Patent Description:
Typical aircraft propulsion systems include one or more gas turbine engines. For certain propulsion systems, the gas turbine engines generally include a fan and a core arranged in flow communication with one another. Additionally, the core of the gas turbine engine generally includes, in serial flow order, a compressor section, a combustion section, a turbine section, and an exhaust section. In operation, air is provided from the fan to an inlet of the compressor section where one or more axial compressors progressively compress the air until it reaches the combustion section. Fuel is mixed with the compressed air and burned within the combustion section to provide combustion gases. The combustion gases are routed from the combustion section to the turbine section. The flow of combustion gases through the turbine section drives the turbine section and is then routed through the exhaust section, e.g., to atmosphere.

Gas turbine engines conventionally include an accessory gearbox to run various accessory systems of the gas turbine engine. For example, the accessory gearbox may provide power to, or receive power from, a lubrication oil system, an electric starter/generator, etc. Typically, these accessory systems are rigidly coupled to an accessory gear of the accessory gearbox, such that rotation of the accessory gear necessarily rotates the accessory system. However, for accessory systems configured to transfer power into the accessory gearbox, e.g., at lower power levels, such may lead to inefficiencies with the accessory system and/or a reduction in a lifespan of the accessory system. Accordingly, a means for attaching an accessory system to an accessory gearbox to ensure power and/or torque over a desired threshold is not transferred back to the accessory system would be useful. <CIT> describes a gas turbine starter comprising a wear-resistant slip clutch. Documents <CIT>, and <CIT> describe further output assemblies for an accessory gearbox of a gas turbine engine.

Claim <NUM> defines an assembly, claim <NUM> defines a gas turbine engine, and claim <NUM> defines a method. In the following, apparatus and/or methods referred to as embodiments that nevertheless do not fall within the scope of the claims should be understood as examples useful for understanding the invention.

For example, the approximating language may refer to being within a <NUM>% margin.

As used herein, the terms "processor" and "computer," and related terms, e.g., "processing device," "computing device," and "controller", are not limited to just those integrated circuits referred to in the art as a computer, but further broadly refers to one or more processing devices including one or more of a microcontroller, a microcomputer, a programmable logic controller (PLC), an application specific integrated circuit, and other programmable circuits, and these terms are used interchangeably herein. In the embodiments described herein, the computer or controller may additionally include memory. The memory may include, but is not limited to, a computer-readable medium, such as a random access memory (RAM), a computer-readable non-volatile medium, such as a flash memory. Alternatively, a floppy disk, a compact disc - read only memory (CD-ROM), a magneto-optical disk (MOD), and/or a digital versatile disc (DVD) may also be used. Also, in the embodiments described herein, the computer or controller may include one or more input channels and/or one or more output channels. The input channels may be, but are not limited to, computer peripherals associated with an operator interface such as a mouse and a keyboard, or sensors, such as engine sensors associated with an engine, such as a gas turbine engine, for determining operating parameters of the engine. Furthermore, in the exemplary embodiment, the output channels may include, but are not limited to, an operator interface monitor. Further, the memory may store software or other instructions, which when executed by the controller or processor allow the controller to perform certain operations or functions, such as one or more of the functions described in the method <NUM>, below. The term "software" may include any computer program stored in memory, or accessible by the memory, for execution by, e.g., the controller, processor, clients, and servers.

Referring now to the drawings, wherein identical numerals indicate the same elements throughout the figures, <FIG> is a schematic cross-sectional view of a gas turbine engine in accordance with an exemplary embodiment of the present disclosure. More particularly, for the embodiment of <FIG>, the gas turbine engine is a high-bypass turbofan jet engine <NUM>, referred to herein as "turbofan engine <NUM>. " As shown in <FIG>, the turbofan engine <NUM> defines an axial direction A1 (extending parallel to a longitudinal centerline <NUM> provided for reference), a radial direction R1, and a circumferential direction C1 (i.e., a direction extending about the axial direction A1). In general, the turbofan <NUM> includes a fan section <NUM> and a core turbine engine <NUM> disposed downstream from the fan section <NUM>.

The exemplary core turbine engine <NUM> depicted generally includes a substantially tubular outer casing <NUM> that defines an annular inlet <NUM>. The outer casing <NUM> encases, in serial flow relationship, a compressor section including a booster or low pressure (LP) compressor <NUM> and a high pressure (HP) compressor <NUM>; a combustion section <NUM>; a turbine section including a high pressure (HP) turbine <NUM> and a low pressure (LP) turbine <NUM>; and a jet exhaust nozzle section <NUM>. The compressor section, combustion section <NUM>, and turbine section together define at least in part a core air flowpath <NUM> of the turbofan engine <NUM>. A high pressure (HP) shaft or spool <NUM> drivingly connects the HP turbine <NUM> to the HP compressor <NUM>. A low pressure (LP) shaft or spool <NUM> drivingly connects the LP turbine <NUM> to the LP compressor <NUM>.

For the embodiment depicted, the fan section <NUM> includes a fan <NUM> having a plurality of fan blades <NUM> coupled to a disk <NUM> in a spaced apart manner. As is depicted, the fan blades <NUM> extend outwardly from disk <NUM> generally along the radial direction R1. The disk <NUM> is covered by rotatable front nacelle <NUM> aerodynamically contoured to promote an airflow through the plurality of fan blades <NUM>. The fan blades <NUM> and disk <NUM> are together rotatable about the longitudinal axis <NUM> by LP shaft <NUM>.

As is depicted, the exemplary turbofan engine <NUM> further includes an accessory gearbox <NUM> attached to the gas turbine engine and mechanically coupled to a spool of the gas turbine engine. More specifically, the accessory gearbox <NUM> is attached to the core turbine engine <NUM> of the turbofan engine <NUM>, and is mechanically coupled to the LP spool <NUM> of the turbofan engine <NUM> through a transfer gearbox <NUM> and transfer shaft <NUM>. Although not depicted, an electric machine (i.e., a starter motor/generator) may be coupled to the accessory gearbox <NUM> for, e.g., starting the turbofan engine <NUM> and/or generating electrical power once the turbofan engine <NUM> is running. It should be appreciated, however, that in other exemplary embodiments, the accessory gearbox <NUM> may instead be coupled to any other suitable section of the gas turbine engine, such as to the HP spool <NUM> of the turbine turbofan engine <NUM> depicted.

Referring still to the exemplary embodiment of <FIG>, the exemplary fan section <NUM> includes an annular fan casing or outer nacelle <NUM> that circumferentially surrounds the fan <NUM> and/or at least a portion of the core turbine engine <NUM>. The nacelle <NUM> is supported relative to the core turbine engine <NUM> by a plurality of circumferentially-spaced outlet guide vanes <NUM>. Additionally, a downstream section <NUM> of the nacelle <NUM> extends over an outer portion of the core turbine engine <NUM> so as to define a bypass airflow passage <NUM> therebetween.

During operation of the turbofan engine <NUM>, such as during flight operations of the turbofan engine <NUM>, a volume of air <NUM> enters the turbofan <NUM> through an associated inlet <NUM> of the nacelle <NUM> and/or fan section <NUM>. As the volume of air <NUM> passes across the fan blades <NUM>, a first portion of the air <NUM> as indicated by arrows <NUM> is directed or routed into the bypass airflow passage <NUM> and a second portion of the air <NUM> as indicated by arrow <NUM> is directed or routed into the LP compressor <NUM>. The ratio between the first portion of air <NUM> and the second portion of air <NUM> is commonly known as a bypass ratio. The pressure of the second portion of air <NUM> is then increased as it is routed through the high pressure (HP) compressor <NUM> and into the combustion section <NUM>, where it is mixed with fuel and burned to provide combustion gases <NUM>.

The combustion gases <NUM> are routed through the HP turbine <NUM> where a portion of thermal and/or kinetic energy from the combustion gases <NUM> is extracted via sequential stages of HP turbine stator vanes <NUM> that are coupled to the outer casing <NUM> and HP turbine rotor blades <NUM> that are coupled to the HP shaft or spool <NUM>, thus causing the HP shaft or spool <NUM> to rotate, thereby supporting operation of the HP compressor <NUM>. The combustion gases <NUM> are then routed through the LP turbine <NUM> where a second portion of thermal and kinetic energy is extracted from the combustion gases <NUM> via sequential stages of LP turbine stator vanes <NUM> that are coupled to the outer casing <NUM> and LP turbine rotor blades <NUM> that are coupled to the LP shaft or spool <NUM>, thus causing the LP shaft or spool <NUM> to rotate, thereby supporting operation of the LP compressor <NUM> and/or rotation of the fan <NUM>.

The combustion gases <NUM> are subsequently routed through the jet exhaust nozzle section <NUM> of the core turbine engine <NUM> to provide propulsive thrust. Simultaneously, the pressure of the first portion of air <NUM> is substantially increased as the first portion of air <NUM> is routed through the bypass airflow passage <NUM> before it is exhausted from a fan nozzle exhaust section <NUM> of the turbofan <NUM>, also providing propulsive thrust. The HP turbine <NUM>, the LP turbine <NUM>, and the jet exhaust nozzle section <NUM> at least partially define a hot gas path <NUM> for routing the combustion gases <NUM> through the core turbine engine <NUM>.

It should be appreciated, however, that the exemplary turbofan engine <NUM> depicted in <FIG> is by way of example only, and that in other exemplary embodiments, the turbofan engine <NUM> may have any other suitable configuration. For example, in other exemplary embodiments, the turbofan engine <NUM> may be configured as a geared turbofan engine (i.e., including a reduction gearbox); may not include variable-pitch fan blades; may include any other suitable number of spools, compressors, or turbines; etc. Additionally, the turbofan engine <NUM> may instead be configured as any other suitable aeronautical gas turbine engine, such as a turboshaft engine, turboprop engine, turbojet engine, etc. Additionally, still, the turbofan engine <NUM> may instead be configured as an aeroderivative gas turbine engine (e.g., for nautical applications), an industrial gas turbine engine, or as any other suitable gas turbine engine.

Referring now to <FIG>, a schematic view is provided of an exemplary accessory gearbox <NUM> for a gas turbine engine in accordance with an exemplary embodiment of the present disclosure. The accessory gearbox <NUM> of <FIG> may be configured to be attached to the exemplary turbofan engine <NUM> of <FIG>, similar to the exemplary accessory gearbox <NUM> depicted in <FIG>, or alternatively may be configured to be attached to any other suitable gas turbine engine.

As is depicted, the exemplary accessory gearbox <NUM> generally includes an outer casing <NUM> surrounding various internal components of the accessory gearbox <NUM>. The accessory gearbox <NUM> may be attached to a gas turbine engine at an outer casing of the gas turbine engine, such as at or within the casing <NUM> of the turbine engine <NUM> (see <FIG>). The accessory gearbox <NUM> additionally includes a plurality of accessory pads <NUM> positioned adjacent to a respective plurality of accessory gears <NUM>. Each of the accessory gears <NUM> is mechanically coupled to one another through, e.g., meshing teeth <NUM> to transmit torque between the plurality of accessory gears <NUM>. Additionally, each of the plurality of accessory gears <NUM> is supported within the outer casing <NUM> of the accessory gearbox <NUM> by one or more bearings <NUM>. Moreover, for the exemplary embodiment depicted, each accessory gear <NUM> defines a cylindrical opening <NUM> with a splined portion <NUM> for coupling to the respective accessory systems (not all shown). For example, during operation of the gas turbine engine, accessory systems may be attached to the respective accessory pads <NUM> and may include a shaft extending into the accessory gearbox <NUM>. The shafts of the accessory systems may extend through the respective cylindrical opening <NUM> and couple to the respective splined portion <NUM> in order to mechanically couple the accessory system to the respective accessory gear <NUM>. Rotation of an accessory gear <NUM> may therefore correspondingly drive a respective accessory system. The accessory systems may include, for example, a lubrication oil system of the gas turbine engine, etc..

It should be appreciated, however, that in other exemplary embodiments the accessory gearbox <NUM> may include any other suitable configuration of accessory pads <NUM> and accessory gears <NUM>. Additionally, in other exemplary embodiments, one or more of the plurality of accessory gears <NUM> may be coupled to a respective accessory system in any other suitable manner.

Referring particularly to the embodiment of <FIG>, the accessory gearbox <NUM> may additionally be used to startup the gas turbine engine. For example, at least one of the accessory pads <NUM> and accessory gears <NUM> is a starter gear 106A and starter pad 104A. A starter motor/generator <NUM> is attached to the starter pad 104A and generally includes a driveshaft <NUM> that extends through the accessory gearbox <NUM> and mechanically couples to the starter gear 106A through a splined connection <NUM>. Additionally, the driveshaft <NUM> of the starter motor/generator <NUM> includes a splined end <NUM> that couples to a transfer gearbox <NUM> (depicted in phantom). The transfer gearbox <NUM> is, in turn, mechanically coupled to the core turbine engine <NUM> (see, e.g., <FIG>).

As will be appreciated, in at least certain exemplary embodiments, the one or more components of the compressor section or the turbine section of the gas turbine engine rotated by the starter motor/generator <NUM> during such startup operations may include a compressor of the compressor section and a turbine of the turbine section, such as the LP compressor <NUM> of the compressor section and the LP turbine <NUM> of the turbine section. By contrast, once the gas turbine engine is operating under its own power, rotational power may be transferred from the core turbine engine <NUM>, through the transfer gearbox <NUM>, through the driveshaft <NUM>, to the starter gear 106A, and accordingly, to the starter motor/generator <NUM> and each of the additional accessory gears <NUM> and accessory systems. Such a configuration allows for the core turbine engine <NUM> to power the various accessory systems during operation of the gas turbine engine.

During flight operations of the gas turbine engine, a temperature of one or more components within the core turbine engine may be relatively elevated. For example, the LP shaft <NUM> may be at a relatively elevated temperature as a result of the combustion gases and high amount of air compression. Accordingly, subsequent to flight operations, under certain conditions, one or more of these components may be susceptible to "bowing" or other plastic deformation. More specifically, a weight of one or more of these components, in combination with the relatively elevated temperatures, may cause the component to deform.

In order to prevent or minimize a risk of the one or more components within the gas turbine engine deforming, the present disclosure includes a turning unit <NUM>. As will be discussed in greater detail below, the turning unit <NUM> generally includes an electric motor <NUM> and an output assembly <NUM>. In certain exemplary embodiments, the electric motor <NUM> may be, e.g., a three-phase electric motor. Additionally, the electric motor <NUM> may be a relatively small electric motor <NUM> configured to generate a maximum power of less than about fifty watts. For example, in certain exemplary embodiments, the electric motor <NUM> may be configured to generate a maximum power less than about forty watts, such as less than about thirty watts, such as less than about twenty watts. It should be appreciated, however, that in other exemplary embodiments, the electric motor <NUM> may instead be configured as a pneumatic or hydraulic motor.

Further, the output assembly <NUM> is mechanically coupled to the accessory gearbox <NUM> and the electric motor <NUM> is operable to rotate, through the output assembly <NUM> and accessory gearbox <NUM>, one or more components of the compressor section or the turbine section of the gas turbine engine at a relatively low rotational speed during a shutdown condition of the gas turbine engine. For example, in certain exemplary aspects, the electric motor <NUM> may be configured to rotate one or more components of the compressor section or the turbine section at a rotational speed less than about fifty revolutions per minute, less than about twenty-five revolutions per minute, less than about ten revolutions per minute, less than about five revolutions per minute, or less than about two revolutions per minute during the shutdown condition of the gas turbine engine. It should be appreciated, that as used herein, a "shut down condition" of the gas turbine engine refers to any operating condition of the gas turbine engine in which the components, such as one or more of the compressors or turbines, are not being rotated by virtue of combustion gases flowing through the turbine section.

Moreover, as is also depicted in <FIG>, it should be appreciated that for the embodiment depicted the electric motor <NUM> of the turning unit <NUM> is configured to be electrically connected to a ground power source <NUM>. As used herein, "ground power source" refers to any source of power external to the gas turbine engine and an aircraft to which the gas turbine engine is attached or installed. Accordingly, the ground power source <NUM> may refer to a power source connected to an electrical grid, an external generator, or other external power source. Such a configuration may allow for the turning unit <NUM> to operate during the shutdown condition of the gas turbine engine where power is not being generated by the gas turbine engine. Notably, the electric motor <NUM> of the turning unit <NUM> may not be connected directly to the ground power source <NUM>, and instead be connected to the ground power source <NUM> through an electrical system of the aircraft with which the gas turbine engine is installed (the electrical system of the aircraft being connected to the ground power source <NUM>). Regardless of the configuration, however, the electric motor <NUM> of the turning unit <NUM> may be considered to be connected to the ground power source <NUM>.

It should be appreciated, however, that in other exemplary embodiments, the electric motor <NUM> may instead be configured to be electrically connected to any other power source, such as a power source internal to the aircraft or gas turbine engine (e.g., an electrical power storage device, such as a battery).

Referring now to <FIG>, a cross-sectional view of a turning unit <NUM> for a gas turbine engine in accordance with an exemplary embodiment of the present disclosure is provided. In certain exemplary embodiments, the turning unit <NUM> of <FIG> may be configured as the turning unit <NUM> described above with reference to <FIG>. Accordingly, and as is depicted, the exemplary turning unit <NUM> of <FIG> generally includes an output assembly <NUM> configured to be mechanically coupled to the gas turbine engine and an electric motor <NUM> operable to rotate, through the output assembly <NUM>, one or more components of the compressor section or the turbine section of the gas turbine engine at a relatively low rotational speed (described more fully above) during a shutdown condition of the gas turbine engine.

As is depicted, the turning unit <NUM> includes an outer casing <NUM> surrounding at least certain of the various components of the turning unit <NUM> and coupling the turning unit <NUM> to the accessory gearbox <NUM>. More specifically, the outer casing <NUM> of the turning unit <NUM> is coupled to an accessory pad <NUM> of the accessory gearbox <NUM>, such as one or more of the accessory pads <NUM> of the accessory gearbox <NUM> depicted in <FIG>.

Additionally, the outer casing <NUM> surrounds and encloses the electric motor <NUM>. The electric motor <NUM> is configured as an in-runner electric motor including a stator <NUM> and a rotor <NUM>, the rotor <NUM> rotatable relative to the stator <NUM> and positioned at a location radially inward of the stator <NUM>. However, in other exemplary embodiments, the electric motor <NUM> may instead be configured as an out-runner electric motor with the stator <NUM> instead positioned radially inward of the rotor <NUM>. As will be discussed in greater detail below, the electric motor <NUM> is operably connected to a controller <NUM> of the turning unit <NUM> via, for the embodiment depicted, a wired connection <NUM>, and is further operably connected to a power source, such as a ground power source <NUM>, also via a wired connection <NUM>.

Referring still to <FIG>, the rotor <NUM> is attached to and rotatable with a first drive shaft, which for the embodiment depicted is an electric motor drive shaft <NUM>. The electric motor drive shaft <NUM> is supported within the outer casing <NUM> of the turning unit <NUM> through the plurality of bearings <NUM>. The bearings <NUM> may be one or more of ball bearings, roller bearings, tapered roller bearings, or any other suitable type of bearing.

As is also depicted in the exemplary embodiment of <FIG>, the turning unit <NUM> additionally includes a reduction gearbox <NUM> and a primary one-way clutch <NUM>. A second shaft <NUM> is provided within the outer casing <NUM>, extending from the reduction gearbox <NUM> to the primary one-way clutch <NUM>. The primary one-way clutch <NUM> is, in turn, connected to the output assembly <NUM>. Accordingly, as will be appreciated, the output assembly <NUM> is rotatable by the electric motor <NUM> across the reduction gearbox <NUM>, and further the electric motor <NUM> is mechanically connected to the output assembly <NUM> through the primary one-way clutch <NUM>.

Referring particularly to the reduction gearbox <NUM>, the reduction gearbox <NUM> may have any suitable configuration for reducing a rotational speed of the second shaft <NUM> relative to the electric motor drive shaft <NUM>. For example, in certain exemplary embodiments, the reduction gearbox <NUM> may include an epicyclic gear set, such as a planetary gear set. As will be appreciated, the reduction gearbox <NUM> therefore allows for the electric motor <NUM> to rotate at a relatively high rotational speed, while turning the second shaft <NUM> and the various components of the gas turbine engine at a relatively low rotational speed. For example, in certain exemplary embodiments, the reduction gearbox <NUM> has a gear ratio at least about <NUM>:<NUM> (i.e., for every <NUM> rotations of the electric motor drive shaft <NUM>, the second shaft <NUM> rotates once). However, in other exemplary embodiments, the reduction gearbox <NUM> may have an even higher gear ratio. For example, in other exemplary embodiments, the reduction gearbox <NUM> may have a gear ratio of at least about <NUM>:<NUM>, of at least about <NUM>:<NUM>, of at least about <NUM>:<NUM>, of at least about <NUM>:<NUM>, or of at least about <NUM>:<NUM>.

Additionally, referring now specifically to the primary one-way clutch <NUM>, as stated, the second shaft <NUM> and the electric motor <NUM> are mechanically connected to the output assembly <NUM> through the primary one-way clutch <NUM>. The primary one-way clutch <NUM> is configured as a passive one-way clutch, as it automatically transfers rotational torque and power when the second shaft <NUM> is rotated in a first circumferential direction relative to the output assembly <NUM> and automatically prevents transfer of rotational torque and power when the second shaft <NUM> is rotated in a second circumferential direction (i.e., a circumferential direction opposite the first circumferential direction) relative to the output assembly <NUM>, such as when the output assembly <NUM> is rotated more quickly than the second shaft <NUM>.

More specifically, for the embodiment depicted, the primary one-way clutch <NUM> is configured as a sprag clutch. Referring briefly to <FIG>, a schematic, axial view of the exemplary primary one-way clutch <NUM> is provided. The exemplary sprag clutch depicted includes a plurality of sprags <NUM> positioned between an inner race <NUM> and an outer race <NUM>. The inner race <NUM> is fixed to, or formed integrally with, the second shaft <NUM> and the outer race <NUM> is coupled to the output assembly <NUM>. When the inner race <NUM> rotates counterclockwise relative to the outer race <NUM> (at least for view of the embodiment depicted), the plurality of sprags <NUM> provide substantially no resistance to such movement. By contrast, when the inner race <NUM> attempts to rotate clockwise relative to the outer race <NUM>, the plurality of sprags <NUM> rotate about each of their respective axes of rotation <NUM> and lock the inner race <NUM> to the outer race <NUM>, such that no relative rotation of the inner race <NUM> to the outer race <NUM> in the clockwise direction is allowed. It should be appreciated, however, that in other embodiments, any other suitable primary one-way clutch <NUM> may be utilized.

As will be appreciated, inclusion of the primary one-way clutch <NUM> within the turning unit <NUM> may allow for the electric motor <NUM> to rotate one or more accessory gears <NUM> of the accessory gearbox <NUM> (and, in turn, rotate one or more components of a compressor section or a turbine section of a gas turbine engine) when the gas turbine engine is in a shutdown operating condition. Additionally, inclusion of the primary one-way clutch <NUM> within the turning unit <NUM> prevents a rotation of the accessory gears <NUM> of the accessory gearbox <NUM> from being transferred back through the turning unit <NUM> to the electric machine <NUM>, e.g., during flight operations of the gas turbine engine wherein such components of the accessory gearbox <NUM> are rotating much more quickly than is desirable for the electric motor <NUM>. Such a configuration may therefore increase a useful life of the turning unit <NUM>.

Referring still to <FIG>, and now also briefly to <FIG>, it will be appreciated that the turning unit <NUM> further includes a lubrication oil system for lubricating the primary one-way clutch <NUM>. <FIG> provides a close-up, cross-sectional view of the primary one-way clutch <NUM> of the turning unit <NUM> of <FIG>. As is depicted, the primary one-way clutch <NUM> generally includes a forward bearing <NUM> and an aft bearing <NUM> located forward and aft, respectively, of the plurality of sprags <NUM> of the primary one-way clutch <NUM>. For the embodiment depicted, each of the forward and aft bearings <NUM>, <NUM> are configured as ball bearings. However, in other embodiments, any other suitable bearing configuration may be provided.

Additionally, for the embodiment depicted, the lubrication oil system includes a lubrication oil delivery cavity <NUM> defined within the outer race <NUM> of the primary one-way clutch <NUM>. A supply line <NUM> is also included providing lubrication oil to the lubrication oil delivery cavity <NUM> through a stationary to rotating connection member <NUM>. The connection member <NUM> is a stationery member (i.e., stationary relative to the outer race <NUM>) defining an opening <NUM> configured to align with the lubrication oil delivery cavity <NUM> defined within the outer race <NUM> and provide the lubrication oil thereto during operation. The supply line <NUM> may receive lubrication oil from a lubrication oil jet (not shown) within the accessory gearbox <NUM> of the gas turbine engine. Additionally, the lubrication oil delivery cavity <NUM> defines an outlet <NUM> immediately radially outward of the plurality of sprags <NUM>, and between the forward and aft bearings <NUM>, <NUM>, such that the lubrication oil delivery cavity <NUM> may provide a flow <NUM> of lubrication oil to both the forward and aft bearings <NUM>, <NUM> and sprags <NUM> during operation.

As is also depicted, the outer race <NUM> of the primary one-way clutch <NUM> further defines an outlet channel <NUM> configured to receive at least a portion of the flow <NUM> of lubrication oil and expel it to an outer cavity <NUM> within the turning assembly. The outer cavity <NUM> may in turn, provide such flow <NUM> of lubrication oil to an outlet line <NUM>, which may return the lubrication oil to the accessory gearbox <NUM>. Inclusion of a lubrication oil system in accordance with the present disclosure may ensure the plurality of bearings, including the forward and aft bearings <NUM>, <NUM>, of the primary one-way clutch <NUM> are provided with a desired amount of lubrication oil during operation. It should be appreciated, however, that in other exemplary embodiments, any other suitable lubrication oil system may be provided.

Referring back generally to <FIG> and <FIG>, it will be appreciated that the exemplary turning unit <NUM> depicted further includes a controller <NUM>. The controller <NUM> is operably connected to the motor <NUM> of the turning unit <NUM>, and is further operably connected to the power source for the motor <NUM>, such as the ground power source <NUM>. For the embodiment depicted, the controller <NUM> is operably connected to the motor <NUM> via a wired connection <NUM>, and similarly, the ground power source <NUM> is electrically connected to the motor <NUM> via a wired connection <NUM>. Moreover, for the embodiment depicted, the turning unit <NUM> includes a temperature sensor <NUM> positioned in or around the electric motor <NUM> for determining a temperature in or around the electric motor <NUM> (<FIG>). The temperature sensor <NUM> is similarly operably connected to the controller <NUM> via, for the embodiment depicted, a wired connection <NUM>.

As stated, the electric motor <NUM> is operable to rotate, through the output assembly <NUM>, one or more components of the compressor section or the turbine section of the gas turbine engine at a relatively low rotational speed during a shutdown condition of the gas turbine engine. More specifically, for the embodiment depicted, the controller <NUM> is configured to operate the electric motor <NUM>, such that the electric motor <NUM> is operable in such a manner. In at least certain exemplary aspects, rotating the gas turbine engine at the relatively low rotational speed during the shutdown condition of the gas turbine engine may include rotating the gas turbine engine substantially continuously for at least a predetermined amount of time (e.g., at least about one hour, such as at least about two hours, such as at least about five hours). The predetermined amount of time correlates to an expected amount of time for certain components of the gas turbine engine to cool sufficiently to reduce the likelihood of deformation. Additionally, or alternatively, rotating the gas turbine engine at the relatively low rotational speed during the shutdown condition of the gas turbine engine may include rotating the gas turbine engine in a pulsed or patterned manner for least the predetermined amount of time. For example, the controller <NUM> may be configured to operate the turning unit <NUM> to rotate the gas turbine engine for certain time intervals or patterns, including, for example: (a) thirty seconds on, thirty seconds off; (b) two minutes on, two minutes off; (c) ten seconds on, fifty seconds off; etc..

Moreover, for the embodiment depicted, the controller <NUM> may determine the gas turbine engine is in a shutdown condition based on a torque applied by the electric motor <NUM> through the turning unit <NUM> to the accessory gearbox <NUM>. For example, if an amount of torque applied by the electric motor <NUM> is below a predetermined minimum threshold, the controller <NUM> may also determine that either the gas turbine engine is operating and rotating more quickly than would otherwise be rotated by the electric motor <NUM>, or alternatively that there has been a failure. Similarly, if an amount of torque applied by the electric motor <NUM> is above a predetermined maximum threshold, the controller <NUM> may also determine that there has been a failure. However, if the amount of torque applied by the electric motor <NUM> is above the predetermined minimum threshold and below the predetermined maximum threshold, the controller <NUM> may determine the turning unit <NUM> is operating as desired to rotate the gas turbine engine at a relatively low rotational speed during a shutdown condition of the gas turbine engine.

Inclusion of a turning unit in accordance with one or more exemplary embodiments of the present disclosure may therefore increase a useful life of a gas turbine engine with which it is installed, by reducing a likelihood of certain components deforming subsequent to flight operations due to the relatively high temperatures to which the components are exposed and the weight of the components being supported. Notably, although the turning unit <NUM> is described herein as a device to prevent or minimize a likelihood of certain components deforming subsequent to flight operations, in certain exemplary embodiments, the turning unit may additionally, or alternatively, be used during inspection of the gas turbine engine through its borescope holes. With such a configuration, the turning unit may instead be permanently installed on the accessory gearbox at any suitably location on the accessory gearbox (such as a dedicated crank point).

Referring now to <FIG>, an output assembly <NUM> is provided in accordance with an exemplary embodiment of the present disclosure. <FIG> provides a perspective view of the exemplary output assembly <NUM>, and <FIG> provides a side, cross-sectional view of the output assembly <NUM>.

For example, the exemplary output assembly <NUM> may be configured in substantially the same manner as the exemplary output assembly <NUM> described above with reference to, e.g., <FIG>, <FIG>, and <FIG>. Accordingly, the exemplary output assembly <NUM> may be configured to transfer a rotational torque and power provided by an accessory system of the gas turbine engine to an accessory gearbox <NUM> of the gas turbine engine, or more particularly, to an accessory gear <NUM> of the accessory gearbox <NUM> of the gas turbine engine. In certain embodiments, the accessory system may be the exemplary turning unit <NUM> described above, in which case, the output assembly <NUM> may be configured to transfer rotational torque and power provided by the electric motor <NUM> (across the reduction gearbox <NUM> and the primary one-way clutch <NUM>) to the gas turbine engine via the accessory gearbox <NUM>. However, in other embodiments, the exemplary output assembly <NUM> of <FIG> may be utilized with any other suitable accessory system (such as a starter motor, etc.).

The exemplary output assembly <NUM> depicted generally defines an axial direction A2 extending along an axis <NUM> of the output assembly <NUM>, a radial direction R2, and a circumferential direction C2. As is depicted, the output assembly <NUM> generally includes a first rotating member <NUM> extending along the axis <NUM> and a second rotating member <NUM> also extending along the axis <NUM>. The first rotating member <NUM> includes a mechanical connector for coupling the output assembly <NUM> to the accessory system. For the embodiment depicted, the mechanical connector is configured as a spline <NUM> configured to mesh with a spline, or splined coupling, of the accessory system. For example, when utilized with the exemplary turning unit <NUM> described above, the spline <NUM> of the first rotating member <NUM> is configured to mesh with a splined coupling <NUM> rigidly connected to the outer race <NUM> of the primary one-way clutch <NUM> (see <FIG>). Similarly, the second rotating member <NUM> includes a mechanical connector for coupling the output assembly <NUM> to the accessory gearbox, or more specifically, to an accessory gear <NUM> of the accessory gearbox <NUM>. Also for the embodiment depicted, the mechanical connector of the second rotating member <NUM> is configured as a spline <NUM> configured to mesh with a spline, or splined coupling <NUM>, of the accessory gear <NUM> of the accessory gearbox <NUM> (see, e.g., <FIG>). Accordingly, the first rotating member <NUM> is configured to mechanically couple the output assembly <NUM> to the accessory system, while the second rotating member <NUM> is configured to mechanically couple the output assembly <NUM> to the accessory gearbox.

As may be seen most clearly in <FIG>, the second rotating member <NUM> is coupled to the first rotating member <NUM> at a first axial position <NUM> and at a second axial position <NUM>. The first and second axial positions <NUM>, <NUM> are spaced from one another along the axial direction A2 of the output assembly <NUM>. For the embodiment depicted, the second rotating member <NUM> is slidably coupled to the first rotating member <NUM> at the first axial position <NUM>, such that the connection permits movement of the second rotating member <NUM> relative to the first rotating member <NUM> along the axial direction A2 of the output assembly <NUM>. For example, the connection may be a splined connection, or any other suitable connection allowing for relative movement along the axial direction A2. Accordingly, it will be appreciated that although the connection allows for movement along the axial direction, A2, the connection restricts any movement of the first rotating member <NUM> relative to the second rotating member <NUM> along the circumferential direction C2. Therefore, a rotational torque and power may be transferred from the second rotating member <NUM> to the first rotating member <NUM> (and vice versa) through the connection at the first axial position <NUM>.

By contrast, the second rotating member <NUM> is coupled to the first rotating member <NUM> at the second axial position <NUM> through a one-way clutch <NUM>. As is depicted, the one-way clutch <NUM> is formed at least in part by the first rotating member <NUM> and at least in part by the second rotating member <NUM>. More specifically, for the embodiment depicted, the one-way clutch <NUM> is configured as a one-way dog clutch, also referred to simply as a "dog clutch". More specifically, for the embodiment depicted the auxiliary one-way clutch <NUM> is formed of a plurality of teeth <NUM> of the first rotating member <NUM> and a plurality of teeth <NUM> of the second rotating member <NUM>. Each of these plurality of teeth <NUM>, <NUM> include a first, active engagement end <NUM> and a second, passive end <NUM>. The first and second ends <NUM>, <NUM> are positioned at opposite sides of the respective teeth <NUM>, <NUM> along the circumferential direction C2 of the output assembly <NUM>. The first, active engagement ends <NUM> are each substantially aligned with the axial direction A2 of the output assembly <NUM> (i.e., with a plane defined by the axial direction A2 and the radial direction R2), such that the first end <NUM> of a tooth <NUM> on the first rotating member <NUM> may transfer power and torque to the first end <NUM> of a tooth <NUM> on the second rotating member <NUM>. By contrast, the second, passive ends <NUM> are slanted with respect to the axial direction A2 of the output assembly <NUM> (i.e., define an angle with a plane defined by the axial direction A2 and the radial direction R2, such as an angle greater than about twenty degrees), such that the second end <NUM> of a tooth <NUM> on the first rotating member <NUM> may not transfer any substantial amount of power or torque to the second end <NUM> of a tooth <NUM> of the second rotating member <NUM>. Or, more notably, the second end <NUM> of a tooth <NUM> on the second rotating member <NUM> may not transfer any substantial amount of power or torque to the second end <NUM> of a tooth <NUM> on the first rotating member <NUM>.

For example, the output assembly <NUM> defines a first rotational direction RD1 along the circumferential direction C2 and a second (and opposite) rotational direction RD2 along the circumferential direction C2. The first rotational direction RD2 may be a clockwise rotational direction (as viewed from an end of the first rotating member <NUM>) and the second rotational direction RD2 may be a counterclockwise rotational direction, each being opposite one another along the circumferential direction C2. During operation of the accessory system, the accessory system may rotate the first rotating member <NUM> in the second rotational direction RD2, such that the spline <NUM> is the driving member and the spline <NUM> is the driven member. By contrast, during operation of the gas turbine engine, the accessory gearbox <NUM> may rotate the second rotating member <NUM> in the second rotational direction RD2, such that the spline <NUM> is the driving member, and the spline <NUM> is the driven member.

When the first rotating member <NUM> is rotated in the second rotational direction RD2 by the accessory system, the engagement ends <NUM> of the teeth <NUM>, <NUM> of the one-way dog clutch <NUM> engage one another to transfer a power and torque between the first and second rotating members <NUM>, <NUM>. By contrast, when the second rotating member <NUM> is rotated in the second rotational direction RD2 by the accessory gearbox <NUM>, the passive ends <NUM> of the teeth <NUM>, <NUM> of the one-way clutch <NUM> are urged towards one another. For example, in such a scenario, and after a designed to fail point of the output assembly <NUM> (discussed below) is broken, the passive ends <NUM> of the teeth <NUM>, <NUM> of the one-way clutch <NUM> are pressed against one another, and may move past one another, such that no substantial amount of power and/or torque may be transferred between the first and second rotating members <NUM>, <NUM> (e.g., less than about <NUM> Newton-meter).

Referring still to <FIG>, the exemplary output assembly <NUM> further includes a spring member <NUM>, which for the embodiment depicted, is coupled (or more specifically, is rigidly coupled) to the first rotating member <NUM>. More specifically, for the embodiment depicted, the second rotating member <NUM> defines an opening <NUM> along the axial direction A2 at the first axial position <NUM>. Additionally, the first rotating member <NUM> includes an extension member <NUM> extending from a body section <NUM> and generally along the axial direction A2 at least partially between the first axial position <NUM> and the second axial position <NUM>. Further, for the embodiment depicted, the extension member <NUM> further extends through the opening <NUM> defined by the second rotating member <NUM>. The spring member <NUM> of the output assembly <NUM> is attached to the extension member <NUM> at a third axial position <NUM>, the third axial position <NUM> being spaced from the first axial position <NUM> along the axial direction A2. The spring member <NUM> extends to the second rotating member <NUM> at a distal end <NUM> of the second rotating member <NUM>, pressing the teeth <NUM> of the second rotating member <NUM> towards the teeth <NUM> of the first rotating member <NUM>. As previously discussed, the second rotating member <NUM> is, for the embodiment depicted, slidably attached to the first rotating member <NUM> at the first axial position <NUM>, such that the spring member <NUM> presses together the one-way clutch <NUM> formed by the first and second rotating members <NUM>, <NUM>.

Notably, with such an exemplary embodiment, the spring member <NUM> creates a resistance for the one-way clutch <NUM> when moved in a passive direction (e.g., when the second rotating member <NUM> is moved in the second rotational direction RD2 by the accessory gearbox <NUM>). More specifically, each of the teeth <NUM>, <NUM> include a distal end surface <NUM> configured to contact a recessed surface <NUM> of the opposing side of the one-way dog clutch <NUM>. The pressing of these two surfaces <NUM>, <NUM> together by, e.g., the spring member <NUM>, creates a resistance that must be overcome in order to rotate the first rotating member <NUM> relative to the second rotating member <NUM> in the passive direction.

Furthermore, as briefly noted above, and referring specifically to <FIG>, the output assembly <NUM> further includes a designed fail point <NUM>. More particularly, the extension member <NUM> includes the designed fail point <NUM>. The designed fail point <NUM> is, for the embodiment depicted, configured as a shear neck. As used herein, the term "shear neck" refers to a position on the extension member <NUM> defining a minimum diameter. For the embodiment depicted, a diameter <NUM> of the shear neck is at least about ten percent less than a diameter <NUM> of a body portion <NUM> of the extension member <NUM>. For example, in certain embodiments, the diameter <NUM> of the shear neck may be at least about fifteen percent less, such as at least about twenty percent less, such as at least about twenty-five percent less, and up to about ninety percent less than the diameter <NUM> of the body portion <NUM> of the extension member <NUM>. It should be appreciated, however, that in other embodiments, the designed fail point <NUM> may instead have any other suitable configuration. For example, in other exemplary embodiments, designed fail point <NUM> may instead be a position on the extension member <NUM> having a plurality of holes or voids therein to reduce a torque limit of such portion of the extension member <NUM>.

It will be appreciated that inclusion of the designed fail point <NUM> in the extension member <NUM> of the first rotating member <NUM> may ensure that no more than a minimum amount of torque is transferred from the accessory gearbox <NUM> to the accessory system. More particularly, the output assembly <NUM> is designed to allow for relatively high amount of torque to be transferred when rotated in one manner (e.g., when the accessory system rotates the first rotating member <NUM> in the second rotational direction RD2), while preventing such high amount of torque to be transferred when rotated in another manner (e.g., when the accessory gearbox <NUM> rotates the second rotating member <NUM> in second rotational direction RD2). For example, the exemplary output assembly <NUM> depicted defines two separate torque paths when rotating in the second rotational direction RD2-a first in which the spline <NUM> is the driving member and a second in which the spline <NUM> is the driving member. More specifically, the first torque path extends from the spline <NUM> of the first rotating member <NUM>, through the one-way clutch <NUM> to the second rotating member <NUM> (more specifically, through the engagement ends <NUM> of the teeth <NUM>, <NUM> of the one-way clutch <NUM>), and through spline <NUM> of the second rotating member <NUM>. The second torque path extends primarily from the spline <NUM> of the first rotating member <NUM>, through the extension member <NUM> of the first rotating member <NUM> (and through the designed fail point <NUM>), through the connection of the first and second rotating members <NUM>, <NUM> at the first axial position <NUM> to the second rotating member <NUM>, and through the spline <NUM> of the second rotating member <NUM>. Notably, a portion of the second torque path also extends through the one-way clutch in the form of friction resistance between the surfaces <NUM>, <NUM> described above. The output assembly <NUM> defines a first torque limit through the first torque path and a second torque limit through the second torque path. The second torque limit is set mainly by the designed fail point <NUM>. Accordingly, for example, the output assembly <NUM> may accommodate a torque transfer in an amount up to the first torque limit when the first rotating member <NUM> is rotated in the second rotational direction RD2 by the accessory system (in which the spline <NUM> is the driving member) and may accommodate a torque transfer an amount up to the second torque limit when the second rotating member <NUM> is rotated in the second rotational direction RD2 by an accessory gear <NUM> of an accessory gearbox <NUM> (in which the spline <NUM> is the driving member).

It will be appreciated that the first torque limit is greater than the second torque limit. For example, the second torque limit may be at least about twenty-five percent lower than the first torque limit, such as at least about thirty-five percent lower, such as at least about fifty percent lower, such as at least about sixty percent lower, and up to about ninety-nine percent lower than the first torque limit.

As stated, the second torque limit is set mainly by the designed fail point <NUM>. More specifically, the second torque limit is set by the designed fail point <NUM> and the friction between the surfaces <NUM>, <NUM>. In at least certain exemplary embodiments, the designed fail point <NUM> defines a torque limit between about thirty (<NUM>) Newton-meters and about one (<NUM>) Newton-meter. For example, in certain embodiments, the designed fail point <NUM> may define a torque limit less than about twenty-five Newton-meters, such as less than about twenty Newton-meters. The overall second torque limit may be within about one Newton-meter of the torque limit of the designed fail point <NUM>. By contrast, the first torque limit may be greater than the second torque limit. For example, the first torque limit may be greater than thirty Newton-meters, such as greater than about fifty Newton-meters, such as greater than about seventy-five Newton-meters, such as greater than about one hundred Newton-meters, and up to about <NUM>,<NUM> Newton-meters.

Inclusion of an output assembly to mechanically couple the accessory system to an accessory gearbox of the gas turbine engine in accordance with an embodiment of the present disclosure may ensure that undesirable, relatively high rotational speeds and/or torques of the accessory gearbox are not transferred to the accessory system. Such may increase a longevity of the accessory system.

It should be appreciated, however, that in other exemplary embodiments, any other suitable configuration may be provided for the output assembly <NUM>. For example, referring now to <FIG> and <FIG>, an output assembly <NUM> in accordance with another exemplary embodiment of the present disclosure is depicted. <FIG> provides an exploded view of the exemplary output assembly <NUM> and <FIG> provides an assembled view of the exemplary output assembly <NUM>. It will be appreciated that the exemplary output assembly <NUM> of <FIG> and <FIG> may be configured in substantially the same manner as the exemplary output assembly <NUM> of <FIG>. Accordingly, the same numbering may refer to the same similar parts.

For example, the exemplary output assembly <NUM> of <FIG> and <FIG> generally includes a first rotating member <NUM> and a second rotating member <NUM>. The second rotating member <NUM> is coupled to the first rotating member <NUM> at a first axial position <NUM> and at a second axial position <NUM>. The second rotating member <NUM> is coupled to the first rotating member <NUM> at the second axial position <NUM> through a one-way clutch <NUM>. By contrast, the second rotating member <NUM> is slidably coupled to the first rotating member <NUM> at the first axial position <NUM>, such that the connection permits movement of the second rotating member <NUM> relative to the first rotating member <NUM> along the axial direction A2 of the output assembly <NUM>.

However, for the embodiment depicted, the slidable connection between the second rotating member <NUM> and the first rotating member <NUM> is provided by an extension member <NUM> including two opposing substantially flat surfaces <NUM> and an opening <NUM> at a distal end <NUM> of the second rotating member <NUM> being an elongated opening having a shape corresponding to the opposing substantially flat surfaces <NUM> of the extension member <NUM> of the first rotating member <NUM>. In such a manner, the first rotating member <NUM> may be slidable relative to the second rotating member <NUM> along the axial direction A2, without being rotatable relative to one another at the first axial position <NUM>. Notably, the output assembly <NUM> of <FIG> and <FIG> is depicted without a spring member <NUM> for clarity.

Referring now to <FIG> a flow diagram is provided of a method <NUM> for operating an accessory system of the gas turbine engine. The method <NUM> may be utilized in certain exemplary aspects with one or more of the exemplary gas turbine engines, accessory systems, and/or output assemblies described above with reference to <FIG>. Accordingly, the gas turbine engine may generally include a compressor section, a combustion section, a turbine section, an accessory gearbox, an accessory system, and an output assembly. The accessory gearbox may be attached to, e.g., a core turbine engine of the gas turbine engine.

The exemplary method generally includes at (<NUM>) applying a first amount of torque with an accessory system to an output assembly in a circumferential direction to rotate an accessory gear of an accessory gearbox. For the embodiment depicted, applying the first amount of torque with the accessory system to the output assembly at (<NUM>) includes at (<NUM>) transferring substantially the first amount of torque from a second rotating member of the output assembly to a first rotating member of the output assembly through a one-way clutch.

The exemplary method <NUM> additionally includes at (<NUM>) applying a second amount of torque with the accessory gear of the accessory gearbox to the output assembly in the circumferential direction (i.e., the same rotational direction as at step (<NUM>), such as a second circumferential direction; see <FIG>). The first and second amounts of torque are each greater than or equal to a torque limit, and more specifically, are each greater than or equal to a torque limit of a designed fail point of an extension member of the first rotating member. Additionally, for the embodiment depicted, the first amount of torque is greater than the second amount of torque.

The exemplary method <NUM> additionally includes at (<NUM>) shearing a portion of the output assembly in response to the application of the second amount of torque to the output assembly in the circumferential direction at (<NUM>). More particularly, for the exemplary aspect depicted, shearing the portion of the output assembly in response to the application of the second amount of torque with the accessory gear to the output assembly in the circumferential direction at (<NUM>) includes at (<NUM>) shearing the extension member of the first rotating member at the designed fail point. In certain exemplary aspects, the designed fail point may be a shear neck.

Further, the exemplary method <NUM> includes at (<NUM>) applying a third amount of torque with the accessory gear of the accessory gearbox to the output assembly in the circumferential direction subsequent to shearing the portion of the output assembly at (<NUM>) such that a second rotating member of the output assembly rotates in the circumferential direction relative to the first rotating member of the output assembly.

Claim 1:
An output assembly (<NUM>) for an accessory system of a gas turbine engine, the gas turbine engine comprising an accessory gearbox (<NUM>), the output assembly (<NUM>) defining an axis (<NUM>) and comprising:
a first rotating member (<NUM>) extending along the axis (<NUM>) and comprising a mechanical connector for coupling the output assembly (<NUM>) to the accessory system;
a second rotating member (<NUM>) extending along the axis (<NUM>) and comprising opposed first end and second end, the first end comprising an opening (<NUM>), the second rotating member (<NUM>) coupled to the first rotating member (<NUM>) at a first axial position (<NUM>) at the opening (<NUM>) of the first end and at a second axial position (<NUM>) at the second end;
a one-way clutch (<NUM>), the second rotating member (<NUM>) coupled to the first rotating member (<NUM>) at the second axial position (<NUM>) through the one-way clutch (<NUM>);
wherein the first rotating member (<NUM>) further comprises an extension member extending at least partially between the first axial position (<NUM>) and the second axial position (<NUM>) and through the opening (<NUM>) of the first end at the first axial position, the extension member including a designed fail point (<NUM>), the output further comprising;
a spring member (<NUM>) attached to the extension member and pressing together the one-way clutch,
wherein the one-way clutch is formed at least in part by the first rotating member (<NUM>) and at least in part by the second rotating member (<NUM>),
the spring member (<NUM>) is attached to the extension member at a third axial position (<NUM>) along an axial direction A2 extending along an axis (<NUM>) of the output assembly (<NUM>),
and the spring member (<NUM>) extends to the second rotating member (<NUM>) at the first end.