Patent Description:
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 they can be serviced.

<CIT> discloses a gas turbine engine according to the preamble of claim <NUM>.

According to a first aspect, there is provided a method for servicing a gas turbine engine as set forth in claim <NUM>.

There is also provided a gas turbine engine as set forth in claim <NUM>.

The fan section <NUM> drives air along a bypass flowpath while the compressor section <NUM> drives air along a core flowpath for compression and communication into the combustor section <NUM> then expansion through the turbine section <NUM>. 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.

The engine <NUM> generally includes a low spool <NUM> and a high spool <NUM> mounted for rotation about an engine central longitudinal axis A relative to an engine static structure <NUM> via several bearing supports <NUM>. The low spool <NUM> generally includes an inner shaft <NUM> that interconnects a fan <NUM>, a low pressure compressor <NUM> and a low pressure turbine <NUM>. The inner shaft <NUM> drives the fan <NUM> through a geared architecture <NUM> to drive the fan <NUM> at a lower speed than the low spool <NUM>. The high spool <NUM> includes an outer shaft <NUM> that interconnects a high pressure compressor <NUM> and high pressure turbine <NUM>. A combustor <NUM> is arranged between the high pressure compressor <NUM> and the high pressure turbine <NUM>. The inner shaft <NUM> and the outer shaft <NUM> are concentric and rotate about the engine central longitudinal axis A which is collinear with their longitudinal axes.

Core airflow is compressed by the low pressure compressor <NUM> then the high pressure compressor <NUM>, mixed with the fuel and burned in the combustor <NUM>, then expanded over the high pressure turbine <NUM> and low pressure turbine <NUM>. The turbines <NUM>, <NUM> rotationally drive the respective low spool <NUM> and high spool <NUM> in response to the expansion.

The main engine shafts <NUM>, <NUM> are supported at a plurality of points by the bearing system <NUM> within the static structure <NUM>. In one non-limiting embodiment, bearing system <NUM> includes a #<NUM> bearing support 38A located within the compressor section <NUM>.

With reference to <FIG>, the engine static structure <NUM> proximate the compressor section <NUM> includes a front center body assembly <NUM> adjacent a #<NUM> bearing support 38A. The front center body assembly <NUM> generally includes a front center body support <NUM>. The #<NUM> bearing support 38A generally includes a seal package <NUM>, a bearing package <NUM>, a flex support <NUM> and a centering spring <NUM>.

With reference to <FIG>, the flex support <NUM> provides a flexible attachment of the geared architecture <NUM> within the front center body support <NUM> (also illustrated in <FIG>). The flex support <NUM> reacts the torsional loads from the geared architecture <NUM> and facilitates vibration absorption as well as other support functions. The centering spring <NUM> is a generally cylindrical cage-like structural component with a multiple of beams which extend between flange end structures (also illustrated in <FIG>). The centering spring <NUM> resiliently positions the bearing package <NUM> with respect to the low spool <NUM>. 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 <NUM> includes a front center body section <NUM> and a bearing section <NUM> defined about axis A with a frustro-conical interface section <NUM> therebetween (<FIG>). The front center body section <NUM> at least partially defines the core flowpath into the low pressure compressor <NUM>. The front center body section <NUM> includes an annular core passage with a multiple of front center body vanes 72A, 72B. The bearing section <NUM> is defined radially inward of the front center body section <NUM>. The bearing section <NUM> locates the bearing package <NUM> and the seal package <NUM> with respect to the low spool <NUM>. The frustro-conical interface section <NUM> combines the front center body section <NUM> and the bearing section <NUM> to form a unified load path, substantially free of kinks typical of a conventional flange joint, from the bearing package <NUM> to the outer periphery of the engine static structure <NUM>. The frustro-conical interface section <NUM> may include a weld W (<FIG>) or, alternatively, be an integral section such that the front center body support <NUM> is a unitary component.

The integral, flange-less arrangement of the frustro-conical interface section <NUM> 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 <NUM>.

With reference to <FIG>, the front center body support <NUM> includes mount features to receive the flex support <NUM>. In one disclosed non-limiting embodiment, the mount features of the front center body support <NUM> includes an internal spline <NUM> and a radial inward directed fastener flange <NUM> on the front center body section <NUM>. The flex support <NUM> includes a corresponding outer spline <NUM> and radially outwardly directed fastener flange <NUM>. The flex support <NUM> is received into the front center body support <NUM> at a splined interface <NUM> formed by splines <NUM>, <NUM> and retained therein such that fastener flange <NUM> abuts fastener flange <NUM>. A set of fasteners <NUM> such as bolts are threaded into the fastener flanges <NUM>, <NUM> to mount the flex support <NUM> within the front center body support <NUM>.

With reference to <FIG>, the fasteners <NUM> are directed forward to provide access from a forward section of the front center body assembly <NUM> opposite the bearing package <NUM> of the number two bearing system 38A. The fasteners <NUM> are thereby readily removed to access a gearbox <NUM> of the geared architecture <NUM>.

A front wall <NUM> aft of the fan <NUM> is mounted to a forward section of the front center body support <NUM> to provide access to the geared architecture <NUM> from the front of the engine <NUM>. The front wall <NUM> includes a flange <NUM> mountable to the front center body support <NUM> at the flange <NUM> by a multiple of fasteners <NUM>, which fasteners <NUM> may in one non-limiting embodiment be bolts. The front wall <NUM> and the front center body support <NUM> define a bearing compartment <NUM> (also shown in <FIG>) which mounts to the bearing package <NUM>. The front wall <NUM> is removable such that the gearbox <NUM> may be accessed as a module. The gearbox <NUM> may thereby be accessed to facilitate rapid on-wing service.

It should be appreciated that various bearing structures <NUM> (illustrated schematically and in <FIG>) and seals <NUM> (illustrated schematically and in <FIG>) may be supported by the front wall <NUM> to contain oil and support rotation of an output shaft <NUM>. The output shaft <NUM> connects with the geared architecture <NUM> to drive the fan <NUM>. Fan blades 42B extend from a fan hub <NUM> which are mounted to the output shaft <NUM> for rotation therewith. It should be appreciated that the bearing structures <NUM> and seals <NUM> may, in the disclosed non-limiting embodiment may be disassembled with the front wall <NUM> as a unit after removal of the fan hub <NUM>.

The gearbox <NUM> is driven by the low spool <NUM> (<FIG>) through a coupling shaft <NUM>. The coupling shaft <NUM> transfers torque through the bearing package <NUM> to the gearbox <NUM> as well as facilitates the segregation of vibrations and other transients. The coupling shaft <NUM> generally includes a forward coupling shaft section <NUM> and an aft coupling shaft section <NUM> which extends from the bearing package <NUM>. The forward coupling shaft section <NUM> includes an interface spline <NUM> which mates with an aft spline <NUM> of the aft coupling shaft section <NUM>. An interface spline <NUM> of the aft coupling shaft section <NUM> connects the coupling shaft <NUM> to the low spool <NUM> through, in this non limiting embodiment, splined engagement with a spline <NUM> on a low pressure compressor hub <NUM> of the low pressure compressor <NUM>.

To remove the gearbox <NUM>, the fan hub <NUM> is disassembled from the output shaft <NUM>. The multiple of fasteners <NUM> are then removed such that the front wall <NUM> is disconnected from the front center body support <NUM>. The multiple of fasteners <NUM> are then removed from the front of the engine <NUM>. The geared architecture <NUM> is then slid forward out of the front center body support <NUM> such that the interface spline <NUM> is slid off the aft spline <NUM> and the outer spline <NUM> is slid off the internal spline <NUM>. The geared architecture <NUM> is thereby removable from the engine <NUM> as a module (<FIG>; illustrated schematically). It should be appreciated that other componentry may need to be disassembled to remove the geared architecture <NUM> from the engine <NUM>, 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 <NUM> and seal <NUM> are also now readily accessible from the front of the engine <NUM>.

Removal of the gearbox <NUM> from the front of the engine <NUM> as disclosed saves significant time and expense. The geared architecture <NUM>, is removable from the engine <NUM> as a module and does not need to be further disassembled. Moreover, although the geared architecture <NUM> must be removed from the engine to gain access to the bearing package <NUM> and the seal <NUM>, the geared architecture <NUM> does not need to be removed from the engine <NUM> to gain access to the engine core itself.

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.

Claim 1:
A method for servicing a gas turbine engine (<NUM>) comprising:
providing access from a forward section of a front center body assembly (<NUM>) to a gearbox (<NUM>) driven by a low spool (<NUM>);
disassembling a fan (<NUM>) mounted to the geared architecture (<NUM>);
removing a first multiple of fasteners (<NUM>) located within the forward section of a front center body assembly (<NUM>) to disassemble a front wall (<NUM>) from a front center body support (<NUM>) of the front center body assembly (<NUM>); and
removing a second multiple of fasteners (<NUM>) to disconnect a flex support (<NUM>) from the front center body support (<NUM>), the second multiple of fasteners (<NUM>) being accessed from a forward section of the front center body assembly (<NUM>).