US20240426529A1 - Refrigerant compressor with return opening - Google Patents

Refrigerant compressor with return opening Download PDF

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Publication number
US20240426529A1
US20240426529A1 US18/826,200 US202418826200A US2024426529A1 US 20240426529 A1 US20240426529 A1 US 20240426529A1 US 202418826200 A US202418826200 A US 202418826200A US 2024426529 A1 US2024426529 A1 US 2024426529A1
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United States
Prior art keywords
refrigerant
inner space
refrigerant compressor
housing
evaporator
Prior art date
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Pending
Application number
US18/826,200
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English (en)
Inventor
Ryuuta Tanaka
Masahiro Nakajima
Hiroki Kobayashi
Yosuke Akamatsu
Seiichiro Yoshinaga
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IHI Corp
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IHI Corp
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Assigned to IHI CORPORATION reassignment IHI CORPORATION ASSIGNMENT OF ASSIGNORS INTEREST (SEE DOCUMENT FOR DETAILS). Assignors: YOSHINAGA, SEIICHIRO, AKAMATSU, YOSUKE, KOBAYASHI, HIROKI, TANAKA, RYUUTA, NAKAJIMA, MASAHIRO
Publication of US20240426529A1 publication Critical patent/US20240426529A1/en
Pending legal-status Critical Current

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    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F25—REFRIGERATION OR COOLING; COMBINED HEATING AND REFRIGERATION SYSTEMS; HEAT PUMP SYSTEMS; MANUFACTURE OR STORAGE OF ICE; LIQUEFACTION SOLIDIFICATION OF GASES
    • F25B—REFRIGERATION MACHINES, PLANTS OR SYSTEMS; COMBINED HEATING AND REFRIGERATION SYSTEMS; HEAT PUMP SYSTEMS
    • F25B39/00—Evaporators; Condensers
    • F25B39/02—Evaporators
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F04—POSITIVE - DISPLACEMENT MACHINES FOR LIQUIDS; PUMPS FOR LIQUIDS OR ELASTIC FLUIDS
    • F04B—POSITIVE-DISPLACEMENT MACHINES FOR LIQUIDS; PUMPS
    • F04B39/00—Component parts, details, or accessories, of pumps or pumping systems specially adapted for elastic fluids, not otherwise provided for in, or of interest apart from, groups F04B25/00 - F04B37/00
    • F04B39/12—Casings; Cylinders; Cylinder heads; Fluid connections
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F04—POSITIVE - DISPLACEMENT MACHINES FOR LIQUIDS; PUMPS FOR LIQUIDS OR ELASTIC FLUIDS
    • F04C—ROTARY-PISTON, OR OSCILLATING-PISTON, POSITIVE-DISPLACEMENT MACHINES FOR LIQUIDS; ROTARY-PISTON, OR OSCILLATING-PISTON, POSITIVE-DISPLACEMENT PUMPS
    • F04C23/00—Combinations of two or more pumps, each being of rotary-piston or oscillating-piston type, specially adapted for elastic fluids; Pumping installations specially adapted for elastic fluids; Multi-stage pumps specially adapted for elastic fluids
    • F04C23/008—Hermetic pumps
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F04—POSITIVE - DISPLACEMENT MACHINES FOR LIQUIDS; PUMPS FOR LIQUIDS OR ELASTIC FLUIDS
    • F04C—ROTARY-PISTON, OR OSCILLATING-PISTON, POSITIVE-DISPLACEMENT MACHINES FOR LIQUIDS; ROTARY-PISTON, OR OSCILLATING-PISTON, POSITIVE-DISPLACEMENT PUMPS
    • F04C29/00—Component parts, details or accessories of pumps or pumping installations, not provided for in groups F04C18/00 - F04C28/00
    • F04C29/12—Arrangements for admission or discharge of the working fluid, e.g. constructional features of the inlet or outlet
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F04—POSITIVE - DISPLACEMENT MACHINES FOR LIQUIDS; PUMPS FOR LIQUIDS OR ELASTIC FLUIDS
    • F04D—NON-POSITIVE-DISPLACEMENT PUMPS
    • F04D17/00—Radial-flow pumps, e.g. centrifugal pumps; Helico-centrifugal pumps
    • F04D17/08—Centrifugal pumps
    • F04D17/10—Centrifugal pumps for compressing or evacuating
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F04—POSITIVE - DISPLACEMENT MACHINES FOR LIQUIDS; PUMPS FOR LIQUIDS OR ELASTIC FLUIDS
    • F04D—NON-POSITIVE-DISPLACEMENT PUMPS
    • F04D17/00—Radial-flow pumps, e.g. centrifugal pumps; Helico-centrifugal pumps
    • F04D17/08—Centrifugal pumps
    • F04D17/10—Centrifugal pumps for compressing or evacuating
    • F04D17/12—Multi-stage pumps
    • F04D17/122—Multi-stage pumps the individual rotor discs being, one for each stage, on a common shaft and axially spaced, e.g. conventional centrifugal multi- stage compressors
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F04—POSITIVE - DISPLACEMENT MACHINES FOR LIQUIDS; PUMPS FOR LIQUIDS OR ELASTIC FLUIDS
    • F04D—NON-POSITIVE-DISPLACEMENT PUMPS
    • F04D29/00—Details, component parts, or accessories
    • F04D29/05—Shafts or bearings, or assemblies thereof, specially adapted for elastic fluid pumps
    • F04D29/056—Bearings
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F04—POSITIVE - DISPLACEMENT MACHINES FOR LIQUIDS; PUMPS FOR LIQUIDS OR ELASTIC FLUIDS
    • F04D—NON-POSITIVE-DISPLACEMENT PUMPS
    • F04D29/00—Details, component parts, or accessories
    • F04D29/05—Shafts or bearings, or assemblies thereof, specially adapted for elastic fluid pumps
    • F04D29/056—Bearings
    • F04D29/058—Bearings magnetic; electromagnetic
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F04—POSITIVE - DISPLACEMENT MACHINES FOR LIQUIDS; PUMPS FOR LIQUIDS OR ELASTIC FLUIDS
    • F04D—NON-POSITIVE-DISPLACEMENT PUMPS
    • F04D29/00—Details, component parts, or accessories
    • F04D29/40—Casings; Connections of working fluid
    • F04D29/42—Casings; Connections of working fluid for radial or helico-centrifugal pumps
    • F04D29/4206—Casings; Connections of working fluid for radial or helico-centrifugal pumps especially adapted for elastic fluid pumps
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F04—POSITIVE - DISPLACEMENT MACHINES FOR LIQUIDS; PUMPS FOR LIQUIDS OR ELASTIC FLUIDS
    • F04D—NON-POSITIVE-DISPLACEMENT PUMPS
    • F04D29/00—Details, component parts, or accessories
    • F04D29/70—Suction grids; Strainers; Dust separation; Cleaning
    • F04D29/701—Suction grids; Strainers; Dust separation; Cleaning especially adapted for elastic fluid pumps
    • F04D29/706—Humidity separation
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F25—REFRIGERATION OR COOLING; COMBINED HEATING AND REFRIGERATION SYSTEMS; HEAT PUMP SYSTEMS; MANUFACTURE OR STORAGE OF ICE; LIQUEFACTION SOLIDIFICATION OF GASES
    • F25B—REFRIGERATION MACHINES, PLANTS OR SYSTEMS; COMBINED HEATING AND REFRIGERATION SYSTEMS; HEAT PUMP SYSTEMS
    • F25B1/00—Compression machines, plants or systems with non-reversible cycle
    • F25B1/04—Compression machines, plants or systems with non-reversible cycle with compressor of rotary type
    • F25B1/053—Compression machines, plants or systems with non-reversible cycle with compressor of rotary type of turbine type
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F25—REFRIGERATION OR COOLING; COMBINED HEATING AND REFRIGERATION SYSTEMS; HEAT PUMP SYSTEMS; MANUFACTURE OR STORAGE OF ICE; LIQUEFACTION SOLIDIFICATION OF GASES
    • F25B—REFRIGERATION MACHINES, PLANTS OR SYSTEMS; COMBINED HEATING AND REFRIGERATION SYSTEMS; HEAT PUMP SYSTEMS
    • F25B31/00—Compressor arrangements
    • F25B31/006—Cooling of compressor or motor
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F25—REFRIGERATION OR COOLING; COMBINED HEATING AND REFRIGERATION SYSTEMS; HEAT PUMP SYSTEMS; MANUFACTURE OR STORAGE OF ICE; LIQUEFACTION SOLIDIFICATION OF GASES
    • F25B—REFRIGERATION MACHINES, PLANTS OR SYSTEMS; COMBINED HEATING AND REFRIGERATION SYSTEMS; HEAT PUMP SYSTEMS
    • F25B31/00—Compressor arrangements
    • F25B31/02—Compressor arrangements of motor-compressor units
    • F25B31/026—Compressor arrangements of motor-compressor units with compressor of rotary type
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F25—REFRIGERATION OR COOLING; COMBINED HEATING AND REFRIGERATION SYSTEMS; HEAT PUMP SYSTEMS; MANUFACTURE OR STORAGE OF ICE; LIQUEFACTION SOLIDIFICATION OF GASES
    • F25B—REFRIGERATION MACHINES, PLANTS OR SYSTEMS; COMBINED HEATING AND REFRIGERATION SYSTEMS; HEAT PUMP SYSTEMS
    • F25B41/00—Fluid-circulation arrangements
    • F25B41/40—Fluid line arrangements
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F25—REFRIGERATION OR COOLING; COMBINED HEATING AND REFRIGERATION SYSTEMS; HEAT PUMP SYSTEMS; MANUFACTURE OR STORAGE OF ICE; LIQUEFACTION SOLIDIFICATION OF GASES
    • F25B—REFRIGERATION MACHINES, PLANTS OR SYSTEMS; COMBINED HEATING AND REFRIGERATION SYSTEMS; HEAT PUMP SYSTEMS
    • F25B1/00—Compression machines, plants or systems with non-reversible cycle
    • F25B1/10—Compression machines, plants or systems with non-reversible cycle with multi-stage compression

Definitions

  • a heat pump has a refrigerant circulation system in which, for example, a refrigerant compressor, a condenser, an expansion valve, and an evaporator are sequentially connected in a ring.
  • the refrigerant circulation system the refrigerant vaporized by the evaporator is compressed in the refrigerant compressor, and then heat is dissipated in the condenser to liquefy the refrigerant.
  • the liquefied refrigerant is supplied to the evaporator through the expansion valve, and is vaporized in the evaporator.
  • the vaporized refrigerant is supplied to the refrigerant compressor again.
  • a shaft is rotatably supported by a pair of bearings provided inside the housing.
  • the refrigerant is compressed by an impeller rotating together with the shaft.
  • An example refrigerant compressor is configured to compress a refrigerant circulating in a refrigerant circulation system.
  • the refrigerant compressor includes: a rotating body including a shaft, and a protruding part protruding from the shaft in a radial direction and configured to rotate together with the shaft; a non-contact bearing unit rotatably supporting the rotating body; a housing including an inner space accommodating the protruding part; a suction inlet opening into the inner space and configured to supply the refrigerant to the inner space; a refrigerant passage communicating with the suction inlet and connected to an evaporator; a discharge port configured to discharge the refrigerant from the inner space; and a return passage communicating the inner space and the evaporator via a return opening provided in the inner space.
  • the return opening is positioned lower than (more downward than) or below the protruding part in a vertical direction.
  • FIG. 1 is a block diagram illustrating the configuration of an example freezer having an example refrigerant compressor.
  • FIG. 2 is a cross-sectional view illustrating the configuration of the example refrigerant compressor of FIG. 1 .
  • FIG. 3 is a cross-section of the example refrigerant compressor taken along line III-III of FIG. 2
  • FIG. 4 A is a schematic cross-sectional view of the example refrigerant compressor during operation.
  • FIG. 4 B is a schematic cross-sectional view of the example refrigerant compressor when not in operation.
  • FIG. 5 is a diagram illustrating the connection configuration between the example refrigerant compressor and an evaporator.
  • FIG. 6 A is a cross-sectional view illustrating a refrigerant compressor of a comparative example when not in operation.
  • FIG. 6 B is a cross-sectional view illustrating the refrigerant compressor of the comparative example during operation.
  • FIG. 7 is a cross-sectional view illustrating another example refrigerant compressor.
  • FIG. 8 is a cross-sectional view illustrating another example refrigerant compressor.
  • An example refrigerant compressor is configured to compress a refrigerant circulating in a refrigerant circulation system.
  • the refrigerant compressor includes: a rotating body having a shaft, and a protruding part protruding from the shaft in a radial direction and configured to rotate together with the shaft; a non-contact bearing unit rotatably supporting the rotating body; a housing having an inner space accommodating the protruding part; a suction inlet opening into the inner space and configured to supply the refrigerant to the inner space; a refrigerant passage communicating (fluidly coupled) with the suction inlet and connected to an evaporator; a discharge port configured to discharge the refrigerant from the inner space; and a return passage communicating (fluidly coupling) the inner space and the evaporator via a return opening provided in the inner space.
  • the return opening is positioned below or lower than (more downward than) the protruding part in a vertical direction.
  • the refrigerant vaporized in the evaporator passes through the refrigerant passage, is supplied to the inner space of the housing from the suction inlet, and is externally discharged from the discharge port.
  • the refrigerant compressor above includes a return passage communicating (fluidly coupling) the inner space and the evaporator via a return opening provided in the inner space of the housing.
  • the return opening is positioned below or lower than (more downward than) the protruding part of the rotating body in the vertical direction.
  • the refrigerant liquefied in the inner space of the housing thus flows out from the inner space of the housing through the return passage before reaching the protruding part.
  • the liquid that flows through the return passage is returned to the evaporator.
  • the evaporator vaporizes the liquid, which is supplied to the refrigerant compressor again as the refrigerant.
  • Such a configuration in which the liquid of the inner space is returned to the evaporator and vaporized enables the liquid to be efficiently removed from the inner space.
  • situations in which the level of the liquid in the inner space reaches the protruding part can be suppressed, and situations in which the rotation of the shaft becomes unbalanced can be suppressed. This makes it possible to suppress deviation in the state of contact between the rotating body and the bearing unit at startup.
  • the return passage may be formed of the refrigerant passage itself.
  • the refrigerant passage has both the function of supplying the vaporized refrigerant from the evaporator, and the function of returning the refrigerant liquefied in the inner space of the housing to the evaporator.
  • This configuration is capable of providing the function of returning the liquefied refrigerant to the evaporator, and the function of supplying the refrigerant from the evaporator through the same passage, thereby simplifying the configuration of the refrigerant compressor.
  • the bearing unit may include a pair of bearings disposed along the axial direction in which the shaft extends, and supporting the shaft in a radial direction.
  • the inner space may include a first inner region, a second inner region, and a third inner region communicating (fluidly coupled) with each other in the axial direction.
  • the second inner region may be positioned between the pair of bearings in the axial direction.
  • the first inner region may be positioned on one side of the pair of bearings in the axial direction.
  • the third inner region may be positioned on another side of the pair of bearings in the axial direction.
  • the suction inlet may communicate (be fluidly coupled) with the third inner region.
  • the discharge port may communicate (be fluidly coupled) with the first inner region. In this case, the refrigerant supplied from the suction inlet passes through the pair of bearings and is discharged from the discharge port, so that the pair of bearings can be cooled using this flow of the refrigerant.
  • the return passage may pass downward through the housing in the vertical direction from the inner space.
  • the liquid generated in the inner space of the housing is capable of easily flowing into the return passage according to gravity. Accordingly, the liquid can be effectively removed from the inner space.
  • the discharge port may pass downward through the housing in the vertical direction from the inner space at a position different from a position of the return passage.
  • the discharge port can also be used as a passage for removing the liquid from the inner space of the housing in addition to the return passage. Accordingly, the liquid can be more effectively removed from the inner space.
  • an inner wall surface of the housing may include an inclined part sloping downward toward the return opening between the discharge port and the return passage.
  • the liquid generated in the inner space of the housing is capable of easily flowing into the return passage than into the discharge port according to gravity. Accordingly, the liquid can be actively flown to the evaporator.
  • the liquid is actively flown to the evaporator that vaporizes the liquid, situations in which the flown liquid is pushed back to the refrigerant compressor does not tend to occur compared, for example, to a case in which the liquid is flown to another device such as a condenser in which the liquid tends to accumulate. Consequently, the liquid can be more effectively removed from the inner space by actively flowing the liquid to the evaporator.
  • the discharge port may pass upward through the housing in the vertical direction from the inner space.
  • the liquid generated in the inner space of the housing can be prevented from flowing into the discharge port, so that situations in which the flown liquid is pushed back to the refrigerant compressor does not tend to occur. Accordingly, the liquid can be more effectively removed from the inner space.
  • An example freezer 1 illustrated in FIG. 1 may be installed, for example, in a building or a factory to generate cooling water for ventilation.
  • the freezer 1 for example, includes a refrigerant compressor 2 , a condenser 3 , an expansion valve 4 , and an evaporator 5 .
  • the refrigerant compressor 2 , the condenser 3 , the expansion valve 4 , and the evaporator 5 form a refrigerant circulation system 6 in which a refrigerant (e.g., fluorocarbon) circulates.
  • a refrigerant e.g., fluorocarbon
  • thermal energy is received and transmitted by the refrigerant undergoing phase changes while circulating the refrigerant compressor 2 , the condenser 3 , the expansion valve 4 , and the evaporator 5 .
  • the refrigerant compressor 2 is connected to the condenser 3 via a passage F 1 .
  • the condenser 3 is connected to the expansion valve 4 via a passage F 2 .
  • the expansion valve 4 is connected to the evaporator 5 via a passage F 3 .
  • the evaporator 5 is connected to the refrigerant compressor 2 via a passage F 4 .
  • These passages F 1 , F 2 , F 3 , and F 4 form a circulation passage for the refrigerant to flow through and circulate the refrigerant compressor 2 , the condenser 3 , the expansion valve 4 , and the evaporator 5 .
  • the refrigerant compressor 2 generates a compressed refrigerant gas R 1 by compressing a refrigerant gas R 3 supplied from the evaporator 5 .
  • the refrigerant compressor 2 supplies the generated compressed refrigerant gas R 1 to the condenser 3 via the passage F 1 .
  • the condenser 3 generates a liquid refrigerant R 2 by cooling and liquefying the compressed refrigerant gas R 1 which has high temperature and high pressure by being compressed by the refrigerant compressor 2 .
  • the condenser 3 supplies the generated liquid refrigerant R 2 to the expansion valve 4 via the passage F 2 .
  • the expansion valve 4 reduces the pressure of the liquid refrigerant R 2 which has been liquefied by the condenser 3 .
  • the expansion valve 4 supplies the liquid refrigerant R 2 having reduced pressure to the evaporator 5 via the passage F 3 .
  • the evaporator 5 generates the refrigerant gas R 3 by evaporating the liquid refrigerant R 2 for which the pressure has been reduced by the expansion valve 4 .
  • the evaporator 5 cools an object to be cooled (e.g., cooling water) by the heat of vaporization generated when the refrigerant gas R 3 is generated due to the evaporation of the liquid refrigerant R 2 .
  • the evaporator 5 supplies the generated refrigerant gas R 3 to the refrigerant compressor 2 via the passage F 4 .
  • the refrigerant gas R 3 supplied to the refrigerant compressor 2 is supplied to the condenser 3 again as the compressed refrigerant gas R 1 after being compressed by the refrigerant compressor 2 .
  • the compressed refrigerant gas R 1 , the liquid refrigerant R 2 , and the refrigerant gas R 3 are examples of the potential states of the refrigerant in the refrigerant circulation system 6 .
  • the refrigerant compressor 2 is a so-called two-stage compressor. As illustrated in FIG. 2 , the refrigerant compressor 2 includes a shaft 10 , a compressor unit 30 , and a motor unit 50 .
  • upward D 1 A refers to upward in a vertical direction (gravity direction) of the refrigerant compressor 2 , when the refrigerant compressor 2 is installed in a location of use
  • downward D 1 B refers to downward in the vertical direction.
  • the refrigerant compressor 2 is disposed such that an axis of rotation L of the shaft 10 extends in a horizontal direction of the refrigerant compressor 2 , when the refrigerant compressor 2 is installed in the location of use. Consequently, an axial direction D 2 in which the axis of rotation L extends is perpendicular to the vertical direction.
  • upstream refers to upstream in a direction of flow of the refrigerant that flows through the refrigerant compressor 2
  • downstream refers to downstream in the direction of flow.
  • the compressor unit 30 has a first impeller 31 , a second impeller 32 , a first impeller housing 41 that accommodates the first impeller 31 , and a second impeller housing 42 that accommodates the second impeller 32 .
  • the first impeller 31 and the first impeller housing 41 form a low pressure-side compression stage.
  • the second impeller 32 and the second impeller housing 42 form a high pressure-side compression stage.
  • the first impeller 31 and the second impeller 32 are attached to one end portion 10 a of the shaft 10 .
  • Each of the first impeller 31 and the second impeller 32 is a protruding part (or a radial projection) that extends outward from the shaft 10 in a radial direction, and rotates about the axis of rotation L integrally with the shaft 10 .
  • the first impeller 31 and the second impeller 32 are, for example, disposed such that rear surfaces thereof face each other in the axial direction D 2 with a gap therebetween.
  • the second impeller 32 is, for example, disposed coaxial with the first impeller 31 , and has the same dimensions as the first impeller 31 .
  • the first impeller 31 is, for example, disposed between the second impeller 32 and the motor unit 50 in the axial direction D 2 .
  • the first impeller housing 41 and the second impeller housing 42 are connected to each other in the axial direction D 2 .
  • An interstage plate 43 is provided between the first impeller housing 41 and the second impeller housing 42 .
  • the interstage plate 43 is connected to the first impeller housing 41 and the second impeller housing 42 in the axial direction D 2 . Consequently, the second impeller housing 42 is connected to the first impeller housing 41 in the axial direction D 2 via the interstage plate 43 .
  • the motor unit 50 has an electric motor 51 and a motor housing 55 that accommodates the electric motor 51 .
  • the electric motor 51 is a drive source for driving the compressor unit 30 .
  • the electric motor 51 includes a stator 52 that is fixed to the motor housing 55 , and a rotor 53 that is fixed to the shaft 10 .
  • the rotor 53 faces the stator 52 with a gap therebetween.
  • the motor housing 55 is connected to the first impeller housing 41 in the axial direction D 2 .
  • the motor housing 55 , the first impeller housing 41 , the interstage plate 43 , and the second impeller housing 42 form a housing 11 of the refrigerant compressor 2 .
  • the shaft 10 to which the first impeller 31 and the second impeller 32 are attached is accommodated in an inner space S of the housing 11 .
  • the inner space S is a space defined by an inner wall surface 11 a of the housing 11 .
  • the shaft 10 extends across the motor housing 55 , the first impeller housing 41 , the interstage plate 43 , and the second impeller housing 42 in the axial direction D 2 in the inner space S.
  • the shaft 10 is supported so as to be rotatable about the axis of rotation L by a pair of bearings 60 , 60 and a pair of bearings 64 , 64 provided inside the motor housing 55 .
  • the pair of bearings 60 , 60 and the pair of bearings 64 , 64 form a “bearing unit”.
  • the pair of bearings 60 , 60 are provided so as to surround the shaft 10 , and are disposed in positions such that the electric motor 51 is disposed therebetween in the axial direction D 2 .
  • the inner space S of the housing 11 has a first inner region (or outlet region) S 1 , a second inner region (or intermediate region) S 2 , and a third inner region (or inlet region) S 3 .
  • the first inner region S 1 , the second inner region S 2 , and the third inner region S 3 are arranged in order along the axial direction D 2 and communicate (be fluidly coupled) with each other.
  • the second inner region S 2 is positioned between the pair of bearings 60 , 60 in the axial direction D 2 .
  • the second inner region S 2 is surrounded by a center portion of the motor housing 55 .
  • the electric motor 51 disposed between the pair of bearings 60 , 60 is disposed in the second inner region S 2 .
  • the first inner region (or outlet region) S 1 is positioned on one side of the pair of bearings 60 , 60 in the axial direction D 2 on which the first impeller 31 and the second impeller 32 are positioned.
  • the first inner region S 1 is surrounded mainly by the first impeller housing 41 , the second impeller housing 42 , and the interstage plate 43 .
  • the third inner region (or inlet region) S 3 is positioned on the other side of the pair of bearings 60 , 60 in the axial direction D 2 .
  • the third inner region S 3 is surrounded by an end portion of the motor housing 55 positioned on the opposite side from the first impeller housing 41 in the axial direction D 2 .
  • the housing 11 has a suction port 12 and a discharge port 13 .
  • the suction port 12 is a port for sucking the refrigerant gas R 3 from the evaporator 5 (see FIG. 1 ) into the inner space S.
  • the suction port 12 communicates (is fluidly coupled) with the inner space S, and is connected to the evaporator 5 via the passage F 4 .
  • the refrigerant gas R 3 sucked into the inner space S is compressed by the first impeller 31 and the second impeller 32 that rotate together with the shaft 10 .
  • the discharge port 13 is a port for discharging the compressed refrigerant gas R 1 compressed in the inner space S from the inner space S to the condenser 3 (see FIG. 1 ).
  • the discharge port 13 communicates (is fluidly coupled) with the inner space S, and is connected to the condenser 3 via the passage F 1 .
  • the suction port 12 is, for example, formed in the motor housing 55 , and communicates (is fluidly coupled) with the third inner region (or inlet region) S 3 .
  • the discharge port 13 is, for example, formed in the second impeller housing 42 , and communicates (is fluidly coupled) with the first inner region (or outlet region) S 1 . Further configurations of the suction port 12 and the discharge port 13 will be described further below.
  • the motor housing 55 for example, has a cylindrical side wall 56 centered about the axis of rotation L, and a disk-shaped end wall 57 that closes one end of the side wall 56 in the axial direction D 2 .
  • the side wall 56 surrounds the rotor 53 that is fixed to the shaft 10 .
  • the stator 52 is fixed to an inner surface 56 a of the side wall 56 .
  • a pair of support parts 61 , 61 that support the pair of bearings 60 , 60 are provided on the inner surface 56 a of the side wall 56 .
  • each of the pair of support parts 61 , 61 includes a ring-like member 62 and four rod-like members 63 .
  • the ring-like member 62 for example, has an annular shape when viewed in the axial direction D 2 .
  • the ring-like member 62 is disposed so as to surround the bearing 60 in a circumferential direction D 3 , and is fixed to the inner surface 56 a of the side wall 56 .
  • the four rod-like members 63 extend in a cross shape centered about the bearing 60 , and connects the bearing 60 to the ring-like member 62 .
  • the shaft 10 is disposed so as to pass through the inside of the bearing 60 .
  • the bearing 60 is a non-contact radial bearing.
  • Examples of the bearing 60 include an air bearing, a gas bearing, and a magnetic bearing.
  • the bearing 60 is disposed with a gap between the rotor 53 (see FIG. 2 ), and supports the rotor 53 and the shaft 10 in the radial direction without contact.
  • the second inner region S 2 communicates (is fluidly coupled) with the first inner region S 1 via the spaces between the rod-like members 63 in the circumferential direction D 3 (see FIG. 3 ) and the gap between the rotor 53 and one of the bearings 60 .
  • the second inner region S 2 communicates (is fluidly coupled) with the third inner region S 3 via the spaces between the rod-like members 63 in the circumferential direction D 3 and the gap between the rotor 53 and the other of the bearings 60 . Consequently, a fluid such as the refrigerant gas R 3 is capable of moving through the first inner region S 1 , the second inner region S 2 , and the third inner region S 3 in the inner space S of the housing 11 .
  • the pair of bearings 64 , 64 are, for example, provided so as to surround the shaft 10 in the third inner region S 3 , and disposed with gaps therebetween in the axial direction D 2 .
  • the pair of bearings 64 , 64 are non-contact thrust bearings. Examples of the pair of bearings 64 , 64 include an air bearing, a gas bearing, and a magnetic bearing.
  • a thrust collar 65 is provided between the pair of bearings 64 , 64 .
  • the thrust collar 65 is a flange-shaped protruding part protruding from the shaft 10 at an end portion 10 b of the shaft, and rotates about the axis of rotation L integrally with the shaft 10 .
  • An annular spacer 67 that surrounds the circumference of the thrust collar 65 is provided between the pair of bearings 64 , 64 .
  • the pair of bearings 64 , 64 and the spacer 67 are fastened so as to be integrated by a plurality of fastening bolts.
  • the pair of bearings 64 , 64 and the spacer 67 integrated with each other are fixed to the inner surface 56 a of the side wall 56 .
  • the pair of bearings 64 , 64 and the spacer 67 define an accommodation space in which the thrust collar 65 is accommodated. In this accommodation space, the thrust collar 65 rotates about the axis of rotation L together with the shaft 10 in a non-contact manner with the pair of bearings 64 , 64 and the spacer 67 .
  • the pair of bearings 64 , 64 , the spacer 67 , and the thrust collar 65 support the rotor 53 and the shaft 10 in an axial direction D 1 without contact.
  • the thrust collar 65 , the impeller 35 , and the shaft 10 rotate integrated with each other to form a rotating body RB.
  • the first impeller housing 41 is disposed so as to close the opening of the side wall 56 opposite from the end wall 57 in the axial direction D 2 .
  • the first impeller housing 41 includes an inlet 41 a , a diffuser passage 41 b , a scroll passage 41 c , and an outlet 41 d .
  • the inlet 41 a is an opening that is coaxial with the shaft 10 , and communicates with the inside of the motor housing 55 . Consequently, the refrigerant gas R 3 sucked into the motor housing 55 flows into the inlet 41 a .
  • the first impeller 31 is disposed inward of the inlet 41 a . Speed energy is applied to the refrigerant gas R 3 by the rotation of the first impeller 31 .
  • the scroll passage 41 c is formed so as to surround the first impeller 31 .
  • the diffuser passage 41 b is formed between the first impeller 31 and the scroll passage 41 c .
  • the diffuser passage 41 b compresses the refrigerant gas R 3 by converting the speed energy applied to the refrigerant gas R 3 into compression energy.
  • the scroll passage 41 c discharges the refrigerant gas R 3 compressed by the diffuser passage 41 b outside the first impeller housing 41 from the outlet 41 d .
  • the outlet 41 d is, for example, an opening that opens on a circumferential surface of the first impeller housing 41 .
  • the second impeller housing 42 includes an inlet 42 a , a diffuser passage 42 b , a scroll passage 42 c , and the discharge port 13 .
  • the inlet 42 a is an opening that is coaxial with the inlet 41 a of the first impeller housing 41 , and faces away from the inlet 41 a .
  • the inlet 42 a is connected to the outlet 41 d of the first impeller housing 41 via an external pipe 70 . Consequently, the refrigerant gas R 3 from the outlet 41 d flows into the inlet 42 a via the external pipe 70 .
  • the second impeller 32 is disposed inward of the inlet 42 a . Speed energy is applied to the refrigerant gas R 3 by the rotation of the second impeller 32 .
  • the scroll passage 42 c is formed so as to surround the second impeller 32 .
  • the diffuser passage 42 b is formed between the second impeller 32 and the scroll passage 42 c .
  • the diffuser passage 42 b further compresses the refrigerant gas R 3 by converting the speed energy applied to the refrigerant gas R 3 into compression energy. As a result, the compressed refrigerant gas R 1 is generated.
  • the scroll passage 42 c discharges the generated compressed refrigerant gas R 1 outside the second impeller housing 42 from the discharge port 13 .
  • the suction port 12 includes a suction inlet 12 a that opens on the inner wall surface 11 a .
  • the suction inlet 12 a is disposed lower (more downward) D 1 B than the protruding part of the rotating body RB in the vertical direction.
  • the suction inlet 12 a being disposed more downward D 1 B than the protruding part of the rotating body RB refers to at least a portion of the suction inlet 12 a being positioned lower or more downward D 1 B than a lower end of the protruding part when the refrigerant compressor 2 is installed in a location of installation.
  • the suction inlet 12 a may be positioned entirely below the protruding part in the vertical direction.
  • the “protruding part” herein may be one of the impeller 35 and the thrust collar 65 that is positioned more downward than the other.
  • the lower end of the “protruding part” refers to a lower end 35 a of the impeller 35 .
  • the suction inlet 12 a is positioned more downward (or lower) D 1 B than at least the lower end 35 a of the impeller 35 .
  • the suction inlet 12 a is positioned within a region RH between an outer surface 56 b positioned at a lower end of the housing 11 , and the lower end 35 a of the impeller 35 .
  • the lower end 35 a of the impeller 35 is a lowest (most downward) D 1 B portion of the impeller 35 . It can be said that the lower end 35 a of the impeller 35 is a lowermost tip end or lowest position of the impeller 35 , that is, a tip end or position of the impeller 35 that is closest to the lower end of the housing 11 .
  • the shaft 10 of the rotating body RB extending in the horizontal direction or axial direction D 2 , the impeller 35 corresponds to a radial projection having an outermost edge in the radial direction that forms the lowermost tip end or lowest position 35 a of the rotating body RB in the vertical direction, such that the suction inlet 12 a is positioned lower than the lowest position 35 a of the rotating body RB in the vertical direction.
  • the suction inlet 12 a being positioned more downward D 1 B than the impeller 35 refers to at least a part of the suction inlet 12 a being positioned more downward D 1 B than the lower end 35 a of the impeller 35 . That is, the suction inlet 12 a has at least a portion that is positioned in the region RH. Consequently, the suction inlet 12 a may have a portion that overlaps the impeller 35 in the horizontal direction.
  • the first impeller 31 and the second impeller 32 are disposed at the same height with each other, and have the same dimensions. Thus, the height of the lower end of the first impeller 31 and the height of the lower end of the second impeller 32 are the same.
  • the lower end 35 a of the impeller 35 may be the lower end of one of the first impeller 31 and the second impeller 32 that has a greater outer diameter.
  • the “protruding part” refers to the thrust collar 65 (i.e., in a case in which the thrust collar 65 is positioned more downward D 1 B than the impeller 35 )
  • the lower end of the “protruding part” refers to a lower end 65 a of the thrust collar 65 .
  • the suction inlet 12 a is positioned more downward (or lower) D 1 B than at least the lower end 65 a of the thrust collar 65 .
  • the lower end 65 a of the thrust collar 65 is a lowest (most downward) D 1 B portion of the thrust collar 65 .
  • the lower end 65 a of the thrust collar 65 is a lowermost tip end or lowest position of the thrust collar 65 , that is, a tip end or position of the thrust collar 65 that is closest to the lower end of the housing 11 .
  • the shaft 10 of the rotating body RB extending in the horizontal direction or axial direction D 2
  • the thrust collar 65 corresponds to a radial projection having an outermost edge in the radial direction that forms the lowermost tip end or lowest position 65 a of the rotating body RB in the vertical direction, such that the suction inlet 12 a is positioned lower than the lowest position 65 a of the rotating body RB in the vertical direction.
  • the suction inlet 12 a being positioned lower than (or more downward) D 1 B than the thrust collar 65 refers to at least a part of the suction inlet 12 a being positioned more downward D 1 B than the lower end 65 a of the thrust collar 65 .
  • Either one of the impeller 35 or the thrust collar 65 may be positioned lower or more downward D 1 B than the other depending on the design. Namely, in a case in which the rotating body includes both the impeller 35 and the thrust collar 65 , the suction inlet 12 a is located lower than both the impeller 35 and the thrust collar 65 . In some examples, the suction inlet 12 a is located radially outwardly of both the impeller 35 and the thrust collar 65 .
  • the suction port 12 is, for example, formed so as to pass downward D 1 B through the side wall 56 from the third inner region S 3 of the motor housing 55 .
  • the suction port 12 passes through a lower end portion 56 c of the side wall 56 surrounding the third inner region S 3 , in the vertical direction, from the inner surface 56 a to the outer surface 56 b .
  • the lower end portion 56 c is a downward D 1 B wall portion of the side wall 56 in the cross-section illustrated in FIG. 2 . Consequently, the suction inlet 12 a opens on the inner surface 56 a of the lower end portion 56 c , and communicates (is fluidly coupled) with the third inner region S 3 .
  • the discharge port 13 is, for example, formed so as to pass downward D 1 B through the second impeller housing 42 from the first inner region S 1 of the second impeller housing 42 . That is, the discharge port 13 passes through a lower end portion 42 d of the second impeller housing 42 surrounding the first inner region S 1 , in the vertical direction.
  • the lower end portion 42 d is a downward D 1 B wall portion of the second impeller housing 42 in the cross-section illustrated in FIG. 2 .
  • the discharge port 13 communicates (is fluidly coupled) with the first inner region S 1 .
  • a discharge outlet 13 a of the discharge port 13 opens on an outer surface 42 e of the lower end portion 42 d.
  • the inner surface 56 a of the side wall 56 has an inclined part P 1 between the suction port 12 and the discharge port 13 in the axial direction D 2 .
  • the inclined part P 1 may be a tapered surface that has a gradually decreasing diameter from the suction port 12 to the discharge port 13 .
  • the inclined part P 1 is inclined so as to slope downward toward the suction inlet 12 a . That is, the inclined part P 1 is inclined so as to be positioned gradually downward D 1 B in the axial direction D 2 , from the discharge port 13 to the suction inlet 12 a .
  • the inclined part P 1 is, for example, formed continuously from an end portion of the side wall 56 closer to the first impeller housing 41 to the suction inlet 12 a .
  • the suction inlet 12 a is formed in the housing at a lowest position of the inner space S.
  • FIG. 4 A and FIG. 4 B A schematic example of the refrigerant compressor 2 as illustrated in FIG. 4 A and FIG. 4 B will be used here for the sake of simplicity.
  • the first impeller 31 and the second impeller 32 are collectively shown as the impeller 35
  • the first impeller housing 41 , the interstage plate 43 , and the second impeller housing 42 are collectively shown as an impeller housing 45 in FIGS. 4 A and 4 B .
  • the pair of bearings 64 , 64 , the thrust collar 65 , and the spacer 67 are omitted, and the “impeller 35 ” is considered the “protruding part” in the example of FIGS. 4 A and 4 B .
  • the “impeller 35 ” in the explanation can be replaced with the “thrust collar 65 .”
  • the refrigerant gas R 3 supplied to the refrigerant compressor 2 from the upstream evaporator 5 is sucked (supplied) into the third inner region S 3 from the suction port 12 formed in downward D 1 B of the motor housing 55 .
  • the refrigerant gas R 3 sucked into the third inner region S 3 passes the second inner region S 2 and the first inner region S 1 in order, during which the refrigerant gas R 3 cools the pair of bearings 60 , 60 , the rotor 53 , and the stator 52 along the flow path.
  • the refrigerant gas R 3 that reaches the impeller 35 in the first inner region S 1 is compressed by the rotation of the impeller 35 .
  • the compressed refrigerant gas R 1 is thus generated.
  • the generated compressed refrigerant gas R 1 is discharged from the discharge port 13 formed in downward D 1 B of the impeller housing 45 to the downstream condenser 3 .
  • the liquid R 4 that flows out from the suction port 12 returns to the evaporator 5 .
  • the liquid R 4 that returns to the evaporator 5 is vaporized in the evaporator 5 , and supplied to the inner space S from the suction port 12 again as the refrigerant gas R 3 .
  • the suction port 12 is an inlet path for the refrigerant gas R 3 that flows into the inner space S of the housing 11 from the upstream evaporator 5 as well as an outlet path for the liquid R 4 that flows out from the inner space S to the upstream evaporator 5 .
  • the return port that returns the liquid R 4 generated in the inner space S to the evaporator 5 is formed by the suction port 12 (i.e., formed integrally with the suction port 12 ). That is, it can be said that the return opening is formed by the suction inlet 12 a that is located at the inlet region S 3 . Namely, a single opening forms the suction inlet 12 a and the return opening.
  • the suction inlet 12 a is connected to the evaporator 5 via the suction port 12 and the passage F 4 (see FIG. 1 ).
  • the suction port 12 and the passage F 4 form a refrigerant passage that supplies the refrigerant gas R 3 from the evaporator 5 to the inner space S. It can be said that the suction port 12 and the passage F 4 form a return passage that returns the liquid R 4 generated in the inner space S to the evaporator 5 . Accordingly, the return passage and the refrigerant passage form a continuous passage that is fluidly coupled with the suction inlet 12 a and the evaporator 5 .
  • the discharge port 13 is formed in downward D 1 B of the impeller housing 45 .
  • the liquid R 4 generated in the first inner region S 1 flows out from the discharge port 13 according to gravity.
  • the liquid R 4 discharged from the discharge port 13 flows to the downstream condenser 3 (see FIG. 1 ), and circulates the refrigerant circulation system 6 . Consequently, some examples are configured so as to externally remove the liquid R 4 generated in the inner space S from the inner space S through the suction port 12 and the discharge port 13 which are formed in downward D 1 B of the housing 11 .
  • FIG. 5 illustrates the connection configuration of the suction inlet 12 a of the refrigerant compressor 2 and the evaporator 5 .
  • the evaporator 5 is positioned more downward D 1 B than the suction inlet 12 a of the refrigerant compressor 2 .
  • the evaporator 5 is connected to the suction inlet 12 a via the passage F 4 and the suction port 12 . It can be said that the passage F 4 and the suction port 12 communicate (fluidly couple) the inner space S of the refrigerant compressor 2 (see FIG. 2 ) and the evaporator 5 via the suction inlet 12 a .
  • the passage F 4 has a linear passage FP 1 and a linear passage FP 2 .
  • the linear passage FP 1 extends downward D 1 B from the suction inlet 12 a .
  • the linear passage FP 2 extends in the axial direction D 2 from a lower end of the linear passage FP 1 , and is connected to a downstream flow port 5 a of the evaporator 5 .
  • the liquid R 4 from the suction inlet 12 a flows through the linear passage FP 2 in the axial direction D 1 , and then flows into the flow port 5 a of the evaporator 5 .
  • This configuration enables the liquid R 4 generated in the refrigerant compressor 2 to return easily to the evaporator 5 using gravity.
  • the connection configuration between the refrigerant compressor 2 and the evaporator 5 is not limited to the example illustrated in FIG. 5 .
  • the passage F 4 may be connected to the downstream flow port 5 a of the evaporator 5 , and another passage may be connected to an upstream flow port 5 b of the evaporator 5 .
  • the flow port 5 b may be connected to the suction inlet 12 a or to an opening other than the suction inlet 12 a via this other passage.
  • the liquid R 4 can be returned to the evaporator 5 by the other passage.
  • a curved part that is curved downward D 1 B may be formed on the entirety or a part of the linear passage FP 2 of the passage F 4 .
  • the refrigerant compressor 2 may have a mechanism to evaporate the accumulated liquid R 4 that may be generated in the curved part.
  • FIG. 6 A and FIG. 6 B schematically illustrate a refrigerant compressor 200 according to a comparative example.
  • a suction port 112 formed in a motor housing 155 of a housing 111 is positioned higher (more upward) D 1 A than an impeller 135 that is attached to a shaft 100 .
  • a discharge port 113 formed in an impeller housing 145 is positioned higher (more upward) D 1 A than the impeller 135 .
  • the refrigerant gas R 3 sucked into an inner space S 100 from the suction port 112 passes through a pair of bearings 160 , 160 , and the like, and reaches the impeller 135 .
  • the refrigerant gas R 3 is compressed by the rotation of the impeller 135 , and is discharged from the discharge port 113 of the impeller housing 145 as the compressed refrigerant gas R 1 .
  • the refrigerant gas R 3 filling the inner space S 100 may liquefy and accumulate in the inner space S 100 as the liquid R 4 , and as a result, the level of the liquid R 4 may reach the impeller 135 in the inner space S 100 as illustrated in FIG. 6 A .
  • the upper portion of the impeller 135 is not soaked in the liquid R 4 , and rotates without being exposed to the large resistive force that acts on the lower portion of the impeller 135 .
  • the rotation of the shaft 100 may become unbalanced or unstable, to thereby cause the shaft 100 to tilt, and apply excessive load on the bearings 160 , 160 that support the shaft 100 .
  • the bearings 160 , 160 may not be able to withstand the load, and the performance of the bearings 160 , 160 may be inhibited due to damage or the like.
  • defects such as reduction in the compression performance may occur.
  • the cost and size of the refrigerant compressor 200 may increase.
  • the suction inlet 12 a is positioned more downward D 1 B than the impeller 35 in the vertical direction.
  • the liquid R 4 generated in the inner space S flows out from the inner space S through the suction port 12 before reaching the impeller 35 .
  • the liquid R 4 that flows through the suction port 12 is returned to the upstream evaporator 5 via the passage F 4 .
  • the evaporator 5 vaporizes the liquid R 4 , and supplies it to the refrigerant compressor 2 again via the passage F 4 and the suction port 12 as the refrigerant gas R 3 .
  • Such a configuration in which the liquid R 4 of the inner space S is returned to the evaporator 5 and vaporized enables the liquid R 4 to be efficiently removed from the inner space S.
  • situations in which the level of the liquid R 4 in the inner space S reaching the impeller 35 can be suppressed, and situations in which the rotation of the shaft 10 becomes unbalanced or unstable can be suppressed.
  • a deviation of the rotating body RB that causes the rotating body RB to contact the bearing unit (pair of bearings 60 , 60 and pair of bearings 64 , 64 ) at startup (start of rotation) can be suppressed.
  • situations in which excessive load is applied on the bearing unit can be suppressed, and situations in which defects such as reduction in the compression performance occur due to reduction in the performance of the bearing unit can be suppressed.
  • the suction port 12 and the passage F 4 also function as a return passage that returns the liquid R 4 of the inner space S to the evaporator 5 . That is, the suction port 12 and the passage F 4 have both the function of sucking in the refrigerant gas R 3 from the evaporator 5 , and the function of returning the liquid R 4 of the inner space S to the evaporator 5 .
  • This configuration is capable of providing the function of returning the liquid R 4 to the evaporator 5 and the function of supplying the refrigerant gas R 3 from the evaporator 5 in the same passage.
  • the configuration of the refrigerant compressor 2 is further simplified, since a return passage that returns the liquid R 4 to the evaporator 5 is not separately provided.
  • the suction inlet 12 a communicates (is fluidly coupled) with the third inner region S 3
  • the discharge port 13 communicates (is fluidly coupled) with the first inner region S 1 .
  • the refrigerant gas R 3 sucked in from the suction inlet 12 a passes through the pair of bearings 60 , 60 and the electric motor 51 and is discharged from the discharge port 13 , so that the pair of bearings 60 , 60 and the electric motor 51 can be cooled using this flow of the refrigerant.
  • This configuration is capable of employing a configuration in which a mechanism for cooling the pair of bearings 60 , 60 and the electric motor 51 is not separately provided.
  • the configuration of the refrigerant compressor 2 can be simplified, since a simplified mechanism for cooling the bearings 60 , 60 and the electric motor 51 can be used.
  • the refrigerant gas R 3 also passes through the pair of bearings 64 , 64 , so that the refrigerant gas R 3 is also capable of cooling the pair of bearings 64 , 64 in addition to cooling the pair of bearings 60 , 60 and the electric motor 51 .
  • the suction port 12 passes downward D 1 B through the side wall 56 from the third inner region S 3 .
  • This configuration enables the liquid R 4 generated in the inner space S to easily flow into the suction inlet 12 a according to gravity. Accordingly, the liquid R 4 can be effectively removed from the inner space S.
  • the discharge port 13 passes downward D 1 B through the second impeller housing 42 from the first inner region S 1 .
  • This configuration also enables the liquid R 4 to be effectively removed from the inner space S, since the discharge port 13 can also be used as a passage for removing the liquid R 4 from the inner space S.
  • the inner surface 56 a of the side wall 56 includes the inclined part P 1 that slopes downward toward the suction inlet 12 a .
  • This configuration enables the liquid R 4 generated in the inner space S to more easily flow into the suction port 12 than into the discharge port 13 according to gravity. Accordingly, the liquid R 4 can be actively flown to the upstream evaporator 5 than to the downstream condenser 3 . In the case in which the liquid R 4 is actively flown to the evaporator 5 that vaporizes the liquid R 4 , situations in which the flown liquid R 4 is pushed back to the inner space S does not tend to occur compared to a case in which the liquid R 4 is actively flown to the condenser 3 in which the liquid R 4 tends to accumulate.
  • the liquid R 4 tends to accumulate in the condenser 3 since the condenser 3 is a device for generating the liquid refrigerant R 2 .
  • the compressed refrigerant gas R 1 flows into the condenser 3 from the discharge port 13 in this state, the liquid R 4 accumulated in the condenser 3 may be pushed back into the inner space S by the amount of the compressed refrigerant gas R 1 that has flown into the condenser 3 .
  • FIG. 7 schematically illustrates an example refrigerant compressor 2 A.
  • the suction port 12 also functions as a return port that returns the liquid R 4 in the inner space S to the evaporator 5 has been described above.
  • a return port 12 B is formed separately from a suction port 12 A is described. That is, in this example, the return port 12 B is not configured by the suction port 12 A, but is configured separately from the suction port 12 A.
  • the suction port 12 A is, for example, formed so as to communicate (be fluidly coupled) with the third inner region S 3 in a motor housing 55 A, and is positioned higher (or more upward) D 1 A than the impeller 35 .
  • the suction port 12 A is connected to the upstream evaporator 5 (see FIG. 1 ) via the passage F 4 .
  • the refrigerant gas R 3 sucked into the third inner region S 3 from the suction port 12 A passes through the second inner region S 2 and the first inner region S 1 in order, during which the refrigerant gas R 3 cools the pair of bearings 60 , 60 , and the electric motor 51 in the flow path.
  • the refrigerant gas R 3 that reaches the impeller 35 in the first inner region S 1 is compressed by the rotation of the impeller 35 .
  • the compressed refrigerant gas R 1 is thus generated.
  • the generated compressed refrigerant gas R 1 is discharged from the discharge port 13 formed in downward D 1 B of the impeller housing 45 to the downstream condenser 3 (see FIG. 1 ).
  • the passage F 4 and the suction port 12 A form a refrigerant passage that supplies the refrigerant gas R 3 from the evaporator 5 to the inner space S.
  • the return port 12 B is formed in the same position as the suction port 12 of the examples described above. That is, the return port 12 B is formed so as to pass downward D 1 B through the motor housing 55 A from the third inner region S 3 of a housing 11 A. Consequently, a return opening 12 b of the return port 12 B that opens on the inner surface 56 a of the motor housing 55 A is positioned more downward D 1 B than the lower end 35 a of the impeller 35 , similarly to the suction inlet 12 a according to the examples described above.
  • the return port 12 B is connected to the upstream evaporator 5 (see FIG. 1 ) via a passage different from the passage F 4 . This passage and the return port 12 B form a return passage for returning the liquid R 4 to the evaporator 5 .
  • the liquid R 4 generated in the inner space S such as when not in operation flows into the return port 12 B from the downward D 1 B return opening 12 b , and is returned to the evaporator 5 via the return port 12 B.
  • the liquid R 4 that is returned to the evaporator 5 is vaporized in the evaporator 5 , and supplied to the inner space S from the suction port 12 A again as the refrigerant gas R 3 .
  • the liquid R 4 generated in the inner space S can be removed from the inner space S through the return port 12 B, so that operation and effects similar to those of the examples described above can be produced.
  • FIG. 8 schematically illustrates another example refrigerant compressor 2 B.
  • the discharge port 13 is formed in downward D 1 B of the impeller housing 45 has been described above.
  • a discharge port 13 A is formed in upward D 1 A of an impeller housing 45 A is described.
  • the discharge port 13 A is, for example, formed so as to pass upward D 1 A through the impeller housing 45 A from the first inner region S 1 of a housing 11 B. That is, the discharge port 13 A passes through an upper end portion 42 f of the impeller housing 45 A that surrounds the first inner region S 1 , in the vertical direction.
  • the upper end portion 42 f may be an upward D 1 A wall portion of the impeller housing 45 A.
  • the liquid R 4 generated in the inner space S can be removed from the inner space S through the suction port 12 , so that operation and effects similar to those of the examples described above can be produced. Furthermore, this example is capable of preventing the liquid R 4 generated in the inner space S from flowing into the discharge port 13 A, which makes it more difficult for situations in which the flown liquid R 4 is pushed back to the refrigerant compressor 2 to occur. Accordingly, the liquid R 4 can be more effectively removed from the inner space S.
  • the present disclosure is not limited to the examples described above, and various other examples are possible. For example, features of different examples may be suitably combined together.
  • the refrigerant compressor 2 has two impellers (first impeller and second impeller).
  • the refrigerant compressor may have one impeller.
  • the orientation of the rear surface of the impeller is not particularly limited, and may be suitably changed.
  • the suction port 12 is formed so as to communicate with the third inner region S 3
  • the discharge port 13 is formed so as to communicate with the first inner region S 1
  • the suction port 12 and the discharge port 13 may both be formed so as to communicate with the first inner region S 1 . That is, the suction port 12 and the discharge port 13 may both be formed in the impeller housing 45 .
  • a port through which a cooling medium flows for cooling the pair of bearings 60 , 60 and the electric motor 51 may be separately formed.
  • the suction port 12 may be formed in the end wall 57 as long as it is positioned more downward D 1 B than the impeller 35 .
  • the present disclosure includes the following configurations.
  • a refrigerant compressor of a configuration [1] may be described as “a refrigerant compressor configured to compress a refrigerant circulating in a refrigerant circulation system, the refrigerant compressor including: a rotating body including a shaft, and a protruding part protruding from the shaft in a radial direction and configured to rotate together with the shaft; a non-contact bearing unit rotatably supporting the rotating body; a housing including an inner space accommodating the protruding part; a suction inlet opening into the inner space and configured to supply the refrigerant to the inner space; a refrigerant passage communicating with the suction inlet and connected to an evaporator; a discharge port configured to discharge the refrigerant from the inner space; and a return passage communicating the inner space and the evaporator via a return opening provided in the inner space, wherein the return opening is positioned more downward than the protruding part in a vertical direction.”
  • the refrigerant compressor of a configuration [2] may be described as “the refrigerant compressor according to the configuration [1], wherein the return passage is formed of the refrigerant passage itself.”
  • the refrigerant compressor of a configuration [3] may be described as “the refrigerant compressor according to the configuration [1] or [2], wherein the bearing unit includes a pair of bearings disposed along an axial direction in which the shaft extends, and supporting the shaft in a radial direction, wherein the inner space includes a first inner region, a second inner region, and a third inner region communicating with each other in the axial direction, wherein the second inner region is positioned between the pair of bearings in the axial direction, wherein the first inner region is positioned on one side of the pair of bearings in the axial direction, wherein the third inner region is positioned on another side of the pair of bearings in the axial direction, wherein the suction inlet communicates with the third inner region, and wherein the discharge port communicates with the first inner region.”
  • the refrigerant compressor of a configuration [ 4 ] may be described as “the refrigerant compressor according to any one of the configurations [ 1 ] to [ 3 ], wherein the return passage passes downward through the housing in the vertical direction from the inner space.”
  • the refrigerant compressor of a configuration [ 5 ] may be described as “the refrigerant compressor according to the configuration [ 4 ], wherein the discharge port passes downward through the housing in the vertical direction from the inner space at a position different from a position of the return passage.”
  • the refrigerant compressor of a configuration [6] may be described as “the refrigerant compressor according to the configuration [5], wherein an inner wall surface of the housing includes an inclined part sloping downward toward the return opening between the discharge port and the return passage.”
  • the refrigerant compressor of a configuration [7] may be described as “the refrigerant compressor according to any one of the configurations [1] to [4], wherein the discharge port passes upward through the housing in the vertical direction from the inner space.”

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