Patent Document

FIELD OF THE INVENTION 
     This present invention relates generally to electrical generator or motor structures and more specifically to brushless electromotive devices of the type which employ a flat coil array or structure operating within an axially-oriented magnetic field having flux lines mostly perpendicular to the working conductor portion of the coils. This may include disc or pancake rotary motors as well as linear motors having such flat coils and magnetic structure. 
     BACKGROUND OF THE INVENTION 
     Motors employing disc-shaped coil armatures and brush commutation have been in use since the late 1950&#39;s. Brushless disc-type motors were later developed, employing rotating magnets, coil stators and electronic commutation. Such motors have been used in large numbers in audio and video tape recorders and computer disc drives. In such a motor, a magnetic rotor disc with alternating North/South pole pieces rotates above and/or below a plane containing several flat, stator coils lying adjacent one another. Current flowing in the conductor wires of the coils interacts with the alternating magnetic flux lines of the disc, producing Lorentz forces perpendicular to the radially directed conductors and thus tangential to the axis of rotation. While current flows through the entire coil, only the radial extending portions of the conductors (called the working conductors) contribute torque to the rotor. See, for example, U.S. Pat. Nos. 3,988,024; 4,361,776; 4,371,801; and 5,146,144. A variation of this arrangement is known in which the circumferential portions (nonworking conductors) of the wire-wound coils overlap each other. See, for example, U.S. Pat. Nos. 4,068,143; 4,420,875; 4,551,645; and 4,743,813. While this arrangement allows closer packing of the working conductors, it also requires that the gap between the rotor&#39;s magnets and flux return be about twice as thick as would be required for a single thickness of a non-overlapping coil, thus reducing the magnetic flux density and thus reducing the motor&#39;s efficiency. 
     SUMMARY OF THE INVENTION 
     In view of the well known disadvantages in the above-mentioned prior art, it is an object of the present invention to provide a novel coil structure which more efficiently provides electromotive interaction between these new coils and the magnets within a rotary motor or generator of the type having a generally flat, ring-shaped coil structure and employing an axial gap magnet structure, such as in disc or pancake motors, while minimizing the thickness of the coil and magnet flux gap. Specifically, the invention relates to the construction and shape of the individual coils making up a coil array (circular or arc-shaped arrangement of coils) so as to allow interlocking or overlapping of multiple coils to form a thin disc coil array having double the density of, but not significantly more thickness than, non-overlapping coil arrays. The radially extending conductor portions of each coil all lie in a first plane while the circumferentially extending portions of each coil&#39;s conductors lie above and below said first plane. 
     Another object of the present invention is to maximize the total length of the working conductors within a circular coil array by overlapping three adjacent coils, so as to maximize the electromotive interaction for a motor or generator of a given diameter. For any given device diameter, conductor cross-sectional area, and magnetic flux density, this technique maximizes the torque which may be produced by a motor, or the voltage produced by a generator. 
     Another object of the invention is to provide a mechanism whereby multiple coil arrays may be closely stacked with corresponding magnetic rotors in alternating layers so as to increase the total coil area within a motor or generator of a given diameter. This increased coil area allows increased interaction between coils and magnets, improving the power conversion with the motor or generator. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       While this specification concludes with claims particularly pointing out and distinctly claiming the subject matter which is now regarded as the invention, it is believed that the broader aspects of the invention, as well as several of the features and advantages thereof, may be better understood by reference to the following detailed description of presently preferred embodiments of the invention when taken in connection with the accompanying drawings in which: 
         FIG. 1a  is an illustration of a prior art (planer) coil assembly; 
         FIG. 1b  is an illustration of a prior art magnet rotor associated with the coil assembly of  FIG. 1a ; 
         FIG. 2  is an illustration of another prior art (partially overlapping) coil assembly; 
         FIG. 3  is an illustration of a single wire-wound coil according to this invention; 
         FIG. 4  is an illustration of three coils of  FIG. 3 , overlapped in their proper orientation according to this invention; 
         FIG. 5  is an illustration of a Segmented Coil Array (“SCA”) coil platter, with a partial cutaway showing the multiple internal coils of  FIG. 3 , according to this invention; 
         FIG. 6  is an enlarged cross-sectional illustration of the SCA plater of  FIG. 5 ; 
         FIG. 7  is an illustration of three coils of an alternative embodiment of the present invention, overlapped in their proper orientation according to this invention; 
         FIG. 8  is an illustration an alternate form of coil having lower resistive losses; 
         FIG. 9  illustrates a basic electromotive device showing three nested coils in their proper orientation to two adjacent magnet rotors; and 
         FIG. 10  is an illustration of three coaxially stacked SCA coil platters of  FIG. 5  suitable for use in an electromotive device. 
     
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     Referring now to the drawings and particularly to  FIG. 1 , there is shown a prior art planer coil assembly  10  and a magnet rotor  11  which may be used to make a typical prior art disc-type motor. This coil assembly  10  consists of several individual coils  13 ,  13 ′,  13 ″ arranged in a circular pattern, each coil  13  having two radially extending conductor portions or legs  14 ,  14 ′, an inner circumferentially extending leg  15  and an outer circumferentially extending leg  16 , all lying in a single plane. In a motor utilizing such a coil assembly, the magnet rotor  11 , having alternating North/South poles  18 ,  19  arranged in a corresponding circular pattern and affixed to a central shaft (not shown), rotates in a plane closely adjacent to, but spaced slightly above and/or below, the plane containing the coils  13 ,  13 ′,  13 ″. While two magnet rotors  11  may be used, one on either side of the coil assembly  10 , only one may be used if a magnetic flux return, such as a soft iron disc (not shown), is placed on the other side of the coil assembly opposite the rotor. In use, electrical current in the radially extending conductors  14 , 14 ′ of the coil assembly  10  interacts with the alternating magnetic flux lines from the north  18  and south  19  poles of the rotor, producing Lorentz forces perpendicular to the radial conductors  14 , 14 ′ and thus tangential to the rotor&#39;s  11  axis of rotation. While current flows through the entire coil  13 , only the radial conductor legs  14 ,  14 ′ (called the working conductors) contribute torque to the rotor  11  while the non-working legs  15 ,  16  merely complete a current path. 
       FIG. 2  shows a somewhat different prior art coil assembly  20  in which the working conductor legs  22 ,  22 ′ of the wire-wound coil  23  overlap the adjacent coils  21 ,  25 . Likewise, the radial legs  24 ,  26  of coil  25  overlap adjacent coils  23 ,  27 . While this overlapping arrangement allows denser packing of the working conductors  22 ,  24 ,  26 , it also requires that the spacing or gap between the rotor&#39;s magnets and flux return be twice as wide as would be required for a single thickness of the coil shown in FIG.  1 . 
       FIG. 3  illustrates one individual coil  30  constructed according to the present invention. The coil  30  comprises round or flat conductor wire spirally wound in a keystone or trapezoidal shape defining a central open space  33 . The open space  33  is bounded by two radially extending side portions or working legs  37  lying in a first plane, an outer circumferentially extending base portion  35  and an inner circumferentially extending base portion  39  lying in a second plane, parallel to but spaced apart from and above the first plane. As will be explained later, the open space  33  must be wide enough to accommodate two adjacent working legs  37 . The electrically conducting coil leads  34 ,  36  extending from the outer circumference of the coil provide a means for applying an electrical current through the coil from an external source (not shown). Near each end of the radially extending legs  37  are offsetting bends  31  and  32  that provide the transition from the second plane to the first plane. These offsetting bends  31  and  32  are an important feature of the present invention and are required for the desired high density packing arrangement presented in  FIG. 4  below. Between the offsetting bends  31  and  32  is working portion  38  of the coil&#39;s radially extending legs  37  to which magnetic flux is applied during use by an adjacent magnet rotor  11 . The length l of this working portion  38  is called the working length. Preferably, the working length l of the individual coils are optimized for maximum torque or voltage production by ensuring that such working length l is about 42% of the distance from the center of the coil platter to the outer point of the coil working length, which distance is called the critical radius of the platter. 
     As one example of a preferred embodiment,  FIG. 4  shows three typical coils  42 ,  44 ,  46  which would be arranged with  45  others in the same manner to form an assembly of  48  coils for this particular diameter array. The coils are arranged such that the working portions  38  of each coil are all in the same first plane and the central open space  33  of one coil  44  (between its working legs  37 ) is filled by one working leg  37 ′ from each of the adjacent coils  42 ,  46 . The rest of the coil  44  (mostly the inner  39  and outer  35  circumferentially extending portions) cannot reside in the same first plane because it would require parts of different coils to pass through the same space. This is the reason the offsetting bends  31  and  32  are important, so that the ends will lie in a second (and third) plane whereby the coils may be nested to achieve a high density. 
     A complete array of coils, affixed to each other and/or to a suitable structural material to form a coil platter (or an arc-shaped portion of the total coil platter) may be referred to as a Segmented Coil Array (“SCA”). A complete coil platter  50  is depicted in FIG.  5 . (This particular illustration does not show the coil leads  34 ,  36  for clarity). This SCA platter  50  is composed of  48  individual coils  30  molded into an epoxy resin or other easily moldable material for support, which optionally may be further strengthened by also molding in layers of fiber reinforcing fabric. Since the inner  39  and outer  35  ends of each coil  30  lie in planes slightly above and below a first plane containing the working legs  37 , the molded platter  50  has a thin center face  54  with a thicker inner rim  52  and outer Tim  56 . Any other even numbers of coils other than  48  may also be used in an SCA, depending on the electrical or mechanical properties desired. 
     It has been discovered that for a given SCA diameter, the working length of the individual coils may be optimized for maximum torque production, in a motor, or voltage production, in a generator. This is done by making the coil working length 42% of the critical radius. This critical radius  58  is indicated in FIG.  5  and is defined as the distance from the center of the coil platter to the outermost points of the working length, before reaching the outer rim  56 . 
     A cross section of a portion of the coil platter  50  of  FIG. 5  is illustrated in FIG.  6 . Preferably, the exterior surface of the center face  54  is coated with one or two layers of PFTE  62 ,  64  to provide abrasion resistance and low friction characteristics. Similarly, one or two pieces of thin fiberglass cloth  63 ,  65  may be added over the coils, under PFTE, to further increase strength and stiffness of the platter. 
       FIG. 7  illustrates three coils of an alternative coil configuration  90 . An SCA formed with alternative coil configuration  90  is comprised of a first and a second multiplicity of coils of equal number. The coils of the first multiplicity of coils (e.g. coils  91 ,  93 ) are formed and circumferentially oriented to lie in a first plane. The coils of the second multiplicity of coils are formed such that the working legs  37  of each coil lie in a first plane, and the outer circumferentially extending base portion  35  and inner circumferentially extending base portion  39  of each coil lie outside the first plane. As previously described with regard to the coil configuration embodiment depicted in  FIG. 3 , offsetting bends  31  and  32  near each end of the radially extending legs  37  of the coils of the second multiplicity of coils provide the transition of the base portions  35  and  39  from the first plane to outside the first plane.  FIG. 7  depicts the angles of the offsetting bends  31  and  32  as being approximately 90 degrees in this alternative coil configuration  90 , but any angle of the offsetting bends  31  and  32  sufficient to allow the first and second multiplicity of coils to nest as depicted such that the working legs  37  of all coils of both the first and second multiplicity of coils lie substantially in a single plane is acceptable. 
       FIG. 8  illustrates yet another alternate coil configuration  70  useful with the present invention and having lower electrical losses than coil  30  above. The coil  70  comprises flat conductor wire or ribbon (i.e. having a rectangular cross-section) spirally wound to form a basic keystone or trapezoidal shape surrounding a central open space  73 , much like coil  30  above. The open space  73  is, like in coil  30 , bounded by two radially extending portions or working legs  77  lying in a first plane, an outer circumferentially extending base portion  75  and an inner circumferentially extending portion  79  lying in a second plane, parallel to but spaced apart from the first plane. In contrast to the offsetting bends  31  of coil  30  that provide a gradual transition from the first plane of the radial legs to the second plane of the base portions, the low-loss coil  70  is machined after winding so that there are abrupt offsetting steps  71  near each end of the radially extending legs  77 . Further, sufficient material is machined away from the radially extending legs  77  so that, at least over the working length  78 , the legs  77  have a smaller cross-sectional area than the base portions  75 ,  79 . The electrical resistance in the larger base portions  75 ,  79  of coil  70  will be less than in corresponding base portions  35 ,  39  of coil  30 , when both have the same sized working legs, thereby reducing the I 2 R losses of coil  70 . As explained earlier, the open space  73  must be wide enough to accommodate two adjacent working legs  77  to achieve the high density nesting shown in FIG.  4 . Coil leads would typically extend from the outer circumference of the coil, but are not shown here to improve clarity. 
     In operation within a typical electromotive device, a circular coil platter  50  is exposed to an axially directed magnetic flux produced by a magnet rotor  11 , i.e. flux perpendicular to the plane containing the coils&#39; working lengths. One such way of providing this flux is illustrated in  FIG. 9  in which a magnet rotor  11  (which could be composed of permanent magnet segments or electromagnets and which would be affixed to a central rotatable shaft, not shown) is positioned adjacent one or both sides of the coil platter to form a basic electromotive device  80 . If only one magnet  11  is used in a particular device, some type of flux return, such as a soft iron disc, should be placed adjacent the opposite side of the coil platter. Here, only three coils  42 ,  44 ,  46  of an entire platter  50  of  48  coils  30  are shown for clarity in this example. As the coils are appropriately energized (by any well known control circuit, not shown), a rotating force or torque is produced in the magnet rotor(s). Depending on the results desired and the corresponding mechanical arrangement, the magnet rotor may cause a shaft to revolve at high speed or merely turn a small angle at high torque. 
     As illustrated in  FIG. 10 , it is beneficial to stack multiple coil platters  50 ,  50 ′,  50 ″ along a common central axis with alternating layers of magnetic rotors  11 . This arrangement increases the total working area, and thus the power, within an electromotive device of given diameter. For clarity, the coil leads and magnet rotors are again not shown in FIG.  10 . The details of various possible mechanical arrangements to adapt the present invention to common industrial devices are so well known that they need not be discussed here. 
     While the present invention has been described in terms more or less specific to preferred embodiments, it is expected that various alterations, modifications, or permutations thereof will be readily apparent to those skilled in the art. For example, the invention may be embodied in an electrical generator as well as a motor. Instead of a circular coil array, the coils of the invention may be formed into a linear array or a partial circle rather than a complete circular array. Therefore, it should be understood that the invention is not to be limited to the specific features shown or described, but it is intended that all equivalents be embraced within the spirit and scope of the invention as defined by the appended claims.

Technology Category: h