Fan drive gear system integrated carrier and torque frame

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.

BACKGROUND

This disclosure relates to a fan drive gear system integrated carrier and torque frame.

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.

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.

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.

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

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.

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.

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.

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.

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.

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.

In a further embodiment of any of the above, the lubrication passageways include a spray bar facing the sun gear.

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.

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.

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.

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.

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.

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.

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.

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.

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.

In a further embodiment of any of the above, the lubrication passageways include a spray bar facing the sun gear.

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.

DETAILED DESCRIPTION

An example gas turbine engine10is schematically illustrated inFIG. 1. The engine10includes turbo-machinery30having a compressor section12and a turbine section14. The turbo-machinery30rotationally drives a fan32, that is arranged in a bypass flow path33, through an epicyclic gear train16. The turbo-machinery30is housed within an inner nacelle42. Flow exit guide vanes31arranged within the bypass flow path support the turbo-machinery30relative to a fan case, which is housed in a fan nacelle44.

A low pressure compressor18and a low pressure turbine20are mounted on a low pressure spool22. A high pressure compressor24and a high pressure turbine26are mounted on a high pressure spool28. A combustor section48is arranged between the high pressure compressor24and the high pressure turbine26.

The low pressure spool22rotationally drives a flex shaft46to which an input gear36(sun gear) is mounted for rotation about an axis A. Intermediate gears38(in the example, star gears) are arranged circumferentially about and intermesh with the input gear36. A ring gear40surrounds and intermeshes with the intermediate gears38. Either the intermediate gears38or the ring gear40rotationally drives the fan shaft34depending upon the type of epicyclic gear train configuration.

One example epicyclic gear train16is illustrated inFIG. 2. The epicyclic gear train16is the type in which the intermediate gears38(star gears, in the example) are rotationally fixed relative to the rotational axis of the input gear36. 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 gear36. The ring gear40is coupled to the fan shaft34and to rotationally drive the fan32. The turbo-machinery30includes fixed structure50comprising a bearing compartment case52and a support member54. A torque frame56is affixed to the support member54to prevent rotation of the torque frame56about the rotational axis A of the input gear36. However, it should be understood that in a planetary gear configuration the torque frame56would rotate about the rotational axis A and the ring gear would be coupled to fixed structure.

The torque frame56includes multiple shafts58integral with a base61that provides first and second support features62,64affixed to the support member54. In the example, the torque frame56includes five equally circumferentially spaced shafts58that correspondingly support five star gears. The base61and shafts58of the torque frame56are 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.

Each shaft58includes a bearing assembly60for rotationally supporting its respective intermediate gear38. An oil baffle66is secured to the torque frame56by fasteners74. The oil baffle66is non-structural. That is, the oil baffle does not support the loads of the intermediate gears38as would a prior art carrier. As a result, the oil baffle66may be constructed from a considerably lower strength lighter weight material, such as an aluminum alloy or composite material.

Both the torque frame56and the oil baffle66provide internal lubrication features for supplying lubricating fluid, such as oil, to the gears of the epicyclic gear train16. As an example, a feed tube68supplies oil to first and second passages70,72provided in the torque frame56. A tube76fluidly interconnects the second passage72to a spray bar78provided integrally in the oil baffle66. The spray bar78includes a first passageway80, which extends in a generally axial direction in the example shown, and one or more second passageways82transverse to the first passageway80. In the example, a pair of second passageways82are oriented to direct lubrication fluid radially inward at teeth84of the input gear36.

Referring toFIG. 3, each shaft58includes an end86that supports a bearing assembly60. The bearing assembly60includes a spherical bearing88supported in a race90on which the intermediate gear38is mounted. The ends86include a threaded portion that each receives a nut91securing the bearing assembly60to the shaft58. The shaft58, spherical bearing88and race90respectively include radially extending first, second and third passageways92,94,96that are aligned with one another to deliver lubricating fluid from the first passage70to bearing surfaces98provided between the race90and the intermediate gear38. A recess99is provided in an outer diameter of the race90to increase lubrication at the bearing surfaces98. In one example, a filter100is arranged in a hole in the shaft58that provides a portion of the first passage70.

Referring toFIGS. 3-5B, the spherical bearing88includes an inner diameter102that is supported by the end86. A convex surface104is provided on an outside of the spherical bearing88and mates with a corresponding concave surface112provided by an inner surface of the race90when fully assembled as illustrated inFIG. 5B. The spherical bearing88includes a pin106that extends through both the inner diameter102and the convex surface104in the example illustrated. The pin106is received by notches110,114respectively provided in the race90and end86to prevent rotation of the spherical bearing88about a bearing axis B (FIG. 5B). The spherical bearing88permits angular movement of the bearing axis B relative to a shaft axis T (FIG. 3) provided by the shaft58during flexing of the shafts58, which provides a near zero moment restraint.

FIGS. 5A and 5Billustrate the assembly process of the bearing assembly60. The spherical bearing88is inserted into slots108of the race90, as shown inFIG. 5A. The pin106is aligned with the notch110and the spherical bearing88is rotated to snap into engagement with the concave surface112with the pin106received in the notch110. In this position, illustrated inFIG. 5B, the second and third passageways94,96are aligned with one another.

The oil baffle66is illustrated in more detail inFIG. 6. The oil baffle66is provided by a body116having circumferentially spaced apart intermediate structures118axially extending from a wall120. The intermediate structures118define gear pockets122within which the intermediate gears38are received with the epicyclic gear train16fully assembled. The input gear36was received in a central opening124provided radially inward of the intermediate structures118. Holes126are provided in the intermediate structures118and receive the fasteners74to secure the oil baffle66to the torque frame56, as illustrated inFIG. 2.