Abstract:
A compact electric motor has a rotor, and a stator ( 10 ) having a alotted lamination stack ( 16 ) defining slots separated by teeth, said teeth having tooth heads ( 153 ). Partial windings ( 17 ) are arranged in said. On at least one axial end of said lamination stack, jumper rings ( 11, 12, 13 ) and a neutral ring ( 14 ) are arranged. The latter has a plurality of inwardly extending radial projections ( 141 ) having free ends ( 142 ) adapted for connection to ends ( 171 ) of said partial windings ( 17 ). Connection of partial windings ( 17 ) in parallel provides a favorable power/size ratio and substantial pour output, even with low operating voltage.

Description:
FIELD OF THE INVENTION  
       [0001]     The prevent invention relates to a stator configuration for an electric motor.  
       BACKGROUND  
       [0002]     In known electric motors, making the connections to the individual windings often leads to problems, such as connecting wires taking up excessive space and being difficult to mount.  
       SUMMARY OF THE INVENTION  
       [0003]     It is therefore an object of the invention, to provide an electric motor structure which overcomes these problems. According to the invention, this object is achieved by providing an electrical neutral or star-point in the form of a ring, having radial inward projections for making connections to partial windings, and connecting a plurality of partial windings in parallel with each other, to serve as each phase.  
         [0004]     Such an electric motor has the advantage, that the assembly of the stator stack with annular jumper rings and the neutral or star-point ring is greatly simplified and the thus-achieved electric connection of the partial windings needs little space. Further, the structure gives the current a high level of symmetry, and losses, arising from differing total resistances of the partial windings are minimized.  
         [0005]     Such an electric motor makes possible a winding of the partial windings, in which the second ends of the partial windings are simply connected to contact projections of the neutral ring  
         [0006]     Further details and advantageous refinements of the invention will be apparent from the following description of preferred embodiments, which are not to be construed as limitations of the invention. 
     
    
     BRIEF FIGURE DESCRIPTION  
       [0007]      FIG. 1  is a perspective view of the stator of the invention;  
         [0008]      FIG. 2  is a plan view of the stator of  FIG. 1 ;  
         [0009]      FIG. 3  is a side view of the stator from direction II of  FIG. 1 ;  
         [0010]      FIG. 4  is a plan view of a jumper ring;  
         [0011]      FIG. 5  is a plan view of a star-point or neutral ring;  
         [0012]      FIG. 6  is a plan view of an insulator ring;  
         [0013]      FIG. 7  is a plan view of a star-point or neutral ring;  
         [0014]      FIG. 8  is a perspective view of a stator tooth with a partial winding thereon;  
         [0015]      FIG. 9  is a plan view of an electric motor having the stator of  FIG. 2  and a 12-pole permanent magnet rotor;  
         [0016]      FIG. 10  is a schematic view of the electric motor of  FIG. 9  in a developed form;  
         [0017]      FIG. 11  is a schematic view of the star-point arrangement of the stator in electrical terms; and  
         [0018]      FIG. 12  is a schematic view of a power stage in the form of a full-bridge circuit.  
     
    
     DETAILED DESCRIPTION  
       [0019]      FIG. 1  is a perspective view of a stator  10  in accordance with the present invention, and  FIG. 2  is a plan view of the stator  10  of  FIG. 1 .  
         [0020]     For end connections, stator  10  has three jumper rings  11 ,  12 ,  13 , a star-point or neutral ring  14 , a lamination stack  16  composed of multiple stator laminations  15 , eighteen teeth (stator poles)  151  with tooth shanks  152  and tooth heads  153 , and eighteen partial windings  17  (shown in  FIG. 8 )  
         [0021]     As shown in  FIG. 4 , jumper ring  11  has six contacts  111  through  116  and a projecting terminal  119 . Jumper ring  12  has six contacts  121  through  126  and a terminal  129 , and jumper ring  13  has six contacts  131  through  136  and a terminal  139 .  
         [0022]     Star-point ring  114  ( FIG. 5 ) has eighteen contacting projections  141  which each have a respective contacting end  142  adjacent to tooth heads  153 . Lamination stack  16  is, in this exemplary embodiment, composed of twenty-eight stator laminations  15  arranged concentrically with each other.  
         [0023]     Stator  10  is shaped essentially like a hollow cylinder, and can have, for example, a height H=26 mm or H=30 mm and an outer diameter D=80 mm. For purposes of clearer illustration, the view in  FIG. 1  exaggerates the height. The width of the annular (hollow cylindrical) part  155  (see  FIG. 7 ) of stator laminations  15 , measured from the inner radius r to the outer radius R of stator  10 , is about 4.5 mm in this exemplary embodiment.  
         [0024]      FIG. 3  is a side view of stator  10  seen from direction II of  FIG. 2 . Stator  10  has, as its base body, the lamination stack  16  of ferromagnetic material, e.g. soft iron.  
         [0025]     On the lamination stack  16 , there are arranged an insulator ring  24 , the star-point ring  14 , an insulator ring  23 , jumper ring  13 , an insulator ring  22 , jumper ring  12 , an insulator ring  21 , and jumper ring  11 . Insulator rings  21 - 24  consist of an insulator, e.g. ceramic, resin, or plastic.  
         [0026]     Jumper rings  11 - 13  and star-point ring  14  are made of an electrically conducting material, e.g. copper, and are electrically insulated from each other, and with respect to lamination stack  16 , by the insulator rings  21 - 24 .  
         [0027]     The complete height H of the stator arrangement in this exemplary embodiment is 30 mm. This height adds up as follows:  
         [0028]     Height of stator laminations: 28*0.86 mm=24 mm  
         [0029]     Height of jumper rings: 3*1 mm=3 mm  
         [0030]     Height of the star-point ring:=1 mm  
         [0031]     Height of the insulator rings: 4*0.5 mm=2 mm  
         [0032]      FIG. 4  is a plan view of a jumper ring  11  of the invention. Jumper ring  11  defines a hollow cylindrical region  118 , from which the six contacts  111  through  116  project radially inwardly, and terminal  119  projects radially outward. Onto each of respective contacts  111  through  116 , an end of a partial winding  17  attaches. As shown, each of contacts  111  through  116  is formed as a U-shape into which the winding wire can be secured.  
         [0033]     Jumper ring  11  is, at least in its annular part  118 , flat, and preferably has a height in the range 0.6 mm to 1.3 mm. Preferably, jumper ring  11  has, in its annular (hollow cylindrical) region  118 , substantially the same width as the annular region  155  (see  FIG. 7 ) of stator laminations  15 . Thereby, the jumper ring has a large cross-section and low resistance. Jumper rings  12  and  13  have the same structure.  
         [0034]      FIG. 5  is a plan view of the star-point ring  14 . The star-point ring  14  forms the electrical neutral for the partial windings  17  and is—unusually for a neutral point—formed as a ring. The contacting projections  141  extend on top of the lamination stack  16  and to the tooth heads  153  ( FIG. 2 ) and serve for contacting of one end of the partial windings wound around the teeth. For this purpose, the contacting projections  141  each have a respective contacting end  142 , which is adapted for contacting and is not electrically insulated. The remainder of each contacting projection is preferably electrically insulated, in order to avoid short-circuit of the winding wire. For insulating purposes, a protective varnish or lacquer is suitable.  
         [0035]     Preferably, star-point ring  14  ( FIG. 5 ) is formed with a terminal  149  at which the potential on star-point ring  14  is measured. This facilitates so-called “sensorless detection,” according to which the rotor position is measured without rotor position sensors.  
         [0036]     Star-point ring  14  is flat, at least in its annular part  145 , and preferably has a height in the range 0.6 mm to 1.3 mm. Preferably, ring  14  has, in its annular region  145 , substantially the same width as the annular region  155  (see  FIG. 7 ) of stator laminations  15 . Thereby, ring  14  has a large cross-section and a low resistance.  
         [0037]     PIG.  6  is a plan view of insulator ring  21 . This is as thin as possible, in order to keep the height of stator  10  small.  
         [0038]     In a preferred refinement of the invention, insulator ring  24  and/or insulator ring  23  have projections corresponding to the projections  141  of star-point ring  14 , which assure reliable insulation of star-point ring  14  from lamination stack  16  and/or from partial windings  17 .  
         [0039]      FIG. 7  is a plan view of one of stator laminations  15 . Stator lamination  15  has an annular region  155  and eighteen stator teeth  151  which each comprise a centrally projecting tooth shank  152  with a tooth head  153  at its end.  
         [0040]      FIG. 8  is a perspective view of a tooth  151  with a partial winding (coil)  17 . Coil  17  consists of a winding wire  179  having a first end  171  and a second end  172 .  
         [0041]     The first end  171  is connected to contact  132  of third jumper ring  13  and the second end  172  is connected to contacting end  142  of star-point ring  14 , e.g. by welding.  
         [0042]     Coil  17  has, in this exemplary embodiment, 30 turns and the winding wire has a diameter of about 0.7 mm.  
         [0043]     The securing of the first and/or second ends  171 ,  172  to the contacts of jumper rings  11 ,  12 ,  13  can be accomplished, for example, by welding, soldering, snap engagement, or by crimping. Contacting by means of extra connectors is also possible.  
         [0044]      FIG. 9  is a plan view of an electric motor with a stator  10  according to the invention, and a 12-pole rotor  18 . The stator was already described with reference to  FIG. 2 . There is an air gap  19  between rotor  18  and stator  10 .  
         [0045]      FIG. 10  is a developed schematic view of the electric motor of  FIG. 9 . In this example, all the partial windings  17  are wound in the same sense. The stator poles are successively numbered S=1 . . . 18, and the rotor poles are successively numbered R=1 . . . 12.  
         [0046]     Current supply of stator poles S=1 occurs via jumper ring  11 , current supply of stator pole S=2 occurs via jumper ring  12 , current supply of stator pole S=3 occurs via jumper ring  13 , and current supply of stator pole S=4 occurs via jumper ring  11  again. This continues in regular sequence through the last stator pole S=18.  
         [0047]      FIG. 11  is a schematic view of the star-configured stator winding of stator  10 . Star-point ring  14  is at the center, from which radiate the three phases to the jumper rings  11 ,  12 ,  13 . Each phase consists of six partial windings connected in parallel.  
         [0048]     Current is supplied when, at respective times, a selected two of the phases are energized, via jumper rings  11 ,  12  and/or  13 . For example, the stator winding between the “points”  11 ,  14  and  13  is energized by applying an operating voltage +U_B to jumper ring  11  and applying a ground potential GND to jumper ring  13 . The winding between “points”  12  and  14  is not energized at this time.  
         [0049]     The parallel connection of the partial windings is particularly advantageous with low-voltage motors, e.g. in autos with 12-volt batteries The maximum power of the motor, for a given voltage, is limited, in particular, by the ohmic resistance of the windings.  
         [0050]     In such a motor with three phases, in which each phase consisted of only one strand or wire, a large wire diameter D (wire gauge), of perhaps 2 mm, would be necessary. Such thick wires are very difficult to work with, particularly making the bends needed to wind around the teeth which becomes scarcely possible. Further, such a wire requires a lot of space and results in a stator which has, for its power, high space requirements.  
         [0051]     By contrast, the parallel connection of six identical windings (coils) to form one phase, and the star-configuration of the phases, according to the present invention, causes the aggregate resistance of the individual phases to be reduced to ⅙ the value of the resistance of a single partial winding. Thus, even given low voltage, the motor can provide high output power, despite a wire diameter of only, for example, 0.7 mm This results in a favorable power/size ratio.  
       FURTHER ADVANTAGES OF THE STATOR STRUCTURE  
       [0052]     Due to the large cross-sections of the jumper rings  11 ,  12 ,  13  and of star-point ring  14 , stator  10  is also suitable for high-current applications.  
         [0053]     The annular shape of jumper rings  11 ,  12 ,  13  and of star-point ring  14  increases the symmetry of the supply from the terminals  119 ,  129 ,  139  to the individual contacts. Asymmetries, which contribute to losses, are substantially avoided.  
         [0054]     Since each of contacts  112 - 116 ,  122 - 126  and  132 - 136  which is not sitting directly adjacent one of terminals  119 ,  129 ,  139  is supplied with current, from the viewpoint of terminals  119 ,  129 ,  139 , from both sides, the resistance of jumper rings  11 ,  12 ,  13  and of star-point ring  14  is further reduced.  
         [0055]     The space required to make connections of the individual windings is very low. Especially shallow motor structures are possible. Prior art structures supplied the windings by using wires instead of rings. Such connection using wires had, in addition to the their higher resistance, the great disadvantage that many wires had to lie atop one another, resulting in greater height and space demands. Further, such connection using wires caused difficulties and costs during manufacture.  
         [0056]     Since contacts  111 - 116 ,  121 - 126  and  131 - 136  of jumper rings  11 ,  12  and  13  lie radially outside with respect to stator poles  151  and the contacting ends  142  of star-point ring  14  lie radially inside, the individual partial windings  17  can be wound either from radially outside to radially inside, or the reverse. Thus, it is not necessary to wind radially in two directions. However, one could, for example, first wind from radially outside to radially inside, then the reverse, and then wind again from radially outside to radially inside.  
         [0057]     Contacts  111 - 116 ,  121 - 126  and  131 - 136  are the only portions of jumper rings  11 ,  12 ,  13  which project into the interior of stator  10 . All other parts of jumper rings  11 ,  12 ,  13  lie radially outside. This is advantageous, since thereby the entire inner region of stator  10  is available to the stator poles  151  and to rotor  18 . The manufacture of stator  10  is made simple by the manner of winding, and therefore economical.  
         [0058]      FIG. 12  is a schematic illustration of a power stage arrangement  200 . It has three upper switches  201 ,  202 ,  203  and three lower switches  204 ,  205 ,  206  which are driven by a driver stage  210 . Stage  210  specifies whether or not the supply voltage U_B and the ground potential GND are to he applied to the respective terminals  119 ,  129 ,  139  of jumper rings  11 ,  12 ,  13 . This kind of circuit is called a “full bridge” circuit.  
         [0059]     Naturally, many variations and modifications are possible within the scope of the inventive concept, so the invention is not limited to the specific exemplary embodiments described.