Inverter system, method and mechanical design for evtol aircraft

Abstract

An electric propulsion system for a vertical take-off and landing (VTOL) aircraft 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 dowel pins. The capacitor assembly includes a central bore, at least one capacitor, a capacitor housing having at least one bus bar, and a plurality of through-holes in the capacitor housing. 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 of the capacitor housing and the at least one PCBA and are connected to the housing.

Description

[0001] This invention application is a divisional application of the invention patent application filed on October 6, 2023, with application number 202380084371X and invention name “Inverter system, method and mechanical design for EVTOL aircraft” (based on PCT international application No. PCT / US2023 / 076253).

[0002] CROSS-REFERENCE TO RELATED APPLICATIONS

[0003] This disclosure claims priority to U.S. Patent Application No. 18 / 306,275, filed on April 25, 2023, entitled “SYSTEMS, METHODS, AND MECHANICAL DESIGNS FOR INVERTERS FOR EVTOL AIRCRAFT,” which in turn claims priority to U.S. Provisional Application No. 63 / 378,536, filed on October 6, 2022, entitled “Tilt Rotor Systems and Methods for eVTOL Aircraft,” and U.S. Provisional Application No. 63 / 378,680, filed on October 7, 2022, entitled “Systems and Methods for Improved Propulsion Systems for eVTOL Aircraft.” The contents of the above applications are incorporated herein by reference in their entirety for all purposes. Technical Field

[0004] The present disclosure generally relates to the field of powered aerial vehicles. More specifically, but not exclusively, 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 specific advantages in aerial vehicles and other types of aircraft powered by electric propulsion systems. Summary of the Invention

[0005] The present disclosure proposes systems, components and technologies for unconventional aircraft that are primarily driven by electric propulsion systems. For example, the tilt-rotor aircraft of the present disclosure can be configured to fly over, enter and leave densely populated areas frequently (e.g., more than 50 flights per weekday), short-duration flights (e.g., less than 100 miles per flight). The aircraft can be configured to carry 4 to 6 passengers or commuters who expect to obtain a comfortable experience of low noise and low vibration. Therefore, it may be necessary to configure and design the components of the aircraft to withstand frequent use without wear and tear, require them to generate less heat and vibration, and require the aircraft to include a mechanism for effectively controlling and managing the heat or vibration generated by the components. In addition, it may be expected that several aircraft in these aircraft will operate close to each other over crowded metropolitan areas. Therefore, it may be necessary to configure and design their components to generate low-level noise inside and outside the aircraft, and to configure and design them to have various safety and backup mechanisms. For example, for safety reasons, it may be necessary for the aircraft to be propelled by a distributed propulsion system to avoid the risk of single-point failures, and require them to be able to perform conventional takeoff and landing on a runway. Furthermore, the aircraft may need to be able to safely take off and land vertically from and into relatively small or confined spaces (e.g., vertiports, parking areas, or lanes) compared to traditional airport runways while transporting multiple passengers or commuters with luggage. These operational requirements may impose design constraints on aircraft size, weight, and operational efficiency (e.g., drag, energy use), which may affect the design and configuration of aircraft components.

[0006] The disclosed embodiments provide for new and improved configurations of aircraft components not observed in conventional aircraft, and / or design criteria for components that differ from those of conventional aircraft. Such alternative configurations and design criteria, combined with addressing the shortcomings and challenges of conventional components, result in the various configurations and designs of components for aircraft powered by electric propulsion systems disclosed herein.

[0007] In some embodiments, an aircraft powered by an electric propulsion system of the present disclosure can be designed to be capable of both vertical takeoff and landing and conventional takeoff and landing, with the distributed electric propulsion system enabling vertical flight, horizontal and lateral flight, and transitions. Thrust can be generated by supplying high-voltage electric power to multiple electric engines of the distributed electric propulsion system, which may include the necessary components to convert the high-voltage electric power into mechanical shaft power to rotate the propellers. Embodiments disclosed herein may involve optimizing the energy density of the electric propulsion system. Embodiments may include electric engines connected to an onboard electric power source, which may include a device capable of storing energy, such as a battery or capacitor, and may include one or more systems for utilizing or generating electricity, such as a fuel-powered generator or a solar panel array. Some disclosed embodiments perform direct current (DC) to alternating current (AC) conversion via an inverter assembly to allow for more powerful AC motors. Some disclosed embodiments reduce the weight and space of components in the aircraft, thereby improving aircraft efficiency and performance. The disclosed embodiments also enhance the safety of passenger transportation using new and improved safety protocols and system redundancy in the event of a failure, minimizing any single point of failure in the aircraft propulsion system. Some disclosed embodiments also provide new and improved methods for meeting and exceeding aviation and transportation laws and regulations. For example, the Federal Aviation Administration enforces federal laws and regulations that require safety features, such as fire barriers, to be located near engines that use oil or other flammable materials in excess of a threshold amount. Fire barriers may include engine components or aircraft components that are designed, constructed, or installed with the primary purpose of being configured to prevent any hazardous amount of air, fluid, or flame from bypassing or passing through the fire barrier and / or to prevent corrosion. In some embodiments, fire barriers may include components separate from the additional components described herein. One of ordinary skill in the art will understand which components within an aircraft (including within an electric propulsion system) will serve the primary function of a fire barrier. In some embodiments, fire barriers may include fire-resistant barriers, fire-blocking barriers, fire-resistant barriers, flame-retardant barriers, or any other barrier capable of ensuring that any hazardous amount of air, fluid, or flame cannot bypass or pass through the barrier and / or prevent corrosion. For example, while a fuselage may be configured to prevent any hazardous amount of air, fluid, or flame from bypassing or passing through the fire barrier and / or to prevent corrosion, the fuselage may not be considered a fire barrier because its primary purpose is not to serve as a fire barrier. In some embodiments, an electric propulsion system provides efficient and effective lubrication and cooling using oil below a threshold oil level, resulting in an aircraft that does not require an engine fire barrier, thereby reducing aircraft weight while maximizing performance and efficiency.

[0008] In some embodiments, a distributed electric propulsion system may include twelve electric engines that may be mounted on booms at the front and rear of the aircraft's main wings. A subset of the electric engines, such as those mounted at the front of the main wings, may be tiltable in flight between a horizontal orientation (e.g., to generate forward thrust for cruising) and a vertical orientation (e.g., to generate vertical lift for takeoff, landing, and hovering). The propellers of the front electric engines may rotate in a clockwise or counterclockwise direction. The propellers may rotate in opposite directions relative to adjacent propellers. The tail electric engines may be fixed in a vertical orientation (e.g., to generate vertical lift). The propellers may also rotate in a clockwise or counterclockwise direction. In some embodiments, the difference in rotation direction may be achieved using the direction of engine rotation. In other embodiments, the engines may all rotate in the same direction, and a gear arrangement may be used to achieve different propeller rotation directions.

[0009] In some embodiments, the aircraft may have a certain number of electric engines in various combinations of front and rear engine configurations. For example, the aircraft may have six front and six rear electric engines, four front and four rear electric engines, or any other combination of front and rear engines, including embodiments in which the number of front and rear electric engines is unequal.

[0010] In some embodiments, for vertical take-off and landing (VTOL) missions, the front electric engine and the tail electric engine can provide vertical thrust during take-off and landing. During the flight phase where the aircraft is moving forward, the front electric engine can provide horizontal thrust, while the propeller of the tail electric engine can be stowed in a fixed position to minimize drag. The tail electric engine can be actively stowed using position monitoring. The transition from vertical flight to horizontal flight and vice versa can be achieved via a tilt propeller subsystem. The tilt propeller subsystem can redirect thrust between a main vertical direction during the vertical flight mode and a horizontal or near-horizontal direction during the forward flight cruise phase. The variable pitch mechanism can change the total angle of the propeller hub assembly blades of the front electric engine for operation during the hover phase, transition phase, and cruise phase.

[0011] In some embodiments, during conventional takeoff and landing (CTOL) missions, the front electric engines can provide horizontal thrust for wing-borne takeoff, cruise, and landing, and the wings can provide vertical lift. In some embodiments, the tail electric engines may not be used to generate thrust during CTOL missions, and the tail propellers may be stowed in place. In other embodiments, the tail electric engines may be used at reduced power to shorten the length of a CTOL takeoff or landing.

[0012] 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 have a central hole, at least one capacitor, a capacitor housing having at least one busbar, 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, the plurality of locating pins extend through the plurality of through-holes in the capacitor housing and the at least one PCBA and connect to the housing.

[0013] In some embodiments, an electric power engine for a vertical take-off and landing aircraft may include or be connected to an inverter assembly. In some embodiments, the centerline of the inverter assembly may be aligned with the main axis of the electric power engine. In some embodiments, airflow driven by the electric power engine may cool the inverter assembly, thereby managing operating temperature and optimizing inverter assembly performance.

[0014] In some embodiments, the inverter assembly can have a housing having a circular shape or other shape designed to minimize drag during flight. Additionally, the inverter assembly can be mounted in a certain orientation so that the housing shape minimizes drag under different flight conditions. BRIEF DESCRIPTION OF THE DRAWINGS

[0015] This patent or application file contains at least one drawing executed in color. Copies of this patent or patent application publication with one or more color drawing(s) will be provided by the Office upon request and payment of the necessary fee.

[0016] Figure 1 is an illustration of a perspective view of an example VTOL aircraft consistent with the disclosed embodiments.

[0017] Figure 2 is another illustration of a perspective view of an example VTOL aircraft in an alternative configuration consistent with embodiments of the present disclosure.

[0018] Figure 3 is an illustration of a top plan view of an example VTOL aircraft consistent with embodiments of the present disclosure.

[0019] Figure 4 is a schematic diagram illustrating example propeller rotation of a VTOL aircraft consistent with the disclosed embodiments.

[0020] Figure 5 is a schematic diagram illustrating example power connections in a VTOL aircraft consistent with the disclosed embodiments.

[0021] Figure 6is a block diagram illustrating an example architecture and design of an electric propulsion unit for a VTOL aircraft consistent with the disclosed embodiments.

[0022] Figure 7 is a schematic diagram illustrating an example tilting electric propulsion system for a VTOL aircraft consistent with the disclosed embodiments.

[0023] Figures 8A-8C is a diagram of an example tilting electric propulsion system for a VTOL aircraft consistent with the disclosed embodiments.

[0024] Figure 9 is a schematic diagram illustrating an example lift electric propulsion system for a VTOL aircraft consistent with the disclosed embodiments.

[0025] Figures 10A-10B is a diagram of an example lift electric propulsion system for a VTOL aircraft consistent with the disclosed embodiments.

[0026] Figures 11A-11C is a cross-sectional illustration of an example electric propulsion system for a VTOL aircraft consistent with the disclosed embodiments.

[0027] Figures 12A-12D is a diagram and block diagram of an example electric propulsion system for a VTOL aircraft consistent with the disclosed embodiments.

[0028] Figure 13 is an illustration of an exploded view of an example electric propulsion system for a VTOL aircraft consistent with the disclosed embodiments.

[0029] Figure 14 is an illustration of an exploded view of an example electric motor assembly for a VTOL aircraft consistent with the disclosed embodiments.

[0030] Figures 15A-15C is an illustration of a stator assembly of a VTOL aircraft consistent with the disclosed embodiments.

[0031] Figures 16A-16C is an exploded view and cross-sectional illustration of a rotor assembly of a VTOL aircraft consistent with the disclosed embodiments.

[0032] Figure 17 is an exploded view of a main shaft assembly of a VTOL aircraft consistent with the disclosed embodiments.

[0033] Figure 18 is an illustration of an example sun gear for a VTOL aircraft consistent with the disclosed embodiments.

[0034] Figure 19 is an illustration of an example ring gear for a VTOL aircraft consistent with the disclosed embodiments.

[0035] Figure 20 is an illustration of an example rack assembly for a VTOL aircraft consistent with the disclosed embodiments.

[0036] Figures 21A-21B is an illustration of an example bell-shaped end cap assembly for a VTOL aircraft consistent with the disclosed embodiments.

[0037] Figure 22 is an illustration of an example inverter assembly for a VTOL aircraft consistent with the disclosed embodiments.

[0038] Figure 23 is an illustration of an exploded view of an inverter assembly for a VTOL aircraft consistent with the disclosed embodiments.

[0039] Figure 24 is an illustration of an example printed circuit board assembly for a VTOL aircraft consistent with the disclosed embodiments.

[0040] Figures 25A-25C is a diagrammatic and example front view of a heat exchanger for a VTOL aircraft consistent with the disclosed embodiments.

[0041] Figure 26 is a diagram of a heat exchanger for a VTOL aircraft consistent with the disclosed embodiments.

[0042] Figures 27A-27B is an illustration of a splitter panel for a VTOL aircraft consistent with the disclosed embodiments.

[0043] Figure 28 is an illustration of a hot plate of a VTOL aircraft consistent with the disclosed embodiments.

[0044] Figure 29 is a diagram of an electric propulsion system for a VTOL aircraft consistent with the disclosed embodiments.

[0045] Figure 30A-Figure 30B is a diagram of an example electric propulsion system for a VTOL aircraft consistent with the disclosed embodiments.

[0046] Figure 31A-Figure 31B is a cross-sectional illustration of an electric propulsion system for a VTOL aircraft consistent with the disclosed embodiments.

[0047] Figures 32A-32D is a cross-sectional illustration of an electric propulsion system for a VTOL aircraft in various phases of flight consistent with the disclosed embodiments.

[0048] Figures 33A-33C is a schematic diagram illustrating an example electric propulsion system including a fire barrier for a VTOL aircraft consistent with the disclosed embodiments.

[0049] Figures 34A-34D is a schematic diagram illustrating an example electric propulsion system for a VTOL aircraft consistent with the disclosed embodiments.

[0050] Figure 35 is a schematic diagram illustrating an example electric propulsion system for a VTOL aircraft consistent with the disclosed embodiments.

[0051] Figure 36A-Figure 36B is a schematic diagram illustrating an example electric propulsion system for a VTOL aircraft consistent with the disclosed embodiments.

[0052] Figure 37 is a schematic diagram illustrating an example electric propulsion system for a VTOL aircraft consistent with the disclosed embodiments.

[0053] Figures 38A-38B is a schematic diagram illustrating an example electric propulsion system for a VTOL aircraft and an example inverter assembly for the electric propulsion system, consistent with the disclosed embodiments.

[0054] Figures 39A-39D are cross-sectional and perspective illustrations and schematic diagrams showing example electric propulsion systems for VTOL aircraft consistent with the disclosed embodiments.

[0055] Figures 40A-40D are diagrams and schematics illustrating an electric propulsion system for a VTOL aircraft consistent with the disclosed embodiments.

[0056] Figure 41 is a cross-sectional illustration of an electric propulsion system for a VTOL aircraft consistent with the disclosed embodiments.

[0057] Figures 42A-42B is a diagram of an example electric propulsion system for a VTOL aircraft consistent with the disclosed embodiments.

[0058] Figures 43A-43D are diagrams and schematics illustrating example electric propulsion systems for VTOL aircraft consistent with the disclosed embodiments.

[0059] Figures 44A-44C is a schematic diagram illustrating an example electric propulsion system for a VTOL aircraft consistent with the disclosed embodiments.

[0060] Figures 45A-45D is a schematic diagram illustrating an example electric propulsion system for a VTOL aircraft consistent with the disclosed embodiments.

[0061] Figures 46A-46B is a schematic diagram illustrating an example electric propulsion system for a VTOL aircraft consistent with the disclosed embodiments.

[0062] Figures 47A-47B is a schematic diagram and cross-sectional illustration of an example electric propulsion system for a VTOL aircraft consistent with the disclosed embodiments.

[0063] Figure 48 is a schematic diagram illustrating an example electric propulsion system for a VTOL aircraft consistent with the disclosed embodiments.

[0064] Figure 49 is an illustration of a cross-sectional view of an example electric propulsion system for a VTOL aircraft consistent with the disclosed embodiments.

[0065] Figure 50 is an illustration of a perspective view of an example rotor of a VTOL aircraft consistent with the disclosed embodiments.

[0066] Figure 51 is a flow chart of an example process for balancing a rotor of a VTOL aircraft, consistent with the disclosed embodiments.

[0067] Figure 52 is another flow chart of an example process for balancing a rotor assembly of a VTOL aircraft, consistent with the disclosed embodiments.

[0068] Figure 53 is a flow chart of an example process for transmitting torque from an electric motor assembly to a propeller assembly of a VTOL aircraft, consistent with the disclosed embodiments.

[0069] Figure 54 is a schematic illustration of a partial cross-sectional view of an example electric motor assembly.

[0070] Figures 55A-55B is an illustration of the interior surfaces of an example rotor hub and an example end plate consistent with disclosed embodiments.

[0071] Figure 55C are simulation results of air velocity and pressure distribution inside the housing consistent with the disclosed embodiments.

[0072] Figure 55D Illustrations showing example interior surfaces of end plates consistent with disclosed embodiments.

[0073] Figure 56A is a diagram showing a cross-sectional view of a press-fit mesh port consistent with disclosed embodiments.

[0074] Figure 56B is a diagram showing a cross-sectional view of a press-in mesh port when operating in an inclined position after installation consistent with the disclosed embodiments.

[0075] Figure 57is an illustration of a cross-sectional perspective view of an integrated sensor on a power strip consistent with disclosed embodiments.

[0076] Figure 58 is an illustration of a perspective view of a flexible PCBA connector consistent with disclosed embodiments.

[0077] Figure 59 is consistent with the disclosed embodiments Figure 58 A cross-sectional view of a serpentine connector of a flexible PCBA is shown, showing a partial cutout.

[0078] Figure 60A is an illustration of a capacitor housing consistent with the disclosed embodiments showing alignment pins

[0079] Figure 60B is an illustration of a heat plate and heat exchanger showing engagement alignment pins, consistent with disclosed embodiments. DETAILED DESCRIPTION

[0080] The disclosed embodiments provide systems, subsystems, and components for new VTOL aircraft having various combinations of electric propulsion systems and cooling systems that maximize performance while minimizing weight.

[0081] In some embodiments, an electric propulsion system as described herein can generate thrust by supplying high voltage (HV) electric power to an electric engine, which in turn converts the HV electric power into mechanical shaft power for rotating a propeller. An aircraft as described herein may include multiple electric engines mounted at the front and rear of the wing. The engines can be mounted directly to the wing, or to one or more booms attached to the wing. The amount of thrust generated by each electric engine can be controlled by torque commands sent to each electric engine by a flight control system (FCS) via a digital communication interface. Embodiments may include a front electric engine that is capable of changing its orientation or tilt. Some embodiments include a front engine that can be of a clockwise (CW) type or a counterclockwise (CCW) type. The front electric propulsion subsystem can consist of a multi-blade controllable pitch propeller and a variable pitch subsystem.

[0082] In some embodiments, the aircraft may include a tail electric engine or lifter that may be of the clockwise (CW) type or the counterclockwise (CCW) type. Some embodiments may include a tail electric engine that utilizes a multi-bladed fixed pitch propeller.

[0083] As described herein, the orientation and use of electric propulsion system components can change throughout the operation of the aircraft. In some embodiments, during vertical takeoff and landing, the front propulsion system and the tail propulsion system can provide vertical thrust during takeoff and landing. During the flight phase when the aircraft is in forward flight mode, the front propulsion system can provide horizontal thrust, while the propellers of the tail propulsion system can be stowed in a fixed position to minimize drag. The tail electric propulsion system can be actively stowed using position monitoring. Some embodiments may include a transition from vertical flight to horizontal flight, and vice versa. In some embodiments, the transition can be achieved via a tilt propeller system (TPS). The TPS can redirect the electric propulsion system 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 front propulsion system propeller blades for operation during the hover phase, cruise phase, and transition phase. Some embodiments may include a conventional takeoff and landing (CTOL) configuration, such that the tiltrotor provides horizontal thrust for wing-borne takeoff, cruise, and landing phases. In some embodiments, the tail electric engine is not used to generate thrust during a CTOL mission and the tail rotor is stowed in a position that minimizes drag.

[0084] In some embodiments, electric engines as described herein may include design features to mitigate and prevent uncontrolled fires, such as utilizing non-hazardous quantities of flammable fluid contained in both the tilt and lift engines. For example, in some embodiments, the electric engine may be configured to utilize less than a quart of oil or another flammable fluid. Some embodiments may include electric engines containing non-hazardous quantities of air, preventing any fire from sustaining a duration sufficient to migrate to another part of the aircraft. In some embodiments, the non-hazardous quantity of air may be in contact with the flammable fluid throughout the electric engine. Some examples may include electric engines containing up to one, two, three, four, five, ten, or twenty liters of air within the electric engine enclosure. In some embodiments, the amount of air present within the electric engine enclosure may be fixed in ratio to the amount of oil or other cooling fluid present within the electric propulsion system. This ratio may be driven by determining the sufficient thermal mass required to adequately cool the electric propulsion system. Some embodiments may include an air-to-oil ratio within the electric propulsion system of approximately 3:1. Some embodiments may include an electric engine enclosure in which 75% of the open volume (i.e., the internal volume not occupied by components of the electric engine) is composed of air, and 25% of the open volume is composed of oil or some other liquid used for cooling and / or lubrication. Some embodiments may also be configured to have no nominal ignition source within the electric engine, have an engine over-temperature operating limit that can be at least 50°C below the auto-ignition temperature of the flammable fluid, have over-temperature detection and protection, over-voltage detection and protection, and / or have over-current detection and protection. Furthermore, some embodiments may include an electric propulsion system in which the overall temperature of the electric propulsion system is below the auto-ignition temperature and flash point of the oil or other liquid present within the electric propulsion system under all normal operating conditions. In some embodiments, abnormal conditions that increase the overall temperature of the electric propulsion system may result in a system response that prevents the oil or other liquid from exceeding its flash point and auto-ignition temperature. In some embodiments, the ratio of air to oil or other liquid may be such that if a fire occurs within the electric engine enclosure, including if an electric arc ignites a fire, the amount of air present within the electric engine enclosure will not allow the fire to propagate to other areas of the aircraft. In some embodiments, these and other design features may result in an electric engine that is considered a non-designated fire zone by one or more guidelines or regulations.

[0085] Reference will now be made in detail to example embodiments, examples of which are illustrated in the accompanying drawings. The following description refers to the accompanying drawings, in which like numerals in different figures represent the same or similar elements unless otherwise specified. The implementations set forth in the following description of the example 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 recited in the appended claims.

[0086] A. Example Electric Aircraft Features

[0087] Figure 1 is an illustration of a perspective view of an example VTOL aircraft consistent with the disclosed embodiments. Figure 2 is another illustration of a perspective view of an example VTOL aircraft in an alternative configuration consistent with embodiments of the present disclosure. Figure 1 and Figure 2 VTOL aircraft 100, 200 are shown in a cruise configuration and a vertical take-off, landing, and hover configuration (also referred to herein as a "lift" configuration), respectively, consistent with embodiments of the present disclosure. Figure 1 and Figure 2 Corresponding elements may have like reference numerals and refer to similar elements of the aircraft 100, 200. The aircraft 100, 200 may include a fuselage 102, 202, wings 104, 204 mounted to the fuselage 102, 202, and one or more rear stabilizers 106, 206 mounted to the rear of the fuselage 102, 202. A plurality of lift propellers 112, 212 may be mounted to the wings 104, 204 and may be configured to provide lift for vertical takeoff, landing, and hovering. A plurality of tilt propellers 114, 214 may be mounted to the wings 104, 204 and may be tiltable between a lift configuration in which the plurality of tilt propellers provide a portion of the lift required for vertical takeoff, landing, and hovering, as well as a cruise configuration. Figure 2 As shown, in the cruise configuration the plurality of tilted propellers provide forward thrust to the aircraft 100 for horizontal flight, as shown in FIG. Figure 1 As used herein, a tilt-propeller lift configuration refers to any tilt-propeller orientation in which the tilt-propeller thrust primarily provides lift to the aircraft, and a tilt-propeller cruise configuration refers to any tilt-propeller orientation in which the tilt-propeller thrust primarily provides forward thrust to the aircraft.

[0088] In some embodiments, the lift propellers 112, 212 can be configured to provide only lift, with all horizontal propulsion being provided by the tilt propellers. Thus, the lift propellers 112, 212 can be configured to have a fixed position and can generate thrust only during takeoff, landing, and hovering phases of flight. Meanwhile, the tilt propellers 114, 214 can be tilted upward into a lift configuration, in which the thrust from the propellers 114, 214 is directed downward to provide additional lift.

[0089] For forward flight, the tilt propellers 114, 214 can be tilted from their lift configuration to their cruise configuration. In other words, the orientation of the tilt propellers 114, 214 can be changed 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 to the aircraft 100, 200). The tilt propeller assembly for a particular electric engine can be tilted about an axis of rotation defined by the mounting point connecting the boom and the electric engine. When the aircraft 100, 200 is in full forward flight, lift can be provided entirely by the wings 104, 204. Meanwhile, in the cruise configuration, the lift propellers 112, 212 can be turned off. The blades 120, 220 of the lift propellers 112, 212 can be maintained in a low-drag position for aircraft cruise. In some embodiments, the lift propellers 112, 212 may each have two blades 120, 220 that may be locked for cruising in a minimum drag position where one blade is directly in front of the other blade, e.g. Figure 1 In some embodiments, the lift propeller 112, 212 has more than two blades. In some embodiments, the tilt propeller 114, 214 may include more blades 116, 216 than the lift propeller 112, 212. For example, Figure 1 and Figure 2 As shown, lift propellers 112, 212 may each include, for example, two blades, while tilt propellers 114, 214 may each include more blades, such as five blades as shown. In some embodiments, each of tilt propellers 114, 214 may have from 2 to 5 blades, and possibly more, depending on the design considerations and requirements of the aircraft.

[0090] 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 at the rear of the wing 104, 204, and at least a portion of the tilt propellers 114, 214 may be located at the front of the wing 104, 204. In some embodiments, all of the lift propellers 112, 212 may be located at the rear of the wing 104, 204, and all of the tilt propellers 114, 214 may be located at the front of the wing 104, 204. According to some embodiments, all of the lift propellers 112, 212 and tilt propellers 114, 214 may be mounted to the wings—that is, none of the lift propellers or tilt propellers may be mounted to the fuselage. In some embodiments, the lift propellers 112, 212 may all be located at the rear of the wing 104, 204, and the tilt propellers 114, 214 may all be located at the front of the wing 104, 204. According to some embodiments, all of the lift propellers 112, 212 and tilt propellers 114, 214 may be positioned inboard of the end of the wing 104, 204.

[0091] In some embodiments, the lift propellers 112, 212 and the tilt propellers 114, 214 can be mounted to the wings 104, 204 via booms 122, 222. The booms 122, 222 can be mounted below the wings 104, 204, on top of the wings, and / or can be integrated into the wing profile. In some embodiments, the lift propellers 112, 212 and the tilt propellers 114, 214 can be mounted directly to the wings 104, 204. In some embodiments, each boom 122, 222 can be mounted with one lift propeller 112, 212 and one tilt propeller 114, 214. The lift propellers 112, 212 can be mounted at the rear end of the booms 122, 222, and the tilt propellers 114, 214 can be mounted at the front end of the booms 122, 222. In some embodiments, the lift propellers 112, 212 can be mounted in fixed positions on the booms 122, 222. In some embodiments, the tilt propeller 114, 214 may be mounted via a hinge to the front end of the boom 122, 222. The tilt propeller 114, 214 may be mounted to the boom 122, 222 such that the tilt propeller 114, 214 is aligned with the body of the boom 122, 222 when in its cruise configuration, thereby forming a continuous extension of the front end of the boom 122, 222 that minimizes drag in forward flight.

[0092] In some embodiments, aircraft 100, 200 may include, for example, one wing on each side of 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 to the upper side of fuselage 102, 202. According to some embodiments, the wing includes control surfaces, such as flaps and / or ailerons. According to some embodiments, wings 104, 204 may have been 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.

[0093] In some embodiments, the rear 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 can have any suitable design. In some embodiments, the wing has a tapered leading edge.

[0094] In some embodiments, a lift propeller 112, 212 or a tilt propeller 114, 214 can be yawed relative to at least one other lift propeller 112, 212 or tilt propeller 114, 214. As used herein, yaw refers to the relative orientation of the axis of rotation of the lift propeller / tilt propeller about a line parallel to the forward-backward direction, similar to the roll degree of freedom of an aircraft. The yaw of the lift propeller and / or tilt propeller can be oriented so that the plane of rotation of the lift propeller / tilt propeller disk (the blades plus the hub to which the blades are mounted) does not intersect with critical parts of the aircraft (such areas of the fuselage where personnel may be located, critical flight control systems, batteries, adjacent propellers, etc.) or other propeller disks to help minimize damage caused by propeller blowout and can provide enhanced yaw control during flight.

[0095] Figure 3 is an illustration of a top plan view of an example VTOL aircraft consistent with an embodiment of the present disclosure. The aircraft 300 shown in the figure may be Figure 1 and Figure 2300. As discussed herein, the aircraft 300 may include twelve 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 booms at the front and rear of the main wing 304 of the aircraft 300. In some embodiments, the rear end length of the boom 324 from the wing 304 to the lift propeller 312 may include similar rear end lengths of the boom 324 across multiple rear ends of the boom. In some embodiments, the rear end length of the boom may vary across the example six rear ends of the boom. For example, each rear end of the boom 324 may include a different length from the wing 304 to the lift propeller 312, or subsets of the rear ends of the boom may be similar in length. In some embodiments, the front end of the boom 322 may include various lengths from the wing 304 to the tilt propeller 314 across the front end of the boom. For example, as Figure 3 As shown, the length of the boom 322 from the tilted propeller 314 closest to the fuselage to the front end of the wing 304 may include a length that is greater than the length of the boom 322 from the wing 304 to the front end of the tilted propeller 314 farthest from the fuselage. Some embodiments may include boom front ends having similar lengths across the six exemplary front ends of the boom, or any other distribution of boom lengths from the wing 304 to the front ends of the tilted propellers 314. Some embodiments may include an aircraft 300 having eight electric propulsion systems, wherein the eight electric propulsion systems have 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, Figure 3 An example embodiment of a VTOL aircraft 300 is depicted with a front propeller 314 in a horizontal orientation for horizontal flight and a tail propeller blade 320 in a stowed position for a forward phase of flight.

[0096] As disclosed herein, the front electric propulsion system and the rear electric propulsion system may be of a clockwise (CW) type or a counterclockwise (CCW) type. Some embodiments may include various front electric propulsion systems having a mix of both CW and CCW types. In some embodiments, the rear electric propulsion system may have a mix of CW and CCW types within the rear electric propulsion system.

[0097] Figure 4 is a schematic diagram illustrating example propeller rotation of a VTOL aircraft consistent with the disclosed embodiments. The aircraft 400 shown in the figure may be Figure 1 、 Figure 2 and Figure 3A top plan view of aircraft 100, 200, and 300 is shown. Aircraft 400 may include six front electric propulsion systems, three of which have a CW type 424 and the remaining three have a CCW type. In some embodiments, three tail electric propulsion systems may have a CCW type 428, while the remaining three tail electric propulsion systems may have a CW type 430. Some embodiments may include aircraft 400 having four front electric propulsion systems and four tail electric propulsion systems, each of which has two CW types and two CCW types. In some embodiments, the propellers may rotate in opposite directions relative to adjacent propellers to eliminate torque steering experienced by the fuselage or wings of the aircraft due to the rotation of the propellers. In some embodiments, the difference in rotation direction can be achieved using the direction of engine rotation. In other embodiments, the engines may all rotate in the same direction, and a gear arrangement may be used to achieve the different propeller rotation directions.

[0098] Some embodiments may include an aircraft 400 having a forward electric propulsion system and a tail electric propulsion system, wherein the amount of CW type 424 and CCW type 426 is unequal in the forward electric propulsion system, in the tail electric propulsion system, or in both the forward electric propulsion system and the tail electric propulsion system.

[0099] Figure 5is a schematic diagram illustrating example power connections in a VTOL aircraft consistent with the disclosed embodiments. A 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 electric engines via high-voltage pathways. In some embodiments, aircraft 500 may include six power systems, including batteries 526, 528, 530, 532, 534, and 536 stored within wings 570 of aircraft 500. In some embodiments, aircraft 500 may include six forward electric propulsion systems with six electric engines 502, 504, 506, 508, 510, and 512, and six aft electric propulsion systems with 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 this configuration, first power system 526 can provide power to power engine 502 via power connection channel 538 and power to power engine 524 via power connection channel 540. In some embodiments, first power system 526 can also be paired with fourth power system 532 via power connection channel 542, which is fused to prevent excessive current from flowing through power systems 526 and 532. Further to this embodiment, VTOL aircraft 500 can include second power system 528 paired with fifth power system 534 via fused power connection channel 548, and can provide power to power engines 510 and 516 via power connection channels 544 and 546, respectively. In some embodiments, third power system 530 can be paired with sixth power system 536 via fused power connection channel 554, and can provide power to power engines 506 and 520 via power connection channels 550 and 552, respectively. The fourth power system 532 can also provide power to the power engines 508 and 518 via power connection paths 556 and 558, respectively. The fifth power system 534 can also provide power to the power engines 504 and 522 via power connection paths 560 and 562, respectively. The sixth power system 536 can also provide power to the power engines 512 and 514 via power connection paths 564 and 566, respectively.

[0100] As disclosed herein, an electric propulsion system may include an electric engine connected to a high-voltage power system (e.g., a battery) located within an aircraft via a high-voltage channel or power connection channel. Some embodiments may include various batteries stored within the aircraft's wings, with the aircraft's wings having high-voltage channels running through the aircraft (including the wings and boom) to the electric propulsion system. 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 in a certain pattern to various batteries or power sources stored throughout the aircraft. It should be appreciated that such a configuration may be beneficial in avoiding the risk of a single point of failure, where a failure of one battery or power source may cause a portion of the aircraft to be unable to maintain the thrust required to continue flight or perform a controlled landing. For example, if a VTOL aircraft has two front electric propulsion systems and two rear propulsion systems, the front electric propulsion system and the rear electric propulsion system on opposite sides of the VTOL aircraft may be connected to the same high-voltage power system. In this configuration, if one high voltage power system fails, the forward and aft electric propulsion systems on the opposite side of the VTOL aircraft will remain operational and provide a more balanced flight or landing than if both the forward and aft electric propulsion systems failed on the same side of the VTOL aircraft. Some embodiments may include four forward 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 so that in the event of a power source failure, the risk of a single point of failure is avoided and the flight phase where the failure occurred can continue, or the aircraft can proceed to an alternative flight phase in response to the failure.

[0101] As discussed above, the electric propulsion system may include an electric engine that provides mechanical shaft power to the propeller assembly to generate thrust. In some embodiments, the electric engine of the electric propulsion system may include a high-voltage power system that supplies high-voltage power to the electric engine and / or a low-voltage system that supplies low-voltage DC power to the electric engine. Some embodiments may include an electric engine that digitally communicates with a flight control system ("FCS") including a flight control computer ("FCC"), which can send and receive signals to and from the electric engine, the signals including commands and response data or status. Some embodiments may include an electric engine that is capable of receiving and transmitting operating parameters from and to the FCC, including speed, voltage, current, torque, temperature, vibration, propeller position, and any other values ​​of operating parameters.

[0102] In some embodiments, the flight control system may include a system capable of communicating with the electric engine to send and receive analog / discrete signals to the electric engine and control a device capable of redirecting the thrust of the tilt propellers between a primarily vertical direction during vertical flight mode and a primarily horizontal direction during 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.

[0103] Figure 6 A block diagram illustrating an example architecture and design of an electric propulsion unit 600 consistent with the disclosed embodiments is shown. In some embodiments, the electric propulsion system 602 may include an electric engine subsystem 604 that can supply torque via an axial propeller subsystem 606 to generate thrust for the electric propulsion system 602. Some embodiments may include the electric engine subsystem 604 receiving low voltage DC (LV DC) power from a low voltage system (LVS) 608. Some embodiments may include the electric engine subsystem 604 receiving high voltage (HV) power from a high voltage power system (HVPS) 610, which includes at least one battery or another device capable of storing energy. In some embodiments, the high voltage power system may include more than one battery or another device capable of storing energy that supplies high voltage power to the electric engine subsystem 604. It should be appreciated that this configuration can be advantageous because there is no single point of failure risk where a single battery failure causes the electric propulsion system 602 to fail.

[0104] Some embodiments may include an electric propulsion system 602 including an electric engine subsystem 604 that receives and sends signals to a flight control system 612. In some embodiments, the flight control system 612 may include a flight control computer capable of using controller area network ("CAN") data bus signals to send commands to and receive status and data from the electric engine subsystem 604. It should be understood that while CAN data bus signals are used between the flight control computer and the electric engine, some embodiments may include any form of communication capable of sending and receiving data from the flight control computer to the electric engine. In some embodiments, the flight control system 612 may also include a tilt-propeller system ("TPS") 614 capable of sending and receiving analog discrete data to and from the tilt-propeller electric engine subsystem 604. Tilt propeller system 614 may include a device capable of communicating operating parameters to electric engine subsystem 604 and articulating the orientation of propeller subsystem 606 to redirect the thrust of the tilt propellers during various phases of flight using mechanical components (e.g., gearbox assemblies, linear actuators, and any other configuration of components that alter the orientation of propeller subsystem 606).

[0105] As discussed throughout, example VTOL aircraft may be equipped with various types of electric propulsion systems, including tilt propellers and lift propellers, including front electric engines that have the ability to tilt during various phases of flight and tail electric engines that remain in one orientation and may be active only during certain phases of flight (i.e., takeoff, landing, and hovering).

[0106] Figure 7 is a schematic diagram illustrating an example tilting electric propulsion system for a VTOL aircraft consistent with the disclosed embodiments. The tilting electric propulsion system 700 may include an electric engine assembly 702 aligned along an axis 724 connected to an output shaft 738 that is mechanically coupled to a propeller assembly 720 including a hub, a rotor, 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 axis 724. In some embodiments, the motor and gearbox assembly 704 may include an electric motor assembly including a stator 706 and a rotor 708. Figure 7As shown, and in some embodiments, the stator 706 may include multiple stator windings connected to the inverter 716. In this configuration, the stator 706 may include one or more redundancies such that in the event of a failure of one set of windings, power will still be transmitted to the stator 706 via one or more remaining windings, allowing the electric engine assembly 702 to maintain power and continue to generate thrust at the propeller assembly 720.

[0107] In some embodiments, the motor and gearbox assembly 704 may include a gearbox 710 aligned along shaft 724 to provide a gear reduction between the torque from shaft 724 of the electric motor assembly, including the stator 706 and rotor 708, and the output shaft 738. The torque applied to the output shaft 738 can be transmitted to the propeller assembly 720. Some embodiments may include a gearbox 710 containing an oil pump. In such embodiments, the oil pump can circulate oil throughout the motor and gearbox assembly 704 at a speed equal to the rotation of the output shaft 738 to cool and lubricate the gearbox and electric motor components. In some embodiments, the oil pump can circulate the oil at a speed greater than or less than the rotation of the output shaft 738. Some embodiments of the motor and gearbox assembly 704 may include a propeller position sensor 712 within the housing. The propeller position sensor can detect the magnetic field generated by the electric motor assembly to determine propeller position. Other embodiments may include a propeller position sensor 712 powered by an inverter 716 and transmitting collected data to the inverter 716.

[0108] In some embodiments, the power engine assembly 702 may further include an inverter assembly 714 substantially aligned along the axis 724. The inverter assembly 714 may include an inverter 716 and an inverter power source 740. The inverter power source 740 may receive low-voltage DC power from a low-voltage system 734 located external to the power engine assembly 702. The inverter power source 740 may receive low-voltage DC power from the high-voltage power system 732 located external to the power engine assembly 702, which has been converted to low-voltage DC power via a DC-DC converter 742. The inverter 716 may supply high-voltage alternating current (AC) to the stator 706 of the power engine assembly located within the motor and gearbox assembly 704 via at least one three-phase winding. The inverter assembly 714 may include an inverter 716, which may receive flight control data from a flight control computing subsystem 736.

[0109] In some embodiments, the motor and gearbox 704 can be located between the inverter assembly 714 and the propeller assembly 720. Some embodiments may also include a separator plate 744 coupled to the motor and gearbox assembly 704 and the inverter assembly 714. The separator plate 744 can create an enclosed environment for the upper portion of the motor and gearbox assembly 704 via a bell-shaped end cap assembly and for the lower portion of the inverter assembly 714 via a heat plate. In some embodiments, the separator plate 744 can serve as an integral mounting bracket for supporting the heat exchanger 718. The heat exchanger 718 can include, for example, folded fins or other types of heat exchangers. In some embodiments, the electric propulsion system 700 can circulate oil or other coolant throughout the electric engine assembly 702, the motor and gearbox assembly 704, or the inverter assembly 714 to transfer heat generated by the components to the oil or other coolant liquid. The heated oil or other coolant liquid can be circulated through the heat exchanger 718 to transfer heat to the air flow 722 passing over the heat exchanger's fins.

[0110] In some embodiments, electric engine assembly 702 can be mounted or coupled to a boom structure 726 of the aircraft. A variable pitch mechanism 730 can be mechanically coupled to propeller assembly 720. In some embodiments, the variable pitch mechanism can be adjacent to electric engine assembly 702. In some embodiments, variable pitch mechanism 730 can be coupled to variable pitch mechanism 730 so that it can be remotely mounted within the boom, wing, or fuselage of the aircraft. In some embodiments, variable pitch mechanism 730 can be included within shaft 724 or adjacent to a shaft or component that runs to propeller assembly 720. Variable pitch mechanism 730 can be used to change the total blade angle of the front electric engine's propeller assembly according to operational needs during hover, transition, and cruise phases. Some embodiments may include electric engine assembly 702 mechanically coupled to a tilt propeller subsystem 728, which can 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 can be adjacent to 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.

[0111] Figures 8A-8C is a diagram of an example tilting electric propulsion system for a VTOL aircraft consistent with the disclosed embodiments. Figures 8A-8CLike reference numerals are provided and refer to similar elements of the tiltable electric propulsion systems 800A, 800B, and 800C. Accordingly, similar design considerations and configurations may be considered throughout the embodiments.

[0112] Figure 8A and Figure 8B A side profile and perspective view of a tiltable electric propulsion system 800A, 800B in a cruise configuration, integrated into a boom 812A, 812B, respectively, consistent with the present disclosure, are shown. The tiltable propeller electric propulsion system 800A, 800B may include an electric engine assembly 802A, 802B housed within the boom 812A, 812B of a VTOL aircraft. In some embodiments, the cruise configuration may include the electric engine assembly 802A, 802B positioned within the boom 812A, 812B. As described herein, the electric engine assembly 802A, 802B may include an electric motor assembly, a gearbox assembly, an inverter assembly having power connection channels 810A, 810B, and a heat exchanger 804A, 804B. The electric engine assembly 802A, 802B may be mechanically coupled to a propulsion assembly 808A, 808B, which includes a shaft flange assembly 806A, 806B, a rotor, and propeller blades.

[0113] Figure 8C A top view along the rotator 808C of a tiltable electric propulsion system 800C in a lift configuration integrated into a boom 812B consistent with the present disclosure is shown. Figure 8C As shown, a tiltable electric propulsion system 800C in a lift configuration may include electric engine assemblies 802A, 802B that are positioned external to a boom 812C and change their orientation relative to the boom 812C.

[0114] As discussed herein, a lift electric propulsion system may be configured to provide thrust in one direction and may not provide thrust during all phases of flight. For example, a lift system may provide thrust during takeoff, landing, and hovering, but may not provide thrust during cruise.

[0115] Figure 9is a schematic diagram illustrating an example lift electric propulsion system for a VTOL aircraft consistent with the 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 axis 940, which is connected to an output shaft 932, which is mechanically coupled to a propeller assembly 920, comprising a hub and pitch propeller blades. In some embodiments, electric engine assembly 902 may include a motor and gearbox assembly housing 904 aligned along axis 940 and mechanically coupled to the shaft. 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 a plurality of stator windings connected to an inverter 916. In such a configuration, stator 906 may include one or more redundancy and backup measures to avoid a single point of failure in the described scenario. For example, stator 906 may include multiple windings such that if a winding fails, power may continue to be transferred to stator 906 via the remaining windings, thereby allowing electric engine assembly 902 to maintain power and continue to generate thrust at propeller assembly 920 .

[0116] In some embodiments, the motor and gearbox assembly housing 904 may include a gearbox 910 aligned along an axis 940 to provide a gear reduction between the torque from the shaft 932 of the electric engine assembly, including the stator 906 and the rotor 908, and the output shaft 932. The torque applied to the output shaft 932 can be transmitted to the propeller assembly 920. Some embodiments may include a gearbox 910 that includes a fluid pump for circulating cooling fluid and / or lubricating fluid. In the illustrated embodiment, the fluid pump is an oil pump. In such an embodiment, the oil pump can drive oil to circulate throughout the motor and gearbox assembly housing 904 at a speed equal to the rotation of the output shaft 932 to cool and lubricate the gearbox and electric motor components. Some embodiments of the motor and gearbox assembly housing 904 may include a propeller position sensor 912 within the housing that can detect the magnetic field generated by the electric engine assembly to determine propeller position. Further embodiments may include propeller position sensors 912 that are powered by inverter 916 and send collected data to inverter 916 , which may be passed to flight control computing system 930 along with other flight control data.

[0117] In some embodiments, the power engine assembly 902 may also include an inverter assembly housing 914 aligned along an axis shared with the axis of the shaft 924. The inverter assembly housing 914 may include an inverter 916 and an inverter power source 934. The inverter power source 934 may receive low-voltage DC power from a low-voltage system 928 located external to the power engine assembly 902. The inverter power source 934 may receive low-voltage DC power from a high-voltage power system 926 located external to the power engine assembly 902, which has been converted to low-voltage DC power via a DC-DC converter 936. The inverter 916 may supply high-voltage AC power to the stator 906 of the power engine assembly located within the motor and gearbox assembly housing 904 via at least one three-phase winding. The inverter assembly 914 may include the inverter 916, which may send and receive data to and from the flight control computing subsystem 930.

[0118] In some embodiments, the motor and gearbox housing 904 can be located between the inverter assembly housing 914 and the propeller assembly 920. Some embodiments may also include a separator plate 938 coupled to the motor and gearbox assembly housing 904 and the inverter assembly housing 914. The separator plate 938 can create an enclosed environment for the upper portion of the motor and gearbox assembly housing 904 via a bell-shaped end cap assembly, and can create an enclosed environment for the lower portion of the inverter assembly housing 914 via a heat plate. In some embodiments, the separator plate 938 can serve as an integral mounting bracket for supporting the heat exchanger 918. The heat exchanger 918 can include, for example, folded fins or other types of heat exchangers. In some embodiments, the electric propulsion system 900 can circulate oil or other coolant fluid throughout the electric engine assembly 902, the motor and gearbox assembly 904, or the inverter assembly 914 to transfer heat generated by the components to the oil or other coolant fluid. The heated oil or other coolant fluid can be circulated through the heat exchanger 918 to transfer heat to the air flow 922 passing over the heat exchanger's fins.

[0119] In some embodiments, the tiltable electric propulsion system and the lift electric propulsion system can have similar components. This can be advantageous for many design considerations within VTOL aircraft. For example, from a manufacturability perspective, having different types of electric propulsion systems with similar components can be beneficial in terms of manufacturing efficiency. Furthermore, having similar components can be beneficial in terms of risk management, as similar components have similar failure points, and these failure points can be better explored and designed for when comparing systems with similar components to systems with different components and configurations.

[0120] While the tiltable electric propulsion system may have additional and, in some embodiments, different components than the electric propulsion system for lift, it should be understood that in some embodiments, the tiltable electric propulsion system and the electric propulsion system for lift may have the same component configuration. For example, in some embodiments, the tiltable electric propulsion system and the electric propulsion system for lift may include the same components, while the electric propulsion system for lift may be coupled to a 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.

[0121] Figures 10A-10B is a diagram of an example lift electric propulsion system for a VTOL aircraft consistent with the disclosed embodiments. Figure 10A and Figure 10B Like reference numerals are provided and refer to similar elements of the lift electric propulsion systems 1000A and 1000B. Accordingly, similar design considerations and configurations may be considered throughout the embodiments.

[0122] Figure 10A A side profile of a lift electric propulsion system 1000A in a lift configuration, integrated into a boom 1010A, consistent with the present disclosure, is shown. The lift electric propulsion system 1000A may include an electric engine assembly 1002A housed within the boom 1010A of a VTOL aircraft. In some embodiments, the lift configuration may include the electric engine assembly 1002A vertically positioned within the boom 1010A. As described herein, the electric engine assembly 1002A may include an electric motor assembly, a gearbox assembly, an inverter assembly having a power connection channel 1008A, and a heat exchanger 1004A. The electric engine assembly 1002A may be mechanically coupled to a propulsion assembly 1006A, which includes a shaft flange assembly and propeller blades.

[0123] Figure 10B A top view of a lift electric propulsion system 1000B in a lift configuration integrated into a boom 1010B consistent with the present disclosure is shown.

[0124] Some embodiments of the disclosed power engine may generate heat during operation and may include a thermal management system to ensure that components of the power engine do not fail during operation. In some embodiments, a coolant may be used and circulated in various components of the engine (e.g., an inverter, gearbox, or motor), through some components or through all components of the engine to help manage the heat present in the engine. Some embodiments may include using air cooling methods to cool the power engine, or using a mixture of coolant and air to manage the heat generated during operation in the power engine. In some embodiments, the coolant used may also be the same liquid used as a lubricant throughout the inverter, gearbox, or motor. For example, liquid or air or a mixture of air and liquid cooling may be used to cool the components of the power engine. As another example, air cooling may be used to cool the motor, while liquid cooling may be used to cool the inverter and gearbox. It should be understood that the cooling mixture may be used for any combination of power engine components or within each component.

[0125] In some embodiments, oil can be used as a lubricant throughout the electric engine and also as a coolant fluid to help manage the heat generated by the engine during operation. Further to this example, varying amounts of oil can be used as both the lubricant and coolant fluid in the electric engine, with or without air cooling assistance, such as less than or equal to 1 quart, 1.5 quarts, 2 quarts, 2.5 quarts, 3 quarts, 5 quarts, or any other amount required to lubricate and cool the electric engine. In some embodiments, the amount of cooling-related oil or fluid used in the system can be determined based on the amount of thermal mass required to drive heat transfer to the components of the electric propulsion system. As disclosed herein, electric engines can have different primary functions, such as being used only for lift and landing and therefore only in one orientation, or being used during all phases of flight, such as lift, landing, and flight. An engine used in all phases of flight can experience various orientations throughout flight and may include more lubricant and coolant than an engine used in only one orientation. Therefore, all engines on an aircraft may not contain the same amounts of lubricant and coolant. For example, an engine operating during lift and landing may require less than a quart of oil, while an engine operating during all phases of flight may require more than a quart of oil. In some embodiments, the amount of oil or liquid used for cooling may be of an appropriate amount to provide sufficient thermal mass to drive heat transfer to components of the electric propulsion system, regardless of the orientation of the electric propulsion system. The embodiments discussed herein are exemplary, non-limiting, and do not dictate limits on the amount of lubricant and coolant that may be used in an electric engine.

[0126] 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 the removal of traditional components that can be used to cool the electric engine. For example, if the electric engine is cooled by another liquid such as ethylene glycol, the engine may include separate heat exchangers for both the lubricant fluid and the coolant fluid. Therefore, in embodiments where a single fluid (such as oil) is used for lubrication and cooling, there will be an increase in oil, but only one heat exchanger will be required, so since fewer heat exchangers are used and other components may not be required, the mass of the entire system can be reduced and a more attractive drag profile may be present. In addition, due to the reduction in mass and the benefits of cooling the engine with a substance rather than relying on air cooling, which may have problems traveling throughout the engine, using a substance to lubricate and cool the engine can improve the efficiency of the system.

[0127] Some embodiments of the electric engine may include various components for monitoring flammable fluids and for preventing flammable materials from entering certain sections of the electric engine. Some embodiments may include an electric engine with a wet area housing, which may be defined by a gearbox, a motor and / or a heat exchanger. In some embodiments, the electric engine may have up to 4 liters or more of air in contact with the engine oil within the motor-gearbox housing. Embodiments of the motor-gearbox housing may use a ventilator to equalize internal and external pressures. Embodiments of the ventilator may include a ventilator that protrudes above a nearby design feature to prevent the inadvertent entry of external fluids. Some embodiments may include a ventilator with a screen and a circuitous entry path to prevent the entry of external debris. Embodiments may include observation windows on both the tilt electric engine and the lift electric engine to check whether the oil is overfilled or underfilled during maintenance.

[0128] Some embodiments of electric engines may include active protection features in the forward and aft electric engines, such as monitoring vibration and internal temperatures throughout the engine, including oil temperature, stator winding assembly temperature, inverter bulk capacitor temperature, power module temperature, control board power module temperature, control board control processor temperature, control board monitoring processor temperature, internal hot spot temperature, and various other operating conditions throughout the engine as needed. This monitoring may be accomplished using various sensors located throughout the electric propulsion system and aircraft. Embodiments may include vibration limits based on known fault points or resonances of components, over-temperature limits set based on known fault temperatures, and operating limits related to the auto-ignition temperature of the fluid. In some embodiments, the various sensors used to monitor operating conditions throughout the engine may report operating conditions to the flight control system. Some embodiments may include threshold operating values ​​that may be required before the operating values ​​are sent 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 the operating condition. Some embodiments may include reducing the amount of power directed to the electric propulsion system to reduce mechanical wear or friction sparking caused by vibration, and / or reducing power to reduce the temperature of components within the electric propulsion system. Additionally, some embodiments may include reducing power to the electric propulsion system if the detected efficiency of the inverter is less than a target efficiency. In some embodiments, for example, where there are twelve electric propulsion systems within an aircraft, the flight control system may be configured to reduce power to or terminate power to a single electric propulsion system while increasing power directed to the remaining electric propulsion systems, or a subset thereof, to offset the reduction in lift generated by one electric propulsion system. In some embodiments, the flight control system may establish various thresholds of operating conditions corresponding to a reduction or increase in power to the electric propulsion system.

[0129] 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 avoid overcurrent events. This overcurrent protection can be activated when the current draw of the electric engine is greater than the overcurrent operation. Therefore, in some embodiments, a fault condition that causes an overcurrent may only result in a transient overheating, arcing, or spark failure. Some embodiments may include a fire threat characterization test ignition source that can be selected to be an ignition source that is more severe than a short circuit that occurs in the electric engine and is disconnected by the engine fuse. In some embodiments, the inverter can detect AC overcurrent and isolate the wrong phase and / or will continuously monitor the input DC voltage and will apply protective action to keep the voltage below the overvoltage operating limit.

[0130] During takeoff, landing, hovering, and cruising, a VTOL aircraft's motors and associated control components can generate heat. This heat must be dissipated to prevent degradation or damage to the VTOL aircraft's motors, control components, and other components. For some types of VTOL aircraft, such as electric VTOL (eVTOL) aircraft, thermal management is also crucial to maintaining optimal energy efficiency for components powered by batteries, for example.

[0131] Some components may generate high heat loads only during certain operating periods. For example, some lift propellers may be used only during takeoff, landing, and hovering, and may be shut down during cruise. Thus, such lift propellers may generate high heat loads during takeoff, landing, and hovering, and little or no heat during cruise.

[0132] B. Example Electric Propulsion System Embodiments

[0133] As described herein, embodiments of an electric propulsion system 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 propulsion system. As disclosed herein, these components or combinations thereof may be substantially aligned along an axis by sharing a common axis or having parallel axes, the parallel axes being spaced apart by less than or equal to 5% of the outer diameter of the component with the largest diameter. For example, the inverter assembly, gearbox assembly, and electric motor assembly may be substantially aligned along a central axis, wherein 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 a distance of less than or equal to 5% of the outer diameter of the electric motor assembly, wherein the electric motor assembly has a larger outer diameter than the gearbox assembly and the inverter assembly. It should be understood that the embodiments described herein are merely examples, and while certain components of an electric propulsion system may be shown adjacent to other components, all adjacent configurations are possible. For example, the gearbox assembly may be shown adjacent to the inverter assembly and the electric motor assembly. Furthermore, in some embodiments, the inverter assembly may be adjacent to the gearbox assembly and the electric motor assembly. Some embodiments may include an electric motor assembly adjacent to a gearbox assembly and an inverter assembly.

[0134] In some embodiments, each of the inverter assembly, gearbox assembly, and electric motor assembly can abut at least one of the other components. Abutment can include direct or indirect contact between components, including the components or the housing in which the components are located. In some embodiments, the electric engine can include an inverter assembly and an electric motor assembly without a gearbox assembly. Some embodiments of the electric engine can include an electric motor assembly and a gearbox assembly without an inverter assembly, or an electric motor assembly without a gearbox assembly or an inverter assembly.

[0135] Figures 11A-11C is a cross-sectional illustration of an example electric propulsion system for a VTOL aircraft consistent with the disclosed embodiments. Figure 11A An example of an electric propulsion system is shown. In some embodiments, an electric engine can directly contribute to the propeller of an aircraft. Electric engine 1100A can include a motor housing 1102A. Electric engine 1100A can also include an electric motor assembly, including components such as a stator 1104A, rotor magnets 1106A, and a rotor 1108A. In some embodiments, rotor 1108A can be mechanically coupled to a main shaft 1110A such that main shaft 1110A rotates at a speed equal to the rotational speed of rotor 1108A. Main shaft 1110A can be mechanically coupled to a shaft flange assembly 1112A. In some embodiments, shaft flange assembly 1112A can be an anchor point for the propeller. The electric motor assembly can be substantially aligned along a central axis 1114A.

[0136] In some embodiments, the electric power engine may include a gearbox. Figure 11BAn example of an electric engine is shown. In some embodiments, the electric engine may include an electric motor assembly and a gearbox assembly substantially aligned along an axis. In some embodiments, the electric motor assembly, gearbox assembly, and shaft may be substantially aligned along axis 1114B. Electric engine 1100B may include a motor housing 1102B, a stator 1104B, rotor magnets 1106B, and a rotor 1108B. In some embodiments, rotor 1108B may be mechanically coupled to main shaft 1110B such that main shaft 1110B rotates at a speed equal to that of rotor 1108B. Main shaft 1110B may be mechanically coupled to shaft flange assembly 1112B such that shaft flange assembly 1112B, and by extension a propeller assembly (not shown), may rotate at a speed equal to the rotational speed of main shaft 1110B. In some embodiments, the gearbox assembly may provide gear reduction and vary the rotational speed of main shaft 1110B. For example, electric motor 1102B may include a gearbox assembly comprising a sun gear 1116B, planetary gears 1118B, a ring gear 1120B, and a planet carrier 1122B. In some embodiments, sun gear 1116B may be mechanically coupled to main shaft 1110B such that sun gear 1116B rotates at a speed equal to that of main shaft 1110B. Sun gear 1116B may engage with planetary gears 1118B, which in turn engage with ring gear 1120B. In embodiments where sun gear 1116B rotates, ring gear 1120B may be fixed to motor housing 1102B. In some embodiments, planetary gears 1118B may rotate about sun gear 1116B due to their interaction with the rotating sun gear 1116B and the fixed ring gear 1120B. Planet carrier 1122B may be mechanically coupled to planetary gears 1118B and may rotate at an equal speed. Some embodiments may include a planet carrier 1122B mechanically coupled to the main shaft 1110B. In some embodiments, the main shaft 1110B may include multiple phases or multiple layers of the shaft so that portions of the shaft can rotate at different speeds. Some embodiments may include a first portion of the main shaft rotating at a speed equal to the speed of the rotor 1108B, and another portion of the main shaft rotating at a speed equal to the speed of the planet carrier 1122B. In some embodiments, the speed of the planet carrier may be less than the speed of the rotor 1108B.

[0137] In some embodiments, electric engine 1100B may include bearings 1124B, 1126B aligned along main shaft 1110B. Some embodiments may include inner races of bearings 1124B, 1126B mechanically coupled to a planet carrier and various bearings such as 1124B and 1126B.

[0138] Figure 11CAn example of an electric propulsion system is shown. In some embodiments, the electric propulsion system may include an electric motor assembly and a gearbox assembly substantially aligned along an axis. In some embodiments, the electric motor assembly may be positioned between the gearbox assembly and the axis flange assembly. Electric propulsion system 1100C may include a motor-gearbox assembly housing 1102C. In some embodiments, electric propulsion system 1100C may include an electric motor assembly comprising a stator 1104C, rotor magnets 1106C, and a rotor 1108C. Electric propulsion system 1100C may also include a gearbox assembly. In some embodiments, the gearbox assembly may include a sun gear 1116C, planet gears 1118C, a ring gear 1120C, and a planet carrier 1122C. Sun gear 1116C may engage with planet gears 1118C, which may also engage with ring gear 1120C. Sun gear 1116C may be mechanically coupled to rotor 1106C such that rotation of rotor 1106C causes sun gear 1116C to rotate at the same rotational speed. Planet carrier 1122B can be mechanically coupled to planet gears 1118C and can rotate at equal speeds. Some embodiments may include planet carrier 1122C mechanically coupled to main shaft 1110C. Main shaft 1110C can be mechanically coupled to shaft flange assembly 1112C. Main shaft 1110C can be substantially aligned along central axis 1114C, such that the gearbox assembly and motor assembly are also substantially aligned along central axis 1114C. In some embodiments, electric propulsion system 1100C can include heat exchanger 1124C, which can be used to cool oil or liquid used to cool or lubricate components of the gearbox assembly or electric motor assembly.

[0139] As described above, electric propulsion systems 1100A-C are example embodiments. However, it should be understood that while electric propulsion system 1100A is capable of providing the required thrust to a VTOL aircraft, it may produce a larger drag profile and contribute more mass to the VTOL aircraft than electric propulsion systems 1100B and 1100C. Electric propulsion systems 1100B and 1100C include a gearbox assembly. Thus, electric propulsion systems 1100B and 1100C include a gear reduction that allows the electric motor assembly, and therefore the electric propulsion system, to have a smaller drag profile and lower mass.

[0140] Electric propulsion system 1100B may include a gearbox assembly between the electric motor assembly and the shaft flange assembly. While this configuration may require less mass than electric propulsion system 1100A, it may require more mass than electric propulsion system 1100C. Electric propulsion system 1100B may include a gearbox assembly such that the input shaft, or sun gear, runs from the electric motor assembly to the gearbox assembly, and the output shaft, or portion of the planet carrier, runs from the gearbox assembly to the shaft flange assembly. In some embodiments, electric propulsion system 1100C may include a sun gear and a main shaft, with the sun gear running from the rotor of the electric motor assembly to the gearbox assembly. The main shaft is coupled to the planet carrier or carrier cover, and the main shaft runs through the sun gear, past the electric motor assembly, and to the shaft flange assembly. This allows electric propulsion system 1100C to include a more compact design, housing, and drag profile compared to electric propulsion system 1100B. This can result in a more efficient drag profile and a more mass-efficient system. Furthermore, electric propulsion system 1100B may include a gearbox assembly without lubrication, which may limit the operating time of the electric propulsion system. The electric propulsion system 1100C may include heat exchangers to cool and lubricate various parts of the system, including the gearbox assembly. This can result in additional efficiency and long flight range.

[0141] Figure 49A cross-sectional view of an example electric propulsion system for a VTOL aircraft consistent with the disclosed embodiments is shown. Electric propulsion system 4900 may include a system that initially sends torque away from the propeller and then brings the torque back to the propeller through other parts of the system. In some embodiments, electric propulsion system 4900 may include 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, electric propulsion system 4900 may include a gearbox assembly including a sun gear 4906, planet gears 4908, a ring gear 4910, and a planet carrier 4912. Sun gear 4906 may be mechanically coupled to rotor 4904. Sun gear 4906 may engage with planet gears 4908. Planet gears 4908 may engage with a ring gear 4910, which may be fixed, such that planet gears 4908 rotate about sun gear 4906 against ring gear 4910. In some embodiments, the planet gears 4908 may include compound planet gears 4908 and 4950. A planet carrier 4912 may be mechanically coupled to the planet gears 4908 via a shaft 4914, which may extend from the planet gears 4908 along a central axis 4916 of the planet gears and be received by the planet carrier 4912. The planet carrier 4912 may rotate at a rate equal to that of the planet gears 4908. The planet carrier 4912 may be mechanically coupled to a main shaft 4918 such that the main shaft 4918 may rotate at a rate equal to that of the planet carrier 4912. In some embodiments, the planet gears 4908 may be mechanically coupled to a carrier cover via a shaft such that the carrier cover may rotate at a rate equal to that of the planet gears 4908. The main shaft 4918 may be mechanically coupled to a shaft flange assembly 4920 such that the shaft flange assembly 4920 may rotate at a rate equal to that of the main shaft 4918. It should be understood that the planetary gear 4908 or compound planetary gear 4908, 4950 may include multiple planetary gears that rotate about the sun gear 4906.

[0142] Due to the mechanical coupling described herein, torque can be transferred from rotor 4904 to sun gear 4906 along path 4930. Sun gear 4906 can transfer torque to planet gears 4908 along paths 4932 and 4934. Planet gears 4908, and in some embodiments, compound planet gears 4908 and 4950, can transfer torque to the planet carrier along paths 4936 and 4938. The planet carrier can transfer torque to main shaft 4918 along path 4940. Main shaft 4918 can transfer torque along its length and to propeller assembly 4920 via path 4944. Propeller assembly 4920 can transfer torque to the propeller via paths 4946 and 4948. It should be understood that the paths discussed above are examples, and all configurations are contemplated that involve sending torque away from the propeller to the gearbox assembly and then back to the propeller through the gearbox assembly and electric motor assembly.

[0143] In some embodiments, using a gearbox assembly to deliver power from an electric engine via a reverse torque path may include driving planetary gears mechanically coupled to a rotor of an electric motor assembly. In some embodiments, the planetary gears may engage 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 a driven planet carrier connected to shafts extending from the planetary gears. The shafts extending from the planetary gears may include shafts aligned along the central axes of the planetary gears. Some embodiments may include a driven carrier cover connected to a shaft extending concentrically from the planetary gears. Some embodiments may include a driven main shaft. Driving the main shaft may include a first portion driving a main shaft mechanically coupled to the carrier cover and transmitting torque along the main shaft to a second portion mechanically coupled to the main shaft of the propeller assembly. Some embodiments may include a heat exchanger as described herein, which may use various oil volumes to cool the gearbox assembly, including 1 quart, 1.5 quarts, 2 quarts, 2.5 quarts, 3 quarts, or 5 quarts.

[0144] In some embodiments, a gearbox assembly may include multiple gearboxes. For example, in some embodiments, the output of a gearbox assembly may be fed into another gearbox assembly to achieve a greater 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 planet carrier. The gearbox may include common gears, such as a common sun gear, a common planetary gear set, and a common ring gear. The embodiments discussed herein can be modified to include multiple gearboxes.

[0145] Figure 53A flow chart illustrating an example process consistent with the disclosed embodiments for transmitting torque from an electric motor assembly to a propeller assembly of a VTOL aircraft 5300. Although the block diagrams may be described below in conjunction with certain embodiments presented in other figures, these embodiments are provided for illustrative purposes only and are not intended to serve as limitations on the block diagrams.

[0146] Figure 53 Process blocks 5302 through 5312 are included. At block 5302, consistent with discussions throughout this disclosure, 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.

[0147] At block 5304, consistent with discussions throughout this disclosure, a process for delivering power from an electric engine using a gearbox assembly may include driving a planet carrier connected to at least one shaft extending concentrically from planet gears.

[0148] At block 5306 , consistent with discussions throughout this disclosure, a process for delivering power from an electric engine using a gearbox assembly may include driving a carrier cap connected to at least one shaft of a set of shafts extending concentrically from the planetary gears.

[0149] At block 5308 , consistent with discussions throughout this disclosure, a process for delivering power from an electric engine using a gearbox assembly may include driving a main shaft.

[0150] At block 5310 , consistent with discussions throughout this disclosure, 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 frame cover.

[0151] At block 5312 , consistent with discussions throughout this disclosure, a process for delivering power from an electric engine using a gearbox assembly may include transferring torque along the main shaft to a second portion of the main shaft mechanically coupled to the propeller assembly.

[0152] Figures 12A-12D is a diagram and block diagram of an example electric propulsion system for a VTOL aircraft consistent with the disclosed embodiments.

[0153] 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 enclosed 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 housing 1202A and housing 1228A can provide various benefits, including lower mass and a more efficient drag profile, as described herein. Additionally, in some embodiments, the gearbox assembly, inverter assembly, and / or electric motor assembly may have a substantially circular profile. As used herein, a profile may be substantially circular, wherein the length of the minor axis of the circular shape and the length of the major axis of the circular shape have a relationship such that the length of the minor axis is at least a threshold amount (e.g., 80%) of the length of the major axis. Additionally, in some embodiments, the gearbox assembly, inverter assembly, and electric motor assembly, or a subset of those listed components, may be sized such that the components have substantially equal radii. As used herein, components may have substantially equal radii, wherein the difference between the radii of two components is less than a threshold amount, such as 10%, of the radius of the largest component. In some embodiments, the outlines of the components comprising the electric propulsion system described herein may include various polygons, such as hexagons, heptagons, octagons, nonagons, decagons, and additional polygons having more than ten sides.

[0154] Electric propulsion system 1200A may include an electric motor assembly including a stator 1204A, rotor magnets 1206A, and a rotor 1208A.

[0155] In some embodiments, the electric motor assembly can interact with a gearbox assembly and, in some embodiments, transfer torque to the gearbox assembly. Electric propulsion system 1200A may include a gearbox assembly comprising a sun gear 1214A, a set of planetary gears 1216A, a planet carrier 1218A, and a carrier cover 1220A. Some embodiments may include a sun gear 1214A having teeth that interact with the teeth of the planetary gears 1216A, and a ring gear (not shown in this figure) having teeth that also interact with the teeth of the planetary gears 1216A. In some embodiments, shaft 1222A may extend through or from the planetary gears 1216A. In some embodiments, planet carrier 1218A may receive a first end of shaft 1222A so that planet carrier 1218A can rotate at the same rate as planetary gears 1216A. In some embodiments, carrier cover 1220A may receive a second end of shaft 1222A so that carrier cover 1220A can rotate at the same rate as planetary gears 1216A. In some embodiments, the planet gears 1216A, the planet carrier 1218A, and the carrier cover 1220A can be mechanically coupled along the axis of the shaft 1222A.

[0156] In some embodiments, the electric propulsion system 1200A may include a main shaft 1210A, which may be mechanically coupled to a shaft flange assembly 1224A to provide mechanical shaft power to rotate a propeller of a propeller assembly. As used herein, components may be mechanically coupled where there is any connection or coupling, direct or indirect, between two components. The shaft flange assembly may include a flange coupled to the main shaft via a spline connection to obtain torque loads from the main shaft and transfer 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 any other component or method used to couple 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 a shaft flange assembly, a propeller, and a rotator. In some embodiments, the shaft flange assembly may also be referred to as a propeller hub.

[0157] 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, a gate drive PCBA 1236A, and a control PCBA 1240A, which may include a power module 1232A. Some embodiments of the inverter assembly of the electric propulsion system 1200A may also include a spacer 1238A among the various PCBAs. In addition, some embodiments may include an energy storage device, such as a DC capacitor that can be stored within a DC capacitor housing 1234A. Some embodiments of the inverter assembly may also include a busbar connector 1244A to supply alternating current to the electric motor assembly. Some embodiments of the inverter assembly may include a power connection 1246A coupled to a high voltage connector to deliver high voltage power to the inverter assembly.

[0158] Some embodiments of the inverter assembly of the electric propulsion system 1200A may include stacking the respective inverter assembly components in a stacked configuration along guide pins 1242A extending through each layer of the inverter assembly. It will be appreciated that utilizing a stacked configuration of the inverter assembly 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, thereby helping to minimize the mass of the electric propulsion system 1200A and minimize the drag experienced due to the packaging of the electric propulsion system. Furthermore, the stacked configuration of the inverter assembly may be advantageous from a manufacturing perspective, as the stacked configuration allows for tolerances within the various parts of the inverter assembly. In some embodiments, structural components may be incorporated into the inverter assembly to help support the stacked configuration with loads experienced during various flight phases. Some embodiments may include inverter assembly components that also serve 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 materials capable of supporting the PCBA and surrounding components.

[0159] In some embodiments, the electric propulsion system 1200A may include a heat exchanger 1226A coupled to the motor-gearbox assembly housing 1202A and the inverter assembly housing 1228A. The heat exchanger 1226 may be coupled to a separator plate comprising a thermal plate 1248A and a bell-shaped end cap plate 1250A. The bell-shaped end cap plate 1250A may be used to enclose the motor-gearbox assembly housing 1202A. The thermal plate 1248A may be used to enclose the inverter assembly housing 1228A. In some embodiments, the separator plate may serve as an integral mounting bracket for supporting the heat exchanger 1226A. The heat exchanger 1226A may include, for example, folded fins or other types of heat exchangers. In some embodiments, the 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 can be circulated through the fins of heat exchanger 1226A via an internal liquid flow path, which can include an inlet and an outlet for the liquid flow path, which can be coupled to the outlet and inlet, respectively, of holes or grooves that may be present in the separator plate. In some embodiments, motor-gearbox housing 1202A can include a sump 1212A. Sump 1212 can be used to collect and recirculate oil or liquid coolant distributed throughout electric propulsion system 1200A.

[0160] In some embodiments, the heat exchanger can be fluidly coupled to the gearbox assembly, the inverter assembly, and / or the electric motor assembly. As used herein, an assembly or component thereof can be fluidly coupled, wherein a liquid flow path from the heat exchanger can interact with, supply liquid to, or engage with the assembly or component thereof.

[0161] Figure 12BAn example schematic diagram of a configuration of an electric propulsion system 1200B is shown. In some embodiments, the electric propulsion system may include a motor assembly and a gearbox assembly. The electric propulsion system 1200B includes a separator 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 enclose the inverter assembly 1204B, and a motor-gearbox housing 1214B may enclose the motor assembly 1202B and the gearbox assembly 1206B. The inverter assembly housing 1216B may be adjacent to 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 can have a path from heat exchanger 1212B to divider plate 1208B, and then to gearbox assembly 1206B and motor assembly 1202B, thereby providing cooling and lubrication for motor assembly 1202B and gearbox assembly 1206B. Oil flow 1218B can then travel from motor assembly 1202B back to heat exchanger 1212B. As described herein, propeller assembly 1210B can drive air flow 1220B from the propeller toward heat exchanger 1212B. Heat exchanger 1212B can transfer heat from oil flow 1218B to air flow 1220B. Oil flow 1218B can be cooled and exit heat exchanger 1212B.

[0162] Figure 12CAn example schematic diagram of a configuration of an electric propulsion system is shown. In some embodiments, electric propulsion system 1200C may include a separator 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, an inverter assembly housing 1216C may enclose inverter assembly 1204C, and a motor-gearbox housing 1214C may enclose motor assembly 1202C and gearbox assembly 1206C. Inverter assembly housing 1216C may be adjacent to motor-gearbox housing 1214C. In some embodiments, electric propulsion system 1200C may include electric motor assembly 1202C positioned between gearbox assembly 1206C and 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 can have a path from heat exchanger 1212C to separator plate 1208B, then to motor assembly 1202C, and then to gearbox assembly 1206C, thereby providing cooling and lubrication for motor assembly 1202C and gearbox assembly 1206C. Oil flow 1218C can then travel from motor assembly 1202C back to heat exchanger 1212C. As described herein, propeller assembly 1210C can drive air flow 1220C from the propeller toward heat exchanger 1212C. Heat exchanger 1212C can transfer heat from oil flow 1218C to air flow 1220C. Oil flow 1218C can be cooled and exit heat exchanger 1212C.

[0163] Figure 12DAn example schematic diagram of a configuration of an electric propulsion system is shown. In some embodiments, the electric propulsion system may include a motor and propeller assembly. Electric propulsion system 1200D may include a separator plate 1208D, a motor assembly 1202D, an inverter assembly 1204D, a heat exchanger 1212D, and a propeller assembly 1210D. In some embodiments, inverter assembly housing 1216D may enclose inverter assembly 1204D, and motor assembly housing 1214D may enclose the motor assembly. Inverter assembly housing 121D may be adjacent to motor assembly housing 1214D. In some embodiments, electric propulsion system 1200C may include an electric motor assembly 1202C that directly drives a main shaft, thereby providing mechanical shaft power to propeller assembly 1210C. In such an embodiment, the main shaft may rotate at a speed equal to the speed of the rotor within electric motor assembly 1202. As described herein, a coolant or lubricant, such as oil, may be distributed throughout the electric propulsion system. For example, oil flow 1218D can have a path from heat exchanger 1212D to separator plate 1208D, and then to motor assembly 1202D, thereby providing cooling and lubrication for motor assembly 1202D and other components of electric propulsion system 1200D. Oil flow 1218D can then travel from motor assembly 1202D back to heat exchanger 1212D. As described herein, propeller assembly 1210D can drive air flow 1220D from the propeller toward heat exchanger 1212D. Heat exchanger 1212D can transfer heat from oil flow 1218D to air flow 1220D. Oil flow 1218D can be cooled and exit heat exchanger 1212D.

[0164] Figure 13 13 is an illustration of an exploded view of an example electric propulsion system for a VTOL aircraft consistent with the disclosed embodiments. Electric engine 1300 may include an inverter assembly 1304, a bell-shaped end cap assembly 1306, a main shaft assembly 1308, a rotor 1310, a stator housing 1312, and a shaft flange assembly 1314. In some embodiments, inverter assembly 1304 may be adjacent to a gearbox assembly. The gearbox assembly may include bell-shaped end cap assembly 1306 and main shaft assembly 1308. In some embodiments, the gearbox assembly may be adjacent to an electric motor assembly. The electric motor assembly may include rotor 1310 and stator housing 1312. In some embodiments, components of the electric propulsion system may be substantially aligned along an axis. In some embodiments, the main axis may represent a central axis along which components of 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 so that different electric propulsion system components are adjacent to each other, as described herein. The housing of the inverter assembly 1304 may be secured to the inverter assembly's thermal plate via screws 1302. In some embodiments, fasteners 1316 may secure the electric engine 1300 to a boom of the aircraft.

[0165] As described herein, embodiments of an electric engine may include an electric motor assembly. Figure 14 is an illustration of an exploded view of an example electric motor assembly for a VTOL aircraft consistent with the disclosed embodiments. Electric motor assembly 1400 may include a stator assembly 1402. In some embodiments, the stator may include laminations and coils of insulated wire. In some embodiments, stator assembly 1402 may include permanent magnets. Stator assembly 1402 may include a stator core 1404 and wire windings 1406. In some embodiments, wire windings 1406 may be composed of copper. Stator assembly 1402 may also include busbars 1408. As an example, busbars 1408 may be electrically coupled to stator assembly 1402 and facilitate electrical conduction of current. Electric motor 1400 may include various bearings, including a bearing retainer 1412 and a roller bearing 1414. Bearing retainer 1412, roller bearing 1414, and shaft seal 1416 may be substantially aligned along a central axis. In some embodiments, bearing retainer 1412 may serve as a cooling oil manifold to facilitate cooling. In some embodiments, roller bearing 1414 may include a spherical shape. Electric motor 1400 may include bearing screws 1410. Bearing screws 1410 may secure bearing retainers 1414 to various components of electric motor 1400, including roller bearings 1414. In some embodiments, stator housing 1418 may enclose stator assembly 1402, roller bearings 1414, bearing retainers 1412, shaft seals 1416, and bearing screws 1410. Stator housing 1418 may have an interference fit or a press fit with stator assembly 1402. For example, stator housing 1418 may be press-fit with the stator laminations. In some embodiments, stator housing 1418 may have a thermal interference fit with stator assembly 1402. As an example, stator housing 1418 may be a common housing that encapsulates the components of stator 1400, thereby providing advantages including reduced mass and the elimination of pipes, hoses, and other connectors. In some embodiments, stator housing 1418 may include a reservoir 1420 for collecting liquid used to cool or lubricate the electric propulsion system, as described herein. Furthermore, in some embodiments, additional components of the electric propulsion system may reside within the stator housing to provide further mass reduction.

[0166] Figures 15A-15C is an illustration of a stator assembly of a VTOL aircraft consistent with the disclosed embodiments. Figure 15A A view of a stator core is shown. In some embodiments, the stator 1500A may include a wound stator assembly 1502A and copper windings 1504A. Figure 15B Another view of a stator core 1500B is shown. Laminations 1502B may separate copper windings 1504B. Figure 15CAn example of a stator slot is depicted. As an example, a stator core 1500C may include copper windings 1506C, which may be housed within a stator core 1502C. Slot liners 1508C may separate the copper windings 1506C from the stator core 1502C. Slot liners 1508C may provide electrical insulation. The contour of the stator core 1502C may mate with slot wedges 1504C, which are positioned above the copper windings 1506C. Slot wedges 1504C may hold the copper windings 1506C in place within the stator core 1502C. In some embodiments, the stator core 1502C may be comprised of stator laminations. The stator laminations may help insulate the core and reduce eddy currents or losses. In some embodiments, the stator assembly may include oil-filled cavities positioned around the stator to facilitate cooling. Such cavities may be fluidically coupled to a heat exchanger, as described herein.

[0167] Figures 16A-16C Like reference numerals are provided and refer to similar elements of the rotor assemblies 1600A and 1600B. Accordingly, similar design considerations and configurations may be considered throughout the embodiments.

[0168] The 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 the rotor to rotate about an axis.

[0169] Figures 16A-16B is an exploded view and cross-sectional illustration of a rotor assembly of a VTOL aircraft consistent with the disclosed embodiments. Figure 16AAn example exploded view of a rotor is shown. Rotor assembly 1600A may include rotor 1602A, which includes rotor hub 1604A. In some embodiments, rotor hub 1604A may be machined and constructed from aluminum. Rotor 1602A may include laminations 1606A and a Halbach array 1608A. Laminations 1606A may have a thermal interference fit with rotor hub 1604A. Rotor 1602A may be surrounded by a rotor overwrap 1610A. In some embodiments, rotor overwrap 1610A may be constructed from carbon fiber. Halbach array 1608A may include magnets. Rotor overwrap 1610A may abut Halbach array 1608A and apply pressure to the magnets in Halbach array 1608A. In some embodiments, rotor 1602A may include a hollow portion. The hollow portion of the rotor can allow various motor assembly or gearbox assembly components to pass through rotor 1602A, thereby enabling configurations that can couple components to rotor 1602A. In some embodiments, the electric motor assembly can be mechanically coupled to the gearbox assembly. The disclosed embodiments include various means for mating the rotor and sun gear. Rotor 1602A can be mechanically coupled to sun gear 1612A and concentrically secured using various means for connecting and aligning components. Rotor 1602A can be mechanically coupled to sun gear 1612A using various fastening means. For example, rotor 1602A can be fastened to sun gear 1612A using a locking nut 1620A, a dowel pin, or a screw 1622A. Bearing 1616A can have an interference fit with rotor assembly 1602A and sun gear 1612A. In some embodiments, sun gear 1612A can include gear teeth 1614A, which can be used in a gearbox assembly as described herein. Sun gear 1612A can include a hollow center. In some embodiments, sun gear 1612A can be mechanically coupled to an oil jacket 1618A, which can use centrifugal force during rotation to assist in distributing cooling or lubricating liquid.

[0170] Figure 16BAdditional views of rotor assembly 1600B are shown. As described herein, rotor 1602B may include a rotor hub 1604B, a lamination stack 1606B, and a Halbach array 1608B. A rotor overpack 1610B may abut Halbach array 1608B and surround stator assembly 1602B. Bearing 1616A may include an inner race and an outer race. In some embodiments, sun gear 1612B may be mechanically coupled to rotor 1602B. Some embodiments may include mechanically coupling sun gear 1612B and rotor 1602B using screws 1622B. Bearing 1616B may assist in mechanically coupling rotor 1602B and sun gear 1612B by providing an interference fit. In some embodiments, the main shaft of the power engine assembly may pass through bearing 1616B, and therefore through sun gear 1612B and rotor 1602B. Additionally, some embodiments may include bearings 1616B for supporting rotor 1602B and rotor hub 1604A, as well as any loads experienced by rotor 1602B or rotor hub 1604B during normal operation. In some embodiments, the inner surface of rotor assembly 1602B may have a diameter equal to that of 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.

[0171] 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 can apply a load. As described herein, an electric propulsion system may include a gearbox assembly and a rotor of an electric motor assembly, both of which can apply a load on a shaft. For example, the gyroscopic effect caused by the rotating rotor being in motion may apply a torque load. The torque load may be on a center path of the shaft. The gearbox assembly, which may include planetary gears, can share torque through several paths, so the sharing of the load may depend on the tolerances of the components within the electric engine. Therefore, a solution that supports the load and resists the moment created by the generated torque while maintaining a low mass and drag profile is advantageous.

[0172] Figure 54 is a schematic illustration of a partial cross-sectional view of an example electric motor assembly. Figure 54 As shown, the electric motor assembly 5400 may include a housing 5402 enclosing a sealed environment 5404, wherein a rotor 5406 and a stator 5408 (and magnets 5418 as part of the stator 5408) are within the housing 5402. In some embodiments, the electric motor assembly 5404 may be positioned such that the propeller assembly ( Figure 545402 ). The side 5410 facing the propeller assembly (i.e., facing the air flow driven by the propeller assembly) is the cold side, while the side 5412 facing away from the propeller assembly (i.e., on the rear side of the air flow generated by the propeller assembly) is the hot side. The air flow 5414 generated by the propeller assembly can be used to cool the housing 5402, making the side 5410 facing the propeller the cold side.

[0173] In some embodiments, as Figure 54 As shown, the rotor 5406 can generate air movement 5416 from the cold side 5410 toward the hot side 5412 within the sealed environment 5404 enclosed by the housing 5402 to provide a cooling effect to one or more components on the exterior of the housing 5402 on the hot side 5412. In other words, heat generated by one or more components on the exterior of the housing 5402 on the hot side 5412 is first dissipated to the cold side 5410 through the air movement 5416 inside the sealed housing 5402, and then further dissipated through the air flow 5414 generated by the propeller assembly.

[0174] In some embodiments, air movement 5416 can also provide a cooling effect to dissipate heat generated by magnets 5418 inside housing 5402. Air movement 5416 facilitates heat dissipation from magnets 5418 through the cooling effect created by air flow 5414.

[0175] Figures 55A-55B is an illustration of example interior surfaces of a portion of a rotor hub and a portion of an end plate. In some embodiments, the interior surfaces (e.g., 5502A, 5502B) of the rotor hub 5500A and the end plate 5500B may have fins (e.g., 5504A, 5504B), respectively, to allow the rotor to more efficiently move within the housing 5402 (by defining an air path with less air resistance). Figures 55A-55B Air movement (e.g., 5416) is generated inside the ).

[0176] like Figure 55A As shown, the fins 5504A on the interior 5502A of the rotor hub 5500A can have different heights and shapes. In this example embodiment, the different shaped fins are all straight (ie, flat), but they can also have different geometries.

[0177] like Figure 55B As shown, the fins 5504B on the interior 5502B of the end plate 5500B all have the same height. In this example embodiment, the height of the fins 5504B can be about 12 mm. Typically, this height can be between about 5 mm and 20 mm.

[0178] In this example embodiment, the fins on the rotor hub and the stator can have a first gap. The first gap can be between 0.4 mm and 1.2 mm, or approximately 0.6 mm. The fins on the end plate and the rotor can have a second gap. The second gap can be between 0.4 mm and 1.2 mm, or approximately 0.6 mm. The first gap and the second gap can be determined so that air inside a sealed environment (e.g., a housing) is pressurized through the 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 directed toward the center of the motor on the cold side.

[0179] Figure 55C is the housing (e.g. Figure 54 The simulation results of the air velocity and pressure distribution inside the shell 5402). Figure 55C In the example shown, white space represents a solid motor structure without the presence of air. The different colors in the left image represent differences in air velocity, showing that the air velocity between rotor 5406 and motor spindle 5502B is significantly higher than on the left, thereby demonstrating that the air within the sealed environment is agitated. In the center image, different colors illustrate the internal pressure distribution within sealed environment 5404. In some embodiments, a larger pressure difference between two points can generate a higher air flow with a higher velocity, which can improve the heat exchange efficiency between the cold and hot sides of the housing, thereby enhancing the cooling effect on the motor.

[0180] Figure 55D is a set of example interior surfaces of the end plates consistent with the disclosed embodiments. The fins on the end plates and rotors can have different geometries and arrangements that can be optimized taking into account different design factors and operating parameters, such as revolutions per minute (RPM), clearances, motor size, weight, rotating mass, and other design and operating parameters that may be affected by fin design and shape.

[0181] In some embodiments, the direction of air flow can be reversed. For example, instead of moving air toward the center of the hot side, the air can instead move from the center to the periphery of the hot side. In such an embodiment, the air flow at the center of the motor will be from the hot side to the cold side. This can be achieved by changing the shape (e.g., curvature) of the fins. Figure 24 Example designs of fin shapes are provided, but the examples shown are not intended to limit the range of potential fin designs and shapes. The fin shapes can be optimized or modified based on the specific needs of the system and evaluation based on experiments and simulations.

[0182] The disclosed embodiments may include a bearing system including a rotor utilizing bearings to support a load. Figure 16CA cross-sectional view of an example embodiment of a rotor assembly consistent with embodiments of the present disclosure is shown. In some embodiments, the rotor assembly may include a bearing system 1600C. Bearing system 1600C may include a rotor hub 1604C, a sun gear 1612C, and a main shaft 1626C. 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 sun gear 1612C. Main shaft 1626C may include an outer surface 1628C, which may abut a shaft flange assembly 1630C. Shaft flange 1630C may abut a bearing 1634C. Bearing 1634C may have an inner race mechanically coupled to main shaft 1626C and an outer race mechanically coupled to rotor hub 1630C. In some embodiments, bearing 1634C can have an inner race mechanically coupled to main shaft 1626C and an outer race mechanically coupled to rotor hub 1630C and sun gear 1612C. In some embodiments, bearing 1634C can abut both rotor hub 1604C and sun gear 1612C. Bearing 1634C can be mechanically coupled to shaft flange assembly 1630C. As described herein, bearing 1634C can support rotor hub 1604C and loads from rotor hub 1604C. For example, rotation and movement of rotor hub 1604 can cause a gyroscopic effect that applies loads. Bearing 1634C can support loads, including radial or axial rotor loads. Bearing 1634C can allow sun gear 1612C to float, which can absorb variations in loads. In some embodiments, bearing 1634C can be a rolling element bearing. For example, bearing 1634C may include rolling elements 1616C that may be immersed in lubricant 1632C within bearing 1634C. In some embodiments, lubricant 1632C may include oil. Other bearings capable of supporting loads and high-speed rotation may be used, such as ball bearings or deep groove ball bearings.

[0183] Embodiments of the disclosed electric propulsion system may also include a guide system for a bearing supporting the rotor. As disclosed herein, the electric propulsion system may include bearings supporting the sun gear and the rotor. The bearing supporting the rotor may include a bearing having an outer race mechanically coupled to the inner surface of the rotor. For example, bearing 1634C may include an outer race mechanically coupled to rotor hub 1604C. Bearing 1634C guides sun gear 1612C and rotor hub 1604C by guiding the alignment or mating of multiple components. For example, a guide may be used to align or mate sun gear 1612C and rotor hub 1604C. Bearing 1634C may support the edges of sun gear 1612C and rotor hub 1604C to rest on the outer race, which may concentrically secure sun gear 1612C and rotor hub 1604C. A first edge of sun gear 1612C and a first edge of rotor hub 1604C may abut and meet on the outer race of bearing 1634C. Bearing 1634C can influence the diameters of sun gear 1612C and the rotor. The diameter of the outer race of bearing 1634C can be substantially similar to the diameter of the inner surface of sun gear 1612C and the inner diameter of the rotor. In some embodiments, rotor hub 1604C and sun gear 1612C can be concentrically fixed. Sun gear 1612C can have a diameter equal to the inner diameter of the rotor. In some embodiments, the guide system for the bearing can include a shoulder. A shoulder can be an edge of a component that abuts one or more edges of another component. For example, the shoulder can include a portion of one or more edges of sun gear 1640B abutting bearing 1616B and a portion of one or more edges of rotor hub 1642B abutting bearing 1616B. The shoulder can cooperate to limit movement of the bearing. For example, the shoulder can cooperate to limit movement of bearing 1616B in the axial direction of the shaft or along axis 1624B. In some embodiments, the guide can include a shoulder to radially capture the bearing. The guide system can reduce mass and prevent the need for additional material. In some embodiments, dowel pins may be used to guide the sun gear and rotor.

[0184] In some embodiments, the rotor bearing system may also include bearings designed to resist moment loads and allow for float to compensate for tolerances in the gearbox. The rotor bearing system may include a hydrodynamic bearing. The hydrodynamic bearing can resist or offset rotor moment loads. In some embodiments, the hydrodynamic bearing may be positioned along the sun gear. For example, the hydrodynamic bearing may be located between the sun gear 1612C and the main shaft 1626C, and the hydrodynamic bearing may be located at a certain location along the length of the sun gear 1612C. In some embodiments, the hydrodynamic bearing may extend along the entire length of the sun gear 1612C. The hydrodynamic bearing may be positioned where the main shaft 1626C has a shoulder or cavity, as described herein. For example, the hydrodynamic bearing may include a fluid between the shoulder or cavity of the sun gear 1612C and 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, which may be determined by the characteristics of the rotor, including changes in mass, velocity, rate of change, and axis or load (including rotational, axial, and radial loads or moments). The fluid dynamic bearing may include a fluid, such as oil, located between the sun gear 1612C and the outer surface 1628C of the main shaft 1626C. The fluid dynamic bearing may help resist the moment loads experienced by the sun gear 1612C. For example, the fluid dynamic bearing may apply a restoring force to resist the rotational load. In some embodiments, the fluid dynamic bearing may include oil. The fluid dynamic bearing may allow the sun gear 1612C or the ring gear to float. The fluid dynamic bearing may allow for tolerances within the various components of the electric propulsion system. The fluid dynamic bearing may include the same fluid, such as oil, that is used for lubrication and cooling throughout the electric propulsion system. As discussed herein, using a single fluid for the fluid dynamic bearing, cooling, and lubrication may provide the advantages of reducing mass and reducing the size of the various components.

[0185] Figure 50 A perspective view of an example rotor for a VTOL aircraft consistent with the disclosed embodiments is shown. In some embodiments, rotor 5000 may include rotor hub 5002. Rotor hub 5002 may include 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 the propeller assembly. Rotor 5000 may be machined from a single piece of material using various types of machines, such as a lathe, a computer numerical control ("CNC") machine, or any other type of machine capable of machining a rotor. Layers 5004 and 5012 may be present on rotor 5000 so as to be sacrificed later to balance rotor 5000. During rotor machining, rotor 5000 may become unbalanced due to manufacturing constraints, such as the precision of the machine. In some embodiments, balancing rotor 5000 may include adding or removing mass from the rotor.

[0186] In some embodiments, the manufacturing constraints of various regions of rotor 5000 may determine the mass of layers 5004 and 5012. For example, layers 5004 and 5012 may have a certain minimum or maximum mass determined by the manufacturing equipment and the steps involved in producing the rotor. Layers 5004 and 5012 may comprise a mass of rotor material sized to offset the manufacturing constraints present in each region of the rotor. In some embodiments, the mass of layers 5004 and 5012 to be removed later during rotor balancing may be determined based on the precision of the machines used to manufacture the various portions of the rotor. For example, in some embodiments, one or more machines may manufacture portions of the rotor with a precision of + / - 5% of a target mass for the portions of the rotor. In such an example, the rotor may comprise layers 5004 and 5012 whose total mass comprises sufficient mass to be removed during rotor balancing, where the mass falls within a composite deviation mass range due to the precision of the machines used to manufacture the rotor. In some embodiments, the material properties of layers 5004 and 5012 may comprise aluminum, steel, or another material that can accommodate the manufacturing precision of the machines used to manufacture the rotor portions. In some embodiments, the thickness or width and depth of layers 5004, 5012 can be thicker or thinner depending on design considerations, system needs, and manufacturing constraints. In some embodiments, the various layers can have substantially similar widths and depths, where substantially similar includes a layer having a width or depth that differs by less than 5% of the larger width or depth.

[0187] 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 circumference of the rotor hub 5002, such as Figure 50 As shown. In some embodiments, rotor 5000 can have multiple layers 5004, 5012 disposed adjacent to each other along the inner surface on opposite sides of the rotor, or any other configuration of layers 5004, 5012 along rotor hub 5002. In some embodiments, layers 5004, 5012 can be positioned along the inner surface of the rotor at a distance from the rotor edge. Some embodiments can include layers at substantially similar distances from the rotor edge. As used herein, substantially similar distances can include a distance variation of less than 5% of a larger distance.

[0188] In some embodiments, layers 5004, 5012 may include grooves 5006 that form portions 5008. In some embodiments, these 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 serve as a liquid flow path for oil or other liquids present within the electric motor assembly. For example, during normal operation, as described herein, oil or liquid may circulate throughout the electric motor assembly to help cool or lubricate components. Thus, grooves 5006 may be used to allow oil or liquid to pass through layers 5004, 5012 so that the oil or liquid does not accumulate within layers 5004, 5012 and return to a sump or other reservoir as described herein. In some embodiments, multiple layers 5004 may be aligned such that the grooves 5006 of each layer are aligned.

[0189] In some embodiments, the rotor 5000 may include through holes 5010. In some embodiments, the rotor 5000 may be machined with through holes 5010. One of ordinary skill in the art will appreciate that mass is a key factor in aircraft design, particularly in VTOL aircraft design. Mass can affect the efficiency, payload, and flight time of a VTOL aircraft. Thus, some embodiments of the rotor may include through holes 5010, which are created by a machining process, a laser machining process, or any other process that removes mass from the rotor. The through holes 5010 can reduce the mass of the rotor 5000 by removing portions of the rotor hub 5002 material (e.g., aluminum). In some embodiments, the through holes can also serve as connection points for the sun gear as described above.

[0190] In some embodiments, the electric motor assembly of a VTOL aircraft as described herein can generate torque by rotating the rotor 5000 at a high rotational rate. At high rotational speeds, an unbalanced rotor having an axis of rotation that is not aligned with the center of mass of the rotor will experience high levels of undesirable vibration and noise. An unbalanced rotor may be caused by production tolerances in the manufacturing process. For example, the magnets present in the rotor assembly may not have uniform mass and may not be evenly 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. Therefore, it should be recognized that a process for balancing the rotor may be advantageous. It is also recognized that mass can be a key 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 unwanted mass remaining on the rotor. In some embodiments, a process for balancing the rotor while achieving the maximum reduction in rotor mass may be used.

[0191] Some disclosed embodiments may include improved processes 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 and 5012. In some embodiments, layers 5004 and 5012 serve as sacrificial layers that can be machined integrally with the rotor so that they can 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 the rotor so that they can be later removed from rotor 5000 to achieve a balanced rotor. It should be appreciated that removable layers and portions added to the rotor after manufacture using fasteners, glue, or similar materials can serve similar purposes as sacrificial layers or portions. However, removable layers and portions require additional mass in the form of attachments, which is detrimental to the overall efficiency of the VTOL. Furthermore, attachments (e.g., fasteners and adhesives) used for removable layers and portions are at risk of failure during flight and may damage other components of the electric propulsion system.

[0192] Some embodiments of a process for balancing a rotor may include determining any imbalance in the rotor by rotating it about its axis of rotation. Determining the imbalance may include rotating the rotor and detecting the phase and corresponding magnitude of the imbalance. Some embodiments may include marking the rotor by laser etching, placing a reflective sticker on the rotor, or any other method that produces a unique marking on the rotor. In some embodiments, rotating the rotor may include rotating the rotor about the axis of rotation at a speed less than the operating speed using a machine, such as a dynamic balancer. The operating speed may include the expected rotation rate of the rotor during any phase of flight. In some embodiments, rotating the rotor may include rotating the rotor at a speed less than the rotor's first resonance. Detecting the phase of the imbalance may include using a machine to monitor the unique marking of the rotor while it is rotating. In some embodiments, the machine used to monitor rotor rotation may be the same machine that rotates the rotor. The machine is capable of tracking the unique marking and calculating its displacement during rotation, thereby indicating an unbalanced rotor. In some embodiments, detecting the phase of the imbalance may also include receiving a signal from an encoder or accelerometer during rotation, or downloading it after rotation, to identify the rotor's position or the forces experienced by the rotor at locations where the encoder, accelerometer, or similar sensor is positioned on the rotor.

[0193] Some embodiments of a process for balancing a rotor may include calculating the amount of mass to add or remove at locations along layers 5004, 5012 to correct for an imbalance present in the rotor. Some embodiments may include a machine or algorithm that analyzes the phase and corresponding magnitude of the imbalance to determine the amount of mass to add or remove and the location of the mass to be added or removed. In some embodiments, the machine that calculates the mass to be added or removed may include a machine that rotates the rotor, detects the imbalance, or may be a separate machine. In some embodiments, the mass added or removed at locations along layers 5004, 5012 may shift the rotor's center of mass so that it coincides with the rotor's axis of rotation. In some embodiments, the rotor may include multiple layers 5004, 5012 positioned along the rotor's inner surface at a distance from the rotor's edge. Thus, balancing the rotor may include balancing the rotor in one or more planes of the rotor by adding or removing mass along one or more layers.

[0194] In some embodiments, removing a certain amount of mass from layers 5004, 5012 may include machining away a portion of the volume of layers 5004, 5012. In some embodiments, removing a certain amount of mass from layers 5004, 5012 may include removing anywhere from 50% to 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 consist solely of sacrificial material for balancing the rotor. Layers 5004, 5012 may be integrally formed with the rotor to provide an integrated rotor balancing material that is removed rather than added. By removing sacrificial rotor material, the balancing process eliminates the need to use adhesives or fastening methods to add balancing weights.

[0195] In some embodiments, after removing material from layers 5004, 5012, the amount of layer mass remaining on the rotor can be the minimum amount of mass required to balance the rotor, and thus, a balanced rotor with minimal mass can be produced. Removing a majority of the volume of layers present on the rotor can allow the mass of the rotor to be reduced so that the rotor does not contain additional material. For example, if a rotor including layers 5004, 5012 is determined to be balanced without removing any portion of layers 5004, 5012, 100% of the volume including layers 5004, 5012 can be machined away because no mass from the layers is required to balance the rotor. In some embodiments, it can be determined that 3% of the volume of layer 5004 will be required to balance the rotor. In such an example, 100% of layer 5012 can be removed and 97% of layer 5004 can be removed to balance the rotor.

[0196] Some embodiments may include utilizing specialized machinery to remove the volume of layers 5004, 5012 when balancing the rotor. Some embodiments may include utilizing machinery capable of machining the volume of layers 5004, 5012 with an accuracy of 0.01% to 0.1% of the volume of the layer. In some embodiments, the machinery may be capable of machining the volume of the layer with a resolution of less than 5 microns, such as a lathe or CNC machine. In such embodiments, utilizing machinery capable of such accuracy can provide the advantage of balancing the rotor with minimal mass. Some embodiments may include utilizing various types of machinery when removing the layer, such as using a less accurate method to remove a significant portion of the mass to be removed than a method to remove the remaining mass to be removed.

[0197] Some embodiments may include calculating an amount of mass to add to balance the rotor at a location along the layers 5004, 5012, and balancing the rotor may include machining away a volume of the layers 5004, 5012 such that the only amount of layer mass remaining is a portion of the layers 5004, 5012 equal to the calculated amount of mass to be added and present at the calculated location. In some embodiments, calculating an amount of mass to remove to balance the rotor at a location along the layers 5004, 5012 may include machining away a volume of the layers 5004, 5012 such that the only amount of layer mass remaining is a portion of the layers 5004, 5012 equal to the calculated amount of mass to be removed and present at a location on the side of the layers opposite the calculated location.

[0198] In some embodiments, calculating the amount of mass to be removed may include calculating the number of sacrificial portions 5008 to be removed. In some embodiments, portion 5008 may be defined by groove 5006. Some embodiments may include removing all or any portion of portion 5008. In some embodiments, removing portion 5008 may include calculating the maximum number of portions to be removed to achieve a balanced rotor. In some embodiments, the number k of portions to be removed may include a number of portions such that if any additional mass were to be removed from the rotor after removing k portions, the rotor would likely never be balanced.

[0199] Figure 51 A flow chart illustrating an example process for balancing a rotor of a VTOL aircraft 5100 consistent with the disclosed embodiments is shown. Although the block diagrams may be described below in conjunction with certain embodiments presented in other figures, these embodiments are provided for illustrative purposes only and are not intended to serve as limitations on the block diagrams.

[0200] Figure 51Process blocks 5102 through 5108 are included. At block 5102, consistent with discussions throughout this disclosure, a process for balancing a rotor of an electric engine of an electric propulsion system may include identifying a rotational axis of the rotor, wherein the rotor includes a sacrificial layer having a mass M formed along a circumference of the rotor.

[0201] At block 5104 , consistent with discussions throughout this disclosure, a process for balancing a rotor of an electric engine of an electric propulsion system may include determining an imbalance present in the rotor by rotating the rotor about an axis of rotation.

[0202] At block 5106 , consistent with discussions throughout this disclosure, a process for balancing a rotor 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 so that the center of mass of the rotor coincides with the axis of rotation of the rotor.

[0203] At block 5108 , consistent with discussions throughout this disclosure, a process for balancing a rotor of an electric engine of an electric propulsion system may include removing an amount of mass r from a sacrificial layer such that an amount of mass n remains along the circumference of the rotor.

[0204] As discussed herein, a rotor assembly of an electric motor assembly may include a rotor mechanically coupled to a sun gear. Similar to the discussion above regarding balanced rotors, balancing the rotor assembly to avoid unwanted vibration and noise during normal operation may be advantageous. Due to manufacturing tolerances and due to the multiple mating parts throughout the rotor assembly, the rotor assembly may be unbalanced.

[0205] 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 an operating speed. In some embodiments, the rotor assembly may be coupled to a machine 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 an imbalance present in the rotor assembly may include using a machine to identify the phase and magnitude of the imbalance by tracking a unique marking on the rotor assembly (e.g., a reflective sticker or a laser-etched marking), or using an electric eye, an encoder, an accelerometer, or the like to track the motion of the rotor assembly.

[0206] Some embodiments may include calculating the amount of mass to be added 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 corresponding location may be accomplished using a machine or algorithm that analyzes the phase and magnitude of the imbalance in various planes of the rotor assembly to determine the amount and location of the mass to be added to the rotor assembly. In some embodiments, the mass to be added may take the form of a rivet. The rivet may include a mass that can be removably attached or permanently fixed 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 fixing or removably attaching the rivet to the rotor via the through-hole to balance the rotor assembly. In some embodiments, the amount of mass to be added may include rivets with different material properties and locations.

[0207] Figure 52 Another flow chart illustrates an example process for balancing a rotor assembly of a VTOL aircraft 5200. Although the block diagrams may be described below in conjunction with certain embodiments presented in other figures, these embodiments are provided for illustrative purposes only and are not intended to serve as limitations on the block diagrams.

[0208] like Figure 52 As shown, the process may begin at block 5202 by identifying an axis of rotation of a rotor, consistent with discussions throughout this disclosure, wherein the rotor includes a sacrificial layer having a mass M formed along a circumference of the rotor.

[0209] At block 5204 , consistent with discussions throughout this disclosure, a process for balancing a rotor assembly may proceed to determine an imbalance present in the rotor by rotating the rotor about an axis of rotation.

[0210] At block 5206, consistent with discussions throughout this disclosure, a 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 so that the center of mass of the rotor coincides with the axis of rotation of the rotor.

[0211] At block 5208 , consistent with discussions throughout this disclosure, a process for balancing the rotor assembly may proceed to include removing an amount of mass r from the sacrificial layer such that an amount of mass n remains along the circumference of the rotor.

[0212] At block 5210 , consistent with discussions throughout this disclosure, a process for balancing a rotor assembly may proceed to identifying an axis of rotation of the rotor assembly, wherein the rotor assembly includes a rotor mechanically coupled to a sun gear.

[0213] At block 5212 , consistent with discussions throughout this disclosure, a process for balancing a rotor assembly may proceed to determine an imbalance present in the rotor assembly by rotating the rotor about an axis of rotation.

[0214] At block 5214 , consistent with discussions throughout this disclosure, the process for balancing the rotor assembly may proceed to calculating a number j of rivets to be added to the rotor assembly so that the center of mass of the rotor assembly coincides with the axis of rotation of the rotor assembly.

[0215] At block 5216 , consistent with discussions throughout this disclosure, a process for balancing a rotor assembly of an electric engine of an electric propulsion system may include adding j rivets to the rotor assembly.

[0216] Embodiments of the disclosed electric propulsion system may include a gearbox assembly, as described herein. The gearbox can facilitate gear reduction in the electric propulsion system. As described herein, some embodiments of the electric propulsion system may include a gearbox assembly positioned between the electric motor assembly and the bell housing assembly. The gearbox assembly may include a main shaft assembly.

[0217] Figure 1717 is an exploded view of a main shaft assembly for a VTOL aircraft consistent with the disclosed embodiments. Main shaft assembly 1700 may include a main shaft 1702, a carrier cover 1714, planetary gears 1704, a pump drive gear 1716, and a planetary carrier 1712. Main shaft assembly 1700 may include a compound planetary gear system such that planetary gears 1704 are mechanically coupled to planetary gears 1706. In some embodiments, shafts 1708 and 1710 may extend from planetary gears 1704. In some embodiments, shafts 1708 and 1710 may extend from first planetary gears 1704 and second planetary gears 1706, respectively. Planetary gears 1704 may engage with a sun gear and a ring gear. In some embodiments, the ring gear may be fixed. In such embodiments, planetary gears 1704, engaged with the ring gear and the sun gear, may rotate about the sun gear. In some embodiments, planetary gears 1706 may engage with the ring gear. In such an embodiment, planet gears 1704 can be engaged with a sun gear, while planet gears 1706 are engaged with a fixed annular gear, wherein the sun gear drives planet gears 1704 and 1706 to rotate about the sun gear. Planet carrier 1712 can be mechanically coupled to planet gears 1704 and 1706 via shaft 1710 or the like, such that when the planet gears, and therefore the corresponding shaft 1710, rotate about the circumference of the sun gear, planet carrier 1712 rotates at the same speed. Planet carrier 1712 can be mechanically coupled to a plurality of planet gears 1704 and 1706. In some embodiments, a carrier cover can be mechanically coupled to planet gears 1704 and 1706 via shaft 1708 or the like, such that when the planet gears, and therefore the corresponding shaft 1708, rotate about the circumference of the sun gear, carrier cover 1714 rotates at the same speed.

[0218] In some embodiments, main shaft assembly 1700 may include a planet carrier 1712 having bearings 1722 to facilitate receiving shaft 1710 by planet carrier 1712. Bearings 1722 may allow shaft 1710 to rotate with planet gears 1704, 1706 while allowing the shaft to be contained within planet carrier 1712. In some embodiments, carrier cover 1714 may have bearings 1718 to facilitate receiving shaft 1708 by carrier cover 1714 so that shaft 1708 can rotate with planet gears 1704, 1706 while allowing shaft 1708 to be contained within carrier cover 1714. In some embodiments, spacers 1720, 1724 may be positioned between planet gears 1704, 1706 and carrier cover 1714 and planet carrier 1712, respectively. The shims 1720, 1724 may be designed to account for machine tolerances in the manufacture of components of the overall gearbox assembly, or to provide a surface for the planet gears 1704, 1706 to rotate against without damaging the planet carrier 1712 or carrier cover 1714. Some embodiments may include mechanically coupling the planet carrier 1712 and carrier cover 1714 using screws 1728 or similar components.

[0219] In some embodiments, carrier cap 1712 can be mechanically coupled to main shaft 1702. In such embodiments, the main shaft will rotate at the same speed as the carrier cap, and therefore at the same speed as planet gears 1704 or compound planet gears 1704 and 1706. In some embodiments, planet carrier 1712 can be mechanically coupled to main shaft 1702. In such embodiments, the main shaft will rotate at the same speed as planet carrier 1712, and therefore at the same speed as planet gears 1704 or compound planet gears 1704 and 1706.

[0220] In some embodiments, main shaft assembly 1700 may include a pump drive gear 1716. The pump drive gear may be positioned between planet carrier 1712 and carrier cover 1716. Furthermore, in some embodiments, pump drive gear 1716 may be positioned between multiple planetary gears, including compound planetary gears 1704 and 1706. Pump drive gear 1716 may be mechanically coupled to various components within the gearbox assembly, including planet carrier 1712, planetary gears 1704 and 1706, or carrier cover 1714. Pump drive gear 1716 may engage with other components within the power engine assembly (not shown here) to circulate oil or other coolant fluid throughout the fluid flow path, as described herein, to cool or lubricate the components within the power engine assembly. For example, pump drive gear 1716 may engage with a pump gear used to pump fluid from a reservoir to a heat exchanger. In such embodiments, the rotational speed of pump drive gear 1716 may determine the rate at which the oil or other fluid circulates throughout the power engine assembly. In some embodiments, the pump drive gear 1716 can 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 can include a dowel pin 1726 or similar alignment feature for aligning the pump drive gear with various components of the main shaft assembly 1700, including the planet carrier 1712 or the carrier cover 1714.

[0221] As described herein, the electric motor assembly can drive the rotation of the rotor. The rotation of the rotor, which can be mechanically coupled to the sun gear, can cause the sun gear to rotate at the rotor speed. The sun gear, rotating at the rotor speed, can engage with planetary gears 1704 or compound planetary gears 1704 and 1706 to generate an output from the gearbox assembly, comprising a new torque value to be supplied to the propeller assembly. In some embodiments, as described herein, a gear reduction can be generated using a combination of a sun gear, planetary gears including compound planetary gears, and a ring gear. Those skilled in the art will appreciate that gear ratios can be calculated based on the gears present in the gearbox assembly. Thus, the characteristics of the gears within the gearbox assembly can determine the gear reduction available in the electric propulsion system. In some embodiments, the gear reduction value can be a relevant design criterion for VTOL aircraft, as the aircraft may require a specific torque value to be 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 will result in an increase in the drag profile and mass of the electric engine. Therefore, the embodiments described herein can provide an optimized electric propulsion system design in terms of drag profile, mass, and payload capacity.

[0222] As described herein, embodiments of a gearbox assembly may include a sun gear. Figure 18 FIG2 is an illustration of an example sun gear for a VTOL aircraft consistent with the disclosed embodiments. Sun gear 1800 can be constructed of stainless steel, plastic, or any material capable of facilitating gear reduction. Sun gear 1800 may include teeth 1802 to facilitate gear reduction. Some embodiments may include splined teeth. In some embodiments, gear teeth 1802 may interact with planetary gears. Sun gear 1800 may include a hollow center. In some embodiments, components of a gearbox may pass through the hollow portion of sun gear 1800. Sun gear 1800 may also include through-holes 1804 to facilitate securing sun gear 1800 to other components of an electric engine. In some embodiments, sun gear 1800 may be mechanically coupled to other components of an electric engine assembly, such as a rotor or output shaft of an electric motor assembly. Some embodiments may include through-holes 1804 to allow for such mechanical coupling. In some embodiments, sun gear 1800 may be fixed and therefore may 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 rotation of the sun gear 1800 .

[0223] Embodiments of the gearbox may include a ring gear. Figure 19is an illustration of an example ring gear for a VTOL aircraft consistent with the disclosed embodiments. Ring gear 1900 may include teeth 1902. Teeth 1902 may engage with one or more planet gears to facilitate gear reduction. Ring gear 1900 may be fixed or free-rotating. A fixed ring gear may remain stationary, allowing the planet gears to rotate about the sun gear. In some embodiments, the ring gear may be fixed by coupling it to various components or structures within the electric propulsion system using through-holes 1904. In other embodiments, the free-rotating ring gear may rotate about fixed planet gears or a fixed sun gear. Ring gear 1900 may include slots 1902 to facilitate fastening or mechanical coupling.

[0224] As described herein, embodiments of a gearbox assembly may include a planet carrier assembly. Figure 20 2 is an illustration of an example carrier assembly for a VTOL aircraft consistent with the disclosed embodiments. In some embodiments, carrier assembly 2000 may include planet carrier 2008, first planetary gears 2006, pump drive gears 2012, second planetary gears 2004, and carrier cover 2010. In some embodiments, planet carrier 2008, first planetary gears 2006, pump drive gears 2012, second planetary gears 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, thereby forming a set of compound planetary gears. For example, first planetary gears 2006 and second planetary gears 2004 may share shaft 2014 and be coaxial along central axis 2018. Carrier assembly 2000 may include shaft 2002. Shafts 2000 may be coaxial along central axis 2016. In some embodiments, the planet carrier 2008, first planetary gears 2006, pump drive gear 2012, second planetary gears 2004, carrier cap 2010, and shaft 2002 can be mechanically coupled such that all components rotate at the same rate. In some embodiments, shaft 2002 can be mechanically coupled to a propeller assembly such that the shaft transmits torque or mechanical shaft power to the propeller assembly. In some embodiments, carrier assembly 2000 can include cavities, ports, or holes to facilitate the distribution of a coolant, such as oil.

[0225] In some embodiments, the electric engine may include an inverter assembly. The inverter assembly may include circuitry configured to receive a direct current input, convert the direct current into alternating current, and provide the alternating current to a stator ring of the electric motor.

[0226] As disclosed herein, embodiments of an electric power engine assembly may include a thermal management system or cooling system that circulates a coolant or lubricant throughout the engine. The lubricant or coolant, such as oil, may reside in a reservoir and be distributed to components throughout the electric power engine assembly. As disclosed herein, the oil may travel from the reservoir to a heat exchanger to various locations in the electric power engine assembly, including an inverter assembly, a gearbox assembly, and an electric motor assembly. As described herein, the electric motor assembly may include a bell-shaped end cap assembly. In some embodiments, the bell-shaped end cap assembly may be adjacent to the inverter assembly.

[0227] Figures 21A-21B is an illustration of an example bell-shaped end cap assembly for a VTOL aircraft consistent with the disclosed embodiments. Figure 21AAn internal view of a bell-shaped end cap plate of a bell-shaped end cap assembly is shown. The bell-shaped end cap plate 2100A may include a plate 2102A made of aluminum, steel, or another type of thermally conductive material. The bell-shaped end cap plate 2100A may include a pump rotor 2104A and a channel rotor 2106A. The channel rotor 2106A may be sized so that the pump rotor 2104A can rotate within the channel rotor 2106A, with multiple areas surrounding the pump rotor 2104A being open when the pump rotor 2014A rotates within 2106A. The pump rotor 2104A may be positioned within the channel rotor 2106A. The pump rotor 2104A may be mechanically coupled to another component of the electric engine assembly (e.g., a pump gear 2114B) and driven to rotate by the other component. In some embodiments, the pump rotor 2104A and the channel rotor 2106A may correspond to an internal gear oil pump (gerotor) or a positive displacement pump having an inner rotor and an outer rotor. Pump rotor 2104A can circulate oil from a sump through pump inlet 2116B. In some embodiments, pump rotor 2104A can rotate within channel rotor 2106A to draw oil from the pump inlet through the open area between pump rotor 2104A and channel rotor 2106A. In some embodiments, the rotation of pump rotor 2104A within channel rotor 2106A can create a vacuum between pump inlet 2116B and the sump containing any liquid. Pump outlet 2118A enables this. For example, the pump can create a vacuum to draw oil from the sump into pump inlet 2116B. In some embodiments, as described herein, a pressure differential can exist between pump outlet 2118A and various distribution points in the cooling system, allowing oil or other liquid to be drawn from the opening between pump rotor 2104A and channel rotor 2106A into pump outlet 2118A and through the cooling system. In some embodiments, bell-shaped end cap plate 2100A can include additional or different components, such as an electric pump or other mechanical configuration, to draw oil or other liquid through pump inlet 2116B. After entering through the pump rotor 2104A and the channel rotor 2016A, the oil or liquid can travel in direction 2120A and can travel from the pump outlet 2118A into the heat exchanger. In some embodiments, the heat exchanger can be mounted to the thermal plate 2100A or a separator plate as discussed herein.

[0228] In some embodiments, the heat exchanger can cool oil or other fluid used to lubricate or cool the inverter assembly, gearbox assembly, and / or electric motor assembly. In some embodiments, a portion of the cooling oil or fluid exiting the heat exchanger can be directed to the inverter assembly to cool these 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 cooling oil or fluid between the inverter assembly, the gearbox assembly, and the electric motor assembly. For example, the inverter assembly may receive 40% of the cooling oil by volume, and the motor-gearbox housing may receive 60%. This ratio can vary based on design considerations and the requirements of a particular implementation. In practice, different types of electric propulsion systems, as described herein, can utilize different fluid distribution percentages. Furthermore, it should be understood that the tilter electric propulsion system and the lifter electric propulsion system can have similar or different distributions of oil from the heat exchanger. The pump corresponding to pump rotor 2104A and pump gear 2114B can provide performance improvements for the gearbox assembly. Furthermore, using a pump to drive the oil delivery not only to the gearbox assembly and the electric motor assembly, but also to the inverter assembly, can eliminate the need for additional components for delivering coolant to the inverter assembly. This advantage can reduce mass and improve the drag profile of the electric propulsion system.

[0229] Cooling oil can enter channel 2108A from the heat exchanger and travel to annulus 2110A in direction 2114A. Annulus 2110 can be aligned along an axis, as described herein. Annulus 2110A can include port 2116A. Oil from channel 2108A can travel to various components of the electric engine through port 2116A, including traveling to the gearbox assembly and motor assembly to provide cooling and lubrication. Oil can also travel from annulus 2110A to channel 2112A. Bell-shaped end cap plate 2100A can also include port 2122A, which allows oil or other liquids to be transferred through bell-shaped end cap assembly 2100B. In some embodiments, a pump can generate pressure that can drive liquid to move through bell-shaped end cap plate 2100A. For example, pressure from a pump (which may be a gerotor or positive displacement pump) may propel oil through passages 2108A, 2112A, annulus 2110A, port 2116A, or other grooves or cavities in the bell-end plate, which may aid in the delivery of liquid.

[0230] Figure 21BA view of an example bell cap assembly is shown. Bell cap assembly 2100B may include bell cap plate 2100. Furthermore, the bell cap assembly may include gears that may be driven by or interact with additional gears in a gearbox assembly, as described herein. In some embodiments, ring gear 2104B may be coupled to bell cap plate 2102B assembly. Ring gear 2106B may include teeth that may engage with additional gears. The teeth of ring gear 2106B may engage with planetary gears of a main shaft assembly, as described herein. In some embodiments, the teeth of a pump drive gear may engage with the teeth of a pump gear 2114B, such that rotation of the pump drive gear drives rotation of pump gear 2114B. Pump gear 2114B may be mechanically coupled to pump rotor 2104A, such that rotation of pump gear 2114B drives rotation of pump rotor 2104A. Thus, pump gear 2114B may drive the delivery of lubricant or coolant throughout the bell cap assembly. In some embodiments, the pump gear 2114B may drive lubricant or coolant from a sump.The bell end cap 2102B may include a port 2118B for draining oil from the hot plate via port 2122A.

[0231] In some embodiments, bell cap assembly 2100B may include a bell cap plate 2102B for sealing against an electric motor assembly housing or a motor-gearbox assembly housing. In some embodiments, bell cap assembly 2100B may include a first circular wall extending away from bell cap plate 2102B. In some embodiments, ring gear 2106B may be coupled to first circular wall 2104B such that ring gear 2106B does not rotate freely, as described herein. In some embodiments, bell cap assembly 2100B may include a second circular wall 2108B extending away from bell cap plate 2102B. In some embodiments, second circular wall 2108B may have a diameter smaller than that of first circular wall 2104B. Second circular wall 2108B may house a bearing 2110B. In some embodiments, bearing 2110B may be mechanically coupled to a shaft, including a main shaft, that can transmit mechanical shaft power to the propeller assembly. In some embodiments, bearing 2110B may include grooves to facilitate the transfer of oil or other fluids. The second circular wall 2108B may also include an annulus containing a port hole 2112B. The port hole 2112B may be aligned with the port 2116A to receive oil or liquid from the heat exchanger. The port hole 2112B may include a supply of oil or other liquid to cool or lubricate components of the electric motor assembly and the gearbox assembly.

[0232] In some embodiments, port hole 2112B can deliver oil or other liquid to the main shaft. In some embodiments, the outer surface of the main shaft can be used as a liquid flow path, wherein the oil or other liquid flows on the main shaft and can be distributed to components within the gearbox assembly and / or electric motor assembly.

[0233] Embodiments of the disclosed inverter assembly may include an inverter assembly having a heat exchanger. Figure 22 is an illustration of an example inverter assembly for a VTOL aircraft consistent with the disclosed embodiments. In some embodiments, the inverter assembly 2200 may include an inverter assembly housing 2202 coupled to a thermal plate 2204. The inverter assembly housing 2202 may be used to house inverter assembly components as discussed herein. The inverter assembly housing 2202, and therefore the inverter assembly 2200, may have a substantially circular profile. As used herein, a profile may be substantially circular having a length of a minor axis of the circular shape and a length of a major axis of the circular shape, wherein the length of the minor axis is at least 80% of the length of the major axis.

[0234] 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 within 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 escape from inverter assembly 2200, regardless of the orientation of the power 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 to or mounted on heat plate 2204. In some embodiments, heat exchanger 2206 may be an integrated heat exchanger. In some embodiments, heat plate 2204 may be welded to heat exchanger 2206. For example, heat plate 2204 may be constructed of aluminum. Assembly of heat plate 2204 and heat exchanger 2206 may include brazing, quenching, aging, and welding. In some embodiments, the thermal plate 2204 and the heat exchanger 2206 can be made of the same material.

[0235] Figure 56A is a diagram showing a cross-sectional view of a press-fit mesh port operating in an inclined position after installation consistent with the disclosed embodiments. In some embodiments, an inverter housing (e.g., Figure 23 The housing 2302 shown) can be configured to have multiple exhaust and / or vents, e.g. Figure 23 The exhaust / vent 2208 is shown. Figure 56AAs shown, each drain and / or vent 5600 may include a press-fit mesh drain and vent port 5602. Each port 5602 may include a mesh 5604 and a press-fit latch 5606 on the mesh 5604. The press-fit latch 5606 may be configured to be pressed into the inverter housing 5608 from the inside ( Figure 56A ) and maintains an angle between 0° and 90°. In some embodiments, this angle can take into account manufacturing difficulties. In some embodiments, the mesh 5604 material can be aluminum, copper, titanium, stainless steel (as used in sintered metal type meshes) or any mesh material with a thermal expansion coefficient (CTE) that matches the material of the housing 2302 (e.g., aluminum). In some embodiments, the drains and / or vents 5600 are positioned along the circumference of the inverter housing 5608 so that the inverter housing 5608 can be discharged through at least one of the multiple drains and / or vents 5600 regardless of the orientation of the inverter housing 5608.

[0236] In some embodiments, the inverter housing 5608 can have a lifter position and a tilter position relative to Figures 32A-32D Corresponding to the scenes described separately.

[0237] In some embodiments, the size of port 5602 can be adjusted according to application needs. Figure 56B is a diagram showing a cross-sectional view of a press-fit mesh port operating in an inclined position after installation consistent with the disclosed embodiments. Figure 56B As shown, for example, the hole size may be approximately 3 mm, and the tilt angle relative to the direction of gravity after installation may be 10° to 25° or up to 35°.

[0238] Some embodiments may include an inverter assembly in which the components of the inverter are adjacent to each other and may share a common housing. In some embodiments, the components of the inverter assembly may be placed on top of each other in a stacked orientation. In some embodiments, the components of the inverter assembly may be substantially aligned along a central axis. The inverter assembly may include various components for sensing, circuitry, and control. Figure 232 is an illustration of an exploded view of an inverter assembly for a VTOL aircraft consistent with the disclosed embodiments. 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 inverter assembly 2300 may be mechanically coupled via various fastening means. For example, the components of inverter assembly 2300, including inverter assembly housing 2302, may be fastened to one another via fasteners 2318. Furthermore, inverter assembly 2300 may include inverter assembly housing 2302, which may be coupled to 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. The inverter assembly housing 2302 may contain connections for power and current used by the components of the inverter assembly 2300, such as a high voltage connector 2322 and a low voltage connector 2320. In some embodiments, the inverter assembly housing 2302 may contain inverter bus bars for high current and low inductance.

[0239] In some embodiments, inverter assembly housing 2302 may be cylindrical, or may have a torus shape (ie, a circular overall shape with a central hole in plan view).The form factor of inverter assembly housing 2302 may provide low drag during flight.

[0240] In some embodiments, the capacitor assembly and at least one PCBA (e.g., 2312, 2314, 2316) can all be stacked and positioned inside the inverter housing 2302. In some embodiments, each component of the stack (e.g., PCBA 2316, board spacer assembly 2314, gate drive PCBA 2312, capacitor assembly 2310, housing gasket 2308, thermal plate assembly 2304) can have multiple through-holes to allow fasteners 2318 to pass through to secure the stack. In some embodiments, fasteners 2318 can be long screws, bolts, or rods.

[0241] In some embodiments, a set of alignment pins 2326 can facilitate alignment 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) in inverter assembly 2310. In some embodiments, alignment pins 2326 can be integrated with the housing of capacitor assembly 2310. Alternatively, in some embodiments, alignment pins 2326 can be a separate component from the assembly. In some embodiments, alignment pins 2326 can be overmolded as a feature of the housing of capacitor assembly 2310.

[0242] In some embodiments, the thermal plate assembly 2304 can have a set of sockets for the alignment pins 2326. The number of sockets can match the number of alignment pins 2326.

[0243] Figure 60A is an illustration of a capacitor housing showing alignment pins according to an example embodiment. Figure 60B is an illustration of a heat plate and heat exchanger consistent with the disclosed embodiments, showing engagement alignment pins. In this example embodiment, two alignment pins 6002A and 6002B may be overmolded as features on a housing 6000A of a capacitor assembly (e.g., 2310). Figure 23 2304), the two sockets 6004A and 6004B can have different shapes. The first socket 6004A can have a circular shape, which is configured to provide a friction fit with the first alignment pin 6002A. The second socket 6004B can have an elongated shape (e.g., an oblong, a slot, etc.) to accommodate dimensional tolerances. The long axis of the elongated shape can be in a radial direction.

[0244] In some example embodiments, alignment pins 6002A and 6002B may extend in two directions on both sides of capacitor housing 6000A. During assembly, the capacitor assembly (e.g., Figure 23 2310) can be obtained by a housing gasket (e.g., Figure 23 2308) and power PCBA (e.g. Figure 23 2324) is positioned on the hot plate 6000B (e.g., Figure 23 The bottom side of the first alignment pin 6002A engages the first socket 6004A, and the bottom side of the second alignment pin 6002B engages the second socket 6004B. These two pairs can be provided together to align a capacitor assembly (e.g., Figure 23 2310) and hot plate 6000B (e.g., Figure 23 Then, the top sides of the alignment pins 6002A and 6002B are aligned with the remaining components of the inverter assembly (e.g., Figure 2323. The thermal plate assembly 2304 (PCBA 2316, board spacer assembly 2314, gate drive PCBA 2312, capacitor assembly 2310, housing gasket 2308, and thermal plate assembly 2304) provides a reference. Each of these components can have a through alignment hole for alignment pins 6002A and 6002B to pass through. For tolerance reasons, these holes can have a clearance fit or be arranged similarly to the sockets on thermal plate 6000B. After all components are stacked, fasteners 2318 can be used to fasten the components together. In some embodiments, sockets 6006 can receive fasteners 2318. Depending on the type of fastener 2318, sockets 6006 can be threaded or have an interference fit or extrusion ribs.

[0245] Now refer to it again Figure 23 In some embodiments, the stacking orientation in the housing can conform to various design shapes (e.g., 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 the design target shape. In some embodiments, the stacking orientation can be achieved by using common structural components that pass through the stack (e.g., designing a stack of different levels), so that common structures (e.g., various bolts of the same length) can pass through each level to form the stacking orientation.

[0246] In some embodiments, using a stacked orientation may create additional obstacles to additional design considerations, such as heat transfer, where the difficulty of managing proper distribution of coolant in such a configuration may increase. Additionally, the use of long bolts to travel through the various levels of the inverter may increase the shock and vibration experienced by the inverter assembly. However, it will also be understood that such a stacked orientation may be advantageous given various design considerations. For example, allowing a stacked orientation may be beneficial from an aerodynamic perspective, where stacking allows the inverter or inverters to be combined with other engine components (such as a gearbox and / or motor) to maintain a low drag profile. Additionally, the stacked orientation may be advantageous from a manufacturability perspective, where fewer components are involved in securing the inverter assembly, and from a mass reduction perspective, where fewer components and potentially less mass are used to secure the components.

[0247] In some embodiments, capacitor assembly 2310 can include at least one capacitor in a capacitor housing having at least one busbar on the exterior. Capacitor assembly 2310 can include a central hole and multiple through-holes in the capacitor housing. Capacitor assembly 2310 can include at least one PCBA positioned within the capacitor housing.

[0248] As disclosed herein, an inverter assembly may include a power PCBA. In some embodiments, the power PCBA may include a power board. Figure 24is an illustration of an example printed circuit board assembly for a VTOL aircraft consistent with the disclosed embodiments. Power board 2400 may also include a sensor assembly. Possible sensors may include, by way of example, sensors for current shunts, motor temperature, and MOSFET module temperature. Furthermore, some embodiments may include various power modules 2402 electrically coupled to power board 2400. As discussed herein, power modules 2402 may generate heat during use and require cooling to ensure proper functionality and efficiency of the overall electric propulsion system.

[0249] Figure 57 is an illustration of 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 can be one of the at least one PCBA of the inverter assembly 2300.

[0250] In some embodiments, the power board 5702 may have sensors integrated thereon. In some embodiments, the power board 5702 may have a rotor position sensor integrated thereon. In some embodiments, the rotor position sensor may be at least two Hall sensors 5704 ( Figure 57 (Only one is shown in the figure). In some embodiments, the propeller assembly's gearbox can have magnets on its planetary carrier. Power board 5702 and gearbox 5706 are placed close together so that at least two Hall sensors 5704 can sense the position of the magnets to determine the propeller's position. In some embodiments, the heating plate 2304 of inverter assembly 2300 and the bell-shaped end cap plate of gearbox 5706 are made of a material that does not block magnetic fields, so that at least two Hall sensors 5704 can sense the position of the magnets.

[0251] In some embodiments, the power board 5702 can have an oil temperature sensor (not shown) integrated therein. In some embodiments, the oil temperature sensor can be positioned to sense the temperature of a cooling fluid (e.g., oil, water, or other fluid or fluid mixture known to have a large heat capacity). In some embodiments, the cooling fluid can be a cooling fluid used to cool MOSFETs, power modules, or other components that generate heat.

[0252] In some embodiments, the power board 5702 may have a secondary speed sensor (not shown) that is connected to a control board of the electric propulsion system (not shown) to provide redundancy.

[0253] Figure 58is an illustration of a perspective view of a flexible PCBA connector consistent with disclosed embodiments. In some embodiments, PCBA 5800 can have a flexible PCBA structure 5802 to electrically connect to power components (not shown) outside the plane of the PCBA. In some embodiments, flexible PCBA 5802 can include contact pads 5804 having electrical contacts (not shown) thereon, and at least one serpentine connector 5806 formed by cutting through a layered printed circuit board (PCB). The electrical contacts can be electrically connected to electronic devices on the rest of the PCBA via at least one of the at least one serpentine connector 5806.

[0254] In some embodiments, each of serpentine connectors 5806 can have a flex factor. The flex factor is defined as the allowable displacement or deflection of the contact pad over the length of the flexible segment (i.e., serpentine connector 5806 and contact pad 5804). The flex factor can be defined for displacement in any direction (i.e., within the plane defined by the PCBA, perpendicular to the plane defined by the PCBA, or in any direction in between). In some embodiments, the flex factor serves as an indicator of the flexibility of flexible PCBA structure 5802 when contact pad 5804 deviates from the plane defined by the PCBA.

[0255] In some embodiments, the flexible PCBA structure 5802 can have more than one serpentine connector 5806 connected to the same contact pad 5804. In some embodiments, at least two of the serpentine connectors 5806 can have the same flex factor.

[0256] In some embodiments, the flex factor of the flexible PCBA structure 5802 can be less than 0.015 or approximately 0.005.

[0257] In some embodiments, contact pad 5804 may have a plurality of standoffs (not shown) thereon.

[0258] In some embodiments, a PCBA (eg, FR4) may include alternating substrate and copper layers.

[0259] In some embodiments, flexible PCBA structure 5802 can allow for electrical connection between the PCBA structure and another electrical contact outside the PCBA without requiring additional components (e.g., pin connectors, wire connectors, flexible circuits, or additional processes such as soldering or welding), thereby saving costs. In some embodiments, an electrical connection can be made by stacking and aligning a PCBA with flexible PCBA structure 5802 onto another structure with another electrical contact. In some embodiments, alignment of the PCBAs can be accomplished by inserting alignment pins 2326 through alignment holes in the PCBA. Because flexible PCBA structure 5802 allows contact pads 5804 to deviate from the plane, electrical connection can be made by pushing contact pads 5804 against another electrical contact. Alternatively, contact pads 5804 can include standoffs on their backsides to provide the necessary support, allowing electrical connection to be made by pushing another component onto the top of contact pads 5804. The electrical connection can be secured in place using conventional means, such as snap-fit, soldering, ultrasonic welding, electric welding, laser welding, or ultrasonic wire bonding. The deflection of the contact pad 5804 can provide a margin for tolerance stacking, making the electrical connection strong and robust.

[0260] In some embodiments, the serpentine connector 5806 may be partially cut away to allow the contact pad 5804 to deflect more. Figure 59 is consistent with the disclosed embodiments Figure 58 A cross-sectional view of a serpentine connector 5806 of a flexible PCBA is shown, showing a partial cutout. In this example embodiment, cutout 5902 is only in substrate layer 5904. Copper layer 5906 can remain intact. In some embodiments, the cutout direction is perpendicular to the instantaneous extension direction of the serpentine connector, meaning that cutout 5902 always cuts across the narrow width of the serpentine connector. Cutout 5902 can further increase the flexibility of the flexible PCBA structure, making it easier for contact pad 5804 to deflect. In other words, cutout 5902 can have the same effect as increasing the flex factor.

[0261] As described above, the electric engines and associated control components of a VTOL aircraft can generate heat during operation. For example, such components may include an inverter assembly, an electric motor assembly, and a gearbox assembly. The engine can accumulate heat generated by mechanical friction between components and by resistive heating within the motor-gearbox assembly. The accumulated heat can be carried to a heat exchanger by a lubricant circulating through one or more components of the engine. The heat must be dissipated to prevent degradation or damage to the motors, control components, and other elements of the VTOL aircraft. This heat can be managed by cooling the engine, including through direct or indirect cooling. In some embodiments, cooling can be assisted by a heat exchanger. The heat exchanger can be configured to receive a circulating heat exchange medium from the electric engine. For example, the heat exchange medium may include oil, and the oil can be used to lubricate and cool the components of the electric engine. The heat exchanger can connect one or more fluids to each other, thereby cooling a fluid at a higher temperature. The heat exchanger can advantageously be located next to the electric engine to minimize the volume (and weight) of material required to perform the cooling and lubrication functions. In some embodiments, the heat exchanger can be fluidically, thermally, and mechanically coupled to the inverter assembly so that the heat exchanger can share a common connection with the inverter assembly, thereby reducing the need for components such as cables, wires, tubes, and hoses, which can add weight and require more space in the electric engine. Heat in the inverter assembly, electric motor assembly, or gearbox assembly can be transferred to a cooling fluid, such as oil. The oil can absorb this heat and then be directed to a sump.

[0262] As described herein, an electric propulsion system may include a heat exchanger. Figures 25A-25C 2 is a diagram and example front view of a heat exchanger for a VTOL aircraft consistent with the disclosed embodiments. Heat exchanger 2504A can be mechanically coupled to a heat plate 2502A of an inverter assembly, as described herein and as shown in example view 2500A. Heat plate 2502A can include a fin array 2506A. Fin array 2506A can provide a heat sink to extract heat from components of the inverter assembly. As described herein, heat exchanger 2504A can be positioned to receive air flow from a propeller. A propeller (not shown) can direct air flow 2508A into heat exchanger 2504A, and exiting air 2510A can exit the heat exchanger. Air flow 2508A (which can be cooler air) can be forced into heat exchanger 2504A, for example, by washing down from propeller blades (not shown). Exiting air 2510A, which can be warmer air, can exit heat exchanger 2504A without entering other components of the electric propulsion system. In some embodiments, heat exchanger 2504A may include cooling fins.

[0263] Figure 25B-Figure 25CExample views of cooling fins 2500B and 2500C in a heat exchanger are shown, respectively. Oil or other lubricant or coolant that can absorb heat from an electric motor assembly, a gearbox assembly, or an inverter assembly can 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, the oil traveling through tubes 2504B can transfer heat to another fluid heat exchange medium. Fins 2502B can be configured to maximize the surface area of ​​heat exchanger 2504A, thereby increasing the surface area contact between tubes 2504B and the fluid. The increased surface area can increase the rate of heat transfer. The fluid may include air. For example, air flow 2508A may enter heat exchanger 2504A, come into thermal contact with fins 2502C, and receive heat from the oil traveling through tubes 2504C. The air may then exit the heat exchanger 2504A as exiting air 2510A. The heat exchanger 2504A may transfer heat via convection.

[0264] Figure 26 26 is an illustration of a heat exchanger for a VTOL aircraft consistent with the disclosed embodiments. Heat exchanger 2600 may include length 2602, height 2604, and depth 2606. As described herein, heat exchanger 2600 may include tubes and fins to facilitate heat transfer between fluids. Heat exchanger 2600 may include multiple cooling paths. Section 2608 illustrates examples of different cooling paths. A lubricant or coolant, such as oil, may travel through tubes 2610. Tubes 2610 may be thermally coupled to fins 2612, as described herein. Tubes 2610 may include hollow tubes for the fluid. Fins 2612 may increase the contact surface area between the air and tubes 2610, thereby increasing the rate of heat transfer from the oil in tubes 2610 to the air, as described herein. In some embodiments, heat exchanger 2600 may include multiple layers of fins 2612 stacked between and thermally coupled to tubes 2610. As a result, oil entering the heat exchanger 2600 may flow into different tubes 2610, thereby creating multiple cooling paths where heat may be transferred from the oil to the air.

[0265] As described herein, embodiments of electric engines may include circulating a lubricant or coolant throughout the engine. A heat exchanger may cool the lubricant or coolant that is directed to engine components, such as a motor, gearbox, or inverter. In some embodiments, heat from the inverter assembly may be conducted directly to a coolant or lubricant, such as oil.

[0266] Figures 27A-27B21 is an illustration of a front view of a separator plate for a VTOL aircraft consistent with the disclosed embodiments. In some embodiments, the separator plate may be comprised of a bell-shaped end cap plate and a thermal plate. The separator plate may include one or more plates sandwiched together and disposed between the motor-gearbox housing and the inverter assembly housing. Additionally, the separator plate may facilitate distribution of lubricant or coolant throughout the engine. In some embodiments, the separator plate may include channels, tubes, ports, cavities, or other features for conveying fluids. Bell-shaped end cap plate 2700 may include similar elements and discussion to the bell-shaped end cap plate of FIG. 21 . In some embodiments, bell-shaped end cap plate 2700A may be coupled to thermal plate 2700B. In some embodiments, bell-shaped end cap plate 2700A may abut a gasket plate, which may abut thermal plate 2700B. The inverter assembly may include thermal plate 2700B. Thermal plate 2700B may be mechanically, thermally, and fluidically coupled to heat exchanger 2710B. In some embodiments, bell-shaped end cap plate 2700A and heat plate 2700B can be positioned above the heat exchanger. The outer circumference of heat plate 2700B can be connected to heat exchanger 2710B. Bell-shaped end cap plate 2700A and heat plate 2700B can include channels to assist in distributing lubricants or coolants. Herein, channels can also refer to grooves, holes, or any other conduits configured to distribute oil or other coolants or lubricants in a planar direction. In some embodiments, the lubricant or coolant can be a liquid, such as oil, as described herein. The heat plate can be thermally and fluidically coupled to the heat exchanger via a liquid, such as oil. In some embodiments, the distribution of the lubricant or coolant can be driven by a pump. Heat plate 2700B can include grooves, holes, liquid flow paths, or any other conduits to assist the pump gear in delivering oil or other liquids from a reservoir. In some embodiments, oil can be delivered from the reservoir to inlet channel 2708A on bell-shaped end cap plate 2700A via channel rotors 2704A, 2704B and pump rotor 2706A. The oil in the inlet channel 2708A can be hot or warm oil traveling in the flow path 2716A. The oil in the inlet channel 2708A can travel to the heat exchanger inlet 2706B in the hot plate 2700B and enter the tube or other liquid flow path of the heat exchanger 2710B. As described herein, the oil circulating through the liquid flow path can be cooled in the heat exchanger 2710B, and the cooled oil can travel to the heat exchanger outlet 2708B in the hot plate 2700B. In some embodiments, the oil transported between the hot plate 2700B and the bell-shaped end cap plate 2700A can travel through the gasket plate. The cooled oil in the heat exchanger outlet 2708B can then travel along the flow path 2718A to the outlet channel 2710A, arriving at the annulus 2712A and channel 2714A of the bell-shaped end cap plate 2700A and the annulus 2712B on the hot plate 2700B.In some embodiments, the oil in the annulus 2712B can flow into the fin array 2714B in the hot plate 2700B to provide cooling and heat transfer. The oil from the fin array 2714B can then be returned to the sump via a port. Some embodiments may include an annulus 2712A that is substantially aligned along a main shaft or an axis shared with a gearbox assembly or an electric motor assembly. In some embodiments, oil or liquid can travel from the annulus 2712A through a port hole to the gearbox assembly or electric motor assembly, as described herein. In some embodiments, channel 2714A can be fluidly connected to an additional liquid flow path within the motor-gearbox housing that can be used to circulate oil or liquid to additional parts of the electric engine, such as a front bearing or a component located near the propeller assembly. In some embodiments, a bell-shaped end cap plate may include a seal in the electric engine. The bell-shaped end cap assembly may be included between the heat exchanger and the inverter assembly to prevent a face seal from leaking oil.

[0267] In some embodiments, a lubricant or coolant can be used to cool the inverter assembly using the thermal plate 2702B. Some embodiments may include hot oil or other liquid entering an inlet channel 2708A, which may be aligned with the heat exchanger inlet 2706B, to enter the heat exchanger 2710B. The cooling oil or other liquid exits the outlet channel 2710A, which is aligned with the heat exchanger outlet 2708B, and a portion or all of the cooling oil or liquid can follow a liquid flow path to the annulus 2712B of the thermal plate. The oil or other liquid in the annulus 2712B can be distributed to a heat sink, such as a fin array 2714B, located on the thermal plate 2702B, and cooling can be provided to the power modules, such as those located within the inverter assembly, by aligning the fin array 2714B with the power modules. Figure 24. It should be understood that the inverter assembly may have components that may perform poorly or inefficiently when exposed to oil or other liquids. Thus, the heat plate may include a heat sink for removing heat from the inverter assembly, and the oil or liquid can then be circulated within the heat plate rather than within the inverter assembly housing to transfer heat from these heat sinks to the oil or liquid to be cooled by the heat exchanger. The heat plate 2702B may include port holes 2716B so that the oil or liquid can pass through the port holes and enter the bell-shaped end cap assembly. In some embodiments, the port holes 2716B can allow the oil to return to the reservoir. In some embodiments, the port holes 2716B can be aligned with the port holes 2720A present on the plate 2702A of the bell-shaped end cap plate 2700A. In some embodiments, the oil from the port holes 2718B can enter the bell-shaped end cap assembly to circulate to the reservoir located in the motor-gearbox housing. In some embodiments, the oil can return to the reservoir along the direction of gravity, and the oil can be warm or hot. Cooling with oil can provide various advantages, including improving the overall performance of the inverter assembly. For example, using fluid to cool the power modules, such as Figure 24 The modules cited in the present invention can improve the performance of the inverter assembly. In addition, liquid convection can improve the durability of the inverter assembly compared to other cooling methods that involve additional components (e.g., air convection methods that require the addition of air cooling fins).

[0268] Disclosed embodiments of electric propulsion systems may include one or more components for distributing lubricants or coolants, as described herein. In some embodiments, lubricants or coolants, such as oil, may be circulated from a reservoir 1212A to a heat exchanger 1226A and then to an inverter assembly, a gearbox assembly, and a motor assembly (e.g., Figure 12A As shown). Figure 21AAs shown, the bell-shaped end cap assembly can contribute to the distribution and circulation of oil. As described herein, the oil traveling from the heat exchanger in passage 2108A can be distributed to annulus 2110A and port 2116A located in annulus 2110A. As described herein, the main shaft that can be substantially aligned with the annulus 2110A of the bell-shaped end cap assembly can extend from the bell-shaped end cap assembly through the gearbox assembly and through the electric motor assembly. In certain embodiments, the portion of the oil in the bell-shaped end cap assembly can be shared between annulus 2110A, port 2116A, port 2122A and various other ports and passages. Centrifugal force, centripetal force or pressure can drive the oil from the groove in annulus 2110A, port 2116A or bearing 2110B along the main shaft and toward the gearbox assembly and electric motor assembly. For example, the pressure in the bell-shaped end cap assembly 2100B can drive the oil to the groove or port hole 2112B in the bearing 2110B. Centrifugal force can then drive the oil along the main shaft to the windings of the stator in the motor assembly. For example, the rotation of the main shaft can apply centrifugal force that propels the oil along the main shaft. In some embodiments, the oil can travel from the bell end cap assembly through holes, pipes, channels, tubes, or ports to the gearbox assembly and the motor assembly. For example, the oil can flow in the annular area between the sun gear and the shaft. In some embodiments, the port can transfer the oil from the bell end cap assembly to a channel or similar structure present within the motor assembly housing to deliver the oil to additional portions of the gearbox assembly or the motor assembly. Some embodiments may include channels or similar structures configured to deliver oil to the propeller assembly, bearings mechanically coupled to the shaft flange, or stator windings within the motor assembly.

[0269] As described herein, by using a fluid, such as oil, to provide both lubrication and cooling, the amount of oil used in an electric propulsion system can be minimized. Furthermore, oil can be used to lubricate various bearings, such as rolling element bearings or hydrodynamic bearings, as described herein. Minimizing the amount of oil used in an electric propulsion system can 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 can keep the total amount of oil in the electric propulsion system below a threshold. For example, as described herein, an electric propulsion system can reduce the amount of oil required for operation by using a heat exchanger. Warm or hot oil already used for lubrication and cooling can reside in a sump, and by using a heat exchanger to cool this oil, the electric propulsion system can reuse it, eliminating the need for additional oil. Furthermore, as described herein, using a common liquid for cooling and lubrication can reduce component mass when compared to other cooling and lubrication methods that use various liquids. This configuration using various liquids may require additional mass and size for the electric propulsion system, such as additional heat exchangers, additional fluid distribution channels or pipes, and additional surface area for receiving cooling air from the propeller assembly.

[0270] In some embodiments, ventilation from the airflow can provide cooling for the lubricant within the heat exchanger. It should be understood that by using oil to both lubricate and cool the electric engine, rather than using another coolant, additional oil will be added to the system, but this additional oil will eliminate the need for traditional components that could be used to cool such an electric engine. For example, if the electric engine were cooled by another liquid, such as ethylene glycol, the engine might include separate heat exchangers for both the lubricant fluid and the coolant fluid. Thus, in embodiments using a single fluid (e.g., oil) for both lubrication and cooling, there would be an increase in oil, but only one heat exchanger would be required. Consequently, since fewer heat exchangers are used and additional components may not be required, the overall system mass can be reduced, and a more attractive drag profile may be achieved. Furthermore, using a single substance to lubricate and cool the engine can improve system efficiency due to the reduced mass and the benefits of using a substance to cool the engine rather than relying on air cooling, which can have issues traveling throughout the engine.

[0271] Some embodiments of the inverter may include an inverter having a coolant path that runs around the outer edge of the inverter but within the inverter housing, rather than utilizing a heat exchanger. For example, the coolant path may run around any printed circuit board assembly, power module, or other inverter components present in the inverter.

[0272] As disclosed herein, embodiments of a power engine may include an inverter assembly. In some embodiments, the inverter assembly may include a thermal plate. Figure 28is an illustration of a thermal plate for a VTOL aircraft consistent with the disclosed embodiments. Thermal plate 2802 can facilitate heat transfer from the inverter assembly, including distributing coolant to the inverter assembly. In some embodiments, thermal plate 2802 can abut a component of the inverter assembly, such as an inverter housing or a printed circuit board. Thermal plate 2802 can be thermally coupled to the inverter assembly. In some embodiments, thermal plate 2802 can abut a bell-shaped end cap assembly. In some embodiments, thermal plate 2802 can abut a gasket, which can abut the bell-shaped end cap assembly. The gasket can be a metal frame gasket. In some embodiments, thermal plate 2802 can abut a heat exchanger 2810. For example, thermal plate 2802 can be mounted on heat exchanger 2810, and coolant can flow through various paths within heat exchanger 2810. As an example, oil can be the coolant flowing through the various paths within heat exchanger 2810. Pump rotor 2804 can drive the oil through the cooling paths, also referred to herein as liquid flow paths, within heat exchanger 2810. In some embodiments, oil or other liquid from a sump can be pumped to a heat exchanger inlet 2806 by a pump rotor 2804. In some embodiments, a heat exchanger 2810 can receive the oil or other liquid from the heat exchanger inlet 2806, cool the oil or liquid, and the cooled oil or liquid can exit the heat exchanger at a heat exchanger outlet 2808. The cooled oil from the heat exchanger 2810 can be driven by pump 2804 to various channels within the heat plate. For example, the oil can be delivered to a distribution channel 2812. In some embodiments, the heat plate 2802 can include a heat sink to assist in heat transfer from the inverter components. As an example, the heat plate 2802 can include a fin array 2818. The fin array 2818 can include cooling fins extending from a base and can increase surface area to improve heat transfer. The fin array 2818 can be located within a cavity within the heat plate 2802. The fin array 2818 can be a heat sink and can be constructed from a material with high thermal conductivity. In some embodiments, the fins can be rectangular or circular in shape and can be constructed from aluminum. Fin array 2818 can extract heat from the thermally and mechanically coupled inverter components to cool components including the switching devices and MOSFETs. Fin array 2818 can be exposed to a flowing fluid. For example, cooling oil in distribution channel 2812 can enter fin array 2818 via channel 2814 and provide cooling and heat transfer to fin array 2818. The oil can then flow from fin array 2818 to collection channel 2816. In other embodiments, the oil can be transferred directly from distribution channel 2812 to collection channel 2816.

[0273] Figure 292 is a diagram of an electric propulsion system for a VTOL aircraft consistent with the disclosed embodiments. In some embodiments, a thermal plate 2900 can be thermally coupled to a motor assembly housing 2902. The thermal plate 2900 can also be fluidly coupled to the motor assembly housing 2902 via one or more coolant or lubricant flow paths. As described herein, the thermal plate 2900 can facilitate the distribution of a coolant or lubricant, such as oil. For example, oil in the thermal plate 2900 can 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 can include a pump rotor 2908, a distribution channel 2916, a fin array 2922, and a collection channel 2920. Cooling oil from the heat exchanger 2914 can enter the distribution channel 2916, flow through the fin array 2922 via a direction 2928, and enter the collection channel 2920 through a channel 2918. As described herein, fin array 2922 can act as a heat sink and help transfer heat from the inverter assembly to cooling oil 2928. In some embodiments, oil in thermal plate 2900 can be transferred to motor assembly housing 2902. For example, oil flow path 2930 can be an example flow path from thermal plate 2900 to motor assembly housing 2902. Oil flow path 2932 can be an example flow path for oil to various components within motor assembly housing 2902. Oil 2930 can also flow to second oil flow path 2934. Oil in various flow paths can flow to the gearbox assembly, electric motor assembly, or other components within motor assembly housing 2902 to provide cooling or lubrication, as described herein. Oil that has been distributed throughout motor assembly housing 2902 can accumulate in sump 2904. The oil can flow through the sump along liquid flow path 2924, then exit sump 2904 and flow back to thermal plate 2900 in return path 2926. Motor assembly 2902 can be mechanically coupled to shaft flange assembly 2906, as described herein. In some embodiments, the location of thermal plate 2900 and heat exchanger 2914 can provide advantages for electric propulsion system. For example, thermal plate 2900 is adjacent to heat exchanger 2914 and is liquid-coupled to heat exchanger 2914 and can eliminate the need for external connection. As discussed herein, oil can travel from heat exchanger 2914 to thermal plate 2900 and be distributed to components of electric propulsion system, such as inverter assembly, gearbox assembly and motor assembly that can be packaged together. This configuration including thermal plate that integrates several components can eliminate the need for external connection and can reduce the risk of leakage and separation of such external connection, for example.

[0274] Figure 30A-Figure 30Bis an illustration of an example electric propulsion system for a VTOL aircraft consistent with the disclosed embodiments. As described herein, electric propulsion system 3000A may include a heat exchanger 3008A mechanically, thermally, and fluidically coupled to a thermal plate 3006A. Thermal plate 3006A may be mechanically coupled to a motor housing 3002A including a fluid reservoir 3004A. Electric propulsion system 3000A may include an axle flange assembly 3010A. In some embodiments, electric propulsion system 3000A may include thermal plate 3006A and motor housing 3002A substantially aligned along axis 3012A. Figure 30B Another view of electric propulsion system 3000B is shown. Heat exchanger 3008B can be mechanically coupled to thermal plate 3006B. Thermal plate 3006B can be mechanically coupled to motor housing 3002B, which can include a sump 3004B. In some embodiments, electric propulsion system 3000B can include thermal plate 3006B and motor housing 3002B substantially aligned along axis 3012B.

[0275] Figure 31A-Figure 31B is a cross-sectional illustration of an electric propulsion system for a VTOL aircraft consistent with the disclosed embodiments. Figure 31A An example embodiment of a tilter electric propulsion system is shown. As disclosed herein, a 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, a heat exchanger 3118A may be thermally, fluidically, and mechanically coupled to the inverter assembly 3104A. An inverter housing 3116A may enclose the inverter assembly 3104A. The gearbox assembly 3106A may be adjacent to the inverter assembly 3104A and the electric motor assembly 3102A. A motor-gearbox assembly housing 3110A may enclose the electric motor assembly 3102A and the gearbox assembly 3106A. A 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 reservoir 3112A can be adjacent to the motor housing 3110A. In some embodiments, the main shaft 3108A extends from the bell-shaped end cap assembly of the sealed 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 can be substantially aligned along the main shaft 3108A. Furthermore, the inverter assembly 3104A can be substantially aligned along an axis that shares the axis of the main shaft 3108A.

[0276] As described above, the tilter can be provided with a variable pitch mechanism for changing the pitch of the propeller blades of the VTOL aircraft. In some embodiments, the variable pitch mechanism can be mounted to the rear of the electric engine assembly, such as the rear of the inverter assembly. In addition, the variable pitch mechanism can interact with the main shaft, as described herein, to change the pitch of the propeller blades. In such an embodiment, as discussed herein, the inverter assembly 3104A, the inverter assembly housing 3116A, and the separator can be provided with a package having a channel through the configuration and housing of the inverter assembly 3104A, the inverter assembly housing 3116A, and the separator to allow the variable pitch mechanism to engage with the main shaft or propeller blades. As discussed throughout, the lifter electric propulsion system may not change the direction of its thrust or the pitch of the blades. Therefore, in some embodiments, the separator may not have a channel such as that present in the tilter electric propulsion system. In addition, the inverter assembly and inverter assembly housing of the lifter electric propulsion system may not have such a channel, but it should be recognized that from a safety testing perspective and a manufacturability perspective, it is beneficial to have the inverter assembly and inverter assembly housing of the lifter electric propulsion system have a packaging that includes a channel similar to the packaging of the tilter electric propulsion system.

[0277] Figure 31B An example embodiment of a lifter electric propulsion system is shown. As disclosed herein, a lifter may refer to an electric propulsion system for lift. 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, fluidically, and mechanically coupled to inverter assembly 3104B. Inverter housing 3116B may enclose inverter assembly 3104A. Gearbox assembly 3106B may be adjacent to inverter assembly 3104B and electric motor assembly 3102B. Motor-gearbox housing 3110B may enclose electric motor assembly 3102B. In some embodiments, a main shaft 3108B extends from a bell-shaped end cap assembly enclosing motor-gearbox housing 3110B through gearbox assembly 3106B to electric motor assembly 3102B. As described herein, the gearbox assembly 3106B and the electric motor assembly 3102B can be substantially aligned along the main shaft 3108B. Additionally, the inverter assembly 3104B can be substantially aligned along an axis that shares the axis of the main shaft 3108B.

[0278] As discussed herein, it should be noted that having similar components between the tilter electric propulsion system and the lifter electric propulsion system is beneficial for the manufacturability of the entire aircraft. Furthermore, using similar components between the tilter electric propulsion system and the lifter electric propulsion system is beneficial in diagnosing problems and ensuring that safety requirements and protocols are met. However, in some embodiments, the lifter and tilter may have components that are not present in the other. For example, the lifter electric propulsion system 3100B may include a locking nut 3112B positioned between the main shaft 3108B and the shaft flange assembly 3120B, which is larger than the locking nut present in the tilter electric propulsion system 3100A. The locking nut 3122B can be used to ensure that the mechanical coupling of the main shaft 3108B and the shaft flange assembly 3120B is not damaged or broken due to the various vibration loads experienced throughout flight. For example, as discussed herein, some flight phases do not require the lifter electric propulsion system to be active, and in such cases, it may be necessary to stow the blades in some manner. However, if the lifter blades are not properly stowed, they may experience drag against the blades, and the mechanical coupling between the main shaft 3108B and the shaft flange assembly 3122B may experience tension. Furthermore, in some embodiments, a locking nut 3112B of the lifter electric propulsion system 3100B can offset operational loads. In some embodiments, for reasons similar to the presence of the locking nut 3122B, the lifter electric propulsion system may also include a propeller flange 3126A that is larger than the tilter shaft flange. Furthermore, the lifter electric propulsion system may also include a bearing 3124A for assisting in the rotation of the propeller flange 3126A. As described herein, the electric propulsion system can achieve different orientation angles during operation. Consequently, fluids in the electric propulsion system, such as coolant or lubricant, may move due to gravity. For example, lubricant or coolant, such as oil, may shift within the electric propulsion system during operation. The oil may reside in a reservoir, and the oil may shift within the reservoir and the electric propulsion system. Regardless of the orientation, some embodiments may require a certain amount of oil or other liquid to act as a coolant or lubricant in all flight phases. Therefore, the cooling system may be designed to allow circulation of oil regardless of the orientation of the aircraft.

[0279] Figures 32A-32D is a cross-sectional illustration of an electric propulsion system for a VTOL aircraft consistent with the disclosed embodiments. Figures 32A-32D Like reference numerals are provided and refer to similar elements of the electric propulsion systems 3200A, 3200B, 3200C, and 3200D. Accordingly, similar design considerations and configurations may be considered throughout the embodiments.

[0280] Figure 32AAn example embodiment of an electric propulsion system in an upright orientation is shown. By way of example, the upright orientation can be achieved during flight operations including, but not limited to, takeoff, landing, or hovering. 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 reservoir 3210A. A lubricant or coolant, such as oil 3212A, may be located in reservoir 3210A. In example orientation 3200A, oil may also be present in volume 3218A at oil level 3216A in reservoir 3210A and in volume 3218A. Oil 3212A may enter pump inlet 3214A and travel to heat exchanger 3208A. Oil 3212A may then be cooled in heat exchanger 3208A and distributed throughout the electric propulsion system, as described herein. In some embodiments, oil may be distributed along the main axis 3206A by centrifugal force.

[0281] Figure 32B An example embodiment of an electric propulsion system 3200B is shown in a first angled orientation (e.g., a hovering orientation at an angle 3222B). As an example, the electric propulsion system 3200B can be oriented along a central axis 3224B at an angle 3222B from a vertical axis 3226B. Figure 32B As shown, although electric propulsion system 3200B is in the angled orientation, pump inlet 3214B remains in contact with oil 3212B and below oil level 3216B to allow the oil to continue to circulate through the liquid flow path as described herein.

[0282] Figure 32C An example embodiment of an electric propulsion system 3200C is shown in a horizontal orientation. As an example, the electric propulsion system 3200C can be in a horizontal orientation during forward flight or a cruise configuration. Figure 32C As shown, during the horizontal orientation, pump inlet 3214C ​​remains in contact with oil 3212C and below oil level 3216C to allow the oil to continue circulating through the liquid flow path as described herein. Additionally, due to gravity, volume 3218C may not contain oil during the horizontal configuration.

[0283] Figure 32D An example embodiment of an electric propulsion system is shown in a second angled orientation (e.g., in a dive at angle 3222D). Figure 32DAs shown, during the dive orientation, pump inlet 3214D remains in contact with oil 3212D and below oil level 3216D to allow the oil to continue circulating through the liquid flow path as described herein. In addition, due to gravity, volume 3218D may not contain oil during the horizontal configuration. 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 the heat generated by the engine during operation. As disclosed herein, the electric engines may have different primary functions and therefore may not contain the same amounts of lubricant and coolant. For example, an engine for lift and landing may require less than a quart of oil, while an engine operating during all phases of flight may require more than a quart of oil. It should be understood that the example embodiments described herein are representative and do not dictate the amounts of lubricant and coolant that may be used in the electric engines.

[0284] It should be understood that by using oil to not only lubricate but also cool the electric engine, rather than using another coolant, this will add additional oil to the system, but this additional oil will eliminate traditional components that can be used to cool such an electric engine. For example, if the electric engine is cooled by another liquid such as ethylene glycol, the engine may include separate heat exchangers for both the lubricant fluid and the coolant fluid. In some embodiments, various liquids can be used to cool the electric engine. Some embodiments include an electric propulsion system that includes multiple heat exchangers that cool their respective liquids flowing in their respective liquid flow paths. In some embodiments, multiple cooling and / or lubricating liquids (such as ethylene glycol and oil) can have corresponding liquid flow paths that circulate through a common heat exchanger, which is also called a dual heat exchanger. In this configuration, the number of heat exchangers can be less than the number of liquid flow path types based on the type of liquid, and the entire propulsion system can save mass by not having multiple or more heat exchangers.

[0285] However, with respect to embodiments utilizing a single fluid (e.g., oil) for both lubrication and cooling, there will be an increase in oil, but only one heat exchanger will be required, so the overall system mass can be reduced and a more attractive drag profile may be achieved due to the use of fewer heat exchangers and the potential elimination of additional components. Furthermore, using a single substance to lubricate and cool the engine can improve the efficiency of the system due to the reduced mass and the benefits of cooling the engine through the substance rather than relying on air cooling, which may have issues traveling throughout the engine.

[0286] 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 features, such as fire barriers, to be placed near engines that use oil or other flammable materials in excess of a threshold amount. Such federal laws and regulations may be enforced by a government entity, such as the Federal Aviation Administration.

[0287] It should be noted that some electric propulsion system embodiments as described herein may not include fire barriers. As used herein, fire barriers may include engine components or aircraft components that are designed, constructed, or installed primarily to prevent hazardous amounts of air, fluid, or flames from bypassing or passing through the fire barrier and / or to prevent corrosion. In some embodiments, each electric propulsion system present on an aircraft may require a fire barrier. Thus, if an aircraft as described herein has, for example, twelve electric propulsion systems, twelve fire barriers may need to be installed on the aircraft. In some embodiments, fire barriers may be required on each wing, or around the fuselage, or in any other configuration based on federal law, regulations, or other safety requirements. Therefore, the presence of fire barriers may add additional mass to the aircraft, thereby reducing the efficiency of the electric propulsion system and further limiting the amount of payload (including passengers) that can be carried on the aircraft. This is particularly relevant for VTOL aircraft designs, in which a single aircraft may have, for example, twelve electric propulsion systems, and therefore any mass increase due to a single fire barrier may be twelvefold.

[0288] While some embodiments described herein do not include fire barriers, additional versions of all embodiments described and contemplated herein may include fire barriers. Additionally, each embodiment as described herein may be provided with fire barriers of various types and locations.

[0289] Figures 33A-33C is a schematic diagram illustrating an example electric propulsion system for a VTOL aircraft including a fire barrier consistent with the disclosed embodiments. Figure 33A An example electric propulsion system 3300A including a fire barrier 3308A consistent with the present disclosure is shown. Fire barrier 3308A may be positioned between an electric engine assembly 3302A mechanically coupled to a propeller assembly 3306A and a boom 3304A, with the primary purpose of preventing any fire or combustion that may occur in electric engine assembly 3302A from spreading to other areas of the aircraft.

[0290] Figure 33B An example VTOL aircraft 3300B consistent with the present disclosure is shown. The VTOL aircraft 3300B may include a fire barrier 3306B mounted or connected to a wing 3304B that is connected to a fuselage 3302B. Figure 33BAs shown, a fire barrier 3306B can be positioned between the electric propulsion system, including the electric engine 3308B and the propeller assembly 3310B, and the wing 3304B of the VTOL aircraft 3300B, with the primary purpose of preventing any fire or combustion. In some embodiments, the fire barrier 3306B can be positioned between the wing 3304B and the boom housing the electric propulsion system.

[0291] Figure 33C An example electric propulsion system 3300C consistent with the present disclosure is shown. Electric propulsion system 3300C may include an electric motor assembly 3302C (including a gearbox assembly in some embodiments) and an inverter assembly 3304C fluidly coupled to a heat exchanger 3306C. In some embodiments, electric motor assembly 3302C may be adjacent to inverter assembly 3304C. Some embodiments may also include an electric engine assembly housing 3308C. Electric engine assembly housing 3308C may include a fire barrier 3310C. In some embodiments, fire barrier 3310C may also be used to accommodate a rear portion of the electric engine assembly and, as shown in this figure, a rear portion of the inverter assembly.

[0292] In some embodiments, fire risk management in aircraft design may not be limited to the inclusion of fire barriers. Additional design considerations may address fire risks, such as the inclusion of additional components to ensure that the aircraft can remain in flight in the event of a fire. For example, an aircraft boom as described herein may feature additional components within the boom to ensure that the aircraft can remain in balanced flight if a fire occurs, a component is lost due to a fire, a component becomes detached due to a fire, or any other loss of function or component occurs.

[0293] C. Example Electric Propulsion System Configuration

[0294] As discussed above and throughout this disclosure, an example electric propulsion system may include components of various configurations, such as the representative configurations described herein, including an electric motor assembly, a gearbox assembly, and an inverter assembly. Example embodiments as discussed herein may include components of the electric propulsion system aligned along a common axis or substantially aligned along a common axis. In some embodiments, the components may be aligned along an axis or main shaft that provides mechanical shaft power to rotate the propeller of the propeller assembly. Some embodiments may include components of the electric propulsion system adjacent to each other in sequence along the axis or substantially aligned along the axis. In some embodiments, the position or positioning of one or more electric propulsion system components may provide a reduction in system mass and produce a more efficient drag profile. For example, one or more components may be substantially aligned along a common axis or adjacent to each other, and additional components (e.g., connecting wires) or additional housing volume for the wires may not be required. Therefore, the corresponding mass and volume typically required to allow for such connecting wires may not be required in the disclosed electric propulsion system.

[0295] In some embodiments, the electric propulsion system may also include a cooling system configured to target multiple heat-generating parts of the electric propulsion system. Some embodiments may include portions of the electric propulsion system being air-cooled by airflow generated by the propeller assembly or by airflow encountered during various phases of flight. Some embodiments may include portions of the electric propulsion system being cooled using one or more liquid flow paths that run through the electric propulsion system. Such embodiments may also include the liquid flow path circulating 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. It should be understood that the components of the electric propulsion system described herein can all be cooled using a common cooling system, can each have their own independent cooling system, or can combine cooling systems of various types and configurations. In some embodiments, the corresponding cooling system of the electric propulsion system can have an impact on the efficiency of the components of the electric propulsion system. For example, in some embodiments, liquid cooling can allow the inverter assembly to operate more efficiently than an inverter assembly utilizing an air cooling system.

[0296] Figures 34A-34D is a schematic diagram illustrating an example electric propulsion system for a VTOL aircraft consistent with the disclosed embodiments. Thus, similar design considerations and configurations can be considered throughout the embodiments.

[0297] Figure 34AAn example electric propulsion system 3400A consistent with the present disclosure is schematically depicted. Electric propulsion system 3400A may include components oriented along an axis extending along shaft 3406A, such as an inverter assembly 3404A, at least one power module 3410A, and an electric motor assembly 3402A. Embodiments may include an electric motor assembly 3402A that provides torque to a propeller assembly 3408A via shaft 3406A. In some embodiments, shaft 3406A may be mechanically coupled to a gearbox assembly (not shown in this example embodiment) to provide gear reduction and increased torque to propeller assembly 3408A. The housings of the components of electric propulsion system 3400A may share a common shape, such as a circular profile centered on shaft 3406A, a rectangular profile oriented along shaft 3406A, or a mixture of profiles. Electric propulsion system 3400A may further include an electric motor assembly 3402A located between and adjacent to inverter assembly 3404A and propeller assembly 3408A. In such an embodiment, shaft 3406A may pass through electric motor assembly 3402A. Some embodiments may include shaft 3406A also passing through inverter assembly 3404A. In some embodiments, power module 3410A may be axially oriented within inverter assembly 3404A so that any heat generated by the power module can escape via path 3412A into the environment outside inverter assembly 3404A. Some embodiments may also include orienting power module 3410A within inverter assembly 3404A so that air flow generated by propeller assembly 3408A or air encountered during flight can be used to cool the power module.

[0298] Figure 34B An example electric propulsion system 3400B consistent with the present disclosure is schematically depicted. The electric propulsion system 3400B may include components aligned along an axis extending along a main shaft 3406B, such as an inverter assembly 3404B, at least one power module 3410B, and an electric motor assembly 3402B. The electric propulsion system 3400B may further include an inverter assembly 3404B positioned between the electric motor assembly 3402B and the propeller assembly 3408B. In some embodiments, the power module 3410B may be positioned on a portion of the inverter assembly 3404B such that it is located below the propeller assembly 3408B and may generate heat that escapes to the environment outside the inverter assembly 3404B via a path 3412B. Some embodiments may include power modules oriented elsewhere in the inverter assembly so that any air flow generated by the propeller assembly 3408B may be used to cool the power modules.

[0299] Figure 34CAn example electric propulsion system 3400C consistent with the present disclosure is schematically depicted. Electric propulsion system 3400C may include components aligned along an axis extending along axis 3406C, such as an inverter assembly 3404C, at least one power module 3410C, and an electric motor assembly 3402C. Electric propulsion system 3400C may further include inverter assembly 3404C positioned between electric motor assembly 3402C and propeller assembly 3408C. In some embodiments, power module 3410C may be positioned on a portion of inverter assembly 3404C such that it is located on a surface of inverter assembly 3404C that is adjacent to electric motor assembly 3402C. In some embodiments, power module 3410C can be located within electric propulsion system 3400C, as shown by path 3412C, rather than within inverter assembly 3404C, where the heat generated by power module 3410C cannot be cooled using air cooling from propeller assembly 3408C or any airflow encountered during flight. In such embodiments, liquid cooling can be used to cool power module 3410C and other components located within inverter assembly 3404C. Additional embodiments may include a liquid cooling system that also thermally manages components of electric motor assembly 3402 and / or components of the gearbox assembly.

[0300] Figure 34D An example electric propulsion system 3400D consistent with the present disclosure is schematically depicted. Electric propulsion system 3400D may include components oriented along an axis extending along axis 3406D, such as an inverter assembly 3404D, at least one power module 3410D, and an electric motor assembly 3402D. Electric propulsion system 4100D may further include an electric motor assembly 3402D positioned between inverter assembly 3404D and propeller assembly 3408D. In some embodiments, power module 3410D may be positioned on a portion of inverter assembly 3404D such that it is located on a surface of inverter assembly 3404D that is adjacent to electric motor assembly 3402D. In some embodiments, power module 3410D can be located within electric propulsion system 3400D, as shown by path 3412D, rather than within inverter assembly 3404D, where the heat generated by power module 3410D cannot be cooled using air cooling from propeller assembly 3408D or any airflow encountered during flight. In such embodiments, liquid cooling can be used to cool power module 3410D and other components located within inverter assembly 3404D. Additional embodiments may include a liquid cooling system that also thermally manages components of electric motor assembly 3402 and / or components of the gearbox assembly.

[0301] 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 ethylene glycol, oil, or any other liquid capable of transferring heat from components of the electric propulsion system to the liquid. Furthermore, some embodiments may include cooling the electric propulsion system using a liquid that is also used to lubricate components of the electric propulsion system. In some embodiments, the electric propulsion system may include a chamber, reservoir, or tank for collecting and circulating the coolant liquid throughout the electric propulsion system.

[0302] Figure 35 35 is a schematic diagram illustrating an example electric propulsion system for a VTOL aircraft consistent with the disclosed embodiments. Electric propulsion system 3500 may include components aligned along axis 3506, such as electric motor assembly 3502, inverter assembly 3504, and tank 3514. Figure 35 As shown, electric motor assembly 3502 can be positioned between tank 3514 and inverter assembly 3504. Electric motor assembly 3502 can provide torque to propeller assembly 3508 via main shaft 3506, which can travel through inverter assembly 3504. In addition, electric motor assembly 3502 can provide torque to propeller assembly 3508 via gear reduction using a gearbox assembly (not shown in this example embodiment). Inverter assembly 3504 can include power connection channel 3518 connected to inverter assembly 3504. Inverter assembly 3504 can include power module 3510, which is positioned on a portion of inverter assembly 3504 opposite to the portion adjacent to electric motor assembly 3502. In addition, some embodiments can include power module 3510 positioned within inverter assembly 3504 so that any heat generated by power module 3510 can escape to the environment outside the inverter assembly via path 3512. Some embodiments may include various cooling methods for components of electric propulsion system 3500. For example, in some embodiments, power module 3510 may be positioned below propeller assembly 3508 so that air from propeller assembly 3508 cools power module 3510. Furthermore, reservoir 3514 may contain liquid for cooling or lubricating electric motor assembly 3502, gearbox assembly, and / or inverter assembly 3504. Some embodiments may include components of electric propulsion system 3500 with various housing profiles, such as a circular housing centered on axis 3506, a hybrid housing profile, and a housing profile that allows for an aerodynamic drag profile. Some embodiments may include component housings with cooling fins attached to the outer surface of the housing.

[0303] like Figure 35As shown, the reservoir 3514 may be provided with cooling fins 3516 on the reservoir 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.

[0304] In some embodiments, the electric propulsion system may include components that are not aligned or substantially aligned along an axis. For example, the electric propulsion system may include an electric motor assembly aligned along an axis 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 is not adjacent to the electric motor assembly, but is instead housed elsewhere within a boom, wing, or fuselage. In such embodiments, wiring may extend from the inverter assembly to the electric motor assembly to transmit alternating current from the inverter. Due to the required wiring and other connecting components, separating the locations of the components of the electric propulsion system may result in an increase in the mass of the aircraft.

[0305] Figure 36A-Figure 36B is a schematic diagram illustrating an example electric propulsion system for a VTOL aircraft consistent with the disclosed embodiments. Thus, similar design considerations and configurations may be considered throughout the embodiments.

[0306] Figure 36AAn example electric propulsion system 3600A consistent with the present disclosure is schematically depicted. The electric propulsion system 3600A may include components, such as an electric motor assembly 3602A, that are centrally aligned along an axis 3606A that provides torque to a propeller assembly 3608A. Embodiments of the electric propulsion system 3600A may also include a rectangular inverter assembly 3604A suspended behind the electric motor assembly 3602A. Additionally, some embodiments may include the inverter assembly 3604A having cooling fins 3610A oriented such that the cooling fins 3610A can utilize air flow from the propeller assembly 3608A to cool power modules, MOSFETs, or other components present in the inverter assembly 3604A. In some embodiments, the electric motor assembly 3602A may be housed in a housing having a variety of profiles, including circular, rectangular, or any other type of profile, depending on the design and needs of the system. Electric motor assembly 3602A can be located in a motor housing that also includes cooling fins to assist in cooling components of electric motor assembly 3602A, such as the stator, stator windings, or any other components of electric motor assembly 3602A. Although not shown in this figure, a gearbox assembly can be located between electric motor assembly 3602B and propeller assembly 3608B, between electric motor assembly 3602B and inverter assembly 3604B, within the housing containing electric motor assembly 3602B, or in any other configuration that allows for gear reduction. Additionally, although not shown in the figure, a gearbox assembly can be located within the motor housing and can also utilize cooling fins to assist in thermal management.

[0307] Figure 36B Schematically depicts the Figure 36A, and provides a forward view from propeller assembly 3608A. Electric propulsion system 3600B may include a circular electric motor assembly 3602B aligned along axis 3606B. Embodiments of electric propulsion system 3600B may also include a rectangular inverter assembly 3604B that may be located behind electric motor assembly 3602B. Inverter assembly 3604B may be adjacent to electric motor assembly 3602B or may be positioned within a boom, wing, or fuselage. Inverter assembly 3604B may be provided with cooling fins 3608B that extend beyond the outer diameter of electric motor assembly 3602B such that cooling fins 3608B are exposed to air flow from propeller assembly 3608A or air flow encountered during flight. Additionally, cooling fins 3608B may be used to extract and transfer heat generated by power modules, MOSFETs, or other components present in inverter assembly 3604A. Cooling fins 3608B can transfer heat to the environment outside the electric propulsion system. Similarly, the electric motor assembly 3602B can also be provided with 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 components.

[0308] In some embodiments, an electric propulsion system may include thermal management, also referred to herein as a cooling system, that includes liquid cooling. As disclosed herein, some example cooling systems may include distributing liquid coolant to components located throughout an electric motor assembly, a gearbox assembly, and an inverter assembly. However, it should be understood that a cooling system as disclosed herein may also include circulating liquid coolant around the periphery of the electric motor assembly, the gearbox assembly, and / or the inverter assembly. For example, the cooling system may include a cavity, jacket, or distribution channel of the cooling system that circulates liquid coolant around the periphery of components located within the electric propulsion system.

[0309] Figure 3737 is a schematic diagram illustrating an example electric propulsion system for a VTOL aircraft consistent with the disclosed embodiments. Electric propulsion system 3700 may include a motor assembly housing 3702 housing an electric motor assembly, adjacent to an inverter assembly housing 3708, with a shaft 3706 extending through motor assembly housing 3702. In some embodiments, motor assembly housing 3702 and inverter assembly housing 3708 may have various shapes or profiles, including, for example, circular housings centered along an axis coincident with shaft 3706, rectangular housings, or any other suitable geometric orientation. Some embodiments may include motor assembly housing 3702 housing a gearbox assembly in addition to the electric motor assembly. Embodiments may include a gearbox assembly positioned between the electric motor assembly and a propeller assembly external to motor assembly housing 3702, an electric motor assembly positioned between the gearbox assembly and the propeller assembly external to motor assembly housing 3702, a gearbox assembly located within motor assembly housing 3702 but not aligned along the axis of the electric motor assembly, or any other configuration of a gearbox assembly sharing a housing with the electric motor assembly. Some embodiments may include an inverter assembly housing 3708 having an inverter assembly 3704 as described herein. Furthermore, the inverter assembly housing 3708 may also include cooling fins 3710 located on the exterior surface of the inverter assembly housing 3708. These cooling fins utilize air currents encountered during flight to assist in cooling the components of the inverter assembly 3704. Some embodiments may also include inverter assembly 3704 utilizing 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, allowing liquid to circulate through the cavity 3714, jacket, or distribution channel to extract heat generated by 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 example liquid flow path for cooling components within the motor assembly housing 3702, where liquid may be moved from a first end of the motor assembly housing to a second end of the motor assembly housing via a distribution channel along the main shaft 3706. Liquid can be distributed radially from the shaft 3706 and can be collected via a collection chamber, sump, or similar component for recirculation throughout the motor assembly housing 3702. In some embodiments, the electric motor assembly housing 3702 can be fluidly connected to the inverter assembly housing 3708 such that liquid coolant can circulate throughout both assemblies via liquid flow paths 3712 and cavity 3714. In some embodiments, the motor assembly housing 3702 and the inverter assembly housing 3708 can utilize air cooling, liquid cooling, or a combination of both to thermally manage components located within each housing.

[0310] As discussed herein, electric propulsion systems may include various component configurations, such as components aligned along an axis, adjacent to one another, substantially aligned along an axis, or connected using wires or other connection methods. Thus, some embodiments may include components that share a housing. For example, as described above, a gearbox assembly may be housed within a motor assembly housing. Additionally, some embodiments may include housing a gearbox assembly, an inverter assembly, or other components, or components thereof, within a propeller assembly. This configuration may be driven by design constraints, such as weight, drag profile, lift, torque, payload, flight time, or any other design constraints associated with a VTOL aircraft.

[0311] Figures 38A-38B is a schematic diagram illustrating an example electric propulsion system for a VTOL aircraft and an example inverter assembly for the electric propulsion system consistent with the disclosed embodiments. Electric propulsion system 3800A may include a motor assembly housing 3802A aligned along a main axis 3806A. Some embodiments may include motor assembly housing 3802A containing an electric motor assembly centrally aligned along main axis 3806A. Some embodiments may include motor assembly housing 3802A housing the electric motor assembly and a gearbox assembly. Some embodiments of electric propulsion system 3800A may also include an inverter assembly 3804A mounted to a circular face of motor assembly housing 3802A, with a low voltage input 3808A located on the face of motor assembly housing 3802A. In some embodiments, inverter assembly 3804A, in addition to being mounted to motor assembly housing 3802A, may also be located within a propeller assembly. For example, an inverter assembly as described herein may be positioned within a rotor of a propeller assembly. This placement of inverter assembly 3704A may be advantageous when other components of electric propulsion system 3800A cannot justify producing a more compact drag profile. For example, a propeller assembly may be sized to meet additional design criteria, such as required torque or lift, and in such an embodiment, the propeller assembly may be sized with a void space to allow inverter assembly 3804A to be placed within the propeller assembly's hub.

[0312] Figure 38B An example inverter assembly 3800B, consistent with the discussion of inverter assembly 3804A and throughout this disclosure, is schematically depicted. The inverter assembly 3800B may include at least one power module 3802B, at least one gate driver 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. In addition, the inverter assembly 3800B may be provided with cooling fins 3812B located on an outer surface of the inverter assembly housing to assist in cooling the various components of the inverter assembly 3800B.

[0313] In some embodiments, an electric propulsion system may include components that reside within various component housings. As discussed herein, the various components of an electric propulsion system may reside within housings and may be organized in various ways within those housings. Some embodiments of an electric propulsion system may include various component configurations to achieve different design goals. Different embodiments may have different primary design components that must be achieved at the expense of other design criteria. For example, some embodiments may include redundant systems that may add additional mass to the aircraft but increase passenger safety by avoiding and / or removing single points of failure. In addition, 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 cooling systems and liquid cooling systems. For example, electric propulsion system components may have, for example, air-cooled designs in which components are mechanically coupled to cooling fins, and liquid-cooled designs in which components are fluidically coupled to a liquid flow path, and a heat exchanger that extracts heat from the liquid and transfers the heat to the outside air.

[0314] Figures 39A-39D is a schematic diagram illustrating an example electric propulsion system for a VTOL aircraft consistent with the disclosed embodiments. Electric propulsion system 3900A may include an inverter assembly 3904A, a gearbox assembly 3906A, and an electric motor assembly 3902A, as well as a main shaft 3908A connected to a flange shaft assembly 3912A. In some embodiments, electric motor assembly 3902A may be positioned between gearbox assembly 3906A and shaft flange assembly 3912A, with both gearbox assembly 3906A and electric motor assembly 3902A aligned along main shaft 3908A. Additionally, inverter assembly 3904A may be adjacent to 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 a common or separate cooling system. For example, motor-gearbox housing 3910A and / or inverter assembly 3904A may utilize air flow encountered during flight or generated by the propeller assembly to cool inverter assembly 3904A, gearbox assembly 3906A, and / or electric motor assembly 3902A.

[0315] Figure 39B Shown Figure 39A A perspective diagram of an example electric propulsion system. Figure 39B and Figure 39A3906A. In some embodiments, the electric propulsion system 3900B may include an electric motor assembly 3902A, and the 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 flange shaft assembly 3912B and may have cooling fins 3914B oriented around the circumference of the electric motor housing 3910B for cooling the electric motor assembly 3902A and the gearbox assembly 3906A using air flow from a propeller assembly (not shown) connected to the flange shaft assembly 3912B or air flow encountered during flight. Additionally, an inverter assembly 3904B may be mechanically coupled to the rear of the motor-gearbox housing 3910B and may also utilize air flow to cool components of the inverter assembly 3904B.

[0316] Figure 39C A schematic diagram of an example electric propulsion system 3900C consistent with embodiments of the present disclosure is provided. 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 an embodiment, a propeller assembly 3912C may be mechanically coupled to a first end of the motor-gearbox assembly 3910C. Some embodiments may include a shaft running through the electric motor assembly 3902C and / or the gearbox assembly 3906C to the propeller assembly 3912C. Figure 39C As shown, example embodiments may include an electric motor assembly 3902C positioned between a gearbox assembly 3906C and a propeller assembly 3912C. Additionally, some embodiments may include an inverter assembly 3904C adjacent a second end of the motor-gearbox assembly 3910C.

[0317] Figure 39D A schematic diagram of an example electric propulsion system consistent with an embodiment of the present disclosure is provided. The electric propulsion system 3900D may include Figure 39C However, electric propulsion system 3900D may include a gearbox assembly 3906D positioned between electric motor assembly 3902D and propeller assembly 3912D connected to a first end of a motor-gearbox housing 3910D, with inverter assembly 3904D adjacent a second end of motor-gearbox housing 3910D.

[0318] Figures 40A-40D is a cross-sectional diagram and illustration of an electric propulsion system for a VTOL aircraft consistent with the disclosed embodiments. Figure 40AA cross-sectional view of an example electric propulsion system 4000A is shown. The electric propulsion system 4000A may include an inverter assembly 4004A, a gearbox assembly 4006A, and an electric motor assembly 4002A, each 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 the inverter assembly housing 4014A. Additionally, the inverter assembly housing 4014A may be mounted to a rear portion 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 in the inverter assembly housing 4014A. Figure 40A In the example embodiment depicted in FIG, power connection channel 4018A can be connected to inverter assembly 4004A behind heat exchanger 4010A. Further for the described embodiment, heat exchanger 4010A can be mounted to motor-gearbox assembly housing 4012A and can be used in conjunction with a distribution channel (not shown) to assist in cooling electric motor assembly 4002A, gearbox assembly 4006A, and / or inverter assembly 4004A via coolant liquid circulated throughout electric propulsion system 4000A. It should be understood that although inverter assembly 4004A, gearbox assembly 4006A, and electric motor assembly 4002A are shown as being consistent with the stacked assembly inverter assembly, planetary gearbox, and electric motor consisting of a stator and rotor described in this figure, this figure is an example and the inverter assembly, gearbox assembly, and electric motor assembly can be of any type as described herein or capable of performing similar functions.

[0319] Figure 40B Shown Figure 40A A perspective view of an example electric propulsion system 4000B is shown 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 can be aligned along a main shaft 4020B connected to the shaft flange assembly 4008B. The motor-gearbox housing 4012B can have cooling fins 4022B oriented around the circumference of the motor-gearbox housing 4012B. Additionally, a heat exchanger 4010B can be mounted to the motor-gearbox housing 4012B and can liquid cool the electric motor assembly 4002A, the gearbox assembly 4006A, and / or the inverter assembly 4004A by cooling a liquid that circulates throughout the electric motor assembly 4002A, the gearbox assembly 4006A, and / or the inverter assembly 4004A to cool the respective components. It should be understood that while Figure 40BThe heat exchanger is depicted as having an inner circumference smaller than the outer circumference of the motor-gearbox housing, but the heat exchanger 4010B can span any distance that is equal to or smaller than the outer circumference of the motor-gearbox housing 4012B. Furthermore, the inverter assembly housing 4014B can be mechanically coupled to the rear of the motor-gearbox housing 4012B and can also be provided with cooling fins 4024B oriented around the circumference of the inverter assembly housing 4014B. Furthermore, the inverter assembly housing 4014B can be provided with connection points for power connection channels 4018B on the outer edge of the inverter assembly housing 4014B and at a location behind the heat exchanger 4010B.

[0320] Figure 40C A schematic diagram of an example electric propulsion system consistent with embodiments of the present disclosure is provided. 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. Furthermore, 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 fluid path 4016C. Some embodiments may include a fluid path 4016C that includes a fluid for cooling, lubricating, or both cooling and lubricating components fluidly coupled to the heat exchanger 4010C. In some embodiments, the heat exchanger 4010C may be mounted directly or indirectly to the motor-gearbox housing 4012C. Liquid path 4016C may include a distribution channel, a device for distributing liquid, or a cavity capable of conveying liquid, distributing the liquid to components fluidly coupled to heat exchanger 4010C, and recirculating the liquid to heat exchanger 4010C. The liquid present in liquid path 4016C can collect heat from the components fluidly coupled to heat exchanger 4010C and transfer the heat to intake air 4018C passing through heat exchanger 4010C. Thus, embodiments may include heat exchanger 4010C positioned so that intake air passing through or from propeller assembly 4008C during flight can pass through and cool the liquid passing through heat exchanger 4010C.

[0321] Figure 40D A schematic diagram of an example electric propulsion system consistent with an embodiment of the present disclosure is provided. The electric propulsion system 4000D may include Figure 40CComponents are arranged similarly to those shown and described. However, electric propulsion system 4000D may include a gearbox assembly 4006D located between electric motor assembly 4002D and propeller assembly 4008D, the propeller assembly being connected to a first end of a motor-gearbox housing 4012D, with inverter assembly 4004D housed within inverter assembly housing 4014D, the inverter assembly housing being connected to a second end of motor-gearbox housing 4012D. Electric propulsion system 4000D may also include gearbox assembly 4006D and electric motor assembly 4002D fluidly coupled to heat exchanger 4010D via fluid path 4016D, the heat exchanger being partially exposed to incoming air 4018D for lubricating and cooling gearbox assembly 4006D and electric motor assembly 4002D.

[0322] The liquid paths 4016C and 4016D are shown at a high level as simple loops. However, it should be understood that the liquid paths may include 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.

[0323] Figure 41 4 is a cross-sectional illustration of an electric propulsion system for a VTOL aircraft consistent with the disclosed embodiments. Electric propulsion system 4100 may include an inverter assembly 4104, a gearbox assembly 4106, and an electric motor assembly 4102, each aligned along a main shaft 4110 mechanically coupled to a shaft flange assembly 4112. Inverter assembly 4104, gearbox assembly 4106, and electric motor assembly 4102 may be located within a housing, such as an inverter assembly housing 4116 and a motor-gearbox assembly housing 4114, wherein inverter assembly housing 4116 is adjacent to motor-gearbox assembly housing 4114. Additionally, power connection channel 4118 may connect to a high-voltage connector in the inverter assembly located within inverter assembly housing 4116. Further to this embodiment, a heat exchanger 4108 can be mounted to the motor-gearbox assembly housing 4114 and can be used in conjunction with a distribution channel (not shown) to assist in liquid cooling of the electric motor assembly 4102, the gearbox assembly 4106, and / or the inverter assembly 4104 by cooling the liquid that circulates throughout the electric motor assembly 4102, the gearbox assembly 4106, and / or the inverter assembly 4104 to cool the respective components. Although in some embodiments the inverter assembly, the gearbox assembly, and the electric motor assembly are shown as being consistent with the stacked assembly inverter assembly, the planetary gearbox, and the electric motor consisting of a stator and a rotor described in this figure, this figure is an example, and the inverter assembly, the gearbox assembly, and the electric motor assembly can be of any type as described herein or capable of performing similar functions.

[0324] Figures 42A-42B 4 is an illustration of an example electric propulsion system for a VTOL aircraft consistent with the disclosed embodiments. Electric propulsion system 4200A may be cooled using liquid cooling. 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 housing 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 shaft flange assembly 4210A. Furthermore, an inverter assembly housing 4204A may abut the gearbox assembly housing 4206A and may also be mechanically connected to a 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. Furthermore, heat exchanger 4212A may be fluidically coupled to the electric motor assembly, gearbox assembly, and inverter assembly via a liquid flow path to provide liquid for cooling and lubricating components within the electric motor assembly, gearbox assembly, and inverter assembly. Some embodiments may include flow paths comprising channels, holes, and cavities capable of conveying liquid throughout the fluidly coupled components of the electric propulsion system 4200B.

[0325] Figure 42B Shown as Figure 42A A perspective view of an example electric propulsion system 4200B discussed herein using a heat exchanger 4212B for liquid cooling, the heat exchanger being fluidly coupled to an electric motor assembly, a gearbox assembly, and an 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 within a gearbox assembly housing 4206B, aligned along a main shaft 4208B mechanically coupled to a flange shaft assembly 4210B. Some embodiments may include a motor assembly housing 4202B and a gearbox assembly housing 4206B having substantially circular profiles with equal radii. The example electric propulsion system 4200B may also include an inverter assembly housed within an inverter assembly housing 4204B having a substantially circular profile, the inverter assembly housing being mechanically coupled to a power connection channel 4214B and the gearbox assembly housing 4206B. Some embodiments may include the inverter assembly housing 4204B having a radius that is greater than the radius of the gearbox assembly housing 4206B and / or the motor assembly housing 4202B.

[0326] Figures 43A-43Dis a diagram and schematic illustrating an example electric propulsion system for a VTOL aircraft consistent with the disclosed embodiments. Electric propulsion system 4300A may include a gearbox assembly 4306A, an electric motor assembly 4302A, and an inverter assembly 4304A, each aligned along a main shaft 4316A connected to a shaft flange assembly 4308A. Inverter assembly 4304A may be located within an inverter assembly housing 4312A. Additionally, gearbox assembly 4306A and electric motor assembly 4302A may be located within a motor-gearbox assembly housing 4310A. Some embodiments may include inverter assembly housing 4312A, and therefore inverter assembly 4303A, located between motor-gearbox assembly housing 4310A and shaft flange assembly 4308A. In this configuration, main shaft 4316A may pass through gearbox assembly 4306A, electric motor assembly 4302A, and inverter assembly 4304A. Additionally, a power connection channel 4314A may extend from a boom, wing, or fuselage of the aircraft through the motor-gearbox assembly housing 4313A to a connection point in the inverter assembly housing 4312A.

[0327] Figure 43B Shown as Figure 43A A perspective view of an example embodiment of the discussed air-cooled electric propulsion system 4300B. 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 have substantially circular profiles with substantially equal radii and be aligned along a main shaft 4316B connected to a flange shaft assembly 4308B. Some embodiments may include an inverter assembly housing 4312B located between the motor-gearbox assembly housing 4310B and the flange shaft assembly 4308B, wherein a power connection channel 4314B extends from a boom, wing, or fuselage of the aircraft through the motor-gearbox assembly housing 4310B to a connection point in the inverter assembly housing 4312B. Another embodiment may include a motor-gearbox housing 4310B and an inverter assembly housing 4312B, each of which has cooling fins 4320B and 4318B on the outer surface of each housing, respectively. The cooling fins 4320B and 4318B can transfer heat from the components housed within the motor-gearbox housing 4310B and the inverter assembly housing 4312B to the outside air passing through the cooling fins 4320B and 4318B.

[0328] Figure 43C A schematic diagram of an example electric propulsion system 4300C consistent with an embodiment of the present disclosure is provided. The electric propulsion system 4300C may include Figure 43A and Figure 43BComponents are arranged similarly to those shown and described. However, the electric propulsion system 4300C may include a gearbox assembly 4306C positioned between the electric motor assembly 4302C and the inverter assembly 4304C, which is connected to the flange shaft assembly 4308C. In this configuration, a main shaft 4316A (not shown in this illustration) can pass through the electric motor assembly 4302C, the gearbox assembly 4306C, and the inverter assembly 4304C. In addition, one or more power connection channels 4314C can extend from the boom of the aircraft through the motor-gearbox assembly housing 4310C to a connection point in the inverter assembly housing 4312C.

[0329] Figure 43D A schematic diagram of an example electric propulsion system 4300D consistent with an embodiment of the present disclosure is provided. The electric propulsion system 4300D may include Figures 43A-43C Similar components are arranged and labeled as those shown and described. Figure 43D Depicts the Figure 43C 4300D, wherein inverter assembly housing 4312D is connected to a power connection channel 4314D extending from the boom of the aircraft and abutting flange shaft assembly 4308D and motor assembly housing 4310D. However, motor assembly housing 4310D houses electric motor assembly 4302D, which provides torque to flange shaft assembly 4308D via a main shaft that travels through inverter assembly 4304D without gear reduction from a gearbox assembly.

[0330] Figures 44A-44Cis a schematic diagram illustrating an example electric propulsion system for a VTOL aircraft consistent with the disclosed embodiments. Example electric propulsion system 4400A may include an inverter assembly 4404A housed within an inverter assembly housing 4416A positioned between an axle flange assembly 4410A and a separator plate 4408A. In addition to inverter assembly housing 4416A, separator plate 4408A may also be coupled to a motor-gearbox housing 4414A housing an electric motor assembly 4402A and a gearbox assembly 4406A. In such a configuration, inverter assembly housing 4416A may include attachment points for a power connection channel 4420A extending from a boom, wing, or fuselage of the aircraft. Furthermore, such a configuration may include a main shaft mechanically coupled to axle flange assembly 4410A, the main shaft extending through inverter assembly housing 4416A and, in some embodiments, through inverter assembly 4404A and separator plate 4408A to reach electric motor assembly 4402A. Some embodiments may include a main shaft extending from a first end of a motor-gearbox assembly housing 4414A mechanically coupled to a separator plate 4408A to a second end of the housing, and thereby extending through or past 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 separator plate 4408A may be used to seal the upper portion of the motor-gearbox assembly housing 4414A via a bell-shaped end cap assembly and to seal the lower portion of the inverter assembly housing 4416A via a heat plate. The separator plate 4408A may include grooves, holes, or other conduits configured to distribute liquid to cool the inverter assembly 4404A and to cool and lubricate the gearbox assembly 4406A and the electric motor assembly 4402A. Liquid flow path 4418A may include circulating liquid to extract heat from components of inverter assembly 4404A, gearbox assembly 4406A, and electric motor assembly 4402A and transfer the heat to air flow 4422A across cooling fins of heat exchanger 4412A.

[0331] Figure 44B A schematic diagram of an example electric propulsion system 4400B consistent with an embodiment of the present disclosure is provided. The electric propulsion system 4400B may include Figure 44A Similar component arrangements to those shown and described. Figure 44B Depicts the Figure 44A4400B, wherein inverter assembly housing 4416A is connected to a power connection channel 4420A extending from a boom, wing, or fuselage of the aircraft and is positioned between flange shaft assembly 4410B and separator plate 4408B. However, separator plate 4408B may also be coupled to a motor-gearbox assembly housing 4414B, which houses a gearbox assembly 4406B, which is located rearward of electric motor assembly 4402B relative to separator plate 4408B. Some embodiments may include a liquid flow path 4418B that fluidly couples a heat exchanger to inverter assembly 4404B, gearbox assembly 4406B, and electric motor assembly 4402B. Additionally, liquid flow path 4418B may include circulating liquid to extract heat from components of inverter assembly 4404B, gearbox assembly 4406B, and electric motor assembly 4402B and transfer that heat to air flow 4422B across cooling fins of heat exchanger 4412B.

[0332] Figure 44C A schematic diagram of an example electric propulsion system 4400C consistent with embodiments of the present disclosure is provided. The electric propulsion system 4400C may include Figures 44A-44B Similar component arrangements to those shown and described. Figure 44C Depicts the Figure 44A Electric propulsion system 4400A and Figure 44B However, electric propulsion system 4400C includes a direct drive system as discussed herein, wherein motor assembly housing 4414C houses electric motor assembly 4402C, which provides torque to shaft flange assembly 4410C without gear reduction from a gearbox assembly.

[0333] Liquid flow paths 4418A, 4418B, and 4418C are shown at a high level of generalization as simple loops. In some embodiments, the liquid flow paths may include branches, sub-loops, or other segmented paths. Generally, 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 the inverter assembly housings 4416A-C.

[0334] Figures 45A-45D is a schematic diagram illustrating an example electric propulsion system for a VTOL aircraft consistent with the disclosed embodiments. The electric engine 4500A may include an electric motor assembly housed within a circular motor assembly housing 4510A, and an inverter assembly housed within an inverter assembly housing 4512A coupled to an outer surface of the motor assembly housing 4510A. Figure 45AInverter assembly housing 4512A is shown tangentially coupled to the outer surface of motor assembly housing 4510A, but in some embodiments, the base of inverter assembly housing 4512A can be coupled to the outer surface of motor assembly housing 4510A in any configuration, including a base of the inverter assembly housing having a radius of curvature similar to that of electric motor assembly housing 4510A. Furthermore, inverter assembly housing 4512A can include busbars 4516A that connect to motor assembly housing 4510A to supply AC power to the electric motor assembly. Inverter assembly housing 4512A can also include cooling fins mounted to a portion of inverter assembly housing 4512A opposite the coupled portion of inverter assembly housing 4512A. Cooling fins 4514A can be used to remove heat generated by components within the inverter assembly and transfer the heat to air flowing through cooling fins 4514A.

[0335] Figure 45B FIGURE 4500B illustrates a perspective view of an example embodiment of a power engine 4500B consistent with the present disclosure. The example power engine 4500B may include Figure 45A Similar components are arranged as those depicted and described in the drawings, and contain similar numerals for the components, such that similar numerical numerals correspond to Figure 45A and Figure 45B The example power engine 4500B may include an electric motor assembly housed within an electric motor assembly housing 4510B, the electric motor assembly housing being coupled to an inverter assembly housing 4512B housing an inverter assembly. In addition, the power engine 4500B may include a bus bar 4516B connected to the motor assembly housing 4510B to supply AC power to the electric motor assembly. Similar to Figure 45A The power engine 4500B may include an inverter assembly housing 4512B including cooling fins 4514B that can be used to remove heat generated by components within the inverter assembly and transfer the heat to the external air flow via the cooling fins 4514B. Additionally, the inverter assembly housing 4512B may include connection points for power connection channels 4518B originating from within the aircraft's boom, wing, or fuselage.

[0336] Figure 45C An example embodiment of a power engine 4500C consistent with the present disclosure is schematically depicted. The example power engine 4500C may include Figure 45A and Figure 45B Similar components are arranged as those depicted and described in the drawings, and contain similar numerals for the components, such that similar numerical numerals correspond to Figure 45A 、 Figure 45B and Figure 45CThe electric engine 4500C may include an electric motor 4502C and a gearbox assembly 4506C housed within a motor assembly housing 4510C, which is mechanically coupled to an inverter assembly housing 4512C housing an inverter assembly 4504C. Figure 45C As shown, some embodiments may be configured with a gearbox assembly 4506C located between the electric motor assembly 4502C and the propeller assembly 4508C. In some embodiments, a power connection channel 4518C may be connected to an inverter assembly housing 4512C originating from a boom, wing, or another location within the aircraft.

[0337] Figure 45D An example embodiment of a power engine 4500D consistent with the present disclosure is schematically depicted. The example power engine 4500D may include Figures 45A-45C Similar components are arranged as those depicted and described in the drawings, and contain similar numerals for the components, such that similar numerical numerals correspond to Figures 45A-45C Electric engine 4500D may include electric engine 4502D and gearbox assembly 4506D housed within motor assembly housing 4510D, coupled to inverter assembly housing 4512D housing inverter assembly 4504D. Some embodiments may include a configuration where electric motor assembly 4502D is located between gearbox assembly 4506D and propeller assembly 4508D. In some embodiments, power connection channel 4518D may connect to inverter assembly housing 4512D originating from a boom, wing, or another location within the aircraft.

[0338] Figures 46A-46B is a schematic diagram illustrating an example electric propulsion system for a VTOL aircraft consistent with the disclosed embodiments. Electric propulsion system 4600A may include an electric motor assembly 4602A and a gearbox assembly 4606A housed within a motor assembly housing 4612A, the motor assembly housing being coupled to an inverter assembly housing 4614A housing an inverter assembly 4604A. Some embodiments may include a gearbox assembly 4606A positioned between electric motor assembly 4602A and propeller assembly 4608A. Some embodiments may include a heat exchanger 4610A coupled to motor assembly housing 4612A and fluidly coupled to electric motor assembly 4602A and gearbox assembly 4606A via a liquid flow path 4616A. Liquid flow path 4616A may be used to extract heat from components present within electric motor assembly 4602A and propeller assembly 4608A. Liquid flow path 4616A may carry the extracted heat to heat exchanger 4610A, which transfers the heat to air flow 4618A across the cooling fins of heat exchanger 4610A.

[0339] Figure 46B An example embodiment of an electric propulsion system 4600B consistent with the present disclosure is schematically depicted. The example electric engine 4600B may include Figure 46A Similar components are arranged as those depicted and described in the drawings, and contain similar numerals for the components, such that similar numerical numerals correspond to Figure 46A and Figure 46B 46. ​​Similar components of the electric propulsion system 4600B. Electric propulsion system 4600B may include an electric motor assembly 4602B and a gearbox assembly 4606B housed within a motor assembly housing 4612B, the motor assembly housing being coupled to an inverter assembly housing 4614B housing an inverter assembly 4604B. Some embodiments may include electric motor assembly 4602B positioned between gearbox assembly 4606B and propeller assembly 4608B. Some embodiments may include a heat exchanger 4610B coupled to motor assembly housing 4612B and fluidly coupled to electric motor assembly 4602B and gearbox assembly 4606B via a liquid flow path 4616B. Liquid flow path 4616B may be used to extract heat from components present within electric motor assembly 4602B and propeller assembly 4608B. Liquid flow path 4616B may carry the extracted heat to heat exchanger 4610B, which transfers the heat to air flow 4618B across the cooling fins of heat exchanger 4610B.

[0340] Liquid paths 4616A and 4616B are shown at a high level as simple loops. In some embodiments, the liquid paths may include branches, sub-loops, or other segmented paths. Generally, the liquid may be circulated in any manner that effectively lubricates and cools the various components present within motor assembly housings 4612A and 4612B.

[0341] Figures 47A-47B is a schematic diagram illustrating an example electric propulsion system for a VTOL aircraft consistent with the disclosed embodiments. Electric propulsion system 4700A may include an electric motor assembly 4702A and a gearbox assembly 4706A located within a motor-gearbox housing 4710A. Figure 47AThe embodiment depicted in FIG4 may include a main shaft passing through or from electric motor assembly 4702A to propeller assembly 4708A located outside motor-gearbox housing 4710A. Furthermore, gearbox assembly 4706A may not share an axis with electric motor assembly 4702A or the main shaft used by electric motor assembly 4702A to provide torque to propeller assembly 4708A. In such an embodiment, gearbox assembly 4706A may still provide a gear reduction between electric motor assembly 4702A and propeller assembly 4708A. Some embodiments may also include an inverter assembly 4704A located in an inverter assembly housing 4712A, which is directly or indirectly mounted to motor-gearbox housing 4710A. While inverter assembly 4704A is shown mounted to the outer edge of motor-gearbox housing 4710A, in some embodiments, the inverter assembly may have a circular profile that surrounds or partially surrounds 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, the gearbox assembly 4706A, and the inverter assembly 4704A may each have various components that create various volumes for each assembly, and thus, the motor-gearbox housing 4710A and the inverter assembly housing 4712A may have various profiles and volumes based on their respective assembly configurations.

[0342] Figure 47B A cross-sectional view of the electric propulsion system 4700B is shown. Figure 47B Can be used with Figure 47A47. Although related, elements identified by similar numbers in the drawings may not refer to the same elements. Some embodiments of electric propulsion system 4700B may include an electric motor assembly 4702A and a gearbox assembly 4706A located in a common motor-gearbox housing 4702B, with a shaft 4712B traveling through electric motor assembly 4702A. Some embodiments may include a propeller assembly mechanically coupled to shaft 4712B. In some embodiments, electric motor assembly 4702A may include a stator 4704B having stator windings 4706B and a rotor 4710B having a magnet array 4708B aligned along shaft 4712B. In some embodiments, rotor 4710B may be directly or indirectly connected to a secondary shaft 4716B surrounding shaft 4712B such that secondary shaft 4716B rotates at a speed equal to the speed of rotor 4710B. Further to this example, an embodiment of secondary shaft 4716B can include a splined shaft that engages with gearbox assembly 4706A adjacent to electric motor assembly 4702A, wherein gearbox assembly 4706A also engages with shaft 4712B to provide torque to propeller assembly 4708A. As described herein, embodiments of gearbox assembly 4706A can include at least a first gear 4722B, a second gear 4720B, and a gearbox shaft 4718B connecting them. In some embodiments, the radius of first gear 4722B can be greater than the diameter of second gear 4720B, or vice versa. Thus, the splined portion of secondary shaft 4716B can interact with first gear 4722B and rotate it at the same speed as rotor 4710B. The rotating first gear 4722B can drive the rotation of gearbox shaft 4718B and second gear 4720B. Second gear 4720B of gearbox assembly 4706A can engage a portion of shaft 4714B having a radius that is different than the radius of the portion of shaft 4712B connected to propeller assembly 4708A. In such an embodiment, gearbox shaft 4718B of gearbox assembly 4706A can be positioned so as not to share an axis with shaft 4712B or electric motor assembly 4702A, yet still provide a gear reduction to shaft 4712B, thereby providing torque to propeller assembly 4708A.

[0343] Figure 484 is a schematic diagram illustrating an example electric propulsion system for a VTOL aircraft consistent with the disclosed embodiments. Electric propulsion system 4800 may include an electric engine housed within an electric engine housing 4802, the electric engine housing being aligned along an axis 4804 extending from the electric engine housing 4802 to a propeller assembly 4808 including a propeller 4810. In some embodiments, 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 electric engine housing 4802 coupled to a boom 4816 of the aircraft via a device 4814 for determining the position of the electric propulsion system. Some embodiments may also include a blade pitch actuator 4812 coupled to a rear portion of the electric engine housing 4802. Depending on the phase of flight the aircraft is engaged in, the components of the electric engine may generate varying amounts of heat. For example, components of an electric engine in a vertical take-off and landing aircraft may generate more heat during the hover phase of flight than during the cruise phase, and therefore, more air flow may be required through heat exchanger 4806 during the hover phase to cool the liquid used to cool and / or lubricate the components of the electric engine than during the cruise phase. Thus, some embodiments may include a boom 4816 that includes a cavity 4818 therein that may house heat exchanger 4806 during the cruise phase. Cavity 4818 may be used to block or reduce air flow into the heat exchanger during flight, as the amount of air required to cool the system decreases during various flight phases.

[0344] The embodiments may be further described using the following terms:

[0345] Clause Set A:

[0346] 1. An inverter assembly for converting direct current (DC) power into alternating current (AC) power for an electric propulsion system, the inverter assembly comprising: a housing; a capacitor assembly having a central hole, at least one capacitor, a capacitor housing having at least one busbar, and a plurality of through-holes in the capacitor housing; at least one printed circuit board assembly (PCBA); and a plurality of locating pins; wherein: the capacitor assembly and the at least one PCBA are positioned inside the housing, the plurality of through-holes are used to position the at least one PCBA, and the plurality of locating pins pass through the plurality of through-holes of the capacitor housing and the at least one PCBA and are connected to the housing.

[0347] 2. The inverter assembly of clause A1, wherein the central aperture is substantially aligned with a main axis of the electric propulsion system.

[0348] 3. The inverter assembly of clause A1 or A2, wherein the at least one PCBA and the capacitor assembly are stacked.

[0349] 4. The inverter assembly of any one of clauses A1 to A3, wherein the at least one PCBA comprises a gate drive PCBA and a power PCBA, wherein the capacitor assembly is positioned between the gate drive PCBA and the power PCBA.

[0350] 5. The inverter assembly of any one of clauses A1 to A4, wherein the central aperture of the capacitor assembly is a through-hole and the inverter assembly has a substantially toroidal shape.

[0351] 6. The inverter assembly of any of clauses A1 to A5, wherein the at least one busbar is positioned external to the capacitor housing.

[0352] 7. The inverter assembly of 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 wherein the heat exchanger is outside the housing.

[0353] 8. The inverter assembly of clause A7, wherein the heat exchanger is coupled to a thermal plate.

[0354] 9. The inverter assembly of clause A8, wherein each of the control board, the thermal plate, and the EMI shield includes a plurality of alignment holes to align with the locating pins.

[0355] 10. The inverter assembly of any of clauses A8 to A9, wherein the plurality of locating pins comprises rods built into the thermal plate.

[0356] 11. The inverter assembly of any of clauses A7 to A10, wherein the heat exchanger is configured to cool the inverter assembly using a fluid.

[0357] 12. The inverter assembly of clause A11, wherein the fluid is oil.

[0358] 13. The inverter assembly of any of clauses A1 to A12, wherein the at least one capacitor is a ring capacitor.

[0359] 14. An inverter assembly as described in any of clauses A1 to A9, wherein the plurality of locating pins are screws.

[0360] 15. The inverter assembly of any of clauses A1 to A9, wherein the plurality of locating pins are bolts.

[0361] 16. The inverter assembly of any one of clauses A1 to A9, wherein the plurality of locating pins are rods pre-fixed to the capacitor housing.

[0362] 17. An electric propulsion system for a vertical take-off and landing (VTOL) aircraft, the electric propulsion system comprising: an electric motor assembly, the electric motor assembly including at least a stator and a rotor; and an inverter assembly, the inverter assembly comprising: a housing; a capacitor assembly, the capacitor assembly having a central hole, at least one capacitor, a capacitor housing having at least one busbar, and a plurality of through-holes in the capacitor housing; at least one printed circuit board assembly (PCBA); and a plurality of locating pins; wherein the capacitor assembly and the at least one PCBA are positioned inside the housing, the plurality of through-holes are used to position the at least one PCBA, and the plurality of locating pins pass through the plurality of through-holes of the capacitor housing and the at least one PCBA and are connected to the housing.

[0363] 18. The electric propulsion system of clause A17, wherein: the electric motor assembly is positioned in a motor housing; and the motor housing and the housing of the inverter assembly are substantially aligned along a main axis.

[0364] 19. The electric propulsion system of clause A18, wherein the main shaft passes through a centerline of the motor housing.

[0365] 20. The electric propulsion system of clause A18 or A19, further comprising a gearbox assembly and a propeller assembly, wherein: the main shaft is substantially aligned with the center hole 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; and the inverter assembly and the propeller assembly are positioned on opposite ends of the main shaft.

[0366] 21. An electric propulsion system for a vertical take-off and landing (VTOL) aircraft, the electric propulsion system comprising: a propeller assembly; a gearbox assembly; an electric motor assembly, the electric motor assembly including at least a stator and a rotor; wherein 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, and the main shaft extends through the gearbox assembly; and an inverter assembly, the inverter assembly comprising: a housing; a capacitor assembly having a central hole substantially aligned with the main shaft, at least one capacitor, a capacitor housing having at least one busbar, and a plurality of through-holes in the capacitor housing; at least one printed circuit board assembly (PCBA); and a plurality of locating pins; wherein: the inverter assembly and the propeller assembly are positioned on different ends of the main shaft, the capacitor assembly and the at least one PCBA are positioned inside the housing, the plurality of through-holes are used to locate the at least one PCBA, and the plurality of locating pins pass through the plurality of through-holes of the capacitor housing and the at least one PCBA and are connected to the housing.

[0367] 22. An electric propulsion system for a vertical take-off and landing (VTOL) aircraft, comprising an inverter assembly according to any of clauses A1 to A16.

[0368] 23. A vertical take-off and landing (VTOL) aircraft comprising an electric propulsion system according to any of clauses A17 to A22.

[0369] Clause Set B:

[0370] 1. A flexible printed circuit board assembly (PCBA) structure comprising:

[0371] A contact pad having an electrical contact; and a serpentine connector; wherein: the contact pad deviates from a plane defined by the PCBA, the contact pad and the serpentine connector are formed by cutting through a printed circuit board, the printed circuit board comprising a substrate layer and a copper layer, and the electrical contact is electrically connected to an electronic device on the printed circuit board through the serpentine connector.

[0372] 2. The flexible PCBA structure according to clause B1, wherein the serpentine connector comprises a partial cutout of the substrate layer.

[0373] 3. The flexible PCBA structure of clause B2, wherein the partial cutout does not extend into the copper layer.

[0374] 4. The flexible PCBA structure according to clause B2 or B3, wherein the partial cutout of the substrate layer is perpendicular to the instantaneous extension direction of the serpentine connector.

[0375] 5. The flexible PCBA structure of any one of clauses B1 to B4, wherein the serpentine connector has an allowable deflection and a length, and a flex factor defined by the allowable deflection over the length.

[0376] 6. The flexible PCBA structure according to any one of clauses B1 to B5, further comprising at least two serpentine connectors having the same flex factor.

[0377] 7. The flexible PCBA structure of clause B6, wherein the flex factor is less than 0.015.

[0378] 8. The flexible PCBA structure of any one of clauses B1 to B7, further comprising a plurality of standoffs on the contact pads.

[0379] 9. A method of stacking and connecting at least one printed circuit board assembly (PCBA), comprising: providing a PCBA, the PCBA comprising: a contact pad having a first electrical contact; and a serpentine connector; wherein: the contact pad is offset from a plane defined by the PCBA, the contact pad and the serpentine connector are formed by cutting through a printed circuit board, the printed circuit board comprising a substrate layer and a copper layer, and the first electrical contact is electrically connected to an electronic device on the rest of the printed circuit board through at least the serpentine connector; stacking an electr...

Claims

1. An inverter assembly for an electric propulsion system, the inverter assembly converting direct current (DC) into alternating current (AC), the inverter assembly comprising: at least one printed circuit board assembly (PCBA); A capacitor assembly, comprising: at least one capacitor, and a capacitor housing having at least one busbar; and a housing, wherein the capacitor assembly and the at least one PCBA are located within the housing, wherein the inverter assembly has a central aperture extending through the capacitor assembly and the at least one PCBA, and a central axis of the central aperture is substantially parallel to a main axis of the electric propulsion system.

2. The inverter assembly according to claim 1, wherein: A plurality of locating pins pass through the capacitor housing and the at least one PCBA and are connected to the housing.

3. The inverter assembly according to claim 1, wherein: The central bore is configured to receive a pitch control shaft coupled to a variable pitch mechanism of the electric propulsion system.

4. The inverter assembly according to claim 1, wherein: A central axis of the central bore is substantially aligned with a main axis of the electric propulsion system.

5. The inverter assembly according to claim 1, wherein: The at least one PCBA and the capacitor assembly are stacked together.

6. The inverter assembly according to claim 5, wherein: The at least one PCBA includes a gate drive PCBA and a power PCBA, and wherein the capacitor assembly is located between the gate drive PCBA and the power PCBA.

7. The inverter assembly according to claim 6, wherein: At least a portion of the power PCBA abuts at least a portion of the capacitor assembly.

8. The inverter assembly according to claim 1, wherein: The central hole of the capacitor assembly is a through hole, and The inverter assembly is substantially in the shape of a ring.

9. The inverter assembly according to claim 1, wherein: The at least one busbar is located outside of the capacitor housing.

10. The inverter assembly according to claim 1, further comprising: Control board with low voltage (LV) logic input; Electromagnetic interference (EMI) shielding; as well as heat exchangers; wherein the control board and the EMI shielding member are located inside the housing; and Wherein, the heat exchanger is located outside the shell.

11. The inverter assembly according to claim 10, wherein: The heat exchanger is coupled to the thermal plate.

12. The inverter assembly according to claim 10, wherein: The heat exchanger is configured to cool the inverter assembly using a fluid.

13. The inverter assembly according to claim 12, wherein: The fluid is oil.

14. The inverter assembly according to claim 1, wherein: The at least one capacitor is a ring capacitor.

15. The inverter assembly according to claim 1, wherein: The at least one PCBA includes a flexible PCBA structure.

16. An electric propulsion system for a vertical take-off and landing (VTOL) aircraft, the electric propulsion system comprising: Propeller assembly; an electric motor assembly, the electric motor assembly comprising at least a stator and a rotor, wherein the electric motor assembly drives the propeller assembly via a main shaft; The inverter assembly according to any one of claims 1 to 15, wherein the inverter assembly is located at an end of the main shaft different from the propeller assembly.

17. The inverter assembly according to claim 16, wherein: The variable pitch mechanism is configured to adjust the pitch of propeller blades of the vertical take-off and landing (VTOL) aircraft electric propulsion system.

18. The electric propulsion system of claim 16, further comprising: A gearbox assembly, wherein the electric motor is located between the gearbox assembly and the propeller assembly, and wherein the main shaft extends through the gearbox assembly.

19. The electric propulsion system according to claim 16, wherein: The inverter assembly and the propeller assembly are located on opposite ends of the main shaft.

20. The electric propulsion system of claim 16, further comprising a heat exchanger disposed outside the housing, wherein the heat exchanger is configured to cool the inverter assembly using a fluid.

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