Stator end ring with hoover features

Abstract

The invention relates to a stator end ring with a ferrule feature. A stator for an electric machine includes a stator core, a winding, a first end ring, and a second end ring. The stator core includes a plurality of slots, and the winding includes a plurality of interconnected conductors extending through the plurality of slots. The winding further includes a U-shaped end turn on the insertion end of the stator core and a welded end turn on the connection end of the stator core. The first end ring is coupled to the insertion end of the stator core and includes a plurality of openings and a plurality of radial ribs. The U-shaped end turns engage the radial ribs of the first end ring. The second end ring is coupled to the connection end of the stator core. The weld end turns are bent around the radial ribs of the second end ring.

Description

[0001] CROSS-REFERENCE TO RELATED APPLICATIONS

[0002] This patent application claims the benefit of U.S. Provisional Application No. 63 / 589,892 filed on October 12, 2023, U.S. Provisional Application No. 63 / 589,915 filed on October 12, 2023, and U.S. Provisional Application No. 63 / 589,931 filed on October 12, 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 apparatus and methods for cooling electric motors. Background Art

[0004] For motors having a flooded or submerged stator design in which the end turns are immersed in oil for cooling, the inner diameter (ID) of the stator must be sealed to prevent oil from entering the air gap present between the stator ID and the rotor outer diameter (OD). Various methods and related devices have been used in the past to seal the stator. Unfortunately, these past devices and methods are often expensive and / or adversely affect the performance of the motor. For example, some past devices and methods for sealing the stator ID reduce the mechanical air gap between the stator and the rotor and cause mechanical losses. As another example, some past devices and methods involve the use of closed slot stator lamination stacks, which allow magnetic flux to easily leak through the closed slot openings, thereby affecting the performance of the motor.

[0005] Therefore, it would be advantageous to provide an improved method and system for sealing the inner diameter of a stator of an electric machine. It would also be advantageous if the system and method were relatively inexpensive to implement and did not adversely affect the performance of the electric machine. Summary of the invention

[0006] A sealed stator for an electric machine includes a stator core, a winding positioned on the stator core, a first end ring coupled to one end of the stator core, and a second end ring coupled to the other end of the stator core. The stator core includes a plurality of slots, and the winding includes a plurality of interconnecting conductors extending through the plurality of slots. The winding also includes U-shaped end turns on the insertion end of the stator core and welded end turns on the connection end of the stator core. The first end ring is coupled to the insertion end of the stator core and includes a plurality of openings and a plurality of radial ribs. The interconnecting conductor extends through the plurality of openings, and the U-shaped end turns engage the radial ribs of the first end ring. The second end ring is coupled to the connection end of the stator core and also includes a plurality of openings and a plurality of radial ribs. The interconnecting conductor extends through the plurality of openings, and the welded end turns are bent around the radial ribs of the second end ring.

[0007] In at least one embodiment, a second end ring on the connection end of the stator includes an axially outward side and an axially inward side. The axially outward side includes a plurality of radial ribs and a plurality of openings arranged circumferentially around the end ring. Each of the plurality of radial ribs defines opposing inclined sides that face each other and gradually converge axially outward from the peripheral edge of the continuous opening and extend to a radially flat upper portion. The axially inward side is generally flat and is positioned on the side of the end ring opposite the axially outward side.

[0008] In at least one embodiment, a first end ring on the insertion end of the stator includes an axially outward side and an axially inward side. The axially outward side includes a plurality of radial ribs and a plurality of openings arranged circumferentially around the end ring. The plurality of radial ribs define a plurality of segments of the end ring, each of the plurality of segments defining a pocket compartment having a pocket floor surrounding each of the plurality of openings. Each of the plurality of radial ribs is defined by two axially outwardly extending surfaces extending to a flat radial upper surface.

[0009] Advantageously, the sealed stator disclosed herein allows cooling oil to contact the full length of the coil and provides improved cooling of the motor. The features and advantages described above and other features and advantages will become more apparent to one of ordinary skill in the art by reference to the following detailed description and accompanying drawings. While it is desirable to provide an electric motor and method of producing the same that provides one or more of these 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 an insertion side perspective view of a sealed stator for an electric machine, the sealed stator including an end ring positioned on an insertion side of a stator core;

[0011] Figure 2 Shows Figure 1 an insertion side perspective view of a sealed stator with the stator windings removed to show the end rings positioned on the insertion side of the stator core;

[0012] Figure 3 It is separated from other parts of the stator Figure 1 A perspective view of the axially outward side of the end ring;

[0013] Figure 4 yes Figure 3 An enlarged perspective view of the recesses and ribs on the axially outward side of the end ring;

[0014] Figure 5 It is around Figure 3 An enlarged perspective view of a chamfered surface formed by a groove opening on an axially inward side of an end ring;

[0015] Figure 6 is located in Figure 2 An enlarged perspective view of a portion of an end ring on a sealing stator;

[0016] Figure 7 It is located on the stator core Figure 1 a plan view of a portion of an end ring of FIG. 1 , wherein the conductor is shown in cross-section and extends through an opening in the end ring;

[0017] Figure 8 yes Figure 7 an enlarged view of the side of the opening in the end ring;

[0018] Fig. 9 It is along Figure 1 A cross-sectional view of the stator conductor and the end ring along line IX-IX;

[0019] Fig.10 yes Fig. 9 An enlarged view of a dashed isolation frame X of FIG. 1 , which shows the outer diameter of the end ring on the stator core;

[0020] Fig.11 yes Fig. 9 An enlarged view of the dotted isolation box XI of FIG. 1 , which shows the inner diameter of the end ring on the stator core;

[0021] Fig.12 yes Figure 1 An illustration of a flat pattern of conductors of a stator winding on an insertion end of a stator core, with the conductors extending through openings in an insertion-side end ring, wherein the conductors are shown in a linear fashion (as opposed to circumferential) and the end ring is shown in cross-section;

[0022] Fig.13 is used to connect the end ring to Figure 1 A plan view of a gasket in the form of an adhesive tape for sealing a stator core in a stator;

[0023] Fig.14 yes Fig.13 An enlarged plan view of a portion of the adhesive tape;

[0024] Fig.15 Is set in Figure 1 A perspective view of the axially outward side of the welding side end ring on the sealing stator;

[0025] Fig.16 yes Fig.15 An enlarged perspective view of the recesses and ribs on the axially outward side of the end ring;

[0026] Fig.17 is extended through Fig.15 A cross-sectional view of a stator conductor of a welded side end ring;

[0027] Fig.18 It is the welded end of the stator core. Figure 1 , a flat pattern illustration of a conductor of a stator winding of , the conductor extending through an opening in a weld-side end ring, wherein the conductor is shown in a linear fashion (as opposed to circumferential) and the end ring is shown in cross-section;

[0028] Fig.19 Is manufacturing Figure 1 A block diagram of a method for sealing a stator;

[0029] Fig. 20 It is used to form Figure 1 Illustration of a series of steps for sealing a conductor winding of a stator;

[0030] Fig.21 Before applying the filler material Figure 1 Illustration of the horizontal axis manufacturing steps of the sealed stator;

[0031] Fig. 22 is to apply the filler material to Figure 1 Illustration of the manufacturing step of the tilted axis during welding ends of the stator;

[0032] Fig.23 is Fig. 22 An illustration of the position of the weld end during the manufacturing steps of; and

[0033] Fig.24 is to apply the filler to Figure 1 Illustration of another tilt-axis manufacturing step during the insertion of the stator end. DETAILED DESCRIPTION

[0034] An electric motor with a sealed stator is disclosed herein. The sealed stator includes a stator core having a plurality of windings arranged thereon. A first end ring is positioned on an insertion side of the stator core and a second end ring is disposed on a welding side of the stator core. Each end ring includes an inner diameter (ID) and an outer diameter (OD), with a plurality of segments formed around the end ring between the ID and the OD. Each segment is defined by two ribs, with a recess and a conductor opening formed between the two ribs. Each end ring is sealed to the housing using a combination of a slot liner material, a molded end ring, a gasket adhesive, and an epoxy / varnish filler material. A separator is located between the coils of the wound rotor of the electric motor, which allows oil to flow along the entire length of the coil, thereby advantageously cooling the coil.

[0035] It will be appreciated that the following description of embodiments of the motor utilizes relative terms that depend on the orientation of the motor at a given time (e.g., during manufacture of the motor or use of the motor in a vehicle). Accordingly, it will be appreciated that many of the terms of orientation and position used herein are defined with reference to what is shown in the accompanying drawings and / or other common positions. Although efforts have been made herein to refer to portions of the motor regarding invariant features, such as reference to the "axial," "radial," and "circumferential" directions and positions of the stator, it will be appreciated that other terms are relative terms that depend on the position of the motor. For example, the terms "top" (or "upper"), "bottom" (or lower), "left," or "right" may be used in conjunction with what is shown in the accompanying drawings, but such positions may switch or change if the motor is placed in a different position. As another example, the term "above" refers to a relative position in which one component is vertically higher than another component, and the term "below" refers to a relative position in which one component is vertically lower than another component.

[0036] stator

[0037] Now refer to Figure 1 and Figure 2 The motor 10 includes a stator 12 and a rotor 16 (in Figure 1 The stator 12 is arranged relative to the housing 18 (not shown in FIG. Figure 1 and Figure 2 shown in; see Fig.17 ) is stationary. The rotor 16 is positioned within the stator 12 and is rotatable relative to the stator 12 and the housing 18. An air gap separates the rotor 16 from the stator 12.

[0038] The stator 12 includes a stator core 20 having a plurality of stator windings 30 wound thereon. The stator core 20 is provided by a stack of laminations formed of sheets of a magnetically permeable material, such as steel. In most embodiments, the stack of laminations is bonded rather than welded. Bonding is preferred over welding because the welds are spaced apart from one another and the areas between the welds may tend to bend. In addition, the heat of the welding process may sometimes deform the stack of laminations. The adhesive also seals the gaps between the laminations. The adhesive used to bond the laminations may advantageously be applied to the entire surface of the laminations (i.e., full bonding as opposed to point bonding).

[0039] The stator core 20 is cylindrical and defines a central axis 11 coaxial with the axis of the rotor 16. An axially outer direction on the stator 12 is defined as a direction parallel to the central axis 11 and also moving away from the center of the stator core 20; an axially inner direction on the stator 12 is defined as a direction parallel to the central axis 11 and also moving toward the center of the stator core 20; a radially inner direction is defined as a direction toward the central axis 11 of the stator core 20; a radially outer direction is defined as a direction away from the central axis 11; and a circumferential direction is defined as a direction moving around the central axis 11.

[0040] The stator core 20 includes a plurality of core slots 22 (or simply referred to as "slots") formed between a plurality of teeth 24. The teeth 24 extend in a radially inner direction from an outer diameter wall 26 of the stator core 20 (the outer surface of which defines the OD of the stator). The core slots 22 are semi-closed slots (i.e., a small gap is formed between each tooth) extending radially inward from a segmented circumferential inner surface 28 of the stator core (the circumferential inner surface 28 defines the ID of the stator). The core slots 22 and the teeth 24 also extend in an axial direction parallel to the central axis 11 of the stator core 20 between a crown end 14 (also referred to herein as an "insertion end") and a welding end 15 (also referred to herein as a "connection end") of the stator core, and the welding end 15 is provided on an end of the stator 12 axially opposite to the crown end 14. The core slots 22 and associated teeth 24 are equally spaced around the circumferential inner surface 28 of the stator core 20, and the corresponding inner surfaces of the teeth 24 extend axially parallel to the central axis 11. A radial opening is provided to each slot 22 between two adjacent teeth 24, wherein the width of the radial opening at the inner peripheral surface 28 (i.e., ID) is less than the width at a position closer to the radial outside (i.e., the slot position closer to OD). Unless I missed something, the yellow highlights are repeated. In addition to the radial openings to the slots 22 passing through the inner peripheral surface 28, axial openings to the slots 22 are also provided on the opposite ends 14, 15 of the stator core 20.

[0041] The conductors 32 forming the stator winding 30 are arranged in the slots 22 of the stator core. The conductors 32 forming the stator winding 30 may be, for example, segmented conductors 32 (which may also be referred to as "U-shaped conductors" or "hairpin conductors"), for example Fig. 20 Each U-shaped conductor 32 includes a U-shaped end turn 34 and two legs 36. The legs 36 of the U-shaped conductor are inserted into the slots 22 of the stator core 20 through the axial openings leading to the slots. After insertion, the U-shaped end turn 34 is located at the crown end 14 of the stator, and the ends of the legs 36 are located at the welding end 15 of the stator. The ends of the legs 36 are interconnected at the welding end 15 to form welded end turns 35 (see Fig.17 and Fig.18). The interconnecting conductors 32 form a winding that is wound around the core 20. Each slot 22 is configured to hold a number of intra-slot segments in a "layer" of the slot, wherein the intra-slot segments are generally arranged in a single row so that each layer of the slot holds a single conductor segment. Segmented windings are known for preparing stator windings, such as those disclosed in U.S. Pat. No. 7,348,705, issued Mar. 25, 2008, the contents of which are incorporated herein by reference.

[0042] The slot liners 38 are positioned in the slots 22 of the stator core 20. The slot liners 38 provide insulation between the conductors 32 and the walls of the slots 22. The slot liners 38 may be provided from any of a variety of materials known to provide insulation for electric machines. For example, the slot liners 38 may be provided from a sheet of insulating material, such as the ELECTRONICS® sold by DuPont. Paper, a film such as polyester film or polyimide, or a similar material. Paper such as Nomex can be porous, so for an overflow stator design, an exemplary slot liner material can be 100% film material, or a laminate consisting of a paper layer and a film layer. The slot liner 38 is provided by forming the sheet into a cylindrical structure (having a cross-section that matches the cross-sectional shape of the slot), wherein two opposing ends of the sheet form an overlapping structure. For an overflow stator, sealing at the ID is more important than sealing at the OD. Therefore, in the embodiments disclosed herein, the overlapping portion is located at the rear of the slot (i.e., the portion closer to the OD), and the front of the slot (i.e., the portion closer to the ID) is a continuous stretch of the sheet. As Figures 6 to 8 As shown, the slot liner 38 lines the wall of each slot and extends axially through the slot. The slot liner 38 extends axially out of the slot 22 and into the opening 60 in the end ring 40, 41, which is explained in further detail below.

[0043] After the windings 30 are mounted on the stator core 20, a coating such as epoxy resin, varnish (e.g., ELAN- ) or other bonding agent / sealant is applied to the OD and ID of the stator core 20, which is explained in further detail herein. The filler material provides insulation and sealing features along the OD and ID over the axial length of the stator 12.

[0044] Insert side end ring for sealing the stator

[0045] Now refer to Figures 2 to 12 , discloses a first end ring 40 for sealing the stator 12. The end ring 40 provides additional insulation and sealing features on the insertion side of the stator 12. Figure 2As shown, the end ring 40 has a shape similar to the insertion end 14 of the stator core 20 and is designed and sized to be placed on the insertion end 14 of the stator core 20. The end ring 40 is an insulating member composed 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 easily conduct electricity and can be used in the motor to provide insulating characteristics to the motor). In at least one embodiment, the end ring 40 is composed of a high glass-filled plastic (e.g., greater than 30% glass filler, preferably about 40% glass filler). For example, the end ring 40 can be composed of polyphenylene sulfide (PPS) with 40% glass filler. The end ring 40 is a one-piece component (i.e., an integral component) in which all parts of the component are integrally formed and cannot be separated without destroying the component (i.e., a single-piece component). Therefore, the end ring 40 can be formed by an injection molding process, 3D printing, or other processes capable of producing such an integral single-piece component.

[0046] like Figure 3 and Figure 4 As best shown, the end ring 40 is a disc-shaped member that includes an inner peripheral lip 42 (which may also be referred to simply as the "inner lip"), an outer peripheral edge 44 (which may also be referred to simply as the "outer edge"), an axially outward side 40a (which may also be referred to herein as the "top side"), and an axially inward side 40b (which may also be referred to herein as the "bottom side").

[0047] The axially outward side 40a of the end ring 40 includes a plurality of ribs 46 extending in a radial direction between the inner lip 42 and the outer edge 44. In the disclosed embodiment, the ribs 46 connect the inner lip 42 and the outer edge 44 and divide the end ring 40 into a plurality of continuous (and overlapping) segments 50 arranged circumferentially around the entire circumference of the end ring 40. Thus, the segments 50 are defined by any two continuous ribs 46, the circumferential space between the two ribs 46, and the segments of the inner lip 42 and the outer edge 44 adjacent to the space. Each segment 50 defines a pocket compartment 52 having an outer pocket floor 54 and an inner opening 60 (also referred to herein simply as an "opening"). As explained in further detail below, the outer edge 54 of the end ring has a circular / annular shape and extends axially outward from the pocket floor 54. In addition, the conductors 32 of the stator winding 30 are inserted into the slots 22 of the stator core through the openings 60 in the end ring 40. As shown Fig.12 As best shown in FIG. 1 , the conductor 32 is bent around and engages the rib 46 at the location where the conductor transitions from the axial in-slot portion to the end turn 34. Thus, the rib 46 prevents the conductor 32 from being over-inserted into the slot 22, thereby properly positioning the conductor at an axial position and insulating the conductor 32 from the core 20.

[0048] Reference Figure 3 , Fig. 9 and Fig.11 , the inner lip 42 is a generally cylindrical wall member that includes an axially outwardly facing surface 42a (i.e., a top surface), an axially inwardly facing surface 42b (i.e., a bottom surface), a radially inwardly facing surface 42c, and a radially outwardly facing surface 42d. The top surface 42a of the inner lip is positioned further outward in the axial direction than any other surface of the end ring 40. The bottom surface 42b is coplanar with the bottom surface of the outer edge 44. Therefore, the distance between the top surface 42a and the bottom surface 42b defines the thickest dimension of the end ring 40 in the axial direction. The bottom surface 42b is also generally flat and smooth and is configured to engage a sealant. In at least some embodiments, the sealant is a sealing gasket 80 (which may also be referred to herein as a "bonding gasket", and which is also incorporated below Fig.13 and Fig.14 described in further detail).

[0049] Continue to refer to Figure 3 , Fig. 9 and Fig.11 , the radially inwardly facing surface 42c of the inner lip 42 is substantially flat and smooth and is configured to engage the inner ring seal 70 (described in further detail below). The top of the radially inwardly facing surface 42c may taper slightly outwardly to aid in the process of sliding the inner ring seal 70 along the ID of the end ring 40 and seating against the inner lip 42. The width of the inner lip 42 measured from the radially inwardly facing surface 42c to the radially outwardly facing surface 42d is typically less than 4 mm, and in the embodiment herein is about 2.8 mm.

[0050] The radially outwardly facing surface 42d of the inner lip 42 is also generally flat and smooth, with some surface features designed to facilitate a good seal between the end ring 40 and the stator core 20. Specifically, a bottom chamfer 62 is formed around the bottom of the radially outwardly facing surface 42d. The chamfer 62 is generally at an angle between about 45° and 75° (e.g., about 60°) relative to the bottom surface 42b and extends upwardly about 0.5 mm to 1 mm along the radially outwardly facing surface 42d. The chamfer 62 is designed to assist in inserting the end ring 40 onto the stator core 20 by preventing wrinkling of the slot liner 38, which is designed to engage the relatively flat lower to middle portion of the radially outwardly facing surface 42d and extends upwardly about 2.8 mm or more from the stator core 20. The top of the radially outwardly facing surface 42d of the inner lip 42 tapers slightly inwardly to limit contact between the end ring 40 and the conductors 32 of the stator winding 30.

[0051] like Figure 3 , Fig. 9 and Fig.10As best shown, the outer edge 44 of the end ring 40 includes an axially outwardly facing surface 44a (i.e., a top surface), an axially inwardly facing surface 44b (i.e., a bottom surface), a radially inwardly facing surface 44c, and a radially outwardly facing surface 44d. The top surface 44a of the outer edge 44 is positioned above the pocket floor 54 of the end ring 40. The bottom surface 44b is coplanar with the bottom surface 42b of the inner lip 42. The bottom surface 44b is also generally flat and smooth and is configured to engage the sealant / sealing gasket 80. The radially inwardly facing surface 44c of the outer edge 44 has a substantially flat and smooth bottom and a top that defines an outer lip 48. The outer lip 48 is configured to engage the outer ring seal 74, which is explained in further detail below. Figure 6 and Fig.10 As best seen in FIG. 4 , the outer edge 44 and the radial ribs 46 have substantially the same axial height (ie, the axially outward facing surface 44a of the outer edge 44 is at the same axial height as the axially outward facing surface of the ribs 46).

[0052] Now refer to Figures 4 to 6 Each segment 50 on the top side 40a of the end ring 40 defines a recessed compartment 52. The recessed compartment 52 on the top side of the end ring 40 is Figure 4 4. As best shown in FIG. 4. Each pocket compartment 52 includes an outer pocket floor 54 and an inner opening 60. The outside of the pocket compartment 52 is defined by two opposing ribs 46, the inwardly facing surface 44b of the outer edge 44, the pocket floor 54, and a step 56 formed between the pocket floor 54 and the outside of the opening 60. The opening 60 through the end ring 40 is located radially inward from the pocket floor 54. In order to achieve a stator with a short axial height, the pocket floor 54 should have an axial thickness of less than 3.2 mm. The inside of the pocket compartment 52 includes the opening 60. The opening 60 is defined between the inner lip 42, the two opposing ribs 46, and a wall 58 opposite the inner lip 42.

[0053] Each opening 60 in the segment 50 of the end ring 40 extends completely through the end ring 40 from the top side to the bottom side. The size of each opening 60 is similar to but slightly larger than the axial opening leading to the slot 22 in the stator core 20. Therefore, the openings 60 in the end ring 40 are configured to receive the conductors 32 of the stator winding 30, which also extend through the slots 22 of the core 20, as shown in FIG. Figure 7 and Figure 8 Because the size of each opening 60 is slightly larger than the size of the associated slot opening, when the end ring 40 is placed on the stator core 20, a cavity 66 is formed on the axially outward side of the end ring between the periphery of the opening 60 and the conductor 32 extending through the slot (see Figure 7 and Figure 8 ). The cavity 66 extends around the entire perimeter of the opening 60. The width of the cavity 66 (i.e., the gap between the conductor 32 and the perimeter of the opening 60, such as Figure 8 4 and 0.3 mm. A minimum cavity width w is provided along the inner lip 42. As explained in further detail below, during manufacture of the stator 12, the cavity 66 is filled with an insulating filler material. The small width w is of sufficient size to provide a capillary action that wicks the insulating filler material (e.g., varnish, epoxy, or other resin material) into the cavity 66, thereby sealing the slot 22, as explained in further detail below. Because sealing along the ID of the stator core 20 is particularly valuable, the width w is smallest at the inner lip 42, and the capillary action wicks the filler material into the space between the end ring 40 and the ID of the stator core 20.

[0054] Now, special reference Figure 5 , the bottom side 40b of the end ring 40 is generally flat, with the openings 60 exposed on the bottom side 40b. The entire perimeter of each opening 60 on the bottom side 40b of the end ring 40 is defined by a chamfer 62. This is the same chamfer 62 previously described in conjunction with the radially outwardly facing surface 42d at the bottom side of the inner lip 42. The chamfer 62 is generally angled between about 45° and 75° (e.g., about 60°) relative to the bottom surface of the end ring 40 and extends upward from the bottom surface by about 0.5 mm to 1.0 mm. Again, the chamfer 62 is designed to aid in inserting the end ring 40 onto the stator core 20 by preventing wrinkling of the slot liner 38 when the end ring 40 is seated against the core 20. Specifically, as the end ring 40 is moved axially toward the stator core 20 during the assembly process, the slot liner 38 first engages the chamfer 62 surrounding the opening 60. As the end ring 40 continues to move axially toward the core 20, the slot liner 38 slides along the chamfered surface 62, which guides the end of the slot liner 38 slightly inward until the end ring 40 is seated against the core 20. Advantageously, the chamfered surface 62 prevents the slot liner 38 from engaging any blunt edges on the end ring 40, thereby preventing wrinkling or other damage to the slot liner 38.

[0055] like Figure 6 As shown, when the end ring 40 is properly seated against the stator core, each slot liner 38 engages the entire perimeter of the associated opening 60 and extends through the opening 60 to the upper pocket compartment 52. The top edge of the slot liner 38 extends beyond the chamfered surface 62 and may also extend above the pocket floor 54. Specifically, the top edge of the slot liner 38 extends axially above the stator core 20 by about 2.8 mm or more (e.g., 1.5 mm). Fig.11). In this position, the slot liner 38 extends longer than typical slot liners in other electric machines and has sufficient length for sealing against the ends of the openings 60 of the end rings 40. This seal is due in part to the chamfered surfaces 62 surrounding each opening 60 of the end rings 40. Therefore, it will be appreciated that slot liners extending at least 2.8 mm above the end faces of the stator laminations are disclosed herein. However, if this dimension of the slot liner is too long, the end turns 34 of the winding 30 will have to be longer, which will result in wasted cost of copper wire and slot liner material. Therefore, it has been determined that a slot liner 38 extending between 2.8 mm and 4.5 mm is advantageous.

[0056] The flat bottom side 40b of the end ring 40 helps facilitate sealing with the flat end on the insertion side of the stator core. Preferably, the flatness of the end of the stator core (e.g., as defined by geometric dimensioning and tolerances (GD&T) such as ASME Y14.5) should be less than 0.4 mm, and preferably about 0.1 mm (+ / - 0.05 mm). For the end ring, the flatness should be less than 0.7 mm, and preferably about 0.4 mm (+ / - 0.05 mm). The material used to form the end ring 40 (e.g., PPS with 40% glass filler) advantageously allows the insulating end ring to have a flatness within a desired tolerance range.

[0057] Ring seals

[0058] The inner lip 42 of the end ring 40 is wide enough and strong enough to receive the lip seal 70 (at Fig.17 The lip seal 70 is located on a portion of the housing or guide 19 of the stator 12 (see FIG. Fig. 9 and Fig.11 ) between the inner lip 42 of the end ring 40. Thus, the lip seal 70 is configured to seal the end ring 40 to the guide 19 (similar to Fig.17 The guide member 19 may be a separate member from the housing 18, or it may be a part of the housing 18. Fig.17 In FIG. 1 , the guide 19 is shown as a separate piece.

[0059] Because the inner lip 42 is relatively wide, and because the inner lip 42 is positioned above the tips of the teeth 24 on the stator core 20, the tip depth of the teeth 24 of the stator core 20 must be slightly increased to allow the innermost conductor in the slot 22 to be arranged further back in the slot (i.e., slightly radially outward). Figure 7The distance d) in the inner lip 42 is increased to 2.88 mm. However, it has been determined that the dimension d should generally be less than 4 mm. When the dimension d is greater than 4 mm, the slot filling of the stator may be impaired, which will impair motor performance and efficiency. Therefore, the width of the inner lip 42 is generally limited to a width of less than 4 mm.

[0060] In at least some embodiments of the stator 12, in addition to the inner ring seal 70, an outer ring seal 74 is provided on the end ring 40 (at Fig.10 The outer ring seal 74 is positioned against the outer side 44d of the outer edge of the end ring 40. The outer ring seal 74 may be in the form of a band having an axial height greater than its thickness, or it may be an O-ring or a sealing member of a similar shape. Fig.10 As shown, the outer ring seal 74 is configured to be retained by and abut the lip 48 provided on the outward facing surface 44d on the outer edge 44 of the end ring 40. Thus, the outward facing surface has a larger diameter on the axially outer side (i.e., upper side) of the outer lip 48 than on the axially inner side (i.e., lower side) of the lip 48. The lip 48 provides a shoulder that engages the outer ring seal 74 and prevents it from sliding axially outward beyond the end ring 40.

[0061] The inner ring seal 70 and the outer ring seal 74 advantageously seal the inner and outer peripheries of the end ring 40. The inner ring seal is particularly advantageous, preventing oil from leaking into the air gap between the rotor 16 and the stator 12. The outer ring seal 74 helps seal the stator 12. The outer edge 44 and the amount of material in the outer edge 44 serve a dual purpose, as it also prevents the end ring 40 from warping during the injection molding and cooling process, and helps balance the material from the ID to the OD of the end ring 40. The non-warping end ring 40 is related to making the bottom side 40b of the end ring 40 relatively flat and smooth to achieve a solid seal provided by the sealant 80.

[0062] washer

[0063] As previously described, a sealant is disposed between the end ring 40 and the stator core 20. In at least some embodiments, the sealant is a liquid or gel-like material applied directly to the surface of the end ring 40 or the stator core. In at least some other embodiments, the sealant is a gasket 80 provided by an adhesive material applied between the bottom side 40b of the end ring 40 and the end surface of the stator core 20, wherein the gasket 80 is an integral component applied to the end ring 40 or the stator core 20 as a unit. The material used to form the gasket 80 (or sealant) can be, for example, a glue, an adhesive, or a sealant material, such as a room temperature vulcanizing (RTV) silicone. Advantageously, the bottom side 40b of the end ring 40 and the end surface of the stator core 20 are flat and relatively smooth, so that the gasket 80 provides a solid seal.

[0064] like Fig.13and Fig.14 As particularly shown in FIG. 1 , in at least one embodiment, the gasket 80 is provided by a double-sided adhesive tape having a shape similar to the bottom surface 40b of the end ring. For example, the tape may include an inner peripheral edge 82, an outer peripheral edge 84, a plurality of radial ribs 86, and a plurality of openings 88, wherein each opening is sized similarly to the bottom surface 40b of the end ring 40. Alternatively, the tape may simply have a shape that matches the inner lip 42 of the end ring. Furthermore, the tape may be provided as an annular ring, or alternatively, may be provided as a plurality of different segments, such as, but not limited to, six (6) 60° segments.

[0065] During the manufacture of the stator 12, the gasket 80 may first be applied to the bottom surface 40b of the end ring 40 or the end surface of the stator core 20. If the gasket 80 is such as Fig.13 and Fig.14 If the tape structure shown is used, the tape may have a backing material on one or both sides to aid in installation. After the first side of the gasket 80 is engaged to the first component (i.e., the end ring 40 or the stator core 20), the backing material is peeled off the second side of the gasket 80 and the second component is engaged with the second side of the gasket. In this way, the gasket 80 is used to provide an adhesive seal between the end ring 40 and the core 20.

[0066] Once the end ring 40 is in place on the stator core 20, the conductors 32 forming the windings 30 are loaded through the end ring 40 and the slots 22 of the stator core 20. The bends of the conductors 32 on the end turns 34 contact the ribs 46 of the end ring 40, which further helps to hold the end ring 40 in place against the tape / adhesive washer 80 and the stator core 20.

[0067] Filler applied to end rings

[0068] The stator also includes a filler material (e.g., varnish, epoxy, or other resin material) applied to the stator windings and end rings 40. The filler material acts as an insulating cement for further sealing the end rings 40 to the ends of the stator core 20. The filler material is designed to adhere well to the slot liners 38, the end rings 40, and to the existing insulation on the conductors 32 of the stator windings 30.

[0069] As previously mentioned, the radial clearance between the opening 60 of the end ring 40 and the slot liner 38 is approximately 0.1 mm to 0.3 mm. This dimension advantageously allows the filler material to wick into the cavity 66. If this dimension is smaller, it will be difficult to assemble the end ring 40 on the stator core 20 without wrinkling the slot liner 38. On the other hand, if this dimension is too large, the filler material will not wick (capillary action) between the slot liner 38 and the end ring 40.

[0070] Welded end rings for sealing stators

[0071] In addition to the above-mentioned end rings 40 on the insertion side 14 of the stator 12, the stator is also equipped with end rings 41 on the welding side 15 of the stator. The welding side end rings 41 are combined Figures 15 to 18 1 and is similar to the insert-side end ring 40. Thus, the weld-side end ring 41 is made of the same material as the insert-side end ring 40 and has similar dimensions and configurations for use with the slot liner 38, gasket 80, and filler material (e.g., epoxy or varnish) to seal the end ring 41 to the stator core 20. However, the weld-side end ring 41 includes some structural changes that make the end ring 41 particularly suitable for use on the weld side of the stator 12.

[0072] like Fig.15 and Fig.16 As best shown, end ring 41 is a disc-shaped member that includes an inner peripheral lip 43, an outer peripheral edge 45, an axially outward side 41a (also referred to herein as the "top side"), and an axially inward side 41b (also referred to herein as the "bottom side").

[0073] The axially outward side 41a of the end ring 40 includes a plurality of ribs 47 extending in a radial direction between the inner lip 43 and the outer edge 45. Each rib 47 is defined by opposed inclined side portions 47a (e.g., at an angle of about 15° to 30° relative to the axial direction) that gradually converge toward each other and converge at a radially flat upper portion 47b. The ribs 47 divide the end ring 41 into a plurality of continuous (and overlapping) segments 51 arranged circumferentially around the entire circumference of the end ring 41. Each segment 51 defines a pocket compartment 53 having an outer pocket floor 55 and an inner opening 61. A chamfer (similar to a combination of a bevel and a bevel) may be formed around the bottom periphery of each opening 61. Figure 5 ). Similar to the insertion side end ring 40, the conductor 32 of the stator winding 30 is inserted into the slot 22 of the stator core through the opening 61 in the welding side end ring 41. Fig.18 As best shown, the conductor 32 is bent about the rib 47 and engages the rib 47 at the location where the conductor transitions from the axial in-slot portion to the end turns 34. Thus, the rib 47 facilitates the bending of the conductor 32 to form the welded end turns 35, thereby helping to secure the end ring 41 to the stator core 20 and insulating the conductor 32 from the core 20.

[0074] Reference Fig.16 and Fig.17 , the inner lip 43 is a generally cylindrical wall member that includes a lip seal 70 configured to engage (see Fig.17 ; Not in Fig.16The bottom side of the radially inner facing surface includes a shoulder 59 that extends radially outward and is configured to engage the bottom of the lip seal 70. The lip seal 70 engages the guide 19 and provides a seal between the end ring 41 and the guide 19. In some embodiments, the guide 19 is separate from the housing 18; in other embodiments, the guide 19 can be a continuous part of the housing. Similar to the insert side end ring 40, the weld side end ring 41 can also include an outer ring seal (not shown). Figures 15 to 18 ), the outer ring seal provides a seal between the outer edge 45 of the end ring 41 and the guide 19 or the housing 18. The outer ring seal can be provided by an O-ring, a lip seal 70, or any of a variety of other types of seals.

[0075] Refer again Fig.18 , it will be appreciated that the ribs 47 act as rounded / cornered plastic bumps that support the wire during the twisting operation of the conductor 32 when forming the weld end turns 35. These plastic bumps can replace the expensive cuff figure tools commonly used in twist forming machines. As is known in the art, hairpin stator forming can involve the insertion of such tools (i.e., "cuff fingers") that are located on the laminations and perform two tasks. First, on the insertion end of the stator, the fingers are used to prevent the hairpin from being inserted too far axially and pressing against the stator laminations. Second, on the weld end of the stator, the cuff fingers support the wire during the hairpin twisting operation. In the embodiments disclosed herein, these cuff finger features are incorporated into the end rings 40 and 41 by means of ribs 46, 47. Fig.12 It is shown how the rib 46 prevents the hairpin from being inserted too far into the slot. Fig.18 It is shown how the ribs 47 support the wire during the hairpin twisting operation. When compared to the ribs 47 on the weld side end ring 41, the ribs 46 on the insert side end ring 40 are more rectangular, but thinner in the circumferential direction to reduce material usage. The ribs 46 on the insert side end ring 40 may also have a different axial height than the ribs 47 on the weld side end ring 41.

[0076] In addition to the foregoing, the weld-side end ring 41 may also include features for holding a temperature sensor (not shown) for the stator 12. In particular, Fig.15 As shown, three L-shaped hooks 90 are provided along the outer edge 45 of the end ring 41. The L-shaped hooks 90 are configured to hold the thermistor or thermistor wire in place: one hook feature is used to hold the wire axially upward, one hook feature is used to hold the wire axially downward, and one feature is used to hold the wire circumferentially. Another feature is a clip 92 having a post for wrapping the wire around for further strength.

[0077] Although the end rings 40 and 41 are described herein as similar rings with slightly different features, it will be appreciated that in some embodiments, the end rings 40 and 41 may be identical. Furthermore, features in the insert-side end ring 40 that are not shown or described as being present in the weld-side end ring 41 may be incorporated into the weld-side end ring 41, and vice versa. For example, the shoulder 59 on the radially inward facing side / surface 41 c of the inner lip 43 of the weld-side end ring 41 may also be incorporated into the insert-side end ring 40. As another example, although the washer 80 is not shown or described in conjunction with the weld-side end ring 41, it will be apparent that the same or similar washer 80 may also be used in conjunction with adhering the weld-side end ring 41 to the stator core 20.

[0078] Method of manufacturing a sealed stator for an electric machine

[0079] Referenced above Figures 1 to 18 The design and arrangement of the sealed stator 12 is described. Referring now to Figures 19 to 24 A method of making a sealed stator is described. Fig.19 is a block diagram 100 illustrating the actions performed in conjunction with the method. Figure 20 to Figure 24 Details are shown regarding the various actions performed using the method.

[0080] like Fig.19 As shown, the method 100 begins at block 110 by placing the slot liner 38 into the slot 22 of the stator core 20. As previously described, the slot liner 38 is inserted into the slot such that the overlapping portion of the slot liner is located at the rear of the slot (ie, the radially outer wall of the slot).

[0081] Next, the method continues to frame 115 by applying the insert side end ring 40 and the weld side end ring 41 to the opposite ends of the stator core 20. As previously described herein, such as Fig.13 The illustrated washers 80 may be used to adhere one or both of the end rings 40 , 41 to opposite ends of the stator core 20 .

[0082] Once the end rings 40 and 41 are in place on the stator core 20 , the method 100 continues at block 120 with forming the stator windings 30 on the core 20 . Fig. 20 An exemplary process for forming a winding is shown. Fig. 20 As shown, the process includes first forming hairpin conductors 32 from lengths of copper wire, the hairpin conductors including U-shaped turns 34 and straight legs 36. Second, the straight legs 36 are inserted into slots 22 of the stator core 20. Third, the ends of the legs 36 are twisted or bent so that the leg ends of one hairpin in one slot are adjacent to the leg ends of a different hairpin in a different slot. Fourth, the adjacent ends of the legs are welded together to form coils around the stator core, which form the stator winding 30.

[0083] Continue to refer to Fig.19 After the stator windings 30 are formed at block 120, the stator is ready for application of insulating filler material (e.g., varnish or epoxy) to the stator windings and end rings 40, 41. As with most stator varnish dripping operations, the stator assembly is rotated during the dripping step and the curing step. Preparation for applying the filler material occurs at block 125, where the stator is preheated at a filler application station and the stator is placed in a horizontal neutral position (i.e., the axis of the stator is arranged horizontally). Fig.21 The stator 12 is shown in this position at a filler application station 190, wherein the shaft 192 of the filler application station is in a horizontal position (ie, as shown in FIG. Fig.21 The stator 12 is shown by arrow 199 in the figure.

[0084] Next, at block 130, the stator is tilted upward in one orientation (e.g., with the weld end facing upward, such as Fig. 22 The degree of inclination may depend in part on the filler material used and the particular arrangement of the stator. An axis inclination of seven degrees (7°) has been determined to be an effective inclination angle (e.g. Fig. 22 ), but any value between two degrees (2°) and fifty degrees (50°) has been determined to be adequate when epoxy filling is used. During this step, the filler material is dripped primarily onto the higher ends of the stator—both the ID and OD—for a first period of time (e.g., eighteen (18) minutes). The filler material is dripped onto the conductors 32 forming the end turns 34, 35, and capillary action causes the filler material to fill between the slot liner 38 and the end rings 40, 41 (i.e., fill to the Figure 7 The filler material in the cavities 66 shown), between the end rings 40, 41 and the stator core 20, between the slot liners 38 and the conductors 32, and between the slot liners 38 and the stator core 20. The filler material in the cavities 66 is particularly advantageous and forms a solid seal between the conductors 32 and the openings 60 of the end rings. More specifically, the filler material in the radially inner portion of the cavities 66 provides an advantageous seal for the ID and prevents oil from leaking into the rotor / stator air gap.

[0085] A plurality of drip tubes are used to drip filler onto the stator 12 at the filler application station 190. The drip tubes include two inner diameter drip tubes located just above the inner lips 42, 23 of the end rings 40, 41 (i.e., vertically relative to the inner lips 42, 23) and two outer diameter drip tubes located just above the outer edges 44, 45 of the end rings 40, 41 (i.e., vertically relative to the outer edges 44, 45). The stator 12 rotates slowly during the dripping process so that the drip tubes cover the entire circumference of the stator during the first time period. Fig.23The positions of the end turns 35 and end rings 41 during the dripping of the filler material are shown. Arrows 198 show that the filler material drips vertically downward due to gravity, contacts the end turns 35 and end rings 41, and spreads in various components on the end of the stator core.

[0086] After applying the filler material for a first period of time, the method Fig.19 Continuing at block 135 of , the stator is returned to a neutral position, wherein the stator axis is in a horizontal position (i.e., zero degrees). At this position, the stator is again dripped with epoxy along the ID and OD (a total of 4 positions) for a second time period as the stator rotates. The second time period is shorter than the first time period. For example, the second time period can be one (1) minute. After the second time period of dripping time, the filler material is partially or fully cured. The filler material can be cured by applying heat (and / or air or light) to the filler material for a period of time.

[0087] Next, the method continues at block 140 by tilting the stator back to the same inclination as the previous inclination (e.g., 7° or whatever inclination was provided at block 130), and again dripping epoxy on the higher end (i.e., welded end) over a third time period (e.g., one (1) minute) at both ID and OD as the stator rotates. At block 145, the method continues by tilting the stator back to a horizontal neutral position (i.e., zero degrees) and again heat curing the stator.

[0088] At this point, the filler material is finished on one end of the stator 12 (e.g., the weld end), and next the filler material is applied to the opposite end (e.g., the crown end). As shown in block 150, the filler material is generally applied to the crown end in a similar manner as the weld end. For example, Fig.24 As shown, the insertion end 14 of the stator 12 can be tilted upward (i.e., the welding end 15 is tilted downward) at a selected inclination (e.g., the axis 192 of the filler application station 190 is tilted negative seven degrees (-7°) or other inclination opposite to the inclination used with the bonding frame 130). The same process is then used to drip filler material onto this end of the stator core for a fourth time period as the stator rotates. Depending on the desired amount of filler material to be applied, the time period can be relatively long (e.g., eighteen (18) minutes) or relatively short (e.g., one (1) minute).

[0089] After the filler material is applied, the process continues at frame 155, returning the stator to a horizontal neutral position. At this point, the most recently applied filler material is heat cured to solidify the filler material. Thereafter, as shown in frame 160, any additional tilting and curing steps, such as those disclosed in conjunction with frames 125, 130, 135, 140, and 145, may be repeated for the opposite end of the stator (i.e., the insertion end 14). For example, each of steps 130, 135, 140, and 145 may be performed on both ends of the stator core. These steps are performed as deemed appropriate by the manufacture of the stator to complete the desired seal between the end rings 40, 41 and the stator core.

[0090] You will realize that when using Fig.19 When applying the filler material according to the application method 100, the end rings 40, 41 include advantageous structures. For example, Fig. 9 As shown, the outer edge 44 of the end ring 40 is made shorter than the inner lip 42 to allow the outer diameter drip tube to be positioned closer to the wire and face of the stator core 20. The inner lips 42, 43 need to be long enough to seal to engage the lip seal 70 and the housing. As another example, the portion of the pocket compartment 52, 53 extending to the radially outer side of the end ring 40, 41 (see Figure 4 and Fig.16 ) is used to capture any overfill epoxy during the trickle process.

[0091] Although this article is related to Figures 1 to 24 One or more embodiments of a sealed stator for an electric machine are provided, but those skilled in the art will appreciate that other implementations and adjustments are possible. As an example, while the ribs 46, 47 between the pockets provide significant strength to the end rings 40, 41, they can also be designed to be shorter in axial height than the height of the outer edges. This will allow excess flow of filler material to flow from one pocket to another before the filler material flows radially outward to the outer edges. As another example, the side of rib 46 can also be similar to rib 47 (see Fig.16 ) are angled to promote flow over the ribs rather than over the outer edge.

[0092] In addition to the foregoing, it will be appreciated that aspects of the various embodiments described herein may be combined or replaced with aspects from other features to obtain embodiments different from those described herein. Therefore, it should be understood that the selected features and functions disclosed above 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 appended claims.

Claims

1. A stator for a motor, the stator comprising: a stator core including a plurality of slots; a winding positioned on the stator core, the winding comprising a plurality of interconnected conductors extending through the plurality of slots, the winding further comprising U-shaped end turns on an insertion end of the stator core and welded end turns on a connection end of the stator core; a first end ring coupled to the insertion end of the stator core, the first end ring comprising a plurality of openings and a plurality of radial ribs, wherein the interconnecting conductor extends through the plurality of openings and the U-shaped end turns engage the radial ribs of the first end ring, the first end ring further comprising an outer edge configured to receive a seal and an inner lip configured to receive a seal; as well as A second end ring is coupled to the connection end of the stator core, the second end ring also including a plurality of openings and a plurality of radial ribs, wherein the interconnecting conductor extends through the plurality of openings and the weld end turns are bent around the radial ribs of the second end ring. 2 . The stator of claim 1 , wherein the first end ring comprises an axially outward side and an axially inward side, wherein a chamfer is formed around a perimeter of each opening on the axially inward side.

3. The stator of claim 2, wherein the slots of the stator include axial openings, and wherein the openings in the first end ring are larger in size than the axial openings to the stator slots.

4. The stator of claim 2 further comprising a plurality of slot liners arranged in the plurality of slots, the plurality of slot liners extending axially through the slots and through the openings in the end rings, each of the plurality of slot liners being positioned between a wall of a slot and a conductor extending through the slot. 5 . The stator of claim 4 , wherein each of the plurality of slot liners extends beyond an end of the stator core by at least 2.8 mm in an axial direction. 6 . The stator of claim 4 , wherein each of the plurality of slot liners includes an overlapping portion disposed along a radially outer wall of the slot.

7. The stator of claim 1 further comprising a first bonding washer positioned between the first end ring and the insertion end of the stator core, and a second bonding washer positioned between the second end ring and the connection end of the stator core.

8. The stator of claim 1, the first end ring further comprising an inner lip extending around an inner diameter of the first end ring, and an outer edge having an outer lip extending around an outer diameter of the first end ring, the stator further comprising an outer ring seal engaging the outer lip of the first end ring.

9. The stator of claim 8, wherein the radial rib connects the outer edge of the first end ring with the inner lip of the first end ring. 10 . The stator of claim 1 , further comprising a temperature sensor mounted on an outer edge of the first end ring or the second end ring.

11. The stator of claim 1 further comprising a cured insulating filler material disposed on the first end ring and the second end ring.

12. The stator of claim 1, wherein the plurality of radial ribs of the first end ring define a plurality of segments of the first end ring, each of the plurality of segments defining a pocket compartment having a pocket floor, wherein the plurality of radial ribs extend axially outward from the pocket floor to a radially flat upper portion.

13. The stator of claim 1 , wherein the plurality of radial ribs of the second end ring define a plurality of segments of the second end ring, each of the plurality of segments defining a pocket compartment having a pocket floor, wherein the plurality of radial ribs are defined by opposing inclined sides that gradually converge toward each other and converge at a radially flat upper portion.

14. The stator of claim 13, wherein the opposed angled sides of the radial ribs extend upward from radial sides of the plurality of openings of the second end ring, and wherein the weld end turns extend parallel to the opposed angled sides of the radial ribs.

15. An end ring for a stator, comprising: an axially outward side portion, the axially outward side portion comprising a plurality of openings and a plurality of radial ribs arranged circumferentially about the end ring, each of the plurality of radial ribs defining opposing inclined side portions that face each other and taper axially outward from a peripheral edge of successive openings and extend to a radially flat upper portion; as well as A flat axially inwardly facing side opposite the axially outwardly facing side.

16. The end ring of claim 15, wherein a chamfered perimeter is formed around each of the plurality of openings on the axially inward side.

17. The end ring of claim 15, wherein the end ring is a monolithic structure constructed of a highly glass filled plastic material.

18. A stator for an electric motor, the stator comprising: a stator core comprising a plurality of slots, a first end, and a second end; windings positioned on the stator core; a first end ring coupled to one of the stator cores, the first end ring including a plurality of openings, wherein the windings extend through the plurality of openings, the first end ring further comprising an outer edge configured to receive a seal and an inner lip configured to receive a seal; as well as A second end ring is coupled to a second end of the stator core, the first end ring including a plurality of openings, wherein the windings extend through the plurality of openings.

19. The stator of claim 18, wherein the second end ring includes an outer edge configured to receive a seal and an inner lip configured to receive a seal.

20. The stator of claim 19, wherein the first end ring includes a plurality of radial ribs, wherein the radial ribs connect the inner lip to the outer edge.

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