US20230193916A1 - Electric compressor - Google Patents
Electric compressor Download PDFInfo
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- US20230193916A1 US20230193916A1 US17/921,488 US202117921488A US2023193916A1 US 20230193916 A1 US20230193916 A1 US 20230193916A1 US 202117921488 A US202117921488 A US 202117921488A US 2023193916 A1 US2023193916 A1 US 2023193916A1
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- United States
- Prior art keywords
- air bearing
- rotary shaft
- air
- carrying capacity
- load carrying
- Prior art date
- Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
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- 230000002093 peripheral effect Effects 0.000 description 41
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- 230000006835 compression Effects 0.000 description 6
- 238000007906 compression Methods 0.000 description 6
- 238000012986 modification Methods 0.000 description 4
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- 229910000990 Ni alloy Inorganic materials 0.000 description 3
- 230000000694 effects Effects 0.000 description 3
- 239000000463 material Substances 0.000 description 3
- 230000002950 deficient Effects 0.000 description 2
- 229910052751 metal Inorganic materials 0.000 description 2
- 239000002184 metal Substances 0.000 description 2
- 239000007769 metal material Substances 0.000 description 2
- RTAQQCXQSZGOHL-UHFFFAOYSA-N Titanium Chemical compound [Ti] RTAQQCXQSZGOHL-UHFFFAOYSA-N 0.000 description 1
- 229910052782 aluminium Inorganic materials 0.000 description 1
- XAGFODPZIPBFFR-UHFFFAOYSA-N aluminium Chemical compound [Al] XAGFODPZIPBFFR-UHFFFAOYSA-N 0.000 description 1
- 230000015572 biosynthetic process Effects 0.000 description 1
- 230000006866 deterioration Effects 0.000 description 1
- 238000004519 manufacturing process Methods 0.000 description 1
- 239000007787 solid Substances 0.000 description 1
- 239000010935 stainless steel Substances 0.000 description 1
- 229910001220 stainless steel Inorganic materials 0.000 description 1
- 239000010936 titanium Substances 0.000 description 1
- 229910052719 titanium Inorganic materials 0.000 description 1
Images
Classifications
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- F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
- F04—POSITIVE - DISPLACEMENT MACHINES FOR LIQUIDS; PUMPS FOR LIQUIDS OR ELASTIC FLUIDS
- F04D—NON-POSITIVE-DISPLACEMENT PUMPS
- F04D29/00—Details, component parts, or accessories
- F04D29/05—Shafts or bearings, or assemblies thereof, specially adapted for elastic fluid pumps
- F04D29/056—Bearings
- F04D29/057—Bearings hydrostatic; hydrodynamic
-
- F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
- F04—POSITIVE - DISPLACEMENT MACHINES FOR LIQUIDS; PUMPS FOR LIQUIDS OR ELASTIC FLUIDS
- F04D—NON-POSITIVE-DISPLACEMENT PUMPS
- F04D17/00—Radial-flow pumps, e.g. centrifugal pumps; Helico-centrifugal pumps
- F04D17/08—Centrifugal pumps
- F04D17/10—Centrifugal pumps for compressing or evacuating
-
- F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
- F04—POSITIVE - DISPLACEMENT MACHINES FOR LIQUIDS; PUMPS FOR LIQUIDS OR ELASTIC FLUIDS
- F04D—NON-POSITIVE-DISPLACEMENT PUMPS
- F04D25/00—Pumping installations or systems
- F04D25/02—Units comprising pumps and their driving means
- F04D25/06—Units comprising pumps and their driving means the pump being electrically driven
Definitions
- the present invention relates to an electric compressor.
- Patent Literature 1 mentions an electric compressor that includes a housing having therein a space, a rotary shaft accommodated in the housing, an impeller connected to one end of the rotary shaft in an axial direction of the rotary shaft, and a pair of air bearings supporting the rotary shaft such that the rotary shaft is rotatable relative to the housing.
- the rotation of the rotary shaft forms an air film between the outer peripheral surface of the rotary shaft and the air bearings, thereby causing the rotary shaft to float off the air bearings. This allows the air bearings to support the rotary shaft without coming into contact with the rotary shaft.
- Patent Literature 1 Japanese Patent Application Publication No. 2011-188612
- Some of electric compressor may include impellers respectively connected to opposite ends of the rotary shaft.
- the impellers of such electric compressors may provide different compression capacities between the one end and the other end of the rotary shaft due to a difference in size between the impellers, so that the load applied by the rotation of the rotary shaft on the one end of the rotary shaft may be different from the load applied by the rotation of the rotary shaft on the other end of the rotary shaft.
- the present invention which has been made in light of the above-mentioned problem, is directed to providing an electric compressor that is capable of preventing an excess or a deficiency of load carrying capacity of an air bearing relative to a necessary load carrying capacity of the air bearing.
- An electric compressor to improve the above-mentioned problem comprising: a housing having therein a space; a rotary shaft accommodated in the housing; an impeller connected to at least a first end portion of the rotary shaft in an axial direction of the rotary shaft, of the first end portion and a second end portion of the rotary shaft in the axial direction; and a pair of air bearings supporting the rotary shaft such that the rotary shaft is rotatable relative to the housing, wherein a load on the first end portion is larger than a load on the second end portion, the pair of air bearings includes a first air bearing, and a second air bearing supporting the rotary shaft at a position closer to the second end portion of the rotary shaft than the first air bearing is, and a load carrying capacity of the first air bearing is larger than a load carrying capacity of the second bearing.
- the rotary shaft When the rotation of the rotary shaft applies a larger load on the first end portion than on the second end portion because the impeller is connected only to the first end portion, the rotary shaft applies a larger load on the first air bearing than on the second air bearing. Also, when the rotation of the rotary shaft applies a larger load on the first end portion than on the second end portion although the first end portion and the second end portion are respectively connected to impellers, the rotary shaft applies a larger load on the first air bearing than on the second air bearing.
- the first air bearing needs a relatively large load carrying capacity
- the second air bearing needs a relatively small load carrying capacity.
- This load carrying capacity is a maximum load that each air bearing can receive without a deformation and a performance deterioration.
- the load carrying capacity of the first air bearing is larger than the load carrying capacity of the second bearing. This prevents a deficiency of the load carrying capacity of the first air bearing and an excess of the load carrying capacity of the second air bearing. This therefore prevents an excess or a deficiency of the load carrying capacity of each air bearing relative to a necessary load carrying capacity of the air bearing.
- a length of the first air bearing may be preferably greater than a length of the second air bearing in the axial direction, so that the load carrying capacity of the first air bearing may be preferably larger than the load carrying capacity of the second air bearing.
- the length of the first air bearing is greater than the length of the second air bearing in the axial direction, so that a supporting surface of the first air bearing for supporting the rotary shaft is larger than a supporting surface of the second air bearing for supporting the rotary shaft.
- This allows the load carrying capacity of the first air bearing to be larger than the load carrying capacity of the second air bearing just by making a difference in length in the axial direction between the first air bearing and the second air bearing without changing the shapes of the first air bearing and the second air bearing. This therefore easily prevents an excess or a deficiency of the load carrying capacity of each air bearing relative to a necessary load capacity of the air bearings.
- the first air bearing and the second air bearing may have different shapes so that the load carrying capacity of the first air bearing is larger than the load carrying capacity of the second air bearing.
- This disclosure prevents an excess or a deficiency of a load carrying capacity of each air bearing relative to a necessary load carrying capacity of each air bearing.
- FIG. 1 is a schematic sectional view of an electric compressor.
- FIG. 2 is an exploded perspective view of a rotary shaft and a first air bearing.
- FIG. 3 is a sectional view of an air bearing mounted on the rotary shaft.
- FIG. 4 is an enlarged sectional view of the air bearing mounted on the rotary shaft.
- FIG. 5 is a schematic view explaining the length of the first air bearing and the length of a second air bearing.
- FIG. 6 is a sectional view of an air bearing mounted on a rotary shaft according to an example.
- FIG. 7 is a sectional view of an air bearing mounted on a rotary shaft according to another example.
- FIG. 8 is a sectional view of an air bearing mounted on a rotary shaft according to another example.
- FIG. 9 is an exploded perspective view of a rotary shaft and a first air bearing according to another example.
- an electric compressor 10 includes a housing 11 having a cylindrical shape and therein a space, and an electric motor 20 accommodated in the housing 11 .
- the housing 11 includes a first housing member 12 having a plate-like shape and a second housing member 13 having a bottomed-cylindrical shape and connected to the first housing member 12 .
- the first housing member 12 and the second housing member 13 are each made of a metallic material, such as aluminum.
- the second housing member 13 has a bottom wall 13 a having a plate-like shape and a peripheral wall 13 b having a cylindrical shape and extending from an outer peripheral portion of the bottom wall 13 a.
- the first housing member 12 is connected to the second housing member 13 with an opening of the peripheral wall 13 b distant from the bottom wall 13 a closed by the second housing member 13 .
- the first housing member 12 has a housing hole 12 c that is formed through the first housing member 12 in the thickness direction of the first housing member 12 .
- the housing hole 12 c is a circular hole.
- the second housing member 13 has a cylindrical boss 13 c protruding from the inner surface of the bottom wall 13 a.
- the axis of the housing hole 12 c is coaxial with the axis of the boss 13 c.
- the electric motor 20 includes a stator 21 and a rotor 22 .
- the stator 21 includes a cylindrical stator core 21 a that is fixed to the inner peripheral surface of the peripheral wall 13 b of the second housing member 13 , and a coil 21 b that is wound around the stator core 21 a.
- the rotor 22 is rotatably disposed radially inside the stator 21 in the housing 11 .
- the rotor 22 includes a cylindrical member 23 , a permanent magnet 24 as a magnetic body, and a rotary shaft 25 .
- the cylindrical member 23 has a circular cylindrical shape.
- the axis of the cylindrical member 23 corresponds to the axes of the housing hole 12 c and the boss 13 c. In this embodiment, a direction along the axis of the cylindrical member 23 is called an axial direction.
- a direction along the radius of the cylindrical member 23 is called a radial direction.
- the cylindrical member 23 has a first opening 23 a and a second opening 23 b respectively at opposite ends of the cylindrical member 23 in the axial direction.
- the cylindrical member 23 is made of a metallic material, such as titanium.
- the permanent magnet 24 has a solid column shape and is magnetized in the radial direction.
- the permanent magnet 24 is press-fitted in the inner peripheral surface of the cylindrical member 23 so as to be fixed into the cylindrical member 23 .
- the axis of the permanent magnet 24 corresponds to the axis of the cylindrical member 23 .
- the length of the permanent magnet 24 is shorter than that of the cylindrical member 23 in the axial direction.
- the rotary shaft 25 has a column-shaped first shaft portion 26 and a column-shaped second shaft portion 27 respectively located opposite sides in the axial direction with respect to the permanent magnet 24 .
- the first shaft portion 26 and the column-shaped second shaft portion 27 are made of metal, for example.
- the first shaft portion 26 has a first small-diameter shaft portion 26 a, and a first large-diameter shaft portion 26 b having a diameter larger than that of the first small-diameter shaft portion 26 a and aligned with the first small-diameter shaft portion 26 a in the axial direction.
- the axis of the first small-diameter shaft portion 26 a and the axis of the first large-diameter shaft portion 26 b extend along the axial direction.
- the second shaft portion 27 has a second small-diameter shaft portion 27 a, and a second large-diameter shaft portion 27 b having a diameter larger than that of the second small-diameter shaft portion 27 a and aligned with the second small-diameter shaft portion 27 a in the axial direction.
- the axis of the second small-diameter shaft portion 27 a and the axis of the second large-diameter shaft portion 27 b extend along the axial direction.
- the first small-diameter shaft portion 26 a and the second small-diameter shaft portion 27 a have the same diameter.
- the first large-diameter shaft portion 26 b and the second large-diameter shaft portion 27 b have the same diameter.
- the first large-diameter shaft portion 26 b is located in the housing hole 12 c of the first housing member 12 .
- the second large-diameter shaft portion 27 b is located in the boss 13 c.
- the first small-diameter shaft portion 26 a is inserted through the first opening 23 a of the cylindrical member 23 and fixed to the cylindrical member 23 so as to close the first opening 23 a.
- the second small-diameter shaft portion 27 a is inserted through the second opening 23 b of the cylindrical member 23 and fixed to the cylindrical member 23 so as to close the second opening 23 b.
- This configuration allows the first shaft portion 26 and the second shaft portion 27 to be rotatable together with the cylindrical member 23 and the permanent magnet 24 .
- each of the first shaft portion 26 and the second shaft portion 27 i.e., the axis of the rotary shaft 25 , corresponds to the cylindrical member 23 .
- the axis of the rotary shaft 25 is illustrated by the axis L.
- One end of the opposite ends of the first large-diameter shaft portion 26 b in the axial direction is connected to the first small-diameter shaft portion 26 a, and the other end of the opposite ends serves as a first end portion 25 a of the rotary shaft 25 .
- One end of the opposite ends of the second large-diameter shaft portion 27 b in the axial direction is connected to the second small-diameter shaft portion 27 a, and the other end of the opposite ends serves as a second end portion 25 b of the rotary shaft 25 .
- the first end portion 25 a of the rotary shaft 25 is connected to an impeller 32 .
- the impeller 32 includes an impeller shaft 32 a extending in the axial direction, a hub 32 b fixed to an outer peripheral surface of the impeller shaft 32 a and configured to rotate together with the impeller shaft 32 a, and a plurality of vanes 32 c arranged in the circumferential direction of the hub 32 .
- the impeller shaft 32 a extends from the first end portion 25 a of the rotary shaft 25 in the axial direction so that the impeller shaft 32 a protrudes outside the housing 11 .
- the hub 32 b has an approximately conical shape and an outer diameter of the hub 32 b expands as the hub 32 b extends from one side to the other side in the axial direction.
- the vanes 32 c are disposed on the outer surface of the hub 32 b and equally spaced from each other in the circumferential direction of the hub 32 b.
- the first housing member 12 is connected to a compressor housing 31 that has a cylindrical shape and has an inlet 31 a.
- the compressor housing 31 has the inlet 31 a at one end thereof in the axial direction.
- the inlet 31 a extends in the axial direction.
- the other end of the compressor housing 31 has an opening that is closed by the first housing member 12 .
- the compressor housing 31 has therein an impeller chamber 33 in which the impeller 32 is accommodated.
- the impeller chamber 33 is communicated with the inlet 31 a.
- the impeller shaft 32 a extends in the axial direction in the impeller chamber 33 .
- the compressor housing 31 has a discharge chamber 34 in which air compressed by the impeller 32 is discharged, and a diffuser passage 35 through which the impeller chamber 33 is communicated with the discharged chamber 34 .
- the diffuser passage 35 is located outward of the impeller chamber 33 in the radial direction of the impeller shaft 32 a and formed into a ring shape surrounding the impeller chamber 33 .
- the discharge chamber 34 is located outward of the diffuser passage 35 in the radial direction of the impeller shaft 32 a and formed into a ring shape.
- the rotor 22 including the rotary shaft 25 is rotated by energization of the coil 21 b.
- the rotation of the rotary shaft 25 rotates the impeller 32 so as to compress the air drawn from the inlet 31 a into the impeller chamber 33 .
- the air compressed by the impeller 32 is further compressed via the diffuser passage 35 and is discharged to the discharge chamber 34 .
- the air in the discharge chamber 34 is discharged outside the compressor housing 31 from an outlet (not illustrated) of the compressor housing 31 .
- the second end portion 25 b of the rotary shaft 25 is not connected to an impeller. That is, in the electric compressor 10 according to the embodiment, although compression is performed by the impeller 32 near the first end portion 25 a of the rotary shaft 25 , compression is not performed near the second end portion 25 b of the rotary shaft 25 . Accordingly, in the electric compressor 10 according to the embodiment, a load applied by the rotation of the rotary shaft 25 on the first end portion 25 a is larger than that on the second end portion 25 b.
- the rotary shaft 25 is rotatably supported by a pair of air bearings 40 relative to the housing 11 .
- the pair of air bearings 40 includes a first air bearing 41 supporting the first shaft portion 26 and a second air bearing 42 supporting the second shaft portion 27 . That is, the second air bearing 42 supports the rotary shaft 25 at a position closer to the second end portion 25 b of the rotary shaft 25 than the first air bearing 41 is.
- the first air bearing 41 and the second air bearing 42 have a cylindrical shape.
- the axis of the first air bearing 41 and the axis of the second air bearing 42 correspond to the axis L of the rotary shaft 25 .
- the first air bearing 41 is disposed between the inner peripheral surface of the housing hole 12 c of the first housing member 12 and the outer peripheral surface of the first large-diameter shaft portion 26 b.
- the second air bearing 42 is disposed between the inner peripheral surface of the boss 13 c of the second housing member 13 and the outer peripheral surface of the second large-diameter shaft portion 27 b.
- the rotary shaft 25 is supported by the housing 11 via the first air bearing 41 and the second air bearing 42 such that the rotary shaft 25 is rotatable relative to the housing 11 .
- the rotary shaft 25 is supported by the first air bearing 41 and the second air bearing 42 with the rotary shaft 25 in contact with the first air bearing 41 and the second air bearing 42 until the rotational speed of the rotary shaft 25 reaches a floating rotational speed at which the rotary shaft 25 floats off the first air bearing 41 and the second air bearing 42 .
- a dynamic pressure is generated between the first air bearing 41 and the first shaft portion 26 and between the second air bearing 42 and the second shaft portion 27 .
- the dynamic pressure allows the rotary shaft 25 to float off the first air bearing 41 and the second air bearing 42 , so that the rotary shaft 25 is supported by the first air bearing 41 and the second air bearing 42 without coming into contact with the first air bearing 41 and the second air bearing 42 .
- the first air bearing 41 and the second air bearing 42 are air dynamic bearings that support the rotary shaft 25 in the radial direction.
- the first air bearing 41 and the second air bearing 42 have the same base configuration. Accordingly, the following description will focus on the configuration of the first air bearing 41 , and will not elaborate the same components of the second air bearing 42 as that of the first air bearing 41 .
- the first air bearing 41 includes a top foil 45 that has an approximately cylindrical shape and surrounds the rotary shaft 25 so as to support the rotary shaft 25 , and a bump foil 50 that has an approximately cylindrical shape and surrounds the top foil 45 .
- the outer peripheral surface of the bump foil 50 is supported by a bearing housing 55 that has a cylindrical shape and surrounds the bump foil 50 .
- the axis of each of the top foil 45 , the bump foil 50 , and the bearing housing 55 corresponds to the axis L of the rotary shaft 25 .
- the first air bearing 41 has a configuration in which the top foil 45 , the bump foil 50 , and the bearing housing 55 are disposed between the outer peripheral surface of the first large-diameter shaft portion 26 b of the first shaft portion 26 and the inner peripheral surface of the housing hole 12 c of the first housing member 12 .
- the second air bearing 42 has a configuration in which the top foil 45 , the bump foil 50 , and the bearing housing 55 are disposed between the outer peripheral surface of the second large-diameter shaft portion 27 b of the second shaft portion 27 and the inner peripheral surface of the boss 13 c of the second housing member 13 .
- the rotary shaft 25 rotates in a clockwise direction indicated by an arrow X in FIG. 3 .
- the top foil 45 is formed of a flexible metallic plate, such as a nickel alloy plate, curved into a cylindrical shape.
- One of the opposite ends of the top foil 45 in a circumferential direction of the top foil 45 is a first fixed end 45 a that is fixed to the bump foil 50 .
- the first fixed end 45 a extends outwardly in the radial direction of the top foil 45 .
- the other of the opposite ends of the top foil 45 is a first free end 45 b that is not fixed to the bump foil 50 .
- the first free end 45 b is spaced from the first fixed end 45 a in the circumferential direction of the top foil 45 . Since the top foil 45 has an approximately cylindrical shape, the distance between the first fixed end 45 a and the first free end 45 b is small.
- the bump foil 50 is formed of a flexible metallic plate, such as a nickel alloy plate, and extends along the outer peripheral surface of the top foil 45 .
- One of the opposite ends of the bump foil 50 in the circumferential direction of the bump foil 50 is a second fixed end 50 a that is fixed to the inner peripheral surface of the bearing housing 55 .
- the first fixed end 45 a of the top foil 45 is placed on and fixed to the second fixed end 50 a. That is, the first fixed end 45 a is fixed to the inner peripheral surface of the bearing housing 55 via the second fixed end 50 a.
- the other of the opposite ends of the bump foil 50 is a second free end 50 b that is not fixed to the bearing housing 55 .
- the second free end 50 b is spaced from the second fixed end 50 a in the circumferential direction of the bump foil 50 . Since the bump foil 50 has an approximately cylindrical shape, the distance between the second fixed end 50 a and the second free end 50 b is small.
- the bump foil 50 has a plurality of projections 51 that project in the radial direction of the bump foil 50 .
- the projections 51 are spaced from each other in the circumferential direction of the bump foil 50 .
- Each of the projections 51 is semi-circular in cross-section in a direction perpendicular to the axial direction.
- the adjacent projections 51 are connected to each other by an extending portion 52 that extends in the circumferential direction of the bump foil 50 .
- the extending portion 52 extends along the inner peripheral surface of the bearing housing 55 , and each of the projections 51 projects so as to be radially and inwardly spaced from the inner peripheral surface of the bearing housing 55 .
- the bump foil 50 is formed into a corrugated shape as a whole.
- the extending portion 52 of the bump foil 50 and the top of the projection 51 are respectively in contact with the inner peripheral surface of the bearing housing 55 and the outer peripheral surface of the top foil 45 when the rotary shaft 25 is not rotated.
- the top foil 45 is elastically and radially outwardly deformed when the rotary shaft 25 is rotated, so that air enters a gap between the outer peripheral surface of the rotary shaft 25 and an inner peripheral surface 45 c of the top foil 45 to form an air film. That is, the rotary shaft 25 is supported by the inner peripheral surface 45 c of the top foil 45 via the air film.
- the inner peripheral surface 45 c of the top foil 45 serves as a supporting surface that supports the rotary shaft 25 .
- the elastic and radially outward deformation of the top foil 45 along with the formation of the air film causes the bump foil 50 to be elastically and radially outwardly deformed via the projections 51 in contact with the outer peripheral surface of the top foil 45 .
- the bump foil 50 has a first thickness T 1 in both of the first air bearing 41 and the second air bearing 42 .
- the thickness of the bump foil 50 corresponds to the thickness of the metallic plate that forms the bump foil 50 .
- the bump foil 50 of the first air bearing 41 and the bump foil 50 of the second air bearing 42 have the same number of the projections 51 in a predetermined length L 3 in the circumferential direction of the bump foil 50 . In other words, the first air bearing 41 and the second air bearing 42 have the same area density of the projections 51 in their bump foils 50 .
- Each of the projections 51 forms a first angle A 1 with the corresponding extending portion 52 in a boundary between the projection 51 and the extending portion 52 in the circumferential direction of the bump foil 50 in both of the first air bearing 41 and the second air bearing 42 .
- the first angle A 1 is greater than 0 degrees and less than 90 degrees.
- the first air bearing 41 and the second air bearing 42 have the same thickness of the bump foil 50 , the same area density of the projections 51 , and the same angle formed by each projection 51 and the corresponding extending portion 52 , so that the first air bearing 41 and the second air bearing 42 have the same shape.
- the circumferential length of the top foil 45 of each of the first air bearing 41 and the second air bearing 42 is determined so that the whole of the inner peripheral surface 45 c of the top foil 45 is in contact with the outer peripheral surface of the rotary shaft 25 when the rotary shaft 25 is not rotated.
- the first air bearing 41 and the second air bearing 42 have the same length of the inner peripheral surface 45 c in the circumferential direction of the top foil 45 .
- the first air bearing 41 and the second air bearing 42 have the same length of the bump foil 50 and the same length of the bearing housing 55 in the circumferential direction.
- the top foil 45 , the bump foil 50 , and the bearing housing 55 of the first air bearing 41 have the same length in the axial direction.
- the top foil 45 , the bump foil 50 , and the bearing housing 55 of the second air bearing 42 have the same length in the axial direction.
- the length of the bearing housing 55 may be slightly greater than the length of the top foil 45 and the length of the bump foil 50 in the axial direction.
- the top foil 45 of the first air bearing 41 has a first length L 1 in the axial direction
- the top foil 45 of the second air bearing 42 has a second length L 2 that is shorter than the first length L 1 . That is, the area of the inner peripheral surface 45 c of the top foil 45 of the first air bearing 41 is larger than that of the second air bearing 42 .
- the larger area of the inner peripheral surface 45 c of the top foil 45 extends the supporting surface, which supports the rotary shaft 25 via the air film when the rotary shaft 25 is rotated, thereby increasing the load carrying capacity of the air bearings 40 . Accordingly, in this embodiment, the load carrying capacity of the first air bearing 41 is larger than the load carrying capacity of the second air bearing 42 .
- the rotation of the rotary shaft 25 applies a larger load on the first air bearing 41 , which supports the rotary shaft 25 at a position adjacent to the first end portion 25 a to which the impeller 32 is connected, than that on the second air bearing 42 . Accordingly, the first air bearing 41 needs a relatively large load carrying capacity, and the second air bearing 42 needs a relatively small load carrying capacity.
- the load carrying capacity of the first air bearing 41 is larger than that of the second air bearing 42 . This allows the respective first air bearing 41 and the second air bearing 42 to have a load carrying capacity satisfying a necessary load carrying capacity.
- This embodiment provides following advantageous effects.
- the load carrying capacity of the first air bearing 41 is larger than the load carrying capacity of the second air bearing 42 . This prevents a deficiency of the load carrying capacity of the first air bearing 41 and an excess of the load carrying capacity of the second air bearing 42 . This therefore prevents an excess or a deficiency of the load carrying capacity of each of the air bearings 40 relative to a necessary load carrying capacity of each of the air bearings 40 .
- the length of the first air bearing 41 is greater than that of the second air bearing 42 in the axial direction, so that the area of the inner peripheral surface 45 c of the top foil 45 of the first air bearing 41 is larger than that of the second air bearing 42 .
- This allows the load carrying capacity of the first air bearing 41 to be larger than that of the second air bearing 42 just by a difference in length in the axial direction between the first air bearing 41 and the second air bearing 42 without changing the shapes of the first air bearing 41 and the second air bearing 42 .
- the bump foil 50 of the first air bearing 41 is divided into more members than the bump foil 50 of the second air bearing 42 in such a manner, so that the first air bearing 41 and the second air bearing 42 have different shapes. More divisions of the bump foil 50 in the axial direction allow distribution of the load applied by the rotary shaft 25 on the bump foil 50 , thereby increasing the stiffness of the bump foil 50 and the load carrying capacity in the air bearings 40 .
- the bump foil 50 of the first air bearing 41 is divided into more members than the bump foil 50 of the second air bearing 42 in the axial direction, so that the load carrying capacity of the first air bearing 41 is larger than that of the second air bearing 42 .
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- Engineering & Computer Science (AREA)
- Mechanical Engineering (AREA)
- General Engineering & Computer Science (AREA)
- Physics & Mathematics (AREA)
- Fluid Mechanics (AREA)
- Support Of The Bearing (AREA)
- Structures Of Non-Positive Displacement Pumps (AREA)
Abstract
An electric compressor includes a housing; a rotary shaft; an impeller connected to at least a first end portion of the rotary shaft in an axial direction of the rotary shaft, of the first end portion and a second end portion of the rotary shaft in the axial direction; and a pair of air bearings supporting the rotary shaft such that the rotary shaft is rotatable relative to the housing. A load on the first end portion is larger than a load on the second end portion. The pair of air bearings includes a first air bearing, and a second air bearing supporting the rotary shaft at a position closer to the second end portion of the rotary shaft than the first air bearing is. A load carrying capacity of the first air bearing is larger than a load carrying capacity of the second bearing.
Description
- The present invention relates to an electric compressor.
- Patent Literature 1 mentions an electric compressor that includes a housing having therein a space, a rotary shaft accommodated in the housing, an impeller connected to one end of the rotary shaft in an axial direction of the rotary shaft, and a pair of air bearings supporting the rotary shaft such that the rotary shaft is rotatable relative to the housing. The rotation of the rotary shaft forms an air film between the outer peripheral surface of the rotary shaft and the air bearings, thereby causing the rotary shaft to float off the air bearings. This allows the air bearings to support the rotary shaft without coming into contact with the rotary shaft.
- Patent Literature 1: Japanese Patent Application Publication No. 2011-188612
- In the electric compressor mentioned in Patent Literature 1, although one end of the rotary shaft in the axial direction of the rotary shaft is connected to the impeller, the other end of the rotary shaft is not connected to an impeller.
- Accordingly, compression is not performed near the other end of the rotary shaft although compression is performed by the impeller near the one end of the rotary shaft, so that a load applied by the rotation of the rotary shaft on the one end of the rotary shaft is different from a load applied by the rotation of the rotary shaft on the other end of the rotary shaft. Some of electric compressor may include impellers respectively connected to opposite ends of the rotary shaft. However, the impellers of such electric compressors may provide different compression capacities between the one end and the other end of the rotary shaft due to a difference in size between the impellers, so that the load applied by the rotation of the rotary shaft on the one end of the rotary shaft may be different from the load applied by the rotation of the rotary shaft on the other end of the rotary shaft.
- If different loads, i.e., a large load and a small load, are applied by the rotation of the rotary shaft on the opposite ends of the rotary shaft, a necessary load carrying capacity is different between the air bearings respectively disposed on the opposite ends of the rotary shaft. If the air bearings have the same load carrying capacity, this load carrying capacity is excessive for one of the air bearings but deficient for the other of the air bearings. Deficient load carrying capacity of the air bearing may deteriorate the air bearing early. Excessive load carrying capacity of the air bearing may increase the manufacturing cost of the air bearing.
- The present invention, which has been made in light of the above-mentioned problem, is directed to providing an electric compressor that is capable of preventing an excess or a deficiency of load carrying capacity of an air bearing relative to a necessary load carrying capacity of the air bearing.
- An electric compressor to improve the above-mentioned problem comprising: a housing having therein a space; a rotary shaft accommodated in the housing; an impeller connected to at least a first end portion of the rotary shaft in an axial direction of the rotary shaft, of the first end portion and a second end portion of the rotary shaft in the axial direction; and a pair of air bearings supporting the rotary shaft such that the rotary shaft is rotatable relative to the housing, wherein a load on the first end portion is larger than a load on the second end portion, the pair of air bearings includes a first air bearing, and a second air bearing supporting the rotary shaft at a position closer to the second end portion of the rotary shaft than the first air bearing is, and a load carrying capacity of the first air bearing is larger than a load carrying capacity of the second bearing.
- When the rotation of the rotary shaft applies a larger load on the first end portion than on the second end portion because the impeller is connected only to the first end portion, the rotary shaft applies a larger load on the first air bearing than on the second air bearing. Also, when the rotation of the rotary shaft applies a larger load on the first end portion than on the second end portion although the first end portion and the second end portion are respectively connected to impellers, the rotary shaft applies a larger load on the first air bearing than on the second air bearing.
- Accordingly, the first air bearing needs a relatively large load carrying capacity, and the second air bearing needs a relatively small load carrying capacity. This load carrying capacity is a maximum load that each air bearing can receive without a deformation and a performance deterioration.
- According to this configuration, the load carrying capacity of the first air bearing is larger than the load carrying capacity of the second bearing. This prevents a deficiency of the load carrying capacity of the first air bearing and an excess of the load carrying capacity of the second air bearing. This therefore prevents an excess or a deficiency of the load carrying capacity of each air bearing relative to a necessary load carrying capacity of the air bearing.
- In the electric compressor, a length of the first air bearing may be preferably greater than a length of the second air bearing in the axial direction, so that the load carrying capacity of the first air bearing may be preferably larger than the load carrying capacity of the second air bearing.
- According to this configuration, the length of the first air bearing is greater than the length of the second air bearing in the axial direction, so that a supporting surface of the first air bearing for supporting the rotary shaft is larger than a supporting surface of the second air bearing for supporting the rotary shaft. This allows the load carrying capacity of the first air bearing to be larger than the load carrying capacity of the second air bearing just by making a difference in length in the axial direction between the first air bearing and the second air bearing without changing the shapes of the first air bearing and the second air bearing. This therefore easily prevents an excess or a deficiency of the load carrying capacity of each air bearing relative to a necessary load capacity of the air bearings.
- In the electric compressor, the first air bearing and the second air bearing may have different shapes so that the load carrying capacity of the first air bearing is larger than the load carrying capacity of the second air bearing.
- This disclosure prevents an excess or a deficiency of a load carrying capacity of each air bearing relative to a necessary load carrying capacity of each air bearing.
-
FIG. 1 is a schematic sectional view of an electric compressor. -
FIG. 2 is an exploded perspective view of a rotary shaft and a first air bearing. -
FIG. 3 is a sectional view of an air bearing mounted on the rotary shaft. -
FIG. 4 is an enlarged sectional view of the air bearing mounted on the rotary shaft. -
FIG. 5 is a schematic view explaining the length of the first air bearing and the length of a second air bearing. -
FIG. 6 is a sectional view of an air bearing mounted on a rotary shaft according to an example. -
FIG. 7 is a sectional view of an air bearing mounted on a rotary shaft according to another example. -
FIG. 8 is a sectional view of an air bearing mounted on a rotary shaft according to another example. -
FIG. 9 is an exploded perspective view of a rotary shaft and a first air bearing according to another example. - The following will describe an embodiment of an electric compressor with reference to accompanying
FIGS. 1 to 5 . - As illustrated in
FIG. 1 , anelectric compressor 10 includes a housing 11 having a cylindrical shape and therein a space, and anelectric motor 20 accommodated in the housing 11. The housing 11 includes afirst housing member 12 having a plate-like shape and asecond housing member 13 having a bottomed-cylindrical shape and connected to thefirst housing member 12. Thefirst housing member 12 and thesecond housing member 13 are each made of a metallic material, such as aluminum. Thesecond housing member 13 has abottom wall 13 a having a plate-like shape and aperipheral wall 13 b having a cylindrical shape and extending from an outer peripheral portion of thebottom wall 13 a. Thefirst housing member 12 is connected to thesecond housing member 13 with an opening of theperipheral wall 13 b distant from thebottom wall 13 a closed by thesecond housing member 13. - The
first housing member 12 has ahousing hole 12 c that is formed through thefirst housing member 12 in the thickness direction of thefirst housing member 12. Thehousing hole 12 c is a circular hole. Thesecond housing member 13 has acylindrical boss 13 c protruding from the inner surface of thebottom wall 13 a. The axis of thehousing hole 12 c is coaxial with the axis of theboss 13 c. - The
electric motor 20 includes astator 21 and arotor 22. Thestator 21 includes acylindrical stator core 21 a that is fixed to the inner peripheral surface of theperipheral wall 13 b of thesecond housing member 13, and acoil 21 b that is wound around thestator core 21 a. Therotor 22 is rotatably disposed radially inside thestator 21 in the housing 11. - The
rotor 22 includes acylindrical member 23, apermanent magnet 24 as a magnetic body, and arotary shaft 25. Thecylindrical member 23 has a circular cylindrical shape. The axis of thecylindrical member 23 corresponds to the axes of thehousing hole 12 c and theboss 13 c. In this embodiment, a direction along the axis of thecylindrical member 23 is called an axial direction. A direction along the radius of thecylindrical member 23 is called a radial direction. Thecylindrical member 23 has a first opening 23 a and a second opening 23 b respectively at opposite ends of thecylindrical member 23 in the axial direction. Thecylindrical member 23 is made of a metallic material, such as titanium. - The
permanent magnet 24 has a solid column shape and is magnetized in the radial direction. Thepermanent magnet 24 is press-fitted in the inner peripheral surface of thecylindrical member 23 so as to be fixed into thecylindrical member 23. The axis of thepermanent magnet 24 corresponds to the axis of thecylindrical member 23. The length of thepermanent magnet 24 is shorter than that of thecylindrical member 23 in the axial direction. - The
rotary shaft 25 has a column-shapedfirst shaft portion 26 and a column-shapedsecond shaft portion 27 respectively located opposite sides in the axial direction with respect to thepermanent magnet 24. Thefirst shaft portion 26 and the column-shapedsecond shaft portion 27 are made of metal, for example. Thefirst shaft portion 26 has a first small-diameter shaft portion 26 a, and a first large-diameter shaft portion 26 b having a diameter larger than that of the first small-diameter shaft portion 26 a and aligned with the first small-diameter shaft portion 26 a in the axial direction. The axis of the first small-diameter shaft portion 26 a and the axis of the first large-diameter shaft portion 26 b extend along the axial direction. Thesecond shaft portion 27 has a second small-diameter shaft portion 27 a, and a second large-diameter shaft portion 27 b having a diameter larger than that of the second small-diameter shaft portion 27 a and aligned with the second small-diameter shaft portion 27 a in the axial direction. The axis of the second small-diameter shaft portion 27 a and the axis of the second large-diameter shaft portion 27 b extend along the axial direction. The first small-diameter shaft portion 26 a and the second small-diameter shaft portion 27 a have the same diameter. The first large-diameter shaft portion 26 b and the second large-diameter shaft portion 27 b have the same diameter. - The first large-
diameter shaft portion 26 b is located in thehousing hole 12 c of thefirst housing member 12. The second large-diameter shaft portion 27 b is located in theboss 13 c. The first small-diameter shaft portion 26 a is inserted through the first opening 23 a of thecylindrical member 23 and fixed to thecylindrical member 23 so as to close the first opening 23 a. The second small-diameter shaft portion 27 a is inserted through the second opening 23 b of thecylindrical member 23 and fixed to thecylindrical member 23 so as to close the second opening 23 b. This configuration allows thefirst shaft portion 26 and thesecond shaft portion 27 to be rotatable together with thecylindrical member 23 and thepermanent magnet 24. - The axis of each of the
first shaft portion 26 and thesecond shaft portion 27, i.e., the axis of therotary shaft 25, corresponds to thecylindrical member 23. The axis of therotary shaft 25 is illustrated by the axis L. - One end of the opposite ends of the first large-
diameter shaft portion 26 b in the axial direction is connected to the first small-diameter shaft portion 26 a, and the other end of the opposite ends serves as afirst end portion 25 a of therotary shaft 25. One end of the opposite ends of the second large-diameter shaft portion 27 b in the axial direction is connected to the second small-diameter shaft portion 27 a, and the other end of the opposite ends serves as asecond end portion 25 b of therotary shaft 25. In this embodiment, thefirst end portion 25 a of therotary shaft 25 is connected to animpeller 32. - The
impeller 32 includes animpeller shaft 32 a extending in the axial direction, a hub 32 b fixed to an outer peripheral surface of theimpeller shaft 32 a and configured to rotate together with theimpeller shaft 32 a, and a plurality ofvanes 32 c arranged in the circumferential direction of thehub 32. Theimpeller shaft 32 a extends from thefirst end portion 25 a of therotary shaft 25 in the axial direction so that theimpeller shaft 32 a protrudes outside the housing 11. The hub 32 b has an approximately conical shape and an outer diameter of the hub 32 b expands as the hub 32 b extends from one side to the other side in the axial direction. Thevanes 32 c are disposed on the outer surface of the hub 32 b and equally spaced from each other in the circumferential direction of the hub 32 b. - The
first housing member 12 is connected to acompressor housing 31 that has a cylindrical shape and has aninlet 31 a. Thecompressor housing 31 has theinlet 31 a at one end thereof in the axial direction. Theinlet 31 a extends in the axial direction. The other end of thecompressor housing 31 has an opening that is closed by thefirst housing member 12. Thecompressor housing 31 has therein animpeller chamber 33 in which theimpeller 32 is accommodated. Theimpeller chamber 33 is communicated with theinlet 31 a. Theimpeller shaft 32 a extends in the axial direction in theimpeller chamber 33. - The
compressor housing 31 has adischarge chamber 34 in which air compressed by theimpeller 32 is discharged, and adiffuser passage 35 through which theimpeller chamber 33 is communicated with the dischargedchamber 34. Thediffuser passage 35 is located outward of theimpeller chamber 33 in the radial direction of theimpeller shaft 32 a and formed into a ring shape surrounding theimpeller chamber 33. Thedischarge chamber 34 is located outward of thediffuser passage 35 in the radial direction of theimpeller shaft 32 a and formed into a ring shape. - In the
electric compressor 10, therotor 22 including therotary shaft 25 is rotated by energization of thecoil 21 b. The rotation of therotary shaft 25 rotates theimpeller 32 so as to compress the air drawn from theinlet 31 a into theimpeller chamber 33. The air compressed by theimpeller 32 is further compressed via thediffuser passage 35 and is discharged to thedischarge chamber 34. The air in thedischarge chamber 34 is discharged outside thecompressor housing 31 from an outlet (not illustrated) of thecompressor housing 31. - In the
electric compressor 10 according to the embodiment, although thefirst end portion 25 a of therotary shaft 25 is connected to theimpeller 32, thesecond end portion 25 b of therotary shaft 25 is not connected to an impeller. That is, in theelectric compressor 10 according to the embodiment, although compression is performed by theimpeller 32 near thefirst end portion 25 a of therotary shaft 25, compression is not performed near thesecond end portion 25 b of therotary shaft 25. Accordingly, in theelectric compressor 10 according to the embodiment, a load applied by the rotation of therotary shaft 25 on thefirst end portion 25 a is larger than that on thesecond end portion 25 b. - The
rotary shaft 25 is rotatably supported by a pair ofair bearings 40 relative to the housing 11. The pair ofair bearings 40 includes afirst air bearing 41 supporting thefirst shaft portion 26 and asecond air bearing 42 supporting thesecond shaft portion 27. That is, thesecond air bearing 42 supports therotary shaft 25 at a position closer to thesecond end portion 25 b of therotary shaft 25 than thefirst air bearing 41 is. - The
first air bearing 41 and the second air bearing 42 have a cylindrical shape. The axis of thefirst air bearing 41 and the axis of the second air bearing 42 correspond to the axis L of therotary shaft 25. Thefirst air bearing 41 is disposed between the inner peripheral surface of thehousing hole 12 c of thefirst housing member 12 and the outer peripheral surface of the first large-diameter shaft portion 26 b. Thesecond air bearing 42 is disposed between the inner peripheral surface of theboss 13 c of thesecond housing member 13 and the outer peripheral surface of the second large-diameter shaft portion 27 b. Therotary shaft 25 is supported by the housing 11 via thefirst air bearing 41 and the second air bearing 42 such that therotary shaft 25 is rotatable relative to the housing 11. - The
rotary shaft 25 is supported by thefirst air bearing 41 and the second air bearing 42 with therotary shaft 25 in contact with thefirst air bearing 41 and thesecond air bearing 42 until the rotational speed of therotary shaft 25 reaches a floating rotational speed at which therotary shaft 25 floats off thefirst air bearing 41 and thesecond air bearing 42. When the rotational speed of therotary shaft 25 reaches the floating rotational speed, a dynamic pressure is generated between thefirst air bearing 41 and thefirst shaft portion 26 and between thesecond air bearing 42 and thesecond shaft portion 27. The dynamic pressure allows therotary shaft 25 to float off thefirst air bearing 41 and thesecond air bearing 42, so that therotary shaft 25 is supported by thefirst air bearing 41 and the second air bearing 42 without coming into contact with thefirst air bearing 41 and thesecond air bearing 42. Thefirst air bearing 41 and thesecond air bearing 42 are air dynamic bearings that support therotary shaft 25 in the radial direction. - Next, the following will describe the
air bearings 40 in more detail. Thefirst air bearing 41 and the second air bearing 42 have the same base configuration. Accordingly, the following description will focus on the configuration of thefirst air bearing 41, and will not elaborate the same components of the second air bearing 42 as that of thefirst air bearing 41. - As illustrated in
FIGS. 2 and 3 , thefirst air bearing 41 includes atop foil 45 that has an approximately cylindrical shape and surrounds therotary shaft 25 so as to support therotary shaft 25, and abump foil 50 that has an approximately cylindrical shape and surrounds thetop foil 45. The outer peripheral surface of thebump foil 50 is supported by a bearinghousing 55 that has a cylindrical shape and surrounds thebump foil 50. The axis of each of thetop foil 45, thebump foil 50, and the bearinghousing 55 corresponds to the axis L of therotary shaft 25. - The
first air bearing 41 has a configuration in which thetop foil 45, thebump foil 50, and the bearinghousing 55 are disposed between the outer peripheral surface of the first large-diameter shaft portion 26 b of thefirst shaft portion 26 and the inner peripheral surface of thehousing hole 12 c of thefirst housing member 12. Thesecond air bearing 42 has a configuration in which thetop foil 45, thebump foil 50, and the bearinghousing 55 are disposed between the outer peripheral surface of the second large-diameter shaft portion 27 b of thesecond shaft portion 27 and the inner peripheral surface of theboss 13 c of thesecond housing member 13. Therotary shaft 25 rotates in a clockwise direction indicated by an arrow X inFIG. 3 . - The
top foil 45 is formed of a flexible metallic plate, such as a nickel alloy plate, curved into a cylindrical shape. One of the opposite ends of thetop foil 45 in a circumferential direction of thetop foil 45 is a firstfixed end 45 a that is fixed to thebump foil 50. The firstfixed end 45 a extends outwardly in the radial direction of thetop foil 45. The other of the opposite ends of thetop foil 45 is a firstfree end 45 b that is not fixed to thebump foil 50. The firstfree end 45 b is spaced from the firstfixed end 45 a in the circumferential direction of thetop foil 45. Since thetop foil 45 has an approximately cylindrical shape, the distance between the firstfixed end 45 a and the firstfree end 45 b is small. - The
bump foil 50 is formed of a flexible metallic plate, such as a nickel alloy plate, and extends along the outer peripheral surface of thetop foil 45. One of the opposite ends of thebump foil 50 in the circumferential direction of thebump foil 50 is a secondfixed end 50 a that is fixed to the inner peripheral surface of the bearinghousing 55. The firstfixed end 45 a of thetop foil 45 is placed on and fixed to the secondfixed end 50 a. That is, the firstfixed end 45 a is fixed to the inner peripheral surface of the bearinghousing 55 via the secondfixed end 50 a. The other of the opposite ends of thebump foil 50 is a secondfree end 50 b that is not fixed to the bearinghousing 55. The secondfree end 50 b is spaced from the secondfixed end 50 a in the circumferential direction of thebump foil 50. Since thebump foil 50 has an approximately cylindrical shape, the distance between the secondfixed end 50 a and the secondfree end 50 b is small. - As illustrated in
FIG. 4 , thebump foil 50 has a plurality ofprojections 51 that project in the radial direction of thebump foil 50. Theprojections 51 are spaced from each other in the circumferential direction of thebump foil 50. Each of theprojections 51 is semi-circular in cross-section in a direction perpendicular to the axial direction. In thebump foil 50, theadjacent projections 51 are connected to each other by an extendingportion 52 that extends in the circumferential direction of thebump foil 50. The extendingportion 52 extends along the inner peripheral surface of the bearinghousing 55, and each of theprojections 51 projects so as to be radially and inwardly spaced from the inner peripheral surface of the bearinghousing 55. Thebump foil 50 is formed into a corrugated shape as a whole. - The extending
portion 52 of thebump foil 50 and the top of theprojection 51 are respectively in contact with the inner peripheral surface of the bearinghousing 55 and the outer peripheral surface of thetop foil 45 when therotary shaft 25 is not rotated. Thetop foil 45 is elastically and radially outwardly deformed when therotary shaft 25 is rotated, so that air enters a gap between the outer peripheral surface of therotary shaft 25 and an innerperipheral surface 45 c of thetop foil 45 to form an air film. That is, therotary shaft 25 is supported by the innerperipheral surface 45 c of thetop foil 45 via the air film. The innerperipheral surface 45 c of thetop foil 45 serves as a supporting surface that supports therotary shaft 25. The elastic and radially outward deformation of thetop foil 45 along with the formation of the air film causes thebump foil 50 to be elastically and radially outwardly deformed via theprojections 51 in contact with the outer peripheral surface of thetop foil 45. - The
bump foil 50 has a first thickness T1 in both of thefirst air bearing 41 and thesecond air bearing 42. The thickness of thebump foil 50 corresponds to the thickness of the metallic plate that forms thebump foil 50. Thebump foil 50 of thefirst air bearing 41 and thebump foil 50 of the second air bearing 42 have the same number of theprojections 51 in a predetermined length L3 in the circumferential direction of thebump foil 50. In other words, thefirst air bearing 41 and the second air bearing 42 have the same area density of theprojections 51 in their bump foils 50. Each of theprojections 51 forms a first angle A1 with the corresponding extendingportion 52 in a boundary between theprojection 51 and the extendingportion 52 in the circumferential direction of thebump foil 50 in both of thefirst air bearing 41 and thesecond air bearing 42. The first angle A1 is greater than 0 degrees and less than 90 degrees. In this embodiment, thefirst air bearing 41 and the second air bearing 42 have the same thickness of thebump foil 50, the same area density of theprojections 51, and the same angle formed by eachprojection 51 and the corresponding extendingportion 52, so that thefirst air bearing 41 and the second air bearing 42 have the same shape. - The circumferential length of the
top foil 45 of each of thefirst air bearing 41 and thesecond air bearing 42 is determined so that the whole of the innerperipheral surface 45 c of thetop foil 45 is in contact with the outer peripheral surface of therotary shaft 25 when therotary shaft 25 is not rotated. Thefirst air bearing 41 and the second air bearing 42 have the same length of the innerperipheral surface 45 c in the circumferential direction of thetop foil 45. Similarly, thefirst air bearing 41 and the second air bearing 42 have the same length of thebump foil 50 and the same length of the bearinghousing 55 in the circumferential direction. - As illustrated in
FIG. 2 , thetop foil 45, thebump foil 50, and the bearinghousing 55 of thefirst air bearing 41 have the same length in the axial direction. Thetop foil 45, thebump foil 50, and the bearinghousing 55 of the second air bearing 42 have the same length in the axial direction. The length of the bearinghousing 55 may be slightly greater than the length of thetop foil 45 and the length of thebump foil 50 in the axial direction. - As illustrated in
FIG. 5 , thetop foil 45 of thefirst air bearing 41 has a first length L1 in the axial direction, and thetop foil 45 of thesecond air bearing 42 has a second length L2 that is shorter than the first length L1. That is, the area of the innerperipheral surface 45 c of thetop foil 45 of thefirst air bearing 41 is larger than that of thesecond air bearing 42. The larger area of the innerperipheral surface 45 c of thetop foil 45 extends the supporting surface, which supports therotary shaft 25 via the air film when therotary shaft 25 is rotated, thereby increasing the load carrying capacity of theair bearings 40. Accordingly, in this embodiment, the load carrying capacity of thefirst air bearing 41 is larger than the load carrying capacity of thesecond air bearing 42. - Next, the following will explain the operation of the electric compressor according to the embodiment.
- When the
rotary shaft 25 is rotated, air enters a gap between the outer peripheral surface of therotary shaft 25 and the innerperipheral surface 45 c of thetop foil 45 and forms an air film. This causes thetop foil 45 to be elastically and radially outwardly deformed and therefore thebump foil 50 to be elastically and radially outwardly deformed via theprojections 51 in contact with the outer peripheral surface of thetop foil 45. - The rotation of the
rotary shaft 25 applies a larger load on thefirst air bearing 41, which supports therotary shaft 25 at a position adjacent to thefirst end portion 25 a to which theimpeller 32 is connected, than that on thesecond air bearing 42. Accordingly, thefirst air bearing 41 needs a relatively large load carrying capacity, and the second air bearing 42 needs a relatively small load carrying capacity. - In this embodiment, since the area of the inner
peripheral surface 45 c of thetop foil 45 of thefirst air bearing 41 is larger than that of thesecond air bearing 42, the load carrying capacity of thefirst air bearing 41 is larger than that of thesecond air bearing 42. This allows the respectivefirst air bearing 41 and the second air bearing 42 to have a load carrying capacity satisfying a necessary load carrying capacity. - This embodiment provides following advantageous effects.
- (1) The load carrying capacity of the
first air bearing 41 is larger than the load carrying capacity of thesecond air bearing 42. This prevents a deficiency of the load carrying capacity of thefirst air bearing 41 and an excess of the load carrying capacity of thesecond air bearing 42. This therefore prevents an excess or a deficiency of the load carrying capacity of each of theair bearings 40 relative to a necessary load carrying capacity of each of theair bearings 40. - (2) The length of the
first air bearing 41 is greater than that of the second air bearing 42 in the axial direction, so that the area of the innerperipheral surface 45 c of thetop foil 45 of thefirst air bearing 41 is larger than that of thesecond air bearing 42. This allows the load carrying capacity of thefirst air bearing 41 to be larger than that of the second air bearing 42 just by a difference in length in the axial direction between thefirst air bearing 41 and the second air bearing 42 without changing the shapes of thefirst air bearing 41 and thesecond air bearing 42. This therefore easily prevents an excess or a deficiency of the load carrying capacity of each of theair bearings 40 relative to the necessary load carrying capacity of each of theair bearings 40. - This embodiment may be modified as below. The embodiment may be combined with the following modification examples within technically consistent range.
-
- As illustrated in
FIG. 6 , thebump foil 50 of thefirst air bearing 41 may have a second thickness T2 that is thicker than the first thickness T1 of thesecond air bearing 42. The difference in thickness between thebump foil 50 of thefirst air bearing 41 and thebump foil 50 of thesecond air bearing 42 makes a difference in shape between thefirst air bearing 41 and thesecond air bearing 42. Thethicker bump foil 50 increases the stiffness of thebump foil 50, thereby increasing the load carrying capacity in theair bearings 40. In this configuration, thebump foil 50 of thefirst air bearing 41 is thicker than that of thesecond air bearing 42, so that the load carrying capacity of thefirst air bearing 41 is larger than that of thesecond air bearing 42. - As illustrated in
FIG. 7 , the number of theprojections 51 of thebump foil 50 of thefirst air bearing 41 may be larger than that of the second air bearing 42 in the predetermined length L3 in the circumferential direction of thebump foil 50. In other words, the area density of theprojections 51 of thebump foil 50 of thefirst air bearing 41 may be greater than that of thesecond air bearing 42. The difference in area density of theprojections 51 between thebump foil 50 of thefirst air bearing 41 and thebump foil 50 of thesecond air bearing 42 makes a difference in shape between thefirst air bearing 41 and thesecond air bearing 42. The greater area density of theprojections 51 of thebump foil 50 increases the stiffness of thebump foil 50, thereby increasing the load carrying capacity in theair bearings 40. In this configuration, the area density of theprojections 51 of thebump foil 50 of thefirst air bearing 41 is greater than that of thesecond air bearing 42, so that the load carrying capacity of thefirst air bearing 41 is larger than that of thesecond air bearing 42. - As illustrated in
FIG. 8 , eachprojection 51 of thebump foil 50 may be divided with respect to the circumferential direction in both of thefirst air bearing 41 and thesecond air bearing 42. In this configuration, eachprojection 51 is formed of afirst projection 51 a and asecond projection 51 b adjacent to each other in the circumferential direction of thebump foil 50. Thefirst projection 51 a is curved in the rotational direction of therotary shaft 25 so as to approach the outer peripheral surface of thetop foil 45 from one end of the extendingportion 52. Thesecond projection 51 b is curved in the rotational direction of therotary shaft 25 so as to approach one end of another extendingportion 52 from the outer peripheral surface of thetop foil 45. The top of thefirst projection 51 a is spaced from the top of thesecond projection 51 b in the circumferential direction. Each of theprojections 51 is formed by thefirst projection 51 a and thesecond projection 51 b into approximately semi-circular in cross-section in a direction perpendicular to the axial direction. - In the second air bearing 42 of this modification example, each of the
first projection 51 a and thesecond projection 51 b forms the first angle A1 with the corresponding extendingportion 52 in a boundary between theprojection 51 and the extendingportion 52 in the circumferential direction of thebump foil 50. Alternatively, in thefirst air bearing 41, this angle may be a second angle A2 that is greater than the first angle A1 and less than 90 degrees. The first angle A1 and the second angle A2 are angles when therotary shaft 25 is not rotated. The difference in angle formed by eachprojection 51 and the corresponding extendingportion 52 between thefirst air bearing 41 and thesecond air bearing 42 makes a difference in shape between thefirst air bearing 41 and thesecond air bearing 42. The greater angle formed by theprojection 51 and the extendingportion 52 and not exceeding 90 degrees increases the stiffness of thebump foil 50, thereby increasing the load carrying capacity in theair bearings 40. In this configuration, the angle formed by theprojection 51 and the extendingportion 52 of thefirst air bearing 41 is greater than that of thesecond air bearing 42, so that the load carrying capacity of thefirst air bearing 41 is larger than that of thesecond air bearing 42. In this configuration, similarly to the embodiment, eachprojection 51 may not be divided in both of thefirst air bearing 41 and thesecond air bearing 42. This configuration allows the angle formed by theprojection 51 and the extendingportion 52 of thefirst air bearing 41 to be greater than that of thesecond air bearing 42, so that the load carrying capacity of thefirst air bearing 41 is larger than that of thesecond air bearing 42. - As illustrated in
FIG. 9 , thebump foil 50 of thefirst air bearing 41 may be divided with respect to the axial direction. In this configuration, thebump foil 50 is formed of a first bump foil member 150 a and a second bump foil member 150 b adjacent to each other in the axial direction. The length of the first bump foil member 150 a and the length of the second bump foil member 150 b are half the length of thetop foil 45 in the axial direction. The first bump foil member 150 a and the second bump foil member 150 b are fixed to the bearinghousing 55 with the first bump foil member 150 a and the second bump foil member 150 b in contact with each other in the axial direction. Accordingly, in thefirst air bearing 41, the length of thewhole bump foil 50 is equal to that of thetop foil 45 in the axial direction. In this configuration, similarly to the embodiment, thebump foil 50 of thesecond air bearing 42 is not divided in the axial direction. Accordingly, thetop foil 45 of thefirst air bearing 41 has the second length L2 that is equal to the length of thetop foil 45 of the second air bearing 42 in the axial direction. The length of each of the first bump foil member 150 a and the second bump foil member 150 b is a third length L4, which is half the length of the second length L2 in the axial direction.
- As illustrated in
- In this configuration, the
bump foil 50 of thefirst air bearing 41 is divided into more members than thebump foil 50 of the second air bearing 42 in such a manner, so that thefirst air bearing 41 and the second air bearing 42 have different shapes. More divisions of thebump foil 50 in the axial direction allow distribution of the load applied by therotary shaft 25 on thebump foil 50, thereby increasing the stiffness of thebump foil 50 and the load carrying capacity in theair bearings 40. In this configuration, thebump foil 50 of thefirst air bearing 41 is divided into more members than thebump foil 50 of the second air bearing 42 in the axial direction, so that the load carrying capacity of thefirst air bearing 41 is larger than that of thesecond air bearing 42. -
- In the modification example as illustrated in
FIG. 9 , thebump foil 50 of thefirst air bearing 41 may be divided into three or more members. Thebump foil 50 of thesecond air bearing 42 may be divided with respect to the axial direction. That is, thebump foil 50 of thefirst air bearing 41 and thebump foil 50 of thesecond air bearing 42 may be divided into any number of members in the axial direction as long as thebump foil 50 of thefirst air bearing 41 is divided into more members than thebump foil 50 of thesecond air bearing 42. - The
bump foil 50 of thefirst air bearing 41 and thebump foil 50 of thesecond air bearing 42 may be made of different materials. For example, if thebump foil 50 of thefirst air bearing 41 may be made of a material with higher Young's modulus than that of the material of thebump foil 50 of thesecond air bearing 42, the load carrying capacity of thefirst air bearing 41 is larger than that of thesecond air bearing 42. - The
top foil 45 and thebump foil 50 may be made of a flexible metal other than nickel alloy, such as stainless steel. - Both of the
first end portion 25 a and thesecond end portion 25 b of therotary shaft 25 may be respectively connected to impellers 32. In this configuration, theimpeller 32 connected to thefirst end portion 25 a may be larger than theimpeller 32 connected to thesecond end portion 25 b, so that the compression capacity provided by theimpeller 32 on thefirst end portion 25 a may be larger than that provided by theother impeller 32 on thesecond end portion 25 b. That is, a load applied by the rotation of therotary shaft 25 on thefirst end portion 25 a may be larger than that on thesecond end portion 25 b. If the load carrying capacity of thefirst air bearing 41 is set larger than the load carrying capacity of the second air bearing 42 as explained in the embodiment and the modification examples for theelectric compressor 10 with such a difference in load, the same advantageous effects as in the above embodiment can be obtained.
- In the modification example as illustrated in
- 10 electric compressor
- 11 housing
- 25 rotary shaft
- 25 a first end portion
- 25 b second end portion
- 32 impeller
- 40 air bearing
- 41 first air bearing
- 42 second air bearing
Claims (3)
1. An electric compressor comprising:
a housing having therein a space;
a rotary shaft accommodated in the housing;
an impeller connected to at least a first end portion of the rotary shaft in an axial direction of the rotary shaft, of the first end portion and a second end portion of the rotary shaft in the axial direction; and
a pair of air bearings supporting the rotary shaft such that the rotary shaft is rotatable relative to the housing, wherein
a load on the first end portion is larger than a load on the second end portion,
the pair of air bearings includes a first air bearing, and a second air bearing supporting the rotary shaft at a position closer to the second end portion of the rotary shaft than the first air bearing is, and
a load carrying capacity of the first air bearing is larger than a load carrying capacity of the second bearing.
2. The electric compressor according to claim 1 , wherein
a length of the first air bearing is greater than a length of the second air bearing in the axial direction so that the load carrying capacity of the first air bearing is larger than the load carrying capacity of the second air bearing.
3. The electric compressor according to claim 1 , wherein
the first air bearing and the second air bearing have different shapes so that the load carrying capacity of the first air bearing is larger than the load carrying capacity of the second air bearing.
Applications Claiming Priority (3)
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JP2020-081290 | 2020-05-01 | ||
JP2020081290A JP2021175884A (en) | 2020-05-01 | 2020-05-01 | Electric compressor |
PCT/JP2021/013652 WO2021220701A1 (en) | 2020-05-01 | 2021-03-30 | Electric compressor |
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US20230193916A1 true US20230193916A1 (en) | 2023-06-22 |
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US17/921,488 Pending US20230193916A1 (en) | 2020-05-01 | 2021-03-30 | Electric compressor |
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US (1) | US20230193916A1 (en) |
JP (1) | JP2021175884A (en) |
CN (1) | CN115485478A (en) |
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WO (1) | WO2021220701A1 (en) |
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CN114941651B (en) * | 2022-05-17 | 2023-05-23 | 烟台东德实业有限公司 | Diffuser with sleeved boss and air bearing based on diffuser |
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JP2000308301A (en) * | 1999-04-22 | 2000-11-02 | Hitachi Ltd | Motor-operated blower |
JP5497489B2 (en) | 2010-03-08 | 2014-05-21 | 本田技研工業株式会社 | Centrifugal compressor |
JP2015178866A (en) * | 2014-03-19 | 2015-10-08 | 株式会社豊田自動織機 | turbo type fluid machine |
US10415634B2 (en) * | 2015-11-18 | 2019-09-17 | Hanon Systems | Air foil bearing |
-
2020
- 2020-05-01 JP JP2020081290A patent/JP2021175884A/en active Pending
-
2021
- 2021-03-30 DE DE112021002532.5T patent/DE112021002532T5/en active Pending
- 2021-03-30 US US17/921,488 patent/US20230193916A1/en active Pending
- 2021-03-30 WO PCT/JP2021/013652 patent/WO2021220701A1/en active Application Filing
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WO2021220701A1 (en) | 2021-11-04 |
CN115485478A (en) | 2022-12-16 |
DE112021002532T5 (en) | 2023-02-23 |
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