Abstract:
A method and mechanism for automatic or manual winding of a stator. A fixed arbor serves to support the stator during the winding process, as well as a wire feed point and wire guide. A mechanism moves the stator in a back and forth motion along the major axis of the arbor. Proper axial position of the wire is maintained by the outer surface of the arbor and the axial slot itself. The arbor has a channel that serves to guide the wire, allowing it exit in each of the two possible longitudinal directions along the major axis of the arbor.

Description:
CROSS REFERENCE TO RELATED PATENT APPLICATIONS  
       [0001]     This application claims the benefit of U.S. Provisional Patent Application Ser. No. 60/831,508 filed on Jul. 18, 2006. The entire teachings of the above application are incorporated herein by reference. 
     
    
     BACKGROUND OF THE INVENTION  
       [0002]     The present disclosure relates to the manufacture of electric machines, such as a motor or generator, and in particular to a machine that automates wire winding of a stator.  
         [0003]     One common type of electric machine is a brushless Direct Current (DC) motor that includes two major elements, a stator and a rotor. The stator typically includes a wire coil having a number of windings. The rotor typically includes permanent magnets. The rotor and stator are arranged such that the rotor can move freely with respect to the mechanically fixed stator. As a result, electromagnetic interaction between the stator and the rotor causes the rotor to move in response to polarity changes in the stator windings.  
         [0004]     One common design has the rotor embedded as a shaft that turns inside a cylindrical stator. The rotor assembly typically includes a number of permanent magnets placed about a shaft. The magnets are held on the shaft by an outer sleeve. The rotor assembly is rotatively supported within the cylindrical stator housing via low friction bearings.  
         [0005]     The stator is often made by laminating a number of disks formed of a ferrous material to form a “back iron.” The disks typically have a center hole with tines formed therein. The laminated stack of disks provides a set of axial slots around which are wrapped copper wire strands to form the motor windings.  
         [0006]     It can be appreciated that much of the cost to manufacture an inside wound motor is due to the need to wrap wires around and/or within the axial slots of the stator.  
         [0007]     A number of somewhat elaborate machines have been devised to automatically wind a stator. In one common approach, windings are formed by a head that comprises a hollow needle through which a wire strand slides. The needle is supported and controlled by an apparatus to reciprocate within and parallel to the axis of the stator. The needle is thus caused to move about the slots, following a substantially elliptical path. The winding needle(s) are operated by a complex series of mechanical drives and gears to follow the required path. See the machines shown in U.S. Pat. No. 6,032,897 and U.S. Pat. No. 4,817,256, which are herein incorporated by reference in its entirety.  
         [0008]     In an approach described in U.S. Pat. No. 5,025,997, which is herein incorporated by reference in its entirety, the stator is held within a fixture such that it can be rotated through a predetermined angle. A wire stopper is attached to one or more ends of the stator. The wire guiding member is slidably supported by a pair of bearings, and driven by a mechanism, so that it is moved periodically through the central hole of the stator, external of the wire stoppers. This winding apparatus requires various components including a stationary frame, a moveable frame, several wire feeding/carrying means, and a wire guiding member fixed to the stationary frame.  
       SUMMARY OF THE INVENTION  
       [0009]     The present disclosure is a simplified method and mechanism for automatic winding of motor stators. According to the present disclosure, a fixed arbor serves to support the stator during the winding process, as well as a wire feed point (an elliptical port), and wire guide. A mechanism moves the stator in a simple back and forth and radial motion along the major axis of the arbor. Proper axial position of the wire is maintained by the outer surface of the arbor and the elliptical port itself. The arbor has a passage that serves to guide the wire, allowing it exit in each of the two possible longitudinal directions along the major axis of the arbor. As the wire/s is pulled into the corners of the ellipse or “eye shaped” vortex of the arbor exit port, it is gathered tightly into a shape suitable to enter the stator slot.  
         [0010]     Several wires can be wound all at once. The prototype arbor has successfully wound 65 wires in a ¼″ bundle into a stator slot at the same time. This is a radical improvement. It is also possible to wind with a single wire using this disclosure but the best logical application is to use several individual wires from several spools at the same time to expedite the process.  
         [0011]     In a process to wind a stator, wire is first fed through one end of the arbor to the feed point. The stator is then turned axially on the arbor so that a first slot is aligned with the feed point. The stator is then moved longitudinally along the arbor, such that the selected slot remains parallel in an appropriate position with the feed point, and so that the wire is fed into the slot. When the stator reaches the other end of the arbor, the stator is turned to the next axial position and then moved back in the opposite direction along the arbor. The process is then repeated to form the desired number of windings.  
         [0012]     In this manner, windings are easily formed on the stator with a minimal complexity mechanism.  
         [0013]     Among other advantages are that because the slot in the stator and the outer surface of the arbor naturally provide a guided channel path for the wire, when used in a manual application, no additional wire feeding or wire guiding mechanisms are required. Stators can be assembled in a radial twist or “skew” as it is typically referred to and the stator is guided on this helical path by the wire or bundle of wires as it is inserted into the stator in a manual application. A servo-motor dictates this helical path in an automatic application.  
         [0014]     According to a first embodiment of the present disclosure, there is provided a method to manufacture a wound stator for an electric motor. The method includes the steps of providing an arbor with an opening, and providing a stator including notches. The stator is positioned relative to the arbor to align a first notch with the opening. The arbor or the stator is moved to lay a conductive material in the first notch.  
         [0015]     The stator or the arbor is then rotated to align a second notch with the opening. The arbor is moved relative to the stator to lay the conductive material in the second notch. The method may further include the step of moving the stator, or the arbor relative to one another in a manual manner, or in an automatic manner.  
         [0016]     The arbor, and the stator can be cylindrically shaped, or have other shapes. The method may further include providing a conductive wire as the conductive material, or a wire bundle as the conductive material. The method lays a predetermined number of windings of the conductive material in the stator with the predetermined number of windings of the conductive material corresponding to a predetermined number of turns for the electric motor for torque and for power. These turns are be closely located to the permanent magnets of a rotor in operation.  
         [0017]     The method may further provide the arbor with an outer diameter, which is measured smaller than an inner diameter of the stator. The arbor has a size that is configured to freely traverse into, and out of the stator to lay the wire bundle. The method further includes providing the arbor with a channel formed therein with the conductive material fed in tension through the channel to the opening.  
         [0018]     In another, alternative, and preferred embodiment, the method further can include providing the arbor with a member inserted therein. The member has a channel. The channel communicates with the opening of the arbor. This channel facilitates insertion of the tensioned conductive material through the arbor, the member, and through the opening. Alternatively, the stator can be provided with notches formed around an inner surface of the stator. The notches can be curved or straight relative to a longitudinal axis of the stator.  
         [0019]     The method may further include moving the arbor or the stator to lay the conductive material in the third notch, and rotating the stator or the arbor to align a fourth notch with the opening. The arbor can be then moved relative to the stator to lay the conductive material in the fourth notch. The method can further lay the conductive wire bundle in other notches, and is not limited to the number described above. The notches may be formed around an outer surface of the stator, instead of around the inner surface.  
         [0020]     A method to manufacture an electric motor is also provided that includes providing a rotor having magnets. The method also provides an arbor. A conductive material extends outside of the arbor at a first end. The conductive material is laid into at least one notch of a stator.  
         [0021]     The conductive material is tensioned through a channel formed through the arbor from a conductive material feeder. The stator includes notches, and the stator is positioned relative to the arbor to align a first notch with the conductive material. The arbor or stator is moved to lay the conductive material in the first notch, and then the stator or the arbor is rotated to align the conductive material with a second notch. The conductive material extends outside of the arbor at the first end. The arbor or the stator is moved to lay the conductive material in the second notch to provide the wound stator.  
         [0022]     The rotor is supported in the stator to form the electric motor. The rotor may have permanent magnets in a sheath, which surrounds the rotor. The conductive wire is then cut when the stator is nearly completely wound. A wire retainer can be introduced into the notches with the conductive wire bundle in at least one of the notches to secure the conductive wire bundle in the notches of the stator. The retainer can be insulation, a potting, or a glass reinforced plastic, or any other suitable adhesive to secure the conductive wire bundle in the notches of the stator. 
     
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0023]     The foregoing will be apparent from the following more particular description of example embodiments of the invention, as illustrated in the accompanying drawings in which like reference characters refer to the same parts throughout the different views. The drawings are not necessarily to scale, emphasis instead being placed upon illustrating embodiments of the present invention.  
         [0024]      FIG. 1  is an exploded, isometric view of the components of one type of motor that can be made according to the present disclosure.  
         [0025]      FIG. 2  is a diagram illustrating the components of a wire winding apparatus according to the disclosure.  
         [0026]      FIG. 3  illustrates the stator in an initial position on the arbor.  
         [0027]      FIG. 4  shows the apparatus after two back and forth passes of the stator over the arbor have been made.  
         [0028]      FIG. 5  illustrates the completed stator before the wire end is cut. 
     
    
     DETAILED DESCRIPTION OF THE INVENTION  
       [0029]     A description of preferred embodiments of the invention follows.  
         [0030]      FIG. 1  is an exploded view of one type of motor  10  that can be made according to the present disclosure. The motor  10  has a stator  12  and rotor  20 . The stator  12  in the illustrated example has three (3) stator sections numbered  14 - 1 ,  14 - 2 , and  14 - 3 , one stator for each operating phase. It will be understood, however, that fewer or more stator sections might be provided.  
         [0031]     The motor  10  is of the inside DC brushless type, in which the rotor  20  is disposed along a central axis to turn inside of the stator  12 . The rotor  20  and stator  12  assemblies are held in relative position with respect to one another by motor housing  30  and by end plates (frames)  32 . The housing  30  and frames  32  may be formed of aluminum, steel, or other suitable metal. The rotor assembly  20  is held in place on frame  32  via front and rear bearings  33 , on which the rotor also freely rotates.  
         [0032]     The rotor assembly  20  includes outer sleeves  21 , an inner rotor shaft  22 , and a number of magnet bars  23 . The rotor  20  actually arranges magnet sections  23  in three rotor sections  25 - 1 ,  25 - 2 ,  25 - 3  in the illustrated embodiment. Thus, there is a front rotor section  25 - 1 , a center rotor section  25 - 2 , and rear rotor section  25 - 3 . Each magnet section  23  electromagnetically interacts with the corresponding one of the stator sections  14 . The permanent magnets  23  may be enclosed in a sheath, such as outer sleeve  21 , which may be made of a non-magnetic material such as stainless steel. The sheath may be crimp-formed or otherwise secured around the magnets to hold them in place, which may be required when high speed operation would produce radial forces that would cause the magnets to separate from the rotor shaft.  
         [0033]     The stator sections  14  each comprise a cylindrical back iron assembly  16 , having a number of internal tines and windings  19 . As is known in the art, the back iron  16  may be built up from a number of flat disk-like pieces that are laminated to one another tines provide a set of radial slots  18  into which wire is wound. The windings  19  provide the desired number of turns for the motor  10 .  
         [0034]     The present disclosure specifically involves an apparatus and method for placing the windings  19  within the stator section  14 . The present disclosure utilizes a fixed arbor  100  which supports the stator  14  during the winding process, as shown in  FIG. 2 . The main body of the arbor  100  is generally an elongated cylinder having three sections. Note that the outer diameter ODa of the arbor  100  is only slightly smaller than the inner diameter IDs of the stator  14 . The difference in diameters is small enough so that the resulting space can contain and guide the wire  101  through axial slots  18  during the winding process. This permits the arbor  100  to be used as both the support for a stator  14  and as a guide for the wire bundle  101  as it is passed through axial slots  18 . A first section  104  and second section  102  serve as supports for the stator  14  and guides for the wiring during the process. The second section  102  has at least one hollow portion  102  therein such that a wire or wire bundle  101  can be fed through to a center section  110 .  
         [0035]     The end of the first section  104  of the arbor  100  is generally the supported end and the end of second section  102  is generally a free end, although either end  102  or  104  of the arbor can be the supported end or free end. It may make more sense to have end  102  be the supported end as that can provide for continuous feed from the wire tensioner, as will be understood.  
         [0036]     The center section  110  of arbor preferably has a channel  112  formed therein through which the wire  101  is fed. Wire  101  is held under tension via tensioner to the right of arbor section  100  (not shown in the drawings).  
         [0037]     The wire  101 , which is used to form the windings for stator  14  is fed at a feed point  114  in a way that it can be easily led out of the channel  112  in one of two directions  106 ,  116 , towards first section  104  or second section  102 . The first direction  116  is generally towards section  104  (to the left in the drawing) and the second direction  106  is towards section  102  (to the right in the drawing). The channel  112  has shaped end taper portions to allow the wire bundle  101  to freely move between position  106  and  116 .  
         [0038]     A channel section  120  generally forms the remainder of the cylinder to form the completed arbor  100 , and has a corresponding channel  122  and feed point  124  that generally mirrors the corresponding channel  112  and feed point  114  in the main body portion of the arbor  100 . Fasteners such as screw holes  115 ,  125  are formed in the arbor  100  and section  120  to permit the fastening section  120  via fasteners  127  such as screws. The channel section facilitates insertion of the wire  101  in the channel  112 .  
         [0039]      FIG. 3  shows an initial starting step of the stator winding process. Here the stator  14  has been placed on the arbor  100 . In this initial position, the wire bundle  101  has been led out to a far end portion of the arbor section  104 . The stator  14  was then fed on the arbor in the direction of the arrow  130  from starting end  100 . During this process the stator  14  was aligned with the feed point  114  such that the wire bundle  101  is fed through one of the axial slots  18 .  
         [0040]     In the next step of the process, the stator  14  is rotated with respect to the arbor  100  to cause the feed point  114  (and hence wire  101 ) to be aligned with a different slot  18 . The stator  14  is generally moved in one of a counter clockwise  140  or clockwise  141  direction on the arbor  100  to accomplish this. At this point, the stator  14  is then drawn back along the arbor towards the right in the direction of arrow  131 .  
         [0041]     The stator  14  is then alternately drawn back and forth in the direction of arrows  131 , then  130 , then  131  etc. rotating to align with a different slot each pass. The stator alternately takes up a position on the first portion  104  of the arbor  100  as shown in  FIG. 4 , and a second position along the second section  102  of the arbor  100  as shown in  FIG. 5 .  
         [0042]      FIG. 5  illustrates a position of the stator  14  when it is nearly completely wound, at which point a cut can be made of the wire bundle  101  at some point beyond the feed point  114 . The wound stator is then moved slightly off of the end of the arbor where wire retainers of an insulating, glass reinforced plastic are installed in the provided passage of the back iron to retain the wires. This can be done manually or as an automatic function of a fully automated machine. The wound stator can also be off-loaded on to another arbor of equal diameter that is held end to end with the winding arbor to maintain capture of the wires while in transit to a plastic loading portion of the automatic machine or used as a hand tool for an operator that is used to off-load the wound stator to be manually loaded with the plastic retainers while the automatic machine is winding the next stator.  
         [0043]     While this invention has been particularly shown and described with references to preferred embodiments thereof, it will be understood by those skilled in the art that various changes in form and details may be made therein without departing from the scope of the invention encompassed by the appended claims.