Patent Publication Number: US-11655848-B2

Title: Hydrodynamic bearing system and method for operating said hydrodynamic bearing system

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     The present application is a continuation application of and claims priority to U.S. patent application Ser. No. 16/776,099, filed on Jan. 29, 2020, the entirety of which is incorporated herein by reference. 
    
    
     BACKGROUND 
     Embodiments of the subject matter disclosed herein relate to hydrodynamic bearing systems and methods for operating hydrodynamic bearing systems in an X-ray source. 
     Hydrodynamic bearings, also known as spiral groove bearings or liquid metal bearings, are used in various operating environments due to their increased longevity and ability to more effectively manage thermal loads, relative to roller bearings. Certain X-ray tubes, for example, utilize hydrodynamic bearings owing at least in part to their thermodynamic characteristics and durability. However, certain hydrodynamic bearings may experience leaks due to the bearing&#39;s boundary conditions and/or may not achieve a desired load carrying capacity. 
     SUMMARY 
     In one aspect, a hydrodynamic bearing system is provided. The hydrodynamic bearing system comprises a sleeve assembly including a cross-member fluidically dividing a first interior cavity from a second interior cavity. The hydrodynamic bearing system further includes a first shaft positioned in the first interior cavity and a second shaft positioned in the second interior cavity. The hydrodynamic bearing system also includes a first journal bearing having a first fluid interface surrounding at least a portion of the first shaft and configured to support radial loads and a second journal bearing having a second fluid interface surrounding at least a portion of the second shaft and configured to support radial loads. 
     The above advantages and other advantages, and features of the present description will be readily apparent from the following Detailed Description when taken alone or in connection with the accompanying drawings. It should be understood that the summary above is provided to introduce in simplified form a selection of concepts that are further described in the detailed description. It is not meant to identify key or essential features of the claimed subject matter, the scope of which is defined uniquely by the claims that follow the detailed description. Furthermore, the claimed subject matter is not limited to implementations that solve any disadvantages noted above or in any part of this disclosure. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The present disclosure will be better understood from reading the following description of non-limiting embodiments, with reference to the attached drawings, wherein below: 
         FIG.  1    is a block schematic diagram of an exemplary X-ray imaging system, according to an embodiment. 
         FIG.  2    is a pictorial view of a portion of an X-ray tube including a hydrodynamic bearing system, according to an embodiment. 
         FIG.  3    is a first exemplary hydrodynamic bearing assembly, according to an embodiment. 
         FIG.  4    is a second exemplary hydrodynamic bearing assembly, according to an embodiment. 
         FIG.  5    is an exemplary method for operation of a hydrodynamic bearing system, according to an embodiment. 
     
    
    
     DETAILED DESCRIPTION 
     The following description relates to various embodiments of hydrodynamic bearing systems. The hydrodynamic bearing systems are designed to fix axial fluid boundary conditions at selected ends of discrete shafts enclosed by different sections of a sleeve. Increased bearing stability and working fluid (e.g., liquid metal) control and a subsequent bearing leak reduction result from the fixed axial fluid boundary conditions. Thus, the bearing leaks may be reduced across different stages of the system (e.g., handling, processing, and operation). To achieve the fixed boundary conditions the sleeve includes a cross-member dividing the sleeve into the two distinct cavities. Further, in certain system embodiments, the shafts are cantilever shafts supported at one end by, for example, a housing of the system. In this way, the structural support of straddle type bearings can be achieved while reducing the hydrodynamic drawbacks of previous straddle bearing designs, thereby expanding the applicability of the bearing system. As such, in one use-case example, the bearing system may be deployed in the X-ray sources or X-ray tubes of computed tomography (CT) imaging systems or scanners having higher gantry loads in comparison to CT imaging systems with X-ray sources supporting a fixed bearing shaft on only one axial end. Providing two cantilever shafts also decreases focal spot motion in X-ray sources or X-ray tubes employing the bearing system in relation to systems using one cantilever shaft. In additional examples, the cross-member may be designed with a targeted amount of compliance to reduce sleeve-shaft misalignment. As a result, the thickness of the fluid interface in the bearing may be reduced, if desired, thereby increasing the bearing&#39;s load carrying capacity and efficiency. 
     An X-ray imaging system including an X-ray source and X-ray controller is shown in  FIG.  1   . An example of a portion of an X-ray tube or X-ray source is shown in  FIG.  2    with a hydrodynamic bearing assembly enabling anode rotation.  FIG.  3    shows a first embodiment of a hydrodynamic bearing system.  FIG.  4    shows a second embodiment of a hydrodynamic bearing system with a flexible cross-member enabling sleeve-shaft misalignment to be reduced.  FIG.  5    shows a method for operation of a hydrodynamic bearing system. 
       FIG.  1    illustrates an X-ray imaging system  100  designed to generate X-rays. The X-ray imaging system  100  is configured as an X-ray imaging system (e.g., CT imaging system, a radiography imaging system, a fluoroscopy imaging system, etc.) in  FIG.  1   . However, the X-ray imaging system  100  has applicability to fields beyond imaging, medical devices, and the like. For instance, the X-ray imaging system  100  may be deployed in crystallography systems, security scanners, baggage scanners, industrial scanners, etc. It will also be appreciated that the hydrodynamic bearing systems described in greater detail herein may be deployed in alternate types of systems utilizing hydrodynamic bearings, in some instances. 
     In the imaging system example, the system may be configured to image a subject  102  such as a patient, an inanimate object, one or more manufactured parts, and/or foreign objects such as dental implants, stents, and/or contrast agents present within the body. 
     The X-ray imaging system  100  may include at least one X-ray source  104  configured to project a beam of X-ray radiation  106 . Specifically, in the illustrated embodiment, the X-ray source  104  is configured to project the X-ray radiation beams  106  towards an X-ray detector array  108  and through the subject  102 . In some system configurations, the X-ray source  104  may project a cone-shaped X-ray radiation beam which is collimated to lie within an X-Y-Z plane of a Cartesian coordinate system. However, other beam profiles and/or systems omitting the detector array have been envisioned. Each detector element of the array produces a separate electrical signal that is a measurement of the X-ray beam attenuation at the detector location. 
     Although  FIG.  1    depicts only a single X-ray source  104  and X-ray detector array  108 , in certain embodiments, multiple X-ray sources and/or detectors may be employed to project a plurality of X-ray radiation beams and detect said beams. For instance, in the CT imaging system use-case example, multiple detectors may be used in tandem with the X-ray sources to acquire projection data at different energy levels corresponding to the subject. 
     The X-ray imaging system  100  may further include an X-ray controller  110  configured to provide power and timing signals to the X-ray source  104 . It will be understood that that system may also include a data acquisition system configured to sample analog data received from the detector elements and convert the analog data to digital signals for subsequent processing. 
     In certain embodiments, the X-ray imaging system  100  may further include a computing device  112  having a processor  114  and controlling system operations based on operator input. The computing device  112  receives the operator input, for example, including commands and/or scanning parameters via an operator console  116  operatively coupled to the computing device  112 . The operator console  116  may include a keyboard, a touchscreen, and/or other suitable input device allowing the operator to specify the commands and/or scanning parameters. 
     Although  FIG.  1    illustrates only one operator console  116 , more than one operator console may be included in the X-ray system  100 , for example, for inputting or outputting system parameters, requesting examinations, plotting data, and/or viewing images. Further, in certain embodiments, the X-ray imaging system  100  may be coupled to multiple displays, printers, workstations, and/or similar devices located either locally or remotely, for example, and connected via wired and/or wireless networks. 
     In one example, the computing device  112  stores the data in a storage device or mass storage  118 . The storage device  118 , for example, may include a hard disk drive, a floppy disk drive, a compact disk-read/write (CD-R/W) drive, a Digital Versatile Disc (DVD) drive, a flash drive, and/or a solid-state storage drive. 
     Additionally, the computing device  112  provides commands to the X-ray controller  110  and other system components for controlling system operations such as X-ray beam formation, data acquisition and/or processing, etc. Thus, in certain embodiments, the computing device  112  controls system operations based on operator input. To elaborate, the computing device  112  may use the operator-supplied and/or system-defined commands and parameters to operate an X-ray controller  110 , which in turn, may control the X-ray source  104 . In this way, the intensity and timing of X-ray beam generation may be controlled. It will also be understood that the rotational speed of a sleeve in the X-ray source may be adjusted by the computing device  112  in conjunction with the X-ray controller  110 . The rotational speed adjustment of the sleeve may induce the flow of liquid metal into a bearing interface in the X-ray source  104 , as described in greater detail herein. 
     The various methods and processes (such as the method described below with reference to  FIG.  5   ) described further herein may be stored as executable instructions in non-transitory memory on a computing device (or controller) in X-ray imaging system  100 . In one embodiment, the X-ray controller may include the executable instructions in non-transitory memory, and may apply the methods described herein to control the X-ray source. In another embodiment, computing device  112  may include the instructions in non-transitory memory, and may relay commands, at least in part, to the X-ray controller which in turn adjusts the X-ray source output. 
     In one embodiment, a display  120  may also be in electronic communication with the computing device  112  and is configured to display graphical interfaces indicating system parameters, control setting, imaging data, etc. 
       FIG.  2    shows a detailed embodiment of a portion of an X-ray tube  200 . The portion of the X-ray tube  200  shown in  FIG.  2    serves as an example of the X-ray source  104  depicted in  FIG.  1   . As such, the X-ray tube  200 , shown in  FIG.  2   , as well as the other X-ray system embodiments described herein may include functional and/or structural features from the X-ray source  104 , shown in  FIG.  1   , or vice versa. Furthermore, alternate embodiments combining features from one or more of the systems have also been envisioned. 
     A rotational axis  250  along with a radial axis  252  are provided in  FIG.  2    as well as  FIGS.  2 - 12    for reference. It will be understood that a radial axis is any axis perpendicular to the rotational axis  250 . 
     The X-ray tube  200  includes a housing  202  having a low-pressure enclosure  204  (e.g., a vacuum enclosure) formed therein. It will be understood that a low-pressure enclosure infers a comparatively low-pressure relative to atmospheric pressure. As such, the pressure in the enclosure may be less than atmospheric. 
     The X-ray tube  200  includes a hydrodynamic bearing system  205  with a sleeve assembly  206  and a shaft assembly  208 . In the illustrated example, the sleeve assembly  206  is a rotational component and the shaft assembly  208  is a stationary component. However, embodiments in which the sleeve assembly is a stationary component and the shaft assembly is a rotational component, have been contemplated. In such an example, an anode  210  may be coupled to the shaft assembly  208  as opposed to the sleeve assembly  206 . Nevertheless, in the illustrated embodiment, the anode  210  is coupled to the sleeve assembly  206 . It will be understood that the motion denoted by the descriptors stationary and rotational denote the relative motion between the components. However, in certain use-case examples, the X-ray tube may be integrated into a moving structure. For instance, in the CT scanner use-case, the X-ray tube may be integrated into a rotating gantry. As such, in smaller scale frame of reference, the shaft is stationary relative to the sleeve but in a larger scale frame of reference, both components exhibit similar rotational motion in the gantry. However, in alternate use-case scenarios, the X-ray tube may be integrated into a stationary structure in regard to the larger scale frame of reference. 
     The sleeve assembly  206  includes a sleeve body  212  and a cross-member  214  partitioning an interior of the body into a first interior cavity  216  and a second interior cavity  218 . Thus, the cross-member  214  fluidically divides interior sleeve cavities. The shaft assembly  208  includes a first shaft  220  residing in the first interior cavity  216  and a second shaft  222  residing in the second interior cavity  218 . The first shaft  220  is shown fixedly coupled to the housing  202  at a first axial end  224  and unsupported at the opposing axial end. However, the first shaft  220  may be fixedly attached to another suitable stationary X-ray tube component, in other examples. Although certain structural details of the second shaft  222  are obscured from view in  FIG.  2   , it will be appreciated that one axial end of the second shaft  222  may be coupled to the housing  202  or other suitable stationary component in the X-ray tube. Thus, the bearing system may be formed as a straddle bearing system. Further, in other embodiments in which the shaft assembly rotates, the sleeve assembly may include two sleeve sections fixedly attached to the housing at an axial end of each section. The structural features of the sleeve and shaft assemblies are elaborated upon in greater detail herein with regard to the embodiments shown in  FIGS.  3 - 4   . 
     The cross-member  214  in the sleeve assembly  206  enables fluid boundary conditions on axial ends of each of the first and second shaft  220  and  222  to be fixed. Fixing the fluid boundary conditions at the axial ends of the shafts allows the stability and control of the fluid in the rotational interfaces in the hydrodynamic bearing system  205  to be increased in relation to systems using a single continuous shaft with a series of hydrodynamic bearings in fluidic communication with one another. Consequently, the likelihood of leaks from the hydrodynamic bearing system is reduced. 
     It will also be understood that the leak reductions may be achieved while jointly increasing load carrying capacity of the assembly via the cantilever attachment of both shafts. Providing two shafts in the shaft assembly  208  fixedly supported at one end, decreases unwanted motion of a focal spot  226  on the anode  210  during operation of the X-ray tube due to the increased bearing support in comparison to systems using a single cantilever shaft. 
     The structural and functional details of the cross-member  214  are expanded upon in greater detail herein with regard to the hydrodynamic bearing system embodiments illustrated in  FIGS.  3 - 4   . The sleeve assembly  206  includes structures designed fix the boundary conditions on axial ends of discrete shafts in the system while also fixedly attaching opposing axial ends of the shafts to stationary components in the system. Fixing the boundary conditions at ends of discrete shafts allows the liquid metal, or other suitable working fluid, to be stabilized such that leaks from the seals in the system are significantly reduced, in relation to systems using a series of hydrodynamic bearings in fluidic communication with one another. 
     The hydrodynamic bearing system  205  includes a plurality of hydrodynamic bearings including a journal bearing  228  and a thrust bearing  230 . The system may however include additional bearings obscured from view in  FIG.  2   . For instance, in the embodiments shown in  FIGS.  3 - 4   , the system includes two journal bearings and two thrust bearing. Still further in other embodiments, the bearing system may include an alternate number and/or types of bearings. For instance, the system may include two journal bearing and one thrust bearing in one example, or more than two journal bearings and two thrust bearings, in other examples. The hydrodynamic journal bearing  228  is designed to support radial loads and hydrodynamic thrust bearing  230  is designed to support axial loads. In this way, loads on the sleeve are managed to enable efficient sleeve rotation. 
     Each of the bearings include an interface  232  in which a working fluid (e.g., liquid metal) serving as a lubricant and supporting loads is provided. The thickness of the interface may be selected based on factors such as the type liquid metal or other working fluid used in the bearing, manufacturing tolerances of the components, expected system operating temperature, etc. Thus, in one use-case example, the liquid metal interface may be on the order of 5 microns (μm)-40 μm. In one example, the liquid metal used as the working fluid in the bearing assembly may include gallium, tin, indium, combinations thereof, etc. However, working fluid other than liquid metal have been envisioned such grease, oil, combinations thereof, etc. 
     In the illustrated embodiment, the anode  210  is coupled to the sleeve assembly  206 . However, as previously mentioned, embodiments with the anode coupled to rotational shaft assemblies have been envisioned. The anode  210  includes the focal spot  226  serving as a surface receiving a beam of electrons from a cathode  234 , during X-ray tube  200  operation. 
     The cathode  234  may receive signals from a controller, such as the X-ray controller  110  shown in  FIG.  1   , to generate an electron beam directed toward a surface of the anode  210 . An X-ray beam  236  is generated when the electron beam from the cathode  234  strikes the focal spot  226  of the anode  210 . The X-rays are emitted through an X-ray window  238  in the housing  202 . 
     A rotor  240  and a stator  242  are also provided in the X-ray tube  200 . The rotor  240  is coupled to the sleeve assembly  206 , in the illustrated embodiment, and is designed to impart rotational motion thereto. However, in embodiments where the shaft assembly rotates the rotor may be coupled to the first and second shafts in the shaft assembly. The stator  242  is shown positioned external to the low-pressure enclosure  204 . However, other suitable stator locations have been envisioned. Typically, the rotor and stator can include windings, magnets, electrical connections, etc., electromagnetically interacting to generate rotor rotation responsive receiving control commands, from for example, the X-ray controller  110 , shown in  FIG.  1   . 
     Various embodiments of the hydrodynamic bearing system designed to reduce leaks from bearings in the system, are described in greater detail herein with regard to  FIGS.  3 - 4   . The embodiments of the hydrodynamic bearing systems depicted in  FIGS.  3 - 4    are examples of the hydrodynamic bearing system  205 , shown in  FIG.  2   . As such, structural and/or functional features from the bearing systems shown in  FIGS.  3 - 4    may be included in the bearing system  205 , shown in  FIG.  2   , in other contemplated embodiments. 
       FIG.  3    shows an example of a hydrodynamic bearing system  300 . The hydrodynamic bearing system  300  includes a shaft assembly  302  and a sleeve assembly  304 . It will be understood that in one example, an anode, such as the anode  210 , shown in  FIG.  2   , may be attached to the sleeve assembly  304 . Thus, during system use, the sleeve assembly rotates while the shaft assembly remains relatively stationary. However, as previously mentioned, embodiments where the sleeve assembly is kept stationary and the shaft assembly rotates, have been envisioned. 
     The sleeve assembly  304  includes a first interior cavity  306  and a second interior cavity  308  formed in a sleeve body  310 . The sleeve body  310  is shown as a monolithic structure. However, sleeves with different sections connected to one another may be used, in other embodiments. For instance, in other embodiments, the sleeve body may manufactured in different sections and the sections may be coupled via mechanical attachment (e.g., bolting), welding, press-fitting, shrink-fitting, combinations thereof, etc. 
     The sleeve assembly  304  further includes a cross-member  312  radially extending across an interior of the sleeve body  310 . To elaborate, the cross-member  312  fluidly divides the first and second interior cavities  306 ,  308  in the sleeve assembly  304 . The cross-member  312  therefore includes a first surface  314  forming a section of the boundary of the first interior cavity  306  and a second surface  316  forming a section of the boundary of the second interior cavity  308 . Thus, the first interior cavity  306  and the second interior cavity  308  are conceptually formed as blind openings. A variety of cross-member constructions have been contemplated such as a construction where the cross-member is a plug inserted into the sleeve assembly. In such an example, the plug may be coupled to the sleeve body via press-fitting, welding, mechanical attachment, combinations thereof, etc. and/or may be formed as a cylinder. In other examples, the body and the cross-member of the sleeve assembly may be jointly formed via suitable manufacturing techniques such as machining, casting, etc. It will therefore be understood that the sleeve body  310  and the cross-member  312  may be formed from a similar material, in some examples, or out of different materials, in other examples. Suitable materials for the sleeve assembly  304  and/or shaft assembly  302  may include metallic materials, ceramic materials, combinations thereof, etc. 
     The cross-member  312  allows the fluid boundary conditions of the bearing interfaces, discussed in greater detail herein, to be fixed, increasing stability of fluid (e.g., liquid metal) capillary forces and pressure. Fluid leaks through seals  356  and  360  in the system can therefore be significantly reduced due to the relatively large reduction in fluid motion. 
     The shaft assembly  302  includes a first shaft  318  and second shaft  320 . The first shaft  318  is fixedly coupled at one axial end  322  to a suitable system component such as the housing  202 , shown in  FIG.  2   . Likewise, the second shaft  320  is fixedly coupled at one axial end  324  to a suitable system component (e.g., the housing  202  shown in  FIG.  2   ). Thus, in the embodiment shown in  FIG.  3   , the first and second shafts  318  and  320  are formed as cantilever shafts. However, as previously mentioned, the sleeve may be fixedly attached to the housing at opposing axial ends in embodiments where the shaft assembly rotates and the sleeve assembly remains substantially stationary during system use. 
     The hydrodynamic bearing system  205  includes a plurality of bearings including fluid interfaces  326  (e.g., liquid metal interfaces) between outer surfaces  328  of the first and second shafts  318  and  320  and interior surfaces  330  of the sleeve assembly  304 . To elaborate, the system includes a first journal bearing  332 , a second journal bearing  334 , a first thrust bearing  336 , and a second thrust bearing  338 , in the illustrated embodiment. However, other bearing arrangements have been envisioned such as bearing arrangements including two journal bearing and one thrust bearing, in one example, or a bearing arrangement including more than two journal bearing and/or more than two thrust bearings, in other examples. The journal bearings support radial loads and the thrust bearings support axial loads. Each of the bearings includes a fluidic interface (e.g., liquid metal interface) between a section of a shaft included in the shaft assembly  302  and the sleeve body  310 . Thus, each of the bearings include a fluid interface circumferentially surrounding the corresponding shaft. The first journal bearing  332  includes a first fluid interface  370 , the second journal bearing  334  includes a second fluid interface  372 , the first thrust bearing  336  includes a third fluid interface  374 , and the second thrust bearing  338  includes a fourth fluid interface  376 . 
     The first shaft  318  and the second shaft  320  are shown with herringbone grooves  340  associated with the first journal bearing  332  and the second journal bearing  334 , respectively. The sleeve assembly  304  may correspondingly include spiral grooves associated with the first and second journal bearings  332 ,  334 . These grooves (herringbone and spiral grooves) may work in conjunction to generate pressure in the working fluid (e.g., liquid metal) to support the bearing load. It will therefore be understood that the bearings described herein may be self-acting bearings designed to generate pressure using the surface geometries at the bearing interface. However, bearing embodiments including alternate groove patterns or embodiments omitting at least a portion of the grooves to alter the bearing&#39;s flow dynamics, have been contemplated. 
     The first thrust bearing  336  includes a flange  342  radially extending from a body  344  of the first shaft  318  toward a complimentary section  346  in the sleeve body  310 . The second thrust bearing  338  correspondingly includes a flange  348  radially protruding from the second shaft  320  into a complimentary section  350  in the sleeve body  310 . The flanges  342 ,  348  have radial ends  352  and axial sides  354  which may form an annular shape, in some cases. 
     The hydrodynamic bearing system  300  may further include seals designed to reduce the amount of fluid leaking from the bearings. The seals may be rotating labyrinth seals providing a circuitous path impeding liquid metal flow in axial directions away from the cross-member  312 . However, additional or alternate types of suitable seals or combinations of seals have been contemplated such as capillary seals, hydrodynamic seals, flange seals, foil seals, etc. The first seal  356  is shown positioned axially outward (indicated via arrow  358 ) from the first journal bearing  332 . The second seal  360  is shown positioned axially outward (indicated via arrow  362 ) from the second journal bearing  334 . The first seal  356  and the second seal  360  are also shown positioned radially outward from the first journal bearing  332  and the second journal bearing  334 , respectively. However, an alternate number of seals and/or seal arrangement may be used, in other embodiments. The first and second thrust bearings  336  and  338  are shown positioned axially between the first and second journal bearings  332  and  334  and the first and second seals  356  and  360 . However, in other examples, the first and/or second thrust bearings may be positioned adjacent to the unsupported axial ends of the first and second shafts  318  and  320 . In such an example, the thrust bearing may be arranged with axially spacing between the unsupported shaft end and the cross-member to allow for thermal growth between the sleeve and the shaft. In this way, the likelihood of bearing wear caused by thermal expansion of system components can be reduced. 
       FIG.  4    shows another embodiment of a bearing system  400 . The bearing system  400  again includes a sleeve assembly  402  and a shaft assembly  404 . The shaft assembly  404  again includes a first shaft  406  and a second shaft  408  fixedly attached to a system component, such as the housing  202  shown in  FIG.  2   , at axial ends of the respective shafts. The hydrodynamic bearing system again includes a first journal bearing  410 , a second journal bearing  412 , a first thrust bearing  414 , and a second thrust bearing  416 . A first seal  418  and a second seal  420  are also shown included in the hydrodynamic bearing system  400 . The shafts, bearing, and seals may have functional and/or structural similarities with the shafts, bearings, and/or seals previously described with regard to  FIG.  3   . As such, redundant description is omitted for brevity. 
     The sleeve assembly  400  shown in  FIG.  4    includes a cross-member  422  with fluidic isolation extensions  424  (e.g., plugs, caps, etc.) and a flexible component  426 . Thus, the extensions  424  seal the interior sleeve cavities. It will be understood that the flexible component has greater compliance than the sleeve sections  432  and  434 . The fluidic isolation extensions  424  again fluidly divide the first interior cavity  428  and the second interior cavity  430 . The extensions  424  may be welded, press-fit, mechanically coupled, etc., to the sections of the sleeve. It will be understood, that when the extensions are welded or press-fit to the sleeve a welded interface and friction interface, respectively, will be formed. 
     The flexible component  426  is positioned axially between the fluidic isolation extensions  424  as well as a first section  432  and a second section  434  of a sleeve body  436 . The flexible component  426  also radially spans an interior diameter of an anode  438 . However, other flexible component profiles have been envisioned and may be selected based on end-use design objectives. Additionally, the first section  432  of the sleeve body  436  and the second section  434  of the sleeve body are shown attached to the anode  438  axially extending across an outer circumference of the cross-member  422 . However, alternate sleeve section arrangements may be utilized in other embodiments. For instance, in another example, a third sleeve body section may extend between the first section  432  and the second section  434  of the sleeve body  436  and circumferentially enclose the flexible component  426 . Continuing with such an example, the anode  438  may be coupled to an outer surface of the third sleeve body section. The configuration and layout of the sleeve body sections may be selected based on packaging constraints, desired flexion characteristics, etc. 
     The flexible component  426  is configured as a compliant member accommodating for flexion between the first section  432  and the second section  434  of the sleeve body  436 . Thus, the flexible component  426  may have less bending stiffness than the first sleeve section  432  and the second sleeve section  434 . Further, in one example, the flexible component may be less compliant under torsional loads than bending loads. In this way, the flexible component may be relatively rotationally stiff but selectively compliant under bending loads. To elaborate, the flexible component  426  in the cross-member  422  conceptually functions as a gimbal without having the mechanical gyroscopic mechanisms. The use of the flexible component in the cross-member consequently decreases sleeve-shaft misalignment. The decreased sleeve-shaft misalignment allows the thickness of the fluid interfaces in the first and second journal bearings  410  and  412  to be reduced, increasing the load carry capacity of the bearings and bearing efficiency, if wanted. Consequently, the sleeve can achieve increased rotational speeds, if desired, during use of the X-ray tube, thereby increasing the applicability of the bearing system. As such, in the CT imaging system use-case, higher scanning speed of the CT gantry may be realized, if desired. 
     The compliance of the flexible component  426  in the cross-member  422  may be achieved by adjusting the geometry and/or material of the flexible component. For instance, in one use-case example, the flexible component may be formed as a slotted spring structure. In another use-case example, selected walls of the cross-member may be thinned to achieve a desired amount of cross-member flexion suiting end-use design goals. In another use-case example, a more flexible alloy may be selected for the material construction of the flexible component of the cross-member when compared to the sleeve body. Still further in other use-case examples, a combination of geometric profiling (e.g., structural wall thinning) and cross-member material construction may be jointly used to achieve compliance objectives. It will be understood, that the amount of cross-member compliance may be selected based on design parameters such as an expected range of speeds of the anode, expected operating temperature range, shaft diameter, sleeve diameter, liquid metal film thickness, etc. 
       FIG.  5    shows a method  500  for operation of a hydrodynamic bearing system. The method  500  as well as the other control strategies described herein may be implemented by any of the systems, assemblies, components, devices, etc., described above with regard to  FIGS.  1 - 4   . However, in other examples, the method  500  may be carried out by other suitable systems, assemblies, components, devices, etc. Instructions for carrying out method  500  and/or the other control strategies described herein may be at least partially executed by a processor based on instructions stored in memory (e.g., non-transitory memory). 
     At step  502 , the method includes determining system operating conditions. The operating conditions may include X-ray beam intensity, X-ray beam duration. Next at step  504 , the method includes rotating the sleeve assembly based on the system operating conditions. It will be appreciated that due to the fixed axial boundary conditions and cantilever shaft design the system may achieve a higher load carrying capacity and increased ability to resist leaks than previous bearing designs. 
     A technical effect of providing a cross-member in a sleeve of a hydrodynamic bearing system which fluidly separates cavities housing discrete shafts is to increase fluid stability in the bearing system to reduce fluid leaks, during for example, handling, processing, and/or use of the system. 
     In another representation, an X-ray tube with a straddle liquid metal bearing assembly is provided. The straddle liquid metal bearing assembly includes a sleeve with an anode coupled thereto, designed to rotate, and including an extension fluidly isolating a first interior opening from a second interior opening, where the first and second interior openings enclose portions of two discrete cantilever shafts and where each of the shafts are fixedly coupled to a stationary component. 
     When introducing elements of various embodiments of the present disclosure, the articles “a,” “an,” and “the” are intended to mean that there are one or more of the elements. The terms “first,” “second,” and the like, do not denote any order, quantity, or importance, but rather are used to distinguish one element from another. The terms “comprising,” “including,” and “having” are intended to be inclusive and mean that there may be additional elements other than the listed elements. As the terms “connected to,” “coupled to,” etc. are used herein, one object (e.g., a material, element, structure, member, etc.) can be connected to or coupled to another object regardless of whether the one object is directly connected or coupled to the other object or whether there are one or more intervening objects between the one object and the other object. In addition, it should be understood that references to “one embodiment” or “an embodiment” of the present disclosure are not intended to be interpreted as excluding the existence of additional embodiments that also incorporate the recited features. As described herein “approximately” and “substantially” refer to values of within plus or minus five percent, unless otherwise noted. 
     In addition to any previously indicated modification, numerous other variations and alternative arrangements may be devised by those skilled in the art without departing from the spirit and scope of this description, and appended claims are intended to cover such modifications and arrangements. Thus, while the information has been described above with particularity and detail in connection with what is presently deemed to be the most practical and preferred aspects, it will be apparent to those of ordinary skill in the art that numerous modifications, including, but not limited to, form, function, manner of operation and use may be made without departing from the principles and concepts set forth herein. Also, as used herein, the examples and embodiments, in all respects, are meant to be illustrative only and should not be construed to be limiting in any manner.