Refrigeration device

Abstract

In a refrigeration device according to the present invention, a compressor (115) includes a casing (11), an electric motor (21) that is disposed in the casing (11), a drive shaft (23) that is driven by the electric motor (21) and that extends along the longitudinal direction of the casing (11), a compression mechanism (30) that is connected to the drive shaft (23), and an oil supply mechanism (29) that carries, to a prescribed sliding part, refrigerator oil which is stored in an oil pool (17) formed in a bottom part of the casing (11), wherein the refrigerator oil includes a refrigerant and a refrigerator oil in which the solubility of the refrigerant is not more than 50 wt%.

Description

Refrigeration equipment

[0001] The present disclosure relates to refrigeration devices.

[0002] The refrigeration system described in Patent Document 1 includes an oil separator and an oil return passage that returns oil from the oil separator to the compressor. A sensor is installed inside the compressor to detect the refrigerant concentration in the lubricating oil in the oil reservoir, and the oil from the oil separator is returned to the compressor based on the detected value of the sensor. This adjusts the viscosity of the lubricating oil in the sliding parts inside the compressor.

[0003] JP 2015-038406 A

[0004] Thus, in order to satisfy reliability requirements such as improved sliding properties and reduced wear of the sliding parts in the compressor, it is important to adjust the viscosity of the refrigeration oil supplied to the sliding parts. Specifically, if the refrigerant is easily soluble in the refrigeration oil, a large amount of the refrigerant will dissolve in the refrigeration oil, which may result in a decrease in the viscosity of the refrigerant supplied to the sliding parts. Therefore, it is important to select a refrigerant and a refrigeration oil in which the refrigerant is appropriately soluble.

[0005] An object of the present disclosure is to ensure lubrication of sliding parts in a compressor even with refrigeration oil in which refrigerant is relatively difficult to dissolve.

[0006] The first aspect is a refrigeration system that performs a refrigeration cycle and includes a refrigerant circuit (101) and a compressor (115) provided in the refrigerant circuit (101). The compressor (115) includes a casing (11), an electric motor (21) disposed in the casing (11), a drive shaft (23) extending along the longitudinal direction of the casing (11) and driven by the electric motor (21), a compression mechanism (30) connected to the drive shaft (23), and an oil supply mechanism (29) that transports refrigeration oil in an oil reservoir (17) formed at the bottom of the casing (11) to predetermined sliding parts, the refrigeration oil including a refrigerant and a refrigerant having a refrigerant solubility of 50 wt % or less.

[0007] In the first aspect, by selecting a combination of a refrigerant and a refrigerating machine oil (in this case, the refrigerant is not dissolved) in which the refrigerant has a solubility of 50 wt % or less, it is possible to suppress dissolution of the refrigerant into the refrigerating machine oil and suppress a decrease in viscosity of the refrigerant-dissolved refrigerating machine oil. As a result, refrigerating machine oil with a suppressed decrease in viscosity is supplied to the sliding parts, thereby ensuring lubrication of the sliding parts.

[0008] In the second aspect, in the first aspect, the oil supply mechanism (29) is provided with a suction port (26a) that is arranged below the oil reservoir (17) and that draws up the refrigeration oil, and a first operation is performed in which the viscosity of the refrigeration oil is higher at the lower part of the oil reservoir (17) than at the upper part.

[0009] It has been found that when a refrigerant is combined with a refrigeration oil in which the refrigerant is relatively insoluble (in this case, the refrigerant is undissolved), it takes time for the refrigerant to dissolve uniformly in the refrigeration oil, resulting in a difference in refrigerant solubility between the upper and lower portions of the oil reservoir (17). Specifically, the refrigerant solubility in the refrigeration oil in the lower portion of the oil reservoir (17) is lower than that in the upper portion. In other words, a viscosity gradient occurs in the oil reservoir (17), and the viscosity of the refrigeration oil in the lower portion of the oil reservoir (17) is higher than that in the upper portion. In response to this, in the second aspect, the suction port (26a) is located in the lower portion of the oil reservoir (17), allowing the oil supply mechanism (29) to draw up refrigeration oil with a relatively high viscosity. This ensures lubrication of the sliding parts.

[0010] The third embodiment is the first or second embodiment, wherein the area of ​​the oil surface of the oil reservoir (17) is 141 mm ２ Over 252 mm ２ In the third mode described below, a first operation is performed in which the circulation rate of the refrigerant flowing into the compressor (115) is 0.3 kg / sec or more and 307 kg / sec or less. This operating condition allows the formation of a viscosity gradient in the oil reservoir (17) in which the viscosity of the refrigeration oil is higher in the lower part than in the upper part.

[0011] A fourth aspect is the second or third aspect, wherein the first operation is an operation in which a plurality of bubbles are generated in at least a part of the oil reservoir (17), causing the refrigeration oil to turn white, and the minimum particle size of the plurality of bubbles is smaller than the inner diameter of a suction port (26a) provided in the oil supply mechanism (29) and used to suck up the refrigeration oil from the oil reservoir (17).

[0012] In the fourth aspect, the refrigeration oil turns white due to a plurality of bubbles generated in a part of the refrigeration oil in the oil reservoir (17). In this state, a viscosity gradient is formed in the vertical direction in the refrigeration oil in the oil reservoir (17).

[0013] A fifth aspect is the second or third aspect, wherein in the first operation, undissolved refrigerant exists in the refrigeration oil in the oil reservoir (17).

[0014] In the fifth aspect, a part of the refrigerating machine oil turns white due to the refrigerant that is not dissolved in the refrigerating machine oil.

[0015] A sixth aspect is the refrigerating machine oil according to any one of the first to fifth aspects, wherein the refrigerating machine oil contains polyalkylene glycol (PAG).

[0016] In the sixth aspect, by using polyalkylene glycol (PAG) as the refrigerating machine oil, it is possible to obtain a refrigerating machine oil in which the solubility of the refrigerant is relatively low.

[0017] A seventh aspect is the refrigerating machine oil according to any one of the first to sixth aspects, wherein the refrigerating machine oil contains a polyalkylene glycol (PAG) having a hydroxyl group ratio of 40 mol % or more and 90 mol % or less based on all terminal groups.

[0018] In the seventh aspect, by selecting a PAG having a hydroxyl group ratio within this range, it is possible to improve the slidability of the sliding parts in the compressor (115).

[0019] An eighth aspect is any one of the first to seventh aspects, wherein the refrigerant is a hydrocarbon.

[0020] In the eighth aspect, the solubility of the refrigerating machine oil is relatively low, and therefore the amount of refrigerant sealed in the refrigerant circuit (101) can be reduced.

[0021] FIG. 1 is a piping diagram of a refrigeration system of this embodiment. FIG. 2 is a block diagram showing the relationship between a control unit and various devices. FIG. 3 is a vertical cross-sectional view showing the configuration of a compressor. FIG. 4 shows the results of an investigation into the phenomenon in which refrigeration oil turns white. FIG. 5 shows the results of an investigation into the viscosity of refrigeration oil. FIG. 6 shows the results of an investigation into the wear resistance of refrigeration oil.

[0022] Hereinafter, embodiments of the present invention will be described with reference to the drawings. Note that the following embodiments are essentially preferred examples and are not intended to limit the scope of the present invention, its applications, or its uses. Furthermore, each configuration of the embodiments, modifications, other examples, etc. described below can be combined or partially substituted within the scope of the present invention.

[0023] (1) Overall Configuration of Air Conditioning Apparatus An air conditioner (100) conditions an indoor space. The air conditioner (100) is an example of a refrigeration apparatus. As shown in FIG. 1 , the air conditioner (100) includes an outdoor unit (110), an indoor unit (120), a liquid connection pipe (102), and a gas connection pipe (103). The outdoor unit (110) and the indoor unit (120) are connected to each other via the liquid connection pipe (102) and the gas connection pipe (103). These connection components form a refrigerant circuit (101). The refrigerant circuit (101) is filled with a refrigerant that operates in a vapor compression refrigeration cycle. The refrigerant will be described in detail later. The refrigerant circuit (101) mainly includes a compressor (115), an outdoor heat exchanger (111), an expansion valve (113), an indoor heat exchanger (121), and a four-way selector valve (114).

[0024] (1-1) Outdoor Unit The outdoor unit (110) is installed outdoors and includes a compressor (115), an outdoor heat exchanger (111), an expansion valve (113), a four-way selector valve (114), and an outdoor fan (112).

[0025] The compressor (115) draws in and compresses low-pressure gas refrigerant. The compressor (115) discharges the compressed refrigerant. The compressor (115) is a variable displacement type in which power is supplied to the electric motor from an inverter circuit. In other words, the compressor (115) is configured so that the operating frequency (number of rotations) of the electric motor is adjustable.

[0026] The outdoor heat exchanger (111) exchanges heat between the refrigerant and outdoor air transported by the outdoor fan (112). The outdoor fan (112) transports the outdoor air passing through the outdoor heat exchanger (111).

[0027] The expansion valve (113) reduces the pressure of the refrigerant and is an electrically operated expansion valve whose opening is adjustable.

[0028] The four-way selector valve (114) has a first port (P1), a second port (P2), a third port (P3), and a fourth port (P4). The first port (P1) is connected to the discharge port of the compressor (115). The second port (P2) is connected to the suction port of the compressor (115). The third port (P3) is connected to the gas end of the outdoor heat exchanger (111). The fourth port (P4) is connected to the gas connection pipe (103). The four-way selector valve (114) is switchable between a first state (shown by the solid line in FIG. 1 ) and a second state (shown by the dashed line in FIG. 1 ).

[0029] (1-2) Indoor Unit The indoor unit (120) is installed indoors and mainly includes an indoor heat exchanger (121) and an indoor fan (122).

[0030] The indoor heat exchanger (121) exchanges heat between the refrigerant and indoor air transported by the indoor fan (122). The indoor fan (122) transports outdoor air passing through the outdoor heat exchanger (111).

[0031] The refrigerant circuit (101) operates in a first refrigeration cycle or a second refrigeration cycle depending on the switching of the four-way selector valve (114). The first refrigeration cycle is a refrigeration cycle in which the indoor heat exchanger (121) serves as an evaporator. The second refrigeration cycle is a refrigeration cycle in which the indoor heat exchanger (121) serves as a radiator.

[0032] (1-3) Control Unit As shown in FIG. 2, the air conditioner (100) has a control unit (AC). The control unit (AC) controls the operation of the compressor (115). The control unit (AC) also controls the operation of various devices of the air conditioner (100) (such as the expansion valve (113), indoor fan (122), and outdoor fan (112)). The control unit (AC) is connected to the various devices of the air conditioner (100) by wire or wirelessly, and controls the operation of the various devices. The control unit (AC) has a microcomputer and a memory device that stores software for operating the microcomputer.

[0033] (2) Compressor The compressor (115) of this embodiment is a scroll compressor. The compressor (115) includes a casing (11), a rotary compression mechanism (30), and a drive mechanism (20) that rotationally drives the compression mechanism (30). The compression mechanism (30) and the drive mechanism (20) are housed in the casing (11).

[0034] (2-1) Casing The casing (11) is configured as a vertically elongated cylindrical sealed container with both ends closed. The interior of the casing (11) is divided into upper and lower sections by an upper bearing housing (50) joined to the inner peripheral surface of the casing (11). The space above the upper bearing housing (50) constitutes an upper space portion (15), and the space below the upper bearing housing (50) constitutes a lower space portion (16).

[0035] An oil reservoir (17) is formed at the bottom of the lower space (16) of the casing (11) to store refrigeration oil for lubricating sliding parts of the compressor (115). The oil reservoir (17) is formed when refrigeration oil in the compressor (115) accumulates at the bottom of the casing (11). That is, the amount of refrigeration oil in the oil reservoir (17) varies depending on the environment in the casing (11), the operating state of the compressor, and the like. In the following description, refrigeration oil in a state in which a portion of the refrigerant sealed in the refrigerant circuit (101) is dissolved in or mixed with the refrigeration oil may be simply referred to as refrigeration oil.

[0036] An intake pipe (18) and a discharge pipe (19) are attached to the casing (11). One end of the intake pipe (18) is connected to an intake pipe joint (47). The discharge pipe (19) passes through the body portion (12). The end of the discharge pipe (19) opens into the lower space (16) of the casing (11).

[0037] (2-2) Drive Mechanism The drive mechanism (20) includes a motor (21) and a crankshaft (drive shaft) (23). The motor (21) is accommodated in the lower space (16) of the casing (11). The motor (21) includes a cylindrical stator (21a) and a rotor (21b). The stator (21a) is fixed to the inner circumferential surface of the casing (11).

[0038] A rotor (21b) is disposed in the hollow portion of the stator (21a). A crankshaft (23) is fixed to the hollow portion of the rotor (21b) so as to pass through the rotor (21b), and the rotor (21b) and the crankshaft (23) rotate integrally. The motor (21) is an example of an electric motor.

[0039] (2-3) Compression Mechanism The compression mechanism (30) is a so-called scroll-type compression mechanism including a movable scroll (35), a fixed scroll (40), and an upper bearing housing (50). The upper bearing housing (50) and the fixed scroll (40) are fastened to each other with bolts, and the movable scroll (35) is housed therebetween.

[0040] (2-3-1) Orbiting Scroll The orbiting scroll (35) has a movable end plate (36) having a substantially circular disk shape. A movable wrap (37) is provided upright on the upper surface of the movable end plate (36). The movable wrap (37) is a wall body that extends in a spiral shape radially outward from near the center of the movable end plate (36). In addition, a boss (38) is provided on the lower surface of the movable end plate (36) to protrude therefrom.

[0041] (2-3-2) Fixed Scroll The fixed scroll (40) has a substantially disc-shaped fixed end plate (41). A fixed wrap (42) stands on the underside of the fixed end plate (41). The fixed wrap (42) is a wall body that extends spirally from near the center of the fixed end plate (41) radially outward and is formed to mesh with the movable wrap (37) of the movable scroll (35). A compression chamber (31) is formed between the fixed wrap (42) and the movable wrap (37).

[0042] The fixed scroll (40) has an outer edge portion (43) that extends radially outward from the outermost peripheral wall of the fixed side wrap (42). The lower end surface of the outer edge portion (43) is fixed to the upper end surface of the upper bearing housing (50). The outer edge portion (43) has an opening (44) that opens upward. The outer edge portion (43) has a suction port (34) that connects the interior of the opening (44) to the outermost peripheral end of the compression chamber (31). The suction port (34) opens at the suction position of the compression chamber (31). The above-mentioned suction pipe joint (47) is connected to the opening (44) of the outer edge portion (43).

[0043] A discharge port (32) is formed in the fixed end plate (41) of the fixed scroll (40) near the center of the fixed wrap (42) and penetrates in the vertical direction. The lower end of the discharge port (32) opens at the discharge position of the compression chamber (31). The upper end of the discharge port (32) opens into a discharge chamber (46) defined in the upper part of the fixed scroll (40). Although not shown, the discharge chamber (46) communicates with the lower space (16) of the casing (11).

[0044] (2-4) Upper Bearing Housing The upper bearing housing (50) is formed in a substantially cylindrical shape. The outer peripheral surface of the upper bearing housing (50) is formed so that the upper portion has a larger diameter than the lower portion. The upper portion of this outer peripheral surface is fixed to the inner peripheral surface of the casing (11).

[0045] The upper bearing housing (50) is a member that divides the interior of the casing (11) into upper and lower compartments. The crankshaft (23) is inserted into the hollow portion of the upper bearing housing (50). The hollow portion of the upper bearing housing (50) is divided into a large diameter portion and a small diameter portion. The large diameter portion is located above the small diameter portion. A crank chamber (54), which will be described later, is formed in the large diameter portion. The small diameter portion is the upper bearing portion (53). An upper bearing (62) is attached to the upper bearing portion (53).

[0046] (2-5) Crank Chamber The crank chamber (54) is a space formed by the large diameter portion of the upper bearing housing (50) and the back surface of the movable scroll (35). The boss portion (38) of the movable scroll (35) is located in the crank chamber (54). A pin bearing (61) is attached to the boss portion (38).

[0047] The upper bearing housing (50) is provided with a seal member (55). The seal member (55) is sandwiched between the upper surface of the upper bearing housing (50) and the back surface of the movable scroll (35). The seal member (55) is provided on the upper surface of the upper bearing housing (50) so as to surround the large diameter portion. The seal member (55) separates the crank chamber (54) from the space outside it.

[0048] (2-6) Lower Bearing Housing The lower bearing housing (28) is provided near the lower end of the body portion (12) of the casing (11). A lower bearing housing (28) is fixed to the lower bearing housing (28). A lower bearing (63) is attached to the lower bearing housing (28).

[0049] (2-7) Crankshaft The crankshaft (23) has a main shaft portion (24) and an eccentric portion (25). The main shaft portion (24) extends in the vertical direction. The eccentric portion (25) is provided on the upper end side of the main shaft portion (24). The eccentric portion (25) is formed with a diameter smaller than the maximum diameter of the main shaft portion (24). The axis of the eccentric portion (25) is eccentric by a predetermined distance with respect to the axis of the main shaft portion (24). The eccentric portion (25) is engaged with the pin bearing (61) of the boss portion (38). As a result, the movable scroll (35) revolves in accordance with the rotational driving of the crankshaft (23). The upper end portion of the main shaft portion (24) of the crankshaft (23) is rotatably supported by the upper bearing (62) of the upper bearing portion (53) of the upper bearing housing (50). The lower end portion of the main shaft portion (24) is rotatably supported by a lower bearing (63) of the lower bearing housing (28). The crankshaft (23) is an example of a drive shaft.

[0050] (2-8) Oil Supply Mechanism The compressor (115) has an oil supply mechanism (29) for supplying refrigeration oil from the oil reservoir (17) to the sliding parts. The oil supply mechanism (29) has an oil supply passage (27) and an oil supply nozzle (26).

[0051] The oil supply nozzle (26) extends axially inside the crankshaft (23). The oil supply passage (27) branches off midway along its axial extension toward the pin bearing (61), the upper bearing (62), and the lower bearing (63).

[0052] The oil supply nozzle (26) is provided at the lower end of the crankshaft (23). The suction port (26a) of the oil supply nozzle (26) draws up refrigeration oil from the oil reservoir (17) of the casing (11). The height position of the suction port (26a) is located at the lower part of the oil reservoir (17). The lower part of the oil reservoir (17) refers to a position below the midpoint between the bottom surface of the lower space portion (16) and the level of the refrigeration oil stored in the oil reservoir (17). The oil level of the refrigeration oil is the boundary between the refrigeration oil and the gas containing refrigerant gas in the oil reservoir (17) of the casing (11). The refrigeration oil level varies depending on the environment in the casing (11), the operating state of the compressor (115), and the like. Therefore, the height of the refrigeration oil level defined here may be the highest oil level (i.e., the oil level when the amount of refrigeration oil stored in the casing (11) is at its maximum), the lowest oil level (i.e., the oil level when the amount of refrigeration oil stored in the casing (11) is at its minimum), or the oil level of the oil reservoir (17) at the start of operation of the compressor (115). Furthermore, if it is assumed that the oil reservoir (17) extends up to the upper end of the lower space (16), the height of the refrigeration oil level defined above may be the height of the upper end of the lower space (16). Specifically, in this embodiment, the height of the oil supply nozzle (26) is 1 mm to 30 mm, preferably 10 mm to 20 mm, from the bottom surface of the lower space (16).

[0053] The discharge port of the oil supply nozzle (26) is connected to an oil supply passage (27) provided inside the crankshaft (23). Refrigeration oil is sucked up from the oil reservoir (17) of the casing (11) by the oil supply nozzle (26) and supplied to sliding parts of the compressor (10), such as the pin bearing (61), the upper bearing (62), and the lower bearing (63). The refrigeration oil is mainly used to lubricate the sliding parts of the compressor (115).

[0054] The refrigeration oil supplied from the oil supply passage (27) to the sliding surface between the pin bearing (61) and the eccentric portion (25) flows down by its own weight into the crank chamber (54). Therefore, the pressure in the crank chamber (54) becomes the same as that in the lower space (16) of the casing (11). The pressure in the crank chamber (54) acts on the back surface of the movable scroll (35) and presses the movable scroll (35) against the fixed scroll (40).

[0055] (3) Operation of the Air Conditioning Apparatus (3-1) Cooling Operation In cooling operation, the control unit (AC) sets the four-way switching valve (114) to state 1. In cooling operation, the control unit (AC) operates the compressor (115), the outdoor fan (112), and the indoor fan (122), and adjusts the opening of the expansion valve (113).

[0056] During the cooling operation, the refrigerant circuit (101) performs a refrigeration cycle (cooling cycle) in which the outdoor heat exchanger (111) functions as a radiator and the indoor heat exchanger (121) functions as an evaporator.

[0057] (3-2) Heating Operation In the heating operation, the control unit (AC) sets the four-way switching valve (114) to the second state. In the heating operation, the control unit (AC) operates the compressor (115), the outdoor fan (112), and the indoor fan (122), and adjusts the opening of the expansion valve (113).

[0058] During the heating operation, the refrigerant circuit (101) performs a refrigeration cycle (heating cycle) in which the indoor heat exchanger (121) functions as a radiator and the outdoor heat exchanger (111) functions as an evaporator.

[0059] (4) Refrigerant and Refrigerating Machine Oil (4-1) Refrigerant The refrigerant of this embodiment is a hydrocarbon refrigerant. A hydrocarbon refrigerant is a refrigerant whose main component is a hydrocarbon (hydrocarbon compound). The number of carbon atoms in the hydrocarbon compound that is the main component of the refrigerant is preferably 1 to 8, and more preferably 1 to 5. Examples of hydrocarbon compounds that are the main component of the refrigerant include methane, ethane, propane, n-butane, isobutane, n-pentane, isopentane, ethylene, and propylene. The refrigerant of this embodiment is R290.

[0060] (4-2) Refrigerating Machine Oil The refrigerating machine oil described here does not contain a refrigerant. In this embodiment, a refrigerating machine oil in which a refrigerant is relatively difficult to dissolve is selected. The refrigerating machine oil of this embodiment has a refrigerant solubility of 50 wt% or less. The refrigerant solubility may be 40 wt% or less, or may be 30 wt% or less. Note that, as an example of the refrigerant solubility condition, the refrigerant solubility may be 37 wt% when the refrigerant condensation saturation temperature (Tc) is 65°C and the refrigerant oil temperature is 67°C. A more specific example of the refrigerating machine oil is preferably a refrigerating machine oil in which the refrigerant solubility is 37 wt% when the refrigerant condensation saturation temperature (Tc) is 65°C and the refrigerant oil temperature is 67°C. Note that the refrigerant solubility (wt%) indicates the amount of refrigerant dissolved in the refrigerating machine oil. Specifically, the refrigerant solubility is expressed by the following formula: Refrigerant solubility (wt%) = Weight (wt) of refrigerant in refrigerating machine oil / Weight (wt) of refrigerating machine oil containing refrigerant Here, the weight of refrigerating machine oil containing refrigerant is the sum of the weight of the refrigerant and the weight of the refrigerating machine oil.

[0061] The refrigerating machine oil contains polyalkylene glycol (PAG). PAG is a compound obtained by addition polymerization of alkylene oxide. The refrigerating machine oil contains, for example, polyethylene glycol, polypropylene glycol, or a copolymer compound of polyethylene glycol and polypropylene glycol. The refrigerating machine oil may contain additives (such as an extreme pressure agent, an acid scavenger, or an antioxidant).

[0062] The PAG preferably has a hydroxyl group ratio of 40 mol% or more and 90 mol% or less of all terminal groups. For example, when the PAG is polyethylene glycol (R1-[CH2CHO]m-R2) (R1 is a hydrogen atom, a hydroxyl group (—OH), or a hydrocarbon group or alkoxy group having 1 to 8 carbon atoms, and R2 is a hydrogen atom, or a hydrocarbon group or alkoxy group having 1 to 8 carbon atoms), the terminal groups are R1 and R2. The hydroxyl group ratio is the ratio of the number of R1 and R2 constituting hydroxyl groups to the total number of R1 and R4. When R1 is a hydroxyl group or when R4 is a hydrogen atom, the terminal groups are hydroxyl groups. For example, when a refrigerating machine oil is composed only of composition A, and all R1 contained in the molecules of composition A are hydrocarbon groups and R4 are hydrogen atoms, the terminal groups including R4 are hydroxyl groups, and the hydroxyl group ratio is 50 mol%.

[0063] (5) Lubrication of Sliding Parts by Refrigeration Oil The compressor (115) has a plurality of sliding parts where two members slide against each other. Specifically, the sliding parts include a part where the upper bearing (53) and the crankshaft (23) slide against each other, a part where the lower bearing (63) and the crankshaft (23) slide against each other, and a part where the pin bearing (61) and the crankshaft (23) slide against each other.

[0064] The refrigeration oil conveyed from the oil reservoir (17) by the oil supply mechanism (29) is supplied to the sliding parts, thereby suppressing seizure and wear of the sliding parts. However, the viscosity of the refrigeration oil containing refrigerant varies depending on the solubility of the refrigeration oil, and if the viscosity is too high or too low, the lubrication or sliding properties between two components at the sliding parts may decrease. Therefore, in order to improve the lubrication of the sliding parts, an appropriate viscosity of the refrigerant-containing refrigeration oil is required.

[0065] Here, the viscosity and refrigerant solubility of refrigerant oils vary depending on the type. Therefore, when selecting a refrigerant oil, it is necessary to consider the viscosity of the refrigerant oil in a state where the refrigerant is dissolved or mixed in the refrigerant oil. For example, in a refrigerant oil in which the refrigerant is relatively poorly soluble, the viscosity of the refrigerant oil is relatively high, and the shear resistance of the refrigerant oil at the sliding parts is also high, which may result in reduced sliding properties at the sliding parts. As such, a refrigerant oil in which the refrigerant is relatively poorly soluble is not suitable for use as a lubricating oil for a compressor. In addition, in the case of a refrigerant oil in which the refrigerant is relatively easily soluble, the theoretical refrigerant solubility can be calculated based on the temperature (oil temperature) and pressure of the refrigerant oil in the oil reservoir (17). However, depending on the operating conditions of the air conditioner, the refrigerant solubility may be higher than the theoretical value (i.e., the viscosity may be lower). Therefore, it cannot be said that such a refrigerant oil provides sufficient lubrication to the sliding parts.

[0066] In response to this, the present embodiment employs a refrigeration oil having a refrigerant solubility of 50 wt % or less, and having a higher viscosity at the bottom of the oil reservoir (17) than at the top in a predetermined operating state of the air conditioner (100). This has been found to suppress a decrease in lubricity at the sliding parts. The first operation, which is the predetermined operating state, will now be described.

[0067] (6) First Operation The first operation is an operation in which the viscosity of the refrigeration oil is higher in the lower part than in the upper part of the oil reservoir (17). ２ Over 252 mm ２ In the following, the first operation is an operation in which the circulation rate of the refrigerant flowing into the compressor (115) is 0.3 kg / sec or more and 307 kg / sec or less. In this case, the circulation rate of the refrigerant flowing into the compressor (115) is the amount of refrigerant compressed by the compressor (115) per unit time. The circulation rate of the refrigerant in the first operation is preferably 0.5 kg / sec or more and 250 kg / sec or less, more preferably 2.3 kg / sec or more and 200 kg / sec or less, and even more preferably 3.2 kg / sec or more and 136 kg / sec or less.

[0068] The first operation is an operation in which a plurality of bubbles are generated in at least a portion of the refrigeration oil in the oil reservoir (17), causing the refrigeration oil to turn white. The minimum particle size of the plurality of bubbles is smaller than the inner diameter of the suction port (26a) of the oil supply nozzle (26). In other words, the inner diameter of the suction port (26a) of the oil supply nozzle (26) is larger than the minimum particle size of the plurality of bubbles generated in the refrigeration oil. The first operation is performed by the control unit (AC) controlling the frequency of the compressor (115), the opening of the expansion valve (113), etc.

[0069] The phrase "at least a part of the refrigeration oil turns white" includes a part of the refrigeration oil becoming cloudy. Also, the phrase "a part of the refrigeration oil turns white" includes a change in the refrigeration oil so that it appears white. The phrase "a part of the refrigeration oil turns white" also includes a change in the refrigeration oil in the oil reservoir (17) from a transparent state to a cloudy white state.

[0070] In the first operation, the air conditioner (100) is controlled to operate in a state in which the viscosity of the refrigeration oil is higher in the lower part of the oil reservoir (17) than in the upper part. The reason why the viscosity of the lower part of the oil reservoir (17) is higher than in the upper part is that, when the refrigerant circulation rate increases, the refrigerant dissolved in the refrigeration oil in the oil reservoir (17) is released from the refrigeration oil before it can be uniformly dissolved in the refrigeration oil. This results in a refrigerant concentration that is higher in the upper part of the oil reservoir (17) and lower in the lower part, resulting in a refrigerant solubility gradient. That is, the viscosity of the refrigeration oil in the oil reservoir (17) is higher in the lower part than in the upper part. For example, when the viscosity of the upper part of the oil reservoir (17) is a reference value at a refrigerant pressure of 1.9 MPa and a refrigeration oil temperature of 70°C, the viscosity of the lower part is 10% or more higher than the reference value. Specifically, in the first operation, the viscosity of the lower part is approximately 40% to 60% higher than the reference value.

[0071] (7) Experimental Examples (7-1) Phenomenon of Refrigerating Machine Oil Turning White Differences in the change in refrigerating machine oil depending on the rotation speed of the compressor (115) were investigated. The refrigerant was R290, and the refrigerating machine oil was SUNICE P-60M5 (manufactured by Nippon Sun Oil Co., Ltd.). Although not shown, after the air conditioner (100) started operating, a portion of the refrigerating machine oil became cloudy when the rotation speed of the compressor (115) reached 11 rps.

[0072] FIG. 4 shows the state of the refrigerating machine oil when the air conditioner (100) reaches a steady state. FIG. 4 is a photograph showing the state of the refrigerating machine oil in a level gauge. The steady state is a state in which the temperature and pressure in the compressor (115) are stable and there is a discharge superheat. Specifically, the condensation saturation temperature (Tc), evaporation saturation temperature (Te), subcooling degree (SC), and superheat degree (SH) are Tc = 55°C, Te = 0°C, SC = 5K, and SH = 8K, respectively. As shown in FIG. 4 , it was found that in the steady state, the refrigerating machine oil turned white overall at speeds of 60 rps or higher. At this time, it was found that a viscosity gradient occurred in the oil reservoir (17), with the viscosity increasing from the top to the bottom.

[0073] (7-2) Viscosity of Refrigerating Machine Oil The difference in viscosity of refrigerating machine oil depending on the rotation speed of the compressor (115) was investigated. The refrigerant and refrigerating machine oil were the same as those described above. The rotation speed, theoretical viscosity, and measured viscosity values ​​were determined in a steady state (Tc=50°C, Te=0°C, SC=4K, SH=3K). The theoretical and measured viscosity values ​​can be determined by known methods.

[0074] The ratio of the measured viscosity value to the theoretical value was evaluated. The closer the measured viscosity value is to the theoretical value (i.e., the closer the ratio of the measured viscosity value to the theoretical value is to 1), the smaller the difference between the measured viscosity value and the theoretical value, and the higher the reliability of the actual viscosity (measured viscosity). As shown in Fig. 5, when the rotation speed of the compressor (115) is 40 rps or more, the ratio of the measured viscosity value to the theoretical value is below 2 in all cases, and it is clear that the actual viscosity is not relatively high compared to the theoretical value.

[0075] (7-3) Lubricity of Sliding Parts The wear amount of the sliding parts of the compressor (115) was measured by a sealed Falex wear test. The pins used in the Falex test were made of FC250 cast iron, and the V-block material was made of A390 aluminum alloy. The pins and V-block material were set in the Falex tester as follows. After refrigerant was blown into the V-block material immersed in refrigeration oil, the V-block material was pressed against the pin and the pin was rotated to measure the wear amount of the pin and the V-block material.

[0076] The test conditions are as shown in Figure 6. Specifically, the test conditions were a load of 667 N, a rotation speed of 290 rpm, a refrigeration oil temperature of 80°C, a test time of 60 minutes, and a refrigerant injection rate of 10 liters / minute. The refrigerant used for comparison was R410A, and the refrigeration oil was FVC68D (manufactured by Idemitsu Kosan Co., Ltd.). The test was conducted multiple times, and the wear amounts of the pins and V-block material were measured. As shown in Figure 6, it was found that the refrigeration oil of this embodiment had a lower wear amount than the comparative oil.

[0077] (8) Features (8-1) Feature 1 In the air conditioner (100) of this embodiment, the compressor (115) includes a casing (11), an electric motor (21) arranged in the casing (11), a drive shaft (23) extending along the longitudinal direction of the casing (11) and driven by the electric motor (21), a compression mechanism (30) connected to the drive shaft (23), and an oil supply mechanism (29) that transports refrigeration oil stored in an oil reservoir (17) formed at the bottom of the casing (11) to predetermined sliding parts, and the refrigeration oil contains a refrigerant and refrigeration oil having a refrigerant solubility of 50 wt % or less.

[0078] By selecting a combination of a refrigerant and a refrigerating machine oil (in this case, the refrigerant is not dissolved) that has a refrigerant solubility of 50 wt % or less, it is possible to suppress dissolution of the refrigerant into the refrigerating machine oil and suppress a decrease in viscosity of the refrigerant dissolved in the refrigerating machine oil. As a result, refrigerating machine oil with a suppressed decrease in viscosity is supplied to the sliding parts, ensuring lubrication of the sliding parts.

[0079] (8-2) Feature 2 In this embodiment, the oil supply mechanism (29) is provided with a suction port (26a) that is disposed below the oil reservoir (17) and that draws up refrigeration oil. The air conditioner (100) performs a first operation in which the viscosity of the refrigeration oil is higher in the lower part of the oil reservoir (17) than in the upper part.

[0080] As described above, in the combination of the refrigerant and the refrigeration oil of this embodiment, a viscosity gradient occurs in the oil reservoir (17), and the viscosity of the refrigeration oil in the lower part of the oil reservoir (17) is higher than that in the upper part. Based on this finding, the suction port (26a) of the oil supply mechanism (29) is located in the lower part of the oil reservoir (17). This allows the oil supply mechanism (29) to suck up the refrigeration oil having a relatively high viscosity, thereby ensuring lubrication of the sliding parts.

[0081] In addition, if the refrigerant has a higher specific gravity than the refrigerating machine oil and the refrigerant is not easily soluble in the refrigerating machine oil, the refrigerant and the refrigerating machine oil will separate in the oil reservoir, and the refrigerant will accumulate at the bottom of the oil reservoir. As a result, the suction port (26a) will suck up more refrigerant than the refrigerating machine oil, resulting in poor lubrication of the sliding parts. However, with the combination of refrigerant and refrigerating machine oil in this embodiment, the specific gravity of the refrigerant is not higher than the specific gravity of the refrigerating machine oil, and separation of the refrigerant and the oil reservoir in the oil reservoir (17) is suppressed, thereby preventing the above-mentioned poor lubrication of the sliding parts.

[0082] (8-3) Feature 3 In the air conditioner (100) of this embodiment, the area of ​​the oil surface of the oil reservoir (17) is 141 mm ２ Over 252 mm ２ In the following, a first operation is performed in which the circulation rate of the refrigerant flowing into the compressor (115) is 0.3 kg / sec or more and 307 kg / sec or less.

[0083] This operating condition allows the formation of a viscosity gradient in the oil reservoir (17) such that the viscosity of the refrigeration oil is higher in the lower part than in the upper part.

[0084] (8-4) Feature 4 In the first operation of the present embodiment, a plurality of bubbles are generated in at least a part of the oil reservoir (17), causing the refrigeration oil to turn white, and the minimum particle size of the plurality of bubbles is smaller than the inner diameter of the suction opening (26a). In this state, a viscosity gradient of the refrigeration oil can be formed in the oil reservoir (17), where the viscosity increases from the top to the bottom.

[0085] (8-5) Feature 5: The refrigerating machine oil of this embodiment contains polyalkylene glycol (PAG), which allows for the production of a refrigerant oil with a relatively low solubility.

[0086] (8-6) Feature 6 The refrigerating machine oil of this embodiment contains polyalkylene glycol (PAG) in which the proportion of hydroxyl groups is 40 mol % or more and 90 mol % or less of all terminal groups.

[0087] It has been found that when the hydroxyl group ratio of the refrigerating machine oil is in the range of 40 mol% or less, the amount of wear is high, and as the hydroxyl group ratio of the refrigerating machine oil increases up to 40 mol%, the amount of wear decreases. According to this, in order to sufficiently reduce the amount of wear, it is preferable that the hydroxyl group ratio of the refrigerating machine oil is 40 mol% or more. It has also been confirmed that when the hydroxyl group ratio of the refrigerating machine oil exceeds 90 mol%, the concentration of the refrigerating machine oil in the oil reservoir (17) increases, making it difficult for the refrigerating machine oil to return to the compressor. Therefore, it is preferable that the hydroxyl group ratio of the refrigerating machine oil is 90 mol% or less.

[0088] (8-7) Feature 7 The refrigerant in this embodiment is a hydrocarbon. Since the solubility of the hydrocarbon in refrigeration oil is relatively low, the amount of refrigerant to be sealed in the refrigerant circuit (101) can be reduced.

[0089] (9) Other Embodiments The above embodiment may be configured as follows.

[0090] In the first operation, the refrigerant may be present in the refrigeration oil in the oil reservoir (17) without being dissolved therein. In this manner, the refrigerant is present in the oil reservoir (17) without being dissolved therein and mixed therewith, and thus, a part of the refrigeration oil turns white when the first operation is performed. As a result, a viscosity gradient of the refrigeration oil is formed in the oil reservoir (17), with the viscosity increasing from the top to the bottom.

[0091] The hydrocarbon-based refrigerant may be a refrigerant consisting solely of hydrocarbon compounds, or may be a mixture of a hydrocarbon compound and a refrigerant other than hydrocarbon compounds. Refrigerants other than hydrocarbon compounds include, for example, fluorine-containing refrigerants such as R-134a and carbon dioxide. When the hydrocarbon-based refrigerant contains a refrigerant other than hydrocarbon compounds, the content of the hydrocarbon compounds is 50 wt% or more, 60 wt% or more, 70 wt% or more, 80 wt% or more, or 90 wt% or more. The hydrocarbon-based refrigerant may contain only one type of hydrocarbon compound, or may contain two or more types of hydrocarbon compounds.

[0092] The refrigerating machine oil may be a refrigerant consisting only of PAG, or may be a mixture of PAG and a lubricating oil other than PAG. The lubricating oil other than PAG is, for example, mineral oil or alkylbenzene. When the refrigerating machine oil contains a lubricating oil other than PAG, the PAG content is 50 wt% or more, 60 wt% or more, 70 wt% or more, 80 wt% or more, or 90 wt% or more. The refrigerating machine oil may contain only one type of PAG, or may contain two or more types of PAG.

[0093] When the refrigeration oil is polypropylene glycol (R3-[CH(CH3)CHO]n-R4), the terminal groups are R3 and R4 contained in the chemical formula of polypropylene glycol, and methyl groups contained in the repeating unit [CH(CH3)CHO]n. In this case, the hydroxyl group ratio is the ratio of the number of R3 and R4 constituting hydroxyl groups to the total number of all R3, R4, and methyl groups. When R3 is a hydroxyl group, or when R4 is a hydrogen atom, the terminal group becomes a hydroxyl group. Furthermore, when the refrigeration oil is a copolymer of polyethylene glycol and polypropylene glycol (R5-[CH2CHO]m-[CH(CH3)CHO]n-R6), the terminal groups are R5 and R6 contained in the chemical formula of the copolymer, and methyl groups contained in the repeating unit [CH(CH3)CHO]p. In this case, the hydroxyl group ratio is the ratio of the number of R5 and R6 constituting hydroxyl groups to the total number of all R5, R6, and methyl groups. When R5 is a hydroxyl group or when R6 is a hydrogen atom, the terminal group is a hydroxyl group. R3 and R5 are hydrogen atoms, hydroxyl groups (—OH), or hydrocarbon or alkoxy groups having 1 to 8 carbon atoms, and R4 and R6 are hydrogen atoms, or hydrocarbon or alkoxy groups having 1 to 8 carbon atoms.

[0094] The compressor in the above embodiment may be a rotary or screw compressor.

[0095] In the above embodiment, the first operation may be an operation in which the rotation speed of the compressor (115) is 11 rps or more. At this time, a part of the refrigeration oil in the oil reservoir (17) turns white. In addition, in the first operation, the rotation speed of the compressor (115) may be 15 rps or more, 30 rps or more, 50 rps or more, or 70 rps or more.

[0096] In the above embodiment, the plurality of bubbles generated in the oil reservoir (17) during the first operation are caused by the liquid refrigerant or gas refrigerant present in the refrigeration oil.

[0097] Although the embodiments and modifications have been described above, it will be understood that various modifications in form and detail are possible without departing from the spirit and scope of the claims. Furthermore, the above embodiments and modifications may be combined or substituted as appropriate as long as the functionality of the subject matter of the present disclosure is not impaired. The terms "first" and "second" described above are used to distinguish the terms to which these terms are attached, and do not limit the number or order of the terms.

[0098] INDUSTRIAL APPLICABILITY As described above, the present disclosure is useful for refrigeration devices.

[0099] 11 casing 21 motor (electric motor) 23 crankshaft (drive shaft) 26a suction port 29 oil supply mechanism 30 compression mechanism 100 air conditioning device (refrigeration device) 101 refrigerant circuit 115 compressor

Claims

1. A refrigeration system comprising a refrigerant circuit (101) and a compressor (115) provided in the refrigerant circuit (101) and performing a refrigeration cycle, wherein the compressor (115) comprises a casing (11), an electric motor (21) arranged in the casing (11), a drive shaft (23) extending along the longitudinal direction of the casing (11) and driven by the electric motor (21), a compression mechanism (30) connected to the drive shaft (23), and an oil supply mechanism (29) that transports refrigeration oil stored in an oil reservoir (17) formed in the bottom of the casing (11) to predetermined sliding parts, wherein the refrigeration oil contains a refrigerant and refrigeration oil having a refrigerant solubility of 50 wt % or less.

2. The refrigeration system according to claim 1, wherein the oil supply mechanism (29) is provided with a suction port (26a) disposed in the lower part of the oil reservoir (17) for drawing up the refrigeration oil, and a first operation is performed in which the viscosity of the refrigeration oil is higher in the lower part of the oil reservoir (17) than in the upper part of the oil reservoir (17).

3. The oil surface area of ​​the oil reservoir (17) is 141 mm ２ More than 252 mm ２ The refrigeration system according to claim 1 , wherein a first operation is performed in which a circulation amount of the refrigerant flowing into the compressor (115) is not less than 0.3 kg / sec and not more than 307 kg / sec.

4. The refrigeration system of claim 2 or 3, wherein the first operation is an operation in which a plurality of bubbles are generated in at least a portion of the oil reservoir (17), causing the refrigeration oil to turn white, and a minimum particle size of the plurality of bubbles is smaller than an inner diameter of a suction port (26a) provided in the oil supply mechanism (29) for sucking up the refrigeration oil from the oil reservoir (17).

5. The refrigeration system according to any one of claims 2 to 4, wherein in the first operation, undissolved refrigerant is present in the refrigeration oil in the oil reservoir (17).

6. The refrigeration device according to any one of claims 1 to 5, wherein the refrigeration oil contains polyalkylene glycol (PAG).

7. A refrigeration device according to any one of claims 1 to 6, wherein the refrigeration oil contains polyalkylene glycol (PAG) in which the proportion of hydroxyl groups is 40 mol % or more and 90 mol % or less of all terminal groups.

8. The refrigeration device according to any one of claims 1 to 7, wherein the refrigerant is a hydrocarbon refrigerant.

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