Abstract:
An armature of the prior art has a lamination packet which leads to a high loss of magnetic flux in the lamination, since it completely encloses the magnets that are disposed in the lamination. 
     An armature ( 1 ) of the invention comprises at least one lamination ( 1 ) that only partly encloses the magnets ( 24 ). Losses in the magnetic flux are thus reduced.

Description:
BACKGROUND OF THE INVENTION 
   The invention is based on an armature for an electrical machine. 
   From Japanese Patent Disclosure JP 2000152535 A, a stack of laminations is known that has only open pockets for magnets, in which the magnets are held by positive and nonpositive engagement. The individual lamination has no external web that retains the magnet on its outer circumference. The mechanical load on the lamination is high. 
   From JP 09046946 A, a stack of laminations is known in which the magnets are disposed entirely in closed pockets of the lamination. By means of the additional iron of the web, which grips the magnets on the outer circumference and closes the pocket, a significant flux loss occurs in the web and in the peripheral region of the magnets; this leads to a reduction in the power of an electrical machine for which the stack of laminations is used. 
   From U.S. Pat. No. 2,323,114, a lamination packet is known in which by means of a special embodiment of the laminations for the lamination packet, magnetic flux losses are reduced because the stator teeth are at least partly disconnected from one another. 
   From U.S. Pat. No. 4,777,397, an armature is known in which a certain of laminations have only closed pockets, in which the magnet is at least partly disposed. The other laminations have only open pockets, and so there the magnet is not surrounded on its outer circumference by a metal sheet. The magnets are secured in the open pockets by an adhesive. This requires two different versions of laminations. 
   SUMMARY OF THE INVENTION 
   The armature of the invention has the advantage over the prior art that magnets are fixed by a lamination packet in a simple way, and the magnetic flux loss is reduced. 
   The magnet can advantageously be fixed in the lamination packet by being spray-coated. This can be done by plastic spraying, for instance. A protection against external environmental factors is thus assured as well. 

   
     BRIEF DESCRIPTION OF THE DRAWINGS 
     One exemplary embodiment of the invention is shown in simplified form in the drawing and explained in further detail in the ensuing description. 
     Shown are 
       FIG. 1 , a lamination for an armature of the invention; 
       FIG. 2 , a lamination packet formed of laminations of  FIG. 1 ; 
       FIG. 3 , an armature of the invention. 
   

   DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     FIG. 1  shows a lamination  1 , which is formed of a base body  2  and a plurality of protrusions  13 , which protrude radially outward from the base body. 
   The base body  2 , which is essentially provided with a square outer contour, has a hole  9  in its middle, in which a rotor shaft  22  ( FIG. 3 ) is disposed. The base body  2  completely surrounds the rotor shaft  2  on its outer radial circumference. 
   The protrusions  13 , provided for instance at corners of the base body  2 , form a pocket, in which a magnet  24  ( FIG. 3 ) is disposed. The lamination  1  has a number n of pockets  3 . A number [n−m] of pockets, where m is less than n and is greater than zero, form closed pockets  5 , for at least one lamination  1 , that are formed such that one web  11  connects two protrusions  13  to one another, in a manner spaced apart from the base body  2 . 
   In this exemplary embodiment, there are four pockets  3 , which are formed by four protrusions  13 , and of these there is one closed pocket  5 . The number n is accordingly four, and the number m is three; that is, there are three open pockets  7 . The protrusions  13  are embodied such that the magnetic flux loss in this peripheral region is reduced considerably. Lugs  14  pointing into the pockets  3  are provided on the protrusions  13 ; they guide the magnets in quasi-punctate form and bring about a reduction in flux losses. 
     FIG. 2  shows how the laminations  1  are disposed to make a lamination packet  15 . In this example, four magnets  24  can be held in the lamination packet  15 . However, the laminations  1  of the lamination packet  15  can also be embodied such there are either fewer than four magnets  24 , or more than four of them. 
   The directly adjacent laminations  1 , for instance, are therefore rotated continuously relative to one another by an angle of 90° (that is, 360° because of the number of magnets, or n). As a result of this stacking of the laminations  1  rotated relative to one another, closed pockets  5  form four receptacles  18 , into which the magnets  24  can be introduced and in which they can be radially secured. 
   As a result of this comblike structure of the lamination packet  15 , the magnetic flux loss is reduced considerably. The laminations  1  are joined together in a known way and then form the lamination packet  15 . Moreover, only one version of a lamination  1  is necessary to form the lamination packet  15 . In the exemplary embodiment shown in  FIG. 2 , protrusions  13  are provided on only two corners of the base body  2  and joined together by the web  11 . 
     FIG. 3  shows an armature  20  of the invention for an electrical machine, such as an electric motor or an electric generator. 
   The armature  20  is formed of at least one rotor shaft  22 , which is disposed in the hole  9  and solidly joined to the lamination packet  15 . The magnets  24  are disposed in the receptacles  18 . The magnet  24  is fixed for instance, among other options, by a press fit in the pocket  5 ,  7  of the lamination  1 . It is also possible for the lamination packet  15  with the magnets  24  to be spray-coated, for instance by plastic spray-coating, thereby fixing the magnet  24  in the lamination packet  15 . The laminations  1  can also be fixed by the spray-coating to form a lamination packet  15 . 
   The armature  20  of the invention is not limited to this exemplary embodiment. Two or three pockets  5  can also be present where the number of magnets is four; in that case, the individual laminations are rotated by an angle of 180°, for instance. Any other number of open and closed pockets  3 , including with a higher or lower number of magnets, is conceivable. It is also possible for there to be laminations  1  at some points in the lamination packet  15  that have only open pockets  7  or only closed pockets  5 . Moreover, not every lamination  1  has to be rotated relative to the lamination  1  directly adjacent to it. Two or more successive identical laminations  1  in one lamination packet  15  may instead not be rotated relative to one another, and can then be followed by at least one lamination that is in turn rotated relative to them.