Abstract:
A lubrication system for a fan drive planetary gear system according to an exemplary aspect of the present disclosure includes, among other things, a stationary first bearing configured to receive a lubricant from a lubricant input, the stationary first bearing is axially aligned with a fan drive shaft. A second bearing is configured to rotate with the fan drive shaft, the first bearing engages the second bearing and is configured to transfer the lubricant from the first bearing to the second bearing and into at least one fluid passage in the fan drive shaft. A conduit fluidly connects the at least one passage in the fan drive shaft with at least one component on the fan drive gear system.

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
       [0001]    This application is a continuation of U.S. application Ser. No. 14/912,535 filed on Feb. 17, 2016 which is a U.S. National phase of International Application No. PCT/US2014/050873 filed Aug. 13, 2014, which claims priority to Provisional Application No. 61/868,115, filed on Aug. 21, 2013. 
     
    
     BACKGROUND 
       [0002]    Planetary gear trains are complex mechanisms that reduce, or occasionally increase, the rotational speed between two rotating shafts or rotors. The compactness of planetary gear trains makes them appealing for use in aircraft engines where space is at a premium. 
         [0003]    The forces and torque transferred through a planetary gear train place stresses on the gear train components that may make them susceptible to breakage and wear. In practice, conditions may be less than ideal and place additional stresses on the gear components. For example the longitudinal axes of a planetary gear train&#39;s sun gear, planet carrier, and ring gear are ideally coaxial with the longitudinal axis of an external shaft that rotates the sun gear. Such perfect coaxial alignment, however, is rare due to numerous factors including imbalances in rotating hardware, manufacturing imperfections, and transient flexure of shafts and support frames due to aircraft maneuvers. The resulting parallel and angular misalignments impose moments and forces on the gear teeth, the bearings which support the planet gears in their carrier, and the carrier itself. These imposed forces and moments may cause gear component wear and increase a likelihood that a component may break in service. Component breakage is undesirable in any application, but particularly so in an aircraft engine. Moreover, component wear necessitates inspections and part replacements which may render the engine and aircraft uneconomical to operate. 
         [0004]    The risk of component breakage may be reduced by making the gear train components larger and therefore stronger. Increased size may also reduce wear by distributing the transmitted forces over correspondingly larger surfaces. However increased size offsets the compactness that makes planetary gear trains appealing for use in aircraft engines, and the corresponding weight increase is similarly undesirable. The use of high strength materials and wear resistant coatings can also be beneficial, but escalates the cost of the gear train and therefore does not diminish the desire to reduce wear. 
         [0005]    Stresses due to misalignments can also be reduced by the use of flexible couplings to connect the gear train to external devices such as rotating shafts or non-rotating supports. For example, a flexible coupling connecting a sun gear to a drive shaft flexes so that the sun gear remains near its ideal orientation with respect to the mating planet gears even though the axis of the shaft is oblique or displaced with respect to a perfectly aligned orientation. Many prior art couplings, however, contain multiple parts that require lubrication and are themselves susceptible to wear. Prior art couplings may also lack adequate rigidity and strength, with respect to torsion about a longitudinal axis, to be useful in high torque applications. 
       SUMMARY 
       [0006]    In one exemplary embodiment, a lubrication system for a fan drive planetary gear system includes a stationary first bearing configured to receive a lubricant from a lubricant input. The stationary first bearing is axially aligned with a fan drive output shaft. A second bearing is configured to rotate with the fan drive output shaft. The stationary first bearing engages the second bearing and is configured to transfer the lubricant from the stationary first bearing to the second bearing and into at least one fluid passageway in the fan drive output shaft. A conduit fluidly connects least one passageway in the fan drive output shaft with at least one component on the fan drive gear system. 
         [0007]    In a further embodiment of any of the above, an inner first race on the stationary first bearing is configured to transfer lubricant to a first opening in registration with the inner first race in the second bearing. 
         [0008]    In a further embodiment of any of the above, the fan drive gear system includes a first axial side and a second axial side. The stationary first bearing, the second bearing, and a fan output drive shaft bearing is located on the first axial side of the fan drive gear system. 
         [0009]    In a further embodiment of any of the above, the stationary first bearing and the second bearing are mounted between two fan rotor bearings. 
         [0010]    In a further embodiment of any of the above, the stationary first bearing and the second bearing are located radially inward from a radially innermost portion of a fan drive output shaft bearing. 
         [0011]    In a further embodiment of any of the above, the fan drive gear system includes a sun gear attached to an input drive shaft configured to rotate at a first rotational speed and an output attached to the fan drive output shaft configured to rotate at a second rotational speed. The first rotational speed being is greater than the second rotational speed. The second bearing is fixedly attached to the fan drive output shaft. 
         [0012]    In a further embodiment of any of the above, the fan drive gear system includes a plurality of planet gears mounted on bearings. The bearing includes at least one of a ball bearing, a roller bearing, and a journal bearing. 
         [0013]    In a further embodiment of any of the above, the stationary first bearing and the second bearing are disposed about a rotational axis. 
         [0014]    In a further embodiment of any of the above, the conduit is parallel to the rotational axis and at least partially radially aligned with a planet gear of the fan drive gear system. 
         [0015]    In a further embodiment of any of the above, at least one fluid passageway extends from a radially outer side of the fan drive output shaft to a radially inner side of the fan drive output shaft and the conduit is flexible. 
         [0016]    In a further embodiment of any of the above, at least one component of the fan drive gear system includes at least one of a ring gear, a sun gear, a planetary gear, and a bearing. 
         [0017]    In a further embodiment of any of the above, the fan drive gear system includes a substantially symmetric carrier. 
         [0018]    In another exemplary embodiment, a fan drive planetary gear system for a gas turbine engine includes a fan drive output shaft that includes at least one fluid passageway. A planetary gear system is coupled to the fan drive output shaft. A stationary first bearing is configured to receive a lubricant from a lubricant input. A second bearing is configured to rotate with the fan drive output shaft and receive the lubricant from the first bearing. A conduit is fluidly connecting at least one fluid passageway in the fan drive output shaft to at least one component of the planetary gear system. 
         [0019]    In a further embodiment of any of the above, an inner first race on the stationary first bearing is configured to transfer lubricant to a first opening in registration with the inner first race in the second bearing. 
         [0020]    In a further embodiment of any of the above, the first bearing and the second bearing are located radially inward from a radially innermost portion of a fan output drive shaft bearing. 
         [0021]    In a further embodiment of any of the above, the second bearing is fixedly attached to the fan drive output shaft and at least one fluid passageway extends from a radially outer side of the fan drive output shaft to a radially inner side of the fan drive output shaft. 
         [0022]    In a further embodiment of any of the above, the planetary gear system includes a substantially symmetric carrier. 
         [0023]    In another exemplary embodiment, a method of lubricating a component on a gas turbine engine includes directing a lubricant through an oil transfer bearing that has a stationary first bearing and a second bearing configured to rotate with a fan drive output shaft. The lubricant is directed from the oil transfer bearing through at least one passageway on the fan drive output shaft. The lubricant is directed through a conduit connecting the at least one passageway on the fan drive output shaft to at least one component on a planetary gear system. 
         [0024]    In a further embodiment of any of the above, the method includes flexing the conduit in response to relative movement between the fan drive output shaft and a carrier on the planetary gear system. 
         [0025]    In a further embodiment of any of the above, the method includes leaking the lubricant from the oil transfer bearing and directing the lubricant leaked from the oil transfer bearing to at least one bearing system on the fan drive output shaft. 
         [0026]    The various features and advantages of this disclosure will become apparent to those skilled in the art from the following detailed description. The drawings that accompany the detailed description can be briefly described as follows. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0027]      FIG. 1  illustrates a schematic view a gas turbine engine. 
           [0028]      FIG. 2  illustrates a sectional view of the gas turbine engine of  FIG. 1 . 
           [0029]      FIG. 3  illustrates a sectional view taken along the lines  3 - 3  of  FIG. 2 . 
           [0030]      FIG. 3A  illustrates a sectional view taken along the line A-A of  FIG. 3 . 
           [0031]      FIG. 3B  illustrates a sectional view taken along the line B-B of  FIG. 3 . 
           [0032]      FIG. 3C  illustrates a sectional view taken along the line C-C  FIG. 3 . 
           [0033]      FIG. 4  illustrates a sectional view taken along line  4 - 4  of  FIG. 2 . 
           [0034]      FIG. 5  illustrates an example carrier. 
           [0035]      FIG. 6  illustrates an example oil transfer bearing. 
       
    
    
     DETAILED DESCRIPTION 
       [0036]      FIG. 1  schematically illustrates a gas turbine engine  20 . The gas turbine engine  20  is disclosed herein as a two-spool turbofan that generally incorporates a fan section  22 , a compressor section  24 , a combustor section  26  and a turbine section  28 . Alternative engines might include an augmentor section (not shown) among other systems or features. The fan section  22  drives air along a bypass flow path B in a bypass duct defined within a fan case or fan duct  15 , while the compressor section  24  drives air along a core flow path C for compression and communication into the combustor section  26  then expansion through the turbine section  28 . Although depicted as a two-spool turbofan gas turbine engine in the disclosed non-limiting embodiment, it should be understood that the concepts described herein are not limited to use with two-spool turbofans as the teachings may be applied to other types of turbine engines including three-spool architectures. 
         [0037]    The exemplary engine  20  generally includes a low speed spool  30  and a high speed spool  32  mounted for rotation about an engine central longitudinal axis A relative to an engine static structure  36  via several bearing systems  38 . It should be understood that various bearing systems  38  at various locations may alternatively or additionally be provided, and the location of bearing systems  38  may be varied as appropriate to the application. 
         [0038]    The low speed spool  30  generally includes an inner shaft  40  that interconnects a fan  42 , a low pressure compressor  44  and a low pressure turbine  46 . The inner shaft  40  is connected to the fan  42  through a speed change mechanism, which in exemplary gas turbine engine  20  is illustrated as a geared architecture  48  to drive the fan  42  at a lower speed than the low speed spool  30 . The high speed spool  32  includes an outer shaft  50  that interconnects a high pressure compressor  52  and high pressure turbine  54 . A combustor  56  is arranged in exemplary gas turbine engine  20  between the high pressure compressor  52  and the high pressure turbine  54 . A mid-turbine frame  57  of the engine static structure  36  is arranged generally between the high pressure turbine  54  and the low pressure turbine  46 . The mid-turbine frame  57  further supports bearing systems  38  in the turbine section  28 . The inner shaft  40  and the outer shaft  50  are concentric and rotate via bearing systems  38  about the engine central longitudinal axis A which is collinear with their longitudinal axes. 
         [0039]    The core airflow is compressed by the low pressure compressor  44  then the high pressure compressor  52 , mixed and burned with fuel in the combustor  56 , then expanded over the high pressure turbine  54  and low pressure turbine  46 . The mid-turbine frame  57  includes airfoils  59  which are in the core airflow path C. The turbines  46 ,  54  rotationally drive the respective low speed spool  30  and high speed spool  32  in response to the expansion. It will be appreciated that each of the positions of the fan section  22 , compressor section  24 , combustor section  26 , turbine section  28 , and the geared architecture  48  may be varied. For example, the geared architecture  48  may be located aft of the combustor section  26  or even aft of turbine section  28 , and fan section  22  may be positioned forward or aft of the location of the geared architecture  48 . 
         [0040]    The engine  20  in one example is a high-bypass geared aircraft engine. In a further example, the engine  20  bypass ratio is greater than about six (6), with an example embodiment being greater than about ten (10), the geared architecture  48  is an epicyclic gear train, such as a planetary gear system or other gear system, with a gear reduction ratio of greater than about 2.3 and the low pressure turbine  46  has a pressure ratio that is greater than about five. In one disclosed embodiment, the engine  20  bypass ratio is greater than about ten (10:1), the fan diameter is significantly larger than that of the low pressure compressor  44 , and the low pressure turbine  46  has a pressure ratio that is greater than about five 5:1. Low pressure turbine  46  pressure ratio is pressure measured prior to inlet of low pressure turbine  46  as related to the pressure at the outlet of the low pressure turbine  46  prior to an exhaust nozzle. The geared architecture  48  may be an epicycle gear train, such as a planetary gear system or other gear system, with a gear reduction ratio of greater than about 2.3:1. It should be understood, however, that the above parameters are only exemplary of one embodiment of a geared architecture engine and that the present invention is applicable to other gas turbine engines including direct drive turbofans. 
         [0041]    A significant amount of thrust is provided by the bypass flow B due to the high bypass ratio. The fan section  22  of the engine  20  is designed for a particular flight condition—typically cruise at about 0.8 Mach and about 35,000 feet. The flight condition of 0.8 Mach and 35,000 ft, with the engine at its best fuel consumption—also known as “bucket cruise Thrust Specific Fuel Consumption (‘TSFC’)”—is the industry standard parameter of lbm of fuel being burned divided by lbf of thrust the engine produces at that minimum point. “Low fan pressure ratio” is the pressure ratio across the fan blade alone, without a Fan Exit Guide Vane (“FEGV”) system. The low fan pressure ratio as disclosed herein according to one non-limiting embodiment is less than about 1.45. “Low corrected fan tip speed” is the actual fan tip speed in ft/sec divided by an industry standard temperature correction of [(Tram ° R)/(518.7° R)] 0.5 . The “Low corrected fan tip speed” as disclosed herein according to one non-limiting embodiment is less than about 1150 ft/second. 
         [0042]      FIG. 2  illustrates an example embodiment of the geared architecture  48  incorporated into the gas turbine engine  20 . In this example, the geared architecture  48  includes a planetary gear system having a sun gear  70 , a fixed ring gear  72  disposed about the sun gear  70 , and planetary gears  74 . Each of the planetary gears  74  includes rolling bearings  76 , such as ball bearings, roller bearings, or journal bearings. A carrier  78  supports each of the planetary gears  74 . In this embodiment, the fixed ring gear  72  does not rotate and is connected to a grounded structure  55  of the gas turbine engine  20 . The inner shaft  40  connects the sun gear  70  with the low pressure turbine  46  and the low pressure compressor  44 . 
         [0043]    A torque frame  80  is coupled to the carrier  78  and drives the fan  42 . The carrier  78  and the torque frame  80  are mechanically connected by known means of reducing misalignment between the carrier  78  and the torque frame  80  according to U.S. Pat. No. 5,391,125 to Turra et al. and U.S. Pat. No. 5,466,198 to McKibbin et al., which are incorporated by reference. The following description provides a means to transfer oil between the carrier  78  and the torque frame  80  in a manner that isolates and reduces misalignment to the geared architecture  48  by allowing the carrier  78  to be symmetrical fore and aft for uniform centrifugal growth under operation. Bearing systems  38  support the torque frame  80  and the inner shaft  40 . An oil transfer bearing  82  engages the torque frame  80  to deliver lubricant to the geared architecture  48  through conduits  180 ,  190 , and  200  ( FIG. 3C ) through the torque frame  80  to flexible jumper tubes  84  extending between the torque frame  80  and the geared architecture  48 . The oil transfer bearing  82  includes a stationary bearing  82   a  and a rotating bearing  82   b  that rotates with the torque frame  80 . 
         [0044]    Referring to  FIG. 3 , the stationary oil transfer bearing  82  is prevented from rotational movement by attachment of a link  90  via tab  92  to an oil input coupling  94  that attaches to a bearing support  96  (see  FIG. 2 ). 
         [0045]    The oil transfer bearing  82  includes a plurality of inputs to provide lubricant to those portions of the geared architecture  48  that require lubrication during operation. For instance, lubricant from first tube  98  is intended to lubricate the bearing systems  38 , oil from second tube  100  is intended to lubricate the bearings  76  (see  FIG. 2 ), and oil from third tube  102  is intended to lubricate the sun gear  70 , the planetary gears  74 , and the ring gear  72 . Though three inputs are shown herein, other numbers of lubricant inputs are contemplated herein. 
         [0046]    Referring to  FIGS. 3A and 3B , the link  90  attaches via a pin  104  to ears  106  extending from the tab  92 . The link  90  extends towards a boss  108  on the oil transfer bearing  82  and is attached thereto by a ball  110  and a pin  112  extending through the ball  110  and a pair of ears  114  on the boss  108  on the oil transfer bearing  82 . The ball  110  allows the oil transfer bearing  82  to flex with the torque frame  80  as torquing moments are experienced by the fan  42  and other portions of the engine  20 . The link  90  prevents the oil transfer bearing  82  from rotating while allowing it to flex. 
         [0047]      FIG. 3C  illustrates a cross-sectional view of the oil transfer bearing  82 . The oil transfer bearing  82  has a first race  160  that has a rectangular shape and extends around an interior surface  165  of the oil transfer bearing  82 , a second race  170  that has a rectangular shape and extends around the interior surface  165  of the oil transfer bearing  82  and a third race  175  that has a rectangular shape and extends around the interior surface  165  of the oil transfer bearing  82 . In the embodiment shown, the tube  100  inputs oil via conduit  180  into the first race  160 . 
         [0048]    The torque frame  80  includes a first oil conduit  180  extending axially therein and communicating with the first race  160  via opening  185 , a second oil conduit  190  extending axially therein and communicating with the second race  170  via opening  195  and a third oil conduit  200  extending axially therein and communicating with the third race  175  via opening  205 . As the torque frame  80  rotates within the oil transfer bearing  82 , the openings  185 ,  195 ,  205  are constantly in alignment with races  160 ,  170 ,  175  respectively so that oil may flow across a rotating gap between the oil transfer bearing  82  and the torque frame  80  through the openings  185 ,  195 ,  205  to the conduits  180 ,  190 ,  200  to provide lubrication to the areas necessary in engine  20 . As will be discussed herein, oil from the first oil conduit  180  flows through pathway A, oil from the second oil conduit  190  flows through pathway B and oil from the third oil conduit  200  flows through pathway C. Oil travels through the pathways A, B, and C to at least one of the flexible jumper tubes  84  to the geared architecture  48 . 
         [0049]      FIG. 4  illustrates a cross-sectional view taken along line A-A of  FIG. 2 . The flexible jumper tubes  84  extend between the torque frame  80  and the carrier  78  in this example. The carrier  78  includes at least one fluid pathway  78   a  that delivers the oil to the necessary parts of the geared architecture  48 , such as the planetary gears  74 , the ring gear  72 , the sun gear  70 , and the bearings  76 . The flexible jumper tube  84  includes grooves  84   a  for accepting at least one O-ring  85  to create a seal between the flexible jumper tube  84  and the torque frame  80  on one end and the carrier  78  on another opposite end. The flexible jumper tube  84  allows for flexing or relative movement between the torque frame  80  and the carrier  78  during operation while preventing oil leaks. 
         [0050]      FIG. 5  illustrates the example carrier  78 . The carrier  78  includes a first plate  130  that is symmetrical to a second plate  132 . The symmetrical first and second plates  130  and  132  allow the carrier  78  to grow uniformly in a radial direction during use. By having uniform growth in the radial direction, misalignment between the carrier  78  and the planetary gears  74 , the sun gear  70 , and the ring gear  72  is reduced. Reduced misalignment reduces the amount of wear on the geared architecture  48  and extends its life. Additionally, uniform growth reduces weight because additional support structures will not be required to maintain proper alignment of the geared architecture  48 . The symmetrical first and second plates  130  and  132  are spaced from each other with spacers  134 . The first and second plates  130  and  132  form pockets  136  with the adjacent spacers  134  to accept one of the planetary gears  74 . Shaft openings  138  extending through the first and second plates  130  and  132  into the pockets  136  accept a shaft  86  and the bearings  76  for each of the planetary gears  74 . 
         [0051]      FIG. 6  illustrates the oil transfer bearing  82  located radially inward from the bearing systems  38  on the torque frame  80 . Bearing systems conduits  38   a  extend through the torque frame  80  to direct lubricant leaking from the oil transfer bearing  82  into the bearing systems  38  on the torque frame shaft. Once the lubricant has leaked from the oil transfer bearing  82 , centrifugal forces from the rotation of the torque frame  80  direct the lubricant toward the bearing system conduits  38   a  and to the bearing systems  38 . Therefore, oil that would otherwise require collection from the oil transfer bearing  82  can be utilized in other areas of the gas turbine engine  20 . 
         [0052]    The preceding description is exemplary rather than limiting in nature. Variations and modifications to the disclosed examples may become apparent to those skilled in the art that do not necessarily depart from the essence of this disclosure. The scope of legal protection given to this disclosure can only be determined by studying the following claims.