Aircraft Propulsion Unit

Abstract

The aircraft propulsion unit includes an electric motor, at least one accessory unit used to operate the electric motor, an inverter module including a plurality of inverters that power the electric motor and the at least one accessory unit, and a cooling system coupled to the electric motor and the inverter module, the cooling system including coolant passages for circulating a coolant through or adjacent to the electric motor and the at least one accessory unit.

Description

[Technical field]

[0001] CROSS-REFERENCE TO RELATED APPLICATIONS This application claims the benefit of U.S. Patent Application No. 63 / 147,560, filed February 9, 2021, the contents of which are incorporated by reference herein as if expressly set forth herein.

[0002] The present invention relates generally to the field of aeronautics, and more particularly to packaging or cooling of aircraft propulsion systems. [Brief description of the drawings]

[0003] To easily identify the description of any particular element or operation, the most significant digit(s) in a reference number refers to the figure number in which that element is first introduced. [Figure 1] FIG. 1 is a top view of an aircraft in accordance with some embodiments. [Diagram 2] FIG. 2 is a schematic diagram of an aircraft energy system for use with the aircraft of FIG. 1 according to some embodiments. [Diagram 3] FIG. 3 illustrates a portion of an aircraft propulsion system 300 for use with the aircraft 100 of FIG. 1 according to some examples. [Figure 4] FIG. 4 further illustrates a portion of the aircraft propulsion system of FIG. 3 according to some examples. [Diagram 5] FIG. 5 illustrates a partial cross-sectional view of the aircraft propulsion system of FIGS. 3 and 4 according to some examples. [Figure 6] FIG. 6 illustrates an inverter board for use in an aircraft propulsion system, according to some examples. [Figure 7] FIG. 7 illustrates thermal interfaces between multiple thermal connections and a cold plate of the inverter board of FIG. 6 according to some examples. [Figure 8] FIG. 8 illustrates a perspective view of the aircraft propulsion system of FIGS. 3 and 4 in accordance with some examples. [Figure 9A-9C]9A, 9B, and 9C illustrate tilting of an aircraft propulsion system and associated components such as a propeller and a nacelle, according to some examples. [Figure 10A-10C] 10A, 10B, and 10C illustrate tilting of an aircraft propulsion system and associated components such as a propeller and a nacelle, according to some examples. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0004] The following description of some embodiments of the invention is not intended to limit the invention to those embodiments, but is intended to enable one of ordinary skill in the art to make and use the invention.

[0005] FIG. 1 is a plan view of an aircraft 100. The aircraft 100 includes a fuselage 114, two wings 112, a tail 110, and a propulsion system 108 embodied as tiltable rotor assemblies 116 disposed in nacelles 118. The aircraft 100 includes one or more power sources embodied in FIG. 1 as nacelle battery packs 104 and wing battery packs 106. In the illustrated embodiment, the nacelle battery packs 104 are disposed in inboard nacelles 102, although it will be understood that the nacelle battery packs 104 may be disposed in other nacelles 118 forming part of the aircraft 100. The battery packs form part of an energy system 200, which will be described with reference to FIG. 2. The aircraft 100 typically includes associated equipment such as electronic infrastructure, control surfaces, cooling systems, landing gear, etc.

[0006] The wings 112 function to generate lift to support the aircraft 100 during forward flight. The wings 112 may additionally or alternatively function to structurally support the battery packs 202, the battery modules 204, and / or the propulsion system 108 under various structural stresses (e.g., aerodynamic forces, gravity, thrust forces, external point loads, distributed loads, and / or body forces, etc.). The wings 112 may have any suitable geometry and / or arrangement on the aircraft.

[0007] 2 is a schematic diagram of an aircraft energy system 200 for use with the aircraft 100 of FIG. 1 in accordance with some embodiments. As shown, the energy system 200 includes one or more battery packs 202. Each battery pack 202 may include one or more battery modules 204, which may include a number of cells 206.

[0008] Typically associated with the battery pack 202 are one or more electric propulsion systems 108, a battery mate 208 for connecting it to other components of the energy system 200, a burst membrane 210 as part of a ventilation system, a fluid circulation system 212 for cooling, and power electronics 214 to regulate the delivery of power (from the operating battery to the charging battery) and provide integration of the battery pack 202 with the electronic infrastructure of the energy system 200. As shown in FIG. 1, the propulsion system 108 may comprise multiple rotor assemblies.

[0009] The electronic infrastructure and power electronics 214 may additionally or alternatively function to integrate the battery packs 202 into the energy system of the aircraft. The electronic infrastructure may include a Battery Management System (BMS), power electronics (HV architecture, power components, etc.), LV architecture (e.g., vehicle wire harness, data connections, etc.), and / or any other suitable components. The electronic infrastructure may include inter-module electrical connections that may transmit power and / or data between the battery packs and / or modules. The inter-module may include bulkhead connections, bus bars, wire harnesses, and / or any other suitable components.

[0010] The battery packs 202 function to rechargeably store electrochemical energy for supplying the propulsion system 108. The battery packs 202 may be positioned and / or distributed around the aircraft in any suitable manner. The battery packs may be positioned within a wing (e.g., inside a wing cavity), inside a nacelle, and / or any other suitable location on the aircraft. In a particular example, the system includes a first battery pack within an inboard portion of the left wing and a second battery pack within an inboard portion of the right wing. In a second particular example, the system includes a first battery pack within an inboard nacelle of the left wing and a second battery pack within an inboard nacelle of the right wing. The battery packs 202 may include multiple battery modules 204.

[0011] The energy system 200 includes a cooling system (e.g., fluid circulation system 212) that functions to circulate a working fluid within the battery pack 202 to remove heat generated by the battery pack 202 during operation or charging. The battery cells 206, battery modules 204, and / or battery pack 202 may be fluidly connected in series and / or parallel by the cooling system in any suitable manner.

[0012] Figure 3 illustrates a portion of an aircraft propulsion system 300 for use with the aircraft 100 of Figure 1 according to some examples. The aircraft propulsion system 300 includes a motor 302 and one or more accessory units used in conjunction with the motor 302 for operation of the aircraft propulsion system 300, which may include, for example, a blade pitching mechanism 304, a tilt mechanism 306, and an inverter system 308. More specifically, Figure 3 illustrates a cross section through one half of the inverter system 308; see further Figure 4 for a cross section through both halves of the inverter system 308.

[0013] Accessory units or systems used in connection with the operation of aircraft propulsion system 300 may also include a radiator 310, a fan 312, a pump 314, and an accumulator 316, which together comprise a cooling system for aircraft propulsion system 300. The cooling system components are connected to each other and coupled to a number of cooling plates 322 via coolant passages 320.

[0014] Inverter system 308 includes an inverter board 324, a control board 326, and a motor inverter board 340 mounted within inverter housing 318. Motor inverter board 340 includes an inverter 350 that provides power to motor 302. Inverter board 324 includes multiple inverters, such as inverter 334 coupled to blade pitching mechanism 304 by electrical connection 348, inverter 336 coupled to tilt mechanism 306 by electrical connection 342, and inverter 338 coupled to integrated pump 314 and fan 312 by electrical connection 344. Motor 302 is coupled to inverter 350 by electrical connection 346.

[0015] Inverter system 308 functions to regulate the power provided to motor 302, blade pitching mechanism 304, tilt mechanism 306, fan 312, and pump 314 to control their operation. More specifically, inverter system 308 functions, in some examples, to control the frequency and / or voltage of the power provided to multiple alternating current (AC) motors in each accessory unit to control the rotational speed, displacement, and / or torque of that particular accessory unit.

[0016] In some examples, the motor 302 is connected to the rotor 120 of the aircraft 100 or is integrated into the hub of the rotor 120. The motor 302 may be an in-runner motor, an outrunner motor, and / or any other suitable type of motor. Preferably, the motor 302 is a large diameter motor and / or a motor designed and configured (with gearing, etc.) to provide high torque and low speed to a propeller. The motor 302 may have any suitable power capability and / or power requirement. Preferably, the motor 302 is a three-phase motor, and more preferably wound as two independent three-phase motors for redundancy and performance. The motor 302 may have power thresholds below 80 kW, 500 kW, above 500 kW, any range bounded by those values, and / or any other suitable power characteristic (e.g., peak power, maximum continuous power, nominal power, maximum power of each set of windings of a dual-winding motor, etc.). In particular examples, motor 302 may rotate rotor 120 at a maximum speed of less than 100 RPM, 100 RPM, less than 5000 RPM, 5000 RPM, greater than 5000 RPM, any range bounded by those values, and / or any suitable speed, and may operate at a maximum torque of less than 10 N-m, 50 N-m, 5000 N-m, greater than 5000 N-m, any range bounded by those values, and / or any suitable maximum torque.

[0017] The inverter 336 is configured to provide regulated power to the tilt mechanism 306, which in some examples functions to pivot and / or translate the motor 302 between a forward configuration and a hovering or vertical flight configuration. The tilt mechanism 306 may be coupled to an aft / inboard portion of the motor 302 (and / or an inverter attached thereto) or a forward / inboard portion of the motor 302, coupling the motor 302 to the body of the aircraft, as shown in more detail in Figures 9A-9C and 10A-10C.

[0018] The inverter housing 318 functions to enclose and / or structurally support the control board 326, the inverter board 324, and the inverter board 340. The inverter housing 318 may additionally or alternatively function to form part of a cooling system, may mount the pump 314 and / or fan 312 of the cooling subsystem, may act as an EMI shield, and / or may perform other functions. The inverter housing 318 is preferably configured to nest within and / or be attached to a portion of the motor 302 (e.g., the rear portion in a forward orientation), but may be configured in other manners.

[0019] The inverter housing 318 may include multiple integral elements that function as part of a cooling subsystem and / or function to transfer thermal energy from the inverter housing 318 to a working fluid (such as air or liquid coolant). The inverter housing 318 may include an integral cooling plate 322 that closes a base and / or a broad side of the inverter housing 318. The inverter housing 318 may also include multiple thermal cooling fins 332 that extend from a periphery of the inverter housing 318. In some examples, such as shown in FIGS. 3 and 4, the base plate of the inverter housing 318 includes the cooling plate 322 having a set of internal cooling channels and multiple cooling fins 332 at an aft portion of the exterior of the inverter housing 318 (e.g., facing aft when the aircraft propulsion system 300 is in a forward configuration).

[0020] The control board 326 functions to receive commands (e.g., from a flight processor or FMS) and control operation of the inverter boards based on the received commands. The control board 326 may additionally function to monitor various sensors and / or control various accessory units or actuators based on sensor feedback and interface with an on-board flight management system (FMS). The control board 326 may be configured to provide field-oriented control (FOC) or vector control, but may additionally or alternatively be configured to provide direct torque control (DTC), scalar control (e.g., via pulse width modulation for low power actuators such as fans), and / or any suitable control for any suitable actuators. Preferably, there is a specific control board 326 located within each individual coolant volume and / or subregion of the inverter housing 318 that is electrically connected to and / or controls each inverter within its respective coolant volume (subregion) of the inverter housing 318. However, additionally or alternatively, there may be a single control board 326 connected to and / or controlling all inverters in the inverter housing, or two or more control boards in each coolant volume. The control board 326 is preferably a printed circuit board (PCB), but may be suitably implemented in other manners. The control board may include a processor card and gate drive circuitry, although the control board may additionally or alternatively include any other suitable components.

[0021] The inverter board 324 and the inverter board 340 function to regulate power supplied to the actuators, such as the motor 302, the blade pitching mechanism 304, the tilt mechanism 306, the fan 312, the pump 314, etc., to control their operation according to signals from the control board 326. More specifically, the inverter boards convert DC power (e.g., from an onboard power source, such as the battery pack 202) into a phase output of a specific frequency and / or voltage (e.g., supplied to the AC actuators to control the rotational speed and / or torque). Each inverter board includes one or more inverter circuits (hereinafter, "inverters") associated with a set of windings of the respective actuators of the set. The inverters include any suitable arrangement, combination, and / or permutation of transformers, resistors, transistors (e.g., MOSFETs), capacitors (e.g., decoupling DC link capacitors), and / or any other suitable electrical components interconnected to configure an electrical circuit specified according to the power requirements of the respective actuators.

[0022] The set of inverter boards preferably includes a primary (e.g., high power) inverter board 340 that includes an inverter circuit for the highest power actuator of the actuator set (e.g., motor 302), and a secondary (e.g., low power) inverter board 324 that includes inverters for the remaining actuators of the actuator set. The power requirements of the high power inverter board 340 (and associated highest power actuator) may exceed the collective power requirements of the remaining actuators of the actuator set such that the maximum power output of the primary inverter board 340 is greater than the maximum power output of the secondary inverter board 324 (e.g., by less than 0.5, 3, 5, more than 5, any ratio therebetween, and / or any other suitable value). However, the multiple inverter boards may additionally or alternatively include a single board housing all inverters, multiple secondary (low power) boards, and / or the multiple inverters may be otherwise distributed across any suitable set of inverter boards.

[0023] The inverter board 324, inverter board 340, and control board 326 are preferably arranged in a "stacked" configuration, but may be otherwise suitably arranged parallel to one or more broad faces / base plates of the inverter housing, perpendicular to the motor's axis of rotation 408, perpendicular to the firewall 410, and / or otherwise. The control board 326 is preferably arranged between the primary inverter board 340 and the secondary inverter board 324, but may additionally or alternatively be arranged on the opposite side of the thickness of the secondary inverter board 324 from the primary inverter board 340, and / or may be otherwise suitably arranged. The set of inverter boards and / or control boards may be distributed in any suitable manner. Low voltage power and data, such as sensors and control signals, may be routed between the control board and the inverter board using flexible printed circuits. Conversely, the power connection between the inverter and the actuators is preferably formed by busbar connections and / or rigid electrical connections (e.g., perpendicular to the broad faces of the laminate boards). However, the power and / or data connections may be suitably routed between the inverter and / or control boards in other manners.

[0024] Coupled to the inverter board 340 are a number of DC link capacitors 328. The DC link capacitors 328 constitute a load balancing energy storage device that helps protect the inverter network from momentary voltage spikes, surges, and EMI. The DC link capacitors 328 can be ceramic, film, and / or a mixture thereof. The DC link capacitors 328 can be disposed along the rear side of the inverter board 340 and / or adjacent to the base plate of the inverter housing 318. In a second example, the DC link capacitors 328 can be disposed distal to the firewall and / or along the perimeter of the inverter. The DC link capacitors 328 can be enclosed within a thermally conductive epoxy 330 that serves to transfer heat from the DC link capacitors 328 to the cooling fins 332 and the cooling plate 322.

[0025] The cold plates 322 and 352 function to remove thermal energy from the heat generating components of the control board 326 and / or inverter board 324 and inverter board 340, as well as the DC link capacitors 328. The aircraft propulsion system 300 may include multiple individual cold plates disposed within respective separate coolant volumes of the housing (e.g., one on each side of the firewall 410 as shown in FIG. 4) and paired with (thermally coupled to) a single multi-inverter, and / or multiple cold plates thermally coupled to multiple multi-inverters. A multi-inverter is a single inverter that regulates power for multiple actuators. There may be a single cold plate thermally within each multi-inverter, multiple cold plates within each multi-inverter, a single cold plate thermally coupled to multiple multi-inverters, and / or any suitable number of cold plates in the system.

[0026] In some examples, the set of cold plates includes a primary cold plate 322 thermally coupled to a heat generation area of ​​the primary inverter board 340 and one or more secondary cold plates 352 thermally coupled to the control board 326 and / or secondary inverter board 324. In a first example, the primary cold plate 322 is disposed between the primary inverter board 340 and the inverter housing 318 (and / or is integrated into the inverter housing 318). In a second example, the one or more secondary cold plates 352 are disposed between and thermally coupled to the secondary inverter board 324 and the control board 326 (e.g., a processor card). In the second example, the projected areas of each heat generation area onto the broad side of the one or more secondary cold plates 352 (from the secondary inverter board 324 and the control board 326) may not overlap or may overlap. However, the one or more secondary cold plates 352 may be disposed in other ways relative to the control board 326 and / or the processing board (and the heat generation areas thereon). In some examples, the multiple cold plates can be integrated into the body of the inverter housing 318 and / or can form a base plate of the inverter housing 318 that closes off (e.g., at the rear end) multiple separate coolant volumes. In such examples, a single cold plate can include an internal volume that extends across the heat generation area and / or broad side of the inverter boards (and / or control boards) of the multiple multi-inverters and is thermally connected to both multi-inverters. In such examples, the cold plate can cool redundant multiple multi-inverters via parallel multiple coolant flow paths, but can additionally or alternatively cool multiple multi-inverters in any suitable combination / permutation of serial and parallel multiple coolant flows. Alternatively, a single cold plate can be thermally connected to multiple multi-inverters with multiple fluid channels (e.g., mechanically separated and forming parallel coolant flow paths).

[0027] The multiple coolant routing components forming the coolant passages 320 function to direct the circulation of coolant (e.g., water / glycol mixture, transformer oil, etc.) through, adjacent to, or around the cold plates 322 and 352 and couple them to the rest of the cooling system (i.e., forming a cooling loop). The multiple coolant routing components may include any fluid manifolds, hoses, tubes, pipes, channels in the housing of the inverter, channels in the body of the motor, and / or any other suitable coolant routing components. Preferably, the coolant passages 320 fluidly connect the primary cold plate 322 to the secondary cold plate 352 in series (e.g., within a multi-inverter / sub-region). The coolant passages 320 may form a single fluid loop (e.g., all components in series, multiple sections of parallel fluid flow that all converge to pass through a section of the loop, etc.) or multiple parallel fluid loops. However, the coolant passages 320 may interconnect the various cooling components of the cooling system in any suitable combination and / or permutation of serial / parallel coolant flow. The multiple coolant routing components may pass through multiple orifices within the thickness of the inverter board (e.g., via fluid manifolds or other fluid routing) and / or may be routed around the periphery of the board. The multiple coolant routing components may include a first coolant routing termination at the rear end of the inverter housing 318 (e.g., proximal to the mounting side, proximal to the pump / radiator, coolant inlet) and a second coolant routing termination at the forward end of the inverter housing 318 (e.g., outlet). The second coolant routing termination is preferably coupled to the motor 302 and the first coolant routing termination is preferably joined to the pump 314, although the coolant passages 320 may otherwise interconnect various components of the cooling system.

[0028] The components of the coolant passage 320 can optionally direct the coolant flow through a radiator 310 that functions to evacuate heat from the coolant to the surrounding environment. In some examples, the radiator 310 can be nested adjacent to and / or adjacent to the tilt mechanism 306 such that the external airflow (e.g., ducted flow by the fan 312) through the radiator 310 is partially and / or completely blocked (e.g., in the direction of flow, lengthwise along the motor's axis of rotation 408, etc.) at one or more locations of the tilt mechanism 306. In particular, closely nesting the radiator 310 and tilt mechanism 306 and / or directly blocking the airflow through the radiator 310 can increase packing density and aerodynamic efficiency during forward flight, reducing power requirements of the motor 302 and inverter board 340 (which in turn eliminates necessary heat from the aircraft propulsion system 300). Similarly, displacing the radiator 310 with the motor 302 and inverter housing 318 during transformation of the tilt mechanism 306 in transition and / or hover configurations can increase the airflow and / or heat rejection achieved by the radiator 310 when the heat load is at its highest as a result of the highest power and / or heat rejection demands. See further FIGS. 9A-9C and 10A-10C. In such cases, the radiator 310 moving with the motor 302 can increase the airflow through the radiator 310, effectively doubling the heat rejection during hover or vertical flight. However, the system can include any other suitable radiator 310 and / or route coolant through the radiator 310 as appropriate. Alternatively, the system can reject heat via a refrigeration system and / or other quasi-ambient cooling architecture.

[0029] In some examples, the coolant routing components can fully fluidly enclose and contain the coolant without pressure exchange with the environment. In such examples, the coolant routing components can direct the coolant through the accumulator 316, thereby regulating the fluid pressure and preventing over-pressurization. Alternatively, the coolant passages 320 can include passive coolant venting to the surrounding environment and / or any other suitable pressure balancing mechanism to prevent gas accumulation within the cooling subsystem.

[0030] The pump 314 functions to circulate the coolant along coolant passages 320 and through the coolant routing components, cold plates, and / or actuators. The pump 314 can additionally or alternatively function to transport the coolant from the motor 302 and / or cold plates 322 to the radiator 310.

[0031] The fan 312 functions to circulate ambient air across a plurality of cooling fins 332 of the inverter housing 318 and / or through the radiator 310. In some examples, the fan 312 can be mechanically connected to a rotating shaft of the pump 314 and / or can be otherwise mechanically integrated with the pump 314. The fan 312 can be directly coupled to the pump 314 and configured to rotate at an angular velocity proportional to the angular velocity of the pump shaft (e.g., an equivalent angular velocity when geared off). The fan 312 can be ducted and / or unducted and / or implemented in any other suitable manner. Additionally or alternatively, the fan 312 can be separate from the pump 314 (e.g., integrated into a radiator assembly, etc.) and / or powered separately.

[0032] The aircraft propulsion system 300 may optionally include multiple sensors that function to monitor the operation of the system. The multiple sensors may include temperature sensors (e.g., thermistors, thermocouples, etc.), inertial sensors (e.g., accelerometers, gyroscopes, IMUs, etc.), impedance sensors, Hall effect sensors, flow sensors (e.g., flow sensors, fluid pressure sensors, etc.), and / or any other suitable sensors. In some examples, multiple temperature sensors may be used to monitor the temperature of the motor windings, bearings, coolant, and / or any other suitable components. In some examples, multiple flow sensors may monitor the coolant pressure and / or flow rate in the coolant subsystem. However, the system may include any other suitable sensors. The multiple sensors are preferably communicatively connected to the control board 326 and may be employed in conjunction with various operational control schemes (e.g., feed-forward, feedback, etc.). However, in some examples, it may be advantageous for multiple sensor inputs to be received on an on-board inverter board (e.g., inverter board 324, top of stack in forward configuration, secondary / triple-inverter board). In some such examples, the sensor inputs may be received at a section of the inverter board 324 that is electrically isolated from the inverters and relayed to the control board 326 (or FMS). Thus, the control board 326 may be considered to be “indirectly” connected to the various sensors of the aircraft propulsion system 300 and / or indirectly connected via the inverter board 324.

[0033] The routing of the coolant is preferably substantially uniform (e.g., varies by less than 10%, less than 20%, less than 50%, or exactly uniform, etc.) and / or provided with a constant cross-sectional area across various portions of the coolant flow path. The coolant is preferably circulated at a high flow rate through multiple coolant routing components (such that the coolant temperature rise through the motor 302 and / or inverter housing 318 can be negligible in some instances, e.g., the coolant temperature rises less than 5° C. through the motor).

[0034] In some examples, the coolant in the coolant passages 320 from the radiator 310 enters the motor 302 at the stator 404, passes through or between the multiple field coils in the stator 404, and then passes through the electrical bussing 406. The coolant in the coolant passages 320 then proceeds into the inverter housing 318 and through the cold plates 352 and 322 before returning to the pump 314 and from there back to the radiator 310. The coolant passages thus provide an integrated cooling system that not only cools the motor 302, but also the inverters of the multiple actuators associated with the aircraft 100. The direction of flow and the order of components in the cooling passages may, of course, be varied or reversed.

[0035] By packaging the inverter outside the actuation mechanism (e.g., tilt mechanism 906), the complexity of cable routing to multiple actuators outside the actuation mechanism (e.g., pump / fan, motor, blade pitch mechanism, etc.) can be reduced.

[0036] FIG. 4 further illustrates a portion of the aircraft propulsion system 300 of FIG. 3 according to some examples. More specifically, shown in FIG. 4 is a cross-sectional view through both halves of the inverter system 308 shown in FIG. 3. In some examples, the inverter housing 318 is configured to extend radially inward of the motor 302, and the stator 404 and / or rotor 402 of the motor 302 are disposed radially outward (with respect to the motor's rotational axis 408) of a portion of the inverter housing 318. In such examples, the inverter housing 318 may extend radially inward of the multiple permanent magnets or stator 404 of the motor 302. The outer periphery of the inverter housing 318 may be flush with the radial inner periphery of the motor 302 and / or may be inserted from the radial outer periphery of the motor 302, but may be otherwise suitably configured. More preferably, the inverter housing 318 may be radially inserted from the electrical bus 406 (e.g., multiple bus rings) of the motor 302 and / or may be surrounded by the housing of the stator 404. However, the inverter housing 318 may be otherwise suitably positioned relative to the motor. The inverter housing 318 may include electrical bus terminals, coolant channels / orifices, thermal fins, and / or any other suitable features in any suitable arrangement. The inverter housing 318 is preferably formed from a metal having a high thermal conductivity (e.g., aluminum), but may additionally or alternatively include thermally insulating, electrically insulating, plastic, composite, ferrous metal (e.g., iron), steel, copper, and / or any other suitable material.

[0037] The inverter housing 318 may include a firewall 410 that functions to subdivide the interior of the inverter housing into multiple (e.g., two) separate coolant volumes (e.g., a first volume 412 and a second volume 414 that are fluidly isolated) and / or to prevent propagation of thermal events between opposing portions of the interior of the inverter housing 318 (e.g., between redundant or secondary isolated volumes within the housing). The firewall 410 preferably extends through the interior of the inverter housing 318 between broad upper and lower surfaces (e.g., perpendicular to the upper and lower surfaces of the inverter housing 318 shown in FIG. 4 ), but may be suitably positioned in other ways). The firewall 410 may be positioned along a sagittal plane relative to the motor's axis of rotation 408 and / or may extend axially and radially relative to the axis of rotation 408, but may additionally or alternatively be suitably positioned in other ways. The multiple coolant volumes defined by firewall 410 within inverter housing 318 are preferably symmetrical and / or of substantially equal volume, although firewall 410 may suitably divide the inverter housing otherwise. Firewall 410 may be formed from the same material as the housing exterior (e.g., aluminum, steel, etc.) and / or any other suitable material.

[0038] The inverter system 308 may include redundant instance(s) of the control board 326 and / or inverter board 324 and inverter board 340, each associated with a separate coolant volume. However, multiple electronics may also be shared among multiple separate coolant volumes of the inverter housing 318. Multiple electronics in a common separate coolant volume are preferably connected together and cooperate to form a single inverter (e.g., a multi-inverter that regulates power for multiple actuators), but may alternatively be disconnected or otherwise configured. Thus, if a set of inverter boards can be considered a "multi-inverter" (e.g., a quad inverter) that can operate each set of actuators separately, the housing may include multiple such multi-inverters that can be thermally, mechanically, and / or electrically isolated on either side of the firewall 410. In a particular example, the firewall can subdivide the inverter housing into two separate portions, such as a first volume 412 and a second volume 414, each volume including a control board 326 and two inverter boards, inverter board 324 and inverter board 340, that cooperate to form a quad inverter. In some examples, the two quad inverters can actuate a set of four actuators cooperatively and / or independently. Thus, the inverter housing 318 can include two (redundant) quad inverters for a total of eight inverters commonly packaged within (and / or cooled by) the inverter housing 318.

[0039] Thus, examples of this technology, when combined with two independent three-phase motors mechanically coupled to each other in a single electric propulsion system, can provide dual redundancy within a single inverter system and / or within a single inverter housing 318. Such examples can utilize dual winding actuators, dual inverters and / or control boards, separate cooling components, and / or provide any other suitable redundancy. Such examples can similarly subdivide the inverter housing 318 into separate coolant volumes (e.g., using firewalls 410) to mitigate propagation of any thermal events between the redundant inverters.

[0040] Figure 5 illustrates a partial cross-sectional view of the aircraft propulsion system 300 of Figures 3 and 4 according to some examples. In particular, as described above with reference to Figure 4, the inverter housing 318 is nested radially inward of the motor 302, and the stator 404 and / or rotor 402 of the motor 302 are disposed radially outward (relative to the motor's axis of rotation 408) of a portion of the inverter housing 318. Also illustrated in Figure 5 are a number of cooling fins 332 for the DC link capacitor 328, an integrated pump / fan 502, a radiator 310, and some of the conduits that form the coolant passages 320.

[0041] This configuration provides high power-density inverter packaging by efficiently routing power and / or cooling through the inverter / control boards. In some examples, the system improves packaging efficiency of a brushless DC motor (e.g., an inverter packaged within the motor) by packaging one or more inverter boards inside the stator and / or rotor. Similarly, this configuration can improve power density by closely integrating a cooling subsystem within or partially within the motor 302 and / or inverter housing 318.

[0042] 6 illustrates an inverter board 604 used in the aircraft propulsion system 300 according to some examples. The inverter board 604 has a number of heat-generating components 602. In some examples, these are SiC switches with inverters 334, 336, and 338 on the inverter board 324. The heat-generating components 602 of the inverter board 604 can be disposed opposite one or more cold plates in the thickness direction of the inverter board 604. In such a case, the inverter board 604 can include a heat transfer path including a number of thermal coins 606 of highly conductive material disposed at the base of (and / or distributed around the heat-generating region of) the one or more heat-generating components 602 that extend through the inverter board 604 and thermally connect the one or more heat-generating components 602 to one or more cold plates, such as the cold plate 322.

[0043] The thermal coils 606 function to reduce the thermal resistance through the thickness of the substrate. The thermal coils 606 are preferably formed from a highly thermally conductive material, such as copper, aluminum, and / or other highly thermally conductive materials, and are preferably electrically insulated from the circuitry of the inverter substrate 604 to avoid shorting the substrate. In one example, the thermal coils 606 can include integrated electrically insulating layers, such as ceramic layers or other electrically insulating layers (e.g., having a lower thermal conductivity than the remainder of the material, a lower thermal conductivity than the substrate, etc.), an example of which is shown in FIG. 7. In a second example, the thermal coils 606 can be electrically insulated by electrically insulating coatings or seals at the periphery (e.g., between the electrical components and the exposed portions of the thermal coils, between the cold plate and the thermal coils, etc.).

[0044] In some examples, the inverter board 604 can include an insulating layer configured to thermally isolate components / areas of the inverter board from a cold plate (e.g., thermally coupled to a different heat generating area of ​​the same inverter board). In one example, the film capacitors are thermally isolated from the cold plate and cooled to ambient air, while the ceramic capacitors are cooled using a liquid coolant. This allows heat generating components with large cooling demands (that can withstand temperatures much higher than ambient temperature), such as MOSFETs, to be cooled separately using a liquid coolant. The insulation between the DC link film capacitors and the cold plate / base plate of the housing can have a thermal conductivity less than that of an air gap (of comparable thickness), have a thermal conductivity greater than that of an air gap, and / or have any other suitable thermal properties.

[0045] 7 illustrates a thermal interface between the thermal coils 606 and the cold plate 322 of the inverter board of FIG. 6 according to some examples. A fluid channel 702 is provided adjacent to the cold plate 322 and is supplied with coolant via the coolant passages 320. A thermally conductive layer 706 is provided between the thermal coils 606 and the cold plate 322 that it cools. An electrical insulation layer 704 is provided to electrically insulate the thermal coils 606 from the cold plate 322 and from each other. In another example, the thermal coils 606 can be attached to an electrical insulator 704, which is attached to the cold plate 322a.

[0046] 8 illustrates a perspective view of the aircraft propulsion system 300 of FIGs. 3 and 4 according to some examples. FIG. 8 illustrates the relative arrangement of the motor 302, the fan 312, the radiator 310, and some of the piping that forms part of the coolant passage 320.

[0047] 9A, 9B, and 9C illustrate the tilting of aircraft propulsion system 300 and associated components such as propeller 902 and nacelle 904, according to some examples. The aircraft is preferably an eVTOL aircraft (e.g., a multi-modal aircraft) as shown, but may additionally or alternatively include any suitable aircraft. Aircraft 100 is preferably a tiltrotor aircraft having multiple aircraft propulsion systems operable between a forward configuration (FIGS. 9A and 10A) and a hovering or vertical flight configuration (FIGS. 9C and 10C). However, the aircraft may alternatively be a fixed-wing aircraft having one or more rotor assemblies or propulsion systems, a helicopter having one or more rotor assemblies (e.g., at least one rotor assembly or aircraft propulsion system is oriented substantially axially to provide horizontal thrust), a tiltwing aircraft, a wingless aircraft (e.g., helicopter, multi-copter, quadcopter), and / or any other suitable rotary-wing aircraft or vehicle propelled by multiple propellers or multiple rotors.

[0048] As shown in Figures 9A-9C, in one example, a nacelle 904 including an aircraft propulsion system 300 (identified as a motor 302, an inverter system 308, and a radiator 310) and a propeller 902 having a blade pitching mechanism 908 can be tilted relative to the rest of the aircraft 100 by a tilt mechanism 906 located toward the rear of the nacelle 904.

[0049] When incorporated into a propulsive tilt mechanism of an aircraft that is configurable between forward and hover configurations, the cooling subsystems can advantageously utilize the increased airflow available in the hover configuration, as described below.

[0050] 10A, 10B, and 10C illustrate the tilting of aircraft propulsion system 300 and several associated components, such as propeller 902, relative to a nacelle 1004, according to some examples. As seen in FIG. 10B and 10C, in this example, aircraft propulsion system 300 (identified as motor 302, inverter system 308, and radiator 310) and propeller 1002 with blade pitching mechanism 1008 are tiltable relative to the nacelle 1004 by a tilt mechanism 1006 located toward the front of the nacelle 1004.

[0051] 10C, in the hovering configuration, the radiator 310 is exposed to the outside air as opposed to being housed within the nacelle 1004 as in the vertical configuration. This results in more airflow through the radiator 310 as a result of the adjacent airflow from the fan 312 and from the propeller 902. Because hovering has higher power requirements than horizontal flight, the additional cooling provided by the increased airflow through the radiator 310 can be advantageous.

[0052] Embodiments of the systems and / or methods may include any combination and permutation of the various system components and various method processes, and one or more examples of the methods and / or processes described herein may be performed asynchronously (e.g., sequentially), simultaneously (e.g., in parallel), or in any other suitable order by and / or using one or more example systems, elements, and / or entities described herein.

[0053] The term "rotor" as utilized herein when referring to a thrust-producing element may refer to a rotor, a propeller, and / or any other suitable rotary aerodynamic actuator. A rotor may refer to a rotary aerodynamic actuator utilizing an articulated or semi-rigid hub (e.g., the blade-to-hub connection may be articulated, flexible, rigid, and / or otherwise connected), and a propeller may refer to a rotary aerodynamic actuator utilizing a rigid hub (e.g., the blade-to-hub connection may be articulated, flexible, rigid, and / or otherwise connected), but as used herein, no such distinction is made, express or implied, and use of "rotor" may refer to either configuration, as well as any other suitable configuration of articulated or rigid blades and / or any other suitable configuration of blade connections to a central member or hub. Similarly, use of "propeller" may refer to either configuration, as well as any other suitable configuration of articulated or rigid blades and / or any other suitable configuration of blade connections to a central member or hub. Thus, a tiltrotor aircraft may be referred to as a tiltpropeller aircraft, a tiltprop aircraft, and / or otherwise appropriately referred to or described.

[0054] The term "board" as used herein in connection with a control board, an inverter board, etc., preferably refers to a circuit board. More preferably, "board" refers to a printed circuit board (PCB) and / or a plurality of electronic components assembled thereon, which may collectively form a printed circuit board assembly (PCBA). In a first example, the control board is a PCBA. In a second example, the inverter board is a PCBA. However, "board" may additionally or alternatively refer to a single-sided PCB, a double-sided PCB, a multi-layer PCB, a rigid PCB, a flexible PCB, and / or have any other suitable meaning.

[0055] The aircraft may include any suitable form of power storage or power storage unit (e.g., batteries, flywheels, ultra-capacitors, batteries, fuel tanks, etc.) that powers one or more actuators (e.g., rotors / propellers, tilt mechanisms, blade pitch mechanisms, cooling systems, etc.). Although the preferred power / fuel source is a battery, the system may be reasonably used with any suitable power / fuel source. The aircraft may include auxiliary and / or redundant power sources (e.g., backup batteries, multiple batteries) or may exclude redundant power sources. The aircraft may use batteries having any suitable cell chemistries (e.g., lithium ion, nickel cadmium, etc.) in any suitable electrical architecture or configuration (e.g., multiple packs, bricks, modules, cells, etc., and in any combination of series and / or parallel architectures).

[0056] In a particular example, the system is integrated into an electric tiltrotor aircraft that includes multiple tiltable rotor assemblies (e.g., six tiltable rotor assemblies). The electric tiltrotor aircraft can operate as a fixed-wing aircraft, a rotary-wing aircraft, and in any liminal configuration between fixed-wing and rotary-wing conditions (e.g., one or more of the multiple tiltrotor assemblies are partially rotated). The control system of the electric tiltrotor aircraft in this example can function to command and control the multiple tiltable rotor assemblies in a fixed-wing configuration, a rotary-wing configuration, and / or between the fixed-wing and rotary-wing configurations.

[0057] As used herein, the term "substantially" can mean exactly, approximately, within a given threshold or tolerance, and / or have any other suitable meaning.

[0058] Alternative embodiments implement the above methods and / or processing modules in a non-transitory computer-readable medium that stores computer-readable instructions. The instructions can be executed by multiple computer-executable components integrated with the computer-readable medium and / or processing system. The computer-readable medium may include any suitable computer-readable medium, such as RAM, ROM, flash memory, EEPROM, optical devices (CD or DVD), hard drives, floppy drives, non-transitory computer-readable media, or any suitable device. The computer-executable components may include a computing system and / or processing system (e.g., including one or more collocated or distributed remote or local processors) connected to the non-transitory computer-readable medium, such as a CPU, GPU, TPUS, microprocessor, or ASIC, although the instructions may alternatively or additionally be executed by any suitable dedicated hardware device.

[0059] Embodiments of the systems and / or methods may include any combination and permutation of the various system components and various method processes, and one or more examples of the methods and / or processes described herein may be performed asynchronously (e.g., sequentially), simultaneously (e.g., in parallel), or in any other suitable order by and / or using one or more example systems, elements, and / or entities described herein.

[0060] As will be appreciated from the foregoing detailed description and the drawings and claims, those skilled in the art can make modifications and variations to the embodiments of the invention without departing from the scope of the invention, which is defined in the following claims.

Claims

1. 1. An aircraft propulsion unit, comprising: An electric motor; at least one accessory unit used to operate the electric motor, the at least one accessory unit including a tilt mechanism for tilting the aircraft propulsion unit between a vertical flight configuration and a horizontal flight configuration; an inverter module including a plurality of inverters for powering the electric motor and the at least one accessory unit; a cooling system coupled to the electric motor and the inverter module, the cooling system including a coolant passage for circulating a coolant through or adjacent to the electric motor and the inverter module.

2. The aircraft propulsion unit of claim 1 , wherein the inverter module is at least partially nested within the electric motor.

3. The aircraft propulsion unit of claim 1 , wherein the inverter module includes one or more cold plates for transferring heat from the plurality of inverters to the coolant in the coolant passages.

4. The aircraft propulsion unit of claim 1 , wherein the at least one accessory unit includes a pump for circulating the coolant through the coolant passages.

5. 5. An aircraft propulsion unit as claimed in claim 4, wherein the cooling system includes a radiator and the pump includes a fan for blowing air through the radiator.

6. 2. The aircraft propulsion unit of claim 1, wherein the cooling system includes a radiator, and wherein airflow through the radiator in use when the aircraft propulsion unit is in the vertical flight configuration is greater than when the aircraft propulsion unit is in the horizontal flight configuration.

7. The aircraft propulsion unit of claim 1 , wherein the at least one accessory unit includes a blade pitching mechanism for adjusting the pitch of rotor blades.

8. 2. The aircraft propulsion unit of claim 1, wherein the inverter module includes an inverter module housing, the inverter module housing including a plurality of cooling fins for transferring heat from the inverter module.

9. 2. The aircraft propulsion unit of claim 1, wherein the inverter module comprises an inverter module housing including a first region and a second region spaced from the first region, the first region and the second region including redundant inverters.

10. 10. The aircraft propulsion unit of claim 9, wherein the first and second regions are separated by a firewall.

11. 2. The aircraft propulsion unit of claim 1, wherein the motor includes a stator and a rotor arranged about a rotational axis of the motor, the inverter module is located inside the stator and the rotor, and the inverter module includes a plurality of circuit boards, the plurality of circuit boards being in a stacked arrangement perpendicular to the rotational axis of the motor.

12. 1. An aircraft, Torso and one or more thrust producing units; one or more propulsion units that drive the thrust producing units; Each propulsion unit is An electric motor; at least one accessory unit used to operate the electric motor, the at least one accessory unit including a tilt mechanism for tilting the aircraft propulsion unit between a vertical flight configuration and a horizontal flight configuration; an inverter module including a plurality of inverters for powering the electric motor and the at least one accessory unit; a cooling system coupled to the electric motor and the inverter module, the cooling system including coolant passages for circulating a coolant through or adjacent to the electric motor and the inverter module; The cooling system further includes a radiator, and wherein airflow through the radiator, in use, when the aircraft propulsion unit is in the vertical flight configuration, is greater than when the aircraft propulsion unit is in the horizontal flight configuration.

13. The aircraft of claim 12 , wherein the inverter module is at least partially nested within the electric motor.

14. The aircraft of claim 12 , wherein the at least one accessory unit includes a blade pitching mechanism for adjusting the pitch of rotor blades.

15. 13. The aircraft of claim 12, wherein the inverter module includes an inverter module housing, the inverter module housing including a first region and a second region spaced from the first region, the first region and the second region including redundant inverters.

16. 1. A method for cooling an aircraft propulsion unit comprising an electric motor, at least one accessory unit used to operate the electric motor, and an inverter module, the inverter module including a housing and a plurality of inverters that provide power to the electric motor and the at least one accessory unit, the method comprising: circulating a coolant through coolant passages formed within said electric motor; circulating the coolant through the housing of the inverter module; circulating the coolant through a heat exchanger; tilting the aircraft propulsion unit between a horizontal flight configuration and a vertical flight configuration such that airflow through the heat exchanger is increased in the vertical flight configuration.

17. the inverter module includes one or more cold plates for transferring heat from the plurality of inverters to the coolant in the coolant passages; The method of claim 16 , further comprising circulating the coolant through the one or more cold plates.

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