Spoke rotor with segmented bulk magnet

Abstract

A rotor assembly for an electric motor includes a rotor core and a plurality of magnets. The rotor core defines an axis of rotation. Each magnet includes a magnet stem portion and a magnet arm portion. The magnet stem portion extends radially relative to the axis of rotation to present a radially outermost stem end. The magnet arm portion is at least partially located radially outward of the stem end. Additionally, the magnet arm portion extends circumferentially in an opposite direction relative to the magnet stem portion.

Description

Technical Field

[0001] The embodiments described herein generally relate to a rotor assembly for an electric motor. More specifically, embodiments of the invention relate to a rotor assembly having segmented, high-capacity magnets. Background Technology

[0002] At least some known spoked rotor motors employ flat, rectangular magnetic plates arranged radially like blades on a propeller wheel, but with disc-shaped laminated steel sectors between each "blade." Spoked rotor motors typically concentrate the flux generated by two adjacent magnetic poles onto the curved surface of a single steel sector, thereby producing a higher flux density than a single magnet mounted on the rotor surface. Consequently, the flux concentration characteristic of spoked rotor motors generally allows for the use of cheaper magnetic materials to achieve motor performance comparable to surface-mount rotor motors containing stronger but more expensive rare-earth materials.

[0003] However, cheaper materials typically produce a much weaker magnetic field per unit volume. Therefore, when concentrated on the poles, a larger magnet volume is needed to provide sufficient total magnetic flux. One of the most important magnet dimensions is the thickness of the magnet plates. Generally, a greater thickness results in better motor performance. However, thicker magnets can interfere with each other near the rotor center. Reducing the radial height of the magnets provides additional space near the rotor center but reduces the available total flux.

[0004] The use of conical magnets can alleviate magnet congestion at the rotor center. However, conical magnets are susceptible to serious manufacturing problems caused by significant variations in the thickness of the ferrite material. Cracking occurs in conical ferrite magnets in most grades of ferrite materials. Therefore, simply making the magnets conical to solve congestion at the rotor center leads to high costs and production problems. Summary of the Invention

[0005] This summary is provided to present the inventive concept in a simplified form, which will be further described below in the detailed description. This summary is not intended to identify key or principal features of the claimed subject matter, nor is it intended to limit the scope of the claimed subject matter. Other aspects and advantages of this disclosure will become apparent from the following detailed description and accompanying drawings of the embodiments.

[0006] In one aspect, a rotor assembly for an electric motor is provided. The rotor assembly includes a rotor core defining an axis of rotation and a plurality of magnets spaced in an arc around the rotor core. Each magnet includes a magnet rod portion and a magnet arm portion. The magnet rod portion extends radially relative to the axis of rotation to present a radially outermost rod end. The magnet arm portion is at least partially located radially outside the rod end and extends circumferentially in the opposite direction relative to the magnet rod portion.

[0007] The advantages of these and other embodiments will become more apparent to those skilled in the art from the following description of exemplary embodiments shown and described by way of illustration. As will be appreciated, the embodiments of the invention described herein may be other different embodiments, and their details may be modified in various aspects. Therefore, the drawings and descriptions should be considered illustrative in nature and not restrictive. Attached Figure Description

[0008] The accompanying drawings described below depict various aspects of the systems and methods disclosed therein. It should be understood that each drawing depicts one embodiment of a specific aspect of the disclosed systems and methods, and each drawing is intended to be consistent with its possible embodiments. Furthermore, where possible, the following description refers to the reference numerals included in the following drawings, wherein features depicted in multiple drawings are indicated by consistent reference numerals.

[0009] Figure 1 This is a perspective view of an exemplary electric motor according to one aspect of the present invention;

[0010] Figure 2 yes Figure 1 An exploded perspective view of at least a portion of the electric motor shown;

[0011] Figure 3 yes Figure 1 The perspective view of the rotor assembly of the electric motor shown illustrates the insertion of a permanent magnet into an axially extending magnet receiving slot in the rotor core.

[0012] Figure 4 yes Figure 3 The front view of the rotor assembly shown;

[0013] Figure 5 It is used to limit Figure 3 A perspective view of the laminated rotor core of the rotor assembly shown;

[0014] Figure 6 yes Figure 5 A frontal plan view of one of the stacked pieces shown;

[0015] Figure 7 yes Figure 6 An enlarged partial front view of the outer portion of the stacked plates shown;

[0016] Figure 8 yes Figure 7 Another enlarged partial front view of the outer portion of the stacked sheets shown; and

[0017] Figure 9 yes Figure 8 An enlarged partial front view of the central portion of the stacked pieces shown.

[0018] Unless otherwise indicated, the accompanying drawings provided herein are intended to illustrate features of embodiments of the present disclosure. These features are thought to be applicable to various systems that include one or more embodiments of the present disclosure. Therefore, the drawings are not intended to include all conventional features that a person of ordinary skill in the art would need to know to practice the embodiments disclosed herein. While the drawings do not necessarily provide precise dimensions or tolerances for the parts or structures shown, they are drawn to scale with respect to the relationships between the parts of the structures shown. Detailed Implementation

[0019] The following detailed description of embodiments of the present disclosure is taken with reference to the accompanying drawings. The embodiments are intended to describe aspects of the present disclosure in sufficient detail to enable those skilled in the art to practice the disclosure. The embodiments of the present disclosure are illustrated by way of example and not by way of limitation. Other embodiments may be adopted, and changes may be made without departing from the scope of the claims. Therefore, the following description is not restrictive. The scope of the present disclosure is defined only by the appended claims and the full scope of their equivalent features.

[0020] In this specification, references to "an embodiment," "an embodiment," or "an embodiment" mean that one or more features mentioned are included in at least one embodiment of the present technology. Individual references to "an embodiment," "an embodiment," or "an embodiment" in this specification do not necessarily refer to the same embodiment and are not mutually exclusive, unless so stated and / or will be apparent to those skilled in the art from the description. For example, features, structures, steps, etc., described in one embodiment may also be included in other embodiments, but are not necessarily included. Therefore, the present technology can include various combinations and / or integrations of the embodiments described herein.

[0021] In the following description and claims, several terms will be used, and these terms should be defined as having the following meanings. The singular forms “a,” “an,” and “the” include multiple referents unless the context clearly indicates otherwise. “Optional” or “optionally” means that the event or situation subsequently described may or may not occur, and the description includes both the occurrence and non-occurrence of the event.

[0022] As used throughout the description and claims, approximate terms may be applied to modify any quantitative representation that allows for changes without altering the essential function it relates to. Therefore, values ​​modified by one or more terms such as “about,” “approximately,” and “generally / substantially” are not limited to the specified precise value. In at least some instances, approximate terms may correspond to the precision of the instrument used to measure that value. Here and throughout the description and claims, scope limitations may be combined and / or interchanged. Unless the context or language otherwise indicates, these scopes are identified and include all subscopes contained herein.

[0023] As used herein, the terms “axial” and “axially” refer to a direction and orientation that extends generally parallel to the longitudinal or rotational axis of the motor assembly. The terms “radial” and “radially” refer to a direction and orientation that extends generally perpendicular to the rotational axis. The terms “tangential” and “tangential direction” refer to a direction and orientation that extends generally perpendicular to the radial direction of the motor assembly. Additionally, as used herein, the terms “circumferential” and “circumferentially” refer to a direction and orientation that extends in a general direction around the rotational axis of the motor assembly (such references are not limited to purely circular extensions or the periphery or outer circumference of an object, unless the context clearly indicates otherwise). Furthermore, directional references such as “top / up,” “bottom / down,” “front / rear,” “back / back,” and “side” are used herein for convenience only and should be understood only relative to each other. For example, in practice, a component may be oriented such that the surfaces referred to herein as “top” and “bottom” are, in practice, laterally, angled, inverted, etc., relative to a chosen frame of reference.

[0024] In summary, this disclosure relates to a spoke-type rotor motor comprising a geometry in each laminated rotor core magnet slot to increase the volume of the permanent magnet housed therein. Each magnet slot is typically defined as a “T” shape, wherein the corresponding magnet comprises two (2) commonly used flat rectangular plate magnets. Simple plate magnets are common and are manufactured in highly optimized production processes. The magnet arms (i.e., the horizontal portion of the “T”) are magnetized to retain the approximate circumferential orientation of the magnetic poles. The magnet shanks (i.e., the vertical portion of the “T”) are positioned in a conventional spoke-type rotor orientation and have a circumferential profile thinner than the circumferential profile of the arm portion, which facilitates positioning and assembly in congested areas near the center of the rotor core. Furthermore, this disclosure provides a geometry for positioning the magnet arms relative to the nominal outer circumferential surface of the rotor core to reduce the demagnetizing field strength that may be generated by the motor windings.

[0025] One advantage of this spoked rotor design is that it eliminates the need for conical magnets, which are prohibitively expensive to manufacture and highly susceptible to cracking. Instead, the simple plate magnets provided by this invention significantly reduce costs and increase productivity. Another benefit is the ability to increase the magnetic flux concentrated on each pole of the rotor by increasing the volume of magnetic material in each pole. Increased magnetic flux contributes to improved motor performance.

[0026] Exemplary electric motor

[0027] Figure 1 This is a perspective view of an exemplary electric motor 10 according to one aspect of the present invention. Figure 2 This is an exploded perspective view of at least a portion of the electric motor 10. In this exemplary embodiment, the electric motor 10 is shown as an internal rotor motor. As will be described, an internal rotor motor has magnets positioned radially inward relative to windings serving as a stator. However, according to some aspects of the invention, the electric motor 10 may alternatively be an external rotor motor or a dual rotor motor.

[0028] like Figure 2 As shown, the illustrated electric motor 10 generally includes a stator assembly 12 and a rotor assembly 14, which are substantially enclosed within a housing 16. The rotor assembly 14 is supported to rotate relative to the stator assembly 12 about a rotation axis “A”. The housing 16 is generally cylindrical in shape and includes a cavity 18 for receiving at least a portion of the stator assembly 12 and the rotor assembly 14.

[0029] The stator assembly 12 is generally annular in form and defines a stator axis coaxial with the rotation axis "A". However, according to some aspects of the invention, these axes may be non-coaxial. The stator assembly 12 preferably includes a stator core 20 and a plurality of coils 22 wound around the stator core 20. Furthermore, in some embodiments, the stator assembly 12 includes a plurality of electrically insulating covers 26 positioned between the stator core 20 and the coils.

[0030] The stator core 20 is preferably made of steel and may be a one-piece or laminated structure. Alternatively or additionally, the stator core 20 may be segmented in form. However, according to certain aspects of the invention, the stator core 20 may be made of any one or more of a variety of suitable materials and / or construction methods.

[0031] The stator core 20 preferably comprises an annular yoke (not shown) and a plurality of arcuately spaced teeth (not shown) extending at least generally radially inward from the yoke. It is contemplated that the stator core 20 may have any number of teeth enabling the motor 10 to function as described herein. A plurality of coils 22 are formed by conductive wiring wound around each tooth. The wiring surrounds each tooth to form a coil 22, wherein each coil 22 corresponds to one of the teeth. The wiring is preferably copper, although aluminum or any one or more of a variety of conductive materials may be used without departing from the scope of the invention.

[0032] In this exemplary embodiment, rotor assembly 14 is depicted as a brushless permanent magnet rotor assembly and includes a rotor core 24, a rotor shaft 28, and a shaft connector 40. The rotor shaft 28 defines the axis of rotation of rotor assembly 14. As will be described in more detail below, rotor assembly 14 also includes a plurality of magnets 48, each magnet including a magnet rod portion 48a and a magnet arm portion 48b. The axis of rotation of rotor assembly 14 is coaxial with the axis of rotation “A”. Note that according to certain aspects of the invention, rotor core 24 may be configured for use in a generator or other motor including stator assembly 12.

[0033] The rotor core 24 is typically cylindrical and preferably made of steel. The rotor core 24 can be a one-piece or laminated structure. Alternatively or additionally, the rotor core 24 can be segmented in form. However, according to certain aspects of the invention, the rotor core 24 can be made of any one or more of a variety of suitable materials and / or construction methods.

[0034] As described above, the electric motor 10 includes a housing 16. The housing 16 is generally cylindrical in shape and extends generally circumferentially around the stator assembly 12. Alternatively, according to certain aspects of the invention, the housing 16 may extend around the stator assembly 12 to provide one or more flat sides or otherwise be shaped. In this exemplary embodiment, the housing 16 has axially opposed first housing ends 32 and second housing ends 34, and extends substantially continuously around the stator assembly 12 and rotor assembly 14 to at least partially enclose the stator assembly 12 and rotor assembly 14. According to certain aspects of the invention, the housing 16 includes openings or slots therethrough. For example, in some embodiments, one or more openings or slots may be provided to facilitate ventilation and / or contact / access.

[0035] The housing 16 forms part of the motor housing 46 of the electric motor 10. The motor housing 46 includes the housing 16 and a first end cover 36 and a second end cover 38. The housing 16, the first end cover 36, and the second end cover 38 together define a motor chamber 30 that at least substantially receives the stator assembly 12 and the rotor assembly 14. More specifically, the first end cover 36 is positioned adjacent to and connected to the first housing end 32. Additionally, the second end cover 38 is positioned adjacent to and connected to the second housing end 34. Specifically, the housing 16 is connected to and held in place therebetween the first end cover 36 and the second end cover 38 by a plurality of fasteners (not shown) extending between and connected to the first end cover 36 and the second end cover 38. It is contemplated that, in some aspects of the invention, one or more of the first end cover 36 and the second end cover 38 may be located inside or spaced outward from the respective first housing end 32 and the second housing end 34.

[0036] The electric motor 10 includes a first bearing assembly 42 and a second bearing assembly 44, which cooperatively and rotatably support the rotor shaft 28 of the rotor assembly 14. A first end cover 36 is configured to support the first bearing assembly 42, while a second end cover 38 is configured to support the second bearing assembly 44. Alternative or additional bearing assembly supports may be provided without departing from the scope of the invention.

[0037] Rotor assembly

[0038] Figure 3 This is a perspective view of the rotor assembly 14 of the electric motor 10, showing a pair of permanent magnet rods 48a and magnet arms 48b inserted into an axially extending magnet receiving slot 50 of the rotor core 24. Figure 4 This is a front plan view of the rotor assembly 14. In this exemplary embodiment, the rotor shaft 28 extends axially through the rotor core 24 to define a rotation axis "A". The rotor shaft 28 is fixedly coupled to the rotor core 24 and positioned concentrically relative to the rotor core. The rotor shaft 28 includes a first end 52 extending forward from the rotor core 24 and a shorter second end 53 extending rearward from the rotor core 24. The rotor shaft 28 includes a keyway 54 defined therein for locking the laminations of the rotor core 24, as described herein. The second end 53 includes a slot 55, although in some aspects of the invention, the slot 55 may be omitted.

[0039] The rotor assembly 14 includes a plurality of magnet receiving slots 50 arranged in an arc around the rotation axis "A" or rotor shaft 28. Preferably, the magnet receiving slots are evenly spaced. However, according to some aspects of the invention, an uneven arrangement or a variable-spaced arrangement is permitted. The rotor assembly 14 also includes a plurality of permanent magnet rods 48a and magnet arms 48b, wherein each magnet receiving slot 50 includes one (1) magnet rod 48a and one (1) magnet arm 48b inserted therein. In this exemplary embodiment, the rotor core 24 and the magnet rods 48a and magnet arms 48b are rigidly connected together and configured to rotate together with the rotor shaft 28.

[0040] In this exemplary embodiment, the rotor core 24 is made of a plurality of laminations 56, each of which can rotate or be offset in an arc / bow shape about the rotation axis "A". The laminations 56 are in the form of plates or laminations 156 (see...). Figure 6 The laminations are arranged in a face-to-face contact manner or stacked, such that the rotor core 24 extends a predetermined length along the rotation axis "A". Each lamination stack 56 has opposing axial faces 110 and 112 (see...). Figure 5 ), wherein one of faces 110 or 112 faces a first axial direction and the other faces the opposite axial direction. The plurality of laminations 156 defining each stack are preferably interlocked (e.g., connected to each other), although some aspects of the invention contemplate the use of loose laminations. In this exemplary embodiment, each lamination 156 is made of a suitable material by, for example, machining, stamping, punching, etc. (materials include, but are not limited to, magnetically conductive materials, such as iron, steel, or steel alloys). Note that in various aspects of the invention, laminations may include laminations of different forms or laminations having substantially the same form.

[0041] As described above, the rotor core 24 includes a plurality of generally radially extending magnet receiving slots 50. Each magnet receiving slot 50 is positioned within a pole sector 58 of the rotor assembly 14. The illustrated embodiment includes ten (10) magnet receiving slots 50, thereby defining ten (10) rotor pole sectors 58. Note that in other aspects of the invention, the rotor core 24 may include more or fewer pole sectors 58, depending on design requirements. It should also be noted that the magnet rod portions 48a and magnet arm portions 48b are shown schematically to some extent for illustrative purposes, but are generally sized to fit snugly within the magnet receiving slots 50 to facilitate a firm, non-moving fit with the rotor core 24. The illustrated embodiment depicts a single pair of magnet rod portions 48a and magnet arm portions 48b extending approximately along the entire axial length of the corresponding magnet receiving slot 50 of each lamination stack 56. However, aspects of the present invention envision a plurality of axially arranged magnet rod portions 48a and magnet arm portions 48b located within each corresponding magnet receiving slot 50.

[0042] Reference Figure 3 In this exemplary embodiment, the rotor assembly 14 includes four (4) laminations 56 defining a rotor core 24. As described herein, the exemplary rotor core 24 is a ten (10) pole rotor core. Figure 3 and Figure 4 Each lamination stack 56 shown is substantially identical. However, to limit the offset of the rotor core 24, axially adjacent lamination stacks 56 are rotated by a predetermined amount relative to each adjacent lamination about the rotation axis "A". In a preferred embodiment, each lamination stack 56 is rotated in the same direction relative to its adjacent lamination by an amount equal to approximately four degrees (4°). For example, each lamination stack 56 may be rotated by an amount in the range of approximately three degrees (3°) to approximately five degrees (5°). In other aspects of the invention, the lamination stacks 56 may be rotated about the rotation axis "A" by any alternative amount that enables the rotor core 24 to function as described herein.

[0043] Exemplary stack

[0044] Figure 5 This is a perspective view of a laminated layer 56 according to one aspect of the present invention. Figure 6 yes Figure 5 A frontal plan view of one of the stacked sheets 156 of the stacked sheets 56 shown. Figure 7 and Figure 8 yes Figure 6 The enlarged partial frontal view of the exterior of the stack 156 shown particularly illustrates its geometric features. Figure 9 yes Figure 6 An enlarged partial front view of the central portion of the stacked piece 156 is shown, highlighting its geometric features. (Refer to...) Figure 6 As described above, the lamination 156 defines ten (10) magnetic pole sectors 58. Each magnet receiving slot 50 is located radially outside the rotation axis “A” of the rotor core 24, which is shown as the center of the lamination 156.

[0045] The lamination 156 includes a plurality of central slot axes 72. A plurality of radial pole nodes 74 extend through the center of the lamination 156 (e.g., the axis of rotation "A"), wherein each radial pole node 74 is angularly centered between adjacent pairs of magnet receiving slots 50, such that each pair of adjacent magnet receiving slots 50 is symmetrically arranged about its respective radial pole node 74. Each radial pole node 74 defines a boundary between two adjacent pole sectors 58, wherein adjacent radial pole nodes 74 define pole sectors 58 between them. Each central slot axis 72 passes through the center of rotation of the lamination 156 and bisects the corresponding pole sector 58 (i.e., angularly centered between adjacent radial pole nodes 74). Figure 6For clarity, only four (4) slot axes 72 are shown.

[0046] The lamination 156 preferably includes a plurality of substantially similar magnetic pole segments 60 arranged in an arc around the axis of rotation "A" (or, alternatively described, around the rotor shaft 28). The magnetic pole segments 60 extend from the central hub 92 of the lamination 156. In a preferred embodiment, as Figure 4 As shown, the magnetic pole segments 60 and the corresponding magnets 48 alternate in an arc shape, such that each of the magnets 48 is inserted between circumferentially adjacent magnetic pole segments 60.

[0047] Preferably, the magnetic pole segments 60 are evenly spaced around the rotation axis "A". Each magnet 48 is preferably centrally positioned between circumferentially adjacent magnetic pole segments 60. Furthermore, each magnet 48 is preferably in direct contact with a circumferentially adjacent magnetic pole segment among the magnetic pole segments 60. However, it should be noted that in some aspects of the invention, non-uniform or variable spacing of the magnetic pole segments 60 may be used.

[0048] In this exemplary embodiment, the lamination stack 56 has a thickness ranging from approximately five-tenths of an inch (0.5”) to approximately seven-tenths of an inch (0.7”). However, in other aspects of the invention, the lamination stack thickness may include any alternative measures that enable the lamination stack 56 to function as described herein. The aforementioned range increases the strength of the rotor core 24 and reduces its manufacturing cost.

[0049] Reference Figure 6 The magnetic pole segment 60 includes a radially outer surface 62, which at least partially and cooperatively defines an annular nominal circumferential surface, indicated by reference numeral "B". Note that the annular nominal circumferential surface "B" is an imaginary shape that substantially corresponds to the radially outermost dimension of the lamination 156.

[0050] In this exemplary embodiment, the magnetic pole segments 60 are formed to be generally symmetrical with respect to the radial magnetic pole nodes 74. Each magnetic pole segment 60 includes a body 64 and a pair of tabs 66. Each tab 66 extends outward from the body 64 in a generally arcuate / curved shape (e.g., generally circumferentially) relative to each other.

[0051] like Figure 6As shown, the body 64 is generally wedge-shaped. Specifically, the body 64 includes a radially outer surface 62 (described above) generally centered on the corresponding radial pole node line 74. The body 64 further includes a pair of arcuately spaced opposing body edges 68 and a pair of arcuately spaced opposing sidewalls 70 extending generally radially from the body edges 68. In a preferred embodiment, the sidewalls 70 of a given pole segment 60 each extend inwardly toward each other (i.e., taper), each sidewall 70 being generally parallel to the corresponding central slot axis 72. Thus, adjacent sidewalls 70 of each pair of adjacent pole segments 60 extend generally parallel to each other. This is advantageous because common flat rectangular plate magnets, such as magnet rods 48a, can be used in the rotor assembly 14.

[0052] Each tab 66 includes a radially outermost arcuate / arc-shaped tab surface 76 that extends generally circumferentially directly from the corresponding body edge 68. However, it is contemplated that, according to some aspects of the invention, the tab surface 76 may be generally planar and / or have other geometric features. Each tab 66 also includes a radially innermost tab surface 78 located radially inside the corresponding tab surface 76. The innermost tab surface 78 extends directly from a corresponding sidewall 70. Each tab 66 also includes an end face 80. Each end face 80 is generally arcuately spaced from the body 64 and extends generally radially between and connects to the corresponding tab surface 76 and tab surface 78.

[0053] In this exemplary embodiment, each of the radially outer surfaces 62 of the magnetic pole segment 60 is formed concentric with the axis of rotation "A". That is, each radially outer surface 62 extends along a circular path and its center of curvature coincides with the axis of rotation "A". Alternatively, in some aspects of the invention, it is conceivable that the radially outer surfaces 62 may include alternative geometries.

[0054] As described above, the outermost tab surface 76 extends generally circumferentially from the body edge 68. Additionally, in this exemplary embodiment, the tab surface 76 extends radially inward from the corresponding body edge 68. That is, each tab surface 76 extends radially inward to be positioned radially inside the annular nominal circumferential surface "B". The innermost tab surface 78 of the tab 66 and each corresponding sidewall 70 form an approximately right angle (i.e., a 90° angle) between them.

[0055] like Figure 7As shown, the body 64 further includes a pair of arch-spaced opposing recesses 82, each recess 82 being defined in a corresponding sidewall 70. Specifically, for each opposing recess 82, the body 64 includes a radially outermost recess surface 84 extending generally circumferentially inward from the sidewall 70 toward a corresponding radial pole node line 74 of the corresponding pole segment 60. The outermost recess surface 84 is radially spaced inward from the annular nominal circumferential surface “B” by a predetermined distance, as further described below. The outermost recess surface 84 and each corresponding sidewall 70 form an approximately right angle (i.e., 90°) between them. The body 64 also includes a tapered wall 86 extending generally inward from the outermost recess surface 84 at an angle α. The angle α is preferably between about thirty degrees (30°) and sixty degrees (60°). In a preferred embodiment, the angle α is about forty-five degrees (45°).

[0056] Furthermore, the body 64 includes a radially innermost recessed surface 88 extending generally circumferentially inward from the sidewall 70. In a preferred embodiment, the innermost recessed surface 88 is generally parallel to the outermost recessed surface 84. The body 64 also includes recessed sidewalls 90. Each recessed sidewall 90 is generally arcuately spaced from the corresponding sidewall 70 and extends generally radially between and connects to the corresponding one of the tapered wall 86 and the recessed surface 88. In particular, in a preferred embodiment, the recessed sidewalls 90 of a given pole segment 60 each extend inward toward each other (i.e., taper gradually) and are generally parallel to the corresponding sidewall 70 (or the corresponding central slot axis 72). Thus, adjacent recessed sidewalls 90 of each pair of adjacent pole segments 60 extend generally parallel to each other. As with the geometry of the sidewalls 70 described above, this is advantageous because common flat rectangular plate magnets, such as magnet arms 48b, can be used in the rotor assembly 14.

[0057] Reference Figure 8 Adjacent pole segments 60 mate to define a "T"-shaped magnet receiving groove 50. A notch 82 mates to define a groove arm portion 120 of the magnet receiving groove 50, which is configured to receive a magnet arm portion 48b therein. Similarly, a sidewall 70 mates to define a groove rod portion 130 of the magnet receiving groove 50, which is configured to receive a magnet rod portion 48a therein. However, it should be noted that according to some aspects of the invention, the pole segments 60 of the lamination 156 may not include opposing notches 82.

[0058] Furthermore, each magnet receiving slot 50 has an open slot 125 that extends between the slot arm 120 and the annular nominal circumferential surface "B". As depicted, the slot 125 is partially defined by tabs 66 of adjacent pairs of magnetic pole segments 60.

[0059] In this exemplary embodiment, the slotted rod portion 130 has a circumferentially extending first slot width W1, the size of which is determined to receive the corresponding magnet rod portion 48a therein. In a preferred embodiment, the first slot width W1 is in the range of approximately 45 percent of an inch (0.45”) to approximately 5 percent of an inch (0.50”). In other aspects of the invention, the first slot width W1 can be any measure that enables the stack 156 to function as described herein.

[0060] The slot arm 120 is located radially outside the slot rod 130 and is oriented substantially perpendicular to the slot rod 130 as described herein. The slot arm 120 has a circumferentially extending second slot width W2, the size of which is determined to receive the corresponding magnet arm 48b therein. In a preferred embodiment, the second slot width W2 is in the range of about 65 percent of an inch (0.65”) to about 75 percent of an inch (0.75”). In other aspects of the invention, the second slot width W2 can be any measure that enables the stack 156 to function as described herein.

[0061] In this exemplary embodiment, the slot 125 located radially outward of the slot arm portion 120 has a circumferentially extending third slot width W3. In a preferred embodiment, the third slot width W3 is in the range of approximately 30 percent of an inch (0.30”) to approximately 40 percent of an inch (0.40”). In other aspects of the invention, the third slot width W3 can be any measure that enables the stack 156 to function as described herein.

[0062] Reference Figure 9 The main body 64 of the magnetic pole segment 60 includes a magnet positioning structure comprising a pair of opposing radially spaced, bow-shaped inner tabs 94. More specifically, the inner tabs 94 include generally circumferentially extending small circular blocks / bumps configured to restrict radially inward displacement of the corresponding magnet 48. (Refer to...) Figure 4 The radially innermost surface 96 of each magnet rod 48a is preferably spaced apart from but adjacent to a corresponding pair of inner tabs 94. In certain other aspects of the invention, alternative or additional methods of limiting such displacement are permitted. In a preferred embodiment, the inner tabs 94 facilitate the fixation of the magnet rod 48a. Furthermore, the magnet rod 48a may be fixed or limited alternatively or additionally by means of radially inner, generally radially extending tabs or other geometric features defined by the pole segments of the lamination 156 and / or the central hub 92.

[0063] exist Figure 9In the exemplary embodiment shown, the central hub 92 includes a central shaft receiving opening 98 defined therethrough. The central shaft receiving opening 98 is substantially concentric with the axis of rotation "A". The central hub 92 includes a pair of arcuately spaced, axially extending grooves 100 and 102 defined along the inner surface 104 of the central shaft receiving opening 98. The grooves 100 and 102 are configured to interact with the keyway 54 (in... Figure 3 (As shown in the figure) This arrangement facilitates locking the laminations 156 of the rotor core 24 in a predetermined position.

[0064] The groove 100 is defined in the central hub 92 and has a central axis 106. In this exemplary embodiment, the central axis 106 of the groove 100 is offset at an angle by a predetermined angle “C” from a corresponding radial pole node line 74. However, in some embodiments, the central axis 106 may be aligned with the corresponding radial pole node line 74. In a preferred embodiment, the predetermined angle “C” is approximately four degrees (4°). However, in other embodiments of the invention, the predetermined angle “C” may be any angular measure that enables the stack 156 to function as described herein.

[0065] Furthermore, the groove 102 also includes a central axis 108. In this exemplary embodiment, the central axis 108 of the groove 102 is offset at an angle by a predetermined angle “D” from the central axis 106 of the groove 100. In a preferred embodiment, the predetermined angle “D” is approximately 152 degrees. However, in other embodiments of the invention, the predetermined angle “D” can be any angular measure that enables the stack 156 to function as described herein.

[0066] Overall reference Figure 3 and 8 As described herein, magnet 48 includes a magnet rod portion 48a and a magnet arm portion 48b. Each of the magnet rod portions 48a and 48b preferably has a generally cubic shape. More specifically, magnet rod portion 48a preferably has a radially innermost surface 96, a radially outermost surface 114, a pair of circumferentially spaced side surfaces 116, and an axially spaced end face 118. Surfaces 96, 114, 116, and 118 are preferably at least generally flat and arranged in a cubic manner. Furthermore, magnet arm portion 48b preferably has a radially outermost surface 122, a radially innermost surface 124, a pair of circumferentially spaced side surfaces 126, and an axially spaced end face 128. Surfaces 122, 124, 126, and 128 are preferably at least generally flat and arranged in a cubic manner. However, according to some aspects of the invention, variations in magnet shape are permitted (e.g., by providing one or more curved surfaces and / or non-orthogonal interfaces between surfaces), although the sides of adjacent magnetic pole segments are preferably shaped complementaryly.

[0067] In this exemplary embodiment, each magnet rod portion 48a is located in a corresponding slotted rod portion 130 and extends radially relative to the rotation axis "A". The radially innermost surface 96 of each magnet rod portion 48a is preferably spaced apart from but adjacent to a corresponding magnet retaining inner protrusion 94 in the magnet retaining inner protrusion 94. Each side surface 116 is preferably directly adjacent to a corresponding one of the magnetic pole segment sidewalls 70. Furthermore, each individual magnet arm portion 48b is located in a corresponding slotted arm portion 120 and extends generally circumferentially relative to the magnet rod portion 48a in the opposite direction. The radially innermost surface 124 of each magnet arm portion 48b is directly adjacent to a corresponding one of the radially outermost surfaces 114 of the magnet rod portion, such that the magnets 48 are continuous. However, in some embodiments, a gap may be defined between the radially innermost surface 124 of each magnet arm portion 48b and a corresponding one of the radially outermost surfaces 114 of the magnet rod portion. Furthermore, in other embodiments of the invention, only a portion of each magnet arm 48b is located radially outside the corresponding one of the radially outermost 114 of the magnet rod. For example, each magnet arm 48b may include a notch in the radially innermost surface 124 for receiving a portion of a corresponding magnet rod 48a and the associated radially outermost 114.

[0068] In this exemplary embodiment, each side 126 of each magnet arm 48b preferably directly abuts a corresponding recessed sidewall 90. The magnet rod 48a and the corresponding magnet arm 48b in the corresponding magnet receiving groove 50 are substantially perpendicular to each other, thereby forming a “T”-shaped magnet 48, as described above. It should be noted that although the exemplary embodiment describes a single rod magnet and a single corresponding arm magnet forming a “T”-shaped magnet, it is conceivable that, in some aspects of the invention, more than one arm magnet can be incorporated into the rotor core. For example, in some embodiments, a single rod magnet may comprise two (2) or more adjacent circumferentially extending arm magnets at least partially positioned radially outward therefrom. The arm magnets may have different circumferential lengths, such that the arm magnets cooperate with the rod magnets to form an inverted stepped wedge shape.

[0069] As described above, the magnet arm 48b is positioned radially inward relative to the nominal outer peripheral surface "B" of the rotor core 24 to facilitate a reduction in the demagnetizing field strength that may be generated by the motor windings. Specifically, the outermost radial portion 122 is spaced apart from the nominal outer peripheral surface "B" by a predetermined distance D1. In a preferred embodiment, the distance D1 is in the range of approximately 25 percent of an inch (0.25") to approximately 30 percent of an inch (0.30") (inclusive). However, it should be noted that in certain other aspects of the invention, the distance D1 can be any measure that enables the rotor core 24 to function as described herein.

[0070] In this exemplary embodiment, the magnet arm 48b has a magnet thickness T1 measured in the radial direction. In a preferred embodiment, the thickness T1 is in the range of approximately 45 percent of an inch (0.45”) to approximately 50 percent of an inch (0.50”). In other aspects of the invention, the magnet thickness T1 can be any measure that enables the magnet arm 48b to function as described herein. Furthermore, the magnet rod 48a has a magnet thickness T2 measured in a tangential direction perpendicular to the radial direction. In a preferred embodiment, the thickness T2 is substantially the same as the thickness T1 of the magnet arm 48b. As described above, the magnet arm 48b (i.e., the horizontal portion of the “T”-shaped magnet 48) is magnetized to retain the generally circumferential orientation of the magnetic poles. That is, the north and south poles of the magnet arm 48b are defined on circumferentially spaced sides 126. The magnet rod 48a is magnetized such that the north and south poles of the magnet rod 48a are defined on circumferentially spaced sides 116. Furthermore, the polarity directions of each pair of magnets 48a and 48b (i.e., magnets 48) are preferably alternate. More specifically, the north pole of the first magnet 48 preferably faces the north pole of the second magnet 48, and so on. That is, each magnetic pole segment 60 is preferably adjacent only to the same magnetic pole of the adjacent magnet 48, wherein the polarity of the magnetic pole segment 60 is thus alternated.

[0071] like Figure 8 As shown, the magnet rod portion 48a defines a radially extending longitudinal axis "D", which is centrally located on the magnet in the tangential direction. Similarly, the magnet arm portion 48b defines a circumferentially extending longitudinal axis "E", which is centrally located on the magnet in the radial direction. In a preferred embodiment, the longitudinal axes "D" and "E" are perpendicular to each other. Furthermore, in a preferred embodiment, the magnet arm portion 48b extends in the opposite direction to the longitudinal axis "D". That is, the magnet arm portion 48b is substantially centered relative to the magnet rod portion 48a, thereby defining a "T"-shaped magnet 48. However, it should be noted that unequal circumferential extension of the magnet arm portion 48b is contemplated in certain aspects of the invention.

[0072] In a preferred embodiment, magnet 48 is a permanent magnet. Furthermore, magnet 48 preferably comprises ferrite. However, according to certain aspects of the invention, other magnetic materials (e.g., neodymium and other rare earth materials) may be used.

[0073] In operation, the rotor assembly 14 is assembled by first manufacturing a plurality of laminations 156 arranged in a plurality of lamination stacks 56. As described above, the laminations 156 can be made of suitable materials, including but not limited to magnetically permeable materials, such as iron, steel, or steel alloys, for example by machining, stamping, punching, and / or using other suitable lamination techniques. After the laminations 156 are manufactured into lamination stacks 56, magnets 48 (e.g., magnet rod portions 48a and magnet arm portions 48b) are inserted into magnet receiving slots 50 as described above. The lamination stacks 56 are oriented and stacked as described below. The plurality of laminations 156 in each lamination stack 56 are preferably interlocked (e.g., connected to each other), although some aspects of the invention contemplate the use of loose laminations.

[0074] As described above, in order to define the skew / offset configuration of the rotor core 24, the axially adjacent laminations 56 are rotated by a predetermined amount relative to each adjacent lamination about the rotation axis "A". In a preferred embodiment, the rotor core 24 includes four laminations 56 (see...). Figure 3 Each stack 56 is offset at an angle from the adjacent stack 56.

[0075] In one example, a first lamination stack 56 (e.g., the lamination stack 56 closest to the first end 52 of the rotor shaft 28) is positioned on the rotor shaft 28, with the groove 100 aligned with the keyway 54 and its axial face 112 facing the first end 52. A second lamination stack 56 is then positioned on the rotor shaft 28, with the groove 102 aligned with the keyway 54 and its axial face 110 facing the first end 52. Thus, the opposing axial faces 110 and 112 of adjacent lamination stacks 56 are abutted against each other in face-to-face contact. Accordingly, the second lamination stack 56 is offset at an angle of approximately four degrees (4°) relative to the adjacent first lamination stack 56. A third lamination stack 56 is then positioned on the rotor shaft 28, with the groove 102 aligned with the keyway 54 and its axial face 112 facing the first end 52. That is, the first and third lamination stacks 56 (arranged in series) have the same axial surface (e.g., axial surface 112) facing the first end 52 of the rotor shaft 28. However, the first and third lamination stacks 56 are angularly offset from the keyway 54 based on different grooves (e.g., grooves 100 and 102). The fourth lamination stack 56 is then positioned on the rotor shaft 28, wherein the groove 110 is aligned with the keyway 54 and its axial surface 112 is facing the first end 52 of the rotor shaft. In this way, each lamination stack 56 is rotated relative to the adjacent lamination in the same direction by an amount equal to about four degrees (4°).

[0076] Reference Figure 4In an alternative embodiment, the open slot 125 extending between the slot arm 120 and the annular nominal circumferential surface "B" can be filled with a nonferrous material 132. The nonferrous material 132—which functions similarly to a simple empty space involving magnetic forces—can replace the empty space defined by the open slot 125, provided that the eddy currents induced by the rapidly changing magnetic field of the motor 10 do not generate excessive power loss in the nonferrous material. The nonferrous material 132 can help secure the magnet arm 48b and helps reduce wind resistance losses caused by the rapidly rotating rotor assembly during operation of the motor 10. Examples of nonferrous materials that can be used to fill the open slot 125 include, but are not limited to, synthetic resins, plastics, epoxy resins, etc.

[0077] Advantageously, embodiments of the invention can be used to increase the volume of magnetic material in the rotor poles of an electric motor without the need for tapered magnets. By providing "T"-shaped magnets made of common flat-plate magnets, the magnetic flux density of each rotor pole can be increased. Using common flat-plate magnets improves manufacturability while reducing the manufacturing cost of the disclosed rotor assembly by reducing the need for specially manufactured magnets. Another advantage of the invention is that by spacing the magnets radially inward on the outer rotor surface, the known demagnetization susceptibility of magnets that may be generated by the motor windings is reduced, while maintaining or increasing the total magnetic flux density by increasing the volume of magnetic material.

[0078] While the foregoing description presents features of preferred embodiments of the invention, other preferred embodiments may also be formed based on the principles of the invention. For example, these other preferred embodiments may include features extracted from one or more of the above embodiments. Furthermore, these other preferred embodiments may include features of the various embodiments described above, particularly where these features, although presented independently as part of separate embodiments in the foregoing description, are suitable for use together.

[0079] Those skilled in the art will understand that any suitable combination of the foregoing embodiments can be made without departing from the spirit of the invention.

[0080] The preferred embodiments of the present invention described above are for illustrative purposes only and should not be construed as limiting the scope of the invention. Those skilled in the art will readily make obvious modifications to the exemplary embodiments described above without departing from the spirit of the invention.

Claims

1. A rotor assembly for an electric motor, the rotor assembly comprising: A rotor core that defines the axis of rotation and has an outer peripheral core surface; The rotor core includes a plurality of axially extending magnet receiving slots, each of which has a slot rod portion, a slot arm portion and a slot hole, the slot rod portion extending radially relative to the rotation axis, and the slot hole extending outward from the slot arm portion; The grooved rod portion and the groove hole are defined by a pair of radially extending opposing sidewalls; Each sidewall has a circumferentially extending protrusion located near the outer peripheral core surface and spaced apart from the groove arm portion; and Multiple magnets spaced in an arc shape around the rotor core. Each of the magnets includes a magnet rod and a magnet arm. The magnet rod is received within the slot rod and extends radially relative to the axis of rotation to present the outermost rod end. The magnet arm is received in the slot arm and is at least partially located radially outside the rod end and extends circumferentially in the opposite direction relative to the magnet rod. The slot extends between the slot arm and the outer peripheral core surface, and is defined between the pair of sidewalls and the opposing circumferentially extending protrusions.

2. The rotor assembly according to claim 1, Each of the magnet rod and the magnet arm has a cubic shape.

3. The rotor assembly according to claim 2, The magnet rod and the magnet arm are arranged approximately perpendicular to each other.

4. The rotor assembly according to claim 3, The magnet arm is located entirely radially outside the magnet rod.

5. The rotor assembly according to claim 4, The magnet rod and the magnet arm are in contact with each other, so that each magnet is continuous.

6. The rotor assembly according to claim 5, The magnet arm is single, such that each magnet is T-shaped and consists of only a single magnet arm located radially outside the magnet rod.

7. The rotor assembly according to claim 6, The magnet arm has an arm thickness measured in the radial direction. The magnet rod has a rod thickness measured in a tangential direction perpendicular to the radial direction. The thickness of the arm and the thickness of the rod are approximately equal.

8. The rotor assembly according to claim 7, The magnet rod defines a longitudinal rod axis that extends radially and is centrally positioned in the tangential direction. The magnet arm extends equally in opposite directions relative to the longitudinal rod axis.

9. The rotor assembly according to claim 8, The magnet arm is spaced apart from the outer peripheral core surface.

10. The rotor assembly according to claim 9, Each slot of the corresponding magnet receiving groove extends between the slot arm and the outer peripheral core surface.

11. The rotor assembly according to claim 10, The slot is open.

12. The rotor assembly according to claim 9, The rotor core has a hub on the radially innermost side that defines a central shaft receiving opening. The magnet rod portion is spaced apart from the hub portion.

13. The rotor assembly according to claim 1, Each of the magnet receiving slots is T-shaped.

14. The rotor assembly according to claim 1, The rotor core includes a plurality of magnetic pole segments spaced apart from each other in the circumferential direction, wherein a corresponding one of the magnet receiving slots is defined between adjacent magnetic pole segments. Each magnetic pole segment includes a magnet positioning structure.

15. The rotor assembly according to claim 14, The magnet positioning structure includes a circumferentially extending radially inwardly projecting piece. The radially inner protrusion extends into the groove portion of the corresponding magnet receiving slot.

16. The rotor assembly according to claim 1, The magnet arm is located entirely radially outside the magnet rod. The magnet rod and the magnet arm are in contact with each other, so that each magnet is continuous.

17. The rotor assembly according to claim 1, The magnet arm is spaced apart from the outer peripheral core surface.

18. The rotor assembly according to claim 17, The groove arm has a first groove width that extends circumferentially. The slot has a second slot width that extends circumferentially. The width of the first slot is greater than the width of the second slot.

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