Title of Invention	A REFRIGERATING UNIT
Abstract	Abstract: The present invention relates to a refrigerating unit using a hudrofluorocarbon system refrigerad in a refrigeration cyld. It has at least one refrigerating machine oil with a polyol ester oil as its base oil. This polyol ester oil is prepared by polymorizing without a catalyst at least one polyol having at least two functional groups with at least one alkyl fatty acid having a straight or branched chaim. The polyester oil has a fluidity point lower than-40C, a two-liquid separation temperature lower than 20C, a total acid value lower than 0.02 mgKOH/g, a viscosity of 8 to 100 cst at 40c. THe hydroflu0orocarbon system refrigerant has a purity higher than 99.95 wt %. The amount of chlorine impurity in the system refrigerant being lower than 80 ppm.

Title of Invention

A REFRIGERATING UNIT

Abstract

Abstract: The present invention relates to a refrigerating unit using a hudrofluorocarbon system refrigerad in a refrigeration cyld. It has at least one refrigerating machine oil with a polyol ester oil as its base oil. This polyol ester oil is prepared by polymorizing without a catalyst at least one polyol having at least two functional groups with at least one alkyl fatty acid having a straight or branched chaim. The polyester oil has a fluidity point lower than-40C, a two-liquid separation temperature lower than 20C, a total acid value lower than 0.02 mgKOH/g, a viscosity of 8 to 100 cst at 40c. THe hydroflu0orocarbon system refrigerant has a purity higher than 99.95 wt %. The amount of chlorine impurity in the system refrigerant being lower than 80 ppm.

Full Text	BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a refrigerating unit having a refrigerating machine oil using polyol ester oil as its base oil in a refrigeration cycle using hydrofluorocarbon system refrigerants as 1,1,1,2-tetrafluoroethane (hereunder to be called R134a). 2. Background Art Compressors for a refrigerator and an automatic vending machine as well as a show case have used in many cases dichlorodifluoromethane (hereunder to be called R12) as a conventional refrigerant. This R12 has become the object of regulated flon because of the problem of destructing the ozone layer. And as the alternative refrigerant of this R12, the hydrofluorocarbon (HFC) refrigerant and the fluorocarbon (FC) refrigerant representing R134a are being studied as the refrigerants for refrigerator, which is disclosed, for example, in the Japanese Patent Laid-Open Publication No. 1-271491. However, there was the problem resulting in the lubrication trouble of compressor because the refrigerant R134a has a worse compatibility with such refrigerating machine oils as mineral oil and alkylbenzene now being used and because of the aggravation of oil return to the compressor and also the suction of isolated refrigerator during its re-start when the refrigerating machine oil had separated from the refrigerant during its stop. For this reason, the inventors studied the polyol ester system oil as the refrigerating machine oil having a compatibility with the refrigerant R134a. However, it is known that this polyol ester system oil causes erosion to the sliding members by the fatty acid being produced after the decomposition of said oil and causes an abrasion if this oil is being used to a refrigerant compressor, especially to a rotary type compressor. And as a result of studying many times in order to combine the R134a as a refrigerant with the polyol ester system oil as a refrigerating machine oil, the inventors have discovered that the polyol ester system oil causes the hydrolysis by the influence of water with the rise of its total acid number, and a metallic soap is produced becoming a sludge, giving an adverse influence on the refrigeration cycle, and that the decomposition, oxidation deterioration and polymerization reaction are caused by the influences of oxygen and chlorine, and the metallic soap and the high molecule sludge are produced exerting an adverse influence on the refrigeration cycle. The inventors have also found out such a problem that the chlorine system refrigerant is also mixed into the hydrofluorocarbon refrigerant being sealed especially during the refrigeration cycle, and if the mixed volume should be much, the chlorine volume becomes much, invites the generation of metallic soap and the generation of high molecule sludge by the decomposition, oxidation deterioration and polymerization reaction of polyol ester oil, and stays stagnant in the evaporator and the liKe of refrigeration cycle. In addition, the inventors have also made sure that the problem as described above is also caused if the volume of chlorine should be much that remains behind the component parts such as the compressor, condenser, various kinds of pipes, etc. building up the refrigerating unit. Moreover, the inventors have also ascertained the generation of such a problem that the mineral oil has been conventionally used during the machining and assembling works of component parts, and because this mineral oil can not be dissolved easily into the refrigerant of hydrofluorocarbon, it gets solidified and stays stagnant on the evaporator and the like during the refrigeration cycle, aggravates the refrigeration capability and damages the equipment if said mineral oil should stay stagnant in excess of a certain level of volume. Therefore, in the refrigerating unit using the polyol ester oil and the hydrofluorocarbon system refrigerant, the Inventors have found out that the said problems can be solved by using a particular polyol ester oil, adding a special additive to said oil, maintaining the purity of hydrofluorocarbon system refrigerant to a high value and suppressing the equilibrium water content or chlorine residual volume of refrigeration cycle. Moreover, the inventors found out that the said problematic point can be solved by installing a sludge catcher for capturing the sludge during the refrigeration cycle. This invention is for solving the said problem and its object is to solve the said problem when the polyol ester system oil having the compatibility with the hydrofluorocarbon system refrigerant (for example, R134a) has been used as the refrigerating machine oil and to obtain a favorable refrigerating unit. SUMMARY OF THE INVENTION Therefore, the present invention has built up a refrigerating unit which has at least one refrigerating machine oil using polyol ester oil as its base oil, whose hydrofluorocarbon system refrigerant has its purity higher than 99.5 wt% and where the mixing of chlorine system refrigerant is less than 80 ppra in at least one refrigeration cycle using the hydrofluorocarbon system refrigerant. In addition, in the refrigerating unit of the invention* the said polyol ester oil has been made the chemical compound which is a polymerized polyol having two functional groups or more with alkyl system fatty acid having a straight chain or a branched chain without catalyst, whose fluidity point is lower than -40°C,, with a two-liquid separation temperature lower than -20°C., total acid value is than 0.02 mgKOH/g, viscosity of 8 to 100 est at 40°C. and viscosity index of more than 80. Also, the refrigerating unit of the invent ion is further characterized in that the said refrigeration cycle is structured by using pipes tor connecting &t least one compressor, one condenser, one pressure reducing unit and one evaporator, and that at least one sludge catcher for capturing the sludge during the cycle is installed at the high pressure side of this refrigeration cycle. Further, the refrigerating unit of the invention is characterized in that the said refrigerating machine oil contains at least one kind of base oil being selected from the group consisting of alkylbenzene system oils or mineral system oils. In a preferred embodiment, the refrigerating unit is characterized in that the polyol having two functional groups or more is selected from the group consisting of neopentylglycol, trimethyrolpropane and pentaerythritol. In addition, the equilibrium water content during the refrigeration cycle (to be shown by the following equation (I) is lower than 200 ppm 10 in the intial state of operation: Residua.1 water content volume during the refrigeration cycle , X 10' (ppm)...(I) Filled oil volume -f Filled refrigerant vo 1 ume In addition, in the refrigerating unit the residual oxygen volume during the refrigeration cycle is made less 20 than 0.01 vol % of the volume inside the refrigeration cycle. Moreover, the refrigerating unit comprises component parts which are at least one compressor, one condenser, one pressure reducing unit and one evaporator, the alkylbenzene hard oil (hereinafter> to be called HAB) or the ester system oil is used as the oil being used during the machining and' assembling processes for component parts making up the refrigerating unit and that the use volume of HAB, if used, has been made lower than 10% of the sealed volume of oil in the refrigerating unit. Further, the chlorine volume remaining in the component parts the refrigerating unit has been made lower than 20 ppm compared to the total volume of oil and its refrigerant sealed into the refrigeration cycle. Moreover, the total volume of the chlorine system refrigerant mixed inside the hydrofluorocarbon system refrigerant that is sealed into the refrigeration cycle and the chlorine volume remaining in the component parts has been made lower than 100 ppm against the total volume of oil and refrigerant sealed into the refrigeration cycle. Additionally, one embodiment of 0.1 to 0.5 wt % of at least one phenol system oxidation preventive agent is added as an additive agent into the polyol ester oil, that is to be selected especially from the group consisting of 2,6-di-. tertiarybutylparacresol (DBPC), 2,6-di-tertiarybutyl-phenol and 2,4,6-tri-tertiarybutyl-phenol. Moreover, at least one copper inactivation agent lower than 20 ppm is added as an additive into the polyol ester oil, that is to be selected especially from the benzotriazole (BTA) system chemical compound. Further, as another feature, at least an extreme pressure additive of lower than 2 wt X is added as the additive into the polyol ester oil, that is to be selected especially from the phosphoric acid triester system chemical compound. Moreover, in the refrigerating unit of the invention, the epoxy system additive of 0,1 to 0.5 wt % is added as the additive into the polyol ester oil. The present invention provides the following mode of operation because it has been structured as described above. Because the purity of hydrofluorocarbon system refrigerant has been made an extremely high one by the structure as mentioned, the foreign materials and CFC hardly get mixed into the refrigeration cycle, there is a suppression of the action of the chlorine in dissolving the polyol ester oil into the formation of fatty acid that reacts with the metals and forms metallic soap. Also, the deposition of sludge can be reduced, the compatibility between the polyol ester oil and the refrigerant is secured and the stable performance can be obtained. Further, the polyol ester oil of this invention makes the compatibility with the hydrofluorocarbon system refrigerant favorable throughout the entire temperature zone to be used in the refrigerating unit because of the structure, and can eliminate the two-layer separation of the refrigerant and the oil. Therefore, because the polyol ester oil exists in its state dissolved into the hydrofluorocarbon system refrigerant (for example, R134a) at all times in the low temperature region lower than -30°C, in the refrigeration cycle and becomes a low viscosity as a whole, the oil return to the compressor favorable. Therefore, the fall of the oil level of the compressor can be eliminated, the oil supply to the bearing sliding areas can be secured and the gnawing and the burning can be prevented. Still more, by such an action that the ester coupling of the oil itself is molecule-oriented mainly on the surfaces of the metallic system sliding area of shaft and bearings of the compressor and by such an action that the said ester coupling can be dissolved easily into' the refrigerant (for example, R134a), the polyol ester oil of this invention can lower the actual viscosity, decrease the machine loss and enhance the actual record coefficient of compressor. In addition, because the sludge catcher (for example, being built up by caking the active alumina particles with a binder) for capturing the sludge in the cycle has been installed to the high pressure side of refrigeration cycle, the sludge being generated in the refrigeration cycle and the fatty acid being caused by the hydrolysis of ester oil can be adsorbed by this sludge catcher to previously prevent the formation of metallic soap. Furthermore, because the. alkylbenzene system oil or the mineral system oil are used as the base oil in addition to the polyol ester oil as the base oil of the refrigerating machine oil, the trouble of polyol ester oil, in other words, the electrolyte by frictional heat and the like of sliding portions of the compressor can be lowered down to the minimum level, suppressing the formation of metallic soap and preventing almost all the sludge. Consequently> the fall of the oil level of the compressor can be eliminated, the oil supply to the bearing sliding portions can be secured, and the gnawing and the burning (seizure) can be prevented. Also, in the initial operation period of refrigerating unit, it is possible to prevent the oil from causing any hydrolysis to decrease the total acid value, to suppress the generation of sludge due to the formation of metallic soap and to secure the lubrication characteristics in the sliding areas. In addition, the invention makes it possible to prevent the oxidation and deterioration of polyol 10 ester oil and the sludge by the polymerization, and to cause the refrigerating unit to have an excellent reliability. Further, because the alkylbenzene hard oil (HAB) and the ester oil that can be easily dissolved into the 15 hydrofluorocarbon system refrigerant are used during the machining and assembling of component parts and the used volume of HAB, if used, has been limited, the residual chlorine volume of component parts can be vastly decreased, its solidification to the evaporator and so forth in the refrigeration cycle can be prevented, and the fall in the refrigeration capability and the damage to the equipment can be prevented in advance. Because the chlorine volume remaining on the component parts of the compressor, condenser, various pipes and the life making up the refrigerating unit has been regulated and prevents the formation of metallic soap and high molecule sludge coming from the decomposition, oxidation/deterioration and polymerization reaction of polyol ester oil can be prevented, and it can also be prevented that the sludge remain stagnant on the evaporator and so forth of refrigeration cycle. Moreover, because the total volume between the mixed volume of the chiorine system refrigerant in the Iiydrof luorocarbon system refrigerant being sealed into the refrigeration cycle and the chiorine volume remaining on the component parts of refrigerating unit has been regulated to a level lower than 100 ppm against the total volume of oil and refrigerant being sealed into the refrigeration cycle, the mixing of chlorine in the refrigeration cycle can be regulated as an entire unit, the formation of metallic soap coming from the decomposition, oxidation.and deterioration, polymerization and reaction arid the formation of high molecule sludge can be prevented, thus being able to provide a refrigerating unit capable of exhibiting a stable performance. Further, the polyoJ ester oil according to the present invention can enhance the oxidation/deterioration stability as compared with the glycol oil and the like, and enhance the performance and reliability of the compressor. Moreover, the invention can suppress the adsorption and its catalyst action on the copper surface which becomes the bearing sliding surfaces, and can suppress the hydrolysis of refrigerating machine oil. In addition, a strong chemical adsorption fiIra if formed on the bearing sliding surfaces to make the lubrication property of the sliding portions better and prevent the gnawing and burning. Besides, the invention can suppress the hydrolysis, decrease the total acid value to suppress the formation of metallic soap and can enhance the reliability of unit. - J, Accordingly, the present invention provides a refrigerating unit comprising a condenser, a compressor, a pressure reducing unit and an evaporator using a hydrofluorocarbon system refrigerant having its purity higher than 99.95 wt% and its amount of chlorine impurity being less than 80 ppm in a refrigeration cycle with at least one refrigerating machine oil with a polyol est^ as its base oil, characterized in that said polyol ester is prepared by polymerizing without a catalyst at least one polyol having at least two fimctional groups with at least one alkyl fatty acid having a strain or branched chain, saJd polyester having a fluidity point lower than -40'C, a two-iiquid separation temperature lower than -20°C, a total acid value lower than 0.02 mgKOH/g and a viscosity of 8 to 100 est at 40°C. With reference to the accompanying drawings, in which: Fig. 1 is a partially cut view indicating the entire reciprocation type compressor showing one embodiment according to the present invention. Fig.2 is a vertical cross sectional view of rotary type compressor showing one embodiment of this uivention. Fig.3 is a circuit diagram of refrigeration cycle testing machine used in this invention. Fig.4 is a graph showing the endurance test result by an actual refrigerating unit. Fig. 5 is a graph showing anotha- endurance test resuh by the actual refrigerating unit. Fig. 5 is a graph biiuwxng a sriJ.! another endurance test result by the actual refrigerating unit. DETAILED DESCRIPTION OF THE PHEFERRED EMBODIMENTS Hereunder, the present invention is to be explained on the basis of the embodiments shown in the drawings. Fig. 1 is a partially cut view of reciprocation type compressor 39, which comprises a compressor unit 36 housed in the upper portion of a hermetic case 38 containing lubricating oil 34 at its bottom, and an electric motor unit 31 housed in the lower portion of said case 38 and connected to the compressor unit 36 by a crankshaft. And said electric motor unit 31 is driven by electric power from a power supply terminal 30. A flon gas sealed into said hermetic case 38 is N through a suction muffler 36 and suction side of a valve unit 35 flown to compression room of said compressor unit 36, and compressed via piston 32 of compressor unit 36. Said oil 34 in the bottom of the case 38 is forced upward through a oil cup 33 by a centrifugal action of the crankshaft. And said oil 34 is supplied to the surfaces of improved lubrication characteristics. In addition, polyol ester oil is used as said lubricating oil 34 and 1,1,1,2-tetrafluoroBthane (HFC-134a) is used as said flon gas. On the other hand. Fig. 2 is a vertical cross section view of rotary type compressor and is a view showing the other structural circuits. Letter A in Fig. 2 is a refrigeration cycle building up the refrigerating unit, and is structured by connecting with pipes a compressor B, a condenser C, a pressure reducing unit D, an evaporator E, a dryer F and a sludge catcher G. Here, the dryer F is formed of molecular sieves which are publicly known materials, while the sludge catcher G is formed by bonding active alumina particles with a binder. And, the above mentioned compressor B has the structure as follows : Numeral 1 denotes a closed vessel, and a motor element 2 and a rotary compressor element 3 being driven by the said motor element are respectively stored on the upper side and the lower side inside this vessel. The motor element 2 is structured of a stator 5 having a winding 4 insulated by an organic system material and a rotor 6 installed inside the said stator. The rotary compressor element 3 is structured of a cylinder 7, a roller 10 turned along the inside wall of cylinder by an eccentric portion 9 of a rotary shaft 8, a vane 12 being pressed against the circumferential face of said roller and pressed by a spring 11 so as to partition the inside of cylinder 7 into its suction side and its discharge side, and an upper bearing 13 and a lower bearing 14 not only for closing the opening of cylinder 7 but also for supporting the rotary shaft 8. And, a discharge hole 15 interconnected with the discharge side of cylinder 7 is installed to the upper bearing 13. Further, a discharge valve 16 for opening and closing the discharge hole 15 and a discharge muffler 17 so as to cover the said discharge valve are mounted on the upper bearing 13. The roller 10 and the vane 12 may be made of ferrous system materials. Further the roller 10 may be made by casting, preferably by continuous casting. In addition, the vane 12 may be made of carbon materials. Hereunder, some concrete embodiments according to the present invention are being explained on the basis of Fig. 2. The oil 18 of polyol ester oil, which consists of herni obtained by polymerizing the chemical compound which ^^^VnnJ.yinPXJ-rigid a polyol having two functional groups or more with a alkyl fatty acid having a straight chain or a branched chain using no catalyst, whose fluidity point is -50°C, two-liquid separation temperature is -30°C, total acid value is lower than 0.01 mgKOH/g, viscosity is 32 est at 40'C, and viscosity index is 95, is stored at the bottom area inside the closed vessel 1. Such polyols having two functional groups or more can be enumerated, for example, as the neopenthylglycol, trimethyrolpropane and pentaerythritol, etc. In addition, such alkyl fatty acids having a straight chain or a branched chain can be enumerated, for example, ap the pentane carbonic acid, hexane carbonic acid, heptane carbonic acid, octane carbonic acid, neopentane carbonic acid, neohexane carbonic acid, neoheptane carbonic acid, 2-methylhexane carbonic acid, 2-ethylhexane carbonic acid, 3,5,5-tri-methylhexane carbonic acid, etc. The paraffin system or naphthane system mineral system oil or alkylbenzene system oil and the like having excellent abrasion resistance, oxidation stability, electric insulation property, etc. and whose dynamic viscosity at 40"C is 36.2 est though its compatibility with such a refrigerant as R134a^is worse may also be mixed into the said refrigerating machine oil. Suniso-IGS (trade name) as mineral system oil and Shrieve 01-150 (trade name) as alkylbenzene system oil can be enumerated. The polyol ester system oil needs to be contained at more than 10 to 15 weight % or more favorably to be contained at more than 20 weight % if being mixed. 0.3 wt % of phenol system oxidation preventive agent of 2,6-di-tertiarybutyl-paracresol (DBPC) as an additive is added into this polyol ester oil for the purpose of preventing the oxidation/deterioration under a long period storage, and 0.25 wt% of epoxy system additive is added for the purpose of preventing the ffiJartrrilysi BH hydrolysis' For Information, the copper inactivation agent of 5 ppm benzotriazole (BTA) and the extreme pressure additive of I wt% trlcresylphosphate (TCP) are added to this polyol ester oil as necessary. The general chemical compounds can be used as the oxidation preventive agent, but the phenol system oxidation preventive agent is especially favorable, and for example, 2,6-di-tertiarybutyl-paracresol, 2,6-di-tertiarybutyl-phenol, 2,4,6-tri-tertiarybutyl-phenol, etc. of said oxidation preventive agent can be used. On the other hand,, the phenylglycydylether, 2-ethylhexyl-glycydylether, 1,2-epoxy-cyclohexane, etc. can be pr6ferab3,y used as the epoxy system additive. The benzotriazol system chemical compound is favorably used as the copper inactivation agent as the copper inactivation agent, and for example, 5-methyl-lH-benzotriazole, l-di-octyl-aminomethyl-benzotriazol, etc, can be used. The phosphoric acid triester system chemical compound is favorably used as the extreme pressure additive, and for example, the triphenyl-phosphagen, tri-tertiarybutylphenyl-phosphate can be used in addition to the trlcresylphosphate of said compound. The hydrofluorocarbon, for example, R134a is sealing into the refrigeration cycle A. The R134a is to be adjusted to its purity at 99.97 Jt%, to the mixture of chlorine system refrigerant of 56 ppm. In addition, the equilibrium water content (shown in the below equation (I) inside the refrigeration cycle A is to be adjusted to be 150 ppm under the initial operation state. Residual water content volume during the refrigeration cycle ■X 10* (ppm) (I) Filled oil volume + Filled refrigerant volume The dryer F used in the refrigeration cycle A has a moisture absorbent with a bore diameter of 3A. In addition, the residual air volume inside the refrigeration cycle A has been adjusted to 0.005 wtSE of the cycle internal volume. Thd residual oxygen volume inside the refrigeration cycle A has been adjusted to less than 0.01 volJE of refriger^iation cycle internal volume. The alkylbenzene hard oil (hereinafter to be called HAB) or the ester system oil is used to the machining and assembling works of component parts of compressor B and condenser C building up the refrigerating unit, and the used volume of HAB has been controlled to less than 10% the sealed volume of oil into the refrigeration cycle A. In addition, the chlorine volume remaining on the component parts of refrigerating unit is controlled to be lower than 20 ppm against the total volume of oils 18 and Rl34a being sealed into the refrigeration cycle A. That is to say, the total volume between the mixed volume of chlorine system refrigerant (CFC, HCFC, etc. ) within the 134a refrigerant being sealed into the refrigeration cycle A and the chlorine volume remaining on the component parts of refrigerating unit is controlled to become lower than 100 ppm against the total volume of oil 18 and refrigerant being sealed into the refrigeration cycle A. In addition, the winding wire 4 out of the motor element 2 of compressor B is covered with the insulation material of two-layer structure where the layer made of heat resistant ester (THEIC) or ester imide is provided to the inside and moreover the layer made of amid imide is provided to the outside, and the PET film of low oligomer specification (lower than 0.6 wt% as a trimer) is used as the insulation film H for insulating the winding wires 4 together. And the oil 18 lubricates the sliding face between the roller 10 and the vane 12. which are sliding members of rotary compressor element 3. The refrigerant flowing into the cylinder 7 of rotary compressor element 3 and being compressed by the cooperative work between the roller 10 and the vane 12 is formed up by the Rl34a having Its compatibility with the oil 18 of polyol eatax system oil. Numeral 19 is a suction pipe fitted to the closed vessel 1 and for guiding the refrigerant to the suction side of cylinder 1, while Numeral 20 is a discharge pipe fitted to the upper wall of closed vessel 1, being compressed by the rotary compressor element 3 and for discharging the refrigerant out of the closed vessel 1 via the motor element 2. In the refrigerating machine oil compound being used to the rotary type compressor which has been structured in this way, the refrigerant R134a flown into the suction side of cylinder 7 from the suction pipe 19 is compressed by the cooperative work between the roller 10 and the vane 12, passes through the discharge hole 15, opens the discharge valve 16 and is discharged into a discharge muffler 17. The refrigerant inside this muffler is discharged to the outside of closed vessel 1 from the discharge pipe 20 via the motor element 2. And the oil 18 is supplied to the sliding faces of sliding members of roller 10 and vane 12 of rotary compressor element 3 for their lubrication, in addition, the refrigerant cosipressed inside the cylinder is prevented from leaking to the low pressure side. The oil is generally discharged to the side of condenser C from the inside of this closed vessel 1 together with the refrigerant being discharged out of the discharge pipe 20 of rotary compressor B, but the refrigerating machine oil flows through the refrigeration cycle A by the refrigerant in the high temperature region high in the refrigerant pressure, but the oil viscosity becomes high and its fluidity is lost in the low temperature region low in refrigerant pressure and tends to stay stagnant inside the refrigeration cycle A. Namely, the refrigerating machine oil tends to remain inside the evaporator E. Especially, in case of the conventional paraffin system and naphthane system mineral oil having a worse compatibility with the refrigerant or the refrigerating machine oil of alkylbenzene oil and che like, the freezing point temperature of this refrigerating machine oil doesn't become lower because of the refrigerant, and the oil viscosity becomes additionally higher inside the evaporator E and its fluidity is conspicuously lost. To solve this problem, the present invention uses as a base oil the polyol ester oil having a compatibility with such a refrigerant as a special Rl34a, further mixes the base oil of nineral oil or alkylbenzene oil and moreover can compensate hydrolysis for the defect of oJieafaPolyBAa and the like of polyol ester sil. Further by mixing it, the refrigerant Rl34a and so forth solutes into the mixed oil, the freezing point :emperature falls down thereby, and the suppression of 'iscosity rise can be achieved so that its fluidity inside :he evaporator E may not be lost. It is possible to prevent the chemical stability of mixed -oil from being damaged by suppressing the polyol ester system oil contained in the mineral oil or the alkylbenzene oil down to 50 weight % from 10 weight %. This fact could be confirmed from the following experiments : Namely, not simply the return state of mixed oil 18 was confirmed using the refrigeration cycle testing machine as shown in Fig. 3 but the total acid value of refrigerating machine oil was evaluated using the iron and the copper as catalysts under the air atmosphere. Numeral 25 denotes a rotary compressor corresponding to the rotary compressor B, Numeral 26 is a heat exchanger corresponding to a condenser C, Numeral 27 is a pressure reducing unit corresponding to the pressure reducing unit (capillary tube)'D, and Numeral 28 is a heat exchanger corresponding to the evaporator E, and they are connected with pipes. A sight glass 29 for confirming the volume of refrigerating machine oil Is mounted to the rotary compressor 25. The test conditions were set as follows to confirm the oil return property of mixed oil 18 when the nixed ratio between the alkylbenzene oil and the polyol ester system oil was changed : The capacity of rotary compressor 15 at 175 W, the condensing temperature of heat exchanger 26 It 40"C, the evaporation temperature of heat exchanger 28 at ■25'C and the R134a as the used refrigerant. Tn addition. \) y( the catalysts of iron and copper were entered into the mixed oil'IS in the air atmosphere, which was heated up to gO'C to measure the total acid value after the lapse of 30 days. Table 1 shows its results. Table 1 : Mixing Ratio Alkyibenzene oil(wt%) 100 95 90 SO 50 20 Polyot ester ml(wl%) 10 20 50 SO 100 Heat stability Total acid value (mgKOH/g) 0.01 0.01 0.02 0.06 0.06 Criteria : Not good Good : The oil level inside the compressor fell down. The oil level inside the compressor hardly changed. A slight corrosion appears to the sliding areas if the total acid value should exceed the level of 0.02 mgKOH/g. As a result, it can be known from Table 1 that the oil return property and heat stability of mixed oil IB is favorable when the polyol ester system oil was contained at 10 to 50 weight % in place of the alkylbenzene oil. This is hydrolysis supposed attributable to the fact that the Q.1i00fr7oli.'«Ji.E of polyol ester system oil by the frictional heat at the sliding areas of rotary compressor 25 can be suppressed by making the volume of polyol ester system oil to be less than the volume of alkylbenzene oil. And the reason why the oil return property becomes better when its mixing percentage becomes higher is supposed to attribute to the fact that the refrigerant of R134a gets dissolved into the polyol ester system oil, the freezing point temperature of mixed oil 18 falls down and therefore the fall of viscosity of mixed oil 18 inside the evaporator 28 is suppressed. According to the present embodiment, the following actions can be provided by the above mentioned structure : Because the purity of R134a refrigerant has been made extremely high, the foreign materials and CFC hardly enter into the refrigeration cycle A, the chlorine cannot decompose the polyol ester oil 18 into the formation of fatty acid, the formation of metallic soap after its reaction with the metals can be prevented, the deposition of sludge can be decreased, the compatibility between the polyol ester oil 18 and the R134a refr igerant can be secured, thus a stable performance can he obtained. Further, the polyol ester oil of this invention provide a better compatibl1i ty wi th the hydrofluorocarbon system refrigerant such as the R134a and the like, over the entire temperature zone being used in the refrigerating unit, and can eliminate the two- layer separation between the refrigerant and the oil. Consequently, because the polyol ester oil 18 exists in the state dissolved into the R134a at all times in the low temperature reg.ion lower than -SO'C in the refrigeration cycle A and becomes a low viscosity as a whole, the oil return to the compressor becomes favorable. Therefore, the oil level fall of compressor B can be eliminated, the oil supply to the bearing sliding portions 8, 13 and 14 can be secured for the prevention of their gnawing and the burning. Still more, by the action that the ester coupling owned by the oil itself mainly molecule-orient on the surfaces of iron system sliding portions of shaft 8 and bearings 13 and 14 of compressor B for enhancing the lubrication property and by the action for said ester oil to get dissolved into the R134a, the actual viscosity of polyol ester oil 18 according to this invention can be lowered to reduce the machine loss and enhance the actual record coefficient of compressor B. In addition, because a sludge catcher G (formed up by bonding the active alumina particles with a binder) for catching the sludge in the cycle has been installed to the high pressure side of refrigeration cycle A, the sludge generated in the refrigeration cycle A and the fatty acid generated by the aAwfoQiJys'iji of ester oil can be adsorbed by this sludge catcher to previously prevent the formation of netallic soap. Further, because the alkylbenzene oil or the mineral oil are used as its base oil in addition to the polyol ester oil as the base oil of refrigerating machine oil 18, the trouble of polyol ester oil, namely, the hydrolysis by the frictional heat of sliding portions 8, 13 and 14 of compressor can be decreased to the minimum level, the formation of metallic soap can be suppressed and the sludge can be almost prevented. Therefore! the fall of oil level of compressor B can be eliminated, the oil supply to the bearing sliding portions 8, 13 and 14 can be secured and their gnawing and burning can be prevented. Moreover, the invention can prevent the oil 18 from causing the hydrolysis in the initial operat ion period of refrigerating unit, decrease the total acid value, suppress the generation of sludge due to the formation of metallic soap and can secure the lubrication characteristics at the siiding portions 8, 13 and 14. This matter was also confirmed from the experiment result by the sealed tube test which sealed the polyol ester system oil 18 of this invention to which the OBPC was added. Namely, according to the polyol ester system oil 18 of this invention to which the DBPC was added under the condition where the water content was adjusted to 200 ppm in the aging of 90°C X 29 days, the total acid value became lower than 0.01 mgKOH/g in the initial stage, and a favorable result could be obtained. In addition, the oxidation/deterioration of polyol ester oil is prevented and the sludge due to the polymerization can result in a refrigerating unit excellent in its reliability. This matter was also confirmed from the experiment result by the sealed tube test sealed the polyol ester system oil of this invention to which the DBPC was added. Namely according to the polyol ester system oil 18 of this invention to which the DBPC was added under the condition where the residual oxygen volume inside the refrigeration cycle A was adjusted to less than 0.01 vol % in the aging of 90°C x 29 days, the total acid value becomes lower than 0.01 mgKOH/g in the initial stage, and a favorable result could be obtained. Further, because the alkylbenzene hard oil (HAS) and the ester oil which are easier to get dissolved into the R134a were used in the machining and assembling of component parts, and the volume of used HAS was limited, the residual chlorine volume of process sub-materials could be vastly decreased to prevent it from caking to the evaporator E and the like in the refrigeration cycle A and to prevent the fall of refrigeration capability and damage of equipment B, C, D, E and F. Because the chlorine volume remaining on the component parts of compressor B, condenser C and a variety of pipes making up the refrigerating unit was regulated, it becomes possible to prevent the formation of metallic soap by the decomposition, oxidation, deterioration and polymerization reaction of polyol ester oil 18 and the formation of high molecule sludge and to prevent the sludge to stay stagnant on the evaporator G and the like of refrigeration cycle A. Moreover, because the total volume of the mixed volume of chlorine system refrigerant in the R134a refrigerant sealed into the refrigeration cycle A and the chlorine volume remaining on the component parts of refrigerating unit has been regulated to less than 100 ppm against the total volume of oil 18 and refrigerant sealed into the refrigeration cycle, the mixing of chlorine in the refrigeration cycle A can be regulated as the entire unit, preventing the formation of metallic soap by the decomposition* oxidation/deterioration and polymerization/reaction of polyol ester oil 18 and the formation of high molecule sludge, and thus resulting in a refrigerating unit capable of exhibiting a stable performance. Further, the polyol ester oil 18 of this invention can enhance the oxidation deterioration stability as compared with the glycol oil and the like and can enhance the performance and reliability of compressor B. This matter could be confirmed also from the experiment results of the sealed tube test using the polyol ester system oil 18 of this invention to which the DBPC was added. That is to say* according to the polyol ester system oil 18 of this invention to which the DBPC was added under the condition where the water content was adjusted to 200 ppm through the aging of 90°C x 29 days, the total acid value became lower than 0.01 mgKOH/g at the initial stage and a favorable result could be obtained. Moreover, the polyol ester oil can be adsorbed on to the copper surfaces which become the bearing sliding faces 8, 10, 13 and 14, suppress its catalytic action and also suppress the hydrolysis of the refrigerating machine oil. In addition, a strong chemical adsorption film can be formed on the bearing sliding faces 8, 10, 13 and 14, making the lubrication property of sliding areas 8, 10, 13 and 14, thus preventing their gnawing and burning. The hydrolysis can be suppressed, which can decrease the total acid value to ^ suppress the formation of metallic soap and enhance the reliability of unit. The said operation results could be confirmed also from the endurance test results by use of the actual machine shown in Fig. 4. In Fig. 4, the endurance test time was taken on the axis of abscissa and the contamination level (sludge volume) was taken on the axis of ordinate. The studied specimens and conditions are as shown in the below Table 2 : Table 2 Additive Manuf actur ing standard I No additive A II X A III Y A IV Z B Additive : Additive X : DBPC + BTA Additive Y : DBPC + BTA + TCP Additive Z : DBPC + BTA + TCP + Epoxy Manufacturing Standard A : (Conventional Standard) Purity of refrigerant : 99.90 wt% Equilibrium water content in refrigeration cycle A ppm 600 Residual oxygen volume in refrigeration cycle A : 0.03 ■vol % Chlorine residue in refrigeration cycle A : 400 ppm Manufacturing Standard B : (Standard of Present Invention) Purity of refrigerant : 99.95 wt% Equilibrium water content in refrigeration cycle A ; 200 ppm Residual oxygen volume in refrigeration cycle A : 0.01 vol % Chlorine residue in refrigeration cycle A : 100 ppm The best result was shown by the specimen IV by the Standard B (where the purity o£ refrigerant and the water content, chlorine and oxygen volumes in refrigeration cycle A were limited as listed above) whose unit manufacturing standard was limited as shown in the present invention) using the specimen Z of polyol ester system oil 18 of this invention to which the additive (DBPC, Epoxy, etc.) was added. Additionally, the operation results in case that the sludge catcher of this invention has been added were confirmed also from the endurance test result by use of the actual machine shown in Fig. 5. In Fig. 5, the endurance test time was taken on the axis of abscissa and the contamination level (sludge volume) was taken on the axis of ordinate similarly to those of Fig. 4. The studied specimens and conditions are as listed in th© following Table 3 : Table 3 Additive Manu facturing standard Sludge catcher V No additive A Absence VI X A Absence VII Y A Absence VIII Y A Presence IX z. B Absence For information, the codes of conditions in Tak^le 3 denote the foregoing conditions. Because the specimen VIII where the sludge catcher G was installed indicated the best result, it can be known that the better contaminant weight reduction can be attempted with the said specimen. In addition, the operation result in case of mixing the polyol ester system oil by this invention with the mineral oil or the alkylbenzene oil could be confirmed also from the endurance teat result by use of the actual machine shown in Fig, 6. In Fig. 6, the endurance test time was taken on the axis of abscissa and the contamination level (sludge volume) was taken on the axis of ordinate similarly to Fig. 4. The studied specimens and conditions are as shown in the following Table 4 : Table 4 Refrigerating machine oil Additive Manufacturing standard X Polyol ester oil alone No additive A XI Mixed oil NO additive A XII Mixed oil X A XIII Mixed oil Y A XIV Mixed oil Z B The codes in the conditions of Table 3 denote the foregoing conditions. Therefore, it was confirmed that the mixed oil can decrease the contamination level more effectively than the polyol ester system oil alone. For information, the present embodiment has been explained using the example of R134a as the hydrofluorocarbon system refrigerant, but should not be limited to this refrigerant along but the polyol ester system oil of this invention can exhibit an excellent compatibility even against the other refrigerants of HFC, and can be applied to these refrigerants. According to the present invention as described hydrolysis above, ■ the by the influence of water content on the polyol ester system oil can be suppressed to decrease the total acid value, suppress the formation of metallic soap for giving an adverse influence on the refrigeration cycle and also suppress the decomposition, oxidation deterioration and polymerization reaction by the influences of oxygen and chlorine to prevent the formation of metallic soap and high molecule sludge and thus being-able to obtain a favorable refrigerating unit by maintaining the purity of hydrofluorocarbon system refrigerant to a high value, using the particular raw material to the used polyol ester system oil, using the raw material of particular physical property range, adding a special additive, suppressing the equilibrium water content of refrigeration cycle, limiting the residual oxygen volume in the refrigeration cycle, using the alkylbenzene hard oil (hereinafter to be called HAB) or the ester system oil to the oil used to the machining and assembling processes of component parts, and limiting t:he mixed volume of chlorine system refrigerant and the chlorine volume remaining on the component parts. This application has been divided out of Indian Pataat Patent Application No.83lMAS/94 (184321). which relates to a refrigerating unit. WE CLAIM: 1. A refiigerating unit comimsmg a condenser, a compressor, a pressure reducing unit and an evaporator using a hydrofluorocarbon system refrigerant having its purity higher than 99.95 wt% and its amount of chlorine inqjurity being less than 80 ppm in a refrigeration cycle with at least one refrigerating machine oil with a polyoJ esl^ as its base oil, characterized in thai said polyol ester is , I- prepared by polymerizing without a catalyst at least one polyol having at least two functional groups with at least one alky! fatty acid having a straigjit or branched chain, said polyester having a fluidity point lower than -40"C, a two-liquid separation temperature lower than -20*'C, a total acid value lower than 0.02 mgKOH/g and a viscosity of 8 to 100 est at 40°C. 2. The refrigerating unit as claimed in claim I, wherein said refrigerating machine oil contains at least one base oil selected from the group consisting of aJkylbenzene system oil and mineral system oil. 3. The refrigerating unit as claimed in any one of the preceding claims, wherein the polyol having at least two ftinctional groups is selected from the ^oup consisting of neopentylglycol, trimethylolpropane and pentaerythritol. 4. The refrigerating unit as claimed in any one of the preceding claims, wherein 0.1 to 0.5 wt % of phenol oxidation preventive agent is added as an additive in the polyol esfter oil; wherein the phenol oxidation preventive agent is selected from the group consisting of 2,6-di-tertiarybutyl-paracresol (DBPC), 2,6-di-tertiarybutyl-phenol and 2,4,6-di-tertiarybulyi-phenol. 5. The refrigerating unit as claimed in any one of the preceding claims, wherein at least one copper inactivation agent selected from benzotriazole and its derivatives of less than 20 ppra is added as an additive to the polyol ester oil. 6. The refrigerating unit as claimed in any one of tlie preceding claims, wherein at least one high pressure additive of a phosporic acid triester compound of less than 2 wt % is added to the polyol ester oil. 7. The refrigerating unit as claimed in any one of the preceding claims, wherein al least one epoxy system additive of 0.1 to 0.5 wt % is added to the polyol ester oil. 8. A refrigerating unit substantially as herein described with reference to the accompanying drawings.

Full Text

BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a refrigerating unit having a refrigerating machine oil using polyol ester oil as its base oil in a refrigeration cycle using hydrofluorocarbon system refrigerants as 1,1,1,2-tetrafluoroethane (hereunder to be called R134a).
2. Background Art
Compressors for a refrigerator and an automatic vending machine as well as a show case have used in many cases dichlorodifluoromethane (hereunder to be called R12) as a conventional refrigerant. This R12 has become the object of regulated flon because of the problem of destructing the ozone layer. And as the alternative refrigerant of this R12, the hydrofluorocarbon (HFC) refrigerant and the fluorocarbon (FC) refrigerant representing R134a are being studied as the refrigerants for refrigerator, which is disclosed, for example, in the Japanese Patent Laid-Open Publication No. 1-271491.
However, there was the problem resulting in the lubrication trouble of compressor because the refrigerant

R134a has a worse compatibility with such refrigerating machine oils as mineral oil and alkylbenzene now being used and because of the aggravation of oil return to the compressor and also the suction of isolated refrigerator during its re-start when the refrigerating machine oil had separated from the refrigerant during its stop.
For this reason, the inventors studied the polyol ester system oil as the refrigerating machine oil having a compatibility with the refrigerant R134a. However, it is known that this polyol ester system oil causes erosion to the sliding members by the fatty acid being produced after the decomposition of said oil and causes an abrasion if this oil is being used to a refrigerant compressor, especially to a rotary type compressor.
And as a result of studying many times in order to combine the R134a as a refrigerant with the polyol ester system oil as a refrigerating machine oil, the inventors have discovered that the polyol ester system oil causes the hydrolysis by the influence of water with the rise of its total acid number, and a metallic soap is produced becoming a sludge, giving an adverse influence on the refrigeration cycle, and that the decomposition, oxidation deterioration and polymerization reaction are caused by the influences of oxygen and chlorine, and the metallic soap and the high molecule sludge are produced exerting an adverse influence on

the refrigeration cycle.
The inventors have also found out such a problem that the chlorine system refrigerant is also mixed into the hydrofluorocarbon refrigerant being sealed especially during the refrigeration cycle, and if the mixed volume should be much, the chlorine volume becomes much, invites the generation of metallic soap and the generation of high molecule sludge by the decomposition, oxidation deterioration and polymerization reaction of polyol ester oil, and stays stagnant in the evaporator and the liKe of refrigeration cycle.
In addition, the inventors have also made sure that the problem as described above is also caused if the volume of chlorine should be much that remains behind the component parts such as the compressor, condenser, various kinds of pipes, etc. building up the refrigerating unit.
Moreover, the inventors have also ascertained the generation of such a problem that the mineral oil has been conventionally used during the machining and assembling works of component parts, and because this mineral oil can not be dissolved easily into the refrigerant of hydrofluorocarbon, it gets solidified and stays stagnant on the evaporator and the like during the refrigeration cycle, aggravates the refrigeration capability and damages the equipment if said mineral oil should stay stagnant in excess of a certain level

of volume.
Therefore, in the refrigerating unit using the polyol ester oil and the hydrofluorocarbon system refrigerant, the Inventors have found out that the said problems can be solved by using a particular polyol ester oil, adding a special additive to said oil, maintaining the purity of hydrofluorocarbon system refrigerant to a high value and suppressing the equilibrium water content or chlorine residual volume of refrigeration cycle. Moreover, the inventors found out that the said problematic point can be solved by installing a sludge catcher for capturing the sludge during the refrigeration cycle.
This invention is for solving the said problem and its object is to solve the said problem when the polyol ester system oil having the compatibility with the
hydrofluorocarbon system refrigerant (for example, R134a) has been used as the refrigerating machine oil and to obtain a favorable refrigerating unit.
SUMMARY OF THE INVENTION
Therefore, the present invention has built up a refrigerating unit which has at least one refrigerating machine oil using polyol ester oil as its base oil, whose hydrofluorocarbon system refrigerant has its purity higher than 99.5 wt% and where the mixing of chlorine system

refrigerant is less than 80 ppra in at least one refrigeration cycle using the hydrofluorocarbon system refrigerant.
In addition, in the refrigerating unit of the invention* the said polyol ester oil has been made the chemical compound which is a polymerized polyol having two functional groups or more with alkyl system fatty acid having a straight chain or a branched chain without catalyst, whose fluidity point is lower than -40°C,, with a two-liquid separation temperature lower than -20°C., total acid value is than 0.02 mgKOH/g, viscosity of 8 to 100 est at 40°C. and viscosity index of more than 80.
Also, the refrigerating unit of the invent ion is further characterized in that the said refrigeration cycle is structured by using pipes tor connecting &t least one compressor, one condenser, one pressure reducing unit and one evaporator, and that at least one sludge catcher for capturing the sludge during the cycle is installed at the high pressure side of this refrigeration cycle.
Further, the refrigerating unit of the invention is characterized in that the said refrigerating machine oil contains at least one kind of base oil being selected from the group consisting of alkylbenzene system oils or mineral system oils.
In a preferred embodiment, the refrigerating unit is characterized in that the polyol having two functional groups or more is selected from the group consisting of neopentylglycol, trimethyrolpropane and pentaerythritol.
In addition, the equilibrium water content during the refrigeration cycle (to be shown by the following equation (I) is lower than 200 ppm 10 in the intial state of operation:

Residua.1 water content volume during
the refrigeration cycle ,
X 10*' (ppm)...(I)
Filled oil volume -f Filled refrigerant vo 1 ume
In addition, in the refrigerating unit the residual oxygen volume during the refrigeration cycle is made less 20 than 0.01 vol % of the volume inside the refrigeration cycle.
Moreover, the refrigerating unit comprises component parts which are at least one compressor, one condenser, one pressure reducing unit and one evaporator, the alkylbenzene hard oil (hereinafter> to be called HAB) or the ester system oil is used as the oil being used during the machining and' assembling processes for component parts making up the refrigerating unit and that the use volume of HAB, if used, has been made lower than 10% of the sealed volume of oil in the refrigerating unit.
Further, the chlorine volume remaining in the component parts the refrigerating unit has been made lower than 20 ppm compared to the total volume of oil and its refrigerant sealed into the refrigeration cycle.
Moreover, the total volume of the chlorine system refrigerant mixed inside the hydrofluorocarbon system refrigerant that is sealed into the refrigeration cycle and the chlorine volume remaining in the component parts has been made lower than 100 ppm against the total volume of oil and refrigerant sealed into the refrigeration cycle.
Additionally, one embodiment of 0.1 to 0.5 wt % of at least one phenol system oxidation preventive agent is added as an additive agent into the polyol ester oil, that is to be selected especially from the group consisting of 2,6-di-.

tertiarybutylparacresol (DBPC), 2,6-di-tertiarybutyl-phenol and 2,4,6-tri-tertiarybutyl-phenol.
Moreover, at least one copper inactivation agent lower than 20 ppm is added as an additive into the polyol ester oil, that is to be selected especially from the benzotriazole (BTA) system chemical compound.
Further, as another feature, at least an extreme pressure additive of lower than 2 wt X is added as the additive into the polyol ester oil, that is to be selected especially from the phosphoric acid triester system chemical compound.
Moreover, in the refrigerating unit of the invention, the epoxy system additive of 0,1 to 0.5 wt % is added as the additive into* the polyol ester oil.
The present invention provides the following mode of operation because it has been structured as described above.
Because the purity of hydrofluorocarbon system refrigerant has been made an extremely high one by the structure as mentioned, the foreign materials and CFC hardly get mixed into the refrigeration cycle, there is a suppression of the action of the chlorine in dissolving the polyol ester oil into the formation of fatty acid that reacts with the metals and forms metallic soap. Also, the deposition of sludge can be reduced, the compatibility between the polyol ester oil and the refrigerant is secured and the stable performance can be obtained.
Further, the polyol ester oil of this invention makes the compatibility with the hydrofluorocarbon system refrigerant favorable throughout the entire temperature zone to be used in the refrigerating unit because of the structure, and can eliminate the two-layer separation of the refrigerant and the

oil. Therefore, because the polyol ester oil exists in its state dissolved into the hydrofluorocarbon system refrigerant (for example, R134a) at all times in the low temperature region lower than -30°C, in the refrigeration cycle and becomes a low viscosity as a whole, the oil return to the compressor favorable. Therefore, the fall of the oil level of the compressor can be eliminated, the oil supply to the bearing sliding areas can be secured and the gnawing and the burning can be prevented. Still more, by such an action that the ester coupling of the oil itself is molecule-oriented mainly on the surfaces of the metallic system sliding area of shaft and bearings of the compressor and by such an action that the said ester coupling can be dissolved easily into' the refrigerant (for example, R134a), the polyol ester oil of this invention can lower the actual viscosity, decrease the machine loss and enhance the actual record coefficient of compressor.
In addition, because the sludge catcher (for example, being built up by caking the active alumina particles with a binder) for capturing the sludge in the cycle has been installed to the high pressure side of refrigeration cycle, the sludge being generated in the refrigeration cycle and the fatty acid being caused by the hydrolysis of ester oil can be adsorbed by this sludge catcher to previously prevent the formation of metallic soap.
Furthermore, because the. alkylbenzene system oil or the mineral system oil are used as the base oil in addition to the polyol ester oil as the base oil of the refrigerating machine oil, the trouble of polyol ester oil, in other words, the electrolyte by frictional heat and the like of sliding portions of the compressor can be lowered down to the minimum level,

suppressing the formation of metallic soap and preventing almost all the sludge. Consequently> the fall of the oil level of the compressor can be eliminated, the oil supply to the bearing sliding portions can be secured, and the gnawing and the burning (seizure) can be prevented.
Also, in the initial operation period of refrigerating unit, it is possible to prevent the oil from causing any hydrolysis to decrease the total acid value, to suppress the generation of sludge due to the formation of metallic soap and to secure the lubrication characteristics in the sliding areas.
In addition, the invention makes it possible to prevent the oxidation and deterioration of polyol 10 ester oil and the sludge by the polymerization, and to cause the refrigerating unit to have an excellent reliability.
Further, because the alkylbenzene hard oil (HAB) and the ester oil that can be easily dissolved into the 15 hydrofluorocarbon system refrigerant are used during the machining and assembling of component parts and the used volume of HAB, if used, has been limited, the residual chlorine volume of component parts can be vastly decreased, its solidification to the evaporator and so forth in the refrigeration cycle can be prevented, and the fall in the refrigeration capability and the damage to the equipment can be prevented in advance.
Because the chlorine volume remaining on the component parts of the compressor, condenser, various pipes and the life making up the refrigerating unit has been regulated and prevents the formation of metallic soap and high molecule sludge coming from the decomposition, oxidation/deterioration and polymerization reaction of polyol ester oil can be prevented, and

it can also be prevented that the sludge remain stagnant on the evaporator and so forth of refrigeration cycle.
Moreover, because the total volume between the mixed volume of the chiorine system refrigerant in the Iiydrof luorocarbon system refrigerant being sealed into the refrigeration cycle and the chiorine volume remaining on the component parts of refrigerating unit has been regulated to a level lower than 100 ppm against the total volume of oil and refrigerant being sealed into the refrigeration cycle, the mixing of chlorine in the refrigeration cycle can be regulated as an entire unit, the formation of metallic soap coming from the decomposition, oxidation.and deterioration, polymerization and reaction arid the formation of high molecule sludge can be prevented, thus being able to provide a refrigerating unit capable of exhibiting a stable performance.
Further, the polyoJ ester oil according to the present invention can enhance the oxidation/deterioration stability as compared with the glycol oil and the like, and enhance the performance and reliability of the compressor.
Moreover, the invention can suppress the adsorption and its catalyst action on the copper surface which becomes the bearing sliding surfaces, and can suppress the hydrolysis of refrigerating machine oil.
In addition, a strong chemical adsorption fiIra if formed on the bearing sliding surfaces to make the lubrication property of the sliding portions better and prevent the gnawing and burning.
Besides, the invention can suppress the hydrolysis, decrease the total acid value to suppress the formation of metallic soap and can enhance the reliability of unit.
- J,

Accordingly, the present invention provides a refrigerating unit comprising a condenser, a compressor, a pressure reducing unit and an evaporator using a hydrofluorocarbon system refrigerant having its purity higher than 99.95 wt% and its amount of chlorine impurity being less than 80 ppm in a refrigeration cycle with at least one refrigerating machine oil with a polyol est^ as its base oil, characterized in that said polyol ester is prepared by polymerizing without a catalyst at least one polyol having at least two fimctional groups with at least one alkyl fatty acid having a strain or branched chain, saJd polyester having a fluidity point lower than -40'C, a two-iiquid separation temperature lower than -20°C, a total acid value lower than 0.02 mgKOH/g and a viscosity of 8 to 100 est at 40°C.
With reference to the accompanying drawings, in which:
Fig. 1 is a partially cut view indicating the entire reciprocation type compressor showing one embodiment according to the present invention.
Fig.2 is a vertical cross sectional view of rotary type compressor showing one embodiment of this uivention.
Fig.3 is a circuit diagram of refrigeration cycle testing machine used in this invention.
Fig.4 is a graph showing the endurance test result by an actual refrigerating unit.
Fig. 5 is a graph showing anotha- endurance test resuh by the actual refrigerating unit.

Fig. 5 is a graph biiuwxng a sriJ.! another endurance test result by the actual refrigerating unit.
DETAILED DESCRIPTION OF THE PHEFERRED EMBODIMENTS
Hereunder, the present invention is to be explained on the basis of the embodiments shown in the drawings.
Fig. 1 is a partially cut view of reciprocation type compressor 39, which comprises a compressor unit 36 housed in the upper portion of a hermetic case 38 containing lubricating oil 34 at its bottom, and an electric motor unit 31 housed in the lower portion of said case 38 and connected to the compressor unit 36 by a crankshaft. And said electric motor unit 31 is driven by electric power from a power supply terminal 30. A flon gas sealed into said hermetic case 38 is N through a suction muffler 36 and suction side of a valve unit 35 flown to compression room of said compressor unit 36, and compressed via piston 32 of compressor unit 36. Said oil 34 in the bottom of the case 38 is forced upward through a oil cup 33 by a centrifugal action of the crankshaft. And said oil 34 is supplied to the surfaces of improved lubrication characteristics. In addition, polyol ester oil is used as said lubricating oil 34 and 1,1,1,2-tetrafluoroBthane (HFC-134a) is used as said flon gas.
On the other hand. Fig. 2 is a vertical cross section view of rotary type compressor and is a view showing

the other structural circuits. Letter A in Fig. 2 is a refrigeration cycle building up the refrigerating unit, and is structured by connecting with pipes a compressor B, a condenser C, a pressure reducing unit D, an evaporator E, a dryer F and a sludge catcher G. Here, the dryer F is formed of molecular sieves which are publicly known materials, while the sludge catcher G is formed by bonding active alumina particles with a binder. And, the above mentioned compressor B has the structure as follows :
Numeral 1 denotes a closed vessel, and a motor element 2 and a rotary compressor element 3 being driven by the said motor element are respectively stored on the upper side and the lower side inside this vessel. The motor element 2 is structured of a stator 5 having a winding 4 insulated by an organic system material and a rotor 6 installed inside the said stator. The rotary compressor element 3 is structured of a cylinder 7, a roller 10 turned along the inside wall of cylinder by an eccentric portion 9 of a rotary shaft 8, a vane 12 being pressed against the circumferential face of said roller and pressed by a spring 11 so as to partition the inside of cylinder 7 into its suction side and its discharge side, and an upper bearing 13 and a lower bearing 14 not only for closing the opening of cylinder 7 but also for supporting the rotary shaft 8.
And, a discharge hole 15 interconnected with the

discharge side of cylinder 7 is installed to the upper bearing 13. Further, a discharge valve 16 for opening and closing the discharge hole 15 and a discharge muffler 17 so as to cover the said discharge valve are mounted on the upper bearing 13.
The roller 10 and the vane 12 may be made of ferrous system materials. Further the roller 10 may be made by casting, preferably by continuous casting. In addition, the vane 12 may be made of carbon materials.
Hereunder, some concrete embodiments according to
the present invention are being explained on the basis of
Fig. 2.
The oil 18 of polyol ester oil, which consists of
herni obtained by polymerizing the chemical compound which ^^^VnnJ.yinPXJ-rigid a polyol having
two functional groups or more with a alkyl fatty acid having
a straight chain or a branched chain using no catalyst, whose
fluidity point is -50°C, two-liquid separation temperature is
-30°C, total acid value is lower than 0.01 mgKOH/g, viscosity
is 32 est at 40'C, and viscosity index is 95, is stored at
the bottom area inside the closed vessel 1.
Such polyols having two functional groups or more
can be enumerated, for example, as the neopenthylglycol,
trimethyrolpropane and pentaerythritol, etc. In addition,
such alkyl fatty acids having a straight chain or a branched
chain can be enumerated, for example, ap the pentane carbonic

acid, hexane carbonic acid, heptane carbonic acid, octane carbonic acid, neopentane carbonic acid, neohexane carbonic acid, neoheptane carbonic acid, 2-methylhexane carbonic acid, 2-ethylhexane carbonic acid, 3,5,5-tri-methylhexane carbonic acid, etc.
The paraffin system or naphthane system mineral system oil or alkylbenzene system oil and the like having excellent abrasion resistance, oxidation stability, electric insulation property, etc. and whose dynamic viscosity at 40"C is 36.2 est though its compatibility with such a refrigerant as R134a^is worse may also be mixed into the said refrigerating machine oil. Suniso-IGS (trade name) as mineral system oil and Shrieve 01-150 (trade name) as alkylbenzene system oil can be enumerated.
The polyol ester system oil needs to be contained at more than 10 to 15 weight % or more favorably to be contained at more than 20 weight % if being mixed.
0.3 wt % of phenol system oxidation preventive agent of 2,6-di-tertiarybutyl-paracresol (DBPC) as an additive is added into this polyol ester oil for the purpose of preventing the oxidation/deterioration under a long period storage, and 0.25 wt% of epoxy system additive is added for the purpose of preventing the ffiJartrrilysi BH hydrolysis*'*
For Information, the copper inactivation agent of 5 ppm benzotriazole (BTA) and the extreme pressure additive of

I wt% trlcresylphosphate (TCP) are added to this polyol ester oil as necessary.
The general chemical compounds can be used as the oxidation preventive agent, but the phenol system oxidation preventive agent is especially favorable, and for example, 2,6-di-tertiarybutyl-paracresol, 2,6-di-tertiarybutyl-phenol, 2,4,6-tri-tertiarybutyl-phenol, etc. of said oxidation preventive agent can be used.
On the other hand,, the phenylglycydylether, 2-ethylhexyl-glycydylether, 1,2-epoxy-cyclohexane, etc. can be pr6ferab3,y used as the epoxy system additive.
The benzotriazol system chemical compound is favorably used as the copper inactivation agent as the copper inactivation agent, and for example, 5-methyl-lH-benzotriazole, l-di-octyl-aminomethyl-benzotriazol, etc, can be used.
The phosphoric acid triester system chemical compound is favorably used as the extreme pressure additive, and for example, the triphenyl-phosphagen, tri-tertiarybutylphenyl-phosphate can be used in addition to the trlcresylphosphate of said compound.
The hydrofluorocarbon, for example, R134a is sealing into the refrigeration cycle A.
The R134a is to be adjusted to its purity at 99.97 Jt%, to the mixture of chlorine system refrigerant of 56 ppm.

In addition, the equilibrium water content (shown in the below equation (I) inside the refrigeration cycle A is to be adjusted to be 150 ppm under the initial operation state.
Residual water content volume during the refrigeration cycle
■X 10* (ppm) (I)
Filled oil volume + Filled refrigerant volume
The dryer F used in the refrigeration cycle A has a moisture absorbent with a bore diameter of 3A. In addition, the residual air volume inside the refrigeration cycle A has been adjusted to 0.005 wtSE of the cycle internal volume.
Thd residual oxygen volume inside the refrigeration cycle A has been adjusted to less than 0.01 volJE of refriger^iation cycle internal volume.
The alkylbenzene hard oil (hereinafter to be called HAB) or the ester system oil is used to the machining and assembling works of component parts of compressor B and condenser C building up the refrigerating unit, and the used volume of HAB has been controlled to less than 10% the sealed volume of oil into the refrigeration cycle A.
In addition, the chlorine volume remaining on the
component parts of refrigerating unit is controlled to be

lower than 20 ppm against the total volume of oils 18 and Rl34a being sealed into the refrigeration cycle A.
That is to say, the total volume between the mixed volume of chlorine system refrigerant (CFC, HCFC, etc. ) within the 134a refrigerant being sealed into the refrigeration cycle A and the chlorine volume remaining on the component parts of refrigerating unit is controlled to become lower than 100 ppm against the total volume of oil 18 and refrigerant being sealed into the refrigeration cycle A.
In addition, the winding wire 4 out of the motor element 2 of compressor B is covered with the insulation material of two-layer structure where the layer made of heat resistant ester (THEIC) or ester imide is provided to the inside and moreover the layer made of amid imide is provided to the outside, and the PET film of low oligomer specification (lower than 0.6 wt% as a trimer) is used as the insulation film H for insulating the winding wires 4 together.
And the oil 18 lubricates the sliding face between the roller 10 and the vane 12. which are sliding members of rotary compressor element 3.
The refrigerant flowing into the cylinder 7 of rotary compressor element 3 and being compressed by the cooperative work between the roller 10 and the vane 12 is formed up by the Rl34a having Its compatibility with the oil

18 of polyol eatax system oil.
Numeral 19 is a suction pipe fitted to the closed vessel 1 and for guiding the refrigerant to the suction side of cylinder 1, while Numeral 20 is a discharge pipe fitted to the upper wall of closed vessel 1, being compressed by the rotary compressor element 3 and for discharging the refrigerant out of the closed vessel 1 via the motor element 2.
In the refrigerating machine oil compound being used to the rotary type compressor which has been structured in this way, the refrigerant R134a flown into the suction side of cylinder 7 from the suction pipe 19 is compressed by the cooperative work between the roller 10 and the vane 12, passes through the discharge hole 15, opens the discharge valve 16 and is discharged into a discharge muffler 17. The refrigerant inside this muffler is discharged to the outside of closed vessel 1 from the discharge pipe 20 via the motor element 2. And the oil 18 is supplied to the sliding faces of sliding members of roller 10 and vane 12 of rotary compressor element 3 for their lubrication, in addition, the refrigerant cosipressed inside the cylinder is prevented from leaking to the low pressure side.
The oil is generally discharged to the side of condenser C from the inside of this closed vessel 1 together with the refrigerant being discharged out of the discharge

pipe 20 of rotary compressor B, but the refrigerating machine
oil flows through the refrigeration cycle A by the
refrigerant in the high temperature region high in the
refrigerant pressure, but the oil viscosity becomes high and
its fluidity is lost in the low temperature region low in
refrigerant pressure and tends to stay stagnant inside the
refrigeration cycle A. Namely, the refrigerating machine oil
tends to remain inside the evaporator E. Especially, in case
of the conventional paraffin system and naphthane system
mineral oil having a worse compatibility with the refrigerant
or the refrigerating machine oil of alkylbenzene oil and che
like, the freezing point temperature of this refrigerating
machine oil doesn't become lower because of the refrigerant,
and the oil viscosity becomes additionally higher inside the
evaporator E and its fluidity is conspicuously lost. To
solve this problem, the present invention uses as a base oil
the polyol ester oil having a compatibility with such a
refrigerant as a special Rl34a, further mixes the base oil of
nineral oil or alkylbenzene oil and moreover can compensate
hydrolysis for the defect of oJieafaPolyBAa and the like of polyol ester
sil. Further by mixing it, the refrigerant Rl34a and so
forth solutes into the mixed oil, the freezing point
:emperature falls down thereby, and the suppression of
'iscosity rise can be achieved so that its fluidity inside
:he evaporator E may not be lost.

It is possible to prevent the chemical stability of mixed -oil from being damaged by suppressing the polyol ester system oil contained in the mineral oil or the alkylbenzene oil down to 50 weight % from 10 weight %. This fact could be confirmed from the following experiments : Namely, not simply the return state of mixed oil 18 was confirmed using the refrigeration cycle testing machine as shown in Fig. 3 but the total acid value of refrigerating machine oil was evaluated using the iron and the copper as catalysts under the air atmosphere.
Numeral 25 denotes a rotary compressor corresponding to the rotary compressor B, Numeral 26 is a heat exchanger corresponding to a condenser C, Numeral 27 is a pressure reducing unit corresponding to the pressure reducing unit (capillary tube)'D, and Numeral 28 is a heat exchanger corresponding to the evaporator E, and they are connected with pipes. A sight glass 29 for confirming the volume of refrigerating machine oil Is mounted to the rotary compressor 25. The test conditions were set as follows to confirm the oil return property of mixed oil 18 when the nixed ratio between the alkylbenzene oil and the polyol ester system oil was changed : The capacity of rotary compressor 15 at 175 W, the condensing temperature of heat exchanger 26 It 40"C, the evaporation temperature of heat exchanger 28 at ■25'C and the R134a as the used refrigerant. Tn addition.

\)

y(

the catalysts of iron and copper were entered into the mixed oil'IS in the air atmosphere, which was heated up to gO'C to measure the total acid value after the lapse of 30 days. Table 1 shows its results.

Table 1 :

Mixing Ratio

Alkyibenzene oil(wt%)

100

95

90

SO

50

20

Polyot ester ml(wl%)

10

20

50

SO

100

Heat stability
Total acid value (mgKOH/g)

0.01

0.01

0.02

0.06

0.06

Criteria : Not good
Good :

The oil level inside the compressor fell down.
The oil level inside the compressor hardly changed.

A slight corrosion appears to the sliding areas if the total acid value should exceed the level of 0.02 mgKOH/g.
As a result, it can be known from Table 1 that the oil return property and heat stability of mixed oil IB is favorable when the polyol ester system oil was contained at
10 to 50 weight % in place of the alkylbenzene oil. This is
hydrolysis
supposed attributable to the fact that the Q.1i00fr7oli.'«Ji.E of
polyol ester system oil by the frictional heat at the sliding

areas of rotary compressor 25 can be suppressed by making the volume of polyol ester system oil to be less than the volume of alkylbenzene oil. And the reason why the oil return property becomes better when its mixing percentage becomes higher is supposed to attribute to the fact that the refrigerant of R134a gets dissolved into the polyol ester system oil, the freezing point temperature of mixed oil 18 falls down and therefore the fall of viscosity of mixed oil 18 inside the evaporator 28 is suppressed.
According to the present embodiment, the following actions can be provided by the above mentioned structure : Because the purity of R134a refrigerant has been made extremely high, the foreign materials and CFC hardly enter into the refrigeration cycle A, the chlorine cannot decompose the polyol ester oil 18 into the formation of fatty acid, the formation of metallic soap after its reaction with the metals can be prevented, the deposition of sludge can be decreased, the compatibility between the polyol ester oil 18 and the R134a refr igerant can be secured, thus a stable performance can he obtained.
Further, the polyol ester oil of this invention provide
a better compatibl1i ty wi th the hydrofluorocarbon system
refrigerant such as the R134a and the like, over the entire
temperature zone being used in the refrigerating unit, and can
eliminate the two-

layer separation between the refrigerant and the oil. Consequently, because the polyol ester oil 18 exists in the state dissolved into the R134a at all times in the low temperature reg.ion lower than -SO'C in the refrigeration cycle A and becomes a low viscosity as a whole, the oil return to the compressor becomes favorable. Therefore, the oil level fall of compressor B can be eliminated, the oil supply to the bearing sliding portions 8, 13 and 14 can be secured for the prevention of their gnawing and the burning. Still more, by the action that the ester coupling owned by the oil itself mainly molecule-orient on the surfaces of iron system sliding portions of shaft 8 and bearings 13 and 14 of compressor B for enhancing the lubrication property and by the action for said ester oil to get dissolved into the R134a, the actual viscosity of polyol ester oil 18 according to this invention can be lowered to reduce the machine loss and enhance the actual record coefficient of compressor B.
In addition, because a sludge catcher G (formed up by bonding the active alumina particles with a binder) for catching the sludge in the cycle has been installed to the high pressure side of refrigeration cycle A, the sludge generated in the refrigeration cycle A and the fatty acid generated by the aAwfoQiJys'iji of ester oil can be adsorbed by this sludge catcher to previously prevent the formation of netallic soap.

Further, because the alkylbenzene oil or the mineral oil are used as its base oil in addition to the polyol ester oil as the base oil of refrigerating machine oil 18, the trouble of polyol ester oil, namely, the hydrolysis by the frictional heat of sliding portions 8, 13 and 14 of compressor can be decreased to the minimum level, the formation of metallic soap can be suppressed and the sludge can be almost prevented. Therefore! the fall of oil level of compressor B can be eliminated, the oil supply to the bearing sliding portions 8, 13 and 14 can be secured and their gnawing and burning can be prevented.
Moreover, the invention can prevent the oil 18 from causing the hydrolysis in the initial operat ion period of refrigerating unit, decrease the total acid value, suppress the generation of sludge due to the formation of metallic soap and can secure the lubrication characteristics at the siiding portions 8, 13 and 14.
This matter was also confirmed from the experiment result by the sealed tube test which sealed the polyol ester system oil 18 of this invention to which the OBPC was added.
Namely, according to the polyol ester system oil 18 of this invention to which the DBPC was added under the condition where the water content was adjusted to 200 ppm in the aging of 90°C X 29 days, the total acid value became lower than 0.01 mgKOH/g in the initial stage, and a favorable result could be obtained.
In addition, the oxidation/deterioration of polyol ester oil is prevented and the sludge due to the polymerization can result in a refrigerating unit excellent in its reliability.
This matter was also confirmed from the experiment result by the sealed tube test sealed the polyol ester system oil of this invention to which the DBPC was added.

Namely according to the polyol ester system oil 18 of this invention to which the DBPC was added under the condition where the residual oxygen volume inside the refrigeration cycle A was adjusted to less than 0.01 vol % in the aging of 90°C x 29 days, the total acid value becomes lower than 0.01 mgKOH/g in the initial stage, and a favorable result could be obtained.
Further, because the alkylbenzene hard oil (HAS) and the ester oil which are easier to get dissolved into the R134a were used in the machining and assembling of component parts, and the volume of used HAS was limited, the residual chlorine volume of process sub-materials could be vastly decreased to prevent it from caking to the evaporator E and the like in the refrigeration cycle A and to prevent the fall of refrigeration capability and damage of equipment B, C, D, E and F.
Because the chlorine volume remaining on the component parts of compressor B, condenser C and a variety of pipes making up the refrigerating unit was regulated, it becomes possible to prevent the formation of metallic soap by the decomposition, oxidation, deterioration and polymerization reaction of polyol ester oil 18 and the formation of high molecule sludge and to prevent the sludge to stay stagnant on the evaporator G and the like of refrigeration cycle A.
Moreover, because the total volume of the mixed volume of chlorine system refrigerant in the R134a refrigerant sealed into the refrigeration cycle A and the chlorine volume remaining on the component parts of refrigerating unit has been regulated to less than 100 ppm against the total volume of oil 18 and refrigerant sealed into the refrigeration cycle, the mixing of chlorine in the refrigeration cycle A can be regulated as the entire unit, preventing the formation of metallic soap by the

decomposition* oxidation/deterioration and polymerization/reaction of polyol ester oil 18 and the formation of high molecule sludge, and thus resulting in a refrigerating unit capable of exhibiting a stable performance.
Further, the polyol ester oil 18 of this invention can enhance the oxidation deterioration stability as compared with the glycol oil and the like and can enhance the performance and reliability of compressor B.
This matter could be confirmed also from the experiment results of the sealed tube test using the polyol ester system oil 18 of this invention to which the DBPC was added.
That is to say* according to the polyol ester system oil 18 of this invention to which the DBPC was added under the condition where the water content was adjusted to 200 ppm through the aging of 90°C x 29 days, the total acid value became lower than 0.01 mgKOH/g at the initial stage and a favorable result could be obtained.
Moreover, the polyol ester oil can be adsorbed on to the copper surfaces which become the bearing sliding faces 8, 10, 13 and 14, suppress its catalytic action and also suppress the hydrolysis of the refrigerating machine oil.
In addition, a strong chemical adsorption film can be formed on the bearing sliding faces 8, 10, 13 and 14, making the lubrication property of sliding areas 8, 10, 13 and 14, thus preventing their gnawing and burning.
The hydrolysis can be suppressed, which can decrease
the total acid value to
^

suppress the formation of metallic soap and enhance the reliability of unit.
The said operation results could be confirmed also from the endurance test results by use of the actual machine shown in Fig. 4. In Fig. 4, the endurance test time was taken on the axis of abscissa and the contamination level (sludge volume) was taken on the axis of ordinate. The studied specimens and conditions are as shown in the below Table 2 :

Table 2
Additive Manuf actur ing standard
I No additive A
II X A
III Y A
IV Z B

Additive :
Additive X : DBPC + BTA
Additive Y : DBPC + BTA + TCP
Additive Z : DBPC + BTA + TCP + Epoxy Manufacturing Standard A : (Conventional Standard)
Purity of refrigerant : 99.90 wt%
Equilibrium water content in refrigeration cycle A
ppm

600

Residual oxygen volume in refrigeration cycle A : 0.03 ■vol %
Chlorine residue in refrigeration cycle A : 400 ppm Manufacturing Standard B : (Standard of Present Invention) Purity of refrigerant : 99.95 wt%
Equilibrium water content in refrigeration cycle A ; 200 ppm
Residual oxygen volume in refrigeration cycle A : 0.01 vol % Chlorine residue in refrigeration cycle A : 100 ppm
The best result was shown by the specimen IV by the Standard B (where the purity o£ refrigerant and the water content, chlorine and oxygen volumes in refrigeration cycle A were limited as listed above) whose unit manufacturing standard was limited as shown in the present invention) using the specimen Z of polyol ester system oil 18 of this invention to which the additive (DBPC, Epoxy, etc.) was added.
Additionally, the operation results in case that the sludge catcher of this invention has been added were confirmed also from the endurance test result by use of the actual machine shown in Fig. 5. In Fig. 5, the endurance test time was taken on the axis of abscissa and the contamination level (sludge volume) was taken on the axis of

ordinate similarly to those of Fig. 4. The studied specimens and conditions are as listed in th© following Table 3 :
Table 3

Additive Manu facturing standard Sludge catcher
V No additive A Absence
VI X A Absence
VII Y A Absence
VIII Y A Presence
IX z. B Absence
For information, the codes of conditions in Tak^le 3 denote the foregoing conditions.
Because the specimen VIII where the sludge catcher G was installed indicated the best result, it can be known that the better contaminant weight reduction can be attempted with the said specimen.
In addition, the operation result in case of mixing the polyol ester system oil by this invention with the mineral oil or the alkylbenzene oil could be confirmed also from the endurance teat result by use of the actual machine shown in Fig, 6. In Fig. 6, the endurance test time was taken on the axis of abscissa and the contamination level (sludge volume) was taken on the axis of ordinate similarly

to Fig. 4. The studied specimens and conditions are as shown in the following Table 4 :
Table 4

Refrigerating machine oil Additive Manufacturing standard
X Polyol ester oil alone No additive A
XI Mixed oil NO additive A
XII Mixed oil X A
XIII Mixed oil Y A
XIV Mixed oil Z B
The codes in the conditions of Table 3 denote the foregoing conditions.
Therefore, it was confirmed that the mixed oil can decrease the contamination level more effectively than the polyol ester system oil alone.
For information, the present embodiment has been explained using the example of R134a as the hydrofluorocarbon system refrigerant, but should not be limited to this refrigerant along but the polyol ester system oil of this invention can exhibit an excellent compatibility even against the other refrigerants of HFC, and can be applied to these refrigerants.

According to the present invention as described hydrolysis above, ■ the by the influence of water content on
the polyol ester system oil can be suppressed to decrease the
total acid value, suppress the formation of metallic soap for
giving an adverse influence on the refrigeration cycle and
also suppress the decomposition, oxidation deterioration and
polymerization reaction by the influences of oxygen and
chlorine to prevent the formation of metallic soap and high
molecule sludge and thus being-able to obtain a favorable
refrigerating unit by maintaining the purity of
hydrofluorocarbon system refrigerant to a high value, using
the particular raw material to the used polyol ester system
oil, using the raw material of particular physical property
range, adding a special additive, suppressing the equilibrium
water content of refrigeration cycle, limiting the residual
oxygen volume in the refrigeration cycle, using the
alkylbenzene hard oil (hereinafter to be called HAB) or the
ester system oil to the oil used to the machining and
assembling processes of component parts, and limiting t:he
mixed volume of chlorine system refrigerant and the chlorine
volume remaining on the component parts.
This application has been divided out of Indian Pataat Patent Application No.83lMAS/94 (184321). which relates to a refrigerating unit.

WE CLAIM:
1. A refiigerating unit comimsmg a condenser, a compressor, a pressure reducing
unit and an evaporator using a hydrofluorocarbon system refrigerant having its
purity higher than 99.95 wt% and its amount of chlorine inqjurity being less
than 80 ppm in a refrigeration cycle with at least one refrigerating machine oil
with a polyoJ esl^ as its base oil, characterized in thai said polyol ester is
, I-
prepared by polymerizing without a catalyst at least one polyol having at least two functional groups with at least one alky! fatty acid having a straigjit or branched chain, said polyester having a fluidity point lower than -40"C, a two-liquid separation temperature lower than -20*'C, a total acid value lower than 0.02 mgKOH/g and a viscosity of 8 to 100 est at 40°C.
2. The refrigerating unit as claimed in claim I, wherein said refrigerating machine oil contains at least one base oil selected from the group consisting of aJkylbenzene system oil and mineral system oil.
3. The refrigerating unit as claimed in any one of the preceding claims, wherein the polyol having at least two ftinctional groups is selected from the ^oup consisting of neopentylglycol, trimethylolpropane and pentaerythritol.

4. The refrigerating unit as claimed in any one of the preceding claims, wherein 0.1 to 0.5 wt % of phenol oxidation preventive agent is added as an additive in the polyol esfter oil; wherein the phenol oxidation preventive agent is selected from the group consisting of 2,6-di-tertiarybutyl-paracresol (DBPC), 2,6-di-tertiarybutyl-phenol and 2,4,6-di-tertiarybulyi-phenol.
5. The refrigerating unit as claimed in any one of the preceding claims, wherein at least one copper inactivation agent selected from benzotriazole and its derivatives of less than 20 ppra is added as an additive to the polyol ester oil.
6. The refrigerating unit as claimed in any one of tlie preceding claims, wherein at least one high pressure additive of a phosporic acid triester compound of less than 2 wt % is added to the polyol ester oil.
7. The refrigerating unit as claimed in any one of the preceding claims, wherein al least one epoxy system additive of 0.1 to 0.5 wt % is added to the polyol ester oil.
8. A refrigerating unit substantially as herein described with reference to the accompanying drawings.

Documents:

506-mas-1999 abstract.pdf

506-mas-1999 claims.pdf

506-mas-1999 correspondence others.pdf

506-mas-1999 correspondence po.pdf

506-mas-1999 description (complete).pdf

506-mas-1999 drawings.pdf

506-mas-1999 form-1.pdf

506-mas-1999 form-13.pdf

506-mas-1999 form-26.pdf

506-mas-1999 form-4.pdf

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Patent Number

193414

Indian Patent Application Number

506/MAS/1999

PG Journal Number

20/2006

Publication Date

19-May-2006

Grant Date

12-Dec-2005

Date of Filing

29-Apr-1999

Name of Patentee

M/S. SANYO ELECTRIC CO LTD

Applicant Address

2-5-5, KEIHANHONDORI MORIGUCHI-SHI, OHSAKA FU

Inventors:

#	Inventor's Name	Inventor's Address
1	YUTAKA HIRANO	528-67, HIGASHIBESSHO, OTHTASHI, GUNMA-KEN
2	TAKEO KOMATUBARA	2-3520-3, HISHICHO, KIRYU-SHI, GUNMA-KEN,
3	TAKASHI SUNAGA	3508, NAKANO, OHRAMACHI, OHRA-GUN, GUNMA-KEN,
4	YASUKI TAKAHASHI	3607-2, HIGASHIKOBOKATA, HIGASHI-MURA, SAWA-GUN, GUNMA-YORIKIDO, OHIZUMI-MACHI, OHRA-GUN, GUNMA-KEN
5	KIYOSHI TANAKA	262-3, YORIKIDO, OHIZUMI-MACHI, OHRA-GUN, GUNMA-KEN,
6	KIYOSHI AKAZAWA	478-14, OHAZANABEYA, CHIYODA-MACHI, OHRA-GUN, GUNMA-KEN
7	MASATO WATANABE	6-14, SUMIYOSHI, OHIZUMI-MACHI, OHRA-GUN, GUNMA-KEN,

PCT International Classification Number

C08F2/00

PCT International Application Number

N/A

PCT International Filing date

PCT Conventions:

#	PCT Application Number	Date of Convention	Priority Country
1			NA