Patent Description:
Various types and configurations of propulsion systems are known in the art for an aircraft (see e.g. document <CIT>). While these known aircraft propulsion systems have various benefits, there is still room in the art for improvement.

According to an aspect of the present disclosure, an assembly is provided for an aircraft. This aircraft assembly includes a carrier, a first gear system, a second gear system and an idler. The first gear system includes a first sun gear, a first ring gear and a plurality of first intermediate gears. Each of the first intermediate gears is between and is meshed with the first sun gear and the first ring gear. Each of the first intermediate gears is rotatably mounted to the carrier. The second gear system includes a second sun gear, a second ring gear and a plurality of second intermediate gears. Each of the second intermediate gears is between and is meshed with the second sun gear and the second ring gear. Each of the second intermediate gears is rotatably mounted to the carrier. The idler gear couples the first ring gear to the second ring gear.

The assembly may include a rotating structure, an epicyclic gear system, a carrier, a first propulsor rotor, a second propulsor rotor and an electric machine. The rotating structure includes a turbine rotor. The epicyclic gear system includes a sun gear, a ring gear and a plurality of intermediate gears. The sun gear is rotatably driven by the rotating structure. Each of the intermediate gears is between and is meshed with the sun gear and the ring gear. The carrier rotatably supports each of the intermediate gears. The first propulsor rotor is coupled to the ring gear. The second propulsor rotor is coupled to the carrier. The electric machine is coupled to the first propulsor rotor and the second propulsor rotor through the epicyclic gear system. The assembly is configured to stop rotation of the first propulsor rotor using the electric machine while the second propulsor rotor continues to rotate. The assembly is also or alternatively configured to stop rotation of the second propulsor rotor using the electric machine while the first propulsor rotor continues to rotate.

The assembly may include a rotating structure, an epicyclic gear system, a carrier, a first propulsor rotor, a second propulsor rotor and a lock system. The rotating structure includes a turbine rotor. The epicyclic gear system includes a sun gear, a ring gear and a plurality of intermediate gears. The sun gear is rotatably driven by the rotating structure. Each of the intermediate gears is between and is meshed with the sun gear and the ring gear. The carrier rotatably supports each of the intermediate gears. The first propulsor rotor is coupled to the ring gear. The second propulsor rotor is coupled to the carrier. The lock system is configured to lock rotation of the ring gear about a centerline axis during a second propulsor mode of operation. The lock system is also or alternatively configured to lock rotation of the carrier about the centerline axis during a first propulsor mode of operation.

The assembly may also include an electric machine coupled to the first propulsor rotor and the second propulsor rotor through the epicyclic gear system. The assembly may be configured to stop rotation of the ring gear using the electric machine to facilitate locking rotation of the ring gear about the centerline axis. The assembly may also or alternatively be configured to stop rotation of the carrier using the electric machine to facilitate locking rotation of the carrier about the centerline axis.

The assembly may include a first lock device configured to lock rotation of the ring gear about a centerline axis when rotation of the first propulsor rotor is stopped. The assembly may also or alternatively include a second lock device configured to lock rotation of the carrier about the centerline axis when rotation of the second propulsor rotor is stopped.

The assembly may also include a second epicyclic gear system and an idler gear. The second epicyclic gear system may include a second sun gear, a second ring gear and a plurality of second intermediate gears. The second sun gear may be rotatably driven by the electric machine. Each of the second intermediate gears may be between and meshed with the second sun gear and the second ring gear. Each of the second intermediate gears may be rotatably mounted to the carrier. The idler gear may be between and meshed with the ring gear and the second ring gear.

The carrier, the first sun gear, the first ring gear, the second sun gear and the second ring gear may each be rotatable about a centerline axis.

The idler gear may be arranged between and may be meshed with the first ring gear and the second ring gear.

The assembly may also include an electric machine configured to drive rotation of the second sun gear about a centerline axis.

The electric machine may be configured to drive the first ring gear down to a zero rotational speed about the centerline axis.

The assembly may also include a lock device configured to lock rotation of the first ring gear about the centerline axis when the first ring gear is at the zero rotational speed.

The lock device may be configured as or otherwise include a splined coupling.

The electric machine may be configured to drive the carrier down to a zero rotational speed about the centerline axis.

The assembly may also include a lock device configured to lock rotation of the carrier about the centerline axis when the first ring gear is at the zero rotational speed.

The assembly may also include a gas turbine engine core. The gas turbine engine core may include a compressor section, a combustor section, a turbine section and a rotating structure. The rotating structure may include a turbine rotor within the turbine section. The rotating structure may be coupled to and configured to drive rotation of the first sun gear.

The assembly may also include a first propulsor rotor and a second propulsor rotor. The first propulsor rotor may be coupled to and configured to be rotatably driven by the first ring gear. The second propulsor rotor may be coupled to and configured to be rotatably driven by the carrier.

The first propulsor rotor may be rotatable about a first axis. The second propulsor rotor may be rotatable about a second axis that is angularly offset from the first axis.

The first propulsor rotor may be configured to generate propulsive force in a first direction. The second propulsor rotor may be configured to generate propulsive force in a second direction that is different than the first direction.

The first propulsor rotor may be configured as or otherwise include a ducted rotor.

The second propulsor rotor may be configured as or otherwise include an open rotor.

The present disclosure may include any one or more of the individual features disclosed above and/or below alone or in any combination thereof as defined by the appended claims.

<FIG> schematically illustrates a propulsion system <NUM> for an aircraft. The aircraft may be an airplane, a helicopter, a drone (e.g., an unmanned aerial vehicle (UAV)), a spacecraft or any other manned or unmanned aerial vehicle. This aircraft may be configured as a vertical take-off and landing (VTOL) aircraft or a short take-off and vertical landing (STOVL) aircraft. The aircraft propulsion system <NUM> of <FIG>, for example, is configured to generate power for first direction propulsion (e.g., propulsive thrust) during a first mode of operation and to generate power for second direction propulsion (e.g., propulsive lift) during a second mode of operation, where the first direction is different than (e.g., angularly offset from) the second direction. The first mode may be a horizontal (e.g., forward) flight mode where the first direction propulsion is substantially horizontal (e.g., within <NUM> degrees, <NUM> degrees, etc. of a horizontal axis) propulsive thrust. The second mode may be a vertical flight and/or hover mode where the second direction propulsion is substantially vertical (e.g., within <NUM> degrees, <NUM> degrees, etc. of a vertical axis) propulsive lift. The aircraft propulsion system <NUM>, of course, may also be configured to generate both the first direction (e.g., horizontal) propulsion and the second direction (e.g., vertical) propulsion during a third (e.g., transition) mode of operation. The aircraft propulsion system <NUM> of <FIG> includes at least one bladed first propulsor rotor <NUM>, at least one bladed second propulsor rotor <NUM> and a gas turbine engine core <NUM> configured to rotatably drive the first propulsor rotor <NUM> and the second propulsor rotor <NUM>.

The first propulsor rotor <NUM> may be configured as a ducted rotor such as a fan rotor. The first propulsor rotor <NUM> of <FIG> is rotatable about a first rotor axis <NUM>. This first rotor axis <NUM> is an axial centerline of the first propulsor rotor <NUM> and may be horizontal when the aircraft is on ground. The first propulsor rotor <NUM> includes at least a first rotor disk <NUM> and a plurality of first rotor blades <NUM> (on visible in <FIG>); e.g., fan blades. The first rotor blades <NUM> are distributed circumferentially around the first rotor disk <NUM> in an annular array. Each of the first rotor blades <NUM> is connected to and projects radially (relative to the first rotor axis <NUM>) out from the first rotor disk <NUM>.

The second propulsor rotor <NUM> may be configured as an open rotor such as a propeller rotor or a helicopter (e.g., main) rotor. Of course, in other embodiments, the second propulsor rotor <NUM> may alternatively be configured as a ducted rotor such as a fan rotor; e.g., see dashed line duct. The second propulsor rotor <NUM> of <FIG> is rotatable about a second rotor axis <NUM>. This second rotor axis <NUM> is an axial centerline of the second propulsor rotor <NUM> and may be vertical when the aircraft is on the ground. The second rotor axis <NUM> is angularly offset from the first rotor axis <NUM> by an included angle <NUM>; e.g., an acute angle or a right angle. This included angle <NUM> may be between sixty degrees (<NUM>°) and ninety degrees (<NUM>°); however, the present disclosure is not limited to such an exemplary relationship. The second propulsor rotor <NUM> includes at least a second rotor disk <NUM> and a plurality of second rotor blades <NUM>; e.g., open rotor blades. The second rotor blades <NUM> are distributed circumferentially around the second rotor disk <NUM> in an annular array. Each of the second rotor blades <NUM> is connected to and projects radially (relative to the second rotor axis <NUM>) out from the second rotor disk <NUM>.

The engine core <NUM> extends axially along a core axis <NUM> between a forward, upstream airflow inlet <NUM> and an aft, downstream exhaust <NUM>. The core axis <NUM> may be an axial centerline of the engine core <NUM> and may be horizontal when the aircraft is on the ground. This core axis <NUM> may be parallel (e.g., coaxial) with the first rotor axis <NUM> and, thus, angularly offset from the second rotor axis <NUM>. The engine core <NUM> of <FIG> includes a compressor section <NUM>, a combustor section <NUM> and a turbine section <NUM>. The turbine section <NUM> of <FIG> includes a high pressure turbine (HPT) section 48A and a low pressure turbine (LPT) section 48B (also sometimes referred to as a power turbine section).

The engine sections <NUM>-48B are arranged sequentially along the core axis <NUM> within an engine housing <NUM>. This engine housing <NUM> includes an inner case <NUM> (e.g., a core case) and an outer case <NUM> (e.g., a fan case). The inner case <NUM> may house one or more of the engine sections <NUM>-48B; e.g., the engine core <NUM>. The outer case <NUM> may house the first propulsor rotor <NUM>. The outer case <NUM> of <FIG> also axially overlaps and extends circumferentially about (e.g., completely around) the inner case <NUM> thereby at least partially forming a bypass flowpath <NUM> radially between the inner case <NUM> and the outer case <NUM>.

Each of the engine sections <NUM>, 48A and 48B includes a bladed rotor <NUM>-<NUM> within that respective engine section <NUM>, 48A, 48B. Each of these bladed rotors <NUM>-<NUM> includes a plurality of rotor blades arranged circumferentially around and connected to one or more respective rotor disks. The rotor blades, for example, may be formed integral with or mechanically fastened, welded, brazed, adhered and/or otherwise attached to the respective rotor disk(s).

The compressor rotor <NUM> is connected to the HPT rotor <NUM> through a high speed shaft <NUM>. At least (or only) these engine components <NUM>, <NUM> and <NUM> collectively form a high speed rotating structure <NUM>. This high speed rotating structure <NUM> is rotatable about the core axis <NUM>. The LPT rotor <NUM> is connected to a low speed shaft <NUM>. At least (or only) these engine components collectively form a low speed rotating structure <NUM>. This low speed rotating structure <NUM> is rotatable about the core axis <NUM>. The low speed rotating structure <NUM> and, more particularly, its low speed shaft <NUM> may project axially through a bore of the high speed rotating structure <NUM> and its high speed shaft <NUM>.

The aircraft propulsion system <NUM> of <FIG> includes a powertrain <NUM> that couples the low speed rotating structure <NUM> to the first propulsor rotor <NUM> and that couples the low speed rotating structure <NUM> to the second propulsor rotor <NUM>. The powertrain <NUM> of <FIG> includes a geartrain <NUM>, an electric machine <NUM>, a transmission <NUM> and a gearing <NUM>; e.g., bevel gearing. The powertrain <NUM> of <FIG> also includes one or more shafts <NUM>-<NUM> and/or other torque transmission devices for coupling the geartrain <NUM> to the first propulsor rotor <NUM> and the second propulsor rotor <NUM>.

Referring to <FIG>, the geartrain <NUM> may be configured as a biased torque differential. This geartrain <NUM> includes a first gear system <NUM>, a second gear system <NUM>, a gear carrier <NUM> and one or more idler gears <NUM> (one visible in <FIG>). Each of these gear systems <NUM> and <NUM> may be configured as an epicyclic gear system. The first gear system <NUM> is configured to transfer power from the low speed rotating structure <NUM> to the first propulsor rotor <NUM> and/or the second propulsor rotor <NUM> (see also <FIG>). The second gear system <NUM> is configured to facilitate locking (e.g., stopping, preventing) rotation of the second propulsor rotor <NUM> about its second rotor axis <NUM> during the first mode of operation and/or locking (e.g., stopping, preventing) rotation of the first propulsor rotor <NUM> about its first rotor axis <NUM> during the second mode of operation.

Referring to <FIG>, the first gear system <NUM> may be operable as a star gear system during a star system mode of operation; e.g., see <FIG>. The first gear system <NUM> may be operable as a planetary gear system during a planetary system mode of operation; e.g., see <FIG>. The first gear system <NUM> may be operable as open gear system during an open mode of operation; e.g., see <FIG>.

The first gear system <NUM> of <FIG> includes a first sun gear <NUM> (e.g., an inner gear), a first ring gear <NUM> (e.g., an outer gear) and one or more first intermediate gears <NUM> (e.g., planet or star gears). The first sun gear <NUM> is rotatable about a centerline axis <NUM> of the geartrain <NUM>, which centerline axis <NUM> may be parallel (e.g., coaxial) with the axis <NUM>, <NUM>. The first ring gear <NUM> is rotatable about the centerline axis <NUM> during at least (or only) the star system mode of operation (see <FIG>). This first ring gear <NUM> extends circumferentially around (e.g., circumscribes) the first sun gear <NUM> and an annular array of the first intermediate gears <NUM>. The first intermediate gears <NUM> are arranged circumferentially about the centerline axis <NUM> in the annular array. Each of the first intermediate gears <NUM> is radially between and meshed with the first sun gear <NUM> and the first ring gear <NUM>. Each of the first intermediate gears <NUM> is rotatable about a respective first intermediate gear axis <NUM>, and is rotatably mounted to and supported by the carrier <NUM>. The carrier <NUM> is rotatable about the centerline axis <NUM> during at least (or only) the planetary system mode of operation (see <FIG>).

Referring to <FIG>, the second gear system <NUM> includes a second sun gear <NUM> (e.g., an inner gear), a second ring gear <NUM> (e.g., an outer gear) and one or more second intermediate gears <NUM> (e.g., planet or star gears). The second sun gear <NUM> is rotatable about the centerline axis <NUM>. The second ring gear <NUM> is rotatable about the centerline axis <NUM>. This second ring gear <NUM> extends circumferentially around (e.g., circumscribes) the second sun gear <NUM> and an annular array of the second intermediate gears <NUM>. The second intermediate gears <NUM> are arranged circumferentially about the centerline axis <NUM> in the annular array. Each of the second intermediate gears <NUM> is radially between and meshed with the second sun gear <NUM> and the second ring gear <NUM>. Each of the second intermediate gears <NUM> is rotatable about a respective second intermediate gear axis <NUM>, and is rotatably mounted to and supported by the carrier <NUM>.

Referring to <FIG>, the idler gears <NUM> are arranged circumferentially about the centerline axis <NUM> in the annular array. These idler gears <NUM> are configured to couple the first ring gear <NUM> and the second ring gear <NUM> together. Each of the idler gears <NUM> of <FIG>, for example, is axially between and meshed with the first ring gear <NUM> and the second ring gear <NUM>.

The electric machine <NUM> of <FIG> is coupled to the second sun gear <NUM>, where the low speed shaft <NUM> provides a power input for the geartrain <NUM>. This electric machine <NUM> is configurable as an electric motor. For example, during a motor mode of operation, the electric machine <NUM> converts electricity received from a power source (e.g., a generator, one or more batteries, etc.) into mechanical power. This mechanical power is used for driving rotation of the second sun gear <NUM>. It is contemplated, however, the electric machine <NUM> may also be (but, need not be) configurable as an electric generator. For example, during a generator mode of operation, the electric machine <NUM> may convert mechanical power received through the geartrain <NUM> and its second gear system <NUM> into electricity. This electricity may be utilized for various purposes within the aircraft propulsion system <NUM> and/or for various purposes outside of the aircraft propulsion system <NUM>. It is further contemplated that the electric machine <NUM> may be coupled to the second sun gear <NUM> through a gear train (and/or other device(s)) such that electric machine <NUM> may reside remotely from sun gear <NUM>; for example, mounted to the inner case <NUM> or the outer case <NUM> of <FIG>.

The first sun gear <NUM> is coupled to the low speed rotating structure <NUM> and its low speed shaft <NUM>, where the low speed shaft <NUM> provides another power input for the geartrain <NUM>. The first ring gear <NUM> is coupled to the first propulsor rotor <NUM> through the first propulsor shaft <NUM>, where the first propulsor shaft <NUM> provides a first power output from the geartrain <NUM>. The carrier <NUM> and, thus, the first intermediate gears <NUM> (and the second intermediate gears <NUM>) are coupled to the second propulsor rotor <NUM> through the system elements <NUM>, <NUM>, <NUM>, <NUM>, <NUM> and <NUM> (see <FIG>), where the geartrain output shaft <NUM> provides a second power output from the geartrain <NUM>. More particularly, the carrier <NUM> of <FIG> is coupled to the transmission <NUM> through the geartrain output shaft <NUM>.

Referring to <FIG>, an output of the transmission <NUM> is connected to the gearing <NUM> through the transmission output shaft <NUM>. This transmission <NUM> may be configured to selectively couple (e.g., transfer mechanical power between) the geartrain output shaft <NUM> and the transmission output shaft <NUM>. During the first mode of operation, for example, the transmission <NUM> may be configured to decouple the geartrain output shaft <NUM> from the transmission output shaft <NUM>, thereby decoupling the low speed rotating structure <NUM> from the second propulsor rotor <NUM>. During the second mode of operation (and the third mode of operation), the transmission <NUM> may be configured to couple the geartrain output shaft <NUM> with the transmission output shaft <NUM>, thereby coupling the low speed rotating structure <NUM> with the second propulsor rotor <NUM>. The transmission <NUM> may be configured as a clutchless transmission.

An output of the gearing <NUM> is connected to the second propulsor rotor <NUM> through the second propulsor shaft <NUM>. This gearing <NUM> provides a coupling between the transmission output shaft <NUM> rotating about the axis <NUM>, <NUM>, <NUM> and the second propulsor shaft <NUM> rotating about the second rotor axis <NUM>. The gearing <NUM> may also provide a speed change mechanism between the transmission output shaft <NUM> and the second propulsor shaft <NUM>. The gearing <NUM>, however, may alternatively provide a <NUM>:<NUM> rotational coupling between the transmission output shaft <NUM> and the second propulsor shaft <NUM> such that these shafts <NUM> and <NUM> rotate at a common (e.g., the same) speed. Furthermore, in some embodiments, the gearing <NUM> and the transmission output shaft <NUM> may be omitted where the functionality of the gearing <NUM> is integrated into the transmission <NUM>. In still other embodiments, the transmission <NUM> may be omitted where decoupling of the second propulsor rotor <NUM> is not required.

During operation of the aircraft propulsion system <NUM>, air enters the engine core <NUM> through the airflow inlet <NUM>. This air is directed into a core flowpath <NUM> which extends sequentially through the compressor section <NUM>, the combustor section <NUM>, the HPT section 48A and the LPT section 48B to the exhaust <NUM>. The air within this core flowpath <NUM> may be referred to as core air.

The core air is compressed by the compressor rotor <NUM> and directed into a (e.g., annular) combustion chamber <NUM> of a (e.g., annular) combustor in the combustor section <NUM>. Fuel is injected into the combustion chamber <NUM> through one or more fuel injectors <NUM> (one visible in <FIG>) and mixed with the compressed core air to provide a fuel-air mixture. This fuel-air mixture is ignited and combustion products thereof flow through and sequentially cause the HPT rotor <NUM> and the LPT rotor <NUM> to rotate. The rotation of the HPT rotor <NUM> drives rotation of the high speed rotating structure <NUM> and its compressor rotor <NUM>. The rotation of the LPT rotor <NUM> drives rotation of the low speed rotating structure <NUM>. The rotation of the low speed rotating structure <NUM> drives rotation of the first propulsor rotor <NUM> through the geartrain <NUM> during a select mode or modes of operation; e.g., the first and the third modes of operation. The rotation of the low speed rotating structure <NUM> drives rotation of the second propulsor rotor <NUM> through the geartrain <NUM> during a select mode or modes of operation; e.g., the second and the third modes of operation. During the first mode of operation, the transmission <NUM> may decouple the low speed rotating structure <NUM> from the second propulsor rotor <NUM> such that the low speed rotating structure <NUM> does not drive rotation of the second propulsor rotor <NUM>. The second propulsor rotor <NUM> may thereby be stationary (or windmill) during the first mode of operation.

During the first and third modes of operation, the rotation of the first propulsor rotor <NUM> propels bypass air (separate from the core air) through the aircraft propulsion system <NUM> and its bypass flowpath <NUM> to provide the first direction propulsion; e.g., the forward, horizontal thrust. During the second and third modes of operation, the rotation of the second propulsor rotor <NUM> propels additional air (separate from the core air and the bypass air) to provide the second direction propulsion; e.g., vertical lift. The aircraft may thereby takeoff, land and/or otherwise hover during the second and third modes of operation, and the aircraft may fly forward or otherwise move during the first and the third modes of operation.

During each mode of operation, the low speed rotating structure <NUM> is coupled to the first propulsor rotor <NUM> through the geartrain <NUM>. As described above, rotation of the first propulsor rotor <NUM> generates horizontal thrust during the first and the third modes of operation to propel the aircraft horizontally forward. However, generating such horizontal thrust (or significant amounts of horizontal thrust) may hinder and/or be less advantageous to certain aircraft takeoff, landing and/or hovering maneuvers during the second mode of operation. Furthermore, producing horizontal thrust with the first propulsor rotor <NUM> during the second mode of operation may also take away engine core power that could otherwise be provided to the second propulsor rotor <NUM> for vertical aircraft lift. The aircraft propulsion system <NUM> of <FIG> is therefore configured with a propulsion control system <NUM> (see also <FIG>) operable to (A) slow and/or stop the rotation of the first propulsor rotor <NUM> during the second and/or the third modes of operation, and (B) slow and/or stop the rotation of the second propulsor rotor <NUM> during the first and the third modes of operation. This propulsion control system <NUM> may also provide a clutch functionality for the transmission <NUM>.

The propulsion control system <NUM> of <FIG> includes the geartrain <NUM>, the electric machine <NUM> and a lock system <NUM>. The lock system <NUM> of <FIG> includes one or more lock devices <NUM> and <NUM>.

The first lock device <NUM> is configured to selectively lock (e.g., stop, prevent) rotation of the first ring gear <NUM> and/or any one or more system elements <NUM> and <NUM> coupled to the first ring gear <NUM> during, for example, the second mode of operation. The first lock device <NUM> is configured to selectively unlock (e.g., permit, facilitate) rotation of the first ring gear <NUM> and/or any one or more system elements <NUM>, <NUM>, <NUM>, and <NUM> coupled to and driven by the first ring gear <NUM> during, for example, the first and the third modes of operation. The second lock device <NUM>, on the other hand, is configured to selectively lock (e.g., stop, prevent) rotation of the carrier <NUM> and/or any one or more system elements <NUM>, <NUM>, <NUM> and <NUM>-<NUM> (see also <FIG>) coupled to the carrier <NUM> during, for example, the first mode of operation. The second lock device <NUM> is configured to selectively unlock (e.g., permit, facilitate) rotation of the carrier <NUM> and/or any one or more system elements <NUM>, <NUM>, <NUM> and <NUM>-<NUM> (see also <FIG>) coupled to and driven by the carrier <NUM> during, for example, the second and the third modes of operation.

Referring to <FIG>, each of the lock devices <NUM> and <NUM> may be configured as a splined coupling. More particularly, each of the lock devices <NUM> and <NUM> include an inner lock element <NUM> (e.g., a splined shaft), an outer lock element <NUM> (e.g., a splined sleeve) and an actuator <NUM>. The inner lock element <NUM> is rotatable about the axis <NUM>, <NUM>, <NUM>. The outer lock element <NUM> is rotational fixed about the axis <NUM>, <NUM>, <NUM>. However, the actuator <NUM> is configured to move (e.g., axially translate) the outer lock element <NUM> along the axis <NUM>, <NUM>, <NUM> and the inner lock element <NUM> between an unlocked position (see dashed line in <FIG>) and a locked position (see solid line in <FIG>; see also <FIG>). At the unlocked position, splines <NUM> of the outer lock element <NUM> are disengaged (e.g., spaced) from splines <NUM> of the inner lock element <NUM>. At the locked position, the splines <NUM> of the outer lock element <NUM> are engaged (e.g., meshed) with the splines <NUM> of the inner lock element <NUM> (see also <FIG>). With this arrangement, when respective lock device <NUM>, <NUM> is unlocked and its outer lock element <NUM> is in the unlocked position, the inner lock element <NUM> may rotate (e.g., freely, unencumbered by the outer lock element <NUM>) about the axis <NUM>, <NUM>, <NUM>. However, when the respective lock device <NUM>, <NUM> is locked and its outer lock element <NUM> is in the locked position of <FIG>, the outer lock element <NUM> is meshed with the inner lock element <NUM> and prevents rotation of the inner lock element <NUM> about the axis <NUM>, <NUM>, <NUM>.

Referring to <FIG> and <FIG>, the inner lock element <NUM> of the first lock device <NUM> may be configured as part of or may be attached (directly or indirectly) to the first propulsor shaft <NUM>, or any other one of the system elements <NUM>, <NUM>, <NUM>, <NUM> of <FIG>. The inner lock element <NUM> of the second lock device <NUM> may be configured as part of or may be attached (directly or indirectly) to the geartrain output shaft <NUM>, or any other one of the system elements <NUM>, <NUM>, <NUM>, <NUM>, <NUM> and <NUM> of <FIG> and <FIG>.

While the inner lock element <NUM> of <FIG> and <FIG> is described above as the rotating element and the outer lock element <NUM> is described as the rotationally fixed element, the operation of these elements <NUM> and <NUM> may be switched in other embodiments. In particular, the inner lock element <NUM> may alternatively be configured as the rotationally fixed element and axially translatable by the actuator <NUM>, and the outer lock element <NUM> may be configured as the rotating element. Furthermore, various other types of rotational lock devices are known in the art, and the present disclosure is not limited to any particular ones thereof.

During operation of the propulsion control system <NUM> of <FIG>, the electric machine <NUM> may be used to facilitate operation of the lock system <NUM>. For example, where both the first lock device <NUM> and the second lock device <NUM> are disengaged (e.g., unlocked), the first sun gear <NUM> and, more particularly, the low speed rotating structure <NUM> (see <FIG>) may drive rotation of the first ring gear <NUM> and the carrier <NUM> (in opposing directions) about the centerline axis <NUM> (see <FIG>). To facilitate engagement of the first lock device <NUM>, the electric machine <NUM> of <FIG> (see also <FIG>) is operated as the electric motor to drive rotation of the second sun gear <NUM> in a first direction about the centerline axis <NUM>. Increasing a rotational speed of the second sun gear <NUM> in the first direction decreases a rotational speed of the first ring gear <NUM> about the centerline axis <NUM>. The electric machine <NUM> may thereby increase the rotational speed of the second sun gear <NUM> in the first direction to drive the rotational speed of the first ring gear <NUM> towards (e.g., down to) a zero rotational speed. Once the first sun gear <NUM> is at a zero rotational speed about the centerline axis <NUM> (e.g., rotationally fixed), the first lock device <NUM> of <FIG> and <FIG> may be engaged. The electric machine <NUM> may then be turned off (or otherwise used), and the first lock device <NUM> of <FIG> may maintain the first ring gear <NUM> rotationally fixed. While the electric machine <NUM> is off, the second sun gear <NUM> may rotate (e.g., windmill) or be stopped via an optional brake. With this arrangement, the first propulsor rotor <NUM> is rotationally fixed, the second propulsor rotor <NUM> is rotatably driven by the low speed rotating structure <NUM> through the geartrain <NUM> and the aircraft propulsion system <NUM> is operated in its second mode of operation.

To switch from the second mode of operation to the first mode of operation, the first lock device <NUM> may be disengaged. The low speed rotating structure <NUM> may thereby rotationally drive both the first propulsor rotor <NUM> and the second propulsor rotor <NUM> through the geartrain <NUM>. To facilitate engagement of the second lock device <NUM>, the electric machine <NUM> of <FIG> (see also <FIG>) is operated as the electric motor to drive rotation of the second sun gear <NUM> in a second direction about the centerline axis <NUM> which is opposite the first direction. Increasing the rotational speed of the second sun gear <NUM> in the second direction decreases a rotational speed of the carrier <NUM> about the centerline axis <NUM>. The electric machine <NUM> may thereby increase the rotational speed of the second sun gear <NUM> in the second direction to drive the rotational speed of the carrier <NUM> towards (e.g., down to) a zero rotational speed. Once the carrier <NUM> is at a zero rotational speed about the centerline axis <NUM> (e.g., rotationally fixed), the second lock device <NUM> of <FIG> and <FIG> may be engaged. The electric machine <NUM> may then be turned off (or otherwise used), and the second lock device <NUM> of <FIG> may maintain the carrier <NUM> rotationally fixed. While the electric machine <NUM> is off, the second sun gear <NUM> may rotate (e.g., windmill) or be stopped via the optional brake. With this arrangement, the second propulsor rotor <NUM> may be rotationally fixed, the first propulsor rotor <NUM> is rotatably driven by the low speed rotating structure <NUM> through the geartrain <NUM> and the aircraft propulsion system <NUM> is operated in its first mode of operation.

During the first mode of operation where the first lock device <NUM> is disengaged and the second lock device <NUM> is engaged, the geartrain <NUM> of <FIG> operates in its star system mode and is configured as the star geartrain. During the second mode of operation of <FIG> where the first lock device <NUM> is engaged and the second lock device <NUM> is disengaged, the geartrain <NUM> operates in its planetary system mode and is configured as the planetary geartrain. During the third mode of operation of <FIG> where the first lock device <NUM> and the second lock device <NUM> are both disengaged, the geartrain <NUM> of <FIG> operates in its open system mode and is configured as the open geartrain where power is transferred from the low speed rotating structure <NUM> to both shafts <NUM> and <NUM>. The aircraft propulsion system <NUM> may be operated in the third mode of operation while transitioning between the first and the second modes of operation.

During the star system mode of <FIG>, the geartrain <NUM> may transfer none of the power received from the low speed rotating structure <NUM> to the second propulsor rotor <NUM> since the carrier <NUM> is stationary. The geartrain <NUM> may therefore transfer (e.g., all, minus powertrain losses) power received from the low speed rotating structure <NUM> to the first propulsor rotor <NUM> to generate the first direction propulsive force; e.g., forward, horizontal thrust. By contrast, during the planetary system mode of <FIG>, the geartrain <NUM> may transfer none of the power received from the low speed rotating structure <NUM> to the first propulsor rotor <NUM> since the first ring gear <NUM> is stationary. The geartrain <NUM> may therefore transfer (e.g., all, minus powertrain losses) power received from the low speed rotating structure <NUM> to the second propulsor rotor <NUM> to generate the second direction propulsive force; e.g., vertical lift. The propulsion control system <NUM> of the present disclosure may thereby facilitate selective power distribution from the low speed rotating structure <NUM> to the first propulsor rotor <NUM> and the second propulsor rotor <NUM>. Providing this selective power distribution may increase aircraft propulsion system efficiency and improve aircraft handling during at least the first and the second modes of operation.

In some embodiments, referring to <FIG>, the low speed rotating structure <NUM> may be configured without a compressor rotor. In other embodiments, referring to <FIG>, the low speed rotating structure <NUM> may include a low pressure compressor (LPC) rotor <NUM>' arranged within a low pressure compressor (LPC) section 46A of the compressor section <NUM>. In such embodiments, the compressor rotor <NUM> may be a high pressure compressor (HPC) rotor within a high pressure compressor (HPC) section 46B of the compressor section <NUM>.

The engine core <NUM> (e.g., see <FIG>) may have various configurations other than those described above. The engine core <NUM>, for example, may be configured with a single spool, with two spools (e.g., see <FIG>), or with more than two spools. The engine core <NUM> may be configured with one or more axial flow compressor sections, one or more radial flow compressor sections, one or more axial flow turbine sections and/or one or more radial flow turbine sections. The engine core <NUM> may be configured with any type or configuration of annular, tubular (e.g., CAN), axial flow and/or reverser flow combustor. The present disclosure therefore is not limited to any particular types or configurations of gas turbine engine cores. Furthermore, it is contemplated the engine core <NUM> of the present disclosure may drive more than the two propulsors <NUM> and <NUM>. The aircraft propulsion system <NUM>, for example, may include two or more of the first propulsor rotors <NUM> and/or two or more of the second propulsor rotors <NUM>. For example, the aircraft propulsion system <NUM> of <FIG> includes multiple second propulsor rotors <NUM> rotatably driven by the low speed rotating structure <NUM>. These second propulsor rotors <NUM> may rotate about a common axis. Alternatively, each second propulsor rotor <NUM> may rotate about a discrete axis where, for example, the second propulsor rotors <NUM> are laterally spaced from one another and coupled to the low speed rotating structure <NUM> through a power splitting geartrain <NUM>.

Claim 1:
An assembly for an aircraft, comprising:
a gear carrier (<NUM>);
a first gear system (<NUM>) including a first sun gear (<NUM>), a first ring gear (<NUM>) and a plurality of first intermediate gears (<NUM>), each of the plurality of first intermediate gears (<NUM>) between and meshed with the first sun gear (<NUM>) and the first ring gear (<NUM>), and each of the plurality of first intermediate gears (<NUM>) rotatably mounted to the carrier (<NUM>);
a second gear system (<NUM>) including a second sun gear (<NUM>), a second ring gear (<NUM>) and a plurality of second intermediate gears (<NUM>), each of the plurality of second intermediate gears (<NUM>) between and meshed with the second sun gear (<NUM>) and the second ring gear (<NUM>), and each of the plurality of second intermediate gears (<NUM>) rotatably mounted to the carrier (<NUM>);
characterised by:
an idler gear (<NUM>) coupling the first ring gear (<NUM>) to the second ring gear (<NUM>).