Electric rotational 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 teeth are disposed in annular arrays that extend about the axis. An annular array of the teeth includes an unbalanced tooth set that counteracts cogging, radial forces, and torque ripple.

Description

[0001] ELECTRIC ROTATIONAL MACHINE

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

[0003] This application claims priority to U.S. Provisional Application No. 63 / 619,438 filed January 10, 2024 and entitled “ELECTRIC ROTATIONAL MACHINE,” and claims priority to U.S. Provisional Application No. 63 / 713,398 filed October 29, 2024 and entitled “ELECTRIC ROTATIONAL 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 motors and / or generators, such as transverse flux motors and / or generators.

[0006] Electric motors utilize electricity to generate a mechanical output. Some electric motors generate rotational outputs. In alternating current (A / C) induction motors, a stator is electrically energized to electromagnetically drive rotation of a rotor about a rotational 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 additional or alternative aspect of the disclosure, an electric rotational machine includes a rotor comprising a plurality of magnets arrayed around an axis of rotation of the rotor; and a stator comprising at least one coil and at least one annular array of teeth. A first plurality of adjacent teeth form at least part of a first annular array of teeth of the at least one annular array of teeth, wherein a non-uniform arrangement of the first plurality of adjacent teeth asymmetrically spreads out radial forces about the axis of rotation.

[0009] According to another additional or alternative aspect of the disclosure, an electric rotational machine includes a rotor comprising a plurality of magnets arrayed around an axis of rotation of the rotor; and a stator comprising at least one coil and at least one annular array of teeth. A first plurality of teeth forms at least part of a first annular array of teeth of the at least one annular array of teeth, the first plurality of teeth including a first tooth, a second tooth circumferentially adjacent to the first tooth, and a third tooth circumferentially adjacent to the second tooth, the first plurality of teeth producing asymmetric radial forces on the first annular array of teeth during operation of the stator. The first tooth has a first geometry and a first annular offset from a first nominal annular position, the second tooth has a second geometry and a second annular offset from a second nominal annular position, and the third tooth has a third geometry and a third annular offset from a third nominal annular position. At least one of (1) the first geometry differs from the second geometry, and the third geometry differs from the first geometry and the second geometry; and (2) the first annular offset differs from the second annular offset, and the third annular offset differs from the first annular offset and the second annular offset.

[0010] According to yet another additional or alternative aspect of the disclosure, an electric rotational machine includes a rotor comprising a plurality of magnets arrayed around an axis of rotation of the rotor; and a stator comprising at least one coil and at least one annular array of teeth. A first plurality of teeth form at least part of a first annular array of teeth of the at least one annular array of teeth, and the first plurality of teeth is disposed in a non-uniform tooth array including at least three circumferentially adjacent teeth of the first annular array of teeth, each tooth of the at least three circumferentially adjacent teeth has a different geometry.

[0011] According to yet another additional or alternative aspect of the disclosure, a flux ring for a stator of an electrical rotational machine is configured to extend about a rotational axis of a rotor of the electrical machine and includes a first tooth; a second tooth disposed circumferentially adjacent to the first tooth; a third tooth disposed circumferentially adjacent to the second tooth. The first tooth has a first geometry and a first annular offset from a first nominal annular position, the second tooth has a second geometry and a second annular offset from a second nominal annular position, and the third tooth has a third geometry and a third annular offset from a third nominal annular position. At least one of (1) the first geometry differs from the second geometry, and the third geometry differs from the first geometry and the second geometry; and (2) the first annular offset differs from the second annular offset, and the third annular offset differs from the first annular offset and the second annular offset.

[0012] According to yet another additional or alternative aspect of the disclosure, an electric rotational machine includes a rotor comprising a plurality of magnets arrayed around an axis of rotation of the rotor; and a stator, the stator comprising at least one coil and at least one annular array of teeth. A first plurality of adjacent teeth form at least part of a first annular array of teeth of the at least one annular array of teeth. The teeth of the first plurality of adjacent teeth are disposed asymmetrically about the axis of rotation.

[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 an isometric view of a fan system.

[0017] FIG. 4A is an isometric view of an electric machine with a housing removed.

[0018] FIG. 4B is a partially exploded isometric view of the electric machine shown in FIG. 4A.

[0019] FIGS. 5A and 5B are isometric cross-sectional views of a portion of a stator phase that demonstrate how flux circuits are formed through flux paired teeth of a stator phase.

[0020] FIG. 5C shows a detailed view of flux paired teeth of a stator phase interacting with concentrators and permanent magnets of a magnet phase of a rotor.

[0021] FIG. 6 is an end view of a portion of a stator phase showing a tooth array demonstrating aspects for shifting the annular positions of teeth.

[0022] FIG. 7 is an end view of a portion of a stator phase showing a tooth array demonstrating aspects for non-uniform tooth distribution.

[0023] FIG. 8 is an end view of a portion of a stator phase showing a tooth array demonstrating aspects for non-uniform tooth distribution.

[0024] FIG. 9 is an end view of a portion of a stator phase showing a tooth array demonstrating aspects for non-uniform tooth distribution.

[0025] FIG. 10 is a chart illustrating variable tooth configurations for a non-uniform distribution of teeth in a tooth array forming a portion of a stator phase.

[0026] FIG. HA is a graph illustrating radial forces at different mechanical angles about an axis of electric machine having a uniform tooth distribution during operation of the electric machine.

[0027] FIG. 1 IB is a chart illustrating distribution of the radial forces shown in FIG. 11A about the axis of the electric machine.

[0028] FIG. 12A is a graph illustrating radial forces at different mechanical angles about an axis of an electric machine having a non-uniform tooth distribution during operation of the electric machine.

[0029] FIG. 12B is a chart illustrating distribution of the radial forces shown in FIG. 12A about the axis of the electric machine. DETAILED DESCRIPTION

[0030] The present disclosure concerns electric rotational machines. Such electric rotational machines include motors and / or generators. While a motor will generally be referenced herein as the main example, any or all aspects referenced and / or shown herein can be implemented in a hybrid motor-generator or simply a generator.

[0031] The main type of electric machine presented herein is a transverse flux machine, which is distinguished from axial or radial flux type electric motors. However, the inventive aspects discussed herein can be applied to various types of electric machines beyond just transverse flux machines.

[0032] The electric machines of this disclosure include a rotor rotatable about a rotational axis and a stator. The stator extends about the axis of rotation and can be around or within the rotor. The stator can be configured to electromagnetically drive rotation of the rotor. According to aspects of the disclosure, the stator of the transverse flux electric motor includes stator phases, such as one, two, three, or more, formed from flux rings and a coil disposed axially between opposing flux rings. The flux rings include teeth that extend radially relative to the rotational axis and towards the rotor.

[0033] Flux rings according to the disclosure can be formed by multiple ring segments that each extend partially about the rotational axis. The ring segments define the flux ring but may not be in direct contact with each other. The ring segments can instead be fixed together by potting compound. In some examples, adjacent ones of the ring segments are not connected together by laminate structure. Instead, the potting compound is the only structure that bridges the circumferential gaps between the adjacent ring segments. A flux ring can include at least one circumferential gap such that the flux ring may not include a single ring of laminate structure in contact fully about the rotational axis (whether monolithic or formed by contacting ring segments).

[0034] The opposing flux rings of a single stator phase can be joined by axial returns contacting each flux ring and disposed on an opposite radial side of the coil from the rotor. The axial returns can form the radial-most portion of the laminate structures of the phases. The axial returns can be fixed by the potting compound.

[0035] The potting compound can be formed by epoxy and can extend from radially beyond the teeth to the stator housing in a continuous matrix.

[0036] The rotor includes permanent magnets and can include concentrators interspersed between the permanent magnets. The interspersed concentrators and permanent magnets form a magnet array of the rotor. The permanent magnet array formed by the interspersed permanent magnets and concentrators can be formed in axially-arrayed magnet phases.

[0037] According to aspects of the disclosure, the flux transfer structure of an electric machine (e.g., the laminas of the stator and / or rotor and / or magnets of the rotor) can be distributed about the axis to mitigate adverse effects that occur during operation of electric machines. For example, the flux transfer structure can be distributed to mitigate torque ripple, cogging, varying radial forces, vibration, noise generation, etc.

[0038] The teeth of a stator are distributed to inhibit adverse operational effects. The stator includes at least one annular array of teeth about the axis. The annular array of teeth can form and / or be part of a flux ring of a stator phase. A first annular array of teeth of the stator includes a plurality of circumferentially adjacent teeth that are non-uniform about the axis. The non-uniform configuration of the multiple adjacent teeth mitigate varying radial forces that can deform components of the electric machine, such as the rotor and stator. The multiple adjacent teeth can be disposed asymmetrically relative to the axis. The non- uniform distribution of the adjacent teeth provides a higher order mode shape for the resultant radial forces, better balancing such forces, which reduces vibration and noise generated during operation of the electric machine.

[0039] The non-uniform distribution of the multiple adjacent teeth within an annular array of teeth can mitigate torque ripple, which is a periodic fluctuation in the output toque of the electric machine as the shaft rotates. Mitigating torque ripple provides a smoother, more consistent rotation of the rotor of the electric machine.

[0040] The non-uniform distribution of the multiple adjacent teeth within an annular array of teeth can mitigate cogging. Cogging is an undesirable effect in which the rotor tends to stick in certain low-energy pole alignments, rotationally between higher energy orientations, creating resistance or reluctance to movement out of the low energy orientations at those specific points.

[0041] The teeth of a flux ring can be asymmetrically disposed about the axis. The teeth can be progressively shifted relative to an even distribution to minimize deleterious operational effects on a motor phase. The distribution of the teeth can be varied and nonprogressive in various examples.

[0042] Stators according to aspects of the disclosure include one or more sets of multiple adjacent teeth in which the teeth within the set of multiple adjacent teeth are structurally disparate. The multiple adjacent teeth can, in some examples, be structurally disparate in that the teeth have different tooth widths relative to each other (e.g., a set of three adjacent teeth each having a different tooth width at the face of the tooth), can be structurally disparate in that the teeth have different annular offsets from nominal evenly annularly arrayed positions, and / or can be structurally disparate in that the teeth have different annular distances between different pairs of teeth within the set of multiple adjacent teeth (e.g., annular distances between circumferential centers of the teeth), among other options.

[0043] The structurally disparate teeth according to aspects of the disclosure provide for a smoother operating electric machine that is less subject to torque ripple and cogging. The structurally disparate teeth according to aspects of the disclosure combats symmetric radial forces that can cause vibration and noise such that the structurally disparate teeth provide for an electric machine that has less wear and quieter operation.

[0044] Stators according to aspects of the disclosure include one or more sets of multiple adjacent teeth in which the teeth within the set of multiple adjacent teeth are in an unbalanced set. The multiple adjacent teeth are unbalanced in that the teeth forming the unbalanced set have different configurations relative to each other. In some examples, the unbalanced set includes at least three teeth, in which a first tooth is adjacent to a second tooth and the second tooth is adjacent to the third tooth, in which all of the of the unbalanced set are differently configured relative to each other. For example, the teeth of the unbalanced set can differ in that the teeth have different tooth widths relative to each other, in that the teeth have different annular offsets from nominal evenly annularly arrayed positions, and / or in that the teeth have different annular distances between different pairs of teeth within the set of multiple adjacent teeth (e.g., annular distances between circumferential centers of the teeth), among other options.

[0045] The configurations of the teeth of a single flux ring can be varied relative to the other teeth of the flux ring to mitigate the deleterious effects on a motor phase. The teeth can be configured such that the teeth of a single flux ring have varying geometry between the teeth. In some examples, adjacent teeth within a flux ring can have varying geometries relative to each other. In some examples, the teeth can be configured such that the width of the teeth vary between the multiple teeth of a single flux ring. In some additional or alternative examples, the teeth can be configured such that the teeth are annularly offset from nominal annular positions of the teeth and such that the annular offset vary between the multiple teeth. In some examples, the teeth of a single flux ring can be disposed such that the teeth are one or both of non-uniformly spaced and non-uniformly shaped.

[0046] Several of the figures of the disclosure show a common axis, which is sometimes referred to as a rotational axis. An axis of rotation of the rotor is disposed coaxially with the common axis. The term annular is used herein, which can refer to a ring shape (continuous or broken) about the common axis, which can be coaxial with the common axis. The term radial is used herein which when referring to a direction is any direction orthogonal to the common axis, unless otherwise noted. The term axial is used herein which when referring to a direction is any direction parallel with the common axis, unless otherwise noted. The terms circumferential or circumferentially as used herein means around the common axis, unless otherwise noted.

[0047] Components can be considered to radially overlap when those components are disposed at common axial locations along an axis. A radial line extending 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 the axially overlapping components. Components can be considered to circumferentially overlap when aligned about the axis, such that a circle centered on the axis passes through the circumferentially overlapping components.

[0048] 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.” Each flux ring 24 can be considered to form a half phase of a stator phase 22.

[0049] 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 axis CA and rotor 12 is configured to rotate on axis CA. Axis CA can be considered to be an axis of rotation of the rotor 12.

[0050] 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. 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. Permanent magnet array 20 can further include a plurality of concentrators, as discussed in more detail below. It is understood that in various examples the rotor body 18 can be formed by flux directing material of the rotor 12 (e.g., by laminas forming the concentrators among other options). In various other examples, the rotor body 18 can be formed separate from such flux directing structure and the permanent magnet array 20 can be mounted on that rotor body 18.

[0051] Stator 14 is formed by stator phases 22 arrayed along the axis CA. 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.

[0052] 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.

[0053] 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. Laminations can also be referred to as laminas.

[0054] In the example show, each stator phase 22 includes axial returns 28 that 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 and may not include axial returns 28.

[0055] 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.

[0056] 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.

[0057] 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.

[0058] During operation, an alternating current (A / C) signal is run through each coil 26. The A / C signal rapidly builds and collapses the magnetic field due to the current reversal of the A / C 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 axis CA while the lamination grain of the axial returns 28 can be axially oriented relative to axis CA. 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.

[0059] The A / C 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 A / C 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 of the permanent magnet array 20 more frequently have flux peaks acting on them, as compared to synchronizing the sinusoidal A / C signals, thereby providing a smoother torque profile acting on the rotor 12 along the axis CA.

[0060] The examples of the electric machine 10 discussed in FIGS. 1 and 2 have three stator phases 22 (corresponding to the three stator phases 22a, 22b, 22c) and respective coils 26 therein. As such, three A / C 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).

[0061] FIG. 3 is an isometric view of fan system 32. Fan system 32 includes electric machine 10, which is configured as a motor in this example, and blade assembly 34. Motor housing 36, supports 38, and drive shaft 40 of electric machine 10 are shown. Motor housing 36 includes stator housing 42 and bearing housing 44. Blades 46 and fan hub 48 of blade assembly 34 are shown.

[0062] Electric machine 10 is shown as an electric motor configured to generate a rotating mechanical output. In the example shown, electric machine 10 is configured to generate the output coaxially with common axis CA. Motor housing 36 encloses other components of electric machine 10. In the example shown, motor housing 36 includes a first, larger diameter portion and a second, smaller diameter portion. The first portion is formed by stator housing 42 and the second portion is formed by bearing housing 44. Both stator housing 42 and bearing housing 44 enclose rotating components of electric machine 10. Electric components of electric machine 10 are disposed, at least partially, within stator housing 42.

[0063] Supports 38 extend axially from stator housing 42 and are configured to interface with a support surface. In some examples, supports 38 can rest on the support surface such that stator housing 42 extends vertically above supports 38. Bearing housing 44 is disposed a lower axial end of stator housing 42 opposite blade assembly 34. Bearing housing 44 can thereby be disposed vertically between stator housing 42 and the support surface. In the example shown, bearing housing 44 has a smaller diameter than stator housing 42 and is located vertically below stator housing 42.

[0064] Blade assembly 34 is connected to electric machine 10 to be rotated by electric machine 10. Drive shaft 40 extends from electric machine 10 to provide the rotating mechanical output from electric machine 10 to blade assembly 34 to rotate blades 46 on common axis CA. Fan hub 48 is disposed at an end of drive shaft 40 opposite electric machine 10. More specifically, fan hub 48 is disposed at a distal end of drive shaft 40 opposite a second distal end of drive shaft 40 extending into bearing housing 44. Blades 46 extend radially outward from fan hub 48. In the example shown, electric machine 10 and blade assembly 34 are disposed coaxially on common axis CA such that blades 46, fan hub 48, drive shaft 40, and the rotor of electric machine 10 rotate coaxially.

[0065] In the example shown, fan system 32 is configured such that blade assembly 34 is disposed vertically above stator 14 and rotor 12. For example, fan system 32 can be configured for use in a cooling tower. It is understood that, while vertically oriented fans are discussed, fans according to the present disclosure can be oriented in any desired orientation and can be used to move any desired fluid, including gas and / or liquid. Further, while electric machine 10 is described as driving blade assembly 34, it is understood that any one or more aspects of electric machine 10 can be implemented in non-fan applications. Electric machine 10 can be configured for use in any desired electric motor assembly. It is thus understood that, while a fan is one implementation of the motor technologies presented herein, other applications, including non-fan applications, are possible and contemplated as within the scope of the disclosure.

[0066] FIG. 4A is an isometric view of electric machine 10 with the housing removed. FIG. 4B is a partially exploded isometric view of the electric machine 10 shown in FIG. 4A. FIGS. 4A and 4B will be discussed together. Drive shaft 40, rotor 12, and stator 14 of electric machine 10 are shown. Stator 14 is formed in stator phases 22a-22c. 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. Rotor 12 includes rotor body 18 and permanent magnet array 20. Rotor 12 is formed in rotor phases 50a-52c in this example, though it is understood that not all examples are so limited. Rotor phase 50a includes rotor hub 68 and magnet phase 54a. Rotor phase 50b includes rotor hub 52 and magnet phase 54b. Rotor phase 50c includes rotor hub 52 and magnet phase 54c.

[0067] Stator 14 and rotor 12 are disposed coaxially in this example to generate a rotational mechanical output based on electrical inputs. In the example shown, rotor 12 is disposed within stator 14 such that electric machine 10 is an inner rotator, though it is understood that other examples of electric machine 10 are configured as outer rotators having a rotor disposed about the stator. Stator 14 defines a cylindrical interior that rotor 12 is disposed within. Stator 14 is formed by stator phases 22 arrayed along common axis CA. Each stator phase 22 is an annular ring disposed about common axis CA.

[0068] The stator phases 22a-22c do not overlap each other along common axis CA. Stator phases 22a-22c do not radially overlap along axis CA, such that a radial line extending from common axis CA passes through at most only one of the stator phases 22 and does not pass through multiple ones of the stator phases 22 at any given location along common axis CA. The electromagnetic components of each stator phase 22 (e.g., lamina structure and coils 26) only radially overlap with components of that same stator phase 22 and do not radially overlap with electromagnetic components of another of the stator phases 22. For example, axial returns 28 of stator phase 22a only support the function of stator phase 22a and not, for example, stator phase 22b or stator phase 22c. The flux rings 24a, 24b of stator phase 22a only support the function of stator phase 22a and not, for example, stator phases 22b, 22c. Each of the stator phases 22a-22c may only contain one coil 26 and two annular flux rings 24 and, in some cases, only two annular laminate pieces forming the flux rings 24.

[0069] Each stator phase 22 includes first and second flux rings 24 (e.g., flux rings 24a, 24b of stator phase 22a) disposed on opposite lateral sides of a coil 26 of that stator phase 22. In some examples, each flux ring 24 is formed by multiple ring segments 56 fixed relative to each other and extending about the common axis CA. In some examples, the flux ring 24 can be formed by a single laminate structure that extends about the axis CA, such that the flux ring 24 does not include multiple ring segments 56. Ring segments 56 are each arcuate portions of laminate structure that together form the annular laminate structure of flux ring 24. Teeth 58 are formed on a radial side of each ring segment 56 facing rotor 12. For example, teeth 58 can project radially inward in examples in which electric machine 10 is an inner rotator and teeth 58 can project radially outward in examples in which electric machine 10 is an outer rotator.

[0070] An annular array of axial returns 28 extends between connects the opposing flux rings 24. The axial returns 28 are disposed on an opposite radial side of the flux rings 24 from rotor 12 and teeth 58. As shown, the axial returns 28 form the outermost electrically conducting portion of stator 14. In the example shown, axial returns 28 form the outermost laminate structure of the electric machine 10 as electric machine 10 is shown as an inner rotator. It is understood that in examples in which electric machine 10 is an outer rotator the axial returns 28 can form the innermost laminate structure of the electric machine 10. The axial returns 28 extend radially outward from the common axis CA further than the flux rings 24 or other laminate or metal superstructure. In the example shown, stator 14 does not include any laminate or metallic superstructure. Stator 14 does not include a support structure on the side of the axial returns 28 opposite rotor 12. In the example shown, stator 14 does not include a support structure on the outer radial side of axial returns 28. It is understood, however, that not all examples are so limited.

[0071] Axial returns 28 can be connected directly to stator housing 42, such as by potting compound, and interface with other laminate portions of stator 14 on only the inner radial side of the axial return 28 and, in some cases, interface with the other laminate portions on one or both circumferential sides of the axial return 28. Axial returns 28 are not disposed radially between laminate structures of stator 14 in this example. Axial returns 28 are not disposed radially between laminate structure that is itself directly connected to teeth 58 by laminate or other electrically conductive structure in this example. It is understood, however, that not all examples are so limited.

[0072] For each stator phase 22, coil 26 is disposed axially between the first and second flux rings 24 of the stator phase 22. Wire ends 68 extend from coil 26 at a location radially between the axial returns 28 and rotor 12 to a location radially outside of the axial returns 28 through wire gaps. Wire ends 68 are thereby exposed outside of electric machine 10 and provide locations for electrical connections to be formed with electric machine 10.

[0073] Rotor 12 is configured similar to stator 14, in the example shown, in that rotor 12 is formed from multiple rotor phases 50 configured to operate together. It is understood, however, that not all examples are so limited. For example, the rotor 12 can include a single magnet array 20 that extends the length of the rotor 12 such that each stator phase 22 interacts with the same magnet array 20 of the rotor 12.

[0074] Rotor body 18 supports permanent magnet array 20. As best seen in FIG. 4B, the rotor 12 includes three rotor phases 50a-50c. Each rotor phase 50 corresponds with a single stator phase 22 of stator 14. It is understood that electric machine 10 can include more or fewer than three rotor phases 50. For example, electric machine 10 can include a single rotor phase 50 that magnetically interacts with each of the multiple stator phases 22 of the stator 14. It is understood that in various other examples the electric machine 10 can include a single permanent magnet array 20 that radially overlaps with all of the stator phases 22 of the stator 14.

[0075] Permanent magnet array 20 is formed by interposed permanent magnets 60 and concentrators 62. Concentrators 62 can be formed by stacks of laminas. For example, concentrators 62 can be formed by lamina sheets that are stacked axially, among other options.

[0076] Rotor 12 is mounted on drive shaft 40. In the example shown, each rotor phase 50 includes a rotor hub 52 connected to the drive shaft 40 and forming a portion of the rotor body 18. In the example shown, each magnet phase 54 is disposed on the outer radial side of an associated rotor hub 52.

[0077] Each stator phase 22 includes two annular arrays of teeth 58 disposed on opposite axial sides of the coil 26 of that stator phase 22. It is understood that in some examples the teeth 58 do not extend to radially overlap with the coil 26 while in various other examples the teeth 58 can include portions that extend at least partially axially to radially overlap with the coil 26.

[0078] Each stator phase 22 includes a first flux ring 24 and a second flux ring 24. The first flux ring 24 (e.g., flux ring 24a of stator phase 22a; flux ring 24c of stator phase 22b; and flux ring 24e of stator phase 22c) and its associated components and aspects can be referred to as forming an A-side of the stator phase 22. The second flux ring 24 (e.g., flux ring 24b of stator phase 22a; flux ring 24d of stator phase 22b; and flux ring 24f of stator phase 22c) and its associated components and aspects can be referred to as forming a B-side of the stator phase 22. The first flux ring 24 has a first annular array of teeth 58 and the second flux ring 24 has a second annular array of teeth 58.

[0079] Within each stator phase 22, the first annular array of teeth 58 is disposed on a first axial side of coil 26 (e.g., spaced in first axial direction ADI from its coil 26) while the second annular array of teeth 58 is disposed on the second, opposite axial side of the coil 26 (e.g., spaced in second axial direction AD2 from its coil 26). Within each stator phase 22, the teeth 58 of the first annular array of teeth 58 are at least partially misaligned or offset (circumferentially and axially) relative to the teeth 58 of the second annular array of teeth 58 (e.g., teeth 58 of flux ring 24a are axially misaligned with teeth 58 of flux ring 24b). This misalignment of the A-side teeth 58 relative to the B-side teeth 58 facilitates flux coupling across the magnet array 20 from oppositely poled teeth 58 of the respective A- side and B-side annular arrays of teeth 58, as discussed in more detail below.

[0080] While the teeth 58 within each stator phase 22 are offset and misaligned (circumferentially and axially), the respective A-side teeth 58 of the multiple stator phases 22 can be axially aligned and the respective B-side teeth 58 of the multiple stator phases 22 can be axially aligned. It is understood, however, that not all examples are so limited. For example, the respective A-side teeth 58 of the multiple stator phases 22 can be axially misaligned relative to each other. For example, the respective A-side teeth 58 of the multiple stator phases 22 in a three phase electric machine 10 can be circumferentially offset and axially misaligned to facilitate driving signals 120-degrees electrically offset through each of the three stator phases 22.

[0081] The A / C signals routed through the coils 26 are 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 A / C signals (e.g., sinusoidal or trapezoidal) delivered through the coils 26 in each stator phase 22a-22c are out of phase with respect to each other. In this way, the permanent magnets 60 forming the permanent magnet array 20 more frequently have flux peaks acting on them, as compared to synchronizing the sinusoidal A / C signals, thereby providing a smoother torque profile acting on the rotor 12 along the axis of rotation of rotor 12.

[0082] The embodiment of the electric machine 10 discussed has three phases corresponding to the three stator phases 22a, 22b, 22c and respective coils 26 therein. As such, three sinusoidal A / C signals are delivered through the coils 26 120-degrees electrically offset. If there were two stator phases 22 and two coils 26, then the two sinusoidal A / C signals would be 180-degrees electrically offset, or 90-degrees electrically offset for sets of four stator phases 22 and four coils 26.

[0083] Stator phases 22a-22c can each be of the same configuration such that a common base stator phase 22 can be used to form any one of the multiple stator phases 22 of the electric machine 10. Two opposite polarized states are shown between FIGS 5A and 5B. As shown, the alternating flux path directions and polarizations are developed through the laminate of the ring segments 56 and axial returns 28. The alternating flux paths can be due to a sinusoidal signal delivered to each coil 26 to flux pair adjacent teeth 58 on opposite sides of the coil 26. These flux paths polarize the teeth 58a relative to teeth 58b to attract or repel the permanent magnets 60 of rotor 12 in synchrony with rotation of the rotor 12 so that flux paired ones of the teeth 58 attract a permanent magnet 60 as the permanent magnet 60 approaches and / or repel the permanent magnet 60 as the permanent magnet 60 passes.

[0084] Flux paired teeth 58 refer to respective closest pairs of teeth 58 of opposed circular tooth arrays of a stator phase 22 (e.g., the teeth 58 of flux ring 24a and teeth 58 of flux ring 24b are flux paired, the teeth 58 of flux rings 24c, 24d are flux paired, the teeth 58 of flux rings 24e, 24f are flux paired). While a subset of teeth 58a, 58b are highlighted as flux paired ones of teeth in FIGS. 5A and 5B, it is understood that these are examples and all teeth 58a, 58b of flux rings 24a, 24b similarly flux pair across the circular arrays of teeth 58a, 58b.

[0085] Each tooth 58a is part of a similar flux circuit with its corresponding flux pair tooth 58b. The flux paired teeth 58a, 58b pair generally axially with a tooth 58a, 58b of the opposing circular array of teeth 58a, 58b, and not circumferentially to the neighbor tooth 58a, 58b of the same circular array of teeth 58a, 58b because all teeth 58a of the circular array of teeth 58a will have the same polarity at any given time while all teeth 58b of the opposed circular arrays of teeth 58b of the same stator phase 22a will have the opposite polarity at any given time. More specifically, each tooth 58a of the circular array of teeth 58a flux pairs with the closest teeth 58b of the circular array of teeth 58b on the other axial side of the coil 26. As shown in FIGS. 5A and 5B, a flux circuit is formed through flux paired teeth 58a, 58b such that the teeth 58a, 58b are respectively polarized, north and south.

[0086] In various examples, each tooth 58 can narrow circumferentially as the tooth 58 extends radially away from the body of its flux ring 24. The lamina structure that the tooth 58 extends from, which can form the body of the flux ring 24 or of a ring segment 56, forms a lamina base 64 from which the teeth 58 extend. Multiple adjacent teeth 58 of an annular array of teeth 58 can extend from a common lamina base 64. In some examples, all teeth 58 of an annular array of teeth 58 can extend from a common lamina base 64 such as in examples in which the flux ring 24 does not include multiple ring segments 56. The teeth 58 can be wholly or partially formed by the laminas that form the common lamina base 64. As such, multiple adjacent ones of the teeth 58 can be formed from the same laminas and monolithic with each other.

[0087] In the example shown, teeth 58 extend to a tooth face 66 oriented towards rotor 12. In the example shown, the teeth 58 each narrow to the tooth face 66, though it is understood that not all examples are so limited. The tooth faces 66 can be planar and / or can be formed tangentially to a circle centered on common axis CA, among other options. The tooth faces 66 provide a narrowed surface area relative to the lamina base 64 and the axial returns 28. Teeth 58 narrow to concentrate flux towards rotor 12 to focus concentrated flux to a limited part of the rotor 12.

[0088] The magnetic flux is generated by coil 26. Specifically, 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. As shown, flux concentrating material of a stator phase 22 is wrapped around at least three sides of the coil 26. In the example shown, the flux rings 24a, 24b and axial returns 28 wrap around at least three sides of the coil 26. The lamination grain of the flux concentrating material is shown in FIGS. 5A-5C. The lamination grain of the concentrators 160 and axial returns 48 can further be seen in FIG. 5C. While the concentrators are shown as including circumferentially stacked lamina sheets that extend axially, it is understood that not all examples are so limited. For example, the lamina sheets forming a concentrator 62 can be stacked axially.

[0089] Generally, flux flows with the grain, along the direction of lamination, as flux will generally follow the path of highest permeability and there is significant resistance to flux jumping from one layer of lamination to another layer of lamination. The lamination grain of the ring segments 56, including the teeth 58a, 58b, is radially orientated while the lamination grain of the axial returns 28 is axially oriented. As such, the flux flows axially through the axial returns 28 and radially through the ring segments 56 and teeth 58a, 58b in a U shape toward the rotor 12, with the base of the U on an opposite side of the coil 26 from the rotor 12 and the legs of the U oriented towards the rotor 12. FIGS. 5A and 5B represent the reversal of the A / C signal and how the poles of the flux paired teeth 58a, 58b are switched.

[0090] The flux paired ones of teeth 58a, 58b are circumferentially offset from each other such that the teeth 58a of one flux ring 24 are not axially aligned with teeth 58b of the other flux ring 24 of the same stator phase 22. Being that the ends of the flux paired teeth 58a, 58b of the same stator phase 22 are not aligned axially, because teeth 58a are offset circumferentially from teeth 58b, the flux circuit travels at least a limited distance circumferentially between the flux paired ones of teeth 58a, 58b. Therefore, a cumulative flux circuit comprised of a plurality of flux paired teeth 58a, 58b can flow in a spiral pattern circumferentially through the teeth 58a, 58b and axial returns 28. It is noted that, while most flux flows between flux paired ones of teeth 58a, 58b, the ring segments 56 permit flux flow between teeth 58a, 58b of the same ring segment 56, such that a limited amount of flux may skip a set of flux paired teeth 58a, 58b to the next-over tooth 58a, 58b of the same ring segment 56. As discussed above, adjacent ring segments 56 of the same flux ring 24 can be separated by one or more circumferential gaps that is bridged only by potting compound. The adjacent ring segments 56 are isolated to prevent flux flow between the adjacent ring segments 56, thereby inhibiting the formation of eddy currents and facilitating efficient operation of electric machine 10.

[0091] FIG. 5C shows a detailed view of flux paired teeth 58a, 58b of the stator 14 interacting with concentrators 62 and permanent magnets 60 of the magnet array 20. The A / C signal through the coil 26 changes the direction of the electric current rapidly and thus changes the north-south polarity of the flux paired teeth 58a, 58b rapidly. The view of FIG. 5C shows an instance in which all teeth 58a of the circular array of teeth 58a have a north polarization while all teeth 58b of the circular array of teeth 58b have a south polarization.

[0092] Also at this instance, the teeth 58a, 58b are aligned with the concentrators 62 that are disposed circumferentially between the permanent magnets 60. The laminate of the concentrators 62 does not have an inherent polarization, but due to the fixed position of concentrators 62 between magnet poles, the concentrators 62 assume an effective permanent polarization as indicated. Each concentrator 62 contacts two permanent magnets 60. Each concentrator 62 contacts the same pole of the two permanent magnets 60. For example, a concentrator 62 will be in contact with two south poles or in contact with two north poles. The concentrators 62 take on alternating north and south polarization on opposite sides of each permanent magnet 60 depending on the polarization adjacent that concentrator 62. As indicated, each permanent magnet 60 is permanently polarized north and south on opposite sides of its short axis. The interleaved arrangement of permanent magnets 60 and concentrators 62 creates circumferential regions of oppositely polarized concentrators 62 and permanent magnet 60 poles.

[0093] The concentrators 62 route the magnetic flux from the permanent magnets 60 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 60) and the flux from the coil 26 (through the teeth 58a, 58b) interact in the air gap 30, and the resulting flux shear forces rotation of the rotor f2. The flux of the present electric machine 10 has an orientation transverse to the axis of rotation (which axis of rotation is coaxial with common axis CA). This is different from the radial flux orientation of traditional A / C and D / C brushless motors.

[0094] 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 60 and concentrators 62 due to rotation of the rotor 12 as well as the change in polarization of the teeth 58a, 58b 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 58a, 58b in time to the concentrators 62 approaching and departing the teeth 58a, 58b to simultaneously push and pull the permanent magnets 60 of the rotor 12 to provide the force that rotates the rotor 12. More specifically, the N-N and S-S interfaces repel while N- S interfaces attract, on approach and departure of alignment.

[0095] 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, which is also the common axis CA.

[0096] Traditional A / C induction motors use a plurality of discrete coils that form an array of coils that 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. Electric machines 10 according to the present disclosure are different from traditional A / C and D / C machines. An aspect of the electric machine 10 is that it contains relatively few coils 26, only three in the illustrated embodiment. Unlike traditional A / C and D / C motors, the coils 26 are formed from loops of wire that extend entirely around the axis of rotation of the rotor 12 (and the common axis CA). The axis of rotation of the rotor 12 (and the common axis CA) extends through each loop (e.g., the center of each loop). Each coil 26 is annular, and the loops of each coil 26 are likewise annular, and the circular planar profile of the coil 26 and loops are orthogonal to the common axis CA. The wire of each coil 26 forms a single hoop, which has multiple loops that overlap and contact one another to form the single hoop assembly. The coils 26 do not include loops that generate flux that rotates the rotor 12 through which the common axis CA 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 surrounding a single coil 26 channel the flux to a plurality of teeth 58 that flux pair across the flux rings 24 of a stator phase 22 to create a plurality of poles from the single coil 26.

[0097] In the example shown, for each stator phase 22, one coil 26 supports multiple poles equal to the number of teeth 58 of a single flux ring 24. For example, if each flux ring 24 includes twenty-four teeth 58, 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 58. 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.

[0098] 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.

[0099] Cogging is a problem in electric motors whereby the rotor tends to stick in certain low-energy pole alignments, rotationally between higher energy orientations, creating resistance or reluctance to movement out of the low energy orientations at those specific points. This can result in a jerky motion and increased torque ripple in the motor. A single revolution of the rotor can include many clogging points, depending on the number of poles of the rotor. Various design aspects can be implemented to minimize clogging. For example, the use of three phases, each at a different orientation, distributes the clogging orientations such that one phase may be in a cogging orientation while one or both the other two phases are not in a cogging orientation for a given point of rotation of the rotor. Further rotation of the rotor causes the one phase that was cogging to no longer be in a cogging orientation while one of the other phases that was previously not in the cogging orientation enters a cogging orientation. This spreads out and dampens cogging, resulting in a smoother spin of the rotor, but does not eliminate cogging.

[0100] U.S Patent No. 8,760,023, assigned to Electric Torque Machines, Inc., the disclosure of which is incorporated by reference herein in its entirety, describes design aspects to further reduce cogging by shifting the center positions of teeth. Generally, such shifting of the center positions of teeth is sequential and / or graduated. One or more of any aspect of tooth layout (e.g., tooth positioning, spacing, shifting, relative relationships between adjacent teeth and / or groups of teeth) and motor design referenced and / or shown in U.S Patent No. 8,760,023 can be implemented in any embodiments within the scope of this disclosure.

[0101] FIG. 6 is an end view of a portion of a stator phase 22. FIG. 7 is an end view of a portion of a stator phase 22. FIG. 8 is an end view of a portion of a stator phase 22. FIG. 9 is an enlarged end view showing a portion of a stator phase 22. FIGS. 6-9 illustrate various aspects that can be implemented together or individually that help to address torque ripple, noise, vibration, radial forces, and / or cogging of the electric machine 10. The aspects discussed with regard to FIGS. 6-9 provide for more efficient operation of the electric machine 10 and for quieter operation with less wear on components of the electric machine 10.

[0102] Tooth array 70a is shown in FIG. 6, tooth array 70b is shown in FIG. 7, tooth array 70c is shown in FIG. 8, and tooth array 70d is shown in FIG. 9. Tooth arrays 70a-70d are collectively referred to herein as “tooth array 70” or “tooth arrays 70.” It is understood that the aspects discussed with regard to any one or more of the tooth arrays 70a-70d can be applied independent of or together with the aspects discussed with regard to the other tooth arrays 70a-70d. For example, a single tooth array 70 can include both the variable offsets / variable spacing as discussed with regard to FIGS. 6 and 7 and the variable tooth width discussed with regard to FIG. 8.

[0103] FIGS. 6-9 show examples of tooth arrays 70 that reduce cogging, reduce torque ripple, and counteract radial forces. The tooth arrays 70 can reduce noise generated by electric machine 10 by counteracting vibration generated during operation. The tooth arrays 70 can counteract vibration to provide for a smoother and quieter output with less wear on components of the electric machine 10. Each tooth array 70 is formed by a plurality of teeth 58. The tooth array 70 includes multiple, up to all, of the teeth 58 in a flux ring 24 of a stator phase 22. The tooth array 70 can include multiple, up to all, of the teeth 58 of a half phase. In the examples shown in FIGS. 6-8, the tooth array 70 includes teeth 58 of a common ring segment 56. It is understood, however, that not all examples are so limited. The tooth array 70 can be distributed on a common ring segment 56. The tooth array 70 can include all of the teeth 58 of a ring segment 56 or less than all of the teeth 58 of the ring segment 56. In some examples, a single flux ring 24 can include multiple tooth arrays 70 distributed annularly about the axis of rotation of the rotor 12. The single flux ring 24 can include a series of repeating tooth arrays 70, such as in examples in which the flux ring 24 is formed by multiple commonly configured ring segments 56. Such a flux ring 24 can include multiple ring segments 56 that each have a commonly configured tooth array 70.

[0104] The tooth array 70 includes a non-uniform arrangement of teeth 58 that minimizes concentrated radial tugging on the stator phase 22. The tooth array 70 is configured to minimize radial tugging by a non-uniform distribution of the tooth faces 66 of the teeth 58, which non-uniform distribution counteracts concentrated radial forces on the stator phase 22. In the examples shown, the tooth arrays 70a-70d include multiple adjacent teeth 58 that form an unbalanced tooth set. The teeth 58 in the unbalanced tooth set vary from each other. For example, the teeth 58 of the unbalanced set can differ in that the teeth 58 have different tooth widths relative to each other, in that the teeth 58 have different annular offsets from nominal evenly annularly arrayed positions, and / or in that the teeth 58 have different annular distances between different pairs of teeth within the set of multiple adjacent teeth (e.g., annular distances between circumferential centers of the teeth 58), among other options. The teeth 58 within an unbalanced tooth set can be considered to be structurally disparate relative to each other. The structural disparity between the teeth 58 provides for a non-uniform distribution of the teeth 58 in an unbalanced tooth set. The structural disparity can be caused by different widths between the teeth 58, different annular offset for the teeth 58, different annular spacings between pairs of the teeth 58, a combination of one or more of differing widths, offset, and / or spacings, among other options. It is understood that a single tooth array 70 can include one or more set of multiple adjacent teeth 58 that exhibit one or more of the aspects of unbalanced teeth discussed herein. FIG. 6 is an end view of a portion of a stator phase 22. Tooth array 70a is shown. In the example shown in FIG. 6, a ring segment 56 of a flux ring 24 of a stator phase 22 is shown. The tooth array 70a is formed across the ring segment 56. The stator phase 22 could be any phase of the stator 14. The other ring segments 56 of the same flux ring 24 can be the same as the flux ring 24 shown in FIG. 6, and the other ring segments 56 of the opposed flux ring 24 of the same stator phase 22 can be the same as the ring segment 56 of FIG. 6. Likewise, other stator phases 22 can utilize the ring segment 56 of FIG. 6. Alternatively, whole flux rings 24 may be used (defining or at least supporting all teeth 58 of the half phase) instead of discrete ring segments 56. It is further understood that while each ring segment 56 of a flux ring 24 can be configured the same, the configurations of the ring segments 56 can vary within a flux ring 24 and / or within a stator phase 22 and / or between stator phases 22 within a stator 14.

[0105] Teeth 58R-58Z of a single tooth array 70a are discussed in more detail. Each tooth 58R-58Z includes a circumferential center 72. The radial lines RL shown in FIG. 6 extend through the circumferential center 72 of each of the teeth 58R-58Z. Such a center 72 can be the center point between the comers (e.g., the center 72 being equidistant from the comers that are on the circumferential edges of the tooth 58, the corners can be at the edges, which can extend parallel with the axis) that define the tooth face 66, which tooth face 66 is the surface of the tooth 58 that faces the rotor 12. Unless otherwise stated herein, the position, spacing, or shifting of a tooth 58 refers to the center 72 of the tooth 58, and does not directly refer to the edges of the tooth 58. For example, the spacing of adjacent teeth 58R, 58S refers to the spacing between the centers 72 of the teeth 58R, 58S, and not the spacing between the edges of the teeth 58R, 58S, which spacing between edges of the teeth 58 depends on the width of the teeth.

[0106] In a non-shifted tooth configuration (not shown), the teeth 58 can be annularly spaced evenly, such that all teeth 58 have the same spacing between adjacent teeth 58. Such even annular spacing can be evenly arraying teeth 58 around a circumference (whether an inner circumference or an outer circumference). Such an annular array can be composed of multiple ring segments 56 or a single ring. Such even spacing can result in undesirable cogging, torque ripple, and radial forces.

[0107] In the example shown, the teeth 58 are individually shifted by small amounts relative to the positions that the teeth 58 would be in had the teeth 58 been evenly annularly arrayed (e.g., over just the ring segment 56). The teeth 58 that are shifted are shifted relative to evenly annularly arrayed nominal positions of those teeth 58. In the example shown, the teeth 58 are arrayed such that two subsets of the teeth 58 are individual shifted by small amounts relative to the nominal positions. The first subset of the teeth 58 includes teeth 58R-58U and the second subset of the teeth 58 includes teeth 58W-58Z. In the example shown, the first subset of teeth 58R-58U are shifted in circumferential direction CD1 about the rotational axis and the second subset of teeth 58W-58Z are shifted in circumferential direction CD2 about the rotational axis. The first and second subsets of the teeth 58 are shifted in opposite circumferential directions in this example. The shifted teeth of a single ring segment 56 are shifted in at least two subsets that are oppositely shifted from each other. In the example shown, the ring segment 56 includes multiple tooth subsets that are shifted circumferentially towards each other.

[0108] Such shifting reduces cogging by further spreading out the poles and thus potential cogging positions to avoid the additive effects of too many poles cogging at one rotational orientation. Specifically, annular offsets 74R-58Z are indicated relative to nominal positions of an even array of the teeth 58. The values of 0, 1, 2, 3, and 4 are indicated, which can be radial degrees or distances, amongst other options. The indicated values are associated with the annular offsets 74R-58Z and represent a magnitude of the annular offset. In the example shown, the annular offset 74R for tooth 58R is indicated as “4” such that the annular offset 74R has a greater magnitude than the annular offset 74S, which has a greater magnitude than the annular offset 74T, which has a greater magnitude than the annular offset 74U. It is understood that while the annular offsets 74R-58Z are shown with a value, the adjacent offsets may not be proportional across the tooth array 70.

[0109] Generally, the sets of outer teeth 58R-58U and 58W-58Z are shifted towards the center tooth 58V. In this particular example, center tooth 58V is not shifted. It is understood that while the tooth array 70a includes a center tooth 58V, not all examples are so limited. For example, the tooth array 70a can include an even number of teeth 58 such that the tooth array 70a does not include a center tooth 58 V. In such an example, each set of outer teeth 58 can be shifted circumferentially towards the center of the tooth array 70a regardless of whether such center includes a center tooth 58V.

[0110] The teeth 58 which are further away from the center tooth 58V are shifted by greater amounts, such that the amount of shifting is progressive and / or graduated (proceeding from 0 to 4, in increments of 1 in this example). Arrows are shown to indicate the direction of each annular offset 74, in a circumferential direction CD1, CD2. The annular offsets 74 can also be considered to extend one of clockwise or counterclockwise. In the example shown, adjacent annular offsets 74 (e.g., annular offsets 74R and 74S are adjacent, annular offsets 74S and 74T are adjacent, while annular offsets 74R and 74T are not adjacent) are in the same direction clockwise or counterclockwise. For example, teeth 58R-58U are shifted clockwise while teeth 58W-58Z are shifted counterclockwise in the view shown. It is understood, however, that not all examples are so limited. A tooth array 70a that does not include a center tooth 58V can include a set of circumferentially adjacent teeth 58 that are shifted in opposite circumferential directions. For example, if center tooth 58V was not present, then the closest teeth of the oppositely shifted sets of outer teeth 58 (teeth 58U and 58W in this example) would be adjacent but shifted in opposite annular directions. In the example shown, all teeth 58 within an outer subset of the teeth 58 (e.g., set of teeth 58R- 58U or teeth 58W-58Z) are shifted in the same circumferential direction.

[0111] While such shifting reduces cogging, noise can be generated by the motor during rotation. For example, shifting the teeth 58R-58U and 58W-58Z towards a center (in this case tooth 58V) can result in annular concentrations of poles (e.g., one concentration point for each ring segment 56). For example, if a flux ring 24 can be thought of as a clock face, then groups of teeth 58 can be shifted teeth 58 to be concentrated at the twelve o’clock, three o’clock, six o’clock, and nine o’clock positions, thus generating uneven forces at these positions. Such concentration of poles can result in uneven forces during operation of the electric machine 10. For example, the net forces around the axis can be in an oblong shape orientated vertically (e.g., the twelve and six o’clock orientation), with such an oblong shape shifting to a horizontal orientation (e.g., the three and nine o’clock orientation) as the phase of the A / C driving signal changes. This can cause cyclic simultaneous compression and elongation of the flux ring 24 in different orientations which can result in unwanted vibration and noise. However, various aspects of the present disclosure demonstrate how shifting the teeth 58 in a less uniform and / or grouped manner can reduce or eliminate such concentration of poles and can reduce or eliminate associated vibration and noise. Such aspects are demonstrated in FIG. 7, which is a different tooth shifting configuration as that demonstrated in FIG. 6.

[0112] Tooth array 70b is shown in FIG. 7. Tooth array 70b is distributed across a single ring segment 56 in the example shown. In tooth array 70b, the annular positions of the teeth 58Q-58Z are shifted by small amounts relative to the nominal positions that the teeth 58Q-58Z would be in had the teeth 58Q-58Z been evenly annularly arrayed (e.g., about an entire circumference or over just the ring segment 56). However, while the teeth 58 of tooth array 70a shown in FIG. 6 are shifted in groups, such as shifted toward middle tooth 58V resulting in pole concentration in graduated amounts, the directions and incremental sequence of shifting of teeth 58 in tooth array 70b is mixed and interspaced to reduce or eliminate such concentration of poles and / or further reduce additive cogging. The non- uniform distribution of the teeth 58 in tooth array 70 can counteract concentrated radial forces, which can combat vibration and noise generation.

[0113] In the example shown, adjacent teeth 58 (e.g., teeth 58Q, 58R or teeth 58W, 58X) are shifted in different directions clockwise and counterclockwise. In the example shown, each pair of adjacent teeth 58 in the tooth array 70b includes teeth 58 that are shifted in opposite circumferential directions relative to each other. As such, a set of multiple adjacent ones of the teeth 58 can include teeth 58 shifted in alternating directions in order of the teeth 58. For example, the set of multiple adjacent teeth 58 including teeth 58Q-58S has a first tooth 58S shifted in circumferential direction CD1, an adjacent second tooth 58R shifted in the opposite circumferential direction CD2, and a third tooth 58S adjacent to the second tooth 58R that is shifted in circumferential direction CD1.

[0114] A set of multiple adjacent teeth 58 including at least three teeth 58 (e.g., teeth 58Q- 58S) includes a pair of teeth 58 (e.g., teeth 58Q, 58S) shifted in a common circumferential direction and then another tooth 58 (e.g., tooth 58R) that is bracketed by the commonly shifted teeth 58 is shifted in the opposite circumferential direction. The shifting within the set of multiple adjacent teeth 58 includes a first pair of teeth 58 that shift circumferentially towards each other to reduce a spacing between the teeth 58 by an amount greater than either individual tooth shift and includes a second pair of teeth 58 that shift circumferentially away from each other to increase a spacing between the teeth 58 by an amount greater than either individual tooth shift. A common tooth 58 (tooth 58R) is disposed in both of the first and second pairs of the teeth 58 within the set of multiple adjacent teeth 58. In the example shown, teeth 58Q, 58R shift in opposite directions and towards each other while teeth 58R, 58S shift in opposite directions and away from each other. Such opposite and paired shifting can distribute the poles in a non-uniform manner that can counteract radial forces generated during operation, can combat cogging, and can combat torque ripple.

[0115] Independent from the interspaced directions of tooth shifting, the amounts of shifting are not progressive or graduated along sets of adjacent teeth 58 (e.g., a set of adjacent teeth 58Q-58T are shifted in values of 5, 1, 4, 3; and not in ordered values of 1, 2, 3, 4 as in the embodiment of FIG. 6). The overall amount and directions of shifting can be the same as the design aspects of FIG. 6 (e.g., there are tooth shifts of values 1, 2, 3, 4, 5 in each circumferential direction CD1, CD2), but interspacing in the manner of FIG. 7 reduces shifting the poles into concentrated areas and thus reduces force asymmetry around the flux ring 24 and associated vibration and noise.

[0116] It is noted that the tooth array 70b shown in FIG. 7 includes one more tooth 58 than the tooth array 70a shown in FIG. 6, which is independent of the inventive aspects demonstrated in FIG. 7, and the aspects can be implemented in ring segments 56 having even or odd numbers of teeth 58.

[0117] Tooth array 70b includes a first plurality of teeth (e.g., teeth 58Q-58Z) that form at least part of a first annular array of teeth of at least one annular array of teeth of a stator phase 22. The at least one annular array of teeth can be the entire annular array of teeth of a flux ring 24. The first plurality of teeth 58Q-58Z are respectively annularly offset by a first plurality of annular offsets 74Q-74Z from a first plurality of evenly annularly arrayed nominal positions. The respective values and counter / clockwise directions of the annular offsets 74Q-74Z are indicated with a value representing relative magnitude and an arrow indicating the direction of the annular offset 74.

[0118] The values of 1 , 2, 3, 4, and 5 are indicated, which can be radial degrees or distances, amongst other options. The indicated values are associated with the annular offsets 74Q- 74Z and represent a magnitude of the annular offset. It is understood that while the annular offsets 74R-74Z are shown with proportional values, the adjacent offsets may not be proportional across the tooth array 70.

[0119] In the example shown, the teeth 58 of tooth array 70b are disposed in an unbalanced tooth set in that the teeth 58 have different annular distances 76 between pairs of the teeth 58. The first plurality of teeth 58Q-58Z are annularly spaced such that at least three different annular distances 76 are between three different adjacent pairs of teeth 58 of the first plurality of teeth 58. For example, due to shifting, a first annular distance 76 (e.g., in degrees or circumferential distance, measured from the tooth center 72) can be between teeth 58Q and 58R, a second annular distance 76 can be between teeth 58R and 58S, and a third annular distance 76 can be between teeth 58S and 58T. The first, second, and third annular distances 76 can each vary from each other. In the example shown, the three pairs of teeth 58 are configured such that two of the pairs of teeth 58 (e.g., first pair of teeth 58Q, 58R and third pair of teeth 58S, 58T) are shifted oppositely to the other pair of teeth 58 (e.g., second pair of teeth 58R, 58S). The first and third pairs of teeth 58 are shifted to decrease the annular distances between the teeth 58 while the second pair of teeth 58 is shifted to increase the annular distance between the teeth 58 of that second pair. In the example shown, each pair of teeth 58 of the three adjacent pairs of teeth 58 shares at least one tooth 58 with another of the set of adjacent pairs of teeth 58. In the example shown, each tooth 58 within one of the pairs of teeth 58 is shifted in the opposite circumferential direction relative to the other tooth 58 within that pair of teeth 58.

[0120] In the example shown, a fourth annular distance 76 is formed between teeth 58T and 58U. Each of the first, second, third, and fourth distances can be different from each other. In some examples, some of the annular distances 76 can be the same as others of the annular distances 76. For example, the second annular distance 76 can be the same as the fourth annular distance 76, though as noted above not all examples are so limited.

[0121] In some examples, the teeth 58 of the tooth array 70b are non-uniformly distributed in offset pairs. An offset pair includes a set of adjacent teeth 58. The adjacent teeth 58 within the offset pair are circumferentially adjacent to each other and are circumferentially offset from a nominal position in opposite directions relative to each other (e.g., teeth 58Q, 58R form an offset pair, teeth 58R, 58S form an offset pair, etc.). In the example shown, the offset pairs of teeth 58 are distributed in an alternating manner circumferentially across the tooth array 70b. The offset pairs alternate in that an offset pair including teeth 58 shifted closer together is adjacent to one or more offset pairs including teeth 58 shifted further apart. While the offset pairs that are uniform in annular distance 76 (e.g., between teeth 58R, 58S and teeth 58T, 58U) are shown as including teeth 58 shifted further apart and the offset pairs that have variable annular distances 76 are shown as including teeth 58 shifted closer together, it is understood that not all examples are so limited. For example, the offset pairs including teeth 58 shifted further apart can include variable spacing while the offset pairs including teeth 58 shifted closer together can include uniform spacing. In some examples, all offset pairs of a tooth array 70b can have a different annular distance 76 from any other offset pair in the tooth array 70.

[0122] In some examples, the magnitudes of the tooth shifts are variable across a set of the offset pairs and uniform within another set of the offset pairs. For example, a first set of the offset pairs can have variable spacing between various ones of the offset pairs and a second set of the offset pairs can have uniform spacing between the offset pairs of the second set. In the example shown, the first set includes offset pairs formed by teeth 58Q, 58R; teeth 58S, 58T; teeth 58U, 58V; teeth 58W, 58X; and teeth 58Y, 58Z. In the example shown, the second set includes offset pairs formed by teeth 58R, 58S; teeth 58T, 58U; teeth 58V, 58W; and teeth 58X, 58Y. The annular spacing between the teeth 58 of the offset pairs in the first set are variable in distance relative to each other while the annular spacing between the teeth 58 of the offset pairs in the first set are uniform. In the example shown, a subset of the first set of offset pairs includes a first offset between teeth 58Q, 58R that is less than a second offset between teeth 58S, 58T that is greater than a third offset between teeth 58U, 58V. The first offset is greater than the third offset. The teeth 58 of the second offset pair of teeth 58S, 58T are disposed circumferentially between the offset pairs 58Q, 58R and 58U, 58V. The circumferentially intermediate offset pair has a larger offset than the other two offset pairs that bracket that intermediate offset pair within the subset of the first set of offset pairs. In such an example, the adjacent offset pairs do not include common teeth between the adjacent pairs.

[0123] As an additional or alternative aspect, the first plurality of annular offsets 74 are not equal to each other and are not in a progressive order annularly about the axis (e.g., the first plurality of annular offsets 74Q-74T are 5, 1, 4, 3, 2, not 1, 2, 3, 4,5 or 5, 4, 3, 2, 1). In another sense, the first plurality of annular offsets 74 are not equal to each other and are not in a graduated order annularly about the axis (e.g., the first plurality of annular offsets 74Q-74T are 5, 1, 4, 3, 2, not 1, 2, 3, 4, 5 or 5, 4, 3, 2, 1). In the example shown, at least some of the annular offsets 74 include the same magnitude as others of the annular offsets 74. However, the teeth 58 that have the same magnitude annular offset 74 are offset in opposite circumferential directions from each other. As such, the tooth array 70b shown does not include any teeth 58 that are offset in the same direction and magnitude as any other tooth 58 in the tooth array 70b, though it is understood that not all examples are so limited.

[0124] In the example shown, tooth array 70b includes at least one annular offset 74 in each circumferential direction CD1, CD2 having the same magnitude. For example, the annular offset 74Q has the same magnitude as the annular offset 74Z, but the annular offsets 74Q, 74Z are in opposite circumferential directions. The tooth array 70b can, in various examples, include only one annular offset 74 having any given magnitude in one circumferential direction. In the example shown, multiple teeth 58 can have the same magnitude of the annular offset 74 with such offsets 74 being in opposite circumferential directions.

[0125] The sizes (e.g., magnitudes) of a first plurality of annular offsets 74 can be interspersed so that relatively smaller annular offsets 74 are interspaced with relatively larger annular offsets 74. In the example shown, the first plurality of annular offsets 74Q- 74T are 5, 1, 4, 3, 2, with the largest annular offset 74Q being next to the smallest annular offset 74R. In the example shown, a first tooth (e.g., tooth 58Q) is adjacent to a second tooth (e.g., tooth 58R), the second tooth 58R is adjacent to a third tooth (e.g., tooth 58S), and the third tooth 58S is adjacent to a fourth tooth (e.g., tooth 58T). The first tooth 58Q is shifted by a first annular offset 74Q from its nominal position, the second tooth 58R is shifted by a second annular offset 74R from its nominal position, the third tooth 58S is shifted by a third annular offset 74S from its nominal position, and the fourth tooth 58T is shifted by a fourth annular offset 74T from its nominal position. The first annular offset 74Q is greater than the second annular offset 74R, the third annular offset 74S is greater than the second annular offset 74R, and the fourth annular offset 74T is less than the third annular offset 74S. As such, the magnitudes of the annular offsets 74 can oscillate between adjacent teeth 58, with relatively smaller annular offsets 74 being directly annularly between relatively larger annular offsets 74.

[0126] In the example shown, the fourth tooth 58T is also adjacent to a fifth tooth (e.g., tooth 58U). The fifth tooth 58U is shifted by a fifth annular offset 74U from its nominal position, and the fifth annular offset 74U is less than the fourth annular offset 74T.

[0127] As an additional or alternative aspect, each annular offset 74 of the first plurality of annular offsets 74Q-74Z is offset in either a clockwise direction or a counterclockwise direction from its nominal position (e.g., tooth 58Q is offset clockwise while tooth 58R is offset counterclockwise) such that the first plurality of annular offsets 74 includes teeth 58 offset in the clockwise direction and teeth 58 offset in the counterclockwise direction.

[0128] As shown in FIG. 7, the teeth 58 offset in the clockwise direction CD1 are interspaced with the teeth 58 offset in the counterclockwise direction CD2. More specifically, a tooth 58 shifted in the clockwise direction (e.g., tooth 58S) is directly annularly surrounded by two teeth (e.g., teeth 58R and 58T) shifted in the counterclockwise direction, and another tooth shifted in the counterclockwise direction (e.g., tooth 58X) is directly annularly surrounded by two teeth shifted in the clockwise direction (e.g., teeth 58W and 58Y).

[0129] In the example shown, a first annular offset (e.g., annular offset 74Q) of the first plurality of annular offsets 74 is adjacent to a second annular offset (e.g., annular offset 74R) of the first plurality of annular offsets 74, a third annular offset (e.g., annular offset 74S) of the first plurality of annular offsets 74 is adjacent to second annular offset 74R, the first annular offset 74Q is in the clockwise direction, the second annular offset 74R is in the counterclockwise direction, and the third annular offset 74S is in the clockwise direction. In some examples, a fourth annular offset (e.g., annular offset 74T) of the first plurality of annular offsets is adjacent to the third annular offset of the first plurality of annular offsets, and the fourth annular offset is in the counterclockwise direction. The annular offsets 74 can thus alternate in circumferential direction between adjacent annular offsets 74. In the example shown, a tooth 58 having an annular offset 74 in one circumferential direction is disposed directly circumferentially between teeth 58 having annular offsets 74 in the opposite circumferential direction, though it is understood that not all examples are so limited.

[0130] The ring segment 56 having tooth array 70b (or a different ring segment having a different layout but including one or more of the same aspects referenced and / or shown herein) can be similar to a plurality of ring segments that form a flux ring 24. Moreover, a flux ring 24 can be formed using the aspects referenced and / or shown herein while being a continuous (not segmented) ring (e.g., a single stack of laminations form the whole ring and / or all teeth 58 of the half phase). A stator phase 22 can be formed by two such flux rings 24, each of the flux rings 24 implementing the aspects discussed herein. Multiple stator phases 22 of an electrical rotational machine 10 (e.g., a motor and / or generator) can likewise be formed from flux rings 24 all of which implement one or more of the aspects of unbalanced teeth as referenced and / or shown herein. Multiple stator phases 22 of an electrical rotational machine 10 (e.g., a motor and / or generator) can likewise be formed from flux rings 24 all of which implement one or more of the aspects of tooth shifting and / or spacing as referenced and / or shown herein.

[0131] FIG. 8 is an end view showing a portion of a stator phase 22. Tooth array 70c is shown in FIG. 8. The tooth array 70c shows additional or alternative tooth shifting aspects. The tooth array 70c includes a non-uniform distribution of the teeth 58 at least partially about the axis of rotation of the rotor 12. The tooth array 70c includes at least one set of structurally disparate teeth 58. The tooth array 70c includes at least one unbalanced tooth set.

[0132] Each tooth 58Q-58Z of the tooth array 70c has a tooth width TW. The tooth width TW can measure the width of the tooth 58 along the tooth face 66 of the tooth 58 that is oriented towards rotor 12. Tooth width values are listed (which are relative and are dimensionless, but could be millimeters amongst other options). In the example shown, teeth 58Q-58Z of tooth array 70c are of various tooth widths TW. For example, tooth 58Q has a tooth width TW of 7.5, tooth 58R has a tooth width TW of 7.2, tooth 58S has a tooth width TW of 9.5, etc. The circumferential extent along which the width TW of the tooth 58Q is taken is indicated in FIG. 8, and it is understood that the tooth widths TW of the rest of the teeth 58 can be measured in the same way (although the spans of the tooth widths TW are not indicated for the other teeth 58R-58Z for simplicity and readability of the figures).

[0133] In the example shown, the tooth array 70c includes at least one unbalanced tooth set that includes three teeth (e.g., teeth 58Q-58S) having different tooth widths TW. Sets of four teeth (e.g., teeth 58T-58W) can have different tooth widths TW. In some examples, all teeth 58 of a tooth array 70c can have different tooth widths TW. In some examples, the tooth array 70c includes all the teeth 58 of a ring segment 56. In such an example, all of the teeth 58Q-58Z of the ring segment 56 have different tooth widths TW. Differing the tooth widths TW between teeth 58 in a tooth array 70c can minimize cogging by changing the alignment of teeth 58 with magnets 60 of the rotor 12. A variety of different tooth widths TW shifts the cogging locations and thus spreads out the additive tooth-magnet cogging points within a phase and further between phases to foster an overall smoother rotation due to less additive cogging. The variable tooth widths TW in tooth array 70c can further counteract radial forces by spreading such radial forces and can counteract vibration and noise.

[0134] As an example, a first plurality of teeth 58Q-58Z have a first plurality of teeth widths TW, respectively. The values (e.g., magnitudes) of the teeth widths, which are dimensionless in this example, are indicated, ranging from 6.0-9.5. The first plurality of teeth 58 and the first plurality of teeth widths TW comprise a set of at least three adjacent teeth (e.g., teeth 58X-58Z) having tooth widths TW that are all different widths relative to each other. The first plurality of teeth 58 and the first plurality of teeth widths TW can include a set of at least four adjacent teeth (e.g., teeth 58U-58X) having tooth widths that are all different widths relative to each other.

[0135] Additionally or alternatively, the tooth array 70c can include a set of at least three teeth 58 (e.g., teeth 58X-58Z) that are circumferentially adjacent and each of different tooth widths TW. The set of teeth 58X-58Z are in progressive order of magnitude for the respective tooth width TW of each of the teeth 58 in the example shown. The tooth width TW of tooth 58X is greater than the tooth width TW of tooth 58Y which is greater than the tooth width TW of tooth 58Z. The progressive tooth widths TW of the set of at least three circumferentially adjacent teeth 58 can descend in order of magnitude of the tooth widths TW circumferentially outward from the center of a tooth array 70 including more than the set of three teeth 58. The progressive tooth widths of the set of three circumferentially adjacent teeth 58 can ascend in order of magnitude of the tooth widths TW circumferentially inward towards the center of the tooth array 70 including more than the set of three teeth 58.

[0136] The tooth array 70c can include an additional or alternative set of at least three teeth 58 (e.g., teeth 58V-58X) that are circumferentially adjacent and each of different tooth widths TW. The set of teeth 58V-58X are in progressive order of magnitude for the respective tooth width TW of each of the teeth 58. The tooth width TW of tooth 58X is greater than the tooth width TW of tooth 58W which is greater than the tooth width TW of tooth 58V. The progressive tooth widths TW of the set of three circumferentially adjacent teeth 58 can ascend in order of magnitude of the tooth widths TW circumferentially outward from the center of a tooth array 70 including more than the set of three teeth 58. The progressive tooth widths TW of the set of three circumferentially adjacent teeth 58 can descend in order of magnitude of the tooth widths TW circumferentially inward towards the center of the tooth array 70 including more than the set of three teeth 58.

[0137] As an additional or alternative example, a set of circumferentially adjacent teeth forming a first plurality of the teeth includes a first tooth (e.g., tooth 58W), a second tooth (e.g., tooth 58X), and a third tooth (e.g., tooth 58Y), the second tooth is located between the first tooth and the third tooth and is disposed immediately circumferentially adjacent to both of the first tooth and the third tooth. The set of teeth 58 forming the first plurality of teeth includes a first tooth width TW (e.g., 6.5), a second tooth width TW (e.g., 9.0), and a third tooth width TW (e.g., 8.5), respectively corresponding to the first tooth, the second tooth, and the third tooth. In this example, the first tooth width is less than the second tooth width, and the third tooth width is less than the second tooth width. The magnitudes of the tooth widths TW can thus oscillate in sets of adjacent teeth 58, such that the width one of decreases or increases between a first tooth and an adjacent second tooth and then the width does the other of increases or decreases between the second tooth and a third tooth adjacent to the second tooth.

[0138] In some examples, the tooth array 70c can include at least one set of three circumferentially adjacent teeth 58 that alternate in order of magnitude of the tooth width TW. In the example shown, a set of three adjacent teeth 58 (e.g., teeth 58W-58Y) that all have different teeth widths TW relative to each other. The teeth widths of the set of three adjacent teeth 58 are not progressive in order of change in magnitude. In this example, the tooth magnitude increases between each of the outer teeth (e.g., teeth 58W, 58Y) and the intermediate tooth (e.g., tooth 58X). The intermediate tooth has a greater tooth width TW than either of the teeth directly adjacent to the intermediate tooth on both circumferential sides of the intermediate tooth.

[0139] In some examples, the tooth array 70c can include at least one set of circumferentially adjacent teeth (e.g., teeth 58V-58Z) that progressively change in order of magnitude towards an intermediate one of the set of adjacent teeth 58. In some examples, the intermediate tooth can be a center tooth of the set of adjacent teeth. In the example shown, a first tooth (e.g., tooth 58V) has a first tooth width TW, a second tooth (e.g., tooth 58W) adjacent to the first tooth has a second tooth width TW greater than the first tooth width TW, and a third tooth (e.g., tooth 58X) adjacent to the second tooth has a third tooth width TW greater than the second tooth width TW. The set of adjacent teeth can include a fourth tooth (e.g., tooth 58Y) circumferentially adjacent to the third tooth that has a fourth tooth width TW less than the third tooth width TW. In some examples, the set of adjacent teeth can include a fifth tooth (e.g., tooth 58Z) circumferentially adjacent to the fourth tooth that has a fifth tooth width TW less than the fourth tooth width TW. As such, examples of the tooth array 70c can include a set of at least four circumferentially adjacent teeth 58 that, when taken in either circumferential direction, ascend in order of magnitude of the tooth width TW towards a widest intermediate tooth, which can be a center tooth, and the set of teeth then descend in order of magnitude of the tooth width TW away from the widest intermediate tooth.

[0140] In some examples, the set of at least four circumferentially adjacent teeth vary in order of magnitude of the tooth width TW based on circumferential positions of the teeth 58 within the set relative to the widest intermediate tooth of the set. In the example shown, the teeth (e.g., teeth 58Y, 58Z) spaced from the widest intermediate tooth (e.g., tooth 58X) in circumferential direction CD 1 all have tooth widths TW greater than the tooth width TW of the widest tooth within the set (e.g., tooth 58W) that is spaced from the widest intermediate tooth in circumferential direction CD2. In some examples, all teeth within the set that are on one circumferential side of the widest intermediate tooth have a greater tooth width then all teeth within the set that are on the other circumferential side of the widest intermediate tooth.

[0141] In some additional or alternative examples, the first plurality of teeth can include a first tooth (e.g., tooth 58Q), a second tooth (e.g., tooth 58R), and a third tooth (e.g., tooth 58S) that form a set of circumferentially adjacent teeth of the tooth array 70. The second tooth is located directly between the first tooth and the third tooth. The second tooth is located immediately adjacent to both of the first tooth and the third tooth. The set of three circumferentially adjacent teeth that form the first plurality of teeth have a respective first tooth width TW (e.g., 7.5), second tooth width TW (e.g., 7.2), and third tooth width TW (e.g., 9.5), respectively corresponding to the first tooth, the second tooth, and the third tooth. In the example shown, the first tooth width TW is greater than the second tooth width TW, and the third tooth width TW is greater than the second tooth width TW. The tooth widths TW can thus vary between the set of circumferentially adjacent teeth such that the magnitudes of the tooth widths TW decrease towards the intermediate (e.g., second tooth 58R) from the outer teeth (e.g., teeth 58Q, 58S). The intermediate tooth can be a central tooth, such as in examples in which the set of circumferentially adjacent teeth includes an odd number of teeth 58.

[0142] In some examples, a set of circumferentially adjacent teeth forming a first plurality of the teeth 58 can include a fourth tooth (e.g., tooth 58T). The fourth tooth can have a fourth tooth width TW (e.g., 6.8) that can vary from the tooth widths TW of the other three teeth in the first plurality of the teeth 58 (e.g., from the tooth widths TW of teeth 58Q-58S). In the example shown, the third tooth width TW (e.g., of tooth 58S) is greater than each of the second tooth width TW (e.g., of tooth 58R) and the fourth tooth width TW (e.g., of tooth 58T). Some examples of a tooth array 70c can thus include or be formed by a set of circumferentially adjacent teeth 58 in which the magnitudes of the tooth width TW of each of the teeth 58 in the set vary between each of the teeth forming the set.

[0143] The magnitudes of the tooth widths TW can vary in that the shift in magnitude between adjacent teeth 58 alternates between each of the adjacent teeth 58 in the set. In this example, the magnitude decreases from the first tooth 58Q to the second tooth 58R, the magnitude then increases from the second tooth 58R to the third tooth 58S, and the magnitude then decreases from the third tooth 58S to the fourth tooth 58T. Such a set can include additional teeth 58, up to a majority or in some examples all of the teeth 58 of the tooth array 70c. In this example, the set of multiple teeth 58 exhibiting alternating magnitude shifts (e.g., alternating increases and decreases in magnitude) includes teeth 58Q-58W.

[0144] In the example tooth array 70c shown in FIG. 8, the tooth width TW of each tooth 58 differs from the tooth width TW of all other teeth 58 in the tooth array 70c. The tooth widths TW are all different from each other for all teeth 58 of a ring segment 56 in this example. In various other examples, only three different tooth widths TW may be present. The three or more different tooth widths TW can be distributed across a set of three or more circumferentially adjacent teeth 58. The three or more different tooth widths TW can be repeated amongst the teeth 58 of the tooth array 70c. The three or more different tooth widths TW can be repeated amongst the teeth 58 of a ring segment 56. In some examples, only four tooth widths TW may be present, and which can, in some examples, be repeated amongst the teeth 58.

[0145] In some examples, the tooth array 70c includes a plurality of teeth 58. For each respective tooth of the first plurality of teeth, one of the two following conditions is true in that either the respective tooth is immediately adjacent two other teeth of the first plurality of teeth which are both wider than the respective tooth (e.g., tooth 58T within the plurality of teeth 58S-58U), or the respective tooth is immediately adjacent two other teeth of the first plurality of teeth which are both narrower than the respective tooth (e.g., tooth 58X within the plurality of teeth 58W-58Y).

[0146] The unbalanced tooth set shown in FIG. 8 is formed by variable tooth widths TW between the adjacent teeth 58 within the unbalanced tooth set. The variable tooth widths TW change the positions of the poles relative to nominal positions and widths. Such pole positional changes can counteract cogging, torque ripple, and radial forces providing for smoother and quieter operation of the electric machine 10.

[0147] FIG. 9 is an enlarged end view of a stator phase 22 showing tooth array 70d. Tooth array 70d includes a plurality of teeth 58 that are disposed annularly about a portion of the rotational axis of the rotor 12. Tooth array 70d includes a plurality of teeth 58, at least three of the teeth 58 in various examples. In the example shown, teeth 58Q-58U of tooth array 70d are shown. The teeth 58 of tooth array 70d are arrayed at least partially about the rotational axis of the rotor 12. The tooth array 70d shown in FIG. 9 illustrates various aspects that are shown collectively but can be implemented individually.

[0148] Tooth array 70d can be considered to include one or more sets of multiple of the teeth 58 that exhibit one or more of the aspects discussed here. The teeth 58 of tooth array 70d are disposed in an unbalanced tooth set. The unbalanced tooth set of tooth array 70d can form a plurality of teeth 58 that exhibit one or more of the aspects discussed herein. In some examples, a tooth array 70d can include multiple unbalanced tooth sets. The teeth 58 within the multiple unbalanced tooth sets can be configured differently from each other such that tooth array 70d is formed as a non-uniform array at least partially about the rotational axis.

[0149] Teeth 58 within a tooth array can have nominal positions which are the positions that the teeth 58 would be in if the teeth 58 are evenly distributed (e.g., across the flux ring 24, across a ring segment 56, etc.). Uniformly distributed teeth 58 have the same annular distance between adjacent ones of the multiple teeth 58. The annular distance between adjacent teeth 58 is measured from the circumferential center 72 of the teeth 58, as discussed above.

[0150] Tooth array 70d includes a non-progressive arrangement of teeth 58 that counteracts concentrated radial tugging on the stator phase 22. The tooth array 70d is configured to minimize radial tugging by the non-uniform distribution of the tooth faces 66 of the teeth 58, which non-uniform distribution counteracts concentrated radial forces on the stator phase 22. The non-uniform distribution provides one or more unbalanced tooth sets in the tooth array 70d.

[0151] The tooth array 70d shown in FIG. 9 is non-uniform and has a variable angular tooth density about the rotational axis of the rotor 12. The tooth array 70d extends between end ones of the teeth 58 (formed by teeth 58Q, 58U in this example). Intermediate ones of the teeth 58 (formed by teeth 58R-58T in this example) are disposed circumferentially between the end ones of the teeth 58 in the tooth array 70d. Angular portions AP are shown between radial lines LA. The angular portions AP are evenly distributed across the tooth array 70d. The angular portions AP can be applied across the tooth array 70d such that the count of angular portions AP for a tooth array 70d is one less than the number of teeth 58 in the tooth array 70d. In some examples, the angular portions AP can be taken between the nominal annular positions of the teeth 58 within the tooth array 70d. With the teeth 58 in the nominal positions and having common tooth widths TW, each angular portion AP includes a common angular tooth density. The angular tooth density is the amount of a circumferential distance between the edges of each angular portion AP that is occupied by material forming the tooth 58. The angular tooth density can be measured based on the circumferential widths of the teeth 58 within each angular portion AP when measured at a common distance from the rotational axis. In some examples, the angular tooth density can be measured based on the tooth widths TW of the tooth faces 66 within each angular portion AP, among other options.

[0152] In the end view of FIG. 9, the tooth density for the angular portion AP between the nominal positions of teeth 58T and 58U is the amount of the gap between the edges of the angular portion AP occupied by the teeth 58 vs. the amount of the gap spanning between the teeth 58. For example, if an angular portion AP includes an inter- tooth gap 78 that is the same circumferential width as the portions of the teeth 58 within the angular portion AP, then the tooth density for that angular portion AP would be 50%. The teeth 58 of tooth array 70d are disposed at least partially about the rotational axis MA of the rotor 12 such that the tooth array 70d has a variable angular tooth density at least partially about the rotational axis. The teeth 58 are arrayed such that at least two circumferentially adjacent angular portions AP have differing tooth densities relative to each other. In some examples, the teeth 58 are arrayed such that at least three circumferentially adjacent angular portions AP (e.g., between teeth 58Q, 58R; between teeth 58R, 58S; between teeth 58S, 58T) have differing tooth densities relative to each other. In some examples, the teeth 58 are arrayed such that at least three circumferentially adjacent angular portions AP (e.g., between teeth 58Q, 58R; between teeth 58R, 58S; between teeth 58S, 58T; between teeth 58T, 58U) have differing tooth densities relative to each other.

[0153] The varied tooth density of the tooth array 70d can distribute poles and reduces cogging by further spreading out the poles and thus potential cogging positions to avoid the additive effects of too many poles cogging at one rotational orientation. The varied tooth density of the tooth array 70d can shift the force waveform in time (e.g., the moment at which the forces are acting on any particular pole) to counteract radial forces. The varied tooth density of the tooth array 70d can change harmonics and magnitude of the forces to counteract vibration and resultant noise. The varied tooth density of the tooth array 70d can spread the forces experienced by the stator 14 to provide a smoother cogging waveform that can cancel with other phases 22 of the stator 14 to provide for a smoother output that counteracts both cogging and torque ripple.

[0154] In some examples, the teeth 58 of the tooth array 70d can have variable annular offsets 74 such that the teeth 58 are shifted from nominal positions of the teeth 58 to vary the angular tooth density. In additional or alternative examples, the teeth 58 of the tooth array 70d can have varying tooth widths TW to vary the tooth density. In additional or alternative examples, the teeth 58 of the tooth array 70d can additionally or alternatively have variable annular distances 76 between sets of adjacent teeth 58 to vary the tooth density. It is thus understood that the unbalanced tooth set can exhibit variable angular tooth density based on one or more of variable tooth widths, variable annular offsets, and variable annular distances. The variable density exhibited across at least portions of the tooth array 70d facilitates smoother operation and output by the electric machine 10.

[0155] In the example shown, at least two adjacent angular portions AP have differing tooth densities relative to each other. A first angular portion AP (e.g., the angular portion AP between the nominal positions of teeth 58Q, 58R) includes a different tooth density than an adjacent second angular portion AP (e.g., the angular portion AP between the nominal positions of teeth 58R, 58S). In the example shown, a first tooth (e.g., tooth 58Q) is shifted in circumferential direction CD1, increasing an amount of that first tooth in the first angular portion AP and a second tooth (e.g., tooth 58R) is shifted in circumferential direction CD2, increasing an amount of that tooth 58R in the first angular portion while also reducing an amount of that second tooth in adjacent the second angular portion (e.g., between teeth 58R, 58S). A third tooth (e.g., tooth 58S) is shifted in circumferential direction CD 1 , decreasing an among of that tooth in the second angular portion. In some examples, the tooth widths TW of the multiple teeth (e.g., teeth 58Q-58S) vary which can also affect the angular tooth density. Some examples include a third angular portion AP adjacent to the second angular portion, which third angular portion (e.g., between the nominal positions of teeth 58S, 58T) can have a different tooth density than either the first angular portion or the second angular portion.

[0156] Teeth 58 in the tooth array 70d form a non-uniform array of teeth 58 at least partially about the rotational axis of the rotor 12. The non-uniform tooth array 70d includes teeth 58 that are configured differently from adjacent teeth 58 within the tooth array 70. For example, multiple of the teeth 58 can be annularly offset from a nominal tooth position in which the teeth 58 are evenly circumferentially distributed within the tooth array 70d. Adjacent ones of the teeth 58 in the tooth array 70d can have different annular offsets relative to each other. For example, the teeth 58 of tooth array 70d can be annularly offset from nominal positions of the teeth 58, such as shown in FIG. 7. A first tooth (e.g., tooth 58Q) can be annularly offset to a greater or lesser degree than an adjacent second tooth (e.g., tooth 58R). The first tooth 58 can be annularly offset in the same circumferential direction or in an opposite circumferential direction from the second tooth 58. In additional or alternative examples, adjacent ones of the teeth 58 in the tooth array 70 can have different tooth widths TW relative to each other, such as shown in FIG. 8. For example, a first tooth (e.g., tooth 58Q) in the tooth array 70d can have a first tooth width that is larger or smaller than the second tooth width of a second tooth (e.g., tooth 58R) in the tooth array 70d that is adjacent to the first tooth 58.

[0157] The tooth array 70d distributes sets of multiple ones of the teeth 58 of the tooth array 70d non-uniformly at least partially around the axis MA. A first plurality of teeth 58 of the tooth array 70d are disposed in a non-uniform array such that a first set of multiple teeth of the first plurality of teeth are configured differently from a second set of multiple teeth of the first plurality of teeth. The teeth of the first set of multiple teeth (e.g., teeth 58Q, 58R) can at least partially overlap with the teeth of the second set of multiple teeth (e.g., teeth 58R, 58S with tooth 58R overlapping as tooth 58R is present in both sets of multiple teeth). In some examples, the first and second sets of multiple teeth 58 are adjacent but not overlapping (e.g., teeth 58Q, 58R forming a first set and teeth 58S, 58T forming a second set). The teeth 58 of the first set can vary in configuration from the teeth 58 of the second set. For example, the teeth 58 in the first set of multiple teeth 58 can have different annular offsets 74, different annular distances 76 between, and / or different tooth widths TW than the teeth 58 in the second set of multiple teeth 58.

[0158] The tooth array 70d can include a non-uniform distribution of teeth 58 in that the tooth array 70d includes a set of multiple adjacent teeth (e.g., at least three adjacent teeth) that are differently configured relative to each other. The set of three adjacent teeth (e.g., teeth 58Q-58S) can have different magnitudes of their respective annular offsets 74. Additionally or alternatively, the set of three adjacent teeth 58 can have annular offsets 74 in varying circumferential directions. Additionally or alternatively, the set of three adjacent teeth 58 can include teeth 58 having differing tooth widths TW.

[0159] Some examples of an unbalanced tooth set of the tooth array 70d include at least four adjacent teeth 58. The four teeth 58 in the set of the multiple teeth 58 can be differently configured relative to each other. The set of four adjacent teeth (e.g., teeth 58Q-58T) can have different magnitudes of their respective annular offsets 74. Additionally or alternatively, the set of four adjacent teeth 58 can have annular offsets 74 in varying circumferential directions. Additionally or alternatively, the set of four adjacent teeth 58 can include teeth 58 having differing tooth widths TW. Additionally or alternatively, the set of four adjacent teeth 58 can have different annular distances 76 between adjacent ones of the teeth 58 forming the set of adjacent teeth 58.

[0160] In the example shown, the teeth 58 within a set of multiple teeth are configured such that at least three adjacent teeth 58 (e.g., teeth 58R-58T) have different geometries relative to each other. The at least three adjacent teeth can have different geometries relative to each other and relative to nominal circumferential positions of those teeth 58. For example, a first tooth (e.g., tooth 58R) can have a different geometry from an adjacent second tooth (e.g., tooth 58S) which can have a different geometry from an adjacent third tooth (e.g., tooth 58T). The geometry of the first tooth can vary from the geometry of the third tooth such that each of the multiple teeth in the set have a geometry that differs from any other tooth in the set of multiple teeth. The geometries of the three adjacent teeth 58 can vary in that the tooth widths TW of the teeth 58 vary. The geometries of the three adjacent teeth 58 can vary in that the annular offsets 74 of the teeth 58 differ in magnitude and / or circumferential direction.

[0161] Any, some or all of the aspects demonstrated in each of FIGS. 6-9 can be implemented together or separately, such as being combined into one embodiment. The various spacing, shifting, and / or width relationship aspects for the teeth 58 demonstrated for a ring segment 56 can be implemented in multiple or all segments of a half phase / flux ring 24 (and further other flux rings 24 and stator phases 22), whether composed as separate ring segments 56 or as a contiguous ring. As such, the various spacing, shifting, and / or width relationship aspects are not limited to ring segments 56. Such various spacing, shifting, and / or width relationship aspects can bridge between ring segments 56 in various examples. As such, two teeth 58 on one ring segment 56 can be part of a set of teeth 58 with one or more teeth 58 from an adjacent ring segment 56 having any of the various spacing, shifting, and / or width relationship aspects referenced and / or shown herein. A tooth array 70 can thus span between adjacent ring segments 56 and include teeth 58 on both of the adjacent ring segments 56. It is understood that in various examples, the teeth 58 forming an unbalanced tooth set are monolithic with each other and formed from the same lamina structure.

[0162] FIG. 10 is a graph illustrating an unbalanced tooth configuration. In the example shown, in FIG. 10, the left-hand vertical axis shows annular offsets, with the positive values being in a first circumferential direction and the negative values being in a second opposite circumferential direction; the right-hand vertical axis shows relative tooth widths; and the horizontal axis shows the various positions of the teeth 58 within a tooth array 70e. The tooth array 70e represented by the graph of FIG. 10 exhibits unbalanced teeth in that sets of circumferentially adjacent ones of the teeth 58. The example tooth array 70e shown includes sixteen teeth 58. Each tooth 58 in the tooth array 70e is configured differently from each other tooth 58 in the tooth array 70e, though it is understood that not all examples are so limited. As shown, the tooth array 70e includes at least one unbalanced tooth set.

[0163] The relative offsets and tooth widths of teeth 58K-58Z of the tooth array 70e. The teeth 58 of the tooth array 70e can be non-uniform in that adjacent ones of the teeth 58 can vary in one or both of the annular offset 74 and tooth width TW for each tooth 58.

[0164] In the example shown, the tooth array 70e includes at least one set of three teeth (e.g., teeth 58L-58N) that are adjacent and have varied configurations. In the example shown, the tooth width TW of a first tooth (e.g., tooth 58L) differs from the tooth width TW of a second tooth (e.g., tooth 58M), and the tooth width TW of the second tooth varies from the tooth width of a third tooth (e.g., tooth 58N). The first tooth width can be greater than the second tooth width, and the third tooth width can be greater than the second tooth width and differ from the first tooth width.

[0165] In the example shown, the tooth array 70e includes at least one set of three teeth (e.g., teeth 58K-58M) that are adjacent and have varied configurations. A first tooth (e.g., tooth 58K) and a second tooth (e.g., tooth 58L) can have the same tooth width TW but have different configurations in that the annular offset 74 of tooth 58K has a greater magnitude than the annular offset 74 of tooth 58L. A third tooth (e.g., tooth 58M) adjacent to the second tooth has both an annular offset 74 and a tooth width TW that differ from both the first tooth and the second tooth.

[0166] In the example shown, the tooth array 70e includes at least one set of teeth that have different tooth widths TW and that have annular offsets 74 in opposite circumferential directions. For example, a first tooth (e.g., tooth 580) can have an annular offset 74 in a first circumferential direction and an adjacent second tooth (e.g., tooth 58P) can have an annular offset 74 in a second circumferential direction. The first tooth can have a first tooth width TW that varies from the tooth width TW of the second tooth. The magnitudes of the annular offsets 74 of the adjacent teeth 58 can vary from each other. As such, the annular offsets 74 of adjacent teeth 58 can vary in both direction and magnitude.

[0167] Tooth array 70e can be considered to include teeth 58 in a flip offset configuration. The tooth array 70e can be considered to include multiple unbalanced tooth sets. The teeth in a first unbalanced tooth set (e.g., teeth 58K-58R) are disposed on a first circumferential side of a center of the tooth array 70e (the center between teeth 58R, 58S in this example) and the teeth in a second unbalanced tooth set (e.g., teeth 58S-58Z) are disposed on a second circumferential side of the center of the unbalanced tooth set. The tooth array 70e is in a flip offset configuration in that the teeth 58 on either side of a center divider have annular offsets 74 of the same magnitude depending on the position of the tooth 58 away from that center divider, except that the annular offsets 74 are flipped in direction between the unbalanced tooth sets. For example, teeth 58R, 58S (first tooth out from the center divider for each unbalanced tooth set) have annular offsets 74 of the same magnitude, except the annular offset 74 of tooth 58R is in an opposite circumferential direction from the annular offset 74 of tooth 58S. Similarly, teeth 58P, 58U (third tooth out from the center divider for each unbalanced tooth set) have annular offsets 74 of the same magnitude, except the annular offset 74 of tooth 58P is in an opposite circumferential direction from the annular offset 74 of tooth 58U. Tooth array 70e can be considered to include tooth in a width mirror configuration. The tooth array 70e can be considered to include multiple unbalanced tooth sets. The teeth in a first unbalanced tooth set (e.g., teeth 58K-58R) are disposed on a first circumferential side of a center of the tooth array 70e (the center between teeth 58R, 58S in this example) and the teeth in a second unbalanced tooth set (e.g., teeth 58S-58Z) are disposed on a second circumferential side of the center of the unbalanced tooth set. The tooth array 70e is in a width mirror configuration in that the teeth 58 on either side of a center divider have the same tooth width TW depending on the position of the tooth 58 away from a center divider. For example, teeth 58R, 58S (first tooth out from the center divider for each unbalanced tooth set) have tooth widths TW of the same magnitude. Similarly, teeth 58P, 58U (third tooth out from the center divider for each unbalanced tooth set) have tooth widths TW of the same magnitude.

[0168] FIG. 10A is a graph illustrating radial force magnitude vs. mechanical angle at different times during operation of an electric machine. FIG. 1 OB is a chart illustrating radial forces experienced by a stator phase of an electric machine about an axis of rotation of the rotor 12. The forces illustrated in FIGS. 10A and 10B are for an electric machine that does not include the variable spacing, shifting, and / or width relationships illustrated in FIGS. 6-10.

[0169] As shown in FIG 10A, each plot line PL1 shows the radial forces experienced at each mechanical angle about the rotational axis for a particular moment in time associated with the electrical angle of the electric current through the coil 26 of that stator phase 22. The force lines FL1 in FIG. 10B illustrate the magnitude of the radial forces experienced by the stator 14 about the rotational axis. As shown in FIGS. 10A and 10B, the radial forces experienced by the electric machine are concentrated 180-degrees apart on the stator. The distribution of the radial forces is elliptical or oblong on the stator. The reversal of the current through the stator can shift the illustrated radial forces by 90-degrees from that shown (e.g., such that the force lines FL1 shown in FIG. 10B are rotated 90-degrees from those shown). The reversal of the current through the coil of the stator phase can thus cause alternating vertical and horizontal elliptical forces on the stator phase. Such a concentrations of the radial forces generates vibration and noise. The concentration of radial forces in the manner shown can cause oblong deformation of the stator vertically and horizontally, increasing wear, vibration, and noise.

[0170] FIG. HA is a graph illustrating radial force magnitude vs. mechanical angle at different times during operation on electric machine 10. FIG. 1 IB is a chart illustrating radial forces experienced by a stator phase 22 of the electric machine 10. The forces illustrated in FIGS. 11A and 11B are for a stator phase 22 including a flux ring 24 having at least an unbalanced tooth configuration.

[0171] As shown in FIG 11 A, each plot line PL2 shows the radial forces experienced at each mechanical angle about the rotational axis for a particular moment in time associated with the electrical angle of the current through the coil 26 of that stator phase 22. The force lines FL2 in FIG. 1 IB illustrate the magnitude of the radial forces experienced by the stator phase 22 about the rotational axis.

[0172] As shown in FIG. 11 A, the radial forces are more evenly distributed about the rotational axis than in the configuration shown in FIG. 10A. The magnitude of the radial forces is not concentrated 180-degrees apart in the example shown in FIG. 11A. The non- uniform set of multiple teeth of a first plurality of teeth of the tooth array distributes the radial forces asymmetrically about the rotational axis. The symmetric distribution of radial forces shown in FIG. 10A generates vibration, wear, and noise due to the concentrations of the radial forces exhibiting a combined elongate elliptical force. The asymmetric force distribution in FIG. 11 A provides a better balance of radial forces about the rotational axis MA, which smooths the output of the electric machine 10, counteracting vibration and thereby reducing noise and wear.

[0173] As shown in FIG. 11B, the radial forces experienced by the electric machine are distributed about the axis MA, not concentrated 180-degrees apart on the stator as shown in FIG. 10B. The distribution of the radial forces asymmetric and not elliptical or oblong. The non-uniform tooth distribution results in a higher order mode shape that counteracts vibration and provides for a smoother, quieter operation of electric machine 10.

[0174] The reversal of the current through the stator can shift the illustrated radial forces by 90-degrees from that shown (e.g., such that the force lines FL2 shown in FIG. 1 IB are rotated 90-degrees from those shown). The reversal of the current through the coil of the stator phase can thus cause alternating patterns of radial forces. The asymmetric distribution of the radial forces counteracts vibration and noise generation that can result from concentrated radial forces. The distribution of radial forces in the manner shown does not cause oblong deformation of the stator vertically and horizontally, thereby preventing wear, vibration, and noise.

[0175] The various aspects for tooth spacing can be expressed or implemented in term of angular distance, center to center of the teeth, in the manner referenced in U.S. Pat. No. 8,760,023. So while absolute distances and spacing are discussed herein, each such discussion and / or embodiment could instead be implemented in terms of angular distance in the same manner as absolute distance. The frame of reference for the angle can be the axis of rotation.

[0176] While a fan embodiment is shown herein, it is understood that the features of this disclosure could be applied to an electric machine of any application, including non- fan applications. It is further understood that any aspect discussed herein with regard to a particular example may be mixed as between the different examples and features. While the invention 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 without departing from the essential scope thereof. Therefore, it is intended that the invention not be limited to the particular embodiment(s) disclosed, but that the invention will include all embodiments falling within the scope of the appended claims.

Claims

CLAIMS:

1. An electric rotational machine comprising: a rotor comprising a plurality of magnets arrayed around an axis of rotation of the rotor; and a stator comprising at least one coil and at least one annular array of teeth; wherein a first plurality of teeth form at least part of a first annular array of teeth of the at least one annular array of teeth, and the first plurality of teeth are disposed in a non-uniform tooth array such that a first set of multiple teeth of the first plurality of teeth are configured differently from a second set of multiple teeth of the first plurality of teeth.

2. The electric rotational machine of claim 1, wherein: each tooth of the first plurality of teeth has a tooth width; the first set of multiple teeth includes a first tooth having a first tooth width and a second tooth having a second tooth width; the second set of multiple teeth includes a third tooth having a third tooth width and a fourth tooth having a fourth tooth width; and the first tooth width differs from the second tooth width, the first tooth width varies from the third tooth width, and the second tooth width varies from the third tooth width.

3. The electric rotational machine of claim 2, wherein the first tooth is circumferentially adjacent to the second tooth, the second tooth is circumferentially adjacent to the third tooth, and the third tooth is circumferentially adjacent to the fourth tooth.

4. The electric rotational machine of any one of claims 2 and 3, wherein the fourth tooth width is different from each of the first tooth width, the second tooth width, and the third tooth width.

5. The electric rotational machine of any one of claims 2-4, wherein the second tooth width is less than the first tooth width and the third tooth width.

6. The electric rotational machine of claim 5, wherein the fourth tooth width is less than the first tooth width and the third tooth width.

7. The electric rotational machine of claim 6, wherein the second tooth width is greater than the fourth tooth width.

8. The electric rotational machine of claim 1, wherein:the first set of multiple teeth includes a first tooth and a second tooth; the second set of multiple teeth includes a third tooth and a fourth tooth; the first tooth is circumferentially adjacent to the second tooth, the third tooth is circumferentially adjacent to the second tooth, and the fourth tooth is circumferentially adjacent to the third tooth; the first plurality of teeth are annularly spaced such that annular distances are formed between adjacent pairs of the teeth of the first plurality of teeth; a first annular distance is disposed between the first tooth and the second tooth; a second annular distance different from the first annular distance is between the second tooth and the third tooth; and a third annular distance different from the first annular distance and the second annular distance is disposed between the third tooth and the fourth tooth.

9. The electric rotational machine of claim 8, wherein the first annular distance is different from the second annular distance and the third annular distance, and the second annular distance is different from the third annular distance.

10. The electric rotational machine of claim 9, wherein the first annular distance is greater than the third annular distance.

11. The electric rotational machine of any one of claims 9 and 10, wherein the second annular distance is greater than the first annular distance and the third annular distance.

12. The electric rotational machine of claim 8, wherein: the first plurality of teeth further comprises a fifth tooth circumferentially adjacent to the fourth tooth and a fourth annular distance is disposed between the fourth tooth and the fifth tooth.

13. The electric rotational machine of claim 12, wherein the first annular distance is different from the second annular distance and the third annular distance, and the second annular distance is different from the third annular distance.

14. The electric rotational machine of claim 13, wherein the fourth annular distance is the same as the second annular distance.

15. The electric rotational machine of any one of claims 13 and 14, wherein the second annular distance is greater than the first annular distance and the third annular distance.

16. The electric rotational machine of claim 1, wherein: the first set of multiple teeth includes a first tooth and a second tooth; the second set of multiple teeth includes a third tooth and a fourth tooth; the first tooth is circumferentially adjacent to the second tooth, the third tooth is circumferentially adjacent to the second tooth, and the fourth tooth is circumferentially adjacent to the third tooth; the first plurality of teeth are respectively annularly offset by a first plurality of annular offsets from a first plurality of evenly annularly arrayed nominal positions; the first tooth is offset from a first nominal position by a first annular offset; the second tooth is offset from a second nominal position by a second annular offset different from the first annular offset; and the third tooth is offset from a third nominal position by a third annular offset different from the first annular offset and the second annular offset.

17. The electric rotational machine of claim 16, wherein each of the first annular offset, the second annular offset, and the third annular offset are in a same circumferential direction about the rotational axis.

18. The electric rotational machine of claim 16, wherein the first annular offset is in a first circumferential direction about the rotational axis and the second annular offset is in the first circumferential direction.

19. The electric machine of claim 18, wherein the first annular offset is greater than the second annular offset.

20. The electric machine of claim 19, wherein the third annular offset is in the first circumferential direction and the third annular offset is less than the second annular offset.

21. The electric machine of claim 20, wherein the fourth tooth is offset from a fourth nominal position by a fourth annular offset, and wherein the fourth annular offset is in the first circumferential direction and less than the third annular offset.

22. The electric machine of claim 16, wherein the first annular offset is in a first circumferential direction about the rotational axis and the second annular offset is in a second circumferential direction opposite the first circumferential direction.

23. The electric machine of claim 22, wherein the first annular offset is greater than the second annular offset.

24. The electric machine of any one of claims 22 and 23, wherein the third annular offset is in the first circumferential direction.

25. The electric machine of claim 24, wherein the first annular offset is greater than the third annular offset.

26. The electric machine of claim 22, wherein the third annular offset is in the first circumferential direction and the fourth annular offset is in the second circumferential direction.

27. The electric machine of claim 26, wherein the first annular offset is greater than the second annular offset and the third annular offset is greater than the second annular offset.

28. The electric machine of claim 27, wherein the first annular offset is greater than the third annular offset.

29. The electric machine of any one of claims 27 and 28, wherein the fourth annular offset is greater than the second annular offset.

30. The electric machine of claim 29, wherein the fourth annular offset is less than the third annular offset and less than the first annular offset.

31. The electric rotational machine of claim 1, wherein the non-uniform tooth array is formed by at least three different annular distances between three different adjacent pairs of teeth of the first plurality of teeth.

32. The electric rotational machine of claim 31, wherein the annular distances are measured from respective circumferential centers of the first plurality of teeth.

33. The electric rotational machine of claim 1, wherein the first set of multiple teeth includes a first tooth and a second tooth circumferentially adjacent to the first tooth, and the second set of multiple teeth includes the second tooth and a third tooth circumferentially adjacent to the second tooth.

34. The electric rotational machine of claim 1, wherein the first set of multiple teeth includes a first tooth and a second tooth circumferentially adjacent to the first tooth, and the second set of multiple teeth includes a third tooth circumferentially adj cent to the second tooth and a fourth tooth circumferentially adjacent to the third tooth.

35. An electric rotational machine comprising: a rotor comprising a plurality of magnets arrayed around an axis of rotation of the rotor; anda stator comprising at least one coil and at least one annular array of teeth; wherein a first plurality of adjacent teeth form at least part of a first annular array of teeth of the at least one annular array of teeth, wherein a non-uniform arrangement of the first plurality of adjacent teeth asymmetrically spreads out radial forces about the axis of rotation.

36. The electric rotational machine of claim 35, wherein the first plurality of adjacent teeth comprises: a first tooth, a second tooth circumferentially adjacent to the first tooth, and a third tooth circumferentially adjacent to the second tooth.

37. The electric rotational machine of claim 36, wherein the non-uniform arrangement is between respective tooth widths of the first plurality of adjacent teeth.

38. The electric rotational machine of claim 37, wherein the first tooth has a first tooth width, the second tooth has a second tooth width different from the first tooth width, and the third tooth has a third tooth width different from the first tooth width and the second tooth width.

39. The electric rotational machine of any one of claims 36-38, wherein the non-uniform arrangement is between respective annular offsets of the first plurality of adjacent teeth relative to a first plurality of evenly annularly arrayed nominal positions.

40. The electric rotational machine of claim 39, wherein the first tooth has a first annular offset, the second tooth has a second annular offset different from the first annular offset, and the third tooth has a third annular offset different from the first annular offset and the second annular offset.

41. The electric rotational machine of claim 40, wherein the second annular offset is in an opposite circumferential direction from the first annular offset.

42. The electric rotational machine of any one of claims 40 and 41, wherein the first annular offset is in a same circumferential direction as the third annular offset.

43. The electric rotational machine of any one of claims 36-42, wherein the non-uniform arrangement is between respective annular distances between respective tooth pairs of the first plurality of adjacent teeth, wherein the respective annular distances are measured from respective circumferential centers of the first plurality of adjacent teeth.

44. The electric rotational machine of claim 43, wherein: a first annular distance is between the first tooth and the second tooth, a second annular distance is between the second tooth and the third tooth, and a third annular distance is between the third tooth and afourth tooth disposed circumferentially adjacent to the third tooth; and the first annular distance differs from the second annular distance, and the third annular distance differs from both the first annular distance and the second annular distance.

45. An electric rotational machine comprising: a rotor comprising a plurality of magnets arrayed around an axis of rotation of the rotor; and a stator comprising at least one coil and at least one annular array of teeth; wherein a first plurality of teeth forms at least part of a first annular array of teeth of the at least one annular array of teeth, the first plurality of teeth including a first tooth, a second tooth circumferentially adjacent to the first tooth, and a third tooth circumferentially adjacent to the second tooth, the first plurality of teeth producing asymmetric radial forces on the first annular array of teeth during operation of the stator; wherein the first tooth has a first geometry and a first annular offset from a first nominal annular position, the second tooth has a second geometry and a second annular offset from a second nominal annular position, and the third tooth has a third geometry and a third annular offset from a third nominal annular position; and wherein at least one of:(1) the first geometry differs from the second geometry, and the third geometry differs from the first geometry and the second geometry; and(2) the first annular offset differs from the second annular offset, and the third annular offset differs from the first annular offset and the second annular offset.

46. An electric rotational machine comprising: a rotor comprising a plurality of magnets arrayed around an axis of rotation of the rotor; and a stator comprising at least one coil and at least one annular array of teeth; wherein a first plurality of teeth form at least part of a first annular array of teeth of the at least one annular array of teeth, and the first pluralityof teeth is disposed in a non-uniform tooth array including at least three circumferentially adjacent teeth of the first annular array of teeth, each tooth of the at least three circumferentially adjacent teeth has a different geometry.

47. The electric rotational machine of claim 46, wherein a first tooth of the at least three circumferentially adjacent teeth has a first tooth width, a second tooth of the at least three circumferentially adjacent teeth has a second tooth width different from the first tooth width, and a third tooth of the at least three circumferentially adjacent teeth has a third tooth width different from the first tooth width and the second tooth width, and wherein the second tooth is disposed directly circumferentially between the first tooth and the third tooth.

48. The electric rotational machine of claim 47, wherein the second tooth width is greater than the first tooth width.

49. The electric rotational machine of claim 47, wherein the second tooth width is less than the first tooth width.

50. The electric rotational machine of any one of claims 48 and 49, wherein the second tooth width is greater than the third tooth width.

51. The electric rotational machine of any one of claims 48 and 49, wherein the third tooth width is greater than the second tooth width.

52. The electric rotational machine of any one of claims 47-51, wherein the at least three circumferentially adjacent teeth includes a fourth tooth circumferentially adjacent to the third tooth, the fourth tooth having a fourth tooth width different from the first tooth width, the second tooth width, and the third tooth width.

53. The electric rotational machine of any one of claims 46-52, wherein each tooth of the at least three circumferentially adjacent teeth is annularly offset from an evenly annularly arrayed nominal position.

54. The electric rotational machine of any one of claims 46-53, a plurality of annular distances are formed between adjacent teeth of the at least three circumferentially adjacent teeth, the plurality of annular distances including at least three annular distances that are each different.

55. The electric rotational machine of claim 46, wherein the teeth of the at least three circumferentially adjacent teeth are respectively annularly offset by a first plurality of annular offsets from a first plurality of evenly annularly arrayed nominal positions.

56. The electric rotational machine of claim 55, wherein the at least three circumferentially adjacent teeth includes: a first tooth that is offset from a first nominal position by a first annular offset; a second tooth circumferentially adjacent to the first tooth, the second tooth being offset from a second nominal position by a second annular offset different from the first annular offset; and a third tooth circumferentially adjacent to the second tooth, the third tooth being offset from a second nominal position by a third annular offset different from the first annular offset and the second annular offset.

57. The electric rotational machine of claim 56, wherein the first annular offset is in a first circumferential direction about the rotational axis, and at least one of the second annular offset and the third annular offset is in a second circumferential direction opposite the first circumferential direction.

58. The electric rotational machine of claim 57, wherein the second annular offset is in the second circumferential direction.

59. The electric rotational machine of any one of claims 57 and 58, wherein the third annular offset is in the first circumferential direction.

60. The electric rotational machine of any one of claims 56-59, wherein the first annular offset has a first magnitude, the second annular offset has a second magnitude different from the first magnitude, and the third annular offset has a third magnitude different from the first magnitude and the second magnitude.

61. The electric rotational machine of claim 60, wherein the second magnitude is less than the first magnitude and the third magnitude.

62. The electric rotational machine of claim 60, wherein the second magnitude is greater than the first magnitude and the third magnitude.

63. The electric rotational machine of claim 60, wherein the first magnitude is greater than the second magnitude and the second magnitude is greater than the third magnitude.

64. The electric rotational machine of claim 46, wherein the at least three circumferentially adjacent teeth are separated by a plurality of annular distances, and the at least three circumferentially adjacent teeth includes: a first tooth;a second tooth circumferentially adjacent to the first tooth, wherein a first annular distance is disposed between the first tooth and the second tooth; a third tooth circumferentially adjacent to the second tooth, wherein a second annular distance different from the first annular distance is disposed between the second tooth and the third tooth; and a fourth tooth circumferentially adjacent to the third tooth, wherein a third annular distance different from the second annular distance is disposed between the third tooth and the fourth tooth.

65. The electric rotational machine of claim 64, wherein the second annular distance is greater than the first annular distance and the third annular distance.

66. The electric rotational machine of any one of claims 64 and 65, wherein the first annular distance is different from the third annular distance.

67. The electric rotational machine of any one of claims 64-67 wherein the plurality of annular distances are measured from respective circumferential centers of the at least three circumferentially adjacent teeth.

68. A flux ring for a stator of an electrical rotational machine, the flux ring configured to extend about a rotational axis of a rotor of the electrical machine, the flux ring comprising: a first tooth; a second tooth disposed circumferentially adjacent to the first tooth; a third tooth disposed circumferentially adjacent to the second tooth; wherein the first tooth has a first geometry and a first annular offset from a first nominal annular position, the second tooth has a second geometry and a second annular offset from a second nominal annular position, and the third tooth has a third geometry and a third annular offset from a third nominal annular position; and wherein at least one of:(1) the first geometry differs from the second geometry, and the third geometry differs from the first geometry and the second geometry; and(2) the first annular offset differs from the second annular offset, and the third annular offset differs from the first annular offset and the second annular offset.

69. The flux ring of claim 68, wherein the flux ring includes a plurality of ring segments that each extend partially about the rotational axis, and wherein the first tooth, the second tooth, and the third tooth are all disposed on a first ring segment of the plurality of ring segments.

70. The flux ring of any one of claims 68 and 69, wherein the first tooth has a first tooth width, the second tooth has a second tooth width different from the first tooth width, and the third tooth has a third tooth width different from the first tooth width and the second tooth width.

71. The flux ring of any one of claims 68-70, wherein the first annular offset has a first magnitude, the second annular offset has a second magnitude different from the first magnitude, and the third annular offset has a third magnitude different from the first magnitude and the second magnitude.

72. The flux ring of any one of claims 68-71 , wherein the first offset is in a first circumferential direction and the second offset is in a second circumferential direction opposite the first circumferential direction.

73. An electric rotational machine comprising: a rotor comprising a plurality of magnets arrayed around an axis of rotation of the rotor; and a stator, the stator comprising at least one coil and at least one annular array of teeth, wherein a first plurality of adjacent teeth form at least part of a first annular array of teeth of the at least one annular array of teeth, and wherein the teeth of the first plurality of adjacent teeth are disposed asymmetrically about the axis of rotation.

74. The electric rotational machine of claim 73, wherein the first plurality of adjacent teeth are annularly spaced such that at least three different annular distances are between three different adjacent pairs of teeth of the first plurality of adjacent teeth.

75. The electric rotational machine of claim 73, wherein the first plurality of teeth are annularly spaced such that at least three different annular distances are between four different adjacent pairs of teeth of the first plurality of teeth.

76. The electric rotational machine of any one of claims 74 and 75, wherein the annular distances are measured from the respective centers of the teeth.

77. The electric rotational machine of any one of claims 74-76, wherein the annular distances are measured as angular distances about the axis.

78. The electric rotational machine of claim 73, wherein the first plurality of adjacent teeth are respectively annularly offset by a first plurality of annular offsets from a first plurality of evenly annularly arrayed nominal positions.

79. The electric rotational machine of claim 78, wherein the first plurality of annular offsets are not equal to each other and are not in a progressive order annularly about the axis.

80. The electric rotational machine of claim 78, wherein the first plurality of annular offsets are not equal to each other and are not in a graduated order annularly about the axis.

81. The electric rotational machine of claim 78, wherein sizes of the first plurality of annular offsets are interspersed so that relatively smaller annular offsets are interspaced with relatively larger offsets.

82. The electric rotational machine of one any of claims 78-81, wherein the first plurality of adjacent teeth includes a first tooth adjacent to a second tooth, the second tooth adjacent to a third tooth, and the third tooth adjacent to a fourth tooth; the first tooth is shifted by a first annular distance from its nominal position, the second tooth is shifted by a second annular distance from its nominal position, the third tooth is shifted by a third annular distance from its nominal position, and the fourth tooth is shifted by a fourth annular distance from its nominal position; and the first annular distance is greater than the second annular distance, the third annular distance is greater than the second annular distance, and the fourth annular distance is less than the third annular distance.

83. The electric rotational machine of claim 82, wherein the fourth tooth is adjacent to a fifth tooth, the fifth tooth is shifted by a fifth annular distance from its nominal position, and the fifth annular distance is greater than the fourth annular distance.

84. The electric rotational machine of any one of claims 78-83, wherein each annular offset of the first plurality of annular offsets is offset in either a clockwise direction or a counterclockwise direction from an associated nominal position such that the first plurality of adjacent teeth includes at least one tooth offset in the clockwise direction and at least one tooth offset in the counterclockwise direction.

85. The electric rotational machine of claim 84, wherein the first plurality of adjacent teeth includes multiple teeth offset in the clockwise direction and multiple teeth offset in the counterclockwise direction.

86. The electric rotational machine of claim 84, wherein the at least one tooth offset in the clockwise direction is interspaced with the at least one tooth offset in the counterclockwise direction.

87. The electric rotational machine of claim 86, wherein a tooth shifted in the clockwise direction is directly annularly surrounded by two teeth shifted in the counterclockwise direction, and another tooth shifted in the counterclockwise direction is directly annularly surrounded by two teeth shifted in the clockwise direction.

88. The electric rotational machine of any one of claims 84-87, wherein a first annular offset of the first plurality of annular offsets is adjacent to a second annular offset of the first plurality of annular offsets, a third annular offset of the first plurality of annular offsets is adjacent to the second annular offset, the first annular offset is in a first circumferential direction about the axis of rotation, the second annular offset is in the a second circumferential direction opposite the first circumferential direction, and the third annular offset is in the first circumferential direction.

89. The electric rotational machine of claim 88, wherein a fourth annular offset of the first plurality of annular offsets is adjacent to the third annular offset, and the fourth annular offset is in the second circumferential direction.

90. The electric rotational machine of any one of claims 73-89, wherein the first plurality of adjacent teeth have a first plurality of teeth widths, respectively.

91. The electric rotational machine of claim 90, wherein the first plurality of adjacent teeth and the first plurality of teeth widths comprise a set of at least three adjacent teeth having tooth widths that are all different relative to each other.

92. The electric rotational machine of claim 90, wherein the first plurality of adjacent teeth and the first plurality of teeth widths comprise a set of at least four adjacent teeth having tooth widths that are all different relative to each other.

93. The electric rotational machine of any one of claims 90-92, wherein: the first plurality of adjacent teeth comprises a first tooth, a second tooth, and a third tooth, the second tooth located between the first tooth and the third tooth, the second tooth located immediately adjacent to both of the first tooth and the third tooth;the first plurality of teeth widths comprises a first tooth width, a second tooth width, and a third tooth width, respectively corresponding to the first tooth, the second tooth, and the third tooth; and the first tooth width is greater than the second tooth width, and the third tooth width is greater than the second tooth width.

94. The electric rotational machine of any one of claims 90-92, wherein: the first plurality of adjacent teeth comprises a first tooth, a second tooth, a third tooth, and a fourth tooth, the second tooth located between the first tooth and the third tooth, the third tooth located between the second tooth and the fourth tooth, the second tooth located immediately adjacent to both of the first tooth and the third tooth, the third tooth located immediately adjacent to both of the second tooth and the fourth tooth; the first plurality of teeth widths comprises a first tooth width, a second tooth width, a third tooth width, and a fourth tooth width, respectively corresponding to the first tooth, the second tooth, the third tooth, and the fourth tooth; and the first tooth width is greater than the second tooth width, and the third tooth width is greater than each of the second tooth width and the fourth tooth width.

95. The electric rotational machine of any one of claims 90-92, wherein: the first plurality of adjacent teeth comprises a first tooth, a second tooth, and a third tooth, the second tooth located between the first tooth and the third tooth, the second tooth located immediately adjacent to both of the first tooth and the third tooth; the first plurality of teeth widths comprising a first tooth width, a second tooth width, and a third tooth width, respectively corresponding to the first tooth, the second tooth, and the third tooth; and the first tooth width is less than the second tooth width, and the third tooth width is less than the second tooth width.

96. The electric rotational machine of any one of claims 90-95, wherein all of the first plurality of teeth widths are different from each other.

97. The electric rotational machine of any one of claims 90-96, wherein, for each respective tooth of the first plurality of adjacent teeth, one of the two following conditions is true: the respective tooth is immediately adjacent two other teeth of the first plurality of teeth which are both wider than the respective tooth; or the respective tooth is immediately adjacent two other teeth of the first plurality of teeth which are both narrower than the respective tooth.

98. The electric rotational machine of any one of claims 73-97, wherein the first plurality of adjacent teeth form at least part of a first half phase, and a second plurality of adjacent teeth form at least part of a second half phase, the second plurality of adjacent teeth having similar tooth positions as the first plurality of adjacent teeth.

99. The electric rotational machine of claim 98, wherein the first half phase and the second half phase are both part of a first stator phase, and a first coil is located axially between the first half phase and the second half phase such that an AC signal within the first coil causes polarization of the first plurality of adjacent teeth to be opposite that of the second plurality of adjacent teeth.

100. The electric rotational machine of claim 98, wherein the first half phase and the second half phase are part of different stator phases of the stator.

101. The electric rotational machine of any one of claims 98-100, wherein the first plurality of adjacent teeth form all teeth of the first half phase and the second plurality of adjacent teeth form all teeth of the second half phase.

102. The electric rotational machine of any one of 73-101, wherein the first plurality of adjacent teeth are all part of a ring segment.

103. The electric rotational machine of claim 102, wherein at least one lamination spans a circumferential width of the ring segment.

104. The electric rotational machine of claim 103, wherein a lamina forms at least part of each tooth of the first plurality of adjacent teeth.

105. The electric rotational machine of any one of claims 102-104, wherein the ring segment is one of a plurality of ring segments of the stator, each ring segment of the plurality of ring segments having similar tooth positions as the ring segment.

106. The electric rotational machine of claim 105, wherein the plurality of ring segments form one flux ring.

107. The electric rotational machine of claim 105, wherein the plurality of ring segments are located in different stator phases of the stator.

108. The electric rotational machine of any one of claims 1-107, wherein the electric rotational machine is an electric motor.

109. The electric rotational machine of any one of claims 1-107, wherein the electric rotational machine is an electric generator.

110. The electric rotational machine of any one of claims 1-109, wherein the first plurality of teeth are offset in a sixth-phase offset.

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