Electric machine with insulator spacer

A stator assembly for an electric machine including a stator core supporting a plurality of electrical conductors. A plurality of elongated insulator spacers is interwoven between the conductors proximate connection ends thereof in axially spaced relation to the stator core.

BACKGROUND AND SUMMARY OF THE INVENTION

The present invention relates generally to electric machines and, more particularly, to insulator spacers provided proximate the connection ends of conductors above a stator core.

Electric machines may be used for a variety of applications, including in connection with automobile power trains. For example, a conventional automobile may use an electric machine as a starting motor for an internal combustion engine, or as an alternator to generate electricity and deliver power to vehicle accessories and/or charge a vehicle's battery. It is also known to use electric machines as traction motors, for example with hybrid/electric vehicles.

It is known in such electric machines to manufacture a stator assembly by using pre-formed conductors. To complete the electrical circuit, the free ends of the conductor are bent or twisted for alignment and then joined together in a particular arrangement. The twisting process, due to complex geometry and the number of conductors, may yield significant variations in spacing from one conductor to another conductor. Inadvertent electric contact between the various conductors may cause the stator assembly to not function properly. In order to accommodate these dimensional variations, the degree of conductor twisting may be minimized, resulting in an increased length of the motor and/or a reduction of power density.

The present disclosure relates to elongated insulator spacers woven between various conductors at the free ends thereof prior to twisting in a pattern that protects the conductors from touching or damaging adjacent conductors. As such, the overall length of the motor may be reduced, or the power may be increased in the same length. Further, such insulator spacers improve the durability and resultant life of the electric machine by preventing potentially damaging contact between adjacent conductors.

According to an illustrative embodiment of the present disclosure, a stator assembly includes a stator core including a sidewall extending about a longitudinal axis. A first conductor layer includes a plurality of circumferentially spaced electrical conductors defining an annular ring, and a second conductor layer including a plurality of circumferentially spaced electrical conductors defining an annular ring, the second conductor layer being positioned radially outwardly from the first conductor layer. A first insulator spacer formed of an electrically non-conductive material is interwoven between the first and second conductive layers by extending alternately between outer and inner surfaces of circumferentially adjacent electrical conductors of the first conductor layer. A second insulator spacer formed of an electrically non-conductive material is interwoven between the first and second conductive layers by extending alternately between outer and inner surfaces of circumferentially adjacent electrical conductors of the second conductor layer.

According to a further illustrative embodiment of the present disclosure a stator assembly including a stator core, and a plurality of electrical conductors supported within the stator core and extending axially between opposing first and second end portions, the first and second end portions positioned outside of the stator core, the plurality of conductors being arranged in a plurality of concentric layers. A first elongated insulator spacer is interwoven in a substantially sinusoidal path between the plurality of conductors proximate the second ends outside of the stator core, the insulator spacer being formed of an electrically non-conductive material.

According to another illustrative embodiment of the present disclosure a method of forming a stator assembly of an electric machine includes the steps of providing a stator core having a plurality of slots extending axially between an insertion end and an opposing connection end, and inserting a plurality of electrical conductors within the slots of the stator core. The method further includes the steps of positioning an insulator spacer in axially spaced relation to the stator core proximate the connection end of the stator core, the insulator spacer formed of an electrically non-conductive material, and aligning the insulator spacer with spaces intermediate the plurality of electrical conductors. The method also includes moving the insulator spacer toward the connection end of the stator core such that the insulator spacer is pushed into the spaces intermediate the plurality of electrical conductors and interwoven in a substantially sinusoidal path between the electrical conductors.

DETAILED DESCRIPTION OF THE DRAWINGS

Referring initially toFIG. 1, an illustrative stator assembly10of an electric machine11prior to final assembly is shown. The stator assembly10includes an insertion end14and an opposing connection end12. The electric machine11when used as a motor (such as a starting motor or traction motor) includes the stator assembly10operably coupled to a rotor (not shown) through magnetic fields in order to convert electric energy to mechanical energy. In a similar manner, the electric machine11may also be used as an alternator or generator to generate electricity by converting mechanical energy to electric energy through magnetic fields and delivering power, for example, to vehicle accessories and/or to charge a vehicle's battery.

The stator assembly10illustratively includes a stator core or stack20, and a plurality of electrical conductors, or windings30. The stator core20includes a cylindrical side wall22extending about a longitudinal axis23and defining an open center portion24. An axial direction A extends through the open center portion24between the insertion end14and the opposing or connection end12of the stator assembly10, and a radial direction R extends perpendicular to the axial direction A away from the longitudinal axis23toward the side wall22. In certain illustrative embodiments, the cylindrical side wall22may include one or more lamination stacks or layers (not shown). In certain illustrative side embodiments, the cylindrical side wall22may be comprised of silicone steel, which reduces hysteresis and eddy current losses during the operation of the electric machine11. Alternatively, the cylindrical side wall22may be comprised of a solid powdered metal body. Furthermore, the stator core20may include a metal (e.g., steel) frame (not shown).

The cylindrical side wall22of the stator core20extends between a circumferential inner surface32and a circumferential outer surface34, and illustratively includes a plurality of circumferentially-spaced, axially-extending slots36(FIG. 6A) through which the conductors30are received. The illustrative stator core20ofFIGS. 1-3includes 60 (sixty) slots36. Openings to the stator slots36are illustratively provided through the inner surface32of the stator core20, as well as the insertion end14and the connection end12of the stator core20.

Illustratively, the slots36each support at least a portion of the conductors30, arranged in armature winding sets, including first (or inner) and second (or outer) winding sets38and40, respectively. More particularly, each slot36illustratively includes a portion of both winding sets, including first winding set38and second winding set40. The first winding set38in each slot36includes two conductors30of one phase, and the second winding set40in each slot36includes two conductors30of another phase. Similarly, each of the other slots36in the illustrative embodiment also comprises two conductors30of one phase and two conductors30of another phase. In other illustrative embodiments, it is also possible that each of the slots36contain all four conductors30of the same phase. The illustrative winding arrangement discloses herein is a three-phase winding arrangement, including phases A, B, and C. However, it should be appreciated that the present disclosure may be applied to other multi-phase winding arrangements.

The conductors30are illustratively formed of an electrically conductive material, such as copper, having a rectangular cross-section, and are used to form the armature winding sets38and40. With reference toFIGS. 1-6A, the conductors30are illustratively arranged in four concentric rings or layers, with a first layer42positioned closest to the inner surface32of the stator core20, followed by a second layer44positioned radially outwardly from the first layer42, a third layer46positioned radially outwardly from the second layer44, and a fourth layer48positioned radially outwardly from the third layer46and positioned closest to the outer surface34of the stator core20. The first and second layers42and44define the first winding set38, while the third and fourth layers46and48define the second winding set40. While rectangular cross-section conductors30may be utilized in order to appropriate the advantages of semi-closed or fully-closed armature slots with a high slot fill ratio (SFR), other conductors (e.g., circular cross-section) may be substituted therefor.

With reference toFIGS. 6A-9, each conductor30illustratively includes a radial inner surface52and a radial outer surface54. Opposing circumferential side surfaces56and58connect the inner and outer surfaces52and54, defining a substantially rectangular cross-section. Each conductor30includes a first or turn end portion59positioned external to the stator core20adjacent to the insertion end14, and an opposing second, connection or weld end portion60positioned external to the stator core20adjacent the connection end12. As further detailed herein, the weld end portions60provide electrical communication between selected conductors30to define the winding sets38and40.

A plurality of electrical insulator spacers62,64,66, and68are illustratively supported adjacent the connection ends of the conductors30in substantially parallel paths extending within planes positioned substantially perpendicular to the longitudinal axis23of the stator core20. As further detailed herein, the insulator spacers62,64,66, and68are illustratively interwoven between the conductor layers42,44,46,48for electrically insulating the connector end portions60of each electrical conductor30from each radially and circumferentially adjacent conductor30.

In the illustrative embodiment shown inFIG. 6A, a first insulator spacer62is formed of an electrically non-conductive material and is interwoven between the first and second conductive layers42and44by extending alternately between inner and outer surfaces52and54of circumferentially adjacent electrical conductors30of the first conductor layer42. A second insulator spacer64formed of an electrically conductive material is interwoven between the first and second conductive layers42and44, and between the second and third conductive layers44and46, by extending alternately between the inner and outer surfaces52and54of circumferentially adjacent electrical conductors of the second conductor layer44. A third insulator spacer66formed of an electrically non-conductive material is interwoven between the second and third conductive layers44and46, and between the third and fourth conductive layers46and48, by extending alternately between inner and outer surfaces52and54of circumferentially adjacent electrical conductors30of the third conductor layer46. Finally, a fourth insulator spacer68formed of an electrically non-conductive material is interwoven between the third and fourth conductive layers46and48by extending alternately between inner and outer surfaces52and54of circumferentially adjacent electrical conductors30of the fourth conductor layer48.

With further reference toFIGS. 6 and 7, the plurality of insulator spacers62,64,66,68provide electrical insulation spacing in both radial and circumferential directions between each adjacent conductor30. More particularly, each insulator spacer62,64,66,68is interwoven between the electrical conductors30of a particular layer42,44,46,48, respectively. In the illustrative embodiment, each insulator spacer62,64,66,68follows a zigzag and illustratively sinusoidal path between inner and outer surfaces52and54of circumferentially adjacent electrical conductors30of a particular layer42,44,46,48. A first portion70of each insulator spacer62,64,66,68forms a radial insulating member, while a second portion72of each insulator spacer62,64,66,68forms a circumferential insulator member (FIG. 6).

With further reference toFIGS. 6A-6B, the insulator spacers62,64,66,68may be interwoven in a variety of manners between the conductors30. For example, each insulator spacer62,64,66,68may span one or more conductors in the circumferential and/or radial direction in a single cycle of its weaving pattern. For example, first insulator spacer62may extend alternately between inner and outer surfaces52and54of circumferentially adjacent electrical conductors30of the first and second conductor layers42and44, respectively. In the illustrative embodiment shown inFIG. 6B, insulator spacers63,65,67,69may crisscross insulator spacers62,64,66,68. In other words, insulator spacers62and63may alternate paths between inner and outer surfaces52and54of conductors30of the first layer42, and insulator spacers64and65may alternate paths between inner and outer surfaces52and54of conductors30of the second layer44. Similarly, insulator spacers66and67may alternate paths between inner and outer surfaces52and54of conductors30of the third layer46, while insulator spacers68and69may alternate paths between inner and outer surfaces52and54of conductors30of fourth layer48.

As described above, the plurality of electrical conductors30includes opposing end portions59and60positioned axially outwardly from the stator core20. The insulator spacers62,64,66,68are positioned axially outwardly from the stator core20adjacent the weld end portions60of the electrical conductors30. With reference toFIG. 7, the weld end portions60of the electrical conductors30are bent to include an inner axial leg74, an outer axial leg76, and an inclined portion78connecting the inner and outer axial legs74and76. Each of the insulator spacers62,64,66,68is configured to engage the inclined portions78of the respective electrical conductors30.

Illustratively, each of the first, second, third, and fourth insulator spacers62,64,66,68may include upper and lower insulator spacers. With reference toFIGS. 2,3, and7, an upper first insulator spacer62ais positioned above a lower first insulator spacer62b, both of which are configured to engage the inclined portions78of the conductors of the first layer42. An upper second insulator spacer64ais positioned above a lower second insulator spacer64b, both of which are configured to engage the inclined portions78of the conductors30of the second layer44. Similarly, an upper third insulator spacer66ais positioned above a lower third insulator spacer66b, both of which are configured to engage the inclined portions78of the conductors30of the third layer46. Finally, an upper fourth insulator spacer68ais positioned above a lower fourth insulator spacer68b, both of which are configured to engage the inclined portions78of the conductors30of the fourth layer48. Illustratively, the upper insulator spacers62a,64a,66a,68aare positioned within a common upper plane while the lower insulator spacers62b,64b,66b,68bare positioned within a common lower plane.

With reference toFIGS. 8 and 9, the insulator spacers62,64,66,68may take different forms or configurations. In the illustrative configurations, the insulator spacers62,64,66,68are formed of continuous, endless loops extending circumferentially 360 degrees proximate the connection end12of the stator core20.FIG. 8illustrates insulator spacers62,64,66,68each formed of an interwoven round cord having a circular cross-section, whileFIG. 9illustrates insulator spacers62,64,66,68each formed of a planar strip having a rectangular cross section. In both configurations, the insulator spacers62,64,66,68may be formed of any electrically non-conductive or insulating material through conventional manufacturing processes (machining, molding, extruding, etc.). In certain embodiments electrically insulating fibers, such as glass, polymer, or aramide (aromatic polyamide) fibers, are woven together to form the desired cross-sectional shape (e.g., round cord or rectangular strip). Aramid fibers may include meta-aramid (Nomex®) and/or para-aramid (Kevlar®) fibers.

An illustrative method of forming the stator assembly10detailed herein includes the steps of providing the stator core20with the plurality of slots36extending axially between opposing insertion and connection ends12and14. A plurality of electrical conductors30are inserted within the slots36of the stator core20resulting in the assembly shown inFIG. 1. The inserting step illustratively includes inserting a plurality of circumferentially spaced electrical conductors30in an annular ring defining a first conductive layer42, inserting a plurality of circumferentially spaced electrical conductors30in an annular ring defining a second conductive layer44positioned radially outwardly from the first conductive layer42, inserting a plurality of circumferentially spaced electrical conductors30in an annular ring defining a third conductive layer46positioned radially outwardly from the second conductive layer44, and inserting a plurality of circumferentially spaced electrical conductors30in an annular ring defining a fourth conductive layer48positioned radially outwardly from the third conductive layer46.

Next, a holding tool80receives and positions the plurality of insulator spacers62,64,66,68in axially spaced relation to the stator core20proximate the connection end12. The holding tool80then aligns the insulator spacers62,64,66,68with spaces intermediate the plurality of electrical conductors30to define the plurality of parallel sinusoidal paths detailed herein. The aligning step further includes aligning the first insulator spacer62to extend alternately between inner and outer surfaces52and54of circumferentially adjacent electrical conductors30of the first conductive layer42, aligning the second insulator spacer64to extend between inner and outer surfaces52and54of circumferentially adjacent electrical conductors30of the second conductive layer44, aligning the third insulator spacer66to extend between inner and outer surfaces52and54of circumferentially adjacent electrical conductors30of the third conductive layer46, and aligning the fourth insulator spacer68to extend between inner and outer surfaces52and54of circumferentially adjacent electrical conductors30of the fourth conductive layer48.

The holding tool80next moves the insulator spacers62,64,66,68toward the connection end12of the stator core20such that the insulator spacers62,64,66,68are pushed into spaces (alternating circumferential and radial spaces) intermediate the plurality of electrical conductors30, and interwoven into substantially sinusoidal paths between the electrical conductors30. The holding tool80illustratively locates the plurality of insulator spacers62,64,66,68at a depth appropriate such that the insulator spacers62,64,66,68contact the inclined portions78of the respective electrical conductors30.

Next, a forming tool82as shown inFIG. 2may be aligned above the sub-assembly for bending or twisting the connector end portions60of the electrical conductors30. The bending step includes bending or twisting connector end portions60of the electrical conductors30such that they include inner axial leg74, outer axial leg76, and inclined portion78. As noted above, the insulator spacers62,64,66,68have been pre-set such that they align with the inclined portions78of the respective electrical conductors30.

Radially adjacent connection end portions60of the electrical conductors30of the first and second conductive layers42and44are illustratively electrically connected together, and radially adjacent connection end portions60of the electrical conductors30of the first and fourth conductor layers46and48are illustratively electrically connected together. Such electrical connections are typically formed through a welding process. Other conventional coupling methods may be substituted for welding, such as soldering or crimping. For example, a welding torch84such as a plasma torch or other conventional heating device for melting and welding metals, may be positioned adjacent the connection end portions60of the conductors30to be welded together. A holding device (not shown) may be utilized to hold the adjacent connection end portions60during the welding process. The torch84welds together the end portions60of the conductors30in order to form a desired weld joint.