JP5023657B2 - Refrigeration cycle equipment - Google Patents

Description

  The present invention relates to a refrigeration cycle apparatus including a compressor and an expander.

  2. Description of the Related Art Conventionally, a compressor that boosts the refrigerant, a gas cooler that cools the refrigerant, an expander that decompresses and expands the refrigerant, and an evaporator that evaporates the refrigerant are connected in order via a refrigerant pipe. A refrigeration cycle apparatus is known.

  In recent years, from the viewpoint of prevention of ozone layer destruction and global warming, an alternative refrigerant suitable for the natural environment has attracted attention, and carbon dioxide has attracted attention as such an alternative refrigerant. In the refrigeration cycle apparatus using carbon dioxide as the refrigerant, the refrigerant is in a supercritical state on the high pressure side of the refrigeration cycle.

  Specifically, in the refrigeration cycle apparatus using carbon dioxide, the refrigerant whose pressure has been increased by the compressor is in a supercritical state, cooled by a gas cooler, and then flows into the expander. The refrigerant that has flowed into the expander is reduced in pressure to become a low-pressure and low-temperature gas-liquid two-phase state, then absorbs heat by the evaporator and evaporates, and returns to the compressor.

  Incidentally, both the compressor and the expander have sliding portions and require lubricating oil. Therefore, an oil sump is provided in each of the compressor and the expander.

  However, when the refrigeration cycle apparatus is started up or when a large load fluctuation occurs, a large amount of lubricating oil flows from one of the compressor and the expander to the other, which may cause a shortage of lubricating oil. Therefore, it is conceivable to connect the compressor and the expander with an oil equalizing pipe and a pressure equalizing pipe.

Patent Document 1 discloses a refrigeration cycle apparatus that is not a refrigeration cycle apparatus including an expander, but includes two compressors arranged in parallel with each other, and the compressors are connected to each other by an oil equalizing pipe and a pressure equalizing pipe. . In this refrigeration cycle apparatus, the oil equalizing pipe is connected to the lower side surface of the casings of both compressors, and the pressure equalizing pipe is connected to the upper side surface of the casings of both compressors. The oil equalizing pipe and the pressure equalizing pipe both extend horizontally.
Japanese Patent Laid-Open No. 03-124170

  However, when the compressor and the expander are connected by the oil equalizing pipe and the pressure equalizing pipe, the oil equalizing pipe 103 is connected to the lower side surface of each casing of the compressor 101 and the expander 102 as shown in FIG. When the pressure equalizing pipe 104 is connected to the upper side surface of each casing and the oil equalizing pipe 103 and the pressure equalizing pipe 104 are arranged horizontally, the following problems occur.

  That is, the internal temperature during operation differs greatly between the compressor 101 and the expander 102. Therefore, as shown in FIG. 8 (a), the oil level 101a of the compressor 101 and the oil level 102a of the expander 102 are kept at the same height when the operation is stopped, but as shown in FIG. 8 (b). During operation, the refrigerant in the expander 102 decreases in temperature and increases in density, whereas the refrigerant in the compressor 101 increases in temperature and decreases in density. As a result, the refrigerant having a high density in the expander 102 pushes down the oil surface 102a, the lubricating oil in the expander 102 flows into the compressor 101, and the lubricating oil in the expander 102 may be insufficient.

  Specifically, in FIG. 8A, since there is a large height difference hd between the pressure equalizing pipe 104 and the oil surfaces 102a and 101a, the refrigerant density in the compressor 101 is ρc, and the refrigerant density in the expander 102 is Assuming that ρe, the oil surface 102a of the expander 102 is pushed down more strongly than the oil surface 101a of the compressor 101 by (ρe−ρc) × hd.

  Therefore, as shown in FIG. 9A, the inventor of the present application forms the pressure equalizing tube 104 as a bent tube, and connects one end of the pressure equalizing tube 104 to the upper side surface of the compressor 101 while the other end of the pressure equalizing tube 104. Was considered to be connected to the lower side surface of the expander 102. According to this configuration, the height difference between one end of the pressure equalizing pipe 104 and the oil level 101a of the compressor 101 is higher than the height difference between the other end of the pressure equalizing pipe 104 and the oil level 102a of the expander 102. The pressure equalizing pipe 104 is increased by the amount Δh. Therefore, as shown in FIG. 9B, correction of the oil level height imbalance between the expander 102 and the compressor 101 is expected.

  However, as a result of intensive studies, the inventor of the present application has found that in the configuration shown in FIG. 9B, the oil level height imbalance between the expander and the compressor cannot actually be corrected.

  The present invention has been made in view of such points, and an object of the present invention is to provide an oil level height imbalance between the expander and the compressor in a refrigeration cycle apparatus including the expander and the compressor. This is to prevent the shortage of lubricating oil in the expander.

  As a result of earnest research, the inventor of the present application has obtained the following knowledge. As shown in FIG. 7, the density of the lubricating oil does not change greatly even when the temperature changes, but the density of carbon dioxide changes greatly as it approaches the normal temperature from the high temperature, and approaches the density of the lubricating oil near the normal temperature. Here, in a refrigeration cycle apparatus using carbon dioxide, the internal temperature of the expander is usually close to room temperature (for example, about 20 ° C.), and the internal temperature of the compressor is higher than room temperature (for example, about 80 ° C.). It becomes. On the other hand, although the pressure equalizing pipe is subjected to heat insulation treatment with a heat insulating material or the like, it is exposed to the external atmosphere, so that the internal temperature of the pressure equalizing pipe is normal. Therefore, the internal temperature of the pressure equalizing pipe is close to the internal temperature of the expander.

  Therefore, when considering the density of the refrigerant, the pressure equalizing pipe can be regarded as a part of the expander. As shown by the phantom line in FIG. 9C, the pressure equalizing pipe is formed by a horizontal straight pipe 104a. There will be no big difference. Therefore, although the apparent height difference is provided by using the bent pipe 104 as the pressure equalizing pipe, the oil level in the expander and the compressor is actually the same as in the example of FIG. 8B. This imbalance cannot be corrected sufficiently.

  Thus, the inventor of the present application thinks that in the configuration shown in FIG. 9B, if the internal temperature of the pressure equalizing pipe and the internal temperature of the expander become close, the oil level height imbalance cannot be corrected sufficiently. It came to make this invention.

Another refrigeration cycle apparatus according to the present invention has a casing having an oil sump formed at the bottom, has a compressor that compresses the refrigerant, and a casing formed with an oil sump at the bottom, and expands the refrigerant. An oil leveling pipe that communicates the oil sump of the compressor and the oil sump of the expander, and one end of the oil level above the oil sump in the casing of the compressor and when the operation of the compressor is stopped. A pressure equalizing pipe connected to the vicinity, and having the other end connected to the upper side of the oil reservoir in the casing of the expander and in the vicinity of the oil level when the expander is stopped, and the one end of the pressure equalizing pipe penetrates the casing of the compressor, away from the oil surface of the oil sump during operation of the compressor, it is what is extended upward or obliquely upward in the casing of the compressor

  The refrigerant may be carbon dioxide.

  As described above, according to the present invention, in the refrigeration cycle apparatus including the expander and the compressor, the oil level height imbalance between the expander and the compressor is corrected, and the lack of lubricating oil in the expander is reduced. Can be prevented.

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

<Embodiment 1>
As shown in FIG. 1, the refrigeration cycle apparatus 1 according to the embodiment includes a compressor 11, a radiator 12, an expander 13, and an evaporator 14, which have refrigerant pipes 15, 16, 17, and 18. The refrigerant circuit 10 is configured by being connected in order. The compressor 11 and the expander 13 are connected via an oil equalizing pipe 30 and a pressure equalizing pipe 40.

  The refrigerant circuit 10 is filled with carbon dioxide as a refrigerant. However, the refrigerant may be other than carbon dioxide. The compressor 11 and the expander 13 are filled with PAG as lubricating oil.

  As shown in FIG. 2, the compressor 11 includes a casing 21, an electric motor 24, a rotary shaft 25 driven by the electric motor 24, a compression mechanism 26 attached to the upper side of the rotary shaft 25, and a lower side of the rotary shaft 25. And an oil pump 27 attached to the side.

  In this embodiment, the casing 21 is formed in a substantially cylindrical shape whose upper end and lower end are closed, and is a vertically long casing whose vertical length is longer than the horizontal length. However, the casing 21 may be a horizontally long casing. The compressor 11 is a so-called high-pressure dome type compressor, and the casing 21 is filled with high-pressure refrigerant discharged from the compression mechanism 26.

  A discharge pipe 15 is connected to the upper wall of the casing 21. A suction pipe 18 that guides the suction refrigerant to the compression mechanism 26 is connected to the upper side surface of the casing 21. A hole 29 is formed on the lower side surface of the casing 21, more specifically, a side surface below the intermediate position in the vertical direction, and a hole 28 is formed below the hole 29. A pressure equalizing tube 40 is inserted into the hole 29, and an oil equalizing tube 30 is inserted into the hole 28. That is, the pressure equalizing pipe 40 and the oil equalizing pipe 30 are connected to the lower side surface of the casing 21.

  An oil sump 31 in which oil is stored is formed at the bottom of the casing 21. The oil pump 27 pumps up the oil in the oil reservoir 31 as the rotary shaft 25 rotates, and is immersed in the oil in the oil reservoir 31. Although the kind of oil pump 27 is not limited at all, here, the oil pump 27 is formed of a trochoid pump.

  A plate 32 is fixed to the lower inner wall of the casing 21, and a bearing 33 is fixed to the plate 32. The bearing 33 rotatably supports the lower part of the rotary shaft 25. The rotary shaft 25 is provided with an oil supply path (not shown) that guides the oil pumped up by the oil pump 27 to the compression mechanism 26.

  The electric motor 24 includes a stator 22 fixed to the inner wall of the casing 21 and a rotor 23 fixed to the rotary shaft 25. The electric motor 24 is disposed substantially at the center in the vertical direction of the casing 21.

  Although the specific structure of the compression mechanism 26 is not limited at all, in this embodiment, the compression mechanism 26 is configured by a scroll-type compression mechanism. However, the compression mechanism 26 may be another type of compression mechanism such as a rotary type.

  The expander 13 includes a casing 34, a generator 37, a rotating shaft 38, an expansion mechanism 39 attached to the upper side of the rotating shaft 38, and an oil pump 41 attached to the lower side of the rotating shaft 38. Yes.

  The casing 34 of the expander 13 is also formed in a substantially cylindrical shape whose upper end and lower end are closed, and is a vertically long casing whose vertical length is longer than the horizontal length. However, the casing 34 may be a horizontally long casing. The expander 13 is a so-called high-pressure dome type expander, and the casing 34 is filled with high-pressure refrigerant sucked from the suction pipe 16.

  The suction pipe 16 passes through the upper side surface of the casing 34 and is connected to the expansion mechanism 39. A discharge pipe 17 that guides the refrigerant discharged from the expansion mechanism 39 is connected to the upper side surface of the casing 34. A hole 45 is formed on the lower side surface of the casing 34, more specifically, a side surface below the intermediate position in the vertical direction, and a hole 46 is formed below the hole 45. The pressure equalizing tube 40 is inserted into the hole 45, and the oil equalizing tube 30 is inserted into the hole 46. As described above, the pressure equalizing pipe 40 and the oil equalizing pipe 30 are connected to the lower side surface of the casing 34.

  An oil sump 42 is formed at the bottom of the casing 34. The oil pump 41 pumps up the oil in the oil reservoir 42 as the rotary shaft 38 rotates, and is immersed in the oil in the oil reservoir 42. In this embodiment, the oil pump 41 of the expander 13 is also constituted by a trochoid pump.

  A plate 43 is fixed to the lower inner wall of the casing 34, and a bearing 44 is fixed to the plate 43. The bearing 44 rotatably supports the lower portion of the rotary shaft 38. The rotating shaft 38 is provided with an oil supply path (not shown) that guides the oil pumped up by the oil pump 41 to the expansion mechanism 39.

  The generator 37 includes a stator 35 fixed to the inner wall of the casing 34 and a rotor 36 fixed to the rotary shaft 38. The generator 37 is disposed at the substantially center of the casing 34 in the vertical direction.

  In the present embodiment, the expansion mechanism 39 is constituted by a rotary expansion mechanism. However, the expansion mechanism 39 may be another type of expansion mechanism such as a scroll type. The specific configuration of the expansion mechanism 39 is not limited at all.

  The oil equalizing pipe 30 communicates the oil reservoir 31 of the compressor 11 and the oil reservoir 42 of the expander 13. In the present embodiment, the oil equalizing pipe 30 is formed of a straight pipe and extends horizontally. However, the oil equalizing pipe 30 may be formed by a bent pipe or may be inclined.

  One end of the pressure equalizing pipe 40 passes through the hole 29 of the casing 21 of the compressor 11 (hereinafter referred to as the compressor casing 21), and extends to the center side (rotary shaft 25 side) in the compressor casing 21. The other end of the pressure equalizing tube 40 is fitted in a hole 45 of a casing 34 (hereinafter referred to as an expander casing 34) of the expander 13. In other words, the pressure equalizing pipe 40 is positioned on the one end side of the main body 40 a spanned between the expander casing 34 and the compressor casing 21, and inside the compressor casing 21, the rotary shaft 25. And an extension 40b extending to the side.

  The pressure equalizing tube 40 is formed in a straight tube shape and extends horizontally. However, the pressure equalizing tube 40 may be inclined or bent. The main body portion 40a and the extension portion 40b may be a single body or separate bodies. That is, the pressure equalizing tube 40 may be formed by a single member or may be formed by combining a plurality of members.

  The vertical position of the pressure equalizing pipe 40 on the compressor 11 side is a position above and near the oil surface 31 a of the oil reservoir 31 when the operation of the compressor 11 is stopped. The vertical position of the pressure equalizing pipe 40 on the expander 13 side is also a position above and in the vicinity of the oil surface 42a of the oil reservoir 42 when the operation of the expander 13 is stopped. The vertical position on the compressor 11 side of the pressure equalizing pipe 40 is equal to the vertical position on the expander 13 side.

  Although illustration is omitted, the main body portion 40a of the pressure equalizing tube 40 is covered with a heat insulating material to be thermally insulated. The pressure equalizing pipe 40 is located outside the compressor casing 21 and the expander casing 34 and is exposed to the outside air through the heat insulating material.

  When the operation of the refrigeration cycle apparatus 1 is stopped, the refrigerant and oil temperatures are the same in the compressor 11 and the expander 13, so the refrigerant density in the compressor 11 and the expander 13 The refrigerant density is equal, and the oil density in the compressor 11 and the oil density in the expander 13 are also equal. As a result, the oil level height of the compressor 11 and the oil level height of the expander 13 become equal.

As described above, in the present embodiment, carbon dioxide is used as the refrigerant of the refrigerant circuit 10, and PAG is used as the lubricating oil. For example, assuming that the atmospheric temperature of the compressor 11 and the expander 13 (the temperature outside the compressor casing 21 and the expander casing 34) is 15 ° C., the temperature of the refrigerant and oil in the compressor 11 and the expander 13 15 ° C., the refrigerant density is 150 kg / m ³ , and the oil density is 1000 kg / m ³ (see FIG. 7).

  During operation of the refrigeration cycle apparatus 1 (see FIG. 1), the refrigerant discharged from the compressor 11 is in a supercritical state. The high-temperature refrigerant discharged from the compressor 11 dissipates heat in the radiator 12 and expands in the expander 13 after the temperature drops. The refrigerant discharged from the expander 13 is sucked into the compressor 11 after being evaporated by the evaporator 14.

  At this time, the temperature in the compressor 11 is higher than room temperature (for example, about 80 ° C., hereinafter simply referred to as high temperature), while the temperature in the expander 13 is room temperature (for example, about 15 ° C.). As described above, since the pressure equalizing tube 40 is exposed to the outside air via a heat insulating material (not shown), the temperature inside the pressure equalizing tube 40 is also normal temperature.

Here, if the temperature in the compressor 11 is 80 ° C. and the temperature in the expander 13 is 15 ° C., the density of the refrigerant and oil in the compressor 11 is 210 kg / m, respectively, as shown in FIG. ^3, 930 kg / ^{m 3,} and the density of the refrigerant and oil in the expander 13 becomes respectively ^{900kg / m 3, 1000kg / m} 3. As a result, the density difference between the oil and the refrigerant in the expander 13 is 1000 kg / m ³ -900 kg / m ³ = 100 kg / m ³ , which is very small. Therefore, the differential pressure generated by the height difference H2-H4 (see FIG. 4) between the pressure equalizing pipe 40 and the oil surface 42a is substantially constant regardless of the oil surface height H4. On the other hand, the refrigerant density (= 210 kg / m ³ ) in the compressor 11 is small, and the oil density (= 930 kg / m ³ ) in the compressor 11 is the refrigerant density (= 900 kg / m) in the expander 13. m ³ ). Therefore, the height H5 of the oil surface 31a of the compressor 11 is substantially equal to the connection position of the pressure equalizing pipe 40 of the expander 13. Further, the internal temperature of the pressure equalizing tube 40 is substantially equal to the internal temperature of the expander 13. Also from this point, the height of the oil surface 31a of the compressor 11 is substantially the same as the connection position of the pressure equalizing pipe 40 in the compressor 11.

  However, according to the present embodiment, the pressure equalizing pipe 40 is connected to a relatively low position in the expander casing 34 and is connected to the vicinity of the oil level 42 a of the expander 13. Further, the pressure equalizing pipe 40 is connected to a relatively low position in the compressor casing 21, and is connected to the vicinity of the oil surface 31 a of the compressor 11. Therefore, in both the compressor 11 and the expander 13, the difference in height between the connection position of the pressure equalizing pipe 40 and the oil level is small, so the refrigerant density in the compressor 11 and the refrigerant density in the expander 13 are greatly different. Even in this case, the pressure to push down the oil level does not differ greatly between the expander and the compressor. That is, if the refrigerant density in the expander 13 is ρe and the refrigerant density in the compressor 11 is ρc, the pressure to push down the oil surface 42a in the expander 13 is ρe (H2-H4). 11, the pressure to push down the oil surface 31a is ρc (H2−H5). Since H2≈H4 and H2≈H5, even if ρe and ρc are greatly different, the difference between them is Near zero. Accordingly, a large amount of oil in the expander 13 does not flow into the compressor 11 through the oil equalizing pipe 30, and an oil level height imbalance between the expander 13 and the compressor 11 can be corrected. Therefore, a shortage of lubricating oil in the expander 13 can be prevented.

  Since the pressure equalizing pipe 40 is located in the vicinity of the oil level of the compressor 11, there is a concern that part of the oil of the compressor 11 flows into the expander 13 through the pressure equalizing pipe 40. However, according to the present embodiment, the pressure equalizing pipe 40 has the extended portion 40b that extends toward the rotary shaft 25 in the compressor casing 21. As conceptually shown in FIG. 3, during the operation of the compressor 11, a rotating flow of the refrigerant is caused by the rotating shaft 25 and the rotor 23, and the oil in the oil reservoir is stirred by the refrigerant and is caused by centrifugal force. It tends to gather on the inner surface side of the compressor casing 21. As a result, the oil surface 31a tends to be in a state of being recessed downward with the rotation shaft 25 as the center. Therefore, it becomes difficult for oil to enter from the extended portion 40b extended to the rotating shaft 25 side. Thus, according to the present embodiment, the pressure equalizing pipe 40 is extended so as to be separated from the oil surface 31a (the oil surface 31a here is an oil surface during operation of the compressor 11). Therefore, even when the extension portion 40b extends horizontally, the extension portion 40b extends away from the oil surface 31a), so that the pressure equalizing pipe 40 is connected to the vicinity of the oil surface of the compressor casing 21. Therefore, the infiltration of oil into the pressure equalizing tube 40 can be suppressed.

<Embodiment 2>
As shown in FIG. 4, the refrigeration cycle apparatus according to the second embodiment is obtained by changing the pressure equalizing tube 40 in the first embodiment. Parts similar to those of the first embodiment are denoted by the same reference numerals, and description thereof is omitted.

  Also in the second embodiment, one end of the pressure equalizing pipe 40 penetrates the lower side surface of the compressor casing 21, and is extended inside the compressor casing 21 so as to be separated from the oil surface 31 a during operation of the compressor 11. . However, in the present embodiment, the pressure equalizing pipe 40 is bent upward in the compressor casing 21. That is, in the present embodiment, the pressure equalizing pipe 40 is located on the one end side of the main body portion 40a and the main body portion 40a spanned between the expander casing 34 and the compressor casing 21, and inside the compressor casing 21. And an extension 40b extending upward. In addition, the bending condition of the pressure equalizing pipe 40 is not particularly limited, and may be bent sharply or gently. That is, the pressure equalizing tube 40 may be bent upward or curved.

  Also in this embodiment, the main body portion 40a of the pressure equalizing tube 40 is formed in a straight tube shape and extends horizontally. The extension 40b extends vertically upward. However, it is also possible to extend the extension part 40b diagonally upward. The main body portion 40a and the extension portion 40b may be a single body or separate bodies.

  The upper and lower positions of the main body 40a on the compressor 11 side are positions above and in the vicinity of the oil surface 31a of the oil reservoir 31 when the operation of the compressor 11 is stopped. The vertical position of the main body 40a on the expander 13 side is also a position above and in the vicinity of the oil surface 42a of the oil reservoir 42 when the operation of the expander 13 is stopped. The vertical position on the compressor 11 side of the main body 40a is equal to the vertical position on the expander 13 side of the main body 40a. However, since the extension 40b of the pressure equalizing pipe 40 is extended upward, the opening height H3 in the compressor casing 21 of the pressure equalizing pipe 40 and the opening height H2 in the expander casing 34 are different.

  Also in the present embodiment, the same effect as in the first embodiment can be obtained. In addition, according to the present embodiment, since the extension portion 40b of the pressure equalizing tube 40 is extended upward, the infiltration of oil into the pressure equalizing tube 40 can be further suppressed. Moreover, since the extension part 40b of the pressure equalizing pipe 40 is opened upward, the infiltration of oil can be further effectively suppressed.

  In addition, although the extension part 40b is extended upwards, since it is arrange | positioned inside the compressor casing 21, the temperature of the extension part 40b becomes equal to the internal temperature of the compressor 11. FIG. Therefore, unlike the main body portion 40 a of the pressure equalizing tube 40, the refrigerant density in the extension 40 b is equal to the refrigerant density in the compressor casing 21. Therefore, there is no possibility that the oil level 31a of the compressor 11 rises to the vicinity of the opening of the extension 40b.

<Embodiment 3>
As shown in FIG. 5, the third embodiment is obtained by changing the extension 40 b of the pressure equalizing tube 40 of the second embodiment, and the motor 24 covers the periphery of the tip of the extension 40 b.

  Specifically, in this embodiment, a groove 22 a extending in the vertical direction is formed in a part of the stator 22 of the electric motor 24. A hole extending in the vertical direction may be formed instead of the groove 22a. And the front-end | tip of the extension part 40b of the pressure equalizing pipe 40 is inserted in the said groove | channel 22a.

  Therefore, according to the present embodiment, the same effect as that of the second embodiment can be obtained. In addition, according to this embodiment, since the periphery of the tip of the pressure equalizing tube 40 is covered by the electric motor 24, the infiltration of oil into the pressure equalizing tube 40 can be further suppressed.

  The grooves 22a and the like of the electric motor may extend obliquely in the up and down direction (direction inclined from the up and down direction), and the extension portion 40b of the pressure equalizing pipe 40 may extend in the obliquely up and down direction so as to be inserted into the groove 22a and the like. . Even in such a case, the above-described effects can be obtained.

<Embodiment 4>
As shown in FIG. 6, the fourth embodiment is a modification of the pressure equalizing tube 40 of the second embodiment, and the main body portion 40 a and the extension portion 40 b of the pressure equalizing tube 40 are formed as separate members.

  In the present embodiment, the main body portion 40a of the pressure equalizing tube 40 is formed by a straight tube extending horizontally, and the extension portion 40b is formed by a bent tube having a smaller diameter than the main body portion 40a. The extension 40b extends upward and opens upward. The main body 40a is inserted into the hole 29 of the compressor casing 21 from the outside. On the other hand, the extension 40b is inserted into the main body 40a from the inside of the compressor casing 21. In addition, the main-body part 40a and the extension part 40b are joined by welding etc., for example.

  According to the present embodiment, the same effect as in the second embodiment can be obtained. In addition, according to the present embodiment, since the pressure equalizing pipe 40 is formed by a plurality of members, the pressure equalizing pipe 40 can be easily assembled to the compressor casing 21.

<Other embodiments>
In each of the above embodiments, the refrigerant is carbon dioxide, and the lubricating oil is PAG. However, there are various combinations of refrigerants and lubricating oils that exhibit the characteristics shown in FIG. 7, not limited to carbon dioxide and PAG. In the present invention, the refrigerant and the lubricating oil are not limited to carbon dioxide and PAG. In addition, the refrigeration cycle apparatus according to the present invention is particularly useful for a combination of a refrigerant and a lubricating oil whose density ratio becomes closer as the temperature changes from high temperature to room temperature. Of course, even combinations of oils can be used.

  As described above, the present invention is useful for a refrigeration cycle apparatus including an air conditioner, a water heater, a refrigerator, a refrigerator, a dehumidifier, and the like.

Refrigerant circuit diagram of refrigeration cycle apparatus according to an embodiment 1 is a longitudinal sectional view of a compressor and an expander according to Embodiment 1. 1 is a longitudinal sectional view of a compressor according to a first embodiment. Vertical section of compressor and expander according to Embodiment 2 A longitudinal sectional view of a compressor and an expander according to Embodiment 3 Vertical section of compressor and expander according to Embodiment 4 Characteristic chart showing density change with temperature of refrigerant (carbon dioxide) and oil (PAG) (A) And (b) is a longitudinal cross-sectional view of the compressor and the expander of the refrigeration cycle apparatus (A)-(c) is a longitudinal cross-sectional view of the compressor and the expander of the refrigeration cycle apparatus

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Refrigeration cycle apparatus 11 Compressor 13 Expander 21 Compressor casing 30 Oil equalizing pipe 31 Oil sump 31a Compressor oil reservoir 31a Oil level of compressor 34 Expander casing 40 Pressure equalizing pipe 40a Main body part 40b Extension part 42 Oil reservoir 42a expansion Oil level of machine

Claims (2)

A compressor having a casing formed with an oil sump at the bottom and compressing the refrigerant;
An expander having a casing with an oil sump formed at the bottom and expanding the refrigerant;
An oil equalizing pipe communicating the oil reservoir of the compressor and the oil reservoir of the expander;
One end is connected above the oil reservoir in the casing of the compressor and in the vicinity of the oil level when the compressor is stopped, and the other end is above the oil reservoir in the casing of the expander and the expander. A pressure equalizing pipe connected in the vicinity of the oil level when the operation is stopped,
The one end of the pressure equalizing pipe extends upward or obliquely upward in the compressor casing so as to penetrate the casing of the compressor and away from the oil level of the oil sump during operation of the compressor. The refrigeration cycle device. The refrigeration cycle apparatus according to claim 1, wherein the refrigerant is carbon dioxide.

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