JP7724478B2 - Improved rotor assembly for axial flux machines - Google Patents

Description

(background)
Permanent magnet axial flux motors and generators are known. Examples of such motors or generators (collectively referred to herein as “machines”) are described in U.S. Patent Nos. 7,109,625, 9,673,688, 9,800,109, 9,673,684, and 10,170,953, and U.S. Patent Application Publication No. 2018-0351441 A1 (the “'441 Publication”), the entire contents of each of which are incorporated herein by reference.

(overview)
In some of the disclosed embodiments, a rotor assembly for an axial flux machine includes at least one magnet and first and second support structures, the first support structure configured to mount the at least one magnet to the first support structure and provide a flux return path for the at least one magnet, and the second support structure configured to be attached to the first support structure to allow torque to be transferred between the at least one magnet and the second support structure via the first support structure, the second support structure further configured to (A) be attached to a rotatable shaft of the axial flux machine or (B) function as an output or input flange of the axial flux machine.

In some embodiments, a method includes mounting at least one magnet to a first support structure of a rotor assembly for an axial flux machine such that the first support structure provides a flux return path for the at least one magnet, and mounting a second support structure to the first support structure to enable torque to be transferred between the at least one magnet and the second support structure via the first support structure, the first support structure mounting the at least one magnet to the first support structure, and the second support structure further configured to (A) be attached to a rotatable shaft of the axial flux machine or (B) function as an output or input flange of the axial flux machine.

In some embodiments, a rotor assembly for an axial flux machine comprises at least one magnet, first means for providing a flux return path for the at least one magnet, and second means configured to be attached to the first means for transferring torque between the at least one magnet via the first means, the second means being further configured to (A) be attached to a rotatable shaft of the axial flux machine or (B) function as an output or input flange of the axial flux machine.
The present invention provides, for example, the following items.
(Item 1)
1. A rotor assembly for an axial flux machine, comprising:
at least one magnet;
a first support structure configured to mount the at least one magnet to the first support structure and to provide a magnetic flux return path for the at least one magnet;
a second support structure configured to be attached to the first support structure to allow torque to be transmitted between the at least one magnet and the second support structure via the first support structure; and
wherein the second support structure is further configured to (A) be attached to a rotatable shaft of the axial flux machine, or (B) function as an output or input flange of the axial flux machine.
(Item 2)
the second support structure is adapted to rotate about an axis of rotation of the axial flux machine;
the at least one magnet has a first surface, the first surface being perpendicular to a magnetization direction of the at least one magnet and facing away from the first support structure;
the first support structure, the second support structure, and the at least one magnet are constructed and arranged such that when the first support structure, the second support structure, and the at least one magnet are stationary with respect to the axis of rotation and unaffected by any other magnetic components, a distance between a first plane and a second plane is substantially greater than zero, the first plane intersecting a first point on the first surface, the axis of rotation being normal to the first plane, the second plane intersecting a second point on the first surface, and the axis of rotation being normal to the second plane;
the second point is at a greater radial distance from the axis of rotation than the first point;
the first support structure, the second support structure, and the at least one magnet are further configured and arranged such that when the first support structure, the second support structure, and the at least one magnet are stationary relative to the axis of rotation and unaffected by any other magnetic components, a half-line intersects the first plane, the half-line extending away from the first surface at the second point and being normal to the first surface;
Item 2. The rotor assembly of item 1.
(Item 3)
the at least one magnet has an inner edge disposed at the first point;
the at least one magnet has an outer edge disposed at the second point, the outer edge being opposite the inner edge;
the first support structure, the second support structure, and the at least one magnet are further configured and arranged such that when the first support structure, the second support structure, and the at least one magnet are stationary relative to the axis of rotation and unaffected by any other magnetic components, a ratio of a distance between the first plane and the second plane to a distance between the first point and the second point is greater than 0.002;
Item 3. The rotor assembly according to item 2.
(Item 4)
4. The rotor assembly of claim 2, wherein the rotor assembly is disposed within the axial flux machine, and wherein a distance between the first plane and the second plane is substantially equal to zero.
(Item 5)
5. The rotor assembly of claim 1, wherein the second support structure further comprises at least one surface, the at least one surface being radially tapered to cause the first support structure to recurve to conform to a shape of the at least one surface when the second support structure is attached to the first support structure.
(Item 6)
6. The rotor assembly of any one of claims 1-5, wherein the second support structure is configured to be mounted to a rotatable shaft of the axial flux machine.
(Item 7)
6. The rotor assembly of any one of claims 1-5, wherein the second support structure is configured to function as an output or input flange of the axial flux machine.
(Item 8)
the first support structure is made from at least one first material;
the second support structure is made from at least one second material different from the at least one first material;
Item 8. The rotor assembly of any one of items 1-7.
(Item 9)
the at least one magnet comprises a magnet piece;
the second support structure is further configured to limit radial movement of the magnet pieces when the magnet pieces are attached to the first support structure and the second support structure is attached to the first support structure.
Item 9. A rotor assembly according to any one of items 1-8.
(Item 10)
10. The rotor assembly of claim 9, wherein the second support structure further comprises a circular edge configured to engage an outermost edge of the magnet pieces to limit the radial movement of the magnet pieces.
(Item 11)
11. The rotor assembly of claim 9 or 10, wherein the first support structure is further configured to allow the magnet pieces to slide radially when the second support structure is detached from the first support structure.
(Item 12)
12. The rotor assembly of any one of claims 9-11, wherein the second support structure is further configured to be removable from the first support structure to allow the magnet pieces to be removed from the first support structure by sliding them radially.
(Item 13)
the at least one magnet comprises a magnet piece;
the first support structure further comprising a rib configured to limit angular movement of the magnet piece when the magnet piece is attached to the first support structure;
Item 13. The rotor assembly of any one of items 1-12.
(Item 14)
9. The rotor assembly of any one of claims 1-8, wherein the at least one magnet comprises a ring magnet configured to be mounted to the first support structure.
(Item 15)
mounting at least one magnet to a first support structure of a rotor assembly for an axial flux machine such that the first support structure provides a flux return path for the at least one magnet;
attaching the second support structure to the first support structure to allow torque to be transmitted between the at least one magnet and the second support structure via the first support structure;
wherein the first support structure mounts the at least one magnet to the first support structure, and the second support structure is further configured to (A) be attached to a rotatable shaft of the axial flux machine, or (B) function as an output or input flange of the axial flux machine.
(Item 16)
the second support structure is adapted to rotate about an axis of rotation of the axial magnetic machine;
the at least one magnet has a first surface, the first surface being perpendicular to a magnetization direction of the at least one magnet and facing away from the first support structure;
the first support structure, the second support structure, and the at least one magnet are constructed and arranged such that when the first support structure, the second support structure, and the at least one magnet are stationary with respect to the axis of rotation and unaffected by any other magnetic components, a distance between a first plane and a second plane is substantially greater than zero, the first plane intersecting a first point on the first surface, the axis of rotation being normal to the first plane, the second plane intersecting a second point on the first surface, and the axis of rotation being normal to the second plane;
the second point is at a greater radial distance from the axis of rotation than the first point;
the first support structure, the second support structure, and the at least one magnet are further configured and arranged such that when the first support structure, the second support structure, and the at least one magnet are stationary relative to the axis of rotation and unaffected by any other magnetic components, a half-line intersects the first plane, the half-line extending away from the first surface at the second point and being normal to the first surface;
Item 16. The method according to item 15.
(Item 17)
the at least one magnet has an inner edge disposed at the first point;
the at least one magnet has an outer edge disposed at the second point, the outer edge being opposite the inner edge;
the first support structure, the second support structure, and the at least one magnet are further configured and arranged such that when the first support structure, the second support structure, and the at least one magnet are stationary relative to the axis of rotation and unaffected by any other magnetic components, a ratio of a distance between the first plane and the second plane to a distance between the first point and the second point is greater than 0.002;
Item 17. The method according to item 16.
(Item 18)
the first support structure is made from at least one first material;
the second support structure is made from at least one second material different from the at least one first material;
18. The method according to any one of items 15 to 17.
(Item 19)
the at least one magnet comprises a magnet piece;
and mounting the second support structure to the first support structure further comprises mounting the second support structure to the first support structure such that the second support structure limits radial movement of the magnet pieces.
19. The method according to any one of items 15 to 18.
(Item 20)
20. The method of claim 19, further comprising detaching the second support structure from the first support structure to allow the magnet pieces to be removed from the first support structure by sliding them radially.

BRIEF DESCRIPTION OF THE DRAWINGS
FIG. 1 shows a cross-sectional view of an exemplary axial flux air gap machine overview with a printed circuit board stator.

FIG. 2 shows the tendency of air gaps in an axial flux motor to collapse due to deformation of the rotor support, potentially causing interference with the stator.

FIG. 3A shows a cross-sectional view of an exemplary rotor support including a tapered portion.

FIG. 3B shows a cross-sectional view of the exemplary rotor support shown in FIG. 3A with a ring magnet attached thereto.

FIG. 4 shows how two rotor assemblies such as those shown in FIG. 3B can be arranged in an axial flux machine so that the equilibrium positions of the rotors are equidistant from the gap centerline.

FIG. 5 shows an exemplary magnet piece that may be used for a rotor assembly having a radius of, for example, greater than about 4 centimeters.

FIG. 6A illustrates an example of a first support structure (i.e., "rotor backing") for a rotor portion (e.g., rotor half) configured in accordance with some embodiments of the present disclosure.

FIG. 6B shows the first support structure shown in FIG. 6A with a set of magnet strips 502 disposed thereon.

FIG. 7 illustrates an example of a second support structure (or "rotor support plate") configured in accordance with some embodiments of the present disclosure.

FIG. 8A shows an example rotor assembly including a first support structure such as that shown in FIG. 6B and a second support structure such as that shown in FIG. 7, with magnet pieces disposed on the first support structure, prior to application of final torque to the assembly screws.

FIG. 8B shows the rotor assembly of FIG. 8A when the screws are tightened to design torque.

FIG. 9 shows the same rotor assembly shown in FIG. 8B, except that the degree of taper is exaggerated for illustrative purposes.

FIG. 10 shows a side view of a pair of pre-recurved rotor assemblies such as those shown in FIG. 9, illustrating how the rotor assemblies can bend into a desired configuration when they are assembled into an axial flux machine.

FIG. 11A shows how two rotor assemblies such as those shown in FIG. 8B can be arranged in an axial flux machine in which the printed circuit board stator is positioned in a substantially uniform gap between the faces of the magnet pieces.

FIG. 11B shows a cross-sectional view of the assembly shown in FIG. 11A.

FIG. 12A shows how two rotor assemblies such as those shown in FIG. 8B can be arranged in an axial flux machine with a shaftless configuration.

FIG. 12B shows a cross-sectional view of the assembly of FIG. 12A.

FIG. 13 shows a cross section of an exemplary axial flux machine in an in and out runner configuration in which the second support structure fits on the outside of the stator and the stator is constructed such that it is mounted to the housing at its inner diameter.

FIG. 14 shows a cross-sectional view of an exemplary axial flux machine with a single-sided rotor.

Detailed Description
This application incorporates by reference, for all purposes, the following patent applications: U.S. Provisional Patent Application No. 17/086,549, entitled "IMPROVED ROTOR ASSEMBLIES FOR AXIAL FLUX MACHINES," filed November 2, 2020; U.S. Provisional Patent Application No. 62/934,059, entitled "IMPROVED ROTOR ASSEMBLIES FOR AXIAL FLUX MACHINES," filed November 12, 2019; and U.S. Provisional Patent Application No. 62/934,059, entitled "IMPROVED ROTOR ASSEMBLIES FOR AXIAL FLUX MACHINES," filed May 18, 2018, published as U.S. Patent Application Publication No. 2018/0351441. The entire contents of U.S. patent application Ser. No. 15/983,985, entitled "MAGNET-STATOR GAP IN AXIAL FLUX MACHINES," U.S. Provisional Patent Application Ser. No. 62/515,251, filed June 5, 2017, entitled "PRE-WARPED ROTORS FOR CONTROL OF MAGNET-STATOR GAP IN AXIAL FLUX MACHINES," and U.S. Provisional Patent Application Ser. No. 62/515,256, filed June 5, 2017, entitled "AIR CIRCULATION IN AXIAL FLUX MACHINES," are each incorporated by reference. This application also incorporates by reference for all purposes the entire contents of each of the following issued patents: U.S. Pat. No. 7,109,625, U.S. Pat. No. 9,673,688, U.S. Pat. No. 9,800,109, U.S. Pat. No. 9,673,684, and U.S. Pat. No. 10,170,953.

Permanent magnet axial flux motors and generators, such as those described in the patent documents referenced above, may feature a planar printed circuit board (PCB) stator assembly positioned between two rotor sections with permanent magnets, or one rotor section with one or more permanent magnets, and a moving or stationary flux return yoke (effectively presenting alternating north-south poles to the PCB stator). The interaction of the current carried by the stator with the magnetic flux density established by the rotor generates torque in motor operation, or the application of torque to the rotor can induce current in the stator in generator operation.

When describing the geometry of an axial flux machine, the terms "axially," "radially," and "angularly" are commonly used to describe the orientation of various components and/or magnetic flux lines. As used herein, the terms "axial" and "axially" refer to directions parallel to the axis of rotation of the machine's rotor, the terms "radial" and "radially" refer to directions intersecting and perpendicular to the axis of rotation of the machine's rotor, and the terms "angular" and "angularly" refer to directions along the curve of a circle in a plane perpendicular to the machine's axis of rotation, the center of the circle being intersected by the axis of rotation.

For rotors below a certain size, it is practical to use a single piece of magnetic material (sometimes called a "ring magnet") that is magnetized with alternating poles. Such a ring magnet may be attached to a rotor support (sometimes called "back iron") that provides mechanical support for the magnet and connection to the machine's shaft.

The '441 publication describes a "pre-recurved" rotor component method in which the rotor support can be machined so that the stator-facing surfaces of the permanent magnets of the two individual rotor halves are "recurved" when the rotor halves are disconnected, but are "flattened" when the two rotor halves are assembled into a machine, so that magnetic forces attract the rotor halves to each other, distorting the structure and thus establishing a uniform gap between the facing surfaces of the permanent magnets. In all of the examples disclosed in that document, the integral support structure also serves to provide a flux return path.

For larger machines (especially those with radii greater than 8 centimeters), the use of ring magnets for magnet construction can be impractical. Individual, or segmented, magnets per pole can be produced and magnetized more easily and economically than solid magnets. Rotor supports for segmented magnets can also include recessed features, or "pockets," that position the individual magnets in an alternating pole pattern. These pockets can constrain the magnets radially and axially. Machining the pockets can involve extra machining effort compared to rotor supports for solid magnets with multiple poles. Additionally, because rotor supports typically provide a flux return path through a soft magnetic material (e.g., steel), the weight and inertia of larger rotors can be significant. Magnets can be difficult to precisely locate within the pockets, and once inserted, they can be difficult to remove. This makes it difficult to repair the rotor in the event of a failed or damaged magnet and can potentially limit the recovery and reuse of magnetic material when the machine is taken out of service.

A rotor design is provided in which rotor support for a portion of the rotor (e.g., half of the rotor) may be made from multiple components, including at least a first support structure and a second support structure. In some implementations, segmented magnets may be disposed on the first support structure. The first support structure may be made from a first material (e.g., steel), for example, that provides a flux return path for the rotor portion. This first support structure may be supported via a second support structure and connected to the shaft of the axial flux machine. In some implementations, the second support structure is made from a second material different from the first material. The first material may be selected for its magnetic properties. The second material may, on the other hand, be selected for its stiffness, tensile strength, low weight, and/or manufacturability.

In some implementations, a first support structure may position the magnets angularly and axially, while a second support structure may position the magnets radially. Further, in some implementations, the first support structure may be supported by a second support structure in a manner that allows the first support structure to be separated from the second support structure. In some such implementations, when the first support structure is separated from the second support structure, individual magnet pieces may be removed and replaced radially.

The designs described herein may be particularly advantageous for larger machines using segmented magnets (e.g., those with radii greater than 8 centimeters). However, the principles described herein may also be applicable to smaller machines using either segmented magnets or ring magnets. The designs may be applied to any type of axial flux machine, including axial flux machines employing not only conventional stator structures (e.g., copper wire windings forming the poles), but also PCB-based stator structures such as those described in the patent documents cited above.

The function of the rotor in an axial flux machine generally involves positioning the magnets to provide a flux return path and maintaining the gap in a prescribed design geometry.

Magnetic location may involve angularly constraining the magnets so that they form a series of alternating poles, which interact with the stator current density to result in the net production of torque. Additionally, the magnets are typically mechanically connected to the shaft so that they can transmit torque to the shaft for useful mechanical output. The magnets may also be radially constrained to maintain pole geometry. When a solid ring magnet is employed, radial and angular constraints may be achieved by the integrity of the ring. However, these constraints must be explicitly considered when the rotor is comprised of segmented magnets.

The rotor flux return function preferably completes the magnetic circuit between the poles without allowing significant amounts of magnetic flux to "leak" outside the intended gap. Rotor flux outside the intended gap does not contribute to torque production/current generation and can induce and interact with currents in conductive materials that increase drag. The flux return function is generally achieved using soft magnetic materials such as steel.

Maintaining the axial location of the magnets, i.e., the gap between the magnet faces, can be critical in many applications. When assembled on a shaft, attractive forces between rotor sections (e.g., rotor halves) tend to collapse the gap between the rotor sections where the stator is installed. Maintaining this gap at the design value can be important to motor/generator performance, and excessive reduction in gap size can result in mechanical interference between the rotor sections and the stator.

An attractive solution is to construct the rotor section as an assembly of components, using materials optimized for the required functionality. In some implementations, one or more magnet pieces may be angularly oriented on a first support structure made of a soft magnetic material (e.g., steel). The first support structure may have, for example, a disk shape. In some implementations, the first support structure may be machined from a single piece of stock material. In other implementations, the first support structure may be assembled from multiple individually formed components. The first support structure (i.e., "back iron") may serve as a flux return or yoke for the magnet pieces. In some implementations, this piece can be fabricated very rapidly and accurately from flat sheet stock material, for example, by water jet, laser, or stamping processes. This is possible, in part, because relatively few features are required and little material needs to be removed. Minimizing the amount of soft magnetic material may avoid time- and energy-intensive machining processes. Minimizing soft magnetic material can be important in some situations because it can reduce the moment of inertia of the machine, reduce the overall mass of the machine, and/or reduce the time constant of the machine.

In some implementations, the functions of radially positioning the magnetic lobes, mechanically coupling the magnetic component to the shaft, and maintaining the gap may be accomplished using a second support structure. In some implementations, such a second support structure may be fabricated from a material (or materials) with a good strength/stiffness-to-weight ratio. Due to the absence of magnetic performance requirements, some relatively strong/rigid materials, such as magnesium alloys, carbon fiber composites, and aluminum, are candidates for this second component. Compared to traditional steel machining, these materials often tend to be easier to form and machine. Furthermore, in some implementations, such a second support structure may be configured to perform additional functions, such as directly integrating components that would otherwise be mounted on an external shaft. As discussed in more detail below in connection with FIGS. 12A, 12B, 13, and 14, such a configuration may facilitate the design of "shaftless" machines that can be more tightly integrated with various loads or torque sources.

The first and second support structures may be fastened together in any of several ways to form an integrated assembly. In some implementations, for example, the first and second support structures may be fastened together using pins, adhesives, and/or fastener placement. In some implementations, such a two-piece assembly may allow the magnet pieces to be easily manipulated and properly aligned with respect to the rotor portions (e.g., rotor halves) without a jig or other mechanism to align and lower the magnet pieces into their respective pockets. Because the first support structure does not need to radially constrain the magnet pieces, it may be possible to insert the magnet pieces radially with less force than inserting the magnet pieces axially into the pockets before the first support structure is assembled to the second support structure. Thus, in some implementations, the first support structure may itself serve as a jig, not only to align and maintain gaps from adjacent magnet pieces, but also to deliver the pole sequence onto the shaft so that the rotor halves are aligned on the final assembly. Once the magnet pieces are assembled to the first support structure, the assembly including the first support structure and magnet pieces may be assembled to a second support structure, which may hold the magnet pieces radially.

In some implementations, as an additional feature of the multi-piece rotor assembly as described herein, a "pre-curve" may be incorporated into the second support structure, which may be easier to machine. Thus, the first support structure may be machined flat in some such implementations. When the first support structure is assembled to the second support structure, both pieces may be distorted. Overall, the assembly of the first and second support structures may approximate a frustum angled away from the gap as the radius increases. When two such rotor sections are assembled to form a gap within the rotor, magnetic forces may further distort the assembly so that the gap is substantially uniform.

Examples of advantages that may be realized using some implementations of the above approaches and techniques include:
1. Significant cost savings in machining operations on multi-piece designs based on the types of operations, materials, and clearances required to produce the correct geometry.
2. Greatly simplified jigless assembly of magnets to rotor back iron.
3. Minimization of soft magnetic material mass.
4. Applicability to magnet strip and ring magnet rotor types.
5. Easier recovery of magnetic material, i.e. radial removal.

Figure 1 shows a cross-sectional view of the overall concept of an exemplary axial flux air-gap machine 100. As shown, the machine 100 may include a printed circuit board (PCB) stator 102 and a rotor including a pair of rotor sections 104a, 104b mechanically coupled to a shaft 108. As shown, the rotor sections 104a, 104b may include rotor supports 112a, 112b, respectively, with individual ring magnets 110a, 110b attached to the rotor supports 112a, 112b. In this case, each of the rotor sections 104a-b (except for the ring magnets 110a-b) is of unitary conventional construction, requiring that the material selected for the rotor support 112 provide good stiffness, strength, and magnetic properties.

Figure 2 shows the tendency of the air gap 106 in an axial flux machine 200 similar to the axial flux machine 100 shown in Figure 1 to collapse due to deformation of the rotor supports 112a-b, potentially causing interference between the ring magnets 110a, 110b and the stator 102. While the illustration is exaggerated, any rotor support 112 machined to the intended balanced geometry will experience some distortion.

Figure 3A shows a cross-sectional view of an example rotor support 302 that includes a tapered surface 304. Figure 3B shows a rotor portion 300 (e.g., half of a rotor) that includes both the rotor support 302 and a ring magnet 110 attached to the tapered surface 304. In some implementations, the rotor support 302 may be configured such that its outer edge 306 deforms relative to the gap centerline to the intended balanced rotor position when assembled as shown in Figure 4.

Figure 4 illustrates how two rotor sections (e.g., rotor halves), such as rotor section 300 shown in Figure 3B, can be disposed within an axial flux machine 400 such that the rotor's balance position is equidistant from the centerline 402 of the gap 106 between the rotor sections. As shown, the backs 404a, 404b of rotor supports 302a, 302b are distorted compared to Figure 3B due to the attractive forces between ring magnets 110a, 110b. Additionally, as also shown, when the rotor sections are disposed within the machine 400, the outer edges 306a, 306b of ring magnets 110a, 110b deform to the intended balance rotor position relative to the centerline 402 of the gap 106.

5 shows a typical magnet piece 502 that may be used for a rotor assembly having a radius of, for example, greater than about 4 centimeters. The magnet piece 502 may have several radius and dimensional tolerance parameters that may make it difficult to machine a pocket that constrains the piece 502 in a plane. As shown, the magnet 502 may have an inner edge 504 and an outer edge 506, with the inner edge 504 having a width _W1 that is shorter than the width _W2 of the outer edge 506.

Figure 6A shows an example of a first support structure 602 (i.e., "rotor back iron") of a rotor portion (e.g., rotor half) configured in accordance with some embodiments of the present disclosure. As shown, in some implementations, the first support structure 602 may have an annular shape with a central opening 608 and may include ribs 604 disposed thereon to receive a magnet piece, such as magnet piece 502 shown in Figure 5. Additionally, in some implementations, the first support structure 602 may include one or more pin and/or screw fastener holes 606 that can be used to secure the first support structure 602 to a second support structure 702, such as that shown in Figure 7. In some implementations, the first support structure 602 may be fabricated from steel.

6B shows what the first support structure 602 may look like when the set of magnet pieces 502 is attached to the first support structure 602, for example, by sliding the magnet pieces 502 between the alignment ribs 604 (but before the first support structure 602 is attached to the second support structure 702, as described below). As shown, the inner edges 504 of the magnet pieces 502 may be positioned a first radial distance _R1 from the center point 610 of the openings 608 in the first support structure 602, and the outer edges 506 of the magnet pieces 502 may be positioned a second radial distance _R2 from the center point 610 of the openings 608 in the first support structure 602.

FIG. 7 shows an example of a second support structure 702 (i.e., a “rotor support plate”) configured according to some embodiments of the present disclosure. As shown, in some implementations, the second support structure 702 may be configured to radially constrain the magnet pieces 502 at a second radial distance _R2 (e.g., via a circular edge 704) and/or to position the first support structure 602 on the shaft 108 (e.g., as shown in FIGS. 11A and 11B ) to feature a tapered surface region 706 that determines how the rotor portions (e.g., rotor halves) deform upon assembly. In some implementations, the second support structure 702 may be fabricated using a lathe and/or rolling-type operation. The second support structure 702 may be fabricated from a magnesium alloy, a carbon fiber composite, or aluminum in some implementations.

8A shows an example rotor assembly 800 including a first support structure 602, such as that shown in FIG. 6B, and a second support structure 702, such as that shown in FIG. 7, with magnet pieces disposed on the first support structure 602, prior to application of final torque to the assembly screws 802. In some implementations, the configuration shown in FIG. 8A may be achieved, for example, by first positioning the magnet pieces 502 between the alignment ribs 604 of the first support structure 602, and then positioning the first support 602 within the circular edge 704 of the second support structure 702. As FIG. 8A illustrates, a gap 804 exists between the first support structure 602 and the second support structure 702 before the screws 802 are tightened.

FIG. 8B shows the rotor assembly 800 of FIG. 8A when the screw 802 is tightened to design torque. As shown, tightening the screw 802 can cause the first support structure 602 to conform to the second support structure 702, thereby transmitting a taper 808 corresponding to the tapered surface 706 (shown in FIG. 7) to the first support structure 602 and, consequently, to the face 810 of the magnet piece 502.

Figure 9 shows the same rotor assembly 800 shown in Figure 8B, except that the extent of the tapered portion 808 has been exaggerated for illustrative purposes. As shown in Figure 9, the magnet piece 502 (or alternatively, the ring magnet 110) may be attached to a surface of the first support structure 602 facing away from the second support structure 702 such that the face 810 of the magnet piece 502 (or the annular face of the ring magnet 110) takes on the shape of the tapered portion 808.

9 , the degree of taper 808 of the tapered surface 706 of the second support structure 702 may be measured by identifying two points 902, 904 on the surface of the second support structure 702 that contact the first support structure 602 and determining the distance _D1 between two planes 906, 908, where the axis of rotation 930 of the rotor assembly 800 is normal to the two planes 906, 908 and the two planes 906, 908 intersect the first point 902 and the second point 904, respectively. In some implementations, the two contact points 902, 904 may be found to be aligned or otherwise aligned with the inner and outer radii _R1 and _R2 of the magnet pieces 502 such that the distance _D1 therebetween is substantially greater than zero. The term “substantially” in this context is intended to exclude slight variations due to processing and/or material imperfections within acceptable tolerances. In some implementations, distance _D1 may be, for example, greater than 0.003 inches, or greater than 0.01 inches, or even greater than 0.02 inches. Additionally or alternatively, in some embodiments, the two contact points 902, 904 may be found such that the ratio of distance _D1 to the distance between the two points and/or the difference between the inner and outer diameters _R1 and _R2 of the corresponding magnet pieces 502 is substantially greater than zero. In some implementations, such a ratio may be, for example, greater than 0.002, or greater than 0.005, or even greater than 0.01.

9 , in some implementations, at least one point 910 can be found on the surface of the second support structure 702 that contacts the first support structure 602, with respect to which a half line ₉₁₂ forms an angle α1 substantially less than 90 degrees with a plane, the half line 912 extending away from the surface (such that the half line 912 is aligned with the magnet's magnetization direction) being normal to the surface, and the rotation axis 930 being normal to the plane. In some implementations, the angle _α1 may be, for example, less than 89.9 degrees, less than 89.7 degrees, or even less than 89.5 degrees. The point 910 may be aligned, for example, with the inner radius _R1 of the magnet piece 502, the outer radius _R2 of the magnet piece 502, or some point between those two radii.

Additionally or alternatively, and as shown in FIG. 9 , the degree of taper 808 transferred to face 810 of magnet piece 502 (or face of ring magnet 110) when first support structure 602 is attached to second support structure 702 may be measured by identifying two points 914, 916 on the surface of magnet piece 502 (or ring magnet 110) (e.g., face 810 of magnet piece 502 shown in FIG. 9 ) that are orthogonal to the direction of magnetization of magnet piece 502 (or ring magnet 110), and determining the distance _D2 between two planes 926, 928, where an axis of rotation 930 is normal to the two planes 926, 928, and where the two planes 926, 928 intersect the first point 914 and the second point 916, respectively. In the example shown, the opposing surface of the magnet piece 502 that contacts the first support structure 602 is also orthogonal to the magnetization direction of the magnet piece 502. In some embodiments, two magnet surface points 914, 916 can be found (at the inner and outer radii _R1 and _R2 of the magnet piece 502 or elsewhere) for which the distance _D2 is substantially greater than zero. In some implementations, the distance _D2 may be greater than 0.002 inches, or greater than 0.005 inches, or even greater than 0.01 inches, for example. Additionally or alternatively, in some embodiments, the two magnet surface points 914, 916 can be found such that the ratio of the distance _D2 to the distance between the two points and/or the difference between the inner and outer radii _R1 and _R2 of the magnet piece 502 is substantially greater than zero. In some implementations, such a ratio may be greater than 0.002, or greater than 0.005, or even greater than 0.01, for example.

Also, as illustrated in FIG. 9 , in some implementations, at least one point 922 may be found on the surface of the magnet piece 502 (or ring magnet 11) that is orthogonal to the direction of magnetization of the magnet piece 502 (or ring magnet 11) and faces away from the first support structure 602 (e.g., face 810 of the magnet piece 502 shown in FIG. 9 ), for which a half-line 924 forms an angle _α2 substantially less than 90 degrees with a plane, the half-line 924 extending away from the surface of the magnet (such that the half-line 924 is aligned with the magnetization direction of the magnet piece 502) and is normal to the surface, and the axis of rotation 930 is normal to the surface. In some implementations, the angle _α2 may be less than 89.9 degrees, less than 89.7 degrees, or even less than 89.5 degrees, for example. Point 922 may be located, for example, at inner radius R ₁ of magnet piece 502, outer radius R ₂ of magnet piece 502, or some point between those two radii. Further, as shown in FIG. 9 , first support structure 602, second support structure 702, and magnet piece 502 may be configured and arranged such that half line 924 (which is normal to and extends away from surface 810 of magnet piece 502 facing away from first support structure 602) intersects plane 926.

As illustrated in Figure 10, when two rotor assemblies 800a, 800b are attached to shaft 108 (not shown in Figure 10) or otherwise disposed in an axial flux machine, the magnetic flux of magnet pieces 502a, 502b may generate an attractive force in gap 1002 between magnet pieces 502a, 502b, which causes rotor assemblies 800a, 800b to recurve such that the ends of rotor assemblies 800a, 800b move toward each other. The dashed lines in Figure 10 illustrate how rotor assemblies 800a, 800b may be shaped after they are assembled into a motor or generator such as those described below in connection with Figures 11A-B, 12A-B, 13, and 14. In some implementations, the rotor assemblies 800 a, 800 b may be pre-recurved prior to assembly so that the surfaces of the two magnet pieces 502 a, 502 b facing each other are substantially parallel in the assembled motor or generator, thus making the width of the gap 1002 substantially uniform throughout. In other implementations, the rotor assemblies 800 a, 800 b may be slightly “over-recurved” once assembled so that an increasing taper is obtained as a function of radius. While this may have the undesirable effect of reducing the gap at larger radii, it may allow the use of a smaller average gap width G, thus increasing the average magnetic field strength, and may preserve the gap at the outer radius _R2 of the magnet pieces 502 a, 502 b.

10 , the amount of recurvation that rotor assembly 800b undergoes upon assembly may be measured, for example, by identifying point 1004 located on outer diameter _R2 of magnet piece 502b and determining the distance _D3 that the point moves in a direction that is aligned with axis of rotation 930 upon assembly. Distance _D3 may be measured, for example, by identifying a plane that intersects point 1004 and to which axis of rotation 930 is normal, and determining the distance that plane moves relative to another plane that intersects point 1006 at or near the center of rotor element assembly 800b and to which axis of rotation 930 is also normal. In some implementations, distance _D3 may be greater than 0.001 inch, or greater than 0.005 inch, or even greater than 0.01 inch. Additionally or alternatively, in some implementations, the ratio of distance _D3 to the average width G of gap 1002 may be greater than 0.01, or greater than 0.05, or even greater than 0.1. Additionally or alternatively, the ratio of distance _D3 to the average gap distance between magnet pieces 502b and the surface of stator 102 (not shown in FIG. 10 ) may be greater than 0.25, or greater than 0.5, or even greater than 1. Thus, in some implementations, rotor assembly 800b may distort much more than the average magnet/stator gap distance.

9 in conjunction with FIG. 10, it should be understood that in some embodiments, rotor assemblies 800a, 800b are constructed and arranged such that when rotor assemblies 800a, 800b are disposed and distorted in a motor or generator as illustrated in FIG. 10, one or more of the following values for each rotor assembly may be reduced by 50 percent or more: (1) the distance _D1 between plane 906 and plane 908; (2) the distance between point 902 and point 904 and/or the ratio of distance _D1 to the difference between inner radius _R1 and outer radius _R2 of magnet piece 502; (3) the distance _D2 between plane 926 and plane 928; and (4) the distance between point 914 and point 916 and/or the ratio of distance _D2 to the difference between inner radius _R1 and outer radius _R2 of magnet piece 502.

11A illustrates how two rotor assemblies, such as the rotor assembly 800 shown in FIG. 8B, can be arranged in an axial flux machine 1100 in which the stator 102 (e.g., a PCB-based stator) is positioned within a substantially uniform gap between the faces of the magnet pieces 502. FIG. 11B illustrates a cross-sectional view of the axial flux machine 1100 shown in FIG. 11A. The "uniform gap" configuration illustrated in FIGS. 11A and 11B can arise because, upon arrangement, attractive forces between the opposing magnet pieces 502 of the two rotor assemblies 800 can distort the rotor assembly 800 such that the first support structure 602 assumes its original nominally flat shape (e.g., as shown in FIG. 6A). Thus, the resulting gap between the faces of the magnet pieces 502 can be substantially uniform as a function of radius.

12A illustrates how two rotor assemblies, such as rotor assembly 800 shown in FIG. 8B, may be arranged in an axial flux machine 1200 with a shaftless configuration. FIG. 12B illustrates a cross-sectional view of the axial flux machine 1200 shown in FIG. 12A. As shown, in some implementations, the axial flux machine 1200 may include a second support structure 1202 that is at least partially exposed to an environment external to the housing 1206, thus allowing the second support structure 1202 to also serve as a mechanical connection for the machine 1200. External components may, for example, be directly mounted to or otherwise mechanically engaged with the exposed portion 1204 of the second support structure 1202. In some implementations, the configuration of the first support structure 602 in the axial flux machine 1200 may be the same as or similar to the first support structure 602 in the axial flux machine 1100 described above in connection with Figures 11A and 11B.

13 illustrates an example of a "shaftless" axial flux machine 1300 in an "outrunner" configuration. As shown, in such a configuration, the stator 102 is fixedly coupled to a housing 1306 at its inner diameter, and two second support structures 1302a, 1302b may be fixedly coupled to each other (e.g., via one or more connectors 1304) on the outside of the stator 102 and may each be rotatable relative to the housing 1306. In some implementations, the configuration of the first support structure 602 in the axial flux machine 1300 may be the same as or similar to the first support structure 602 in the axial flux machine 1100 described above in connection with FIGS. 11A and 11B.

FIG. 14 shows an example of a "shaftless" axial flux machine 1400 with a single-sided rotor. In such a configuration, one of the two rotor halves may be replaced with magnetic material 1402 that provides a flux return path and is fixed to a housing 1404. As shown, the stator 102 may be installed between the fixed magnetic material 1402 and the magnet pieces 502 of a single rotor assembly, which includes a first support structure 602 (to which the magnet pieces 502 may be mounted) and a second support structure 1406 (which may provide a mechanical connection between the magnetic elements and one or more components external to the machine 1400). In some implementations, the configuration of the first support structure 602 in the axial flux machine 1400 may be the same as or similar to the first support structure 602 in the axial flux machine 1100 described above in connection with FIGS. 11A and 11B.

Examples of inventive concepts/features/techniques
The following paragraphs describe examples of novel concepts, features, and/or techniques disclosed herein.

(A1) A rotor for an axial flux motor or generator, the rotor comprising at least one magnet disposed on a first support structure made from at least one first material, the first support structure providing a flux return path for the at least one magnet and connected to a shaft via a second support structure made from at least one second material.

(A2) The rotor described in paragraph (A1), wherein the at least one magnet includes a magnet segment, and the first support structure provides radial alignment of the magnet segment.

(A3) A rotor as described in paragraph (A1) or paragraph (A2), wherein the at least one magnet includes a magnet piece, and the first support structure is configured to be removable from the second support structure to allow the magnet piece to be removed by sliding it radially.

(A4) A rotor described in any one of paragraphs (A1)-(A3), wherein the at least one magnet includes a magnet piece, and the first support structure includes a rib that provides angular alignment of the magnet piece.

(A5) A rotor described in any one of paragraphs (A1) to (A4), wherein the second support structure is configured such that an assembly including the first support structure and the at least one magnet is pre-curved when the assembly is attached to the second support structure.

(A6) A rotor described in any one of paragraphs (A1)-(A5), wherein a pre-curved feature is incorporated into the first support structure.

(A7) A rotor described in any one of paragraphs (A1) to (A6), wherein the first support structure is in the shape of a disk.

(A8) A rotor described in any one of paragraphs (A1)-(A7), wherein the first support structure includes multiple parts assembled to form a disk shape.

(A9) A rotor described in any one of paragraphs (A1)-(A8), wherein the second support structure is configured to function as an output or input flange of the motor or the generator.

(B1) A rotor for an axial flux motor or generator, the rotor comprising a ring magnet disposed on a first support structure made from at least one first material, the first support structure providing a flux return path for the ring magnet and connected to a shaft via a second support structure made from at least one second material.

(B2) The rotor described in paragraph (B1), wherein the second support structure is configured such that when an assembly including the first support structure and the ring magnet is attached to the second support structure, the assembly is pre-curved.

(B3) A rotor described in paragraph (B1) or paragraph (B2), wherein a pre-curved portion is incorporated into the first support structure.

(B4) A rotor described in any one of paragraphs (B1) to (B3), wherein the first support structure is in the shape of a disk.

(B5) A rotor described in any one of paragraphs (B1) to (B4), wherein the first support structure includes multiple parts assembled to form a disk shape.

(B6) A rotor described in any one of paragraphs (B1) to (B5), wherein the second support structure is configured to function as an output or input flange of the motor or the generator.

(C1) A rotor for an axial flux motor or generator, the rotor comprising at least one magnet disposed on a first support structure made from at least one first material, the first support structure providing a magnetic flux return path for the at least one magnet, and attached to a second support structure made from at least one second material, the second support structure configured to provide torque to a mechanical load or receive torque from a mechanical driver.

(C2) The rotor described in paragraph (C1), wherein the at least one magnet includes a magnet segment, and the first support structure provides radial alignment of the magnet segment.

(C3) A rotor as described in paragraph (C1) or paragraph (C2), wherein the at least one magnet includes a magnet piece, and the first support structure is configured to be removable from the second support structure to allow the magnet piece to be removed by sliding it radially.

(C4) A rotor described in any one of paragraphs (C1)-(C3), wherein the at least one magnet includes a magnet piece, and the first support structure includes a rib that provides angular alignment of the magnet piece.

(C5) A rotor described in any one of paragraphs (C1) to (C4), wherein the second support structure is configured such that an assembly including the first support structure and the at least one magnet is pre-curved when the assembly is attached to the second support structure.

(C6) A rotor described in any one of paragraphs (C1)-(C5), wherein a pre-curved feature is incorporated into the first support structure.

(C7) A rotor described in any one of paragraphs (C1) to (C6), wherein the first support structure is in the shape of a disk.

(C8) A rotor described in any one of paragraphs (C1) to (C7), wherein the first support structure includes multiple parts assembled to form a disk shape.

(C9) A rotor described in any one of paragraphs (C1)-(C8), wherein the second support structure is configured to function as an output or input flange for the motor or the generator.

(D1) A rotor for an axial flux motor or generator, the rotor comprising a ring magnet disposed on a first support structure made from at least one first material, the first support structure providing a flux return path for the ring magnet, and attached to a second support structure made from at least one second material, the second support structure configured to provide torque to a mechanical load or receive torque from a mechanical driver.

(D2) The rotor described in paragraph (D1), wherein the second support structure is configured such that when an assembly including the first support structure and the ring magnet is attached to the second support structure, the assembly is pre-curved.

(D3) A rotor described in paragraph (D1) or paragraph (D2), wherein a pre-curved portion is incorporated into the first support structure.

(D4) A rotor described in any one of paragraphs (D1)-(D3), wherein the first support structure is in the shape of a disk.

(D5) A rotor described in any one of paragraphs (D1)-D4), wherein the first support structure includes multiple parts assembled to form a disk shape.

(D6) A rotor described in any one of paragraphs (D1)-(D5), wherein the second support structure is configured to function as an output or input flange of the motor or the generator.

(E1) A rotor assembly for an axial flux machine, comprising: at least one magnet; a first support structure configured to mount the at least one magnet to the first support structure and to provide a flux return path for the at least one magnet; and a second support structure configured to be attached to the first support structure to enable torque to be transferred between the at least one magnet and the second support structure via the first support structure, wherein the second support structure is further configured to (A) be attached to a rotatable shaft of the axial flux machine or (B) function as an output or input flange of the axial flux machine.

(E2) The rotor assembly described in paragraph (E1), wherein the second support structure is configured to be attached to a rotatable shaft of the axial flux machine.

(E3) The rotor assembly described in paragraph (E1), wherein the second support structure is configured to function as an output or input flange for the axial flux machine.

(E4) A rotor assembly described in any one of paragraphs (E1) to (E3), wherein the first support structure is made from at least one first material and the second support structure is made from at least one second material different from the at least one first material.

(E5) A rotor assembly described in any one of paragraphs (E1) to (E4), wherein the at least one magnet comprises a magnet piece, and the second support structure is further configured to limit radial movement of the magnet piece when the magnet piece is attached to the first support structure and the second support structure is attached to the first support structure.

(E6) A rotor assembly as described in paragraph (E5), wherein the second support structure further comprises a circular edge configured to engage the outermost edges of the magnet pieces to limit radial movement of the magnet pieces.

(E7) A rotor assembly as described in paragraph (E5) or paragraph (E6), wherein the first support structure is further configured to allow the magnet pieces to slide radially when the second support structure is removed from the first support structure.

(E8) A rotor assembly described in any one of paragraphs (E5)-(E7), wherein the second support structure is further configured to be removable from the first support structure to allow the magnet pieces to be removed from the first support structure by sliding them radially.

(E9) A rotor assembly described in any one of paragraphs (E1) to (E8), wherein the at least one magnet comprises a magnet segment, and the first support structure further comprises a rib configured to limit angular movement of the magnet segment when the magnet segment is attached to the first support structure.

(E10) A rotor assembly described in any one of paragraphs (E1) to (E9), wherein the second support structure further comprises at least one surface, the at least one surface being radially tapered to cause the first support structure to recurve to conform to the shape of the at least one surface when the second support structure is attached to the first support structure.

(E11) A rotor assembly described in any one of paragraphs (E1)-(E4), (E9)-(E10), wherein the at least one magnet comprises a ring magnet configured to be attached to the first support structure.

(E12) The second support structure is adapted to rotate about a rotation axis of the axial magnetic machine, and the at least one magnet has a first surface that is perpendicular to the magnetization direction of the at least one magnet and faces away from the first support structure, and the first support structure, the second support structure, and the at least one magnet are configured and arranged such that when the first support structure, the second support structure, and the at least one magnet are stationary with respect to the rotation axis and are not influenced by any other magnetic components, the distance between a first plane and a second plane is substantially greater than zero, and the first plane intersects a first point on the first surface, and the rotation axis is normal to the first plane. The rotor assembly of any one of paragraphs (E1)-(E11), wherein the second plane intersects a second point on the first surface, the axis of rotation is normal to the second plane, the second point is at a greater radial distance from the axis of rotation than the first point, and the first support structure, the second support structure, and the at least one magnet are further configured and arranged such that when the first support structure, the second support structure, and the at least one magnet are stationary with respect to the axis of rotation and are not influenced by any other magnetic components, a half-line intersects the first plane, the half-line extending away from the first surface at the second point and being normal to the first surface.

(E13) The rotor assembly of paragraph (E12), wherein the at least one magnet has an inner edge positioned at the first point, the at least one magnet has an outer edge positioned at the second point, the outer edge being opposite the inner edge, and the first support structure, the second support structure, and the at least one magnet are further configured and arranged such that, when the first support structure, the second support structure, and the at least one magnet are stationary with respect to the axis of rotation and unaffected by any other magnetic components, the ratio of the distance between the first plane and the second plane to the distance between the first point and the second point is greater than 0.002.

(E14) A rotor assembly according to any one of paragraphs (E1) to (E13), wherein the rotor assembly is disposed in an axial flux machine, and the distance between the first plane and the second plane is substantially equal to zero.

(F1) A method comprising: mounting at least one magnet to a first support structure of a rotor assembly for an axial flux machine such that the first support structure provides a flux return path for the at least one magnet; and mounting the second support structure to the first support structure to enable torque to be transferred between the at least one magnet and a second support structure via the first support structure, wherein the first support structure mounts the at least one magnet to the first support structure, and the second support structure is further configured to (A) be attached to a rotatable shaft of the axial flux machine or (B) function as an output or input flange of the axial flux machine.

(F2) The method of paragraph (F1), wherein the second support structure is configured to be attached to a rotatable shaft of the axial flux machine.

(F3) The method of paragraph (F1), wherein the second support structure is configured to function as an output or input flange for the axial flux machine.

(F4) The method of any one of paragraphs (F1)-(F3), wherein the first support structure is made from at least one first material and the second support structure is made from at least one second material different from the at least one first material.

(F5) The method of any one of paragraphs (F1)-(F4), wherein the at least one magnet comprises a magnet segment, and mounting the second support structure to the first support structure further comprises mounting the second support structure to the first support structure such that the second support structure limits radial movement of the magnet segment.

(F6) The method of paragraph (F5), further comprising detaching the second support structure from the first support structure to allow the magnet pieces to be removed from the first support structure by sliding them radially.

(F7) The method of any one of paragraphs (F1)-(F6), wherein the second support structure further comprises at least one radially tapered surface, and wherein attaching the second support structure to the first support structure further comprises attaching the second support structure to the first support structure so as to recurve the first support structure to conform to the shape of the at least one surface.

(F8) The second support structure is adapted to rotate about the rotation axis of the axial magnetic machine, and the at least one magnet has a first surface, the first surface being perpendicular to the magnetization direction of the at least one magnet and facing away from the first support structure, and the first support structure, the second support structure, and the at least one magnet are configured and arranged such that when the first support structure, the second support structure, and the at least one magnet are stationary with respect to the rotation axis and are not influenced by any other magnetic components, the distance between a first plane and a second plane is substantially greater than zero, the first plane intersects a first point on the first surface, and the rotation axis is perpendicular to the first plane. The method of any one of paragraphs (F1)-(F7), wherein the axis of rotation is normal to the second plane, the second point intersects a second point on the first surface, the axis of rotation is normal to the second plane, the second point is at a greater radial distance from the axis of rotation than the first point, the first support structure, the second support structure, and the at least one magnet are further configured and arranged such that when the first support structure, the second support structure, and the at least one magnet are stationary relative to the axis of rotation and are not influenced by any other magnetic components, a half-line intersects the first plane, the half-line extending away from the first surface at the second point and is normal to the first surface.

(F9) The method of paragraph (F8), wherein the at least one magnet has an inner edge located at the first point, the at least one magnet has an outer edge located at the second point, the outer edge being opposite the inner edge, and the first support structure, the second support structure, and the at least one magnet are further configured and arranged such that when the first support structure, the second support structure, and the at least one magnet are stationary with respect to the axis of rotation and unaffected by any other magnetic components, the ratio of the distance between the first plane and the second plane to the distance between the first point and the second point is greater than 0.002.

(F10) The method of any one of paragraphs (F1)-(F9), further comprising disposing the rotor assembly within the axial flux machine so that the distance between the first plane and the second plane is substantially equal to zero.

While several aspects of at least one embodiment have been described above, it should be understood that various alterations, modifications, and improvements will readily occur to those skilled in the art. Such alterations, modifications, and improvements are intended to be part of this disclosure and are intended to be within the spirit and scope of this disclosure. Accordingly, the foregoing description and drawings are by way of example only.

Various aspects of the present disclosure may be used alone, in combination, or in various arrangements not specifically discussed in the embodiments described above, and therefore, this application is not limited to the details and arrangements of components set forth in the foregoing description or illustrated in the drawings. For example, aspects described in one embodiment may be combined in any manner with aspects described in other embodiments.

Also, the disclosed aspects may be embodied as a method, examples of which have been provided. The acts performed as part of the method may be ordered in any suitable manner. Thus, although shown as sequential acts in the illustrative embodiments, embodiments may be constructed in which the acts are performed in a different order than that shown, and may include performing some acts simultaneously.

The use of ordinal terms such as "first," "second," and "third" in the claims to modify claim elements does not by itself imply any priority, precedence, or order of one claim element over another or the chronological order in which the actions of the method are performed, but is used merely as a label to distinguish one claim element having a certain name from another claim element having the same name (except for the use of ordinal terms).

Also, the phraseology and terminology used herein is for purposes of description and should not be regarded as limiting. The use of "including," "comprising," "having," "containing," "with," and variations thereof herein are intended to cover not only the items listed thereafter, but also equivalents thereof and additional items.

Claims (27)

1. A rotor assembly for an axial flux machine, comprising:
at least one magnet;
a first support structure having a first annular surface on a first side and a second annular surface on a second side opposite the first side, the at least one magnet being mounted to the first annular surface such that the first support structure provides a magnetic flux return path for the at least one magnet;
a second support structure configured to be attached to the second annular surface of the first support structure to enable torque to be transferred between the at least one magnet and the second support structure via the first support structure, the second support structure being further configured to (A) be attached to a rotatable shaft of the axial flux machine, or (B) function as an output or input flange of the axial flux machine;
the second support structure is adapted to rotate about an axis of rotation of the axial flux machine;
the at least one magnet has a first magnet surface that is orthogonal to a magnetization direction of the at least one magnet and faces away from the first annular surface of the first support structure;
the second support structure comprises at least one surface that is radially tapered to cause the first support structure to recurve to conform to a shape of the at least one surface of the second support structure when the second support structure is attached to the second annular surface of the first support structure, such that when the second support structure is attached to the second annular surface of the first support structure and the rotor assembly is not influenced by any other magnetic components, a distance between a first plane and a second plane is substantially greater than zero, the first plane intersects a first point on the first magnet surface, the axis of rotation is normal to the first plane, the second plane intersects a second point on the first magnet surface, the axis of rotation is normal to the second plane, and the second point is at a different radial distance from the axis of rotation than the first point;
Rotor assembly. The rotor assembly of claim 1, wherein the second support structure is configured to be attached to a rotatable shaft of the axial flux machine. The rotor assembly of claim 1, wherein the second support structure is configured to function as an output or input flange for the axial flux machine. the first support structure is made from a first material;
the second support structure is made from a second material different from the first material;
The rotor assembly of claim 1 . the at least one magnet comprises a magnet piece;
the second support structure is further configured to limit radial movement of the magnet pieces.
The rotor assembly of claim 1 . The rotor assembly of claim 5, wherein the second support structure further comprises a circular edge configured to engage the outermost edges of the magnet pieces to limit the radial movement of the magnet pieces. A rotor assembly as described in claim 5, wherein the first support structure is further configured to allow the magnet pieces to slide radially when the second support structure is removed from the first support structure. The rotor assembly of claim 7, wherein the second support structure is further configured to be removable from the first support structure to allow the magnet pieces to be removed from the first support structure by sliding them radially. the at least one magnet comprises a magnet piece;
the first support structure further comprising a rib configured to limit angular movement of the magnet piece;
The rotor assembly of claim 1 . The rotor assembly of claim 1, wherein the at least one magnet comprises a ring magnet. the second support structure is attached to the second annular surface of the first support structure;
the rotor assembly is disposed within the axial flux machine;
the axial flux machine further comprises a stator including at least a first winding adapted to carry current;
the rotor assembly is configured to rotate relative to the stator;
the at least one magnet is arranged such that a first half line extending away from the first magnet surface and normal to the first magnet surface intersects the first winding;
The rotor assembly of claim 1 . the second point is at a greater radial distance from the axis of rotation than the first point;
the first support structure, the second support structure, and the at least one magnet are further configured and arranged such that when the second support structure is attached to the second annular surface of the first support structure and the rotor assembly is not influenced by any other magnetic components, a second half-line intersects the first plane, the second half-line extending away from the first magnet surface at the second point and being normal to the first magnet surface.
The rotor assembly of claim 1 . the at least one magnet has an inner edge disposed at the first point;
the at least one magnet has an outer edge disposed at the second point, the outer edge being opposite the inner edge;
the first support structure, the second support structure, and the at least one magnet are further configured and arranged such that when the second support structure is attached to the second annular surface of the first support structure and the rotor assembly is not influenced by any other magnetic components, a ratio of a distance between the first plane and the second plane to a distance between the first point and the second point is greater than 0.002.
The rotor assembly of claim 1 . the second support structure is attached to the second annular surface of the first support structure;
the rotor assembly is disposed within the axial flux machine;
the axial flux machine includes at least one additional magnet that interacts with the at least one magnet to cause the distance between the first plane and the second plane to be substantially equal to zero;
A rotor assembly according to any one of claims 1 to 13. 1. A method, comprising:
mounting at least one magnet on a first annular surface of a first support structure of a rotor assembly for an axial flux machine such that the first support structure provides a flux return path for the at least one magnet, the first support structure further comprising a second annular surface on a side of the first support structure opposite the first annular surface;
and attaching the second support structure to the second annular surface of the first support structure to which the at least one magnet is attached, to enable torque to be transmitted between the at least one magnet and the second support structure via the first support structure;
the second support structure is configured to (A) be attached to a rotatable shaft of the axial flux machine, or (B) function as an output or input flange of the axial flux machine;
the second support structure is adapted to rotate about an axis of rotation of the axial flux machine;
the at least one magnet has a first magnet surface that is orthogonal to a magnetization direction of the at least one magnet and faces away from the first annular surface of the first support structure;
the first support structure having an original substantially planar shape before the second support structure is attached to the second annular surface of the first support structure;
the second support structure comprises at least one surface that is radially tapered to cause the first support structure to recurve from its original substantially flat shape to conform to a shape of the at least one surface of the second support structure when the second support structure is attached to the second annular surface of the first support structure, such that after the second support structure is attached to the second annular surface of the first support structure and when the rotor assembly is not influenced by any other magnetic components, a distance between a first plane and a second plane is substantially greater than zero, the first plane intersects a first point on the first magnet surface, the axis of rotation is normal to the first plane, the second plane intersects a second point on the first magnet surface, the axis of rotation is normal to the second plane, and the second point is at a different radial distance from the axis of rotation than the first point.
method. The method of claim 15, wherein the second support structure is configured to be attached to a rotatable shaft of the axial flux machine. The method of claim 15, wherein the second support structure is configured to function as an output or input flange for the axial flux machine. the first support structure is made from a first material;
the second support structure is made from a second material different from the first material;
16. The method of claim 15. the at least one magnet comprises a magnet piece;
and mounting the second support structure to the first support structure further comprises mounting the second support structure to the first support structure such that the second support structure limits radial movement of the magnet pieces.
16. The method of claim 15. 20. The method of claim 19, wherein the second support structure further comprises a circular edge configured to engage the outermost edge of the magnet piece to limit the radial movement of the magnet piece. 20. The method of claim 19, further comprising detaching the second support structure from the first support structure to allow the magnet pieces to be removed from the first support structure by sliding them radially. the at least one magnet comprises a magnet piece;
the first support structure further comprising a rib configured to limit angular movement of the magnet piece;
16. The method of claim 15. The method of claim 15, wherein the at least one magnet comprises a ring magnet. 16. The method of claim 15, further comprising, after attaching the second support structure to the second annular surface of the first support structure, disposing the rotor assembly within the axial flux machine such that the at least one magnet is arranged such that a first half-line extending away from the first magnet surface and normal to the first magnet surface intersects the stator windings of the axial flux machine. the second point is at a greater radial distance from the axis of rotation than the first point;
after the second support structure is attached to the second annular surface of the first support structure, and when the rotor assembly is not influenced by any other magnetic components, a second ray that is normal to the first magnet surface and extends away from the first magnet surface at the second point intersects the first plane;
16. The method of claim 15. the at least one magnet has an inner edge disposed at the first point;
the at least one magnet has an outer edge disposed at the second point, the outer edge being opposite the inner edge;
after the second support structure is attached to the second annular surface of the first support structure, and when the rotor assembly is not influenced by any other magnetic components, a ratio of a distance between the first plane and the second plane to a distance between the first point and the second point is greater than 0.002;
16. The method of claim 15. The method of any one of claims 15-26, further comprising, after attaching the second support structure to the second annular surface of the first support structure, disposing the rotor assembly within the axial flux machine such that at least one additional magnet of the axial flux machine interacts with the at least one magnet to cause the distance between the first plane and the second plane to be substantially equal to zero.