Abstract:
An armature and method of winding the armature that improves coil density by winding adjacent poles so that the resulting windings have outer surfaces that taper in opposite directions that extend over a bisecting axially extending plane between the pole teeth at opposite ends thereof. The poles having the greatest radial extent relative to the pole axis at their base ends that are wound first.

Description:
BACKGROUND OF INVENTION 
     This invention relates to the armature of a rotating electrical machine and more particularly to the coil winding thereof and the method of forming such winding. 
     The armature of a rotating electrical machine is generally comprised of a core consisting of a circular core portion from which a plurality of circumferentially spaced teeth radially extend. Coils are wound around these teeth and cooperate with circumferentially spaced permanent magnets. Such constructions are employed in both electric motors and generators. 
     Generally the coils are wound around the pole teeth by feeding a wire in looping fashion around the pole teeth. The wire is fed from a feeding needle that is extended into the space between the adjacent teeth and the needle is passed in a circular fashion around the pole tooth and the wire is deposited thereon in coils. As the winding continues the needle is gradually moved along the length of the tooth so that it is fully wound. 
     The resulting structure is shown in FIG. 1 which is a partial view of an armature being wound in the conventional prior are method. The armature is indicated generally by the reference numeral  21  and has a ferromagnetic core consisting of a circular ring portion  22  from which pole teeth  23  radially extend. The core is preferably formed from a plurality of laminated sheets. The pole teeth  23  are circumferentially spaced to define gaps  24  therebetween. The ends of these pole teeth are formed with projections  25  to define a narrow mouth  26  opening into the gap  24 . 
     A winding needle  27  is passed into the gap  24  through the mouths  26  and feeds a wire  28  around an insulating bobbin (not shown) that encircles each pole tooth  23 . As the needle  27  is passed around the pole teeth in a circular pattern the wire is looped onto the pole teeth  23  to form the coils, indicated generally at  29 . 
     Thus it is clear that the number of turns around each pole tooth  23  is limited due to the necessity of providing clearance for the needle. To overcome this disadvantage and to permit greater winding density, inventors of the assignee hereof have proposed a construction as disclosed in U.S. Pat. No. 6,590,310, issued Jul. 8, 2003, entitled “STATOR COIL STRUCTURE FOR REVOLVING-FIELD ELECTRICAL MACHINE AND METHOD OF MANUFACTURING SAME”. Certain inventors hereof have also invented several improvements thereon presently pending. 
     These inventions either eliminate totally or minimize the projection of the winding needle into the slot during winding. This is accomplished by providing an insulating projection on one or both radially extending, axially spaced faces of the pole teeth. The wire end is restrained at an end of the pole tooth and as the winding occurs the wire is caused to slide along the pole tooth until it is stopped by contact with the ring portion of the armature of the previous coil winding. In this way the coils pile up and it is possible for the windings on one pole tooth to fill nearly all of area on one side of the gap between adjacent pole teeth. The remainder of the gap is nearly filled by the winding around the adjacent pole tooth. 
     Although these inventions greatly improve the winding density, there can be further improvement. For example, with those inventions there is a possibility of interference between adjacent windings in the area of the slot causing the possibility of damage to the insulation of the winding and/or the winding may bulge out of the mouth of the slot. Thus some clearance is provided. 
     It is, therefore, a principle object of this invention to provide an armature construction and winding method that permits greater coil density. 
     SUMMARY OF INVENTION 
     A first feature of the invention is adapted to be embodied in an electrical armature comprised of a core having a plurality of pole teeth extending radially from a circular ring portion. A plurality of winding coils each encircle a respective one of the pole teeth. The coil windings on adjacent of the pole teeth are wound such that the radial extent of the windings relative to an axis of the respective pole tooth is not the same at all positions along the length of the pole tooth axis. The radially outermost winding of at least one of the adjacent pole teeth extends across an axially extending plane positioned equidistant between the adjacent pole teeth. 
     Another feature of the invention is adapted to be embodied in a method of winding an electrical armature. The armature is comprised of a core having a plurality of pole teeth extending radially from a circular ring portion. The method comprises winding an electric wire around a first of said pole teeth to form a plurality of winding coils the radial extent of which relative to an axis of the respective pole tooth is not the same at all positions along the length of the wound pole tooth axis so that the radially outermost winding extends across an axially extending plane positioned equidistant between adjacent pole teeth. 
    
    
     BRIEF DESCRIPTION OF DRAWINGS 
     FIG. 1 is a partial cross sectional view of an armature having a construction of a prior art type and wound in accordance with a prior art method. 
     FIG. 2 is a partial cross sectional view, in part similar to FIG. 1, but showing a first concept of the invention. 
     FIG. 3 is a partial cross sectional view, in part similar to FIGS. 1 and 2, but showing the first step of a winding method embodying the invention. 
     FIG. 4 is a partial cross sectional view, in part similar to FIG. 3, showing the first step of the winding method embodying the invention. 
     FIG. 5 is a cross sectional view taken along the line  5 — 5  of FIG. 4 but with the windings removed. 
     FIG. 6 is a cross sectional view taken along the line  6 — 6  of FIG.  5 . 
     FIG. 7 is a cross sectional view taken along the line  7 — 7  of FIG.  5 . 
     FIG. 8 is a cross sectional view taken along the line  8 — 8  of FIG. 4 but with the windings removed. 
     FIG. 9 is a cross sectional view taken along the line  9 — 9  of FIG.  8 . 
     FIG. 10 is a side elevational view of the entire armature during the winding operation. 
     FIG. 11 is a partially developed view of the armature showing the path of the winding needle. 
     FIG. 12 is a view taken perpendicular to FIG.  11  and shows the path of the winding needle. 
    
    
     DETAILED DESCRIPTION 
     Referring now in detail to the remaining figures of the drawings the basic construction of the armature core is the same as the prior art, where components are the same they will be identified by the same reference numerals and will be described again only where necessary to understand the invention. As noted above, the construction disclosed in U.S. Pat. No. 6,590,310 is effective in increasing the winding density. However it, like the prior art generally has like windings on each of the pole teeth and thus presents gaps in the winding even though it attempts to provide substantial winding coverage. That is each tooth has the same number of turns on it and thus there will exist some clearance on both sides of a plane that extends axially through the center of the gap between adjacent teeth. 
     Therefore the inventors hereof have conceived that the winding density could be improved if adjacent teeth were wound differently as shown in FIG.  2 . This figure shows the use of the method of the aforenoted patent and the insulators formed on at least one axial face of the pole teeth  23  are indicated generally by the reference numeral  31 . These insulators  31  can have any of the shapes disclosed in the aforenoted patent. As seen in FIG. 2, the left side pole tooth of the pair, designated  23   a  has an equal number of windings  32  along its length and these windings ( 3  in number) all lie on one side of the bisecting axial plane  33 . On the other hand the remaining pole tooth of the adjacent pair, designated as  23   b  also has an equal number of windings  34  along its length ( 4 ) and thus some of these windings lie on the same side of the plane  33  as the windings  32 . This increases the winding density, but still leaves a gap  35 . 
     Therefore and as shown in the remaining figures, another winding configuration and method is employed to still further improve the winding density. As seen in FIGS. 5,  8  and  12  the pole teeth  23  are divided into two groups  23   c  and  23   d  in alternating fashion. Thus adjacent pairs of the pole teeth  23  consist of one pole tooth from each group ( 23   c  and  23   d ). These figures also show the insulating bobbins, indicated generally as  36 . The bobbin  36  may, as in the prior art be formed from two mating halves. They consist of annular ring portions  37  from which pole tooth encircling portions  38  extend in embracing fashion to the pole teeth  23 . 
     Projections  39  extend axially outwardly from the ring portion at the base of each pole tooth  23 . In a similar manner, projections  41  are formed on the axial outer sides of the bobbin  36  at the radial outer tip of the pole teeth. The construction of the bobbin as thus far described is the same for the pole teeth  23   c  and  23   d . However insulators are provided in the axial outer sides of the bobbin tooth encircling portions  38  and these insulators as will next be apparent have a different configuration. 
     The insulators associated with the pole teeth  23   c  are indicated generally by the reference numeral  42  and their configuration is best shown in FIGS. 5-7. These insulators  42  have a generally rectangular cross section portion  43  that extends from the tip of the teeth  23   c  nearly to their roots. Then the insulators are formed with a steeply tapered portion  44  that has a curves cross section, as shown in FIG.  7 . The reason for this shape will be described shortly. 
     The shape of the insulators associated with the pole teeth  23   d  is shown in FIGS. 8 and 9 and they are indicated generally by the reference numeral  45 . These insulators have a slight inclination for their full length as indicated at  46  that has a curved cross section as seen in FIG.  9 . 
     The winding method will now be described by reference to FIGS. 3,  4   11  and  12 . This comprises the winding of the pole teeth  23   c  before the pole teeth  23   d . The path of the winding needle, indicated by the reference numeral  47 , is the same for each pole tooth  23 . However the shape of the winding on the pole teeth  23   c  is different from that on the pole teeth  23   d.    
     When winding the pole teeth  23   c , the needle  47 , which has a tubular configuration feeds a coil wire  48 . The needle  47  is carried by a head  49 . The coil wire  48  is unwound and fed out of a coil wire roll  49 , passed through a passage hole  51  in the head  49 , and drawn out of the tip of the needle  47  (as shown with an arrow R) as the coil winding operation continues. Initially the end of the coil wire  48  is secured with a clamp (not shown) at a supporting position indicated with a symbol x in FIG. 12 provided at the root of the magnetic pole tooth upon which the coil is being wound. 
     The head  49  reciprocates as indicated with an arrow Q in the direction of its axis C inside the circumference of the armature  21 . Depending upon the axial length of the armature  21 , the needle  47  reciprocates between a bottom position (indicated in solid lines in FIG. 12) that is below the projection  39  of the lower bobbin portion and a top position (indicated in broken lines in FIG. 12) that is above the projection  39  of the upper bobbin portion. The head  49  also rotates about its axis C as indicated with an arrow P in FIGS. 10 and 12 and moves laterally as indicated by an arrow W in FIG. 10 by the width of the magnetic pole tooth  23  when the needle  47  is in both the top and bottom positions vertically outside of the armature  21  and specifically outside the mouth  26  of the slot  24 . 
     During the coil winding operation, the needle  47  does not move in any significant amount into the slot  24 . The tip of the needle  47  is maintained in the area of the slot opening  26 . The coil winding operation is performed, as shown in FIGS. 11 and 12 with the needle  47  moving around each magnetic pole tooth  23   c . In other words, the tip of the needle  47  moves along a rectangular locus made up of vertical and lateral strokes in the sequence of E, F, G, H, and back to E, to make one turn of the coil. The coil wire  44 , with its end secured at the place x, slips off over the tapered portion  44  to be wound in order from the bottom or root side of the magnetic pole tooth  23   c  during the looping movement. 
     In other words, the coil wire  48  is wound at a constant position on the tapered portion  44 when the winding starts (the higher side). Since the end of the coil wire  48  is clamped outside the lower side of the tapered portion  44 , the coil wire  48  is drawn out successively as the winding operation of the needle  47  goes on, and wound around the tapered portion  44  of the magnetic pole tooth. Since the wire wound on the tapered portion  44  receives a tensile force between the outer side (lower side) and the inner side (higher side) of the tapered surface, the wire slips off along the slope surface due to the component of the tensile force along the tapered surface and the pressing force of the wire subsequently wound. In this way, the coil wire  48  is pushed out sequentially on the tapered surface  44  to form the first layer of the coil. 
     The second layer is wound, again starting from the root side by returning the coil wire  48  to the root side and holding it at an appropriate position. The remainder of the coils are then wound to result in the structure as shown in FIG. 3 Although the drawing shows only one needle, this is merely to simplify the illustration. Preferably a plural number of needles  47  are used to wind plural coils simultaneously at different circumferential positions. For example, three needles may be provided at 120 degree intervals radially to wind coils around three magnetic pole teeth  23   c  at the same time. 
     As a coil winding method without inserting the needle into the slot, a lasso method may be used together with or separately from the slip off method. According to such a lasso method, the coil wire  48  is drawn out of the needle tip  47  such that the length of one loop of the locus of the needle tip is longer than that of one turn of the coil so that a slack is provided. The draw-out support point x of the coil wire  48  is fixed to the outer side of the bottom of the slot  35  and the coil wire  48  having the slack is wound at a speed, so that the coil wire  48  is moved toward the draw-out support point x by lasso effect. In this way the coil is wound around the magnetic pole tooth  23   c.    
     In such a “lasso” method, the needle  47  is moved so that the amount of slack decreases on each succeeding turn either continuously or in steps so the coil is wound around the magnetic pole tooth along its length. The slack may be provided to the coil wire  48  in several ways include (1) increasing the vertical movement in the stroke of the needle  47 , (2) increasing the lateral (rotary) movement in the stroke of the needle  47 , (3) moving the needle  47  back and forth when the needle is in a position outside the opening of the slot (indicated with E, F, G, or H in the drawing), or combinations of these methods. 
     Because the tapered portion  44  is formed mainly at the base or root portions of the pole teeth  23   c , a greater number of windings will be formed in this area as clearly seen in FIG. 3 The number of windings decreases toward the tip end of the pole teeth  23   c , these windings are identified by the reference number  52 . At the base of the pole teeth  23   c , the winding  52  extend substantially over the bisecting axial plane toward the adjacent pole teeth  23   d  on opposite sides of the wound pole teeth  23   c . In essence the outer surface of the winding  52  tapers from its widest point at the base or root of the pole teeth  23   c  to their inner or tip end extremities. 
     After the pole teeth  23   c  have all been wound, then the remaining pole teeth  23   d  are wound in the same manner. However, because of the more gradual taper of the insulators  45  the number of windings at the base or root of the teeth  23   d  and the existence of the windings  52  will be less and will progressively increase toward the inner or tip end thereof as clearly seen in FIG.  4 . As also seen in this figure the windings on the pole teeth  23   d , indicated by the reference numeral  53  will extend over the bisecting axial plane between the pole teeth. Thus the winding density is substantially increased over the prior art. 
     Of course those skilled in the art will readily understand that the described embodiments are preferred embodiments of the invention and various changes and modifications may be made within the spirit and scope of the invention, as define by the appended claims.