Electric turbo compressor

Abstract

The first impeller (51) has a first hub (51H) fixed to the rotation axis (40) and a plurality of first blades (51B) arranged on the first hub (51H). The second impeller (52) has a second hub (52H) fixed to the rotation axis (40) and a plurality of second blades (52B) arranged on the second hub (52H). The housing (10) is provided with a first shroud (53a) that forms a first impeller chamber (28) that accommodates a first impeller (51) while facing a first blade (51B), and a second shroud (53b) that forms a second impeller chamber (33) that accommodates a second impeller (52) while facing a second blade (52B). The first rear end gap (61b), which is the gap between the rear end (51Ba) of the first blade (51B) and the first shroud (53a), is smaller than the second rear end gap (62b), which is the gap between the rear end (52Ba) of the second blade (52B) and the second shroud (53b).

Description

Technology Field

[0001] The present disclosure relates to an electric turbo compressor. Background Technology

[0002] A conventional electric turbo compressor is disclosed, for example, in Japanese Patent Publication No. 2015-194151 (Patent Document 1). The electric turbo compressor comprises a rotating shaft that is driven by rotation, and a first impeller and a second impeller installed on the rotating shaft. Prior art literature

[0003] Japanese Patent Publication No. 2015-194151 The problem to be solved

[0004] In the present disclosure, an electric turbo compressor capable of efficient two-stage compression is proposed. means of solving the problem

[0005] According to conventional knowledge, the efficiency of a compressor is determined by the relationship between the impeller outlet blade height and chip clearance, and it is known that if the outlet blade height is small, the efficiency deteriorates unless the chip clearance is also reduced. The inventors carefully examined the improvement of efficiency in a turbo compressor performing two-stage compression and discovered that the influence of chip clearance differs from the above conventional knowledge, and thus devised the following configuration.

[0006] That is, according to the present disclosure, an electric turbo compressor is proposed comprising a housing, an electric motor housed within the housing, a rotating shaft housed within the housing and driven by the electric motor, and a first impeller and a second impeller that rotate integrally with the rotating shaft. The electric motor, the first impeller, and the second impeller are arranged in this order along the axial direction of the rotating shaft. The first impeller has a first hub fixed to the rotating shaft and a plurality of first blades arranged on the first hub. The second impeller has a second hub fixed to the rotating shaft and a plurality of second blades arranged on the second hub. The first impeller conveys gas from the front end to the rear end of the first blade by rotation. The second impeller conveys the gas conveyed by the first impeller from the front end to the rear end of the second blade by rotation. The housing is provided with a first shroud that forms a first impeller chamber facing the first blade and accommodating the first impeller, and a second shroud that forms a second impeller chamber facing the second blade and accommodating the second impeller. If the gap between the rear end of the first blade and the first shroud is set to a first rear end gap that is the shortest distance between the first blade and the first shroud, and the gap between the rear end of the second blade and the second shroud is set to a second rear end gap that is the shortest distance between the second blade and the second shroud, then the first rear end gap is smaller than the second rear end gap.

[0007] By setting the gap in this way, disturbances in the refrigerant flow in the first impeller can be suppressed, and the electric turbo compressor can perform efficient two-stage compression. In addition, since contact with the housing of the second impeller can be suppressed, the reliability of the electric turbo compressor can be improved.

[0008] In the above electric turbo compressor, if the height of the rear end of the first blade facing the first rear gap is set as the first outlet height and the height of the rear end of the second blade facing the second rear gap is set as the second outlet height, the first outlet height may be higher than the second outlet height. By improving the compression efficiency of the first impeller and increasing the pressure of the refrigerant discharged from the first impeller, the flow velocity of the refrigerant entering the second impeller can be reduced. Accordingly, the effect of enabling efficient two-stage compression by making the first rear gap smaller than the second rear gap can be obtained more reliably.

[0009] In the above electric turbo compressor, the outer diameter of the first impeller may be larger than the outer diameter of the second impeller. By improving the compression efficiency of the first impeller and increasing the pressure of the refrigerant discharged from the first impeller, the flow velocity of the refrigerant entering the second impeller can be reduced. Accordingly, the effect of enabling efficient two-stage compression by making the first rear clearance smaller than the second rear clearance can be obtained more reliably.

[0010] In the above electric turbo compressor, if the gap between the front of the first blade and the first shroud is set to a first front gap that is the shortest distance between the first blade and the first shroud, and the gap between the front of the second blade and the second shroud is set to a second front gap that is the shortest distance between the second blade and the second shroud, the first front gap may be smaller than the second front gap. By setting the gaps in this way, disturbance of the refrigerant flow can be suppressed, and efficient two-stage compression can be achieved. In addition, since contact with the housing of the second impeller can be suppressed, reliability can be improved.

[0011] The above electric turbo compressor may compress the refrigerant circulating in the refrigeration cycle. Accordingly, by making the first rear gap smaller than the second rear gap, it becomes possible to realize efficient and highly reliable two-stage compression. Effects of the invention

[0012] According to the electric turbo compressor of the present disclosure, efficient two-stage compression can be achieved. Brief explanation of the drawing

[0013] FIG. 1 is a side cross-sectional view showing an electric turbo compressor in an embodiment. FIG. 2 is a cross-sectional view showing an enlarged view of the periphery of an impeller. FIG. 3 is a cross-sectional view showing an enlarged view of the periphery of the rear end of a first blade. FIG. 4 is a cross-sectional view showing an enlarged view of the periphery of the rear end of a second blade. FIG. 5 is a cross-sectional view showing an enlarged view of the periphery of the front end of a first blade. FIG. 6 is a cross-sectional view showing an enlarged view of the periphery of the front end of a second blade. FIG. 7 is a schematic diagram showing a modified example of the impeller arrangement. Specific details for implementing the invention

[0014] The embodiments are described below based on the drawings. In the following description, identical parts are given the same reference numerals. Their names and functions are also identical. Therefore, detailed descriptions thereof are not repeated.

[0015] The electric turbo compressor of the embodiment is used, for example, in an air conditioning system. The fluid to be compressed by the electric turbo compressor is a refrigerant circulating in a refrigeration cycle. FIG. 1 is a side cross-sectional view showing the electric turbo compressor (1) in the embodiment.

[0016] As shown in FIG. 1, the electric turbo compressor (1) is equipped with a tubular housing (10). The housing (10) has a rear housing (11), a motor housing (12), a first compressor housing (13), a second compressor housing (14), a partition wall (15), a first intermediate housing (16), and a second intermediate housing (17). The rear housing (11), the motor housing (12), the first compressor housing (13), the second compressor housing (14), the partition wall (15), the first intermediate housing (16), and the second intermediate housing (17) are each made of a metal material, for example, aluminum.

[0017] The motor housing (12) is a cylindrical shape with a bottom having a plate-shaped end wall (12a) and a perimeter wall (12b) extending in a cylindrical shape from the outer perimeter of the end wall (12a). A second intermediate housing (17) is connected to the motor housing (12) with the opening on the opposite side of the end wall (12a) in the perimeter wall (12b) closed. The motor room (18) is partitioned by the end wall (12a) and perimeter wall (12b) of the motor housing (12) and the second intermediate housing (17). An intake hole (not shown) for sucking in refrigerant is formed in the motor housing (12). The intake hole is connected to the motor room (18). Thus, refrigerant is sucked into the motor room (18) through the intake hole.

[0018] In the central part of the second intermediate housing (17), a shaft insertion passage hole (17a) in the shape of a circular hole is formed. The second intermediate housing (17) has a first bearing retaining part (19) in the shape of a cylinder. The first bearing retaining part (19) is formed on the inner circumference of the second intermediate housing (17). The inner side of the first bearing retaining part (19) is in communication with the shaft insertion passage hole (17a). The center axis of the first bearing retaining part (19) and the center axis of the shaft insertion passage hole (17a) coincide with each other. A first radial bearing (20) is retained in the first bearing retaining part (19).

[0019] The end wall portion (12a) of the motor housing (12) has a cylindrical second bearing retaining portion (21). The second bearing retaining portion (21) is formed in the center of the end wall portion (12a) of the motor housing (12). The center axis of the first bearing retaining portion (19) and the center axis of the second bearing retaining portion (21) coincide. A second radial bearing (22) is retained in the second bearing retaining portion (21). The first radial bearing (20) and the second radial bearing (22) are disposed within the housing (10).

[0020] On the outer surface opposite to the motor chamber (18) in the second intermediate housing (17), a first chamber-forming recess (17b) is formed. The first chamber-forming recess (17b) is connected to the shaft insertion through hole (17a). The second intermediate housing (17) has a plurality of connecting holes (23). Each connecting hole (23) is located in a region near the outer circumference of the second intermediate housing (17). Each connecting hole (23) penetrates the second intermediate housing (17). The connecting holes (23) are connected to the motor chamber (18) and the first chamber-forming recess (17b).

[0021] The first intermediate housing (16) is connected to the second intermediate housing (17). The first intermediate housing (16) is connected to the second intermediate housing (17) to close the opening of the first seal-forming recess (17b). The thrust bearing receiving chamber (25) is partitioned by the first seal-forming recess (17b) of the first intermediate housing (16) and the second intermediate housing (17). A circular shaft insertion passage hole (16a) is formed in the central part of the first intermediate housing (16).

[0022] The first intermediate housing (16) has a plurality of communication holes (16b). Each communication hole (16b) is located in a region near the outer circumference of the first intermediate housing (16). Each communication hole (16b) penetrates the first intermediate housing (16). On the outer surface opposite to the thrust bearing receiving chamber (25) in the first intermediate housing (16), a second seal-forming recess (16c) is formed. The second seal-forming recess (16c) is in communication with the shaft insertion through hole (16a). Each communication hole (16b) is in communication with the thrust bearing receiving chamber (25) and the second seal-forming recess (16c).

[0023] The first compressor housing (13) is a tubular shape having a first suction port (24) in the shape of a circular hole. The first compressor housing (13) is connected to the first intermediate housing (16) such that the center axis of the first suction port (24) coincides with the center axis of the shaft insertion through hole (16a). The first suction port (24) is connected to the second chamber forming recess (16c).

[0024] The partition wall (15) is connected to the cross-section opposite to the first intermediate housing (16) in the first compressor housing (13). The partition wall (15) is plate-shaped. A circular through hole (27) (Fig. 2) is formed in the center of the partition wall (15). The through hole (27) penetrates the partition wall (15) in the thickness direction of the partition wall (15). The partition wall (15) is connected to the first compressor housing (13) such that the center axis of the through hole (27) coincides with the center axis of the first suction port (24).

[0025] FIG. 2 is a cross-sectional view showing an enlarged view of the periphery of the impeller. As shown in FIG. 1 and 2, between the partition wall (15) and the first compressor housing (13), a first impeller chamber (28) communicating with the first suction port (24), a first discharge chamber (29) extending around the first impeller chamber (28) along the central axis of the first suction port (24), and a first diffuser passage (30) communicating with the first impeller chamber (28) and the first discharge chamber (29) are formed.

[0026] The second compressor housing (14) is connected to the end of the partition wall (15) opposite to the first compressor housing (13). An intermediate pressure chamber (31) is formed across the first compressor housing (13), the partition wall (15), and the second compressor housing (14). The intermediate pressure chamber (31) is connected to the first discharge chamber (29) through a passage not shown. The second compressor housing (14) has a second suction port (32) in the shape of a circular hole that is connected to the intermediate pressure chamber (31). The first discharge chamber (29) and the second suction port (32) are connected through the intermediate pressure chamber (31).

[0027] Between the partition wall (15) and the second compressor housing (14), a second impeller chamber (33) communicating with the second suction port (32), a second discharge chamber (34) extending around the second impeller chamber (33) along the central axis of the second suction port (32), and a second diffuser passage (35) communicating with the second impeller chamber (33) and the second discharge chamber (34) are formed.

[0028] The housing (10) has a first impeller chamber (28) and a second impeller chamber (33). A partition wall (15) separates the first impeller chamber (28) and the second impeller chamber (33).

[0029] The rear housing (11) is connected to the second compressor housing (14). The rear housing (11) partitions the intermediate pressure chamber (31). The rear housing (11) is plate-shaped.

[0030] The electric turbo compressor (1) is equipped with a rotating shaft (40). The rotating shaft (40) extends in the axial direction of the housing (10) by passing through the inner side of the second bearing retaining part (21), the motor chamber (18), the inner side of the first bearing retaining part (19), the shaft insertion passage hole (17a), the thrust bearing receiving chamber (25), the shaft insertion passage hole (16a), the first suction port (24), the first impeller chamber (28), the through hole (27), the second impeller chamber (33), and the second suction port (32). The rotating shaft (40) is positioned across the first impeller chamber (28) and the second impeller chamber (33) while inserted through the through hole (27).

[0031] The rotating shaft (40) has a first end (40a) at one end and a second end (40b) at the other end. The first end (40a) is placed within the second compressor housing (14). The second end (40b) is placed within the end wall (12a) of the motor housing (12). The rotating shaft (40) is housed within the housing (10).

[0032] The axis (L) of the rotation axis (40) coincides with the center axis of each of the first bearing retaining part (19), the second bearing retaining part (21), the shaft insertion through hole (17a), the shaft insertion through hole (16a), the first suction port (24), the through hole (27), and the second suction port (32). In the following description, the “axial direction of the rotation axis (40)”, which is the direction in which the axis (L) of the rotation axis (40) extends, may be described as the “thrust direction,” and the “radial direction of the rotation axis (40)” may be described as the “radial direction.”

[0033] The first radial bearing (20) and the second radial bearing (22) support the rotation axis (40) so as to be rotatable in the radial direction. The first radial bearing (20) and the second radial bearing (22) may be air dynamic bearings.

[0034] The electric turbo compressor (1) is equipped with a disc-shaped support plate (75) installed on a rotating shaft (40). The support plate (75) protrudes outward in the radial direction from the outer surface of the rotating shaft (40). The support plate (75) rotates integrally with the rotating shaft (40). The support plate (75) is placed in a thrust bearing receiving chamber (25).

[0035] A thrust bearing (80) is disposed between the first intermediate housing (16) and the support plate (75), and between the second intermediate housing (17) and the support plate (75). Both thrust bearings (80) support the rotation axis (40) so as to be rotatable in the thrust direction. Both thrust bearings (80) may be air dynamic bearings.

[0036] The electric turbo compressor (1) is equipped with an electric motor (41). The electric motor (41) is housed in a motor room (18). The electric motor (41) is housed within a housing (10). The electric motor (41) is an example of a driving source that rotates and drives a rotating shaft (40). The electric motor (41) is equipped with a stator (42) and a rotor (43).

[0037] The stator (42) has a cylindrical stator core (44) and a coil (45) wound around the stator core (44). The stator core (44) is fixed to the inner circumference of the circumferential wall (12b) of the motor housing (12).

[0038] The rotor (43) is positioned in the diametrically inner side of the stator core (44) in the motor chamber (18). The rotor (43) rotates integrally with the rotation axis (40). The rotor (43) has a rotor core (43a) fixed to the rotation axis (40) and a plurality of unillustrated permanent magnets installed in the rotor core (43a). Power controlled by an unillustrated inverter device is supplied to the coil (45), thereby causing the rotor (43) of the electric motor (41) to rotate. The rotation axis (40) rotates integrally with the rotor (43).

[0039] The electric turbo compressor (1) is equipped with a first impeller (51) and a second impeller (52). The first impeller (51) and the second impeller (52) are made of, for example, aluminum. The first impeller (51) and the second impeller (52) are connected to a rotating shaft (40). The first impeller (51) and the second impeller (52) rotate integrally with the rotating shaft (40).

[0040] The second impeller (52) is positioned closer to the first end (40a) of the rotation axis (40) than the first impeller (51). The first impeller (51) and the second impeller (52) are positioned closer to the first end (40a) of the rotation axis (40) than the first radial bearing (20). The first impeller (51) is positioned closer to the electric motor (41) than the second impeller (52). The electric motor (41), the first impeller (51), and the second impeller (52) are arranged in this order along the axial direction of the rotation axis (40). As shown in FIG. 2, the first impeller (51) is housed in the first impeller chamber (28). The second impeller (52) is housed in the second impeller chamber (33).

[0041] The first impeller (51) has a first hub (51H). The first hub (51H) is fixed to a rotation axis (40). The first hub (51H) has a back surface (51a), a front surface (51b), an outer surface (51c), and a radial outer edge (51d). The back surface (51a), the front surface (51b), the outer surface (51c), and the radial outer edge (51d) form part of the outer surface of the first hub (51H). The first hub (51H) has a roughly truncated cone shape, with the outer diameter expanding as it extends from the front surface (51b), located on the side of the first suction port (24), toward the back surface (51a).

[0042] The back surface (51a) forms the rear end of the first hub (51H). The back surface (51a) is the outer surface of the first hub (51H) that does not form a refrigerant flow path. When the first impeller (51) is connected to the rotation shaft (40) and the electric turbo compressor (1) is assembled, the back surface (51a) faces the partition wall (15) in the axial direction of the rotation shaft (40). The partition wall (15) has a first opposing surface (15a) that faces the back surface (51a) of the first hub (51H) in the axial direction of the rotation shaft (40).

[0043] The front end surface (51b) forms the front end of the first hub (51H). The front end surface (51b) forms one end of the first impeller (51) in the axial direction of the rotation axis (40). The front end surface (51b) is the end of the first hub (51H) on the side where the refrigerant flows into the first impeller (51).

[0044] The outer surface (hub surface) (51c) forms part of the inner wall surface of the first impeller chamber (28). The outer surface (51c) is a concave curved surface facing the axis (L) of the rotation axis (40). At least a portion of the outer surface (51c) faces outward in the diameter direction of the rotation axis (40). The outer surface (51c) is formed such that its diameter gradually increases from the front surface (51b) to the back surface (51a) along the axial direction of the rotation axis (40). As the outer surface (51c) faces from the front surface (51b) to the back surface (51a), it gradually slopes outward in the diameter direction.

[0045] The radial outer edge (51d) is the part of the first impeller (51) where the outer diameter is maximum. The radial outer edge (51d) has a single-axis cylindrical shape. The first impeller (51) has an outer diameter (R1). The outer diameter (R1) of the first impeller (51) is the distance between the axis (L) of the rotation axis (40) in the radial direction of the rotation axis (40) and the radial outer edge (51d) of the first impeller (51).

[0046] The first impeller (51) has a plurality of first blades (51B). The plurality of first blades (51B) are installed on the outer surface (51c) of the first hub (51H). The plurality of first blades (51B) are arranged in the circumferential direction of the first hub (51H). The plurality of first blades (51B) divide the first impeller chamber (28) in the circumferential direction and form a flow path for refrigerant between a pair of first blades (51B) adjacent in the circumferential direction. The plurality of first blades (51B) protrude outward in the radial direction from the outer surface (51c) of the first hub (51H). The plurality of first blades (51B) are arranged at equal intervals in the circumferential direction on the outer surface (51c) of the first hub (51H). The spacing between adjacent first wings (51B) in the circumferential direction of the first hub (51H) gradually widens as it goes from the front end to the rear end of the first hub (51H).

[0047] The first blade (51B) has a rear end (51Ba), a front end (51Bb), and a front end surface (51Bc). The rear end (51Ba), the front end (51Bb), and the front end surface (51Bc) form part of the edge portion of the first blade (51B). The front end (51Bb) of the first blade (51B) faces the first suction port (24). The rear end (51Ba) of the first blade (51B) faces the first diffuser passage (30). The front end surface (51Bc) of the first blade (51B) faces the first compressor housing (13). The front end (51Bb) extends in the diameter direction of the rotation axis (40). The rear end (51Ba) extends in the axial direction of the rotation axis (40).

[0048] The front end surface (51Bc) is curved. The front end surface (51Bc) is formed so that its diameter gradually increases from the front end (51Bb) to the rear end (51Ba) along the axial direction of the rotation axis (40). The front end surface (51Bc) gradually slopes outward in the diameter direction as it goes from the front end (51Bb) to the rear end (51Ba). The curvature of the front end surface (51Bc) of the first wing (51B) is greater than the curvature of the outer surface (51c) of the first hub (51H).

[0049] The front end (51Bb) is the edge portion of the first wing (51B) on the upstream side in the direction of refrigerant flow. Refrigerant flows from the first suction port (24) through the front end (51Bb) and into the space between a pair of circumferentially adjacent first wings (51B). The rear end (51Ba) is the edge portion of the first wing (51B) on the downstream side in the direction of refrigerant flow. The refrigerant flows outward in the radial direction through the space between a pair of circumferentially adjacent rear ends (51Ba).

[0050] The second impeller (52) has a second hub (52H). The second hub (52H) is fixed to the rotation axis (40). The second hub (52H) has a back surface (52a), a front surface (52b), an outer surface (52c), and a radial outer edge (52d). The back surface (52a), the front surface (52b), the outer surface (52c), and the radial outer edge (52d) form part of the outer surface of the second hub (52H). The second hub (52H) has a roughly truncated cone shape, with the outer diameter expanding as it extends from the front surface (52b), located on the side of the second suction port (32), toward the back surface (52a).

[0051] The back surface (52a) forms the rear end of the second hub (52H). The back surface (52a) is the outer surface of the second hub (52H) that does not form a refrigerant flow path. When the second impeller (52) is connected to the rotation shaft (40) and the electric turbo compressor (1) is assembled, the back surface (52a) faces the partition wall (15) in the axial direction of the rotation shaft (40). The partition wall (15) has a second opposing surface (15b) that faces the back surface (52a) of the second hub (52H) in the axial direction of the rotation shaft (40).

[0052] The front end surface (52b) forms the front end of the second hub (52H). The front end surface (52b) forms one end of the second impeller (52) in the axial direction of the rotation axis (40). The front end surface (52b) is the end of the second hub (52H) on the side where the refrigerant flows into the second impeller (52).

[0053] The outer surface (hub surface) (52c) forms part of the inner wall surface of the second impeller chamber (33). The outer surface (52c) is a concave curved surface facing the axis (L) of the rotation axis (40). At least a portion of the outer surface (52c) faces outward in the diameter direction of the rotation axis (40). The outer surface (52c) is formed so that its diameter gradually increases from the front surface (52b) to the back surface (52a) along the axial direction of the rotation axis (40). As the outer surface (52c) faces from the front surface (52b) to the back surface (52a), it gradually slopes outward in the diameter direction.

[0054] The radial outer edge (52d) is the part of the second impeller (52) where the outer diameter is maximum. The radial outer edge (52d) has a single-axis cylindrical shape. The second impeller (52) has an outer diameter (R2). The outer diameter (R2) of the second impeller (52) is the distance between the axis (L) of the rotation axis (40) in the radial direction of the rotation axis (40) and the radial outer edge (52d) of the second impeller. As shown in FIG. 2, the outer diameter (R1) of the first impeller (51) is larger than the outer diameter (R2) of the second impeller (52).

[0055] The second impeller (52) has a plurality of second blades (52B). The plurality of second blades (52B) are installed on the outer surface (52c) of the second hub (52H). The plurality of second blades (52B) are arranged in the circumferential direction of the second hub (52H). The plurality of second blades (52B) divide the second impeller chamber (33) in the circumferential direction and form a flow path for refrigerant between a pair of circumferentially adjacent second blades (52B). The plurality of second blades (52B) protrude outward in the radial direction from the outer surface (52c) of the second hub (52H). The plurality of second blades (52B) are arranged at equal intervals in the circumferential direction on the outer surface (52c) of the second hub (52H). The spacing between adjacent second wings (52B) in the circumferential direction of the second hub (52H) gradually widens as it goes from the front end to the rear end of the second hub (52H).

[0056] The second blade (52B) has a rear end (52Ba), a front end (52Bb), and a front end surface (52Bc). The rear end (52Ba), the front end (52Bb), and the front end surface (52Bc) form part of the edge portion of the second blade (52B). The front end (52Bb) of the second blade (52B) faces the second suction port (32). The rear end (52Ba) of the second blade (52B) faces the second diffuser passage (35). The front end surface (52Bc) of the second blade (52B) faces the second compressor housing (14). The front end (52Bb) extends in the diameter direction of the rotation axis (40). The rear end (52Ba) is extended in the axial direction of the rotation axis (40).

[0057] The front end surface (52Bc) is curved. The front end surface (52Bc) is formed so that its diameter gradually increases from the front end (52Bb) to the rear end (52Ba) along the axial direction of the rotation axis (40). The front end surface (52Bc) gradually slopes outward in the diameter direction as it goes from the front end (52Bb) to the rear end (52Ba). The curvature of the front end surface (52Bc) of the second wing (52B) is greater than the curvature of the outer surface (52c) of the second hub (52H).

[0058] The front end (52Bb) is the edge portion of the second wing (52B) on the upstream side in the direction of refrigerant flow. Refrigerant flows from the second suction port (32) through the front end (52Bb) and into the space between a pair of adjacent second wings (52B) in the circumferential direction. The rear end (52Ba) is the edge portion of the second wing (52B) on the downstream side in the direction of refrigerant flow. The refrigerant flows outward in the radial direction through the space between a pair of adjacent rear ends (52Ba) in the circumferential direction.

[0059] The electric motor (41) rotates the rotating body, which includes a rotating shaft (40), a first impeller (51), and a second impeller (52), and rotates the rotating body integrally around the axis (L). The first impeller (51) rotates integrally with the rotating shaft (40) to transport gaseous refrigerant from the front end (51Bb) of the first blade (51B) to the rear end (51Ba) and compress the refrigerant. The second impeller (52) rotates integrally with the rotating shaft (40) to transport gaseous refrigerant, which has been transported by the first impeller (51) and compressed by the first impeller (51), from the front end (52Bb) of the second blade (52B) to the rear end (52Ba) and compress the refrigerant. A first impeller (51) is positioned on the upstream side in the direction of refrigerant flow, and a second impeller (52) is positioned on the downstream side.

[0060] The first impeller (51) and the second impeller (52) are installed on a rotating shaft (40) such that the back surface (51a) of the first hub (51H) and the back surface (52a) of the second hub (52H) face each other through a partition wall (15). A hollow cylindrical spacer (54) is disposed between the first impeller (51) and the second impeller (52). The spacer (54) has a first stage facing the back surface (51a) of the first hub (51H) and a second stage facing the back surface (52a) of the second hub (52H). The dimensions of the spacer (54) in the axial direction of the rotation axis (40) are slightly larger than the gap between the first opposing surface (15a) and the second opposing surface (15b) of the partition wall (15). The spacer (54) has the function of sealing the gap between the outer surface of the rotation axis (40) and the inner surface of the through hole (27).

[0061] A fitting member (55) is attached to the outer surface of the rotating shaft (40) at the first end (40a) of the rotating shaft (40). The fitting member (55) has a hollow tubular shape. The fitting member (55) is attached to the rotating shaft (40), for example, by a screw action. The fitting member (55) is in contact with the front end surface (52b) of the second hub (52H). The fitting member (55) supports the second impeller (52) in the axial direction of the rotating shaft (40).

[0062] The first compressor housing (13) has a first shroud (53a) that partitions the first impeller chamber (28) in cooperation with the partition wall (15). The first shroud (53a) is truncated cone-shaped and covers the first impeller (51) from the outer side in the radial direction. The first shroud (53a) faces the outer surface (51c) of the first hub (51H). The first shroud (53a) extends along the outer surface (51c) of the first hub (51H) from the back surface (51a) of the first hub (51H) to the front surface (51b). The first shroud (53a) surrounds a plurality of first blades (51B). The first shroud (53a) faces the leading edge (51Bc) of the first blade (51B) and forms part of the inner wall surface of the first impeller chamber (28). A refrigerant flow path is formed radially by a pair of first blades (51B), the first hub (51H), and the first shroud (53a) adjacent to the circumferential direction of the first hub (51H).

[0063] A first chip clearance (61) is formed between the first impeller (51) and the first shroud (53a). This first chip clearance (61) is a gap extending from the front end (51Bb) of the first blade (51B) to the rear end (51Ba) between the front end surface (51Bc) of the first blade (51B) and the first shroud (53a) of the first compressor housing (13).

[0064] The second compressor housing (14) has a second shroud (53b) that partitions the second impeller chamber (33) in cooperation with the partition wall (15). The second shroud (53b) is a truncated cone shape that covers the second impeller (52) from the outer side in the radial direction. The second shroud (53b) faces the outer surface (52c) of the second hub (52H). The second shroud (53b) extends along the outer surface (52c) of the second hub (52H) from the back surface (52a) of the second hub (52H) to the front surface (52b). The second shroud (53b) surrounds a plurality of second blades (52B). The second shroud (53b) faces the leading edge (52Bc) of the second blade (52B) and forms part of the inner wall surface of the second impeller chamber (33). A refrigerant flow path is formed radially by a pair of adjacent second blades (52B), the second hub (52H), and the second shroud (53b) in the circumferential direction of the second hub (52H).

[0065] A second chip clearance (62) is formed between the second impeller (52) and the second shroud (53b). This second chip clearance (62) is a gap extending from the front end (52Bb) of the second blade (52B) to the rear end (52Ba) between the front end surface (52Bc) of the second blade (52B) and the second shroud (53b) of the second compressor housing (14).

[0066] FIG. 3 is a cross-sectional view showing an enlarged view of the periphery of the rear end (51Ba) of the first wing (51B). The first chip clearance (61) includes a first rear end clearance (61b), which is a thrust direction gap between the front end surface (51Bc) and the first shroud (53a) at the rear end (51Ba) of the first wing (51B). The first rear end clearance (61b) is a gap between the rear end (51Ba) of the first wing (51B) and the first shroud (53a), and is a gap that is the minimum value or shortest distance between the first wing (51B) and the first shroud (53a). The first rear gap (61b) is the gap with the smallest gap dimensions among the gaps between the front face (51Bc) of the first wing (51B) and the first shroud (53a).

[0067] FIG. 4 is a cross-sectional view showing an enlarged view of the periphery of the rear end (52Ba) of the second wing (52B). The second chip clearance (62) includes a second rear end clearance (62b), which is a thrust direction gap between the front end surface (52Bc) and the second shroud (53b) at the rear end (52Ba) of the second wing (52B). The second rear end clearance (62b) is a gap between the rear end (52Ba) of the second wing (52B) and the second shroud (53b), and is a gap that is the minimum value or shortest distance between the second wing (52B) and the second shroud (53b). The second rear gap (62b) is the gap with the smallest dimensions among the gaps between the front face (52Bc) of the second wing (52B) and the second shroud (53b).

[0068] As shown in FIG. 3 and 4, the length (H1), which is the gap dimension in the thrust direction of the first rear gap (61b), is smaller than the length (H2), which is the gap dimension in the thrust direction of the second rear gap (62b). At the position of the rear end (51Ba) of the first blade (51B), the shortest distance between the front end surface (51Bc) of the first blade (51B) and the first shroud (53a) of the first compressor housing (13) is smaller than the shortest distance between the front end surface (52Bc) of the second blade (52B) and the second shroud (53b) of the second compressor housing (14) at the position of the rear end (52Ba) of the second blade (52B).

[0069] FIG. 5 is a cross-sectional view showing an enlarged view of the periphery of the shear (51Bb) of the first wing (51B). The first chip clearance (61) includes a first shear gap (61a), which is a radial gap between the leading edge surface (51Bc) and the first shroud (53a) in the shear (51Bb) of the first wing (51B). The first shear gap (61a) is a gap between the shear (51Bb) of the first wing (51B) and the first shroud (53a), and is a gap that is the minimum value or shortest distance between the first wing (51B) and the first shroud (53a). The first shear gap (61a) is the gap with the smallest dimensions among the gaps between the leading edge (51Bc) of the first wing (51B) and the first shroud (53a).

[0070] FIG. 6 is a cross-sectional view showing an enlarged view of the periphery of the shear (52Bb) of the second wing (52B). The second chip clearance (62) includes a second shear gap (62a), which is a radial gap between the leading edge surface (52Bc) and the second shroud (53b) in the shear (52Bb) of the second wing (52B). The second shear gap (62a) is a gap between the shear (52Bb) of the second wing (52B) and the second shroud (53b), and is a gap that is the minimum value or shortest distance between the second wing (52B) and the second shroud (53a). The second shear gap (62a) is the gap with the smallest dimensions among the gaps between the leading edge (52Bc) of the second wing (52B) and the second shroud (53b).

[0071] As shown in FIG. 5 and 6, the length (H3), which is the radial gap dimension of the first shear gap (61a), is smaller than the length (H4), which is the radial gap dimension of the second shear gap (62a). At the position of the shear (51Bb) of the first blade (51B), the shortest distance between the leading edge surface (51Bc) of the first blade (51B) and the first shroud (53a) of the first compressor housing (13) is smaller than the shortest distance between the leading edge surface (52Bc) of the second blade (52B) and the second shroud (53b) of the second compressor housing (14) at the position of the shear (52Bb) of the second blade (52B).

[0072] Also, as shown in FIG. 3 and 4, the first outlet height (T1), which is the axial dimension of the first blade (51B) at the rear end (51Ba) of the first blade (51B) of the first impeller (51), is greater than the second outlet height (T2), which is the axial dimension of the second blade (52B) at the rear end (52Ba) of the second blade (52B) of the second impeller (52). The outlet blade height of the first impeller (51) is greater than the outlet blade height of the second impeller (52).

[0073] The first exit height (T1) is the height of the rear end (51Ba) of the first wing (51B) facing the first rear end gap (61b). The first exit height (T1) is the height of the rear end (51Ba) of the first wing (51B) protruding from the outer surface (51c) of the first hub (51H) toward the first rear end gap (61b), and the protruding height becomes the highest height of the first wing (51B). The second exit height (T2) is the height of the rear end (52Ba) of the second wing (52B) facing the second rear end gap (62b). The second exit height (T2) is the height of the rear end (52Ba) of the second wing (52B) that protrudes from the outer surface (52c) of the second hub (52H) toward the second rear end gap (62b), and the protruding height becomes the highest height of the second wing (52B).

[0074] In an electric turbo compressor (1), refrigerant is drawn into the motor chamber (18) from an intake hole not shown. The refrigerant drawn into the motor chamber (18) passes through the inside of each connecting hole (23), the thrust bearing receiving chamber (25), each connecting hole (16b), and the second chamber forming recess (16c), and is drawn into the first intake port (24). The refrigerant drawn into the first intake port (24) is pressurized by the centrifugal action of the first impeller (51), transferred from the first impeller chamber (28) to the first diffuser path (30), and further pressurized in the first diffuser path (30). The refrigerant that has passed through the first diffuser path (30) is discharged into the first discharge chamber (29).

[0075] The refrigerant discharged into the first discharge chamber (29) passes through the intermediate pressure chamber (31) and is sucked into the second suction port (32). The refrigerant sucked into the second suction port (32) is pressurized by the centrifugal action of the second impeller (52), transferred from the second impeller chamber (33) to the second diffuser path (35), and further pressurized in the second diffuser path (35). The refrigerant passing through the second diffuser path (35) is discharged into the second discharge chamber (34). The second discharge chamber (34) is connected to a discharge port not shown. The refrigerant compressed by the electric turbo compressor (1) is discharged from the discharge port to the outside of the electric turbo compressor (1).

[0076] In the electric turbo compressor (1) of the embodiment described above, as shown in FIG. 3 and 4, the first rear gap (61b), which is the minimum gap between the first blade (51B) and the first shroud (53a), is formed to be smaller than the second rear gap (62b), which is the minimum gap between the second blade and the second shroud, which is the gap between the second blade (52B) and the second shroud (53b).

[0077] The second impeller (52) compresses the refrigerant after it has been compressed by the first impeller (51). The pressure of the refrigerant flowing through the second impeller chamber (33) is higher than the pressure of the refrigerant flowing through the first impeller chamber (28). Since the density of the refrigerant flowing through the first impeller chamber (28) is lower than the density of the refrigerant flowing through the second impeller chamber (33), it is necessary to allow the volumetric flow rate to be higher in the first impeller (51). Therefore, the flow velocity of the refrigerant flowing through the first impeller chamber (28) is greater than the flow velocity of the refrigerant flowing through the second impeller chamber (33). In addition, the compression ratio of the refrigerant by the first impeller (51) is greater than the compression ratio of the refrigerant by the second impeller (52).

[0078] When the refrigerant flow rate is high, the influence of chip clearance increases. In the first impeller (51) where the refrigerant flow rate is high, if the first chip clearance (61) is large, the flow of the refrigerant becomes disordered. In the second impeller (52) where the refrigerant flow rate is low, even if the second chip clearance (62) is large, the influence on performance is small. By making the chip clearance of the first impeller (51) small and setting the first rear clearance (61b) smaller than the second rear clearance (62b), the disordering of the refrigerant flow can be suppressed. Therefore, the electric turbo compressor (1) of the embodiment can perform efficient two-stage compression.

[0079] The second impeller (52) is positioned closer to the first end (40a) of the rotation shaft (40) than the first impeller (51). The second impeller (52), positioned at the front end of the rotation shaft (40), may have greater shaking during operation than the first impeller (51). By setting the second rear end gap (62b) larger than the first rear end gap (61b), contact between the second impeller (52) and the second compressor housing (14) can be suppressed. Thus, the reliability of the electric turbo compressor (1) can be improved.

[0080] As shown in FIG. 3 and 4, the first exit height (T1), which is the height at which the rear end (51Ba) of the first wing (51B) protrudes from the outer surface (51c) of the first hub (51H) toward the first rear end gap (61b), is greater than the second exit height (T2), which is the height at which the rear end (52Ba) of the second wing (52B) protrudes from the outer surface (52c) of the second hub (52H) toward the second rear end gap (62b).

[0081] Since both the first impeller (51) and the second impeller (52) rotate integrally with the rotation shaft (40), the rotational speeds of the first impeller (51) and the second impeller (52) are equal. In this case, by making the first outlet height (T1) larger than the second outlet height (T2), the compression efficiency of the first impeller (51) can be improved. By making the pressure of the refrigerant discharged from the first impeller (51) larger, the flow velocity of the refrigerant entering the second impeller (52) can be made smaller. Accordingly, even if the second chip clearance (62) is made larger, the impact on performance can be reduced, so the effect of enabling efficient two-stage compression by making the first rear clearance (61b) smaller than the second rear clearance (62b) can be obtained more reliably.

[0082] As shown in FIG. 2, the outer diameter (R1) of the first impeller (51) is larger than the outer diameter (R2) of the second impeller (52). By doing so, the compression efficiency of the first impeller (51) can be improved, and the pressure of the refrigerant discharged from the first impeller (51) can be increased, thereby allowing the flow rate of the refrigerant entering the second impeller (52) to be reduced. Accordingly, even if the second chip clearance (62) is increased, the impact on performance can be reduced, so the effect of enabling efficient two-stage compression by making the first rear clearance (61b) smaller than the second rear clearance (62b) can be obtained more reliably.

[0083] As shown in FIGS. 5 and 6, the first shear gap (61a), which is the minimum gap between the first blade (51B) and the first shroud (53a) as the gap between the first blade (51B) (51Bb) and the first shroud (53a), is formed to be smaller than the second shear gap (62a), which is the minimum gap between the second blade (52B) and the second shroud (53b) as the gap between the second blade (52B) (52Bb) and the second shroud (53b). By making the chip clearance of the first impeller (51) smaller and setting the first shear gap (61a) smaller than the second shear gap (62a), the disturbance of the refrigerant flow can be suppressed. Therefore, efficient two-stage compression can be achieved. Also, since contact between the second impeller (52) and the second compressor housing (14) can be suppressed, reliability can be improved.

[0084] Since the fluid to be compressed by the electric turbo compressor (1) is a refrigerant circulating in the refrigeration cycle, the impact on performance can be reduced even if the second chip clearance (62) is increased. Accordingly, it is possible to realize efficient and highly reliable two-stage compression by making the first rear clearance (61b) smaller than the second rear clearance (62b).

[0085] In the description of the embodiments so far, an example of an arrangement in which the back surface (51a) of the first hub (51H) of the first impeller (51) and the back surface (52a) of the second hub (52H) of the second impeller (52) face each other with a partition wall (15) interposed between them was described. The arrangement of the first impeller (51) and the second impeller (52) is not limited to this example. FIG. 7 is a schematic diagram showing a modified example of the arrangement of impellers. As shown in FIG. 7, the first impeller (51) and the second impeller (52) may be arranged such that the front surfaces (51b, 52b) face toward the second end (40b) of the rotation axis (40) and the back surfaces (51a, 52a) face toward the first end (40a) of the rotation axis (40). In this case, the second impeller (52) is positioned closer to the first end (40a) of the rotation axis (40), and the first rear gap (61b) is set smaller than the second rear gap (62b), thereby enabling efficient and reliable two-stage compression.

[0086] The electric turbo compressor (1) described in the embodiment is a centrifugal compressor, but the technical concept of the present disclosure is also applicable to a diagonal flow compressor.

[0087] Although embodiments have been described above, the embodiments disclosed herein should be considered illustrative in all respects and not restrictive. The scope of the invention is disclosed by the claims rather than by the description above, and it is intended to include all modifications within the meaning and scope equivalent to the claims. Explanation of the symbols

[0088] 1 : Electric turbo compressor 10 : Housing 11 : Rear housing 13 : First compressor housing 14 : Second compressor housing 15 : Partition wall 15a : First opposing surface 15b : Second opposing surface 24 : First suction port 27 : Through hole 28 : First impeller chamber 29 : First discharge chamber 30 : First diffuser passage 31 : Intermediate pressure chamber 32 : Second suction port 33 : Second impeller chamber 34 : Second discharge chamber 35 : Second diffuser passage 40 : Rotating shaft 40a : First end 40b : Second end 41 : Electric motor 51 : First impeller 51B : First blade 51Ba, 52Ba : Rear end 51Bb, 52Bb : Front end 51Bc, 52Bc : Front end surface 51H : First hub 51a, 52a: Back surface 51b, 52b: Front surface 51c, 52c: Outer circumference 51d, 52d: Diametrical outer edge 52: Second impeller 52B: Second blade 52H: Second hub 53a: First shroud 53b: Second shroud 54: Spacer 55: Fit member 61: First chip clearance 61a: First shear clearance 61b: First rear clearance 62: Second chip clearance 62a: Second shear clearance 62b: Second rear clearance H1, H2, H3, H4: Length L: Axis R1, R2: Outer diameter

Claims

Claim 1 A housing, an electric motor housed within the housing, a rotating shaft housed within the housing and driven by the electric motor, and a first impeller and a second impeller rotating integrally with the rotating shaft are provided, wherein the electric motor, the first impeller, and the second impeller are arranged in this order along the axial direction of the rotating shaft, the first impeller has a first hub fixed to the rotating shaft and a plurality of first blades arranged on the first hub, the second impeller has a second hub fixed to the rotating shaft and a plurality of second blades arranged on the second hub, the first impeller conveys gas from the front end to the rear end of the first blade by rotation, and the second impeller conveys the gas conveyed by the first impeller from the front end to the rear end of the second blade by rotation, and the housing is opposite to the first blade and the An electric turbo compressor comprising a first shroud forming a first impeller chamber that accommodates a first impeller, and a second shroud forming a second impeller chamber that accommodates the second impeller while facing the second blade, wherein the gap between the rear end of the first blade and the first shroud is set as a first rear end gap that is the shortest distance between the first blade and the first shroud, and the gap between the rear end of the second blade and the second shroud is set as a second rear end gap that is the shortest distance between the second blade and the second shroud, such that the first rear end gap is smaller than the second rear end gap. Claim 2 An electric turbo compressor according to claim 1, wherein the height of the rear end of the first blade facing the first rear end gap is set as the first outlet height and the height of the rear end of the second blade facing the second rear end gap is set as the second outlet height, and the first outlet height is higher than the second outlet height. Claim 3 An electric turbo compressor according to claim 1 or 2, wherein the outer diameter of the first impeller is larger than the outer diameter of the second impeller. Claim 4 An electric turbo compressor according to claim 1 or 2, wherein the gap between the front of the first blade and the first shroud is a first front gap that is the shortest distance between the first blade and the first shroud, and the gap between the front of the second blade and the second shroud is a second front gap that is the shortest distance between the second blade and the second shroud, such that the first front gap is smaller than the second front gap. Claim 5 An electric turbo compressor according to claim 1 or 2, which compresses a refrigerant circulating in a refrigeration cycle.

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