Aircraft propulsion unit

Abstract

To provide an aircraft propulsion unit including a preferable cooling system.SOLUTION: An aircraft propulsion unit includes: an electric motor; at least one accessory unit used for operating the electric motor; an inverter module including a plurality of inverters for powering 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 comprising a coolant path for circulating a coolant through or adjacent to the electric motor and the at least one accessory unit.SELECTED DRAWING: Figure 3

Description

Technical Field

[0001] Cross - Reference to Related Applications This application claims the benefit of U.S. Patent Application No. 63 / 147,560, filed on Feb. 9, 2021, the content of which is incorporated herein by reference as if explicitly set forth.

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

Brief Description of the Drawings

[0003] To facilitate the identification of any particular element or operation description, the most significant digit in the reference number refers to the figure number in which the element is first introduced.

Figure 1

Figure 2

Figure 3

Figure 4

Figure 5

Figure 6

Figure 7

Figure 8

Figures 9A - 9C

Figures 10A - 10C

[0004] The following description of some embodiments of the present invention is not intended to limit the present invention to these embodiments, but is intended to enable one of ordinary skill in the art to manufacture and use the present 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 a plurality of tiltable rotor assemblies 116 disposed within a plurality of nacelles 118. The aircraft 100 includes one or more power sources embodied as a plurality of nacelle battery packs 104 and a plurality of wing battery packs 106 in FIG. 1. In the illustrated embodiment, the plurality of nacelle battery packs 104 are disposed within a plurality of inboard nacelles 102, although it will be understood that the plurality of nacelle battery packs 104 can be disposed within other nacelles 118 that form part of the aircraft 100. The battery packs form part of an energy system 200 described with reference to FIG. 2. The aircraft 100 typically includes associated equipment such as an electronic infrastructure, control surfaces, a cooling system, a landing gear, and the like.

[0006] The wing 112 functions to generate lift for supporting the aircraft 100 during forward flight. The wing 112 can additionally or alternatively function to structurally support the battery pack 202, the battery module 204, and / or the propulsion system 108 under the influence of various structural stresses (such as aerodynamic forces, gravity, propulsion forces, external point loads, distributed loads, and / or body forces, etc.). The wing 112 can have any suitable geometry and / or arrangement on the aircraft.

[0007] FIG. 2 is a schematic diagram of an aircraft energy system 200 for use in the aircraft 100 of FIG. 1 according to 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, and the battery module 204 may comprise several 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 the ventilation system, a fluid circulation system 212 for cooling, and power electronics 214 that regulates the delivery of power (from an operating battery to a charging battery) and provides integration of the battery pack 202 with the electronic infrastructure of the energy system 200. As shown in FIG. 1, the propulsion system 108 can comprise a plurality of rotor assemblies.

[0009] The electronic infrastructure and power electronics 214 can additionally or alternatively function to integrate the battery pack 202 into the aircraft's energy system. The electronic infrastructure can include a battery management system (BMS), power electronics (HV architecture, power components, etc.), LV architecture (e.g., vehicle wire harness, data connection, etc.), and / or any other suitable components. The electronic infrastructure can include an inter-module electrical connection capable of transmitting power and / or data between the battery pack and / or modules. The inter-module can include a bulkhead connection, busbar, wire harness, and / or any other suitable components.

[0010] The battery pack 202 functions to store electrochemical energy in a rechargeable manner for supply to the propulsion system 108. The battery pack 202 can be arranged and / or distributed around the aircraft in any suitable manner. The battery pack can be arranged inside the wing (e.g., inside the wing cavity), inside the nacelle, and / or at any other suitable location on the aircraft. In a particular embodiment, the system includes a first battery pack in the inboard portion of the left wing and a second battery pack in the inboard portion of the right wing. In a second particular embodiment, the system includes a first battery pack in the inboard nacelle of the left wing and a second battery pack in the inboard nacelle of the right wing. The battery pack 202 can include a plurality of 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 can be fluidly connected to the cooling system in series and / or in parallel in any suitable manner.

[0012] Figure 3 shows a portion of an aircraft propulsion system 300 for use in the aircraft 100 of FIG. 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 the operation of the aircraft propulsion system 300, and the accessory units can include, for example, a blade pitching mechanism 304, a tilt mechanism 306, and an inverter system 308. More specifically, FIG. 3 shows a cross-section through one half of the inverter system 308. For a cross-section through both halves of the inverter system 308, see further FIG. 4.

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

[0014] The inverter system 308 includes an inverter substrate 324, a control substrate 326, and a motor inverter substrate 340 mounted within an inverter housing 318. The motor inverter substrate 340 includes an inverter 350 that supplies power to the motor 302. The inverter substrate 324 includes a plurality of inverters, for example, an inverter 334 coupled to the blade pitching mechanism 304 by an electrical connection 348, an inverter 336 coupled to the tilt mechanism 306 by an electrical connection 342, and an inverter 338 coupled to the integrated pump 314 and fan 312 by an electrical connection 344. The motor 302 is coupled to the inverter 350 by an electrical connection 346.

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

[0016] In some examples, the motor 302 is connected to the rotor 120 of the aircraft 100 or incorporated into the hub of the rotor 120. The motor 302 can 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 (having a gear device, etc.) designed and configured to provide high torque and low speed to the propeller. The motor 302 can have any suitable power capacity and / or power requirement value. Preferably, the motor 302 is a three-phase motor, and more preferably, it is wound as two independent three-phase motors for redundancy and performance. The motor 302 can have a power threshold (e.g., peak power, maximum continuous power, nominal power, maximum power of an individual set of windings of a double-wound motor, etc.) less than 80 kW, 500 kW, greater than 500 kW, any range bounded by those values, and / or any other suitable power characteristic. In a particular example, the motor 302 can rotate the rotor 120 at a maximum speed 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 can operate at a maximum torque 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 supply 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 can be coupled to the rear / inboard portion of the motor 302 (and / or an inverter attached thereto) or the front / inboard portion of the motor 302, as shown in more detail by FIGS. 9A-9C and FIGS. 10A-10C, and couples the motor 302 to the airframe of the aircraft.

[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 can additionally or alternatively function to form part of a cooling system, can attach the pump 314 and / or the fan 312 of the cooling subsystem, can function as an EMI shield, and / or can 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 the forward configuration), but can be configured in other ways.

[0019] The inverter housing 318 can include a plurality of 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 a liquid coolant). The inverter housing 318 can include an integral cooling plate 322 that closes the base and / or wide face of the inverter housing 318. The inverter housing 318 can also include a plurality of thermal cooling fins 332 that extend from the perimeter of the inverter housing 318. In some examples, such as those shown in FIGS. 3 and 4, the base plate of the inverter housing 318 includes a cooling plate 322 having a set of internal cooling channels and a plurality of cooling fins 332 that are located at a rear portion external to the inverter housing 318 (e.g., facing rearward when the aircraft propulsion system 300 is in a forward configuration).

[0020] The control board 326 receives a plurality of commands (for example, from a flight processor or FMS) and functions to control the operation of a plurality of inverter boards based on the received plurality of commands. In addition, the control board 326 monitors various sensors and / or controls various accessory units or actuators based on sensor feedback and can function to interface with an on-board flight management system (FMS). The control board 326 can be configured to provide field-oriented control (FOC) or vector control, but additionally or alternatively, can be configured to provide direct torque control (DTC), scalar control (such as by pulse width modulation for low-power actuators like fans), and / or can be configured to provide any suitable control for any suitable plurality of actuators. Preferably, there is a specific control board 326 disposed within each individual coolant volume and / or subregion of the inverter housing 318, and this control board 326 is electrically connected to and / or controls each inverter within each 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 of the inverters within the inverter housing, or two or more control boards within each coolant volume. The control board 326 is preferably a printed circuit board (PCB), but can also be appropriately implemented in other ways. The control board can include a processor card and gate drive circuitry, but the control board can additionally or alternatively include any other suitable components.

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

[0022] A 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., the 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 requirement of the high-power inverter board 340 (and the associated highest-power actuator) can exceed the combined power requirement 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 (by, for example, less than 0.5, 3, 5, more than 5, any ratio therebetween, and / or any other suitable value). However, the plurality of inverter boards can additionally or alternatively include a single board that houses all the inverters, a plurality of secondary (low-power) boards, and / or the plurality of inverters can be otherwise distributed among any suitable set of inverter boards.

[0023] The inverter board 324, the inverter board 340, and the control board 326 are preferably arranged in a "stacked" configuration, but in other ways, parallel to one or more wide surfaces / base plates of the inverter housing, perpendicular to the motor's rotational axis 408, perpendicular to the firewall 410, and / or otherwise appropriately arranged. The control board 326 is preferably arranged between the primary inverter board 340 and the secondary inverter board 324, but additionally or alternatively, it may be arranged on the opposite side of the primary inverter board 340 in the thickness direction of the secondary inverter board 324, and / or otherwise appropriately arranged. A set of inverter boards and / or control boards can be dispersed in any suitable way. Low-voltage power and data such as sensors and control signals can be routed between the control board and the inverter board using flexible printed circuits. Conversely, the power connection between the inverter and the actuator is preferably formed by a bus bar connection and / or a robust electrical connection (e.g., perpendicular to the wide surface of the laminated board). However, the power and / or data connections can be appropriately routed between the inverter and / or control boards in other ways.

[0024] A plurality of DC link capacitors 328 are coupled to the inverter board 340. The plurality of DC link capacitors 328 constitute a load balancing energy storage device, which helps protect the inverter network from instantaneous voltage spikes, surges, and EMI. The DC link capacitors 328 can be ceramic, film, and / or mixtures thereof. The plurality of DC link capacitors 328 can be arranged 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 plurality of DC link capacitors 328 can be arranged distal to the firewall and / or along the perimeter of the inverter. The plurality of DC link capacitors 328 can be enclosed within a thermally conductive epoxy 330 that serves to transfer heat from the plurality of DC link capacitors 328 to the plurality of cooling fins 332 and the cooling plate 322.

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

[0026] In some examples, a set of cooling plates includes a primary cooling plate 322 thermally coupled to a heat generating region of the primary inverter substrate 340 and one or more secondary cooling plates 352 thermally coupled to the control substrate 326 and / or the secondary inverter substrate 324. In a first example, the primary cooling plate 322 is disposed (and / or integrated with) the inverter housing 318 between the primary inverter substrate 340 and the inverter housing 318. In a second example, one or more secondary cooling plates 352 are disposed between and thermally coupled to the secondary inverter substrate 324 and the control substrate 326 (e.g., a processor card). In the second example, the projected area of each heat generating region onto the wide surface of one or more secondary cooling plates 352 (from the secondary inverter substrate 324 and the control substrate 326) may or may not overlap. However, one or more secondary cooling plates 352 may be arranged in other ways with respect to the control substrate 326 and / or the processing substrate (and the heat generating regions thereon). In some examples, the plurality of cooling 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 a plurality of individual coolant volumes (e.g., at the rear end). In such examples, a single cooling plate can extend across the heat generating regions and / or wide surfaces of the inverter substrates (and / or control substrates) of a plurality of multi-inverters and include an internal volume thermally connected to both multi-inverters. In such examples, the cooling plate can cool a plurality of multi-inverters via a plurality of redundant refrigerant flow paths in parallel, but additionally or alternatively can cool a plurality of multi-inverters in any suitable combination / permutation of a plurality of refrigerant flows in series and in parallel. Alternatively, a single cooling plate can be thermally connected to a plurality of multi-inverters having a plurality of fluid channels (e.g., mechanically separated and forming parallel refrigerant flow paths).

[0027] The plurality of coolant routing components that form the coolant passage 320 direct the circulation of coolant (e.g., water / glycol mixture, transformer oil, etc.) through, adjacent to, or around the cooling plates 322 and 352 and couple those cooling plates to the remainder of the cooling system (i.e., form a cooling loop). The plurality of coolant routing components can include any fluid manifold, hose, tube, pipe, channels within the housing of an inverter, channels within the body of a motor, and / or any other suitable coolant routing components. Preferably, the coolant passage 320 fluidly connects the primary cooling plate 322 to the secondary cooling plate 352 in series (e.g., within a multi-inverter / small area). The coolant passage 320 can 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) or multiple parallel fluid loops. However, the coolant passage 320 can interconnect the various cooling components of the cooling system in any suitable combination and / or permutation of series / parallel coolant flow. The plurality of coolant routing components can pass through a plurality of orifices within the thickness of the inverter substrate (e.g., via a fluid manifold or other fluid routing) and / or can be routed around the perimeter of the substrate. The plurality of coolant routing components can include a first coolant routing termination at the rearward 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, but the coolant passage 320 can otherwise interconnect the 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 discharge heat from the coolant to the ambient environment. In some examples, the radiator 310 can be nested in one or more arrangements of the tilt mechanism 306 such that an external air flow through the radiator 310 (e.g., ducted flow by the fan 312) is partially and / or completely blocked (e.g., in terms of the direction of the flow, the longitudinal direction along the motor's axis of rotation 408, etc.) in contact with and / or adjacent to the tilt mechanism 306. In particular, closely nesting the radiator 310 and the tilt mechanism 306 and / or directly blocking the air flow through the radiator 310 can increase the implementation density and aerodynamic efficiency during forward flight, reducing the power requirements of the motor 302 and the inverter board 340 (and thus eliminating the necessary heat from the aircraft propulsion system 300). Similarly, displacing the radiator 310 together with the motor 302 and the inverter housing 318 during the transformation of the tilt mechanism 306 during transition and / or in a hovering configuration can increase the air flow and / or waste heat achieved by the radiator 310 when the heat load is maximum as a result of the maximum power and / or waste heat requirements. See also FIGS. 9A - 9C and FIGS. 10A - 10C. In such cases, the radiator 310 moving with the motor 302 can effectively double the waste heat during hovering or vertical flight, increasing the air flow through the radiator 310. However, the system can include any other suitable radiator 310 and / or can appropriately send the coolant through the radiator 310. Alternatively, the system can discharge heat by a refrigeration system and / or other quasi-ambient cooling architectures.

[0029] In some embodiments, the plurality of coolant routing components can fully and fluidly enclose and contain the coolant without pressure exchange with the environment. In such examples, the plurality of coolant routing components can direct the coolant through the accumulator 316, thereby regulating the fluid pressure and preventing overpressure. Alternatively, the coolant passage 320 can include passive coolant venting to the ambient 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 the coolant passage 320 through the coolant routing components, the cooling plates, and / or the actuators. The pump 314 can additionally or alternatively function to transport the coolant from the motor 302 and / or the cooling plate 322 to the radiator 310.

[0031] The fan 312 functions to circulate ambient air across the 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 the rotating shaft of the pump 314 and / or can be mechanically integrated with the pump 314 in other ways. The fan 312 can be configured to be directly coupled to the pump 314 and rotate at an angular velocity proportional to the angular velocity of the pump shaft (e.g., the equivalent angular velocity when the gears are removed). The fan 312 can be ducted and / or ductless and / or can be otherwise suitably mounted. Additionally or alternatively, the fan 312 can be separate from the pump 314 (e.g., integrated into a radiator assembly, etc.) and / or can be separately powered.

[0032] The aircraft propulsion system 300 can optionally include a plurality of sensors that function to monitor the operation of the system. The plurality of sensors can 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 rate sensors, fluid pressure sensors, etc.), and / or any other suitable sensors. In some examples, a plurality of temperature sensors can be used to monitor the temperature of motor windings, bearings, coolant, and / or any other appropriate components. In some examples, a plurality of flow sensors can monitor the coolant pressure and / or flow rate within the coolant subsystem. However, the system can include any other appropriate sensors. The plurality of sensors are preferably communicatively connected to the control board 326 and can be employed in conjunction with various actuation control schemes (e.g., feedforward, feedback, etc.). However, in some examples, it may be advantageous for a plurality of sensor inputs to be received at an on-board inverter board (e.g., the inverter board 324 at the head of the stack in the forward arrangement, secondary / triple-inverter board). In some such examples, the plurality of sensor inputs can be received in a section of the inverter board 324 that is electrically isolated from the plurality of inverters and relayed to the control board 326 (or FMS). Thus, the control board 326 can 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 supplied substantially uniformly (e.g., varying by less than 10%, less than 20%, less than 50%, or exactly uniformly) and / or 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 a plurality of coolant routing components (e.g., such that the coolant temperature rise through the motor is less than 5°C, and in some examples, the coolant temperature rise through the motor 302 and / or the inverter housing 318 can be ignored).

[0034] In some examples, the coolant in the coolant passage 320 from the radiator 310 enters the motor 302 at the stator 404, passes through or between a plurality of field coils in the stator 404, and then passes through the electrical bussing 406. The coolant in the coolant passage 320 then proceeds into the inverter housing 318, passes through the cooling plate 352 and the cooling plate 322, and then returns to the pump 314, from which it returns to the radiator 310. Thus, the coolant passage provides an integrated cooling system that cools not only the motor 302 but also the inverters of a plurality of actuators associated with the aircraft 100. Of course, the direction of flow and the order of components in the cooling passage can be changed or reversed.

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

[0036] FIG. 4 further shows a portion of the aircraft propulsion system 300 of FIG. 3 according to some examples. More particularly, FIG. 4 shows 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 rotational axis 408 of the motor) of a portion of the inverter housing 318. In such examples, the inverter housing 318 can extend radially inward of a plurality of permanent magnets or the stator 404 of the motor 302. The outer perimeter of the inverter housing 318 may be disposed in the same plane as the radially inner perimeter of the motor 302 and / or may be inserted from the radially outer perimeter of the motor 302, but may be otherwise appropriately configured. More preferably, the inverter housing 318 can be inserted radially from the electrical buses 406 (e.g., a plurality of bus rings) of the motor 302 and / or can be surrounded by the housing of the stator 404. However, the inverter housing 318 can be otherwise appropriately disposed with respect to the motor. The inverter housing 318 can include electrical bus terminals, coolant channels / orifices, thermal (heat) fins, and / or any other appropriate features in any appropriate arrangement. The inverter housing 318 is preferably formed from a metal having a high thermal conductivity (e.g., aluminum), but additionally or alternatively can include insulation, electrical insulation, plastic, composite materials, ferrous metals (e.g., iron), steel, copper, and / or any other appropriate materials.

[0037] The inverter housing 318 can include a firewall 410 that functions to subdivide the interior of the inverter housing into a plurality (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 the propagation of thermal events between opposing portions within 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 a wide top surface and a bottom surface (e.g., perpendicular to the top and bottom surfaces of the inverter housing 318 shown in FIG. 4), but can be appropriately arranged in other ways. The firewall 410 can be arranged along a sagittal plane with respect to the rotational axis 408 of the motor and / or can extend axially and radially with respect to the rotational axis 408, but additionally or alternatively, can be appropriately arranged in other ways. The plurality of coolant volumes defined by the firewall 410 within the inverter housing 318 are preferably symmetric and / or of substantially equal volume, but the firewall 410 can appropriately divide the inverter housing otherwise. The firewall 410 can be formed from the same material as the exterior of the housing (e.g., aluminum, steel, etc.) and / or any other suitable material.

[0038] The inverter system 308 can include redundant instances of the control board 326 and / or the inverter boards 324 and 340, each associated with a separate coolant volume. However, multiple electronic devices can also be shared across separate coolant volumes of the inverter housing 318. Multiple electronic devices within 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 alternatively can be isolated 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 can include multiple such multi-inverters that can be thermally, mechanically, and / or electrically insulated on both sides 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 the control board 326 and two inverter boards, the inverter board 324 and the inverter board 340, that cooperate to form a quad inverter. In some examples, the two quad inverters can operate 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 that are commonly packaged (and / or cooled thereby) within the inverter housing 318.

[0039] Accordingly, examples of this technology can provide dual redundancy within a single inverter system and / or within a single inverter housing 318 when coupled to two independent three-phase motors mechanically coupled to each other within a single electric propulsion system. 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 also subdivide the inverter housing 318 into separate coolant volumes (e.g., using a firewall 410) to mitigate the propagation of any thermal events between redundant inverters.

[0040] FIG. 5 shows a partial cross-sectional view of the aircraft propulsion system 300 of FIGS. 3 and 4 according to some examples. In particular, as described above with reference to FIG. 4, the inverter housing 318 is nested radially inside the motor 302, and the stator 404 and / or rotor 402 of the motor 302 are disposed radially outside a portion of the inverter housing 318 (with respect to the rotational axis 408 of the motor). Also shown in FIG. 5 are some of the plurality of cooling fins 332 for the DC link capacitor 328, the integrated pump / fan 502, the radiator 310, and the plurality of conduits forming the coolant passage 320.

[0041] This configuration provides high power-density inverter packaging by efficiently routing power and / or cooling through the inverter / control board. In some examples, the system improves the 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 and / or partially within the motor 302 and / or the inverter housing 318.

[0042] FIG. 6 shows an inverter board 604 used in an aircraft propulsion system 300 according to some examples. The inverter board 604 has a plurality of heat-generating components 602. In some examples, these are SiC switches including inverters 334, 336, and 338 on the inverter board 324. The plurality of heat-generating components 602 of the inverter board 604 can be arranged to face one or more cooling plates in the thickness direction of the inverter board 604. In such cases, the inverter board 604 includes a heat transfer path that extends through the inverter board 604 and thermally connects one or more heat-generating components 602 to one or more cooling plates, such as cooling plate 322, and includes a plurality of thermal coins 606 of a highly conductive material disposed at the base of (and / or distributed around) the heat-generating regions of the one or more heat-generating components 602.

[0043] The plurality of thermal coins 606 function to reduce the thermal resistance through the thickness of the substrate. The plurality of thermal coins 606 are preferably formed from a highly conductive material such as copper, aluminum, and / or other highly thermally conductive materials, and are preferably electrically insulated from the circuit of the inverter board 604 to avoid short-circuiting the substrate. In one example, the plurality of thermal coins 606 can include a plurality of integrated electrical insulation layers such as a ceramic layer or other electrical insulation layer (e.g., having a lower thermal conductivity than the rest 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 plurality of thermal coins 606 can be electrically insulated by an electrical insulation coating or seal around (e.g., between the electrical component and the exposed portion of the thermal coin, between the cooling plate and the thermal coin, etc.).

[0044] In some examples, the inverter substrate 604 can include a barrier layer configured to thermally isolate components / regions of the inverter substrate from a cooling plate (e.g., thermally coupled to different heat generating regions of the same inverter substrate). In one example, a plurality of film capacitors are thermally isolated from the cooling plate and cooled by ambient air, while a plurality of ceramic capacitors are cooled using a liquid coolant. Thereby, heat generating components having large cooling requirements (e.g., capable of withstanding high temperatures far exceeding ambient temperature) such as MOSFETs can be cooled separately using a liquid coolant. The thermal insulation between the DC link film capacitor and the cooling plate / base plate of the housing can have a thermal conductivity smaller than that of an air gap (of equivalent thickness), a thermal conductivity larger than that of an air gap, and / or any other suitable thermal properties.

[0045] FIG. 7 shows a thermal interface between a plurality of thermal coins 606 of the inverter substrate of FIG. 6 and a cooling plate 322 according to some examples. A fluid channel 702 is provided adjacent to the cooling plate 322, and a coolant is supplied to this fluid channel via a coolant passage 320. A thermal conduction layer 706 is provided between the plurality of thermal coins 606 and the cooling plate 322 to be cooled. An electrical insulation layer 704 is provided to electrically insulate the plurality of thermal coins 606 from the cooling plate 322 and from each other. In other examples, the plurality of thermal coins 606 can be attached to an electrical insulator 704, and this electrical insulator 704 is attached to a cooling plate 322a.

[0046] FIG. 8 shows a perspective view of an aircraft propulsion system 300 of FIGS. 3 and 4 according to some examples. FIG. 8 shows the relative arrangement of a motor 302, a fan 312, a radiator 310, and a portion of the piping forming a portion of the coolant passage 320.

[0047] Figures 9A, 9B, and 9C show the tilting of an aircraft propulsion system 300 according to several examples and a plurality of associated components such as a propeller 902 and a nacelle 904. The aircraft is preferably an eVTOL aircraft (e.g., a multi-modal aircraft) as illustrated, but additionally or alternatively, can include any suitable aircraft. The aircraft 100 is preferably a tiltrotor aircraft having a plurality of 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 can 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 substantially axially oriented to provide horizontal thrust), a tiltwing aircraft, a wingless aircraft (e.g., a helicopter, a multi-copter, a quadcopter), and / or any other suitable rotary-wing aircraft or vehicle propelled by a plurality of propellers or a plurality of rotors.

[0048] As shown in FIGS. 9A-9C, in one example, a nacelle 904 including an aircraft propulsion system 300 (identified as motor 302, inverter system 308, and radiator 310) and a propeller 902 having a blade pitching mechanism 908 is tiltable relative to the remainder of the aircraft 100 by a tilt mechanism 906 disposed near the rear of the nacelle 904.

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

[0050] Figures 10A, 10B, and 10C show the tilting of a plurality of related components, such as the aircraft propulsion system 300 and the propeller 902, with respect to the nacelle 1004 according to several examples. As seen in FIGS. 10B and 10C, in this example, the aircraft propulsion system 300 (identified as the motor 302, the inverter system 308, and the radiator 310) and the propeller 1002 having the blade pitching mechanism 1008 are tiltable with respect to the nacelle 1004 by a tilt mechanism 1006 disposed near the front of the nacelle 1004.

[0051] As seen in FIG. 10C, which is a 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 air flow through the radiator 310 as a result of the adjacent air flow from the fan 312 and from the propeller 902. Since hovering has a higher power demand than horizontal flight, the additional cooling provided by the increased air flow through the radiator 310 can be advantageous.

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

[0053] As used herein when referring to a thrust generating element, the term "rotor" may refer to a rotor, a propeller, and / or any other suitable rotary aerodynamic actuator. A rotor may refer to a rotary aerodynamic actuator that utilizes a gimbaled or semi-rigid hub (e.g., the connection between the blade and the hub can be gimbaled, flexible, rigid, and / or connected in another way), and a propeller may refer to a rotary aerodynamic actuator that utilizes a rigid hub (e.g., the connection between the blade and the hub can be gimbaled, flexible, rigid, and / or connected in another way). However, when used herein, such a distinction is neither explicit nor implicit, and the use of "rotor" may refer to either configuration, and may also refer to any other suitable configuration of gimbaled or rigid blades and / or any other suitable configuration of blade connection to a central member or hub. Similarly, the use of "propeller" may refer to either configuration, and may also refer to any other suitable configuration of gimbaled or rigid blades and / or any other suitable configuration of blade connection to a central member or hub. Thus, a tiltrotor aircraft can be referred to as a tiltprop aircraft, a tiltprop airplane, and / or otherwise appropriately referred to or described.

[0054] As used herein in connection with a control board, an inverter board, etc., the term "board" preferably refers to a circuit board. More preferably, a "board" refers to a printed circuit board (PCB) and / or a plurality of electronic components assembled thereon that can collectively form a printed circuit board assembly (PCBA: printed circuit board assembly). In a first example, the control board is a PCBA. In a second example, the inverter board is a PCBA. However, a "board" can 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 can have any other suitable meaning.

[0055] The aircraft can include any suitable form of power storage or power storage unit (such as a battery, flywheel, ultra - capacitor, battery, fuel tank, etc.) that supplies power to one or more actuators (such as rotors / propellers, tilt mechanisms, blade pitch mechanisms, cooling systems, etc.). A preferred power / fuel source is a battery, but the system can be reasonably used with any suitable power / fuel source. The aircraft can include an auxiliary power source and / or redundant power sources (such as backup batteries, multiple batteries), or can exclude redundant power sources. The aircraft can use batteries having any suitable cell chemistries (such as lithium - ion, nickel - cadmium, etc.) in any suitable electrical architecture or configuration (such as a combination of series and / or parallel architectures, for example, multiple packs, bricks, modules, cells, etc.).

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

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

[0058] Alternative embodiments implement the above methods and / or processing modules in a non-transitory computer-readable medium storing computer-readable instructions. The instructions can be executed by a plurality of computer-executable components integrated with the computer-readable medium and / or processing system. The computer-readable medium can include any suitable computer-readable medium, such as RAM, ROM, flash memory, EEPROM, optical devices (CD or DVD), hard drives, floppy (registered trademark) drives, non-transitory computer-readable media, or any suitable device. The computer-executable components can include a computing system and / or processing system (e.g., including one or more co-located or distributed remote or local processors) connected to the non-transitory computer-readable medium, such as a CPU, GPU, TPUs, microprocessors, or ASICs. However, the instructions can alternatively or additionally be executed by any suitable dedicated hardware device.

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

[0060] Those skilled in the art can make modifications and changes to the embodiments of the present invention without departing from the scope of the present invention as defined in the following claims, as will be recognized from the foregoing detailed description, drawings, and claims.

Claims

Claim 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 supplying power to 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. An aircraft propulsion unit comprising the above. Claim 2 The aircraft propulsion unit according to claim 1, wherein the inverter module is at least partially nested within the electric motor. Claim 3 The aircraft propulsion unit according to claim 1, wherein the inverter module includes one or more cooling plates for transferring heat from the plurality of inverters to the coolant within the coolant passage. Claim 4 The aircraft propulsion unit according to claim 1, wherein the at least one accessory unit includes a pump for circulating the coolant through the coolant passage. Claim 5 The aircraft propulsion unit according to claim 4, wherein the cooling system includes a radiator, and the pump includes a fan for blowing air through the radiator. Claim 6 The aircraft propulsion unit according to claim 1, wherein the cooling system includes a radiator, and the airflow through the radiator during 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. Claim 7 The aircraft propulsion unit according to claim 1, wherein the at least one accessory unit includes a blade pitching mechanism for adjusting the pitch of the rotor blade. Claim 8 The aircraft propulsion unit according to claim 1, wherein the inverter module includes an inverter module housing, and the inverter module housing includes a plurality of cooling fins for transferring heat from the inverter module. Claim 9 The inverter module includes an inverter module housing, the inverter module housing including a first region and a second region spaced apart from the first region, the first region and the second region including redundant plural inverters, the aircraft propulsion unit according to claim 1.

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

11. The motor includes a stator and a rotor disposed around a rotation axis of the motor, the inverter module being located inside the stator and the rotor, the inverter module including plural circuit boards, the plural circuit boards being arranged stacked perpendicularly to the rotation axis of the motor, the aircraft propulsion unit according to claim 1.

12. An aircraft, a fuselage and one or plural thrust generating units, and one or plural propulsion units for driving the thrust generating units, comprising: Each propulsion unit an electric motor, and 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 arrangement and a horizontal flight arrangement, an inverter module including plural inverters for supplying power to 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 a coolant passage for circulating a coolant through or adjacent to the electric motor and the inverter module, The cooling system further includes a radiator, and an airflow through the radiator during use when the aircraft propulsion unit is in the vertical flight arrangement is larger than when the aircraft propulsion unit is in the horizontal flight arrangement, the aircraft.

13. The aircraft according to claim 12, wherein the inverter module is at least partially nested inside the electric motor.

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

15. The inverter module includes an inverter module housing, the inverter module housing includes a first region and a second region spaced apart from the first region, and the first region and the second region include redundant multiple inverters. The aircraft according to claim 12.

16. 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, wherein the inverter module includes a housing and a plurality of inverters for supplying power to the electric motor and the at least one accessory unit. The method includes: circulating a coolant through a coolant passage formed in the 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 the vertical flight configuration such that an airflow through the heat exchanger in the vertical flight configuration is increased. A method comprising.

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

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