A negative q flux interior permanent magnet for a rotor assembly

Abstract

A rotor, an electric motor, and an electric vehicle are provided. The rotor includes a rotor core having multiple poles, multiple rotor cavities defined by each of the multiple poles, and multiple permanent magnets disposed in the rotor cavities. The rotor cavities include a first subgroup and a second subgroup spaced apart from each other. The first subgroup includes a first inner cavity and a second inner cavity, and the second subgroup includes a first outer cavity and a second outer cavity. The second subgroup is located between the first subgroup and an outer rotor surface. The multiple permanent magnets include a first inner magnet disposed in the first inner cavity and a second inner magnet disposed in the second inner cavity, the second inner magnet being shorter than the first inner magnet.

Description

Technical Field

[0001] This disclosure relates to an electric motor rotor, and more particularly to an electric motor having a permanent magnet arrangement structure. Background Technology

[0002] The rotary motor used in the electric drive system of an electric vehicle operates in electric mode, delivering output torque to a connected load (e.g., one or more wheels of the vehicle) and / or in generator mode, utilizing the rotation of the machine to generate electricity. In a typical configuration, the motor comprises a cylindrical rotor formed by an annular stack of thin magnetic rotor laminates. The cylindrical rotor may include multiple permanent magnets.

[0003] Permanent magnets can include, for example, neodymium (Nd) magnets, also known as NdFeB, NIB, or Neo magnets. Neodymium magnets are rare-earth magnets made of neodymium (Nd), iron (Fe), and / or boron (B) alloys. Neodymium magnets have high coercivity (i.e., resistance to demagnetization) and high magnetic energy density. Permanent magnets can be placed in openings or slots in the rotor to generate motor flux with a magnetic field along a predetermined path, which can be enhanced and / or canceled. Enhancing the flux field will increase the torque production of the motor, while suppressing the flux field will limit the torque production of the motor. The configuration and / or topology of the permanent magnets within the rotor determine the power density of the motor.

[0004] While the current rotor has achieved its intended purpose, new and improved rotors are still needed to provide higher torque generation and power density within the motor. Summary of the Invention

[0005] According to several aspects of this disclosure, a rotor is provided. The rotor includes: a rotor core defining an outer rotor surface and an inner rotor surface opposite to the outer rotor surface; a plurality of rotor cavities defined by each of a plurality of poles; and a plurality of permanent magnets respectively disposed in one of the plurality of rotor cavities. The rotor core includes a plurality of poles arranged in a ring about a rotation axis. The rotor cavity is disposed near the outer rotor surface, and the plurality of rotor cavities include at least a first subgroup and a second subgroup spaced apart from each other. The first subgroup includes a first inner cavity and a second inner cavity arranged in a V-shape, and the second subgroup includes a first outer cavity and a second outer cavity arranged in a V-shape. The second subgroup is located between the first subgroup and the outer rotor surface. The plurality of permanent magnets includes a first inner magnet disposed in the first inner cavity and a second inner magnet disposed in the second inner cavity, the second inner magnet being shorter than the first inner magnet.

[0006] According to another aspect of this disclosure, the plurality of permanent magnets comprise alloys of rare earth elements, including at least one of neodymium or samarium.

[0007] According to another aspect of this disclosure, the length of the second inner magnet is equal to the length of each of the plurality of permanent magnets in the second subgroup.

[0008] According to another aspect of this disclosure, the second inner cavity includes a mechanical bridge disposed between the second inner magnet and the outer rotor surface, and the mechanical bridge is aligned with the q-axis.

[0009] According to another aspect of this disclosure, the leakage bridge is disposed between the second cavities and aligned with the q-axis.

[0010] According to another aspect of this disclosure, a mechanical web is disposed between the first inner cavity and the second inner cavity, and the mechanical web is offset from the central pole axis extending through the center of the rotor to the pole center, such that the mechanical web is closer to the second inner magnet than the first inner magnet.

[0011] According to another aspect of this disclosure, a first magnet and a second magnet are disposed in the second inner cavity, and the first magnet and the second magnet have different grades.

[0012] According to another aspect of this disclosure, the first magnet is of a higher grade than the second magnet, and the first magnet is located closer to the rotor center than the second magnet.

[0013] According to another aspect of this disclosure, the width of the second magnet is greater than the width of the first magnet, the first edge of the second magnet is aligned with the first edge of the first magnet, and the second edge of the second magnet is offset from the second edge of the first magnet.

[0014] According to another aspect of this disclosure, the width of the second magnet is greater than the width of the first magnet, the first side of the length of the second magnet deviates from the first side of the length of the first magnet, and the second side of the length of the second magnet deviates from the second side of the length of the first magnet.

[0015] According to several aspects of this disclosure, an electric motor is provided. The electric motor includes a stator having a plurality of electrical conductors and a rotor concentrically disposed relative to the stator. The rotor is rotatable relative to the stator about an axis of rotation, and the rotor is spaced apart from the stator to define an air gap between the stator and the rotor. The rotor includes: a rotor core defining an outer rotor surface and an inner rotor surface opposite to the outer rotor surface; a plurality of rotor cavities defined by each of a plurality of poles; and a plurality of permanent magnets respectively disposed in one of the plurality of rotor cavities. The rotor core includes a plurality of poles arranged in a ring about an axis of rotation. The rotor cavity is disposed near the outer rotor surface, and the plurality of rotor cavities include at least a first subgroup and a second subgroup spaced apart from each other. The first subgroup includes a first inner cavity and a second inner cavity arranged in a V-shape, and the second subgroup includes a first outer cavity and a second outer cavity arranged in a V-shape. The second subgroup is located between the first subgroup and the outer rotor surface. The plurality of permanent magnets includes a first inner magnet disposed in the first inner cavity and a second inner magnet disposed in the second inner cavity, the second inner magnet being shorter than the first inner magnet.

[0016] According to another aspect of this disclosure, the length of the second inner magnet is equal to the length of each of the plurality of permanent magnets in the second subgroup.

[0017] According to another aspect of this disclosure, the second inner cavity includes a mechanical bridge disposed between the second inner magnet and the outer rotor surface, and the mechanical bridge is aligned with the d-axis.

[0018] According to another aspect of this disclosure, the leakage bridge is disposed between the second cavities and aligned with the q-axis.

[0019] According to another aspect of this disclosure, a mechanical mesh is disposed between the first inner cavity and the second inner cavity, and the mechanical mesh is offset from the central pole axis extending through the center of the rotor to the pole center, such that the mechanical mesh is closer to the second inner magnet than the first inner magnet.

[0020] According to another aspect of this disclosure, a first magnet and a second magnet are disposed in the second inner cavity, and the first magnet and the second magnet have different grades.

[0021] According to another aspect of this disclosure, the first magnet is of a higher grade than the second magnet, and the first magnet is closer to the central pole axis than the second magnet.

[0022] According to another aspect of this disclosure, the width of the second magnet is greater than the width of the first magnet, the first side of the length of the second magnet is aligned with the first side of the length of the first magnet, and the second side of the length of the second magnet is offset from the second side of the length of the first magnet.

[0023] According to another aspect of this disclosure, the width of the second magnet is greater than the width of the first magnet, the first side of the length of the second magnet deviates from the first side of the length of the first magnet, and the second side of the length of the second magnet deviates from the second side of the length of the first magnet.

[0024] According to several aspects of this disclosure, an electric vehicle is provided. The electric vehicle includes an electric drive system having an electric motor including a stator and a rotor, the stator including a plurality of electrical conductors, and the rotor being concentrically disposed relative to the stator. The rotor is rotatable relative to the stator about an axis of rotation, and the rotor is spaced apart from the stator to define an air gap between the stator and the rotor. The rotor includes: a rotor core defining an outer rotor surface and an inner rotor surface opposite to the outer rotor surface; a plurality of rotor cavities defined by each of a plurality of poles; and a plurality of permanent magnets respectively disposed in one of the plurality of rotor cavities. The rotor core includes a plurality of poles arranged in a ring about an axis of rotation. The rotor cavities are disposed near the outer rotor surface, and the plurality of rotor cavities include at least a first subgroup and a second subgroup spaced apart from each other. The first subgroup includes a first inner cavity and a second inner cavity arranged in a V-shape, and the second subgroup includes a first outer cavity and a second outer cavity arranged in a V-shape. The second subgroup is located between the first subgroup and the outer rotor surface. The multiple permanent magnets include a first inner magnet disposed in a first inner cavity and a second inner magnet disposed in a second inner cavity, wherein the length of the second inner magnet is shorter than that of the first inner magnet.

[0025] The above-described features and advantages, as well as other features and advantages, of the currently disclosed systems and methods are readily apparent from the detailed description (including the claims) and examples taken in conjunction with the accompanying drawings. Attached Figure Description

[0026] This disclosure can be more fully understood through the following detailed description and accompanying drawings, wherein:

[0027] Figure 1 This is a schematic diagram of a vehicle including an electric motor according to the present disclosure.

[0028] Figure 2 Based on this disclosure Figure 1 The motor and rotor shown are along Figure 1 A schematic diagram of the cross section taken by section line 2-2.

[0029] Figure 3 This illustrates the provisions of this disclosure. Figure 1 The diagram shows a cross-sectional view of multiple pole sections of the rotor, as well as the q-axis and d-axis, wherein the pole sections include multiple asymmetric permanent magnets.

[0030] Figure 4 This illustrates the provisions of this disclosure. Figure 1 The diagram shows a cross-sectional view of the magnetic flux in multiple pole segments of a rotor, where each pole segment comprises multiple asymmetric permanent magnets.

[0031] Figure 5 This illustrates the provisions of this disclosure. Figure 1 The diagram shows a cross-sectional view of multiple pole segments of a rotor, where each pole segment includes multiple asymmetric permanent magnets and a mechanical bridge in each pole segment.

[0032] Figure 6 This illustrates the provisions of this disclosure. Figure 1 The diagram shows a cross-sectional view of multiple pole segments of a rotor, wherein each pole segment comprises multiple asymmetric permanent magnets and mechanical bridges.

[0033] Figure 7 This illustrates the provisions of this disclosure. Figure 1 The diagram shows a cross-sectional view of multiple pole segments of the rotor, wherein each pole segment includes multiple asymmetric permanent magnets, a mechanical bridge, a leakage bridge, and an offset mechanical mesh.

[0034] Figure 8 This illustrates the provisions of this disclosure. Figure 1 The diagram shows a cross-sectional view of multiple pole sections of a rotor, wherein each pole section comprises multiple asymmetric permanent magnets of different grades.

[0035] Figure 9 This illustrates the provisions of this disclosure. Figure 1 The diagram shows a cross-sectional view of multiple pole sections of a rotor, wherein each pole section comprises multiple asymmetric permanent magnets with different grades and demagnetization adjustment dimensions.

[0036] Figure 10 This illustrates the provisions of this disclosure. Figure 1 The diagram shows a cross-sectional view of multiple pole segments of a rotor, wherein each pole segment comprises multiple asymmetric permanent magnets with different grades and demagnetization adjustment dimensions and positions. Detailed Implementation

[0037] The following description is merely exemplary in nature and is not intended to limit this disclosure, its application, or its uses. Furthermore, it is not intended to be bound by any express or implied theory set forth in the foregoing technical field, background art, summary of the invention, or the following detailed description. It should be understood that throughout the drawings, corresponding reference numerals indicate the same or corresponding parts and features.

[0038] Reference will now be made in detail to several examples of this disclosure illustrated in the accompanying drawings. Wherever possible, the same or similar reference numerals are used in the drawings and description to refer to the same or similar parts or steps. The drawings are simplified and not drawn to scale. The following description is merely exemplary in nature and is not intended to limit the scope, application, or purpose of this disclosure.

[0039] This paper discloses a rotor, an electric motor, and an electric vehicle. The rotor includes an asymmetric permanent magnet arrangement. The rotor and electric motor provide higher efficiency in the driving cycle and use fewer permanent magnets. The asymmetric arrangement of the permanent magnets is used to orient the magnetic flux density in the rotor along the negative q-axis when unloaded, thereby delaying rotor saturation and increasing reluctance torque.

[0040] Figure 1 A vehicle 10 is shown, which includes an electric motor 12 (i.e., an electric motor) configured to drive the vehicle 10. The electric motor 12 can be configured to provide torque or force to another component of the vehicle 10, thereby driving the vehicle 10. Therefore, the electric motor 12 is part of a propulsion system 13 of the vehicle 10. In addition to driving the vehicle 10, the electric motor 12 can also be used to power other suitable devices. The electric motor 12 may be a brushless electric motor and includes six substantially identical interconnecting segments 12A arranged side-by-side along a rotation axis X defined along the length of the electric motor 12. However, it is contemplated that the electric motor 12 may include more or fewer segments 12A. The number of interconnecting segments 12A is directly related to the torque that the electric motor 12 is capable of generating to power the vehicle 10. The vehicle 10 includes a body 11 to which the electric motor 12 is coupled.

[0041] Vehicle 10 includes a drivetrain 14 having a gearbox and a drive shaft (not shown). Drivetrain 14 is operatively connected between electric motor 12 and driven wheel 16 via one or more suitable couplers (e.g., constant velocity joints and universal joints (not shown)). This operative connection between electric motor 12 and drivetrain 14 enables electric motor 12 to supply torque to drive wheel 16 to propel vehicle 10.

[0042] The propulsion system 13 also includes a battery (or battery pack) 18 configured to supply electrical energy to the electric motor 12 and other vehicle systems (not shown). For this purpose, the battery 18 is electrically connected to the electric motor 12. Due to this electrical connection, the electric motor 12 is configured to receive electrical energy from the battery 18 and can operate as a generator when driven by a power source external to the vehicle 10. This external power can be provided, for example, by an internal combustion engine (not shown) or by the drive wheels 16 via vehicle inertia.

[0043] Figure 2 A cross-sectional view of a portion of an electric motor 12 taken along a virtual plane P is shown. The electric motor 12 includes a stator 20 having a stator core 19. The stator core 19 has a hole 22, and the stator 20 includes an electrical conductor 24 disposed within the hole 22. The electrical conductor 24 is electrically connected to a battery 18. Figure 1 This electrical connection allows battery 18 ( Figure 1Electrical energy is supplied to the conductor 24. The stator 20 may have a generally annular shape and may be disposed about the axis of rotation X. Furthermore, the stator 20 may define an outer stator surface 23 and an inner stator surface 25 opposite to the outer stator surface 23. Both the outer stator surface 23 and the inner stator surface 25 may define a circumference about the axis of rotation X. The aperture 22 may be disposed closer to the inner stator surface 25 than to the outer stator surface 23, and each aperture is shaped and sized to accommodate one or more conductors 24. As used herein, the term "aperture" includes, but is not limited to, slots, openings, or any cavity in the stator 20 configured and shaped to accommodate at least one conductor 24. The conductors 24 may be made of a suitable conductive material, such as metallic materials like copper and aluminum. The conductors 24 may be configured as strips or windings and may have any suitable shape, such as generally rectangular, cuboid, and cylindrical. Regardless of their shape, the shape and size of each conductor 24 are designed to be accommodated in an aperture 22.

[0044] The electric motor 12 also includes a rotor 26 disposed about the rotation axis X and located within the stator 20. The stator 20 may be concentrically disposed with the rotor 26. The rotor 26 may include various rotor types, as long as the rotor has an integrated permanent magnet motor (IPM) layout. The rotor 26 includes a rotor core 21 formed wholly or partially of a metallic material (e.g., stainless steel), which may have a generally annular shape and defines a plurality of rotor cavities 30 and a plurality of permanent magnets 32 disposed within the rotor cavities 30. The rotor core 21 and the stator 20 may be made of "electrical steel" or "silicon steel" and may include multiple stacks (e.g., each layer about 0.25 mm thick). It is contemplated that the rotor cavities 30 may be configured as slots, although the rotor cavities 30 may have alternative configurations. In addition, the rotor 26 may include different cavity 30 configurations (e.g., one-layer cavity 30, two-layer cavity 30, three-layer cavity 30, etc.). The permanent magnet 32 ​​is tightly mounted in the rotor cavity 30 and may comprise an alloy of rare earth elements such as neodymium and samarium, or any other suitable ferromagnetic material. Suitable ferromagnetic materials may include, for example, neodymium iron boron (NdFeB) alloys and / or samarium cobalt (SmCo) alloys. The permanent magnet 32 ​​may be arranged in a ring around the axis of rotation X and may be configured to magnetically interact with the electrical conductor 24. When the motor 12 is running, the rotor 26 rotates relative to the stator 20 about the axis of rotation X in response to the magnetic flux generated between the electrical conductor 24 and the permanent magnet 32, thereby generating driving torque to power the vehicle 10.

[0045] Rotor 26 defines an outer rotor surface 27 and an inner rotor surface 29 opposite to the outer rotor surface 27. Both the outer rotor surface 27 and the inner rotor surface 29 define a circumference around the axis of rotation X. Motor 12 may define an air gap 31 between the inner stator surface 25 and the outer rotor surface 27. The air gap 31 may have a generally annular shape and may span the rotor 26. Rotor 26 includes a plurality of poles 42 arranged in a ring around a rotor center C, which may coincide with the axis of rotation X. Each pole 42 represents a magnetic pole of motor 12. Although eight poles 42 are shown in the figure, rotor 26 may include more or fewer poles 42. Interpole bridges 44 separate consecutive poles 42 and may extend along their respective interpole shafts 46. Each interpole shaft 46 extends through the rotor center C and substantially through the middle of the corresponding interpole bridge 44 and defines a boundary line between two consecutive poles 42. Consecutive poles 42 have opposite magnetic polarities. Each pole 42 also defines a central pole axis 49 that extends through the rotor center C and substantially through the middle of the pole 42. The central pole axis 49 of each pole 42 may also intersect the axis of rotation X.

[0046] Each pole 42 includes a plurality of magnetic layers 33. In the illustrated embodiment, in each pole 42, the plurality of magnetic layers 33 include a first subgroup 35 and a second subgroup 37. Figure 2 In the illustrated embodiment, the first subgroup 35 is closer to the inner rotor surface 29 than the second subgroup 37, and the second subgroup 37 is closer to the outer rotor surface 27 than the first subgroup 35. In the illustrated embodiment, the first subgroup 35 is the magnetic layer 33 closest to the inner rotor surface 29. Therefore, no other magnetic layer 33 is closer to the inner rotor surface 29 than the first subgroup 35.

[0047] Each magnetic layer 33 includes a plurality of permanent magnets 32 disposed within a rotor cavity 30. The rotor cavity 30 is arranged in a cavity layer 48, corresponding to the magnetic layer 33. In each pole 42, the magnetic layers 33 are spaced apart from each other in the radial direction indicated by arrow R. Although two magnetic layers 33 are shown in the figure, each pole 42 may include more or fewer magnetic layers 33. In the illustrated embodiment, each magnetic layer 33 includes only two permanent magnets 32 spaced apart from each other in the tangential direction indicated by arrow T. In other words, as a non-limiting example, each magnetic layer 33 includes only two permanent magnets 32 to maximize the reluctance torque of the motor 12 without increasing rotational losses. The tangential direction (as indicated by arrow T) may be perpendicular to the radial direction (as indicated by arrow R). Each permanent magnet 32 ​​may be a monolithic structure (i.e., a single-piece structure), or in some cases, the permanent magnet 32 ​​may include multiple magnets.

[0048] Figure 3 and Figure 4A rotor segment 300 with two poles 42 is shown. The rotor segment 300 includes a first subgroup 35 and a second subgroup 37. In this embodiment, rotor cavities 30 are disposed near the outer rotor surface 27. Each rotor cavity 30 includes at least a first subgroup 35 and a second subgroup 37 spaced apart from each other. The first subgroup 35 includes a first inner cavity 302 and a second inner cavity 304 configured in a V-shape, while the second subgroup 37 includes a first outer cavity 306 and a second outer cavity 308, also configured in a V-shape. The second subgroup 37 is disposed between the first subgroup 35 and the outer rotor surface 27. A plurality of permanent magnets 32 may be disposed in each of the plurality of rotor cavities 30. The plurality of permanent magnets 32 includes a first inner magnet 310 disposed in the first inner cavity 302 and a second inner magnet 312 disposed in the second inner cavity 304. In this embodiment, the length L of the second inner magnet 312 is shorter than that of the first inner magnet 310, and the second inner magnet 312 is located deep within the second inner cavity 304 (e.g., away from the air gap). Placing the second inner magnet 312 deep within the cavity 304 allows the magnetic flux to be oriented towards the negative q-axis. In some embodiments, the length of the second inner magnet 312 is equal to the length of each of the plurality of permanent magnets 32 in the second subgroup 37. Positive and negative d-axis (direct axes) and positive and negative q-axis (quadrature axes) are shown. The d-axis is aligned with the magnetic field of the permanent magnets 32 on the rotor 26 and represents the magnetic field component directly aligned with the rotor magnetic field. The q-axis is orthogonal (90 degrees) to the d-axis and represents the magnetic field component perpendicular to the rotor magnetic field. The q-axis current is responsible for generating torque, while the d-axis current can be used to control the magnetic field strength. When the d-axis current is negative, it weakens the magnetic field; this technique is called "magnetic field weakening." To maximize torque density, both the rotor 26 and stator 20 of the motor 12 are designed with strong saturation. Reluctance torque is highly sensitive to the saturation of the rotor material. The length L of the second inner magnet 312 is shorter than the length L of the first inner magnet 310 to reduce the number of magnets and to delay saturation-enhanced torque when the magnetic flux is oriented in the negative q-axis direction. Figure 3 In the example shown, one second inner magnet 312 is oriented along the positive d-axis and the negative q-axis (d+; q-), while the other second inner magnet 312 is oriented along the negative d-axis and the positive q-axis (d-; q+).

[0049] Figure 4 It shows Figure 3 The rotor segment 300 is shown. In this view, the magnetic field 402 and magnetic flux density orientation are shown to be aligned with the negative d-axis when there is no load (i.e., no stator current and no torque). Since the length L of the second inner magnet 312 is shorter than that of the first inner magnet 310, the magnetic field 402 undergoes flux bending along the negative q-axis as saturation 404 is delayed. Figure 4 As shown.

[0050] Figure 5An embodiment of a rotor segment 500 with a mechanical bridge 502 is shown, which is used to increase the bending of the no-load magnetic flux and generate magnetic leakage. In this embodiment, the second inner cavity 304 includes a mechanical bridge 502 disposed between the second inner magnet 312 and the outer rotor surface 27, wherein the mechanical bridge 502 is partially oriented along the q-axis. The mechanical bridge 502 may include a segment of rotor material passing through the second inner cavity 304 and being within the pole. The mechanical bridge 502 generates a leakage path saturated by the q-axis magnetic flux (i.e., the flux that generates torque) and the negative d-axis magnetic flux. As described above, the mechanical bridge 502 is located only within the second inner cavity 304 to achieve the aforementioned advantages and does not act as a flux barrier relative to the flux that generates torque. Within each pole 42, the mechanical bridge 502 is positioned closer to the outer rotor surface 27 than to the inner rotor surface 29.

[0051] Figure 6 An embodiment of a rotor segment 600 is shown, which has a mechanical bridge 502 that provides mechanical strength and also generates magnetic leakage. A second inner cavity 304 extends to the outer rotor surface 27 but does not penetrate it. The mechanical bridge 502 is aligned with the q-axis and reduces saturation of the q-axis center path due to the return flux.

[0052] Figure 7 An embodiment of a rotor segment 700 with a mechanical bridge 502, a leakage bridge 602, and a mechanical mesh 702 is shown. The mechanical mesh 702 is disposed between a first inner cavity 302 and a second inner cavity 304, and is offset from the rotor pole axis 704 extending along the pole edge toward the rotor center 42, such that the mechanical mesh 702 is closer to the second inner magnet 312 than the first inner magnet 310. The closer position of the mechanical mesh 702 to the second inner magnet 312 reduces the magnetic flux loops on the mechanical mesh. The magnetic flux in the positive q-axis direction near the mechanical mesh 702 is used to increase saturation.

[0053] Figure 8 An embodiment of a rotor segment 800 having a plurality of permanent magnets disposed within a second inner cavity 304 is shown. In this example, the plurality of magnets includes a first magnet 802 and a second magnet 804. The first magnet 802 and the second magnet 804 have different grades (e.g., higher grades), and the first magnet 802 is located closer to the inner rotor surface 29 than the second magnet 804, which is located closer to the outer rotor surface 27. Furthermore, the first magnet 802 has a width w1 and a length L1, and the second magnet 804 has a width w2 and a length L2. In this embodiment, the width w1 and the width w2 are the same, and the length L1 is greater than the length L2.

[0054] Different grades of permanent magnet 32 ​​may include total magnetic strength and / or resistance to demagnetization. Some examples of different grades of permanent magnet 32 ​​include neodymium magnets (NdFeB) (which are currently the strongest permanent magnets available, with high magnetic field strength and high energy density), samarium cobalt magnets (SmCo) (with lower energy than neodymium magnets), ceramic (ferrite) magnets (which have good resistance to demagnetization), AlNiCo magnets, and / or bonded magnets. In a specific example, the first magnet 802 includes neodymium magnets, while the second magnet includes samarium magnets. It should be understood that the first magnet 802 and the second magnet 804 may include other types of magnets and / or configurations. When different grades of permanent magnets are combined together, a negative q-axis flux mode can be obtained.

[0055] Figure 9 An embodiment of a rotor segment 900 having a plurality of magnets disposed within a second inner cavity 304 is shown. In this example, the plurality of magnets includes a first magnet 802 and a second magnet 804. The first magnet 802 and the second magnet 804 have different grades, and the first magnet 802 is positioned closer to the inner rotor surface 29 than the second magnet 804, while the second magnet 804 is positioned closer to the outer rotor surface 27. Furthermore, the first magnet 802 has a width w1 and a length L1, and the second magnet 804 has a width w2 and a length L2. In this embodiment, the width w2 is greater than the width w1, and the length L1 is greater than the length L2. Furthermore, the first edge 902 of the second magnet 804 is aligned and flush with the first edge 904 of the first magnet 804, and the second edge 908 of the second magnet 804 is offset from the second edge 906 of the first magnet 802. Using a second magnet 804 with a larger width w2 can prevent demagnetization of the second magnet 804.

[0056] Figure 10 An embodiment of a rotor segment 1000 having a plurality of magnets disposed within a second inner cavity 304 is shown. In this example, the plurality of magnets includes a first magnet 802 and a second magnet 804. The first magnet 802 and the second magnet 804 have different grades, and the first magnet 802 is located closer to the inner rotor surface 29 than the second magnet 804, while the second magnet 804 is located closer to the outer rotor surface 27. Furthermore, the first magnet 802 has a width w1 and a length L1, and the second magnet 804 has a width w2 and a length L2. In this embodiment, the width w2 is greater than the width w1, and the length L1 is greater than the length L2. Furthermore, the first edge 902 of the first magnet 802 is offset from the first edge 904 of the second magnet 804, and the second edge 908 of the second magnet 804 is offset from the second edge 906 of the first magnet 802. Using a second magnet 804 with a larger width w2 can avoid demagnetization of the second magnet 804 and avoid center path saturation.

[0057] The rotor 26 and motor 12 disclosed herein offer advantages and benefits over the prior art. The rotor 26 and motor 12 provide higher efficiency in the drive cycle and use fewer permanent magnets. The permanent magnets are arranged asymmetrically to orient the magnetic flux density in the rotor 26 along the negative q-axis, thereby delaying rotor saturation and increasing reluctance torque.

[0058] This description is illustrative in nature and is not intended to limit the scope of this disclosure, its application, or its uses. The broad teachings of this disclosure can be implemented in many forms. Therefore, although this disclosure includes specific examples, its true scope should not be limited thereto, as other modifications will become apparent upon examination of the drawings, specification, and appended claims.

Claims

1. A rotor, comprising: A rotor core defining an outer rotor surface and an inner rotor surface opposite to the outer rotor surface, wherein the rotor core includes a plurality of poles arranged annularly about a rotation axis; A plurality of rotor cavities, each defined by a plurality of poles, wherein the rotor cavities are disposed near the outer rotor surface, wherein the plurality of rotor cavities include at least a first subgroup and a second subgroup spaced apart from each other, wherein the first subgroup includes a first inner cavity and a second inner cavity configured in a V-shape, wherein the second subgroup includes a first outer cavity and a second outer cavity configured in a V-shape, and wherein the second subgroup is disposed between the first subgroup and the outer rotor surface; as well as Multiple permanent magnets are respectively disposed in each of the multiple rotor cavities, wherein the multiple permanent magnets include a first inner magnet disposed in the first inner cavity and a second inner magnet disposed in the second inner cavity, wherein the length of the second inner magnet is shorter than that of the first inner magnet.

2. The rotor according to claim 1, wherein, The plurality of permanent magnets comprise an alloy of rare earth elements, wherein the rare earth elements include at least one of neodymium or samarium.

3. The rotor according to claim 1, wherein, The length of the second inner magnet is equal to the length of each of the plurality of permanent magnets in the second subgroup.

4. The rotor according to claim 1, wherein, The second inner cavity includes a mechanical bridge disposed between the second inner magnet and the outer rotor surface, wherein the mechanical bridge is aligned with the q-axis.

5. The rotor according to claim 4, wherein, The leakage bridge is disposed between the second inner cavities and aligned with the q-axis.

6. The rotor according to claim 1, wherein, A mechanical mesh is disposed between the first inner cavity and the second inner cavity, wherein the mechanical mesh is offset from the central pole axis extending through the center of the rotor to the pole center, such that the mechanical mesh is closer to the second inner magnet than the first inner magnet.

7. The rotor according to claim 1, wherein, The second inner cavity is provided with a first magnet and a second magnet, wherein the first magnet and the second magnet have different grades.

8. The rotor according to claim 7, wherein, The first magnet is of a higher grade than the second magnet, and the first magnet is closer to the rotor center than the second magnet.

9. The rotor according to claim 7, wherein, The width of the second magnet is greater than the width of the first magnet, the first edge of the second magnet is aligned with the first edge of the first magnet, and the second edge of the second magnet is offset from the second edge of the first magnet.

10. The rotor according to claim 7, wherein, The width of the second magnet is greater than the width of the first magnet, the first side of the length of the second magnet deviates from the first side of the length of the first magnet, and the second side of the length of the second magnet deviates from the second side of the length of the first magnet.

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