Abstract:
In one exemplary embodiment, a gas turbine engine includes a fan, a speed reduction device driving the fan, and a lubrication system for lubricating components across a rotation gap. The lubrication system includes a lubricant input. A stationary first bearing receives lubricant from the lubricant input and has a first race in which lubricant flows. A second bearing for rotation is within the first bearing. The second bearing has a first opening in registration with said first race such that lubricant may flow from the first race through the first opening into a first conduit. The first bearing also has a second race into which lubricant flows. The second bearing has a second opening in registration with the second race such that lubricant may flow from the second race through the second opening into a second conduit. The first and second conduits deliver lubricant to distinct locations.

Description:
CROSS-REFERENCE TO RELATED APPLICATION 
       [0001]    This application is a continuation of U.S. Ser. No. 13/428,491, filed Mar. 23, 2012, which is a continuation-in-part application of U.S. Ser. No. 12/902,525, filed Oct. 12, 2010. 
     
    
     FIELD 
       [0002]    This invention relates to planetary gear trains and more particularly to a lubricating system for a planetary gear train. 
       BACKGROUND 
       [0003]    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. 
         [0004]    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. 
         [0005]    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. 
         [0006]    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 
       [0007]    In one exemplary embodiment, a gas turbine engine includes a fan, a speed reduction device driving the fan, and a lubrication system for lubricating components across a rotation gap. The lubrication system includes a lubricant input. A stationary first bearing receives lubricant from the lubricant input and has a first race in which lubricant flows. A second bearing for rotation is within the first bearing. The second bearing has a first opening in registration with said first race such that lubricant may flow from the first race through the first opening into a first conduit. The first bearing also has a second race into which lubricant flows. The second bearing has a second opening in registration with the second race such that lubricant may flow from the second race through the second opening into a second conduit. The first and second conduits deliver lubricant to distinct locations. 
         [0008]    In a further embodiment of the above, there is a first compressor rotor and a second compressor rotor. 
         [0009]    In a further embodiment of any of the above, there is a first turbine rotor and a second turbine rotor. The first turbine rotor drives the second compressor rotor as a high spool. The second turbine rotor drives said first compressor rotor as part of a low spool. 
         [0010]    In a further embodiment of any of the above, the fan and the first compressor rotor rotate in the same direction. 
         [0011]    In a further embodiment of any of the above, the high spool operates at higher pressures than the low spool. 
         [0012]    In a further embodiment of any of the above, the first bearing and the second bearing are centered about a common axis. 
         [0013]    In a further embodiment of any of the above, the first conduit is parallel to the axis and the first opening is perpendicular to the axis. 
         [0014]    In a further embodiment of any of the above, there is a rotating carrier that supports a planetary gear. The second bearing extends from the rotating carrier about an axis. 
         [0015]    In a further embodiment of any of the above, the first conduit is parallel to the axis and the first opening is perpendicular to the axis. 
         [0016]    In a further embodiment of any of the above, the first conduit lubricates the planetary gear system. 
         [0017]    In a further embodiment of any of the above, a first spray bar is disposed on the carrier. 
         [0018]    In a further embodiment of any of the above, the fan rotates slower than the first compressor stage. 
         [0019]    In a further embodiment of any of the above, there is at least a third race. The second bearing has a third opening in registration with the third race such that lubricant may flow from the third race through the third opening into a third conduit. The third conduit delivers lubricant to a distinct location from the first and second conduits. 
         [0020]    In a further embodiment of any of the above, the speed reduction device includes an epicyclic gear train. 
         [0021]    In a further embodiment of any of the above, the epicyclic gear train includes a sun gear. A plurality of planetary gears is configured to rotate about the sun gear. A stationary ring gear and a carrier are attached to the fan. 
         [0022]    In a further embodiment of any of the above, the carrier is configured to rotate in the same rotational direction as said sun gear. 
         [0023]    In one exemplary embodiment, a gas turbine engine includes a fan, a speed reduction device driving the fan and a lubrication system for lubricating components across a rotation gap. The lubrication system includes a lubricant input. A stationary first bearing receives lubricant from the lubricant input and has a first race in which lubricant flows. A second bearing for rotation is within the first bearing. The second bearing has a first opening in registration with the first race such that lubricant may flow from the first race through the first opening into a first conduit. There is a rotating carrier for supporting at least one planetary gear. The second bearing extends from the rotating carrier about an axis. A first spray bar is disposed on the carrier. The first bearing has a second race. The second bearing has a second opening in registration with the second race and a second conduit for passing lubricant to the spray bar. 
         [0024]    In a further embodiment of the above, there is a first compressor rotor and a second compressor rotor. 
         [0025]    In a further embodiment of any of the above, there is a first turbine rotor and a second turbine rotor. The first turbine rotor drives the second compressor rotor as a high spool. The second turbine rotor drives said first compressor rotor as part of a low spool. 
         [0026]    In a further embodiment of any of the above, the fan and the first compressor rotor rotate in the same direction. 
         [0027]    In a further embodiment of any of the above, the high spool operates at higher pressures than the low spool. 
         [0028]    In a further embodiment of any of the above, the first bearing and the second bearing are centered about a common axis. 
         [0029]    In a further embodiment of any of the above, the speed reduction device includes an epicyclic gear train. 
         [0030]    In a further embodiment of any of the above, the epicyclic gear train includes a sun gear. A plurality of planetary gears is configured to rotate about the sun gear. A stationary ring gear and a carrier are attached to said fan. 
         [0031]    In another exemplary embodiment, a method of designing a gas turbine engine includes configuring a speed reduction device for driving a fan and configuring a lubrication system for lubricating components across a rotation gap. The lubrication system includes a lubricant input. A stationary first bearing receives lubricant from the lubricant input and has a first race in which lubricant flows. A second bearing for rotation is within the first bearing. The second bearing has a first opening in registration with the first race such that lubricant may flow from the first race through the first opening into a first conduit. The first bearing is configured to also include a second race into which lubricant flows. The second bearing has a second opening in registration with the second race such that lubricant may flow from the second race through the second opening into a second conduit. The first and second conduits deliver lubricant to distinct locations. 
         [0032]    In a further embodiment of the above, the first bearing and the second bearing are centered about a common axis and the first conduit is parallel to the axis and the first opening is perpendicular to the axis. 
         [0033]    In a further embodiment of any of the above, the speed reduction device includes a rotating carrier for supporting at least one planetary gear. The second bearing extends from the rotating carrier about an axis. 
         [0034]    In a further embodiment of any of the above, the first conduit is parallel to the axis. The first opening is perpendicular to the axis. The first conduit lubricates the planetary gears. 
         [0035]    In a further embodiment of any of the above, a first spray bar is disposed on the carrier. 
         [0036]    In a further embodiment of any of the above, the speed reduction device includes an epicyclic gear train that has a sun gear. A plurality of planetary gears is configured to rotate about the sun gear. A stationary ring gear and a carrier are attached to the fan. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0037]    The various features and advantages of the disclosed examples 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. 
           [0038]      FIG. 1  is a schematic view, partially in section, of a gas turbine engine. 
           [0039]      FIG. 2  is a sectional view taken along the lines  2 - 2  in  FIG. 1 . 
           [0040]      FIG. 2A  is a sectional view through the gear drive. 
           [0041]      FIG. 3  is a sectional view taken along the lines  3 - 3 . 
           [0042]      FIG. 3A  is a sectional view taken along the line A-A of  FIG. 3 . 
           [0043]      FIG. 3B  is a sectional view taken along the line B-B of  FIG. 3 . 
           [0044]      FIG. 3C  is a sectional view taken along the line C-C  FIG. 3 . 
           [0045]      FIG. 4  is a sectional view of a portion of oil flow path A. 
           [0046]      FIG. 5  is a sectional view of an upper portion of the planetary gear system of  FIG. 1 . 
           [0047]      FIG. 6  is a sectional view of a lower portion of the planetary gear system of  FIG. 1 . 
           [0048]      FIG. 7  is a sectional view of a flow of oil into gutters. 
       
    
    
     DETAILED DESCRIPTION 
       [0049]      FIG. 1  shows a schematic cross-section of gas turbine engine  10 . Gas turbine engine  10  includes low pressure spool  12 , high pressure spool  14  and fan drive gear system (“FDGS”)  16 . Low pressure spool  12  includes low pressure compressor  18  and low pressure turbine  20 , which are connected by low pressure shaft  22 . High pressure spool  14  includes high pressure compressor  24  and high pressure turbine  26 , which are connected by high pressure shaft  28 . Fan drive gear system  16  includes epicyclic gear train  30  that drives a fan assembly  32  by way of a carrier shaft  34 . Epicyclic gear train  30  includes sun gear  36 , ring gear  38  and planetary gears  40  as will be shown hereinbelow. A carrier  50  is shown schematically in  FIG. 4  between shaft  34  and ring gear  38 . Details of this connection are better shown in  FIG. 2 . 
         [0050]    Low pressure spool  12  and high pressure spool  14  are covered by engine nacelle  42 , and fan assembly  32  and nacelle  42  are covered by fan nacelle  44 . Low pressure spool  12 , high pressure spool  14  and fan assembly  32  comprise a two-and-a-half spool gas turbine engine in which epicyclic gear train  30  couples fan assembly  32  to low pressure spool  12  with input shaft  46 . 
         [0051]    Fan assembly  32  generates bypass air for producing thrust that is directed between engine nacelle  42  and fan nacelle  44 , and core air that is directed into engine nacelle  42  for sequential compression with low pressure compressor  18  and high pressure compressor  24 . Compressed core air is routed to combustor  48  wherein it is mixed with fuel to sustain a combustion process. High energy gases generated in combustor  48  are used to turn high pressure turbine  26  and low pressure turbine  20 . High pressure turbine  26  and low pressure turbine  20  rotate high pressure shaft  28  and low pressure shaft  22  to drive high pressure compressor  24  and low pressure compressor  18 , respectively. Low pressure shaft  22  also drives input shaft  46 , which connects to epicyclic gear train  30  to drive fan assembly  32 . 
         [0052]    Referring now to  FIG. 2  and  FIG. 2A , a view of the planetary gear system having exemplary oil supply system is shown. The system is comprised of an input shaft  46 , sun gear  36  attaching thereto a plurality of planetary gears  40  that rotate about the sun gear  36 , stationary ring gear  38 , and a carrier  50  that rotates about the star gear to drive the fan assembly  32 . As the ring gear  38  is stationary, the rotation of the sun gear  36  causes each planetary gear  40  to counter-rotate relative to the direction of rotation of the sun gear  36  and simultaneously to orbit the sun gear  36  in the direction of the sun gear&#39;s rotation. In other words, whereas each planetary gear  40  individually counter-rotates relative to the sun gear  36 , the group of planetary gears  40  co-rotates with the sun gear  36 . Moreover, as the carrier  50  is driven by the rotation of the group of planetary gears  40 , the carrier  50  also co-rotates with respect to the sun gear  36 . Finally, as the fan  32  is driven by the carrier  50  (via shaft  34 ), the fan  32  also co-rotates with respect to the sun gear  36  and the low spool shaft  46 . Thus, in this embodiment, the fan  32  rotates in the same direction as the low pressure compressor  18 . 
         [0053]    A first spray bar  41  is mounted to the carrier  50  in between each planetary gear  40  that lubricates the planet gears  40  and ring gear  38 . A second spray bar  53  is attached to the first spray bar  41  and extends forward to provide lubrication to the carrier shaft  34  that is supported by tapered bearings  55  that are tensioned by spring  60 . 
         [0054]    The carrier  50  has a shaft  34  for driving the fan assembly  32 , a circular body  65  for holding the planetary gears  40  and a cylinder  70  projecting aft about the input shaft  46 . The cylinder  70  also closely interacts with a stationary oil transfer bearing  75 . 
         [0055]    A grounding structure  80  holds the FDGS  16 , the ring gear  38 , forward gutter  90  and aft gutter  95 . The flexible coupling  85  is disposed around the rotary input shaft  46 . The forward gutter  90  and an aft gutter  95  attach to and around the outer edge of the ring gear  38  to collect oil used by the system for reuse as will be discussed herein. Oil is input through the stationary oil transfer bearing  75  to the cylinder  70  (e.g. also a bearing) as will be discussed herein. 
         [0056]    Referring now to  FIG. 3 , a side, sectional view of the oil transfer bearing  75  is shown. The oil transfer bearing  75  is prevented from rotational movement by attachment of a link  100  via tab  110  to an oil input coupling  105  that attaches to the stationary aft gutter  95  (see also  FIG. 2 ). 
         [0057]    The oil transfer bearing  75  has a plurality of inputs to provide oil to those portions of the FDGS  16  that require lubrication during operation. For instance, oil from tube  115  is intended to lubricate the tapered bearings  55 , oil from tube  120  is intended to lubricate the planet gear bearings  125  (see  FIG. 5 ), and oil from tube  130  is intended to lubricate the planet and ring gears,  38 ,  40 . Though three inputs are shown herein, other numbers of oil inputs are contemplated herein. 
         [0058]    Referring now to  FIGS. 3A and 3B , the link  100  attaches via a pin  135  to the ears  140  extending from the tab  110 . The link  100  extends towards a boss  145  on the oil transfer bearing  75  and is attached thereto by a ball  150  and a pin  155  extending through the ball and a pair of ears  159  on the boss  145  on the oil transfer bearing  75 . The ball  150  allows the oil transfer bearing  75  to flex with the rotary input shaft  46  as torqueing moments are experienced by the fan assembly  32  and other portions of the engine  10 . The link  100  prevents the oil transfer bearing  75  from rotating while allowing it to flex. 
         [0059]    Referring now to  FIG. 3C , a cross-sectional view of the oil transfer bearing  75  is shown. The oil transfer bearing has a first race  160  that has a rectangular shape and extends around the interior surface  165  of the oil transfer bearing  75 , a second race  170  that has a rectangular shape and extends around the interior surface  165  of the oil transfer bearing  75  and a third race  175  that has a rectangular shape and extends around the interior surface  165  of the oil transfer bearing  75 . In the embodiment shown, tube  120  inputs oil via conduit  180  into the first race  160 . 
         [0060]    Cylinder  70  which extends from the carrier circular body  65 , has 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 cylinder  70  rotates within the oil transfer bearing  75 , 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  75  and the cylinder  65  through the openings  185 ,  195 ,  205  to the conduits  180 ,  190 ,  200  to provide lubrication to the areas necessary in engine  10 . As will be discussed herein, oil from conduit  180  flows through pathway A, oil from conduit  190  flows through pathway B and oil from conduit  200  flows through pathway C as will be shown herein. 
         [0061]    Referring now to  FIGS. 4 and 6 , oil from the tube  115  flows into second race  170 , through opening  195  into conduit  190 . From conduit  190 , the oil flows through path B into a pipe  210  in the first spray bar  41  to the second spray bar  53  where it is dispersed through nozzles  215 . Pipe  210  is mounted into fixtures  220  in the circular body  65  by o-rings  225  the oil  FIG. 4 , the journal oil bearing input passes through tube, and tube into transfers tubes through tube into the interior of each planetary gear. Each planetary gear has a pair of transverse tubes communicating with the interior of the planetary journal bearing to distribute oil between the planetary gear and the ring gear and a set of gears to provide lubricating area oil to the journal bearings  235  themselves. 
         [0062]    Referring now to  FIGS. 3C and 5 , the flow of oil through path A is shown. The oil leaves conduit  180  through tube  230  and flows around journal bearings  235  that support the planet gear  40  and into the interior of shaft  240 . Oil then escapes from the shaft  240  through openings  245  to lubricate between the planetary gears  40  and the ring gear  38 . 
         [0063]    Referring to  FIG. 6 , the conduit  200  provides oil through pathway C into manifold  250  in the first spray bar  41  which sprays oil through nozzles  255  on the sun gear. 
         [0064]    Referring now to  FIG. 7 , oil drips (see arrows) from the planetary gears  40  and the sun gear  36  about the carrier  50  and is trapped by the forward gutter  90  and the aft gutter  95 . Oil captured by the forward gutter  90  is collected through scupper  265  for transport into an auxiliary oil tank  270 . Similarly, oil captured by the aft gutter  95  travels through opening  275  and opening  280  in the ring gear support  285  into the forward gutter  90  to be similarly collected by the scupper  265  to go to the auxiliary oil tank  270 . Some oil passes through openings  290 ,  295  within the ring gear  38  and drips upon the flexible coupling  85  and migrates through holes  300  therein and drains to the main scavenge area (not shown) for the engine  10 . 
         [0065]    As is clear from  FIGS. 5 and 7 , there is a recess adjacent the outer periphery of the ring gear  38 . The recess identified by  602 , can be seen to be formed by half-recess portions in each of two separate gear portions  600  which form the ring gear  38 . As is clear, the recess  602  is radially outwardly of the gear teeth  603  on the ring gear  38 . This recess helps balance force transmitted through the ring gear as the various interacting gear members shift orientation relative to each other. 
         [0066]    Referring now to the Figures, In view of these shortcomings a simple, reliable, unlubricated coupling system for connecting components of an epicyclic gear train  30  to external devices while accommodating misalignment therebetween is sought. 
         [0067]    Although a combination of features is shown in the illustrated examples, not all of them need to be combined to realize the benefits of various embodiments of this disclosure. In other words, a system designed according to an embodiment of this disclosure will not necessarily include all of the features shown in any one of the Figures or all of the portions schematically shown in the Figures. Moreover, selected features of one example embodiment may be combined with selected features of other example embodiments. 
         [0068]    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.