Rotor with compression structural element

Abstract

A rotor for an electric machine includes a rotor core having at least one internal cavity. A pair of features are defined by the rotor core and extend into the cavity. A structural element is compressed between the features so that a preload can be established between the features and the structural element.

Description

Technical Field

[0001] The present invention relates to electric machines and rotors thereof, and more particularly to rotors having multiple internal cavities that can house permanent magnets or serve as flux barriers and that feature compressed structural elements to achieve high performance operation. Background Art

[0002] A rotor, such as for an interior permanent magnet (IPM) machine or a synchronous reluctance (SR) machine, comprises a rotor core assembled around a rotating shaft. Such a rotor having a segmented construction typically comprises a plurality of stacked laminations forming a core. The core typically comprises a cavity as a flux barrier to affect the operating characteristics of the motor. The laminations of the core are formed into a disk shape having a central opening for assembly on a rotating shaft. The flux barriers are distributed around the shaft opening, typically having ends adjacent to the circumference of the laminations and typically extending toward the shaft opening. The flux barrier cavity may or may not include a magnet.

[0003] The physical size, number, and location of the flux barrier cavities affect the performance of the motor. Thus, even a large flux barrier placed in a non-optimal location may not result in optimal performance. Additionally, synchronous reluctance motors are particularly susceptible to flux leakage through lamination features around flux barriers that may be structurally required. These factors lead to the design and positioning of flux barriers that result in only thin structural features being left to support portions of the rotor core. These thin lamination features may limit the performance and speed that the motor can achieve without placing excessive stress on the rotor core and without excessively increasing feature size. Due to the presence of the flux barrier cavities, the rotor may be structurally weakened and therefore may not be suitable for high speed applications.

[0004] Therefore, it is desirable to provide an economical rotor for an electric machine that achieves high performance with minimal structural feature size. Furthermore, other desirable features and characteristics of the present invention will become apparent from the subsequent detailed description and the appended claims, taken in conjunction with the accompanying drawings and the foregoing technical field and background. Summary of the invention

[0005] In various embodiments, a rotor for an electric machine includes a rotor core having at least one internal cavity. The internal cavity is surrounded by a wall defined by the rotor core. A structural element is disposed in the cavity and is compressible between a pair of wall features of the wall. A preload is established between the first and second wall features and the structural element.

[0006] In further embodiments, the structural element comprises a magnet.

[0007] In further embodiments, the structural element comprises a non-magnetic material.

[0008] In further embodiments, the structural element includes a plurality of sides defining a plurality of corners, wherein the wall features include beams that engage the structural element at non-adjacent corners.

[0009] In other embodiments, the non-adjacent corners include one corner disposed at a junction of the radially inner side and the radially outer side; and another corner disposed at a junction of another radially inner side and another radially outer side.

[0010] In further embodiments, the structural element includes a plurality of segments that are wedged against the first wall feature and the second wall feature to establish the preload.

[0011] In further embodiments, the segments include pentagonal and trapezoidal shapes.

[0012] In further embodiments, the beams comprise a deformable material and the structural element is press fit between the beams to establish the preload.

[0013] In another embodiment, the rotor includes a plurality of cavities. The cavities are partially defined by struts and bridges. The structural elements are configured to offset loads otherwise carried by the struts and bridges.

[0014] In further embodiments, at least one of the structural element and the rotor causes a wedging action on the structural element.

[0015] In many further embodiments, a rotor for an electric machine includes a rotor core having a plurality of internal cavities defining magnetic poles of the rotor. A pair of wall features defined by the rotor core extend into at least one of the cavities. A structural element is compressed between the wall features, thereby establishing a preload between the wall features and the structural element.

[0016] In further embodiments, the cavities are arranged in a plurality of layers, and the struts extend through at least one of the layers to support the rotor core.

[0017] In further embodiments, the structural elements are disposed in one of the layers, the one of the layers having a larger open cross-sectional area than the other layers. The layer having the structural elements may have thinner struts, or may not include struts.

[0018] In further embodiments, the structural element comprises a magnet.

[0019] In further embodiments, the structural element comprises a non-magnetic material.

[0020] In other embodiments, the structural element includes a plurality of sides defining a plurality of corners. The wall feature includes a beam joined to the structural element at non-adjacent corners, the non-adjacent corners including one corner disposed at a junction of a radially inner side and a radially outer side and another corner disposed at a junction of another radially inner side and another radially outer side.

[0021] In further embodiments, the structural element comprises a plurality of segments wedged against the first wall feature and the second wall feature to establish the preload. At least one of the segments comprises a trapezoidal shape.

[0022] In further embodiments, the beams comprise a deformable material and the structural element is press fit between the beams to establish the preload.

[0023] In further embodiments, the cavity is defined in part by the struts and bridges.The structural element is configured to counteract loads otherwise carried by the struts and bridges.

[0024] In many other embodiments, a rotor for an electric machine includes a rotor core having a plurality of internal cavity groups. Each cavity group includes a plurality of cavities and defines magnetic poles of the rotor. At least one strut is included in each cavity group to support the rotor core. A pair of features defined by the rotor core extends into at least one cavity. A structural bar is compressed between the features. A preload is established between the features and the structural bar. The preload causes the structural bar to apply a radially inward force to the rotor core to counteract the centrifugal load on the strut. BRIEF DESCRIPTION OF THE DRAWINGS

[0025] Hereinafter, exemplary embodiments will be described in conjunction with the following drawings, wherein like reference numerals denote like elements, and wherein:

[0026] Figure 1 is a schematic diagram of a portion of a motor according to various embodiments;

[0027] Figure 2 According to various embodiments, generally along the Figure 1 A partial cross-sectional view of the rotor taken along line 2-2 of the motor;

[0028] Figure 3 According to various embodiments Figure 2 A plan view of the laminations of the rotor;

[0029] Figure 4-5 is a partial free body diagram of a portion of a lamination without a compression structural element according to the prior art;

[0030] Figure 6 According to various embodiments Figure 2 A partial schematic diagram of a rotor;

[0031] Figure 7It is shown according to each embodiment. Figure 6 A partial schematic diagram of the beam and compression structural elements;

[0032] Figure 8-9 According to various embodiments, Figure 6 Compression of structural elements Figure 3 Local free body diagram of a portion of the lamination;

[0033] Fig.10 According to various embodiments Figure 2 A partial schematic diagram of a rotor;

[0034] Fig.11 is a partial schematic diagram of a rotor of an SR motor according to various embodiments; and

[0035] Fig.12 is a cross-sectional view of a segmented, multi-piece compression structural element according to various embodiments. DETAILED DESCRIPTION

[0036] The following detailed description is merely exemplary in nature and is not intended to limit the present application and uses. Furthermore, there is no intention to be bound by any expressed or implied theory presented in the preceding technical field, background, brief summary or the following detailed description.

[0037] As disclosed herein, the rotor includes a core / laminate feature that enables the use of a compressive structural element to transfer loads from a thin, relatively weak portion of the core to an area with a higher load-bearing capacity. As used herein, the term structural element refers to a load-bearing object without limitation. In addition, the term "compressive" does not require deformation of the structural element, but means that a compressive load 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 structural element can be made of any material that is sufficiently rigid to withstand the applied load, and can be formed in any shape and configuration, such as a bar, a rod, a block, a tube, etc. The compressive structural elements described herein can be included without negatively affecting the magnetic properties of the rotor. In some embodiments, the compressive structural element can be the internal magnet of the rotor itself, and can include a magnetic strip. In other embodiments that do not include permanent magnets, non-ferrous and / or non-conductive materials can be used as compressive structural elements. In multiple embodiments, the compressive structural element may include multiple assemblies / segments. The compressive load can be achieved by a variety of methods, such as press fit, tapered elements, formed segments, deformable lamination components, or others. Higher rotor speeds and required magnetic performance can be achieved while maintaining desirable thin and light lamination features (such as struts and bridges), resulting in relatively low material cost, weight, and compact size.

[0038] refer to Figure 1 , schematically illustrates selected components of an electric machine 20, including a stator assembly 22 and a rotor assembly 24 configured to rotate about an axis 25. In this figure, the rotor assembly 24 is shown external to the stator assembly 22 for visibility. In this embodiment, the electric machine 20 is configured as an electric motor, wherein current that produces torque in the rotor assembly 24 is induced by a magnetic field generated by energizing the stator assembly 22. In many embodiments, the electric machine 20 is an AC motor suitable for applications requiring modulated speed control, such as for vehicle traction motors, although the present disclosure is not limited to those applications.

[0039] The stator assembly 22 is a generally annular component that can be configured for single-phase power or multi-phase power such as three-phase. In this embodiment, the stator assembly 22 includes a core 26 made of stacked laminations 28. The laminations 28 can be formed by a stamping that is slotted to receive windings (not shown) and is made of a soft magnetic material (e.g., silicon steel). The laminations 28 can be insulated from each other by a thin non-conductive coating. In other embodiments, another ferromagnetic material can be used. The stator assembly 22 may include windings for energizing.

[0040] The rotor assembly 24 includes an iron core 30 including stacked laminations 32 configured to receive a shaft 34. The laminations 32 may be stamped or otherwise formed. The laminations 32 are made of a ferromagnetic material and may be insulated from one another by a thin non-conductive coating, or may be made of another material. End rings 42, 44 are formed at the ends of the iron core 30. In the current embodiment, the end rings 42, 44 are made of an aluminum material to reduce weight. The rotor assembly 24 is configured with a plurality of magnetic poles to generate a magnetic circuit of the rotor assembly 24 that depends on the angular position of the rotor assembly 24 to interact with a magnetic circuit induced by the stator assembly 22 of the motor 20. As described below, these magnetic poles may be generated at least in part by flux barriers.

[0041] exist Figure 2, the rotor assembly 24 is shown in cross section with the side 48 of one of the laminations 32 exposed and visible. The laminations 32 include a plurality of openings, referred to as cavities, that can be used for a variety of purposes. Eight cavity groups 51-58 are distributed around the rotor assembly 24 near its periphery 50, each cavity group being formed in two angled layers. The cavities in the cavity groups 51-58 extend through the stacked rotor laminations 32 of the core 30 in a longitudinal direction 59 parallel to the axis 25. The cavity groups 51-58 operate as barriers to magnetic flux and help define the magnetic poles of the rotor assembly 24. Thus, in the current embodiment, the rotor assembly 24 has eight magnetic poles. The rotor assembly 24 also includes a layer of openings 61-68 that are arranged around the shaft 34 and are partially arranged between the shaft 34 and the opening groups 51-58 in a radial direction 75. The openings 61-68 are each angularly oriented between an adjacent pair of cavity groups 51-58, leaving a series of webs 71-78, each oriented along a radial line extending in a radial direction 75 from the axis 25 that bisects one of the cavity groups 51-58, such as radial line 79 of cavity group 52. The openings 61-68 are operable to radially focus the flux lines at the eight magnetic poles in the rotor assembly 24.

[0042] refer to Figure 3 , one lamination stack 32 of the rotor assembly 24 is shown. Each cavity group 51-58 is similar, and the details of cavity group 51 will be described with the understanding that the other cavity groups 52-58 include similar elements. Cavity group 51 includes two layers 81, 82 of flux barriers, which will be referred to as magnet cavities in the current embodiment of the IPM motor. Layers 81, 82 include four magnet cavities 83-86, which are shown without magnets for simplicity. Magnet cavities 83, 84 form the outer layer 81 and are set at an angle relative to each other, thereby defining a sector of flux path elements 88 that pass through the remaining generally triangular steel portions of the lamination stack 32. Magnet cavities 85, 86 form the inner layer 82 and are also set at an angle relative to each other. A V-shaped flux path element 90 is defined between layers 81, 82 by the remaining steel portions of the lamination stack 32. Layers 81, 82 define structural features of the remaining steel of lamination 32 in the form of struts 91, 92 and bridges 93-96. Struts 91, 92 and bridges 93-96 hold the outer portions of lamination 32 (e.g., flux path elements 88, 90) together against rotationally induced forces during operation of motor 20.

[0043] Figure 4A free body diagram of a sector flux path element 88 arranged according to the prior art is depicted, which does not include a compression structural element. When the rotor assembly 24 rotates, the centrifugal force 102 acting on the laminations 32 is applied to the flux path element 88 in a radially outward direction to attempt to move the flux path element 88 away from the center of the rotor assembly 24. In addition, the magnets (not shown) in the magnet cavities 83, 84 can exert magnetic forces 103, 104 generated by the centrifugal force acting on the magnets accommodated. The support 91 and the bridges 94, 95 hold the flux path element 88 in an appropriate position to resist the centrifugal and magnetic forces 102-104. The support 91 and the bridges 94, 95 carry loads 105-107, respectively, to counteract the forces 102-104, and the loads they carry are proportional to their stiffness. The support 91 can be significantly more rigid than the bridges 94, 95. The support 91 and the bridge are limiting factors in the performance of the rotor assembly 24 because centrifugal forces exceeding their load-bearing capacity cannot be generated. At the same time, the size of the struts 91 and bridges 94, 95 affect the magnetic performance of the rotor assembly 24, and therefore, their size is limited.

[0044] Figure 5 A free body diagram of a V-shaped flux path element 90 arranged in accordance with the prior art is similarly depicted, which does not include a compressive structural element. As the rotor assembly 24 rotates, centrifugal forces 111-113 acting on the laminations 32 are exerted on the flux path element 90 in a radially outward direction, attempting to move the flux path element 90 away from the center of the rotor assembly 24. In addition, the magnets in the magnet cavities 85, 86 exert magnetic forces 114, 115 due to the centrifugal forces acting on the contained magnets (not shown). The struts 91 and bridges 93, 96 hold the flux path in place against the centrifugal and magnetic forces 102-104. The struts 91 and bridges 93, 96 carry loads 116-118, respectively, and the loads they carry are proportional to their stiffness.

[0045] exist Figure 4-5 , the struts 91, 92 may be significantly more rigid than the bridges 93-96. The struts 91, 92 and bridges 93-96 are limiting factors in the performance of the rotor assembly 24 because centrifugal forces exceeding their load-bearing capacity cannot be generated. In addition, it is desirable to keep the struts 91, 92 and bridges as thin as possible, so simply increasing their size to carry more load is not a preferred approach.

[0046] refer to Figure 6, showing the area of ​​the rotor assembly 24 surrounding the cavity group 51. The magnet cavities 83-86 contain compressed structural elements, which are implemented as magnets 121-124 in the current embodiment. Each of the magnets 121-124 extends through its respective cavity in the axial direction 59 and can be shaped as a bar with a rectangular cross-section having an extended length. Therefore, the structural element in this example can be referred to as a structural bar or a magnetic bar. The current embodiment incorporates magnet retention features to reorient the load away from the pillars 91, 92 and / or bridges 93-96. In particular, the magnets 121-124 are placed in a compressed state, resulting in the load being carried by the magnets and away from selected portions of the laminations 32 of the rotor assembly 24. The retention features of each magnet 121-124 include a pair of wall features that overhang into the magnet cavity 83-86. The wall features are formed by aligned tabs of each individual stacked lamination 32 and extend along the length of the laminations of the rotor core 30, thereby forming a beam-like structure. For example, beams 131 and 132 engage magnets 121 at non-adjacent corners 133, 134, respectively. In this example, non-adjacent means that the corners have no common sides.

[0047] exist Figure 7 1 and 13. The beams 131, 132 and the magnet 121 are shown in a separate manner in FIG. In this example, the magnet 121 is configured as a structural bar having an elongated rectangular shape. The magnet 121 has four corners 133-136 extending along the axial direction 59. The beam 131 engages with the magnet 121 at the corner 133, and the beam 132 engages with the magnet 121 at the corner 134. A compressive preload 138 is applied to the magnet 121 by the beams 131, 132. A load path 137 exists between the beams 131, 132 and passes through the magnet 121, through which the magnet 121 applies a reaction force to the beams 131, 132. The reaction force through the load path 137 has a component in the radial direction 75 and therefore, the magnet 121 applies a load with a radial component, which can be adjusted to counteract the centrifugal force of a selected portion of the rotor core 30.

[0048] Reference again Figure 6 , the flux path element 88 side of magnet 121 is held by beam 132, which extends from flux path element 88 as a wall feature. Similarly, the flux path element 90 side of magnet 21 is held by beam 131, which extends from flux path element 90 as a wall feature. The flux path element 88 side of magnet 121 is the radially outward facing side 152 of magnet 121, which is generally facing away from axis 25 (at a certain angle) in radial direction 75. Figure 2 ) and is adjacent to flux path element 88. The flux path element 90 side of magnet 121 is a radially inward side 150 of magnet 121 that is generally oriented (at an angle) in radial direction 75 toward axis 25 ( Figure 2) and abuts flux path element 90. Magnet 121 also includes a radially outward side 142 disposed between sides 150-152, and includes a radially inward side 146 disposed opposite radially outward side 142 and between sides 150, 152. Corner 133 is at a common edge of radially outward side 142 and radially inward side 150 of magnet 121 and is formed by a junction therebetween. Corner 134 is at a common edge of radially inward side 146 and radially outward side 152 of magnet 121 and is formed by a junction therebetween. Corners 135, 136 do not have joined wall features. The magnets 122-124 are similarly retained by their respective beams 161-162, 163-164 and 165-166, wherein the magnets 122-124 are each retained at non-adjacent corners by pairs of wall features where one corner is located at the junction of a radially inward side and a radially outward side and the other corner is located at the junction of a different radially inward side and a different radially outward side.

[0049] refer to Figure 8 , showing Figure 6 FIG. 2 is a free body diagram of a sector flux path element 88. As the rotor assembly 24 rotates, centrifugal force 170 and magnetic forces 171, 172 act on the flux path element 88. The forces 170-172 are balanced by forces 174-176 at the struts 91 and bridges 94, 95 and forces 177, 178 across the magnets 121, 122. The forces 177, 178 push on the flux path element 88 at contact areas 173, 179 between the magnets 121, 122 and the flux path element 88. Due to the position of the beams 132, 161, the forces 177, 178 include radially inward components 180, 181. As a result, the radially inward components 180, 181 assist the struts 91 and bridges 94, 95 in resisting the forces 174-176. As a result, the forces 174 - 176 are lower than they would be without the magnets 121 , 122 acting as compressive structural elements, where the magnets 121 , 122 would force the flux path elements 88 radially inward.

[0050] Fig. 9 Shows Figure 6FIG. 2 is a free body diagram of a V-shaped flux path element 90. As the rotor assembly 24 rotates, centrifugal forces 182-184 and magnetic forces 185, 186 act on the flux path element 90. The forces 182-186 are balanced by forces 187-189 at the struts 92 and bridges 93, 96 and forces 190, 191 across the magnets 123, 124. The forces 190, 191 push on the flux path element 90 at the contact areas 193, 194 between the magnets 123, 124 and the flux path element 90. Due to the position of the beams 164, 165, the forces 190, 191 include radially inward components 195, 196. As a result, the radially inward components 195, 196 assist the struts 92 and bridges 93, 96 in resisting the forces 182-184. As a result, forces 187-189 are lower than they would be without magnets 123, 124 acting as compressive structural elements, where magnets 123, 124 would force flux path element 90 radially inward. The free body diagram indicates forces 197, 198 applied to beams 161, 162 by magnets 121, 122, which may have a radially outward component. However, magnets 121, 122 are smaller than magnets 123, 124 and carry less preload, and forces 197, 198 are directed toward a bridge that is less sensitive to load than the struts. Therefore, the forces they apply are greater than those offset by forces 190, 191.

[0051] Reference Fig.10 , showing the ability to eliminate or exclude Figure 6 91, 92 of the embodiment. The rotor assembly 200 includes two layers 201, 202 of flux barriers in the form of magnet cavities 204, 206. The magnet cavity 204 contains four magnets 211-214, and the magnet cavity 206 contains four magnets 215-218. Each of the magnets 211-218 is held by a pair of beams extending into its respective cavity 204, 206. For example, magnet 216 is held by beams 220, 222, which engage magnet 216 at non-adjacent corners 224, 226. Corners 225, 227 have no engaged beams. Magnets 211-215 and 217-218 are similarly held by their respective beams. In the case of each magnet 211-218, a pair is held at non-adjacent corners, with one non-adjacent corner at the junction of a radially inward side and a radially outward side, and the other non-adjacent corner at the junction of a different radially inward side and a different radially outward side. As a compressive structural element, the magnets 211-218 exert a force having a radially inwardly directed component on the rotor assembly 200 and help to sufficiently counteract the centrifugal force to eliminate the need for a post. Eliminating the post can improve the magnet performance of the rotor assembly 200.

[0052] Fig.11A cross section of a rotor assembly 300 for an SR motor is shown. It will be understood that one sector of the rotor assembly 300 is shown as having one grouped cavity, and that additional sectors of the rotor assembly 300 will include additional cavity groups defining magnetic poles around the circumference of the rotor assembly 300. In this example, the cavities do not require magnets, so they are referred to as flux barrier cavities 301-308. The flux barrier cavities 301-308 are configured in four layers 311-314. Layer 311 includes flux barrier cavities 301, 302 separated by pillars 320. Layer 312 includes flux barrier cavities 304, 305 separated by pillars 322. Layer 313 includes flux barrier cavities 306, 307, which are separated by pillars 324. Layer 314 includes a continuous flux barrier cavity 308, which is V-shaped. Layer 314 does not include pillars, but instead contains two compression structural elements 330, 332. The compression structural elements 330, 332 are made of a non-magnetic material, and in the current embodiment each comprises a strip of ceramic material.

[0053] The compression structural element 330 is retained by beams 334, 336 that engage its non-adjacent corners 341, 343. Corners 342, 344 do not engage with retaining wall features. Beams 334 extend from flux elements 346 on the radial side of flux barrier cavity 308 into flux barrier cavity 308, and beams 336 extend from flux elements 348 on the radial outside of flux barrier cavity 308 into flux barrier cavity 308. The compression structural element 330 is compressed between beams 334, 336, thereby applying a force to beams 336. The compression structural element 330 is strategically placed to apply a force having a radially inward component to flux path element 348 to counteract the centrifugal force on flux path element 348. The compression structural element 330 can apply a force having a radially outward component to beams 334, but beams 334 are connected to the main structural portion of rotor assembly 300, and therefore, the force does not compromise the integrity of the structure. Notably, flux barrier cavity 308 and its layer 314 have the largest open cross-sectional dimensions of flux barrier cavities 310 - 308 / layers 311 - 314 and do not require struts.

[0054] The compression structural element 332 is similarly retained by beams 350, 352 engaging its non-adjacent corners 354, 356. Corners 355, 357 do not engage retaining wall features. Beam 350 extends from flux element 348 on the radially outer side of flux barrier cavity 308 into flux barrier cavity 308, and beam 352 extends from flux element 346 on the radially inner side of flux barrier cavity 308 into flux barrier cavity 308. The compression structural element 332 is compressed between beams 350, 352, and as a result, a force is applied to beam 350. The compression structural element 332 is strategically placed to apply a force having a radially inward component to flux path element 348 to counteract the centrifugal force on flux path element 348. The compression structural element 332 can apply a force having a radially outward component to beam 352, however, beam 352 is connected to a majority of the structural portion of rotor assembly 300, and therefore, the force does not compromise the integrity of the structure.

[0055] refer to Fig.12 It will be appreciated that the magnet / compression structural element of the present disclosure may each comprise a segmented assembly of multiple parts. For example, the use of a segmented assembly may desirably reduce eddy currents compared to a one-piece magnet. The use of a segmented compression structural element enables a method of applying a preload to the compression structural element. Fig.12 In the example of FIG. 4 , the compression structural element 400 includes six segments 401-406, each segment having a pentagonal or truncated pentagonal (trapezoidal) shape to fill the space between the beams 410, 412 in the flux barrier cavity 414. The segments 401-406 are inserted into the stacked laminations of the rotor assembly, for example by sliding them into the flux barrier cavity 414 before adding at least one end cap ( Figure 1 ). The trapezoidal segments 401, 406 are wedged between the pentagonal segments 402-405 and the beams 410, 412, thereby compressing the compression structural element 400 and the beams 410, 412 to apply a load 416. In response, the compression structural element 400 applies a preload 418 to the beams 410, 412 to counteract the centrifugal force. In other embodiments, the beams 410, 412 may be elastically deformable so that a press fit may be applied between the oversized compression structural element and its retaining wall features. For example, the wall features may be made of an elastically deformable steel material. For example, Figure 6 The magnet 123 may be sized so that a press fit is required to slide it into the magnet cavity 84 between the beams 163, 164, it may deform sufficiently to allow insertion and may then attempt to return to its original shape to apply a preload to the magnet 123. In either preload method, the wedging action or interference fit may be designed to result in a specific amount of preload 418 to counteract a desired amount of centrifugal force.

[0056] Therefore, the compression structural element can increase the motor performance / operating speed without increasing the size of the bridge / pillar, and can reduce / eliminate the size of the structural member to improve the magnetic performance. The compression structural element is compressible between the wall features to transfer the load through the compression structural element to the heavier structural part of the rotor. Although at least one exemplary embodiment has been presented in the foregoing detailed description, it should be understood that there are a large number of variations. It should also be understood that one or more exemplary embodiments are merely examples and are not intended to limit the scope, applicability or configuration of the present disclosure in any way. On the contrary, the foregoing detailed description will provide a convenient roadmap for those skilled in the art to implement 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 the present disclosure as set forth in the appended claims and their legal equivalents.

Claims

1. A rotor for a motor, comprising: a rotor core having a lamination stack of individual laminations between ends of the rotor core, the rotor core having at least one cavity within the rotor core, the at least one cavity being surrounded by a wall defined by the rotor core, the lamination stack having a length between the ends; and a structural element disposed in the at least one cavity and compressible between the first wall feature and the second wall feature, wherein the first wall feature and the second wall feature comprise a beam-like structure formed by aligned tabs of a single lamination in the lamination stack, the beam-like structure extending the length of the lamination stack, A preload is established between the first wall feature and the second wall feature and the structural element.

2. The rotor according to claim 1, wherein: The structural element includes a magnet, wherein the magnet is configured to provide a load path between the beam-like structures so that the magnet applies a reaction force having a radial component to the beam-like structures to counteract the centrifugal force on the rotor core.

3. The rotor according to claim 1, wherein: The structural element comprises a non-magnetic material.

4. The rotor according to claim 1, wherein: The structural element comprises a plurality of sides defining corners, and wherein the first wall feature and the second wall feature comprise a beam joined to the structural element at two corners that are non-adjacent to one another, wherein non-adjacent means that no number of sides are in common.

5. The rotor according to claim 4, wherein: The non-adjacent corner portions include a first corner portion disposed at a junction of a first radially inner side and a first radially outer side, and a second corner portion disposed at a junction of a second radially inner side and a second radially outer side.

6. The rotor according to claim 1, wherein: The structural element includes a plurality of segments that are wedged against the first wall feature and the second wall feature to establish the preload.

7. The rotor according to claim 6, wherein: The segments include pentagonal and trapezoidal shapes.

8. The rotor according to claim 1, wherein: The wall features include a deformable material, and the structural element is press-fitted between the wall features to establish the preload.

9. The rotor of claim 2, comprising a plurality of cavities, wherein: The cavity is defined in part by the struts and bridges, and wherein the structural element is configured to counteract via a reaction force all loads along the length that would otherwise be carried by the struts and bridges.

10. The rotor according to claim 1, wherein: At least one of the structural element and the rotor causes a wedging action on the structural element.

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