Abstract:
An electric motor comprises a stator assembly having at least two armature coils, and a rotor assembly arranged radially inward of the stator assembly. The rotor assembly has a rotor core, a magnetic ring, and a plurality of permanent magnets. The rotor core is substantially cylindrical in shape and constructed of a diamagnetic material. The magnetic ring is positioned about the rotor core, and the permanent magnets are positioned in the magnetic ring in such a way that magnetic fields created by the armature coils provide an attractive force which selectively attracts the permanent magnets toward the armature coils so as to impart rotational mechanical energy to the rotor assembly.

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
       [0001]    This application claims priority to U.S. provisional application Ser. No. 61/793,348, filed on Mar. 15, 2013, the entire disclosure of which is hereby expressly incorporated herein by reference. 
     
    
     BACKGROUND 
       [0002]    Electric motors are well known in the art, and multiple attempts have been made to increase the efficiency of such electric motors. Electric motors generally include a stationary part called a stator having armature windings therein, and a moving part called a rotor which rotates relative to the stator. The stator and the rotor of electric motors use the electromagnetic repulsion or attraction between opposing pairs of magnets and coils separated by an air gap to generate rotational motion by typically supplying current to the coils so that the resulting electromagnetic field pushes or pulls on the magnets to generate rotational movement of the rotor. Some electric motors use permanent magnets, and some electric motors use electromagnets. 
         [0003]    With electric motors being found in products ranging from toothbrushes to heavy industrial machines, they have become ubiquitous. Nevertheless, a constant search still exists for ways to maximize the efficiency and reduce the price of electric motors. For example, recent International Electrotechnical Commission standards establish minimum efficiency standards for several classes of electric motors for new electric motors manufactured after Jan. 1, 2015. The recent emergence of hybrid and electric vehicles has made the quest for more efficient electric motors the focus of private and government-sponsored research and development to the tune of millions of U.S. dollars per year. 
         [0004]    Existing electric motors have several inherent inefficiencies and problems. For example, existing electric motors utilize relatively large amounts of electrical current supplied to coils. The relative large current supplied to the coils of existing electric motors is subject to electrical resistance in the coils according to Joule&#39;s first law which states that the energy lost increases as the square of the current through the windings, and in proportion to the electrical resistance of the conductors in the windings. This loss is termed winding loss (“I squared R loss” or “I 2 R loss”), and results in a significant power loss and a relatively large amount of heat being generated by existing electric motors. This relatively large amount of heat, if left unchecked, may cause electric motors to overheat and/or demagnetization of the magnets. To account for the resistive heat generation by the coils, existing electric motors incorporate cooling devices such as heat sinks or air fans, which further reduce the efficiency and increase the cost of existing electric motors. A large portion of the energy of the current is converted to heat, rather than to mechanical energy. 
         [0005]    Accordingly, a need exists for an electric motor configured to maximize efficiency, while minimizing cost, power input, and heat generation. It is to such an electric motor that the inventive concepts disclosed herein are directed. 
       SUMMARY 
       [0006]    Generally, but not by way of limitation, the inventive concepts disclosed herein are directed to an electric motor of the permanent magnet type. More particularly, but not by way of limitation, the inventive concepts disclosed herein are directed to permanent magnet electric motors and to a method of focusing the power of permanent magnets as the primary power source of an electric motor by reducing the length of the flux path and reducing other magnetic interferences. Relatively low power input to the coils is used primarily to release the potential energy of the permanent magnets and as a speed-control to control the speed of the electric motor. 
         [0007]    In an exemplary embodiment, the electric motor has a substantially cylindrical rotor which includes a diamagnetic core having a cylindrical magnetic ring (e.g., a magnetic ring) on its periphery, into which magnetic ring at least two, or a plurality of permanent magnets are embedded so that the permanent magnets are spaced a distance from one another and are oriented substantially parallel to an axis of rotation of the rotor. The surfaces of the permanent magnets are positioned on an axial surface of the magnetic ring. An air gap separates the surfaces of the permanent magnets from a substantially cylindrical stator having a plurality of windings or coils integrated therein. The rotor core and the magnetic ring cooperate to focus the magnetic flux of the permanent magnets by reducing the length of the flux path (e.g., by directing the flux or fluctuating magnetic field of the permanent magnets away from the rotor core), thus allows the permanent magnets to serve as the primary power source for the electric motor. Consequently, a relatively low-power input is provided to the coils to operate the electric motor. 
         [0008]    In some exemplary embodiments, an electric motor according to the inventive concepts disclosed herein may include a stator having at least two armature coils arranged on an inner periphery of the stator. The electric motor also has a rotor arranged radially inward the stator and separated from the stator by an air gap, the rotor including a diamagnetic rotor core having an axis of rotation and a substantially annular magnetic ring positioned between the rotor core and the stator. At least two permanent magnets are associated with the magnetic ring, the permanent magnets spaced apart from one another by a gap and oriented substantially parallel to the axis of rotation, the permanent magnets having outer surfaces separated from the coils by the air gap. The magnetic ring is configured to provide a magnetic path for the magnetic fields of the permanent magnets repelled by the rotor core in a direction away from the rotor core so as to focus the magnetic fields of the permanent magnets toward the stator. The permanent magnets may be rare-earth permanent magnets and may be configured to operate as the primary power source for the electric motor. The permanent magnets may be at least partially embedded into the magnetic ring, and the outer surfaces of the permanent magnets may be substantially flush with a radial surface of the magnetic ring. 
         [0009]    In some exemplary embodiments, a rotor assembly for an electric motor or generator according to the inventive concepts disclosed herein may include a substantially cylindrical rotor core constructed of a diamagnetic material and having an axis of rotation, and a substantially annular magnetic ring constructed of a magnetic material connected to the rotor core and having a substantially arcuate radial surface oriented substantially parallel to the axis of rotation. At least two permanent magnets may be associated with the magnetic ring so that the permanent magnets are separated at a distance from one another, each of the permanent magnets having an outer surface oriented substantially parallel to the axis of rotation along the substantially arcuate radial surface of the magnetic ring, adjacent outer surfaces having alternating polarities. The magnetic ring is configured to function as a magnetic return path to direct the magnetic fields of the permanent magnets away from the rotor core. The permanent magnets may be connected to the radial surface of the magnetic ring or may be at least partially embedded in the radial surface of the magnetic ring. The permanent magnets can also be substantially completely embedded in the radial surface of the magnetic ring so that the outer surfaces of the permanent magnets are substantially level with the radial surface of the magnetic ring. The permanent magnets can be rare-earth magnets. The magnetic ring can be constructed of a laminated magnetic material. 
         [0010]    In some exemplary embodiments, a permanent magnet electric motor according to the inventive concepts disclosed herein may have a rotor assembly which includes a substantially cylindrical rotor core constructed of a diamagnetic material and having an axis of rotation. The electric motor also has a magnetic ring constructed of a magnetic material having a first surface connected to the rotor core and having a substantially arcuate radial surface oriented substantially parallel to the axis of rotation. At least two permanent magnets are associated with the radial surface of the magnetic ring so that the permanent magnets are separated at a distance from one another, each of the permanent magnets having an outer surface oriented substantially parallel to the axis of rotation along the substantially arcuate radial surface of the magnetic ring, adjacent outer surfaces having alternating polarities. The magnetic ring is configured to function as a magnetic return path to direct the magnetic fields of the permanent magnets away from the rotor core. The motor also has a diamagnetic shaft extending through the rotor core substantially coaxially with the axis of rotation. The motor further has a stator assembly, including a stator core rotatably connected to the shaft and at least two coils associated with the stator core so that the coils are positioned circumferentially and coaxially with the outer surfaces of the permanent magnets, and so that the coils are separated from the permanent magnets at a distance such that the coils and the permanent magnets cooperate to define an air gap. 
         [0011]    Further, in some exemplary embodiments electric motors according to the inventive concepts disclosed herein may be operated as electromagnetic generators by providing mechanical energy to the rotor, as will be appreciated by persons of ordinary skill in the art. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0012]      FIG. 1  is a partially cutaway, elevational view of an electric motor constructed in accordance with the inventive concepts disclosed herein. 
           [0013]      FIG. 2  is a cross-sectional view of a stator assembly and a rotor assembly of the electric motor of  FIG. 1 . 
           [0014]      FIG. 3  is an enlarged cross-sectional view of a portion of the stator assembly and the rotor assembly. 
           [0015]      FIG. 4  is an enlarged cross-sectional view of a portion of the rotor assembly. 
           [0016]      FIG. 5  is a diagrammatic view illustrating magnetic flux path of the electric motor. 
           [0017]      FIG. 6  is a cross-sectional view of another embodiment of an electric motor constructed in accordance with the inventive concepts disclosed herein. 
       
    
    
     DETAILED DESCRIPTION OF EXEMPLARY EMBODIMENTS 
       [0018]    Before explaining at least one embodiment of the inventive concepts disclosed herein in detail, it is to be understood that the presently disclosed and claimed inventive concepts are not limited in their application to the details of construction, experiments, exemplary data, and/or the arrangement of the components set forth in the following description or illustrated in the drawings. The presently disclosed and claimed inventive concepts are capable of other embodiments or of being practiced or carried out in various ways. Also, it is to be understood that the phraseology and terminology employed herein is for purpose of description and should not be regarded as limiting. 
         [0019]    Referring to the drawings, and more particularly to  FIGS. 1-3 , an exemplary embodiment of an electric motor  100  according to the inventive concepts disclosed includes a stator assembly  102 , a rotor assembly  104 , and a control system  106 . An external housing  108  may be implemented to house the various components of the electric motor  100  and to protect the various components from dirt, moisture, damage, and other environmental hazards, for example. 
         [0020]    The stator assembly  102  includes a stator core  110  and one or more coils  112  arranged in the stator core  110 . The stator core  110  may be substantially annular in shape and may be constructed of any desired material, such as metals, composites, ceramics, alloys, polymers, diamagnetic materials, laminated material, magnetic materials, and combinations thereof, for example. The stator core  110  may define a substantially cylindrical opening therethrough to receive the rotor assembly  104  therein so that the stator assembly  102  and the rotor assembly  104  are spaced a distance from one another so as to define an air gap  116  (best shown in  FIG. 3 ). The air gap  116  may have any desired size and is desirably as small as possible to increase the efficiency of the electric motor  100 . 
         [0021]    The coils  112  may be implemented as any suitable armature windings and may be associated with the stator core  110 , in any desired manner, such as by being wrapped around the stator core  110  in series, lap, or as mush windings, for example. In some exemplary embodiments, any desired number of coils  112  may be used, such as thirty-six, or any other desired number. The coils  112  may be separated from one another by feet  113  of the stator core  110 , for example. In one exemplary embodiment, where the electric motor  100  is operated as a three-phase electric motor  100 , the coils  112  may be controlled by the control system  106  so that three-phase control and/or power signals are provided sequentially to the coils  112 , as will be appreciated by a person of ordinary skill in the art. 
         [0022]    Referring now to  FIGS. 1-4 , the rotor assembly  104  includes a rotor core  118 , a shaft  120 , a magnetic ring  122 , and a plurality of permanent magnets  124   a - n . The rotor core  118  is substantially cylindrical in shape, and is desirably constructed of a suitable diamagnetic material, such as polymers, ceramics, aluminum, diamagnetic steel, polymers, ceramics, diamagnetic metals, diamagnetic alloys, and combinations thereof. However, in some embodiments, it may be desirable to construct the rotor core  118  from a magnetic material. The rotor core  118  may have any desired diameter or size, for example. 
         [0023]    The shaft  120  is shown as a substantially cylindrical shaft  120  extending substantially through the center of the rotor core  118 . The shaft  120  may be associated with the rotor core  118  in any desired manner, such as by being press-fitted, welded, glued, bolted, or otherwise attached to the rotor core  118 . In some exemplary embodiments, the shaft  120  and the rotor core  118  may be formed as a unitary component. The shaft  120  is desirably constructed of a suitable diamagnetic material having sufficient strength to withstand the torque outputted by the electric motor  100 , such as aluminum, diamagnetic steel, polymers, ceramics, diamagnetic metals, diamagnetic alloys, and combinations thereof. 
         [0024]    The shaft  120  defines an axis about which the rotor assembly  104  rotates. As shown in  FIG. 1 , the shaft  120  may be rotatably connected to the housing  108  and/or to the stator assembly  102 , for example. One or more optional bearings (not shown), such as ball bearings or magnetic bearings may be implemented to rotatably connect the shaft  120  with the housing  108  and/or the stator assembly  102 , as will be appreciated by a person of ordinary skill in the art. 
         [0025]    The magnetic ring  122  is substantially annular in shape and is constructed of a suitable magnetic or ferromagnetic material, such as laminated steel or iron, magnetic steel, magnetic iron, magnetic metals, magnetic alloys, and combinations thereof, for example. The magnetic ring  122  has a thickness T ( FIG. 4 ) which may be by way of example about 1.25 inches, or any desired thickness, to cooperate with the magnetic ring  122  in such a way that the magnetic flux of the permanent magnets  124   a - n  is focused toward the coils  112 , as will be described below. The magnetic ring  122  has an inner peripheral surface  126  associated with the rotor core  118  and an outer peripheral surface  128 . The magnetic ring  122  may be associated with the rotor core  118  in any desired manner, such as by being wound around the rotor core  118 , or by being connected with the rotor core  118  via welds, joints, bolts, adhesives, press-fitted, and combinations thereof, for example. 
         [0026]    The permanent magnets  124   a - n  may be associated with the magnetic ring  122  in any desired fashion such that the permanent magnets  124   a - n  are in magnetic communication with the magnetic ring  122 . In one embodiment, the permanent magnets  124   a - n  have radial outward surfaces  130  (e.g., substantially arcuate outer surfaces) which are exposed to cooperate with the outer peripheral surface  128  of the magnetic ring  122  to define the air gap  116 . The permanent magnets  124   a - n  may be associated with the magnetic ring  122  by being at least partially or substantially completely embedded in the outer peripheral surface  128 , and secured thereto by using bolts, welds, brackets, adhesives, joints, flanges, and combinations thereof, to associate the permanent magnets  124   a - n  and the magnetic ring  122 , for example. 
         [0027]    It is to be understood that while the permanent magnets  124   a - n  are shown as being embedded into the outer peripheral surface  128  of the magnetic ring  122  so that the radial outward surface  130  of each of the permanent magnets  124   a - n  is substantially flush with the outer peripheral surface  128  of the magnetic ring  122 . However, in some exemplary embodiments, the radial outward surface  130  of the permanent magnets  124   a - n  may be set below or above the outer peripheral surface  128  of the magnetic ring  122 , for example. 
         [0028]    The permanent magnets  124   a - n  may be implemented as any desired permanent magnets, such as rare-earth type or lanthanide-type magnets, or any other strong permanent magnets. For example, the permanent magnets  124   a - n  may include samarium-cobalt magnets and/or neodymium-iron-boron (NIB) magnets. The permanent magnets  124   a - n  may have any desired shape, size, and orientation. For example, the permanent magnets  124   a - n  may be oriented substantially parallel to one another and to the axis along the outer peripheral surface  128  of the magnetic ring  122 , and may have a thickness of about 0.25 inches, or any other desired thickness. The permanent magnets  124   a - n  are shown as being substantially rectangular in shape and as being oriented substantially parallel to the axis, but it is to be understood that the permanent magnets  124   a - n  may have any desired sizes, shapes and orientation, including having a first permanent magnet  124   a  having a first size, shape, or orientation, and a second permanent magnet  124   b  having a second size, shape, or orientation, for example. The permanent magnets  124   a - n  may be substantially rectangular, or may be arcuate in shape, for example. 
         [0029]    In the exemplary embodiment, the rotor assembly  104  has thirty-six permanent magnets  124   a - n  substantially equally spaced around the magnetic ring  122 . The stator assembly  102  may have thirty-six coils  112  separated from the thirty-six permanent magnets  124   a - n  by the air gap  116 , for example. As illustrated in  FIG. 4 , the permanent magnets  124   a - n  are arranged so that half of the permanent magnets  124   a - n  have their north (N) pole on the radial outward surface  130  facing the air gap  116 , and the other half of the permanent magnets  124   a - n  have their south (S) pole on the radial outward surface  130  facing the air gap  116 , with adjacent magnets having the same orientation, except where the first N-facing half and the S-facing half meet. This orientation will result in a dual-pole orientation of the permanent magnets  124   a - n , and therefore a dial-pole operation of the electric motor  100  as will be readily appreciated by a person of ordinary skill in the art. It is to be understood, however, that in some embodiments, adjacent alternating magnets  124   a - n  may have alternating poles facing the air gap  116 , resulting in a multi-pole arrangement of the permanent magnets  124   a - n , and multi-pole operation of the electric motor  100 . Further, in some exemplary embodiments, alternating quarters of the 36 permanent magnets  124   a - n  may have alternating poles facing the air gap  116 , resulting in a four-pole orientation of the permanent magnets  124   a - n , and a four-pole operation of the electric motor  100 . 
         [0030]    The permanent magnets  124   a - n  are shown as being separated laterally from one another by gaps  132 , which are shown as having a width W (e.g., about 0.29 inches) which may be any desired width, depending on the strength of the permanent magnets  124   a - n  used, the thickness and diameter of the magnetic ring  122 , and/or the diameter of the rotor core  118 , for example. Further, while the permanent magnets  124   a - n  are shown as being spaced a substantially equidistance from one another, in some exemplary embodiments the width of the gap  132  between a first magnet  124   a  and a second magnet  124   b  may be different from the width of the gap  132  between the second magnet  124   b  and a third magnet  124   c.    
         [0031]    The control system  106  ( FIG. 1 ) can be implemented as any suitable device or group of devices (e.g., one or more of a switch, a relay, a capacitor, a circuit-breaker, a sensor, a contactor, a starter, and combinations thereof) that function to control the electric motor  100  according to the inventive concepts disclosed herein, and may include manual and/or automatic devices for starting and stopping the electric motor  100 , controlling the direction and speed of rotation of the electric motor  100 , regulating the torque output of the electric motor  100 , and combinations thereof. In an exemplary embodiment, the control system  106  may be configured for three-phase control of the coils  112 , such as by providing a three-phase control signal to the coils  112 . It is to be understood that in some exemplary embodiments, a two-phase, or more than three-phase control signals may be provided to the coils  112  by the control system  106 . The amount of current provided to the coils  112  may be any desired amount. 
         [0032]    The housing  108  may be constructed of any desired material, such as a diamagnetic metal, alloy, or other diamagnetic material, for example. In some exemplary embodiments, the housing  108  may functions as a heat sink as will be appreciated by persons of ordinary skill in the art, while in some embodiments, the housing  108  may be omitted. 
         [0033]    In operation, the electric motor  100  according to the inventive concepts disclosed herein may operate as follows. A relatively low current (e.g., about 0.5 watts, or 6 V times 0.08333 A) is provided to the coils  112  by the control system  106 . The relatively low current creates weak magnetic fields in the coils  112  which are less than the magnetic fields of the permanent magnets  124 - n  and which weak magnetic fields may be switched by the control system  106  to provide three-phase operation of the electric motor  100 . The weak magnetic fields in the coils  112  attract the respective magnetic poles of the radial outward surfaces  130  of the permanent magnets  124   a - n  of the rotor assembly  104  causing the rotor assembly  104  to rotate relative to the stator assembly  102 , for example. 
         [0034]    The rotor core  118  repels the magnetic flux of the permanent magnets  124   a - n . The magnetic ring  122  cooperates with the rotor core  118  to carry and focus the magnetic flux of the permanent magnets  124   a - n , including that portion of the magnetic flux repelled by the rotor core  118 , outward and towards the coils  112 . The number and spacing of the permanent magnets  124   a - n  also serves to focus the magnetic field outward towards the coils  112 , as described above, for example. This configuration of the electric motor  100  allows the permanent magnets  124   a - n  to function as the primary power source of the electric motor  100 . The amount of power or current provided to the coils  112  by the control system  106  is low enough so that substantially no electromagnetic flux enters the rotor core  118  as a result. Because of the low amount of current provided to the coils  112 , a relatively low amount of resistive heat is generated by the coils  112 . In some exemplary embodiments, the rotor core  118 , the shaft  120 , and/or the housing  108  may operate as heat sinks to dissipate any heat generated by the operation of the electric motor  100 , and is some exemplary embodiments no additional cooling mechanisms other than the heat-sink rotor core  118  and housing  108  are used. 
         [0035]    The electric motor  100  according to the inventive concepts disclosed herein is configured to focus the power of permanent magnets, such as the magnets  124   a - n , and use such power as the primary power source driving the electric motor  100 . Embedding the permanent magnets  124   a - n  in the magnetic ring  122  of the rotor assembly  104  with the radial outward surfaces  130  of the permanent magnets  124   a - n  exposed to the air gap  116 , allows an electric motor  100  according to the inventive concepts disclosed herein to maximize the benefit of the permanent magnets  124   a - n . The electric motor  100  may be configured to utilize the permanent magnets  124   a - n  as the primary power source, so that a relatively low amount of current is provided to the coils  112  and a relatively large amount of power is output by the electric motor  100 . For example, as seen in  FIG. 5 , the magnetic flux of the permanent magnets  124   a - n  is directed towards the coils  112  by the rotor core  118  so that substantially no magnetic flux enters the rotor core  118 . The magnetic ring  122  and the rotor core  118  thus effectively focus the flux path of the permanent magnets  124   a - n  and maximize their potential to drive the electric motor  100 . 
         [0036]    The low stator input provided according to the inventive concepts disclosed herein does not interfere with the magnetic output of the permanent magnets  124   a - n . Instead, the stator assembly  102  is configured to act as a speed-control device using a three-phase signal as a means of controlling the speed of the rotor assembly  104  and of attracting the magnetic force of the permanent magnets  124   a - n  in some exemplary embodiments. Low winding (or I 2 R) losses reduce the heat generated by electric motors  100  according to the inventive concepts disclosed herein. The magnetic ring  122  in which the permanent magnets  124   a - n  are embedded according to the inventive concepts disclosed herein focuses the flux from the permanent magnets  124   a - n  outward from the rotor core  118  to interact with the magnetic field of the stator coils  112  and thereby drive the electric motor  100 . 
         [0037]    Further, an electric motor according to the inventive concepts disclosed herein may be configured for dual polar or multipolar operation, as will be appreciated by persons of ordinary skill in the art having the benefit of the instant disclosure.  FIG. 6  illustrates an exemplary embodiment of a dual-pole electric motor  100   a  according to the inventive concepts disclosed herein. The electric motor  100   a  may be implemented and function similarly to the electric motor  100 , with the exception that the electric motor  100   a  has two magnets  124   a  and  124   b  separated laterally by gaps, rather than a plurality of magnets  124   a - n.    
         [0038]    As will be appreciated by persons of ordinary skill in the art, electric motors according to the inventive concepts disclosed herein may be operated as generators of electrical energy by supplying rotational energy to the shaft of the electric motors, capturing the resulting current induced in the coils, and allowing such current to flow through an external circuit (not shown). The current may be processed as needed such as via a transformer, for example. 
         [0039]    From the above description, it is clear that the inventive concepts disclosed and claimed herein are well adapted to carry out the objects and to attain the advantages mentioned herein, as well as those inherent in the instant inventive concepts. While exemplary embodiments of the inventive concepts have been described for purposes of this disclosure, it will be understood that numerous changes may be made which will readily suggest themselves to those skilled in the art and which are accomplished within the spirit of the inventive concepts disclosed and/or defined in the appended claims.