Abstract:
An improved armature winding arrangement for a rotating electrical machine such as a specifically illustrated DC motor for driving a vehicle wheel. The assembly is such that the armature core can be formed from two laminated pieces that are rigidly connected to each other and held against axial movement. This eliminates the need for bonding adhesive. In addition, an improved bobbin arrangement is employed for both permitting attachment of a wiring plate directly to the core but also for retaining the ends of the individual windings to prevent them from becoming loose either during assembly or in operation.

Description:
BACKGROUND OF INVENTION  
         [0001]    This invention relates to a coil winding for a DC machine and more particularly to an improved, simplified and lower cost coil-winding assembly for such machines.  
           [0002]    It has been the practice to provide a coil winding for DC machines wherein the winding core is comprised of radially spaced inner and outer annular elements. The armature cores are formed as extending teeth on one or the other of these elements. As is well known, the core is preferably formed from a plurality of laminated electromagnetic steel plates such as silicate steel or the like. The outer periphery of the inner element is shrunk fit into the inner periphery of the outer element so as to form a complete assembly.  
           [0003]    Prior to this, however, coil windings are formed on the core teeth. This is frequently done by placing insulating bobbins around which the coils have been wound on the core teeth before the two elements are shrunk fit together.  
           [0004]    Although this expedient provides a very good assembly, there are some difficulties, which may arise. The shrink fit, for example, may result in imprecise axial positioning between the two elements. This problem is aggravated by the lamination of the elements.  
           [0005]    In order to maintain the elements in their position, it has been proposed to bond the elements to each one once they have been shrunk fit. This is generally done by embedding them in a resin material. However, this still does not provide a rigid enough connection. For example, this type of mechanism is frequently used as a DC motor to power a wheel of a vehicle. The vibrations associated with such applications however, can cause a slipping between the elements and affects the coupling accuracy between the bobbins and the magnetic poles.  
           [0006]    In addition, it is frequently the practice to embed or immerse the electric motor in oil for improving its cooling. However, the lubricating oil used may attack the resin employed for the bonding and cause the connection to become weakened.  
           [0007]    It is, therefore, a principal object to this invention to provide an improved coil winding for an electric machine wherein the coil winding can be formed from interconnected radially inner and outer annular elements, one of which has extending core teeth.  
           [0008]    It is a further object to this invention to provide a more rigid location arrangement for locating the inner and outer elements relative to each other that does not necessarily require adhesive bonding.  
           [0009]    With the aforenoted construction, it is necessary to connect the coil windings to each other in a predetermined fashion and to supply or extract electrical power from them in a timed sequence when phased windings are employed. This requires a contact plate or wiring board to which the coil ends are connected. Previously, these windings boards have been mounted separately and complicate the arrangement for making the wiring connections.  
           [0010]    It is, therefore, a still further object to this invention to provide an improved coil winding for an electric machine wherein the associated wiring board can be conveniently and rigidly mounted relative to the windings and thus improve the physical retention of the elements relative to each other.  
           [0011]    In connection with extracting the wiring from the coil windings and connecting it to the control circuit, there is a risk that the coil ends can become loose and shift. This will cause the entire winding to loosen and may result in breaking of the electrical connections.  
           [0012]    It is, therefore, a still further object to this invention to provide an improved bobbin arrangement for use with a coil winding of this type and wherein the bobbins provide a retainer assembly for retaining the ends of the wires of the coil windings.  
         SUMMARY OF INVENTION  
         [0013]    A first feature of this invention is adapted to be embodied in an electrical coil winding assembly for a rotating electrical machine. The winding assembly comprises a core that is formed of annular radially inner and outer elements, which form a plurality of radially extending armature cores. Electrical coils are wound around the armature cores. Circumferentially spaced and radially extending interengaging parts on the core elements maintain the axial relationship between the core elements.  
           [0014]    Another feature of the invention is also adapted to be embodied in an electrical coil winding assembly for a rotating electrical machine. In accordance with this feature of the invention, the winding assembly comprises a core that is formed by annularly radially inner and radially outer elements forming a plurality of radially extending armature cores. Each of a plurality of bobbins surrounds a respective one of the armature cores. Electrical coils are wound around each of the bobbins. The bobbins and respective electrical coils are detachably connected to the core element that forms the armature cores by retaining clips. At least some of the retaining clips have end portions that extend in an axial direction beyond the core elements and a wiring plate is carried by such retaining clip end portions.  
           [0015]    Yet another feature of the invention is also adapted to be embodied in an electrical coil winding assembly for a rotating electrical machine. The assembly comprises a core that is formed by annular, radially inner and radially outer elements that form a plurality of radially extending armature cores. Each of a plurality of bobbins around which the respective electrical coils are wound surrounds a respective one of the armature cores. The bobbins have portions that form a retainer for retaining the conductor ends of the respective coils against movement. 
       
    
    
     BRIEF DESCRIPTION OF DRAWINGS  
       [0016]    [0016]FIG. 1 is a cross sectional view of vehicle wheel driven by an electric motor constructed in accordance with an embodiment of the invention.  
         [0017]    [0017]FIG. 2 is an end elevational view showing the winding assembly of the electric motor employed in the arrangement shown in FIG. 1.  
         [0018]    [0018]FIG. 3 is an end elevational view of the winding assembly looking in the opposite direction from FIG. 2.  
         [0019]    [0019]FIG. 4 is a cross sectional view of the winding assembly taken along the line  4 - 4  of FIG. 2.  
         [0020]    [0020]FIG. 5 is an exploded view of certain of the winding assembly elements illustrating the manner and sequence of assembly.  
         [0021]    [0021]FIG. 6 is an enlarged perspective view showing the bobbins and the retaining structure associated therewith. 
     
    
     DETAILED DESCRIPTION  
       [0022]    Referring now in detail to the drawings and initially primarily to FIG. 1, an electric motor constructed in accordance with an embodiment of the invention is indicated generally by the reference numeral  11 . The electric motor  11  is used in the exemplary, described embodiment for powering a vehicle wheel  12  for driving an associated vehicle (not shown) along the ground. Although the invention is described in conjunction with an electric motor, it should be readily apparent that the invention can be utilized in conjunction with other rotating electrical machines such as electrical generators. The specific embodiment illustrated, however, is one in which a number of the problems noted in the Background section are particularly prevalent and are solved by the construction.  
         [0023]    The motor  11  is contained within a motor case assembly, indicated generally by the reference numeral  13  that is affixed in a suitable manner to the aforenoted associated vehicle. This motor case is comprised of an inner housing element  14  and an outer housing element  15 , which are secured to each other in a suitable manner and which enclose the motor  11 . A suitable lubricant is filled into the motor case assembly  13 .  
         [0024]    The motor  11  is comprised of a stator, which forms a winding assembly, which is indicated generally by the reference numeral  16 , and a rotor, indicated generally by the reference numeral  17 . The rotor  17  is fixed to a stub shaft  18 . The stub shaft  18  is, in turn, journalled in the inner housing element  14  by a first anti-friction bearing  19 . A second anti-friction bearing  21  journals the stub shaft  18  and rotor  17  on an axial shaft  22 . The axial shaft  22  is, in turn, journalled in the outer housing element  15  by a pair of bearings  23  and  24 . An oil seal  25  encloses the bearings and the interior of the motor case assembly  13  to prevent leakage of the lubricant contained therein.  
         [0025]    The wheel  12  is comprised of a rim portion  26  that mounts a suitable tire (not shown) and which is affixed to a disk portion  27 . The disk portion  27  is, in turn, connected by fasteners  28  to a hub  29 . The hub  29  has a splined connection to the axial shaft  22  and hence, the wheel  12  rotates with this axial shaft  22 .  
         [0026]    A step-down planetary transmission interconnects the motor rotor  17  with the axle shaft  22  for driving it and the wheel  12 . This step-down transmission is of the planetary type and is indicated generally by the reference numeral  31 . It is comprised of a sun gear  32  that is fixed for rotation with the stub shaft  18  and is enmeshed with a plurality of planet gears  33  that are carried by a carrier  34 . The carrier  34  is formed in part integrally with the axial shaft  22 .  
         [0027]    These planet gears  33  are journalled on the carrier  34  by a plurality of stub shafts  35 . The exterior periphery of these planet gears  33  are enmeshed with a ring gear  36  that is fixed relative to the motor outer housing element  15  by a carrier plate  37  that is fixed to the outer housing element  15  by threaded fasteners  38 .  
         [0028]    The wheel  12  also forms an integral drum brake assembly. To this end, the hub  29  is formed with a drum brake inner surface  39  which is formed integrally with it and which is engaged by brake shoes  41  carried by actuator elements  42 . These actuator elements  42  are operated by a suitable brake actuator for bringing the brake shoes  41  into engagement with the drum brake inner surface  39  for halting the rotation of the wheel  12 .  
         [0029]    It should be understood that the foregoing description is primarily made to provide an environment in which the invention can be utilized. The invention deals primarily with the construction of the electric motor  11  and particularly the stator or armature winding assembly  16  thereof which forms a plurality of armature cores. These armature cores are formed from laminated plates comprised of an outer member  43  and an inner member  44  which are secured together in a manner to be described. The inner member  44  forms a plurality of poles around which coil windings  45  are formed in a manner, which will be described in more detail shortly by reference to FIGS. 2 through 6.  
         [0030]    These coil windings  45  cooperate with permanent magnets  46  that are affixed to the periphery of the motor rotor  17  via a laminated electromagnetic steel plate annular magnetic bushing  50 . It should be noted that the rotor  17  is primarily formed from aluminum or an aluminum alloy. These permanent magnets  46  are arranged so as to have alternate poles alternating in a circumferential direction around the rotor  17  of the motor  11  and in a preferred embodiment there are 12 permanent magnets  46 . The permanent magnets  46  are formed from a material with a large magnetic flux density, such as neodymium-iron-boron.  
         [0031]    Referring now additionally to the remaining figures and initially primarily to FIGS. 4 and 5, the armature winding assembly  16  is comprised of a pair of ring-like elements comprised of an outer element, indicated generally by the reference numeral  47  and an inner element, indicated generally by the reference numeral  48 . Both of these elements  47  and  48  are formed from a plurality of laminated sheets of material having high magnetic properties such as electromagnetic steel plates.  
         [0032]    The inner element  48  has a hub portion  49 , which forms a continuous ring from which pole teeth  51  extend radially outwardly. In a preferred embodiment there are 18 of these pole teeth  51 . The outer diameter of the pole teeth  51  is preferably slightly greater than the inner diameter  52  of the outer element  47  so as to permit shrink fit attachment there between.  
         [0033]    The outer element  47  has a plurality of lugs  53  formed thereon, each of which has an opening  54  so as to pass a threaded fastener  55  (FIG. 1) for fixation against rotation to the motor housing inner housing element  14 .  
         [0034]    Bobbins, indicated generally by the reference numeral  56  and shown in most detail in FIG. 6, are provided for embracing the teeth  51  and around which individual coil windings  45  are formed, in a manner to be described. In accordance with the invention, the bobbins  56  are formed from a suitable insulating material such as a resin or the like and they comprise generally rectangular shaped tubular sections  57  which embrace the individual teeth  51  and inner and outer flanges  58  and  59 . The inner flange  58  is engaged with the hub portion  49  of the inner element  48  while the outer flange  59  is spaced outwardly at the outer peripheral edge of the teeth  51 .  
         [0035]    The inner periphery of the rectangular section  57  is formed with a plurality of resilient locking teeth  61  which will snugly engage the outer periphery of the pole teeth  51  to provide good attachment thereto. In addition a key or tooth  62  is formed at one axial end of the bobbin  56  and which is designed so as to extend radially outwardly beyond the outer periphery of the pole teeth  51  and into proximity with the outer element  47  so as to engage one side thereof as clearly shown in FIG. 4 and to provide axial alignment between the inner and outer elements  47  and  48 .  
         [0036]    On the other axial side of the pole teeth  51 , certain of the bobbins  56  are formed with a recess  63 , which receives one leg  64  of a L-shaped retainer key  65 . This retainer key  65  has barb like edges  66  so that when pressed into the recess  63  the retainer key  65  will be permanently retained in the bobbin  56 . In the illustrated embodiment seven (7) of the bobbins  56  receive such retainer keys  65  for a reason that will become apparent shortly.  
         [0037]    The leg  64  extends radially outwardly beyond the outer periphery of the pole teeth  51  as seen at  67  in FIG. 4 and engages the side of the outer element  47  opposite that engaged by the keys or teeth  62 . Thus, the accurate and rigid axial positioning between the elements  47  and  48  insures good electrical and magnetic properties.  
         [0038]    The remaining leg of the retainer key  65  is provided with elongated projections  68  for a reason, which will be described shortly. It will be seen that the elongated projections  68  extends in an axial direction radially beyond the coil windings  45  and to pass through a like number of slotted openings  69  formed in a wiring board  71 . The wiring board  71  may be affixed rigidly to complete the assembly by applying solder to the projecting ends of the elongated projections  68 .  
         [0039]    The steps of assembly of the coil winding assembly can be best understood by reference to FIG. 5. First, at the step  1  the inner element  48  is positioned and the wound bobbins  56  are slid onto the teeth  51 . Then at the step  2  the outer element is slipped over it and shrunk fit. This may be done by either cooling the inner element  48 , heating the other outer element  47  or both and permitting these components to return to their temperature. Then, after the outer ring  47  has been shrunk onto the inner element  48 , the retainer key  65  are inserted to complete the axial locking at the step  3 . Then at the step  4 , the wiring board is inserted and attached by the aforenoted-soldering step.  
         [0040]    The construction of wiring board  71  and its relation to the coil windings  45  will now be described by primary reference to FIGS. 2 through 4 and  6 , except as will be hereinafter noted.  
         [0041]    Referring first to FIG. 6, it will be seen that the side of the bobbin flange  59  opposite that that receives the retainer key  65  is formed with a slotted opening  72  across which a resilient tab  73  extends. The winding end, indicated at  74  may be looped under this tab  73  by lifting its outer edge  75 . Thus, the coil windings  45  will be retained tightly in place relative to the bobbin  56  both during assembly and after assembly. This avoids the likelihood that the windings can be loosened in use.  
         [0042]    These winding ends  74  are then connected to the wiring board  71  in a manner, which will be described by primary reference to FIGS. 2 through 4.  
         [0043]    Referring first to FIGS. 2 and 4, it should be noted that the coil windings  45  are connected to each other for use in a three-phase circuit having phases identified as “U”, “V” and “W”, each having a phase difference of 120 °. Thus, on the insulating surface of the wiring board  71  there are attached three metal conductors  76 ,  77  and  78 , each of which is associated with the respective phases “U”, “V” and “W”. One end of each of these strips is provided with a respective terminal end  79 ,  81  and  82 , respectively which have grooves for attachment to an external conductor which includes a terminal box  83  (FIG. 1) mounted in the motor case assembly  13  and specifically its inner housing element  14  and which is connected to an internal wiring harness that goes to these individual conductors  76 ,  77  and  78 .  
         [0044]    The insulating plate of the wiring board  71  is formed with peripheral notches  84  over which the ends of the respective wires may be passed from the individual coil ends  74 . As seen in FIG. 2 by the dotted lines, this shows how the individual coil windings may be connected to the respective terminal boards through conductors which may be formed either integrally with or separately attached to the insulating base.  
         [0045]    Three coils are grouped with each set as may be seen by the dotted line views in FIG. 2 which are done for clarity so as to show how this connection is made. The remaining ends of the coil windings  45  are grouped and passed through openings in the insulating plate and which are sealed by a sealant  85  as seen in FIG. 3. The retaining structure shown in FIG. 6 facilitates the completion of this wiring upon assembly.  
         [0046]    In addition, there is provided an angle sensor, as shown in FIG. 1 by the reference numeral  86  which cooperates with timing projections  87  formed on the rotor  17  in alignment with the respective poles for effectively switching the current flow to obtain the desired motor operation. Driving torque may be controlled by pulse controlling the “U”, “V” and “W” phase currents.  
         [0047]    Finally, the wiring board  71  is also provided with a pair of terminals  88  and  89  (FIGS. 2 and 3), which may also be connected through the wiring harness to the terminal box  83 . These may be provided for temperature sensors (not shown) that detect the temperature of the stator armature assembly.  
         [0048]    Thus, from the foregoing description it should be readily apparent that the described construction provides a very accurate way in which the windings may be assembled and formed and also how the electrical connections may be made to insure long life and good performance. Of course, the foregoing description is that of a preferred embodiment of the invention and various changes and modifications may be made without departing from the spirit and scope of the invention, as defined by the appended claims.