Abstract:
A gas turbine engine includes a central body support that provides an inner annular wall for a core flow path. The central body support includes a first mount feature. A geared architecture interconnects a spool and a fan rotatable about an axis. A flex support interconnects the geared architecture to the central body support. The flex support includes a second mount feature that cooperates with the first mount feature for transferring torque there between. A method of disassembling a front architecture of a gas turbine engine includes the steps of accessing forward-facing fasteners that secure a central body support to a flex support, wherein the flex support includes a geared architecture supported thereon, removing the fasteners, and decoupling first and second mount features respectively provided on the central body support and the flex support.

Description:
CROSS REFERENCE TO RELATED APPLICATIONS 
     The present disclosure is a continuation of U.S. patent application Ser. No. 13/407,916, filed on Feb. 29, 2012, which is a continuation-in-part application of U.S. patent application Ser. No. 13/282,919, filed 27 Oct. 2011, which is a continuation-in-part application of U.S. patent application Ser. No. 13/087,579, filed 15 Apr. 2011, and U.S. patent application Ser. No. 13/275,286, filed 17 Oct. 2011, now abandoned. 
    
    
     BACKGROUND 
     The present disclosure relates to a gas turbine engine, and in particular, to a case structure therefor. 
     Gas turbine engines typically include one or more rotor shafts that transfer power and rotary motion from a turbine section to a compressor section and fan section. The rotor shafts are supported within an engine static structure, which is typically constructed of modules with individual case sections which are joined together at bolted flanges. The flanges form a joint capable of withstanding the variety of loads transmitted through the engine static structure. An ongoing issue for gas turbine engines is the ease and speed at which certain components in such engines can be serviced. 
     SUMMARY 
     In one exemplary embodiment, a gas turbine engine includes a central body support that provides an inner annular wall for a core flow path. The central body support includes a first mount feature. A geared architecture interconnects a spool and a fan rotatable about an axis. A flex support interconnects the geared architecture to the central body support. The flex support includes a second mount feature that cooperates with the first mount feature for transferring torque there between. 
     In a further embodiment of the above, the central body support includes circumferentially spaced apart vanes that radially extend between and interconnect the inner annular wall and an outer annular wall. 
     In a further embodiment of the above, the first mount feature includes tooth groups including multiple teeth. The tooth groups are circumferentially spaced apart from one another with untoothed regions arranged between the tooth groups. 
     In a further embodiment of the above, the vanes are circumferentially aligned with the untoothed regions. 
     In a further embodiment of the above, the second mount feature includes corresponding tooth groups configured to circumferentially align and mate with the tooth groups of the first splines, and corresponding untoothed regions arranged between the tooth groups of the corresponding tooth groups. 
     In a further embodiment of the above, the central body support includes multiple fastener bosses circumferentially spaced from one another. The fastener bosses are aligned with the tooth groups. 
     In a further embodiment of the above, the untoothed region is provided by a stiffening rail protruding radially inward from a central body section providing the inner annular wall. 
     In a further embodiment of the above, the central body support includes an annular recess and an annular pocket axially spaced apart from one another to provide first and second lateral sides on the stiffening rail. 
     In a further embodiment of the above, the tooth groups include internal teeth having roots provided at a first tooth radius and extending radially inward to crests provided at a second tooth radius. The stiffening rail extends radially inward to a rail radius that is less than the first tooth radius. 
     In a further embodiment of the above, the geared architecture includes an epicyclic gear train having a sun gear, a ring gear, and intermediate gears arranged circumferentially about the sun gear and intermeshing with the sun gear and the ring gear. 
     In a further embodiment of the above, the intermediate gears are star gears grounded to the flex support against rotation about the axis. The sun gear is supported by the spool and the ring gear is interconnected to the fan. 
     In a further embodiment of the above, the central body support includes a first inner face arranged near the first spline and the flex support includes a first outer face arranged in an interference fit relationship with the first inner face to radially locate the flex support relative to the central body support. 
     In a further embodiment of the above, the central body support includes a second inner face and the flex support includes a second outer face arranged in an interference fit relationship with the second inner face. The first inner and outer faces are arranged forward of the first mount feature and the second inner and outer faces are arranged aft of the first mount feature. The second outer face is positioned radially inward relative to the first outer face. 
     In a further embodiment of the above, the gas turbine engine includes fasteners securing the flex support to the central body support. The fasteners include heads facing forward. 
     In a further embodiment of the above, the central body support includes circumferentially spaced fastener bosses and the flex support includes a radially outward extending fastener flange abutting the fastener bosses to axially locate the flex support relative to the central body support. 
     In a further embodiment of the above, the fastener flange includes apertures arranged circumferentially spaced from one another and receiving the fasteners. 
     In a further embodiment of the above, the first and second mount features are axially aligned with one another. 
     In a further embodiment of the above, the first and second mount features are circumferentially adjacent to one another. 
     In a further embodiment of the above, the first mount feature is arranged radially outward of the second mount feature. 
     In another exemplary embodiment, a method of disassembling a front architecture of a gas turbine engine includes the steps of accessing forward-facing fasteners that secure a central body support to a flex support, wherein the flex support includes a geared architecture supported thereon, removing the fasteners, and decoupling first and second mount features respectively provided on the central body support and the flex support. 
     In a further embodiment of the above, the accessing step includes the step of detaching a fan module from a fan shaft bearing support, with the fan shaft bearing support remaining secured to the central body support. 
     In a further embodiment of the above, the accessing step includes the step of detaching the fan shaft bearing support from the central support body without removing the geared architecture. 
     In a further embodiment of the above, the decoupling step includes removing a geared architecture module that includes the geared architecture and the flex support. The decoupling step leaves undisturbed a bearing that supports a front of a spool operatively connectable with the geared architecture. 
     In a further embodiment of the above, the first and second mount features are axially aligned with one another during the accessing step. 
     In a further embodiment of the above, the first and second mount features are circumferentially adjacent to one another during the accessing step. 
     In a further embodiment of the above, the first mount feature is arranged radially outward of the second mount feature during the accessing step. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       Various features will become apparent to those skilled in the art from the following detailed description of the disclosed non-limiting embodiment. The drawings that accompany the detailed description can be briefly described as follows: 
         FIG. 1  is a schematic cross-section of an embodiment of a gas turbine engine; 
         FIG. 2  is an enlarged cross-section of a front center body assembly portion of the gas turbine engine embodiment shown in  FIG. 1 ; 
         FIG. 3  is an enlarged cross-section of the geared architecture of the gas turbine engine embodiment shown in  FIG. 1 ; 
         FIG. 4  is an exploded perspective view of the front center body assembly of the turbine engine embodiment shown in  FIG. 1 ; 
         FIG. 5  is an enlarged perspective partial cross-section of a front center body support of the front center body assembly of the turbine engine embodiment shown in  FIG. 1 ; 
         FIG. 6  is an enlarged sectional view of the front center body support of the turbine engine embodiment shown in  FIG. 1 ; 
         FIG. 6A  is a perspective view of the center body support of the turbine engine embodiment shown in  FIG. 1 ; 
         FIG. 6B  is an end view of the center body support of the turbine engine embodiment shown in  FIG. 1 ; 
         FIG. 7  is an exploded view of the front center body support of the turbine engine embodiment shown in  FIG. 1 ; and 
         FIG. 8  is a schematic view of an embodiment of a forward gearbox removal from a gas turbine engine. 
     
    
    
     DETAILED DESCRIPTION 
       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 flowpath B while the compressor section  24  drives air along a core flowpath C for compression and communication into the combustor section  26  then expansion through the turbine section  28 . Although depicted as a 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 turbofans as the teachings may be applied to other types of turbine engines including three-spool architectures. 
     The 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 . The low speed spool  30  generally includes an inner shaft  40  that interconnects a fan  42 , a low pressure (or first) compressor section  44  and a low pressure (or first) turbine section  46 . The inner shaft  40  is connected to the fan  42  through a geared architecture  48  to drive the fan  42  at a lower speed than the low speed spool  30 . A #2 bearing support  38 A located within the compressor section  24  supports a forward end of the inner shaft  40 . It should be understood that various bearing systems  38  at various locations may alternatively or additionally be provided. 
     The high speed spool  32  includes an outer shaft  50  that interconnects a high pressure (or first) compressor section  52  and high pressure (or first) turbine section  54 . A combustor  56  is arranged between the high pressure compressor  52  and the high pressure turbine  54 . As used herein, a “high pressure” compressor or turbine experiences a higher pressure than a corresponding “low pressure” compressor or turbine. 
     The core airflow C 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 turbines  46 ,  54  rotationally drive the respective low speed spool  30  and high speed spool  32  in response to the expansion. 
     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 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 5. In one example, the geared architecture  48  includes a sun gear, a ring gear, and intermediate gears arranged circumferentially about the sun gear and intermeshing with the sun gear and the ring gear. The intermediate gears are star gears grounded to a flex support  68  (shown in  FIG. 6 ) against rotation about the axis A. The sun gear is supported by the low speed spool  30 , and the ring gear is interconnected to the fan  42 . 
     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 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 2.5:1. 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. 
     A significant amount of thrust is provided by a 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. The above parameters for the engine  20  are intended to be exemplary. 
     With reference to  FIG. 2 , the engine static structure  36  proximate the compressor section  24  includes a front center body assembly  60  adjacent to the #2 bearing support  38 A. The front center body assembly  60  generally includes a front center body support  62 . The #2 bearing support  38 A generally includes a seal package  64 , a bearing package  66  and a centering spring  70 . 
     With reference to  FIGS. 2 and 3 , a flex support  68  provides a flexible attachment of the geared architecture  48  within the front center body support  62  (also illustrated in  FIG. 4 ). The flex support  68  reacts the torsional loads from the geared architecture  48  and facilitates vibration absorption as well as other support functions. The centering spring  70  is a generally cylindrical cage-like structural component with a multiple of beams that extend between flange end structures (also illustrated in  FIG. 4 ). The centering spring  70  resiliently positions the bearing package  66  with respect to the low speed spool  30 . In one embodiment, the beams are double-tapered beams arrayed circumferentially to control a radial spring rate that may be selected based on a plurality of considerations including, but not limited to, bearing loading, bearing life, rotor dynamics, and rotor deflection considerations. 
     The front center body support  62  includes a front center body section  72  and a bearing section  74  defined about axis A with a frustro-conical interface section  76  therebetween ( FIG. 5 ). The front center body section  72  at least partially defines the core flowpath into the low pressure compressor  44 . The front center body section  72  includes an annular core passage with circumferentially arranged front center body vanes  71  having leading and trailing edges  72 A,  72 B shown in section in  FIG. 3 . The bearing section  74  is defined radially inward of the front center body section  72 . The bearing section  74  locates the bearing package  66  and the seal package  64  with respect to the low speed spool  30 . The frustro-conical interface section  76  combines the front center body section  72  and the bearing section  74  to form a unified load path, substantially free of kinks typical of a conventional flange joint, from the bearing package  66  to the outer periphery of the engine static structure  36 . The frustro-conical interface section  76  may include a weld W ( FIG. 5 ) or, alternatively, be an integral section such that the front center body support  62  is a unitary component. 
     The integral, flange-less arrangement of the frustro-conical interface section  76  facilitates a light weight, reduced part count architecture with an increased ability to tune the overall stiffness and achieve rotor dynamic requirements. Such an architecture also further integrates functions such as oil and air delivery within the bearing compartment which surrounds bearing package  66 . 
     With reference to  FIG. 6 , the front center body support  62  includes mount features to receive the flex support  68 . The flex support  68  includes a conical support  158  that supports an integral flex member  160 , which provides a fold for absorbing vibrations. In one disclosed non-limiting embodiment, the mount features of the front center body support  62  includes first splines  78 , which are internal in the example, and radially inward directed fastener bosses  80  on the front center body section  72 . The flex support  68  includes corresponding second splines  82 , which are external in the example, and radially outwardly directed fastener flange  84 . The flex support  68  is received into the front center body support  62  at a splined interface  86  formed by first and second splines  78 ,  82  and retained therein such that fastener flange  84  abuts fastener bosses  80 . The splined interface  86  transfers torque between the first and second splines  78 ,  82 . A set of fasteners  88 , such as bolts, are threaded into the fastener bosses  80  and the fastener flange  84  to mount the flex support  68  within the front center body support  62 . The fasteners  88  include heads  89  facing forward for access from the front of the engine  20 . 
     Referring to  FIGS. 5-6A , the central body support  62  provides an inner annular wall  128  for the core airflow C. The vanes  71  interconnect the inner annular wall  128  to an outer annular wall  129  to provide a unitary structure. The first splines  78  include tooth groups  146  including multiple teeth. The tooth groups  146  are circumferentially spaced apart from one another with untoothed regions arranged between the tooth groups  146 . The vanes  71  are circumferentially aligned with an untoothed region to structurally reinforce the interface between the first and second splines  78 ,  82 . The second splines  82  include corresponding tooth groups that are configured to circumferentially align and mate with the tooth groups  146  of the first splines  78 . Corresponding untoothed regions are arranged between the tooth groups of the second splines  82 . 
     In the example, the fastener bosses  80  are arranged in clusters circumferentially spaced from one another, as shown in  FIG. 6A . The fastener bosses  80  are aligned with the tooth groups  146 . However, it should be understood that the fastener bosses  80  may be arranged in other configurations. The fastener flange  84  extends radially outward from an annular flange  127  that axially extends from the second splines  82 . The fastener flange  84  includes an aft surface  142  that abuts a face  144  of the fastener bosses  80  to axially locate the flex support  68  relative to the central body support  62 . The fastener flange  84  includes apertures  132  that are arranged in clusters circumferentially spaced from one another and receive the fasteners  88 , which are secured in holes  130  of the fastener bosses  80 . The fastener flange  84  may include interruptions or recesses that permit componentry to pass through the flex support  68  at the perimeter of the fasteners flange  84 . 
     The untoothed region is provided by a stiffening rail  148  protruding radially inward from the central body section  72  that provides the inner annular wall  128 . The central body support  62  includes an annular recess  150  and an annular pocket  152  that are axially spaced apart from one another to provide first and second lateral sides  154 ,  156  on the stiffening rail  148 . The teeth of the tooth groups  146  include roots provided at a first tooth radius T 1  and extend radially inward to crests provided at a second tooth radius T 2 . As shown in  FIG. 6B , the stiffening rail  148  extends radially inward to a rail radius R that is less than the first tooth radius T 1 , and in one example, equal to the second tooth radius T 2 . The stiffening rail  148  and its circumferential alignment with the vanes  71  ensures improved cylindricity of the central body section  72  during engine operation. 
     The central body support  62  includes a first inner face  134  arranged near the first spline  78  and is provided by the annular recess  150 . The flex support  68  includes a first outer face  138  arranged in an interference fit relationship at room temperature with the first inner face  134  to radially locate the flex support  68  relative to the central body support  62 . A second inner face  136  is provided on the central body support  62 , and the flex support  68  includes a second outer face  140  arranged in an interference fit relationship at room temperature with the second inner face  136 . The first inner and outer faces  134 ,  138  are arranged forward of the first spline  78 , and the second inner and outer faces  136 ,  140  are arranged aft of the first spline  78 . The second outer face  140  is smaller than the first outer face  138  to facilitate assembly and disassembly of the flex support  68  from the front of the engine  20 . 
     With reference to  FIG. 7 , the heads  89  of the fasteners  88  are directed forward to provide access from a forward section of the front center body assembly  60  opposite the bearing package  66  of the number two bearing system  38 A. The fasteners  88  are thereby readily removed to access a gearbox  90  of the geared architecture  48 . 
     A fan shaft bearing support front wall  102  aft of the fan  42  is mounted to a forward section of the front center body support  62  to provide access to the geared architecture  48  from the front of the engine  20 . The front wall  102  includes a flange  103  mountable to the front center body support  62  at the flange  61  by a multiple of fasteners  105 , which fasteners  105  may in one non-limiting embodiment be bolts. The front wall  102  and the front center body support  62  define a bearing compartment  100  (also shown in  FIG. 2 ) which mounts to the bearing package  66 . The front wall  102  is removable such that the gearbox  90  may be accessed as a module. The gearbox  90  may thereby be accessed to facilitate rapid on-wing service. 
     It should be appreciated that various bearing structures  104  (illustrated schematically and in  FIG. 2 ) and seals  106  (illustrated schematically and in  FIG. 2 ) may be supported by the front wall  102  to contain oil and support rotation of an output shaft  108 . The output shaft  108  connects with the geared architecture  48  to drive the fan  42 . Fan blades  42 B extend from a fan hub  110  which are mounted to the output shaft  108  for rotation therewith. It should be appreciated that the bearing structures  104  and seals  106  may, in the disclosed non-limiting embodiment may be disassembled with the front wall  102  as a unit after removal of the fan hub  110 . 
     The gearbox  90  is driven by the low speed spool  30  ( FIG. 1 ) through a coupling shaft  112 . The coupling shaft  112  transfers torque through the bearing package  66  to the gearbox  90  as well as facilitates the segregation of vibrations and other transients. The coupling shaft  112  generally includes a forward coupling shaft section  114  and an aft coupling shaft section  116  which extends from the bearing package  66 , however, more or fewer pieces may be used to provide the coupling shaft  112 . The forward coupling shaft section  114  includes an interface spline  118  which mates with an aft spline  120  of the aft coupling shaft section  116 . An interface spline  122  of the aft coupling shaft section  116  connects the coupling shaft  112  to the low speed spool  30  through, in this non limiting embodiment, splined engagement with a spline  124  on a low pressure compressor hub  126  of the low pressure compressor  44 . 
     As a high level summary, the front architecture of the engine  20  is disassembled by detaching the fan module from a fan shaft bearing support. The fan shaft bearing support (front wall  102 ) remains secured to the central body support  62  over the gear box  90 . The fan shaft bearing support (front wall  102 ) is detached from the central support body  62  without removing the gear box  90 . The forward-facing fasteners  88  are accessed and removed. The first and second splines  78 ,  82  are decoupled, and the gear box  90  is removed with the fan shaft bearing support (front wall  102 ) and the flex support  68 . The bearing  38 A is left undisturbed. 
     To remove and isolate the gearbox  90 , the fan hub  110  is disassembled from the output shaft  108 . The multiple of fasteners  105  are then removed such that the front wall  102  is disconnected from the front center body support  62 ; the front wall  102  is thereafter removed from the engine. The multiple of fasteners  88  are then removed from the front of the engine  20 . The geared architecture  48  is then slid forward out of the front center body support  62  such that the interface spline  118  is slid off the aft spline  120  and the outer spline  82  is slid off the internal spline  78 . The geared architecture  48  is thereby removable from the engine  20  as a module ( FIG. 8 ; illustrated schematically). It should be appreciated that other componentry may need to be disassembled to remove the geared architecture  48  from the engine  20 , however, such disassembly is relatively minor and need not be discussed in detail. It should be further appreciated that other components such as the bearing package  66  and seal  64  are also now readily accessible from the front of the engine  20 . 
     Removal of the gearbox  90  from the front of the engine  20  as disclosed saves significant time and expense. The geared architecture  48 , is removable from the engine  20  as a module and does not need to be further disassembled. Moreover, although the geared architecture  48  must be removed from the engine to gain access to the bearing package  66  and the seal  64 , the geared architecture  48  does not need to be removed from the engine  20  to gain access to the engine core itself. 
     It should be understood that like reference numerals identify corresponding or similar elements throughout the several drawings. It should also be understood that although a particular component arrangement is disclosed in the illustrated embodiment, other arrangements will benefit herefrom. 
     Although particular step sequences are shown, described, and claimed, it should be understood that steps may be performed in any order, separated or combined unless otherwise indicated and will still benefit from the present invention. 
     Although the different examples have specific components shown in the illustrations, embodiments of this invention are not limited to those particular combinations. It is possible to use some of the components or features from one of the examples in combination with features or components from another one of the examples. 
     The foregoing description is exemplary rather than defined by the limitations within. Various non-limiting embodiments are disclosed herein, however, one of ordinary skill in the art would recognize that various modifications and variations in light of the above teachings will fall within the scope of the appended claims. It is therefore to be understood that within the scope of the appended claims, the invention may be practiced other than as specifically described. For that reason the appended claims should be studied to determine true scope and content.