Patent Publication Number: US-10767655-B2

Title: Centrifugal compressor

Description:
BACKGROUND ART 
     The present invention relates to a centrifugal compressor. 
     Japanese Laid-Open Patent Publication No. 2016-186238 describes an example of a compressor including a speed increaser. One example of a speed increaser includes a ring member, a high-speed shaft, rollers, and a speed increaser chamber. The rotation of a low-speed shaft rotates the ring member. The high-speed shaft is located at the inner side of the ring member. The rollers are located between the ring member and the high-speed shaft in contact with both of the ring member and the high-speed shaft. The speed increaser chamber accommodates the ring member, the high-speed shaft, and the rollers. 
     In the speed increaser, the location where the rollers contact the ring member and the location where the rollers contact the high-speed shaft need to be oiled to reduce wear and avoid seizure. 
     The compressor of Japanese Laid-Open Patent Publication No. 2016-186238 includes a reservoir chamber that is separate from the speed increaser chamber and located near the outer surface of a housing. This enlarges the compressor. To avoid enlargement of the compressor, the speed increaser chamber can be configured to also serve as the reservoir chamber. In this case, the ring member will be immersed in the oil that is stored in the speed increaser chamber. This will increase the agitation resistance when the ring member rotates and lower the efficiency of the speed increaser. 
     SUMMARY 
     It is an object of the present invention to provide a centrifugal compressor that reduces the agitation resistance. 
     A centrifugal compressor that solves the above problem is provided with an electric motor coupled to a low-speed shaft, an impeller, and a speed increaser. The speed increaser includes a ring member, a high-speed shaft, a plurality of rollers, a speed increaser housing member, a discharge passage, and a partition. The ring member includes a circumferential wall and is configured to be rotated when the low-speed shaft rotates. The high-speed shaft is located at an inner side of the circumferential wall and coupled to the impeller. The rollers are located between the circumferential wall and the high-speed shaft. The speed increaser housing member stores oil and accommodates the ring member, part of the high-speed shaft, and the rollers. The discharge passage is configured to discharge the oil out of the ring member. The partition is located between an inner surface of the speed increaser housing member and the circumferential wall in a radial direction of the circumferential wall. Power is transmitted from the low-speed shaft to the high-speed shaft by the ring member and the rollers. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The invention, together with objects and advantages thereof, may best be understood by reference to the following description of the presently preferred embodiments together with the accompanying drawings in which: 
         FIG. 1  is a schematic cross-sectional view showing one embodiment of a centrifugal compressor; 
         FIG. 2  is an enlarged cross-sectional view of a speed increaser in the centrifugal compressor shown in  FIG. 1 ; 
         FIG. 3  is a perspective view of a partition in the centrifugal compressor shown in  FIG. 1 ; 
         FIG. 4  is a cross-sectional view of the speed increaser shown in  FIG. 2  taken along line  4 - 4  in  FIG. 1 ; and 
         FIG. 5  is a perspective view showing a modified example of the partition. 
     
    
    
     DETAILED DESCRIPTION OF THE EMBODIMENTS 
     One embodiment of a centrifugal compressor will now be described. The centrifugal compressor of the present embodiment includes a speed increaser and is installed in a fuel cell vehicle (FCV) that is powered by a fuel cell. The centrifugal compressor supplies the fuel cell with air. 
     As shown in  FIG. 1 , a centrifugal compressor  10  includes a low-speed shaft  11 , a high-speed shaft  12 , an electric motor  13  that rotates the low-speed shaft  11 , a speed increaser  60 , and an impeller  52 . The speed increaser  60  increases the rotation speed of the low-speed shaft  11  and transmits the rotation to the high-speed shaft  12 . The impeller  52  is rotated by the high-speed shaft  12  to compress fluid (air in the present embodiment). The two shafts  11  and  12  are formed from, for example, a metal, specifically, iron or an iron alloy. 
     The centrifugal compressor  10  includes a housing  20  that forms the outer shell of the centrifugal compressor  10 . The housing  20  accommodates the two shafts  11  and  12 , the electric motor  13 , and a speed increasing mechanism  61  that forms part of the speed increaser  60 . The housing  20  is, for example, substantially tubular (specifically, cylindrical) as a whole. 
     The housing  20  includes a motor housing member  21  that accommodates the electric motor  13 , a speed increaser housing member  23  that accommodates the speed increasing mechanism  61 , and a compressor housing member  50  including a suction port  50   a  that draws in fluid. Among the two end surfaces  20   a  and  20   b  of the housing  20  in the axial direction, the suction port  50   a  is located in the first end surface  20   a . The compressor housing member  50 , the speed increaser housing member  23 , and the motor housing member  21  are aligned in this order from the side closer to the suction port  50   a  in the axial direction of the housing  20 . In the present embodiment, the speed increasing mechanism  61  and the speed increaser housing member  23  form the speed increaser  60 . 
     The motor housing member  21  is tubular (specifically, cylindrical) as a whole and includes a closed end  22  (end wall). The second end surface  20   b  defines the outer surface of the closed end  22  of the motor housing member  21  and is located at the side of the housing  20  opposite to the first end surface  20   a , which includes the suction port  50   a . The speed increaser housing member  23  includes a main body  25  and a cover  26 . The main body  25  is tubular (specifically, cylindrical) and includes a closed end  24  (end wall). The cover  26  is located at the side opposite to the closed end  24  in the axial direction of the main body  25 . 
     The motor housing member  21  and the speed increaser housing member  23  are coupled to each other with the open end of the motor housing member  21  joined with the closed end  24  of the main body  25 . The closed end  24  has an end surface  24   a  covered by the motor housing member  21 . The inner surface of the motor housing member  21  and the end surface  24   a  define a motor accommodation chamber S 1 . The motor accommodation chamber S 1  accommodates the electric motor  13 . Further, the motor accommodation chamber S 1  accommodates the low-speed shaft  11  in a state in which the low-speed shaft  11  is coaxial with the housing  20 . 
     The low-speed shaft  11  is supported by the housing  20  in a rotatable manner. The centrifugal compressor  10  includes a first bearing  31 . The first bearing  31  is arranged in the closed end  22  of the motor housing member  21 . The low-speed shaft  11  includes a first end  11   a  supported by the first bearing  31 . Part of the first end  11   a  is inserted through the first bearing  31  and fitted into the closed end  22  of the motor housing member  21 . 
     The closed end  24  of the main body  25  includes an insertion hole  27  that is slightly larger than a second end lib of the low-speed shaft  11  located at the side opposite to the first end  11   a . The centrifugal compressor  10  includes a second bearing  32 , which is located in the insertion hole  27 , and a seal  33 . The second end  11   b  of the low-speed shaft  11  is supported by the second bearing  32 . The seal  33  restricts the leakage of oil O from the speed increaser housing member  23  to the motor accommodation chamber S 1 . 
     The second end  11   b  of the low-speed shaft  11  is inserted into the insertion hole  27  of the main body  25 . Part of the low-speed shaft  11  is located in the speed increaser housing member  23 . 
     The electric motor  13  includes a rotor  41  that is fixed to the low-speed shaft  11  and a stator  42  that is located at the radially outer side of the rotor  41 . The stator  42  is fixed to the inner surface of the motor housing member  21 . The stator  42  includes a cylindrical stator core  43  and a coil  44  wound around the stator core  43 . The rotor  41  and the low-speed shaft  11  rotate integrally when current flows to the coil  44 . 
     The cover  26 , which is one element of the speed increaser housing member  23 , is disk-shaped and has the same diameter as the speed increaser housing member  23 . The two sides of the cover  26  in the axial direction respectively define first and second plate surfaces  26   a  and  26   b . The speed increaser housing member  23  is assembled by joining the open end of the main body  25  with the first plate surface  26   a . The first plate surface  26   a  of the cover  26  and the inner surface of the speed increaser housing member  23  define a speed increaser chamber S 2 . The speed increaser chamber S 2  accommodates the speed increasing mechanism  61 . 
     The cover  26  includes a cover insertion hole  28  that allows for insertion of the high-speed shaft  12 , which forms part of the speed increasing mechanism  61 . Part of the high-speed shaft  12  is inserted through the cover insertion hole  28  and located in the compressor housing member  50 . 
     The centrifugal compressor  10  includes a seal  34  located between the high-speed shaft  12  and the wall surface of the cover insertion hole  28 . The seal  34  restricts the leakage of the oil  0  from the speed increaser housing member  23  to the compressor housing member  50 . 
     The compressor housing member  50  is substantially tubular and includes a through hole  51  that extends through the compressor housing member  50  in the axial direction. The two axial ends of the compressor housing member  50  respectively define a first end surface  50   b  and a second end surface  50   c . The first end surface  50   b  of the compressor housing member  50  defines the first end surface  20   a  of the housing  20 . The through hole  51  opens in the first end surface  50   b  and functions as the suction port  50   a.    
     The compressor housing member  50  and the cover  26  are coupled to each other with the second end surface  50   c  joined with the second plate surface  26   b . The second end surface  50   c  is the end surface of the compressor housing member  50  at the side opposite to the first end surface  50   b , and the second plate surface  26   b  is the end surface of the cover  26  at the side opposite to the first plate surface  26   a . The wall surface of the through hole  51  and the second plate surface  26   b  of the cover  26  define an impeller chamber S 3 . The impeller chamber S 3  accommodates the impeller  52 . The through hole  51  functions as the suction port  50   a  and defines the impeller chamber S 3 . The suction port  50   a  is in communication with the impeller chamber S 3 . 
     The through hole  51  has a diameter that is constant from the suction port  50   a  to an intermediate position in the axial direction. The through hole  51  from the intermediate position has the form of a substantially truncated cone of which the diameter gradually increases toward the cover  26 . Thus, the impeller chamber S 3  defined by the wall surface of the through hole  51  substantially has the form of a truncated cone. 
     The impeller  52  has a contour that is gradually reduced in diameter from the basal end surface  52   a  toward the distal end surface  52   b . The impeller  52  includes an insertion hole  52   c  that extends in the axial direction of the impeller  52  and allows for insertion of the high-speed shaft  12 . The impeller  52  is coupled to the high-speed shaft  12  with part of the high-speed shaft  12  inserted through the insertion hole  52   c  and projected into the through hole  51 . The impeller  52  is rotated integrally with the high-speed shaft  12 . Thus, the rotation of the high-speed shaft  12  rotates the impeller  52  and compresses the fluid drawn through the suction port  50   a.    
     Further, the centrifugal compressor  10  includes a diffuser passage  53  and a discharge chamber  54 . The fluid compressed by the impeller  52  flows into the diffuser passage  53 . The fluid that passes through the diffuser passage  53  enters the discharge chamber  54 . The through hole  51  includes an open end that opens toward the second plate surface  26   b  of the cover  26  and is continuous with the diffuser passage  53 . The diffuser passage  53  is defined by the second plate surface  26   b  and the surface of the compressor housing member  50  opposing the second plate surface  26   b . The diffuser passage  53  is located outward from the impeller chamber S 3  in the radial direction of the high-speed shaft  12  and has a closed shape (specifically, circular shape) so as to surround the impeller  52  and the impeller chamber S 3 . The discharge chamber  54  has a closed shape and is located outward from the diffuser passage  53  in the radial direction of the high-speed shaft  12 . The impeller chamber S 3  is in communication with the discharge chamber  54  through the diffuser passage  53 . The fluid compressed by the impeller  52  is further compressed in the diffuser passage  53  and then discharged out of the discharge chamber  54 . 
     The speed increaser  60  will now be described. The speed increaser  60  of the present embodiment is of a traction drive type (friction roller type). 
     As shown in  FIGS. 2 and 3 , the speed increasing mechanism  61  of the speed increaser  60  includes a ring member  62  that is coupled to the second end  11   b  of the low-speed shaft  11 . The ring member  62  includes a disk-shaped base  63  and a circumferential wall  64 . The base  63  is coupled to the second end  11   b  of the low-speed shaft  11 , and the circumferential wall  64  is ring-shaped and extends in the axial direction from the circumferential edge of the base  63 . The circumferential wall  64  has an inner diameter that is larger than the diameter of the second end  11   b  of the low-speed shaft  11 . 
     In the present embodiment, the ring member  62  is coupled to the low-speed shaft  11  in a state in which the base  63  (ring member  62 ) is coaxial with the low-speed shaft  11 . The circumferential wall  64  is also coaxial with the low-speed shaft  11 . The rotation of the low-speed shaft  11  rotates the ring member  62 . 
     Part of the high-speed shaft  12  is located at the inner side of the circumferential wall  64 . The speed increasing mechanism  61  include three rollers  71  located between the high-speed shaft  12  and the circumferential wall  64  in contact with both of the circumferential wall  64  and the high-speed shaft  12 . In the present embodiment, the three rollers  71  are identically shaped. The rollers  71  each include a cylindrical roller portion  72 , first and second end surfaces  72   a  and  72   a  in the axial direction of the roller portion  72 , a cylindrical first projection  73  that projects from the first end surface  72   a , and a cylindrical second projection  74  that projects from the second end surface  72   b . The roller portion  72  is coaxial with the first projection  73  and the second projection  74 . The axial direction of the roller portion  72  will hereinafter be referred to as the axial direction Z of the rollers  71 . 
     The roller portion  72  has a diameter (length in direction orthogonal to axial direction Z) that is larger than that of the high-speed shaft  12 . The axial direction Z coincides with the rotation axis of the high-speed shaft  12 . The rollers  71  are arranged in the circumferential direction of the high-speed shaft  12  spaced apart from one another. The rollers  71  are each formed from, for example, a metal. More specifically, the rollers  71  are formed from the same metal as the high-speed shaft  12 , for example, iron or an iron alloy. 
     As shown in  FIGS. 2 and 4 , the speed increasing mechanism  61  includes a support  80 . The support  80  cooperates with the cover  26  to support the rollers  71  so that the rollers  71  are rotatable. The support  80  is located at the inner side the circumferential wall  64 . The support  80  includes a disk-shaped support base  81  that is slightly smaller in diameter than the circumferential wall  64  and three posts  82  that extend in the axial direction from the support base  81 . The support base  81  is opposed to the cover  26  in the axial direction Z. The support base  81  includes an opposing plate surface  81   a  that is opposed to the first plate surface  26   a  of the cover  26 . The three posts  82  extend from the opposing plate surface  81   a  toward the cover  26  filling three gaps that are each defined between the inner circumferential surface of the circumferential wall  64  and the outer circumferential surfaces of two adjacent ones of the roller portions  72 . 
     As shown in  FIG. 2 , the posts  82  each include a bolt hole  84  that allows for insertion of a bolt  83  extending in the axial direction Z. The cover  26  includes threaded holes  85  corresponding to the bolt holes  84 . Each bolt hole  84  is in communication with the corresponding threaded hole  85 . In a state in which the distal end surfaces of the posts  82  are joined with the first plate surface  26   a , the posts  82  are fixed to the cover  26  by inserting each bolt  83  through the corresponding bolt hole  84  and fastening the bolt  83  to the corresponding threaded hole  85 . 
     The speed increaser  60  includes first roller bearings  76  and second roller bearings  77  that support the rollers  71  in a rotatable manner. The first roller bearings  76  are arranged in the cover  26 . The second roller bearings  77  are arranged in the support base  81 . The rollers  71  are supported by the first roller bearings  76  and the second roller bearings  77  so as to be held between the cover  26  and the support base  81 . 
     As shown in  FIG. 4 , the rollers  71 , the ring member  62 , and the high-speed shaft  12  form a unit with each roller portion  72  forced against the high-speed shaft  12  and the circumferential wall  64 . The high-speed shaft  12  is supported by the three roller portions  72  in a rotatable manner. The location where the outer circumferential surface of each roller portion  72  contacts the inner circumferential surface of the circumferential wall  64  is referred to as the ring contact location Pa, and the location where the outer circumferential surface of each roller portion  72  contacts the circumferential surface of the high-speed shaft  12  is referred to as the shaft contact location Pb. A pressing load is applied to the ring contact locations Pa and the shaft contact locations Pb. The contact locations Pa and Pb each extend in the axial direction Z. 
     As shown in  FIG. 1 , the high-speed shaft  12  includes two flanges  12   a  that are spaced apart and opposed to each other in the axial direction of the high-speed shaft  12 . Each roller portion  72  is held between the two flanges  12   a  in the axial direction. This restricts displacement of the high-speed shaft  12  and the roller portions  72  in the axial direction of the high-speed shaft  12 . 
     As shown in  FIG. 2 , in a state in which the speed increaser  60  is fixed to the cover  26 , a discharge passage  65  is defined between an end surface  64   a  of the open end of the circumferential wall  64  and the first plate surface  26   a  of the cover  26 . The inner and outer sides of the circumferential wall  64  are in communication through the discharge passage  65 . 
     As shown in  FIG. 1 , the centrifugal compressor  10  includes an oil supplying mechanism  100  that supplies the oil O to the speed increasing mechanism  61 . The oil supplying mechanism  100  includes a pump  101  and an oil passage  102 . The pump  101  is driven so that the oil O circulates through the oil passage  102  and flows to the speed increaser chamber S 2 . 
     The pump  101  is arranged in the closed end  22  of the motor housing member  21 . The pump  101  of the present embodiment is of a displacement type. The pump  101  includes an accommodation portion  103 , which is located in the closed end  22 , and a rotation body  104 . The first end  11   a  of the low-speed shaft  11  is coupled to the rotation body  104 . 
     The motor housing member  21  includes a first oil conduit  111  and a second oil conduit  112  that form part of the oil passage  102 . The first oil conduit  111  includes a first end that opens in the accommodation portion  103  and a second end that opens in an end surface  21   a  of the open end of the motor housing member  21  at a location where the end surface  21   a  contacts the end surface  24   a . The second oil conduit  112  includes a first end that opens in the accommodation portion  103  and a second end that opens in the end surface  21   a  of the motor housing member  21  at a location where the end surface  21   a  contacts the end surface  24   a.    
     The main body  25  includes a third oil conduit  113  and a fourth oil conduit  114  that form part of the oil passage  102 . The third oil conduit  113  opens in the two axial end surfaces of the main body  25 . The third oil conduit  113  includes a first end that opens in the end surface of the main body  25  at a position opposing the second end of the first oil conduit  111  and is in communication with the first oil conduit  111 . The fourth oil conduit  114  includes a first end that opens in the end surface of the main body  25  at a position opposing the second end of the second oil conduit  112  and is in communication with the second oil conduit  112 . The fourth oil conduit  114  also includes a second end defining an opening  114   a  that opens in the inner circumferential surface of the main body  25 . 
     The cover  26  includes a fifth oil conduit  115  that forms part of the oil passage  102 . The fifth oil conduit  115  includes a first end that opens in the first plate surface  26   a  at a position opposing a second end of the third oil conduit  113  and is in communication with the third oil conduit  113 . The fifth oil conduit  115  also includes a second end that opens in the first plate surface  26   a  at a position opposing the posts  82 . 
     The posts  82  include a sixth oil conduit  116  that forms part of the oil passage  102 . The sixth oil conduit  116  includes a first end that opens in the end surfaces of the posts  82  at a position opposing the second end of the fifth oil conduit  115  and is in communication with the fifth oil conduit  115 . The sixth oil conduit  116  also includes a second end that opens in the outer surfaces of the posts  82  at a position opposing the roller portion  72 . Although not shown in the drawings, there are two fifth oil conduits  115  and two sixth oil conduits  116  branched from the third oil conduit  113 . The oil O is supplied to the inside of the ring member  62  through the sixth oil conduit  116  that extends through two of the three posts  82 . 
     The centrifugal compressor  10  is used with the portion inside the speed increaser housing member  23  that is in communication with the fourth oil conduit  114  located at the lowermost position in the vertical direction. The opening  114   a  of the fourth oil conduit  114  is directed upward in the vertical direction. Gravitational force stores the oil O inside the speed increaser housing member  23  at the location that is in communication with the fourth oil conduit  114 . 
     When the pump  101  is driven, the oil O sequentially flows through the fourth oil conduit  114 , the second oil conduit  112 , the accommodation portion  103 , the first oil conduit  111 , the third oil conduit  113 , the fifth oil conduit  115 , and the sixth oil conduit  116 . The oil O that flows to the sixth oil conduit  116  is supplied to the inside of the ring member  62  to lubricate the rollers  71 . The oil O is discharged out of the ring member  62  through the discharge passage  65 . The oil O discharged out of the ring member  62  collects in the speed increaser chamber S 2 . The speed increaser chamber S 2  functions as a reservoir chamber that stores the oil O. The lower portion of the ring member  62  is immersed in the oil O inside the speed increaser chamber S 2 . Thus, when the ring member  62  rotates, the oil O increases the rotation resistance of the ring member  62 . 
     With the above structure, the rotation of the rollers  71  forms a thin film of the oil O that is solidified, or an elastohydrodynamic lubrication (EHL) film, at the ring contact locations Pa and the shaft contact locations Pb. In other words, a thin film of the oil O exists between the circumferential surface of each roller portion  72  and the inner circumferential portion of the circumferential wall  64 . In the same manner, a thin film of the oil O that is solidified exists between the circumferential surface of the high-speed shaft  12  and the circumferential surface of each roller portion  72 . The thin film of the solidified oil O between the circumferential surface of the high-speed shaft  12  and the circumferential surface of each roller portion  72  transmits the rotation force of the roller  71  to the high-speed shaft  12  and consequently rotates the high-speed shaft  12 . The circumferential wall  64  rotates at the same speed as the low-speed shaft  11 , and the rollers  71  each rotate at a higher speed than the low-speed shaft  11 . Further, the high-speed shaft  12 , which is smaller in diameter than each roller portion  72 , is rotated at a higher speed than the roller portion  72 . In this manner, the speed increaser  60  rotates the high-speed shaft  12  at a higher speed than the low-speed shaft  11 . The speed increaser  60  connects the impeller  52 , which is coupled to the high-speed shaft  12 , and the electric motor  13 , which rotates the low-speed shaft  11 . 
     When the ring member  62  rotates, the circumferential wall  64  lifts and agitates the oil  0  in the speed increaser chamber S 2 . To reduce the agitation resistance, the speed increaser  60  of the present embodiment includes a partition  90 . 
     As shown in  FIGS. 2 and 3 , the partition  90  includes a ring-shaped partition body  91  and a ring-shaped partition flange  92 . The partition flange  92  extends from a first axial end of the partition body  91 . The partition  90  includes openings through which the inner and outer sides of the partition  90  are in communication, more specifically, holes  93  that extend through the partition body  91  in the radial direction. The discharge passage  65  and the holes  93  are laid out at non-overlapping positions in the radial direction and axial direction of the circumferential wall  64 . 
     The partition body  91  is longer than the ring member  62  in the axial direction. The partition body  91  is shorter than the speed increaser chamber S 2  in the axial direction Z, that is, shorter than the distance between the inner surfaces of the speed increaser housing member  23  opposed in the axial direction Z. The inner diameter of the partition body  91  is larger than the outer diameter of the circumferential wall  64  of the ring member  62 . 
     The partition  90  is coupled to the speed increaser housing member  23  by fastening the partition flange  92  to the cover  26  with bolts (not shown). The partition  90  is located between the outer circumferential surface of the ring member  62  and the inner circumferential surface of the speed increaser housing member  23 . The partition  90  is arranged in concentricity with the partition body  91  and the ring member  62 . The partition  90  is located between the opening  114   a  and the ring member  62  (circumferential wall  64 ) so as to block the opening  114   a  from the ring member  62 . 
     The speed increaser  60  includes a communication passage  96  extending between a second axial end of the partition body  91 , which is the one of the two axial ends located at the side opposite to the partition flange  92 , and the closed end  24  of the main body  25 . In the description hereafter, the radial direction refers to the radial direction of the high-speed shaft  12 . The radial direction of the partition  90  coincides with the radial direction of the circumferential wall  64  and the radial direction of the high-speed shaft  12 . Further, the axial direction refers to the axial direction of the high-speed shaft  12 . The axial direction of the partition  90  coincides with the axial direction of the circumferential wall  64 , the axial direction of the high-speed shaft  12 , and the axial direction of the rollers  71 . 
     In the speed increaser chamber S 2 , the region extending radially inward from the partition  90  defines an agitation region  94  and the region extending radially outward from the partition  90  defines a reservoir region  95 . The agitation region  94  and the reservoir region  95  are in communication through the communication passage  96 . Further, the agitation region  94  and the reservoir region  95  are in communication through the holes  93 . The reservoir region  95  is in communication with the fourth oil conduit  114 . The oil O discharged out of the ring member  62  through the discharge passage  65  enters the agitation region  94 . The oil O then flows through the communication passage  96  and the holes  93  to the reservoir region  95 . The size of the communication passage  96  and the number and area of the holes  93  are determined in accordance with the displacement of the pump  101  and the lubrication properties required for the speed increaser  60 . 
     The operation of the speed increaser  60  and the centrifugal compressor  10  in the present embodiment will now be described. 
     When the electric motor  13  is driven, the rotation of the low-speed shaft  11  drives the pump  101  and supplies the oil O to the inside of the ring member  62 . The oil O supplied to the inside of the ring member  62  is discharged out of the ring member  62  through the discharge passage  65 . The rotation of the ring member  62  agitates the oil O as the circumferential wall  64  lifts the oil O that has been discharged out of the ring member  62  through the discharge passage  65 . During the rotation of the ring member  62 , centrifugal force scatters the agitated oil O outward in the radial direction. The oil O is scattered throughout the agitation region  94 . The partition  90  restricts radially outward scattering of the oil O beyond the partition  90 . Accordingly, the partition  90  reduces the force of the oil O. The oil O is discharged out of the agitation region  94  through the communication passage  96  and into the reservoir region  95 . The oil O is also discharged out of the holes  93  into the reservoir region  95 . 
     The oil O agitated by the ring member  62  is primarily the oil O in the agitation region  94 . The amount of oil O agitated by the rotation of the ring member  62  is limited in the reservoir region  95 . Accordingly, the absolute amount of the oil O agitated by the rotation of the ring member  62  is less than that when the partition  90  is not present. 
     Further, by limiting the agitated amount of the oil O in the reservoir region  95 , less gas is contained in the oil O. Without the partition  90 , when the oil O is entirely agitated in the speed increaser chamber S 2 , the oil O will entirely contain gas. Consequently, the pump  101  will pump the oil O that contains gas. This will reduce the flow rate of the pump  101 . In contrast, the pump  101  of the present embodiment pumps the oil O that includes a limited amount of gas from the reservoir region  95 . This avoids situations in which the oil O reduces the flow rate. 
     In addition, the rotation of the ring member  62  applies force acting in the rotation direction of the ring member  62  to the oil O that is agitated in the agitation region  94 . Thus, the agitation resistance is small in the agitation region  94 . 
     The present embodiment has the advantages described below. 
     (1) The partition  90  restricts radially outward scattering of the oil O agitated by the ring member  62 . This reduces the force of the oil O and limits disturbance in the flow of the oil O in the speed increaser chamber S 2 . Disturbance in the flow of the oil O is one factor that increases the agitation resistance. Thus, the agitation resistance can be decreased by limiting disturbance in the flow of the oil O. 
     (2) The partition body  91  has a closed shape and separates the agitation region  94  from the reservoir region  95 . Thus, the absolute amount of the oil O agitated by the rotation of the ring member  62  is less than that when the partition  90  is not present. This decreases the agitation resistance of the oil O. 
     (3) The partition body  91  includes the holes  93 . Thus, the oil O flows through the holes  93  from the agitation region  94  to the reservoir region  95 . The flow of the oil O from the agitation region  94  to the reservoir region  95  reduces the oil amount in the agitation region  94  and decreases the agitation resistance. Further, since the oil O flows through the holes  93 , the force of the oil O is weakened when the oil O exits the holes  93 . This limits disturbance in the flow of the oil O. 
     (4) The discharge passage  65  and the holes  93  are non-overlapped in the radial and axial directions of the circumferential wall  64 . Thus, the oil O discharged from the discharge passage  65  easily strikes the inner circumferential surface of the circumferential wall  64 . Accordingly, the oil O discharged out of the ring member  62  easily flows into the agitation region  94 . Further, the oil O discharged out of the discharge passage  65  does not directly flow to the reservoir region  95 . This limits disturbance in the flow of the oil O. 
     (5) The second end of the fourth oil conduit  114  serves as the opening  114   a  that opens in the inner circumferential surface of the speed increaser housing member  23  (main body  25 ). The partition  90  is located between the opening  114   a  and the ring member  62  (circumferential wall  64 ) to block the opening  114   a  from the ring member  62 . This prevents the agitated oil O from being directly discharged out of the speed increaser housing member  23  and limits the amount of gas that the oil O entirely contains. 
     It should be apparent to those skilled in the art that the present invention may be embodied in many other specific forms without departing from the spirit or scope of the invention. Particularly, it should be understood that the present invention may be embodied in the following forms. 
     The positions of the holes  93  may be changed. For example, the holes  93  may be located at positions opposing the discharge passage  65 . Further, the holes  93  may be located in a vertically lower or upper portion of the partition body  91  at any position in the horizontal direction. 
     As shown in  FIG. 5 , a modified example of the partition body  91  may include an opening  120  that is a cutout extending in the axial direction from the axial end located at the side opposite to the partition flange  92 . The opening  120  of the partition body  91  may extend over the entire partition body  91  in the axial direction. Further, the partition body  91  may include multiple openings  120  having different dimensions. 
     As long as the partition body  91  includes the holes  93 , the communication passage  96  does not have to be formed. That is, the axial dimension of the partition body  91  may be the same as that of the speed increaser chamber S 2 . Even in this case, the oil O flows from the agitation region  94  to the reservoir region  95  through the holes  93 . 
     The discharge passage  65  and the holes  93  may be laid out to partially overlap one another in at least one of the radial and axial directions of the circumferential wall  64 . 
     The partition body  91  does not have to include the holes  93 . 
     The partition  90  may be fixed to the closed end  24  of the main body  25 . 
     The region between the cover  26  and the circumferential wall  64  defines the discharge passage  65 . Instead, the circumferential wall  64  may include a hole that defines a discharge passage. 
     The fifth oil conduit  115  and the sixth oil conduit  116  may be changed in number. For example, the oil O may be supplied from every one of the posts  82 . Alternatively, the oil O may be supplied from only one of the posts  82 . 
     The partition body  91  may have a closed shape that is not the shape of a ring. For example, the closed shaped may be a polygon such as a tetragon. 
     The partition body  91  does not need to have a closed shape. For example, a partition body may extend over only one circumferential half of the partition body  91  in the circumferential direction. In this case, the partition body  91  is semicircular. It is also desirable in this case that the partition body  91  be located at a vertically lower position in the speed increaser chamber S 2 . 
     The pump does not have to be incorporated in the centrifugal compressor and may be an external pump. 
     The rollers  71  may be changed in number. For example, the number of the rollers  71  may be four or five. 
     The speed increaser  60  may use a wedge effect. In this case, at least one of the rollers is a movable roller moved by the rotation of the ring member  62 . 
     The centrifugal compressor  10  may be applied to any subject, and the subject compressed by the centrifugal compressor  10  may be any fluid. For example, the centrifugal compressor  10  may be used in an air conditioner, and the fluid that is subject to compression may be a refrigerant. Further, the centrifugal compressor  10  does not have to be installed in a vehicle and may be installed in any subject. 
     The present examples and embodiments are to be considered as illustrative and not restrictive, and the invention is not to be limited to the details given herein, but may be modified within the scope and equivalence of the appended claims.