Permanent magnet rotor with enhanced demagnetization protection

Abstract

A permanent magnet motor includes a rotor and an irregular polyhedron-shaped magnet assembly. The rotor may define at least one magnet opening and may be configured to rotate within a circular opening defined by a stator. The irregular polyhedron-shaped magnet assembly may be disposed in the magnet opening and may define a magnetization direction, wherein a height along the magnetization direction and perpendicular to a lamination plane of the rotor is greater at both ends than at a central portion disposed therebetween.

Description

Technical Field

[0001] The present application generally relates to permanent magnet arrangements for rotors of electric machines. Background Art

[0002] Hybrid electric vehicles and electric vehicles utilize one or more electric motors to provide propulsion for the vehicle. Various motor technologies are available for such applications. Permanent magnet motors are a typical choice for vehicle applications. A permanent magnet motor includes a stator and a rotor. The rotor is constructed with permanent magnets. The coils in the stator are energized to generate electromagnetic flux, which interacts with the electromagnetic flux generated by the permanent magnets of the rotor. The interaction of the fluxes causes the rotor to rotate. When subjected to an external magnetic field (including the field generated by the stator windings) and / or temperature changes, the magnetic properties of the permanent magnets may change, resulting in demagnetization, which may affect the performance of the motor. As an example, demagnetization may reduce the output torque and efficiency of the motor. Summary of the Invention

[0003] A permanent magnet motor includes a rotor and an irregular polyhedron-shaped magnet assembly. The rotor may define at least one magnet opening and may be configured to rotate within a circular opening defined by a stator. The irregular polyhedron-shaped magnet assembly may be disposed in the magnet opening and may define a magnetization direction, wherein a height along the magnetization direction and perpendicular to a lamination plane of the rotor is greater at both ends than at a center portion disposed therebetween.

[0004] A permanent magnet motor includes a rotor defining at least one magnet opening and a fractal-polyhedron-shaped magnet assembly. The fractal-polyhedron-shaped magnet assembly can be disposed in the magnet opening, has a magnetization direction, and has a cross-sectional area whose cross-sectional area at outer surfaces along an axis perpendicular to the magnetization direction and parallel to a lamination plane of the rotor is greater than its cross-sectional area at a center portion disposed between the outer surfaces.

[0005] A permanent magnet motor includes a rotor and an irregular polyhedron-shaped magnet assembly. The rotor may define at least one magnet opening and may be configured to rotate within a circular opening defined by a stator. The irregular polyhedron-shaped magnet assembly, disposed in the magnet opening, may define an axis perpendicular to the magnetization direction of the magnet assembly and parallel to the rotor laminations, and may have a coercivity that varies along the axis. BRIEF DESCRIPTION OF THE DRAWINGS

[0006] Figure 1 is a diagram showing a hybrid vehicle including a typical power train and energy storage components including an electric machine.

[0007] Figure 2A is a top view of the rotor laminations.

[0008] Figure 2BA side view of a rotor consisting of a series of rotor laminations.

[0009] Figure 3 It is part of the rotor and stator laminations.

[0010] Figure 4 It is a perspective view of the rotor and stator.

[0011] Figure 5 is a side view of the rotor laminations and permanent magnets embedded in the rotor, showing demagnetization.

[0012] Figure 6 is a side view of a rotor and a fractal-polyhedron-shaped magnet assembly including two quadrilateral permanent magnets embedded in the rotor configured to reduce demagnetization of the magnet assembly.

[0013] Figure 7 is a side view of a rotor and a fractal-polyhedron-shaped magnet assembly including two quadrilateral permanent magnets embedded in the rotor configured to reduce demagnetization of the magnet assembly.

[0014] Figure 8 is a side view of a rotor and a fractal-polyhedron-shaped magnet assembly including two quadrilateral permanent magnets embedded in the rotor configured to reduce demagnetization of the magnet assembly.

[0015] Figure 9 is a side view of a rotor and a pair of fractal-polyhedron-shaped magnet assemblies, each of which includes three quadrilateral permanent magnets embedded in the rotor configured to reduce demagnetization of the magnet assemblies.

[0016] Figure 10 is a side view of a rotor and a pair of fractal-polyhedron-shaped magnet assemblies, each of which includes two quadrilateral permanent magnets embedded in the rotor configured to reduce demagnetization of the magnet assemblies.

[0017] Figure 11 is a side view of a rotor and a pair of fractal-polyhedron-shaped magnet assemblies, each of which includes three quadrilateral permanent magnets embedded in the rotor configured to reduce demagnetization of the magnet assemblies.

[0018] Figure 12 is a side view of a rotor and a pair of fractal-polyhedron-shaped magnet assemblies, each of which includes three quadrilateral permanent magnets embedded in the rotor configured to reduce demagnetization of the magnet assemblies.

[0019] Figure 13 is a side view of a rotor and a pair of fractal-polyhedron-shaped magnet assemblies, each of which includes two quadrilateral permanent magnets embedded in the rotor configured to reduce demagnetization of the magnet assemblies.

[0020] Figure 14is a side view of a rotor and a pair of fractal-polyhedron-shaped magnet assemblies, each of which includes two quadrilateral permanent magnets embedded in the rotor configured to reduce demagnetization of the magnet assemblies.

[0021] Figure 15 is a side view of a rotor and a pair of fractal-polyhedron-shaped magnet assemblies, each of which includes two quadrilateral permanent magnets embedded in the rotor configured to reduce demagnetization of the magnet assemblies.

[0022] Figure 16 is a side view of a rotor and a pair of fractal-polyhedron-shaped magnet assemblies, each of which includes two quadrilateral permanent magnets embedded in the rotor configured to reduce demagnetization of the magnet assemblies.

[0023] Figure 17 is a side view of a rotor and a pair of fractal-polyhedron-shaped magnet assemblies, each of which includes three quadrilateral permanent magnets embedded in the rotor configured to reduce demagnetization of the magnet assemblies. DETAILED DESCRIPTION

[0024] Embodiments of the present disclosure are described herein. However, it should be understood that the disclosed embodiments are merely examples, and other embodiments may take various and alternative forms. The drawings are not necessarily to scale; certain features may be exaggerated or minimized to show details of particular components. Therefore, the specific structural and functional details disclosed herein should not be interpreted as limiting, but merely as a representative basis for teaching those skilled in the art to use the invention in various ways. As will be understood by those of ordinary skill in the art, the various features shown and described with reference to any one of the accompanying drawings may be combined with features shown in one or more other drawings to produce embodiments that are not explicitly shown or described. The combinations of features shown provide representative embodiments of typical applications. However, various combinations and modifications of features consistent with the teachings of the present disclosure may be required for specific applications or implementations.

[0025] During operation of a permanent magnet motor, the magnets may experience demagnetization caused by the stator current, resulting in uneven demagnetization on the surface of the magnets. In some cases, the two corners of the magnet may become demagnetized while the center portion does not. The two corners of the magnet are typically the corners closest to the stator and where the induced magnetic field of the stator is largest. Here, the magnets are configured to reduce corner demagnetization by changing the magnet thickness of the magnets to reduce or eliminate demagnetization at the corners. The thickness of the magnets is changed along the magnetization axis of the magnets, and the magnetic field is generated by the current in the stator windings so that the magnetic field extends into the rotor.

[0026] The magnetization direction of a magnet is the direction in which the magnetic flux lines in the magnet extend parallel to each other after the magnet is magnetized. If the magnet is anisotropic, the magnetization direction is aligned with the magnet's easy magnetization axis. If the magnet is anisotropic, the magnetization direction is aligned with the magnet's easy magnetization axis. The orientation of a magnet can be described by its magnetization direction. For example, consider a magnet in a rotor that is a rectangular prism with a height H, a length L, and a width. The height dimension is along the magnet's magnetization direction, the length dimension is along the rotor's axial direction, and the width dimension is along a direction orthogonal to the height and length directions. For reference, consider a magnet in a rotor that is a rectangular prism. The top of the magnet is the surface of the magnet that is substantially perpendicular to the magnet's easy magnetization axis and closest to the stator, and the bottom of the magnet is the surface of the magnet that is substantially perpendicular to the magnet's magnetization direction and farthest from the stator. Furthermore, the front of the magnet is the surface of the magnet that is substantially parallel to the magnet's magnetization direction and closest to the stator, and the back of the magnet is the surface of the magnet that is substantially parallel to the magnet's magnetization direction and farthest from the stator.

[0027] Here, the shape of the magnet is designed to reduce or substantially eliminate demagnetization at the corners of the magnet. To achieve this reduction in demagnetization, the magnet is constructed into a non-rectangular prism shape so that the thickness of the magnet edges (i.e., the front and rear surfaces) is greater than the thickness in the center. The advantage of this variable thickness magnet is that for the same magnet demagnetization requirement, the magnet volume can be reduced to reduce cost, or for the same demagnetization requirement, the performance of the motor can be improved with the same magnet volume.

[0028] Figure 1 A vehicle 12, which may be referred to as a plug-in hybrid electric vehicle (PHEV), is depicted. The vehicle 12 may include one or more electric motors 14 mechanically coupled to a hybrid transmission 16. The electric motors 14 may be capable of operating as either a motor or a generator. In addition, the hybrid transmission 16 is mechanically coupled to an engine 18. The hybrid transmission 16 is also mechanically coupled to a drive shaft 20, which is mechanically coupled to wheels 22. The electric motors 14 can provide propulsion and deceleration capabilities when the engine 18 is turned on or off. The electric motors 14 can also function as generators and provide fuel economy benefits by recovering energy that would normally be lost as heat in the friction braking system. The electric motors 14 can also reduce vehicle emissions by allowing the engine 18 to operate at a more efficient speed and allowing the vehicle 12 to operate in an electric mode in which the engine 18 is shut down under certain conditions. The vehicle 12 may also be a battery electric vehicle (BEV). In a BEV configuration, the engine 18 may not be present. In other configurations, the vehicle 12 may be a full hybrid electric vehicle (FHEV) without plug-in capability.

[0029] The traction battery (or battery pack) 24 stores energy that can be used by the electric motor 14. The traction battery 24 can provide a high-voltage direct current (DC) output. The traction battery 24 can be electrically coupled to one or more power electronics modules 26. One or more contactors 42 isolate the traction battery 24 from other components when open and connect the traction battery 24 to the other components when closed. The power electronics module 26 is also electrically coupled to the electric motor 14 and provides the ability to transfer energy bidirectionally between the traction battery 24 and the electric motor 14. For example, the traction battery 24 can provide a DC voltage, while the electric motor 14 may operate on three-phase alternating current (AC) to function. The power electronics module 26 can convert the DC voltage to a three-phase AC voltage to operate the electric motor 14. In regenerative mode, the power electronics module 26 can convert the three-phase AC voltage from the electric motor 14, which acts as a generator, to a DC voltage compatible with the traction battery 24.

[0030] The vehicle 12 may include a variable voltage converter (VVC) 52 electrically coupled between the traction battery 24 and the power electronics module 26. The VVC 52 may be a DC / DC boost converter configured to increase or boost the voltage provided by the traction battery 24. By increasing the voltage, current requirements may be reduced, resulting in a reduction in the wiring size of the power electronics module 26 and the electric machine 14. Additionally, the electric machine 14 may operate with greater efficiency and lower losses.

[0031] In addition to providing energy for propulsion, the traction battery 24 can also provide energy for other vehicle electrical systems. The vehicle 12 may include a DC / DC converter module 28 that converts the high-voltage DC output of the traction battery 24 into a low-voltage DC power supply compatible with low-voltage vehicle loads. The output of the DC / DC converter module 28 can be electrically coupled to an auxiliary battery 30 (e.g., a 12V battery) for charging the auxiliary battery 30. Low-voltage systems can be electrically coupled to the auxiliary battery 30. One or more electrical loads 46 can be coupled to the high-voltage bus. The electrical loads 46 can have associated controllers that operate and control the electrical loads 46 where appropriate. Examples of electrical loads 46 may be fans, electric heating elements, and / or air conditioning compressors.

[0032] The vehicle 12 can be configured to recharge the traction battery 24 from an external power source 36. The external power source 36 can be a connection to an electrical outlet. The external power source 36 can be electrically coupled to a charger or electric vehicle supply equipment (EVSE) 38. The external power source 36 can be a distribution network or grid provided by an electric utility company. The EVSE 38 can provide circuitry and controls for regulating and managing energy transfer between the external power source 36 and the vehicle 12. The external power source 36 can provide DC or AC power to the EVSE 38. The EVSE 38 can have an EVSE connector 40 for plugging into a charging port 34 of the vehicle 12. The charging port 34 can be any type of port configured to transfer power from the EVSE 38 to the vehicle 12. The charging port 34 can be electrically coupled to a charger or an onboard power conversion module 32. The power conversion module 32 can condition the power supplied from the EVSE 38 to provide appropriate voltage and current levels to the traction battery 24. The power conversion module 32 can interface with the EVSE 38 to coordinate power delivery to the vehicle 12. The EVSE connector 40 may have prongs that mate with corresponding recesses of the charging port 34. Alternatively, the various components described as being electrically coupled or connected may use wireless inductive coupling to transfer power.

[0033] One or more wheel brakes 44 may be provided to decelerate the vehicle 12 and prevent it from moving. The wheel brakes 44 may be hydraulically actuated, electrically actuated, or some combination thereof. The wheel brakes 44 may be part of a braking system 50. The braking system 50 may include other components for operating the wheel brakes 44. For simplicity, the figures depict a single connection between the braking system 50 and one of the wheel brakes 44. Connections between the braking system 50 and the other wheel brakes 44 are implied. The braking system 50 may include a controller for monitoring and coordinating the braking system 50. The braking system 50 may monitor the braking components and control the wheel brakes 44 to decelerate the vehicle. The braking system 50 may respond to driver commands and may also operate autonomously to implement features such as stability control. The controller of the braking system 50 may implement a method for applying a requested braking force when requested by another controller or sub-function.

[0034] The electronic modules in the vehicle 12 can communicate over one or more vehicle networks. The vehicle network can include multiple channels for communication. One channel of the vehicle network can be a serial bus, such as a controller area network (CAN). One channel of the vehicle network can include Ethernet as defined by the Institute of Electrical and Electronics Engineers (IEEE) 802 series of standards. Additional channels of the vehicle network can include discrete connections between modules and can include power signals from the auxiliary battery 130. Different signals can be passed over different channels of the vehicle network. For example, a video signal can be passed over a high-speed channel (e.g., Ethernet), while control signals can be transmitted over CAN or discrete signals. The vehicle network can include any hardware and software components that facilitate the transmission of signals and data between modules. The vehicle network is not described in detail in the accompanying drawings. Figure 1 1 , but it is implied that the vehicle network may be connected to any electronic module present in the vehicle 12. A vehicle system controller (VSC) 48 may be present to coordinate the operation of the various components.

[0035] The electric machine 14 may be an interior permanent magnet (IPM) machine including a stator 222 and a rotor 220 . Figure 2A An exemplary rotor lamination 238 is depicted, and Figure 2B A side view of a configuration of a stator 222 and a rotor 220 is depicted having a plurality of rotor laminations 238 and a plurality of stator laminations 236 arranged in an axially stacked relationship. The rotor laminations 238 may define a circular central opening 260 about a central axis 270 for receiving a drive shaft having a keyway that may receive a drive key 262. The rotor laminations 238 may define a plurality of magnet openings 242 that are symmetrically disposed with respect to adjacent pairs of magnet openings 242.

[0036] A plurality of rotor sectors 224 corresponding to the rotor magnetic poles may be defined by a plurality of interpolar axes (e.g., 280, 284) radiating from the rotational center axis 270 to the outer surface 250 of the rotor laminations 238. Each sector 224 may include a pair of magnet openings 242. The interpolar axes (e.g., 280, 284) may be positioned midway between adjacent magnet openings 242. Notably, Figure 2A Only two possible interpole axes 280 , 284 are shown and not all possible interpole axes are shown. Figure 2B A series of axially stacked rotor laminations 238 are depicted stacked along a central axis 270 about which the rotor 220 is configured to rotate.

[0037] Figure 3 A partial radial cross-sectional view depicts possible configurations of the rotor 220 and stator 222 . Figure 32 depicts a portion of stator laminations 236 and a portion of rotor laminations 238. Rotor laminations 238 and stator laminations 236 may be constructed from an iron alloy. A small air gap 240 is located between the inner periphery of stator laminations 236 and an outer surface 250 of rotor laminations 238. Stator laminations 236 may define a radially extending opening.

[0038] The rotor laminations 238 may define symmetrically positioned magnet openings 242 about an outer surface 250 of each rotor lamination 238. Each magnet opening 242 may be configured to receive a magnet 244. Depending on design choice, any number of laminations may be used in a given design. The rotor laminations 238 and stator laminations 236 may be arranged in a stack along a central axis 270. The axially stacked rotor laminations 238 and magnets 244 may define a plurality of magnetic poles distributed about the central axis 270.

[0039] Stator 222 may include conductors disposed in radially extending openings to form windings. Stator 222 may include an iron core formed from stacked stator laminations 236 and a winding arrangement of conductors that carry an excitation current. Current flowing through the stator windings generates stator electromagnetic flux. The stator flux can be controlled by adjusting the magnitude and frequency of the current flowing through the stator windings.

[0040] The rotor 220 may include an iron core made of a stack of rotor laminations 238 and a plurality of sets of magnets 244 inserted into holes or magnet openings 242 defined by the iron core. The magnets 244 in the rotor 220 may generate rotor magnetic flux. The stator flux and the rotor flux may be distributed in the air gap 240. The interaction between the stator flux and the rotor flux causes the rotor 220 to rotate about the central axis 270.

[0041] The magnetic poles of the rotor 220 can be geometrically defined to correspond to the sectors 224 defined by the rotor laminations 238. Each magnetic pole can be represented by a sector 224. The magnetic pole position can be generally defined by a central magnetic pole axis 282, which extends radially from the central axis 270 toward the outer surface 250 of the rotor laminations 238 along the midpoint between adjacent magnet openings 242. The interpolar axes (e.g., 280, 284) can extend radially from the central axis 270 toward the outer surface 250 of the rotor laminations 238 between adjacent magnetic poles. The angular distance between two adjacent magnetic poles can define a magnetic pole pitch parameter. The arc length on the circumferential rotor outer surface 250 between two adjacent magnetic poles of the rotor can be referred to as the magnetic pole pitch. The magnetic pole pitch can be measured circumferentially around the outer rotor outer surface 250 between adjacent central magnetic pole axes 282. Each magnetic pole can have an associated surface area on the outer surface 250 of the rotor 220. Each magnetic pole may be represented by an arc length on the surface between adjacent interpolar axes 280 , 284 .

[0042] Figure 42 is a perspective view of rotor 220 and stator 222. Stator 222 has teeth 234 separated by stator winding cavities or slots, which are configured to support a set of stator windings. When current passes through the stator windings in the slots, a magnetic field is induced in teeth 234 that extends outward toward rotor 220 and through rotor 220.

[0043] Figure 5 FIG2 is a side view of rotor 220 and magnets 244 embedded in magnet openings 242 of the rotor, illustrating demagnetized regions 502 resulting from the interaction of the magnetic field emitted from teeth 234 with magnets 244. The magnetic field induced by the stator current passes through teeth 234 and rotor 220 to interact with magnets 244 in magnet openings 242. Due to the opposing magnetic field generated by the stator current and directed to magnets 244 by teeth 234 during operation, some areas of magnets 244 in magnet openings 242 may become demagnetized. Additionally, magnets 244 in magnet openings 242 may become partially demagnetized due to heat generated by energy loss in the magnets caused by the changing magnetic field in the magnets.

[0044] Here Figure 5 , the demagnetized region 502 is shown on the top surface of the magnet. As described above, when no external magnetic field is applied, the rectangular prismatic magnet 244 has field lines (not shown) running substantially parallel to the thickness of the magnet interior and causing the magnetic field to radiate from the front (e.g., north or south pole) and the back (e.g., south or north pole) of the magnet. Here, the orientation of the magnet is specified so that the top of the magnet is the surface with the two demagnetized regions 502 and is perpendicular to the plane of the rotor laminations, while the bottom of the magnet is opposite the top of the magnet.

[0045] Figure 6 is a side view of the rotor 220, teeth 234, and fractal-shaped magnets (602, 606) including two quadrilateral magnets (602, 606) embedded in the rotor 220 configured to reduce demagnetization of the magnet assembly.

[0046] Typically, a polyhedron is a three-dimensional solid with flat polygonal faces, straight edges, and sharp corners or vertices. However, in this application, the term polyhedron is a three-dimensional solid that may include curved polygonal faces, curved edges, and rounded corners or vertices. Similarly, in this application, an irregular polyhedron is a three-dimensional solid with flat polygonal faces, straight edges, and sharp corners or vertices in three dimensions. In practice, and in this application, magnets do not have sharp corners but have rounded corners, and the pole surfaces are not limited to flat polygonal faces. In this application, the sharp corners actually have a small roundness, which is common in industry.

[0047] Additionally, in two-dimensional space, a quadrilateral or tetragon is a polygon with four sides (or sides) and four vertices or corners, while a pentagon has five sides and a hexagon has six sides. A convex quadrilateral or trapezoid has all interior angles less than 180° and both diagonals lie within the quadrilateral. Furthermore, a concave surface curves inward or concaves, while a convex surface curves outward or extends. If one surface is curved and the opposite surface is straight, the object can be referred to as a plano-concave or plano-convex element.

[0048] exist Figure 6 In FIG, the irregular polyhedron-shaped magnet assembly is shown as two magnets (602, 606), the first magnet 602 is shown as a quadrilateral prism, which is a three-dimensional solid having two quadrilateral surfaces or faces (e.g., substantially parallel to the rotor laminations) at either end joined by four rectangular faces (604A, 604B, 604C, and 604D). Here, the pole surfaces are perpendicular to the magnet magnetization direction. In other words, the magnet's poles are rectangular faces 604B and 604D. The second magnet 606 is shown as a quadrilateral prism with four rectangular faces (608A, 608B, 608C, and 608D). Here, the magnet's poles are rectangular faces 608B and 608D. The magnets (602, 606) are arranged so that if the rectangular face 604B of the first magnet is a north pole and the rectangular face 604D of the first magnet is a south pole, then the rectangular face 608B of the second magnet will be a north pole and the rectangular face 608D of the second magnet will be a south pole, so that they will be parallel. Having the magnets parallel creates a magnetic field through the two magnets, which, when current is modulated through the stator windings (not shown), can interact with the teeth 234 to generate a torque at the rotor 220 that causes the rotor 220 to rotate relative to the stator 222. The magnetic assembly is shown as having six corners, corner 610A of the first magnet assembly, corner 610B of the second magnet assembly, corner 610C of the third magnet assembly, corner 610D of the fourth magnet assembly, corner 610E of the fifth magnet assembly, and corner 610F of the sixth magnet assembly. When the motor is in operation, the interaction between the induced magnetic fields from the teeth 234 acting on the magnets (602, 606) causes demagnetization in certain areas. By changing the shape and arrangement of the magnets, demagnetization can be reduced. Here, the magnets (602, 606) are configured so that the cross-sectional area including the height along the magnetization direction of the rectangular face 604A and the rectangular face 608C (i.e., between corners 610A and 610F or between corners 610C and 610D) is larger than the rectangular face 604C and the rectangular face 608A at the center portion along the magnetization direction (i.e., between corners 610B and 610E). Here, the magnet assembly is shown as two quadrilateral prisms, also known as quadrilateral prisms.

[0049] In one embodiment, the magnet assembly is a single irregular polyhedron-shaped magnet in which the side faces are pentagonal, wherein the top surface defined by the two planes has a single internal angle greater than 180 degrees. This can be referred to as a single pentagonal prism in which the single internal angle of one corner (e.g., 610B) is greater than 180 degrees. In another embodiment, the top surface (i.e., the surface between corners 610A, 610B, and 610C) can be curved and not a straight line.

[0050] Figure 7 is a side view of a rotor and a fractal-polyhedron-shaped magnet assembly including two quadrilateral permanent magnets embedded in the rotor configured to reduce demagnetization of the magnet assembly. Figure 7 In FIG, the irregular polyhedron-shaped magnet assembly is shown as two magnets (702, 706), the first magnet 702 is shown as a quadrilateral prism, which is a three-dimensional solid having two quadrilateral surfaces or faces (e.g., substantially parallel to the rotor laminations) at either end joined by four rectangular faces (704A, 704B, 704C, and 704D). Here, the magnet's poles are rectangular faces 704B and 704D. The second magnet 706 is shown as a quadrilateral prism with four rectangular faces (708A, 708B, 708C, and 708D). Here, the magnet's poles are rectangular faces 708B and 708D. Magnets (702, 706) are arranged so that if the rectangular face 704B of the first magnet is the North Pole and the rectangular face 704D of the first magnet is the South Pole, then the rectangular face 708B of the second magnet will be the North Pole and the rectangular face 708D of the second magnet will be the South Pole, so that they will be parallel. By changing the shape and arrangement of the magnets, demagnetization can be reduced. Here, magnets (702, 706) are configured so that the cross-sectional area including the height along the magnetization direction of rectangular face 704A and rectangular face 708C (i.e., between point 710A and 710F or between point 710C and 710D) is greater than the rectangular face 704C and rectangular face 708A as the center part (i.e., between point 710B and 710E). Here, the magnet assembly is shown as two quadrilateral prisms, also referred to as quadrilateral prisms. In this embodiment, the magnet assembly has an arched structure.

[0051] A frustum is a portion of a cone or pyramid that remains after its upper portion is cut by a plane parallel to its base or is intercepted between two such planes. The top of the frustum, where the plane cuts the upper portion, is the vertex of the frustum. When two frustums are connected, it is called a bifrustum. Typically, a bifrustum is two frustums connected by their bases, however, two frustums can be connected at the vertex to form a bow-tie structure (for example, a bifrustum joined at the vertex). In addition, a quadrilateral is a polygon with four sides (or sides) and four vertices or corners, which is consistent with a pentagon (5 sides) and a hexagon (6 sides). A trapezoid is a specific type of quadrilateral that is a convex quadrilateral with at least one pair of parallel sides. When considering a bow-tie structure (for example, a bifrustum joined at the vertex), another way to describe it is a concave hexagon, and if the bow-tie structure has a square or rectangular center, the object can be described as a concave octagon. In other embodiments, the bow-tie shaped structure may have curves on the top and / or bottom surfaces.

[0052] In one embodiment, the magnet assembly is a single irregular polyhedron-shaped magnet in which the side faces are hexagonal, wherein the top surface defined by the two planes has two relative interior angles greater than 180 degrees. This can be referred to as a single hexagonal prism in which the two interior angles of the two relative corners (e.g., 710B and 710E) are greater than 180 degrees. In another embodiment, the top surface (i.e., the surface between points 710A, 710B, and 710C) can be curved and not a straight line. The curve can follow a circular curve, a parabolic curve, a hyperbolic curve, an elliptical or other common curved shapes.

[0053] exist Figure 8, the irregular polyhedron-shaped magnet assembly is shown as two magnets (802, 806), the first magnet 802 is shown as a quadrilateral prism, which is a three-dimensional solid having two quadrilateral surfaces or faces (e.g., substantially parallel to the rotor laminations) at either end joined by four rectangular faces (804A, 804B, 804C, and 804D). Here, the magnet's poles are rectangular face 804B and rectangular face 804D. The second magnet 806 is shown as a quadrilateral prism with four rectangular faces (808A, 808B, 808C, and 808D). Here, the magnet's poles are rectangular face 808B and rectangular face 808D. The magnets (802, 806) are arranged so that if the rectangular face 804B of the first magnet is a north pole and the rectangular face 804D of the first magnet is a south pole, then the rectangular face 808B of the second magnet will be a north pole and the rectangular face 808D of the second magnet will be a south pole, so that they will be parallel. Having the magnets parallel creates a magnetic field through the two magnets, which, when current is modulated through the stator windings (not shown), can interact with the stator magnetic flux to generate a torque at the rotor 220 that causes the rotor 220 to rotate relative to the stator 222. The magnetic assembly is shown as having six corners, corner 810A of the first magnet assembly, corner 810B of the second magnet assembly, corner 810C of the third magnet assembly, corner 810D of the fourth magnet assembly, corner 810E of the fifth magnet assembly, and corner 810F of the sixth magnet assembly. When the motor is in operation, the interaction between the induced magnetic field from the teeth 234 acting on the magnets (802, 806) causes demagnetization in certain areas of the magnets. By changing the shape and arrangement of the magnets, demagnetization can be reduced. Here, the magnets (802, 806) are configured so that the cross-sectional area including the height along the magnetization direction of the rectangular face 804A and the rectangular face 808C (i.e., between corners 810A and 810F or between corners 810C and 810D) is greater than the rectangular face 804C and the rectangular face 808A at the center (i.e., between corners 810B and 810E). Here, the magnet assembly is shown as two quadrilateral prisms, also referred to as quadrilateral prisms.

[0054] In an embodiment where the magnet assembly is a single irregular polyhedron-shaped magnet, the side surfaces are pentagonal, wherein the top surface defined by the two planes has a single internal angle greater than 180 degrees. This can be referred to as a single pentagonal prism, wherein the single internal angle of one corner (e.g., 810E) is greater than 180 degrees. In another embodiment, the bottom surface (i.e., the surface between corners 810D, 810E, and 810F) can be curved and not a straight line.

[0055] Figure 9 is a side view of a rotor and a pair of irregular polyhedron-shaped magnet assemblies, wherein each magnet assembly includes three quadrilateral permanent magnets embedded in the rotor and configured to reduce demagnetization of the magnet assembly. Figure 9 , the first irregular polyhedron-shaped magnet assembly has an A side, a B side, a C side, and a D side, and the second irregular polyhedron-shaped magnet assembly has an A' side, a B' side, a C' side, and a D' side. Referring back to the first irregular polyhedron-shaped magnet assembly, the magnet assembly is shown as three magnets (902A, 904A, and 906A), the first magnet 902A is shown as a quadrilateral prism, which is a three-dimensional solid having two quadrilateral surfaces or faces (e.g., substantially parallel to the rotor laminations) at either end where four rectangular faces along the A side, B side, C side, and D side are joined. Here, the magnetic poles of the magnet are the B side and the D side. The second magnet 904A is shown as a quadrilateral prism (e.g., a rectangular prism) with four rectangular faces along the A side, B side, C side, and D side and the magnetic poles of the magnet are the B side and the D side. The third magnet 906A is shown as a quadrilateral prism, which is a three-dimensional solid having two quadrilateral surfaces or faces (e.g., substantially parallel to the rotor laminations) at either end where four rectangular faces along the A side, B side, C side, and D side meet, with the magnet's poles located at the B side and D side. The magnets (902A, 904A, and 906A) are arranged so that if the B side of the first magnet is a north pole and the D side of the first magnet is a south pole, then the B side of the second magnet will be a north pole and the D side of the second magnet will be a south pole, and so on for the third magnet, so that they will be parallel. Parallelizing the magnets creates a magnetic field through the three magnets, which, when current is modulated through the stator windings (not shown), can interact with the stator magnetic field to generate a torque at the rotor 220 that causes the rotor 220 to rotate relative to the stator. The magnetic assembly is shown as having eight corners. When the motor is in operation, the interaction between the induced magnetic fields from the stator teeth acting on the magnets (902A, 904A, and 906A) causes demagnetization in certain areas of the magnets. By changing the shape and arrangement of the magnets, demagnetization can be reduced. Here, the magnets (902A, 904A, and 906A) are configured so that the cross-sectional area including the height along the magnetization direction of the side A of the magnet 902A and the side C of the third magnet 906A is greater than the side C of the magnet 902A and the side A of the third magnet 906A at the center (i.e., the minimum thickness of the magnet 904A).

[0056] In one embodiment, the magnet assembly is a single irregular polyhedron-shaped magnet in which the sides are octagonal, in which the top surface defined by two planes has two interior angles greater than 180 degrees. This can be referred to as a single octagonal prism in which the two interior angles of two adjacent corners are greater than 180 degrees. In another embodiment, the top surface (i.e., the surface facing the B side) and / or the bottom surface (i.e., the surface facing the D side) can be curved and not straight. Figure 9, a mirrored magnet assembly is shown where magnets ( 902B, 904B, and 906B) are mirror images of magnets ( 902A, 904A, and 906A) along faces A', B', C', and D'.

[0057] Figure 10 is a side view of a rotor and a pair of irregular polyhedron-shaped magnet assemblies, each of which includes two quadrilateral permanent magnets embedded in the rotor configured to reduce demagnetization of the magnet assembly. Figure 10 , the first irregular polyhedron-shaped magnet assembly has an A side, a B side, a C side, and a D side, and the second irregular polyhedron-shaped magnet assembly has an A' side, a B' side, a C' side, and a D' side. Referring back to the first irregular polyhedron-shaped magnet assembly, the magnet assembly is shown as two magnets (1002A and 1004A), the first magnet 1002A is shown as a quadrilateral prism (e.g., a square prism), which is a three-dimensional solid having two quadrilateral surfaces or faces (e.g., substantially parallel to the rotor laminations) at either end where four rectangular faces along the A side, B side, C side, and D side are joined. Here, the poles of the magnet are the B side and the D side. The second magnet 1004A is shown as a quadrilateral prism (e.g., a rectangular prism) where the four rectangular faces are along the A side, B side, C side, and D side and the poles of the magnet are the B side and the D side. The magnets (1002A and 1004A) are arranged so that if the B side of the first magnet is a north pole and the D side of the first magnet is a south pole, the B side of the second magnet will be a north pole and the D side of the second magnet will be a south pole, so that they will be parallel. This paralleling of the magnets creates a magnetic field through the two magnets, which, when current is modulated through the stator windings (not shown), can interact with the stator teeth to generate a torque at the rotor 220 that causes the rotor 220 to rotate relative to the stator. The magnetic assembly is shown as having seven corners. When the motor is operating, the interaction between the induced magnetic fields from the stator teeth acting on the magnets (1002A and 1004A) causes demagnetization in certain areas of the magnets. By changing the shape and arrangement of the magnets, demagnetization can be reduced. Here, the magnets (1002A and 1004A) are configured so that the cross-sectional area including the height along the magnetization direction of side A and side C of the first magnet 1002A is larger than that of side A and side C of the second magnet 1004A. In another embodiment, the composition of the first magnet 1002A may be such that it has a greater coercivity than the second magnet 1004A, such that demagnetization of the magnetic assembly is reduced.

[0058] In one embodiment, the magnet assembly can be a single irregular polyhedron-shaped magnet in which the side faces are multi-faceted polygons, in which the top surface defined by two planes has two interior angles greater than 180 degrees. This can be referred to as a single hexagonal prism in which one interior angle is greater than 180 degrees. In another embodiment, the top surface (i.e., the face facing the B side) and / or the bottom surface (i.e., the surface facing the D side) can be curved and not straight.

[0059] exist Figure 10 , a mirrored magnet assembly is shown, wherein magnets ( 1002B and 1004B) are mirror images of magnets ( 1002A and 1004A) along faces A′, B′, C′, and D′.

[0060] Figure 11 is a side view of a rotor and a pair of irregular polyhedron-shaped magnet assemblies, each of which includes three quadrilateral permanent magnets embedded in the rotor configured to reduce demagnetization of the magnet assembly. Figure 11, the first irregular polyhedron-shaped magnet assembly has an A side, a B side, a C side, and a D side, and the second irregular polyhedron-shaped magnet assembly has an A' side, a B' side, a C' side, and a D' side. Referring back to the first irregular polyhedron-shaped magnet assembly, the magnet assembly is shown as three magnets (1102A, 1104A, 1106A), the first magnet 1102A is shown as a quadrilateral prism (e.g., a rectangular prism), which is a three-dimensional solid having two quadrilateral surfaces or faces (e.g., substantially parallel to the rotor laminations) at either end where the four rectangular faces along the A side, B side, C side, and D side are joined. Here, the magnetic poles of the magnet are the B side and the D side. The second magnet 1104A is shown as a quadrilateral prism (e.g., a rectangular prism) with the four rectangular faces along the A side, B side, C side, and D side and the magnetic poles of the magnet are the B side and the D side. The third magnet 1106A is shown as a quadrilateral prism (e.g., a rectangular prism) with four rectangular faces along the A side, the B side, the C side, and the D side and the magnetic poles of the magnet are the B side and the D side. The magnets (1102A, 1104A, and 1106A) are arranged so that if the B side of the first magnet is the north pole and the D side of the first magnet is the south pole, then the B side of the second magnet will be the north pole and the D side of the second magnet will be the south pole and the third magnet will be parallel. Making the magnets parallel creates a magnetic field through the two magnets, which can interact with the stator magnetic field when modulating current through the stator winding (not shown) to generate a torque at the rotor 220 that causes the rotor 220 to rotate relative to the stator. The magnetic assembly is shown as having multiple corners. When the motor is operating, the interaction between the induced magnetic fields from the stator teeth acting on the magnets (1102A, 1104A, and 1106A) causes demagnetization in certain areas of the magnets. By changing the shape and arrangement of the magnets, demagnetization can be reduced. Here, the magnets (1102A, 1104A, and 1106A) are configured so that the cross-sectional area including the height along the magnetization direction of side A and side C of the first magnet 1102A and the third magnet 1106A is greater than the side A and side C of the second magnet 1104A. In another embodiment, the composition of the first magnet 1102A can be such that it has a greater coercivity than the second magnet 1104A, thereby reducing demagnetization of the magnetic assembly.

[0061] In one embodiment, the magnet assembly is a single irregular polyhedron-shaped magnet in which the side faces are multi-faceted polygons, in which the top surface defined by two planes has two internal angles greater than 180 degrees. This can be referred to as a single polygonal prism in which the two internal angles of two adjacent corners are greater than 180 degrees. In another embodiment, the top surface (i.e., the face facing the B side) and / or the bottom surface (i.e., the surface facing the D side) can be curved and not straight.

[0062] exist Figure 11 , a mirrored magnet assembly is shown where magnets ( 1102B, 1104B, and 1106B) are mirror images of magnets ( 1102A, 1104A, and 1106A) along faces A′, B′, C′, and D′.

[0063] Figure 12 is a side view of a rotor and a pair of irregular polyhedron-shaped magnet assemblies, each of which includes three quadrilateral permanent magnets embedded in the rotor configured to reduce demagnetization of the magnet assembly. Figure 12 In the figure, the first irregular polyhedron-shaped magnet assembly has an A side, a B side, a C side, and a D side, and the second irregular polyhedron-shaped magnet assembly has an A' side, a B' side, a C' side, and a D' side. Referring back to the first irregular polyhedron-shaped magnet assembly, the magnet assembly is shown as three magnets (1202, 1204, 1206), the first magnet 1202 is shown as a quadrilateral prism (e.g., a rectangular prism) having a short height along the first axis 1214 and a long length along the second axis 1216. A quadrilateral prism is a three-dimensional solid having two quadrilateral surfaces or faces (e.g., substantially parallel to the rotor laminations) at either end where the four rectangular faces along the A side, B side, C side, and D side are joined. Here, the magnetic poles of the magnet are the B side and the D side. The second magnet 1204 is shown as a quadrilateral prism having a long height along the first axis 1214 and a short length along the second axis 1216. The third magnet 1206 is shown as a quadrilateral prism that also has a long height along the first axis 1214 and a short length along the second axis 1216. In this figure, the second magnet 1204 and the third magnet 1206 are approximately equal in size, however, in other embodiments, the second magnet 1204 can be larger than the third magnet 1206. Figure 12, the end magnets (1204 and 1206) have a greater coercivity than the central first magnet 1202. The second magnet 1204 and the third magnet 1206 both have four rectangular faces along the A side, the B side, the C side, and the D side, and the magnetic poles of each magnet (1204, 1206) are along the B side and the D side. The magnets (1202, 1204, and 1206) are arranged so that if the B side of the first magnet is the north pole and the D side of the first magnet is the south pole, then the B side of the second magnet will be the north pole and the D side of the second magnet will be the south pole and so on for the third magnet so that they will be parallel. Making the magnets parallel creates a magnetic field through the three magnets, which, when current is modulated through the stator windings (not shown), can interact with the stator magnetic field to generate a torque at the rotor 220 that causes the rotor 220 to rotate relative to the stator. The magnetic assembly is shown as having multiple corners. When the motor is in operation, the interaction between the induced magnetic fields from the stator teeth acting on the magnets (1202, 1204, and 1206) causes demagnetization in certain areas of the magnets. By changing the shape and composition of the magnets, demagnetization can be reduced. Here, the magnets (1202, 1204, and 1206) are configured so that the second magnet 1204 and the third magnet 1206 have a shorter length along the first axis 1214 than the first magnet 1202, and the second magnet 1204 and the third magnet 1206 have a higher coercivity than the first magnet 1202, thereby making it possible to reduce the magnet volume for the same demagnetization requirement.

[0064] exist Figure 12 , a mirrored magnet assembly is shown, wherein magnets ( 1208 , 1210 , and 1212 ) are mirrored along mirror axes 1218 and 1220 to magnets ( 1202 , 1204 , and 1206 ), with faces A′, B′, C′, and D′.

[0065] Figure 13 is a side view of a rotor and a pair of irregular polyhedron-shaped magnet assemblies, each of which includes two quadrilateral permanent magnets embedded in the rotor configured to reduce demagnetization of the magnet assembly. Figure 13In the embodiment of the present invention, the first irregular polyhedron-shaped magnet assembly has an A side, a B side, a C side, and a D side, and the second irregular polyhedron-shaped magnet assembly has an A' side, a B' side, a C' side, and a D' side. Referring back to the first irregular polyhedron-shaped magnet assembly, the magnet assembly is shown as two magnets (1302, 1304), the first magnet 1302 being shown as a generally quadrilateral prism, but here the side facing the A side is curved and not straight, so that the first magnet 1302 has a short height along the first axis 1310 and a long length along the second axis 1312. In general, a quadrilateral prism is a three-dimensional solid having two quadrilateral surfaces or faces (e.g., substantially parallel to the rotor laminations) at either end where the four rectangular faces along the A side, B side, C side, and D side are joined. Here, one surface (i.e., the A surface) is not along a straight line but follows a curved surface. And the poles of the magnet are the B side and the D side. The second magnet 1304 is shown as a quadrilateral prism having a long height along the first axis 1310 and a short length along the second axis 1312. Here, the second magnet 1304 has a greater coercivity than the first magnet 1302. The first magnet 1302 and the second magnet 1304 are configured to mate with each other so that the magnetic poles of each magnet (1302, 1304) are along the B side and the D side. The magnets (1302 and 1304) are arranged so that if the B side of the first magnet is the north pole and the D side of the first magnet is the south pole, then the B side of the second magnet will be the north pole and the D side of the second magnet will be the south pole, so that they will be parallel. Making the magnets parallel creates a magnetic field through the two magnets, which, when current is modulated through the stator winding (not shown), can interact with the stator teeth to generate a torque at the rotor 220 that causes the rotor 220 to rotate relative to the stator. The magnetic assembly is shown as having multiple corners. When the motor is operating, the interaction between the induced magnetic fields from the stator teeth acting on the magnets (1302 and 1304) causes demagnetization in certain areas. Demagnetization can be reduced by changing the shape and composition of the magnets. Here, the magnets (1302 and 1304) are configured so that the coercivity at the first magnetic pole (i.e., the side facing A) is greater than the coercivity at the center portion disposed between the poles (i.e., the coercivity of the center magnet 1302 is lower than the coercivity of the first magnet 1304), so that demagnetization of the magnetic assembly can be reduced.

[0066] exist Figure 13 , a mirrored magnet assembly is shown, wherein magnets ( 1306 and 1308 ) are mirrored to magnets ( 1302 and 1304 ) along mirror axes 1314 and 1316 , with faces A′, B′, C′, and D′.

[0067] Figure 14is a side view of a rotor and a pair of irregular polyhedron-shaped magnet assemblies, each of which includes two quadrilateral permanent magnets embedded in the rotor configured to reduce demagnetization of the magnet assembly. Figure 14 , the first irregular polyhedron-shaped magnet assembly has an A side, a B side, a C side, and a D side, and the second irregular polyhedron-shaped magnet assembly has an A' side, a B' side, a C' side, and a D' side. Referring back to the first irregular polyhedron-shaped magnet assembly, the magnet assembly is shown as two magnets (1402, 1404), the first magnet 1402 being shown as a quadrilateral prism such that the first magnet 1402 has a short height along the first axis 1410 and a long length along the second axis 1412. Typically, a quadrilateral prism is a three-dimensional solid having two quadrilateral surfaces or faces (e.g., substantially parallel to the rotor laminations) at either end where the four rectangular faces along the A side, B side, C side, and D side are joined. And the magnetic poles of the magnet are the A side and the C side. The second magnet 1404 is shown as a quadrilateral prism having a long height along the first axis 1410 and a short length along the second axis 1412. Here, second magnet 1404 has a greater coercivity than first magnet 1402. First magnet 1402 and second magnet 1404 are configured to mate with each other so that the magnetic poles of each magnet (1402, 1404) are along the B-side and D-side. Magnets (1402 and 1404) are arranged so that if the B-side of the first magnet is a north pole and the D-side of the first magnet is a south pole, the B-side of the second magnet will be a north pole and the D-side of the second magnet will be a south pole, so that they will be parallel. Making the magnets parallel creates a magnetic field through the two magnets, which, when current is modulated through the stator winding (not shown), can interact with the stator teeth to generate torque at rotor 220 that causes rotor 220 to rotate relative to the stator. The magnetic assembly is shown as having multiple corners. When the motor is operating, the interaction between the induced magnetic fields from the stator teeth acting on the magnets (1402 and 1404) causes demagnetization in certain areas. Demagnetization can be reduced by changing the shape and composition of the magnets. Here, the magnets (1402 and 1404) are configured such that the coercivity at the second magnet 1404 is greater than the coercivity of the first magnet 1402, thereby enabling reduced demagnetization of the magnetic assembly.

[0068] exist Figure 14 , a mirrored magnet assembly is shown, wherein magnets ( 1406 and 1408 ) are mirrored to magnets ( 1402 and 1404 ) along mirror axes 1414 and 1416 , with faces A′, B′, C′, and D′.

[0069] Figure 15 is a side view of a rotor and a pair of irregular polyhedron-shaped magnet assemblies, each of which includes two quadrilateral permanent magnets embedded in the rotor configured to reduce demagnetization of the magnet assembly. Figure 15 , the first irregular polyhedron-shaped magnet assembly has an A side, a B side, a C side, and a D side, and the second irregular polyhedron-shaped magnet assembly has an A' side, a B' side, a C' side, and a D' side. Referring back to the first irregular polyhedron-shaped magnet assembly, the magnet assembly is shown as two magnets (1502, 1504), the first magnet 1502 being shown as a quadrilateral prism such that the first magnet 1502 has a short height along the first axis 1510 and a long length along the second axis 1512. Typically, a quadrilateral prism is a three-dimensional solid having two quadrilateral surfaces or faces (e.g., substantially parallel to the rotor laminations) at either end where the four rectangular faces along the A side, B side, C side, and D side are joined. And the magnetic poles of the magnet are the B side and the D side. The second magnet 1504 is shown as a quadrilateral prism having a long height along the first axis 1510 and a short length along the second axis 1512. Here, second magnet 1504 has a greater coercivity than first magnet 1502. First magnet 1502 and second magnet 1504 are configured to mate with each other so that the magnetic poles of each magnet (1502, 1504) are along the B-side and D-side. Magnets (1502 and 1504) are arranged so that if the B-side of the first magnet is a north pole and the D-side of the first magnet is a south pole, the B-side of the second magnet will be a north pole and the D-side of the second magnet will be a south pole, so that they will be in series. The magnet assembly generates a magnetic field that, when current is modulated through the stator winding (not shown), interacts with the stator magnetic field to generate a torque at rotor 220 that causes rotor 220 to rotate relative to the stator. The magnetic assembly is shown as having multiple corners. When the motor is operating, the interaction between the induced magnetic fields from the stator teeth acting on the magnets (1502 and 1504) causes demagnetization in certain areas. Demagnetization can be reduced by changing the shape and composition of the magnets. Here, the magnets (1502 and 1504) are configured such that the coercivity of the second magnet 1504 is greater than the coercivity of the first magnet 1502, thereby reducing demagnetization of the magnetic assembly.

[0070] exist Figure 15 , a mirrored magnet assembly is shown, wherein magnets ( 1506 and 1508 ) are mirrored to magnets ( 1502 and 1504 ) along mirror axes 1514 and 1516 , with faces A′, B′, C′, and D′.

[0071] Figure 16 is a side view of a rotor and a pair of irregular polyhedron-shaped magnet assemblies, each of which includes two quadrilateral permanent magnets embedded in the rotor configured to reduce demagnetization of the magnet assembly. Figure 16, the first irregular polyhedron-shaped magnet assembly has an A side, a B side, a C side, and a D side, and the second irregular polyhedron-shaped magnet assembly has an A' side, a B' side, a C' side, and a D' side. Referring back to the first irregular polyhedron-shaped magnet assembly, the magnet assembly is shown as two magnets (1602, 1604), the first magnet 1602 being shown as a two-part quadrilateral prism such that the first magnet 1602 has a short height along the first axis 1610 and a long length along the second axis 1612. Typically, a quadrilateral prism is a three-dimensional solid having two quadrilateral surfaces or faces (e.g., substantially parallel to the rotor laminations) at either end where the four rectangular faces along the A side, B side, C side, and D side are joined. And the magnetic poles of the magnet are the B side and the D side. Here, the first magnet 1602 can be a single pentagonal prism, or can be two separate prisms (1602A and 1602B). The second magnet 1604 is shown as a pentagonal prism having a long height along the first axis 1610 and a short length along the second axis 1612. Similarly, the second magnet 1604 can be a single pentagonal prism, or can be two separate prisms (1604A and 1604B). Here, the second magnet 1604 has a greater coercivity than the first magnet 1602. The first magnet 1602 and the second magnet 1604 are configured to mate with each other so that the poles of each magnet (1602, 1604) are along the B side and the D side. The magnets (1602 and 1604) are arranged so that if the B side of the first magnet is the north pole and the D side of the first magnet is the south pole, then the B side of the second magnet will be the north pole and the D side of the second magnet will be the south pole, so that they will be in series. The magnet assembly generates a magnetic field that interacts with the stator magnetic field when current is modulated through the stator winding (not shown) to generate a torque at the rotor 220 that causes the rotor 220 to rotate relative to the stator. The magnetic assembly is shown as having multiple corners. When the motor is operating, the interaction between the induced magnetic fields from the stator teeth acting on the magnets (1602 and 1604) causes demagnetization in certain areas of the magnets. Demagnetization can be reduced by changing the shape and composition of the magnets. Here, the magnets (1602 and 1604) are configured so that the coercivity of the second magnet 1604 is greater than the coercivity of the first magnet 1602, thereby reducing demagnetization of the magnetic assembly.

[0072] exist Figure 16 , a mirrored magnet assembly is shown, wherein magnets ( 1606 and 1608 ) are mirrored to magnets ( 1602 and 1604 ) along mirror axes 1614 and 1616 , with faces A′, B′, C′, and D′.

[0073] Figure 17is a side view of a rotor and a pair of fractal-polyhedron-shaped magnet assemblies, each of which includes three quadrilateral permanent magnets embedded in the rotor configured to reduce demagnetization of the magnet assemblies.

[0074] exist Figure 17 , the first irregular polyhedron-shaped magnet assembly has an A side, a B side, a C side, and a D side, and the second irregular polyhedron-shaped magnet assembly has an A' side, a B' side, a C' side, and a D' side. Referring back to the first irregular polyhedron-shaped magnet assembly, the magnet assembly is shown as two magnets (1702, 1704), the first magnet 1702 being shown as a three-part quadrilateral prism such that the first magnet 1702 has a short height along the first axis 1710 and a long length along the second axis 1712. Typically, a quadrilateral prism is a three-dimensional solid having two quadrilateral surfaces or faces (e.g., substantially parallel to the rotor laminations) at either end where the four rectangular faces along the A side, B side, C side, and D side are joined. And the magnetic poles of the magnet are the B side and the D side. Here, the first magnet 1702 can be a single hexagonal prism, or can be three separate prisms (1702A, 1702B, and 1702C). The second magnet 1704 is shown as a hexagonal prism having a long height along the first axis 1710 and a short length along the second axis 1712. Similarly, the second magnet 1704 can be a single hexagonal prism, or can be three separate prisms (1704A, 1704B, and 1704C). Here, the second magnet 1704 has a greater coercivity than the first magnet 1702. The first magnet 1702 and the second magnet 1704 are configured to mate with each other so that the poles of each magnet (1702, 1704) are along the B side and the D side. The magnets (1702 and 1704) are arranged so that if the B side of the first magnet is a north pole and the D side of the first magnet is a south pole, then the B side of the second magnet will be a north pole and the D side of the second magnet will be a south pole, so that they will be in series. The magnet assembly generates a magnetic field that interacts with the stator magnetic field when current is modulated through the stator winding (not shown) to generate a torque at the rotor 220 that causes the rotor 220 to rotate relative to the stator. The magnetic assembly is shown as having multiple corners. When the motor is operating, the interaction between the induced magnetic fields from the stator teeth acting on the magnets (1702 and 1704) causes demagnetization in certain areas of the magnets. Demagnetization can be reduced by changing the shape and composition of the magnets. Here, the magnets (1702 and 1704) are configured so that the coercivity of the second magnet 1704 is greater than the coercivity of the first magnet 1702, thereby reducing demagnetization of the magnetic assembly.

[0075] exist Figure 17, a mirrored magnet assembly is shown, wherein magnets ( 1706 and 1708 ) are mirrored to magnets ( 1702 and 1704 ) along mirror axes 1714 and 1716 , with faces A′, B′, C′, and D′.

[0076] Although exemplary embodiments have been described above, it is not intended that these embodiments describe all possible forms covered by the claims. The terms used in the specification are descriptive and not restrictive, and it should be understood that various changes may be made without departing from the spirit and scope of the present disclosure. As previously mentioned, the features of the various embodiments may be combined to form other embodiments of the present invention that may not be explicitly described or illustrated. Although various embodiments may be described as providing advantages or being superior to other embodiments or prior art implementations relative to one or more desired characteristics, those of ordinary skill in the art recognize that one or more features or characteristics may be compromised to achieve the desired overall system properties, depending on the specific application and implementation. These properties may include, but are not limited to, cost, strength, durability, life cycle cost, marketability, appearance, packaging, size, maintainability, weight, manufacturability, ease of assembly, etc. Therefore, embodiments described as being less desirable than other embodiments or prior art implementations relative to one or more characteristics are not outside the scope of the present disclosure and may be desirable for specific applications.

[0077] According to the present invention, there is provided a permanent magnet electric machine having a rotor defining at least one magnet opening and configured to rotate within a circular opening defined by a stator; and an irregular polyhedron-shaped magnet assembly disposed in the magnet opening and defining a magnetization direction, wherein a height along the magnetization direction and perpendicular to a lamination plane of the rotor is greater at both ends than at a central portion disposed therebetween.

[0078] According to an embodiment, the fractal polyhedron-shaped magnet assembly comprises at least one concave surface substantially perpendicular to the magnetization direction and perpendicular to the lamination plane.

[0079] According to an embodiment, the at least one concave surface comprises at least two flat surfaces.

[0080] According to an embodiment, the at least one concave surface comprises first and second concave surfaces, and wherein the first and second concave surfaces are located on a top and a bottom of the magnet assembly.

[0081] According to an embodiment, the at least one concave surface is a curved surface.

[0082] According to an embodiment, the at least one concave surface is two concave surfaces.

[0083] According to an embodiment, the magnet assembly comprises at least two magnets.

[0084] According to an embodiment, the magnet assembly includes two irregular polyhedron-shaped magnets configured as a double frustum joined at an apex, each magnet having an apex.

[0085] According to an embodiment, the magnet assembly includes three irregular polyhedron-shaped magnets, and the coercivity of the magnets at both ends is greater than the coercivity of the magnets disposed therebetween.

[0086] According to the present invention, a permanent magnet motor is provided, comprising: a rotor defining at least one magnet opening; and an irregular polyhedron-shaped magnet assembly disposed in the magnet opening, having a magnetization direction, and having a cross-sectional area, wherein the cross-sectional area at outer surfaces along an axis perpendicular to the magnetization direction and parallel to a lamination plane of the rotor is larger than the cross-sectional area at a center portion disposed between the outer surfaces.

[0087] According to an embodiment, the irregular polyhedron-shaped magnet assembly is a trapezoidal prism.

[0088] According to an embodiment, the magnet assembly comprises first and second polyhedron-shaped magnets, and wherein a height of the first polyhedron-shaped magnet is greater than a height of the second polyhedron-shaped magnet along the axis.

[0089] According to an embodiment, the coercivity of the first polyhedron-shaped magnet is greater than the coercivity of the second polyhedron-shaped magnet.

[0090] According to an embodiment, the irregular polyhedron-shaped magnet assembly includes three irregular polyhedron-shaped magnets.

[0091] According to an embodiment, the three irregular polyhedral magnets include two outer magnets and a central magnet, which are joined at two planes bisecting the axis such that the height of the outer magnets is greater than that of the central magnet.

[0092] According to an embodiment, the coercivity of the outer polyhedron-shaped magnets is greater than the coercivity of the central magnet.

[0093] According to an embodiment, the magnet assembly comprises outer and central rectangular magnets, wherein the outer thickness of the outer magnets is less than the central thickness of the central magnet, and the coercivity of the outer magnets is greater than the coercivity of the central magnet.

[0094] According to the present invention, a permanent magnet motor is provided, comprising: a rotor defining at least one magnet opening and configured to rotate within a circular opening defined by a stator; and an irregular polyhedron-shaped magnet assembly disposed in the magnet opening, defining an axis perpendicular to the magnetization direction of the magnet assembly and parallel to the rotor laminations, and having a coercivity that varies along the axis.

[0095] According to an embodiment, the irregular polyhedron-shaped magnet assembly includes at least two irregular polyhedron-shaped magnets.

[0096] According to an embodiment, the fractal polyhedron shaped magnet assembly includes two outer magnets and a central magnet, which are joined at two planes bisecting an axis, such that the coercivity of the outer magnets is greater than that of the central magnet.

Claims

1. A permanent magnet motor, comprising: a rotor defining at least one magnet opening and configured to rotate within a circular opening defined by the stator, the at least one magnet opening extending in a lamination plane of the rotor being inclined relative to a radial direction of the rotor; as well as An irregular polyhedron-shaped magnet assembly is disposed in the magnet opening and defines a magnetization direction perpendicular to an extension direction of the magnet opening, wherein a thickness of the irregular polyhedron-shaped magnet assembly along the magnetization direction in a lamination plane of the rotor is greater at both ends than at a central portion disposed therebetween.

2. The permanent magnet motor according to claim 1, wherein: The fractal-polyhedron-shaped magnet assembly includes at least one concave surface that is substantially perpendicular to the magnetization direction and perpendicular to the plane of the laminations.

3. The permanent magnet motor according to claim 2, wherein: The at least one concave surface includes at least two flat surfaces.

4. The permanent magnet motor according to claim 2, wherein: The at least one concave surface includes a first concave surface and a second concave surface, and wherein the first concave surface and the second concave surface are located on a top and a bottom of the fractal-polyhedron-shaped magnet assembly.

5. The permanent magnet motor according to claim 2, wherein: The at least one concave surface is a curved surface.

6. The permanent magnet motor according to claim 5, wherein: The at least one concave surface is two concave surfaces.

7. The permanent magnet motor according to claim 1, wherein: The irregular polyhedron-shaped magnet assembly includes at least two magnets.

8. The permanent magnet motor according to claim 7, wherein: The fractal-polyhedron-shaped magnet assembly includes a pair of congruent frustum-shaped magnets joined to each other at vertices to form a double frustum having a bowtie shape.

9. The permanent magnet motor according to claim 7, wherein: The irregular polyhedron magnet assembly includes three irregular polyhedron magnets, and the coercivity of the magnets at both ends is greater than the coercivity of the magnets disposed therebetween.

10. A permanent magnet motor comprising: a rotor defining at least one magnet opening; as well as A quadrilateral magnet assembly is disposed in one of the at least one magnet openings and includes a first magnet and a second magnet, wherein the cross-section of the first magnet has three straight sides and a first curved side, and the cross-section of the second magnet has two straight sides and a second curved side extending between the two straight sides, wherein the first curved side and the second curved side match each other to engage the first magnet and the second magnet in the quadrilateral magnet assembly.

11. The permanent magnet motor according to claim 10, wherein: The permanent magnet motor also includes another quadrilateral magnet assembly, which is arranged in another magnet opening in the at least one magnet opening, and the other quadrilateral magnet assembly includes a third magnet and a fourth magnet, the cross-section of the third magnet has three straight sides and a first curved side, and the cross-section of the fourth magnet has two straight sides and a second curved side extending between the two straight sides, wherein the first curved side and the second curved side match each other to engage the third magnet and the fourth magnet in the other quadrilateral magnet assembly.

12. The permanent magnet motor according to claim 10, wherein: The coercivity of the first magnet is smaller than the coercivity of the second magnet.

13. The permanent magnet motor according to claim 10, wherein: An extension direction of the magnet opening in a lamination plane of the rotor is inclined relative to a radial direction of the rotor, and the second magnet is closer to an outer edge of the rotor than the first magnet.

Images