Patent Description:
The present invention is defined by the accompanying independent claim <NUM>.

Turning to the drawings, <FIG> illustrates an exemplary permanent magnet motor <NUM>. The exemplary motor <NUM> comprises a frame <NUM> capped at each end by drive and opposite drive end caps <NUM>,<NUM>, respectively. The frame <NUM> and the drive and opposite drive end caps <NUM>,<NUM> cooperate to form the enclosure or motor housing for the motor <NUM>. The drive and opposite drive end caps <NUM>,<NUM> may include mounting and transportation features, such as the illustrated mounting feet <NUM> and eyehooks <NUM>. A conduit box <NUM> houses the electrical connection between the terminal leads and the external power source. A rotor shaft <NUM> coupled to the rotor rotates in conjunction with the rotor, and may be coupled to any number of drive machine elements, such as pumps, compressors, fans, conveyors, and so forth.

<FIG>, not representing the invention, is a partial cross-section view of the motor <NUM> of <FIG> along plane <NUM>-<NUM>. To simplify the discussion, only the top portion of the motor <NUM> is shown, as the structure of the motor <NUM> is essentially mirrored along its centerline. Within the enclosure or motor housing resides a plurality of stator laminations <NUM> juxtaposed and aligned with respect to one another to form a lamination stack, such as a contiguous stator core <NUM>. In the exemplary motor <NUM>, the stator laminations <NUM> are substantially identical to one another, and each stator lamination <NUM> includes features that cooperate with adjacent laminations to form cumulative features for the contiguous stator core <NUM>. For example, each stator lamination <NUM> includes a central aperture that cooperates with the central aperture of adjacent stator laminations to form a rotor chamber <NUM> that extends the length of the stator core <NUM> and that is sized to receive a rotor. Additionally, each stator lamination <NUM> includes a plurality of stator slots disposed circumferentially about the central aperture. These stator slots cooperate to receive one or more stator windings <NUM>, which are illustrated as coil ends in <FIG>, that extend the length of the stator core <NUM>.

In the exemplary motor <NUM>, a rotor assembly <NUM> resides within the rotor chamber <NUM>. Similar to the stator core <NUM>, the rotor assembly <NUM> comprises a plurality of rotor components, such as laminations <NUM> aligned and adjacently placed with respect to one another in a stack <NUM>. A stack <NUM> of rotor components, such as laminations, may comprise a contiguous rotor core <NUM> or a part of a rotor core. When assembled, the rotor laminations <NUM> cooperate to form a shaft chamber that extends through the center of the stack <NUM> and rotor core <NUM>, and that is configured to receive the rotor shaft <NUM> therethrough. The rotor shaft <NUM> is secured with respect to the rotor core <NUM> such that the rotor core <NUM> and the rotor shaft <NUM> rotate as a single entity about a rotor center axis <NUM>. Although <FIG> shows the generally like laminations <NUM> arranged side by side in a single stack <NUM> that forms the entire contiguous rotor core <NUM>, the generally like laminations may be arranged side by side to form the stacks <NUM> of laminations and the stacks <NUM> of side by side laminations may be arranged in a spaced apart manner from one another along the rotor center axis <NUM> to form the rotor core <NUM>, for instance, for a radially ducted motor, which by way of example is shown in <FIG>, and which will be explained in greater detail below. Although the drawings show a rotor core with a side by side arrangement of laminations, the rotor core may include other rotor components, for instance, alternating soft magnetic blocks with soft magnetic composites.

The exemplary motor <NUM> includes drive and opposite drive bearing sets <NUM>,<NUM>, respectively, that are secured to the rotor shaft <NUM> and that facilitate rotation of the rotor assembly <NUM> within the stationary stator core <NUM>. Each bearing set <NUM>,<NUM> includes an inner race <NUM>, an outer race <NUM> and rotational elements <NUM>, which are disposed between the inner and outer races <NUM>,<NUM>.

<FIG> provide further detail of illustrative embodiments of the rotor component using laminations <NUM> as an example to form the stack and the rotor, although other rotor components may be used. Each rotor lamination <NUM> has a generally circular cross-section and is formed of a magnetic permeable material, such as electrical steel. Extending from end-to-end, i.e., transverse to the cross-section, each lamination <NUM> includes features that, when aligned with adjacent laminations <NUM>, form cumulative features that extend axially through the stack of laminations, which may be the entire rotor core. For example, each exemplary rotor lamination <NUM> has a circular shaft aperture <NUM> located in the center of the lamination <NUM>. The shaft apertures <NUM> of adjacent laminations <NUM> cooperate to form a shaft chamber configured to receive the rotor shaft <NUM> (see <FIG>) therethrough. Additionally, each lamination <NUM> includes apertures <NUM> that are arranged at positions about the lamination such that when assembled, the apertures cooperate to form passages <NUM> that extend through the stack, and which may extend through the rotor core <NUM> depending upon the arrangement of the stack(s). Depending upon the application, some of the passages <NUM> may be configured to receive magnet material <NUM>, which may be by way of example, sintered magnets, permanent magnets, or magnetizable material. Depending upon the application, some of the passages <NUM> may be configured to receive a fixation material <NUM> to fix the laminations together. Depending upon the application, the passages <NUM> that receive the magnet material <NUM> may also receive fixation material <NUM>. <FIG> and <FIG> show examples of magnet material <NUM> received in the passages <NUM> and the fixation material <NUM> received in the same passages <NUM> to fix the laminations. The magnet material <NUM> may be received in the passage to a certain length dimension relative to the stack length dimension, and the fixation material may be received in the passage to fill the passage, and/or form a sprue as will be described below. The passages <NUM> are be configured to receive the magnet material <NUM>. After those passages <NUM> are filled with the magnet material <NUM>, the fixation material <NUM> is introduced into those passages and other vacant passages to provide additional fixation for the stack and flux shaping as needed. Depending upon the application, the fixation material may be used in selected passages, and the magnet material may be omitted from the rotor, for instance, in the case of a synchronous reluctance type motor.

The fixation material <NUM> and/or magnet material <NUM> may be filled into the passages <NUM> as part of an injection molding process or compression molding process. The magnet material <NUM> comprises a polymer bonded composite magnet material and the fixation material <NUM> may comprise a neat polymer, nylon, or a fiber reinforced polymer. For further mechanical integrity and strength of the fixation material <NUM>, reinforcing fibers may be included in the fixation material. A non-exhaustive list of fixation materials includes Acrylonitrile Butadiene Styrene (ABS), Polyamide- Nylon with or without glass filling (PA), polycarbonate (PC), Polyethylene (PE), Polypropylene (PP), Polystyrene (PS), Acetal (POM), Low Density Polyethylene (LDPE), and Density Modified High Gravity Compounds.

As a result of the injection molding or compression molding process, one or more sprues <NUM> are formed on the axial face of the stack <NUM>. Depending upon the application and the arrangement of the injection molding or compression molding process, one or more sprues <NUM> may be provided on axially opposite ends of the stack <NUM>, or rotor core <NUM> as the case may be. According to the invention, the sprue <NUM> is shaped and formed as needed depending upon the application. As described below, the sprue(s) <NUM> may be configured as a cylindrical body(ies) or end plate(s). In addition, the sprue(s) <NUM> may be configured and formed for additional functionalities such as cooling fins or with locating structures defining reference positions for measuring equipment, and/or the attachment of fixtures and/or tooling used during the injection molding or compressing molding process. The sprue(s) may also be configured to locate, retain, or secure an end ring or other plate to provide additional structural integrity for the rotor assembly.

In <FIG>, not representing the invention, the sprue <NUM>,<NUM>' is formed in a contiguous manner on the entire outer face of the axial outermost lamination of the stack <NUM>, thereby forming an end plate for the stack with a thickness. While one sprue <NUM>,<NUM>' is shown in <FIG> on one axial side of the stack <NUM>, a similar sprue may be formed on the opposite axial side of the stack. In the arrangement shown in <FIG>, a mold may be formed around the axial end of the stack <NUM> and after magnet material <NUM> is inserted in the passages <NUM>, the fixation material <NUM> is filled in the passages and out beyond the axial outermost lamination of the stack to form the sprue <NUM>,<NUM>' as an end plate covering the outermost lamination of the stack. In the arrangement shown in <FIG>, the end plate formed sprue <NUM> may have a generally flat structure. In the arrangement shown in <FIG>, the end plate formed sprue <NUM>' may have a pocketed outer axial face <NUM> forming a cellular or honeycomb type structure with a plurality of open cells <NUM>. To balance the rotor of <FIG>, the end plate formed sprue <NUM> may be selectively machined, and/or balancing material added, as needed to adjust the weight of the sprue and its weight/mass distribution, and rotationally balance the rotor about the rotor center axis <NUM>. To balance the rotor of <FIG>, balancing material may be inserted into any one of a plurality of open cells <NUM> in the pocketed face, open cellular, honeycomb- type structure <NUM> to adjust the weight of the sprue <NUM>' and rotationally balance the rotor about the rotor center axis <NUM>. To the extent material needs to be removed for balancing, a portion of sprue comprising the pocketed face, open cellular, honeycomb- type structure <NUM> or the end plate may be removed as necessary.

<FIG> show alternate embodiments of a stack <NUM> where several sprues <NUM> are formed about the outer face of the axial outermost lamination of the stack. While several sprues are shown in each of the embodiments of <FIG> on one axial side of the stack, sprues may be formed in a like manner on the opposite axial side of the stack. Depending upon the application, the sprues <NUM> shown by example in <FIG> may be preferred to the sprues <NUM>,<NUM>' of <FIG> in that it allows for less material to be used for fixation. According to the invention, in <FIG>, the sprue <NUM> are formed in a sector (e.g., in the drawings, a quadrant) of the stack <NUM>, which correspond to a pole of the rotor. The magnet material <NUM> is filled into the passages <NUM> designated as magnet slots of the lamination <NUM>, and the fixation material <NUM> is then filled into the same passages to form the substantially cylindrically shaped sprue <NUM> shown in the Figures in a sector of the rotor. Certain of the passageways <NUM> may contain both permanent magnets or magnet material <NUM>, and the fixation material <NUM>. Certain other passages may solely contain the fixation material <NUM>. For instance, in the embodiment shown in <FIG>, not representing the invention, the radially outermost U-shaped passage may be reserved solely for fixation material <NUM>, while other radially inward U-shaped passages may contain both fixation material <NUM> and magnet material <NUM>. A synchronous reluctance motor may omit the magnet material and fixation material may be filled in selected passages <NUM>. <FIG> show an alternate embodiment where the stack <NUM> contains passageways <NUM> radially inward adjacent to the shaft aperture <NUM> that solely contain fixation material, and the other radially inward U-shaped passages <NUM> may contain both fixation material <NUM> and magnet material <NUM>. As described before, the sprues <NUM> may be machined as necessary to adjust the weight of the sprues and rotationally balance the rotor about the rotor center axis <NUM>. Additionally, balancing material may be inserted in one or more of the sprues <NUM> for adjusting the weight of the sprues and rotationally balancing the rotor about the rotor center axis <NUM>. In the embodiment shown in <FIG>, representing an aspect of the invention, the fixation material <NUM> may be removed from the radially inward passages <NUM> to further assist in balancing.

<FIG> show an alternate embodiment, not representing the invention, and construction for the stack <NUM> comprising a plurality of surface magnets <NUM> formed from the magnet material <NUM>. Again, the like laminations <NUM> are arranged side-by-side to form the stack <NUM>. The apertures <NUM> in the laminations are aligned in a manner so as to cooperate and form channels <NUM> that extend axially through the stack <NUM>. The channels may extend radially inward in the lamination from the outer diameter surface of the lamination to provide additional structure integrity for the magnets. The magnet material <NUM> may be filled into certain locations around the rotor to form the surface magnets, and then the fixation material <NUM> may be filled and molded over the magnet material to lock the magnet material in place in an overmolded arrangement. The fixation material <NUM> may extend from the outer face of the outermost axial lamination in the form of a sprue <NUM>. The sprue <NUM> may have the form of an annular, end ring-type structure extending axially outward from the axial outermost lamination of the stack. The sprue <NUM> in the form of the annular, end ring-type structure may then be adjusted as needed to rotationally balance the rotor about the rotor center axis. Balancing material may be inserted in the sprue <NUM> or the sprue may be machined in order to adjust the weight of the sprue and rotationally balance the rotor about the rotor center axis <NUM>.

<FIG> shows an embodiment, representing an aspect of the invention, of a rotor <NUM>' for the motor where a plurality of stacks <NUM>' of laminations are arranged side-by-side in spaced apart arrangement along the rotor with their apertures aligned to form passages <NUM> extending axially through the stack <NUM>'. After magnet material <NUM> is filled into the passages <NUM>, the fixation material <NUM> may be filled through the passages <NUM>. The mold used in the injection molding or compressing molding process may include forms which create ducts <NUM> extending through the passages <NUM>. The ducts <NUM> may extend axially through the stacks and overall through the rotor. The ducts <NUM> may also extend radially outward between adjacent spaced apart stacks of laminations <NUM>'. As the fixation material is filled, it may flow around the forms and define the ducts <NUM> in the passages while locking the laminations together and overmolding the magnet material. The sprue <NUM> may comprise the form of an end place as described above in reference to <FIG> or may comprise the cylindrical structure as described above in reference to <FIG>, and may be adjusted in the same ways discussed above to rotationally balance the rotor <NUM>' about the rotor center axis <NUM>.

<FIG> show additional aspects, not representing the invention, of the radially ducted rotor of <FIG>. In particular, <FIG> shows a stack <NUM>' with a plurality of passages <NUM> comprising V-shaped magnets slots configured to receive magnet material <NUM> as described previously. The passages <NUM> comprising the magnets slots of the stack <NUM>' may extend actually through the stack in the manner described previously. The magnet material <NUM> may be filled in the passages <NUM> comprising the magnet slots to a certain depth. Once the magnet material <NUM> is filled in the passages, the fixation material <NUM> may be filled in the passages <NUM> comprising the magnets slots, and may include a sprue <NUM> extending axially from the face of the stack <NUM>'. The magnet material <NUM>, fixation material <NUM>, and/or sprue <NUM> may be compression or injected molded as described above. The sprue <NUM> on the axial face of the stack <NUM>' may function as a locator or retainer as shown for an end ring configuration as shown in <FIG> or may form the radially spoked arrangement for a radially ducting of the stack <NUM>' forming the rotor assembly <NUM>. In <FIG>, the sprue <NUM> may comprises the spoke configuration extending from the axial face of the stack. In <FIG>, the sprue <NUM> may comprise a cylindrical nub that enables attachment of an separate end ring or the sprue may be formed as an end ring. Thus in the embodiment of the radially ducted motor shown in <FIG>, a plurality of stacks of the type shown in <FIG> may be arranged in an axially spaced apart manner to form the axially inward portion of the rotor assembly, and stacks of the type shown in <FIG> may form the axial outward portions of the rotor assembly with the stacks having the sprues with radial spokes therebetween.

Claim 1:
A method for forming a rotor, the rotor comprising a rotational center axis (<NUM>) and four quadrant sectors that each correspond to a pole of the rotor,
the method comprising:
arranging a plurality of stacks (<NUM>; <NUM>) of laminations (<NUM>) in a stack (<NUM>; <NUM>) as to form at least part of the rotor, the plurality of laminations (<NUM>) having apertures (<NUM>) that are aligned in the stack to form passages (<NUM>) extending axially through the stack (<NUM>; <NUM>), and passageways (<NUM>) radially inward adjacent to the apertures (<NUM>);
filling magnet material (<NUM>) into the passages (<NUM>), and filling polymer based fixation material (<NUM>) through the passages (<NUM>) to lock the plurality of laminations (<NUM>) together and overmold the magnet material (<NUM>), and filling, solely, the polymer based fixation material (<NUM>) through the passageways (<NUM>);
wherein filling the passages (<NUM>) with the fixation material (<NUM>) is accomplished by use of a mold that includes forms,
wherein as the fixation material (<NUM>) is filled in the passages (<NUM>), it flows around the forms while locking the laminations (<NUM>) together and overmolds the magnet material (<NUM>) with the fixation material (<NUM>), forming a sprue (<NUM>; <NUM>) projecting from an axial face of the stack (<NUM>; <NUM>); the method comprises adjusting a weight of the sprue (<NUM>; <NUM>) to rotationally balance the rotor about the rotor center axis (<NUM>), wherein the sprue (<NUM>; <NUM>) is formed in exactly four portions, and each portion of the sprue (<NUM>; <NUM>) is formed in each of the four quadrant sectors of the stack (<NUM>; <NUM>) that correspond to a pole of the rotor.