Centrifugal compressor and refrigeration cycle device

Abstract

A compressor (10) has a partition wall (50), a power transmission mechanism (60), and a bearing element (70). The partition wall (50) partitions the interior of a casing (11) into a first space (S1) in which at least a stator (21) of an electric motor (20) is disposed and a second space (S2) in which a compression mechanism (C) is disposed. The power transmission mechanism (60) includes a first transmission unit (61) disposed in the first space (S1) and a second transmission unit (62) disposed in the second space (S2), and transmits the power of the electric motor (20) on the first space (S1) side to the compression mechanism (C) via the first transmission unit (61) and the second transmission unit (62). The bearing element (70) includes aerodynamic bearings (71, 72, 73, 74).

Description

Centrifugal compressor and refrigeration cycle device

[0001] The present disclosure relates to a centrifugal compressor and a refrigeration cycle device.

[0002] Patent Document 1 discloses a compressor for use with ammonia gas as a corrosive refrigerant. In this compressor, the space where the motor stator is located is sealed with a can 13, thereby preventing ammonia from leaking into the space on the stator side (see FIG. 1, paragraph 0018).

[0003] Japanese Patent Application Laid-Open No. 2004-32841

[0004] When so-called oil bearings lubricated by lubricating oil are used as bearings for the rotating shaft, an oil supply pump is required. As described in Patent Document 1, when the compressor is used with a corrosive refrigerant, the oil supply pump must be corrosion-resistant. This makes the oil supply pump and its surrounding structure complex.

[0005] An object of the present disclosure is to simplify the structure of a compressor that can be used with a corrosive refrigerant.

[0006] The first aspect is directed to a centrifugal compressor (10). The centrifugal compressor (10) includes an electric motor (20) having a stator (21) and a rotor (22), a rotary shaft (25) rotated by the electric motor (20), a compression mechanism (C) having impellers (41, 42, 43) driven by the rotary shaft (25) and compressing a refrigerant, a casing (11) accommodating the electric motor (20), the rotary shaft (25), and the compression mechanism (C), and a first space (S) defining the inside of the casing (11) in which at least the stator (21) of the electric motor (20) is disposed. The compressor includes a partition wall (50) that separates the first space (S1) into a first space (S1) and a second space (S2) in which a compression mechanism (C) is disposed, a first transmission part (61) that is disposed in the first space (S1) and a second transmission part (62) that is disposed in the second space (S2), and the power transmission mechanism (60) transmits power of the first space (S1) side of the electric motor (20) to the impellers (41, 42, 43) via the first transmission part (61) and the second transmission part (62), and a bearing element (70) that rotatably supports the rotating shaft (25). The bearing element (70) includes dynamic pressure gas bearings (71, 72, 73, 74).

[0007] In the first aspect, the second space (S2) in which the compression mechanism (C) is disposed and the first space (S1) in which the stator (21) is disposed are separated by a partition wall (50). This prevents refrigerant from flowing around the stator (21) on the compression mechanism (C) side. This prevents corrosion of the coil of the stator (21) when a corrosive refrigerant is used. The power transmission mechanism (60) transmits power from the stator (21) side to the impeller (43), enabling the compression mechanism (C) to compress the refrigerant. The bearing element (70) includes dynamic pressure gas bearings (71, 72, 73, 74). The use of the dynamic pressure gas bearings (71, 72, 73, 74) eliminates the need for an oil supply pump. This simplifies the structure of the centrifugal compressor (10).

[0008] In the second aspect, the cooling device of the first aspect further includes a refrigerant flow path (80) located in the second space (S2) and through which the refrigerant flows. The dynamic pressure gas bearings (71, 72, 73, 74) are arranged in the refrigerant flow path (80).

[0009] In the second aspect, the dynamic pressure gas bearings (71, 72, 73, 74) can be cooled by the refrigerant flowing through the refrigerant flow path (80).

[0010] In the third aspect, in the second aspect, the second transfer part (62) is arranged in the refrigerant flow path (80).

[0011] In the third aspect, the second transmission part (62) of the power transmission mechanism (60) can be cooled by the refrigerant flowing through the refrigerant flow path (80).

[0012] In a fourth aspect, in the third aspect, the dynamic pressure gas bearings (71, 72, 73, 74) are arranged in the refrigerant flow path (80) upstream of the second transfer part (62) in the refrigerant flow direction.

[0013] In the fourth aspect, the refrigerant flows through the refrigerant flow path (80) in the order of the dynamic pressure gas bearings (71, 72, 73, 74) and the second transmission part (62). The dynamic pressure gas bearings (71, 72, 73, 74) are more likely to generate heat than the second transmission part (62), and therefore the dynamic pressure gas bearings (71, 72, 73, 74) can be efficiently cooled.

[0014] In a fifth aspect, in any one of the second to fourth aspects, the refrigerant flow path (80) is a flow path that returns a portion of the refrigerant on the discharge side of the compression mechanism (C) to the suction side of the compression mechanism (C).

[0015] In the fifth aspect, the refrigerant can be caused to flow through the refrigerant flow path (80) by utilizing the differential pressure of the refrigerant between the discharge side and the suction side of the compression mechanism (C).

[0016] In a sixth aspect, in any one of the first to fifth aspects, the dynamic pressure gas bearings (71, 72, 73, 74) include a thrust gas bearing (74). The thrust gas bearing (74) is integrated with the second transmission part (62).

[0017] In the sixth aspect, the thrust gas bearing (74) and the second transmission part (62) are integrated together, thereby simplifying the structures of the bearing element (70) and the power transmission mechanism (60).

[0018] In a seventh aspect, in any one of the first to sixth aspects, the power transmission mechanism (60) is configured to transmit the electromagnetic force of the stator (21) as the first transmission part (61) to the rotor (22) as the second transmission part (62) via the partition wall (50).

[0019] In the seventh aspect, the partition wall (50) is provided between the stator (21) and the rotor (22), thereby preventing the stator (21) from being exposed to the corrosive refrigerant.

[0020] In an eighth aspect, in any one of the first to sixth aspects, the rotating shaft (25) includes a first shaft (27) disposed in the first space (S1) and provided with a first transmission part (61), and a second shaft (28) disposed in the second space (S2) and provided with a second transmission part (62). The power transmission mechanism (60) is a magnetic transmission mechanism that transmits the rotational force of the first transmission part (61) to the second transmission part (62) by magnetic force.

[0021] In the eighth aspect, by providing a partition wall (50) between the first transmission part (61) and the second transmission part (62) of the magnetic transmission mechanism, it is possible to prevent the stator (21) from being exposed to the corrosive refrigerant.

[0022] In a ninth aspect, in the eighth aspect, the second transmission part (62) has a cylindrical part (64a) whose axis is the rotation shaft (25). The dynamic pressure gas bearings (71, 72, 73, 74) include a thrust gas bearing (74). The thrust gas bearing (74) is disposed inside the cylindrical part (64a).

[0023] In the ninth aspect, the thrust gas bearing (74) is disposed inside the cylindrical portion (64a) of the second transmission part (62), thereby simplifying the structures of the bearing element (70) and the power transmission mechanism (60).

[0024] In a tenth aspect, in any one of the first to ninth aspects, the compression mechanism (C) is configured to suck refrigerant from one axial end side of the rotating shaft (25). The dynamic pressure gas bearings (71, 72, 73, 74) include a first thrust gas bearing (73) and a second thrust gas bearing (74) that is farther from the one axial end side than the first thrust gas bearing (73). A diameter of a bearing surface of the first thrust gas bearing (73) is larger than a diameter of a bearing surface of the second thrust gas bearing (74).

[0025] A force is likely to act on the rotating shaft (25) on the suction side of the compression mechanism (C) due to a pressure difference of the refrigerant in the compression mechanism (C). In the tenth aspect, the diameter of the bearing surface of the first thrust gas bearing (73) close to the suction side of the compression mechanism (C) is made larger than the bearing surface of the second thrust gas bearing (74). This makes it possible to increase the bearing surface against a load directed from the discharge side to the suction side.

[0026] An eleventh aspect is a refrigeration cycle apparatus having the centrifugal compressor (10) of any one of the first to tenth aspects, and performing a refrigeration cycle using a refrigerant containing a corrosive refrigerant.

[0027] In the eleventh aspect, the stator (21) can be protected from corrosive refrigerant. The centrifugal compressor (10) does not require an oil supply pump, and therefore the centrifugal compressor (10) can be simplified.

[0028] Fig. 1 is a schematic refrigerant circuit diagram of a refrigeration cycle device of an embodiment. Fig. 2 is a schematic view showing a vertical cross section of a centrifugal compressor. Fig. 3 is a schematic view showing a vertical cross section of a centrifugal compressor of Modification 1. Fig. 4 is a schematic view showing a vertical cross section of a centrifugal compressor of Modification 2. Fig. 5 is a schematic view showing a vertical cross section of a centrifugal compressor according to another embodiment.

[0029] Hereinafter, embodiments of the present disclosure will be described in detail with reference to the drawings. The present disclosure is not limited to the embodiments shown below, and various modifications are possible within the scope of the technical concept of the present disclosure. Since the drawings are intended to conceptually explain the present disclosure, dimensions, ratios, or numbers may be exaggerated or simplified as necessary to facilitate understanding.

[0030] The centrifugal compressor (10) of this embodiment is provided in a refrigeration cycle apparatus (1). The refrigeration cycle apparatus (1) performs a refrigeration cycle by circulating a refrigerant. The refrigeration cycle apparatus (1) of this embodiment is an air conditioner that adjusts the temperature of air.

[0031] (1) Refrigeration Cycle Apparatus As shown in FIG. 1, a refrigeration cycle apparatus (1) has a refrigerant circuit (2) filled with a refrigerant. The refrigerant includes a corrosive first refrigerant. The first refrigerant is ammonia. When the first refrigerant comes into contact with a component, the component corrodes, impairing its function.

[0032] The refrigerant circuit (2) includes a centrifugal compressor (hereinafter also referred to as a compressor (10)), a radiator (3), an expansion valve (4) as an expansion mechanism, and an evaporator (5). The compressor (10) compresses the refrigerant. The compressor (10) of the present disclosure is applicable to corrosive refrigerants. The radiator (3) is a heat exchanger that radiates heat from the refrigerant to air. The radiator (3) may be a water heat exchanger that exchanges heat between the refrigerant and water. The expansion valve (4) reduces the pressure of the refrigerant. The evaporator (5) is a heat exchanger that absorbs heat from the refrigerant. The evaporator (5) may be a water heat exchanger that exchanges heat between the refrigerant and water. In the refrigerant circuit (2), a refrigeration cycle is performed in which the refrigerant compressed by the compressor (10) releases heat or condenses in the radiator (3), is depressurized by the expansion valve (4), and evaporates in the evaporator (5).

[0033] (2) Compressor The compressor (10) of this embodiment is a two-stage compression type. The configuration of the compressor (10) will be described with reference to Fig. 2. In the following description, "axial direction" refers to the direction along the axis of the rotating shaft (25), "radial direction" refers to the direction perpendicular to the axial direction, "circumferential direction" refers to the direction of rotation of the rotating shaft (25), "one end in the axial direction" refers to the left end in Fig. 2, and "the other end in the axial direction" refers to the right end in Fig. 2.

[0034] (2-1) Basic Configuration The compressor (10) includes a casing (11), an electric motor (20), a rotating shaft (25) driven to rotate by the electric motor (20), and a low-stage compression mechanism (C1) and a high-stage compression mechanism (C2) as a compression mechanism (C) connected to the rotating shaft (25). The compressor (10) includes a partition wall (50), a power transmission mechanism (60), and bearing elements (70).

[0035] (2-2) Casing The casing (11) accommodates the electric motor (20), the rotary shaft (25), and the compression mechanism (C). The casing (11) is a cylindrical sealed container with both ends closed. The casing (11) is disposed with its axis substantially horizontal. The casing (11) has a body (12), a first closing portion (13), and a second closing portion (14). The body (12) is formed in a cylindrical shape with both axial ends open. The first closing portion (13) closes the open portion at one axial end of the body (12). The first closing portion (13) constitutes a housing (H) that constitutes the compression mechanism (C). The second closing portion (14) constitutes a closing plate that closes the open portion at the other axial end of the body (12).

[0036] (2-3) Electric Motor The electric motor (20) is disposed inside the body (12). The electric motor (20) constitutes a drive source for the compression mechanism (C). The electric motor (20) has a stator (21) and a rotor (22). The stator (21) is fixed to the inner peripheral surface of the body (12) of the casing (11). The stator (21) has a stator core (21a) formed of a plurality of electromagnetic steel plates stacked in the axial direction, and a coil (21b) wound around the stator core (21a). The stator (21) is formed in a substantially cylindrical shape. The rotor (22) and the rotating shaft (25) are disposed inside the stator (21). The rotor (22) is fixed to the outer peripheral surface of the rotating shaft (25). The rotor (22) has a rotor core formed of a plurality of electromagnetic steel plates stacked in the axial direction.

[0037] The electric motor (20) is controlled by an inverter device (not shown). In other words, the electric motor (20) is an inverter type whose rotation speed (operating frequency) is variable.

[0038] (2-4) Rotating Shaft The rotating shaft (25) extends horizontally along the axial center of the casing (11). One end of the rotating shaft (25) is located inside the housing (H). The other end of the rotating shaft (25) is located near the second closing portion (14). An internal flow path (26) is formed inside the rotating shaft (25). In this embodiment, the internal flow path (26) extends from the other end of the rotating shaft (25) to the compression mechanism (C).

[0039] The rotary shaft (25) has a shaft body (25a), and a flange-shaped first thrust disk (25b) and a second thrust disk (25c) extending radially outward from the shaft body (25a).

[0040] (2-5) Housing The housing (H) is formed with a suction port (31), a low-stage impeller chamber (32), a relay passage (33), a high-stage impeller chamber (34), a diffuser passage (35), and an involute passage (36).

[0041] The suction port (31) is formed at one axial end of the housing (H). The suction port (31) is connected to a low-pressure line (suction line) of the refrigerant circuit (2) via a suction pipe (not shown) of the refrigerant circuit (2). The suction port (31) draws in low-pressure refrigerant.

[0042] The low-stage impeller chamber (32) is disposed near one axial end of the housing (H), and the high-stage impeller chamber (34) is disposed near the other axial end of the housing (H). The low-stage impeller chamber (32) and the high-stage impeller chamber (34) form a substantially trapezoidal conical space centered on the axis of the rotating shaft (25). One axial end (suction side) of the low-stage impeller chamber (32) communicates with the suction port (31). The outer circumferential side (discharge side) of the low-stage impeller chamber (32) is connected to the inlet end of the relay flow path (33).

[0043] The relay flow path (33) connects the low-stage impeller chamber (32) and the high-stage impeller chamber (34). An outlet end of the relay flow path (33) communicates with one axial end (suction side) of the high-stage impeller chamber (34). An outer circumferential side (discharge side) of the high-stage impeller chamber (34) communicates with the diffuser flow path (35).

[0044] The diffuser flow path (35) extends radially outward from the high-stage impeller chamber (34). The radially outer end of the diffuser flow path (35) is connected to the involute flow path (36). The involute flow path (36) surrounds the high-stage impeller chamber (34). The involute flow path (36) has a spiral shape when viewed in a cross section perpendicular to the axial direction. The outlet end of the involute flow path (36) is connected to a high-pressure line (discharge line) of the refrigerant circuit (2) via a discharge pipe (not shown).

[0045] (2-6) Compression Mechanism A low-stage compression mechanism (C1) and a high-stage compression mechanism (C2) are provided inside the housing (H) as the compression mechanism (C). The low-stage compression mechanism (C1) has a low-stage impeller chamber (32) and a low-stage impeller (41) disposed inside the low-stage impeller chamber (32). The high-stage compression mechanism (C2) has a high-stage impeller chamber (34) and a high-stage impeller (42) disposed inside the high-stage impeller chamber (34). The low-stage impeller (41) and the high-stage impeller (42) are constituted by impellers connected to the rotary shaft (25). The low-stage impeller (41) and the high-stage impeller (42) are rotationally driven by the rotary shaft (25).

[0046] (3-1) Partition Wall The partition wall (50) separates the inside of the casing (11) into a first space (S1) and a second space (S2). The partition wall (50) forms the first space (S1) that is tightly separated from the second space (S2). The partition wall (50) has a function of preventing a corrosive refrigerant from leaking into the first space (S1) in which the stator (21) is present. In this embodiment, the partition wall (50) separates the stator (21) from the rotor (22). Specifically, the partition wall (50) forms a cylindrical first space (S1) around the axis of the rotating shaft (25). The stator core (21a) and the coil (21b) are housed in the first space (S1).

[0047] The partition wall (50) of this example has a cylindrical inner wall (51) formed around the rotor (22) and an annular first end wall (52) continuous with one axial end of the inner wall (51). In this embodiment, the radially outer open portion of the inner wall (51) is closed by the inner wall of the trunk portion (12). The other axial open portion of the inner wall (51) is closed by the second closing portion (14) of the casing (11).

[0048] The partition wall (50) may further include an outer wall that radially surrounds the stator (21). The partition wall (50) may include an annular second end wall that is continuous with the inner wall (51) and closes an open portion at the other axial end of the inner wall (51). In other words, the partition wall (50) may be a cylindrical hollow member that houses the stator (21).

[0049] The partition wall (50) is made of a corrosion-resistant resin material or a thin metal material. The partition wall (50) is made of a magnetically permeable material. This allows the electromagnetic force of the stator (21) to be transmitted through the partition wall (50) to the rotor (22).

[0050] (3-2) Power Transmission Mechanism The compressor (10) has a power transmission mechanism (60). The power transmission mechanism (60) includes a first transmission part (61) arranged in the first space (S1) and a second transmission part (62) arranged in the second space (S2), and transmits the power of the electric motor (20) on the first space (S1) side to the compression mechanism (C) via the first transmission part (61) and the second transmission part (62).

[0051] In this embodiment, the stator (21) constitutes the first transmission part (61), and the rotor (22) constitutes the second transmission part (62). The power transmission mechanism (60) is configured to transmit the electromagnetic force of the stator (21) to the rotor (22) through the partition wall (50). This makes it possible to drive the rotating shaft (25) and further the compression mechanism (C) while preventing the refrigerant in the second space (S2) from leaking into the first space (S1).

[0052] (3-3) Bearing Elements The compressor (10) has bearing elements (70) for rotatably supporting the rotating shaft (25). The bearing elements (70) of this embodiment have a first radial gas bearing (71), a second radial gas bearing (72), a first thrust gas bearing (73), and a second thrust gas bearing (74). All of these bearings are dynamic pressure gas bearings (71, 72, 73, 74). The dynamic pressure gas bearings (71, 72, 73, 74) support the rotating shaft (25) by utilizing the dynamic pressure of a fluid between the rotating shaft (25) and a bearing portion. The dynamic pressure gas bearings (71, 72, 73, 74) are configured as, for example, herringbone bearings or bump foil bearings.

[0053] The first radial gas bearing (71) is arranged around a portion of the rotating shaft (25) between the low-stage impeller (41) and the high-stage impeller (42). The first radial gas bearing (71) is held inside an intermediate member (45) located inside the housing (H). The first radial gas bearing (71) is formed in a cylindrical shape with which the outer peripheral surface of the rotating shaft (25) comes into sliding contact.

[0054] The second radial gas bearing (72) is arranged around a portion of the rotating shaft (25) between the high-stage impeller (42) and the electric motor (20). The second radial gas bearing (72) is held inside the annular first bearing holder (46). The second radial gas bearing (72) is formed in a cylindrical shape with which the outer peripheral surface of the rotating shaft (25) comes into sliding contact.

[0055] The first thrust gas bearing (73) is arranged around a portion of the rotating shaft (25) between the second radial gas bearing (72) and the electric motor (20). The first thrust gas bearing (73) is held inside the second bearing holder (47). The first thrust gas bearing (73) is in sliding contact with one axial end of the first thrust disk (25b). The first thrust gas bearing (73) constitutes a disk-shaped first thrust bearing surface.

[0056] The second thrust gas bearing (74) is arranged around a portion of the rotating shaft (25) between the electric motor (20) and the second closing portion (14). The second thrust gas bearing (74) is held inside the third bearing holder (48). The second thrust gas bearing (74) is in sliding contact with the other axial end of the second thrust disk (25c). The second thrust gas bearing (74) constitutes two disk-shaped thrust bearing surfaces. The third bearing holder (48) is fixed to the inner surface of the second closing portion (14).

[0057] The second thrust gas bearing (74) is farther from one end in the axial direction than the first thrust gas bearing (73). In other words, the first thrust gas bearing (73) is located closer to the suction port (31) of the compression mechanism (C) than the second thrust gas bearing (74). As shown in Fig. 2, a diameter D1 of a first thrust bearing surface of the first thrust gas bearing (73) is larger than a diameter D2 of a second thrust bearing surface of the second thrust gas bearing (74).

[0058] A force is likely to act on the rotating shaft (25) of the compressor (10) from the discharge side (the other axial end) toward the suction side (one axial end) due to a pressure difference in the compression mechanism (C). In contrast, in this embodiment, the diameter D1 of the bearing surface of the first thrust gas bearing (73) near the suction side of the compression mechanism (C) is made larger than the diameter D2 of the bearing surface of the second thrust gas bearing (74). This allows the bearing element (70) to have an increased area of ​​the thrust bearing surface for receiving a load acting from the other axial end (discharge side) toward one axial end (suction side).

[0059] In this embodiment, the first thrust gas bearing (73) and the rotor (22) serving as the second transmission part are integrated together. Specifically, the first thrust gas bearing (73) is integrated with the rotor (22) via the first thrust disk (25b).

[0060] (3-4) Refrigerant Flow Channel The compressor (10) has a refrigerant flow channel (80) for cooling the bearing element (70). The refrigerant flow channel (80) is formed only in the second space (S2) of the first space (S1) and the second space (S2). Here, the refrigerant flow channel (80) does not include a flow channel inside the compression mechanism (C). The refrigerant flow channel (80) includes a first cooling flow channel (81), a second cooling flow channel (82), a third cooling flow channel (83), and a fourth cooling flow channel (84). These cooling flow channels (81, 82, 83, 84) are configured as part of the sliding surfaces of the corresponding dynamic pressure gas bearings (71, 72, 73, 74). These cooling flow channels (81, 82, 83, 84) may be formed radially outward of the corresponding bearings (71, 72, 73, 74). In this case, the cooling channel (81, 82, 83, 84) is a circular channel when viewed in axial cross section, and one or more cooling channels (81, 82, 83, 84) are provided around the bearing (71, 72, 73, 74). These cooling channels (81, 82, 83, 84) are annular channels when viewed in axial cross section, and only one cooling channel (81, 82, 83, 84) may be provided around the bearing (71, 72, 73, 74).

[0061] The refrigerant flow path (80) includes a one-end space (85), a other-end space (87), and the internal flow path (26). The one-end space (85) is formed between the first bearing holder (46) and the second bearing holder (47). The other-end space (87) is formed between the rotor (22) and the second closing portion (14).

[0062] The first cooling flow path (81) is formed along the sliding surface of the first radial gas bearing (71). An inlet end of the first cooling flow path (81) is connected to the relay flow path (33), and an outlet end of the first cooling flow path (81) is connected to the suction side of the low-stage compression mechanism (C1). In other words, the first cooling flow path (81) connects the discharge side and suction side of the low-stage compression mechanism (C1).

[0063] The second cooling flow path (82) is formed along the sliding surface of the second radial gas bearing (72). An inlet end of the second cooling flow path (82) is connected to the discharge side of the high-stage compression mechanism (C2), more precisely, to the diffuser flow path (35). An outlet end of the second cooling flow path (82) is connected to the one-end space (85).

[0064] The third cooling flow path (83) is formed along the sliding surface of the first thrust gas bearing (73). An inflow end of the third cooling flow path (83) communicates with the one end space (85). An outflow end of the third cooling flow path (83) communicates with the other end space (87).

[0065] The fourth cooling flow path (84) is formed along the sliding surface of the second thrust gas bearing (74). The inflow end of the fourth cooling flow path (84) communicates with the intermediate space (86). The outflow end of the fourth cooling flow path (84) is connected to the other end space (87). The other end space (87) is connected to the suction side of the high-stage compression mechanism (C2) via the internal flow path (26) of the rotary shaft (25). The fourth cooling flow path (84) may be formed along the second bearing surface of the second thrust gas bearing (74).

[0066] (4) Operation of Compressor When the refrigeration cycle device (1) is operating, the compressor (10) is in an operating state. When the compressor (10) is operating, the electric motor (20) is energized. As a result, the electromagnetic force of the stator (21) is transmitted to the rotor (22) through the partition wall (50), and the rotating shaft (25) is rotated. In the low-stage compression mechanism (C1), the low-stage impeller (41) rotates, and in the high-stage compression mechanism (C2), the high-stage impeller (42) rotates.

[0067] The low-pressure refrigerant drawn into the low-stage impeller chamber (32) through the suction port (31) is compressed by centrifugal force to become an intermediate-pressure refrigerant. The intermediate-pressure refrigerant flows through the relay flow path (33) and is then drawn into the high-stage impeller chamber (34). The high-pressure refrigerant is compressed by the centrifugal force of the high-stage impeller (42) to become a high-pressure refrigerant. The high-pressure refrigerant flows through the diffuser flow path (35) and the involute flow path (36) and then flows out into the discharge pipe of the refrigerant circuit (2).

[0068] When the rotating shaft (25) rotates, dynamic pressure of a fluid is generated between the rotating shaft (25) and the dynamic pressure gas bearings (71, 72, 73, 74). This dynamic pressure can be used to support the rotating shaft (25) by the dynamic pressure gas bearings (71, 72, 73, 74). By using the dynamic pressure gas bearings (71, 72, 73, 74) as the bearing elements (70), an oil supply pump for supplying lubricating oil to the bearing elements (70) is not required.

[0069] (5) Cooling Operation During operation of the compressor (10), the dynamic pressure gas bearings (71, 72, 73, 74) are cooled by the refrigerant. In FIG. 2, the flow of the refrigerant is indicated by dashed arrows. The intermediate-pressure refrigerant compressed by the low-stage compression mechanism (C1) passes through the relay flow path (33) and then flows through the first cooling flow path (81). The first cooling flow path (81) is formed along the sliding surface of the first radial gas bearing (71), and therefore the first radial gas bearing (71) can be cooled by the refrigerant. In this way, in the refrigerant flow path (80), a portion of the refrigerant on the discharge side of the low-stage compression mechanism (C1) is used to cool the first radial gas bearing (71) and then returns to the suction side of the low-stage compression mechanism (C1).

[0070] The high-pressure refrigerant compressed by the high-stage compression mechanism (C2) flows through the second cooling flow path (82). The second cooling flow path (82) is formed along the sliding surface of the second radial gas bearing (72), and therefore the second radial gas bearing (72) can be cooled by the refrigerant. The refrigerant that has flowed out of the second cooling flow path (82) passes through the one-end space (85) and flows through the third cooling flow path (83). The third cooling flow path (83) is formed along the sliding surface of the first thrust gas bearing (73), and therefore the first thrust gas bearing (73) can be cooled by the refrigerant.

[0071] The refrigerant that has flown out of the third cooling channel (83) passes through the rotor (22) or between the rotor (22) and the partition wall (50) in the axial direction, thereby cooling the rotor (22).

[0072] The refrigerant that has passed through the rotor (22) flows into the fourth cooling flow path (84) from the other end space (87). The fourth cooling flow path (84) is formed along the sliding surface of the second thrust gas bearing (74), so that the second thrust gas bearing (74) can be cooled by the refrigerant. The refrigerant that has flowed out of the fourth cooling flow path (84) flows through the internal flow path (26). The refrigerant in the internal flow path (26) returns to the suction side of the high-stage compression mechanism (C2). In this way, in the refrigerant flow path (80), a portion of the refrigerant on the discharge side of the high-stage compression mechanism (C2) is used to cool the second radial gas bearing (72), the first thrust gas bearing (73), the rotor (22), and the second thrust gas bearing (74), and then returns to the suction side of the high-stage compression mechanism (C2). In this way, the refrigerant flow path (80) includes a transient flow path from the discharge side to the suction side of the high-stage compression mechanism (C2).

[0073] (6) Features (6-1) To supply lubricating oil to the bearings of a compressor, an oil supply pump is required. In addition, an oil supply passage for supplying oil from the oil supply pump to the bearings, an oil reservoir for storing the oil after lubrication, and an oil return passage for returning the oil from the oil reservoir to the oil supply pump are required. As a result, the structure related to oil supply becomes complex. In particular, when the compressor uses a corrosive refrigerant, measures to prevent corrosion of the oil supply pump are also required, further complicating the device structure. The compressor (10) of this embodiment solves this problem.

[0074] (6-2) The compressor (10) of this embodiment includes a partition wall (50) and a power transmission mechanism (60). The partition wall (50) divides the interior of the casing (11) into a first space (S1) in which the stator (21) is disposed and a second space (S2) in which the compression mechanism (C) is disposed. The power transmission mechanism (60) includes a first transmission part (61) disposed in the first space (S1) and a second transmission part (62) disposed in the second space (S2), and transmits power from the first space (S1) side of the electric motor (20) to the compression mechanism (C) via the first transmission part (61) and the second transmission part (62). With this configuration, when a corrosive refrigerant is used, the compression mechanism (C) can be driven while preventing the refrigerant from coming into contact with the stator (21).

[0075] The bearing element (70) that rotatably supports the rotating shaft (25) includes dynamic pressure gas bearings (71, 72, 73, 74). With this configuration, the rotating shaft (25) can be supported without using an oil supply pump. As a result, corrosion protection measures for the oil supply pump are not required, and the compressor (10) can be simplified and made smaller. The simplification of the compressor (10) also increases the degree of freedom in the structure of the partition wall (50), the power transmission mechanism (60), and other components that can be used to protect against corrosive refrigerant.

[0076] (6-3) The compressor (10) of this embodiment includes a partition wall (50) and a power transmission mechanism (60). The partition wall (50) divides the interior of the casing (11) into a first space (S1) in which the stator (21) is disposed and a second space (S2) in which the compression mechanism (C) is disposed. The power transmission mechanism (60) includes a first transmission part (61) disposed in the first space (S1) and a second transmission part (62) disposed in the second space (S2), and transmits power from the first space (S1) side of the electric motor (20) to the compression mechanism (C) via the first transmission part (61) and the second transmission part (62). With this configuration, when a corrosive refrigerant is used, the compression mechanism (C) can be driven while preventing the refrigerant from coming into contact with the stator (21).

[0077] (6-4) The compressor (10) is located in the second space (S2) and further includes a refrigerant flow path (80) through which a refrigerant flows. The dynamic pressure gas bearings (71, 72, 73, 74) are arranged in the refrigerant flow path (80). Therefore, the dynamic pressure gas bearings (71, 72, 73, 74) can be cooled by the refrigerant flowing through the refrigerant flow path (80).

[0078] In addition, the rotor (22) serving as the second transmitting part (62) is disposed in the refrigerant flow path (80), so that the rotor (22) can be cooled by the refrigerant flowing through the refrigerant flow path (80).

[0079] In the refrigerant flow path (80), the first thrust gas bearing (73) is disposed upstream of the rotor (22) serving as the second transmission part (62) in the refrigerant flow direction. In other words, in the refrigerant flow from the discharge side of the compression mechanism (C) (part indicated by DP in FIG. 2 ), which is the start of the refrigerant flow path (80), to the suction side of the compression mechanism (C) (part indicated by SP in FIG. 2 ), which is the end of the refrigerant flow path (80), the refrigerant flows sequentially through the dynamic pressure gas bearings (71, 72, 73, 74) and the second transmission part (62). The first thrust gas bearing (73) tends to generate heat more easily than the rotor (22), but the first thrust gas bearing (73) can be efficiently cooled by the refrigerant.

[0080] The partition wall (50) separates the refrigerant flow path (80) from the first space (S1). This prevents the refrigerant flowing through the refrigerant flow path (80) from leaking into the first space (S1). This prevents the stator core (21a) and the coil (21b) from being corroded by the refrigerant while allowing the hydrodynamic gas bearings (71, 72, 73, 74) to be cooled by the refrigerant.

[0081] (6-5) The refrigerant flow path (80) includes a flow path that returns a portion of the refrigerant on the discharge side of the low-stage compression mechanism (C1) to the suction side of the low-stage compression mechanism (C1). The refrigerant flow path (80) includes a flow path that returns a portion of the refrigerant on the discharge side of the high-stage compression mechanism (C2) to the suction side of the high-stage compression mechanism (C2). Therefore, the refrigerant can be caused to flow in the refrigerant flow path (80) by utilizing the pressure difference of the compression mechanism (C).

[0082] (6-6) The power transmission mechanism (60) is configured to transmit the electromagnetic force of the stator (21) serving as the first transmission part (61) to the rotor (22) serving as the second transmission part (62) via the partition wall (50). This allows the volume of the second space (S2) in which the refrigerant is present to be relatively large, thereby increasing the number of dynamic pressure gas bearings (71, 72, 73, 74) that can be cooled by the refrigerant. In this embodiment, four dynamic pressure gas bearings (71, 72, 73, 74) can be cooled by the refrigerant.

[0083] (6-7) The first thrust gas bearing (73) is integrated with the rotor (22), which is the second transmission part. This simplifies the structures of the bearing element (70) and the power transmission mechanism (60). In addition, the refrigerant can cool both the first thrust gas bearing (73) and the rotor (22).

[0084] (7) Modifications The embodiment may have the following modified configurations. In principle, the following will describe only the differences from the embodiment.

[0085] (7-1) Modification 1 Modification 1 differs from the embodiment mainly in the configuration of the power transmission mechanism (60) and its surroundings. As shown in FIG. 3 , a partition wall (50) divides the interior of the casing (11) in the axial direction. Inside the casing (11), a second space (S2) is formed at one axial end side of the partition wall (50), and a first space (S1) is formed at the other axial end side. The entire electric motor (20) is disposed in the first space (S1). In other words, the stator (21) and the rotor (22) are disposed in the first space (S1).

[0086] The rotating shaft (25) has a first shaft (27) disposed in the first space (S1) and a second shaft (28) disposed in the second space (S2). The first shaft (27) and the second shaft (28) are separated from each other by a partition wall (50). A rotor (22) is provided around the second shaft (28). A first thrust disk (25b) and a second thrust disk (25c) are provided around the first shaft (27).

[0087] The power transmission mechanism (60) is configured to magnetically couple the first shaft (27) and the second shaft (28). The power transmission mechanism (60) includes a pair of magnetic members (63, 64). The pair of magnetic members (63, 64) is configured, for example, by a magnetic coupling or a magnetic gear. The pair of magnetic members (63, 64) are coupled to each other by magnetic force with the partition wall (50) sandwiched therebetween. The pair of magnetic members (63, 64) includes a first magnetic member (63) provided at one end of the first shaft (27) and a second magnetic member (64) provided at the other end of the second shaft (28). The first magnetic member (63) constitutes a first transmission part (61), and the second magnetic member (64) constitutes a second transmission part (62). The first magnetic member (63) and the second magnetic member (64) face each other in the axial direction with the partition wall (50) sandwiched therebetween. The power transmission mechanism (60) is a magnetic transmission mechanism that transmits the rotational force of the first magnetic member (63) to the second magnetic member (64) by means of magnetic force.

[0088] The first magnetic member (63) is formed in a cylindrical shape coaxial with the rotating shaft (25). The first magnetic member (63) is fixed to the outer peripheral surface of one end of the first shaft (27). The second magnetic member (64) has a cylindrical tube portion (64a) coaxial with the rotating shaft (25). The second magnetic member (64) is arranged on the outer peripheral side of the other end of the rotating shaft (25).

[0089] The bearing element (70) of the first modification includes a first radial gas bearing (71), a second radial gas bearing (72), a first thrust gas bearing (73), and a second thrust gas bearing (74). These are dynamic pressure gas bearings (71, 72, 73, 74) as in the embodiment. The bearing element (70) of the first modification includes auxiliary bearings arranged in the first space (S1). The auxiliary bearings of the first modification include a first radial magnetic bearing (75) and a second radial magnetic bearing (76). These magnetic bearings (75, 76) rotatably support the first shaft (27) by electromagnetic force. The auxiliary bearings may be other types of bearings, such as rolling bearings, or may be dynamic pressure gas bearings. However, the compressor (10) does not have an oil supply pump for lubricating the auxiliary bearings or a flow path for cooling the auxiliary bearings with a corrosive refrigerant.

[0090] The second thrust gas bearing (74) of the first modification is disposed inside the cylindrical portion (64a) of the second magnetic member (64). Strictly speaking, inside the cylindrical portion (64a), the thrust gas bearings (73, 74) are held between the second thrust disk (25c) and the partition wall (50). By disposing the second thrust gas bearing (74) inside the cylindrical portion (64a) of the second magnetic member (64) in this manner, it is possible to simplify and reduce the size of the compressor (10).

[0091] The cooling flow paths (81, 82, 83, 84) of the first modification include a first cooling flow path (81), a second cooling flow path (82), a third cooling flow path (83), a one-end space (85), and an internal flow path (26), similar to the embodiment. The internal flow path (26) of the first modification is formed only inside the second shaft (28). In the first modification, the refrigerant that has passed through the second cooling flow path (82) flows sequentially through the one-end space (85) and the third cooling flow path (83). The refrigerant passes over the surface of the second magnetic member (64) or through a flow path therein. As a result, the second magnetic member (64) can be cooled by the refrigerant. In the refrigerant flow path (80), the second radial gas bearing (72) and the first thrust gas bearing (73) are disposed upstream of the second magnetic member (64) in the refrigerant flow direction. This allows these bearings (72, 73) to be efficiently cooled.

[0092] The refrigerant that has passed through the second magnetic member (64) passes through the fourth cooling flow path (84) and the internal flow path (26), and then returns to the suction side of the high-stage compression mechanism (C2).

[0093] (7-2) Modification 2 The compressor (10) of Modification 2 differs from Modification 1 in the structures of the partition wall (50), the rotating shaft (25), and the power transmission mechanism (60). As shown in Fig. 4, an expanded diameter portion (29) extending radially outward is formed at one axial end of the first shaft (27) of the rotating shaft (25). The first magnetic member (63) extends from the outer peripheral end of the expanded diameter portion (29) toward the one axial end.

[0094] The partition wall (50) of the second modification has an annular plate portion (54) coaxial with the rotary shaft (25) and a cylindrical protrusion portion (55) extending from the plate portion (54) to the other end in the axial direction. The protrusion portion (55) fits into the first magnetic member (63) and the expanded diameter portion (29).

[0095] The second magnetic member (64) and the second thrust gas bearing (74) are disposed inside the first magnetic member (63) with the protrusion (55) of the partition wall (50) sandwiched therebetween. The first magnetic member (63) and the second magnetic member (64) face each other in the radial direction with the partition wall (50) sandwiched therebetween. This allows the compressor (10) to be reduced in size in the axial direction. The second thrust gas bearing (74) is held inside the cylindrical portion (64a) of the second magnetic member (64). Strictly speaking, the thrust gas bearings (73, 74) are held inside the cylindrical portion (64a) between the second thrust disk (25c) and the partition wall (50).

[0096] In the second modification, the refrigerant that has passed through the second cooling flow path (82) flows sequentially through the one-end space (85) and the third cooling flow path (83). The refrigerant passes over the surface of the second magnetic member (64) or through a flow path inside the second magnetic member (64). As a result, the refrigerant can cool the second magnetic member (64). In the refrigerant flow path (80), the second radial gas bearing (72) and the first thrust gas bearing (73) are disposed upstream of the second magnetic member (64) in the refrigerant flow direction. This allows these bearings (72, 73) to be efficiently cooled.

[0097] The refrigerant that has passed through the second magnetic member (64) passes through the fourth cooling flow path (84) and the internal flow path (26), and then returns to the suction side of the high-stage compression mechanism (C2).

[0098] (8) Other Embodiments The above-described embodiment and each modification may have the following configuration.

[0099] The refrigeration cycle apparatus (1) may be an air conditioner that has a switching valve for switching the direction of refrigerant flow and switches between cooling operation and heating operation. The refrigeration cycle apparatus (1) does not have to be an air conditioner. The refrigeration cycle apparatus (1) may be a stationary refrigeration apparatus that cools the interior of a warehouse, a showcase, or the like, a transport-type refrigeration apparatus that cools the interior of a container or a trailer, a heat pump apparatus that generates chilled water or hot water, a hot water supply apparatus, or the like.

[0100] The compressor (10) may be a single-stage compressor having one compression mechanism (C). FIG. 5 shows an example of the above-described embodiment in which the compression mechanism (C) is a single-stage compressor. The compression mechanism (C) has one impeller chamber (37) and one impeller (43) disposed in the impeller chamber (37). The first radial gas bearing (71) and the first cooling passage (81) are omitted. The impeller chamber (37) communicates with a discharge pipe via the diffuser passage (35) and the involute passage (36). As in the above-described embodiment, a portion of the refrigerant discharged from the compression mechanism (C) flows through the refrigerant passage (80) and returns to the suction side of the compression mechanism (C). The compressor (10) of Modification 1 or Modification 2 may be a single-stage compressor having one compression mechanism (C).

[0101] The bearing element (70) may include at least one dynamic pressure gas bearing, and may also include other types of bearings.

[0102] The refrigerant for cooling the dynamic pressure gas bearings (71, 72, 73, 74) may be a liquid refrigerant or a low-pressure refrigerant. However, when the refrigerant is a liquid refrigerant, the compressor (10) has a seal structure to prevent the liquid refrigerant from entering the sliding surfaces of the dynamic pressure gas bearings (71, 72, 73, 74). The start end of the refrigerant flow path (80) may be connected to the refrigerant circuit (2). For example, the refrigerant flow path (80) may be a flow path that returns high-pressure refrigerant or intermediate-pressure refrigerant from the refrigerant circuit (2) to the suction side of the compression mechanism (C).

[0103] The expansion mechanism of the refrigerant circuit (2) may be a capillary tube or an expansion fluid machine.

[0104] Although the embodiments and modifications have been described above, it will be understood that various modifications in form and details are possible without departing from the spirit and scope of the claims. Furthermore, the above embodiments, modifications, and other embodiments may be combined or substituted as appropriate as long as the functionality of the subject matter of the present disclosure is not impaired.

[0105] The above-mentioned descriptions such as "first," "second," "third," etc. are used to distinguish the words to which these descriptions are attached, and do not limit the number or order of the words.

[0106] INDUSTRIAL APPLICABILITY As described above, the present disclosure is useful for centrifugal compressors and refrigeration cycle devices.

[0107] REFRIGERATION CYCLE DEVICE 1 REFRIGERATION CYCLE DEVICE 11 CASING 20 ELECTRIC MOTOR 21 STATOR 22 ROTOR 25 ROTATING SHAFT 27 FIRST SHAFT 28 SECOND SHAFT 41, 42, 43 IMPELLER 50 PARTITION 60 POWER TRANSMISSION MECHANISM 61 FIRST TRANSMISSION PORTION 62 SECOND TRANSMISSION PORTION 64a CYLINDER 70 BEARING ELEMENT 71, 72, 73, 74 HYDRODYNAMIC GAS BEARING 73 FIRST THRUST GAS BEARING 74 SECOND THRUST GAS BEARING 80 REFRIGERANTIC FLOW PLANE C COMPRESSION MECHANISM S1 FIRST SPACE S2 SECOND SPACE

Claims

1. An electric motor (20) having a stator (21) and a rotor (22); a rotary shaft (25) rotated by the electric motor (20); a compression mechanism (C) having an impeller (41, 42, 43) driven by the rotary shaft (25) and compressing a refrigerant; a casing (11) accommodating the electric motor (20), the rotary shaft (25), and the compression mechanism (C); and a partition wall (50) dividing the interior of the casing (11) into a first space (S1) in which at least the stator (21) of the electric motor (20) is disposed and a second space (S2) in which the compression mechanism (C) is disposed. a power transmission mechanism (60) including a first transmission part (61) arranged in the first space (S1) and a second transmission part (62) arranged in the second space (S2), the power transmission mechanism transmitting power of the electric motor (20) on the first space (S1) side to the impeller (41, 42, 43) via the first transmission part (61) and the second transmission part (62); and a bearing element (70) rotatably supporting the rotating shaft (25), the bearing element (70) including dynamic pressure gas bearings (71, 72, 73, 74).

2. The centrifugal compressor according to claim 1, further comprising a refrigerant flow path (80) located in the second space (S2) and through which a refrigerant flows, and the dynamic pressure gas bearings (71, 72, 73, 74) are arranged in the refrigerant flow path (80).

3. The centrifugal compressor according to claim 2, wherein the second transmission part (62) is arranged in the refrigerant flow path (80).

4. The centrifugal compressor according to claim 3, wherein the dynamic pressure gas bearing (72) is arranged in the refrigerant flow path (80) upstream of the second transmission part (62) in the refrigerant flow direction.

5. The centrifugal compressor according to any one of claims 2 to 4, wherein the refrigerant flow path (80) is a flow path that returns a portion of the refrigerant on the discharge side of the compression mechanism (C) to the suction side of the compression mechanism (C).

6. The centrifugal compressor according to any one of claims 1 to 5, wherein the hydrodynamic gas bearings (71, 72, 73, 74) include a thrust gas bearing (74), and the thrust gas bearing (74) is integrated with the second transmission part (62).

7. The centrifugal compressor according to any one of claims 1 to 6, wherein the power transmission mechanism (60) is configured to transmit an electromagnetic force of the stator (21) as the first transmission part (61) to the rotor (22) as the second transmission part (62) via the partition wall (50).

8. The centrifugal compressor according to any one of claims 1 to 6, wherein the rotating shaft (25) includes a first shaft (27) disposed in the first space (S1) and provided with the first transmission part (61), and a second shaft (28) disposed in the second space (S2) and provided with the second transmission part (62), and the power transmission mechanism (60) is a magnetic transmission mechanism that transmits the rotational force of the first transmission part (61) to the second transmission part (62) by magnetic force.

9. The centrifugal compressor according to claim 8, wherein the second transmission part (62) has a cylindrical part (64a) whose axis is the rotating shaft (25), and the hydrodynamic gas bearings (71, 72, 73, 74) include a thrust gas bearing (74), and the thrust gas bearing (74) is arranged inside the cylindrical part (64a).

10. A centrifugal compressor according to any one of claims 1 to 9, wherein the compression mechanism (C) is configured to suck refrigerant from one axial end side of the rotating shaft (25), and the dynamic pressure gas bearings (71, 72, 73, 74) include a first thrust gas bearing (73) and a second thrust gas bearing (74) that is farther from the one axial end side than the first thrust gas bearing (73), and the diameter of the bearing surface of the first thrust gas bearing (73) is larger than the diameter of the bearing surface of the second thrust gas bearing (74).

11. A refrigeration cycle device comprising the centrifugal compressor (10) according to any one of claims 1 to 10, which performs a refrigeration cycle using a refrigerant containing a corrosive refrigerant.

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