Inverter assembly and electric propulsion system

Abstract

To provide an electric propulsion system for vertical takeoff and landing (VTOL) aircrafts.SOLUTION: An electric propulsion system 1200A for vertical takeoff and landing (VTOL) aircrafts includes an electric motor assembly and an inverter assembly. The inverter assembly includes a housing, a capacitor assembly, at least one printed circuit board assembly (PCBA), and a plurality of positioning pins. The capacitor assembly includes a center hole, at least one capacitor, a capacitor housing 1234A having at least one bus bar, and a plurality of through-holes in the capacitor housing 1234A. The capacitor assembly and the at least one PCBA are positioned inside the housing. The positioning pins pass through the through-holes in the capacitor housing 1234A and the at least one PCBA and are connected to the housing.SELECTED DRAWING: Figure 12A

Description

[Technical Field]

[0001] CROSS-REFERENCE TO RELATED APPLICATIONS This disclosure claims priority to U.S. patent application Ser. No. 18 / 306,275, entitled "SYSTEMS, METHODS, AND MECHANICAL DESIGNS FOR INVERTERS FOR EVTOL AIRCRAFT," filed April 25, 2023, which claims priority to U.S. Provisional Application Ser. No. 63 / 378,536, entitled "Tilt Rotor Systems and Methods for eVTOL Aircraft," filed October 6, 2022, and U.S. Provisional Application Ser. No. 63 / 378,680, entitled "Systems and Methods for Improved Propulsion Systems for eVTOL Aircraft," filed October 7, 2022, the contents of which are incorporated herein by reference in their entirety for all purposes.

[0002] The present disclosure relates generally to the field of powered aerial vehicles. More specifically, but not by way of limitation, the present disclosure relates to innovations in aircraft powered by electric propulsion systems. Certain aspects of the present disclosure generally relate to improvements in electric engines, gearboxes, and power inverters that provide particular advantages in aerial vehicles and other types of vehicles powered by electric propulsion systems. Summary of the Invention

[0003] This disclosure primarily addresses systems, components, and technologies for use in non-traditional aircraft powered by electric propulsion systems. For example, a tiltrotor aircraft of the present disclosure may be configured for frequent (e.g., more than 50 flights per working day), short-duration flights (e.g., less than 100 miles per flight) to and from densely populated areas. The aircraft may be configured to carry four to six passengers or commuters who expect a comfortable experience with low noise and vibration. Therefore, it may be desirable for the aircraft's components to be configured and designed to withstand frequent use without wear, to generate less heat and vibration, and for the aircraft to include mechanisms for effectively controlling and managing the heat or vibration generated by the components. Furthermore, some of these aircraft may be intended to operate in close proximity to each other over congested metropolitan areas. Therefore, it may be desirable for the components to be configured and designed to generate low levels of noise both inside and outside the aircraft and to have various safety and backup mechanisms. For example, for safety reasons, it may be desirable for an aircraft to be propelled by a distributed propulsion system, avoiding the risk of a single point of failure, and capable of conventional takeoff and landing on a runway. Furthermore, it may be desirable for an aircraft to be able to safely take off and land vertically from or in a relatively small or restricted space (e.g., a vertiport, parking lot, or driveway) compared to a conventional airport runway, while carrying several passengers or commuters along with their associated baggage. These service requirements may impose design constraints on the size, weight, and operational efficiency (e.g., drag, energy use) of the aircraft, which may affect the design and configuration of aircraft components.

[0004] The disclosed embodiments provide new and improved configurations of aircraft components not observed in conventional aircraft and / or identified design criteria for components that differ from conventional aircraft components. Such alternative configurations and design criteria have resulted in the disclosed embodiments herein for various configurations and designs of components for aircraft powered by electric propulsion systems, in combination to address shortcomings and challenges of conventional components.

[0005] In some embodiments, an aircraft powered by an electric propulsion system may be designed to be capable of both vertical and conventional takeoff and landing, with a distributed electric propulsion system enabling vertical flight, horizontal and lateral flight, and transitions. Thrust may be generated by supplying high-voltage power to multiple electric engines of the distributed electric propulsion system, which may include the components necessary to convert the high-voltage power into mechanical shaft power to rotate propellers. Embodiments disclosed herein may involve optimizing the energy density of the electric propulsion system. Embodiments may include an electric engine connected to an onboard power source, which may include a device capable of storing energy, such as a battery or capacitor, and one or more systems for harnessing or generating electricity, such as a fuel-powered generator or a solar panel array. Some disclosed embodiments provide direct current (DC) to alternating current (AC) conversion via an inverter assembly to enable more powerful AC motors. Some disclosed embodiments provide weight and space reduction for components within the aircraft, increasing the efficiency and performance of the aircraft. The disclosed embodiments also improve safety in passenger transportation by using new and improved safety protocols and system redundancy in the event of a failure to minimize any single point of failure in the aircraft propulsion system. Some disclosed embodiments also provide new and improved approaches to meeting and exceeding aviation and transportation laws and regulations. For example, the Federal Aviation Administration implements federal laws and regulations that require safety components, such as fire barriers, adjacent to engines that use oil or other flammable materials in amounts above a threshold. A fire barrier may include an engine component or an aircraft component that is designed, constructed, or installed primarily to prevent dangerous amounts of air, fluid, or flame from passing around or through the fire barrier and / or to protect against corrosion. In some embodiments, a fire barrier may include a component that is separated from additional components, as described herein.Those skilled in the art will understand which components within an aircraft, including within an electric propulsion system, serve the primary function of being a fire barrier. In some embodiments, a fire barrier may include a firewall, fire barrier, fire-resistant barrier, flame-retardant barrier, or other barrier that can ensure that dangerous amounts of air, fluid, or flame do not pass around or through the barrier and / or that can protect against corrosion. For example, a fuselage may be constructed to prevent dangerous amounts of air, fluid, or flame from passing around or through the fire barrier and / or to protect against corrosion, but the fuselage may not be considered a fire barrier because its primary purpose is not to be a fire barrier. In some embodiments, an electric propulsion system provides efficient and effective lubrication and cooling using oil below a threshold level, resulting in an aircraft that does not require an engine fire barrier, maximizing performance and efficiency while saving weight on the aircraft.

[0006] In some embodiments, the distributed electric propulsion system may include 12 electric engines that may be mounted on forward and aft booms of the aircraft's wings. A subset of the electric engines, such as those mounted forward of the wings, may be tiltable in flight between a horizontal position (e.g., generating forward thrust for cruise) and a vertical position (e.g., generating vertical lift for takeoff, landing, and hovering). The propellers of the forward electric engines may rotate in a clockwise or counterclockwise direction. The propellers may be counter-rotating relative to adjacent propellers. The aft electric engines may be fixed in a vertical position (e.g., generating vertical lift). The propellers may also rotate in a clockwise or counterclockwise direction. In some embodiments, the difference in rotational direction may be achieved using engine rotation direction. In other embodiments, the engines may all rotate in the same direction, and gearing may be used to achieve different propeller rotation directions.

[0007] In some embodiments, an aircraft may possess a quantity of electric engines in various combinations of forward and aft engine configurations. For example, an aircraft may possess six forward and six aft electric engines, four forward and four aft electric engines, or any other combination of forward and aft electric engines, including embodiments in which the number of forward and aft electric engines is unequal.

[0008] In some embodiments, for vertical take-off and landing (VTOL) missions, the forward and aft electric engines may provide vertical thrust during take-off and landing. During forward flight phases, the forward electric engine may provide horizontal thrust, while the aft electric engine's propeller may be retracted in a fixed position to minimize drag. The aft electric engine may be actively retracted with position monitoring. Transition from vertical to horizontal flight and vice versa may be achieved via a tilt propeller subsystem. The tilt propeller subsystem may redirect thrust between a primarily vertical orientation during vertical flight mode to a horizontal or near-horizontal orientation during the forward flight cruise phase. A variable pitch mechanism may vary the collective angle of the forward electric engine's propeller hub assembly blades for operation during the hover, transition, and cruise phases.

[0009] In some embodiments, for conventional takeoff and landing (CTOL) missions, the forward electric engine may provide horizontal thrust for fixed-wing takeoff, cruise, and landing, and the wing may provide vertical lift. In some embodiments, the aft electric engine need not be used to generate thrust during CTOL missions, and the aft propeller may be stowed in place. In other embodiments, the aft electric engine may be used at reduced power to shorten the length of a CTOL takeoff or landing.

[0010] In some embodiments, an inverter assembly for converting direct current (DC) power to alternating current (AC) power for an electric propulsion system may include a housing, a capacitor assembly, at least one printed circuit board assembly (PCBA), and a plurality of locating pins. In some embodiments, the capacitor assembly may include a capacitor housing having a central hole, at least one capacitor, and at least one bus bar, and a plurality of through holes in the capacitor housing. In some embodiments, the capacitor assembly and the at least one PCBA are positioned within the housing. In some embodiments, a plurality of locating pins pass through the plurality of through holes in the capacitor housing and the at least one PCBA and are connected to the housing.

[0011] In some embodiments, an electric engine for a vertical take-off and landing aircraft may include or be connected to an inverter assembly. In some embodiments, a centerline of the inverter assembly may be aligned with a main shaft of the electric engine. In some embodiments, airflow driven by the electric engine may cool the inverter assembly, thereby managing operating temperatures and optimizing performance of the inverter assembly.

[0012] In some embodiments, the inverter assembly may have a housing with a rounded or other shape designed to minimize drag during flight. Additionally, the inverter assembly may be oriented such that the housing shape minimizes drag under different flight conditions. [Brief explanation of the drawings]

[0013] This patent or application contains at least one drawing executed in color. Copies of this patent or patent application publication with color drawing(s) will be provided by the Office upon request and payment of the necessary fee.

[0014] [Figure 1]FIG. 1 is a perspective view of an exemplary VTOL aircraft consistent with disclosed embodiments.

[0015] [Figure 2] FIG. 2 is another perspective view of an exemplary VTOL aircraft in an alternative configuration consistent with an embodiment of the present disclosure.

[0016] [Figure 3] FIG. 1 is a top view of an exemplary VTOL aircraft consistent with an embodiment of the present disclosure.

[0017] [Figure 4] FIG. 1 is a diagram illustrating an exemplary propeller rotation of a VTOL aircraft, consistent with disclosed embodiments.

[0018] [Figure 5] FIG. 1 is a schematic diagram illustrating exemplary power connections in a VTOL aircraft, consistent with disclosed embodiments.

[0019] [Figure 6] FIG. 1 is a block diagram illustrating an example architecture and design of an electric propulsion unit for a VTOL aircraft, consistent with disclosed embodiments.

[0020] [Figure 7] FIG. 1 is a schematic diagram illustrating an exemplary tilt electric propulsion system for a VTOL aircraft, consistent with disclosed embodiments.

[0021] [Figure 8A] FIG. 1 is a diagram of an exemplary tilt electric propulsion system for a VTOL aircraft, consistent with disclosed embodiments. [Figure 8B] FIG. 1 is a diagram of an exemplary tilt electric propulsion system for a VTOL aircraft, consistent with disclosed embodiments. [Figure 8C] FIG. 1 is a diagram of an exemplary tilt electric propulsion system for a VTOL aircraft, consistent with disclosed embodiments.

[0022] [Figure 9] FIG. 1 is a schematic diagram illustrating an exemplary ascent electric propulsion system for a VTOL aircraft, consistent with disclosed embodiments.

[0023] [Figure 10A] FIG. 1 is a diagram of an exemplary ascent electric propulsion system for a VTOL aircraft, consistent with disclosed embodiments. [Figure 10B] FIG. 1 is a diagram of an exemplary ascent electric propulsion system for a VTOL aircraft, consistent with disclosed embodiments.

[0024] [Figure 11A] 1 is a cross-sectional view of an exemplary electric propulsion system for a VTOL aircraft, consistent with disclosed embodiments. [Figure 11B] 1 is a cross-sectional view of an exemplary electric propulsion system for a VTOL aircraft, consistent with disclosed embodiments. [Figure 11C] 1 is a cross-sectional view of an exemplary electric propulsion system for a VTOL aircraft, consistent with disclosed embodiments.

[0025] [Figure 12A] 1 is a diagram and block diagram of an exemplary electric propulsion system for a VTOL aircraft, consistent with disclosed embodiments. [Figure 12B] 1 is a diagram and block diagram of an exemplary electric propulsion system for a VTOL aircraft, consistent with disclosed embodiments. [Figure 12C] 1 is a diagram and block diagram of an exemplary electric propulsion system for a VTOL aircraft, consistent with disclosed embodiments. [Figure 12D] 1 is a diagram and block diagram of an exemplary electric propulsion system for a VTOL aircraft, consistent with disclosed embodiments.

[0026] [Figure 13] FIG. 1 is an exploded view of an exemplary electric propulsion system for a VTOL aircraft, consistent with disclosed embodiments.

[0027] [Figure 14]FIG. 1 is an exploded view of an exemplary electric motor assembly for a VTOL aircraft, consistent with disclosed embodiments.

[0028] [Figure 15A] FIG. 1 is a diagram of a stator assembly for a VTOL aircraft, consistent with disclosed embodiments. [Figure 15B] FIG. 1 is a diagram of a stator assembly for a VTOL aircraft, consistent with disclosed embodiments. [Figure 15C] FIG. 1 is a diagram of a stator assembly for a VTOL aircraft, consistent with disclosed embodiments.

[0029] [Figure 16A] 1 is an exploded and cross-sectional view of a rotor assembly of a VTOL aircraft consistent with disclosed embodiments; [Figure 16B] 1 is an exploded and cross-sectional view of a rotor assembly of a VTOL aircraft consistent with disclosed embodiments; [Figure 16C] 1 is an exploded and cross-sectional view of a rotor assembly of a VTOL aircraft consistent with disclosed embodiments;

[0030] [Figure 17] FIG. 1 is an exploded view of a main shaft assembly for a VTOL aircraft, consistent with disclosed embodiments.

[0031] [Figure 18] FIG. 1 is a diagram of an exemplary sun gear for a VTOL aircraft, consistent with disclosed embodiments.

[0032] [Figure 19] FIG. 1 is a diagram of an exemplary ring gear for a VTOL aircraft, consistent with disclosed embodiments.

[0033] [Figure 20] FIG. 1 is a diagram of an exemplary carrier assembly for a VTOL aircraft, consistent with disclosed embodiments.

[0034] [Figure 21A] FIG. 1 is a diagram of an exemplary end bell assembly for a VTOL aircraft, consistent with disclosed embodiments. [Figure 21B] FIG. 1 is a diagram of an exemplary end bell assembly for a VTOL aircraft, consistent with disclosed embodiments.

[0035] [Figure 22] FIG. 1 is a diagram of an exemplary inverter assembly for a VTOL aircraft, consistent with disclosed embodiments.

[0036] [Figure 23] FIG. 1 is an exploded view of an inverter assembly for a VTOL aircraft, consistent with disclosed embodiments.

[0037] [Figure 24] FIG. 1 is a diagram of an exemplary printed circuit board assembly for a VTOL aircraft, consistent with disclosed embodiments.

[0038] [Figure 25A] 1 is a diagram and an exemplary front view of a heat exchanger for a VTOL aircraft, consistent with disclosed embodiments; [Figure 25B] 1 is a diagram and an exemplary front view of a heat exchanger for a VTOL aircraft, consistent with disclosed embodiments; [Figure 25C] 1 is a diagram and an exemplary front view of a heat exchanger for a VTOL aircraft, consistent with disclosed embodiments;

[0039] [Figure 26] FIG. 1 is a diagram of a heat exchanger for a VTOL aircraft, consistent with disclosed embodiments.

[0040] [Figure 27A] FIG. 1 is a diagram of a divider plate for a VTOL aircraft, consistent with disclosed embodiments. [Figure 27B] FIG. 1 is a diagram of a divider plate for a VTOL aircraft, consistent with disclosed embodiments.

[0041] [Figure 28] FIG. 1 is a diagram of a thermal plate for a VTOL aircraft, consistent with disclosed embodiments.

[0042] [Figure 29] FIG. 1 is a diagram of an electric propulsion system for a VTOL aircraft, consistent with disclosed embodiments.

[0043] [Figure 30A] FIG. 1 is a diagram of an exemplary electric propulsion system for a VTOL aircraft, consistent with disclosed embodiments. [Figure 30B] FIG. 1 is a diagram of an exemplary electric propulsion system for a VTOL aircraft, consistent with disclosed embodiments.

[0044] [Figure 31A] FIG. 1 is a cross-sectional view of an electric propulsion system for a VTOL aircraft, consistent with disclosed embodiments. [Figure 31B] FIG. 1 is a cross-sectional view of an electric propulsion system for a VTOL aircraft, consistent with disclosed embodiments.

[0045] [Figure 32A] 1A-1C are cross-sectional views of an electric propulsion system for a VTOL aircraft during various phases of flight, consistent with disclosed embodiments. [Figure 32B] 1A-1C are cross-sectional views of an electric propulsion system for a VTOL aircraft during various phases of flight, consistent with disclosed embodiments. [Figure 32C] 1A-1C are cross-sectional views of an electric propulsion system for a VTOL aircraft during various phases of flight, consistent with disclosed embodiments. [Figure 32D] 1A-1C are cross-sectional views of an electric propulsion system for a VTOL aircraft during various phases of flight, consistent with disclosed embodiments.

[0046] [Figure 33A] FIG. 1 is a schematic diagram illustrating an exemplary electric propulsion system for a VTOL aircraft with a fire barrier, consistent with disclosed embodiments. [Figure 33B]FIG. 1 is a schematic diagram illustrating an exemplary electric propulsion system for a VTOL aircraft with a fire barrier, consistent with disclosed embodiments. [Figure 33C] FIG. 1 is a schematic diagram illustrating an exemplary electric propulsion system for a VTOL aircraft with a fire barrier, consistent with disclosed embodiments.

[0047] [Figure 34A] FIG. 1 is a schematic diagram illustrating an exemplary electric propulsion system for a VTOL aircraft, consistent with disclosed embodiments. [Figure 34B] FIG. 1 is a schematic diagram illustrating an exemplary electric propulsion system for a VTOL aircraft, consistent with disclosed embodiments. [Figure 34C] FIG. 1 is a schematic diagram illustrating an exemplary electric propulsion system for a VTOL aircraft, consistent with disclosed embodiments. [Figure 34D] FIG. 1 is a schematic diagram illustrating an exemplary electric propulsion system for a VTOL aircraft, consistent with disclosed embodiments.

[0048] [Figure 35] FIG. 1 is a schematic diagram illustrating an exemplary electric propulsion system for a VTOL aircraft, consistent with disclosed embodiments.

[0049] [Figure 36A] FIG. 1 is a schematic diagram illustrating an exemplary electric propulsion system for a VTOL aircraft, consistent with disclosed embodiments. [Figure 36B] FIG. 1 is a schematic diagram illustrating an exemplary electric propulsion system for a VTOL aircraft, consistent with disclosed embodiments.

[0050] [Figure 37] FIG. 1 is a schematic diagram illustrating an exemplary electric propulsion system for a VTOL aircraft, consistent with disclosed embodiments.

[0051] [Figure 38]38A and 38B are schematic diagrams illustrating an example electric propulsion system for a VTOL aircraft and an example inverter assembly for the electric propulsion system, consistent with disclosed embodiments.

[0052] [Figure 39A] 1A-1C are cross-sectional and perspective views and schematic diagrams illustrating an exemplary electric propulsion system for a VTOL aircraft, consistent with disclosed embodiments. [Figure 39B] 1A-1C are cross-sectional and perspective views and schematic diagrams illustrating an exemplary electric propulsion system for a VTOL aircraft, consistent with disclosed embodiments. [Figure 39C] 1A-1C are cross-sectional and perspective views and schematic diagrams illustrating an exemplary electric propulsion system for a VTOL aircraft, consistent with disclosed embodiments. [Figure 39D] 1A-1C are cross-sectional and perspective views and schematic diagrams illustrating an exemplary electric propulsion system for a VTOL aircraft, consistent with disclosed embodiments.

[0053] [Figure 40A] 1A and 1B are diagrams and schematics illustrating an electric propulsion system for a VTOL aircraft, consistent with disclosed embodiments. [Figure 40B] 1A and 1B are diagrams and schematics illustrating an electric propulsion system for a VTOL aircraft, consistent with disclosed embodiments. [Figure 40C] 1A and 1B are diagrams and schematics illustrating an electric propulsion system for a VTOL aircraft, consistent with disclosed embodiments. [Figure 40D] 1A and 1B are diagrams and schematics illustrating an electric propulsion system for a VTOL aircraft, consistent with disclosed embodiments.

[0054] [Figure 41] FIG. 1 is a cross-sectional view of an electric propulsion system for a VTOL aircraft, consistent with disclosed embodiments.

[0055] [Figure 42A] FIG. 1 is a diagram of an exemplary electric propulsion system for a VTOL aircraft, consistent with disclosed embodiments. [Figure 42B] FIG. 1 is a diagram of an exemplary electric propulsion system for a VTOL aircraft, consistent with disclosed embodiments.

[0056] [Figure 43A] 1A and 1B are diagrams and schematics illustrating an exemplary electric propulsion system for a VTOL aircraft, consistent with disclosed embodiments. [Figure 43B] 1A and 1B are diagrams and schematics illustrating an exemplary electric propulsion system for a VTOL aircraft, consistent with disclosed embodiments. [Figure 43C] 1A and 1B are diagrams and schematics illustrating an exemplary electric propulsion system for a VTOL aircraft, consistent with disclosed embodiments. [Figure 43D] 1A and 1B are diagrams and schematics illustrating an exemplary electric propulsion system for a VTOL aircraft, consistent with disclosed embodiments.

[0057] [Figure 44A] FIG. 1 is a schematic diagram illustrating an exemplary electric propulsion system for a VTOL aircraft, consistent with disclosed embodiments. [Figure 44B] FIG. 1 is a schematic diagram illustrating an exemplary electric propulsion system for a VTOL aircraft, consistent with disclosed embodiments. [Figure 44C] FIG. 1 is a schematic diagram illustrating an exemplary electric propulsion system for a VTOL aircraft, consistent with disclosed embodiments.

[0058] [Figure 45A] FIG. 1 is a schematic diagram illustrating an exemplary electric propulsion system for a VTOL aircraft, consistent with disclosed embodiments. [Figure 45B] FIG. 1 is a schematic diagram illustrating an exemplary electric propulsion system for a VTOL aircraft, consistent with disclosed embodiments. [Figure 45C] FIG. 1 is a schematic diagram illustrating an exemplary electric propulsion system for a VTOL aircraft, consistent with disclosed embodiments. [Figure 45D] FIG. 1 is a schematic diagram illustrating an exemplary electric propulsion system for a VTOL aircraft, consistent with disclosed embodiments.

[0059] [Figure 46A] FIG. 1 is a schematic diagram illustrating an exemplary electric propulsion system for a VTOL aircraft, consistent with disclosed embodiments. [Figure 46B] FIG. 1 is a schematic diagram illustrating an exemplary electric propulsion system for a VTOL aircraft, consistent with disclosed embodiments.

[0060] [Figure 47A] 1A and 1B are schematic and cross-sectional views of an exemplary electric propulsion system for a VTOL aircraft, consistent with disclosed embodiments. [Figure 47B] 1A and 1B are schematic and cross-sectional views of an exemplary electric propulsion system for a VTOL aircraft, consistent with disclosed embodiments.

[0061] [Figure 48] FIG. 1 is a schematic diagram illustrating an exemplary electric propulsion system for a VTOL aircraft, consistent with disclosed embodiments.

[0062] [Figure 49] 1 is a cross-sectional view of an exemplary electric propulsion system for a VTOL aircraft, consistent with disclosed embodiments.

[0063] [Figure 50] FIG. 1 is a perspective view of an exemplary rotor for a VTOL aircraft, consistent with disclosed embodiments.

[0064] [Figure 51] 1 is a flowchart of an exemplary process for balancing a rotor of a VTOL aircraft, consistent with disclosed embodiments.

[0065] [Figure 52] 10 is another flowchart of an exemplary process for balancing a rotor assembly of a VTOL aircraft, consistent with disclosed embodiments.

[0066] [Figure 53] 1 is a flowchart of an exemplary process for transferring torque from an electric motor assembly to a propeller assembly of a VTOL aircraft, consistent with disclosed embodiments.

[0067] [Figure 54] FIG. 1 is a schematic diagram of an exemplary electric motor assembly in partial cross section.

[0068] [Figure 55A] 1 is a view of an inner surface of an example rotor hub and an example end plate, consistent with disclosed embodiments. [Figure 55B] 1 is a view of an inner surface of an example rotor hub and an example end plate, consistent with disclosed embodiments.

[0069] [Figure 55C] 10 is a simulation result of air velocity and pressure distribution within a case consistent with disclosed embodiments.

[0070] [Figure 55D] 1 illustrates an exemplary inner side view of an end plate consistent with a disclosed embodiment.

[0071] [Figure 56A] FIG. 1 illustrates a cross-sectional view of a press-in mesh port consistent with a disclosed embodiment.

[0072] [Figure 56B] FIG. 10 illustrates a cross-sectional view of an installed press-in mesh port when operating in a tilted position, consistent with a disclosed embodiment.

[0073] [Figure 57] FIG. 10 is a cross-sectional perspective view of an integrated sensor on a power board consistent with disclosed embodiments.

[0074] [Figure 58]FIG. 1 is a perspective view of a flexible PCBA connection consistent with a disclosed embodiment.

[0075] [Figure 59] FIG. 59 is a cross-sectional view of the serpentine connection of the flexible PCBA shown in FIG. 58, showing a partial cut-out consistent with a disclosed embodiment.

[0076] [Figure 60A] 1 is a diagram of a capacitor housing showing alignment pins, consistent with a disclosed embodiment;

[0077] [Figure 60B] FIG. 10 is a diagram of a thermal plate and heat exchanger showing mating alignment pins, consistent with a disclosed embodiment. DETAILED DESCRIPTION OF THE INVENTION

[0078] The disclosed embodiments provide systems, subsystems, and components for new VTOL aircraft with various combinations of electric propulsion and cooling systems that maximize performance while minimizing weight.

[0079] In some embodiments, the electric propulsion systems described herein may generate thrust by supplying high-voltage (HV) power to an electric engine, which in turn converts the HV power into mechanical shaft power used to rotate a propeller. The aircraft described herein may include multiple electric engines mounted fore and aft of the wings. The engines may be mounted directly to the wings or on one or more booms attached to the wings. The amount of thrust generated by each electric engine may be controlled by torque commands from a flight control system (FCS) via a digital communication interface to each electric engine. Embodiments may include forward electric engines capable of changing their orientation, or cant. Some embodiments include forward engines that may be clockwise (CW) or counterclockwise (CCW) types. The forward electric propulsion subsystem may consist of a multi-blade adjustable pitch propeller as well as a variable pitch subsystem.

[0080] In some embodiments, the aircraft may include an aft electric engine or lifter, which may be of the clockwise (CW) or counterclockwise (CCW) type. Some embodiments may include an aft electric engine that utilizes a multi-blade fixed pitch propeller.

[0081] As described herein, the orientation and use of electric propulsion system components may vary throughout the operation of the aircraft. In some embodiments, during vertical takeoff and landing, the forward propulsion system and the aft propulsion system may provide vertical thrust during takeoff and landing. During flight phases in which the aircraft is in forward flight mode, the forward propulsion system may provide horizontal thrust, while the aft propulsion system propellers may be retracted in a fixed position to minimize drag. The aft electric propulsion system may be actively retracted while providing position monitoring. Some embodiments may include transitioning from vertical flight to horizontal flight and vice versa. In some embodiments, the transition may be achieved via a tilt propeller system (TPS). The TPS redirects thrust between a primarily vertical direction during vertical flight mode and a primarily horizontal direction during forward flight mode. Some embodiments may include a variable pitch mechanism that can change the collective angle of the forward propulsion system propeller blades for operation during hover, cruise, and transition phases. Some embodiments may include a conventional takeoff and landing (CTOL) configuration, with the tilter providing horizontal thrust for fixed-wing takeoff, cruise, and landing phases. In some embodiments, the aft electric engine is not used to generate thrust during CTOL missions, and the aft propeller is stowed in place to minimize drag.

[0082] In some embodiments, the electric engines described herein may possess design features to mitigate and prevent uncontained fires, such as utilizing non-hazardous amounts of flammable fluid contained in both the tilt engine and the lift engine. For example, in some embodiments, the electric engine may be configured to utilize less than one quart of oil or another flammable fluid. Some embodiments may include an electric engine containing a non-hazardous amount of air so that any fire cannot be sustained for a duration that could allow it to migrate to another portion of the aircraft. In some embodiments, the non-hazardous amount of air may be in contact with flammable liquid throughout the electric engine. Some examples may include an electric engine containing up to 1 liter, 2 liters, 3 liters, 4 liters, 5 liters, 10 liters, or 20 liters of air within the electric engine housing. In some embodiments, the amount of air present within the electric engine housing may have a fixed ratio to the amount of oil or other cooling liquid present within the electric propulsion system. Such a ratio may be driven by a determination of the sufficient amount of heat required to adequately cool the electric propulsion system. Some embodiments may include an approximately 3:1 ratio of air to oil present within the electric propulsion system. Some embodiments may include an electric engine housing in which 75% of the open volume, i.e., the interior volume not occupied by the electric engine components, is comprised of air, and 25% of the open volume is comprised of oil or some other liquid for cooling and / or lubrication. Some embodiments may also be configured without a nominal ignition source within the electric engine, may possess an engine that exceeds temperature operating limits that may be more than 50°C below the flammable fluid auto-ignition temperature, and may possess overheat detection and protection, overvoltage detection and protection, and / or overcurrent detection and protection. Furthermore, some embodiments may include an electric propulsion system in which the bulk temperature of the electric propulsion system is below the auto-ignition temperature and flash point of the oil or other liquid present in the electric propulsion system under all normal operating conditions. In some embodiments, abnormal conditions that increase the bulk electric propulsion system temperature may lead to a system response that prevents the oil or other liquid, flash point, and auto-ignition temperature from being exceeded.In some embodiments, the ratio of air to oil or other liquid may be such that if a fire occurs within the electric engine housing, including if an arc causes a fire, the amount of air present within the electric engine housing may prevent the fire from spreading to other areas of the aircraft. In some embodiments, these and other design features may result in the electric engine being considered not to be in a fire zone designated by one or more guidelines or regulations.

[0083] Reference will now be made in detail to the exemplary embodiments, examples of which are illustrated in the accompanying drawings. The following description refers to the accompanying drawings, in which like numbers in different drawings represent the same or similar elements, unless otherwise indicated. The implementations set forth in the following description of the exemplary embodiments do not represent all implementations consistent with the present disclosure. Instead, they are merely examples of apparatus and methods consistent with aspects related to the subject matter set forth in the appended claims.

[0084] A. Exemplary Electric Aircraft Features FIG. 1 is a perspective view of an exemplary VTOL aircraft consistent with disclosed embodiments. FIG. 2 is another view of a perspective view of an exemplary VTOL aircraft in an alternative configuration consistent with embodiments of the present disclosure. FIGS. 1 and 2 respectively illustrate VTOL aircraft 100, 200 in a cruise configuration and a vertical takeoff, landing, and hovering configuration (also referred to herein as a "climb" configuration) consistent with embodiments of the present disclosure. Corresponding elements in FIGS. 1 and 2 may bear similar numerals and may refer to similar elements of the aircraft 100, 200. The aircraft 100, 200 may include a fuselage 102, 202, wings 104, 204 attached to the fuselage 102, 202, and one or more aft stabilizers 106, 206 attached to the aft portion of the fuselage 102, 202. Multiple lift propellers 112, 212 may be attached to the wings 104, 204 and configured to provide lift for vertical takeoff, landing, and hovering. Multiple tilt propellers 114, 214 may be mounted on wings 104, 204 and may be tiltable between a climb configuration, as shown in Figure 2, that provides a portion of the lift required for vertical takeoff, landing, and hovering, and a cruise configuration, as shown in Figure 1, that provides forward thrust to the aircraft 100 for horizontal flight. As used herein, a tilt propeller climb configuration refers to any tilt propeller orientation in which the tilt propeller thrust is primarily providing lift to the aircraft, and a tilt propeller cruise configuration refers to any tilt propeller orientation in which the tilt propeller thrust is primarily providing forward thrust to the aircraft.

[0085] In some embodiments, the lift propellers 112, 212 may be configured to provide only lift, with all horizontal propulsion being provided by the tilt propellers. Thus, the lift propellers 112, 212 may be configured in a fixed position and may generate thrust only during the takeoff, landing, and hovering phases of flight. Meanwhile, the tilt propellers 114, 214 may be tilted upward into a lift configuration in which thrust from the propellers 114, 214 is directed downward to provide additional lift.

[0086] For forward flight, the tilt propellers 114, 214 may tilt from their climb configuration to their cruise configuration. In other words, the orientation of the tilt propellers 114, 214 may change from an orientation in which the tilt propeller thrust is directed downward (to provide lift during vertical takeoff, landing, and hovering) to an orientation in which the tilt propeller thrust is directed rearward (to provide forward thrust for the aircraft 100, 200). The tilt propeller assembly for a particular electric engine may tilt about an axis of rotation defined by the attachment point connecting the boom and the electric engine. When the aircraft 100, 200 is in full forward flight, lift may be provided entirely by the wings 104, 204. Meanwhile, in the cruise configuration, the lift propellers 112, 212 may be shut off. The blades 120, 220 of the lift propellers 112, 212 may be held in a low-drag position for aircraft cruise. In some embodiments, the lift propellers 112, 212 may each have two blades 120, 220 that can be locked for cruising in a minimum-drag position, with one blade immediately ahead of the other, as illustrated in FIG. 1. In some embodiments, the lift propellers 112, 212 have three or more blades. In some embodiments, the tilt propellers 114, 214 may include more blades 116, 216 than the lift propellers 112, 212. For example, as illustrated in FIGS. 1 and 2, the lift propellers 112, 212 may each include, for example, two blades, while the tilt propellers 114, 214 may each include more blades, such as the five blades shown. In some embodiments, the tilt propellers 114, 214 may each have two to five blades, or possibly more, depending on the design considerations and requirements of the aircraft.

[0087] In some embodiments, the aircraft may include a single wing 104, 204 on each side of the fuselage 102, 202 (or a single wing extending across the entire aircraft). At least a portion of the lift propellers 112, 212 may be located aft of the wings 104, 204, and at least a portion of the tilt propellers 114, 214 may be located forward of the wings 104, 204. In some embodiments, all of the lift propellers 112, 212 may be located aft of the wings 104, 204, and all of the tilt propellers 114, 214 may be located forward of the wings 104, 204. According to some embodiments, all of the lift propellers 112, 212 and tilt propellers 114, 214 may be mounted on the wings, i.e., the lift propellers or tilt propellers may not be mounted on the fuselage. In some embodiments, the lift propellers 112, 212 may all be located aft of the wings 104, 204, and the tilt propellers 114, 214 may all be located forward of the wings 104, 204. According to some embodiments, all of the lift propellers 112, 212 and tilt propellers 114, 214 may be positioned inboard of the ends of the wings 104, 204.

[0088] In some embodiments, the lift propellers 112, 212 and tilt propellers 114, 214 may be attached to the wings 104, 204 by booms 122, 222. The booms 122, 222 may be attached below the wings 104, 204, above the wings, and / or integrated into the wing profile. In some embodiments, the lift propellers 112, 212 and tilt propellers 114, 214 may be attached directly to the wings 104, 204. In some embodiments, one lift propeller 112, 212 and one tilt propeller 114, 214 may be attached to each boom 122, 222. The lift propellers 112, 212 may be attached to the aft end of the booms 122, 222, and the tilt propellers 114, 214 may be attached to the forward end of the booms 122, 222. In some embodiments, the lift propeller 112, 212 may be mounted in a fixed position on the boom 122, 222. In some embodiments, the tilt propeller 114, 214 may be mounted via a hinge to the forward end of the boom 122, 222. The tilt propeller 114, 214 may be mounted to the boom 122, 222 such that when in its cruise configuration, the tilt propeller 114, 214 is aligned with the body of the boom 122, 222 and forms a continuous extension of the forward end of the boom 122, 222 that minimizes drag for forward flight.

[0089] In some embodiments, the aircraft 100, 200 may include, for example, one wing on each side of the fuselage 102, 202 or a single wing extending across the aircraft. According to some embodiments, at least one wing 104, 204 is a high wing mounted on the upper side of the fuselage 102, 202. According to some embodiments, the wing includes control surfaces such as flaps and / or ailerons. According to some embodiments, the wing 104, 204 may be designed with a profile that reduces drag during forward flight. In some embodiments, the wing tip profile may be curved and / or tapered to minimize drag.

[0090] In some embodiments, the aft stabilizer 106, 206 includes control surfaces such as one or more rudders, one or more elevators, and / or one or more combined rudder-elevators. The wing(s) may have any suitable design. In some embodiments, the wing has a tapered leading edge.

[0091] In some embodiments, the lift propeller 112, 212 or tilt propeller 114, 214 can tilt relative to at least one other lift propeller 112, 212 or tilt propeller 114, 214. As used herein, canting refers to the relative orientation of the lift / tilt propeller's axis of rotation about a line parallel to the longitudinal direction, similar to the roll degree of freedom of an aircraft. Tilting of the lift and / or tilt propeller can help minimize damage from propeller bursts and provide enhanced yaw control during flight by orienting the plane of rotation of the lift / tilt propeller disk (the blades and the hub to which they are attached) so as not to intersect critical parts of the aircraft (areas of the fuselage where personnel may be positioned, critical flight control systems, batteries, adjacent propellers, etc.) or other propeller disks.

[0092] FIG. 3 is a top view of an exemplary VTOL aircraft consistent with embodiments of the present disclosure. The aircraft 300 shown in the figure may be a top view of the aircraft 100, 200 shown in FIGS. 1 and 2, respectively. As discussed herein, the aircraft 300 may include 12 electric propulsion systems distributed across the aircraft 300. In some embodiments, the distribution of the electric propulsion systems may include six forward electric propulsion systems 314 and six aft electric propulsion systems 312 mounted on forward and aft booms of the main wing 304 of the aircraft 300. In some embodiments, the length of the aft end of the boom 324 from the wing 304 to the lift propeller 312 may include similar aft ends of the length of the boom 324 across multiple aft ends of the boom. In some embodiments, the length of the aft end of the boom may vary across the exemplary six aft ends of the boom. For example, each aft end of the boom 324 may include a different length from the wing 304 to the lift propeller 312, or a subset of the aft ends of the boom may be similar in length. In some embodiments, the forward end of the boom 322 may include various lengths from the wing 304 to the tilt propeller 314 across the forward end of the boom. For example, as shown in FIG. 3 , the length of the forward end of the boom 322 from the tilt propeller 314 closest to the fuselage to the wing 304 may include a longer length than the length of the forward end of the boom 322 from the wing 304 to the tilt propeller 314 farthest from the fuselage. Some embodiments may include forward ends of the booms having similar lengths across the example six forward ends of the booms, or any other distribution of the lengths of the forward ends of the booms from the wing 304 to the tilt propeller 314. Some embodiments may include an aircraft 300 with eight electric propulsion systems, having four forward electric propulsion systems 314 and four aft electric propulsion systems 312, or any other distribution of forward and aft electric propulsion systems, including embodiments in which the number of forward electric propulsion systems 314 is less than or greater than the number of aft electric propulsion systems 312. Additionally, FIG. 3 depicts an exemplary embodiment of VTOL aircraft 300 with forward propeller 314 oriented horizontally for horizontal flight and aft propeller blades 320 in a stowed position for forward flight.

[0093] As disclosed herein, the forward and aft electric propulsion systems may be clockwise (CW) or counterclockwise (CCW) types. Some embodiments may include a variety of forward electric propulsion systems having a mixture of both CW and CCW types. In some embodiments, the aft electric propulsion system may possess a mixture of CW and CCW types of systems among the aft electric propulsion systems.

[0094] FIG. 4 is a schematic diagram illustrating example propeller rotation for a VTOL aircraft consistent with disclosed embodiments. The aircraft 400 shown in the figure may be a top view of the aircraft 100, 200, and 300 shown in FIGS. 1, 2, and 3, respectively. The aircraft 400 may include six forward electric propulsion systems, with three of the forward electric propulsion systems being CW type 424 and the remaining three forward electric propulsion systems being CCW type. In some embodiments, the three aft electric propulsion systems may be CCW type 428 and the remaining three aft electric propulsion systems are CW type 430. Some embodiments may include the aircraft 400 with four forward electric propulsion systems and four aft electric propulsion systems, each having two CW type and two CCW type. In some embodiments, the propellers may counter-rotate relative to adjacent propellers to cancel torque steer generated by the propeller rotation and experienced by the aircraft fuselage or wings. In some embodiments, the difference in rotation direction may be achieved using engine rotation direction. In other embodiments, the engines may all rotate in the same direction and gearing may be used to achieve different propeller rotation directions.

[0095] Some embodiments may include an aircraft 400 possessing forward and aft electric propulsion systems, where the amount of CW type 424 and CCW type 426 is unequal between the forward electric propulsion systems, between the aft electric propulsion systems, or between the forward and aft electric propulsion systems.

[0096] FIG. 5 is a schematic diagram illustrating example power connections in a VTOL aircraft, consistent with disclosed embodiments. The VTOL aircraft may have various power systems connected to diagonally opposed electric propulsion systems. In some embodiments, the power systems may include high-voltage power systems. Some embodiments may include high-voltage power systems connected to the electric engines via high-voltage channels. In some embodiments, the aircraft 500 may include six power systems including batteries 526, 528, 530, 532, 534, and 536 housed within wings 570 of the aircraft 500. In some embodiments, the aircraft 500 may include six forward electric propulsion systems having six electric engines 502, 504, 506, 508, 510, and 512 and six aft electric propulsion systems having six electric engines 514, 516, 518, 520, 522, and 524. In some embodiments, the batteries may be connected to the diagonally opposed electric engines. In such a configuration, first power system 526 may supply power to electric engine 502 via power connection channel 538 and may supply power to electric engine 524 via power connection channel 540. In some embodiments, first power system 526 may be paired with fourth power system 532 via power connection channel 542 that has a fuse to prevent excessive current from flowing through power systems 526 and 532. Further to this embodiment, VTOL air vehicle 500 may include second power system 528 that is paired with fifth power system 534 via power connection channel 548 that has a fuse, and may supply power to electric engines 510 and 516 via power connection channels 544 and 546, respectively. In some embodiments, third power system 530 may be paired with sixth power system 536 via fused power connection channel 554 and may supply power to electric engines 506 and 520 via power connection channels 550 and 552, respectively. Fourth power system 532 may also supply power to electric engines 508 and 518 via power connection channels 556 and 558, respectively. Fifth power system 534 may also supply power to electric engines 504 and 522 via power connection channels 560 and 562, respectively.Sixth power system 536 may also provide power to electric engines 512 and 514 via power connection channels 564 and 566, respectively.

[0097] As disclosed herein, an electric propulsion system may include an electric engine connected to a high-voltage power system, such as batteries located within the aircraft, via a high-voltage channel or power connection channel. Some embodiments may include various batteries housed within the aircraft wings with high-voltage channels going to the electric propulsion systems throughout the aircraft, including the wings and boom. In some embodiments, multiple high-voltage power systems may be used to create an electric propulsion system with multiple high-voltage power sources to avoid the risk of a single point of failure. In some embodiments, an aircraft may include multiple electric propulsion systems that may be wired to various batteries or power sources housed throughout the aircraft. It is recognized that such a configuration may be beneficial to avoid the risk of a single point of failure, where a failure of one battery or power source could result in a portion of the aircraft being unable to maintain the amount of thrust required to continue flight or perform a controlled landing. For example, if a VTOL possessed two forward electric propulsion systems and two aft electric propulsion systems, the forward electric propulsion system and the aft electric propulsion system on opposite sides of the VTOL aircraft may be connected to the same high-voltage power system. In such a configuration, if one high-voltage power system fails, the forward and aft electric propulsion systems on opposite sides of the VTOL aircraft may remain operational, providing a more balanced flight or landing compared to failed forward and aft electric propulsion systems on the same side of the VTOL aircraft. Some embodiments may include four forward electric propulsion systems and four aft electric propulsion systems, with diagonally opposed electric engines connected to a common battery or power source. Some embodiments may include various configurations of electric engines electrically connected to the high-voltage power systems, such that in the event of a power failure, the risk of a single point of failure is avoided, and the flight phase in which the failure occurs may continue, or the aircraft may perform an alternate phase of flight in response to the failure.

[0098] As discussed above, an electric propulsion system may include an electric engine that provides mechanical shaft power to a propeller assembly to generate thrust. In some embodiments, the electric engine of an electric propulsion system may include a high-voltage power grid that supplies high-voltage power to the electric engine and / or a low-voltage grid that supplies low-voltage DC power to the electric engine. Some embodiments may include the electric engine(s) in digital communication with a flight control system (“FCS”) that includes a flight control computer (“FCC”) that may send and receive signals to and from the electric engine including command and response data or status. Some embodiments may include the electric engine capable of receiving operating parameters from the FCC and communicating the operating parameters to the FCC, including speed, voltage, current, torque, temperature, vibration, propeller position, and any other value of the operating parameter.

[0099] In some embodiments, the flight control system may include a system that communicates with the electric engines and can send and receive analog / discrete signals to the electric engines to control devices that can redirect the thrust of the tilt propellers between a primarily vertical orientation in vertical flight mode and a primarily horizontal orientation in forward flight mode. In some embodiments, this system may be referred to as a tilt propeller system (“TPS”) and may be capable of communicating and directing additional features of the electric propulsion system.

[0100] FIG. 6 illustrates a block diagram of an example architecture and design of an electric propulsion unit 600 consistent with disclosed embodiments. In some embodiments, electric propulsion system 602 may include an electric engine subsystem 604 that may provide torque to a propeller subsystem 606 via a shaft to generate thrust for electric propulsion system 602. Some embodiments may include electric engine subsystem 604 receiving low-voltage DC (LV DC) power from a low-voltage power system (LVS) 608. Some embodiments may include electric engine subsystem 604 receiving high-voltage (HV) power from a high-voltage power system (HVPS) 610 that includes at least one battery or other device capable of storing energy. In some embodiments, the high-voltage power system may include two or more batteries or other devices capable of storing energy and providing high-voltage power to electric engine subsystem 604. It is recognized that such a configuration may be advantageous in that failure of a single battery does not risk a single point of failure that could lead to failure of electric propulsion system 602.

[0101] Some embodiments may include an electric propulsion system 602 including an electric engine subsystem 604 that receives signals from and sends signals to a flight control system 612. In some embodiments, the flight control system 612 may include a flight control computer that can send commands to and receive status and data from the electric engine subsystem 604 using controller area network (“CAN”) data bus signals. While CAN data bus signals are used between the flight control computer and the electric engine(s), it should be understood that some embodiments may include any form of communication capable of sending and receiving data from the flight control computer to the electric engine(s). In some embodiments, the flight control system 612 may also include a tilt propeller system (“TPS”) 614 that can send and receive analog discrete data to and from the tilt propeller electric engine subsystem 604. The tilt propeller system 614 may include devices that communicate operating parameters to the electric engine subsystem 604 and that can articulate the orientation of the propeller subsystem 606 to redirect tilt propeller thrust during various phases of flight using mechanical means such as gearbox assemblies, linear actuators, and any other configuration of components for changing the orientation of the propeller subsystem 606.

[0102] As discussed throughout, exemplary VTOL aircraft may possess various types of electric propulsion systems, including tilt and lift propellers, including forward electric engines that have the ability to tilt during various phases of flight, and aft electric engines that may remain in one orientation and be active only during certain phases of flight (i.e., takeoff, landing, and hovering).

[0103] FIG. 7 is a schematic diagram illustrating an exemplary tilt electric propulsion system for a VTOL aircraft consistent with disclosed embodiments. The tiltable electric propulsion system 700 may include an electric engine assembly 702 aligned along a shaft 724 connected to an output shaft 738 mechanically coupled to a propeller assembly 720 comprising a hub, a spinner, and tilting propeller blades. In some embodiments, the electric engine assembly 702 may include a motor and gearbox assembly 704 aligned along and mechanically coupled to the shaft 724. In some embodiments, the motor and gearbox assembly 704 may include an electric motor assembly comprising a stator 706 and a rotor 708. As shown in FIG. 7 and in some embodiments, the stator 706 may include multiple stator windings connected to an inverter 716. In such a configuration, the stator 706 may incorporate one or more redundancies such that if one or more sets of windings fail, power can still be transferred to the stator 706 through one or more remaining windings, such that the electric engine assembly 702 retains power and continues to generate thrust at the propeller assembly 720.

[0104] In some embodiments, motor and gearbox assembly 704 may include a gearbox 710 aligned along shaft 724 to provide a gear reduction between torque on shaft 724 from an electric engine assembly including stator 706 and rotor 708 and output shaft 738. Torque applied to output shaft 738 may be transmitted to propeller assembly 720. Some embodiments may include gearbox 710 including an oil pump. In such embodiments, the oil pump may drive the circulation of oil throughout motor and gearbox assembly 704 at a speed equivalent to the rotation of output shaft 738 to cool and lubricate gearbox and electric motor components. In some embodiments, the oil pump may drive the circulation of oil at a speed greater than or less than the rotation of output shaft 738. Some embodiments of motor and gearbox assembly 704 may include a propeller position sensor 712 present within the housing that may detect a magnetic field generated by the electric engine assembly to determine propeller position. Further embodiments may include a propeller position sensor 712 that is powered by the inverter 716 and transmits collected data to the inverter 716 .

[0105] In some embodiments, electric engine assembly 702 may also include an inverter assembly 714 substantially aligned along shaft 724. Inverter assembly 714 may include an inverter 716 and an inverter power supply 740. Inverter power supply 740 may receive low-voltage DC power from a low-voltage system 734 located outside electric engine assembly 702. Inverter power supply 740 may receive low-voltage DC power from a high-voltage power system 732 located outside electric engine assembly 702 that has been converted to low-voltage DC power via a DC-DC converter 742. Inverter 716 may supply high-voltage alternating current (AC) via at least one three-phase winding to a stator 706 of the electric engine assembly located within motor and gearbox assembly 704. Inverter assembly 714 may include inverter 716, which may receive flight control data from a flight control computing subsystem 736.

[0106] In some embodiments, motor and gearbox 704 may be located between inverter assembly 714 and propeller assembly 720. Some embodiments may also include a divider plate 744 coupled to motor and gearbox assembly 704 and inverter assembly 714. Divider plate 744 may create an enclosed environment for the upper part of motor and gearbox assembly 704 via the end bell assembly and for the lower part of inverter assembly 714 via the thermal plate. In some embodiments, divider plate 744 may serve as an integrated mounting bracket to support heat exchanger 718. Heat exchanger 718 may include, for example, folded fins or other types of heat exchangers. In some embodiments, electric propulsion system 700 may circulate oil or other coolant throughout electric engine assembly 702, motor and gearbox assembly 704, or inverter assembly 714 to transfer heat generated from the components to the oil or other coolant liquid. Heated oil or other coolant liquid may be circulated through the heat exchanger 718 to transfer heat to an airflow 722 passing through the fins of the heat exchanger.

[0107] In some embodiments, electric engine assembly 702 may be mounted or coupled to a boom structure 726 of the aircraft. Variable pitch mechanism 730 may be mechanically coupled to propeller assembly 720. In some embodiments, the variable pitch mechanism may abut electric engine assembly 702. In some embodiments, variable pitch mechanism 730 may be coupled to variable pitch mechanism 730 such that variable pitch mechanism 730 may be remotely mounted within a boom, wing, or fuselage of the aircraft. In some embodiments, variable pitch mechanism 730 may include a shaft or component that travels within or adjacent shaft 724 to propeller assembly 720. Variable pitch mechanism 730 may serve to change the collective angle of the propeller hub assembly blades of the forward electric engine as needed for operation during hover, transition, and cruise phases. Some embodiments may include electric engine assembly 702 mechanically coupled to a tilt propeller subsystem 728 that may redirect thrust between a primarily vertical direction during vertical flight mode and a primarily horizontal direction during forward flight mode. In some embodiments, the tilt propeller subsystem may be adjacent to the variable pitch mechanism 730. Some embodiments may include a tilt propeller subsystem 728 that includes various components located in various locations. For example, components of the tilt propeller subsystem may be coupled to the electric engine assembly 702, and other components may be coupled to the variable pitch mechanism 730. These various components of the tilt propeller subsystem 728 may work together to redirect the thrust of the tiltable electric propulsion system 700.

[0108] 8A-8C are diagrams of an exemplary tilt electric propulsion system for a VTOL aircraft consistent with disclosed embodiments. 8A-8C share similar numerals and refer to similar elements of tiltable electric propulsion systems 800A, 800B, and 800C. As such, similar design considerations and configurations may be considered throughout the embodiments.

[0109] 8A and 8B illustrate side profile and perspective views, respectively, of tiltable electric propulsion systems 800A, 800B in a cruise configuration integrated with booms 812A, 812B consistent with the present disclosure. The tiltable propeller electric propulsion systems 800A, 800B may include electric engine assemblies 802A, 802B housed within the booms 812A, 812B of the VTOL aircraft. In some embodiments, the cruise configuration may include electric engine assemblies 802A, 802B located within the booms 812A, 812B. The electric engine assemblies 802A, 802B may include electric motor assemblies, gearbox assemblies, inverter assemblies with power connection channels 810A, 810B, and heat exchangers 804A, 804B, as described herein. The electric engine assemblies 802A, 802B may be mechanically coupled to propulsion assemblies 808A, 808B that include shaft flange assemblies 806A, 806B, spinners, and propeller blades.

[0110] 8C illustrates a top-down view along spinner 808C of tiltable electric propulsion system 800C in a raised configuration integrated with boom 812B consistent with the present disclosure. As shown in FIG. 8C, tiltable electric propulsion system 800C in the raised configuration may include electric engine assemblies 802A, 802B positioned outside of boom 812C and changing its orientation relative to boom 812C.

[0111] As discussed herein, an ascent electric propulsion system may be configured to provide thrust in one direction and may not provide thrust during all phases of flight. For example, an ascent system may provide thrust during takeoff, landing, and hovering, but not during cruise.

[0112] FIG. 9 is a schematic diagram illustrating an exemplary lift electric propulsion system for a VTOL aircraft consistent with disclosed embodiments. Lift electric propulsion system 900 may be mounted or coupled to a boom structure 924 of the aircraft. Lift electric propulsion system 900 may include an electric engine assembly 902 aligned along a shaft 940 connected to an output shaft 932 mechanically coupled to a propeller assembly 920 comprising hub and tilting propeller blades. In some embodiments, electric engine assembly 902 may include a motor and gearbox assembly housing 904 aligned along and mechanically coupled to shaft 940. In some embodiments, motor and gearbox assembly housing 904 may include an electric motor assembly comprising a stator 906 and a rotor 908. Stator 906 may include multiple stator windings connected to an inverter 916. In such a configuration, stator 906 may incorporate one or more redundancy and backup measures to avoid a single point of failure in case of an emergency. For example, stator 906 may include multiple windings such that if a winding fails, power can continue to be transferred to stator 906 through the remaining windings, allowing electric engine assembly 902 to maintain power and continue to generate thrust at propeller assembly 920.

[0113] In some embodiments, motor and gearbox assembly housing 904 may include a gearbox 910 aligned along shaft 940 to provide a gear reduction between torque on shaft 932 from an electric engine assembly comprising stator 906 and rotor 908 and output shaft 932. Torque applied to output shaft 932 may be transmitted to propeller assembly 920. Some embodiments may include gearbox 910 including a fluid pump for circulating a cooling and / or lubricating fluid. In the embodiment shown, the fluid pump is an oil pump. In such an embodiment, the oil pump may drive the circulation of oil throughout motor and gearbox assembly housing 904 at a speed equivalent to the rotation of output shaft 932 to cool and lubricate gearbox and electric motor components. Some embodiments of motor and gearbox assembly housing 904 may include a propeller position sensor 912 present within the housing that may detect a magnetic field generated by the electric engine assembly to determine propeller position. Further embodiments may include a propeller position sensor 912 that is powered by inverter 916 and transmits collected data to inverter 916, which may be forwarded to flight control computing system 930, among other flight control data.

[0114] In some embodiments, electric engine assembly 902 may also include an inverter assembly housing 914 aligned along an axis coextensive with the axis of shaft 924. Inverter assembly housing 914 may include an inverter 916 and an inverter power supply 934. Inverter power supply 934 may receive low-voltage DC power from a low-voltage system 928 located outside electric engine assembly 902. Inverter power supply 934 may receive low-voltage DC power from a high-voltage power system 926 located outside electric engine assembly 902 that has been converted to low-voltage DC power via a DC-DC converter 936. Inverter 916 may provide high-voltage AC power via at least one three-phase winding to a stator 906 of the electric engine assembly located within motor and gearbox assembly housing 904. Inverter assembly 914 may include inverter 916, which may send data to and receive data from a flight control computing subsystem 930.

[0115] In some embodiments, motor and gearbox housing 904 may be located between inverter assembly housing 914 and propeller assembly 920. Some embodiments may include a divider plate 938 coupled to motor and gearbox assembly housing 904 and inverter assembly housing 914. Divider plate 938 may create an enclosed environment for the upper part of motor and gearbox assembly housing 904 via the end bell assembly and for the lower part of inverter assembly housing 914 via the thermal plate. In some embodiments, divider plate 938 may serve as an integrated mounting bracket to support heat exchanger 918. Heat exchanger 918 may include, for example, folded fins or other types of heat exchangers. In some embodiments, electric propulsion system 900 may circulate oil or other coolant liquid throughout electric engine assembly 902, motor and gearbox assembly 904, or inverter assembly 914 to transfer heat generated from the components to the oil or other coolant liquid. Heated oil or other coolant liquid may be circulated through the heat exchanger 918 to transfer heat to an airflow 922 passing over the fins of the heat exchanger.

[0116] In some embodiments, the tiltable electric propulsion system and the lift electric propulsion system may possess similar components. This may be advantageous with respect to many design considerations present in VTOL aircraft. For example, from a manufacturability perspective, different types of electric propulsion systems with similar components may be beneficial from a manufacturing efficiency perspective. Furthermore, having similar components may be beneficial from a risk management perspective because similar components have similar failure points that can be better identified and designed around when comparing a system with similar components to a system with different components and configurations.

[0117] It should be understood that while the tiltable electric propulsion system may have additional, and in some embodiments, different, components compared to the lift electric propulsion system, in some embodiments the tiltable electric propulsion system and the lift electric propulsion system may have the same configuration of components. For example, in some embodiments the tiltable and lift electric propulsion systems may include the same components, and the lift electric propulsion system may be coupled to the boom, wing, or fuselage of the aircraft such that it may not be able to provide thrust in as many directions as the tiltable electric propulsion system.

[0118] 10A-10B are diagrams of an exemplary electric ascent propulsion system for a VTOL aircraft consistent with disclosed embodiments. 10A and 10B share similar numerals and refer to similar elements of electric ascent propulsion systems 1000A and 1000B. As such, similar design considerations and configurations may be considered throughout the embodiments.

[0119] 10A illustrates a side profile of an electric lift propulsion system 1000A in a lift configuration integrated with a boom 1010A consistent with the present disclosure. The electric lift propulsion system 1000A may include an electric engine assembly 1002A housed within the boom 1010A of the VTOL aircraft. In some embodiments, the lift configuration may include an electric engine assembly 1002A positioned vertically within the boom 1010A. The electric engine assembly 1002A may include an electric motor assembly, a gearbox assembly, an inverter assembly with a power connection channel 1008A, and a heat exchanger 1004A, as described herein. The electric engine assembly 1002A may be mechanically coupled to a propulsion assembly 1006A comprising a shaft flange assembly and propeller blades.

[0120] FIG. 10B illustrates a top-down view of an electric lift propulsion system 1000B in a lift configuration integrated with a boom 1010B consistent with the present disclosure.

[0121] Some embodiments of the disclosed electric engine may generate heat during operation and may include a thermal management system to ensure that components of the electric engine do not fail during operation. In some embodiments, a coolant may be used and circulated throughout individual components of the engine, such as the inverter, gearbox, or motor, through some of the components, or through all of the engine's components to help manage the heat present within the engine. Some embodiments may include using an air-cooling method to cool the electric engine, or using a mixture of coolant and air to manage the heat generated by the electric engine during operation. In some embodiments, the coolant used may also be the same liquid used as a lubricant throughout the inverter, gearbox, or motor. For example, the components of the electric engine may be cooled using liquid or air, or using a mixture of air and liquid cooling. As another example, the motor may be cooled using air cooling, and the inverter and gearbox may be cooled using liquid cooling. It should be understood that a mixture of cooling may be used for any combination of electric engine components or within each component.

[0122] In some embodiments, oil may be used as a lubricant throughout the electric engine and as a coolant fluid to help manage heat generated by the engine during operation. Further to this example, different amounts of oil may be used to function as both a lubricant and a coolant fluid within the electric engine, in combination with 1 quart, 1.5 quarts, 2 quarts, 2.5 quarts, 3 quarts, 5 quarts, or any other amount of oil needed to lubricate and cool the electric engine, with or without the assistance of air cooling. In some embodiments, the amount of oil or liquid used in the system in connection with cooling may be determined based on the amount of heat needed to drive heat transfer from the components of the electric propulsion system. As disclosed herein, electric engines may have different primary functions, such as being used only for ascent and landing and thus only in one orientation, or being used during all phases of flight, such as ascent, landing, and flight. An engine used during all phases of flight may experience various orientations throughout flight and may contain more lubricant and coolant than an engine used only in one orientation. As such, all engines on an aircraft may not contain the same amount of lubricant and coolant. For example, ascent and landing engines may require less than one quart of oil, while engines operating during all phases of flight may require more than one quart of oil. In some embodiments, the amount of cooling oil or liquid may be adequate to provide sufficient thermal mass to drive heat transfer from the components of the electric propulsion system, regardless of the orientation of the electric propulsion system. The embodiments discussed herein are exemplary and non-limiting and do not determine the limits on the amounts of lubricants and coolants that may be used in an electric engine.

[0123] Some embodiments may use oil to lubricate and cool the electric engine. Such embodiments may require an additional volume of oil. In such embodiments, the additional oil may allow for the elimination of conventional components that may be used to cool such an electric engine. For example, if the electric engine were cooled by another liquid, such as glycol, the engine may include separate heat exchangers for both the lubricant fluid and the coolant fluid. Thus, in embodiments in which a single fluid is used for both lubrication and cooling, such as oil, there would be an increase in oil, but only the need for one heat exchanger, so the overall system may have a reduced mass due to using fewer heat exchangers and potentially other components not being needed, and there may be a more attractive drag profile. Furthermore, using one substance to lubricate and cool the engine may increase the efficiency of the system due to the reduced mass and the benefits of cooling the engine with a substance rather than relying on air cooling, which can be problematic to manage throughout the engine.

[0124] Some embodiments of the electric engine may include various components for monitoring flammable fluids and preventing flammable materials from entering certain sections of the electric engine. Some embodiments may include an electric engine with a wet zone enclosure, which may be defined by the gearbox, motor, and / or heat exchanger. In some embodiments, the electric engine may have up to four liters or more of air within the motor gearbox housing, which is in contact with the engine oil. Some embodiments of the motor gearbox housing may use a breather to equalize internal and external pressure. Some embodiments of the breather may include a protrusion over a nearby design feature to prevent the inadvertent intrusion of external fluids. Some embodiments may include a breather with a screen and bypass entry path to prevent the intrusion of external debris. Some embodiments may include sight glasses present on both the tilt electric engine and the lift electric engine to ensure the oil is not overfilled or underfilled during maintenance.

[0125] Some embodiments of the electric engine may include active protection features in the forward and aft electric engines, as needed, such as monitoring vibrations throughout the engine and internal temperatures throughout the engine, such as oil temperature, stator winding setpoint temperature, inverter bulk capacitor temperature, power module temperature, control board power module temperature, control board control processor temperature, control board monitor processor temperature, internal hot spot temperature, and various other operating conditions. Such monitoring may be achieved using various sensors located throughout the electric propulsion system and the aircraft. Embodiments may include vibration limits based on known fault points or component resonances, and overheat limits set based on known fault temperatures and operating limits related to fluid autoignition temperatures. In some embodiments, the various sensors used to monitor operating conditions throughout the engine may report operating conditions to a flight control system. Some embodiments may include threshold operating values ​​that may be required before an operating value is transmitted to or flagged by the flight control system. In some embodiments, the flight control system may act to reduce the amount of power directed to the electric propulsion system in response to detecting an operating condition. Some embodiments may include reducing the amount of power to an electric propulsion system to reduce mechanical wear or friction sparks from vibrations and / or reducing power in an attempt to reduce the temperature of components present within the electric propulsion system. Additionally, some embodiments may include reducing power to an electric propulsion system whose detected inverter efficiency is below a target efficiency. In some embodiments, for example, if 12 electric propulsion systems are present in an aircraft, the flight control system may act to reduce or terminate power to a single electric propulsion system while increasing power directed to the remaining electric propulsion systems or a subset thereof to counteract a reduction in lift generated by one electric propulsion system. In some embodiments, the flight control system may establish various thresholds for operating conditions to correspond to a reduction or increase in power to the electric propulsion systems.

[0126] Some embodiments may include a high-voltage power system that may have a fuse at the high-voltage battery terminal that can quickly and irreversibly disconnect the engine electrical connection to mitigate and prevent an overcurrent event. Such overcurrent protection may be activated when the current draw of the electric engine is greater than the overcurrent operation. Thus, in some embodiments, a fault condition that leads to an overcurrent may result only in temporary overheating, arcing, or sparking. Some embodiments may include a fire threat characterization test ignition source that may be selected to be a more severe ignition source than a short circuit that occurs within the electric engine and is opened by the engine fuse. In some embodiments, the inverter may detect AC overcurrents, isolate faulty phases, and / or continuously monitor the input DC voltage and apply protective action to maintain the voltage below the overvoltage operation limit.

[0127] During takeoff, landing, hovering, and cruising, the motors and associated control components of a VTOL aircraft may generate heat. The heat must be dissipated to prevent degradation or damage to the motors, control components, and other elements of the VTOL aircraft. In some types of VTOL aircraft, such as electric VTOL (eVTOL) aircraft, thermal control is also important, for example, to maintain optimal energy efficiency of battery-powered components.

[0128] Some elements may generate high heat loads only during certain periods of operation. For example, some lift propellers may be used only during takeoff, landing, and hovering and may be shut off during cruise. Thus, such lift propellers may generate high heat loads during takeoff, landing, and hovering, but generate little or no heat during cruise.

[0129] B. Exemplary Electric Propulsion System Embodiments As described herein, embodiments of an electric engine may include an inverter assembly, a gearbox assembly, and an electric motor assembly, or various combinations thereof. In some embodiments, the inverter assembly, gearbox assembly, and electric motor assembly may be substantially aligned along a central axis of the electric engine. As disclosed herein, these assemblies or combinations thereof may be substantially aligned along an axis by sharing a common axis or by having parallel axes that are within 5% or less of the outer diameter of the components having the largest diameters of each other. For example, the inverter assembly, gearbox assembly, and electric motor assembly may be substantially aligned along central axes where the central axis of the inverter assembly, the central axis of the gearbox assembly, and the central axis of the electric motor assembly are within 5% or less of the outer diameter of the electric motor assembly having a larger outer diameter than the gearbox assembly and the inverter assembly. The embodiments described herein are merely exemplary, and while certain components of an electric propulsion system may be shown abutting other components, it should be understood that all abutting configurations are possible. For example, the gearbox assembly may be shown abutting the inverter assembly and the electric motor assembly. Further, in some embodiments, the inverter assembly may abut the gearbox assembly and the electric motor assembly. Some embodiments may include an electric motor assembly abutting the gearbox assembly and the inverter assembly.

[0130] In some embodiments, each of the inverter assembly, gearbox assembly, and electric motor assembly may abut at least one of the other assemblies. The abutment may include direct or indirect contact between components comprising the assembly or housing in which the assembly is located. In some embodiments, the electric engine may include an inverter assembly and an electric motor assembly without a gearbox assembly. Some embodiments of the electric engine may include an electric motor assembly and gearbox assembly without an inverter assembly, or an electric motor assembly without a gearbox assembly or an inverter assembly.

[0131] 11A-11C are cross-sectional views of an exemplary electric propulsion system for a VTOL aircraft consistent with disclosed embodiments. FIG. 11A illustrates an example of an electric propulsion system. In some embodiments, the electric engine may directly assist the propulsion of a propeller of the aircraft. The electric engine 1100A may include a motor housing 1102A. The electric engine 1100A may also include an electric motor assembly including components such as a stator 1104A, a rotor magnet 1106A, and a rotor 1108A. In some embodiments, the rotor 1108A may be mechanically coupled to the main shaft 1110A such that the main shaft 1110A rotates at a speed comparable to the rotational speed of the rotor 1108A. The main shaft 1110A may be mechanically coupled to a shaft flange assembly 1112A. In some embodiments, the shaft flange assembly 1112A may be an anchor point for the propeller. The electric motor assembly may be substantially aligned along a central axis 1114A.

[0132] In some embodiments, the electric engine may include a gearbox. FIG. 11B illustrates an example of an electric engine. In some embodiments, the electric engine may include an electric motor assembly and a gearbox assembly substantially aligned along a shaft. In some embodiments, the electric motor assembly, the gearbox assembly, and the shaft may be substantially aligned along an axis 1114B. The electric engine 1100B may include a motor housing 1102B, a stator 1104B, a rotor magnet 1106B, and a rotor 1108B. In some embodiments, the rotor 1108B may be mechanically coupled to the main shaft 1110B such that the main shaft 1110B rotates at a speed equivalent to that of the rotor 1108B. The main shaft 1110B may be mechanically coupled to the shaft flange assembly 1112B such that the shaft flange assembly 1112B, and by extension, the propeller assembly (not shown), may rotate at a speed equal to the rotational speed of the main shaft 1110B. In some embodiments, the gearbox assembly may provide gear reduction and vary the speed of rotation of the main shaft 1110B. For example, the electric engine 1102B may include a gearbox assembly including a sun gear 1116B, planetary gears 1118B, a ring gear 1120B, and a planetary carrier 1122B. In some embodiments, the sun gear 1116B may be mechanically coupled to the main shaft 1110B such that the sun gear 1116B rotates at a speed equal to that of the main shaft 1110B. The sun gear 1116B may interface with planetary gears 1118B, which also interface with a ring gear 1120B. In such embodiments in which the sun gear 1116B rotates, the ring gear 1120B may be fixed to the motor housing 1102B. In some embodiments, the planetary gears 1118B may rotate around the sun gear 1116B due to interaction with the rotating sun gear 1116B and the fixed ring gear 1120B. The planetary carrier 1122B may be mechanically coupled to the planetary gear 1118B and may rotate at the same speed. Some embodiments may include a planetary carrier 1122B mechanically coupled to the main shaft 1110B.In some embodiments, the main shaft 1110B may include multiple phases or layers of the shaft so that portions of the shaft may rotate at different speeds. Some embodiments may include a first portion of the main shaft that rotates at a speed equal to the speed of the rotor 1108B and another portion of the main shaft that rotates at a speed equal to the speed of the planetary carrier 1122B. In some embodiments, the speed of the planetary carrier may be less than the speed of the rotor 1108B.

[0133] In some embodiments, the electric engine 1100B may include bearings 1124B, 1126B aligned along the main shaft 1110B. Some embodiments may include inner races of the bearings 1124B, 1126B mechanically coupled to the planetary carrier and various bearings, such as 1124B and 1126B.

[0134] FIG. 11C illustrates an example of an electric propulsion system. In some embodiments, the electric propulsion system may include an electric motor assembly and a gearbox assembly substantially aligned along a shaft. In some embodiments, the electric motor assembly may be positioned between the gearbox assembly and the shaft flange assembly. The electric propulsion system 1100C may include a motor gearbox assembly housing 1102C. In some embodiments, the electric propulsion system 1100C may include an electric motor assembly including a stator 1104C, a rotor magnet 1106C, and a rotor 1108C. The electric propulsion system 1100C may also include a gearbox assembly. In some embodiments, the gearbox assembly may include a sun gear 1116C, planetary gears 1118C, a ring gear 1120C, and a planetary carrier 1122C. The sun gear 1116C may interface with the planetary gears 1118C, which may also interface with the ring gear 1120C. The sun gear 1116C may be mechanically coupled to the rotor 1106C such that rotation of the rotor 1106C may cause the sun gear 1116C to rotate at the same rotational speed. The planetary carrier 1122B may be mechanically coupled to the planetary gears 1118C and may rotate at equivalent speeds. Some embodiments may include a planetary carrier 1122C mechanically coupled to the main shaft 1110C. The main shaft 1110C may be mechanically coupled to the shaft flange assembly 1112C. The main shaft 1110C may be substantially aligned along the central axis 1114C such that the gearbox assembly and the motor assembly are also substantially aligned along the central axis 1114C. In some embodiments, the electric propulsion system 1100C may include a heat exchanger 1124C that may be used to cool oil or liquid used to cool or lubricate components of the gearbox assembly or the electric motor assembly.

[0135] As discussed above, electric propulsion systems 1100A-C are exemplary embodiments. However, it is understood that electric propulsion system 1100A may be capable of providing the thrust required for the VTOL aircraft, but may create a larger drag profile and provide more mass to the VTOL aircraft than electric propulsion systems 1100B and 1100C. Electric propulsion systems 1100B and 1100C include gearbox assemblies. As such, electric propulsion systems 1100B and 1100C possess electric motor assemblies and, therefore, gear reductions that enable the electric propulsion systems to have smaller drag profiles and less mass.

[0136] The electric propulsion system 1100B may have a gearbox assembly between the electric motor assembly and the shaft flange assembly. This configuration may require less mass than the electric propulsion system 1100A, but more mass than the electric propulsion system 1100C. The electric propulsion system 1100B may have a gearbox assembly in which an input shaft or sun gear passes from the electric motor assembly to the gearbox assembly, and an output shaft or a portion of the planetary carrier passes from the gearbox assembly to the shaft flange assembly. The electric propulsion system 1100C, in some embodiments, may have a sun gear passing from the rotor of the electric motor assembly to the gearbox assembly, and a main shaft coupled to the planetary carrier or carrier cover passing through the sun gear, past the electric motor assembly, and to the shaft flange assembly. In this way, the electric propulsion system 1100C may have a more compact design, housing, and drag profile compared to the electric propulsion system 1100B. This may result in a more efficient drag profile and a more mass-efficient system. Furthermore, the electric propulsion system 1100B may have a gearbox assembly without lubrication, which may limit the run time of the electric propulsion system. The electric propulsion system 1100C may include heat exchangers to cool and lubricate portions of the system, including the gearbox assembly, which may lead to greater efficiency and longer flight range.

[0137] FIG. 49 illustrates a cross-sectional view of an exemplary electric propulsion system for a VTOL aircraft consistent with disclosed embodiments. The electric propulsion system 4900 may comprise a system that first sends torque away from the propeller and then returns the torque through a portion of the system to the propeller. In some embodiments, the electric propulsion system 4900 may comprise a motor gearbox assembly housing 4922, an inverter assembly housing 4924, and a heat exchanger 4926. In some embodiments, the electric motor assembly may include a stator 4902 and a rotor 4904. In some embodiments, the electric propulsion system 4900 may comprise a gearbox assembly including a sun gear 4906, planetary gears 4908, a ring gear 4910, and a planetary carrier 4912. The sun gear 4906 may be mechanically coupled to the rotor 4904. The sun gear 4906 may interface with the planetary gears 4908. The planetary gears 4908 may interface with a ring gear 4910, which may be fixed such that the planetary gears 4908 rotate about the sun gear 4906 relative to the ring gear 4910. In some embodiments, the planetary gears 4908 may comprise compound planetary gears 4908, 4950. A planetary carrier 4912 may be mechanically coupled to the planetary gears 4908 via a shaft 4914, which may extend from the planetary gears 4908 along a planetary gear central axis 4916 and be received by the planetary carrier 4912. The planetary carrier 4912 may rotate at a speed equal to the speed of the planetary gears 4908. The planetary carrier 4912 may be mechanically coupled to a main shaft 4918 such that the main shaft 4918 may rotate at a speed equal to the speed of the planetary carrier 4912. In some embodiments, the planetary gears 4908 may be mechanically coupled to the carrier cover via a shaft such that the carrier cover may rotate at a speed equal to that of the planetary gears 4908. The main shaft 4918 may be mechanically coupled to the shaft flange assembly 4920 such that the shaft flange assembly 4920 may rotate at a speed equal to that of the main shaft 4918.It should be understood that the planetary gear 4908 or compound planetary gear 4908, 4950 may comprise multiple planetary gears that rotate around the sun gear 4906.

[0138] Due to the mechanical coupling described herein, torque may be transmitted from the rotor 4904 to the sun gear 4906 along path 4930. The sun gear 4906 may transmit torque to the planetary gears 4908 along paths 4932 and 4934. The planetary gears 4908, and in some embodiments, the compound planetary gears 4908, 4950, may transmit torque to the planetary carrier along paths 4936 and 4938. The planetary carrier may transmit torque along path 4940 to the main shaft 4918. The main shaft 4918 may transmit torque along its length via path 4944 to the propeller assembly 4920. The propeller assembly 4920 may transmit torque to the propellers via paths 4946 and 4948. It should be understood that the paths discussed above are exemplary and that all configurations of transmitting torque away from the propeller to a gearbox assembly and then back to the propeller via the gearbox assembly and electric motor assembly are contemplated.

[0139] In some embodiments, the process of delivering power from the electric engine using the gearbox assembly via a counter torque path may include driving a planetary gear mechanically coupled to a rotor of the electric motor assembly. In some embodiments, the planetary gear may interface with a sun gear and a ring gear. Some embodiments may include a hollow sun gear and a fixed ring gear. Some embodiments may include driving a planetary carrier connected to a shaft extending from the planetary gear. The shaft extending from the planetary gear may include a shaft aligned along a central axis of the planetary gear. Some embodiments may include driving a carrier cover connected to the shaft from a shaft extending concentrically from the planetary gear. Some embodiments may include driving a main shaft. Driving the main shaft may include driving a first portion of the main shaft mechanically coupled to the carrier cover and transmitting torque along the main shaft to a second portion of the main shaft mechanically coupled to the propeller assembly. Some embodiments may include a heat exchanger that may cool the gearbox assembly using various amounts of oil, which may include 1 quart, 1.5 quarts, 2 quarts, 2.5 quarts, 3 quarts, or 5 quarts, as described herein.

[0140] In some embodiments, a gearbox assembly may include multiple sets of gearboxes. For example, in some embodiments, the output of a gearbox assembly may be fed to another gearbox assembly to achieve a larger gear reduction. Such an embodiment may include at least one sun gear, at least one set of planetary gears, at least one ring gear, and at least one planetary carrier. The gearboxes may possess common gears, such as a common sun gear, a common set of planetary gears, and a common ring gear. The embodiments discussed herein may be modified to include multiple sets of gearboxes.

[0141] 53 illustrates a flowchart of an exemplary process for transferring torque from an electric motor assembly to a propeller assembly of a VTOL aircraft 5300, consistent with disclosed embodiments. While the block diagram may be described below with reference to specific implementation embodiments presented in other figures, those implementations are provided for illustrative purposes only and are not intended to serve as limitations on the block diagram.

[0142] 53 includes process blocks 5302-5312. In block 5302, a process for delivering power from an electric engine using a gearbox assembly may include driving a planetary gear mechanically coupled to a rotor of an electric motor, consistent with discussion throughout this disclosure.

[0143] At block 5304, a process for delivering power from an electric engine using a gearbox assembly may include driving a planetary carrier connected to at least one shaft extending concentrically from the planetary gear, consistent with discussions throughout this disclosure.

[0144] At block 5306, a process for delivering power from an electric engine using a gearbox assembly may include driving a carrier cover connected to at least one shaft from a set of shafts extending concentrically from the planetary gear, consistent with discussion throughout this disclosure.

[0145] At block 5308, a process for delivering power from the electric engine using a gearbox assembly may include driving a main shaft, consistent with discussion throughout this disclosure.

[0146] At block 5310, a process for delivering power from an electric engine using a gearbox assembly may include driving a first portion of a main shaft mechanically coupled to a carrier cover, consistent with discussion throughout this disclosure.

[0147] At block 5312, a process for delivering power from the electric engine using a gearbox assembly may include transmitting torque along the main shaft to a second portion of the main shaft mechanically coupled to the propeller assembly, consistent with discussion throughout this disclosure.

[0148] 12A-12D are diagrams and block diagrams of an exemplary electric propulsion system for a VTOL aircraft, consistent with disclosed embodiments.

[0149] As described herein, the electric propulsion system may include an inverter assembly, a gearbox assembly, and an engine assembly. In some embodiments, the electric propulsion system 1200A may include components packaged in various housings, including a motor gearbox assembly housing 1202A and an inverter assembly housing 1228A. Enclosing the various components of the electric propulsion system 1200A in housings 1202A and 1228A may provide various advantages, including lower mass and a more efficient drag profile, as described herein. Furthermore, in some embodiments, the gearbox assembly, inverter assembly, and / or electric motor assembly may possess a substantially circular profile. As used herein, a profile may be substantially circular if the length of the minor circular axis and the length of the major circular axis possess a relationship such that the length of the minor circular axis is at least a threshold amount, such as 80% of the length of the major circular axis. Furthermore, in some embodiments, the gearbox assembly, inverter assembly, and electric motor assembly, or a subset of those listed, may be sized such that the assemblies have substantially equivalent radii. As used herein, two assemblies may possess substantially equivalent radii if the difference in radius between them is less than a threshold amount, e.g., 10%, of the radius of the largest assembly. In some embodiments, the profiles of the components making up the electric propulsion systems described herein may include various polygons, such as hexagons, heptagons, octagons, nonagons, decagons, and additional polygons with more than 10 sides.

[0150] The electric propulsion system 1200A may include an electric motor assembly including a stator 1204A, a rotor magnet 1206A, and a rotor 1208A.

[0151] In some embodiments, the electric motor assembly may interact with a gearbox assembly and, in some embodiments, may transmit torque to the gearbox assembly. The electric propulsion system 1200A may include a gearbox assembly including a sun gear 1214A, a set of planetary gears 1216A, a planetary carrier 1218A, and a carrier cover 1220A. Some embodiments may include the sun gear 1214A having teeth that interact with the teeth of the planetary gears 1216A and a ring gear (not shown in this view) having teeth that also interact with the teeth of the planetary gears 1216A. In some embodiments, the shaft 1222A may extend through or from the planetary gears 1216A. In some embodiments, the planetary carrier 1218A may receive a first end of the shaft 1222A such that the planetary carrier 1218A may rotate at the same speed as the planetary gears 1216A. In some embodiments, the carrier cover 1220A can receive the second end of the shaft 1222A such that the carrier cover 1220A can rotate at the same speed as the planetary gear 1216A. In some embodiments, the planetary gear 1216A, the planetary carrier 1218A, and the carrier cover 1220A can be mechanically coupled along the axis of the shaft 1222A.

[0152] In some embodiments, the electric propulsion system 1200A may include a main shaft 1210A that may be mechanically coupled to a shaft flange assembly 1224A to provide mechanical shaft power for rotating a propeller of a propeller assembly. As used herein, a component may be mechanically coupled when there is any connection or coupling, whether direct or indirect, between the two components. The shaft flange assembly may include a flange coupled to the main shaft with a spline connection for receiving torque loads from the main shaft and transmitting the torque to the propeller coupled to the flange. The flange may also be coupled to the main shaft using fasteners, by welding, by brazing, or by any other use of components or methods for coupling the main shaft and flange. In some embodiments, the main shaft and flange may be machined together to form a single component. In some embodiments, the shaft flange assembly may be a component of a propeller assembly, which may include the shaft flange assembly, a propeller, and a spinner. In some embodiments, the shaft flange assembly may also be referred to as a propeller hub.

[0153] In some embodiments, the electric propulsion system 1200A may include components for an inverter assembly, as described herein. For example, the electric propulsion system 1200A may include a printed circuit board assembly (PCBA), such as a power PCBA 1230A, which may include a power module 1232A, a gate drive PCBA 1236A, and a control PCBA 1240A. Some embodiments of the inverter assembly of the electric propulsion system 1200A may also include a spacer board 1238A among the various PCBA. Additionally, some embodiments may include an energy storage device, such as a DC capacitor, which may be stored in a DC capacitor housing 1234A. Some embodiments of the inverter assembly may also include a bus bar connector 1244A for supplying alternating current to the electric motor assembly. Some embodiments of the inverter assembly may include a power connection 1246A coupled to the high-voltage connector to deliver high-voltage power to the inverter assembly.

[0154] Some embodiments of the inverter assembly of the electric propulsion system 1200A may include layering each inverter assembly component in a stacked configuration along guide pins 1242A extending through each layer of the inverter assembly. It is recognized that inverter assemblies utilizing a stacked configuration along guide pins 1242A may be beneficial in various design criteria associated with VTOL aircraft. For example, the stacked configuration may allow for more compact packaging of the inverter assembly, thus minimizing the mass of the electric propulsion system 1200A and helping to minimize drag due to the electric propulsion system packaging. Furthermore, the stacked configuration of the inverter assembly may be advantageous from a manufacturing standpoint because the stacked configuration may allow for tolerances within various portions of the inverter assembly. In some embodiments, structural components may be introduced into the inverter assembly to help support the stacked configuration under loads experienced during various phases of flight. Some embodiments may include inverter assembly components that also function as structural components. For example, the DC capacitor housing 1234A may house the capacitors and other components for the inverter assembly and may be made of plastic or other material capable of supporting the PCBA and other components surrounding it.

[0155] In some embodiments, electric propulsion system 1200A may include a heat exchanger 1226A coupled to motor gearbox assembly housing 1202A and inverter assembly housing 1228A. Heat exchanger 1226A may be coupled to a divider plate including a thermal plate 1248A and an end bell plate 1250A. End bell plate 1250A may serve to close motor gearbox assembly housing 1202A. Thermal plate 1248A may serve to close inverter assembly housing 1228A. In some embodiments, the divider plate may serve as an integrated mounting bracket to support heat exchanger 1226A. Heat exchanger 1226A may comprise, for example, folded fins or other types of heat exchangers. In some embodiments, electric propulsion system 1200A may circulate oil or other coolant throughout the electric motor assembly, gearbox assembly, or inverter assembly to transfer heat generated from the components to the oil or other coolant liquid. Heated oil or other coolant liquid may be circulated through the fins of the heat exchanger 1226A by internal liquid passages that may have inlets and outlets for the liquid passages that may be coupled to outlets and inlets, respectively, of bores or grooves that may be present on the divider plate. In some embodiments, the motor gearbox housing 1202A may include a sump 1212A. The sump 1212 may serve to collect and recirculate oil or liquid coolant distributed throughout the electric propulsion system 1200A.

[0156] In some embodiments, the heat exchanger may be fluidly coupled to a gearbox assembly, an inverter assembly, and / or an electric motor assembly. As used herein, an assembly, or a component therein, may be fluidly coupled, and a liquid flow path from the heat exchanger may interact with, supply liquid to, or interface with the assembly, or a component therein.

[0157] FIG. 12B shows an example schematic diagram of the configuration of an electric propulsion system 1200B. In some embodiments, the electric propulsion system may include a motor assembly and a gearbox assembly: electric propulsion system 1200B, a divider plate 1208B, a motor assembly 1202B, an inverter assembly 1204B, a gearbox assembly 1206B, a heat exchanger 1212B, and a propeller assembly 1210B. In some embodiments, an inverter assembly housing 1216B may surround the inverter assembly 1204B, and a motor gearbox housing 1214B may surround the motor assembly 1202B and the gearbox assembly 1206B. The inverter assembly housing 1216B may abut the motor gearbox housing 1214B. In some embodiments, the electric propulsion system 1200B may include a gearbox assembly 1206B positioned between the electric motor assembly 1202B and the inverter assembly 1204B. As described herein, a coolant or lubricant, such as oil, may be distributed throughout the electric propulsion system. For example, oil flow 1218B may be routed from heat exchanger 1212B to divider plate 1208B and then to gearbox assembly 1206B and motor assembly 1202B, providing cooling and lubrication to motor assembly 1202B and gearbox assembly 1206B. Oil flow 1218B may then proceed from motor assembly 1202B back to heat exchanger 1212B. As described herein, propeller assembly 1210B may drive air flow 1220B from the propeller toward heat exchanger 1212B. Heat exchanger 1212B may transfer heat from oil flow 1218B to air flow 1220B. Oil flow 1218B may be cooled and discharged from heat exchanger 1212B.

[0158] FIG. 12C illustrates an example schematic diagram of an electric propulsion system configuration. In some embodiments, the electric propulsion system 1200C may include a divider plate 1208C, a motor assembly 1202C, an inverter assembly 1204C, a gearbox assembly 1206C, a heat exchanger 1212C, and a propeller assembly 1210C. In some embodiments, the inverter assembly housing 1216C may surround the inverter assembly 1204C, and the motor gearbox housing 1214C may surround the motor assembly 1202C and the gearbox assembly 1206C. The inverter assembly housing 1216C may abut the motor gearbox housing 1214C. In some embodiments, the electric propulsion system 1200C may include an electric motor assembly 1202C positioned between the gearbox assembly 1206C and the inverter assembly 1204C. As described herein, a coolant or lubricant, such as oil, may be distributed throughout the electric propulsion system. For example, oil flow 1218C may be routed from heat exchanger 1212C to divider plate 1208B, then to motor assembly 1202C, and then to gearbox assembly 1206C, providing cooling and lubrication to motor assembly 1202C and gearbox assembly 1206C. Oil flow 1218C may then proceed from motor assembly 1202C back to heat exchanger 1212C. As described herein, propeller assembly 1210C may drive air flow 1220C from the propeller toward heat exchanger 1212C. Heat exchanger 1212C may transfer heat from oil flow 1218C to air flow 1220C. Oil flow 1218C may be cooled and discharged from heat exchanger 1212C.

[0159] FIG. 12D illustrates an example schematic diagram of an electric propulsion system configuration. In some embodiments, the electric propulsion system may include a motor and propeller assembly. The electric propulsion system 1200D may include a divider plate 1208D, a motor assembly 1202D, an inverter assembly 1204D, a heat exchanger 1212D, and a propeller assembly 1210D. In some embodiments, an inverter assembly housing 1216D may surround the inverter assembly 1204D, and a motor assembly housing 1214D may surround the motor assembly. The inverter assembly housing 1216D may abut the motor assembly housing 1214D. In some embodiments, the electric propulsion system 1200C may include an electric motor assembly 1202C that directly drives a main shaft that provides mechanical shaft power to the propeller assembly 1210C. In such embodiments, the main shaft rotates at a speed equal to the speed of the rotor in the electric motor assembly 1202C. As described herein, a coolant or lubricant, such as oil, may be distributed throughout the electric propulsion system. For example, oil flow 1218D may have a path from heat exchanger 1212D to divider plate 1208D and then to motor assembly 1202D, providing cooling and lubrication to motor assembly 1202D and other components of electric propulsion system 1200D. Oil flow 1218D may then proceed from motor assembly 1202D back to heat exchanger 1212D. As described herein, propeller assembly 1210D may drive air flow 1220D from the propeller toward heat exchanger 1212D. Heat exchanger 1212D may transfer heat from oil flow 1218D to air flow 1220D. Oil flow 1218D may be cooled and discharged from heat exchanger 1212D.

[0160] 13 is an exploded view of an exemplary electric propulsion system for a VTOL aircraft consistent with disclosed embodiments. The electric engine 1300 may include an inverter assembly 1304, an end bell assembly 1306, a main shaft assembly 1308, a rotor 1310, a stator housing 1312, and a shaft flange assembly 1314. In some embodiments, the inverter assembly 1304 may abut a gearbox assembly. The gearbox assembly may include an end bell assembly 1306 and a main shaft assembly 1308. In some embodiments, the gearbox assembly may abut an electric motor assembly. The electric motor assembly may include a rotor 1310 and a stator housing 1312. In some embodiments, the components of the electric propulsion system may be substantially aligned along an axis. In some embodiments, the main shaft may represent a central axis about which the components of the electric propulsion system 1300 may be substantially aligned. In alternative embodiments, the order of the inverter assembly, gearbox assembly, and motor assembly may be rearranged, as described herein, such that different electric propulsion system components abut one another. The housing of the inverter assembly 1304 may be secured to the inverter assembly thermal plate by screws 1302. In some embodiments, fasteners 1316 may secure the electric engine 1300 to the boom of the aircraft.

[0161] An embodiment of the electric engine may include an electric motor assembly, as described herein. FIG. 14 is an exploded view of an exemplary electric motor assembly for a VTOL aircraft consistent with disclosed embodiments. The electric motor assembly 1400 may include a stator assembly 1402. In some embodiments, the stator may include insulated wire laminations and coils. In some embodiments, the stator assembly 1402 may include permanent magnets. The stator assembly 1402 may include a stator core 1404 and windings 1406. In some embodiments, the wire windings 1406 may be constructed of copper. The stator assembly 1402 may also include bus bars 1408. By way of example, the bus bars 1408 may be electrically coupled to the stator assembly 1402 and may assist in the electrical conduction of current. The electric motor 1400 may include various bearings, including a bearing retainer 1412 and roller bearings 1414. The bearing retainer 1412, the roller bearing 1414, and the shaft seal 1416 may be substantially aligned along the central axis. In some embodiments, the bearing retainer 1412 may assist in cooling as a cooling oil manifold. In some embodiments, the roller bearing 1414 may have a spherical shape. The electric motor 1400 may include a bearing screw 1410. The bearing screw 1410 may fasten the bearing retainer 1414 to various components of the electric motor 1400, including the roller bearing 1414. In some embodiments, a stator housing 1418 may enclose the stator assembly 1402, the roller bearing 1414, the bearing retainer 1412, the shaft seal 1416, and the bearing screw 1410. The stator housing 1418 may have an interference fit or a press fit with the stator assembly 1402. For example, the stator housing 1418 may have a press fit with the stator laminations. In some embodiments, the stator housing 1418 can have a thermal interference fit to the stator assembly 1402. As an example, the stator housing 1418 can be a common housing that packages the components of the stator 1400 together, providing benefits including mass reduction and elimination of tubes, hoses, and other connectors.In some embodiments, the stator housing 1418 may include a sump 1420 for collecting liquid used for cooling or lubricating the electric propulsion system, as described herein. Additionally, in some embodiments, additional components of the electric propulsion system may reside within the stator housing to provide further mass reduction.

[0162] 15A-15C are diagrams of a stator assembly for a VTOL aircraft consistent with disclosed embodiments. FIG. 15A illustrates a diagram of a stator core. In some embodiments, the stator 1500A can include a winding stator assembly 1502A and copper windings 1504A. FIG. 15B illustrates an additional view of the stator core 1500B. The laminations 1502B can separate the copper windings 1504B. FIG. 15C depicts an example of a stator slot. As an example, the stator core 1500C can include copper windings 1506C, which can be housed in the stator iron 1502C. Slot liners 1508C can separate the copper windings 1506C from the stator iron 1502C. The slot liners 1508C can provide electrical insulation. The stator iron 1502C may be contoured to fit the slot wedges 1504C, which reside over the copper windings 1506C. The slot wedges 1504C may hold the copper windings 1506C in place within the stator iron 1502C. In some embodiments, stator laminations may be constructed from the stator iron 1502C. The stator laminations may help insulate the core and reduce eddy currents or losses. In some embodiments, the stator assembly may include an oil-filled cavity placed around the stator to aid in cooling. Such a cavity may be fluidly coupled to a heat exchanger, as described herein.

[0163] 16A-16C share like numerals and refer to like elements of rotor assemblies 1600A and 1600B, and as such, similar design considerations and configurations may be considered throughout the embodiments.

[0164] Disclosed embodiments of the electric motor assembly may include a rotor. In some embodiments, an electromagnetic field generated by a stator in the electric motor assembly may drive rotation of the rotor about an axis.

[0165] 16A-16B are exploded and cross-sectional views of a rotor assembly for a VTOL aircraft consistent with disclosed embodiments. FIG. 16A illustrates an example exploded view of a rotor. The rotor assembly 1600A may include a rotor 1602A including a rotor hub 1604A. In some embodiments, the rotor hub 1604A may be machined and constructed of aluminum. The rotor 1602A may include laminations 1606A and a Halbach array 1608A. The laminations 1606A may have a thermal interference fit to the rotor hub 1604A. The rotor 1602A may be surrounded by a rotor overlap 1610A. In some embodiments, the rotor overlap 1610A may be constructed of carbon fiber. The Halbach array 1608A may include magnets. The rotor overlap 1610A may abut against the Halbach array 1608A and apply pressure to the magnets of the Halbach array 1608A. In some embodiments, the rotor 1602A may include a hollow portion. The hollow portion of the rotor may allow various motor assembly or gearbox assembly components to pass through the rotor 1602A, enabling configurations in which components may be coupled to the rotor 1602A. In some embodiments, an electric motor assembly may be mechanically coupled to the gearbox assembly. The disclosed embodiments include various means for mating the rotor and sun gear. The rotor 1602A may be mechanically coupled to the sun gear 1612A and concentrically secured by various means for connecting and aligning the components. The rotor 1602A may be mechanically coupled to the sun gear 1612A by various fastening means. As an example, the rotor 1602A may be fastened to the sun gear 1612A using a lock nut 1620A, a dowel pin, or a screw 1622A. The bearing 1616A may have an interference fit with the rotor assembly 1602A and the sun gear 1612A. In some embodiments, the sun gear 1612A can include gear teeth 1614A, which can be used in a gearbox assembly as described herein. The sun gear 1612A can include a hollow center. In some embodiments, the sun gear 1612A can be mechanically coupled to an oil sleeve 1618A, which can help distribute cooling or lubricating liquid using centrifugal force during rotation.

[0166] FIG. 16B illustrates an additional view of the rotor assembly 1600B. As described herein, the rotor 1602B may include a rotor hub 1604B, a lamination stack 1606B, and a Halbach array 1608B. The rotor overlap 1610B may abut the Halbach array 1608B and surround the stator assembly 1602B. The bearing 1616A may include an inner race and an outer race. In some embodiments, the sun gear 1612B may be mechanically coupled to the rotor 1602B. Some embodiments may include mechanically coupling the sun gear 1612B and the rotor 1602B using screws 1622B. The bearing 1616B may assist in mechanically coupling the rotor 1602B and the sun gear 1612B by providing an interference fit. In some embodiments, the main shaft of the electric engine assembly may travel through bearing 1616B and thus through sun gear 1612B and rotor 1602B. Additionally, some embodiments may include bearing 1616B to help support rotor 1602B and rotor hub 1604A under any load experienced by rotor 1602B or rotor hub 1604B during normal operation. In some embodiments, the inner surface of rotor assembly 1602B may possess a diameter equal to the outer race of bearing 1616B. Sun gear 1612B may include gear teeth 1614B. In some embodiments, rotor assembly 1612B and sun gear 1612B may be substantially aligned along central axis 1624B.

[0167] As described herein, disclosed embodiments of an electric propulsion system may include a motor assembly and a gearbox assembly. In some embodiments, the gearbox assembly may include a torque path that may exert a load. As described herein, the electric propulsion system may include a gearbox assembly and a rotor of an electric motor assembly, both of which may exert a load on the shaft. For example, the gyroscopic effect of the rotating rotor in motion may exert a moment load. The moment load may be on a concentrated path of the shaft. Because the gearbox assembly, which may include planetary gears, may share torque through several paths, the load sharing may depend on the tolerances of the components within the electric engine. Thus, a solution that supports the load and resists the moment caused by the generated torque while maintaining a low mass and drag profile may be advantageous.

[0168] FIG. 54 is a schematic diagram of an exemplary electric motor assembly in partial cross section. As shown in FIG. 54, the electric motor assembly 5400 may include a case 5402 that encloses a sealed environment 5404, with both the rotor 5406 and stator 5408 (as well as a magnet 5418 as part of the stator 5408) inside the case 5402. In some embodiments, the electric motor assembly 5404 may be positioned so that the propeller assembly (not shown in FIG. 54) it drives can drive air toward it to provide a cooling effect. Thus, the side 5410 facing the propeller assembly (i.e., facing the airflow driven by the propeller assembly) is the cold side, and the side 5412 facing away from the propeller assembly (i.e., on the backside of the airflow generated by the propeller assembly) is the hot side. The airflow 5414 created by the propeller assembly can be used to cool the case 5402, thus making the side 5410 facing the propeller the cooler side.

[0169] 54 , the rotor 5406 may create air movement 5416 inside the sealed environment 5404 enclosed by the case 5402 from the cold side 5410 toward the hot side 5412 to provide a cooling effect to one or more components outside the case 5402 on the hot side 5412. In other words, heat generated by one or more components outside the case 5402 on the hot side 5412 is first dissipated to the cold side 5410 through the air movement 5416 within the sealed case 5402, and then further dissipated by the airflow 5414 created by the propeller assembly.

[0170] In some embodiments, the air movement 5416 may also provide a cooling effect to dissipate heat generated by the magnets 5418 within the case 5402. The air movement 5416 facilitates heat dissipation from the magnets 5418 due to the cooling effect created by the airflow 5414.

[0171] 55A-55B are views of example inner surfaces of a portion of a rotor hub and a portion of an end plate. In some embodiments, the inner surfaces (e.g., 5502A, 5502B) of rotor hub 5500A and end plate 5500B, respectively, can have fins (e.g., 5504A, 5504B) to define a low-resistance air path, thereby making the rotor more efficient at creating air movement (e.g., 5416) within case 5402 (not shown in FIGS. 55A-55B).

[0172] 55A, the fins 5504A on the interior 5502A of the rotor hub 5500A can have different heights and shapes. In this exemplary embodiment, the differently shaped fins are all straight (i.e., flat), but they can have different geometric shapes as well.

[0173] As shown in Figure 55B, the fins 5504B on the inner side 5502B of the end plate 5500B all have the same height. The height of the fins 5504B in this exemplary embodiment may be approximately 12 mm. Generally, this height may be approximately 5 mm to 20 mm.

[0174] In this exemplary embodiment, the fins on the rotor hub and the stator may have a first clearance. The first clearance may be 0.4 mm to 1.2 mm, or approximately 0.6 mm. The fins on the end plates and the rotor may have a second clearance. The second clearance may be 0.4 mm to 1.2 mm, or approximately 0.6 mm. The first and second clearances may be determined such that air in a sealed environment (e.g., a case) is pressurized through a gap formed between the fins and the rotor, and the air is directed from the edge of the hot side toward the center of the motor on the hot side and then toward the center of the motor on the cold side.

[0175] FIG. 55C is a simulation result of air velocity and pressure distribution within a case, such as case 5402 of FIG. 54. In the example shown in FIG. 55C, the white space indicates a solid motor structure where no air is present. The different colors in the left image represent differences in air velocity, indicating a substantially higher air velocity between rotor 5406 and motor arbor 5502B than the left, thus indicating that the air inside the sealed environment is agitated. In the middle image, the different colors indicate the internal pressure distribution within sealed environment 5404. In some embodiments, a larger pressure difference between the two points can result in higher airflow at higher velocities, which can increase the efficiency of heat exchange between the cold and hot sides of the case, thus enhancing the cooling effect on the motor.

[0176] 55D is an example set of inner surfaces of an end plate consistent with disclosed embodiments. The fins on the end plate and rotor can have different geometries and arrangements that can be optimized considering different design factors and operating parameters, such as revolutions per minute (RPM), clearance, motor size, weight, rotating mass, and other design and operating parameters that can be affected by fin design and shape.

[0177] In some embodiments, the direction of airflow may be reversed. For example, rather than moving air toward the center of the hot side, air may instead be moved from the center of the hot side to the periphery. In such an embodiment, the airflow at the center of the motor would be from the hot side to the cold side. This may be achieved by modifying the shape (e.g., curvature) of the fins. FIG. 24 provides an example design of the fin shape, but the examples shown are not intended to limit the range of potential fin designs and shapes. The fin shape may be optimized or modified depending on the specific needs of the system and may be evaluated based on experimentation and simulation.

[0178] Disclosed embodiments may include a bearing system comprising a rotor that utilizes bearings to support a load. FIG. 16C illustrates a cross-sectional view of an exemplary embodiment of a rotor assembly consistent with embodiments of the present disclosure. In some embodiments, the rotor assembly may include a bearing system 1600C. The bearing system 1600C may include a rotor hub 1604C, a sun gear 1612C, and a main shaft 1626C. The bearing system 1600C may use various types of bearings to reduce loads experienced by components substantially aligned along the shaft. As described herein, the rotor assembly may be mechanically coupled to the sun gear 1612C. The main shaft 1626C may include an outer surface 1628C that may abut a shaft flange assembly 1630C. The shaft flange 1630C may abut a bearing 1634C. The bearing 1634C may have an inner race mechanically coupled to the main shaft 1626C and an outer race mechanically coupled to the rotor hub 1630C. In some embodiments, the bearing 1634C may have an inner race mechanically coupled to the main shaft 1626C and an outer race mechanically coupled to the rotor hub 1630C and the sun gear 1612C. In some embodiments, the bearing 1634C may abut both the rotor hub 1604C and the sun gear 1612C. The bearing 1634C may be mechanically coupled to the shaft flange assembly 1630C. As described herein, the bearing 1634C may support the rotor hub 1604C and may support loads from the rotor hub 1604C. For example, rotation and movement of the rotor hub 1604C may cause a gyroscopic effect that exerts loads. The bearing 1634C may support loads including radial or axial rotor loads. The bearing 1634C may allow the sun gear 1612C to float, which may allow load fluctuations to be absorbed. In some embodiments, the bearing 1634C may be a rolling element bearing. For example, the bearing 1634C may include rolling elements 1616C that may be immersed in a lubricant 1632C within the bearing 1634C.In some embodiments, the lubricant 1632C may include oil. Other bearings, such as ball bearings or deep groove ball bearings, may be used to support loads and high speed rotation.

[0179] Disclosed embodiments of the electric propulsion system may also include a guide (pilot) system for the bearings supporting the rotor. As disclosed herein, the electric propulsion system may include bearings supporting a sun gear and a rotor. The bearings supporting the rotor may include bearings having an outer race mechanically coupled to the inner surface of the rotor. For example, the bearing 1634C may include an outer race mechanically coupled to the rotor hub 1604C. The bearing 1634C may guide the sun gear 1612C and the rotor hub 1604C by guiding the alignment or mating of multiple components. For example, the guide may help align or mate the sun gear 1612C and the rotor hub 1604C. The bearing 1634C may rest on the outer race, which may support edges of the sun gear 1612C and the rotor hub 1604C to concentrically secure the sun gear 1612C and the rotor hub 1604C. A first edge of the sun gear 1612C and a first edge of the rotor hub 1604C may abut and contact the outer race of the bearing 1634C. The bearing 1634C may influence the diameter of the sun gear 1612C and the rotor. The diameter of the outer race of the bearing 1634C may be substantially similar to the diameter of the inner surface of the sun gear 1612C and the inner diameter of the rotor. In some embodiments, the rotor hub 1604C and the sun gear 1612C may be concentrically fixed. The sun gear 1612C may have a diameter equal to the inner diameter of the rotor. In some embodiments, the guide system for the bearing may include a shoulder. A shoulder may be an edge of a component that abuts one or more edges of another component. For example, the shoulder may include a portion of the sun gear 1640B abutting one or more edges of the bearing 1616B and a portion of the rotor hub 1642B abutting one or more edges of the bearing 1616B. The shoulders may cooperate to limit movement of the bearing. For example, the shoulders may cooperate to limit movement of the bearing 1616B axially or along the axis 1624B. In some embodiments, the guides may include shoulders to capture the bearing radially. The guide system may reduce mass and prevent the need for additional material.In some embodiments, dowel pins may be used to guide the sun gear and rotor.

[0180] In some embodiments, the rotor bearing system may also include bearings that resist moment loads and allow floating to compensate for tolerances in the gearbox. The rotor bearing system may include hydrodynamic bearings. The hydrodynamic bearings may resist or counter rotor moment loads. In some embodiments, the hydrodynamic bearings may be positioned along the sun gear. For example, the hydrodynamic bearings may be located between the sun gear 1612C and the main shaft 1626C, and the hydrodynamic bearings may be located at positions along the length of the sun gear 1612C. In some embodiments, the hydrodynamic bearings may extend along the entire length of the sun gear 1612C. The hydrodynamic bearings may be positioned where the main shaft 1626C has a shoulder or cavity, as described herein. For example, the hydrodynamic bearings may comprise fluid between the sun gear 1612C and a shoulder or cavity of the main shaft 1626C. In some embodiments, the size or shape of the shoulder may be determined by the characteristics of the rotor. For example, the shoulder may have a depth and width that may be determined by rotor characteristics, including mass, speed, rate of change, and axial or load changes (including gyroscopic, axial, and radial loads or moments). The hydrodynamic bearing may comprise a fluid, such as oil, positioned between the sun gear 1612C and the outer surface 1628C of the main shaft 1626C. The hydrodynamic bearing may assist in resisting moment loads experienced by the sun gear 1612C. For example, the hydrodynamic bearing may exert a restoring force to resist gyroscopic loads. In some embodiments, the hydrodynamic bearing may include oil. The hydrodynamic bearing may allow the sun gear 1612C or ring gear to float. The hydrodynamic bearing may allow for tolerances within various components of the electric propulsion system. The hydrodynamic bearing may include the same liquid, such as oil, used throughout the electric propulsion system for lubrication and cooling. As discussed herein, utilizing a single liquid for hydrodynamic bearings, cooling, and lubrication may provide advantages of reducing mass and reducing the size of various components.

[0181] FIG. 50 illustrates a perspective view of an exemplary rotor for a VTOL aircraft consistent with disclosed embodiments. In some embodiments, rotor 5000 may include rotor hub 5002. Rotor hub 5002 may possess layers 5004 and 5012. Rotor 5000 may be manufactured to include rotor hub 5002 and layers 5004 and 5012. Rotor 5000 may be made of aluminum, steel, or other materials capable of transmitting torque to a propeller assembly. Rotor 5000 may be machined from a single piece of material using various types of machines, such as a lathe, a computer numerically controlled (“CNC”) machine, or any other type of machine capable of machining rotors. Layers 5004, 5012 may be present on rotor 5000 to be later sacrificed to balance rotor 5000. Rotor 5000 may become unbalanced during rotor machining due to manufacturing constraints, such as machine precision. In some embodiments, balancing the rotor 5000 may involve adding or removing mass from the rotor.

[0182] In some embodiments, manufacturing constraints in various areas of the rotor 5000 may determine the mass of the layers 5004, 5012. For example, the layers 5004, 5012 may have specific minimum or maximum masses determined by the manufacturing equipment and steps used to create the rotor. The layers 5004, 5012 may include a mass of rotor material sized to accommodate the manufacturing constraints present in each area of ​​the rotor. In some embodiments, the mass of the layers 5004, 5012 to be removed later during balancing of the rotor may be determined based on the accuracy of the machine(s) manufacturing various portions of the rotor. For example, in some embodiments, a machine may manufacture a portion of the rotor with an accuracy of ±5% of the target mass of the portion of the rotor. In such an example, the rotor may include layers 5004, 5012 having an overall mass that includes mass that falls within the combined deviation mass due to the accuracy of the machine(s) manufacturing the rotor and sufficient mass to be removed during balancing of the rotor. In some embodiments, the material properties of the layers 5004, 5012 may include aluminum, steel, or another material that can accommodate the manufacturing precision of the machine(s) that manufacture the rotor portions. In some embodiments, the thickness, or width and depth, of the layers 5004, 5012 may be thicker or thinner depending on design considerations, system needs, and manufacturing constraints. In some embodiments, the various layers may have substantially similar widths and depths, where substantially similar includes the width or depth of a layer differing by less than 5% of the greater width or depth.

[0183] In some embodiments, the rotor 5000 may include multiple layers 5004, 5012. For example, the rotor 5000 may include a layer 5004 on the inner surface or circumferential edge of the rotor hub 5002, as shown in FIG. 50 . In some embodiments, the rotor 5000 may possess multiple layers 5004, 5012 disposed adjacent to each other along the inner surface, on opposite sides of the inner surface of the rotor, or any other configuration of layers 5004, 5012 along the rotor hub 5002. In some embodiments, the layers 5004, 5012 may be positioned a constant distance from the edge of the rotor along the inner surface of the rotor. Some embodiments may include layers that are a substantially similar distance from the edge of the rotor. As used herein, substantially similar distance may include a variation in distance of less than 5% of a greater distance.

[0184] In some embodiments, layers 5004, 5012 may include grooves 5006 that create portions 5008. In some embodiments, the portions may be made of aluminum. Additionally, some embodiments may include grooves 5006 that may be made of aluminum. In some embodiments, grooves 5006 may function as liquid flow paths for oil or other liquids present within the electric motor assembly. For example, as described herein, in normal operation, oil or liquid may be circulated throughout the electric motor assembly to aid in cooling or lubricating components. Thus, grooves 5006 may act to allow oil or liquid to pass through layers 5004, 5012 so that the oil or liquid does not collect within layers 5004, 5012 and is returned to a sump or other reservoir as described herein. In some embodiments, multiple layers 5004 may be aligned such that the grooves 5006 in each layer are aligned.

[0185] In some embodiments, the rotor 5000 may include through-holes 5010. In some embodiments, the rotor 5000 may be machined with the through-holes 5010. Those skilled in the art will appreciate that mass is an important factor in aircraft design, particularly VTOL aircraft design. Mass may affect the efficiency, payload, and flight time of a VTOL aircraft. Therefore, some embodiments of the rotor may include through-holes 5010 created by a machining process, a laser machining process, or any other process that removes mass from the rotor. The through-holes 5010 may reduce the mass of the rotor 5000 by removing sections of rotor hub 5002 material, such as aluminum. In some embodiments, the through-holes may also serve as connection points for the sun gear, as discussed above.

[0186] In some embodiments, as described herein, the electric motor assembly of a VTOL aircraft may generate torque by rotating the rotor 5000 at high rotational speeds. At high rotational speeds, an unbalanced rotor, having an axis of rotation that is not aligned with the rotor's center of mass, experiences high levels of undesirable vibration and noise. An unbalanced rotor may result from production tolerances in the manufacturing process. For example, magnets present in a rotor assembly may not have uniform mass and may not be uniformly positioned along the rotor or lamination stack. Furthermore, in some embodiments, the through-holes 5010 may be produced using a machining process, and production tolerances may result in an unbalanced rotor. As such, it is recognized that a process for balancing the rotor may be advantageous. It is also recognized that mass may be a critical design criterion in a VTOL aircraft, and therefore, traditional rotor balancing techniques that involve adding mass to the rotor or removing a minimal amount of mass may result in undesirable mass remaining on the rotor. In some embodiments, a process may be used to balance the rotor while achieving the greatest reduction in rotor mass.

[0187] Some disclosed embodiments may comprise an improved process for balancing the rotor of an electric motor assembly. Some embodiments may include identifying the rotor's axis of rotation. As discussed herein, rotor 5000 may include layers 5004, 5012. In some embodiments, layers 5004, 5012 serve as sacrificial layers that can be machined integrally with rotor 5000 to be later removed from rotor 5000 to achieve a balanced rotor. In some embodiments, portion 5008 may serve as a sacrificial portion that can be machined integrally with rotor 5000 to be later removed from rotor 5000 to achieve a balanced rotor. It is recognized that detachable layers and portions added to the rotor after it is manufactured via fasteners, adhesives, or similar materials can serve a similar purpose as sacrificial layers or portions. However, detachable layers and portions would require additional mass in the form of attachments that are not beneficial to the overall efficiency of the VTOL. Furthermore, attachments used for detachable layers and portions, such as fasteners and adhesives, risk failure during flight and may damage other components of the electric propulsion system.

[0188] Some embodiments of a process for balancing a rotor may include determining an imbalance present in the rotor by rotating the rotor about an axis of rotation. Determining the imbalance may include rotating the rotor and detecting the phase and respective magnitude of the imbalance. Some embodiments may include marking the rotor by laser etching the rotor, placing reflective stickers on the rotor, or any other method of creating characteristic marks on the rotor. In some embodiments, rotating the rotor may include using a machine, such as a dynamic balancer, to rotate the rotor about the axis of rotation at a speed less than an operating speed. The operating speed may include an expected rotational speed of the rotor for any phase of flight. In some embodiments, rotating the rotor may include rotating the rotor at a speed less than a first resonance of the rotor. Detecting the phase of the imbalance may include using a machine to monitor the characteristic marks on the rotor during rotation. In some embodiments, the machine that monitors the rotor rotation may be the same machine that rotates the rotor. The machine may track the characteristic marks and calculate the displacement of the marks during rotation, which may indicate an unbalanced rotor. In some embodiments, detecting the phase of the imbalance may include receiving a signal from an encoder or accelerometer during rotation, or downloading after rotation, to identify the rotor position or forces experienced by the rotor at the location where the encoder, accelerometer, or similar sensor is positioned on the rotor.

[0189] Some embodiments of a process for balancing a rotor may include calculating the amount of mass to add or remove at locations along the layers 5004, 5012 to correct any imbalances present in the rotor. Some embodiments may include a machine or algorithm that analyzes the phase and respective magnitude of the imbalance to determine the amount of mass to add or remove and the location of the added or removed mass. In some embodiments, the machine that calculates the mass to add or remove may be the machine rotating the rotor, the machine detecting the imbalance, or a separate machine. In some embodiments, adding or removing mass at locations along the layers 5004, 5012 may change the center of mass of the rotor to coincide with the rotor's axis of rotation. In some embodiments, the rotor may have multiple layers 5004, 5012 positioned along the inner surface of the rotor at a distance from the edge of the rotor. Thus, balancing a rotor may include balancing the rotor across one or more planes of the rotor by adding or removing mass along one of the layers or along two or more of the layers.

[0190] In some embodiments, removing a quantity of mass from layers 5004, 5012 may include machining to remove a portion of the volume of layers 5004, 5012. In some embodiments, removing a quantity of mass from layers 5004, 5012 may include removing anywhere between 50% and 100% of the volume of layers 5004, 5012. Removing 50% to 100% of the volume of layers 5004, 5012 may reduce the mass of the rotor. In some embodiments, layers 5004, 5012 may be present solely to be sacrificial material when balancing the rotor. Layers 5004, 5012 may be integrally formed with the rotor, providing integrated rotor balancing material that is removed rather than added. By removing sacrificial rotor material, the balancing process may not require the use of adhesives or fastening methods to add balancing weight.

[0191] In some embodiments, after removing material from layers 5004, 5012, the amount of layer mass remaining on the rotor may be the minimum amount of mass required to balance the rotor, thus resulting in a balanced rotor with minimized mass. Removing a majority of the volume of a layer present on a rotor may allow for a reduction in the rotor's mass such that the rotor does not include additional material. For example, if it is determined that a rotor having layers 5004, 5012 can be balanced without removing any portion of layers 5004, 5012, 100% of the volume comprising layers 5004, 5012 may be machined, since none of the mass from the layers is required to balance the rotor. In some embodiments, it may be determined that 3% of the volume of layer 5004 needs to be present to balance the rotor. In such an example, 100% of layer 5012 may be removed, and 97% of layer 5004 may be removed to balance the rotor.

[0192] Some embodiments may include utilizing specific machines to remove volumes of layers 5004, 5012 when balancing the rotor. Some embodiments may include utilizing machines capable of removing volumes of layers 5004, 5012 with an accuracy of 0.01% to 0.1% of the layer. In some embodiments, the machine may be used to machine the volume of layers, such as a lathe or CNC machine, to remove volumes of layers with a resolution of less than 5 microns. In such embodiments, using a machine capable of such accuracy may achieve the benefit of a balanced rotor with minimal mass. Some embodiments may include utilizing different types of machines when removing layers, such as removing a majority of the removed mass in a manner less accurate than the remaining amount of removed mass.

[0193] Some embodiments may include calculating an amount of mass to be added at a location along the layers 5004, 5012 to balance the rotor, and balancing the rotor may include machining to remove a volume of the layers 5004, 5012 such that the only amount of mass remaining in the layers is the portion of the layers 5004, 5012 that is equal to the calculated amount of mass to be added and that is located at the calculated location. In some embodiments, calculating an amount of mass to be removed at a location along the layers 5004, 5012 to balance the rotor may include machining to remove a volume of the layers 5004, 5012 such that the only amount of remaining layer mass is the portion of the layers 5004, 5012 that is equal to the calculated amount of mass to be removed and that is located at the opposite side of the layer from the calculated location.

[0194] In some embodiments, calculating the amount of mass to be removed may include calculating a number of sacrificial portions 5008 to remove. In some embodiments, the portions 5008 may be defined by grooves 5006. Some embodiments may include removing all portions 5008 or any partial amount of portions 5008. In some embodiments, removing portions 5008 may include calculating a maximum amount of portions to be removed to achieve a balanced rotor. In some embodiments, the k portions to be removed may include an amount of portions such that if any additional mass were to be removed from the rotor after the k portions have been removed, the rotor may not be able to achieve balance.

[0195] 51 illustrates a flowchart of an exemplary process for balancing the rotors of a VTOL aircraft 5100, consistent with disclosed embodiments. While the block diagram may be described below with reference to specific implementation embodiments presented in other figures, those implementations are provided for illustrative purposes only and are not intended to serve as limitations on the block diagram.

[0196] 51 includes process blocks 5102 through 5108. In block 5102, a process for balancing a rotor of an electric engine of an electric propulsion system may include identifying an axis of rotation of the rotor, consistent with discussion throughout this disclosure, the rotor comprising a sacrificial layer having a mass M formed along the circumference of the rotor.

[0197] In block 5104, the process for balancing the rotor of the electric engine of the electric propulsion system may include determining an imbalance present in the rotor by rotating a root about an axis of rotation consistent with the discussion throughout this disclosure.

[0198] At block 5106, the process for balancing the rotor of the electric engine of the electric propulsion system may include calculating an amount of mass k to add at a position p along the sacrificial layer such that the center of mass of the rotor is aligned with the axis of rotation of the rotor, consistent with the discussion throughout this disclosure.

[0199] At block 5108, the process for balancing the rotor of the electric engine of the electric propulsion system may include removing an amount of mass r from the sacrificial layer such that there is an amount of remaining mass n along the circumference of the rotor consistent with discussions throughout this disclosure.

[0200] As discussed herein, a rotor assembly of an electric motor assembly may include a rotor mechanically coupled to a sun gear. Similar to the above discussion regarding balancing the rotor, it may be advantageous to balance the rotor assembly to avoid unwanted vibrations and noise during normal operation. The rotor assembly may become unbalanced due to manufacturing tolerances and due to multiple mating parts throughout the rotor assembly.

[0201] In some embodiments, a process for balancing a rotor assembly may include identifying an axis of rotation of the rotor assembly and rotating the rotor assembly at a speed less than the operating speed. In some embodiments, the rotor assembly may be coupled to a machine that may be capable of rotating the rotor assembly at a speed less than the operating speed. In some embodiments, the rotor assembly may be rotated at a speed less than a first resonance of the rotor assembly. Some embodiments may include determining an imbalance present in the rotor assembly. Determining the imbalance present in the rotor assembly may include using a machine to identify the phase and magnitude of the imbalance by tracking a distinctive mark on the rotor assembly, such as a reflective sticker or laser-etched mark, or by using an electrical eye, encoder, accelerometer, or similar component to track the movement of the rotor assembly.

[0202] Some embodiments may include calculating an amount of mass to add to the rotor assembly so that the center of mass of the rotor assembly coincides with the axis of rotation of the rotor assembly. Calculating the amount of mass and its respective location may be performed using a machine or algorithm that analyzes the phase and magnitude of imbalances in various planes of the rotor assembly to determine the amount and location of mass to add to the rotor assembly. In some embodiments, the added mass may be in the form of a rivet. The rivet may include a mass that may be removably or permanently attached to the through-hole 5010 of the rotor 5000. The rivet may be made of aluminum, copper, steel, or any other material capable of balancing the rotor assembly. Adding the rivet may include permanently or removably attaching the rivet to the rotor through the through-hole so that the rotor assembly is balanced. In some embodiments, the amount of mass to add may include rivets with different material properties and locations.

[0203] 52 illustrates another flowchart of an exemplary process for balancing a rotor assembly of a VTOL aircraft 5200. While the block diagram may be described below with reference to specific implementation embodiments presented in other figures, those implementations are provided for illustrative purposes only and are not intended to serve as limitations on the block diagram.

[0204] As shown in FIG. 52, the process may begin at block 5202 by identifying the axis of rotation of a rotor, consistent with the discussion throughout this disclosure, the rotor comprising a sacrificial layer having a mass M formed along the circumference of the rotor.

[0205] At block 5204, the process for balancing the rotor assembly may proceed to determine any imbalance present in the rotor by rotating the rotor about an axis of rotation consistent with the discussion throughout this disclosure.

[0206] At block 5206, the process for balancing a rotor assembly of an electric engine of an electric propulsion system may include calculating an amount of mass k to add at a location p along the sacrificial layer such that the center of mass of the rotor is aligned with the axis of rotation of the rotor, consistent with discussions throughout this disclosure.

[0207] At block 5208, the process for balancing the rotor assembly may proceed to include removing an amount of mass r from the sacrificial layer such that there is a remaining amount of mass n along the circumference of the rotor, consistent with the discussion throughout this disclosure.

[0208] At block 5210, a process for balancing a rotor assembly, consistent with the discussion throughout this disclosure, may proceed to identifying an axis of rotation of the rotor assembly, the rotor assembly comprising a rotor mechanically coupled to a sun gear.

[0209] At block 5212, the process for balancing the rotor assembly may proceed to determine any imbalance present in the rotor assembly by rotating the rotor about an axis of rotation consistent with the discussion throughout this disclosure.

[0210] At block 5214, the process for balancing the rotor assembly may proceed to calculate the number of rivets j to add to the rotor assembly so that the center of mass of the rotor assembly coincides with the axis of rotation of the rotor assembly, consistent with the discussion throughout this disclosure.

[0211] At block 5216, the process for balancing a rotor assembly of an electric engine of an electric propulsion system may include adding j rivets to the rotor assembly consistent with discussion throughout this disclosure.

[0212] Disclosed embodiments of the electric propulsion system may include a gearbox assembly, as described herein. The gearbox may assist in gear reduction of the electric propulsion system. Some embodiments of the electric propulsion system may include a gearbox assembly, as described herein, located between the electric motor assembly and the end bell assembly. The gearbox assembly may include a main shaft assembly.

[0213] 17 is an exploded view of a main shaft assembly of a VTOL aircraft consistent with disclosed embodiments. The main shaft assembly 1700 may include a main shaft 1702, a carrier cover 1714, a planetary gear 1704, a pump drive gear 1716, and a planetary carrier 1712. The main shaft assembly 1700 may include a compound planetary gear such that the planetary gear 1704 is mechanically coupled to the planetary gear 1706. In some embodiments, shafts 1708 and 1710 may extend from the planetary gear 1704. In some embodiments, shafts 1708 and 1710 may extend from the first planetary gear 1704 and the second planetary gear 1706, respectively. The planetary gear 1704 may interface with a sun gear and a ring gear. In some embodiments, the ring gear may be fixed. In such embodiments, the planetary gear 1704, which interfaces with the ring gear and the sun gear, may rotate around the sun gear. In some embodiments, the planetary gears 1706 may interface with a ring gear. In such embodiments, the planetary gears 1704 may interface with a sun gear, while the planetary gears 1706 interface with a fixed ring gear that drives the planetary gears 1704 and 1706 to rotate about the sun gear. A planetary carrier 1712 may be mechanically coupled to the planetary gears 1704 and 1706, such as via a shaft 1710, such that when the planetary gears, and therefore the corresponding shafts 1710, rotate around the circumference of the sun gear, the planetary carrier 1712 rotates at the same speed. The planetary carrier 1712 may be mechanically coupled to multiple planetary gears 1704 and 1706. In some embodiments, the carrier cover may be mechanically coupled to the planetary gears 1704 and 1706, such as via a shaft 1708, such that when the planetary gears, and therefore the corresponding shaft 1708, rotate around the circumference of the sun gear, the carrier cover 1714 rotates at the same speed.

[0214] In some embodiments, the main shaft assembly 1700 may include a planetary carrier 1712 having a bearing 1722 that assists the planetary carrier 1712 in receiving the shaft 1710. The bearing 1722 may allow the shaft 1710 to rotate with the planetary gears 1704, 1706 while allowing the shaft to be housed within the planetary carrier 1712. In some embodiments, the carrier cover 1714 may have a bearing 1718 that assists the carrier cover 1714 in receiving the shaft 1708 such that the shaft 1708 rotates with the planetary gears 1704, 1706 while allowing the shaft 1708 to be housed within the carrier cover 1714. In some embodiments, washers 1720, 1724 may be positioned between the planetary gears 1704, 1706 and the carrier cover 1714 and planetary carrier 1712, respectively. The washers 1720, 1724 may be designed to account for mechanical tolerances in the manufacturing of components throughout the gearbox assembly, or may provide a counter-rotating surface for the planetary gears 1704, 1706 without damaging the planetary carrier 1712 or carrier cover 1714. Some embodiments may include mechanically coupling the planetary carrier 1712 and carrier cover 1714 using screws 1728 or similar components.

[0215] In some embodiments, the carrier cover 1712 may be mechanically coupled to the main shaft 1702. In such embodiments, the main shaft will rotate at the same speed as the carrier cover, and therefore will rotate at the same speed as the planetary gears 1704 or the compound planetary gears 1704 and 1706. In some embodiments, the planetary carrier may be mechanically coupled to the main shaft 1702. In such embodiments, the main shaft will rotate at the same speed as the planetary carrier 1712, and therefore will rotate at the same speed as the planetary gears 1704 or the compound planetary gears 1704 and 1706.

[0216] In some embodiments, the main shaft assembly 1700 may include a pump drive gear 1716. The pump drive gear may be disposed between the planetary carrier 1712 and the carrier cover 1716. Further, in some embodiments, the pump drive gear 1716 may be disposed between multiple planetary gears comprising the compound planetary gears 1704, 1706. The pump gear drive 1716 may be mechanically coupled to various components present within the gearbox assembly, including the planetary carrier 1712, the planetary gears 1704, 1706, or the carrier cover 1714. The pump drive gear 1716 may interface with other components (not shown here) within the electric engine assembly to circulate oil or other coolant liquid throughout the liquid flow path in an attempt to cool or lubricate the components present within the electric engine assembly, as described herein. For example, the pump drive gear 1716 may interface with a pump gear that functions to draw liquid from a sump to a heat exchanger. In such embodiments, the rotational speed of the pump gear drive 1716 may determine the rate at which oil or other liquid circulates throughout the electric engine assembly. In some embodiments, the pump drive gear 1716 may be mechanically coupled to the main shaft 1702 such that the pump drive gear rotates at the speed of the main shaft 1702. In some embodiments, the main shaft assembly 1700 may include a dowel pin 1726 or similar alignment component that helps align the pump drive gear with various components of the main shaft assembly 1700, including the planetary carrier 1712 or the carrier cover 1714.

[0217] As described herein, the electric motor assembly may drive the rotation of the rotor. Rotation of the rotor, which may be mechanically coupled to the sun gear, may rotate the sun gear at rotor speed. The sun gear, rotating at rotor speed, may interface with the planetary gear 1704 or compound planetary gears 1704 and 1706 to generate a gearbox assembly output including a new torque value that is supplied to the propeller assembly. In some embodiments, the combination of using a sun gear, planetary gears including compound planetary gears, and a ring gear as described herein may result in a gear reduction. One skilled in the art will understand that the gear ratio can be calculated from the gears present in the gearbox assembly. In this manner, the characteristics of the gears in the gearbox assembly may determine the gear reduction available to the electric propulsion system. In some embodiments, the gear reduction value may be a relevant design criterion for a VTOL aircraft, as the aircraft may require a specific value for the torque applied to the propeller assembly to achieve lift for the payload. However, it should be understood that increasing the gear size to generate a larger gear reduction results in an increased drag profile and mass of the electric engine. Thus, the embodiments described herein may provide an electric propulsion system design that is optimized in terms of drag profile and mass-to-payload capability.

[0218] As described herein, embodiments of the gearbox assembly may include a sun gear. FIG. 18 is a diagram of an exemplary sun gear for a VTOL aircraft consistent with disclosed embodiments. The sun gear 1800 may be constructed of stainless steel, plastic, or any material capable of assisting gear reduction. The sun gear 1800 may include teeth 1802 to assist in gear reduction. Some embodiments may include splined teeth. In some embodiments, the gear teeth 1802 may interface with planetary gears. The sun gear 1800 may include a hollow center. In some embodiments, gearbox components may pass through the hollow portion of the sun gear 1800. The sun gear 1800 may also include through-holes 1804 to assist in fastening the sun gear 1800 to other components of the electric engine. In some embodiments, the sun gear 1800 may be mechanically coupled to other components of the electric engine assembly, such as the rotor or output shaft of the electric motor assembly. Some embodiments may include through-holes 1804 to enable such mechanical coupling. In some embodiments, the sun gear 1800 may be fixed and therefore not rotate. In such embodiments, the planetary gears and ring gear may rotate freely. Some embodiments may include a through hole 1804 that is fastened to another component or surface to limit the rotation of the sun gear 1800.

[0219] Embodiments of the gearbox may include a ring gear. FIG. 19 is a diagram of an exemplary ring gear for a VTOL aircraft consistent with disclosed embodiments. The ring gear 1900 may include teeth 1902. The teeth 1902 may interface with one or more planetary gears to assist in gear reduction. The ring gear 1900 may be fixed or free to rotate. A fixed ring gear may be stationary, allowing the planetary gears to rotate around the sun gear. In some embodiments, the ring gear may be fixed by using through-holes 1904 to couple the ring gear to various components or structures within the electric propulsion system. In other embodiments, the free ring gear may rotate around a fixed planetary gear or a fixed sun gear. The ring gear 1900 may include slots 1902 to assist in fastening or mechanical coupling.

[0220] As described herein, embodiments of a gearbox assembly may include a planetary carrier assembly. Figure 20 is a diagram of an exemplary carrier assembly for a VTOL aircraft consistent with disclosed embodiments. In some embodiments, carrier assembly 2000 may include a planetary carrier 2008, a first planetary gear 2006, a pump drive gear 2012, a second planetary gear 2004, and a carrier cover 2010. In some embodiments, planetary carrier 2008, first planetary gear 2006, pump drive gear 2012, second planetary gear 2004, and carrier cover 2010 may rotate about central axis 2016 or shaft 2002. One or more planetary gears of carrier assembly 2000 may be substantially aligned along shaft 2014 or central axis 2018 to form a compound planetary gear set. For example, the first planetary gear 2006 and the second planetary gear 2004 may share a shaft 2014 and be coaxial along a central axis 2018. The carrier assembly 2000 may include a shaft 2002. The shaft 2000 may be coaxial along a central axis 2016. In some embodiments, the planetary carrier 2008, the first planetary gear 2006, the pump drive gear 2012, the second planetary gear 2004, the carrier cover 2010, and the shaft 2002 may be mechanically coupled such that these components all rotate at the same speed. In some embodiments, the shaft 2002 may be mechanically coupled to a propeller assembly such that the shaft transmits torque or mechanical shaft power to the propeller assembly. In some embodiments, the carrier assembly 2000 may include cavities, ports, or holes to assist in the distribution of a coolant, such as oil.

[0221] In some embodiments, the electric engine may include an inverter assembly that may include circuitry configured to receive a direct current input, convert the direct current to alternating current, and provide the alternating current to a stator ring of the electric motor.

[0222] As disclosed herein, embodiments of the electric engine assembly may include a thermal management system or cooling system that may circulate a coolant or lubricant throughout the engine. The lubricant or coolant, such as oil, may reside in a sump and be distributed to components throughout the electric engine assembly. As disclosed herein, the oil may proceed from the sump to a heat exchanger to various locations within the electric engine assembly, including the inverter assembly, gearbox assembly, and electric motor assembly. As described herein, the electric motor assembly may include an end bell assembly. In some embodiments, the end bell assembly may abut the inverter assembly.

[0223] 21A-21B are diagrams of an exemplary end bell assembly for a VTOL aircraft consistent with disclosed embodiments. FIG. 21A illustrates an internal view of an end bell plate of the end bell assembly. The end bell plate 2100A may comprise a plate 2102A made of aluminum, steel, or another type of thermally conductive material. The end bell plate 2100A may include a pump rotor 2104A and a passage rotor 2106A. The passage rotor 2106A may be sized to be able to rotate within the passage rotor 2106A such that multiple areas are open around the pump rotor 2104A while the pump rotor 2104A rotates within the passage rotor 2106A. The pump rotor 2104A may be positioned within the passage rotor 2106A. The pump rotor 2104A may be mechanically coupled to and have its rotation driven by another component of the electric engine assembly, such as a pump gear 2114B. In some embodiments, the pump rotor 2104A and the passage rotor 2106A may correspond to inner and outer rotors, or a gerotor with a positive displacement pump. The pump rotor 2104A may circulate oil from a sump through a pump inlet 2116B. In some embodiments, the pump rotor 2104A may rotate within the passage rotor 2106A, drawing oil from the pump inlet through the open area between the pump rotor 2104A and the passage rotor 2106A. In some embodiments, the rotation of the pump rotor 2104A within the passage rotor 2106A may create a vacuum between the pump inlet 2116B and a sump containing any liquid, such as a pump outlet 2118A. For example, the pump may create a vacuum to draw oil from a sump into the pump inlet 2116B. In some embodiments, a pressure differential may exist between the pump outlet 2118A and various distribution points of the cooling system, as described herein, so that oil or other liquid may be drawn from openings between the pump rotor 2104A and the passage rotor 2106A to the pump outlet 2118A and through the cooling system. In some embodiments, the end bell plate 2100A may include additional or different components, such as an electric pump or other mechanical configuration for drawing oil or other liquid through the pump inlet 2116B.Upon entering through the pump rotor 2104A and the passage rotor 2016A, the oil or liquid may proceed in direction 2120A and through the pump outlet 2118A to a heat exchanger. In some embodiments, the heat exchanger may be attached to the thermal plate 2100A or a partition plate as described herein.

[0224] In some embodiments, the heat exchanger may cool oil or other liquid used to lubricate or cool the inverter assembly, gearbox assembly, and / or electric motor assembly. In some embodiments, a certain portion of the cooled oil or liquid exiting the heat exchanger may be directed to the inverter assembly to cool such components, or to the motor gearbox housing to cool components of the gearbox assembly and / or electric motor assembly. Some embodiments may include different partitioning of the cooled oil or liquid between the inverter assembly and the gearbox assembly and the electric motor assembly. For example, the inverter assembly may receive 40% of the cooled oil volume, and the motor gearbox hose may receive 60%. The ratios may vary depending on design considerations and the requirements of a particular implementation. Indeed, different types of electric propulsion systems described herein may use different fluid distribution percentages. Furthermore, it should be understood that tilter electric propulsion systems and lifter electric propulsion systems may have similar or dissimilar distributions of oil from the heat exchanger. The pump corresponding to pump rotor 2104A and pump gear 2114B may provide performance improvements to the gearbox assembly. Furthermore, using the pump to drive the delivery of oil to the inverter assembly, as well as the gearbox assembly and electric motor assembly, may eliminate the need for extra components to deliver coolant to the inverter assembly. Such benefits may reduce mass and improve the drag profile of the electric propulsion system.

[0225] From the heat exchanger, cooled oil may enter channel 2108A and proceed in direction 2114A to annulus 2110A. Annulus 2110 may be aligned along the shaft as described herein. Annulus 2110A may include port 2116A. Oil from channel 2108A may proceed through port 2116A to various components of the electric engine, including the gearbox assembly and motor assembly, to provide cooling and lubrication. Oil may also proceed from annulus 2110A to channel 2112A. End bell plate 2100A may also include port 2122A to allow oil or other liquid to be transported through end bell assembly 2100B. In some embodiments, a pump may generate pressure that may drive movement of liquid through end bell plate 2100A. For example, pressure from a pump, which may be a gerotor or positive displacement pump, may drive the oil forward in channels 2108A, 2112A, annulus 2110A, port 2116A, or other grooves or cavities in the end bell plate that may assist in the transport of liquid.

[0226] FIG. 21B illustrates a diagram of an exemplary end bell assembly. The end bell assembly 2100B may include an end bell plate 2100. Additionally, the end bell assembly may include gears that may be driven by or interact with additional gears in the gearbox assembly, as described herein. In some embodiments, a ring gear 2104B may be coupled to the end bell plate 2102B assembly. The ring gear 2106B may include teeth that may interface with additional gears. The teeth of the ring gear 2106B may interface with planetary gears of the main shaft assembly, as described herein. In some embodiments, the teeth of the pump drive gear may interface with the teeth of the pump drive gear 2114B such that rotation of the pump drive gear drives rotation of the pump gear 2114B. The pump gear 2114B may be mechanically coupled to the pump rotor 2104A such that rotation of the pump gear 2114B may drive rotation of the pump rotor 2104A. As a result, the pump gear 2114B can drive the transport of lubricant or coolant throughout the end bell assembly. In some embodiments, the pump gear 2114B can drive the lubricant or coolant from a sump. The end bell 2102B can include a port 2118B for draining oil from the thermal plate via port 2122A.

[0227] In some embodiments, the end bell assembly 2100B may include an end bell plate 2102B that serves to seal the electric motor assembly housing or the motor gearbox assembly housing. In some embodiments, the end bell assembly 2100B may include a first circular wall extending away from the end bell plate 2102B. In some embodiments, the ring gear 2106B may be coupled to the first circular wall 2104B to prevent the ring gear 2106B from freely rotating, as described herein. In some embodiments, the end bell assembly 2100B may include a second circular wall 2108B extending away from the end bell plate 2102B. In some embodiments, the second circular wall 2108B may have a diameter less than the diameter of the first circular wall 2104B. The second circular wall 2108B may house a bearing 2110B. In some embodiments, the bearing 2110B may be mechanically coupled to a shaft, including a main shaft, that may transmit mechanical shaft power to a propeller assembly. In some embodiments, the bearing 2110B may include grooves to assist in the transfer of oil or other liquid. The second circular wall 2108B may also include an annular portion that includes a port hole 2112B. The port hole 2112B may be aligned with the port 2116A for receiving oil or liquid from a heat exchanger. The port hole 2112B may include a supply of oil or other liquid for cooling or lubricating components of the electric motor assembly and gearbox assembly.

[0228] In some embodiments, the portholes 2112B may transfer oil or other liquid to the main shaft, hi some embodiments, the outer surface of the main shaft may serve as a liquid flow passage through which oil or other liquid may flow over the main shaft and be distributed to components within the gearbox assembly and / or electric motor assembly.

[0229] Disclosed embodiments of an inverter assembly may include an inverter assembly having a heat exchanger. FIG. 22 is a diagram of an exemplary inverter assembly for a VTOL aircraft consistent with disclosed embodiments. In some embodiments, inverter assembly 2200 may include an inverter assembly housing 2202 coupled to a thermal plate 2204. Inverter assembly housing 2202 may serve to house inverter assembly components as discussed herein. Inverter assembly housing 2202, and therefore inverter assembly 2200, may possess a substantially circular profile. As used herein, a profile may be substantially circular, having a circular minor axis length and a circular major axis length, the minor axis length being at least 80% of the major axis length.

[0230] In some embodiments, inverter assembly 2200 may include a high-voltage connector 2212 and a low-voltage connector 2210. High-voltage connector 2212 may have a low profile. High-voltage connector 2212 may receive high-voltage power from a high-voltage power system located elsewhere in the aircraft via a high-voltage channel. Inverter assembly 2212 may include at least one drain 2208. Drain 2208 may be configured to allow any oil or liquid present within the inverter assembly to drain from inverter assembly 2200 regardless of the orientation of the electric engine assembly. In alternative embodiments, inverter assembly 2200 may also include a vent. In some embodiments, inverter assembly 2200 may include a heat exchanger 2206 coupled or attached to thermal plate 2204. In some embodiments, heat exchanger 2206 may be an integrated heat exchanger. In some embodiments, thermal plate 2204 may be welded to heat exchanger 2206. For example, thermal plate 2204 may be constructed of aluminum. The assembly of the thermal plate 2204 and the heat exchanger 2206 may include brazing, hardening, aging, and welding. In some embodiments, the thermal plate 2204 and the heat exchanger 2206 may be machined from the same material.

[0231] FIG. 56A illustrates a cross-sectional view of an installed press-in mesh port when operating in an inclined position, consistent with disclosed embodiments. In some embodiments, an inverter housing, such as housing 2302 shown in FIG. 23, can have multiple drains and / or vents, such as drain / vent 2208 shown in FIG. 23. As shown in FIG. 56A, each of the drains and / or vents 5600 can include a press-in mesh drain and vent port 5602. Each of the ports 5602 can include a mesh 5604 and a press-fit latch 5606 on the mesh 5604. The press-fit latch 5606 can be press-fit into the inverter housing 5608 (only partially shown in FIG. 56A) from the inside and can be configured to rest at an angle between 0° and 90°. In some embodiments, this angle can account for manufacturing difficulties. In some embodiments, the material of the mesh 5604 can be aluminum, copper, titanium, stainless steel (as used in sintered metal type meshes), or any mesh material that has a coefficient of thermal expansion (CTE) matched to the material (e.g., aluminum) of the housing 2302. In some embodiments, the drains and / or vents 5600 are positioned around the circumference of the inverter housing 5608 such that water can drain through at least one of the multiple drains and / or vents 5600 regardless of the orientation of the inverter housing 5608.

[0232] In some embodiments, the inverter housing 5608 can have lifter and tilter positions corresponding to the scenarios separately described with respect to Figures 32A-32D.

[0233] In some embodiments, the size of the port 5602 can be tailored to the needs of the application. Figure 56B illustrates a cross-sectional view of an installed press-in mesh port when operating in an inclined position, consistent with disclosed embodiments. In some exemplary embodiments, as shown in Figure 56B, the hole size can be approximately 3 mm, and the inclination angle after installation can be 10° to 25°, or up to 35°, relative to the direction of gravity.

[0234] Some embodiments may include an inverter assembly in which inverter components abut one another and may share a common housing. In some embodiments, the inverter assembly components may be positioned on top of one another in a stacked orientation. In some embodiments, the inverter assembly components may be substantially aligned along a central axis. The inverter assembly may include various components for sensing, circuitry, and control. FIG. 23 is an exploded view of an inverter assembly for a VTOL aircraft consistent with disclosed embodiments. The inverter assembly 2300 may include a control printed circuit board assembly (“PCBA”) 2316, a board spacer assembly 2314, a gate drive PCBA 2312, a capacitor assembly 2310, a power PCBA 2324, a housing gasket 2308, a thermal plate assembly 2304, and a heat exchanger 2306. The components of the inverter assembly 2300 may be mechanically coupled by various fastening means. For example, the components of the inverter assembly 2300, including the inverter assembly housing 2302, may be fastened together by fasteners 2318. Additionally, inverter assembly 2300 may include an inverter assembly housing 2302 that may be coupled to a thermal plate assembly 2304 to enclose the inverter assembly components and protect them from any liquids, debris, or other materials that may be harmful to the inverter assembly components. Inverter assembly housing 2302 may include connections for power and current used by the components of inverter assembly 2300, such as a high voltage connector 2322 and a low voltage connector 2320. In some embodiments, inverter assembly housing 2302 may include inverter bus bars for high current and low inductance.

[0235] In some embodiments, the inverter assembly housing 2302 may be cylindrical or have a donut-like shape (i.e., a generally round shape with a central hole in plan view). The form factor of the inverter assembly housing 2302 may provide low drag during flight.

[0236] In some embodiments, the capacitor assembly and at least one PCBA (e.g., 2312, 2314, 2316) may all be stacked and positioned inside the inverter housing 2302. In some embodiments, each of the stacked components (e.g., PCBA 2316, board spacer assembly 2314, gate drive PCBA 2312, capacitor assembly 2310, housing gasket 2308, thermal plate assembly 2304) may have multiple through locating holes to allow fasteners 2318 to pass through and fasten the stacked structure. In some embodiments, the fasteners 2318 may be long screws, bolts, or rods.

[0237] In some embodiments, a set of alignment pins 2326 may facilitate alignment of stacked components within the inverter assembly 2310 (e.g., PCBA 2316, substrate spacer assembly 2314, gate drive PCBA 2312, capacitor assembly 2310, housing gasket 2308, thermal plate assembly 2304). In some embodiments, the alignment pins 2326 may be integrated with the housing of the capacitor assembly 2310. Alternatively, in some embodiments, the locating pins 2326 may be a separate component from the assembly. In some embodiments, the locating pins 2326 may be overmolded as a feature of the housing of the capacitor assembly 2310.

[0238] In some embodiments, the thermal plate assembly 2304 can have a set of receptacles for the alignment pins 2326. The number of receptacles can match the number of alignment pins 2326.

[0239] FIG. 60A is a diagram of a capacitor housing showing alignment pins according to an exemplary embodiment. FIG. 60B is a diagram of a thermal plate and heat exchanger showing mating alignment pins, consistent with a disclosed embodiment. In this exemplary embodiment, two alignment pins 6002A and 6002B may be overmolded as features on the housing 6000A of the capacitor assembly (e.g., 2310). On the thermal plate 6000B (e.g., 2304 in FIG. 23), two recepticles 6004A and 6004B may have different shapes. The first recepticle 6004A may have a round shape configured to provide a friction fit for the first alignment pin 6002A. The second recepticle 6004B may have an elongated shape (e.g., an elongated oval, slot, or the like) to accommodate a dimensional trench. The major axis of the elongated shape may be radial.

[0240] In some exemplary embodiments, the alignment pins 6002A and 6002B may extend in both directions on either side of the capacitor housing 6000A. In the assembly process, the capacitor assembly (e.g., 2310 in FIG. 23 ) may be positioned on top of the thermal plate 6000B (e.g., 2304 in FIG. 23 ) through the housing gasket (e.g., 2308 in FIG. 23 ) and the power PCBA (e.g., 2324 in FIG. 23 ). The bottom surface of the first alignment pin 6002A engages with the first receptacle 6004A, and the bottom surface of the second alignment pin 6002B engages with the second receptacle 6004B. Together, both pairs may provide guides for aligning the capacitor assembly (e.g., 2310 in FIG. 23 ) and the thermal plate 6000B (e.g., 2304 in FIG. 23 ). The top surfaces of the alignment pins 6002A and 6002B then provide data for the remaining components of the inverter assembly (e.g., PCBA 2316, substrate spacer assembly 2314, gate drive PCBA 2312, capacitor assembly 2310, housing gasket 2308, thermal plate assembly 2304 of FIG. 23). Each of these components may have through alignment holes for the alignment pins 6002A and 6002B to pass through. These holes may have a clearance fit or an arrangement similar to the receptacles on the thermal plate 6000B for tolerance reasons. After all components are stacked, a fastener 2318 may be applied to the fastened components. In some embodiments, a receptacle 6006 may receive the fastener 2318. The receptacle 6006 may be threaded or may have an interference fit or crush ribs, depending on the type of fastener 2318.

[0241] 23 , in some embodiments, the stack orientation within the housing can accommodate various design shapes, such as a circular shape with a diameter proportional to the diameter of the motor or gearbox, or any other design shape. The internal components of the inverter can be arranged to help achieve that design target shape. In some embodiments, the stack orientation can be achieved by using common structural components throughout the stack, for example, by designing the different levels of the stack so that common structures, such as various bolts of the same length, can pass through each level to create the stack orientation.

[0242] In some embodiments, using a stack orientation may create additional obstacles with respect to additional design considerations, such as heat transfer, where the difficulty of managing proper distribution of coolant may increase in such a configuration. Furthermore, using long bolts to run through the various levels of inverters may increase the shock and vibration experienced by the inverter assembly. However, it is also understood that such a stack orientation may be advantageous in terms of various design considerations. For example, enabling a stack orientation may be beneficial from an aerodynamic perspective, where stacking allows for the inverter, or the inverter in combination with other engine components such as a gearbox and / or motor, to maintain a low drag profile. Additionally, a stack orientation may be advantageous from a manufacturability perspective, where fewer components are involved in securing the inverter assembly, as well as from a mass reduction perspective, where fewer components, and potentially less mass, are used to secure the components.

[0243] In some embodiments, the capacitor assembly 2310 can have at least one capacitor in a capacitor housing with at least one bus bar on the exterior. The capacitor assembly 2310 can have a center hole and multiple through-holes on the capacitor housing. The capacitor assembly 2310 can have at least one PCBA positioned within the capacitor housing.

[0244] As disclosed herein, the inverter assembly may include a power PCBA. In some embodiments, the power PCBA may include a power board. FIG. 24 is a diagram of an exemplary printed circuit board assembly for a VTOL aircraft consistent with disclosed embodiments. The power board 2400 may also include a sensor assembly. By way of example, possible sensors may include sensors for current shunts, motor temperature, and MOSFET module temperature. Additionally, some embodiments may include various power modules 2402 electrically coupled to the power board 2400. As discussed herein, the power modules 2402 may generate heat during use and require cooling to ensure proper functionality and efficiency of the overall electric propulsion system.

[0245] 57 is a cross-sectional perspective view of an integrated sensor on a power board according to some embodiments of the present disclosure. In some embodiments, the power board may be one of the at least one PCBA of the inverter assembly 2300.

[0246] In some embodiments, the power board 5702 may have sensors integrated therein. In some embodiments, the power board 5702 may have a rotor position sensor integrated therein. In some embodiments, the rotor position sensor may be at least two Hall sensors 5704 (only one shown in FIG. 57 ) integrated therein. In some embodiments, the gearbox of the propeller assembly may have magnets on its planet carrier. The power board 5702 and the gearbox 5706 are positioned in close proximity to each other so that the at least two Hall sensors 5704 can sense the position of the magnets to determine the position of the propeller. In some embodiments, the heat plate 2304 of the inverter assembly 2300 and the end bell plates of the gearbox 5706 are made of materials that do not block magnetic fields so that the at least two Hall sensors 5704 can sense the position of the magnets.

[0247] In some embodiments, the power board 5702 may have an oil temperature sensor (not shown) integrated into it. In some embodiments, the oil temperature sensor may be positioned to sense the temperature of a cooling fluid (e.g., oil, water, or other fluid, or a mixture of fluids known to have a large heat capacity). In some embodiments, the cooling fluid may be one used to cool MOSFETs, power modules, or other components that generate heat.

[0248] In some embodiments, the power board 5702 may have a secondary speed sensor (not shown) connected to the control board of the electric propulsion system (not shown) to provide redundancy.

[0249] 58 is a perspective view of a flexible PCBA connection consistent with disclosed embodiments. In some embodiments, a PCBA 5800 can have a flexible PCBA structure 5802 for making electrical connections with electrical components (not shown) from a plane of the PCBA. In some embodiments, the flexible PCBA 5802 can include contact pads 5804 having electrical contacts (not shown) thereon and at least one serpentine connection 5806 formed by cutting a layered printed circuit board (PCB). The electrical contacts can be electrically connected to electronics on the remainder of the PCBA through at least one of the at least one serpentine connection 5806.

[0250] In some embodiments, each of the serpentine connections 5806 can have a flex coefficient. The flex coefficient is defined as the allowable displacement or deflection of the contact pads over the length of the flexible section (i.e., the serpentine connections 5806 and the contact pads 5804). The flex coefficient can be defined for displacement along any direction, i.e., within the plane defined by the PCBA, perpendicular to the plane defined by the PCBA, or any direction between the two aforementioned directions. In some embodiments, the flex coefficient serves as an indication of the flexibility of the flexible PCBA structure 5802 when the contact pads 5804 deflect from the plane defined by the PCBA.

[0251] In some embodiments, the flexible PCBA structure 5802 may have two or more serpentine connections 5806 connected to the same contact pad 5804. In some embodiments, at least two of the serpentine connections 5806 may have the same bending coefficient.

[0252] In some embodiments, the flexural modulus of the flexible PCBA structure 5802 may be less than 0.015, or about 0.005.

[0253] In some embodiments, the contact pad 5804 may have multiple standoffs (not shown) thereon.

[0254] In some embodiments, the PCBA (eg, FR4) may include alternating substrate layers and copper layers.

[0255] In some embodiments, the flexible PCBA structure 5802 may enable an electrical connection between the PCBA structure and another electrical contact from the PCBA without the need for additional components (e.g., pin connectors, wire connectors, flex circuits, or additional processes such as soldering or welding), thus saving costs. In some embodiments, the electrical connection may be made by stacking the PCBA with the flexible PCBA structure 5802 and aligning it over another structure having other electrical contacts. In some embodiments, the PCBA alignment may be made by having the alignment pins 2326 pass through the alignment holes in the PCBA. Because the flexible PCBA structure 5802 allows the contact pads 5804 to deflect out of plane, an electrical connection may be made by pressing the contact pads 5804 against another electrical contact. Alternatively, the contact pads 5804 may include standoffs on the backside to provide the necessary support, so that an electrical connection may be made by pressing another component over the contact pads 5804. The electrical connections may be secured in place by conventional means, such as snap fits, soldering, ultrasonic welding, electric welding, laser welding, ultrasonic wire bonding, etc. Deflection of the contact pads 5804 may provide tolerance stack-up and thus make the electrical connections secure and robust.

[0256] In some embodiments, the serpentine connection 5806 can be partially cut out to allow for more deflection of the contact pads 5804. FIG. 59 is a cross-sectional view of the serpentine connection 5806 of the flexible PCBA shown in FIG. 58, illustrating a partial cutout consistent with disclosed embodiments. In this exemplary embodiment, the cutout 5902 is only on the substrate layer 5904. The copper layer 5906 can remain intact. In some embodiments, the cutout direction is perpendicular to the instantaneous elongation direction of the serpentine connection, i.e., the cutout 5902 is always cut across a narrow width of the serpentine connection. The cutout 5902 can further increase the flexibility of the flexible PCBA structure, allowing the contact pads 5804 to deflect more easily. In other words, the cutout 5902 can have the same effect as increasing the bending coefficient.

[0257] As discussed above, the electric engine and associated control components of a VTOL aircraft may generate heat during operation. For example, such components may include an inverter assembly, an electric motor assembly, and a gearbox assembly. The engine may accumulate heat buildup resulting from mechanical friction between parts and from resistive heating within the motor-gearbox assembly. The accumulated heat may be carried to a heat exchanger by a lubricant circulating through one or more portions of the engine. Dissipation of heat is necessary to prevent deterioration or damage to the motor, control components, and other elements of the VTOL aircraft. Such heat may be managed by cooling the engine, including direct or indirect cooling. In some embodiments, cooling may be assisted by a heat exchanger. The heat exchanger may be configured to receive a circulating heat exchange medium from the electric engine. For example, the heat exchange medium may include oil, which may be used to lubricate and cool components of the electric engine. The heat exchanger may interface one or more fluids with each other, thereby cooling a fluid at a higher temperature. The heat exchanger may be advantageously located next to the electric engine, thereby minimizing the volume (and weight) of materials required to accomplish cooling and lubrication functions. In some embodiments, the heat exchanger may be fluidly, thermally, and mechanically coupled to the inverter assembly such that the heat exchanger may share common connections with the inverter assembly, reducing the need for components such as cables, wires, tubes, and hoses that may add weight and require more space within the electric engine. Heat from the inverter assembly, electric motor assembly, or gearbox assembly may be transferred to a cooling fluid, such as oil. The oil may absorb such heat, and the oil may then be directed to a sump.

[0258] As described herein, the electric propulsion system may include a heat exchanger. FIGS. 25A-25C are diagrams and example front views of a heat exchanger for a VTOL aircraft consistent with disclosed embodiments. The heat exchanger 2504A may be mechanically coupled to a thermal plate 2502A of the inverter assembly as described herein and as shown in example diagram 2500A. The thermal plate 2502A may include a fin array 2506A. The fin array 2506A may provide a heat sink that draws heat from the inverter assembly components. As described herein, the heat exchanger 2504A may be positioned to receive airflow from a propeller. The propeller (not shown) may direct an airflow 2508A into the heat exchanger 2504A, and exhaust air 2510A may be exhausted from the heat exchanger. The airflow 2508A, which may be cooler air, may be forced into the heat exchanger 2504A, for example, as downwash from a propeller blade (not shown). The exhaust air 2510A, which may be warmer air, may be exhausted from the heat exchanger 2504A without entering other components of the electric propulsion system. In some embodiments, the heat exchanger 2504A may include cooling fins.

[0259] 25B-25C illustrate exemplary views of cooling fins 2500B and 2500C within heat exchangers, respectively. Oil or other lubricant or coolant, which may absorb heat from an electric motor assembly, a gearbox assembly, or an inverter assembly, may be circulated through the fins of heat exchanger 2504A. Heat exchanger 2504A may include tubes 2504B and fins 2502B. Tubes 2504B may carry oil, and fins 2502B may be thermally coupled to tubes 2504B. As a result, oil traveling within tubes 2504B may transfer heat to another fluid heat exchange medium. Fins 2502B may be configured to maximize the surface area of ​​heat exchanger 2504A and increase surface area contact between tubes 2504B and a fluid. The increased surface area may increase the rate of heat transfer. The fluid may include air. For example, airflow 2508A may enter heat exchanger 2504A, be in thermal contact with fins 2502C, and receive heat from oil traveling within tubes 2504C. The air may then be discharged from heat exchanger 2504A as exhaust air 2510A. Heat exchanger 2504A may transfer heat via convection.

[0260] FIG. 26 is a diagram of a heat exchanger for a VTOL aircraft, consistent with disclosed embodiments. The heat exchanger 2600 may include a length 2602, a height 2604, and a depth 2606. As described herein, the heat exchanger 2600 may include tubes and fins to assist in heat transfer between fluids. The heat exchanger 2600 may include multiple cooling paths. Section 2608 shows examples of different cooling paths. A lubricant or coolant, such as oil, may travel within tubes 2610. The tubes 2610 may be thermally coupled to fins 2612, as described herein. The tubes 2610 may comprise hollow tubes for the fluid. The fins 2612, as described herein, may increase the contact surface area between the air and the tubes 2610, thereby increasing the rate of heat transfer from the oil to the air within the tubes 2610. In some embodiments, the heat exchanger 2600 may include multiple layers of fins 2612 stacked between and thermally coupled to the tubes 2610. As a result, oil entering the heat exchanger 2600 may flow into different tubes 2610, creating multiple cooling paths through which heat can be transferred from the oil to the air.

[0261] As described herein, embodiments of an electric engine may include circulating a lubricant or coolant throughout the engine. A heat exchanger may cool the lubricant or coolant directed to engine components such as the motor, gearbox, or inverter. In some embodiments, heat from the inverter assembly may be conducted directly to the coolant or lubricant, such as oil.

[0262] 27A-27B are front views of a divider plate for a VTOL aircraft consistent with disclosed embodiments. In some embodiments, the divider plate may be comprised of an end bell plate and a thermal plate. The divider plate may comprise one or more plates sandwiched together and disposed between the motor gearbox housing and the inverter assembly housing. Additionally, the divider plate may aid in the distribution of lubricant or coolant throughout the engine. In some embodiments, the divider plate may include channels, tubes, ports, cavities, or other features for transporting liquids. End bell plate 2700 may include elements and discussion similar to the end bell plate of FIG. 21. In some embodiments, end bell plate 2700A may be coupled to thermal plate 2700B. In some embodiments, end bell plate 2700A may abut a gasket plate, which may abut thermal plate 2700B. The inverter assembly may include thermal plate 2700B. The thermal plate 2700B can be mechanically, thermally, and fluidly coupled to the heat exchanger 2710B. In some embodiments, the end bell plate 2700A and the thermal plate 2700B can be positioned above the heat exchanger. The periphery of the thermal plate 2700B can be connected to the heat exchanger 2710B. The end bell plate 2700A and the thermal plate 2700B can include channels to aid in the distribution of a lubricant or coolant. As used herein, a channel can also refer to a groove, bore, or any other conduit configured to distribute oil or other coolant or lubricant in a planar direction. In some embodiments, the lubricant or coolant can be a liquid, such as oil, as described herein. The thermal plate can be thermally and fluidly coupled to the heat exchanger by a liquid, such as oil. In some embodiments, the distribution of the lubricant or coolant can be driven by a pump. The thermal plate 2700B may include grooves, bores, liquid channels, or any other conduits that assist the pump gear in transporting oil or other liquid from the sump.In some embodiments, oil may be transported from the sump through passage rotors 2704A, 2704B and pump rotor 2706A to inlet channel 2708A on end bell plate 2700A. The oil in inlet channel 2708A may be hot or warm oil traveling through flow path 2716A. The oil in inlet channel 2708A may proceed to heat exchanger inlet 2706B in thermal plate 2700B and enter the tubes or other liquid flow path of heat exchanger 2710B. As described herein, the oil circulating through the liquid flow path may be cooled in heat exchanger 2710B, and the cooled oil may proceed to heat exchanger outlet 2708B in thermal plate 2700B. In some embodiments, oil transported between thermal plate 2700B and end bell plate 2700A may proceed through a gasket plate. The cooled oil in the heat exchanger outlet 2708B may then proceed along flow path 2718A to outlet channel 2710A to annulus 2712A and channels 2714A of end bell plate 2700A and annulus 2712B on thermal plate 2700B. In some embodiments, the oil in annulus 2712B may flow into fin array 2714B in thermal plate 2700B to provide cooling and heat transfer. Oil from fin array 2714B may then return to the sump via ports. Some embodiments may include annulus 2712A that is substantially aligned along a main shaft or axis shared with a gearbox assembly or electric motor assembly. In some embodiments, oil or liquid may proceed from annulus 2712A through portholes to the gearbox assembly or electric motor assembly, as described herein. In some embodiments, channel 2714A may be fluidly connected to additional liquid flow paths within the motor gearbox housing, which may serve to circulate oil or liquid to additional portions of the electric engine, such as front bearings or components located near the propeller assembly. In some embodiments, the end bell plate may include a seal within the electric engine. The end bell assembly may include a face seal between the heat exchanger and the inverter assembly to prevent oil leakage.

[0263] In some embodiments, a lubricant or coolant may be used to cool the inverter assembly using the thermal plate 2702B. Some embodiments may include hot oil or other liquid entering the inlet channel 2708A, which may be aligned with the heat exchanger inlet 2706B, to enter the heat exchanger 2710B. The cooled oil or other liquid exiting the outlet channel 2710A, which is aligned with the heat exchanger outlet 2708B, and some or all of the cooled oil or liquid may follow a liquid flow path to the annular portion 2712B of the thermal plate. The oil or other liquid in the annular portion 2712B may be distributed to a heat sink located on the thermal plate 2702B, such as the fin array 2714B, and by aligning the fin array 2714B with the power modules located in the inverter assembly, may provide cooling to the power modules, such as those referenced in FIG. 24 . It should be understood that the inverter assembly may have components that may not function well or efficiently when exposed to oil or other liquid. In this manner, the thermal plate may include heat sinks to remove heat from the inverter assembly, and then circulate oil or liquid within the thermal plate rather than within the inverter assembly housing to transfer heat from those heat sinks to the oil or liquid cooled by the heat exchanger. Thermal plate 2702B may include port holes 2716B to allow oil or liquid to pass through the port holes and enter the end bell assembly. In some embodiments, port holes 2716B may allow oil to return to the sump. In some embodiments, port holes 2716B may align with port holes 2720A present on plate 2702A of end bell plate 2700A. In some embodiments, oil from port holes 2718B may enter the end bell assembly to circulate to a sump located within the motor gearbox housing. In some embodiments, the oil may return to the sump along the direction of gravity, and such oil may be warm or hot. Cooling with oil may provide various benefits, including improving the overall performance of the inverter assembly.For example, using fluid to cool the power modules as shown in Figure 24 may improve the performance of the inverter assembly. Additionally, liquid convection may improve the durability of the inverter assembly compared to other cooling methods that involve additional components, such as air convection methods that require the addition of air-cooled fins.

[0264] Disclosed embodiments of electric propulsion systems may include one or more components for distributing a lubricant or coolant, as described herein. In some embodiments, a lubricant or coolant, such as oil, may be circulated from a sump 1212A to a heat exchanger 1226A and then to an inverter assembly, a gearbox assembly, and a motor assembly (as illustrated in FIG. 12A). As illustrated in FIG. 21A, an end bell assembly may assist in the distribution and circulation of oil. As described herein, oil traveling from the heat exchanger in a channel 2108A may be distributed to an annulus 2110A and a port 2116A located within the annulus 2110A. As described herein, a main shaft, which may be substantially aligned with the annulus 2110A of the end bell assembly, may extend from the end bell assembly, through the gearbox assembly, and through the electric motor assembly. In some embodiments, a portion of the oil in the end bell assembly may be shared among the annulus 2110A, the port 2116A, the port 2122A, and various other ports and channels. Centrifugal, centripetal, or pressure forces can drive oil from the annulus 2110A, the port 2116A, or grooves in the bearing 2110B along the main shaft toward the gearbox assembly and electric motor assembly. For example, pressure in the end bell assembly 2100B can drive oil into grooves in the bearing 2110B or porthole 2112B. Centrifugal force can then drive the oil along the main shaft to the windings of the stator in the motor assembly. For example, rotation of the main shaft can exert a centrifugal force that drives the oil along the main shaft. In some embodiments, oil can pass from the end bell assembly through holes, pipes, channels, tubes, or ports to the gearbox assembly and motor assembly. For example, oil can flow into the annular area between the sun gear and the shaft. In some embodiments, a port can transfer oil from the end bell assembly to a channel or similar structure present in the motor assembly housing for delivery of oil to additional portions of the gearbox assembly or motor assembly.Some embodiments may include a channel or similar structure configured to deliver oil to a propeller assembly, a bearing mechanically coupled to a shaft flange, or a stator winding in a motor assembly.

[0265] As described herein, the amount of oil used in an electric propulsion system may be minimized by using a fluid such as oil to provide both lubrication and cooling. Furthermore, oil may be used to lubricate various bearings, such as rolling bearings or hydrodynamic bearings, as described herein. Minimizing the amount of oil used in an electric propulsion system may reduce the mass and drag profile of the electric propulsion system. Furthermore, minimizing the amount of oil required for operation of the electric propulsion system may allow the total amount of oil in the electric propulsion system to remain below a threshold amount. For example, an electric propulsion system may reduce the amount of oil required for operation by using a heat exchanger, as described herein. Warm or hot oil used for lubrication and cooling may reside in a sump, and by using a heat exchanger to cool such oil, the electric propulsion system may reuse the oil, eliminating the need for additional oil. Furthermore, as described herein, the use of a common liquid for both cooling and lubrication may lead to a reduction in component mass compared to other methods of cooling and lubrication that use different liquids. Such configurations using different liquids may require additional mass and size of the electric propulsion system, such as additional heat exchangers, additional fluid distribution channels or tubes, and additional surface area to receive cooling air from the propeller assembly.

[0266] In some embodiments, ventilation from the airflow may provide cooling for the lubricant in the heat exchanger. It should be understood that using oil to not only lubricate but also cool the electric engine rather than a separate coolant adds additional oil to the system, but eliminates traditional components that may be used to cool such an electric engine. For example, if the electric engine were cooled by a separate liquid, such as glycol, the engine may include separate heat exchangers for both the lubricant fluid and the coolant fluid. Thus, in embodiments where a single fluid is used for both lubrication and cooling, such as oil, there would be an increase in oil, but only the need for one heat exchanger, so the overall system may have a reduced mass due to using fewer heat exchangers and potentially other components not being needed, and a more attractive drag profile. Furthermore, using one material to lubricate and cool the engine may increase the efficiency of the system due to the reduced mass and the benefits of cooling the engine with a material rather than relying on air cooling, which can be problematic to manage throughout the engine.

[0267] Some embodiments of the inverter may include an inverter that does not utilize a heat exchanger but has a coolant path that travels around the periphery of the inverter but within the inverter housing, for example, the coolant path may travel around any printed circuit board assemblies, power modules, or other inverter components present within the inverter.

[0268] As disclosed herein, embodiments of the electric engine may include an inverter assembly. In some embodiments, the inverter assembly may include a thermal plate. FIG. 28 is a diagram of a thermal plate for a VTOL aircraft consistent with disclosed embodiments. The thermal plate 2802 may assist in heat transfer of the inverter assembly, including distributing coolant to the inverter assembly. In some embodiments, the thermal plate 2802 may abut components of the inverter assembly, such as the inverter housing or printed circuit board. The thermal plate 2802 may be thermally coupled to the inverter assembly. In some embodiments, the thermal plate 2802 may abut an end bell assembly. In some embodiments, the thermal plate 2802 may abut a gasket that may abut the end bell assembly. The gasket may be a metal carrier gasket. In some embodiments, the thermal plate 2802 may abut a heat exchanger 2810. For example, the thermal plate 2802 may be mounted on the heat exchanger 2810, and the coolant may travel through various paths within the heat exchanger 2810. As an example, oil may be a coolant that travels through various paths within the heat exchanger 2810. The pump rotor 2804 may drive oil through cooling paths, also referred to herein as liquid flow paths, within the heat exchanger 2810. In some embodiments, oil or other liquid from a sump may be drawn through the pump rotor 2804 to the heat exchanger inlet 2806. In some embodiments, the heat exchanger 2810 may receive oil or other liquid from the heat exchanger inlet 2806, cool the oil or other liquid, and the cooled oil or other liquid may exit the heat exchanger at the heat exchanger outlet 2808. The cooled oil from the heat exchanger 2810 may be driven by the pump 2804 into different channels within the thermal plate. For example, the oil may be transported to the distribution channel 2812. In some embodiments, the thermal plate 2802 may include a heat sink to assist in heat transfer of the inverter assembly. As an example, the thermal plate 2802 may include a fin array 2818.The fin array 2818 may include cooling fins extending from the base to increase surface area for improved heat transfer. The fin array 2818 may be located within a cavity in the thermal plate 2802. The fin array 2818 may be a heat sink and may be constructed of a material with high thermal conductivity. In some embodiments, the fins may be rectangular or circular and constructed of aluminum. The fin array 2818 may draw heat from the thermally and mechanically coupled inverter assembly to cool components including the switching devices and MOSFETs. The fin array 2818 may be exposed to a flowing fluid. For example, cooled oil in the distribution channels 2812 may enter the fin array 2818 via channels 2814 and provide cooling and heat transfer to the fin array 2818. From the fin array 2818, the oil may then flow to the collection channels 2816. In other embodiments, the oil may be transported directly from the distribution channels 2812 to the collection channels 2816.

[0269] FIG. 29 is a diagram of an electric propulsion system for a VTOL aircraft consistent with disclosed embodiments. In some embodiments, a thermal plate 2900 may be thermally coupled to a motor assembly housing 2902. The thermal plate 2900 may also be fluidly coupled to the motor assembly housing 2902 by one or more coolant or lubricant channels. As described herein, the thermal plate 2900 may assist in the distribution of a coolant or lubricant, such as oil. For example, oil within the thermal plate 2900 may enter a heat exchanger 2914 via a heat exchanger inlet 2912 and exit the heat exchanger 2914 via a heat exchanger outlet 2910. The thermal plate 2900 may include a pump rotor 2908, distribution channels 2916, a fin array 2922, and collection channels 2920. Cooled oil from the heat exchanger 2914 may enter the distribution channels 2916, flow through the fin array 2922 via direction 2928, and enter the collection channels 2920 via channels 2918. As described herein, the fin array 2922 may be a heat sink, assisting in transferring heat from the inverter assembly to the cooled oil 2928. In some embodiments, the oil in the thermal plate 2900 may be transported to the motor assembly housing 2902. For example, oil flow path 2930 may be an exemplary flow path from the thermal plate 2900 to the motor assembly housing 2902. Oil flow path 2932 may be an exemplary flow path for oil to various components within the motor assembly housing 2902. The oil 2930 may also proceed to a second oil flow path 2934. The oil in the various flow paths may proceed to the gearbox assembly, the electric motor assembly, or other components within the motor assembly housing 2902 to provide cooling or lubrication, as described herein. Oil distributed throughout the motor assembly housing 2902 may accumulate in a sump 2904. The oil may flow through the sump along liquid flow paths 2924 and then drain from the sump 2904 and flow back to the thermal plate 2900 on a return path 2926. The motor assembly 2902 may be mechanically coupled to a shaft flange assembly 2906 as described herein.In some embodiments, the location of the thermal plate 2900 and heat exchanger 2914 may provide advantages to the electric propulsion system. For example, the thermal plate 2900 abutting and fluidly coupled to the heat exchanger 2914 may eliminate the need for external connections. As discussed herein, oil may pass from the heat exchanger 2914 to the thermal plate 2900 and be distributed to components of the electric propulsion system, such as the inverter assembly, gearbox assembly, and motor assembly, which may be packaged together. Such a configuration, including a thermal plate that integrates several components together, may eliminate the need for external connections and may reduce the risk of leakage, dislodgment, etc. of such external connections.

[0270] 30A-30B are diagrams of an exemplary electric propulsion system for a VTOL aircraft consistent with disclosed embodiments. As described herein, the electric propulsion system 3000A may include a heat exchanger 3008A mechanically, thermally, and fluidly coupled to a thermal plate 3006A. The thermal plate 3006A may be mechanically coupled to a motor housing 3002A comprising a liquid sump 3004A. The electric propulsion system 3000A may include a shaft flange assembly 3010A. In some embodiments, the electric propulsion system 3000A may include a thermal plate 3006A and a motor housing 3002A substantially aligned along an axis 3012A. FIG. 30B provides an additional view of the electric propulsion system 3000B. The heat exchanger 3008B may be mechanically coupled to the thermal plate 3006B. The thermal plate 3006B may be mechanically coupled to a motor housing 3002B, which may comprise a liquid sump 3004B. In some embodiments, the electric propulsion system 3000B may include a thermal plate 3006B and a motor housing 3002B substantially aligned along an axis 3012B.

[0271] 31A-31B are cross-sectional views of an electric propulsion system for a VTOL aircraft consistent with disclosed embodiments. FIG. 31A illustrates an exemplary embodiment of a tilter electric propulsion system. As disclosed herein, tilter may refer to an electric propulsion system for tilting. The tilter 3100A may include an inverter assembly 3104A, a gearbox assembly 3106A, and an electric motor assembly 3102A. As described herein, the heat exchanger 3118A may be thermally, fluidly, and mechanically coupled to the inverter assembly 3104A. The inverter housing 3116A may enclose the inverter assembly 3104A. The gearbox assembly 3106A may abut the inverter assembly 3104A and the electric motor assembly 3102A. The motor gearbox assembly housing 3110A may enclose the electric motor assembly 3102A and the gearbox assembly 3106A. The sump 3112A may include a fluid inlet 3114A for transferring oil or other liquid to the heat exchanger 3118A. In some embodiments, the sump 3112A may be a reservoir for holding oil. The sump 3112A may abut the motor housing 3110A. In some embodiments, the main shaft 3108A extends from an end bell assembly that seals the motor gearbox assembly housing 3110A, through the gearbox assembly 3106A and the electric motor assembly 3102A, to the shaft flange assembly 3120A. As described herein, the gearbox assembly 3106A and the electric motor assembly 3102A may be substantially aligned along the main shaft 3108A. Additionally, the inverter assembly 3104A may be substantially aligned along an axis that shares the axis of the main shaft 3108A.

[0272] As mentioned above, the tilter may possess a variable pitch mechanism that serves to change the pitch of the VTOL aircraft's propeller blades. In some embodiments, the variable pitch mechanism may be mounted to the rear of the electric engine assembly, such as the rear of the inverter assembly. Furthermore, the variable pitch mechanism may interact with the main shaft to change the pitch of the propeller blades, as described herein. In such embodiments, as discussed herein, the inverter assembly 3104A, inverter assembly housing 3116A, and divider plate may possess packaging with passages through their configurations and housings to allow the variable pitch mechanism to interface with the main shaft or propeller blades. As discussed throughout, the lifter electric propulsion system may not change the direction of blade thrust or pitch. Thus, in some embodiments, the divider plate may not possess passages like those present in the tilter electric propulsion system. Furthermore, while the inverter assembly and inverter assembly housing of the lifter electric propulsion system may not possess such passages, it is recognized that from a safety testing perspective and a manufacturability perspective, it may be beneficial for the inverter assembly and inverter assembly housing of the lifter electric propulsion system to possess similar packaging, including the passages of the tilter electric propulsion system.

[0273] FIG. 31B illustrates an exemplary embodiment of a lifter electric propulsion system. As disclosed herein, lifter may refer to an electric propulsion system for lift. The lifter 3100B may include an inverter assembly 3104B, a gearbox assembly 3106B, and an electric motor assembly 310BA. As described herein, a heat exchanger 3118B may be thermally, fluidly, and mechanically coupled to the inverter assembly 3104B. An inverter housing 3116B may surround the inverter assembly 3104A. The gearbox assembly 3106B may abut the inverter assembly 3104B and the electric motor assembly 3102B. A motor gearbox housing 3110B may surround the electric motor assembly 3102B. In some embodiments, a main shaft 3108B extends from an end bell assembly that seals the motor gearbox housing 3110B, through the gearbox assembly 3106B, and to the electric motor assembly 3102B. As described herein, the gearbox assembly 3106B and the electric motor assembly 3102B may be substantially aligned along the main shaft 3108B. Additionally, the inverter assembly 3104B may be substantially aligned along an axis that shares the axis of the main shaft 3108B.

[0274] As discussed herein, it should be noted that having similar components between the tilter and lifter electric propulsion systems can be beneficial for the manufacturability of the overall aircraft. Furthermore, using similar components between the tilter and lifter electric propulsion systems can be beneficial in diagnosing problems and ensuring safety requirements and protocols are met. However, in some embodiments, the lifter and tilter may possess components that are not present in the other. For example, the lifter electric propulsion system 3100B may include a lock nut 3112B located between the main shaft 3108B and the shaft flange assembly 3120B that is larger than the lock nut present in the tilter electric propulsion system 3100A. The lock nut 3122B may help ensure that the mechanical connection between the main shaft 3108B and the shaft flange assembly 3120B is not damaged or broken due to various vibration loads experienced during flight. For example, as discussed herein, some phases of flight may not require the lifter electric propulsion system to be active, and in such cases, the blades may need to be retracted in a particular manner. However, if the lifter blades are not properly retracted, they may experience drag forces against the blades, and the mechanical connection between the main shaft 3108B and the shaft flange assembly 3122B may experience tension. Furthermore, in some embodiments, the lock nut 3112B of the lifter electric propulsion system 3100B may offset operating loads. In some embodiments, the lifter electric propulsion system may also include a larger propeller flange 3126A compared to the tilter shaft flange for reasons similar to the presence of the lock nut 3122B. Furthermore, the lifter electric propulsion system may also include a bearing 3124A to assist in the rotation of the propeller flange 3126A. As described herein, the electric propulsion system may achieve different orientation angles during operation. In this manner, fluids within the electric propulsion system, including coolants or lubricants, may move due to gravity. For example, lubricants or coolants, such as oil, may shift within the electric propulsion system during operation.Oil may reside in a sump, and oil may shift within the sump and the electric propulsion system. Regardless of orientation, some embodiments may require some amount of oil or other liquid to act as a coolant or lubricant throughout the entire phase of flight. In this manner, the cooling system may be designed to allow circulation of oil regardless of the orientation of the aircraft.

[0275] 32A-32D are cross-sectional views of electric propulsion systems for VTOL aircraft consistent with disclosed embodiments. Figures 32A-32D share similar numerals and refer to similar elements of electric propulsion systems 3200A, 3200B, 3200C, and 3200D. As such, similar design considerations and configurations may be considered throughout the embodiments.

[0276] FIG. 32A illustrates an exemplary embodiment of an electric propulsion system in an upright orientation. By way of example, the upright orientation may be achieved during flight maneuvers, including, but not limited to, takeoff, landing, or hovering. The electric propulsion system 3200A may include a motor gearbox assembly housing 3202A, an inverter assembly housing 3204A, a main shaft 3206A, a shaft flange assembly 3120, a heat exchanger 3208A, and a sump 3210A. A lubricant or coolant, such as oil 3212A, may be located within the sump 3210A. In the exemplary orientation 3200A, oil may also be present within volume 3218A and at an oil level 3216A within the sump 3210A. The oil 3212A may enter a pump inlet 3214A and proceed to the heat exchanger 3208A. The oil 3212A may then be cooled in the heat exchanger 3208A and distributed throughout the electric propulsion system, as described herein. In some embodiments, the oil may be distributed along the main shaft 3206A by centrifugal force.

[0277] 32B illustrates an exemplary embodiment of electric propulsion system 3200B in a first angled orientation, e.g., a hovering orientation at angle 3222B. As an example, electric propulsion system 3200B may be oriented along central axis 3224B at angle 3222B from vertical axis 3226B. As shown in FIG. 32B, while electric propulsion system 3200B is in the angled orientation, pump inlet 3214B remains in contact with oil 3212B and is below oil level 3216B, allowing oil to continue circulating through the liquid flow path as described herein.

[0278] FIG. 32C illustrates an exemplary embodiment of electric propulsion system 3200C in a horizontal orientation. As an example, electric propulsion system 3200C may be in a horizontal orientation during a forward flight or cruise configuration. As shown in FIG. 32C, during the horizontal orientation, pump inlet 3214C ​​remains in contact with oil 3212C and is below oil level 3216C, allowing oil to continue circulating through the liquid flow paths as described herein. Additionally, volume 3218C may be free of oil during the horizontal configuration due to gravity.

[0279] FIG. 32D illustrates an exemplary embodiment of an electric propulsion system in a second angled orientation, e.g., dive, at angle 3222D. As shown in FIG. 32D, during the dive orientation, pump inlet 3214D remains in contact with oil 3212D and is below oil level 3216D, allowing oil to continue circulating through the liquid flow paths as described herein. Furthermore, volume 3218D may be free of oil in a horizontal configuration due to gravity. In some embodiments, oil or other flammable liquid may be used as a lubricant throughout the electric engine and may also be used as a coolant fluid to help manage heat generated by the engine during operation. As disclosed herein, electric engines may have different primary functions and thus may not include the same amounts of lubricant and coolant. For example, ascent and landing engines may require less than one quart of oil, while engines operating during all phases of flight may require more than one quart of oil. It should be understood that the exemplary embodiments as referred to herein are representative and do not determine the limits of the amounts of lubricant and coolant that may be used in an electric engine.

[0280] It should be understood that using oil to not only lubricate the electric engine but also cool it rather than a separate coolant adds additional oil to the system, but eliminates traditional components that may be used to cool such an electric engine. For example, if the electric engine is cooled by another liquid, such as glycol, the engine may include separate heat exchangers for both the lubricant fluid and the coolant fluid. In some embodiments, the electric engine may be cooled using a variety of liquids. Some embodiments may include an electric propulsion system with multiple heat exchangers that cool the respective liquids flowing in the respective liquid flow paths. In some embodiments, multiple cooling and / or lubricating liquids, such as glycol and oil, may have their respective liquid flow paths circular through a common heat exchanger, also known as a dual heat exchanger. In such a configuration, the number of heat exchangers, based on the liquid type, may be less than the number of types of liquid flow paths, and the overall propulsion system may save mass by not possessing multiple or more heat exchangers.

[0281] However, for embodiments utilizing a single fluid for both lubrication and cooling, such as oil, there would be an increase in oil, but because there would only be the need for one heat exchanger, there could be a reduction in mass in the overall system due to using fewer heat exchangers and potentially other components not being needed, and there could be a more attractive drag profile. Additionally, using one substance to lubricate and cool the engine may increase the efficiency of the system due to the reduction in mass and the advantage of cooling the engine with a substance rather than relying on air cooling, which can be problematic to manage throughout the engine.

[0282] With respect to the use of oil or other flammable liquids in the electric propulsion systems described herein, federal laws and regulations may require safety components, such as fire barriers, adjacent to engines that use oil or other flammable materials above a threshold amount. Such federal laws and regulations may be enforced by government agencies, such as the Federal Aviation Administration.

[0283] It should be noted that some embodiments of the electric propulsion systems described herein may not include a fire barrier. As used herein, a fire barrier may include an engine component or aircraft component that is designed, constructed, or installed primarily to prevent dangerous amounts of air, fluid, or flame from passing around or through the fire barrier and / or to protect against corrosion. In some embodiments, a fire barrier may be required for each electric propulsion system present on the aircraft. Thus, as described herein, if an aircraft possesses, for example, 12 electric propulsion systems, 12 fire barriers may need to be installed on the aircraft. In some embodiments, fire barriers may be required to be present on each wing, surround the fuselage, or be in any other configuration based on federal law, regulation, or other safety requirements. As such, the presence of a fire barrier adds additional mass to the aircraft, thus reducing the efficiency of the electric propulsion systems and further limiting the amount of payload, including passengers, that may be present on the aircraft. This is particularly relevant to VTOL aircraft designs, where a single aircraft may possess, for example, 12 electric propulsion systems; therefore, any increase in mass due to a single fire barrier may be experienced by a factor of 12.

[0284] Although some embodiments described herein do not include a fire barrier, all embodiments described and contemplated herein may include a fire barrier. Additionally, each embodiment described herein may possess fire barriers of various types and locations.

[0285] 33A-33C are schematic diagrams illustrating an example electric propulsion system for a VTOL aircraft with a fire barrier, consistent with disclosed embodiments. Figure 33A illustrates an example electric propulsion system 3300A with a fire barrier 3308A, consistent with the present disclosure. Fire barrier 3308A may be placed between electric engine assembly 3302A, which is mechanically coupled to propeller assembly 3306A, and boom 3304A, and its primary purpose is to stop any fire or combustion that may occur in electric engine assembly 3302A from spreading to other areas of the aircraft.

[0286] FIG. 33B illustrates an exemplary VTOL air vehicle 3300B consistent with the present disclosure. The VTOL air vehicle 3300B may include a fire barrier 3306B mounted on or connected to a wing 3304B connected to a fuselage 3302B. As shown in FIG. 33B, the fire barrier 3306B may be placed between an electric propulsion system comprising an electric engine 3308B and a propeller assembly 3310B and the wing 3304B of the VTOL air vehicle 3300B, and its primary purpose is to stop any fire or combustion. In some embodiments, the fire barrier 3306B may be placed between the wing 3304B and a boom housing the electric propulsion system.

[0287] FIG. 33C illustrates an example electric propulsion system 3300C consistent with the present disclosure. The electric propulsion system 3300C may include an electric motor assembly 3302C, which in some embodiments includes a gearbox assembly, and an inverter assembly 3304C fluidly coupled to a heat exchanger 3306C. In some embodiments, the electric motor assembly 3302C may abut the inverter assembly 3304C. Some embodiments may also include an electric engine assembly housing 3308C. The electric engine assembly housing 3308C may include a fire barrier 3310C. In some embodiments, the fire barrier 3310C may also serve to house the rear of the electric engine assembly and, as shown in this figure, the inverter assembly.

[0288] In some embodiments, fire risk management in aircraft design may not be limited to including fire barriers. Additional design considerations may address fire risks, such as additional components to ensure that the aircraft can maintain flight in the event of a fire. For example, an aircraft boom, as described herein, may feature additional components present within the boom, such that if a fire is present, a component is lost due to fire, a component is separated due to fire, or other loss of functionality or component occurs, the aircraft can still maintain balanced flight.

[0289] C. Exemplary Electric Propulsion System Configurations As discussed above and throughout this disclosure, an example electric propulsion system may include components comprising an electric motor assembly, a gearbox assembly, and an inverter assembly in various configurations, such as the representative configurations described herein. The example embodiments discussed herein may include electric propulsion system components aligned along a common axis or substantially aligned along a common axis. In some embodiments, the components may be aligned along a shaft or main shaft that provides mechanical shaft power to rotate the propellers of the propeller assembly. Some embodiments may include electric propulsion system components that abut each other in axial order or substantially aligned along an axis. In some embodiments, the location or positioning of one or more electric propulsion system components may provide a reduction in system mass and result in a more efficient drag profile. For example, one or more components may be substantially aligned along a common axis or abut each other, eliminating the need for additional components, such as connecting wires or additional housing volume, to accommodate the wires. In this manner, the respective masses and volumes typically required to accommodate such connecting wires may not be required in the disclosed electric propulsion systems.

[0290] In some embodiments, the electric propulsion system may include a cooling system configured to target multiple heat-generating portions of the electric propulsion system. Some embodiments may include portions of the electric propulsion system that are air-cooled by airflow generated from the propeller assembly or by airflow encountered during various phases of flight. Some embodiments may include portions of the electric propulsion system that are cooled using one or more liquid flow paths throughout the electric propulsion system. Such embodiments may also include a liquid flow path that circulates through a heat exchanger exposed to the airflow so that any heat contained in the liquid flow path can be transferred to the air flowing through the heat exchanger. As described herein, it should be understood that all components of the electric propulsion system may be cooled using a common cooling system, each may have its own independent cooling system, or various types and configurations of cooling systems may be combined. In some embodiments, the cooling system for each of the electric propulsion system may affect the efficiency of the electric propulsion system components. For example, in some embodiments, liquid cooling may enable an inverter assembly to operate more efficiently than an inverter assembly that utilizes an air-cooling system.

[0291] 34A-34D are schematic diagrams illustrating example electric propulsion systems for VTOL aircraft consistent with disclosed embodiments. As such, similar design considerations and configurations may be considered throughout the embodiments.

[0292] FIG. 34A schematically depicts an example electric propulsion system 3400A consistent with the present disclosure. The electric propulsion system 3400A may include components such as an inverter assembly 3404A, at least one power module 3410A, and an electric motor assembly 3402A oriented along an axis extending along a shaft 3406A. Embodiments may include the electric motor assembly 3402A providing torque to a propeller assembly 3408A via the shaft 3406A. In some embodiments, the shaft 3406A may be mechanically coupled to a gearbox assembly (not shown in this exemplary embodiment) to provide gear reduction and increased torque to the propeller assembly 3408A. The housings of the components of the electric propulsion system 3400A may share a common shape, such as a circular profile centered on the shaft 3406A, a rectangular profile oriented along the shaft 3406A, or a mix of profiles. The electric propulsion system 3400A may further include an electric motor assembly 3402A positioned between and abutting the inverter assembly 3404A and the propeller assembly 3408A. In such embodiments, the shaft 3406A may pass through the electric motor assembly 3402A. Some embodiments may include a shaft 3406A that also passes through the inverter assembly 3404A. In some embodiments, the power module 3410A may be axially oriented within the inverter assembly 3404A so that any heat generated by the power module may escape via a path 3412A toward the environment external to the inverter assembly 3404A. Some embodiments may also include orienting the power module 3410A within the inverter assembly 3404A so that airflow generated by the propeller assembly 3408A or air encountered during flight can be used to cool the power module.

[0293] FIG. 34B schematically depicts an example electric propulsion system 3400B consistent with the present disclosure. The electric propulsion system 3400B may include components such as an inverter assembly 3404B, at least one power module 3410B, and an electric motor assembly 3402B aligned along an axis extending along a main shaft 3406B. The electric propulsion system 3400B may further include an inverter assembly 3404B positioned between the electric motor assembly 3402B and a propeller assembly 3408B. In some embodiments, the power module 3410B may be positioned below the propeller assembly 3408B and may be positioned as part of the inverter assembly 3404B such that the power module 3410B may generate heat that escapes via a path 3412B toward an environment external to the inverter assembly 3404B. Some embodiments may include a power module oriented elsewhere in the inverter assembly such that any airflow generated by the propeller assembly 3408B can be used to cool the power module.

[0294] 34C schematically depicts an example electric propulsion system 3400C consistent with the present disclosure. The electric propulsion system 3400C may include components such as an inverter assembly 3404C, at least one power module 3410C, and an electric motor assembly 3402C aligned along an axis extending along a shaft 3406C. The electric propulsion system 3400C may further include an inverter assembly 3404C positioned between the electric motor assembly 3402C and a propeller assembly 3408C. In some embodiments, the power module 3410C may be positioned on a portion of the inverter assembly 3404C such that it is located on a surface of the inverter assembly 3404C that abuts the electric motor assembly 3402C. In some embodiments, the power module 3410C may be located within the electric propulsion system 3400C, as shown by path 3412C, as opposed to being located in the inverter assembly 3404C where heat generated by the power module 3410C cannot be cooled using air cooling from the propeller assembly 3408C or any airstreams encountered during flight. In such embodiments, liquid cooling may be used to cool the power module 3410C as well as other components located within the inverter assembly 3404C. Further embodiments may include a liquid cooling system that also thermally manages components of the electric motor assembly 3402 and / or components of the gearbox assembly.

[0295] 34D schematically depicts an example electric propulsion system 3400D consistent with the present disclosure. The electric propulsion system 3400D may include components such as an inverter assembly 3404D, at least one power module 3410D, and an electric motor assembly 3402D oriented along an axis extending along a shaft 3406D. The electric propulsion system 4100D may further include an electric motor assembly 3402D positioned between the inverter assembly 3404D and a propeller assembly 3408D. In some embodiments, the power module 3410D may be positioned on a portion of the inverter assembly 3404D such that it is located on a surface of the inverter assembly 3404D that abuts the electric motor assembly 3402D. In some embodiments, the power module 3410D may be located within the electric propulsion system 3400D, as shown by path 3412D, as opposed to being located in the inverter assembly 3404D, where heat generated by the power module 3410D cannot be cooled using air cooling from the propeller assembly 3408D or any airstreams encountered during flight. In such embodiments, liquid cooling may be used to cool the power module 3410D as well as other components located within the inverter assembly 3404D. Further embodiments may include a liquid cooling system that also thermally manages components of the electric motor assembly 3402 and / or components of the gearbox assembly.

[0296] In some embodiments, the electric propulsion system may include a cooling system that utilizes liquid cooling. In some embodiments, the cooling system liquid may include glycol, oil, or any other liquid that allows for the transfer of heat from the electric propulsion system components to the liquid. Additionally, some embodiments may include cooling the electric propulsion system using a liquid that is also used to lubricate the electric propulsion system components. In some embodiments, the electric propulsion system may include a cavity, reservoir, or sump for collecting and circulating coolant liquid throughout the electric propulsion system.

[0297] FIG. 35 is a schematic diagram illustrating an example electric propulsion system for a VTOL aircraft, consistent with disclosed embodiments. The electric propulsion system 3500 may include components such as an electric motor assembly 3502, an inverter assembly 3504, and a sump 3514 aligned along a shaft 3506. As shown in FIG. 35, the electric motor assembly 3502 may be positioned between the sump 3514 and the inverter assembly 3504. The electric motor assembly 3502 may provide torque to the propeller assembly 3508 via a main shaft 3506 that may travel through the inverter assembly 3504. Furthermore, the electric motor assembly 3502 may provide torque to the propeller assembly 3508 via a gear reduction using a gearbox assembly (not shown in this exemplary embodiment). The inverter assembly may include a power connection channel 3518 connected to the inverter assembly 3504. The inverter assembly 3504 may include a power module 3510 positioned on a portion opposite the inverter assembly 3504 from the portion that abuts the electric motor assembly 3502. Further, some embodiments may include a power module 3510 positioned within the inverter assembly 3504 such that any heat generated by the power module 3510 can escape via a path 3512 toward the environment external to the inverter assembly. Some embodiments may include various cooling methods for the components of the electric propulsion system 3500. For example, in some embodiments, the power module 3510 may be positioned below the propeller assembly 3508 such that air from the propeller assembly 3508 cools the power module 3510. Furthermore, a sump 3514 may contain liquid to cool or lubricate the electric motor assembly 3502, the gearbox assembly, and / or the inverter assembly 3504. Some embodiments may include components of the electric propulsion system 3500 possessing various housing profiles, such as a circular housing centered about the shaft 3506, a housing profile that allows for a mix of housing profiles and aerodynamic drag profiles.Some embodiments may include a component housing having cooling fins attached to the exterior surface of the housing.

[0298] 35, the sump 3514 may have cooling fins 3516 on the sump housing to assist in extracting heat from the liquid used to lubricate or cool the electric motor assembly 3502, the gearbox assembly, and / or the inverter assembly 3504. While some embodiments discussed herein may include electric propulsion system components aligned along a common axis, some embodiments include components that are substantially aligned along a common axis.

[0299] In some embodiments, an electric propulsion system may include components that are not aligned or substantially not aligned along an axis. For example, an electric propulsion system may include an electric motor assembly aligned along a shaft that provides mechanical shaft power to a propeller assembly and an inverter assembly that supplies alternating current to the electric motor assembly located elsewhere in the aircraft. Some embodiments may include an inverter assembly that does not abut the electric motor assembly but is instead housed elsewhere in a boom, wing, or fuselage. In such embodiments, wiring may extend from the inverter assembly to the electric motor assembly to transmit the alternating current from the inverter. Separating the locations of electric propulsion system components may result in increased mass of the aircraft due to the required wiring and other connecting components.

[0300] 36A-36B are schematic diagrams illustrating an example electric propulsion system for a VTOL aircraft, consistent with disclosed embodiments. As such, similar design considerations and configurations may be considered throughout the embodiments.

[0301] FIG. 36A schematically depicts an example electric propulsion system 3600A consistent with the present disclosure. The electric propulsion system 3600A may include components such as an electric motor assembly 3602A centrally aligned along a shaft 3606A that provides torque to a propeller assembly 3608A. Embodiments of the electric propulsion system 3600A may also include a rectangular inverter assembly 3604A cantilevered behind the electric motor assembly 3602A. Additionally, some embodiments may include an inverter assembly 3604A possessing cooling fins 3610A oriented such that the cooling fins 3610A may utilize airflow from the propeller assembly 3608A in cooling power modules, MOSFETs, or other components present within the inverter assembly 3604A. In some embodiments, the electric motor assembly 3602A may be housed in a housing with various profiles, including circular, rectangular, or any other type of profile, depending on the design and needs of the system. The electric motor assembly 3602A may also reside within a motor housing possessing cooling fins to assist in cooling elements of the electric motor assembly 3602A, such as the stator, stator windings, or any other elements of the electric motor assembly 3602A. Although not shown in this figure, a gearbox assembly may reside between the electric motor assembly 3602B and the propeller assembly 3608B, between the electric motor assembly 3602B and the inverter assembly 3604B, within a housing containing the electric motor assembly 3602B, or in any other configuration that allows for a gear reduction to reside. Additionally, although not shown in the drawings, the gearbox assembly may reside within the motor housing and may also utilize cooling fins to assist in thermal management.

[0302] FIG. 36B schematically depicts the example electric propulsion system 3600B disclosed in FIG. 36A, providing a front view from the propeller assembly 3608A. The electric propulsion system 3600B may include a circular electric motor assembly 3602B aligned along a shaft 3606B. An embodiment of the electric propulsion system 3600B may also include a rectangular inverter assembly 3604B, which may be located behind the electric motor assembly 3602B. The inverter assembly 3604B may abut the electric motor assembly 3602B or may be positioned within the boom, wing, or fuselage. The inverter assembly 3604B may possess cooling fins 3608B extending beyond the outer diameter of the electric motor assembly 3602B so that the cooling fins 3608B are exposed to airflow from the propeller assembly 3608A or airflow encountered during flight. Additionally, the cooling fins 3608B can be used to extract and transfer heat generated by the power modules, MOSFETs, or other components present within the inverter assembly 3604A. The cooling fins 3608B may transfer heat to an environment external to the electric propulsion system. Similarly, the electric motor assembly 3602B may also have its own cooling fins (not shown) positioned on the housing of the electric motor assembly to assist in thermal management of the electric motor assembly 3602B and any gearbox assembly.

[0303] In some embodiments, the electric propulsion system may include thermal management, also referred to herein as a cooling system, including liquid cooling. As disclosed herein, some example cooling systems may include distributing liquid coolant to components located throughout the electric motor assembly, gearbox assembly, and inverter assembly. However, it should be understood that the cooling systems disclosed herein may also include liquid coolant circulating around the electric motor assembly, gearbox assembly, and / or inverter assembly. For example, the cooling system may include a cooling system cavity, jacket, or distribution channel that circulates liquid coolant around components located within the electric propulsion system.

[0304] 37 is a schematic diagram illustrating an exemplary electric propulsion system for a VTOL aircraft consistent with disclosed embodiments. The electric propulsion system 3700 may include a motor assembly housing 3702 that houses an electric motor assembly and abuts a shaft 3706 that travels through the motor assembly housing 3702 and an inverter assembly housing 3708. In some embodiments, the motor assembly housing 3702 and the inverter assembly housing 3708 may have various shapes or profiles, including, for example, a circular housing centered on an axis coincident with the shaft 3706, a rectangular housing, or any other suitable geometric orientation. Some embodiments may include the motor assembly housing 3702 housing a gearbox assembly in addition to housing the electric motor assembly. Embodiments may include a gearbox assembly positioned between the electric motor assembly and a propeller assembly external to the motor assembly housing 3702, an electric motor assembly positioned between the gearbox assembly and a propeller assembly external to the motor assembly housing 3702, a gearbox assembly located within the motor assembly housing 3702 but not aligned along the axis of the electric motor assembly, or any other configuration of a gearbox assembly that shares a housing with the electric motor assembly. Some embodiments may include an inverter assembly housing 3708 that possesses an inverter assembly 3704 as described herein. Furthermore, the inverter assembly housing 3708 may also possess cooling fins 3710 located on the exterior of the inverter assembly housing 3708 that utilize airflow encountered during flight to assist in cooling the components of the inverter assembly 3704. Some embodiments may also include an inverter assembly 3704 that utilizes liquid cooling rather than air cooling for thermal management.Such embodiments may include a cavity 3714, jacket, or distribution channel surrounding the inverter assembly 3704, such that liquid may be circulated through the cavity 3714, jacket, or distribution channel to extract heat generated from the components of the inverter assembly 3704. Additionally, liquid may be used to cool components within the motor assembly housing 3702. Path 3712 depicts an exemplary liquid flow path for cooling components located within the motor assembly housing 3702, where liquid may travel from a first end of the motor assembly housing to a second end of the motor assembly housing through a distribution channel along the main shaft 3706. Liquid may be distributed radially from the shaft 3706, collected via a collection chamber, sump, or similar component, and recirculated throughout the motor assembly housing 3702. In some embodiments, the electric motor assembly housing 3702 may be fluidly connected to the inverter assembly housing 3708 such that liquid coolant may be circulated throughout both assemblies via the liquid flow path 3712 and the cavity 3714. In some embodiments, the motor assembly housing 3702 and the inverter assembly housing 3708 may utilize air cooling, liquid cooling, or a mixture of the two to thermally manage the components located within each housing.

[0305] As discussed herein, electric propulsion systems may include various configurations of components, such as axially aligned, abutting each other, substantially axially aligned, or connected using wires or other connection methods. Thus, some embodiments may include components that share a housing. For example, as discussed above, a gearbox assembly may be housed within a motor assembly housing. Furthermore, some embodiments may include housing a gearbox assembly, an inverter assembly, or other assemblies or components thereof within a propeller assembly. Such configurations may be driven by design constraints, such as weight, drag profile, lift, torque, payload, flight time, or any other design constraints associated with VTOL aircraft.

[0306] 38A-38B are schematic diagrams illustrating an example electric propulsion system and an example inverter assembly for an electric propulsion system for a VTOL aircraft, consistent with disclosed embodiments. The electric propulsion system 3800A may include a motor assembly housing 3802A aligned along a main shaft 3806A. Some embodiments may include a motor assembly housing 3802A including an electric motor assembly centrally aligned along the main shaft 3806A. Some embodiments may include a motor assembly housing 3802A that houses the electric motor assembly and a gearbox assembly. Some embodiments of the electric propulsion system 3800A may also include an inverter assembly 3804A mounted on a circular face of the motor assembly housing 3802A and having a low-voltage input 3808A located on the face of the motor assembly housing 3802A. In some embodiments, the inverter assembly 3804A may be located within the propeller assembly in addition to being mounted to the motor assembly housing 3802A. For example, the inverter assemblies described herein may be positioned within the spinner of the propeller assembly. Such placement of the inverter assembly 3704A may be advantageous when other components of the electric propulsion system 3800A do not justify creating a more compact drag profile. For example, a propeller assembly may have a specific size to meet additional design criteria, such as required torque or lift, and in such an embodiment, the size of the propeller assembly may possess free space to allow the inverter assembly 3804A to be placed within the hub of the propeller assembly.

[0307] 38B schematically depicts an example inverter assembly 3800B consistent with the discussion of inverter assembly 3804A throughout this disclosure. Inverter assembly 3800B may include at least one power module 3802B, at least one gate drive 3804B, at least one control board 3806B, at least one DC capacitor or low-inductance connector 3808B, and at least one DC current input port 3810B. Additionally, inverter assembly 3800B may possess cooling fins 3812B located on the exterior surface of the inverter assembly housing to aid in cooling of the various components of inverter assembly 3800B.

[0308] In some embodiments, an electric propulsion system may include components residing in various component housings. As discussed herein, various components of an electric propulsion system may reside in housings and may be organized in various ways within those housings. Some embodiments of an electric propulsion system may include various configurations of components to achieve various design goals. Different embodiments may possess different key design elements that must be achieved at the expense of other design criteria. For example, some embodiments may include redundant systems that may add extra mass to the aircraft but increase passenger safety by avoiding and / or eliminating single points of failure. Furthermore, some embodiments of an electric propulsion system may include various types of thermal management systems, also referred to herein as cooling systems. Some electric propulsion systems may include a combination of cooling systems, such as air-cooled and liquid-cooled systems. For example, electric propulsion system components may possess an air-cooled design, such as in which the components are mechanically coupled to cooling fins, as well as a liquid-cooled design in which the components are fluidly coupled to liquid flow paths and heat exchangers that extract heat from the liquid and transfer it to the outside air.

[0309] 39A-39D are schematic diagrams illustrating an exemplary electric propulsion system for a VTOL aircraft consistent with disclosed embodiments. Electric propulsion system 3900A may include inverter assembly 3904A, gearbox assembly 3906A, and electric motor assembly 3902A, and main shaft 3908A connected to flange shaft assembly 3912A. In some embodiments, electric motor assembly 3902A may be positioned between gearbox assembly 3906A and shaft flange assembly 3912A, and both gearbox assembly 3906A and electric motor assembly 3902A are aligned along main shaft 3908A. Furthermore, inverter assembly 3904A may abut motor gearbox housing 3910A, and inverter assembly 3904A may have a rectangular profile. In some embodiments, inverter assembly 3904A, electric motor assembly 3902A, and gearbox assembly 3908A may have common or individual cooling systems. For example, the motor gearbox housing 3910A and / or the inverter assembly 3904A may utilize airflow encountered during flight or generated by the propeller assembly to cool the inverter assembly 3904A, the gearbox assembly 3906A, and / or the electric motor assembly 3902A.

[0310] FIG. 39B illustrates a perspective view of the example electric propulsion system of FIG. 39A. While FIG. 39B and FIG. 39A are related, the figures may have like numerals that do not refer to the same elements. In some embodiments, the electric propulsion system 3900B may include an electric motor assembly 3902A, and a gearbox assembly 3906A may be located within a motor gearbox housing 3910B. The motor gearbox housing 3910B may be aligned along a main shaft 3908B connected to a flanged shaft assembly 3912B and may have cooling fins 3914B oriented around the circumference of the electric engine housing 3910B to cool the electric motor assembly 3902A and the gearbox assembly 3906A using airflow from a propeller assembly (not shown) connected to the flanged shaft assembly 3912B or airflow encountered during flight. Additionally, an inverter assembly 3904B may be mechanically coupled to the rear of the motor gearbox housing 3910B and may utilize the airflow in cooling the components of the inverter assembly 3904B.

[0311] FIG. 39C provides a schematic diagram of an exemplary electric propulsion system 3900C consistent with embodiments of the present disclosure. The electric propulsion system 3900C may include an electric motor assembly 3902C and a gearbox assembly 3906C located within a motor gearbox housing 3910C. In such embodiments, a propeller assembly 3912C may be mechanically coupled to a first end of the motor gearbox assembly 3910C. Some embodiments may include a shaft that travels through the electric motor assembly 3902C and / or the gearbox assembly 3906C to the propeller assembly 3912C. As shown in FIG. 39C, an exemplary embodiment may include an electric motor assembly 3902C located between the gearbox assembly 3906C and the propeller assembly 3912C. Additionally, some embodiments may include an inverter assembly 3904C abutting a second end of the motor gearbox assembly 3910C.

[0312] 39D provides a schematic diagram of an exemplary electric propulsion system consistent with embodiments of the present disclosure. The electric propulsion system 3900D may include a similar arrangement of components to that depicted in FIG. 39C. However, the electric propulsion system 3900D may include a gearbox assembly 3906D positioned between an electric motor assembly 3902D and a propeller assembly 3912D connected to a first end of a motor gearbox housing 3910D, and an inverter assembly 3904D abutting a second end of the motor gearbox housing 3910D.

[0313] 40A-40D are cross-sectional views and diagrams of an electric propulsion system for a VTOL aircraft consistent with disclosed embodiments. FIG. 40A illustrates a cross-sectional view of an example electric propulsion system 4000A. The electric propulsion system 4000A may include an inverter assembly 4004A, a gearbox assembly 4006A, and an electric motor assembly 4002A aligned along a main shaft 4020A connected to a shaft flange assembly 4008A. The gearbox assembly 4006A and the electric motor assembly 4002A may be located within a motor gearbox assembly housing 4012A, and the inverter assembly 4004A may be located within an inverter assembly housing 4014A. Further, the inverter assembly housing 4014A may be mounted to the rear of the motor gearbox assembly housing 4012A. Additionally, a power connection channel 4018A may be connected to a connector of the inverter assembly 4004A located within the inverter assembly housing 4014A. As depicted in the exemplary embodiment of FIG. 40A , the power connection channel 4018A can be connected to the inverter assembly 4004A after the heat exchanger 4010A. In addition to this embodiment, the heat exchanger 4010A can be mounted to the motor gearbox assembly housing 4012A and used in conjunction with a distribution channel (not shown) to aid in cooling the electric motor assembly 4002A, the gearbox assembly 4006A, and / or the inverter assembly 4004A by cooling the liquid circulating throughout the electric propulsion system 4000A. While the inverter assembly 4004A, gearbox assembly 4006A, and electric motor assembly 4002A are shown in this illustration to be consistent with the described stacked assembly inverter assembly, planetary gearbox, and electric motor consisting of a stator and rotor, it should be understood that this illustration is exemplary and the inverter assembly, gearbox assembly, and electric motor assembly can be of any type as described herein or can achieve similar functionality.

[0314] FIG. 40B illustrates a perspective view of the example electric propulsion system 4000B of FIG. 40A , in which the electric motor assembly 4002A and the gearbox assembly 4006A are located within a motor gearbox housing 4012B. In some embodiments, the motor gearbox housing 4012B may be aligned along a main shaft 4020B connected to a shaft flange assembly 4008B. The motor gearbox housing 4012B may possess cooling fins 4022B oriented around the circumference of the motor gearbox housing 4012B. Additionally, a heat exchanger 4010B may be attached to the motor gearbox housing 4012B and used to liquid-cool the electric motor assembly 4002A, the gearbox assembly 4006A, and / or the inverter assembly 4004A by cooling a liquid circulating throughout the electric motor assembly 4002A, the gearbox assembly 4006A, and / or the inverter assembly 4004A to cool the respective components. While Figure 40B depicts the inner periphery of the heat exchanger as being smaller than the outer periphery of the motor gearbox housing, it should be understood that the heat exchanger 4010B may span any distance equal to or less than the outer periphery of the motor gearbox housing 4012B. Furthermore, the inverter assembly housing 4014B may be mechanically coupled to the rear of the motor gearbox housing 4012B and may possess cooling fins 4024B oriented around the circumference of the inverter assembly housing 4014B. Additionally, the inverter assembly housing 4014B may possess connection points for the power connection channels 4018B at locations on the outer edge of the inverter assembly housing 4014B and behind the heat exchanger 4010B.

[0315] FIG. 40C provides a schematic diagram of an exemplary electric propulsion system consistent with embodiments of the present disclosure. The electric propulsion system 4000C may include components such as an electric motor assembly 4002C and a gearbox assembly 4006 housed within a motor gearbox housing 4012C, and an inverter assembly 4004C housed within an inverter assembly housing 4014C. Additionally, the electric propulsion system may include a propeller assembly 4008C and a heat exchanger 4010C fluidly coupled to the electric motor assembly 4002C and the gearbox assembly 4006C via a liquid path 4016C. Some embodiments may include a liquid path 4016C containing a liquid used for cooling, lubrication, or cooling and lubrication components fluidly coupled to the heat exchanger 4010C. In some embodiments, the heat exchanger 4010C may be directly or indirectly attached to the motor gearbox housing 4012C. The liquid path 4016C may comprise a distribution channel, a device for distributing liquid, or a cavity that can transport liquid, distribute the liquid to components fluidly coupled to the heat exchanger 4010C, and recirculate the liquid to the heat exchanger 4010C. The liquid present in the liquid path 4016C may collect heat from components fluidly coupled to the heat exchanger 4010C and transfer the heat to the incoming air 4018C passing through the heat exchanger 4010C. Thus, an embodiment may include a heat exchanger 4010C positioned such that incoming air experienced in flight or from the propeller assembly 4008C may pass through the heat exchanger 4010C and cool the liquid passing through the heat exchanger 4010C.

[0316] FIG. 40D provides a schematic diagram of an exemplary electric propulsion system consistent with embodiments of the present disclosure. The electric propulsion system 4000D may include a similar arrangement of components to that depicted and described in FIG. 40C. However, the electric propulsion system 4000D may include a gearbox assembly 4006D positioned between an electric motor assembly 4002D and a propeller assembly 4008D connected to a first end of a motor gearbox housing 4012D, with an inverter assembly 4004D housed within the inverter assembly 4014D connected to a second end of the motor gearbox housing 4012D. The electric propulsion system 4000D may also include a gearbox assembly 4006D and an electric motor assembly 4002D fluidly coupled via a liquid path 4016D to a heat exchanger 4010D partially exposed to incoming air 4018D for the purposes of lubricating and cooling the gearbox assembly 4006D and the electric motor assembly 4002D.

[0317] The liquid paths 4016C and 4016D are illustrated at a high level of generality as simple loops. However, it should be understood that the liquid paths may comprise branches, sub-loops, or other segmented paths. In general, the liquid may be circulated in any manner that effectively lubricates and cools the various components present within the motor gearbox housings 4012C and 4012D.

[0318] 41 is a cross-sectional view of an electric propulsion system for a VTOL aircraft consistent with disclosed embodiments. The electric propulsion system 4100 may include an inverter assembly 4104, a gearbox assembly 4106, and an electric motor assembly 4102 aligned along a main shaft 4110 mechanically coupled to a shaft flange assembly 4112. The inverter assembly 4104, the gearbox assembly 4106, and the electric motor assembly 4102 may be located within housings such as an inverter assembly housing 4116 and a motor gearbox assembly housing 4114, with the inverter assembly housing 4116 abutting the motor gearbox assembly housing 4114. Additionally, a power connection channel 4118 may be connected to a high-voltage connector located within the inverter assembly within the inverter assembly housing 4116. Further to this embodiment, a heat exchanger 4108 may be mounted to the motor gearbox assembly housing 4114 and used with distribution channels (not shown) to assist in liquid cooling of the electric motor assembly 4102, gearbox assembly 4106, and / or inverter assembly 4104 by cooling the liquid that circulates throughout the electric motor assembly 4102, gearbox assembly 4106, and / or inverter assembly 4104 to cool the respective components. In some embodiments, while the inverter assembly, gearbox assembly, and electric motor assembly are shown in this illustration to be consistent with the described stacked assembly inverter assembly, planetary gears, and electric motor consisting of a stator and rotor, this illustration is exemplary and the inverter assembly, gearbox assembly, and electric motor assembly may be of any type as described herein or may achieve similar functionality.

[0319] 42A-42B are diagrams of an exemplary electric propulsion system for a VTOL aircraft consistent with disclosed embodiments. The electric propulsion system 4200A is cooled using liquid cooling. The electric propulsion system 4200A may include an electric motor assembly located within a motor assembly housing 4202A and a gearbox assembly located within a gearbox assembly 4206A aligned along a main shaft 4208A connected to a shaft flange assembly 4210A. In some embodiments, the electric motor assembly may be located between the gearbox assembly and the shaft flange assembly 4210A. Additionally, an inverter assembly housing 4204A may abut the gearbox assembly housing 4206A and may be mechanically connected to the power connection channel 4214A. In some embodiments, a heat exchanger 4212A may be coupled to the gearbox assembly housing 4206A and the inverter assembly housing 4204A. Additionally, the heat exchanger 4212A may be fluidly coupled to the electric motor assembly, the gearbox assembly, and the inverter assembly via liquid flow paths to provide liquid for cooling and lubricating components within the electric motor assembly, the gearbox assembly, and the inverter assembly. Some embodiments may include flow paths including channels, bores, and cavities that can transport liquid throughout the fluidly coupled components of the electric propulsion system 4200B.

[0320] FIG. 42B illustrates a perspective view of the example electric propulsion system 4200B discussed with respect to FIG. 42A that is liquid-cooled using a heat exchanger 4212B fluidly coupled to the electric motor assembly, gearbox assembly, and inverter assembly. The example electric propulsion system 4200B may include an electric motor assembly located within a motor assembly housing 4202B and a gearbox assembly housed with a gearbox assembly housing 4206B aligned along a main shaft 4208B mechanically coupled to a flanged shaft assembly 4210B. Some embodiments may include a motor assembly housing 4202B and a gearbox assembly housing 4206B with substantially circular profiles having equal radii. The example electric propulsion system 4200B may also include an inverter assembly housed within an inverter assembly housing 4204B with a substantially circular profile mechanically coupled to a power connection channel 4214B and the gearbox assembly housing 4206B. Some embodiments may include an inverter assembly housing 4204B that possesses a radius that is larger than the radius of the gearbox assembly housing 4206B and / or the motor assembly housing 4202B.

[0321] 43A-43D are diagrams and schematics illustrating an exemplary electric propulsion system for a VTOL aircraft consistent with disclosed embodiments. The electric propulsion system 4300A may include a gearbox assembly 4306A, an electric motor assembly 4302A, and an inverter assembly 4304A aligned along a main shaft 4316A connected to a shaft flange assembly 4308A. The inverter assembly 4304A may be located within an inverter assembly housing 4312A. Further, the gearbox assembly 4306A and the electric motor assembly 4302A may be located within a motor gearbox assembly housing 4310A. Some embodiments may include an inverter assembly 4312A, and therefore an inverter assembly 4303A, located between the motor gearbox assembly housing 4310A and the shaft flange assembly 4308A. In such a configuration, the main shaft 4316A may pass through the gearbox assembly 4306A, the electric motor assembly 4302A, and the inverter assembly 4304A. Additionally, a power connection channel 4314A may extend through the motor gearbox assembly housing 4313A from the boom, wing, or fuselage of the aircraft to a connection point within the inverter assembly housing 4312A.

[0322] FIG. 43B illustrates a perspective view of an exemplary embodiment of an electric propulsion system 4300B as discussed with respect to FIG. 43A that is air-cooled. The electric propulsion system 4300B may include an electric motor assembly 4302A and a gearbox assembly 4306A housed within a motor gearbox housing 4310B, and an inverter assembly housed within an inverter assembly housing 4312B. The motor gearbox housing 4310B and the inverter assembly housing 4312B may possess substantially circular profiles with substantially equal radii and be aligned along a main shaft 4316B connected to a flanged shaft assembly 4308B. Some embodiments may include an inverter assembly housing 4312B positioned between the motor gearbox assembly housing 4310B and the flanged shaft assembly 4308B, with a power connection channel 4314B extending through the motor gearbox assembly housing 4310B from the boom, wing, or fuselage of the aircraft to a connection point within the inverter assembly housing 4312B. Further embodiments may include respect to the motor gearbox housing 4310B and the inverter assembly housing 4312B possessing cooling fins 4320B and 4318B on the exterior surfaces of each housing. The cooling fins 4320B, 4318B may transfer heat from the components contained within the motor gearbox housing 4310B and the inverter assembly housing 4312B to the outside air passing through the cooling fins 4320B, 4318B.

[0323] FIG. 43C provides a schematic diagram of an exemplary electric propulsion system 4300C consistent with embodiments of the present disclosure. The electric propulsion system 4300C may include an arrangement of components similar to those depicted and described in FIGS. 43A and 43B. However, the electric propulsion system 4300C may include a gearbox assembly 4306C positioned between an electric motor assembly 4302C and an inverter assembly 4304C connected to a flanged shaft assembly 4308C. In such a configuration, a main shaft 4316A, not shown in this view, may pass through the electric motor assembly 4302C, the gearbox assembly 4306C, and the inverter assembly 4304C. Additionally, one or more power connection channels 4314C may extend from the aircraft boom through the motor gearbox assembly housing 4310C to a connection point within the inverter assembly housing 4312C.

[0324] FIG. 43D provides a schematic diagram of an exemplary electric propulsion system 4300D consistent with embodiments of the present disclosure. The electric propulsion system 4300D may include similar component arrangements and labeling as those depicted and described in FIGS. 43A-43C. FIG. 43D depicts an electric propulsion system 4300D similar to the electric propulsion system 4300C of FIG. 43C, in which an inverter assembly housing 4312D is connected to a power connection channel 4314D extending from the aircraft boom and abuts a flange shaft assembly 4308D and a motor assembly housing 4310D. However, the motor assembly housing 4310D houses an electric motor assembly 4302D that provides torque to the flange shaft assembly 4308D via a main shaft that passes through the inverter assembly 4304D without a gear reduction from a gearbox assembly.

[0325] 44A-44C are schematic diagrams illustrating an example electric propulsion system for a VTOL aircraft consistent with disclosed embodiments. The example electric propulsion system 4400A may include an inverter assembly 4404A housed within an inverter assembly housing 4416A positioned between a shaft flange assembly 4410A and a divider plate 4408A. In addition to the inverter assembly housing 4416A, the divider plate 4408A may be coupled to a motor gearbox housing 4414A that houses an electric motor assembly 4402A and a gearbox assembly 4406A. In such a configuration, the inverter assembly housing 4416A may include attachment points for power connection channels 4420A extending from the aircraft's boom, wing, or fuselage. Further, such a configuration may include a main shaft mechanically coupled to the shaft flange assembly 4410A that passes through the inverter assembly housing 4416A and, in some embodiments, the inverter assembly 4404A, and the divider plate 4408A to the electric motor assembly 4402A. Some embodiments may include a main shaft extending from a first end of the motor gearbox assembly housing 4414A mechanically coupled to the divider plate 4408A to a second end of the housing, and thus through or passing through the gearbox assembly 4406A to the electric motor assembly 4402A. Some embodiments may include a heat exchanger 4412A fluidly coupled to the inverter assembly 4404A, the gearbox assembly 4406A, and the electric motor assembly 4402A via a fluid flow path 4418A. The divider plate 4408A may act to seal the top of the motor gearbox assembly housing 4414A via the end bell assembly and the bottom of the inverter assembly housing 4416A via a thermal plate. The divider plate 4408A may include grooves, bores, or other conduits configured to distribute fluid for cooling the inverter assembly 4404A and for cooling and lubricating the gearbox assembly 4406A and the electric motor assembly 4402A.The liquid flow path 4418A may include circulating a liquid to extract heat from the components of the inverter assembly 4404A, the gearbox assembly 4406A, and the electric motor assembly 4402A and transfer the heat to the airflow 4422A that passes through the cooling fins of the heat exchanger 4412A.

[0326] FIG. 44B provides a schematic diagram of an exemplary electric propulsion system 4400B consistent with embodiments of the present disclosure. The electric propulsion system 4400B may include a similar arrangement of components to those depicted and described in FIG. 44A. FIG. 44B depicts an electric propulsion system 4400B similar to that of the electric propulsion system 4400A of FIG. 44A, in which an inverter assembly housing 4416A is connected to a power connection channel 4420A extending from the boom, wing, or fuselage of the aircraft and is positioned between a flange shaft assembly 4410B and a divider plate 4408B. However, the divider plate 4408B may also be coupled to a motor gearbox assembly housing 4414B that houses a gearbox assembly 4406B located behind the electric motor assembly 4402B relative to the divider plate 4408B. Some embodiments may include a liquid flow path 4418B fluidly coupling the heat exchanger to the inverter assembly 4404B, the gearbox assembly 4406B, and the electric motor assembly 4402B. Additionally, the liquid flow path 4418B may include circulating liquid to extract heat from the components of the inverter assembly 4404B, the gearbox assembly 4406B, and the electric motor assembly 4402B and transfer the heat to the airflow 4422B that passes through the cooling fins of the heat exchanger 4412B.

[0327] FIG. 44C provides a schematic diagram of an exemplary electric propulsion system 4400C consistent with embodiments of the present disclosure. The electric propulsion system 4400C may include an arrangement of components similar to those depicted and described in FIGS. 44A-44B. FIG. 44C depicts an electric propulsion system 4400C similar to electric propulsion system 4400A of FIG. 44A and electric propulsion system 4400B of FIG. 44B. However, the electric propulsion system 4400C includes a direct drive system as discussed herein, in which a motor assembly housing 4414C houses an electric motor assembly 4402C that provides torque to a shaft flange assembly 4410C without gear reduction via a gearbox assembly.

[0328] The liquid flow paths 4418A, 4418B, and 4418C are illustrated at a high level of generality as simple loops. In some embodiments, the liquid flow paths may comprise branches, sub-loops, or other segmented paths. In general, the liquid may be circulated in any manner that effectively lubricates and cools the various components present within the motor gearbox housings 4414A-C and inverter assembly housings 4416A-C.

[0329] 45A-45D are schematic diagrams illustrating an example electric propulsion system for a VTOL aircraft consistent with disclosed embodiments. The electric engine 4500A may include an electric motor assembly housed within a circular motor assembly housing 4510A with an inverter assembly housed therein, with the inverter assembly housing 4512A coupled to the outer surface of the motor assembly housing 4510A. While FIG. 45A depicts the inverter assembly housing 4512A tangentially coupled to the outer surface of the motor assembly housing 4510A, in some embodiments, the base of the inverter assembly housing 4512A may be coupled to the outer surface of the motor assembly housing 4510A in any configuration, including a base of the inverter assembly housing having a radius of curvature similar to the radius of the electric motor assembly housing 4510A. Additionally, the inverter assembly housing 4512A may include a bus bar 4516A connected to the motor assembly housing 4510A to supply alternating current to the electric motor assembly. The inverter assembly housing 4512A may also include cooling fins mounted to a portion of the inverter assembly housing 4512A opposite the mating portion of the inverter assembly housing 4512A. The cooling fins 4514A may act to remove heat generated from components present within the inverter assembly and transfer the heat to airflow passing through the cooling fins 4514A.

[0330] FIG. 45B illustrates a drawing of a perspective view of an exemplary embodiment of an electric engine 4500B consistent with the present disclosure. The example electric engine 4500B may include a similar arrangement of components as depicted and described in FIG. 45A and similar labeling of components, such that similar numerical labeling corresponds to similar components throughout FIG. 45A and FIG. 45B. The example electric engine 4500B may include an electric motor assembly housed within an electric motor assembly 4510B coupled to an inverter assembly 4512B that houses the inverter assembly. Further, the electric engine 4500B may include a bus bar 4516B connected to the motor assembly housing 4510B to provide alternating current to the electric motor assembly. Similar to FIG. 45A, the electric engine 4500B may possess an inverter assembly housing 4512B with cooling fins 4514B that may act to remove heat generated from components present within the inverter assembly and transfer the heat to an external airflow through the cooling fins 4514B. Additionally, the inverter assembly housing 4512B may include a connection point for a power connection channel 4518B that originates within the boom, wing, or fuselage of the aircraft.

[0331] FIG. 45C schematically depicts an exemplary embodiment of an electric engine 4500C consistent with the present disclosure. The exemplary electric engine 4500C may include a similar arrangement of components as depicted and described in FIGS. 45A and 45B and similar labeling of components, such that similar numerical labeling corresponds to similar components throughout FIGS. 45A, 45B, and 45C. The electric engine 4500C may include an electric motor 4502C and a gearbox assembly 4506C housed within a motor assembly housing 4510C mechanically coupled to an inverter assembly housing 4512C, which houses an inverter assembly 4504C. As shown in FIG. 45C, some embodiments may be configured with the gearbox assembly 4506C located between the electric motor assembly 4502C and the propeller assembly 4508C. In some embodiments, the power connection channel 4518C may be connected to the inverter assembly housing 4512C originating from a boom, wing, or another location within the aircraft.

[0332] FIG. 45D schematically depicts an exemplary embodiment of an electric engine 4500D consistent with the present disclosure. The exemplary electric engine 4500D may include a similar component arrangement and component labeling as depicted and described in FIGS. 45A-45C, with similar numerical labeling corresponding to similar components throughout. The electric engine 4500D may include an electric engine 4502D and a gearbox assembly 4506D housed within a motor assembly housing 4510D mechanically coupled to an inverter assembly housing 4512D, which houses an inverter assembly 4504D. Some embodiments may include a configuration in which the electric motor assembly 4502D is located between the gearbox assembly 4506D and the propeller assembly 4508D. In some embodiments, the power connection channel 4518D may be connected to the inverter assembly housing 4512D originating from a boom, wing, or another location within the aircraft.

[0333] 46A-46B are schematic diagrams illustrating an example electric propulsion system for a VTOL aircraft consistent with disclosed embodiments. The electric propulsion system 4600A may include an electric motor assembly 4602A and a gearbox assembly 4606A housed within a motor assembly housing 4612A coupled to an inverter assembly housing 4614A that houses an inverter assembly 4604A. Some embodiments may include a gearbox assembly 4606A positioned between the electric motor assembly 4602A and a propeller assembly 4608A. Some embodiments may include a heat exchanger 4610A coupled to the motor assembly housing 4612A and fluidly coupled to the electric motor assembly 4602A and the gearbox assembly 4606A via a liquid flow path 4616A. The liquid flow path 4616A may be used to extract heat from components present within the electric motor assembly 4602A and the propeller assembly 4608A. The liquid flow path 4616A may transport the extracted heat to the heat exchanger 4610A, which transfers the heat to an airflow 4618A that passes through the cooling fins of the heat exchanger 4610A.

[0334] FIG. 46B schematically depicts an example embodiment of an electric propulsion system 4600B consistent with the present disclosure. The example electric engine 4600B may include a similar arrangement of components as depicted and described in FIG. 46A and similar labeling of components, such that similar numerical labeling corresponds to similar components throughout FIG. 46A and FIG. 46B. The electric propulsion system 4600B may include an electric motor assembly 4602B and a gearbox assembly 4606B housed within a motor assembly housing 4612B coupled to an inverter assembly housing 4614B that houses an inverter assembly 4604B. Some embodiments may include an electric motor assembly 4602B positioned between the gearbox assembly 4606B and a propeller assembly 4608B. Some embodiments may include a heat exchanger 4610B coupled to the motor assembly housing 4612B and fluidly coupled to the electric motor assembly 4602B and the gearbox assembly 4606B via a liquid flow path 4616B. The liquid flow path 4616B may be used to extract heat from components present within the electric motor assembly 4602B and the propeller assembly 4608B. The liquid flow path 4616B may transport the extracted heat to the heat exchanger 4610B, which transfers the heat to an airflow 4618B that passes through the cooling fins of the heat exchanger 4610B.

[0335] The liquid paths 4616A and 4616B are illustrated at a high level of generality as simple loops. In some embodiments, the liquid paths may comprise branches, sub-loops, or other segmented paths. In general, the liquid may be circulated in any manner that effectively lubricates and cools the various components present within the motor assembly housings 4612A and 4612B.

[0336] 47A-47B are schematic diagrams illustrating an example electric propulsion system for a VTOL aircraft consistent with disclosed embodiments. The electric propulsion system 4700A may include an electric motor assembly 4702A and a gearbox assembly 4706A located within a motor gearbox housing 4710A. The embodiment depicted in FIG. 47A may include a main shaft that runs through or from the electric motor assembly 4702A to a propeller assembly 4708A located outside the motor gearbox housing 4710A. Furthermore, the gearbox assembly 4706A may not share an axis with the electric motor assembly 4702A or the main shaft used by the electric motor assembly 4702A to provide torque to the propeller assembly 4708A. In such an embodiment, the gearbox assembly 4706A may still provide a gear reduction between the electric motor assembly 4702A and the propeller assembly 4708A. Some embodiments may also include an inverter assembly 4704A located in an inverter assembly 4712A that is mounted directly or indirectly to the motor gearbox housing 4710A. While the inverter assembly 4704A is shown mounted to the outer edge of the motor gearbox housing 4710A, in some embodiments, the inverter assembly may have a circular profile that wraps around or partially around the motor gearbox housing 4710A. Additionally, some embodiments may include an inverter assembly housing 4704A that may be coupled to an outer surface of the motor gearbox assembly housing opposite the propeller assembly 4708A. In some embodiments, the electric motor assembly 4702A, gearbox assembly 4706A, and inverter assembly 4704A may each possess different components that give rise to different volumes for each assembly, and thus the motor gearbox housing 4710A and inverter assembly housing 4712A may possess different profiles and volumes based on their respective assembly configurations.

[0337] FIG. 47B illustrates a cross-sectional view of an electric propulsion system 4700B. FIG. 47B may be related to FIG. 47A, although elements identified with like numerals may not refer to the same elements throughout the figures. Some embodiments of the electric propulsion system 4700B may include an electric motor assembly 4702A and a gearbox assembly 4706A located within a common motor gearbox housing 4702B having a shaft 4712B passing through the electric motor assembly 4702A. Some embodiments may include a propeller assembly mechanically coupled to the shaft 4712B. In some embodiments, the electric motor assembly 4702A may include a stator 4704B having stator windings 4706B and a rotor 4710B possessing a magnet array 4708B aligned along the shaft 4712B. In some embodiments, the rotor 4710B may be directly or indirectly connected to a secondary shaft 4716B that surrounds the rotor 4712B such that the secondary shaft 4716B rotates at a speed equal to the speed of the rotor 4710B. Further to this example, an embodiment of the secondary shaft 4716B may have a splined shaft that interfaces with a gearbox assembly 4706A adjacent to the electric motor assembly 4702A, which in turn interfaces with a shaft 4712B that provides torque to the propeller assembly 4708A. The embodiments of the gearbox assembly 4706A described herein may include at least a first gear 4722B, a second gear 4720B, and a gearbox shaft 4718B connecting them. In some embodiments, the radius of the first gear 4722B may be larger than the diameter of the second gear 4720B, or vice versa. In this manner, the splined portion of the secondary shaft 4716B may interact with the first gear 4722B at the speed of the rotating rotor 4710B, causing the first gear 4722B to rotate. The rotating first gear 4722B may drive the rotation of the gearbox shaft 4718B and the second gear 4720B. The second gear 4720B of the gearbox assembly 4706A may interface with a portion of the shaft 4714B having a different radius than the radius of the portion of the shaft 4712B that is connected to the propeller assembly 4708A.In such an embodiment, the gearbox shaft 4718B of the gearbox assembly 4706A may be positioned so as not to share an axis with the shaft 4712B or the electric motor assembly 4702A, but may still provide a gear reduction to the shaft 4712B that provides torque to the propeller assembly 4708A.

[0338] FIG. 48 is a schematic diagram illustrating an example electric propulsion system for a VTOL aircraft, consistent with disclosed embodiments. The electric propulsion system 4800 may include an electric engine housed within an electric engine housing 4802 aligned along a shaft 4804 that travels from the electric engine housing 4802 to a propeller assembly 4808 that includes a propeller 4810. In some embodiments, the electric propulsion system 4800 may include a heat exchanger 4806 fluidly coupled to components of the electric engine via a fluid flow path present within the electric engine housing 4802. Some embodiments may include the electric engine housing 4802 coupled to a boom 4816 of the aircraft via an apparatus 4814 for articulating the position of the electric propulsion system. Some embodiments may also include a blade pitch actuator 4812 coupled to the aft of the electric engine housing 4802. The electric engine components may generate varying amounts of heat depending on the phase of flight in which the aircraft is engaged. For example, electric engine components of a vertical take-off and landing aircraft may generate more heat during the hover phase of flight than during the cruise phase, and therefore may require more airflow through the heat exchanger 4806 to cool the liquid used to cool and / or lubricate the electric engine components during the hover phase than during the cruise phase. Thus, some embodiments may include a boom 4816 with a cavity 4818 therein, wherein the heat exchanger 4806 may be housed during the cruise phase. The cavity 4818 may act to block or reduce airflow into the heat exchanger during flight due to the reduced air needed to cool the system during various stages of flight.

[0339] The embodiments may be further described using the following clauses. Clause Set A: 1. An inverter assembly for converting direct current (DC) power into alternating current (AC) power for an electric propulsion system, comprising: a housing; a capacitor assembly having a capacitor housing having a central hole, at least one capacitor, and at least one bus bar; and a plurality of through holes in the capacitor housing; at least one printed circuit board assembly (PCBA); and a plurality of positioning pins, wherein the capacitor assembly and the at least one PCBA are positioned inside the housing, the plurality of through holes are provided for positioning the at least one PCBA, and the plurality of positioning pins pass through the plurality of through holes in the capacitor housing and the at least one PCBA and are connected to the housing. 2. The inverter assembly of clause A1, wherein the central bore is substantially aligned with a main shaft of the electric propulsion system. 3. The inverter assembly of clause A1 or A2, wherein at least one PCBA and capacitor assembly are stacked. 4. An inverter assembly as described in any one of clauses A1 to A3, wherein the at least one PCBA comprises a gate drive PCBA and a power PCBA, and the capacitor assembly is positioned between the gate drive PCBA and the power PCBA. 5. The inverter assembly of any one of clauses A1-A4, wherein the central hole of the capacitor assembly is a through hole and the inverter assembly has a substantially donut shape. 6. The inverter assembly of any one of clauses A1-A5, wherein at least one bus bar is positioned outside the capacitor housing. 7. An inverter assembly as described in any one of clauses A1 to A6, further comprising a control board having a low voltage (LV) logic input, an electromagnetic interference (EMI) shield, and a heat exchanger, wherein the control board and the EMI shield are positioned inside the housing and the heat exchanger is outside the housing. 8. The inverter assembly of clause A7, wherein the heat exchanger is coupled to the thermal plate. 9. The inverter assembly of clause A8, wherein the control board, thermal plate, and EMI shield each include a plurality of alignment hol...

Claims

1. 1. An inverter assembly for converting direct current (DC) power to alternating current (AC) power for an electric propulsion system, comprising: Housing and 1. A capacitor assembly comprising: A central hole; at least one capacitor; a capacitor housing having at least one bus bar; a plurality of through holes in the capacitor housing; and at least one printed circuit board assembly (PCBA); a plurality of locating pins; the capacitor assembly and the at least one PCBA are positioned inside the housing; an inverter assembly, wherein the plurality of locating pins pass through the plurality of through holes in the capacitor housing and the at least one PCBA and are connected to the housing.

2. The inverter assembly of claim 1 , wherein the central bore is substantially aligned with a main shaft of the electric propulsion system.

3. The inverter assembly of claim 1 or 2, wherein the at least one PCBA and the capacitor assembly are stacked.

4. 4. The inverter assembly of claim 1, wherein the at least one PCBA comprises a gate drive PCBA and a power PCBA, and the capacitor assembly is positioned between the gate drive PCBA and the power PCBA.

5. the central hole of the capacitor assembly is a through hole; The inverter assembly of any one of claims 1 to 4, wherein the inverter assembly has a substantially donut shape.

6. The inverter assembly of any one of claims 1 to 5, wherein the at least one bus bar is positioned outside the capacitor housing.

7. a control board having a low voltage (LV) logic input; an electromagnetic interference (EMI) shield; a heat exchanger, the control board and the EMI shield are positioned inside the housing; The inverter assembly of any one of claims 1 to 6, wherein the heat exchanger is external to the housing.

8. The inverter assembly of claim 7 , wherein the heat exchanger is coupled to a thermal plate.

9. The inverter assembly of claim 8 , wherein the control board, the thermal plate, and the EMI shield each include a plurality of alignment holes for aligning with the locating pins.

10. 10. The inverter assembly of claim 8 or 9, wherein the plurality of locating pins comprise rods embedded in the thermal plate.

11. The inverter assembly of any one of claims 7 to 10, wherein the heat exchanger is configured to use a fluid to cool the inverter assembly.

12. The inverter assembly of claim 11 , wherein the fluid is oil.

13. An inverter assembly according to any preceding claim, wherein the at least one capacitor is a ring capacitor.

14. The inverter assembly of any preceding claim, wherein the plurality of locating pins include screws.

15. The inverter assembly of claim 1 , wherein the plurality of locating pins include bolts.

16. The inverter assembly of any one of claims 1 to 9, wherein the plurality of positioning pins include rods pre-fixed to the capacitor housing.

17. The inverter assembly of any preceding claim, wherein the at least one PCBA comprises a flexible PCBA structure.

18. An inverter assembly according to any preceding claim, wherein the at least one PCBA comprises a rotor position sensor integrated into the at least one PCBA.

19. 1. An electric propulsion system for a vertical take-off and landing (VTOL) aircraft, comprising: an electric motor assembly including at least a stator and a rotor; an inverter assembly, the inverter assembly comprising: Housing and 1. A capacitor assembly comprising: A central hole; at least one capacitor; a capacitor housing having at least one bus bar; a plurality of through holes in the capacitor housing; and at least one printed circuit board assembly (PCBA); a plurality of locating pins; the capacitor assembly and the at least one PCBA are positioned inside the housing; the plurality of positioning pins pass through the plurality of through holes in the capacitor housing and the at least one PCBA and are connected to the housing.

20. the electric motor assembly is positioned within a motor housing; The electric propulsion system of claim 19 , wherein the motor housing and the housing of the inverter assembly are substantially aligned along a main shaft.

21. the motor housing having a hot side and a cold side; the motor housing enclosing a sealed environment; 21. The electric propulsion system of claim 20, wherein the rotor is configured to create air movement inside the sealed environment from the cold side toward the hot side to provide a cooling effect to one or more components on the hot side outside the motor housing.

22. 22. The electric propulsion system of claim 20 or 21, wherein the main shaft passes through a centerline of the motor housing.

23. further comprising a gearbox assembly and a propeller assembly; the main shaft is substantially aligned with the central bore of the capacitor assembly; the electric motor assembly drives the propeller assembly through the main shaft; the main shaft passes through the gearbox assembly; the electric motor assembly is positioned between the gearbox assembly and the propeller assembly; An electric propulsion system according to any one of claims 20 to 22, wherein the inverter assembly and the propeller assembly are positioned at opposite ends of the main shaft.

24. 1. An electric propulsion system for a vertical take-off and landing (VTOL) aircraft, comprising: a propeller assembly; a gearbox assembly; 1. An electric motor assembly including at least a stator and a rotor, the electric motor assembly drives the propeller assembly through a main shaft; the electric motor is positioned between the gearbox assembly and the propeller assembly; an electric motor assembly, the main shaft extending through the gearbox assembly; an inverter assembly, the inverter assembly comprising: Housing and 1. A capacitor assembly comprising: a central bore substantially aligned with the main shaft; at least one capacitor; a capacitor housing having at least one bus bar; a plurality of through holes in the capacitor housing; and at least one printed circuit board assembly (PCBA); a plurality of locating pins; the inverter assembly and the propeller assembly are located at different ends of the main shaft; the capacitor assembly and the at least one PCBA are positioned inside the housing; the plurality of positioning pins pass through the plurality of through holes in the capacitor housing and the at least one PCBA and are connected to the housing.

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