Abstract:
An electric motor for electric hand power tools has a housing, a stator received in the housing and having a stator body composed of a plurality of axially abutting lamellas, at least one of the lamellas located in at least one end side end region of the stator body having raised portions which axially extend over a lamella surface, the stator body being clamped between radially extending housing parts in an axially force-transmitting manner.

Description:
BACKGROUND OF THE INVENTION 
   The present invention relates to an electrical machine, in particular to an electric motor for electric hand power tools. 
   Permanent magnet excited small-size motors, such as for example the motors which are used in electric hand power tools for craftsmen or armateurs, have a stator and a rotor which surrounds the stator and carries permanent magnets located on a rotor shaft for joint rotation with it. The stator is received non-rotatably in a housing, in which also a rotor shaft is rotatably supported. The stator has a stator body with axial grooves and a stator winding inserted in the axial grooves. The stator body is assembled of sheet metal lamellas which have an identical blank profile with a central, circular opening for passage of a rotor and the same number of groove openings, which in a stator body composed of the layers coincide with one another to form the axial grooves for receiving the stator winding. The connection of the individual sheet metal lamellas to form the stator bodies performed by a so-called stamping. The stator body with the windings is inserted in the housing and fixed axially non-displaceably and non-rotatably by glueing, pressing, caulking, screwing or shrinking. 
   It is believed that the known electrical machine can be further improved. 
   SUMMARY OF THE INVENTION 
   Accordingly, it is an object of the present invention to provide an electrical machine of this type which avoids the disadvantages of the prior art. 
   In keeping with these objects and with others which will become apparent hereinafter, one feature of the present invention resides, briefly stated, in an electric motor for electric hand power tools, comprising a housing, a stator received in said housing and having a stator body composed of a plurality of axially abutting lamellas, at least one of said lamellas located in at least one end side end region of said stator body having raised portions which axially extend over a lamella surface, said stator body being clamped between radially extending housing parts in an axially force-transmitting manner. 
   The electrical machine designed in accordance with the present invention has the advantage that the axial lifted or raised portions formed in the lamellas of the stator body are pressed during the axial clamping of the stator body between the radially extending housing portions into the neighboring lamellas and into the housing parts and thereby produce a form-locking and force-transmitting securing against rotation of the stator in the housing. 
   For mounting of the stator in the housing after its insertion, in addition to the application of the axial pressing force, for example by axial screwing of the radially extending housing parts, no further mounting steps are needed. In addition, with the inventive axial lifted or raised portions, an axial tolerance compensation is possible, that allows moreover coarser tolerances in the lamellas thickness. The shortened mounting time and the allowed greater tolerance region lead to reduction of the manufacturing costs. 
   In accordance with a preferable embodiment of the invention, in each end region of the stator body at least one lamella provided with the raised portions is available. Preferably, the at least one lamella is the outwardly located end lamella which presses with the axial lifted portions or raised portions against the radial housing parts. Thereby the securing against rotation between the housing and the stator body is obtained, which reliably prevents the relative movement of stator body relative to the housing. 
   In accordance with an advantageous embodiment of the present invention, in each end region of the stator body several neighboring lamellas are provided with the raised portions. This raised portions can be arranged so that they are in alignment with one another, and in the assembled stator body engage with one another. However, they can be arranged in the neighboring lamellas, so that they are turned relative to one another. With these features they securing against turning within the lamellas pack is obtained, and moreover a greater axial tolerance compensation is possible. 
   In accordance with another embodiment of the invention, the raised or lifted portions can be formed by corrugations or notches which are pressed in the lamellas. However, they can be also formed by punching of cuts in the lamellas with subsequent bending. 
   The novel features which are considered as characteristic for the present invention are set forth in particular in the appended claims. The invention itself, however, both as to its construction and its method of operation, together with additional objects and advantages thereof, will be best understood from the following description of specific embodiments when read in connection with the accompanying drawings. 

   
     BRIEF DESCRIPTION OF THE DRAWINGS 
       FIG. 1  is a per respective view of an electric motor for an electric hand power tool in a semi section, showing a housing, a stator and a rotor; 
       FIG. 2  is a cut-out portion of a plan view of a lamella of the stator of the inventive electric motor of  FIG. 1 ; 
       FIG. 3  is a view showing a section taken along the line III—III in FIG.  2  through the inventive electric motor; 
       FIG. 4  is a same view as in  FIG. 3 , but with modified lamellas of the inventive electric motor. 
   

   DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     FIG. 1  shows a perspective view of sectioned half of a permanent magnet-excited electric motor for an electric hand power tool, as an example of the present invention. The electric motor has a cup-shaped housing  10  with a hollow-cylindrical wall  101  and a cup bottom  102 . Cooling ribs  11  are formed on the outer surface of the cup wall  101 . A stator  12  and a rotor  13  are located in the housing  10 . 
   The rotor  13  is arranged non-rotatably on a rotor shaft  14  which is rotatably supported in the housing  10 . One end of the rotor shaft  14  is received in a radial bearing  15  formed in the cup bottom  102 . The other end of the rotor shaft  14  is received, by means of a second radial bearing  16 , in a bearing plate  17  arranged at the end side and closing the cup opening of the housing  10 . Only bearing shells of the radial bearings  15  and  16  are shown in FIG.  1 . 
   The cylindrical cup wall  101  extends radially at an axial distance from the cup bottom  102 , so that a wall portion  101   a  is formed next to the cup bottom  102 . It has a smaller inner diameter than the cup wall portion located before it, so as to form a ring-shaped, radially inwardly extending supporting portion  101   b . A ring web  171  extends from the inner side of the bearing flange  17  which faces the cup opening. During placing of the bearing flange  17  on the housing  10 , it is introduced into the interior of the housing  10  and beveled on the inner surface of the cup wall  101 . 
   The rotor  13  which is schematically shown in FIG.  1  and carries shell-shaped permanent magnet segments  19  on the outer surface of a rotor core  18 , which is preferably composed of metal plates. The permanent magnet segments  19  are magnetized in a radial direction, so that in the neighboring permanent magnet segments the magnetization direction is inverse. 
   The stator  12  has a stator body  20  with a plurality of axial grooves  21  which are arranged equidistantly over the circumference, and also a stator windings inserted in the axial grooves  21 . In  FIG. 1  for the sake of clarity they are not shown, so that only the stator body  20  of the stator  12  is illustrated. The winding wire for the stator winding is wound conventionally many times in the axial grooves  21 . In each the axial groove  21  a plurality of parallel electrical conductors are inserted, which are connected with one another by winding heads extending over the end sides of the stator body  20 . The stator body  20  concentrically surrounds the rotor  13  with a working air gap  22  to the permanent magnet segments  19 . The stator body  20  is assembled of a plurality of individual metal plate lamellas  23  that have an identical blank profile and are arranged on one another in the axial direction of the rotor body  20 . 
     FIG. 2  shows a section of a plan view of a lamella  23  of the stator body  20 . It has a central opening  24  which is determined by the outer diameter of the rotor  13  and the radial width of the air gap  22 , and also a plurality of equidistant groove openings  25 . The shape of their inner cress-section corresponds to the axial grooves  21 . The lamellas  23  which are punched with the above described blank are layered over one another to form the stator body  20 . The groove openings  25  are in alignment with one another and follow the axial grooves  21  in the stator body  20 . The stator body  20  provided with the wound stator windings is inserted axially through the cup opening into the housing  10 , until the frontmost end lamella  23 , as considered in the insertion direction, abuts against the abutment shoulder  101   b  formed in the housing  10 . After this the bearing flange  171  is placed on the housing  10 , and its ring web  171  abuts with its ring-shaped end surface against the other end lamella  23 , which is the last in the insertion direction of the stator body. When the bearing plate  17  is screwed to the housing  10 , the ring web  171  presses against the stator body  20  in a force-transmitting manner. For screwing the bearing flange  17 , lugs  26  are uniformly distributed over the circumference and provided with throughgoing openings  27  for the screws, and axial threaded openings are provided in the cup wail  101  or in the cooling ribs  11  for screwing-in of the screws. 
   For fixing the stator body  20  non-rotatably In the housing  10 , the both end lamellas  23 , or in other words both outermost lamellas of the stator body  20 , are provided with axial lifted over raised portions  28 . They project on the lamella surface of the both lamellas  23  at the side facing the cup bottom  102  over the bearing flange  17 .  FIG. 2  shows the raised portions  28  for the left end lamella  23  of the stator  20  of FIG.  1 . These raised portions  28  are produced for example by corrugations  30  or notches, which are pressed in the other lamella surface of the end lamella  23 . The profile of such a corrugation  30  or a notch is shown in FIG.  3 . Alternatively, a raised portion  28  can be also formed by a cut  29  which is punched or cut in the end lamella  23  and then bent out of the lamella plane as shown In FIG.  4 . 
   When the bearing flange  17  is fixed by the screws on the housing  20  the pack of the lamellas  23 , which abuts against the abutment shoulder  101   b  and forms the stator body  20 , is compressed by the ring web  171  on the bearing plate  17 . Thereby the raised portions  28  press in the end lamellas  23  in the abutment shoulder  101   b  and in the ring-shaped end surface of the ring web  171  and form a reliable protection from turning, which blocks a relative turning of the stator body  20  in the housing  10 . 
   The above described shape of the raised portions  28  which are formed as corrugations  30  in  FIG. 3  or bent cuts  29  of  FIG. 4 , must not be limited only to the both end lamellas  23  of the stator body  20 . As shown in  FIGS. 3 and 4 , several neighboring lamellas  23 , located for example in the end regions of the stator body  20 , can be also provided with such raised portions  28 . Thereby an increased safety from turning between the lamellas  23  is facilitated and additionally a greater axial tolerance compensation for compression of several raised portions  28  located near one another in the axial direction is possible. The raised portions  28  in the neighboring lamellas  23  can be oriented so that they coincide with one another, so that the raised portions  28  of one lamella  23  engage in the depressions of the other lamella  23 , formed for production of the raised portions  28  in the lamella  23  by making corrugations or bending of the cut  29 . The raised portions  28  can be oriented arbitrarily, so that always one raised portion  28  abuts against a plane surface of the neighboring lamella  23 . 
   It will be understood that each of the elements described above, or two or more together, may also find a useful application in other types of constructions differing from the types described above. 
   While the invention has been illustrated and described as embodied in electric machine, it is not intended to be limited to the details shown, since various modifications and structural changes may be made without departing in any way from the spirit of the present invention. 
   Without further analysis, the foregoing will so fully reveal the gist of the present invention that others can, by applying current knowledge, readily adapt it for various applications without omitting features that, from the standpoint of prior art, fairly constitute essential characteristics of the generic or specific aspects of this invention.