LAMINATE FOR STATOR CORE WITH FLUID CONTAINMENT FEATURE

A laminate for a stator core, the laminate includes an annular body defining an inner edge, a plurality of wire slots extending radially outward from the inner edge, and a containment zone disposed radially outward of the plurality of wire slots. The containment zone is configured to contain fluid applied radially outward from the plurality of wire slots.

FIELD

The present disclosure relates to electric motors, and more particularly to maintenance of electric motor components.

BACKGROUND

Electric propulsion systems in vehicles use electric motors to propel the vehicle as an alternative or in addition to internal combustion engines. Generally, varnish is applied to the electric motors to protect against corrosion and contaminant, thereby improving an operation life of the electric propulsion system. The varnish can be applied with a machine designed to apply the varnish to various components of the motors. During application, varnish may flow away from an intended location or component that uses the varnish, increasing the total amount of varnish used and potentially disrupting operation of other parts of the electric motor.

The present disclosure addresses challenges related to varnish application to electric motors.

SUMMARY

A stator assembly for an electric motor includes a stator core including a cylindrical body defining a bore providing an inner surface, a plurality of wire slots extending radially outward from the inner surface, and a containment zone disposed radially outward of the plurality of wire slots. The containment zone is configured to contain fluid applied to a surface of the stator core spaced from the wire slot.

In variations of the assembly, which may be implemented individually or in combination: the cylindrical body comprises a plurality of laminates, and the containment zone is defined in an outermost one of the plurality of laminates; the cylindrical body further defines a fastener slot, wherein the containment zone is disposed radially inward of the fastener slot; the stator core further comprises a visible pattern formed on an outer surface of the cylindrical body, wherein the containment zone is disposed radially inward of the visible pattern; the containment zone is a chamber defined within the cylindrical body; the chamber is defined between an outermost laminate and an adjacent laminate.

In another form, a laminate for a stator core includes an annular body defining an inner edge, a plurality of wire slots extending radially outward from the inner edge, and a containment zone disposed radially outward of the plurality of wire slots. The containment zone is configured to contain fluid applied radially outward from the plurality of wire slots.

In variations of the laminate, which may be implemented individually or in combination: further including an adhesive disposed radially outward of at least one of the plurality of wire slots; the containment zone is disposed radially outward of the adhesive; the containment zone is disposed between the adhesive and at least one of the plurality of wire slots; further including a visible pattern formed on an outer surface of the annular body, wherein the containment zone is disposed radially inward of the visible pattern; the annular body further defines a fastener slot, wherein the containment zone is disposed radially inward of the fastener slot; the annular body further defines a plurality of containment zones disposed circumferentially around the laminate; the containment zone is a hole extending through the annular body; the hole is substantially arcuate.

In another form, a stator core assembly for an electric motor includes a stator core including a plurality of laminates arranged in an axial direction, each laminate defining a plurality of wire slots extending radially from an inner edge. The plurality of laminates includes an outermost laminate defining a containment zone disposed radially outward of the plurality of wire slots of the outermost laminate and extending axially toward an adjacent laminate. The containment zone of the outermost laminate is configured to collect fluid applied on an outermost surface of the stator core away from the plurality of wire slots.

In variations of the assembly, which may be implemented individually or in part: further including an adhesive adhering adjacent ones of the plurality of laminates, wherein the containment zone is disposed radially outward of the adhesive; further including an adhesive adhering adjacent ones of the plurality of laminates, wherein the containment zone is disposed radially between the adhesive and at least one of the plurality of wire slots; the containment zone is a chamber defined by a hole extending through the outermost laminate to an adjacent laminate; the stator core further comprises a visible pattern formed on an outer surface of the cylindrical body, wherein the containment zone is disposed radially inward of the visible pattern.

DETAILED DESCRIPTION

Among other components, an electric motor includes a stator that is a stationary component generating an electromagnetic field and a rotor which rotates relative to the stator due to the electromagnetic field. The electric motor is a component of an electric propulsion for a motor vehicle such as an “electric vehicle.” The electric motor propels the motor vehicle by rotating one or more wheels of the motor vehicle. In one example, the electric motor is a sole propulsion of the vehicle, such as in a fully electric vehicle. Alternatively, the electric motor can be part of a hybrid propulsion that includes an internal combustion engine, such as in a hybrid-electric vehicle.

With reference toFIGS.1-2, an example of a stator20for an electric motor is illustrated and includes a stator core22and a plurality of wires24. The stator core22has a substantially cylindrical body26defining a bore28extending therethrough. The bore28provides an inner surface30of the body26. The stator core22further defines a plurality of slots32extending radially outward from the inner surface30.

In one form, one or more wires24from among the plurality of wires24reside in each slot32. The wires24are formed of an electrically conducting material, such as copper. With the wires24arranged in the slots32, electric current flow through the wire24generating electromagnetic field that drives the rotor.

With reference toFIG.2, a cross-sectional view of the stator20is shown. To inhibit corrosion or deterioration of electrical properties of the wires24and to improve durability of the stator20by holding stator laminates and/or copper wires and/or intermediate paper layers together in a generally rigid manner, a varnish (not shown) is applied to the stator during assembly of the electric motor and hardens or cures into a generally rigid form that holds the components of the stator20together. The varnish is typically applied to an outermost surface of the stator core22with a varnish injector34having an injector nozzle. In an example application, varnish is applied to the slot32and onto the wires24as well as into a gap between a surface of the slot32and the intermediate paper layer (not shown). Specifically, the varnish flows in narrow spaces (i.e., capillaries), such as the slot32, by adhesion, viscosity, and/or surface tension with the slot32without significant influence by, or even against, the force of gravity. During application, the stator core22is rotated to allow the varnish injector34to apply the varnish to each of the slots32and the wires24therein. When applying varnish to the stator core22, excess varnish spreading away from the slot32(i.e., “stray” varnish) may interfere with other parts of the stator20, potentially inhibiting operation thereof, and increases a total amount of varnish needed for the stator core22. Controlling flow of varnish into the slots32reduces a total amount of varnish used and improves manufacturing of the electric motor, addressing this concern with conventional stator cores.

In one application, the stator core22includes a plurality of laminates40, including an outermost laminate40aas shown inFIG.3and one or more inner laminates40b, shown inFIGS.4A-4B. The outermost laminate40ahas an annular body42defining an inner edge44that forms part of the inner surface30facing the bore28. A plurality of wire slots46extend radially outward from the inner edge44. The wire slots46extend axially toward respective wire slots46of adjacent laminates40, forming the slots32of the stator core22when the laminates40are stacked together. The laminate40may also include one or more fastener slots48configured to receive a fastener (not shown), such as a bolt. The fastener extends through the fastener slots48of the laminates40to secure the laminates40of the stator core22to each other.

In one form, the laminates40include an adhesive56that adheres the annular body42of one of the laminates40with an adjacent laminate40of the stator core22. The adhesive56is applied to the annular body42in a suitable manner, shown as dots of adhesive56. The adhesive dots56are arranged circumferentially around the annular body42radially outward of the plurality of wire slots46to provide substantially consistent adhesion to the other laminate40. In one form, the adhesive56is disposed both radially inward and outward of the containment zones50, described below. In other forms shown below, the adhesive56is disposed between the containment zones50and the wire slots46. In yet another form not shown, the adhesive56is disposed only radially outward of the containment zones50. In yet another form, the stator core22lacks adhesive56entirely, and the laminates40are joined by another method such as welding.

The laminates40define at least one containment zone50disposed radially outward of the plurality of wire slots46. In this context, a “containment zone” is a portion of the laminates40configured to contain fluid (such as varnish) applied to a surface of the stator core22. In the form ofFIGS.3-4B, the containment zone50is a hole, slot, or other void defined in a portion of the laminate40spaced away from the wire slots46. When the laminates40are stacked to form the cylindrical body26, the void defines a chamber delimited between the outermost laminate40aand the surface of an adjacent laminate40b. Stray varnish collects in the chamber, thereby contained in the containment zone50. In this form, the annular body42defines a plurality of containment zones50disposed circumferentially around the laminate40a. In general, the chamber of the containment zone50is defined between two adjacent parts of the cylindrical body26of the stator core22, such as the outermost laminate40aand an adjacent inner laminate40b. In another form, the chamber of the containment zone50is defined between more than two adjacent parts, such as the outermost laminate40athat defines a portion of the void of the chamber, an intermediate laminate (not shown) that includes the remainder of the void, and an inner laminate40bthat defines a surface that ends the chamber. In such a form, more varnish may be collected in the chamber than a form in which only the outermost laminate40adefines the containment zone50.

Referring back toFIG.4A, the containment zones50in this form include inner arcuate slots52and outer angular slots54. As the varnish travels along the surface of the laminate40a, the varnish may first arrive at the inner arcuate slots52. Because the varnish is viscous, the surface tension of the varnish may form a dam53along the edge of the inner arcuate slot52, holding the varnish out of the inner arcuate slot52. Then, as more varnish accumulates, the surface tension can no longer hold the dam53, and the varnish flows into the chamber defined by the inner arcuate slot52. If varnish continues to accumulate, the varnish fills the chamber and overflows toward the outer angular slots54, forming another varnish dam55that inhibits movement of the varnish. As varnish continues to accumulate further, the dam55breaks and the varnish flows into the chamber defined by the outer angular slot54. The outer angular slots54are angled to direct the varnish toward a center portion of the outer angular slots54, i.e., the portion of the containment zone50that forms the angle of the angular slots54.

In another form, the voids defining the containment zones50have different shapes, such as outer arcuate slots, inner angular slots, substantially straight slots, sinusoidally-shaped slots, and combinations thereof. In addition, one or more voids having same or different shapes may be employed in each containment zone50. The containment zones50thus collect varnish that could otherwise interfere with other parts of the stator core22.

With reference toFIG.5, another form of containment zones are provided on a laminate60. In this form, the annular body62includes containment zones64that are substantially arcuate slots66arranged radially outward of adhesive68, shown as adhesive dots68. The slots66are staggered into two circumferential arrangements, collecting varnish along an entire circumference of the annular body62. That is, an inner set70of arcuate slots66and an outer set72of arcuate slots66are arranged to overlap radially at specified locations, forming a complete circumference to collect varnish flowing away from any of the wire slots74. As such, stray varnish flowing radially outward on the surface of the laminate60may be collected by at least one of the arcuate slots66.

Now referring toFIG.6, another form of containment zones are provided on a laminate80. In this form, the annular body82defines the containment zones84that are disposed at selected location, such as proximate to the fastener slots86and a visible pattern88. In this form, the containment zones84are located to protect specific portions of the laminate80from varnish contamination. One of these specific portions, the fastener slot86, houses a fastener that secures the laminates80, and varnish contamination of the fastener slot86may inhibit the fastening strength of the fastener. The containment zones84are located radially inward of the fastener slots86to collect varnish moving radially outward from the wire slots90.

Another specific portion of the laminate80may include a visible pattern88that provides identifying information about the electric motor. The visible pattern88is formed on an outer surface of the annular body82for detection by a vision system or laser reader. The varnish, which may be opaque or glossy, may interfere with readability of the visible pattern88. The containment zone84thus is disposed radially inward of the visible pattern88to inhibit the varnish from interfering with the visible pattern88. By using fewer containment zones84focused on specific portions of the laminate80, less of the annular body82is removed, and the overall strength of the laminate80is increased relative to the laminates40,60shown inFIGS.3-5. The containment zones84in this form are located between the specified portions of the laminate80and the adhesive92, just as inFIG.5. In another form, the surface of the laminate80including the visible pattern88lacks adhesive92because the surface with the visible pattern88is an outermost surface of the stator core22. The outermost surface is not bonded to another laminate80to allow the vision system or laser reader to identify the visible pattern88.

In another form, not shown in the FIGS., the stator core may be a monolithic body, i.e., formed of a single piece of material into which the containment zones are defined. In such a form, the containment zones may be voids that are machined out of the monolithic stator core or defined during an additive manufacturing process that builds the stator core. As an example, when the stator core is additively manufactured, additively layered material may be placed to define a void between adjacent portions of the layers. As additional layers of material are placed, the layers form walls delimiting the void, these walls and the void defining the containment zone. In yet another form, the laminates40,60,80described above may be additively manufactured to define the containment zones50,64,84.