Abstract:
A fluid pump is disclosed. The fluid pump may comprise a housing, a tapered bearing, a drive shaft, a first fluid chamber, and a second fluid chamber. The housing defines a bore. The tapered bearing is received within the bore of the housing. The drive shaft is received within the tapered bearing. The first fluid chamber is defined between the housing and the drive shaft on a first side of the tapered bearing. The second fluid chamber is defined between the housing and the drive shaft on a second side of the tapered bearing. The second fluid chamber is separated from the first fluid chamber by the tapered bearing. The housing includes a fluid passage fluidly coupling the first fluid chamber and the second fluid chamber.

Description:
TECHNICAL FIELD 
     The present disclosure is directed to a pump and, more particularly, to a bearing arrangement for a pump. 
     BACKGROUND 
     Fluid pumps are available in a number of different configurations and are used for a multitude of different applications. In many of these applications, the internal components of the pump require some sort of lubrication. One of the most common ways to provide this lubrication is to expose the internal components of the pump to a lubricant, such as oil. However, because the fluid that is being pumped is often a different fluid than the lubricant, care must be taken to ensure that the pumped fluid and the lubricant do not mix. 
     Such contamination can be avoided in different ways, depending the on the configuration of the pump being used. One relatively common pump configuration utilizes a primary drive shaft that includes a driven member (e.g., a member, such as a gear, that engages the power source that provides the power to operate the pump) on one end and a working member (e.g., an element or elements, such as an impeller or a set of gears, that cooperate together to provide a pumping action) on the other end. The drive shaft is generally supported within the pump housing by at least two bearings, one provided near each end of the drive shaft. The end of the drive shaft with the driven member is often exposed to a lubricant (e.g., oil) while the end with the working member is exposed to the fluid that is being pumped. To avoid contamination of the pumped fluid and oil with one another, at least one seal that keeps the lubricant and pumped fluid separate is generally provided at some point along the drive shaft. The seal is normally provided on the side of the bearing that is opposite the driven member to ensure that the bearing near the driven member of the drive shaft is lubricated. 
     For pumps with such a configuration, the lubricant (e.g., oil) may become substantially trapped between the bearing and the seal. Friction with the rotating drive shaft and seal may cause this trapped volume of oil to overheat. When the oil overheats, carbon particles may be generated within the oil that, over time, may lead to seal or shaft wear and eventually leakage of oil between the shaft and the seal. 
     The disclosed pump is directed to overcoming one or more of the problems set forth above or other problems. 
     SUMMARY 
     According to one exemplary embodiment, a fluid pump comprises a housing, a tapered bearing, a drive shaft, a first fluid chamber, and a second fluid chamber. The housing defines a bore. The tapered bearing is received within the bore of the housing. The drive shaft is received within the tapered bearing. The first fluid chamber is defined between the housing and the drive shaft on a first side of the tapered bearing. The second fluid chamber is defined between the housing and the drive shaft on a second side of the tapered bearing. The second fluid chamber is separated from the first fluid chamber by the tapered bearing. The housing includes a fluid passage fluidly coupling the first fluid chamber and the second fluid chamber. 
     According to another exemplary embodiment, a method of providing fluid circulation between a first chamber and a second chamber, where each of the first chamber and the second chamber are defined between a housing and a shaft rotatably received within the housing, comprises the step of supporting the shaft within the housing with a tapered bearing located between the first chamber and the second chamber. The method also comprises the step of providing a fluid passage between the first chamber and the second chamber. The method also comprises the steps of circulating fluid from the first chamber to the second chamber through the tapered bearing during rotation of the shaft and circulating fluid from the second chamber to the first chamber through the fluid passage during rotation of the shaft. 
     According to another exemplary embodiment, an engine comprises at least one combustion chamber and a fuel system. The fuel system is for transferring fuel to the at least one combustion chamber and includes a fuel transfer pump. The fuel transfer pump includes a housing, a tapered bearing, a second bearing, a drive shaft, a first seal, a first fluid chamber, and a second fluid chamber. The housing defines a bore. The tapered bearing and a second bearing are received within the bore of the housing. The drive shaft is rotatably received within the tapered bearing and the second bearing. The first seal is located between the tapered bearing and the second bearing and forms a seal between the drive shaft and the bore of the housing. The first fluid chamber is defined at least in part by the tapered bearing and the first seal. The second fluid chamber is located on the opposite side of the tapered bearing as the first fluid chamber and is separated from the first fluid chamber by the tapered bearing. The housing includes a fluid passage fluidly coupling the first fluid chamber and the second fluid chamber. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a schematic illustration of a fuel system according to one exemplary embodiment. 
         FIG. 2  is a diagrammatic illustration of a pump according to one exemplary embodiment. 
         FIG. 3  is a partial cross-sectional illustration of the pump of  FIG. 2  taken along line  3 - 3 . 
     
    
    
     Although the drawings depict exemplary embodiments or features of the present disclosure, the drawings are not necessarily to scale, and certain features may be exaggerated in order to provide better illustration or explanation. The exemplifications set out herein illustrate exemplary embodiments or features, and such exemplifications are not to be construed as limiting the inventive scope in any manner. 
     DETAILED DESCRIPTION 
     Reference will now be made in detail to specific embodiments or features, examples of which are illustrated in the accompanying drawings. Generally, the same or corresponding reference numbers will be used throughout the drawings to refer to the same or corresponding parts. 
     Referring generally to  FIG. 1 , a fuel system  10  is shown according to one exemplary embodiment. Fuel system  10  is a system of components that cooperate to deliver fuel (e.g., diesel, gasoline, heavy fuel, etc.) from a location where fuel is stored to the combustion chamber(s)  13  of an engine  12  where it will combust and where the energy released by the combustion process will be captured by engine  12  and used to generate a mechanical source of power. Although depicted in  FIG. 1  as a fuel system for a diesel engine, fuel system  10  may be the fuel system of any type of engine (e.g., an internal combustion engine such as a gaseous fuel or gasoline engine, a turbine, etc.). According to one exemplary embodiment, fuel system  10  includes a tank  14 , a transfer pump  16 , a high-pressure pump  18 , a common rail  20 , fuel injectors  22 , and an electronic control module (ECM)  24 . 
     Tank  14  is a storage container that stores the fuel that fuel system  10  will deliver. Transfer pump  16  pumps fuel from tank  14  and delivers it at a generally low pressure to high-pressure pump  18 . High-pressure pump  18 , in turn, pressurizes the fuel to a high pressure and delivers the fuel to common rail  20 . Common rail  20 , which is intended to be maintained at the high pressure generated by high-pressure pump  18 , serves as the source of high-pressure fuel for each of fuel injectors  22 . Fuel injectors  22  are located within engine  12  in a position that enables fuel injectors  22  to inject high-pressure fuel into combustion chambers  13  of engine  12  (or into pre-chambers or ports upstream of combustion chambers  13  in some cases) and generally serve as metering devices that control when fuel is injected into the combustion chamber, how much fuel is injected, and the manner in which the fuel is injected (e.g., the angle of the injected fuel, the spray pattern, etc.). Each fuel injector  22  is continually fed fuel from common rail  20  such that any fuel injected by a fuel injector  22  is quickly replaced by additional fuel supplied by common rail  20 . ECM  24  is a control module that receives multiple input signals from sensors associated with various systems of engine  12  (including fuel system  10 ) and indicative of the operating conditions of those various systems (e.g., common rail fuel pressure, fuel temperature, throttle position, engine speed, etc.). ECM  24  uses those inputs to control, among other engine components, the operation of high-pressure pump  18  and each of fuel injectors  22 . The general purpose of fuel system  10  is to ensure that the fuel is continually being fed to engine  12  in the appropriate amounts, at the right times, and in the right manner to support the operation of engine  12 . 
     Referring now to  FIG. 2 , fuel transfer pump  16  is a device or component that draws fuel from tank  14  and transfers it under pressure to high-pressure pump  18 . According to one exemplary embodiment, fuel transfer pump  16  includes a housing  26 , an input assembly  28 , a drive shaft assembly  30 , a pump apparatus  32 , tapered bearing  34 , bearing  36 , a oil seal  38 , and a fuel seal  40 . 
     Housing  26  is a generally rigid member that provides the structure that supports the other components of pump  16  and that cooperates with other components to enable the pumping action of pump  16 . According to one exemplary embodiment, housing  26  includes an input chamber  42 , a bore  44 , a fluid passage  46 , a pump chamber  48 , an inlet, an outlet, and a drain passage  50 . Input chamber  42  is a cavity within housing  26  that is configured to receive input assembly  28  and a portion of drive shaft assembly  30 . Input chamber  42  also serves as a reservoir for lubricant (e.g., oil) that provides the lubrication for input assembly  28  and drive shaft assembly  30 . Bore  44  is a generally cylindrical opening within housing  26  that extends between input chamber  42  and pump chamber  48  and that is configured to receive a portion of drive shaft assembly  30 . Bore  44  includes an end  54  near input chamber  42 , an end  56  near pump chamber  48 , and a central region  58  that extends between ends  54  and  56 . Bore  44  may include one or more steps or transitions in its diameter (such as in the region of end  56 ) to facilitate, among other things, the use of different bearing or seal configurations at different points along the axis of bore  44 . 
     Referring now to  FIGS. 2 and 3 , fluid passage  46  is provided near end  54  of bore  44  and serves as a duct or conduit that allows fluid to pass between input chamber  42  and bore  44  without having to pass through tapered bearing  34 . According to one exemplary embodiment, fluid passage  46  is a groove, notch, or channel in the wall of bore  44  and extends axially into bore  44  beginning from input chamber  42  and extending to a position along bore  44  beyond the location of tapered bearing  34  so as to form a fluid path between fluid chambers on each side of tapered bearing  34 . According to various exemplary and alternative embodiments, the fluid passage may take any one of a variety of different shapes, sizes and configurations. For example, the cross-sectional shape of the fluid passage, taken in a plane perpendicular to the axis of bore  44 , may be rectangular, semi-circular, arc-shaped, v-shaped, barrel-shaped, or any other suitable shape. Similarly, the cross-sectional shape of the fluid passage, taken in a plane that includes the axis of bore  44 , may be rectangular, triangular, semi-circular, arc-shaped, trapezoid-shaped, generally flat with rounded or radiused ends, or any other suitable shape. According to other various exemplary and alternative embodiments, the fluid passage may be any channel, duct, conduit, passage, or groove that fluidly couples a chamber formed on one side of tapered bearing  34  with a chamber formed on the other side of tapered bearing  34 . For example, the fluid passage could be a hole within the housing that extends from one portion of bore  44  to another portion of bore  44  (at the opposite side of tapered bearing  34 ), or that extends from a portion of bore  44  into input chamber  42 . Depending on the orientation of pump  16  when in use, housing  26  may include one or more fluid passages  46 , each of which may be provided at different locations around the circumference of bore  44 . According to one exemplary embodiment, at least one fluid passage  46  is provided at a location around the circumference of bore  44  at which the lubricant will pool or collect, or in most cases, at the lowest elevational point of bore  44  (which will depend on the orientation of pump  16  when it is in use) to allow any pooling lubricant to flow through fluid passage  46 . 
     Pump chamber  48  is a cavity within housing  26  that is configured to receive and cooperate with pump apparatus  32  and a portion of drive shaft assembly  30  to draw a pumped fluid from a source (e.g, tank  14 ) and pump the pumped fluid to a desired location (e.g, high pressure pump  18 ). Depending on the configuration of pump apparatus  32  (e.g., cooperating gears, an impeller, vane assembly, etc.), pump chamber  48  may take one of a variety of different shapes and sizes. Pump chamber  48  includes an inlet, from which the pumped fluid enters pump chamber  48 , and an outlet, from which the pumped fluid exits pump chamber  48 . Drain passage  50  is a duct or conduit provided within housing  26  that serves to fluidly couple a portion of bore  44  to a drain (or to the atmosphere) such that fluid within bore  44  in the area of drain passage  50  may be drained from bore  44 . 
     According to various alternative and exemplary embodiments, housing  26  may be integrally formed as a single unitary body or as two or more separate members coupled together. Housing  26  may also be formed from any one or more of a variety of different materials, depending at least in part on the environment in which it will be used and on the fluids into which it will come into contact. For example, the housing may be made from various metals, polymers, elastomers, ceramics, composites, and/or other suitable materials. According to other various alternative and exemplary embodiments, the housing may take one of a multitude of different forms or shapes, or be provided in a variety of different sizes, that make it suitable for incorporation into a particular fuel system or other fluid system or suitable for placement within a certain physical space. For example, the housing may include one or more different interfaces or engagements points (e.g., threaded interfaces, etc.) that allow it to be fluidly coupled to one or more other fluid system components. The housing may also include one or more brackets, flanges, projections, recesses, grooves, or other structures that facilitate the physical coupling of the housing to one or more other structures, such as an engine block, high-pressure pump  18 , a frame member, or other structures. 
     Input assembly  28  is an assembly of components that serve to transfer power or torque provided by an external source, such as the crankshaft of engine  12  or other source, such as an internal or external electric motor, to drive shaft assembly  30  and then ultimately to pump apparatus  32  (via drive shaft assembly  30 ). Depending on the source of power for pump  16 , the configuration of pump  16 , where and how pump  16  is mounted or coupled within a particular system, and other factors, input assembly  28  may take any one of a variety of different configurations. According to one exemplary embodiment, input assembly includes an input shaft  60  and a drive gear  62 . Input shaft  60  is configured to be coupled to a power source and to transfer torque from the power source to drive gear  62 . To facilitate the coupling of input shaft  60  with a power source, it may be coupled to a gear, it may be formed so as to have gear teeth formed in the end of the shaft, it may be keyed or splined, or it may be configured in any one of a variety of different ways that facilitate the transfer of torque from the power source to input shaft  60 . Drive gear  62  is coupled to input shaft  60  and serves to transfer torque from input shaft  60  to drive shaft assembly  30 . According to various exemplary and alternative embodiments, input assembly may take one or more of a variety of different configurations. In other embodiments, drive shaft assembly  30  may be coupled directly to a power source, in which case input assembly  28  may not be provided. 
     Drive shaft assembly  30  generally serves to transfer torque provided by input assembly  28  to pump apparatus  32 . Depending on the configuration of pump  16 , drive shaft assembly  30  may take one of a variety of different configurations and may include one or more of a variety of different components to facilitate the transfer of torque and the mounting of drive shaft assembly  30  within housing  26 . According to one exemplary embodiment, drive shaft assembly  30  includes a driven gear  64  and a shaft  66 . Driven gear  64  is configured to mate with drive gear  62  of input assembly  28  in order facilitate the transfer of torque from drive gear  62  to driven gear  64 . According to various exemplary and alternative embodiments, both driven gear  64  and drive gear  62  may take one of a variety of different mating configurations and forms. For example, driven gear  64  and drive gear  62  may be selected from a variety of different gearing arrangements, such as helical gears, spur gears, bevel gears, face gears, worm gears, bevel gears, spiral gears, or other types of gear arrangements. The driven gear and drive gear could also be replaced with pulleys or sprockets or other members and may engage one another through belts, chains, clutches, couplers, etc. Shaft  66  is an elongated, generally cylindrical bar or pin that serves to transfer torque from driven gear  64  to pump apparatus  32 . Shaft  66  includes an end  68  that is coupled to driven gear  64  and an end  70  that is coupled to pump apparatus  32 . 
     Pump apparatus  32  (e.g., working member) is an element or assembly of components or elements that cooperate together and with pump chamber  48  of housing  26  to draw a pumped fluid into the inlet of housing  26  and force it out of the outlet of housing  26 . According to one exemplary embodiment, pump apparatus  32  includes two cooperating gears, a drive gear  72  and a driven gear  74 . Drive gear  72  is coupled to end  70  of shaft  66  and rotates along with shaft  66 . Driven gear  74  is rotatably coupled to housing  26  and is driven by drive gear  72 . Together with pump chamber  48  of housing  26 , drive gear  72  and driven gear  74  form a gear pump that draws the pumped fluid into the inlet of housing  26  and forces the pumped fluid out of the outlet of housing  26 . According to various other exemplary and alternative embodiments, the pump apparatus may be any other type of element or assembly that operates to draw fluid from one source and transfer it to another location. For example, the pump apparatus may be an impeller, a vane assembly (such as that used vane type pumps), or other type or style of pump apparatus. 
     Tapered bearing  34  is a friction reducing member or device that is coupled between the inner surface of bore  44  of housing  26  and shaft  66  of drive shaft assembly  30 , proximate end  68  of shaft  66 , to facilitate the coupling and rotation of drive shaft assembly  30  within housing  26 . According to one exemplary embodiment, tapered bearing  34  includes an inner race  76 , an outer race  78 , and rolling elements  80  positioned between inner race  76  and outer race  78 . Inner race  76  includes an inner surface  82  that fits over shaft  66  and a tapered outer surface  84  that engages roller elements  80 . Tapered outer surface  84  is tapered such that its diameter increases in a direction toward end  70  of shaft  66 . Outer race  78  includes a tapered inner surface  86  that engages rolling elements  80  and an outer surface  88  that fits within an inner surface of bore  44 . Tapered inner surface  86  is also tapered such that its diameter increases in a direction toward end  70  of shaft  66 . Multiple rolling elements  80  are provided between inner race  76  and outer race  78  and generally serve to allow the rotation of inner race  76  relative to outer race  76  with relatively little friction. According to one exemplary embodiment, rolling elements  80  are generally cylindrical rollers and tapered bearing  34  is a tapered roller bearing. According to other exemplary and alternative embodiments, the rolling element may take other shapes (e.g., balls, barrels, needles, etc.) and the bearing may be a different type of bearing (e.g., ball bearing, needle bearing, etc.). According to another alternative embodiment, the direction of tapered bearing  34  may be reversed, such that tapered outer surface  84  of inner race  76  and tapered inner surface  86  of outer race  78  are tapered such that their diameter decreases in a direction toward end  70  of shaft  66 . According to still other exemplary and alternative embodiments, the outer surface of the outer race of the tapered bearing and/or the inner surface of the inner race of the tapered bearing may include one or more fluid passages similar to those exemplary and alternative embodiments described above in connection with fluid passage  46 . Such fluid passages may be provided as an alternative to fluid passages  46  in housing  26  or in addition to fluid passages  46 . 
     Due to its tapered configuration, tapered bearing  34  may provide a pumping action when exposed to a fluid. As shaft  66  rotates, inner race  76  will rotate along with shaft  66 . The rotation of inner race  76  will cause lubricant to rotate along with it. As the lubricant rotates with inner race  76 , centrifugal force will force the lubricant radially outwardly onto tapered inner surface  86  of outer race  78 . The lubricant will then flow axially along tapered inner surface  86  to progressively larger diameter regions of tapered inner surface  86  until the lubricant will eventually exit the side of tapered bearing  34  where tapered inner surface  86  of outer race  78  has the largest diameter. In this way, fluid on the side of tapered bearing  34  where tapered inner surface  86  of outer race has the smallest diameter is “pumped” or forced to the opposite side of tapered bearing  34 , the side of tapered bearing  34  where tapered inner surface  86  of outer race  78  has the largest diameter. 
     Bearing  36  is a friction reducing member or device that is coupled between the inner surface of bore  44  of housing  26  and shaft  66  of drive shaft assembly  30 , proximate end  70  of shaft  66 , to facilitate the coupling and rotation of drive shaft assembly  30  within housing  26 . According to one exemplary embodiment, bearing  36  is a bushing formed from a relatively short and thin tube that is constructed from a low-friction, wear resistant material. According to other alternative and exemplary embodiments, bearing  36  may be any one of a variety of different types of bearings or bushings, including a ball bearing, a roller bearing, a tapered roller bearing, a plain bearing, etc. 
     Oil seal  38  is an element, member, or assembly that extends between the inner surface of bore  44  and shaft  66  and that serves to create a seal that prevents, or substantially prevents, any fluid from passing by it. According to one exemplary embodiment, oil seal  38  is provided on the opposite side of tapered bearing  34  as input chamber  42  so as to create a lubricant chamber  90  formed by tapered bearing  34 , oil seal  38 , shaft  66 , and the inner surface of bore  44 . Oil seal  38  may take any one of a variety of different configurations. For example, oil seal  38  may be one of the different varieties of radial shaft seals. Oil seal  38  may also be made from one or more of a variety of different materials, such as metal, polymers, elastomers, rubber, composites, etc. 
     Fuel seal  40  is an element, member, or assembly that extends between the inner surface of bore  44  and shaft  66  and that serves to create a seal that prevents, or substantially prevents, any fluid from passing by it. According to one exemplary embodiment, fuel seal  40  is provided on the opposite side of bearing  36  as pump chamber  48  so as to create a fuel chamber  92  formed by bearing  36 , fuel seal  40 , shaft  66 , and the inner surface of bore  44 . Fuel seal  40  and oil seal  38  may be spaced apart from one another to form a leak chamber  94  that would contain any fuel that leaked past fuel seal  40  and any oil that leaked past oil seal  38 . Leak chamber  94  cooperates with drain passage  50  of housing  26  to allow any leakage to be removed from leak chamber  94 . Thus, drain passage  50  may serve as a tell-tale or weep hole such that any leakage from drain passage  50  can alert an operator of a potential failure (e.g., with the seals or other pump components) within pump  16 . Fuel seal  40  may take any one of a variety of different configurations. For example, the fuel seal may be one of the different varieties of radial shaft seals. Fuel seal  40  may also be made from one or more of a variety of different materials, such as metal, polymers, elastomers, rubber, composites, etc. Fuel seal  40  may be the same seal as oil seal  38 , or they may be different. 
     According to various alternative and exemplary embodiments, the various elements of pump  16  may be arranged into a multitude of different combinations and configurations. For example, more than two bearings may be utilized, both bearings may be tapered roller bearings, the bearings and seals may be provided in different locations along the length of shaft  66 , one seal may be used instead of two seals, the size and relative proportions of the components may be different, and a multitude of other changes may be made to pump  16  without departing from the intended scope of the present disclosure. 
     Although illustrated and generally described in conjunction with an external gear pump used as a fuel transfer pump, the bearing arrangement including tapered bearing  34  and the cooperating fluid passage  46  may be used with any type of pump (e.g., vane pump, centrifugal pump, etc.), as part of any of a variety of different types of fluid systems (hydraulic, coolant, lubrication, hydraulic actuation systems, etc.), and with any of a variety of different fluids. The disclosed bearing arrangement may also be used in connection with other devices that include a rotating shaft and a tapered bearing that separates two different chambers, between which the flow of fluid is desirable. 
     INDUSTRIAL APPLICABILITY 
     Pumps are utilized in a variety of different applications and are available in a variety of different configurations. One common pump configuration utilizes a main drive shaft that transfers torque from a power source to a pumping device or object, such as mating gears or an impeller. Bearings are often used to retain the drive shaft within a housing of the pump while providing relatively little resistance to the rotation of the drive shaft. In many cases, at least some of the bearings and other components of a pump will require lubrication, and the lubricant used for lubrication will be different than the fluid that the pump is being used to pump. In these cases, seals are often used to keep the lubricant and the pumped fluid separate. However, when both seals and bearings are used, a situation could arise where a chamber is formed between one of the bearings and one of the seals that eventually fills up with fluid (e.g., the lubricant or the pumped fluid). It is then possible for that fluid to become essentially trapped within the chamber. When the pump is used, friction between the fluid and the rotating drive shaft may cause this relatively small volume of trapped fluid to overheat. Depending on the characteristics of the trapped fluid, overheating may lead to the formation of carbon particles within the fluid. Over time, these carbon particles create wear on the drive shaft, the bearing, and/or the seal, which may eventually lead to the premature failure of the pump. The pump and bearing arrangement described in this disclosure are intended to reduce the likelihood of such a pump failure by providing a simple means for circulating fluid through what was formerly a substantially trapped volume. 
     Referring now to  FIGS. 2 and 3 , the operation of pump  16  will now be described. Input assembly  28  is configured to be coupled to an external power source, such as the crankshaft of engine  12 , which rotates input assembly  28 . Input assembly  28  is coupled to drive shaft assembly  30  such that rotation of input assembly  28  causes drive shaft assembly  30  to rotate. Drive shaft assembly  30  is coupled to pump apparatus  32  such that rotation of drive shaft assembly  30  causes drive gear  72  and driven gear  74  to rotate. The rotation of drive gear  72  and driven gear  74  (which together with pump chamber  48  of housing  26  form the core of an external gear pump) draws fuel from tank  14  into the inlet of housing  26  and pumps it out of the outlet of housing  26  to high pressure pump  18 . 
     To keep the interface between input assembly  28  and drive shaft assembly  30  sufficiently lubricated, input chamber  42  of housing  26  may be at least partially filled with lubricant  52  (e.g., oil). As described above, tapered bearing  34  generates a pumping effect that “pumps” lubricant  52  from input chamber  42  into lubricant chamber  90 . At the same time lubricant  52  is being pumped into lubricant chamber  90  from input chamber  42 , lubricant  52  is being forced out of lubricant chamber  90  and back into input chamber  42  through fluid passage  46 . Thus, the combination of tapered bearing  34  and fluid passage  46  creates a lubricant flow path (indicated by the arrows in  FIG. 2 ) that allows lubricant  52  to circulate through lubricant chamber  90  rather than become trapped within lubricant chamber  90 . The circulation of lubricant  52  between lubricant chamber  90  and input chamber  42  helps to keep lubricant  52  from overheating, which in turn reduces the formation of carbon particles within lubricant  52 , which then reduces the likelihood of any wear or damage caused by the carbon particles. 
     It is important to note that the construction and arrangement of the elements of the fuel transfer pump and the bearing arrangement as shown in the exemplary and other alternative embodiments is illustrative only. Although only a few embodiments of the pump and bearing arrangement have been described in detail in this disclosure, those skilled in the art who review this disclosure will readily appreciate that many modifications are possible (e.g., variations in sizes, dimensions, structures, shapes and proportions of the various elements, values of parameters, mounting arrangements, use of materials, orientations, component locations, etc.) without materially departing from the novel teachings and advantages of the subject matter recited. For example, elements shown as integrally formed may be constructed of multiple parts or elements shown as multiple parts may be integrally formed, the operation of the interfaces (e.g., the drive and driven gears, input shafts, etc.) may be reversed or otherwise varied, and/or the length, width, diameter, or other dimensions of the structures and/or members or connectors or other elements of the system may be varied. It should be noted that the elements and/or assemblies of the pump and the bearing arrangement may be constructed from any of a wide variety of materials that provide sufficient strength or durability, and in any of a wide variety of combinations. It should also be noted that the pump and/or bearing arrangement may be used in association with any of a wide variety of fluid systems or fluid subsystems in any of a wide variety of applications. Accordingly, all such modifications are intended to be included within the scope of the present disclosure. Other substitutions, modifications, changes and omissions may be made in the design, operating conditions and arrangement of the exemplary and other alternative embodiments without departing from the spirit of the present disclosure.