US20090136376A1

US20090136376A1 - Hermetic compressor and refrigeration system

Info

Publication number: US20090136376A1
Application number: US12/327,113
Authority: US
Inventors: Yoichiro Nakamura
Original assignee: Panasonic Corp
Current assignee: Panasonic Corp
Priority date: 2007-06-29
Filing date: 2008-12-03
Publication date: 2009-05-28
Also published as: CN101541931A; WO2009004752A1; EP2044180A1; KR20090023552A

Abstract

As an refrigerating machine oil (108) that is enclosed in a sealed vessel (106) along a motor element (111), and a compression element (112) driven by the motor element (111), oil that has as base oil a carboxylic ester compound whose kinematic viscosity is 6 mm²/s or less at 40 degrees, and 2 mm²/s or less at 100 degrees, and that has one ester group as a chief ingredient is used. Thereby, the extraction force of oligomer contained in an organic material can be suppressed to hold comparatively much oligomer in the oil, and the oligomer can be kept from precipitating, and depositing in a refrigeration system, thereby blocking a refrigerant passage, such as a muffler or piping is suppressed.

Description

REFERENCE TO THE RELATED APPLICATIONS

This application is a continuation of PCT/JP2008/000965, filed on Apr. 14, 2008, which claims priority to Japanese Application No. JP2007-171462, filed on Jun. 29, 2007. The entire contents of these applications are incorporated herein by reference.

BACKGROUND OF THE INVENTION

1. Field of the Invention
The present invention relates to a hermetic compressor and a refrigeration system.
2. Description of the Related Arts
Conventionally, as disclosed in Patent Document 1 or Patent Document 2, the refrigerant used for a refrigeration system using a hermetic compressor is R12 and R134a that are chlorofluocarbon refrigerants. However, since the chlorofluocarbon refrigerants has large ozone depletion potential or global warming potential, hydrocarbon refrigerants, such as R600a and R290, have recently been used as alternatives of the chlorofluocarbon refrigerant. Refrigerating machine oil used for R600a that is a hydrocarbon refrigerant includes Mineral oil, alkylbenzene, ester oil, and the like.
FIG. 8 is a longitudinal sectional view of a conventional hermetic compressor disclosed in Patent Document 1.
In FIG. 8, refrigerant 2 consisting of hydrocarbons is filled in sealed vessel 1, and refrigerating machine oil 3 is reserved at a bottom of the vessel, and motor element 6 composed of stator 4 and rotor 5, and reciprocal compression element 7 driven by the motor element are housed in the sealed vessel. Specifically, R600a that is a hydrocarbon refrigerant is used as refrigerant 2.
Next, the details of compression element 7 will be explained below. Crankshaft 8 is composed of main shaft 9 into which rotor 5 is fixedly press-fitted, and eccentric shaft 10 formed eccentrically from main shaft 9, and a lower end of the crankshaft is provided with oil supply pump 11 that communicates with refrigerating machine oil 3. Cylinder block 12 forms substantially cylindrical bore 13, and bearing 14 that journals main shaft 9.
Piston 15 that is loosely fitted into bore 13 forms compression chamber 16 along with bore 13, and is connected to eccentric shaft 10 via piston pin 17 by connecting rod 18 that is a connecting means. An end face of bore 13 is sealed with valve plate 19.
Head 20 forms a high-pressure chamber, and is fixed to the portion of valve plate 19 opposite bore 13. Muffler 21 is sandwiched by valve plate 19 and head 20.
Suction tube 22 and discharge tube 23 are fixed to sealed vessel 1, and are connected to a refrigeration system (not shown). Suction tube 22 guides refrigerant 2 into sealed vessel 1, and discharge tube 23 delivers refrigerant 2 to the refrigeration system (not shown).
The operation and effects of the hermetic compressor configured as described above will be explained below.
The electric power supplied from a commercial power supply (not shown) is supplied to motor element 6 to rotate rotor 5 of motor element 6, thereby rotating crankshaft 8. By the rotation of crankshaft 8, eccentric motion of the eccentric shaft 10 drives piston 15 via piston pin 17 from connecting rod 18 serving as a connecting means, whereby piston 15 reciprocates in bore 13. Thereby, refrigerant 2 guided into sealed vessel 1 through suction tube 22 from the refrigerating cycle (not shown) is sucked from muffler 21, and is continuously compressed within compression chamber 16. Compressed refrigerant 2 is delivered from discharge tube 23 to the refrigerating cycle.
In such a hermetic compressor, the reliability of the hermetic compressor is improved by using mineral oil, alkylbenzene, or ester oil whose stability against the refrigerant R600a is high and whose compatibility with internal parts is high, as refrigerating machine oil 3.
However, if a low-viscosity refrigerating machine oil whose kinematic viscosity is 6 mm²/s or less at 40 degrees centigrade (hereinafter referred to as degrees), and 2 mm²/s or less at 100 degrees is applied as the above conventional refrigerating machine oil 3 in order to reduce the friction loss of a sliding portion, molecules that constitute the refrigerating machine oil become small relatively. Therefore, it is considered that an organic material is used for elements (hereinafter referred to as the inside of the hermetic compressor) that constitute the inside of the hermetic compressor. However, if an organic material is used for the inside of the hermetic compressor, the refrigerating machine oil easily permeates through an organic material, and oligomer is easily extracted. Meanwhile, it is difficult to completely remove the oligomer ingredient contained in such an organic material.
Particularly if a polyester-based organic material is used, and in a case where mineral oil is used as refrigerating machine oil 3, the amount of oligomer that can be held in refrigerating machine oil 3 is little, and there is a possibility that the oligomer may deposit, thereby deteriorating the capability of the hermetic compressor or the refrigeration system, and damaging the reliability thereof.
Further, in a case where alkylbenzene is used as refrigerating machine oil 3, and in a case where a material having a benzene ring in a skeleton texture, such as polyester or polyphenylene sulfide, is used as the organic material, the amount of extraction of oligomer may increase. As a result, there is a possibility that the oligomer may deposit, thereby deteriorating the capability of the hermetic compressor or the refrigeration system, and damaging the reliability thereof.
Further, in a case where ester oil is used as refrigerating machine oil 3, divalent to tetravalent ester oils are often used from the viewpoint of wear resistance.
If a polyester-based organic material having the same ester binding is used, the extraction force of the oligomer becomes large. As a result, there is a possibility that the oligomer may precipitate and deposit in a refrigerant passage, thereby deteriorating the capability of the hermetic compressor or the refrigeration system, and damaging the reliability thereof.
Patent Document 1: Japanese Patent Unexamined Publication No.
Patent Document 2: Japanese Patent Unexamined Publication No.

DISCLOSURE OF THE INVENTION

The invention solves the above-mentioned conventional problems, and realizes a high reliable hermetic compressor.
In the hermetic compressor of the invention, the refrigerating machine oil has as base oil a carboxylic ester compound whose kinematic viscosity is 6 mm²/s or less at 40 degrees, and 2 mm²/s or less at 100 degrees, and is composed of a carboxylic ester compound that has one ester group expressed by Formula 1 as a chief ingredient.
—COOR1 [Chem. 1]
(In the Above Formula, R1 Represents Hydrocarbon Radical)
This makes it possible to reduce the amount of precipitation of oligomer contained in an organic material, and keep the oligomer from blocking piping or a muffler inlet port, thereby realizing a high efficient and high reliable hermetic compressor.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a schematic diagram of a refrigeration system in Embodiment 1 of the invention;

FIG. 2 is a longitudinal sectional view of the hermetic compressor in this embodiment;

FIG. 3 is a schematic diagram of a refrigeration system in Embodiment 2 of the invention;

FIG. 4 is a longitudinal sectional view of a hermetic compressor of Embodiment 2 of the invention;

FIG. 5 is a sectional view taken along a line 5-5 of FIG. 4;

FIG. 6 is an enlarged view of a portion B of FIG. 5;

FIG. 7 is an enlarged view of a portion C of FIG. 6; and

FIG. 8 is a longitudinal sectional view of a conventional hermetic compressor.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

A hermetic compressor of the invention includes a sealed vessel that reserves refrigerating machine oil, and houses a motor element, and a compression element driven by the motor element. The compression element compresses a refrigerant that has hydrocarbons as a chief ingredient, and the refrigerating machine oil has as base oil a carboxylic ester compound whose kinematic viscosity is 6 mm²/s or less at 40 degrees, and 2 mm²/s or less at 100 degrees, and is composed of a carboxylic ester compound that has one ester group expressed by Formula as a chief ingredient.
—COOR1 [Chem. 1]
(In the Above Formula, R1 Represents Hydrocarbon Radical)
Thereby, the amount of extraction of oligomer contained in an organic material can be reduced, and the amount of oligomer that can be held in the oil can be increased. Accordingly, oligomer can be kept from precipitating and depositing on a refrigerant passage in the refrigeration system, and high efficient and high reliable hermetic compressor and refrigeration system can be realized.
Further, in the hermetic compressor of the invention, the motor element has a stator provided with an insulator, and the insulator is made of at least one selected from polyesters, polyamideimide, polyamides, polyphenylene sulfide, polyetheretherketone, polyether ketone, and a liquid crystal polymer.
Thereby, even in a combination of refrigerating machine oil that has a carboxylic ester compound as base oil, and a hydrocarbon refrigerant, compatibility as the insulator can be made high, deterioration of the insulator can be suppressed, and reliability can be improved.
Further, in the hermetic compressor of the invention, the motor element has a stator provided with winding, and the winding is a monolayer coating enameled wire having at least one insulating coating layer selected from a group consisting of polyester imide, polyamideimide ester, polyamideimide, polyimide, polyesters, and polyamides, or a multilayer coating enameled wire having at least two insulating coating layers selected from the group.
Thereby, even in a combination of refrigerating machine oil that has a carboxylic ester compound as base oil, and a hydrocarbon refrigerant, compatibility as the winding can be made high, deterioration of the insulator can be suppressed, and reliability can be improved.
Further, in the hermetic compressor of the invention, the winding is at least one of the monolayer coating enameled wire, the multilayer coating enameled wire, and a composite electric wire obtained by combining the monolayer coating enameled wire or multilayer coating enameled wire with fibers or a film.
Thereby, similarly to the above, even in a combination of refrigerating machine oil that has a carboxylic ester compound as base oil, and a hydrocarbon refrigerant, compatibility as the winding can be made high, deterioration of the insulator can be suppressed, and reliability can be improved.
Further, in the hermetic compressor of the invention, the motor element has the stator provided with the winding, and a binding yarn for fixing the winding to the stator is made of at least one selected from polyesters, polyphenylene sulfide, polybutylene terephthalate, polysulfone, polyetheretherketone, polyamideimide, polyimide, polyamides, and a liquid crystal polymer.
Thereby, even in a combination of refrigerating machine oil that has a carboxylic ester compound as base oil, and a hydrocarbon refrigerant, compatibility as the binding yarn can be made high, deterioration of the insulator can be suppressed, and reliability can be improved.
Further, in the hermetic compressor of the invention, the motor element has the stator provided with the winding, and an insulating coating layer having a self-lubricating property is formed on the surface of the winding.
Since this can suppress any damage of the winding even if fine sliding occurs between portions of the winding by the operation of the compressor, the reliability of the winding is further improved.
Further, in the hermetic compressor of the invention, the compression element has a muffler, and the muffler is formed of at least one selected from polyesters, polyamideimide, polyamide, polyphenylene sulfide, polyetheretherketone, polyether ketone, and a liquid crystal polymer.
Thereby, even in a combination of refrigerating machine oil that has a carboxylic ester compound as base oil, and a hydrocarbon refrigerant, compatibility as the muffler can be made high, deterioration of the insulator can be suppressed, and reliability can be improved.
Further, in the hermetic compressor of the invention, the compression element has sliding parts that slides on each other, and one sliding part is made of an iron-based material.
Thereby, since an ester group is adsorbed on the iron surface of one sliding part, an oil film is easily formed and wear resistance is further improved.
Further, in the hermetic compressor of the invention, the surface of the sliding part made of an iron-based material is subjected to at least one of phosphate coating, carburizing, ion nitriding, and solid lubricant coating.
Thereby, the wear resistance on a sliding surface can be further improved, and reliability can be improved.
Further, in the hermetic compressor of the invention, the iron-based material is a sintered body, and coating that has an iron oxide as a chief ingredient is formed in a surface opening of the sintered body, thereby making a dispersion of a density of a sliding surface layer (hereinafter referred as to a surface density) which is within a few mm depth from the surface is 2% or less.
Thereby, since leak of a refrigerant can be suppressed, efficiency can be further improved.
Further, in the hermetic compressor of the invention, the other sliding part is formed from an aluminum material, and is made to have a hardness of HRB 78 or more.
Thereby, wear resistance can be further improved.
Further, in the hermetic compressor of the invention, the refrigerating machine oil contains an acid scavenger.
Thereby, even if air or moisture remains slightly in the hermetic compressor, deterioration of oil can be suppressed, and reliability can be further improved.
Further, in the hermetic compressor of the invention, the refrigerating machine oil contains an antioxidant.
Thereby, similarly to the above, even if air or moisture remains slightly in the hermetic compressor, deterioration of oil can be suppressed, and reliability can be further improved.
Further, in the hermetic compressor of the invention, the refrigerating machine oil contains an extreme-pressure additive.
Thereby, the wear resistance of a sliding part can be further improved, and reliability can be improved.
Further, a refrigeration system of the invention includes any one of the hermetic compressors described in the above, and an evaporator, a condenser, and an expansion mechanism.
Thereby, a high reliable refrigeration system can be provided.
Hereinafter, an embodiment of the invention will be explained with reference to the drawings. The invention is not limited by the embodiment.

Mode for the Invention 1

FIG. 1 is a schematic diagram of a refrigeration system in Embodiment 1 of the invention, and FIG. 2 is a longitudinal sectional view of a hermetic compressor in this embodiment.
In FIG. 1, the refrigeration system of this embodiment includes hermetic compressor 101, condenser 102 for performing heat exchange of refrigerant with the ambient air to condense the refrigerant, and dryer 103 for removing the moisture in the refrigerant discharged through condenser 102. Moreover, the refrigeration system includes expansion mechanism 104 for expanding the refrigerant from which the moisture has been removed by dryer 103, and evaporator 105 for performing heat exchange of the refrigerant, which has passed through expansion mechanism 104, with the ambient air, to evaporate the refrigerant.
Next, the details of hermetic compressor 101 will be explained with reference with FIG. 2. Refrigerant 107 is filled in sealed vessel 106, and refrigerating machine oil 108 is reserved at a bottom of the vessel. Moreover, motor element 111 composed of stator 109 and rotor 110, and compression element 112 reciprocally driven by motor element 111 are housed in the sealed vessel.
Specifically, R600a that is a hydrocarbon refrigerant is used as refrigerant 107. Further, as refrigerating machine oil 108, oil that has as base oil a carboxylic ester compound whose kinematic viscosity is 6 mm²/s or less at 40 degrees, and is 2 mm²/s or less at 100 degrees is used.
The carboxylic ester compound used for refrigerating machine oil 108 has one ester group expressed by Formula 1 as a chief ingredient thereof.
Next, the details of compression element 112 will be explained. Crankshaft 113 made of an iron-based metal is composed of main shaft 114 to which rotor 110 that is a motor element is fixedly pressed-fitted, and eccentric shaft 115 formed eccentrically from main shaft 114. Moreover, a lower end of main shaft 114 is provided with oil supply pump 116 that communicates with refrigerating machine oil 108.
Cylinder block 117 forms substantially cylindrical bore 118, and bearing 119 that journals main shaft 114. Between bearing 119 and crankshaft 113, main bearing 120 made of an aluminum material is provided.
Piston 121 that is loosely fitted into bore 118 and made of an iron-based metal forms compression chamber 122 along with bore 118, and is connected to eccentric shaft 115 via piston pin 123 by connecting rod 124 that is a connecting means.
Valve plate 125 is disposed so as to seal an end face of bore 118. Head 126 is fixed to valve plate 125 opposite bore 118. Muffler 127 is sandwiched by valve plate 125 and head 126.
Suction tube 128 and discharge tube 129 are fixed to sealed vessel 106, and are connected to evaporator 105 (refer to FIG. 1) and condenser 102 (refer to FIG. 1) that constitute a refrigerating cycle. Suction tube 128 guides refrigerant 107 into sealed vessel 106, and discharge tube 129 delivers refrigerant 107 to the refrigerating cycle.
The operation and effects of the refrigeration system configured as described above will be explained below. The electric power supplied from a commercial power supply (not shown) is supplied to motor element 111 to rotate rotor 110 of motor element 111. Rotor 110 rotates crankshaft 113, and the eccentric motion of eccentric shaft 115 drives piston 121 via piston pin 123 from connecting rod 124 serving as a connecting means, whereby piston 121 reciprocates in bore 118.
Then, refrigerant 107 guided into sealed vessel 106 is sucked into compression chamber 122 through muffler 127 from suction tube 128.
Refrigerant 107 sucked into compression chamber 122 is compressed continuously, and compressed refrigerant 107 is delivered from discharge tube 129 to the refrigerating cycle. Refrigerant 107 delivered to the refrigerating cycle sequentially passes through condenser 102, dryer 103, expansion mechanism 104, and evaporator 105 that are shown in FIG. 1, and is again guided into sealed vessel 106 from suction tube 128.
Hereinafter, the investigation test 1 to 4 about the compatibility between refrigerating machine oil 108 and the inside of the hermetic compressor is described.
In Test 1, the compatibility among refrigerant 107, refrigerating machine oil 108, and the polybutylene terephthalate inside the hermetic compressor was tested. Table 1 shows the results of the test.
Test 1 was performed by enclosing refrigerant 107 and refrigerating machine oil 108 in sealed vessel 106. Muffler 127 made of polybutylene terephthalate is enclosed in sealed vessel 106 so as to be immersed in refrigerating machine oil 108. Sealed vessel 106 was sealed, and aging was performed for two weeks at 140 degrees.
R600a that is a hydrocarbon refrigerant was enclosed as refrigerant 107. As refrigerating machine oil 108, oils (which have univalent, divalent, and tetravalent ester oils as base oils, respectively), mineral oil, and alkylbenzene that have a kinematic viscosity of 6 mm²/s at 40 degrees, were enclosed and tested. Here, the “ester oil” is oil that has a carboxylic ester compound as base oil, and the “univalent” means that the ester group expressed by Formula 1 is one.
Furthermore, oil that has a kinematic viscosity of 4 mm²/s at 40 degrees, and has univalent ester oil as base oil was also tested. In any refrigerating machine oil 108, the kinematic viscosity at 100 degrees is 2 mm²/s or less.

	TABLE 1

	Kind of Oil

		Oil Having
Oil Having	Oil Having	Divalent and
Univalent	Univalent	Tetravalent
Ester Oil As	Ester Oil As	Ester Oil As	Mineral
Base Oil	Base Oil	Base Oil	Oil	Alkylbenzene

Kinematic

	6	4	6	6	6
Viscosity of Oil
(40° C.)/mm²· S⁻¹
Precipitation	Almost None	Almost None	Yes	Yes	Yes
of Oligomer

From Table 1, although a large amount of oligomer was precipitated in the oil that has divalent and tetravalent ester oil as base oil, mineral oil, and alkylbenzene, precipitation of oligomer was suppressed to an extremely small amount in the refrigerating machine oil that has univalent ester oil as base oil.
It is believed that this is because molecular size becomes small relatively in a case where oil that has a low kinematic viscosity of 6 mm²/s at 40 degrees in mineral oil is used as refrigerating machine oil 108. That is, it is inferred that, if the molecular size becomes small relatively, since it becomes easy to permeate through an organic material, the amount of extraction of oligomer increases, and the amount of oligomer that can be held in the refrigerating machine oil is small, this leads to the precipitation of a large amount of oligomer.
Further, it is believed that this is because polybutylene terephthalate has a benzene ring in a skeleton texture in addition to the fact that viscosity is low in a case where alkylbenzene is used as refrigerating machine oil 108. That is, in the case of alkylbenzene, it is believed that it becomes still easy to permeate through polybutylene terephthalate that is an organic material as compared with the mineral oil, and the amount of extraction of oligomer increases, which leads to precipitation.
Further, it is believed that this is because an ester group is contained even in polybutylene terephthalate, and therefore, the amount of oligomer that is held in the refrigerating machine oil increases, in a case where the oil that have divalent and tetravalent ester oil as base oil is used as refrigerating machine oil 108. However, it is inferred that, since the above oil has two or four ester groups, the transparency to muffler 127 made of polybutylene terephthalate was improved to increase the amount of extraction of oligomer, and precipitation may occur beyond a limit amount that can be held in the refrigerating machine oil.
However, in a case where the oil that has univalent ester oil as base oil was used as refrigerating machine oil 108, precipitation of oligomer was not observed even if the kinematic viscosity at 40 degrees was set to 4 mm²/s.
It is believed that this is because univalent ester oil is used to suppress the transparency to muffler 127 made of polybutylene terephthalate, and the amount of oligomer that is held in the refrigerating machine oil can be increased by the effect that polybutylene terephthalate contains an ester group, thereby suppressing the precipitation of oligomer.
Accordingly, by using univalent ester oil that has as base oil a carboxylic ester compound whose kinematic viscosity is 6 mm²/s or less at 40 degrees, and is 2 mm²/s or less at 100 degrees, in a hydrocarbon refrigerant, the precipitation of oligomer can be suppressed. This keeps oligomer from depositing on a refrigerant passage in the refrigeration system, thereby obtaining high efficient and high reliable hermetic compressor 101. Accordingly, the high efficient and high reliable refrigeration system including hermetic compressor 101, condenser 102, expansion mechanism 104, and evaporator 105 can be obtained.
Further, even if aging was performed in R600a that is a hydrocarbon refrigerant and in the refrigerating machine oil that has univalent ester oil as base oil, deterioration was not observed in muffler 127 made of polybutylene terephthalate, and the refrigerating machine oil was not polluted. Thereby, it is believed that polybutylene terephthalate is a material with high compatibility to the refrigerating machine oil that has univalent ester oil as base oil, and the hydrocarbon refrigerant.
In addition, although an example in which polybutylene terephthalate is used for muffler 127 has been illustrated in this embodiment, the same effect was obtained even if polyethylene terephthalate, polybutylene terephthalate, polyethylene naphthalate, etc. that are polyester-based organic materials (polyester).
In addition, in a case where organic materials, such as polyamideimide, polyphenylene sulfide, polyetheretherketone, and polyether ketone were used for muffler 127, they had a larger surface hardness as compared with polyester-based resins, and were harder to transmit refrigerating machine oil having a lower viscosity than polyester-based organic materials. Thus, the precipitation of oligomer could be further suppressed.
In addition, in a case where organic materials, such as polyamide and a liquid crystal polymer were used for muffler 127, affinity with ester oil that has an ester group was suppressed. Thus, the transmission of ester oil could be suppressed, and thereby precipitation of oligomer could be suppressed.
In addition, the same effect is also obtained even if complexes are formed by combining the above polyester-based organic materials, polyamideimide, polyamide, polyphenylene sulfide, polyetheretherketone, polyether ketone, and the liquid crystal polymer, and foams may be adopted. Moreover, inorganic fillers, such as glass fibers, may be added.
In Test 2, the compatibility between refrigerating machine oil 108, and crankshaft 113 that is a sliding part inside the hermetic compressor was tested. Table 2 shows the results of the test.
In Test 2, the amount of wear about refrigerating machine oil 108 was tested using FC250 that is cast iron as crankshaft 113. Under the conditions that the condensing temperature and evaporating temperature are 54.4 degrees and −23.3 degrees, respectively, R600a was used as refrigerant 107. Further, reliability tests were performed using as refrigerating machine oil 108 mineral oil whose kinematic viscosity is 5 mm²/s at 40 degrees, and is 2 mm²/s at 100 degrees, and univalent ester oil, respectively. The “ester oil” is oil that has a carboxylic ester compound as base oil, and the “univalent” (Formula 1) means that the ester group expressed by Formula 1 is one.

	TABLE 2

	Kind of Oil

	Oil Having Univalent
	Ester Oil As Base Oil	Mineral Oil

Amount of Wear of	0.5 μm or less	0.5 μm
Crankshaft

It can be seen from Table 2 that, when the mineral oil and the univalent ester oil are compared with each other, the univalent ester oil is smaller in the amount of surface wear of crankshaft 113. It is believed that this is because the absorption force of the ester group constituting ester oil to crankshaft 113 made of cast iron is strong compared with the mineral oil, and therefore, an oil film that is stronger than the mineral oil is formed.
In addition, the same effect was obtained even if a sintered material of iron-based metal and other cast irons were used as the material used for crankshaft 113.
Accordingly, not only the precipitation of oligomer can be suppressed by using the univalent ester oil, but the reliability of hermetic compressor 101 can be improved when at least one of sliding parts is formed of an iron-based material. Accordingly, the reliability of the refrigeration system including such hermetic compressor 101, condenser 102, expansion mechanism 104, and evaporator 105 can be improved.
In addition, the surface of a sliding part made of an iron-based material was subjected to at least one of phosphate coating, carburizing, ion nitriding, and solid lubricant coating, thereby improving the wear resistance of the sliding part. For this reason, the reliability of hermetic compressor 101 that is subjected to such processing can be further improved. Accordingly, the reliability of the refrigeration system including hermetic compressor 101 that is subjected to such processing, condenser 102, expansion mechanism 104, and evaporator 105 can be further improved.
In Test 3, the compatibility between refrigerating machine oil 108 and bearing 119 that is a sliding part inside the hermetic compressor was tested. Table 3 shows the results of the test.
In Test 3, the amount of wear about refrigerating machine oil 108 was tested using an aluminum material as bearing 119. FC250 that is cast iron was used for crankshaft 113 that is a mating material of the sliding part. Under the conditions that the condensing temperature and evaporating temperature are 54.4 degrees and −23.3 degrees, respectively, R600a was used as refrigerant 107. Further, a reliability test was performed using as refrigerating machine oil 108 the univalent ester oil whose kinematic viscosity is 5 mm²/s at 40 degrees, and is 2 mm²/s at 100 degrees. The “ester oil” is refrigerating machine oil 108 that has a carboxylic ester compound as base oil, and the “univalent” (Formula 1) means that the ester group expressed by Formula 1 is one.
The hardness of bearing 119 was adjusted by changing the content of Si (silicon) contained in an aluminum material. Specifically, an aluminum material whose hardness is HRB 78 or more, and an aluminum material whose hardness is HRB 75 were used. Only the results when the aluminum material whose hardness is HRB 78 or more was used are shown in Table 3. In addition, the hardness is a value measured using the Rockwell hardness meter, and using B scales.

	TABLE 3

	Kind of Oil

	Oil Having Univalent
	Ester Oil As Base Oil	Mineral Oil

Amount of Wear of	0.5 μm or less	0.5 μm
Crankshaft

From Table 3, when the hardness is HRB 78 or more, the wear of both the aluminum material and crankshaft 113 was suppressed. On the other hand, although not shown in Table 3, when the hardness is HRB 75, wear occurred in the aluminum material.
It is believed that this is because that the hardness of the surface of the aluminum material is reduced, in addition to the fact that the force that forms an oil film is reduced by making the viscosity of refrigerating machine oil 108 low. That is, it is inferred that wear occurred in an aluminum material that is softer than iron, due to a difference in hardness from crankshaft 113 that is an iron-based metal.
As such, not only the precipitation of oligomer can be suppressed by using the univalent ester oil, but the wear resistance of a sliding part is improved by using an aluminum material having a hardness of HRB 78 or more for one of sliding parts. Therefore, the reliability of such hermetic compressor 101 can be improved. Accordingly, the reliability of the refrigeration system including such hermetic compressor 101, condenser 102, expansion mechanism 104, and evaporator 105 can be improved.
In Test 4, the compatibility between refrigerating machine oil 108, and piston 121 inside the hermetic compressor was tested. Table 4 shows the results of the test.
In Test 4, the refrigerating capacity over the dispersion of the surface density of the piston when a iron-based sintered metal is used for piston 121 was tested. Under the conditions that the condensing temperature and evaporating temperature are 54.4 degrees and −23.3 degrees, respectively, R600a was used for refrigerant 107. Further, as refrigerating machine oil 108, the univalent ester oil whose kinematic viscosity is 5 mm²/s at 40 degrees, and is 2 mm²/s at 100 degrees was used. The “ester oil” is oil that has a carboxylic ester compound as base oil, and the “univalent” (Formula 1) means that the ester group expressed by Formula 1 is one.
The apparent density of piston 121 is an apparent density of 6.5 g/cm³, and by performing steam treatment, coating having an iron oxide as a chief ingredient is formed at a surface opening of the piston. Further, the dispersion of the surface density is changed by adjusting the steam treatment.

	TABLE 4

	Dispersion of
	Surface Density

	1.5%	2.0%	2.5%

Refrigeration	100	100	95
Capacity

It can be seen from Table 4 that, when the dispersion of the surface density is 2% or less, a change did not occur in refrigerating capacity, but when the dispersion of the surface density is 2.5%, the refrigerating capacity was only 95% and the drop of 5% occurred, assuming that the capacity is 100% at a dispersion of the surface density of 2% or less.
It is inferred that this is because the formation state of an oil film becomes uneven and refrigerant 107 is apt to leak, due to the dispersion of the surface density, in addition to the fact that an oil film becomes thin as the viscosity of refrigerating machine oil 108 is made low.
Accordingly, the precipitation of oligomer can be suppressed by using the univalent ester oil, first. In addition to this, in a case where a sintered body is used for the iron-based material, coating that has an iron oxide as a chief ingredient is formed in a surface opening of the sintered body, thereby making the dispersion of the surface density 2% or less. Thereby, efficient hermetic compressor 101 was obtained. Accordingly, the high reliable refrigeration system including such hermetic compressor 101, condenser 102, expansion mechanism 104, and evaporator 105 can be obtained.
In addition, if an additive that has an acid capturing effect or an anti-oxidation effect is added to refrigerating machine oil 108, the effect of capturing moisture or air to suppress formation of an acid substance, or the effect of capturing or decomposing the generated acid substance is obtained. Thereby the reliability of hermetic compressor 101 can be further improved by suppressing generation of copper ions. Accordingly, the reliability of the refrigeration system including such hermetic compressor 101, condenser 102, expansion mechanism 104, and evaporator 105 can be further improved.
Further, in this embodiment, both an acid scavenger as an additive having the effect of capturing moisture or air, or an antioxidant as an additive having the effect of capturing or decomposing the generated acid substance may be added.
In addition, if an extreme-pressure additive is added to refrigerating machine oil 108, hermetic compressor 101 that can improve wear resistance as the extreme-pressure additive is adsorbed on a sliding surface is obtained. Accordingly, the reliability of the refrigeration system including such hermetic compressor 101, condenser 102, expansion mechanism 104, and evaporator 105 can be further improved.
In addition, in this embodiment, R600a was used for refrigerant 107. However, the same effect was obtained even if hydrocarbon refrigerants, such as R290 and R600 were used.
As described above, this embodiment provides a hermetic compressor using as base oil a carboxylic ester compound whose kinematic viscosity is 6 mm²/s or less at 40 degrees, and 2 mm²/s or less at 100 degrees, and using refrigerating machine oil composed of a carboxylic ester compound that has one ester group as a chief ingredient, and a refrigeration system including the hermetic compressor, an evaporator, a condenser, and an expansion mechanism. According to this embodiment, the reliability of the hermetic compressor and the refrigeration system can be improved greatly.

Mode for the Invention 2

FIG. 3 is a schematic diagram of a refrigeration system in Embodiment 2 of the invention. FIG. 4 is a longitudinal sectional view of the hermetic compressor in this embodiment. FIG. 5 is a sectional view taken along a line 5-5 of FIG. 4, FIG. 6 is an enlarged view of a portion B of FIG. 5, and FIG. 7 is an enlarged view of a portion C of FIG. 6.
In FIG. 3, the refrigeration system of this embodiment includes hermetic compressor 201, condenser 202 for performing heat exchange of refrigerant with the ambient air to condense the refrigerant, and dryer 203 for removing the moisture in the refrigerant discharged through condenser 202. Moreover, the refrigeration system includes expansion mechanism 204 for expanding the refrigerant from which the moisture has been removed by dryer 203, and evaporator 205 for performing heat exchange of the refrigerant, which has passed through expansion mechanism 204, with the ambient air, to evaporate the refrigerant.
Next, the details of hermetic compressor 201 will be explained with reference with FIG. 4. Refrigerant 207 is filled in sealed vessel 206, and refrigerating machine oil 208 is reserved at a bottom of the vessel. Moreover, motor element 211 composed of stator 209 and rotor 210, and reciprocal compression element 212 driven by the motor element are housed in the sealed vessel. Specifically, R600a that is a hydrocarbon refrigerant was used for refrigerant 207. Further, as refrigerating machine oil 208, oil that has as base oil a carboxylic ester compound whose kinematic viscosity is 6 mm²/s or less at 40 degrees, and is 2 mm²/s or less at 100 degrees was used.
Further, the carboxylic ester compound used for refrigerating machine oil 208 has one ester group expressed by Formula 1 as a chief ingredient thereof.
Next, the details of compression element 212 will be explained. Crankshaft 213 has main shaft 214 fixed to rotor 210, and eccentric shaft 215 formed eccentrically from main shaft 214, and cylinder block 216 has substantially cylindrical compression chamber 217.
Piston 218 is reciprocally and slidably inserted into compression chamber 217 of cylinder block 216, and is connected to eccentric shaft 215 by connecting rod 219 that is a connecting means with eccentric shaft 215.
Suction tube 220 and discharge tube 221 are fixed to sealed vessel 206, and are connected to a refrigerating cycle (not shown). Suction tube 220 guides refrigerant 207 into sealed vessel 206, and discharge tube 221 delivers refrigerant 207 to the refrigerating cycle.
Next, the details of the driving element 211 will be explained. FIG. 5 is a sectional view taken along a line 5-5 of FIG. 4, FIG. 6 is an enlarged view of a portion B of FIG. 5, and FIG. 7 is an enlarged view of a portion C of FIG. 6.
Motor element 211 forms an induced motor including stator 209 (refer to FIGS. 5 and 6) to which winding 223 is wound around core 222, and rotor 210, and is fixed with binding yarn 224 (refer to FIG. 4).
As shown in FIGS. 5 and 6, stator 209 is wound so that main winding 223 a and auxiliary winding 223 b may pass through slot 225. Each of main winding 223 a and auxiliary winding 223 b is wound around correlation insulating paper 226 a that is insulator 226 so as not to contact each other within slot 225. Moreover, slot insulation paper 226 b is fitted into an inner wall of slot 225 that is insulator 226 so that each of main winding 223 a and auxiliary winding 223 b may not contact each other within slot 225. As shown in FIG. 7, winding 223 is a multilayer coating enameled wire in which insulating coating layer 227 composed of upper layer 227 a and lower layer 227 b is coated with enameled wire 228.
The operation of the refrigeration system configured as described above will be explained below. When a current is supplied to main winding 223 a and auxiliary winding 223 b from a commercial power supply (not shown), rotor 210 starts to rotate. When main shaft 214 is rotationally driven by rotor 210, piston 218 reciprocates inside compression chamber 217 via connecting rod 219 by the eccentric motion of eccentric shaft 215.
Then, refrigerant 207 guided into sealed vessel 206 is sucked into compression chamber 217 from suction tube 220. Refrigerant 207 sucked into compression chamber 217 is compressed continuously, and compressed refrigerant 207 is delivered from discharge tube 221 to the refrigeration system. Refrigerant 207 delivered to the refrigeration system sequentially passes through condenser 202, dryer 203, expansion mechanism 204, and evaporator 205, and is again guided into sealed vessel 206 from suction tube 220.
In this embodiment, as Test 5, the compatibility between refrigerant 207 and refrigerating machine oil 208, and winding 223, binding yarn 224, and insulator 226 are investigated and tested. Table 5 shows the results of the test.
In Test 5 of this embodiment, operation was performed for 2000 hours under the conditions that the condensing temperature and evaporating temperature are 54.4 degrees and −23.3 degrees, respectively, and the multilayer coating enameled wire that is winding 223 and insulator 226 was evaluated by a change in the amount of leakage current before and after the test. As for the evaluation of the multilayer coating enameled wire, enameled wires that are a combination of upper-layer polyamide and lower-layer polyester, and a combination of upper-layer amideimide and lower-layer esterimide other than a combination of upper-layer amideimide and lower-layer denatured polyester were also evaluated.
Further, as for the evaluation of insulator 226, complexes of polyester and polyamide, such as polyphenylene sulfide, a liquid crystal polymer, polyetheretherketone, polyetherketone, and polysulfone, other than polyethylene terephthalate that are polyesters, were evaluated.
Further, as binding yarn 224, polyethylene terephthalate and polyamide that are polyesters were used.
Here, the amount of leakage current is obtained by measuring a current difference between the portion of an external wall of a bottom of sealed vessel 206 where refrigerating machine oil 208 is reserved, and the ground.

TABLE 5

Wiring	Upper	Amide-	Poly-	Amide-	Amide-	Amide-	Amide-
	Layer	imide	amide	imide	imide	imide	imide
	Lower	Denatured	Poly-	Ester-	Denatured	Denatured	Denatured
	Layer	Ester	ester	imide	Polyester	Polyester	Polyester

Insulator	PET 1	PPS 2	Liquid	PEEK 3	PEK 4	Poly-
			Crystal			sulfone
			Polymer
Binding Yarn	PET 1	PET 1	PET 1	PET 1	Polyamide	Polyamide
Deterioration	None	None	None	None	None	None
of Winding
Deterioration	None	None	None	None	None	None
of Insulator
Deterioration	None	None	None	None	None	None
of Binding Yarn
Amount of	No	No	No	No	No	No
Leakage Amount	Change	Change	Change	Change	Change	Change

1 PET = polyethylene terephthalate
2 PPS = polyphenylene sulfide
3 PEEK = polyetheretherketone
4 PEK = polyetherketone

It can be seen from Table 5 that, in a case where the following things are used as the multilayer coating enameled wire 228, insulator 226, and binding yarn 224, the amount of leakage current before and after a test in hermetic compressor 201 does not change, and winding 223, binding yarn 224, and insulator 226 does not deteriorate.
That is, the multilayer coating enameled wire is any one of a combination of upper-layer amideimide and lower-layer denatured polyester, a combination of upper-layer polyamide and lower-layer polyester, and a combination of upper-layer amideimide and lower-layer esterimide.
Insulator 226 is any one of polyethylene terephthalate, polyphenylene sulfide, a liquid crystal polymer, polyetheretherketone, and polysulfone.
Binding yarn 224 is any one of polyethylene terephthalate and polyamide.
Accordingly, when imide binding having a strong intermolecular force is taken into consideration, it is considered that amideimide and its ester derivatives, polyimide and its ester derivatives, polyamide, polyethylene terephthalate, polyphenylene sulfide, a liquid crystal polymer, polyetheretherketone, polyetherketone, and polysulfone are compatible with R600a that is a hydrocarbon refrigerant, and ester oil.
From the foregoing, winding 223 may be a monolayer coating enameled wire or multilayer coating enameled wire made of at least one selected from polyester imide, polyamideimide ester, polyamideimide, polyimide, polyesters, and a polyamide-based organic material (polyamides).
Binding yarn 224 may be made of at least one selected from polyester, polyphenylene sulfide, polybutylene terephthalate, polysulfone, polyetheretherketone, polyamideimide, polyimide, polyamide, and a liquid crystal polymer.
Insulator 226 may be made of at least one selected from polyester, polyamideimide, polyamide, polyphenylene sulfide, polyetheretherketone, polyether ketone, and a liquid crystal polymer.
By selecting the materials as described above, the reliability of hermetic compressor 201 can be improved, and the reliability of the refrigeration system including hermetic compressor 201 can be improved.
In addition, the same effect is obtained even if polybutylene terephthalate and polyethylene naphthalate other than polyethylene terephthalate are used as the polyesters used as insulator 226 and binding yarn 224.
In addition, by combining fibers or a film with a monolayer coating enameled wire or multilayer coating enameled coated with one insulating coating layer made of at least one selected from polyester imide, polyamideimide ester, polyamideimide, polyimide, polyesters, and polyamides in order to obtain winding 223, insulation and proof stress can be further improved.
Accordingly, in this embodiment, the reliability of hermetic compressor 201 having such motor element 6 can be further improved. Further, the reliability of the refrigeration system including such hermetic compressor 201, condenser 202, expansion mechanism 204, and evaporator 205 can be further improved.
In addition, by providing winding 223 with insulating coating layer 227 that is made to have a self-lubricating property by causing a material having a high lubricating property, such as PTFE (polytetrafluoroethylene), to be added to or coated on a coating layer, the wear of winding 223 can be reduced even if fine sliding occurs in hermetic compressor 201 and portions of winding 223 contact each other.
Accordingly, in this embodiment, the reliability of hermetic compressor 201 having such motor element 6 can be further improved. Further, the reliability of the refrigeration system including such hermetic compressor 201, condenser 202, expansion mechanism 204, and evaporator 205 can be further improved.
In addition, in this embodiment, R600a was used for refrigerant 207. However, the same effect is obtained even if hydrocarbon refrigerants, such as R290 and R600, are used.
As described above, this embodiment provides a hermetic compressor using as base oil a carboxylic ester compound whose kinematic viscosity is 6 mm²/s or less at 40 degrees, and 2 mm²/s or less at 100 degrees, and using refrigerating machine oil composed of a carboxylic ester compound that has one ester group as a chief ingredient. According to this embodiment, the high reliability of the hermetic compressor can be realized. Moreover, this embodiment is a refrigeration system including such a hermetic compressor. According to this embodiment, the high reliability of the refrigeration system can be realized similarly.

INDUSTRIAL APPLICABILITY

As described above, the invention is a hermetic compressor and a refrigeration system with high reliability, and can be widely applied to apparatuses using a refrigerating cycle.

Claims

1. A hermetic compressor comprising:

a sealed vessel that reserves refrigerating machine oil, and houses a motor element, and a compression element driven by the motor element, the compression element compresses a refrigerant that has hydrocarbons as a chief ingredient, and the refrigerating machine oil has as base oil a carboxylic ester compound whose kinematic viscosity is 6 mm²/s or less at 40 degrees centigrade, and 2 mm²/s or less at 100 degrees centigrade, and is composed of a carboxylic ester compound that has one ester group expressed by Chem. 1 as a chief ingredient.

—COOR1 [Chem. 1]

(In the above Formula, R1 represents hydrocarbon radical)

2. The hermetic compressor according to claim 1,

wherein the motor element has a stator provided with an insulator, and the insulator is made of at least one selected from polyesters, polyamideimide, polyamides, polyphenylene sulfide, polyetheretherketone, polyether ketone, and a liquid crystal polymer.

3. The hermetic compressor according to claim 1,

wherein the motor element has a stator provided with winding, and the winding is a monolayer coating enameled wire having at least one insulating coating layer selected from a group consisting of polyester imide, polyamideimide ester, polyamideimide, polyimide, polyesters, and polyamides, or a multilayer coating enameled wire having at least two insulating coating layers selected from the group.

4. The hermetic compressor according to claim 3,

wherein the winding is at least one of the monolayer coating enameled wire, the multilayer coating enameled wire, and a composite electric wire obtained by combining the monolayer coating enameled wire or multilayer coating enameled wire with fibers or a film.

5. The hermetic compressor according to claim 1,

wherein the motor element has a stator provided with a winding, and a binding yarn for fixing the winding to the stator is made of at least one selected from polyesters, polyphenylene sulfide, polybutylene terephthalate, polysulfone, polyetheretherketone, polyamideimide, polyimide, polyamides, and a liquid crystal polymer.

6. The hermetic compressor according to claim 3,

wherein the motor element has the stator provided with the winding, and an insulating coating layer having a self-lubricating property is formed on the surface of the winding.

7. The hermetic compressor according to claim 1,

wherein the compression element has a muffler, and the muffler is formed of at least one selected from polyesters, polyamideimide, polyamide, polyphenylene sulfide, polyetheretherketone, polyether ketone, and a liquid crystal polymer.

8. The hermetic compressor according to claim 1,

wherein the compression element has sliding parts that slides on each other, one of the sliding part is made of an iron-based material.

9. The hermetic compressor according to claim 8,

wherein the surface of the sliding part made of an iron-based material is subjected to at least one of phosphate coating, carburizing, ion nitriding, and solid lubricant coating.

10. The hermetic compressor according to claim 8,

wherein the iron-based material is a sintered body, and coating that has an iron oxide as a chief ingredient is formed in a surface opening of the sintered body, thereby making a dispersion of a density of a sliding surface layer 2% or less.

11. The hermetic compressor according to claim 8,

wherein the other sliding part is formed from an aluminum material, and is made to have a hardness of HRB 78 or more.

12. The hermetic compressor according to claim 1,

wherein the refrigerating machine oil contains an acid scavenger.

13. The hermetic compressor according to claim 1,

wherein the refrigerating machine oil contains an antioxidant.

14. The hermetic compressor according to claim 1,

wherein the refrigerating machine oil contains an extreme-pressure additive.

15. A refrigeration system comprising:

the hermetic compressor according to claim 1,

and an evaporator, a condenser, and an expansion mechanism.