Electric propulsion unit housing with integrated cooling fluid channels

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; at least one fan mounted external to the housing and driven by the motor shaft; a first set of channels formed in the stator or the housing; and a second set of channels formed in the housing, radially outward relative to the first set of channels.

Description

Electric Propulsion Unit Housing with Integrated Cooling Fluid ChannelsCROSS REFERENCE TO RELATED APPLICATION

[0001] The present application claims priority to U.S. Provisional Application No. 63 / 701,064 filed on September 30, 2024, the entire contents of which are herein incorporated by reference as if fully set forth in this descnption.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 cunent in wire windings to generate force in the form of rotation of a shaft. Electric motors can be powered by direct cunent (DC) sources, such as from batteries, motor vehicles or rectifiers, or by alternating cunent (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 cunent or electric power is input through the wire windings, and increasing 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. Some configurations involve routing coolant from a housing of a motor to an external heat exchanger via external fluid lines (e.g., hoses). Such configurations are complex, use numerous parts, fittings, and hoses to implement a cooling loops. This increases parts count, cost, complexity, and reduces reliability7of the system. 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 an electric propulsion unit housing with integrated cooling fluid channels.

[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; at least one fan mounted external to the housing and driven by the motor shaft; a first set of channels formed in the stator or the housing; and a second set of channels formed in the housing, radially outward relative to the first set of channels. The one or more pumps draw coolant from the heat exchanger through the one or more fluid lines, then provide coolant through the first set of channels to cool the electric motor, wherein coolant then flows through the second set of channels, then through the one or more fluid lines back to 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 (EPU), 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 3 illustrates a partial front view of the EPU of Figures 2A-2B depicting coolant routing through the EPU, according to exemplary embodiments of the present invention.

[0016] Figure 4 illustrates a partial perspective view of a stator and a manifold for routing fluid, according to exemplary' embodiments of the present invention.

[0017] Figure 5 illustrates a partial side view of an EPU with a fan being dow nstream of a heat exchanger, according to exemplary embodiments of the present invention.DETAILED DESCRIPTION

[0018] 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 may provide a desired thermal boundary condition for the motor, inverter, and other parts of an EPU. Providing such desired thermal condition may involve cooling, heating, and / or pre-conditioning of the EPU and surrounding components.

[0019] Particularly, the disclosed EPU involves integrating fluid distribution channels within a housing of the EPU, which may enhance cooling efficiency, reduce overall part count, and reduce leakage probability through a sealed configuration. Integrating these fluid channels directly into the housing of the EPU provides efficient cooling. In some embodiments, all fluid is contained in the EPU’s housing, reducing external fluidic connection points, thereby reducing the probability of failure and leakage. The terms “coolant'’ and “fluid” are used interchangeably herein.

[0020] 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; at least one fan mounted external to the housing and driven by the motor shaft; a first set of channels formed in the stator or the housing; and a second set of channels formed in the housing, radially outward relative to the first set of channels. The one or more pumps draw coolant from the heat exchanger through the one or more fluid lines, then provide coolant through the first set of channels to cool the electric motor, wherein coolant then flows through the second set of channels, then through the one or more fluid lines back to 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.

[0021] 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.

[0022] 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).

[0023] 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.

[0024] 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 isdriven 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.

[0025] 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.

[0026] 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.

[0027] 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.

[0028] 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.

[0029] 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.

[0030] The batery 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 the vehicle 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 batery7modules 148. The EMSs 158 are configured as electronic regulators that monitor and control the charging and discharging of the batery' modules 148.

[0031] 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 batery modules 148 as well as ensuring safe operation of the batery modules 148. Safe operation includes, as examples, operating below a threshold temperature to elongate the life of the batery modules 148, preclude overheating, preclude failure of the batery modules 148. etc.

[0032] The EMSs 158 can monitor and control parameters of the batery modules 148. For example, the EMSs 158 monitor and control main power voltage, batery or cell voltage, charging and discharge rates of the batery' modules 148, temperatures of the batery’ modules 148 or their individual cells, health of the batery' modules 148 or their individual cells, coolant temperature and flow for air or liquid cooling parameters of a cooling system of the batery modules 148 or their individual cells, etc.

[0033] 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 batery 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 batery module of the batery 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 batery module. For example, the EMSs 158 control the power flow to and from the baterymodules 148 based on power demand from the various electric motors, and accordingly control the CCUs to enable power flow from particular battery' modules as desired.

[0034] The vehicle 100 may7be 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.

[0035] 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.

[0036] 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.

[0037] 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. In particular, it may be desirable to integrate fluid / coolant distribution channels directly into a housing of the EPU. Such channels can be formed or positioned to target the most heat-intensive areas, ensuring efficient cooling and fluid management within the EPU. The reduction of external components and connections of such configuration may minimize potential points of failure, thus improvingthe overall reliability of the EPU. The integrated channels configuration also reduces the risk of leaks and other issues associated with traditional cooling systems.

[0038] 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).

[0039] 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.

[0040] 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.

[0041] The EPU 200 also includes at least one inverter such as 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 torotate. The rotor 212 is supported by a first bearing 217 to facilitate rotation of the rotor 212 relative to the first housing portion 204.

[0042] 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.

[0043] 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 Figure 5) to drive any of the propellers or lift rotors described above with respect to Figure 1.

[0044] 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.

[0045] 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 show n to reduce visual clutter in the draw ing).

[0046] 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, and the heat exchanger 232. For example, the cooling arrangement 224 includes fluid line 234, fluid line 236, fluid line 238, and fluid line 240.

[0047] 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.

[0048] 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.

[0049] 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 filtersuch that the pumps 226, 228 draw coolant through such filter to remove any foreign objects or debris from the coolant.

[0050] 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.

[0051] Any type of coolant pumps may be used. For example, the pumps 226, 228 can be piston, gerotor. gear, vane, or centrifugal pumps.

[0052] 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. The cores may also have different types of coolants to support multiple fluidic networks or loops as described below.

[0053] Figure 3 illustrates a partial front view of the EPU 200 depicting coolant routing through the EPU 200. according to exemplary embodiments of the present invention. As shown, during operation of the EPU 200, the pumps 226, 228 may draw7cold coolant from the heat exchanger 232 via the fluid lines 234, 238, then displace the coolant under pressure through a first set of channels 300 in the housing 202.

[0054] In an example embodiment, the first set of channels 300 are formed radially inward in the housing 202 (the first housing portion 204) closer to the electric motor 208, thus indirectly cooling the electric motor 208. Additionally or alternatively, the first set of channels 300 may be formed in the stator 210, thus directly cooling the electric motor 208.

[0055] As shown in Figure 3, the coolant may also flow' through one or more channels 302 formed in the coldplate 222 or formed near (e.g.. in the second housing portion 206) the coldplate 222 to allow7the coolant to cool the inverter 216. 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 flow s through or near the coldplate 222.

[0056] In some embodiments, with this configuration, cold coolant is provided in a manner that targets the most heat-intensive areas (e.g., the electric motor 208 and the inverter 216), which may ensure efficient cooling within the EPU 200.

[0057] Coolant that is heated by the electric motor 208 may flow back through a second set of channels 304 formed in the housing 202 (the first housing portion 204). In some embodiments, the second set of channels 304 are formed radially outw ard from the first set of channels 300 as shown. Coolant heated by the inverter 216 may also return through respective return channels formed in the coldplate 222 or the second housing portion 206. Returning heated coolant from both the second set of channels 304 and the respective channels in the coldplate 222 or the second housing portion 206 may then be routed through the fluid lines 236, 240, back to the heat exchanger 232.

[0058] Particularly, hot coolant may flow through heat exchanger channels 306. The fan 230 provides the air flow that reduces the temperature of the coolant as it flows through the heat exchanger channels 306 to dissipate heat into ambient air. Cooled coolant may then be routed through heat exchanger channels 308, then through the fluid lines 234, 238 to begin the coolant circuit or loop again.

[0059] The fan 230 may be 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., thevehicle 100) is driven or flown. The fan 230 can be an axial fan or a radial fan based on the application in which the EPU 200 is used.

[0060] Further, the direction of air flow can be changed based on the type of the fan 230. Particularly, in one embodiment, the fan 230 may pull air around the housing 202, then push it toward the heat exchanger 232 as shown in Figure 3. In another embodiment, the fan 230 may pull the air through the heat exchanger 232 and push it toward the housing 202.

[0061] As mentioned above, in some embodiments, the first set of channels 300 can be formed in either the housing 202 (e.g., in the first housing portion 204) or the stator 210. In example embodiments where the first set of channels 300 are formed in the stator 210, a manifold may be disposed within the housing 202 to route or distribute fluid from the first set of channels 300 to the second set of channels 304 formed in the housing 202. In some embodiments, the first set of channels 300 and / or the second set of channels 304 may be machined. In other embodiments, the first set of channels 300 and / or the second set of channels 304 may be cast.

[0062] Figure 4 illustrates a partial perspective view of the stator 210 and a manifold 400 for routing fluid, according to exemplary’ embodiments of the present invention. As shown in Figure 4, the first set of channels 300 may be configured as longitudinal channels forming a circular array about an exterior surface of the stator 210. The stator 210 or the housing 202 may further have respective channels 404 that routes coolant between the first set of channels 300 and the manifold 400. In an example embodiment, the manifold 400 is disposed within the housing 202 (e.g., the first housing portion 204) and is configured to route coolant (e.g.. via the depicted quarter turn structures) from the respective channels 404 to the second set of channels 304 shown in Figure 4.

[0063] Advantageously, the channels formed in various components of the EPU 200 may be customized to suit specific applications. Particularly, the geometry’ of the channels may betailored based on the operational requirements of the EPU 200. Example channel geometries include dual pass channel, serpentine, single pass, etc. This flexibility may support a wide range of EPU configurations and power levels.

[0064] Further, fluid lines and channels are integrated into the EPU 200 (e.g., into the housing 202), allowing for the coolant to drain back into the same location in case of a failure. Particularly, the cooling system is integrated within the EPU 200 (e.g., within the housing 202), and is configured such that in the event of a failure (e.g., a rupture or disconnection), the coolant is directed or drained internally to a designated collection or return area. This ensures that any leakage does not escape into the internal compartments of the EPU 200, thereby preventing potential damage to electrical or mechanical components. The integration of return channels and fluid pathways provides containment and protection, enhancing system reliability and safety.

[0065] In one example embodiment, a single fluid loop may be implemented in the EPU 200. In this example embodiment, both of the pumps 226, 228 circulate fluid in the manner described above.

[0066] In another example embodiment, a multi-fluid thermal management configuration may be used. Particularly, to provide redundancy and reduce the likelihood of failure, two or more fluidic loops may be incorporated. For instance, 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.

[0067] The loops may have the same or different fluid and cooling capacities to support different loads and components. For example, if direct motor cooling is used where the first set of channels 300 are formed in the stator 210, the coolant used for the loop associated withcooling the electric motor 208 may be a dielectric coolant (e.g.. Paratherm LR. Slytherm 800, or Shell Diala). On the other hand, the coolant used for the inverter loop may be a water-glycol mixture. Separating the motor and inverter cooling loops allows for use of water-glycol mixture, which has enhanced thermal transfer properties, for the inverter 216, therefore improving the thermal performance of the EPU 200. In these examples, the heat exchanger 232 may have multiple cores therein to handle the multiple respective cooling loops and coolants.

[0068] The arrangement of the EPU 200 shown in Figures 2A-2B and 3 is one example embodiment. Other arrangements are contemplated. For example, the axial order of components (e.g., how the components stack up) in an EPU may be changed, while maintaining the advantageous features of the EPU 200 described above.

[0069] Figure 5 illustrates a partial side view of an EPU 500 with the fan 230 being downstream 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.

[0070] While the EPU 200 shown in Figures 2A-2B and Figure 3 has the fan 230 axially interposed between the heat exchanger 232 on one side and the electric motor 208 and the housing 202 on the other side, Figure 5 shows an implementation of an EPU where 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. Coolant may be routed similar to the routing configurations described above with respect to Figures 3-4. Further, as depicted in Figure 5, the motor shaft 219 can extend through the heat exchanger 232, and coolant may be routed through or around the motor shaft 219 in some examples.

[0071] 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 and through features built into the housing 202 as described above, where channels are formed in the housing 202 and / or the stator 210.

[0072] As such, the EPU 200, 500 provides several advantages over other systems. Particularly, the EPU 200 involves integrating fluid distribution channels (e.g., the channels 300, 302) within the housing 202 to enhance cooling efficiency, reduce overall part count, and reduce leakage probability through a sealed configuration. Integrating these fluid channels directly into the housing 202 of the EPU 200. 500 may provide efficient cooling. Fluid is contained in the housing 202, reducing external fluidic connection points (e.g.. external fittings), thereby reducing the probability of failure and leakage. Thus, the overall weight, size, and complexity’ of the EPU 200 and its cooling system may be reduced.

[0073] Further, in some embodiments, the cooling channels (e.g., the first set of channels 300 and the channels 302) are positioned to target the most heat-intensive areas (e.g., the electric motor 208 and the inverter 216), ensuring efficient cooling and fluid management within the EPU 200, 500. Also, multiple cooling loops and customized channel geometries may be used to further enhance cooling efficiency.

[0074] 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.

[0075] 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 necessary7for each implementation.

[0076] 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.

[0077] 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.

[0078] 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.

[0079] 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 are described are functional entities that may be implemented as discrete ordistributed components or in conjunction with other components, in any suitable combination and location.

[0080] 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.

[0081] Implementations of the present disclosure can thus relate to one of the enumerated example embodiments (EEEs) listed below.

[0082] 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; at least one fan mounted external to the housing and driven by the motor shaft; a first set of channels formed in the stator or the housing; and a second set of channels formed in the housing, radially outward relative to the first set of channels, wherein the one or more pumps draw coolant from the heat exchanger through the one or more fluid lines, then provide coolant through the first set of channels to cool the electric motor, wherein coolant then flows through the second set of channels, then through the one or more fluid lines back to 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.

[0083] EEE 2 is the electric propulsion unit of EEE 1, further comprising: an inverter mounted to a coldplate inside the housing; and one or more channels formed in or proximate thecoldplate, wherein the one or pumps provide coolant through the one or more channels to reduce a respective temperature of the inverter.

[0084] EEE 3 is the electric propulsion unit of EEE 2, wherein a first coolant circulates through a first loop to cool the electric motor, and wherein a second coolant circulates through a second loop to cool the inverter.

[0085] EEE 4 is the electric propulsion unit of EEE 3, wherein the first coolant is a dielectric coolant, and wherein the second coolant is a water-glycol mixture.

[0086] EEE 5 is the electric propulsion unit of any of EEEs 1 -4, wherein the one or more pumps comprise: a first pump mounted to the housing and having a shaft protruding inside the housing to be driven by the motor shaft; and a second pump mounted to the housing and having a respective shaft protruding inside the housing to be driven by the motor shaft.

[0087] EEE 6 is the electric propulsion unit of any of EEEs 1-5. 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.

[0088] EEE 7 is the electric propulsion unit of EEE 6, wherein the first set of channels are formed in the stator or the first housing portion, and wherein the second set of channels are formed in the first housing portion.

[0089] EEE 8 is the electric propulsion unit of any of EEEs 6-7, further comprising: an inverter mounted to a coldplate inside the second housing portion; and one or more channels formed in the second housing portion or the coldplate, wherein the one or pumps provide coolant through the one or more channels to reduce a respective temperature of the inverter. 1

[0090] EEE 9 is the electric propulsion unit of any of EEEs 1-8, wherein the first set of channels are configured as longitudinal channels forming a circular array about an exterior surface of the stator.

[0091] EEE 10 is the electric propulsion unit of EEE 9, further comprising: a manifold disposed within the housing and configured to route coolant from the first set of channels to the second set of channels.

[0092] EEE 11 is the electric propulsion unit of any of EEEs 1-10, wherein the at least one fan is axially interposed between the housing and the heat exchanger.

[0093] EEE 12 is the electric propulsion unit of any of EEEs 1-11, wherein the heat exchanger is axially interposed between the housing and the at least one fan.

[0094] EEE 13 is a vehicle comprising: a propeller; and the electric propulsion unit of any of EEEs 1-12. wherein the motor shaft of the electric propulsion unit is coupled to and configured to be the propeller.

[0096] EEE 14 is a method of operating the electric propulsion unit of any of EEEs 1-12 or the vehicle of EEE 13.

[0097] EEE 15 is a method of assembling the electric propulsion unit of any of EEEs 1-12.

Claims

CLAIMSWhat is claimed is:

1. 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; at least one fan mounted external to the housing and driven by the motor shaft; a first set of channels formed in the stator or the housing; and a second set of channels formed in the housing, radially outward relative to the first set of channels, wherein the one or more pumps draw coolant from the heat exchanger through the one or more fluid lines, then provide coolant through the first set of channels to cool the electric motor, wherein coolant then flows through the second set of channels, then through the one or more fluid lines back to 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 one or more channels formed in or proximate the coldplate, wherein the one or pumps provide coolant through the one or more channels to reduce a respective temperature of the inverter.

3. The electric propulsion unit of claim 2, wherein a first coolant circulates through a first loop to cool the electric motor, and wherein a second coolant circulates through a second loop to cool the inverter.

4. The electric propulsion unit of claim 3, wherein the first coolant is a dielectric coolant, and wherein the second coolant is a water-glycol mixture.

5. 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 driven by the motor shaft; and a second pump mounted to the housing and having a respective shaft protruding inside the housing to be driven by the motor shaft.

6. 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.

7. The electric propulsion unit of claim 6. wherein the first set of channels are formed in the stator or the first housing portion, and wherein the second set of channels are formed in the first housing portion.

8. The electric propulsion unit of claim 6, further comprising:an inverter mounted to a coldplate inside the second housing portion; and one or more channels formed in the second housing portion or the coldplate, wherein the one or pumps provide coolant through the one or more channels to reduce a respective temperature of the inverter.

9. The electric propulsion unit of claim 1, wherein the first set of channels are configured as longitudinal channels forming a circular array about an exterior surface of the stator.

10. The electric propulsion unit of claim 9, further comprising: a manifold disposed within the housing and configured to route coolant from the first set of channels to the second set of channels.

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

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

13. 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, at least one fan mounted external to the housing and driven by the motor shaft, a first set of channels formed in the stator or the housing, and a second set of channels formed in the housing, radially outward relative to the first set of channels, wherein the one or more pumps draw coolant from the heat exchanger through the one or more fluid lines, then provide coolant through the first set of channels to cool the electric motor, wherein coolant then flows through the second set of channels, then through the one or more fluid lines back to 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.

14. The vehicle of claim 13, wherein the electric propulsion unit further comprises: an inverter mounted to a coldplate inside the housing; and one or more channels formed in or proximate the coldplate, wherein the one or pumps provide coolant through the one or more channels to reduce a respective temperature of the inverter.

15. The vehicle of claim 14. wherein a first coolant circulates through a first loop to cool the electric motor, and wherein a second coolant circulates through a second loop to cool the inverter, wherein the first coolant is a dielectric coolant, and wherein the second coolant is a water-glycol mixture.

16. The vehicle of claim 13, wherein the one or more pumps comprise: a first pump mounted to the housing and having a shaft protruding inside the housing to be driven by the motor shaft; and a second pump mounted to the housing and having a respective shaft protruding inside the housing to be driven by the motor shaft.

17. The vehicle of claim 13, 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, wherein the first set of channels are formed in the stator or the first housing portion, and wherein the second set of channels are formed in the first housing portion.

18. The vehicle of claim 17, further comprising: an inverter mounted to a coldplate inside the second housing portion; and one or more channels formed in the second housing portion or the coldplate, wherein the one or pumps provide coolant through the one or more channels to reduce a respective temperature of the inverter.

19. The vehicle of claim 13, wherein the first set of channels are configured as longitudinal channels forming a circular array about an exterior surface of the stator, and wherein the electric propulsion unit further comprises:a manifold disposed within the housing and configured to route coolant from the first set of channels to the second set of channels.

20. The vehicle of claim 13, wherein the at least one fan is axially interposed between the housing and the heat exchanger, and wherein the heat exchanger is axially interposed between the housing and the at least one fan.

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