Abstract:
A gas turbine engine includes a bearing and a bearing support having a second wall extending between first and second ends and operatively supported by the bearing at a first end. An engine case is secured to the second end radially outward of the first end. A second wall integral with and extending transversely from the first wall provides a flexible support. The second wall has a flange, and a gear train component is secured to the flange. A gas turbine engine includes a support structure which supports the main rotatable structure via bearings and gear train components. The support provides both the necessary structural support for the rotor structure as well as desired flexibility for a fan drive gear system.

Description:
BACKGROUND 
       [0001]    This disclosure relates to a gas turbine engine having a gear train used to drive a fan, and more particularly, the disclosure relates to structure used to support a portion of the gear train relative to a main bearing. 
         [0002]    A main bearing is used to rotationally support a compressor rotor and input coupling. In a turbine engine having a gear train, which is used to drive a fan, the same main bearing may be used to rotationally support a gear train component. The gear train component is “soft mounted” to enable the gear train to deflect relative to the main bearing during engine operation. This deflection minimizes gear and bearing stresses by reducing the overall forces exerted within the fan drive system. 
         [0003]    In one example arrangement, a main bearing support extends from the main bearing to the engine case. The “soft mount” is provided by a separate flexible structure that includes a steel outer disc that is bolted to the main support where it attaches to the engine case, providing a joint with three flanges. In one example, the main bearing support is constructed from titanium. The flexible support is provided by a stamped steel plate that is welded to a steel inner disc and the outer disc. A torque frame of the gear train is bolted to the inner disc plate. 
       SUMMARY 
       [0004]    A gas turbine engine includes a bearing and a bearing support having a second wall extending between first and second ends and operatively supported by the bearing at a first end. An engine case is secured to the second end radially outward of the first end. A second wall integral with and extending transversely from the first wall provides a flexible support. The second wall has a flange, and a gear train component is secured to the flange. 
         [0005]    A method of manufacturing a gas turbine engine includes providing the bearing support having a first wall extending between first and second ends, and a second wall integral with the first wall. An engine case is secured to the second end. A torque frame is secured to a flange provided on the second wall. A bearing is mounted to a centering spring, and the centering spring and bearing are axially inserted through the torque frame. The centering spring is secured to the first end subsequent to the torque frame being secured to the flange. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0006]    The disclosure can be further understood by reference to the following detailed description when considered in connection with the accompanying drawings wherein: 
           [0007]      FIG. 1  is a schematic cross-sectional view of an example geared turbofan engine. 
           [0008]      FIG. 2  is an enlarged cross-sectional view of the engine shown in  FIG. 1  illustrating one example integrated gear and bearing support. 
           [0009]      FIG. 3  is an enlarged cross-sectional view of the engine shown in  FIG. 1  illustrating another example integrated gear and bearing support. 
       
    
    
     DETAILED DESCRIPTION 
       [0010]    A geared turbofan engine  10  is illustrated in a highly schematic fashion in  FIG. 1 . Engine  10  includes a fan section  12  arranged within a fan case  14 . The fan section  12  includes multiple blades arranged at an inlet  18  of the fan case  14 . A core  20  is supported relative to the fan case  14  by flow exit guide vanes  21 . The core  20  includes a low pressure compressor section  22 , a high pressure compressor section  24 , a combustor section  26 , a high pressure turbine section  28  and a low pressure turbine section  30 . In one example, the low pressure compressor section  22  and low pressure turbine section  30  are supported on a low spool  34  rotatable about an axis A. The high pressure compressor section  24  and high pressure turbine section  28  are supported on a high spool  32  rotatable about the axis A. 
         [0011]    In the example engine  10 , a gear train  36  is arranged between the low spool  34  and the fan section  12  to rotationally drive the fan blades  16  at a desired rotational speed that is lower than the low spool rotational speed. Referring to  FIG. 2 , the gear train  36  includes an input gear  38  that is operatively coupled to the fan section  12  (shown in  FIG. 1 ). A ring gear  42  is coupled to a member  44 , which rotationally drives the fan section  12  via multiple intermediate gears  40  arranged about the input gear  38  and intermeshed with the input gear  38  and the ring gear  42 . Other epicyclic gear configurations may be used. 
         [0012]    A torque frame  46  is operatively coupled to a case  48  of the core  20  for fixing the intermediate gears  40  against rotation. The torque frame  46  includes fingers that are illustrated by dashed lines in  FIGS. 2 and 3 . The fingers support a carrier  47  to which the intermediate gears  40  are mounted. 
         [0013]    The low spool  34  rotationally drives compressor blades  50  in one or more stages of the low pressure compressor section  22 . An input coupling  52  is rotationally supported relative to the low spool  34  by a main bearing  58 , which is a ball bearing in one example. The input coupling  52  axially extends from the main bearing  58  to the input gear  38 , which is splined to an end of the input coupling  52 . The input coupling  52  is mounted to a hub  54 , which is part of the low spool  34 , and retained thereto by a nut  56 . 
         [0014]    An inner race  60  of the main bearing  58  is mounted to the input coupling  52 , and an outer race  62  of the main bearing  58  is mounted to a centering spring  64 . A main bearing support  66 , which comprises a portion of the core support structure, is affixed to the centering spring  64 . In the example illustrated, the frustoconical main bearing support  66  includes a first support  68  at a first end, and the centering spring  64  includes a centering spring flange  70  that engages the first support  68 . In one example, the first support  68  includes a surface having a radius sized to accommodate the centering spring flange  70 , which has a first radius R 1 . Multiple flange fasteners  72  are received in holes  69 , secure the centering spring flange  70  to the first support  68 . 
         [0015]    A flexible support  74  is integral with the main bearing support  66 , and are cast or forged from titanium, for example. By “integral” it is meant that the flexible support  74  and main bearing support  66  are permanently affixed to one another, rather than removably affixed such as by fasteners. By “permanently affixed” it is meant that destructive means such as cutting would be required to separate the flexible support  74  and main bearing support  66 . The torque frame  46  includes a second flange  84  that is secured to a first flange  82  of the flexible support  74  by fasteners  86 . The joint provided by the first and second flanges  82 ,  84  have a second radius R 2  that is large enough to accommodate the centering spring flange  70  (and its first radius R 1 ) during assembly. 
         [0016]    The main bearing support  66  includes a first wall  76 , and the flexible support  74  includes a second wall  78  that is spaced apart from the first wall  76  to provide a pocket  80 . The first and second walls  76 ,  78  are integral with one another to provide the integrated flexible support  74  and main bearing support  66 . Drain holes  87  are provided in at least one of the main bearing support  66  and the flexible support  74  and in communication with the pocket  80  to prevent oil from collecting within the pocket  80  during operation. 
         [0017]    The first wall  76  of the main bearing support  66  extends from the first support  68  to a second support  88  at a second end of the main bearing support  66 . The case  48  includes a case flange  90  that is secured to the second support  88  with second support fasteners  92  received by holes  91 . A recess  94  is provided in one of the main bearing support  66  and the rotor  48 . A seal  96  is disposed in the recess  94  to provide a seal between the rotor  48  and the main bearing support  66 . 
         [0018]    Another integrated main bearing support  166  and flexible support  174  is shown in  FIG. 3 . The low pressure compressor section  122  is rotationally driven with the low spool  134  within the core  120 . The member  144 , mounted to the ring gear  142 , is rotationally driven by the input gear  138  via the intermediate gears  140 . The intermediate gears  140  are retained in their circumferential position by the carrier  147  and torque frame  146 . 
         [0019]    The first wall  176  in the example is provided by first and second portions  198 ,  200 . The first and second portions  198 ,  200 , respectively include first and second edges  102 ,  104  that are secured to one another by a weld  106  or similar manufacturing/affixing method. Providing the first and second portions  198 ,  200  as two parts enables the pocket  180  to be machined more easily. Machining of the pocket  180  is desirable to obtain the desired wall thickness for the first and/or second walls  176 ,  178  for balance and strength of the structure in that area. First flange  182  of the second wall  178  is secure to the second flange  184  of the torque frame  146 . Forming the first and second walls  176 ,  178  during a near-net forging operation may avoid the need to machine the pocket  180 , for example. The drain holes  187  may be machined or cast, for example. 
         [0020]    The main bearing support  166  is provided by an intermediate support  197  and a separate main support  108  that is supported by the main bearing  158  and secured to the centering spring  164 . The intermediate support  197  includes an intermediate flange  210  that is mounted to and secured between the main support  108  and the centering spring  164  in the example shown. In one example, the main bearing support  166 , flexible support  174  is constructed from titanium and the main support  108  is constructed from aluminum. A nickel alloy may also be used, for example. A seal flange  102  extends from the intermediate support  197 . A recess  214  is provided in the main support  108  and receives a seal  216  that engages the seal flange  212 . 
         [0021]    During assembly, the case flange  190  of the case  148  is secured to the main bearing support  166  at the second support  188  by fasteners  192 . The input coupling  152 , main bearing  158  and centering spring  164  are assembled to one another. This assembly is installed onto the hub  154  with the main bearing support  166  in place to facilitate assembly, the centering spring  164  outer diameter R 1  (and corresponding surface provided by the first support  168 ) is smaller than the joint inner diameter R 2  of the torque frame/first flange joint. The centering spring  164  is secured to the main bearing support  166  with the flange fasteners  172  at the centering spring flange  170  and the input coupling  152  is secured to the hub  154  with the nut  156 . The torque frame  146  is secured to the flexible support  174  with the fasteners  186 . The gear train  136  is splined or affixed onto the input coupling  152 . Assembly of the arrangement illustrated in  FIG. 2  is similar to that described above in relation to the arrangement of  FIG. 3 . 
         [0022]    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.