unit 2 mainly has a compressor 11, a four-way switching valve 12, an outdoor heat exchanger 13, an expansion valve 9, a high-pressure receiver 8, a low-pressure receiver 14, an outdoor fan 15, a liquid-side shut-off valve 17, and a gas-side shut-off valve 16.

[0051] The compressor 11 is a device that compresses a low-pressure refrigerant in the refrigeration cycle until it reaches a high pressure. For example, a compressor in which a compression element such as a rotary or scroll type is rotationally driven by a compressor motor can be used as the compressor 11, and details of the compressor 11 in this embodiment will be described later. The compressor motor is used to change the capacity, and the operating frequency can be controlled by an inverter. For example, the rotation speed of the compressor 11 is controlled with a predetermined target evaporation temperature as a target value during cooling operation, and with a predetermined target condensing temperature as a target value during heating operation.

[0052] The four-way switching valve 12 can switch between a first connection state (see solid line in Figure 1) in which the discharge side of the compressor 11 is connected to the outdoor heat exchanger 13 while connecting the suction side of the compressor 11 to the gas side shut-off valve 16, and a second connection state (see dotted line in Figure 1) in which the discharge side of the compressor 11 is connected to the gas side shut-off valve 16 while connecting the suction side of the compressor 11 to the outdoor heat exchanger 13, by switching the connection state in the refrigerant circuit 10.

[0053] The outdoor heat exchanger 13 is a heat exchanger that functions as a condenser or radiator for high-pressure refrigerant in the refrigeration cycle during cooling operation and as an evaporator for low-pressure refrigerant in the refrigeration cycle during heating operation. The outdoor heat exchanger 13 includes a plurality of heat transfer tubes (not shown) through which refrigerant flows and a plurality of heat transfer fins (not shown) through which air flows through gaps between them. The plurality of heat transfer tubes are aligned vertically, and each heat transfer tube extends substantially horizontally. The plurality of heat transfer fins extending vertically are aligned at predetermined intervals along the extension direction of the heat transfer tubes. The plurality of heat transfer fins and the plurality of heat transfer tubes are combined so that the plurality of heat transfer tubes penetrate each heat transfer fin.

[0054] The outdoor fan 15 supplies outdoor air to the outdoor heat exchanger 13 in the outdoor unit 2, where it exchanges heat with the refrigerant, and then generates an air flow that is discharged outside the outdoor unit 2. The outdoor fan 15 is driven to rotate by an outdoor fan motor.

[0055] The expansion valve 9 is provided between the liquid side end of the outdoor heat exchanger 13 and the high-pressure receiver 8. The expansion valve 9 is, for example, an electronic expansion valve whose valve opening degree can be adjusted by control, and will be described in detail later.

[0056] The high-pressure receiver 8 is provided between the expansion valve 9 and the liquid-side shut-off valve 17. The high-pressure receiver 8 is a refrigerant container capable of storing excess refrigerant as liquid refrigerant.

[0057] The low-pressure receiver 14 is provided between the suction side of the compressor 11 and one of the connection ports of the four-way switching valve 12, and is a refrigerant container capable of storing excess refrigerant in the refrigerant circuit 10 as liquid refrigerant.

[0058] The liquid-side shutoff valve 17 is a manual valve arranged at the connection portion between the outdoor unit 2 and the liquid refrigerant communication pipe 6.

[0059] The gas-side shutoff valve 16 is a manual valve arranged at the connection between the outdoor unit 2 and the gas refrigerant communication pipe 5.

[0060] The outdoor unit 2 has an outdoor unit control unit 71 that controls the operation of each part that makes up the outdoor unit 2. The outdoor unit control unit 71 has a microcomputer including a CPU, memory, etc. The outdoor unit control unit 71 is connected to the indoor unit control units 72 of each indoor unit 3 via a communication line, and transmits and receives control signals, etc.

[0061] The outdoor unit 2 is equipped with a discharge temperature sensor 75, an intake temperature sensor 76, an outdoor heat exchanger temperature sensor 77, an outdoor air temperature sensor 78, an oil temperature sensor 79, and other sensors. Each of these sensors is electrically connected to the outdoor unit control unit 71 and transmits a detection signal to the outdoor unit control unit 71. The discharge temperature sensor 75 detects the temperature of the refrigerant flowing through the discharge pipe 4d connecting the discharge side of the compressor 11 to one of the connection ports of the four-way valve 12. The intake temperature sensor 76 detects the temperature of the refrigerant flowing through the intake pipe 4e, which extends from the low-pressure receiver 14 to the intake side of the compressor 11, in the intake passage connecting the intake side of the compressor 11 to one of the connection ports of the four-way valve 12. The outdoor heat exchanger temperature sensor 77 detects the temperature of the refrigerant flowing through the liquid side outlet of the outdoor heat exchanger 13, which is opposite the side connected to the third pipe 4c. The outdoor air temperature sensor 78 detects the temperature of the outdoor air before passing through the outdoor heat exchanger 13. The oil temperature detection sensor 79 detects the temperature of the refrigeration oil stored in the oil reservoir 37 of the compressor 11 .

[0062] (1-2) Indoor unit 3 The indoor unit 3 is installed on the wall or ceiling of the room, which is the target space. The indoor unit 3 is connected to the outdoor unit 0 via a liquid refrigerant connection pipe 6 and a gas refrigerant connection pipe 5, and constitutes part of the refrigerant circuit 10.

[0063] The indoor unit 3 has an indoor heat exchanger 18 and an indoor fan 19.

[0064] The liquid side of the indoor heat exchanger 18 is connected to the liquid refrigerant connection pipe 6, and the gas side end is connected to the gas refrigerant connection pipe 5. The indoor heat exchanger 18 is a heat exchanger that functions as an evaporator of low-pressure refrigerant in the refrigeration cycle during cooling operation, and as a condenser or radiator of high-pressure refrigerant in the refrigeration cycle during heating operation.

[0065] The indoor fan 19 draws indoor air, which is the space to be air-conditioned, into the indoor unit 3, exchanges heat with the refrigerant in the indoor heat exchanger 18, and then generates an air flow that is discharged to the outside of the indoor unit 3. The indoor fan 19 is rotationally driven by an indoor fan motor.

[0066] The indoor unit 3 also has an indoor unit control unit 72 that controls the operation of each part that makes up the indoor unit 3. The indoor unit control unit 72 has a microcomputer including a CPU, memory, etc. The indoor unit control unit 72 is connected to the outdoor unit control unit 71 via a communication line, and transmits and receives control signals, etc.

[0067] The indoor unit 3 is provided with an indoor liquid-side heat exchanger temperature sensor 73, an indoor air temperature sensor 74, etc. Each of these sensors is electrically connected to the indoor unit control unit 72 and sends a detection signal to the indoor unit control unit 72. The indoor liquid-side heat exchanger temperature sensor 73 detects the temperature of the refrigerant flowing through the liquid-side outlet of the indoor heat exchanger 18, which is the side opposite to the side to which the gas refrigerant communication pipe 5 is connected. The indoor air temperature sensor 74 detects the temperature of the indoor air before it passes through the indoor heat exchanger 18.

[0068] (1-3) Controller 7 In the air conditioner 1, an outdoor unit control section 71 and an indoor unit control section 72 are connected via a communication line to form a controller 7 that controls the operation of the air conditioner 1.

[0069] The controller 7 mainly has a processor such as a CPU (Central Processing Unit) and memories such as ROM and RAM. Note that the various processes and controls performed by the controller 7 are realized by the integrated functioning of the various units included in the outdoor unit control unit 71 and / or the indoor unit control unit 72.

[0070] The controller 7 controls the components of the refrigerant circuit 10 of the air conditioner 1 so that the temperature of the refrigerant oil stored in the oil reservoir 37 is maintained at 120°C or less. As an example of such control, the controller 7 controls the rotation speed of the compressor 11 so that the temperature of the refrigerant oil detected by the oil temperature detection sensor 79 is maintained at 120°C or less.

[0071] (1-4) Remote Control 70 The remote control 70 is placed in a room that is a space to be air-conditioned or in a specific space of a building that includes the space to be air-conditioned, and is used by a user or the like to issue operation control commands for the air conditioner 1 and monitor the operating status.

[0072] The remote control 70 includes a reception unit 70a such as operation buttons or a touch panel for receiving information input by a user or the like, and a display 70b capable of displaying various information. The remote control 70 is connected to the outdoor unit control unit 71 and the indoor unit control unit 72 via communication lines, and is capable of supplying information received from the user at the reception unit 70a to the controller 7. Information received from the controller 7 can also be output on the display 70b.

[0073] The information received by the reception unit 70a from the user, etc., is not particularly limited, but includes various information such as a command to execute the cooling operation mode, a command to execute the heating operation mode, a command to stop operation, a set temperature specification, etc. The information displayed on the display 70b is not particularly limited, but includes the current operation mode status (cooling or heating), the set temperature, information indicating the occurrence of various abnormalities, etc.

[0074] (2) Structure of Compressor 11 As the compressor 11, for example, a scroll compressor as shown in FIG. 3 can be used.

[0075] The compressor 11 includes a casing 20 , a scroll compression mechanism 21 , a drive motor 24 , a crankshaft 25 , a lower bearing 26 , and a balance weight 30 .

[0076] The casing 20 includes a cylindrical member 20a having a generally cylindrical shape with open top and bottom ends, and an upper cover 20b and a lower cover 20c attached to the upper and lower ends of the cylindrical member 20a. The cylindrical member 20a, the upper cover 20b, and the lower cover 20c are fixed to each other by welding to maintain airtightness. The casing 20 accommodates components of the compressor 11, including the scroll compression mechanism 21, the drive motor 24, the crankshaft 25, and the lower bearing 26. An oil reservoir 37 is formed inside the casing 20 from the lower end to a predetermined height. The oil reservoir 37 has an oil reservoir space So for storing refrigeration oil O for lubricating the scroll compression mechanism 21 and other components. The oil reservoir 37 is provided with an oil temperature detection sensor 79 for detecting the temperature of the refrigeration oil stored therein. In this embodiment, the oil temperature detection sensor 79 is attached to the outer surface of the lower cover 20c to detect the temperature of the refrigeration oil stored in the oil reservoir 37. An suction pipe 4e is provided at an upper portion of the casing 20, penetrating the upper cover 20b. The suction pipe 4e draws in low-pressure gas refrigerant in the refrigeration cycle of the refrigerant circuit 10 and supplies the gas refrigerant to the scroll compression mechanism 21. The lower end of the suction pipe 4e is connected to a fixed scroll 22 of the scroll compression mechanism 21. The suction pipe 4e communicates with a compression chamber Sc of the scroll compression mechanism 21, which will be described later. A discharge pipe 4d is provided at an intermediate portion of the cylindrical member 20a of the casing 20, through which refrigerant discharged to the outside of the casing 20 passes. The discharge pipe 4d is arranged such that an end of the discharge pipe 4d inside the casing 20 protrudes into a high-pressure space Sh formed below a housing 27 of the scroll compression mechanism 21. High-pressure refrigerant in the refrigeration cycle after compression by the scroll compression mechanism 21 flows through the discharge pipe 4d.

[0077] The scroll compression mechanism 21 mainly includes a housing 27, a fixed scroll 22 disposed above the housing 27, and a movable scroll 23 that is combined with the fixed scroll 22 to form a compression chamber Sc.

[0078] The fixed scroll 22 has a flat fixed end plate 22a, a spiral fixed wrap 22b protruding from the front surface of the fixed end plate 22a, and an outer edge portion 22c surrounding the fixed wrap 22b. A non-circular discharge port 22d communicating with the compression chamber Sc of the scroll compression mechanism 21 is formed in the center of the fixed end plate 22a and penetrates the fixed end plate 22a in the thickness direction. Refrigerant compressed in the compression chamber Sc is discharged from the discharge port 22d, passes through a refrigerant passage (not shown) formed in the fixed scroll 22 and the housing 27, and flows into the high-pressure space Sh. Note that this compressor 11 is a high-pressure dome-type compressor in which high-pressure refrigerant is present in a region of the casing 20 outside the scroll compression mechanism 21.

[0079] The movable scroll 23 has a flat movable end plate 23a, a spiral movable wrap 23b protruding from the front surface of the movable end plate 23a, and a cylindrical boss portion 23c protruding from the back surface of the movable end plate 23a. The fixed wrap 22b of the fixed scroll 22 and the movable wrap 23b of the movable scroll 23 are combined with each other such that the lower surface of the fixed end plate 22a faces the upper surface of the movable end plate 23a. A compression chamber Sc is formed between the adjacent fixed wrap 22b and movable wrap 23b. As the movable scroll 23 revolves relative to the fixed scroll 22 as described below, the volume of the compression chamber Sc changes periodically, and the scroll compression mechanism 21 draws, compresses, and discharges refrigerant. The boss portion 23c is a cylindrical portion with a closed upper end. The movable scroll 23 and the crankshaft 25 are connected by inserting an eccentric portion 25b of the crankshaft 25 (described later) into the hollow portion of the boss portion 23c. The boss portion 23c is disposed in an eccentric space 28 formed between the movable scroll 23 and the housing 27. The eccentric space 28 communicates with the high-pressure space Sh via an oil supply path 39 of the crankshaft 25 (described later), and high pressure acts on the eccentric space 28. This pressure presses the lower surface of the movable end plate 23a in the eccentric space 28 upward toward the fixed scroll 22. This force brings the movable scroll 23 into close contact with the fixed scroll 22. The movable scroll 23 is supported by the housing 27 via an Oldham ring 29 disposed in an "Oldham ring space Sr." The Oldham ring 29 is a member that prevents the movable scroll 23 from rotating on its axis and allows it to revolve. By using the Oldham ring 29, when the crankshaft 25 rotates, the movable scroll 23 connected to the crankshaft 25 at the boss portion 23c revolves relative to the fixed scroll 22 without rotating, and the refrigerant in the compression chamber Sc is compressed.

[0080] The housing 27 is press-fitted into the cylindrical member 20a and fixed to the cylindrical member 20a along its entire outer circumferential surface. The housing 27 and the fixed scroll 22 are fixed with bolts (not shown) or the like so that the upper end surface of the housing 27 is in close contact with the lower surface of the outer peripheral portion 22c of the fixed scroll 22. The housing 27 has a recess 27a recessed in the center of its upper surface and an upper bearing portion 27b located below the recess 27a. The recess 27a surrounds the side of an eccentric portion space 28 in which the boss portion 23c of the movable scroll 23 is located. An upper bearing 35, which is a cylindrical metal member that supports the main shaft 25a of the crankshaft 25, is located in the upper bearing portion 27b. The upper bearing 35 rotatably supports the main shaft 25a inserted in the upper bearing 35. The housing 27 also has an Oldham ring space Sr in which an Oldham ring 29 is located.

[0081] The drive motor 24 has an annular stator 33 fixed to the inner wall surface of the cylindrical member 20a, and a rotor 32 rotatably housed inside the stator 33 with a small gap (air gap passage) between them. The stator 33 is configured with a coil. The rotor 32 is connected to the movable scroll 23 via a crankshaft 25 arranged to extend in the vertical direction along the axis of the cylindrical member 20a. As the rotor 32 rotates, the movable scroll 23 revolves relative to the fixed scroll 22.

[0082] The crankshaft 25 transmits the driving force of the drive motor 24 to the movable scroll 23. The crankshaft 25 is disposed to extend vertically along the axis of the cylindrical member 20a and connects the rotor 32 of the drive motor 24 to the movable scroll 23 of the scroll compression mechanism 21. The crankshaft 25 has a main shaft 25a whose central axis coincides with the axis of the cylindrical member 20a and an eccentric portion 25b that is eccentric with respect to the axis of the cylindrical member 20a. As described above, the eccentric portion 25b is inserted into the boss portion 23c of the movable scroll 23. A pin bearing 31, which is a cylindrical metal member that supports the eccentric portion 25b, is provided radially outward of the eccentric portion 25b. The main shaft 25a is rotatably supported by the pin bearing 31, an upper bearing 35 of the upper bearing portion 27b of the housing 27, and a lower bearing 26 (described later). The main shaft 25a is connected to the rotor 32 of the drive motor 24 between the upper bearing 35 and the lower bearing 26. An oil supply path 39 is formed inside the crankshaft 25 to supply refrigeration oil O to the scroll compression mechanism 21 and the like. The lower end of the main shaft 25a is located in an oil reservoir space So of an oil reservoir 37 formed in the lower part of the casing 20, and the refrigeration oil O in the oil reservoir space So is supplied to the scroll compression mechanism 21 and the like through the oil supply path 39.

[0083] The balance weight 30 is a separate member from the crankshaft 25, has an annular shape, and is fitted onto the main shaft 25a. The balance weight 30 has a cylindrical portion 30a and an eccentric portion 30b formed on a portion of the circumference of the cylindrical portion 30a. The center of gravity of the cylindrical portion 30a is located on the axis of the crankshaft 25, and the balance weight 30 has a circular shape when viewed in the axial direction. The center of gravity of the eccentric portion 30b is eccentric from the axis of the crankshaft 25. Specifically, the center of gravity of the eccentric portion 30b is eccentric from the axis of the crankshaft 25 in a predetermined direction. As a result, the center of gravity of the entire balance weight 30 is also eccentric from the axis of the crankshaft 25 in the predetermined direction. As described above, the movable scroll 23 is slidably supported near its center by the eccentric portion 25b of the crankshaft 25. As a result, the movable scroll 23 is also eccentric in the same direction as the eccentric portion 25b. With the above structure, by arranging the balance weight 30 on the main shaft 25a with a predetermined direction facing opposite to the eccentric direction of the eccentric portion 25b, it is possible to balance with the movable scroll 23, thereby preventing the crankshaft 25 from vibrating.

[0084] The lower bearing 26 is disposed below the drive motor 24. The lower bearing 26 is fixed to the lower inside of the cylindrical member 20a. The lower bearing 26 constitutes a bearing on the lower end side of the crankshaft 25 and is a cylindrical metal member that rotatably supports the main shaft 25a of the crankshaft 25.

[0085] Next, the operation of the compressor 11 will be described.

[0086] When the drive motor 24 is started, the rotor 32 rotates relative to the stator 33, thereby rotating the crankshaft 25 fixed to the rotor 32. As the crankshaft 25 rotates, the movable scroll 23 connected to the crankshaft 25 revolves relative to the fixed scroll 22. Then, low-pressure gas refrigerant in the refrigeration cycle passes through the suction pipe 4e and is drawn into the compression chamber Sc from the peripheral edge side of the compression chamber Sc. As the movable scroll 23 revolves, communication between the suction pipe 4e and the compression chamber Sc is lost. Then, as the volume of the compression chamber Sc decreases, the pressure in the compression chamber Sc begins to rise.

[0087] The refrigerant in the compression chamber Sc is compressed as the volume of the compression chamber Sc decreases, and finally becomes high-pressure gas refrigerant. The high-pressure gas refrigerant is discharged from a discharge port 22d located near the center of the fixed-side end plate 22a. The high-pressure gas refrigerant then passes through a refrigerant passage (not shown) formed in the fixed scroll 22 and the housing 27, and flows into the high-pressure space Sh. The high-pressure gas refrigerant in the refrigeration cycle that has flowed into the high-pressure space Sh and been compressed by the scroll compression mechanism 21 is discharged from a discharge pipe 4d.

[0088] (3) Structure of expansion valve 9 As the expansion valve 9, for example, an electronic expansion valve using a valve element 93 having a needle 93b as shown in FIG. 4 can be used.

[0089] The expansion valve 9 mainly includes a coil 91, a rotor 92, a valve body 93, a casing 94, a valve seat member 95, and the like.

[0090] The coil 91 is provided in the circumferential direction when the longitudinal direction of the valve body 93 is taken as the axial direction.

[0091] The rotor 92 is rotationally driven by the coil 91. When the rotor 92 rotates, it moves in the direction of the screw axis.

[0092] The valve element 93 is composed of a shaft 93a and a needle 93b. The shaft 93a is cylindrical and extends vertically, with one end attached coaxially to the rotor 92 and moving axially together with the rotor 92. The needle 93b is conically shaped and faces downward at the lower end of the shaft 93a. The needle 93b protrudes into a valve element side space 96, which will be described later.

[0093] The casing 94 accommodates the coil 91, the rotor 92, the shaft 93a of the valve body 93, and the like.

[0094] The valve seat member 95 is provided below the casing 94. The valve seat member 95 has a first connecting portion 97, a second connecting portion 98, a valve body side space 96 for connecting the first connecting portion 97 and the second connecting portion 98, and a valve seat 99 provided between the valve body side space 96 and the first connecting portion 97. The valve seat 99 is formed in a funnel shape so as to face the needle 93b of the valve body 93 from below and radially outward.

[0095] In this way, the high-pressure liquid refrigerant flowing in from the first connecting portion 97 or the second connecting portion 98 is decompressed by passing through the gap between the needle 93b and the valve seat 99. The degree of decompression at this time is adjusted by moving the valve element 93 back and forth with the rotation of the rotor 92 to change the size of the gap between the needle 93b and the valve seat 99.

[0096] The valve element 93 having the needle 93b can be made of, for example, stainless steel or brass. Examples of the SUS valve element 93 include stainless steel, such as SUS304, which is a steel with a chromium content of 10.5% by mass or more and a carbon content of 1.2% by mass or less. Examples of the brass valve element 93 include a copper alloy with a zinc content of 20% by mass or more. Even if the valve element 93 having the needle 93b is made of such a material, in the air conditioner 1 of this embodiment, the air pressure inside the refrigerant circuit 10 is 667 Pa or less, the refrigerant oil contains 3.0% by weight to 5.0% by weight of an acid scavenger, and the temperature of the refrigerant oil in the oil reservoir 37 is maintained at 120°C or less. This suppresses decomposition of the refrigerant and suppresses corrosion of the valve element 93 due to decomposition products.

[0097] (4) Features of the embodiment 1,2-Difluoroethylene and other hydrofluoroolefins used as refrigerants are unstable and prone to decomposition. In contrast, in this embodiment, instead of using 1,2-difluoroethylene or other hydrofluoroolefins alone, a mixed refrigerant containing 1,2-difluoroethylene and one or more hydrofluorocarbons, a mixed refrigerant containing 1,2-difluoroethylene and one or more hydrofluoroolefins, or a mixed refrigerant containing one or more hydrofluorocarbons and one or more hydrofluoroolefins is used as the refrigerant. This makes it possible to suppress the disproportionation reaction of 1,2-difluoroethylene and other hydrofluoroolefins.

[0098] It has also been found that 1,2-difluoroethylene and other hydrofluoroolefins are susceptible to decomposition in high-temperature environments, particularly in parts of the refrigerant circuit where they are present together with high-temperature refrigeration oil. The thermal decomposition of the refrigerant generates refrigerant degradation products, which can generate acids such as hydrofluoric acid, which can corrode the components of the refrigerant circuit.

[0099] In contrast, in the air conditioner 1 of the present embodiment, the air pressure inside the refrigerant circuit 10 is set to 667 Pa or less, and not only is the refrigerating machine oil made to contain 3.0 wt % to 5.0 wt % of an acid scavenger, but the temperature of the refrigerating machine oil in the oil reservoir 37 is maintained at 120°C or less. This sufficiently suppresses decomposition of the refrigerant present together with the refrigerating machine oil, suppresses the generation of acids such as hydrofluoric acid from the decomposition products, and suppresses corrosion of the components of the refrigerant circuit 10. In particular, in the present embodiment, the temperature of the refrigerating machine oil in the oil reservoir 37 can be raised to 120°C, thereby widening the range of operable conditions.

[0100] 5 shows the relationship between the temperature of the discharge gas discharged from the compressor 11 and the acid value when 3.0 wt% of an acid scavenger is blended into the refrigerant circuit 10 of the air conditioner 1 of this embodiment and the air pressure is varied. Here, a mixed refrigerant of 1,2-difluoroethylene and HFO-1234yf (weight ratio: 40 parts by mass: 60 parts by mass) was used as the refrigerant, and a refrigerant oil (PVE) blended with 3.0 wt% of an epoxy-based acid scavenger was used as the acid scavenger. The acid value of the refrigerant oil after 2000 hours of rated operation was measured according to the JIS K 2211 standard. The acid value is the number of milligrams (mg) of potassium hydroxide (KOH) required to neutralize the acidic components contained in 1 g of the sample.

[0101] Furthermore, Fig. 6 shows the relationship between the temperature of the discharge gas discharged from the compressor 11 and the acid value when 2.0 wt% of an acid scavenger was blended into the refrigerating machine oil and the air pressure was changed while other conditions were the same as those for the measurement shown in Fig. 5. Here, refrigerating machine oil (PVE) blended with 2.0 wt% of an epoxy-based acid scavenger as the acid scavenger was used.

[0102] 5 and 6, it can be seen that the lower the pressure of the air contained in the refrigerant circuit 10, the smaller the acid value can be kept. In the air conditioner 1 of this embodiment, the pressure of the air in the refrigerant circuit 10 is 667 Pa or less, and the discharge gas temperature of the compressor 11 is maintained at 120°C or less, so the acid value can be kept at the reference value of 0.10 (mgKOH / g) or less, and corrosion of the components of the refrigerant circuit 10 is suppressed. Note that, here, the refrigeration oil stored in the oil reservoir 37 is located on the higher pressure side than the compression mechanism 21 of the compressor 11 and is subjected to high pressure, so the discharge gas temperature of the compressor 11 corresponds to the temperature detected by the oil temperature detection sensor 79.

[0103] (5) Other embodiments (5-1) Other embodiment A In the above embodiment, an air conditioning apparatus 1 was described as an example in which the air pressure inside the refrigerant circuit 10 is 667 Pa or less, the refrigerating machine oil contains 3.0 wt % to 5.0 wt % of an acid scavenger, and the temperature of the refrigerating machine oil in the oil reservoir 37 is maintained at 120°C or less.

[0104] However, the air conditioner 1 is not limited to this, and may be, for example, an air conditioner in which the air pressure inside the refrigerant circuit 10 is 1333 Pa or less, the refrigerating machine oil does not contain an acid scavenger or contains less than 3.0 wt % of an acid scavenger, and the temperature of the refrigerating machine oil in the oil reservoir 37 is maintained at 100° C. or less, or may be an air conditioner in which the temperature is maintained at 900° C. or less. In this case, the refrigerating machine oil may contain 1.0 wt % to 2.5 wt %, or even 2.0 wt %, of an acid scavenger.

[0105] Even in this case, as understood from the test results in Figures 5 and 6, decomposition of the refrigerant present with the refrigerant oil is sufficiently suppressed, and corrosion of the components of the refrigerant circuit 10 due to decomposition products is suppressed. Specifically, a comparison of Figures 5 and 6 shows that when the blending amount of acid scavenger in the refrigerant oil is about 1.0 wt% lower, decomposition of the refrigerant is suppressed and corrosion of the components of the refrigerant circuit 10 due to decomposition products is suppressed by maintaining the upper limit temperature of the refrigerant oil in the oil reservoir 37 at a temperature about 20°C lower, more preferably about 30°C lower. Furthermore, Figures 5 and 6 show that even when the air pressure inside the refrigerant circuit 10 increases by about 667 Pa, decomposition of the refrigerant is suppressed and corrosion of the components of the refrigerant circuit 10 due to decomposition products is suppressed by maintaining the upper limit temperature of the refrigerant oil in the oil reservoir 37 at a temperature about 20°C lower.

[0106] (5-2) Other embodiment B The air conditioner 1 may also be, for example, an air conditioner in which the air pressure inside the refrigerant circuit 10 is 2000 Pa or less, the refrigerating machine oil contains 3.0 wt % to 5.0 wt % of an acid scavenger, and the temperature of the refrigerating machine oil in the oil reservoir 37 is maintained at 100°C or less.

[0107] In this case as well, as can be seen from the test results in FIG. 5, decomposition of the refrigerant present together with the refrigerating machine oil is sufficiently suppressed, and corrosion of the components of the refrigerant circuit 10 due to the decomposition products is suppressed.

[0108] (5-3) Other embodiment C The air conditioner 1 may also be an air conditioner in which the air pressure inside the refrigerant circuit 10 is 2000 a or less, the refrigerating machine oil does not contain an acid scavenger or contains less than 3.0 wt % of an acid scavenger, and the temperature of the refrigerating machine oil in the oil reservoir 37 is maintained at 80° C. In this case, the refrigerating machine oil may contain 1.0 wt % to 2.5 wt % of an acid scavenger.

[0109] Even in this case, as understood from the test results in Figures 5 and 6, decomposition of the refrigerant present with the refrigerant oil is sufficiently suppressed, and corrosion of the components of the refrigerant circuit 10 due to decomposition products is suppressed. Specifically, a comparison of Figures 5 and 6 shows that when the blending amount of acid scavenger in the refrigerant oil is about 1.0 wt% lower, decomposition of the refrigerant is suppressed and corrosion of the components of the refrigerant circuit 10 due to decomposition products is suppressed by maintaining the upper limit temperature of the refrigerant oil in the oil reservoir 37 at a temperature about 20°C lower, more preferably about 30°C lower. Furthermore, Figures 5 and 6 show that even when the air pressure inside the refrigerant circuit 10 increases by about 667 Pa, decomposition of the refrigerant is suppressed and corrosion of the components of the refrigerant circuit 10 due to decomposition products is suppressed by maintaining the upper limit temperature of the refrigerant oil in the oil reservoir 37 at a temperature about 20°C lower. From these, it can be seen that when the air pressure inside the refrigerant circuit 10 is 2000a or less, the air conditioner is sufficient as long as the temperature of the refrigerating machine oil in the oil reservoir 37 is maintained at 80°C or less.

[0110] (5-4) Other embodiment D The air conditioner 1 may also be, for example, an air conditioner in which the air pressure inside the refrigerant circuit 10 is 4000 Pa or less, the refrigerating machine oil contains 3.0 wt % to 5.0 wt % of an acid scavenger, and the temperature of the refrigerating machine oil in the oil reservoir 37 is maintained at 80°C or less.

[0111] Even in this case, as can be seen from the test results of FIG. 5, decomposition of the refrigerant present together with the refrigerating machine oil is sufficiently suppressed, and corrosion of the components of the refrigerant circuit 10 due to the decomposition products is suppressed.

[0112] (5-5) Other embodiment E In the above embodiment and other embodiments, the case where the temperature of the refrigeration oil stored in the oil reservoir 37 is controlled to be equal to or lower than a predetermined upper limit value has been described as an example.

[0113] Alternatively, for example, the predetermined upper limit temperature of the refrigeration oil stored in the oil reservoir 37 may be determined based on the air pressure inside the refrigerant circuit 10. Specifically, the temperature of the refrigeration oil determined by substituting the value of the air pressure inside the refrigerant circuit 10 into the following equation may be used as the upper limit temperature. The following equation was obtained based on experimental results showing the state of refrigerant decomposition depending on the refrigeration oil temperature and the air pressure inside the refrigerant circuit 10. 0.1=((8×10 -5 × 133.322 × air pressure (Pa)) + 0.0017) × (refrigerant oil temperature (℃)) + (-0.0032 × 133.322 × air pressure (Pa) - 0.15)

[0114] (5-6) Other embodiment F The air conditioner 1 may also be, for example, an air conditioner in which the air pressure inside the refrigerant circuit 10 is 667 Pa or less, the refrigerating machine oil contains 2.0% by weight or more of an acid scavenger, and the temperature of the refrigerating machine oil in the oil reservoir 37 is maintained at 120°C or less.

[0115] (5-7) Other embodiment G The air conditioner 1 may also be, for example, an air conditioner in which the air pressure inside the refrigerant circuit 10 is 667 Pa or less, the refrigerating machine oil contains 0.3 wt % or more of an acid scavenger, and the temperature of the refrigerating machine oil in the oil reservoir 37 is maintained at 100°C or less.

[0116] (5-8) Other embodiment H The air conditioner 1 may also be, for example, an air conditioner in which the air pressure inside the refrigerant circuit 10 is 1333 Pa or less, the refrigerating machine oil contains 0.3 wt % or more of an acid scavenger, and the temperature of the refrigerating machine oil in the oil reservoir 37 is maintained at 80°C or less.

[0117] (5-9) Other Embodiments I In the above embodiment, the case where the components of the refrigerant circuit 10 such as the compressor 11 are controlled based on the temperature of the refrigeration oil detected by the oil temperature detection sensor 79 has been described as an example.

[0118] In response to this, for example, the correlation between the rotation speed of the compressor 11 and the temperature of the refrigeration oil in the oil reservoir 37 may be stored as data in memory, and the rotation speed may be controlled based on this data so that the temperature of the refrigeration oil in the oil reservoir 37 is maintained below a predetermined value.

[0119] In addition, for example, the correlation between the discharge temperature, which is the temperature of the refrigerant discharged from the compressor 11, and the temperature of the refrigeration oil in the oil reservoir 37 may be stored as data in memory, and the discharge temperature may be controlled based on the data so that the temperature of the refrigeration oil in the oil reservoir 37 is maintained below a predetermined value.

[0120] Furthermore, for example, the correlation between the discharge pressure, which is the pressure of the refrigerant discharged from the compressor 11, and the temperature of the refrigeration oil in the oil reservoir 37 may be stored as data in memory, and the discharge pressure may be controlled based on the data so that the temperature of the refrigeration oil in the oil reservoir 37 is maintained below a predetermined value.

[0121] (5-10) Other embodiments J In the above embodiment, the air conditioner 1 having the refrigerant circuit 10 using a high-pressure dome type compressor 11 has been described as an example.

[0122] In contrast to this, for example, the air conditioner 1 may have a refrigerant circuit 10 that uses a low-pressure dome-type compressor 11a. The refrigerant and refrigerating machine oil used are the same as those in the above embodiment.

[0123] An air conditioner 1 according to another embodiment J has a refrigerant circuit 10 shown in Fig. 7. Note that the same parts as those in the above embodiment are given the same reference numerals, and description thereof will be omitted.

[0124] This refrigerant circuit 10 has a first expansion valve 9a and a second expansion valve 9b instead of the expansion valve 9 of the above embodiment, and is equipped with an injection pipe 4f. The first expansion valve 9a is provided between the high-pressure receiver 8 and the outdoor heat exchanger 13. The second expansion valve 9b is provided between the high-pressure receiver 8 and a liquid-side shut-off valve 17. The injection pipe 4f connects the high-pressure receiver 8 and a compressor 11a. The compressor 11a will be described in detail below.

[0125] The compressor 11a is a so-called low-pressure dome-type scroll compressor. As shown in Fig. 8, the compressor 11a mainly includes a casing 54, a compression mechanism 40, a floating member 47, a housing 52, a seal member 55, a motor 58, a crankshaft 59, and a lower bearing housing 62.

[0126] The casing 54 includes a substantially cylindrical member 54a, an upper lid 54b attached to the upper end of the cylindrical member 54a, and a lower lid 54c attached to the lower end of the cylindrical member 54a. The cylindrical member 54a, the upper lid 54b, and the lower lid 54c are fixed to each other by welding to maintain airtightness. The casing 54 accommodates components of the compressor 11a, including the compression mechanism 40, the floating member 47, the housing 52, the seal member 55, the motor 58, the crankshaft 59, and the lower bearing housing 62.

[0127] The compression mechanism 40 is installed in the upper part of the casing 54. The floating member 47 and the housing 52 are installed below the compression mechanism 40. The motor 58 is installed below the housing 52. The lower bearing housing 62 is installed below the motor 58.

[0128] An oil reservoir 37a is formed at the bottom of the casing 54. The oil reservoir 37a has an oil reservoir space So in which refrigeration oil for lubricating the compression mechanism 40 and the like is stored. The oil reservoir 37a is part of the casing 54 and corresponds to the portion below the lower bearing housing 62. For example, as shown in FIG. 8, the oil reservoir 37a is made up of the lower cover 54c and the lower end of the cylindrical member 54a. An oil temperature detection sensor 79 is attached to the outer surface of the oil reservoir 37a. The oil temperature detection sensor 79 measures the temperature of the refrigeration oil stored in the oil reservoir 37a.

[0129] The internal space of the casing 54 is divided into a first space S1 and a second space S2 by a first flow path 56. The first space S1 is the space below the first flow path 56. The second space S2 is the space above the first flow path 56. The first flow path 56 is fixed to the compression mechanism 40 and the casing 54 by welding so as to maintain airtightness between the first space S1 and the second space S2.

[0130] The first flow passage 56 is a plate-like member formed in an annular shape in a plan view. The inner circumferential side of the first flow passage 56 is fixed to the upper part of the fixed scroll 41 of the compression mechanism 40 along the entire circumference. The outer circumferential side of the first flow passage 56 is fixed to the inner surface of the casing 54 along the entire circumference.

[0131] The first space S1 is a space in which the motor 58 is installed. The first space S1 is a space into which refrigerant flows from the refrigerant circuit 10 having the compressor 11a before being compressed by the compressor 11a. The first space S1 is a space into which low-pressure refrigerant in the refrigeration cycle flows.

[0132] The second space S2 is a space into which the refrigerant discharged from the compression mechanism 40 (refrigerant compressed by the compression mechanism 40) flows. The second space S2 is a space into which high-pressure refrigerant in the refrigeration cycle flows.

[0133] The casing is provided with a suction pipe 4e, a discharge pipe 4d, and an injection pipe 4f, which are attached to the casing so as to communicate between the inside and outside of the casing.

[0134] The suction pipe 4e is attached near the center of the casing 54 in the up-down direction (vertical direction). Specifically, as shown in Fig. 8, the suction pipe 4e is attached horizontally to the cylindrical member 54a at a height position between the housing 52 and the motor 58. The suction pipe 4e communicates between the outside of the casing 54 and a first space S1 inside the casing 54. The refrigerant before compression (low-pressure refrigerant in the refrigeration cycle) flows through the suction pipe 4e into the first space S1.

[0135] The discharge pipe 4d is attached to the upper part of the casing 54 at a height position higher than the first flow path 56. Specifically, as shown in Fig. 8, the suction pipe 4e is attached horizontally to the upper lid 54b. The discharge pipe 4d connects the outside of the casing 54 with the second space S2 inside the casing 54. The refrigerant compressed by the compression mechanism 40 and flowing into the second space S2 (high-pressure refrigerant in the refrigeration cycle) passes through the discharge pipe 4d and flows out of the compressor 11a.

[0136] The injection pipe 4f is attached to the upper part of the casing 54 at a height position below the first flow path 56. Specifically, as shown in FIG. 8, the injection pipe 4f is attached horizontally to the cylindrical member 54a at a height position above the compression mechanism 40. As shown in FIG. 8, the end of the injection pipe 4f on the inner side of the casing 54 is connected to the fixed scroll 41 of the compression mechanism 40. The injection pipe 4f communicates with the compression chamber Sc in the middle of compression inside the compression mechanism 40 via a passage (not shown) formed in the fixed scroll 41. An intermediate-pressure refrigerant (a refrigerant with a pressure intermediate between low pressure and high pressure in the refrigeration cycle) is supplied to the compression chamber Sc in the middle of compression from the refrigerant circuit 10 having the compressor 11a through the injection pipe 4f.

[0137] The compression mechanism 40 mainly includes a fixed scroll 41 and a movable scroll 42. The fixed scroll 41 and the movable scroll 42 are combined with each other to form a compression chamber Sc. The compression mechanism 40 compresses the refrigerant in the compression chamber Sc and discharges the compressed refrigerant.

[0138] 8, the fixed scroll 41 is placed on a housing 52. The fixed scroll 41 and the housing 52 are fixed to each other by fixing means such as bolts.

[0139] The fixed scroll 41 has a disk-shaped fixed end plate 41a, a spiral-shaped fixed wrap 41b, and a peripheral edge 41c. The fixed wrap 41b and the peripheral edge 41c extend from the front surface (lower surface) of the fixed end plate 41a toward the movable scroll 42 (downward). When the fixed scroll 41 is viewed from below, the fixed wrap 41b is formed in a spiral shape (involute shape) from near the center of the fixed end plate 41a toward the outer periphery. The peripheral edge 41c has a cylindrical shape. The peripheral edge 41c is located on the outer periphery of the fixed end plate 41a so as to surround the fixed wrap 41b.

[0140] During operation of the compressor 11a, the movable scroll 42 orbits relative to the fixed scroll 41. As a result, the refrigerant (low-pressure refrigerant in the refrigeration cycle) that flows from the first space S1 into the peripheral compression chamber Sc is compressed as it moves toward the innermost (central) compression chamber Sc. A discharge port 41d that discharges the refrigerant compressed in the compression chamber Sc is formed near the center of the fixed side end plate 41a and penetrates the fixed side end plate 41a in its thickness direction (vertical direction). The discharge port 41d communicates with the innermost compression chamber Sc. A discharge valve 43 that opens and closes the discharge port 41d is attached above the fixed side end plate 41a. When the pressure in the innermost compression chamber Sc that communicates with the discharge port 41d becomes greater than the pressure in the space above the discharge valve 43 (second space S2) by a predetermined value or more, the discharge valve 43 opens, and the refrigerant flows from the discharge port 41d into the second space S2.

[0141] A relief hole 41e is formed on the outer circumferential side of the discharge port 41d of the fixed side end plate 41a, penetrating the fixed side end plate 41a in its thickness direction. The relief hole 41e is in communication with a compression chamber Sc formed on the outer circumferential side of the innermost compression chamber Sc that is in communication with the discharge port 41d. The relief hole 41e is in communication with a compression chamber Sc in the middle of compression in the compression mechanism 40. A plurality of relief holes 41e may be formed in the fixed side end plate 41a. A relief valve 44 that opens and closes the relief hole 41e is attached above the fixed side end plate 41a. When the pressure in the compression chamber Sc that is in communication with the relief hole 41e becomes higher than the pressure in the space above the relief valve 44 (second space S2) by a predetermined value or more, the relief valve 44, which is a safety valve, opens, and refrigerant flows from the relief hole 41e into the second space S2.

[0142] The movable scroll 42 has a disk-shaped movable end plate 42a, a spiral-shaped movable end wrap 42b, and a cylindrical boss portion 42c. The movable end wrap 42b extends from the front surface (upper surface) of the movable end plate 42a toward the fixed scroll 41 (upward). The boss portion 42c extends from the back surface (lower surface) of the movable end plate 42a toward the motor 58 (downward). When the movable scroll 42 is viewed from above, the movable end wrap 42b is formed in a spiral shape (involute shape) from near the center of the movable end plate 42a toward the outer periphery.

[0143] The fixed-side wrap 41b of the fixed scroll 41 and the movable-side wrap 42b of the movable scroll 42 are fitted together to form a compression chamber Sc. The fixed scroll 41 and the movable scroll 42 are fitted together so that the front surface (lower surface) of the fixed-side end plate 41a faces the front surface (upper surface) of the movable-side end plate 42a. This forms a compression chamber Sc surrounded by the fixed-side end plate 41a, the fixed-side wrap 41b, the movable-side wrap 42b, and the movable-side end plate 42a.

[0144] The compression mechanism 40 has a symmetric wrap structure or an asymmetric wrap structure. In a compression mechanism 40 having a symmetric wrap structure, a first compression chamber surrounded by the outer peripheral surface of the movable-side wrap 42b and the inner peripheral surface of the fixed-side wrap 41b, and a second compression chamber surrounded by the inner peripheral surface of the movable-side wrap 42b and the outer peripheral surface of the fixed-side wrap 41b are formed symmetrically about a point when viewed vertically. In a compression mechanism 40 having an asymmetric wrap structure, the first compression chamber and the second compression chamber are not formed symmetrically about a point when viewed vertically.

[0145] The movable side end plate 42a is disposed above the floating member 47. During operation of the compressor 11a, the floating member 47 is pressed toward the movable scroll 42 by the pressure of a back pressure space Sb formed below the floating member 47. As a result, when the pressing portion 50 at the upper part of the floating member 47 comes into contact with the back surface (lower surface) of the movable side end plate 42a, the floating member 47 presses the movable scroll 42 toward the fixed scroll 41. The force with which the floating member 47 presses the movable scroll 42 toward the fixed scroll 41 causes the movable scroll 42 to come into close contact with the fixed scroll 41. This suppresses refrigerant leakage from the gap between the tooth tip (tip end surface) of the fixed side wrap 41b and the bottom surface (main surface in contact with the tooth tip) of the movable side end plate 42a, and from the gap between the tooth tip of the movable side wrap 42b and the bottom surface of the fixed side end plate 41a.

[0146] The back pressure space Sb is a space formed between the floating member 47 and the housing 52. As shown in FIG. 9, the back pressure space Sb is formed mainly on the rear side (lower side) of the floating member 47. The refrigerant in the compression chamber Sc of the compression mechanism 40 is guided into the back pressure space Sb. The back pressure space Sb and the first space S1 surrounding the back pressure space Sb are sealed. During operation of the compressor 11a, the pressure in the back pressure space Sb is higher than the pressure in the first space S1.

[0147] An Oldham coupling 45 is disposed between the movable scroll 42 and the floating member 47. The Oldham coupling 45 slidably engages with both the movable scroll 42 and the floating member 47. The Oldham coupling 45 allows the movable scroll 42 to orbit relative to the fixed scroll 41 while suppressing rotation of the movable scroll 42.

[0148] The boss portion 42c is disposed in an eccentric portion space 51 surrounded by the inner surface of the floating member 47. A first bearing metal 46 is disposed inside the boss portion 42c. The first bearing metal 46 is, for example, press-fitted and fixed inside the boss portion 42c. An eccentric portion 60 of the crankshaft 59 is inserted into the first bearing metal 46. By inserting the eccentric portion 60 into the first bearing metal 46, the movable scroll 42 and the crankshaft 59 are connected.

[0149] The floating member 47 is disposed on the back side of the movable scroll 42 (the side opposite to the side on which the fixed scroll 41 is disposed). The floating member 47 is pressed toward the movable scroll 42 by the pressure in the back pressure space Sb, thereby pressing the movable scroll 42 toward the fixed scroll 41. A portion of the floating member 47 also functions as a bearing that supports the crankshaft 59.

[0150] The floating member 47 mainly includes a cylindrical main body portion 47 a, a pressing portion 50 , and an upper bearing housing 48 .

[0151] The main body 47a defines an eccentric space 51 surrounded by the inner surface of the main body 47a. The boss 42c of the movable scroll 42 is disposed in the eccentric space 51.

[0152] The pressing portion 50 is a cylindrical member extending from the upper end of the main body portion 47a toward the movable scroll 42. As shown in FIG. 9 , a thrust surface 50a at the upper end of the pressing portion 50 faces the back surface of the movable end plate 42a of the movable scroll 42. The thrust surface 50a is formed in an annular shape in a plan view. When the floating member 47 is pressed toward the movable scroll 42 by the pressure in the back pressure space Sb, the thrust surface 50a comes into contact with the back surface of the movable end plate 42a, pressing the movable scroll 42 toward the fixed scroll 41.

[0153] The upper bearing housing 48 is a cylindrical member disposed below the main body 47a (below the eccentric space 51). A second bearing metal 49 is disposed inside the upper bearing housing 48. The second bearing metal 49 is, for example, press-fitted and fixed inside the upper bearing housing 48. The second bearing metal 49 rotatably supports a main shaft 61 of the crankshaft 59.

[0154] The housing 52 is a substantially cylindrical member that is disposed below the fixed scroll 41 and the floating member 47. The housing 52 supports the floating member 47. A back pressure space Sb is formed between the housing 52 and the floating member 47. The housing 52 is attached to the inner surface of the casing 54 by, for example, press fitting.

[0155] The seal member 55 is a member for forming a back pressure space Sb between the floating member 47 and the housing 52. The seal member 55 is, for example, a gasket such as an O-ring. As shown in FIG. 9, the seal member 55 divides the back pressure space Sb into a first chamber B1 and a second chamber B2. The first chamber B1 and the second chamber B2 are spaces formed in a substantially annular shape in a plan view. The second chamber B2 is disposed inside the first chamber B1. In a plan view, the area of ​​the first chamber B1 is larger than the area of ​​the second chamber B2.

[0156] The first chamber B1 is in communication with the compression chamber Sc in the middle of compression via a first flow path 56. The first flow path 56 is a flow path that guides the refrigerant in the middle of compression in the compression mechanism 40 (intermediate-pressure refrigerant) to the first chamber B1. The first flow path 56 is formed in the fixed scroll 41 and the housing 52.

[0157] The second chamber B2 is in communication with the discharge port 41d of the fixed scroll 41 via a second flow path 57. The second flow path 57 is a flow path that guides the refrigerant (high-pressure refrigerant) discharged from the compression mechanism 40 to the second chamber B2. The second flow path 57 is formed in the fixed scroll 41 and the housing 52.

[0158] During operation of the compressor 11a, the pressure in the second chamber B2 is higher than the pressure in the first chamber B1. However, because the area of ​​the first chamber B1 is larger than the area of ​​the second chamber B2 in a plan view, the pressure in the back pressure space Sb does not tend to press the movable scroll 42 against the fixed scroll 41 excessively. Because the second chamber B2 is located more inward than the first chamber B1, a balance is easily maintained between the force with which the movable scroll 42 is pressed downward by the pressure in the compression chamber Sc and the force with which the floating member 47 presses the movable scroll 42 upward.

[0159] The motor 58 drives the movable scroll 42. The motor 58 has a stator 58a and a rotor 58b. The stator 58a is an annular member fixed to the inner surface of the casing 54. The rotor 58b is a cylindrical member disposed inside the stator 58a. A small gap (air gap) is formed between the inner peripheral surface of the stator 58a and the outer peripheral surface of the rotor 58b.

[0160] A crankshaft 59 passes through the rotor 58b along its axial direction. The rotor 58b is connected to the movable scroll 42 via the crankshaft 59. The motor 58 drives the movable scroll 42 by rotating the rotor 58b, causing the movable scroll 42 to orbit relative to the fixed scroll 41.

[0161] The crankshaft 59 connects the rotor 58b of the motor 58 and the movable scroll 42 of the compression mechanism 40. The crankshaft 59 extends in the vertical direction. The crankshaft 59 transmits the driving force of the motor 58 to the movable scroll 42.

[0162] The crankshaft 59 mainly includes an eccentric portion 60 and a main shaft 61 .

[0163] The eccentric portion 60 is disposed above the main shaft 61. The central axis of the eccentric portion 60 is eccentric with respect to the central axis of the main shaft 61. The eccentric portion 60 is connected to the first bearing metal 46 disposed inside the boss portion 42c of the movable scroll 42.

[0164] The main shaft 61 is rotatably supported by a second bearing metal 49 disposed in the upper bearing housing 48 of the floating member 47 and a third bearing metal 63 disposed in the lower bearing housing 62. The main shaft 61 is connected to the rotor 58b of the motor 58 between the upper bearing housing 48 and the lower bearing housing 62. The main shaft 61 extends in the vertical direction.

[0165] An oil passage (not shown) is formed inside the crankshaft 59. The oil passage has a main path and a branch path. The main path extends in the axial direction of the crankshaft 59 from the lower end to the upper end of the crankshaft 59. The branch path extends from the main path in the radial direction of the crankshaft 59. Refrigeration oil in the oil reservoir 37a is pumped up by a pump (not shown) provided at the lower end of the crankshaft 59 and supplied through the oil path to sliding parts between the crankshaft 59 and each of the first bearing metal 46, the second bearing metal 49, and the third bearing metal 63, sliding parts of the compression mechanism 40, etc.

[0166] The lower bearing housing 62 is fixed to the inner surface of the casing 54. The lower bearing housing 62 is disposed below the motor 58. A third bearing metal 63 is disposed inside the lower bearing housing 62. The third bearing metal 63 is, for example, press-fitted and fixed inside the lower bearing housing 62. The main shaft 61 of the crankshaft 59 passes through the third bearing metal 63. The third bearing metal 63 rotatably supports the lower side of the main shaft 61 of the crankshaft 59.

[0167] The operation of the compressor 11a in a normal state will be described below. The normal state is a state in which the pressure of the refrigerant discharged from the discharge port 41d of the compression mechanism 40 is higher than the pressure in the compression chamber Sc during compression.

[0168] When the motor 58 is driven, the rotor 58b rotates, and the crankshaft 59 connected to the rotor 58b also rotates. When the crankshaft 59 rotates, the Oldham coupling 45 causes the movable scroll 42 to orbit relative to the fixed scroll 41 without rotating on its axis. Low-pressure refrigerant that flows into the first space S1 from the suction pipe 4e passes through a refrigerant passage (not shown) formed in the housing 52 and is drawn into the compression chamber Sc on the peripheral side of the compression mechanism 40. When the movable scroll 42 orbits, communication between the first space S1 and the compression chamber Sc is lost, the volume of the compression chamber Sc decreases, and the pressure of the compression chamber Sc increases. Intermediate-pressure refrigerant is injected from the injection pipe 4f into the compression chamber Sc during compression. The pressure of the refrigerant increases as it moves from the compression chamber Sc on the peripheral side (outer side) to the compression chamber Sc on the central side (inner side), eventually reaching high pressure in the refrigeration cycle. The refrigerant compressed by the compression mechanism 40 is discharged from the discharge port 41d of the fixed side end plate 41a into the second space S2. The high-pressure refrigerant in the second space S2 is discharged from the discharge pipe 4d.

[0169] In the compressor 11a described above, the refrigeration oil stored in the oil reservoir 37a is located on the low-pressure side relative to the compression mechanism 40, and low pressure is applied to the refrigeration oil. Therefore, it is easier to suppress the rise in temperature of the refrigeration oil compared to when a high-pressure refrigerant acts as in the high-pressure dome-type compressor 11 of the above embodiment.

[0170] 10 shows the relationship between the temperature of the gas discharged from the compressor 11a and the acid value when the air pressure is changed for the refrigerant circuit 10 included in the air conditioner 1 of another embodiment J. Here, a mixed refrigerant of 1,2-difluoroethylene and HFO-1234yf (weight ratio of 40 parts by mass:60 parts by mass) was used as the refrigerant, and a refrigerating machine oil (PVE) containing 3.0 wt% of an epoxy acid scavenger was used as the acid scavenger. The refrigerating machine oil after 2000 hours of rated operation was measured according to the provisions of JIS K 2211.

[0171] 10, it can be seen that the air conditioner 1 using the low-pressure dome-type compressor 11a of another embodiment J has a lower acid number than the air conditioner 1 using the high-pressure dome-type compressor 11 of the above embodiment, even at the same discharge temperature. This is thought to be because the oil reservoir 37a of the low-pressure dome-type compressor 11a is located on the lower pressure side than the compression mechanism 40, and a low-pressure refrigerant acts on it, thereby keeping the temperature of the refrigeration oil stored in the oil reservoir 37a low. For this reason, when the low-pressure dome-type compressor 11a is used, corrosion of the components of the refrigerant circuit 10 is particularly suppressed.

[0172] For example, the air conditioner 1 using the low-pressure dome-type compressor 11a may be one in which the air pressure inside the refrigerant circuit 10 is set to 667 Pa or less, the refrigerant oil is blended with 3.0 wt % to 5.0 wt % of an acid scavenger, and the temperature of the refrigerant oil in the oil reservoir 37a is maintained at 140° C. or less. Furthermore, the air conditioner 1 using the low-pressure dome-type compressor 11a may be one in which the air pressure inside the refrigerant circuit 10 is set to 1333 Pa or less, the refrigerant oil is blended with 3.0 wt % to 5.0 wt % of an acid scavenger, and the temperature of the refrigerant oil in the oil reservoir 37a is maintained at 140° C. or less. Furthermore, the air conditioner 1 using the low-pressure dome-type compressor 11a may be configured such that the air pressure inside the refrigerant circuit 10 is set to 2000 Pa or less, and the refrigerant oil is blended with an acid scavenger in an amount of 3.0 wt % to 5.0 wt % while the temperature of the refrigerant oil in the oil reservoir 37a is maintained at 135°C or less.

[0173] (Addendum) Although the embodiments of the present disclosure have been described above, it will be understood that various changes in form and details can be made without departing from the spirit and scope of the present disclosure as defined in the claims. [Explanation of symbols]

[0174] 1. Air conditioning equipment (refrigerant cycle equipment) 5 Gas refrigerant connecting piping 6 Liquid refrigerant connecting piping 7 Control Unit 9 Expansion valve 10 Refrigerant circuit 11 Compressor 11a compressor 13 Outdoor heat exchanger 18 Indoor heat exchanger 21 Compression mechanism 37 Oil reservoir 37a Oil reservoir 79 Oil temperature detection sensor (temperature detection part) 93 Valve body 93b Needle (needle part) [Prior art documents] [Patent documents]

[0175] [Patent Document 1] Japanese Patent Application Publication No. 2019-196312

Claims

1. A refrigerant circuit (10) having a low-pressure dome-type compressor (11, 11a), The compressor has a compression element (21) that compresses a refrigerant and an oil reservoir (37, 37a) in which refrigeration oil is stored, The air pressure inside the refrigerant circuit is 1333 Pa or less, The refrigerating machine oil contains 3.0 wt % or more and 5.0 wt % or less of an acid scavenger, The temperature of the refrigeration oil in the oil reservoir is maintained at 140° C. or less. In the refrigeration cycle device (1), Use of at least one of a mixed refrigerant containing 1,2-difluoroethylene and one or more hydrofluorocarbons and a mixed refrigerant containing 1,2-difluoroethylene and one or more hydrofluoroolefins as a refrigerant.

2. A refrigerant circuit (10) having a low-pressure dome-type compressor (11, 11a), The compressor has a compression element (21) that compresses a refrigerant and an oil reservoir (37, 37a) in which refrigeration oil is stored, The air pressure inside the refrigerant circuit is 2000 Pa or less, The refrigerating machine oil contains 3.0 wt % or more and 5.0 wt % or less of an acid scavenger, The temperature of the refrigeration oil in the oil reservoir is maintained at 135° C. or less. In the refrigeration cycle device (1), Use of at least one of a mixed refrigerant containing 1,2-difluoroethylene and one or more hydrofluorocarbons and a mixed refrigerant containing 1,2-difluoroethylene and one or more hydrofluoroolefins as a refrigerant.

3. A refrigerant circuit (10) having a low-pressure dome-type compressor (11, 11a), The compressor has a compression element (21) that compresses a refrigerant and an oil reservoir (37, 37a) in which refrigeration oil is stored, The air pressure inside the refrigerant circuit is 667 Pa or less, The refrigerating machine oil does not contain an acid scavenger or contains less than 3.0 wt. % of an acid scavenger, The temperature of the discharge gas discharged from the compressor is maintained at 140° C. or less. In the refrigeration cycle device (1), Use of at least one of a mixed refrigerant containing 1,2-difluoroethylene and one or more hydrofluorocarbons and a mixed refrigerant containing 1,2-difluoroethylene and one or more hydrofluoroolefins as a refrigerant.

4. A refrigerant circuit (10) having a low-pressure dome-type compressor (11, 11a), The compressor has a compression element (21) that compresses a refrigerant and an oil reservoir (37, 37a) in which refrigeration oil is stored, The air pressure inside the refrigerant circuit is 4000 Pa or less, The refrigerating machine oil does not contain an acid scavenger or contains less than 3.0 wt. % of an acid scavenger, The temperature of the discharge gas discharged from the compressor is maintained at 120° C. or less. In the refrigeration cycle device (1), Use of at least one of a mixed refrigerant containing 1,2-difluoroethylene and one or more hydrofluorocarbons and a mixed refrigerant containing 1,2-difluoroethylene and one or more hydrofluoroolefins as a refrigerant.

5. The temperature of the refrigeration oil in the oil reservoir is maintained at or below a value obtained by substituting the air pressure inside the refrigerant circuit into the following formula: Use of the composition as a refrigerant in a refrigeration cycle apparatus according to any one of claims 1 to 4. 0.1 = ((8 x 10 －５ x 133.322 x air pressure (Pa)) + 0.0017) x (refrigeration oil temperature (°C)) + (-0.0032 x 133.322 x air pressure (Pa) - 0.15)

6. The refrigerating machine oil contains at least one of polyvinyl ether and polyol ester. Use of the composition as a refrigerant in a refrigeration cycle apparatus according to any one of claims 1 to 5.

7. The amount of moisture inside the refrigerant circuit is 300 ppm or less relative to the amount of the refrigerant sealed in the refrigerant circuit. Use of the composition as a refrigerant in a refrigeration cycle apparatus according to any one of claims 1 to 6.

8. The refrigerant circuit includes an expansion valve (9) having a needle portion (93b), The needle portion is made of SUS or brass. Use of the composition as a refrigerant in a refrigeration cycle apparatus according to any one of claims 1 to 7.

9. The refrigerant is any one of a refrigerant consisting of 1,2-difluoroethylene and R32, a refrigerant consisting of 1,2-difluoroethylene and R1234yf, and a refrigerant consisting of 1,2-difluoroethylene, R32, and R1234yf. Use of the composition as a refrigerant in a refrigeration cycle apparatus according to any one of claims 1 to 8.

10. The refrigeration cycle device includes a temperature detection unit (79) that detects the temperature of the refrigeration oil in the oil reservoir, and the rotation speed of the compressor is controlled based on the detection result of the temperature detection unit. Use of the composition as a refrigerant in a refrigeration cycle apparatus according to any one of claims 1 to 9.