centrifugal compressor

Abstract

Centrifugal compressor (10) comprising the following: a case (20); a ring component (62) which is housed in the housing (20), wherein the ring component (62) rotates in accordance with a rotation of a low-speed shaft (11) and has a circumferential wall (64); a high-speed shaft (12) located on an inner side of the circumferential wall (64) and having two flanges (12a) spaced apart from each other and opposite to each other in the axial direction of the high-speed shaft (12); a plurality of rollers (71) located between the circumferential wall (64) and the high-speed shaft (12); a wheel (52) which rotates in one piece with the high-speed shaft (12); a subdivision (26) that separates an empty space in the housing (20) into a speed transmission device chamber (S2) and an impeller chamber (S3), wherein the speed transmission device chamber (S2) houses the ring component (62) and the rollers (71) and the impeller chamber (S3) houses the impeller (52); an insertion hole (28) provided in the subdivision (26), wherein the high-speed shaft (12) is inserted through the insertion hole (28); a seal (34) located in the insertion hole (28) to seal a boundary between the subdivision (26) and the high-speed shaft (12); an oil supply passage (107) located in the housing (20) and having an open end in the insertion hole (28) and designed to supply oil to the seal (34); a plurality of pairs of roller bearings (76, 77), each pair of roller bearings (76, 77) supporting two axial ends of a corresponding roller (71); and a plurality of bearing bushings (90) located in the subdivision (26), each bearing bushing (90) accommodating one of a corresponding pair of roller bearings (76, 77), and wherein a roller bearing (76) of each plurality of pairs of roller bearings (76, 77) partially projects to a large-diameter section (29) of the insertion hole (28) in the radial direction of the high-speed shaft (12), wherein the subdivision (26) has a connecting passage (93) which allows a connection between a section of the insertion hole (28), which is closer to the speed transmission device chamber (S2) than the seal (34), and the bearing bushings (90), the insertion hole (28) has the large-diameter section (29) and a small-diameter section (30) which is smaller than the large-diameter section (29), the seal (34) is provided in the small diameter section (30), and one of the flanges (12a) is provided in the large diameter section (29).

Description

[0001] The present invention relates to a centrifugal compressor.

[0002] JP 2016-194251 A describes an example of a centrifugal compressor including a speed increaser. The centrifugal compressor has a housing and a partition that divides the empty space in the housing into an impeller chamber and a speed increaser chamber. The speed increaser chamber houses a speed increaser mechanism. The impeller chamber houses an impeller. The speed increaser mechanism includes a ring member, a high-speed shaft, and rollers. The ring member is rotated by rotation of a low-speed shaft. The high-speed shaft is located on the inner side of the ring member. The rollers are located between the ring member and the high-speed shaft, in contact with both the ring member and the high-speed shaft. Each of the rollers is supported by roller bearings.The roller bearings are housed in bearing housings or bushings located in the subdivision. The speed reduction mechanism is supplied with oil to lubricate the rollers.

[0003] Each of the rollers covers an axial end surface of the corresponding roller bearing that supports the rollers. Therefore, any of the rollers can block the oil supply to the corresponding roller bearings.

[0004] JP 2005-140306 A discloses a centrifugal compressor comprising: a casing; an annular member housed in the casing, the annular member rotating in accordance with rotation of a low-speed shaft and having a peripheral wall; a high-speed shaft located on an inner side of the peripheral wall; a plurality of rollers located between the peripheral wall and the high-speed shaft; an impeller rotating integrally with the high-speed shaft; a partition separating an empty space in the casing into a speed-increasing device chamber and an impeller chamber, the speed-increasing device chamber housing the annular member and the rollers, and the impeller chamber housing the impeller; an insertion hole provided in the partition, the high-speed shaft being inserted through the insertion hole.a seal located in the insertion hole to seal a boundary between the partition of the high-speed shaft; and an oil supply passage located in the housing and having an open end in the insertion hole; wherein the partition has a communication passage that allows communication between a portion of the insertion hole, which is closer to the speed-transforming device chamber than the seal, and the rollers.

[0005] US 2015 / 0 260 194 A1 discloses a centrifugal compressor having a plurality of rollers, a plurality of pairs of roller bearings, each pair of the roller bearings supporting two axial ends of a corresponding one of the rollers, and a plurality of bearing bushes located in a partition, each of the bearing bushes housing one of a corresponding pair of the roller bearings.

[0006] Another centrifugal compressor is known from US 4 249 784 A.

[0007] It is an object of the present invention to provide a centrifugal compressor that limits a shortage of oil supply to roller bearings that support rollers.

[0008] The object of the invention is achieved with a centrifugal compressor according to claim 1. Advantageous developments of the invention are the subject of the dependent claims.

[0009] The embodiments, 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. Figure 1 is a schematic cross-sectional view of a centrifugal compressor; Fig. Figure 2 is a partial perspective view of a speed reduction mechanism; Fig. 3 is a partially enlarged cross-sectional view of a speed reduction device; Fig. 4 is a diagram showing the relationship between bearing bushes and an insertion hole; Fig. 5 is a view of a cover in which bearing bushes are separated from an insertion hole.

[0010] An embodiment of a centrifugal compressor will now be described. The centrifugal compressor of the present embodiment has a speed increasing device and is installed in a fuel cell vehicle (FCV) powered by a fuel cell. The centrifugal compressor supplies air to the fuel cell.

[0011] As 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-increasing device 60, and an impeller 52. The speed-increasing device 60 increases the rotational 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 high-speed shaft 12 has two flanges 12a that are spaced apart from and opposite to each other in the axial direction of the high-speed shaft 12. The two shafts 11 and 12 are formed of, for example, a metal, specifically, iron or an iron alloy.

[0012] The centrifugal compressor 10 includes a housing 20 that forms the outer shell of the centrifugal compressor 10. The housing 20 houses the two shafts 11 and 12, the electric motor 13, and a speed-transmitting mechanism 61 that forms part of the speed-transmitting device 60. The housing 20 is, for example, substantially tubular (in particular, cylindrical) as a whole.

[0013] The housing 20 includes a motor housing member 21 that houses the electric motor 13, a speed-increasing device housing member 23 that houses the speed-increasing mechanism 61, and a compressor housing member 50 that has a suction port 50a that sucks fluid. Among the two end surfaces 20a and 20b of the housing 20 in the axial direction, the suction port 50a is located in the first end surface 20a. The compressor housing member 50, the speed-increasing device housing member 23, and the motor housing member 21 are aligned in this order from the side closer to the suction port 50a in the axial direction of the housing 20. In the present embodiment, the speed-increasing mechanism 61 and the speed-increasing device housing member 23 constitute the speed-increasing device 60.

[0014] The motor housing component 21 is tubular (specifically, cylindrical) as a whole and has a closed end 22 (end wall). The second end surface 20b defines the outer surface of the closed end 22 of the motor housing component 21 and is located on the side of the housing 20 opposite the first end surface 20a, which has the suction port 50a. The speed reduction device housing component 23 includes a main body 25 and a cover 26. The main body 25 is tubular (specifically, cylindrical) and has a closed end 24 (end wall). The cover 26 is located on the side opposite the closed end 24 in the axial direction of the main body 25.

[0015] The motor housing member 21 and the speed reducer housing member 23 are coupled to each other, with the open end of the motor housing member 21 joined to the closed end 24 of the main body 25. The closed end 24 has an end surface 24a covered by the motor housing member 21. The inner surface of the motor housing member 21 and the end surface 24a define a motor housing chamber S1. The motor housing chamber S1 houses the electric motor 13. Further, the motor housing chamber S1 houses the low-speed shaft 11 in a state where the low-speed shaft 11 is coaxial with the housing 20.

[0016] The low-speed shaft 11 is rotatably supported by the housing 20. The centrifugal compressor 10 includes a first bearing 31. The first bearing 31 is disposed in the closed end 22 of the motor housing component 21. The low-speed shaft 11 has a first end 11a supported by the first bearing 31. A portion of the first end 11a is inserted through the first bearing 31 and fitted into the closed end 22 of the motor housing component 21.

[0017] The closed end 24 of the main body 25 has an insertion hole 27 slightly larger than a second end 11b of the low-speed shaft 11 located on the side opposite the first end 11a. The centrifugal compressor 10 includes a second bearing 32 located in the insertion hole 27 and a motor seal 33. The second end 11b of the low-speed shaft 11 is supported by the second bearing 32. The motor seal 33 restricts the leakage of oil O from the speed-transformer housing member 23 to the motor housing chamber S1.

[0018] The second end 11b of the low-speed shaft 11 is inserted into the insertion hole 27 of the main body 25. A part of the low-speed shaft 11 is located in the speed reduction device housing component 23.

[0019] The electric motor 13 includes a rotor 41 fixed to the low-speed shaft 11 and a stator 42 located on 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 a current flows to the coil 44.

[0020] The cover 26 is, for example, disc-shaped and has the same diameter as the speed-transmitting device housing member 23. The two sides of the cover 26 in the axial direction define first and second plate surfaces 26a and 26b, respectively. The speed-transmitting device housing member 23 is assembled by joining the open end of the main body 25 to the first plate surface 26a. The first plate surface 26a of the cover 26 and the inner surface of the speed-transmitting device housing member 23 define a speed-transmitting device chamber S2. The speed-transmitting device chamber S2 houses the speed-transmitting mechanism 61.

[0021] The cover 26 forming the speed-increasing device housing component 23 has an insertion hole 28 for inserting the high-speed shaft 12, which forms part of the speed-increasing mechanism 61. The insertion hole 28 has a large-diameter portion 29 and a small-diameter portion 30 that has a smaller diameter than the large-diameter portion 29. The large-diameter portion 29 is open in the first plate surface 26a. The small-diameter portion 30 is open in the second plate surface 26b. One of the flanges 12a of the high-speed shaft 12 is located in the large-diameter portion 29. A part of the high-speed shaft 12 is inserted through the insertion hole 28 and located in the compressor housing component 50.

[0022] The centrifugal compressor 10 includes a seal 34 located between the wall surface of the insertion hole 28 and the high-speed shaft 12 to seal the boundary between the wall surface of the insertion hole 28 and the high-speed shaft 12. The seal 34 restricts the leakage of oil O from the speed reducer housing member 23 into the compressor housing member 50. The seal 34 is located in the small-diameter portion 30. A mechanical seal is used as the sealing member 34 of the present embodiment.

[0023] The compressor housing member 50 is substantially tubular and has a through-hole 51 extending through the compressor housing member 50 in the axial direction. The two axial ends of the compressor housing member 50 each define a first end surface 50b and a second end surface 50c. The first end surface 50b of the compressor housing member 50 defines the first end surface 20a of the housing 20. The through-hole 51 opens in the first end surface 50b and functions as the suction port 50a.

[0024] The compressor housing member 50 and the cover 26 are coupled to each other with the first end surface 50c joined or connected to the second plate surface 26b. The second end surface 50c is the end surface of the compressor housing member 50 on the side opposite to the first end surface 50b, and the second plate surface 26b is the end surface of the cover 26 on the side opposite to the first plate surface 26a. The wall surface of the through-hole 51 and the second plate surface 26b of the cover 26 define an impeller chamber S3. The impeller chamber S3 houses the impeller 52. The through-hole 51 functions as the suction port 50a and defines the impeller chamber S3. The suction port 50a is in communication with the impeller chamber S3. The cover 26, which is located between the speed transmission device chamber S2 and the impeller chamber S3, corresponds to a partition that separates the two chambers S2 and S3.

[0025] The through-hole 51 has a diameter that is constant from the suction port 50a to an intermediate position in the axial direction. From the intermediate position, the through-hole 51 has a substantially truncated cone shape, whose diameter gradually increases toward the cover 26. Therefore, the impeller chamber S3 defined by the wall surface of the through-hole 51 has a substantially truncated cone shape.

[0026] The impeller 52 has a contour that gradually decreases in diameter from the basal end surface 52a to the distal end surface 52b. The impeller 52 has a shaft insertion hole 52c that extends in the axial direction of the impeller 52 and allows insertion of the high-speed shaft 12. The impeller 52 is coupled to the high-speed shaft 12 with a part of the high-speed shaft 12 inserted through the shaft insertion hole 52c and protruding into the through hole 51. The impeller 52 is rotated integrally with the high-speed shaft 12. The basal end surface 52a of the impeller 52 and the second plate surface 26b of the cover 26 define a rear surface region S4. The rotation of the high-speed shaft 12 rotates the impeller 52 and compresses the fluid sucked through the suction port 50a.

[0027] 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 passing through the diffuser passage 53 enters the discharge chamber 54. The through-hole 51 has an open end opening toward the second plate surface 26b of the cover 26 and is continuous with the diffuser passage 53. The diffuser passage 53 is defined by the second plate surface 26b and the surface of the compressor housing member 50 opposite the second plate surface 26b. The diffuser passage 53 is located outward from the impeller chamber S3 in the radial direction of the high-speed shaft 12 and has a closed shape (specifically, a circular shape) so as to surround the impeller 52 and the impeller chamber S3.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 S3 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 is then discharged from the discharge chamber 54.

[0028] 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).

[0029] The speed increase mechanism 61 of the speed increase device 60 includes an annular member 62 coupled to the second end 11b of the low-speed shaft 11. The annular member 62 includes a disc-shaped base 63 and a peripheral wall 64. The base 63 is coupled to the second end 11b of the low-speed shaft 11, and the peripheral wall 64 is annular and extends in the axial direction from the peripheral edge of the base 63. The peripheral wall 64 has an inner diameter larger than the diameter of the second end 11b of the low-speed shaft 11.

[0030] In the present embodiment, the ring member 62 is coupled to the low-speed shaft 11 in a state where the base 63 (ring member 62) is coaxial with the low-speed shaft 11. The peripheral wall 64 is also coaxial with the low-speed shaft 11. The rotation of the low-speed shaft 11 rotates the ring member 62.

[0031] A part of the high-speed shaft 12 is located on the inner side of the peripheral wall 64 in the radial direction of the ring member 62. The speed reduction mechanism 61 has three rollers 71 located between the high-speed shaft 12 and the peripheral wall 64 in contact with both the peripheral wall 64 and the high-speed shaft 12.

[0032] As in Fig. 2 and Fig. As shown in Figure 3, the three rollers 71 are identically shaped. The rollers 71 each include a cylindrical roller portion 72, first and second end surfaces 72a and 72b in the axial direction of the roller portion 72, a cylindrical first projection portion 73 projecting from the first end surface 72a, and a cylindrical second projection 74 projecting from the second end surface 72b. The roller portion 72 is coaxial with the first projection 73 and the second projection 74. The axial direction of the roller portion 72 is hereinafter referred to as the axial direction Z of the rollers 71.

[0033] The roller portion 72 has a diameter (length in a direction orthogonal to the axial direction Z) larger than that of the high-speed shaft 12. The axial direction Z coincides with the rotational axis of the high-speed shaft 12. The rollers 71 are spaced apart from each other in the circumferential direction of the high-speed shaft 12. The rollers 71 are each formed of a metal, for example. More specifically, the rollers 71 are formed of the same metal as the high-speed shaft 12, for example, iron or an iron alloy.

[0034] As in Fig. 2 and Fig. 4, the speed reduction mechanism 61 includes a support 80. The support 80 cooperates with the cover 26 to support the rollers 71 such that the rollers 71 are rotatable. The support 80 is located on the inner side of the peripheral wall 64. The support 80 includes a disc-shaped support base 81 that is slightly smaller in diameter than the peripheral wall 64, and three posts 82 extending in the axial direction from the support base 81. The support base 81 is opposite to the cover 26 in the axial direction Z. The support base 81 has an opposite plate surface 81a that is opposite to the first plate surface 26a of the cover 26. The three posts 82 extend from the opposite plate surface.Counter plate surface 81a toward the cover 26, filling three gaps each defined between the inner peripheral surface of the peripheral wall 64 and the outer peripheral surfaces of two adjacent ones of the roller sections 62.

[0035] As in Fig. 1 and Fig. 2, the support 80 has screw holes 84, each extending through the corresponding pile 82 and allowing insertion of a screw 83. The cover 26 has threaded holes 85 corresponding to the screw holes 84. Each screw hole 84 is in communication with the corresponding threaded hole 85. In a state where the distal end surfaces of the piles 82 are joined to the first plate surface 26a, the piles 82 are fixed to the cover 26 by inserting each screw 83 through the corresponding screw hole 84 and tightening the screw 83 to the corresponding threaded hole 85.

[0036] The speed reduction device 60 includes three pairs of first roller bearings 76 and second roller bearings 77, each pair of first roller bearings 76 and second roller bearings 77 supporting a corresponding one of the rollers 71 in a rotatable manner. The first roller bearings 76 are disposed in the cover 26. The second roller bearings 77 are disposed in the support base 81. The rollers 71 are supported by the first roller bearings 76 and second roller bearings 77 to be held between the cover 26 and the support base 81.

[0037] More precisely, as in Fig. 3 and Fig. As shown in Fig. 4, the cover 26 has three bearing sleeves 90 recessed from the first plate surface 26a in the thickness direction. Each bearing sleeve 90 houses the corresponding first roller bearing 76. The bearing sleeves 90 are arranged around the insertion hole 28 in the circumferential direction of the cover 26 or the circumferential direction of the high-speed shaft 12. The pitch or interval of adjacent ones of the bearing sleeves 90 in the circumferential direction of the cover 26 is set in conformity with the pitch or interval of the corresponding rollers 71.

[0038] The bearing sleeves 90 are in communication with the large-diameter portion 29 of the insertion hole 28. In the present embodiment, the bearing sleeves 90 are continuously connected to the large-diameter portion 29 of the insertion hole 28. More specifically, the bearing sleeves 90 are directly connected to the insertion hole 28 without any other gaps existing therebetween in the radial direction of the high-speed shaft 12. The seal 34 is located in the small-diameter portion 30, and the bearing sleeves 90 are in communication with the large-diameter portion 29. Accordingly, the bearing sleeves 90 are in communication with portions of the insertion hole 28 that are closer to the speed-transforming device chamber S2 than to the seal 34.

[0039] Each bearing sleeve 90 is defined by an arcuate wall surface 91. The continuous connection of the bearing sleeves 90 to the large-diameter portion 29 of the insertion hole 28 partially interrupts the wall surfaces 91. As indicated by the double-dashed lines in Fig. 4, each circle C including the arc of the wall surface 91 has a slightly larger diameter than the first roller bearings 76. In other words, the wall surface 91 has the shape of a circle that is partially cut out or truncated.

[0040] The discontinuous portions of each wall surface 91 are connected to each other at a boundary 93 of the bearing sleeves 90 and the insertion hole 28 by a distance or dimension L1 with the minimum distance. The dimension L1 is smaller than the diameter of the first roller bearing 76. This restricts the removal of the first roller bearing 76 into the insertion hole 28 caused by the connection of the bearing sleeve 90 and the insertion hole 28. The boundary 93 of each bearing sleeve 90 and the insertion hole 28 corresponds to a communication passage that enables communication between the bearing sleeve 90 and the insertion hole 28.

[0041] When the bearing sleeves 90 accommodate the first roller bearings 76, the first roller bearings 76 partially protrude from the boundaries 93 to the large-diameter portion 29 in the radial direction and are located in the large-diameter portion 29.

[0042] The cover 26 has recesses 92 recessed from the bottom of each bearing sleeve 90 in the thickness direction. Each recess 92 is circular when viewed in the axial direction Z. The recess 92 has a smaller diameter than the first roller bearings 76. The axial direction of the recess 92 coincides with the axial direction of the bearing sleeve 90.

[0043] As described above, the flange 12a of the high-speed shaft 12 is located in the large-diameter portion 29. The bearing sleeve 90 and the first roller bearings 76 housed in the bearing sleeves 90 oppose the flange 12a in the radial direction of the high-speed shaft 12. The bearing sleeves 90 and the first roller bearings 76 housed in the bearing sleeves 90 do not oppose the seal 34 located in the small-diameter portion 30 in the radial direction of the high-speed shaft 12.

[0044] As in Fig. 1 and Fig. As shown in Figure 2, the support base 81 has three support sleeves 86 recessed from the opposing plate surface 81a in the thickness direction. Each support sleeve 86 is opposite the corresponding bearing sleeve 90 in the axial direction Z. The support sleeve 86 is circular when viewed in the axial direction Z. The support sleeve 86 has a slightly larger diameter than the second roller bearings 77. The support sleeve 86 houses the corresponding second roller bearing 77.

[0045] The first projection 73 of each roller 71 is inserted into the corresponding first roller bearing 76. The second projection 74 of the roller 71 is inserted into the corresponding second roller bearing 77. Therefore, the rollers 71 are supported in a rotatable manner.

[0046] The rollers 71, the ring member 62, and the high-speed shaft 12 form a unit with each roller section 72 being forced against the high-speed shaft 12 and the peripheral wall 64. The high-speed shaft 12 is rotatably supported by the three roller sections 72. A pressing load is applied to the location where the outer peripheral surface of each roller section 72 contacts the inner peripheral surface of the peripheral wall 64 and to the location where the outer peripheral surface of each roller section 72 contacts the peripheral surface of the high-speed shaft 12.

[0047] As in Fig. As shown in Figure 1, each roller portion 72 is held between the two flanges 12a in the axial direction. This limits displacement of the high-speed shaft 12 and the roller portions 72 in the axial direction Z of the high-speed shaft 12.

[0048] The centrifugal compressor 10 includes an oil supply mechanism 100 that supplies oil O to the speed-increasing mechanism 71. The oil supply mechanism 100 includes a pump 101 and an oil passage 102. The pump 101 is driven such that the oil O circulates through the oil passage 102 and flows to the speed-increasing device chamber S2.

[0049] The pump 101 is arranged in the closed end 22 of the motor housing component 21. The pump 101 of the present embodiment is of an offset type. The pump 101 includes a housing portion 103 located in the closed end 22 and a rotating body 104. The first end 11a of the low-speed shaft 11 is coupled to the rotating body 104.

[0050] The housing 20 has a supply passage 105 forming part of the oil passage 102, and a circulation passage 106 forming part of the oil passage 102. The supply passage 105 and the circulation passage 106 are defined in the inner wall of the housing 20. The supply passage 105 includes an oil passage 109, a first branch passage 107, and a second branch passage 108. One end of the oil passage 109 is in communication with the accommodation portion 103. The other end of the oil passage 109 branches into the first branch passage 107 and the second branch passage 108. One end of the first branch passage 107 is open in the insertion hole 28. The other end of the first branch line is open at the point where the first branch line 107 and the second branch line 108 branch.

[0051] At least one of the piles 82 has a speed-increasing device-side supply passage 110 that forms part of the oil passage 102. One end of the speed-increasing device-side supply passage 110 is open in the second branch line 108 and communicates with the second branch line 108. The other end of the speed-increasing device-side supply passage 110 is open in an end face of the pile 82 at a position opposite the corresponding roller portion 82.

[0052] The circulation passage 106 connects the accommodation section 103 and the speed increaser chamber S2. The centrifugal compressor 10 is used with the portion of the speed increaser housing member 23 that communicates with the circulation passage 106, which is located at the lower side in the vertical direction. Therefore, gravitational force stores the oil O in the portion of the speed increaser housing member 23 that communicates with the circulation passage 106.

[0053] When the pump 101 is driven, the oil O flows sequentially through the circulation passage 106, the accommodation portion 103, and the supply passage 105, and is supplied from the first branch line 107 to the seal 34. Furthermore, the oil O supplied from the second branch line 108 to the speed-increasing device-side supply passage 110 is supplied to the speed-increasing mechanism 61 (rollers 71). The first branch line 107 corresponds to an oil supply passage that supplies the oil O to the seal 34.

[0054] With the above configuration, when the rollers 71 rotate, the peripheral surfaces of the roller portions 72 contact the inner peripheral surface of the peripheral wall 64 with a thin film of oil O interposed therebetween. Similarly, the peripheral surface of the high-speed shaft 12 contacts the peripheral surfaces of the roller portions 72 with a thin film of solidified oil O interposed therebetween. The rotating force of the rollers 71 is transmitted to the high-speed shaft 12 via the thin film of solidified oil O formed between the peripheral surface of the high-speed shaft 12 and the peripheral surfaces of the roller portions 72, thus rotating the high-speed shaft 12. The peripheral wall 64 rotates at the same speed as the low-speed shaft 11. Each roller 71 rotates at a higher speed than the low-speed shaft 11.Furthermore, the high-speed shaft 12, which has a smaller diameter than the roller sections 72, rotates at a higher speed than the roller sections 72. In this way, the speed transmission device 60 rotates the high-speed shaft 12 at a higher speed than the low-speed shaft 11.

[0055] The operation of the centrifugal compressor 10 of the present embodiment will now be described.

[0056] When the electric motor 13 is driven, the low-speed shaft 11 is rotated to drive the pump 101. The second branch line 108 supplies the oil O to the speed-increasing mechanism 61, and the first branch line 107 supplies the oil O to the seal 34. The rollers 71 cover the axial end surfaces of the first roller bearings 76. This prevents the oil O supplied from the speed-increasing device-side supply passage 110 from reaching the first roller bearings 76.

[0057] The oil O supplied from the first branch line 107 to the seal 34 flows into the insertion hole 28 to the speed reducer chamber S2 from the seal 34, that is, to the large-diameter portion 29. When the high-speed shaft 12 rotates, the centrifugal force of the high-speed shaft 12 urges the oil O to the radially outer side of the large-diameter portion 29. Since the large-diameter portion 29 is in communication with the bearing bushes 90, the oil O flowing to the large-diameter portion 29 is supplied to the bearing bushes 90. Therefore, the first roller bearings 76 are supplied with the oil O.

[0058] In the centrifugal compressor 10, the rear surface area S4 is defined between the basal end surface 52a of the impeller 52 and the cover 26 to prevent contact of the basal end surface 52a of the impeller 52 with the cover 26. A fluid compressed by the impeller 52 enters the rear surface area S4. The compressed fluid pushes the impeller 52 toward the suction port 50a. An axial force directed from the speed-increasing device chamber S2 to the impeller chamber S3 acts on the high-speed shaft 12. The axial force is transmitted to the rollers 71 via one of the two flanges 12a of the high-speed shaft 12, which is opposite to the second end surface 72b of the roller portions 72. The axial force is applied from the rollers 71 to the first roller bearings 76.The first roller bearings 76 tend to generate heat compared to the second roller bearings 77, however, the oil O is easily supplied to the first roller bearings 76 and limits the heat production and wear of the first roller bearings 76.

[0059] Additionally, in the present embodiment, the first roller bearings 76 partially protrude into the insertion hole 28. This limits the enlargement of the centrifugal compressor 10.

[0060] As in Fig. 5, when bearing bushes 200 are separated from an insertion hole 201, a wall of the cover 26 is provided between the bearing bushes 200 and the insertion hole 201. The insertion hole 201 shown in Fig. 5 has a smaller diameter than the insertion hole 28 of the embodiment. The size or diameter of the seal 34 varies depending on the type of seal. For example, if a mechanical seal is selected as the seal 34 to ensure sealing capability between the speed increaser chamber S2 and the impeller chamber S3, the seal 34 tends to be larger than a lip seal. In addition, the diameter of the insertion hole 201 is increased.

[0061] In this case, as indicated by the double dashed line in Fig.As shown in Fig. 5, if the distance between each bearing sleeve 200 and the insertion hole 201 needs to be maintained, the bearing sleeve 200 is located farther from the axis of the insertion hole 201 in the radial direction of the roller 71, and also the first roller bearing 76 is located farther from the axis of the insertion hole 201. Accordingly, the roller portions 72 need to have larger diameters so that the high-speed shaft 12 contacts the rollers 71. Further, the ring member 62 is enlarged. Enlarging the ring member 62 causes a decrease in a transmission ratio and also causes an enlargement of the speed increaser housing member 23 that houses the ring member 62, which causes an enlargement of the entire centrifugal compressor 10.

[0062] As in the present embodiment, when the wall separating the bearing bushings 90 from the insertion hole 28 is partially removed, the first roller bearings 76 are able to partially protrude into the insertion hole 28. Therefore, even if the diameter of the insertion hole 28 is increased to enlarge the seal 34, the first roller bearings 76 are not placed farther away from the axis of the insertion hole 28.

[0063] The foregoing embodiment has the advantages described below. (1) The oil O flows from the insertion hole 28 into the bearing bushes 90. This allows the oil O supplied to the seal 34 to be supplied to the first roller bearings 76. Accordingly, a shortage of supply of the oil O to the first roller bearings 76 is limited. (2) The insertion hole 28 is continuously connected to the bearing bushes 90. The first roller bearings 76 partially protrude into the insertion hole 28. This allows the first roller bearings 76 to be placed closer to the axis of the insertion hole 28, compared to when the insertion hole 28 is separated from the bearing bushes 90 and the first roller bearings 76 do not protrude into the insertion hole 28. Consequently, the diameter of each roller 71 (diameter of each roller portion 72) does not need to be increased to the point where the high-speed shaft 12 contacts the roller 71. The speed reducer housing member 23 housing the rollers 71 is not enlarged. Furthermore, a reduction in the transmission ratio caused by an increase in the ring member 62 is limited. (3) A mechanical seal is used as the seal 34. A mechanical seal requires a larger amount of oil than a lip seal. Accordingly, a large amount of oil O is supplied to the first roller bearings 76. This further limits a shortage of oil O supply to the first roller bearings 76. (4) The cover 26 has the recesses 92 recessed by the bearing bushes 90 in the thickness direction. The arrangement of the recesses 92 allows the oil O to enter the recesses 92 and further limits a shortage of the supply of the oil O to the first roller bearings 76.

[0064] The embodiment can be modified as follows.

[0065] Instead of a mechanical seal, a different type of seal, for example a lip seal, may be used as the seal 34.

[0066] The first roller bearings 76 do not need to partially protrude into the insertion hole 28. In other words, the bearing bushes 90 do not need to be continuously connected to the insertion hole 28. In this case, the cover 26 has a connecting passage that enables communication between the bearing bushes 90 and the insertion hole 28. The connecting passage connects the insertion hole 28 to the bearing bushes 90. The oil O is supplied to the bearing bushes 90 through the connecting passage.

[0067] The pump does not have to be integrated into the centrifugal compressor 10 and can be an external pump.

[0068] The number of rollers 71 can be changed. For example, the number of rollers 71 can be four or five. In this case, the number of each of the bearing bushes 90, the first roller bearings 76, and the second roller bearings 77 is also changed in accordance with the number of rollers 71.

[0069] The diameter of the insertion hole 28 can be constant.

[0070] The speed-transmitting device 60 can exhibit a wedge effect. In this case, at least one of the rollers 71 is a movable roller that is moved by the rotation of the ring member 62.

[0071] The centrifugal compressor 10 can be applied to any object, and the object compressed by the centrifugal compressor 10 can be any fluid. For example, the centrifugal compressor 10 can be used in an air conditioner, and the fluid subject to compression can be a refrigerant. Furthermore, the centrifugal compressor 10 does not need to be installed in a vehicle and can be installed in any object.

Claims

[1] Centrifugal compressor (10) comprising: a housing (20); a ring member (62) housed in the housing (20), the ring member (62) rotating in accordance with rotation of a low-speed shaft (11) and having a peripheral wall (64); a high-speed shaft (12) located on an inner side of the peripheral wall (64) and having two flanges (12a) spaced apart from and opposite to each other in the axial direction of the high-speed shaft (12); a plurality of rollers (71) located between the peripheral wall (64) and the high-speed shaft (12); an impeller (52) rotating integrally with the high-speed shaft (12); a partition (26) which separates an empty space in the housing (20) into a speed transmission device chamber (S2) and an impeller chamber (S3), wherein the speed transmission device chamber (S2) houses the ring member (62) and the rollers (71) and the impeller chamber (S3) houses the impeller (52); an insertion hole (28) provided in the partition (26), the high-speed shaft (12) being inserted through the insertion hole (28); a seal (34) located in the insertion hole (28) for sealing a boundary between the partition (26) and the high-speed shaft (12); an oil supply passage (107) located in the housing (20) and having an open end in the insertion hole (28) and configured to supply oil to the seal (34); a plurality of pairs of roller bearings (76, 77), each pair of roller bearings (76, 77) supporting two axial ends of a corresponding one of the rollers (71); and a plurality of bearing bushes (90) located in the partition (26), each of the bearing bushes (90) housing one of a corresponding pair of the roller bearings (76, 77), and one roller bearing (76) of each of the plurality of pairs of roller bearings (76, 77) partially projecting toward a large-diameter portion (29) of the insertion hole (28) in the radial direction of the high-speed shaft (12), wherein the partition (26) has a communication passage (93) which enables communication between a portion of the insertion hole (28) which is closer to the speed transmission device chamber (S2) than the seal (34) and the bearing bushes (90), the insertion hole (28) has the large-diameter section (29) and a small-diameter section (30) which is smaller than the large-diameter section (29), the seal (34) is provided in the small diameter portion (30), and one of the flanges (12a) is provided in the large diameter portion (29). [2] Centrifugal compressor (10) according to claim 1, wherein the bearing bushes (90) are continuously connected to the insertion hole (28), the roller bearings (76, 77) are partially located in the portion of the insertion hole (28) which is closer to the speed transmission device chamber (S2) than the seal (34), the connecting passage (93) is located at a boundary of the bearing bushes (90) and the insertion hole (28). [3] Centrifugal compressor (10) according to claim 1 or 2, wherein the seal (34) is a mechanical seal.

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