Method for heat treating the magnet web region of a rotor

Abstract

The present invention relates to a method for heat treating a magnet web region of a rotor. A method for constructing a rotor assembly for use with a rotating electric machine includes forming an annular rotor lamination from a metal billet. Each lamination has a radial axis and an outer diameter surface. A plurality of magnet web regions are defined near the outer diameter surface. Each web region includes an asymmetric opening defined by radially extending struts and an arc-shaped peripheral bridge. The method includes coaxially stacking the laminations into a rotor stack, which includes positioning every other lamination at a predetermined angular distance to expose the bridges and / or struts and masking the remaining surface areas of the laminations. The rotor stack is subjected to a heat treatment process to harden only the unmasked bridges and / or struts. The method includes connecting a rotor shaft to the stack to construct a rotor assembly, wherein the web regions correspond to corresponding rotor poles.

Description

Background Art

[0001] Traction motors, generators and motor-generator units are collectively referred to in the art as rotating electrical machines. Electrical machines typically include a stator, which is separated from a rotor by a short distance by a radial or axial air gap. In radial flux type machines in particular, equally spaced stator teeth protrude radially inwardly toward the rotor. Adjacent stator teeth are separated from one another by corresponding stator slots. Stator windings are formed by winding stator teeth with wires or by filling stator slots with solid bar conductors. In a multi-phase machine, an AC input voltage is applied to the phase leads of the stator windings to energize the stator and, thereby, generate a rotating stator magnetic field.

[0002] The rotor of an interior permanent magnet (IPM) type motor includes an array of embedded strong permanent magnets. Unlike the stator electromagnets, which are generated by the sequential energization of the stator windings mentioned above, the rotor's embedded permanent magnets collectively establish a time-invariant magnetic field. The magnetic fields of the stator and rotor interact with each other to generate and maintain power within the stator-rotor air gap. Such forces ultimately impart rotation to the rotor and the connected rotor shaft. The torque from the rotor and rotor shaft is then directed to the coupled load. Other motors, such as the synchronous reluctance motor, forgo the use of permanent magnets in the rotor, but act on the coupled load with a similar effect.

[0003] A typical electric motor rotor includes a cylindrical rotor stack consisting of a stack of thin layers of steel or another magnetically-permeable material. Each individual layer is generally referred to in the art as a rotor lamination. Each rotor lamination defines a set of openings. When these rotor laminations are stacked together, cavities are formed from these openings, wherein the openings of the IPM structure of the rotor receive corresponding permanent magnets therein. The IPM rotor structure can use a "single V" or "double V" arrangement structure of solid bar magnets positioned adjacent to the outer diameter surface of the rotor to form its rotor poles. In a typical magnet construction, the angular orientation or "V angle" of the arranged rotor magnets can be open toward the outer diameter surface of the rotor.

[0004] Whether it is an IPM or synchronous reluctance rotor variation, the above-mentioned rotor openings of each rotor lamination are separated by narrow strips of lamination material called "bridges" and "pillars", where the bridges and pillars of a given rotor pole are collectively referred to herein as the "magnet web region". The bridges extend around the outer periphery of the annular laminations and are therefore arcuate in their plan view shape and peripheral in their position relative to the laminations, while the pillars extend radially between the inner distal ends of these rotor openings. Together, these bridges and pillars provide the necessary structural support around the rotor openings. However, these bridges and pillars may also short-circuit beneficial flux paths within the rotor, which in turn may reduce the operating efficiency of the motor.

[0005] In order to increase the strength of the magnet web area, rotor manufacturing technology sometimes includes subjecting the individual rotor laminations to a heat treatment process before constructing the rotor stack. Such a process also has the benefit of reducing the magnetic resistance of the arc-shaped peripheral bridge and radial pillars, which in turn helps to solve the flux path short-circuiting problem mentioned above. During the heat treatment, the surface area of ​​the lamination other than the web area can be masked using a suitable masking material, so that the bridge and pillar are exposed to high temperature and gaseous heat treatment atmosphere. Then, after completing the heat treatment process, the masking material is carefully removed. Thereafter, the resulting rotor laminations are stacked together and connected to the rotor shaft and end rings to complete the assembly of the rotor. Summary of the invention

[0006] The present disclosure relates to an improved method for selectively heat treating bridges and struts of a rotor for use in a rotating electrical machine. As is well known in the art, each magnet web region of a given rotor lamination corresponds to a magnetic pole of the rotor. These bridges and struts together define individual rotor openings adjacent to the outer diameter surface of the rotor. As part of the disclosed method, these rotor laminations are assembled into a rotor stack so that when viewed along the central axis of the rotor stack, the bridges and / or struts or portions thereof of adjacent laminations are offset relative to each other. That is, when the rotor stack is viewed along its central axis, the offset geometry effectively masks the surface areas of the laminations that are located outside the magnet web region while exposing the bridges and / or struts. Therefore, depending on the embodiment, during the subsequent heat treatment process of the assembled rotor stack, the exposed bridges and / or struts are exposed to the heat treatment atmosphere. Therefore, the present method eliminates the additional time required to apply masking materials and remove masking materials from the rotor laminations, as well as the manufacturing costs associated therewith.

[0007] The disclosed method can be used to help ensure that the bridges and / or struts are fully and effectively hardened via heat treatment of the rotor stack before or after connection to the rotor shaft without reducing the magnetic permeability of the remaining structure of the rotor lamination. The strengthened web region can help enable higher speed operation of the rotor without a corresponding increase in the thickness of the bridges and / or struts.

[0008] In an exemplary embodiment, a method of constructing a rotor assembly for use with a rotating electric machine includes forming an annular rotor lamination from a metal blank, such as a 0.25 mm steel sheet metal blank. Each lamination has a radial axis and an outer diameter surface, and defines a plurality of spaced magnet web regions about the outer diameter surface, i.e., the circular outer periphery of the rotor lamination. The magnet web regions correspond to respective magnetic poles of the rotor.

[0009] Each magnet web region includes a plurality of asymmetric rotor openings having inner distal ends and outer distal ends, wherein "outer" and "inner" refer to the outer diameter surface and inner diameter surface that are relatively close to the laminations, respectively. The opposing inner and outer distal ends are defined by radial struts and arcuate bridges, respectively, wherein the rotor openings are further defined by transverse reluctance paths. Thus, the magnet web region described herein includes struts, bridges, and reluctance paths.

[0010] The method according to this particular embodiment includes coaxially stacking rotor laminations to form a rotor stack, which includes rotating or otherwise positioning every other lamination in the laminations about its axis at a predetermined angle relative to an adjacent lamination in the laminations. This is used to expose the bridges and / or struts. And masking the remaining surface area of ​​the laminations, wherein the asymmetry mentioned above enables such masking. When viewed along the central axis / rotational axis of the rotor, the alternating bridges and / or struts are offset relative to each other and visible through the rotor opening. In different embodiments, the specific axis around which the above-mentioned rotation occurs can be the radial axis or the central axis of the lamination / rotor stack, depending on which parts of the web area will be exposed during the heat treatment process.

[0011] The methods described herein may include connecting the rotor shaft to the rotor stack to construct the rotor assembly before or after the rotor stack is subjected to a heat treatment process. Such a process hardens the unmasked bridges and / or struts without hardening the remaining surface areas of the laminations.

[0012] Forming the annular rotor laminations may include pressing or stamping asymmetric rotor openings in each lamination. In such embodiments, the asymmetric rotor openings may optionally include one or more groups of V-shaped rotor openings separated by corresponding struts, wherein each opening defines a V angle opening toward the outer diameter surface.

[0013] The metal blank may be coated with an insulating material. In such an embodiment, the method may include removing the insulating material from the web region prior to subjecting the rotor assembly to a heat treatment process.

[0014] The method may further include stacking the laminations in a predetermined stacking pattern prior to forming the rotor stack such that legs of an adjacent pair of laminations do not overlap, and subsequently etching the insulating material from the web region.

[0015] The heat treatment process in various non-limiting exemplary embodiments may be a ferrite nitrocarburizing process, a gas nitriding process, a plasma nitriding process, or a salt bath nitriding process.

[0016] Possible embodiments of the method further include positioning the rotor assembly radially within the stator assembly to construct a rotating electrical machine. In certain embodiments, the rotating electrical machine may be used to provide torque to a transmission of a motor vehicle.

[0017] A rotating electric machine is also disclosed herein, which has a rotor assembly radially disposed within a stator assembly. The rotor assembly includes a rotor stack consisting of coaxially stacked annular rotor laminations, each of which includes a radial axis and an outer diameter surface. Each lamination also defines a plurality of spaced apart asymmetric heat-treated magnet web regions near the outer diameter surface. These magnet web regions include a plurality of rotor openings defined by radially extending struts and one or more arc-shaped peripheral bridges, wherein, in some non-limiting embodiments, each of these openings may contain a permanent magnet. Every other lamination in these laminations rotates at a predetermined angle relative to the radial axis or the center axis. A pair of end plates are connected to the respective axial ends of the rotor stack. The rotor shaft is connected to the inner diameter surface of these laminations. These magnet web regions correspond to the respective magnetic poles of the rotor assembly.

[0018] An exemplary method for constructing a rotating electric machine includes forming an annular rotor lamination from a metal billet. Each rotor lamination has a radial axis and an outer diameter surface, and defines a plurality of spaced magnet web regions adjacent to the outer diameter surface. Each magnet web region includes a pair of asymmetric V-shaped rotor openings defined by radially extending struts and an arcuate peripheral bridge, wherein the rotor openings have a V angle opening toward the outer diameter surface.

[0019] In this particular embodiment, the method includes coaxially stacking annular rotor laminations to form a rotor stack, which includes positioning every other lamination of the laminations at a predetermined angle relative to the radial axis or the central axis to expose the bridges and / or struts and masking the remaining surface areas of the laminations. The magnet web areas correspond to the corresponding magnetic poles of the rotor. The method may include: removing insulating material from the web areas, subjecting the rotor stack as a whole to a predetermined heat treatment process to harden only the unmasked peripheral bridges and / or radial struts, and then, radially positioning the rotor assembly within the stator assembly to thereby construct a rotating electrical machine. The method may include connecting the rotor shaft to the rotor stack to construct the rotor assembly before or after performing the heat treatment process.

[0020] The present invention also includes the following technical solutions.

[0021] Solution 1. A method of constructing a rotor assembly for use with a rotating electrical machine, the method comprising:

[0022] forming a plurality of annular rotor laminations from a metal billet, wherein each of the rotor laminations has an outer diameter surface and defines a plurality of magnet web regions adjacent the outer diameter surface, and wherein each respective one of the magnet web regions includes a plurality of asymmetric openings having first and second distal ends defined by respective radially extending struts and arcuate peripheral bridges;

[0023] coaxially stacking the annular rotor laminations to thereby form a rotor stack, including positioning the laminations at a predetermined angular distance relative to a radial axis or a longitudinal center axis of the rotor stack to thereby not cover or expose the struts and / or the bridges and to cover or mask the remaining surface area of ​​the laminations; and

[0024] The rotor stack is subjected to a heat treatment process to thereby harden only the uncovered or unmasked bridges and / or struts.

[0025] Option 2. The method according to Option 1, wherein the predetermined angular distance is 180 degrees.

[0026] Option 3. The method according to Option 1, wherein forming the plurality of annular rotor laminations comprises pressing or punching one or more asymmetric V-shaped openings as the asymmetric openings in each of the magnet web regions of the laminations.

[0027] Option 4. A method according to Option 3, wherein the asymmetric V-shaped openings include a first group and a second group of V-shaped openings, the first group and the second group of V-shaped openings are separated by a corresponding one of the pillars and each defines a V angle opening toward the outer diameter surface.

[0028] Option 5. The method according to Option 1, wherein the metal blank is coated with an insulating material, the method further comprising removing the insulating material from the web region before subjecting the rotor assembly to the heat treatment process.

[0029] Option 6. The method according to Option 5 also includes stacking the plurality of laminations in a predetermined pattern so that the pillars and / or the bridges of an adjacent pair of laminations do not overlap, and then, before subjecting the rotor stack to the heat treatment process, etching the insulating material from the web area.

[0030] Option 7. The method according to Option 1 further includes coating the laminations with an insulating material without coating the web region after forming the plurality of annular rotor laminations and before subjecting the rotor assembly to the heat treatment process.

[0031] Option 8. The method according to Option 1, wherein the surface of the metal blank is coated with an insulating material, and the method further comprises removing the insulating material only from the web region before subjecting the rotor stack to the heat treatment process.

[0032] Aspect 9. The method according to aspect 1, wherein subjecting the rotor component to the heat treatment process includes subjecting the rotor component to a ferrite nitrocarburizing process, a gas nitriding process, or a salt bath nitriding process.

[0033] Solution 10. The method according to Solution 1 further includes:

[0034] connecting a rotor shaft to the rotor stack to thereby construct the rotor assembly, wherein the magnet web regions correspond to respective magnetic poles of the rotor; and

[0035] The rotor assembly is positioned radially within the stator assembly to thereby construct the rotating electrical machine.

[0036] Option 11. The method of Option 10 further includes using the rotating electric machine to provide torque to a transmission of a motor vehicle.

[0037] Solution 12. A rotating electrical machine comprising:

[0038] stator assembly; and

[0039] a rotor assembly disposed radially within the stator assembly and having:

[0040] A rotor stack comprised of a plurality of coaxially stacked annular rotor laminations, wherein each of said rotor laminations has a radial axis and an outer diameter surface and defines a plurality of asymmetric heat-treated magnet web regions proximate said outer diameter surface, each of said asymmetric magnet web regions comprising a plurality of openings defined by radially extending struts and one or more arcuate peripheral bridges, and wherein every other one of said laminations is positioned at a predetermined angular distance relative to a radial axis or a central axis of said rotor stack so as to thereby not cover or expose said bridges and / or said struts and to cover or mask the remaining surface area of ​​said laminations;

[0041] a pair of end plates, each connected to an opposite axial end of the rotor stack; and

[0042] a rotor shaft connected to the inner diameter surface of the laminations;

[0043] Wherein, the magnet web regions correspond to corresponding magnetic poles of the rotor assembly.

[0044] Solution 13. The rotating electrical machine according to Solution 12, wherein the predetermined angular distance is 180 degrees.

[0045] Solution 14. A rotating electric machine according to Solution 12, wherein the asymmetric openings include a first group and a second group of V-shaped openings, the first group and the second group of V-shaped openings are each separated by a corresponding one of the pillars and each define a V angle opening toward the outer diameter surface.

[0046] Embodiment 15. The rotating electric machine according to embodiment 12, wherein the rotating electric machine is connected to a transmission of a motor vehicle.

[0047] Embodiment 16. The rotating electric machine of embodiment 12, wherein the rotating electric machine is an interior permanent magnet motor, and wherein a respective permanent magnet is located within each of the openings.

[0048] Solution 17. A method for constructing a rotating electrical machine, the method comprising:

[0049] forming a plurality of annular rotor laminations from a metal billet, wherein each of the rotor laminations has a radial axis and an outer diameter surface and thereby defines a plurality of magnet web regions adjacent the outer diameter surface, wherein each of the magnet web regions includes a pair of asymmetrical V-shaped openings defined by radially extending struts and one or more arcuate peripheral bridges and having a V-angle opening toward the outer diameter surface;

[0050] coaxially stacking the annular rotor laminations to thereby form a rotor stack, comprising positioning every other lamination of the laminations at a predetermined angular distance relative to the radial axis or a longitudinal center axis of the rotor stack to expose the bridges and / or the struts and mask the remaining surface area of ​​the laminations;

[0051] removing insulation material from said web region;

[0052] subjecting the rotor stack as a whole to a heat treatment process to harden only the unmasked bridges and / or struts;

[0053] connecting a rotor shaft to the rotor stack to construct the rotor assembly, wherein the magnet web regions correspond to respective magnetic poles of the rotor; and

[0054] The rotor assembly is positioned radially within the stator assembly to thereby construct the rotating electrical machine.

[0055] Option 18. The method according to Option 17, wherein the predetermined angular distance is 180 degrees.

[0056] Embodiment 19. The method of embodiment 17, wherein removing the insulating material from the web region comprises:

[0057] stacking the plurality of laminations in a predetermined pattern such that the struts of adjacent laminations do not overlap; and

[0058] Thereafter, the insulating material is etched from the web region before subjecting the rotor stack to the heat treatment process.

[0059] Embodiment 20. The method according to embodiment 17, wherein subjecting the rotor stack to the heat treatment process includes subjecting the rotor stack to a ferrite nitrocarburizing process, a gaseous nitriding process, a plasma nitriding process, or a salt bath nitriding process.

[0060] The above summary is not intended to represent every possible embodiment of the present disclosure or every aspect of the present disclosure. On the contrary, the above summary is intended to illustrate some of the novel aspects and features disclosed herein. The above features and advantages and other features and advantages of the present disclosure will be apparent from the following detailed description of representative embodiments and modes for implementing the present disclosure when combined with the accompanying drawings and the appended claims. BRIEF DESCRIPTION OF THE DRAWINGS

[0061] Figure 1 is a schematic exploded perspective view of a portion of a prior art rotor stack, the construction of which is modified as set forth herein.

[0062] Figure 2is a schematic perspective view of a stator and rotor assembly having a rotor stack constructed as described herein.

[0063] Figure 3 yes Figure 2 Schematic cross-sectional side view of portions of a rotor assembly shown in .

[0064] Figure 3A is a schematic plan view of an offset rotor lamination according to the present disclosure.

[0065] Figure 4 and Figure 5 are schematic cross-sectional views of two possible step stacking patterns that may be used to optimize the etchant path to remove insulating material from rotor laminations.

[0066] The present disclosure is susceptible to modification and alternative forms, wherein representative embodiments are shown as examples in the drawings and described in detail below. The inventive aspects of the present disclosure are not limited to the disclosed embodiments. On the contrary, the present disclosure is intended to cover modifications, equivalents, combinations and alternatives that fall within the scope of the present disclosure as defined by the appended claims. DETAILED DESCRIPTION

[0067] Referring to the drawings, in which like reference numerals designate the same or similar parts throughout the several views, Figure 1 , a portion of a prior art rotor stack 10A having a longitudinal center axis 11 is schematically depicted. When the rotor stack 10A is incorporated into a rotor assembly, the center axis 11 becomes the axis of rotation of the rotor assembly. As will be appreciated by one of ordinary skill in the art, the rotor stack 10A may be comprised of a number of thin annular rotor laminations 12A suitable for the application, wherein, in a typical embodiment, each lamination 12A has a thickness of approximately 0.20-0.30 mm. In the annular form, each lamination 12A has a circular outer diameter surface 14 and a circular inner diameter surface 16. The laminations 12A may define radial teeth or splines 15 that engage the rotor shaft. As will be described in detail below, Figure 1 The lamination 12A shown in FIG. 1 is modified as described herein to constitute Figure 3A The laminations 12 are subjected to heat treatment in a targeted manner in the magnet web region 22 thereof. Figure 1 1 and 2. This magnet web region 22 of lamination 12A is depicted in FIG. 1 without the offset geometry of lamination 12 of the present disclosure, wherein the structures of laminations 12A and 12 are otherwise identical.

[0068] For a typical rotor stack 10A, the axial orientation of each rotor lamination 12A is the same along the entire length of the central axis 11. As described above, prior to constructing the rotor stack 10A, each rotor lamination 12A is subjected to a heat treatment process, sometimes after carefully masking the magnet web area 22 using a suitable masking material. The magnet web area 22 of a typical rotor lamination 12A and the laminations 12 of the present disclosure may include one or more pairs of V-shaped rotor openings 18. In a non-limiting internal permanent magnet embodiment, each opening 18 may be configured to receive a corresponding permanent magnet 20, i.e., as Figure 1 20L or the relatively small bar-type permanent magnet 20S shown on the right side of FIG. Other configurations that forgo the use of permanent magnets 20 are conceivable, such as synchronous reluctance motors, and therefore, permanent magnets 20 may or may not be included in the configuration of rotor stack 10A. However, for clarity of description, opening 18 is hereinafter referred to as magnet opening 18, regardless of whether permanent magnets 20 are present therein.

[0069] Each magnet opening 18 extends between a radially inner distal end 18I and a radially outer distal end 18O, wherein the outer distal end 18O is adjacent to the outer diameter surface 14 and is separated therefrom by an arcuate thin strip of lamination material referred to herein as a bridge 50. The inner distal ends 18I are separated from each other by radially extending thin strips of lamination material referred to herein as pillars 52. The remainder of the magnet opening 18 is defined by surrounding material referred to as transverse reluctance paths 53, wherein the pillars 52 intersect or terminate in one of the transverse reluctance paths 53 as shown and as understood in the art.

[0070] As will be referenced below Figure 2-5 This method modifies Figure 1 The depicted configuration of the laminations 10A, and the sequence of assembly and heat treatment, so that adjacent laminations 12 ( Figure 3 and Figure 3A ) are oriented alternately along the central axis 11. The alternating orientation of the laminations 12, when viewed along the central axis 11, ultimately results in the bridges 50 and / or struts 52 of the magnet web region 22 being exposed / unshielded from the heat treatment atmosphere, while at the same time, the remaining surface area of ​​the laminations 12 is effectively shielded from such an atmosphere by adjacent laminations 12.

[0071] The rotor laminations 12 of the present disclosure may be individually pressed or stamped from a thin sheet metal blank, such as machine steel or another magnetically conductive material. Such blanks may be coated with a dielectric insulating material, such as insulating varnish, before or after pressing. Figure 1As shown in the lamination 12A of the present disclosure, the lamination 12 of the present disclosure is annular and, therefore, also has a circular outer diameter surface 14 and inner diameter surface 16. When a sufficient number of laminations 12 are stacked one on top of another, the rotor stack 10 presents as Figure 2 , so as to be contained within the rotor assembly 26 .

[0072] Brief reference Figure 3A , Figure 2 The rotor stack 10 may be configured for use in an internal permanent magnet (IPM) rotating electrical machine. To this end, the magnet openings 18 of the various laminations 12 are asymmetric. Each magnet opening 18 in this non-limiting IPM embodiment is configured to receive a corresponding permanent magnet 20 therein, such as Figure 1 The term "asymmetric" as used herein means that, relative to an imaginary axis bisecting a given rotor pole, the magnet opening 18 is slightly larger on one side of the axis than on the opposite side. For example, this may result in Figure 3A The bridges 50 may be formed in a similar asymmetrical manner such that the bridges 50 are not centered about the axis X, Y, YX, or XY, and / or the bridges 50 are formed in a similar asymmetrical manner so that flipping the laminations 12 about the appropriate axis has the desired effect of offsetting the bridges 50 of two adjacent laminations 12. Such geometric features allow the bridges 50 and / or the struts 52 of each web region 22 to be exposed to the heat treatment atmosphere while the remaining surface area of ​​the lamination 12 is shielded by the overlapping structure of the adjacent or nearest adjacent / neighboring laminations 12.

[0073] The rotor stack 10 is formed Figure 2 The magnetic poles of the rotor assembly 26 can be optionally constructed using an asymmetric "single V" or "double V" arrangement of four such permanent magnets 20, wherein the permanent magnets 20 are positioned adjacent to the outer diameter surface 14. A first pair of small magnets 20S and a second pair of large magnets 20L can be arranged end to end in a V shape, where "S" and "L" are abbreviations for "small" and "large", respectively, and indicate that the small magnets 20S are smaller than the large magnets 20L (see Figure 1 ). The first pair of small magnets 20S and the second pair of large magnets 20L are arranged at an angle known in the art as a V angle, which in the illustrated embodiment opens toward the outer diameter surface 14. The magnet openings 18 mentioned above are separated from each other by narrow strips of lamination material forming magnet web areas 22, wherein each web area 22 is as described below with reference to Figure 3-5 As described, the material is arranged and selectively heat treated.

[0074] The permanent magnet 20 in various non-limiting exemplary embodiments may be formed of a bar magnet of neodymium iron boron (NdFeB), samarium cobalt (SmCo), ferrite, or another magnetic material suitable for the application. Figure 1 and Figure 3A An exemplary 8-pole embodiment is depicted in each of the figures, wherein the present teachings can be readily extended to these and other pole configurations. Each asymmetric magnet opening 18 receives therein Figure 1 The magnet opening 18 is sized and shaped to facilitate insertion of the permanent magnet 20 into the rotor stack 10 in the axial direction.

[0075] Reference again Figure 2 Once the following reference has been Figure 3-5 The method described fully constructs the rotor stack 10, and before or after the rotor stack 10 is subjected to a heat treatment process, the rotor stack 10 is journaled, splined or otherwise securely connected to the rotor shaft 24. The rotor stack 10 is then sandwiched between a pair of annular end plates 25 disposed at opposite axial ends of the rotor stack 10 to thereby form a rotor assembly 26. To construct a rotating electrical machine 28, the rotor assembly 26 may be mated with a stator assembly 30, for example, by radially positioning the rotor assembly 26 within the stator assembly 30 such that the stator assembly 30 surrounds / circumscribes the rotor assembly 26. Its distal end is from Figure 2 A plurality of stator teeth 32 , visible from a perspective of FIG. 8 , protrude radially from a cylindrical stator core or housing 34 , wherein adjacent stator teeth 32 are separated from one another by corresponding stator slots (not shown) filled with stator windings 36 .

[0076] In such a multi-phase embodiment of the rotating electric machine 28, an AC input voltage (VAC) is applied to the terminals of the phase wires 38 of the stator windings 36 to thereby energize the stator assembly 30 and thereby generate a rotating stator magnetic field. Figure 1 The permanent magnets 20 visible in the figure together establish a time-invariant rotor magnetic field. The magnetic fields of the stator and rotor interact to generate and maintain power within the stator-rotor air gap, wherein this force ultimately imparts rotation when used as part of an electric machine 28. Figure 2 The resulting rotation of the rotor assembly 26 about its axis 11 can be utilized to perform work in many electromechanical systems.

[0077] One non-limiting exemplary system that benefits from this rotation is the electric powertrain 31 of the illustrated motor vehicle 40, which may variously be implemented as a hybrid electric or battery electric vehicle. The motor torque (arrow T M ) can be transmitted to a transmission (T) 42 of the motor vehicle 40 alone or together with engine torque from an internal combustion engine (not shown). The output torque (arrow T O) can be transmitted to one or more wheels 44 of the motor vehicle 40 to propel the motor vehicle 40 along a road surface 46. When constructed as described herein, other applications can benefit from the rotor assembly 26 and motor 28, including other types of vehicles, such as ships, airplanes, and trains. Mobile platforms and robots can also benefit from the present teachings, as can fixed applications, such as power plants, cranes, etc.

[0078] Reference again Figure 3 and Figure 3A , which depicts the arrangement on the central axis 11 Figure 2 Schematic side view of the rotor assembly 26, wherein the annular end plate 25 is omitted for simplicity of illustration. The rotor shaft 24 is provided at the inner diameter surface 16 (see Figure 3A ) is coupled to the rotor stack 10, wherein when in the completed construction of the rotating electrical machine 28 Figure 2 When the stator assembly 30 is energized, the rotor stack 10 and the rotor shaft 24 rotate in unison about the axis 11. Figure 3 The section line 3A-3A is taken Figure 3A The laminations 12 shown in plan view in FIG. 1 have either a forward orientation ("FO") 12F or a rearward orientation ("RO") 12R. Each lamination 12 is identically constructed but oppositely oriented, i.e., the terms "forward" and "rearward" are nominal directions that denote that each successive lamination 12 positioned along axis 11 is rotated 180° about its radial / vertical axis Y or X, or in some embodiments, about central axis 11. Using the analogy of obverse / reverse coin faces, the forward orientation 12F may be considered the "obverse" side of the coin, while the rearward orientation may be considered the "reverse" side, with similar obverse or reverse orientations of a given lamination 12 alternating from left to right along axis 11, as shown in FIG. Figure 3 This progressive flipping or alternative forward-reverse orientation of the laminations 12 enables selective and isolated heat treatment of the magnet web regions 22 to occur once the rotor stack 10 is fully constructed.

[0079] like Figure 3A As best shown in FIG. 1 , each magnet web region 22 of a given lamination 12 includes the above-mentioned bridges 50 and struts 52, which together with Figure 1 The transverse reluctance paths 53 of the laminations 12 together define individual magnet openings 18 adjacent to the outer diameter surface 14 of the laminations 12. As part of the disclosed method, Figure 3AIn the illustrated 8-pole embodiment of , the sides of a given magnet web region 22 are slightly offset from the center, i.e., axis Y, X, XY, or YX. As a result, when viewed along axis 11, the offset progression of the web region 22 exposes the bridges 50 and / or struts 52 of the adjacent nearest neighboring laminations 12 while simultaneously masking the remaining surface area of ​​the nearest neighboring laminations 12. As a result, a specified portion of the magnet web region 22 is left uncovered and fully exposed to the gaseous atmosphere employed in subsequent heat treatment of the assembled rotor stack 10. In this way, the entire rotor stack 10 can be heat treated, wherein the alternating orientation of the laminations 12 masks portions of the rotor stack 10 that should not be heat treated.

[0080] After the rotor stack 10 is constructed, the present method facilitates heat treatment and strengthening of the isolation of the bridges 50 and / or legs 52 of the magnet web regions 22. To do this, each web region 22 is asymmetrical about the center axis Y, X, XY, or YX of the eight exemplary double-V magnet configurations. That is, each magnet opening 18 is slightly offset from its corresponding center axis, with the effect that the magnet opening 18 on one side of its corresponding axis is slightly larger than the magnet opening 18 on the opposite side of the center axis.

[0081] As described above, the laminations 12 are typically pressed from thin metal billets or sheets of steel or another ferrous material and are subsequently heat treated individually prior to assembly into a rotor stack. However, heat treating the laminations 12 individually may have the undesirable effect of increasing the magnetic resistance of the regions of the laminations 12 that are outside the bridges 50 and struts 52 and may also increase cycle time while potentially introducing warping issues. Likewise, applying and removing masking material adds cost and time to the manufacturing process. In contrast, the present method presses the laminations 12 and subsequently removes the insulating material, if present, from the bridges 50 and struts 52. Thereafter, the method includes heat treating the laminations 12 as explained above and Figure 3 and Figure 3A The rotor stack 10 is constructed by alternately orienting the laminations 12 in an offset pattern as shown in FIG. The rotor stack 10 as a whole is then subjected to a heat treatment process as opposed to heat treating individual laminations.

[0082] For example, a blank sheet of sheet metal may be rolled and uniformly coated with an insulating material. The coated blank is then stamped or pressed to produce Figure 3A Then, the laminate 12 is arranged in Figure 3The rotor stack 10 is then placed on the rotor shaft 24 to reduce cycle time, ensure maximum stack factor, and eliminate the possibility of stacking warped laminations 12. During assembly, a certain pattern or assembly may be used so that the bridges 50 and struts 52 of adjacent laminations 12 do not overlap each other. Then, before heat treatment, for example, the insulating material is removed from the web area 22 using a mechanical process such as grinding or a chemical process such as etching. The rotor stack 10 is then subjected to a predetermined heat treatment process, wherein non-limiting exemplary heat treatment processes that may be used with the rotor stack 10 include nitrocarburizing, gas nitriding, plasma nitriding, salt bath nitriding, or other high temperature heat treatment processes where masking of the laminations 12 is feasible.

[0083] Due to this change in the manufacturing sequence of the rotor assembly 26 relative to conventional methods, these conventional methods, when fully heat treated, perform the rotor assembly 26 prior to assembling the rotor stack. Figure 1 In order to heat treat each of the laminations 12A, it may be necessary to target the application of the insulating material around the magnet web area 22 to avoid coating the bridges 50 and the pillars 52. Alternatively, the entire lamination 12 may be coated and thereafter the insulating material removed from the bridges 50 and the pillars 52. When the application of the insulating material is targeted, the method may include rolling the insulating material onto the major surface of the lamination using a patterned brush or applicator, wherein the brush or applicator is configured with a raised or patterned surface that does not contact the web area 22 as the brush / applicator passes over the lamination 12. Such a method would avoid the need to apply masking material on the web area 22 and the attendant need to remove such masking material.

[0084] Alternatively, and with reference to Figure 4 and Figure 5 , the exposed surface of the lamination 12 may be uniformly coated with an insulating material, wherein the web region 22 is subsequently stripped of the material using a mechanical or chemical process. For example, when the insulating material is to be chemically removed from the web region 22 using a suitable etchant such as a nitric acid solution. For example, in forming Figure 1 and Figure 3 Prior to the rotor stack 10, the laminations 12 may be arranged in two possible "stepped" stacking patterns to provide an optimized etchant flow path.

[0085] Figure 4 The pattern 60 may need to be formed as Figure 3 12F and a plurality of laminations 12 having a front orientation 12F and a rear orientation 12R as shown in FIG. 1 , and laminations 12 having a symmetrical orientation, i.e., wherein the magnet openings 18 mentioned above are symmetrical (“S”). That is, the struts 52S having a symmetrical orientation may be Figure 3AThe etchant is then free to flow through the exposed pillars 52S, 52F, and 52R, wherein the pillars 52F and 52R have respective front and rear orientations. As will be appreciated by those skilled in the art, a similar pattern 60 may be used for etching of the bridge 50. Figure 5 The pattern 62 illustrates six pillars 52 arranged in an alternating pattern such that an overall step profile is formed by the pillars 52, which will enable the etchant to flow through the pillars 52 in different manners.

[0086] The present teaching enables implementation of Figure 2 A method of a rotor assembly 26 for use with a rotating electric machine 28. As will be appreciated by one of ordinary skill in the art based on this disclosure, possible embodiments of the method include forming a plurality of annular rotor laminations 12 from a metal billet, wherein each lamination 12 has: a radial axis, e.g., Figure 3A The outer diameter surface 14 is formed by defining a plurality of spaced apart magnet web areas 22 near the outer diameter surface 14. Each magnet web area includes a plurality of magnet openings 18, which are formed by radially extending struts 52 and one or more bridges 50 and Figure 1 The transverse magnetic resistance path 53 is defined.

[0087] In this embodiment, the method may include coaxially stacking annular rotor laminations 12 to form a rotor stack 10, which includes rotating or positioning every other lamination 12 in the laminations 12 about or relative to one of its radial axes at a predetermined angular distance. For example, each lamination 12 may be rotated 180° relative to its adjacent neighboring laminations relative to the radial axis to expose the struts 52 and mask the remaining surface area of ​​the laminations 12. Other rotation patterns may be used to achieve similar effects, such as, for example, rotation of a first lamination 12 to expose the bridge 50 of an immediately adjacent second lamination 12 through the magnet opening 18 of the first lamination 12, such as Figure 3A The bridges 50 and / or struts 52 may be exposed in a desired manner, as indicated by arrow B in FIG. 1 , or by using more than two orientation stages or modes along the central axis 11 .

[0088] The method may include, before or after heat treating the rotor stack 10, Figure 2 and Figure 3 The rotor shaft 24 is connected to the rotor stack 10 to construct the rotor assembly 26, wherein the magnet web areas 22 correspond to the respective magnetic poles of the rotor assembly 26. Thereafter, the rotor assembly 26 may be subjected to a predetermined heat treatment process, such as a ferrite nitrocarburizing process, a gas nitriding process, or a salt bath nitriding process, to harden only the unmasked magnet web areas 22.

[0089] In various embodiments of the method, forming the annular rotor laminations 12 may include pressing or stamping asymmetric V-shaped magnet openings 18 in each lamination 12. The asymmetric V-shaped magnet openings 18 may include a double V configuration having a first set and a second set of V-shaped magnet openings 18, such as Figure 1 and Figure 3A As shown in FIG. 1 , the first and second sets of V-shaped magnet openings 18 are each separated by a respective one of the struts 52 and each define a V-angle that opens toward the outer diameter surface 14 .

[0090] The metal blanks mentioned above may be coated with an insulating material. In such a case, the method may include removing the insulating material from the web region 22 before subjecting the rotor assembly 26 to a predetermined heat treatment process. Stacking the laminations 12 may occur in a predetermined stepped pattern, for example, corresponding to Figure 4 and Figure 5 The pattern 60 or 62 occurs such that the legs 52 of adjacent laminations 12 do not overlap one another. Thereafter, the method may include etching the insulating material from the web region 22 prior to subjecting the rotor assembly 26 to a predetermined heat treatment process.

[0091] When forming the annular rotor laminations 12 and before subjecting the rotor assembly 26 to a predetermined heat treatment process, the method may include coating the laminations with an insulating material without coating the web region 22. The surface of the metal blank mentioned above may be uniformly coated with the insulating material, in which case the method may include removing the insulating material from the web region 22 before subjecting the rotor assembly 26 to a predetermined heat treatment process. Embodiments of the method may include Figure 2 The rotor assembly 26 is radially positioned within the stator assembly 30 to thereby construct a rotating electric machine 28. The electric machine 28 can be used to Figure 2 A transmission 42 of a motor vehicle 40 , shown schematically in FIG. 4 , provides torque.

[0092] Therefore, the present method purposefully uses the opposite orientation of adjacent laminations 12 to Figure 3A The bridge 50 and the support 52 are exposed to the heat treatment atmosphere while masking the remaining surface area of ​​the adjacent laminations 12. This method prevents the bridge 50 and the support 52 from conducting electricity even when the insulating coating is completely removed. As a result, the magnet web area 22 is fully and effectively hardened without reducing the magnetic permeability of the ferrous area of ​​the rotor laminations 12 located outside the magnet web area 22. In addition, the enhanced magnet web area 22 can help enable higher speed operation and provide other structural benefits without the need for a corresponding increase in the thickness of the magnet web area 22. In view of the foregoing disclosure, one of ordinary skill in the art will readily appreciate these and other benefits.

[0093] Although the best mode and some of the other embodiments have been described in detail, there are various alternative designs and embodiments for practicing the present teachings defined in the appended claims. Those skilled in the art will recognize that the disclosed embodiments may be modified without departing from the scope of the present disclosure. In addition, the present concept explicitly includes combinations and sub-combinations of the described elements and features. The detailed description and drawings are support and description of the present teachings, and the scope of the present teachings is limited only by the claims.

Claims

1. A method of constructing a rotor assembly for use with a rotating electrical machine, the method comprising: forming a plurality of annular rotor laminations from a metal billet, wherein each of the annular rotor laminations has an outer diameter surface and defines a plurality of magnet web regions adjacent the outer diameter surface, and wherein the annular rotor laminations are coated with an insulating material, the insulating material not covering the magnet web regions, each respective one of the magnet web regions including a plurality of asymmetric openings having first and second distal ends defined by respective radially extending struts and arcuate peripheral bridges, each opening being separated from the outer diameter surface by one of the peripheral bridges; Coaxially stacking the annular rotor laminations to thereby form a rotor stack includes positioning the annular rotor laminations at a predetermined angular distance relative to a radial axis or a longitudinal center axis of the rotor stack to thereby not cover or expose the struts and / or the peripheral bridges and to cover or mask the remaining surface area of ​​the annular rotor laminations; and The rotor stack is subjected to a heat treatment process to thereby harden only the uncovered or unmasked peripheral bridges and / or struts.

2. The method according to claim 1, wherein: The predetermined angular distance is 180 degrees.

3. The method according to claim 1, wherein: Forming the plurality of annular rotor laminations includes pressing or stamping one or more asymmetric V-shaped openings as the asymmetric openings in each of the magnet web regions of the annular rotor laminations.

4. The method according to claim 3, wherein: The asymmetric V-shaped openings include first and second groups of V-shaped openings separated by a respective one of the struts and each defining a V angle opening toward the outer diameter surface.

5. The method according to claim 1, wherein: The metal blank is coated with an insulating material prior to forming an annular rotor lamination, the method further comprising removing the insulating material from the web region prior to subjecting the rotor assembly to the heat treatment process.

6. The method of claim 5 further comprising stacking the plurality of annular rotor laminations in a predetermined pattern such that the struts and / or the peripheral bridges of an adjacent pair of the annular rotor laminations do not overlap, and subsequently etching the insulating material from the web region prior to subjecting the rotor stack to the heat treatment process.

7. The method of claim 1 further comprising coating the annular rotor laminations with an insulating material without coating the web region after forming the plurality of annular rotor laminations and before subjecting the rotor assembly to the heat treatment process.

8. The method according to claim 1, wherein: The surface of the metal blank is coated with an insulating material, and the method further comprises removing the insulating material only from the web region before subjecting the rotor stack to the heat treatment process.

9. The method according to claim 1, wherein: Subjecting the rotor component to the heat treatment process includes subjecting the rotor component to a ferrite nitrocarburizing process, a gas nitriding process, or a salt bath nitriding process.

10. The method according to claim 1, further comprising: connecting a rotor shaft to the rotor stack to thereby construct the rotor assembly, wherein the magnet web regions correspond to respective magnetic poles of the rotor; as well as The rotor assembly is positioned radially within the stator assembly to thereby construct the rotating electrical machine.

11. The method of claim 10, further comprising using the rotary electric machine to provide torque to a transmission of a motor vehicle.

12. A rotating electrical machine, comprising: stator assembly; as well as a rotor assembly disposed radially within the stator assembly and having: a rotor stack comprised of a plurality of coaxially stacked annular rotor laminations, wherein each of the annular rotor laminations has a radial axis and an outer diameter surface and defines a plurality of asymmetric heat-treated magnet web regions proximate the outer diameter surface, the annular rotor laminations being coated with an insulating material, the insulating material not covering the magnet web regions, each of the asymmetric magnet web regions including a plurality of asymmetric openings defined by radially extending struts and one or more arcuate peripheral bridges, each opening being separated from the outer diameter surface by one of the peripheral bridges, and wherein every other annular rotor lamination in the annular rotor laminations is positioned at a predetermined angular distance relative to a radial axis or a central axis of the annular rotor stack so as to thereby not cover or expose the peripheral bridges and / or the struts and to cover or mask the remaining surface area of ​​the annular rotor laminations; a pair of end plates, each connected to an opposite axial end of the rotor stack; and a rotor shaft connected to the inner diameter surface of the annular rotor laminations; Wherein, the magnet web regions correspond to corresponding magnetic poles of the rotor assembly.

13. The rotating electric machine according to claim 12, wherein: The predetermined angular distance is 180 degrees.

14. The rotating electric machine according to claim 12, wherein: The asymmetric openings include first and second groups of V-shaped openings, each separated by a respective one of the struts and each defining a V-angle opening toward the outer diameter surface.

15. The rotating electric machine according to claim 12, wherein: The rotating electrical machine is connected to a transmission of a motor vehicle.

16. The rotating electric machine according to claim 12, wherein: The rotating electrical machine is an interior permanent magnet motor and wherein a respective permanent magnet is located within each of the openings.

17. A method for constructing a rotating electrical machine, the method comprising: forming a plurality of annular rotor laminations from a metal billet, wherein each of the annular rotor laminations has a radial axis and an outer diameter surface and thereby defines a plurality of magnet web regions adjacent the outer diameter surface, wherein the annular rotor laminations are coated with an insulating material, the insulating material not covering the magnet web regions, each of the magnet web regions including a pair of asymmetrical V-shaped openings defined by radially extending struts and one or more arcuate peripheral bridges and having a V-angle opening toward the outer diameter surface, each opening being separated from the outer diameter surface by one of the peripheral bridges; coaxially stacking the annular rotor laminations to thereby form a rotor stack, comprising positioning every other one of the annular rotor laminations at a predetermined angular distance relative to the radial axis or a longitudinal center axis of the rotor stack to expose the peripheral bridge and / or the struts and mask the remaining surface area of ​​the annular rotor laminations; removing insulation material from said web region; subjecting the rotor stack as a whole to a heat treatment process to harden only the unmasked peripheral bridges and / or struts; connecting a rotor shaft to the rotor stack to construct a rotor assembly, wherein the magnet web regions correspond to respective magnetic poles of the rotor; and The rotor assembly is positioned radially within the stator assembly to thereby construct the rotating electrical machine.

18. The method according to claim 17, wherein: The predetermined angular distance is 180 degrees.

19. The method according to claim 17, wherein: Removing the insulating material from the web region comprises: stacking the plurality of annular rotor laminations in a predetermined pattern such that the legs of adjacent annular rotor laminations do not overlap; and Thereafter, the insulating material is etched from the web region before subjecting the rotor stack to the heat treatment process.

20. The method according to claim 17, wherein: Subjecting the rotor stack to the heat treatment process includes subjecting the rotor stack to a ferritic nitrocarburizing process, a gaseous nitriding process, a plasma nitriding process, or a salt bath nitriding process.

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