Synchronous reluctance motor with ferrite-assisted reluctance rotor

Abstract

To provide a synchronous reluctance rotor in which permanent magnetic inserts are disposed within a reluctance void.SOLUTION: A motor 12 includes: a stator 10 having windings that generate an electromagnetic field within a rotor cavity 74 when selectively energized; and a rotor 160 located within the rotor cavity of the stator and performing electromagnetic communication with windings 14 and the electromagnetic field. The rotor includes a drive shaft, a rotor body extending around the drive shaft and defining a plurality of reluctance voids 122, and a magnetic insert 162 located in the reluctance voids. The magnetic inserts occupy at least a portion of a space defined by the reluctance voids. The magnetic inserts and the reluctance voids cooperate with the electromagnetic field to generate electromagnetic torque.SELECTED DRAWING: Figure 27

Description

[Technical Field]

[0001] The present invention relates generally to electric motors, and more particularly to a synchronous reluctance rotor having a series of stacked rotor laminations joined together to form a reluctance void, with permanent magnet inserts disposed within the reluctance void to form a rotor that generates reluctance torque as well as magnetic torque when acted upon by an electromagnetic field from a stator. [Background technology]

[0002] An electric motor typically includes a stator and a rotor, where the stator includes windings that can be energized to create an electromagnetic field that interacts with the rotor. The interaction between the stator's electromagnetic field and the rotor generates an electromotive force that causes the rotor to rotate relative to the stator. Summary of the Invention

[0003] According to one aspect of the disclosure, a motor includes a stator having windings that, when selectively energized, generate an electromagnetic field within a rotor cavity, and a rotor disposed within the rotor cavity of the stator in electromagnetic communication with the windings and the electromagnetic field. The rotor includes a drive shaft, a rotor body extending around the drive shaft and defining a plurality of reluctance voids, and magnetic inserts disposed within the reluctance voids. The magnetic inserts occupy at least a portion of the space defined by the reluctance voids. The magnetic inserts and the reluctance voids cooperate with the electromagnetic field to generate electromagnetic torque.

[0004] According to another aspect, a rotor includes a drive shaft and a plurality of stacked rotor laminations forming a rotor body. The rotor body extends around the drive shaft. Each stacked rotor lamination has a connecting web that forms a reluctance void within the plurality of stacked rotor laminations. The rotor further includes a magnetic insert disposed within the reluctance void. The magnetic insert occupies at least a portion of a space defined by the reluctance void. The magnetic insert and the reluctance void are configured to cooperate with an electromagnetic field from a stator winding to generate an electromagnetic torque having a reluctance torque component and a magnetic torque component.

[0005] According to another aspect, a method for forming a rotor for an electric motor includes forming rotor laminations having reluctance portions removed from each of the rotor laminations to define connecting webs, stacking the rotor laminations to form a rotor body, the connecting webs being aligned to define reluctance voids in the rotor body, positioning magnet inserts in the reluctance voids, disposing opposing end caps on the rotor body to enclose the reluctance voids, and overmolding the rotor body with an overmold material, the opposing end caps preventing the overmold material from penetrating the reluctance voids.

[0006] These and other aspects, objects, and features of the present disclosure will be understood and appreciated by those skilled in the art upon review of the following specification, claims, and accompanying drawings.

[0007] The drawings are as follows: [Brief explanation of the drawings]

[0008] [Figure 1]FIG. 1 is a perspective view of an electric motor incorporating aspects of the stator and rotor configurations described herein. [Figure 2] 2 is a schematic cross-sectional view of the electric motor of FIG. 1 taken along line II-II. [Figure 3] FIG. 1 is a perspective view of a stator incorporating an outer ring positioned around the periphery of the stator teeth. [Figure 4] FIG. 4 is a partially exploded perspective view of the stator of FIG. 3, with the stator separated from the overmold. [Figure 5] FIG. 5 is an exploded perspective view of the stator of FIG. 4. [Figure 6] FIG. 6 is a schematic perspective view showing the assembly of stator teeth for the stator of FIG. 5 using structural rings and stacked tooth laminations. [Figure 7] 5 is a side perspective view of a stack of tooth laminations positioned between adjacent structural rings to form the stator of FIG. 2; FIG. 6 is a top perspective view of the stator core of the stator of FIG. 5; [Figure 8] FIG. 8 is an exploded perspective view of the stator core of FIG. 7. [Figure 9] FIG. 1 is a schematic diagram illustrating the assembly of stator teeth on a stator core using structural rings and stacked tooth laminations. [Figure 10] FIG. 1 is a partially exploded view of a stator incorporating a plurality of pre-wound tooth segments, showing the stator separated from the overmold. [Figure 11] FIG. 11 is an exploded perspective view of the stator of FIG. [Figure 12] FIG. 12 is an exploded perspective view of the stator core shown in FIG. [Figure 13] FIG. 11 is a perspective view of a pre-wound tooth segment of the stator of FIG. [Figure 14] FIG. 14 is an exploded perspective view of the pre-wound tooth segment of FIG. 13. [Figure 15] FIG. 1 is a perspective view of a rotor incorporating reluctance voids within the rotor body. [Figure 16]FIG. 16 is an exploded perspective view of the rotor of FIG. 15. [Figure 17] FIG. 17 is a cross-sectional view of the stator of FIG. 15 taken along line XVII-XVII. [Figure 18] 18 is a cross-sectional view of the stator of FIG. 15 taken along XVIII-XVIII. [Figure 19] FIG. 1 is a schematic flow diagram illustrating a method for forming a stator for an electric motor. [Figure 20] FIG. 1 is a schematic flow diagram illustrating a method for forming a stator for an electric motor. [Figure 21] FIG. 1 is a schematic flow diagram illustrating a method for forming a stator for an electric motor. [Figure 22] FIG. 1 is a perspective view of a rotor incorporating magnetic inserts within reluctance voids in the rotor body. [Figure 23] FIG. 23 is an exploded perspective view of the rotor of FIG. 22. [Figure 24] 24 is a cross-sectional view of the rotor of FIG. 22 taken along line XXIV-XXIV. [Figure 25] 23 is a cross-sectional view of the rotor of FIG. 22 taken along line XXV-XXV. [Figure 26] FIG. 1 is a cross-sectional schematic diagram of a stator and rotor combination, including an embodiment of a rotor with linear reluctance voids in a two-pole rotor configuration. [Figure 27] FIG. 27 is a schematic diagram of the rotor and stator combination of FIG. 26, showing a portion of the reluctance void filled with a magnet insert. [Figure 28] FIG. 28 is a schematic cross-sectional view of the stator and rotor combination of FIG. 27 showing additional magnet inserts positioned within the reluctance voids. [Figure 29] FIG. 1 is a schematic cross-sectional view of a stator and rotor combination showing a four-pole configuration of a ferrite-assisted reluctance rotor. [Figure 30] FIG. 10 is a schematic diagram illustrating an example configuration of magnet inserts positioned within the reluctance voids to produce a desired ratio of magnetic and reluctance torque components. [Figure 31] FIG. 10 is a schematic diagram illustrating another exemplary configuration of magnet inserts disposed within the reluctance voids to produce a desired ratio of magnetic and reluctance torque components. [Figure 32] FIG. 10 is a schematic diagram illustrating another exemplary configuration of magnet inserts disposed within the reluctance voids to produce a desired ratio of magnetic and reluctance torque components. [Figure 33] FIG. 1 is a schematic cross-sectional view of a ferrite-assisted reluctance rotor with reluctance voids completely occupied by magnet inserts. [Figure 34] FIG. 1 is a schematic cross-sectional view of a stator and rotor combination including an embodiment of a ferrite-assisted reluctance rotor having a single cavity corresponding to each rotor pole. [Figure 35] FIG. 1 is a schematic flow diagram illustrating a method for forming a rotor for an electric motor. DETAILED DESCRIPTION OF THE INVENTION

[0009] Where necessary, detailed embodiments of the present disclosure are disclosed herein; however, it should be understood that the disclosed embodiments are merely exemplary of the invention, which may be embodied in various and alternative forms. The figures are not necessarily to detailed design, and some schematic diagrams may be exaggerated or minimized to show an outline of functionality. Therefore, specific structural and functional details disclosed herein should not be construed as limiting, but merely as a representative basis for teaching those skilled in the art how to employ the present invention in various ways.

[0010] For purposes of description herein, the terms "top," "bottom," "right," "left," "back," "front," "vertical," "horizontal," and their derivatives refer to the present concepts as oriented in FIGS. 1-35. However, it should be understood that the present concepts may assume various alternative orientations, unless expressly specified to the contrary. It should also be understood that the specific devices and processes illustrated in the accompanying drawings and described in the following specification are merely exemplary embodiments of the inventive concepts defined in the appended claims. Hence, specific dimensions and other physical characteristics related to the embodiments disclosed herein are not to be considered limiting, unless the claims expressly state otherwise.

[0011] The presently described embodiments reside primarily in a combination of method steps and apparatus components related to an electric motor having a formed and overmolded stator with pre-wound winding sections attached to the stator teeth, and an overmolded rotor including reluctance voids contained between outer laminations and at least partially filled with magnetic inserts. Accordingly, the apparatus components and method steps, where applicable, have been represented by conventional numerals in the drawings showing only those specific details relevant to understanding the embodiments of the present disclosure, so as not to obscure the disclosure with details that will be readily apparent to those skilled in the art having the benefit of the description herein. Furthermore, like numerals in the description and drawings represent like elements.

[0012] As used herein, the term "and / or," when used in a list of two or more items, means that any one of the listed items can be employed alone, or any combination of two or more of the listed items can be employed. For example, if a composition is described as containing components A, B, and / or C, the composition can include A alone, B alone, C alone, a combination of A and B, a combination of A and C, a combination of B and C, or a combination of A, B, and C.

[0013] In this document, relative terms such as first and second, top and bottom, etc. are used only to distinguish one entity or action from another, without necessarily requiring or implying any such actual relationship or order between such entities or actions. The terms "comprises," "comprising," or any other variation thereof, are intended to cover a non-exclusive inclusion, such that a process, method, article, or apparatus that comprises a list of elements does not include only those elements, but may also include other elements not expressly listed or inherent in such process, method, article, or apparatus. An element preceded by "comprises...a" does not, without further constraints, exclude the presence of additional identical elements in a process, method, article, or apparatus that comprises that element.

[0014] As used herein, the term "about" means that amounts, sizes, formulations, parameters, and other quantities and characteristics are not, and need not be, exact, but may be approximate and / or larger or smaller, as desired, to reflect tolerances, conversion factors, rounding, measurement error, and the like, as well as other factors known to those of ordinary skill in the art. When the term "about" is used in describing a value or endpoint of a range, the disclosure should be understood to include the specific value or endpoint referenced. Regardless of whether a numerical value or endpoint of a range herein is described as "about," the numerical value or endpoint of the range is intended to include two embodiments: one modified by "about" and one not modified by "about." It will further be understood that each endpoint of a range is significant both in relation to the other endpoint and independently of the other endpoint.

[0015] As used herein, the terms "substantial," "substantially," and variations thereof are intended to note that a described characteristic is equal to or approximately equal to a value or description. For example, a "substantially planar" surface is intended to describe a surface that is planar or approximately planar. Furthermore, "substantially" is intended to describe two values ​​that are equal or approximately equal. In some embodiments, "substantially" can describe values ​​that are within about 10% of each other, such as within about 5% of each other or within about 2% of each other.

[0016] As used herein, the terms "the," "a," or "an" mean "at least one" and should not be limited to "only one" unless expressly indicated to the contrary. Thus, for example, reference to "a component" includes embodiments having two or more such components, unless the context clearly indicates otherwise.

[0017] 1-35 , reference numeral 10 generally refers to a stator 10 incorporated within an electric motor 12, the stator 10 including one or more windings 14 positioned on teeth 16 for the stator 10. The windings 14 are energized to generate a magnetic field that rotates a rotor 18 positioned relative to the stator 10. The windings 14 are typically energized by a controller that manages the delivery of current to one or more phases of the windings 14. Depending on the configuration of the electric motor 12, the rotor 18 may be positioned within an inner circumference 20 of the stator 10 or may be positioned outside an outer circumference 22 of the stator 10. Typically, configurations described herein are directed to a rotor 18 that rotates within the inner circumference 20 of the stator 10. Accordingly, configurations described herein are directed to devices and methods for constructing the stator 10 and positioning the windings 14 for the stator 10 on an inner-rotor configured motor 12.

[0018] 3-9, the motor 12 includes a stator 10 comprised of a plurality of structural rings 24 that may define a number of stator teeth 16 contained within the stator 10. The tooth sections 26 are comprised of stacks 28 of tooth laminations 30. The stacks 28 of tooth laminations 30 are positioned within each tooth 16 and between adjacent structural rings 24. Thus, each stator tooth 16 of the stator 10 is comprised of an alternating arrangement of structural rings 24 and stacks 28 of tooth laminations 30 that cooperate to form the stator tooth 16. A bobbin 32 is positioned around a portion of each tooth 16 of the stator 10. A winding section 34 of conductive material is slidably positioned on the bobbin 32, respectively, for each tooth 16 of the stator 10. At this point, the winding sections 34 are separated from one another as they are installed on each of the plurality of stator teeth. The winding sections 34 are coupled together to define a continuous winding 14 for the stator 10 that forms a plurality of stator poles 36 that are configured to be selectively energized to generate an electromagnetic field.

[0019] An outer ring 38 is positioned around the outer periphery 22 of the teeth 16 of the stator 10. The outer ring 38 acts as a backiron 40 and also functions to house the winding sections 34 within a stator cavity 42. The stator cavity 42 is defined within the outer ring 38 and outside of a connecting portion 62 of the structural ring 24 that extends radially between adjacent stator teeth 16. Stated another way, the stator cavity 42 is defined within the outer ring 38 and outside of a core 44 of the stator 10 from which the teeth 16 of the stator 10 extend and which is made up of the connecting portion of the structural ring 24. An overmold 46 extends around the outer ring 38, the winding sections 34, the plurality of teeth 16, and the core 44 to form an overmolded stator 10. In one particular embodiment of the device, the outer ring 38 may include alignment channels 52 that interact with alignment protrusions 54 on the tooth sections 26, which are comprised of the structural ring 24 and the stack of tooth laminations 30. In this manner, the outer ring 38 may be aligned in one or more desired orientations relative to the tooth sections 26 of the stator 10. This may also be used as a locking device to ensure a secure fit between the outer ring 38 and the tooth sections 26, which form the stator cavity 42 in which the winding sections 34 are secured.

[0020] In certain embodiments of the device, as illustrated in FIGS. 3-9 , the winding sections 34 may be connected together using a bus ring 48. The bus ring 48 includes a plurality of connectors 50 that link certain winding sections 34 together. The connectors 50 attach to wire ends 60 of the winding sections 34 to complete the winding 14. Certain wire ends 60 are not attached to the connectors 50 so that they can be attached to wiring to deliver current through the winding 14. Those wire ends 60 that are not connected to the connectors 50 of the bus ring 48 may extend from the overmold 46 and be positioned to connect with electrical leads to a power source. The winding sections 34 are coupled together by the bus ring 48, which defines subsets 64 of the winding sections 34. These subsets 64 form various phases of the winding 14 that are in electrical communication with each other. The bus ring 48 includes a plurality of winding connections 72 that form the subsets 64 of the winding sections 34. Again, the subsets 64 of winding sections 34 correspond to phases of the plurality of stator poles 36. By way of example and not limitation, the plurality of winding connections 72 may include three winding connections corresponding to the three phases of the plurality of stator poles 36. To define the various phases, the winding connections 72 on the bus ring 48 are typically separated by insulating spacers 82 that electrically isolate the winding connections 72. The insulating spacers 82 provide for dedicated and separate current delivery to the subsets 64 of winding sections 34 to generate multi-phase operation of the stator 10.

[0021] Through this configuration, the stator 10, being an inner rotor configuration, can be wound from the outer periphery 22 before the outer ring 38 is placed around the winding sections 34. The outer ring 38 can then be placed around the stator 10 to accommodate the winding sections 34 on the teeth 16 of the stator 10. This configuration allows for the inner rotor configuration of the stator 10 to be manufactured without having to locate the windings 14 within the limited space inside the rotor cavity 74 of the stator 10. Additionally, the windings 14 can be applied as pre-wound winding sections 34, as described more fully herein.

[0022] According to various aspects of the device, as illustrated in FIGS. 4 and 5 , the winding sections 34 slidably positioned on each bobbin 32 and on each tooth 16 for the stator 10 can be pre-wound as formed winding sections 34. Each winding section 34 is then placed on the bobbin 32 for the respective tooth 16 of the stator 10. In certain aspects of the device, the winding sections 34 can be placed on the bobbin 32, and the bobbin 32 with the winding sections 34 thereon can be placed on the respective tooth 16 of the stator 10. Thus, the winding sections 34 and the corresponding bobbin 32 members form a bobbin assembly 76 as a single component that is placed on the corresponding stator tooth 16. Using this configuration, multiple winding sections 34 and multiple bobbins 32 can be pre-fabricated and paired for installation on the stator teeth 16. The wire ends 60 extending from each winding section 34 can be connected to adjacent winding sections 34 to form one or more continuous windings 14 extending around the stator 10. After the winding sections 34 are connected together to form a continuous winding or windings 14, an overmold 46 is defined by placing overmold material over the components to form the stator 10, which is now insulated.

[0023] As illustrated in FIGS. 3-9 , the various bobbins 32 extending over the teeth 16 for the stator 10 can be formed by one or more bobbin sections 70 or end caps slidably positioned over each tooth 16 having an enlarged tooth end 108. In various embodiments of the device, as illustrated in FIGS. 13-14 , the bobbin 32 can include two opposing bobbins 70 that slide over each tooth 16 from opposite directions, such as top and bottom, or from side to side, to form the complete bobbin 32 structure, wrapping behind the tooth end. A winding section 34 of conductive material is then positioned over the two-piece or multi-piece bobbin 32. The winding section 34 can be wound around the bobbin section 70, or, if the tooth does not include an enlarged tooth end, can be slidably installed in the bobbin section 70. The bobbin 32 serves to insulate the winding section 34 from the material of the structural ring 24 and stack 28 of tooth laminations 30 that form each tooth 16 for the stator 10. In certain embodiments of the device, such as where the teeth 16 do not have enlarged tooth ends 108, a single-piece bobbin 32 can be used in place of the multi-part bobbin 32 having the bobbin section 70. In such embodiments of the device, the pre-wound winding section 34 can also be slidably disposed within the bobbin 32.

[0024] Referring again to FIGS. 3-9 , during the formation of the stator 10, a die 130 in the shape of the completed stator 10 may be used to assemble the various components that make up the stator 10. Within the die, a first outer structural ring 80 may be positioned within the base of the die. Tooth laminations 30 may then be added around the die in position for each tooth 16 of the stator 10. These tooth laminations 30 may be positioned one at a time for each tooth 16, or multiple tooth laminations 30 formed in stacks 28 may be positioned within each die as the various teeth 16 for the stator 10 are built within the die. The number of tooth laminations 30 within a stack 28 may vary depending on the design of the stator 10. Typically, the number of tooth laminations 30 stacked between adjacent structural rings 24 will be consistent. This is to ensure that the structural rings 24 are generally parallel throughout the stator 10. The number of tooth laminations 30 in a particular stack 28 can be in the range of about 3 tooth laminations to about 10 tooth laminations, or in the range of about 5 tooth laminations to about 8 tooth laminations, or in the range of about 2 tooth laminations to about 15 tooth laminations.

[0025] Referring again to FIG. 9 , typically, a sheet of metal stock is moved over the die. Successive structural rings 24 and tooth laminations 30 are stamped from the sheet of metal stock and directed into the die. This sheet stock is made of ferrous metal, which will form the stator 10 as described herein. Using the metal stock, the stator 10 is built layer by layer. The structural rings 24 are stamped and placed into the die. Successive layers of stamped tooth laminations 30 are then directed into the die cavities. Additionally, along with each stamped portion of the sheet of metal stock, alignment protrusions 90 are stamped into each lamination that will form one of the teeth 16 for the stator 10. These protrusions 90 operate in a nested configuration to lock the layers together to structurally support the stator 10. In this manner, the processes of stamping the components of the stator 10 and forming these components into the stator 10 are combined into a single operation.

[0026] During the formation of stator 10, assembly involves two stamping configurations. One stamping operates to form structural rings 24 from sheets of metal stock. Another stamping operates to form layers of tooth laminations 30. As stator 10 is built layer by layer, the appropriate stamping is positioned over a die to stamp the next layer of stator 10 into the die. Again, the stamped components are directed into the die immediately after being stamped.

[0027] During this assembly of the stator 10, layers of tooth laminations 30 are successively punched into a die to form stacks 28 of tooth laminations 30 for each tooth 16. Thus, these stacks 28 of tooth laminations 30 are formed simultaneously to maintain a consistent height for each tooth 16 during assembly of the stator 10. Stated differently, as the stator 10 is constructed, each die position receives one tooth lamination 30 from a sheet of metal stock. In certain aspects of the device, multiple sheets can be punched simultaneously so that the same number of tooth laminations 30 are placed in the die. Structural rings 24 are then punched to rest on a predetermined number of tooth laminations 30 for multiple teeth 16, with each structural ring 24 evenly resting on the various stacks 28 of tooth laminations 30. In this manner, as the teeth 16 for the stator 10 are constructed, the laminations and structural rings 24 are evenly distributed among the tooth 16 positions in the die.

[0028] Periodically, additional structural rings 24 are positioned on top of the stack 28 of tooth laminations 30 to reinforce the structure of the stator 10. Once the desired height of the stator 10 is achieved, a final outer structural ring 80 is positioned on top of the stack 28 of tooth laminations 30 and on top of the stator 10 to complete the construction of the stator 10. Through this configuration, the stator 10 is formed from multiple tooth laminations 30 that are positioned and reinforced through the use of intermittent structural rings 24 and pairs of outer structural rings 80.

[0029] To aid in the assembly of the various tooth laminations 30 and structural rings 24 for the stator 10, a portion of each tooth lamination 30 and structural ring 24 of the various stator teeth 16 can be stamped to form protrusions 90. Each protrusion 90 forms a nested configuration with an adjacent tooth lamination 30. This nested configuration further positions and reinforces the structure of the stator 10. These protrusions 90 can also function as positioning features to ensure that the stack 28 of tooth laminations 30 is properly aligned with the other tooth laminations 30 as well as the structural ring 24 that forms the stator 10. Through the use of the protrusions 90, lateral displacement or misalignment of the tooth laminations 30 and structural ring 24 is largely minimized or eliminated.

[0030] 10-14, the stator 10 may include a plurality of tooth segments 100. Each tooth segment 100 may be formed from a plurality of tooth laminations 30 that are stacked to form a desired tooth height for the teeth 16 of the stator 10. After the stacked tooth laminations 30 are positioned to form each tooth segment 100, a bobbin 32 is slidably positioned over the tooth portion 102 of the tooth segment 100. A pre-wound tooth winding 14 is then slidably positioned over the bobbin 32 to form a pre-wound stator segment 106.

[0031] As discussed herein, the winding sections 34 may be placed within the bobbin 32, and the assembled bobbin 32 and winding sections 34 may be placed on the tooth portion 102 of the tooth segment 100 to form a stator segment 106. Each pre-wound stator segment 106, having a pre-mounted bobbin 32 and winding section 34, is then coupled to two adjacent pre-wound stator segments 106 to form a stator core 44 having a plurality of pre-wound stator poles 36 extending inwardly therefrom. The core portions 104 of the tooth segments 100 include mating geometries that interlock to form the core 44 of the stator 10. The winding sections 34 of each tooth segment 100 are then connected together to form one or more windings 14 of the stator 10. In this manner, each winding section 34 of a stator segment 106 is coupled with a corresponding winding section 34 to form a phase of the winding 14 of the plurality of stator segments 106. Typically, the windings 14 have three phases. The phases of the windings 14 and the windings 14 generally define a plurality of stator poles 36 that are configured to be selectively energized. After the windings 14 are attached together in a desired configuration, an overmold material is placed over the plurality of stator segments 106 to form the overmold 46 for the stator 10, which is insulated by the overmold 46. In certain aspects of the device, the individual winding sections 34 can be attached together after the overmold 46 is completed. In such a configuration, the wire ends 60 of each winding section 34 can protrude from the overmold 46 and be connected together to form the desired winding configuration.

[0032] According to various aspects of the device, the desired winding configuration may be in the form of a single-phase winding 14, a three-phase winding 14, a stepper motor 12, or other similar motor configuration. Typically, the winding sections 34 are attached together before applying the overmold material that forms the insulated stator 10. As discussed herein, a bus ring 48 used to attach the winding sections 34 together may be used to define the phase configuration of the winding 14. The bus ring 48 may take the form of one or more bus bars or other similar electrical brackets that are circularly shaped to match the profile of the stator 10. The various bus bars of the bus ring 48 are dedicated to connecting with the various winding sections 34 to define the phases of the windings 14 of the stator 10.

[0033] The use of pre-wound winding sections 34 attached to the tooth sections 26 of the stator 10 provides more efficient winding of a desired motor configuration. In particular, the winding configurations described herein can achieve more efficient filling of the slots 110 defined between the teeth 16 of the stator 10. Furthermore, the configurations described herein enable the use of larger gauge wire for the pre-wound winding sections 34. Larger gauge wire can be used because the assembly for winding the stator 10 does not need to weave around and between the stator core 44, which has pre-positioned teeth 16, which can be difficult to navigate. The pre-wound winding sections 34 can be formed into a desired shape and then slidably positioned over each tooth 16 of the stator 10 or tooth portion 102 of the tooth segment 100. This pre-assembled configuration of the stator segment 106 allows the completed windings 14 to occupy more of each slot 110 because space is not required to accommodate the assembly for weaving the wire for the windings 14 around the teeth 16 of the stator 10.

[0034] Additionally, the motor 12 formed via the stator 10 described herein does not require the use of rare earth materials as in permanent magnet motors. It achieves competitive power density without the use of permanent magnets. Furthermore, the insulating structure described herein, through the use of the insulating overmold 46, allows the stator 10 components surrounded by the overmold material to be exposed to corrosive environments without damage. Because the stator 10 described herein utilizes higher gauge wire and has increased filling of the slots 110 between the teeth 16, power density is not lost compared to other conventional electric motor systems.

[0035] In accordance with various aspects of the device, the stator 10 configurations described herein may be used with any one of a variety of rotors 18, including the rotor 18 configurations described herein. Additionally, the disclosure of rotors 18 having reluctance voids 122, as described herein, is provided as an exemplary, non-limiting type of rotor 18 that may be used in connection with the stator 10 configurations described herein, as well as other types of stators 10.

[0036] Referring now to FIGS. 2, 15-18, and 22-34, the rotor 18 of the synchronous reluctance motor 12 includes a stack 28 of rotor laminations 120, typically made from electrical-grade steel, to form a rotor body 140. Reluctance voids 122 are stamped out of the rotor laminations 120 that form the rotor body 140 of the rotor 18. The reluctance voids 122 may also be stamped as part of each rotor lamination 120. A single end lamination 124 may be positioned at each opposing end of the rotor 18 to act as a cover. The opposing end laminations 124 are generally solid within the cross-section of the rotor 18 and do not include reluctance voids 122. The opposing end laminations 124 are located to prevent wind noise that could occur if the reluctance voids 122 were exposed. Space is typically provided for a drive member, such as a drive shaft. After placing the end laminations 124, the rotor 18 is then encapsulated with an overmold material that at least partially encapsulates the outer surface 126 of the rotor 18 to form a rotor overmold 128. Typically, the overmold material is in the form of a non-metallic resin material. The resin may also be in the form of a non-magnetic material, such as a resin, polymer, or other similar overmold material. Because the ends of the rotor 18 are covered by the end laminations 124, the overmold material cannot penetrate the reluctance voids 122. With the reluctance voids 122 free of overmold material, the rotor 18 remains balanced with a consistent thickness of overmold around the rotor body 140. If the overmold material penetrates one or more reluctance voids 122, an imbalance-causing effect will appear in the rotor 18, which could result in undesirable vibration or wobble. Therefore, the shape and size of the reluctance voids 122 can be maintained throughout the assembly and overmold process of the rotor 18. The use of an overmold around the rotor body 140 also limits the occurrence of corrosion within the rotor laminations 120 and the opposing end laminations 124 .

[0037] As described herein, the reluctance voids 122 may be maintained as hollow spaces within the rotor body 140. Additionally, magnetic inserts 162 may be located within one or more of the reluctance voids 122. These magnetic inserts 162 may partially or completely occupy the space defined by the reluctance voids 122. The presence and size of the magnetic inserts 162 relative to the space defined by the reluctance voids 122 may vary as a particular magnetic interaction between the electromagnetic field 164 of the charged windings 14 and the rotor 18 is desired to operate the rotor 18 within the stator 10.

[0038] 15-18 , during formation of the rotor 18 having hollow reluctance voids 122, the connecting webs 150 of the rotor body that define the reluctance voids 122 can be demagnetized, or at least partially demagnetized, to increase the reluctance characteristics of the rotor 18. Stated another way, demagnetizing the connecting webs 150 reduces the reluctance of the connecting webs 150, which in turn provides a more defined path of minimum reluctance 152 through which the magnetic flux 154 can flow through the rotor 18. This demagnetization of the connecting webs 150 has the effect of making the interaction between the electromagnetic field 164 generated by the stator 10 and the rotor 18 more effective. Demagnetizing the rotor can be achieved by localized heating, such as with a laser or other heat source, or by imparting additional induced mechanical stresses within the rotor body.

[0039] 15-18 , during operation of the stator 10 and rotor 18, the controller operates to control the delivery of current to one or more phases of the windings 14. The controller may also operate in conjunction with a position sensor that monitors the rotational position of the rotor 18 relative to the stator 10 or one or more windings 14 of the stator 10. Commutation of the current may be achieved by electrically energizing electromagnetic phases of the windings 14 to selectively attract and align the reluctance of the rotor 18 in a desired direction to induce rotation of the rotor 18. Additionally, sensor feedback of the rotor 18 position delivered to the controller allows for smooth and controllable current flow to the windings 14, which may then be used to control the speed and torque output of the motor 12.

[0040] In certain embodiments of the device, the controller operates in a sensorless configuration. In an exemplary, non-limiting embodiment of the device, a voltage sensor or voltage monitor may be used at the center of the back electromotive force (EMF) voltage. This is compared to typical half of the supplied DC bus voltage to calculate the relative inductance to determine the position of the rotor 18 relative to the phases of the windings 14. When the position of the rotor 18 is known, smooth, controllable current to the windings 14 can be used to control the speed and torque of the motor 12 without separate position-sensing components.

[0041] Referring now to FIGS. 1-19 , which illustrate various aspects of a stator 10 and rotor 18 for an electric motor 12, a method 400 for forming a stator 10 for an electric motor 12 is disclosed. According to method 400, step 402 includes placing a bottom outer structural ring 80 in a die. Layers of stacked tooth laminations 30 are then placed on the bottom outer structural ring 80 (step 404). Intermittent structural rings 24 are placed in an alternating configuration between adjacent layers of stacked tooth laminations 30 (step 406). As discussed herein, the various tooth laminations 30 are simultaneously positioned relative to each tooth 16 to maintain a consistent height of each tooth 16 for the stator 10 during assembly of the stator 10. Then, a top outer structural ring 80 is placed on the top layer of the stacked tooth laminations 30 to form the laminated stator 10 (step 408). The laminated stator 10 is then removed from the die (step 410). A bobbin assembly 76 is positioned over each tooth 16 of the laminated stator 10 (step 412). As described herein, the bobbin 32 may be in the form of a single-piece bobbin 32 or a multi-part bobbin 32 that can be assembled over each tooth 16 of the laminated stator 10. The bobbin assembly 76 may include a bobbin 32 and pre-wound winding sections 34 that can be slidably positioned over the tooth 16 as a single assembly. In an alternative aspect, it is contemplated that the bobbin 32 and winding sections 34 may be sequentially positioned over the tooth 16. With all of the bobbin assemblies 76 installed over the stator teeth 16, the winding sections 34 form a segmented stator winding. The pre-wound winding sections 34 of the segmented stator winding are then attached using a bus ring 48 to form the completed stator winding 14 (step 414). An outer ring 38 is placed around the stator windings 14 and laminated stator 10 (step 416). The outer ring 38 prevents outward movement of the winding sections 34 along each tooth 16 for the stator 10.The laminated stator 10 and stator windings 14 are then overmolded with an overmolding material (step 418). As described herein, the use of pre-wound winding sections 34 provides for greater slot filling and also the use of larger gauge wire that can generate a more effective electromagnetic field when energized with electrical current.

[0042] As part of the method 400 for forming the stator 10, the structural ring 24 and tooth laminations 30 can be made less magnetic. By way of example and not limitation, thin sections, such as the connecting portions of the structural ring 24, can be metallurgically modified to make them less magnetic. This is typically done by heating the steel, such as with the use of a laser. In certain aspects of the device, the connecting portions of the structural ring 24 can be turned over using a laser or via mechanical debridging means to reduce or eliminate magnetic effects that may be generated by the presence of the connecting portions. It is contemplated that only a portion of the connecting portions may be turned over or removed to provide structure to the stator 10.

[0043] 1-18 and 20, which illustrate various aspects of the electric motor 12, a method 500 for forming a stator 10 for the electric motor 12 is disclosed. According to the method 500, laminated tooth sections 26 are formed (step 502). A bobbin 32 is placed over each tooth portion 102 of the laminated tooth segments 100 (step 504). A pre-wound winding section 34 is then placed over the tooth portion 102 of each laminated tooth segment 100 and onto the respective bobbin 32 (step 506). The laminated tooth segments 100 with their pre-wound winding sections 34 are then attached together to form the circular core 44 of the stator 10 (step 508). The pre-wound winding sections 34 are then attached together to form the desired configuration of windings 14 for the stator 10 (step 510). The core 44, teeth 16, and windings 14 are then overmolded using an overmolding material (step 512).

[0044] Typically, the use of stacked winding sections 34, which are pre-wound and then attached together, is utilized in the inner rotor configuration generally illustrated in Figures 11-18. The star configuration of structural rings 24 for stator 10 illustrated in Figure 4 can be used in either the inner rotor configuration or the outer rotor configuration, depending on the design of motor 12.

[0045] 1-18 and 21 , which illustrate various aspects of the device, a method 600 for forming a rotor 18 for an electric motor 12 is disclosed. According to method 600, steel rotor laminations 120 are formed with sections removed from each of the rotor laminations 120 to form reluctance voids 122 (step 602). The rotor laminations 120 are stacked to form the structure of the rotor 18 (step 604). The removed rotor lamination sections are placed or otherwise aligned to define the reluctance voids 122 within the rotor 18. Opposing end laminations 124, or end caps, are then placed on the ends of the rotor 18 to enclose the reluctance voids 122 (step 606). As discussed herein, closure of the reluctance voids 122 prevents infiltration of overmolding material from entering and occupying the reluctance voids 122. The rotor 18 is then overmolded with overmolding material (step 608). The opposing end laminations 124, as described herein, prevent the overmolding material from penetrating into the reluctance voids 122, which could adversely affect the operation and efficiency of the reluctance voids 122 when operating in conjunction with the current-carrying windings 14 of the stator 10.

[0046] The assembly method described herein for the synchronous reluctance motor 12 allows for bobbin winding of the motor assembly, which provides additional and more efficient filling of the slots 110 for the stator 10. The configuration described herein also allows for more efficient use and easier winding of heavier gauge wire, as well as improved slot filling over conventional needle-wound stators 10. Overmolding the stator 10 and overmolding the rotor 18 allows the motor 12 to be exposed to corrosive fluids without corroding the ferrous stator 10 or ferrous rotor 18. Additionally, closing each end of the stack 28 of rotor laminations 120 before overmolding, as described herein, prevents injection-molded non-metallic resin material from flowing into the reluctance voids 122. This seepage could potentially cause rotor imbalance. The use of an overmold on the rotor 18 provides a smooth overmold surface that reduces wind noise that may be caused from voids 122 in the rotor 18, as well as the elimination of "paddle" drag in wet rotor designs, particularly when the voids 122 are exposed to fluids that may cause increased drag on the rotor 18 when rotating in a wet rotor configuration.

[0047] Additionally, when the non-metallic resin material is overmolded to surround the stator 10 and windings 14, the overmold material is configured to at least partially encapsulate the inner diameter of the stator teeth 16. As described herein, this configuration provides for use of the stator 10 in liquid and corrosive environments. The use of the overmold 46 on the inner diameter of the stator teeth 16 prevents these materials from corroding or otherwise damaging the laminations of the stator 10.

[0048] 22-34 , the electric motor 12 may include a stator 10 having one or more windings 14 that, when selectively energized, generate an electromagnetic field 164 within a rotor cavity 74. A ferrite-assisted reluctance rotor 160 is disposed within the rotor cavity 74 of the stator 10. The ferrite-assisted reluctance rotor 160 is in electromagnetic communication with the windings 14 and the electromagnetic field 164 generated thereby. The ferrite-assisted reluctance rotor 160 may include a drive shaft 202 and a rotor body 140 extending around the drive shaft 202. The rotor body 140 may define a plurality of reluctance voids 122. The magnet inserts 162 may be positioned within the reluctance voids 122. The magnet inserts 162 occupy at least a portion of the space defined by the reluctance voids 122. The magnet inserts 162 and reluctance voids 122 cooperate with the electromagnetic field 164 to generate an electromagnetic torque 170 .

[0049] 22-34 , the electromagnetic torque 170 generated by the ferrite-assisted reluctance rotor 160 includes a magnetic torque component 172 defined by the electromagnetic interaction between the electromagnetic field 164 and the magnet inserts 162. In addition, the electromagnetic torque 170 includes a reluctance torque component 174 defined by the electromagnetic interaction between the reluctance voids 122 and the connecting webs 150 that define the electromagnetic field 164. As described herein, the connecting webs 150 define a path of minimum reluctance 152 along which the magnetic flux 154 tends to travel, which in turn aligns the magnetic flux path with the electromagnetic field 164, generating the reluctance torque component 174 of the electromagnetic torque 170. This combination of the magnetic torque component 172 and the reluctance torque component 174 together generates the overall electromagnetic torque 170 on the rotor 18.

[0050] According to various aspects of the device, the reluctance torque component 174 may be in a range of about 20% to about 60% of the total electromagnetic torque 170. It is also contemplated that the reluctance torque component 174 may be about 30% to about 50% of the total electromagnetic torque 170. It is further contemplated that the reluctance torque component 174 may be about 40% of the total electromagnetic torque 170. It should be understood that the range of ratios of the reluctance torque component 174 and the magnetic torque component 172 may be achieved through various configurations of the reluctance voids 122 and the magnet inserts 162, as described more fully herein.

[0051] Using a combination of reluctance voids 122 and magnet inserts 162, the ferrite-assisted reluctance rotor 160 generates a hybrid torque configuration including both a reluctance torque component 174 and a magnetic torque component 172. Using this configuration, the magnet inserts 162 can be made from a range of magnetic materials other than rare earth magnets and still generate electromagnetic torque 170 with performance similar to that of a conventional brushless DC (BLDC) electric motor 12 using rare earth magnets. In this manner, the hybrid ferrite-assisted reluctance rotor 160 described herein generates similar electromagnetic torque 170 using magnets with lower magnetic output compared to conventional motors using more expensive rare earth magnets with greater magnetic output. The use of magnet inserts 162 is used, in part, to generate a back electromagnetic force (back EMF). By creating a back EMF within the motor 12 as described herein, sensorless control can be implemented to monitor the rotational position of the rotor 18 relative to the stator 10 and electromagnetic field 164. Therefore, the lower output magnet insert 162 is effective for generating the desired magnetic torque component 172 while also generating the back EMF required for sensorless control. These advantages of the motor 12 described herein are achieved through the use of relatively low-cost materials for the magnet insert 162.

[0052] Additionally, to achieve these advantages of the motor 12 described herein, the magnet insert 162 can be designed and positioned to occupy only a portion of the reluctance void 122. Also, for reluctance voids 122 that include a magnet insert 162, the magnet insert 162 may occupy only a portion of the space defined by the reluctance void 122. Thus, the reluctance void 122 typically includes a combination of air and the magnet insert 162.

[0053] According to various aspects of the device, as illustrated in Figures 15-18 and 23-28, the reluctance voids 122 may be positioned in a two-pole configuration. In this configuration, the reluctance voids 122 are oriented in a generally parallel configuration relative to the center plane 220 of the rotor body 140. The reluctance voids 122 may include an enlarged outer section 222 of the reluctance voids 122. The central section 224 of the reluctance voids 122 may include an arcuate section 226 that extends consistently around the drive shaft 202 of the rotor 18. In this manner, the generally parallel configuration extends along the center plane 220 of the rotor body 140. These reluctance voids 122 in the generally parallel configuration may be linear and parallel to one another. The reluctance voids 122 in the generally parallel configuration may also include undulations 230 that conform to the geometry of the rotor body 140 and the drive shaft 202. In this manner, the center plane 220 of the rotor body 140, which extends along the central axis 232 of the two-pole configuration, is accentuated to define the path of minimum reluctance 152 for defining the reluctance torque component 174 or electromagnetic torque 170 of the motor 12. Additionally, in areas where the reluctance void 122 is larger, such as adjacent the enlarged outer section 222, the connecting web 150 has a smaller thickness. This smaller thickness can be used to more precisely define the path of minimum reluctance that can interact with aspects of the stator poles 36 and electromagnetic field 164 of the stator 10. This configuration can be used to provide greater resolution of the ferrite-assisted reluctance rotor 160 when the rotor 18 operates within the stator 10.

[0054] Studies of the disclosed device indicate that this equivalent power output between the hybrid ferrite-assisted reluctance rotor 160 described herein and a conventional BLDC rotor 18 can be achieved with equivalent electrical input. Thus, the overall system utilizing the hybrid ferrite-assisted reluctance rotor 160 provides higher efficiency and generates electromagnetic torque 170 using lower cost magnetic material with less magnetic output.

[0055] According to various aspects of the device, as illustrated in FIGS. 22-34 , the ferrite-assisted reluctance rotor 160 achieves similar performance in terms of electromagnetic torque 170 compared to conventional BLDC motors utilizing more expensive rare earth magnets. Additionally, the inclusion of magnet inserts 162 within the ferrite-assisted reluctance rotor 160 generates a back EMF. The generation of the back EMF by the magnet inserts 162 allows the ferrite-assisted reluctance rotor 160 to be used in conjunction with a sensorless configuration of the electric motor 12. Conventional reluctance rotors 18 require a sensor to determine the rotational position of the rotor 18 within the rotor cavity 74 at any particular time. Again, the inclusion of magnet inserts 162 within the ferrite-assisted reluctance rotor 160 generates a back EMF to provide sensorless operation of the ferrite-assisted reluctance rotor 160.

[0056] According to various aspects of the device, the air gap 180 defined between the outer surface 126 of the rotor 18 and the inner surface of the stator 10 may be increased in the ferrite-assisted reluctance rotor 160. The inclusion of the magnetic torque component 172 of the electromagnetic torque 170, combined with the reluctance torque component 174 of the electromagnetic torque 170, may provide a greater tolerance in the thickness of the air gap 180. This increased tolerance may provide an increased air gap 180 compared to a conventional reluctance rotor 18. This may also help reduce noise generated by the ferrite-assisted reluctance rotor 160 due to the wider tolerance and air gap 180 between the ferrite-assisted reluctance rotor 160 and the stator 10. At the same time, the enlarged outer section 222 of the reluctance void 122 and the configuration of the magnet inserts 162, if present, help provide this greater resolution of the ferrite-assisted reluctance rotor 160 relative to the stator poles 36.

[0057] According to various aspects of the device, as illustrated in Figures 24-34, the magnet insert 162 can occupy a portion of the reluctance void 122 or can occupy the entire reluctance void 122. Varying the ratio of the space within the reluctance void 122 compared to the space occupied by the magnet insert 162 can achieve different ranges of electromagnetic torque 170 and different ratios of the reluctance torque component 174 and the magnetic torque component 172. Additionally, placing the magnet insert 162 within the enlarged outer section 222 and / or arcuate section 226 of the two-pole configuration of the rotor 18 can also be used to adjust the ratio of the reluctance torque component 174 and the magnetic torque component 172.

[0058] As described herein, the reluctance voids 122 of the ferrite-assisted reluctance rotor 160 can be positioned in a two-pole configuration (illustrated in FIGS. 24-28), a four-pole configuration (illustrated in FIGS. 29-34), and other pole configurations within the ferrite-assisted reluctance rotor 160. The configuration of the reluctance voids 122 and magnet inserts 162 of the ferrite-assisted reluctance rotor 160 can vary depending on the design of the stator 10, stator windings 14, and other components of the electric motor 12. As described herein, the reluctance voids 122 and magnet inserts 162 cooperate to define a plurality of rotor poles that can be manufactured in a variety of configurations. The two-pole configuration described herein can include a generally parallel configuration of the reluctance voids 122. The generally parallel configuration of the reluctance voids 122 tends to align with the center plane 220 of the rotor body 140. This central plane 220 tends to align with an axis of symmetry 240 of the reluctance void 122. The four-pole configuration of the reluctance void 122 tends to define a series of arcuate sections 226 that extend symmetrically and non-concentrically about a central axis 232 of the drive shaft 228 of the rotor 18.

[0059] According to various aspects of the device, the magnetic poles formed in the hybrid ferrite-assisted reluctance rotor 160 may be comprised of multiple magnet inserts 162 positioned within multiple corresponding reluctance voids 122. It is also contemplated that each pole of the multiple magnetic poles may include a single magnet insert 162 positioned within the corresponding reluctance void 122 (as shown in FIG. 34).

[0060] 22-34 , the rotor body 140 includes a plurality of stacked rotor laminations 120. Each lamination of the plurality of stacked rotor laminations 120 includes a connecting web 150 that aligns to form a reluctance void 122. Stated another way, when configured as a plurality of stacked rotor laminations 120, the connecting webs 150 of each rotor lamination 120 align with one another to form a reluctance void 122 that extends substantially through, or through the entire rotor body 140.

[0061] It should be understood that the use of the term substantially through the rotor body 140 in this context indicates that at least one end of the rotor body 140 defines an opening that provides access to the reluctance voids 122 for disposing the magnet inserts 162 within the reluctance voids 122. The reluctance voids 122 may extend a majority of the distance through the rotor body 140 or may extend through a majority of the stacked rotor laminations 120. In certain aspects of the device, the ferrite-assisted reluctance rotor 160 may include reluctance voids 122 that may be accessible from each end of the rotor body 140 or that may be accessible from only one end of the rotor body 140. Still further, the rotor body 140 may have a first set of reluctance voids 122 accessible from one end of the rotor body 140 and a second set of reluctance voids 122 accessible from the opposing end of the rotor body 140.

[0062] The magnet inserts 162 of the ferrite-assisted reluctance rotor 160 may be made from a variety of magnetic materials, typically in the form of aluminum nickel cobalt (AlNiCo) magnets, ferrite magnets, and other similar magnets. Typically, the magnet inserts 162 do not include rare earth magnets. As discussed herein, the configuration of the ferrite-assisted reluctance rotor 160 achieves equivalent electromagnetic torque 170 without the need to use rare earth magnets. Thus, the ferrite-assisted reluctance rotor 160 can be manufactured to achieve equivalent electromagnetic torque 170 while using non-rare earth magnets.

[0063] To accommodate the magnet inserts 162 within the rotor body 140, opposing end laminations 124 may be positioned at opposing ends of the rotor body 140 to close the reluctance voids 122. The opposing end laminations 124 are configured to reduce wind noise during operation of the rotor 18 within the rotor cavity 74. This is especially true when the magnet inserts 162 occupy only a portion of the reluctance voids 122 within the rotor body 140 and leave space within the reluctance voids 122. Additionally, the end laminations 124 provide closure of the reluctance voids 122 so that the overmold material of the rotor overmold 128 disposed about the rotor body 140 does not penetrate the reluctance voids 122 during manufacture of the ferrite-assisted reluctance rotor 160.

[0064] According to various aspects of the device, the ferrite-assisted reluctance rotor 160, including the reluctance voids 122 and magnet inserts 162, provides hybrid operation of the ferrite-assisted reluctance rotor 160 relative to the electromagnetic field 164 generated by the current-carrying windings 14 of the stator 10. The reluctance portion 190 of the ferrite-assisted reluctance rotor 160, which extends around the reluctance voids 122, creates a reluctance path around the reluctance voids 122 and through the rotor body 140. The rotor 18 tends to align with the electromagnetic field 164, creating a path of minimum reluctance 152 such that the reluctance path of the ferrite-assisted reluctance rotor 160 tends toward an aligned orientation relative to the electromagnetic field 164 of the stator 10. At the same time, the magnet inserts 162, located within the reluctance voids 122, provide a separate interaction with the electromagnetic field 164 of the stator 10. In this manner, the magnetic field of each magnet insert 162 tends to be oriented in alignment with the electromagnetic field 164 of the current-carrying portion of the windings 14 of the stator 10. The paths of minimum reluctance 152 and the magnetic fields of the magnet inserts 162 are at different radial locations relative to the ferrite-assisted reluctance rotor 160. Thus, the magnetic fields of the magnet inserts 162 and the paths of minimum reluctance 152, also referred to herein as reluctance portions 190 of the rotor body 140, each separately but cooperatively tend to align with the current-carrying portions of the windings 14 for the stator 10. This provides multiple electromagnetic interactions between the ferrite-assisted reluctance rotor 160 and the stator 10 to generate the hybrid electromagnetic torque 170.

[0065] Again, as discussed herein, electromagnetic torque 170 is comprised of reluctance torque component 174 generated by the tendency of reluctance portion 190, or minimum reluctance path 152, of ferrite-assisted reluctance rotor 160 to align with electromagnetic field 164 of windings 14 of stator 10. Additionally, magnetic torque component 172 operates where the magnetic field of magnet insert 162 tends to align with electromagnetic field 164 of windings 14 for stator 10. These torque components combine to produce electromagnetic torque 170 that allows rotor 18 to achieve similar torque output compared to conventional BLDC motors utilizing rare earth magnets.

[0066] According to various aspects of the device, as illustrated in FIGS. 22-34 , a ferrite-assisted rotor for an electric motor 12 can include a drive shaft 202 and a plurality of stacked rotor laminations 120 forming a rotor body 140. The rotor body 140 extends around the drive shaft 202. Each rotor lamination 120 of the plurality of stacked rotor laminations 120 includes a connecting web 150 that forms a reluctance void 122 within the plurality of stacked rotor laminations 120. A magnet insert 162 is disposed within the reluctance void 122. The magnet insert 162 occupies at least a portion of the space defined by the reluctance void 122. The magnet insert 162 and the reluctance void 122 are configured to cooperate with an electromagnetic field 164 generated by the current-carrying winding 14 for the stator 10. This interaction generates an electromagnetic torque 170 having a reluctance torque component 174 and a magnetic torque component 172.

[0067] In a conventional reluctance motor, the reluctance rotor is typically much longer than the stator to provide greater interaction between the paths of minimum reluctance within the rotor body.

[0068] According to various aspects of the device, as illustrated in FIGS. 22-34 , the inclusion of magnet inserts 162 has been shown to provide a consistent, equivalent electromagnetic torque 170 using a ferrite-assisted reluctance rotor 160 having a rotor body 140 that is substantially the same as or equal to the height of the rotor cavity 74 of the stator 10. Thus, using a ferrite-assisted reluctance rotor 160, the motor 12 can be more compact than other conventional reluctance motors. Again, this equivalent electromagnetic torque 170 can be achieved without the need for rare earth magnets. Rather, the ferrite-assisted reluctance rotors 160 described herein can utilize non-rare earth magnet inserts 162 within the reluctance voids 122 to generate the equivalent electromagnetic torque 170.

[0069] 22-35, which illustrate various aspects of a ferrite-assisted reluctance rotor 160, a method 700 for forming a rotor 18 for an electric motor 12 is disclosed. According to method 700, step 702 includes forming rotor laminations 120 having reluctance blanks 200 or sections removed from each of the rotor laminations 120. These reluctance blanks 200 or sections also define connecting webs 150 extending around each of the removed reluctance blanks 200. After the laminations are formed, the rotor laminations 120 are stacked (step 704) to form a rotor body 140 comprised of a plurality of stacked rotor laminations 120. As discussed herein, the connecting webs 150 of the reluctance portions 190 for each of the laminations are aligned to define a reluctance void 122 that extends or substantially extends through the rotor body 140. After a plurality of stacked rotor laminations 120 are positioned to form the rotor body 140 and define the reluctance voids 122 therein, the magnet inserts 162 are positioned within the reluctance voids 122 (step 706). To maintain the magnet inserts 162 within the reluctance voids 122, at least one, and typically two, opposing end caps 70 are placed on the rotor body 140 to enclose the reluctance voids 122 and any space within the reluctance voids 122 that cannot be occupied by the magnet inserts 162 (step 708). Typically, the entire space defined by the reluctance void 122 is occupied by the magnet inserts 162, leaving little or no space. It is contemplated that opposing end caps 70 are disposed at the ends of the rotor body 140 to prevent movement of the magnet inserts 162 during operation of the ferrite-assisted reluctance rotor 160 and during placement of the overmold 46 around the rotor body 140 and magnet inserts 162.After placing the magnet inserts 162 within the rotor body 140, the rotor body 140 is overmolded with an overmolding material (step 710). As discussed herein, the opposing end caps 70 prevent the overmolding material from penetrating the reluctance voids 122 and also prevent movement of the magnet inserts 162 within the reluctance voids 122.

[0070] According to one aspect of the disclosure, a motor includes a stator having windings that, when selectively energized, generate an electromagnetic field within a rotor cavity, and a rotor disposed within the rotor cavity of the stator in electromagnetic communication with the windings and the electromagnetic field. The rotor includes a drive shaft, a rotor body extending around the drive shaft and defining a plurality of reluctance voids, and magnetic inserts disposed within the reluctance voids. The magnetic inserts occupy at least a portion of the space defined by the reluctance voids. The magnetic inserts and the reluctance voids cooperate with the electromagnetic field to generate electromagnetic torque.

[0071] According to another aspect, the magnetic insert does not include a rare earth magnet.

[0072] According to another aspect, the magnetic insert is at least one of an aluminum nickel cobalt (AlNiCo) magnet and a ferrite magnet.

[0073] According to another aspect, the stator and rotor do not include a position sensor for sensing the rotational position of the rotor relative to the stator.

[0074] According to another aspect, the rotational position of the rotor relative to the stator is estimated using the back EMF generated by the magnet inserts.

[0075] According to another aspect, the electromagnetic torque includes a magnetic torque component generated by the interaction of the magnet insert with an electromagnetic field.

[0076] According to another aspect, the electromagnetic torque includes a reluctance torque component produced by the interaction of the rotor body with an electromagnetic field.

[0077] According to another aspect, the rotor body includes a connecting web that defines a reluctance void.

[0078] According to another aspect, the reluctance torque component of the electromagnetic torque is generated by the interaction of the connecting webs of the rotor body with the electromagnetic field.

[0079] According to another aspect, at least one of the magnet inserts occupies only a portion of the space of a corresponding one of the reluctance voids.

[0080] According to another aspect, the opposing end laminations and overmold layers surround the reluctance voids of the rotor and fix the position of the magnet inserts within the reluctance voids.

[0081] According to another aspect of the present disclosure, a rotor includes a drive shaft and a plurality of stacked rotor laminations forming a rotor body. The rotor body extends around the drive shaft. Each stacked rotor lamination has a connecting web that forms a reluctance void within the plurality of stacked rotor laminations. The rotor further includes a magnetic insert disposed within the reluctance void. The magnetic insert occupies at least a portion of the space defined by the reluctance void. The magnetic insert and the reluctance void are configured to cooperate with an electromagnetic field from a stator winding to generate an electromagnetic torque having a reluctance torque component and a magnetic torque component.

[0082] According to another aspect, each magnet insert occupies only a portion of a respective one of the reluctance voids.

[0083] According to another aspect, the rotor includes a two-pole configuration, with the reluctance voids positioned in a configuration generally parallel to the center plane of the rotor body.

[0084] According to another aspect, the magnetic insert includes at least four magnetic inserts positioned in a generally parallel configuration.

[0085] According to another aspect, the rotor includes a four-pole configuration and the reluctance voids are positioned in a non-coaxial configuration relative to the axis of rotation of the rotor body.

[0086] According to another aspect, the magnetic insert does not include a rare earth magnet.

[0087] According to another aspect, the magnetic insert is at least one of an aluminum nickel cobalt (AlNiCo) magnet and a ferrite magnet.

[0088] According to yet another aspect of the present disclosure, a method for forming a rotor for an electric motor includes forming rotor laminations having reluctance portions removed from each of the rotor laminations to define connecting webs, stacking the rotor laminations to form a rotor body, the connecting webs being aligned to define reluctance voids in the rotor body, positioning magnet inserts in the reluctance voids, disposing opposing end caps on the rotor body to enclose the reluctance voids, and overmolding the rotor body with an overmold material, wherein the opposing end caps prevent the overmold material from entering the reluctance voids.

[0089] According to another aspect, the step of forming the rotor lamination includes stamping a reluctance blank to form at least six reluctance voids positioned in a generally parallel configuration relative to the rotor body.

[0090] It is to be understood that changes and modifications can be made to the structure described above without departing from the concepts of the present disclosure, and further that such concepts are intended to be covered by the following claims unless those claims expressly recite otherwise by their language.

Claims

1. A motor, a stator having windings that, when selectively energized, generate an electromagnetic field within the rotor cavity; a rotor disposed within the rotor cavity of the stator and in electromagnetic communication with the windings and the electromagnetic field, the rotor comprising: A drive shaft; a rotor body extending around the drive shaft, the rotor body defining a reluctance void; a magnet insert disposed within the reluctance void, the magnet insert occupying at least a portion of a space defined by the reluctance void, the magnet insert and the reluctance void cooperating with the electromagnetic field to generate an electromagnetic torque.

2. The motor of claim 1 , wherein the magnet insert does not include a rare earth magnet.

3. The motor of claim 1 , wherein the magnetic insert is at least one of an aluminum nickel cobalt (AlNiCo) magnet and a ferrite magnet.

4. 2. The motor of claim 1, wherein the stator and the rotor do not include a position sensor for sensing the rotational position of the rotor relative to the stator.

5. The motor of claim 4 , wherein the rotational position of the rotor relative to the stator is estimated using back EMF generated by the magnet insert.

6. The motor of claim 1 , wherein the electromagnetic torque includes a magnetic torque component generated by interaction of the magnet insert with the electromagnetic field.

7. The motor of claim 6 , wherein the electromagnetic torque includes a reluctance torque component produced by interaction of the rotor body with the electromagnetic field.

8. The motor of claim 7 , wherein the rotor body includes a connecting web that defines the reluctance void.

9. The motor of claim 8 , wherein the reluctance torque component of the electromagnetic torque is generated by the interaction of the connecting web of the rotor body with the electromagnetic field.

10. The motor of claim 1 , wherein at least one of the magnet inserts occupies only a portion of the space of a corresponding one of the reluctance voids.

11. The motor of any preceding claim, wherein opposing end laminations and overmold layers surround the reluctance voids of the rotor and fix the position of the magnet inserts within the reluctance voids.

12. A rotor, A drive shaft; a plurality of stacked rotor laminations forming a rotor body extending around the drive shaft, each stacked rotor lamination having a connecting web that forms a reluctance void within the plurality of stacked rotor laminations; a magnet insert disposed within the reluctance void, the magnet insert occupying at least a portion of a space defined by the reluctance void, the magnet insert and the reluctance void configured to cooperate with an electromagnetic field from a stator winding to generate an electromagnetic torque having a reluctance torque component and a magnetic torque component.

13. The rotor of claim 12 , wherein each magnet insert occupies only a portion of a respective one of the reluctance voids.

14. The rotor of claim 12 , wherein the rotor includes a two-pole configuration, and the reluctance voids are positioned in a generally parallel configuration relative to a center plane of the rotor body.

15. The rotor of claim 14 , wherein the magnetic inserts include at least four magnetic inserts positioned in the generally parallel configuration.

16. The rotor of claim 12 , wherein the rotor includes a four-pole configuration and the reluctance voids are positioned in a non-coaxial configuration relative to the axis of rotation of the rotor body.

17. The rotor of claim 12 , wherein the magnetic insert is at least one of an aluminum nickel cobalt (AlNiCo) magnet and a ferrite magnet.

18. A rotor according to any one of claims 12 to 17, wherein the magnetic insert does not include a rare earth magnet.

19. 1. A method for forming a rotor for an electric motor, the method comprising: forming rotor laminations, the rotor laminations having a reluctance blank removed from each of the rotor laminations to define a connecting web; stacking the rotor laminations to form a rotor body, the connecting webs being aligned to define reluctance voids within the rotor body; positioning a magnetic insert within the reluctance void; placing opposing end caps on the rotor body to enclose the reluctance void; and overmolding the rotor body with an overmold material, wherein the opposing end caps prevent the overmold material from entering the reluctance voids.

20. 20. The method of claim 19, wherein forming the rotor lamination comprises stamping the reluctance blank to form at least six reluctance voids positioned in a generally parallel configuration relative to the rotor body.

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