Synchronous reluctance motor with ferrite auxiliary reluctance rotor

Abstract

A motor includes a stator having windings that generate an electromagnetic field within a rotor cavity when selectively energized, and a rotor disposed within the rotor cavity of the stator and in electromagnetic communication with the windings and the electromagnetic field. The rotor includes a drive shaft, a rotor body extending about the drive shaft and defining a plurality of reluctance gaps, and magnet inserts disposed within the reluctance gaps. The magnet insert occupies at least a portion of a space defined by the reluctance void. The magnet insert and the reluctance void cooperate with the electromagnetic field to generate an electromagnetic torque.

Description

Technical Field

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

[0002] An electric motor typically includes a stator and a rotor, wherein 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 present disclosure, a motor includes a stator and a rotor. The stator has windings that generate an electromagnetic field within a rotor cavity when selectively energized. The rotor is disposed within the rotor cavity of the stator and is 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 gaps, and magnet inserts disposed within the reluctance gaps. The magnet inserts occupy at least a portion of the space defined by the reluctance gaps. The magnet inserts and the reluctance gaps 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 gap within the plurality of stacked rotor laminations. The rotor also includes a magnet insert disposed within the reluctance gap. The magnet insert occupies at least a portion of the space defined by the reluctance gap. The magnet insert and the reluctance gap are configured to cooperate with the electromagnetic field from the stator winding to generate an electromagnetic torque having a reluctance torque component and a magnetic torque component.

[0005] According to another aspect, a method of forming a rotor for an electric motor includes the steps of forming rotor laminations, wherein a reluctance portion is removed from each of the rotor laminations to define a connecting web; stacking the rotor laminations to form a rotor body, wherein the connecting webs are aligned to define a reluctance gap within the rotor body; positioning a magnet insert within the reluctance gap; providing opposing end caps on the rotor body to close the reluctance gap; and overmolding the rotor body with an overmold material. The opposing end caps prevent the overmold material from penetrating the reluctance gap.

[0006] Those skilled in the art will understand and appreciate these and other aspects, objects, and features of the present disclosure from a study of the following specification, claims, and drawings. BRIEF DESCRIPTION OF THE DRAWINGS

[0007] In the attached figure:

[0008] Figure 1 is a perspective view of an electric motor incorporating one aspect of the stator and rotor configurations described herein;

[0009] Figure 2 It is taken along line II-II Figure 1 A schematic cross-sectional view of an electric motor;

[0010] Figure 3 is a perspective view of a stator incorporating an outer ring positioned around the periphery of teeth for the stator;

[0011] Figure 4 yes Figure 3 A partially exploded perspective view of a stator of FIG. 1 , wherein the stator is separated from the overmold;

[0012] Figure 5 yes Figure 4 An exploded perspective view of a stator;

[0013] Figure 6 The use of structural rings and stacked tooth laminations to assemble a Figure 5 A schematic perspective view of a stator tooth of a stator;

[0014] Figure 7 yes Figure 5 A top perspective view of the stator core of the stator is positioned between adjacent structural rings to form Figure 2 a side perspective view of a stack of stator tooth laminations;

[0015] Figure 8 yes Figure 7 An exploded perspective view of a stator core;

[0016] Figure 9 is a schematic diagram showing the assembly of stator teeth of a stator core using structural rings and stacked tooth laminations;

[0017] Figure 10 is a partially exploded view of a stator incorporating a plurality of pre-wound tooth segments and showing the stator separated from the overmold;

[0018] Figure 11 yes Figure 10 An exploded perspective view of a stator;

[0019] Figure 12 yes Figure 11 An exploded perspective view of the stator core shown in FIG;

[0020] Figure 13 yes Figure 10 A perspective view of a pre-wound tooth segment of a stator;

[0021] Figure 14 yes Figure 13 An exploded perspective view of a pre-wound tooth segment;

[0022] Figure 15 is a perspective view of a rotor incorporating a reluctance gap within a rotor body;

[0023] Figure 16 yes Figure 15 An exploded perspective view of a rotor;

[0024] Figure 17 It is cut along XVII-XVII Figure 15 A cross-sectional view of a stator;

[0025] Figure 18 It is cut along XVIII-XVIII Figure 15 A cross-sectional view of a stator;

[0026] Figure 19 is a schematic flow chart illustrating a method for forming a stator for an electric motor;

[0027] Figure 20 is a schematic flow chart illustrating a method for forming a stator for an electric motor;

[0028] Figure 21 is a schematic flow chart illustrating a method for forming a stator for an electric motor;

[0029] Figure 22 is a perspective view of a rotor incorporating a magnet insert within a reluctance gap of a rotor body;

[0030] Figure 23 yes Figure 22 An exploded perspective view of a rotor;

[0031] Figure 24 It is cut along XXIV-XXIV Figure 22 A cross-sectional view of a rotor;

[0032] Figure 25 It is cut along XXV-XXV Figure 22 A cross-sectional view of a rotor;

[0033] Figure 26 is a schematic cross-sectional view of a stator and rotor combination including an aspect of a rotor having a linear reluctance gap in a two-pole rotor configuration;

[0034] Figure 27 yes Figure 26 Schematic diagram of a rotor and stator combination and showing a portion of a reluctance gap filled with a magnet insert;

[0035] Figure 28 yes Figure 27 a schematic cross-sectional view of a stator and rotor combination of FIG, and showing an additional magnet insert disposed within the reluctance gap;

[0036] Figure 29 is a schematic cross-sectional view of a stator and rotor combination showing a four-pole configuration of a ferrite-assisted reluctance rotor;

[0037] Figure 30 is a schematic diagram illustrating an exemplary configuration of a magnet insert disposed within a reluctance gap to generate a desired ratio of a magnetic torque component to a reluctance torque component;

[0038] Figure 31 is a schematic diagram illustrating another exemplary configuration of a magnet insert disposed within a reluctance gap to generate a desired ratio of a magnetic torque component to a reluctance torque component;

[0039] Figure 32 is a schematic diagram illustrating another exemplary configuration of a magnet insert disposed within a reluctance gap to generate a desired ratio of a magnetic torque component to a reluctance torque component;

[0040] Figure 33 is a schematic cross-sectional view of a ferrite-assisted reluctance rotor having a reluctance gap completely occupied by a magnet insert;

[0041] Figure 34 is a schematic cross-sectional view of a stator and rotor combination including an aspect of a ferrite assisted reluctance rotor having a single cavity corresponding to each rotor pole; and

[0042] Figure 35 is a schematic flow chart illustrating a method for forming a rotor for an electric motor. DETAILED DESCRIPTION

[0043] As required, detailed embodiments of the present disclosure are disclosed herein; however, it should be understood that the disclosed embodiments are merely illustrative of the present invention and may be embodied in various and alternative forms. The drawings are not necessarily detailed; some schematic diagrams may be exaggerated or minimized to provide an overview of functionality. Therefore, the specific structural and functional details disclosed herein should not be interpreted as limiting, but merely as a representative basis for teaching one skilled in the art to variously employ the present invention.

[0044] For the purpose of this description, the terms "upper", "lower", "right", "left", "rear", "front", "vertical", "horizontal" and their derivatives will refer to the following: Figures 1 to 35However, it should be understood that the present content may assume various alternative orientations unless expressly specified to the contrary. It should also be understood that the specific devices and processes shown in the drawings and described in the following specification are merely exemplary embodiments of the inventive concepts defined in the appended claims. Therefore, specific dimensions and other physical characteristics related to the embodiments disclosed herein should not be considered limiting unless the claims expressly state otherwise.

[0045] The presently illustrated embodiments reside primarily in a combination of method steps and apparatus components associated with an electric motor having a shaped and overmolded stator having pre-wound winding segments attached to the teeth of the stator and an overmolded rotor including a reluctance gap contained between outer laminations and at least partially filled with magnet inserts. Accordingly, where appropriate, apparatus components and method steps have been represented by conventional symbols in the drawings, with only those specific details relevant to understanding the embodiments of the present disclosure being shown so as not to obscure the present disclosure with details that would be apparent to one of ordinary skill in the art having the benefit of the description herein. Furthermore, like reference numerals in the specification and drawings represent like elements.

[0046] As used herein, when the term "and / or" is used in conjunction with a list of two or more items, it means that any one of the listed items can be used alone, or any combination of two or more of the listed items can be used. For example, if a composition is described as comprising components A, B, and / or C, the composition can comprise 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.

[0047] In this document, relational terms such as first and second, top and bottom, etc. may be used only to distinguish one entity or action from another entity or action, and do not necessarily require or imply any actual such relationship or order between such entities or actions. As used herein, the terms "comprises," "comprising," or any other variants thereof are intended to cover non-exclusive inclusion, such that a process, method, article, or apparatus comprising a series of elements includes not only those elements, but may also include other elements not expressly listed or inherent to such process, method, article, or apparatus. Without further limitation, an element beginning with "comprises ..." does not preclude the presence of additional identical elements in the process, method, article, or apparatus comprising the elements.

[0048] 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 needed, thereby reflecting tolerances, conversion factors, rounding, measurement errors, etc. and other factors known to those skilled in the art. When the term "about" is used to describe a value or a range endpoint, the disclosure should be understood to include the specific value or endpoint mentioned. Regardless of whether the value or range endpoint in the specification lists "about", the value or endpoint of the range is intended to include two embodiments: one modified by "about" and one not modified by "about". It should be further understood that the endpoint of each range is significant relative to the other endpoint and independently of the other endpoint.

[0049] As used herein, the terms "substantially," "substantially," and variations thereof are intended to indicate that the described feature is equal to or approximately equal to a value or description. For example, a "substantially flat" surface is intended to mean a flat or approximately flat surface. Additionally, "substantially" is intended to mean that two values are equal or approximately equal. In some embodiments, "substantially" can mean values that are within about 10% of each other, such as within about 5% of each other, or within about 2% of each other.

[0050] As used herein, the terms "the," "a," or "an" mean "at least one" and should not be limited to "only one" unless clearly 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.

[0051] Now refer to Figures 1 to 35 , reference numeral 10 generally designates a stator 10 incorporated within an electric motor 12, wherein the stator 10 includes one or more windings 14 positioned on teeth 16 of 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. The rotor 18 may be positioned within an inner periphery 20 of the stator 10, or may be positioned outside an outer periphery 22 of the stator 10, depending on the configuration of the electric motor 12. Generally, the configurations described herein relate to a rotor 18 that rotates within an inner periphery 20 of the stator 10. Accordingly, the configurations described herein relate to apparatus and methods for constructing the stator 10 and positioning the windings 14 of the stator 10 on an inner rotor configuration motor 12.

[0052] Now refer to Figures 3 to 9The motor 12 includes a stator 10 constructed from a plurality of structural rings 24 that define a plurality of stator teeth 16 included within the stator 10. The tooth segments 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 configuration 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. For each tooth 16 of the stator 10, a winding segment 34 of conductive material is slidably positioned on the bobbin 32. The winding segments 34 are then separated from one another as they are mounted on the plurality of stator teeth. The winding segments 34 are coupled together to define a continuous winding 14 for the stator 10, which forms a plurality of stator poles 36 configured to be selectively energized to generate an electromagnetic field.

[0053] An outer ring 38 is positioned around the outer periphery 22 of the teeth 16 of the stator 10. The outer ring 38 serves as a back iron 40 and also serves to house the winding segments 34 within a stator cavity 42. The stator cavity 42 is defined within the outer ring 38 and outside the connecting portion 62 of the structural ring 24, which extends radially between adjacent stator teeth 16. In other words, the stator cavity 42 is defined within the outer ring 38 and outside the core 44 of the stator 10, from which the teeth 16 of the stator 10 extend, wherein the core 44 is formed by the connecting portion of the structural ring 24. An overmold 46 extends around the outer ring 38, the winding segments 34, the plurality of teeth 16, and the core 44 to form the overmold stator 10. In certain aspects of the device, the outer ring 38 may include alignment grooves 52 that interact with alignment protrusions 54 of the tooth segments 26, which are formed by the stack of structural rings 24 and tooth laminations 30. In this way, the outer ring 38 can be aligned in one or more desired orientations relative to the teeth section 26 of the stator 10. This also serves as a securing means to ensure a secure fit between the outer ring 38 and the teeth section 26, thereby forming the stator cavity 42 that secures the winding section 34.

[0054] In some aspects of the device, such as Figures 3 to 9As illustrated in FIG, the winding sections 34 can be connected together using a bus ring 48. The bus ring 48 includes a plurality of connectors 50 that link specific winding sections 34 together. The connectors 50 are attached to wire ends 60 of the winding sections 34 to complete the winding 14. Some of the wire ends 60 are not attached to the connectors 50 so that they can be attached to wiring used to carry current through the winding 14. These wire ends 60 of the connectors 50 that are not connected to the bus ring 48 can be positioned to extend from the overmold 46 to connect to electrical leads to and from 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 individual phases of the winding 14 that are electrically connected to each other. The bus ring 48 includes a plurality of winding connections 72 that form the subsets 64 of the winding sections 34. Similarly, the subsets 64 of the winding sections 34 correspond to the 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 three phases of the plurality of stator poles 36. To define the individual phases, the winding connections 72 of the bus ring 48 are typically separated by insulating spacers 82 that electrically separate the winding connections 72. The insulating spacers 82 provide for dedicated and separate current delivery to the subsets 64 of the winding sections 34 to produce multi-phase operation of the stator 10.

[0055] With this configuration, the stator 10, as 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 enables the manufacture of an inner rotor configuration of the stator 10 without requiring the windings 14 to be positioned within the confined space within 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.

[0056] According to various aspects of the device, such as Figure 4 and Figure 5As illustrated, a winding segment 34 slidably positioned over each bobbin 32 and over each tooth 16 of the stator 10 can be pre-wound into a shaped winding segment 34. Each winding segment 34 is then placed on the bobbin 32 for a corresponding tooth 16 of the stator 10. In certain aspects of the apparatus, the winding segment 34 can be placed on the bobbin 32, and the bobbin 32 with the winding segment 34 thereon can be placed over a corresponding tooth 16 of the stator 10. Thus, the winding segment 34 and the corresponding bobbin 32 member form a bobbin assembly 76 that is placed as a single component over the corresponding stator tooth 16. Using this configuration, multiple winding segments 34 and multiple bobbins 32 can be pre-manufactured and paired for installation on the stator teeth 16. The wire ends 60 extending from each winding segment 34 can be connected to adjacent winding segments 34 to form one or more continuous windings 14 extending around the stator 10. After the winding sections 34 are connected together to form one or more continuous windings 14 , an overmold 46 is defined by placing an overmold material over the components to form the now insulated stator 10 .

[0057] like Figures 3 to 9 As shown, each bobbin 32 extending over the teeth 16 of the stator 10 may be formed from one or more bobbin segments 70 or end caps slidably positioned over each tooth 16 having an enlarged tooth end 108. Figures 13 to 14 As shown, in various aspects of the device, the bobbin 32 may include two opposing bobbin segments 70 that slide over and around each tooth 16 from opposite directions (such as from above and below, or from side to side) behind the tooth tip to complete the structure of the bobbin 32. A winding section 34 of conductive material is then positioned on the two-piece or multi-piece bobbin 32. The winding section 34 can be wound around the bobbin segment 70, or, if the tooth does not include an enlarged tooth tip, the winding section can be slidably mounted on the bobbin segment 70. The bobbin 32 serves to insulate the winding section 34 from the material of the stack 28 of tooth laminations 30 and the structural ring 24 that forms each tooth 16 of the stator 10. In certain aspects of the device, such as where the tooth 16 does not have an enlarged tooth tip 108, a single-piece bobbin 32 can be used instead of a multi-part bobbin 32 having bobbin segments 70. In such aspects of the device, the pre-wound winding section 34 can also be slidably disposed in the bobbin 32.

[0058] Reference again Figures 3 to 9During the formation of the stator 10, a mold 130 in the shape of the finished stator 10 may be used to assemble the various components that make up the stator 10. Within the mold, a first outer structural ring 80 may be positioned within the base of the mold. Then, tooth laminations 30 may be added around the mold at the location of 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 into a stack 28 may be positioned within each mold as each tooth 16 of the stator 10 is constructed within the mold. 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 extend generally parallel through the stator 10. The number of tooth laminations 30 in a particular stack 28 may range from approximately 3 to approximately 10 tooth laminations; or approximately 5 to approximately 8 tooth laminations; or approximately 2 to approximately 15 tooth laminations.

[0059] Reference again Figure 9 Typically, a sheet of metal stock is moved over a die. Next, structural rings 24 and tooth laminations 30 are punched out of the sheet of metal stock and directed into the die. As described herein, the sheet of stock is made of a ferrous metal that forms the stator 10. Using the metal stock, the stator 10 is constructed layer by layer. The structural ring 24 is punched and placed in the die. Subsequently, successive layers of the punched tooth laminations 30 are directed into the cavity of the die. In addition, for each punched portion of the metal stock, alignment protrusions 90 are punched out in each lamination that forms one of the teeth 16 of the stator 10. These protrusions 90 operate in a nested configuration to lock the layers together to structurally support the stator 10. In this way, the process of stamping the components of the stator 10 and forming these components into the stator 10 is combined into a single operation.

[0060] During the formation of the stator 10, the assembly includes two punch configurations. One punch is used to form the structural ring 24 from a sheet of metal stock. The other punch is used to form the layers of the tooth laminations 30. As the stator 10 is built layer by layer, the appropriate punch is positioned over the die to punch the next layer of the stator 10 into the die. Once again, the stamped parts are immediately introduced into the die.

[0061] During this assembly of the stator 10, layers of tooth laminations 30 are sequentially punched into the die to form a stack 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. In other words, as the stator 10 is built, each position of the die receives one tooth lamination 30 from the sheet of metal stock. In certain aspects of the apparatus, 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 each of the teeth 16, such that each structural ring 24 rests evenly on each stack 28 of tooth laminations 30. In this manner, as the teeth 16 of the stator 10 are built, the laminations and structural rings 24 are evenly distributed between the positions of the teeth 16 of the die.

[0062] Periodically, additional structural rings 24 are positioned above the stack 28 of tooth laminations 30 to reinforce the structure of the stator 10. When the desired height of the stator 10 is achieved, a final outer structural ring 80 is positioned over the stack 28 of tooth laminations 30 and at the top of the stator 10 to complete the structure of the stator 10. With this configuration, the stator 10 is formed from a plurality of tooth laminations 30 that are positioned and reinforced using intermittent structural rings 24 and a pair of outer structural rings 80.

[0063] To aid in assembling the various tooth laminations 30 and structural rings 24 for the stator 10, a portion of each tooth lamination 30 and structural ring 24 for each stator tooth 16 may be stamped to form protrusions 90. Each protrusion 90 forms a nested configuration with adjacent tooth laminations 30. This nested configuration further positions and strengthens the structure of the stator 10. These protrusions 90 also serve as locating features for ensuring that the stack 28 of tooth laminations 30 is properly aligned relative to the other tooth laminations 30 and the structural ring 24 that form the stator 10. By using the protrusions 90, lateral displacement or misalignment of the tooth laminations 30 and structural ring 24 is greatly minimized or eliminated.

[0064] Now refer to Figures 10 to 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 the desired tooth height of the teeth 16 of the stator 10. After the stacked tooth laminations 30 are positioned to form each tooth segment 100, the bobbin 32 may be slidably positioned over the tooth portion 102 of the tooth segment 100. The pre-wound tooth winding 14 may then be slidably positioned on the bobbin 32 to form a pre-wound stator segment 106.

[0065] As discussed herein, the winding segments 34 can be placed in the bobbin 32, and the assembled bobbin 32 and winding segments 34 can be placed onto the tooth portion 102 of the tooth segment 100 to form the stator segments 106. Each pre-wound stator segment 106, with the pre-attached bobbin 32 and winding segments 34, is then coupled to two adjacent pre-wound stator segments 106 to form the stator core 44, which has a plurality of pre-wound stator poles 36 extending inwardly from the stator core 44. The core portion 104 of the tooth segment 100 includes mating geometries that interlock to form the core 44 of the stator 10. The winding segments 34 of each tooth segment 100 are then connected together to form one or more windings 14 of the stator 10. In this manner, the respective winding segments 34 of the stator segments 106 are coupled with the corresponding winding segments 34 to form the phases of the windings 14 of the plurality of stator segments 106. Typically, the winding 14 has three phases. The phases and windings 14 generally define a plurality of stator poles 36 configured to be selectively energized. After the windings 14 are attached together in the desired configuration, an overmold material is placed over the plurality of stator segments 106 to form an overmold 46 for the stator 10, with the stator being 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.

[0066] Depending on 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 segments 34 are attached together prior to applying the overmold material that forms the insulating stator 10. As discussed herein, a bus ring 48 used to attach the winding segments 34 together may be used to define the phase configuration of the winding 14. The bus ring 48 may be in the form of one or more busbars or other similar electrical supports formed in an annular shape to match the contour of the stator 10, with each busbar of the bus ring 48 being used to connect exclusively to each winding segment 34 to define a phase of the winding 14 of the stator 10.

[0067] Using pre-wound winding sections 34 attached to the teeth sections 26 of the stator 10 provides for more efficient winding of the desired motor configuration. Specifically, the winding configuration described herein enables more efficient filling of the slots 110 defined between the teeth 16 of the stator 10. Additionally, the configuration described herein allows for the use of larger gauge wire for the pre-wound winding sections 34. Larger gauge wire can be used because the components used to wind the stator 10 do not need to be woven around the stator core 44, which has pre-positioned teeth 16 that can be difficult to navigate around and between. The pre-wound winding sections 34 can be formed into the desired shape and then slidably positioned over the corresponding teeth 16 of the stator 10 or the tooth portions 102 of the tooth segments 100. This pre-assembled configuration of the stator segments 106 allows the finished windings 14 to occupy more of each slot 110 because no space is required to accommodate the components used to weave the wire of the windings 14 around the teeth 16 of the stator 10.

[0068] Furthermore, the motor 12 formed by the stator 10 described herein does not require the use of rare earth materials similar to permanent magnet motors. Competitive power density is achieved without the use of permanent magnets. Furthermore, the insulation configuration described herein, through the use of insulating overmold 46, allows exposure to corrosive environments without damaging the components of the stator 10 surrounded by the overmold material. Because the stator 10 described herein utilizes larger gauge wire and increases the filling of the slots 110 between the teeth 16, power density is not compromised compared to other conventional electric motor systems.

[0069] Depending on aspects of the device, the stator 10 configurations described herein may be used with any of a variety of rotors 18, including the rotor 18 configurations described herein. Additionally, as described herein, the disclosure of a rotor 18 having a reluctance gap 122 is provided as an exemplary and non-limiting type of rotor 18 that may be used in conjunction with the stator 10 configurations described herein, as well as other types of stators 10.

[0070] Now refer to Figure 2 、 Figures 15 to 18 and Figures 22 to 34The rotor 18 of the synchronous reluctance motor 12 includes a stack 28 of rotor laminations 120, typically made of electrical-grade steel, to form a rotor body 140. Reluctance air gaps 122 are stamped from the rotor laminations 120 that form the rotor body 140 of the rotor 18. Reluctance air gaps 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 serve as a cap. The opposing end laminations 124 are typically solid within the cross-section of the rotor 18 and do not include a reluctance air gap 122. The opposing end laminations 124 are installed to prevent windage noise that may occur if the reluctance air gaps 122 are exposed. This typically provides space for drive components, such as a drive shaft. After the end laminations 124 are positioned, the rotor 18 is then encapsulated with an overmold material that at least partially encapsulates an 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 overmolding material. Because the ends of the rotor 18 are covered by the end laminations 124, the overmolding material cannot penetrate into the reluctance gaps 122. Without the overmolding material of the reluctance gaps 122, the rotor 18 is maintained in balance by the consistent thickness of the overmolding around the rotor body 140. Penetration of the overmolding material into one or more of the reluctance gaps 122 may have the effect of causing an imbalance in the rotor 18, which may result in undesirable vibration or wobble. Therefore, the shape and size of the reluctance gaps 122 can be maintained throughout the assembly and overmolding process of the rotor 18. The use of overmolding around the rotor body 140 also limits the occurrence of corrosion within the rotor laminations 120 and the opposing end laminations 124.

[0071] As described herein, the reluctance gaps 122 may remain as hollow spaces within the rotor body 140. Additionally, magnet inserts 162 may be installed within one or more of the reluctance gaps 122. These magnet inserts 162 may partially or completely occupy the space defined by the reluctance gaps 122. The presence of the magnet inserts 162 and the size of the magnet inserts 162 relative to the space defined by the reluctance gaps 122 may vary because a specific magnetic interaction is required between the electromagnetic field 164 of the energized windings 14 and the rotor 18 for operation of the rotor 18 within the stator 10.

[0072] Now refer to Figures 15 to 18During formation of the rotor 18 having the hollow reluctance gaps 122, the connecting webs 150 of the rotor body that define the reluctance gaps 122 may be demagnetized, or at least partially demagnetized, to increase the reluctance characteristics of the rotor 18. In other words, demagnetizing the connecting webs 150 reduces the reluctance of the connecting webs 150, which in turn provides a more defined minimum reluctance path 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 efficient. Demagnetization of the rotor may be achieved by localized heating, such as with a laser or other heat source, or by applying additional induced mechanical stresses within the rotor body.

[0073] Still refer to Figures 15 to 18 During operation of the stator 10 and rotor 18, a controller is used 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 current is achieved by energizing the electromagnetic phases of the windings 14 to selectively attract the magnetic resistance of the rotor 18 and align it in a desired direction to cause rotation of the rotor 18. In addition, sensor feedback of the position of the rotor 18 transmitted to the controller enables smooth and controllable current flow to the windings 14. This, in turn, can be used to control the speed and torque output of the motor 12.

[0074] In certain aspects of the device, the controller operates in a sensorless configuration. In an exemplary and non-limiting aspect of the device, a voltage sensor or voltage monitor can be used at the center point of the back electromotive force (EMF) voltage. This is compared to the typical half of the supply DC bus voltage to calculate the relative inductance used to determine the position of the rotor 18 relative to the phase of the winding 14. When the position of the rotor 18 is known, the speed and torque of the motor 12 can be controlled using a smooth and controllable current flowing to the winding 14 without the need for separate position sensing components.

[0075] Now refer to Figures 1 to 19Having described various aspects of the stator 10 and rotor 18 for the electric motor 12, a method 400 for forming the stator 10 for the electric motor 12 is disclosed. According to the method 400, step 402 includes placing a bottom outer structural ring 80 within a mold. Layers of stacked tooth laminations 30 are then placed onto the bottom outer structural ring 80 (step 404). Intermittent structural rings 24 are placed between adjacent layers of the stacked tooth laminations 30 in an alternating configuration (step 406). As discussed herein, each tooth lamination 30 is positioned simultaneously relative to each tooth 16 to maintain a consistent height for each tooth 16 of the stator 10 during assembly of the stator 10. A top outer structural ring 80 is then placed onto 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 mold (step 410). The bobbin assembly 76 is positioned over each tooth 16 of the laminated stator 10 (step 412). As described herein, the bobbin 32 can be 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 can include the bobbin 32 and the pre-wound winding segments 34 that can be slidably positioned into the teeth 16 as a single assembly. It is contemplated that, in alternative aspects, the bobbin 32 and winding segments 34 can be positioned sequentially over the teeth 16. With all bobbin assemblies 76 installed over the stator teeth 16, the winding segments 34 form a segmented stator winding. The pre-wound winding segments 34 of the segmented stator winding are then attached using the bus ring 48 to form the complete stator winding 14 (step 414). The outer ring 38 is placed around the stator winding 14 and the laminated stator 10 (step 416). The outer ring 38 prevents the winding segments 34 from moving outward along each tooth 16 of 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 provides for the use of larger gauge wire that can generate a more efficient electromagnetic field when energized with current.

[0076] As part of the method 400 for forming the stator 10, the structural ring 24 and the tooth laminations 30 can be fabricated to have reduced magnetic properties. By way of example and not limitation, thin portions, such as the connecting portion of the structural ring 24, can be metallurgically altered to have reduced magnetic properties. This is typically performed by heating the steel, such as by using a laser. In certain aspects of the device, the connecting portion of the structural ring 24 can be upset using a laser or by mechanical de-bridging to reduce or eliminate magnetic effects that may be caused by the presence of the connecting portion. It is contemplated that only a portion of the connecting portion may be upset or removed to provide structure to the stator 10.

[0077] Now refer to Figures 1 to 18 and Figure 20Having described various aspects of the motor 12, a method 500 for forming the stator 10 of the electric motor 12 is disclosed. According to the method 500, the laminated tooth segments 26 are formed (step 502). The bobbin 32 is placed onto the tooth portion 102 of each laminated tooth segment 100 (step 504). The pre-wound winding segment 34 is then placed onto the tooth portion 102 of each laminated tooth segment 100 and over the corresponding bobbin 32 (step 506). The laminated tooth segments 100 with the pre-wound winding segments 34 are then attached together to form the circular core 44 of the stator 10 (step 508). The pre-wound winding segments 34 are then attached together to form the desired configuration for the windings 14 of the stator 10 (step 510). The core 44, teeth 16, and windings 14 are then overmolded using an overmolding material (step 512).

[0078] Usually, in Figures 11 to 18 The inner rotor configuration generally illustrated in FIG. 1 uses laminated winding sections 34 that are pre-wound and then attached together. Figure 4 The star-shaped configuration of the structural ring 24 for the stator 10 illustrated in FIG. 1 may be used in either an inner rotor configuration or an outer rotor configuration, depending on the design of the motor 12 .

[0079] Now refer to Figures 1 to 18 and Figure 21 Having described various aspects of the apparatus, a method 600 for forming the rotor 18 of the electric motor 12 is disclosed. According to the method 600, steel rotor laminations 120 are formed, having portions removed from each rotor lamination 120 to form a reluctance gap 122 (step 602). The rotor laminations 120 are stacked to form the structure of the rotor 18 (step 604). The removed portions of the rotor laminations are arranged or otherwise aligned to define the reluctance gap 122 within the rotor 18. Opposing end laminations 124, or end caps, are then positioned on the ends of the rotor 18 to close the reluctance gap 122 (step 606). As discussed herein, closing the reluctance gap 122 prevents overmold material from penetrating into and occupying the reluctance gap 122. The rotor 18 is then overmolded with the overmold material (step 608). As discussed herein, the opposing end laminations 124 prevent the overmold material from penetrating into the reluctance gap 122. This penetration of the overmold material may negatively impact the operation and efficiency of the reluctance gap 122 when operating in conjunction with the energized windings 14 of the stator 10 .

[0080] The assembly method for a synchronous reluctance motor 12 described herein results in bobbin windings for the motor assembly, providing additional and more efficient filling of the slots 110 of 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 compared to conventional needle-wound stators 10. Overmolding of the stator 10 and overmolding of the rotor 18 allow the motor 12 to be exposed to corrosive fluids without corroding the ferrous stator 10 or ferrous rotor 18. Additionally, as described herein, closing each end of the stack 28 of rotor laminations 120 prior to overmolding prevents the injection-molded non-metallic resin material from flowing into the reluctance voids 122. Such infiltration could potentially lead to rotor imbalance. Overmolding the rotor 18 provides a smooth overmolded surface, thereby reducing windage noise that could be caused by the voids 122 in the rotor 18 and eliminating "blade" drag in wet rotor designs, particularly where the voids 122 are exposed to fluid, which could result in increased drag on the rotor when the rotor 18 rotates in a wet rotor configuration.

[0081] Additionally, when the non-metallic resin material is overmolded around 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 enables the stator 10 to be used in liquid and corrosive environments. The use of overmold 46 at the inner diameter of the stator teeth 16 prevents these materials from corroding or otherwise damaging the laminations of the stator 10.

[0082] Now refer to Figures 22 to 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 about the drive shaft 202. The rotor body 140 may define a plurality of reluctance gaps 122. Magnet inserts 162 may be positioned within the reluctance gaps 122. The magnet inserts 162 occupy at least a portion of the space defined by the reluctance gaps 122. The magnet inserts 162 and the reluctance gaps 122 cooperate with the electromagnetic field 164 to generate an electromagnetic torque 170.

[0083] Reference again Figures 22 to 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 insert 162. In addition, the electromagnetic torque 170 includes a reluctance torque component 174 defined by the electromagnetic interaction between the connecting webs 150 defining the reluctance gap 122 and the electromagnetic field 164. As described herein, the connecting webs 150 define a path of least reluctance 152 through which the magnetic flux 154 tends to travel, and in turn aligns with the electromagnetic field 164 to generate the reluctance torque component 174 of the electromagnetic torque 170. The combination of this magnetic torque component 172 and the reluctance torque component 174 together produces the overall electromagnetic torque 170 of the rotor 18.

[0084] According to aspects of the device, the reluctance torque component 174 can be in the range of about 20% to about 60% of the total electromagnetic torque 170. It is also contemplated that the reluctance torque component 174 can be about 30% to about 50% of the total electromagnetic torque 170. It is further contemplated that the reluctance torque component 174 can be about 40% of the total electromagnetic torque 170. It should be understood that a range of ratios of the reluctance torque component 174 to the magnetic torque component 172 can be achieved through various configurations of the reluctance gap 122 and the magnet insert 162, as will be more fully described herein.

[0085] Using the combination of the reluctance gap 122 and the magnet insert 162, the ferrite-assisted reluctance rotor 160 generates a hybrid torque configuration that includes both a reluctance torque component 174 and a magnetic torque component 172. Using this configuration, the magnet insert 162 can be made of a range of magnetic materials other than rare earth magnets and still generate an electromagnetic torque 170 that is similar in performance to a conventional brushless DC (BLDC) electric motor 12 that uses rare earth magnets. In this way, the hybrid ferrite-assisted reluctance rotor 160 described herein generates similar electromagnetic torque 170 using magnets with lower magnetic output compared to conventional motors that use more expensive rare earth magnets with greater magnetic output. The use of the magnet insert 162 is, in part, used to generate a back electromagnetic force (back EMF). As described herein, by generating a back EMF within the motor 12, sensorless control for monitoring the rotational position of the rotor 18 relative to the stator 10 and the electromagnetic field 164 can be achieved. Thus, the lower output magnet insert 162 effectively produces the desired magnetic torque component 172 while also producing the back EMF required for sensorless control. These advantages of the motor 12 described herein are achieved by using relatively low-cost materials for the magnet insert 162 .

[0086] Furthermore, to achieve the advantages of the motor 12 described herein, the magnet insert 162 may be designed and installed to occupy only a portion of the reluctance gap 122. Furthermore, for reluctance gaps 122 that do include a magnet insert 162, the magnet insert 162 may occupy only a portion of the space defined by the reluctance gap 122. Thus, the reluctance gap 122 typically contains a combination of air and the magnet insert 162.

[0087] According to various aspects of the device, such as Figures 15 to 18 and Figures 23 to 28 As shown, the reluctance gaps 122 can be positioned in a two-pole configuration. In this configuration, the reluctance gaps 122 are oriented in a generally parallel configuration relative to the center plane 220 of the rotor body 140. The reluctance gaps 122 can include an enlarged outer portion 222 of the reluctance gaps 122. The center portion 224 of the reluctance gaps 122 can include an arcuate portion 226 that extends uniformly 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. The reluctance gaps 122 in the generally parallel configuration can be linear and parallel to each other. The reluctance gaps 122 in the generally parallel configuration can 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 center axis 232 of the two-pole configuration, is emphasized to define the minimum reluctance path 152 for limiting the reluctance torque component 174 or electromagnetic torque 170 of the motor 12. Additionally, the connecting web 150 has a smaller thickness in areas where the reluctance gap 122 is larger, such as near the enlarged outer portion 222. This smaller thickness can be used to more precisely define the minimum reluctance path that can interact with various aspects of the stator poles 36 and the 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 is operated within the stator 10.

[0088] Studies of the disclosed device have shown that comparable output can be achieved with comparable electrical input between the hybrid ferrite-assisted reluctance rotor 160 described herein and the conventional BLDC rotor 18. Thus, the overall system utilizing the hybrid ferrite-assisted reluctance rotor 160 provides higher efficiency and generates electromagnetic torque 170 using lower-cost magnetic materials with smaller magnetic output.

[0089] According to various aspects of the device, such as Figures 22 to 34As shown, the ferrite assisted reluctance rotor 160 achieves similar performance in terms of electromagnetic torque 170 as compared to a conventional BLDC motor using more expensive rare earth magnets. In addition, the inclusion of the magnet insert 162 within the ferrite assisted reluctance rotor 160 generates a back EMF. The generation of the back EMF by the magnet insert 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 sensors to determine the rotational position of the rotor 18 within the rotor cavity 74 at any particular time. Likewise, the inclusion of the magnet insert 162 within the ferrite assisted reluctance rotor 160 generates a back EMF to provide sensorless operation of the ferrite assisted reluctance rotor 160.

[0090] 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 can be increased in the ferrite-assisted reluctance rotor 160. The combination of the magnetic torque component 172 of the electromagnetic torque 170 and the reluctance torque component 174 of the electromagnetic torque 170 can provide a greater tolerance in the thickness of the air gap 180. This increased tolerance can provide an increased air gap 180 compared to conventional reluctance rotors 18. This can also serve to reduce the noise generated by the ferrite-assisted reluctance rotor 160 due to the larger tolerance and air gap 180 between the ferrite-assisted reluctance rotor 160 and the stator 10. At the same time, the enlarged outer portion 222 of the reluctance gap 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.

[0091] According to various aspects of the device, such as Figures 24 to 34 As shown, the magnet insert 162 can occupy a portion of the reluctance gap 122 or can occupy the entire reluctance gap 122. Various ratios of air space within the reluctance gap 122 compared to the space occupied by the magnet insert 162 can achieve a varying range of electromagnetic torques 170 and different ratios of the reluctance torque component 174 to the magnetic torque component 172. Additionally, placing the magnet insert 162 within the enlarged outer portion 222 and / or the arcuate portion 226 of the two-pole configuration of the rotor 18 can also be used to adjust the ratio of the reluctance torque component 174 to the magnetic torque component 172.

[0092] As described herein, the reluctance gaps 122 of the ferrite assisted reluctance rotor 160 may be positioned in a two-pole configuration within the ferrite assisted reluctance rotor 160 (at Figures 24 to 28 ), quadrupole configuration (in Figures 29 to 34) and other magnetic pole configurations. The configuration of the reluctance gaps 122 and magnet inserts 162 of the ferrite assisted reluctance rotor 160 can vary depending on the design of the stator 10, the stator windings 14, and other components of the electric motor 12. As described herein, the reluctance gaps 122 and the magnet inserts 162 cooperate to define a plurality of rotor poles that can be manufactured in a variety of configurations. As described herein, the two-pole configuration can include a generally parallel configuration of the reluctance gaps 122. The generally parallel configuration of the reluctance gaps 122 tends to be aligned with a center plane 220 of the rotor body 140. The center plane 220 tends to be aligned with an axis of symmetry 240 of the reluctance gaps 122. The four-pole configuration of the reluctance gaps 122 tends to define a series of arcuate portions 226 that extend in a symmetrical, non-concentric configuration about a center axis 232 of the drive shaft 228 of the rotor 18.

[0093] According to aspects of the apparatus, the magnetic poles formed within the hybrid ferrite assisted reluctance rotor 160 may be comprised of a plurality of magnet inserts 162 positioned within a plurality of corresponding reluctance gaps 122. It is also contemplated that each of the plurality of magnetic poles may include a single magnet insert 162 positioned within a corresponding reluctance gap 122 (e.g., Figure 34 shown).

[0094] See again Figures 22 to 34 , the rotor body 140 includes a plurality of stacked rotor laminations 120. Each lamination in the plurality of stacked rotor laminations 120 includes connecting webs 150 aligned to form a reluctance gap 122. In other words, when configured as a plurality of stacked rotor laminations 120, the connecting webs 150 of each rotor lamination 120 are aligned with each other to form a reluctance gap 122 that extends substantially through or completely through the rotor body 140.

[0095] It should be understood that the term "substantially through the rotor body 140" is used in this context to indicate that at least one end of the rotor body 140 defines an aperture that provides access to the reluctance gaps 122 for positioning the magnet inserts 162 into the reluctance gaps 122. The reluctance gaps 122 may extend through a majority of the distance of 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 gaps 122 that are accessible from each end of the rotor body 140, or accessible from only one end of the rotor body 140. Further, the rotor body 140 may have a first set of reluctance gaps 122 accessible from one end of the rotor body 140 and a second set of reluctance gaps 122 accessible from an opposite end of the rotor body 140.

[0096] The magnet inserts 162 of the ferrite-assisted reluctance rotor 160 can be made of 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 contain rare earth magnets. As discussed herein, the configuration of the ferrite-assisted reluctance rotor 160 achieves comparable electromagnetic torque 170 without the use of rare earth magnets. Thus, the ferrite-assisted reluctance rotor 160 can be manufactured while achieving comparable electromagnetic torque 170 using non-rare earth magnets.

[0097] To accommodate the magnet insert 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 gap 122. The opposing end laminations 124 are configured to reduce windage noise during operation of the rotor 18 within the rotor cavity 74. This is particularly true when the magnet insert 162 occupies only a portion of the reluctance gap 122 within the rotor body 140 and empty space exists within the reluctance gap 122. Additionally, the end laminations 124 provide closure of the reluctance gap 122 so that overmold material of the rotor overmold 128 disposed about the rotor body 140 does not penetrate into the reluctance gap 122 during manufacture of the ferrite assisted reluctance rotor 160.

[0098] According to aspects of the device, the ferrite-assisted reluctance rotor 160, including the reluctance gap 122 and the magnet inserts 162, provides for hybrid operation of the ferrite-assisted reluctance rotor 160 relative to the electromagnetic field 164 generated by the energized windings 14 of the stator 10. The reluctance portion 190 of the ferrite-assisted reluctance rotor 160, which extends around the reluctance gap 122, creates a reluctance path around the reluctance gap 122 and through the rotor body 140. The rotor 18 tends to align with the electromagnetic field 164 to create a minimum reluctance path 152, such that the reluctance path of the ferrite-assisted reluctance rotor 160 tends to be aligned with the electromagnetic field 164 of the stator 10. Simultaneously, the magnet inserts 162 disposed within the reluctance gap 122 provide for independent interaction with the electromagnetic field 164 of the stator 10. In this manner, the magnetic field of the respective magnet inserts 162 tends to be aligned with the electromagnetic field 164 of the energized portion of the windings 14 of the stator 10. The magnetic fields of the minimum reluctance path 152 and the magnet insert 162 are at different radial positions relative to the ferrite assisted reluctance rotor 160. As a result, the magnetic fields of the magnet insert 162 and the minimum reluctance path 152 (also referred to herein as the reluctance portion 190 of the rotor body 140) each tend to align individually but cooperatively with the energized portions of the windings 14 of the stator 10. This provides for numerous electromagnetic interactions between the ferrite assisted reluctance rotor 160 and the stator 10 to produce a hybrid electromagnetic torque 170.

[0099] Likewise, as discussed herein, the electromagnetic torque 170 is comprised of a reluctance torque component 174 that occurs due to the tendency of the reluctance portion 190, or path of minimum reluctance 152, of the ferrite-assisted reluctance rotor 160 to align with the electromagnetic field 164 of the windings 14 of the stator 10. Additionally, the magnetic torque component 172 operates where the magnetic field of the magnet insert 162 tends to align with the electromagnetic field 164 of the windings 14 of the stator 10. These torque components combine to produce the electromagnetic torque 170 that allows the rotor 18 to achieve a torque output similar to that of conventional BLDC motors utilizing rare earth magnets.

[0100] According to various aspects of the device, such as Figures 22 to 34 As shown, a ferrite-assisted rotor for an electric motor 12 may 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 in the plurality of stacked rotor laminations 120 includes a connecting web 150 that forms a reluctance gap 122 within the plurality of stacked rotor laminations 120. A magnet insert 162 is disposed within the reluctance gap 122. The magnet insert 162 occupies at least a portion of the space defined by the reluctance gap 122. The magnet insert 162 and the reluctance gap 122 are configured to cooperate with an electromagnetic field 164 generated by the energized windings 14 of the stator 10. This interaction generates an electromagnetic torque 170 having a reluctance torque component 174 and a magnetic torque component 172.

[0101] In a conventional reluctance motor, the reluctance rotor is typically much longer than the stator to provide greater interaction between the paths of least reluctance within the rotor body.

[0102] According to various aspects of the device, such as Figures 22 to 34 As shown, the inclusion of magnet inserts 162 has been shown to provide an electromagnetic torque 170 that is consistent and comparable to a ferrite-assisted reluctance rotor 160 having a rotor body 140 having a height substantially similar to or equal to the rotor cavity 74 of the stator 10. Thus, by using the ferrite-assisted reluctance rotor 160, the motor 12 can be made more compact than other conventional reluctance motors. Likewise, this comparable electromagnetic torque 170 can be achieved without the need for rare earth magnets. In contrast, the ferrite-assisted reluctance rotor 160 described herein can utilize non-rare earth magnet inserts 162 within the reluctance gap 122 to generate a comparable electromagnetic torque 170.

[0103] Now refer to Figures 22 to 35Having described various aspects of the ferrite assisted reluctance rotor 160, a method 700 for forming the rotor 18 of the electric motor 12 is disclosed. According to the method 700, step 702 includes forming a rotor lamination 120 having a reluctance blank 200 or portion removed from each of the rotor laminations 120. These reluctance blanks 200 or portions further define a connection web 150 extending around each of the removed reluctance blanks 200. After forming the laminations, the rotor laminations 120 are stacked to form a rotor body 140 comprised of a plurality of stacked rotor laminations 120 (step 704). As discussed herein, the connection webs 150 of the reluctance portion 190 of each of the laminations are aligned to define a reluctance gap 122 extending through or substantially through the rotor body 140. After the plurality of stacked rotor laminations 120 are positioned to form the rotor body 140 and the reluctance gap 122 is defined therein, the magnet insert 162 is positioned within the reluctance gap 122 (step 706). To retain the magnet insert 162 within the reluctance gap 122, at least one (and typically two) opposing end caps 70 are disposed on the rotor body 140 to enclose the reluctance gap 122 and any space within the reluctance gap 122 not occupied by the magnet insert 162 (step 708). Typically, the entire space defined by the reluctance gap 122 is occupied by the magnet insert 162, leaving little space. It is contemplated that the opposing end caps 70 are disposed on the ends of the rotor body 140 to prevent the magnet insert 162 from moving during operation of the ferrite-assisted reluctance rotor 160 and during placement of the overmold 46 around the rotor body 140 and the magnet insert 162. After the magnet inserts 162 are positioned within the rotor body 140 , the rotor body 140 is overmolded with an overmold material (step 710 ). As discussed herein, the opposing end caps 70 prevent the overmold material from penetrating into the reluctance gap 122 and also prevent the magnet inserts 162 from moving within the reluctance gap 122 .

[0104] According to one aspect of the present disclosure, a motor includes a stator and a rotor. The stator has windings that generate an electromagnetic field within a rotor cavity when selectively energized. The rotor is disposed within the rotor cavity of the stator and is 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 gaps, and magnet inserts disposed within the reluctance gaps. The magnet inserts occupy at least a portion of the space defined by the reluctance gaps. The magnet inserts and the reluctance gaps cooperate with the electromagnetic field to generate electromagnetic torque.

[0105] According to another aspect, the magnet insert is free of rare earth magnets.

[0106] According to another aspect, the magnet insert is at least one of an aluminum nickel cobalt (AlNiCo) magnet and a ferrite magnet.

[0107] According to another aspect, the stator and rotor are free of position sensors for sensing the rotational position of the rotor relative to the stator.

[0108] According to another aspect, the rotational position of the rotor relative to the stator is estimated using the back electromotive force generated by the magnet insert.

[0109] According to another aspect, the electromagnetic torque includes a magnetic torque component generated by the interaction of the magnet insert and the electromagnetic field.

[0110] According to another aspect, the electromagnetic torque includes a reluctance torque component generated by the interaction of the rotor body and the electromagnetic field.

[0111] According to another aspect, the rotor body includes connecting webs defining a reluctance gap.

[0112] 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 and the electromagnetic field.

[0113] 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 gaps.

[0114] According to another aspect, the opposing end laminations and the overmold layer close the reluctance gap of the rotor and secure the position of the magnet insert within the reluctance gap.

[0115] 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 gap within the plurality of stacked rotor laminations. The rotor also includes a magnet insert disposed within the reluctance gap. The magnet insert occupies at least a portion of the space defined by the reluctance gap. The magnet insert and the reluctance gap are configured to cooperate with the electromagnetic field from the stator winding to generate an electromagnetic torque having a reluctance torque component and a magnetic torque component.

[0116] According to another aspect, each magnet insert occupies only a portion of a respective one of the reluctance gaps.

[0117] According to another aspect, the rotor includes a two-pole configuration, and the reluctance gaps are positioned in a generally parallel configuration relative to a center plane of the rotor body.

[0118] According to another aspect, the magnet insert includes at least four magnet inserts positioned in a generally parallel configuration.

[0119] According to another aspect, the rotor includes a four-pole configuration, and the reluctance gaps are positioned in a non-concentric configuration relative to the axis of rotation of the rotor body.

[0120] According to another aspect, the magnet insert is free of rare earth magnets.

[0121] According to another aspect, the magnet insert is at least one of an aluminum nickel cobalt (AlNiCo) magnet and a ferrite magnet.

[0122] According to another aspect of the present disclosure, a method of forming a rotor for an electric motor includes the steps of forming rotor laminations, wherein a reluctance portion is removed from each of the rotor laminations to define a connecting web; stacking the rotor laminations to form a rotor body, wherein the connecting webs are aligned to define a reluctance gap within the rotor body; positioning a magnet insert within the reluctance gap; providing opposing end caps on the rotor body to close the reluctance gap; and overmolding the rotor body with an overmold material. The opposing end caps prevent the overmold material from penetrating the reluctance gap.

[0123] According to another aspect, the step of forming the rotor laminations includes stamping a reluctance blank to form at least six reluctance gaps positioned in a generally parallel configuration relative to the rotor body.

[0124] It will be understood that changes and modifications may be made in the foregoing constructions without departing from the inventive concepts, and it will be further understood that such concepts are intended to be covered by the appended claims unless such claims by their language expressly state otherwise.

Claims

1. A motor comprising: a stator having windings that, when selectively energized, generate an electromagnetic field within the rotor cavity; as well as a rotor disposed within the rotor cavity of the stator and in electromagnetic communication with the winding and the electromagnetic field, the rotor comprising: drive shaft; a rotor body extending around the drive shaft, the rotor body defining a reluctance gap; and A magnet insert is disposed within the reluctance gap, wherein the magnet insert occupies at least a portion of a space defined by the reluctance gap, wherein the magnet insert and the reluctance gap cooperate with the electromagnetic field to generate an electromagnetic torque. 2 . The motor of claim 1 , wherein the magnet insert is free of rare earth magnets. 3 . The motor of claim 1 , wherein the magnet insert is at least one of an aluminum nickel cobalt (AlNiCo) magnet and a ferrite magnet. 4 . The motor of claim 1 , wherein the stator and the rotor are free of a position sensor for sensing a 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 electromotive force 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 and the electromagnetic field. 7 . The motor according to claim 6 , wherein the electromagnetic torque includes a reluctance torque component generated by interaction between the rotor body and the electromagnetic field.

8. The motor of claim 7, wherein the rotor body includes connecting webs defining the reluctance gap. 9 . The motor according to claim 8 , wherein the reluctance torque component of the electromagnetic torque is generated by interaction between the connection web of the rotor body and 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 gaps.

11. The motor of any one of claims 1-10, wherein opposing end laminations and an overmold layer close the reluctance gap of the rotor and secure the position of the magnet insert within the reluctance gap.

12. A rotor comprising: drive shaft; a plurality of stacked rotor laminations forming a rotor body extending about the drive shaft, each stacked rotor lamination having a connecting web forming a reluctance gap within the plurality of stacked rotor laminations; as well as a magnet insert disposed within the reluctance gap, wherein the magnet insert occupies at least a portion of a space defined by the reluctance gap, wherein the magnet insert and the reluctance gap 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.

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

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

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

16. The rotor of claim 12, wherein the rotor comprises a four-pole configuration, and wherein the reluctance gaps are positioned in a non-concentric configuration relative to an axis of rotation of the rotor body.

17. The rotor of claim 12, wherein the magnet 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 magnet inserts are free of rare earth magnets.

19. A method for forming a rotor for an electric motor, the method comprising the steps of: forming rotor laminations, wherein reluctance blanks are removed from each of the rotor laminations to define connecting webs; stacking the rotor laminations to form a rotor body, wherein the connecting webs are aligned to define a reluctance gap within the rotor body; positioning a magnet insert within the reluctance gap; providing opposite end covers on the rotor body to close the reluctance gap; as well as The rotor body is overmolded with an overmold material, wherein the opposing end caps prevent the overmold material from penetrating into the reluctance gap.

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

Images