Insulation assembly for a stator core

An assembly for providing electrical insulation in a stator core of a vehicular electric machine is provided. The stator core has a channel and the assembly comprises a first conductive element disposed through the channel, and a second conductive element disposed through the channel and substantially adjacent to the first conductive element. The assembly also comprises a first electrically insulating film having a first end residing between the first and second conductive elements.

TECHNICAL FIELD

The present invention generally relates to vehicular electric machines, and more particularly relates to an assembly for electrically insulating conductive elements in the stator core of a vehicular electric machine.

BACKGROUND OF THE INVENTION

In recent years, advances in technology have led to substantial changes in the design of automobiles. One of these changes involves the complexity, as well as the power usage, of various electrical systems within automobiles, particularly alternative fuel vehicles. For example, alternative fuel vehicles such as hybrid vehicles often use electrochemical power sources, such as batteries, ultracapacitors, and fuel cells, to power the electric traction machines (or motors) that drive the wheels, sometimes in addition to another power source, such as an internal combustion engine.

Such traction machines typically include a rotor assembly that rotates on a shaft within a stationary stator assembly. The rotor and stator assemblies each generate magnetic fields that interact with each other to cause the rotor assembly to rotate and produce mechanical energy. The stator assembly typically includes a core having multitude of ferromagnetic annular layers (or laminations) arranged as a stack. Each lamination has several openings that, when aligned, form axial pathways that extend through the length of the core. Conductive elements such as rods, wires, or the like, typically made from copper or a copper alloy, are wound around the lamination core through these openings. Current passing through these conductors driven by a power source such as a battery or fuel cell generates electromagnetic flux that can be modulated as needed to control the speed of the motor.

Conductive elements are typically insulated to prevent shorting between each other and with adjacent stator core laminations. Such insulation generally includes both a non-conductive coating applied to the surface of each conductive element, and an insulating layer placed around a portion of each element's periphery. However, an insulating layer that more completely circumscribes the conductive elements in a stator core is desirable to further reduce the possibility of shorting and increase the overall reliability of electric machines.

Accordingly, it is desirable to provide an assembly for electrically insulating conductive elements in the stator core of a vehicular electric machine having improved insulating characteristics. Further, other desirable features and characteristics of the present invention will become apparent from the subsequent detailed description and the appended claims, taken in conjunction with the accompanying drawings and the foregoing technical field and background.

SUMMARY OF THE INVENTION

In accordance with an embodiment, by way of example only, an assembly for providing electrical insulation in a stator core of a vehicular electric machine is provided. The stator core has a channel and the assembly comprises a first conductive element disposed through the channel, and a second conductive element disposed through the channel and substantially adjacent to the first conductive element. The assembly also comprises a first electrically insulating film having a first end residing between the first and second conductive elements.

DESCRIPTION OF AN EXEMPLARY EMBODIMENT

The various embodiments of the present invention described herein provide an assembly for electrically insulating conductive elements in the stator core of a vehicular electric machine. The insulating layer is configured to circumscribe the peripheries of two adjacent conductive elements and provide a continuous barrier that electrically isolates these elements from each other and from the surfaces of adjacent stator core laminations. The insulating layer configured in this manner contains only minimal self-overlap while providing a more reliable insulating barrier compared to conventional designs.

FIG. 1is a schematic diagram of an exemplary vehicle10, such as an automobile, according to one embodiment of the present invention. The automobile10includes a chassis12, a body14, four wheels16, and an electronic control system (or electronic control unit (ECU))18. The body14is arranged on the chassis12and substantially encloses the other components of the automobile10. The body14and the chassis12may jointly form a frame. The wheels16are each rotationally coupled to the chassis12near a respective corner of the body14.

The automobile10may be any one of a number of different types of automobiles, such as, for example, a sedan, a wagon, a truck, or a sport utility vehicle (SUV), and may be two-wheel drive (2WD) (i.e., rear-wheel drive or front-wheel drive), four-wheel drive (4WD), or all-wheel drive (AWD). The automobile10may also incorporate any one of, or combination of, a number of different types of engines (or actuators), such as, for example, a gasoline or diesel fueled combustion engine, a “flex fuel vehicle” (FFV) engine (i.e., using a mixture of gasoline and alcohol), a gaseous compound (e.g., hydrogen and/or natural gas) fueled engine, or a fuel cell, a combustion/electric motor hybrid engine, and an electric motor.

In the exemplary embodiment illustrated inFIG. 1, the automobile10is a hybrid vehicle, and further includes an actuator assembly (or powertrain)20, a battery array22, a battery state of charge (SOC) system24, a power electronics bay (PEB)26, and a radiator28. The actuator assembly20includes an internal combustion engine30and an electric motor/generator (or electric traction machine) system (or assembly)32. The battery array22is electrically coupled to PEB26and, in one embodiment, comprises a lithium ion (Li-ion) battery including a plurality of cells, as is commonly used. Electric traction machine32typically includes a plurality of electric components, including stator and rotor assemblies. The stator assembly includes an annular core containing a multitude of annular core laminations, and a plurality of conductors (or conductive elements) extending through these laminations. At least one pair of these conductive elements is electrically isolated from adjacent conductive elements and core laminations by an insulating layer configured in accordance with an exemplary embodiment of the invention. The insulating layer substantially circumscribes the peripheries of the pair of conductive elements and provides a continuous insulating barrier between the conductive elements and other stator core elements.

FIG. 2is a cross-sectional side view of vehicular electric machine32, in accordance with an exemplary embodiment. It should be noted that many detailed elements commonly found in such an electric machine have been omitted for greater clarity. Electric machine32includes a housing36, a stator assembly42, a rotor assembly46, and a shaft50. Stator assembly42is contained within and fixedly coupled to housing36. Rotor assembly46is fixedly coupled to shaft50, both elements configured for rotation within stator assembly42about an axis of rotation A-A′. A set of bearings54is coupled to housing36proximate either end thereof, and provide support for, and rotational coupling to, shaft50. Stator assembly42also includes a stator lamination core56having a first end57and a second end58, and having a plurality of individual annular laminations60-68arranged parallel to each other in a stacked, columnar array between these ends. Each individual lamination has at least one opening (or channel) aligned with like openings in each lamination throughout core56. The aligned openings form an axial (substantially parallel to axis of rotation A-A′) pathway through core56that may contain any number of conductive elements (represented by conductive element69) electrically isolated from other elements within core56by an insulating layer to be described in greater detail below. During operation, current flows through conductive element69of core56generating magnetic flux that interacts with flux emanating from rotor assembly46. The flux interaction between core56and assembly46causes assembly46to rotate with shaft50about axis A-A′ generating mechanical energy thereby.

FIG. 3is a cross-sectional front view of electric machine32, in accordance with an exemplary embodiment. Electric machine32includes housing36, lamination core56, rotor assembly46, and shaft50. Stator core56is circumscribed about rotor assembly46, and is fixedly coupled to housing36. Shaft50is rotationally coupled to and supported by bearings54(FIG. 2). Rotor assembly46rotates with shaft50substantially concentrically within core56. Lamination core56includes lamination60proximate a first end57thereof (FIG. 2) having a ferromagnetic annulus70with an inner circumferential edge72substantially concentric within an outer circumferential edge74. Annulus70also includes a plurality of slotted openings78-97merged with inner circumferential edge72, and aligned with similarly arranged slotted openings in each of the laminations of core56. While lamination60is illustrated as having20slotted openings, it is understood that, depending upon the overall design of electric machine32, individual laminations within a stator core may contain any number of such openings.

Four conductive elements are disposed through each of slotted openings78-97, and extend the length of lamination core56substantially axially aligned to each other. For example, conductive elements100-103are disposed through first slotted opening78, each of these conductive elements extending through similar openings in each of the laminations of core56. While four such conductive elements are described and illustrated inFIG. 3as extending through each slotted opening, it is understood that each opening may contain any number of such conductive elements. Elements100-103may assume any form such as that of a rod, a wire, a tube, or the like, having a suitable cross-sectional shape such as, for example, substantially rectangular or circular. Elements100-103are made of an electrically conducting material such as, for example, copper or an alloy of copper. Conductive elements100-103are coated with a suitable non-conducting coating to provide electrical isolation from other adjacent elements including a side surface99of annulus70which forms the boundary of first slotted opening78. Additional insulation is provided by an insulating layer, to be described in greater detail below, which circumscribes adjacent conductive elements into a pairing and forms a substantially continuous electrically insulating barrier around the peripheries of each element.

During operation, current flows through conductive elements100-103in first slotted opening78generating magnetic flux thereby. Pairings of conductive elements are surrounded by an electrically insulating layer that protects each individual conductive element from shorting to adjacent conductive elements and stator core surfaces.

FIG. 4is a cross-sectional view of a portion of lamination60in accordance with an exemplary embodiment, and magnified to more clearly illustrate various features of the invention. Lamination60includes ferromagnetic annulus70having outer circumferential edge74, and first slotted opening78bordering and merged with inner circumferential edge72. First slotted opening78contains first and second conductive elements100and101, respectively, disposed therethrough. First conductive element100has a first side104and second conductive element101has a second side106, both sides substantially axially aligned and adjacent each other. A first electrically insulating layer110resides in first slotted opening78and provides an electrical barrier for the pairing of conductive elements100and101that separates each element from the other and from side surface99. First insulating layer110may be made of a suitable insulating film such as, for example, Nomex® paper. Layer110has a first end118adjacent first side104, that overlaps with a second end120adjacent second side106. Ends118and120are each disposed through first slotted opening78, residing between and substantially aligned with first and second sides104and106. First insulating layer110also has a first section122intermediate between ends118and120that substantially surrounds the remaining peripheries of first and second conductive elements100and101. In one embodiment, first section122substantially surrounds the remaining peripheries of first and second conductive elements100and101without passing between sides104and106. In another embodiment, first insulating layer110has a first edge124proximate first end57of lamination core56(FIG. 2) extending between first and second ends118and120and configured to be B-shaped.

WhileFIG. 4shows first and second ends118and120overlapping substantially over a width126of first and second sides104and106, the region of overlap is not limited to this distance, and may comprise any amount of overlap between sides104and106. Further, while ends118and120overlap each other between sides104and106, first section122surrounds the remaining peripheries of first and second conductive elements100and101without containing an overlapping region. Accordingly, insulating layer110provides an improved insulating barrier for shielding elements100and101from each other and from the side surfaces99of first opening78. Further, the minimal self-overlap of ends118and120only marginally adds extra insulating material inside the slotted openings.

Third and fourth conductive elements102and103are disposed through first slotted opening78and have third and fourth sides128and130, respectively, substantially aligned to each other and to first and second sides104and106. A second insulating layer111substantially surrounds conductive elements102and103as a pairing, and electrically isolates each of these elements from the other, and from adjacent conductive elements and side surface99. Layer111includes a first end132adjacent third side128overlapping with a second end134adjacent fourth side130. Layer111also includes a section136intermediate ends132and134that substantially surrounds the remaining peripheries of third and fourth conductive elements102and103without passing therebetween. In one embodiment, first and second sections122and136overlap each other between second and third conductive elements101and102.

During operation, first and second insulating layers110and111provide insulation to conductive elements100and101, and102and103, respectively. Each insulating layer forms an electrically insulating barrier which substantially surrounds the individual conductive elements of a pairing of conductive elements to prevent shorting to other conductive elements and other surfaces of lamination60such as side surface99.

FIG. 5is an isometric view of a portion of the individual stator core lamination60shown inFIGS. 2-4, and having a plurality of insulating layers integrated therein, in accordance with an embodiment of the invention. Lamination60includes annulus70having a plurality of slotted openings78-81merged into inner circumferential edge72. Each of slotted openings78-81is arranged so as to align with like openings in adjacent laminations forming a continuous channel or pathway that extends substantially axially through stator lamination core56(FIG. 2). Two members of insulating layers110-117are disposed in each of slotted openings78-81. For example, first and second insulating layers110and111, respectively, are disposed in first opening78, each layer extending axially as a continuous film through lamination core56(FIG. 2). Insulating layers110-117are each configured to form a “B” shape in cross-section, and have two openings. Each opening is thus substantially bounded by a portion of an insulating layer to provide electrical isolation to an individual conductive element.

For the sake of clarity, only first insulating layer110is depicted as containing such a pairing of conductive elements, while second insulating layer111is shown without conductive elements to better illustrate the form and spatial arrangement of an insulating layer. That is, first insulating layer110forms first and second openings140and142, respectively, these openings axially aligned and configured to receive first and second conductive elements100and101, respectively. Second insulating layer111includes first and second ends132and134adjacent and overlapping each other, and extending axially through first opening78and across the length of lamination core56(FIG. 2). Second insulating layer111also includes second section136intermediate between first and second ends132and134that, in conjunction therewith, forms third and fourth openings144and148, respectively. Openings144and148are each configured to receive and electrically insulate a conductive element (not illustrated) similar to elements100or101. While the foregoing description includes insulating layers described as having ends and sections, it should be understood that each insulating layer is a continuous, integrally-formed layer or film, and that such descriptors refer to portions of the continuous layer rather than to discreetly separate elements thereof.

The various embodiments of the present invention described herein provide an insulating layer for conductive elements in a stator lamination core of a vehicular electric machine. The insulating layer has a “B-shaped” cross sectional configuration, and forms an electrically insulating barrier by substantially surrounding the peripheries of each of a pair of conductive elements. The insulating layer thereby prevents these elements from shorting to each other or to core lamination surfaces. This configuration features only minimal self-overlap of the insulating layer, and thus adds only marginal additional weight to a stator assembly. Accordingly, the insulating layer provides enhanced electrical isolation for stator core conductive elements, and may be conveniently incorporated into existing stator assembly designs.