BACKGROUND

1. Field

The present disclosure relates to power transfer, and more particularly to transferring power within a power plant for aerospace applications.

2. Description of Related Art

Aircraft power plants, including turboshaft engines, turboprop engines, turbofan engines, hybrid-electric power plants, and the like, can have multiple sources of rotational power. For example in a hybrid-electric power plant there can be an internal combustion engine, one or more turbochargers, and one or more electric motors. One or more transmissions are needed to deliver the power from these sources of rotational power to an air mover such as a propeller.

The conventional techniques have been considered satisfactory for their intended purpose. However, there is an ever present need for improved systems and methods for power transfer in hybrid-electric power plants such as for aerospace applications. This disclosure provides a solution for this need.

SUMMARY

An epicyclic gear system includes an input sun gear configured to receive rotational input from a turbine of a turbo charger. A first set of planet gears is distributed around and meshes with the input sun gear. A carrier holds the first set of planet gears and defines a rotational axis about which the carrier rotates. A second set of planet gears is mounted to the carrier. An output sun gear is included, wherein the second set of planet gears are distributed around and mesh with the output sun. The output sun gear is configured to deliver rotational power to an internal combustion engine. The carrier is configured to selectively be driven by a variable speed drive to regulate output to the output sun over a range of input rotational speeds of the input sun gear. Each gear of the second set of planet gears can be on a common shaft with a respective one of the gears of the first set of planet gears so the first and second sets of planet gears rotate together about the rotational axis with rotation of the carrier. Each gear of the second set of planet gears can be rotationally fixed relative to the respective one of the planet gears of the first set of planet gears to rotate together around an axis of the respective common shaft as they also revolve around the rotational axis with rotation of the carrier.

The input sun gear can be smaller than the output sun gear. Each gear of first set of planet gears can be larger than each of the respective gears of the second set of planet gears. The system can be devoid of a ring gear surrounding and meshing with the first set of planet gears. The system can be devoid of a ring gear surrounding and meshing with the second set of planet gears.

The variable speed drive can be connected to drive the carrier with variable speed to regulate output to the output sun over a range of input rotational speeds of the input sun gear. The variable speed drive can be a hydraulic system. The variable speed drive can connect directly to drive the carrier without connecting to the carrier by way of a ring gear meshing with the first or second sets of planet gears.

The system can include the internal combustion engine connected to be driven by the output sun gear. The turbo charger turbine can be connected to the input sun gear to provide power to the internal combustion engine. One or more accessory gears can be operatively connected to the output sun gear to drive accessory devices. The variable speed drive can include an input gear operatively connected to the output sun gear to provide input drive to the variable speed drive. The input gear can be mounted to a bearing having a fixed outer race and an inner race that rotates with the input gear relative to the outer race. The variable speed drive can include an output gear operatively connected to drive the carrier, wherein the variable speed drive includes an internal mechanism configured to drive the output gear at a different speed from the input gear, and to vary the ratio of speed difference between the input gear and the output gear. The carrier can be mounted to a bearing having a fixed outer race and an inner race that rotates with the carrier relative to the outer race.

A method includes providing rotational power as input to an input sun gear and driving planet gears with the input sun gear, wherein the planet gears are operatively connected to a carrier to revolve around the input sun gear. The method includes controlling revolution speed of the carrier with a variable speed drive and providing rotational output power from the planet gears to an output sun gear, wherein the rotational output power is speed regulated by controlling revolution speed and direction of the carrier and variable speed drive.

Controlling revolution speed of the carrier with the variable speed drive can include driving the variable speed drive with at least one gear operatively connected to the output sun gear. The method can include varying output speed of the variable speed drive given a constant input speed to the variable speed drive. The method can include varying rotational direction of rotational output of the variable speed drive. Controlling revolution speed of the carrier with the variable speed drive can include altering speed of the carrier to maintain constant output speed of the output sun gear given variable input speed to the input sun gear.

These and other features of the systems and methods of the subject disclosure will become more readily apparent to those skilled in the art from the following detailed description of the preferred embodiments taken in conjunction with the drawings.

