Abstract:
A moving element is connected to a rotor of an electric motor in a manner locked in terms of torque and, together with the rotor, forms a rotation element. An angle of inclination of the moving element in relation to the rotor is defined by bearing elements which are arranged on a circumference about the axis of rotation of the rotor, wherein the bearing elements each define axial distances between the rotor and the moving element. Each bearing element is formed by a first and a second axial section, and the moving element can be brought into different rotational positions in relation to the rotor so as to produce different pairings of the first and second sections, said pairings corresponding to different angles of inclination.

Description:
BACKGROUND OF THE INVENTION 
       [0001]    Electric motors comprise a stator and a rotor which are rotatably mounted with respect to one another. A mass of the rotor is, under certain circumstances, not distributed in a precisely rotationally symmetrical fashion, with the result that the rotor has an unbalance which may be static and/or dynamic. During operation of the electric motor, the unbalance causes vibrations, which inter alia can propagate in the form of solid-borne sound and can lead to increased noise and vibration loading. In order to reduce an unbalance of the rotor, the rotor has to be balanced. The rotor is preferably balanced together with a moving element which is connected to the rotor in a locking fashion in terms of torque and which is to be driven by the electric motor. The balancing process has to be carried out individually for each rotor, which increases manufacturing costs for the rotor, and therefore for the electric motor. 
       SUMMARY OF THE INVENTION 
       [0002]    The invention is based on the object of specifying a rotation element of an electric motor and a method for mounting the rotation element by means of which balancing can be carried out in a simplified way. 
         [0003]    According to the invention, a rotation element of an electric motor comprises a rotor of the electric motor having a rotational axis and a moving element which is connected to the rotor in a locking fashion in terms of torque. An angle of inclination of the moving element with respect to the rotor is defined by bearing elements which are arranged on a circumference around the rotational axis of the rotor, wherein the bearing elements each define axial distances between the rotor and the moving element. Each bearing element is formed by a first axial section and a second axial section, and the moving element can be moved into different rotational positions with respect to the rotor in such a way that different pairings of first and second sections which correspond to different angles of inclination are produced. 
         [0004]    By means of the angle of inclination, an oblique position can be brought about between the moving element and the rotor, which position can be used to compensate an unbalance. By simply rotating the moving element with respect to the rotor before the mounting of the moving element on the rotor it is therefore possible to reduce the unbalance. In this context, the number of adjustable angles of inclination is limited by the necessarily finite number of first and second sections, which can contribute to simplifying the balancing process. 
         [0005]    Contact points at which the first sections respectively bear against the second sections can lie in a plane which is perpendicular to the rotational axis. As a result, for example, a moving element can be used whose sections which are assigned to it are all of the same length. This is a customary embodiment for many moving elements, with the result that sections of the bearing elements of different lengths have to be formed only on the rotor. In a corresponding way, the sections which are of the same length can also be formed on the rotor, and the sections which are of unequal length on the moving element. 
         [0006]    First sections which are adjacent to one another can each enclose identical angles with one another with respect to the rotational axis. The moving element can then be rotated through this angle with respect to the rotor without changing the angle of inclination in the process. Second sections which are adjacent to one another and which can form a bearing element with the same first section can enclose identical angles with one another with respect to the rotational axis. By rotating the moving element with respect to the rotor through this angle, which can be smaller than the angle between the adjacent first sections, the size of the angle of inclination can be varied. 
         [0007]    Taken together, the bearing elements can be arranged and embodied in such a way that depending on the rotational position as many different angles of inclination can be set as the number of second sections which can form a bearing element with one of the first sections, wherein each adjustable angle of inclination can be set with respect to each first section. This embodiment can be directly reproduced by a person mounting the moving element on the rotor with the result that balancing can be carried out by selective implementation. 
         [0008]    One of the bearing elements can have a coaxial receptacle for a connecting element for bringing about the torque lock between the moving element and the fan. The bearing elements can therefore be used in an integrated fashion for the torque-locked connection. As a result, the complexity of the rotor and/or of the moving element can be reduced, which as a result permits manufacturing costs to be lowered. 
         [0009]    The moving element and the rotor preferably have marks for identifying a rotational position. In one particularly preferred embodiment, the moving element is an impeller wheel. 
         [0010]    In one method for reducing an unbalance of the described rotation element, in a first rotational position the moving element is attached to the rotor. The rotation element is rotated about the rotational axis and a first deviation from a run-out of the rotation element is determined. The moving element is subsequently rotated with respect to the rotor in such a way that the angle of inclination and/or the orientation of the angle of inclination with respect to the rotor is changed. Thereafter, the rotation element is rotated about the rotational axis again and a second deviation from the run-out of the rotation element is determined. On the basis of the first and the second deviation which is determined, an angle of inclination and an orientation of the moving element with respect to the rotor are determined in such a way that the deviation from the run-out of the rotation element is minimized. A rotational position of the moving element with respect to the rotor is determined as optimization of the angle of inclination at the determined angle of inclination, and of the orientation of the angle of inclination to the specific orientation. Finally, the moving element is attached in a locking fashion in terms of torque to the rotor in the determined rotational position. 
         [0011]    Further parts of the method, such as the rotation of the rotation element, the determination of the deviations from the run-out, the determination of the angle of inclination and of the orientation as well as the determination of the rotational position can be carried out by machine or in an automated fashion. An assembly worker must simply insert the rotor and the moving element in different positions in a rotational device and subsequently carry out the mounting process of the moving element on the rotor in a predefined rotational position. As a result, the method can be carried out promptly and cost-effectively. 
         [0012]    The rotation of the rotational element is preferably carried out by means of a device which is in engagement with the rotor on a side of the rotor facing away from the moving element. The device can engage with the rotor in the same way as the stator of the electric motor engages later. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0013]    The invention will now be described in more detail with respect to the appended figures, of which: 
           [0014]      FIG. 1  shows a longitudinal section through an electric motor with an impeller wheel; 
           [0015]      FIG. 2  shows a detail from  FIG. 1 ; 
           [0016]      FIG. 3  shows a rotor of the electric motor from  FIGS. 1 and 2 ; and 
           [0017]      FIG. 4  shows a flowchart of a method for mounting the electric motor in  FIGS. 1 to 3 . 
       
    
    
     DETAILED DESCRIPTION 
       [0018]      FIG. 1  shows a longitudinal section through an electric motor with an impeller wheel. A fan  100  comprises an impeller wheel  110  and an electric motor  120 . The electric motor  120  is formed by a stator  130  and a rotor  140 . A bearing  150  connects the stator  130  to the rotor  140  in such a way that the rotor  140  is mounted in such a way that it can rotate with respect to the stator  130  about a rotational axis  160 . The impeller wheel  110  is connected in a locking fashion with respect to torque to the rotor  140  by means of a plurality of bearing elements  170 . 
         [0019]    The illustrated fan  100  serves merely as an example for explaining the invention. A specific design of the fan  100  and, in particular of the electric motor  120  is not intended to be implied thereby. It is, for example, irrelevant for the invention whether the electric motor  120  has permanent magnets and whether they are arranged on the stator  130  or on the rotor  140 . The impeller wheel  110  is illustrated only in the region of the electric motor  120  since precise shaping of the blades of the impeller wheel  110  is likewise irrelevant for the invention. 
         [0020]    The impeller wheel  110  and the rotor  140  together form a rotation element  180  which rotates about the rotational axis  160  during the operation of the electric motor  120 . A static unbalance of the rotation element  180  occurs when a centroid axis of the rotation element  180  is offset in parallel with the rotational axis  160 . A dynamic unbalance occurs if the rotational axis  160  encloses an angle with the centroid axis which is unequal to zero. Through selective oblique positioning of the impeller wheel  110  with respect to the rotor  140  it is possible, in particular, to reduce or compensate an existing dynamic unbalance of the rotation element  180 . 
         [0021]      FIG. 2  shows a detail from  FIG. 1  in the region of the bearing element  170 . In the illustrated portion from  FIG. 1 , the rotor  140  has three bushings which extend to different degrees in the upward direction, specifically a short bushing  210 , medium bushing  220  and a long bushing  230 . The impeller wheel  110  has a downward-extending counter-bushing  240 . The counter-bushing  240  bears axially against the medium bushing  220  and forms one of the bearing elements  170  from  FIG. 1  together with said medium bushing  220 . A screw  250  is guided through the counter-bushing  240  and the medium bushing  220 . The three bushings of the rotor  140  have internal threads, with the result that the screw  250  secures the impeller wheel  110  with the rotor  140  in the axial direction. In other embodiments, a self-tapping screw can also be used. The torque lock between the impeller wheel  110  and the rotor  140  is mainly produced by frictional forces in the region of the counter-bushing  240  and the medium bushing  220  which adjoin one another. 
         [0022]    The counter-bushing  240  can be brought into abutment with any of the other bushings  210  to  230 . As a result, a distance between the impeller wheel  110  and the rotor  140  in the region of the bearing element  170  is changed. Depending on which other distances are defined by the further bearing elements  170  between the impeller wheel  110  and the rotor  140 , different angles of inclination can therefore be set between the impeller wheel  110  and the rotor  140  from  FIG. 1 . In this context, the angle of inclination is an angle which occurs between the rotational axis  160  and a further axis, which is positionally fixed with respect to the impeller wheel  110 , wherein the positionally fixed axis corresponds to the rotational axis  160  if all the bearing elements  170  define identical distances between the impeller wheel  110  and the rotor  140 . Alternatively, the angle of inclination can also be defined between a centroid axis of the impeller wheel  110  and the rotational axis  160  of the rotor  140 . 
         [0023]    In a further embodiment, illustrated in a corresponding way to that in  FIG. 2 , a plurality of bushings of different lengths are attached to the impeller wheel  110 , and a corresponding counter-bushing is attached to the rotor  140 . In yet another embodiment, the bushings  210 - 230  comprise equalizing elements which define the different lengths of the bushings. The equalizing elements can be spacer washers or shims. 
         [0024]      FIG. 3  show a rotor element  300  of the rotor  140  from  FIGS. 1 and 2 . The rotor element  300  is that section of the rotor  140  on which the bushings  210  to  230  of the rotor  140  are formed in order to produce the bearing elements  170 . 
         [0025]    In each case three short bushings  210 , three medium bushings  220  and three long bushings  230  are arranged on a circular circumference around the rotational axis  160 , wherein in each case three bushings  210  to  230  of different lengths form a group  310 . Marks  320 , which denote the different groups  310  or the different bushings  210  to  230  of the respective groups  310 , are provided on the rotor element  300 . For example, the medium bushing  220  illustrated at the 12 o&#39;clock position, is denoted as A 2  by means of the marks  320 . 
         [0026]    The designation of each of the bushings  210  to  230  in each of the groups  310  is clear. In the text which follows, the symbols used in  FIG. 3  are therefore used. 
         [0027]    Angles which are enclosed between bushings  210  to  230 , which are of equal length, of different groups  310 , for example between A 1  and B 2 , are identical and are 120°. At least three bearing elements  170  are necessary to clearly define the angle of inclination between the impeller wheel  110  and the rotor  140 . For this reason, no fewer than three groups  310  of bushings  210  to  230  are preferably provided, but the number of groups  310  can also be larger than three. Identical angles, of the order of magnitude of approximately 20° in the illustration in  FIG. 3  also lie between adjacent bushings  210  to  230  of each group  310 . 
         [0028]    The impeller wheel  110  has counter-bushings  240  which are also offset with respect to one another by 120° with respect to the rotational axis  160  and lie on a corresponding circular circumference to that of the bushings  210  to  230  of the groups  310 . One of the counter-bushings  240  has a mark, with the result that by specifying a position on the hub  300 , for example A 2 , a clear rotational position is defined in which the marked counter-bushing  240  is aligned with the bushing  220  in the position A 2  on the hub  300  of the rotor  120 . 
         [0029]    In one exemplary embodiment, heights of the bushings  210  to  230  are distributed in the following table: 
         [0000]    
       
         
               
               
               
             
               
               
               
             
           
               
                   
                   
               
               
                   
                 Position 
                 Relative height 
               
               
                   
                   
               
             
             
               
                   
               
             
          
           
               
                   
                 A1 
                 +1 
               
               
                   
                 A2 
                 0 
               
               
                   
                 A3 
                 +2 
               
               
                   
                 B1 
                 −1 
               
               
                   
                 B2 
                 0 
               
               
                   
                 B3 
                 −2 
               
               
                   
                 C1 
                 −1 
               
               
                   
                 C2 
                 0 
               
               
                   
                 C3 
                 −2 
               
               
                   
                   
               
             
          
         
       
     
         [0030]    The relative heights which are given in the table are converted into absolute heights by a common factor. The factor can be, for example, 0.1 mm. The absolute heights relate here to the bushings  210  to  240 ; an absolute height at an external diameter of the impeller wheel  110  may be larger in accordance with the lever ratios. 
         [0031]    If the marked counter-bushing  240  of the impeller wheel  110  is placed in alignment with, for example, the bushing at the position A 3 , the other counter-bushings  240  of the impeller wheel  110  bear against the bushings with the positions B 3  and C 3 . The oblique position or the angle of inclination between the impeller wheel  110  and the rotor  140  is produced according to the diameter of the impeller wheel  110  and the scaling of the relative height to absolute height differences. At the positions A 2 , B 2  and C 2 , the angle of inclination is the same, specifically V In a specific example, as a result an oblique positioning of 0.6 mm is achieved at an outer edge of the impeller wheel  110  with an external diameter of 500 mm, as a result of which approximately 20,000 g·mm 2  unbalance can be compensated. 
         [0032]    In other embodiments, other relative heights are possible, in particular the possibility of the counter-bushings  240  of the impeller wheel  110  having different lengths is not excluded. 
         [0033]      FIG. 4  shows a flow chart of a method  400  for mounting the rotation element  180  or the electric motor  120  in  FIGS. 1 to 3 . The method  400  comprises steps  405  to  450 . 
         [0034]    In the step  405 , the method  400  is in the starting state. In step  410 , the impeller wheel  120  is attached to the rotor  140 , with the result that the rotation element  180  is produced. In the step  415 , the rotation element  180  is rotated about its rotational axis  160 . For this purpose, a rotational device can be used which is either connected to the impeller wheel  110  or to the rotor  140 . In this context, the bearing  150  can already be attached to the stator  140 . The run-out is determined by sensing an axial variation at an outer circumference of the impeller wheel  110 . In another embodiment, the rotational device can be mounted in a sprung fashion, and in step  160  a rotational-angle-related deflection of the rotational device in the direction of the suspension can be determined during the rotation. 
         [0035]    Subsequently in step  420  the impeller wheel  110  is rotated on the rotor  140  with the result that another angle of inclination and/or another orientation of the angle of inclination between the impeller wheel  110  and the rotor  140  is set. In the step  425 , the run-out of the rotation element  180  is determined again, as is stated above with respect to step  415 . 
         [0036]    In step  430 , an angle of inclination and an orientation, which the impeller wheel  110  ideally assumes with respect to the rotor  140  in order to minimize the deviations from the run-out of the rotation element  180 , are determined on the basis of the measured values which are acquired in steps  415  and  425 . On the basis of these requirements, in step  435  the rotational position of the impeller wheel  110  with respect to the rotor  140  is determined. In the step  440 , the impeller wheel  110  is mounted in the determined rotational position on the rotor  140 , for example by means of the screws  250  in  FIG. 2 . 
         [0037]    In the optional step  445 , the rotation element  180  is mounted on the stator  130  of the electric motor  120 . In an alternative embodiment, the impeller wheel  110  can also be temporarily removed from the rotor  140  in order to mount the rotor  140  on the stator  130 . The already determined rotational position can be brought about during the subsequent mounting of the impeller wheel  110  on the rotor  140 , for which purpose the marks  320  can be helpful. 
         [0038]    The method  400  is subsequently in the final state  450 .