JP2016130589A - Freezer and hermetic electric compressor - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a freezer capable of improving the fatigue life of a roller bearing while restricting the abrasion of a compressor slide member in a freezing air conditioner using difluoromethane and a hermetic electric compressor.SOLUTION: In a freezing air conditioner including difluoromethane coolant and ice machine oil, the ice machine oil is terminal denaturation polyalkylene glycol in which the viscosity-pressure coefficient of the ice machine oil is larger than 11 GPaand which is represented by the following chemical formula (1) (in the formula, Rand Rdenote an alkyl group having 1 to 4 carbon atoms or an acyl group having 2 to 5 carbon atoms, any one of them including the acyl group; and Rdenotes an alkylene group having 2 to 4 carbon atoms) and the low-temperature side critical solution temperature of the coolant and the ice machine oil is -30°C or less. The chemical formula (1):R-(O-R)m-OR.SELECTED DRAWING: Figure 3

Description

  The present invention relates to a refrigeration apparatus using a heat pump cycle and a hermetic electric compressor.

  R410A [HFC (Hydrofluorocarbons) 32 / HFC125 (50/50 wt%)] and R404A [HFC125 / HFC143a / HFC134a (44/52/4 wt%)] of refrigerants used in refrigeration and air conditioners are GWP (Global Warming). Since (Potential) is high at R410A = 1924 and R404A = 3940, it is an urgent need to develop a refrigeration air conditioner using an alternative refrigerant with a low GWP.

  As an alternative refrigerant, difluoromethane (HFC32) is a candidate for reasons such as thermophysical properties, low GWP, low toxicity, and low flammability. Other refrigerants include 2,3,3,3-tetrafluoropropene (HFO1234yf (Hydrofluoroolefin) (GWP = 0), 1,3,3,3-tetrafluoropropene (HFO1234ze) (GWP = 1) or HFO Examples include refrigerants mixed with HFC32, HFC125, HFC134a, etc., hydrocarbons such as propane and propylene, and low GWP hydrofluorocarbons such as fluoroethane (HFC161) and difluoroethane (HFC152a). Difluoromethane (HFC32) was selected from the viewpoints of flammability, air conditioning capacity, equipment efficiency decline due to temperature gradient of non-azeotropic refrigerant, ease of handling, equipment configuration change (development), etc. Commercialized

  Refrigerating machine oil for a refrigerating and air-conditioning apparatus is used in a hermetic electric compressor and plays a role of lubrication, sealing, cooling and the like of a sliding portion thereof. The most important characteristic of refrigerating machine oil for refrigerating and air-conditioning is compatibility with refrigerant. When two-layer separation of liquid refrigerant and refrigerating machine oil occurs in a compressor installed in an outdoor unit, the liquid separated into each sliding part There is a concern that the refrigerant will be supplied, resulting in poor lubrication. Furthermore, refrigeration oil is mist-like due to mechanical action during compressor operation, and is discharged to the cycle side. However, if the compatibility is inferior, the refrigeration oil stays at the low temperature part of the cycle, and the compressor oil enters the compressor. The amount of oil return decreases. Particularly in packaged air conditioners and refrigerators, since the pipes constituting the cycle are long, it is necessary to use refrigerator oil having excellent compatibility with the refrigerant. The two-layer separation characteristics of the refrigerant and the oil can be evaluated by a two-layer separation temperature curve with respect to the oil concentration. The two-layer separation characteristic on the low temperature side is an upwardly convex curve, with the upper side of the curve being compatible and the lower side representing the two-layer separation state. The maximum value of this curve is called the low temperature side two-layer separation temperature, and the lower the temperature, the better the compatibility. In a packaged air conditioner or refrigerator using difluoromethane as a refrigerant, the low temperature side critical dissolution temperature needs to be −30 ° C. or lower.

  As a refrigerating and air-conditioning apparatus using a refrigerating machine oil for refrigerating and air conditioning that is compatible with difluoromethane, there is a refrigerating apparatus using polyvinyl ether oil with respect to difluoromethane described in Patent Document 1. However, polyvinyl ether oil does not have a low-temperature side critical dissolution temperature with difluoromethane of -30 ° C. or lower, and the compatibility is insufficient. Patent Documents 2 and 3 disclose compositions using difluoromethane and polyol ester oil, but chemically stable extreme pressure additives such as tricresyl phosphate do not work effectively. For this reason, it is difficult to suppress wear of the sliding portion of the compressor. 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, when the scroll wrap is made of an aluminum alloy for the purpose of reducing the weight of the scroll compressor, there is a problem that the space between the wraps is significantly worn by a tribochemical reaction.

Japanese Patent No. 3956589 JP 2010-235960 A JP 2002-129178 A

  In packaged air conditioners and refrigerators, the pipes that make up the cycle are long and the operating environment is low, resulting in two-layer separation in the current combination of difluoromethane and refrigeration oil. It stays and the amount of oil return to the compressor decreases. Also, the two-layer separation of the difluoromethane liquid and the refrigeration oil occurs in the compressor, and the oil-rich phase with low density is in the upper layer and the liquid refrigerant-rich phase with high density is in the lower layer, so it exists at the bottom of the compressor There is a concern that a liquid refrigerant rich phase with poor lubricity is supplied from the fuel filler opening to each compressor sliding portion, resulting in poor lubrication. Furthermore, in a structure having a rolling bearing on the compressor rotating 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 refrigerating and air-conditioning apparatus and a hermetic 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 a refrigeration air conditioner and a hermetic electric compressor using difluoromethane, 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 sectional drawing which shows the scroll-type hermetic compressor of a refrigerating air conditioner.

  Hereinafter, a refrigerating and air-conditioning apparatus and a hermetic electric compressor according to an embodiment of the present invention will be described.

The hermetic electric compressor used in the above-described refrigerating and air-conditioning apparatus includes a refrigerant compression section having a sliding section, and encloses difluoromethane and refrigerating machine 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 difluoromethane having a global warming potential (GWP) of 677, and the refrigerating machine oil has a terminal-modified polyalkylene glycol represented by the following chemical formula (1) having a pressure viscosity coefficient of 10 GPa ⁻¹ or more (formula R ¹ and R ³ are each an alkyl group having 1 to 4 carbon atoms or an acyl group having 2 to 5 carbon atoms, one of which contains an acyl group, and R ² is an alkyl group having 2 to 4 carbon atoms. Refrigerating machine oil having a low-temperature side critical dissolution temperature with difluoromethane of −30 ° C. or lower was enclosed.

[Chemical formula 1] R ^1- (O-R ² ) _n -OR ³ (1)
The terminal-modified polyalkylene glycol of the refrigerating machine oil used in the air conditioner and refrigerator of the examples has a high viscosity index, so the viscosity grade to be used varies depending on the type of the compressor, but in the scroll compressor, the viscosity at 40 ° C. Is preferably in the range of 32 to 68 mm ² / s. Moreover, in a rotary compressor, the viscosity in 40 degreeC has the preferable range of 15-56 mm < ² > / s.

  Even if a lubricity improver, an antioxidant, an acid scavenger, an antifoaming agent, a metal deactivator, etc. are added to the refrigerating machine oil, there is no problem. As the lubricity improver, extreme pressure additives are effective, and thermochemically stable tertiary phosphates (such as tricresyl phosphate) should be blended to 2.0% by weight or less with respect to the base oil. preferable. As the 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 this embodiment. The air conditioner includes an outdoor unit 1 and an indoor unit 2.

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

  When the room is cooled, the high-temperature and high-pressure refrigerant gas compressed adiabatically by the compressor 3 is cooled by the outdoor heat exchanger 5 (used as a condensing means) through the discharge pipe and the four-way valve 4, It becomes a high-pressure liquid refrigerant. This refrigerant expands in the expansion means 6 (for example, a temperature type expansion valve), becomes a low-temperature low-pressure liquid containing a slight amount of gas, reaches the indoor heat exchanger 7 (used as an evaporation means), and indoor air The heat is obtained from the gas and then passes through the four-way valve 4 again in the state of low-temperature gas before entering the accumulator 8. The low-temperature and low-pressure liquid refrigerant that could not be evaporated by 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, and the reverse action occurs.

  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 includes a compressor 11, a condenser 12, a supercooler 13, expansion means 14 and 17 (expansion part), and an accumulator 16. The compressor 11 includes a refrigerant compression unit having a built-in motor and a sliding portion. The cooler unit 10 includes an evaporator 15.

  The high-temperature and high-pressure refrigerant gas compressed adiabatically by the compressor 11 is cooled by the condenser 12 through the discharge pipe, becomes a high-pressure liquid refrigerant and is supercooled by the subcooler 13, and then the expansion means 14. It expands by (for example, a temperature type expansion valve etc.), becomes a low-temperature / low-pressure liquid slightly containing gas, and is sent into the cooler unit 10. Next, the evaporator 15 obtains heat from the air, 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 high refrigerant compression ratio of about 10 to 20, and the refrigerant gas tends to become high temperature. Therefore, the liquid refrigerant exiting the condenser 12 is branched, a low-temperature and low-pressure liquid containing gas is obtained by the expansion means 17 (for example, a capillary tube), and the high-pressure liquid refrigerant in the main system is further cooled by the subcooler 13. After that, the discharge temperature is lowered by returning to the compressor 11.

  As the compressors 3 and 11, scroll type hermetic compressors were 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 perpendicular to an end plate, a revolving scroll member 21 having a wrap 20 having substantially the same shape as the fixed scroll member 19, and a revolving A frame 22 that supports the scroll member 21, a crankshaft 23 that turns the orbiting scroll member 21, an electric motor 24, and a pressure vessel 25 that incorporates these are included. The spiral wrap 18 and the wrap 20 are engaged with each other so as to form a compression mechanism. When the orbiting scroll member 21 is revolved by the crankshaft 23, the outermost compression chamber 26 among the compression chambers 26 formed between the fixed scroll member 19 and the orbiting scroll member 21 revolves. As the volume is gradually reduced, the fixed scroll member 19 and the orbiting scroll member 21 move toward the center. When the compression chamber 26 reaches the vicinity of the center 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. 3 and 11 are discharged to the outside.

  In the compressors 3 and 11, the crankshaft 23 rotates at a constant speed or a rotational speed corresponding to a voltage controlled by an inverter (not shown) to perform a compression operation. An oil sump 29 is provided below the electric motor 24, and the oil in the oil sump 29 passes through the oil hole 30 provided in the crankshaft 23 due to a pressure difference, and the orbiting scroll member 21. It is supplied to the lubrication of the sliding part with the crankshaft 23, the rolling bearings of the main bearing 31 and the auxiliary 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 ethanoyl groups at both ends)
(B) Polyalkylene glycol oil (PAG)
(Polypropylene glycol oil with ethanoyl group and methyloxy group at both ends)
(Comparative Examples 1-7)
(C) Polyalkylene glycol oil (PAG)
(Polypropylene glycol oil with hydroxyl groups at both ends)
(D) Polyalkylene glycol oil (PAG)
(Polypropylene glycol oil with methyloxy groups 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 oils with methyloxy groups at both ends)
(G) Polyvinyl ether oil (PVE)
(Alkoxy vinyl polymer, ether oil whose alkoxy group is ethyloxy group)
(H) Hindered type polyol ester oil (H-POE)
(Pentaerythritol / dipentaerythritol 2-methylbutanoic acid / 2-ethylhexanoic acid mixed fatty acid ester oil)
(I) Hindered type polyol ester oil (H-POE)
(Dipentaerythritol-based pentanoic acid / 2-methylbutanoic acid mixed fatty acid ester oil)
(Low temperature critical solution temperature)
In the compressor for refrigerating and air-conditioning, refrigerant and refrigerating machine oil are enclosed. As described above, the compatibility between the refrigerant and the refrigeration oil guarantees the reliability of the compressor and the heat exchange efficiency, such as oil return from the refrigeration cycle to the compressor (to ensure the amount of oil inside the compressor) or lubrication. This is one of the important characteristics.

  The compatibility evaluation of difluoromethane and refrigerating machine 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 while the temperature was changed. When the content was cloudy, it was judged as two-layer separation, and when it was transparent, it was judged as dissolved. The oil concentration dependency of the temperature at which the two layers are separated is generally a curve having a maximum value. This maximum value was taken as the low temperature side critical dissolution temperature.

(Viscosity pressure coefficient)
Using a falling body type high-pressure viscometer, the high-pressure viscosity at 20 ° C. to 160 ° C. and 1 to 130 MPa was measured, 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 unisteel test in IP305 / 79 (The Institute of Petroleum). Rotation speed 1500 / min, load 4800N, bearing no. Eleven tests were conducted at 51110, an oil amount of 150 ml, and an oil temperature of 120 ° C., and the fatigue life of the rolling bearing was calculated as an average life time based on the Weibull distribution.

Table 1 shows the low-temperature critical solution temperature, the viscosity pressure coefficient, and the fatigue average life results of rolling bearings for each refrigeration oil. In Examples 1 and 2, the viscosity pressure coefficient was 13 MPa ⁻¹ or more, and it was found that the rolling bearing fatigue average life exceeded 150 hours. In the refrigeration air conditioner, the low-temperature critical solution temperature is -30 ° C., which is necessary for preventing the deterioration of lubricity by returning oil from the refrigeration cycle to the compressor or supplying a high-concentration refrigerant, and for preventing the heat exchange efficiency of the refrigeration cycle from decreasing. Must be: The refrigeration oils of Examples 1 and 2 are necessary to satisfy the refrigeration air conditioner and the compressor reliability in the overall view. On the other hand, in Comparative Examples 1-7, it became a result in which either characteristic is inferior, and it turned out that it is inadequate as a refrigerating machine oil for sealed compressors using difluoromethane.

Example 3
In this example, a 3000-hour endurance test under high speed and high load conditions was performed using a packaged air conditioner 14.0 kW model equipped with the scroll type hermetic compressor described above. The compressor was operated at a rotational speed of 6000 min ⁻¹ . A 250 μm heat-resistant PET film (type B 130 ° C.) was used for the insulation between the motor core and the coil, and a double coated copper wire coated with a polyesterimide-amideimide double coat was used for the main insulation of the coil. . Difluoromethane was used as the refrigerant, and 4000 g was sealed in the cycle. In the refrigerating machine 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 sealed in advance in the compressor. This refrigerating machine oil has 0.5 wt% of an epoxy acid scavenger as an additive, 0.25 wt% of DBPC (2,6-di-t-butyl-p-cresol) as an acid scavenger, 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 occurrence of flaking on the rolling bearing were examined.

The results of the durability test using the actual machine were as follows. There is no flaking on the rolling elements of the main and sub-roller rolling bearings of the scroll type hermetic compressor and the raceway surfaces of the inner and outer rings. It turns out that it is very few. In addition, since the low-temperature compatibility with difluoromethane is excellent, a sufficient amount of oil remains in the compressor after dismantling, and it is estimated that the low-temperature compatibility with difluoromethane was excellent. Further, as a judgment on the deterioration of refrigerating machine oil, the total acid value was measured by a titration method, and the residual amount of additive was measured by gas chromatography. The total acid value after the test was 0.01 mg KOH / g, which was the same value as the new oil. It was confirmed that the remaining amount of the acid scavenger was 50% or more, and about 90% of the antioxidant and the extreme pressure additive remained, and there was no problem.
(Comparative Example 8)
For comparison, a test was conducted using the polyol ester oil used in Comparative Example 6 only for the refrigerating machine oil under the same conditions as in Example 3. The additive for the refrigerating machine oil includes 0.5% by weight of an epoxy acid scavenger, 0.25% by weight of DBPC (2,6-di-t-butyl-p-cresol) as an acid scavenger, and extreme pressure. As an additive, 1.0% by weight of tricresyl phosphate was blended.

In Comparative Example 8, flaking marks were seen on the inner ring raceway surfaces of the rolling bearings of the main bearing and the auxiliary bearing, and the wear of other sliding portions was increased. Further, the total acid value after the test increased to 0.08 mg KOH / g, and the residual amount of the acid scavenger decreased to about 20%.
Example 4
This embodiment is a scroll using a fixed scroll member, an orbiting scroll member, and an aluminum-silicon eutectic alloy containing 10 to 12% of silicon having a high strength and excellent wear resistance in a frame and containing aluminum as a main component. In the closed type compressor, the same test as in Example 3 was performed for 500 hours. This aluminum silicon alloy member is not subjected to surface treatment.

As a result of this test, in the present example, although the surface treatment was not performed, the large wear due to the tribochemical reaction did not progress in the aluminum silicon alloy member. Further, the total acid value of the refrigerating machine oil was not increased to 0.01 mgKOH / g.
(Comparative Example 9)
Further, using the scroll-type hermetic compressor of Example 4, the same refrigerating machine oil as that of Comparative Example 8 was enclosed, and the same test as in Example 4 was performed.

  In Comparative Example 9, the tribochemical reaction was accelerated by friction between the aluminum silicon members, the wear increased, and the test was interrupted in 72 hours. The total acid value of the refrigerating machine oil was greatly increased to 0.53 mgKOH / g, and deterioration was progressing.

  It has been found that the refrigerating machine oil according to the present embodiment suppresses wear of the compressor sliding member and improves the fatigue life of the rolling bearing when difluoromethane having a small environmental load is used. Further, it has been found that when an aluminum alloy is used for a sliding member such as a scroll or a frame, the tribochemical reaction hardly occurs due to friction between members, and wear of the member can be suppressed. In the scroll, if at least one of the fixed scroll member and the orbiting scroll member is an aluminum alloy, both wear 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: compressor 12: condensation Unit 13: Supercooler 14: Expansion means 15: Evaporator 16: Accumulator 17: Expansion means 18: Spiral wrap 19: Fixed scroll member 20: Lap 21: Orbiting 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: Sub bearing

Claims (4)

A hermetic electric compressor that sucks and compresses difluoromethane refrigerant, has a sliding portion, and contains refrigeration oil, a heat exchanger that dissipates the refrigerant discharged from the compressor, and flows out of the heat exchanger In the refrigerating apparatus including a decompressor that decompresses the refrigerant to be cooled and a refrigeration cycle that circulates through a heat exchanger that absorbs the refrigerant decompressed by the decompressor, the viscosity pressure coefficient of the refrigerating machine oil is 11 GPa ⁻¹ or more A terminal-modified polyalkylene glycol represented by the following chemical formula (1), wherein R ¹ and R ³ are alkyl groups having 1 to 4 carbon atoms or acyl groups having 2 to 5 carbon atoms, One side contains an acyl group, and R ² represents an alkylene group having 2 to 4 carbon atoms), and the low-temperature critical solution temperature between the refrigerant and the refrigerating machine oil is −30 ° C. or lower. Refrigeration equipment.
[Chemical formula 1] R ^1- (O-R ² ) _n -OR ³ (1)   2. The scroll compressor according to claim 1, wherein the compressor is a scroll type compressor having a fixed scroll member having a spiral wrap and a turning scroll member having a wrap having the same shape as the fixed scroll member. At least one of the scroll members is made of an aluminum alloy. In a hermetic electric compressor that includes a refrigerant compression part having a sliding part and encloses difluoromethane, which is a refrigerant, and refrigerating machine oil, the refrigerating machine oil has a viscosity-pressure coefficient of 11 GPa ⁻¹ or more and the following chemical formula (1 Terminal-modified polyalkylene glycol represented by the formula (wherein R ¹ and R ³ are alkyl groups having 1 to 4 carbon atoms or acyl groups having 2 to 5 carbon atoms, either of which contains an acyl group) , R ² represents an alkylene group having 2 to 4 carbon atoms), and a low-temperature critical solution temperature between the refrigerant and the refrigerating machine oil is −30 ° C. or lower.
[Chemical formula 1] R ^1- (O-R ² ) _n -OR ³ (1)   4. The scroll compressor according to claim 3, comprising a fixed scroll member having a spiral wrap and a orbiting scroll member having a wrap having the same shape as the fixed scroll member, and at least one of the fixed scroll member or the orbiting scroll member. Is a hermetic electric compressor for refrigerating and air-conditioning, characterized in that is made of an aluminum alloy.