Thermal management system architecture and packaging of an electric propulsion unit

Abstract

An example electric propulsion unit includes: a housing; an electric motor disposed within the housing, wherein the electric motor has stator and a rotor; a motor shaft coupled to the rotor and extending outside the housing; a heat exchanger mounted external to the housing and coupled to the housing via one or more fluid lines; one or more pumps mounted to the housing and driven by the motor shaft; and at least one fan mounted external to the housing and driven by the motor shaft, wherein the one or more pumps circulate coolant through the one or more fluid lines, one or more channels formed in housing and / or the stator of the electric motor, and the heat exchanger, while the at least one fan provides air flow to reduce a temperature of coolant as coolant flows through the heat exchanger.

Description

Thermal Management System Architecture and Packaging of an Electric Propulsion UnitCROSS REFERENCE TO RELATED APPLICATION

[0001] The present application claims priority to U.S. Provisional Application No. 63 / 701,071 filed on September 30, 2024, the entire contents of which are herein incorporated by reference as if fully set forth in this description.BACKGROUND

[0002] Many systems involving machinery or vehicles are being electrified. Particularly, electric motors are used to drive rotary components such as propellers, wheels, or any other rotary component.

[0003] An example system may include an electric power source (e.g., battery) and a plurality of electric motors. An electric motor is an electrical machine that converts electrical energy into mechanical energy. Most electric motors operate through the interaction between the motor’s magnetic field and electric current in wire windings to generate force in the form of rotation of a shaft. Electric motors can be powered by direct current (DC) sources, such as from batteries, motor vehicles or rectifiers, or by alternating current (AC) sources, such as a power grid, inverters or electrical generators.

[0004] In examples, a motor and a respective inverter are packaged in an assembly. During operation of such motor and inverter, heat is generated and may cause damage to components of the assembly if the temperature is not controlled. Thus, the power output of the motor can be limited by heat generation. Particularly, the torque and power generated at the shaft of the motor are limited by how much current or electric power is input through the wire windings, andincreasing current beyond a certain limit can increase the temperature of the wire windings to an unacceptable level and cause damage to the wires and the electric motor.

[0005] It may thus be desirable to configure a cooling system that enhances heat removal from such an assembly to increase power density of the assembly. It may also be desirable to integrate the electric motor, inverter, and cooling system in a light-weight and compact assembly that is suitable for applications where weight and space are a concern. It is with respect to these and other considerations that the disclosure made herein is presented.SUMMARY

[0006] The present disclosure describes implementations that relate to a thermal management system architecture and packaging of an electric propulsion unit.

[0007] In a first example implementation, the present disclosure describes an electric propulsion unit. The electric propulsion unit includes: a housing; an electric motor disposed within the housing, wherein the electric motor has stator and a rotor; a motor shaft coupled to the rotor and extending outside the housing; a heat exchanger mounted external to the housing and coupled to the housing via one or more fluid lines; one or more pumps mounted to the housing and driven by the motor shaft; and at least one fan mounted external to the housing and driven by the motor shaft, wherein the one or more pumps circulate coolant through the one or more fluid lines, one or more channels formed in housing and / or the stator of the electric motor, and the heat exchanger, while the at least one fan provides air flow to reduce a temperature of coolant as coolant flows through the heat exchanger.

[0008] In a second example implementation, the present disclosure describes a vehicle. The vehicle includes: a propeller; and the electric propulsion unit of the first example implementation, wherein the motor shaft of the electric propulsion unit is coupled to and configured to drive the propeller.

[0009] In a third example implementation, the present disclosure describes a method of operating the electric propulsion unit of the first example implementation or the vehicle of the second example implementation.

[0010] In a fourth example implementation, the present disclosure describes a method of assembling the electric propulsion unit of the first example implementation.

[0011] The foregoing summary is illustrative only and is not intended to be in any way limiting. In addition to the illustrative aspects, implementations, and features described above, further aspects, implementations, and features will become apparent by reference to the figures and the following detailed description.BRIEF DESCRIPTION OF THE FIGURES

[0012] Figure 1 is a block diagram of a vehicle, according to exemplary embodiments of the present invention.

[0013] Figure 2A illustrates a front view of an electric propulsion unit, according to exemplary embodiments of the present invention.

[0014] Figure 2B illustrates perspective partial cross-sectional view of the electric propulsion unit of Figure 2A, according to exemplary embodiments of the present invention.

[0015] Figure 3A illustrates a perspective view of a blade of a fan of the electric propulsion unit of Figures 2A-2B, according to exemplary embodiments of the present invention.

[0016] Figure 3B illustrates a bottom view of a fan, according to exemplary embodiments of the present invention.

[0017] Figure 3C illustrates a partial bottom view of the fan of Figure 3B showing connection of a blade with a hub of the fan, according to exemplary embodiments of the present invention.

[0018] Figure 4A illustrates a top view of a fan, according to exemplary embodiments of the present invention.

[0019] Figure 4B illustrates a top view of the fan of Figure 4A after breakage of a blade of the fan, according to exemplary embodiments of the present invention.

[0020] Figure 5A illustrates a front view of a dual fan having a first fan mounted to first hub and a second fan mounted to a second hub, according to exemplary embodiments of the present invention.

[0021] Figure 5B illustrates a bottom view of the dual fan of Figure 5A, according to exemplary embodiments of the present invention.

[0022] Figure 5C illustrates a bottom view of the second fan of Figure 5B, according to exemplary embodiments of the present invention.

[0023] Figure 6 illustrates a side view of an electric propulsion unit with a fan being upstream of a heat exchanger, according to exemplary embodiments of the present invention.

[0024] Figure 7 illustrates a side view of an electric propulsion unit with a fan being downstream of a heat exchanger, according to exemplary embodiments of the present invention.DETAILED DESCRIPTION

[0025] Disclosed herein are systems, vehicles, and assemblies involving an architecture of an electric propulsion unit (EPU) with an integrated thermal management system. The disclosed thermal management system provides a desired thermal boundary condition for the motor, inverter, and other parts of an EPU. Providing such desired thermal condition can involve cooling, heating, and / or pre-conditioning of the EPU and surrounding components. The disclosed EPU also includes at least one fan with fail safe features that allows the EPU to accommodate partial failures in the at least one fan, while maintaining cooling operations and protecting propulsion capabilities of the EPU.

[0026] Within example embodiments, disclosed herein is an EPU having a housing; an electric motor disposed within the housing, wherein the electric motor has stator and a rotor; a motor shaft coupled to the rotor and extending outside the housing; a heat exchanger mounted external to the housing and coupled to the housing via one or more fluid lines; one or more pumps mounted to the housing and driven by the motor shaft; and at least one fan mounted external to the housing and driven by the motor shaft, wherein the one or more pumps circulate coolant through the one or more fluid lines, one or more channels formed in housing and / or the stator of the electric motor, and the heat exchanger, while the at least one fan provides air flow to reduce a temperature of coolant as coolant flows through the heat exchanger.

[0027] The disclosed systems, assemblies, and EPUs may be utilized in any device or application that utilizes a motor. For example, the motor may be used to power or drive a vehicle, including but not limited to a ground vehicle (i.e., an automobile), a sea vehicle (such as a boat), or a flying craft (such as an aerial, floating, soaring, hovering, airborne, aeronautical aircraft, airplane, plane, spacecraft, a helicopter, an airship, or an unmanned aerial vehicle, a vertical take-off and landing(VTOL) craft, or a drone). The disclosed embodiments of the present invention may be utilized in any of these applications in order to obtain advantages such as compactness, light weight, enhanced power density, and higher efficiency.

[0028] Figure 1 is a block diagram of a vehicle 100, according to an exemplary embodiment of the present invention. In some embodiments, and as noted above, the vehicle 100 may be a VTOL, which may or may not use electric power to hover, takeoff, and / or land. It should be understood that in other embodiments, the vehicle 100 may be any other type of vehicle that may be able to utilize the advantages of the present invention, such as a ground vehicle (i.e., an automobile), a sea vehicle (such as a boat), or a flying craft (such as an aerial, floating, soaring, hovering, airborne, aeronautical aircraft, airplane, plane, spacecraft, a helicopter, an airship, or an unmanned aerial vehicle, or a drone).

[0029] In some embodiments, the vehicle 100 may include one or more propellers or rotors used to drive the vehicle 100. Each propeller may be configured, for examples, as tiltrotors, lift rotors, or any other type of rotors. In other embodiments, the vehicle 100 may include one or more turbine engines, one or more tires, one or more ski-structures, or the like instead of the one or more propellers used to drive the vehicle.

[0030] For example, a first propeller 102 may be driven by a gearbox 106, which in turn is driven by one or more motors such as propeller motor 108, propeller motor 110, and propeller motor 112. Similarly, a second propeller 104 is driven by a gearbox 114, which in turn is driven by one or more motors such as propeller motor 116, propeller motor 118, and propeller motor 120. In some embodiments, the motors may be electric motors.

[0031] The vehicle 100 also may include multiple lift rotors, such as multiple lift rotors that can facilitate vertical takeoff and landing of the vehicle 100. For example, the vehicle 100 can include a lift rotor 122, a lift rotor 124, a lift rotor 126, and a lift rotor 128.

[0032] The lift rotor 122 is driven by a gearbox 130, which in turn is driven by a motor 132. The lift rotor 124 is driven by a gearbox 134, which in turn is driven by a motor 136. The lift rotor 126 is driven by a gearbox 138, which in turn is driven by a motor 140. The lift rotor 128 is driven by a gearbox 142, which in turn is driven by a motor 144.

[0033] Any of the propellers or lift rotors described herein may be a tilting propeller. In some embodiments, the tilting propellers may also be referred to as a tilting prop, rotor, or proprotor, depending on their design details.

[0034] In one embodiment, each of the motors described above may include one or more respective motor controllers (e.g., including inverters) integrated therewith. For example, the lift motor 132 has one or more motor controllers 146 integrated therewith. An assembly or packaging of an electric motor, an inverter, and possibly a respective gearbox can be referred to as an EPU.

[0035] In some embodiments, the various motors of the vehicle 100 may be electric motors driven by electric power provided by a plurality of batteries. As depicted in in Figure 1, the vehicle 100 can have “n” battery modules 148, such as battery module 150, battery module 152, battery module 154, and battery module 156. In an example, the battery modules can be Lithium-ion (Li-Ion) batteries. Each battery module can include a housing or enclosure that houses a plurality of battery cells arranged in rows and columns.

[0036] The battery modules 148 are configured to store electric power, and provide electric power to the various electric motors when commanded by respective energy management systems of thevehicle 100. Particularly, in an example implementation, the vehicle 100 can have a plurality (“m”) of energy management systems (EMSs) 158 that are in communication with the battery modules 148. The EMSs 158 are configured as electronic regulators that monitor and control the charging and discharging of the battery modules 148.

[0037] In an example, the EMSs 158 are configured to measure voltages of the battery modules 148 and stop charging them when a desired voltage is reached. Further, the EMSs 158 can be configured to monitor parameters that affect life and / or performance of the battery modules 148 as well as ensuring safe operation of the battery modules 148. Safe operation includes, as examples, operating below a threshold temperature to elongate the life of the battery modules 148, preclude overheating, preclude failure of the battery modules 148, etc.

[0038] The EMSs 158 can monitor and control parameters of the battery modules 148. For example, the EMSs 158 monitor and control main power voltage, battery or cell voltage, charging and discharge rates of the battery modules 148, temperatures of the battery modules 148 or their individual cells, health of the battery modules 148 or their individual cells, coolant temperature and flow for air or liquid cooling parameters of a cooling system of the battery modules 148 or their individual cells, etc.

[0039] The vehicle 100 may further include multiple contactor control units (CCUs), such as CCU 160, CCU 162, CCU 164, and CCU 166, which are electrically coupled to the battery modules 148, and are in communication with the EMSs 158. In one embodiment, as illustrated in Figure 1, each CCU is coupled to a respective battery module of the battery modules 148. A contactor is an electrically-controlled switch used for switching an electrical power circuit. A CCU controls the actuation of the contactor to allow power flow to and from the respective battery module. For example, the EMSs 158 control the power flow to and from the battery modules 148 based onpower demand from the various electric motors, and accordingly control the CCUs to enable power flow from particular battery modules as desired.

[0040] The vehicle 100 may be configured to include a distributed electric propulsion system configured to provide the vehicle 100 with the required energy to power the multiple propellers and lift rotors via an electric transmission system. Particularly, the vehicle 100 can include a redundant distribution module 168 in communication with the EMSs 158, and the redundant distribution module 168 is electrically coupled to the battery modules 148 via the respective CCUs, and is configured to provide electric power, via transmission lines, to the multiple electric motors of the vehicle 100.

[0041] The EMSs 158 along with the redundant distribution module 168 can provide for redundancy in the vehicle 100 such that if, for example, one propeller or one lift rotor fails, power can be distributed to other propellers or lift rotors to maintain operation of the vehicle 100.

[0042] As described above, due to weight and space constraints in a vehicle such as the vehicle 100, it may be desirable to integrate components in a manner that increases power density and efficiency, while reducing envelope size of the assemblies. For example, it may be desirable to integrate an electric motor with its inverter in an EPU. It may also be desirable to integrate a cooling arrangement within the EPU to enhance cooling, address space constraints, and enhance power density of the EPU. It may further be desirable to render the EPU fail safe and capable of handling partial failures in the cooling components, while maintaining cooling operations and protecting propulsion capabilities of the EPU. Described next is an assembly or an EPU of an electric motor integrated with an inverter and a cooling configuration. The EPU can represent any of the electric motors described above with respect to Figure 1 and associated components (e.g., inverters and cooling components).

[0043] Figure 2A illustrates a front view of an EPU 200, and Figure 2B illustrates a perspective partial cross-sectional view of the EPU 200, according to exemplary embodiments of the present invention. Referring to Figures 2A-2B together, the EPU 200 includes a housing 202, which may be formed as an assembly of a first housing portion 204 and a second housing portion 206. Particularly, the first housing portion 204 may include attachment ears or bosses such as boss 205, and the second housing portion 206 may include respective attachment ears or bosses such as boss 207. Fasteners may then be inserted and screwed into the mating bosses to couple the first housing portion 204 to the second housing portion 206.

[0044] The EPU 200 includes an electric motor 208 that is disposed within the first housing portion 204 as shown in Figure 2B. In an example, the electric motor 208 may be configured as a permanent magnet motor having a stator 210, a rotor 212, and a plurality of magnets 214 radially interposed therebetween and attached to the rotor 212. Other types of motors may be used.

[0045] The EPU 200 also includes an inverter 216 disposed in the second housing portion 206 and configured to power the electric motor 208. Particularly, the inverter 216 may convert DC power provided from a battery (e g., any of the battery modules 148) to AC power provided to wire windings of the stator 210. A magnetic field is then generated, which interacts with the plurality of magnets 214, causing them and the rotor 212 to rotate. The rotor 212 is supported by a first bearing 217 to facilitate rotation of the rotor 212 relative to the first housing portion 204.

[0046] The rotor 212 may have splines 218 formed in interior peripheral surface thereof to facilitate coupling a motor shaft 219 shown in Figure 2A to the rotor 212 via a spline arrangement. The motor shaft 219 may be supported by a second bearing 220 shown in Figure 2B to facilitate rotation of the motor shaft 219 relative to the second housing portion 206.

[0047] The motor shaft 219 extends outside the housing 202 (through a bottom of the housing 202) as shown. The motor shaft 219 may also extend from the other side of the housing 202 (see Figures 6-7) to drive any of the propellers or lift rotors described above with respect to Figure 1.

[0048] As shown in Figure 2B, the inverter 216 is mounted to a coldplate 222 disposed within the second housing portion 206. The coldplate 222 is a component that cools the inverter 216 and other power electronics by transferring heat from the inverter 216 as described below. This way, the coldplate 222 may help to ensure stable performance and prevent overheating, and it may have a precise heat dissipation configuration to avoid excessive temperature differences in the EPU 200. The coldplate 222 is also configured to have a light weight to avoid reducing the energy density of the EPU 200.

[0049] The EPU 200 further includes a cooling arrangement 224 integrated therein. The cooling arrangement 224 includes one or more cooling pumps such as pump 226 and pump 228 mounted to the second housing portion 206. Particularly, shafts driving the pumps 226, 228, such as shaft 227 and shaft 229 shown in Figure 2B, protrude inside the second housing portion 206 and are configured to be driven by the motor shaft 219 (e.g., via any driving or rotary motion transmission arrangement involving, gears, pulleys, or other transmission mechanisms, which are not shown to reduce visual clutter in the drawing).

[0050] The cooling arrangement 224 also includes an impeller or a fan 230 that is driven by the motor shaft 219 to provide air flow for cooling purposes as described below. The cooling arrangement 224 further includes a heat exchanger 232 (e.g., a radiator). The cooling arrangement 224 also includes several fluid lines (e.g., tubes, hoses, or pipes) that facilitate transfer of coolant between the components of the electric motor 208 and the inverter 216, the pumps 226, 228, andthe heat exchanger 232. For example, the cooling arrangement 224 includes fluid line 234, fluid line 236, fluid line 238, and fluid line 240.

[0051] In addition to facilitating the transfer of coolant between the various components of the EPU 200, the fluid lines 234-240 may also operate as mountings for the heat exchanger 232. This way, the heat exchanger 232 is coupled to the housing 202 (e.g., the second housing portion 206) via the fluid lines 234-240, thereby allowing the EPU 200 to be formed as an assembly of the electric motor 208, the inverter 216, and the cooling arrangement 224.

[0052] In some embodiments, the pumps 226, 228 are configured to operate as a positive pressure source of coolant that draw coolant from a sump or reservoir and circulate the coolant throughout the EPU 200 (e.g., through the heat exchanger 232, the housing 202 and / or the stator 210, and the coldplate 222 to which the inverter 216 is mounted). The reservoir may be a separate tank or accumulator (a volume of fluid which is under pressure by a piston or bladder). The reservoir provides a way to collect the coolant, provides extra capacity if a small leakage occurs, provides positive pressure upstream the pumps 226, 228, and provides volume to support expansion and contraction of the coolant because of variations in temperature during operation of the EPU 200.

[0053] In one example, the reservoir may be a separate component integrated into the EPU 200 (e g., within the housing 202). In another example, the reservoir may be integrated into the heat exchanger 232. In an example, the EPU 200 may further include an inline strainer or filter such that the pumps 226, 228 draw coolant through such filter to remove any foreign objects or debris from the coolant.

[0054] Although two pumps are shown in Figures 2A-2B, the EPU 200 may include fewer or more pumps in other example embodiments. If more than one pump are used, such as the pumps 226,228 in the example embodiment of Figures 2A-2B, the pumps 226, 228 may be arranged in series or in parallel.

[0055] Any type of coolant pumps may be used. For example, the pumps 226, 228 may be piston, gerotor, gear, vane, or centrifugal pumps.

[0056] In an example, a clutching mechanism may be used to couple the pumps 226, 228 to the motor shaft 219 to allow the EPU 200 to continue operating if a failure occurs as a result of jamming or clogging of a respective pump. In other words, if a pump fails, such clutching mechanism may disengage the pump from the motor shaft 219 such that the EPU 200 may maintain operation as a propulsion unit rather than getting jammed because of the pump.

[0057] In some embodiments, the heat exchanger 232 is configured to transfer heat between two fluids, e.g., between a coolant flowing through the EPU 200 and air. Particularly, the fan 230 may provide air flow to reduce temperature of a liquid coolant flowing through tubes of the heat exchanger 232 by transferring heat from the coolant to the surrounding air provided by the fan 230.

[0058] Any type of heat exchanger may be used. For example, the heat exchanger 232 may have a shell and tube configuration, plate and frame configuration, a finned tube configuration, depending on the design and fluid flow configuration. The heat exchanger 232 may have one or more cores to increase reliability and provide redundancy. In examples, the cores may target different coolant temperature ranges through the fluidic network of the EPU 200.

[0059] Thus, during operation of the EPU 200, the pumps 226, 228 may draw coolant from the reservoir (e.g., through a filter and one or more of the fluid lines 234-240), then displace the coolant under pressure through one or more of the fluid lines 234-240, then through channels in the housing202, indirectly cooling the electric motor 208, and / or channels in the stator 210, directly cooling the electric motor 208. The coolant may also flow through channels in or near the coldplate 222 to cool the inverter 216.

[0060] The coldplate 222 may be configured to have a large surface area to increase heat transfer from the inverter 216. The inverter 216 may be mounted directly on the coldplate 222, and the heat generated by the inverter 216 is then transferred to the coolant that flows through or near the coldplate 222.

[0061] In some embodiments, coolant that is heated by the electric motor 208 and the inverter 216 then flows back through one or more of the fluid lines 234-240 to the heat exchanger 232. The fan 230 provides the air flow that reduce the temperature of the coolant as it flows through the heat exchanger 232 to dissipate heat into ambient air.

[0062] In one example, a single fluid loop may be implemented in the EPU 200. In another example, to provide redundancy and reduce the likelihood of failure, two or more fluidic loops may be incorporated. For example, one of the pump 226 circulates coolant through one loop to cool a subset of components, and the pump 228 circulates coolant through another loop to cool another subset of components. Some components such as the heat exchanger 232 may be shared between the loops. The loops may have the same or different fluid and cooling capacities to support different loads and components.

[0063] In examples when indirect motor cooling is used where the coolant does not come in contact with the stator 210 or other components of the electric motor 208, any type of coolant may be used. In other examples, where coolant flows through channels in the stator 210, directly cooling the electric motor 208, the coolant is selected to be a dielectric coolant (e.g., Paratherm LR, Slytherm 800, or Shell Diala).

[0064] Thus, in some embodiments, the fan 230 is configured to provide a positive air pressure for cooling the EPU 200 in addition to the potentially available rotor down wash or ram air as a vehicle (e.g., the vehicle 100) is driven or flown. The fan 230 may be an axial fan or a radial fan based on the application in which the EPU 200 is used.

[0065] Axial fans have flat blades that push air in a single direction, while radial fans have convex blades that direct air outward. Radial fans are usually wider than axial fans. Thus, an axial fan may displace or provide large volumes of air at low pressure, while a radial fan may displace smaller volumes of air at high pressure.

[0066] Axial fans are generally more energy-efficient in low-pressure, high-flow applications, while radial fans are more efficient in high-pressure environments. Radial fans tend to be noisier than axial fans, especially at higher speeds. Further, axial fans are generally easier to install and maintain than radial fans. Axial fans may be installed and may be preferable in confined spaces. However, while axial fans are preferable for cooling spaces, radial fans are preferable for cooling smaller areas. Using either an axial fan or a radial fan is contemplated herein.

[0067] Notably, in some embodiments, the fan 230 is configured to provide fail safe operation. As mentioned above, the fan 230 is driven by the motor shaft 219 coupled to the rotor 212. A clutching mechanism may be used to disengage the fan 230 from the motor shaft 219 in case of jamming or clogging. Particularly, if the fan 230 is jammed, such clutching mechanism may disengage the fan 230 to allow the electric motor 208 to continue operating and providing propulsion. Other configurations may be used to prevent jamming, while allowing the fan 230 to continue providing air flow.

[0068] Figure 3A illustrates a perspective view of a blade 300 of the fan 230, Figure 3B illustrates a bottom view of the fan 230, and Figure 3C illustrates a partial bottom view of the fan 230 showingconnection of the blade 300 with a hub 302 of the fan 230, according to exemplary embodiments of the present invention. As shown, the blade 300 is coupled to a base 304 having a dovetail configuration 306 to facilitate mounting the blade 300 to the hub 302 of the fan 230. For example, the hub 302 may have a cavity that is configured to have a shape corresponding the dovetail configuration 306 such that the blade 300 may be “dropped” or inserted in a transversal direction (parallel to an axis of rotation of the fan 230) into the cavity as shown in Figure 3C.

[0069] This arrangement operates as a breakaway configuration or feature that allows the rotor 212 of the electric motor 208 to keep rotating if the blade 300 stops suddenly (e.g., hits a foreign object or is jammed). Particularly, in such condition, the blade 300 may break, allowing the fan 230 and the rotor 212 to continue rotating, advantageously maintaining air flow.

[0070] Figure 4A illustrates a top view of the fan 230, and Figure 4B illustrates a top view of the fan 230 after breakage of the blade 300 of the fan 230, according to exemplary embodiments of the present invention. As mentioned above, the blades of the fan 230 may be attached to the hub 302 such that if a resistance or blockage occurs, a blade such as the blade 300 breaks or detaches from the hub 302, allowing the other blades to continue providing air flow and positive pressure.

[0071] For example, if the fan 230 is an axial fan as shown in Figure 4A with four blades, one blade such as the blade 300 may detach, and the fan 230 may continue rotating with three blades. Advantageously, the total air flow rate may be reduced by 25% rather than having the entire fan jammed or blocked from rotation, eliminating air flow entirely.

[0072] A dovetail configuration is used herein as an example, and other attachment and breakaway mechanisms, features, or configurations could be used. For example, a clutch or a brake configuration that may maintain engagement of the blade 300 with the hub 302 until torque exceeds a threshold torque value could be used. Any other friction device that slips once a maxtorque value is reached by use of one or more bushings or a mechanical slip joint like a mildly self-holding taper interface could be used.

[0073] In another example, a sacrificial material connection between the fan 230 or its blades and the hub 302 could be used. In this example, a Woodruff key, a similar soft material mechanical link, or an engineered weak spot in the “coupling” may be configured to break under high load. The sacrificial part may be replaceable by an the operator.

[0074] In some embodiments, the broken or detached fan blade may be ejected from the EPU 200, In another example embodiment, a mesh or similar capturing device may be added to the EPU 200 to capture the detached blade and prevent it from impacting any other object or component of the vehicle 100. This ways, the detached blade can be contained, while allowing the EPU 200 to continue operating.

[0075] In another example, to enhance the reliability and redundancies in the EPU 200, rather than using a single fan, a compound fan having two or more concentric or non-concentric shafts or hubs to which blades are attached could be used. If a failure occurs, only the failed fan may stop through a clutching or breakaway configuration, for example, while the other fan may continue rotating and providing positive air pressure.

[0076] Figure 5A illustrates a front view of a dual fan 400 having a first fan 402 having a first hub 404 and a second fan 406 having a second hub 408, and Figure 5B illustrates a bottom view of the dual fan 400, according to exemplary embodiments of the present invention. As shown, the hubs 404, 408 may be concentric in this example embodiment. The hubs 404, 408 may be coupled to the motor shaft 219 via respective independent clutches or breakaway features. If one of the fans 402, 406 fails (e.g., is blocked or jammed), its respective clutch or breakaway mechanism may disengage the fan from the motor shaft 219, while the other fan may continue rotating.

[0077] Figure 5C illustrates a bottom view of the fan 402, according to exemplary embodiments of the present invention. As mentioned above, if a resistance or blockage cause the fan 406 to stop, it may be disengaged from the motor shaft 219, allowing the fan 402 to continue providing air flow and positive pressure. Advantageously, the total air flow rate may be reduced by half, as three blades only are functional, as opposed to six in this example embodiments, rather than having both fans jammed or blocked from rotation, eliminating air flow entirely.

[0078] As mentioned above, in some embodiments, a mesh or similar capturing device may be added to the EPU 200 to capture the detached fan and prevent it from impacting any other object or component of the vehicle 100. This ways, the detached fan can be contained, while allowing the EPU 200 to continue operating.

[0079] Further, as an additional safety feature, the fan or fans may be coupled to the motor shaft 219 via a weak point or structure such that, if the fan is blocked from rotating for any reason, it may break away from the motor shaft 219, allowing the rotor 212 to continue rotating, and the electric motor 208 to continue providing critical propulsion functionality. For example, referring back to Figure 2A, the fan 230 or its hub is attached to the motor shaft 219 via a neck portion 242.

[0080] The neck portion 242 operates as a fail-safe feature or a weak point that could fail (if its tensile strength limited is reached), allowing the fan 230 to break off prior to such failure (e.g., fracture) propagating to or causing the motor shaft 219 to be subject to high stresses leading to failure. This way, if the fan 230 jams or breaks, the motor shaft 219 may continue rotating, allowing the EPU 200 to continue providing propulsion functionality.

[0081] The arrangement of the EPU 200 shown in Figures 2A-2B is an example embodiment.Other arrangements are contemplated. For example, the axial order of components (e.g., how thecomponents stack up) may be changed, while maintaining the advantageous features of the EPU200 described above.

[0082] Figure 6 illustrates a side view of the EPU 200 with the fan 230 being upstream of the heat exchanger 232, according to exemplary embodiments of the present invention. The EPU 200 is depicted in a simplified manner and some of the components are not shown to reduce visual clutter in the drawing. As shown in Figures 2A-2B and Figure 6, the fan 230 is axially interposed between the heat exchanger 232 on one side and the electric motor 208 and the housing 202 on the other side. In other implementations, the stack up order may change.

[0083] Figure 7 illustrates a side view of the EPU 200 with the fan 230 being downstream of the heat exchanger 232, according to exemplary embodiments of the present invention. As shown in Figure 7, the heat exchanger 232 is axially interposed between the fan 230 on one side and the electric motor 208 and the housing 202 on the other side.

[0084] With the configurations of the EPUs disclosed herein, components of the EPU and the thermal management system may be disposed within the housing 202, except for the fan 230 and the heat exchanger 232, which are disposed external to the housing 202 to have access to free air flow. The coolant distribution and flow may be accomplished through pipes and hoses inside the EPU or through features built into the housing 202 as described above, where channels are formed in the housing 202 and / or the stator 210.

[0085] The detailed description above describes various features and operations of the disclosed systems with reference to the accompanying figures. The illustrative implementations described herein are not meant to be limiting. Certain aspects of the disclosed systems can be arranged and combined in a wide variety of different configurations, all of which are contemplated herein.

[0086] Further, unless context suggests otherwise, the features illustrated in each of the figures may be used in combination with one another. Thus, the figures should be generally viewed as component aspects of one or more overall implementations, with the understanding that not all illustrated features are necessary for each implementation.

[0087] Additionally, any enumeration of elements, steps, or blocks in this specification or the claims is for purposes of clarity. Thus, such enumeration should not be interpreted to require or imply that these elements, steps, or blocks adhere to a particular arrangement or are carried out in a particular order.

[0088] Further, devices or systems may be used or configured to perform functions presented in the figures. In some instances, components of the devices and / or systems may be configured to perform the functions such that the components are actually configured and structured (with hardware and / or software) to enable such performance. In other examples, components of the devices and / or systems may be arranged to be adapted to, capable of, or suited for performing the functions, such as when operated in a specific manner.

[0089] By the term “substantially” or “about” it is meant that the recited characteristic, parameter, or value need not be achieved exactly, but that deviations or variations, including for example, tolerances, measurement error, measurement accuracy limitations and other factors known to those with skill in the art, may occur in amounts that do not preclude the effect the characteristic was intended to provide.

[0090] The arrangements described herein are for purposes of example only. As such, those skilled in the art will appreciate that other arrangements and other elements (e.g., machines, interfaces, operations, orders, and groupings of operations, etc.) can be used instead, and some elements may be omitted altogether according to the desired results. Further, many of the elements that aredescribed are functional entities that may be implemented as discrete or distributed components or in conjunction with other components, in any suitable combination and location.

[0091] While various aspects and implementations have been disclosed herein, other aspects and implementations will be apparent to those skilled in the art. The various aspects and implementations disclosed herein are for purposes of illustration and are not intended to be limiting, with the true scope being indicated by the following claims, along with the full scope of equivalents to which such claims are entitled. Also, the terminology used herein is for the purpose of describing particular implementations only, and is not intended to be limiting.

[0092] Implementations of the present disclosure can thus relate to one of the enumerated example embodiments (EEEs) listed below.

[0093] EEE 1 is an electric propulsion unit comprising: a housing; an electric motor disposed within the housing, wherein the electric motor has stator and a rotor; a motor shaft coupled to the rotor and extending outside the housing; a heat exchanger mounted external to the housing and coupled to the housing via one or more fluid lines; one or more pumps mounted to the housing and driven by the motor shaft; and at least one fan mounted external to the housing and driven by the motor shaft, wherein the one or more pumps circulate coolant through the one or more fluid lines, one or more channels formed in housing and / or the stator of the electric motor, and the heat exchanger, while the at least one fan provides air flow to reduce a temperature of coolant as coolant flows through the heat exchanger.

[0094] EEE 2 is the electric propulsion unit of EEE 1, further comprising: an inverter mounted to a coldplate inside the housing; and respective channels formed in or proximate the coldplate, wherein the one or pumps provide coolant through the respective channels to reduce a respective temperature of the inverter.

[0095] EEE 3 is the electric propulsion unit of any of EEEs 1 -2, wherein the one or more pumps comprise: a first pump mounted to the housing and having a shaft protruding inside the housing to be drive by the motor shaft; and a second pump mounted to the housing and having a respective shaft protruding inside the housing to be drive by the motor shaft.

[0096] EEE 4 is the electric propulsion unit of any of EEEs 1-3, wherein the housing comprises: a first housing portion in which the electric motor is disposed; and a second housing portion coupled to the first housing portion, wherein the one or more pumps are mounted to the second housing portion.

[0097] EEE 5 is the electric propulsion unit of EEE 4, further comprising: a first bearing supporting the rotor and facilitating rotation of the rotor relative to the first housing portion; and a second bearing supporting the motor shaft and facilitating rotation of the motor shaft relative to the second housing portion.

[0098] EEE 6 is the electric propulsion unit of any of EEEs 4-5, further comprising: an inverter mounted to a coldplate inside the second housing portion.

[0099] EEE 7 is the electric propulsion unit of any of EEEs 1-6, wherein the at least one fan is axially interposed between the housing and the heat exchanger.

[0100] EEE 8 is the electric propulsion unit of any of EEEs 1-7, wherein the heat exchanger is axially interposed between the housing and the at least one fan.

[0101] EEE 9 is the electric propulsion unit of any of EEEs 1-8, wherein the at least one fan comprises a plurality of blades coupled to a hub of the at least one fan, wherein each blade is coupled to the hub via a breakaway feature, wherein as the blade is blocked, jammed, or forcedinto a sudden stop, the breakaway feature allows the blade to disengage from the hub, allowing the at least one fan to continue rotating.

[0102] EEE 10 is the electric propulsion unit of any of EEEs 1-9, wherein the breakaway feature comprises a dovetail configuration.

[0103] EEE 1 1 is the electric propulsion unit of any of EEEs 9-10, wherein the breakaway feature comprises a friction device or a mechanical slip joint that slips once a torque applied to a respective blade exceeds a threshold torque value.

[0104] EEE 12 is the electric propulsion unit of any of EEEs 1-11, wherein the at least one fan comprises a dual fan comprising: a first fan having a first hub coupled to the motor shaft; and a second fan having a second hub coupled to the motor shaft.

[0105] EEE 13 is the electric propulsion unit of EEE 12, wherein the first hub and the second hub are concentric.

[0106] EEE 14 is the electric propulsion unit of any of EEEs 12-13, wherein the first fan and the second fan are coupled to the motor shaft via respective breakaway features, such that if the first fan or the second fan is blocked, jammed, or forced into a sudden stop, a respective breakaway feature allows one fan to disengage from the motor shaft, allowing the other fan to continue rotating.

[0107] EEE 15 is the electric propulsion unit of any of EEEs 1-14, wherein the at least one fan has a hub attached to the motor shaft via a neck portion.

[0108] EEE 16 is a vehicle comprising: a propeller; and the electric propulsion unit of any of EEEs 1-15, wherein the motor shaft of the electric propulsion unit is coupled to and configured to drive the propeller.

[0109] EEE 17 is a method of operating the electric propulsion unit of any of EEEs 1 -15 or the vehicle of EEE 16.

[0110] EEE 18 is a method of assembling the electric propulsion unit of any of EEEs 1-15.

Claims

CLAIMSWhat is claimed is:1 . An el ectri c propul si on unit compri si ng : a housing; an electric motor disposed within the housing, wherein the electric motor has stator and a rotor; a motor shaft coupled to the rotor and extending outside the housing; a heat exchanger mounted external to the housing and coupled to the housing via one or more fluid lines; one or more pumps mounted to the housing and driven by the motor shaft; and at least one fan mounted external to the housing and driven by the motor shaft, wherein the one or more pumps circulate coolant through the one or more fluid lines, one or more channels formed in housing and / or the stator of the electric motor, and the heat exchanger, while the at least one fan provides air flow to reduce a temperature of coolant as coolant flows through the heat exchanger.

2. The electric propulsion unit of claim 1, further comprising: an inverter mounted to a coldplate inside the housing; and respective channels formed in or proximate the coldplate, wherein the one or pumps provide coolant through the respective channels to reduce a respective temperature of the inverter.

3. The electric propulsion unit of claim 1, wherein the one or more pumps comprise: a first pump mounted to the housing and having a shaft protruding inside the housing to be drive by the motor shaft; and a second pump mounted to the housing and having a respective shaft protruding inside the housing to be drive by the motor shaft.

4. The electric propulsion unit of claim 1, wherein the housing comprises: a first housing portion in which the electric motor is disposed; and a second housing portion coupled to the first housing portion, wherein the one or more pumps are mounted to the second housing portion.

5. The electric propulsion unit of claim 4, further comprising: a first bearing supporting the rotor and facilitating rotation of the rotor relative to the first housing portion; and a second bearing supporting the motor shaft and facilitating rotation of the motor shaft relative to the second housing portion.

6. The electric propulsion unit of claim 4, further comprising: an inverter mounted to a coldplate inside the second housing portion.

7. The electric propulsion unit of claim 1, wherein the at least one fan is axially interposed between the housing and the heat exchanger.

8. The electric propulsion unit of claim 1, wherein the heat exchanger is axially interposed between the housing and the at least one fan.

9. The electric propulsion unit of claim 1, wherein the at least one fan comprises a plurality of blades coupled to a hub of the at least one fan, wherein each blade is coupled to the hub via a breakaway feature, wherein as the blade is blocked, jammed, or forced into a sudden stop, the breakaway feature allows the blade to disengage from the hub, allowing the at least one fan to continue rotating.

10. The electric propulsion unit of claim 9, wherein the breakaway feature comprises a dovetail configuration.

11. The electric propulsion unit of claim 9, wherein the breakaway feature comprises a friction device or a mechanical slip joint that slips once a torque applied to a respective blade exceeds a threshold torque value.

12. The electric propulsion unit of claim 1, wherein the at least one fan comprises a dual fan comprising: a first fan having a first hub coupled to the motor shaft; and a second fan having a second hub coupled to the motor shaft.

13. The electric propulsion unit of claim 12, wherein the first hub and the second hub are concentric.

14. The electric propulsion unit of claim 12, wherein the first fan and the second fan are coupled to the motor shaft via respective breakaway features, such that if the first fan or the second fan is blocked, jammed, or forced into a sudden stop, a respective breakaway feature allows one fan to disengage from the motor shaft, allowing the other fan to continue rotating.

15. The electric propulsion unit of claim 1, wherein the at least one fan has a hub attached to the motor shaft via a neck portion.

16. A vehicle comprising: a propeller; and an electric propulsion unit comprising: a housing, an electric motor disposed within the housing, wherein the electric motor has stator and a rotor, a motor shaft coupled to the rotor and extending outside the housing, wherein the motor shaft is coupled to and configured to drive the propeller, a heat exchanger mounted external to the housing and coupled to the housing via one or more fluid lines, one or more pumps mounted to the housing and driven by the motor shaft, and at least one fan mounted external to the housing and driven by the motor shaft, wherein the one or more pumps circulate coolant through the one or more fluid lines, one or more channels formed in housing and / or the stator of the electric motor, and the heatexchanger, while the at least one fan provides air flow to reduce a temperature of coolant as coolant flows through the heat exchanger.

17. The vehicle of claim 16, wherein the at least one fan comprises a plurality of blades coupled to a hub of the at least one fan, wherein each blade is coupled to the hub via a breakaway feature, wherein as the blade is blocked, jammed, or forced into a sudden stop, the breakaway feature allows the blade to disengage from the hub, allowing the at least one fan to continue rotating.

18. The vehicle of claim 17, wherein the breakaway feature comprises a dovetail configuration.

19. The vehicle of claim 17, wherein the breakaway feature comprises a friction device or a mechanical slip joint that slips once a torque applied to a respective blade exceeds a threshold torque value.

20. The vehicle of claim 16, wherein the at least one fan comprises a dual fan comprising: a first fan having a first hub coupled to the motor shaft; and a second fan having a second hub coupled to the motor shaft.

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