Abstract:
A method of assembling a fan drive gear system includes the steps of installing spherical bearings into respective races to provide a plurality of bearing assemblies, mounting at least one of the bearing assemblies onto a corresponding shaft of a torque frame, each of the shafts fixed relative to one another, installing at least one gear onto at least one of the bearing assemblies, the gears meshing with a ring gear and a centrally located sun gear and grounding the torque frame to a static structure to prevent rotation of the torque frame.

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
       [0001]    This disclosure is a continuation of U.S. patent application Ser. No. 13/095,324 filed Apr. 27, 2011. 
     
    
     BACKGROUND 
       [0002]    This disclosure relates to a fan drive gear system integrated carrier and torque frame. 
         [0003]    One type of gas turbine engine includes a fan drive gear system that is mechanically arranged between the turbo-machinery of the engine and a fan. The turbo-machinery is composed of two concentric shafts rotating at different speeds containing independent compressors and turbines. The turbo-machinery rotationally drives the fan, via the gear system, to move fluid through a nacelle which divides the fluid flow into two streams. An inner stream supplies the turbo-machinery and the outer stream consists of fluid which bypasses the inner stream and is solely compressed and moved by the fan. 
         [0004]    Typically the fan drive gear system is provided by an epicyclic gear train and includes a centrally located input gear driven by the turbo-machinery, intermediate gears circumferentially arranged about and intermeshing with the input gear and a ring gear provided about and intermeshing the intermediate gears. Depending upon the configuration, either the intermediate gears or the ring gear rotationally drives the fan in response to rotation of the input gear. 
         [0005]    The intermediate gears are typically supported in a carrier by a journal extending between spaced apart walls of the carrier. The carrier is typically constructed from a high strength metallic alloy such as steel, titanium or nickel. The carrier is bolted to a torque frame, which is secured to fixed structure or rotating structure depending upon the particular type of gear system. 
         [0006]    One type of gear system for helicopter applications has been used which directly supports the intermediate gears on an integrated carrier and torque frame. This integrated torque frame includes shafts that directly support the intermediate gears in a cantilevered fashion by conventional rolling element bearings. This arrangement is subjected to vibrational stresses that may cause the integrated torque frame to fail. 
       SUMMARY 
       [0007]    In one exemplary embodiment, a method of assembling a fan drive gear system includes the steps of installing spherical bearings into respective races to provide a plurality of bearing assemblies, mounting at least one of the bearing assemblies onto a corresponding shaft of a torque frame, each of the shafts fixed relative to one another, installing at least one gear onto at least one of the bearing assemblies, the gears meshing with a ring gear and a centrally located sun gear and grounding the torque frame to a static structure to prevent rotation of the torque frame. 
         [0008]    In a further embodiment of the above, the installing spherical bearings step includes inserting a spherical bearing into slots in the race and rotating the spherical bearing and the race relative to one another to seat the spherical bearing within the race. 
         [0009]    In a further embodiment of any of the above, the installing spherical bearings step includes aligning first and second lubrication passageways provided in the spherical bearing and race with one another. 
         [0010]    In a further embodiment of any of the above, the installing spherical bearings step includes locating a pin within a notch and the mounting step includes securing a fastening element to the shaft to retain the at least one bearing assembly on the torque frame. 
         [0011]    In a further embodiment of any of the above, the method includes the step of engaging the torque frame to a first structure and engaging the sun gear to a second structure. The installing step includes installing intermediate gears around the sun gear. 
         [0012]    In a further embodiment of any of the above, the method includes the step of engaging an oil baffle to the torque frame and fluidly connecting lubrication passages in the torque frame to lubrication passageways in the oil baffle. 
         [0013]    In a further embodiment of any of the above, the lubrication passageways include a spray bar facing the sun gear. 
         [0014]    In another exemplary embodiment, a fan drive gear lubrication system includes a torque frame that supports multiple gears and includes at least one torque frame lubrication passage. An oil baffle engages the torque frame and includes a central opening and multiple circumferentially spaced gear pockets arranged about the central opening and receiving the multiple gears. The oil baffle includes at least one oil baffle lubrication passageway that is in fluid communication with the torque frame lubrication passage. The torque frame includes a base with integrated gear shafts circumferentially spaced relative to one another and supporting the multiple gears. A bearing assembly is mounted on each gear shaft and includes a race receiving a spherical bearing and at least one bearing passageway that extends through each of the spherical bearings and the race. At least one bearing passageway is in fluid communication with the torque frame lubrication passage. A gear is supported for rotation about a bearing axis provided by the race. The gear is configured to slidingly rotate on and about the race. 
         [0015]    In a further embodiment of any of the above, at least one oil baffle lubrication passageway includes a spray bar that is configured to direct lubricating fluid at teeth of a gear. 
         [0016]    In a further embodiment of any of the above, the torque frame is constructed from a high strength metallic alloy and the oil baffle is constructed from a lower strength, lighter weight alloy than the high strength metallic alloy. 
         [0017]    In another exemplary embodiment, a method of designing a fan drive gear system includes the steps of defining spherical bearings to be installed into corresponding races to provide a plurality of bearing assemblies, defining at least one of the bearing assemblies to be mounted onto a respective shaft of a torque frame, each of the shafts defined to be fixed relative to one another, defining at least one gear to be installed onto a corresponding bearing assembly, the gears defined to mesh with a ring gear and a centrally located sun gear and defining the torque frame to be grounded to a static structure to prevent rotation of the torque frame. 
         [0018]    In a further embodiment of the above, the spherical bearing defining step includes defining a spherical bearing to be inserted into slots in the race and the spherical bearing and the race defined to be rotated relative to one another to seat the spherical bearing within the race. 
         [0019]    In a further embodiment of any of the above, the spherical bearing defining step includes aligning first and second lubrication passageways provided in the spherical bearing and race with one another. 
         [0020]    In a further embodiment of any of the above, the spherical bearing defining step includes locating a pin within a notch. The bearing assembly defining step includes defining a fastening element to be secured to the shaft to retain at least one bearing assembly on the torque frame. 
         [0021]    In a further embodiment of any of the above, the method includes the step of defining the torque frame to engage a first structure and defining the sun gear to engage a second structure. The gear defining step includes defining intermediate gears around the sun gear. 
         [0022]    In a further embodiment of any of the above, the method includes the step of defining an oil baffle to engage the torque frame and fluidly connecting lubrication passages in the torque frame to lubrication passageways in the oil baffle. 
         [0023]    In a further embodiment of any of the above, the lubrication passageways include a spray bar facing the sun gear. 
         [0024]    In a further embodiment of any of the above, the torque frame is defined to be constructed from a high strength metallic alloy, and the oil baffle is defined to be constructed from a lower strength lighter weight alloy than the high strength metallic alloy. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0025]    The disclosure can be further understood by reference to the following detailed description when considered in connection with the accompanying drawings wherein: 
           [0026]      FIG. 1  is a schematic cross-sectional view of an example gas turbine engine. 
           [0027]      FIG. 2  is a cross-sectional view of an example fan drive gear system. 
           [0028]      FIG. 3  is an enlarged cross-sectional view of a portion of the fan drive gear system illustrated in  FIG. 2 . 
           [0029]      FIG. 4  is a perspective view of an example spherical bearing. 
           [0030]      FIG. 5A  is an elevational view of the spherical bearing of  FIG. 4  inserted into a race in an assembly position. 
           [0031]      FIG. 5B  is an elevational view of the spherical bearing of  FIG. 4  fully assembled into the race to provide a bearing assembly. 
           [0032]      FIG. 6  is an elevational view of an example oil baffle used in the fan drive gear system and illustrated in  FIGS. 2 and 3 . 
       
    
    
     DETAILED DESCRIPTION 
       [0033]    An example gas turbine engine  10  is schematically illustrated in  FIG. 1 . The engine  10  includes turbo-machinery  30  having a compressor section  12  and a turbine section  14 . The turbo-machinery  30  rotationally drives a fan  32 , that is arranged in a bypass flow path  33 , through an epicyclic gear train  16 . The turbo-machinery  30  is housed within an inner nacelle  42 . Flow exit guide vanes  31  arranged within the bypass flow path support the turbo-machinery  30  relative to a fan case, which is housed in a fan nacelle  44 . 
         [0034]    A low pressure compressor  18  and a low pressure turbine  20  are mounted on a low pressure spool  22 . A high pressure compressor  24  and a high pressure turbine  26  are mounted on a high pressure spool  28 . A combustor section  48  is arranged between the high pressure compressor  24  and the high pressure turbine  26 . 
         [0035]    The low pressure spool  22  rotationally drives a flex shaft  46  to which an input gear  36  (sun gear) is mounted for rotation about an axis A. Intermediate gears  38  (in the example, star gears) are arranged circumferentially about and intermesh with the input gear  36 . A ring gear  40  surrounds and intermeshes with the intermediate gears  38 . Either the intermediate gears  38  or the ring gear  40  rotationally drives the fan shaft  34  depending upon the type of epicyclic gear train configuration. 
         [0036]    One example epicyclic gear train  16  is illustrated in  FIG. 2 . The epicyclic gear train  16  is the type in which the intermediate gears  38  (star gears, in the example) are rotationally fixed relative to the rotational axis of the input gear  36 . That is, the star gears are permitted to rotate about their respective rotational axes but do not rotate about the rotational axis of the input gear  36 . The ring gear  40  is coupled to the fan shaft  34  and to rotationally drive the fan  32 . The turbo-machinery  30  includes fixed structure  50  comprising a bearing compartment case  52  and a support member  54 . A torque frame  56  is affixed to the support member  54  to prevent rotation of the torque frame  56  about the rotational axis A of the input gear  36 . However, it should be understood that in a planetary gear configuration the torque frame  56  would rotate about the rotational axis A and the ring gear would be coupled to fixed structure. 
         [0037]    The torque frame  56  includes multiple shafts  58  integral with a base  61  that provides first and second support features  62 ,  64  affixed to the support member  54 . In the example, the torque frame  56  includes five equally circumferentially spaced shafts  58  that correspondingly support five star gears. The base  61  and shafts  58  of the torque frame  56  are unitary and formed by a one-piece structure, for example, by a cast steel structure. Other high strength metallic alloys, such titanium or nickel, may also be used. 
         [0038]    Each shaft  58  includes a bearing assembly  60  for rotationally supporting its respective intermediate gear  38 . An oil baffle  66  is secured to the torque frame  56  by fasteners  74 . The oil baffle  66  is non-structural. That is, the oil baffle does not support the loads of the intermediate gears  38  as would a prior art carrier. As a result, the oil baffle  66  may be constructed from a considerably lower strength lighter weight material, such as an aluminum alloy or composite material. 
         [0039]    Both the torque frame  56  and the oil baffle  66  provide internal lubrication features for supplying lubricating fluid, such as oil, to the gears of the epicyclic gear train  16 . As an example, a feed tube  68  supplies oil to first and second passages  70 ,  72  provided in the torque frame  56 . A tube  76  fluidly interconnects the second passage  72  to a spray bar  78  provided integrally in the oil baffle  66 . The spray bar  78  includes a first passageway  80 , which extends in a generally axial direction in the example shown, and one or more second passageways  82  transverse to the first passageway  80 . In the example, a pair of second passageways  82  are oriented to direct lubrication fluid radially inward at teeth  84  of the input gear  36 . 
         [0040]    Referring to  FIG. 3 , each shaft  58  includes an end  86  that supports a bearing assembly  60 . The bearing assembly  60  includes a spherical bearing  88  supported in a race  90  on which the intermediate gear  38  is mounted. The ends  86  include a threaded portion that each receives a nut  91  securing the bearing assembly  60  to the shaft  58 . The shaft  58 , spherical bearing  88  and race  90  respectively include radially extending first, second and third passageways  92 ,  94 ,  96  that are aligned with one another to deliver lubricating fluid from the first passage  70  to bearing surfaces  98  provided between the race  90  and the intermediate gear  38 . A recess  99  is provided in an outer diameter of the race  90  to increase lubrication at the bearing surfaces  98 . In one example, a filter  100  is arranged in a hole in the shaft  58  that provides a portion of the first passage  70 . 
         [0041]    Referring to  FIGS. 3-5B , the spherical bearing  88  includes an inner diameter  102  that is supported by the end  86 . A convex surface  104  is provided on an outside of the spherical bearing  88  and mates with a corresponding concave surface  112  provided by an inner surface of the race  90  when fully assembled as illustrated in  FIG. 5B . The spherical bearing  88  includes a pin  106  that extends through both the inner diameter  102  and the convex surface  104  in the example illustrated. The pin  106  is received by notches  110 ,  114  respectively provided in the race  90  and end  86  to prevent rotation of the spherical bearing  88  about a bearing axis B ( FIG. 5B ). The spherical bearing  88  permits angular movement of the bearing axis B relative to a shaft axis T ( FIG. 3 ) provided by the shaft  58  during flexing of the shafts  58 , which provides a near zero moment restraint. 
         [0042]      FIGS. 5A and 5B  illustrate the assembly process of the bearing assembly  60 . The spherical bearing  88  is inserted into slots  108  of the race  90 , as shown in  FIG. 5A . The pin  106  is aligned with the notch  110  and the spherical bearing  88  is rotated to snap into engagement with the concave surface  112  with the pin  106  received in the notch  110 . In this position, illustrated in  FIG. 5B , the second and third passageways  94 ,  96  are aligned with one another. 
         [0043]    The oil baffle  66  is illustrated in more detail in  FIG. 6 . The oil baffle  66  is provided by a body  116  having circumferentially spaced apart intermediate structures  118  axially extending from a wall  120 . The intermediate structures  118  define gear pockets  122  within which the intermediate gears  38  are received with the epicyclic gear train  16  fully assembled. The input gear  36  was received in a central opening  124  provided radially inward of the intermediate structures  118 . Holes  126  are provided in the intermediate structures  118  and receive the fasteners  74  to secure the oil baffle  66  to the torque frame  56 , as illustrated in  FIG. 2 . 
         [0044]    Although an example embodiment has been disclosed, a worker of ordinary skill in this art would recognize that certain modifications would come within the scope of the claims. For that reason, the following claims should be studied to determine their true scope and content.