Patent Publication Number: US-2023163652-A1

Title: Stator core with cuffed slot liner

Description:
TECHNICAL FIELD 
     This disclosure relates to electric machines. 
     BACKGROUND 
     Electric machines are used to propel and brake vehicles. They often include wires wound within a stator core. 
     SUMMARY 
     An electric machine includes a stator core defining a plurality of slots, slot liners disposed within the slots and configured to cover inner surfaces of the slots, and windings wound within and between the slots. Each of the slot liners has an end extending away from a face of the stator core and defining a flange that includes a rim in direct contact with the face and a terminating lip that is wider than the rim. The flange may taper from the lip to the rim. The flange may include a curved portion between the lip and the rim. Each of the slot liners may have a plurality of groves extending between opposite faces of the stator core. The grooves may be wavy. The electric machine may further include varnish around portions of the windings and within the grooves that mechanically retains the windings within the slot liners. The slot liners may comprise epoxy resin. 
     A method of making an electric machine includes positioning a support between a face of a stator core of the electric machine and a terminating lip of a flange of a slot liner that is within a slot of the stator core such that the support is underneath the terminating lip and adjacent to a rim of the slot liner, bending a wire extending out and away from the slot over the terminating lip and support, and removing the support from underneath the terminating lip. The method may further include filling the slot liner with varnish such that grooves defined by the slot liner take up some of the varnish. 
     A slot liner for a slot of an electric machine includes walls configured to cover inner surfaces of a slot of a stator core, and an end contiguous with the walls that is configured to extend away from a face of the stator core, and defining a flange. The flange includes a rim configured to be carried by and in direct contact with the face and a terminating lip that is wider than the rim. The flange may taper from the lip to the rim. The flange may further include a curved portion between the lip and the rim. The walls may define a plurality of groves extending between opposite ends thereof. The grooves may be wavy. A material of the slot liner may be epoxy resin. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG.  1    is a side view of portions of an electric machine. 
         FIG.  2    is a perspective view of the stator core, slots, and slot liners of the electric machine of  FIG.  1   . 
         FIG.  3    is a perspective view of one of the slot liners of  FIG.  2   . 
         FIG.  4    is a close-up view of the stator core, and one of the slots and slot liners of  FIG.  2   . 
         FIG.  5   . is a close-up view of the electric machine of  FIG.  1    during assembly. 
         FIG.  6    is a block diagram of a vehicle. 
     
    
    
     DETAILED DESCRIPTION 
     Embodiments are described herein. It is to be understood, however, that the disclosed embodiments are merely examples and other embodiments may take various and alternative forms. The figures are not necessarily to scale. Some features could be exaggerated or minimized to show details of particular components. Therefore, specific structural and functional details disclosed herein are not to be interpreted as limiting, but merely as a representative basis for teaching one skilled in the art. 
     Various features illustrated and described with reference to any one of the figures may be combined with features illustrated in one or more other figures to produce embodiments that are not explicitly illustrated or described. The combinations of features illustrated provide representative embodiments for typical applications. Various combinations and modifications of the features consistent with the teachings of this disclosure, however, could be desired for particular applications or implementations. 
     An electric machine includes a number of windings that are electrically driven to produce torque, and may be a three-phase machine that is driven by a three-phase inverter. The windings of the electric machine may be connected to the inverter in a delta or a wye configuration. 
     An electrified vehicle may include a plurality of electric machines. In some examples, one of the electric machines may function primarily as a motor and the other may function primarily as a generator. The motor may operate to convert electricity to mechanical power and the generator may operate to convert mechanical power to electricity. In other examples, an electric machine may be disposed at one or more wheels to provide propulsion and/or regeneration. 
     Referring to  FIGS.  1  and  2   , an electric machine  10  includes a stator core  12 , slots  14 , slot liners  16 , and windings  18 . The stator core  12  is formed by a stack of laminations, and defines a central cavity in which a rotor is sized for disposal and operation. A shaft may be operably connected to the rotor to receive drive torque resulting from electric machine output rotation of the rotor about its axis. 
     The slots  14 , and slot liners  16  therein, are spaced around the stator core  12 . The windings  18  are wound within the slots  14  and about the stator core  12  to generate an electromechanical field within the central cavity when energized to drive the rotor. The windings  18  may be routed throughout the slots  14  in a serpentine fashion to create one or more winding paths to transmit current though the stator core  12 . Based on the arrangement of the windings  18 , portions thereof may protrude from a twist side  20  and a crown side  22  of the stator core  12 . The windings  18 , in some examples, comprise copper hairpins that are inserted axially through the slots  14  such that end portions  24  thereof protrude beyond the twist side  20  as shown. 
     During electric machine assembly, the end portions  24  may initially be straight before being bent or twisted into the form shown with the assistance of various tools. Direct contact between such tools and the end portions  24  may result in loss of any coating on the end portions  24 . 
     Referring to  FIGS.  2 ,  3 , and  4   , the slot liners  16  have walls  26  that cover inner surfaces of the slots  14  to prevent direct contact between the stator core  12  and windings  18 . Moreover, the slot liners  16  extend away from the twist and crown sides  20 ,  22  of the stator core  12 . In this example, each of the slot liners  16  has, in cross-section, a generally rectangular-shape matching a shape of the slots  14  and defines an open portion  26  that the windings  18  may pass through when being wound onto the stator core  12 . 
     Ends  28  of the slot liners  16  extending away from the twist face  20  of the stator core  12  each define a flange that includes a rim  30  in direct contact with and carried by the twist face  20  of the stator core  12 , and a terminating lip  32  that is wider than the rim  30 . The terminating lip  32  thus provides a platform over which the windings  18  extending out from the slots  14  may be bent. The flange further defines a concave or tapered portion  34  between the rim  30  and terminating lip  32 , which further supports the platform provided by the terminating lip  32 . 
     The walls  26 , in this example, include optional grooves or hairline crevices  36  that extend between opposite ends of the slot liner  16 . The grooves  36  may be straight, wavy, or have any other type of desired configuration to reduce insertion forces during winding and provide retention cavities for varnish  38  filling the slot liner  16  during assembly. 
     The slot liners  16  may be over-molded onto the stator core  12  in epoxy resin or similar materials, and the walls  26  may have a thickness in the range, for example, of 0.2 mm to 0.3 mm. 
     Referring to  FIG.  5   , a support tool  40  is positioned under the terminating lip  32  and adjacent to the rim  30  of one of the slot liners  16 . The windings  18  extending from within and away from the slot  14  can then be bent over the terminating lip  32  and support tool  40  without contacting the support tool  40 . Once complete, the varnish  38  is then added to fill the slots  14 , surround the windings  18  contained therein, and is taken up by the grooves  36  via capillary action. The varnish  38 , once cured, thus mechanically retains the windings  18  within the slots  14 . 
     The electric machine  10  may be used within the context of an automotive vehicle as suggested above. Referring to  FIG.  6   , a hybrid-electric vehicle  41  includes an electrified propulsion system having one or more the electric machines  10  mechanically coupled to a hybrid transmission (not shown). The electric machines  10  may be capable of operating as a motor or a generator. In addition, the hybrid transmission is mechanically coupled to an internal combustion engine  42 . The electric machines  10  are arranged to provide propulsion torque as well as slowing torque capability either while the engine  42  is operated or turned off. The electric machines  10  are capable of operating as generators to provide fuel economy benefits by recovering energy that would normally be lost as heat in a friction braking system. The electric machines  10  may additionally impart a reaction torque against the engine output torque to generate electricity for recharging a traction battery while the vehicle  41  is operating. The electric machines  10  may further reduce vehicle emissions by allowing the engine  42  to operate near the most efficient speed and torque ranges. When the engine  42  is off, the vehicle  41  may be operated in an electric-only drive mode using the electric machines  10  as the sole source of propulsion. The hybrid transmission is also mechanically coupled to road wheels to output torque from the electric machines  10  and/or combustion engine  42 . 
     A traction battery or battery pack  44  stores energy that can be used to power the electric machines  10 . The battery pack  44  provides a high-voltage direct current (DC) output. One or more contactors  46  may isolate the traction battery  44  from a DC high-voltage bus  48  when opened and couple the traction battery  44  to the DC high-voltage bus  48  when closed. The traction battery  44  is electrically coupled to one or more power electronics modules  50  via the DC high-voltage bus  48 . The power electronics module  50  is also electrically coupled to the electric machines  10  and provides the ability to bi-directionally transfer energy between an alternating current (AC) high-voltage bus  52  and the electric machines  10 . In some examples, the traction battery  44  may provide DC while the electric machines  10  operate using three-phase AC. The power electronics module  50  may convert the DC to three-phase AC to operate the electric machines  10 . In regenerative mode, the power electronics module  50  may convert the three-phase AC current output from the electric machines  10  acting as generators to DC compatible with the traction battery  44 . The description herein is equally applicable to an all-electric vehicle without a combustion engine. 
     In addition to providing energy for propulsion, the traction battery  44  may provide energy for other vehicle electrical systems. The vehicle  41  may include a DC/DC converter module  54  that is electrically coupled to the high-voltage bus  48 . The DC/DC converter module  54  may be electrically coupled to a low-voltage bus  56 . The DC/DC converter module  54  may convert the high-voltage DC output of the traction battery  44  to a low-voltage DC supply that is compatible with low-voltage vehicle loads  58 . High-voltage loads  60  are also electrically coupled to the high-voltage bus  48 . 
     The traction battery  44  may be recharged by an off-board power source  62 , which may be a connection to an electrical outlet. The external power source  62  may be electrically coupled to a charger or another type of electric vehicle supply equipment (EVSE)  64 . The off-board power source  62  may be an electrical power distribution network or grid as provided by an electric utility company. The EVSE  64  provides circuitry and controls to regulate and manage the transfer of energy between the power source  62  and the vehicle  41 . The off-board power source  62  may provide DC or AC electric power to the EVSE  64 . The EVSE  64  is outfitted with a connector  66  that mates with a charge port  68  of the vehicle  41 . The charge port is electrically coupled with a charge module  70  that can be electrically coupled with the traction battery  44  via the one or more contactors  46 . 
     The various components discussed may have one or more associated controllers to control, monitor, and coordinate the operation of the components. The controllers may communicate via a serial bus (e.g., Controller Area Network (CAN)) or via discrete conductors. In addition, a vehicle system controller  72  may be provided to coordinate the operation of the various components such as governing electrical flow to and from the one or more electric machines  10 . 
     While exemplary embodiments are described above, it is not intended that these embodiments describe all possible forms encompassed by the claims. The words used in the specification are words of description rather than limitation, and it is understood that various changes may be made without departing from the spirit and scope of the disclosure. 
     As previously described, the features of various embodiments may be combined to form further embodiments of the invention that may not be explicitly described or illustrated. While various embodiments could have been described as providing advantages or being preferred over other embodiments or prior art implementations with respect to one or more desired characteristics, those of ordinary skill in the art recognize that one or more features or characteristics may be compromised to achieve desired overall system attributes, which depend on the specific application and implementation. These attributes may include, but are not limited to strength, durability, marketability, appearance, packaging, size, serviceability, weight, manufacturability, ease of assembly, etc. As such, embodiments described as less desirable than other embodiments or prior art implementations with respect to one or more characteristics are not outside the scope of the disclosure and may be desirable for particular applications.