JP7518705B2 - Compressor and refrigerator equipped with said compressor - Google Patents

Description

The present invention relates to a compressor used in a refrigerator, and in particular to a lubrication structure for the compressor's bearings.

Compression refrigerators used in refrigeration and air conditioning equipment are configured as closed systems filled with refrigerant. Compression refrigerators generally consist of an evaporator that removes heat from the fluid to be cooled, causing the refrigerant to evaporate and produce a refrigerating effect, a compressor that compresses the refrigerant gas evaporated by the evaporator to produce high-pressure refrigerant gas, and a condenser that cools and condenses the high-pressure refrigerant gas with a cooling fluid, all connected by refrigerant piping.

The compressor is equipped with an impeller for compressing the refrigerant gas, and bearings that support the rotor to which the impeller is fixed. To prevent the bearings from seizing or wearing out, the bearings are lubricated with oil. An oil that is generally compatible with the refrigerant liquid is selected. Compression refrigerators have an entirely sealed structure, and any oil that leaks into the refrigerant flow path is dissolved in the refrigerant liquid and circulates inside the refrigerator together with the refrigerant liquid.

JP 2008-14577 A

However, in order to reuse the oil dissolved in the refrigerant liquid to lubricate the bearings, a structure is required to separate the oil from the refrigerant liquid and supply the separated oil to the bearings, which makes the structure of the entire refrigerator complex. Furthermore, when the oil and the refrigerant liquid mix, the viscosity of the oil decreases, and the lubricating performance of the oil decreases. Furthermore, the oil adheres to the heat exchanger of the evaporator and inhibits heat transfer. Also, when the refrigerant liquid evaporates, the oil turns into bubbles, making it impossible to supply liquid oil to the bearings, resulting in insufficient lubrication of the bearings.

Therefore, the present invention provides a compressor with a structure that prevents the lubricant from mixing with the refrigerant liquid, and a refrigerator equipped with the compressor.

In one aspect, there is provided a compressor for compressing refrigerant gas in a refrigerator, the compressor comprising: an impeller, a rotating body rotatable integrally with the impeller, a rolling bearing rotatably supporting the rotating body, a lubricant held in the rolling bearing, a bearing housing forming a bearing chamber in which the rolling bearing is disposed, a gas supply passage communicating with the bearing chamber and for supplying refrigerant gas compressed by the compressor into the bearing chamber, a communication passage communicating with a space outside the bearing chamber and communicating with a region having a lower pressure than the pressure in the bearing chamber, and a pressure equalizing passage connecting two spaces facing both sides of the rolling bearing, the two spaces being within the bearing chamber, the bearing housing being disposed in the space outside the bearing chamber, the space outside the bearing chamber having a lower pressure than the pressure in the bearing chamber, the bearing chamber being filled with the compressed refrigerant gas supplied from the gas supply passage, and the two spaces being filled with the compressed refrigerant gas .

The rolling bearing is disposed in a bearing chamber, which is filled with compressed refrigerant gas (i.e., high-pressure refrigerant gas). Since the pressure in the bearing chamber is higher than the pressure in the space outside the bearing chamber, the refrigerant liquid present outside the bearing chamber cannot enter the bearing chamber and does not come into contact with the lubricant held in the rolling bearing. As a result, the lubricant is not mixed with the refrigerant liquid, and the refrigerant liquid and the lubricant can perform their respective functions. Furthermore, the oil circulation line for supplying lubricating oil to the rolling bearing can be omitted, which greatly simplifies the configuration. Furthermore, since no oil leaks into the refrigerant side, a mechanism for separating the oil and the refrigerant is not required.
The pressure equalizing passage can equalize the pressure of the refrigerant gas on both sides of the rolling bearing, thereby preventing uneven distribution or leakage of the lubricant caused by a pressure difference.

In one embodiment, the bearing further includes a seal for sealing a gap between the bearing housing and the rotating body.
The seal can minimize leakage of refrigerant gas from the bearing chamber, which in turn increases the pressure difference between the inside and outside of the bearing chamber and reliably prevents refrigerant liquid from entering the bearing chamber.

In one embodiment, the pressure equalizing passage is formed in the rotor.
In one aspect, the pressure equalizing passage is formed within the bearing housing.
In one aspect, the pressure equalization passage is connected to the bearing housing.

In one embodiment, the rolling bearing includes a plurality of rolling elements and lubricant retaining rings disposed on both sides of the plurality of rolling elements.
The lubricant retaining ring has the function of retaining the lubricant inside the rolling bearing, and therefore not only can the lubricant retaining ring maintain the performance of the rolling bearing, but also can prevent the lubricant from mixing with the refrigerant liquid.

In one embodiment, the lubricant is a semi-fluid lubricant.
Unlike fluid oil, semi-fluid lubricants (such as grease) are less likely to flow out of rolling bearings, making it possible to eliminate the need for an oil circulation mechanism that was previously required.

In one aspect, a refrigerator is provided in which a refrigerant circulates inside, the refrigerator comprising an evaporator that evaporates a refrigerant liquid to produce a refrigerant gas, a compressor that compresses the refrigerant gas, and a condenser that condenses the compressed refrigerant gas to produce the refrigerant liquid.

The present invention provides a compressor in which the lubricant does not mix with the refrigerant liquid.

1 is a schematic diagram showing an embodiment of a refrigerator in which a refrigerant circulates; FIG. 2 is an enlarged cross-sectional view of the compressor shown in FIG. FIG. 4 is an enlarged view of the first rolling bearing and the first bearing housing. 4 is a cross-sectional view taken along line AA in FIG. 3. FIG. 4 illustrates an embodiment of a first pressure equalizing passage. FIG. 4 illustrates an embodiment of a first pressure equalizing passage. FIG. 4 illustrates an embodiment of a first pressure equalizing passage. FIG. 4 illustrates an embodiment of a first pressure equalizing passage. FIG. 4 is an enlarged view of the second rolling bearing and the second bearing housing. FIG. 13 is a schematic diagram showing still another embodiment of the refrigerator. This is a modification of the embodiment shown in FIG. 11 is another modification of the embodiment shown in FIG.

Hereinafter, an embodiment of the present invention will be described with reference to the drawings.
FIG. 1 is a schematic diagram showing an embodiment of a refrigerator in which a refrigerant circulates. The refrigerator of this embodiment is a turbo refrigerator (centrifugal refrigerator) equipped with a centrifugal compressor 1. As shown in FIG. 1, the refrigerator includes an evaporator 2 that evaporates a refrigerant liquid to generate a refrigerant gas, a compressor 1 that compresses the refrigerant gas, and a condenser 3 that condenses the compressed refrigerant gas to generate a refrigerant liquid. The suction port of the compressor 1 is connected to the evaporator 2 by a refrigerant pipe 4A. The discharge port of the compressor 1 is connected to the condenser 3 by a refrigerant pipe 4B. An expansion valve 21 is attached to the refrigerant pipe 4C extending from the condenser 3 to the evaporator 2. The expansion valve 21 is an actuator-driven flow control valve configured to be adjustable in its opening degree, and is configured, for example, by a motor-operated valve with a variable opening degree.

In this embodiment, the compressor 1 is a single-stage centrifugal compressor. More specifically, the compressor 1 includes a single-stage impeller 11, a rotor 12 that can rotate integrally with the impeller 11, and an electric motor 13 that rotates the rotor 12 and the impeller 11. In one embodiment, the rotor 12 is a rotating shaft, and the impeller 11 is fixed to the rotating shaft. In another embodiment, the impeller 11 may be integrally formed with the rotor 12. The rotor 12 is rotatably supported by bearings 25 and 26. The bearings 25 and 26 are disposed inside the electric motor 13. More specifically, the bearings 25 and 26 are disposed in bearing chambers 31 and 32 formed in the electric motor 13, respectively. In one embodiment, the compressor 1 may be a multi-stage centrifugal compressor equipped with a multi-stage impeller.

Guide vanes 16 are arranged at the suction port of the compressor 1 to adjust the suction flow rate of refrigerant gas to the impeller 11. The guide vanes 16 are located on the suction side of the impeller 11. The guide vanes 16 are arranged radially, and the opening degree of the guide vanes 16 is changed by each guide vane 16 rotating synchronously with each other by a predetermined angle around its own axis. The refrigerant gas sent from the evaporator 2 passes through the guide vanes 16 and is then pressurized by the rotating impeller 11. The pressurized refrigerant gas is sent to the condenser 3 through the refrigerant piping 4B.

The evaporator 2 removes heat from the fluid to be cooled (e.g., cold water) and the refrigerant liquid evaporates to produce a refrigeration effect. The compressor 1 compresses the refrigerant gas produced in the evaporator 2, and the condenser 3 cools and condenses the compressed refrigerant gas with a cooling fluid (e.g., cooling water) to produce refrigerant liquid. The refrigerant liquid is depressurized by passing through the expansion valve 21. The depressurized refrigerant liquid is sent to the evaporator 2. In this way, the refrigerator is configured as a closed system in which the refrigerant is sealed.

The refrigerator further includes a refrigerant liquid transfer pipe 40 branching off from the refrigerant piping 4C, and a refrigerant pump 41 connected to the refrigerant liquid transfer pipe 40. The refrigerant liquid transfer pipe 40 extends from the refrigerant piping 4C via the refrigerant pump 41 to the electric motor 13 of the compressor 1. The refrigerant liquid transfer pipe 40 is connected to a refrigerant nozzle 18 disposed within the electric motor 13 of the compressor 1. The refrigerant nozzle 18 is disposed facing components of the electric motor 13, such as the motor stator.

Most of the refrigerant liquid flowing through the refrigerant pipe 4C is sent to the evaporator 2, but some of the refrigerant liquid flowing through the refrigerant pipe 4C flows into the refrigerant liquid transfer pipe 40 and is sent to the refrigerant nozzle 18 by the refrigerant pump 41. The refrigerant liquid is sprayed from the refrigerant nozzle 18 into the inside of the motor 13 to cool the inside of the motor 13. The inside of the motor 13 is connected to the inside of the evaporator 2 by the refrigerant liquid return pipe 45. More specifically, one end of the refrigerant liquid return pipe 45 is connected to the bottom of the motor 13, and the other end of the refrigerant liquid return pipe 45 is connected to the evaporator 2. The refrigerant liquid sprayed from the refrigerant nozzle 18 is collected in the motor 13 and returned to the evaporator 2 through the refrigerant liquid return pipe 45.

Figure 2 is an enlarged cross-sectional view of the compressor 1 shown in Figure 1. The compressor 1 includes an impeller 11, an impeller casing 14 that houses the impeller 11, a rotor 12 that can rotate integrally with the impeller 11, a first rolling bearing 25 and a second rolling bearing 26 that rotatably support the rotor 12, and an electric motor 13 that rotates the impeller 11 and the rotor 12. A compression chamber 17 is formed in the impeller casing 14, and the impeller 11 is disposed in the compression chamber 17.

The electric motor 13 includes a motor rotor 13A fixed to the rotor 12, a motor stator 13B surrounding the motor rotor 13A, and a motor housing 13C accommodating the motor rotor 13A and the motor stator 13B. The motor housing 13C is connected to the impeller casing 14. The refrigerant nozzle 18 is fixed to the motor housing 13C and faces the motor stator 13B and the motor rotor 13A. The refrigerant liquid is sprayed from the refrigerant nozzle 18 onto the motor stator 13B and the motor rotor 13A, cooling the motor stator 13B and the motor rotor 13A. The refrigerant liquid is returned to the evaporator 2 through a refrigerant liquid return pipe 45 connected to the bottom of the motor housing 13C.

The rotating body 12 is supported by a first rolling bearing 25 and a second rolling bearing 26 arranged on both sides of the motor rotor 13A. The first rolling bearing 25 is surrounded by a first bearing housing 35. More specifically, the first bearing housing 35 forms a first bearing chamber 31 therein, and the first rolling bearing 25 is arranged in the first bearing chamber 31. The first bearing housing 35 is supported by the impeller casing 14. In this embodiment, the first bearing housing 35 and the impeller casing 14 are configured as separate members, and the first bearing housing 35 is fixed to the impeller casing 14. In one embodiment, the first bearing housing 35 may be integral with the impeller casing 14. Furthermore, in one embodiment, the first bearing housing 35 may be supported by the motor housing 13C. For example, the first bearing housing 35 may be fixed to the motor housing 13C or may be integral with the motor housing 13C.

The first bearing housing 35 is not in contact with the rotor 12, and a gap is formed between the first bearing housing 35 and the rotor 12. The first bearing chamber 31 is connected to the compression chamber 17 in which the impeller 11 is disposed through the first gas supply passage 51. The first gas supply passage 51 is formed in the rear wall 14a of the impeller casing 14. Most of the refrigerant gas compressed by the rotating impeller 11 is sent to the condenser 3 through the refrigerant piping 4B, while a portion of the compressed refrigerant gas flows from the compression chamber 17 through the first gas supply passage 51 into the first bearing chamber 31, and the first bearing chamber 31 is filled with refrigerant gas (high-pressure gas).

The first bearing housing 35 is disposed in the motor housing 13C. The internal space of the motor housing 13C (i.e., the space outside the first bearing chamber 31) is connected to a region with a lower pressure than the pressure inside the first bearing chamber 31. More specifically, the internal space of the motor housing 13C (i.e., the space outside the first bearing chamber 31) is connected to the evaporator 2 (see FIG. 1) through the refrigerant liquid return pipe 45. Since the evaporator 2 is connected to the suction side of the compressor 1, the pressure inside the evaporator 2 is lower than the pressure inside the first bearing chamber 31. Therefore, the internal space of the motor housing 13C (i.e., the space outside the first bearing chamber 31) is at a lower pressure than the pressure inside the first bearing chamber 31. In this embodiment, the communication flow path that communicates with the space outside the first bearing chamber 31 and communicates with a region with a lower pressure than the pressure inside the first bearing chamber 31 is constituted by the refrigerant liquid return pipe 45.

With the above configuration, the pressure of the refrigerant gas in the first bearing chamber 31 is higher than the pressure in the internal space of the motor housing 13C (i.e., the space outside the first bearing chamber 31). Therefore, the refrigerant liquid sprayed from the refrigerant nozzle 18 as a cooling liquid cannot penetrate into the first bearing chamber 31 filled with high-pressure refrigerant gas, and does not come into contact with the first rolling bearing 25.

The second rolling bearing 26 is surrounded by the second bearing housing 36. More specifically, the second bearing housing 36 defines a second bearing chamber 32 therein, and the second rolling bearing 26 is disposed within the second bearing chamber 32. The second bearing housing 36 is fixed to the motor housing 13C. The second bearing housing 36 may be integral with the motor housing 13C.

The second bearing housing 36 is not in contact with the rotating body 12, and a gap is formed between the second bearing housing 36 and the rotating body 12. The second bearing chamber 32 is connected to the condenser 3 (see FIG. 1) through the second gas supply passage 52. The condenser 3 is connected to the discharge port of the compressor 1 through the refrigerant piping 4B (see FIG. 1), and refrigerant gas compressed by the compressor 1 is present inside the condenser 3. A portion of the compressed refrigerant gas in the condenser 3 is sent into the second bearing chamber 32 through the second gas supply passage 52. The second bearing chamber 32 is filled with refrigerant gas (high-pressure gas).

In this embodiment, the second gas supply passage 52 extends from the condenser 3 to the second bearing housing 36, but in one embodiment, the second gas supply passage 52 may extend from the refrigerant pipe 4B to the second bearing housing 36. In this case, a portion of the compressed refrigerant gas flowing through the refrigerant pipe 4B is sent to the second bearing chamber 32 through the second gas supply passage 52.

Like the first bearing housing 35, the second bearing housing 36 is also disposed within the motor housing 13C. In the internal space of the motor housing 13C (i.e., the space outside the second bearing chamber 32), there is refrigerant at a pressure lower than the pressure within the second bearing chamber 32.

With the above configuration, the pressure of the refrigerant gas in the second bearing chamber 32 is higher than the pressure in the internal space of the motor housing 13C (i.e., the space outside the second bearing chamber 32). Therefore, the refrigerant liquid sprayed from the refrigerant nozzle 18 as a cooling liquid cannot penetrate into the second bearing chamber 32 filled with high-pressure refrigerant gas, and does not come into contact with the second rolling bearing 26.

Fig. 3 is an enlarged view of the first rolling bearing 25 and the first bearing housing 35, and Fig. 4 is a cross-sectional view taken along line A-A in Fig. 3. In this embodiment, the first rolling bearing 25 includes two coaxially arranged back-to-back duplex angular bearings 61. The two angular bearings 61 are in contact with each other without any gaps being formed between them. Since there is no gap between the angular bearings 61, high-pressure refrigerant gas does not get between the angular bearings 61, and undesirable pressure fluctuations do not occur in the first bearing chamber 31. Furthermore, the coaxially arranged back-to-back duplex angular bearings 61 have the following advantages.
1) The contact angle of the rolling elements is inclined, so that a large axial load can be supported.
2) By controlling the internal clearance, preload can be applied to increase shaft rigidity.

In one embodiment, the first rolling bearing 25 may include only one angular bearing, or may include three or more angular bearings. In a further embodiment, various rolling bearings, such as deep groove ball bearings, may be provided instead of the angular bearings.

Each angular bearing 61 holds a lubricant 65 inside. The lubricant 65 is a semi-fluid lubricant (e.g., grease) that has a higher viscosity than lubricating oil. Unlike fluid oil, the semi-fluid lubricant (e.g., grease) 65 is less likely to flow out of the first rolling bearing 25. Therefore, the oil circulation mechanism that was previously required can be eliminated.

Each angular bearing 61 includes a plurality of rolling elements 61A and lubricant retaining rings 61B arranged on both sides of the plurality of rolling elements 61A. The lubricant retaining rings 61B are held by the outer ring (fixed ring) of each angular bearing 61 and are not in contact with the inner ring (rotating ring) of each angular bearing 61. The lubricant retaining ring 61B is made of, for example, an annular metal plate or an annular resin plate. The lubricant retaining ring 61B has the function of retaining the lubricant 65 inside the first rolling bearing 25. Therefore, the lubricant retaining ring 61B can not only maintain the performance of the first rolling bearing 25, but also prevent the lubricant 65 from mixing with the refrigerant liquid.

The compressor 1 is provided with seals 68A, 68B that seal the gap between the first bearing housing 35 and the rotor 12. In this embodiment, the seals 68A, 68B are labyrinth seals, which are an example of a non-contact seal. The seals 68A, 68B are disposed on both sides of the first rolling bearing 25. In one embodiment, only the seal 68B on the motor rotor side may be provided.

As shown in FIG. 3, the refrigerant gas compressed by the compressor 1 flows into the first bearing chamber 31 through the seal 68A on the impeller side and fills the first bearing chamber 31. The refrigerant gas passes through the seal 68B on the motor rotor side and flows out little by little into the internal space of the motor housing 13C. The seals 68A and 68B can minimize the leakage of the refrigerant gas from the first bearing chamber 31. As a result, the pressure difference between the inside and outside of the first bearing chamber 31 increases, and the intrusion of the refrigerant liquid into the first bearing chamber 31 can be reliably prevented. From the viewpoint of minimizing the leakage of the refrigerant gas from the first bearing chamber 31, the seals 68A and 68B may be contact seals, but contact seals are not suitable for high-speed operation.

The compressor 1 further includes a first pressure equalizing passage 70 that connects two spaces facing both sides of the first rolling bearing 25. These two spaces are located within the first bearing chamber 31. The first pressure equalizing passage 70 is formed in the rotor 12. More specifically, a plurality of grooves extending in the axial direction are formed in the outer peripheral surface of the rotor 12, and these grooves form the first pressure equalizing passage 70. As shown in FIG. 4, the plurality of first pressure equalizing passages (grooves) 70 are distributed at equal intervals around the axis of the rotor 12. The number and arrangement of the first pressure equalizing passages 70 are not limited to this embodiment. In one embodiment, only one first pressure equalizing passage (groove) 70 may be provided.

The axial length of the first pressure equalizing passage 70 is greater than the axial length of the first rolling bearing 25. Therefore, both ends of each first pressure equalizing passage 70 are connected to two spaces in the first bearing chamber 31. In other words, the two spaces facing both sides of the first rolling bearing 25 are connected through the first pressure equalizing passage 70. The refrigerant gas compressed by the compressor 1 flows into the first bearing chamber 31 through the seal 68A on the impeller side, flows through the first pressure equalizing passage 70, and fills the entire first bearing chamber 31. The first pressure equalizing passage 70 can equalize the pressure of the refrigerant gas on both sides of the first rolling bearing 25. Therefore, it is possible to prevent the lubricant 65 from being biased or leaking out due to the pressure difference of the refrigerant gas.

The first rolling bearing 25 is disposed in the first bearing chamber 31, which is filled with compressed refrigerant gas (i.e., high-pressure refrigerant gas). The pressure in the first bearing chamber 31 is higher than the pressure in the space outside the first bearing chamber 31 (i.e., the internal space of the motor housing 13C). Therefore, the refrigerant liquid present outside the first bearing chamber 31 cannot penetrate into the first bearing chamber 31 and does not come into contact with the lubricant 65 held in the first rolling bearing 25. As a result, the lubricant 65 is not mixed with the refrigerant liquid, and the refrigerant liquid and the lubricant 65 can perform their respective functions. Furthermore, the configuration can be greatly simplified because the oil circulation line can be omitted. In addition, since there is no leakage of oil to the refrigerant side, a separation mechanism for the oil and the refrigerant is not required.

As shown in FIG. 5 and FIG. 6, the first pressure equalizing passage 70 may be a hole formed in the rotor 12, so long as it is connected to two spaces facing both sides of the first rolling bearing 25. Furthermore, the first pressure equalizing passage 70 may be formed in the first bearing housing 35. For example, as shown in FIG. 7, the first pressure equalizing passage 70 may be a groove formed on the inner surface of the first bearing housing 35. Alternatively, although not shown, the first pressure equalizing passage 70 may be a hole formed in the first bearing housing 35. As shown in FIG. 8, the first pressure equalizing passage 70 may be composed of a pipe connected at both ends to the first bearing housing 35.

Figure 9 is an enlarged view of the second rolling bearing 26 and the second bearing housing 36. The configuration and effects not specifically described are the same as those of the embodiment described with reference to Figures 3 and 4, so the overlapping description will be omitted. In this embodiment, the second rolling bearing 26 includes a back-to-back combination angular bearing 81 arranged coaxially. The two angular bearings 81 are in contact with each other without forming a gap between them. Since there is no gap between the angular bearings 81, high-pressure refrigerant gas does not enter between the angular bearings 81, and undesirable pressure fluctuations do not occur in the second bearing chamber 32. The advantageous effects of the two coaxially arranged angular bearings 81 are the same as those described for the angular bearing 61, so the overlapping description will be omitted.

In one embodiment, the second rolling bearing 26 may include only one angular bearing, or may include three or more angular bearings. In a further embodiment, various rolling bearings, such as deep groove ball bearings, may be provided instead of the angular bearings.

Each angular bearing 81 holds a lubricant 85 therein. The lubricant 85 is a semi-fluid lubricant (e.g., grease) and has a higher viscosity than lubricating oil. Each angular bearing 81 has a plurality of rolling elements 81A and a lubricant retaining ring 81B arranged on both sides of the plurality of rolling elements 81A. The lubricant retaining ring 81B is held by the outer ring (fixed ring) of each angular bearing 81 and is not in contact with the inner ring (rotating ring) of each angular bearing 81. The lubricant retaining ring 81B is made of, for example, an annular metal plate or an annular resin plate. The lubricant retaining ring 81B has the function of retaining the lubricant 85 inside the second rolling bearing 26.

The compressor 1 is provided with a seal 88 that seals the gap between the second bearing housing 36 and the rotor 12. The seal 88 is a labyrinth seal, which is an example of a non-contact seal. In this embodiment, the end of the rotor 12 is in the second bearing chamber 32, so the seal 88 is provided only on the motor rotor side. The refrigerant gas compressed by the compressor 1 flows from the condenser 3 through the second gas supply passage 52 into the second bearing chamber 32 and fills the second bearing chamber 32. The refrigerant gas passes through the seal 88 on the motor rotor side and flows out little by little into the internal space of the motor housing 13C. The seal 88 can minimize leakage of the refrigerant gas from the second bearing chamber 32. The seal 88 may be a contact seal, but a contact seal is not suitable for high-speed operation.

The compressor 1 further includes a second pressure equalizing passage 90 that connects two spaces facing both sides of the second rolling bearing 26. These two spaces are in the second bearing chamber 32. The second pressure equalizing passage 90 is formed in the rotor 12. More specifically, a plurality of grooves extending in the axial direction are formed in the outer peripheral surface of the rotor 12, and these grooves form the second pressure equalizing passage 90. The plurality of second pressure equalizing passages (grooves) 90 are distributed at equal intervals around the center of the rotor 12. The number and arrangement of the second pressure equalizing passages 90 are not limited to this embodiment. In one embodiment, only one second pressure equalizing passage (groove) 90 may be provided. Each embodiment of the first pressure equalizing passage 70 described with reference to Figures 5 to 8 can also be applied to the second pressure equalizing passage 90.

The axial length of the second pressure equalizing passage 90 is greater than the axial length of the second rolling bearing 26. Therefore, both ends of each second pressure equalizing passage 90 are connected to two spaces in the second bearing chamber 32. In other words, the two spaces facing both sides of the second rolling bearing 26 are connected through the second pressure equalizing passage 90. The refrigerant gas compressed by the compressor 1 flows into the second bearing chamber 32 through the second gas supply passage 52, flows through the second pressure equalizing passage 90, and fills the entire second bearing chamber 32. The second pressure equalizing passage 90 can equalize the pressure of the refrigerant gas on both sides of the second rolling bearing 26. Therefore, it is possible to prevent the lubricant 85 from being biased or leaking out due to the pressure difference of the refrigerant gas.

The second rolling bearing 26 is disposed in the second bearing chamber 32, which is filled with compressed refrigerant gas (i.e., high-pressure refrigerant gas). The pressure in the second bearing chamber 32 is higher than the pressure in the space outside the second bearing chamber 32 (i.e., the internal space of the motor housing 13C). Therefore, the refrigerant liquid present outside the second bearing chamber 32 cannot enter the second bearing chamber 32 and does not come into contact with the lubricant 85 held in the second rolling bearing 26. As a result, the lubricant 85 is not mixed with the refrigerant liquid, and the refrigerant liquid and the lubricant 85 can perform their respective functions. Furthermore, the configuration can be greatly simplified because the oil circulation line can be omitted. In addition, since there is no leakage of oil to the refrigerant side, a separation mechanism for the oil and the refrigerant is not required.

Figure 10 is a schematic diagram showing yet another embodiment of the refrigerator. The configuration of this embodiment that is not specifically described is the same as the embodiment described with reference to Figures 1 to 9, so duplicated descriptions will be omitted. The refrigerator includes an economizer 95 disposed between the condenser 3 and the evaporator 2. The refrigerant piping 4C has an upstream piping 4Ca that extends from the condenser 3 to the economizer 95, and a downstream piping 4Cb that extends from the economizer 95 to the evaporator 2.

The economizer 95 is connected to the compressor 1 by a refrigerant pipe 4E. The economizer 95 is an intercooler disposed between the condenser 3 and the evaporator 2. An expansion valve 21 is attached to the upstream pipe 4Ca extending from the condenser 3 to the economizer 95, and an expansion valve 22 is attached to the downstream pipe 4Cb extending from the economizer 95 to the evaporator 2. The expansion valves 21 and 22 are actuator-driven flow control valves configured so that their opening degree can be adjusted, and are composed of, for example, motor-operated valves with variable opening degree.

In this embodiment, the compressor 1 is a multi-stage centrifugal compressor. More specifically, the compressor 1 is a two-stage centrifugal compressor, and includes a first-stage impeller 11A, a second-stage impeller 11B, and an electric motor 13 that rotates the impellers 11A and 11B. The guide vane 16 is located on the suction side of the first-stage impeller 11A. The refrigerant gas sent from the evaporator 2 passes through the guide vane 16 and is then sequentially pressurized by the rotating impellers 11A and 11B. The pressurized refrigerant gas is sent to the condenser 3 through the refrigerant piping 4B.

The evaporator 2 removes heat from the fluid to be cooled (e.g., cold water) and evaporates the refrigerant liquid to produce a refrigeration effect. The compressor 1 compresses the refrigerant gas generated in the evaporator 2, and the condenser 3 cools and condenses the compressed refrigerant gas with a cooling fluid (e.g., cooling water) to generate refrigerant liquid. The refrigerant liquid is depressurized by passing through the expansion valve 21. The refrigerant gas present in the depressurized refrigerant liquid is separated by the economizer 95 and sent to the intermediate suction port 97 provided between the first stage impeller 11A and the second stage impeller 11B of the compressor 1. The refrigerant liquid that has passed through the economizer 95 is depressurized by passing through the expansion valve 22 and is further sent to the evaporator 2.

Figure 11 is a modified example of the embodiment shown in Figure 10. As shown in Figure 11, the branch pipe 99 branches off from the refrigerant pipe 4E that connects the economizer 95 and the compressor 1, and extends to the second bearing chamber 32. The second bearing chamber 32 is connected to the economizer 95 through the refrigerant pipe 4E and the branch pipe 99. In this embodiment, a gas supply passage for supplying the refrigerant gas compressed by the compressor 1 to the second bearing chamber 32 is composed of a part of the refrigerant pipe 4E and the branch pipe 99. The refrigerant gas separated by the economizer 95 is sent to the second bearing chamber 32 through the refrigerant pipe 4E and the branch pipe 99. The second bearing chamber 32 is filled with refrigerant gas (high-pressure gas).

12 is another modified example of the embodiment shown in FIG. 10. As shown in FIG. 12, one end of the refrigerant liquid return pipe 45 is connected to the bottom of the electric motor 13, and the other end of the refrigerant liquid return pipe 45 is connected to the economizer 95. The refrigerant liquid sprayed from the refrigerant nozzle 18 is collected in the electric motor 13 and returned to the economizer 95 through the refrigerant liquid return pipe 45. The internal space of the motor housing 13C (i.e., the space outside the first bearing chamber 31 and the second bearing chamber 32) is connected to the economizer 95 through the refrigerant liquid return pipe 45. The pressure in the economizer 95 is lower than the pressure in the first bearing chamber 31 and the second bearing chamber 32. Therefore, the pressure in the first bearing chamber 31 and the second bearing chamber 32 is higher than the internal space of the motor housing 13C (i.e., the space outside the first bearing chamber 31 and the second bearing chamber 32). In this embodiment, the communication flow path that communicates with the space outside the first bearing chamber 31 and the second bearing chamber 32 and that communicates with an area with a lower pressure than the pressure inside the first bearing chamber 31 and the second bearing chamber 32 is formed by the refrigerant liquid return pipe 45.

Even in the embodiment shown in Figures 10 to 12, the refrigerant liquid present outside the bearing chambers 31, 32 cannot penetrate into the bearing chambers 31, 32 and does not come into contact with the lubricant held in the rolling bearings 25, 26. As a result, the lubricant does not mix with the refrigerant liquid, and the refrigerant liquid and the lubricant can perform their respective functions. Furthermore, the configuration can be greatly simplified because the oil circulation line can be omitted. In addition, since there is no leakage of oil into the refrigerant side, a mechanism for separating the oil and the refrigerant is not required.

The above-described embodiments have been described for the purpose of enabling a person having ordinary knowledge in the technical field to which the present invention pertains to practice the present invention. Various modifications of the above-described embodiments would naturally be possible for a person skilled in the art, and the technical ideas of the present invention may also be applied to other embodiments. Therefore, the present invention is not limited to the described embodiments, but is to be interpreted in the broadest scope in accordance with the technical ideas defined by the scope of the claims.

1 Compressor 2 Evaporator 3 Condenser 4A, 4B, 4C, 4E Refrigerant piping 11, 11A, 11B Impeller 12 Rotor 13 Electric motor 13A Motor rotor 13B Motor stator 13C Motor housing 14 Impeller casing 16 Guide vane 17 Compression chamber 18 Refrigerant nozzle 21, 22 Expansion valve 25 First rolling bearing 26 Second rolling bearing 31 First bearing chamber 32 Second bearing chamber 35 First bearing housing 36 Second bearing housing 40 Refrigerant liquid transfer pipe 41 Refrigerant pump 45 Refrigerant liquid return pipe 51 First gas supply passage 52 Second gas supply passage 61 Angular bearing 61A Rolling element 61B Lubricant retaining ring 65 Lubricant 68A, 68B Seal 70 First pressure equalizing passage 81 Angular bearing 81A Rolling element 81B Lubricant retaining ring 85 Lubricant 88 Seal 90 Second pressure equalizing passage 95 Economizer 97 Intermediate suction port 99 Branch pipe

Claims (7)

A compressor for compressing a refrigerant gas in a refrigerator,
An impeller,
A rotor that can rotate integrally with the impeller;
A rolling bearing that rotatably supports the rotating body;
A lubricant held within the rolling bearing; and
a bearing housing that defines a bearing chamber in which the rolling bearing is disposed;
a gas supply passage communicating with the bearing chamber for supplying a refrigerant gas compressed by the compressor into the bearing chamber;
an electric motor that rotates the rotor and the impeller;
a communication passage located outside the bearing chamber, the communication passage communicating with an internal space of a motor housing of the electric motor and communicating with a region having a pressure lower than the pressure in the bearing chamber;
a refrigerant nozzle that sprays a refrigerant liquid into an internal space of the motor housing;
a pressure equalizing passage connecting two spaces facing both sides of the rolling bearing ;
a labyrinth seal for sealing a gap between the bearing housing and the rotor ,
The labyrinth seal is located between the bearing chamber and the internal space of the motor housing,
The two spaces are located within the bearing chamber,
the bearing housing is disposed within the interior space of the motor housing , the interior space of the motor housing having a pressure lower than a pressure in the bearing chamber;
the bearing chamber is filled with the compressed refrigerant gas supplied from the gas supply passage,
The two spaces are filled with the compressed refrigerant gas ,
a gap is provided between the labyrinth seal and the rotor, through which the refrigerant gas flows from the bearing chamber into the internal space of the motor housing ; The compressor according to claim 1, wherein the pressure equalizing passage is formed in the rotor. The compressor according to claim 1, wherein the pressure equalizing passage is formed in the bearing housing. The compressor according to claim 1, wherein the pressure equalizing passage is connected to the bearing housing. 5. The compressor according to claim 1, wherein the rolling bearing comprises a plurality of rolling elements and lubricant retaining rings arranged on both sides of the plurality of rolling elements. The compressor according to claim 1 , wherein the lubricant is a semi-fluid lubricant. A refrigerator in which a refrigerant circulates inside,
an evaporator for evaporating a refrigerant liquid to generate a refrigerant gas;
A compressor according to any one of claims 1 to 6 , which compresses the refrigerant gas;
a condenser that condenses the compressed refrigerant gas to produce the refrigerant liquid.

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