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] Cross - Reference to Related Applications

[0002] This disclosure claims priority to U.S. Patent Application No. 18 / 306,275, filed Apr. 25, 2023, titled "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 Oct. 6, 2022, titled "Tilt Rotor Systems and Methods for eVTOL Aircraft" and U.S. Provisional Application No. 63 / 378,680, filed Oct. 7, 2022, titled "Systems and Methods for Improved Propulsion Systems for eVTOL Aircraft". The content of the above applications is incorporated herein by reference in its entirety for all purposes. TECHNICAL FIELD

[0003] This disclosure generally relates to the field of powered aerial vehicles. More specifically but not limited thereto, this disclosure relates to innovations in aircraft powered by electric propulsion systems. Certain aspects of this disclosure generally relate to improvements in electric engines, gearboxes, and power inverters that provide specific advantages in aerial vehicles and other types of vehicles powered by electric propulsion systems. SUMMARY OF THE INVENTION

[0004] The present disclosure presents systems, components, and techniques primarily for unconventional aircraft powered by electric propulsion systems. For example, the tilt-rotor aircraft of the present disclosure can be configured for frequent (e.g., more than 50 flights per weekday), short-duration flights (e.g., less than 100 miles per flight) over, into, and out of populated areas. The aircraft can be configured to carry 4 to 6 passengers or commuters who desire a comfortable experience with low noise and low vibration. Thus, it may be necessary for the components of the aircraft to be configured and designed to withstand frequent use without wearing out, to generate less heat and vibration, and for the aircraft to include mechanisms for effectively controlling and managing the heat or vibration generated by the components. Additionally, it may be expected that several of these aircraft operate in close proximity to each other over crowded metropolitan areas. Thus, it may be necessary for their components to be configured and designed to generate low levels of noise both inside and outside the aircraft, and to be configured and designed with 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, avoiding the risk of single-point failures, and for them to be able to take off and land conventionally on a runway. Moreover, when transporting multiple passengers or commuters with luggage, it may be necessary for the aircraft to be able to take off and land vertically from and to a relatively small or restricted space (e.g., a vertical takeoff and landing airport, a parking lot, or a driveway) compared to a traditional airport runway. These usage requirements can impose design constraints on the size, weight, and operational efficiency (e.g., drag, energy usage) of the aircraft, which can affect the design and configuration of the aircraft components.

[0005] The disclosed embodiments provide new and improved configurations of aircraft components not observed in conventional aircraft, and / or design criteria identified for components different from those of conventional aircraft. This alternative configuration and design criteria combination addresses the drawbacks and challenges of conventional components to yield the various configurations and designs of the components for aircraft powered by electric propulsion systems disclosed herein.

[0006] In some embodiments, an aircraft driven 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, where the distributed electric propulsion system enables vertical flight, horizontal and lateral flight, and transitions. Thrust can be generated by supplying high-voltage electrical power to a plurality of electric engines of the distributed electric propulsion system, which may include the necessary components to convert the high-voltage electrical power into mechanical shaft power to rotate the propellers. Embodiments disclosed herein may relate to optimizing the energy density of the electric propulsion system. Embodiments may include electric engines connected to an on-board electrical power source, which may include devices capable of storing energy, such as batteries or capacitors, and may include one or more systems for utilizing or generating electrical power, such as fuel-powered generators or solar panel arrays. Some disclosed embodiments perform direct current (DC) to alternating current (AC) conversion through 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 use new and improved safety protocols and system redundancy in the event of a failure to improve the safety of passenger transportation, minimizing any single point of failure in the aircraft propulsion system. Some disclosed embodiments also provide new and improved methods to meet and exceed aviation and transportation laws and regulations. For example, the Federal Aviation Administration in the United States enforces federal laws and regulations that require safety components, such as fire barriers, to be close to engines that use more than a threshold amount of oil or other combustible materials. A fire barrier may include engine components or aircraft components that are designed, constructed, or installed primarily for the purpose of being configured such that any hazardous amount of air, fluid, or flame cannot bypass or pass through the fire barrier and / or prevent corrosion. In some embodiments, the fire barrier may include components separate from the additional components described herein. Those of ordinary skill in the art will understand which components within the aircraft (including within the electric propulsion system) will serve as the primary function of a fire barrier. In some embodiments, the fire barrier may include a firewall, a fire barrier, a fire-resistant barrier, a flame-retardant barrier, 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, although the fuselage may be constructed such that any hazardous amount of air, fluid, or flame cannot bypass or pass through the fire barrier and / or prevent corrosion, the fuselage may not be considered a fire barrier because the primary purpose of the fuselage is not to be used as a fire barrier. In some embodiments, the electric propulsion system uses an oil level below the threshold to provide efficient and effective lubrication and cooling, resulting in an aircraft that does not require an engine fire barrier, thereby reducing the weight of the aircraft while maximizing performance and efficiency.

[0007] In some embodiments, a distributed electric propulsion system may include twelve electric engines that can be mounted on the front and tail booms of the main wings of an aircraft. Subgroups of the electric engines, such as the electric engines mounted on the front of the main wings, may be tiltable between a horizontal orientation position (e.g., to generate forward thrust for cruising) and a vertical orientation position (e.g., to generate vertical lift for takeoff, landing, and hovering) during flight. The propellers of the front electric engines may rotate in a clockwise or counterclockwise direction. The propellers may rotate in a direction opposite to adjacent propellers. The tail electric engines may be fixed in a vertical orientation position (e.g., to generate vertical lift). The propellers may also rotate in a clockwise or counterclockwise direction. In some embodiments, the difference in the 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 mechanism may be used to achieve different propeller rotation directions.

[0008] In some embodiments, an aircraft may have a certain number of electric engines in various combinations of front engine configurations and tail engine configurations. For example, the aircraft may have six front electric engines and six tail electric engines, four front electric engines and four tail electric engines, or any other combination of front and tail engines, including embodiments where the number of front and tail electric engines is not equal.

[0009] In some embodiments, for vertical takeoff and landing (VTOL) missions, the front and tail electric engines may provide vertical thrust during takeoff and landing. During the flight phase when the aircraft is moving forward, the front electric engines may provide horizontal thrust, and the propellers of the tail electric engines may be retracted in a fixed position to minimize drag. The tail electric engines may be actively retracted using position monitoring. The transition from vertical flight to horizontal flight and vice versa may be achieved via a tilt propeller subsystem. The tilt propeller subsystem may redirect the thrust between the primarily vertical direction during vertical flight mode and the horizontal or near-horizontal direction during the forward flight cruise phase. A variable pitch mechanism may change the total blade angle of the propeller hub assembly of the front electric engines for operation during the hover phase, transition phase, and cruise phase.

[0010] In some embodiments, for conventional takeoff and landing (CTOL) missions, the front electric engines may provide horizontal thrust for wing-borne takeoff, cruising, and landing, and the wings may 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 retracted in place. In other embodiments, the tail electric engines may be used at reduced power to shorten the length of CTOL takeoff or landing.

[0011] 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 at least one PCBA are positioned inside the housing. In some embodiments, the plurality of locating pins pass through the plurality of through-holes of the capacitor housing and at least one PCBA and are connected to the housing.

[0012] In some embodiments, an electric motor for a vertical takeoff and landing (VTOL) aircraft may include or be connected to the inverter assembly. In some embodiments, a centerline of the inverter assembly may be aligned with a main shaft of the electric motor. In some embodiments, an airflow driven by the electric motor may cool the inverter assembly, thereby managing the operating temperature and optimizing the performance of the inverter assembly.

[0013] In some embodiments, the inverter assembly may have a housing having a circular shape or other shape designed to minimize drag during flight. Additionally, the inverter assembly may be mounted in a certain orientation such that the housing shape minimizes drag under different flight conditions. BRIEF DESCRIPTION OF THE DRAWINGS

[0014] This patent or application file contains at least one color drawing. Copies of this patent or patent application publication with one or more color drawings will be provided by the Patent Office upon request and payment of the necessary fees.

[0015] Figure 1 is an illustration of a perspective view of an example VTOL aircraft consistent with the disclosed embodiments.

[0016] Figure 2 is another illustration of a perspective view of an example VTOL aircraft in an alternative configuration consistent with the present disclosure.

[0017] Figure 3 is an illustration of a top plan view of an example VTOL aircraft consistent with the present disclosure.

[0018] Figure 4 is a schematic diagram showing an example propeller rotation of a VTOL aircraft consistent with the disclosed embodiments.

[0019] Figure 5 is a schematic diagram showing an example power connection in a VTOL aircraft consistent with the disclosed embodiments.

[0020] Figure 6is a block diagram showing an example architecture and design of an electric propulsion unit of a VTOL aircraft consistent with the disclosed embodiments.

[0021] Figure 7 is a schematic diagram showing an example tilt electric propulsion system of a VTOL aircraft consistent with the disclosed embodiments.

[0022] Figures 8A - 8C is an illustration of an example tilt electric propulsion system of a VTOL aircraft consistent with the disclosed embodiments.

[0023] Figure 9 is a schematic diagram showing an example lift electric propulsion system of a VTOL aircraft consistent with the disclosed embodiments.

[0024] Figures 10A - 10B is an illustration of an example lift electric propulsion system of a VTOL aircraft consistent with the disclosed embodiments.

[0025] Figures 11A - 11C is a cross-sectional illustration of an example electric propulsion system of a VTOL aircraft consistent with the disclosed embodiments.

[0026] Figures 12A - 12D is an illustration and block diagram of an example electric propulsion system of a VTOL aircraft consistent with the disclosed embodiments.

[0027] Figure 13 is an illustration of an exploded view of an example electric propulsion system of a VTOL aircraft consistent with the disclosed embodiments.

[0028] Figure 14 is an illustration of an exploded view of an example electric motor assembly of a VTOL aircraft consistent with the disclosed embodiments.

[0029] Figures 15A - 15C is an illustration of a stator assembly of a VTOL aircraft consistent with the disclosed embodiments.

[0030] Figures 16A - 16C is an illustration of an exploded view and cross-section of a rotor assembly of a VTOL aircraft consistent with the disclosed embodiments.

[0031] Figure 17 is an exploded view of a main shaft assembly of a VTOL aircraft consistent with the disclosed embodiments.

[0032] Figure 18 is an illustration of an example sun gear of a VTOL aircraft consistent with the disclosed embodiments.

[0033] Figure 19 is an illustration of an example ring gear of a VTOL aircraft consistent with the disclosed embodiments.

[0034] Figure 20 It is a diagram of an example frame assembly of a VTOL aircraft consistent with the disclosed embodiments.

[0035] Figures 21A - 21B It is a diagram of an example bell end cap assembly of a VTOL aircraft consistent with the disclosed embodiments.

[0036] Figure 22 It is a diagram of an example inverter assembly of a VTOL aircraft consistent with the disclosed embodiments.

[0037] Figure 23 It is a diagram of an exploded view of an inverter assembly of a VTOL aircraft consistent with the disclosed embodiments.

[0038] Figure 24 It is a diagram of an example printed circuit board assembly of a VTOL aircraft consistent with the disclosed embodiments.

[0039] Figures 25A - 25C It is a diagram and an example front view of a heat exchanger of a VTOL aircraft consistent with the disclosed embodiments.

[0040] Figure 26 It is a diagram of a heat exchanger of a VTOL aircraft consistent with the disclosed embodiments.

[0041] Figures 27A - 27B It is a diagram of a partition plate of a VTOL aircraft consistent with the disclosed embodiments.

[0042] Figure 28 It is a diagram of a hot plate of a VTOL aircraft consistent with the disclosed embodiments.

[0043] Figure 29 It is a diagram of an electric propulsion system of a VTOL aircraft consistent with the disclosed embodiments.

[0044] Figures 30A - 30B It is a diagram of an example electric propulsion system of a VTOL aircraft consistent with the disclosed embodiments.

[0045] Figures 31A - 31B It is a cross-sectional diagram of an electric propulsion system of a VTOL aircraft consistent with the disclosed embodiments.

[0046] Figures 32A - 32D It is a cross-sectional diagram of an electric propulsion system of a VTOL aircraft in various flight stages consistent with the disclosed embodiments.

[0047] Figures 33A - 33C It is a schematic diagram showing an example electric propulsion system of a VTOL aircraft including a fire barrier consistent with the disclosed embodiments.

[0048] Figures 34A - 34D is a schematic diagram showing an example electric propulsion system of a VTOL aircraft consistent with the disclosed embodiments.

[0049] Figure 35 is a schematic diagram showing an example electric propulsion system of a VTOL aircraft consistent with the disclosed embodiments.

[0050] Figures 36A - 36B is a schematic diagram showing an example electric propulsion system of a VTOL aircraft consistent with the disclosed embodiments.

[0051] Figure 37 is a schematic diagram showing an example electric propulsion system of a VTOL aircraft consistent with the disclosed embodiments.

[0052] Figures 38A - 38B is a schematic diagram showing an example electric propulsion system of a VTOL aircraft and an example inverter assembly of the electric propulsion system consistent with the disclosed embodiments.

[0053] Figures 39A - 39D is a cross-sectional view, perspective view, and schematic diagram showing an example electric propulsion system of a VTOL aircraft consistent with the disclosed embodiments.

[0054] Figures 40A - 40D is a diagrammatic view and schematic diagram showing the electric propulsion system of a VTOL aircraft consistent with the disclosed embodiments.

[0055] Figure 41 is a cross-sectional diagrammatic view of the electric propulsion system of a VTOL aircraft consistent with the disclosed embodiments.

[0056] Figures 42A - 42B is a diagrammatic view of an example electric propulsion system of a VTOL aircraft consistent with the disclosed embodiments.

[0057] Figures 43A - 43D is a diagrammatic view and schematic diagram showing an example electric propulsion system of a VTOL aircraft consistent with the disclosed embodiments.

[0058] Figures 44A - 44C is a schematic diagram showing an example electric propulsion system of a VTOL aircraft consistent with the disclosed embodiments.

[0059] Figures 45A - 45D is a schematic diagram showing an example electric propulsion system of a VTOL aircraft consistent with the disclosed embodiments.

[0060] Figures 46A - 46B is a schematic diagram showing an example electric propulsion system of a VTOL aircraft consistent with the disclosed embodiments.

[0061] Figures 47A - 47B is a schematic diagram and a cross-sectional illustration of an example electric propulsion system of a VTOL aircraft consistent with the disclosed embodiments.

[0062] Figure 48 is a schematic diagram showing an example electric propulsion system of a VTOL aircraft consistent with the disclosed embodiments.

[0063] Figure 49 is an illustration of a cross-sectional view of an example electric propulsion system of a VTOL aircraft consistent with the disclosed embodiments.

[0064] Figure 50 is an illustration of a perspective view of an example rotor of a VTOL aircraft consistent with the disclosed embodiments.

[0065] Figure 51 is a flowchart of an example process for balancing the rotor of a VTOL aircraft consistent with the disclosed embodiments.

[0066] Figure 52 is another flowchart of an example process for balancing the rotor assembly of a VTOL aircraft consistent with the disclosed embodiments.

[0067] Figure 53 is a flowchart of an example process for transmitting torque from an electric motor assembly of a VTOL aircraft to a propeller assembly consistent with the disclosed embodiments.

[0068] Figure 54 is a schematic illustration of a partial cross-sectional view of an example electric motor assembly.

[0069] Figures 55A - 55B is an illustration of the inner surfaces of an example rotor hub and an example end plate consistent with the disclosed embodiments.

[0070] Figure 55C is the simulation result of the air velocity and pressure distribution inside a housing consistent with the disclosed embodiments.

[0071] Figure 55D shows an illustration of an example inner surface of an end plate consistent with the disclosed embodiments.

[0072] Figure 56A is an illustration showing a cross-sectional view of a press-fit mesh port consistent with the disclosed embodiments.

[0073] Figure 56B is an illustration showing a cross-sectional view of a press-fit mesh port after installation when operating in an inclined position consistent with the disclosed embodiments.

[0074] Figure 57Illustration of a cross-sectional perspective view of an integrated sensor on a power board consistent with the disclosed embodiments.

[0075] Figure 58 Illustration of a perspective view of a flexible PCBA connector consistent with the disclosed embodiments.

[0076] Figure 59 is consistent with the disclosed embodiments Figure 58 Cross-sectional view of the serpentine connector of the flexible PCBA shown, showing a partial cut.

[0077] Figure 60A Illustration of a capacitor housing consistent with the disclosed embodiments, showing alignment pins

[0078] Figure 60B Illustration of a hot plate and a heat exchanger consistent with the disclosed embodiments, showing mating alignment pins. Detailed Description

[0079] The disclosed embodiments provide systems, subsystems, and components for a novel VTOL aircraft having various combinations of electric propulsion systems and cooling systems that maximize performance while minimizing weight.

[0080] In some embodiments, an electric propulsion system as described herein can generate thrust by supplying high-voltage (HV) electrical power to an electric engine, which in turn converts the HV electrical power into mechanical shaft power for rotating a propeller. An aircraft as described herein can include multiple electric engines mounted at the front and rear of the wings. The engines can be mounted directly to the wings or to one or more booms attached to the wings. The amount of thrust generated by each electric engine can be controlled by a torque command sent by a flight control system (FCS) to each electric engine via a digital communication interface. Embodiments can include front electric engines capable of changing their orientation or tilt. Some embodiments include front engines that can be of the clockwise (CW) type or counterclockwise (CCW) type. The front electric propulsion subsystem can consist of a multi-blade variable pitch propeller and a variable pitch subsystem.

[0081] In some embodiments, the aircraft can include a rear electric engine or a lifter that can be of the clockwise (CW) type or counterclockwise (CCW) type. Some embodiments can include rear electric engines that utilize multi-blade fixed pitch propellers.

[0082] As described herein, the orientation and use of components of an electric propulsion system can be varied throughout the operation of an aircraft. In some embodiments, during vertical takeoff and landing, both a front propulsion system and a 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 retracted in a fixed position to minimize drag. The tail electric propulsion system can be actively retracted using position monitoring. Some embodiments can 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 the primarily vertical direction during vertical flight mode and the primarily horizontal direction during forward flight mode. Some embodiments can include a variable pitch mechanism that can vary the collective angle of the front propulsion system propeller blades for operation during hover, cruise, and transition phases. Some embodiments can include a conventional takeoff and landing (CTOL) configuration such that the tilters provide horizontal thrust for wingborne takeoff, cruise, and landing phases. In some embodiments, the tail electric engines are not used to generate thrust during CTOL missions and the tail propellers are retracted in a position that minimizes drag.

[0083] In some embodiments, a power engine as described herein can have design features to mitigate and prevent a runaway fire, such as by utilizing a non-hazardous amount of combustible fluid contained in both a tilt engine and a lift engine. For example, in some embodiments, a power engine can be configured to utilize less than one quart of oil or another combustible fluid. Some embodiments can include a power engine that contains a non-hazardous amount of air such that any fire cannot sustain a duration that can migrate to another part of the aircraft. In some embodiments, the non-hazardous amount of air can be in contact with the combustible liquid throughout the power engine. Some examples can include a power engine that has up to one liter, two liters, three liters, four liters, five liters, ten liters, or twenty liters of air within the power engine housing. In some embodiments, the amount of air present within the power engine housing can have a fixed ratio to the amount of oil or other liquid used for cooling present within the electric propulsion system. Such a ratio can be driven by determining the sufficient thermal mass required to properly cool the electric propulsion system. Some embodiments can include an air-to-oil ratio within the electric propulsion system of about 3:1. Some embodiments can include a power engine housing where 75% of the open volume (i.e., the internal volume not occupied by components of the power engine) is composed of air, while 25% of the open volume is composed of oil or some other liquid used for cooling and / or lubrication. Some embodiments can also be configured to have no nominal ignition source within the power engine, have an engine over-temperature operating limit that can be more than 50 °C lower than the auto-ignition temperature of the combustible fluid, have over-temperature detection and protection, over-voltage detection and protection, and / or have over-current detection and protection. Additionally, some embodiments can include an electric propulsion system where the overall temperature of the electric propulsion system is lower than 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, an abnormal condition that raises the overall temperature of the electric propulsion system can result in a system response that prevents the oil or other liquid from exceeding the flash point and auto-ignition temperature. In some embodiments, the ratio of air to oil or other liquid can be such that if a fire occurs within the power engine housing, including if an arc causes the fire, the amount of air present within the power engine housing will not allow the fire to spread to other areas of the aircraft. In some embodiments, these and other design features can result in a power engine that is considered a non-designated fire zone by one or more guidelines or regulations.

[0084] Reference will now be made in detail to example embodiments, which are illustrated in the accompanying drawings. The following description refers to the accompanying drawings in which, unless otherwise indicated, the same numbers in different drawings represent the same or similar elements. The embodiments set forth in the following description of the example embodiments do not represent all embodiments consistent with the present disclosure. Instead, they are merely examples of devices and methods consistent with aspects related to the subject matter recited in the appended claims.

[0085] A. Example Electric Aircraft Features

[0086] Figure 1 Illustrated is a perspective view of an example VTOL aircraft consistent with the disclosed embodiments. Figure 2 Illustrated is another perspective view of an example VTOL aircraft consistent with the embodiments of the present disclosure in an alternative configuration. Figure 1 and Figure 2 show VTOL aircraft 100, 200 consistent with the embodiments of the present disclosure in a cruise configuration and a vertical takeoff, landing, and hover configuration (also referred to herein as a “lift” configuration), respectively. Corresponding elements to Figure 1 and Figure 2 may have similar reference numerals and refer to like elements of aircraft 100, 200. Aircraft 100, 200 may include fuselages 102, 202, wings 104, 204 mounted to fuselages 102, 202, and one or more rear stabilizers 106, 206 mounted to the rear of fuselages 102, 202. A plurality of lift propellers 112, 212 may be mounted to 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 wings 104, 204 and may tilt between a lift configuration and a cruise configuration, in which the plurality of tilt propellers provide a portion of the lift required for vertical takeoff, landing, and hovering, as Figure 2 shown, and in which the plurality of tilt propellers provide forward thrust to aircraft 100 for horizontal flight in the cruise configuration, as Figure 1 shown. As used herein, a tilt propeller lift configuration refers to any tilt propeller orientation in which tilt propeller thrust predominantly provides lift to the aircraft, and a tilt propeller cruise configuration refers to any tilt propeller orientation in which tilt propeller thrust predominantly provides forward thrust to the aircraft.

[0087] In some embodiments, lift propellers 112, 212 may be configured to provide only lift, where all horizontal propulsive forces are provided by tilt propellers. Thus, lift propellers 112, 212 may be configured to have a fixed position and may generate thrust only during the takeoff, landing, and hover phases of flight. At the same time, tilt propellers 114, 214 may be tilted upward into a lift configuration in which thrust from propellers 114, 214 is directed downward to provide additional lift.

[0088] For forward flight, the tilt rotors 114, 214 can be tilted from their lift configuration to their cruise configuration. In other words, the orientation of the tilt rotors 114, 214 can change from an orientation where the tilt rotor thrust is directed downward (to provide lift during vertical takeoff, landing, and hovering) to an orientation where the tilt rotor thrust is directed backward (to provide forward thrust to the aircraft 100, 200). The tilt rotor assemblies for a particular electric engine can be tilted about a rotational axis defined by the mounting points that connect the pylon and the electric engine. When the aircraft 100, 200 are in full forward flight, the lift can be provided entirely by the wings 104, 204. At the same time, in the cruise configuration, the lift rotors 112, 212 can be shut down. The blades 120, 220 of the lift rotors 112, 212 can be held in a low drag position for aircraft cruise. In some embodiments, each of the lift rotors 112, 212 can have two blades 120, 220, and the two blades can be locked for cruising in a minimum drag position, in which one blade is directly in front of the other blade, as Figure 1 shown. In some embodiments, the lift rotors 112, 212 have more than two blades. In some embodiments, the tilt rotors 114, 214 can include more blades 116, 216 than the lift rotors 112, 212. For example, as Figure 1 and Figure 2 shown, each of the lift rotors 112, 212 can include, for example, two blades, while each of the tilt rotors 114, 214 can include more blades, such as the five blades shown. In some embodiments, each of the tilt rotors 114, 214 can have from 2 to 5 blades, and possibly more, depending on the design considerations and requirements of the aircraft.

[0089] 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 wings 104, 204, and at least a portion of the tilt propellers 114, 214 may be located at the front of the wings 104, 204. In some embodiments, all of the lift propellers 112, 212 may be located at the rear of the wings 104, 204, and all of the tilt propellers 114, 214 may be located at the front of the wings 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, no lift propeller or tilt propeller is mounted to the fuselage. In some embodiments, the lift propellers 112, 212 may all be located at the rear of the wings 104, 204, and the tilt propellers 114, 214 may all be located at the front of the wings 104, 204. According to some embodiments, all of the lift propellers 112, 212 and tilt propellers 114, 214 may be positioned inside the ends of the wings 104, 204.

[0090] In some embodiments, the lift propellers 112, 212 and tilt propellers 114, 214 may be mounted to the wings 104, 204 via struts 122, 222. The struts 122, 222 may be mounted below the wings 104, 204, on top of the wings, and / or may be integrated into the wing profile. In some embodiments, the lift propellers 112, 212 and tilt propellers 114, 214 may be mounted directly to the wings 104, 204. In some embodiments, each strut 122, 222 may be mounted with one lift propeller 112, 212 and one tilt propeller 114, 214. The lift propellers 112, 212 may be mounted at the rear end of the struts 122, 222, and the tilt propellers 114, 214 may be mounted at the front end of the struts 122, 222. In some embodiments, the lift propellers 112, 212 may be mounted in fixed positions on the struts 122, 222. In some embodiments, the tilt propellers 114, 214 may be mounted to the front end of the struts 122, 222 via hinges. The tilt propellers 114, 214 may be mounted to the struts 122, 222 such that the tilt propellers 114, 214 are aligned with the body of the struts 122, 222 when in their cruise configuration, thereby forming a continuous extension of the front end of the struts 122, 222 that minimizes the drag during forward flight.

[0091] In some embodiments, the aircraft 100, 200 may include, for example, one wing on each side of the fuselage 102, 202 or a single wing that extends across the aircraft. According to some embodiments, at least one wing 104, 204 is a high wing mounted to the upper side of the fuselage 102, 202. According to some embodiments, the wing includes control surfaces, such as flaps and / or ailerons. According to some embodiments, the 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.

[0092] In some embodiments, the rear stabilizers 106, 206 include control surfaces, such as one or more rudders, one or more elevators, and / or one or more combined rudder-elevators. The wings can have any suitable design. In some embodiments, the wings have a tapered leading edge.

[0093] In some embodiments, the lift propellers 112, 212 or tilt propellers 114, 214 may be deflected relative to at least one other lift propeller 112, 212 or tilt propeller 114, 214. As used herein, deflection 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. Deflection of the lift propeller and / or tilt propeller can be achieved by orienting the plane of rotation of the lift propeller / tilt propeller disk (blades plus the hub that mounts the blades) so as not to intersect critical parts of the aircraft (such areas where personnel in the fuselage may be located, critical flight control systems, batteries, adjacent propellers, etc.) or other propeller disks, to assist in minimizing damage caused by propeller burst, and can provide enhanced yaw control during flight.

[0094] Figure 3 is an illustration of a top plan view of an example VTOL aircraft consistent with embodiments of the present disclosure. The aircraft 300 shown in the figure may be respectively at Figure 1 and Figure 2Top plan views of the aircraft 100, 200 shown. 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 front electric propulsion systems 314 and six rear 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 length of the boom 324 from the wing 304 to the rear end of the lift propeller 312 may include the rear lengths of similar booms 324 across multiple rear ends of the boom. In some embodiments, the rear length of the boom may vary across six example 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 a subgroup of the rear ends of the boom may be similar in length. In some embodiments, the front ends of the booms 322 may include various lengths from the wing 304 to the tilt propellers 314 across the front ends of the booms. For example, as Figure 3 shown, the front length of the boom 322 from the tilt propeller 314 closest to the fuselage to the wing 304 may include a greater length than the front length of the boom 322 from the wing 304 to the tilt propeller 314 furthest from the fuselage. Some embodiments may include boom fronts with similar lengths across six example front ends of the boom, or any other length distribution of the booms from the wing 304 to the tilt propellers 314. Some embodiments may include an aircraft 300 with eight electric propulsion systems, where the eight electric propulsion systems have four front electric propulsion systems 314 and four rear electric propulsion systems 312, or any other distribution of front and rear electric propulsion systems, including embodiments where the number of front electric propulsion systems 314 is less than or greater than the number of rear electric propulsion systems 312. Additionally, Figure 3 depicts an example embodiment of a VTOL aircraft 300 having front propellers 314 in a horizontal orientation for horizontal flight and tail propeller blades 320 in a stowed position for the forward flight phase.

[0095] As disclosed herein, the front electric propulsion systems and the rear electric propulsion systems may be of the clockwise (CW) type or the counterclockwise (CCW) type. Some embodiments may include various front electric propulsion systems having a mixture of both CW and CCW types. In some embodiments, the rear electric propulsion systems may have a mixture of CW and CCW type systems among the rear electric propulsion systems.

[0096] Figure 4 is a schematic diagram showing an example propeller rotation of a VTOL aircraft consistent with the disclosed embodiments. The aircraft 400 shown in the figure may be respectively at Figure 1 , Figure 2 and Figure 3Top plan views of the aircraft 100, 200, and 300 shown. The aircraft 400 may include six front electric propulsion systems, where three of these front electric propulsion systems have a CW type 424 and the remaining three front electric propulsion systems have a CCW type. In some embodiments, three rear electric propulsion systems may have a CCW type 428 while the remaining three rear electric propulsion systems may have a CW type 430. Some embodiments may include an aircraft 400 having four front electric propulsion systems and four rear electric propulsion systems, with the four front electric propulsion systems and the four rear electric propulsion systems each having two CW types and two CCW types. In some embodiments, the propellers may rotate in opposite directions relative to adjacent propellers to cancel out the torque steer experienced by the fuselage or wings of the aircraft due to the rotation of the propellers. In some embodiments, the difference in the direction of rotation may be achieved using the direction of rotation of the engines. 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.

[0097] Some embodiments may include an aircraft 400 having front electric propulsion systems and rear electric propulsion systems, where the amounts of CW type 424 and CCW type 426 are not equal among the front electric propulsion systems, among the rear electric propulsion systems, or among the front and rear electric propulsion systems.

[0098] Figure 5FIG. 0 is a schematic diagram showing an example power connection in a VTOL aircraft consistent with the disclosed embodiments. The VTOL aircraft may have various power systems connected to diagonally opposed electric propulsion systems. In some embodiments, the power system may include a high-voltage power system. Some embodiments may include a high-voltage power system connected to an electric engine via a high-voltage channel. In some embodiments, the aircraft 500 may include six power systems, including batteries 526, 528, 530, 532, 534, and 536 stored within the wings 570 of the aircraft 500. In some embodiments, the aircraft 500 may include six front electric propulsion systems having six electric engines 502, 504, 506, 508, 510, and 512 and six rear electric propulsion systems having six electric engines 514, 516, 518, 520, 522, and 524. In some embodiments, the batteries may be connected to diagonally opposed electric engines. In such a configuration, the first power system 526 may supply power to the electric engine 502 via a power connection channel 538 and to the electric engine 524 via a power connection channel 540. In some embodiments, the first power system 526 may also be paired with the fourth power system 532 via a power connection channel 542, and the power connection channel 542 includes a fuse to prevent excessive current from flowing through the power systems 526 and 532. Further for this embodiment, the VTOL aircraft 500 may include a second power system 528 paired with the fifth power system 534 via a power connection channel 548 having a fuse, and may supply power to the electric engines 510 and 516 via power connection channels 544 and 546, respectively. In some embodiments, the third power system 530 may be paired with the sixth power system 536 via a power connection channel 554 having a fuse, and may supply power to the electric engines 506 and 520 via power connection channels 550 and 552, respectively. The fourth power system 532 may also supply power to the electric engines 508 and 518 via power connection channels 556 and 558, respectively. The fifth power system 534 may also supply power to the electric engines 504 and 522 via power connection channels 560 and 562, respectively. The sixth power system 536 may also supply power to the electric engines 512 and 514 via power connection channels 564 and 566, respectively.

[0099] As disclosed herein, an electric propulsion system may include an electric engine connected via a high-voltage channel or a power connection channel to a high-voltage power system (such as a battery) located within an aircraft. Some embodiments may include various batteries stored within an aircraft wing, the aircraft wing having a high-voltage channel that travels through the aircraft (including the wing and the boom) to the electric propulsion system. In some embodiments, multiple high-voltage power systems may be used to create an electric propulsion system having multiple high-voltage power sources to avoid the risk of single-point failure. In some embodiments, an aircraft may include multiple electric propulsion systems, the multiple electric propulsion systems being wired in a certain pattern to various batteries or power sources stored throughout the aircraft. It should be recognized that such a configuration may be beneficial in avoiding the risk of single-point 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 flying or to make a controlled landing. For example, if a VTOL has two front electric propulsion systems and two rear propulsion systems, the front electric propulsion system and the rear propulsion system on opposite sides of the VTOL aircraft may be connected to the same high-voltage power system. In such a configuration, if one high-voltage power system fails, the front electric propulsion system and the rear propulsion system on opposite sides of the VTOL aircraft will remain operational and may provide a more balanced flight or landing compared to the front electric propulsion system and the rear propulsion system that have failed on the same side of the VTOL aircraft. Some embodiments may include four front electric propulsion systems and four rear electric propulsion systems, where diagonally opposite electric engines are connected to a common battery or power source. Some embodiments may include various configurations of electric engines electrically connected to a high-voltage power system such that the risk of single-point failure is avoided in the event of a power source failure and the failed flight phase may continue, or the aircraft may perform an alternative flight phase in response to the failure.

[0100] As discussed above, an electric propulsion system may include an electric engine that provides mechanical shaft power to a propeller assembly to generate thrust. In some embodiments, the electric engine of 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"), the flight control system being capable of sending signals to and receiving signals from the electric engine, the signals including commands and response data or status. Some embodiments may include an electric engine capable of receiving operating parameters from the FCC and transmitting operating parameters to the FCC, these operating parameters including speed, voltage, current, torque, temperature, vibration, propeller position, and any other values of operating parameters.

[0101] In some embodiments, a flight control system can include a system that is capable of communicating with an electric engine to send and receive analog / digital signals to and from the electric engine and control a device that can redirect the thrust of a tilt propeller between a primary vertical direction during a vertical flight mode and a primary horizontal direction during a forward flight mode. In some embodiments, this system can be referred to as a tilt propeller system (“TPS”) and is capable of communicating with and directing additional features of an electric propulsion system.

[0102] 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, an electric propulsion system 602 can include an electric engine subsystem 604 that can supply torque via an axial propeller subsystem 606 to generate thrust of the electric propulsion system 602. Some embodiments can include an electric engine subsystem 604 that receives low voltage DC (LV DC) power from a low voltage system (LVS) 608. Some embodiments can include an electric engine subsystem 604 that receives high voltage (HV) power from a high voltage power system (HVPS) 610 that includes at least one battery or another device capable of storing energy. In some embodiments, the high voltage power system can 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 as there is no single point of failure risk where a single battery failure results in failure of the electric propulsion system 602.

[0103] Some embodiments may include an electric propulsion system 602 that includes an electric engine subsystem 604 that receives signals from and sends signals to a flight control system 612. In some embodiments, the flight control system 612 may include a flight control computer that is 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 although 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 that is capable of sending analog discrete data to and receiving analog discrete data from the electric engine subsystem 604 of the tilt propeller. The tilt propeller system 614 may include a device that is capable of transferring operating parameters to the electric engine subsystem 604 and articulating the orientation of the propeller subsystem 606 to redirect the thrust of the tilt propeller during various phases of flight using mechanical components (such as a gearbox assembly, a linear actuator, and components of any other configuration that change the orientation of the propeller subsystem 606).

[0104] As discussed throughout, example VTOL aircraft may include various types of electric propulsion systems that include tilt propellers and lift propellers that include a front electric engine capable of tilting during various phases of flight and a rear electric engine that remains in one orientation and may be active only during certain phases of flight (i.e., takeoff, landing, and hover).

[0105] Figure 7 is a schematic diagram showing an example tilt electric propulsion system of a VTOL aircraft consistent with the disclosed embodiments. The tiltable electric propulsion system 700 may include an electric engine assembly 702 aligned along an axis 724 that is connected to an output shaft 738 that is mechanically coupled to a propeller assembly 720 that includes a hub, a spinner, and tilt propeller blades. In some embodiments, the electric engine assembly 702 may include a motor and gearbox assembly 704 aligned along the axis 724 and mechanically coupled to the axis. In some embodiments, the motor and gearbox assembly 704 may include an electric motor assembly that includes a stator 706 and a rotor 708. As Figure 7As shown and present in some embodiments, the stator 706 may include a plurality of stator windings connected to an inverter 716. In such a configuration, the stator 706 may include one or more redundancies such that in the event of a failure of a set of windings, power will still be transmitted to the stator 706 via one or more remaining windings, enabling the electric power engine assembly 702 to maintain power and continue to generate thrust at the propeller assembly 720.

[0106] In some embodiments, the motor and gearbox assembly 704 may include a gearbox 710 aligned along the shaft 724 to provide a gear reduction between the torque of the shaft 724 from the electric power engine assembly including the stator 706 and the rotor 708 and the output shaft 738. The torque applied to the output shaft 738 may be transmitted to the propeller assembly 720. Some embodiments may include a gearbox 710 containing an oil pump. In such embodiments, the oil pump may drive the circulation of 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 may drive the circulation of 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 present within the housing, which may detect the magnetic field generated by the electric power engine assembly to determine the propeller position. Additional embodiments may include a propeller position sensor 712 that is powered by the inverter 716 and sends the collected data to the inverter 716.

[0107] In some embodiments, the electric power engine assembly 702 may further include an inverter assembly 714 aligned substantially along the shaft 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 electric power engine assembly 702. The inverter power source 740 may receive low-voltage DC power that has been converted to low-voltage DC power via a DC-DC converter 742 from a high-voltage power system 732 located external to the electric power engine assembly 702. The inverter 716 may supply high-voltage alternating current (AC) to the stator 706 of the electric power engine assembly within the motor and gearbox assembly 704 via at least one three-phase winding. The inverter assembly 714 may include an inverter 716 that may receive flight control data from a flight control computing subsystem 736.

[0108] In some embodiments, the motor and gearbox 704 can be located between the inverter assembly 714 and the propeller assembly 720. Some embodiments can 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 housing end cap assembly and an enclosed environment for the lower portion of the inverter assembly 714 via a heat plate. In some embodiments, the separator plate 744 can function 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 from 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 an air stream 722 passing through the fins of the heat exchanger.

[0109] In some embodiments, the electric engine assembly 702 can be mounted or coupled to a strut structure 726 of an aircraft. A variable pitch mechanism 730 can be mechanically coupled to the propeller assembly 720. In some embodiments, the variable pitch mechanism can be adjacent to the electric engine assembly 702. In some embodiments, the variable pitch mechanism 730 can be coupled to the variable pitch mechanism 730 such that it can be remotely mounted within a strut, wing, or fuselage of the aircraft. In some embodiments, the variable pitch mechanism 730 can be included within or travel adjacent to a shaft 724 to a shaft or component of the propeller assembly 720. The variable pitch mechanism 730 can be used to vary the total blade angle of the propeller assembly of the front electric engine during hover, transition, and cruise phases according to operational needs. Some embodiments can include an electric engine assembly 702 mechanically coupled to a tilt propeller subsystem 728 that 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 the variable pitch mechanism 730. Some embodiments can include a tilt propeller subsystem 728 that includes various components located at various positions. For example, components of the tilt propeller subsystem can be coupled to the electric engine assembly 702 and other components can be coupled to the variable pitch mechanism 730. These various components of the tilt propeller subsystem 728 can work together to redirect the thrust of the tiltable electric propulsion system 700.

[0110] Figures 8A - 8C is an illustration of an example tilt electric propulsion system for a VTOL aircraft consistent with the disclosed embodiments. Figures 8A - 8CHave similar reference numerals and refer to similar elements of tiltable electric propulsion systems 800A, 800B, and 800C. Thus, similar design considerations and configurations can be considered throughout the embodiments.

[0111] Figure 8A and Figure 8B show side profiles and perspective views, respectively, of tiltable electric propulsion systems 800A, 800B in cruise configuration integrated into booms 812A, 812B in accordance with the present disclosure. The tiltable propeller electric propulsion systems 800A, 800B can include electric engine assemblies 802A, 802B housed within booms 812A, 812B of a VTOL aircraft. In some embodiments, the cruise configuration can include electric engine assemblies 802A, 802B disposed within booms 812A, 812B. As described herein, electric engine assemblies 802A, 802B can include an electric motor assembly, a gearbox assembly, an inverter assembly having power connection channels 810A, 810B, and heat exchangers 804A, 804B. The electric engine assemblies 802A, 802B can be mechanically coupled to propulsion assemblies 808A, 808B, which include shaft flange assemblies 806A, 806B, a spinner, and propeller blades.

[0112] Figure 8C shows a top view along spinner 808C of tiltable electric propulsion system 800C in lift configuration integrated into boom 812B in accordance with the present disclosure. As Figure 8C shown, the tiltable electric propulsion system 800C in lift configuration can include electric engine assemblies 802A, 802B that are disposed external to boom 812C and that change their orientation relative to boom 812C.

[0113] As discussed herein, a lift electric propulsion system can be configured to provide thrust in one direction and may not provide thrust during all phases of flight. For example, a lift system can provide thrust during takeoff, landing, and hover, but may not provide thrust during cruise.

[0114] Figure 9FIG. 0 is a schematic diagram showing an exemplary lift electric propulsion system of a VTOL aircraft consistent with the disclosed embodiments. The lift electric propulsion system 900 may be mounted or coupled to the pylon structure 924 of the aircraft. The lift electric propulsion system 900 may include an electric engine assembly 902 aligned along an axis 940, the axis being connected to an output shaft 932 that is mechanically coupled to a propeller assembly 920, the propeller assembly including a hub and tilting propeller blades. In some embodiments, the electric engine assembly 902 may include a motor and gearbox assembly housing 904 aligned along the axis 940 and mechanically coupled to the axis. In some embodiments, the motor and gearbox assembly housing 904 may include an electric motor assembly that includes a stator 906 and a rotor 908. The stator 906 may include a plurality of stator windings connected to an inverter 916. In such a configuration, the stator 906 may include one or more redundancy and backup measures to avoid single point of failure in such cases. For example, the stator 906 may include multiple windings such that if a winding fails, power can continue to be transferred to the stator 906 via the remaining windings, thereby allowing the electric engine assembly 902 to maintain power and continue to generate thrust at the propeller assembly 920.

[0115] In some embodiments, the motor and gearbox assembly housing 904 may include a gearbox 910 aligned along the axis 940 to provide a gear reduction between the torque of the axis 932 from 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 may be transferred to the propeller assembly 920. Some embodiments may include a gearbox 910 that includes a fluid pump for circulating a cooling fluid and / or a lubricating fluid. In the illustrated embodiment, the fluid pump is an oil pump. In such an embodiment, the oil pump may 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 the electric motor components. Some embodiments of the motor and gearbox assembly housing 904 may include a propeller position sensor 912 present within the housing, the propeller position sensor being able to detect the magnetic field generated by the electric engine assembly to determine the propeller position. Further embodiments may include a propeller position sensor 912 that is powered by the inverter 916 and sends the collected data to the inverter 916, the collected data being transferable to the flight control computing system 930 along with other flight control data.

[0116] In some embodiments, the electric power engine assembly 902 may further 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 outside the electric power engine assembly 902. The inverter power source 934 may receive low-voltage DC power that has been converted to low-voltage DC power via a DC-DC converter 936 from a high-voltage power system 926 located outside the electric power engine assembly 902. The inverter 916 may supply high-voltage alternating current to the stator 906 of the electric 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 data to and receive data from the flight control computing subsystem 930.

[0117] In some embodiments, the motor and gearbox housing 904 may be located between the inverter assembly housing 914 and the propeller assembly 920. Some embodiments may further include a separator plate 938 coupled to the motor and gearbox assembly housing 904 and the inverter assembly housing 914. The separator plate 938 may create an enclosed environment for the upper portion of the motor and gearbox assembly housing 904 via a bell end cap assembly and may 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 may act as an integral mounting bracket for supporting the heat exchanger 918. The heat exchanger 918 may include, for example, folded fins or other types of heat exchangers. In some embodiments, the electric propulsion system 900 may circulate oil or other coolant fluid throughout the electric power engine assembly 902, the motor and gearbox assembly 904, or the inverter assembly 914 to transfer heat generated from the components to the oil or other coolant liquid. The heated oil or other coolant liquid may be circulated through the heat exchanger 918 to transfer heat to the air stream 922 passing through the fins of the heat exchanger.

[0118] In some embodiments, the tiltable electric propulsion system and the lift electric propulsion system may have similar components. This can be advantageous for many design considerations present within a VTOL aircraft. For example, from a manufacturability perspective, different types of electric propulsion systems with similar components can be beneficial in terms of manufacturing efficiency. Additionally, having similar components can be beneficial in terms of risk management because similar components have similar failure points, and these failure points can be well explored and designed when comparing systems with similar components to systems with different components and configurations.

[0119] Although a tiltable electric propulsion system can have additional and in some embodiments different components compared to a lift electric propulsion system, it should be understood that in some embodiments, a tiltable electric propulsion system and a lift electric propulsion system can have the same component configuration. For example, in some embodiments, a tiltable electric propulsion system and a lift electric propulsion system can include the same components, while a lift electric propulsion system can be coupled to a strut, wing, or fuselage of an aircraft such that it may not be able to provide thrust in as many directions as a tiltable electric propulsion system.

[0120] Figures 10A - 10B is an illustration of an example lift electric propulsion system of a VTOL aircraft consistent with the disclosed embodiments. Figure 10A and Figure 10B have similar reference numerals and refer to similar elements of lift electric propulsion systems 1000A and 1000B. Accordingly, similar design considerations and configurations can be considered throughout the embodiments.

[0121] Figure 10A shows a side profile of lift electric propulsion system 1000A in a lift configuration integrated into strut 1010A consistent with the present disclosure. Lift electric propulsion system 1000A can include an electric engine assembly 1002A housed within strut 1010A of a VTOL aircraft. In some embodiments, the lift configuration can include electric engine assembly 1002A vertically disposed within strut 1010A. As described herein, electric engine assembly 1002A can include an electric motor assembly, a gearbox assembly, an inverter assembly having a power connection channel 1008A, and a heat exchanger 1004A. Electric engine assembly 1002A can be mechanically coupled to propulsion assembly 1006A, which includes a shaft flange assembly and propeller blades.

[0122] Figure 10B shows a top view of lift electric propulsion system 1000B in a lift configuration integrated into strut 1010B consistent with the present disclosure.

[0123] Some embodiments of the disclosed power engines can 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 can be used and circulated through various components of the engine (such as an inverter, a gearbox, or a 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 an air cooling method 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 can also be the same liquid that serves as a lubricant throughout the inverter, gearbox, or motor. For example, a liquid or air or a mixture of air and liquid cooling can be used to cool components of the power engine. As another example, air cooling can be used to cool the motor, while liquid cooling can be used to cool the inverter and the gearbox. It should be understood that a cooling mixture can be used for any combination of power engine components or within each component.

[0124] In some embodiments, oil can be used as a lubricant throughout the power engine and can also be used as a coolant fluid to help manage the heat generated by the engine during operation. Further for this example, with or without air cooling assistance, different amounts of oil can be used to act as a lubricant and a coolant fluid in the power engine, 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 of oil required to lubricate and cool the power engine. In some embodiments, the amount of oil or liquid used in relation to cooling can be determined based on the amount of thermal mass required for heat transfer of the components driving the electric propulsion system. As has been disclosed herein, the power engine can have different primary functions, such as being used only for lifting and landing and thus only in one orientation, or being used during all flight phases such as lifting, landing, and in-flight maneuvers. An engine used during all flight phases can experience various orientations throughout the flight and may include more lubricant and coolant than an engine used only in one orientation. Therefore, all engines on an aircraft may not contain the same amount of lubricant and coolant. For example, a lift and landing engine may only require less than one quart of oil, while an engine operating during all flight phases may require more than one quart of oil. In some embodiments, the amount of oil or liquid used for cooling can be an appropriate amount to provide sufficient thermal mass to drive heat transfer of the 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 prescribe bounds on the amount of lubricant and coolant that can be used in a power engine.

[0125] Some embodiments may use oil to lubricate and cool an electric engine. Such embodiments may require an additional volume of oil. In such embodiments, the additional oil may allow for the removal of conventional components that may 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. Thus, in embodiments that use a single fluid (such as oil) for lubrication and cooling, there will be an increase in oil, but only one heat exchanger will be required, so the mass of the overall system may be reduced due to the use of fewer heat exchangers and potentially no other components, and there may be a more attractive drag profile. Additionally, 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 issues traveling throughout the engine, using one substance to lubricate and cool the engine can improve the efficiency of the system.

[0126] Some embodiments of an electric engine may include various components for monitoring a combustible fluid and for preventing combustible materials from entering certain sections of the electric engine. Some embodiments may include an electric engine having a wet zone 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 engine oil within a motor-gearbox housing. Embodiments of the motor-gearbox housing may use a breather to equalize internal and external pressures. Embodiments of the breather may include a breather that protrudes above nearby design features to prevent external fluids from inadvertently entering. Some embodiments may include a breather having a screen and a circuitous entry path to prevent external debris from entering. Embodiments may include a viewing window present on both an inclined electric engine and a lift electric engine to check for overfilling or underfilling of oil during maintenance.

[0127] Some embodiments of an electric engine can include active protection features in a front electric engine and a tail electric engine, such as monitoring the vibration and internal temperature of the entire engine, such as oil temperature, stator winding kit 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 of the entire engine as needed. Such monitoring can be accomplished using various sensors located throughout the electric propulsion system and the aircraft. Embodiments can include vibration limits based on known failure points or resonances of components and over-temperature limits based on known failure temperatures and operating limits related to the autoignition temperature of fluids. In some embodiments, the various sensors for monitoring the operating conditions of the entire engine can report the operating conditions to a flight control system. Some embodiments can 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 can act in response to detecting an operating condition to reduce the amount of power directed to the electric propulsion system. Some embodiments can include reducing the amount of power to the electric propulsion system to reduce mechanical wear or frictional sparks caused by vibration, and / or reducing power in an attempt to lower the temperature of components present within the electric propulsion system. Additionally, some embodiments can include reducing the power to the electric propulsion system in the event that the detected efficiency of the inverter is less than a target efficiency. In some embodiments, for example, in the case where there are twelve electric propulsion systems within an aircraft, the flight control system can be used to reduce the power to or terminate the power to a single electric propulsion system while increasing the 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 can establish various thresholds of operating conditions corresponding to the reduction or increase of power to the electric propulsion system.

[0128] Some embodiments can include a high-voltage power system that can have a fuse at a high-voltage battery terminal, which can quickly and irreversibly disconnect the engine electrical connection to mitigate and avoid overcurrent events. Such overcurrent protection can be activated when the current consumption of the electric engine is greater than the overcurrent operation. Thus, in some embodiments, a fault condition that results in an overcurrent may only result in transient overheating, arcing, or spark faults. Some embodiments can include a fire threat characterization test ignition source that can be selected to be a more severe ignition source 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 faulty phase and / or continuously monitor the input DC voltage, and will apply protection actions to keep the voltage below the overvoltage operating limit.

[0129] During takeoff, landing, hovering, and cruising, the motors and associated control components of a VTOL aircraft can generate heat. The heat must be dissipated to prevent degradation or damage to the motors, control components, and other elements of the VTOL aircraft. For some types of VTOL aircraft, such as electric VTOL (eVTOL) aircraft, thermal control is also important for maintaining optimal energy efficiency of components powered by, for example, batteries.

[0130] Some elements 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 turned off during cruising. Thus, such lift propellers can generate high heat loads during takeoff, landing, and hovering and little or no heat during cruising.

[0131] B. Example Electric Propulsion System Embodiments

[0132] As described herein, embodiments of an electric engine may include an inverter assembly, a gearbox assembly, and an electric motor assembly or various combinations thereof. In some embodiments, the inverter assembly, the gearbox assembly, and the electric motor assembly may be substantially aligned along a central axis of the electric engine. As disclosed herein, these assemblies or combinations thereof may be substantially aligned along an axis by sharing a common axis or having parallel axes, the parallel axes being less than or equal to 5% of the outer diameter of the component having the largest diameter from each other. For example, the inverter assembly, the gearbox assembly, and the electric motor assembly may be substantially aligned along the 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 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 although certain components of the electric propulsion system may be shown as adjacent to other components, all adjacent configurations may exist. For example, the gearbox assembly may be shown adjacent to the inverter assembly and the electric motor assembly. Additionally, in some embodiments, the inverter assembly may be adjacent to the gearbox assembly and the electric motor assembly. Some embodiments may include the electric motor assembly adjacent to the gearbox assembly and the inverter assembly.

[0133] In some embodiments, each of the inverter assembly, the gearbox assembly, and the electric motor assembly may be adjacent to at least one of the other assemblies. Adjacency may include direct or indirect contact between components including the assemblies or the housings in which the assemblies are located. In some embodiments, the electric engine may include the inverter assembly and the electric motor assembly without a gearbox assembly. Some embodiments of the electric engine may include the electric motor assembly and the gearbox assembly without the inverter assembly, or include the electric motor assembly without the gearbox assembly or the inverter assembly.

[0134] Figures 11A - 11C It is a cross-sectional view of an exemplary electric propulsion system of 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 propelling the aircraft's propeller. The electric engine 1100A can include a motor housing 1102A. The electric engine 1100A can also include an electric motor assembly that includes components such as a stator 1104A, a rotor magnet 1106A, and a rotor 1108A. In some embodiments, the rotor 1108A can be mechanically coupled to a main shaft 1110A such that the main shaft 1110A rotates at a speed equal to the rotational speed of the rotor 1108A. The main shaft 1110A can be mechanically coupled to a shaft flange assembly 1112A. In some embodiments, the shaft flange assembly 1112A can be an anchoring point for the propeller. The electric motor assembly can be substantially aligned along a central axis 1114A.

[0135] In some embodiments, the electric engine can include a gearbox. Figure 11BAn example of an electric power engine is shown. In some embodiments, the electric power engine may include an electric motor assembly and a gearbox assembly that are substantially aligned along an axis. In some embodiments, the electric motor assembly, the gearbox assembly, and the axis may be substantially aligned along axis 1114B. The electric power engine 1100B may include a motor housing 1102B, a stator 1104B, rotor magnets 1106B, and a rotor 1108B. In some embodiments, the rotor 1108B may be mechanically coupled to a main shaft 1110B such that the main shaft 1110B rotates at a speed equal to the speed of the rotor 1108B. The main shaft 1110B may be mechanically coupled to a shaft flange assembly 1112B such that the shaft flange assembly 1112B and the extension through a propeller assembly (not shown) may rotate at a speed equal to the rotational speed of the main shaft 1110B. In some embodiments, the gearbox assembly may provide a gear reduction and change the rotational speed of the main shaft 1110B. For example, the electric power engine 1102B may include a gearbox assembly that includes a sun gear 1116B, planet gears 1118B, a ring gear 1020B, and a planet carrier 1122B. In some embodiments, the sun gear 1116B may be mechanically coupled to the main shaft 1110B such that the sun gear 1116B rotates at a speed equal to the speed of the main shaft 1110B. The sun gear 1116B may engage the planet gears 1118B, which also engage the ring gear 1120B. In this embodiment where the sun gear 1116B rotates, the ring gear 1120B may be fixed to the motor housing 1102B. In some embodiments, the planet gears 1118B may rotate around the sun gear 1116B due to their interaction with the rotating sun gear 1116B and the fixed ring gear 1120B. The planet carrier 1122B may be mechanically coupled to the planet gears 1118B and may rotate at an equal speed. Some embodiments may include a planet carrier 1122B that is mechanically coupled to the main shaft 1110B. In some embodiments, the main shaft 1110B may include multiple phases or multiple layers of the shaft such that portions of the shaft may 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.

[0136] In some embodiments, the electric power engine 1100B may include bearings 1124B, 1126B that are aligned along the main shaft 1110B. Some embodiments may include the inner races of the bearings 1124B, 1126B that are mechanically coupled to the planet carrier and various bearings such as 1124B and 1126B.

[0137] 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 that are substantially aligned along an axis. In some embodiments, the electric motor assembly may be positioned between the gearbox assembly and the shaft flange assembly. The electric propulsion system 1100C may include a motor-gearbox assembly housing 1102C. In some embodiments, the electric propulsion system 1100C may include an electric motor assembly that includes a stator 1104C, rotor magnets 1106C, and a rotor 1108C. The electric propulsion system 1100C may also include a gearbox assembly. In some embodiments, the gearbox assembly may include a sun gear 1116C, planet gears 1118C, a ring gear 1120C, and a planet carrier 1122C. The sun gear 1116C may be engaged with the planet gears 1118C, which may also be engaged with the ring gear 1120C. The sun gear 1116C may be mechanically coupled to the rotor 1106C such that rotation of the rotor 1106C may cause the sun gear 1116C to rotate at the same rotational speed. The planet carrier 1122B may be mechanically coupled to the planet gears 1118C and may rotate at an equal speed. Some embodiments may include a planet carrier 1122C that is mechanically coupled to a main shaft 1110C. The main shaft 1110C may be mechanically coupled to a shaft flange assembly 1112C. The main shaft 1110C may be substantially aligned along a central axis 1114C such that the gearbox assembly and the motor assembly are also substantially aligned along the central axis 1114C. In some embodiments, the electric propulsion system 1100C may include a heat exchanger 1124C that may be used to cool oil or a liquid that cools or lubricates components of the gearbox assembly or the electric motor assembly.

[0138] As described above, the electric propulsion systems 1100A-C are example embodiments. However, it should be understood that while the electric propulsion system 1100A is capable of providing the required thrust to a VTOL aircraft, compared to the electric propulsion systems 1100B and 1100C, the electric propulsion system 1100A may produce a greater drag profile and contribute more mass to the VTOL aircraft. The electric propulsion systems 1100B and 1100C include a gearbox assembly. Thus, the electric propulsion systems 1100B and 1100C have gear reduction, which allows the electric motor assembly and thus the electric propulsion system to have a smaller drag profile and a smaller mass.

[0139] The electric propulsion system 1100B may include a gearbox assembly between the electric motor assembly and the shaft flange assembly. Although such a configuration may require less mass than the electric propulsion system 1100A, it may require more mass than the electric propulsion system 1100C. The electric propulsion system 1100B may include a gearbox assembly such that the input shaft or sun gear travels from the electric motor assembly to the gearbox assembly, and a portion of the output shaft or planet carrier travels from the gearbox assembly to the shaft flange assembly. In some embodiments, the electric propulsion system 1100C may include a sun gear and a main shaft, the sun gear travels from the rotor of the electric motor assembly to the gearbox assembly, the main shaft is coupled to the planet carrier or carrier cover, the main shaft travels through the sun gear, through the electric motor assembly to the shaft flange assembly. Thus, compared with the electric propulsion system 1100B, the electric propulsion system 1100C may include a more compact design, housing and drag profile. This may result in a more efficient drag profile and a more mass-efficient system. In addition, the electric propulsion system 1100B may include a gearbox assembly without a lubrication device, which may limit the operating time of the electric propulsion system. The electric propulsion system 1100C may include a heat exchanger to cool and lubricate parts of the system, including the gearbox assembly. This may result in additional efficiency and long flight range time.

[0140] Figure 49A cross-sectional view of an example electric propulsion system for a VTOL aircraft consistent with the disclosed embodiments is shown. The 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 parts of the system. In some embodiments, the 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, the electric propulsion system 4900 may include a gearbox assembly that includes a sun gear 4906, planet gears 4908, a ring gear 4910, and a planet carrier 4912. The sun gear 4906 may be mechanically coupled to the rotor 4904. The sun gear 4906 may engage the planet gears 4908. The planet gears 4908 may engage the possibly fixed ring gear 4910 such that the planet gears 4908 rotate around the sun gear 4906 against the ring gear 4910. In some embodiments, the planet gears 4908 may include compound planet gears 4908, 4950. The planet carrier 4912 may be mechanically coupled to the planet gears 4908 via a shaft 4914 that may extend from the planet gears 4908 along the 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 the rate 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 the rate of the planet carrier 4912. In some embodiments, the planet gears 4908 may be mechanically coupled to a cover via a shaft such that the cover may rotate at a rate equal to the rate 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 the rate of the main shaft 4918. It should be understood that the planet gears 4908 or the compound planet gears 4908, 4950 may include multiple planet gears that rotate around the sun gear 4906.

[0141] Due to the mechanical coupling as described herein, torque can be transmitted from the rotor 4904 to the sun gear 4906 along path 4930. The sun gear 4906 can transmit torque to the planet gears 4908 along paths 4932 and 4934. The planet gears 4908 and in some embodiments the compound planet gears 4908, 4950 can transmit torque to the carrier along paths 4936 and 4938. The carrier can transmit torque to the main shaft 4918 along path 4940. The main shaft 4918 can transmit torque along its length via path 4944 and transmit torque to the propeller assembly 4920. The propeller assembly 4920 can transmit torque to the propeller via paths 4946 and 4948. It should be understood that the paths discussed above are examples, and all configurations consisting of sending torque away from the propeller to the gearbox assembly and then sending the torque back to the propeller through the gearbox assembly and the electric motor assembly are contemplated.

[0142] In some embodiments, the process of delivering power from an electric engine via a reverse torque path using a gearbox assembly may include driving a planet gear that is mechanically coupled to the rotor of the electric motor assembly. In some embodiments, the planet gear 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 driving a carrier that connects to a shaft extending from the planet gear. The shaft extending from the planet gear may include a shaft aligned along the central axis of the planet gear. Some embodiments may include driving a carrier cover that connects from a shaft extending concentrically from the planet gear to the shaft. Some embodiments may include driving a main shaft. The driving main shaft may include a first portion of the main shaft that drives and is mechanically coupled to the carrier cover, and transmits torque along the main shaft to a second portion of the main shaft that is mechanically coupled to the propeller assembly. Some embodiments may include a heat exchanger as described herein that can use various amounts of oil to cool the gearbox assembly, and the amounts of oil may include 1 quart, 1.5 quarts, 2 quarts, 2.5 quarts, 3 quarts, or 5 quarts.

[0143] In some embodiments, the gearbox assembly may include multiple sets of gearboxes. For example, in some embodiments, the output of the gearbox assembly can be fed into another gearbox assembly to achieve greater gear reduction. Such embodiments may include at least one sun gear, at least one set of planet gears, at least one ring gear, and at least one carrier. The gearbox may have common gears, such as a common sun gear, a common set of planet gears, and a common ring gear. The embodiments discussed herein can be modified to include multiple sets of gearboxes.

[0144] Figure 53A flowchart showing an example process for transmitting torque from an electric motor assembly of a VTOL aircraft 5300 to a propeller assembly, consistent with the disclosed embodiments. Although the block diagrams may be described below in connection with certain implementations presented in other figures, these implementations are provided for illustrative purposes only and are not intended to be limiting of the block diagrams.

[0145] Figure 53 It includes process blocks 5302 to 5312. At block 5302, consistent with the discussion throughout this disclosure, the process for delivering power from an electric engine using a gearbox assembly may include driving a planetary gear that is mechanically coupled to the rotor of an electric motor.

[0146] At block 5304, consistent with the discussion throughout this disclosure, the process for delivering power from an electric engine using a gearbox assembly may include driving a carrier that is connected to at least one shaft that extends concentrically from the planetary gear.

[0147] At block 5306, consistent with the discussion throughout this disclosure, the process for delivering power from an electric engine using a gearbox assembly may include driving a cage cover that is connected to at least one shaft that extends concentrically from the planetary gear in a set of shafts.

[0148] At block 5308, consistent with the discussion throughout this disclosure, the process for delivering power from an electric engine using a gearbox assembly may include driving a main shaft.

[0149] At block 5310, consistent with the discussion throughout this disclosure, the process for delivering power from an electric engine using a gearbox assembly may include driving a first portion of the main shaft that is mechanically coupled to the cage cover.

[0150] At block 5312, consistent with the discussion throughout this disclosure, the 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 that is mechanically coupled to the propeller assembly.

[0151] Figures 12A - 12D Is an illustration and block diagram of an example electric propulsion system for a VTOL aircraft, consistent with the disclosed embodiments.

[0152] As described herein, an electric propulsion system can include an inverter assembly, a gearbox assembly, and an engine assembly. In some embodiments, the electric propulsion system 1200A can include components encapsulated in various housings, the 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 the housings 1202A and 1228A can provide various benefits, including lower mass and a more efficient drag profile, as described herein. Additionally, in some embodiments, the gearbox assembly, the inverter assembly, and / or the electric motor assembly can have a substantially circular profile. As used herein, a profile can be substantially circular, where 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. Further, in some embodiments, the gearbox assembly, the inverter assembly, and the electric motor assembly, or a subgroup of those listed assemblies, can be sized such that the assemblies have substantially equal radii. As used herein, an assembly can have substantially equal radii, where the difference between the radii of two assemblies is less than a threshold amount of the radius of the largest assembly, e.g., 10%. In some embodiments, the profiles of the components that make up the electric propulsion system as described herein can include various polygons, such as hexagons, heptagons, octagons, nonagons, decagons, and additional polygons having more than ten sides.

[0153] The electric propulsion system 1200A can include an electric motor assembly that includes a stator 1204A, rotor magnets 1206A, and a rotor 1208A.

[0154] In some embodiments, an electric motor assembly can interact with a gearbox assembly and, in some embodiments, transfer torque to the gearbox assembly. The electric propulsion system 1200A can include a gearbox assembly that includes a sun gear 1214A, a set of planetary gears 1216A, a planet carrier 1218A, and a carrier cover 1220A. Some embodiments can 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, a shaft 1222A can extend through or from the planetary gears 1216A. In some embodiments, the planet carrier 1218A can receive a first end of the shaft 1222A such that the planet carrier 1218A can rotate at the same rate as the planetary gears 1216A. In some embodiments, the carrier cover 1220A can receive a second end of the shaft 1222A such that the carrier cover 1220A can rotate at the same rate as the planetary gears 1216A. In some embodiments, the planetary gears 1216A, the planet carrier 1218A, and the carrier cover 1220A can be mechanically coupled along the axis of the shaft 1222A.

[0155] In some embodiments, the electric propulsion system 1200A can include a main shaft 1210A that can 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 can be mechanically coupled where there is any direct or indirect connection or coupling between two components. The shaft flange assembly can include a flange that is coupled to the main shaft by a spline connection to receive a torque load from the main shaft and transfer torque to a propeller coupled to the flange. The flange can also be coupled to the main shaft using fasteners, by welding, by brazing, or any other use of components or methods for coupling the main shaft and the flange. In some embodiments, the main shaft and the flange can be machined together to form a single component. In some embodiments, the shaft flange assembly can be a component of a propeller assembly that can include the shaft flange assembly, a propeller, and a spinner. In some embodiments, the shaft flange assembly can also be referred to as a propeller hub.

[0156] 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 that may include a power module 1232A, a gate drive PCBA 1236A, and a control PCBA 1240A. Some embodiments of the inverter assembly of the electric propulsion system 1200A may also include spacers 1238A in the various PCBA. Additionally, some embodiments may include an energy storage device, such as a DC capacitor that may 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 an 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.

[0157] Some embodiments of the inverter assembly of the electric propulsion system 1200A may include guide pins 1242A that extend through each layer of the inverter assembly to stack corresponding inverter assembly components in a stacked configuration. It should be appreciated that the inverter assembly in a stacked configuration along the guide pins 1242A may be beneficial in various design criteria related to VTOL aircraft. For example, the stacked configuration may allow for a more compact packaging of the inverter assembly and may thus help to minimize the mass of the electric propulsion system 1200A and minimize the drag experienced due to the packaging of the electric propulsion system. Additionally, from a manufacturing perspective, the stacked configuration of the inverter assembly may be advantageous because the stacked configuration may allow for tolerances within the individual parts of the inverter assembly. In some embodiments, structural components may be introduced into the inverter assembly to help support the stacked configuration using the loads experienced during the 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 capacitor as well as other components for the inverter assembly and may be made of plastic or other materials capable of supporting the PCBA and other components around it.

[0158] 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 that includes a hot plate 1248A and a bell end cover plate 1250A. The bell end cover plate 1250A may be used to enclose the motor-gearbox assembly housing 1202A. The hot plate 1248A may be used to enclose the inverter assembly housing 1228A. In some embodiments, the separator plate may act as an integral mounting bracket for supporting the heat exchanger 1226A. The heat exchanger 1226A may include, for example, fin-folds 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. The heated oil or other coolant liquid may be circulated through the fins of the heat exchanger 1226A via an internal liquid flow path that may have an inlet and an outlet for the liquid flow path, and the inlet and the outlet may be coupled to the outlet and the inlet of holes or grooves that may be present on the separator plate. In some embodiments, the motor-gearbox housing 1202A may include a reservoir 1212A. The reservoir 1212 may be used to collect the oil or liquid coolant distributed throughout the electric propulsion system 1200A and recycle the oil or liquid coolant.

[0159] In some embodiments, the heat exchanger may be fluidly coupled to the gearbox assembly, the inverter assembly, and / or the electric motor assembly. As used herein, a component or a part thereof may be fluidly coupled, where a liquid flow path from the heat exchanger may interact with, supply liquid to, or engage with the component or a part thereof.

[0160] Figure 12BExemplary schematic diagram showing the configuration of the electric propulsion system 1200B. In some embodiments, the electric propulsion system may include a motor assembly and a gearbox assembly. The electric propulsion system 1200B includes a partition plate 1208B, a motor assembly 1202B, an inverter assembly 1204B, a gearbox assembly 1206B, a heat exchanger 1212B, and a propeller assembly 1210B. In some embodiments, the inverter assembly housing 1216B may enclose the inverter assembly 1204B, and the 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, the oil flow 1218B may have a path from the heat exchanger 1212B to the partition plate 1208B, then to the gearbox assembly 1206B and the motor assembly 1202B, thereby providing cooling and lubrication for the motor assembly 1202B and the gearbox assembly 1206B. The oil flow 1218B may then travel from the motor assembly 1202B back to the heat exchanger 1212B. As described herein, the propeller assembly 1210B may drive the air flow 1220B from the propeller towards the heat exchanger 1212B. The heat exchanger 1212B may transfer heat from the oil flow 1218B to the air flow 1220B. The oil flow 1218B may be cooled and leave the heat exchanger 1212B.

[0161] Figure 12CAn example schematic diagram showing the configuration of a marine propulsion system is shown. In some embodiments, the marine propulsion system 1200C may include a bulkhead 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 the inverter assembly 1204C, and a motor-gearbox housing 1214C may enclose the motor assembly 1202C and the gearbox assembly 1206C. The inverter assembly housing 1216C may be adjacent to the motor-gearbox housing 1214C. In some embodiments, the marine propulsion system 1200C may include an electric motor assembly 1202C positioned between the gearbox assembly 1206C and the inverter assembly 1204C. As described herein, a coolant or lubricant, such as oil, may be distributed throughout the marine propulsion system. For example, an oil flow 1218C may have a path from the heat exchanger 1212C to the bulkhead 1208B, then to the motor assembly 1202C, then to the gearbox assembly 1206C, thereby providing cooling and lubrication for the motor assembly 1202C and the gearbox assembly 1206C. The oil flow 1218C may then travel from the motor assembly 1202C back to the heat exchanger 1212C. As described herein, the propeller assembly 1210C may drive an air flow 1220C from the propeller towards the heat exchanger 1212C. The heat exchanger 1212C may transfer heat from the oil flow 1218C to the air flow 1220C. The oil flow 1218C may be cooled and leave the heat exchanger 1212C.

[0162] Figure 12DAn example schematic diagram showing the configuration of a power propulsion system is presented. In some embodiments, the power propulsion system may include a motor and a propeller assembly. The power propulsion system 1200D may include a partition plate 1208D, a motor assembly 1202D, an inverter assembly 1204D, a heat exchanger 1212D, and a propeller assembly 1210D. In some embodiments, the inverter assembly housing 1216D may enclose the inverter assembly 1204D, and the motor assembly housing 1214D may enclose the motor assembly. The inverter assembly housing 121D may be adjacent to the motor assembly housing 1214D. In some embodiments, the power propulsion system 1200C may include an electric motor assembly 1202C that directly drives a main shaft to provide mechanical shaft power to the propeller assembly 1210C. In such an embodiment, the main shaft may rotate at a speed equal to the speed of the rotor within the electric motor assembly 1202. As described herein, a coolant or lubricant, such as oil, may be distributed throughout the power propulsion system. For example, the oil flow 1218D may have a path from the heat exchanger 1212D to the partition plate 1208D, and then to the motor assembly 1202D, thereby providing cooling and lubrication for the motor assembly 1202D and other components of the power propulsion system 1200D. The oil flow 1218D may then travel back from the motor assembly 1202D to the heat exchanger 1212D. As described herein, the propeller assembly 1210D may drive the air flow 1220D from the propeller towards the heat exchanger 1212D. The heat exchanger 1212D may transfer heat from the oil flow 1218D to the air flow 1220D. The oil flow 1218D may be cooled and leave the heat exchanger 1212D.

[0163] Figure 13 is an illustration of an exploded view of an example power propulsion system of a VTOL aircraft consistent with the disclosed embodiments. The power engine 1300 may include an inverter assembly 1304, a bell 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, the inverter assembly 1304 may be adjacent to a gearbox assembly. The gearbox assembly may include a bell end cap assembly 1306 and a main shaft assembly 1308. In some embodiments, the gearbox assembly may be adjacent to an electric motor assembly. The electric motor assembly may include a rotor 1310 and a stator housing 1312. In some embodiments, the components of the power propulsion system may be substantially aligned along an axis. In some embodiments, the main shaft may represent the central axis along which the components of the power propulsion system 1300 may be substantially aligned. In alternative embodiments, the order of the inverter assembly, the gearbox assembly, and the motor assembly may be rearranged such that different power propulsion system components are adjacent to each other, as described herein. The housing of the inverter assembly 1304 may be fixed to the heat plate of the inverter assembly by screws 1302. In some embodiments, fasteners 1316 may fix the power engine 1300 to the boom of the aircraft.

[0164] As described herein, embodiments of an electric powerplant may include an electric motor assembly. Figure 14 FIG. is an illustration of an exploded view of an exemplary electric motor assembly of a VTOL aircraft that is consistent with the disclosed embodiments. The 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, the stator assembly 1402 may include permanent magnets. The stator assembly 1402 may include a stator core 1404 and a wire winding 1406. In some embodiments, the wire winding 1406 may be constructed of copper. The stator assembly 1402 may also include a bus bar 1408. As an example, the bus bar 1408 may be electrically coupled to the stator assembly 1402 and facilitate the electrical conduction of current. The electric motor 1400 may include various bearings, including a bearing retainer 1412 and a roller bearing 1414. The bearing retainer 1412, the roller bearing 1414, and the shaft seal 1416 may be substantially aligned along a central axis. In some embodiments, the bearing retainer 1412 may function as a cooling oil manifold to facilitate cooling. In some embodiments, the roller bearing 1414 may include a spherical shape. The electric motor 1400 may include bearing screws 1410. The bearing screws 1410 may fasten the bearing retainer 1414 to various components of the electric motor 1400, including fastening to the roller bearing 1414. In some embodiments, a stator housing 1418 may enclose the stator assembly 1402, the roller bearing 1414, the bearing retainer 1412, the shaft seal 1416, and the bearing screws 1410. The stator housing 1418 may have an interference fit or a press fit with the stator assembly 1402. For example, the stator housing 1418 may have a press fit with the stator laminations. In some embodiments, the stator housing 1418 may have a thermal interference fit with the stator assembly 1402. As an example, the stator housing 1418 may be a common housing that encapsulates the components of the stator 1400, thereby providing advantages including reduced mass and elimination of tubes, hoses, and other connectors. In some embodiments, the stator housing 1418 may include a reservoir 1420 for collecting liquids for cooling or lubricating the electric propulsion system, as described herein. Additionally, in some embodiments, additional components of the electric propulsion system may reside within the stator housing to provide further mass reduction.

[0165] Figures 15A - 15C FIG. is an illustration of a stator assembly of a VTOL aircraft that is consistent with the disclosed embodiments. Figure 15A A view of the stator core is shown. In some embodiments, the stator 1500A may include a wound stator assembly 1502A and a copper winding 1504A. Figure 15B Another view of the stator core 1500B is shown. The laminations 1502B may separate the copper winding 1504B. Figure 15CDepicts an example of a stator slot. By way of example, the stator core 1500C may include a copper winding 1506C, which may be received within the stator iron core 1502C. A slot liner 1508C may separate the copper winding 1506C from the stator iron core 1502C. The slot liner 1508C may provide electrical insulation. The profile of the stator iron core 1502C may mate with a slot wedge 1504C, where the slot wedge 1504C is located above the copper winding 1506C. The slot wedge 1504C may hold the copper winding 1506C in place within the stator iron core 1502C. In some embodiments, the stator laminations may be formed by the stator iron core 1502C. The stator laminations may help insulate the core and reduce eddy currents or losses. In some embodiments, the stator assembly may include an oil-filled cavity that is positioned around the stator to aid in cooling. Such a cavity may be fluidly coupled to a heat exchanger as described herein.

[0166] Figures 16A - 16C Have like reference numerals and refer to like elements of rotor assemblies 1600A and 1600B. Accordingly, like design considerations and configurations may be considered throughout the embodiments.

[0167] Embodiments of the disclosed electric motor assembly may include a rotor. In some embodiments, an electromagnetic field generated by a stator in the electric motor assembly may drive rotation of the rotor about an axis.

[0168] Figures 16A - 16B Is an illustration of an exploded view and a cross-section of a rotor assembly of a VTOL aircraft that is consistent with the disclosed embodiments. Figure 16AShows an example exploded view of a rotor. The rotor assembly 1600A may include a rotor 1602A, which includes a rotor hub 1604A. In some embodiments, the rotor hub 1604A may be machined and formed from aluminum. The rotor 1602A may include laminations 1606A and a Halbach array 1608A. The laminations 1606A may have a thermal interference fit with the rotor hub 1604A. The rotor 1602A may be surrounded by a rotor outer package 1610A. In some embodiments, the rotor outer package 1610A may be made of carbon fiber. The Halbach array 1608A may include magnets. The rotor outer package 1610A may be adjacent to the Halbach array 1608A and apply pressure on the magnets of the Halbach array 1608A. In some embodiments, the rotor 1602A may include a hollow portion. The hollow portion of the rotor may allow various motor assembly or gearbox assembly components to travel through the rotor 1602A, enabling configurations where components can be coupled to the rotor 1602A. In some embodiments, an electric motor assembly may be mechanically coupled to a gearbox assembly. The disclosed embodiments include various means for mating the rotor and the sun gear. The rotor 1602A may be mechanically coupled to a sun gear 1612A and concentrically fixed by various means for connecting and aligning the components. The rotor 1602A may be mechanically coupled to the sun gear 1612A by various fastening means. As an example, the rotor 1602A may be fastened to the sun gear 1612A using a lock nut 1620A, a dowel pin, or a screw 1622A. A bearing 1616A may have an interference fit with the rotor assembly 1602A and the sun gear 1612A. In some embodiments, the sun gear 1612A may include gear teeth 1614A, which may be used in a gearbox assembly as described herein. The sun gear 1612A may include a hollow center. In some embodiments, the sun gear 1612A may be mechanically coupled to an oil jacket 1618A, which may use centrifugal force during rotation to assist in distributing cooling or lubricating liquid.

[0169] Figure 16BShows an additional view of the rotor assembly 1600B. As described herein, the rotor 1602B may include a rotor hub 1604B, a stack of laminations 1606B, and a Halbach array 1608B. The rotor outer packaging 1610B may be adjacent to the Halbach array 1608B and surround the stator assembly 1602B. The bearing 1616A may include an inner race and an outer race. In some embodiments, the sun gear 1612B may be mechanically coupled to the rotor 1602B. Some embodiments may include mechanically coupling the sun gear 1612B and the rotor 1602B using screws 1622B. The bearing 1616B may assist in mechanically coupling the rotor 1602B and the sun gear 1612B by providing an interference fit. In some embodiments, the main shaft of the electric power engine assembly may travel through the bearing 1616B and thus through the sun gear 1612B and the rotor 1602B. Additionally, some embodiments may include the bearing 1616B for supporting the rotor 1602B and the rotor hub 1604A and any loads experienced by the rotor 1602B or the rotor hub 1604B during normal operation. In some embodiments, the inner surface of the rotor assembly 1602B may have a diameter equal to the outer race of the bearing 1616B. The sun gear 1612B may include gear teeth 1614B. In some embodiments, the rotor assembly 1612B and the sun gear 1612B may be substantially aligned along the central axis 1624B.

[0170] As described herein, the disclosed embodiments of the 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, the electric propulsion system may include the rotor of the gearbox assembly and the electric motor assembly, both of which can apply a load on the shaft. For example, the gyroscopic effect caused by the rotating rotor being in motion may apply a moment load. The moment load may be on the central path of the shaft. The gearbox assembly that may include planetary gears may share torque through several paths, and thus the sharing of the load may depend on the tolerances of the components within the electric power engine. Therefore, a solution that supports the load and resists the moment formed by the generated torque while maintaining a low mass and drag profile is advantageous.

[0171] Figure 54 is a schematic illustration of a partial cross-sectional view of an example electric motor assembly. As Figure 54 shown, the electric motor assembly 5400 may include a housing 5402 that encloses a sealed environment 5404, where the rotor 5406 and the stator 5408 (and the magnet 5418 that is part of the stator 5408) are both within the housing 5402. In some embodiments, the electric motor assembly 5404 may be positioned such that the propeller assembly it drives ( Figure 54The (not shown in the figure) can drive air towards it to provide a cooling effect. Therefore, the side 5410 facing the propeller assembly (i.e., facing the air flow driven by the propeller assembly) is the cold side; 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.

[0172] In some embodiments, as Figure 54 shown, the rotor 5406 can generate an air movement 5416 from the cold side 5410 towards the hot side 5412 within a sealed environment 5404 enclosed by the housing 5402 to provide a cooling effect to one or more components outside the housing 5402 on the hot side 5412. In other words, the heat generated by one or more components outside 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.

[0173] In some embodiments, the air movement 5416 can also provide a cooling effect to dissipate the heat generated by the magnet 5418 inside the housing 5402. The air movement 5416 promotes the heat dissipation of the magnet 5418 through the cooling effect generated by the air flow 5414.

[0174] Figures 55A - 55B is a diagram of an example internal surface that is part of the rotor hub and part of the end plate. In some embodiments, the internal surfaces (e.g., 5502A, 5502B) of the rotor hub 5500A and the end plate 5500B can respectively have fins (e.g., 5504A, 5504B) to make the rotor more effectively generate an air movement (e.g., 5416) inside the housing 5402 ( Figures 55A - 55B not shown in the figure) by defining an air path with less air resistance.

[0175] As Figure 55A shown, the fins 5504A on the inside 5502A of the rotor hub 5500A can have different heights and shapes. In this example embodiment, the fins of different shapes are all straight (i.e., flat), but they can also have different geometries.

[0176] As Figure 55B shown, the fins 5504B on the inside 5502B of the end plate 5500B all have the same height. In this example embodiment, the height of the fins 5504B can be approximately 12 mm. Generally, this height can be between approximately 5 mm and 20 mm.

[0177] In this exemplary embodiment, the fins on the rotor hub and the stator may have a first gap. The first gap may be between 0.4 mm and 1.2 mm, or approximately 0.6 mm. The fins on the end plate and the rotor may have a second gap. The second gap may be between 0.4 mm and 1.2 mm, or approximately 0.6 mm. The first gap and the second gap may be determined such that the air inside the sealed environment (e.g., the housing) is pressurized through the void formed between the fins and the rotor, and the air is guided from the edge on the hot side towards the center of the motor on the hot side and then towards the center of the motor on the cold side.

[0178] Figure 55C is a simulation result of the air velocity and pressure distribution inside the housing (e.g., Figure 54 housing 5402). In the Figure 55C example shown, the white space represents the solid motor structure where there is no air. The different colors in the left figure represent the differences in air velocity, showing that the air velocity between the rotor 5406 and the motor spindle 5502B is significantly higher on the left side, thus showing that the air inside the sealed environment is agitated. In the middle figure, the different colors show the internal pressure distribution inside the 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 side and the hot side of the housing, thereby enhancing the cooling effect on the motor.

[0179] Figure 55D is a set of example internal surfaces of the end plate consistent with the disclosed embodiments. The fins on the end plate and the rotor may have different geometries and arrangements, and the geometries and arrangements can be optimized considering different design factors and operating parameters, such as revolutions per minute (RPM), gap, motor size, weight, rotational mass, and other design and operating parameters that may be affected by the fin design and shape.

[0180] In some embodiments, the direction of the air flow may be reversed. For example, instead of moving the air towards the center on the hot side, the air may alternatively move from the center to the periphery on the hot side. In such an embodiment, the air flow at the motor center 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 the fin shapes are provided, but the examples shown are not intended to limit the scope of potential fin designs and shapes. The fin shapes can be optimized or modified according to the specific needs of the system and based on experimental and simulation evaluations.

[0181] The disclosed embodiments may include a bearing system that includes a rotor that uses 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. The bearing system 1600C may include a rotor hub 1604C, a sun gear 1612C, and a main shaft 1626C. The bearing system 1600C may use various types of bearings to reduce the loads experienced by components that are substantially aligned along the axis. As described herein, the rotor assembly may be mechanically coupled to the sun gear 1612C. The main shaft 1626C may include an outer surface 1628C that may abut a shaft flange assembly 1630C. The shaft flange 1630C may abut a bearing 1634C. The bearing 1634C may have an inner race mechanically coupled to the main shaft 1626C and an outer race mechanically coupled to the rotor hub 1630C. In some embodiments, the bearing 1634C may have an inner race mechanically coupled to the main shaft 1626C and an outer race mechanically coupled to the rotor hub 1630C and the sun gear 1612C. In some embodiments, the bearing 1634C may abut both the rotor hub 1604C and the sun gear 1612C. The bearing 1634C may be mechanically coupled to the shaft flange assembly 1630C. As described herein, the bearing 1634C may support the rotor hub 1604C and support the loads from the rotor hub 1604C. For example, the rotation and movement of the rotor hub 1604 may cause a gyroscopic effect that applies a load. The bearing 1634C may support the loads, including radial or axial rotor loads. The bearing 1634C may allow the sun gear 1612C to float, which may allow for the absorption of load variations. In some embodiments, the bearing 1634C may be a rolling element bearing. For example, the bearing 1634C may include rolling elements 1616C that may be submerged in a lubricant 1632C within the bearing 1634C. In some embodiments, the lubricant 1632C may include oil. Other bearings that are capable of supporting loads and high-speed rotation may be used, such as ball bearings or deep groove ball bearings.

[0182] Embodiments of the disclosed electric propulsion system may also include a guide system for bearings that support the rotor. As disclosed herein, the electric propulsion system may include bearings that support the sun gear and the rotor. The bearings that support the rotor may include bearings 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 may guide sun gear 1612C and rotor hub 1604C by guiding the alignment or mating of multiple components. For example, the 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 fix sun gear 1612C and rotor hub 1604C. The first edge of sun gear 1612C and the first edge of rotor hub 1604C may abut and meet on the outer race of bearing 1634C. Bearing 1634C may affect the diameters of the sun gear 1612C and the rotor. The diameter of the outer race of bearing 1634C may 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 may be concentrically fixed. Sun gear 1612C may have a diameter equal to the inner diameter of the rotor. In some embodiments, the guide system for the bearings may include shoulders. The shoulders may be edges of one component that abut one or more edges of another component. For example, the shoulders may include portions of sun gear 1640B that abut one or more edges of bearing 1616B, and portions of rotor hub 1642B that abut one or more edges of bearing 1616B. The shoulders may mate to limit the movement of the bearing. For example, the shoulders may mate to limit the movement of bearing 1616B in the axial direction of the shaft or along axis 1624B. In some embodiments, the guide may include shoulders to radially capture the bearing. The guide system may reduce mass and prevent the need for additional materials. In some embodiments, dowel pins may be used to guide the sun gear and the rotor.

[0183] In some embodiments, the rotor bearing system may further include a bearing for resisting moment loads and allowing floating to compensate for tolerances in the gearbox. The rotor bearing system may include a hydrodynamic bearing. The hydrodynamic bearing can resist or counteract 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 position 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 at a location where the main shaft 1626C has a shoulder or cavity, as described herein. For example, the hydrodynamic bearing may include a fluid between the sun gear 1612C and the shoulder or cavity of the main shaft 1626C. In some embodiments, the size or shape of the shoulder may be determined by the characteristics of the rotor. For example, the shoulder may have a depth and width that may be determined by the characteristics of the rotor, including mass, speed, rate of change, and changes in the axis or loads (including gyroscopic, axial, and radial loads or moments). The hydrodynamic bearing may include a fluid, such as oil, located between the outer surface 1628C of the sun gear 1612C and the main shaft 1626C. The hydrodynamic bearing can help resist the moment loads experienced by the sun gear 1612C. For example, the hydrodynamic bearing can apply a restoring force to resist gyroscopic loads. In some embodiments, the hydrodynamic bearing may include oil. The hydrodynamic bearing can allow the sun gear 1612C or the ring gear to float. The hydrodynamic bearing can allow for tolerances within various components of the electric propulsion system. The hydrodynamic bearing may include the same liquid used for lubrication and cooling throughout the electric propulsion system, such as oil. As discussed herein, using a single liquid for the hydrodynamic bearing, cooling, and lubrication can provide the advantages of reducing mass and decreasing the size of various components.

[0184] Figure 50 Perspective view of an example rotor of a VTOL aircraft consistent with the disclosed embodiments. In some embodiments, the rotor 5000 may include a rotor hub 5002. The rotor hub 5002 may include a layer 5004 and a layer 5012. The rotor 5000 may be manufactured to include the rotor hub 5002 and the layers 5004 and 5012. The rotor 5000 may be made of aluminum, steel, or other materials capable of transmitting torque to the propeller assembly. The rotor 5000 may be machined from a single piece of material using various types of machines, such as lathes, computer numerical control (“CNC”) machines, or any other type of machine capable of machining the rotor. The layers 5004, 5012 may be present on the rotor 5000 to be sacrificed later to balance the rotor 5000. During the machining of the rotor, the rotor 5000 may be unbalanced due to manufacturing constraints, such as the precision of the machine. In some embodiments, balancing the rotor 5000 may include adding mass or removing mass from the rotor.

[0185] In some embodiments, the manufacturing constraints of the various regions of rotor 5000 can determine the quality of layers 5004, 5012. For example, layers 5004, 5012 can have a certain minimum or maximum quality determined by the manufacturing equipment and the steps for producing the rotor. Layers 5004, 5012 can contain a certain quality of rotor material, and the size of the rotor material can counteract the manufacturing constraints present in each region of the rotor. In some embodiments, the quality of layers 5004, 5012 to be removed later when balancing the rotor can be determined based on the precision of the machines that manufacture the various parts of the rotor. For example, in some embodiments, one or more machines can manufacture parts of the rotor with a precision of + / - 5% of the target quality of the parts of the rotor. In such an example, the rotor can include layers 5004, 5012, and the total quality of the layers contains enough quality to be removed when balancing the rotor, where the quality falls within a composite deviation quality range due to the precision of the machines that manufacture the rotor. In some embodiments, the material properties of layers 5004, 5012 can include aluminum, steel, or another material that can accommodate the manufacturing precision of the machines that manufacture parts of the rotor. In some embodiments, depending on design considerations, system requirements, and manufacturing constraints, the thickness or width and depth of layers 5004, 5012 can be thicker or thinner. In some embodiments, the various layers can have substantially similar widths and depths, where substantially similar includes a difference in the width or depth of the layers that is less than 5% of the larger width or depth.

[0186] In some embodiments, rotor 5000 can include multiple layers 5004, 5012. For example, rotor 5000 can include layer 5004 on the inner surface or the edge of the circumference of rotor hub 5002, as Figure 50 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 inner surface of the rotor, or layers 5004, 5012 in any other configuration along rotor hub 5002. In some embodiments, layers 5004, 5012 can be disposed along the inner surface of the rotor at a certain distance from the edge of the rotor. Some embodiments can include layers at substantially similar distances from the edge of the rotor. As used herein, substantially similar distances can include a distance variation that is less than 5% of the larger distance.

[0187] In some embodiments, layers 5004, 5012 may include grooves 5006 that form part 5008. In some embodiments, these parts 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 aid in cooling or lubricating components. Thus, grooves 5006 may be used to allow oil or liquid to pass through layers 5004, 5012 such that the oil or liquid does not accumulate within layers 5004, 5012 and returns to a reservoir or other storage as described herein. In some embodiments, multiple layers 5004 may be aligned such that the grooves 5006 of each layer are aligned.

[0188] In some embodiments, rotor 5000 may include through-holes 5010. In some embodiments, rotor 5000 may be machined with through-holes 5010. Those of ordinary skill in the art will understand that mass is a critical 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 that are created by a machining process, a laser machining process, or any other process that removes mass from the rotor. Through-holes 5010 may reduce the mass of rotor 5000 by removing portions of the material (e.g., aluminum) of rotor hub 5002. In some embodiments, the through-holes may also serve as connection points for the sun gear as described above.

[0189] In some embodiments, the electric motor assembly of a VTOL aircraft as described herein may generate torque by rotating rotor 5000 at a high rotational rate. At high rotational speeds, an unbalanced rotor having a rotational axis that is not aligned with the centroid of the rotor will experience a high level of undesirable vibration and noise. An unbalanced rotor may be caused by production tolerances in the manufacturing process. For example, magnets present in the rotor assembly may not have uniform mass and may not be placed uniformly along the rotor or stack. Additionally, in some embodiments, through-holes 5010 may be created 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 may be a critical design criterion in VTOL aircraft, and thus, 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 may be used that balances the rotor while achieving a maximum reduction in rotor mass.

[0190] Some of the disclosed embodiments may include an improved process for balancing the rotor of an electric motor assembly. Some embodiments may include identifying the axis of rotation of the rotor. As discussed herein, the rotor 5000 may include layers 5004, 5012. In some embodiments, the layers 5004, 5012 serve as sacrificial layers, which may be machined to be integral with the rotor so as to be later removed from the rotor 5000 to effect rotor balance. In some embodiments, the portion 5008 may serve as a sacrificial portion, which may be machined to be integral with the rotor so as to be later removed from the rotor 5000 to effect rotor balance. It should be recognized that removable layers and portions added to the rotor after rotor manufacture by fasteners, glue, or similar materials may serve a purpose similar to that of sacrificial layers or sacrificial portions. However, the removable layers and portions will require additional mass in the form of attachments, which is detrimental to the overall efficiency of the VTOL. In addition, the attachments (e.g., fasteners and adhesives) for the removable layers and portions are at risk of failure during flight and may damage other components of the electric propulsion system.

[0191] Some embodiments of the process for balancing the rotor may include determining the imbalance present in the rotor by rotating the rotor about the 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 the rotor, placing reflective stickers on the rotor, or any other method of creating a unique mark on the rotor. In some embodiments, rotating the rotor may include using a machine to rotate the rotor about the axis of rotation at a speed less than the operating speed, such as a dynamic balancer. The operating speed may include the expected rotational rate of the rotor at any stage of flight. In some embodiments, rotating the rotor may include rotating the rotor at a speed less than the first resonance of the rotor. Detecting the phase of the imbalance may include using a machine to monitor the unique mark as the rotor rotates. In some embodiments, the machine used to monitor the rotation of the rotor may be the same machine that rotates the rotor. The machine is capable of tracking the unique mark and calculating the displacement of the mark during rotation, thereby indicating an unbalanced rotor. In some embodiments, detecting the phase of the imbalance may further include receiving signals from an encoder or accelerometer during rotation, or downloading after rotation, to identify the position of the rotor or the forces experienced by the rotor at the location where the encoder, accelerometer, or similar sensor is positioned on the rotor.

[0192] Some embodiments of a process for balancing a rotor may include calculating the amount of mass to be added or removed at positions 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 be added or removed and the location at which the mass is 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 and detects the imbalance, or may be a separate machine. In some embodiments, the mass added or removed at positions along layers 5004, 5012 may change the center of mass of the rotor such that it coincides with the axis of rotation of the rotor. In some embodiments, the rotor may include a plurality of layers 5004, 5012 disposed along the inner surface of the rotor at a distance from the edge of the rotor. Thus, balancing the rotor may include adding or removing mass along one or more layers to balance the rotor in one or more planes of the rotor.

[0193] 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 any amount from 50% to 100% of the volume of layers 5004, 5012. Removing from 50% to 100% of the volume of layers 5004, 5012 may reduce the mass of the rotor. In some embodiments, layers 5004, 5012 may exist only as sacrificial material for balancing the rotor. Layers 5004, 5012 may be formed integrally with the rotor to provide integrated rotor balancing material that is removed rather than added. By removing the sacrificial rotor material, the balancing process will not require the use of adhesives or fastening methods to add balancing weights.

[0194] In some embodiments, after removing material from layers 5004, 5012, the amount of layer mass remaining on the rotor may be the amount of minimum mass required to balance the rotor, and thus may result in a balanced rotor with a minimum mass. Removing most of the volume of the layers present on the rotor may allow the mass of the rotor to be reduced such that the rotor does not contain extra material. For example, if a rotor with layers 5004, 5012 is determined to be balanced without removing any portion of layers 5004, 5012, then 100% of the volume including layers 5004, 5012 may be machined away because no mass from the layers is required to balance the rotor. In some embodiments, it may be determined that 3% of the volume of layer 5004 will be required when balancing the rotor. In such an example, 100% of layer 5012 may be removed and 97% of layer 5004 may be removed to balance the rotor.

[0195] Some embodiments may include using a specific machine to remove the volume of layers 5004, 5012 when balancing the rotor. Some embodiments may include using a machine capable of machining the volume of layers 5004, 5012 with an accuracy of 0.01% to 0.1% of the layer. In some embodiments, the machine can be used to machine off the volume of the layer with a resolution of less than 5 microns, such as a lathe or a CNC machine. In such embodiments, using a machine capable of such accuracy can achieve the advantage of minimizing the mass of the balanced rotor. Some embodiments may include using various types of machines when removing the layer, such as removing most of the mass to be removed by a method with lower accuracy than the method of removing the remaining amount of the mass to be removed.

[0196] Some embodiments may include calculating the amount of mass to be added to the balanced rotor at positions along layers 5004, 5012, and the balanced rotor may include machining off the volume of layers 5004, 5012 such that only the remaining amount of layer mass is a portion of layers 5004, 5012 that is equal to the calculated amount of mass to be added and present at the calculated positions. In some embodiments, the amount of mass calculated to be removed from the balanced rotor at positions along layers 5004, 5012 may include machining off the volume of layers 5004, 5012 such that only the remaining amount of layer mass is a portion of layers 5004, 5012 that is equal to the calculated amount of mass to be removed and present at a position on the opposite side of the layer from the calculated position.

[0197] 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, portions 5008 may be defined by grooves 5006. Some embodiments may include removing all of portions 5008 or any partial amount of portions 5008. In some embodiments, removing portions 5008 may include calculating the maximum amount of portions to be removed to achieve a balanced rotor. In some embodiments, the number k of portions to be removed may include an amount of portions such that if any additional mass is to be removed from the rotor after removing k portions, the rotor may never be able to be balanced.

[0198] Figure 51 A flowchart of 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 implementations presented in other figures, these implementations are provided for illustrative purposes only and are not intended to be used as a limitation on the block diagrams.

[0199] Figure 51Includes process blocks 5102 through 5108. At block 5102, consistent with the discussion throughout this disclosure, the process for balancing the rotor of an electric propulsion system's electric motor may include identifying the axis of rotation of the rotor, where the rotor includes a sacrificial layer having a mass M formed along the circumference of the rotor.

[0200] At block 5104, consistent with the discussion throughout this disclosure, the process for balancing the rotor of an electric propulsion system's electric motor may include determining the imbalance present in the rotor by rotating the rotor about the axis of rotation.

[0201] At block 5106, consistent with the discussion throughout this disclosure, the process for balancing the rotor of an electric propulsion system's electric motor may include calculating the amount of mass k to be added at a position p along the sacrificial layer such that the center of mass of the rotor coincides with the axis of rotation of the rotor.

[0202] At block 5108, consistent with the discussion throughout this disclosure, the process for balancing the rotor of an electric propulsion system's electric motor may include removing an amount of mass r from the sacrificial layer such that an amount of remaining mass n exists along the circumference of the rotor.

[0203] As discussed herein, the rotor assembly of an electric motor assembly may include a rotor mechanically coupled to a sun gear. Similar to the discussion above regarding balancing the rotor, it may be advantageous to balance the rotor assembly to avoid unwanted vibrations and noise during normal operation. Due to manufacturing tolerances and due to the multiple mating parts throughout the rotor assembly, the rotor assembly may be unbalanced.

[0204] In some embodiments, the process for balancing the rotor assembly may include identifying the axis of rotation of the rotor assembly and rotating the rotor assembly at a speed less than the operating speed. In some embodiments, the rotor assembly may be coupled to a machine 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 the first resonance of the rotor assembly. Some embodiments may include determining the imbalance present in the rotor assembly. Determining the imbalance present in the rotor assembly may include using a machine to identify the phase and magnitude of the imbalance by tracking unique markings (such as reflective stickers or laser-etched markings) on the rotor assembly, or using an electric eye, encoder, accelerometer, or similar components to track the movement of the rotor assembly.

[0205] Some embodiments may include calculating the amount of mass to be added to a rotor assembly to align the center of mass of the rotor assembly with the axis of rotation of the rotor assembly. Calculating the amount of mass and its corresponding location can be done 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 a 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 such that the rotor assembly is balanced. In some embodiments, the amount of mass to be added may include rivets with different material properties and locations.

[0206] Figure 52 Another flowchart illustrates an example process for balancing a rotor assembly of a VTOL aircraft 5200. While the block diagrams may be described below in conjunction with certain implementations presented in other figures, these implementations are provided for illustrative purposes only and are not intended to be limiting of the block diagrams.

[0207] As Figure 52 shown, the process may begin at block 5202, consistent with the discussion throughout this disclosure, by identifying the axis of rotation of the rotor, where the rotor includes a sacrificial layer having a mass M formed along the circumference of the rotor.

[0208] At block 5204, consistent with the discussion throughout this disclosure, the process for balancing the rotor assembly may proceed to determine the imbalance present in the rotor by rotating the rotor about the axis of rotation.

[0209] At block 5206, consistent with the discussion throughout this disclosure, the process for balancing the rotor assembly of an electric engine of an electric propulsion system may include calculating the amount of mass k to be added at a certain location p along the sacrificial layer to align the center of mass of the rotor with the axis of rotation of the rotor.

[0210] At block 5208, consistent with the discussion throughout this disclosure, the 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 remaining mass n exists along the circumference of the rotor.

[0211] At block 5210, consistent with the discussion throughout this disclosure, the process for balancing the rotor assembly may proceed to identify the axis of rotation of the rotor assembly, where the rotor assembly includes a rotor mechanically coupled to a sun gear.

[0212] In block 5212, consistent with the discussion throughout this disclosure, the process for balancing the rotor assembly can proceed to determining the imbalance present in the rotor assembly by rotating the rotor about the axis of rotation.

[0213] In block 5214, consistent with the discussion throughout this disclosure, the process for balancing the rotor assembly can proceed to calculating the number j of rivets to be added to the rotor assembly to cause the center of mass of the rotor assembly to coincide with the axis of rotation of the rotor assembly.

[0214] In block 5216, consistent with the discussion throughout this disclosure, the process for balancing the rotor assembly of an electric propulsion system may include adding j rivets to the rotor assembly.

[0215] Embodiments of the disclosed electric propulsion system may include a gearbox assembly as described herein. The gearbox may contribute to the gear reduction of the electric propulsion system. As described herein, some embodiments of the electric propulsion system may include a gearbox assembly located between the electric motor assembly and the bell housing assembly. The gearbox assembly may include a main shaft assembly.

[0216] Figure 17Is an exploded view of the main shaft assembly of a VTOL aircraft consistent with the disclosed embodiments. The main shaft assembly 1700 may include a main shaft 1702, a housing cover 1714, planet gears 1704, a pump drive gear 1716, and a planet carrier 1712. The main shaft assembly 1700 may include compound planet gears such that the planet gear 1704 is mechanically coupled to the planet gear 1706. In some embodiments, the shafts 1708 and 1710 may extend from the planet gear 1704. In some embodiments, the shafts 1708 and 1710 may extend from the first planet gear 1704 and the second planet gear 1706, respectively. The planet gear 1704 may engage with a sun gear and an annular gear. In some embodiments, the annular gear may be fixed. In such an embodiment, the planet gear 1704 engaging with the annular gear and the sun gear may rotate around the sun gear. In some embodiments, the planet gear 1706 may engage with the annular gear. In such an embodiment, the planet gear 1704 may engage with the sun gear, while the planet gear 1706 engages with a fixed annular gear, where the sun gear drives the planet gears 1704 and 1706 to rotate around the sun gear. The planet carrier 1712 may be mechanically coupled to the planet gears 1704 and 1706 via the shaft 1710 or the like, such that when the planet gears and thus the corresponding shaft 1710 rotate around the circumference of the sun gear, the planet carrier 1712 rotates at the same speed. The planet carrier 1712 may be mechanically coupled to a plurality of planet gears 1704 and 1706. In some embodiments, the housing cover may be mechanically coupled to the planet gears 1704 and 1706 via the shaft 1708 or the like, such that when the planet gears and thus the corresponding shaft 1708 rotate around the circumference of the sun gear, the housing cover 1714 rotates at the same speed.

[0217] In some embodiments, the main shaft assembly 1700 may include a planet carrier 1712 having bearings 1722 to assist the planet carrier 1712 in receiving the shaft 1710. The bearings 1722 may allow the shaft 1710 to rotate with the planet gears 1704, 1706 while allowing the shaft to be received within the planet carrier 1712. In some embodiments, the housing cover 1714 may have bearings 1718 to assist the housing cover 1714 in receiving the shaft 1708, such that the shaft 1708 can rotate with the planet gears 1704, 1706 while allowing the shaft 1708 to be received within the housing cover 1714. In some embodiments, shims 1720, 1724 may be positioned between the planet gears 1704, 1706 and the housing cover 1714 and the planet carrier 1712, respectively. The shims 1720, 1724 may be designed to account for machine tolerances in the manufacture of components of the entire gearbox assembly or to provide a surface for the planet gears 1704, 1706 to rotate against without damaging the planet carrier 1712 or the housing cover 1714. Some embodiments may include mechanically coupling the planet carrier 1712 and the housing cover 1714 using screws 1728 or similar components.

[0218] In some embodiments, the carrier cover 1712 may be mechanically coupled to the main shaft 1702. In such embodiments, rotation of the main shaft will rotate at the same speed as the carrier cover and thus at the same speed as the planetary gear 1704 or the compound planetary gears 1704 and 1706. In some embodiments, the planet carrier may be mechanically coupled to the main shaft 1702. In such embodiments, rotation of the main shaft will rotate at the same speed as the planet carrier 1712 and thus at the same speed as the planetary gear 1704 or the compound planetary gears 1704 and 1706.

[0219] In some embodiments, the main shaft assembly 1700 may include a pump drive gear 1716. The pump drive gear may be disposed between the planet carrier 1712 and the carrier cover 1716. Additionally, in some embodiments, the pump drive gear 1716 may be disposed among a plurality of planetary gears including the compound planetary gears 1704, 1706. The pump gear driver 1716 may be mechanically coupled to various components present within the gearbox assembly, including the planet carrier 1712, the planetary gears 1704, 1706, or the carrier cover 1714. The pump drive gear 1716 may engage other components (not shown herein) within the power engine assembly to circulate oil or other coolant liquid throughout the liquid flow path as described herein to serve to cool or lubricate the components present within the power engine assembly. For example, the pump drive gear 1716 may engage a pump gear for pumping liquid from a reservoir to a heat exchanger. In such embodiments, the rotational speed of the pump gear driver 1716 may determine the speed at which oil or other liquid circulates throughout the power engine assembly. In some embodiments, the pump drive gear 1716 may be mechanically coupled to the main shaft 1702 such that the pump drive gear rotates at the speed of the main shaft 1702. In some embodiments, the main shaft assembly 1700 may include a dowel pin 1726 or a similar alignment component 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.

[0220] As described herein, an electric motor assembly can drive the rotation of a 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 the planetary gear 1704 or the compound planetary gears 1704 and 1706 to produce an output of the gearbox assembly, the output including a new torque value to be supplied to the propeller assembly. In some embodiments, as described herein, the use of a combination of a sun gear, planetary gears including compound planetary gears, and a ring gear can produce a gear reduction. One of ordinary skill in the art will understand that the gear ratio 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 a VTOL aircraft, as the aircraft may need to apply a specific torque value to the propeller assembly to provide lift for the payload. However, it should be understood that increasing the gear size to produce a greater gear reduction will result in an increase in the drag profile and mass of the electric engine. Thus, the embodiments described herein can provide an optimized electric propulsion system design in terms of drag profile and mass versus payload capacity.

[0221] As described herein, embodiments of the gearbox assembly can include a sun gear. Figure 18 FIG. is an illustration of an example sun gear of a VTOL aircraft consistent with the disclosed embodiments. The sun gear 1800 can be constructed of stainless steel, plastic, or any material capable of contributing to gear reduction. The sun gear 1800 can include teeth 1802 to contribute to gear reduction. Some embodiments can include splined teeth. In some embodiments, the gear teeth 1802 can interact with the planetary gears. The sun gear 1800 can include a hollow center. In some embodiments, components of the gearbox can travel through the hollow portion of the sun gear 1800. The sun gear 1800 can also include through holes 1804 to facilitate fastening the sun gear 1800 to other components of the electric engine. In some embodiments, the sun gear 1800 can be mechanically coupled to other components of the electric engine assembly, such as the rotor or output shaft of the electric motor assembly. Some embodiments can include through holes 1804 that allow such mechanical coupling. In some embodiments, the sun gear 1800 can be fixed and thus can not rotate. In such embodiments, the planetary gears and the ring gear can rotate freely. Some embodiments can include through holes 1804 that are fastened to another component or surface to limit the rotation of the sun gear 1800.

[0222] Embodiments of the gearbox can include a ring gear. Figure 19Illustration of an exemplary annulus gear of a VTOL aircraft consistent with the disclosed embodiments. The annulus gear 1900 may include teeth 1902. The teeth 1902 may engage with one or more planet gears to facilitate gear reduction. The annulus gear 1900 may be fixed or free rotating. A fixed annulus gear may remain stationary, allowing the planet gears to rotate around the sun gear. In some embodiments, the annulus gear may be fixed by coupling it to various components or structures within an electric propulsion system using through holes 1904. In other embodiments, a free annulus gear may rotate around a fixed planet gear or a fixed sun gear. The annulus gear 1900 may include slots 1902 to facilitate fastening or mechanical coupling.

[0223] As described herein, embodiments of a gearbox assembly may include a carrier assembly. Figure 20 Illustration of an exemplary carrier assembly of a VTOL aircraft consistent with the disclosed embodiments. In some embodiments, the carrier assembly 2000 may include a carrier 2008, a first planet gear 2006, a pump drive gear 2012, a second planet gear 2004, and a carrier cover 2010. In some embodiments, the carrier 2008, the first planet gear 2006, the pump drive gear 2012, the second planet gear 2004, and the carrier cover 2010 may rotate around a central axis 2016 or a shaft 2002. One or more of the planet gears of the carrier assembly 2000 may be substantially aligned along a shaft 2014 or a central axis 2018, forming a set of compound planet gears. For example, the first planet gear 2006 and the second planet gear 2004 may share a shaft 2014 and be coaxial along the central axis 2018. The carrier assembly 2000 may include a shaft 2002. The shaft 2000 may be coaxial along the central axis 2016. In some embodiments, the carrier 2008, the first planet gear 2006, the pump drive gear 2012, the second planet gear 2004, the carrier cover 2010, and the shaft 2002 may be mechanically coupled such that the components all rotate at the same rate. In some embodiments, the shaft 2002 may be mechanically coupled to a propeller assembly such that the shaft transfers torque or mechanical shaft power to the propeller assembly. In some embodiments, the carrier assembly 2000 may include cavities, ports, or holes to facilitate the distribution of a coolant such as oil.

[0224] In some embodiments, an electric engine may include an inverter assembly. The inverter assembly may include circuitry configured to receive an input of direct current, convert the direct current to alternating current, and provide the alternating current to a stator ring of an electric motor.

[0225] As disclosed herein, embodiments of an electric power engine assembly may include a thermal management system or a cooling system that may circulate a coolant or lubricant throughout the engine. A lubricant or coolant, such as oil, may reside in a reservoir and may be distributed to components throughout the electric power engine assembly. As disclosed herein, the oil may travel from the reservoir to a heat exchanger and to various locations within 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 housing assembly. In some embodiments, the bell housing assembly may be adjacent to the inverter assembly.

[0226] Figures 21A - 21B is an illustration of an exemplary bell housing assembly of a VTOL aircraft that is consistent with the disclosed embodiments. Figure 21AShows an internal view of the bell-shaped end cover plate of the bell-shaped end cover assembly. The bell-shaped end cover plate 2100A may include a plate 2102A made of aluminum, steel, or another type of thermally conductive material. The bell-shaped end cover plate 2100A may contain a pump rotor 2104A and a channel rotor 2106A. The size of the channel rotor 2106A may be designed such that the pump rotor 2104A may be able to rotate within the channel rotor 2106A, such that when the pump rotor 2014A rotates within 2106A, a plurality of regions around the pump rotor 2104A are open. The pump rotor 2104A may be positioned within the channel rotor 2106A. The pump rotor 2104A may be mechanically coupled to and driven to rotate by another component (such as a pump gear 2114B) of the power engine assembly. 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. The pump rotor 2104A may circulate oil from a reservoir through a pump inlet 2116B. In some embodiments, the pump rotor 2104A may rotate within the channel rotor 2106A to suction oil through the open area between the pump rotor 2104A and the channel rotor 2106A from the pump inlet. In some embodiments, the rotation of the pump rotor 2104A within the channel rotor 2106A may create a vacuum between the pump inlet 2116B and a reservoir containing any liquid. The pump outlet 2118A enables. For example, the pump may create a vacuum to suction oil from the reservoir to the pump inlet 2116B. In some embodiments, as described herein, there may be a pressure difference between the pump outlet 2118A and various distribution points of the cooling system such that oil or other liquid may be suctioned from the opening between the pump rotor 2104A and the channel rotor 2106A to the pump outlet 2118A and through the cooling system. In some embodiments, the bell-shaped end cover plate 2100A may contain additional or different components, such as an electric pump or other mechanical configurations, to suction oil or other liquid through the pump inlet 2116B. After entering through the pump rotor 2104A and the channel rotor 2016A, the oil or liquid may travel in direction 2120A and may travel from the pump outlet 2118A into a heat exchanger. In some embodiments, the heat exchanger may be mounted to the heat plate 2100A or a partition plate as discussed herein.

[0227] In some embodiments, the heat exchanger can cool oil or other liquids used to lubricate or cool inverter components, gearbox components, and / or electric motor components. In some embodiments, a portion of the cooled oil or liquid exiting the heat exchanger can be directed to the inverter components to cool these components, or can be directed to the motor-gearbox housing to cool components of the gearbox component and / or the electric motor component. Some embodiments can include a different partitioning of the cooling oil or liquid between the inverter component and the gearbox component and the electric motor component. For example, the inverter component can receive 40% by volume of the cooling oil, and the motor-gearbox hose can receive 60%. This ratio can vary depending on design considerations and the requirements of a particular implementation. In fact, different types of electric propulsion systems as described herein can use different fluid distribution percentages. Additionally, it should be understood that the tilter electric propulsion system and the lifter electric propulsion system can have similar or dissimilar distributions of oil from the heat exchanger. Pumps corresponding to the pump rotor 2104A and the pump gear 2114B can provide performance improvements to the gearbox component. Additionally, using pumps to drive the conveyance of oil to not only the gearbox component and the electric motor component, but also to the inverter component, can eliminate the need for additional components for conveying coolant to the inverter component. Such advantages can reduce mass and improve the drag profile of the electric propulsion system.

[0228] Cooling oil can enter passage 2108A from the heat exchanger and travel in direction 2114A to the annulus 2110A. The annulus 2110 can be aligned along the axis as described herein. The annulus 2110A can include ports 2116A. Oil from passage 2108A can travel through ports 2116A to various components of the power engine, including traveling to the gearbox component and the motor component, to provide cooling and lubrication. Oil can also travel from the annulus 2110A to passage 2112A. The bell end cover plate 2100A can also include ports 2122A that allow oil or other liquid to pass through the bell end cover assembly 2100B. In some embodiments, a pump can generate pressure that can drive the movement of the liquid through the bell end cover plate 2100A. For example, pressure from a pump (which can be an internal gear oil pump or a positive displacement pump) can propel the oil to travel in passage 2108A, 2112A, the annulus 2110A, ports 2116A, or other grooves or cavities in the bell end cover plate, which can assist in the conveyance of the liquid.

[0229] Figure 21BA view of an exemplary bell end cap assembly is shown. The bell end cap assembly 2100B may include a bell end cap plate 2100. Additionally, the bell end cap assembly may include a gear that may be driven by or interact with an additional gear in a gearbox assembly as described herein. In some embodiments, an annular gear 2104B may be coupled to the bell end cap plate 2102B assembly. The annular gear 2106B may include teeth that may engage an additional gear. The teeth of the annular gear 2106B may engage the planetary gear of the main shaft assembly as described herein. In some embodiments, the teeth of a pump drive gear may engage the teeth of a pump gear 2114B such that rotation of the pump drive gear drives rotation of the pump gear 2114B. The pump gear 2114B may be mechanically coupled to a pump rotor 2104A such that rotation of the pump gear 2114B may drive rotation of the pump rotor 2104A. Thus, the pump gear 2114B may drive the conveyance of lubricant or coolant throughout the bell end cap assembly. In some embodiments, the pump gear 2114B may drive lubricant or coolant from a reservoir. The bell end cap 2102B may include a port 2118B for discharging oil from a hot plate via port 2122A.

[0230] In some embodiments, the bell end cap assembly 2100B may include a bell end cap plate 2102B for sealing an electric motor assembly housing or a motor-gearbox assembly housing. In some embodiments, the bell end cap assembly 2100B may include a first circular wall extending away from the bell end cap plate 2102B. In some embodiments, an annular gear 2106B may be coupled to the first circular wall 2104B such that the annular gear 2106B does not rotate freely as described herein. In some embodiments, the bell end cap assembly 2100B may include a second circular wall 2108B extending away from the bell end cap plate 2102B. In some embodiments, the second circular wall 2108B may have a diameter less than the diameter of the first circular wall 2104B. The second circular wall 2108B may accommodate a bearing 2110B. In some embodiments, the bearing 2110B may be mechanically coupled to a shaft, including a main shaft that may transfer mechanical shaft power to a propeller assembly. In some embodiments, the bearing 2110B may include grooves to facilitate the transfer of oil or other liquid. The second circular wall 2108B may also include an annulus that includes a port hole 2112B. The port hole 2112B may be aligned with port 2116A to receive oil or liquid from a heat exchanger. The port hole 2112B may include supplying oil or other liquid to cool or lubricate components of the electric motor assembly and the gearbox assembly.

[0231] In some embodiments, the port hole 2112B can transfer 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, where oil or other liquid flows on the main shaft and can be distributed to components within the gearbox assembly and / or the electric motor assembly.

[0232] Embodiments of the disclosed inverter assembly can include an inverter assembly having a heat exchanger. Figure 22 is an illustration of an example inverter assembly of a VTOL aircraft consistent with the disclosed embodiments. In some embodiments, the inverter assembly 2200 can include an inverter assembly housing 2202 coupled to a hot plate 2204. The inverter assembly housing 2202 can be used to house the inverter assembly components as discussed herein. The inverter assembly housing 2202 and thus the inverter assembly 2200 can have a substantially circular profile. As used herein, the profile can be substantially circular, having the length of the minor axis of a circular shape and the length of the major axis of a circular shape, where the length of the minor axis is at least 80% of the length of the major axis.

[0233] In some embodiments, the inverter assembly 2200 can include a high-voltage connector 2212 and a low-voltage connector 2210. The high-voltage connector 2212 can have a low profile. The high-voltage connector 2212 can receive high-voltage power via a high-voltage channel from a high-voltage power system located elsewhere within the aircraft. The inverter assembly 2212 can include at least one drain port 2208. The drain port 2208 can be configured to allow any oil or liquid present within the inverter assembly to leave the inverter assembly 2200, regardless of the orientation of the power engine assembly. In alternative embodiments, the inverter assembly 2200 can further include vents. In some embodiments, the inverter assembly 2200 can include a heat exchanger 2206 coupled or mounted to the hot plate 2204. In some embodiments, the heat exchanger 2206 can be an integrated heat exchanger. In some embodiments, the hot plate 2204 can be welded to the heat exchanger 2206. For example, the hot plate 2204 can be made of aluminum. The assembly of the hot plate 2204 and the heat exchanger 2206 can include brazing, quenching, aging, and welding. In some embodiments, the hot plate 2204 and the heat exchanger 2206 can be machined from the same material.

[0234] Figure 56A is an illustration showing a cross-sectional view of a press-fit mesh port in an inclined position during operation after installation consistent with the disclosed embodiments. In some embodiments, the inverter housing (e.g., Figure 23 the housing 2302 shown) can be configured to have a plurality of drain ports and / or vents, such as Figure 23 the drain port / vent 2208 shown. As Figure 56AAs shown, each discharge port and / or vent 5600 may include a press-fit mesh discharge 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 press-fitted into the inverter housing 5608 from the inside ( Figure 56A only partially shown therein), and maintain an angle between 0° and 90°. In some embodiments, this angle may account for manufacturing difficulties. In some embodiments, the mesh 5604 material may be aluminum, copper, titanium, stainless steel (such as used in sintered metal type meshes), or any mesh material with a coefficient of thermal expansion (CTE) that matches the material of the housing 2302 (e.g., aluminum). In some embodiments, the discharge ports and / or vents 5600 are positioned along the circumference of the inverter housing 5608 such that the inverter housing 5608 can be discharged through at least one of the plurality of discharge ports and / or vents 5600 regardless of the orientation of the inverter housing 5608.

[0235] In some embodiments, the inverter housing 5608 may have a lifter position and an incliner position, corresponding to scenarios described separately Figures 32A - 32D therein.

[0236] In some embodiments, the size of the port 5602 may be adjusted for application needs. Figure 56B is an illustration showing a cross-sectional view of a press-fit mesh port in an inclined position during operation after installation consistent with the disclosed embodiments. In some example embodiments, as Figure 56B shown, for example, the hole size may be about 3 mm, and the inclination angle relative to the direction of gravity after installation may be 10° to 25° or up to 35°.

[0237] Some embodiments may include an inverter assembly where 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 23Illustrated is an exploded view of an inverter assembly of a VTOL aircraft consistent with the disclosed embodiments. The inverter assembly 2300 may include a control printed circuit board assembly (“PCBA”) 2316, a board spacer assembly 2314, a gate drive PCBA 2312, a capacitor assembly 2310, a power PCBA 2324, a housing gasket 2308, a hot plate assembly 2304, and a heat exchanger 2306. The components of the inverter assembly 2300 may be mechanically coupled by various fastening means. For example, the components of the inverter assembly 2300, including the inverter assembly housing 2302, may be fastened to each other by fasteners 2318. Additionally, the inverter assembly 2300 may include an inverter assembly housing 2302, which may be coupled to the hot plate assembly 2304 to enclose the inverter assembly components and protect the inverter assembly components from any liquids, debris, or other materials that may be harmful to the inverter assembly components. The inverter assembly housing 2302 may include connectors 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 include an inverter busbar for high current and low inductance.

[0238] In some embodiments, the inverter assembly housing 2302 may be cylindrical or may have an annulus shape (i.e., a circular monolithic shape with a central hole in a plan view). The form factor of the inverter assembly housing 2302 may provide low drag during flight.

[0239] In some embodiments, the capacitor assembly and at least one PCBA (e.g., 2312, 2314, 2316) may all be stacked and positioned inside the inverter housing 2302. In some embodiments, each of the stacked components (e.g., PCBA 2316, board spacer assembly 2314, gate drive PCBA 2312, capacitor assembly 2310, housing gasket 2308, hot plate assembly 2304) may have a plurality of through-locating holes to allow the fasteners 2318 to pass through to fasten the stacked structure. In some embodiments, the fasteners 2318 may be long screws, bolts, or rods.

[0240] In some embodiments, a set of alignment pins 2326 may facilitate the alignment of the stacked components (e.g., PCBA 2316, board spacer assembly 2314, gate drive PCBA 2312, capacitor assembly 2310, housing gasket 2308, hot plate assembly 2304) in the inverter assembly 2310. In some embodiments, the alignment pins 2326 may be integrated with the housing of the capacitor assembly 2310. Alternatively, in some embodiments, the locating pins 2326 may be a separate component from the assembly. In some embodiments, the locating pins 2326 may be overmolded as a feature of the housing of the capacitor assembly 2310.

[0241] In some embodiments, the hot plate assembly 2304 may have a set of sockets for the alignment pins 2326. The number of sockets may match the number of alignment pins 2326.

[0242] Figure 60A is an illustration of a capacitor housing according to an example embodiment, showing the alignment pins. Figure 60B is an illustration of a hot plate and a heat exchanger consistent with the disclosed embodiments, showing the engagement alignment pins. In this example embodiment, two alignment pins 6002A and 6002B may be overmolded as features on the housing 6000A of a capacitor assembly (e.g., 2310). On the hot plate 6000B (e.g., Figure 23 2304 in), two sockets 6004A and 6004B may have different shapes. The first socket 6004A may have a circular shape configured to provide a friction fit with the first alignment pin 6002A. The second socket 6004B may have an elongated shape (e.g., oval, slot, etc.) to accommodate dimensional tolerances. The major axis of the elongated shape may take a radial direction.

[0243] In some example embodiments, the alignment pins 6002A and 6002B may extend in two directions on both sides of the capacitor housing 6000A. During the assembly process, the capacitor assembly (e.g., Figure 23 2310 in) may be positioned on top of the hot plate 6000B (e.g., Figure 23 2308 in) and the power PCBA (e.g., Figure 23 2324 in) via a housing gasket (e.g., Figure 23 2308 in). The bottom side of the first alignment pin 6002A engages with the first socket 6004A, and the bottom side of the second alignment pin 6002B engages with the second socket 6004B. These two pairs together may provide a guide for aligning the capacitor assembly (e.g., Figure 23 2310 in) and the hot plate 6000B (e.g., Figure 23 2304 in). Then, the top sides of the alignment pins 6002A and 6002B serve as guides for the remaining components of the inverter assembly (e.g., Figure 23The PCBA 2316, board spacer assembly 2314, gate drive PCBA 2312, capacitor assembly 2310, housing gasket 2308, and hot plate assembly 2304) provide a reference. Each of these components may have through alignment holes for alignment pins 6002A and 6002B to pass through. For tolerance reasons, these holes may have a clearance fit or an arrangement similar to the sockets on the hot plate 6000B. After stacking all the components, the components can be fastened together using fasteners 2318. In some embodiments, the socket 6006 can receive the fastener 2318. Depending on the type of fastener 2318, the socket 6006 can be threaded, or have an interference fit or crimp ribs.

[0244] Now referring again to Figure 23 , in some embodiments, the stacking orientation in the housing can conform to various design shapes (e.g., a circular shape having 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 designed target shape. In some embodiments, the stacking orientation can be achieved by using a common structural component passing through the stack (e.g., a stack of different levels of design), such that a common structure (e.g., various bolts of the same length) can pass through each level to form the stacking orientation.

[0245] In some embodiments, using a stacking orientation may pose additional obstacles to additional design considerations, such as heat transfer, and the difficulty of managing the proper distribution of coolant in such a configuration may increase. Additionally, using long bolts traveling through the various levels of the inverter may increase the shock and vibration experienced by the inverter assembly. However, it should also be understood that such a stacking orientation can be beneficial considering various design considerations. For example, from an aerodynamic perspective, allowing a stacking orientation can be beneficial, where the stack allows the inverter or the combination of the inverter with other engine components (e.g., gearbox and / or motor) to maintain a low drag profile. Additionally, from a manufacturability perspective, the stacking orientation can be beneficial such that fewer components are involved in fixing the inverter assembly, and from a mass reduction perspective, it is beneficial where fewer components and potentially less mass are used to fix the components.

[0246] In some embodiments, the capacitor assembly 2310 may have at least one capacitor in a capacitor housing, and the capacitor housing has at least one bus bar on the outside. The capacitor assembly 2310 may have a central hole and a plurality of through positioning holes on the capacitor housing. The capacitor assembly 2310 may have at least one PCBA positioned inside the capacitor housing.

[0247] As disclosed herein, the inverter assembly may include a power PCBA. In some embodiments, the power PCBA may include a power supply board. Figure 24FIG. 0 is an illustration of an example printed circuit board assembly of a VTOL aircraft consistent with the disclosed embodiments. The power board 2400 may also include a sensor assembly. As an example, possible sensors may include sensors for current shunts, motor temperature, and MOSFET module temperature. Additionally, some embodiments may include various power modules 2402 electrically coupled to the power board 2400. As discussed herein, the power modules 2402 may generate heat during use and require cooling to ensure proper functionality and efficiency of the overall electric propulsion system.

[0248] Figure 57 FIG. 4 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 may be one of at least one PCBA of the inverter assembly 2300.

[0249] 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 integrated thereon ( Figure 57 only one is shown). In some embodiments, the gearbox of the propeller assembly may have a magnet on its planet carrier. The power board 5702 and the gearbox 5706 are placed close to each other such that at least two Hall sensors 5704 can sense the position of the magnet to determine the position of the propeller. In some embodiments, the heating plate 2304 of the inverter assembly 2300 and the bell end cover plate of the gearbox 5706 are made of a material that does not block the magnetic field such that at least two Hall sensors 5704 can sense the position of the magnet.

[0250] In some embodiments, the power board 5702 may have an oil temperature sensor (not shown) integrated thereon. In some embodiments, the oil temperature sensor may be positioned to sense the temperature of a cooling fluid (e.g., oil, water, or other fluid or fluid mixture known to have a large heat capacity). In some embodiments, the cooling fluid may be a cooling fluid for cooling MOSFETs, power modules, or other components that generate heat.

[0251] In some embodiments, the power board 5702 may have a secondary speed sensor (not shown) connected to a control board of an electric propulsion system (not shown) to provide redundancy.

[0252] Figure 58FIG. 0 is a diagrammatic illustration of a perspective view of a flexible PCBA connector in accordance with the disclosed embodiments. In some embodiments, the PCBA 5800 may have a flexible PCBA structure 5802 for making electrical connections to electrical components (not shown) out of the plane of the PCBA. In some embodiments, the flexible PCBA 5802 may include contact pads 5804 having electrical contacts (not shown) thereon, and at least one serpentine connector 5806 formed by cutting through a laminated printed circuit board (PCB). The electrical contacts may be electrically connected to electronics on the remainder of the PCBA by at least one of the at least one serpentine connector 5806.

[0253] In some embodiments, each of the serpentine connectors 5806 may have a flex factor. The flex factor is defined as the contact pad having an allowable displacement or deflection over the length of the flexible section (i.e., the serpentine connector 5806 and the contact pad 5804). The flex factor may be defined for displacement in any direction (i.e., a direction in the plane defined by the PCBA, a direction perpendicular to the plane defined by the PCBA, or any direction between the two aforementioned directions). In some embodiments, the flex factor serves as an indication of the flexibility of the flexible PCBA structure 5802 when the contact pad 5804 is displaced out of the plane defined by the PCBA.

[0254] In some embodiments, the flexible PCBA structure 5802 may 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 may have the same flex factor.

[0255] In some embodiments, the flex factor of the flexible PCBA structure 5802 may be less than 0.015 or approximately 0.005.

[0256] In some embodiments, the contact pad 5804 may have a plurality of supports (not shown) thereon.

[0257] In some embodiments, the PCBA (e.g., FR4) may include alternating substrate layers and copper layers.

[0258] In some embodiments, the flexible PCBA structure 5802 can permit an electrical connection between the PCBA structure and another electrical contact outside the PCBA without the need for additional components (e.g., pin connectors, wire connectors, flexible circuits, or additional processes such as soldering, welding), thereby saving costs. In some embodiments, the electrical connection can be made by stacking and aligning the PCBA having the flexible PCBA structure 5802 to another structure having another electrical contact. In some embodiments, the alignment of the PCBA can be accomplished by passing alignment pins 2326 through alignment holes in the PCBA. Since the flexible PCBA structure 5802 permits the contact pads 5804 to be off-plane, the electrical connection can be made by pushing the contact pads 5804 against another electrical contact. Alternatively, the contact pads 5804 can include pedestals on the back side to provide the necessary support, and thus the electrical connection can be made by pushing another component onto the top of the contact pads 5804. The electrical connection can be fixed in place by conventional means such as snap-fit, soldering, ultrasonic welding, electric welding, laser welding, ultrasonic wire bonding. The deflection of the contact pads 5804 can provide a tolerance for stack-up, making the electrical connection secure and robust.

[0259] In some embodiments, the serpentine connection 5806 can be partially cut away to allow for more deflection of the contact pads 5804. Figure 59 is consistent with the disclosed embodiments Figure 58 Cross-sectional view of the serpentine connection 5806 of the flexible PCBA shown, showing a partial cut. In this example embodiment, the cut 5902 is only on the substrate layer 5904. The copper layer 5906 can remain intact. In some embodiments, the cut direction is perpendicular to the instantaneous extension direction of the serpentine connection, i.e., the cut 5902 always cuts across the narrow width of the serpentine connection. The cut 5902 can further increase the flexibility of the flexible PCBA structure, making it easier for the contact pads 5804 to deflect. In other words, the cut 5902 can have the same effect as increasing the flexure factor.

[0260] As described above, the electric engines and associated control components of a VTOL aircraft can generate heat during operation. For example, such components can include inverter assemblies, electric motor assemblies, and gearbox assemblies. The engines can accumulate heat generated by mechanical friction between components and by resistive heating within the motor-gearbox assemblies. The accumulated heat can be carried to a heat exchanger by a lubricant that circulates through one or more components of the engine. 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 by 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 can include oil, and the oil can be used for lubrication as well as cooling components of the electric engine. The heat exchanger can bring one or more fluids into contact with each other to cool the fluid at a higher temperature. The heat exchanger can advantageously be located next to the electric engine, thereby minimizing the volume (and weight) of materials required to achieve the cooling and lubrication functions. In some embodiments, the heat exchanger can be fluidly, thermally, and mechanically coupled to the inverter assembly such 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 that 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 can then be directed to a reservoir.

[0261] As described herein, a power propulsion system can include a heat exchanger. Figures 25A - 25C is an illustration and example front view of a heat exchanger of a VTOL aircraft consistent with the disclosed embodiments. The heat exchanger 2504A can be mechanically coupled to a heat plate 2502A of the inverter assembly, as described herein and as shown in example view 2500A. The heat plate 2502A can include a fin array 2506A. The fin array 2506A can provide a radiator to draw heat from components of the inverter assembly. As described herein, the heat exchanger 2504A can be positioned to receive an air flow from a propeller. The propeller (not shown) can direct the air flow 2508A into the heat exchanger 2504A, and the exiting air 2510A can exit the heat exchanger. The air flow 2508A (which can be cooler air) can be forced into the heat exchanger 2504A, such as by being flushed downward from the propeller blades (not shown). The exiting air 2510A, which can be warmer air, can exit the heat exchanger 2504A without entering other components of the power propulsion system. In some embodiments, the heat exchanger 2504A can include cooling fins.

[0262] Figures 25B - 25CExemplary 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 circulate through the fins of heat exchanger 2504A. Heat exchanger 2504A can include tubes 2504B and fins 2502B. Tubes 2504B can carry oil, and fins 2502B can be thermally coupled to tubes 2504B. As a result, the oil traveling in 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 can include air. For example, air stream 2508A can enter heat exchanger 2504A, be in thermal contact with fins 2502C, and receive heat from the oil traveling in tubes 2504C. Then, the air can leave heat exchanger 2504A as exiting air 2510A. Heat exchanger 2504A can transfer heat via convection.

[0263] Figure 26 is an illustration of a heat exchanger of a VTOL aircraft consistent with the disclosed embodiments. Heat exchanger 2600 can include a length 2602, a height 2604, and a depth 2606. As described herein, heat exchanger 2600 can include tubes and fins to assist in heat transfer between fluids. Heat exchanger 2600 can include multiple cooling paths. Section 2608 shows an example of different cooling paths. A lubricant or coolant such as oil can travel in tubes 2610. Tubes 2610 can be thermally coupled to fins 2612, as described herein. Tubes 2610 can include hollow tubes for the fluid. Fins 2612 can 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 can include multiple layers of fins 2612 stacked between tubes 2610 and thermally coupled to the tubes. As a result, the oil entering heat exchanger 2600 can flow into different tubes 2610, thereby creating multiple cooling paths where heat can be transferred from the oil to the air.

[0264] As described herein, embodiments of an electric engine can include circulating a lubricant or coolant throughout the engine. A heat exchanger can cool the lubricant or coolant that is directed to engine components such as a motor, a gearbox, or an inverter. In some embodiments, heat from an inverter assembly can be directly conducted to a coolant or lubricant such as oil.

[0265] Figures 27A - 27BIllustration of a front view of a baffle of a VTOL aircraft consistent with the disclosed embodiments. In some embodiments, the baffle may be composed of a bell-shaped end cover plate and a hot plate. The baffle may include one or more plates sandwiched together and disposed between the motor-gearbox housing and the inverter assembly housing. Additionally, the baffle may assist in the distribution of lubricant or coolant throughout the engine. In some embodiments, the baffle may contain channels, tubes, ports, cavities, or other features for conveying a liquid. The bell-shaped end cover plate 2700 may contain elements and discussions similar to the bell-shaped end cover plate of FIG. 21. In some embodiments, the bell-shaped end cover plate 2700A may be coupled to the hot plate 2700B. In some embodiments, the bell-shaped end cover plate 2700A may be adjacent to a gasket plate, and the gasket plate may be adjacent to the hot plate 2700B. The inverter assembly may include the hot plate 2700B. The hot plate 2700B may be mechanically, thermally, and fluidly coupled to the heat exchanger 2710B. In some embodiments, the bell-shaped end cover plate 2700A and the hot plate 2700B may be positioned above the heat exchanger. The outer circumference of the hot plate 2700B may be connected to the heat exchanger 2710B. The bell-shaped end cover plate 2700A and the hot plate 2700B may contain channels for assisting in the distribution of lubricant or coolant. Herein, the channels may also refer to grooves, holes, or any other conduits configured to distribute oil or other coolant or lubricant in a planar direction. In some embodiments, the lubricant or coolant may be a liquid such as oil, as described herein. The hot plate may be thermally and fluidly coupled to the heat exchanger by a liquid such as oil. In some embodiments, the distribution of lubricant or coolant may be driven by a pump. The hot plate 2700B may contain grooves, holes, liquid flow paths, or any other conduits for assisting the pump gear in conveying oil or other liquid from a reservoir. In some embodiments, oil may be conveyed from the reservoir through the channel rotors 2704A, 2704B and the pump rotor 2706A to the inlet channel 2708A on the bell-shaped end cover plate 2700A. The oil in the inlet channel 2708A may be hot oil or warm oil traveling in the flow path 2716A. The oil in the inlet channel 2708A may 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 may be cooled in the heat exchanger 2710B, and the cooled oil may travel to the heat exchanger outlet 2708B in the hot plate 2700B. In some embodiments, the oil conveyed between the hot plate 2700B and the bell-shaped end cover plate 2700A may travel through the gasket plate. Then, the cooled oil in the heat exchanger outlet 2708B may travel along the flow path 2718A to the outlet channel 2710A, reaching the annulus 2712A and the channel 2714A of the bell-shaped end cover 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. Then, the oil from the fin array 2714B can return to the reservoir via the port. Some embodiments may include an annulus 2712A that is substantially aligned along the main axis or an axis shared with the gearbox assembly or the electric motor assembly. In some embodiments, oil or liquid can travel from the annulus 2712A through the port hole to the gearbox assembly or the electric motor assembly, as described herein. In some embodiments, the channel 2714A can be fluidly connected to an additional liquid flow path within the motor-gearbox housing, and the additional liquid flow path can be used to circulate oil or liquid to additional parts of the power engine, such as the front bearing or components located near the propeller assembly. In some embodiments, the bell end cover plate may include a seal in the power engine. The bell end cover assembly may include a face seal between the heat exchanger and the inverter assembly to prevent oil leakage.

[0266] In some embodiments, a lubricant or coolant can be used to cool the inverter assembly using the hot plate 2702B. Some embodiments may include a hot oil or other liquid entering an inlet channel 2708A that can be aligned with the heat exchanger inlet 2706B to enter the heat exchanger 2710B. The cooled oil or other liquid exits an outlet channel 2710A that is aligned with the heat exchanger outlet 2708B, and a portion or all of the cooled oil or liquid can travel along the liquid flow path to the annulus 2712B of the hot plate. The oil or other liquid in the annulus 2712B can be distributed to the radiators located on the hot plate 2702B, such as the fin array 2714B, and can provide cooling to the power module by aligning the fin array 2714B with the power module located within the inverter assembly, such as Figure 24Those modules cited in Figure 24 can improve the performance of the inverter assembly. In addition, compared with other cooling methods involving additional components (e.g., air convection methods that require adding air cooling fins), liquid convection can improve the durability of the inverter assembly.

[0267] The disclosed embodiments of the electric propulsion system may include one or more components for distributing lubricant or coolant, as described herein. In some embodiments, a lubricant or coolant, such as oil, may be circulated from the reservoir 1212A to the heat exchanger 1226A and then to the inverter assembly, gearbox assembly, and motor assembly (as Figure 12A shown). As Figure 21AAs shown, the bell housing assembly can assist in the distribution and circulation of oil. As described herein, oil traveling from the heat exchanger in passageway 2108A can be distributed to annulus 2110A and port 2116A located within annulus 2110A. As described herein, a main shaft that can be substantially aligned with annulus 2110A of the bell housing assembly can extend from the bell housing assembly through the gearbox assembly and through the electric motor assembly. In some embodiments, portions of the oil in the bell housing assembly can be shared between annulus 2110A, port 2116A, port 2122A, and various other ports and passageways. Centrifugal force, centripetal force, or pressure can drive the oil from annulus 2110A, port 2116A, or a groove in bearing 2110B along the main shaft and toward the gearbox assembly and the electric motor assembly. For example, pressure in bell housing assembly 2100B can drive the oil into a groove in bearing 2110B or port hole 2112B. Centrifugal force can then drive the oil along the main shaft to the windings of the stator in the motor assembly. For example, rotation of the main shaft can apply a centrifugal force that propels the oil along the main shaft. In some embodiments, oil can travel from the bell housing assembly to the gearbox assembly and the motor assembly through holes, conduits, passageways, tubes, or ports. For example, oil can flow in an annular area between the sun gear and the shaft. In some embodiments, ports can transfer oil from the bell housing assembly to passageways or similar structures present within the motor assembly housing to deliver the oil to additional portions of the gearbox assembly or the motor assembly. Some embodiments can include passageways or similar structures configured to deliver oil to a propeller assembly, a bearing mechanically coupled to a shaft flange, or the windings of the stator within the motor assembly.

[0268] 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. Additionally, oil can be used to lubricate various bearings, such as rolling bearings or hydrodynamic bearings, as described herein. Minimizing the amount of oil used in an electric propulsion system can reduce the mass and drag profile of the electric propulsion system. Additionally, minimizing the amount of oil required for operation of the electric propulsion system can enable the total amount of oil in the electric propulsion system to remain below a threshold amount. 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 that has been used for lubrication and cooling can reside in a reservoir, and by using a heat exchanger to cool this oil, the electric propulsion system can reuse the oil, thereby eliminating the need for additional oil. Additionally, as described herein, using a common liquid for cooling and lubrication can result in a reduction in component mass when compared to other cooling and lubrication methods that use various liquids. Such a configuration using various liquids may require additional mass and size of the electric propulsion system, such as additional heat exchangers, additional fluid distribution passageways or tubes, and additional surface area for receiving cooling air from a propeller assembly.

[0269] 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 not only lubricate but also cool the electric motor, rather than using another coolant, this will add additional oil to the system, but this additional oil will eliminate the need for conventional components that may be used to cool such an electric motor. For example, if the electric motor is cooled by another liquid such as ethylene glycol, the motor may include separate heat exchangers for both the lubricant fluid and the coolant fluid. Thus, in embodiments where a single fluid (such as oil) is used for both lubrication and cooling, there will be an increase in oil, but only one heat exchanger will be required, so the mass of the entire system may be reduced due to the use of fewer heat exchangers and potentially the elimination of other components, and there may be a more attractive drag profile. Additionally, due to the reduction in mass and the benefits of cooling the motor with a substance rather than relying on air cooling which may have issues traveling throughout the motor, using one substance to lubricate and cool the motor can improve the efficiency of the system.

[0270] Some embodiments of the inverter may include an inverter having a coolant path that travels around the outer edge of the inverter but within the inverter housing, rather than utilizing a heat exchanger. For example, the coolant path may travel around any printed circuit board assemblies, power modules, or other inverter components present in the inverter.

[0271] As disclosed herein, embodiments of the electric motor may include an inverter assembly. In some embodiments, the inverter assembly may include a hot plate. Figure 28FIG. is an illustration of a hot plate of a VTOL aircraft consistent with the disclosed embodiments. The hot plate 2802 may facilitate heat transfer of the inverter assembly, including distributing coolant to the inverter assembly. In some embodiments, the hot plate 2802 may be adjacent to components of the inverter assembly, such as the inverter housing or the printed circuit board. The hot plate 2802 may be thermally coupled to the inverter assembly. In some embodiments, the hot plate 2802 may be adjacent to the bell end cap assembly. In some embodiments, the hot plate 2802 may be adjacent to a gasket, which may be adjacent to the bell end cap assembly. The gasket may be a metal frame gasket. In some embodiments, the hot plate 2802 may be adjacent to the heat exchanger 2810. For example, the hot plate 2802 may be mounted on the heat exchanger 2810, and coolant may travel through various paths in the heat exchanger 2810. As an example, oil may be the coolant traveling through various paths in the heat exchanger 2810. The pump rotor 2804 may drive the oil through the cooling path in the heat exchanger 2810, also referred to herein as the liquid flow path. In some embodiments, oil or other liquid from the reservoir may be suctioned into the heat exchanger inlet 2806 by the pump rotor 2804. In some embodiments, the heat exchanger 2810 may receive oil or other liquid from the heat exchanger inlet 2806, cool the oil or other liquid, and the cooled oil or other liquid may leave the heat exchanger at the heat exchanger outlet 2808. The cooled oil from the heat exchanger 2810 may be driven by the pump 2804 into different channels in the hot plate. For example, the oil may be delivered to the distribution channel 2812. In some embodiments, the hot plate 2802 may include a heat sink for assisting heat transfer of the inverter assembly. As an example, the hot plate 2802 may include a fin array 2818. The fin array 2818 may include cooling fins extending from a base, and may increase the surface area to improve heat transfer. The fin array 2818 may be located in a cavity in the hot plate 2802. The fin array 2818 may be a heat sink and may be made of a material with high thermal conductivity. In some embodiments, the shape of the fins may be rectangular or circular and may be made of aluminum. The fin array 2818 may draw heat from the thermally and mechanically coupled inverter assembly to cool components including switching devices and MOSFETs. The fin array 2818 may be exposed to the flowing fluid. For example, the cooling oil in the distribution channel 2812 may enter the fin array 2818 via the channel 2814 and provide cooling and heat transfer to the fin array 2818. Then, the oil may flow from the fin array 2818 to the collection channel 2816. In other embodiments, the oil may be directly transferred from the distribution channel 2812 to the collection channel 2816.

[0272] Figure 29FIG. 0 is an illustration of an electric propulsion system of a VTOL aircraft consistent with the disclosed embodiments. In some embodiments, a hot plate 2900 may be thermally coupled to a motor assembly housing 2902. The hot plate 2900 may also be fluidly coupled to the motor assembly housing 2902 via one or more coolant or lubricant flow paths. As described herein, the hot plate 2900 may help distribute a coolant or lubricant such as oil. For example, oil in the hot plate 2900 may enter a heat exchanger 2914 via a heat exchanger inlet 2912 and leave the heat exchanger 2914 via a heat exchanger outlet 2910. The hot plate 2900 may include a pump rotor 2908, a distribution channel 2916, a fin array 2922, and a collection channel 2920. Cooled oil from the heat exchanger 2914 may enter the distribution channel 2916, flow through the fin array 2922 in direction 2928, and enter the collection channel 2920 via channel 2918. As described herein, the fin array 2922 may be a radiator and may help transfer heat from an inverter assembly to the coolant oil 2928. In some embodiments, oil in the hot plate 2900 may be transferred to the motor assembly housing 2902. For example, an oil flow path 2930 may be an example flow path from the hot plate 2900 to the motor assembly housing 2902. An oil flow path 2932 may be an example flow path of oil to various components within the motor assembly housing 2902. The oil 2930 may also travel to a second oil flow path 2934. Oil in the various flow paths may travel to a gearbox assembly, an electric motor assembly, or other components within the motor assembly housing 2902 to provide cooling or lubrication, as described herein. Oil that has been distributed throughout the motor assembly housing 2902 may accumulate in a reservoir 2904. The oil may flow through the reservoir along a liquid flow path 2924, then leave the reservoir 2904 and flow back to the hot plate 2900 in a return path 2926. The motor assembly 2902 may be mechanically coupled to a shaft flange assembly 2906, as described herein. In some embodiments, the location of the hot plate 2900 and the heat exchanger 2914 may provide advantages for the electric propulsion system. For example, the hot plate 2900 being adjacent to and fluidly coupled to the heat exchanger 2914 may eliminate the need for external connections. As discussed herein, oil may travel from the heat exchanger 2914 to the hot plate 2900 and be distributed to components of the electric propulsion system such as an inverter assembly, a gearbox assembly, and a motor assembly that may be packaged together. Such a configuration including a hot plate that integrates several components together may eliminate the need for external connections and may reduce risks such as leakage and separation of such external connections.

[0273] Figures 30A - 30BFIG. is an illustration of an example electric propulsion system of a VTOL aircraft consistent with the disclosed embodiments. As described herein, the electric propulsion system 3000A may include a heat exchanger 3008A that is mechanically, thermally, and fluidly coupled to a hot plate 3006A. The hot plate 3006A may be mechanically coupled to a motor housing 3002A that includes a reservoir 3004A. The electric propulsion system 3000A may include a shaft flange assembly 3010A. In some embodiments, the electric propulsion system 3000A may include a hot plate 3006A and a motor housing 3002A that are substantially aligned along an axis 3012A. Figure 30B FIG. shows another view of the electric propulsion system 3000B. The heat exchanger 3008B may be mechanically coupled to the hot plate 3006B. The hot plate 3006B may be mechanically coupled to a motor housing 3002B, which may include a reservoir 3004B. In some embodiments, the electric propulsion system 3000B may include a hot plate 3006B and a motor housing 3002B that are substantially aligned along an axis 3012B.

[0274] Figures 31A - 31B FIG. is a cross-sectional illustration of an electric propulsion system of a VTOL aircraft consistent with the disclosed embodiments. Figure 31A FIG. shows an example embodiment of a tilter electric propulsion system. 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, the heat exchanger 3118A may be thermally, fluidly, 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 reservoir 3112A may include a fluid inlet 3114A for transferring oil or other liquid to the heat exchanger 3118A. In some embodiments, the reservoir 3112A may be a storage tank for containing oil. The reservoir 3112A may be adjacent to the motor housing 3110A. In some embodiments, a main shaft 3108A extends from a bell end cap assembly that seals the motor-gearbox assembly housing 3110A, through the gearbox assembly 3106A and the electric motor assembly 3102A to a shaft flange assembly 3120A. As described herein, the gearbox assembly 3106A and the electric motor assembly 3102A may be substantially aligned along the main shaft 3108A. Additionally, the inverter assembly 3104A may be substantially aligned along an axis that shares the axis of the main shaft 3108A.

[0275] As described above, the swashplate may include a variable pitch mechanism for changing the pitch of the propeller blades of a VTOL aircraft. In some embodiments, the variable pitch mechanism may be mounted to the rear of the electric engine assembly, such as the rear of the inverter assembly. Additionally, the variable pitch mechanism may interact with the main shaft, as described herein, to change the pitch of the propeller blades. In such embodiments, as discussed herein, the inverter assembly 3104A, the inverter assembly housing 3116A, and the separator plate may include an enclosure having passages through the configuration and housing of the inverter assembly 3104A, the inverter assembly housing 3116A, and the separator plate to allow the variable pitch mechanism to engage the main shaft or the propeller blades. As discussed throughout, the lift electric propulsion system may not change the orientation of its thrust or the pitch of the blades. Thus, in some embodiments, the separator plate may not include passages such as those present in a swashplate electric propulsion system. Additionally, the inverter assembly and the inverter assembly housing of the lift electric propulsion system may not include such passages, but it should be recognized that it may be beneficial, from a safety testing perspective and a manufacturability perspective, for the inverter assembly and the inverter assembly housing of the lift electric propulsion system to include an enclosure with passages similar to the enclosure of the swashplate electric propulsion system.

[0276] Figure 31B An example embodiment of a lift electric propulsion system is shown. As disclosed herein, a lift may refer to an electric propulsion system for lift. The lift 3100B may include an inverter assembly 3104B, a gearbox assembly 3106B, and an electric motor assembly 310BA. As described herein, the heat exchanger 3118B may be thermally, fluidly, and mechanically coupled to the inverter assembly 3104B. The inverter housing 3116B may enclose the inverter assembly 3104A. The gearbox assembly 3106B may be adjacent to the inverter assembly 3104B and the electric motor assembly 3102B. The motor-gearbox housing 3110B may enclose the electric motor assembly 3102B. In some embodiments, the main shaft 3108B extends from the bell housing assembly that seals the motor-gearbox housing 3110B through the gearbox assembly 3106B to the electric motor assembly 3102B. As described herein, the gearbox assembly 3106B and the electric motor assembly 3102B may be substantially aligned along the main shaft 3108B. Additionally, the inverter assembly 3104B may be substantially aligned along an axis that shares the axis of the main shaft 3108B.

[0277] As discussed herein, it should be noted that having similar components between a tiltrotor electric propulsion system and a liftrotor electric propulsion system is beneficial for the manufacturability of the overall aircraft. Additionally, using similar components between the tiltrotor electric propulsion system and the liftrotor electric propulsion system is beneficial in diagnosing problems and ensuring compliance with safety requirements and protocols. However, in some embodiments, the liftrotor and tiltrotor may have components that do not exist in the other. For example, the liftrotor electric propulsion system 3100B may include a lock nut 3112B positioned between the main shaft 3108B and the shaft flange assembly 3120B, which is larger than the lock nut present in the tiltrotor electric propulsion system 3100A. The lock 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 disrupted due to the various vibratory loads experienced throughout the flight. For example, as discussed herein, some flight phases do not require the liftrotor electric propulsion system to be active, and in such cases, the blades may need to be stowed in some manner. However, if the liftrotor blades are not properly stowed, they may experience drag forces on the blades, and the mechanical coupling of the main shaft 3108B and the shaft flange assembly 3122B may experience tension. Additionally, in some embodiments, the lock nut 3112B of the liftrotor electric propulsion system 3100B can counteract operating loads. In some embodiments, for reasons similar to the presence of the lock nut 3122B, the liftrotor electric propulsion system may also include a propeller flange 3126A that is larger than the shaft flange of the tiltrotor. Additionally, the liftrotor electric propulsion system may also include a bearing 3124A for assisting the rotation of the propeller flange 3126A. As described herein, the electric propulsion system can achieve different takeoff orientation angles during operation. Therefore, fluids containing coolant or lubricant in the electric propulsion system can move due to gravity. For example, a lubricant or coolant such as oil can shift within the electric propulsion system during operation. The oil can reside in a reservoir, and the oil can 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 during all flight phases. Therefore, the cooling system can be designed to allow the circulation of oil regardless of the orientation of the aircraft.

[0278] Figures 32A - 32D is a cross-sectional illustration of an electric propulsion system of a VTOL aircraft consistent with the disclosed embodiments. Figures 32A - 32D Elements having similar reference numerals and referring to similar elements of the electric propulsion systems 3200A, 3200B, 3200C, and 3200D. Thus, similar design considerations and configurations can be considered throughout the embodiments.

[0279] Figure 32AAn example embodiment of an electric propulsion system in an upright orientation is shown. As an example, the upright orientation can be achieved during flight operations including, but not limited to, takeoff, landing, or hovering. The electric propulsion system 3200A can 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, can be located in the reservoir 3210A. In the example orientation 3200A, oil can also be present in the volume 3218A at the oil level 3216A in the reservoir 3210A. The oil 3212A can enter the pump inlet 3214A and proceed to the heat exchanger 3208A. Then, the oil 3212A can be cooled in the heat exchanger 3208A and distributed throughout the electric propulsion system as described herein. In some embodiments, the oil can be distributed along the main shaft 3206A by centrifugal force.

[0280] Figure 32B An example embodiment of an electric propulsion system 3200B in a first angled orientation (e.g., a hovering orientation at an angle 3222B) is shown. As an example, the electric propulsion system 3200B can be oriented at an angle 3222B with respect to the vertical axis 3226B along a central axis 3224B. As Figure 32B shown, although the electric propulsion system 3200B is in an angled orientation, the pump inlet 3214B remains in contact with the oil 3212B and below the oil level 3216B to allow the oil to continue to circulate through the liquid flow path as described herein.

[0281] Figure 32C An example embodiment of an electric propulsion system 3200C in a horizontal orientation is shown. As an example, the electric propulsion system 3200C can be in a horizontal orientation during forward flight or cruise configuration. As Figure 32C shown, during the horizontal orientation, the pump inlet 3214C remains in contact with the oil 3212C and below the oil level 3216C to allow the oil to continue to circulate through the liquid flow path as described herein. Additionally, due to gravity, the volume 3218C can be free of oil during the horizontal configuration.

[0282] Figure 32D An example embodiment of an electric propulsion system in a second angled orientation (e.g., a dive at an angle 3222D) is shown. As Figure 32DAs shown, during the dive orientation, the pump inlet 3214D remains in contact with the oil 3212D and below the oil level 3216D to allow the oil to continue to circulate through the liquid flow path as described herein. Additionally, due to gravity, the volume 3218D may not contain oil during the horizontal configuration. In some embodiments, oil or other combustible liquids may be used as lubricants throughout the electric engine and may also be used as coolant fluids to help manage the heat generated by the engine during operation. As has been disclosed herein, electric engines may have different primary functions and may therefore not contain the same amounts of lubricant and coolant. For example, a lift and landing engine may only require less than a quart of oil, while an engine operating during all flight phases may require more than a quart of oil. It should be understood that the example embodiments mentioned herein are representative and do not prescribe bounds on the amounts of lubricant and coolant that may be used in an electric engine.

[0283] It should be understood that by using oil to not only lubricate but also cool the electric engine rather than using another coolant, this would add additional oil to the system, but this additional oil would eliminate conventional components available for cooling such an electric engine. For example, if the electric engine were 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 may be used to cool the electric engine. Some embodiments of electric propulsion systems include 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) may have respective liquid flow paths that circulate through a common heat exchanger, also referred to as a dual heat exchanger. In such a configuration, the number of heat exchangers may be less than the number of liquid flow path types based on the liquid types, and the overall propulsion system may save mass by not having multiple or more heat exchangers.

[0284] However, with respect to embodiments that utilize a single fluid (such as oil) for lubrication and cooling, there will be an increase in oil, but only one heat exchanger will be required, so the overall system mass may be reduced due to using fewer heat exchangers and potentially not requiring other components, and there may be a more appealing drag profile. Additionally, due to the mass reduction and the benefits of cooling the engine with a substance rather than relying on air cooling that may have issues traveling throughout the engine, using one substance to lubricate and cool the engine can improve the efficiency of the system.

[0285] Regarding the use of oil or other flammable liquids in the electric propulsion systems described herein, federal laws and regulations may require safety components such as fire barriers to be close to engines that use more than a threshold amount of oil or other flammable materials. Such federal laws and regulations may be enforced by a government entity such as the Federal Aviation Administration of the United States.

[0286] It should be noted that some electric propulsion system embodiments as described herein may not include a fire barrier. A fire barrier as used herein may include engine components or aircraft components that are designed, constructed, or installed primarily to prevent a hazardous amount of air, fluid, or flame 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, then twelve fire barriers may need to be installed on the aircraft. In some embodiments, the fire barriers may be required on each wing, or around the fuselage, or any other configuration based on federal laws, regulations, or other safety requirements. Thus, the presence of fire barriers can add additional mass to the aircraft, thereby reducing the efficiency of the electric propulsion system and further limiting the amount of payload (including passengers) present on the aircraft. This is particularly relevant for VTOL aircraft designs where a single aircraft may have, for example, twelve electric propulsion systems, and thus any mass increase due to a single fire barrier may be experienced twelve-fold.

[0287] Although some embodiments described herein do not include a fire barrier, additional versions of all embodiments described and contemplated herein may include a fire barrier. Additionally, each embodiment as described herein may have fire barriers of various types and locations.

[0288] Figures 33A - 33C is a schematic diagram showing an example electric propulsion system of 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. The fire barrier 3308A may be positioned between an electric engine assembly 3302A mechanically coupled to a propeller assembly 3306A and a pylon 3304A, and its primary purpose is to prevent any fire or combustion that may occur in the electric engine assembly 3302A from spreading to other areas of the aircraft.

[0289] Figure 33B An example VTOL aircraft 3300B consistent with the present disclosure is shown. The VTOL aircraft 3300B may include a fire barrier 3306B that is mounted or attached to a wing 3304B that is connected to a fuselage 3302B. As Figure 33BAs shown, fire barrier 3306B can be placed between the electric propulsion system including electric engine 3308B and propeller assembly 3310B and wing 3304B of VTOL aircraft 3300B, and its main purpose is to prevent any fire or burning. In some embodiments, fire barrier 3306B can be placed between wing 3304B and the boom that houses the electric propulsion system.

[0290] Figure 33C An example electric propulsion system 3300C consistent with the present disclosure is shown. The 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, the electric motor assembly 3302C may be adjacent to the inverter assembly 3304C. Some embodiments may also include an electric engine assembly housing 3308C. The electric engine assembly housing 3308C may include a fire barrier 3310C. In some embodiments, the fire barrier 3310C may also be used to accommodate the rear of the electric engine assembly and, as shown in the figure, the rear of the inverter assembly.

[0291] 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 present within the boom to ensure that the aircraft can remain in balanced flight if there is a fire, components are lost due to a fire, components are separated due to a fire, or any other loss of function or components occurs.

[0292] C. Example Electric Propulsion System Configuration

[0293] As discussed above and throughout this disclosure, example electric propulsion systems can include components of various configurations, such as the representative configurations described herein, including electric motor assemblies, gearbox assemblies, and inverter assemblies. Example embodiments discussed herein can include components of the electric propulsion system being aligned or substantially aligned along a common axis. In some embodiments, the components can be aligned along a shaft or spindle that provides mechanical shaft power to rotate a propeller of a propeller assembly. Some embodiments can include components of the electric propulsion system being adjacent to each other in sequence along an axis or substantially aligned along an axis. In some embodiments, the position or orientation of one or more electric propulsion system components can provide a reduction in system mass and result in a more efficient drag profile. For example, one or more components can be substantially aligned along a common axis or adjacent to each other and may not require additional components (such as connecting wires) or additional enclosure volume for the wires. Thus, the corresponding mass and volume typically required to permit such connecting wires may not be needed in the disclosed electric propulsion systems.

[0294] In some embodiments, the electric propulsion system can further include a cooling system configured for a plurality of heat-generating portions of the electric propulsion system. Some embodiments can include portions of the electric propulsion system being air-cooled by an air flow generated by the propeller assembly or an air flow encountered during various stages of flight. Some embodiments can include portions of the electric propulsion system being cooled using one or more liquid flow paths through the electric propulsion system. Such embodiments can also include the liquid flow path circulating through a heat exchanger exposed to the air flow such 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 as described herein can all be cooled using a common cooling system, can each have their own independent cooling system, or can combine various types and configurations of cooling systems. 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.

[0295] Figures 34A - 34D is a schematic diagram showing an example electric propulsion system of a VTOL aircraft consistent with the disclosed embodiments. Thus, similar design considerations and configurations can be considered throughout the embodiments.

[0296] Figure 34ASchematically depicts an example electric propulsion system 3400A consistent with the present disclosure. The electric propulsion system 3400A may include components oriented along an axis extending along axis 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 the propeller assembly 3408A. The housings of the components of the electric propulsion system 3400A may share a common shape, such as a circular profile centered on shaft 3406A, a rectangular profile oriented along shaft 3406A, or a combination of profiles. The electric propulsion system 3400A may further include an electric motor assembly 3402A located between and adjacent to the inverter assembly 3404A and the propeller assembly 3408A. In such an embodiment, shaft 3406A may pass through the electric motor assembly 3402A. Some embodiments may include a shaft 3406A that also passes through the inverter assembly 3404A. In some embodiments, the power module 3410A may be axially oriented within the inverter assembly 3404A such that any heat generated by the power module may escape via path 3412A into the environment external to the inverter assembly 3404A. Some embodiments may also include orienting the power module 3410A within the inverter assembly 3404A such that an air flow generated by the propeller assembly 3408A or air encountered during flight may be used to cool the power module.

[0297] Figure 34B Schematically depicts an example electric propulsion system 3400B consistent with the present disclosure. 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 located 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 via path 3412B into the environment external to the inverter assembly 3404B. Some embodiments may include a power module oriented elsewhere within the inverter assembly such that any air flow generated by the propeller assembly 3408B may be used to cool the power module.

[0298] Figure 34CSchematically depicts an example electric propulsion system 3400C consistent with the present disclosure. The 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. The electric propulsion system 3400C may further include an inverter assembly 3404C positioned between the electric motor assembly 3402C and the propeller assembly 3408C. In some embodiments, the power module 3410C may be positioned on a portion of the inverter assembly 3404C such that it lies on a surface of the inverter assembly 3404C adjacent to the electric motor assembly 3402C. In some embodiments, the power module 3410C may be positioned within the electric propulsion system 3400C, as shown by path 3412C, rather than within the inverter assembly 3404C where heat generated by the power module 3410C cannot be cooled using air from the propeller assembly 3408C or any airflow encountered during flight. In such embodiments, liquid cooling may be used to cool the power module 3410C and other components located within the inverter assembly 3404C. Additional embodiments may include a liquid cooling system that also thermally manages components of the electric motor assembly 3402 and / or components of the gearbox assembly.

[0299] Figure 34D Schematically depicts an example electric propulsion system 3400D consistent with the present disclosure. The 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. The electric propulsion system 4100D may further include an electric motor assembly 3402D positioned between the inverter assembly 3404D and the propeller assembly 3408D. In some embodiments, the power module 3410D may be positioned on a portion of the inverter assembly 3404D such that it lies on a surface of the inverter assembly 3404D adjacent to the electric motor assembly 3402D. In some embodiments, the power module 3410D may be positioned within the electric propulsion system 3400D, as shown by path 3412D, rather than within the inverter assembly 3404D where heat generated by the power module 3410D cannot be cooled using air from the propeller assembly 3408D or any airflow encountered during flight. In such embodiments, liquid cooling may be used to cool the power module 3410D and other components located within the inverter assembly 3404D. Additional embodiments may include a liquid cooling system that also thermally manages components of the electric motor assembly 3402 and / or components of the gearbox assembly.

[0300] In some embodiments, a 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. Additionally, some embodiments may include using the liquid that cools the electric propulsion system to also lubricate components of the electric propulsion system. In some embodiments, the electric propulsion system may include cavities, reservoirs, or tanks for collecting and circulating coolant liquid throughout the electric propulsion system.

[0301] Figure 35 is a schematic diagram showing an example electric propulsion system of a VTOL aircraft consistent with the disclosed embodiments. The electric propulsion system 3500 may include components aligned along an axis 3506, such as an electric motor assembly 3502, an inverter assembly 3504, and a reservoir 3514. As Figure 35 shown, the electric motor assembly 3502 may be positioned between the reservoir 3514 and the inverter assembly 3504. The electric motor assembly 3502 may provide torque to a propeller assembly 3508 via a main shaft 3506 that may travel through the inverter assembly 3504. Additionally, the electric motor assembly 3502 may provide torque to the propeller assembly 3508 via gear reduction using a gearbox assembly (not shown in this example embodiment). The inverter assembly may include a power connection channel 3518 connected to the inverter assembly 3504. The inverter assembly 3504 may include a power module 3510 positioned on a portion of the inverter assembly 3504 opposite the portion adjacent to the electric motor assembly 3502. Additionally, some embodiments may include the power module 3510 positioned within the inverter assembly 3504 such that any heat generated by the power module 3510 may escape to the environment external to the inverter assembly via a path 3512. Some embodiments may include various cooling methods for components of the electric propulsion system 3500. For example, in some embodiments, the power module 3510 may be positioned below the propeller assembly 3508 such that air from the propeller assembly 3508 cools the power module 3510. Additionally, the reservoir 3514 may contain a liquid for cooling or lubricating the electric motor assembly 3502, the gearbox assembly, and / or the inverter assembly 3504. Some embodiments may include various housing profiles for components of the electric propulsion system 3500, such as a circular housing centered on the axis 3506, a hybrid housing profile, and a housing profile that allows for an aerodynamic drag profile. Some embodiments may include component housings having cooling fins attached to an outer surface of the housing.

[0302] As Figure 35As shown, the storage tank 3514 may have cooling fins 3516 on the outer shell of the storage tank 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. Although some embodiments discussed herein may include components of an electric propulsion system aligned along a common axis, some embodiments include components that are substantially aligned along a common axis.

[0303] In some embodiments, the electric propulsion system may include components that are misaligned 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 within the aircraft. Some embodiments may include an inverter assembly that is not adjacent to the electric motor assembly, but is 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.

[0304] Figures 36A - 36B is a schematic diagram showing an example electric propulsion system of a VTOL aircraft consistent with the disclosed embodiments. Thus, similar design considerations and configurations may be considered throughout the embodiments.

[0305] Figure 36ASchematically depicts an example electric propulsion system 3600A consistent with the present disclosure. The electric propulsion system 3600A may include components such as an electric motor assembly 3602A, which are centered along a shaft 3606A that provides torque to a propeller assembly 3608A. Embodiments of the electric propulsion system 3600A may also include a rectangular inverter assembly 3604A suspended behind the electric motor assembly 3602A. Additionally, some embodiments may include an inverter assembly 3604A having cooling fins 3610A oriented such that the cooling fins 3610A can utilize an air flow from the propeller assembly 3608A to cool power modules, MOSFETs, or other components present in the inverter assembly 3604A. In some embodiments, depending on the design and requirements of the system, the electric motor assembly 3602A may be housed in an enclosure having various profiles, including circular, rectangular, or any other type of profile. The electric motor assembly 3602A may be located in a motor housing that also has cooling fins to assist in cooling elements of the electric motor assembly 3602A, such as the stator, stator windings, or any other element of the electric motor assembly 3602A. Although not shown in this figure, a gearbox assembly may be present between the electric motor assembly 3602B and the propeller assembly 3608B, between the electric motor assembly 3602B and the inverter assembly 3604B, within the enclosure containing the electric motor assembly 3602B, or in any other configuration that allows for gear reduction. Additionally, although not shown in the figure, a gearbox assembly may be present within the motor housing and may also utilize cooling fins to assist in thermal management.

[0306] Figure 36B Schematically depicts as Figure 36AThe exemplary electric propulsion system 3600B disclosed in [reference], and provides a forward view from the propeller assembly 3608A. The electric propulsion system 3600B may include a circular electric motor assembly 3602B aligned along the axis 3606B. Embodiments of the electric propulsion system 3600B may also include a rectangular inverter assembly 3604B that may be located behind the electric motor assembly 3602B. The inverter assembly 3604B may be adjacent to the electric motor assembly 3602B or may be located within a boom, wing, or fuselage. The inverter assembly 3604B may include cooling fins 3608B that extend beyond the outer diameter of the electric motor assembly 3602B such that the cooling fins 3608B are exposed to the air flow from the propeller assembly 3608A or the air flow encountered during flight. Additionally, the cooling fins 3608B may be used to extract and transfer heat generated by power modules, MOSFETs, or other components present in the inverter assembly 3604A. The cooling fins 3608B may transfer the heat to the environment external to the electric propulsion system. Similarly, the electric motor assembly 3602B may also include its own cooling fins (not shown) that are positioned on the outer housing of the electric motor assembly to assist in the thermal management of the electric motor assembly 3602B and any gearbox assemblies.

[0307] In some embodiments, the 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 a liquid coolant to components located throughout the electric motor assembly, gearbox assembly, and inverter assembly. However, it should be understood that the cooling systems disclosed herein may also include a liquid coolant that circulates around the perimeter of the electric motor assembly, gearbox assembly, and / or inverter assembly. For example, the cooling system may include a cavity, sheath, or distribution channel of the cooling system that causes the liquid coolant to circulate around the perimeter of the components located within the electric propulsion system.

[0308] Figure 37FIG. 0 is a schematic diagram showing an example electric propulsion system of a VTOL aircraft consistent with the disclosed embodiments. The electric propulsion system 3700 may include a motor assembly housing 3702 that houses an electric motor assembly adjacent to an inverter assembly housing 3708, wherein a shaft 3706 travels through the motor assembly housing 3702. In some embodiments, the motor assembly housing 3702 and the inverter assembly housing 3708 may have various shapes or profiles, including, for example, a circular housing centered along an axis coinciding with the shaft 3706, a rectangular housing, or any other suitable geometric orientation. Some embodiments may include a motor assembly housing 3702 that houses 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 the motor assembly housing 3702, an electric motor assembly positioned between the gearbox assembly and a propeller assembly external to the motor assembly housing 3702, a gearbox assembly located within the motor assembly housing 3702 but not aligned along the axis of the electric motor assembly, or any other configuration of a gearbox assembly that shares a housing with the electric motor assembly. Some embodiments may include an inverter assembly housing 3708 that houses an inverter assembly 3704 as described herein. Additionally, the inverter assembly housing 3708 may also include cooling fins 3710 located on an outer surface of the inverter assembly housing 3708, which utilize the air flow encountered during flight to assist in cooling the components of the inverter assembly 3704. Some embodiments may also include the inverter assembly 3704 using liquid cooling instead of air cooling for thermal management. Such embodiments may include a cavity 3714, a sheath, or a distribution channel surrounding the inverter assembly 3704 such that a liquid can circulate through the cavity 3714, the sheath, or the distribution channel to extract heat generated by the components of the inverter assembly 3704. Additionally, the liquid may be used to cool components within the motor assembly housing 3702. Path 3712 depicts an example liquid flow path for cooling components located within the motor assembly housing 3702, wherein the liquid may move from a first end of the motor assembly housing to a second end of the motor assembly housing through a distribution channel along the main shaft 3706. The liquid may be radially distributed from the shaft 3706 and may be collected via a collection chamber, reservoir, or similar component for recirculation throughout the motor assembly housing 3702. In some embodiments, the electric motor assembly housing 3702 may be fluidly connected to the inverter assembly housing 3708 such that a liquid coolant may circulate throughout the two components via the liquid flow path 3712 and the cavity 3714. In some embodiments, the motor assembly housing 3702 and the inverter assembly housing 3708 may utilize air cooling, liquid cooling, or a combination of both to thermally manage the components located within each housing.

[0309] As discussed herein, a electric propulsion system can include various component configurations, such as components aligned along an axis, adjacent to each other, substantially aligned along an axis, or components connected using wires or other connection methods. Thus, some embodiments can include components that share a housing. For example, as described above, a gearbox assembly can be housed within a motor assembly housing. Additionally, some embodiments can include housing a gearbox assembly, an inverter assembly, or other assemblies or components of these assemblies within a propeller assembly. Such a configuration can be driven by design constraints such as weight, drag profile, lift, torque, payload, flight time, or any other design constraint associated with a VTOL aircraft.

[0310] Figures 38A - 38B FIG. 4 is a schematic diagram showing an example electric propulsion system of a VTOL aircraft and an example inverter assembly of the electric propulsion system consistent with the disclosed embodiments. The electric propulsion system 3800A can include a motor assembly housing 3802A aligned along a main shaft 3806A. Some embodiments can include a motor assembly housing 3802A that includes an electric motor assembly centered along the main shaft 3806A. Some embodiments can include a motor assembly housing 3802A that houses an electric motor assembly and a gearbox assembly. Some embodiments of the electric propulsion system 3800A can further include an inverter assembly 3804A mounted to a circular face of the motor assembly housing 3802A, where a low voltage input 3808A is located on this face of the motor assembly housing 3802A. In some embodiments, the inverter assembly 3804A can be located within the propeller assembly in addition to being mounted to the motor assembly housing 3802A. For example, an inverter assembly as described herein can be positioned within a spinner of the propeller assembly. Such placement of the inverter assembly 3704A can be advantageous when other components of the electric propulsion system 3800A do not justify creating a more compact drag profile. For example, the propeller assembly can be sized to meet additional design criteria such as required torque or lift, and in such embodiments, the size of the propeller assembly can have vacant space to allow the inverter assembly 3804A to be placed within the hub of the propeller assembly.

[0311] Figure 38B FIG. 8 schematically depicts an example inverter assembly 3800B consistent with the discussion of the inverter assembly 3804A and throughout the present disclosure. The inverter assembly 3800B can 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. Additionally, the inverter assembly 3800B can include 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.

[0312] In some embodiments, a electric propulsion system may include components that reside within various component enclosures. As discussed herein, the various components of the electric propulsion system may be present within enclosures and may be organized within these enclosures in various ways. Some embodiments of the 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. Additionally, some embodiments of the electric propulsion system may include various types of thermal management systems, also referred to herein as cooling systems. Some electric propulsion systems may include combinations of cooling systems, such as air cooling systems and liquid cooling systems. For example, electric propulsion system components may have, for example, an air cooling design where the components are mechanically coupled to cooling fins, and a liquid cooling design where the components are fluidly coupled to a liquid flow path, and a heat exchanger that extracts heat from the liquid and transfers the heat to the external air.

[0313] Figures 39A - 39D is a schematic diagram showing an example electric propulsion system of a VTOL aircraft consistent with the disclosed embodiments. The 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, the electric motor assembly 3902A may be positioned between the gearbox assembly 3906A and the shaft flange assembly 3912A, and both the gearbox assembly 3906A and the electric motor assembly 3902A are aligned along the main shaft 3908A. Additionally, the inverter assembly 3904A may be adjacent to the motor-gearbox housing 3910A, and the inverter assembly 3904A may have a rectangular profile. In some embodiments, the inverter assembly 3904A, the electric motor assembly 3902A, and the gearbox assembly 3908A may have a common or separate cooling system. For example, the motor-gearbox housing 3910A and / or the inverter assembly 3904A may utilize the air flow encountered during flight or generated by the propeller assembly to cool the inverter assembly 3904A, the gearbox assembly 3906A, and / or the electric motor assembly 3902A.

[0314] Figure 39B shows Figure 39A a perspective view of an example electric propulsion system. Although Figure 39B and Figure 39ARelated, but these figures may have similar numbers that do not refer to the same components. In some embodiments, the electric propulsion system 3900B may include an electric motor assembly 3902A, and the gearbox assembly 3906A may be located within the motor-gearbox housing 3910B. The motor-gearbox housing 3910B may be aligned along a main shaft 3908B that is connected to a flange shaft assembly 3912B, and may have cooling fins 3914B circumferentially oriented around the electric motor housing 3910B for cooling the electric motor assembly 3902A and the gearbox assembly 3906A using an air flow from a propeller assembly (not shown) connected to the flange shaft assembly 3912B or an air flow encountered during flight. Additionally, the inverter assembly 3904B may be mechanically coupled to the rear of the motor-gearbox housing 3910B, and may also utilize an air flow to cool the components of the inverter assembly 3904B.

[0315] 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 that travels through the electric motor assembly 3902C and / or the gearbox assembly 3906C to the propeller assembly 3912C. As Figure 39C shown, an example embodiment may include an electric motor assembly 3902C located between the gearbox assembly 3906C and the propeller assembly 3912C. Additionally, some embodiments may include an inverter assembly 3904C adjacent to a second end of the motor-gearbox assembly 3910C.

[0316] Figure 39D A schematic diagram of an example electric propulsion system consistent with embodiments of the present disclosure is provided. The electric propulsion system 3900D may include a component arrangement similar to those Figure 39C shown. However, the electric propulsion system 3900D may include a gearbox assembly 3906D that is located between an electric motor assembly 3902D and a propeller assembly 3912D, and the propeller assembly is connected to a first end of the motor-gearbox housing 3910D, where the inverter assembly 3904D is adjacent to a second end of the motor-gearbox housing 3910D.

[0317] Figures 40A - 40D is a cross-sectional view and illustration of an electric propulsion system of a VTOL aircraft consistent with the disclosed embodiments. Figure 40AA cross-sectional view of an exemplary 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, which are aligned along a main shaft 4020A connected to a shaft flange assembly 4008A. The gearbox assembly 4006A and the electric motor assembly 4002A may be located within a motor-gearbox assembly housing 4012A, and the inverter assembly 4004A may be located within an inverter assembly housing 4014A. Additionally, the inverter assembly housing 4014A may be mounted to the rear of the motor-gearbox assembly housing 4012A. Further, a power connection channel 4018A may be connected to a connector of the inverter assembly 4004A located within the inverter assembly housing 4014A. As Figure 40A depicted in the exemplary embodiment of, the power connection channel 4018A may be connected to the inverter assembly 4004A behind a heat exchanger 4010A. Further for the embodiment, the heat exchanger 4010A may be mounted to the motor-gearbox assembly housing 4012A and may be used in conjunction with a distribution channel (not shown) to assist in cooling the electric motor assembly 4002A, the gearbox assembly 4006A, and / or the inverter assembly 4004A via a coolant liquid circulating throughout the electric propulsion system 4000A. It should be understood that although the inverter assembly 4004A, the gearbox assembly 4006A, and the electric motor assembly 4002A are shown as being consistent with the stacked component inverter assembly, planetary gearbox, and electric motor consisting of a stator and a rotor described in this figure, the figure is an example, and the inverter assembly, gearbox assembly, and electric motor assembly may have any type as described herein or capable of achieving similar functions.

[0318] Figure 40B is shown Figure 40A A perspective view of an exemplary electric propulsion system 4000B is shown, where the electric motor assembly 4002A and the gearbox assembly 4006A are located within a motor-gearbox housing 4012B. In some embodiments, the motor-gearbox housing 4012B may be aligned along a main shaft 4020B connected to a shaft flange assembly 4008B. The motor-gearbox housing 4012B may include cooling fins 4022B oriented circumferentially around the motor-gearbox housing 4012B. Additionally, a heat exchanger 4010B may be mounted to the motor-gearbox housing 4012B and may liquid-cool the electric motor assembly 4002A, the gearbox assembly 4006A, and / or the inverter assembly 4004A by cooling a liquid circulating throughout the electric motor assembly 4002A, the gearbox assembly 4006A, and / or the inverter assembly 4004A. It should be understood that although Figure 40BDepicts that the inner circumference of the heat exchanger is smaller than the outer circumference of the motor - gearbox housing, but the heat exchanger 4010B can span any distance equal to or less than the outer circumference of the motor - gearbox housing 4012B. Additionally, the inverter assembly housing 4014B can be mechanically coupled to the rear of the motor - gearbox housing 4012B and can also have cooling fins 4024B oriented around the circumference of the inverter assembly housing 4014B. Further, the inverter assembly housing 4014B can have connection points for power connection channels 4018B at positions on the outer edge of the inverter assembly housing 4014B and behind the heat exchanger 4010B.

[0319] Figure 40C A schematic illustration of an example electric propulsion system consistent with embodiments of the present disclosure is provided. The electric propulsion system 4000C can include, for example, components such as an electric motor assembly 4002C and a gearbox assembly 4006 housed within a motor - gearbox housing 4012C and an inverter assembly 4004C housed within an inverter assembly housing 4014C. Additionally, the electric propulsion system can include a propeller assembly 4008C and a heat exchanger 4010C fluidly coupled to the electric motor assembly 4002C and the gearbox assembly 4006C via a liquid path 4016C. Some embodiments can include a liquid path 4016C that includes a liquid for cooling, lubricating, or both cooling and lubricating components fluidly coupled to the heat exchanger 4010C. In some embodiments, the heat exchanger 4010C can be directly or indirectly mounted to the motor - gearbox housing 4012C. The liquid path 4016C can include distribution channels, means for distributing the liquid, or cavities capable of transporting the liquid, distributing the liquid to components fluidly coupled to the heat exchanger 4010C, and recirculating the liquid back to the heat exchanger 4010C. The liquid present in the liquid path 4016C can collect heat from components fluidly coupled to the heat exchanger 4010C and transfer the heat to incoming air 4018C passing through the heat exchanger 4010C. Thus, embodiments can include a heat exchanger 4010C positioned such that incoming air experienced during flight or from the propeller assembly 4008C can pass through and cool the liquid passing through the heat exchanger 4010C.

[0320] Figure 40D A schematic illustration of an example electric propulsion system consistent with embodiments of the present disclosure is provided. The electric propulsion system 4000D can include Figure 40CComponent arrangements similar to those shown and described. However, the electric propulsion system 4000D may include a gearbox assembly 4006D located between the electric motor assembly 4002D and the propeller assembly 4008D. The propeller assembly is connected to the first end of the motor-gearbox housing 4012D, where the inverter assembly 4004D is housed within the inverter assembly housing 4014D, and the inverter assembly housing is connected to the second end of the motor-gearbox housing 4012D. The electric propulsion system 4000D may further include a gearbox assembly 4006D and an electric motor assembly 4002D that are fluidly coupled to a heat exchanger 4010D via a liquid path 4016D. The heat exchanger is partially exposed to incoming air 4018D to lubricate and cool the gearbox assembly 4006D and the electric motor assembly 4002D.

[0321] Liquid paths 4016C and 4016D are shown highly schematically as simple loops. However, it should be understood that the liquid paths may include branches, sub-loops, or other segmented paths. Generally, the liquid can be circulated in any manner that effectively lubricates and cools the various components present within the motor-gearbox housings 4012C and 4012D.

[0322] Figure 41 is a cross-sectional view of an electric propulsion system of a VTOL aircraft consistent with the disclosed embodiments. The electric propulsion system 4100 may include an inverter assembly 4104, a gearbox assembly 4106, and an electric motor assembly 4102 that are respectively aligned along a main shaft 4110 mechanically coupled to a shaft flange assembly 4112. The inverter assembly 4104, the gearbox assembly 4106, and the electric motor assembly 4102 may be located within housings such as the inverter assembly housing 4116 and the motor-gearbox assembly housing 4114, where the inverter assembly housing 4116 abuts the motor-gearbox assembly housing 4114. Additionally, a power connection channel 4118 may be connected to a high-voltage connector in the inverter assembly located within the inverter assembly housing 4116. Further for this embodiment, a heat exchanger 4108 may be mounted to the motor-gearbox assembly housing 4114 and may 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 circulated throughout the electric motor assembly 4102, the gearbox assembly 4106, and / or the inverter assembly 4104 to cool the corresponding components. Although in some embodiments the inverter assembly, the gearbox assembly, and the electric motor assembly are shown as consistent with the stacked component inverter assembly, planetary gearbox, and 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 may have any type as described herein or capable of achieving similar functions.

[0323] Figures 42A - 42B It is a diagram of an example electric propulsion system of a VTOL aircraft consistent with the disclosed embodiments. The electric propulsion system 4200 can use liquid cooling for cooling. The electric propulsion system 4200A may include an electric motor assembly located within the motor assembly housing 4202A and a gearbox assembly located within the gearbox assembly housing 4206A, which are aligned along the main shaft 4208A connected to the shaft flange assembly 4210A. In some embodiments, the electric motor assembly can be located between the gearbox assembly and the shaft flange assembly 4210A. Additionally, the inverter assembly housing 4204A can be adjacent to the gearbox assembly housing 4206A and can also be mechanically connected to the power connection channel 4214A. In some embodiments, the heat exchanger 4212A can be coupled to the gearbox assembly housing 4206A and the inverter assembly housing 4204A. Further, the heat exchanger 4212A can be fluidly coupled to the electric motor assembly, the gearbox assembly, and the inverter assembly via a liquid flow path to provide liquid for cooling and lubricating components within the electric motor assembly, the gearbox assembly, and the inverter assembly. Some embodiments may include flow paths that include channels, holes, and cavities capable of transporting liquid throughout the fluidly coupled components of the electric propulsion system 4200B.

[0324] Figure 42B Shows a perspective view of an example electric propulsion system 4200B using liquid cooling with a heat exchanger 4212B as discussed with respect to Figure 42A The heat exchanger is fluidly coupled to the electric motor assembly, the gearbox assembly, and the inverter assembly. The example electric propulsion system 4200B may include an electric motor assembly located within the motor assembly housing 4202B and a gearbox assembly housed within the gearbox assembly housing 4206B, which are aligned along the main shaft 4208B mechanically coupled to the flange shaft assembly 4210B. Some embodiments may include a motor assembly housing 4202B and a gearbox assembly housing 4206B having a substantially circular profile with equal radii. The example electric propulsion system 4200B may further include an inverter assembly housed within an inverter assembly housing 4204B having a substantially circular profile, the inverter assembly housing being mechanically coupled to the power connection channel 4214B and the gearbox assembly housing 4206B. Some embodiments may include the radius of the inverter assembly housing 4204B being greater than the radius of the gearbox assembly housing 4206B and / or the motor assembly housing 4202B.

[0325] Figures 43A - 43Dis an illustration and schematic diagram showing an example electric propulsion system of a VTOL aircraft consistent with the disclosed embodiments. The electric propulsion system 4300A may include a gearbox assembly 4306A, an electric motor assembly 4302A, and an inverter assembly 4304A, which are aligned along a main shaft 4316A connected to a shaft flange assembly 4308A respectively. The inverter assembly 4304A may be located within an inverter assembly housing 4312A. Additionally, the gearbox assembly 4306A and the electric motor assembly 4302A may be located within a motor-gearbox assembly housing 4310A. Some embodiments may include the inverter assembly housing 4312A and thus the inverter assembly 4303A located between the motor-gearbox assembly housing 4310A and the shaft flange assembly 4308A. In this configuration, the main shaft 4316A may pass through the gearbox assembly 4306A, the electric motor assembly 4302A, and the inverter assembly 4304A. Additionally, a power connection channel 4314A may extend from a boom, wing, or fuselage of the aircraft through the motor-gearbox assembly housing 4313A to a connection point within the inverter assembly housing 4312A.

[0326] Figure 43B shows an example embodiment of an air-cooled electric propulsion system 4300B as discussed with respect to Figure 43A A perspective view of an example embodiment of an air-cooled electric propulsion system 4300B is shown. 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 the inverter assembly housing 4312B located between the motor-gearbox assembly housing 4310B and the flange shaft assembly 4308B, where 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 within the inverter assembly housing 4312B. Further embodiments may include the motor-gearbox housing 4310B and the inverter assembly housing 4312B having cooling fins 4320B and 4318B respectively on the outer surfaces of each housing. The cooling fins 4320B, 4318B may transfer heat from components housed within the motor-gearbox housing 4310B and the inverter assembly housing 4312B to the outside air passing through the cooling fins 4320B, 4318B.

[0327] Figure 43C A schematic diagram of an example electric propulsion system 4300C consistent with the embodiments of the present disclosure is provided. The electric propulsion system 4300C may include in connection with Figure 43A and Figure 43BComponent arrangements similar 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, and the inverter assembly is connected to the flange shaft assembly 4308C. In this configuration, the main shaft 4316A (not shown in this figure) may pass through the electric motor assembly 4302C, the gearbox assembly 4306C, and the inverter assembly 4304C. Additionally, one or more power connection channels 4314C may extend from the boom of the aircraft through the motor-gearbox assembly housing 4310C to a connection point in the inverter assembly housing 4312C.

[0328] Figure 43D A schematic diagram of an exemplary electric propulsion system 4300D consistent with embodiments of the present disclosure is provided. The electric propulsion system 4300D may include component arrangements and markings similar to those Figures 43A - 43C shown and described. Figure 43D depicts an electric propulsion system 4300D similar to the Figure 43C electric propulsion system 4300C in which the inverter assembly housing 4312D is connected to a power connection channel 4314D extending from the boom of the aircraft and is adjacent to the flange shaft assembly 4308D and the motor assembly housing 4310D. However, the motor assembly housing 4310D houses the electric motor assembly 4302D, and the electric motor assembly provides torque to the flange shaft assembly 4308D via a main shaft passing through the inverter assembly 4304D without gear reduction from a gearbox assembly.

[0329] Figures 44A - 44CFIG. is a schematic illustration of an example electric propulsion system for a VTOL aircraft consistent with the disclosed embodiments. The example electric propulsion system 4400A may include an inverter assembly 4404A housed within an inverter assembly housing 4416A positioned between a shaft flange assembly 4410A and a separator plate 4408A. In addition to the inverter assembly housing 4416A, the separator plate 4408A may also be coupled to a motor-gearbox housing 4414A that houses an electric motor assembly 4402A and a gearbox assembly 4406A. In such a configuration, the inverter assembly housing 4416A may include an attachment point for a power connection channel 4420A extending from a boom, wing, or fuselage of the aircraft. Additionally, such a configuration may include a main shaft mechanically coupled to the shaft flange assembly 4410A that travels through the inverter assembly housing 4416A and, in some embodiments, through the inverter assembly 4404A and the separator plate 4408A to the electric motor assembly 4402A. Some embodiments may include the main shaft extending from a first end of the motor-gearbox assembly housing 4414A mechanically coupled to the separator plate 4408A to a second end of the housing and thus 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 liquid flow path 4418A. The separator plate 4408A may be used to seal an upper portion of the motor-gearbox assembly housing 4414A via a bell end cap assembly and to seal a 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. The liquid flow path 4418A may include circulating liquid to extract heat from components of the inverter assembly 4404A, the gearbox assembly 4406A, and the electric motor assembly 4402A and to transfer the heat to an air flow 4422A passing through cooling fins of the heat exchanger 4412A.

[0330] Figure 44B A schematic illustration of an example electric propulsion system 4400B consistent with embodiments of the present disclosure is provided. The electric propulsion system 4400B may include a component arrangement similar to those shown and described. Figure 44A Figure 44B Depicted is Figure 44A ​The electric propulsion system 4400A in is similar to the electric propulsion system 4400B, where the inverter assembly housing 4416A is connected to a power connection channel 4420A extending from a boom, wing, or fuselage of an aircraft and is positioned between a flange shaft assembly 4410B and a partition plate 4408B. However, the partition plate 4408B can also be coupled to a motor - gearbox assembly housing 4414B that houses a gearbox assembly 4406B, and the gearbox assembly is located behind an electric motor assembly 4402B relative to the partition plate 4408B. Some embodiments can include a liquid flow path 4418B that fluidly couples a heat exchanger to the inverter assembly 4404B, the gearbox assembly 4406B, and the electric motor assembly 4402B. Additionally, the liquid flow path 4418B can include circulating liquid to extract heat from components of the inverter assembly 4404B, the gearbox assembly 4406B, and the electric motor assembly 4402B and transfer the heat to an air flow 4422B passing through cooling fins of a heat exchanger 4412B.

[0331] 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 can include a component arrangement similar to those Figures 44A - 44B shown and described. Figure 44C Depicted is Figure 44A the electric propulsion system 4400A in Figure 44B and the electric propulsion system 4400B in

[0332] The liquid flow paths 4418A, 4418B, and 4418C are highly schematically shown as simple loops. In some embodiments, the liquid flow path can include branches, sub - loops, or other segmented paths. Generally, the liquid can 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.

[0333] Figures 45A - 45D is a schematic diagram showing an example electric propulsion system of a VTOL aircraft consistent with the disclosed embodiments. The electric engine 4500A can 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. Although Figure 45AShows an inverter component housing 4512A tangentially coupled to the outer surface of a motor component housing 4510A, but in some embodiments, the base of the inverter component housing 4512A can be coupled to the outer surface of the motor component housing 4510A in any configuration, including that the radius of curvature of the base of the inverter component housing is similar to the radius of the electric motor component housing 4510A. Additionally, the inverter component housing 4512A can include a bus bar 4516A that is connected to the motor component housing 4510A to supply alternating current to the electric motor component. The inverter component housing 4512A can also include cooling fins mounted to a portion of the inverter component housing 4512A that is opposite the coupled portion of the inverter component housing 4512A. The cooling fins 4514A can be used to remove heat generated by components present within the inverter component and transfer the heat to an air flow passing through the cooling fins 4514A.

[0334] Figure 45B A figure showing a perspective view of an example embodiment of a power engine 4500B consistent with the present disclosure. The example power engine 4500B can include a component arrangement similar to those depicted and described in Figure 45A including similar markings of components such that similar numerical markings correspond to Figure 45A and Figure 45B similar components. The example power engine 4500B can include an electric motor component housed within an electric motor component housing 4510B, the electric motor component housing being coupled to an inverter component housing 4512B that houses an inverter component. Additionally, the power engine 4500B can include a bus bar 4516B that is connected to the motor component housing 4510B to supply alternating current to the electric motor component. Similar to Figure 45A , the power engine 4500B can include an inverter component housing 4512B that includes cooling fins 4514B that can be used to remove heat generated by components present within the inverter component and transfer the heat to an external air flow through the cooling fins 4514B. Additionally, the inverter component housing 4512B can include connection points for a power connection channel 4518B originating within a boom, wing, or fuselage of an aircraft.

[0335] Figure 45C Schematically depicts an example embodiment of a power engine 4500C consistent with the present disclosure. The example power engine 4500C can include a component arrangement similar to those depicted and described in Figure 45A and Figure 45B including similar markings of components such that similar numerical markings correspond to Figure 45A , Figure 45B and Figure 45CSimilar components. The electric engine 4500C may include an electric motor 4502C housed within a motor assembly housing 4510C and a gearbox assembly 4506C, and the motor assembly housing is mechanically coupled to an inverter assembly housing 4512C that houses an inverter assembly 4504C. As Figure 45C 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 the inverter assembly housing 4512C that originates from another location within a boom, wing, or aircraft.

[0336] Figure 45D An example embodiment of an electric engine 4500D consistent with the present disclosure is schematically depicted. The example electric engine 4500D may include a component arrangement similar to those depicted and described in Figures 45A - 45C , including similar markings of the components, such that similar numerical markings correspond to Figures 45A - 45C similar components. The electric engine 4500D may include an electric engine 4502D and a gearbox assembly 4506D housed within a motor assembly housing 4510D, and the motor assembly housing is coupled to an inverter assembly housing 4512D that houses an inverter assembly 4504D. Some embodiments may include a configuration in which the electric motor assembly 4502D is located between the gearbox assembly 4506D and the propeller assembly 4508D. In some embodiments, a power connection channel 4518D may be connected to the inverter assembly housing 4512D that originates from another location within a boom, wing, or aircraft.

[0337] Figures 46A - 46B is a schematic diagram showing an example electric propulsion system of a VTOL aircraft consistent with the disclosed embodiments. The electric propulsion system 4600A may include an electric motor assembly 4602A and a gearbox assembly 4606A housed within a motor assembly housing 4612A, and the motor assembly housing is coupled to an inverter assembly housing 4614A that houses an inverter assembly 4604A. Some embodiments may include a gearbox assembly 4606A positioned between the electric motor assembly 4602A and the propeller assembly 4608A. Some embodiments may include a heat exchanger 4610A that is coupled to the motor assembly housing 4612A and is fluidly coupled to the electric motor assembly 4602A and the gearbox assembly 4606A via a liquid flow path 4616A. The liquid flow path 4616A may be used to extract heat from components present within the electric motor assembly 4602A and the propeller assembly 4608A. The liquid flow path 4616A may convey the extracted heat to the heat exchanger 4610A, which transfers the heat to an air flow 4618A passing through cooling fins of the heat exchanger 4610A.

[0338] 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 a component arrangement similar to those depicted and described in Figure 46A , including similar markings of components, such that similar numerical markings correspond to Figure 46A and Figure 46B similar components. The 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 that houses an inverter assembly 4604B. Some embodiments may include an electric motor assembly 4602B positioned between the gearbox assembly 4606B and a propeller assembly 4608B. Some embodiments may include a heat exchanger 4610B that is coupled to the motor assembly housing 4612B and fluidly coupled to the electric motor assembly 4602B and the gearbox assembly 4606B via a liquid flow path 4616B. The liquid flow path 4616B may be used to extract heat from components present within the electric motor assembly 4602B and the propeller assembly 4608B. The liquid flow path 4616B may convey the extracted heat to the heat exchanger 4610B, which transfers the heat to an air flow 4618B passing through cooling fins of the heat exchanger 4610B.

[0339] The liquid paths 4616A and 4616B are highly schematically shown as simple loops. In some embodiments, the liquid path 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 assembly housings 4612A and 4612B.

[0340] Figures 47A - 47B is a schematic diagram showing an example electric propulsion system of a VTOL aircraft consistent with the disclosed embodiments. The electric propulsion system 4700A may include an electric motor assembly 4702A and a gearbox assembly 4706A located within a motor-gearbox housing 4710A. Figure 47AThe embodiments depicted may include a main shaft passing through or traveling from the electric motor assembly 4702A to a propeller assembly 4708A located outside the motor-gearbox housing 4710A. Additionally, the gearbox assembly 4706A may not share an axis with the electric motor assembly 4702A or the main shaft used by the electric motor assembly 4702A to provide torque to the propeller assembly 4708A. In such embodiments, the gearbox assembly 4706A may still provide gear reduction between the electric motor assembly 4702A and the propeller assembly 4708A. Some embodiments may also include an inverter assembly 4704A located within an inverter assembly housing 4712A, the inverter assembly housing being directly or indirectly mounted to the motor-gearbox housing 4710A. Although the inverter assembly 4704A is shown as being mounted to the outer edge of the motor-gearbox housing 4710A, in some embodiments, the inverter assembly may have a circular profile that surrounds or partially surrounds the motor-gearbox housing 4710A. Additionally, some embodiments may include an inverter assembly housing 4704A that may be coupled to an outer surface of the motor-gearbox assembly housing that is opposite the propeller assembly 4708A. In some embodiments, the electric motor assembly 4702A, the gearbox assembly 4706A, and the inverter assembly 4704A may each include various components that generate various volumes for each component, and thus, the motor-gearbox housing 4710A and the inverter assembly housing 4712A may have various profiles and volumes based on their respective component configurations.

[0341] Figure 47B A cross-sectional view of a marine propulsion system 4700B is shown. Although Figure 47B may be associated with Figure 47AHowever, in the drawings, elements identified by like numerals may not refer to the same element. Some embodiments of the electric propulsion system 4700B may include an electric motor assembly 4702A and a gearbox assembly 4706A located within a common motor-gearbox housing 4702B, where a shaft 4712B passes through the electric motor assembly 4702A. Some embodiments may include a propeller assembly mechanically coupled to the shaft 4712B. In some embodiments, the electric motor assembly 4702A may include a stator 4704B having a stator winding 4706B and a rotor 4710B having a magnet array 4708B aligned along the shaft 4712B. In some embodiments, the rotor 4710B may be directly or indirectly connected to a secondary shaft 4716B surrounding the shaft 4712B such that the secondary shaft 4716B rotates at a speed equal to the speed of the rotor 4710B. Further for this example, embodiments of the secondary shaft 4716B may have a splined shaft that engages a gearbox assembly 4706A adjacent to the electric motor assembly 4702A, where the gearbox assembly 4706A also engages the shaft 4712B to provide torque to the propeller assembly 4708A. Embodiments of the gearbox assembly 4706A as described herein may include at least a first gear 4722B, a second gear 4720B, and a gearbox shaft 4718B connecting them. In some embodiments, the radius of the first gear 4722B may be greater than the diameter of the second gear 4720B, and vice versa. Thus, the splined portion of the secondary shaft 4716B may interact with the first gear 4722B and rotate the first gear 4722B at the speed of rotation of the rotor 4710B. The rotating first gear 4722B may drive the rotation of the gearbox shaft 4718B and the second gear 4720B. The second gear 4720B of the gearbox assembly 4706A may engage a portion of the shaft 4714B that has a radius different from the radius of the portion of the shaft 4712B connected to the propeller assembly 4708A. In such embodiments, the gearbox shaft 4718B of the gearbox assembly 4706A may be positioned so as not to share an axis with the shaft 4712B or the electric motor assembly 4702A, but still provide a gear reduction to the shaft 4712B and thus provide torque to the propeller assembly 4708A.

[0342] Figure 48FIG. is a schematic diagram showing an example electric propulsion system of a VTOL aircraft consistent with the disclosed embodiments. The electric propulsion system 4800 may include an electric engine housed within an electric engine housing 4802, and the electric engine housing is aligned along an axis 4804 that travels from the electric engine housing 4802 to a propeller assembly 4808 including a propeller 4810. In some embodiments, the electric propulsion system 4800 may include a heat exchanger 4806 that is fluidly coupled to components of the electric engine via a liquid flow path present within the electric engine housing 4802. Some embodiments may include an electric engine housing 4802 that is coupled to a boom 4816 of the aircraft via a device 4814 for defining the position of the electric propulsion system. Some embodiments may also include a blade pitch actuator 4812 coupled to the rear of the electric engine housing 4802. Depending on the flight phase in which the aircraft is engaged, components of the electric engine may generate various amounts of heat. For example, components of the electric engine in a vertical takeoff and landing aircraft may generate more heat during the hover phase of flight than during the cruise phase, and thus, more air flow may be required through the heat exchanger 4806 during the hover phase than during the cruise phase to cool the liquid used to cool and / or lubricate components of the electric engine. Thus, some embodiments may include a boom 4816 that includes a cavity 4818 in the boom, where the heat exchanger 4806 may be housed during the cruise phase. Since the air required for the cooling system is reduced during various flight phases, the cavity 4818 may be used to block or reduce the air flow into the heat exchanger during flight.

[0343] The embodiments can be further described using the following clauses:

[0344] Clause Set A:

[0345] 1. An inverter assembly for converting direct current (DC) power to 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 bus bar, 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 for positioning the at least one PCBA, and the plurality of locating pins pass through the plurality of through holes in the capacitor housing and the at least one PCBA and are connected to the housing.

[0346] 2. The inverter assembly according to clause A1, wherein the central hole is substantially aligned with the main shaft of the electric propulsion system.

[0347] 3. The inverter assembly according to clause A1 or A2, wherein the at least one PCBA and the capacitor assembly are stacked.

[0348] 4. The inverter assembly according to any one of clauses A1 to A3, wherein the at least one PCBA includes a gate drive PCBA and a power PCBA, and wherein the capacitor assembly is positioned between the gate drive PCBA and the power PCBA.

[0349] 5. The inverter assembly according to any one of clauses A1 to A4, wherein: the central hole of the capacitor assembly is a through hole, and the inverter assembly has a substantially annular shape.

[0350] 6. The inverter assembly according to any one of clauses A1 to A5, wherein the at least one busbar is positioned outside the capacitor housing.

[0351] 7. The inverter assembly according to 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.

[0352] 8. The inverter assembly according to clause A7, wherein the heat exchanger is coupled to a hot plate.

[0353] 9. The inverter assembly according to clause A8, wherein each of the control board, the hot plate, and the EMI shield includes a plurality of alignment holes for aligning with the positioning pins.

[0354] 10. The inverter assembly according to any one of clauses A8 to A9, wherein the plurality of positioning pins includes rods built into the hot plate.

[0355] 11. The inverter assembly according to any one of clauses A7 to A10, wherein the heat exchanger is configured to cool the inverter assembly using a fluid.

[0356] 12. The inverter assembly according to clause A11, wherein the fluid is oil.

[0357] 13. The inverter assembly according to any one of clauses A1 to A12, wherein the at least one capacitor is an annular capacitor.

[0358] 14. The inverter assembly according to any one of clauses A1 to A9, wherein the plurality of positioning pins are screws.

[0359] 15. The inverter assembly according to any one of clauses A1 to A9, wherein the plurality of locating pins are bolts.

[0360] 16. The inverter assembly according to any one of clauses A1 to A9, wherein the plurality of locating pins are rods pre-fixed to the capacitor housing.

[0361] 17. A power propulsion system for a vertical takeoff and landing (VTOL) aircraft, the power propulsion system comprising: an electric motor assembly comprising at least a stator and a rotor; and an 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 capac...

Claims

1. An inverter assembly for converting direct current (DC) power to alternating current (AC) power for use in an electric propulsion system, the inverter assembly comprising: A housing; A capacitor assembly, the capacitor assembly comprising: 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 located inside the housing, and The plurality of locating pins pass through the plurality of through holes in the capacitor housing and the at least one PCBA and are connected to the housing.

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

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

4. The inverter assembly according to any one of claims 1 to 3, 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.

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

6. The inverter assembly according to any one of claims 1 to 5, wherein the at least one busbar is located outside the capacitor housing.

7. The inverter assembly according to any one of claims 1 to 6, further comprising: A control board having low voltage (LV) logic inputs; An electromagnetic interference (EMI) shield; And A heat exchanger; Wherein the control board and the EMI shield are located inside the housing; and Wherein the heat exchanger is outside the housing.

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

9. The inverter assembly according to claim 8, wherein each of the control board, the hot plate, and the EMI shield includes a plurality of alignment holes for alignment with the locating pins.

10. The inverter assembly according to claim 8 or 9, wherein the plurality of locating pins includes rods built into the hot plate.

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

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

13. The inverter assembly according to any one of claims 1 to 12, wherein the at least one capacitor is an annular capacitor.

14. The inverter assembly according to any one of claims 1 to 9, wherein the plurality of locating pins comprise screws.

15. The inverter assembly according to any one of claims 1 to 9, wherein the plurality of locating pins comprise bolts.

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

17. The inverter assembly according to any one of claims 1 to 16, wherein the at least one PCBA includes a flexible PCBA structure.

18. The inverter assembly according to any one of claims 1 to 17, wherein the at least one PCBA includes a rotor position sensor integrated into the at least one PCBA.

19. A power propulsion system for a vertical takeoff and landing (VTOL) aircraft, the power 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 including: A housing; A capacitor assembly, the capacitor assembly including: 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 positioning pins; Wherein The capacitor assembly and the at least one PCBA are positioned inside the housing, and The plurality of positioning pins pass through the plurality of through holes in the capacitor housing and the at least one PCBA and are connected to the housing.

20. The power propulsion system according to claim 19, 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.

21. The power propulsion system according to claim 20, wherein: The motor housing has a hot side and a cold side; The motor housing encloses a sealed environment; and The rotor is configured to generate an air movement from the cold side towards the hot side within the sealed environment to provide a cooling effect to one or more components on the hot side outside the motor housing.

22. The power propulsion system according to claim 20 or 21, wherein the main axis passes through the center line of the motor housing.

23. The power propulsion system according to any one of claims 20 to 22, further comprising a gearbox assembly and a propeller assembly, wherein: The main axis is substantially aligned with the central hole of the capacitor assembly; The electric motor assembly drives the propeller assembly through the main axis; The main axis 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 at opposite ends of the main axis.

24. A power propulsion system for a vertical takeoff and landing (VTOL) aircraft, the power 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 axis, The electric motor is positioned between the gearbox assembly and the propeller assembly, and The main axis extends through the gearbox assembly; And An inverter assembly, the inverter assembly including: A housing; a capacitor assembly having: A central hole, the central hole being substantially aligned with the main shaft; At least one capacitor; A capacitor housing having at least one bus bar; and A plurality of through holes in the capacitor housing; At least one printed circuit board assembly (PCBA); and A plurality of locating pins; Wherein: The inverter assembly and the propeller assembly are positioned at different ends of the main shaft, The capacitor assembly and the at least one PCBA are positioned inside the housing, 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.

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