Oleophilic surface treatment for enhanced heat transfer properties of electrical machines

Abstract

Oilophilic surface treatments for electric machines, methods for making / using such electric machines, and vehicles employing traction motors having stator windings that are oilophilically treated on selected surfaces are presented. An electric machine includes an outer housing with a direct-cooling thermal management system fluidly connected to the housing to circulate a coolant fluid thereto. A stator assembly attached to the housing includes a stator core with one or more electromagnetic windings mounted to the stator core. A rotor assembly is movably mounted to the housing adjacent the stator assembly. The rotor assembly includes a rotor core with one or more magnets mounted to the rotor core, for example, spaced apart from the windings across an air gap. Selected components of the stator assembly have target surfaces that are oilophilically surface treated that expand a wetted area of the target surfaces and increase a coolant mass of the coolant fluid that contacts the target surfaces.

Description

Technical Field

[0001] This disclosure generally relates to electric motors. More specifically, aspects of this disclosure relate to surface features for enhancing the heat transfer characteristics of oil-cooled electric traction motors. Background Technology

[0002] Modern motor vehicles, such as modern cars, were originally equipped with a powertrain that operated to propel the vehicle and power its onboard electronics. For example, in automotive applications, the vehicle powertrain is typically represented by a prime mover that transmits drive torque to the vehicle's final drive system (e.g., differential, axles, cornering modules, wheels, etc.) via an automatic or manual transmission. Historically, automobiles have been powered by reciprocating piston internal combustion engine (ICE) components due to their availability and relatively low cost, light weight, and overall efficiency. As some non-limiting examples, such engines include compression ignition (CI) diesel engines, spark ignition (SI) gasoline engines, two-stroke, four-stroke, and six-stroke architectures, and rotary engines. Hybrid electric and fully electric vehicles (collectively referred to as "electric drive"), on the other hand, utilize alternative power sources to propel the vehicle and, therefore, minimize or eliminate reliance on fossil fuel-based engines for traction power.

[0003] All-electric vehicles (FEVs), commonly known as "electric vehicles," are a type of electric-drive vehicle configuration that completely omits the internal combustion engine and associated peripheral components from its powertrain system, relying solely on a rechargeable energy storage system (RESS) and traction motors for wheel propulsion. In battery-based FEVs, the engine components, fuel supply system, and exhaust system of ICE-based vehicles are replaced by one or more traction motors, a traction battery pack, and battery cooling and charging hardware. In contrast, hybrid electric vehicles (HEVs) use multiple traction power sources to propel the vehicle, most commonly combining battery-powered or fuel cell-powered traction motors to operate the internal combustion engine components. Because hybrid electric vehicles can obtain power from sources other than the engine, the HEV engine can be completely or partially shut off when the vehicle is propelled by electric motors.

[0004] The high-voltage (HV) electrical system controls the power transfer between the traction motor and the rechargeable traction battery pack, which stores and supplies the necessary power for operating many hybrid and all-electric powertrains. Modern traction battery packs can group battery cells (e.g., 8-16 cells / pack) into individual battery modules (e.g., 10-40 modules / group), electrically interconnected in series or parallel, and mounted to the vehicle chassis, for example, via a battery pack housing or support tray. A front-end DC-DC power converter, located on the battery side of the HV electric system, is electrically connected to the traction battery pack to increase the voltage supplied to the main DC bus and the DC-AC power inverter module (PIM). High-frequency, high-capacity capacitors can be arranged across the positive and negative terminals of the HV main DC bus to provide electrical stability and store supplemental energy. A dedicated electronic battery control module (EBCM) controls the operation of the battery pack and traction motor through coordinated operation with the powertrain control module (PCM) and the power electronics packages of each motor.

[0005] There are three main types of motors used for traction motors in modern electric vehicle powertrains: brushed direct current (DC) motors, brushless DC permanent magnet (PM) motors, and multiphase alternating current (AC) PM motors. ACPM motors convert electrical energy into rotational mechanical energy using a stator with multiphase electromagnetic windings and a rotatable rotor supported by permanent magnets. In radial flux PM motor designs, the rotor supporting the magnets can be coaxially nested inside the stator, and the stator is immovably mounted inside the motor housing. Alternatively, PM motors can employ an axial flux arrangement, where the stator and rotor are facing coaxial disks. The rotor, with multiple surface-mounted or internally mounted permanent magnets, is separated from the stator by a small air gap. The rotation of the rotor is influenced by a magnetic field generated by the current flowing through the stator windings, which interacts with the magnetic field generated by the permanent magnets of the rotor. During operation of the PM motor, the rotational friction of the rotating rotor and the resistance of the electromagnetic stator generate a significant amount of heat. To improve motor efficiency and increase the expected service life of the motor, the heat generated by the rotor and stator can be mitigated through air-cooled, water-cooled, or oil-cooled thermal management systems. Summary of the Invention

[0006] This document presents an oleophilic surface treatment for an electric motor, a method for manufacturing and using an oleophilic surface-treated electric motor, and an electric drive vehicle employing a traction motor having a multiphase stator winding with an oleophilic target surface. In a non-limiting example, the multiphase electric motor / generator unit (MGU) employs a direct oil-cooled thermal management system with a coolant jacket encompassing the axial ends of a concentrically aligned rotor and stator. Pressurized or gravity-supplyed dielectric oil is volumetric pumped from a dedicated or shared oil sump into the coolant jacket; the oil is guided across hairpin crowns (also referred to as “end turns”) protruding from the axial ends of the stator of the multiphase winding. To increase the coolant mass, surface energy, and wetting area on the target surface of the winding, an oleophilic coating or surface texture is applied over the entire multiphase stator winding or to selected sections of the hairpin crowns and / or legs. Oleophilic surface treatments can include ultraviolet (UV) ozone treatment, UV / plasma / flame / acid surface etching, and / or chemical deposition of inorganic silanes or dodecyltrimethoxysilanes (DTMS). These surface treatments can be applied over a resin coating, a varnish coating, or other dielectric layers applied to the target surface. Furthermore, by selectively reducing the contact angle between the oil and the target surface, there is a visible increase in oil distribution, accompanied by an increase in total wetting area and a decrease in peak and average temperatures.

[0007] At least some of the disclosed contingent benefits include oleophilic surface treatments for the motor that help improve system cooling efficiency. For example, by increasing the wetting area and coolant mass of the target surface, a reduction in the required coolant fluid for maintaining the calibrated maximum or average operating temperature is achieved, resulting in a reduction in system coolant charge. With less coolant in the thermal management system, energy consumption for the operating system pumps is reduced, leading to improved overall vehicle efficiency and increased driving range. Additionally, reducing the contact angle between the dielectric oil and the target surface (e.g., reducing it to approximately 35 degrees or less) provides a measurable increase in oil distribution across adjacent target surfaces, along with a significant increase in total wetting area and a corresponding reduction in peak and average temperatures.

[0008] This disclosure relates to electric motors, such as motors, generators, transformers, inductors, power meters, converters, etc., with oleophilic surface treatments on one or more target surfaces. For example, a representative motor includes a protective outer housing selectively cooled by a direct-cooling thermal management system. The thermal management system is fluidly connected to the outer housing and operable to circulate a coolant fluid, such as an engineered full-immersion liquid coolant or a lubricating dielectric transmission fluid, to it. A stator assembly is attached to the outer housing, the stator assembly including one or more electromagnetic windings, such as multiphase U-shaped hairpin windings, mounted to a stationary stator core. A rotor assembly is movably mounted adjacent to the stator assembly, for example, within the outer housing. For at least some applications, the rotor assembly is rotatably disposed inside the stator assembly and thus surrounded by the stator assembly. The rotor assembly includes one or more magnets, such as individual permanent magnet bars, mounted to the rotor core in a spaced-apart relationship with the stator windings. The stator assembly includes one or more target surfaces with oleophilic surface treatments designed to increase the wetting area of ​​the target surfaces while also increasing the coolant mass of the coolant fluid in contact with the target surfaces.

[0009] Additional aspects of this disclosure relate to motor vehicles employing traction motors with multiphase stator windings having an oleophilic surface treatment. As used herein, the terms "vehicle" and "motor vehicle" are used interchangeably and synonymously to include any relevant vehicle platform, such as buses (ICE, HEV, FEV, FCH, fully and partially autonomous buses, etc.), commercial vehicles, industrial vehicles, tracked vehicles, off-road and all-terrain vehicles (ATVs), motorcycles, electric bicycles, electric scooters, agricultural equipment, boats, aircraft, etc. For non-automotive applications, the disclosed concepts can be used for any logically related purpose, including stand-alone power plants, commercial or residential generators, pumping equipment, machine tools, electrical appliances, etc. In examples, a motor vehicle includes a vehicle body with a passenger compartment, multiple wheels rotatably mounted to the vehicle body (e.g., via wheel corner modules coupled to an integrated chassis or frame-body chassis), and other standard original equipment. In electric vehicle applications, one or more electric traction motors operate individually (e.g., for FEV powertrains) or in combination with internal combustion engine components (e.g., for HEV powertrains) to selectively drive one or more of the wheels, thereby propelling the vehicle.

[0010] Continuing with the above example, each traction motor includes a motor housing fluidly connected to a dedicated or shared direct oil-cooled thermal management system to receive dielectric oil from it. A stator assembly rigidly mounted within the motor housing includes an annular stator core with a hollow center and a plurality of stator slots circumferentially spaced around the stator core. A series of U-shaped electromagnetic hairpin windings are at least partially encapsulated within the stator slots. A rotor assembly rotatably disposed within the hollow center of the annular stator core includes a cylindrical rotor core with a plurality of rotor slots circumferentially spaced around the rotor core. A permanent magnet array is at least partially mounted within the rotor slots in a spaced-apart relationship with the hairpin windings. Each hairpin winding has one or more target surfaces with an oleophilic surface treatment that increases the wetting area of ​​the target surface and simultaneously increases the coolant mass of the coolant fluid in contact with the target surface.

[0011] Other aspects of this disclosure relate to manufacturing processes, control logic, and computer-readable media (CRM) for making or using any of the disclosed electric motors, PM motors, and / or vehicles. In an example, a method for assembling an electric motor is proposed. This representative method, in any order and in any combination with any of the options and features disclosed above and below, includes: providing an outer housing of the motor; fluidly connecting a direct-cooling thermal management system to the outer housing to circulate coolant fluid thereto; attaching a stator assembly to the outer housing, the stator assembly including a stator core and electromagnetic windings mounted to the stator core; applying an oleophilic surface treatment to a target surface of the stator assembly, the oleophilic surface treatment being configured to increase the wetting area of ​​the target surface and increase the coolant mass of the coolant fluid in contact with the target surface; and movably mounting a rotor assembly adjacent to the stator assembly, the rotor assembly including a rotor core and magnets spaced apart from the windings and mounted to the rotor core.

[0012] For any disclosed electric motor, vehicle, and method, only the electromagnetic winding of the stator assembly includes a target surface treated with an oleophilic finish. In a more specific, but limiting, example, the electromagnetic winding is fabricated with a pair of hairpin legs projecting from a hairpin crown; these hairpin legs extend through stator slots in the stator core. In this case, only the exposed portions of the hairpin crown and / or the legs projecting from the axial ends of the stator core include the target surface treated with an oleophilic finish. Each winding may optionally be coated with a varnish coating before, during, or after the oleophilic finish, for example, to insulate the winding from contaminants to promote heat dissipation.

[0013] For any disclosed electric motor, vehicle, and method, the oleophilic surface treatment includes a UV ozone treatment applied to the electromagnetic windings. It is desirable that only the exposed sections of the crown and legs protruding from the stator core have the UV ozone treatment, which can be applied to a varnish coating. Alternatively, the oleophilic surface treatment may include a chemical deposition treatment of an inorganic compound applied to the electromagnetic windings. The inorganic compound may include silane materials and / or dodecyltrimethoxysilane materials. It is desirable that only the exposed sections of the crown and legs have the inorganic compound surface treatment, which can be applied to a varnish coating via chemical deposition. The surface treatment may have a thickness of about 5 micrometers to about 0.1 millimeters.

[0014] For any disclosed motor, vehicle, and method, the oleophilic surface treatment includes surface etching having an isotropic pattern applied to the windings. The surface etching may include ultraviolet etching, plasma etching, flame etching, and / or acid etching. It is desirable that only the exposed sections of the hairpin crown and legs include surface etching, which may be applied to a varnish coating. The surface etching may include a series of parallel grooves, each recessed into the exposed section of the hairpin crown / leg.

[0015] The above description of the invention does not represent every embodiment or aspect of this disclosure. Rather, the above features and advantages, as well as other features and incidental advantages, of this disclosure will readily become apparent from the following detailed description of illustrative examples and models for carrying out this disclosure, taken in conjunction with the accompanying drawings and claims. Furthermore, this disclosure expressly includes any and all combinations and sub-combinations of the elements and features described above and below.

[0016] The present invention also includes the following technical solutions.

[0017] Technical Solution 1. An electric motor, comprising: External casing; A direct-cooling thermal management system, which is fluidly connected to the outer housing and configured to circulate coolant fluid thereto; Stator assembly, the stator assembly being attached to the outer housing and including a stator core having electromagnetic windings mounted thereon; and A rotor assembly movable relative to the stator assembly and including a rotor core having magnets mounted thereon at a distance from the windings. The stator assembly has a target surface that has undergone an oleophilic surface treatment, which is configured to increase the wetting area of ​​the target surface and increase the coolant mass of the coolant fluid in contact with the target surface.

[0018] Technical Solution 2. The motor according to Technical Solution 1, wherein only the electromagnetic winding of the stator assembly includes a target surface that has undergone oleophilic surface treatment.

[0019] Technical Solution 3. The motor according to Technical Solution 2, wherein the electromagnetic winding includes a hairpin crown having a pair of hairpin legs protruding from the hairpin crown and extending through a stator slot in the stator core, and wherein only the exposed portions of the hairpin crown and the legs protruding from the stator core include a target surface treated with an oleophilic surface.

[0020] Technical Solution 4. The motor according to Technical Solution 1, wherein the oleophilic surface treatment includes ultraviolet (UV) ozone treatment applied to the electromagnetic winding.

[0021] Technical Solution 5. The motor according to Technical Solution 4, wherein the winding includes a hairpin crown having a pair of hairpin legs protruding from the hairpin crown and extending through a stator slot in the stator core, and wherein only the exposed portions of the hairpin crown and the legs protruding from the stator core include a varnish coating, wherein UV ozone treatment is applied to the varnish coating.

[0022] Technical Solution 6. The motor according to Technical Solution 1, wherein the oleophilic surface treatment includes a chemical deposition treatment of an inorganic compound applied to the electromagnetic winding.

[0023] Technical Solution 7. The motor according to Technical Solution 6, wherein the inorganic compound includes silane materials and / or dodecyltrimethoxysilane materials.

[0024] Technical Solution 8. The motor according to Technical Solution 7, wherein the winding includes a hairpin crown having a pair of hairpin legs protruding from the hairpin crown and extending through a stator slot in the stator core, and wherein only the exposed portions of the hairpin crown and the legs protruding from the stator core include a varnish coating, wherein an inorganic compound is applied to the varnish coating.

[0025] Technical Solution 9. The motor according to Technical Solution 7, wherein the inorganic compound has a thickness of about 5 micrometers to about 0.1 mm.

[0026] Technical Solution 10. The motor according to Technical Solution 1, wherein the oleophilic surface treatment includes surface etching, the surface etching having an isotropic pattern applied to the winding.

[0027] Technical Solution 11. The motor according to Technical Solution 10, wherein the surface etching is ultraviolet etching, plasma etching, flame etching and / or acid etching.

[0028] Technical Solution 12. The motor according to Technical Solution 11, wherein the electromagnetic winding includes a hairpin crown having a pair of hairpin legs protruding from the hairpin crown and extending through a stator slot in the stator core, and wherein only the exposed portions of the hairpin crown and the legs protruding from the stator core include a varnish coating, wherein surface etching is applied to the varnish coating.

[0029] Technical Solution 13. The motor according to Technical Solution 11, wherein the surface etching includes a series of mutually parallel grooves recessed into the exposed sections of the hair clip crown and the hair clip legs.

[0030] Technical Solution 14. A motor vehicle comprising: Vehicle body; Multiple wheels attached to the vehicle body; and A traction motor attached to the vehicle body and operable to drive one or more of the wheels to propel the motor vehicle, the traction motor comprising: Motor housing; A direct oil-cooled thermal management system fluidly connected to the motor housing and configured to circulate dielectric oil thereto; A stator assembly rigidly mounted within the motor housing, the stator assembly including an annular stator core defining a hollow center and a plurality of circumferentially spaced stator slots, and a plurality of U-shaped electromagnetic hairpin windings encapsulated within the stator slots; and A rotor assembly rotatably disposed within the hollow center of the annular stator core, the rotor assembly comprising a cylindrical rotor core defining a plurality of circumferentially spaced rotor slots, and a plurality of permanent magnets mounted in the rotor slots at intervals from the hairpin windings. Each of the hairpin windings of the stator assembly has a corresponding target surface that has undergone an oleophilic surface treatment, the oleophilic surface treatment being configured to increase the wetting area of ​​the target surface and increase the coolant mass of the coolant fluid in contact with the target surface.

[0031] Technical Solution 15. A method for assembling a motor, the method comprising: Provide an outer housing for the motor; A direct-cooling thermal management system is fluidly connected to the outer housing to circulate coolant fluid to it; The stator assembly is attached to the outer housing, the stator assembly including a stator core and an electromagnetic winding mounted to the stator core; An oleophilic surface treatment is applied to a target surface of the stator assembly, the oleophilic surface treatment being configured to increase the wetting area of ​​the target surface and increase the coolant mass of the coolant fluid in contact with the target surface; and A rotor assembly, comprising a rotor core and magnets spaced apart from the windings, is movably mounted adjacent to the stator assembly.

[0032] Technical Solution 16. The method according to Technical Solution 15, wherein only the electromagnetic winding of the stator assembly includes a target surface that has undergone oleophilic surface treatment.

[0033] Technical Solution 17. The method according to Technical Solution 16, wherein the electromagnetic winding includes a hairpin crown having a pair of hairpin legs protruding from the hairpin crown and extending through a stator slot in the stator core, and wherein only the exposed portions of the hairpin crown and the legs protruding from the stator core include a target surface treated with an oleophilic surface.

[0034] Technical Solution 18. The method according to Technical Solution 17, wherein the oleophilic surface treatment includes applying ultraviolet ozone treatment to the exposed sections of the hairpin crown and leg.

[0035] Technical Solution 19. The method according to Technical Solution 17, wherein the oleophilic surface treatment comprises applying an inorganic compound to the exposed sections of the hairpin crown and leg via chemical deposition.

[0036] Technical Solution 20. The method according to Technical Solution 17, wherein the oleophilic surface treatment includes applying a surface etching having an isotropic pattern to the exposed sections of the hairpin crown and leg. Attached Figure Description

[0037] Figure 1 This is a schematic illustration of a representative electric drive vehicle equipped with a hybrid electric powertrain according to aspects of this disclosure, the hybrid electric powertrain having a multiphase induction motor / generator unit (MGU) with a hairpin-wound stator supporting conductive hairpin windings with an oleophilic surface treatment.

[0038] Figure 2 This is a schematic end view of a representative electric motor with a rotor assembly and a stator assembly according to aspects of this disclosure, the rotor assembly including a rotor core supporting a plurality of permanent magnets, and the stator assembly having an annular stator ring supporting a plurality of hairpin windings with an oleophilic surface treatment.

[0039] Figure 3 It has a direct oil-cooled thermal management system. Figure 2 A front perspective view of a representative electric motor.

[0040] Figure 4 It is based on the aspects of the publicly disclosed concept. Figure 2 and Figure 3 An enlarged perspective view of a selected portion of a representative stator assembly, with an inset showing an enlarged cross-section of a hairpin winding with an oleophilic surface treatment.

[0041] Representative embodiments of this disclosure are illustrated by way of non-limiting example in the accompanying drawings and are described in detail below. However, it should be understood that the novel aspects of this disclosure are not limited to the specific forms illustrated in the drawings enumerated above. Rather, this disclosure will cover all modifications, equivalents, combinations, sub-combinations, permutations, groupings, and alternatives that fall within the scope of this disclosure as included, for example, by the appended claims. Detailed Implementation

[0042] This disclosure allows for numerous different forms of embodiments. Representative embodiments of this disclosure are shown in the accompanying drawings and are described in detail herein as to be understood to be illustrative of the disclosed principles and not limitations on the broad aspects of this disclosure. For this purpose, elements and limitations described, for example in the abstract, introduction, summary, description of the drawings, and detailed description sections, but not expressly set forth in the claims, should not be incorporated into the claims, individually or collectively, by implication, inference, or otherwise. Furthermore, the drawings discussed herein may not be drawn to scale and are provided for illustrative purposes only. Therefore, the specific and relative dimensions shown in the drawings should not be construed as limiting.

[0043] For the purposes of this specific embodiment, unless specifically denied, the singular includes the plural, and vice versa; the words “and” and “or” should be both conjunctions and antonymous conjunctions; the words “any” and “all” should both mean “any and all”; and the words “including,” “contains,” “includes,” “has,” and their arrangement should each mean “including but not limited to.” Furthermore, approximate words (such as “about,” “almost,” “basically,” “approximately,” etc.) may each be used herein in the meaning of, for example, “in,” “nearly,” or “within 0-5%,” or “within acceptable manufacturing tolerances,” or any logical combination thereof. Finally, directional adjectives and adverbs (such as forward, aft, inside, outside, starboard, port, vertical, horizontal, upward, downward, forward, aft, left, right, etc.) may be relative to the motor vehicle, for example, the forward driving direction of the motor vehicle when the vehicle is operably oriented on a level driving surface.

[0044] Referring now to the accompanying drawings, in which similar reference numerals refer to similar features throughout several views, Figure 1 A schematic illustration of a representative automobile, generally designated 10, is shown herein and depicted for illustrative purposes as a passenger vehicle with a parallel dual-clutch (P2) hybrid electric powertrain. The illustrated automobile 10 (also referred to herein simply as a "motor vehicle" or "vehicle") is merely an exemplary application by which the novel aspects of this disclosure can be practiced. Similarly, embodiments of the present concept practiced in a hybrid electric powertrain should also be understood as representative embodiments of the novel concepts disclosed herein. Accordingly, it will be understood that aspects of this disclosure can be applied to other powertrain architectures, incorporated into any logically related type of motor vehicle, and similarly applied to both automotive and non-automotive applications. Finally, only selected components have been shown and will be described in further detail herein. However, the motors and motor vehicles discussed below may include numerous additional and alternative features, as well as other available peripheral components for performing the various methods and functions of this disclosure.

[0045] Representative vehicle powertrain systems Figure 1 The prime mover (represented herein by a restartable internal combustion engine (ICE) assembly 12 and an electric motor / generator unit 14) is driven to the drive shaft 15 of the final drive system 11 via a multi-speed automatic transmission 16. The engine 12 preferably transmits power to the input side of the transmission 16 via engine crankshaft 13 (“engine output member”). Engine torque is first transmitted via crankshaft 13 to rotate the engine-driven torsional damper assembly 26, and subsequently transmitted via torsional damper assembly 26 to engine disconnect device 28. When operably engaged, this engine disconnect device 28 transmits the torque received from the ICE assembly 12 via damper 26 to the input structure of torque converter (TC) assembly 18. As the name suggests, engine disconnect device 28 can be selectively disengaged to drively disconnect the engine 12 from the MGU 14 (also referred to herein as the “traction motor” or simply the “motor”), TC assembly 18, and transmission 16.

[0046] To propel the hybrid vehicle 10, the transmission 16 is adapted to receive traction power from the engine 12 and the motor 14, selectively manipulate them, and distribute them to the vehicle’s final drive system 11 (represented herein by the drive shaft 15, the rear differential 22, and a pair of rear wheels 20). Figure 1The powertrain 16, motor 14, and torque converter 18 may share a common transmission oil pan or "sump" 32 for the supply of hydraulic fluid. A shared transmission pump 34 provides sufficient hydraulic pressure to selectively actuate the transmission 16, the TC assembly 18, and, in some embodiments, the hydraulically activated element of the engine disconnect device 28. For at least some embodiments, it may be preferred that the engine disconnect device 28 includes an active clutch mechanism (such as a controller-actuated selectable one-way clutch (SOWC) or a friction plate clutch) or a passive clutch mechanism (such as a ratchet mechanism or a braced flywheel OWC assembly).

[0047] The ICE component 12 operates, for example, independently of the electric traction motor 14 in an "engine-only" operating mode, or, for example, in a "vehicle start" or "motor-assisted" operating mode, in cooperation with the motor 14 to propel the vehicle 10. Figure 1 In the example illustrated, ICE component 12 can be any available or later-developed engine, such as a compression-ignition diesel engine or a spark-ignition gasoline or flexible fuel engine, which is easily adapted to typically provide its available power output in revolutions per minute (RPM). Although in Figure 1 Although not explicitly described, it should be understood that the final drive system 11 can adopt any available configuration, including front-wheel drive (FWD) layout, rear-wheel drive (RWD) layout, four-wheel drive (4WD) layout, all-wheel drive (AWD) layout, six-by-four (6X4) layout, and so on.

[0048] Figure 1 An electric motor / generator unit (“motor”) 14 is also illustrated, which is operatively connected to a hydraulic torque converter 18 via a motor support hub, shaft, or belt 29 (“motor output member”). The torque converter 18 then drivesly connects the motor 14 to the input shaft 17 (“transmission input member”) of the transmission 16. The electric MGU 14 consists of an annular stator assembly 21 that surrounds and is concentric with a cylindrical rotor assembly 23. Electrical power is supplied to the stator 21 via a high-voltage electrical system including electrical conductors / cables 27 that pass through the motor housing via suitable sealed and insulated feedthroughs (not shown). Conversely, electrical power can be supplied from the MGU 14 to the on-board traction battery pack 30, for example, via regenerative braking. The operation of any of the illustrated powertrain components can be controlled by an on-board or remote vehicle controller, such as a programmable electronic control unit (ECU) 25. Although shown as a P2 hybrid electric architecture with a single motor connected to the power flow in parallel with a single engine assembly, vehicle 10 can adopt other HEV powertrain configurations, including P0, P1, P2.5, P3 and P4 hybrid powertrains, or can be adapted to BEV, PHEV, range-extended hybrid vehicles, fuel cell hybrid vehicles, FEV and so on.

[0049] The powertrain 16 may use a differential gear arrangement 24 to selectively achieve variable torque and speed ratios between the input shaft 17 and the output shaft 19, for example, while sending all or part of its power via variable elements. One form of differential gear arrangement is a planetary gear arrangement. Planetary gear arrangements offer the advantages of compactness and different torque and speed ratios among all members of a subset of planetary gear arrangements. Traditionally, hydraulically actuated torque-building devices such as clutches and brakes (the term "clutch" is used to refer to both clutches and brakes) are selectively engaged to activate the aforementioned gear elements to establish the desired forward and reverse speed ratios between the input shaft 17 and the output shaft 19 of the transmission. Although conceived as an 8-speed automatic transmission, the powertrain 16 may optionally employ other functionally appropriate configurations, including continuously variable transmission (CVT) architectures, automated manual transmissions, and so on.

[0050] Figure 1 The hydraulic torque converter assembly 18 acts as a fluid coupler for operatively connecting the engine 12 and motor 14 to the internal rotary gear assembly 24 of the power transmission 16. A bladed impeller 36, juxtaposed with a bladed turbine 38, is arranged within the internal fluid chamber of the torque converter assembly 18. The impeller 36 is positioned in series with the turbine 38 in series power flow communication, with a stator (not shown) inserted between the impeller 36 and the turbine 38 to selectively alter the fluid flow therebetween. The transmission of torque via the TC assembly 18 from the engine and motor output members 13, 29 to the transmission 16 is energized by the agitation of hydraulic fluid (e.g., transmission fluid) within the internal fluid chamber of the TC caused by the rotation of the blades of the impeller and turbine 36, 38. To protect these components, the torque converter assembly 18 is constructed with a TC pump housing, which is mainly defined by a transmission-side pump housing 40, which is fixedly attached to the engine-side pump cover 42, for example by electron beam welding, MIG or MAG welding, laser welding, etc., so that a working hydraulic fluid chamber is formed therebetween.

[0051] Figure 2 Another example of the illustrated motor 114 employs a magnetic material to exchange electromagnetic force with conductive windings to convert electrical energy into mechanical energy. As discussed below, motor 114 utilizes a multiphase hairpin-wound stator assembly 116 nested therein and surrounding the synchronous reluctance rotor assembly 118 supporting the PM. While similar applications are possible in both automotive and non-automotive applications, Figure 2 The motor 114 is particularly suitable for use as a traction motor in a hybrid electric powertrain (e.g., ICE assembly 12) for use with an engine (e.g., Figure 1The motor 114 operates in at least engine start mode, regenerative charging mode, and torque assist mode. The motor 114 can be designed to achieve: relatively high efficiency, such as at least about 85% efficiency over a calibrated output power and speed range; relatively high power density (e.g., greater than about 1500 watts / liter) and torque density (e.g., greater than about 5 Nm / liter); a relatively wide peak power range (e.g., about 4 to 6 kilowatts or greater); a maximum speed of at least about 18,000 rpm; reduced mass and inertia (e.g., for rapid dynamic response to user output demands); and suitability for a relatively small package size. The motor 114 can employ various alternative embodiments (including alternative rotor assembly architectures and / or alternative stator assembly architectures) to meet similar or alternative operating parameters.

[0052] Continue to refer to Figure 2 The stator assembly 116 is coaxial with and surrounds the rotor assembly 118, while maintaining a small air gap 115 therebetween. According to the illustrated example, this air gap 115 may be no less than about 0.2 mm and no more than about 1.0 mm, for example, in order to maximize power output and minimize the number of permanent magnets 120 supported by the rotor assembly 118 to provide the desired power output. Figure 2 Representative stator and rotor assemblies 116 and 118 (both depicted as truncated straight cylinders with a generally annular shape) are concentrically aligned about the longitudinal central axis A of the motor 114. The stator assembly 116 has a hollow stator core 122 in which the rotor assembly 118 is nested; the rotor assembly 118 has connections to the motor shaft (e.g., via keyways, splines, welds, etc.). Figure 1 The hollow rotor core 124 of the motor output component 29. The protective motor housing can surround the outer periphery of the stator body 126 and can support the motor shaft of the motor 114.

[0053] Figure 2The rotor assembly 118 is fabricated with a rotor body 128 for supporting a plurality of permanent magnets 120 (twenty-four (24) PMs in the illustrated example) spaced circumferentially around the rotor core 124. Specifically, the rotor body 128 is stamped, precision machined, and assembled with a plurality of rotor slots 130 arranged in radially spaced barrier layers (e.g., four different barrier layers). The first barrier layer 130A of the slot 130 can be positioned closest to the inner periphery of the rotor body 128, while the fourth barrier layer 130D of the slot 130 can be positioned furthest from the inner periphery of the rotor body than the other barrier layers. The second barrier layer 130B of the slot 130 can be radially inserted between the first and third barrier layers 130A, 130C, while the third barrier layer 130C of the slot 130 can be radially inserted between the second and fourth barrier layers 130B, 130D. In at least some embodiments, only selected barrier layers (e.g., first and third barrier layers 130A, 130C) may accommodate the magnet 120, while other selected barrier layers (e.g., second and fourth barrier layers 130B, 130D) do not accommodate the magnet 120 and thus act as flux barriers. In other embodiments, only one or all barrier layers may include slots in which permanent magnets are stored. The rotor body 128 may be made of metallic materials, including high-grade steel, and is engineered to maintain high-speed rotational stress within predetermined limits.

[0054] Figure 2 The stator assembly 116 is fabricated with a stator body 126 having a plurality of axially elongated and radially aligned stator slots 132 (e.g., a total of 60 slots) spaced circumferentially around the stator body 126. Each stator slot 132 extends longitudinally through the stator body 126 along the rotation axis A of the motor 114. The stator slots 132 accommodate complementary legs of conductive multiphase stator windings 134. The stator windings 134 (also referred to herein as “hairpin windings”) can be grouped into several different groups, each of which can carry the same number of current phases, such as three, five, six, or seven phases. In addition, the stator windings 134 can extend axially beyond the longitudinal end of the stator body 126. The ratio of the outer diameter of the stator body 126 to the axial length of the stator assembly 116 (i.e., the distance along axis A between the longitudinal ends of the body excluding any extension of the stator winding 134) may be no less than 1.5 and no more than 3.5, for example, to meet predetermined packaging space constraints for the specific application of the motor 114.

[0055] For ease of manufacture, simplified assembly, and increased cost savings, it is desirable that all permanent magnets 120 share the same rectangular polyhedral shape. However, it should be recognized that any one or more or all PM bodies can take on a multitude of shapes and sizes, including other polyhedral block magnets, toroidal (ring-shaped) magnets, breadstick-shaped magnets (with a cross-section of a quadrilateral having adjacent semi-elliptical sections), curved patchwork magnets, and so on. In a non-limiting example, each permanent magnet 120 may have a thickness of approximately 1.5 mm to 2.5 mm to fit within a slot 130 having complementary dimensions. In at least one embodiment, the total mass of the magnet material used by the motor 114 (i.e., the mass of all magnets 120) may be approximately 150 grams to approximately 250 grams. The permanent magnets 120 of the motor 114 may all be made of the same material, such as neodymium iron boron (NdFeB); alternatively, any one or more or all of the magnets 120 may be made of different materials, such as any combination of samarium cobalt (SmCo), alnico (AlNiCo) or rare earth magnet materials.

[0056] Similar to Figure 2 The permanent magnet 120 is expected to allow all multiphase stator windings 134 to share the same construction, including material composition, manufacturing method, and final geometry. Each stator winding 134 can be made from a single rod-shaped conductor, said rod-shaped conductor being formed by a pair of hairpin legs 133 ( Figure 3 The hairpin has a U-shaped geometry defined by the hairpin legs 133, which are parallel to each other and extend from the curved hairpin crown 135. Figure 4 The opposite ends of the hairpins protrude. Hairpin legs 133 are inserted into slots 132 of the stator body 126, with each leg 133 extending through a different stator slot 132, such that the hairpin crown 135 (also referred to as an "end turn") extends over several stator slots 132 (e.g., the crown may extend across three, four, or five slots). Groups 137 of the hairpin stator windings 134 can be inserted relative to adjacent hairpins in a "staggered" or "interleaved" pattern, such as... Figure 3 As best shown. Any given stator slot 132 may include multiple hairpin legs 133 (e.g., in...). Figure 2 (In the illustrated example, there are four). Once all the hairpin windings 134 are inserted into the slots 132 of the stator body 126, the ends of the hairpin legs 133 protruding from the longitudinal end of the stator core 122 are bent; then each winding 134 is electrically connected.

[0057] During operation of motor 114, for example in regenerative charging mode, rotor assembly 118 rotates via motor shaft, while stator assembly 116 remains relatively stationary. In doing so, permanent magnet 120 moves through multiphase stator windings 134; the magnetic field emitted by permanent magnet 120 induces a current in windings 134 via electromagnetic induction. This induced current can be used to power a load (e.g., for...). Figure 1 (The traction battery pack 30 is recharged). Conversely, during operation of the motor 114, such as in engine start mode, EV motor drive mode, or torque assist mode, current is supplied to the stator windings 134 from a suitable power source (e.g., the traction battery pack 30). The supplied current passing through the multiphase stator windings 134 generates a magnetic field at the stator teeth 136. The magnetic field output from the stator teeth 136 interacts with the permanent magnets 120 in the rotor assembly 118, causing the rotor body 128 and the attached motor shaft to rotate to generate rotational driving force.

[0058] Figure 3 yes Figure 2 A perspective view of a representative motor 114, operably connected to a direct oil-cooled thermal management system 140 to selectively cool specific components within the motor assembly. In the direct-cooling system, coolant fluid 142 (such as engineered fully immersed liquid coolant or lubricating dielectric transmission fluid, e.g., pumped from transmission fluid pan 32) Figure 4 The heated "target" surface S of the contact component T1 or S T2 To extract heat directly from the component. For example, as mentioned above... Figure 1 When configured as a motor / generator unit 14, the motor 114 can be cooled via a common cooling circuit shared with the vehicle's transmission 16. An alternative architecture may employ a dedicated cooling circuit not in fluid communication with the transmission 16 to cool the MGU 14. Regardless of whether a common or dedicated system is used, coolant fluid 142 is delivered through one or more coolant fluid inlets 144 to the cooling jacket section of the protective outer motor housing 146 of the motor 114. This coolant fluid 142 is distributed across the exposed sections of the crown of the multiphase stator winding 134 and / or the legs protruding from the axial ends of the stator core 122. After cooling the motor 114, the heat-laden oil is discharged from the motor 114 through one or more coolant fluid outlets 148 in the motor housing 146.

[0059] To achieve maximum cooling efficiency, it is generally desirable to direct the maximum possible volume and mass of coolant fluid to the target surface of the component being cooled. Furthermore, since heat transfer typically increases linearly with wetting area, it is generally desirable to direct coolant fluid to the maximum possible contact area of ​​the target surface of the component being cooled. This document presents oleophilic surface coatings and texturing, engineered to enhance the cooling efficiency of the coolant fluid in direct contact with the target component. These oleophilic surface treatments help increase the surface energy and wetting area of ​​the target surface, which in turn helps retain coolant on the target surface, accompanied by an increase in the mass of coolant on the target surface. As used herein, the term "wetting area" may be defined to include its common and customary meaning as attributed to it by those skilled in the art, including the total surface area of ​​a target surface immersed in, in direct contact with, or otherwise connected to a fluid medium. Similarly, the term "oleophilic" may be defined to include its common and customary meaning as attributed to it by those skilled in the art, including objects that have a chemical affinity for oils and oil-based substances while exhibiting chemical intolerance or aversion to water.

[0060] Figure 4 Illustration Figure 2 and Figure 3 One of the axial ends of the stator assembly 116 shows an exposed hairpin crown 135 of a multiphase stator winding 134 extending from the stator core 122. To facilitate efficient cooling of the stator windings 134, and thus the stator assembly 116 and the machine 114, each winding 134 has a target surface manufactured by means of an oleophilic surface treatment. In at least some embodiments, only the exposed surface of the hairpin winding crown is oleophilicly surface treated. Other sections of the hairpin winding and other components of the motor 114 (such as the exposed ends of the hairpin winding legs) are also oleophilically treated. Figure 2 The application of an oleophilic surface treatment to the axial surfaces of the stator core 122 and the rotor core 124 or the outer circumference of the stator core 122 and the rotor core 124 is also within the scope of this disclosure.

[0061] The disclosed oleophilic surface treatment expands the wetting area of ​​its target surface while increasing the mass of coolant fluid in contact with the target surface. Figure 4The illustrations within illustrate two non-limiting examples of oleophilic surface treatments: an oleophilic surface coating 150A and an oleophilic surface texture 150B. Before or simultaneously with the application of the oleophilic surface coating 150A or texture 150B (collectively referred to below as "oleophilic surface treatment"), each of the hairpin windings 134 may be covered with a dielectric coating 152. The dielectric coating 152 may be a base oil and resin varnish, which helps protect the windings 134 from contamination, insulates the windings 134 to prevent short circuits, and promotes heat dissipation from the group 137 of the windings. The oleophilic surface coating 150A may be formed using an ultraviolet irradiation and ozone (UV / O3) system, applied directly to the electromagnetic windings 134, or indirectly applied to the dielectric coating 152 via application as shown. In this example, only the exposed surfaces of the hairpin legs 133 and the crown 135 include the UV ozone surface coating 150A applied to the dielectric coating 152.

[0062] continue Figure 4 As discussed herein, the oleophilic surface coating 150A may comprise a chemical deposition treatment of an inorganic compound applied to the electromagnetic winding 134, or, for any of the examples described herein, may consist substantially of such a compound. As shown, the inorganic compound is formed wholly or partially of a silane material and / or a dodecyltrimethoxysilane material. Similar to the UV ozone example, only the exposed sections of the hairpin legs and / or crown 133, 135 are provided with the inorganic compound surface coating 150A applied to the dielectric coating 152. The oleophilic surface coating 150A may have a thickness of about 5 micrometers to about 0.1 millimeters.

[0063] Each multiphase stator winding 134 can be treated with an oleophilic surface texture 150B as a supplement to or alternative to the coating-based treatment. The outer surface of the winding 134, or alternatively the outer surface of the coating 152 on the winding 134, can be made with a surface etching that exhibits isotropic wetting behavior and oleophilic properties when contacted by an oil-based dielectric coolant. The surface etching can be formed by any suitable technique, including ultraviolet (UV) etching, plasma etching, flame etching, and / or acid etching. The target surfaces of the hairpin legs / crowns 133, 135 exposed only at the ends of the stator core 122 are treated with the dielectric coating 152 and a surface-based texture 150B applied to the dielectric coating 152. According to the illustrated example, the surface etching can be represented by a series of mutually parallel grooves, each recessed into the exposed section of the hairpin crown 135 and legs 133.

[0064] Aspects of this disclosure have been described in detail with reference to the illustrated embodiments; however, those skilled in the art will recognize that many modifications can be made thereto without departing from the scope of this disclosure. This disclosure is not limited to the precise construction and composition disclosed herein; any and all modifications, alterations, and variations that are apparent from the foregoing description are within the scope of this disclosure as defined by the appended claims. Furthermore, this concept explicitly includes any and all combinations and sub-combinations of the foregoing elements and features.

Claims

1. An electric motor, comprising: External casing; A direct-cooling thermal management system, which is fluidly connected to the outer housing and configured to circulate coolant fluid thereto; A stator assembly, the stator assembly being attached to the outer housing and including a stator core having electromagnetic windings mounted thereon; as well as A rotor assembly movable relative to the stator assembly and including a rotor core having magnets mounted thereon at a distance from the windings. The stator assembly has a target surface that has undergone an oleophilic surface treatment, which is configured to increase the wetting area of ​​the target surface and increase the coolant mass of the coolant fluid in contact with the target surface. The oleophilic surface treatment includes ultraviolet (UV) ozone treatment applied to the electromagnetic winding; The electromagnetic winding includes a hairpin crown with a pair of hairpin legs that protrude from the hairpin crown and extend through a stator slot in the stator core, and wherein only the exposed portions of the hairpin crown and the legs protruding from the stator core include a varnish coating, wherein UV ozone treatment is applied to the varnish coating.

2. The motor according to claim 1, wherein, The electromagnetic windings of the stator assembly alone include a target surface that has undergone an oleophilic surface treatment.

3. The motor according to claim 2, wherein, The electromagnetic winding includes a hairpin crown with a pair of hairpin legs that protrude from the hairpin crown and extend through a stator slot in the stator core, wherein only the exposed portions of the hairpin crown and the legs protruding from the stator core include a target surface treated with an oleophilic surface.

4. The motor according to claim 1, wherein, The oleophilic surface treatment includes a chemical deposition treatment of inorganic compounds applied to the electromagnetic winding.

5. The motor according to claim 4, wherein, The inorganic compounds include silane materials and / or dodecyltrimethoxysilane materials.

6. The motor according to claim 5, wherein, The winding includes a hairpin crown having a pair of hairpin legs that protrude from the hairpin crown and extend through a stator slot in the stator core, and wherein only the exposed portions of the hairpin crown and the legs protruding from the stator core include a varnish coating, wherein an inorganic compound is applied to the varnish coating.

7. The motor according to claim 5, wherein, The inorganic compound has a thickness of 5 micrometers to 0.1 mm.

8. The motor according to claim 1, wherein, The oleophilic surface treatment includes surface etching having an isotropic pattern applied to the winding.

9. The motor according to claim 8, wherein, The surface etching is ultraviolet etching, plasma etching, flame etching, and / or acid etching.

10. The motor according to claim 9, wherein, The electromagnetic winding includes a hairpin crown with a pair of hairpin legs that protrude from the hairpin crown and extend through a stator slot in the stator core, and wherein only the exposed portions of the hairpin crown and the legs protruding from the stator core include a varnish coating, wherein surface etching is applied to the varnish coating.

11. The motor according to claim 9, wherein, The surface etching includes a series of parallel grooves recessed into the exposed sections of the hairpin crown and the hairpin legs.

12. A motor vehicle comprising: Vehicle body; Multiple wheels attached to the body of the vehicle; as well as A traction motor attached to the vehicle body and operable to drive one or more of the wheels to propel the motor vehicle, the traction motor comprising: Motor housing; A direct oil-cooled thermal management system fluidly connected to the motor housing and configured to circulate dielectric oil thereto; A stator assembly rigidly mounted within the motor housing, the stator assembly including an annular stator core defining a hollow center and a plurality of circumferentially spaced stator slots, and a plurality of U-shaped electromagnetic hairpin windings encapsulated within the stator slots; and A rotor assembly rotatably disposed within the hollow center of the annular stator core, the rotor assembly comprising a cylindrical rotor core defining a plurality of circumferentially spaced rotor slots, and a plurality of permanent magnets mounted in the rotor slots at intervals from the hairpin windings. Each of the hairpin windings of the stator assembly has a corresponding target surface that has undergone an oleophilic surface treatment, the oleophilic surface treatment being configured to increase the wetting area of ​​the target surface and increase the coolant mass of the coolant fluid in contact with the target surface; The oleophilic surface treatment includes ultraviolet (UV) ozone treatment applied to the hairpin winding; The hairpin winding includes a hairpin crown with a pair of hairpin legs that protrude from the hairpin crown and extend through a stator slot in the stator core, and wherein only the exposed portions of the hairpin crown and the legs protruding from the stator core include a varnish coating, wherein UV ozone treatment is applied to the varnish coating.

13. A method for assembling an electric motor, the method comprising: Provide an outer housing for the motor; A direct-cooling thermal management system is fluidly connected to the outer housing to circulate coolant fluid to it; The stator assembly is attached to the outer housing, the stator assembly including a stator core and an electromagnetic winding mounted to the stator core; An oleophilic surface treatment is applied to a target surface of the stator assembly, the oleophilic surface treatment being configured to increase the wetting area of ​​the target surface and increase the coolant mass of the coolant fluid in contact with the target surface; as well as A rotor assembly, comprising a rotor core and magnets spaced apart from the windings, is movably mounted adjacent to the stator assembly. The oleophilic surface treatment includes ultraviolet (UV) ozone treatment applied to the electromagnetic winding; The electromagnetic winding includes a hairpin crown with a pair of hairpin legs that protrude from the hairpin crown and extend through a stator slot in the stator core, and wherein only the exposed portions of the hairpin crown and the legs protruding from the stator core include a varnish coating, wherein UV ozone treatment is applied to the varnish coating.

14. The method according to claim 13, wherein, The electromagnetic windings of the stator assembly alone include a target surface that has undergone an oleophilic surface treatment.

15. The method according to claim 13, wherein, The oleophilic surface treatment includes applying an inorganic compound to the exposed sections of the hairpin crown and legs via chemical deposition.

16. The method according to claim 13, wherein, The oleophilic surface treatment includes applying an isotropic patterned surface etching to the exposed sections of the hairpin crown and legs.

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