Patent Application
20090082232
The present invention relates to refrigerating machine oil compositions, and compressors and refrigerating apparatuses using the compositions, and more particularly to refrigerating machine oil compositions obtained by adding a specific compound to a base oil which are used for compressors having sliding portions coated with a lubrication film-forming composition containing a binder and a solid lubricant, and compressors and refrigerating apparatuses using the compositions.
Lubrication of respective sliding portions of a compressor used for a refrigerator is ensured by a lubricating oil having a good miscibility with a refrigerant contained in a cooling medium returned thereto. However, upon starting operation of the compressor, a certain period of time is required until the returned refrigerant in the compressor is fully supplied to the respective sliding portions, thereby causing such a problem that defective lubrication may occur at the sliding portions upon the starting. In order to compensate the defective lubrication upon starting operation of the compressor, there has been proposed the method of coating these sliding portions with a lubrication film-forming composition containing a solid lubricant (for example, refer to JP 7-247493A).
However, only such a coating lubrication film formed on a surface of the respective sliding portions fails to impart a fully satisfactory lubrication performance thereto upon the starting. Under some conditions, the coating lubrication film tends to suffer from abrasion, resulting in occurrence of seizing at the sliding portions.
Also, even under a steady operational condition of the compressor, a bearing surface pressure of the respective sliding portions thereof tends to be unsuitably increased depending upon kind of refrigerant used, for example, when using a carbon dioxide refrigerant, etc. As a result, even if the coating lubrication film is formed on the sliding portions, the coating layer tends to suffer from abrasion owing to the increased bearing surface pressure, thereby causing defective lubrication of the sliding portions.
The present invention has been made in view of the above conventional problems. An object of the present invention is to provide a refrigerating machine oil composition capable of ensuring good lubrication of sliding portions of a compressor for a refrigerator upon starting the operation thereof and during the operation, and a compressor and a refrigerating apparatus using the composition.
As a result of intensive and extensive researches for achieving the above object, the inventors have found that the conventional problems can be overcome by coating a sliding surface of at least a part of constitutional members of the compressor with a lubrication film-forming composition containing a binder and a solid lubricant, and using the thus coated structure in combination with a specific refrigerating machine oil composition. The present invention has been accomplished on the basis of the finding.
Thus, the present invention provides a refrigerating machine oil composition for use in a compressor for a refrigerator in which a sliding surface of at least a part of constitutional members of the compressor is coated with a lubrication film-forming composition containing a resin having a heat distortion temperature of 100° C. or higher as a binder, and a solid lubricant, said refrigerating machine oil composition comprising a base oil made of a polyoxyalkylene glycol having a kinematic viscosity of from 3 to 50 mm2/s as measured at 100° C., and at least one compound selected from the group consisting of those compounds represented by the following general formulae (1) to (3) which is contained in an amount of from 0.01 to 1% by mass on the basis of a total amount of the refrigerating machine oil composition:
R1—CO—NR2R3 (1)
wherein R1 is an alkyl group having 6 to 30 carbon atoms or an alkenyl group having 6 to 30 carbon atoms; and R2 and R3 are each independently a hydrogen atom, a hydrocarbon group having 1 to 10 carbon atoms, a nitrogen-containing hydrocarbon group having 1 to 10 carbon atoms or an oxygen-containing hydrocarbon group having 1 to 10 carbon atoms;
R4—CO—NR5—R6—COO—X (2)
wherein R4 is an alkyl group having 6 to 30 carbon atoms or an alkenyl group having 6 to 30 carbon atoms; R5 is a hydrogen atom or an alkyl group having 1 to 4 carbon atoms; R6 is an alkylene group having 1 to 8 carbon atoms; and X is a hydrogen atom, an alkali metal atom, a hydrocarbon group having 1 to 30 carbon atoms, a nitrogen-containing hydrocarbon group having 1 to 30 carbon atoms or an oxygen-containing hydrocarbon group having 1 to 30 carbon atoms; and
R7—NR8R9 (3)
wherein R7 is an alkyl group having 6 to 30 carbon atoms or an alkenyl group having 6 to 30 carbon atoms; and R8 and R9 are each independently a hydrogen atom or an alkyl group having 1 to 4 carbon atoms.
The refrigerating machine oil composition according to the present invention is capable of ensuring a good lubrication of sliding portions of a compressor for a refrigerator upon starting an operation thereof or and during the operation.
The present invention is characterized by coating a sliding surface of at least a part of constitutional members of a compressor for a refrigerator with a lubrication film-forming composition containing a resin having a heat distortion temperature of 100° C. or higher as a binder, and a solid lubricant.
The “heat distortion temperature (HDT)” used herein means the temperature at which a plastic material undergoes deformation when heating the material at a constant rate while applying a constant load thereto. In the present invention, the heat distortion temperature is expressed by a temperature as measured by the “Heat Distortion Temperature Test” (1.8 MPa) according to ASTM D648.
In the present invention, it is required that a resin having a heat distortion temperature of 100° C. or higher is used as a binder. The heat distortion temperature of the binder is preferably 150° C. or higher, more preferably 200° C. or higher and still more preferably 250° C. or higher.
Specific examples of the binder include epoxy resins, phenol resins, fluororesins, unsaturated polyesters, polyacetals, polyimides, polyamide imides, polycarbonates, polysulfones, polyphenylene sulfides and polybenzazoles. Among these resins, from the viewpoint of a similar structure to those of compounds added to the refrigerating machine oil composition of the present invention, preferred are nitrogen-containing resins, and more preferred are polyimides, polyamide imides and polybenzazoles.
Examples of the polyimides include aromatic polyimides, polyether imides and modified products thereof. Examples of the polyamide imides include aromatic polyamide imides and modified products thereof. Examples of the suitable polybenzazoles include polybenzimidazole. These resins may be used alone or in the form of a mixture of any two or more thereof.
In the present invention, the above binder is contained in the lubrication film-forming composition, and the lubrication film-forming composition is coated onto a sliding surface of at least a part of constitutional members of the compressor. The content of the binder in the lubrication film-forming composition is preferably from 20 to 80% by mass on the basis of a total amount of the composition. When the content of the binder in the lubrication film-forming composition is 20% by mass or more, the below-mentioned solid lubricant can be firmly retained in the lubrication film obtained from the composition. When the content of the binder in the lubrication film-forming composition is 80% by mass or less, the resultant composition exhibits a sufficient lubricating property. From the above viewpoints, the content of the binder in the lubrication film-forming composition is more preferably in the range of from 30 to 70% by mass.
The solid lubricant is not particularly limited as long as it can exhibit a good lubricating property in a solid state. Specific examples of the solid lubricant include graphite, molybdenum disulfide, tungsten sulfide, fluororesins and boron nitride. Among these solid lubricants, preferred are molybdenum disulfide and fluororesins. These solid lubricants may be used alone or in the form of a mixture of any two or more thereof.
The average particle size of the solid lubricant in the resultant lubrication film is not particularly limited, and is preferably from 1 to 100 μm in view of forming a dense lubrication film.
The content of the solid lubricant in the lubrication film-forming composition is preferably from 20 to 80 parts by mass on the basis of 100 parts by mass of the binder resin. When the content of the solid lubricant is 20 parts by mass or more, the resultant composition exhibits a sufficient lubricating property. When the content of the solid lubricant is 80 parts by mass or less, the solid lubricant is free from deteriorated retention in the obtained lubrication film owing to a less content of the binder, and further can be prevented from suffering from abrasion and peeling. From the above viewpoints, the content of solid lubricant in the lubrication film-forming composition is more preferably in the range of from 30 to 70 parts by mass on the basis of 100 parts by mass of the binder resin.
Also, the lubrication film-forming composition preferably contains a film-forming assistant. Examples of the suitable film-forming assistant include epoxy group-containing compounds and silane coupling agents. The film-forming assistant is capable of improving retention of the solid lubricant in the lubrication film.
The content of the film-forming assistant based on the binder resin is preferably controlled such that a mass ratio of the binder resin to the film-forming assistant is in the range of from 99:1 to 70:30.
The lubrication film-forming composition may also contain various known additives, if required. Examples of the additives include extreme pressure agents, e.g., phosphoric acid esters such as tricresyl phosphate (TCP) and phosphorous acid esters such as trisnonylphenyl phosphite; antioxidants such as phenol-based compounds and amine-based compounds; stabilizers such as phenyl glycidyl ether, cyclohexene oxide and epoxidated soybean oil; and copper deactivators such as benzotriazole and derivatives thereof. These additives may be respectively blended in an appropriate amount in the lubrication film-forming composition. In addition to these additives, the lubrication film-forming composition may also contain, if required, other additives such as load-resisting additives, chlorine scavengers, detergent dispersants, viscosity index improvers, oiliness agents, rust preventives, corrosion inhibitors and pour point depressants. The content of these additives in the lubrication film-forming composition is usually from 0.5 to 10% by mass.
The thickness of the lubrication film formed from the above lubrication film-forming composition is not particularly limited as long as the effects of the present invention can be exhibited, and is preferably in the range of from 2 to 50 μm. When the thickness of the lubrication film is 2 μm or more, the resultant lubrication film can ensure a sufficient lubricating property. When the thickness of the lubrication film is 50 μm or less, the resultant lubrication film can maintain a good fatigue resistance. From the above viewpoints, the thickness of the lubrication film is more preferably in the range of from 4 to 25 μm.
The lubrication film-forming composition is applied onto a sliding surface of at least a part of constitutional members of the compressor. The method of coating the sliding surface with the lubrication film-forming composition is not particularly limited. For example, there may be used the method of dispersing the solid lubricant in an organic solvent solution of the binder to prepare a lubrication film-forming composition, and then directly applying the thus prepared composition onto the sliding portions, the method of immersing the sliding portions in the lubrication film-forming composition, or the like. The lubrication film-forming composition applied onto the sliding portions is formed into a lubrication film by removing the solvent therefrom by the suitable methods such as drying.
The refrigerating machine oil composition of the present invention contains, as a base oil, a polyoxyalkylene glycol having a kinematic viscosity of from 3 to 50 mm2/s as measured at 100° C. More specifically, the polyoxyalkylene glycol is preferably represented by the following general formula (4):
R10—O—(AO)m—R11 (4)
In the general formula (4), R10 and R11 are each independently a hydrogen atom or a hydrocarbon group having 1 to 8 carbon atoms, and both of R10 and R11 are preferably a methyl group. R10 and R11 may be the same or different. Next, A is an alkylene group having 2 to 8 carbon atoms and, in particular, is preferably an alkylene group having 3 carbon atoms. The suffix m is an integer of 1 or more, and when m is 2 or more, a plurality of A groups may be the same or different. Meanwhile, when a plurality of the A groups are present, the AO groups may be either random-copolymerized or block-copolymerized.
The refrigerating machine oil composition of the present invention contains, in addition to the above polyoxyalkylene glycol, at least one compound selected from the group consisting of those compounds represented by the following general formulae (1) to (3).
R1—CO—NR2R3 (1)
In the general formula (1), R1 is an alkyl group having 6 to 30 carbon atoms or an alkenyl group having 6 to 30 carbon atoms. These alkyl groups and alkenyl groups may be either linear, branched or cyclic. Also, R2 and R3 are each independently a hydrogen atom, a hydrocarbon group having 1 to 10 carbon atoms, a nitrogen-containing hydrocarbon group having 1 to 10 carbon atoms or an oxygen-containing hydrocarbon group having 1 to 10 carbon atoms. These hydrocarbon groups may be either linear, branched or cyclic and may also contain an aromatic ring, an unsaturated bond, etc. In addition, R2 and R3 may be the same or different.
Examples of the compounds represented by the general formula (1) include amides produced by the reaction between a fatty acid and an amine. Specific examples of the fatty acid used in the reaction include stearic acid, isostearic acid, oleic acid, ricinolic acid, lauric acid and coconut oil fatty acids. Among these fatty acids, especially preferred are stearic acid and oleic acid. Specific examples of the amine used in the reaction include tetraethylenepentamine, ammonia, diethanol amine and diethylaminoethylamine. Among these amines, especially preferred is diethyl amino ethyl amine.
R4—CO—NR5—R6—COO—X (2)
In the general formula (2), R4 is an alkyl group having 6 to 30 carbon atoms or an alkenyl group having 6 to 30 carbon atoms, i.e., is the same as R1 of the general formula (1). Also, R5 is a hydrogen atom or an alkyl group having 1 to 4 carbon atoms, R6 is an alkylene group having 1 to 8 carbon atoms, and X is a hydrogen atom, an alkali metal atom, a hydrocarbon group having 1 to 30 carbon atoms, a nitrogen-containing hydrocarbon group having 1 to 30 carbon atoms or an oxygen-containing hydrocarbon group having 1 to 30 carbon atoms. Meanwhile, these hydrocarbon groups may be either linear, branched or cyclic, and may contain an aromatic ring, an unsaturated bond, etc.
The compounds represented by the general formula (2) may be produced by the reaction between a fatty acid and an amino acid, an amino acid salt or an amino acid ester. Examples of the fatty acid include stearic acid, isostearic acid, oleic acid, ricinolic acid, lauric acid and coconut oil fatty acids. Among these fatty acids, in view of a good solubility, preferred are stearic acid, isostearic acid and oleic acid, and in view of a good availability, preferred are oleic acid, lauric acid and coconut oil fatty acids. Specific examples of the amino acid include sarcosine (N-methyl glycine), glycine and glutamic acid. Specific examples of the amino acid salt include potassium salts, sodium salts, etc., of the above amino acids. Specific examples of the amino acid ester include amino acid isopropyl esters, amino acid 2-hydroxyhexadecyl esters, amino acid 2-hydroxytetradecyl esters and amino acid 2-hydroxydodecyl esters. Among these compounds, in view of a good availability and an easiness of synthesis, especially preferred are amino acid 2-hydroxyfatty esters such as amino acid 2-hydroxyhexadecyl esters, amino acid 2-hydroxytetradecyl esters and amino acid 2-hydroxydodecyl esters.
R7—NR8R9 (3)
In the general formula (3), R7 is an alkyl group having 6 to 30 carbon atoms or an alkenyl group having 6 to 30 carbon atoms, i.e., is the same as R1 of the general formula (1). R8 and R9 are each independently a hydrogen atom or an alkyl group having 1 to 4 carbon atoms, and may be the same or different.
The compounds represented by the general formula (3) are aliphatic amines. Specific examples of the compounds represented by the general formula (3) include oleyl amine and diisopropyl amine.
The refrigerating machine oil composition of the present invention may also contain various known additives, if required. The refrigerating machine oil composition of the present invention preferably contains a phosphorus-based extreme pressure agent. Examples of the preferred phosphorus-based extreme pressure agent include an acid phosphoric ester compound and/or an amine salt thereof, and an acid phosphorous ester compound and/or an amine salt thereof. Among these compounds, especially preferred are the acid phosphoric ester compound and/or the amine salt thereof. Specific examples of the acid phosphoric ester compound and/or the amine salt thereof include di-n-butyl phosphate, and a dodecylamine salt, a n-octylamine salt and a cyclohexylamine salt of di-n-butyl phosphate; and di-2-ethylhexyl phosphate, and a n-octylamine salt, a n-butylamine salt, a n-ethylamine salt and a cyclohexylamine salt of di-2-ethylhexyl phosphate. Specific examples of the acid phosphorous ester compound and/or the amine salt thereof include dioleyl hydrogen phosphite, and a dodecylamine salt, a n-octylamine salt and a cyclohexylamine salt of dioleyl hydrogen phosphite; and dilauryl hydrogen phosphite, and a dodecylamine salt, a n-octylamine salt and a cyclohexylamine salt of dilauryl hydrogen phosphite.
In addition, the refrigerating machine oil composition of the present invention preferably contains an antioxidant or an acid scavenger.
Examples of the antioxidant include phenol-based antioxidants and amine-based antioxidants. Specific examples of the phenol-based antioxidants include 2,6-di-tert-butyl-4-methyl phenol (DBPC), 2,4-dimethyl-6-tert-butyl phenol and 2,6-di-tert-butyl phenol. Specific examples of the amine-based antioxidants include N,N′-diisopropyl-p-phenylene diamine, N,N′-di-sec-butyl-p-phenylene diamine and a-naphthyl amine.
Examples of the acid scavenger include glycidyl ether group-containing compounds, epoxidated fatty acid monoesters, epoxidated soybean oil, epoxycycloalkyl group-containing compounds, a-olefin epoxides and glycidyl ester group-containing compounds.
In addition, the refrigerating machine oil composition of the present invention may also contain other known additives used in the conventional lubricating oils, for example, extreme pressure agents other than those described above. Examples of the other extreme pressure agents include organosulfur compounds such as monosulfides, polysulfides, sulfoxides, sulfones, thiosulfinates, sulfurized fats and oils, thiocarbonates, thiophenes, thiazoles and methanesulfonic acid esters; thiophosphoric ester compounds such as thiophosphoric triesters; ester-based compounds such as higher fatty acid esters, hydroxyaryl fatty acid esters, polyhydric alcohol esters and acrylic esters; organochlorine-based compounds such as chlorinated hydrocarbons and chlorinated carboxylic acid derivatives; organofluorine-based compounds such as fluorinated aliphatic carboxylic acids, fluorinated ethylene resins, fluorinated alkyl polysiloxanes and fluorinated graphites; alcohol-based compounds such as higher alcohols; and metal compounds such as naphthenic acid salts (such as lead naphthenate), fatty acid salts (such as fatty acid lead salts), thiophosphoric acid salts (such as zinc dialkyldithiophosphates), thiocarbamic acid salts, organomolybdenum compounds, organotin compounds, organogermanium compounds and boric acid esters.
Further, the refrigerating machine oil composition of the present invention may also be appropriately blended with stabilizers such as phenyl glycidyl ethers, cyclohexene oxides and epoxidated soybean oils; and copper deactivators such as benzotriazole and derivatives thereof. Furthermore, other additives such as load-resisting additives, chlorine scavengers, detergent dispersants, viscosity index improvers, oiliness agents, rust preventives, corrosion inhibitors and pour point depressants may be added to the refrigerating machine oil composition of the present invention, if required. The content of these additives in the refrigerating machine oil composition is usually from 0.5 to 10% by mass.
The refrigerating machine oil composition of the present invention can be suitably used for various refrigerants such as, for example, carbon dioxide-based refrigerants, hydrocarbon-based refrigerants, ammonia-based refrigerants and flon-based refrigerants. In particular, among these refrigerants, the composition of the present invention can be more suitably used for the carbon dioxide-based refrigerants.
Next, the compressor of the present invention is characterized in that the above refrigerating machine oil composition is used therein, and a sliding surface of a constitutional member of the compressor is coated with a lubrication film-forming composition containing a nitrogen-containing resin as a binder and at least one compound selected from the group consisting of molybdenum disulfide and fluororesins. Examples of the constitutional member of the compressor include a swash plate, a piston and a shoe in the case of a swash plate-type compressor. By coating the sliding surface of the respective members with the above lubrication film-forming composition and further using the above refrigerating machine oil composition in the compressor, a good lubrication of the sling surface can be ensured.
The swash plate-type compressor usually includes a pair of cylinder blocks butt-joined together in a front-to-back direction so as to form a swash plate chamber communicating with a suction port for a refrigerant returned thereto, at a joint portion therebetween. Both outside ends of the cylinder blocks are closed by front and rear housings, respectively, through a valve plate. The housings are each provided therein with a suction chamber and a discharge chamber. The discharge chamber disposed in the rear housing is communicated with a discharge port for discharging the refrigerant therefrom. The cylinder blocks have a common center axis hole into which a drive shaft is inserted and supported. A swash plate is fixed onto the drive shaft and rotatably accommodated within the swash plate chamber. Also, the cylinder blocks have plural pairs of bores arranged in the front-to-back direction and disposed in parallel with each other around the drive shaft. A double-ended piston anchored to the swash plate through a shoe is inserted into each bore so as to be linearly movable therein. The valve plates are respectively formed with a suction port communicating with the suction chamber of each housing through a suction valve between the respective bores, and formed with a discharge port communicating with the discharge chamber of each housing through a discharge valve between the respective bores. The swash plate chamber and the suction chamber of each housing are communicated with each other through a suction passage formed in each cylinder block, and the discharge chamber formed in the front housing is communicated with the discharge chamber formed in the rear housing through a discharge passage formed in the cylinder blocks.
In the above swash plate-type compressor, the returned refrigerant is introduced from the refrigerating circuit into the swash plate chamber through the suction port, and the returned refrigerant in the swash plate chamber is then introduced into the front and rear suction chambers through the suction passage. When the drive shaft is rotated, the respective pistons connected thereto through the swash plate are caused to linearly move in each bore, so that the returned refrigerant filled within the respective suction chambers is sucked through the respective suction ports into the bores which are now expanding their volumes. Thereafter, the refrigerant compressed in the bores which are now reducing their volumes is discharged through the respective discharge ports into the front and rear discharge chambers. The compressed refrigerant filled in the front discharge chamber is collected into the rear discharge chamber through the discharge passage. Then, the compressed refrigerant collected in the rear discharge chamber is discharged into the refrigerating circuit through the discharge port and circulated again through the refrigerating circuit.
Also, the present invention involves such a refrigerating apparatus in which carbon dioxide as a refrigerant is circulated through a refrigerating circuit constituted from the above compressor, a radiator, an expansion mechanism and an evaporator.
The present invention will be described in more detail by referring to the following examples. However, it should be noted that these examples are only illustrative and not intended to limit the invention thereto.
The refrigerating machine oil composition was evaluated by a reciprocating friction/abrasion test (Bauden Leben Test). Specifically, the evaluation was made by subjecting a sliding member to the above test to measure a friction coefficient thereof after 5, 100 and 200 reciprocating strokes.
The testing conditions are as follows.
Ball (Sphere): SUJ2; 3/16 inch
Plate: A cut piece of a swash plate available from Toyota Industries Corporation., was used. More specifically, the swash plate was worked as follows. That is, a FCD700 base material for the plate was coated with a lubrication film-forming composition containing a polyamide imide as a binder and a solid lubricant composed of molybdenum disulfide, graphite and polytetrafluoroethylene (PTFE) to form a coating film having a thickness of 30 μm thereon, and then processed such that the thickness of the coating film was from 10 to 20 μm, and the surface roughness Rz (10 point-mean roughness) thereof was 3.2 μm or less.
Load applied: 0.5 kgf
Velocity: 20 mm/s
Stroke: 10 mm
Testing temperature: room temperature
Atmosphere: air
A polyalkylene glycol containing propyleneoxide repeating units and methyl groups bonded to both terminal ends thereof and having a viscosity of 10 mm2/s as measured at 100° C. was used as a base oil, and the additives as shown in Table 1 below as well as 0.5% by mass of 2,6-di-tert-butyl-p-cresol (DBPC) as an antioxidant, 1.5% by mass of a-olefin epoxide as an acid scavenger and 0.9% by mass of tricresyl phosphate (TCP) were added to the base oil to prepare a refrigerating machine oil composition. The thus prepared composition was evaluated according to the above method. The results are shown in Table 1.
Meanwhile, the numeral “0.115” as a friction coefficient appearing in Table 1 represents the friction coefficient measured at the time at which the coating layer was worn so that the plate (FCD700 as the base material) and the ball (SUJ2) were contacted with each other.
The refrigerating machine oil composition of the present invention as well as a compressor and a refrigerating apparatus using the composition can ensure good lubrication of sliding portions upon starting operation of a compressor for a refrigerator and during the operation.
| Number | Date | Country | Kind |
|---|---|---|---|
| 2005-138890 | May 2005 | JP | national |
| Filing Document | Filing Date | Country | Kind | 371c Date |
|---|---|---|---|---|
| PCT/JP2006/308877 | 4/27/2006 | WO | 00 | 4/25/2008 |
