Deflection limiter for a gas turbine engine

A gas turbine engine includes a turbine section that includes a fan drive turbine. A geared architecture includes a sun gear in driving engagement with the fan drive turbine. A plurality of planet gears surrounds the sun gear. A ring gear surrounds the plurality of planet gears. A deflection limiter mechanically attaches the ring gear to an engine static structure. The deflection limiter includes a first support fixed to the ring gear that has a first interlocking feature and a second support fixed to the engine static structure that has a second interlocking feature. The first and second interlocking features define at least one of a radial clearance of between 0.005 inches (0.127 mm) and 0.080 inches (2.032 mm) or a circumferential clearance of between 0.005 inches (0.127 mm) and 0.250 inches (2.032 mm). A fan section includes a plurality of fan blades in driving engagement with the geared architecture through a fan drive shaft.

BACKGROUND

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.

SUMMARY

In one exemplary embodiment, a gas turbine engine includes a turbine section that includes a fan drive turbine. A geared architecture includes a sun gear in driving engagement with the fan drive turbine. A plurality of planet gears surrounds the sun gear. A ring gear surrounds the plurality of planet gears. A deflection limiter mechanically attaches the ring gear to an engine static structure. The deflection limiter includes a first support fixed to the ring gear that has a first interlocking feature and a second support fixed to the engine static structure that has a second interlocking feature. The first and second interlocking features define at least one of a radial clearance of between 0.005 inches (0.127 mm) and 0.080 inches (2.032 mm) or a circumferential clearance of between 0.005 inches (0.127 mm) and 0.250 inches (2.032 mm). A fan section includes a plurality of fan blades in driving engagement with the geared architecture through a fan drive shaft.

In a further embodiment of any of the above, the radial clearance is between 0.030 inches (0.762 mm) and 0.050 inches (1.270 mm).

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 0.030 inches (0.762 mm) up to 0.050 inches (1.270 mm) and the circumferential clearance is between 0.030 (0.762 mm) inches and 0.250 inches (6.350 mm).

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 0.030 inches (0.762 mm) up to 0.050 inches (1.270 mm).

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, the radial clearance is between 0.030 inches (0.762 mm) up to 0.050 inches (1.270 mm).

In a further embodiment of any of the above, one of the first support and the second support include an aperture and the other of the first support and the second support include a projection located within a cavity at least partially defined by the aperture.

In a further embodiment of any of the above, the aperture is rectangular in cross section.

In a further embodiment of any of the above, the aperture is elliptical in cross section.

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 30 and 50 corresponding pairs of apertures and projections.

In another exemplary embodiment, a method of operating a gas turbine engine includes the step of driving a fan section through a geared architecture with a fan drive turbine. The geared architecture includes a plurality of planet gears in engagement with a sun gear and a ring gear. Movement of the ring gear is limited with deflection limiter in at least one of a radial direction of up to 0.080 inches (2.032 mm) or the circumferential direction of up to 0.0250 inches (6.350 mm).

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

DETAILED DESCRIPTION

FIG. 2illustrates an example geared architecture48in driving engagement with the plurality of fan blades42in the fan section22. The geared architecture48is driven by the low pressure turbine46, or fan drive turbine, through the low speed spool30. The low speed spool30is attached to a sun gear70of the geared architecture48through a flexible input coupling72. The flexible input coupling72allows the low speed spool30to transfer rotational movement to the sun gear70while allowing a central longitudinal axis of the sun gear70to vary relative to a longitudinal axis of the low speed spool30. The flexible input coupling72also segregates vibrations between the low speed spool30and the geared architecture48.

The sun gear70is surrounded by multiple planet gears74that are supported by a carrier76with a central longitudinal axis of each of the planet gears74rotating around the engine axis A. A ring gear78is located on an opposite radial side of the planet gears74from the sun gear70. 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 gear78is fixed from rotating relative to the engine static structure36through a flexible ring gear support80. One feature of the flexible ring gear support80is the ability to maintain the ring gear78in alignment with the planet gears74and the sun gear70when loads are applied to the geared architecture48through a fan drive shaft82from the fan blades42.

The loads from the fan blades42can cause the geared architecture48to pivot about a pair of bearings systems38A and move the gears out of alignment because the geared architecture48is cantilevered relative to the pair of bearing systems38A. In the illustrated example, the geared architecture48is connected to the fan drive shaft82through the carrier76. The flexible support80allows the ring gear78to move in at least one of a radial direction or a circumferential direction to accommodate for movement from the fan drive shaft82. The pair of bearing systems38A each include an inner race that rotates with the fan drive shaft82and an outer race that is fixed relative to the engine static structure36. Additionally, the flexible input coupling72and the flexible support80function together to maintain the gears of the geared architecture48in alignment during operation.

Because the ring gear78can move in at least one of a radial or a circumferential direction, a deflection limiter84is used in connection with the engine configuration ofFIG. 2. The deflection limiter84provides a maximum radial or circumferential movement for the ring gear78. The deflection limiter84used in connection with the configuration ofFIG. 2can include any of the deflection limiters84A-D described below. Additionally, in the illustrated example, the deflection limiters84A-D are fluid free deflection limiters and do not provide fluid damping of vibrations.

As shown inFIGS. 2 and 3, the deflection limiter84A includes a first support86A fixed or integral with the ring gear78and a second support88A fixed to the engine static structure36to prevent the second support88A from rotating relative to the engine static structure36. The second support88A can be secured with bolts91to the engine static structure36to serve as a mechanical ground. The first support86A includes a first set of teeth90A in an intermeshing relationship with a second set of teeth92on the second support88A. The first set of teeth are located on an outer circumference of the first support86A and the second set of teeth92are located on a radially inner circumference of the second support88A.

The first and second set of teeth90and92include a radial clearance94A defined between a distal end of one of the first or second teeth90,92and a corresponding trough between adjacent teeth of the other of the first and second teeth90,92. Additionally, a circumferential clearance96A is located between opposing circumferential sides of one of first teeth90and an adjacent one of the second teeth92. In one example, the radial clearance94A is from 0.005 inches (0.127 mm) up to 0.080 inches (2.032 mm) and in another example, the radial clearance94A is from 0.030 inches (0.762 mm) up to 0.050 inches (1.270 mm). Furthermore, in one example, the circumferential clearance96A is from 0.005 inches (0.127 mm) up to 0.250 inches (6.350 mm) and in another example, the circumferential clearance96A is from 0.030 (0.762 mm) inches up to 0.250 inches (6.350 mm).

FIGS. 4A-6illustrates another example deflection limiter84B. The deflection limiter84B is similar to the deflection limiter84A except where described below or shown in the Figures. The deflection limiter84B includes a first support86A fixed or integral with the ring gear78and a second support88B fixed relative to the engine static structure36. As shown inFIG. 4B, the second support88A can be fixed to the engine static structure36with bolts91.

The first support86B includes a plurality of apertures89B extend in a direction parallel of the engine axis A and accept a projection87B fixed to the second support88B. In another example, the apertures89B could be located in the second support89B and the projections87B could be located on the first support86B. A corresponding pair of apertures89B and projections87B are circumferentially spaced every one to three inches (2.54-7.62 cm) around the first and second supports86B,88B, respectively. Alternatively, there are between 3 and 50 or 30 and 50 corresponding pairs of apertures89B and projections87B circumferentially spaced around the first and second supports86B,88B, respectively.

In the illustrated example, the projections87B are cylindrical and also extend in a direction parallel to the engine axis A. The projections87B are configured to limit relative motion in the radial and circumferential directions between the first support86B and the second support88B. The limiting function of the projections87B and the apertures89B provide a maximum amount of deflection that the ring gear78can experience relative to the engine static structure36during operation. In the illustrated example, the projections87B do not limit axial movement. Because the apertures89B are elliptical in shape, the projections87B are able travel further in a circumferential direction than in a radial direction relative to the axis A.

The apertures89B and projections87B provide the greatest radial clearance94B in a single radial direction when there is not any circumferential deflection (SeeFIG. 5). Additionally, the greatest circumferential clearance96B occurs when there is not any radial deflection (SeeFIG. 6). The curvilinear profile defined the edge of the aperture89B 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. 7illustrates another example deflection limiter84C. The deflection limiter84C is similar to the deflection limiters84A-B except where described below or shown in the Figures. The deflection limiter84C includes a first support86C fixed or integral with the ring gear78and a second support88C fixed relative to the engine static structure36.

The first support86C includes a plurality of apertures89C that accept a projection87C fixed to the second support88C. In the illustrated example, the projections87C are cylindrical and extend in a direction parallel to the engine axis A. The projections87C are configured to limit relative motion in the radial and circumferential direction between the first support86C and the second support88C. Because the aperture89C is cylindrical in shape, the projection87C has a circumferential clearance96C that is equal to a radial clearance94C. Additionally, the curvilinear profile of the edge of the aperture89C provides a non-linear relationship between deflection limits in the radial and circumferential directions.

FIG. 8illustrates another example deflection limiter84D. The deflection limiter84D is similar to the deflection limiters84A-C except where described below or shown in the Figures. The deflection limiter84D includes a first support86D fixed or integral with the ring gear78and a second support88D fixed to the engine static structure36.

The first support86D includes a plurality of apertures89D that accept a projection87D fixed to the second support88D. In the illustrated example, the projections87D are cylindrical and extend in a direction parallel to the engine axis A. The projections87D are configured to limit relative motion in the radial and circumferential direction between the first support86D and the second support88D. Because the aperture89D defines a rectangular cross-sectional profile, the aperture89D allows for maximum circumferential clearance96D and radial clearance94D at the same time. Furthermore, the aperture89D can include a square cross-sectional profile instead of a rectangular cross-sectional profile to allow for maximum circumferential and radial clearance96D,94D at the same time.

FIG. 9illustrates another configuration of the geared architecture48in driving engagement with the plurality of fan blades42in the fan section22. The configuration ofFIG. 9is similar to the configuration ofFIG. 2except where described below or shown in the Figures. The geared architecture48is driven by the low pressure turbine46through the low speed spool30. The low speed spool30is attached to the sun gear70of the geared architecture through the flexible input coupling72.

The sun gear70is surrounded by multiple planet gears74that are supported by the carrier76. The ring gear78is located on an opposite radial side of the planet gears74form the sun gear70. The ring gear78is fixed from rotating relative to the engine static structure36. In the illustrated example, the ring gear78is attached to the engine static structure36through the flexible support80. The carrier76includes a forward carrier plate76A and an aft carrier plate76B that are each configured to rotate with the fan drive shaft82.

To prevent unwanted movement of the geared architecture48resulting from movement of the fan drive shaft82, a forward bearing system38B is located forward of the geared architecture48and rotates with the forward carrier plate76A and an aft bearing system38C is located aft of the geared architecture48and rotates with the aft carrier plate76B. In the illustrated example, an inner race of the forward bearing system38B rotates with the fan drive shaft82and the forward carrier plate76A and the outer race of the forward bearing system38B is fixed from rotating relative to the engine static structure36. Similarly, an inner race of the aft bearing system38C rotates with the aft carrier plate76B and the fan drive shaft82and an outer race of the aft bearing system38C is fixed from rotating relative to the engine static structure36.

Because the geared architecture48is surrounded axially or straddled by the forward and aft bearing systems38B,38C, the geared architecture48is less susceptible to movement in a radial direction as compared to the engine configuration ofFIG. 2. Therefore, the deflection limiter84used in connection with the engine configuration ofFIG. 8, 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 systems38B,38C surrounding the geared architecture48limit radial loads through the fan drive shaft from other parts of the gas turbine engine20. Therefore, a value for the radial clearance94A-D is of less importance than a value for the circumferential clearance96A-D because the configuration of the geared architecture48and fan section inFIG. 10is less likely to move radially during operation.

FIG. 10illustrates yet another configuration of the geared architecture48in driving engagement with the plurality of fan blades42in the fan section22. The configuration ofFIG. 10is similar to the configuration ofFIGS. 2 and 9except where described below or shown in the Figures. The geared architecture48is driven by the low pressure turbine46through the low speed spool30. The low speed spool30is attached to the sun gear70of the geared architecture through the flexible input coupling72.

The sun gear70is surrounded by multiple planet gears74that are supported by the carrier76. The ring gear78is located on an opposite radial side of the planet gears74from the sun gear70. The ring gear78is fixed from rotating relative to the engine static structure36. In the illustrated example, the ring gear78is attached to the engine static structure36through the flexible support80. The forward carrier plate76A and the aft carrier plate76B of the carrier76are configured to rotate with the fan drive shaft82.

To prevent unwanted movement of the geared architecture resulting from movement of the fan drive shaft82, the forward bearing system38B is located forward of the geared architecture48and rotates with the forward carrier plate76A and the aft bearing system38C is located aft of the geared architecture48and rotates with the aft carrier plate76B. In the illustrated example, the inner race of the forward bearing system38B rotates with the forward carrier plate76A and the fan drive shaft82and the outer race of the bearing system38B is fixed from rotating relative to the engine static structure36. Similarly, the inner race of the aft bearing system38C rotates with the aft carrier plate76B and an outer race of the aft bearing system38B is fixed from rotating relative to the engine static structure36.

Furthermore, the fan drive shaft82is connected to the forward carrier plate76A or output of the geared architecture48through a flexible output coupling79that transmits rotational movement between the fan drive shaft82and the output of the geared architecture48. The flexible output coupling79reduces or eliminates the transfer of radial loads or vibrations to the geared architecture48that can lead to misalignment of the gears. The fan drive shaft82is supported by the pair of fan drive shaft support bearing systems38A. Additionally, the bearing systems38A-38C used in the configurations shown inFIGS. 2 and 9-10are structural support bearings as opposed to oil transfer bearings that deliver oil to the geared architecture48.

Because the geared architecture48inFIG. 10is surrounded axially or straddled by the forward and aft bearing systems38B,38C, the geared architecture48is less susceptible to movement in a radial direction as compared to the engine configuration ofFIG. 2. Therefore, the deflection limiter84used in connection with the engine configuration ofFIG. 8, is less concerned with movement in the radial direction. Therefore, a value for the radial clearance94A-D is of less importance than a value for the circumferential clearance96A-D because the geared architecture48inFIG. 10is less likely to move radially.

Although the different non-limiting examples are illustrated as having specific components, the examples of this disclosure are not limited to those particular combinations. It is possible to use some of the components or features from any of the non-limiting examples in combination with features or components from any of the other non-limiting examples.

It should be understood that like reference numerals identify corresponding or similar elements throughout the several drawings. It should also be understood that although a particular component arrangement is disclosed and illustrated in these exemplary embodiments, other arrangements could also benefit from the teachings of this disclosure.