System and method for liquid-cooled stator

Abstract

The invention relates to a system and method for a liquid-cooled stator. The stator includes a stator core positioned within the housing, the stator core including a plurality of teeth and a back iron defining an outer diameter portion (OD) of the stator. A winding arrangement is positioned on the stator core and includes end turns positioned on axial ends of the stator. At least one shroud is positioned on the axial end of the stator and covers the plurality of end turns. A stator cooling path is configured to direct a continuous flow of liquid from the at least one liquid inlet to the at least one liquid outlet, the stator cooling path including one section configured to direct liquid through the at least one shroud and through the plurality of first end turns and an additional section configured to direct liquid over the OD of the stator core.

Description

[0001] CROSS-REFERENCE TO RELATED APPLICATIONS

[0002] This application claims priority to U.S. Provisional Patent Application No. 63 / 596,851 filed on November 7, 2023 and U.S. Provisional Patent Application No. 63 / 596,865 filed on November 7, 2023, the entire contents of which are incorporated herein by reference. Technical Field

[0003] The present disclosure relates to the field of electric machines, and more particularly to a fluid-cooled stator for an electric machine. Background Art

[0004] Electric motors must be operated under controlled temperature conditions for efficient operation. This is particularly true for electric motors with high torque outputs, such as those used in electric vehicles and hybrid electric vehicles. Thermal management / cooling systems are employed in these vehicles to control the temperature of the electric motors, particularly the temperature of the stator windings. Examples of such thermal management systems include those that utilize oil drop cooling pipes to deliver cooling oil to the stator and overflow stator designs. Unfortunately, these prior art thermal management systems for vehicle electric motors are typically inefficient. Oil drop cooling systems are typically limited by poor heat transfer coefficients (HTC) and high pressure drops. Overflow stators are also limited by low HTC. For example, in an overflow stator with segmented windings, the tightly packed and painted end turns do not provide sufficient surface area for high HTC. In addition, prior art overflow hairpin stators typically utilize complex and expensive methods to seal the stator.

[0005] In view of the above, it would be advantageous to provide a thermal management system for a stator having a high HTC. Additionally, it would be advantageous if such a thermal management system was relatively simple and could be implemented inexpensively in a flooded hairpin stator. Summary of the invention

[0006] In at least one embodiment, a liquid-cooled stator includes a housing, a stator core, a winding arrangement, a first shield, and a second shield. The stator core is positioned within the housing and includes a plurality of teeth and a guard iron, the guard iron defining an outer diameter portion (OD) having a plurality of circumferential channels extending around the stator core. The winding arrangement is positioned on the stator core and includes a plurality of first end turns on a first axial end of the stator and a plurality of second end turns on a second axial end of the stator. The first shield is positioned on the first axial end of the stator and covers the plurality of first end turns. The second shield is positioned on the second axial end of the stator and covers the plurality of second end turns. A stator cooling path is defined within the stator and is configured to direct a continuous flow of liquid from at least one liquid inlet to at least one liquid outlet, the stator cooling path including a first section configured to direct liquid through the plurality of first end turns, a second section configured to direct liquid through the plurality of second end turns, and a third section configured to direct liquid through the circumferential channels extending around the stator core.

[0007] In at least one additional embodiment, a liquid-cooled stator for an electric machine includes a stator core positioned within a housing, the stator core including a plurality of teeth and a guard iron defining an outer diameter (OD) of the stator. A winding arrangement is positioned on the stator core and includes end turns positioned on an axial end of the stator. At least one first shield is positioned on the axial end of the stator and covers the plurality of end turns. A stator cooling path is configured to direct a continuous flow of liquid from at least one liquid inlet to at least one liquid outlet, the stator cooling path including a section configured to direct liquid through the plurality of first end turns and an additional section configured to direct liquid through the OD of the stator core.

[0008] In yet another embodiment, a method of cooling a stator includes directing a continuous flow of cooling fluid through a channel in an outer diameter (OD) of the stator. The method also includes directing the continuous flow of cooling fluid through end turns on an axial end of the stator, wherein the end turns are retained within a shroud on the axial end of the stator.

[0009] The above features and advantages, as well as other features and advantages, will become more readily apparent to those of ordinary skill in the art by reference to the following detailed description and accompanying drawings. While it is desirable to provide an electric machine having a stator that provides one or more of the above or other advantageous features that are apparent to a person reading this disclosure, the teachings disclosed herein extend to those embodiments that fall within the scope of the appended claims, regardless of whether they include or achieve one or more of the advantages or features mentioned herein. BRIEF DESCRIPTION OF THE DRAWINGS

[0010] Figure 1 is a side view of an electric machine including a liquid-cooled stator having end turn shrouds;

[0011] Figure 2 yes Figure 1 A cross-sectional view of a stator of an electric machine showing the arrangement of windings on the stator core;

[0012] Figure 3 is separated from the winding arrangement Figure 2 A top perspective view of a stator core;

[0013] Figure 4A yes Figure 3 A top perspective view of a stator core of FIG. 1 , wherein a winding arrangement is positioned on the stator core, the winding arrangement comprising diamond-shaped coils;

[0014] Figure 4B yes Figure 4A An enlarged view of a portion of a stator within a separate frame B;

[0015] Figure 5 yes Figure 4A A side perspective view of a diamond-shaped coil of a winding arrangement, the coil including slot segments, end turns and coil leads;

[0016] Figure 6 yes Figure 1 A perspective view of the lead ends of a stator with the lead end shield removed from the stator core to expose the lead guides;

[0017] Figure 7 yes Figure 6 An enlarged perspective view of a lead wire guide on a stator;

[0018] Figure 8 yes Figure 6 A cross-sectional view of a lead end shield of FIG. 1 showing placement over end turns of a winding arrangement and connection to a stator core and a sleeve extending along an inner diameter (ID) of the stator;

[0019] Fig. 9 is included in Figure 8 A cross-sectional view of the plastic reinforcement ring on the ID of the lead end shield;

[0020] Fig.10 yes Figure 1 a perspective view of a crown end of a stator with the crown end shield positioned on the stator core and the lead end shield removed from the stator core;

[0021] Fig.11 yes Fig.10 A cross-sectional view of a crown end shield showing the location of the end turns of the diamond coils of the winding arrangement below the crown end shield;

[0022] Fig.12 yes Fig.10An axial outward perspective view of a portion of a crown end shield of FIG. 1 , showing the corrugations on the shield;

[0023] Fig.13 It is along Fig.10 A cross-sectional view of the crown end shield and end turns of the winding arrangement of the stator of line XIII-XIII;

[0024] Fig.14 yes Fig.13 A cross-sectional view of an alternative embodiment of a crown end shield and end turns showing the location of undercuts on the circumferential wall of the shield;

[0025] Fig.15 yes Fig.14 a perspective cross-sectional view of a crown end shield and end turns of a crown end shield, wherein an undercut is introduced into the circumferential wall of the shield;

[0026] Fig.16 yes Fig.14 Another perspective cross-sectional view of the crown end shroud and end turns of the stator core, which reveals additional portions of the shroud and stator core;

[0027] Fig.17 yes Fig.13 A cross-sectional cutaway view of another alternative embodiment of a crown end shroud and end turns, wherein the shroud includes an undercut spacer;

[0028] Fig.18A Shows Figure 3 A cross-sectional side view of an outer diameter (OD) portion of a stator core of FIG. 1 showing lamination plates of different sizes forming a circumferential channel around the core;

[0029] Fig.18B yes Fig.18A An enlarged view of the stator OD in a separate box B;

[0030] Fig.19 is a cross-sectional view through a first axial plane, showing a cooling oil delivery system for delivering cooling oil to Figure 1 stator system;

[0031] Fig. 20 yes Fig.19 another cross-sectional view of the system through a second axial plane;

[0032] Fig.21 It is used to deliver cooling oil to Figure 1 A cross-sectional side view of an alternative embodiment of a system of a stator;

[0033] Fig. 22 It is used to deliver cooling oil to Figure 1 a cross-sectional side view of another alternative embodiment of a system of a stator of; and

[0034] Fig.23 It shows the use of Fig.19 A constant velocity diagram of the oil flow rate around the end turns of a system for delivering cooling oil. DETAILED DESCRIPTION

[0035] This article discloses an electric machine with a liquid-cooled stator. Figure 1 and Figure 2 , the electric machine 10 includes a stator 12 and a rotor (not shown). The stator 12 includes a core 20 having a plurality of windings 30 arranged thereon. A first shield 60 is positioned on the crown end 14 of the stator core, and a second shield 80 is positioned on the lead end 16 of the stator core. A center sleeve 50 extends axially outward from an inner diameter (ID) 28 of the stator core on both the crown end and the lead end of the stator core. The first shield 60 extends between the center sleeve 50 and the crown end of the core 20 and covers the end turns 34 of the windings 30 on the crown end 14 of the stator. The second end turn shield 80 extends between the center sleeve 50 and the lead end of the core and covers the end turns 34 of the windings on the lead end 16 of the stator. The stator 12 is configured to receive a flow of oil or other cooling liquid and direct the flow of cooling liquid to the crown end and the lead end of the core 20. During operation of the motor 10, the cooling liquid flows through the end turns 34 and cools the stator 12. The cooling liquid is confined by the shrouds 60, 80 and the center sleeve 50 to the crown ends and lead ends of the stator core.

[0036] It should be appreciated that the following description of embodiments of the stator of an electric machine utilizes relative terms that depend on the orientation of the electric machine at a given time (e.g., during manufacture or use of the electric machine in a vehicle). Therefore, it should be appreciated that many of the orientation and position terms used herein are defined with reference to what may be shown in the accompanying drawings and / or other common positions. Although efforts have been made herein to refer to the various parts of the electric machine relative to non-varying features (e.g., the "axial," "radial," and "circumferential" directions and associated positions of the stator), it should be appreciated that other terms are relative terms that depend on the position of the electric machine. For example, the terms "top" (or "upper"), "bottom" (or lower), "left," or "right" may be used herein in conjunction with what is shown in the accompanying drawings, but such positions may switch or change if the electric machine is placed in a different position. As another example, the term "above" refers to the relative position of one component being higher than another component in a vertical direction, and the term "below" refers to the relative position of one component being lower than another component in a vertical direction.

[0037] Stator core

[0038] Figure 3A view of the stator core 20 is shown separated from the winding arrangement 30. The stator core 20 is composed of a magnetically conductive material such as steel and is typically formed of a plurality of steel sheets that are stamped and stacked on top of each other to provide a core in the form of a lamination stack. As another alternative, the stator core 20 may include a soft magnetic composite material ("SMC"). The stator core 20 is a generally cylindrical shape defined by a central axis 18 and includes a guard iron 21 having a plurality of teeth 24 extending radially inwardly from the guard iron 21. The outer peripheral surface of the guard iron 21 defines an outer diameter portion (OD) of the stator. The inner peripheral surfaces of the teeth 24 define an inner diameter portion (ID) of the stator. An internal cylindrical space is also defined within the ID of the stator, and the rotor of the motor is positioned within the internal cylindrical space. When referred to herein, the internal cylindrical space is not limited by the axial length of the core 20, but extends in the axial direction from one end of the stator 12 to the opposite end.

[0039] A plurality of teeth 24 extend inwardly from the back iron 21 (i.e., the teeth 24 extend from the back iron 21 toward the central axis 18). Each tooth 24 extends radially inwardly and terminates at an inner peripheral surface (ID). Axial slots 22 are formed between the teeth 24 of the stator core 20. Each slot 22 is defined between two adjacent teeth, so that the two adjacent teeth form two opposing radial walls of one slot. Both the teeth 24 and the slots 22 extend from the first end 14 to the second end 16 of the core 20.

[0040] The slots 22 may be open or semi-enclosed along the inner peripheral surface of the stator core 20. When the slots 22 are semi-enclosed, the width of each slot 22 at the inner peripheral surface is less than the width at a radially outer position (i.e., a slot position closer to the outer peripheral surface). When the slots are open, the conductors may be radially inserted into the slots via the openings along the ID. In addition to the radial openings through the inner peripheral surface leading to the slots 22 (i.e., for the open slots and the semi-enclosed slots), axial openings leading to the slots 22 are also provided on the opposite ends 14, 16 of the stator core 20.

[0041] Although in Figure 3 An exemplary stator core 20 is shown in FIG. 1 , but it should be appreciated that the stator core may also be provided in other forms. For example, in the following combination Fig.18A and Fig.18B In at least one embodiment described in further detail, the lamination stack may include sheets of magnetically conductive material having different OD dimensions, thereby resulting in a circumferential channel formed around the core 20. In yet another embodiment, the lamination stack may be divided into two halves that are spaced apart from one another to allow oil or other cooling liquid to flow between the two halves and more easily reach an axially center location on the core.

[0042] In addition to the central axis 18, Figure 3Also shown are axes 17 and 19, which are perpendicular to each other and also to the central axis. Thus, axes 17 and 18 lie in one cross-sectional plane, and axes 18 and 19 lie in another cross-sectional plane. These two cross-sectional planes are described in further detail herein. Fig.19 and Fig. 20 To mention.

[0043] Winding arrangement

[0044] Now refer to Figure 4A and Figure 4B , the stator core 20 is configured to hold a winding arrangement 30 within the slots 22 of the stator core 20. The winding arrangement 30 is formed by a plurality of interconnected conductors 32 held within the slots 22. In the embodiments disclosed herein, the conductors 32 form a plurality of defined coils 40 wound around the teeth 24 of the core. In other embodiments, the conductors 32 may be configured differently, such as a wave winding wound around the core.

[0045] Now refer to Figure 5 , one of the coils 40 of the winding arrangement 30 is shown separated from the winding arrangement. Figure 5 As shown, each coil is a diamond-shaped coil that includes a plurality of linear slot conductors 42, a plurality of end turns 44, and a plurality of coil leads 38. The linear slot conductors 42 (which may also be referred to herein as "slot segments" or "branches") extend through the slots 22 from one end of the core 20 to the opposite end of the core (i.e., from the first end 14 to the second end 16). Two groups 42a and 42b of slot segments 42 are associated with each coil 40. Each group 42a, 42b of slot segments 42 extends through a different slot of the core. A plurality of slot segments are included in each group 42a, 42b. Figure 5 In an embodiment, each group 42a, 42b includes four in-slot segments 42. The four in-slot segments are arranged in a single row within the slot 22 (i.e., in a "layer" of conductors within the slot). Each slot 22 is configured to hold a certain number of in-slot segments per layer of slot. In at least one embodiment, the slot 22 is configured to hold twice the number of in-slot segments 42 as the number of conductors in each group 42a, 42b (e.g., each group 42a, 42b includes four in-slot conductors 42, and each slot is configured to have a total of eight layers of in-slot conductors).

[0046] In addition to the slot segments 42, each coil 40 includes end turns 44 and coil leads 48. The end turns 44 and coil leads 48 are provided as part of the winding head 36 of the winding arrangement 30 (see Figure 4A and Figure 4B), and are therefore arranged axially outside the respective ends 14, 16 of the stator core 20. It should be noted that reference numeral 44 is used herein to refer to one coil of the winding arrangement (such as Figure 5 The reference numeral 34 is used herein to collectively refer to all the end turns of the winding arrangement (e.g. Figure 4A shown).

[0047] Continue to refer to Figure 5 , end turns 44 (which may also be referred to herein as "end loops") extend between the in-slot segments of the two groups 42a, 42b. In other words, each end turn 44 provides a bridge from the end of the conductor in one group 42a to the end of the conductor in the other group 42b. Each end turn 44 has a U-shaped or V-shaped structure having a first inclined portion (which may also be referred to herein as a "first segment") and a second inclined portion (which may also be referred to herein as a "second segment") that intersect at a circular end 46. The circular end 46 defines the portion of the end turn where the coil 40 changes direction (e.g., changes from a direction moving away from the axial direction of the core back to a direction moving toward the axial direction of the core) as it is wound on the core. The circular end 46 of the end turn 44 forms an eyelet hole 47. Advantageously, the eyelet hole 47 is configured to allow cooling oil to easily flow around the end turn 44, which is described in further detail below.

[0048] Continue to refer to Figure 5 , each coil 40 includes two coil leads 48. Each coil lead 48 provides a path to enter or exit the annular portion of each coil 40. In other words, if the coil body is considered to include the slot segments 42 and the end turns 44 that form a loop, the coil leads 48 provide a path to the coil body. Figure 5 Two coil leads are shown extending axially outward. These coil leads 48 can be bent or otherwise manipulated to provide appropriate connections between the coils 40 of the winding arrangement 30.

[0049] From the foregoing it should be understood that Figure 5 The coil is a diamond coil 40 that includes a conductor strand wound into a loop to include a set of left branches 42a, a set of right branches 42b, and end turns 44 on opposite ends 14, 16 of the core. The left branch 42a and the right branch 42b are both elongated in the axial direction and parallel to each other. The end turns 44 connect the branches 42 in series so that the coil 40 is formed, thereby allowing power to flow from a first lead 48a at one end of the coil through all the branches 42 and reach the second lead 48b at the same end of the coil 40. Multiple coils 40 are connected together via leads to form multiple paths for the winding arrangement 30.

[0050] In the embodiments disclosed herein, no leads 48 are provided on the first end 14 of the core, and this end may also be referred to as a "crown end". Only end turns 44 are provided on the crown end 14 of the core 20. In contrast, all leads 48 of the winding arrangement 30 are provided on the second end 16 of the core, which may be referred to as a "lead end". Similar to the crown end 14, the lead end 16 also includes a plurality of end turns 44.

[0051] In addition to the coil leads 48, the winding arrangement 30 also includes winding leads 38 located on the lead ends 16 of the stator core. The winding leads 38 connect the multiple paths for the winding arrangement in a desired configuration. Specifically, the winding leads 38 provide a neutral connection and a phase connection for the winding arrangement 30. Exemplary winding leads 38 extend circumferentially between various conductor paths, busbars, and phase terminals, such as Figure 6 and Figure 7 In at least one embodiment, the winding arrangement includes three phase windings (e.g., a U phase winding, a V phase winding, and a W phase winding), each phase having multiple paths. Depending on the desired winding configuration, the three phase windings can be star ("Y") or delta ("Δ") connected.

[0052] Refer again Figure 4B It should be noted that when the diamond coils are positioned on the stator core, the rounded tips 46 of the end turns 44 are radially aligned in multiple groups of tips 46, and the eyelet holes 47 of each group are circumferentially aligned. The rounded tips 46 also tend to bend slightly radially outward toward the OD when moving axially outward from the core 20. When used in conjunction with other features of the stator 12, the rounded tips 46 and the significant surface area provided by the end turns of the diamond coils facilitate cooling of the windings, which is explained in further detail herein.

[0053] Although diamond-shaped coils formed from continuous wire segments are disclosed herein in conjunction with the winding arrangement 30, it should be appreciated that any number of other conductor and winding configurations may be utilized. For example, in at least one embodiment, the conductors of the winding arrangement 30 are provided by segmented conductors, such as those disclosed in U.S. Pat. No. 7,348,705, issued Mar. 25, 2008. In at least one embodiment, such segmented conductors may be formed with end turns including rounded ends 46 on the crown end 14, but the end turns on the lead end 16 may be formed from the ends of axially extending branch ends welded together.

[0054] Center sleeve on stator core

[0055] Now refer to Figure 2 and Figure 7, the center sleeve 50 is connected to the ID of the stator core 20. In at least one embodiment, the sleeve 50 is provided by a sheet of material that is rolled into a toroidal / cylindrical shape and then secured to the ID of the stator core 20 using epoxy or other adhesive material.

[0056] The sheet of material used to form the sleeve 50 is composed of a fluid-impermeable material such as polyetheretherketone (PEEK), polyamide-imide (PAI), polyester film (e.g., ) or any of a variety of other thermoplastic materials or other suitable fluid-impermeable materials. In at least some embodiments, the sleeve may include additional materials such as meta-aramid fibers (e.g., ). For example, the sheet may be a laminate, such as Nomex-Mylar-Nomex.

[0057] Because the sleeve 50 is adapted to be connected to the ID of the stator core 20, it will be appreciated that the sleeve 50 will be positioned in the air gap of the motor (i.e., in the small gap between the stator and the rotor). A typical air gap is about 0.8 mm. Therefore, the sleeve 50 should be thin and strong enough to withstand the pressure of the oil (or other cooling fluid) and the vacuum created by the rotating rotor. It has been determined that the thickness of the sleeve should therefore be between 0.1 mm and 0.3 mm.

[0058] To form the sleeve 50, the outside of the sleeve 50 is coated with a B-stage epoxy or other adhesive material (which will eventually cure to the inner surface of the teeth 24 and be used to connect the sleeve 50 to the ID of the stator core). Thereafter, the sheet of material is rolled into an annular / cylindrical shape that forms the sleeve 50. At this point, the previously opposite ends of the sheet overlap on the sleeve 50, and the two ends are loosely held together by the adhesive material (e.g., B-stage epoxy) on the outside of the sleeve. In the event that the ends of the sleeve 50 overlap, the ends can be thinned by squeezing the ends together with a force sufficient to reduce the thickness of the overlapping sheets. In this way, the overlapping portion of the sleeve is not too thick (i.e., not twice the thickness). In the event that the sheet is a laminate, the sheet can be made thinner at the overlapping section so that when the opposite ends of the sheet overlap, the thickness of the sleeve at the overlap is similar to the thickness of the rest of the sleeve.

[0059] After being rolled into a cylindrical shape forming the sleeve 50, the cylindrical sheet of material is inserted into the inner cylindrical space defined by the ID of the stator core 20. The axial length of the sleeve 50 is greater than the axial length of the core 20, and therefore the sleeve 50 extends axially beyond the core 20 on both the crown end 14 and the lead end 16 of the stator. In at least some embodiments, the sleeve also extends axially beyond the end turns 34 on the crown end and the lead end of the stator. Next, after the sleeve is inserted into the inner cylindrical space of the core 20, the inner annular surface 52 of the cylindrical sheet of material is pressed radially outward so that the two ends slide relative to each other and produce a perfect match with the ID of the stator laminations. The pressing can be provided by compressed air, air bags, an expanding mandrel, or other means of providing radially outward pressure. Once fully pressed onto the ID, the sleeve 50 is heated to cure the B-stage epoxy and connect the outer annular surface of the sleeve 50 to the ID of the stator core 20. Thereafter, a shroud 60, 80 is placed on each axial end of the stator and welded or adhered to the sleeve, as explained in further detail below.

[0060] Although sleeve 50 has been disclosed herein as being provided in the form of a sheet of material rolled into a cylinder, it should be appreciated that in other embodiments, the sheet can be provided in other forms. For example, in at least one embodiment, the sleeve is a plastic cylinder formed by an extrusion molding process. As another example, instead of being held together by epoxy resin or adhesive, the ends of the sheet can be held together by other appropriate means (such as laser or ultrasonic welding). In other embodiments, the two axial ends of sleeve 50 can be folded or crimped to increase the strength of sleeve 50.

[0061] Lead end shield

[0062] Now refer to Figures 6 to 8 , a lead end shield 80 is shown in conjunction with the stator core 20 and the windings 30. In the embodiments disclosed herein, the lead end shield 80 is constructed of two distinct parts, including an inner lead grid 82 and an outer shell 90. The inner lead grid 82 isolates each lead 38 of the winding arrangement 30 so as to facilitate connection between the leads 38. The outer shell 90 covers the lead grid 82 radially outwardly and axially outwardly of the end turns. When the outer shell 90 is sealed to the center sleeve 50 and the stator core 20, as further described in detail herein, the outer shell provides a sealed volume that houses the end turns and receives a flow of cooling fluid. Both the inner lead grid 82 and the outer shell are constructed of a polymer or other non-conductive material (the term "non-conductive material" as used herein refers to any of a variety of materials that do not readily conduct electricity and can be used in an electric machine to provide insulating characteristics for the electric machine).

[0063] The lead grid 82 of the lead end shield 80 is an annular disk-shaped member having a plurality of ribs 84 extending between an inner peripheral ring 86 and an outer peripheral ring 88. A plurality of openings are formed between the ribs. Each rib 84 has a curvature such that the rib gradually bends in radially outward and axially inward directions as one moves along the rib from the inner peripheral ring 86 to the outer peripheral ring 88. The ribs 84 of the lead grid 82 extend over the end turns 34 on the lead ends of the stator core 20. Openings are formed between the ribs 84, and the winding leads 38 extend through the openings. Figure 7 As best shown, the openings in the lead grid 82 serve to separate the winding leads 38 from each other, thereby making it easier to make weld connections on the lead ends 16 of the stator. The lead grid also facilitates the handling and routing of jumpers and other connections between the leads 38. For example, when a jumper extends between two different leads, the jumper can be routed around and against the outer peripheral ring. The lead grid 82 also serves to further isolate the neutral connection bar and the phase terminals from the winding leads 38. At the same time, the ribs 84 in the lead grid 82 create protrusions that mix the cooling fluid and prevent the fluid from flowing through the shroud 80 in a straight path.

[0064] The housing 90 of the lead end shield 80 is configured to cover the lead grid 82 and enclose the lead ends 16 of the stator core 20. The housing is an annular disc-shaped member including a radial wall 92 and a circumferential wall 96. The radial wall 92 provides the axially outermost portion of the shield 80. The radial wall 92 extends in the radial direction and includes an outer surface 93 facing axially outward from the core 20 and an inner surface facing axially inward. A circumferential inner lip 94 is defined along the radially inward peripheral edge of the radial wall 92. The inner peripheral lip 94 is significantly thicker than the rest of the radial wall in the axial direction. The thick inner lip 94 provides a radially inwardly facing surface 95 connected to the center sleeve 50. The inner lip 94 can be connected to the center sleeve 50 using any suitable means (such as adhesive, laser or ultrasonic welding). The connection between the inner lip 94 and the center sleeve provides a liquid-impermeable tight seal.

[0065] The circumferential wall 96 of the housing 90 surrounds the end turns 34 on the lead ends 16 of the stator core and extends from the core 20 in a generally axially outward direction. The circumferential wall 96 provides the radially outermost portion of the shield 80. The circumferential wall 96 includes an outer surface facing radially outward away from the core 20 and an inner surface facing radially inward. A circumferential outer lip 98 is defined along the axially inward peripheral edge of the circumferential wall 96. The outer peripheral lip 98 is significantly thicker than the rest of the circumferential wall 96 in the radial direction. The thick outer lip 98 provides an axially inwardly facing surface 99 of the back iron 21 connected to the core 20. O-rings, adhesives or other seals are used to connect the outer lip 98 to the stator core 20. Therefore, the connection between the outer lip 98 and the stator core includes a liquid-tight seal. With the housing 90 connected to both the core 20 and the center sleeve, the shield surrounds the end turns 34 and forms a fluid chamber on the lead ends 16 of the stator core. Although not disclosed herein, the housing 90 of the shroud 80 also includes openings for the phase terminals, and these openings are sealed (eg, with epoxy or other sealant) to maintain a sealed fluid chamber.

[0066] Now refer to Fig. 9 In at least one embodiment, an annular support ring 54 is connected to the shroud 80 and extends into the inner cylindrical space defined by the ID of the stator core 20. The support ring 54 is constructed of plastic or other non-conductive material. The support ring 54 includes an axially outer lip 56 and a radially inner cylindrical portion 58. The lip 56 partially extends across the outer surface 93 of the radial wall 92 of the housing 90 and is connected to the outer surface 93 using any suitable connection method (e.g., welding, adhesive, etc.). The cylindrical portion 58 extends axially downward and engages the inner annular surface 52 of the center sleeve 50. In at least some embodiments, the cylindrical portion 58 only abuts the inner annular surface 52 without being connected thereto. In any case, the support ring 54 provides additional support for the center sleeve 50 and prevents it from buckling under pressure when oil or other cooling liquid flows through the shroud 80.

[0067] In at least some additional embodiments, the housing 15 of the motor 10 may have details that compress the shield 80 (and the O-ring or other seal) axially toward the stator core. In this embodiment, before the center sleeve 50 is welded to the shield 80, the shield 80 may be manually squeezed to compress the O-ring to the appropriate height.

[0068] Crown end guard

[0069] Now refer to Figures 10 to 14, the crown end shield 60 is disposed on the non-lead axial end of the stator core (i.e., opposite to the lead end shield 80). Similar to the lead end shield 80, the crown end shield 60 is also a disk-shaped annular member made of a polymer (or other non-conductive material). In at least some embodiments, the shield 60 is a single integral part. However, in other embodiments, the shield 60 may be provided as multiple parts. Similar to the shield 80, the shield 60 is also connected to the central sleeve 50 and the stator core 20. When sealed to the central sleeve 50 and the stator core 20, the crown end shield 60 defines a sealed volume that houses the end turns and receives the flow of cooling fluid.

[0070] The crown end shield 60 includes a corrugated radial wall 62 and an outer peripheral wall 72. The corrugated radial wall 62 provides the axially outermost portion of the shield 60. The corrugated radial wall 62 extends generally in the radial direction and includes a degree of curvature. The degree of curvature of the radial wall 62 is similar to the curvature of the circular ends 46 on the end turns 44 of the coil 40.

[0071] The corrugated radial wall 62 defines a plurality of ridges 66 and a plurality of grooves 68 on the axially outward face 64 of the radial wall 62. The plurality of ridges 66 are positioned above (i.e., axially outward from) the circular ends 46 on the end turns 44 of each coil 40 of the winding arrangement 30. The plurality of grooves 68 are positioned between pairs of adjacent end turns 44. The shape of the ridges 66 also follows the shape of the circular ends 46. Specifically, the ridges 66 are axially and radially aligned with the circular ends 46 and extend across an arc length defined on at least a portion of the circular ends 46.

[0072] The corrugated nature of the radial wall means that the ridges 66 on the axially outward face 64 form recesses on the axially inward face. In this way, the ridges are designed and sized to receive the outermost portions of the circular ends 46 of the end turns 44, maintaining a small gap between the corrugated radial wall 62 and the circular ends. As Fig.14 best shown, this small gap (g) is a relatively constant space between the ridges. This gap can be, for example, 2.0 mm to 3.0 mm, with a certain small tolerance range (e.g., + / - 2.0 mm). As a result, a relatively small constant distance (e.g., 1.0 mm < g < 5.0 mm) is maintained between the circular ends 46 and the shield 60. In addition, the grooves 68 extend axially inward between the ridges 66 (i.e., into the blank space between adjacent end turns). As a result, each groove 68 is positioned between a pair of adjacent end turns. The grooves 68 help to maintain a constant distance (g) between the circular ends 46 and the shield 60 over a larger portion of the circular ends 46. The ridges 66 and the grooves 68 together facilitate the oil (or other cooling fluid) flowing through the shield 60 to closely surround the end turn 44 conductors for better cooling of the conductors. This oil flow is Fig.14 shown by the arrow 70.

[0073] like Fig.11 As best shown, the shroud 60 includes a circumferential inner lip 65 defined along the radially inward peripheral edge of the corrugated radial wall 62. The inner peripheral lip 65 is significantly thicker in the axial direction than the remainder of the radial wall 62. The thick inner lip 65 provides a radially inward facing surface 67 that connects to the center sleeve 50. The inner lip 65 can be connected to the center sleeve 50 using any suitable means, such as laser or ultrasonic welding. The connection between the inner lip 65 and the center sleeve 50 provides a liquid-impermeable tight seal.

[0074] The circumferential wall 72 of the crown end shield 60 surrounds the end turns 34 on the crown end 14 of the stator core and extends from the core 20 in a generally axially outward direction. The circumferential wall 72 (which may also be referred to herein as the "axially extending sidewall" of the shield 60) provides the radially outermost portion of the shield 60. The circumferential wall 72 includes an outer surface facing radially outward away from the core 20 and an inner surface facing radially inward. A circumferential outer lip 74 is defined along the axially inward peripheral edge of the circumferential wall 72. The outer peripheral lip 74 is significantly thicker than the rest of the circumferential wall 72 in the radial direction. The thick outer lip 74 provides an axially inward facing surface 75 of the back iron 21 connected to the core 20. O-rings, adhesives, or other seals may be used to connect the outer lip 74 to the stator core 20. Thus, the connection between the outer lip 74 and the stator core includes a liquid-tight seal.

[0075] With the shroud 60 connected to both the core 20 and the center sleeve 50, the shroud 60 surrounds the end turns 34 of the winding 30 and forms a fluid chamber on the crown end 14 of the stator core 20. Fig.11 As best shown, fluid inlet / outlet ports 76 may also be included on the circumferential wall 72 to provide access to the fluid chamber defined by the shroud 60. The fluid inlet / outlet ports 76 provide access to a fluid cooling path within the stator 12.

[0076] As previously described, the crown end shield 60 tightly surrounds the rounded tip 46 of the end turn 44 to improve conductor cooling.

[0077] This small gap between the shroud 60 and the end turns 44 improves the cooling performance of the stator. However, because the end turns 44 of the diamond coils 40 tend to bend outward over the ends of the lamination stack, it should be appreciated that larger gaps between the shroud 60 and the end turns 44 can be found closer to the stator core 20, and in particular, larger gaps between the outer peripheral wall 72 and the end turn locations are near the stator core. These larger gaps are Fig.13 is shown by the dotted ellipse 71 and in Fig.14Thus, in order to make the shield 60 fit the end turns 44 more closely over the entire axial length of the end turns, in at least one embodiment, the shield 60 is provided with an undercut 78, such as by Fig.14 The undercut 78 is only a portion of the outer peripheral wall 72 that extends radially inward toward the end turns 44 near the stator core 20. Fig.15 Shows Fig.14 A shroud 60 in which such an undercut 78 is introduced into the shroud 60 .

[0078] The undercut 78 provided along the peripheral wall 72 can be provided in different forms. Fig.15 As shown, the undercut 78 can be provided by a three-part circumferential wall 72, including a first portion 72a extending axially outward (upward) from the circumferential outer lip edge 74, a second inclined portion 72b extending radially and axially outward at a certain angle (e.g., 20° to 30°) relative to the first portion 72a, and a third portion 72c extending axially outward and generally parallel to the first portion 72a until it intersects the corrugated radial wall 62.

[0079] Fig.16 Another example of an undercut 78 is shown in FIG. 1 , where the undercut in the peripheral wall 72 is provided by a more gently curved wall. Fig.16 In the embodiment of the present invention, the undercut 78 in the peripheral wall is provided by a more continuous curvature and is not easily Fig.15 The three parts 72a, 72b and 72c are identified.

[0080] exist Fig.15 and Fig.16 In each of the embodiments of the present invention, the undercut 78 prevents the shield 60 from being positioned above the end turns 34 of the winding 30 in the axial direction. Therefore, in these embodiments, the shield 60 is not a single integral component, but is provided by two or more arc-shaped components. The two or more arc-shaped components are inserted into the core 20 in the radial direction and surround the end turns 34 (for example, the two components are moved onto the core 20 from opposite radial sides of the end turns 34). Once positioned on the core 20, the two or more arc-shaped components are welded or otherwise connected together to form an annular cover of the shield 60.

[0081] In yet another embodiment, the undercut 78 may be formed by Fig.1772 and the like. The annular gasket 79 shown in FIG. 7 is provided. In this embodiment, the annular gasket 79 is positioned against the core 20 and is positioned between the peripheral wall 72 and the end turns 34. The annular gasket 79 is also made of a non-conductive material and is adjacent to or connected to the peripheral wall 72. A small gap is provided between the gasket 79 and the end turns 34 to allow oil to flow around the end turns. Therefore, the annular gasket 79 has a trapezoidal cross-sectional shape, the outer side of which is adjacent to and follows the shape of the peripheral wall 72, and the inner side is separated from the end turns 44 but follows the shape of the end turns 44. The gasket 79 can be provided as two or more arc-shaped parts, which are inserted into the core 20 in the radial direction and surround the end turns 34. The parts of the annular gasket 79 are fixed to the back iron 21 of the stator core 20. Once the gasket 79 is in place, the peripheral wall 72 of the shield can be slid on the gasket 79 in the axial direction. The circumferential wall 72 and the gasket 79 together form the outer wall of the shield 60.

[0082] It should be appreciated that the undercut 78 is provided to maintain a relatively small gap between the shroud 60 and the end turns 34, thereby improving the cooling performance of the stator. Although the gap between the shroud 60 and the end turns has been described herein as being constant (within a certain tolerance range), it should be noted that the gap may be different in different portions of the winding. For example, in some embodiments, the shroud may be fitted closer at the ID (e.g., 0.5mm-1.0mm gap) than at the OD (e.g., 0.9mm-3.0mm gap). In any case, because the shroud 60 tightly surrounds the end turns 34, the shroud facilitates continuous flow of oil over the entire length of the end turns and prevents excessive flow of oil at locations within the shroud away from the end turns.

[0083] Circumferential channel on the OD of the stator core

[0084] As previously discussed herein, the lamination stack providing the stator core 20 may be provided by sheets of magnetically conductive material having different / alternating OD dimensions, thereby resulting in a circumferential OD channel formed around the core 20. Fig.18A and Fig.18B , a portion of the OD 26 of the stator core 20 is shown in cross section to illustrate the circumferential OD channels 27. The lamination stack includes laminations 25a having a smaller OD (which may also be referred to herein as "small laminations") arranged between laminations 25b having a larger OD (which may also be referred to herein as "large laminations"). Stacks of one or more small laminations 25a are alternated with stacks of one or more large laminations 25b on the core 20. This results in a finned lamination stack in which the large laminations 25b form fins around the OD and circumferential OD channels 27 are formed between the fins. More specifically, the fins are provided by the large laminations 25b, and the OD channels 27 are formed radially outward from the small laminations 25a.

[0085] The OD channels 27 are designed to be wide enough and deep enough to allow oil to flow around the OD of the stator and thus provide increased cooling area. However, at the same time, the OD channels 27 are also designed to be small enough to force oil to flow into other areas. In other words, the OD channels 27 are small enough so that they do not starve some areas of the stator cooling path of the oil flow. In at least some embodiments, the OD channels 27 are about six (6) laminations wide (i.e., six small laminations 25a are stacked adjacent to each other and are terminated by two large laminations 25b) and about 4.0 mm deep (e.g., the small laminations 25a can be about 8.0 mm OD smaller than the large laminations 25b). In such an embodiment, the laminations can be 0.27 mm thick (in the axial direction), so the OD channels 27 are about 1.62 mm wide (in the axial direction) (i.e., 0.27 x 6 = 1.62). Similarly, the fins can also be formed by stacking six (6) large laminations 25b so that the fins have a width similar to the OD channels 27. In at least some embodiments, the width of the OD channel 27 ranges from three (3) to nine (9) laminations.

[0086] Flow path for cooling fluid

[0087] Now refer to Figures 19 to 22 , discloses different embodiments of the stator 12, each of which includes a different flow path for a cooling fluid (the flow path may also be referred to herein as a "cooling path"). Figures 19 to 22 In each embodiment of the present invention, the stator is shown with the central axis 18 extending horizontally across the page, so that the crown end 14 of the stator is shown on the left side of the figure and the lead end 16 of the stator is shown on the right side of the figure (i.e., the axial direction of the stator 12 is from left to right and from right to left). This exemplary orientation is a common orientation when the stator 12 is used in an electric motor for an electric vehicle.

[0088] Combination Fig.19 and Fig. 20 A first embodiment of a flow path 100 for a cooling fluid is shown. Fig.19 A first cross-sectional view of the stator 12 is shown (eg, by Figure 3 17 and 18 of the stator 12 to illustrate several inlets and outlets of the flow path 100 of the stator 12 and the associated fluid flow directions. Fig. 20 Shows relative to Fig.19 Another cross-sectional view of the stator 12 rotated about 90° about the central axis (e.g., by Figure 3 18 and 19) to illustrate the direction of fluid flow at the location of the stator with the inlet and outlet removed.

[0089] like Fig.19As shown, the fluid inlet 102 is positioned at the top of the stator between the crown end 14 and the lead end 16 of the stator 12 (i.e., at a first radial position). The fluid inlet 102 extends through the housing 15 and is configured to receive a pressurized flow of oil or other cooling fluid, as shown by arrow 104. The fluid inlet 102 opens into a first / top axially extending cavity 106 formed in the housing 15. The top axially extending cavity 106 is radially inward from the wall of the housing 15 and adjacent to the stator core 20. The top axially extending cavity 106 is connected to each of the channels 27 formed along the OD of the stator core 20. The channels 27 extend circumferentially around the OD between the fins 25 in a clockwise (CW) direction and a counterclockwise (CCW) direction until they reach a second / bottom axially extending cavity 108 opposite the top axially extending cavity 106. The first axially extending cavity 106, the circumferential channels 27, and the second axially extending cavity 108 together define a first segment of a flow path for the stator 12. In particular, the fluid pumped into the top chamber 106 flows directly into the OD passage 27 and flows downward and circumferentially around the stator core 20 via the OD passage 27, as shown in FIG. Fig.19 The fluid flows through the passage 27 in a clockwise and counterclockwise direction as shown by the directional flow arrows 109 in FIG. The fluid then flows into the bottom chamber 108 and is forced axially outward to the shroud passages 110 , 112 located on the opposite axial sides of the stator core 20 .

[0090] The shield passages 110, 112 are provided by small circumferential portions of the shields 60, 80 that are not connected to the stator core 20. As previously described, the circumferential outer lips of the shields (i.e., 74 of the shield 60 and 98 of the shield 80, respectively) are connected to the back iron 21 of the stator core 20. This connection extends substantially around the entirety of the circumferential outer lips 74, 98 (e.g., approximately 355°, but not a full 360°). However, a small portion (e.g., a 5° arc) of each circumferential lip 74, 98 is not connected to the core 20, but is instead connected to the housing 15, as shown in FIG. Fig.19 1. As shown in FIG. 1, the shroud-casing connection 111 at the bottom of the stator. Thus, the pressurized fluid in the axially extending cavity 108 is forced axially outward and through the shroud passages 110, 112 at this bottom position.

[0091] Fluid flowing through the shroud passages 110, 112 enters the respective shroud cavities 116, 118 formed by the shrouds 60, 80. Because the shrouds 60, 80 are sealed against the stator core 20 and the center sleeve 50, the shroud cavities 116, 118 are fluid-tight and do not allow cooling fluid to flow out of the shroud cavities 116, 118 except through designated inlet / outlet areas, including the shroud passages 110, 112 and the fluid outlet ports 120, 122. The fluid outlet ports 120, 122 are positioned at the top of the stator 12 and may be provided by ports introduced into the wall of the shrouds 60, 80, such as the fluid inlet / outlet ports 78 (e.g., Fig.11 1 and described in conjunction with the crown end shroud 60). The cooling fluid flowing within the shroud is directed over the end turns 34 of the winding 30 (i.e., the winding heads 36) and generally upwardly and circumferentially through the shroud cavities 116, 118 and toward the fluid outlet ports 120, 122, as shown in FIG. Fig.19 and Fig. 20 17, 119. These shroud cavities 116, 118 define second and third segments of the flow path for the stator 12. It should be appreciated that the fluid in the passage 27 flows in series with the fluid in the shrouds 110 and 112 (i.e., the first segment is in series with the second and third segments). The fluid in the shroud 110 flows in parallel with the fluid in the shroud 112 (i.e., the second segment is parallel to the third segment).

[0092] The fluid outlet ports 120, 122 of the shields 60, 80 are sealed to the fluid outlets 124, 126 of the housing 15. Similar to the fluid inlet 102, the fluid outlets 124, 126 in the housing 15 are also positioned at the top of the stator 12 and extend through the housing 15. The fluid outlets 124 and 126 are positioned on the opposite axial ends of the stator 12 and receive the pressurized fluid that leaves the shields 60, 80. After passing through the fluid outlets 124, 126 of the housing, the cooling fluid is cooled in a cooling system associated with the motor. For example, the cooling fluid can be directed through a vehicle radiator to release heat from the fluid and cool the fluid. Thereafter, the fluid returns to the fluid inlet 102 and recirculates again through the various sections of the cooling flow path (i.e., through the cylindrical cavity 106 surrounding the housing and then through the shield cavities 116, 118).

[0093] Fig.21 A second embodiment of a flow path 100 for a cooling fluid within a stator is shown. Fig.21 As shown, the inlet and outlet are located at the bottom of the stator (with Fig.19 and Fig. 20 opposite to the top of the Fig.19 and Fig. 20The opposite of what is shown. The fluid inlet ports 120, 122 open directly into the shroud cavities 116, 118. The cooling fluid then flows upward and circumferentially around the end turns 34 of the winding arrangement 30, as shown by directional flow arrows 117, 119. After reaching the top of the stator core 20, the fluid flows through the shroud passages 110, 112 and is directed into the top axially extending cavity 106 within the housing 15. The fluid in the cavity 106 then flows downward within the passage 27 and flows circumferentially around the stator core 20 to the bottom axially extending cavity 108. The fluid then flows to the bottom fluid outlet 103. After reaching the fluid outlet 103, the fluid exits the stator (as shown by arrows 105) and cools within a cooling system associated with the electric machine, whereupon the fluid returns to the fluid inlet ports 120, 122 and is again recirculated through the various sections of the cooling flow path. Figures 19 to 21 The first and second embodiments of the present invention may be considered to provide a "series" flow path in that a single liquid input provides a flow path that includes a first segment that extends circumferentially around the stator core and then divides into two additional segments in series with the first segment (i.e., a second path segment through shroud cavity 116 and a third path segment through shroud cavity 118), and separate liquid outputs are provided at opposite ends of the stator for each of the two additional segments (e.g., Figures 19 to 20 As shown, vice versa, two liquid input ends are combined into one liquid output end, such as Fig.21 shown).

[0094] Fig. 22 A third embodiment of a flow path 100 for a cooling fluid within a stator is shown. Fig. 22, the fluid inlet 102 is positioned at the bottom of the stator between the crown end 14 and the lead end 16 of the stator 12 (i.e., at a first radial position). Similarly, the fluid outlet 103 is positioned at the top of the stator 180° opposite the fluid inlet 102. The shrouds 60, 80 do not include a fluid inlet and a fluid outlet. Instead, both the top and bottom of the stator include shroud passages 110, 112 that allow oil to flow out of and into the top and bottom axially extending cavities 106, 108. In operation, pressurized oil enters the bottom axially extending cavity 108 through the fluid inlet 102, as shown by arrow 104. The oil then flows upward through the cavity 27 surrounding the cylindrical stator core, as shown by flow path arrow 109. Simultaneously (i.e., parallel to the flow through cavity 27), the pressurized oil flows into the shroud cavities 116, 118 and then flows upward around the winding head 36, as shown by flow path arrows 117, 119. The oil in the shroud cavities 116, 118 then enters the top axially extending cavity 106. The pressurized oil is then forced out of the fluid outlet 103 (as shown by arrow 105) and is cooled within a cooling system associated with the motor. The cooled oil is then returned to the fluid inlet 102 and recirculated again through the various sections of the cooling flow path. This third embodiment can be considered to provide a "parallel" flow path because one liquid input end provides a flow path including a first section that extends circumferentially around the stator core and then splits into two additional sections (i.e., a second path section through the shroud cavity 116 and a third path section through the shroud cavity 118), wherein the two additional sections exit at one liquid output end after being combined at the fourth section (i.e., the section extending along the stator core). In other words, the second section and the third section are formed in parallel between the first section and the fourth section of the flow path.

[0095] In addition to the different possible embodiments of the cooling flow path 100 for the stator 12, the diamond coils 40 and the shapes of the shrouds 60, 80 further facilitate cooling of the stator 12. Specifically, when the winding 30 of the stator 12 includes the diamond coils 40, the structure of the shrouds 60, 80 is such that the shrouds cause the cooling fluid in the shroud cavities 116, 118 to tightly surround the conductors of the end turns 44, thereby improving cooling of the end turns. In particular, the corrugated radial surface 62 of the crown end shroud 60 and the internal lead grid 82 of the lead end shroud 80 include features that cause the cooling fluid to flow regularly through the conductors forming the end turns 44 of the diamond coils 40. In addition, the diamond shape of the coils 40 (including the eyelet holes 47 formed by the rounded ends 46 of the end turns 44) also improves fluid flow through the end turns. Increased velocity is also provided to the fluid flow, thereby improving heat transfer from the conductors of the winding arrangement 30 to the cooling fluid.

[0096] Fig.23A heat map of coolant velocity within the shroud cavity (ie, a segment of the flow path 100) at the crown end of the stator core is shown. Fig.23 As shown, the fluid flowing through the shield cavity is generally annular. The flow rate is relatively constant throughout the annulus. However, a ring 130 of increased velocity is clearly identified within the annular shape. This ring 130 represents the increase in velocity of the fluid flowing through the eyelet holes 47 of the end turns 44.

[0097] It should be appreciated from the accompanying drawings and the foregoing text that a flooded stator with improved cooling is disclosed herein. The stator includes a flow path for a cooling fluid, the flow path including several sections, including a section provided by a cylindrical cavity surrounding the stator core and an additional section provided by a shroud cavity at the opposite axial ends of the stator. The flow path provides a series cooling fluid flow that extends through the cylindrical cavity and then floods the end turns at the opposite axial ends of the stator core (or vice versa). In at least some embodiments, the stator winding is formed by a diamond coil. The diamond coil includes a significant surface area and has an eyelet hole in the middle of the end loop. Other winding configurations (e.g., hairpin type, continuous hairpin type, etc.) do not include such an eyelet hole. With the flooded stator and diamond coil disclosed herein, oil flows through each eyelet hole in a circular pattern and provides an increased cooling effect for the winding. The shroud fits tightly to the end turns to force the oil to flow through the eyelet hole. The shroud also includes axial protrusions / ridges that will fit into or roughly fit into the space between the end loops of the diamond coils. These protrusions cause the oil flow to zigzag in and out of the peaks of the diamond coil end loops, resulting in higher surface area exposure and better cooling of the end loops. In addition, because the cooling oil takes the easiest path to flow, the shroud is close to the end turns, resulting in the easiest flow through the eyelet holes. Therefore, the oil flow through the eyelet holes has a higher velocity than found in other flow paths. Because the HTC (heat transfer coefficient) is improved by the overflow diamond cooling design, the oil outlet may be too hot. In order to compensate for the increased HTC, the flow rate of the oil can be increased. For example, for conventional oil cooling, the flow rate can be about 1-2 liters per minute (LPM), but for the overflow stator disclosed in this article, a flow rate of 3-5LPM is more desirable for HTC because it results in cooler oil temperatures and cooler stator end turns.

[0098] Although various embodiments have been provided herein, it will be appreciated by those skilled in the art that other embodiments and adjustments are possible. For example, in order to help cool the wire segments in the stator core, the laminations may be composed of two halves spaced apart from each other. Such a separated lamination stack will allow some oil to flow between the two halves and reach the wire located in the center of the stack. As another example, in at least some embodiments, cooling oil may also be allowed to flow from one axial end of the stator slot to the other axial end (e.g., between the innermost wire and the inner sleeve), thereby providing additional cooling of the conductors of the winding arrangement. Of course, many other examples of adjustments and different embodiments of the stator core may be envisioned. In addition, aspects of the various embodiments described herein may be combined or replaced with aspects from other features to arrive at embodiments different from those described herein. Therefore, it should be understood that various above-disclosed and other features and functions or their alternatives may be desirably combined into many other different systems or applications. Various currently unforeseen or unanticipated substitutions, modifications, changes or improvements may then be made by those skilled in the art, which are also intended to be covered by any final attached claims.

Claims

1. A liquid-cooled stator, comprising: case; a stator core positioned within the housing, the stator core comprising a plurality of teeth and a back iron defining an outer diameter (OD) having a plurality of circumferential channels extending around the stator core; a winding arrangement positioned on the stator core, the winding arrangement comprising a first plurality of end turns on a first axial end of the stator and a second plurality of end turns on a second axial end of the stator; a first shroud positioned on the first axial end of the stator and covering the plurality of first end turns; a second shroud positioned on the second axial end of the stator and covering the second plurality of end turns; as well as A stator cooling path, the stator cooling path is configured to guide a continuous flow of liquid from at least one liquid inlet to at least one liquid outlet, the stator cooling path includes a first section, a second section and a third section, the first section is configured to guide liquid through the plurality of first end turns, the second section is configured to guide liquid through the plurality of second end turns, and the third section is configured to guide liquid through the plurality of circumferential channels extending around the stator core. 2 . The liquid-cooled stator of claim 1 , wherein the at least one liquid inlet is arranged on a first radial side of the stator between the first axial end and the second axial end of the stator. 3 . The liquid-cooled stator of claim 2 , wherein the at least one liquid outlet is arranged on a second radial side of the stator between the first axial end and the second axial end of the stator. 4 . The liquid-cooled stator of claim 2 , wherein the at least one liquid outlet comprises a first liquid outlet disposed on the first shroud and a second liquid outlet disposed on the second shroud.

5. The liquid-cooled stator of claim 1 , wherein the at least one liquid inlet comprises a first liquid inlet disposed on the first shroud and a second liquid inlet disposed on the second shroud, and wherein the at least one liquid outlet is disposed on a radial side of the housing between the first axial end and the second axial end of the stator.

6. The liquid-cooled stator of claim 1, wherein the first shroud includes an outer periphery of the back iron connected to the stator core, and the second shroud also includes an outer periphery of the back iron connected to the stator core.

7. The liquid-cooled stator of claim 6, wherein the outer periphery of the first shroud is provided by an outer lip having an axially facing surface, and wherein the outer periphery of the second shroud is also provided by an outer lip having an axially facing surface.

8. The liquid-cooled stator according to claim 7, wherein: The outer lip of the first shield includes a first circumferential portion and a second circumferential portion, The first circumferential portion of the outer lip is connected to the back iron, and The second circumferential portion of the outer lip is connected to the housing.

9. The liquid-cooled stator of claim 1, further comprising an inner sleeve connected to an inner diameter (ID) of the stator core, the inner sleeve extending axially beyond the stator core at both the first axial end and the second axial end of the stator. 10 . The liquid-cooled stator of claim 9 , wherein the first shroud includes an inner periphery connected to the inner sleeve, and the second shroud includes an inner periphery connected to the inner sleeve.

11. The liquid-cooled stator of claim 10, wherein the inner periphery of the first shroud is provided by an inner lip having a radially facing surface, and wherein the inner periphery of the second shroud is also provided by an inner lip having a radially facing surface.

12. The liquid-cooled stator of claim 1, wherein the winding arrangement comprises a plurality of diamond-shaped coils, each of the plurality of diamond-shaped coils comprising end turns, the end turns comprising rounded ends with holes defined therein, The first axial end is a crown end of the stator, The first shroud includes a corrugated radial wall having an axially outward face defining a plurality of ridges and a plurality of grooves, and The plurality of ridges of the first shield extend over the rounded ends of the end turns, and the plurality of grooves are disposed between the end turns.

13. The liquid-cooled stator of claim 1, wherein the stator core is a split core, wherein the stator cooling path includes a fourth section extending through the split core.

14. The liquid-cooled stator according to claim 1, wherein: The stator cooling path is configured as follows: directing a continuous flow of liquid in a first section parallel to the second section, and directing a continuous flow of liquid in a third section in series with the first section and the second section; directing a continuous flow of liquid from the at least one liquid inlet directly to the third section; directing a continuous flow of liquid in a clockwise direction and a counterclockwise direction in a third section; directing a continuous flow of liquid from the third section directly to the first section and the second section; directing the continuous flow of liquid from the third section directly to the first section and the second section; and directing the continuous flow of liquid in the first section parallel to the second section; Wherein the shroud includes a channel configured to allow fluid to flow from the third section to the first section and the second section.

15. A liquid-cooled stator, comprising: case; a stator core positioned within the housing, the stator core comprising a plurality of teeth and a back iron defining an outer diameter (OD) of the stator; a winding arrangement positioned on the stator core, the winding arrangement comprising end turns positioned on axial ends of the stator; at least one shroud positioned on the axial end of the stator and covering the plurality of end turns; as well as A stator cooling path configured to direct a continuous flow of liquid from at least one liquid inlet to at least one liquid outlet, the stator cooling path including a section configured to direct liquid through the at least one shroud and across the end turns and an additional section configured to direct liquid across the outer diameter of the stator core.

16. The liquid-cooled stator of claim 15, wherein the outer diameter of the stator includes a plurality of circumferential channels extending around the stator core, and the additional section of the stator cooling path is configured to direct liquid through the circumferential channels.

17. The liquid-cooled stator of claim 15, wherein the at least one liquid inlet is arranged on a first radial side of the stator between a first axial end and a second axial end of the stator, and wherein the at least one liquid outlet is arranged on a second radial side of the stator between the first axial end and the second axial end of the stator.

18. The liquid-cooled stator of claim 15, wherein the at least one shroud comprises a first shroud on a first axial end of the stator and a second shroud on a second axial end of the stator, wherein the liquid inlet comprises a first liquid inlet arranged on the first shroud and a second liquid inlet arranged on the second shroud, and wherein the at least one liquid outlet is arranged on a radial side of the stator between the first axial end and the second axial end of the stator.

19. The liquid-cooled stator of claim 15, wherein the at least one shroud comprises a first shroud on a first axial end of the stator and a second shroud on a second axial end of the stator, wherein the at least one liquid outlet comprises a first liquid outlet arranged on the first shroud and a second liquid outlet arranged on the second shroud, and wherein the at least one liquid inlet is arranged on a radial side of the stator between the first axial end and the second axial end of the stator.

20. A method of cooling a stator, comprising: directing a continuous flow of cooling fluid through a passage in an outer diameter (OD) of the stator, and The continuous flow of cooling fluid is directed through end turns on an axial end of the stator, wherein the end turns are retained within a shroud on the axial end of the stator.

Images