Electric machine

Abstract

An electric machine includes a rotor configured to rotate on an axis and a stator spaced radially from the rotor. The stator includes a plurality of stator phases arrayed along the axis, each stator phase including a pair of flux rings and a coil extending about the axis and disposed between the pair of flux rings. Each flux ring includes a plurality of teeth. The teeth are configured to route magnetic flux. The laminas of the stator or rotor can include different lamina densities to effectuate routing of the magnetic flux. The air gap between the rotor and stator can be a variable distance.

Description

[0001] ELECTRIC MACHINE

[0002] CROSS-REFERENCE TO RELATED APPLICATION(S)

[0003] This application claims priority to U.S. Provisional Application No. 63 / 605,294 filed December 1, 2023 and entitled “ELECTRIC MACHINES HAVING LAMINAS FEATURES,” and claims priority to U.S. Provisional Application No. 63 / 707,433 filed October 15, 2024 and entitled “ELECTRIC MACHINE,” the disclosures of which are hereby incorporated by reference in their entireties.

[0004] BACKGROUND

[0005] The present disclosure relates generally to electric machines. More specifically, the present disclosure relates to transverse flux electric machines.

[0006] Electric motors utilize electricity to generate a mechanical output. Some electric motors generate rotational outputs. In alternating current (AC) induction motors, a stator is electrically energized to electromagnetically drive rotation of a rotor about a motor axis. The stator includes laminates and windings. The rotor includes permanent magnets that are acted on by the electromagnetic field induced by current through the stator to cause rotation of the rotor. Such electric motors include coils that extend axially relative to the rotational axis and that extend axially beyond the ends of the rotor to wrap around and form the ends of the coil windings.

[0007] SUMMARY

[0008] According to an aspect of the disclosure, an electric machine includes a rotor that rotates about an axis; and a stator configured to magnetically drive the rotor to rotate about the axis, the stator comprising a plurality of teeth. Each tooth of the plurality of teeth comprises a tooth face oriented towards the rotor, the tooth face including a first surface and a second surface, both of the first surface and the second surface directly facing the rotor, and wherein the first surface is closer to the rotor then the second surface.

[0009] According to an additional or alternative aspect of the disclosure, an electric machine includes a rotor that rotates about an axis; and a stator configured to magnetically drive the rotor to rotate about the axis, the stator comprising a plurality of teeth. A first tooth of the plurality of teeth is formed from a stack of laminas, the stack of laminas including a first portion having a first lamina density and a second portion having a second lamina density, wherein the second lamina density is greater than the first lamina density.

[0010] According to another additional or alternative aspect of the disclosure, an electric machine includes a rotor that rotates about an axis, the rotor including a stack of rotor laminas, wherein at least a portion of the stack of rotor laminas has a rotor lamina density; and a stator configured to magnetically drive the rotor to rotate about the axis, the stator comprising a plurality of teeth. A first tooth of the plurality of teeth is formed from a stack of stator laminas, the stack of stator laminas including a first portion having a first lamina density, wherein the first lamina density is greater than the rotor lamina density.

[0011] According to yet another additional or alternative aspect of the disclosure, an electric machine includes a rotor that rotates about an axis, the rotor including a stack of rotor laminas, wherein at least a portion of the stack of rotor laminas has a rotor lamina density; and a stator configured to magnetically drive the rotor to rotate about the axis. Adjacent rotor laminas of the stack of rotor laminas are separated by at least one standoff.

[0012] According to yet another additional or alternative aspect of the disclosure, a method of forming a portion of a stator of an electric machine includes stacking a plurality of laminas to form a lamina stack, the lamina stack forming a plurality of teeth; and bending the lamina stack to form a stator ring segment of a flux ring of the stator, the stator ring segment being arcuate.

[0013] BRIEF DESCRIPTION OF THE DRAWINGS

[0014] FIG. 1 is a block diagram of an electric machine.

[0015] FIG. 2 is a block diagram of an electric machine.

[0016] FIG. 3 is a simplified cross-sectional view of an electric machine.

[0017] FIG. 4 is an isometric view of a rotor portion of an electric machine.

[0018] FIG. 5 is an isometric view of a stator portion of an electric machine.

[0019] FIG. 6 is a cross-sectional view of a phase assembly taken along line 6-6 in FIG. 5.

[0020] FIG. 7 A is an isometric view of a stator ring segment in a pre-shaped configuration.

[0021] FIG. 7B is an isometric view of the stator ring segment in a shaped configuration.

[0022] FIG. 8A is an isometric view of a first lamina of a stator ring segment.

[0023] FIG. 8B is an isometric view of a second lamina of a stator ring segment.

[0024] FIG. 8C is an isometric view of a third lamina of a stator ring segment.

[0025] FIG. 9 shows stages for forming the laminas of a stator ring segment.

[0026] FIG. 10 is a simplified view showing a lamina stack with inter-lamina gaps.

[0027] FIG. 11 is simplified sectional view showing variable lamina densities.

[0028] FIG. 12 is a graph illustrating flux reluctance relative to lamina density.

[0029] FIG. 13 is a graph illustrating eddy current and torque relative to rotor lamina density. FIG. 14 is an enlarged isometric cross-sectional view showing a portion of a rotor and a portion of a stator.

[0030] FIG. 15 A is a side view of the portion of the rotor and the portion of the stator shown in FIG. 14.

[0031] FIG. 15B is an enlarged view of detail B in FIG. 15A.

[0032] FIG. 16 is an axial end view of a rotor lamina.

[0033] FIG. 17 shows a standoff pattern for a rotor lamina.

[0034] FIG. 18 is a simplified schematic diagram of a portion of an electric machine.

[0035] FIG. 19 is a simplified schematic diagram of a portion of an electric machine.

[0036] DETAILED DESCRIPTION

[0037] The present disclosure concerns electric machines. While the main embodiments referenced herein will be that of motors, the teachings of the present disclose apply equally to generators and such aspects will not be separately explained for generators with the understanding that the teachings apply to various generators. It is also noted that a motor can function as a generator and vice versa. The main type of electric machine presented herein is a transverse flux machine, which is distinguished from axial or radial flux type electric machines. However, the inventive aspects discussed herein can be applied to various types of electric machines beyond just transverse flux electric machines. The electric machines of this disclosure include a rotor rotatable on a rotational axis and a stator disposed about the axis and spaced radially from the rotor. The stator can drive rotation of the rotor in examples in which the electric machine is an electric motor.

[0038] According to aspects of the disclosure, the stator of the transverse flux electric machine includes stator phases, such as one, two, three, or more, formed from flux rings and a coil disposed axially between opposing flux rings. In examples including three phases, such phases can operate 120-degrees electrically offset with respect to each other. The phases, which operate offset with respect to each other, are arrayed along and about the axis of rotation of the rotor. Likewise, the coils which generate electromagnetic flux are coaxial with the axis of rotation and the multiple coils of the different phases are arrayed along the axis of rotation. Aspects of the disclosure discussed herein can be implemented in other types of electric machines, but transverse flux motors will be discussed further herein.

[0039] According to aspects of the disclosure, the rotor and / or stator of the electric machine can be formed by stacks of laminas. The laminations can be formed from material which is readily susceptible to polarization from the fields generated by the coils. Such material is typically ferromagnetic. The ferromagnetic materials can be metal such as iron or an alloy of iron, such as steel. More specially, laminations can be formed from silicon steel, among other options. Ferromagnetic material can be a ceramic that is doped or otherwise embedded with ferromagnetic elements. The laminations can be stacked together to form lamination stacks.

[0040] The laminas forming the rotor and / or stator can be stacked to have variable densities within and / or between the lamina structures. The lamina density is the amount of steel that is within an area of the lamina structure, while air gaps between the steel reduces the density. For example, a lamina structure having 50% density would have air gaps between adjacent lamina portions that are the same width as the laminas, such that such a portion is half filled by laminas and half filled by gaps. The lamina density can vary between the stacked laminas of the rotor and the stacked laminas of the stator. In some examples, the lamina density can vary within a lamina stack, such as between portions within a single lamina stack of the stator, within portions of a single lamina stack of the rotor, etc.

[0041] Electric machines according to the disclosure can, in some examples, have a lamina density that varies within a single lamina structure. For example, the stator can include one or more ring portions that are assembled together to form phases of the stator. The ring portions can be formed by stacked laminas and the density of those stacked laminas can vary within a single ring portion. In some examples, the lamina density can vary within the one or more teeth of the ring portions. In some examples, the stator can have different densities in portions of the lamina structure having different grain orientations. For example, a first portion of the stator having laminas with a first grain orientation (e.g., radial) can have a first density that differs from a second density of a second portion of the stator that has laminas with a second grain orientation (e.g., transverse).

[0042] Some additional or alternative examples of electric machines according to the disclosure can include variable spacing between the stator and the rotor. In some examples, some portions of the lamina structure of the stator can be disposed physically closer to laminas of the rotor than other portions of the lamina structure of the stator. In some examples, the face of a stator tooth that directly opposes the rotor can be variably spaced from the laminas of the rotor.

[0043] According to some aspects of the disclosure, a face of the stator tooth that opposes the rotor can extend between a heel and a toe. In some examples, the tooth can be configured such that one of the toe and the heel is disposed physically closer to the rotor than the other one of the toe and the heel. For example, the distance between the rotor and the tooth face surface can vary such that the heel is furthest from the rotor and the tip is closest to the rotor, though it is understood that not all examples are so limited. In some examples, the tooth face surface can be sloped such that the distance between the rotor and the tooth face varies across the axial length of the tooth face.

[0044] Some examples of electric machines according to the disclosure include a variable width air gap directly radially between the rotor and the stator. The variable width air gap can be formed between lamina structure of the stator and the outer radial surface of the rotor. The variable width air gap can be directly between the tooth face surface of a stator tooth and the rotor.

[0045] Some examples of electric machines according to the disclosure include flux rings, which can also be referred to as “half phases.” The flux rings can be formed by one or more ring arc segments. Each ring arc segment can be formed by a stack of laminas.

[0046] According to some examples, the laminas of a lamina stack, such as for a ring arc segment of a flux ring, can be formed by progressive die stamping. In some examples, the progressive die can include a series of fixed and movable punching stations. The laminas can be formed in series to form a full stack of laminas of a single lamina structure (e.g., a flux ring, a ring arc segment, etc.).

[0047] According to some aspects of the disclosure, the ring arc segment includes multiple teeth of the half phase. The ring segment can be formed in a pre-shaped configuration by stacking a plurality of formed and unbent laminas. The ring segment can include a series of bend connections that are disposed between adjacent teeth of the ring arc segment. The ring segment can be bent from the pre-shaped configuration to an arcuate shaped configuration. The ring segment can bend at the bend connections to form the arcuate ring arc segment.

[0048] The term annular is used herein, which can refer to a ring shape (continuous or broken) about the axis, which can be coaxial with the axis. The term radial is used herein which when referring to a direction is any direction orthogonal to the axis, which can be 360-degrees about the axis, unless otherwise noted. The term axial is used herein which when referring to a direction is any direction along, such as parallel with, an axis, unless otherwise noted. The terms circumferential or circumferentially as used herein means around the axis, unless otherwise noted.

[0049] Components can be considered to radially overlap when those components are disposed at common axial locations along an axis and such that a line extending radially from the axis will extend through each of the radially overlapping components. Components can be considered to axially overlap when those components are disposed at common radial and circumferential locations relative to an axis such that an axial line parallel to the axis extends through each of the axially overlapping components. Components can be considered to circumferentially overlap when aligned about the axis at a common radial distance from the axis such that a circle centered on the axis passes through each of the circumferentially overlapping components.

[0050] It is noted that for the discussion of this disclosure, some structures may be shown multiple times in a single example but only discussed or labeled once, for brevity. However, similar structures shown elsewhere can be constructed and function similarly as described and / or shown.

[0051] FIG. 1 is a block diagram of electric machine 10. FIG. 2 is a block diagram of electric machine 10. FIG. 1 shows electric machine 10 in an outer rotator configuration in which the rotor 12 is spaced radially outward from the stator 14. FIG. 2 shows electric machine 10 in an inner rotator configuration in which the rotor 12 is spaced radially inward from the stator 14. FIGS. 1 and 2 are discussed together. Electric machine 10 includes rotor 12, stator 14, and motor controller 16. Rotor 12 includes rotor body 18 and permanent magnet array 20. Stator 14 includes stator phases 22a, 22b, 22c (collectively herein “stator phase 22” or “stator phases 22”). Stator phase 22a includes flux rings 24a, 24b, coil 26, and axial returns 28. Stator phase 22b includes flux rings 24c, 24d, coil 26, and axial returns 28. Stator phase 22c includes flux rings 24e, 24f, coil 26, and axial returns 28. Flux rings 24a-24f are referred to collectively herein as “flux rings 24” or “flux ring 24.” As discussed above, each flux ring 24 can be considered to form a half phase of a stator phase 22.

[0052] Rotor 12 is spaced radially from stator 14 such that air gap 30 is formed between rotor 12 and stator 14. Electric machine 10 extends along motor axis MA and rotor 12 is configured to rotate about motor axis MA. Motor axis MA can be considered to be an axis of rotation of the rotor 12.

[0053] In the example shown in FIG. 1, rotor 12 surrounds stator 14 such that electric machine 10 is an outer rotator. In the example shown in FIG. 2, electric machine 10 includes stator 14 extending about rotor 12 such that electric machine 10 is an inner rotator.

[0054] Permanent magnet array 20 is supported by the rotor body 18. Permanent magnet array 20 is disposed across air gap 30 from stator 14 such that permanent magnet array 20 is spaced radially from stator 14. Permanent magnet array 20 includes a plurality of permanent magnets disposed annularly about motor axis MA. Stator 14 is formed by stator phases 22 arrayed along the motor axis MA. Each stator phase 22 includes paired flux rings 24 that are disposed on opposite axial sides of a coil 26 of that stator phase 22. The coil 26 is disposed directly axially between the flux rings 24 of the same stator phase 22. Flux rings 24a, 24b are paired to form stator phase 22a and are disposed on opposite axial sides of the coil 26 of stator phase 22a. Flux rings 24c, 24d are paired to form stator phase 22b and are disposed on opposite axial sides of the coil 26 of stator phase 22b. Flux rings 24e, 24f are paired to form stator phase 22c and are disposed on opposite axial sides of the coil 26 of stator phase 22c.

[0055] In some examples, portions of each flux ring 24 can extend axially over the coil 26. As such, portions of each flux ring 24 can be disposed directly radially between the coil 26 and rotor 12. Flux rings 24 are formed by laminations and can include powdered metal components, though not all examples are so limited.

[0056] Laminations can be formed from material which is readily susceptible to polarization from the electromagnetic fields generated by coils 26. Such material is typically ferromagnetic. The ferromagnetic materials can be metal such as iron or an alloy of iron, such as steel. More specially, laminations can be formed from silicon steel, among other options. Ferromagnetic material can be a ceramic that is doped or otherwise embedded with ferromagnetic elements. The laminations can be stacked together to form lamination stacks.

[0057] For each stator phase 22, axial returns 28 are disposed on an opposite radial side of coil 26 from permanent magnet array 20. Axial returns 28 extend between and connect paired ones of the flux rings 24 in each stator phase assembly 22. Axial returns 28 electromagnetically connect the paired flux rings 24. Axial returns 28 can be formed by stacked laminations having an axially oriented lamination grain (e.g., parallel with the motor axis MA). The laminations forming the axial returns 28 can be stacked circumferentially along a width of the axial return and extend axially along a length of the axial return 28. While electric machine 10 is shown as including axial returns 28, it is understood that not every example is so limited. For example, the electric machine 10 can be configured as a double air gap electric machine 10

[0058] Each coil 26 is a winding, typically copper, around the motor axis MA. Thus, each coil 26 could be a continuous winding of multiple loops (e.g., 2, 3, 4, 5, 10, 15, 20, 40, 50, 100, or more) around the motor axis MA. Examples of the winding can be formed by round wire or ribbon strand. Controller 16 is operably connected to electric machine 10, electrically or communicatively, to control operation of electric machine 10, thereby controlling the rotational output of electric machine 10. Controller 16 can be of any desired configuration for controlling operation of electric machine 10 and can include control circuitry (e.g., one or more of a processor, a microprocessor, a controller, a digital signal processor (DSP), an application specific integrated circuit (ASIC), a field-programmable gate array (FPGA), a graphics processing unit (GPU), a system-on-module (SOM), or other equivalent discrete or integrated logic circuitry) and computer-readable memory.

[0059] Controller 16 is configured to store executable code, implement functionality, and / or process instructions. Controller 16 is configured to perform any of the functions discussed herein, including controlling operation of any components referenced herein. Controller 16 can be of any suitable configuration for controlling operation of electric machine 10, gathering data, processing data, etc. Controller 16 can include hardware, firmware, and / or stored software. Controller 16 can be of any type suitable for operating in accordance with the techniques described herein. While controller 16 is illustrated as a single unit, it is understood that controller 16 can be entirely or partially mounted on one or more circuit boards. In some examples, controller 16 can be implemented as a plurality of discrete circuitry subassemblies.

[0060] During operation, an alternating current (AC) signal is run through each coil 26. The AC signal rapidly builds and collapses the magnetic field due to the current reversal of the AC signal through the coil 26. Flux concentrating material of each stator phase assembly 22 (e.g., the lamina stacks) is wrapped around at least three sides of the coil 26. Generally, magnetic flux flows with the grain, along the direction of lamination, as flux will generally follow the path of highest permeability and there is resistance to flux jumping from one layer of lamination to another layer of lamination. At least a portion of the lamination grain of the flux rings 24 can be radially orientated relative to motor axis MA while the lamination grain of the axial returns 28 can be axially oriented relative to motor axis MA. As such, the flux can flow axially through the axial returns 28 and radially through flux rings 24 in a U-shaped path about coil 26 and towards rotor 12.

[0061] The AC signal routed through the coil 26 is synchronized to develop magnetic fields through the flux rings 24 in time with the rotational position of permanent magnet array 20 to drive rotation of rotor 12. The respective AC signals (e.g., sinusoidal or trapezoidal) delivered through the coils 26 in each stator phase 22a, 22b, 22c are out of phase with respect to each other. In this way, the magnets forming the permanent magnet array 20 more frequently have flux peaks acting on them, as compared to synchronizing the sinusoidal AC signals, thereby providing a smoother torque profile acting on the rotor 12 along the motor axis MA.

[0062] The examples of the electric machine 10 discussed in FIGS. 1 and 2 have three stator phases corresponding to the three stator phases 22a, 22b, 22c and respective coils 26 therein. As such, three AC signals are delivered through the coils 26 120-degrees electrically offset. It is understood that not all examples are so limited. For example, the machine 10 can include two phases (e.g., with 180-degrees electrically offset signals), four phases (e.g., with 90-degrees electrically offset signals), six phases (e.g., with 60-degrees electrically offset signals), etc. In some examples, pairs of the phases (e.g., three phase pairs in a six phase example) can be provided with electrically aligned signals such that the electric signals are electrically offset between phase pairs but electrically aligned within a phase pair (e.g., three phase pairs for a six phase example).

[0063] FIG. 3 shows a cross-sectional view of an electric machine 10. The axis of rotation MA of the rotor 14 is indicated. The electric machine 10 includes a rotor 14 and a stator 12. The rotor 14 is mounted on a shaft 32. Bearings 34 support the shaft 32. The rotor body 18 is supported by the shaft 32 and the rotor body 18 is configured to support magnet array 20. The magnet array 20 includes permanent magnets 36 (FIG. 4). The magnetic array 20 can include concentrators 38 (FIG. 4) (e.g., formed from stacked lamina or powdered metal) interspersed with the magnets 36. In some examples, the rotor body 18 is formed by stacked laminas. In some examples, the concentrators 38 are formed by the laminas that also form at least a portion of the rotor body 18.

[0064] While the rotor 14 is located within the stator 12 in the example shown such that machine 10 is an inner rotator, in some other examples the rotor 14 is located radially outward from the stator 12 such that the machine 10 is an outer rotator. The bearings 34 interface with the shaft 32 to rotatably support the rotor 14 relative to a housing (not shown).

[0065] The laminas of each lamina stack (e.g., forming the stator 14 or rotor 12, or other stacks of laminas referenced herein) can be pressed, staked, pinned, welded, glued, or in some other manner fixed to one another. For both the rotor 12 and the stator 14, a single thin layer of material the conducts electromagnetic flux is referred to herein as a lamina, while multiple stacked layers are referred to herein as laminas. A preferred metal is steel, such as silicon steel. While steel is used herein as an example herein, other types of flux concentrating / magnetically permeable metal or other material can be used. The rotor 12 is shown in isolation from the stator 14 in the cross-sectional view in FIG. 3, which in three dimensions is generally concentric about the axis. The rotor 12 spins about the axis radially inward with respect to the stator 14 in this example, but in various other examples the rotor 12 spins about the axis radially outward with respect to the stator 14. Both the rotor 12 and the stator 14 are cylindrical and are orientated coaxial with the indicated axis.

[0066] The electric machine 10 is shown to include shaft 32 and bearings 34. The rotor 12 is mounted on the shaft 32 and the bearings 34 support the shaft 32 while rotating. However, it is noted that the electric machine 10 can be embodied without the shaft 32 and / or bearings 34. As such, an electric machine 10 may include or exclude the shaft 32 and / or bearings 34.

[0067] FIG. 4 is an isometric view of a rotor 14 mounted on shaft 32. Shaft 32 extends axially outward from rotor body 18 in the example shown. A bearing 34 is shown. The bearing rotatably supports the shaft 32 and the rotor 12 is mounted to shaft 32 such that rotation of rotor 12 causes rotation of shaft 32.

[0068] The rotor 14 includes an annular array of magnets 36 supported by rotor body 18. The plurality of magnets 36 can be magnetized sections of a material or can be discreet magnets, arrayed around the axis. Interspaced with the magnets 36 are concentrators 38, which can be stacked steel laminations, amongst other options. The concentrators 38 can be stacks of laminas circumferentially interspaced with the plurality of magnets 36.

[0069] In the example shown, the concentrator 38 and rotor body 18 are together formed by stacks of laminas. The concentrators 38 can rotor body 18 can be formed by monolithic portions of laminas. Each rotor lamina 44r includes a series of spokes 46 that extend radially outward form a lamina hub 48 of that rotor lamina 44r. The spokes 46 are stacked axially together to form the concentrators 38. In the example shown, the rotor laminas 44r have a radial grain orientation and are stacked axially. The magnets 36 are circumferentially bracketed by concentrators 38 and the concentrators 38 are circumferentially bracketed by magnets 36.

[0070] The concentrators 38 can direct the flow of electromagnetic flux from an air gap 30 between the rotor 12 and the stator 14 to the plurality of magnets 36, which electromagnetically couple the stator 14 to the rotor 12 so that the stator 14 can drive and rotate the rotor 12.

[0071] FIG. 5 is an isometric view of stator 14. FIG. 6 is a cross-sectional view showing a portion of stator phase 22a taken along line 6-6 in FIG. 5. FIGS. 5 and 6 are discussed together. Stator phases 22 are shown. In the example shown, the stator 14 includes three stator phases 22, however different examples can include different number of stator phases 22. In the examples shown, the driving signals for the coil 26 of each stator phase 22 are generally 120-degrees electrically offset relative to the signals of the coils 26 of the other stator phases 22. Each stator phase 22 comprises two annular flux rings 24, which can include solid structure extending fully about the axis MA or can be formed by ring segments arrayed about the axis MA. Each flux ring 24 includes an array of teeth 40 disposed about the axis MA. The teeth 40 extend towards the rotor 12 and are configured to concentrate magnetic flux towards the rotor 12. Each stator phase 22 includes a coil 26 between the two annular rings of teeth 40. The coil 26 receives an A / C signal to generate electromagnetic flux which travels through the flux rings 24 to concentrate the flux across the air gap 30 between the rotor 12 and the stator 14. Magnets 36 of the rotor 12 are then pushed and / or pulled by the electromagnetic flux to rotate the rotor 12 relative to the stator 14. Electrical current can be inducted in the coils 26 by rotation of the rotor 12 by an external force in the manner of a generator, in some examples.

[0072] Each stator phase 22 includes two rings (e.g., flux rings 24a, 24b of stator phase 22a). Each flux ring 24 can be segmented or continuous. Each flux ring 24 can be formed as a plate. The flux rings 24 are aligned coaxial with respect to each other (and coaxial with the axis of rotation of the rotor 12), and are arranged opposite to each other with a coil 26 disposed directly between the two flux rings 24 of a single stator phase 22. The coil 26 can be an assembly of copper (or other electrically conductive material) wire (e.g., round or ribbon strand) wound into a ring, the ring coaxial with the axial direction (including coaxial with the axis of rotation of the rotor 12).

[0073] Each stator phase 22 includes a plurality of teeth 40. The plurality of teeth 40 are circumferentially arrayed around the axis MA. For example, the annular arrays of teeth 40 can be coaxial with the axis MA. In particular, each stator phase 22 can include two annular arrays of interleaved teeth 40 (e.g., teeth of flux ring 24a and teeth of flux ring 24b for stator phase 22a). The two annular arrays of interleaved teeth 40 can be part of the opposed flux rings 24 of a single stator phase 22, with the teeth 40 of each respective flux ring 24 pointed in opposite directions.

[0074] In the example shown, the teeth 40 of flux ring 24a extend in first direction ADI while the teeth of flux ring 24b extend in second direction AD2. In the example shown, the teeth of the flux rings 24a, 24b extend axially such that the first and second directions ADI, AD2 are axial directions relative to the axis of rotation of the rotor 12. It is understood, however, that not all examples are so limited. For example, aspects of the present disclosure can be applied, individually or in conjunction, to electric machines having one or more air gaps that are not disposed parallel to the axis of rotation.

[0075] It is noted that the flux rings 24 can be formed from continuous material or can be composed of multiple arc subsections. For example, each lamina layer of the lamina stack forming a flux ring 24 can be formed by one continuous lamina that extends about the axis MA or can be formed by multiple arcuate lamina that each extend partially about the axis MA. In the example shown, each flux ring 24 includes a hoop-like superstructure that also forms the plurality of teeth 40. In various other examples, the hoop-like superstructure forms the flux rings 24 but does not formed the plurality of teeth 40. The multiple stator phases 22 can form multiple circumferential arrays of teeth 40, the circumferential arrays of teeth 40 arrayed along the axis and / or coaxial with the axis.

[0076] Between the two flux rings 24 of each stator phase 22 is a coil 26. Each coil 26 can be formed from copper or other wire material. Each coil 26 can include one wire wound multiple times around the axis or multiple wires wound multiple times around the axis MA. Each coil 26 can extend around the axis MA. Each coil 26 can be coaxial with the axis MA, such that multiple coils 26 of multiple stator phases 22 can be arrayed along the axis MA. Each stator phase 22 operates by alternating current signal (e.g., sinusoidal, trapezoidal, etc.) connecting through the coil 26 to generate electromagnetic flux that oppositely polarizes adjacent teeth 40 of the stator phase 22, such oppositely polarized adjacent teeth 40 electromagnetically interacting across the air gap with the magnet 36 of the rotor 12 that is across the air gap from the oppositely polarized adjacent teeth 40. As such, a single coil 26 of a stator phase 22 can generate a plurality of poles circumferentially about the rotor 12 to drive the magnets 36 and consequently the rotor 12 to rotate about the axis MA. The electromagnetic flux across the air gap 30 may be directed by the concentrators 38 to the polarized sides of the magnet 36.

[0077] In the example show, each stator phase 22 includes a plurality of axial returns 28, though it is understood that not all examples are so limited. The axial returns 28 can be circumferentially arrayed around the axis. The axial returns 28 can electromagnetically connect adjacent teeth 40 of opposed flux rings 24 of a stator phase 22 to facilitate polarization of the adjacent teeth 40. In some examples, the axial returns 28 are integrated into the flux rings 24, however as illustrated in this particular example, each axial return 28 is a separate stack of laminas and separate from the stacks of laminas forming the flux rings 24. The grain orientation of the stack of laminas of each axial return 28 can be parallel with the axis. The grain orientation of the stack of laminas of each axial return 28 can be different from the grain orientation of the stack of laminas of the flux rings 24. The grain orientation of the stack of laminas of each axial return 28 can be different form the grain orientation of the stack of laminas of the concentrators 38.

[0078] Adjacent flux rings 24 of a stator phase 22 form flux pairs to generate a transverse orientated flux field which interacts, across a stator-rotor air gap 30, with the concentrators 38 and magnets 36 to accelerate rotation of the rotor 12 with respect to the stator 14. Flux paired teeth 40 refer to respective closest pairs of teeth 40 of opposed flux rings 24 (e.g., the teeth 40 of flux ring 24a and teeth 40 of flux ring 24b are flux paired, the teeth 40 of flux rings 24c, 24d are flux paired, the teeth 40 of flux rings 24e, 24f are flux paired).

[0079] Each tooth 40 is part of a similar flux circuit with its corresponding flux paired tooth 40 of the opposed flux ring 24. The flux paired teeth 40 pair generally axially with a tooth 40 of the opposing circular array of teeth 40, and not circumferentially to the neighbor tooth 40 of the same circular array of teeth 40 because all teeth 40 of a flux ring 24 will have the same polarity at any given time while all teeth 40 of the opposed flux ring 24 of the same stator phase 22 will have the opposite polarity at any given time. More specifically, each tooth 40 of a first flux ring 24 flux pairs with the closest teeth 40 of the opposed flux ring 24 on the other axial side of the coil 26.

[0080] The flux field is generated by running current through the coil 26. An A / C signal is run through coil 26 which rapidly builds and collapses the magnetic field due to the current reversal of the A / C signal through the coil 26. For example, a sinusoidal signal can be run through the coil 26. The reversing nature of the signal through the windings of the coil 26 builds and reverses the polarity between the adjacent pairs of teeth 40 of opposed flux rings 24. In the example shown, the flux pairing of adjacent teeth 40 is facilitated by the axial returns 28 which form electromagnetic loops between the adjacent teeth 40. Each such pair of teeth 40 can form a pole, with multiple such pairs forming an array of poles circumferentially around the stator phase 22. As such, the plurality of teeth 40 interleaved in flux pairs form an annular array of poles between adjacent teeth 40 that is coaxial with the axis of rotation MA. Each pole formed by flux paired teeth 40 magnetically pushes and / or pulls the magnets 36 of the rotor 12 as the magnets 36 pass the paired teeth 40, such that that annular array of poles are formed simultaneously, and which are all poled in the same orientation about the axis MA. Being that all the poles of a particular stator phase 22 are activated by the single coil 26 of that stator phase 22, all poles become polarized, and reverse their polarity, simultaneously. Such an arrangement and manner of operation results in a high pole count relative to radial or axial flux motors, providing improved operating efficiency and providing for a more compact configuration of electric machine 10.

[0081] The flux paired ones of teeth 40 (e.g., teeth of flux ring 24a and flux ring 24b) are circumferentially offset from each other such that the teeth 40 of one flux ring 24 are not axially aligned with teeth 40 of the other flux ring 24 of the same stator phase 22. Being that the ends of the flux paired teeth 40 of the same stator phase 22 are not aligned axially, because teeth 40 of flux ring 24a are offset circumferentially from teeth 40 of flux ring 24b, the flux circuit travels at least a limited distance circumferentially between the flux paired ones of teeth 40. Therefore, a cumulative flux circuit comprised of a plurality of flux paired teeth 40 can flow in a spiral pattern circumferentially through the teeth 40 and axial returns 28 (in examples including axial returns 28). It is noted that, while most flux flows between flux paired ones of teeth 40, the ring segments 64 permit flux flow between teeth 40 of the same ring segment 64, such that a limited amount of flux may skip a set of flux paired teeth 40 to the next-over tooth 40 of the same ring segment 64.

[0082] The concentrators 38 route the magnetic flux from the permanent magnets 36 toward the stator 14. Flux circuits are completed across the air gap 30 between the stator 14 and rotor 12. The flux from the rotor 12 (specifically the permanent magnets 36) and the flux from the coil 26 (through the teeth 40) interact in the air gap 30, and the resulting flux shear forces rotation of the rotor 12. The flux of the present machine 10 has an orientation transverse to the axis of rotation MA. This is different from the radial flux orientation of traditional A / C and D / C brushless motors.

[0083] The flux generated by the stator 14 and acting on the rotor 12 is constantly changing due to both changing position of the permanent magnets 36 and concentrators 38 due to rotation of the rotor 12 as well as the change in polarization of the teeth 40 due to the change in the A / C signal through the coil 26. As such, the A / C signal routed through the coil 26 is synchronized with rotation of the rotor 12 to develop magnetic fields through the teeth 40 in time to the concentrators 38 approaching and departing the teeth 40 to simultaneously push and pull the permanent magnets 36 of the rotor 12 to provide the force that rotates the rotor 12.

[0084] At least some of the respective A / C signals (e.g., sinusoidal or trapezoidal) delivered through the multiple coils 26 forming stator 14 are out of phase with respect to each other. In this way, the rotor 12 (along its axial length) more frequently has flux peaks acting on it, as compared to synchronizing the sinusoidal A / C signals, for a smoother torque profile acting on the rotor 12 along the axis of rotation of the rotor 12. Traditional A / C induction motors use a plurality of discrete coils that form an array of discrete coils that together extend circumferentially around the axis of rotation of the rotor. Each coil represents a potential pole for acting on a magnet. The discrete coils arrayed circumferentially around the axis of rotation in a conventional A / C induction motor are out of phase with respect to each other. The discrete coils can interact with a small subset of the magnets at any given instance. The potential torque generated is proportional to the number of poles. The number of poles in such a motor is limited by the ability to fit discrete coils circumferentially around the axis of rotation within the motor. Coil windings can be made smaller, and the diameter of the stator can be made bigger, to accommodate more coils to support more poles, but this increases the size, weight, and cost of the motor and still has limits. Power can also be increased when the rotor is rotating at a relatively high rate, whereby more coil-magnet passes can be experienced per unit time. But such power increase requires the motor to operate at relatively high speed when some applications may desire low-speed output. Providing reduction gearing to reduce speed and increase torque to the desired high torque and low speed increases cost, weight, size, and friction.

[0085] Electric machines 10 according to the present disclosure are different from traditional A / C and D / C brushless motors. An aspect of the electric machine 10 is that it contains relatively few coils 26, only three in the illustrated examples. Unlike traditional A / C and D / C brushless motors, the coils 26 are formed from loops that extend entirely around the axis of rotation of the rotor 12. The axis of rotation of the rotor 12 extends through each loop (e.g., the center of each loop). Each coil 26 is annular, and the turns of each coil 26 are likewise annular, and the circular planar profile of the coil 26 and turns are orthogonal to the axis MA. The coils 26 do not include loops that generate flux that rotates the rotor 12 through which the axis MA does not extend. Instead of adding a coil for each pole as in traditional A / C induction motors, the flux rings 24 and axial returns 28 (in examples including axial returns 28) surrounding a single coil 26 channel the flux to a plurality of teeth 40 that flux pair across the stator phase 22 to create a plurality of poles from the single coil 26. As such, activating one coil 26 activates many poles, whereas in some traditional A / C and D / C brushless motors activation of one coil activates only one pole.

[0086] One coil 26 supports multiple poles equal to the number of teeth 40 of a single flux ring 24. For example, if each flux ring 24 includes twenty-four teeth 40, then twenty-four poles will be formed from the single coil 26 between those flux rings 24. It is understood that lower and higher poles can be created depending on the number of teeth 40. As such, activating one coil 26 activates many poles, whereas in some traditional A / C and D / C motors activation of one coil activates only one pole. Multiple coils 26 are arrayed along the axis of rotation of the rotor 12 with each coil 26 interacting with the magnet array 20, thereby multiplying the number of poles.

[0087] The high pole count eliminates or reduces the need for reduction gearing for outputs from electric machine 10, reducing off-center forces as well as reducing weight and friction, allowing for a more compact arrangement of electric machine 10. The electric machines 10 of the present disclose can generate high torque with a small package size, even at low speed. Therefore, gear reduction of a drive can be minimized or entirely excluded, providing savings on cost, size, weight, and friction.

[0088] Returning to the structure of the teeth 40, each tooth 40 in the example shown includes a base 50. The base 50 can be part of, or extend from, the hoop-like superstructure of the flux ring 24. Each tooth 40 further comprises a spur 52. The spur 52 branches from the base 50. In various examples, and as shown, the spur 52 can be cantilevered from the base 50. The spur 52 has a single point of connection with the base 50 and is not otherwise directly connected to other structures of the flux ring 24. The spur 52 can project in an orientation that is transverse to the orientation of the base 50. The spur 52 can project in an orientation that is orthogonal to the orientation of the base 50.

[0089] The tooth face 90 of each tooth 40 is oriented towards the rotor 12. The tooth face 90 can partially directly overlap with the base 50 and can partially directly overlap with the spur 52. In some examples, the base 50 and the spur 52 together form a tooth face 90. The tooth face 90 directly faces the rotor 12. In the example shown, each tooth is formed by a stack of stator laminas 44s. In the example shown, each stator lamina 44s extends to a termination 58 that forms at least a portion of the tooth face 90. In the example shown, the terminations 58 are disposed in a saw-tooth configuration such that the tooth face 90 includes a series of steps along the tooth face 90 between the heel 60 and the toe 62. In the example shown, the tooth face 90 extends axially between the heel 60 and the toe 62, though it is understood that not all examples are so limited. For example, the tooth face 90 can extend radially in examples including axial air gaps rather than radial air gaps as shown. It is understood, however, that not all examples include a saw-tooth configuration; for example, the tooth face 90 can be flat without such steps.

[0090] The spur 52 and base 50 can both be formed by stacked stator laminas 44s. The stacked stator laminas 44s of the base 50 can extend radially relative to the axis MA, such as in configurations with a radial air gap between the stator 14 and rotor 12. The stacked stator laminas 44s of the spur 52 can extend both radially and axially such that the stacked laminas of the spur 52 have a grain orientation transverse to the grain orientation of the base 50. The stacked stator laminas 44s of the spurs 52 can include a grain orientation that is transverse to the grain orientation of the rotor laminas 44r.

[0091] In the example shown, the base 50 and the spur 52 are formed by the same stator laminas 44s. The stator laminas 44s can be monolithic between the base 50 and the spur 52. In the example shown, each stator lamina 44s includes a base arm 54 and a spur arm 56. The base 50 is formed by the stacked base arms 54. The spur 52 is formed by the stacked spur arms 56. Bends 57 are formed in the spur laminas 44 between the base arm 54 and the spur arm 56. The bend 57 reorients the lamina grain between the base arm 54 and the spur arm 56.

[0092] The flux ring 24 can be formed such that the lengths of the base arms 54 and the spur arms 56 vary between adjacent stator laminas 44s. The bends 57 of the various stator laminas 44s of the tooth 40 move progressively closer to rotor 12 from the innermost stator lamina 44si (e.g., closest to the coil 26) of the stator laminas 44s to the axially outermost stator lamina 44so (e.g., furthest from the coil 26). In the example shown, the stator lamina 44si can be referred to as an axially outermost stator lamina and the stator lamina 44so can be referred to as an axially innermost stator lamina. The bends 57 of the stator laminas 44s are stacked

[0093] Stator 14 can include brackets 42 that hold together stator phases 22. The brackets 42 are on opposite axial sides of the flux rings 24 of a stator phase 22, sandwiching the flux rings 24 therebetween. The brackets 42 also hold the axial returns 28 on the flux rings 24 in the example shown.

[0094] FIG. 7A is an isometric view of a stator ring segment 64 in a pre-shaped configuration. FIG. 7B is an isometric view of the stator ring segment 64 in a shaped configuration. FIGS. 7 A and 7B show how a stator ring segment 64 can be formed. Multiple stator ring segments 64 can form a flux ring 24. In this particular example, two stator ring segments 64 form the flux ring 24; however, other sizes of stator ring segments 64 can be used such that one, three, four, or other number of stator ring segments 64 can form a flux ring 24.

[0095] Each stator ring segment 64 is formed from a stack of stator laminas 44s. Each stator lamina 44s can be a sheet of ferrous material, such as steel among other options. The stator laminas 44s can be stacked such that adjacent stator laminas 44s contact each other or are evenly spaced by a separation distance. It is understood that a lamina 44 (either stator lamina 44s or rotor lamina 44r) can be considered to contact each other if the structure of the lamina 44 is in contact with the structure of another lamina 44, including if coatings on the steel or other ferrous material are in contact even if such coatings prevent direct steel-to-steel contact. Such separation distance may be filled in with potting material, such as epoxy or such space may be left as an air gap.

[0096] Each stator ring segment 64 defines multiple teeth 40. The ring segment 64 includes multiple segment portions 66. Each segment portion 66 can include a tooth 40, though it is understood that not all segment portions necessarily include a tooth 40. Further, it is understood that each segment portion 66 can include more than one tooth 40 in various other examples.

[0097] Each stator ring segment 64 includes a bend connection 68 disposed between adjacent teeth 40 within the ring segment 64. The bend connections 68 can connect adjacent segment portions 66 of the stator ring segment 64. The bend connection 68 can be considered to connect the bases 50 of adjacent teeth 40. The bend connection 68 includes a bend bridge 70 and a bend gap 72. The bend bridge 70 is formed by the stacked stator lamina 44s in this example. The bend bridge 70 provides a structural connection between adjacent segment portions 66 of the ring segment 64. The bend bridge 70 provides a structural connection between adjacent teeth 40 of the ring segment 64 in the example shown. The bend gap 72 is aligned with the bend bridge 70 and disposed directly between laminas of each segment portion 66 of the ring segment 64. The bend gap 72 is at least partially defined by the bend bridge 70. The bend gap 72 is disposed directly circumferentially between the adjacent segment portions 66.

[0098] Stator laminas 44s can be stacked as shown in FIG. 7A as straight segments, to form the ring segment 64 having the pre-shaped configuration. The ring segment 64 can then be bent at the bend connections 68 into the bent segment shown in FIG. 7B, which can be referred to as a shaped configuration.

[0099] The bend bridge 70 can be thinner (e.g., radially thinner) than the bases 50 on either side of the bend bridge 70. Each bend bridge 70 can have a curved shape, before the stator ring segment 64 is formed into the curved profile of FIG. 7B, that itself bends in a predictive manner when the straight stator ring segment 64 of FIG. 7A is bent into the arced stator ring segment 64 of FIG. 7B. Bending the stator ring segments 64 simplifies manufacturing of stator ring segments 64. Each stator lamina 44s can be formed in the straight configuration and the multiple stator ring segments 64 can then be stacked together prior to bending the ring segment 64 into the curved configuration. Such a configuration can simplify manufacturing in that it is easier to stack straight laminas shown in FIG. 7A than already curved laminas as shown in FIG. 7B.

[0100] FIG. 8A shows a stator lamina 44sa having a first configuration. FIG. 8B shows a stator lamina 44sb having a second configuration. FIG. 8C shows a stator lamina 44sc having a third configuration. The stator laminas 44sa-44sc can be stacked, together with other stator laminas 44s, to form the stator ring segments 64 previously shown (e.g., as shown in FIGS. 7A and 7B). The portions of the stator laminas 44sa-44sc forming the bases 50 are similar while portions of the stator laminas 44sa-44sc forming the spurs 52 have different lengths, accounting for how the stator laminas 44s that form the spurs 52 terminate across the tooth face 90. As shown, the bends 57 of each stator lamina 44sa- 44sc can be disposed at different distances from the hoop-like superstructure of the ring segment 64. As such, the base arms 54 of each stator lamina 44s can have a different length.

[0101] FIG. 9 illustrates a method for forming the stator laminas 44s of a stator ring segment 64. FIG. 9 generally shows an overhead view of a lamina sheet 74. Sequential steps are represented 900a-900d on different parts of the lamina sheet 74.

[0102] A stator ring segment 64 can be formed by stacking a plurality of stator laminas 44s together to form a lamina stack. The teeth 40 of the stator ring segment 64 are formed by the stacked stator laminas 44s. The lamina stack can then be bent to form the stator ring segment 64 in an arcuate configuration. The laminas can be bent concurrently after being formed into the lamina stack having an unbent configuration, such that all laminas 44s of that lamina stack are bent together. The lamina stack can be bent to form the stator ring segment 64 by bending a segment body of the lamina stack but not bending the teeth 40 formed by the lamina stack. As such, the lamina stack can be bent at locations between adjacent teeth 40 of the lamina stack.

[0103] In the step 900a, one or more moveable punches are used to trim what will be the terminations 58 of the spur 52. Step 900a determines the lengths of the spur arms 56, which spur arms 56, as previously shown, can be different lengths depending on the particular layer of the lamina stack that the stator lamina 44s being formed will be positioned in. For example, stator laminas 44s closer to the coil 26 can have longer spur arms 56 while stator laminas 44s further from the coil 26 can have shorter spur arms 56. The punch removes material from the lamina sheet 74 to set the overall length of the tooth 40; along the base arm 54, bend 57, and spur arm 56; along this stator lamina 44s, such as from the hoop-like superstructure to the termination 58. Step 900b is similar in that punches are again used, but in step 900b the punches trim the lamina sheet 74 to define the sides 76 of the teeth 40. For example, the sides of the spurs 52 and, in some examples, the sides of the bases 50 are formed in step 900b. The punch utilized in step 900b can be a fixed punch such that the shaping of the sides 76 of the spurs 52 can be uniform across all stator laminas 44s regardless of location within the lamina stack. Material is removed from lamina sheet 74. The tooth 40 can be formed as a cantilevered lamina portion after step 900b. The stator lamina 44s exiting from step 900b has the sides 76 and termination 58 of the tooth 40 of that stator lamina 44s formed.

[0104] In some examples, portions of ring segment 64 that facilitate manipulation from the pre-shaped configuration (FIG. 8A) to the shaped configuration (FIG. 8B) can also be formed by a fixed punch, such as during step 900b. For example, at least a portion of each bend gap 72 and / or bend bridge 70 can be formed during step 900b.

[0105] In the example shown, the sides 76 of tooth 40 have the same configuration for each stator lamina 44s forming the tooth 40. It is understood that, in some examples, the side profile of the tooth 40 can vary between stator laminas 44s depending on the location of the stator lamina 44s within the lamina stack. In such a configuration the punch utilized in step 900b can be a movable punch. After step 900b, the tooth portion 78 of the stator lamina 44s is formed, but in an unbent configuration.

[0106] In step 900c, the three sided tooth portion 78 is bent with respect to the rest of the lamina sheet 74, forming three dimensional lamina, although in this step the base arms 54 that will be stacked to form the bases 50 of the teeth 40 are still part of the lamina sheet 74. The spur arm 56 and portion of the stator lamina 44s that will form the bend 57 are separated from the rest of the lamina sheet 74. In some examples, the spur arms 56 can be bent upwards with respect to the rest of the lamina sheet, though it is understood that not all examples are so limited. The punch utilized to form the bends 57 can be a movable punch. As such, the bends 57 can be placed at desired locations along the length of the tooth 40 to position the bend 57 at a desired location for stacking with the other bends 57 and forming the tooth 40. The bend 57 can thus be placed at a desired location along the tooth portion 78 to form a base arm 54 and spur arm 56 having desired lengths.

[0107] In step 900d, the stator lamina 44s that forms a layer of the stator ring segment 64 is cut. The forming taking place in step 900b can be done by a fixed position punch. The tool that removes the formed stator lamina 44s from the lamina sheet 74 can have a fixed position and cut such that the same, fixed punch configuration can be used for each stator lamina 44s regardless of the stacking position within the lamina stack of the stator lamina 44s being formed.

[0108] In the example shown, each stator lamina 44s forming a stack of stator laminas 44s to form a ring segment 64 can be formed by a series of punches. The series of punches include both fixed and movable punches in this example. Indexing of the punches can be performed to account for the different spur lengths and shapes for a stator ring segments 64. The layers can then be stacked to form the stator ring segment 64. As discussed above, each stator lamina 44s can be formed in the straight configuration and stacked together to form a ring segment 64 in the configuration shown in FIG. 7A. The ring segment 64 in the pre-shaped configuration can then be bent to the shaped, curved configuration.

[0109] In some examples, the ring segment 64 can be formed by a series of punches in which each punch has a fixed configuration. For example, a ring segment 64 formed by a stack of thirty stator lamina 44s can include a series of thirty sets of fixed punches.

[0110] The process shown in FIG. 9 provides significant advantages. In step 900b, the sides 76 of each tooth 40 are formed by a fixed position punch. In steps 900a, 900c the termination 58 of each stator lamina 44s is formed and the bend 57 of each stator lamina 44s is formed. The terminations 58 and bends 57 are located at different positions depending on the location of that stator lamina 44s within the lamina stack of the ring segment 64. The movable punches for forming the terminations 58 and bends 57 facilitates a simplified manufacturing process that can facilitate ordered manufacturing and stack up of the stator lamina 44s.

[0111] The stator lamina 44s can be formed in an ordered series conforming with the stacking order of the stator lamina 44s. For example, the method can be implemented such that the stator lamina 44s are formed in the stacking order (e.g., from furthest from the coil 26 to closest to the coil 26), facilitating ordered assembly in the straight configuration. The aligned and stacked stator lamina 44s can then be bent to the desired bent configuration. For example, the outermost stator lamina 44so (e.g., stator lamina 44s furthest from coil 26) (FIG. 6) can be formed first. The stator lamina 44s between the outermost stator lamina 44so and the innermost lamina 44si, which can also be referred to as intermediate lamina, can be formed in order from the stator lamina 44s closest to the outermost stator lamina 44so to the stator lamina 44s closest to the innermost stator lamina 44si. The innermost stator lamina 44si can be the last stator lamina 44s formed and the last placed on the lamina stack forming the ring segment 64. The configuration of the fixed and movable punches facilitates ordered formation of the stator laminas 44s such that the stator laminas 44s can be collected and directly stacked after punching at step 900d. Such a configuration can simplify and expedite formation of ring segments 64, thereby decreasing costs and increasing manufacturing efficiency.

[0112] FIG. 10 is a simplified schematic diagram showing a lamina stacks with interlamina gaps 82 between adjacent laminas 44. FIG. 11 is simplified sectional view showing variable lamina densities. FIG. 12 is a graph illustrating flux reluctance relative to lamina density. FIG. 13 is a graph illustrating eddy current and torque relative to rotor lamina density. FIGS. 10-13 are discussed together.

[0113] As shown in FIG. 10, the lamina stacks 80 can be formed with inter-lamina gaps 82 that are disposed between adjacent laminas 44 within the lamina stack 80. It is understood that the adjacent laminas 44 can be formed as stator laminas 44s or rotor laminas 44r, unless specifically discussed as applying to one and not another. The inter-lamina gaps 82 can be filled with air or a bonding compound (e.g., epoxy among other options), among other fillers configured to inhibit cross-lamina flux flow. The cross-lamina direction CLD is indicated in FIG. 10. The lamination plane direction LPD is also indicated in FIG. 10. Electromagnetic flux is encouraged to flow within a lamina plane and not across the interlamina gap 82 due to the electrical resistance of the lamina encouraging magnetic flux flow and the electrical resistance of the inter-lamina gap 82 discouraging magnetic flux flow.

[0114] Electromagnetic flux generally flows along the orientation of the parallel layers of laminas (e.g., in the lamination plane direction LPD), which is referred to herein as the grain of the laminas (which is different from the grain of the metal of a single lamina). For example, the electromagnetic flux generally flows along a radial plane in the rotor 12 due to the laminas being orientated radially. The closer the laminas 44 are to each other (e.g., the smaller the inter-lamina gap 82), the more likely electromagnetic flux is to jump between adjacent laminas (e.g., cross in the cross-lamina direction CLD), which results in eddy currents, loss, and ultimately unwanted heat generation. Separating adjacent laminas 44 (e.g., forming and / or enlarging the inter-lamina gaps 82) helps avoid electromagnetic flux from jumping between adjacent laminas 44 and helps avoid associated heat generation. If there is an inter-lamina gap 82 between the adjacent laminas 44, the inter-lamina gaps 82 may be filled with potting material, such as epoxy amongst other options, or the interlamina gap 82 may be left as an air gap.

[0115] It is understood, however, that more separation is not necessarily better as lesser dense stacks (having greater separation distance between adjacent laminas 44) supports less dense flow of electromagnetic flux while less or no separation between adjacent lamina 44 (i.e. higher density) increases permeability, which makes it easier to move flux through the laminations (e.g., in the cross-lamina direction CLD). Separation or larger separation between adjacent lamina (i.e. lower density) reduces the likelihood of flux crossing between adjacent laminations, minimizing losses and thus heat generation.

[0116] Various examples of electric machine 10 can include a first portion of a stack of laminas having a first separation between adjacent laminas, and a second portion of the same or different stack of laminas have a second separation between adjacent laminas, the first separation different from the second separation. The first separation may be less than the second separation, such that the first portion is denser with laminas on a volumetric basis than the second portion. The first separation may be zero, such that the adjacent laminas are in continuous contact and are parallel with each other, and the second separation may be greater than zero such that the adjacent laminas are not in continuous contact while still being parallel with each other.

[0117] The first portion and the second portion can be different areas of the rotor 12, or different areas of the stator 14, or respectively located in the rotor 12 and stator 14. The first portion and the second portion can be different portions of the same stack of laminas (e.g., different portions within a single stack of stator laminas 44s, among other options).

[0118] In some examples, the first portion and the second portion having different lamina densities can both be in the same tooth 40. The first portion can be along the base 50 of the tooth 40 while the second portion can be along the spur 52. The first portion and the second portion may be in separate stacks of laminas, such that a first stack includes only the density of the first portion and not the density of the second portion and a second stack includes only the density of the second portion and not the density of the first portion. In some examples, the laminas forming the first portion can be monolithic with the laminas forming the second portion.

[0119] In some examples, the first portion and the second portion can be formed by laminas extending in different orientations. The laminas of the first portion can extend one of parallel to and perpendicular to the axis of rotation and the laminas of the second portion can extend transverse to the first portion. In some examples, the laminas of the second portion can extend transverse to the axis of rotation, but not orthogonal to the axis of rotation. In some examples, the laminas forming the second portion can extend towards the portion of the rotor 12 spaced across the air gap 30 from the tooth 40. In one example, the second portion includes spur arms 56 and the first portion includes base arms 54. In some examples, the laminas 44 can extend such that a distal end of a lamina in the second portion is spaced away from an end of that lamina adjacent the portion of that lamina in the first portion. The distal end of that lamina in the second portion can be disposed closer to the rotor and can be spaced away from the portion of that lamina in the first portion such that the distal end is not disposed directly between the rotor 12 and the portion of that lamina in the first portion.

[0120] The first portion and the second portion can, in some examples, be separated in the stator 14 and rotor 12 respectively, or be within the rotor 12 and stator 14 respectively. The relative densities and / or the relative positioning of the first portion and the second portion can increase the performance of the electric rotation machine while minimizing unwanted heat rise.

[0121] In some examples, the electric machine 10 can include more than two distinct lamina density portions. In one example, the stator 14 can include multiple lamina density portions and the rotor 12 can include a further lamina density portion. For example, a tooth 40 of the stator 14 can include a first density portion having a first lamina density and a second density portion having a second lamina density, while the rotor 12 can include a third density portion having a third lamina density. The third lamina density can differ from the first and second lamina densities, and the second lamina density can vary from the first lamina density. In one example, the third lamina density is less than (i.e., less dense so fewer laminas per volume)

[0122] As shown in FIG. 11, multiple different portions of the lamina structures of the electric machine 10 can have different lamina densities. The example shown in FIG. 11 is a simplified view of portions of a rotor 12 and stator 14. The view shown in FIG. 11 shows multiple aspects of the disclosure that can be utilized independently or together. The features shown herein of variable laminas density and / or variable rotor-stator separation distance can be practiced independent of each other or together. Furthermore, such different aspects can be implemented for every tooth 40 of every phase 22. Such different aspects can be implemented differently between adjacent teeth 40 within a flux ring 24 or within a phase 22.

[0123] In the example shown in FIG. 11 , a first density portion 84 is formed in the stator 14, a second density portion 86 is formed in the stator 14, and a third density portion 88 is formed in the rotor 12. The first density portion 84 and the second density portion 86 are both formed in a tooth 40 of the stator 14 in the example shown. In the example shown, the first density portion 84, the second density portion 86, and the third density portion 88 each have different lamina densities, though it is understood that not all examples are so limited.

[0124] In the example shown, each density portion 84, 86, 88 includes laminas having the same lamina grain within that density portion 84, 86, 88. The multiple laminas 44 within each density portion can each extend parallel to each other, among other options. The lamina grains can vary between at least some of the lamina portions 84, 86, 88. In the example shown, the stator laminas 44s within the second density portion 86 extend transverse to the stator laminas 44s within the first density portion 84. In the example shown, the stator laminas 44s in the second density portion 86 extend transverse to the rotor laminas 44r in the third density portion 88.

[0125] In some additional or alternative examples, the laminas of multiple of the different density portions 84, 86, 88 can extend parallel to each other. For example, the stator laminas 44s of the first density portion 84 can extend parallel to the rotor laminas 44r of the third density portion 88.

[0126] In the example shown in FIG. 11 , the first density portion 84 is formed in the base 50 of the tooth 40 and the second density portion 86 is formed in the spur 52 of the tooth 40. The stator 14 can include inter-lamina gaps 82a between adjacent stator laminas 44s and can include inter-lamina gaps 82b between adjacent stator laminas 44s, in examples in which the stator 14 has multiple different density regions. The separation between stator laminas 44s in the base 50 can be formed such that the adjacent laminas are in parallel and in continuous contact with each other. In some examples, the base 50 can be configured such that the first density portion 84 has a lamina density of about 95%. It is understood that adjacent laminas can be considered to be in contact when the structure of the adjacent laminas (e.g., including the ferro-magnetic sheet, any coating, etc.) is in contact.

[0127] The separation between stator laminas 44s in the spur 52 can be formed such that the adjacent stator laminas 44s are in parallel, or near parallel, but not in contact with each other. The separation between stator laminas 44s of the second density portion 86 (e.g., between spur arms 56 in this example) can be created depending on the bend 57 in the stator lamina 44s. The bend can be configured such that portions of the stator laminas 44s forming the base 50 can be tight with each other but due to the bend 57 redirecting the grain of stator laminas 44s between the base 50 and spur 52 (e.g., from radial / axial (depending on the configuration of the electric machine 10) to transverse) allows the stator laminas 44s to project out in the manner in which the stator laminas 44s are slightly spread out and have a separation distance between adjacent stator laminas 44s. The first density portion 84 can be the entirety of the base 50 or maybe a limited portion of the base 50. The second density portion 86 may be the entirety of the spur 52 or maybe a limited portion of the spur 52.

[0128] In some examples, the second density portion 86 has a lamina density of up to about 75%. In some examples, the second density portion 86 has a lamina density at least about 10% less than the lamina density of the first density portion 84. In some examples, the second density portion 86 has a lamina density at least about 20% less than the lamina density of the first density portion 84.

[0129] As shown, rotor 12 can include third density portion 88. The rotor 12 includes interlamina gaps 82c between adjacent rotor laminas 44r. In the example shown, the separation distance between adjacent rotor laminas 44r of the rotor 12 can be greater than the separation distance in the second density portion 86, and the second density portion 86 can have greater separation than the first density portion 84. As such, three different densities can be exhibited between laminas 44 in different parts of the electric machine 10. In some examples, the lamina density of the rotor 12 can be up to about 70%. In some examples, the lamina density of the rotor 12 can be up to about 65%.

[0130] FIG. 12 is a graph illustrating permeability for flow of electromagnetic flux in plane (e.g., along direction LPD (FIG. 10)) and cross-plane (e.g., along direction CLD (FIG. 10)) relative to lamina density. The vertical axis is a logarithmic scale illustrating relative permeability. The lower the permeability the more resistive to flow of electromagnetic flux. The horizontal axis shows various lamina densities. Inhibiting cross-lamina flow in direction CLD improves efficiency of the electric machine 10, prevents eddy currents, prevents losses, and prevents undesirable heat generation.

[0131] As shown in FIG. 12, increasing the size of the inter-lamina gap 82, which results in lower lamina density, provides a significant improvement in the resistance to the electromagnetic flux crossing between adjacent laminas. As shown in FIG. 12, a 10% reduction in lamina density (from 100% at point Pl to 90% at point P2) results in about a lOOx change in resisting electromagnetic flux crossing between adjacent laminas 44. Such a reduction causes minimal impact to the flow of electromagnetic flux along the lamina 44 in plane (from point P3 to point P4), about a l.lx change.

[0132] FIG. 13 is a graph illustrating eddy current generation and torque relative to rotor lamina density. The left vertical axis is a scale showing eddy current losses in the rotor laminas 44r as measured in Watts (W). The right vertical axis is a scale showing toque percentage drop relative to 100% torque at 95% lamina density in the rotor 12. The horizontal axis shows various lamina densities for the rotor 12. As shown, the lower the density of the laminas 44 in the rotor 12, the less eddy currents that are generated. Reducing the lamina density in the rotor 12 from 95% to about 80% results in about a 45% reduction in eddy current losses in the rotor 12 (from point El at 95% density to point E2 at 80% density). Such a reduction also results in about a 1.5% reduction in toque (from point T1 at 95% density to point T2 at 80% density). Reducing the lamina density in the rotor 12 from 95% to about 50% results in about an 80% reduction in eddy current losses (to point E3) in the rotor 12. Such a reduction also results in less than 3% reduction in torque (to point T3) (about 2.75% reduction in torque) in the example shown. The reduction in lamina density in the rotor 12 results in a significant reduction in eddy currents. Inhibiting eddy current formation results in improved efficiency of the electric machine 10 and results in reduction in unwanted heat generation.

[0133] Returning specifically to the structure shown in FIG. 11, the tooth 40 shown includes a variable distance air gap 30 directly between the tooth 40 and the rotor 12. The air gap 30 can be disposed directly radially between the tooth 40 and the rotor 12 in examples including radial air gaps. The air gap 30 can be disposed directly axially between the tooth 40 and the rotor 12 in examples including axial air gaps 30.

[0134] The distance between the lamina structure of the stator 14 and the lamina structure of the rotor 12 can vary along the length L of the tooth face 90. It is understood that the features shown herein of variable laminas density and / or variable rotor-stator separation distance can be practiced independent of each other or together.

[0135] The tooth face 90 can be considered to include a base surface portion 92 and a spur surface portion 94. The base surface portion 92 is formed by that portion of the tooth face 90 that directly overlaps with the base 50. In the example shown, the base surface portion 92 radially overlaps with the base 50. The spur surface portion 94 is formed by the portion of the tooth face 90 that projects beyond the base 50. In the example shown, the spur surface portion 94 projects axially away from the base 50. The spur surface portion 94 can be formed by the portions of the stator laminas 44s that do not radially overlap with the base 50, such as by one or more spur arms 56.

[0136] In the example shown, the tooth 40 is configured such that there are different separation distances between the stator laminas 44s and the exterior surface of the rotor 12 along the length L of the tooth 40. The tooth 40 can be considered to have a heel 60 and a toe 62. The heel 60 is formed at an outer end of tooth 40 (e.g., on an outer side of the flux ring 24 oriented away from the coil 26 of that stator phase 22). The toe 62 is formed at an inner end of the tooth 40 (e.g., on an inner side of the flux ring 24 that is oriented towards the coil 26 of that stator phase 22). The toe 62 is disposed at an opposite end of the tooth 40 from the heel 60. The toe 62 is disposed at an opposite axial end of the tooth 40 from the heel 60 in the example shown.

[0137] Tooth 40 can be configured such that a gap distance GDI is formed between the heel 60 and the rotor surface 96 and gap distance GD2 is formed between the toe 62 and the rotor surface 96. The gap distance GD 1 and the gap distance GD2 can be taken between the lamina structure of the stator 14 and the lamina structure of the rotor 12. The gap distance GDI is greater than the gap distance GD2. As such, the heel 60 is disposed further from the rotor surface 96 than the toe 62. In the example shown, the heel 60 is disposed further radially from the rotor surface 96 than the toe 62.

[0138] The spur surface portion 94 can be disposed radially closer to the rotor 12 than the base surface portion 92. In some examples, the gap distance between the rotor surface 96 and the base surface portion 92 can vary lengthwise along the base surface portion 92. For example, a portion of the base surface portion 92 at the interface between base surface portion 92 and spur surface portion 94 can be disposed closer to the rotor surface 96 than the heel 60. In some additional or alternative examples, the gap distance between the rotor surface 96 and the spur surface portion 94 can vary lengthwise along the spur surface portion 94. For example, the toe 62 can be disposed closer to the rotor surface 96 than a portion of the spur surface portion 94 at the interface between base surface portion 92 and spur surface portion 94.

[0139] In some examples, the tooth face 90, including the spur surface portion 94 and the base surface portion 92, can be smooth. In other examples, the tooth face 90 can include a saw-tooth shape. It is understood that even if a saw-tooth shape is exhibited, then the relative distances of the spur surface portion 94 and the base surface portion 92 to the rotor surface 96 are averaged to account for the mean distance between the tooth face 90 and the rotor surface 96 being such that the mean spacing distance of the spur surface portion 94 is closer to the rotor surface 96 than the mean spacing distance of the base surface portion 92 is to the rotor surface 96.

[0140] While higher density of laminas 44 and shorter, more direct flux flow paths can support greater electromagnetic flow through such paths, electromagnetic flux is less likely to go through lower density of laminas and longer and / or indirect paths. That can make it harder to utilize the entirety of the spur 52 in communicating electromagnetic flux across the air gap 30 because the electric magnetic flux is more likely to go straight down the base 50 and through the base surface portion 92 of the tooth 40. Such electric magnetic flux is less likely to go through the spur 52 in particular through the spur surface 94 and across the air gap 30.

[0141] In order to make full use of the spur 52, thereby improving operating efficiency, the air gap 30 is effectively increased along the base surface portion 92 relative to the spur surface portion 94. In this way, the portion of the tooth 40 along the spur surface portion 94 is physically closer to the rotor surface 96 than the potion of the tooth 40 along base surface portion 92 is to the rotor surface 96. In some examples, the entirety of the tooth face 90 can be angled along its length L between the heel 60 and the toe 62; the tooth face 90 can include step sections with varied gap distances between the rotor 12 and those step sections; amongst other options.

[0142] As shown in FIG. 11 , variable X demonstrates the angling of the tooth face 90 to position the spur surface portion 94 closer to the rotor surface 96 than the base surface portion 92 is to the rotor surface 96. Line TF is a line along the tooth face 90 and line AA is a line parallel to the rotational axis MA and along the rotor surface 96. The variable X can represent a size of an air gap between the surface of the rotor 12 and the laminas of the stator 14. It is understood that, in some examples, the air gap 30 can at least partially be filled with epoxy or other potting compound.

[0143] As shown, the distance X between the tooth face profile line TF and the line AA changes based on the lengthwise position along the tooth face 90. A larger air gap 30 is formed between the rotor surface 96 and base surface portion 92 than between rotor surface 96 and spur surface portion 94. Such larger air gap 30 along the base surface portion 92 discourages electromagnetic flux going across the air gap 30 and directly to the laminas of the base 50 and thereby encourages the surplus electromagnetic flux to cross the air gap 30 along the shorter distance of the opposing interface between the spur surface portion 94 and the rotor surface 96. Such a difference in separation distance makes better use out of the spur 52 of the tooth 40. Such a configuration of the tooth 40 balances permeance between the heel 60 and the toe 62 for more balanced flow of electromagnetic flux, providing for smoother and more efficient operation.

[0144] Electric machine 10 provides significant advantages. The variable density regions provide spacing gaps between adjacent laminas within a lamina stack. Such a configuration discourages cross-lamina flux (i.e., increases cross-lamination reluctance). Reducing / inhibiting cross-lamina flux flow reduces the formation of eddy currents, thereby reducing unwanted heat generation caused by such eddy currents and increasing the operational efficiency of the machine 10. Increasing the spacing gaps between adjacent laminas 44 (i.e., decreasing the lamina density) leads to a large reduction in cross-lamina permeability while maintaining in-plane permeability at a desired level. The difference between cross-lamina permeability and in-plane permeability increases by orders of magnitude as the lamina density decreases. Increasing the difference between cross-lamina and in-plane permeability encourages the magnetic flux to remain in-plane within a lamina and not jump between lamias, which cross-lamina flow leads to generation of eddy currents.

[0145] The stator 14 can, in some examples, include multiple regions that have different lamina densities. The portion having lower lamina density is disposed closer to the rotor 12 than the portion having higher lamina density. In the example shown, the multiple regions with different lamina densities are disposed in the tooth 40. The spur 52, which projects over the coil 26 and directly between the coil 26 and the rotor 12, has a lower lamina density than the base 50, which connects to the spur 52 and extends away from the rotor 12. The lower lamina density in the spur 52 encourages in-plan flux flow and discourages cross-lamina flux flow. Such a configuration encourages the flux to flow through the spur 52 and within a lamina 44 rather than across laminas 44. Such a configuration can inhibit formation of eddy currents, increases efficiency, and reduces unwanted heating.

[0146] The rotor 12 can include inter-lamina gaps that space out the rotor laminas 44r of the rotor 12. The rotor 12 can, in some examples, include a lamina density different from one or more lamina densities of the stator 14. In some examples, the rotor 12 can include a third density portion 88 that has a lamina density different than a first density portion 84 of the stator 14 and a second density portion 86 of the stator 14. The first density portion 84 and second density regions 86 can have different lamina densities from each other and from the third density portion 88. Reducing the lamina density in the rotor 12 leads to a significant reduction in eddy current generation, reducing unwanted heating and providing for more efficient operation. Reducing the lamina density does not lead to a proportional drop in torque. Instead, there are minimal drops in torque while providing for a correspondingly large drop in eddy current losses (e.g., less than -3% loss in torque for a corresponding greater than 80% reduction in eddy current losses).

[0147] The variable rotor-stator spacing distance provides advantages independent of the lamina density regions. The variable rotor-stator spacing places a toe 62 of the spur 52 closer to the rotor surface 96 than the heel 60 of the spur 52 is to the rotor surface 96. The toe 62 of the spur 52 being physically closer to the rotor 12 encourages electromagnetic flux to flow through the spur 52 rather than jumping to the base 50. The variable rotor- stator spacing distance balances flux in the tooth 40, which inhibits cross-lamina flux in the rotor 12 thereby discouraging formation of eddy currents. The variable rotor-stator spacing distance balances permeance in the tooth 40, preventing cross-lamina flux flow.

[0148] FIG. 14 is an enlarged isometric cross-sectional view showing a portion of rotor 12 and a portion of stator 14. FIG. 15A is a side view of the portion of rotor 12 and the portion of stator 14 shown in FIG. 14. FIG. 15B is an enlarged view of detail B in FIG. 15A. FIGS. 14-15B are discussed together. A single flux ring 24 of a phase assembly 22 of the stator 14 is shown with the coil 26 and other flux ring 24 omitted for clarity.

[0149] Air gap 30 is located between stator 14 and rotor 12. Air gap 30 is disposed directly between stator 14 and rotor 12. In various examples, air gap 30 can be disposed directly radially between rotor 12 and stator 14. It is understood that in various additional or alternative examples, an air gap 30 can be disposed directly axially between rotor 12 and stator 14.

[0150] Lamina structure of stator 14 and rotor 12 can, in some examples, be embedded in potting compound, such as epoxy. As such, a surface of the stator 14 defining the air gap 30 that is filled with air between the rotor 12 and stator 14 and a surface of the rotor 12 defining that air gap 30 can be at least partially formed by potting compound. It is understood, however, for purposes of this disclosure that the air gap 30 is considered to be the gap formed between flux directing structure of the rotor 12 (e.g., rotor laminas 44r) and flux directing structure of the stator 14 (e.g., stator laminas 44s). The potting compound is not flux directing. The variable rotor-stator spacing and / or defined lamina density regions are directed to the flux directing structure.

[0151] Rotor surface 96 can at least partially define the air gap 30. It is understood that, while rotor laminas 44r and magnets 36 of rotor 12 are shown, such components can be embedded in potting compound, such as epoxy, such that the rotor surface 96 is wholly or partially formed by the potting compound. Rotor surface 96 faces the stator 14. In particular, the rotor surface 96 faces the tooth face 90. The tooth faces 90 of the teeth 40 directly oppose the rotor 12 across the air gap 30.

[0152] Rotor 12 includes multiple rotor lamina 44r that are stacked axially in the example shown. The concentrators 38 of rotor 12 are formed by the stacked rotor lamina 44r. Magnets 36 are disposed circumferentially between concentrators 38. Each magnet 36 can, in some examples, extend a full axial length of the lamina structure of the rotor 12. Interlamina gaps 82c are formed between adjacent rotor lamina 44r. Stator 14 is separated from rotor 12 across air gap 30. The teeth 40 of stator 14 extend towards rotor 12. Base 50 of each tooth 40 projects towards the rotor 12. In the example shown, the base 50 extends radially towards the rotor, though it is understood that not all examples are so limited. The spur 52 extends from the base 50. The spur 52 extends both radially and axially in the example shown. The tooth 40 is formed by multiple stator lamina 44s that are stacked together to form the flux ring 24 and thus the teeth 40 of the flux ring 24. Multiple, up to all, of the stator lamina 44s forming the tooth 40 include base arm 54 that extends towards the rotor 12, bend 57 that reorients the stator lamina 44s, and spur arm 56 that extends from the bend 57 and away from the base 50. In the example shown, base arm 54 extends radially towards the rotor 12 and bend 57 reorients the stator lamina 44s such that the spur arm 56 extends both axially and radially. The spur arm 56 can, in some examples, extend transverse to the base arms 54. The spur arm 56 can, in some examples, extends transverse to the rotor laminas 44r.

[0153] Each tooth 40 includes a tooth face 90 that is oriented towards the rotor 12. The tooth face 90 directly opposes the rotor surface 96 across the air gap 30. The tooth face 90 includes spur surface portion 94 and base surface portion 92. The spur surface portion 94 corresponds with the portion of the spur 52 spaced outward away from the base 50 and along which the spur 52faces the rotor 12. The spur surface portion 94 is not disposed directly between portions of the base 50 and the rotor 12. Instead, the spur surface portion 94 forms a portion of the tooth face 90 that is spaced outward from the base 50. In the example shown, the spur surface portion 94 does not radially overlap with portions of the base 50.

[0154] The base surface portion 92 corresponds with the portion of the tooth face 90 that overlap with the base 50 and along which the base 50 faces the rotor surface 96. The base surface portion 92 is disposed directly between portions of the base 50 and the rotor 12. In the example shown, the base surface portion 92 radially overlaps with the base 50 and the rotor 12.

[0155] The rotor laminas 44r are spaced from each other to provide inter-lamina gaps 82c that provide separation between adjacent rotor laminas 44r. In the example shown, standoffs 98 engage with rotor laminas 44r to provide spacing between adjacent laminas 44 to form the inter-lamina gaps 82c. In particular, standoff 98 exists to spread out the rotor laminas 44r of the rotor 12. The standoff 98 can create a separation distance between adjacent rotor laminas 44r to form the inter-lamina gaps 82c. In the example shown, the standoff 98 is a standout formed in each rotor lamina 44r. In particular, the standoff 98 is a bump or other projection formed in the lamina 44. For example, the standoff 98 can be formed by embossing or in any other desired manner. The standoff 98 can, in some examples, be formed as a half-sphere or dimple, among other shaping options. As shown, the convex side of the standoff 98 engages an adjacent lamina 44 at the location of the standoff 98 of the adjacent laminas 44. The standoffs 98 are sized to provide a desired size inter-lamina gap 82c for providing the desired rotor lamina density.

[0156] The standoff 98 is formed on a spoke 46 of the rotor lamina 44r. In some example, multiple, up to all, of the spokes 46 of a rotor lamina 44r can include a standoff 98. The standoffs 98 of the axially stacked rotor laminas 44r are axially aligned with each other such that the standoffs 98 act together to provide desired spacing throughout the rotor 12. Stacking the standoffs 98 on top of each other spreads out the rotor laminas 44r as shown such that the rotor laminas 44r have inter-lamina gaps 82c between adjacent rotor laminas 44r.

[0157] As best seen in FIG. 15B, tooth 40 includes multiple lamina density portions. In the example shown, base 50 includes first density portion 84 with stator laminas 44s having a first separation or separation distance. The first separation can form inter-lamina gaps 82a in the first density portion 84. Such first separation may be the adjacent stator laminas 44s in parallel continuous contact with each other, as such the inter-lamina gaps 82a can be zero or greater. The spur 52 includes second density portion 86 having stator laminas 44s with a second separation or separation distance. Such second separation may be adjacent stator laminas 44s in parallel, or near parallel, but not in contact with each other. The second separation can form inter-lamina gaps 82b in the second density portion 86.

[0158] The separation between laminas of the second density portion 86 can be created based on the bends 57 of the stator laminas 44s. The length of the base arms 54 within the base 50 and the curvature of the bend 57 can provide for the desired spacing within the second density portion 86. For example, a portion of the stator laminas 44s forming the base 50 (e.g., base arms 54) can be tight with each other (e.g., 95% or greater lamina density) but due to the bend 57 redirecting the grain of stator laminas 44s, the spur arms 56 of the stator laminas 44s can project out in the manner in which the stator laminas 44s are slightly spread out and have a separation distance between adjacent stator laminas 44s. The second density portion 86 has a reduced lamina density as compared to the first density portion 84. The first density portion 84 can be the entirety of the base 50 or maybe a limited portion of the base 50. The second density portion 86 can be the entirety of the spur 52 or may be a limited portion of the spur 52. It is understood that, in some examples, the base 50 can have the same lamina density as the spur 52 (e.g., with increased separation distance rather than tight stacking).

[0159] Separation distances between adjacent rotor laminas 44r can be greater than the separation distances in the second density portion 86 for the stator lamina 44s. The separation distance in the second density portion 86 can be greater than the separation distance in the first density portion 84. As such, some examples of machine 10 can include three different lamina densities between laminas in different parts of the electric machine 10.

[0160] FIG. 15 A demonstrates an independent aspect that can increase performance. While higher density of laminas and shorter, more direct flux flow paths can support greater magnetic flux flow through such paths, electromagnetic flux is less likely to go through lower density of laminas and longer and / or indirect paths. That can make it harder to utilize the entirety of the spur 52 in communicating electromagnetic flux across the air gap 30, because the electromagnetic flux is more likely to go straight down the base 50 through the base surface portion 92 of the tooth 40. Such electromagnetic flux is less likely to go through the spur 52 in particular through the spur surface portion 94 and across the air gap 30. Therefore, in order to make full use of the spur 52, the air gap 30 is effectively increased along the base surface portion 92 relative to the spur surface portion 94. In this way, the spur surface portion 94 is closer to the rotor surface 96 than the base surface portion 92 is to the rotor surface 96.

[0161] In the example shown, the tooth 40 is configured such that the air gap 30 spacing differs lengthwise along the tooth 40 between the heel 60 and the toe 62. In the example shown, the toe 62 is closer to the rotor surface 96 than the heel 60. The variable rotor-stator spacing distance can be formed by angling the entirety of the tooth face 90, or by having step sections along the axial length of the tooth face 90, amongst other options. Variable X demonstrates the angling of the tooth face 90 to position the spur surface portion 94 closer to the rotor surface 96 than the base surface portion 92. As shown, line TF is a line along the tooth face 90 and line AA is a line parallel to the rotor surface 96 (also parallel to the axis of rotation in this example). The distance X varies between the tooth face TF and the line AA lengthwise along the tooth 40. As shown, the distance X is greater at the heel 60 than at the toe 62 such that the toe 62 is disposed physically closer to the rotor 12 than the heel 60. Such a larger air gap 30 along the base surface portion 92 discourages electromagnetic flux going across the air gap 30 at that location and instead encourages the electromagnetic flux to cross the air gap 30 along the shorter distance of the opposing interface between the spur surface portion 94 and the rotor surface 96. Such a difference in spacing from the rotor 12 makes better use out of the spur 52 of the tooth 40. Such difference in spacing from the rotor 12 between the spur surface and the base surface portion 92 encourages flow of electromagnetic flux across the full length of the tooth face 90, providing for improved operating efficiency and discouraging formation of eddy currents.

[0162] The tooth face 90, including the spur surface portion 94 and the base surface portion 92, can be smooth. In such a case, the saw-tooth shape shown in the figures of the tooth face 90 may not be embodied. Even if a saw-tooth shape is exhibited, then the relative distances of the spur surface portion 94 and the base surface portion 92 are averaged to account for the mean spur surface portion 94 being closer to the rotor surface 96 than the mean base surface portion 92 is to the rotor surface 96.

[0163] The features shown herein of variable laminas density and / or variable air gap distance can be practiced independent of each other or together. Furthermore, such different aspects can be implemented for every tooth 40 of every phase 22.

[0164] FIG. 16 is an end view of a rotor lamina 44r. FIG. 17 shows standoffs 102 for a rotor lamina 44r. As discussed above, a rotor 12 can be formed by a plurality of rotor laminas 44r that are stacked together axially. The rotor laminas 44r can be spaced from each other by inter-lamina gaps 82c that provides a separation distance between the adjacent rotor laminas 44r. Increasing the size of the inter-lamina gap 82c decreases lamina density, thereby discouraging formation of eddy currents.

[0165] In the example shown, the rotor lamina 44r includes a lamina hub 48 and a plurality of spokes 46 that radiate outward from the lamina hub 48. The lamina hub 48 can be mounted on a shaft, such as shaft 32 (FIG. 3). The lamina spokes 46 of multiple of the rotor lamina 44r are aligned with each other to form the concentrators 38 of the rotor 12. Magnet gaps 100 are formed between circumferentially adjacent ones of the spokes 46. The magnets 36 are disposed in the magnet gaps 100 such that the magnets 36 are disposed circumferentially between concentrators 38 formed by the stacked lamina spokes 46.

[0166] Rotor laminas 44r are spaced apart from each other to provide the desired lamina density. In the example shown, the rotor laminas 44r are spaced apart by providing a physical standoff between adjacent rotor laminas 44r. The physical standoff holds the rotor laminas 44r apart at the desired separation distance. The physical standoff can, in some examples, maintain spacing between the rotor laminas 44r during potting of the rotor 12, which potting material fixes the rotor laminas 44r relative to each other.

[0167] In the example shown, standoffs 102 are applied to one or both axial sides of the rotor lamina 44r. The standoffs are applied as a series of discrete projections on the rotor lamina 44r. In some examples, the standoffs are formed by ink that is applied to the rotor lamina 44r. The ink standoffs 102 can be printed on the axial face of the rotor lamina 44r. The ink standoff 102 can, in some examples, be applied to the rotor lamina 44r by screen printing. In the example shown, the ink standoff 102 is applied in a half tone pattern. The half tone pattern is formed by a series of ink dots. The ink dots are spaced from each other which can improve bonding between adjacent rotor laminas 44r as the potting compound is able to flow between the ink dots that form the standoffs 102.

[0168] In the example shown, the standoffs are applied to each spoke 46 of the rotor lamina 44r. The standoffs are further applied to the lamina hub 48. The standoffs 102 on the spokes 46 provides for desired spacing between aligned spokes 46 of adjacent rotor laminas 44r, thereby providing desired spacing within the concentrators 38. The standoffs 102 on the lamina hub 48 provides for desired spacing between aligned lamina hubs 48 of adjacent rotor laminas 44r.

[0169] The ink standoffs can be applied in one or multiple layers. For example, a first ink layer can be applied to the rotor lamina 44r, that ink layer can be flashed to dry, and then additional ink layers can be added to increase the thickness of the standoff 102 at each location. In this way, the ink standoff 102 can be built to a desired height for forming the desired lamina density within the rotor 12.

[0170] During assembly, on or more, up to all, of the multiple rotor laminas 44r forming the rotor 12 are stacked together. The lamina spokes 46 are aligned to form the concentrators. In the example shown, the lamina spokes 46 are axially aligned to form the concentrators 38. The lamina stack can then be compressed until inter-lamina gaps 82c having the desired gap size are formed. The ink forming the standoffs 102 is softer than the steel forming the rotor laminas 44r. As such, the ink will deform and compress without deforming the rotor laminas 44r. The standoffs 102 can thus be built to a height equal to or greater than the desired spacing for the inter-lamina gaps 82c and the standoffs 102 can be compressed between adjacent rotor laminas 44r until the desired spacing distance is achieved. As discussed above, the standoffs 102 can be applied in a half tone pattern in which a series of ink dots are applied to form the desired pattern. It is understood, however, that not all standoffs are applied in a half tone pattern. The half tone pattern facilitate potting material flowing between the ink dots such that the standoffs 102 are encapsulated by the potting material. Such a configuration provides good bonding and adherence between the adjacent rotor laminas 44r while also maintaining the standoffs 102 in a desired configuration for maintaining the spacing of the inter-lamina gaps 82c.

[0171] In some examples, the ink forming the standoffs 102 can be selected based on a cure temperature of both the ink and the potting compound. In some examples, the ink can be a PVC (polyvinyl chloride) based ink. Such PVC ink can have a curing temperature of about 130-degrees C (about 260-degrees F), which is approximately the same as the curing temperature for the potting compound. Selecting a material for the standoff 102 and potting compound that cure at about the same temperature provides for a consistent cure through the rotor 12 and prevents under- or over-curing of the material forming the standoff 102.

[0172] Providing standoffs 102 between adjacent rotor laminas 44r by application of a print pattern provides significant advantages. The ink can be applied by a screen printing process, facilitating quick and easy application of the standoffs 102 (formed by the ink) to the rotor laminas 44r. The standoffs 102 can be applied in a half tone pattern formed by a series of discrete dots. The standoff 102 dots are spaced from each other such that potting compound can fill in between the discrete ink dots forming the standoffs 102. Forming the standoffs 102 at least partially from ink dots provides high quality bonding between adjacent rotor laminas 44r.

[0173] The standoffs can be formed by material that has a hardness less than that of the rotor laminas 44r. As such, the rotor laminas 44r can be pressed together to cause the standoffs 102 to compress between the rotor laminas 44r until a desired spacing distance is achieved. The standoffs 102 being less hard than the rotor laminas 44r facilitates deformation of the standoffs 102 without deforming the material forming the rotor lamina 44r. Such a configuration maintains the desired shape and configuration of the rotor lamina 44r.

[0174] Further, forming the standoffs 102 from ink prevents direct contact between adjacent laminas 44. The ink forming the standoffs 102 and the potting compound fill into the inter-lamina gaps 82c and provides spacing between the adjacent rotor laminas 44r. Preventing any contact between adjacent rotor laminas 44r further inhibits cross-lamina flux travel, thereby inhibiting formation of eddy currents and increasing motor operating efficiency. FIG. 18 is a simplified diagram of an electric machine 10' having multiple radial air gaps. FIG. 19 is a simplified diagram of an electric machine 10" having axial air gaps. Electric machine 10' is substantially similar to electric machine 10, except that electric machine 10' includes multiple of the air gaps 30. Electric machine 10" is substantially similar to electric machine 10 and electric machine 10' except that the air gap 30 is oriented transverse rather than parallel to the axis of rotation of the electric machine 10".

[0175] In the example shown in FIG. 18, the air gaps 30 are disposed radially between components of the stator 14 and components of the rotor 12. A first air gap 30 is disposed radially inward between the stator 14 and rotor 12a. A second air gap 30 is disposed radially outward between stator 14 and rotor 12b. It is understood that rotor 12a and rotor 12b can be formed as separate rotating structures in various examples. In the example shown, electric machine 10' includes a first array of interleaved teeth 40 that directly oppose rotor 12a and includes a second array of interleaved teeth 40 that oppose rotor 12b. It is understood that one or more, up to all, of the teeth 40 of the first array of interleaved teeth 40 and / or the second array of interleaved teeth 40 can be configured as discussed herein for teeth 40 (e.g., with variable lamina density and / or variable air gap spacing).

[0176] In various of the examples shown throughout the disclosure, the teeth 40 of a flux ring 24 extend axially (e.g., in one of a first direction ADI and a second direction AD2). In the various examples shown herein, the teeth 40 of the flux rings 24 extend such that the first and second directions AD 1 , AD2 are axial directions relative to the axis of rotation of the rotor 12. The one or more air gaps are disposed radially between a rotator and a tooth face 90 of the tooth 40. It is understood, however, that not all examples are limited to radial air gaps.

[0177] In the example shown in FIG. 19, the air gap 30 is disposed between teeth 40 that have tooth faces 90 oriented axially and a portion of the rotor 12 oriented axially. Aspects of the present disclosure can be applied, individually or in conjunction, to electric machines having one or more axial air gaps between the teeth 40 and the rotator. In such an example, the air gap can be oriented tangential to the axis of rotation of the rotator, such as for the electric machine 10" shown in FIG. 19. In various examples, such an axial air gap can be oriented orthogonal to the axis of rotation of the rotator. It is understood that electric machines according to the disclosure can include one or more of the axial air gaps.

[0178] It is further understood that aspects of the disclosure can additionally or alternatively be applied in electric machines including both one or more axial air gaps and one or more radial air gaps. As such, electric machines according to the disclosure can include both axial and radial air gaps.

[0179] It is understood that in various examples, a single tooth 40 can be configured the same or differently from other teeth 40, such as other teeth 40 of the same flux ring 24. In some examples, the teeth 40 of a single tooth array (e.g., an array of interleaved teeth 40 facing a rotator across an air gap) can be configured the same or different (e.g., same or different lengths, slopes, lamina density, tooth face 90 configurations, etc.) as the teeth 40 of another tooth array (e.g., another array of interleaved teeth 40 facing the same or another rotator across another air gap). For example, the teeth 40 opposing rotor 12a in FIG. 18 can be configured the same or different as the teeth 40 opposing rotor 12b in FIG. 18.

[0180] While an electric motor has been used herein as an example, the machines and aspects of the same can be used as, or implemented in, electrical generators. As such, the present disclosure is not limited to motors, and can include electrical generators. An embodiment can be both a motor and a generator. The term electrical machine is used herein to refer to various embodiments which can be either or both.

[0181] While the invention(s) has been described with reference to an exemplary embodiment(s), it will be understood by those skilled in the art that various changes may be made and equivalents may be substituted for elements thereof without departing from the scope of the invention. In addition, many modifications may be made to adapt a particular situation or material to the teachings of the invention(s) without departing from the essential scope thereof. Therefore, it is intended that the invention(s) not be limited to the particular embodiment(s) disclosed, but that the invention(s) may include all embodiments falling within the scope of the appended claims. Any single feature, or any combination of features from one embodiment show herein, may be utilized in a different embodiment independent from the other features shown in the embodiment herein. Accordingly, the scope of the invention(s) and any claims thereto are not limited to the particular to the embodiments and / or combinations of the features shown herein, but rather can include any combination of one, two, or more features shown herein.

Claims

CLAIMS:

1. An electric machine comprising: a rotor that rotates about an axis; and a stator configured to magnetically drive the rotor to rotate about the axis, the stator comprising a plurality of teeth; wherein each tooth of the plurality of teeth comprises a tooth face oriented towards the rotor, the tooth face including a first surface and a second surface, both of the first surface and the second surface directly facing the rotor, and wherein the first surface is closer to the rotor then the second surface.

2. The electric machine of claim 1 , wherein the first surface being closer to the rotor than the second surface promotes increased flow of electromagnetic flux through the first surface as compared to the first surface and the second surface being equidistant from the rotor.

3. The electric machine of any one of claims 1 and 2, wherein each tooth of the plurality of teeth comprises a base and a spur, the spur extending outward from the base to project axially relative to the base.

4. The electric machine of claim 3, wherein the first surface is located on one of the base and the spur and the second surface is located on an other one of the base and the spur.

5. The electric machine of any one of claims 3 and 4, wherein the first surface radially overlaps with the base and the second surface does not radially overlap with the base.

6. The electric machine of claim 4, wherein the first surface radially overlaps with the base and at least a portion of the second surface does not radially overlap with the base.

7. The electric machine of claim 4, wherein the tooth face extends between a heel and a toe, the toe disposed at an end of the spur, wherein the tooth face is configured such that the heel is disposed further from the rotor than the toe.

8. The electric machine of claim 4, wherein the first surface extends axially across an entirety of a portion of the spur facing the rotor and the second surface extends axially across an entirety of a portion of the base facing the rotor.

9. The electric machine of any one of claims 3-8, wherein a portion of the tooth radially overlapped with the second surface is radially thicker than a portion of the tooth radially overlapped with the first surface.

10. The electric machine of any of claims 3-9, wherein the spur narrows as the spur extends axially away from the base.

11. The electric machine of claim 10, wherein a radial thickness of the spur narrows as the spur extends axially away from the base.

12. The electric machine of any one of claims 1-11, wherein each tooth of the plurality of teeth is formed from a stack of laminas.

13. The electric machine of claim 12, wherein: a first tooth of the plurality of teeth includes a first stack of laminas; the first stack of laminas including a first portion and a second portion separate from the first portion; laminas of the first portion have a first density and laminas of the second portion have a second density that is different from the first density; the difference in density between the first density and the second density is due to different separation distances between adjacent laminas of the first portion as compared to adjacent laminas of the second portion.

14. The electric machine of any one of claims 12 and 13, wherein the stack of laminas is formed from steel or other ferrous material.

15. The electric machine of any one of claims 1-14, wherein an air gap exists between the rotor and the stator along each tooth, and for the plurality of teeth the air gap is variable in distance axially along each tooth.

16. The electric machine of any one of claims 1 and 2, further comprising at least one stack of laminas.

17. The electric machine of claim 16, wherein the at least one stack of laminas forms at least part of one or both of the stator and the rotor.

18. The electric machine of any one of claims 16 and 17, wherein the at least one stack of laminas comprises a first portion and a second portion separate from the first portion, wherein laminas of the first portion have a first density and laminas of the second portion have a second density that is higher than the first density of the first portion, the difference in density between the first density and the second density due to different separation between adjacent laminas of the first portion as compared to adjacent laminas of the second portion.

19. The electric machine of claim 18, wherein the adjacent laminas of the first portion are separated while the adjacent laminas of the second portion are in contact.

20. The electric machine of claim 18, wherein the adjacent laminas of the first portion are separated by a first separation distance while the adjacent laminas of the second portion are separated by a second separation distance that is less than the first distance.

21. The electric machine of claim 18, wherein the adjacent laminas of the first portion are separated by standoffs.

22. The electric machine of claim 21, wherein the standoffs are formed by the laminas of the first portion.

23. The electric machine of claim 22, wherein the standoffs are formed by bumps in the laminas of the first portion.

24. The electric machine of claim 21, wherein the standoffs are formed by ink.

25. The electric machine of claim 24, wherein the ink is screenprinted on the adjacent laminas.

26. The electric machine of any one of claims 24 and 25, wherein the standoffs include a plurality of ink dots.

27. The electric machine of any one of claims 24-26, wherein the ink is disposed in a half tone pattern.

28. The electric machine of any one of claims 18-27, wherein potting material is located between the adjacent laminas of the first portion.

29. The electric machine of any one of claims 18-27, wherein air is located between the adjacent laminas of the first portion.

30. The electric machine of any one of claims 18-29, wherein the first portion is part of the rotor while the second portion is part of the stator.

31. The electric machine of claim 18, wherein the first portion forms concentrators, the concentrators located between magnets of the rotor, and the second portion forms at least a portion of a tooth of the plurality of teeth.

32. The electric machine of any one of claims 18-31, wherein the laminas of the first portion have a first grain orientation, the laminas of the second portion have a second grain orientation, and the first grain orientation is different than the second grain orientation.

33. The electric machine of claim 32, wherein the first grain orientation extends radially while the second grain orientation extends other than radially.

34. The electric machine of any one of claims 32 and 33, wherein a first tooth of the plurality of teeth includes the laminas of the first portion and the laminas of the second portion.

35. The electric machine of claim 34, wherein the first portion forms a spur of the tooth and the second portion forms a base of the tooth, the spur extending away from the base.

36. The electric machine of claim 35, wherein the base of the tooth extends radially towards the rotor, and the spur of the tooth extends axially and radially from the base of the tooth.

37. The electric machine of any one of claims 18-20 and 34-36, wherein the laminas of the first portion are respectively contiguous with the laminas of the second portion such that the first portion and the second portion are different sections of a single stack of laminas.

38. The electric machine of any one of claims 18-37, wherein the at least one stack of laminas comprises a plurality of first portions including the first portion and a plurality of second portions including the second portion separate from the plurality of first portions, wherein laminas of the plurality of first portions have a lower density than laminas of the plurality of second portions, the difference in density between the plurality of first portions and the plurality of second portions due to different separation between adjacent laminas of the first portions as compared to the second portions.

39. The electric machine of claim 38, wherein the plurality of first portions are all part of a first flux ring of the stator, and the plurality of second portions are all part of the first flux ring.

40. The electric machine of any one of claims 1-38, wherein the stator includes one or more stator phases, each stator phase of the one or more stator phases comprising a first flux ring and a second flux ring.

41. The electric machine of claim 40, wherein the first flux ring is formed from a plurality of ring arc segments.

42. The electric machine of claim 41, wherein each ring arc segment of the plurality of ring arc segments is formed from a stack of arc segment laminas, the stack of arc segment laminas forming multiple teeth of the plurality of teeth.

43. The electric machine of claim 42, wherein the stack of arc segment laminas include a plurality of bends in which the laminas of the stack of arc segment laminas are first stacked and then the bends are bent to arc the ring arc segment.

44. The electric machine of any one of claims 1-43, further comprising one or more coils, each coil of the one or more coils coaxial with the axis.

45. The electric machine of any one of claims 1-44, wherein the plurality of teeth are arrayed around the axis.

46. An electric machine comprising: a rotor that rotates about an axis; and a stator configured to magnetically drive the rotor to rotate about the axis, the stator comprising a plurality of teeth; wherein a first tooth of the plurality of teeth is formed from a stack of laminas, the stack of laminas including a first portion having a first lamina density and a second portion having a second lamina density, wherein the second lamina density is greater than the first lamina density.

47. The electric machine of claim 46, wherein adjacent laminas of the first portion are separated by a first separation distance and adjacent laminas of the second portion are separated by a second separation distance, the second separation distance greater than the first separation distance.

48. The electric machine of any one of claims 46 and 47, wherein the adjacent laminas of the first portion are in contact.

49. The electric machine of any one of claims 46 and 47, wherein the first lamina density is at least 95-percent.

50. The electric machine of any one of claims 46-49, wherein the second lamina density is less than or equal to 90-percent.

51. The electric machine of claim 50, wherein the second lamina density is less than or equal to 80-percent.

52. The electric machine of claim 51 , wherein the second lamina density is less than or equal to 75-percent.

53. The electric machine of any one of claims 46-52, wherein the first tooth comprises: a base extending towards the rotor; and a spur projecting from the base.

54. The electric machine of claim 53, wherein the first portion is in the spur and the second portion is in the base.

55. The electric machine of any one of claims 46-54, wherein at least part of the first portion radially overlaps with at least part of the second portion.

56. The electric machine of any one of claims 46-55, wherein the first portion is disposed radially closer to the rotor than the second portion.

57. The electric machine of any one of claims 46-56, wherein a plurality of laminas forming the stack of laminas are contiguous between the first portion and the second portion.

58. The electric machine of claim 46, wherein each lamina of the plurality of laminas includes a base arm extending radially towards the rotor, a spur arm extending away from the base arm, and a bend connecting the base arm and the spur arm.

59. The electric machine of claim 58, wherein adjacent spur arms of the plurality of laminas have the first lamina density and adjacent base arms of the plurality of laminas have the second lamina density.

60. The electric machine of any one of claims 58-59, wherein the spur arm extends radially and axially from the base arm.

61. The electric machine of any one of claims 58-60, wherein the spur arm is cantilevered from the base arm.

62. The electric machine of any one of claims 46-61 , wherein the rotor includes a stack of rotor laminas, and wherein at least a portion of the stack of rotor laminas have a third lamina density different from the first lamina density and different from the second lamina density.

63. The electric machine of claim 62, wherein the third lamina density is less than the second lamina density.

64. The electric machine of any one of claims 62 and 63, wherein the third lamina density is less than the first lamina density.

65. The electric machine of any one of claims 62-64, wherein the third lamina density is less than or equal to 70-percent.

66. The electric machine of claim 65, wherein the third lamina density is less than or equal to 65-percent.

67. The electric machine of any one of claims 62-66, wherein adjacent rotor lamina of the stack of rotor lamina are separated by standoffs.

68. The electric machine of claim 67, wherein the standoffs are formed by the rotor laminas.

69. The electric machine of any one of claims 67 and 68, wherein the standoffs are formed by bumps of the rotor laminas.

70. The electric machine of claim 69, wherein the bumps are formed as hemispherical projections.

71. The electric machine of claim 67, wherein the standoffs are formed by material other than the rotor laminas.

72. The electric machine of any one of claims 67 and 71, wherein the standoffs are formed by ink.

73. The electric machine of claim 72, wherein the ink is disposed in a print pattern.

74. The electric machine of claim 73, wherein the ink is disposed in a half tone pattern.

75. The electric machine of any one of claims 72-74, wherein the ink comprises a plurality of ink dots.

76. The electric machine of claim 75, wherein potting compound is disposed between the adjacent rotor laminas and in spaces between the plurality of ink dots.

77. The electric machine of any one of claims 62-76, wherein each rotor lamina of the plurality of rotor lamina comprises a lamina hub extending at least partially about the axis and a plurality of spokes extending radially outward from the lamina hub.

78. The electric machine of claim 77, wherein axial stacks of the spokes of adjacent rotor laminas form concentrators of the rotor.

79. The electric machine of claim 78, wherein the rotor includes a plurality of magnets, and wherein each magnet of the plurality of magnets is disposed in a gap disposed circumferentially between adjacent axial stacks of the spokes of the adjacent rotor laminas.

80. The electric machine of any one of claims 62-77, wherein the rotor includes a plurality of magnets interleaved with a plurality of concentrators, and wherein each concentrator of the plurality of concentrators is formed by the stack of rotor laminas.

81. The electric machine of any one of claims 62-77, wherein the rotor includes a plurality of magnets interleaved with a plurality of concentrators, and wherein each concentrator of the plurality of concentrators is formed a plurality of the rotor laminas.

82. An electric machine comprising: a rotor that rotates about an axis, the rotor including a stack of rotor laminas, wherein at least a portion of the stack of rotor laminas has a rotor lamina density; anda stator configured to magnetically drive the rotor to rotate about the axis, the stator comprising a plurality of teeth; wherein a first tooth of the plurality of teeth is formed from a stack of stator laminas, the stack of stator laminas including a first portion having a first lamina density, wherein the first lamina density is greater than the rotor lamina density.

83. The electric machine of claim 82, wherein the rotor lamina density is less than or equal to 70-percent.

84. The electric machine of claim 83, wherein the rotor lamina density is less than or equal to 65-percent.

85. The electric machine of any one of claims 82-85, wherein the stack of stator laminas further comprises a second portion having a second lamina density, the second lamina density greater than the rotor lamina density and different from the first lamina density.

86. The electric machine of claim 85, wherein the second lamina density is greater than the first lamina density.

87. The electric machine of claim 86, wherein the first portion of the stack of stator laminas extends closer to the rotor than the second portion of the stack of stator laminas.

88. The electric machine of any one of claims 82-87, wherein the stack of rotor laminas are separated by at least one standoff.

89. The electric machine of claim 88, wherein, for adjacent rotor laminas of the stack of rotor laminas, a first rotor lamina of the adjacent rotor laminas includes a projection that contacts a second rotor lamina of the adjacent rotor laminas to brace the second rotor lamina and form a spacing gap between the first rotor lamina and the second rotor lamina, the projection forming the at least one standoff.

90. The electric machine of claim 89, wherein the first rotor lamina includes a plurality of the projections.

91. The electric machine of claim 90, wherein the plurality of the projections are arrayed about the axis.

92. The electric machine of any one of claims 89-91, wherein the projection is formed as a bump.

93. The electric machine of any one of claims 89-92, wherein the projection includes a convex side extending towards and contacting the second rotor lamina.

94. The electric machine of any one of claims 89-93, wherein the second rotor lamina includes a second projection, and wherein the projection of the first rotor lamina is axially aligned with the second projection.

95. The electric machine of claim 94, wherein the projection extends at least partially into a concavity of the second projection.

96. The electric machine of any one of claims 88, wherein, for adjacent rotor laminas of the stack of rotor laminas, an ink layer is disposed between a first rotor lamina of the adjacent rotor laminas and a second rotor lamina of the adjacent rotor laminas to form a spacing gap between the first rotor lamina and the second rotor lamina, the ink layer forming the at least one standoff.

97. The electric machine of claim 96, wherein the ink layer is formed by a plurality of ink dots.

98. The electric machine of claim 97, wherein the plurality of ink dots are disposed in a half tone pattern.

99. The electric machine of any one of claims 96-98, wherein the ink layer is compressed between the first rotor lamina and the second rotor lamina.

100. An electric machine comprising: a rotor that rotates about an axis, the rotor including a stack of rotor laminas, wherein at least a portion of the stack of rotor laminas has a rotor lamina density; and a stator configured to magnetically drive the rotor to rotate about the axis; wherein adjacent rotor laminas of the stack of rotor laminas are separated by at least one standoff.

101. The electric machine of claim 100, wherein, for adjacent rotor laminas of the stack of rotor laminas, a first rotor lamina of the adjacent rotor laminas includes a projection that contacts a second rotor lamina of the adjacent rotor laminas to brace the second rotor lamina and form a spacing gap between the first rotor lamina and the second rotor lamina, the projection forming the at least one standoff.

102. The electric machine of claim 101, wherein the first rotor lamina includes a plurality of the projections.

103. The electric machine of claim 102, wherein the plurality of the projections are arrayed about the axis.

104. The electric machine of any one of claims 101-103, wherein the projection is formed as a bump.

105. The electric machine of any one of claims 101-104, wherein the projection includes a convex side extending towards and contacting the second rotor lamina.

106. The electric machine of any one of claims 101-105, wherein the second rotor lamina includes a second projection, and wherein the projection of the first rotor lamina is axially aligned with the second projection.

107. The electric machine of claim 106, wherein the projection extends at least partially into a concavity of the second projection.

108. The electric machine of any one of claims 100, wherein, for adjacent rotor laminas of the stack of rotor laminas, an ink layer is disposed between a first rotor lamina of the adjacent rotor laminas and a second rotor lamina of the adjacent rotor laminas to form a spacing gap between the first rotor lamina and the second rotor lamina, the ink layer forming the at least one standoff.

109. The electric machine of claim 108, wherein the ink layer is formed by a plurality of ink dots.

110. The electric machine of claim 109, wherein the plurality of ink dots are disposed in a half tone pattern.

111. The electric machine of any one of claims 108-110, wherein the ink layer is compressed between the first rotor lamina and the second rotor lamina.

112. The electric machine of any one of claims 101-111, wherein each rotor lamina of the stack of rotor laminas comprises: a lamina hub extending at least partially about the axis; and a plurality of spokes extending radially outward from the lamina hub.

113. The electric machine of claim 112, wherein the at least one standoff is disposed on a spoke of the plurality of spokes.

114. The electric machine of any one of claims 112 and 113, wherein axial stacks of the spokes of adjacent rotor laminas of the stack of rotor laminas form concentrators of the rotor.

115. The electric machine of claim 114, wherein the rotor includes a plurality of magnets, and wherein each magnet of the plurality of magnets is disposed in a gap disposed circumferentially between adjacent axial stacks of the spokes of the adjacent rotor laminas.

116. The electric machine of any one of claims 100-115, wherein the rotor includes a plurality of magnets interleaved with a plurality of concentrators, and wherein each concentrator of the plurality of concentrators is formed by the stack of rotor laminas.

117. The electric machine of any one of claims 100-115, wherein the rotor includes a plurality of magnets interleaved with a plurality of concentrators, and wherein each concentrator of the plurality of concentrators is formed a plurality of the rotor laminas.

118. The electric machine of claim 100, wherein each rotor lamina of the stack of rotor laminas comprises: a lamina hub extending at least partially about the axis; and a plurality of spokes extending radially outward from the lamina hub; wherein the at least one standoff is disposed on a spoke of the plurality of spokes.

119. The electric machine of claim 118, wherein, for adjacent rotor laminas of the stack of rotor laminas, an ink layer is disposed between a first rotor lamina of the adjacent rotor laminas and a second rotor lamina of the adjacent rotor laminas to form a spacing gap between the first rotor lamina and the second rotor lamina, the ink layer forming the at least one standoff.

120. The electric machine of claim 119, wherein the ink layer is disposed on multiple spokes of the plurality of spokes of the first rotor lamina.

121. The electric machine of any one of claims 119 and 120, wherein the ink layer is disposed on each spoke of the plurality of spokes of the first rotor lamina.

122. The electric machine of any one of claims 119-121 , wherein the ink layer is disposed on the rotor hub of the first rotor lamina.

123. The electric machine of any one of claims 119-122, wherein the ink layer includes a plurality of ink dots.

124. The electric machine of any one of claims 119-123, wherein the ink layer is disposed in a half tone pattern.

125. The electric machine of claim 118, wherein, for adjacent rotor laminas of the stack of rotor laminas, a first rotor lamina of the adjacent rotor laminas includes a projection that contacts a second rotor lamina of the adjacent rotor laminas to brace the second rotor lamina and form a spacing gap between the first rotor lamina and the second rotor lamina, the projection forming the at least one standoff.

126. The electric machine of claim 125, wherein the at least one standoff includes a plurality of standoffs disposed on multiple spokes of the plurality of spokes of the first rotor lamina.

127. The electric machine of any one of claims 125 and 126, wherein each spoke of the plurality of spokes of the first rotor lamina includes a standoff of the at least one standoff.

128. A method of forming a portion of a stator of an electric machine, the method comprising: stacking a plurality of laminas to form a lamina stack, the lamina stack forming a plurality of teeth; and bending the lamina stack to form a stator ring segment of a flux ring of the stator, the stator ring segment being arcuate.

129. The method of claim 128, wherein bending the lamina stack to form the stator ring segment of the flux ring of the stator includes not bending the plurality of teeth while bending a segment body of the lamina stack.

130. The method of any one of claims 128 and 129, wherein bending the lamina stack to form the stator ring segment of the flux ring of the stator includes bending the lamina stack at bend connections connecting adjacent teeth of the plurality of teeth.

131. The method of any one of claims 128-130, further comprising: forming a lamina sheet of the plurality of laminas by a progressive die.

132. The method of claim 131, wherein forming the lamina sheet of the plurality of laminas comprises: stamping, by a first movable punch, a metallic sheet to define a tip of a tooth arm; stamping, by a first fixed punch, the metallic sheet to defines sides of the tooth arm; bending, by a second movable punch, the tooth arm to form a base portion of the tooth arm and a spur portion of the tooth arm; stamping, by a second fixed punch, the metallic sheet an outline of the lamina sheet to form the lamina sheet.

133. The method of claim 132, wherein forming the lamina sheet of the plurality of laminas includes: stamping, by the first movable punch, the metallic sheet to define the tip of the tooth arm before stamping, by the first fixed punch, the metallic sheet to define the sides of the tip arm.

134. The method of claim 132, wherein forming the lamina sheet of the plurality of laminas includes:stamping, by the first fixed punch, the metallic sheet to define the sides of the tip arm before stamping, by the first movable punch, the metallic sheet to define the tip of the tooth arm.

135. The method of any one of claims 128-134, wherein stacking a plurality of laminas to form the lamina stack, the lamina stack forming the plurality of teeth comprises: forming an axially outermost lamina of the lamina stack; forming a plurality of intermediate laminas of the lamina stack after forming the axially outermost lamina of the lamina stack and progressively stacking the plurality of intermediate laminas of the lamina stack on the axially outermost lamina of the lamina stack; and forming an axially innermost lamina of the lamina stack after forming the plurality of intermediate laminas of the lamina stack and stacking the axially innermost lamina on the plurality of intermediate laminas of the lamina stack.

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