JP6522345B2 - Refrigerating apparatus and sealed electric compressor - Google Patents

Description

  The present invention relates to a refrigeration system and a sealed electric compressor using a heat pump cycle.

  The refrigerants R410A [HFC (Hydrofluorocarbons) 32 / HFC 125 (50/50 wt%)] and R404A [HFC 125 / HFC 143a / HFC 134a (44/52/4 wt%)] used in the refrigeration air conditioning system are GWP (Global Warming). It is urgently necessary to develop a refrigeration air conditioning system using a substitute refrigerant with a low GWP because the Potential is as high as R410A = 1924 and R404A = 3940.

  As this alternative refrigerant, difluoromethane (HFC32) is considered as a candidate because of its thermal physical properties, low GWP, low toxicity, low flammability and the like. Other refrigerants include 2,3,3,3-tetrafluoropropene (HFO1234yf (Hydrofluoroolefin) (GWP = 0), 1,3,3,3-tetrafluoropropene (HFO1234ze) (GWP = 1) or HFO A mixed refrigerant with HFC 32, HFC 125, HFC 134a, etc., a hydrocarbon such as propane or propylene, and a low GWP hydrofluorocarbon such as fluoroethane (HFC 161), difluoroethane (HFC 152a), etc. are mentioned. Difluoromethane (HFC32) is selected from the viewpoints of flammability, air conditioning and heating capacity, equipment efficiency decrease due to temperature gradient of non-azeotropic refrigerant, ease of handling, change of equipment configuration (development), etc., and some air conditioners It has been commercialized

  Refrigerating machine oil for a refrigerating air conditioner is used in a sealed electric compressor, and plays a role of lubricating, sealing, cooling and the like of a sliding portion thereof. The most important characteristic of the refrigeration air for refrigeration air conditioning is compatibility with the refrigerant, and when two-layer separation of the liquid refrigerant and the refrigerator oil occurs in the compressor disposed in the outdoor unit, the liquid separated in each sliding portion The refrigerant may be supplied, which may cause a lubrication failure. Furthermore, during operation of the compressor, refrigeration oil is misted and discharged to the cycle side by mechanical action, but if compatibility is poor, refrigeration oil will stagnate in the low temperature part of the cycle, and the compressor Oil return amount is reduced. In particular, in a packaged air conditioner or a refrigerator, since a pipe constituting a cycle is long, it is necessary to use a refrigerator oil which is excellent in compatibility with a refrigerant. The two-phase separation characteristics of the refrigerant and oil can be evaluated by a two-phase separation temperature curve with respect to the oil concentration. The two-layer separation characteristic on the low temperature side is an upward convex curve, and the upper side of the curve is compatible, and the lower side represents a two-layer separation state. The maximum value of this curve is called the low temperature two-layer separation temperature, and the lower the temperature is, the better the compatibility is. In the case of a packaged air conditioner or refrigerator using difluoromethane as a refrigerant, the low temperature side critical solution temperature needs to be −30 ° C. or less.

  As a refrigeration air conditioner using a refrigeration air for refrigeration air conditioning that is compatible with difluoromethane, there is a refrigeration system using polyvinyl ether oil as opposed to difluoromethane described in Patent Document 1. However, polyvinyl ether oil does not have a low temperature side critical solution temperature with difluoromethane of -30 ° C. or less, and the compatibility is insufficient. Patent documents 2 and 3 disclose compositions using difluoromethane and a polyol ester oil, but chemically stable extreme pressure additives such as tricresyl phosphate do not work effectively. Therefore, it is difficult to suppress the wear of the compressor sliding portion. Furthermore, in a compressor having a rolling bearing for the purpose of increasing the efficiency of the compressor, the fatigue life of the rolling bearing is reduced because the pressure viscosity coefficient of the polyol ester oil is small. In addition, in the aluminum alloying of the scroll wrap for the purpose of reducing the weight of the scroll compressor, there has been a problem that the lap between the wraps is significantly abraded by the tribochemical reaction.

Patent 3956589 JP, 2010-235960, A JP 2002-129178 A

  In package air conditioners and refrigerators, the pipes that make up the cycle are long and the operating environment is low temperature, so two-layer separation occurs in the current combination of difluoromethane and refrigeration oil, and the oil in the low temperature part of the cycle It stagnates and the amount of oil return to the compressor decreases. In addition, since a two-phase separation of difluoromethane liquid and refrigeration oil occurs in the compressor, an oil rich phase with low density is in the upper layer, and a liquid refrigerant rich phase with high density is in the lower layer. A liquid refrigerant rich phase with poor lubricity is supplied to each compressor sliding portion from the filler port, which may cause a lubrication failure. Furthermore, in the structure having a rolling bearing on the compressor rotation shaft, a refrigeration oil having a low pressure viscosity coefficient causes a problem of reducing the rolling fatigue life.

  An object of the present invention is to suppress wear of a compressor sliding member and improve the fatigue life of a rolling bearing in a refrigeration air conditioner and a sealed electric compressor using difluoromethane.

  In order to achieve the above object, for example, the configuration described in the claims is adopted.

  According to the present invention, in the refrigeration air conditioner and the sealed electric compressor using difluoromethane, the wear of the compressor sliding member can be suppressed, and the fatigue life of the rolling bearing can be improved.

It is the schematic which shows the structure of an air conditioner. It is the schematic which shows the structure of a refrigerator. It is a cross-sectional view showing a scroll type hermetic compressor of a refrigeration air conditioning system.

  Hereinafter, a refrigeration air conditioner and a sealed electric compressor according to an embodiment of the present invention will be described.

The sealed type electric compressor used for the above-mentioned refrigeration air conditioning system is provided with a refrigerant compression part which has a sliding part, and encloses difluoromethane and refrigeration oil. Examples of the compressor include a scroll compressor, a rotary compressor, a twin rotary compressor, a two-stage compression rotary compressor, and a swing compressor in which a roller and a vane are integrated. The refrigerant of the example is a difluoromethane having a global warming potential (GWP) of 677, and the refrigeration oil has a pressure viscosity coefficient of 10 GPa ⁻¹ or more. A terminally modified polyalkylene glycol represented by the following chemical formula (1) Among them, R ¹ and R ^{3 each} represent an alkyl group having 1 to 4 carbon atoms, or an acyl group having 2 to 5 carbon atoms, and one of them contains an acyl group, and R ² has 2 to 4 carbon atoms. It is an alkylene group), and the refrigeration oil whose low temperature side critical solution temperature with difluoromethane is -30 ° C or less was enclosed.

[Formula 1] R ^1- (O-R ² ) _n -OR ³ ..... (1)
The terminal modified polyalkylene glycol of refrigeration oil used for the air conditioner and refrigerator of the example has a high viscosity index, so the viscosity grade used differs depending on the type of compressor, but the scroll compressor has a viscosity at 40 ° C. Is preferably in the range of 32 to 68 mm ² / s. In the rotary compressor, the viscosity at 40 ° C. is preferably in the range of 15 to 56 mm ² / s.

  There is no problem at all even if a lubricity improver, an antioxidant, an acid scavenger, an antifoamer, a metal deactivator, etc. are added to the above-mentioned refrigerator oil. An extreme pressure additive is effective as a lubricity improver, and 2.0 wt% or less of a thermochemically stable tertiary phosphate (such as tricresyl phosphate) may be added to the base oil. preferable. As an antioxidant, DBPC (2,6-di-t-butyl-p-cresol) which is a phenol type is preferable. As the acid scavenger, an aliphatic epoxy compound or a carbodiimide compound which is a compound having an epoxy ring is generally used.

  FIG. 1 shows an outline of the air conditioner used in the present embodiment. The air conditioner is composed of an outdoor unit 1 and an indoor unit 2.

  The outdoor unit 1 incorporates a compressor 3, a four-way valve 4, an outdoor heat exchanger 5, expansion means 6 (expansion portion) and an accumulator 8. The compressor 3 is provided with a refrigerant compression unit having a sliding unit built in a motor. Further, the indoor unit 2 incorporates an indoor heat exchanger 7.

  When cooling the room, the high-temperature high-pressure refrigerant gas adiabatically compressed by the compressor 3 passes through the discharge pipe and the four-way valve 4 and is cooled by the outdoor heat exchanger 5 (used as a condensing unit) It becomes a high pressure liquid refrigerant. This refrigerant is expanded by the expansion means 6 (for example, a thermal expansion valve etc.), turns into a low temperature low pressure liquid containing a slight amount of gas, and reaches the indoor heat exchanger 7 (used as an evaporation means). The heat is obtained from the above, and in the state of low temperature gas, it passes through the four-way valve 4 again and then enters the accumulator 8. The low temperature and low pressure liquid refrigerant which can not be evaporated in the indoor heat exchanger is separated in the accumulator 8, and the low temperature and low pressure gas reaches the compressor 3. When the room is heated, the flow of the refrigerant is changed in the reverse direction by the four-way valve 4 to cause the reverse action.

  FIG. 2 shows an outline of the refrigerator used in this example. The refrigerator is composed of an outdoor unit 9 and a cooler unit 10 such as a showcase.

  The outdoor unit 9 incorporates a compressor 11, a condenser 12, a subcooler 13, expansion means 14 and 17 (expansion portion), and an accumulator 16. The compressor 11 is provided with a refrigerant compression unit having a sliding unit and a built-in motor. In addition, the evaporator 15 is incorporated in the cooler unit 10.

  The high-temperature and high-pressure refrigerant gas adiabatically compressed by the compressor 11 is cooled by the condenser 12 through the discharge pipe and becomes a high-pressure liquid refrigerant and is supercooled by the subcooler 13 before the expansion means 14 It is expanded by a thermal expansion valve (for example, a thermal expansion valve), and is sent into the cooler unit 10 as a low-temperature low-pressure liquid containing a slight amount of gas. Then, heat is obtained from the air in the evaporator 15, passes through the accumulator 16 in the state of low temperature gas, and returns to the compressor 11. The compressor for a refrigerator has a refrigerant compression ratio as high as about 10 to 20, and the refrigerant gas tends to have a high temperature. For this purpose, the liquid refrigerant leaving the condenser 12 is branched, and a low-temperature low-pressure liquid containing gas is obtained by the expansion means 17 (for example, capillary tube etc.), and the high-pressure liquid refrigerant in the main system is further cooled by the subcooler 13 After that, it returns to the compressor 11 and makes discharge temperature low.

  As the compressors 3 and 11, a scroll-type hermetic compressor was used. FIG. 3 shows a schematic structure of a scroll-type hermetic compressor.

  The compressors 3 and 11 include a fixed scroll member 19 having a spiral wrap 18 provided perpendicularly to an end plate, a turning scroll member 21 having a wrap 20 having substantially the same shape as the fixed scroll member 19, and It includes a frame 22 for supporting the scroll member 21, a crankshaft 23 for pivotally moving the orbiting scroll member 21, an electric motor 24, and a pressure vessel 25 containing these. The spiral wrap 18 and the wrap 20 are engaged with each other to form a compression mechanism. When the orbiting scroll member 21 is caused to pivot by the crankshaft 23, the compression chamber 26 located on the outermost side among the compression chambers 26 formed between the fixed scroll member 19 and the orbiting scroll member 21 performs a pivoting motion While moving toward the center of the fixed scroll member 19 and the orbiting scroll member 21 while gradually reducing the volume. When the compression chamber 26 reaches near the central portion of the fixed scroll member 19 and the orbiting scroll member 21, the compression chamber 26 communicates with the discharge port 27, and the compressed gas discharged into the pressure vessel 25 is discharged from the discharge pipe 28 to the compressor. It is discharged to the outside of 3, 11.

  In the compressors 3 and 11, the crankshaft 23 is rotated at a constant speed or a rotational speed corresponding to a voltage controlled by an inverter (not shown) to perform a compression operation. Further, an oil reservoir 29 is provided below the electric motor 24, and the oil in the oil reservoir 29 passes through an oil hole 30 provided in the crankshaft 23 due to a pressure difference, and the orbiting scroll member 21 and The lubricant is supplied to the sliding portion with the crankshaft 23, the rolling bearings of the main bearing 31 and the sub bearing 32, and the like.

Examples of the present invention and comparative examples will be described below.
[Examples 1 and 2]
The refrigerating machine oils of Examples 1 and 2 are as follows.
(A) Polyalkylene glycol oil (PAG)
(Polypropylene glycol oil with ethanolyl at both ends)
(B) Polyalkylene glycol oil (PAG)
(Polypropylene glycol oil with ethanoyl and methyloxy groups at both ends)
(Comparative Examples 1 to 7)
(C) Polyalkylene glycol oil (PAG)
(Polypropylene glycol oil with hydroxyl groups at both ends)
(D) Polyalkylene glycol oil (PAG)
(Polypropylene glycol oil with methyloxy group at both ends)
(E) Polyalkylene glycol oil (PAG)
(Polypropylene glycol oil with methyloxy and hydroxyl groups at both ends)
(F) Polyalkylene glycol oil (PAG)
(Polyethylene glycol and polypropylene glycol copolymer oil with methyloxy group at both ends)
(G) Polyvinyl ether oil (PVE)
(Polymer of alkoxy vinyl, ether oil of which alkoxy group is ethyloxy group)
(H) Hindered type polyol ester oil (H-POE)
(A mixed fatty acid ester oil of 2-methylbutanoic acid / 2-ethylhexanoic acid based on pentaerythritol / dipentaerythritol)
(I) Hindered type polyol ester oil (H-POE)
(Dipentaerythritol-based pentanoate / 2-methylbutanoic acid mixed fatty acid ester oil)
(Low temperature side critical solution temperature)
In the refrigeration air conditioning compressor, the refrigerant and the refrigeration oil are enclosed. The compatibility between the refrigerant and the refrigeration oil ensures the oil return from the refrigeration cycle to the compressor (retaining the amount of oil inside the compressor) or the reliability of the compressor such as lubricity and the heat exchange efficiency as described above. It is one of the important characteristics in terms of

  The compatibility evaluation of difluoromethane and a refrigerator oil was measured according to JIS K 2211. The refrigerant was sealed in a pressure resistant glass container at an arbitrary oil concentration, and the contents were observed in the state where the temperature was changed. When the contents were cloudy, it was judged to be two-layer separation, and when it was transparent, it was determined to be dissolution. The oil concentration dependency of the temperature separated into the two layers is generally a curve having a maximum value. This maximum value is defined as the low temperature side critical solution temperature.

(Viscosity pressure coefficient)
The high pressure viscosity at 20 ° C. to 160 ° C. and 1 to 130 MPa was measured using a falling-type high pressure viscometer, and the viscosity pressure coefficient at 60 ° C. was calculated according to the following literature.

Reference: Hata et al., Tribologist, 55 (9), 635 (2010).
(Rolling bearing fatigue life)
The fatigue life of the rolling bearing was evaluated by a uni-steel test at IP 305/79 (The Institute of Petroleum). Rotation speed 1500 / min, load 4800 N, bearing no. Eleven tests were conducted at 51 110, oil amount 150 ml, oil temperature 120 ° C., and fatigue life of the rolling bearing was calculated as average life time by Weibull distribution.

The low temperature side critical solution temperature of each refrigerating machine oil, the viscosity pressure coefficient, and the fatigue average life results of the rolling bearing are shown in Table 1. In Examples 1 and 2, it was found that the rolling bearing fatigue life was over 150 hours when the viscosity pressure coefficient was 13 G Pa ^-1 or more. The low temperature side critical solution temperature required to prevent the decrease in lubricity due to the return of oil from the refrigeration cycle to the compressor or the supply of concentrated refrigerant liquid in the refrigeration air conditioner, and the decrease in heat exchange efficiency of the refrigeration cycle It must be below. In order to satisfy the above-described overall condition of the refrigeration air conditioner and the compressor reliability, the refrigerator oils of the first and second embodiments are required. On the other hand, in Comparative Examples 1 to 7, it was found that one of the characteristics is inferior, and it is found that the refrigerating machine oil for a hermetic compressor using difluoromethane is insufficient.

[Example 3]
In the present embodiment, the package air conditioner 14.0 kW type equipped with the scroll type hermetic compressor described above is subjected to a 3000 hour durability test under high speed and high load conditions. The rotational speed of the compressor was operated at 6000 min ^-1 . A 250 μm heat-resistant PET film (class B 130 ° C.) was used to insulate the core of the motor from the coil, and a double coated copper wire coated with polyesterimide-amideimide was used for the main insulation of the coil. . As a refrigerant, difluoromethane was used, and 4,000 g of it was sealed in the cycle. In the refrigerator oil, 1000 ml of the polyalkylene glycol oil having a kinematic viscosity of 46 mm ² / s at 40 ° C. used in Example 1 was previously sealed in the compressor. This refrigerator oil contains 0.5% by weight of an epoxy acid scavenger as an additive, 0.25% by weight of DBPC (2,6-di-t-butyl-p-cresol) as an acid scavenger, and an extreme pressure As an additive, 1.0% by weight of tricresyl phosphate was blended. After operating the packaged air conditioner in this embodiment for 3000 hours, the mounted scroll-type hermetic compressor was disassembled, and the state of wear and the state of occurrence of flaking of the rolling bearing were examined.

The result of the endurance test using a real machine was as follows. No flaking is observed on the rolling elements of the main bearings and sub bearings of the scroll-type hermetic compressor, and on the raceways of the inner ring and outer ring, and wear of sliding parts such as turning and fixed scroll tips and Oldham rings It turned out that there are very few. Moreover, since the low temperature compatibility with difluoromethane is excellent, a sufficient amount of oil is left inside the compressor after dismantling, and it is presumed that the low temperature compatibility with difluoromethane was excellent. Moreover, as a deterioration judgment of a refrigerating machine oil, the total acid value was measured by a titration method, and the additive residual amount was measured by gas chromatography. The total acid number after the test was 0.01 mg KOH / g and showed the same value as that of the new oil. The residual amount of the acid scavenger was 50% or more, and about 90% of the antioxidant and the extreme pressure additive remained, confirming that there was no problem.
(Comparative example 8)
In addition, as a comparison, a test was performed using the polyol ester oil used in Comparative Example 6 only for the refrigerator oil under the same conditions as in Example 3. The additive of this refrigerator oil is 0.5 wt% of epoxy acid scavenger, 0.25 wt% of DBPC (2,6-di-t-butyl-p-cresol) as acid scavenger, extreme pressure As an additive, 1.0% by weight of tricresyl phosphate was blended.

In Comparative Example 8, flaking marks were found on the inner ring raceway surface of the rolling bearing of the main bearing and the secondary bearing, and the wear of the other sliding parts was further increased. The total acid number after the test also increased to 0.08 mg KOH / g, and the residual amount of the acid scavenger decreased to about 20%.
Example 4
In this embodiment, the fixed scroll member and the orbiting scroll member, and the scroll using the aluminum-silicon eutectic alloy containing aluminum as the main component, containing 10 to 12% silicon having high strength and excellent wear resistance in the frame The same test as in Example 3 was conducted for 500 hours in the closed type compressor. The aluminum silicon alloy member is not subjected to surface treatment.

As a result of this test, in this example, although not subjected to surface treatment, in the aluminum silicon alloy member, large wear resulting from the tribochemical reaction did not progress. In addition, the total acid number of the refrigerator oil did not increase to 0.01 mg KOH / g.
(Comparative example 9)
Further, using the scroll-type hermetic compressor of Example 4, the same refrigerator oil as that of Comparative Example 8 was sealed, and the same test as that of Example 4 was performed.

  In Comparative Example 9, the tribochemical reaction was promoted by the friction between the aluminum silicon members, the wear increased, and the test was interrupted at 72 hours. The total acid number of the refrigerator oil also greatly increased to 0.53 mg KOH / g and the deterioration progressed.

  It has been found that, in the case of the refrigeration oil of the present embodiment described above, when difluoromethane having a small environmental load is used, the wear of the compressor sliding member is suppressed and the fatigue life of the rolling bearing is improved. Furthermore, when an aluminum alloy was used for sliding members, such as a scroll and a frame, it turned out that a tribochemical reaction does not produce easily also by friction of members, and it can control wear of a member. In the scroll, when at least one of the fixed scroll member and the orbiting scroll member is an aluminum alloy, the wear of both can be suppressed. Similar effects were obtained not only in the air conditioner, but also in the refrigerator shown in FIG.

1: outdoor unit 2: indoor unit 3: compressor 4: four-way valve 5: outdoor heat exchanger 6: expansion means 7: indoor heat exchanger 8: accumulator 9: outdoor unit 10: cooler unit 11: cooler unit 11: compressor 12: condensation 13: Subcooler 14: Expansion means 15: Evaporator 16: Accumulator 17: Expansion means 18: Spiral wrap 19: Fixed scroll member 20: Wrap 21: Rotating scroll member 22: Frame 23: Crankshaft 24: Electric motor 25: pressure vessel 26: compression chamber 27: discharge port 28: discharge pipe 29: oil reservoir 29
30: Oil hole 31: Main bearing 32: Secondary bearing

Claims (4)

A sealed electric compressor that sucks and compresses a difluoromethane refrigerant, has a sliding portion, and is sealed with a refrigerator oil, a heat exchanger that dissipates the refrigerant discharged from the compressor, and an outflow from the heat exchanger The refrigeration pressure of the refrigeration oil is 13.2 GPa ⁻ , and the refrigeration system includes a refrigeration cycle that decompresses the refrigerant to be circulated and a heat cycle that circulates through a heat exchanger that absorbs the refrigerant decompressed by the decompression unit. A terminal-modified polyalkylene glycol represented by the following chemical formula (1) which is ¹ or more and 13.5 GPa ^-1 or less, wherein R ¹ and R ^{3 each} represent an alkyl group having 1 to 4 carbon atoms, or 2 to 2 carbon atoms 5 an acyl group, one of which contains an acyl group, R ² is an alkylene group having 2 to 4 carbon atoms), and the low temperature side critical solution temperature of the refrigerant and the refrigerator oil is −30 Refrigeration characterized by being less than Location.
[Formula 1] R ^1- (O-R ² ) _n -OR ³ ..... (1)   The scroll compressor according to claim 1, wherein the compressor is a scroll compressor having a fixed scroll member having a spiral wrap and an orbiting scroll member having a wrap having the same shape as the fixed scroll member. A refrigeration apparatus characterized in that at least one of the scroll members is made of an aluminum alloy. In a sealed electric compressor provided with a refrigerant compression unit having a sliding unit and enclosing difluoromethane as a refrigerant and refrigeration oil, the viscosity pressure coefficient of the refrigeration oil is 13.2 GPa ^-1 or more and 13.5 GPa terminal-modified polyalkylene glycol (wherein represented by ^-1 or less the following chemical formula (1), R ¹ and R ³ is an alkyl group having 1 to 4 carbon atoms, or an acyl group having 2 to 5 carbon atoms And R ² represents an alkylene group having 2 to 4 carbon atoms), and the low-temperature critical solution temperature of the refrigerant and the refrigerator oil is −30 ° C. or less Hermetically sealed electric compressor.
[Formula 1] R ^1- (O-R ² ) _n -OR ³ ..... (1)   The scroll compressor according to claim 3, wherein the scroll compressor includes a fixed scroll member having a spiral wrap and an orbiting scroll member having a wrap having the same shape as that of the fixed scroll member, the fixed scroll member or at least one of the orbiting scroll members. A sealed electric compressor for refrigeration air conditioning characterized in that the aluminum alloy is used.