Abstract:
A rotor for an electric machine includes a base body and a plurality of support bodies that are fixed on the base body and support permanent magnets. The rotor is characterized in that two first support bodies that are located at a distance from one another form a receiving region for a second support body, allowing the first support body to be positively connected to the second support body.

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     This application represents a National Stage application of PCT/DE2009/001567 entitled “Synchronous Machine” filed Nov. 5, 2009, pending. 
     BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The invention relates to a rotor for an electric machine, e.g. an electricity generator or an electric motor, comprising a base body and a plurality of support bodies that are fixed on the base body and support permanent magnets. 
     2. Discussion of the Prior Art 
     The structure of such rotors has been known for a long time. For an equally long period there have been problems concerning fastening the permanent magnets, that are usually bonded to support bodies, on the rotor&#39;s base body. For the task of assembly, special safety measures are taken for the personnel, it having to be ensured in particular on account of the considerable magnetic fields produced by the permanent magnets that only non-magnetic materials are introduced into the work rooms and in particular only non-magnetic tools are used. In addition the installation takes place in clean rooms so as to rule out any contamination that could adversely affect the operation of the electric machines to be assembled. 
     When assembling the permanent magnets on the outer circumference of the rotor&#39;s base body the problem exists in particular that magnets arranged on neighbouring support bodies exert strong attractive and repulsive forces on each other and thus make assembly difficult to a considerable extent. During operation of the machine there are also centrifugal forces that act on the support bodies in addition to the magnetic forces, making it necessary to produce an extremely safe and durable connection between the permanent magnets and/or the support bodies and the base body of the rotor. 
     The connection between the rotor&#39;s base body and the support body is usually made by means of a positively locking connection where a groove on the shape of a dovetail is machined in the base body of the rotor, into which a dovetail-shaped pin formed on the base bodies can be introduced. Such designs are for example known from EP 1 439 626 A1 and DE 197 05 432 A1. 
     Even though this design ensures that the support bodies and thus the permanent magnets fitted thereon can be attached successively by pushing into the groove on the rotor&#39;s base body, such that they can be loaded in each case. However the implementation of this connection is very labour consuming and requires a high degree of precision for the necessary manufacturing tolerances to be kept. The manufacture of the rotors is therefore also very cost intensive. 
     SUMMARY OF THE INVENTION 
     It is therefore the object of the invention to produce a rotor for an electric machine that can be assembled more easily but just as safely. In particular, the invention relates to a rotor for an electric machine, comprising a base body and a plurality of support bodies that are fixed on the base body and support permanent magnets. The rotor is characterized in that two first support bodies that are located at a distance from one another form a receiving region for a second support body, allowing the first support body to be positively connected to the second support body. 
    
    
     
       DETAILED DESCRIPTION OF THE DRAWINGS 
       The invention will now be explained in more detail with reference to a preferred exemplary embodiment illustrated in the drawings, in which: 
         FIG. 1  shows a perspective view of a rotor according to the invention; 
         FIG. 2  shows a detail of an axial view of the rotor according to a particularly preferred exemplary embodiment from  FIG. 1 ; 
         FIG. 3  shows a detail of an axial view during an assembly phase of the rotor from  FIG. 1 ; 
         FIG. 4  shows a radial view of the rotor during a further assembly phase; 
         FIG. 5  shows a detail of an axial view of the rotor according to an alternative exemplary embodiment to that shown in  FIG. 2 ; and 
         FIG. 6  shows a detail of an axial view of the rotor according to a further alternative exemplary embodiment to that shown in  FIG. 2 . 
     
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     Instead of a groove to be milled into base body of the rotor  10 , the basic idea of the invention is to shape the support bodies  30   a ,  30   b  of the permanent magnets  40  in such a way that the flanges, that face each other, of two first support bodies  30   a  arranged spaced apart from a receiving region into which a second support body  30   b  of complementary design to its flanges can be pushed, as a result of which a positive connection between first support bodies  30   a  and second support body  30   b  is achieved in the radial direction. 
     The advantage of attaching to the base body  20  of the rotor  10  two first support bodies  30   a  that initially are spaced relatively far apart lies in the fact that the attracting and repulsing forces acting between the permanent magnets  40  are minimized in the case of a larger working distance and the support bodies  30   a  are thus more easy to handle. At the same time work safety is increased. 
       FIG. 1  shows a rotor of particularly preferable design according to the invention. The rotor  10  exhibits a base body  20  on which the support bodies  30   a ,  30   b  that support the permanent magnets  40  are attached. As specified in  FIG. 1  the first support bodies  30   a  are arranged on the circumference of the base body  20  of the rotor  10  so as to alternate with the second support bodies  30   b.    
     The receiving region formed by the first support bodies  30   a  is preferably of dovetail design—as can be seen in FIG.  2 —, the second support body  30   b  itself being of dovetail shape. As an alternative or in addition the first support bodies  30   a  and the second support body  30   b  can have a tongue connection, as it is shown in  FIGS. 5 and 6 . In the process the tongue connection can also be designed like a tongue and groove connection, an element  70  being preferably introduced into the grooves provided in the (almost) identical support bodies  30   a ,  30   b . Particularly preferably the element  70  is firmly connected either to the first support body  30   a  or to the second support body  30   b.    
     The first and second support bodies  30   a ,  30   b  are preferably shaped with the same overlapping area, the first and second support bodies  30   a ,  30   b  being particularly preferably of identical design and the permanent magnets  40  being attached on the first and second bodies  30   a ,  30   b  on facing sides. 
     To this end, the first support bodies  30   a  can also have a sector-shaped design in cross section and the second support body  30   b  can be of complementary design thereto. 
     The second support bodies  30   b  are pushed into the receiving regions formed by the first support bodies  30   a  so that the second support bodies  30   b  are securely held in the receiving region and thus are prevented by the receiving region from yielding to the attractive forces of the first support bodies  30   a.    
     After the second support bodies  30   b  have been pushed in between the first support bodies  30   a  that are attached on the base body  20  of the rotor  10  in the axial direction, and secured by a positive connection against being displaced radially, they are additionally immobilized on the base body  20 . 
     When assembling the inventive rotor  10  for example for a synchronous generator of a wind turbine, one would proceed as follows, as shown as an example in  FIGS. 3 and 4 : 
     Initially at least two first support bodies  30   a  are brought near to the base body  20  of the rotor  10  using a tool  100  and attached thereto at a spacing relative to each other such that a second support body  30   b  can be accommodated between the first support bodies  30   a . With their flanges that are oriented towards each other, the first support bodies  30   a  form a receiving region for the second support body  30   b.    
     The second support body  30   b  is then pushed into the receiving region formed by the first support bodies  30   a , the flanges of the second support body  30   b  being of complementary design to the flanges of the first support bodies  30   a , so that in this way a radial positively locking connection takes place between first and second support bodies  30   a ,  30   b  that counteracts a radial lifting-off of the second support body  30   b.    
     The second support bodies  30   b  are preferably fastened directly on the base body  20 , e.g. by means of screws. 
     When the support bodies  30   a ,  30   b  are fastened with the base body  20  by means of screw connections  50  there is in particular the possibility, during assembly, of not yet tightening fully the first support bodies  30   a , that for example exhibit stud screws (not shown) provided on the support body  30   a , on the base body  20  so that a clearance remains initially and thus manufacturing tolerances as large as possible are being made possible when manufacturing the support bodies  30   a ,  30   b . It is not until after the second support bodies  30   b  have been moved into the receiving region formed by the first support bodies  30   a  that the first and second support bodies  30   a ,  30   b  are brought into their final position by tightening the screw connections  50  without work safety being put at risk. 
     Then all the steps mentioned are repeated until all first and second support bodies  30   a ,  30   b  are attached to the base body  20  of the rotor  10 . 
     As an alternative at first all first support bodies  30   a  required for a rotor  10  can be attached to the base body of the rotor  10  and then between them the second support bodies  30   b  are pushed in and immobilized. 
     It can also be provided that the first and second support bodies  30   a ,  30   b  preferably have fastening means designed as (threaded) holes that are arranged differently so that first support bodies  30   a  differ from second support bodies  30   b  on account of different “hole patterns”. Fastening means  50  can then be inserted into these holes (not shown). This design likewise contributes to increased work safety because of a work sequence with improved structure. 
     Firmly tightening the support bodies  30   a ,  30   b  to the base body  20  of the rotor  10  to form a unit that is firmly interconnected has the further advantage, in addition to the above mentioned aspects relating to the work process, that air-gap losses can be minimized. 
     Particularly preferably the inventive method is carried out in such a way that at least one place holder  60  (a so called “dummy”; see  FIG. 3 ) is fastened on the base body  20  of the rotor  10  that keeps free the space for the second support body  30   b  and that is removed after fastening the first support bodies  30   a  and before introducing the at least one second base body  30   b . This guarantees that the first support bodies  30   a  are fastened at a distance from one another that ensures that a second support body  30   b  can be pushed in between the first support bodies  30   a . To this end the place holder  60  has approximately the same dimensions as the second support body  30   b.    
     However it can also be provided that the place holder has a somewhat larger design than the second support body  30   b  to account for manufacturing tolerances.