Laminated stator tooth comprising soft magnetic composition

Abstract

A composite stator tooth for a stator of an electric machine is described. The stator tooth includes a soft magnetic composite material and a plurality of stacked stator laminates. The shape of the magnetic composite material is complementary to a shape of the plurality of stacked stator laminates. Methods of making and using the stator tooth are also described.

Description

Laminated Stator Tooth Comprising Soft Magnetic CompositionCROSS-REFERENCE TO RELATED APPLICATION

[0001] This disclosure claims the benefit of U.S. Provisional Application No. 63 / 614,335, filed December 22, 2023, the entire contents of which is incorporated herein by reference.FIELD OF INVENTION

[0002] This disclosure generally relates to systems and methods of making and using soft magnetic compositions.INTRODUCTION

[0003] Soft magnetic composites (SMC) may be used to provide materials having competitive magnetic properties, such as, better relative permeability and magnetic saturation as well as high electrical resistivity, for example. The high resistivity makes these materials attractive in low loss applications, particularly at high frequencies. Unlike conventional laminated materials, the magnetic permeability is isotropic and the isotropy of properties removes the constraints on design imposed on conventional electrical machines by lamination. SMCs may include a ferromagnetic particle coated with an insulating material which produces the high bulk electrical resistivity. As well, the SMC precursor powder may be formulated to produce a high density product when cold or warm compacted.

[0004] SMCs may be used to fully or partially replace laminates in certain applications. By replacing the laminates, the SMCs may reduce the cost and enhance productivity by decreasing the scrap generation problems accompanying laminates. A key to achieving this goal, however, is the availability of a SMC material components with lamination materials.

[0005] Accordingly, more efficient and / or cost effective systems and methods of making and using SMC material cores in conjunction with lamination cores may be desirable.DESCRIPTION OF THE DRAWINGS

[0006] This disclosure may be better understood by reference to the accompanying drawing figures, in which:

[0007] FIGS. 1A-C include laminations.

[0008] FIGS. 2A-C include methods of making laminations.

[0009] FIGS. 3A-C include methods of making stators.

[0010] FIGS. 4A-B include stators according to the invention

[0011] FIGS. 5A-B include a stator tooth.

[0012] FIGS. 6A-B include a stator tooth comprising opposing exterior SMC portions and an inner lamination portion according to the invention.

[0013] FIG. 7 and FIG. 8 include method steps to manufacture a stator tooth comprising opposing exterior SMC portions and an inner lamination portion according to the invention.

[0014] FIGS. 9A-D include examples of yokeless axial flux tooth designs manufactured according to the present invention.

[0015] FIGS. 10A-D include examples of a stator tooth comprising opposing exterior SMC portions and an inner lamination portion according to the invention.

[0016] FIGS. 11A-E include a stator tooth comprising a molded SMC core wrapped with lamination material according to the present invention. The method of making the stator tooth may comprise molding the SMC core and wrapping the lamination material around the SMC core. Alternatively, a pre-wound lamination material may be positioned over the SMC core, or a pre-wound lamination material may be heated sufficiently to expand the lamination material (without material deformation or loss of properties), and positioned over the SMC core and then cooled. This may provide more intimate contact between the SMC core and the lamination material.

[0017] FIG. 12 includes a stator tooth comprising two separate pieces of a laminated stack to take advantage of the material properties associated with lamination steels while removing adverse issues associated with the orientation of the laminating stack. Here, the outside lamination stack may facilitate transmitting the magnetic flux inward to the center lamination stack where the flux may flow uninterrupted in the desired direction for the motor function.

[0018] FIGS. 13A-E include examples of yokeless axial flux tooth designs manufactured according to the present invention.

[0019] FIG. 14 include a toroid used to generate electric motor data described in FIGS. 15-17. The toroid includes two outer SMC portions (0.075” tall) and one lamination portion (0.110” tall), with an ID of 1.260” and OD of 1.570”. The SMC material has a permeability of 650, while the laminations reach 5,000, compared to the standard range for current SMCs approximately (300-850) and laminations approximately (1 ,500-20,000). This combination yields a permeability over 2,000, indicating a significant enhancement as evidenced by the DC BH curve data and AC core loss data.

[0020] FIG. 15 includes DC BH curve data for the toroid illustrated in FIG. 14.

[0021] FIG. 16 includes AC core loss data for the toroid illustrated in FIG. 14.

[0022] FIG. 17 includes data for the toroid illustrated in FIG. 14.DETAILED DESCRIPTION

[0023] This disclosure generally describes systems and methods of making and using a stator comprising of SMC and a lamination materials comprising a plurality of layers. It is understood, however, that this disclosure also embraces numerous alternative features, aspects, and advantages that may be accomplished by combining any of the various features, aspects, and / or advantages described herein in any combination or sub-combination that one of ordinary skill in the art may find useful. Such combinations or sub-combinations are intended to be included within the scope of this disclosure. As such, the claims may be amended to recite any features, aspects, and advantages expressly or inherentlydescribed in, or otherwise expressly or inherently supported by, this disclosure. Further, any features, aspects, and advantages that may be present in the prior art may be affirmatively disclaimed. Accordingly, this disclosure may comprise, consist of, consist essentially or be characterized by one or more of the features, aspects, and advantages described herein. As used herein, the term “and / or” includes any and all combinations of one or more of the associated listed items.

[0024] All numerical quantities stated herein are approximate, unless stated otherwise. Accordingly, the term “about” may be inferred when not expressly stated. The numerical quantities disclosed herein are to be understood as not being strictly limited to the exact numerical values recited. Instead, unless stated otherwise, each numerical value stated herein is intended to mean both the recited value and a functionally equivalent range surrounding that value. At the very least, and not as an attempt to limit the application of the doctrine of equivalents to the scope of the claims, each numerical value should at least be construed in light of the number of reported significant digits and by applying ordinary rounding processes. Typical exemplary degrees of error may be within 20%, 10%, or 5% of a given value or range of values. Alternatively, the term “about” refers to values within an order of magnitude, potentially within 5- fold or 2-fold of a given value. Notwithstanding the approximations of numerical quantities stated herein, the numerical quantities described in specific examples of actual measured values are reported as precisely as possible. Any numerical values, however, inherently contain certain errors necessarily resulting from the standard deviation found in their respective testing measurements.

[0025] All numerical ranges stated herein include all sub-ranges subsumed therein. For example, a range of “1 to 10” or “1-10” is intended to include all sub-ranges between and including the recited minimum value of 1 and the recited maximum value of 10 because the disclosed numerical ranges are continuous and include every value between the minimum and maximum values. Any maximum numerical limitation recited herein is intended to include all lower numerical limitations. Any minimum numerical limitation recited herein is intended to include all higher numerical limitations.

[0026] In the following description, certain details are set forth in order to provide a better understanding of various features, aspects, and advantages the invention. However, one skilled in the art will understand that these features, aspects, and advantages may be practiced without these details. In other instances, well-known structures, methods, and / or processes associated with methods of practicing the various features, aspects, and advantages may not be shown or described in detail to avoid unnecessarily obscuring descriptions of other details of the invention.

[0027] The terminology used herein is for the purpose of describing particular examples only and is not intended to be limiting. As used herein, the singular forms “a”, “an”, and “the” may be intended to include the plural forms as well, unless the context clearly indicates otherwise. The terms “comprises”, “comprising”, “including”, “having”, and “characterized by”, are inclusive and therefore specify the presence of stated features, elements, compositions, steps, integers, operations, and / or components, but do not preclude the presence or addition of one or more other features, integers, steps, operations, elements, components, and / or groups thereof. Although these open-ended terms are to be understood as a non-restrictive term used to describe and claim various aspects set forth herein, in certain aspects, the term may alternatively be understood to instead be a more limiting and restrictive term, such as “consisting of’ or “consisting essentially of.” Thus, for any given embodiment reciting compositions, materials, components, elements, features, integers, operations, and / or process steps, described herein also specifically includes embodiments consisting of, or consisting essentially of, such recitedcompositions, materials, components, elements, features, integers, operations, and / or process steps. In the case of “consisting of’, the alternative embodiment excludes any additional compositions, materials, components, elements, features, integers, operations, and / or process steps, while in the case of “consisting essentially of’, any additional compositions, materials, components, elements, features, integers, operations, and / or process steps that materially affect the basic and novel characteristics are excluded from such an embodiment, but any compositions, materials, components, elements, features, integers, operations, and / or process steps that do not materially affect the basic and novel characteristics can be included in the embodiment.

[0028] As used herein, the term “motor” refers to any device that changes a form of energy into mechanical energy to produce motion. The term “motor” includes, but is not limited to, an axial flux motor, a radial flux motor, a transverse flux motor, a direct current electromagnetic motor, an alternating current electromagnetic motor, an electric motor, a permanent magnet synchronous motor, and the like. The motor may be suitable for a vehicle, automobile, motorcycle, truck, ship, plane, train, hand tool, house hold appliance, ariel or ground, or amphibious drone, lawn and garden tools, wind turbines, water turbines, or gas powered generator and any other motorized device. The motor may comprise an electric motor.

[0029] Any method steps, processes, and operations described herein are not to be construed as necessarily requiring their performance in the particular order discussed or illustrated, unless specifically identified as an order of performance. It is also to be understood that additional or alternative steps may be employed, unless otherwise indicated.

[0030] A motor may include a stator or a plurality of stator cores that are circumferentially arranged about a rotor shaft. The stator cores may comprise soft magnetic composite (SMC) material that is capable of being formed into a variety of shapes. Soft magnetic composite materials are described in US Patent Publication No. 20240371552. SMCs may comprise iron powder particles coated with an electrically insulating layer to reduce / prevent electrical conductivity among the iron powder particles.

[0031] In general, SMC materials may be formed by pressing powder, such as iron powder and / or a mixture of powders, for example, and then heating. A die may be filled with SMC powder with a fill of 1 .9 to 3:1 . For a one inch part, the fill may be 1 .9 inches to 3 inches depending on the desired final part density. The part may then be pressed with a compaction pressure of 5 to 100 tons per square inch depending on desired part density and features being formed. In certain aspects, a compaction pressure between 45 and 50 TSI may be used to achieve a part density in the range of 7.1 g / cc3to 7.5 g / cc3while minimizing the risk of tool failure. Once the part has been pressed, it may be heated to burn away the material lubricant that may have been added to the material to aid in part ejection from the die, oxidize any oxide precursor that may aid in electrical resistivity, and / or create the calcination environment for a ferrite coating and / or relax the cold work introduced during the compaction step. These stresses and defects may hinder the movement of magnetic domains, which may impact the magnetic properties of iron. By heating the material, these internal stresses may be relieved, and the metal may become less rigid, facilitating easier domain movement. The thermal relaxation temperature may be from 800°F to 2200T. The closer the component’s temperature to 1550°F, the more effective the heating step may be at annealing the component; however, care should to taken so that the component is not heated above the temperature that can be survived by the specific SMC coating. In certain aspects, the temperature of the component may not exceed 1000°F without causing damage to the SMC coating.

[0032] SMC (soft magnetic composite) powder may comprise a high purity iron powder coated with an oxide precursor and / or an electrically insulated coating or pre calcination coating. The powder may be used with conventional powder metal press compaction to form net shape or near net shape components. After the component is pressed, it then goes through a thermal process, which in some cases turns the oxide precursor into an electrically insulating coating. During the thermal process, the component may be annealed, or partially annealed, to remove the cold work introduced during the compaction step. In many cases, the electrically insulating coating may not survive a temperature high enough to fully anneal the iron and fully remove the cold work introduced during the compaction step.

[0033] The SMC may be formed by an insulated material, such as pure iron powder particles that are coated with a very thin, electrically insulated layer. The SMC may provide some advantages over stators that are made with a traditional lamination stack technique. The SMC may be formed into shapes that are not possible with laminations and may be created to produce isotropic 3-D electro-magnetic flux patterns. The isotropic properties of the SMC allow the material to carry magnetic flux in all directions as opposed to a laminated stack. The high resistivity of the SMC allows easier design to precisely direct the flow of current within the system. Additionally, near net shape processing may be used to form the SMC, eliminating waste and saves cost. Additional advantages of using SMC materials to form the stator may include the minimization of hysteresis and eddy current losses over a wide range of frequencies and lower labor cost and higher quality due to powder metallurgy processing.

[0034] One of the benefits of SMC materials and processing may be the unique shape making capability of the powder metal processing. The three-dimensional shape making coupled with the isotropic SMC material may allow for the use of this material in designs that require or benefit from a 3D flux path. The three-dimensional shape may improve the effectiveness of the copper winding. By being able to have curved geometry, the copper winding may be wound very tightly without the undesirable airgaps typically seen when wrapping around a corner in conventional processes.

[0035] One of the benefits of SMC materials and processing may be high induction levels, such as 1.9 T or higher, for example. This is a calculation of density. Without wishing to be bound to any particular theory, SMC materials may be 99.5% pure iron such that a saturation calculation may be described as part density I 7.85 (theoretical iron full density) X 2.15 (saturation of pure iron), For example, an SMC component having 7.4 g / cc3may be 7.4 / 7.85 = 0.9426 X 2.15 = 2.026 T. Without wishing to be bound to any particular theory, the saturation may be related to the maximum amount of magnetic field that may be pushed through an iron core. The higher the induction level, the more max torque that may be applied to a motor or actuator.

[0036] In the case of a 3% silicon lamination steel, the base material may have a saturation flux density of about 1 .8 T. The saturation induction may be reduced depending on stack density. For example, when a stack density is 95%, then the saturation may be represented as 1 .8 T X 0.9 = 1 .62 T.

[0037] One of the benefits of SMC materials and processing may be low eddy current generation. In iron cores for electric motors, heat buildup may be a major loss factor that limits power. Eddy currents in the iron core may be a major contributing factor to heat buildup. Eddy currents may be described as loops of electrical current induced within conductors by a changing magnetic field in the conductor according to Faraday’s law of induction. Eddy currents flow in closed loops within conductors, in planes perpendicular to the magnetic field. One way to reduce eddy currents may be to reduce the cross section of the ironcore. In the case of SMC materials, the cross section may be small based on the size of the powder particle being used in the SMC materials.

[0038] The SMC materials may be characterized by at least one of the following benefits: unique shape making capability; 3D flux path; reduction in eddy current iron losses; high saturation induction; and more effective use of copper end turns.

[0039] Two contributing loss factors of an iron core may be hysteresis losses and eddy current losses. Although conventional SMC materials may have low eddy current losses, they may have high hysteresis losses because they cannot be annealed after compaction to a temperature high enough to fully remove the cold work that may introduced during the compaction process.

[0040] Conventional SMC materials may have reduction in magnetic permeability because the magnetic flux has to jump from particle to particle rather then being able to travel straight through a lamination sheet. This reduction in permeability may cause a motor made from SMC materials to be less effective at low induction levels.

[0041] Conventional SMC materials may suffer from at least one of high hysteresis losses; low magnetic permeability; and low mechanical strength.

[0042] Referring to FIG. 1 , when manufacturing a motor stator having laminations, the layout of the laminations may facilitate the flow of magnetic flux in the direction of the lamination sheets but reduce / impede the flow of magnetic flux in the direction against the lamination sheets. Accordingly, an axial flux stator made from laminations may use progressive stamping or roll, machine, and anneal as illustrated in FIG 1. In contrast, using powder metal and the SMC material allows the geometry to be molded in a very cost-effective manner and have a 3D flux path.

[0043] A method of constructing motor stator components according to the present invention may synergistically combine the use of soft magnetic composite (SMC) materials and lamination materials. When only lamination materials are used to create a motor stator, many design limitations dictate the geometry possible and may have dramatic cost implications. When only SMC material are used to create a motor stator, although design flexibility may be enhanced, magnetic performance may be limited. The hybrid construction according to the present invention capitalizes on the unique advantages of each material system. The SMC materials have excellent 3D shape capabilities, enable the creation of complex geometries in the stator design, a feat that is challenging to achieve with conventional laminations. This flexibility in design allows for an optimization of 3D magnetic flux paths, enhancing the motor’s operational efficiency.

[0044] Conversely, the laminated materials, traditionally favored for their superior magnetic properties, including high permeability and low hysteresis losses, may be utilized in areas of the stator where these properties are desirable. The incorporation of SMC materials may contribute to a reduction in eddy current losses, especially beneficial in variable speed drive applications, where such losses may be more pronounced in laminated cores.

[0045] The combination of these materials may allow for improved thermal management within the motor. The differing thermal conductivity properties of laminations and SMCs may be strategically employed to enhance cooling and heat distribution. From a manufacturing standpoint, this hybridapproach may offer a reduction in complexity and cost. The SMCs may be used in parts of the stator that are intricate to manufacture with laminations, leading to a more streamlined production process.

[0046] The present invention may not only facilitate customization for specific motor applications, addressing various performance demands, but also may achieve an optimal balance in terms of weight and size of the motor. The use of SMCs may contribute to a lighter motor design, while the strategic placement of laminations maintains performance. The present invention represents a significant advancement in motor stator component design, merging the benefits of both SMC and lamination materials to achieve a synergistic, superior, cost-effective, and efficient solution.

[0047] SMC materials are highly versatile in terms of shape and may be pressed into complex three- dimensional geometries that are difficult or impossible to achieve with laminations. This capability allows for more innovative stator designs, potentially improving motor efficiency by optimizing the magnetic flux paths.

[0048] The SMC may comprise powder magnetic materials that are sintered metals formed by mixing a magnetic metallic powder, such as an iron powder, and a resin, molding the mixture by a press, and heating to harden (that is, sintering) the molded mixture. The resin may to establish insulations between particles of the magnetic metallic powder. The SMC may comprise, based on total weight of the composite: 95 to 99 weight percent iron; 0.1 to 5 weight percent of at least one resin, such as an electrically insulating material and / or lubricant; and a balance of incidental impurities. The electrically insulating material may comprise an electrically insulating oxide. The electrically insulating material may comprise at least one of phosphorous acid, phosphorous oxide, and silica oxide. The organic lubricant may comprise at least one of ethylene bis-stearamide, zinc stearate, or lithium stearate, for example. The balance of the composite may comprise incidental impurities, such as copper, aluminum, silicon, tungsten, and cobalt and other materials derived from the starting materials and / or through processing.

[0049] Referring to FIG. 2 and FIG. 6, a yokeless axial flux motor is illustrated. The yokeless axial flux motor may be characterized by a similar flux orientation as a conventional axial flux motor even though it lacks a yoke, or back iron, and uses a rotor on both the top and the bottom of the stator segments. The yokeless axial flux motor may be difficult to manufacture.

[0050] Referring to FIG. 3, a conventional single tooth and a single tooth made from laminations are illustrated. The lamination may be molded into the SMC component, or glued or assembled as distinct components. Each lamination may have a unique geometry, which creates difficult manufacturing situations. However, this motor design may provide high torque density when made from SMC material.

[0051] Referring to FIG. 4, a yokeless axial flux single tooth according to the present invention may comprise a SMC portion and a lamination portion. Combining the two material systems of laminations and SMC materials may provided at least one advantage over conventional devices and methods. The SMC may provide the three-dimensional geometry where desirable and the lamination material may provide superior magnetic permeability and reduction of hysteresis losses. In other words, the method of making a yokeless axial flux single tooth according to the present invention may allow the unique geometry that is desirable for a yokeless axial flux motor design to be made using a cost-effective process without sacrificing as much magnetic performance.

[0052] Each stator may comprise a stator core and a stator winding that is wound around the stator core. The stator cores may be made from a magnetically permeable, resistive material while the stator windings may be made from an electrically conductive material such as copper, aluminum, or gold. Each of the stator cores may be attached to an end housing so that the stator cores remain stationary during operation of an axial flux motor.

[0053] The stator may comprise an interior potion comprising laminations and an exterior portion comprising SMC materials. The interior portion may be intermediate a first exterior portion and a second exterior portion. The interface between the interior portion and exterior portion may extend in a radial direction and / or an axial direction. An insulation layer may be arranged between the interior portion and exterior portion. A motor may comprise a plurality of rotators and stators. The stators may comprise at least one stator comprising laminations and SMC materials. The stator may comprise a plurality of windings wrapped about a stator core. The windings may comprise copper, copper alloys, aluminum, aluminum alloys or other suitable winding materials. A diverse array of lamination materials may be utilized, specifically tailored to enhance the performance and efficiency of motor stators. For example, silicon steel, also known as electrical steel, has suitable magnetic properties and may be used. Available in different grades, electrical steel may be enriched with silicon content from 0.3% and up to 6%, based on weight, enhancing electrical resistivity and reducing eddy current losses, an important factor for high- frequency motor operation. Depending on the desired motor design and magnetic flux properties, both grain-oriented and non-grain-oriented types of silicon steel may be employed.

[0054] Electrical steel sheets may be stamped and then stacked together to make laminations to form the core of a stator tooth. Electrical steel may comprise iron alloys that have favorable magnetic properties for electric machine construction. Iron alloys suitable for electrical steel may include a percentage of silicon. Electrical steel sheet may have various thicknesses, typically in the range from 0.65 mm to 0.1 mm.

[0055] Electrical steel laminates may be coated on one or both surfaces to increase electrical resistance between the laminations and reduce eddy current loss. The coating may provide resistance to corrosion or rusting. ASTM A9760-3 classifies the different types of coating for electrical steels from CO to C6. The coating materials may be non-ferromagnetic and non-ferrimagnetic with relative magnetic permeability pr= 1 . In other words, the coating material may be treated as an airgap in the lamination stack, which leads to very low permeability along the stack’s normal direction and have low saturation flux density.

[0056] Additionally, nickel-iron alloys, such as PERMALLOY, having a nickel content from 20-80%, based on weight, may be incorporated for the superior magnetic permeability and low coercivity. These properties may make nickel-iron alloys particularly beneficial for motor stators having minimal hysteresis loss, thereby improving the motor’s precision and efficiency. Cobalt-iron alloys, such as SUPERMENDUR, having high cobalt content, may be included when exceptional magnetic saturation is desirable, making them useful for high-power motor stator applications.

[0057] The laminations in motor stators may have various thicknesses to suit specific operational needs. Ultra-thin laminations, having a thickness from 0.05 mm to 0.2 mm, such as 0.05-0.1 mm or 0.1- 0.2 mm, for example, may be useful for stators in high-frequency motors to minimize eddy current losses. Standard thickness laminations, having a thickness from greater than 0.2 mm to 0.5 mm, such as 0.2- 0.35 mm or 0.35-0.5 mm, for example, may provide a balance of performance, manufacturing ease, andcost. For motor stators operating at lower frequencies or where additional mechanical strength is desirable, thick laminations, having a thickness greater than 0.5 mm may be used.

[0058] This selection of lamination materials and their respective thicknesses may provide motor stators precisely tailored for a variety of applications. Factors such as the motor’s operating frequency, desired magnetic properties, mechanical strength, and thermal performance may be considered in selecting the appropriate material and thickness.

[0059] An insulation layer may be arranged between a plurality of laminations. The shape of the laminations may be a four sided rectangle. Additional geometry may be desirable to optimize the shape for motor performance. Special cut out features may be added to allow for a mechanical interlocking feature between the SMC portion and laminated portion on the stator tooth. Features may also be added to the lamination portion to aid in the manufacturing process, such as, for example groves to hold the stack straight if the lamination is being molded with the SMC material. Features may also be added to help during a gluing process to bond the lamination and SMC components together. Referring to FIG. 3, in certain applications, each sheet of lamination material may be identical geometry in a stator tooth, simply stacked on top of one another to form the 3D-shape of the lamination portion of the stator tooth.

[0060] EXAMPLES

[0061] The SMC as well as methods of making and using the same described herein may be better understood when read in conjunction with the following representative examples. The following examples are included for purposes of illustration and not limitation.

[0062] Methods for manufacturing a motor stator, suitable for various motor designs, such as axial flux, yokeless axial flux, transverse flux, and radial flux, for example, are described. The methods may utilize a combination of soft magnetic composite (SMC) and lamination materials to produce motor stators that are higher performing, more cost-effective, and / or both.

[0063] Referring to FIG. 4 and FIG. 5, a method of manufacturing a yokeless axial flux stator tooth may comprise integrating the lamination stack during the molding process. The lamination stack may be secured in place within the powder metal die tooling and / or maintained in position by a center pin. The die cavity may be filled with uncompacted SMC powder on both sides of the lamination stack by moving a fill shoe over the die. Atop punch may compress the powder in the die cavity, with the pin enabling the lamination stack to descend synchronously with the powder compaction, to generate a fully compacted part. The bottom punch and pin may provide its stability during ejection from the die, producing a yokeless axial flux core segment comprising both SMC and lamination materials.

[0064] A method of manufacturing a yokeless axial flux stator tooth may comprise joining two SMC core halves to a central lamination stack. Each of the SMC core halves may comprise the same or different geometries. The geometry may be complex geometries. The SMC core halves may be molded separately and then attached to a lamination stack via mechanical interlock and / or adhesive. The lamination assembly may comprise a three-dimensional rectangle or may include additional features for mechanical interlocking. The lamination assembly may be held together by the motor housing and / or bonded with adhesive for enhanced mechanical strength before winding with a conductive material, referred to as the coil. The SMC and lamination material may be bounded together with a magneticallyconductive adhesive to provide improved magnetic performance by creating a magnetic transition between the lamination material and the SMC material.

[0065] Methods of making the lamination stack may comprise gluing, welding, and / or stamping and indentation to ensure the laminations are oriented parallel to the motor’s axis of rotation. This orientation is desirable for optimizing magnetic performance in axial or yokeless axial flux designs. Optimal magnetic performance may be achieved when the lamination layers are aligned parallel to the motor’s rotational axis and perpendicular to the coil windings on the stator tooth. The coil windings form a loop around the stator tooth in which the inner and outer diameters may represent the end turns, and the sides of the tooth may represent the other two sides of the winding.

[0066] For radial flux designs using laminations having SMC components, the laminations may be oriented perpendicular to the axis of rotation for the desired magnetic performance.

[0067] A method for manufacturing an SMC and laminated axial flux stator tooth may comprise wrapping thin lamination material (having a thickness less than 0.1 mm) around a finished SMC component to generate a smooth surface for coil windings. This may provide a tight wrap having minimal risk of damaging the winding material’s insulation. When the highest permeability magnetic material is closest to the electrical conductor, the magnetic performance of the stator and motor efficiency may be improved.

[0068] Further clarification on the lamination orientation and detailed descriptions of these manufacturing methods may be provided in the accompanying images and diagrams.

[0069] Referring to FIG. 12, in the development of radial flux electric motor stators, one of the advantages of using laminations is the ability to form the complete stator geometry from a single electrical steel lamination geometry. This process involves transforming a thin steel stamping into a three- dimensional stator by stacking multiple thin sheets. These thin sheets can range in thickness from about 0.05 mm to 1 mm. This method may be particularly efficient for radial flux stators as it uses only one stamping tool and the laminations are naturally aligned in a direction that facilitates the effective transmission of magnetic flux in relation to the coil winding.

[0070] However, the fabrication of yokeless axial flux stators presents different challenges. If a single stamping tool is utilized, the geometry is typically limited to a basic rectangle, which may not be optimal. Additionally, in such a configuration, the lamination sheets might not be stacked in the most effective orientation for the transmission of magnetic flux, which is crucial for efficient interaction with the motor's rotor magnetic field for torque generation.

[0071] An economical approach to constructing a yokeless axial flux stator tooth, while ensuring the correct orientation of lamination sheets, involves joining two separate lamination stacks into a single component. The first stack, forming the interior of the stator, would be rectangular with lamination sheets aligned parallel to the axis of rotation. The second stack would form the outer part of the stator and would be shaped like a sector — a pie-slice-like portion of a circle, enclosed by two radii and an arc, representing a fraction of the circle's total area. This could also resemble a trapezoid with radii connecting two sides of equal length.

[0072] By adopting this method, only two sets of stamping tools are required. The inner and outer stator stacks are assembled together using a minimal interference press fit, ranging from 0.0001 inches to 0.010 inches. This press fit minimizes magnetic conducting interference between the inner and outer stacks. The outer stator stack captures the magnetic flux from the coil and transmits it to the inner stack, which then channels it towards the rotor. At the rotor, the magnetic field interacts with the rotor's magnetic field to generate rotational torque.

[0073] The method of manufacturing a stator tooth according to the present invention may comprise adhering a plurality of SMC components and SMC / lamination components together. Without wishing to be bound to any particular theory, it is believed that the orientation of the segment the SMC component may impact the magnetic performance. When the SMC component is split perpendicular to the direction of the magnetic flux flows, there may be a drop in magnetic performance. Alternatively, when the SMC component is split parallel to the direction of the magnetic flux flows, there may be no or reduced decrease in magnetic performance.

[0074] The chart below shows a comparison of a toroid SMC component that was segmented into two segments and four segments and then put back together with different adhesives. One adhesive included magnetically permeable particles while the other adhesive lacked magnetically permeable particles.

[0075] Without wishing to be bound to any particular theory, using conventional thermally set epoxy, in two segments there was a reduction in the magnetic permeability of 18.7% in the magnetic circuit while with four segments there was a reduction of magnetic permeability of 36.5% in the magnetic circuit.

[0076] When using a thermally set epoxy including magnetically permeable material, in two segments there was a reduction in the magnetic permeability of 5.5% while with four segments there was a reduction of magnetic permeability of 12.1 % in the magnetic circuit, which represented a substantial improvement.

[0077] FIG. 10 illustrates stator tooths manufactured according to the present invention.

[0078] Aside from the magnetic performance improvements in the component there are also some other benefits. One of them is better length control.

[0079] Referring to FIG. 11 E, the powder metal process has process variation in the direction that the parts may be molded of about ± 0.003 inches so by stacking two parts on top of one may results in a total of ± 0.006 inches of total length variation in the molded and assembled direction.

[0080] In contrast, if the part is split in the other direction, the more important length dimension, will be formed by the die ion the compaction process and will have very little process variability, for example, about ± 0.0005 inches. The variability will instead be in the opposite direction which will have less impact on motor performance.

[0081] Another benefit to splitting in this direction may be that the magnets from the rotors exert a pulling force parallel to the glue joint. For this reason, the glue may not experience high forces on the glue joint during motor operation as opposed to splitting the tooth in the other direction, the rotor would constantly be exerting a force trying to pull the glue joint apart.

[0082] Referring to FIG. 10G, alternatively this component split may also be split in to two SMC pieces and a lamination stack. It may also be desirable to add a mechanical interlocking feature to the lamination and SMC component to reduce / prevent the rotor forces from moving the lamination component out of the SMC component.

[0083] Referring to FIGS. 15-17, conventional SMC components may have a permeability ranging from 300 to 850, while conventional laminations may have a permeability ranging from 1 ,500 to 20,000 or more. The combination of SMC and lamination material according to the present invention may provide a permeability exceeding 2,000 is easily attainable. The DC BH curve and the AC core loss data illustrated in FIGS. 15-17 was observed when testing a toroidal test specimen made from SCM material top and bottom portions and lamination inner material as pictured above.

[0084] The following aspects are described in this disclosure:

[0085] Aspect 1 . A laminated stator tooth comprising a lamination and a soft magnetic composition as described in the specification and accompanying drawings.

[0086] Aspect 2. A method of making a laminated stator tooth comprising a lamination and a soft magnetic composition as substantially described in the specification and accompanying drawings.

[0087] Aspect 3. A method of using a laminated stator tooth comprising a lamination and a soft magnetic composition as substantially described in the specification and accompanying drawings.

[0088] Aspect 4. An article of manufacture comprising a laminated stator tooth comprising a lamination and a soft magnetic composition as described in the specification and accompanying drawings.

[0089] Aspect 5. A laminated stator tooth comprising a plurality of lamination sheet stack (and lacking a soft magnetic composition), wherein the plurality of lamination sheet stack comprise an outer lamination sheet stack and an inner lamination sheet stack, wherein the outer lamination sheet stack captures the magnetic flux from the coil and transfers the magnetic flux to the inner lamination sheet stack, and wherein the inner lamination sheet stack is oriented to transmit the magnetic flux to interact with the motor rotor magnetic field as described in the specification and accompanying drawings.

[0090] Aspect 6. A method of making a laminated stator tooth comprising a plurality of lamination sheet stack (and lacking a soft magnetic composition), wherein the plurality of lamination sheet stack comprise an outer lamination sheet stack and an inner lamination sheet stack, wherein the outer lamination sheet stack captures the magnetic flux from the coil and transfers the magnetic flux to the inner lamination sheet stack, and wherein the inner lamination sheet stack is oriented to transmit the magnetic flux to interact with the motor rotor magnetic field as described in the specification and accompanying drawings.

[0091] Aspect 7. A method of using a laminated stator tooth comprising a plurality of lamination sheet stack (and lacking a soft magnetic composition), wherein the plurality of lamination sheet stack comprise an outer lamination sheet stack and an inner lamination sheet stack, wherein the outer lamination sheet stack captures the magnetic flux from the coil and transfers the magnetic flux to the inner lamination sheet stack, and wherein the inner lamination sheet stack is oriented to transmit the magnetic flux to interact with the motor rotor magnetic field as described in the specification and accompanying drawings.

[0092] Aspect 8. An article of manufacture comprising a plurality of lamination sheet stack (and lacking a soft magnetic composition), wherein the plurality of lamination sheet stack comprise an outer lamination sheet stack and an inner lamination sheet stack, wherein the outer lamination sheet stack captures the magnetic flux from the coil and transfers the magnetic flux to the inner lamination sheet stack, and wherein the inner lamination sheet stack is oriented to transmit the magnetic flux to interact with the motor rotor magnetic field as described in the specification and accompanying drawings.

[0093] Aspect 9. A composite stator tooth for a stator of an electric machine, the stator tooth comprising: a lamination portion comprising a plurality of stacked stator laminates; and a SMC portion comprising a soft magnetic composite material, wherein a shape of the SMC portion is complementary to a shape of the lamination portion to form the composite stator tooth.

[0094] Aspect 10. The stator tooth of any of the foregoing aspects, wherein the lamination portion comprises an interior portion of the stator tooth and the SMC portion comprises an exterior portion of the stator tooth; or wherein the SMC portion comprises an interior portion of the stator tooth and the lamination portion comprises an exterior portion of the stator tooth.

[0095] Aspect 11 . The stator tooth of any of the foregoing aspects, wherein the SMC portion comprises a first SMC portion and a second SMC portion, and the lamination portion is intermediate the first SMC portion and the second SMC portion.

[0096] Aspect 12. The stator tooth of any of the foregoing aspects, wherein the stator tooth is shaped to have a long axis and a short axis orthogonal to the long axis, wherein the long axis is parallel to a direction of magnetic flux, and wherein the lamination portion is intermediate the first SMC portion and the second SMC portion along the long axis.

[0097] Aspect 13. The stator tooth of any of the foregoing aspects, wherein the plurality of stacked stator laminates are stacked in a direction along the short axis.

[0098] Aspect 14. The stator tooth of any of the foregoing aspects, wherein the plurality of stacked stator laminates comprise at least a portion of a front surface of the stator tooth and at least a portion of a rear surface of the stator tooth.

[0099] Aspect 15. The stator tooth of any of the foregoing aspects, wherein the plurality of stacked stator laminates comprise at least a portion of a rear surface of the stator tooth but not at least a portion of a front surface of the stator tooth.

[0100] Aspect 16. The stator tooth of any of the foregoing aspects, wherein the plurality of stacked stator laminates comprise at least a portion of a top surface of the stator tooth.

[0101] Aspect 17. The stator tooth of any of the foregoing aspects comprising an adhesive to couple the lamination portion to the SMC portion, and wherein the adhesive comprises magnetically permeable particles.

[0102] Aspect 18. The stator tooth of any of the foregoing aspects comprising a joint to couple the lamination portion to the SMC portion.

[0103] Aspect 19. The stator tooth of any of the foregoing aspects, wherein the SMC portion is trapezoidal in shape.

[0104] Aspect 20. The stator tooth of any of the foregoing aspects, wherein the SMC portion is stepped.

[0105] Aspect 21 . The stator tooth of any of the foregoing aspects, wherein the soft magnetic composite material comprises iron powder particles.

[0106] Aspect 22. The stator tooth of any of the foregoing aspects, wherein the iron powder particles are coated with an electrically insulated layer.

[0107] Aspect 23. The stator tooth of any of the foregoing aspects, wherein the lamination portion comprises an outer lamination stack and an inner lamination stack, and wherein the outer lamination stack is orientated to facilitate transmitting magnetic flux inward to the inner lamination stack.

[0108] All documents cited herein are incorporated herein by reference, but only to the extent that the incorporated material does not conflict with existing definitions, statements, or other documents set forth herein. To the extent that any meaning or definition of a term in this document conflicts with any meaning or definition of the same term in a document incorporated by reference, the meaning or definition assigned to that term in this document shall govern. The citation of any document is not to be construed as an admission that it is prior art with respect to this application.

[0109] While particular embodiments have been illustrated and described, it would be obvious to those skilled in the art that various other changes and modifications may be made without departing from the spirit and scope of the invention. Those skilled in the art will recognize or be able to ascertain using no more than routine experimentation, numerous equivalents to the specific apparatuses and methods described herein, including alternatives, variants, additions, deletions, modifications and substitutions. This application including the appended claims is therefore intended to cover all such changes and modifications that are within the scope of this application.

Claims

ClaimsWhat is claimed is:1 . A composite stator tooth for a stator of an electric machine, the stator tooth comprising: a lamination portion comprising a plurality of stacked stator laminates; and a SMC portion comprising a soft magnetic composite material, wherein a shape of the SMC portion is complementary to a shape of the lamination portion to form the composite stator tooth.

2. The stator tooth of claim 1 , wherein the lamination portion comprises an interior portion of the stator tooth and the SMC portion comprises an exterior portion of the stator tooth; or wherein the SMC portion comprises an interior portion of the stator tooth and the lamination portion comprises an exterior portion of the stator tooth3. The stator tooth of claim 1 , wherein the SMC portion comprises a first SMC portion and a second SMC portion, and the lamination portion is intermediate the first SMC portion and the second SMC portion.

4. The stator tooth of claim 1 , wherein the stator tooth is shaped to have a long axis and a short axis orthogonal to the long axis, wherein the long axis is parallel to a direction of magnetic flux, and wherein the lamination portion is intermediate the first SMC portion and the second SMC portion along the long axis.

5. The stator tooth of claim 4, wherein the plurality of stacked stator laminates are stacked in a direction along the short axis.

6. The stator tooth of claim 4, wherein the plurality of stacked stator laminates comprise at least a portion of a front surface of the stator tooth and at least a portion of a rear surface of the stator tooth.

7. The stator tooth of claim 4, wherein the plurality of stacked stator laminates comprise at least a portion of a rear surface of the stator tooth but not at least a portion of a front surface of the stator tooth.

8. The stator tooth of claim 4, wherein the plurality of stacked stator laminates comprise at least a portion of a top surface of the stator tooth.

9. The stator tooth of any of the foregoing claims comprising an adhesive to couple the lamination portion to the SMC portion, and wherein the adhesive comprises magnetically permeable particles.

10. The stator tooth of any of the foregoing claims comprising a joint to couple the lamination portion to the SMC portion.11 . The stator tooth of any of the foregoing claims, wherein the SMC portion is trapezoidal in shape.

12. The stator tooth of any of the foregoing claims, wherein the SMC portion is stepped.

13. The stator tooth of any of the foregoing claims, wherein the soft magnetic composite material comprises iron powder particles.

14. The stator tooth of claim 9, wherein the iron powder particles are coated with an electrically insulated layer.

15. The stator tooth of claim 1 , wherein the lamination portion comprises an outer lamination stack and an inner lamination stack, and wherein the outer lamination stack is orientated to facilitate transmitting magnetic flux inward to the inner lamination stack.

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