Electric machine with in-slot stator cooling

Abstract

A rotating electric machine includes a rotor assembly, a stator, a stator winding, and a coolant manifold. The rotor assembly includes a rotor and a rotor shaft. The stator is spaced apart from the rotor by a stator-rotor air gap and has stator teeth defining encapsulated stator slots. The distal ends of adjacent stator teeth are coupled together or formed integrally so that the encapsulated stator slots are not connected to the air gap. The stator winding is constructed of hairpin or bar conductors and extends axially through the stator within the encapsulated stator slots. The coolant manifold is in fluid communication with a coolant supply and is configured to seal against an axial end surface of the stator to encapsulate a portion of the stator winding. The manifold receives coolant from the coolant supply and directs the coolant through the axial end surface into the encapsulated stator slots to cool the stator via forced convection.

Description

Technical Field

[0001] The present disclosure relates to an electric machine with in-slot stator cooling. Background Art

[0002] Electric traction motors and motor generators, which are generally referred to as rotary electric machines in the art, are used to implement work in various electromechanical systems. Such machines include a rotating member, i.e., a rotor, which is spaced a short distance from a stationary member or stator. In a typical stator configuration, a plurality of stator teeth are attached to a cylindrical stator core at one end to protrude radially toward the rotor. Adjacent stator teeth are separated from each other by corresponding stator slots, wherein the distal ends of adjacent stator teeth are spaced from each other by tooth gaps. Each stator slot is filled with a wire or a solid bar segment to form a set of stator windings. In a multi-phase rotary electric machine, an alternating current ("AC") input voltage is applied to the stator windings to energize the stator. The interaction between the corresponding magnetic fields of the rotor and the stator ultimately generates a force in the rotor-stator air gap. This results in the rotation of the rotor, wherein this rotation is thereafter directed to the load.

[0003] Rotating electrical machines can generate significant amounts of heat. This is especially true when the machine is operated at high speeds and high output torque levels. Although the stator windings described above are adequately insulated to ensure electrical isolation of the individual phase windings, heat is still generated during sustained high power operation. The heat generated by copper and iron losses within the stator may eventually degrade the insulation. Therefore, a thermal management system is used in the construction of the stator to regulate the stator temperature. For example, the end windings of the stator (which may be exposed at the distal end of the stator) are typically sprayed with a coolant, or the stator housing may be wrapped in a cooling jacket. Summary of the invention

[0004] The present disclosure relates to enhanced convection-based cooling of a stator within a rotating electrical machine. In particular, each of the above-mentioned stator slots is completely enclosed at its two radial ends to construct an in-slot coolant passage. A coolant suitable for the application (such as but not limited to automatic transmission fluid) circulates to a coolant manifold disposed at the axial ends of the stator. The coolant manifold guides the coolant axially into the in-slot coolant passage, after which the incoming coolant flows axially through the stator. By enclosing the stator slots in this manner, a uniform / 360° flow of coolant is established around the bar conductors forming the stator windings. Thereby, the electromagnetic efficiency of the motor is optimized with minimal degradation in torque performance by removing heat from the stator, directly from its source (i.e., the energized stator windings).

[0005] In an exemplary embodiment, the rotating electric machine includes a rotor assembly, a stator, a stator winding, and the coolant manifold described above. The rotor assembly includes a rotor and a rotor shaft connected together and configured to rotate about an axis of rotation. The stator, which is separated from the rotor by a stator-rotor air gap, has a set of stator teeth that together define stator slots. The distal radial ends of adjacent pairs of the stator teeth are coupled together or formed integrally so that the stator slots are completely enclosed, i.e., not connected to the air gap. As contemplated herein, the stator winding is constructed of bar-shaped or "hairpin-shaped" conductors that extend axially through the stator within the stator slots.

[0006] In this particular embodiment, a coolant manifold is in fluid communication with a coolant supply, is constructed of a non-magnetic material, and is configured to seal against an axial end surface of the stator. As will be appreciated by one of ordinary skill in the art, sealing in this manner encloses a portion of the stator windings (i.e., the exposed turns of the stator windings). The coolant manifold receives coolant from the coolant supply, directs the received coolant through the axial end surface of the stator into the closed stator slots, and thereby cools the stator via forced convection.

[0007] The cross-sectional shape of the stator windings may be a non-rectangular polygon in some embodiments, and may be a rectangular shape in other embodiments.

[0008] The outer peripheral surface of at least one of the stator windings may optionally define a concave channel configured to direct more coolant along the outer peripheral surface.

[0009] The coolant manifold may include opposing axial walls connected by a radial wall, such that a manifold channel is defined by the coolant manifold and the axial end surfaces of the stator. The axial walls abut and seal against the end surfaces of the stator, thereby encapsulating the stator windings within the manifold channel. One of the axial walls may include an inclined surface, wherein the stator windings are skewed in a radially outward direction via the inclined surface.

[0010] A biasing member may be used to apply a continuous compressive force to the coolant manifold. For example, the biasing member may be a fastener, a beam, or other structure configured to react against a stationary member to apply the continuous compressive force.

[0011] The spacing between adjacent stator windings within each of the encapsulated stator slots can be unevenly distributed so that more coolant is directed to the stator windings positioned close to the outer diameter surface of the stator relative to the distribution to the stator windings positioned close to the inner diameter surface of the stator.

[0012] In certain applications, the rotor shaft may be connected to a driven load, for example on board a motor vehicle having a coolant pump. In this embodiment, a coolant is circulated via the coolant pump.

[0013] An electric propulsion system is also disclosed herein. An embodiment of the electric propulsion system includes a coolant supply, a high-voltage battery pack, a direct current to direct current ("DC-DC") converter connected to the high-voltage battery pack, a traction power inverter module ("TPIM") connected to the DC-DC converter and configured to output an alternating current ("AC") voltage, and the above-mentioned rotating electric machine. In this embodiment, the electric machine is a multi-phase rotating electric machine connected to the TPIM and charged via the AC voltage.

[0014] A method for cooling a stator of a rotating electric machine is also disclosed. The method may include providing a stator as described above, the stator being spaced apart from the rotor by a stator-rotor air gap and having stator teeth that together define stator slots. Distal radial ends of adjacent pairs of the stator teeth are coupled together or integrally formed such that the stator slots are not connected to the air gap. The stator winding is constructed of hairpin or bar conductors and extends axially through the stator within the stator slots.

[0015] The method includes sealing an annular coolant manifold against an axial end surface of the stator, thereby enclosing a portion of the stator winding therein. The method also includes circulating coolant from a coolant supply through the axial end surface of the stator via the annular coolant manifold to the enclosed stator slots, thereby cooling the stator via forced convection.

[0016] The above summary of the invention is not intended to represent every possible embodiment or every aspect of the present disclosure. On the contrary, the foregoing summary of the invention is intended to illustrate some novel aspects and features disclosed herein. In conjunction with the accompanying drawings and the appended claims, the above features and advantages of the present disclosure and other features and advantages will be readily apparent from the following detailed description of representative embodiments and modes for carrying out the present disclosure.

[0017] The invention also discloses the following technical solution.

[0018] Technical Solution 1. A rotating electrical machine for use with a coolant supply unit, comprising:

[0019] a rotor assembly having a rotor and a rotor shaft connected together and configured to rotate about a rotation axis;

[0020] a stator spaced apart from the rotor by a stator-rotor air gap and having stator teeth that collectively define enclosed stator slots, wherein distal ends of adjacent pairs of the stator teeth are coupled together or integrally formed such that the enclosed stator slots are not connected to the air gap;

[0021] stator windings constructed from hairpin or bar conductors and extending axially through the stator within the stator slots; and

[0022] a coolant manifold in fluid communication with the coolant supply, constructed of a non-magnetic material, and configured to seal against an axial end surface of the stator to enclose a portion of the stator winding therein, wherein the coolant manifold is configured to receive coolant from the coolant supply, direct the received coolant through the axial end surface of the stator into the enclosed stator slots, and thereby cool the stator via forced convection.

[0023] Technical Solution 2. The rotating electric machine according to Technical Solution 1 further includes an additional coolant manifold, which is fluidically connected to the coolant supply portion, is constructed of the non-magnetic material, and is configured to be sealed against another axial end surface, wherein the additional coolant manifold is configured to receive coolant from the enclosed stator slots.

[0024] Technical Solution 3. The rotating electric machine according to Technical Solution 1, wherein an outer peripheral surface of at least one of the stator windings defines a concave channel configured to guide the coolant along the outer peripheral surface.

[0025] Technical Solution 4. An electric motor according to Technical Solution 1, wherein the coolant manifold includes relative axial walls connected by radial walls, so that a manifold channel is defined by the coolant manifold and the axial end surfaces of the stator, and wherein the axial walls are adjacent to the end surface of the stator and sealed against the end surface of the stator, thereby encapsulating the stator winding in the manifold channel.

[0026] Technical Solution 5. The motor according to Technical Solution 4, wherein one of the axial walls includes an inclined surface, and the stator winding is skewed in a radially outward direction via the inclined surface.

[0027] Technical Solution 6. The electric machine according to Technical Solution 5 further comprises a biasing member configured to apply a continuous compressive force to the coolant manifold.

[0028] Technical Solution 7. The motor according to Technical Solution 6, wherein the biasing member is a bolt or a beam configured to react against the stationary member to apply the continuous compressive force.

[0029] Technical Solution 8. An electric motor according to Technical Solution 1, wherein the available spacing between the stator windings within each of the encapsulated stator slots is unevenly distributed, so that more coolant is directed to the stator windings positioned close to the outer diameter surface of the stator than to the stator windings positioned close to the inner diameter surface of the stator.

[0030] Technical Solution 9. The rotating electrical machine according to Technical Solution 1, wherein the rotor shaft is connected to a driven load carried on a motor vehicle having a coolant pump, and the coolant circulates via the coolant pump.

[0031] Technical Solution 10. An electric propulsion system, comprising:

[0032] High voltage battery pack;

[0033] a direct current to direct current ("DC-DC") converter connected to the high voltage battery pack;

[0034] a traction power inverter module (“TPIM”) connected to the high voltage battery pack and configured to output an alternating current (“AC”) voltage;

[0035] a multi-phase rotating electric machine connected to the TPIM and energized via the AC voltage, the rotating electric machine comprising:

[0036] a rotor assembly having a rotor and a rotor shaft connected together and configured to rotate about a rotation axis;

[0037] a stator spaced apart from the rotor by a stator-rotor air gap and having stator teeth that collectively define enclosed stator slots, wherein distal ends of adjacent pairs of the stator teeth are coupled together or integrally formed such that the enclosed stator slots are not connected to the air gap;

[0038] stator windings constructed of hairpin or bar conductors and extending axially through the stator within the enclosed stator slots;

[0039] an annular coolant manifold in fluid communication with a coolant supply, constructed of a non-magnetic material, and configured to seal against an axial end surface of the stator to enclose a portion of the stator windings therein, wherein the coolant manifold is configured to receive coolant from the coolant supply, direct the received coolant through the axial end surface of the stator into the enclosed stator slots, and thereby cool the stator via forced convection;

[0040] an additional coolant manifold in fluid communication with the coolant supply, constructed of the non-magnetic material, and configured to seal against the other axial end surface, wherein the additional coolant manifold is configured to receive coolant from the enclosed stator slots; and

[0041] A driven load is connected to the rotor shaft and is powered via torque from the electric machine.

[0042] Technical Solution 11. The electric propulsion system according to Technical Solution 10, wherein the driven load is a set of road wheels of a motor vehicle having a coolant pump, and the coolant circulates via the coolant pump.

[0043] Technical Solution 12. The electric propulsion system according to Technical Solution 10, wherein an outer peripheral surface of at least one of the stator windings defines a concave channel configured to guide the coolant along the outer peripheral surface.

[0044] Technical Solution 13. An electric propulsion system according to Technical Solution 10, wherein the annular coolant manifold includes relative axial walls connected by radial walls, so that a manifold channel is defined by the axial end surfaces of the coolant manifold and the stator, and wherein the axial walls are adjacent to the end surface of the stator and sealed against the end surface of the stator, thereby encapsulating the stator winding in the manifold channel.

[0045] Technical Solution 14. An electric propulsion system according to Technical Solution 13, wherein one of the axial walls includes an inclined surface, and the stator winding is skewed in a radially outward direction via the inclined surface, and the electric propulsion system further includes a biasing member configured to apply a continuous compressive force to the coolant manifold.

[0046] Technical Solution 15. An electric propulsion system according to Technical Solution 10, wherein the available spacing between the stator windings within each of the encapsulated stator slots is unevenly distributed, so that more coolant is directed to the stator windings positioned close to the outer diameter surface of the stator than to the stator windings positioned close to the inner diameter surface of the stator.

[0047] Technical Solution 16. A method for cooling a stator of a rotating electrical machine, the method comprising:

[0048] providing a stator spaced from the rotor by a stator-rotor air gap and having stator teeth that together define enclosed stator slots, wherein distal ends of adjacent pairs of the stator teeth are coupled together or integrally formed such that the enclosed stator slots are not connected to the air gap, and wherein the stator windings are constructed of hairpin or bar conductors and extend axially through the stator within the enclosed stator slots;

[0049] sealing an annular coolant manifold against an axial end surface of the stator to enclose a portion of the stator windings therein;

[0050] Coolant is circulated from a coolant supply through the axial end surface of the stator via the annular coolant manifold into the enclosed stator slots, thereby cooling the stator via forced convection.

[0051] Technical Solution 17. The method according to Technical Solution 16, wherein circulating the coolant from the coolant supply into the enclosed stator slots includes circulating the coolant along a concave channel defined by an outer peripheral surface of at least one of the stator windings.

[0052] Technical Solution 18. The method according to Technical Solution 16, wherein sealing the annular coolant manifold against the axial end surface of the stator includes enclosing a portion of the stator winding within a manifold channel defined by opposing axial walls connected by radial walls of the coolant manifold.

[0053] Technical Solution 19. A method according to Technical Solution 18, wherein one of the axial walls includes an inclined surface, and sealing the annular coolant manifold includes tilting the stator winding in a radially outward direction via the inclined surface, and using a biasing member to apply a continuous compressive force to the coolant manifold. BRIEF DESCRIPTION OF THE DRAWINGS

[0054] Figure 1 is a schematic illustration of an exemplary mobile platform having a rotating electric machine whose stator is cooled via forced convection within a slot as described herein.

[0055] Figure 2 yes Figure 1 A schematic cross-sectional illustration of a portion of an electric machine shown in , depicting enclosed stator slots acting as in-slot coolant passages.

[0056] Figure 3A and Figure 3B It can be used for Figure 2 Schematic cross-sectional illustration of a bar conductor in a stator shown in .

[0057] Figure 4 Includes a coolant manifold for in-slot stator cooling Figure 1 A cross-sectional illustration of the electric machine shown in FIG.

[0058] The present disclosure is susceptible to modification and alternative forms, wherein representative embodiments are shown in the drawings by way of example and described in detail below. The inventive aspects of the present disclosure are not limited to the disclosed embodiments. On the contrary, the present disclosure is intended to cover modifications, equivalents, combinations and alternatives that fall within the scope of the present disclosure as defined by the appended claims. DETAILED DESCRIPTION

[0059] Referring to the drawings, in which like reference numerals refer to the same or similar components in the several views, an electric propulsion system 10 is schematically depicted in Figure 1 The electric propulsion system 10 includes a rotating electric machine 12 having a rotor assembly ("R") 14 and a stator ("S") 16. The stator 16 generates heat during a sustained high power / high torque operating mode of the electric machine 12. Therefore, the present teachings are directed to achieving efficient real-time forced convection-based cooling of the stator 16 using a coolant manifold 60A as set forth herein.

[0060] A coolant 21 suitable for the application (e.g., automatic transmission fluid (“ATF”) or a diluted glycol mixture) may be stored in a sump 22 and circulated using a coolant pump (“P”) 20, thereby creating a flow of coolant 21 indicated by arrows F. The coolant 21 is directed into a coolant manifold 60A, which in turn is sealed against the stator 16. The coolant manifold 60A directs the coolant 21 into the stator 16 where it flows axially through the stator 16 via an encapsulated slot structure, as described below with reference to FIG. Figure 2-Figure 4 Detailed description, so that in some embodiments, the coolant is finally passed through the additional coolant manifold 60B (see Figure 4 )leave.

[0061] exist Figure 1 In the exemplary electric propulsion system 10 depicted in FIG. 1 , the rotor assembly 14 is positioned adjacent to the stator 16 and is spaced apart by an air gap G (see FIG. Figure 2) separate therefrom. In some configurations of the electric machine 12, the rotor assembly 14 may be concentrically disposed within the stator 16, i.e., the stator 16 may circumscribe and surround the rotor assembly 14. Thus, the electric machine 12 would implement a radial flux type machine, and the air gap G described above would be a radial stator-rotor air gap. Other configurations of the electric machine 12 may be implemented in which the relative positions of the rotor assembly 14 and the stator 16 are reversed, in which the rotor assembly 14 circumscribes and surrounds the stator 16, and in which the air gap G remains radial. For consistency of description, the rotor assembly 14 will be described below as residing radially within the stator 16. Figure 1 , without limiting the configuration to this configuration.

[0062] The electric propulsion system 10 includes an alternating current (“AC”) voltage bus 13. The AC voltage bus 13 may be powered by a high voltage battery pack (“B HV ”) 24 (e.g., multi-cell lithium-ion, lithium-sulfur, nickel metal hydride, or other high energy voltage supply) is selectively charged via a traction power inverter module (“TPIM”) 28. The AC voltage bus 13 directs AC voltage (“VAC”) to or from the phase windings of the motor 12 to produce an output torque (arrow T M Then, when operating in drive or motor mode, the output torque from the charging motor 12 (arrow T M ) is applied to the connected rotor shaft 50 and directed to the coupled load ("L") 52, for example by (but not necessarily limited to) a road wheel, propeller shaft or drive belt of a motor vehicle.

[0063] Schematically shown in Figure 1 The electric propulsion system 10 in the embodiment may also include a DC voltage bus 15 to which a direct current to direct current (“DC-DC”) converter 26 is connected. As will be appreciated by one of ordinary skill in the art, the DC-DC converter 26 is configured to step down or step up a relatively high DC voltage (“VDC”) as needed via internal switching and filtering operations. The DC-DC converter 26 is connected between the battery pack 24 and the TPIM 28 via the positive (+) and negative (-) rails on the high voltage side of the DC voltage bus 15. In some configurations, the low voltage / auxiliary battery pack (“B AUX ”) 124 can be connected to the positive (+) and negative (-) rails of the low voltage side of the DC voltage bus 15, wherein the auxiliary battery pack 124 may be implemented as a lead-acid battery or a battery constructed of another chemistry suitable for the application and is configured to store a 12-15V auxiliary voltage (“VAUX”) or supply a 12-15V auxiliary voltage (“VAUX”) to one or more connected auxiliary devices (not shown).

[0064] refer to Figure 2, the electric machine 12 includes the above-described rotor assembly 14. Some embodiments of the rotor assembly 14 include a cylindrical rotor 40 having a set of embedded rotor magnets 55. The rotor magnets 55 can be implemented, for example, as permanent magnets constructed of ferrite, neodymium iron boron ("NdFeB"), samarium cobalt ("SmCo"), or another magnet material suitable for the application. The rotor magnets 55 can be mounted to and / or embedded within a separate steel laminate layer of the rotor 40. The configuration of the rotor 40 can vary depending on the application, and therefore, Figure 2 An example of just one possible embodiment of the rotor 40 is depicted in FIG.

[0065] In the exemplary embodiment depicted, the stator 16 is cylindrical in shape so as to circumscribe the like cylindrical rotor 40 of the rotor assembly 14 and is separated from the rotor 40 by the aforementioned air gap G. In this configuration, the stator 16 and rotor 40 may be constructed from respective stacks of thin laminated layers (e.g., 2-5 mm thick) of electrical steel or another ferrous material, as will be appreciated by one of ordinary skill in the art.

[0066] The stator 16 also has radially protruding stator teeth 32. Each stator tooth 32 extends radially inward from a cylindrical stator housing 30, wherein the stator housing has an outer diameter surface 160. Thus, the stator teeth 32 extend inward from the stator housing 30 toward the outer diameter surface 140 of the rotor 40. Adjacent stator teeth 32 are separated from each other by corresponding stator slots 33, i.e., each stator slot 33 is defined by and laterally connected to adjacent pairs of stator teeth 32. The stator winding 35 is then positioned within the stator slots 33.

[0067] In the depicted embodiment, the stator windings 35 are constructed as bar-shaped segments constructed of copper or another conductive material. Thus, the bar-shaped conductors (often referred to as "hairpin" conductors) are thicker and more rigid than the cylindrical copper wires that are typically wrapped or wound around the stator teeth 32. As described above, when the stator windings 35 are powered by an AC output voltage (e.g., from Figure 1 When the TPIM 28 depicted in FIG. 1 is sequentially energized, a rotating stator magnetic field is generated. The stator magnetic poles formed by the generated rotating stator field will interact with the rotor poles provided by the various rotor magnets 55 of the rotor 40. The force generated in the stator-rotor air gap G ultimately causes Figure 1 The rotor shaft 50 and the coupled load 52 rotate.

[0068] As will be appreciated by one of ordinary skill in the art, the stator teeth of a typical stator will extend radially inwardly toward the rotor so that each stator tooth is cantilevered by a distal end. Adjacent stator teeth are separated from each other by a short distance by openings or tooth gaps, wherein the tooth gaps are connected to the stator-rotor air gap G. In other words, the stator slots of a typical rotating electric machine open into the stator-rotor air gap G. In contrast, Figure 2As shown in FIG. 1 , each of the stator teeth 32 of the present disclosure has an end 360 connected to the stator housing 30 and a distal end 33E located adjacent to the outer diameter surface 140 of the rotor 40. The distal ends 33E together define the inner diameter surface 260 of the stator 16, wherein two directly adjacent distal ends 33E are located adjacent to each other. Figure 2 36. Thus, the stator slots 33 of adjacent stator teeth 32 are completely enclosed in the region 36, so that none of the stator slots 33 is connected to the stator-rotor air gap G or opens into the stator-rotor air gap G.

[0069] To construct the stator 16 having this configuration, the stator teeth 32 are coupled together or integrally formed during the manufacture of the stator 16. For example, the above-mentioned thin laminate layers may be formed with Figure 2 The stator slots 33 of the desired shape are punched separately by a tool (not shown). When such laminated layers are stacked and coupled together, the stator slots 33 will be produced. Then, the produced slots 33 between adjacent stator teeth 32 (hereinafter referred to as in-slot coolant passages 33C) are used as the cooling medium for the stator teeth 32. Figure 1 The coolant 21 circulates axially through the fluid ducts of the stator 16. Thus, cooling of the stator 16 by forced convection is achieved.

[0070] Brief reference Figure 3A and Figure 3B , alternatively, Figure 2 The stator winding 35 may be implemented as a stator winding 135 ( Figure 3A ) or 235 ( Figure 3B ).exist Figure 2 In the slots 33, closest to the inner diameter surface 260 of the stator 16, copper losses may be higher. Therefore, it would be advantageous to configure the stator windings 35, 135, or 235 to direct more coolant 21 to the area located closer to the inner diameter surface 260. For example, instead of using Figure 2 Rather than stator windings 35 of rectangular cross-section, one or more outer peripheral surfaces 135P of stator windings 135 may be modified to direct more coolant 21 relative to other outer peripheral surfaces 135P or relative to a square or rectangular cross-sectional shape.

[0071] For example, you can remove Figure 3A one or more corners 37 of the stator winding 135 to direct more coolant 21 to a particular area, and / or Figure 3B The outer peripheral surface 235P of the stator winding 235 may be punched or otherwise formed to form semicircular grooves 39. Some of these grooves 39 are closest to the Figure 2 The inner diameter surface 260 of the stator 16 may be larger, for example Figure 3BThe size, shape and / or placement of such grooves 39 or 39A may vary with the application to provide a Figure 2 The desired flow rate and distribution of the coolant 21 is provided in the slot coolant passage 33C. Likewise, it is contemplated that the stator winding 35 has other non-rectangular profiles or features not described herein, such as a star, triangle, or another polygonal shape, and thus, Figure 3A and Figure 3B The exemplary shapes of illustrate the present teachings but do not limit the present teachings.

[0072] refer to Figure 4 , depicted relative to the rotational axis AA of the rotor assembly 14 Figure 1 A representative cross section of the motor 12. As will be appreciated, for simplicity of illustration, the motor 12 is shortened in the axial direction via the jagged cut-away lines, and therefore, Figure 4 Intended to be schematic and not necessarily drawn to scale. That is, when the stator windings 35 are energized, the rotor assembly 14 including the ("R") rotor 40 and the rotor shaft 50 will rotate within the stator ("S") 16. The rotor shaft 50 may be splined or journaled to the rotor 40 or integrally formed with the rotor 40 for common rotation of the rotor 40 and the rotor shaft 55. In the illustrated embodiment, the rotor magnets 55 are embedded within the rotor 40. The stator 16 resides radially outside the rotor 40, wherein the rotor 40 is rotatably supported at each end by a bearing assembly (not shown), as will be appreciated by one of ordinary skill in the art.

[0073] To convectively cool the stator 16 in accordance with the present disclosure, Figure 1 The coolant manifold 60A, schematically shown in outline in FIG. 1 , has an annular / ring-like shape in plan view and is mounted to the distal end surface 70 of the stator 16. The coolant manifold 60A, which circumscribes the axis of rotation AA in the "installed" position shown, can be constructed of aluminum, plastic, or another non-magnetic material. In a possible configuration, the coolant manifold 60A includes opposing axial walls 74 connected by radial walls 75, so that a manifold channel 76 is defined by the coolant manifold 60A and the end surface 70 of the stator 16.

[0074] For example, the end surface 74E of the axial wall 74 abuts and seals against the end surface 70 of the stator 16, thereby enclosing the stator winding 35 within the manifold channel 76 as shown. To ensure proper sealing, the biasing member 65 (e.g., a bolt or beam) can react against the stationary member 80 to apply a continuous compressive force (arrow FC) to the coolant manifold 60A. In addition, the end surface 74E defines a hole or slot 79 that allows the stator winding 35 to pass through into the stator slot 33 (see Figure 2 ).Then, Figure 1The incoming coolant 21 is directed downwardly into the coolant manifold 60A (as indicated by arrow F), for example, through the fluid inlet 78 defined by the uppermost axial wall 74. The incoming coolant 21 then flows through the Figure 2 The in-slot coolant passage 33C shown in FIG. 1 flows axially through the stator 16 .

[0075] Another coolant manifold 60B is also shown. Figure 4 The coolant manifold 60B is configured to allow coolant flow (arrow F) to exit the stator 16 at one or more desired locations, such as via a fluid outlet 79. As will be appreciated, this end may also include a coolant extending through the fluid outlet 79 and ultimately connected to the stator 16. Figure 1 28 of the TPIM 28. If a perfectly annular embodiment of the coolant manifold 60B were employed, the exposed phase windings and possibly other structure (e.g., gear sets and bearings) might make it relatively difficult to completely seal the coolant manifold 60B to the stator 16. Therefore, for clarity and simplicity, the depicted annular configuration of the coolant manifold 60B may be modified as necessary to accommodate such intervening or surrounding structure, and thus, a perfectly annular configuration (i.e., where the coolant manifold 60B has a circular perimeter in plan view) might only be possible at one end of the electric machine 12.

[0076] As described above, the coolant 21 in the form of ATF is typically sprayed and / or spilled directly onto the exposed phase leads of the stator 16. Thereafter, the coolant 21 settles via gravity and is recirculated to the Figure 1 Therefore, assuming Figure 1 16 is configured to maintain a desired flow rate of coolant 21 through the stator 16, it is not necessary for the coolant manifold 60A to be completely sealed around its perimeter. Some spillage or overflow may occur and may actually be beneficial. The stator windings 35 may be skewed radially outward, such as via an inclined surface 174 of one of the axial walls 74, as shown, so that the coolant manifold 60A is provided with a thicker or stiffer construction. By substantially enclosing the stator slots 33 of the stator 16 in the manner described above, uniform / 360° flow is achieved around each of the stator windings 35, so that the coolant 21 removes heat directly from its source.

[0077] Figure 4 Proper spacing of the stator windings 35 within the manifold passages 76 will help ensure that the coolant 21 is Figure 2That is, if the surrounding space between adjacent stator windings 35 in the slot 33 is too large, suboptimal cooling may result as the coolant 21 rapidly settles toward the radially inward region of the slot coolant passage 33C as it approaches the rotor 40. However, if the space between adjacent stator windings 35 is too small, the flow of coolant 21 in the slot coolant passage 33C will tend to be uniform. At the same time, additional fluid pressure may be required to circulate the coolant 21 through the slot coolant passage 33C.

[0078] Reference again Figure 2 For example, the slot 33 may have an elongated rectangular shape in a cross-sectional view, i.e., extending radially between the inner diameter surface 260 of the stator 16 toward the outer diameter surface 160. As described above, adjacent stator teeth 32 are completely enclosed at the region 36, so that the stator slot 33 is not connected to or leads to the stator-rotor air gap G. In this embodiment, the spacing may be about 50 mm with a slot 33 area. 2 The cross-sectional area of ​​the stator winding 35 in the slot 33 (as shown, using six copper bars) is about 35 mm 2 As will be appreciated, the stator slots 33 will also include insulating material around their perimeter, consuming another 8 mm 2 . Therefore, in this non-limiting exemplary embodiment, 50 mm 2 The total slot area is reduced to about 7mm 2 Therefore, 7mm 2 The available space may be distributed within the slots 33 such that the outer diameter surface 160 proximate the stator 16 provides more space adjacent to the stator windings 35 .

[0079] As will be appreciated, the above disclosure itself provides a method for cooling the stator 16. For example, the method may include providing Figure 2 The stator 16 is a stator 16 that is spaced apart from the rotor 40 by a stator-rotor air gap G and has stator teeth 32 that jointly define stator slots 33. Distal ends 33E of adjacent pairs of stator teeth 32 are coupled together or formed integrally so that the stator slots 33 are not connected to the air gap G. The stator winding 35 is constructed of a hairpin-shaped or bar-shaped conductor and extends axially through the stator 16 within the stator slots 33.

[0080] The method may include sealing the coolant manifold 60A (eg, Figure 4 ), thereby enclosing a portion of the stator winding 35 therein. The additional coolant manifold 60B may be sealed against the opposite distal end of the stator 16, for example using another biasing member 65, as explained above. Figure 1The coolant 21 of the reservoir 22 or another coolant supply is guided to the coolant manifold 60A through the axial end surface 70. Figure 2 The stator 16 is cooled by forced convection. In some embodiments, circulating the coolant 21 into the encapsulated stator slots 33C may include circulating the coolant 21 along the Figure 3B The concave channel 39 or 39A circulates.

[0081] Sealing the coolant manifold 60A against the axial end surface 70 of the stator 16 may include enclosing a portion of the stator windings 35 within a manifold passage 76 such as Figure 4 174, and the coolant manifold 60A may be sealed with the axial wall 74. Figure 4 The biasing member 65 skews the stator windings 35 in a radially outward direction to apply a continuous compressive force (arrow FC) to the coolant manifold 60A.

[0082] Therefore, as explained above, encapsulating the stator slots 33 to form the slot cooling passages 33C provides a variety of benefits in addition to efficient cooling of the stator 16. Some benefits are primarily mechanical or structural in nature. For example, the stator teeth of a typical motor form a cantilever. Since the cantilever is supported at only one end by definition, the free end of this stator tooth is prone to vibration and noise. Encapsulating the stator slots 33 according to the present disclosure eliminates such cantilevers and thereby increases structural rigidity to the stator 16. Slot noise caused by torque fluctuations and the resulting undesirable NVH effects are reduced. Similarly, the disclosed construction of the stator 16 reduces torque fluctuations due to minimization of the slotting effect within the stator-rotor air gap G (including the possible reduction of windage or drag losses in the stator-rotor air gap G). In view of the foregoing disclosure, those of ordinary skill in the art will readily understand these and other possible benefits.

[0083] Although some best modes and other embodiments have been described in detail, there are various alternative designs and embodiments to practice the present teachings defined in the appended claims. Those skilled in the art will recognize that modifications may be made to the disclosed embodiments without departing from the scope of the present disclosure. In addition, the present concept explicitly includes combinations and sub-combinations of the elements and features described. The specific embodiments and the accompanying drawings are support and descriptions of the present teachings, wherein the scope of the present teachings is limited only by the claims.

Claims

1. A rotating electrical machine for use with a coolant supply, comprising: a rotor assembly having a rotor and a rotor shaft connected together and configured to rotate about a rotation axis; a stator spaced apart from the rotor by a stator-rotor air gap and having stator teeth that collectively define enclosed stator slots, wherein distal ends of adjacent pairs of the stator teeth are coupled together or integrally formed such that the enclosed stator slots are not connected to the air gap; stator windings constructed from hairpin or bar conductors and extending axially through the stator within the stator slots; and a coolant manifold in fluid communication with the coolant supply, constructed of a non-magnetic material, and configured to seal against an axial end surface of the stator to enclose a portion of the stator winding therein, wherein the coolant manifold is configured to receive coolant from the coolant supply, direct the received coolant through the axial end surface of the stator into the enclosed stator slots, and thereby cool the stator via forced convection, wherein the available spacing between the stator windings within each of the enclosed stator slots is unevenly distributed such that more coolant is directed to the stator windings located closer to the outer diameter surface of the stator than to the stator windings located closer to the inner diameter surface of the stator, The outer peripheral surface of the stator winding forms semicircular grooves, and the size, shape and / or placement of the grooves vary with the application to provide a desired flow rate and distribution of the coolant in the coolant passage in the slot.

2. The rotating electric machine of claim 1 further comprising an additional coolant manifold in fluid communication with the coolant supply, constructed of the non-magnetic material, and configured to seal against another axial end surface, wherein: The additional coolant manifold is configured to receive coolant from the enclosed stator slots.

3. The rotating electrical machine according to claim 1, wherein: An outer peripheral surface of at least one of the stator windings defines a concave channel configured to direct the coolant along the outer peripheral surface.

4. The rotating electrical machine according to claim 1, wherein: The coolant manifold includes opposing axial walls connected by radial walls such that a manifold channel is defined by the coolant manifold and the axial end surfaces of the stator, and wherein the axial walls abut and seal against the axial end surfaces of the stator to encapsulate the stator windings within the manifold channel.

5. The rotating electrical machine according to claim 4, wherein: One of the axial walls includes an inclined surface, and the stator winding is skewed in a radially outward direction via the inclined surface. 6 . The rotating electric machine of claim 5 , further comprising a biasing member configured to apply a continuous compressive force to the coolant manifold.

7. The rotating electrical machine according to claim 6, wherein: The biasing member is a bolt or beam configured to react against the stationary member to apply the continuous compressive force.

8. The rotating electrical machine according to claim 1, wherein: The rotor shaft is connected to a driven load carried on a motor vehicle having a coolant pump, and the coolant circulates via the coolant pump.

9. An electric propulsion system comprising: High voltage battery pack; a DC to DC converter connected to the high voltage battery pack; a traction power inverter module connected to the high voltage battery pack and configured to output an AC voltage; A multi-phase rotating electric machine connected to the traction power inverter module and charged via the AC voltage, the rotating electric machine comprising: a rotor assembly having a rotor and a rotor shaft connected together and configured to rotate about a rotation axis; a stator spaced apart from the rotor by a stator-rotor air gap and having stator teeth that collectively define enclosed stator slots, wherein distal ends of adjacent pairs of the stator teeth are coupled together or integrally formed such that the enclosed stator slots are not connected to the air gap; stator windings constructed of hairpin or bar conductors and extending axially through the stator within the enclosed stator slots; an annular coolant manifold in fluid communication with a coolant supply, constructed of a non-magnetic material, and configured to seal against an axial end surface of the stator to enclose a portion of the stator windings therein, wherein the coolant manifold is configured to receive coolant from the coolant supply, direct the received coolant through the axial end surface of the stator into the enclosed stator slots, and thereby cool the stator via forced convection; an additional coolant manifold in fluid communication with the coolant supply, constructed of the non-magnetic material, and configured to seal against the other axial end surface, wherein the additional coolant manifold is configured to receive coolant from the enclosed stator slots; and a driven load connected to the rotor shaft and powered via torque from the electric machine, wherein the available spacing between the stator windings within each of the enclosed stator slots is unevenly distributed such that more coolant is directed to the stator windings located closer to the outer diameter surface of the stator than to the stator windings located closer to the inner diameter surface of the stator, The outer peripheral surface of the stator winding forms semicircular grooves, and the size, shape and / or placement of the grooves vary with the application to provide a desired flow rate and distribution of the coolant in the coolant passage in the slot.

10. The electric propulsion system according to claim 9, wherein: The driven load is a set of road wheels of a motor vehicle having a coolant pump, and the coolant is circulated via the coolant pump.

11. The electric propulsion system according to claim 9, wherein: An outer peripheral surface of at least one of the stator windings defines a concave channel configured to direct the coolant along the outer peripheral surface.

12. The electric propulsion system according to claim 9, wherein: The annular coolant manifold includes opposing axial walls connected by radial walls such that a manifold channel is defined by the coolant manifold and the axial end surfaces of the stator, and wherein the axial walls abut and seal against the axial end surfaces of the stator to encapsulate the stator windings within the manifold channel.

13. The electric propulsion system according to claim 12, wherein: One of the axial walls includes an inclined surface, and the stator winding is skewed in a radially outward direction via the inclined surface, and the electric propulsion system further includes a biasing member configured to apply a continuous compressive force to the coolant manifold.

14. A method for cooling a stator of a rotating electrical machine, the method comprising: providing a stator spaced from the rotor by a stator-rotor air gap and having stator teeth that together define enclosed stator slots, wherein distal ends of adjacent pairs of the stator teeth are coupled together or integrally formed such that the enclosed stator slots are not connected to the air gap, and wherein stator windings are constructed of hairpin or bar conductors and extend axially through the stator within the enclosed stator slots; sealing an annular coolant manifold against an axial end surface of the stator to enclose a portion of the stator windings therein; circulating coolant from a coolant supply through the axial end surface of the stator via the annular coolant manifold into the enclosed stator slots to cool the stator via forced convection, wherein the available spacing between the stator windings within each of the enclosed stator slots is unevenly distributed such that more coolant is directed to the stator windings located closer to the outer diameter surface of the stator than to the stator windings located closer to the inner diameter surface of the stator, The outer peripheral surface of the stator winding forms semicircular grooves, and the size, shape and / or placement of the grooves vary with the application to provide a desired flow rate and distribution of the coolant in the coolant passage in the slot.

15. The method according to claim 14, wherein: Circulating coolant from the coolant supply into the enclosed stator slots includes circulating the coolant along a concave channel defined by an outer peripheral surface of at least one of the stator windings.

16. The method according to claim 14, wherein: Sealing the annular coolant manifold against the axial end surface of the stator includes enclosing a portion of the stator windings within a manifold passage defined by opposing axial walls coupled by radial walls of the coolant manifold.

17. The method according to claim 16, wherein: One of the axial walls includes an inclined surface, and sealing the annular coolant manifold includes skewing the stator windings in a radially outward direction via the inclined surface and applying a continuous compressive force to the coolant manifold using a biasing member.

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