JP2011202589A - Centrifugal compressor - Google Patents

Abstract

PROBLEM TO BE SOLVED: To increase the efficiency of a centrifugal compressor by effectively using the compressed air generated by the rotation of a rotating shaft unit as far as possible.SOLUTION: A compressed air flow passage 76 allowing a compressed air to flow therethrough in contact with the outer surface of a rotor 20, an introduction side passage 78 which allows the compressed air to flow therethrough along the outer peripheral side of an impeller side bearing holder 57A and one end of which communicates with the gap S between the outer peripheral end 26a of an impeller 26 and a scroll 70 and the other end of which communicates with the inlet side of the compressed air flow passage 76, and a lead-out side passage 80 which is provided to a thrust canceller side bearing holder 57B and one end of which communicates with the outlet side of the compressed air flow passage 76 and the other end of which communicates with a canceller chamber 36 are formed in a casing 12 which constitutes the centrifugal compressor 10.

Description

  The present invention relates to a centrifugal compressor in which a rotor unit provided with a permanent magnet, a pair of bearing shafts, an impeller, and a rotary shaft unit provided with a thrust canceller shaft are accommodated in a casing.

  In general, a centrifugal compressor is employed as a supercharger that efficiently supplies compressed air. For example, various centrifugal compressors are used as an auxiliary machine that supplies compressed air to an engine or an auxiliary machine that supplies compressed air that is an oxidant gas to a fuel cell.

  In this type of centrifugal compressor, impellers are provided on both sides of the rotating shaft, and there is a problem that the entire centrifugal compressor is increased in size and weight. For this reason, in order to reduce the size and cost of the centrifugal compressor, a configuration in which an impeller is provided only on one of the rotating shafts is employed.

  For example, in the electric compressor disclosed in Patent Document 1, as shown in FIG. 7, an impeller 2, a rotating shaft 3, a thrust canceller 4, and a motor unit 5 are built in a housing 1. The rotary shaft 3 is pivotally supported by a thrust air bearing 6a and a radial air bearing 6b.

  Therefore, when the rotational speed of the impeller 2 increases, a thrust load is generated on the rotating shaft 3, while the pressure of the compressed air acts on the pressure chamber 7 from the compressed air outlet 8 through the compressed air passage 9. . For this reason, the pressure of the compressed air acts on the canceller shaft 4a, and the thrust load is canceled by causing the rotating shaft 3 to generate a load toward the rear.

JP 2009-257165 A

  By the way, since the impeller 2 rotates, a gap is formed between the outer peripheral end 2a of the impeller 2 and the scroll 1a constituting the housing 1. Therefore, when the impeller 2 rotates at a relatively high speed, the compressed air tends to leak into the housing 1 from the gap between the outer peripheral end 2a of the impeller 2 and the scroll 1a. The leaked compressed air is discharged to the outside without being used at all, and it is desired to improve the pump efficiency by effectively using the compressed air.

  The present invention responds to this type of request, and is a centrifugal compressor capable of effectively using as much as possible compressed air generated by the rotation of the rotary shaft unit and improving efficiency. The purpose is to provide.

  The present invention is provided with a rotor provided with a permanent magnet, a pair of bearing shafts provided at both axial ends of the rotor, an impeller provided at an end of one of the bearing shafts, and an end of the other bearing shaft. A rotating shaft unit comprising a thrust canceller shaft, a stator facing the outer peripheral surface of the rotor, an impeller side bearing holder and a thrust canceller side bearing holder for holding a pair of bearing shafts, a scroll in which the impeller is housed, The present invention relates to a centrifugal compressor including a canceller chamber in which a thrust canceller shaft is accommodated, and a casing provided with a central casing in which a pair of bearing shafts and a stator are accommodated.

  In the housing, a compressed air flow passage through which compressed air is circulated in contact with the outer surface of the rotor, the compressed air is circulated along the outer peripheral side of the impeller side bearing holder, and one end side is an outer peripheral end of the impeller An inlet side passage that communicates with a gap between the scroll and the other end side communicates with an inlet side of the compressed air flow passage, a thrust canceller side bearing holder, and one end side communicates with an outlet side of the compressed air flow passage and A lead-out side passage having the other end communicating with the canceller chamber is formed.

  The compressed air flows from the gap toward the introduction side passage, the compressed air flow passage, the outlet side passage, and the canceller chamber.

  The impeller side bearing holder is preferably provided with an inclined guide surface that is inclined toward the rotor side and guides the compressed air flowing through the introduction side passage toward the inlet side of the compressed air flow passage.

  Further, it is preferable that the casing forms a refrigerant flow path along the outer periphery of the stator, and the introduction side passage has a cooling passage portion extending along the outer periphery of the refrigerant flow path.

  Furthermore, it is preferable that the pair of bearing shafts constitute a gas bearing.

  In the present invention, a part of the compressed air generated when the impeller rotates is introduced into the introduction-side passage through the gap between the outer peripheral end of the impeller and the scroll. The compressed air flows along the outer peripheral side of the impeller side bearing holder, is introduced into the compressed air flow passage, and flows in contact with the outer surface of the rotor. Further, the compressed air flows from the outlet side passage provided in the thrust canceller side bearing holder to the canceller chamber.

  Accordingly, the compressed air leaking from the gap between the outer peripheral end of the impeller and the scroll can be used as cooling air for cooling the pair of bearing shafts and the rotor, and is introduced into the canceller chamber to generate the canceller pressure. It can be used as pressurized air. Thereby, the compressed air generated by the rotation of the rotary shaft unit can be effectively used as much as possible, and the efficiency of the entire centrifugal compressor can be easily improved.

It is a section explanatory view of the centrifugal compressor concerning a 1st embodiment of the present invention. It is principal part sectional explanatory drawing of the said centrifugal compressor. It is the III-III sectional view taken on the line of the centrifugal compressor in FIG. It is a perspective explanatory view of a thrust air bearing constituting the centrifugal compressor. FIG. 5 is a sectional view of the thrust air bearing taken along line VV in FIG. 4. It is a section explanatory view of the centrifugal compressor concerning a 2nd embodiment of the present invention. It is explanatory drawing of the electric compressor currently disclosed by patent document 1. FIG.

  As shown in FIG. 1, the centrifugal compressor (electric centrifugal compressor) 10 according to the first embodiment of the present invention includes a housing 12. A rotating shaft unit 14 is rotatably mounted in the housing 12.

  As shown in FIGS. 1 and 2, the rotary shaft unit 14 is provided with an annular permanent magnet 16 and a cylindrical shape that is provided on the outer periphery of the permanent magnet 16 and accommodates (for example, shrink fit) the permanent magnet 16. The rotor 20 constituted by the protective ring 18, at least one of axial end portions of the rotor 20, in the first embodiment, bearing shafts 22, 24 provided on both, the rotor shaft 20 side of the bearing shaft 22 And an impeller 26 provided at the opposite axial end.

  The impeller 26 constitutes a centrifugal compression part 28 and an end surface thereof abuts on the large diameter part 30 a of the tension shaft 30. On the tension shaft 30, the bearing shaft 22, the rotor 20, and the bearing shaft 24 are arranged in this order from the impeller 26 side, and these are integrally held by a fixing member 32 that is screwed into the tension shaft 30.

  The fixed member 32 is provided with a canceller mechanism 34 having a function of reducing a thrust force generated in the direction of the arrow A1 when the rotary shaft unit 14 rotates. As shown in FIG. 1, the canceller mechanism 34 includes a thrust canceller shaft 38 that can slide in a canceller chamber (pressurizing chamber) 36 in the direction of arrow A.

  An annular stator 42 is mounted in the casing 12 so as to be positioned on the outer periphery of the rotor 20. The stator 42 and the rotor 20 constitute a motor unit 46.

  The protection ring 18 constituting the rotor 20 is required to have high rigidity and is made of a nickel-based superalloy, for example, Inconel (trade name of Special Metal). A plurality of cooling water flow paths (refrigerant flow paths) 48 are formed around the outer periphery of the stator 42.

  As shown in FIG. 2, the protection ring 18 is provided with cylindrical protrusions 18 a and 18 b protruding outward in the axial direction from the end surfaces 16 a and 16 b of the permanent magnet 16 on the end surfaces where the bearing shafts 22 and 24 are provided.

  The bearing shaft 22 has a cylindrical portion 22a opened at one end in the axial direction, and forms a bottom portion 22b protruding radially inward at the other end in the axial direction. Similarly, the bearing shaft 24 has a cylindrical portion 24a opened at one axial end and a bottom 24b projecting radially inward at the other axial end.

  The bottom 22b of the bearing shaft 22 is in contact with one cylindrical protrusion 18a of the protection ring 18, and the bottom 24b of the bearing shaft 24 is in contact with the other cylindrical protrusion 18b of the protection ring 18. The bottom portions 22b and 24b and the end surfaces 16a and 16b of the permanent magnet 16 are separated by distances S1 and S2, respectively.

  A foil type gas bearing 50 is provided which faces the outer peripheral surfaces of the bearing shafts 22 and 24 and holds the bearing shafts 22 and 24. The foil type gas bearing 50 includes journal air bearings 52 a and 52 b that hold the radial positions of the bearing shafts 22 and 24, and a thrust air bearing 54 that holds the axial position of the bearing shaft 22.

  The bearing shafts 22 and 24 constitute journal air bearings 52a and 52b, and are made of, for example, a nickel-based superalloy that is the same material as the protective ring 18. Each of the journal air bearings 52a and 52b includes ring members 56A and 56B that are arranged with a predetermined gap around the outer periphery of the bearing shafts 22 and 24.

  The ring members 56A, 56B rotatably support the bearing shafts 22, 24, and are fixed to the impeller side bearing holder 57A and the thrust canceller side bearing holder 57B so as not to rotate. The impeller side bearing holder 57A and the thrust canceller side bearing holder 57B are provided with inclined guide surfaces 57a and 57b which are inclined in a tapered shape or an arc shape toward the rotor 20 side.

  As shown in FIG. 3, the corrugated bump foil 58 and the flat top foil 60 are arranged in this order on the inner peripheral surface 56 a of the ring member 56 </ b> A. The bump foil 58 is composed of one sheet or a plurality of sheets. One end 58a of the bump foil 58 is welded to the inner peripheral surface 56a of the ring member 56A, and the other end forms a free end. The top foil 60 has a flat plate curved in an annular shape, and one end 60a is welded to the inner peripheral surface 56a of the ring member 56A, while the other end is a free end. The ring member 56B is configured similarly to the ring member 56A described above.

  As shown in FIGS. 1 and 2, a large-diameter flange portion 62 constituting a thrust air bearing 54 is provided on the outer peripheral portion of the bearing shaft 22. Ring members 64a and 64b are arranged on both sides in the axial direction across the large-diameter flange portion 62.

  As shown in FIG. 4, the ring members 64 a and 64 b are provided with a corrugated bump foil 66 and a flat top foil 68 on the surfaces facing the large-diameter flange portion 62. A plurality of the bump foil 66 and the top foil 68 are arranged in an annular shape around the inner peripheral surfaces of the ring members 64a and 64b.

  As shown in FIG. 5, each bump foil 66 has one end 66a welded to the ring members 64a and 64b and the other end 66b constituting a free end. Each top foil 68 has one end 68a welded to the ring members 64a and 64b, while the other end 68b is a free end.

  As shown in FIG. 2, the outer peripheral end (axial end) 26 a of the impeller 26 is fitted coaxially with the cylindrical portion 22 a of the bearing shaft 22 (inlay structure). As for the bearing shafts 22 and 24, each bottom part 22b and 24b fits coaxially to the cylindrical projection parts 18a and 18b of the protection ring 18 (inlay structure).

  The housing 12 is provided with a scroll 70 in which the impeller 26 is accommodated, a canceller chamber 36 in which a thrust canceller shaft 38 is accommodated, a central casing 72 in which a pair of bearing shafts 22 and 24 and a stator 42 are accommodated, and the scroll. 70 is provided with a compressor outlet 74.

  As shown in FIGS. 1 and 2, in the housing 12, the compressed air flow passage 76 through which the compressed air flows in contact with the outer surface of the rotor 20 and the outer peripheral side of the impeller side bearing holder 57A are described above. The compressed air is circulated, an introduction side passage 78 having one end side communicating with the clearance S between the outer peripheral end 26a of the impeller 26 and the scroll 70, and the other end side communicating with the inlet side of the compressed air flow passage 76, a thrust Provided in the canceller side bearing holder 57 </ b> B is formed an outlet side passage 80 having one end communicating with the outlet side of the compressed air flow passage 76 and the other end communicating with the canceller chamber 36.

  The impeller side bearing holder 57A is formed with a passage portion 82 constituting the introduction side passage 78, while the thrust canceller side bearing holder 57B is formed with a passage portion 84 constituting the outlet side passage 80.

  The operation of the centrifugal compressor 10 configured as described above will be described below.

  First, by energizing the stator 42 constituting the electric motor, the permanent magnet 16 and the protective ring 18 constituting the rotor 20 rotate integrally with the tension shaft 30. For this reason, the impeller 26 held by the tension shaft 30 rotates at a relatively high speed, and air is sucked from the atmosphere via the centrifugal compressor 28.

  The air sucked by the impeller 26 is pumped by the centrifugal compressor 28 and is sent to, for example, an oxidant gas supply system of a fuel cell (not shown). Fuel gas (hydrogen gas) is supplied to the fuel cell from a fuel gas supply system (not shown). Therefore, power generation is performed by a reaction between air supplied to the cathode side and hydrogen supplied to the anode side.

  In this case, in the first embodiment, a part of the air sucked by the centrifugal compressor 28 is introduced into the gap S between the outer peripheral end 26a of the impeller 26 and the scroll 70, and the introduction side passage communicating with the gap S is provided. 78 is distributed. In the introduction side passage 78, the compressed air flows along the outer peripheral side of the impeller side bearing holder 57A, and passes through the passage portion 82 under the guiding action of the inclined guide surface 57a formed in the impeller side bearing holder 57A. It circulates toward the rotor 20 side.

  The introduction side passage 78 communicates with the inlet side of the compressed air flow passage 76. For this reason, the compressed air cools the outer surface of the rotor 20 while moving in the arrow A2 direction along the compressed air flow passage 76. The outlet side passage 80 communicates with the outlet side of the compressed air flow passage 76, and the compressed air passes from the inclined guide surface 57 b of the thrust canceller side bearing holder 57 B through the passage portion 84 to the canceller chamber of the canceller mechanism 34. 36.

  Therefore, the compressed air generates a canceller pressure in the canceller chamber 36, and the thrust canceller shaft 38 is urged in the direction of the arrow A2 in the canceller chamber 36. For this reason, the thrust force generated in the direction of the arrow A1 when the rotary shaft unit 14 rotates is effectively reduced.

  As described above, in the first embodiment, when the impeller 26 rotates, the compressed air leaked from the clearance S between the outer peripheral end 26a of the impeller 26 and the scroll 70 is the bearing shaft 22, the rotor 20, and the bearing shaft 24. Can be used as cooling air for cooling the air, and can also be used as pressurized air that is introduced into the canceller chamber 36 to generate a cancel pressure.

  Thereby, the compressed air generated by the rotation of the rotary shaft unit 14 can be effectively used as much as possible, and the effect of easily improving the efficiency of the entire centrifugal compressor 10 can be obtained.

  Further, the pressure inside the housing 12 is maintained at the same pressure as the pressure inside the canceller chamber 36. For this reason, the viscosity of air rises, and in particular, the foil type gas bearing 50 has the advantage that the ability to form an air film is improved and it can contribute to stable rotation.

  FIG. 6 is a cross-sectional explanatory view of a centrifugal compressor 90 according to the second embodiment of the present invention.

  In addition, the same referential mark is attached | subjected to the component same as the centrifugal compressor 10 which concerns on 1st Embodiment, and the detailed description is abbreviate | omitted.

  The centrifugal compressor 90 includes a housing 92. In the housing 92, one end side communicates with the gap S between the outer peripheral end 26a of the impeller 26 and the scroll 70, and the other end side is a compressed air flow passage 76. An introductory side passage 94 is formed which communicates with. The introduction side passage 94 has a cooling passage portion 94 a extending along the outer periphery of the cooling water passage 48. The cooling passage portion 94a extends in the arrow A2 direction on the outer periphery of the cooling water passage 48, and then turns back and extends in parallel with the arrow A1 direction.

  In the second embodiment configured as described above, the same effects as those of the first embodiment described above can be obtained, and in particular, the compressed air introduced into the introduction side passage 94 is placed on the outer periphery of the cooling water passage 48. It circulates through the cooling passage portion 94a extending along. Therefore, the compressed air is once cooled by flowing through the cooling passage portion 94 a and then supplied from the introduction side passage 94 to the compressed air flow passage 76. For this reason, the compressed air immediately before cooling the bearing shaft 22, the rotor 20, and the bearing shaft 24 can be cooled in advance, and the cooling effect by the compressed air is further improved.

DESCRIPTION OF SYMBOLS 10, 90 ... Centrifugal compressor 12, 92 ... Case 14 ... Rotating shaft unit 16 ... Permanent magnet 18 ... Protective ring 20 ... Rotor 22, 24 ... Bearing shaft 22a, 24a ... Cylindrical shape part 22b, 24b ... Bottom part 26 ... Impeller 30 ... Tension shaft 32 ... Fixing member 34 ... Cancer mechanism 36 ... Cancer chamber 38 ... Thrust canceller shaft 42 ... Stator 46 ... Motor 48 ... Cooling water flow path 50 ... Foil type gas bearings 52a, 52b ... Journal air bearing 54 ... Thrust Air bearing 56A, 56B ... Ring member 57A ... Impeller side bearing holder 57a, 57b ... Inclined guide surface 57B ... Thrust canceller side bearing holder 56a ... Inner peripheral surface 58, 66 ... Bump foil 60, 68 ... Top foil 70 ... Scroll 72 ... Central casing 7 ... compressed air channels 78,94 ... introduction side passage 80 ... outlet side passage 82, 84 ... passage 94a ... cooling passage

Claims (4)

A rotor provided with a permanent magnet, a pair of bearing shafts provided at both axial ends of the rotor, an impeller provided at one end of the bearing shaft, and a thrust canceller shaft provided at an end of the other bearing shaft A rotating shaft unit comprising:
A stator facing the outer peripheral surface of the rotor;
An impeller side bearing holder and a thrust canceller side bearing holder for holding the pair of bearing shafts;
A housing for providing a scroll for storing the impeller, a canceller chamber for storing the thrust canceller shaft, and a central casing for storing the pair of bearing shafts and the stator;
A centrifugal compressor comprising:
In the housing, a compressed air flow passage through which compressed air flows in contact with the outer surface of the rotor;
The compressed air flows along the outer peripheral side of the impeller side bearing holder, one end side communicates with the gap between the outer peripheral end of the impeller and the scroll, and the other end side communicates with the inlet side of the compressed air flow passage. An introductory passage to
An outlet side passage provided in the thrust canceller side bearing holder, one end side communicating with the outlet side of the compressed air flow passage and the other end side communicating with the canceller chamber;
Is formed, and the compressed air flows from the gap toward the introduction side passage, the compressed air flow passage, the outlet side passage, and the canceller chamber.   2. The centrifugal compressor according to claim 1, wherein the impeller side bearing holder is inclined toward the rotor side and guides the compressed air flowing through the introduction side passage toward an inlet side of the compressed air flow passage. A centrifugal compressor characterized in that an inclined guide surface is provided. The centrifugal compressor according to claim 1 or 2, wherein the casing forms a refrigerant flow path along an outer periphery of the stator.
The centrifugal compressor according to claim 1, wherein the introduction side passage has a cooling passage portion extending along an outer periphery of the refrigerant flow path.   The centrifugal compressor according to any one of claims 1 to 3, wherein the pair of bearing shafts constitute a gas bearing.

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