Patent Description:
A gas turbine engine may include a geared architecture that drives a fan at a slower rotational speed than a fan drive turbine. The geared architecture is supported relative to an engine static structure using a support. The support is generally attached to one of a ring gear or a carrier in the geared architecture depending on the configuration of the geared architecture.

<CIT> discloses a coupling system for a planetary gear train.

<CIT> discloses a multi-directional gearbox deflection limiter for a gas turbine engine.

<CIT> discloses a method of assembly for a fan drive gear system with a rotating carrier.

According to one aspect of the present invention, a gas turbine engine is provided in accordance with claim <NUM>.

In an embodiment of the above, the radial clearance is between <NUM> inches (<NUM>) and <NUM> inches (<NUM>).

In a further embodiment of any of the above, the deflection limiter includes a maximum circumferential clearance that is greater than a maximum radial clearance.

In a further embodiment of any of the above, a ring gear flexible support supports the ring gear relative to the engine static structure.

In a further embodiment of any of the above, the fan drive turbine drives a low speed spool and the low speed spool is in driving engagement with the sun gear through a flexible input.

In a further embodiment of any of the above, the geared architecture is supported in a cantilever position with at least two fan drive shaft bearing systems supporting the fan drive shaft axially between the plurality of fan blades and the geared architecture.

In a further embodiment of any of the above, the radial clearance is between <NUM> inches (<NUM>) up to <NUM> inches (<NUM>) and the circumferential clearance is between <NUM> (<NUM>) inches and <NUM> inches (<NUM>).

In a further embodiment of any of the above, the geared architecture is located between a first fan drive shaft support bearing system located axially forward of the geared architecture. A second fan drive shaft support bearing system is located axially aft of the geared architecture.

In a further embodiment of any of the above, the radial clearance is between <NUM> inches (<NUM>) up to <NUM> inches (<NUM>).

In a further embodiment of any of the above, a flexible output shaft connects an output of the geared architecture and the fan drive shaft.

In a further embodiment of any of the above, the fan drive shaft is supported by at least two fan drive shaft bearing systems.

In a further embodiment of any of the above, the geared architecture is located between a first fan drive shaft support bearing system located axially forward of the geared architecture and a second fan drive shaft support bearing system located axially aft of the geared architecture.

In a further embodiment of any of the above, a corresponding pair of the aperture and the projection are positioned every one to three inches circumferentially around an axis of rotation of the gas turbine engine.

In a further embodiment of any of the above, the gas turbine includes between <NUM> and <NUM> corresponding pairs of apertures and projections.

According to another aspect of the present invention, a method of operating a gas turbine engine is provided in accordance with claim <NUM>.

In an embodiment of the above, the deflection limiter allows for unequal amounts in movement between the radial direction and the circumferential direction.

The fan section <NUM> drives air along a bypass flow path B in a bypass duct defined within a housing <NUM>, such as a fan case or nacelle, and also drives air along a core flow path C for compression and communication into the combustor section <NUM> then expansion through the turbine section <NUM>.

The low speed spool <NUM> generally includes an inner shaft <NUM> that interconnects, a first (or low pressure) compressor <NUM> and a first (or low pressure) turbine <NUM>. The high speed spool <NUM> includes an outer shaft <NUM> that interconnects a second (or high pressure) compressor <NUM> and a second (or high pressure) turbine <NUM>.

It should be understood, however, that the above parameters are only exemplary of one embodiment of a geared architecture engine and that the present disclosure is applicable to other gas turbine engines including direct drive turbofans.

<FIG> illustrates an example geared architecture <NUM> in driving engagement with the plurality of fan blades <NUM> in the fan section <NUM>. The geared architecture <NUM> is driven by the low pressure turbine <NUM>, or fan drive turbine, through the low speed spool <NUM>. The low speed spool <NUM> is attached to a sun gear <NUM> of the geared architecture <NUM> through a flexible input coupling <NUM>. The flexible input coupling <NUM> allows the low speed spool <NUM> to transfer rotational movement to the sun gear <NUM> while allowing a central longitudinal axis of the sun gear <NUM> to vary relative to a longitudinal axis of the low speed spool <NUM>. The flexible input coupling <NUM> also segregates vibrations between the low speed spool <NUM> and the geared architecture <NUM>.

The sun gear <NUM> is surrounded by multiple planet gears <NUM> that are supported by a carrier <NUM> with a central longitudinal axis of each of the planet gears <NUM> rotating around the engine axis A. A ring gear <NUM> is located on an opposite radial side of the planet gears <NUM> from the sun gear <NUM>. In this disclosure, radial or radially, circumferential or circumferentially, and axial or axially is in relation to the engine axis A unless stated otherwise. The ring gear <NUM> is fixed from rotating relative to the engine static structure <NUM> through a flexible ring gear support <NUM>. One feature of the flexible ring gear support <NUM> is the ability to maintain the ring gear <NUM> in alignment with the planet gears <NUM> and the sun gear <NUM> when loads are applied to the geared architecture <NUM> through a fan drive shaft <NUM> from the fan blades <NUM>.

The loads from the fan blades <NUM> can cause the geared architecture <NUM> to pivot about a pair of bearings systems 38A and move the gears out of alignment because the geared architecture <NUM> is cantilevered relative to the pair of bearing systems 38A. In the illustrated example, the geared architecture <NUM> is connected to the fan drive shaft <NUM> through the carrier <NUM>. The flexible support <NUM> allows the ring gear <NUM> to move in at least one of a radial direction or a circumferential direction to accommodate for movement from the fan drive shaft <NUM>. The pair of bearing systems 38A each include an inner race that rotates with the fan drive shaft <NUM> and an outer race that is fixed relative to the engine static structure <NUM>. Additionally, the flexible input coupling <NUM> and the flexible support <NUM> function together to maintain the gears of the geared architecture <NUM> in alignment during operation.

Because the ring gear <NUM> can move in at least one of a radial or a circumferential direction, a deflection limiter <NUM> is used in connection with the engine configuration of <FIG>. The deflection limiter <NUM> provides a maximum radial or circumferential movement for the ring gear <NUM>. The deflection limiter <NUM> used in connection with the configuration of <FIG> can include any of the deflection limiters 84A-D described below. Additionally, in the illustrated example, the deflection limiters 84A-D are fluid free deflection limiters and do not provide fluid damping of vibrations.

As shown in <FIG>, the deflection limiter 84A includes a first support 86A fixed or integral with the ring gear <NUM> and a second support 88A fixed to the engine static structure <NUM> to prevent the second support 88A from rotating relative to the engine static structure <NUM>. The second support 88A can be secured with bolts <NUM> to the engine static structure <NUM> to serve as a mechanical ground. The first support 86A includes a first set of teeth 90A in an intermeshing relationship with a second set of teeth <NUM> on the second support 88A. The first set of teeth are located on an outer circumference of the first support 86A and the second set of teeth <NUM> are located on a radially inner circumference of the second support 88A.

The first and second set of teeth <NUM> and <NUM> include a radial clearance 94A defined between a distal end of one of the first or second teeth <NUM>, <NUM> and a corresponding trough between adjacent teeth of the other of the first and second teeth <NUM>, <NUM>. Additionally, a circumferential clearance 96A is located between opposing circumferential sides of one of first teeth <NUM> and an adjacent one of the second teeth <NUM>. In one example, the radial clearance 94A is from <NUM> inches (<NUM>) up to <NUM> inches (<NUM>) and in another example, the radial clearance 94A is from <NUM> inches (<NUM>) up to <NUM> inches (<NUM>). Furthermore, in one example, the circumferential clearance 96A is from <NUM> inches (<NUM>) up to <NUM> inches (<NUM>) and in another example, the circumferential clearance 96A is from <NUM> (<NUM>) inches up to <NUM> inches (<NUM>).

<FIG> illustrates another example deflection limiter 84B. The deflection limiter 84B is similar to the deflection limiter 84A except where described below or shown in the Figures. The deflection limiter 84B includes a first support 86A fixed or integral with the ring gear <NUM> and a second support 88B fixed relative to the engine static structure <NUM>. As shown in <FIG>, the second support 88A can be fixed to the engine static structure <NUM> with bolts <NUM>.

The first support 86B includes a plurality of apertures 89B extend in a direction parallel of the engine axis A and accept a projection 87B fixed to the second support 88B. In another example, the apertures 89B could be located in the second support 88B and the projections 87B could be located on the first support 86B. A corresponding pair of apertures 89B and projections 87B are circumferentially spaced every one to three inches (<NUM> - <NUM>) around the first and second supports 86B, 88B, respectively. Alternatively, there are between <NUM> and <NUM> or <NUM> and <NUM> corresponding pairs of apertures 89B and projections 87B circumferentially spaced around the first and second supports 86B, 88B, respectively.

In the illustrated example, the projections 87B are cylindrical and also extend in a direction parallel to the engine axis A. The projections 87B are configured to limit relative motion in the radial and circumferential directions between the first support 86B and the second support 88B. The limiting function of the projections 87B and the apertures 89B provide a maximum amount of deflection that the ring gear <NUM> can experience relative to the engine static structure <NUM> during operation. In the illustrated example, the projections 87B do not limit axial movement. Because the apertures 89B are elliptical in shape, the projections 87B are able travel further in a circumferential direction than in a radial direction relative to the axis A.

The apertures 89B and projections 87B provide the greatest radial clearance 94B in a single radial direction when there is not any circumferential deflection (See <FIG>). Additionally, the greatest circumferential clearance 96B occurs when there is not any radial deflection (See <FIG>). The curvilinear profile defined the edge of the aperture 89B provides a non-linear relationship between deflection limits in the radial and circumferential directions. One feature of the curvilinear profile is an ability to select a predetermined relationship between movement in the radial and circumferential directions.

<FIG> illustrates another non claimed example deflection limiter 84C. The deflection limiter 84C is similar to the deflection limiters 84A-B except where described below or shown in the Figures. The deflection limiter 84C includes a first support 86C fixed or integral with the ring gear <NUM> and a second support 88C fixed relative to the engine static structure <NUM>.

The first support 86C includes a plurality of apertures 89C that accept a projection 87C fixed to the second support 88C. In the illustrated example, the projections 87C are cylindrical and extend in a direction parallel to the engine axis A. The projections 87C are configured to limit relative motion in the radial and circumferential direction between the first support 86C and the second support 88C. Because the aperture 89C is cylindrical in shape, the projection 87C has a circumferential clearance 96C that is equal to a radial clearance 94C. Additionally, the curvilinear profile of the edge of the aperture 89C provides a non-linear relationship between deflection limits in the radial and circumferential directions.

<FIG> illustrates another non claimed example deflection limiter 84D. The deflection limiter 84D is similar to the deflection limiters 84A-C except where described below or shown in the Figures. The deflection limiter 84D includes a first support 86D fixed or integral with the ring gear <NUM> and a second support 88D fixed to the engine static structure <NUM>.

The first support 86D includes a plurality of apertures 89D that accept a projection 87D fixed to the second support 88D. In the illustrated example, the projections 87D are cylindrical and extend in a direction parallel to the engine axis A. The projections 87D are configured to limit relative motion in the radial and circumferential direction between the first support 86D and the second support 88D. Because the aperture 89D defines a rectangular cross-sectional profile, the aperture 89D allows for maximum circumferential clearance 96D and radial clearance 94D at the same time. Furthermore, the aperture 89D can include a square cross-sectional profile instead of a rectangular cross-sectional profile to allow for maximum circumferential and radial clearance 96D, 94D at the same time.

<FIG> illustrates another configuration of the geared architecture <NUM> in driving engagement with the plurality of fan blades <NUM> in the fan section <NUM>. The configuration of <FIG> is similar to the configuration of <FIG> except where described below or shown in the Figures. The geared architecture <NUM> is driven by the low pressure turbine <NUM> through the low speed spool <NUM>. The low speed spool <NUM> is attached to the sun gear <NUM> of the geared architecture through the flexible input coupling <NUM>.

The sun gear <NUM> is surrounded by multiple planet gears <NUM> that are supported by the carrier <NUM>. The ring gear <NUM> is located on an opposite radial side of the planet gears <NUM> form the sun gear <NUM>. The ring gear <NUM> is fixed from rotating relative to the engine static structure <NUM>. In the illustrated example, the ring gear <NUM> is attached to the engine static structure <NUM> through the flexible support <NUM>. The carrier <NUM> includes a forward carrier plate 76A and an aft carrier plate 76B that are each configured to rotate with the fan drive shaft <NUM>.

To prevent unwanted movement of the geared architecture <NUM> resulting from movement of the fan drive shaft <NUM>, a forward bearing system 38B is located forward of the geared architecture <NUM> and rotates with the forward carrier plate 76A and an aft bearing system 38C is located aft of the geared architecture <NUM> and rotates with the aft carrier plate 76B. In the illustrated example, an inner race of the forward bearing system 38B rotates with the fan drive shaft <NUM> and the forward carrier plate 76A and the outer race of the forward bearing system 38B is fixed from rotating relative to the engine static structure <NUM>. Similarly, an inner race of the aft bearing system 38C rotates with the aft carrier plate 76B and the fan drive shaft <NUM> and an outer race of the aft bearing system 38C is fixed from rotating relative to the engine static structure <NUM>.

Because the geared architecture <NUM> is surrounded axially or straddled by the forward and aft bearing systems 38B, 38C, the geared architecture <NUM> is less susceptible to movement in a radial direction as compared to the engine configuration of <FIG>. Therefore, the deflection limiter <NUM> used in connection with the engine configuration of <FIG>, is less concerned with limiting a magnitude of movement in the radial direction. The decreased concern regarding radial movement is because the forward and aft bearing systems 38B, 38C surrounding the geared architecture <NUM> limit radial loads through the fan drive shaft from other parts of the gas turbine engine <NUM>. Therefore, a value for the radial clearance 94A-D is of less importance than a value for the circumferential clearance 96A-D because the configuration of the geared architecture <NUM> and fan section in <FIG> is less likely to move radially during operation.

<FIG> illustrates yet another configuration of the geared architecture <NUM> in driving engagement with the plurality of fan blades <NUM> in the fan section <NUM>. The configuration of <FIG> is similar to the configuration of <FIG> and <FIG> except where described below or shown in the Figures. The geared architecture <NUM> is driven by the low pressure turbine <NUM> through the low speed spool <NUM>. The low speed spool <NUM> is attached to the sun gear <NUM> of the geared architecture through the flexible input coupling <NUM>.

The sun gear <NUM> is surrounded by multiple planet gears <NUM> that are supported by the carrier <NUM>. The ring gear <NUM> is located on an opposite radial side of the planet gears <NUM> from the sun gear <NUM>. The ring gear <NUM> is fixed from rotating relative to the engine static structure <NUM>. In the illustrated example, the ring gear <NUM> is attached to the engine static structure <NUM> through the flexible support <NUM>. The forward carrier plate 76A and the aft carrier plate 76B of the carrier <NUM> are configured to rotate with the fan drive shaft <NUM>.

To prevent unwanted movement of the geared architecture resulting from movement of the fan drive shaft <NUM>, the forward bearing system 38B is located forward of the geared architecture <NUM> and rotates with the forward carrier plate 76A and the aft bearing system 38C is located aft of the geared architecture <NUM> and rotates with the aft carrier plate 76B. In the illustrated example, the inner race of the forward bearing system 38B rotates with the forward carrier plate 76A and the fan drive shaft <NUM> and the outer race of the bearing system 38B is fixed from rotating relative to the engine static structure <NUM>. Similarly, the inner race of the aft bearing system 38C rotates with the aft carrier plate 76B and an outer race of the aft bearing system 38B is fixed from rotating relative to the engine static structure <NUM>.

Furthermore, the fan drive shaft <NUM> is connected to the forward carrier plate 76A or output of the geared architecture <NUM> through a flexible output coupling <NUM> that transmits rotational movement between the fan drive shaft <NUM> and the output of the geared architecture <NUM>. The flexible output coupling <NUM> reduces or eliminates the transfer of radial loads or vibrations to the geared architecture <NUM> that can lead to misalignment of the gears. The fan drive shaft <NUM> is supported by the pair of fan drive shaft support bearing systems 38A. Additionally, the bearing systems 38A-38C used in the configurations shown in <FIG> and <FIG> are structural support bearings as opposed to oil transfer bearings that deliver oil to the geared architecture <NUM>.

Because the geared architecture <NUM> in <FIG> is surrounded axially or straddled by the forward and aft bearing systems 38B, 38C, the geared architecture <NUM> is less susceptible to movement in a radial direction as compared to the engine configuration of <FIG>. Therefore, the deflection limiter <NUM> used in connection with the engine configuration of <FIG>, is less concerned with movement in the radial direction. Therefore, a value for the radial clearance 94A-D is of less importance than a value for the circumferential clearance 96A-D because the geared architecture <NUM> in <FIG> is less likely to move radially.

Claim 1:
A gas turbine engine (<NUM>) comprising:
a turbine section (<NUM>) including a fan drive turbine (<NUM>);
a geared architecture (<NUM>) including:
a sun gear (<NUM>) in driving engagement with the fan drive turbine (<NUM>);
a plurality of planet gears (<NUM>) surrounding the sun gear (<NUM>); and
a ring gear (<NUM>) surrounding the plurality of planet gears (<NUM>);
a deflection limiter (<NUM>) mechanically attaching the ring gear (<NUM>) to an engine static structure (<NUM>), wherein the deflection limiter (<NUM>) includes a first support (86A-D) fixed to the ring gear (<NUM>) having a first interlocking feature and a second support (88A-D) fixed to the engine static structure (<NUM>) having a second interlocking feature, wherein the first and second interlocking features define a radial clearance (94A) of between <NUM> inches (<NUM>) and <NUM> inches (<NUM>) and/or a circumferential clearance (96A) of between <NUM> inches (<NUM>) and <NUM> inches ( <NUM>); and
a fan section (<NUM>) including a plurality of fan blades (<NUM>) in driving engagement with the geared architecture (<NUM>) through a fan drive shaft (<NUM>), wherein one of the first support (86A-D) and the second support (88A-D) includes an aperture (89B-D) and the other of the first support (86A-D) and the second support (88A-D) includes a projection (87B-D) located within a cavity at least partially defined by the aperture (89B-D), and the aperture (89B-D) is elliptical in cross section.