Abstract:
A rotor for connection to a rotating member for use in an electric machine is provided. The rotor includes a first member connected to the rotating member and generally positioned perpendicularly thereto and a second member connected to one of the rotating member and the first member.

Description:
BACKGROUND OF THE INVENTION 
     The embodiments described herein relate generally to a rotor for use in an electric machine, and more specifically, to an apparatus and method associated with a rotor for use in an axial flux electric motor. 
     A common configuration for an electric motor is radial-flux, which is composed from two cylinders, a cylindrical stator and a cylindrical rotor (having an axial shaft), with a cylindrical air gap in between and in which the flux travels across the air gap in a direction that is radial to the shaft on the rotor. In order to hold the two cylinders concentric and thus keep the air gap constant thickness in a radial flux motor, it is necessary to support the shaft at each end of the motor. 
     Given that many applications which are mechanically powered by a radial-flux electric motor do not intrinsically require a shaft, it is desirable to eliminate the necessity for a shaft and thus provide a cheaper and simpler structure. An axial flux motor is one such structure. 
     Further, many applications which are mechanically powered by a radial-flux electric motor provide for ample landscape for a large diameter motor but little room along the longitudinal axis of the shaft. An axial flux motor is well suited to such applications as the axial flux motor with high motor power capacity may indeed have a very short axial shaft length. 
     Typically an axial flux motor includes a rotor having one or more permanent magnets mounted to a face of the rotor and a stator having a stator winding connected to a power source. The motor also includes a bearing positioned between the rotor and the stator for rotationally supporting movement of the rotor relative to the stator. The bearing provides an air gap between the rotor and the stator. The permanent magnets can be replaced by a magnet field induced by an electrical winding. 
     Due to its high speed operation, it is desirable to provide a rotor with a low mass. To provide a motor with sufficient power in operation, it is desirable to provide a rotor with a large diameter rotor. Providing a motor with a rotor that has both a large diameter and a low mass, yet able to be sufficiently rigid for high speed operation provides a challenge. Further, providing such a rotor at low cost is increasingly difficult. 
     The efficiency of motors may be improved by providing the magnetic flux of the rotor with permanent magnets attached to the rotor. Such magnets are typically called permanent magnet motors and are typically more efficient than motors that do not use permanent magnets, typically induction motors. One type of permanent magnet motor utilizes electronics to time the energizing of the stator coils and is called an electronically commutated motor or ECM motor. 
     Such permanent magnet and ECM motors may use stronger magnets to further improve their efficiency. One type of such stronger magnet are called rare earth magnets and are made of rare earth metals, for example, neodymium. Neodymium magnets have been very expensive and their cost has been very volatile, particularly in recent years. 
     The present invention is directed to alleviate at least some of these problems with the prior art. 
     BRIEF DESCRIPTION OF THE INVENTION 
     According to an embodiment of the present invention, an axial flux electric motor is provided. The motor includes a housing and a stator. The housing defines an inner periphery and an outer periphery of the housing. The stator has a solitary ferrous core and is fixedly secured to the housing. The motor further includes a solitary rotor rotatably secured to said housing, the rotor including a ferrite magnet, the magnet defining at least one an outer periphery extending beyond said stator in a direction normal to the rotation of said rotor and an inner periphery extending beyond said stator in a direction normal to the rotation of said rotor, at least one of said stator or said rotor adapted for use in a fluid moving application. 
     According to an aspect of the present invention, the ferrite magnet may be generally ring shaped. 
     According to another aspect of the present invention, the ferrite magnet may have a plurality of magnet segments. 
     According to another aspect of the present invention, a skewed magnetic field may be induced into the magnet. 
     According to another aspect of the present invention, the outer periphery of the ferrite magnet may extend beyond the stator in a direction normal to the rotation of the ring. 
     According to another aspect of the present invention, the inner periphery of the ferrite magnet may extend beyond the stator in a direction normal to the rotation of the ring. 
     According to another aspect of the present invention, the outer periphery of the magnet may extend beyond the stator in a direction normal to the rotation of the rotor a first extension distance, the inner periphery of the magnet may extend beyond the stator in a direction normal to the rotation of the rotor a second extension distance, the ferrous core may be generally ring shaped defining a ferrous core radial distance and the first extension distance and the second extension distance may be as large as the ferrous core radial distance. 
     According to another aspect of the present invention, the outer periphery of the magnet may extend beyond the stator in a direction normal to the rotation of the rotor. The outer periphery of the magnet may define a magnet diameter. The ferrous core of the stator may define a stator core diameter and the magnet diameter may be as much as 50 percent larger than stator core diameter. 
     According to another aspect of the present invention, the rotor may further include a rotor core. The rotor core may be generally ring shaped. The rotor core may define a rotor core inner periphery, an rotor core outer periphery, and a rotor core radial distance between the rotor core inner periphery and the rotor core outer periphery. The outer periphery of the magnet may extends beyond the rotor core in a direction normal to the rotation of the rotor a first extension distance. The inner periphery of the magnet may extend beyond the rotor core in a direction normal to the rotation of the rotor a second extension distance. The first extension distance and the second extension distance may be as large as the rotor core radial distance. 
     According to another aspect of the present invention, the rotor may further include a rotor core. The rotor core may be generally ring shaped. The rotor core may define a rotor core inner periphery, a rotor core outer periphery, and a rotor core radial distance between the rotor core inner periphery and the rotor core outer periphery. The outer periphery of the magnet may extend beyond the rotor core in a direction normal to the rotation of the rotor. The outer periphery of the magnet may define a magnet diameter. The rotor core of the rotor may define a rotor core diameter and the magnet diameter may be as much as 50 percent larger than rotor core diameter. 
     According to another aspect of the present invention, the ferrite magnet may include a protrusion or a recess. The rotor may include a protrusion or a recess. The protrusion or recess of the ferrite magnet may cooperate with the protrusion or recess of the rotor to secure the ferrite magnet to the rotor. 
     According to another aspect of the present invention, the fluid moving application may be an air flowing application, a liquid pumping application. a HVAC application or a blower premix application. 
     According to another aspect of the present invention, a rotor assembly is rotatably secured to a motor housing. The rotor assembly includes a rotor rotatably secured to the housing. The rotor includes a ferrite magnet. The magnet may define an outer periphery extending beyond the stator in a direction normal to the rotation of the rotor and an inner periphery extending beyond the stator in a direction normal to the rotation of the rotor, The stator or the rotor may be adapted for use in a fluid moving application. 
     According to another aspect of the present invention, the ferrite magnet may be generally ring shaped. 
     According to another aspect of e present invention, the ferrite magnet may include a plurality of magnet segments 
     According to another aspect of the present invention, a skewed magnetic field may be induced into the magnet. 
     According to another aspect of the present invention, the outer periphery of the ferrite magnet may extend beyond the stator in a direction normal to the rotation of the ring. 
     According to another aspect of the present invention, the inner periphery of the ferrite magnet may extend beyond the stator in a direction normal to the rotation of the ring. 
     According to another aspect of the present invention, the fluid moving application may be an air flowing application, a HVAC application or a blower premix application. 
     According to another embodiment of the present invention, a method for fabricating a motor is provided. The method includes the step of fabricating a first set of motor parts. The motor parts may include a first rotor using neo magnets and a first stator for use in a neo motor. The method also includes the step of fabricating a second set of motor parts including a second rotor using ferrite magnets for use in a ferrite motor. The method also includes the steps of ascertaining the motor magnet type, ferrite or neo and selecting one of the first rotor and the second rotor in accordance with desired motor magnet type. The method also includes the step of assembling a motor with one of first rotor and the second rotor and first stator such that the desired motor magnet type is substantially provided. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is an cross sectional plan view of an axial flux motor according to the present invention; 
         FIG. 2  is exploded perspective view of the motor of  FIG. 1 ; 
         FIG. 3  is a an end view of an axial flux motor according to another embodiment of the present invention having a ferrite ring magnet; 
         FIG. 4  is a perspective view of the stator core of the motor of  FIG. 3 ; 
         FIG. 5  is a perspective view of the rotor of the motor of  FIG. 3 ; 
         FIG. 6  is another perspective view of the rotor of the motor of  FIG. 3 , showing the hub of the rotor; 
         FIG. 7  is cross sectional view of the rotor of  FIG. 6  along the line  7 - 7  in the direction of the arrows; 
         FIG. 8  is an end view of the magnet of the motor of  FIG. 1 ; 
         FIG. 9  is a plan view of the magnet of  FIG. 6 ; 
         FIG. 10  is a plan view of an axial flux motor according to another embodiment of the present invention for a high speed application; and 
         FIG. 11  is a flow chart of an exemplary method for providing a motor according to another embodiment of the present invention. 
     
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     Given that many applications which are mechanically powered by a radial-flux electric motor do not intrinsically require a shaft, it is desirable to eliminate the necessity for a shaft and thus provide a cheaper and simpler structure. An axial flux motor is one such structure. Due to its high speed operation, it is desirable to provide a rotor with a low mass. To provide a motor with sufficient power in operation, it is desirable to provide a rotor with a large diameter rotor. Providing a motor with a rotor that has both a large diameter and a low mass, yet able to be sufficiently rigid for high speed operation provides a challenge. Further, providing such a rotor at low cost is increasingly difficult. The efficiency of motors may be improved by providing the magnetic flux of the rotor with permanent magnets attached to the rotor. Such magnets are typically called permanent magnet motors and are typically more efficient than motors that do not use permanent magnets, typically induction motors. One type of permanent magnet motor utilizes electronics to time the energizing of the stator coils and is called an electronically commutated motor or ECM motor. 
     Such permanent magnet and ECM motors may use stronger magnets to further improve their efficiency. One type of such stronger magnet are called rare earth magnets and are made of rare earth metals, for example, neodymium. Neodymium magnets have been very expensive and their cost has been very volatile, particularly in recent years. Ferrite magnets are lower cost alternatives to neodymium magnets, but provide a much weaker magnetic field. Due to increased customer and industry demands, lower costs, and improved performance in capacity and efficiency are desirable in the design and manufacture of devices powered by electric motors. The methods, systems, and apparatus described herein facilitate lower costs and improved performance in capacity and efficiency for an electric machine. This disclosure provides designs and methods to lower costs and improve performance in capacity and efficiency. Technical effects of the methods, systems, and apparatus described herein include at least one of improved performance and quality and reduced operating costs. 
       FIGS. 1-2  of the drawings show an axial motor  3  which is exemplary of a motor using the rotor of the present invention. The components of the motor can be best seen in the exploded view shown in  FIG. 2 . These components include a housing  4 , incorporating end shields  5  and  7  and a side wall  9 , a stator  11  (although the windings are not shown in the drawings) mounted within the housing. A rotor disc  13  is mounted on a shaft  15  which is rotatable within the housing by means of bearings  17  and  19 . A wave washer  21  is also included between the bearing  17  and the end shield  5  so as to reduce noise produced by the bearing and promote quieter operation of the motor  3 . 
     As can be seen in the cross sectional side view shown in  FIG. 1 , the rotor disc  13  includes a plurality of permanent magnets  23 , which are preferably ferrite magnets. As can also be seen in  FIG. 1 , an air gap exists between the top face of the magnet positioning device  1  (attached to the rotor disc  13 ) and a lower face of the stator  11 . 
     According to an embodiment of the present invention and referring now to  FIG. 3 , an axial flux electric motor  110  is provided. The motor  110  is generally similar to the motor  3  of  FIGS. 1-2 , except the motor  110  includes a rotor assembly  112  that is different than the rotor disc  13  of the motor  3  of  FIGS. 1-2 . The motor  110  includes a housing  114  and a stator assembly  116 . The housing  114  may have any suitable size and shape. The housing  114  may be made of any suitable durable material, such as a metal or a polymer. The housing  114  may be integral or be made from a plurality of components. For example, the housing  114  may include opposed endcap  118  and  120  and a shell  122 . The housing  114  defines an inner periphery  124  and an outer periphery  126  of the housing  114 . 
     Referring now to  FIGS. 3 and 4 , the stator assembly  116  includes a stator core  128 . The core  128  is fixedly secured to the housing  114 . The stator assembly  116  further includes a plurality of coils  130  including magnet wire  132  wound around protrusions in the form of teeth  134  formed in the stator core  128 . The coils are electrically energized in a sequence to create a timed cycle of magnetic impulses to cause the rotor  112  to rotate relative to the stator assembly  116  at a desired speed or speeds. The stator core  128  may have any suitable size and shape. The stator core  128  may be made of any suitable durable magnetically conductive material, for example as a ferrous metal. The stator core  128  may be integral or be made from a plurality of components. As shown in  FIGS. 3 and 4  and to reduce core losses, the stator core  128  is made of laminations that are connected to form the stator core  128 . The teeth  134  are formed in the core  128 . 
     The rotor assembly  112  includes a rotor  136  supported by a shaft  138  which is rotatably connected to endcaps  118  and  120  by, for example, bearings  140  and  142 , respectively. The rotor assembly  112  also includes a magnet  144  connected to a surface  146  of the rotor  136 . 
     Referring now to  FIGS. 5-7 , the rotor  136  is shown in greater detail. The rotor  136  may have any suitable size and shape. The rotor  136  may be made of any suitable durable material, such as a metal, that for example may be cast or laminated, or a composite of ferrous metal. The rotor  136  may be integral or be made from a plurality of components. The rotor  136  may be made from a metal and may be cast generally into its final form, with some machining provided after casting. Alternatively, the rotor may be made from sheet metal and formed into a general final shape and may also have some final machining. 
     As shown in  FIGS. 6 and 7 , the rotor  136  may include a central hub  148  that defines a central bore  150 . The rotor is rotatably secured to the shaft  138  (see  FIG. 3 ) at central bore  150  of hub  148 . A disc shaped portion  152  of the rotor  136  extends outwardly from the hub  148 . The disc shaped portion  152  includes a face  154  normal to shaft longitudinal axis  156 . The magnet  144  (see  FIG. 3 ) is secured to face  154 . The magnet may be secured to the face  154  in any suitable way. For example, the magnet  144  may be secured to face  154  by adhesives. Alternatively or in addition, additional features (for example protrusions and voids not shown) can be placed on the magnet  144  and/or the face  154  of the rotor  136  to secure the magnet  144  to the face  154 . Further a retainer (not shown) may be used to secure the magnets to the rotor. 
     Referring now to  FIGS. 8 and 9 , the magnet  144  is shown in greater detail. As shown in  FIG. 8 , the magnet  144  is a solitary ring having opposed faces  158  and  160  and a central bore or opening  162 . The magnet  144  also includes an outer diameter  164 . The magnet  144 , unlike the magnets  23  of the motor  3  of  FIGS. 1-2 , is made of an inexpensive magnetizible material, for example a hard ferrite. For example, the magnetizible material may be Alnico or Samarium Cobalt. The magnet  144 , unlike the magnets  23 , is a solitary magnet. The solitary magnet is less expensive to produce and easier to secure to the rotor that a set of individual magnets. While the magnet  144  is as shown a solitary ring, it should be appreciated that a modular or multicomponent magnet made of an inexpensive magnetizible material may be utilized in accordance with the invention. 
     While as stated above, the magnet  144  may be secured to face  154  of the rotor  136  by adhesives, to provide addition securement of the magnet to the rotor  136 , the magnet and rotor may include features in the form of, for example, protrusions and void, to secure the magnet to the rotor and to provide an anti rotation feature. For example and as shown, the rotor  136  may include a Radial (not shown) or circular groove  166  formed in face  154  of the rotor  136  that is sized to match a radial protrusion (not shown) or a circular protrusion  168  extending from face  158  of the magnet  144 . The protrusion  168  may be in interference with the groove  166  and/or may include features (not shown) in the form of tabs and indents to secure the magnet  144  to the rotor  136  with or without the use of adhesives. 
     Typically the magnet  144  is manufactured from a magnetizable material and later permanently magnetized by magnetizing coils. For the magnet to operate efficiently in a motor the magnet is magnetized with a plurality of poles  170  with a first number of magnet poles that is typically used with a second number of stator coils or stator teeth (there being one coil per tooth). For example, a few of the typical combination of stator teeth and rotor magnet poles include 12 teeth with 10 poles and 18 teeth with 16 poles. For the motor  110  of  FIGS. 3-8 , the stator assembly  116  includes 24 teeth, so the rotor  136  typically would have 20 poles  170 . The rotor  136  is thus magnetized to provide the 20 poles  170 . For optimum efficiency the poles  170  have an axial magnetic orientation and a radial geometric orientation. 
     To reduce cogging torque and corresponding motor noise, the orientation of the poles  170  may, as shown, not have an exact radial orientation or may be skewed. The orientation of the poles  170  may be oriented an angle α of, for example, 1-3 degrees from radial centerline  172 . This skewing can be easily accomplished by skewing the magnetizing coils during the manufacture of the coils. 
     To orient the angular position of the poles  170  of the magnet  144  with the rotor  136 , the rotor and/or the magnet  144  may include an angular orientation feature in the form of a radial groove  174  formed in the rotor  136  that mates with a radial protrusion  176  formed in the magnet  144 . Any other angular orientation feature, either temporary or permanent may be used, for example, marks on the magnets and the rotor. 
     Since magnetized ferrite magnets provide a weaker magnetic field per unit volume than neodymium magnets, the ferrite magnet  144  is typically thicker than the neodymium magnet it is intended to replace. For example the ferrite magnet  144  may have a thickness t that is from 2 to 5 times a thick as a neodymium magnet. For example a neodymium magnet with a thickness of 6 millimeters may be replaced with a ferrite magnet  144  with a thickness of 12 to 18 millimeters. 
     To provide additional magnetic field strength to the ferrite magnet  144  the ferrite magnet  144  may have the central bore  162  the outer diameter  164  overhang or extend beyond envelopes of the rotor  136  or the stator core  128  either radially outwardly or radially inwardly, or both. The overhang of the magnet  144  is only limited by the size of the shaft  138  and the size of the shell  122 . The ferrous core of the stator may define a stator core diameter and the magnet diameter may be as much as 50 percent larger than stator core diameter. The rotor core of the rotor may define a rotor core diameter and the magnet diameter may be as much as 50 percent larger than rotor core diameter. 
     For example and as shown in  FIG. 9 , the outer diameter  164  of the magnet  144  has an outer diameter size ODS which is larger than an outer diameter size SOD of the stator core  128  and which is also larger than an outer diameter size ROD of the rotor  136 . Similarly, the bore  162  of the magnet  144  has an inner diameter size IDS which is smaller than an inner diameter size SID of the stator core  128  and which is also smaller than an inner diameter size RID of the rotor  136 . 
     The magnet  144  may have the outer diameter size ODS that may be as much as 25 percent larger, 50 percent larger, 75 percent larger or more than the outer diameter size SOD of the stator core  128 . Similarly the magnet  144  may have the outer diameter size ODS that may be as much as 25 percent larger, 50 percent larger, 75 percent larger or more than the outer diameter size ROD of the rotor  136 . 
     The bore  162  of the magnet  144  may have an inner diameter size IDS that may be as much as 25 percent smaller, 50 percent smaller, 75 percent smaller or less than the inner diameter size SID of the stator core  128 . Similarly, the bore  162  of the magnet  144  may have an inner diameter size IDS that may be as much as 25 percent smaller, 50 percent smaller, 75 percent smaller or less than the inner diameter size RID of the rotor  136   
     It should be appreciated that by increasing the overhang of the magnet  144 , either radially outwardly or radially inwardly, or both, beyond the rotor  136  and/or the stator core  128  and by increasing the thickness t of the magnet  144 , an inexpensive ferrite magnet may be used with the same overall magnet field strength as a that of a set of neodymium magnets. Further it is possible to design an axial flux motor with a set of neodymium magnets and to design an axial flux motor with an inexpensive ferrite magnet ring that can use common components, where only the rotor assemblies need to be different. Any difference in rotor component diameters could be accommodated if the constraints of the shell and the shaft were considered and any difference in rotor thickness could be accommodated by component position relative to the motor shaft. 
     It should be appreciated that the motor  110  of  FIGS. 3-9  may be an air flowing application, a liquid pumping application, a HVAC application or a blower premix application. 
     It should also be appreciated that for high speed applications, where core loss is predominant and copper loss is minimal, flux weakening can be achieved by using negative overhang (having the magnet peripheries be within or inside those of the stator or rotor). For example and as shown in  FIG. 10 , a motor  210  according to the present invention may be provided such that outside diameter OD 2  of outside diameter  264  of magnet  244  may be smaller than the stator core outside diameter COD 2  of stator core  228  and inside diameter ID 2  of bore  262  of the magnet  244  may be larger than stator core inside diameter CID 2   
     According to another embodiment of the present invention and referring to  FIG. 11 , a method  310  for fabricating a motor is provided. The method includes step  312  of fabricating a first set of motor parts. The motor parts may include a first rotor using neo magnets and a first stator for use in a neo motor. The method also includes step  314  of fabricating a second set of motor parts including a second rotor using ferrite magnets for use in a ferrite motor. The method also includes the step  316  of ascertaining the motor magnet type, ferrite or neo and the step  318  of selecting one of the first rotor and the second rotor in accordance with desired motor magnet type. The method also includes the step  320  of assembling a motor with one of first rotor and the second rotor and first stator such that the desired motor magnet type is substantially provided. 
     The methods, systems, and apparatus described herein provide improved rigidity and durability of an electric motor. Exemplary embodiments of methods, systems, and apparatus are described and/or illustrated herein in detail. The methods, systems, and apparatus are not limited to the specific embodiments described herein, but rather, components of each apparatus and system, as well as steps of each method, may be utilized independently and separately from other components and steps described herein. Each component, and each method step, can also be used in combination with other components and/or method steps. 
     When introducing elements/components/etc. of the methods and apparatus described and/or illustrated herein, the articles “a”, “an”, “the”, and “the” are intended to mean that there are one or more of the element(s)/component(s)/etc. The terms “comprising”, “including”, and “having” are intended to be inclusive and mean that there may be additional element(s)/component(s)/etc. other than the listed element(s)/component(s)/etc. 
     This written description uses examples to disclose the invention, including the best mode, and also to enable any person skilled in the art to practice the invention, including making and using any devices or systems and performing any incorporated methods. The patentable scope of the invention is defined by the claims, and may include other examples that occur to those skilled in the art. Such other examples are intended to be within the scope of the claims if they have structural elements that do not differ from the literal language of the claims, or if they include equivalent structural elements with insubstantial differences from the literal language of the claims. 
     Described herein are exemplary methods, systems and apparatus utilizing designs with improved strength and rigidity that reduces or eliminates excessive noise and vibration. Furthermore, the exemplary methods system and apparatus reduced noise while reducing or eliminating an increase in manufacturing cost of the motor. The methods, system and apparatus described herein may be used in any suitable application. However, they are particularly suited for HVAC and pump applications. 
     Exemplary embodiments of the rotor and motor are described above in detail. The electric motor and its components are not limited to the specific embodiments described herein, but rather, components of the systems may be utilized independently and separately from other components described herein. For example, the components may also be used in combination with other motor systems, methods, and apparatuses, and are not limited to practice with only the systems and apparatus as described herein. Rather, the exemplary embodiments can be implemented and utilized in connection with many other applications. 
     Although specific features of various embodiments of the disclosure may be shown in some drawings and not in others, this is for convenience only. In accordance with the principles of the disclosure, any feature of a drawing may be referenced and/or claimed in combination with any feature of any other drawing. 
     This written description uses examples to disclose the invention, including the best mode, and also to enable any person skilled in the art to practice the invention, including making and using any devices or systems and performing any incorporated methods. The patentable scope of the invention is defined by the claims, and may include other examples that occur to those skilled in the art. Such other examples are intended to be within the scope of the claims if they have structural elements that do not differ from the literal language of the claims, or if they include equivalent structural elements with insubstantial differences from the literal languages of the claims.