Rotor for an electric machine, electric machine for a vehicle, and vehicle

Abstract

A rotor for an electric machine and a method for manufacturing a rotor for an electric machine are provided. An exemplary method includes assembling a lamination stack structure to form a rotor core having an outer surface. The rotor core defines one to five interior cavities, and an interior permanent magnet is positioned in a selected interior cavity. The method also includes positioning a non-magnetic structural element in the selected interior cavity. Further, the method includes applying a press force on the outer surface of the rotor core with an annular sleeve.

Description

Technical Field

[0001] This technical field generally relates to rotors for electric motors, and more specifically to rotors having an internal cavity accommodating an internal permanent magnet and having a compression sleeve. Background Technology

[0002] A rotor, such as that for an internal permanent magnet (IPM) motor, includes a rotor core assembled around a rotating shaft. Typically, the rotor consists of segments assembled to form laminations, which are then stacked to form the rotor core. The rotor core typically includes cavities that act as flux barriers to influence the operating characteristics of the motor. The laminations of the rotor core are formed as discs with a central opening for assembly onto the rotating shaft. Flux barriers are distributed around the shaft opening. The flux barriers typically extend from an end adjacent to the circumference of the laminations toward the shaft opening. As described herein, the flux barrier cavities surround or contain permanent magnets.

[0003] The physical size, number, and positioning of flux barrier cavities affect motor performance. Therefore, even a large flux barrier placed in a suboptimal location may not result in optimal performance. Furthermore, motors are prone to flux leakage through lamination features surrounding flux barriers that might be structurally necessary. These factors lead to flux barrier design and positioning that leaves only thin structural features to support the rotor core. These thin lamination features may limit the achievable performance and speed of the motor without placing excessive stress on the rotor core or excessively increasing feature size. The presence of flux barrier cavities may structurally weaken the rotor, making it unsuitable for high-speed applications.

[0004] Therefore, it is desirable to provide an economical rotor for an electric motor that achieves high performance with minimal structural feature dimensions. Furthermore, it is desirable to provide a rotor for an electric motor that includes an annular sleeve and non-magnetic structural elements to provide compressive force, preventing cavity collapse or rotor deformation. In addition, other desirable features and characteristics of the embodiments will become readily apparent from the accompanying drawings and the foregoing technical and background information, based on the following detailed description and appended claims. Summary of the Invention

[0005] A rotor for an electric motor, an electric motor for a vehicle, a vehicle, and a method of manufacturing the same are provided. In an exemplary embodiment, a method for manufacturing a rotor for an electric motor is provided. An exemplary method includes assembling a laminated stack structure to form a rotor core having an outer surface. The rotor core defines one to five layers of internal cavities, and internal permanent magnets are positioned in at least one selected internal cavity. The method also includes positioning non-magnetic structural elements in the selected internal cavities. Furthermore, the method includes applying a compressive force to the outer surface of the rotor core using an annular sleeve.

[0006] In some embodiments, applying compressive force to the outer surface of the rotor core using an annular sleeve includes providing a pre-formed annular sleeve and press-fitting the pre-formed annular sleeve onto the outer surface of the rotor core.

[0007] In some embodiments, applying compressive force to the outer surface of the rotor core using an annular sleeve includes stretching and winding fibers around the outer surface of the rotor core and curing the fibers to form an annular sleeve on the outer surface of the rotor core.

[0008] In some embodiments, the annular sleeve is a mesh with multiple radial openings.

[0009] In some embodiments, the profile of the outer surface of the rotor core is designed to define a recess, and an annular sleeve is received within the recess.

[0010] In some embodiments, the maximum thickness of the annular sleeve is less than 5 millimeters (mm), for example, less than 2 mm.

[0011] In some embodiments, positioning the non-magnetic structural element in a selected internal cavity includes injecting a polymeric resin into the selected internal cavity and curing the polymeric resin. In other embodiments, the polymeric resin is bonded to the walls of the selected internal cavity of the rotor and to an internal permanent magnet.

[0012] In some embodiments, the selected internal cavity is a V-shaped cavity and includes a first leg-shaped portion and a second leg-shaped portion, the internal permanent magnet includes a first internal permanent magnet located in the first leg-shaped portion of the selected internal cavity, the internal permanent magnet includes a second internal permanent magnet located in the second leg-shaped portion of the selected internal cavity, and the non-magnetic structural element extends from contact with the first internal permanent magnet to contact with the second internal permanent magnet.

[0013] In some embodiments, assembling the lamination stack structure to form a rotor core includes assembling lamination segments to form each lamination having a cavity, inserting a magnet layer into the cavity, and stacking the laminations.

[0014] In another exemplary embodiment, a rotor for an electric motor is provided. In one embodiment, the rotor includes a rotor core having an outer surface. The rotor core defines one to five layers of internal cavities. The rotor also includes internal permanent magnets located in selected internal cavities. The rotor also includes non-magnetic structural elements located in selected internal cavities. Furthermore, the rotor includes an annular sleeve surrounding the outer surface of the rotor core and applying compressive force thereon.

[0015] In some embodiments, the annular sleeve is a mesh component with multiple radial openings.

[0016] In some embodiments, the profile of the outer surface of the rotor core is designed to define a recess in which an annular sleeve is received.

[0017] In some embodiments, the maximum thickness of the annular sleeve is less than 5 millimeters (mm), for example, less than 2 mm.

[0018] In some embodiments, the rotor core has a maximum outer diameter of 100 to 200 mm and a maximum axial length of 50 to 200 mm.

[0019] In some embodiments, the structural elements are injected polymer resin. In other embodiments, the structural elements are injected polymer resin that is attached to the walls of selected internal cavities of the rotor and internal permanent magnets.

[0020] In some embodiments, the selected internal cavity is a V-shaped cavity and includes a first leg-shaped portion and a second leg-shaped portion, the internal permanent magnet includes a first internal permanent magnet located in the first leg-shaped portion of the selected internal cavity, the internal permanent magnet includes a second internal permanent magnet located in the second leg-shaped portion of the selected internal cavity, and the non-magnetic structural element extends from contact with the first internal permanent magnet to contact with the second internal permanent magnet.

[0021] In some embodiments, selected internal cavities of the rotor core are separated from the outer surface of the rotor core by bridging portions of the rotor core.

[0022] In another exemplary embodiment, a vehicle is provided. The exemplary vehicle includes an electric motor configured to actuate the vehicle. In the exemplary embodiment, the electric motor includes a rotor and a stator. The exemplary rotor includes a rotor core having an outer surface, wherein the rotor core defines an internal cavity. Furthermore, the exemplary rotor includes an internal permanent magnet located within the internal cavity and a non-magnetic structural element located within the internal cavity. Additionally, the exemplary rotor includes an annular sleeve surrounding the outer surface of the rotor core and applying a compressive force to the outer surface of the rotor core.

[0023] This summary is provided to introduce some concepts in a simplified form, which will be further described in the detailed description below. This summary is not intended to identify key or essential features of the claimed subject matter, nor is it intended to help determine the scope of the claimed subject matter. Attached Figure Description

[0024] Exemplary embodiments will be described below in conjunction with the accompanying drawings, wherein the same reference numerals denote the same elements, and wherein:

[0025] Figure 1 These are diagrams illustrating exemplary embodiments of a vehicle having an electric motor, according to various embodiments;

[0026] Figure 2 According to various embodiments Figure 1 A schematic diagram of the motor;

[0027] Figure 3 It is a section taken approximately along line 3-3 according to various embodiments. Figure 2 A partial sectional view of the rotor core;

[0028] Figure 4 According to various embodiments Figure 3 A plan view of the laminations of the rotor core;

[0029] Figure 5 This is a partial cross-sectional view of another rotor core according to various embodiments;

[0030] Figure 6 According to various embodiments Figure 5 A plan view of the rotor laminations;

[0031] Figure 7 It is a plan view of another rotor core and the surrounding annular sleeve according to various embodiments;

[0032] Figure 8 According to various embodiments Figure 7 An exploded view of a portion of the rotor core and annular sleeve, showing the internal permanent magnets located within the rotor core; and

[0033] Figure 9 and Figure 10 Provided similar Figure 8 The view shows adjacent rotor laminations having slotted outer surfaces to receive mesh-like annular sleeves according to various embodiments. Detailed Implementation

[0034] The following detailed description is merely exemplary in nature and is not intended to limit application or use. Furthermore, it is not intended to be bound by any express or implied theory presented in the foregoing technical field, background art, invention summary, or the following detailed description.

[0035] As used herein, the word “exemplary” means “serving as an example, instance, or illustration.” As used herein, unless otherwise stated, “a” or “described” means one or more types. The term “or” can be connected or separate. In some embodiments, figures indicating the amount, ratio, physical properties, and / or use of materials in this specification may be understood to be modified by the word “about.” The term “about,” used in conjunction with numerical values ​​and claims, indicates a range of precision familiar and acceptable to those skilled in the art. Typically, such a range of precision is ±10%. Unless otherwise expressly stated, all figures indicating the amount, ratio, physical properties, and / or use of materials in this specification may be understood to be modified by the word “about.”

[0036] As used herein, unless otherwise stated, “%” or “percentage” as described in this disclosure means weight percentage. Furthermore, as used herein, an element identified as “material” comprises at least 50% by weight of the material. As used herein, an element identified as “main material” is a material comprising at least 90% by weight of the material.

[0037] Furthermore, terms such as “upper,” “lower,” “above,” “below,” “above,” “under,” “upward,” “downward,” etc., are used to describe the accompanying drawings and do not imply a limitation on the scope of the subject matter as defined by the appended claims. Any numerical designations, such as “first” or “second” and “minor” or “primary,” are merely illustrative and not intended to limit the scope of the subject matter in any way. It should be noted that while embodiments may be described herein with respect to automotive applications, those skilled in the art will recognize its broader applicability.

[0038] The embodiments described herein relate to rotors in electric motors for vehicles, and specifically to maintaining or improving the structural or mechanical strength of such rotors while maintaining or improving their magnetic properties, i.e., minimizing magnetic leakage. In the embodiments described herein, the rotor includes an internal permanent magnet. This magnet is located within the rotor core and is radially spaced from the outer surface of the rotor core's outer diameter.

[0039] The embodiments described herein include features enabling the use of annular sleeves as tensile structural elements for transferring loads to relatively thin portions of the rotor core. As used herein, the term structural element refers to an unrestricted load-bearing object. Furthermore, the term "compressive" does not require deformation of the structural element but rather implies that compressive loads can be applied to the structural element, and in response, the compressive structural element applies a preload to the core, wherein the preload can be zero or greater when the rotor is stationary. For example, the compressive annular sleeve can be made of any material with sufficient rigidity to bear the applied load. Compressive annular sleeves can be included without negatively impacting the rotor's magnetism. Higher rotor speeds and desired magnetic properties can be achieved while maintaining desired thin and lightweight laminated features, such as webs, struts, and bridging elements, resulting in relatively low material costs, weight, and compact dimensions.

[0040] As described herein, exemplary embodiments prestress or preload the rotor core prior to operation by applying compressive force to the outer surface of the rotor core using an annular sleeve. Furthermore, such embodiments provide sufficient mechanical or structural strength to the rotor core to withstand the compressive force of the annular sleeve by at least partially filling the rotor cavity with one or more non-magnetic structural elements. Therefore, the rotor core will not buckle, collapse, or otherwise deform when compressive stress is applied by the annular sleeve.

[0041] During motor operation, the rotor must withstand centrifugal forces or loads. The extruded annular sleeve and non-magnetic structural elements work together to bear the mechanical loads applied during motor operation. For example, the non-magnetic structural elements can transfer forces from the axial region of the rotor to the annular sleeve. Therefore, magnetic structural elements, such as the internal web formed of electrical steel, can be reduced in size or thickness, or can be eliminated from the rotor core.

[0042] The exemplary embodiments reduce magnetic leakage while maintaining structural integrity, enabling the motor to operate reliably. Furthermore, the exemplary embodiments provide safe and reliable operation of the motor at higher rotational speeds.

[0043] Furthermore, exemplary embodiments may provide reduced mass, lower component costs, increased torque, reduced magnet content, high-speed operation, reduced active material mass, and improved packaging.

[0044] Figure 1 This is a basic diagram of an exemplary embodiment of a vehicle 10 including an exemplary embodiment of an electric motor 20. The electric motor 20 is formed by a stator 30 and a rotor 40 arranged within the stator 30. The electric motor 20 is designed to actuate or drive the vehicle 10. Therefore, the vehicle 10 can be an electric vehicle or a hybrid vehicle.

[0045] Figure 2 The structure of the motor 20 is shown in more detail. As shown, the motor 20 includes a stator 30 and a rotor 40, and the rotor 40 is configured to rotate about an axis 25 defined by the motor 20. In the figure, the rotor 40 is shown outside the stator 30 for visibility.

[0046] In the illustrated embodiment, motor 20 is configured as a motor, wherein the current in the rotor 40 that generates torque is induced from the magnetic field generated by the energization of the stator 30. In several embodiments, motor 20 is an AC motor suitable for applications requiring regulated speed control (such as for vehicle traction motors), but this disclosure is not limited to these applications.

[0047] An exemplary stator 30 is a generally annular component that may be constructed for single-phase or multi-phase power, such as three-phase. In an exemplary embodiment, the stator 30 includes a stator core 31 made of a stacked structure of stator laminations 32. The stator laminations 32 may be formed from stampings slotted to receive windings (not shown) and made of a soft magnetic material such as silicon steel. The stator laminations 32 may be insulated from each other by a thin, non-conductive coating. In other embodiments, another ferromagnetic material may be used. The stator 30 may include windings for energizing.

[0048] like Figure 2As shown, the exemplary rotor 40 includes a rotor core 41 surrounded by an annular sleeve 42. In the illustration, a portion of the annular sleeve 42 is broken to allow view of the rotor core 41 below. The exemplary rotor core 41 is formed of a stacked structure of rotor laminations 43 and configured to receive a shaft 44. The exemplary rotor core 41 has a maximum outer diameter of 100 to 200 mm and a maximum axial length of 50 to 200 mm. The exemplary rotor laminations 43 may be stamped or otherwise formed. The exemplary rotor laminations 43 are made of a ferromagnetic material and may be insulated from each other by a thin, non-conductive coating, or may be made of another material. The exemplary rotor laminations 43 are formed of electrical steel. End rings 45, 46 are formed at the ends of the rotor core 41. In an exemplary embodiment, the end rings 45, 46 are made of a lightweight aluminum material. The rotor 40 is configured with a plurality of magnetic poles to generate a magnetic circuit of the rotor 40 that, depending on the angular position of the rotor 40, interacts with a magnetic circuit induced by the stator 30 of the motor 20. These magnetic poles can be generated at least in part by the flux barrier described below.

[0049] Figure 3 Shown separately and in more detail Figure 2 Rotor core 41. In Figure 3 In the image, the rotor core 41 is shown in cross-section, with one of the laminations 43 having its side 48 exposed and visible.

[0050] As shown, the laminate 43 includes multiple openings, referred to as cavities, which can be used for various purposes. Distributed around the rotor core 41 near the outer surface of the outer periphery 50 are eight cavity groups 51, each cavity group 51 forming two angled layers including a secondary inner cavity 52 and a primary inner cavity 53. The inner cavities 52 and 53 in each cavity group 51 extend through the stacked rotor laminations 43 in a longitudinal direction 54 parallel to the axis 25 of the shaft 44. The cavity groups 51 act as barriers to magnetic flux and help define the magnetic poles of the rotor. Therefore, in the illustrated embodiment, the rotor has eight poles. The rotor can be formed with any suitable desired number of poles. For example, the rotor can be formed with six poles.

[0051] like Figure 3 As shown, each internal cavity 52 and 53 is generally V-shaped, such that each V-shaped cavity includes a first leg-like portion 55 and a second leg-like portion 56 that merge together at the opening confluence 57. In the exemplary embodiments herein and as shown, the first leg-like portion 55 and the second leg-like portion 56 are not separated from each other by any web or other structural member. Instead, each individual cavity 52 or 53 is formed by and includes the leg-like portion 55 and the leg-like portion 56.

[0052] Figure 4 It is shown Figure 3A plan view of the side surface 48 of the rotor core 41. Figure 4 In the diagram, dashed lines indicate each cavity group 51. (As shown...) Figure 4 As shown, each cavity 52 or 53 extends from and terminates at the first end 65 and the second end 66. More specifically, each first leg-shaped portion 55 extends from the first end 65 to the opening confluence portion 57, and each second leg-shaped portion 56 extends from the second end 66 to the opening confluence portion 57. At the opening confluence portion 57, the leg-shaped portions 55 and 56 meet and are laterally defined by the inner confluence edge 67 and the outer confluence edge 68.

[0053] like Figure 4 As shown, each internal cavity 52 or 53 can be closed by a bridging portion 58 of the laminations 43 (and the rotor core 41 defined by the stacked structure of the laminations 43), such that no internal cavity 52 or 53 communicates with the outer surface of the outer periphery 50 of the rotor core 41. In other words, each end 65 and 66 of cavities 52 and 53 is spaced from the outer surface of the outer periphery 50 by a distance greater than zero.

[0054] In addition, Figure 4 In each cavity group 51, the corresponding first end 65, first leg-like portion 55, confluence portion 57, second leg-like portion 56, and second end 66 of the secondary internal cavity 52 and the main internal cavity 53 are separated from each other by a V-shaped web 59, which extends continuously from near the first end 65 to near the second end 66. In other words, in each cavity group 51, the V-shaped web 59 separates the main V-shaped internal cavity 53 from the secondary V-shaped internal cavity 52.

[0055] As mentioned above, Figure 3 and Figure 4 The rotor core 41 with cavities 52 and 53 is shown, meaning there are no internal permanent magnets or structural elements within the internal cavities. This is presented in this manner for convenience and clarity. Figure 3 and Figure 4 . Figure 5 and Figure 6 The embodiments are also shown without internal permanent magnets.

[0056] exist Figure 5 and Figure 6 Another embodiment of the rotor core 140 is shown in the image. Similar to... Figure 3 and Figure 4 The rotor core 140 is shown separately and in detail. Figure 5 In the image, the rotor core 141 is shown in cross-section, with one of the laminations 143 having its side 148 exposed and visible.

[0057] As shown in the figure, the rotor core 140 includes eight cavity groups 151 (in Figure 6(Separated by dashed lines). Each cavity group includes a main layer 153 and a secondary layer 152 of linear cavities 155 and 156. Within each layer 152 and 153, linear cavities 155 and 156 are separated from each other by a web portion 157. If the rotor is designed not to use an annular sleeve for compressing the rotor core 140 and not to use non-magnetic structural elements (described below), the web portion 157 must be designed to be thick enough to bear substantially all the centrifugal loads and withstand the stresses applied at the rotor's maximum speed. However, in such a design, the increased thickness of the web portion required to withstand stresses at increased rotational speeds would cause the web portion to become a source of magnetic leakage. Therefore, as described below, the use of a compressible annular sleeve and non-magnetic structural elements provides a reduced thickness of the web portion to bear only a portion of the centrifugal loads, or to eliminate the web portion entirely.

[0058] Therefore, in some embodiments herein, and as Figure 3 and Figure 4 As shown, the web portion 157 has been removed from the rotor core 41. In other embodiments herein, and as... Figure 5 and Figure 6 As shown, there is a web portion 157, but compared to embodiments where the web portion 157 must bear the entire load, the web portion 157 has a reduced size or thickness due to the load borne by the non-magnetic structural elements and the compressive force applied by the annular sleeve.

[0059] Figure 7 An embodiment of a rotor 40 with a rotor core 41 is shown, wherein only a single cavity 52 is provided in each cavity group 51. Furthermore, Figure 7 The rotor core 41 is provided with six cavity groups 51, which define six magnetic poles.

[0060] Figure 7 An annular sleeve 42 surrounding the rotor core 41 is also shown. The exemplary annular sleeve 42 applies a preload force of 0.1% to 1.5%. In other words, the exemplary annular sleeve 42 is stretched to a value between 0.1% and 1.5% to apply the preload force. As shown, the annular sleeve 42 contacts the outer surface of the outer periphery 50 and has a thickness 69. In an exemplary embodiment, the maximum thickness of the annular sleeve is less than about 5 millimeters (mm), for example, less than 2 mm. The annular sleeve 42 may be a solid, continuous annular sheet having only an open top and an open bottom, or, as described below, the annular sleeve 42 may be formed with perforations or radial openings, for example, in the form of a mesh or fabric. In an exemplary embodiment, the annular sleeve 42 is formed of a composite material of carbon fibers held together with resin. Various high-strength fibers are suitable for use, including glass or other oxide fibers (e.g., basalt, alumina), and extremely high-strength polymer fibers (e.g., available from DuPont). Heat-resistant para-aramid synthetic fibers may be available from Honeywell. Polyethylene fibers, boron fibers, or metal fibers. Suitable resins may include epoxy resins, polyurethanes, phenolic resins, bismaleimide, etc.

[0061] Figure 8 yes Figure 7 An exploded view of a portion of the rotor 40 shows a single cavity assembly 51 and a single cavity 52 therein, the outer surface of the outer periphery 50, and the annular sleeve 42 thereon. Furthermore, Figure 8 An internal permanent magnet 70 located in cavity 52 is shown.

[0062] It should be noted that the embodiments described herein include rotors 40 with any suitable arrangement of cavity 52, such as those having... Figure 3 and Figure 4 Each of them comprises multiple layers of a single cavity, having, for example... Figure 5 and Figure 6 Each of them comprises multiple layers with multiple cavities, having, for example... Figure 7 A single layer with a single cavity, a single layer with multiple cavities, or other arrangements, including Figure 4-8 The combination of features shown.

[0063] exist Figure 8 In one embodiment, each internal permanent magnet 70 is received within a corresponding leg portion of cavity 52. ​​It is conceivable that, in the embodiments herein, the internal permanent magnet 70 is located in each leg portion 55 and 56 of each cavity 52 (and 53, when present), in the leg portions 55 and 56 of selected cavities 52 (and / or 53, when present), or in selected leg portions 55 and 56 of selected cavities 52 (and / or 53, when present). In other embodiments, a single internal permanent magnet 70 may be accommodated within cavity 52.

[0064] like Figure 8As shown, the internal permanent magnet 70 is fitted into a cavity 52 within the rotor core 41. As used herein, "internal" means that the permanent magnet 70 is located within the rotor core, not on its outer surface. The internal permanent magnet 70 may not fill the cavity 52, such that some portions of the cavity 52 (such as the end portion 71 and the central portion 72) remain "empty," i.e., filled only with ambient air or gas. Furthermore, while some portions of the outer surface 73 of the internal permanent magnet 70 may directly contact the cavity wall 74 defined by the rotor core 41, other portions of the outer surface 73 of the internal permanent magnet 70 may be spaced apart from adjacent cavity walls 74, forming a gap 75 between them. For example, a gap may be provided between the cavity wall 74 and the outer surface 73 of the internal permanent magnet 70 to facilitate placement of the internal permanent magnet 70 within the cavity 52. ​​In an exemplary embodiment, the gap is approximately 0.1 mm on all sides of the internal permanent magnet 70. Therefore, a portion of the outer surface 73 of the internal permanent magnet 70 can be spaced 0.2 mm or less from the adjacent cavity wall 74.

[0065] like Figure 8 As shown, in the exemplary rotor 40, a non-magnetic structural element 80 is also located in the cavity 52. ​​The non-magnetic structural element 80 is formed of a non-magnetic or non-ferromagnetic material (i.e., a material not attracted by a magnet). The non-magnetic structural element 80 is provided to resist the preload force applied by the extrusion annular sleeve, such that the rotor core is subjected to extrusion stress without buckling, collapsing, or otherwise deforming. Therefore, the exemplary non-magnetic structural element 80 fills sufficient space in the cavity so that the rotor core is not deformed due to the extrusion force of the sleeve. The structural element 80 may fill or at least partially fill the ends 71, the central portion 72, and the gap 75 of the cavity 52. ​​For example, the structural element 80 may fill at least 50% of the remaining volume in the cavity 52 after the internal permanent magnet 70 is assembled in the cavity 52, such as at least 60%, at least 70%, at least 80%, at least 90%, or at least 95% of the remaining volume in the cavity 52 after the internal permanent magnet 70 is assembled in the cavity 52. In the illustrated embodiment, the non-magnetic structural element 80 extends from contact with one internal permanent magnet 70 to contact with another internal permanent magnet 70.

[0066] In an exemplary embodiment, the structural element 80 is formed by injecting a flowable material, such as a liquid or gel, into the cavity 52 and curing the flowable material. For example, the structural element 80 can be formed by injecting a polymeric resin into the cavity 52 and curing the polymeric resin. In other embodiments, the structural element 80 may be a solid member inserted into the cavity 52. ​​Such a solid member may be flexible and / or extrudable. Furthermore, in some embodiments, the structural element 80 may be formed by a combination of injected flowable material and inserted one or more solid members.

[0067] An exemplary structural element 80 is incorporated into the outer surface 73 and cavity wall 74 of each internal permanent magnet 70. For example, the polymer resin used to form the structural element can be an adhesive. Any suitable material can be used to form the structural element 80, but the selection should be based on stability and mechanical strength during the operating temperature range. To select the structural element, the coefficient of thermal expansion should be as closely matched as possible to the coefficients of thermal expansion of other materials. For example, to fill an otherwise empty cavity in a steel core, the coefficient of thermal expansion (CoTE) should ideally be approximately the same as that of steel over the automotive electric motor temperature range of -40°C to 150°C. Further consideration should be given to selecting a structural element for use with magnets exhibiting odd thermal expansion characteristics. Furthermore, a suitable structural element 80 has a Young's modulus greater than approximately 8 GPa. Additionally, a suitable structural element 80 has a tensile strength exceeding 50 MPa. Furthermore, a suitable structural element 80 is formed from a material compatible with automatic transmission fluids and retains its properties over the range of -40°C to 150°C. This typically means a glass transition temperature greater than 150°C. In an exemplary embodiment, the structural elements are formed of a polymer, which is typically filled with particles or short fibers to obtain these performance characteristics. These particles and / or fibers can be glass, minerals, or various oxides.

[0068] As described above, during motor operation, structural element 80 is configured to bear tensile loads from the portion 81 of the rotor core 41 located between cavity 52 and axis 25. Figure 8 In one embodiment, where the web portion 157 is absent, the structural element 80 alone bears the tensile load. In an embodiment where the web portion 157 has a reduced thickness, a portion of the load is borne by the web portion 157, and a portion of the load is borne by the structural element 80.

[0069] exist Figure 8 In this embodiment, the annular sleeve 42 is shown on the outer surface of the outer periphery 50. In an exemplary embodiment, the minimum distance between the outer surface of the outer periphery 50 and the cavity wall 74 of the cavity 52 is typically about 0.5 mm to 1 mm, and can be as large as 3 mm to 4 mm. In other words, the bridging portion 58 has a minimum thickness of 0.5 to 4 mm, such as 0.5 mm, 1 mm, 3 mm, or 4 mm.

[0070] In some embodiments, adding a continuous annular sleeve to the outer periphery 50 of the rotor core 41 will undesirably increase the effective air gap, i.e., the air space between the rotor core and the stator. Therefore, in some embodiments (and as in...) Figure 9 and Figure 10 As shown), the outer surface of the outer periphery 50 is shaped to include a slot to receive a discontinuous annular sleeve in order to prevent the need to increase the effective air gap.

[0071] Figure 9 and Figure 10 Provided similar Figure 8 of Figure 7 An exploded view of a portion of rotor 40. However, Figure 9 and Figure 10 It is shown that the outer periphery 50 may be formed or have a slot 82. Therefore, an extension 83 of the outer periphery 50 is formed at a first radial distance from the axis 25, and a slotted or recessed portion 84 of the outer periphery 50 is formed at a second radial distance from the axis 25. As shown, the first radial distance is greater than the second radial distance.

[0072] The outer periphery 50 and the slot 82 can be designed to optimize magnetic properties by simultaneously considering the effects on magnetic flux and reluctance torque through the positioning slot 82 (and the extension 83). In an exemplary embodiment, the slot 82 is located where magnet leakage would otherwise be a problem, such as directly radially outward from the bridging portion 58.

[0073] from Figure 9 and Figure 10 It is understood that in this embodiment, the annular sleeve 42 is discontinuous, for example, a mesh. It is conceivable that the annular sleeve 42 is formed with a rectangular or diamond mesh pattern, or any other suitable geometry with radially extending openings. As shown, the annular sleeve is located within the slot 82 and not on the extension 83 of the outer periphery 50. Positioning the annular sleeve 42 within the slot 82 rather than above the extension 83 allows the annular sleeve 42 to be added to the rotor core 41 without increasing the effective air gap between the rotor and stator.

[0074] Understandable. Figure 9 and Figure 10 The diagram shows adjacent and alternating laminations in the stacked structure forming the rotor core 41, and may provide a diamond-patterned meshing annular sleeve 42.

[0075] This document also provides a method for manufacturing a rotor for an electric motor. In an exemplary embodiment, the method includes assembling a laminated stack structure to form a rotor core having an outer surface, wherein the rotor core defines an internal cavity, and wherein an internal permanent magnet is positioned within the internal cavity. More specifically, the method may include assembling laminate segments to form each laminate having a cavity. Furthermore, the method may include inserting magnet layers into the cavities of the laminates. It is conceivable that the method includes inserting magnet layers only into selected cavities, i.e., not all cavities, or inserting them into all cavities. The method may continue to stack the laminates and the magnet layers therein. The laminates are aligned such that the cavities in adjacent laminates and the magnet layers therein are aligned to form the rotor core and the internal permanent magnet. The method may include insulating the laminates from each other with a thin, non-conductive coating.

[0076] Exemplary methods also include positioning a nonmagnetic structural element within an internal cavity. As described above, the nonmagnetic structural element may be formed of a flowable material such as a liquid or gel. Inserting the nonmagnetic structural element may include injecting the flowable material into the internal cavity. Other embodiments may include inserting a solid nonmagnetic structural element into the cavity, or injecting and / or inserting a combination of flowable and solid materials.

[0077] An exemplary method further includes applying a compressive force to the outer surface of the rotor core using an annular sleeve after the non-magnetic structural element has been positioned in the internal cavity. In an exemplary embodiment, the annular sleeve applies a preload force of 0.1% to 1.5%. In an exemplary embodiment, the sleeve is pre-formed and press-fitted or slidable onto the rotor. In other embodiments, the sleeve is formed by stretching and winding fibers around the outer surface of the rotor core and curing the fibers to form an annular sleeve on the outer surface of the rotor core. In any embodiment, the internal permanent magnet and non-magnetic structural element are located in the rotor cavity before the sleeve is placed onto the rotor.

[0078] While at least one exemplary embodiment has been presented in the foregoing detailed description, it should be understood that numerous variations exist. It should also be understood that the one or more exemplary embodiments are merely examples and are not intended to limit the scope, applicability, or configuration of this disclosure in any way. Rather, the foregoing detailed description will provide those skilled in the art with a convenient roadmap for implementing one or more exemplary embodiments. It should be understood that various changes can be made to the function and arrangement of the elements without departing from the scope of this disclosure as set forth in the appended claims and their legal equivalents.

Claims

1. A method for manufacturing a rotor for an electric motor, the method comprising: Assemble a lamination stack structure to form a rotor core having an outer surface, wherein the profile of the outer surface is formed to define a slot and an extension, wherein the extension defines the outer periphery of the rotor core, wherein the rotor core defines one to five layers of internal cavities, and wherein an internal permanent magnet is positioned in at least one selected internal cavity. Positioning non-magnetic structural elements within the selected internal cavity; and Applying compressive force to the outer surface of the rotor core using an annular sleeve, wherein the annular sleeve is discontinuous and located in the slot rather than on the extension, wherein applying compressive force to the outer surface of the rotor core using an annular sleeve comprises: stretching and winding fibers around the outer surface of the rotor core and curing the fibers to form the annular sleeve in the slot of the outer surface of the rotor core.

2. The method according to claim 1, wherein, Applying compressive force to the outer surface of the rotor core using an annular sleeve includes: providing a pre-formed annular sleeve and press-fitting the pre-formed annular sleeve onto the outer surface of the rotor core and into the slot.

3. The method according to claim 1, wherein, Positioning the non-magnetic structural element in the selected internal cavity includes injecting polymeric resin into the selected internal cavity and curing the polymeric resin.

4. The method according to claim 1, wherein: The selected internal cavity is a V-shaped cavity and includes a first leg-shaped portion and a second leg-shaped portion; The internal permanent magnet includes a first internal permanent magnet located in the first leg-shaped portion of the selected internal cavity; The internal permanent magnet includes a second internal permanent magnet located in the second leg-shaped portion of the selected internal cavity; and The non-magnetic structural element extends from contact with the first internal permanent magnet to contact with the second internal permanent magnet.

5. A rotor for an electric motor, comprising: A rotor core having an outer surface and defining an axis, wherein the rotor core defines one to five layers of internal cavities, wherein the outer surface is formed with an extension and a slot, wherein the outer surface in the extension is located at a first radial distance from the axis, wherein the outer surface in the slot is located at a second radial distance from the axis, and wherein the first radial distance is greater than the second radial distance. An internal permanent magnet is located in a selected internal cavity; A non-magnetic structural element, wherein the non-magnetic structural element is located in a selected internal cavity; and An annular sleeve surrounds the outer surface of the rotor core and applies a compressive force to the outer surface of the rotor core in the slot, wherein the annular sleeve is not located at a radial distance from the axis greater than a first radial distance.

6. The rotor according to claim 5, wherein, The annular sleeve is not located radially outside the extension.

7. The rotor according to claim 5, wherein, The annular sleeve is located only in the slot.

8. The rotor according to claim 5, wherein: The selected internal cavity is a V-shaped cavity and includes a first leg-shaped portion and a second leg-shaped portion; The internal permanent magnet includes a first internal permanent magnet located in the first leg-shaped portion of the selected internal cavity; The internal permanent magnet includes a second internal permanent magnet located in the second leg-shaped portion of the selected internal cavity; and The non-magnetic structural element extends from contact with the first internal permanent magnet to contact with the second internal permanent magnet.

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