Insulation assembly for electric machine

An insulation assembly is provided that includes a generally annularly-shaped main body and at least two spaced-apart fingers extending radially inwards from the main body. The spaced-apart fingers define a gap between the fingers. A slot liner may be inserted within the gap. The main body may include a plurality of circumferentially distributed segments. Each one of the plurality of segments may be operatively connected to another of the plurality of segments to form the continuous main body. The slot liner may be formed as a single extruded piece defining a plurality of cavities. A plurality of conductors (extendable from the stator assembly) may be axially inserted within a respective one of the plurality of cavities. The insulation assembly electrically isolates the conductors in the electric motor from the stator stack and from other conductors.

TECHNICAL FIELD

The present invention relates, generally, to an electric motor, and more specifically, to an insulation assembly for a stator assembly of the electric motor.

BACKGROUND

Electric motors include stator assemblies which have conductors for the motor. The stator stack for the stator assembly includes spaced-apart teeth that extend radially from the stator stack and define stator slots. The conductors are threaded into the stator slots and individually twisted into their required positions. Generally, metal tooling is used to assist in maintaining the desired position of the conductors during the assembly and twisting operation. The metal tooling generally has a number of metal fingers that extend radially between the individual conductors being threaded into the stator stack. After assembly is complete, the metal fingers are removed. The conductors must be electrically isolated from the stator stack to prevent phase-to-ground shorts, and from one another to prevent phase-to-phase shorts from occurring.

SUMMARY

An insulation assembly is provided that includes a generally annularly-shaped main body and at least two spaced-apart fingers extending radially inwards from the main body. The spaced-apart fingers define a gap between the fingers. A slot liner may be inserted within the gap. The slot liner may be formed as a single extruded piece defining a plurality of cavities. A plurality of conductors, extendable from the stator assembly, may be axially inserted within a respective one of the plurality of cavities. The insulation assembly electrically isolates the conductors in the electric motor from the stator stack and from other conductors. The insulation assembly also functions as an assembly device, no longer requiring separate metal tooling to assist in maintaining the position of the conductors.

The main body may include a plurality of circumferentially distributed segments. Each one of the plurality of segments may be operatively connected to another of the plurality of segments to form the continuous main body. A plurality of attachment features may be spaced about the main body. The main body may be made of a moldable plastic material. The slot liner may include an end wall defining a first inwardly tapered portion. The slot liner may include a side wall defining a second inwardly tapered portion. The first and second inwardly tapered portions may be adapted to retain the slot liner in the gap.

Each of the spaced-apart fingers may have at least one side which defines a chamfer. The chamfer may be adapted to align respective ones of the plurality of slot liners. Each of the spaced-apart fingers has at least one side which defines an angled surface. The angled surface may be adapted to guide insertion of the slot liner in the gap. Each of the spaced-apart fingers has at least one side which defines a curved surface. The curved surface may be adapted to guide the insertion of each of said plurality of conductors in the respective one of the plurality of cavities. A method of assembling a stator assembly is also provided.

DETAILED DESCRIPTION

Referring to the Figures, wherein like reference numbers refer to the same or similar components throughout the several views,FIG. 1is a schematic perspective view of an insulation assembly10. The insulation assembly10includes a generally annularly-shaped main body12surrounding a central opening14.FIG. 2is an enlarged partial schematic perspective view of a portion16of the insulation assembly10, looking outward from the center of the opening14. The insulation assembly10includes at least two spaced-apart fingers20extending from the main body12and protruding radially inwards toward the central opening14. The spaced-apart fingers20define a gap22in between the fingers20. A slot liner24may be inserted or adapted to fit into each gap22. The slot liner24engages with the fingers20to provide a complete insulation system for the stator assembly26.

Referring toFIG. 3, the insulation assembly10may be used in a stator assembly26for an electric motor27.FIG. 3is a partial schematic perspective view of the insulation assembly10from a twist-side28of the stator assembly26. The insulation assembly10may be attached to one or both of the twist side28and a crown side (not shown) of the stator assembly26. The stator assembly26includes a stator stack30. The stator stack30for the stator assembly26defines a plurality of stator slots32(shown inFIG. 3) which extend entirely through the stator stack30. Each gap22in the insulation assembly10corresponds to one of the stator slots32in the stator stack30.

The slot liner24may be a multi-lumen slot liner24that defines a plurality of cavities36, as shown inFIG. 2. A plurality of conductors34(shown inFIGS. 2-3) are threaded through respective ones of the plurality of cavities36. The conductors34extend from both the twist-side28and the crown side (not shown) of the stator stack30. The insulation assembly10electrically isolates the conductors34from one another and from the ends of the stator stack30. The number and shape of the cavities36are determined by the number and shape of conductors34which are assembled within each stator slot32. In the embodiment shown, there are four conductors34per stator slot32. The conductors34may be formed from wire having a square cross-sectional shape. The number and shape of the conductors34, and thus cavities36, may vary according to the design and purpose of the electric motor27. One skilled in the art would be able to determine the appropriate number and shape of the conductors34and cavities36for a particular configuration.

The slot liner24may be formed as a one-piece slot liner24by extrusion from a dielectric material. Providing an extruded slot liner24reduces the number of burrs and folds in the material of the slot liner24, making it less susceptible to tearing during insertion or due to relative motion between the slot liner24and the stator stack30. Alternatively, the slot liner24may be formed by bonding together individually extruded straws (each defining a single cavity) to form a single piece slot liner24assembly having multiple cavities.

A method of assembly for the stator stack30includes attaching the main body12and the spaced apart fingers20(that extend from the main body12) onto the stator stack30. The slot liner24may be inserted into the gap22between adjacent fingers20. The conductors34may be inserted into the individual cavities36defined by the slot liner24. The slot liner24may be pre-cut to the required length for a particular electric motor27. Alternatively, the slot liner24may be provided as a continuous roll and cut to length at the time of assembly within the stator stack30. Thus the length of the slot liner24may be selected as required by the application. Because the insulation assembly10may be assembled on the stator stack30prior to insertion of the conductors34, the insulation assembly10may act as an assembly device to assist in assembly of the stator assembly26.

The fingers20may include a first surface37and a second surface38, shown inFIG. 2. The first surface37and the second surface38are connected by a first side40and second side41. The first side40and second side41each define a curved surface42. The curved surface42(shown inFIG. 2) may correspond to a curve44(shown inFIG. 3) of the conductors34. In other words, the radius of the curved surface42(shown inFIG. 2) may correspond to the desired radius of a curve44(shown inFIG. 3) on the conductors34once the twist operation is complete. The curved surface42assists in aligning the conductors34during assembly and preventing movement, i.e. pulling, of the conductors34during the twist operation. The first side40and second side41of the fingers20also each define an angled surface46. The angled surface46assists in guiding the placement of slot liner24into the gap22between adjacent fingers20. By having an angled surface46instead of a sharp edge, damage to the slot liner24during assembly may be minimized.

The first side40and second side41of the fingers20each define a chamfer48. The chamfer48is located at the same axial position on the stator stack30as the slot liner24. Thus, the chamfer48aligns the slot liner24in the desired axial position relative to the stator stack30. The chamfer48also protects the slot liner24during assembly of the stator assembly26and reduces the stress placed on the ends of the slot liner24from the conductors34. The cross-sectional shape of the fingers20may vary from one application to another depending on the application and the specific stator assembly26being used. Any shape according to the specific stator assembly may be employed. Fingers20also define an inner wall52.

The embodiment described above is for a stator assembly26having axially inserted conductors34. However, the insulation assembly10may also be utilized with radially inserted conductors34as well. Because the insulation assembly10is an electrical isolator, the insulation assembly10can remain with the stator assembly26once the assembly is complete and not effect operation of the stator assembly26. A second insulation assembly (not shown) may be assembled on the stator stack30prior to insertion of the plurality of conductors34from the crown-side (not shown) of the stator stack30. The second insulation assembly may have a common shape with the insulation assembly that is located on the twist side28of the stator stack30.

The generally annularly-shaped main body12may be formed as a single piece, as shown inFIG. 1. Optionally, the main body12may be formed as a number of segments50(shown inFIGS. 2 and 4) that are circumferentially distributed.FIG. 4is a partial schematic plan view of a portion54of the insulation assembly10.FIG. 4shows a first segment56and a second segment58. The first segment56is operatively connected to the second segment58through a first portion60that is shaped to fit into a corresponding second portion62. Each segment50is operatively connected to another two segments in order to form a closed, continuous ring, as shown inFIG. 1. Any configuration or shape may be employed for keying or retention of the segments50.

Optionally, the segments50may be attached using adhesive or any suitable material. The segments50may be connected to each other to form a continuous annularly-shaped main body12prior to being positioned or assembled on the stator stack30. Alternatively, the segments50may be individually and sequentially placed on the stator stack30and then assembled into a continuous annularly-shaped main body12.

Optionally, attachment features64(shown inFIG. 1) may be located at various locations of the main body12. The attachment features64may be used to secure the insulation assembly10to the stator stack30. The attachment features64may include a tab66(shown inFIGS. 1 and 3) which protrudes radially outward from the main body12. A pin68(shown inFIG. 1) may extend from the tab66and be shaped to fit into a corresponding hole (not shown) formed in the stator stack30.

The main body12, fingers20and slot liner24may be made from an electrically isolating material, such as plastic. The main body12may be manufactured by injection molding. Optionally, the main body12may be manufactured from a conductive material and coated in an electrically isolating material.

FIG. 5is a partial schematic perspective view of a slot liner24. As noted above, the slot liner24may be a multi-lumen slot liner24that defines a plurality of cavities36. The slot liner24has a pair of opposing side walls70, a pair of opposing end walls72, and at least one dividing wall74. The opposing side walls70have a first thickness76, the opposing end walls72have a second thickness78, and the dividing walls74have a third thickness80. The slot liner24may be extruded as a single piece so that the dividing walls74do not have double thickness, as sometimes occurs when bending sheets of material to form the desired shape. In order to reduce the package area required by the slot liner24and the conductors34, the slot liner24may be formed with side walls70, end walls72, and dividing walls74having the smallest thickness possible while maintaining electrical isolation.

In the embodiment shown, the first, second, and third thicknesses76,78,80are equal such that the side walls70, end walls72, and dividing walls74are of equal thickness. Alternatively, the first thickness76, the second thickness78, and/or the third thickness80may be different thicknesses to provide different amounts of electrical isolation. For example, end walls72may require less electrical isolation than the dividing walls74and therefore the second thickness78may be less than the third thickness80. One skilled in the art would be able to determine the required thickness for each of the side walls70, end walls72, or dividing walls74.

Additionally, the side walls70, the end walls72, and the dividing walls74enclose the cavities36around a portion of the length of the conductor34. The ends of the conductor34, which extend axially from the stator stack30, remain exposed as required for operation of the electric motor27.

The slot liner24has a length82, a first end84and a second end86. The first end84of the slot liner24is fittable or adapted to fit into the gap22that is in between adjacent fingers20. The slot liner24may be attached or fused to the first and second sides40,41of the fingers20with adhesive or any other suitable material. Any suitable method of attaching or fusing may be used. One such method includes applying ultrasonic vibrations locally while holding the pieces together under pressure in order to create an ultrasonic bond. Optionally, the slot liner24may be integrally formed with the main body12.

FIG. 6illustrates an alternative embodiment for a slot liner100. The slot liner100includes a plurality of cavities102fully enclosed by a pair of opposing side walls104, a pair of opposing end walls106and at least one dividing wall108. In the embodiment shown, there are four cavities102, however, any number of cavities may be formed to hold a corresponding number of conductors. The opposing side walls104have a first thickness110, the opposing end walls106have a second thickness112, and the dividing walls108have a third thickness114. The slot liner100has a length116, a first end118and a second end120. The slot liner100is inserted into the gap22between adjacent fingers20of the insulation assembly10.

Referring toFIG. 6, the slot liner100may define a first tapered portion122at one or both of the end walls106. The slot liner100may define a second tapered portion124at one or both of the opposing side walls104. The first and second tapered portions122,124may be inwardly tapered and formed at the first end118of the slot liner100. The slot liner100may have a length116that is longer than the length of the stator stack30, to account for the first and second tapered portions122,124.

When the slot liner100is inserted into the gap22between adjacent fingers20, the first tapered portion122may be adapted to be in contact with or rest above the inner wall52of the fingers20(shown inFIG. 2). When the slot liner100is inserted into the gap22between adjacent fingers20, the second tapered portion124may be adapted to be in contact with or rest above the curved surface42of the fingers20. The first and second tapered portions122,124may prevent the slot liner100from falling through the fingers20and into the stator stack30. In other words, the first and second tapered portions122,124may assist in retaining the position of the slot liner100in the gap22without the use of adhesives, fusing, or other materials.