Integral bearing support and centering spring assembly for a gas turbine engine

A bearing support assembly for supporting a bearing assembly within a bearing compartment of a gas turbine engine includes a centering spring and a bearing support member integrally joined together to form a one piece structure. The centering spring connects to the bearing assembly and has a portion that extends conically relative to a centerline axis of the gas turbine engine. The bearing support member extends from the centering spring to connect to an engine case of the gas turbine engine.

BACKGROUND

The present invention relates to gas turbine engines, and more particularly, to an integral bearing support member and centering spring assembly.

The rotating shafts and other rotating turbomachinery of gas turbine engines are supported from a non-rotating structure by arrays of anti-friction bearings. In many engines, anti-friction bearings are enclosed in bearing compartments that allow the anti-friction bearings to be more easily lubricated and cooled.

Many bearing compartments, especially those located in the forward portions of gas turbine engines, have small profiles that make their interiors small and difficult to access for component assembly, routine maintenance, and repair. To support the anti-friction bearings within the bearing compartments, an outer race of the anti-friction bearings is typically press fit into a centering spring, which in turn is fastened to a bearing support member. The bearing support member is connected to a static casing of the gas turbine engine.

The aforementioned arrangement holds the centerline of the gas turbine engine in an appropriate position and allows for load and vibration transfer from the rotating shafts and other rotating machinery to the stator case of the gas turbine engine. Unfortunately, conventional centering springs and bearing support members are costly to fabricate as multiple parts must be sized and machined. For example, with the conventional configuration, centering springs must be machined to include a flange “kink” that turns 90° relative to the remainder of the centering spring. In addition to adding machining operations to the fabrication process, the flange “kink” comprises a region of stress concentration and has been known to deflect axially relative to a centerline of the gas turbine engine, which is not optimal.

SUMMARY

A bearing support assembly for supporting a bearing assembly within a bearing compartment of a gas turbine engine includes a centering spring and a bearing support member integrally joined together to form a one piece structure. The centering spring connects to the bearing assembly and has a portion that extends conically relative to a centerline axis of the gas turbine engine. The bearing support member extends from the centering spring to connect to an engine case of the gas turbine engine.

In another aspect, a gas turbine engine includes a bearing compartment and a one-piece bearing support assembly. The bearing compartment is disposed within the gas turbine engine and houses a bearing assembly therein. The bearing support assembly is comprised of a bearing support member integrally joined with the centering spring. The centering spring has both a portion that extends conically relative to a centerline axis of the gas turbine engine and a main body that contacts and extends generally axially along the bearing assembly.

DETAILED DESCRIPTION

The present application describes an integral bearing support assembly that serves as both a bearing support member and a centering spring for a gas turbine engine. The integral assembly reduces the part count of the gas turbine engine, and thereby, can reduce the size and weight of the engine. Additionally, the integral assembly reduces costs and simplifies fabrication by reducing the number of parts and by eliminating features such as a flange of the centering spring associated with the prior art. The integral assembly has improved stiffness and tolerances. Additionally, the integral assembly provides for a smooth transition along its extent. This allows for an optimized load path that reduces radial deflection of the integral assembly. The improved load path allows the overall length of the gas turbine engine to be reduced.

FIG. 1shows a forward section of a gas turbine engine10illustrated above engine centerline CL. Gas turbine engine10includes a bearing compartment12, a bearing support assembly14, a bearing assembly16, a carbon seal assembly18, a engine shaft20, a fan drive gear system22, a fan shaft24, a forward bearing assembly26, a forward bearing compartment28, a fan hub30, a fan nose32, fan blades34, a compressor section36, and a engine case38.

Bearing compartment12is disposed adjacent engine shaft20and houses bearing assembly16therein. Bearing compartment12is bounded by engine shaft20, bearing support assembly14, and carbon seal assembly18. Engine shaft20rotates about an axis that aligns with engine centerline axis CLand is supported on bearing assembly16. Bearing assembly16is connected to and supported by bearing support assembly14which connects to stator portions of gas turbine engine10. More particularly, bearing support assembly18extends to connect to a non-rotational frame such as engine case38of gas turbine engine10.

Engine shaft20connects to fan shaft24via fan drive gear system22. Fan shaft24is supported by forward bearing assembly26which is disposed in forward bearing compartment28. Fan hub30connects to fan nose32and also connects to and turns fan blades34through fan hub30. Compressor section36is disposed radially outward of engine centerline CLand is connected to engine shaft28. Compressor section36is bounded by engine case38.

The operational principles of gas turbine engine10are well known in the art, and therefore, will not be discussed in great detail. As illustrated inFIG. 1, gas turbine engine10comprises a high bypass ratio geared turbofan engine. In other embodiments, gas turbine engine10can comprise another type of gas turbine engine used for aircraft propulsion or power generation.

Fan shaft24and compressor section36are connected to a turbine section (not shown) through engine shaft20. Inlet air A enters engine10whereby it is divided into streams of a primary air APand a secondary air ASafter passing through the fan blades34. The fan blades34are rotated by turbine section (not shown) of engine10through engine shaft20to accelerate the secondary air AS(also known as bypass air) through exit guide vanes34, thereby producing a significant portion of the thrust output of engine10. The primary air AP(also known as gas path air) is directed into compressor section36. Compressor section36works to incrementally increase the pressure and temperature of primary air AP.

FIG. 2shows a cross-sectional view of bearing compartment12, bearing support assembly14, bearing assembly16, and carbon seal assembly18. Bearing support assembly14includes fasteners40A and40B, a bearing support member42, and a centering spring44. The centering spring44includes beams46(only one of which is illustrated inFIG. 2), a main body48, and a squeeze film damper50. Bearing assembly16includes outer race52, nut54, ball56, and inner race58. Bearing compartment12includes an oil jet60with a passage62. Carbon seal assembly18includes a seal housing64, a carbon seal seat66, a carbon seal68, a bias element70, and lubricant passages72A and72B.

Fastener40A is received by holes in bearing support member42and engine case38and connects bearing support member42to engine case38. As part of bearing support assembly14, bearing support member42extends from engine case38, is generally aligned with and transitions to become centering spring44. Thus, bearing support assembly14comprises a one-piece assembly where bearing support member42is integrally joined with centering spring44(which comprises beams46and main body48) making a smooth transition therebetween. Centering spring44and bearing support member42can be integrally joined by machining a single piece stock, forging, casting, or welding, for example.

Fastener40B is received by holes in an intermediate connection section49of bearing support assembly14. Intermediate connection section49comprises the connection point between bearing support assembly14and carbon seal assembly18. Fastener40B connects bearing support assembly14to carbon seal assembly18. The portion of centering spring44adjacent fastener40B comprises a plurality of beams46(only one of which is illustrated inFIG. 2). Each beam46is disposed diagonally so as to extend conically away from intermediate connection section49relative to the centerline axis CLof the gas turbine engine10. Thus, each beam46has both radial and axial extent relative to the centerline axis CLand is generally aligned with the support member42which also extends conically relative to the centerline axis CL. Each beam46provides a transition from support member42to main body48. Although not shown inFIG. 2, beams46are circumferentially spaced apart from one another and are disposed annularly about bearing compartment12. Main body48is configured to extend generally axially with respect to engine centerline CLand contact, receive, and support outer race52of bearing assembly16.

Squeeze film damper50comprises a cavity50cthat is disposed between main body48and seal housing64. Squeeze film damper50is bordered by axially set apart seals50s. Inner diameter surface of main body48of centering spring44has threads that receive the threaded outer diameter of nut54, or similar fastening attachment therein. Nut54contacts a forward portion of outer race52and holds outer race52in a desired position relative to centering spring44and other components of gas turbine engine10. Nut54can be removed for assembly and repair of bearing assembly16and bearing support assembly14.

Outer race52has an arcuate shape and is disposed about engine centerline CL. The inner surface of outer race52is shaped to receive a plurality of balls56therein (only a single ball56is illustrated in the section shown inFIG. 2). Ball56is also received by the outer surface of inner race58. Inner race58is disposed on engine shaft20adjacent carbon seal seat66, carbon seal68, and bias element70of carbon seal assembly18.

Oil jet60extends within bearing compartment12adjacent engine shaft20. Oil jet60is a static assembly that connects with static bearing support assembly14, and in particular, centering spring44. Oil jet60contains passage62which communicates lubricant that eventually reaches squeeze film damper50. More particularly, in one embodiment oil jet60communicates with passages (not shown) in seal housing64via a jumper tube (not shown) that allow for the circulation of oil to cavity50C of squeeze film damper50between the inner radial portion64iof seal housing64and the outer radial surface of main body48of centering spring44. In other embodiments, oil jet60and/or jumper tube can extend to communicate more directly with squeeze film damper50through bearing support assembly14and seal housing64.

Static seal housing64comprises a portion of carbon seal assembly18and has an arcuate outer radial portion64othat is connected to bearing support assembly14by fastener40B. Arcuate outer portion64oof seal housing64extends around bearing assembly16and connects to the remainder of bearing assembly18. Outer portion64oforms portions of lubricant passages72A and72B. Inner radial portion64iof seal housing64is integrally connected to outer portion64oand contacts and interfaces (and forms part of cavity50cthat is part of squeeze film damper50) with main body48. Thus, inner radial portion64ihas a generally axial extent relative to the engine10centerline CL. Bias element70, in one embodiment a spring, contacts and exerts a desired axial (in other embodiments radial) force on stator carbon seal68, which interfaces with rotating carbon seal seat66. The force exerted by bias element70on carbon seal68allows a desired amount of air to flow between carbon seal68and carbon seal seat66into bearing compartment12. This arrangement keeps lubricant inside bearing compartment12. Seal housing64also has lubricant passages72A and72B that scavenge oil away from bearing compartment12by providing a drain path for lubricant to be carried away from the bearing compartment to appropriate lubricant collection and transport apparatuses (not shown).

Bearing support assembly14supports and maintains the position of the outer race52relative engine shaft20, inner race58, and balls56. Bearing support assembly14has a spring rate capable of reacting loads to engine case38from engine shaft20via bearing assembly16. The spring rate of centering spring44(and thus bearing support assembly14) can be adjusted and optimized as desired by selecting the number, size, and shape of beams46. Additionally, squeeze film damper systems such as the one disclosed herein are well known in the art and are used to shift critical speeds and/or to increase the dynamic stability of a rotor-bearing system. In particular, as shown inFIG. 2squeeze film damper50provides damping to bearing assembly16to damp vibrations in engine shaft20using a pressurized damping lubricant, in most instances oil. As previously explained, the lubricant is pressurized and transported to bearing compartment12where, as previously explained, it is communicated by oil jet60, jumper tube, and other passages in seal housing64to squeeze film damper50.

Although the invention was illustrated adjacent a forward bearing compartment of gas turbine engine10, the invention can be used to support bearing assemblies in any location within gas turbine engine10. Additionally, while the invention has been described with reference to an exemplary embodiment(s), it will be understood by those skilled in the art that various changes may be made and equivalents may be substituted for elements thereof without departing from the scope of the invention. In addition, many modifications may be made to adapt a particular situation or material to the teachings of the invention without departing from the essential scope thereof. Therefore, it is intended that the invention not be limited to the particular embodiment(s) disclosed, but that the invention will include all embodiments falling within the scope of the appended claims.