Refrigeration device

Abstract

In a refrigeration device, a compressor (115) is provided with: a casing (11); an electric motor (21) arranged inside the housing (11); a drive shaft (23) that extends in the longitudinal direction of the housing (11) and is driven by the motor (21); a compression mechanism (30) connected to the drive shaft (23); and an oil supply mechanism (29) for conveying the refrigerating machine oil stored in an oil storage part (17) formed at the bottom of the housing (11) to a predetermined sliding part. The refrigerating machine oil contains a refrigerant and refrigerating machine oil having a refrigerant solubility of 50 wt% or less.

Description

Technical Field

[0001] This disclosure relates to a refrigeration device. 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 installed inside the compressor to detect the refrigerant concentration in the lubricating oil in the oil reservoir. Based on the sensor's detection value, the oil in the oil separator is returned to the compressor. This adjusts the viscosity of the lubricating oil in the sliding parts of the compressor.

[0003] Existing technical documents

[0004] Patent documents

[0005] Patent Document 1: Japanese Patent Application Publication No. 2015-038406 Summary of the Invention

[0006] -The technical problem the invention aims to solve-

[0007] Therefore, in order to meet reliability requirements such as improved sliding performance and reduced wear of the sliding parts within the compressor, adjusting the viscosity of the refrigeration oil supplied to the sliding parts is crucial. Specifically, if the refrigerant is easily soluble in the refrigeration oil, a large amount of refrigerant will dissolve into the refrigeration oil. As a result, the viscosity of the refrigeration oil supplied to the sliding parts may decrease. Therefore, selecting a refrigerant and a refrigeration oil that can adequately dissolve the refrigerant is important.

[0008] The purpose of this disclosure is to ensure the lubrication of sliding parts within the compressor, even when using refrigeration oils that are difficult to dissolve in refrigerants.

[0009] - Technical solutions used to solve technical problems -

[0010] The first aspect relates to a refrigeration apparatus comprising a refrigerant circuit 101 and a compressor 115 disposed in the refrigerant circuit 101, the refrigeration apparatus performing a refrigeration cycle. The compressor 115 includes: a housing 11; an electric motor 21 disposed within the housing 11; a drive shaft 23 extending along the length of the housing 11 and driven by the electric motor 21; a compression mechanism 30 connected to the drive shaft 23; and an oil supply mechanism 29 for supplying refrigeration oil from an oil reservoir 17 formed at the bottom of the housing 11 to a predetermined sliding portion, the refrigeration oil containing a refrigerant and refrigeration oil having a refrigerant solubility of 50 wt% or less.

[0011] In the first aspect, in the combination of refrigerant and refrigeration oil (in the undissolved refrigerant state), by selecting a refrigerant and refrigeration oil with a refrigerant solubility of 50 wt% or less, it is possible to suppress the dissolution of refrigerant into the refrigeration oil, thereby suppressing the viscosity reduction of the refrigeration oil containing dissolved refrigerant. Therefore, since refrigeration oil with suppressed viscosity reduction is supplied to the sliding parts, the lubrication of the sliding parts can be ensured.

[0012] Secondly, based on the first aspect, an intake port 26a is provided on the oil supply mechanism 29. The intake port 26a is arranged in the lower part of the oil storage section 17 and draws up the refrigeration oil. The refrigeration device performs a first operation. In the first operation, the viscosity of the refrigeration oil in the lower part of the oil storage section 17 is higher than the viscosity of the refrigeration oil in the upper part of the oil storage section 17.

[0013] As a point of view, it is understood that when a refrigerant is combined with refrigeration oil (in its undissolved state), which is relatively difficult to dissolve in the refrigerant, it takes time for the refrigerant to dissolve uniformly in the refrigeration oil. As a result, 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 refrigerant solubility of the refrigeration oil in the lower part is lower than that in the upper part. In other words, a viscosity gradient is generated in the oil reservoir 17, with the viscosity of the refrigeration oil in the lower part of the oil reservoir 17 being higher than that in the upper part. In contrast, in the second aspect, by arranging the suction port 26a in the lower part of the oil reservoir 17, the oil supply mechanism 29 can draw up the refrigeration oil with higher viscosity. This ensures the lubrication of the sliding parts.

[0014] Thirdly, based on the first or second aspect, the refrigeration device performs a first operation, during which the oil surface area in the oil storage section 17 is 141 mm². 2 Above and 252mm 2 In the following cases, the circulation rate of refrigerant flowing into the compressor 115 is 0.3 kg / s or more and 307 kg / s or less.

[0015] In the third aspect, depending on the operating conditions, a viscosity gradient can be formed in the oil reservoir 17, where the viscosity of the lower refrigeration oil is higher than that of the upper refrigeration oil.

[0016] The fourth aspect is based on the second or third aspect, wherein the first operation is an operation in which multiple bubbles are generated in at least a portion of the oil storage section 17, causing the refrigeration oil to turn white, wherein the minimum particle size of the multiple bubbles is smaller than the inner diameter of the suction port 26a, which is provided on the oil supply mechanism 29 for sucking up the refrigeration oil in the oil storage section 17.

[0017] In the fourth aspect, the refrigeration oil turns white due to multiple air bubbles generated in a portion of the refrigeration oil in the oil reservoir 17. In this state, a viscosity gradient is formed in the vertical direction for the refrigeration oil in the oil reservoir 17.

[0018] The fifth aspect, based on the second or third aspect, is that during the first operation, there is refrigerant in the refrigeration oil that is not dissolved in the oil storage section 17.

[0019] In the fifth aspect, a portion of the refrigeration oil turns white due to the refrigerant that has not dissolved in it.

[0020] The sixth aspect is based on any one of the first to fifth aspects, wherein the refrigeration oil contains polyalkylene glycol (PAG).

[0021] In the sixth aspect, by using polyalkylene glycol (PAG) as refrigeration oil, it is possible to obtain refrigeration oil with low refrigerant solubility.

[0022] The seventh aspect is based on any one of the first to sixth aspects, wherein the refrigeration oil contains polyalkylene glycol (PAG) in a proportion of hydroxyl groups to all terminal groups of 40 mol% or more and 90 mol% or less.

[0023] In the seventh aspect, by selecting PAG with a hydroxyl content falling within the aforementioned range, the sliding properties of the sliding parts within the compressor 115 can be improved.

[0024] The eighth aspect, based on any one of the first to seventh aspects, is that the refrigerant is a hydrocarbon refrigerant.

[0025] In the eighth aspect, since the refrigerant solubility of the refrigeration oil is relatively low, the amount of refrigerant injected into the refrigerant circuit 101 can be reduced. Attached Figure Description

[0026] Figure 1 This is a piping system diagram of the refrigeration device in this embodiment.

[0027] Figure 2 It is a block diagram showing the relationship between the control unit and various devices.

[0028] Figure 3 This is a longitudinal sectional view showing the structure of the compressor.

[0029] Figure 4 The results of a study on the phenomenon of refrigeration oil turning white are shown.

[0030] Figure 5 The results of a study on the viscosity of refrigeration oil are shown.

[0031] Figure 6 The results of a study on the wear resistance of different refrigeration oils are shown. Detailed Implementation

[0032] The embodiments of the present invention will now be described with reference to the accompanying drawings. It should be noted that the following embodiments are essentially preferred examples and are not intended to limit the scope of the present invention, its application, or its uses. The various embodiments, modifications, and other examples described below can be combined or partially substituted within the scope of implementing the present invention.

[0033] (1) Overall structure of the air conditioning unit

[0034] Air conditioning unit 100 regulates the air in an indoor space. Air conditioning unit 100 is an example of a refrigeration unit. Figure 1 As shown, the air conditioning unit 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 interconnected via the liquid connection pipe 102 and the gas connection pipe 103. By connecting them, a refrigerant circuit 101 is formed. The refrigerant circuit 101 is filled with refrigerant that performs a vapor compression refrigeration cycle. Details of the refrigerant will be described 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 reversing valve 114.

[0035] (1-1) Outdoor unit

[0036] The outdoor unit 110 is installed outdoors. The outdoor unit 110 includes a compressor 115, an outdoor heat exchanger 111, an expansion valve 113, a four-way reversing valve 114, and an outdoor fan 112.

[0037] Compressor 115 draws in low-pressure gaseous refrigerant and compresses it. Compressor 115 then discharges the compressed refrigerant. Compressor 115 is a variable-capacity compressor that supplies power to the electric motor from a variable frequency circuit. In other words, compressor 115 is configured to adjust the operating frequency (speed) of the electric motor.

[0038] The outdoor heat exchanger 111 allows outdoor air supplied by the outdoor fan 112 to exchange heat with the refrigerant. The outdoor fan 112 supplies outdoor air that has passed through the outdoor heat exchanger 111.

[0039] Expansion valve 113 reduces the pressure of the refrigerant. Expansion valve 113 is an electrically operated expansion valve with adjustable opening.

[0040] The four-way reversing valve 114 has a first valve port P1, a second valve port P2, a third valve port P3, and a fourth valve port P4. The first valve port P1 is connected to the discharge section of the compressor 115. The second valve port P2 is connected to the suction section of the compressor 115. The third valve port P3 is connected to the gas-side end of the outdoor heat exchanger 111. The fourth valve port P4 is connected to the gas connection pipe 103. In its first state (…), the four-way reversing valve 114… Figure 1 The state shown in solid lines in the middle) and the second state ( Figure 1 Switching between states (shown by dashed lines).

[0041] (1-2) Indoor unit

[0042] The indoor unit 120 is installed indoors. The indoor unit 120 mainly includes an indoor heat exchanger 121 and an indoor fan 122.

[0043] The indoor heat exchanger 121 enables heat exchange between the indoor air delivered by the indoor fan 122 and the refrigerant. The indoor fan 122 delivers indoor air through the indoor heat exchanger 121.

[0044] The refrigerant circuit 101 operates in a first refrigeration cycle and a second refrigeration cycle based on the switching of the four-way reversing valve 114. The first refrigeration cycle uses the indoor heat exchanger 121 as an evaporator. The second refrigeration cycle uses the indoor heat exchanger 121 as a radiator.

[0045] (1-3) Control Department

[0046] like Figure 2 As shown, the air conditioning unit 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 conditioning unit 100 (expansion valve 113, indoor fan 122, outdoor fan 112, etc.). The control unit AC is connected to various devices of the air conditioning unit 100 via wired or wireless means to control the operation of various devices. The control unit AC has a microcomputer and a storage device for storing software used to operate the microcomputer.

[0047] (2) Compressor

[0048] The compressor 115 in this embodiment is a scroll compressor. The compressor 115 includes a housing 11, a rotary compression mechanism 30, and a drive mechanism 20 that drives the compression mechanism 30 to rotate. The compression mechanism 30 and the drive mechanism 20 are housed in the housing 11.

[0049] (2-1) Casing

[0050] The housing 11 is a long, cylindrical, sealed container with both ends sealed. The interior of the housing 11 is divided into upper and lower sections by an upper bearing seat 50 that is joined to the inner circumferential surface of the housing 11. The space above the upper bearing seat 50 constitutes the upper space section 15, and the space below the upper bearing seat 50 constitutes the lower space section 16.

[0051] An oil reservoir 17 is formed at the bottom of the lower space 16 of the housing 11. This oil reservoir 17 stores refrigerant oil that lubricates the sliding parts of the compressor 115. The oil reservoir 17 is formed by storing the refrigerant oil inside the compressor 115 at the bottom of the housing 11. That is, the amount of refrigerant oil in the oil reservoir 17 varies depending on the environment inside the housing 11 and the operating state of the compressor. In the following description, the refrigerant oil, in which a portion of the refrigerant sealed in the refrigerant circuit 101 is dissolved in or mixed with the refrigerant oil, is sometimes simply referred to as refrigerant oil.

[0052] An intake pipe 18 and an exhaust pipe 19 are mounted on the housing 11. One end of the intake pipe 18 is connected to an intake pipe connector 47. The exhaust pipe 19 passes through the torso 12. The end of the exhaust pipe 19 opens in the lower space 16 of the housing 11.

[0053] (2-2) Drive mechanism

[0054] The drive mechanism 20 includes a motor 21 and a crankshaft (drive shaft) 23. The motor 21 is housed within the lower space 16 of the housing 11. The motor 21 includes a stator 21a and a rotor 21b, both formed in a cylindrical shape. The stator 21a is fixed to the inner circumferential surface of the housing 11.

[0055] A rotor 21b is arranged in the hollow portion of the stator 21a. A crankshaft 23 is fixed through the hollow portion of the rotor 21b, and the rotor 21b rotates integrally with the crankshaft 23. The motor 21 is an example of an electric motor.

[0056] (2-3) Compression mechanism

[0057] The compression mechanism 30 is a so-called scroll compression mechanism, which includes a moving scroll 35, a stationary scroll 40, and an upper bearing housing 50. The upper bearing housing 50 and the stationary scroll 40 are fastened together by bolts, and the moving scroll 35 is housed between them.

[0058] (2-3-1) Moving vortex disk

[0059] The moving scroll plate 35 has a generally circular end plate portion 36. A moving scroll 37 is erected on the upper surface of the moving end plate portion 36. The moving scroll 37 is a wall extending radially outward from near the center of the moving end plate portion 36 in a vortex shape. In addition, a flange portion 38 is provided protruding on the lower surface of the moving end plate portion 36.

[0060] (2-3-2) Static vortex disk

[0061] The stationary scroll 40 has a stationary end plate portion 41 that is generally circular. A stationary scroll 42 is erected on the lower surface of the stationary end plate portion 41. The stationary scroll 42 extends radially outward from near the center of the stationary end plate portion 41 in a vortex shape and is formed as a wall that engages with the moving scroll 37 of the moving scroll 35. A compression chamber 31 is formed between the stationary scroll 42 and the moving scroll 37.

[0062] The stationary scroll 40 has an outer edge 43 that extends radially outward from the outermost peripheral wall of the stationary scroll 42. The lower end face of this outer edge 43 is fixed to the upper end face of the upper bearing housing 50. Furthermore, an upward-opening opening 44 is formed on this outer edge 43. A suction port 34, communicating with the interior of this opening 44 to the outermost peripheral end of the compression chamber 31, is formed on the outer edge 43. This suction port 34 opens at the suction position of the compression chamber 31. It should be noted that the aforementioned suction pipe connector 47 is connected to the opening 44 of the outer edge 43.

[0063] An outlet 32 ​​is formed on the stationary end plate portion 41 of the stationary vortex disk 40. The outlet 32 ​​is located near the center of the stationary vortex disk 42 and extends through the stationary end plate portion 41 in a vertical direction. The lower end of the outlet 32 ​​opens at the ejection position of the compression chamber 31. The upper end of the outlet 32 ​​opens toward the ejection chamber 46, which is divided in the upper part of the stationary vortex disk 40. Furthermore, although not shown, the ejection chamber 46 communicates with the lower space portion 16 of the housing 11.

[0064] (2-4) Upper bearing housing

[0065] The upper bearing housing 50 is formed in a generally cylindrical shape. The outer peripheral surface of the upper bearing housing 50 is formed such that the diameter of the upper portion is larger than the diameter of the lower portion. Moreover, the upper portion of this outer peripheral surface is fixed to the inner peripheral surface of the housing 11.

[0066] The upper bearing housing 50 is a component that divides the interior of the housing 11 vertically. A crankshaft 23 is inserted into the hollow portion of the upper bearing housing 50. The hollow portion of the upper bearing housing 50 has a large-diameter section and a small-diameter section. The large-diameter section is positioned higher than the small-diameter section. A crankshaft chamber 54, described later, is formed in the large-diameter section. The small-diameter section is the upper bearing section 53. An upper bearing 62 is installed in the upper bearing section 53.

[0067] (2-5) Crankshaft chamber

[0068] The crankshaft chamber 54 is a space formed by the large-diameter portion of the upper bearing housing 50 and the back of the moving scroll 35. The flange portion 38 of the moving scroll 35 is located inside the crankshaft chamber 54. A pin bearing 61 is installed in the flange portion 38.

[0069] A sealing member 55 is provided on the upper bearing housing 50. The sealing member 55 is sandwiched between the upper surface of the upper bearing housing 50 and the back of the moving scroll plate 35. The sealing member 55 is configured on the upper surface of the upper bearing housing 50 to surround the large-diameter portion. The crankshaft chamber 54 is separated from the space outside by the sealing member 55.

[0070] (2-6) Lower bearing housing

[0071] The lower bearing housing 28 is located near the lower end of the body 12 of the housing 11. A lower bearing 63 is installed in the lower bearing housing 28.

[0072] (2-7) Crankshaft

[0073] The crankshaft 23 has a main shaft portion 24 and an eccentric portion 25. The main shaft portion 24 extends vertically. The eccentric portion 25 is located on the upper end side of the main shaft portion 24. The diameter of the eccentric portion 25 is smaller than the maximum diameter of the main shaft portion 24. The axis of the eccentric portion 25 is offset from the axis of the main shaft portion 24 by a predetermined distance. The eccentric portion 25 engages with the pin bearing 61 of the flange portion 38. In this way, the moving scroll 35 revolves as the crankshaft 23 rotates. The upper end portion of the main shaft portion 24 of the crankshaft 23 is supported by the upper bearing 62 of the upper bearing portion 53 of the upper bearing housing 50 and can rotate. The lower end portion of the main shaft portion 24 is supported by the lower bearing 63 of the lower bearing housing 28 and can rotate. The crankshaft 23 is an example of a drive shaft.

[0074] (2-8) Oil supply mechanism

[0075] The compressor 115 has an oil supply mechanism 29 that supplies refrigeration oil from the oil reservoir 17 to the sliding part. The oil supply mechanism 29 has an oil supply passage 27 and an oil supply nozzle 26.

[0076] The oil supply nozzle 26 extends along the axial direction inside the crankshaft 23. The oil supply passage 27 branches towards the pin bearing 61, the upper bearing 62, and the lower bearing 63 midway along the axial direction.

[0077] The oil supply nozzle 26 is located at the lower end of the crankshaft 23. The suction port 26a of the oil supply nozzle 26 draws up the refrigerant oil from the oil reservoir 17 of the housing 11. 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 lower than the midpoint between the bottom surface of the lower space 16 and the oil level of the refrigerant oil stored in the oil reservoir 17. The oil level of the refrigerant oil is the interface between the refrigerant oil in the oil reservoir 17 of the housing 11 and the gas containing refrigerant gas. It should be noted that since the oil level of the refrigeration oil changes depending on the environment inside the housing 11 and the operating state of the compressor 115, the oil level height defined here can be the highest oil level (i.e., the oil level height when the amount of refrigeration oil stored in the housing 11 is the largest), the lowest oil level (i.e., the oil level height when the amount of refrigeration oil stored in the housing 11 is the smallest), or the oil level height of the oil reservoir 17 when the compressor 115 starts running. Furthermore, assuming that the oil reservoir 17 extends to the upper end of the lower space 16, the oil level height defined above can also be the height of the upper end of the lower space 16. Specifically, in this embodiment, the distance between the height of the oil supply nozzle 26 and the bottom surface of the lower space 16 is 1mm to 30mm, preferably 10mm to 20mm.

[0078] The nozzle 26 is connected to the oil supply passage 27 located inside the crankshaft 23. Refrigeration oil drawn from the oil reservoir 17 of the housing 11 by the nozzle 26 is supplied to the sliding parts of the compressor 115, including the pin bearing 61, upper bearing 62, and lower bearing 63. The refrigeration oil is primarily used to lubricate the sliding parts of the compressor 115.

[0079] The refrigerant oil supplied from the oil supply passage 27 to the sliding surface of the pin bearing 61 and the eccentric portion 25 flows down due to its own weight and into the crankshaft chamber 54. Therefore, the pressure in the crankshaft chamber 54 becomes the same as the pressure in the lower space 16 of the housing 11. Furthermore, the pressure in the crankshaft chamber 54 acts on the back of the moving scroll plate 35, pushing the moving scroll plate 35 towards the stationary scroll plate 40.

[0080] (3) Operation of the air conditioning unit

[0081] (3-1) Refrigeration operation

[0082] During refrigeration operation, the control unit AC sets the four-way reversing valve 114 to its first state. During refrigeration 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.

[0083] The refrigerant circuit 101 in the cooling operation process is a cooling cycle in which the outdoor heat exchanger 111 acts as a radiator and the indoor heat exchanger 121 acts as an evaporator.

[0084] (3-2) Heating Operation

[0085] During heating operation, the control unit AC sets the four-way reversing valve 114 to the second state. During 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.

[0086] The refrigerant circuit 101 in the heating operation process is a cooling cycle in which the indoor heat exchanger 121 acts as a radiator and the outdoor heat exchanger 111 acts as an evaporator.

[0087] (4) Refrigerant and refrigeration oil

[0088] (4-1) Refrigerant

[0089] The refrigerant in this embodiment is a hydrocarbon refrigerant. Hydrocarbon refrigerants are refrigerants whose main component is hydrocarbons (hydrocarbons). The hydrocarbons that are the main components of the refrigerant preferably have 1 to 8 carbon atoms, more preferably 1 to 5. Examples of hydrocarbons that are the main components of the refrigerant include methane, ethane, propane, n-butane, isobutane, n-pentane, isopentane, ethylene, and propylene. The refrigerant in this embodiment is R290.

[0090] (4-2) Refrigeration oil

[0091] The refrigeration oil described herein does not contain refrigerant. In this embodiment, a refrigeration oil with relatively poor refrigerant solubility was selected. The refrigerant solubility of the refrigeration oil in this embodiment is 50 wt% or less. The refrigerant solubility can be 40 wt% or less, or 30 wt% or less. It should be noted that, as one example of the above-mentioned refrigerant solubility conditions, the refrigerant solubility can be 37 wt% when the condensation saturation temperature Tc of the refrigerant is 65°C and the refrigeration oil temperature is 67°C. As a more specific example of the refrigeration oil, a refrigeration oil with a refrigerant solubility of 37 wt% when the condensation saturation temperature Tc of the refrigerant is 65°C and the refrigeration oil temperature is 67°C is preferred. It should be noted that the refrigerant solubility (wt%) represents the amount of refrigerant dissolved in the refrigeration oil. Specifically, the refrigerant solubility is expressed by the following formula.

[0092] Refrigerant solubility (wt%) = Weight of refrigerant in refrigeration oil (wt) / Weight of refrigeration oil containing refrigerant (wt)

[0093] Here, the weight of the refrigeration oil containing refrigerant is the sum of the weight of the refrigerant and the weight of the refrigeration oil.

[0094] Refrigeration oils contain polyalkylene glycols (PAGs). PAGs are compounds obtained by the addition polymerization of alkylene oxides. Refrigeration oils may contain, for example, polyethylene glycol, polypropylene glycol, or copolymers of polyethylene glycol and polypropylene glycol. It should be noted that refrigeration oils may also contain additives (extreme pressure agents, acid scavengers, antioxidants, etc.).

[0095] PAGs are preferably PAGs in which the proportion of hydroxyl groups relative to all terminal groups is 40 mol% or more and 90 mol% or less. For example, in the case of PAGs that are polyethylene glycol (R1-[CH2CH2O]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 proportion of hydroxyl groups is the ratio of the number of R1 and R2 constituting the hydroxyl groups to the total number of R1 and R4. In the case where R1 is a hydroxyl group, or in the case where R4 is a hydrogen atom, the terminal group is a hydroxyl group. For example, in the case where the refrigeration oil is composed only of composition A, and all molecules of composition A contain R1 as a hydrocarbon group and R4 as a hydrogen atom, the terminal group containing R4 is a hydroxyl group, and the hydroxyl group ratio is 50 mol%.

[0096] (5) Regarding the use of refrigeration oil for lubrication of sliding parts

[0097] The compressor 115 has multiple sliding parts in which two components slide against each other. Specifically, the sliding parts include: the part where the upper bearing 53 slides against the crankshaft 23; the part where the lower bearing 63 slides against the crankshaft 23; and the part where the pin bearing 61 slides against the crankshaft 23.

[0098] The refrigeration oil supplied from the oil reservoir 17 via the oil supply mechanism 29 is delivered to the sliding parts, thereby suppressing burning and wear of the sliding parts. However, the viscosity of the refrigerant-containing refrigeration oil varies depending on the refrigerant solubility in the oil. If the viscosity is too high or too low, the lubrication or sliding properties between the two parts of the sliding parts may decrease. Therefore, in order to improve the lubrication of the sliding parts, the refrigerant-containing refrigeration oil needs to have an appropriate viscosity.

[0099] Here, the viscosity and solubility of refrigerant in refrigeration oil vary depending on the type. Therefore, when selecting refrigeration oil, it is necessary to consider the viscosity of the oil in the state where the refrigerant is dissolved in it or mixed with it. For example, when using refrigeration oil with a refrigerant that is difficult to dissolve, the viscosity of the oil is relatively high. On the other hand, the shear resistance of the oil in the sliding parts will also increase, and the sliding properties of the sliding parts may decrease. Thus, refrigeration oil with a refrigerant that is difficult to dissolve is not suitable as a lubricant for the compressor. Furthermore, when using refrigeration oil with a refrigerant that is easy to dissolve, although the theoretical value of the refrigerant solubility can be calculated based on the temperature (oil temperature) and pressure of the oil in the oil reservoir 17, depending on the operating conditions of the air conditioning unit, the refrigerant solubility may sometimes be higher than the theoretical value (i.e., the viscosity is lower). Such refrigeration oil cannot be said to have sufficient lubrication for the sliding parts.

[0100] In this embodiment, a refrigeration oil with a refrigerant solubility of 50 wt% or less is used, and under the specified operating conditions of the air conditioning unit 100, the viscosity of the refrigeration oil at the lower part of the oil reservoir 17 is higher than that at the upper part. Therefore, it is understood that using the aforementioned refrigeration oil can suppress the reduction of lubricity in sliding parts. The first operation, as a specified operating condition, will be described below.

[0101] (6) First operation

[0102] The first operation involves making the viscosity of the refrigeration oil in the lower part of the oil reservoir 17 higher than that in the upper part. In this embodiment, the first operation is performed when the oil surface area of ​​the oil reservoir 17 is 141 mm². 2 Above and 252mm 2 The following operation involves refrigerant circulation rates in the compressor 115 of 0.3 kg / s or more and 307 kg / s or less. In this case, the refrigerant circulation rate in the compressor 115 is the amount of refrigerant compressed by the compressor 115 per unit time. The refrigerant circulation rate during the first operation is preferably 0.5 kg / s or more and 250 kg / s or less, more preferably 2.3 kg / s or more and 200 kg / s or less, and even more preferably 3.2 kg / s or more and 136 kg / s or less.

[0103] The first operation involves the formation of multiple bubbles in at least a portion of the refrigeration oil in the oil reservoir 17, causing it to turn white. The minimum particle size of these multiple bubbles is smaller than the inner diameter of the suction inlet 26a of the oil supply nozzle 26. In other words, the inner diameter of the suction inlet 26a of the oil supply nozzle 26 is larger than the minimum particle size of the multiple bubbles generated in the refrigeration oil. This first operation is performed by controlling the frequency of the compressor 115, the opening degree of the expansion valve 113, etc., via the control unit AC.

[0104] "At least a portion of the refrigeration oil has turned white" includes a situation where a portion of the refrigeration oil becomes cloudy white. Furthermore, "a portion of the refrigeration oil has turned white" includes a situation where the refrigeration oil appears to have turned white. "A portion of the refrigeration oil has turned white" also includes a situation where the refrigeration oil in the oil reservoir 17 changes from a transparent state to producing a cloudy white substance.

[0105] In the first operation, the air conditioning unit 100 is controlled to operate in a state where the viscosity of the refrigerant oil in the lower part of the oil reservoir 17 is higher than that in the upper part. The higher viscosity in the lower part of the oil reservoir 17 is due to the fact that as the refrigerant circulation rate increases, the refrigerant dissolved in the oil reservoir 17 is released from the oil before it can be uniformly dissolved, resulting in a high refrigerant concentration in the upper part of the oil reservoir 17 and a low concentration in the lower part, thus creating a gradient in refrigerant solubility. In other words, the viscosity of the refrigerant oil in the oil reservoir 17 is higher in the lower part than in the upper part. For example, when using the viscosity of the upper part of the oil reservoir 17 at a refrigerant pressure of 1.9 MPa and an oil temperature of 70°C as a reference value, the viscosity of the lower part is more than 10% 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.

[0106] (7) Experimental Example

[0107] (7-1) Regarding the phenomenon of refrigeration oil turning white

[0108] The differences in refrigeration oil changes caused by varying compressor speeds 115 were investigated. The refrigerant was set to R290, and the refrigeration oil was set to SUNICE P-60M5 (manufactured by Taiyo Oil Co., Ltd., Japan). After the air conditioning unit 100 started operating, when the compressor speed 115 reached 11 rpm, a portion of the refrigeration oil was observed to become cloudy white; this was not illustrated.

[0109] Figure 4 The condition of the refrigeration oil is shown when the air conditioning unit 100 is in a stable state. Figure 4 This is a photograph showing the condition of the refrigeration oil in the level gauge. The stable state refers to a state where the temperature and pressure inside compressor 115 are stable, and where there is superheat. Specifically, the condensing saturation temperature Tc, evaporating saturation temperature Te, subcooling degree SC, and superheat degree SH are Tc=55℃, Te=0℃, SC=5K, and SH=8K, respectively. Figure 4 As shown, under stable conditions, the refrigeration oil turns white when the viscosity is above 60 rpm. At this point, a viscosity gradient with increasing viscosity from top to bottom is generated in the oil reservoir 17.

[0110] (7-2) Regarding the viscosity of refrigeration oil

[0111] The viscosity differences of refrigeration oil caused by different compressor speeds (115) were investigated. The refrigerant and refrigeration oil were the same as described above. The theoretical and measured viscosity values ​​for each speed were determined at steady state (Tc=50℃, Te=0℃, SC=4K, SH=3K). The theoretical and measured viscosity values ​​can be obtained using known methods.

[0112] The ratio of measured viscosity values ​​to theoretical values ​​was evaluated. Generally speaking, the closer the measured viscosity is to the theoretical value (i.e., the closer the ratio of measured to theoretical value is to 1), the smaller the difference between the measured and theoretical values, and the higher the reliability of the actual viscosity (measured value). Figure 5 As shown, when the compressor speed is above 40 rpm, the ratio of the measured viscosity to the theoretical viscosity is less than 2. Compared with the theoretical viscosity, the actual viscosity does not increase relatively.

[0113] (7-3) Regarding the lubrication of sliding parts

[0114] The wear of the sliding parts of compressor 115 was measured using a closed Falex wear test. The pin used in the Falex test was made of FC250 cast iron, and the V-block material was A390 aluminum alloy. The pin and V-block material were arranged in the Falex testing machine as shown below. After refrigerant was blown into the V-block material, which was immersed in refrigeration oil, the V-block material was pressed against the pin, and the pin was rotated, thereby measuring the wear of the pin and V-block material.

[0115] Test conditions such as Figure 6 As shown. Specifically, the test conditions were: load of 667 N, rotation speed of 290 rpm, refrigeration oil temperature of 80°C, test time of 60 minutes, and refrigerant injection rate of 10 liters / minute. As a comparison, the refrigerant was R410A, and the refrigeration oil was FVC68D (manufactured by Idemitsu Kosan Co., Ltd.). The test was conducted multiple times, and the wear of the pins and V-blocks was measured. Figure 6 As shown, the wear of the refrigeration oil in this embodiment is reduced compared to the refrigeration oil of the comparison object.

[0116] (8) Characteristics

[0117] (8-1) Feature 1

[0118] In the air conditioning device 100 of this embodiment, the compressor 115 includes: a housing 11; an electric motor 21 arranged in the housing 11; a drive shaft 23 extending along the length direction of the housing 11 and driven by the electric motor 21; a compression mechanism 30 connected to the drive shaft 23; and an oil supply mechanism 29 for supplying refrigeration oil stored in an oil reservoir 17 formed at the bottom of the housing 11 to a predetermined sliding part, wherein the refrigeration oil contains a refrigerant and refrigeration oil with a refrigerant solubility of 50 wt% or less.

[0119] In a combination of refrigerant and refrigeration oil (in its undissolved state), by selecting a refrigerant and refrigeration oil with a refrigerant solubility of 50 wt% or less, it is possible to suppress the dissolution of refrigerant into the refrigeration oil, thereby suppressing the viscosity reduction of the refrigeration oil containing dissolved refrigerant. Therefore, since refrigeration oil with suppressed viscosity reduction is supplied to the sliding parts, the lubrication of the sliding parts can be ensured.

[0120] (8-2) Feature 2

[0121] In this embodiment, an intake port 26a is provided on the oil supply mechanism 29. The intake port 26a is located at the lower part of the oil storage section 17 and draws up the refrigerant oil. During the first operation of the air conditioning unit 100, the viscosity of the refrigerant oil in the lower part of the oil storage section 17 is higher than that in the upper part.

[0122] As described above, in the combination of refrigerant and refrigeration oil in this embodiment, a viscosity gradient is generated in the oil reservoir 17, with the refrigeration oil in the lower part of the oil reservoir 17 having a higher viscosity than the refrigeration oil in the upper part. Based on this understanding, the suction port 26a of the oil supply mechanism 29 is arranged in the lower part of the oil reservoir 17. In this way, the oil supply mechanism 29 can draw up the refrigeration oil with higher viscosity, thereby ensuring the lubrication of the sliding parts.

[0123] Furthermore, if the refrigerant has a higher specific gravity than the refrigeration oil, and the refrigerant is difficult to dissolve in the refrigeration oil, the refrigerant and refrigeration oil will separate in the oil reservoir, and the refrigerant will accumulate in the lower part of the oil reservoir. As a result, more refrigerant is drawn up by the suction port 26a than refrigeration oil, which leads to poor lubrication of the sliding parts. However, according to the combination of refrigerant and refrigeration oil in this embodiment, the specific gravity of the refrigerant is not higher than that of the refrigeration oil, and the separation of refrigerant and refrigeration oil in the oil reservoir 17 is suppressed. Therefore, the poor lubrication of the sliding parts as described above can be suppressed.

[0124] (8-3) Feature 3

[0125] In this embodiment, the air conditioning unit 100 performs a first operation. During this first operation, the oil surface area in the oil reservoir 17 is 141 mm². 2Above and 252mm 2 The following conditions apply: the refrigerant circulation rate flowing into compressor 115 is 0.3 kg / s or more and 307 kg / s or less.

[0126] Under these operating conditions, a viscosity gradient can be formed in the oil reservoir 17, where the viscosity of the lower refrigeration oil is higher than that of the upper refrigeration oil.

[0127] (8-4) Feature 4

[0128] The first operation of this embodiment involves generating multiple bubbles in at least a portion of the oil reservoir 17, causing the refrigeration oil to turn white. The minimum particle size of the multiple bubbles is smaller than the inner diameter of the suction port 26a. In this state, a viscosity gradient of the refrigeration oil, where the viscosity increases from the top to the bottom, can be formed in the oil reservoir 17.

[0129] (8-5) Feature 5

[0130] The refrigeration oil of this embodiment contains polyalkylene glycol (PAG). Therefore, a refrigeration oil with relatively low refrigerant solubility can be obtained.

[0131] (8-6) Feature 6

[0132] The refrigeration oil of this embodiment contains polyalkylene glycol (PAG) in which the proportion of hydroxyl groups to all terminal groups is 40 mol% or more and 90 mol% or less.

[0133] It has been observed that refrigeration oil exhibits high wear when its hydroxyl content is below 40 mol%, and decreases as the hydroxyl content increases to 40 mol%. Therefore, as a condition for sufficiently reducing wear, the hydroxyl content of the refrigeration oil is preferably 40 mol% or higher. Furthermore, it has been confirmed that if the hydroxyl content of the refrigeration oil exceeds 90 mol%, the concentration of the refrigeration oil in the oil reservoir 17 becomes high, making it difficult for the refrigeration oil to return to the compressor. Therefore, the hydroxyl content of the refrigeration oil is preferably 90 mol% or lower.

[0134] (8-7) Feature 7

[0135] In this embodiment, the refrigerant is a hydrocarbon. Since the refrigerant solubility in refrigeration oil is relatively low, the amount of refrigerant injected into the refrigerant circuit 101 can be reduced.

[0136] (9) Other implementation methods

[0137] The above-described implementation can also be configured as follows.

[0138] During the first operation, refrigerant that is not dissolved in the refrigeration oil in the oil reservoir 17 may also be present. Thus, because refrigerant that is not dissolved in the refrigeration oil is mixed with it in the oil reservoir 17, a portion of the refrigeration oil turns white during the first operation. Consequently, a viscosity gradient of the refrigeration oil, where the viscosity increases from top to bottom, is formed in the oil reservoir 17.

[0139] Hydrocarbon refrigerants can be refrigerants composed solely of hydrocarbons, or they can be mixtures of hydrocarbons and other refrigerants. Examples of refrigerants other than hydrocarbons include fluorinated refrigerants such as R-134a and carbon dioxide. When a hydrocarbon refrigerant contains other refrigerants besides hydrocarbons, the hydrocarbon content is 50 wt% or more, 60 wt% or more, 70 wt% or more, 80 wt% or more, or 90 wt% or more. Hydrocarbon refrigerants can contain only one type of hydrocarbon, or they can contain two or more types of hydrocarbons.

[0140] Refrigeration oil can be a refrigerant consisting solely of PAGs, or it can be a mixture of PAGs and lubricants other than PAGs. Examples of lubricants other than PAGs include mineral oils and alkylbenzenes. When refrigeration oil contains lubricants other than PAGs, 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. Refrigeration oil may contain only one type of PAG, or it may contain two or more types of PAGs.

[0141] When the refrigeration oil is polypropylene glycol (R3-[CH(CH3)CH2O]n-R4), the terminal groups are R3, R4, and the methyl group contained in the repeating unit [CH(CH3)CH2O]n, all contained in the chemical formula of polypropylene glycol. In this case, the hydroxyl rate is the proportion of the number of R3 and R4 constituting the hydroxyl group to the total number of R3, R4, and methyl groups. When R3 is a hydroxyl group, or when R4 is a hydrogen atom, the terminal group is a hydroxyl group. Furthermore, when the refrigeration oil is a copolymer of polyethylene glycol and polypropylene glycol (R5-[CH2CH2O]m-[CH(CH3)CH2O]n-R6), the terminal groups are R5, R6, and the methyl group contained in the repeating unit [CH(CH3)CH2O]p, all contained in the chemical formula of the copolymer. In this case, the hydroxyl rate is the proportion of the number of R5 and R6 constituting the hydroxyl group to the total number of 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. It should be noted that R3 and R5 are hydrogen atoms, hydroxyl groups (-OH), or hydrocarbon groups or alkoxy groups with 1 to 8 carbon atoms, and R4 and R6 are hydrogen atoms, or hydrocarbon groups or alkoxy groups with 1 to 8 carbon atoms.

[0142] The compressor in the above embodiments can be a rotary compressor or a screw compressor.

[0143] The first operation of the above embodiment can also be an operation where the compressor 115 rotates at a speed of 11 rpm or higher. At this time, a portion of the refrigerant oil in the oil reservoir 17 turns white. Furthermore, during the first operation, the compressor 115 can rotate at a speed of 15 rpm or higher, 30 rpm or higher, 50 rpm or higher, or 70 rpm or higher.

[0144] In the above embodiment, the multiple bubbles in the oil storage section 17 generated during the first operation are generated by liquid or gaseous refrigerant present in the refrigeration oil.

[0145] The embodiments and modifications have been described above, but it should be understood that various changes can be made to the manner and specific details without departing from the spirit and scope of the claims. Furthermore, the above embodiments and modifications can be appropriately combined or substituted as long as the function of the object of this disclosure is not affected. The terms "first," "second," etc., used above are only used to distinguish statements containing these terms and are not intended to limit the number or order of the statements.

[0146] -Industry Applicability-

[0147] In summary, this disclosure is useful for refrigeration devices.

[0148] - Symbol Explanation -

[0149] 11. Chassis

[0150] 21. Motor (electric motor)

[0151] 23 Crankshaft (Drive Shaft)

[0152] 26a Inlet

[0153] 29. Oil supply organizations

[0154] 30 Compression Mechanism

[0155] 100 Air conditioning unit (refrigeration unit)

[0156] 101 Refrigerant Circuit

[0157] 115 Compressor

Claims

1. A refrigeration device comprising a refrigerant circuit (101) and a compressor (115) disposed in the refrigerant circuit (101), the refrigeration device performing a refrigeration cycle, characterized in that: The compressor (115) includes: a housing (11); an electric motor (21) disposed within the housing (11); a drive shaft (23) extending along the length of the housing (11) and driven by the electric motor (21); a compression mechanism (30) connected to the drive shaft (23); and an oil supply mechanism (29) for supplying refrigeration oil stored in an oil reservoir (17) formed at the bottom of the housing (11) to a predetermined sliding portion. The refrigeration oil contains refrigerant and refrigeration oil with a refrigerant solubility of less than 50 wt%.

2. The refrigeration device according to claim 1, characterized in that: A suction port (26a) is provided on the oil supply mechanism (29). The suction port (26a) is located at the lower part of the oil storage section (17) and draws up the refrigeration oil. The refrigeration device is in its first operation, during which the viscosity of the refrigeration oil in the lower part of the oil storage section (17) is higher than that of the refrigeration oil in the upper part of the oil storage section (17).

3. The refrigeration device according to claim 1, characterized in that: The refrigeration device undergoes a first operation, during which the oil surface area in the oil storage section (17) is 141 mm². 2 Above and 252mm 2 When the refrigerant circulation rate flowing into the compressor (115) is above 0.3 kg / s and below 307 kg / s, the following conditions apply.

4. The refrigeration device according to claim 2 or 3, characterized in that: The first operation is an operation in which multiple bubbles are generated in at least a portion 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 the suction port (26a), which is provided on the oil supply mechanism (29) for drawing up the refrigeration oil in the oil storage section (17).

5. The refrigeration apparatus according to any one of claims 2 to 4, characterized in that: During the first operation, there is refrigerant in the refrigeration oil that is not dissolved in the oil reservoir (17).

6. The refrigeration apparatus according to any one of claims 1 to 5, characterized in that: The refrigeration oil contains polyalkylene glycol.

7. The refrigeration apparatus according to any one of claims 1 to 6, characterized in that: The refrigeration oil contains polyalkylene glycols in which the proportion of hydroxyl groups to all terminal groups is more than 40 mol% and less than 90 mol%.

8. The refrigeration apparatus according to any one of claims 1 to 7, characterized in that: The refrigerant is a hydrocarbon refrigerant.

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