Device for fixing rotor core

Abstract

The present disclosure provides an apparatus for securing a rotor core. An apparatus for securing a rotor core includes an upper plate and a lower plate. The lower plate is spaced apart from the upper plate and is configured to support the rotor core between the upper plate and the lower plate. The lower plate has an upper side facing the upper plate in a first direction and a lower side facing away from the upper plate in a second direction. The upper side includes a cavity recessed in the second direction relative to an upper surface of the upper side. The upper side includes a plurality of tabs configured to engage the rotor core and extend from an inner periphery of the lower plate into the cavity.

Description

Technical Field

[0001] This disclosure relates to an apparatus for fixing a rotor core. Background Technology

[0002] The statements in this section are provided only as background information in connection with this disclosure and may not constitute prior art.

[0003] With the continued development of the electrification trend in motor vehicles, electric motors and other related components of electric vehicle powertrain systems are under development for mass production. These electric motors are complex assemblies, typically consisting of a stator and a rotor, with the rotor composed of multiple rotor cores in which multiple magnets are arranged in cavities.

[0004] Given the complexity of the rotor core and its embedded magnets, assembling these electric motors can be time-consuming and challenging. Furthermore, achieving assembly efficiency for high-volume production while providing a secure connection between multiple magnets within the rotor core cavity can be difficult. Adhesive materials have been used to secure the magnets within the rotor core cavity; however, precisely controlling the volume of the adhesive and its curing behavior has proven challenging.

[0005] This disclosure solves these problems related to the manufacture of electric motors, including the problem of fixing magnets in the rotor core cavity. Summary of the Invention

[0006] This section provides a general overview of this disclosure and is not a full disclosure of its entire scope or all its features.

[0007] In one embodiment, this disclosure provides an apparatus for fixing a rotor, the apparatus including an upper plate and a lower plate. The lower plate is spaced apart from the upper plate and configured to support the rotor core between the upper plate and the lower plate. The lower plate has an upper side facing the upper plate in a first direction and a lower side facing away from the upper plate in a second direction. The upper side includes a cavity recessed in the second direction relative to the upper surface of the upper side. The upper side includes a plurality of tabs configured to engage the rotor core and extending from an inner periphery of the lower plate into the cavity.

[0008] In a variation of the device according to the previous paragraph, which can be implemented individually or in any combination: a central spindle extends between the upper plate and the lower plate and is configured to extend through the rotor core; the lower plate includes a plurality of openings extending therethrough, the openings being circumferentially spaced around the lower plate, and wherein the openings are located within the cavity; each tab includes a proximal end extending from the inner periphery of the lower plate and a distal end located within the cavity, and wherein the tab tapers from the proximal end toward the distal end; the lower plate includes a plurality of openings extending therethrough, the openings being circumferentially spaced around the lower plate, and each tab includes a proximal end extending from the inner periphery of the lower plate and a distal end located between two of the plurality of openings; the device further includes: the rotor core, the rotor core including a plurality of stacked laminations fixed to each other; the tabs having a triangular shape; and the tabs being circumferentially positioned around the upper side of the lower plate.

[0009] In another embodiment, this disclosure provides an apparatus for fixing a rotor, the apparatus including an upper plate, a lower plate, and a rotor core. The lower plate is spaced apart from the upper plate and has an upper side facing the upper plate in a first direction and a lower side facing away from the upper plate in a second direction. The upper side includes a cavity recessed in the second direction relative to the upper surface of the upper side. The rotor core is located between the upper plate and the lower plate and engages the upper plate and the lower plate. The rotor core includes a plurality of cavities extending along an axial direction of the rotor core. Each of the plurality of cavities extends from a first axial end of the rotor core to a second axial end of the rotor core and is configured to receive a magnet insert. The lower plate includes a plurality of tabs that engage the rotor core and extend from an inner periphery of the lower plate into the cavity. Each of the plurality of tabs engages the rotor core at a location below a corresponding cavity of the plurality of cavities to cover the corresponding cavity.

[0010] In a variation of the device according to the previous paragraph, which can be implemented individually or in any combination: a central spindle extends between the upper plate and the lower plate and extends through the rotor core; the lower plate includes a plurality of openings extending therethrough, the openings being circumferentially spaced around the lower plate and the openings being located within the recess; each tab includes a proximal end extending from the inner periphery of the lower plate and a distal end located within the recess, and the tab tapers from the proximal end toward the distal end; the lower plate includes a plurality of openings extending therethrough, the openings being circumferentially spaced around the lower plate, and each tab includes a proximal end extending from the inner periphery of the lower plate and a distal end located between two of the plurality of openings; the rotor core includes a plurality of stacked laminations fixed to each other; each tab has a triangular shape; the tabs are circumferentially positioned around the upper side of the lower plate; and the plurality of cavities are formed near the outer periphery of the rotor core.

[0011] In another embodiment, this disclosure provides an apparatus for fixing a rotor, the apparatus including an upper plate, a lower plate, a rotor core, and a central spindle. The lower plate is spaced apart from the upper plate and has an upper side facing the upper plate in a first direction and a lower side facing away from the upper plate in a second direction. The upper side includes a cavity recessed in the second direction relative to the upper surface of the upper side. The rotor core is located between the upper plate and the lower plate and engages the upper plate and the lower plate. The rotor core includes a stack of laminations fixed to each other. Each lamination in the stack includes a plurality of circumferentially spaced cavities extending from a first axial end of the lamination to a second axial end of the lamination and configured to receive a magnet insert. The central spindle extends between the upper plate and the lower plate and extends through the rotor core. The lower plate includes a plurality of tabs that engage the lowermost lamination in the stack and extend from the inner periphery of the lower plate into the cavity. Each tab engages with the lowest tab at a position below the corresponding cavity in the plurality of cavities to cover the corresponding cavity.

[0012] In a variation of the device described in the previous paragraph, which can be implemented individually or in any combination: circumferentially spaced cavities of the first stack are rotatably offset relative to corresponding circumferentially spaced cavities of the adjacent second stack, and the corresponding circumferentially spaced cavities of the first stack are fluidly coupled to the corresponding circumferentially spaced cavities of the adjacent second stack.

[0013] Further applicability will become apparent from the description provided herein. It should be understood that the descriptions and specific examples are intended for illustrative purposes only and are not intended to limit the scope of this disclosure. Attached Figure Description

[0014] To facilitate a good understanding of this disclosure, various forms of the disclosure will now be described by way of example with reference to the accompanying drawings, in which:

[0015] Figure 1A This is a perspective view of an electrical converter manufactured in accordance with the teachings of this disclosure;

[0016] Figure 1B yes Figure 1A Exploded view of the rotor core and magnetizable insert of the electric converter;

[0017] Figure 2 This is a schematic cross-sectional view of a device for securing a magnetizable insert within the rotor core of an electric converter, based on the teachings of this disclosure.

[0018] Figure 3 yes Figure 2 A perspective view of a portion of the equipment, the portion including a stack of upper tools, lower tools, and rotor core;

[0019] Figure 4 yes Figure 2 A bottom perspective view of a portion of the device, the portion including an upper tool and a lower tool;

[0020] Figure 5 yes Figure 2 A perspective view of the lower tools of the device;

[0021] Figure 6 It is along Figure 3 A cross-sectional view of the device taken by line 6-6;

[0022] Figure 7 yes Figure 2 A bottom perspective view of the portion of the device, the portion including a stack of an upper tool, a lower tool, and a rotor core;

[0023] Figure 8 yes Figure 2 The image shows a cross-sectional view of the portion of the device and illustrates a flow path for molten polymer and gas flow according to the principles of this disclosure, the portion comprising a stack of an upper tool, a lower tool, and a rotor core;

[0024] Figure 9 This is a flowchart illustrating a method for fixing a magnetizable insert within the rotor core of an electric converter according to the teachings of this disclosure;

[0025] Figure 10A This is a perspective view of a stack of rotor cores having magnetizable inserts fixed within their cavity, as taught in this disclosure, after the molding process; and

[0026] Figure 10B yes Figure 10A An enlarged view of a portion of the stack of rotor cores.

[0027] The accompanying drawings described herein are for illustrative purposes only and are not intended to limit the scope of this disclosure in any way. Detailed Implementation

[0028] The following description is merely exemplary in nature and is not intended to limit this disclosure, its application, or its uses. It should be understood that throughout the drawings, corresponding reference numerals indicate the same or corresponding parts and features.

[0029] refer to Figure 1A and Figure 1B An electrical converter 10 is provided, and is generally indicated by reference numeral 10. The electrical converter 10 includes a stack of rotor cores 12 and a plurality of magnetizable inserts 14 disposed within cavities 16 of the rotor cores 12. The cavities 16 of each rotor core 12 are circumferentially spaced around the rotor core 12 and are in fluid communication with the cavities 16 of other rotor cores 12 in the stack of rotor cores 12. For example, a cavity 16 of one rotor core 12 is in fluid communication with a cavity 16 of an adjacent rotor core 12. In this way, the cavities 16 of the rotor cores 12 are in fluid communication with each other along the axial direction of the electrical converter 10, allowing adhesive material to flow through each cavity 16 during the molding process, as described in more detail below. In the illustrated example, a cavity 16 of one rotor core 12 is rotationally offset or misaligned relative to a cavity 16 of an adjacent rotor core 12. In some forms, the cavities 16 of the rotor core 12 may be rotationally aligned with the cavities 16 of adjacent rotor cores 12. Each rotor core 12 may be formed by a stack of laminations (not specifically shown) fixed to each other. Each lamination in the stack may include a plurality of circumferentially spaced cavities extending from a first axial end of the lamination to a second axial end of the lamination. When the laminations are stacked one on top of the other, the cavities of the stack of laminations form cavities 16 of the rotor core 12. An example construction of an electric converter including rotor cores is described in detail in U.S. Publication No. 2018 / 0287439, which is incorporated herein by reference in its entirety.

[0030] refer to Figure 2A device 18 is provided for securing a magnetizable insert 14 within a rotor core 12. The device 18 is disposed within a transfer molding press 20, which includes a plunger 22 disposed within a housing 24. The plunger 22 is used to displace an adhesive during molding, in one form being a polymer preform 25. The polymer preform 25 generally defines a cylindrical or disc-shaped geometry prior to molding. However, it should be understood that other geometries may be employed while remaining within the scope of this disclosure. In one form, the polymer preform 25 is a thermosetting material, such as, for example, epoxy resin. However, it should be understood that other types of thermosetting or polymeric materials (e.g., thermoplastics) may be employed while remaining within the scope of this disclosure.

[0031] The device 18 includes an upper tool or upper plate 27, a stack of rotor cores 12, a central spindle 28, and a lower tool or lower plate 30. (Reference) Figures 2 to 6 The upper tool 27 includes a lower side 32 facing the lower plate 30 in a first direction Y1 and an upper side 34 facing away from the lower plate 30 in a second opposite direction Y2. (See reference) Figure 3 The upper tool 27 includes a runner cavity 31, a plurality of runners or slots 33, and a plurality of gates 36. Both the runner cavity 31 and the runners 33 are formed along the upper side 34 of the upper tool 27. In the illustrated example, the runner cavity 31 is formed in or near the central region of the upper side 34 of the upper tool 27, and the runners 33 extend in the radial direction X to connect the runner cavity 31 to the gates 36. The gates 36 extend from the runners 33 to the cavity 16 of the rotor core 12. The runners 33 and the gates 36 guide the flow of liquid adhesive through the device 18 during the molding process, as will be described in more detail below.

[0032] In the illustrated example, the upper tool 27 is formed of an upper plate 38a and a lower plate 38b, the lower plate being secured to the upper plate 38a using mechanical fasteners, adhesives, or another suitable attachment means. The upper plate 38a includes the upper portion of a runner cavity 31, a runner 33, and a gate 36, while the lower plate 38b includes the lower portion of the gate 36. In some forms, the upper tool 27 may be formed from a single plate including the runner cavity 31, the runner 33, and the gate 36.

[0033] A central spindle 28 extends between the upper tool 27 and the lower tool 30, and extends through the center of the stack of rotor cores 12. In the illustrated example, the central spindle 28 includes a keyway or groove 40. Figure 5 The keyway or groove mates with the tabs (not specifically shown) of the rotor core 12 to properly position and align the rotor core 12 within the device 18. In the illustrated example, the central spindle 28 also includes a series of cuts 44 extending circumferentially around the central spindle 28. Figure 5 ) and spine 46 ( Figure 5 Ridge 46 provides a reduced contact area with rotor core 12, thereby reducing friction when removing rotor core 12 from lower tool 30 and central spindle 28 after the molding process.

[0034] The lower plate 30 is spaced apart from the upper plate 27 and supports the rotor core 12, such that the rotor core 12 is sandwiched between the upper plate 27 and the lower plate 30. In the illustrated example, the lower plate 30 has an annular shape. In some forms, the lower plate 30 may have a rectangular shape, a square shape, or any other suitable shape that can support the rotor core 12. The lower plate 30 has an upper side 50 facing the upper plate 27 in the second direction Y2 and a lower side 52 facing away from the upper plate 27 in the first direction Y1.

[0035] refer to Figure 5 and Figure 7 The lower plate 30 includes a cavity 54. Figure 5 ), multiple openings 56, one or more tool openings 58 ( Figure 7 ) and multiple positioning holes 60 ( Figure 7 A cavity 54 is formed in or near the central region of the lower plate 30 and is recessed relative to the upper surface 62 of the upper side 50 in a first direction Y1, such that the cavity 54 defines an intermediate surface 64 spaced apart from the upper surface 62 and the rotor core 12. The cavity 54 may surround a central spindle 28 and may define an inner periphery 66 spaced apart from the outer periphery 68 of the lower plate 30. In one form, the inner periphery 66 may have a sharp edge. In another form, the inner periphery 66 may have a chamfered edge. In yet another form, the edge of the inner periphery 66 may be profiled.

[0036] The opening 56 is circumferentially spaced around the lower plate 30 and located within the cavity 54. That is, the opening 56 extends from the lower surface 72 of the lower plate 30 to the intermediate surface 64 of the cavity 54. The opening 56 is related to the opening 74 formed in the rotor core 12. Figure 1B and Figure 10A Fluid communication is provided to offer a heating channel or conduit for airflow during the molding process. A tool opening 58 may extend partially through the lower plate 30 and can be used to insert a tool (not shown) to remove or eject the rotor core 12 from the central spindle 28 and the lower plate 30. A positioning aperture 60 is formed in the lower surface 72 of the lower plate 30 and abuts with a feature (not shown) of the transfer molding press 20 to position the lower plate 30 for the molding process.

[0037] The lower plate 30 further includes a plurality of tabs 76 located on the upper side 50 of the lower plate 30 and engaging the lowermost rotor core 12. In other words, the tabs 76 are circumferentially spaced around the inner periphery 66 of the lower plate 30 and cover the respective cavities 16 of the rotor core 12. In the illustrated example, the tabs 76 have a triangular shape. In some forms, the tabs 76 may include a semi-circular shape or any other suitable shape that can support the rotor core 12 and cover the cavities 16 of the rotor core 12. In the illustrated example, each tab 76 extends from the inner periphery 66 into a recess 54 and includes an upper surface 80 coplanar with the upper surface 62 of the lower plate 30. Each tab 76 is disposed between the inner periphery 66 and an opening 56 and includes a proximal end 78a and a distal end 78b. The proximal end 78a extends from the inner periphery 66 of the lower plate 30, and the distal end 78b is located within the recess 54 between two of the plurality of openings 56. The splice 76 tapers from the proximal end 78a toward the distal end 78b.

[0038] Each of the plurality of tabs 76 is spaced apart from the central mandrel 28. The lower plate 30 also includes ventilation openings 82 formed on the upper surface 80 and / or the tabs 76. The ventilation openings 82 provide ventilation for air to escape from the device 18 during the molding process.

[0039] refer to Figure 9 A method 100 is provided for securing a magnetizable insert 14 within a rotor core 12. At 104, the method includes placing a stack of rotor cores 12 in a transfer molding press 20. Prior to placement in the transfer molding press 20, an attachment feature 92 can be used. Figure 2 The stack of rotor cores 12 is secured to each other. In one form, the attachment feature 92 is an adhesive placed between the laminations (not specifically shown) of each rotor core 12 in the stack of rotor cores 12 to secure the laminations and adjacent rotor cores 12 to each other. In another form, the attachment feature 92 is an interlocking element located between the laminations of each rotor core 12 in the stack of rotor cores 12 to secure the laminations and adjacent rotor cores 12 to each other. In the illustrated example, the attachment feature 92 secures the laminations of the stack of rotor cores 12 and adjacent rotor cores 12 to each other at a location located inside the cavity 16 containing the magnetizable insert 14. The magnetizable insert 14 is disposed within the cavity 16 of the rotor core 12 before the stack of rotor cores 12 is placed in the transfer molding press 20. In some embodiments, the stack of rotor cores 12 and the polymer preform 25 may be preheated before being placed in the transfer molding press 20. In another embodiment, the assembly comprising the stack of rotor cores 12, the lower tool 30, the central mandrel 28, and / or the upper tool 27 may be preheated before being placed in the molding press 20.

[0040] At 108, the polymer preform 25 is placed in the housing 24 below the plunger 22 of the transfer molding press 20 and adjacent to the stack of rotor core 12. Alternatively, the polymer preform 25 can be placed on top of the upper tool 27 before molding. At 112, heat and transfer pressure are applied within the transfer molding press 20, and the plunger 22 moves downward to displace the polymer preform 25, causing it to change state (i.e., from solid to liquid) and flow from the runner cavity 31 through the runner 34, through the gate 36, and subsequently through the cavity 16 of the rotor core 12. Figure 8 As shown, the stack of upper tool 27, lower tool 30, and rotor core 12 is illustrated to illustrate the flow path of molten polymer and airflow through the stack of rotor core 12 during the molding process. The opening 56 of the lower plate 30 is in fluid communication with the opening 74 formed in the rotor core 12 to provide a heating channel or conduit for the airflow during the molding process.

[0041] At point 116, a clamping force is provided by the transfer molding press 20 to the upper tool 27 and the lower tool 30, the clamping force varying in magnitude according to the number and size of the rotor cores 12 and the volume of the cavity 16 filled with the polymer preforms 25. In one embodiment, the lower tool 30 is spring-loaded to apply additional force during clamping. After all the liquid polymer preforms 25 have been pressed by the plunger 22, the clamping force continues to be provided within the transfer molding press 20 for a predetermined time period or curing time. In one example, the curing time is 120 seconds for the liquid polymer preforms. The transfer pressure (applied by the plunger 22) is also a function of the volume of the cavity 16 filled with the polymer preforms 25.

[0042] At 120, after the cavity 16 has been filled with the liquid polymer preform 25, and after a predetermined curing time, the stack of rotor cores 12 is removed from the transfer molding press 20. Now refer to... Figure 10A and Figure 10B The illustration shows a complete stack of rotor cores 12, wherein magnetizable inserts 14 are fixed within a cavity 16 by a cured polymer material 90. That is, the polymer material 90 has been cured around the magnetizable inserts 14, thereby forming a bond between the magnetizable inserts 14 and the rotor cores 12.

[0043] This disclosure provides an apparatus 18 for securing a stack of rotor cores 12 during a molding process, the apparatus including a lower tool 30. The lower tool 30 includes a cavity 54 and a plurality of tabs 76 that cooperate to guide the clamping load path of plates 27, 30 to a location of the cavity 16 of the stack of rotor cores 12 (i.e., at or near the outer periphery of the stack of rotor cores 12), rather than guiding it to the area around the attachment feature 92 located near the inner periphery of the stack of rotor cores 12. In other words, the clamping load of plates 27, 30 is guided to the tabs 76 covering the respective cavities 16 of the stack of rotor cores 12. This load is guided around the cavity 16 of the stack of rotor cores 12, facilitating clamping function during the molding process and reducing, for example, epoxy resin forced away from the periphery of the stack of rotor cores 12 during the molding process.

[0044] Unless otherwise expressly indicated herein, all numerical values ​​indicating mechanical / thermal properties, percentage of composition, dimensions and / or tolerances or other characteristics should be understood as being modified by the words “about” or “approximately” when describing the scope of this disclosure. Such modification is desired for various reasons, including: industrial practice; material, manufacturing and assembly tolerances; and testing capabilities.

[0045] As used herein, the phrases A, B, and C at least one should be interpreted as using the non-exclusive logic "or" to represent logic (A or B or C), and should not be interpreted as meaning "at least one of A, at least one of B, and at least one of C".

[0046] The description in this disclosure is merely exemplary in nature, and therefore, variations thereof are intended to be made within the scope of this disclosure without departing from its spirit. Such variations should not be considered as departing from the spirit and scope of this disclosure.

[0047] According to the present invention, an apparatus is provided comprising: an upper plate; a lower plate spaced apart from the upper plate and having an upper side facing the upper plate in a first direction and a lower side facing away from the upper plate in a second direction, the upper side including a cavity recessed in the second direction relative to the upper surface of the upper plate; and a rotor core located between the upper plate and the lower plate and engaging the upper plate and the lower plate, the rotor core including a plurality of cavities extending along an axial direction of the rotor core, each of the plurality of cavities being connected from a first axial end of the rotor core to a second axial end of the rotor core and configured to receive a magnet insert, wherein the lower plate includes a plurality of tabs engaging the rotor core and extending from an inner periphery of the lower plate into the cavity, each of the plurality of tabs engaging the rotor core at a position below a corresponding cavity of the plurality of cavities to cover the corresponding cavity.

[0048] According to one embodiment, the invention is further characterized by a central spindle that extends between the upper plate and the lower plate and extends through the rotor core.

[0049] According to one embodiment, the lower plate includes a plurality of openings extending therethrough, the openings being circumferentially spaced around the lower plate, and the openings being located within the cavity.

[0050] According to one embodiment, each tab includes a proximal end extending from the inner periphery of the lower plate and a distal end located within the cavity, wherein the tab tapers from the proximal end toward the distal end.

[0051] According to one embodiment, the lower plate includes a plurality of openings extending therethrough, the openings being circumferentially spaced around the lower plate, and each tab includes a proximal end extending from the inner periphery of the lower plate and a distal end located between two of the plurality of openings.

[0052] According to one embodiment, the rotor core includes a plurality of stacked laminations fixed to each other.

[0053] According to one embodiment, each patch has a triangular shape.

[0054] According to one embodiment, the tab is circumferentially positioned around the upper side of the lower plate.

[0055] According to one embodiment, the plurality of cavities are formed near the outer periphery of the rotor core.

[0056] According to the present invention, an apparatus is provided comprising: an upper plate; a lower plate spaced apart from the upper plate and having an upper side facing the upper plate in a first direction and a lower side facing away from the upper plate in a second direction, the upper side including a cavity recessed in the second direction relative to the upper surface of the upper plate; and a rotor core located between the upper plate and the lower plate and engaging the upper plate and the lower plate, the rotor core comprising a stack of laminations fixed to each other, each lamination in the stack comprising a plurality of circumferentially spaced cavities, the plurality of cavities being... A circumferentially spaced cavity extends from a first axial end of the lamination to a second axial end of the lamination and is configured to receive a magnet insert; and a central spindle extends between the upper plate and the lower plate and through the rotor core, wherein the lower plate includes a plurality of tabs that engage the lowermost lamination of the stack of laminations and extend from the inner periphery of the lower plate into the cavity, each tab engaging the lowermost lamination at a position below a corresponding cavity of the plurality of cavities to cover the corresponding cavity.

[0057] According to one embodiment, the circumferentially spaced cavities of the first stack are rotatedly offset relative to the corresponding circumferentially spaced cavities of the adjacent second stack.

[0058] According to one embodiment, the circumferentially spaced cavities of the first lamination are fluidly connected to the corresponding circumferentially spaced cavities of the adjacent second lamination.

Claims

1. An apparatus for fixing a rotor core, the apparatus comprising: upper plate; as well as A lower plate, spaced apart from the upper plate and configured to support the rotor core between the upper and lower plates, the lower plate having an upper side facing the upper plate in a first direction and a lower side facing away from the upper plate in a second direction, the upper side including a cavity recessed in the second direction relative to the upper surface of the upper side, wherein the upper side includes a plurality of tabs configured to engage the rotor core and extend from the inner periphery of the lower plate into the cavity.

2. The device as claimed in claim 1, further comprising: A central spindle extends between the upper plate and the lower plate and is configured to extend through the rotor core.

3. The device of claim 1, wherein the lower plate includes a plurality of openings extending therethrough, the plurality of openings being circumferentially spaced around the lower plate, and wherein the plurality of openings are located within the recess.

4. The device of claim 1, wherein each tab includes a proximal end extending from the inner periphery of the lower plate and a distal end located within the cavity, and wherein the tab tapers from the proximal end toward the distal end.

5. The device as claimed in claim 1, wherein: The lower plate includes a plurality of openings extending therethrough, the plurality of openings being circumferentially spaced around the lower plate, and Each tab includes a proximal end extending from the inner periphery of the lower plate and a distal end located between two of the plurality of openings.

6. The device of claim 1, further comprising: The rotor core comprises a plurality of stacked laminations fixed to each other.

7. The device of claim 6, wherein the lower plate includes a plurality of tabs that engage the lowermost of the plurality of stacked tabs and extend from the inner periphery of the lower plate into the cavity, each tab engaging the lowermost tab at a location below a corresponding cavity in the plurality of cavities to cover the corresponding cavity.

8. The device of claim 7, wherein the lower plate includes a plurality of openings extending therethrough, the plurality of openings being circumferentially spaced around the lower plate, wherein circumferentially spaced cavities of the first stack are rotationally offset relative to corresponding circumferentially spaced cavities of adjacent second stacks.

9. The device of claim 8, wherein the circumferentially spaced cavities of the first stack are fluidly connected to the corresponding circumferentially spaced cavities of the adjacent second stack.

10. The device of claim 1, wherein the plurality of tabs have a triangular shape.

11. The device of claim 1, wherein the tab is circumferentially positioned around the upper side of the lower plate.

12. The device of claim 1, further comprising: The rotor core is located between and engages the upper plate and the lower plate. The rotor core includes a plurality of cavities extending along the axial direction of the rotor core. Each of the plurality of cavities extends from a first axial end of the rotor core to a second axial end of the rotor core and is configured to receive a magnet insert.

13. The device of claim 12, wherein the lower plate includes a plurality of tabs that engage the rotor core and extend from the inner periphery of the lower plate into the cavity, each of the plurality of tabs engaging the rotor core at a location below a corresponding cavity among the plurality of cavities to cover the corresponding cavity.

14. The device of claim 12, wherein the plurality of cavities are formed near the outer periphery of the rotor core.

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