Rotor assembly with containment ring for electric motor

Abstract

The present disclosure provides a rotor assembly with a containment ring for an electric motor. A rotor assembly for an electric motor includes a rotor core, a plurality of magnets, and a rotor core mold member. The rotor core defines a rotor bore and a plurality of cavities distributed around the rotor bore and extending through the rotor core. And the plurality of magnets are arranged in the plurality of cavities. The rotor core mold member extends through the plurality of cavities to retain the plurality of magnets therein and extends from the cavities to a first end of the rotor core to form a containment ring at the first end. The containment ring forms a rim over a surface of the first end to restrict fluid flow to an outside surface of the rotor core.

Description

Technical Field

[0001] The present disclosure relates to a rotor assembly for an electric motor and more particularly for an electric motor that receives a cooling fluid. Background Art

[0002] Electric motors, such as those employed in electric vehicles, employ a rotor and a stator to generate torque. In a non-limiting example, a vehicle electric motor is powered by a traction battery to provide propulsion power to the vehicle. Such vehicle electric motors are typically three-phase motor powered. Summary of the invention

[0003] In one form, the present disclosure relates to a rotor assembly for an electric motor. The rotor assembly includes a rotor core, a plurality of magnets, and a rotor core mold member. The rotor core defines a rotor hole and a plurality of cavities distributed around the rotor hole and extending through the rotor core. The plurality of magnets are disposed in the plurality of cavities. The rotor core mold member extends through the plurality of cavities to retain the plurality of magnets therein, and extends from the cavities to a first end of the rotor core to form a containment ring at the first end. The containment ring forms a rim above a surface of the first end to limit fluid flow to an outer side surface of the rotor core.

[0004] In one form, the present disclosure is directed to a method comprising: providing a rotor core defining a plurality of cavities distributed around a rotor bore and having a plurality of magnets disposed in the plurality of cavities; arranging a mold cover defining a groove at a first end of the rotor core; injecting a resin into the rotor having the plurality of magnets so that the resin coats the magnets within the cavities and protrudes from the groove at the first end; and curing the resin to form a rotor core mold member having a containment ring at least partially formed by the groove to form a rotor assembly.

[0005] In one form, the present disclosure relates to a rotor assembly for an electric motor. The rotor assembly includes a rotor core, a plurality of magnets, and a rotor core mold member. The rotor core defines a rotor hole, a plurality of cavities distributed around the rotor hole and extending through the rotor core, and a plurality of fluid channels extending from the rotor core to a first end. The plurality of magnets are disposed in the plurality of cavities. The rotor core mold member extends through the plurality of cavities to retain the plurality of magnets therein, and extends from the cavities to a first end of the rotor core to form a containment ring at the first end. The containment ring forms an edge above a surface of the first end and surrounds an outlet of the fluid channel at the first end of the rotor core to limit fluid flow from the outlet to an outer side surface of the rotor core. BRIEF DESCRIPTION OF THE DRAWINGS

[0006] Figure 1 is a perspective view of an electric motor having a stator assembly and a rotor assembly according to the teachings of the present disclosure;

[0007] Figure 2 According to the teachings of this disclosure Figure 1 A perspective view of a rotor assembly;

[0008] Figure 3 According to the teachings of this disclosure Figure 1 A partial cross-sectional view of an electric motor;

[0009] Figure 4 is an example molding procedure for forming a rotor core mold member; and

[0010] Figure 5 is a perspective view of a mold cover employed during a molding process in accordance with the teachings of the present disclosure. DETAILED DESCRIPTION

[0011] As required, detailed embodiments of the present invention are disclosed herein; however, it should be understood that the disclosed embodiments are merely examples of the present invention that can be implemented in various forms and alternative forms. The drawings are not necessarily drawn to scale; some features may be enlarged or minimized to show details of specific components. Therefore, the specific structural details and functional details disclosed herein are not to be interpreted as limiting, but merely as a representative basis for teaching those skilled in the art to adopt the present invention in various ways.

[0012] refer to Figures 1 to 3 The electric motor 100 includes, among other components, a stator assembly 102 defining a stator bore 104 and a rotor assembly 106 disposed in the stator bore 104. In one form, the stator assembly 102 includes a set of windings 110 and a stator core 112 defining the stator bore 104 and a plurality of winding cavities 114. The set of windings 110 may be made of copper or other suitable material and disposed in the plurality of winding cavities 114. Ends of the set of windings extend beyond a first end 116A of the stator core 112, and in some applications, portions of the set of windings 110 extend beyond a second end 116B of the stator core 112.

[0013] In one form, the rotor assembly 106 includes a rotor core 120 defining a plurality of cavities 122 and a plurality of magnets 124 disposed in the plurality of cavities 122. The rotor core 120 further defines a rotor bore 126 for a rotor shaft (not shown) fixed to and rotated by the rotor core 120. The rotor core 120 further defines a plurality of fluid passages 130 extending from the rotor bore 126 to at least one end 127 of the rotor core 120 to define an outlet 132 at the end 127 of the rotor core 120.

[0014] During operation, current is applied to the windings 110 of the stator assembly 102 to generate electromagnetic (EM) forces that rotate the rotor assembly 106. Due to various design and operating factors, such as, but not limited to, the presence of eddy currents and the amount of power applied, heat is generated at the stator assembly 102 (e.g., windings 110) and the rotor assembly 106 (e.g., magnets 124), thereby increasing the temperature of the electric motor 100.

[0015] In one form, to control the temperature of the electric motor 100, a cooling fluid is provided and flowed through the electric motor 100 to extract heat from the rotor assembly 106 and the stator assembly 102. In a non-limiting example, the cooling fluid is fed from an external source (e.g., a transmission system of a vehicle) through the center of the rotor shaft and flows through the rotor shaft and then radially outward to the fluid channels 130 of the rotor core 120. The channels 130 are formed proximate to the magnets 124 so that the cooling fluid extracts heat from the magnets 124, which are the primary heat generators in the rotor assembly 106.

[0016] The cooling fluid is provided from the rotor fluid passage 130 to the winding 110 of the stator assembly 102 to cool the stator assembly 102. The cooling fluid will be directed to the winding 110 without overflowing into the gap 140 between the rotor assembly 106 and the stator assembly 102. That is, in order to suppress or reduce the drag loss, the electric motor 100 may include an added component to suppress the cooling fluid from flowing from the outlet 132 to the gap 140.

[0017] For example, separate end plates are typically provided at the ends of the rotor assembly 106 to create the offset required to prevent the cooling fluid from entering the gap 140. Instead of additional components and manufacturing steps, the rotor assembly 106 of the present disclosure includes a rotor core mold member 150 that is an integrated component having a containment ring 152 to restrict the flow of cooling fluid.

[0018] In one form, the containment ring 152 protrudes from the end 127 of the rotor core 120 and has a rim 154 extending above the end 127 of the rotor core 120 to direct the cooling fluid away from the outer side surface of the rotor assembly 106 or more specifically away from the gap 140. In addition, the containment ring 152 surrounds the outlet 132 of the fluid passage 130 to retain and prevent the cooling fluid exiting the fluid passage 130 from flowing radially to the gap 140. More specifically, the cooling fluid flows radially outward due to the centrifugal force generated by the rotor assembly 106. The containment ring 152 prevents the cooling fluid from flowing radially along the end 127 of the rotor core 120 toward the gap 140, and directs the cooling fluid away from the end 127 and the gap 140 to flow radially outward onto the ends of the windings 110 of the stator assembly 102. Figure 3An example flow path 156 for the cooling fluid is provided in . The cooling fluid further absorbs heat from the windings 110 of the stator assembly 102 to cool the stator assembly 102 and is then directed to an external source where the now heated cooling fluid is cooled using known techniques.

[0019] In one form, the rotor core mold member 150 is formed during the molding process of the rotor assembly 106, wherein the rotor core 120 having the magnets 124 disposed in the cavity 122 is injected with liquid resin to secure the magnets 124 in the cavity 122. More specifically, referring to Figure 4 , an example molding procedure 200 for forming a rotor core mold member 150 is provided. At 202, a mold cover is disposed at the end 127 of the rotor core 120. The rotor core, magnets 124, and mold cover may be collectively referred to as a core assembly.

[0020] refer to Figure 5 , an example of a mold cover 250 is provided, and the mold cover is adapted to substantially cover the end 127 of the rotor core 120. The mold cover 250 defines a groove 254, which is adapted to align with a plurality of cavities 122 having magnets 124 and at least one gap ( Figure 2 ). The groove 254 is also adapted to surround the outlet 132 of the fluid passage 130. The contour and / or size of the groove 254 is designed to provide the desired contour and size of the containment ring 152 (ie, the containment ring 152 is formed by the groove 254 of the mold cover 250).

[0021] In some processes, the core assembly is fixed in a fixture to provide an axial compressive force on the core assembly. Using known techniques, at 202, resin is injected into the rotor core 120, and specifically into the cavity 122 with the magnet 124, so that the resin coats the magnet 124 in the cavity and then flows to the end 127 of the rotor core 120 to protrude from the groove 254. Using at least a mold cover 250, the resin is blocked from entering the fluid channel 130. At 206, the resin is cured to form a rotor core mold member 150 with a containment ring 152, and once cooled, the rotor core 120 with the magnet 124 and the rotor core mold member 150 is removed from the fixture at 208. To form electric motor 100 , rotor assembly 106 is positioned within stator bore 104 of stator assembly 102 such that set of windings 110 extend from end 116A of stator assembly 102 that aligns with end 127 of rotor core 120 having containment ring 152 .

[0022] Continue to refer Figures 1 to 3As part of rotor core mold member 150, containment ring 152 is adapted to contact at least two or more of the plurality of cavities 122, and in some variations, to contact all of the cavities 122 to enhance contact and support containment ring 152 to rotor core 120. In addition, containment ring 152 is adapted to be formed in at least one molded gap 158 (defined between magnet 124 and cavity 122 receiving magnet 124) between the magnet 124 and the cavity 122. Figure 2 ) extends above. Specifically, portions of rotor core mold member 250 include a cured resin disposed in a gap between magnet 124 and cavity 122. For ease of illustration, molded gap 158 is configured as a circle arranged between magnet 124 and cavity 122. However, it should be readily understood that the shape of molded gap 158 is determined based at least on the space between magnet 124 and cavity 122, and thus the form of molded gap 158 varies and should not be limited to the accompanying drawings. In some variations, containment ring 152 is connected to a cured resin film, which is further connected to the cured resin in cavity 122 to secure containment ring 152 at end 127 of rotor core 120.

[0023] In some variations, if the rotor assembly 106 has a non-uniform configuration in the lateral direction, the rotor core mold member 150 may include a shell formed along the outer diameter of the rotor core 120 that may connect the portions of the rotor core mold member 150 including the containment ring 152 together and allow for simultaneous molding.

[0024] In some variations, the rotor core mold member 150 may be provided as a single connected piece of molding compound having at least the containment ring 152 and the molding void 158 surrounding the magnets 124 in the cavity.

[0025] In the example shown, containment ring 152 has a circular shape and a triangular cross-section. Although containment ring is shown as a circular ring with uniform height and triangular cross-section, containment ring 152 can be configured in various suitable ways, such as but not limited to different shapes, uniform / variable heights, uniform / variable thicknesses, different cross-sections, etc., achieved by, for example, adjusting the physical characteristics of the groove of the mold cover (e.g., adjusting the shape, size).

[0026] Although containment ring 152 is shown as being located at one end of rotor assembly 106, rotor core mold member 150 may form a second containment ring at a second end of rotor core 120 opposite end 127 of rotor core 120. Thus, during the molding process, a second mold cap may be provided at the second end of rotor core 120 before injecting resin to form the second containment ring.

[0027] With the containment ring, additional different components (such as end plates) can be removed to control the flow of the coolant fluid. This can reduce the manufacturing process of the rotor assembly and the complexity and weight of the electric motor while still providing fluid flow control at the end of the rotor core.

[0028] Using a rotor core mold member with a containment ring, the rotor assembly may also allow for internal rotor cooling in a rotor assembly architecture that may not typically be possible due to known issues associated with balancing rotor assemblies. That is, the rotor assembly may need to be balanced by inserting pins into discrete locations at the ends of the rotor core, which may require exposed ends (i.e., no end plates and therefore no internal rotor cooling). Using the rotor core mold member of the present disclosure, the ends of the rotor core may remain exposed to receive balancing pins while using containment rings to strategically direct cooling fluid away from the gap and onto the stator end windings.

[0029] Although exemplary embodiments are described above, these embodiments are not intended to describe all possible forms of the present invention. Rather, the words used in the specification are descriptive rather than restrictive terms, and it should be understood that various changes may be made without departing from the spirit and scope of the present invention. In addition, the features of the various embodiments of implementation may be combined to form other embodiments of the present invention.

[0030] According to the present invention, a rotor assembly for an electric motor is provided, the rotor assembly having: a rotor core, the rotor core defining a rotor hole and a plurality of cavities, the plurality of cavities being distributed around the rotor hole and extending through the rotor core; a plurality of magnets, the plurality of magnets being disposed in the plurality of cavities; and a rotor core mold member, the rotor core mold member extending through the plurality of cavities to retain the plurality of magnets therein, and extending from the cavities to a first end of the rotor core to form a containment ring at the first end, wherein the containment ring forms an edge above a surface of the first end to limit fluid flow to an outer surface of the rotor core.

[0031] According to an embodiment, the rotor core defines a plurality of fluid channels extending from the rotor bore to the first end, wherein the fluid can flow from the rotor bore through the fluid channels and to the first end, and the containment ring surrounds outlets of the fluid channels at the first end.

[0032] According to an embodiment, the rotor core has a second end opposite the first end, and the rotor core mold member extends to the second end and includes a second containment ring located at the second end.

[0033] According to an embodiment, the containment ring has a varying height and thickness.

[0034] According to an embodiment, the height and thickness of the containment ring are uniform.

[0035] According to an embodiment, the rotor core mould member is defined by a resin material that hardens during a curing process.

[0036] According to an embodiment, the rotor core mould member is adapted to directly contact each cavity of the plurality of cavities.

[0037] According to the present invention, there is provided an electric motor having: a stator assembly defining a stator bore; and a rotor assembly of the previous embodiment disposed in the stator bore of the stator assembly.

[0038] According to an embodiment, the stator assembly includes a set of windings extending from at least one end of the stator assembly, and the fluid may flow from the first end of the rotor core to an end of the set of windings extending from the at least one end of the stator assembly.

[0039] According to the present invention, a method includes: providing a rotor core, which defines a plurality of cavities distributed around a rotor hole and has a plurality of magnets arranged in the plurality of cavities; arranging a mold cover defining a groove at a first end of the rotor core; injecting resin into the rotor having the plurality of magnets so that the resin coats the magnets in the cavities and protrudes from the groove at the first end; and curing the resin to form a rotor core mold member, the rotor core mold member having a containment ring at least partially formed by the groove to form a rotor assembly.

[0040] In one aspect of the invention, the method includes positioning the rotor assembly in a stator bore of a stator assembly, the stator assembly having a set of windings extending from at least one end of the stator assembly aligned with the first end of the rotor core.

[0041] In one aspect of the invention, the method includes disposing a second mold cover defining a groove at a second end of the rotor core, wherein the rotor core mold member has a second containment ring formed at least in part by the groove of the second mold cover.

[0042] In one aspect of the present invention: the rotor core defines a plurality of fluid channels extending from the rotor hole to the first end, the mold cover is adapted to cover outlets of the fluid channels at the first end such that the groove is defined around the outlets, and injecting the resin also includes providing an axial compression force to the mold cover and the rotor core, wherein the containment ring surrounds the outlets of the fluid channels at the first end.

[0043] According to the present invention, a rotor assembly for an electric motor is provided, the rotor assembly having: a rotor core, the rotor core defining: a rotor hole; a plurality of cavities, the plurality of cavities being distributed around the rotor hole and extending through the rotor core; and a plurality of fluid channels, the plurality of fluid channels extending from the stator core to a first end; and a plurality of magnets, the plurality of magnets being disposed in the plurality of cavities; and a rotor core mold member, the rotor core mold member extending through the plurality of cavities to retain the plurality of magnets therein, and extending from the cavities to the first end of the rotor core to form a containment ring at the first end, wherein: the containment ring forms an edge above a surface of the first end, and the containment ring surrounds an outlet of the fluid channel at the first end of the rotor core to restrict fluid from flowing from the outlet to an outer surface of the rotor core.

[0044] According to an embodiment, the rotor core has a second end opposite the first end, and the rotor core mold member extends to the second end and includes a second containment ring located at the second end.

[0045] According to an embodiment, the rotor core mould member is defined by a resin material that hardens during a curing process.

[0046] According to an embodiment, the rotor core mould member is adapted to directly contact each cavity of the plurality of cavities.

[0047] According to an embodiment, the containment ring is connected to portions of the rotor core mold member disposed in at least two cavities of the plurality of cavities.

[0048] According to the present invention, there is provided an electric motor having: a stator assembly defining a stator bore; and a rotor assembly of the previous embodiment disposed in the stator bore of the stator assembly.

[0049] According to an embodiment, the stator assembly includes a set of windings extending from at least one end of the stator assembly, and the fluid may flow from the first end of the rotor core to an end of the set of windings extending from the at least one end of the stator assembly.

Claims

1. A rotor assembly for an electric motor, comprising: a rotor core defining a rotor bore and a plurality of cavities distributed about the rotor bore and extending through the rotor core; a plurality of magnets, the plurality of magnets being disposed in the plurality of cavities; as well as A rotor core mold member extends through the plurality of cavities to retain the plurality of magnets therein and extends from the cavities to a first end of the rotor core to form a containment ring at the first end, wherein the containment ring forms a rim over a surface of the first end to restrict fluid flow to an outside surface of the rotor core.

2. The rotor assembly according to claim 1, wherein: The rotor core defines a plurality of fluid passages extending from the rotor bore to the first end, wherein the fluid is capable of flowing from the rotor bore through the fluid passages and to the first end, and The containment ring surrounds an outlet of the fluid passage at the first end. 3 . The rotor assembly of claim 1 , wherein the rotor core has a second end opposite the first end, and the rotor core mold member extends to the second end and includes a second containment ring located at the second end.

4. The rotor assembly of claim 1, wherein the containment ring has a varying height and thickness.

5. The rotor assembly of claim 1, wherein the height and thickness of the containment ring are uniform. 6 . The rotor assembly of claim 1 , wherein the rotor core mold member is defined by a resin material that hardens during a curing process. 7 . The rotor assembly of claim 1 , wherein the rotor core mold member is adapted to directly contact each cavity of the plurality of cavities.

8. An electric motor comprising: a stator assembly defining a stator bore; as well as The rotor assembly according to claim 1, wherein the rotor assembly is disposed in the stator hole of the stator assembly.

9. The electric motor of claim 8, wherein: The stator assembly includes a set of windings extending from at least one end of the stator assembly, and The fluid is capable of flowing from the first end of the rotor core to ends of the set of windings extending from the at least one end of the stator assembly.

10. A method comprising: providing a rotor core defining a plurality of cavities distributed about a rotor bore and having a plurality of magnets disposed in the plurality of cavities; disposing a mold cover defining a groove at a first end of the rotor core; injecting a resin into the rotor having the plurality of magnets so that the resin coats the magnets within the cavities and protrudes from the recesses at the first end; as well as The resin is cured to form a rotor core mold member having a containment ring formed at least in part by the groove to form a rotor assembly.

11. The method of claim 10, further comprising positioning the rotor assembly in a stator bore of a stator assembly, the stator assembly having a set of windings extending from at least one end of the stator assembly aligned with the first end of the rotor core.

12. The method of claim 10, further comprising disposing a second mold cover defining a groove at a second end of the rotor core, wherein the rotor core mold member has a second containment ring formed at least in part by the groove of the second mold cover.

13. The method of claim 10, wherein: The rotor core defines a plurality of fluid passages extending from the rotor bore to the first end, The mold cover is adapted to cover an outlet of the fluid passage at the first end such that the groove is defined around the outlet, and Injecting the resin further includes providing an axial compressive force to the mold cover and the rotor core, wherein the containment ring surrounds the outlet of the fluid passage at the first end.

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