RADIAL COMPRESSOR IMPELLER INCLUDING A SHROUD AND AERODYNAMIC BEARING BETWEEN SHROUD AND HOUSING

Abstract

A compressor for a heat pump circuit and/or a refrigerating system circuit, including a housing and a rotor rotatably supported around a rotation axis, the housing being situated at least partially on the circumference of the rotor, the rotor including at least one hub and at least one blade situated radially on the outside of the hub, the blade being designed to convey a main fluid flow, the rotor including a shroud situated radially on the outside of the blade, the shroud being situated radially spaced apart from the housing, a bearing structure being provided radially on the outside of the shroud, the bearing structure is designed to form a bearing fluid flow between the shroud and the housing in order to form a fluid-dynamic bearing for supporting the rotor in the housing.

Description

FIELD

The present invention relates to a compressor for a heat pump circuit and/or a refrigerating system circuit, including a housing and a rotor rotatably supported around a rotation axis, the housing being situated at least partially on the circumference of the rotor, the rotor including at least one hub and at least one blade situated radially on the outside of the hub, the blade being designed to convey a main fluid flow, the rotor including a shroud situated radially on the outside of the blade, the shroud being situated radially spaced apart from the housing, a bearing structure being provided radially on the outside of the shroud, the bearing structure being designed to form a bearing fluid flow between the shroud and the housing in order to form a fluid-dynamic bearing for supporting the rotor in the housing.

BACKGROUND INFORMATION

Compressors for heat pump circuits and/or refrigerating system circuits have a rotor which is rotatably supported with the aid of roller bearings or plain bearings and is driven by a drive unit. The compressors are thereby designed to apply pressure to a fluid from an input side toward an output side and thus to compress the fluid.

It is an object of the present invention to provide an improved compressor which has a particularly good support and at the same time may be manufactured particularly cost-efficiently.

SUMMARY

According to the present invention, it has been found that an improved compressor may be provided, that the compressor includes a housing and a rotor rotatably supported around a rotation axis. In an example embodiment, the housing is situated at least partially on the circumference of the rotor. The rotor has at least one hub and at least one blade situated radially on the outside of the hub. The blade is designed to convey a main fluid flow. The rotor has a shroud situated radially on the outside of the blade. The shroud is situated radially spaced apart from the housing. A bearing structure is provided radially on the outside of the shroud and is designed to form a bearing fluid flow between the shroud and the housing to form a fluid-dynamic bearing for supporting the rotor in the housing.

This design may have the advantage that a fluid-dynamic support of the rotor in the housing may be provided and thus conventional plain bearings and roller bearings may be omitted. Thus, a particularly quiet support of the rotor is provided which is particularly cost-efficient and at the same time also has a particularly long service life.

In another specific embodiment, the rotor has an input side and an output side. The blades are designed to convey the main fluid flow from the input side to the output side. The bearing structure is designed to convey the fluid flow from the output side to the input side. In this way, it may be ensured that, at a pressure increase between the input side and the output side in the main fluid flow, this main fluid flow lifts the bearing fluid flow and thus a reliable fluid-dynamic support of the rotor is ensured. In addition, a particularly reliable support may thereby be ensured even at low rotational speeds of the rotor.

In another specific embodiment, the input side is situated radially on the inside and the output side is situated radially on the outside of the rotor, the bearing structure being designed to be at least partially helical. This design has the advantage that a particularly smooth bearing fluid flow may be provided, which rotates in the circumferential direction and is also conveyed in the axial direction in the direction of the input.

In another specific embodiment, the bearing structure includes a sealing element, the sealing element being situated between the shroud and the housing, the sealing element being designed to delimit the bearing fluid flow in the axial direction. In this way, it may be ensured that the compressor has a particularly high efficiency and the bearing fluid flow does not unnecessarily reduce the delivery volume of the compressor.

It is hereby particularly advantageous if the sealing element is designed as a labyrinth seal.

In another specific embodiment, the bearing structure is designed in a fishbone pattern and/or the bearing structure has a surface texture (for example, according to EN ISO 25178, previously called roughness) in the range from 1 Rz through 60 Rz. Thus, the bearing structure may be cost-efficiently designed to be flat.

In another specific embodiment, the bearing structure has at least one recess and/or one bulge which is/are situated obliquely or transversely to the circumferential direction of the hub. In this way, a particularly high circumferential speed of the bearing fluid flow may be reached. Thus, a particularly stable support of the rotor in the housing may be ensured.

In another specific embodiment, the rotor has a second hub, at least one second blade being provided situated radially on the outside of the second hub. The second blade is designed to convey a second main fluid flow. The second hub is coupled to the hub via a shaft. The rotor includes a second shroud situated radially on the outside of the second blade. The second shroud is situated radially spaced apart from the housing. The housing encompasses the second shroud at least partially on the circumferential side. A second bearing structure is provided radially on the outside of the second shroud and is designed to provide a second bearing fluid flow between the second shroud and the housing. This design has the advantage that the rotor is axially fixed in its defined position by the two structures situated diametrically opposite without second bearing structures having to be provided for this purpose.

It is thereby particularly advantageous if the second bearing structure and the bearing structure are designed axis-symmetrically to an axis of symmetry situated between the two hubs. It may thus be prevented that different axial bearing forces are generated by the bearing structure and the second bearing structure, which would result in an unbalanced orientation of the rotor in the compressor.

In another specific embodiment, at least one magnet is situated between the two hubs, the magnet being connected in a torque-locked manner with the shaft. At least one coil ring is provided radially on the outside of the shaft to provide an alternating magnetic field, the alternating magnetic field being designed to engage in operative connection with the magnet in order to generate a rotational movement of the rotor. Thus, the rotor may be driven particularly easily.

The present invention will be subsequently explained in greater detail based on the figures.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 shows a schematic sectional view through a compressor according to a first specific embodiment.

FIG. 2 shows a section of the sectional view shown in FIG. 1.

FIG. 3 shows a sectional view through the compressor shown in FIGS. 1 through 2 along a section plane A-A shown in FIG. 1.

FIG. 4 shows a schematic sectional view through a compressor according to a second specific embodiment.

FIG. 5 shows a schematic sectional view through a compressor according to a third specific embodiment.

DETAILED DESCRIPTION OF EXAMPLE EMBODIMENTS

FIG. 1 shows a sectional view through a compressor 10 according to a first specific embodiment and FIG. 2 shows a section of the sectional view shown in FIG. 1. FIG. 3 shows a sectional view through compressor 10 shown in FIGS. 1 through 2 along a section plane A-A shown in FIG. 1. Compressor 10 includes a rotor 15 and a housing 20. Housing 20 includes a first housing part 25 which is situated on the left in FIGS. 1 and 2. Housing 20 further includes a second housing part 30 situated on the right in FIG. 1. Rotor 15 is coupled to a drive unit 35. Rotor 15 includes a shaft 40 which is connected to drive unit 35. Shaft 40 is thereby rotatable around a rotation axis 45.

Compressor 10 has an input side 50 and an output side 55. Input side 50 is designed as a single channel in the specific embodiment, input side 50 then branching into two feed channels 51. The two feed channels 51 are thus switched in parallel with respect to their flow. It is, of course, also possible that compressor 10 has multiple different input sides 50 with corresponding feed channels 51 separated from each other. Thus, feed channels 51 may also be switched in series with respect to their flow, output side 55 of a first rotor section 110 emptying into input side 50 of a second rotor section 115. Rotor 15 is designed to convey a fluid 60 from input side 50 to output side 55 and to thereby increase a pressure p₁ prevailing at the input side to a pressure p₂ prevailing at the output side. Fluid 60 may thereby be a coolant, for example, CO₂, R-134a, or R-410a. Other fluids are, of course, also possible. Here, fluid 60 is present in its gaseous phase or its liquid phase. Compressor 10 may be a turbo compressor for a refrigerating system circuit and/or heat pump circuit. Of course, another application is also possible. Thus, it is possible to use compressor 10 in a heating circuit including a solar collector and to convey the fluid present in the heating circuit with the aid of compressor 10.

Rotor 15 has first rotor section 110 situated on the left of drive unit 35 and second rotor section 115 situated on the right of drive unit 35. First rotor section has a first hub 65, first blades 70, and a first shroud 75. First blades 70 are thereby situated radially on the outside of first hub 65 and extend from radially inside to radially outside. First blades 70 are thereby situated on first hub 65 at a uniform distance from each other in the circumferential direction. First shroud 75 is joined radially on the outside with first blades 70. First shroud 75 is situated radially spaced apart from first housing part 25. First housing part 25 encompasses first shroud 75 on the circumferential side and is formed on an inner first housing surface 76 facing shroud 75, which corresponds to an outer circumferential surface 77 of first shroud 75. Due to the spaced arrangement, a first gap 80 with a gap width s₁ is provided between first housing part 25 and first shroud 75. First shroud 75 and first hub 65 delimit a first conveying channel 85. Due to the cone-shaped design of first hub 65 and the likewise cone-shaped design of first shroud 75, first conveying channel 85 runs in the axial direction from input side 50 to drive unit 35 radially from the inside to the outside, and has a cross section tapering radially outwardly.

First blades 70 are thereby designed to suction fluid 60 radially inwardly and to convey it during operation in the axial direction in the direction of output side 55 or drive unit 35. In order to further increase the pressure, rotor 15 is designed as a radial compressor and conveys fluid 60 radially from the inside to the outside, pressure p increasing from input side 50 toward output side 55. To prevent an imbalance of rotor 15, first hub 65 and first shroud 75 are designed to be rotationally symmetrical to rotation axis 45. First blades 70 are further situated on first hub 65 at uniform spacing in the circumferential direction.

Rotor 15 has a second hub 90, second blades 95, and a second shroud 100. Second hub 90 is thereby situated on the right side, diametrically opposite to hub 65 situated on the left side. Second blades 95 are provided radially on the outside of second hub 90. Second shroud 100 is connected to second blades 95 radially on the outside of the ends of blades 95 diametrically opposite to second hub 90. Second shroud 100 is spaced apart from second housing part 30 via a second gap 105 with a gap width s₂. An inner second housing surface 108, which faces an outer circumferential surface 107 of second shroud 100, is formed corresponding to outer circumferential surface 107 of second shroud 100. Second hub 90 has a conical shape like second shroud 100. Second shroud 100 and second hub 90 delimit a second conveying channel 106. Second conveying channel 106 is guided radially from the inside radially to the outside in an axial direction from input side 50 toward drive unit 35. Second conveying channel 106 is also designed to taper from input side 50 toward output side 55. It is, of course, also possible that conveying channels 85, 106 also have a constant or expanding cross section. To prevent an imbalance of rotor 15, second hub 90 and second shroud 100 are also provided rotationally symmetrically to rotation axis 45. Second blades 95 are further situated on second hub 90 at a uniform spacing in the circumferential direction. Second blades 95 are also used like first blades 70 for the purpose of conveying fluid 60 from input side 50 toward output side 55 through second conveying channel 106 and thereby apply pressure p to fluid 60.

In the specific embodiment, rotor section 110 situated on the left side of drive unit 35 is formed axially symmetrically to second rotor section 115 situated on the right side of the drive unit and to an axis of symmetry 120 situated between both rotor sections 110, 115. Each rotor section 110, 115 is connected to an assigned feed channel 51 of input side 50.

Of course, an asymmetrical design of rotor 15 is also possible. If compressor 10 has multiple input sides 50, then, for example, one input side 50 may each be assigned to each rotor section 110, 115. Due to an asymmetrical design of rotor 15, rotor 15 may be adjusted to different input sides 50.

Drive unit 35 has at least one magnet 125 which is situated between both rotor sections 110, 115 and is connected in a torque-locked manner to shaft 40. Further, drive unit 35 includes a coil ring 130 including multiple coils 155 and which encompasses the circumferential side of shaft 40 in the area of magnets 125. Coil ring 130 is connected to a control unit 140 via a connection 135. Control unit 140 is connected to an energy source 150 via a second connection 145. Control unit 140 is designed to energize the coils 155 situated in coil ring 130 in such a way that an alternating magnetic field is provided by coil ring 130 which engages in operative connection with magnets 125 and causes a rotation of shaft 40 in order to shift rotor 15 into a rotation.

When rotor 15 rotates around rotation axis 45, then a first main fluid flow 160 is conveyed by first blades 70 from input side 50 to output side 55 via first conveying channel 85. First main fluid flow 160 is guided due to the design of first blades 70 radially from inside to outside and pressure P₂ is applied in the process. Pressure P₂ at output side 55 is thus higher than at input side 50.

In second rotor section 115, the delivery is carried out analogous to first rotor section 110. In second rotor section 115, a second main fluid flow 161 is conveyed with the aid of second blades 95 in the axial direction of drive unit 35 and radially from inside to outside and the pressure is applied.

Due to the pressure difference between output side 55 and input side 50, fluid 60, compressed in output side 55, flows into first and second gap 80, 105 as first and second bearing fluid flow 165, 166 between shrouds 75, 100 and housing parts 25, 30. Gap width s₁, s₂ is thereby selected in such a way that bearing fluid flow 165, 166 between housing part 25, 30 and shroud 75, 100 is smaller than main fluid flow 160, 161. The flow direction of bearing fluid flow 165, 166 is from output side 55 in the direction of input side 50.

A bearing structure 170, 175 is provided circumferentially on shroud 75, 100 on an outer circumferential surface facing housing part 25, 30. Bearing structure 170, 175 accelerates bearing fluid flow 165, 166 flowing into gap 80, 105 in the direction of rotation of rotor 15. A fluid film 176 thereby forms between housing part 25, 30 and shroud 75, 100. Bearing structure 170, 175 may thereby be designed differently in order to accelerate bearing fluid flow 165, 166 in the circumferential direction. Thus, bearing structure 170, 175 may be provided with a surface texture. In FIGS. 1 through 3, the acceleration is generated with the aid of the surface texture of shroud 75, 100. Depending on the speed, a surface texture in the range of 1 Rz through 60 Rz is thereby sufficient. It is also alternatively possible that surface structure 170, 175 has bulges (compare FIG. 5) and/or recesses (compare FIG. 4), which are designed to convey bearing fluid flow 165, 166 in the circumferential direction. Thus, bearing fluid flow 165, 166 has a speed component in the axial direction and also in the circumferential direction, the speed component prevailing in the circumferential direction.

If bearing fluid flow 165 is brought to a predefined speed in the circumferential direction by rotation of rotor 15, a pressure cushion 185 of fluid film 176 or of bearing fluid flow 165, 166 builds up at first/second shroud 75, 100 with a bearing force P₁, P₂. The curved design of shroud 75, 100 and housing 20 has as a consequence that bearing force P₁, P₂ runs obliquely to individual axes of a coordinate system 190. Coordinate system 190 is designed, for example, as a right angle coordinate system and is to be used for facilitated directional reference of the forces. Thus, bearing force P₁, P₂ has a bearing force P_x1, P_x2 running in the axial direction x and a bearing force P_y1, P_y2 running perpendicularly to rotation axis 45 and to the x-axis. Bearing forces P_y1, P_y2 in the y-direction are thereby oriented counter to a weight force F of rotor 15. If bearing forces P_y1, P_y2 in the y-direction or pressure cushion 185 are strong enough, then rotor 15 lifts and is exclusively supported via pressure cushion 185. Thus, bearing fluid flow 165, 166 forms a fluid-dynamic fluid bearing 180 between first shroud 75 and first housing part 25 and between second shroud 100 and second housing part 30, by which rotor 15 may be supported contact-free in housing 20. This takes place, in particular, if gap width s₁, s₂ of gap 80, 105 is at every point of gap 80, 105 in the range from 1 μm through 30 μm, preferably between 1 μm through 20 μm during operation of compressor 10.

Due to the weight of rotor 15 or also due to other influences, rotation axis 45 is situated offset to a housing axis 195, for example, in the direction of weight force F. Housing axis 195 thereby runs on the x-axis of coordinate system 190. Due to the offset of rotor 15, gap width s₁, s₂ also differs in the circumferential direction during operation of compressor 10, gap width s₁, s₂ being smaller on the under side than on the upper side of rotor 15.

During the start up or the acceleration of rotor 15 to operating rotational speed, i.e., when combined bearing forces P_y1, P_y2 in the y-direction are smaller than weight force F, the underside of bearing structure 170, 175 contacts housing part 25, 30. During the start up, bearing structure 170, 175 forms, together with housing parts 25, 30 respectively, a plain bearing in order to support rotor 15 in housing 20.

Due to the symmetrical design of shrouds 75, 100 and the assigned housing parts 25, 30, and due to the self-adjusting gap widths s₁ and s₂, the axial bearing forces P_x1, P_x2 of both rotor sections 110, 115 cancel each other out since the bearing forces are directed in the diametrically opposite direction due to bearing fluid flow 165, 166 flowing away from axis of symmetry 120 on both sides. Thus, no second axial fixing of rotor 15 in housing 20 is necessary.

After flowing through gap 80, 105, bearing fluid flow 165, 166 is sucked again into the input side of rotor 15 and compressed again together with main fluid flow 160, 161.

Due to the brushless configuration of drive unit 35 and the situation of coil ring 130 spaced apart from shaft 40, rotor 15 may be reliably supported in housing 20 with the aid of bearing fluid flow 165 and an offset of rotation axis 45 of rotor 15 to a housing axis 195, which runs parallel to rotation axis 45, may be compensated for at the same time.

Due to fluid bearing 180, additional plain or roller bearings may be omitted for supporting rotor 15 so that compressor 10 is designed particularly cost efficiently. In addition, a particularly simple support may be provided, in particular for a particularly fast rotating rotor 15. Due to the omission of plain or roller bearings, compressor 10 is designed to be smaller over all, so that compressor 10 has a more compact installation space requirement.

Due to the provision of two rotor sections 110, 115 symmetrical to axis of symmetry 120, additional bearing systems may be completely omitted. In addition, this design has a particularly high delivery rate.

FIG. 4 shows a schematic sectional view through a compressor 200 according to a second specific embodiment. Rotor 15 is represented in section above rotation axis 45 and in a top view below rotation axis 45. Compressor 200 is designed generally identical to compressor 10 shown in FIG. 1. Deviating therefrom, bearing structure 175 has additional recesses 205 situated in a fishbone pattern and situated on shroud 75, 100 at uniform spacing on the circumferential side.

It is pointed out here that rotor 15 in FIG. 4 is designed to be axially symmetrical to axis of symmetry 120, and recesses 205 are also provided on second rotor section 115 situated on the right side (not shown). In addition, recesses 205 may, of course, also be provided as bulges which extend radially outwardly in the direction of housing part 25.

Bearing structure 175 in the specific embodiment is situated in a single row on shroud 75, 100. It is, of course, also possible that multiple rows of bearing structure 175 are provided as recesses 205 or bulges situated in a fishbone pattern on the circumferential side of outer circumferential surface of shroud 75, 100 facing housing part 25, 30. Recesses 205 have one first recess section 206 and one second recess section 207. Recess sections 206, 207 enclose an opening angle α. The opening angle is smaller than 180°. Recess sections 206, 207 are situated in such a way that recesses 205 are open toward the rotational direction of rotor 15. Thus, a particularly high circumferential speed may be induced in bearing fluid flow 165, so that a particularly stable pressure cushion may be formed by bearing fluid flow 165 in the area of recesses 205, which pressure cushion supports rotor 15 particularly well.

FIG. 5 shows a sectional view through a compressor 300 according to a third specific embodiment, rotor 15 being shown in a top view. Compressor 300 is designed generally identical to compressors 10, 200 shown in FIGS. 1 through 4. Deviating therefrom, bearing structure 175 has bulges 305 which are situated helically on shroud 75 on the circumferential side. Bulges 305 are thereby designed to be blade like. Alternatively, bulges 305 may be connected in the circumferential direction to form a screw. Thus, during a counter-clockwise rotation, bearing fluid flow 165 may be conveyed particularly well in the direction of a sealing element 310 of bearing structure 170, 175 situated radially inside on the input side. Sealing element 310 is designed in the specific embodiment as a labyrinth seal, whereby a friction contact between rotor 15 and housing 20 may be prevented. A particularly high efficiency of compressor 300 is thereby ensured. In addition, sealing element 310 has the advantage that bearing fluid flow 165 may be conveyed from output side 55 to input side 50 and may be simultaneously accelerated in the circumferential direction due to the helical design of bulges 305. Simultaneously, bearing fluid flow 165 backs up in front of sealing element 310 so that a pressure p_s may be maintained particularly high within first gap 80. A stable support may thereby already be ensured even at low rotational speeds of rotor 15.

First/second gap 80, 105 is designed to taper from output side 55 toward input side 50 in the specific embodiment. It is, of course, also possible that gap 80, 105 has a constant gap width s₁, s₂ across gap 80, 105.

It is pointed out, that sealing element 310 may be situated also at another position on the circumferential side on housing part 25, 30 or rotor 15 instead of on the input side. It is, of course, also possible that the sealing element is provided on an embodiment of rotor 15 shown in FIG. 1 or 2. It is also possible that sealing element 310 is omitted.

Bearing structure 175 is provided as an example in FIGS. 1 through 4. It is, of course, also possible that bearing structures having another design are provided; however, it is thereby essential that a bearing fluid flow 165 is lifted up by bearing structure 175 which provides a fluid-dynamic bearing point between rotor 15 and housing 20 in order to be able to omit plain or roller bearings for supporting rotor 15.

Drive unit 35 is an example in the specific embodiment. It is, of course, also possible that drive unit 35 may be designed differently. Drive unit 35 shown in FIGS. 1 through 5 has, however, the advantage that, due to the noncontact design of drive unit 35 between shaft 40 and coil ring 130, shaft 40 is displaceable in the radial direction by gap width s₁, s₂ so that, depending on the load of rotor 15, bearing fluid flow 165 may support rotor 15 in the axial and also in the radial direction, regardless of the orientation of compressor 10, 200, 300.

Claims

1-10. (canceled)

11. A compressor for a heat pump circuit or refrigerating system circuit, comprising: a housing;a rotor rotatably supported around a rotation axis, the housing being situated at least partially on the circumference of the rotor, the rotor including at least one hub and at least one blade situated radially on an outside of the hub, the blade being designed to convey a main fluid flow, the rotor including a shroud situated radially on the outside of the blade, the shroud being situated radially spaced apart from the housing; anda bearing structure provided radially outside of the shroud, the bearing structure being designed to form a bearing fluid flow between the shroud and the housing to form a fluid-dynamic bearing for supporting the rotor in the housing.

12. The compressor as recited in claim 11, wherein the rotor includes an input side and an output side, the blade being designed to convey the main fluid flow from the input side toward the output side, the bearing structure being designed to convey the bearing fluid flow from the output side toward the input side.

13. The compressor as recited in claim 12, wherein the input side is situated radially on an inside of the rotor and the output side is situated radially on an outside of the rotor, the bearing structure being at least partially helically.

14. The compressor as recited in claim 12, wherein the bearing structure includes a sealing element, the sealing element being situated between the shroud and the housing, the sealing element being designed to delimit the bearing fluid flow in the axial direction.

15. The compressor as recited in claim 12, wherein the sealing element is designed as a labyrinth seal.

16. The compressor as recited in claim 12, wherein at least one of: i) the bearing structure is designed in a fishbone pattern, and ii) the bearing structure has a surface texture in the range from 1 Rz through 60 Rz.

17. The compressor as recited in claim 12, wherein the bearing structure has at least one of: i) at least one recess, and ii) at least one bulge, situated obliquely or transversely to a circumferential direction of the hub.

18. The compressor as recited in claim 12, wherein the rotor has a second hub, at least one second blade being situated radially on the outside of the second hub, the second blade being designed to convey a second main fluid flow, the second hub being coupled to the hub via a shaft, the rotor including a second shroud situated radially on an outside of the second blade, the second shroud being situated radially spaced apart from the housing, the housing encompassing the second shroud at least partially on a circumferential side, a second bearing structure being provided radially outside of the second shroud and being designed to provide a second bearing fluid flow between the second shroud and the housing.

19. The compressor as recited in claim 18, wherein the second bearing structure and the bearing structure are designed axially symmetrically to an axis of symmetry situated between the hub and the second hub.

20. The compressor as recited in claim 19, wherein at least one magnet is situated on the shaft between the hub and the second hub, the magnet being connected in a torque-locked manner to the shaft, at least one coil ring being provided radially on the outside of the shaft to provide an alternating magnetic field, the alternating magnetic field being designed to engage in operative connection with the magnet in order to induce a rotation of the rotor.