Foil bearing and drive shaft assembly and compressor including the same

Abstract

A bearing system (220) includes a foil bearing assembly (226) positioned within a cylindrical bore of a sleeve (224). The foil bearing includes a top foil layer and an outer layer. The bearing system includes a drive shaft (250) including a recess (280) axially aligned with the top foil layer. The recess defines a cavity having a volume and includes a forward end at a first circumferential position and a rearward end at a second circumferential position.

Description

[0001] Cross - reference to related applications

[0002] This application claims the benefit of priority to U.S. Patent Application No. 18 / 056,218, filed on November 16, 2022, the disclosure of which is incorporated herein by reference in its entirety. Technical field

[0003] The present disclosure generally relates to bearings and compressors, and more particularly, to foil bearings and drive shaft assemblies for use in compressors. Background art

[0004] Centrifugal compressors used in refrigeration and cooling systems can include foil bearings to support a drive shaft that transfers power from a motor to an impeller, which imparts kinetic energy to the incoming refrigerant. Typically, foil bearings are well - suited for the typical high - speed operating environment of centrifugal compressors, are compatible with all refrigerant compositions, and can be used with a wider variety of drive shaft materials, thereby allowing the use of lighter materials to reduce the amount of energy required to operate the compressor.

[0005] Conventionally, a foil bearing includes a compliant foil element surrounding the drive shaft. The foil bearing supports the drive shaft through a pressure distribution of a lubricating fluid, such as air and / or refrigerant, which is established between the drive shaft and the foil element by the rotation of the drive shaft. When the drive shaft reaches a sufficient speed called the lift - off speed, the pressure distribution of the lubricating fluid can create a complete radial separation between the drive shaft and the foil element. However, when the drive shaft typically rotates at speeds below the lift - off speed during the start - up and shut - down periods of the refrigeration cycle, the pressure distribution may not fully form, causing a frictional engagement between the drive shaft and the foil element, which can potentially lead to wear and / or failure. Therefore, there is a need to improve the performance of foil bearings, particularly at lower drive shaft rotation speeds.

[0006] This background section is intended to introduce to the reader various aspects of the art that may be related to various aspects of the present disclosure, which are described and / or claimed below. This discussion is believed to facilitate providing background information to the reader to enhance a better understanding of the various aspects of the present disclosure. Accordingly, it should be understood that these statements are to be read from this perspective and not as an admission of prior art. Summary of the invention

[0007] In one aspect, a bearing system includes a sleeve having a radially inner surface defining a cylindrical bore, wherein a foil bearing assembly is positioned within the cylindrical bore. The foil bearing includes a top foil layer and an outer layer positioned between the top foil layer and the radially inner surface. The bearing system includes a drive shaft that includes a recess axially aligned with the top foil layer. The recess defines a cavity having a volume and includes a front end portion located at a first circumferential position and a rear end portion located at a second circumferential position.

[0008] In another aspect, a compressor includes a compressor housing, a bearing housing mounted to the compressor housing, and a bearing system. The bearing system includes a sleeve having a radially inner surface defining a cylindrical bore, wherein a foil bearing assembly is positioned within the cylindrical bore. The foil bearing includes a top foil layer and an outer layer positioned between the top foil layer and the radially inner surface. The bearing system includes a drive shaft that includes a recess axially aligned with the top foil layer. The recess defines a cavity having a volume and includes a front end portion located at a first circumferential position and a rear end portion located at a second circumferential position.

[0009] In yet another aspect, a method of assembling a compressor including a compressor housing includes mounting a bearing housing to the compressor housing. The bearing housing includes a sleeve having a radially inner surface defining a cylindrical bore. The method includes inserting the outer layer within the cylindrical bore and inserting the top foil within the outer layer such that the outer layer is positioned between the cylindrical bore and the top foil. The method includes inserting the drive shaft within the top foil such that the drive shaft is rotatably supported within the compressor housing, the drive shaft including a recess axially aligned with the top foil layer. The recess defines a cavity having a volume and includes a front end portion located at a first circumferential position and a rear end portion located at a second circumferential position.

[0010] There are various improvements to the features noted in the above aspects. Other features may also be incorporated in the above aspects. These improvements and additional features may exist alone or in any combination. For example, each of the features discussed below with respect to any of the illustrated embodiments may be incorporated alone or in any combination into any of the above aspects. BRIEF DESCRIPTION OF THE DRAWINGS

[0011] The following drawings illustrate various aspects of the present disclosure.

[0012] Figure 1 is a perspective view of an assembled compressor.

[0013] Figure 2 is a cross-sectional view of the compressor taken along line 2-2 Figure 1 wherein the external conduit is removed.

[0014] Figure 3 is Figure 2Cross-sectional view of a compressor, where the outer compressor housing is removed.

[0015] Figure 4 Is a side view of an impeller mounted to the end of a drive shaft, where the drive shaft is supported by a bearing housing.

[0016] Figure 5 Is for use with Figure 1 The drive shaft, the first foil bearing assembly, and the second foil bearing assembly shown in the compressor in

[0017] Figure 6 Is an exploded view of a part of the drive shaft, showing the arrangement of the first foil bearing assembly relative to the drive shaft.

[0018] Figure 7 Is Figure 5 Cross-sectional view along line 7-7 of the drive shaft and the first foil bearing and the second foil bearing.

[0019] Figure 8 Is Figure 7 Detailed view of area 8 shown in

[0020] Figure 9 Is Figure 5 Cross-sectional view along line 9-9 of the drive shaft and the first foil bearing assembly.

[0021] Figure 10 Is Figure 6 Cross-sectional view along line 10-10 of the drive shaft.

[0022] Figure 11 Is Figure 10 Detailed view of area 11 shown in

[0023] Throughout the drawings, corresponding reference numerals indicate corresponding components. Detailed Description

[0024] Referring to Figure 1 , a compressor in the form of a two-stage refrigerant compressor is generally designated by 100. The compressor 100 generally includes a compressor housing 102 formed with at least one sealed cavity where refrigerant compression for each stage is completed. The compressor 100 includes: a first refrigerant inlet 110 for introducing refrigerant vapor into the first compression stage ( Figure 1 not labeled in Figure 1into (not shown in the figure); and a second refrigerant outlet 120. The refrigerant transfer conduit 112 is operatively connected to the first refrigerant outlet 114 and the second refrigerant inlet 118 at opposite ends respectively. The second refrigerant outlet 120 conveys the compressed refrigerant from the second compression stage to a cooling system in which the compressor 100 is incorporated. The refrigerant transfer conduit 112 may also include, for example, a refrigerant port 122 for energy saving.

[0025] Referring to Figure 2 , the compressor housing 102 encloses a first compression stage 124 and a second compression stage 126 at opposite ends of the compressor 100. The first compression stage 124 includes a first impeller 106 configured to increase the kinetic energy of the refrigerant entering via the first refrigerant inlet 110. The kinetic energy imparted to the refrigerant by the first impeller 106 is converted into increased refrigerant pressure (i.e., compression) as the speed of the refrigerant slows down when it is transferred to the diffuser 136. Similarly, the second compression stage 126 includes a second impeller 116 configured to increase the kinetic energy of the refrigerant that is transferred from the first compression stage 124 and enters via the second refrigerant inlet 118. The kinetic energy imparted to the refrigerant by the second impeller 116 is converted into increased refrigerant pressure (i.e., compression) as the speed of the refrigerant slows down when it is transferred to the diffuser 138. The compressed refrigerant leaves the second compression stage 126 via the second refrigerant outlet 120 ( Figure 2 not shown in the figure).

[0026] Referring to Figure 2 and Figure 3 , the first-stage impeller 106 and the second-stage impeller 116 are connected at opposite ends of the drive shaft 104. The drive shaft 104 is operatively connected to a motor 108 positioned between the first-stage impeller 106 and the second-stage impeller 116 such that the first-stage impeller 106 and the second-stage impeller 116 rotate at a selected rotational speed to compress the refrigerant to a preselected pressure at which it exits the second refrigerant outlet 120. Any suitable motor, including but not limited to an electric motor, may be incorporated into the compressor 100.

[0027] Referring to Figure 3 and Figure 4, the drive shaft 104 is supported by a first foil bearing assembly 220 and a second foil bearing assembly 222 respectively positioned within sleeves 204 of a first bearing housing 200 and a second bearing housing 202. In particular, the sleeve 204 includes a radially inner surface defining a cylindrical bore 206, and the first foil bearing assembly 220 and the second foil bearing assembly 222 are positioned within the cylindrical bore 206. Each of the first bearing housing 200 and the second bearing housing 202 includes a mounting structure 210 for connecting the respective first bearing housing 200 and second bearing housing 202 to the compressor housing 102. Each bearing housing 200, 202 ( Figure 4 only the bearing housing 200 is illustrated) supports the drive shaft 104, and the drive shaft 104 projects through the bearing housings 200, 202 in a manner opposite to the sleeve 204, and the impellers 106, 116 are connected to the projecting ends of the drive shaft 104.

[0028] Referring to Figure 5 and Figure 6 , the first foil bearing assembly 220 and the second foil bearing assembly 222 include an outer compliant component or outer layer 224 positioned adjacent to the radially inner surface of the sleeve 204, and an Figure 6The inner compliant foil assembly or inner foil layer 226 (also referred to as the "top foil layer") visible in [reference]. The first foil bearing assembly 220 and the second foil bearing assembly 222, which include the outer layer 224 and the top foil layer 226, form a generally cylindrical tube sized to receive the drive shaft 104. The components of the foil bearing assemblies 220, 222, such as the outer layer 224 and / or the top foil layer 226, can be made of any suitable material that enables the foil bearing assemblies 220, 222 to function as described herein. Suitable materials include, for example, and are not limited to, metal alloys. In some embodiments, for example, each of the outer layer 224 and the top foil layer 226 is made of stainless steel (e.g., 17-4 stainless steel). The top foil layer 226 can be formed from a relatively thin sheet or "foil" material. For example, the foil layer 226 can be made of a metal sheet having a thickness in the range of 0.003 inches to 0.007 inches. In some embodiments, the first foil bearing assembly 220 and the second foil bearing assembly 222 include a waved foil layer (not shown) disposed between the outer layer 224 and the top foil layer 226. The waved foil layer having a series of corrugations serves as a biasing mechanism between the top foil 226 and the outer layer 224. In the illustrated embodiment, the foil bearing assemblies 220 and 222 do not include a waved foil layer. The outer layer 224 can be made of a compliant material and serves as a biasing mechanism between the top foil layer 226 and the radially inner surface of the sleeve 204. The outer layer 224 can be made of polyvinyl chloride (PVC). In other embodiments, the outer layer 224 can be made of any suitable material. The outer layer 224 can include a groove 228 sized and shaped to receive a retaining feature 230 on the top foil layer 226. The engagement of the retaining feature 230 with the groove 228 connects the top foil layer 22 to the outer layer 224.

[0029] Referring Figures 5 to 7 , the drive shaft 104 includes a first bearing portion 250 disposed near the first impeller 106. The first bearing portion 250 is axially aligned with the first foil bearing assembly 220. The drive shaft 104 includes a second bearing portion 252 disposed near the second impeller 116, and the second bearing portion 252 is axially aligned with the second foil bearing assembly 222. The drive shaft 104 further includes a drive shaft longitudinal axis A extending between the first bearing portion 250 and the second bearing portion 252. The motor 108 rotates the drive shaft 104 about the longitudinal axis A. The axial direction is oriented along the longitudinal axis A and the radial direction extends radially outward and / or perpendicular to the axial direction. The drive shaft 104 is cylindrical in shape and includes an outer surface 254 extending around the circumference of the drive shaft 104. The drive shaft 104 includes a diameter D defined by the outer surface 254 254 . In the illustrated embodiment, the drive shaft 104 includes one or more stepped portions having a diameter different from the outer diameter D 254 . Generally, the diameter D 254is the diameter of the first bearing portion 250 and the second bearing portion 252.

[0030] During refrigerant compression, rotation of the drive shaft 104 causes the top foil layer 226 to move radially outward away from the drive shaft 104, which is caused by hydrodynamic pressure resulting from the accumulation of the pressure distribution of the lubricating fluid layer around the circumference of the drive shaft 104. The lubricating fluid can include any medium that enables the drive shaft 104 to rotate, such as air or refrigerant, or a mixture of air and refrigerant. When the drive shaft 104 rotates at a sufficient rotational speed, the pressure of the lubricating fluid layer is sufficient to create a complete radial separation between the top foil layer 226 and the drive shaft 104, for example, there is no contact between the drive shaft 104 and the top foil layer 226. Similarly, at "lower" rotational speeds, the top foil layer 226 can be radially closer to the drive shaft 104 and the lubricating fluid layer can be thin and / or negligible, and in some cases, the top foil layer 226 or a portion of the top foil layer 226 can contact the drive shaft 104.

[0031] Referring Figures 6 to 8 , the drive shaft 104 includes one or more recesses 260 formed thereon, such as by machining. The recesses 260 can be axially aligned with either or both of the foil bearing assemblies 220 and 222. Each of the recesses 260 defines the boundary of a cavity 266. A certain volume of fluid, such as a gas including air and / or refrigerant, can be contained within the cavity 266 and be radially inward of the top foil layer 226 at any rotational speed of the drive shaft 104. For example, during the startup phase of refrigerant compression, such as when the drive shaft 104 is not rotating or the drive shaft 104 is rotating at a low rotational speed, such as less than 5,000 rpm, the cavity 266 can contain a certain volume of fluid. Additionally, prior to the takeoff speed of the drive shaft 104, a certain volume of fluid can be contained within the cavity 266 and be radially inward of the top foil layer 226. Generally, the takeoff speed is the speed at which a fluid layer is formed around the entire circumference of the drive shaft 104. Compared to a drive shaft that does not include the recesses 260, the drive shaft 104 having one or more recesses 260 can form a complete pressure distribution of the lubricating fluid between the drive shaft 104 and the top foil layer 226 at a lower takeoff speed, such as a takeoff speed below 30,000 rpm.

[0032] The recess 260 can be tapered, for example, the width and / or depth decreasing such that the volume of the cavity 266 decreases towards one end of the recess 260. The fluid contained within and / or surrounding the drive shaft 104 can be generally stationary and / or move in a direction opposite to the direction of rotation of the drive shaft 104 such that the fluid has a relative motion opposite to the direction of rotation of the drive shaft 104. Thus, the fluid moves towards the tapered end of the recess 260. The fluid moving into the tapered cavity 266 compresses the fluid and increases the pressure of the fluid. The increase in fluid pressure radially outwardly presses the top foil layer 226 away from the drive shaft 104, thereby facilitating the development of a complete fluid layer around the entire circumference of the drive shaft 104. The volume of the fluid contained in the cavity 266 defined by the recess 260 improves the start-up and shut-down performance of the compressor 100. The recess 260 also improves the performance, such as stability, of the drive shaft 104 and the foil bearing assemblies 220 and 222 at higher rotational speeds of the drive shaft 104, such as greater than 30,000 rpm and / or greater than 50,000 rpm. Additionally, the drive shaft 104 including the tapered recess 260 is suitable for use with foil bearing assemblies 220, 222 that do not include wave foil layers.

[0033] In the illustrated embodiment, the first bearing portion 250 includes a first set 262 of recesses 260 formed therein that are axially aligned with the first foil bearing assembly 220, and the second bearing portion 252 includes a second set 264 of recesses 260 formed therein that are axially aligned with the second foil bearing assembly 222.

[0034] Referring Figure 6 , each recess 260 in the recesses 260 includes a front end portion 272 disposed at a first radial position and a rear end portion 270 disposed at a second radial position and circumferentially offset from the front end portion 272. The front end portion 272 and the rear end portion 270 of the recess 260 can include walls and / or surfaces that at least partially define the boundary of the cavity 266. The front end portion 272 is disposed in front of the rear end portion 270 with respect to the direction of rotation of the drive shaft 104. For example, if the drive shaft 104 rotates clockwise, the front end portion 272 is disposed clockwise with respect to the rear end portion 270. Similarly, if the drive shaft 104 rotates counterclockwise, the front end portion 272 is disposed counterclockwise with respect to the rear end portion 270. Each recess 260 in the recesses 260 includes a recess arc length L extending between the front end portion 272 and the rear end portion 270 弧 . The recess 260 includes a recess arc angle α between the front end portion 272 and the rear end portion 270 260 . See Figure 10 .

[0035] The recess 260 includes a first axial end 276 and a second axial end 278 that is axially offset from the first axial end 276, such as walls and / or surfaces that at least partially define the boundary of the cavity 266. The recess 260 includes an axial length L that extends between the first axial end 276 and the second axial end 278 轴向 . In some embodiments, the first axial end 276 and the second axial end 278 are parallel. In some embodiments, the first axial end 276 and the second axial end 278 are not parallel. The top foil layer 226 includes an axial length L 224 that is the same as or substantially the same as the axial length L of the outer layer 224 226 . The axial length L of the recess 260 轴向 may be the same as or substantially the same as the axial length L of the top foil layer 226, such as within 1 mm to 2 mm. In the illustrated embodiment, the axial length L of the recess 260 226 is slightly less than the axial length L 轴向 , such that the top foil layer 226 axially extends beyond the first axial end 276 and the second axial end 278 with a gap C. See 226 . The gap C may be in the range of 1 mm to 6 mm. Figure 8

[0036] The recess 260 further includes a base surface 280 that is recessed from the outer surface 254. The base surface 280 extends in the axial direction between the first axial end 276 and the second axial end 278 and extends in the circumferential direction between the front end 272 and the rear end 270. The depth T of the recess 260 260 extends between the outer surface 254 of the drive shaft 104 and the base surface 280 of the recess 260. See Figure 11 . The depth T of the recess 260 260 may vary between the front end 272 and the rear end 270 such that the depth T of the recess 260 260 varies in the radial direction between the front end 272 and the rear end 270. The depth T of the recess 260 in the radial direction 260 may also be defined by the height of the first axial end 276 and the second axial end 278, which is variable in the radial direction.

[0037] Referring to Figure 11 , the depth T of the recess 260 260 is maximum near the front end 272 and minimum near the rear end 270. The depth T 260 is suitably between 0 and 1 mm at the front end 272. In some embodiments, the depth T 260 is suitably between 0.010 mm and 0.08 mm at the front end 272. In some embodiments, the depth T 260 ​At the front end portion 272, it is appropriately between 0.013 mm and 0.076 mm. The depth T of the recess 260 260 decreases from the front end portion 272 to the rear end portion 270 such that the depth T of the recess 260 260 includes a peak depth T at the front end portion 272 260 . In this embodiment, the base surface 280 is arched. In some embodiments, the radius of curvature of the base surface 280 is less than the radius of curvature of the drive shaft 104. In some embodiments, the center of curvature of the base surface 280 is not aligned with the center of curvature of the drive shaft 104. In some embodiments, the base surface 280 is arched and has a radius of curvature substantially the same as the radius of curvature of the drive shaft 104.

[0038] The rear end portion 270 has a depth T that is substantially zero, or approximately zero, or close to zero 260 . In some embodiments, the depth T of the rear end portion 270 260 is 0 ± 0.001 mm. For example, the depth T at the rear end portion 270 260 is negligible in either or both of the radial and axial directions. Thus, the rear end portion 270 of the recess 260 does not cause a sudden change in the diameter D of the drive shaft 104 254 . The depth T that decreases as it approaches the rear end portion 270 260 compresses the fluid 226 that is contained within the cavity 266 and located radially inward of the top foil layer, thereby increasing the pressure of the fluid. The gradual taper can also produce more laminar flow of the fluid that surrounds the drive shaft 104. In the illustrated embodiment, the depth T of the recess 260 along the axial direction between the first axial end 276 and the second axial end 278 260 can be substantially constant. For example, the depth T of the recess 260 at the front end 272 260 is substantially constant along the axial length of the front end portion 272.

[0039] In an alternative embodiment, the depth T in the radial direction 260 can be constant between the front end portion 272 and the rear end portion 270. In such an embodiment, the base surface 280 is arched. In some other alternative embodiments, the base surface 280 can be substantially planar and extend along a chord with respect to the circumference of the drive shaft 104. For example, the base surface 280 can be substantially perpendicular to the radial direction.

[0040] In another alternative embodiment, both the front end portion 272 and the rear end portion 270 can be flush with the outer surface 254 of the drive shaft 104. For example, the depth T of the recess 260 in the radial and axial directions 260May be zero or substantially zero at the front end portion 272 and the rear end portion 270. Thus, the recess depth T at both the front end portion 272 and the rear end portion 270 260 does not cause a sudden change in the outer surface 254 of the drive shaft 104. In some other alternative embodiments, the depth T 260 may taper and / or slope from the front end portion 272 and the rear end portion 270 to a radial midpoint, at which the recess depth T 260 is maximum. In an alternative embodiment, the base surface 280 may be concave. In an alternative embodiment, the recess 260 includes a peak, such as the maximum depth T at the radial midpoint between the front end portion 272 and the rear end portion 270 of the recess 260 260 .

[0041] Referring again to Figure 6 , the front end portion 272 and the rear end portion 270 are linear such that the front end portion 272 and the rear end portion 270 are parallel to each other and extend parallel to the longitudinal axis A. In this embodiment, the lengths of the front end portion 272 and the rear end portion 270 may be substantially the same length. For example, the axial lengths of both the front end portion 272 and the rear end portion 270 are the axial length L of the recess 260 轴向 .

[0042] Alternatively, the axial length of the front end portion 272 may be different from the axial length of the rear end portion 270. For example, the axial length of the front end portion 272 may be greater than the axial length of the rear end portion 270 such that the cavity 266 tapers as it approaches the rear end portion 270. Thus, in some embodiments, the recess 260 tapers from the wider front end portion 272 to the narrower rear end portion 270. Additionally, in some embodiments, the recess 260 tapers simultaneously in both depth and width from the front end portion 272 to the rear end portion 270. Additionally, in some alternative embodiments, the front end portion 272 and / or the rear end portion 270 may be arched relative to the axial direction. In some embodiments, the front end portion 272 is arched between the first axial end 276 and the second axial end 278. For example, the front end portion 272 may be convex and extend forward in the direction of rotation of the drive shaft 104

[0043] Referring to Figure 10, the recesses 260 of the first set 262 and the second set 264 include any suitable number of recesses 260 arranged in any suitable pattern. In the illustrated embodiment, the recesses 260 of the first set 262 include three recesses 260 arranged in a radially symmetric pattern about the axis A. In other words, the recesses 260 are radially spaced apart at equal distances. In particular, the drive shaft 104 includes one or more spacer portions 286 extending between adjacent recesses 260. For example, the spacer portion 286 extends between the rear end portion 270 of the first recess and the front end portion 272 of the second recess adjacent to the first recess. The spacing distance A 286 is a circumferential distance along the outer surface 254 of the drive shaft 104 having an arc length A 286 . The spacer portion 286 includes an intervening arc angle α 286 spanning between the rear end portion 270 of the first recess in the recesses 260 and the front end portion 272 of the adjacent recess in the recesses 260. The radially symmetric pattern of the recesses 260 of the first set 262 causes the spacing distance A 286 to be substantially equal between each pair of adjacent recesses 260. In some embodiments, the arc angle α 260 is between 50° and 60°. In some embodiments, the arc angle α 260 is between 40° and 70°.

[0044] In some embodiments, the recesses 260 of the second set 264 have the same number and the same arrangement as the recesses 260 of the first set 262. In the illustrated embodiment, the recesses 260 of the second set 264 include three recesses 260 and three spacer portions 286. In some embodiments, the recesses 260 in the recesses 260 of the first set 262 and the recesses 260 in the recesses 260 of the second set 264 are circumferentially aligned. For example, the first recess in the recesses 260 of the first set 262 is circumferentially aligned with the first recess in the second set 264 but is offset in the axial direction. Alternatively, the recesses 260 of the first set 262 and the recesses 260 of the second set 264 may be circumferentially offset. In some embodiments, the recesses 260 of the first set 262 include a different number of recesses 260 than the number of recesses 260 in the recesses 260 of the second set 264, i.e., more or fewer recesses 260 than the number of recesses 260 in the recesses 260 of the second set 264.

[0045] The number of recesses 260 and the radial arrangement of the recesses 260 in the first set 262 and the second set 264 may be selected based on the characteristics of the drive shaft 104 and / or compressor operating parameters such as rotational speed, drive shaft diameter D 254 and compressor load. Additionally, the recess arc length L 弧It can be selected based on the number of recesses 260 and the circumferential position of the recesses 260. For example, in some embodiments, the recesses 260 of the first set 262 and the second set 264 may include four, five, and / or six recesses 260. Additionally and / or alternatively, the shape and size of the recesses 260 may be selected at least in part based on the operating conditions of the compressor. In some embodiments, the arc length L 弧 and the axial length L 轴向 are the same for all the recesses. In some embodiments, the recesses 260 of the first set 262 and the recesses 260 of the second set have all the same arc length L 弧 and axial length L 轴向 .

[0046] Referring to Figure 11 , the rear end portion 270 is planar and extends along the radial direction. For example, the rear end portion 270 is perpendicular to the longitudinal axis A. In some alternative embodiments, at least one of the front end portion 272 and the rear end portion 270 may be arcuate and / or inclined, for example, with respect to the radial direction.

[0047] The drive shaft 104 having the recesses 260 of the first set 262 and the second set 264 can be used in combination with other bearing systems, standard / conventional foil bearings, bearings, and / or magnetic bearings. In addition, the drive shaft 104 can be combined with other types of compressors such as scroll compressors, screw compressors, etc. The drive shaft 104 can also be used with other types of machinery.

[0048] The foil bearing assemblies 220, 222 and the drive shaft 104 of the present disclosure can be used as part of a method of assembling a compressor, such as the compressor 100. The assembling method includes installing the bearing housings 200, 202 to the compressor housing 102 using the mounting structure 210 of the bearing housing as described above. The assembling method further includes inserting the foil bearing assemblies, such as 220, 222, into the cylindrical holes 206, and connecting the foil bearing assemblies to the bearing housing by matingly engaging the bearing retaining features of the foil bearing assemblies with the bearing assembly locking features to hold the foil bearing assemblies in a fixed rotational position within the bearing housing.

[0049] In some embodiments, connecting the foil bearing assemblies to the bearing housing includes connecting a plurality of individual pad modules to the bearing housing, where each pad module has an individual bearing retaining feature. The method further includes inserting at least one foil retaining clip into a circumferential groove (not shown) formed in the inner surface of the cylindrical hole 206 to hold the foil bearing assemblies in a fixed axial position relative to the cylindrical hole 206. The method further includes inserting the drive shaft 104 into the foil bearing assemblies such that the plurality of recesses 260 are axially aligned with and / or axially centered on the top foil layer 226.

[0050] In some embodiments, the assembly method includes assembling the top foil layer 226 and the outer layer 224 by inserting the top foil layer 226 into an opening of the outer layer 224 and axially aligning the top foil layer 226 with the outer layer 224. In some embodiments, the method includes connecting a retaining feature 230 of the top foil layer 226 to a groove 228 formed on the outer layer 224.

[0051] The method may further include forming a recess 260 on the drive shaft 104. Forming the recess 260 may include, for example, machining using a computer numerical control (CNC) machine tool and / or machining tools to form the recess 260 on the drive shaft 104. In other embodiments, forming the recess 260 on the drive shaft 104 includes using an etching process.

[0052] Compared with existing systems and methods, embodiments of the described systems and methods achieve superior results. In particular, the exemplary foil bearing assembly and the drive shaft including the recesses contribute to improving the aerodynamic performance and enhancing the development of the lubricating fluid around the drive shaft. The recesses store fluid and facilitate the formation of a complete fluid layer around the drive shaft. In particular, at any rotational speed of the drive shaft, a certain volume of fluid is contained within each recess and is located radially inward of the top foil layer.

[0053] Exemplary embodiments of systems and methods including a drive shaft, such as a refrigerant compressor incorporating the disclosed drive shaft and a method of assembling a compressor including the disclosed drive shaft, have been described in detail above. The drive shaft systems and methods are not limited to the specific embodiments described herein. Rather, the components of the systems and methods can be used independently and separately from other components described herein. For example, the drive shaft described herein can be used in compressors other than refrigerant compressors, such as turbocharger compressors, etc. The drive shaft described herein can be used in other types of bearing assemblies to facilitate the formation of a complete radial pressure distribution between the drive shaft and the bearing assembly.

[0054] When introducing elements of the present disclosure or its embodiments, the articles "a", "an", "the", and "said" are intended to mean that there is one or more of the elements. The terms "comprising", "including", "containing", and "having" are intended to be inclusive and mean that there may be additional elements in addition to the recited elements. The use of terms indicating a specific orientation (e.g., "top", "bottom", "side", etc.) is for ease of description and does not require any specific orientation of the object being described.

[0055] Since various changes can be made to the above structures and methods without departing from the scope of the present disclosure, it is intended that all matter contained in the above description and shown in the drawings be interpreted as illustrative and not in a limiting sense.

Claims

1. A bearing system, the bearing system comprising: a sleeve, the sleeve including a radially inner surface defining a cylindrical bore; and a foil bearing assembly positioned within the cylindrical bore of the sleeve, wherein the foil bearing assembly includes: a top foil layer; and an outer layer positioned between the top foil layer and the radially inner surface; and a drive shaft including a recess axially aligned with the top foil layer, the recess defining a cavity having a volume, the recess including a front end portion at a first circumferential position and a rear end portion at a second circumferential position.

2. The bearing system according to claim 1, wherein The recess depth of the recess is maximum at the front end portion, and wherein the volume of the cavity decreases from the front end portion to the rear end portion.

3. The bearing system according to claim 1 or claim 2, wherein, The front end portion includes a first axial length and the rear end portion includes a second axial length, wherein the first axial length is longer than the second axial length.

4. The bearing system according to any one of claims 1 to 3, wherein, The recess depth of the recess decreases from the front end portion to the rear end portion, wherein the recess depth is zero at the rear end portion.

5. The bearing system according to claim 1, wherein The drive shaft includes a plurality of the recesses arranged in a radially symmetric pattern about the rotational axis of the drive shaft.

6. The bearing system according to claim 4, wherein, The drive shaft includes three of the recesses arranged in a radially symmetric pattern, wherein each of the recesses includes a recess arc angle α between the front end portion and the rear end portion, and wherein the recess arc angle α is between 50° and 60°.

7. The bearing system according to claim 1, wherein, The drive shaft includes a first portion and an opposite second portion axially offset from the first portion, wherein the drive shaft further includes at least one of the recesses of a first group formed at the first portion and at least one of the recesses of a second group formed at the second portion.

8. The bearing system according to claim 7, wherein, The first group includes a plurality of the recesses arranged in a radially symmetric pattern, and the second group includes the same number of recesses as the first group, and wherein the second group is arranged in the same radially symmetric pattern as the radially symmetric pattern of the first group.

9. The bearing system according to any one of claims 1 to 6, wherein, The recess has a base surface extending between the front end portion and the rear end portion, wherein the base surface is arched and has a radius of curvature smaller than the radius of curvature of the outer surface of the drive shaft.

10. A compressor, the compressor comprising: a compressor housing; a bearing housing mounted to the compressor housing; and a bearing system supported by the bearing housing, the bearing system comprising: a sleeve, the sleeve including a radially inner surface defining a cylindrical bore; and a foil bearing assembly positioned within the cylindrical bore of the sleeve, wherein the foil bearing assembly includes: a top foil layer; and an outer layer positioned between the top foil layer and the radially inner surface; and a drive shaft including a recess axially aligned with the top foil layer, the recess defining a cavity having a volume, the recess including a front end portion at a first circumferential position and a rear end portion at a second circumferential position.

11. The compressor according to claim 10, wherein, The recess depth of the recess is maximum at the front end portion, and wherein the volume of the cavity decreases from the front end portion to the rear end portion.

12. The compressor according to claim 10 or claim 11, wherein, The front end portion includes a first axial length and the rear end portion includes a second axial length, wherein the first axial length is longer than the second axial length.

13. The compressor according to claim 10, wherein, The recess includes a recess depth that decreases from the front end portion to the rear end portion, wherein the recess depth is zero at the rear end portion.

14. The compressor according to any one of claims 10 to 13, wherein, The drive shaft includes a plurality of the recesses arranged in a radially symmetric pattern about the rotational axis of the drive shaft.

15. The compressor according to any one of claims 13 to 14, wherein, The drive shaft includes three of the recesses arranged in a radially symmetric pattern, wherein each of the three recesses includes a recess arc angle α between the front end portion and the rear end portion, wherein the recess arc angle α is between 50° and 60°.

16. The compressor according to claim 10, wherein, The drive shaft includes a first portion and an opposite second portion that is axially offset from the first portion, wherein the drive shaft further includes at least one of the recesses of a first group formed at the first portion and at least one of the recesses of a second group formed at the second portion.

17. The compressor according to claim 16, wherein, The first group includes a plurality of the recesses arranged in a radially symmetric pattern, and the second group includes the same number of recesses as the first group, and wherein the second group is arranged in the same radially symmetric pattern as the radially symmetric pattern of the first group.

18. The compressor according to claim 10, wherein, The recess has a base surface that extends between the front end portion and the rear end portion, wherein the base surface is arched and has the same radius of curvature as the outer surface of the drive shaft.

19. The compressor according to claim 16, wherein, The first group includes a plurality of the recesses arranged in a radially symmetric pattern, and the second group includes a different number of recesses from the first group, and wherein the second group is arranged in a radially symmetric pattern.

20. A method of assembling a compressor including a compressor housing, the method comprising: Mounting a bearing housing to the compressor housing, the bearing housing including a sleeve having a radially inner surface defining a cylindrical bore; Inserting an outer layer into the cylindrical bore; Inserting a top foil into the outer layer such that the outer layer is positioned between the cylindrical bore and the top foil; and Inserting a drive shaft into the top foil such that the drive shaft is rotatably supported within the compressor housing, the drive shaft including a recess axially aligned with the top foil layer, the recess defining a cavity having a volume, the recess including a front end portion at a first circumferential position and a rear end portion at a second circumferential position.

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