Systems and methods for oil maintenance in gearboxes for eVTOL aircraft
An electric propulsion system comprising an electric motor assembly. The electric motor assembly may include a housing having an internal volume, a stator ring disposed about a perimeter of the internal volume, and a rotor positioned within the stator. The electric motor assembly may include a main shaft connected to the rotor via a gear reduction, wherein the main shaft extends through the rotor. The electric motor assembly may include a collar connected to the main shaft, wherein the collar encircles the main shaft, and at least a portion of the collar is configured to direct a fluid away from the main shaft and toward the stator ring.
1 . A motor assembly for an electric propulsion system, the motor assembly comprising:
a housing having an internal volume;
a stator ring disposed about a perimeter of the internal volume;
a rotor positioned within the stator ring;
a hollow shaft attached to the rotor, comprising a gear of a gear reduction;
at least one fluid distribution chamber located on an outer surface of the hollow shaft, the at least one fluid distribution chamber configured to rotate with the hollow shaft and distribute fluid radially towards the stator ring via a first opening of the at least one fluid distribution chamber, wherein the first opening and a location at which the stator ring receives the fluid are substantially aligned;
a main shaft connected to the hollow shaft via the gear reduction; and
a hydrodynamic bearing disposed between the hollow shaft and the main shaft, wherein the hydrodynamic bearing is configured to resist a load experienced by the hollow shaft.
2 . The motor assembly of claim 1 , wherein the rotation of the hollow shaft is configured to propel fluid through the first opening toward the stator ring.
3 . The motor assembly of claim 1 , wherein the rotation of the hollow shaft is configured to propel the fluid through the first opening toward one or more end turns of the stator ring.
4 . The motor assembly of claim 1 , wherein an inner surface of the hollow shaft defines at least one fluid collection chamber with an outer surface of the main shaft, and the at least one fluid collection chamber is configured to accumulate the fluid between the hollow shaft and the main shaft.
5 . The motor assembly of claim 4 , further comprising a passageway formed in the hollow shaft for transferring the fluid from the at least one fluid collection chamber to the at least one fluid distribution chamber.
6 . The motor assembly of claim 5 , wherein the passageway is configured to transfer the fluid due to the rotation of the hollow shaft.
7 . The motor assembly of claim 1 , wherein the at least one fluid distribution chamber includes at least one second opening positioned to direct the fluid toward the rotor during the rotation of the hollow shaft.
8 . The motor assembly of claim 7 , wherein the first opening and the at least one second opening are bleed holes.
9 . The motor assembly of claim 1 , wherein the electric propulsion system is configured to provide propulsion for an electric aircraft.
10 . The system of claim 9 , wherein the electric aircraft is an electric vertical takeoff and landing (eVTOL) aircraft.
11 . The motor assembly of claim 1 , wherein the motor assembly is configured to feed the fluid to the main shaft using a sump pump.
12 . The motor assembly of claim 11 , further comprising a power inverter mounted to a first end of the housing, wherein the stator ring is configured to receive electricity from the power inverter.
13 . The motor assembly of claim 12 , wherein a portion of the main shaft extends beyond a second end of the housing opposite the first end.
14 . The motor assembly of claim 1 , wherein the fluid comprises oil.
15 . The motor assembly of claim 1 , wherein the internal volume is circular.
16 . The motor assembly of claim 1 , wherein the gear comprises a sun gear of the gear reduction.
17 . A method of operating an electric propulsion system for a vertical take-off and landing (VTOL) aircraft, the method comprising:
rotating a propeller by an electric motor assembly, the electric motor assembly comprising:
a housing having an internal volume;
a stator ring disposed about a perimeter of the internal volume;
a rotor positioned within the stator ring;
a hollow shaft attached to the rotor, comprising a gear of a gear reduction;
at least one fluid distribution chamber located on an outer surface of the hollow shaft and configured to rotate with the hollow shaft, the at least one fluid distribution chamber including a first opening;
a main shaft connected to the hollow shaft via the gear reduction, wherein, the main shaft extends through the hollow shaft, and the fluid distribution chamber includes a first opening; and
a hydrodynamic bearing disposed between the hollow shaft and the main shaft, wherein the hydrodynamic bearing is configured to resist a load experienced by the hollow shaft; and
directing a fluid radially toward the stator ring during a rotation of the hollow shaft through the first opening, wherein the stator ring is configured to receive the fluid at a location that is substantially aligned with the first opening.
18 . The method of claim 17 , wherein the rotation of the hollow shaft is configured to propel fluid through the first opening toward the stator ring.
19 . The method of claim 17 , wherein the rotation of the hollow shaft is configured to propel the fluid through the first opening toward one or more end turns of the stator ring.
20 . The method of claim 17 , wherein an inner surface of the hollow shaft defines at least one fluid collection chamber with an outer surface of the main shaft, and the at least one fluid collection chamber is configured to accumulate the fluid between the hollow shaft and the main shaft.
21 . The method of claim 20 , wherein the electric propulsion system further comprises a passageway formed in the hollow shaft for transferring the fluid from the at least one fluid collection chamber to the at least one fluid distribution chamber.
22 . The method of claim 21 , wherein the passageway is configured to transfer the fluid due to the rotation of the hollow shaft.
23 . The method of claim 17 , wherein the at least one fluid distribution chamber includes at least one second opening positioned to direct the fluid toward the rotor during the rotation of the hollow shaft.
24 . The method of claim 23 , wherein the first opening and the at least one second opening are bleed holes.
25 . The method of claim 17 , wherein the electric motor assembly is configured to feed the fluid to the main shaft using a sump pump.
26 . The method of claim 17 , wherein the electric propulsion system further comprises a power inverter mounted to a first end of the housing, wherein the stator ring is configured to receive electricity from the power inverter.
27 . The method of claim 26 , wherein a portion of the main shaft extends beyond a second end of the housing opposite the first end.
28 . The method of claim 17 , wherein the fluid comprises oil.
29 . The method of claim 17 , wherein the internal volume is circular.
30 . The method of claim 17 , wherein the gear comprises a sun gear of the gear reduction.
31 . A motor assembly for an electric propulsion system, the motor assembly comprising:
a housing having an internal volume;
a stator ring disposed about a perimeter of the internal volume;
a rotor positioned within the stator ring;
a hollow shaft attached to the rotor, comprising a gear of a gear reduction;
at least one fluid distribution chamber located on an outer surface of the hollow shaft and configured to rotate with the hollow shaft,
wherein the at least one fluid distribution chamber comprises a first opening configured to radially distribute fluid to the stator and a second opening configured to radially distribute fluid to the rotor;
a main shaft connected to the hollow shaft via the gear reduction; and
a hydrodynamic bearing disposed between the hollow shaft and the main shaft, wherein the hydrodynamic bearing is configured to resist a load experienced by the hollow shaft.
32 . The motor assembly of claim 1 , further comprising a passageway formed in the hollow shaft for transferring the fluid to the fluid distribution chamber, wherein the passageway is axially spaced apart from a location that the hollow shaft abuts the hydrodynamic bearing.
33 . The motor assembly of claim 1 , wherein the hydrodynamic bearing comprises oil.