Die assembly and method for manufacturing wound motor laminated article

A stator core is formed from a continuous strip of wound sheet stock material, in which the sheet stock material is converted from the sheet stock to a formed material including winding slot cutouts. This strip of formed material is then wound into the stator core, with the winding slot cutouts in the formed material maintained at a substantially constant width throughout most of the radial extent of the resulting winding slots in the finished article. However, one or more of the radially innermost and radially outermost layers may define winding slot cutouts that are wider than the other winding slot cutouts. Where several radial layers are altered in this way, the cutout widths are progressively expanded such that the resulting winding slot has terminal ends with edges that are effectively “radiused” or rounded, thereby protecting windings near the edge of such slots.

BACKGROUND OF THE INVENTION

1. Technical Field

The present disclosure relates generally to a progressive stamping die assembly apparatus, and more particularly to an apparatus for the manufacture of a wound stator core made from a continuous strip of material.

2. Description of the Related Art

The manufacture of parts, e.g., stators and rotors for electric motors, ignition assembly cores, or other parts which employ stacked laminas is well known in the art. Typically, individual laminas are blanked from a continuous strip of stock material and are then stacked and bound together to form the completed part. Progressive die assemblies are used for producing such lamina stacks, in which a strip of lamina material is fed through a sequence of punching steps to progressively form the individual laminas to the desired end configurations.

Individual laminas are typically formed as a plurality of discreet parts which are layered over one another to create a lamina stack having the overall shape and dimension of the desired finished part. For stator cores, each lamina within the stack includes a central opening, a plurality of pole piece portions extending radially into or away from the central opening, and winding slots between each neighboring pair of pole piece portions.

Such stacked laminar articles are made from a plurality of individual laminas which are manufactured as separate discrete layers that are then stacked upon one another. This stack of discrete layers are then joined to one another to form the final laminated article such as a stator core or other component. Stated another way, the flat, generally planar material from which the individual laminas are formed creates generally planar laminas which are arranged perpendicular to the longitudinal axis of the final laminated article, such as the axis of a generally cylindrical stator core.

Alternatively, a wound laminated article may be created by winding a continuous strip of material around a spool, in the manner of a spooled tape, such that the substantially cylindrical stator core is created by winding several layers of the continuous strip over one another.

What is needed is a die assembly and method which is an improvement over the foregoing.

SUMMARY

The present disclosure provides a method and apparatus for forming a metal article, such as a stator core from a continuous strip of wound sheet stock material, in which the sheet stock material is converted from the sheet stock to a formed material including winding slot cutouts. This strip of formed material is then wound around a spool into a finished article, such as a stator core, with the plane of the incoming formed strip material remaining substantially parallel with a longitudinal axis of the finished article.

The winding slot cutouts in the formed material are maintained at a substantially constant width throughout most of the radial extent of the resulting winding slots in the finished article, except that one or more of the first and/or last wound layers (i.e., the radially innermost and radially outermost layers) may define winding slot cutouts that are wider than the other winding slot cutouts. Where several radial layers are altered in this way, the cutout widths are progressively expanded such that the resulting winding slot has terminal ends with edges that are effectively “radiused” or rounded. This rounded edge profile protects windings projecting radially into or outwardly from the winding slots near the edge of such slots.

In one form thereof, the present disclosure provides a production machine, the assembly including: a punch press comprising: an upper die assembly comprising a plurality of dies longitudinally arranged with respect to one another along a die path direction; a lower die assembly configured to cooperate with the plurality of dies of the upper die assembly to punch a plurality of lamina features into a strip of material substantially within the plane of the strip; a material feed path passing between the upper die assembly and the lower die assembly along a direction transverse to the die path direction, such that the plurality of dies are selectively engageable with the material feed path to selectively punch one of the plurality of lamina features into the strip; a rewinding apparatus positioned downstream of the punch press, the rewinding apparatus rotatable to take up material from the material feed path after the lamina features are punched into the strip.

In another form thereof, the present disclosure provides a method of producing a wound article from a strip of material, the method including: feeding a strip of bulk material to a punch press; punching a plurality of winding slot cutouts into the bulk material to create a formed material; winding the formed material around itself such that a substantially cylindrical structure is created, the plurality of winding slot cutouts selectively align with one another to create at least one winding slot, wherein the step of punching a plurality of winding slot cutouts comprises punching a cutout having a first cutout width for intermediate radial layers of the wound formed material and a second cutout width for at least one of an radially innermost and radially outermost layers of the wound formed material, the second cutout width greater than the first cutout width such that at least one axial end of the winding slot defines a rounded corner.

In yet another form thereof, the present disclosure provides a stator core including: a central opening bounded at its periphery by an innermost layer having at least one innermost winding slot cutout having an innermost cutout width; an outermost layer radially spaced from the innermost layer and having at least one outermost winding slot cutout having an outermost cutout width; and a main stator body including a plurality of intermediate layers between the innermost layer and the outermost layer, each of the plurality of intermediate layers having at least one intermediate winding slot cutout having an intermediate cutout width, wherein the innermost layer, outermost layer and intermediate layers are formed from a continuous strip of wound material such that the innermost winding slot cutout, the outermost winding slot cutout and the intermediate winding slot cutouts are aligned with one another to form a winding slot, and wherein at least one of the innermost cutout width and the outermost cutout width is larger than the intermediate cutout width, whereby the winding slot approximates a rounded edge and a radial terminal end thereof.

Corresponding reference characters indicate corresponding parts throughout the several views. The exemplification set out herein illustrates an embodiment of the disclosure and such exemplification is not to be construed as limiting the scope of the invention in any manner.

DETAILED DESCRIPTION

Referring now toFIG. 1, the present disclosure provides wound laminated article10, formed as a stator core having a plurality of winding slots20(e.g., twelve slots20as illustrated) extending from radially innermost layer12to radially outermost layer14of the continuous strip of material used to form article10, as described in detail below. Interposed between neighboring pairs of winding slots20are winding poles24, which define a relatively narrow width at innermost pole pieces16A and a relatively wider width at outermost pole pieces16B, as also described below. Winding poles24extend axially outwardly from base18of article10along longitudinal axis A defined by the generally cylindrical arrangement of article10as shown. Winding poles24optionally include lateral extensions26disposed axially opposite article base18which partially (but not fully) enclose winding slots20. It is also contemplated that lateral extensions26can be omitted such that the sidewalls of slots20extends axially to the axial terminal end of slots20.

When used in a motor or generator assembly, for example, bundles of windings are received within winding slots20and interconnected with one another. When article10is placed into a rotor (not shown), the windings can electrically interact with the rotor to form a rotor system capable of converting electrical charge to a motive force. Such rotor systems are used in electromotive devices such as electric generators, electric motors, sirens or the like.

Winding wire28(FIG. 2) may form a part of a bundle of windings, protruding radially outwardly from winding slot20. Wire28is positioned such that, in some cases, wire28is made to bend sharply around outer layers14,30,32of wound laminated article10as illustrated. As described in further detail below, radially outermost layer14and underlying outer layers30,32may define progressively narrowing winding slot widths W5, W4, W3et seq to provide a generally rounded edge profile at the radial end of winding slot20, thereby avoiding or minimizing damage to winding wire28and other sharply bending portions of the motor windings.

Turning now toFIG. 4, wound laminated article10is formed by winding a continuous strip of material around a circular core, such as takeup reel101, starting with radially innermost layer12(FIG. 1) and progressively winding additional layers of material thereupon until a desired finished diameter is reached at radially outermost layer14. Such winding is accomplished in the manner of a spiral, in similar fashion to the winding of tape onto a spool, such that the finished product is substantially cylindrical as illustrated.

As described in detail below, each successive layer of formed material126wound around takeup reel101is geometrically sized and configured by punch press104to precisely overlay the preceding layer such that winding slots20extend continuously radially outwardly from innermost layer12to outermost layer14. Stated another way, all winding slot cutouts150(FIGS. 8A, 8B) are formed to align with one another upon winding, such that winding slots150extend in an uninterrupted fashion throughout their radial extents, and have a desired width profile (such as with a standard width across the radial extent as shown).

However, as noted herein, the width of winding slots20flares outwardly at the radial terminal ends of winding slots20, i.e., the ends adjacent to innermost layer12and outermost layer14(FIG. 2). These outward flares provide an approximation of a “radiused” or rounded lateral edge at such radial ends to protect winding wires engaging these edges, such as winding wire28as shown inFIG. 2.

In addition to formation of such uninterrupted winding slots20, the process of creating wound article10(i.e., stamping bulk material106and rewinding formed material126as described below) also creates weld slots34in a surface of article base18opposite winding poles24, as shown inFIG. 3. Upon completion of the winding process which finishes article10, weld slots34can be used to permanently bind each adjacent radial layer of article10to one another to create a unitary, substantially cylindrical laminated article such as the stator core shown in the exemplary embodiment of the present figures.

Winding slot cutouts150are aligned with one another in wound article10such that winding slots20each extends radially outwardly along winding respective slot axes, such as axis ASshown inFIG. 1. Slots20extend directly radially outwardly, such that their respective longitudinal axes (including axis AS) each intersect the center of the circle defined by innermost and outermost layers12,14at axis A. In the illustrated embodiment, slots20also defines a constant width and cross-sectional geometry their longitudinal extents, except for the inner and outer layers with progressively widening slot cutouts150as described herein.

However, it is contemplated that the nature of the alignment of winding slot cutouts150can be altered to produce any longitudinal and cross-sectional geometry for winding slots20, as required or desired for a particular application. Referring toFIG. 9A, for example, winding slots20A of alternative wound article10A may define axes ASAwhich remain substantially perpendicular with respect to axis A but are skewed with respect to the strictly radial directionality of axis ASof slot20(FIG. 1). Thus, axis ASAnever intersects axis A defined by article10A.FIG. 9Billustrates alternative article10B with winding slots20B having an arcuate longitudinal axial profile.FIG. 9Cillustrates alternative article10C with winding slots20C having a double-arcuate longitudinal axial profile, in which the curvature of the arcuate profile changes between innermost layer12C and outermost layer14C.FIG. 9Dillustrates alternative article10D with winding slots20D having a double-skewed longitudinal axial profile, in which longitudinal axis ASDangles between innermost layer12D and outermost layer14D as shown. Finally,FIG. 9Eillustrates alternative article10E with winding slots20E having transverse axes ASEwhich are skewed with respect to axis A of article10, i.e., transverse axis ASEis substantially parallel to axis A but angled with respect thereto. Moreover, any combination of the above winding slot profile modifications, and any other modifications of profile cross-sectional geometry and/or arrangement, may be utilized in accordance with the present disclosure.

Turning again toFIG. 4, an exemplary method and apparatus for producing wound laminated article10will now be described with respect to production machine100. Production begins with a spool of wound bulk material, shown as material spool102inFIG. 4. Although material spool102is a convenient solution for providing a continuous feed of bulk material to punch press104as described in detail below, it is of course contemplated that such bulk material may be provided in other ways, such as directly from a material production line or from a stack of individual lengths of material.

Bulk material106is fed from material spool102to intake108of production machine100. Intake108may include various apparatuses for preprocessing of the bulk material106, as required or desired for a particular design and desired end product. For example, a first preprocessing step may be performed at intake108by material cleaner112, which removes particulate matter, grease, or other impurities from one or both sides of bulk material106. Removal of such impurities may be desirable to maintain fine control over the subsequent punching and rewinding of formed material126. In addition, intake may include edge guide114to monitor and/or adjust the alignment of bulk material106with respect to punch press104. Edge guide114maintains bulk material106in a desired spatial arrangement with respect to upper and lower die assemblies116,118of punch press104, even if bulk material106is unevenly wound upon material spool102. Other preprocessing steps and/or apparatuses may be employed as required or desired for a particular application, such as for trimming bulk material106to a desired width, creating cuts or perforations at desired locations, printing upon material surfaces, or the like.

Upon exiting a downstream end of intake108, bulk material106enters the upstream end of punch press104. As used herein, an “upstream” direction is toward the source of bulk material106(e.g., material spool102), while a “downstream” direction is opposed to the upstream direction and oriented toward the destination of formed material126(e.g., takeup reel101). Production machine100generally moves materials106,126in a downstream direction along feed direction DF, though it is appreciated that intermittent upstream travel of materials106,126may sometimes be desirable to facilitate certain material processing steps.

As best illustrated inFIG. 5, punch press104includes lower die assembly118having die insert120received therein. Upper die assembly116includes upper die121disposed above lower die assembly118and acted upon by press122. When press122pushes upper die assembly116downwardly, upper die121engages die insert120to stamp out a predetermined shape from bulk material106. When such stamping is complete, the removed material, known as a blank, is allowed to fall away from material106via chute124formed in lower die assembly118, while formed material126advances toward rewinder110as described further below. In the illustrated embodiment ofFIG. 5, upper die assembly116includes press plate128and die holder130, with press plate128selectively actuating under the force of press122upon command from controller145(FIG. 4). Die holder130is guided along guide rails132as holder130is urged downwardly by press plate128. Guide rails132, in turn, are received within lower die assembly118, thereby ensuring proper alignment between upper and lower die assemblies116,118during the punching process.

Turning now toFIG. 6, a plan view of punch press104illustrates the transversely movable functionality of upper and lower die assemblies116,118(though only lower die assembly118is shown for clarity). This transverse movement functionality enables variable widths W1through W5of winding slot cutouts150at selected layers of article10(e.g., innermost and outermost layers12,14), and thereby enables winding slots20with rounded edges as described herein.

InFIG. 6, lower die118having a plurality of die inserts120of varying widths W1, W2, W3, W4, W5is transversely movable along direction DT, which runs transverse to feed direction DFof bulk and formed materials106,126. As described in further detail below, upper and lower die assemblies116,118are advanced transversely along direction DTby actuator134at the beginning and end stages of formation of wound article10, such that relatively wider dies are employed for the first several innermost and last several outermost layers (including innermost layer12and outermost layer14, respectively) to produce the progressively widening profile of winding slot20at the terminal radial ends thereof. This progressively widening profile, in turn, creates the radiused or rounded appearance of such axial ends to protect winding wire28(FIG. 2) and other adjacent winding materials.

One exemplary system and method for transversely moving a die station with respect to other adjacent structures is disclosed in U.S. Pat. No. 6,742,239, filed Oct. 1, 2002 and entitled PROGRESSIVE STAMPING DIE ASSEMBLY HAVING TRANSVERSELY MOVABLE DIE STATION AND METHOD OF MANUFACTURING A STACK OF LAMINAE THEREWITH, the entire disclosure of which is hereby expressly incorporated by reference herein. Particular structures and systems for providing motive force to move upper and lower die assemblies116,118may be similarly arranged to the system of U.S. Pat. No. 6,742,239, or may be differently arranged (i.e., hydraulically or pneumatically driven systems, manual slides, and the like).

Turning back toFIG. 5, punch press104further includes pin punch136, which is configured and positioned to place pin hole138(FIG. 8C) into a leading edge of formed material126. Pin hole138is sized and positioned to engage a correspondingly formed pin (not shown) in takeup reel101upon initial engagement therebetween, such that the engagement draws formed material126into the initial wrap around takeup reel101(thereby forming radially innermost layer12).

Turning back toFIG. 6, lower die assembly118may include weld apertures140, which are engaged by a correspondingly formed weld aperture die (not shown) in upper die assembly116to form weld slot notches142in formed material126at selected, periodically spaced locations along bulk material106. Weld slot notches142cooperate to form weld slots34(FIG. 3) after article10is wound around takeup reel101as described in detail below.

Turning back toFIG. 4, the downstream end of production machine100includes rewinder110having takeup reel101and material measurement device144. Measurement device144measures the distance between itself and the material being collected upon takeup reel101, such as via sonar measurement, laser measurement, or the like. Signals collected from measurement device144indicative of the measured distance between device144and the adjacent layer of formed material126are relayed to controller145, which is operably connected to takeup reel101.

Turning toFIG. 7, controller145activates takeup reel101when formed material126is received thereupon. Takeup reel101is initially in an upper position directly abutting a spatially fixed pressure roll146. Formed material126is progressively collected upon takeup reel101, starting with radially innermost layer12and progressing with another layer for each360degree rotation of takeup reel101. As this progressive build up of wound formed material126collects, takeup reel101moves downwardly along direction DR. This downward movement may be controlled by controller145in response to the signal received from measurement device144. More particularly, controller145seeks to maintain a constant measurement reading from measurement device144such that pressure roll146is always in light but firm abutting contact with the incoming stream of formed material126.

To compensate for slight variations or inconsistencies in the downward travel of takeup reel101, pressure roll146may have a slight give (e.g., provided by an internal spring preload) to maintain such constant pressure upon incoming formed material126). In addition, auxiliary pressure roll assemblies148may be provided along the outer surface of takeup reel101, as shown inFIG. 7. Auxiliary pressure roll assemblies148are movable along direction DA, DA′ to maintain constant contact along the outer surface of the collected formed material126. In an exemplary embodiment, auxiliary pressure roll assemblies148are spring loaded to provide constant pressure against the adjacent material. In the illustrated embodiment ofFIG. 7, auxiliary pressure roll assemblies148are shown abutting the outer surface of laminated article10after collection of formed material126is complete.

The motive force for advancing materials106,126may be provided by takeup reel101, which “pulls” such material along direction DF(FIG. 6). However, the amount of angular movement of reel101needed to effect a given linear advancement of materials106,126along direction DFchanges depending on the diameter of the partially completed wound article10. Controller145may perform the mathematical calculations to convert the angular rotations into linear distance based on the effective diameter of the partially finished article10. Alternatively, a dedicated driven roller may be provided to advance materials106,126by a set amount regardless of the rewind diameter.

A method of operation of production machine100to produce wound laminated article10will now be described.

As noted above, bulk material106is first provided from material spool102to punch press104via intake108. Initially, punch press104is configured such that the widest die insert120and the associated widest die121are aligned below and above bulk material106. This configuration will allow radially innermost layer12to have winding slot cutout150(FIG. 8A) defining width W5, which is the widest of all available widths in the present exemplary embodiment. The resulting wider width of winding slot20at the inner radial end thereof facilitates creation of the rounded edge (similar to the radially outward rounded edge shown inFIG. 2and described further herein).

With bulk material106so aligned between upper and lower die assemblies116,118, punch press104is activated by controller145to create a first winding slot cutout150(FIG. 8A) defining width W5. The next length of bulk material106is advanced into alignment with upper and lower die assemblies116,118, and the stamping process is repeated. In the present exemplary embodiment shown inFIG. 1, a total of twelve stamping procedures creates innermost layer12of article10, because article10includes twelve winding slots20. Of course, any number of winding slots20may be provided, and the initial punching processes utilizing relatively wider width W5can be replicated as many times as needed to correspond to the desired number of winding slots.

As noted above, bulk material106(and the newly finished formed material126as shown inFIG. 8A) is advanced by distance DA1between punching of winding slot cutouts150. Distance DA1is calculated to produce twelve evenly spaced and evenly sized winding slot cutouts150around the inner periphery of radially innermost layer12. Because this periphery is the smallest of any winding around article10, inner pole pieces16A (FIGS. 1 and 8A) are relatively narrow.

For the next set of twelve winding slot cutouts150, upper and lower die assemblies116,118are indexed along direction DT(FIG. 6) to the next set of die insert120and die121having width W4, which is slightly smaller than width W5described above. For the second innermost layer of article10, another set of twelve winding slot cutouts150are punched with the reduced width W4and taken up on takeup reel101over innermost layer12. As described in detail below with respect to outermost layer14and the associated outer layers30,32et seq, (FIG. 2), this width reduction in winding slot cutouts150produces the beginning of the radiused or rounded general appearance of the innermost layers of article10.

In addition, advancement of formed material126must now be along a distance slightly larger than distance DA1(FIG. 8a) in order to maintain the alignment of winding slot20across this new layer. This is because the second layer including the second set of twelve winding slot cutouts150must circumnavigate not only the circumference of takeup reel101, but also the additional circumference imparted by the presence of the radially innermost layer12. Controller145calculates this incrementally larger distance based on the thickness of formed material126and increases the advancement distance accordingly.

In the illustrated embodiment ofFIG. 6, five arrangements of die insert120and die121are provided having five progressively smaller widths W5, W4, W3, W2, W1. With each progressive set of twelve winding slot cutouts150(or however many are provided in a full annular set of such cutouts), upper and lower die assemblies116,118are advanced along direction DTto present the next narrowest width as described above. In this manner, the first five layers wound around takeup reel101, which become the five innermost layers of article10, have progressively narrowing winding slot cutout widths W5through W1. This progressive narrowing imparts a generally radiused or rounded configuration at the innermost radial end of winding slots20, similar to the radiused configuration at the outermost radial end shown inFIG. 2.

In order to maintain a constant width of winding slot20through the next several layers, the die insert120/die121combination having width W1may be used repeatedly for as many layers as are desired. During this time, with each increase in circumference of article10resulting from the addition of another layer of formed material126taken up by takeup reel101, the distance of advancement of material126along direction DFis increased accordingly. By the time radially outermost layer14is ready for forming at punch press104and takeup by takeup reel101, advancement distance DA2(FIG. 8B) is needed between adjacent neighboring pairs of winding slot cutouts150to ensure alignment with cutout slots20. DA2is substantially larger than DA1, as illustrated by comparison toFIGS. 8A and 8B, and is the maximum advancement distance for article10.

In addition, the final, outermost five layers wound of formed material126′ around article10may employ ever increasing widths W1, W2, W3, W4, W5of winding slot cutouts150, as shown inFIG. 2. This is accomplished by advancing upper die assembly116and lower die assembly118along direction DT, in the reverse order as was used for the five innermost layers described above. InFIG. 2, the third from outermost layer32, second from outermost layer30and radially outermost layer14are shown for clarity, it being understood that the two layers further inward (i.e., the fourth outermost layer and fifth outermost layer) define winding slot cutouts150having widths W2and W1, respectively. As illustrated, outer layer32defines width W3, because winding slot cutouts150were created by the die insert120/die121combination defining width W3. Similarly, outer layer30defines width W4and radially outermost layer14defines the widest available width, width W5. This arrangement of steadily increasing widths W1through W5creates the radiused, rounded appearance at the radially outward axial ends of winding slots20as shown inFIG. 2.

The timing and amount of advancement of materials106,126, as well as the actuation of punch press104and any structures provided in intake108are controlled and monitored by controller145. Controller145is programmed to steadily increase the advancement distance from DA1at the beginning of the winding process to DA2at the end of the winding process in order to maintain radial continuity of winding slots20as described in detail above.

Controller145is also programmed to halt the advance of materials106,126by stopping the driven advancement of takeup reel101(or other powered roller), in order to actuate punch press104to create winding slot cutout150, pin hole138, and/or weld slot notch142. Edge guide114is actuated as necessary by controller145, or by its own internal controller, to maintain the spatial relationship of bulk material106with respect to punch press104, as noted above. Controller145may further monitor the status and operation of material cleaner112to ensure proper operation thereof, together with any other systems which may be chosen for intake108, material spool102, or the other systems of production machine100.

When radially outermost layer14is complete and wound upon article10, formed material126′ may be severed and the process may restart by again beginning creation of formed material126, as illustrated inFIG. 8B. In this way, continuous material processing may take place without any substantial interruption. Laminated article10may be removed from takeup reel101, and fixed in its finished form by welding the various layers of formed material126,126′ to one another by welding along weld slots34.