JP5721480B2 - Refrigeration cycle equipment - Google Patents

Description

  The present invention relates to a refrigeration cycle apparatus such as an air conditioner, a refrigerator, and a heat pump, and more particularly to a refrigeration oil used in a refrigeration cycle apparatus using hydrocarbons as a refrigerant.

As a conventional technique, there is known an example in which oil having compatibility with a refrigerant is used in a refrigeration cycle apparatus using a compressor using a hydrocarbon as a refrigerant and having a discharge pressure inside the sealed container (high-pressure shell type). ing. In this prior art, the problem is that a large amount of hydrocarbon dissolves in mineral oil and the viscosity of the refrigerating machine oil is greatly reduced, and in order to ensure the sliding resistance (or lubrication performance) of the compressor in that system It has been shown that a refrigerating machine oil having a viscosity of 46 cSt or higher at 40 ° C. is used (for example, see Patent Document 1).
In addition, in this document, as a refrigerating machine oil having compatibility with hydrocarbons, paraffin hydrocarbons, naphthenic hydrocarbons, carbonate oils, alkylbenzenes, alkylene glycols are described as single products or mixed oils thereof. The data showing the basis for the necessity of a viscosity of 46 cSt or higher is based on mineral oil (paraffinic hydrocarbons or naphthenic hydrocarbons), and specific examples of combinations of other refrigerating machine oils and hydrocarbons. There is no specific description.
Also, if the alkylene glycol exhibits a substance equivalent to the polyalkylene glycol described later, the solubility of the hydrocarbon in the polyalkylene glycol is small compared to the conventionally used CFC / HCFC. , The problem to be solved by the invention is that "the reliability of the equipment is reduced by the fact that the refrigerant melts more into the refrigeration oil and the viscosity of the refrigeration oil decreases and the mechanical lubricity of the compressor decreases. The statement that “sexuality is reduced” does not apply. In addition, the value of 46 cSt of the viscosity of the oil itself is, for example, considering that the viscosity of the compatible refrigeration oil used in a high-pressure shell compressor for a general air conditioner of HCFC refrigerant is about 56 cSt. In addition, it is added that the numerical value setting is contrary to the idea that “the refrigerating machine oil to be used needs to be conditioned to a certain degree of viscosity in order to ensure lubricity”.

  In other prior art, by using refrigerating machine oil containing a ketone compound that does not mutually dissolve with hydrocarbon-based refrigerant, the amount of refrigerant that dissolves in refrigerating machine oil is suppressed, and the amount of flammable hydrocarbon refrigerant is reduced (For example, refer to Patent Document 2).

The following conventional examples are described with supplementary explanations of general matters relating to refrigerants and refrigeration oil.
First, “compatibility” used in the description of the present invention is generally defined by “the property that two or more substances have an affinity for each other and form a solution or a mixture”. Is done. In the relationship between the refrigerant and the refrigerating machine oil, a certain amount of refrigerant is dissolved in the refrigerating machine oil, and the refrigerating machine oil is dissolved in a certain amount in the liquid refrigerant. Therefore, depending on the mixing ratio of refrigerant and refrigerating machine oil, temperature and pressure, there are cases where an admixture corresponding to the above definition of “compatibility” is formed, and there are cases where the total amount cannot be made into an admixture and is separated into two layers. is there. In general, a combination of refrigerant and refrigerating machine oil that has a sufficiently large amount of mutual dissolution and does not separate into two layers regardless of the mixing ratio of refrigerant and refrigerating machine oil, temperature or pressure, or has a behavior that makes it difficult to separate two layers. It is called “incompatible” or “weakly compatible” if it is difficult to dissolve each other and is separated into two layers in a range of combinations of refrigerant and refrigerating machine oil, temperature and pressure. "Resolve"). In the case of “incompatible”, the refrigerant dissolves to some extent in the refrigeration oil, but the refrigeration oil dissolves only in a small amount in the liquid refrigerant. It is difficult to define a clear boundary for the above-mentioned “compatible” and “incompatible”, but what is currently considered “incompatible” clearly differs from “compatible”. It is difficult to dissolve.

As an example of “incompatible”, a combination of an HFC refrigerant and an alkylbenzene oil or polyalphaolefin oil is shown (for example, see Patent Document 3). In particular, the combination of HFC refrigerant and alkylbenzene oil has been successfully commercialized in refrigerators and room air conditioners.
The actual solubility in “incompatible” cannot be found from the literature, but in the combination of HFC refrigerant and alkylbenzene oil that are actually commercialized, the refrigerant solubility in the refrigeration oil is about 20 to 30% at maximum, The solubility of refrigeration oil in liquid refrigerant is about 1%.

  In Patent Document 3, in a refrigeration cycle using oil that is smaller in density than liquid refrigerant and incompatible with refrigerant ("incompatible oil"), the refrigeration oil separated from the refrigerant in the accumulator is returned to the compressor. Technology is disclosed.

  Conventionally used HFC refrigerants such as R410A, R407C, and R134a have a density higher than that of refrigerating machine oil in the range of operating conditions generally used for air conditioning, etc. Therefore, when incompatible oil is used, there is a problem that a liquid refrigerant layer is formed on the lower side of the oil and obstructs oil supply from an oil supply hole provided in the lower part of the compressor. On the other hand, the technique which stirs oil in the oil supply hole part of the lower part of a compressor and guides oil to an oil supply hole is disclosed (for example, refer patent document 4).

Japanese Patent Laid-Open No. 9-264619 JP-A-11-302675 Japanese Patent No. 2803451 Japanese Patent Laid-Open No. 10-082392

Many conventional refrigeration oils for hydrocarbon refrigerants have high compatibility with the refrigerant and a large amount of refrigerant dissolved in the refrigeration oil, as disclosed in Patent Document 1, so that the refrigeration oil in the compressor is refrigerated. The viscosity of the oil is greatly reduced by the refrigerant dissolved in the machine oil. Therefore, in order to have sufficient sliding resistance (or lubrication performance) in a state where the refrigerant is melted in the compressor, it is necessary to set the viscosity of the base oil to be high. For example, the viscosity of a general base oil of a compatible refrigerating machine oil used for a high-pressure shell compressor (state in which refrigerant is not dissolved) is 56 mm in kinematic viscosity at 40 ° C. in the case of an HCFC (R22) refrigerant system. ² / s (= 56 cSt), and in the case of the R410A refrigerant system, it is about 46-74 mm ² / s. For example, in the combination of propane (R290) and paraffinic mineral oil, the compatibility is high. In order to achieve the same viscosity, the kinematic viscosity at 40 ° C. needs to be 100 mm ² / s or more. In the following description, “viscosity” represents kinematic viscosity.

  As described above, in conventional refrigeration oil for hydrocarbons, the difference between the viscosity of the oil during compressor operation (when the refrigerant is dissolved) and the viscosity of the base oil is large. Due to the change in the refrigerant dissolution amount, the oil dissolution viscosity (the kinematic viscosity of the admixture in a state where the refrigerant is dissolved in the refrigerating machine oil) changes significantly. Specifically, under conditions where the degree of superheat of the refrigerant gas in the compressor with a relatively small amount of refrigerant dissolved (difference from the boiling point of the superheated steam temperature) is large, the viscosity of the oil is too high and the refrigerant in the compressor with a large amount of refrigerant dissolved There was a problem that the oil viscosity was too low under conditions where the degree of superheating of the gas was small.

  In addition, compatible refrigerating machine oils used for hydrocarbon refrigerants need to be set to a higher base oil viscosity in order to ensure the melt viscosity in the compressor. However, the fluidity of the oil is poor, and there is a problem that variations in the amount of oil are likely to occur.

  In addition, when incompatible refrigerating machine oil is used, liquid refrigerant and oil are separated in the refrigerating circuit, and as shown in Patent Document 3, in order to ensure oil return from the refrigerating circuit to the compressor. There is a problem that special technology is required and the design of the refrigeration circuit is complicated.

  Further, when the liquid refrigerant and the refrigeration oil are separated in the compressor, the liquid refrigerant having a high density sinks below the refrigeration oil, so that the oil is sucked into the oil supply hole as shown in Patent Document 4. Therefore, there is a problem of cost increase accompanying an increase in the number of parts.

  The present invention has been made in order to solve the above-described problems. The first object of the present invention is that when a hydrocarbon is used as the refrigerant, the refrigerant solubility in the refrigerating machine oil is more than necessary in the compressor. An object of the present invention is to obtain a refrigeration cycle apparatus using a refrigerating machine oil that is not increased but can prevent a significant decrease in viscosity of the refrigerating machine oil.

  The second object of the present invention is that the liquid refrigerant has an appropriate refrigerant solubility in the refrigeration circuit, and in normal use, the refrigeration oil can be dissolved in the liquid refrigerant in the refrigeration circuit without being separated. It is to obtain a refrigeration cycle apparatus using refrigeration oil.

A refrigeration cycle apparatus according to the present invention includes a refrigeration circuit configured by connecting a compressor, a condenser, an expansion valve, and an evaporator with piping, and the refrigeration circuit enclosed in the refrigeration circuit compresses, condenses, expands, and evaporates. And a refrigerating machine oil composed of a polyalkylene glycol in which propylene oxide and ethylene oxide are copolymerized and enclosed together with the refrigerant. The alkylene glycol is in a two-layer separation state between the refrigerant and the refrigerating machine oil in the entire temperature range from the condensation temperature to the evaporation temperature when the refrigerant circulates, and the propylene oxide and the ethylene oxide in the component ratios, it is constituted by component ratio in a predetermined range including the least configuration the ratio of the ethylene oxide, wherein the poly-a The lower limit of the component ratio of the ethylene oxide Killen glycol is at the highest condensation temperature used in the refrigeration cycle, the refrigerating machine oil and the refrigerant is to a component ratio to separate two layers.

  The refrigeration cycle apparatus of the present invention uses a hydrocarbon as a refrigerant sealed in a refrigeration circuit, and a polyalkylene glycol in which propylene oxide (PO) and ethylene oxide (EO) are copolymerized as refrigeration oil. (PAG), the PAG is a PO and EO in which the refrigerant and the refrigerating machine oil are separated into two layers and the EO component ratio is the smallest in the entire temperature range from the condensation temperature to the evaporation temperature used in the refrigeration cycle. Therefore, the solubility of the refrigerant in the refrigerating machine oil can be reduced, and the amount of the refrigerating machine oil dissolved in the liquid refrigerant can be more than a certain level. Therefore, it is possible to reduce the change in melt viscosity of refrigerating machine oil due to pressure and temperature conditions, and to improve the reliability of sliding parts. A.

  In addition, the amount of oil returned from the refrigeration circuit can be ensured by a certain amount of refrigeration oil dissolved in the liquid refrigerant, and the refrigeration cycle required when using an incompatible oil as shown in Patent Document 3 Therefore, there is an effect that the device for returning the refrigeration oil to the compressor becomes unnecessary.

  Furthermore, since the solubility of the refrigerant in the refrigeration oil can be lowered, the viscosity of the base oil of the refrigeration oil can be made lower than when mineral oil or the like is used, and the effect of improving the sealing performance of the refrigeration oil can be improved. is there.

It is a freezing circuit diagram which shows an example of the refrigerating-cycle apparatus which concerns on Embodiment 1 of this invention. It is sectional drawing of the rotary compressor shown as an example of the high pressure shell type compressor in Embodiment 1 of this invention. It is a figure which shows the refrigerant | coolant dissolution amount characteristic in the refrigerating machine oil by the temperature in a compatible oil system, and the refrigerant | coolant dissolution amount characteristic of the incompatible oil is also shown for the comparison. It is a figure which shows the oil viscosity characteristic by the refrigerant | coolant fraction in a compatible oil system. It is a figure which shows the two-layer separation temperature curve when the compatibility of a refrigerant | coolant and refrigerator oil changes. It is a figure which shows the profit and loss comparison of a compatible oil and an incompatible oil. It is a figure which shows the change by the temperature of the saturated liquid density of various refrigerant | coolants, and the density of refrigeration oil. It is a figure which shows the relationship between a refrigerant | coolant / refrigerator oil mixing ratio and the viscosity of refrigerator oil. It is a figure which shows the melt viscosity of the refrigeration oil corresponding to the superheat degree of a refrigerant | coolant.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings.

Embodiment 1 FIG.
FIG. 1 is a refrigeration circuit diagram showing an example of a refrigeration cycle apparatus 10 according to Embodiment 1 of the present invention.
As shown in FIG. 1, the refrigeration cycle apparatus 10 according to the first embodiment connects a compressor 1, a condenser 2, an expansion valve 3, an evaporator 4, and an accumulator 5 in order with a pipe 6, and a refrigerant described later. And refrigeration oil is enclosed and the refrigeration circuit is formed. The refrigerant in the refrigeration circuit is compressed into a high-temperature and high-pressure refrigerant by the compressor 1 and sent to the condenser 2. The high-temperature and high-pressure refrigerant sent to the condenser 2 is condensed by exchanging heat with a medium such as air in the condenser 2, and the refrigerant whose temperature has dropped is sent to the expansion valve 3. The refrigerant sent to the expansion valve 3 is expanded (depressurized) by the expansion valve to become a low-temperature and low-pressure refrigerant and sent to the evaporator 4. The low-temperature and low-pressure refrigerant sent to the evaporator 4 evaporates by exchanging heat with a medium such as air in the evaporator 4, and the heated refrigerant returns to the compressor again through the accumulator 5 and is compressed. The That is, in the refrigeration circuit, the refrigerant circulates in the refrigeration circuit as shown by the arrows in the figure, and the refrigeration cycle repeats compression, condensation, decompression, and evaporation. By applying such a refrigeration cycle apparatus 10 to an air conditioner, for example, a cooling operation or a heating operation can be performed. At this time, the refrigerating machine oil sealed together with the refrigerant is also mixed or dissolved in the refrigerant and circulated in the refrigeration circuit.

FIG. 2 is a cross-sectional view of a rotary compressor shown as an example of a high-pressure shell type compressor in Embodiment 1 of the present invention.
A rotary compressor that is an example of the high-pressure shell type compressor 1 includes a compression mechanism unit 101 that compresses a refrigerant and an electric mechanism unit 102 that drives the compression mechanism unit 101 inside a sealed container 11. The compression mechanism unit 101 and the electric mechanism unit 102 are coaxially connected via the drive shaft 12. Refrigerating machine oil 13 is stored at the bottom of the sealed container 11, and the refrigerating machine oil 13 is supplied to the compression mechanism unit 101 by a pump action through an oil supply path 14 provided on the drive shaft 12, and the sliding part of the compression mechanism unit 101. (Including the bearing portion) is lubricated. The lower end portion of the drive shaft 12 is immersed in the refrigeration oil 13, and the oil supply path 14 extends from the oil supply hole 15 at the lower end of the drive shaft 12 in the axial direction to each part that requires lubrication. It consists of a branch path that leads to it.

The refrigerant gas is sucked into the compression mechanism 101 from the suction pipe 16 through the accumulator 5. The sucked refrigerant gas is compressed by the compression mechanism unit 101, and the high-temperature and high-pressure refrigerant gas is once discharged from the compression mechanism unit 101 into the sealed container 11. Furthermore, the high-temperature and high-pressure refrigerant gas in the sealed container 11 is discharged to the discharge pipe 17 and flows into the condenser 2 of FIG.
In the present embodiment, R290 (propane) is used as the refrigerant, and the refrigerating machine oil 13 uses polyalkylene glycol described later.

Before explaining the technical contents of the present invention, first, general techniques regarding the compatibility of refrigerant and refrigerating machine oil will be explained.
FIG. 3 is a characteristic diagram showing the solubility of the refrigerant in the refrigeration oil with respect to the degree of superheat of the mixture of the refrigerant and the refrigeration oil when the pressure is constant, and shows the compatibility between the compatible oil (completely compatible) and the incompatible oil. The characteristics are shown.
As shown in FIG. 3, the refrigerant solubility in oil tends to increase as the degree of superheat decreases. In general, incompatible oil has lower refrigerant solubility than compatible oil. In the case of compatible oil, since the oil and refrigerant are not separated, the state in which the refrigerant is dissolved in the oil and the state in which the oil is dissolved in the refrigerant appear continuously, whereas in the case of the incompatible oil, Since the refrigerant does not dissolve in oil in a certain amount or more, it is separated into an oil-based layer and a refrigerant-based layer. That is, two layers are separated.

FIG. 4 is a diagram showing characteristics indicating the oil viscosity according to the refrigerant fraction in the compatible oil system. A refrigerant fraction of 0% indicates 100% oil. The vertical axis in FIG. 4 is a double logarithmic axis.
As shown in FIG. 4, the viscosity of the oil tends to decrease as the refrigerant fraction in the oil increases. In the case of an incompatible oil, since the refrigerant fraction becomes a certain ratio or more and two layers are separated, a line connecting the whole refrigerant fraction cannot be drawn.

FIG. 5 is a diagram showing the two-layer separation characteristics based on the compatibility between the refrigerant and the refrigerating machine oil. The vertical axis in FIG. 5 represents the temperature of the mixture of refrigerant and refrigerating machine oil, and the horizontal axis represents the oil fraction, which is the ratio of refrigerating machine oil in the mixture. That is, FIG. 5 shows that when the oil content is 0 wt%, the refrigerant in the mixture is 100 wt%, and when the oil content is 100 wt%, the refrigerant in the mixture is 0 wt%. When the refrigerant melts into the refrigerating machine oil or the refrigerating machine oil dissolves into the refrigerant, it is a dissolution area mainly composed of liquid refrigerant when the oil content is small, and indicates that the refrigerating machine oil is dissolved into the refrigerant, and when the oil content is large, the refrigerating machine oil It shows a state in which the refrigerant is dissolved in the refrigerating machine oil as a main dissolution zone. Moreover, (a) to (h) in FIG. 5 shows a state in which the compatibility is gradually lowered by changing the component ratio of the refrigerating machine oil and the like from the state (a) to the state (h). (A) is in a completely compatible state and does not have a two-layer separation region in the temperature range from the condensation temperature to the evaporation temperature in the refrigeration cycle used. (H) represents a two-layer separation curve of oil, which is called incompatible or weakly compatible, and the two layers are separated in the entire temperature range from the highest condensation temperature to the lowest evaporation temperature used in the refrigeration cycle. In addition, in the conventionally used combination of HFC refrigerant and alkylbenzene, when the oil-based dissolution region has a large oil content, that is, on the right side of the figure, the refrigerant dissolution amount is about 20 to 30%, and the liquid refrigerant has a small oil content. In the dissolution zone, that is, on the left side of the figure, the oil dissolution amount is about 1%.
There is an intermediate region between (a) and (h). When the change is described in order from (a) to (h), first, a region where two layers are separated into a high temperature region and a low temperature region begins to appear (b), and the region where the two layers are separated together with a decrease in compatibility is It tends to spread toward the middle temperature range (ce). Thereafter, the two-layer separation region on the high-temperature side and the low-temperature side are connected, and a dissolution region is formed in the direction in which the oil content increases and decreases in the two-layer separation region, that is, on the left and right in the figure (f). A region where the oil content is small, that is, the left side of the figure is a dissolution region mainly composed of liquid refrigerant, and a region where the oil content is large, that is, the right side of the diagram is an oil-based dissolution region. When the compatibility further decreases, the left and right dissolution regions tend to be gradually narrowed (g to h).

Conventionally, in a room air conditioner using an HFC refrigerant, both compatible oil and non-compatible oil are used, and each has advantages and disadvantages. The effect of oil compatibility in the refrigeration circuit appears mainly on the characteristics for the three items required for the refrigerator oil shown below.
1) Maintaining proper oil viscosity in the compressor 2) Oil can always be sucked from the oil supply hole at the bottom of the compressor 3) Oil released into the refrigeration circuit returns to the compressor Figure 6 shows compatible oils for the above three items The advantages and disadvantages of the incompatible oil are indicated by ○ and Δ. In FIG. 6, examples of the intermediate phase dissolved oil of the present invention to be described later are also shown.

  Each of the above items will be described. First, in order to maintain an appropriate oil viscosity in the compressor of 1), an incompatible oil with a small amount of refrigerant dissolved is superior to a compatible oil. In particular, under conditions where the degree of superheat of the discharged gas is small, the incompatible oil has a small amount of dissolved refrigerant, so that the viscosity of the oil does not easily decrease, and the refrigerant does not dissolve more than a certain amount. By separating, the viscosity of the oil can be maintained. On the other hand, in the case of compatible oil, the refrigerant can be dissolved without any limitation (the oil is in a state of being dissolved in the refrigerant from the middle), so that the oil may be diluted to cause a significant decrease in viscosity. When the viscosity of the oil is reduced, it is not possible to form an appropriate oil film in the sliding part and the bearing part in the compressor, which may cause a reduction in the reliability of the compressor.

  Next, with respect to the fact that oil can always be sucked from the oil supply hole at the lower part of the compressor in 2), that is, the oil is present in the oil supply hole at the lower part of the compressor, the compatible oil is superior to the incompatible oil. . As described above, when the superheat degree of the discharge gas is reduced and the amount of liquid refrigerant in the compressor is increased, the liquid refrigerant and oil are separated in the case of incompatible oil. When the liquid refrigerant and the oil are separated, in the HFC refrigerant, the liquid refrigerant having a high density sinks downward, and the oil tends to float on it. For this reason, liquid refrigerant having a very low viscosity may be sucked from the oil supply hole located in the lower part of the compressor instead of oil, which may cause a reduction in the reliability of the compressor.

  Finally, with respect to the oil released into the refrigeration circuit of 3) returning to the compressor, the compatible oil is superior to the incompatible oil. In the case of the compatible oil, a large amount of oil can be dissolved in the liquid refrigerant, so that the oil is also conveyed in the liquid refrigerant in the refrigeration circuit. In contrast, with incompatible oils, only a very small amount of oil is dissolved in the liquid refrigerant. Therefore, if the amount of oil discharged from the compressor exceeds a certain amount, the oil may not return to the compressor from the refrigeration circuit. It was.

  As described above, compatibilized oil and incompatible oil have advantages and disadvantages, but with regard to oil positioned between the two, liquid refrigerant and oil are separated into two layers, and liquid refrigerant sinks below the oil. This problem is recovered by measures on the compressor side (for example, measures such as providing a partition plate having a plurality of holes of different sizes around the oil supply hole shown in Patent Document 4) and control of the refrigeration circuit. Because it is necessary, there is not so much merit and there is no use example.

  When propane or propylene is used as the refrigerant, the above-mentioned concept is partially changed. In FIG. 7, the change of each density with respect to the saturated liquid refrigerant density of various refrigerant | coolants and the temperature of refrigeration oil is shown. The density of propane and propylene is smaller than the density of refrigeration oil compared to the HFC-based refrigerant that has been used conventionally. That is, even when the refrigerant and the oil are separated into two layers, the refrigerating machine oil sinks under the liquid refrigerant, so that the above problem 2) is naturally solved.

  For propane and propylene, most oils such as mineral oil, POE oil, PVE oil, and alkylbenzene, which have been used in the past, have a problem in that the viscosity of the oil is greatly reduced due to the compatibility and solubility. However, there are oils that can solve the problem. That is, in the present invention, the use of polyalkylene glycol as a refrigerating machine oil makes it possible to reduce the solubility of the refrigerant in the oil.

  Polyalkylene glycol is a copolymer of propylene oxide and ethylene oxide, and is defined by the following structural formula.

In the formula (1), CH ₂ —CH (CH ₃ ) —O represents a propylene / oxide component, and CH ₂ —CH ₂ —O represents an ethylene / oxide component. N and m represent the ratio of propylene oxide to ethylene oxide. R1 and R2 are preferably methyl groups, but may be hydroxyl groups or carboxylic acids.

Hereinafter, characteristic portions of the present invention will be described.
Compatibility with propane and propylene is adjusted by changing the copolymerization ratio of propylene oxide and ethylene oxide in polyalkylene glycol oil. Therefore, a wide range of characteristics from compatible to incompatible can be created.

Hydrocarbon refrigerants such as propane and propylene, even when two-layer separation is performed as described above, the liquid refrigerant floats on the refrigerating machine oil, and there is no problem with the refueling of the compressor. It is desirable to select the solubility with the least problem with respect to both of the problems (1) and (3)) associated with incompatibility and incompatibility. Specifically, it is desirable to separate the two layers in order to prevent endless dilution by the refrigerant of the refrigerating machine oil. It is desirable that the refrigerating machine oil solubility in the liquid refrigerant can be increased as much as possible. That is, the component ratio of propylene oxide and ethylene oxide has a mixing ratio at which the liquid refrigerant and the refrigerating machine oil are separated into two layers in the entire temperature range from the highest condensation temperature to the lowest evaporation temperature used in the refrigeration cycle ( Among the component ratios (close to incompatibility), the component ratio that exhibits the lowest ethylene oxide ratio (closest to compatibility) (component ratio that exhibits intermediate properties between "compatible" and "incompatible") That is, the state shown in FIG. 5F is a desirable state. Since this state is intermediate between compatible and incompatible, it will be described as “intermediate compatible” hereinafter.
Hereinafter, a specific range of the intermediate compatibility will be described.

  The ethylene oxide ratio (component ratio of propylene oxide and ethylene oxide) that can achieve an intermediate compatible state is the ratio of ethylene oxide in the viscosity grade ISO VG32 of polyalkylene glycol oil when the refrigerant is propane. Is 20%, the viscosity grade ISO VG46 has an ethylene oxide ratio of 15%, and the viscosity grade ISO VG68 has an ethylene oxide ratio of about 10%.

  Solving the problems of conventional compatible and non-compatible oils by setting the copolymer component ratio of propylene oxide and ethylene oxide of polyalkylene glycol oil (PAG oil) to the above intermediate compatible state can do. Specifically, in the entire temperature range from the highest condensation temperature to the lowest evaporation temperature used in the refrigeration cycle, the liquid refrigerant and the refrigerating machine oil each have a mixing ratio that separates into two layers. Preventing the viscosity of the refrigeration oil from dropping below a certain level, ensuring the reliability of the sliding part of the compressor, and making the component ratio with the smallest ethylene oxide ratio among them Thus, the amount of refrigerating machine oil that can be dissolved in the liquid refrigerant can be maximized, and the oil return property from the refrigeration cycle can be improved as compared with the incompatible oil.

  In the above description, as an ideal state of the present invention, the component ratio and the effect have been described with respect to one point where the intermediate compatible state is obtained, but the component ratio at which the above effect is partially obtained may be used. The scope is defined as follows. First, the lower limit of the ethylene oxide ratio (component ratio of propylene oxide and ethylene oxide) is as follows. The load applied to each sliding portion of the compressor tends to increase as the pressure on the high pressure (condensation) side is higher. Therefore, if the two-layer separation region exists near the maximum high pressure (condensation side) condition of the refrigeration cycle that is actually used, the effect of the present invention can be obtained, so that the high temperature side as in the state of FIG. The lower limit is the ethylene oxide ratio at which the two-layer separation region starts to reach the maximum condensation temperature (maximum saturation temperature) in the refrigeration cycle, that is, the two-layer separation state occurs at the highest condensation temperature. The maximum condensation temperature is about 65 ° C. for an air conditioner and about 80 ° C. for a water heater. In the description of the present invention, the following ethylene / oxide ratio (component of propylene / oxide and ethylene / oxide) is assumed to be 80 ° C. Ratio).

  Next, the upper limit of the ethylene oxide ratio (component ratio of propylene oxide and ethylene oxide) is as follows. That is, it is only necessary to ensure sufficient oil return from the refrigerant circuit. The oil discharge amount of a normal high-pressure shell type compressor is considered to be about 2% even when the oil discharge amount is large, so it is sufficient that about 2% of refrigerating machine oil is dissolved in the liquid refrigerant. Since the amount of refrigeration oil dissolved in the liquid refrigerant tends to decrease as the temperature decreases, it is sufficient that 2% or more of the refrigeration oil can be dissolved in the liquid refrigerant at the lowest evaporation temperature (minimum saturation temperature) in the refrigeration cycle. In other words, the upper limit is the ethylene oxide ratio at which the refrigerating machine oil dissolution at point A shown in FIG. The minimum condensation evaporation temperature is about −10 ° C. to −30 ° C. for air conditioners and water heaters. In the description of the present invention, the following ethylene oxide ratio (propylene oxide and ethylene oxide) is assumed to be −30 ° C. Component ratio).

  The component ratio of ethylene oxide capable of realizing the above-mentioned definitions of the lower limit and the upper limit is in the range of ± 10% with respect to the component ratio at which the intermediate compatibility is achieved. That is, when propane is used as the refrigerant, the viscosity of polyalkylene glycol oil is ISO VG32 and the ethylene oxide ratio is 10 to 30%, and the viscosity grade ISO VG46 is 5 to 25% of ethylene / oxide ratio. In grade ISO VG68, the ethylene oxide ratio is about 0 to 20%. In the refrigerating machine oil having the viscosity between the above, the component ratio complemented from the curve connecting the data of the viscosity grade ISO VG32, 46, 68 may be applied.

FIG. 8 is a diagram showing the relationship between the refrigerant / refrigeration oil mixing ratio and the viscosity of the refrigerating machine oil, and shows the behavior of oil when liquid refrigerant (refrigerant superheat degree is 0) and oil are mixed.
As shown in the figure, in the case of a compatible oil that does not separate into two layers (mineral oil or the like), the viscosity of the oil decreases endlessly as the refrigerant ratio increases, but the oil of the present invention separates into two layers, so the viscosity on the oil side Does not drop below a certain value.

FIG. 9 is a diagram showing the melt viscosity of refrigerating machine oil corresponding to the degree of superheat of the refrigerant, and shows the oil viscosity in a state where the heated refrigerant (gas) is dissolved in the oil.
As shown in FIG. 9, the amount of superheated refrigerant dissolved in oil varies depending on the degree of superheat. That is, the oil is more easily dissolved as the degree of superheat is smaller. In addition, the more the refrigerant melts, the lower the oil viscosity. Mineral oil is easy to dissolve, so the amount of dissolution is large and the viscosity is greatly reduced accordingly.
On the other hand, the oil of the present invention is difficult to dissolve in the oil even when the superheat degree of the refrigerant is small, and the viscosity of the melt can be kept high.

  In the above description, the characteristics when the refrigerant is propane are shown, but the refrigerant may be propylene. When the refrigerant is propylene, the specific ethylene oxide ratio that can be realized in an intermediate compatible state is unknown, but when the ethylene oxide ratio is higher than that of propane, the state of (f) in FIG. It is feasible, and it is estimated that the ethylene oxide ratio is about 50%.

Next, the operation will be described. First, the state of the refrigerant and oil in the refrigeration circuit will be described.
The compressor 1 sucks a low-pressure refrigerant gas from the suction pipe 16, compresses the refrigerant gas to a high pressure by the compression mechanism unit 101, and then discharges it once into the sealed container 11, and then opens into the sealed container 11. The discharge pipe 17 is discharged out of the sealed container 11. At this time, a small amount of the refrigerating machine oil 13 used for lubrication in the compressor 1 is also discharged together with the refrigerant gas. In a high-pressure shell type compressor, the amount of refrigerating machine oil discharged together with the refrigerant gas is about 2% at maximum under normal operating conditions. The high-pressure refrigerant gas and a small amount of refrigeration oil discharged from the compressor 1 enter the condenser 2 in FIG. 1, and the refrigerant gas is condensed and liquefied, and becomes liquid refrigerant and moves to the expansion valve 3.

  In addition, the amount of refrigerating machine oil 13 that is the same as the amount discharged from the compressor 1 is also included in the liquid refrigerant, but the refrigerating machine oil 13 can dissolve the liquid refrigerant by 2% or more as described above. The refrigerating machine oil 13 moves to the expansion valve 3 together with the liquid refrigerant without being separated.

  The liquid refrigerant is decompressed by the expansion valve 3 to be in a gas-liquid two-phase state, and moves to the evaporator 4. Also in the evaporator 4, the refrigerating machine oil 13 is in a state of being dissolved in the liquid phase. In the evaporator 4, the refrigerant is vaporized, and accordingly, the refrigeration oil 13 gradually precipitates. When the liquid refrigerant is completely gasified, the refrigerant and the oil are separated. Also, since the amount of refrigerant dissolved in oil in the low pressure space is small, the viscosity of the oil tends to increase. However, since the viscosity grade of the base oil is set to a low level of about ISO VG 32 to 68, the oil is a refrigerant. The gas can move without problems and return to the compressor 1.

As described above, by selecting a refrigerating machine oil having intermediate compatibility characteristics with respect to the hydrocarbon refrigerant, good characteristics are exhibited with respect to all the above three characteristics required for the refrigerating machine oil.
1) Maintaining proper oil viscosity in the compressor ・ The amount of refrigerant dissolved in the refrigerating machine oil is relatively small, and the refrigerating machine oil and liquid refrigerant are separated. It does not increase and the proper oil viscosity is maintained.
2) Oil can always be sucked from the oil supply hole at the bottom of the compressor. Even when the refrigeration oil and the liquid refrigerant are separated in a closed container, the hydrocarbon refrigerant has a lower density than the refrigeration oil. -Even under temperature conditions, the oil can sink below the hydrocarbon refrigerant and keep the refrigerating machine oil in the oil supply hole at the bottom of the compressor.
3) The oil released to the refrigeration circuit returns to the compressor. • Since the amount of refrigeration oil that dissolves in the liquid refrigerant is 2% or more, the amount of oil released from the normal compressor (2% or less) Since it can circulate in the refrigeration circuit while being dissolved in the liquid refrigerant, sufficient oil return can be ensured.

  Furthermore, since this refrigerating machine oil is separated into two layers at all / a part of the range of the condensation temperature used in the refrigerating circuit, the amount of refrigerant dissolved in the refrigerating machine oil does not increase beyond the double layer separation concentration, There is an effect that the unlimited dilution can be prevented and the reliability of the sliding portion of the compressor can be improved.

  Also, when liquid refrigerant and refrigerating machine oil are separated into two layers, the density of liquid refrigerant of propane and propylene is smaller than that of refrigerating machine oil. Therefore, there is no need for a special device for supplying the refrigeration oil floating above the liquid refrigerant to the oil supply hole of the compressor as in the conventional example, and there is an effect that an inexpensive refrigeration cycle apparatus can be obtained.

  In the refrigeration circuit, 2% or more of the refrigeration oil can be dissolved in the liquid refrigerant, so that the refrigeration oil discharged together with the refrigerant from the compressor can be dissolved in the liquid refrigerant in a normal operation state. There is an effect that sufficient oil return property can be secured.

  FIG. 2 showing the compressor in the embodiment of the present invention shows a high-pressure shell type rotary compressor, but the type of the compressor is not particularly limited to a high-pressure shell type or a low-pressure shell type. Other compression formats such as a scroll compressor may be used. In addition, regarding the positional relationship between the compression mechanism unit and the electric mechanism unit, FIG. 2 shows a configuration in which the compression mechanism unit is disposed on the lower side. However, the refrigerating machine oil 13 is stored on the lower side of the compressor and is supplied with oil. If the hole 15 is configured to open to the refrigeration machine oil storage section on the lower side of the compressor, the same effect can be obtained even if the compression mechanism section is arranged on the upper side.

  DESCRIPTION OF SYMBOLS 1 Compressor, 2 Condenser, 3 Expansion valve, 4 Evaporator, 5 Accumulator, 6 Piping, 10 Refrigeration cycle apparatus, 11 Airtight container, 12 Drive shaft, 13 Refrigerator oil, 14 Oil supply path, 15 Oil supply hole, 16 Inhalation Pipe, 17 Discharge pipe, 101 Compression mechanism part, 102 Electric mechanism part.

Claims (7)

A refrigeration circuit configured by connecting a compressor, a condenser, an expansion valve, and an evaporator with piping;
A refrigerant composed of hydrocarbons that are enclosed in the refrigeration circuit and circulate repeatedly in the refrigeration circuit through compression, condensation, expansion, and evaporation;
Refrigerating machine oil composed of polyalkylene glycol encapsulated with the refrigerant and copolymerized with propylene oxide and ethylene oxide,
With
The poly-alkylene glycol is in a two-layer separation state between the refrigerant and the refrigerating machine oil in the entire temperature range from the condensation temperature to the evaporation temperature when the refrigerant circulates, and the propylene oxide and the ethylene In the component ratio of oxide, the ratio of the ethylene oxide is configured with a component ratio in a predetermined range including a configuration with the smallest ratio,
The lower limit of the ethylene oxide component ratio of the polyalkylene glycol is a component ratio at which the refrigerant and the refrigerating machine oil are separated into two layers at the highest condensation temperature used in the refrigeration cycle. apparatus. A refrigeration circuit configured by connecting a compressor, a condenser, an expansion valve, and an evaporator with piping;
A refrigerant composed of hydrocarbons that are enclosed in the refrigeration circuit and circulate repeatedly in the refrigeration circuit through compression, condensation, expansion, and evaporation;
Refrigerating machine oil composed of polyalkylene glycol encapsulated with the refrigerant and copolymerized with propylene oxide and ethylene oxide,
With
The poly-alkylene glycol is in a two-layer separation state between the refrigerant and the refrigerating machine oil in the entire temperature range from the condensation temperature to the evaporation temperature when the refrigerant circulates, and the propylene oxide and the ethylene In the component ratio of oxide, the ratio of the ethylene oxide is configured with a component ratio in a predetermined range including a configuration with the smallest ratio,
The upper limit of the component ratio of the ethylene oxide of the poly-alkylene glycol, and characterized in that at the lowest evaporating temperature to be used in refrigeration cycle, the component ratio of the refrigerating machine oil in the refrigerant is dissolved 2% or more It is that refrigeration cycle apparatus. Propane is used as the refrigerant, viscosity grade ISO VG32 polyalkylene glycol is used as the refrigerating machine oil, and the ethylene oxide component ratio in the polyalkylene glycol is 10 to 30%. The refrigeration cycle apparatus according to claim 1 or 2 . Propane is used as the refrigerant, viscosity grade ISO VG46 polyalkylene glycol is used as the refrigerating machine oil, and the component ratio of ethylene oxide in the polyalkylene glycol is 5 to 25%. The refrigeration cycle apparatus according to claim 1 or 2, characterized in that Propane is used as the refrigerant, viscosity grade ISO VG68 polyalkylene glycol is used as the refrigerating machine oil, and the ethylene oxide component ratio in the polyalkylene glycol is 0 to 20%. The refrigeration cycle apparatus according to claim 1 or 2 . A refrigeration circuit configured by connecting a compressor, a condenser, an expansion valve, and an evaporator with piping;
A refrigerant composed of hydrocarbons that are enclosed in the refrigeration circuit and circulate repeatedly in the refrigeration circuit through compression, condensation, expansion, and evaporation;
Refrigerating machine oil composed of polyalkylene glycol encapsulated with the refrigerant and copolymerized with propylene oxide and ethylene oxide,
With
The poly-alkylene glycol is in a two-layer separation state between the refrigerant and the refrigerating machine oil in the entire temperature range from the condensation temperature to the evaporation temperature when the refrigerant circulates, and the propylene oxide and the ethylene In the component ratio of oxide, the ratio of the ethylene oxide is configured with a component ratio in a predetermined range including a configuration with the smallest ratio,
Propane is used as the refrigerant, polyalkylene glycol of viscosity grade ISO VG32 to 68 is used as the refrigerating machine oil, and the component ratio of ethylene oxide in the polyalkylene glycol is determined according to viscosity grade ISO VG32. , VG46, refrigerating cycle apparatus characterized in that the area to be complemented from curve connecting the values shown relative to VG68. The refrigeration cycle apparatus according to claim 1 or 2 , wherein propylene is used as the refrigerant, and polyalkylene glycol is used as the refrigerating machine oil.

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