Apparatus and methods for lamination stack insertion

Abstract

Disclosed herein are apparatus and methods for lamination stack insertion. A method of installing a lamination stack to a magnet assembly includes loading the lamination stack to a clamping tool, loading the magnet assembly to a press tool, applying cooling to the loaded lamination stack, aligning the loaded lamination stack and the loaded magnet assembly, and pressing, with the press tool, the loaded lamination stack into the loaded magnet assembly. The apparatus may include a clamping tool having a first portion and a second portion that is disposed opposite to the first portion, a pressing tool configured to receive the magnet assembly. The clamping tool may retain the lamination stack and the clamping tool may be configured to be aligned with the pressing tool.

Description

PATENT Agent Ref. 16500-0009-00304 APPARATUS AND METHODS FOR LAMINATION STACK INSERTIONCROSS-REFERENCE TO RELATED APPLICATIONS

[0001] This disclosure claims priority to U.S. Provisional Application No. 63 / 777,450, titled “APPARATUS AND METHODS FOR LAMINATION STACK INSERTION,” filed March 25, 2025, the contents of which are incorporated herein in their entirety for all purposes.TECHNICAL FIELD

[0002] This disclosure relates generally to the field of rotor manufacturing. More particularly, and without limitation, the present disclosure relates to innovations in the assembly of lamination stacks for rotors.BACKGROUND

[0003] Typical or conventional electric motors may include a rotor having a lamination stack that supports magnets. A lamination stack can provide structural and electromagnetic support for magnets in a rotor. Further, in some use cases of rotors, such as high-performance applications or aerospace applications, rotors that are lightweight but also capable of producing high torque are desired. For example, conventional rotors can include surface mounted magnets glued to a lamination stack. However, conventional processes for assembling rotors present a variety of drawbacks, and can result in damages to such rotors. For example, conventional processes of mating a lamination stack with magnets can result in high friction between the laminations and magnets, thereby damaging the laminations. The apparatus and methods for lamination stack insertion disclosed in the present disclosure enable damage free installation of lamination stacks for high-performance rotors.SUMMARY

[0004] Some embodiments of the present disclosure provide a method of installing a lamination stack to a magnet assembly comprising a plurality of magnets. The method may comprise loading the lamination stack to a clamping tool; loading the magnet assembly to a press tool; applying cooling to the loaded lamination stack, wherein the cooling shrinks a diameter of the lamination stack; aligning the loaded lamination stack and the loaded magnet assembly; and pressing, with the press tool, the loaded lamination stack into the loaded magnet assembly.

[0005] Some embodiments of the present disclosure provide an apparatus for inserting a lamination stack into a magnet assembly comprising a plurality of magnets. The apparatusPATENT Agent Ref. 16500-0009-00304 may comprise: a clamping tool having a first portion and a second portion that is disposed opposite to the first portion, the clamping tool configured to receive the lamination stack between the first portion and the second portion; a pressing tool configured to receive the magnet assembly; wherein the clamping tool retains the lamination stack; and wherein the clamping tool is configured to be aligned with the pressing tool.BRIEF DESCRIPTION OF FIGURES

[0006] Figure 1 is an exploded view of a rotor assembly, consistent with disclosed embodiments.

[0007] Figures 2A and 2B illustrate views of a magnet assembly, consistent with disclosed embodiments.

[0008] Figures 3A-3H illustrate a process flow of components and steps for lamination stack insertion, consistent with disclosed embodiments.

[0009] Figure 4 is a cross-sectional view of an exemplary propulsion system, consistent with disclosed embodiments.

[0010] Figures 5A and 5B are illustrations of a perspective view of an exemplary VTOL aircraft, consistent with disclosed embodiments.

[0011] Figure 6 is a flow diagram of an exemplary process for lamination stack insertion, consistent with disclosed embodiments.DETAILED DESCRIPTION

[0012] Reference will now be made in detail to exemplary embodiments, examples of which are illustrated in the accompanying drawings. The following description refers to the accompanying drawings in which the same numbers in different drawings may represent the same or similar elements unless otherwise represented. The implementations set forth in the following description of exemplary embodiments do not represent all implementations consistent with the disclosure. Instead, they are merely examples of apparatuses and methods consistent with aspects related to the subject matter recited in the appended claims.

[0013] The disclosed embodiments relate to apparatus and processes for assembling rotors, and in particular, installing lamination stacks for rotors. The disclosed embodiments may be applicable to any use of a motor such as any aircraft use (e.g., vertical take-off and landing (VTOL) aircraft), automotive use, high performance uses (e.g., turbochargers) alternators, generators, manufacturing motors (e.g., conveyors), or the like. For example, the disclosedPATENT Agent Ref. 16500-0009-00304 embodiments may relate to rotors including surface-mounted magnets. It will be recognized that a lamination stack may provide structural and electromagnetic support for magnets in a rotor, and can contact the rotor magnets in some examples. For example, in the case of surface mounted magnets, rotor magnets can surround the lamination stack, and an interference fit may couple the lamination stack and rotor magnets. A secure fit between the lamination stack and rotor magnets may assist in reducing electromagnetic losses. However, during installation of lamination stacks, conventional installation processes can involve frictional forces as the lamination stack contacts the rotor magnets (causing relative motion), thereby resulting in shearing forces. High shearing forces can be detrimental to the lamination stack and magnets, and shearing forces can be especially damaging to laminations when laminations are thin and / or held together by adhesives. Furthermore, some conventional installation processes can involve heating rotor magnets to cause thermal expansion so the lamination stack can be installed, however, applying heat to magnets can be damaging to the magnets and can cause demagnetization. The disclosed embodiments provide improved installation of lamination stacks, including by cooling lamination stacks to allow insertion, thereby reducing damage to lamination stacks and magnets, increasing rotor lifespan, and enabling optimal rotor performance. Further, the disclosed embodiments may provide improvements to efficiency and speed of assembling rotors.

[0014] FIG. 1 illustrates an exploded view of a rotor assembly 100, consistent with embodiments of the present disclosure. Rotor assembly 100 may include a magnet assembly including one or more magnets. For example, a magnet assembly may include a plurality of magnets, such as magnets 104. In some embodiments, a magnet assembly may also include a second plurality of magnets, such as magnets 108. For example, magnets 104 may be pole magnets, which can contribute to main interactions between the stator and the rotor (e.g., driving poles), and magnets 108 may be side magnets, such that the pole magnets have stronger magnetic forces (e.g., attraction force) with a stator than the side magnets, while the side magnets provide an opposing (e.g., repelling force). Rotor assembly 100 may include a lamination stack 102. A lamination stack may include a core or structural element of a rotor. A lamination stack may also refer to a back iron, core, or the like. Magnets may be mounted to lamination stack 102. For example, lamination stack 102 may contact or be adjacent to surface-mounted magnets in rotor assembly 100, such as magnets 104 and / or magnets 108. Lamination stack 102 may include one or more laminations (e.g., sheets) that can assist in reducing eddy current losses during operation of rotor assembly 100. For example, laminationPATENT Agent Ref. 16500-0009-00304 stack 102 may include multiple sheets of magnetic materials, such as Cobalt-Iron (CoFe) sheets, steel, Silicon-Steel, Nickel-Iron, or other various alloys, as non-limiting examples.

[0015] The laminations may be thin. For example, in high-performance applications such as electric aircraft, the laminations may have thicknesses of between, e.g., 20 and 200 micrometers, such as between 50 and 150 micrometers. Some applications, such as in the automotive industry, may allow for thicker laminations, such as between 200 and 500 micrometers. Thicker laminations may enable easier manufacturing. For example, thicker laminations may be produced by a die cut stacking method, and may not require clamping to prevent delamination during an insertion process.

[0016] By reducing losses, lamination stack 102 may enable improved thermal efficiency (e.g., reduced heat). In some embodiments, laminations of lamination stack 102 may be held together by adhesives. Rotor assembly 100 may include sleeve 106. Sleeve 106 may assist in retaining magnets 104 and magnets 108, as will be described. In some embodiments, rotor assembly 100 may include one or more rotor hubs, such as rotor hub 110 and rotor hub 112. Rotor hubs may assist in connecting components in rotor assembly 100 as well as retaining components such as sleeve 106, lamination stack 102, and / or magnets 104 and magnets 108. It will be recognized that magnets 104 and magnets 108 may experience centrifugal force during operation of rotor assembly 100 (e.g., due to rotation of rotor assembly 100) that may cause the magnets to move or separate from lamination stack 102. The disclosed embodiments may include components to prevent such separation, such as sleeve 106. Sleeve 106 may be a stretchable sleeve, and to prevent the magnets from separating from the rotor during rotation, sleeve 106 may apply a force sufficient to compensate for centrifugal forces, such as centrifugal forces expected at operational rotational speeds. Sleeve 106 may be a premade sleeve, and magnets 104 and magnets 108 can be inserted into the sleeve, which may eliminate the need to wind material such as carbon fiber onto the magnets. Winding, or other methods of applying a sleeve after the magnets have been assembled, may not provide the necessary tension (e.g., preload) to retain the magnets when spinning at the operational speeds of the motor, thus requiring larger air gaps between the rotor and stator (e.g., distance between rotor magnets and copper windings of the stator) which can reduce rotor efficiency. For example, when wrapping carbon fiber around magnets (e.g., where adhesives may be used to secure magnets to a back iron), the tension used to wind the carbon fiber may not provide an optimal preload for retaining the magnets. Further, as the sleeve can stretch when the magnets are arranged in the sleeve, the tension in the sleeve may cause a force to bePATENT Agent Ref. 16500-0009-00304 applied on the magnets in an opposing direction (e.g., radially inward) to the centrifugal force (e.g., which may be radially outward). The sleeve may apply force on the magnets by preloading the magnets against lamination stack 102, thereby providing sufficient retention on the magnets and allowing higher torque to be generated by rotor assembly 100. For example, sleeve 106 may include carbon fiber. However, it may be difficult to insert a lamination stack into the undersized geometry of a sleeve-wrapped magnet assembly without damaging the laminations or compromising the sleeve.

[0017] FIG. 2A illustrates a view of a magnet assembly 200, consistent with embodiments of the present disclosure. Magnet assembly 200 may include magnets 104, magnets 108, and sleeve 106. In some embodiments, magnet assembly 200 may include one or more tapered magnets. For example, magnets 104 may be tapered. Additionally, or alternatively, magnets 108 may be tapered. In FIG. 2A, the taper of magnets may be exaggerated for illustrative purposes. A tapered magnet may involve a magnet with a dimension that narrows, diminishes, or gradually lessens in size. For example, a tapered magnet may have a first length or width and a second length or width, with the second length of width being smaller than the first. In some embodiments, the amount of taper may be determined by properties of the rotor assembly such as the dimensions of the rotor, the amount of expansion in the sleeve needed, and the amount of pressure or force desired to be generated in the sleeve. The angle or amount of taper may influence the amount of circumferential displacement, and therefore the amount of stretch obtained, in the sleeve as the magnets are inserted against one another along the axial direction 215 into the sleeve. In some embodiments, a tapered magnet may include a taper angle (e.g., incline) of 0.1 to 45 degrees. In some examples, the tapered magnet may include a taper angle on opposing faces of 7 degrees or less. As an example, a tapered magnet may have a trapezoidal shape, with an incline of 0.6 degrees. In some embodiments, a tapered magnet may include an incline of 0.6 degrees on one surface, or an incline of 0.6 degrees on opposing surfaces. For example, the width at first side 205 of magnet 108 may be greater than the width at second side 207 of magnet 108. First side 205 may be parallel to second side 207. First tapered side 211 and second tapered side 209 may be inclined relative to the first side 205 and second side 207. In some embodiments, first tapered side 211 and second tapered side 209 may form a tapered magnet such that second side 207 may be smaller in width than first side 205. Similar considerations may apply to magnets 104. The magnets may be positioned along an inner diameter 204 of the sleeve 106. In some embodiments, the direction of taper of magnets 108 may be opposite to the directionPATENT Agent Ref. 16500-0009-00304 of taper in magnets 104. In some embodiments, the plurality of tapered magnets may be circumferentially inserted against one another, such as in an axial direction 215.Circumferentially inserted may involve placing the magnets along the circumference of the sleeve and inserting them against one another to form a ring of magnets inside the sleeve 106. The magnet arrangement may be of such a size that the arrangement, before the magnets are pushed together, fits inside the diameter of the sleeve.

[0018] FIG. 2B illustrates a view of magnet assembly 200, consistent with embodiments of the present disclosure. FIG. 2B illustrates magnet assembly 200 in an inserted or operable configuration, in which magnets 104 and magnets 108 have been inserted together. The magnets may be disposed on the inside of the sleeve 106 such that the magnets are distributed over the circumference of the sleeve. The inclined, or tapered, sides of magnets 104 may contact the inclined sides of magnets 108. In some embodiments, tapered magnets may be wedges, such that when tapered magnets in opposing orientations contact each other, the magnets may cause displacement and stretch the sleeve 106. For example, magnets 104 may be wedged between an adjacent pair of magnets 108 and vice-versa. With this arrangement, as each magnet (e.g., 104 or 108) is inserted in an axial direction, the magnet may exert a force, in a circumferential direction, on its neighboring magnet having an opposite taper, resulting in an increased diameter of the magnet arrangement as the opposing magnets push each other apart, thereby stretching sleeve 106 and inducing tension in the sleeve. In some embodiments, the amount of strain tolerated by the sleeve may contribute to determining how much the sleeve may stretch without breaking, thus contributing to determining sizes of the sleeve (e.g. diameter) and magnets (e.g., length, width, taper angle). Friction between magnets 104 and magnets 108 may secure or lock the magnets in a fixed position. It will be appreciated that in some embodiments, circumferentially inserting the magnets using a premade sleeve may provide higher achievable cylinder stress and pressure to retain the magnets compared to direct winding.

[0019] It will be appreciated that magnet assemblies including tapered magnets (as illustrated FIGs 2A-2B) may be advantageous in enabling a greater stretch in sleeve 106, as the magnets wedge against each other, thereby enabling greater preload in sleeve 106. However, the disclosed embodiments are not limited to tapered magnets. The disclosed embodiments may involve any configuration of magnet assemblies including surface-mounted magnets. As described herein, it may be desired to reduce air gaps between magnet assembly 200 and lamination stack 102, as air gaps between lamination stack 102 and magnets 104 may resultPATENT Agent Ref. 16500-0009-00304 in decreased flux transfer. Therefore, a secure fit between lamination stack 102 and magnets 104 may be desired. For example, an outer circumference of lamination stack 102 may be disposed within an inner circumference of magnet assembly 200, such that the outer circumference of lamination stack 102 may abut magnets 104 and magnets 108, resulting in an interference fit. However, as described herein, installing lamination stack 102 with magnet assembly 200 may be challenging with conventional processes, as shearing forces may damage the magnets and / or lamination stack if the components are inserted together. Further, heating the magnet assembly (e.g., to cause expansion) may be detrimental, as heating can cause demagnetization. In addition, sleeve 106 may have low thermal expansion, and thus may not be able to expand to accommodate the inserted lamination stack.

[0020] FIGs. 3A-3G illustrate an improved process and apparatus for inserting a lamination stack, consistent with embodiments of the present disclosure. For example, the process may comprise: loading the lamination stack to a clamping tool that applies a clamping force on the lamination stack in an axial direction of the lamination stack; loading the magnet assembly to a press tool configured to press the lamination stack into the magnet assembly; applying cooling to the loaded lamination stack to shrink the diameter of the lamination stack; aligning the loaded and cooled lamination stack with the loaded magnet assembly in the press tool; and pressing, with the press tool, the loaded lamination stack into the loaded magnet assembly.

[0021] FIG. 3A illustrates a lamination stack 102 and clamping tool 302. As described herein, lamination stack 102 may include a plurality of laminations. Clamping tool 302 may be configured to support lamination stack 102 in an axial direction 215, such as by applying a clamping force in the axial direction 215. In some embodiments, clamping tool 302 may be configured to support the lamination stack 102 in a way that allows insertion of the lamination stack 102 into magnet assembly 200 while the lamination stack 102 remains clamped (such as, e.g., by supporting the lamination stack 102 in the axial direction 215). In this way, a single clamping tool 302 may be used to handle the lamination stack during the entire cooling and pressing process, i.e., from before the lamination stack is cooled until after it is inserted into magnet assembly 200. The clamping tool 302 may be formed of materials having desirable structural and thermal properties for performing the clamping function throughout the wide range of temperatures experienced during the cooling and insertion process. For example, clamping tool 302 may be formed of metals, ceramics, or other materials that are capable of applying and maintaining a sufficient clamping force on thePATENT Agent Ref. 16500-0009-00304 lamination stack 102 to prevent delamination or other damage to the lamination stack 102 during cooling or insertion. Further, to minimize thermal deformations, the clamping tool materials may be selected have a same or similar coefficient of thermal expansion (CTE) as that of the lamination stack materials. In some embodiments, the clamping tool may comprise one or more materials that are the same as one or more materials of the lamination stack, or may comprise, e.g., an alloy having at least one constituent material in common. For example, the clamping tool 302 may comprise, e.g., Cobalt, Iron, CoFe, steel, Silicon-Steel, Nickel-Iron, or other various alloys.

[0022] In some embodiments, the lamination stack may be loaded into the clamping tool after it is cooled. For example, the lamination stack may be cooled at a cooling station, subsequently clamped, and inserted using a press tool. However, clamping the lamination stack prior to cooling may be preferable for a number of reasons. For example, the cooled lamination stack may be more difficult to handle than a lamination stack at room temperature. Thus, the clamping tool may provide handles or other structures for, e.g., easily moving the lamination stack from one station to another. At the same time, this difficulty in handling makes the clamping process itself more difficult. Further, the lamination stack may be prone to damage when attempting to apply a clamping force while it is cooled to extremely low temperatures. Finally, clamping prior to cooling can minimize the transfer time between cooling and insertion steps. For example, in some embodiments it may be desirable to transfer the lamination stack from a cooling station to a press tool very rapidly (such as, e.g., in a matter of seconds, for example, in less than five seconds or less than three seconds). Because this time constraint is not conducive to accurate and damage-free clamping, it may be advantageous to perform the clamping before cooling takes place.

[0023] In some embodiments, the lamination stack may be inserted without clamping at all. For example, as discussed above, thicker laminations may not require clamping.

[0024] Clamping tool 302 may comprise any component(s) that can hold or support lamination stack 102. Clamping tool 302 may include a first portion 304, radial guides 305, a second portion 306, and one or more axial positioning mechanisms 308. Clamping tool 302 may receive the lamination stack 102 between the first portion 304 and second portion 306. The second portion 306 may be disposed opposite to first portion 304. In some embodiments, first portion 304 and / or second portion 306 may be removable from clamping tool 302. For example, lamination stack 102 may be loaded onto clamping tool by moving or removing second portion 306, setting the lamination stack onto first portion 304, and replacing secondPATENT Agent Ref. 16500-0009-00304 portion 306 above the lamination stack 102 and first portion 304. Radial guides on the first portion 304 and second portion 306 can be used to axially align the lamination stack 102 with clamping tool 302. Axial positioning mechanism 308 can be used to adjust the height or distance between first portion 304 and second portion 306 and to clamp the lamination stack 102. For example, depending on the height of lamination stack 102 (e.g., in axial direction 215), axial positioning mechanism 308 can be increased or decreased such that the first portion 304 and second portion 306 clamp lamination stack 102 in the axial direction 215.

[0025] In some embodiments, clamping tool 302 may further comprise one or more handles (not shown). For example, handles 324a may be configured to be held by, e.g., a human operator wearing thermal protective gear, an end effector or other robotic device, etc., to allow an operator or automated system to transfer the loaded lamination stack through various processing stages.

[0026] FIG. 3B illustrates a loaded lamination stack 312. Loaded lamination stack 312 may include lamination stack 102 and clamping tool 302. Clamping tool 302 may retain lamination stack 102. For example, lamination stack 102 may be sandwiched between first portion 304 and second portion 306, which may support lamination stack 102 in axial direction 215. It will be appreciated that by supporting lamination stack 102 with first portion 304 and second portion 306, shearing between lamination sheets (e.g., relative motion in axial direction 215) may be reduced, thereby mitigating damage such as delamination to lamination stack 102.

[0027] In some embodiments, cooling may be applied to achieve an interference (e.g., shrink) fit between lamination stack 102 and magnet assembly 200. As described herein, it may be desired to insert lamination stack 102 into magnet assembly 200, without exerting excessive shearing forces on lamination stack 102. The disclosed embodiments involve applying cooling to lamination stack 102 to cause shrinkage of lamination stack 102.Applying cooling to lamination stack 102 may involve cooling lamination stack 102 to a temperature suitable to maintain the lamination stack in a shrunken state during the subsequent insertion process. For example, lamination stack 102 may be exposed to one or more coolants that provide cooling, such as by immersing the lamination stack 102 in a coolant.

[0028] FIG. 3C illustrates a cooling station 320 for cooling a lamination stack. Cooling station 320 may comprise a stationary or a mobile unit for applying cooling to loaded lamination stack 312. In some embodiments, cooling station 320 can include a preparationPATENT Agent Ref. 16500-0009-00304 area 325, cooling chamber 322, coolant supply 327, and monitoring system 328. Preparation area 325 may comprise various tools for preparing the loaded lamination stack 102 for cooling. For instance, preparation area 325 may comprise a dipping basket 324 mounted on a hanger 326, as further discussed below. Cooling chamber 322 may include coolants, including liquid-based coolants or cryogenic coolants from a coolant supply 327. For example, the coolants supplied to cooling chamber 322 may include, e.g., liquid nitrogen or carbon dioxide. Cooling chamber 322 may receive loaded lamination stack 312, and loaded lamination stack 312 may be submerged in cooling chamber 322. For example, cooling chamber 322 may be a liquid nitrogen bath configured to receive the lamination stack 102 and clamping tool 302. In some examples, cooling chamber 322 may maintain a given amount of the coolant (e.g., liquid nitrogen) in order to sequentially cool multiple lamination stacks, or cooling chamber 322. Upon cooling, loaded lamination stack 312 may shrink. For example, due to the cooling, the diameter of the lamination stack 102 may shrink. For example, in some embodiments, the loaded lamination stack may be immersed in liquid nitrogen for a period of, e.g., one to three minutes to reduce the loaded lamination stack to a temperature between, e.g., -140° and -160° C (-220° and -256° F).

[0029] In some embodiments, cooling station 320 may include dipping basket 324 located at, e.g., preparation area 325. Loaded lamination stack 312 can be placed on dipping basket 324, and the dipping basket can be used to lower loaded lamination stack 312 into cooling chamber 322, such as by using handles 324a. For example, handles 324a may be configured to be held by, e.g., a human operator wearing thermal protective gear, an end effector or other robotic device, etc. Additionally, cooling station 320 may include systems for monitoring the cooling process, such as monitoring system 328 comprising, e.g., sensors or displays to monitor temperature, coolant amounts, and / or time of cooling. For example, cooling station 320 may include a sensor that detects temperature or amount of liquid nitrogen in cooling chamber 322, and cooling station 320 may actively adjust the amount of liquid nitrogen in cooling chamber 322 by controlling valves that allow for entry of liquid nitrogen (e.g., from a source into the cooling chamber) and exit of liquid nitrogen (e.g., out of the cooling chamber).

[0030] FIG. 3D illustrates magnet assembly 200 and a press tool 332. Press tool 332 may include any tool configured to apply force. For example, press tool 332 may include manual or hydraulic presses. Press tool 332 may include one or more guides 334, as well as one or more pressing portions such as a ram 338. Press tool 332 may receive magnet assembly 200.PATENT Agent Ref. 16500-0009-00304 For example, press tool 332 may receive magnet assembly 200 between guides 334 or guides 334 may assist in aligning magnet assembly 200. In addition, press tool 332 may include one or more alignment pins 335. FIG. 3E illustrates a loaded magnet assembly 336. Loaded magnet assembly 336 may be formed by loading magnet assembly 200 onto press tool 332. In some embodiments, the loaded lamination stack 312 may be loaded on press tool 332. FIG.3F illustrates a loaded magnet assembly 336 and loaded lamination stack 312. The loaded lamination stack 312 (e.g., including clamping tool 302 and lamination stack 102) can be aligned with the loaded magnet assembly 336 (e.g., including magnet assembly 200 and press tool 332). For example, guides inside and / or outside of press tool 332 can assist in aligning the loaded lamination stack 312 and loaded magnet assembly 336. Additionally, alignment pins 335 can assist in aligning the loaded lamination stack 312, such as when lamination stack 102 and / or clamping tool 302 include slots or other features to receive the alignment pins 335. For example, lamination stack 102 can include one or more notches 337 (as illustrated in FIG. 3H), and alignment pins 335 can interface with notches 337 to provide alignment. In some embodiments, the loaded lamination stack 312 can be positioned above loaded magnet assembly 336. Press tool 332 may be moved onto, e.g., the upper portion 306 to press and apply force to the loaded lamination stack 312 and / or loaded magnet assembly 336. For example, force may be applied (e.g., by ram 338 of press tool 332) onto second portion 306 of clamping tool 302, resulting in the loaded lamination stack 312 being inserted into loaded magnet assembly 336 as the lamination stack slides into the magnet assembly. It will be appreciated that due to cooling applied to it, the laminations of loaded lamination stack 312 may have an outer diameter that is smaller than an inner diameter of loaded magnet assembly 336. Further, portions of the clamping tool 302 that are made to be passed through the loaded magnet assembly 336 may be designed to have a smaller outer diameter even at room temperature. For example, lower portion 304 may have an outer diameter that is smaller than an inner diameter of loaded magnet assembly 336, while second portion may or may not have an outer diameter that is smaller than an inner diameter of loaded magnet assembly 336. As such, the loaded lamination stack 312 can be inserted with minimal frictional forces, and thereby minimum shearing between the lamination stack and magnets. As the insertion of loaded lamination stack 312 may occur in ambient temperature (e.g., a temperature greater than that of cooling chamber 322), the amount of shrinkage in the lamination stack 102 may subside, and the lamination stack may begin to expand to its original diameter and / or exert additional radial tension on magnet assembly 200.PATENT Agent Ref. 16500-0009-00304

[0031] As such, it will be recognized that large amounts of time should not pass between removal of the lamination stack from the cooling chamber and the insertion of the lamination stack into the magnet assembly. For example, in some embodiments, it may be desirable to transfer the lamination stack to the press tool, or to press the lamination stack into the motor assembly, within a predetermined time of removing it from the coolant. For example, in some embodiments the predetermined time may comprise, e.g., three seconds, five seconds, ten seconds, or twenty seconds.

[0032] In some embodiments, cooling station 320 and press tool 332 may be integrated into an assembly system to enable rapid transfer between them. For example, a robotic or other automated assembly system may be configured to move the lamination stack horizontally or vertically between stations that or oriented horizontally or vertically. In some embodiments, an integrated assembly system may comprise a combination cooling station / press tool. For example, a support platform may be configured to raise the lamination stack out of a cooling chamber 322 and into a loaded magnet assembly that is held above the lamination stack on ram 338, in order to align, cool, and insert the lamination stack along a single axis.

[0033] FIG. 3G illustrates a cross-sectional assembly of an inserted lamination stack disposed on press tool 332. Upon insertion, lamination stack 102 may abut magnets of magnet assembly 200, thereby coupling lamination stack 102 to magnet assembly 200 by way of interference fit (e.g., shrink fit). The inserted lamination stack 102 can be removed from clamping tool 302 and pressing tool 332. FIG. 3H illustrates a lamination stack 102 inserted into magnet assembly 200. In some embodiments, lamination stack 102 may include one or more notches 337. A notch may include an indented region or a region of removed material such as a cut or incision. Notches 337 can assist with alignment of components during assembly, such as when notches 337 can be aligned with pressing tool 332, as described herein. In some embodiments, notches 337 can provide torque transmission from the inserted lamination stack 102 to rotor hubs 110, 112, as illustrated in FIG. 1. For example, rotor hubs 110, 112 may be coupled to a shaft of an engine. Various portions (e.g., projections) of rotor hubs 110, 112 may align and abut with notches 337, thereby mating the notches 337 with the rotor hubs 110, 112. As electromagnet forces between a stator and magnet assembly 200 cause rotation of rotor assembly 100, lamination stack 102 coupled to magnet assembly 200 may rotate and drive torque to the rotor hubs 110, 112, with the notches 337 providing enhanced torque transmission to the rotor hubs and thereby to the rotated shaft.PATENT Agent Ref. 16500-0009-00304

[0034] FIG. 4 illustrates an exemplary embodiment of a propulsion system 400, consistent with embodiments of the present disclosure. Propulsion system 400 may be an electric propulsion system or a hybrid propulsion system. In some embodiments, propulsion system 400 may include an electric motor. In some embodiments, propulsion system 400 may additionally include a combustion motor to form a hybrid propulsion system. Propulsion system 400 may include an inverter assembly 404, and an electric motor assembly 402, and optionally, a gearbox assembly 406. Propulsion system 400 may include a heat exchanger 418 that may be thermally, fluidically, and / or mechanically coupled to inverter assembly 404. Propulsion system 400 may include a shaft 408. Electric motor assembly 402 may include a stator 440 and rotor assembly 100. In some embodiments, rotor assembly 100 may be coupled to shaft 408. Electromagnetic interactions between stator 440 and rotor assembly 100 may drive rotation of rotor assembly 100, thereby driving rotation of shaft 408. In some embodiments, propulsion system 400 may include a gearbox assembly 406. Gearbox assembly 406 may abut the inverter assembly 404 and the electric motor assembly 402. For example, gearbox assembly 406 may interface with rotor assembly 200 and also be coupled to shaft 408, such that rotations of rotor assembly 200 may drive a gear reduction that drives shaft 408. In some embodiments, shaft 408 may be coupled to a propeller flange 420.

[0035] In some embodiments, propulsion system 400 may comprise an engine for a VTOL aircraft. FIGs. 5A and 5B illustrate a VTOL aircraft, consistent with embodiments of the present disclosure. In particular, FIGs. 5A and 5B illustrate a VTOL aircraft 500 in a cruise configuration and a vertical take-off, landing, and hover configuration (also referred to herein as a “lift” configuration), respectively, consistent with embodiments of the present disclosure. Aircraft 500 represents an example of an apparatus that may utilize rotor assembly 100, including lamination stack 102 inserted into magnet assembly 200. For example, aircraft 500 may include one or more propulsion systems 400 that drive propellers of the aircraft. The aircraft 500 may include a fuselage 502, wings 504 mounted to the fuselage 502, tail 505, and one or more rear stabilizers 506 mounted to the tail 505 or the rear of the fuselage 502. A plurality of lift propellers 512 may be mounted to wings 504 and configured to provide lift for vertical take-off, landing, and hover. A plurality of tilt propellers 514 may be mounted to wings 504 and may be tiltable between the cruise configuration in which they provide forward thrust to aircraft 500 for horizontal flight, as shown in FIG. 5 A, and the lift configuration in which they provide a portion of the lift required for vertical take-off, landing, and hovering, as shown in FIG. 5B. As used herein, a lift configuration may refer to a tiltPATENT Agent Ref. 16500-0009-00304 propeller orientation in which the tilt propeller thrust is providing primarily lift to the aircraft. A cruise configuration may refer to a tilt propeller orientation in which the tilt propeller thrust is providing primarily forward thrust to the aircraft. Alternatively, a cruise configuration may refer to a configuration in which a lift propeller is stowed.

[0036] In some embodiments, lift propellers 512 may be configured for providing lift only, with all propulsion being provided by the tilt propellers. Accordingly, lift propellers 512 may be in fixed positions and may only generate thrust during take-off, landing, and hover.Meanwhile, tilt propellers 514 may be tilted to lift configurations in which their thrust is directed vertically for providing additional lift.

[0037] For forward flight, tilt propellers 514 may tilt from their lift configurations to their cruise configurations. In other words, the pitch and tilt angle of tilt propellers 514 may be varied from an orientation in which the tilt propeller thrust is directed vertically (to provide lift during vertical take-off, landing, and hover) to an orientation in which the tilt propeller thrust is directed horizontally (to provide forward thrust to aircraft 500). The tilt propellers may tilt about axes that may be perpendicular to the forward direction of the aircraft 500. When the aircraft 500 is in full forward flight during the cruise configuration, lift may be provided entirely by wings 504. Meanwhile, lift propellers 512 may be shut off. The blades 520 of lift propellers 512 may be locked in low-drag positions for aircraft cruising. In some embodiments, lift propellers 512 may each have two blades 520 that may be locked for cruising in minimum drag positions in which one blade is directly in front of the other blade as illustrated in FIG. 5A. In some embodiments, lift propellers 512 have more than two blades. In some embodiments, there may be more blades 518 on tilt propellers 514 than on lift propellers 512. For example, as illustrated in FIGs. 5A and 5B, lift propellers 512 may each include, e.g., two blades and tilt propellers 514 may each include, e.g., five blades. In some embodiments, tilt propellers 514 may have, e.g., from 2 to 5 blades.

[0038] In some embodiments, the aircraft may include only one wing 504 on each side of fuselage 502 (or a single wing that extends across the entire aircraft) and at least a portion of lift propellers 512 may be located rearward of wings 504 and at least a portion of tilt propellers 514 may be located forward of wings 504. In some embodiments, all of lift propellers 512 may be located rearward of wings 504 and all of tilt propellers 514 may be located forward of wings 504. According to some embodiments, all lift propellers 512 and tilt propellers 514 may be mounted to the wings — i.e., no lift propellers or tilt propellers may be mounted to the fuselage. In some embodiments, lift propellers 512 may be all locatedPATENT Agent Ref. 16500-0009-00304 rearwardly of wings 504 and tilt propellers 514 may be all located forward of wings 504. According to some embodiments, all lift propellers 512 and tilt propellers 514 may be positioned inwardly of the wing tips 509.

[0039] In some embodiments, lift propellers 512 and tilt propellers 514 may be mounted to wings 504 by booms 522. Booms 522 may be mounted beneath wings 504, on top of the wings, and / or may be integrated into the wing profile. In some embodiments, one lift propeller 512 and one tilt propeller 514 may be mounted to each boom 522. Lift propeller 512 may be mounted at a rear end of boom 522 and tilt propeller 514 may be mounted at a front end of boom 522. In some embodiments, lift propeller 512 may be mounted in a fixed position on boom 522. In some embodiments, tilt propeller 514 may mounted to a front end of boom 522 via a hinge. Tilt propeller 514 may be mounted to boom 522 such that tilt propeller 514 is aligned with the body of boom 522 when in the cruise configuration, forming a continuous extension of the front end of boom 522 that minimizes drag for forward flight.

[0040] In some embodiments, aircraft 500 may include, e.g., one wing on each side of fuselage 502 or a single wing that extends across the aircraft. According to some embodiments, the at least one wing 504 is a high wing mounted to an upper side of fuselage 502. According to some embodiments, the wings include control surfaces, such as flaps, ailerons or flaperons. According to some embodiments, the wings may have curved wing tips 509 for reduced drag during forward flight.

[0041] In some embodiments, rear stabilizers 506 include control surfaces, such as one or more rudders, one or more elevators, and / or one or more combined rudder-elevators. The wing(s) may have any suitable design. For example, the wings have a tapering leading edge or a tapering trailing edge. In some embodiments, the wings may have a substantially straight leading edge in the central section of wings 504.

[0042] Aircraft 500 may include at least one door 510 for passenger entry and exit. In some embodiments, the door 510 may be located beneath and forward of wings 504 as seen in FIGs. 5A and 5B

[0043] FIG. 6 illustrates a flow chart of a process 600 for inserting a lamination stack, consistent with embodiments of the present disclosure. In some embodiments, various steps in process 600 may be performed by a human. In some embodiments, various steps in process 600 may be performed with the assistance of machines (e.g., robots) or autonomously.PATENT Agent Ref. 16500-0009-00304

[0044] In some embodiments, process 600 includes a step 602 of loading a lamination stack and magnet assembly. For example, step 602 may include loading lamination stack 102 to clamping tool 302, as well as loading magnet assembly 200 to press tool 332.

[0045] In some embodiments, process 600 includes a step 604 of applying cooling to a lamination stack. It will be appreciated that applying cooling to a lamination stack can result in shrinking of the lamination stack. Step 604 may involve cooling the lamination stack for an amount of time to sufficiently expose the lamination stack to the coolant, and the cooling time may be dependent on the mass / size of the lamination stack, temperature / amount of coolant, and desired amount of shrinkage. For example, step 604 may involve submerging the lamination stack that has been loaded to clamping tool 302 in cooling chamber 322 (e.g., containing liquid nitrogen) for a period of approximately, e.g., two minutes.

[0046] In some embodiments, process 600 includes a step 606 of aligning the lamination stack and magnet assembly. Step 606 may involve removing the loaded lamination stack from the cooling chamber 322, and aligning the loaded lamination stack with the magnet assembly. For example, the magnet assembly may be loaded on press tool 332, and press tool 332 may have features that assist with alignment of the magnet assembly and the lamination stack.

[0047] In some embodiments, process 600 includes a step 608 of pressing the aligned lamination stack into the magnet assembly. For example, press tool 332 may exert a force on a portion of the loaded lamination stack (e.g., portion 306), thereby pressing the loaded lamination stack into the loaded magnet assembly. An exemplary amount of force may be, e.g., between 20 and 60 kN, such as 50 kN. The amount of applied force required may be function of, e.g., the tolerances between an outer diameter of the cooled lamination stack and an inner diameter of magnet assembly. It will be appreciated that steps 606 and 608 may be executed within a certain amount of time from removal of the lamination stack from the cooling chamber, as the lamination stack may begin to expand from its shrunk configuration upon exposure to temperatures (e.g., ambient temperature) greater than that of the cooling chamber. For example, alignment and / or pressing may be executed within, e.g., approximately five seconds from the time of removal of the lamination stack from the cooling chamber. It will be recognized that the amount of time between removal and insertion can depend on a variety of factors including cooling time, mass / size of the lamination stack, ambient and cooling chamber temperatures, and desired shrinkage / expansion. In some embodiments, upon insertion into the magnet assembly, step 608 may involve the laminationPATENT Agent Ref. 16500-0009-00304 stack expanding due to exposure to room temperature or active heating s discussed below. Thus, the lamination stack may abut the magnet assembly, causing an interference fit and thereby coupling the lamination stack to the magnet assembly. As the temperature of the lamination stack increases, the thermal expansion may result in both compression forces being exerted on the lamination stack and expansion forces being exerted on the magnet assembly. This expansion may serve to add further tension to the sleeve. The clamping tool may help to minimize buckling of the laminations during this transition back to room temperature.

[0048] In some embodiments, the inserted lamination stack may be actively heated using, e.g., an oven, air blower, etc., for example, at a temperature between 50 and 70 degrees C. Reducing the amount of warming time through active heating may reduce the risk of condensation forming on surfaces of the lamination stack, which could rust or otherwise degrade its components.

[0049] At least some of the embodiments disclosed herein can be described using the following clauses:Clause 1. A method of installing a lamination stack to a magnet assembly comprising a plurality of magnets, the method comprising:loading the lamination stack to a clamping tool;loading the magnet assembly to a press tool;applying cooling to the loaded lamination stack, wherein the cooling shrinks a diameter of the lamination stack;aligning the loaded lamination stack and the loaded magnet assembly; and pressing, with the press tool, the loaded lamination stack into the loaded magnet assembly.Clause 2. The method of claim 1, further comprising allowing the loaded lamination stack to expand.Clause 3. The method of claim lor 2 wherein applying cooling comprises submerging the lamination stack in a coolant.Clause 4. The method of claim 3, wherein the coolant comprises liquid nitrogen. Clause 5. The method of any of claims 1-4, wherein the clamping tool is configured to support a first side and a second side of the lamination stack in an axial direction of the lamination stack.PATENT Agent Ref. 16500-0009-00304 Clause 6. The method of any of claims 1-5, wherein the plurality of magnets comprises a plurality of tapered magnets.Clause 7. The method of claim 6, wherein two or more magnets of the plurality of tapered magnets are axially tapered.Clause 8. The method of any of claims 1-7, wherein the magnet assembly comprises a sleeve configured to retain the plurality of magnets.Clause 9. The method of claim 8, wherein the sleeve comprises carbon fiber. Clause 10. The method of any of claims 1-9, wherein the lamination stack comprises a plurality of laminations held together with an adhesive.Clause 11. An apparatus for inserting a lamination stack into a magnet assembly comprising a plurality of magnets, the apparatus comprising:a clamping tool having a first portion and a second portion that is disposed opposite to the first portion, the clamping tool configured to receive the lamination stack between the first portion and the second portion;a pressing tool configured to receive the magnet assembly; andwherein the clamping tool retains the lamination stack, andwherein the clamping tool is configured to be aligned with the pressing tool. Clause 12. The apparatus of claim 11, further comprising a cooling chamber configured to cool the clamping tool.Clause 13. The apparatus of any of claims 11-12, wherein the magnet assembly comprises a plurality of tapered magnets.Clause 14. The apparatus of claim 13, wherein two or more magnets of the plurality of magnets are axially tapered.Clause 15. The apparatus of any of claims 11-14, wherein the magnet assembly is disposed within an inner diameter of the lamination stack.Clause 16. The apparatus of any of claims 11-15, wherein the clamping tool and lamination stack are configured to be shrink-cooled.Clause 17. The apparatus of any of claims 11-16, wherein the magnet assembly comprises a sleeve configured to retain a plurality of magnets.Clause 18. The apparatus of claim 17, wherein the lamination stack comprises a plurality of laminations, and the sleeve comprises carbon fiber.

[0050] The embodiments disclosed herein are intended to be non-limiting. Those of ordinary skill in the art will appreciate that certain components and configurations of components mayPATENT Agent Ref. 16500-0009-00304 be modified without departing from the scope of the disclosed embodiments. It is also intended that the sequence of steps shown in figures are only for illustrative purposes and are not intended to be limited to any particular sequence of steps. As such, those skilled in the art can appreciate that these steps can be performed in a different order while implementing the same method.

Claims

PATENT Agent Ref. 16500-0009-00304 CLAIMS1. A method of installing a lamination stack to a magnet assembly comprising a plurality of magnets, the method comprising:loading the lamination stack to a clamping tool;loading the magnet assembly to a press tool;applying cooling to the loaded lamination stack, wherein the cooling shrinks a diameter of the lamination stack;aligning the loaded lamination stack and the loaded magnet assembly; and pressing, with the press tool, the loaded lamination stack into the loaded magnet assembly.

2. The method of claim 1, further comprising allowing the loaded lamination stack to expand.

3. The method of claim lor 2 wherein applying cooling comprises submerging the lamination stack in a coolant.

4. The method of claim 3, wherein the coolant comprises liquid nitrogen.

5. The method of any of claims 1-4, wherein the clamping tool is configured to support a first side and a second side of the lamination stack in an axial direction of the lamination stack.

6. The method of any of claims 1-5, wherein the plurality of magnets comprises a plurality of tapered magnets.

7. The method of claim 6, wherein two or more magnets of the plurality of tapered magnets are axially tapered.

8. The method of any of claims 1-7, wherein the magnet assembly comprises a sleeve configured to retain the plurality of magnets.

9. The method of claim 8, wherein the sleeve comprises carbon fiber.PATENT Agent Ref. 16500-0009-00304 10. The method of any of claims 1-9, wherein the lamination stack comprises a plurality of laminations held together with an adhesive.

11. An apparatus for inserting a lamination stack into a magnet assembly comprising a plurality of magnets, the apparatus comprising:a clamping tool having a first portion and a second portion that is disposed opposite to the first portion, the clamping tool configured to receive the lamination stack between the first portion and the second portion;a pressing tool configured to receive the magnet assembly; andwherein the clamping tool retains the lamination stack, andwherein the clamping tool is configured to be aligned with the pressing tool.

12. The apparatus of claim 11, further comprising a cooling chamber configured to cool the clamping tool.

13. The apparatus of any of claims 11-12, wherein the magnet assembly comprises a plurality of tapered magnets.

14. The apparatus of claim 13, wherein two or more magnets of the plurality of magnets are axially tapered.

15. The apparatus of any of claims 11-14, wherein the magnet assembly is disposed within an inner diameter of the lamination stack.

16. The apparatus of any of claims 11-15, wherein the clamping tool and lamination stack are configured to be shrink-cooled.

17. The apparatus of any of claims 11-16, wherein the magnet assembly comprises a sleeve configured to retain a plurality of magnets.

18. The apparatus of claim 17, wherein the lamination stack comprises a plurality of laminations, and the sleeve comprises carbon fiber.

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