Refrigeration equipment

Abstract

To suppress deterioration of lubricity of a sliding portion in a compressor.SOLUTION: In a refrigerator, a compressor (115) includes: a casing (11); an electric motor (21) disposed in the casing (11); a drive shaft (23) extending in the longitudinal direction of the casing (11) and driven by the electric motor (21); a compression mechanism (30) coupled to the drive shaft (23); and an oil supply mechanism (29) for conveying a refrigerating machine oil stored in an oil reservoir (17) formed in a bottom part of the casing (11) to a predetermined sliding portion. The refrigerating machine oil includes: a refrigerant; and refrigerating machine oil with 50 wt% of refrigerant solubility.SELECTED DRAWING: Figure 6

Description

[Technical field]

[0001] The present disclosure relates to refrigeration devices. [Background technology]

[0002] The refrigeration device 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 provided in the compressor to detect the refrigerant concentration in the lubricating oil in the oil reservoir, and the oil in the oil separator is returned to the compressor based on the detection value of the sensor. This adjusts the viscosity of the lubricating oil in the sliding parts in the compressor. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] JP 2015-038406 A Summary of the Invention [Problem to be solved by the invention]

[0004] In this way, in order to satisfy reliability such as improving the sliding properties and reducing wear in the sliding parts of 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, the refrigerant will dissolve in a large amount in the refrigeration oil, which may result in a decrease in the viscosity of the refrigeration oil supplied to the sliding parts. Therefore, it is important to select a refrigerant and a refrigeration oil in which the refrigerant is moderately soluble.

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

[0006] The first aspect is a refrigeration system including a refrigerant circuit (101) and a compressor (115) provided in the refrigerant circuit (101) and performing a refrigeration cycle. 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 The casing (11) includes an oil supply mechanism (29) that transports refrigeration oil in an oil reservoir (17) formed at the bottom of the casing (11) to a predetermined sliding portion, and the refrigeration oil contains a refrigerant and a refrigeration oil 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 solubility of the refrigerant is 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 refrigerating machine oil in which the refrigerant is dissolved. As a result, the refrigerating machine oil with a suppressed decrease in viscosity is supplied to the sliding parts, so that the lubrication of the sliding parts can be ensured.

[0008] The second aspect is the first aspect, The oil supply mechanism (29) is provided with a suction port (26a) that is disposed below the oil reservoir (17) and that draws up the refrigeration oil, 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).

[0009] When a refrigerant is combined with a refrigeration oil in which the refrigerant is relatively difficult to dissolve (here, the refrigerant is not dissolved), it takes time for the refrigerant to dissolve uniformly in the refrigeration oil, and as a result, it has been found that there is a difference in the solubility of the refrigerant between the upper and lower parts of the oil reservoir (17). Specifically, in the oil reservoir (17), the solubility of the refrigerant in the refrigeration oil in the lower part is lower than that in the upper part. In other words, 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. In response to this, in the second aspect, the suction port (26a) is disposed in the lower part of the oil reservoir (17), so that the oil supply mechanism (29) can suck up the refrigeration oil with a relatively high viscosity. This ensures lubrication in the sliding parts.

[0010] The third aspect is the first or second aspect, The oil surface area of ​​the oil reservoir (17) is 141 mm 2 More than 252mm 2 In the following, a first operation is performed in which the circulation amount of the refrigerant flowing into the compressor (115) is 0.3 kg / sec or more and 307 kg / sec or less. In the third aspect, this operating condition can form a viscosity gradient in the oil reservoir (17) such that the viscosity of the refrigeration oil is higher in the lower portion than in the upper portion.

[0011] The fourth aspect is the second or third aspect, 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, The minimum particle size of the plurality of bubbles is smaller than the inner diameter of a suction port (26a) that is provided in the oil supply mechanism (29) and that draws up the refrigeration oil from the oil reservoir (17).

[0012] In the fourth mode, 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] The fifth aspect is the second or third aspect, In the first operation, undissolved refrigerant is present 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 any one of the first to fifth aspects, The refrigeration oil contains polyalkylene glycol (PAG).

[0016] In the sixth embodiment, 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 any one of the first to sixth aspects, The refrigerating machine oil contains polyalkylene glycol (PAG) in which the proportion of hydroxyl groups is 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, the slidability of the sliding parts in the compressor (115) can be improved.

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

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

[0021] [Figure 1] FIG. 1 is a piping diagram of a refrigeration system according to this embodiment. [Diagram 2] FIG. 2 is a block diagram showing the relationship between the control unit and various devices. [Diagram 3] FIG. 3 is a vertical cross-sectional view showing the configuration of the compressor. [Figure 4] FIG. 4 shows the results of an investigation into the phenomenon in which refrigeration oil turns white. [Diagram 5] FIG. 5 shows the results of a study on the viscosity of refrigeration oil. [Figure 6] FIG. 6 shows the results of a study on wear resistance due to refrigeration oil. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[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 in which the present invention can be implemented.

[0023] (1) Overall configuration of air conditioning system The air conditioner (100) conditions an indoor space. The air conditioner (100) is an example of a refrigeration device. 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). The connection of these components forms a refrigerant circuit (101). The refrigerant circuit (101) is filled with a refrigerant that performs 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 switching 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 switching 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 of 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 (rotation speed) of the electric motor is adjustable.

[0026] The outdoor heat exchanger (111) exchanges heat between the refrigerant and outdoor air delivered by the outdoor fan (112). The outdoor fan (112) delivers 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 switching 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 portion of the compressor (115). The second port (P2) is connected to the suction portion of the compressor (115). The third port (P3) is connected to the gas end portion of the outdoor heat exchanger (111). The fourth port (P4) is connected to the gas connection pipe (103). The four-way switching valve (114) is switched between a first state (a state indicated by a solid line in FIG. 1) and a second state (a state indicated by a 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 delivered by the indoor fan (122). The indoor fan (122) delivers outdoor air passing through the outdoor heat exchanger (111).

[0031] The refrigerant circuit (101) performs a first refrigeration cycle or a second refrigeration cycle according to switching of the four-way switching 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 section 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), the indoor fan (122), and the 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 rotates 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 a sealed container in the shape of a vertically long cylinder 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 circumferential 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) in the casing (11) to store refrigeration oil for lubricating sliding parts of the compressor (115). The oil reservoir (17) is formed when the 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) and the operating state of the compressor. In the following description, refrigeration oil in a state in which a part 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] A suction pipe (18) and a discharge pipe (19) are attached to the casing (11). One end of the suction pipe (18) is connected to a suction pipe joint (47). The discharge pipe (19) passes through the body portion (12). The other end of the discharge pipe (19) opens into the lower space (16) of the casing (11).

[0037] (2-2) Driving 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 together. 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 that includes 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) Movable scroll The movable scroll (35) has a movable end plate (36) having a substantially circular plate shape. A movable wrap (37) is provided on the upper surface of the movable end plate (36). The movable wrap (37) is a wall body that extends radially outward in a spiral shape from near the center of the movable end plate (36). 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 disk-shaped fixed end plate (41). A fixed wrap (42) stands on the lower surface of the fixed end plate (41). The fixed wrap (42) is a wall body that extends radially outward in a spiral shape from near the center of the fixed end plate (41) 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 continues radially outward from the outermost peripheral wall of the fixed side wrap (42). A lower end surface of the outer edge portion (43) is fixed to an upper end surface of the upper bearing housing (50). An opening portion (44) that opens upward is formed in the outer edge portion (43). A suction port (34) that connects the inside of the opening portion (44) to the outermost peripheral end of the compression chamber (31) is formed in the outer edge portion (43). The suction port (34) opens at a suction position of the compression chamber (31). The above-mentioned suction pipe joint (47) is connected to the opening portion (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 penetrating 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 circumferential 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 the outer circumferential surface is fixed to the inner circumferential 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) Crankcase The crank chamber (54) is a space defined 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 an upper surface of the upper bearing housing (50) and a rear 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 outside space.

[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 (63) 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 to have a diameter smaller than the maximum diameter of the main shaft portion (24). The axis of the eccentric portion (25) is eccentric to the axis of the main shaft portion (24) by a predetermined distance. The eccentric portion (25) engages with the pin bearing (61) of the boss portion (38). As a result, the movable scroll (35) revolves in accordance with the rotational drive of the crankshaft (23). An upper end portion of the main shaft portion (24) of the crankshaft (23) is rotatably supported by an upper bearing (62) of an 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) which supplies refrigeration oil from the oil reservoir (17) to 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 the axis of the oil supply passage (27) 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 oil 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 in the oil reservoir (17) of the casing (11) and a gas containing refrigerant gas. The oil level of the refrigeration oil varies depending on the environment in the casing (11) and the operating state of the compressor (115), and the like. Therefore, the height position of the oil level of the refrigeration oil defined here may be the highest oil level (i.e., the oil level when the amount of the refrigeration oil stored in the casing (11) is at its maximum), the lowest oil level (i.e., the oil level when the amount of the refrigeration oil stored in the casing (11) is at its minimum), or the oil level of the oil reservoir (17) at the start of the operation of the compressor (115). In addition, when it is assumed that the oil reservoir (17) is formed up to the upper end of the lower space (16) at the maximum, the height position of the oil level of the refrigeration oil defined above may be the height position of the upper end of the lower space (16). Specifically, in this embodiment, the height position of the oil supply nozzle (26) is 1 mm to 30 mm, and 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 sucked up from the oil reservoir (17) in the casing (11) by the oil supply nozzle (26) is 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 air conditioning equipment (3-1) Cooling operation In the cooling operation, the control unit (AC) sets the four-way switching valve (114) to the first state. In the cooling operation, the control unit (AC) operates the compressor (115), the outdoor fan (112), and the indoor fan (122) to adjust the opening of the expansion valve (113).

[0056] In 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] In 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) Refrigerants and refrigeration oils (4-1) Refrigerant The refrigerant of this embodiment is a hydrocarbon-based refrigerant. The hydrocarbon-based refrigerant is a refrigerant whose main component is a hydrocarbon (hydrocarbon compound). The carbon number of the hydrocarbon compound that is the main component of the refrigerant is preferably 1-8, more preferably 1-5. Examples of the hydrocarbon compound that is 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 refrigerant oil described here does not contain a refrigerant. In this embodiment, a refrigerant oil in which the refrigerant is relatively difficult to dissolve is selected. The refrigerant oil in 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. An example of the condition of the refrigerant solubility may be that the refrigerant condensation saturation temperature (Tc) is 65°C and the refrigerant solubility is 37 wt% when the refrigerant oil temperature is 67°C. As a more specific example of the refrigerant oil, a refrigerant oil having a refrigerant condensation saturation temperature (Tc) of 65°C and a refrigerant solubility of 37 wt% when the refrigerant oil temperature is 67°C is preferable. The refrigerant solubility (wt%) indicates the amount of refrigerant dissolved in the refrigerant oil. Specifically, the refrigerant solubility is expressed by the following formula. Refrigerant solubility (wt%) = weight of refrigerant in refrigeration oil (wt) / weight of refrigeration oil containing refrigerant (wt) Here, the weight of the refrigerating machine oil containing the refrigerant is the sum of the weight of the refrigerant and the weight of the refrigerating machine oil.

[0061] The refrigeration oil contains polyalkylene glycol (PAG). PAG is a compound obtained by addition polymerization of alkylene oxide. The refrigeration oil contains, for example, polyethylene glycol, polypropylene glycol, or a copolymer compound of polyethylene glycol and polypropylene glycol. The refrigeration oil may contain additives (extreme pressure agents, acid scavengers, antioxidants, etc.).

[0062] The PAG preferably has a hydroxyl group ratio of 40 mol% or more and 90 mol% or less with respect to 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 an alkoxy group having 1-8 carbon atoms, and R2 is a hydrogen atom, or a hydrocarbon group or an alkoxy group having 1-8 carbon atoms), the terminal groups are R1 and R2. The ratio of hydroxyl groups is the ratio of the number of R1 and R2 constituting hydroxyl groups to the number of all R1 and R4. When R1 is a hydroxyl group or R4 is a hydrogen atom, the terminal group is a hydroxyl group. For example, when the refrigeration oil is composed of only composition A, and all R1s contained in the molecules of composition A are hydrocarbon groups and R4 is a hydrogen atom, the terminal group including R4 is a hydroxyl group, and the hydroxyl group ratio is 50 mol%.

[0063] (5) Lubrication of sliding parts with 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 part (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 oil supply mechanism (29) delivers refrigeration oil from the oil reservoir (17) to the sliding parts, thereby preventing the sliding parts from seizing or wearing. 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 solubility of the refrigerant in the refrigerant oil differ depending on the type of refrigerant oil, so when selecting the 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 the case of a refrigerant oil in which the refrigerant is relatively difficult to dissolve, the viscosity of the refrigerant oil is relatively high, while the shear resistance of the refrigerant oil in the sliding parts is also high, and there is a risk that the sliding properties at the sliding parts will decrease. In this way, a refrigerant oil in which the refrigerant is relatively difficult to dissolve 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 easy to dissolve, the theoretical value of the refrigerant solubility can be obtained based on the temperature (oil temperature) and pressure of the refrigerant oil in the oil reservoir (17), but 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), and it cannot be said that the lubrication of the sliding parts of such a refrigerant oil is sufficient.

[0066] In response to this, the present embodiment employs a refrigeration oil whose refrigerant solubility is 50 wt % or less and whose viscosity is higher 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 in 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 of the oil reservoir (17) than in the upper part. In the first operation of this embodiment, the area of ​​the oil surface in the oil reservoir (17) is 141 mm 2 More than 252mm 2 In the following, the operation is such that the amount of refrigerant circulating into the compressor (115) is 0.3 kg / sec or more and 307 kg / sec or less. In this case, the amount of refrigerant circulating into the compressor (115) is the amount of refrigerant compressed by the compressor (115) per unit time. In the first operation, the amount of refrigerant circulating 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 part of the refrigeration oil in the oil reservoir (17), causing the refrigeration oil to turn white. The minimum particle size of the 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 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] "At least a part of the refrigeration oil turns white" includes a part of the refrigeration oil becoming cloudy. Also, "a part of the refrigeration oil turns white" includes the refrigeration oil changing to look white. "A part of the refrigeration oil turns white" also includes the refrigeration oil in the oil reservoir (17) changing from a transparent state to a cloudy white state.

[0070] In the first operation, the air conditioner (100) is controlled to operate in such a way that 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 that of the upper part is that, when the amount of refrigerant circulating increases, the refrigerant dissolved in the refrigeration oil in the oil reservoir (17) is released from the refrigeration oil before it is uniformly dissolved in the refrigeration oil, resulting in a state in which the concentration of the refrigerant is high in the upper part of the oil reservoir (17) and low in the lower part, and thus a gradient in refrigerant solubility is generated. 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) at a refrigerant pressure of 1.9 MPa and the temperature of the refrigeration oil of 70°C is taken as a reference value, 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 about 40% to 60% higher than the reference value.

[0071] (7) Experimental Example (7-1) The phenomenon in which refrigeration oil turns white A study was conducted to examine the difference in the change in refrigeration oil depending on the rotation speed of the compressor (115). The refrigerant was R290, and the refrigeration oil was SUNICE P-60M5 (manufactured by Nippon Sun Oil Co., Ltd.). Although not shown, after the air conditioner (100) started operating, when the rotation speed of the compressor (115) reached 11 rps, part of the refrigeration oil became cloudy.

[0072] FIG. 4 shows the state of the refrigeration oil when the air conditioner (100) is in a steady state. FIG. 4 is a photograph showing the state of the refrigeration 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), degree of subcooling (SC), and degree of superheat (SH) are Tc=55° C., Te=0° C., SC=5K, and SH=8K, respectively. As shown in FIG. 4, it was found that the refrigeration oil turned white overall at 60 rps or more in the steady state. At this time, it was found that a viscosity gradient occurred in the oil reservoir (17) in which the viscosity increased from the top to the bottom.

[0073] (7-2) Viscosity of refrigeration oil The difference in viscosity of refrigeration oil depending on the rotation speed of the compressor (115) was studied. The refrigerant and refrigeration oil were the same as above. The rotation speed, theoretical viscosity value, and actual viscosity value were obtained in a steady state (Tc=50°C, Te=0°C, SC=4K, SH=3K). The theoretical and actual viscosity values ​​can be obtained by known methods.

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

[0075] (7-3) Lubrication in 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 FC250 cast iron, and the V-block material was A390 aluminum alloy. The pins and V-block material were set in the Falex tester as follows. After blowing refrigerant 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 FIG. 6. Specifically, the test conditions are a load of 667N, 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 for comparison is R410A, and the refrigeration oil is FVC68D (manufactured by Idemitsu Kosan Co., Ltd.). The test was carried out multiple times, and the wear amount of the pin and V-block material was measured. As shown in FIG. 6, it was found that the wear amount of the refrigeration oil of this embodiment is smaller than that of the comparison object.

[0077] (8) Features (8-1) Feature 1 In the air conditioning apparatus (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 in the bottom of the casing (11) to predetermined sliding parts, and the refrigeration oil contains a refrigerant and a refrigeration oil having a refrigerant solubility of 50 wt % or less.

[0078] In the combination of the refrigerant and the refrigeration oil (in this case, the refrigerant is not dissolved), by selecting a refrigerant and a refrigeration oil in which the solubility of the refrigerant is 50 wt% or less, the dissolution of the refrigerant into the refrigeration oil can be suppressed, and the viscosity drop of the refrigeration oil in which the refrigerant is dissolved can be suppressed. As a result, the refrigeration oil with a suppressed viscosity drop is supplied to the sliding parts, ensuring the 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 of the oil reservoir (17), based on the finding that the suction port (26a) of the oil supply mechanism (29) is disposed 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 refrigeration oil and the refrigerant is not easily soluble in the refrigeration oil, the refrigerant and the refrigeration oil will separate in the oil pool and the refrigerant will accumulate at the bottom of the oil pool, resulting in the suction port (26a) sucking up more refrigerant than the refrigeration oil, resulting in poor lubrication of the sliding parts. However, with the combination of the refrigerant and the refrigeration oil in the present embodiment, the specific gravity of the refrigerant is not higher than the specific gravity of the refrigeration oil, and separation of the refrigerant and the oil pool in the oil pool (17) is suppressed, thereby making it possible to suppress 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 in the oil reservoir (17) is 141 mm 2 More than 252mm 2 In the following, a first operation is performed in which the circulation rate of the refrigerant flowing into the compressor (115) is not less than 0.3 kg / sec and not more than 307 kg / sec.

[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 port (26a). In this state, a viscosity gradient of the refrigeration oil can be formed in the oil reservoir (17), with the viscosity increasing from the top to the bottom.

[0085] (8-5) Feature 5 The refrigeration oil of the present embodiment contains polyalkylene glycol (PAG), which makes it possible to obtain a refrigeration oil with a relatively low solubility of a refrigerant.

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

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

[0088] (8-7) Feature 7 The refrigerant in this embodiment is a hydrocarbon. Since the solubility of the refrigerant in refrigeration oil is relatively low, the amount of the refrigerant to be charged 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, when the first operation is performed, part of the refrigeration oil turns white. 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 of only a hydrocarbon compound, or may be a mixture of a hydrocarbon compound and a refrigerant other than a hydrocarbon compound. The refrigerant other than a hydrocarbon compound is, for example, a fluorine-containing refrigerant such as R-134a, and carbon dioxide. When the hydrocarbon-based refrigerant contains a refrigerant other than a hydrocarbon compound, the content of the hydrocarbon compound 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 refrigeration oil may be a refrigerant consisting of only PAG, or may be a mixture of PAG and lubricating oil other than PAG. The lubricating oil other than PAG is, for example, mineral oil and alkylbenzene. When the refrigeration oil contains a lubricating oil other than PAG, the content of PAG is 50wt% or more, 60wt% or more, 70wt% or more, 80wt% or more, or 90wt% or more. The refrigeration 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 group is R3, R4, and the methyl group contained in the repeating unit [CH(CH3)CHO]n contained in the chemical formula of polypropylene glycol. In this case, the hydroxyl group ratio is the ratio of the number of R3 and R4 constituting hydroxyl groups to the 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. When the refrigeration oil is a copolymer of polyethylene glycol and polypropylene glycol (R5-[CH2CHO]m-[CH(CH3)CHO]n-R6), the terminal group is R5, R6, and the methyl group contained in the repeating unit [CH(CH3)CHO]p contained in the chemical formula of the copolymer. In this case, the hydroxyl group ratio is the ratio of the number of R5 and R6 constituting hydroxyl groups to the 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. Note that R3 and R5 are hydrogen atoms, hydroxyl groups (-OH), or hydrocarbon groups or alkoxy groups having 1 to 8 carbon atoms, and R4 and R6 are hydrogen atoms, or hydrocarbon groups or alkoxy groups having 1 to 8 carbon atoms.

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

[0095] In the first operation of the above embodiment, the rotation speed of the compressor (115) may be 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 pool (17) during the first operation are due to 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 of form and details are possible without departing from the spirit and scope of the claims. Furthermore, the above embodiments and modifications may be appropriately combined or substituted as long as the functions of the subject of the present disclosure are not impaired. The descriptions "first" and "second" described above are used to distinguish the words to which these descriptions are attached, and do not limit the number or order of the words. [Industrial Applicability]

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

[0099] 1 1 Casing 21 Motor (electric motor) 23 Crankshaft (drive shaft) 26a Intake port 29 Oil supply mechanism 30 Compression Mechanism 100 Air conditioning equipment (refrigeration equipment) 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, 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), and a compression mechanism (30) connected to the drive shaft (23). an oil supply mechanism (29) that transports refrigeration oil stored in an oil reservoir (17) formed at the bottom of the casing (11) to a predetermined sliding portion, the refrigeration oil including a refrigerant and a refrigeration oil having a refrigerant solubility of 50 wt % or less, The oil supply mechanism (29) is disposed below the oil reservoir (17) and is provided with a suction port (26a) for sucking up the refrigeration oil, performing a first operation in which the viscosity of the refrigeration oil is higher in a lower part of the oil reservoir (17) than in an upper part of the oil reservoir (17); 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. Refrigeration equipment.

2. The area of ​​the oil surface of the oil reservoir (17) is 141 mm ２ More than 252 mm ２ In the following, a first operation is performed in which the circulation amount of the refrigerant flowing into the compressor (115) is 0.3 kg / sec or more and 307 kg / sec or less.

2. The refrigeration system of claim 1.

3. 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).

3. A refrigeration system according to claim 1 or 2.

4. In the first operation, the refrigerant that is not dissolved in the refrigeration oil in the oil reservoir (17) is present.

3. A refrigeration system according to claim 1 or 2.

5. The refrigeration oil contains polyalkylene glycol (PAG).

3. A refrigeration system according to claim 1 or 2.

6. The refrigeration 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.

3. A refrigeration system according to claim 1 or 2.

7. The refrigerant is a hydrocarbon refrigerant.

3. A refrigeration system according to claim 1 or 2.

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