Electric machine with a non-magnetic laminate bridge

Abstract

This application relates to an electric machine having a non-magnetic laminated bridge portion. A method of constructing a laminate for a rotating electric machine includes forming an annular laminate from a core material having a first relative permeability. The laminate defines through-holes, for example, for permanent magnets or conductors. A peripheral bridge portion made of the core material extends between the through-holes and an outer diameter surface or an inner diameter surface of the laminate. The method includes diffusing an alloy material having a second relative permeability into the bridge portion to form an austenitic bridge portion, wherein the second relative permeability is less than the first relative permeability. The rotating electric machine includes a stator and a rotor. A vehicle includes a rotating electric machine that is connected to a battery pack and a load-bearing wheel and has a rotor and / or a stator constructed according to the above method.

Description

Background Art

[0001] Electric motors, generators, and motor - generator units, collectively referred to in the art as rotating electrical machines, typically include a stator that is spaced a short distance from a rotor by a radial or axial air gap. In a radial - flux type machine, the rotor is coaxially surrounded by the stator, where stator teeth extend radially inwardly toward the rotor. Adjacent stator teeth are separated from each other by respective stator slots. The stator winding is formed by filling the stator slots with wire or solid bar conductors. In a polyphase rotating electrical machine, an AC input voltage is applied to the phase leads of the stator winding to energize the stator and thereby generate a rotating stator magnetic field.

[0002] The stator and rotor typically use corresponding laminations constructed from stacks of multiple layers of relatively soft ferromagnetic material, such as electrical steel sheets that are 0.2 mm - 0.3 mm thick. Individual layers or "laminations" are coaxially arranged and may be welded and / or bonded together to form a lamination stack. Cavities are formed by through - holes in adjacent laminations, where depending on the specific construction of the lamination stack, the cavities are filled with electrical conductors or permanent magnets.

[0003] The through - holes of a given lamination may be separated from each other by narrow crossovers of the lamination material. Depending on the location, such crossovers may be variously referred to as peripheral bridges, radial struts, or transverse ribs. The bridges, struts, and ribs together define a connection region (web region) that provides structural support around the through - holes, where each connection region typically corresponds to a pole in the finished construction of the rotating electrical machine. Summary of the Invention

[0004] The present disclosure relates to a rotating electrical machine having non - magnetic or austenitic peripheral bridges, a method for constructing a rotor or stator lamination having such bridges, and a method for constructing a rotating electrical machine using such laminations. As will be understood by one of ordinary skill in the art, individual laminations including bridges, struts, and other rib structures are stamped from thin sheets of electrical steel or other application - suitable core materials. When the laminations are assembled into a finished cylindrical stack, the ribs can act as undesirable flux paths, each flux path forming a potential source of flux leakage. Flux leakage in turn reduces the operating efficiency and peak operating torque of the electrical machine.

[0005] Accordingly, the present teachings relate to improving the operating efficiency and peak operating torque in an electric machine by locally alloying the above-described peripheral bridges, where "peripheral" refers to the location of the bridges close to the inner diameter and / or outer diameter of the laminate. The alloying process contemplated herein austenitizes the bridges at room temperature. In practical terms, the bridges and possibly the resulting annular inner and / or outer edges appear more like air than like iron core material to an incident magnetic field. In other words, the austenitic bridges act as flux barriers rather than flux paths. This structural property avoids an undesirable short circuit of the rotor's magnetic field through the treated bridges. As a result, the magnetic flux can be more effectively linked to the stator magnetic field.

[0006] As used herein, in some embodiments, the term "non-magnetic" corresponds to a relative permeability less than about 10% of the relative permeability of the iron core material. For example, when a silicon / electrical steel material having a relative permeability of 4000 is used to form a separate rotor or stator laminate, the bridges can be locally alloyed to obtain a relative permeability of 400 or less, or 100 or less in other configurations. The values of 4000 and 400 or less illustrate possible "magnetic" and "non-magnetic" levels, respectively, and thus the values are non-limiting unless otherwise specified herein.

[0007] According to an embodiment of a method for constructing a laminate for use with a rotating electric machine disclosed herein, the method includes forming an annular laminate from an iron core material, such as by stamping or laser cutting the laminate from a thin blank or sheet of the iron core material. The iron core material has a first relative permeability μ R1 . The laminate having an inner diameter surface and an outer diameter surface defines a through hole. The through hole can be close to the outer diameter surface and / or the inner diameter surface of the laminate.

[0008] The method includes diffusing an alloy material having a second relative permeability μ R2 into the bridges to form austenitic bridges, i.e., diffusing only into the bridges and not also into the remaining core material of the laminate. As described above, μ R1 is greater than μ R2 . For example, in a possible implementation, μ R1 can be at least 1000, and μ R2 can be less than 100, or μ R1 and μ R2 can be at least 4000 and less than 400, respectively.

[0009] The annular laminate can include a central hole. Such a central hole defines the above-described inner diameter surface, which in turn defines the annular inner edge of the laminate. The method can include diffusing the alloy material into the inner diameter surface to form an austenitic inner edge.

[0010] In some embodiments, the annular inner edge may include the abutting ends of adjacent stator teeth.

[0011] The alloy material may include, in one possible configuration, a suitable mixture of elements such as manganese and nickel, where other materials or combinations thereof are possible in other embodiments as described herein.

[0012] The diffusion alloy material may optionally include performing a direct powder spraying process or a wire feeding process by applying heat from a heat source. In a non-limiting embodiment, the heat source is, for example, a laser beam. The diffusion alloy material may alternatively include using a deposition process prior to a laser treatment process.

[0013] In another alternative method, the method may include forming a plurality of annular laminations from a core material and coaxially stacking the annular laminations to form a cylindrical rotor or stator stack.

[0014] Diffusing the alloy material may occur along the axial length of the stack. For each magnetic pole of the electric machine, diffusing the alloy material may occur continuously between opposite distal ends of the stack, or it may occur discontinuously along the axial length such that, in the latter case, a plurality of austenite bridge segments are formed between opposite distal ends of the stack.

[0015] A rotating electric machine is also disclosed. In a possible configuration, the electric machine includes a rotor disposed radially within a stator. The rotor includes a coaxial stack of annular rotor laminations, each respective annular rotor lamination of the annular rotor laminations being constructed of a core material having a first relative permeability μ R1 and an outer diameter surface. Each rotor lamination defines a through hole proximate the outer diameter surface. A peripheral bridge made of the core material extends between the through hole and the outer diameter surface to form an annular outer edge.

[0016] In this embodiment, at least some of the peripheral bridges are austenite bridges. That is, the austenite bridges are constructed of an alloy material having a second relative permeability μ R2 where the alloy material is diffused into the core material. As described above, μ R1 may be at least 10 times μ R2

[0017] ​The present disclosure also discloses a motor vehicle having load-bearing wheels and a rotating electric machine, wherein the rotating electric machine in the motor vehicle is connected to a battery pack and one or more of the load-bearing wheels. The electric machine includes a rotor disposed radially within a stator having an annular stator lamination, wherein the rotor has a coaxial stack of annular rotor laminations. At least some of the peripheral bridge portions of the stator and / or the annular inner edge are constructed of electrical steel and an alloy material that has a relative magnetic permeability, for example, of less than 100 in this particular non-limiting embodiment. The stator can be similarly constructed, for example, where the stator tips of adjacent stator teeth are locally alloyed with the same or a similar alloy material.

[0018] Technical solution 1. A method of constructing an annular lamination for a rotating electric machine, the method comprising:

[0019] forming the annular lamination from a core material having a first relative magnetic permeability, wherein the annular lamination defines a plurality of through holes such that peripheral bridge portions made of the core material extend between the through holes and the peripheral surface of the annular lamination; and

[0020] diffusing an alloy material having a second relative magnetic permeability less than the first relative magnetic permeability into the peripheral bridge portions to form austenitic bridge portions.

[0021] Technical solution 2. The method according to technical solution 1, wherein the first relative magnetic permeability is at least 1000 and the second relative magnetic permeability is less than 100.

[0022] Technical solution 3. The method according to technical solution 1, wherein the annular lamination includes a central hole that defines an inner diameter surface as the peripheral surface, and the method further comprises: diffusing the alloy material into the inner diameter surface to form an austenitic inner edge.

[0023] Technical solution 4. The method according to technical solution 1, wherein the alloy material includes at least one of the following: nickel, manganese, chromium, molybdenum, or carbon.

[0024] Technical solution 5. The method according to technical solution 4, wherein the alloy material is a mixture of manganese and nickel.

[0025] Technical solution 6. The method according to technical solution 1, wherein diffusing the alloy material includes performing a direct powder spraying process or a wire feeding process in combination with the application of heat from a heat source.

[0026] Technical solution 7. The method according to technical solution 6, wherein the heat source includes a laser beam.

[0027] Technical solution 8. The method according to technical solution 1, wherein diffusing the alloy material includes using a deposition process before the laser treatment process.

[0028] Technical solution 9. The method according to technical solution 1, further comprising:

[0029] forming a plurality of the annular laminations from the core material; and

[0030] coaxially stacking the annular laminations to form a lamination stack.

[0031] Technical solution 10. The method according to technical solution 9, wherein diffusing the alloy material occurs along the axial length of the lamination stack after coaxially stacking the annular laminations.

[0032] Technical solution 11. The method according to technical solution 10, wherein diffusing the alloy material occurs continuously between opposite distal ends of the lamination stack.

[0033] Technical solution 12. The method according to technical solution 10, wherein diffusing the alloy material occurs discontinuously along the axial length of the stack such that a plurality of austenite axial segments are formed between opposite distal ends of the lamination stack.

[0034] Technical solution 13. The method according to technical solution 1, wherein the annular lamination is a stator lamination having a plurality of stator teeth, each respective stator tooth of the plurality of stator teeth has a corresponding adjacent pair of stator teeth, and the peripheral bridge portion includes the surfaces of the adjacent pair of stator teeth.

[0035] Technical solution 14. A rotating electrical machine, comprising:

[0036] a stator; and

[0037] a rotor disposed radially within the stator and having:

[0038] a coaxial stack of annular rotor laminations, each respective rotor lamination of the rotor laminations being constructed from a core material having a first relative permeability and an outer diameter surface such that the rotor laminations define a plurality of through holes adjacent to the outer diameter surface, wherein a peripheral bridge portion made of the core material extends between each of the through holes and the outer diameter surface;

[0039] wherein at least some of the peripheral bridge portions are austenite bridge portions, the austenite bridge portions being at least partially constructed from an alloy material having a second relative permeability diffused into the core material, and wherein the first relative permeability is at least 10 times the second relative permeability.

[0040] Technical solution 15. The rotating electric machine according to technical solution 14, wherein the annular rotor laminate includes corresponding central holes, the central holes being configured to receive a rotor shaft therein and defining an austenitic edge, each corresponding central hole defining an inner diameter surface diffused with the alloy material to form the austenitic edge.

[0041] Technical solution 16. The rotating electric machine according to technical solution 14, wherein the core material is electrical steel, and the alloy material includes manganese and nickel.

[0042] Technical solution 17. The rotating electric machine according to technical solution 14, wherein the stator includes a coaxial stack of annular stator laminates, the annular stator laminates being constructed of the core material and having a plurality of T-shaped stator teeth, ends of the T-shaped stator teeth abutting corresponding ends of an adjacent pair of stator teeth, and wherein the ends of the T-shaped stator teeth are alloyed with the alloy material.

[0043] Technical solution 18. The rotating electric machine according to technical solution 14, wherein some of the peripheral bridge portions do not include the alloy material.

[0044] Technical solution 19. The rotating electric machine according to technical solution 14, wherein the rotor is an interior permanent magnet rotor or an induction rotor.

[0045] Technical solution 20. A vehicle, comprising:

[0046] Load-bearing wheels;

[0047] A battery pack; and

[0048] A rotating electric machine connected to the battery pack and connected to at least some of the load-bearing wheels, the rotating electric machine comprising:

[0049] A stator having an annular stator laminate; and

[0050] A rotor disposed radially within the stator and having a coaxial stack of annular rotor laminates, each corresponding one of the annular rotor laminates and the annular stator laminates respectively defining a plurality of through holes adjacent to an outer diameter surface of the rotor laminate or adjacent to an inner diameter surface of the stator laminate, wherein a peripheral bridge portion formed of electrical steel extends between the through holes of the rotor laminate and the outer diameter surface, and an annular inner edge is defined to surround the inner diameter surface of the stator;

[0051] Wherein at least some of the annular inner edge of the stator and / or the peripheral bridge portion are constructed of electrical steel having a relative permeability of at least 1000 and an alloy material having a relative permeability of less than 100.

[0052] The above summary of the invention is not intended to represent every possible embodiment or every aspect of the present disclosure. Instead, the foregoing summary of the invention is intended to illustrate some novel aspects and features disclosed herein. From the following detailed description of representative embodiments and modes for carrying out the present disclosure in conjunction with the drawings, the above features and advantages of the present disclosure, as well as other features and advantages, will be apparent. BRIEF DESCRIPTION OF THE DRAWINGS

[0053] Figure 1 is a schematic exploded perspective view illustration of an electric powertrain having a rotating electrical machine constructed as set forth herein.

[0054] Figure 2 is a schematic illustration of a representative process for forming a laminate or a stack thereof in accordance with the present disclosure.

[0055] Figure 3 and Figure 4 are plan view illustrations of two possible embodiments.

[0056] Figure 5 is a schematic perspective view illustration of an exemplary rotor constructed in accordance with an embodiment of the present method.

[0057] Figure 6 is a schematic cross-sectional view illustration of an exemplary stator laminate constructed in accordance with the present disclosure.

[0058] The present disclosure is susceptible to modifications and alternative forms, with representative embodiments shown by way of example in the drawings and described in detail below. The inventive aspects of the present disclosure are not limited to the disclosed embodiments. Instead, the present disclosure is intended to cover modifications, equivalents, combinations, and alternatives falling within the scope of the present disclosure. DETAILED DESCRIPTION

[0059] Referring to the drawings, in which like reference numerals refer to the same or similar components throughout the several views, vehicle 10 is schematically depicted in Figure 1 as a non-limiting exemplary system having an electric powertrain 12. In the illustrated configuration, vehicle 10 may be variously implemented as a hybrid electric vehicle or a battery electric vehicle having a body 11 and load-bearing wheels 13, such as four load-bearing wheels 13 in the illustrated motor vehicle configuration, or more / fewer load-bearing wheels 13 in other embodiments.

[0060] The electric powertrain 12 in the illustrated embodiment is operable to transmit motor output torque (arrow T O ) from a rotating electrical machine (M E)16 is transmitted to one or more of the load-bearing wheels 13 to propel the vehicle 10 along the road surface 15. Portions of such an electric motor 16 may be locally alloyed in accordance with the present teachings, as described below with reference to Figures 2-6 Although the vehicle 10 is depicted as a motor vehicle for purposes of illustration, the present teachings may be applied to other mobile systems, such as, ships, aircraft, spacecraft, rail vehicles, robots, construction equipment, agricultural equipment, etc. Similarly, the electric drivetrain 12 may be used as part of a power plant, crane, or other stationary system, and thus Figure 1 the motor vehicle 10 of Figure 1 merely represents one possible application.

[0061] The electric motor 16 includes a rotor 16R that is positioned relative to a stator 16S. The rotor 16R may be variously configured as a radial flux type interior permanent magnet motor, an induction motor, or another synchronous or asynchronous machine. As described below, specific portions of the rotor 16R and / or the stator 16S are processed in accordance with the present disclosure to diffuse a target portion thereof with a non-magnetic alloy. The resulting structure may help to minimize flux leakage through undesired flux paths and thereby increase the average peak torque.

[0062] An output member 17 of the rotor 16R, such as a rotor shaft, may be connected to a driven load, which, in a non-limiting Figure 1 embodiment, includes one or more of the load-bearing wheels 13 described above. Such torque (arrow T O ) may be transmitted to a transmission (not shown) of the vehicle 10 either alone or in combination with engine torque (not shown), depending on the configuration of the vehicle 10. When the electric motor 16 is implemented as a polyphase device as shown, the phase windings of the stator 16S are electrically connected to a power inverter module (PIM) 20 via an AC voltage bus (VAC). The PIM 20 is in turn connected to a high voltage battery pack (BATT) 18 via a DC voltage bus (VDC). The electric drivetrain 12 may include additional components not described herein but known in the art, such as a low / auxiliary voltage bus and one or more auxiliary devices connected thereto, a DC-DC converter, and an auxiliary battery, etc.

[0063] Reference Figure 2 is made to Figure 1 a method 100 for constructing a laminate 16-LAM for use with a Figure 1 rotating electric motor 16. The method 100 may be used to construct Figure 2 the stator 16S and / or the rotor 16R, where the specific non-limiting embodiment shown in Figure 6 is configured for use with the rotor 16R. An exemplary laminate 316-LAM configured for use with the stator 16S is described below with particular reference to

[0064] According to a possible embodiment, Figure 2 method 100 includes, at block B102, forming an annular rotor laminate 16-LAM from a core material 36. For example, a given annular rotor laminate 16-LAM can be formed by stamping or laser cutting a sheet metal blank, such as a blank of electrical steel, cobalt steel, or other iron-containing metal suitable for applications with high relative magnetic permeability, which is, for example, 0.20 mm - 0.30 mm thick, where "high relative magnetic permeability" is, for example, 1000 - 4000 or possibly higher. The rotor laminate 16-LAM is annular, i.e., ring-shaped, and thus has an inner diameter surface 131 and an outer diameter surface 31.

[0065] As Figure 2 shown, the laminate 16-LAM defines a plurality of narrow peripheral bridges 32 that surround a central axis A C of the laminate 16-LAM. In the illustrated configuration, the peripheral bridges 32 are in close proximity to the outer diameter surface 31, i.e., the circular outer perimeter of the illustrated laminate 16-LAM. Generally, when the laminate 16-LAM is used as part of a rotor 16R, each peripheral bridge 32 is located within a corresponding magnetic pole of the rotor 16R. As described above, exemplary embodiments are described below with reference to Figure 6 where the laminate 16-LAM is used as part of a stator 16S. Figure 6

[0066] Each laminate 16-LAM defines a plurality of through-holes 33 that are close to the outer diameter surface 31, where, for clarity, the through-holes 33 are individually labeled "P" to indicate that, as part of block B102, the through-holes 33 are punched or otherwise cut or separated from the core material 36. In this embodiment, the peripheral bridges 32, which are mainly composed of the core material 36, extend between the through-holes 33 and the outer diameter surface 31. The shape, number, and arrangement of the through-holes 33 will vary with the configuration of the laminate 16-LAM, and one or more magnets or electrical conductors (not shown) can fill the voids jointly defined by stacking a number of adjacent rotor laminates 16-LAM. For example, Figure 2 , Figure 3 and Figure 5 depict an interior permanent magnet (IPM) configuration, while Figure 4 depicts an induction motor embodiment.

[0067] Method 100 includes, at block B104, diffusing an application-suitable alloy material 26 into the core material 36 of the peripheral bridges 32 to thereby form austenitic bridges 32A. The core material 36 and the alloy material 26 have respective first and second relative magnetic permeabilities, i.e., μ R1 and μ R2。In various embodiments, μ R1 is greater than μ R2 , where the diffusion of the alloy material 26 into the peripheral bridge portion 32 renders the properties of a given bridge portion 32 austenitized relative to the remaining core material 36. Thus, when the core material 36 has a relative permeability of 1000 or greater, in possible embodiments, the resulting austenitic bridge portion 32A may have a relative permeability of less than 100.

[0068] As part of block B104, method 100 may include coaxially stacking a suitable amount of laminations 16-LAM to form a stack, such as Figure 5 stack 19. Alternatively, the alloying process described herein may be performed individually on each rotor lamination 16-LAM before assembling a specific number of such laminations 16-LAM into such a stack 19.

[0069] One possible method includes melting a local surface of the peripheral bridge portion 32 to form a molten pool 29 before introducing the alloy material 26 into the melted local surface of the peripheral bridge portion 32. As Figure 2 shown in process 22A, for example, a pre-set coating process may be used, where the alloy material 26 is applied as a paste, foil, or powder to the target area of the lamination 16-LAM, in this case the bridge portion 32. The alloy material 26 and the surrounding material of the lamination 16-LAM are then fused via heat from an incident heat source 24, such as a laser beam, an infrared energy beam, and / or induction heating, to form the austenitic bridge portion 32A.

[0070] Figure 2 The annular lamination 16-LAM of includes a central hole 41. When the lamination 16-LAM is used as Figure 1 an integral part of the rotor 16R as shown in , the central hole 41 is configured to receive the rotor shaft 17R therein (see Figure 5 ), as will be understood by those of ordinary skill in the art. Alternatively, as Figure 6 shown in , the lamination 16-LAM may be part of the stator 16S, in which case the central hole 41 is configured to receive the rotor 16R therein, as will be understood by those skilled in the art.

[0071] The central hole 41 may define an annular inner edge 132-I ( Figure 2 ) or 232-I ( Figure 6 ) having a corresponding inner diameter surface 131 or 231. In addition to treating the bridge portion 32, method 100 may include diffusing the alloy material 26 into a portion of the inner diameter surface 131 to form an austenitic inner edge 132A ( Figure 2 ) or 232A ( Figure 6)。The inner edge 132-I or 232-I can be austenitized around its entire circumference, or a section of the inner edge 132-I or 232-I can be processed. Processing less than the entire circumference of the inner edge 132-I or 232-I can be performed, for example, to minimize the costs associated with the alloying process. In this case, the root 47 near the radial laminate spoke 38 can be locally alloyed, where the root 47 is the connected area of the radial laminate spoke 38 and the inner edge 132-I in this case.

[0072] Alternatively, as Figure 2 shown in process 22B of

[0073] , the alloy material 26 can be supplied to the molten pool 29 during processing, for example, by a direct powder injection or wire feeding process. The alloy material 26 can be deposited by thermal spraying or diffusion coating, sputtering, or another suitable deposition process such as inkjet printing or pattern screening before the laser processing to locally change the chemical properties of the bridge 32. Upon cooling, the local area is essentially austenitic. This process can be carried out before or after punching the through-hole 33.

[0074] As Figure 2 shown by the advancement of arrows A and B in Figure 5 , the result of the alloying process(es) is one or more laminates 16-LAM having an austenitic bridge 32A and / or an austenitic inner edge 132A. When the laminate 16-LAM is processed individually, for example, with the laser beam embodiment of the heat source 24, the axis of the laser beam is perpendicular to the plane of the laminate 16-LAM. In other embodiments, the

[0075] stack 19 of Figure 2 or its variant can be processed after the construction stack 19. In this case, the axis of the laser beam will be parallel to the laminate plane, i.e., the laser beam irradiates the edge of the laminate 16-LAM.

[0075] At Figure 2 box B106 of Figure 1 , as shown by the advancement of arrow C, a stack 19 composed of an appropriate number of laminates 16-LAM can be assembled and then integrated with the stator 16S or the rotor 16R respectively to construct Figure 1 the rotating electric machine 16.

[0076] Briefly referring to Figure 5 , Figure 2The frame B104 may include a plurality of annular laminations 16-LAM formed of a core material 36, and the annular laminations 16-LAM are coaxially stacked to form a lamination stack, such as stack 19. Diffusion of the alloy material 26 may occur along the axial length L of the stack 19 after the annular laminations 16-LAM are coaxially stacked. The method 100 may include continuously diffusing the alloy material 26 between opposite distal ends E1 and E2 of the stack 19 to form a continuous austenitic axial bridge 50. Alternatively, diffusion of the alloy material 26 may occur discontinuously along the axial length L of the stack 19 such that a plurality of austenitic axial segments 150 are formed between opposite distal ends E1 and E2.

[0077] Once formed in this manner, the method 100 may include constructing Figure 1 the electric machine 16. When constructing the rotor 16R, for example, subsequent processes may include inserting permanent magnets (not shown) into the through holes 33 in the IPM configuration, if such installation has not already occurred prior to process 22A or 22B. Alternatively, conductors may be inserted Figure 4 into the through holes 33 in the induction machine embodiment. When the laminations 16-LAM are used to construct the stator 16S, for example, as Figure 6 shown, the through holes 133 may be filled with stator windings (not shown). After constructing the rotor 16R and / or the stator 16S in this manner, the rotor 16R may be disposed radially within Figure 1 the stator 16S of, and the constructed electric machine 16 is thereafter connected to a driven load and a power source, such as a load wheel 13 and a battery pack 18 / PIM 20.

[0078] As described above, the laminations 16-LAM may be processed on the outer diameter surface 31 and / or the inner diameter surface 131, respectively, in a stack level. The corresponding peripheral bridges 32 and / or the inner edges 132 or stator teeth 40 ( Figure 6 ) are adjacent to each other such that, when viewed from a perspective of Figure 5 , the adjacent and neighboring bridges 32 together form a continuous austenitic axial bridge 50 extending from one distal end E1 to the other distal end E2 ( Figure 5 ). Alternatively, a plurality of axial austenitic axial bridge segments 150 may be separated from each other by untreated bridge segments 55, for example, to reduce losses when alloying the laminations 16-LAM in the stack 19. Insertion of the untreated axial bridge segments 150 increases the resistance to the conduction paths that may be followed by eddy currents, and a larger number of axial bridge segments 150 having shorter lengths may reduce eddy current losses.

[0079] Once the stack 19 has been assembled, Figure 2The direct powder spraying or pre - deposited adhesion coating processes 22A and 22B described above are used to form the continuous austenitic axial bridge 50 or axial bridge section 150. In each case, the inner diameter surface 131 can optionally be treated in the same way. If untreated, it may be advantageous to enlarge the bridge 32 so that the bridge 32 can better carry stress and support the rotor laminate 16 - LAM.

[0080] As described above, Figure 2 An alternative construction of the exemplary laminate 16 - LAM having an austenitic bridge 32A is depicted as laminate 116 - LAM and 216 - LAM in Figure 3 and Figure 4 respectively, and in Figure 3 and Figure 4 the laminates 116 - LAM and 216 - LAM are used as part of the rotor 16R shown in Figure 1 In Figure 3 for example, the present teachings can be applied to the V - shaped arrangement of permanent magnets 34 disposed within the through - hole 33. Those of ordinary skill in the art will understand that the IPM rotor construction can form rotor poles in a suitable shape and arrangement, such as using block magnets, or a "single V" or "double V" arrangement of flat / rectangular bar magnets positioned adjacent to the outer diameter surface 31. In a typical magnet construction, the angular orientation or "V - angle" of the arranged rotor magnets can be open towards the outer diameter surface of the rotor 16R. Desirably, the supports 39 or other surrounding rib structures that typically exist radially inwards from the bridge 32 around the perimeter of the laminate 16 - LAM can be eliminated to further optimize the peak torque capability, or other techniques can be used to treat such supports 39 so that the supports become non - magnetic.

[0081] Regarding Figure 4 the present teachings can be extended to the laminate 216 - LAM as an induction construction, which has a circular through - hole 133. As will be understood, such a construction abandons the use of permanent magnets. Instead, the through - hole 133 forms an outer ring filled with electrical conductors (not shown). In such an embodiment, the austenitic bridge 32A remains adjacent to the outer diameter surface 31 as shown, and the alloying treatment of the laminate 216 - LAM is carried out in the manner described above.

[0082] Referring to Figure 6 the present teachings can be extended to make Figure 1The magnetic flux leakage in the stator 16S is minimized. The through-hole 133 is partially defined by the inner edge 232-I, where the stator teeth 40 extend radially therebetween. As will be understood by those of ordinary skill in the art, the stator teeth 40 may terminate in ends 40T such that each of the stator teeth 40 has a T-shaped cross-section as shown. In one possible embodiment, the ends 40T of an adjacent pair of stator teeth 40 are adjacent to and in contact with each other to further define the through-hole 133. In such a case, the peripheral bridge 32 may include surface regions 140 proximate to the adjacent pair of stator teeth 40. That is, the treated portion of the austenitic inner edge 232A formed in this embodiment includes at least the adjacent or adjoining surfaces of the ends 40T, or in other embodiments includes the entire inner edge 232-I.

[0083] As will be understood by those of ordinary skill in the art in view of the foregoing disclosure, the present teachings enable, for example, the rotor 16R and / or the stator 16S of the electric machine 16 as shown in Figure 1 to be locally rendered non-magnetic by diffusing the alloy material 26 into the target regions of the core material 36, the target regions specifically being the peripheral bridge 32 and / or possibly the inner edge 132-I ( Figure 2 ) and / or 232-I ( Figure 6 ). The disclosed method 100 is adapted to reduce or eliminate the leakage of magnetic flux through the target structural regions. Using the present method does not compromise the structural integrity of the core material 36. That is, the diffusion of the alloy material 26 into the target regions is characterized by the absence of a ceramic or other masking material prior to heat treatment, which otherwise would have to be stripped and processed away prior to the stacking configuration. In view of the present disclosure, those of ordinary skill in the art will readily understand these and other benefits.

[0084] Although some best modes and other embodiments have been described in detail, there are various alternative designs and embodiments for practicing the present teachings. Those skilled in the art will recognize that modifications may be made to the disclosed embodiments without departing from the scope of the present disclosure. Additionally, the present concepts expressly include combinations and sub-combinations of the described elements and features. The detailed description and the drawings are supportive of and descriptive of the present teachings.

Claims

1. A method of constructing an annular laminate for a rotating electrical machine, the method comprising: forming the annular laminate from a core material having a first relative permeability, wherein the annular laminate defines a plurality of through-holes such that a peripheral bridge portion made of the core material extends between the through-holes and a peripheral surface of the annular laminate; and diffusing an alloy material having a second relative permeability less than the first relative permeability into the peripheral bridge portion to form an austenitic bridge portion; forming a plurality of the annular laminates from the core material; and coaxially stacking the annular laminates to form a laminate stack; wherein diffusing the alloy material occurs discontinuously along an axial length of the stack such that a plurality of austenitic axial segments are formed between opposite distal ends of the laminate stack, and a plurality of axial austenitic axial bridge segments are separated from each other by untreated bridge segments to reduce losses when alloying the laminates in the stacked configuration; wherein the annular laminate is a stator laminate having a plurality of stator teeth, each respective stator tooth of the plurality of stator teeth has a corresponding adjacent pair of stator teeth, and the peripheral bridge portion includes surfaces of the adjacent pair of stator teeth.

2. The method according to claim 1, wherein the first relative permeability is at least 1000 and the second relative permeability is less than 100.

3. The method according to claim 1, wherein the annular laminate includes a central hole that defines an inner diameter surface as the peripheral surface, and the method further comprises: diffusing the alloy material into the inner diameter surface to form an austenitic inner edge.

4. The method according to claim 1, wherein the alloy material includes at least one of: nickel, manganese, chromium, molybdenum, or carbon.

5. The method according to claim 4, wherein the alloy material is a mixture of manganese and nickel.

6. The method according to claim 1, wherein diffusing the alloy material includes performing a direct powder spraying process or a wire feeding process in combination with the application of heat from a heat source.

7. The method according to claim 6, wherein the heat source includes a laser beam.

8. The method according to claim 1, wherein diffusing the alloy material includes using a deposition process prior to a laser treatment process.

9. The method according to claim 1, wherein diffusing the alloy material occurs along an axial length of the laminate stack after coaxially stacking the annular laminates.

10. The method according to claim 9, wherein diffusing the alloy material occurs continuously between opposite distal ends of the laminate stack.

11. A rotating electrical machine, comprising: a stator; and a rotor disposed radially within the stator and having: Coaxial stacking of annular rotor laminations, each respective rotor lamination of the rotor laminations being constructed of a core material having a first relative permeability and an outer diameter surface such that the rotor laminations define a plurality of through-holes proximate the outer diameter surface, wherein a peripheral bridge portion made of the core material extends between each of the through-holes and the outer diameter surface; wherein at least some of the peripheral bridge portions are austenitic bridge portions, the austenitic bridge portions being at least partially constructed of an alloy material having a second relative permeability diffused into the core material, and wherein the first relative permeability is at least 10 times the second relative permeability; wherein the diffusion of the alloy material occurs discontinuously along the axial length of the stack such that a plurality of austenitic axial segments are formed between opposite distal ends of the lamination stack, and a plurality of axial austenitic axial bridge segments are separated from each other by untreated bridge segments to reduce losses when alloying the laminations in the stacked configuration; wherein the stator includes a coaxial stack of annular stator laminations constructed of the core material and having a plurality of T-shaped stator teeth, the ends of the T-shaped stator teeth abutting the respective ends of an adjacent pair of stator teeth, and wherein the ends of the T-shaped stator teeth are alloyed with the alloy material.

12. The rotating electrical machine according to claim 11, wherein, the annular rotor laminations include respective central holes configured to receive a rotor shaft therein and defining austenitic edges, each respective central hole defining an inner diameter surface into which the alloy material is diffused to form the austenitic edges.

13. The rotating electrical machine according to claim 11, wherein, the core material is electrical steel and the alloy material includes manganese and nickel.

14. The rotating electrical machine according to claim 11, wherein, some of the peripheral bridge portions do not include the alloy material.

15. The rotating electrical machine according to claim 11, wherein, the rotor is an interior permanent magnet rotor or an induction rotor.

16. A vehicle, comprising: load-bearing wheels; a battery pack; and a rotating electrical machine connected to the battery pack and connected to at least some of the load-bearing wheels, the rotating electrical machine including: a stator having an annular stator lamination; and a rotor radially disposed within the stator and having a coaxial stack of annular rotor laminations, each respective one of the annular rotor laminations and the annular stator laminations defining a plurality of through-holes proximate the outer diameter surface of the rotor laminations or proximate the inner diameter surface of the stator laminations, wherein a peripheral bridge portion formed of electrical steel extends between the through-holes of the rotor laminations and the outer diameter surface, and an annular inner edge is defined around the inner diameter surface of the stator; wherein at least some of the annular inner edge of the stator and / or the peripheral bridge portions are constructed of electrical steel having a relative permeability of at least 1000 and an alloy material having a relative permeability of less than 100; Therein, the diffusion of the alloy material occurs discontinuously along the axial length of the stack such that a plurality of austenitic axial segments are formed between opposite distal ends of the laminate stack, and a plurality of axial austenitic axial bridge segments are separated from each other by untreated bridge segments to reduce losses during alloying of the laminate in the stacked form; wherein the stator comprises a coaxial stack of annular stator laminates constructed of core material and having a plurality of T-shaped stator teeth, the ends of the T-shaped stator teeth abutting the corresponding ends of an adjacent pair of stator teeth, and wherein the ends of the T-shaped stator teeth are alloyed with the alloy material.

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