Abstract:
A rotor of an electric machine includes a rotor lamination stack connected to a rotor shaft for conjoint rotation therewith. The rotor lamination stack extends from a first axial face of the rotor lamination stack to a second axial face when viewed in the direction of an axis of rotation of the rotor lamination stack. The rotor lamination stack has bores distributed around the axis of rotation and extending from the first axial face to the second axial face. A tie rod which protrudes from the axial faces when viewed in the direction of the axis of rotation is inserted into each bore. Fastening elements are attached to the tied rods at both axial faces so that the rotor laminations of the rotor lamination stack are pressed together. A fan is attached to the tie rods on the first axial face of the rotor lamination stack.

Description:
CROSS-REFERENCES TO RELATED APPLICATIONS 
     This application is the U.S. National Stage of International Application No. PCT/EP2013/067318, filed Aug. 20, 2013, which designated the U.S. and has been published as International Publication No. WO 2014/033015 and which claims the priority of German Patent Application, Serial. No.10 2012 215 236.9, filed Aug. 28, 2012, pursuant to 35 U.S.C. 119(a)-(d). 
     BACKGROUND OF THE INVENTION 
     The present invention relates to a rotor of an electrical machine,
         wherein the rotor has a rotor laminated core connected to a rotor shaft of the rotor in a rotationally-fixed manner,   wherein the rotor laminated core extends from a first axial end face of the rotor laminated core to a second axial end face of the rotor laminated core when viewed in the direction of an axis of rotation of the rotor laminated core,   wherein the rotor laminated core has recesses that are distributed around the axis of rotation and extend from the first axial end face to the second axial end face when viewed in the direction of the axis of rotation,   wherein a tie rod, which projects beyond the axial end faces when viewed in the direction of the axis of rotation, is introduced into each of the recesses,   wherein fastening elements are positioned on the tie rods on both axial end faces.       

     The present invention furthermore relates to an electric machine
         wherein the electric machine has a stator and a rotor,   wherein the rotor is mounted in bearings so that it can be rotated about an axis of rotation of the rotor.       

     A rotor of this type and an electric machine of this type are known for example from EP 0 909 004 B1. 
     A rotor of an electric machine, which has a rotor laminated core, is likewise known from US 2011/0 074 242 A1. The rotor laminated core extends from a first axial end face of the rotor laminated core to a second axial end face of the rotor laminated core when viewed in the direction of an axis of rotation of the rotor laminated core. The rotor laminated core has recesses that are distributed around the axis of rotation and extend from the first axial end face to the second axial end face when viewed in the direction of the axis of rotation. A tie rod, which projects beyond the axial end faces when viewed in the direction of the axis of rotation, is introduced into each of the recesses. Fastening elements, by means of which the rotor sheets are pressed against one another, are positioned on the tie rods. 
     A rotor of an electric machine, which has a rotor laminated core, is known from US 2012/0098359 A1. The rotor laminated core extends from a first axial end face of the rotor laminated core to a second axial end face of the rotor laminated core when viewed in the direction of an axis of rotation of the rotor laminated core. The rotor laminated core has recesses that are distributed around the axis of rotation and extend from the first axial end face to the second axial end face when viewed in the direction of the axis of rotation. A rivet, which projects beyond the axial end faces when viewed in the direction of the axis of rotation, is introduced into each of the recesses. Balance elements are positioned on the rivet. 
     In the prior art the rotor laminated core is attached to the rotor shaft. The so-called bundling pressure is applied via rotor pressure rings which are positioned on the two end faces of the rotor laminated core. The bundling pressure is transmitted via the rotor pressure rings to the rotor shaft. The bundling pressure causes a deflection of the rotor pressure rings. The rotor pressure rings must therefore be embodied so as to be accordingly stable in order to avoid an excessive deflection of the rotor pressure rings. Any possible fan is generally arranged directly at the rotor shaft. 
     SUMMARY OF THE INVENTION 
     The object of the present invention consists in providing an electric machine which is simple in design, does not require rotor pressure rings and in which in particular the fan can easily be connected to the rotor. 
     The object is achieved according to the invention by a rotor of an electric machine
         wherein the rotor has a rotor laminated core connected to a rotor shaft of the rotor in a rotationally-fixed manner,   wherein the rotor laminated core extends from a first axial end face of the rotor laminated core to a second axial end face of the rotor laminated core when viewed in the direction of an axis of rotation of the rotor laminated core,   wherein the rotor laminated core has recesses that are distributed around the axis of rotation and extend from the first axial end face to the second axial end face when viewed in the direction of the axis of rotation,   wherein a tie rod, which projects beyond the axial end faces when viewed in the direction of the axis of rotation, is introduced into each of the recesses,   wherein fastening elements are positioned on the tie rods on both axial end faces, so that the rotor sheets of the rotor laminated core are pressed against one another by means of the fastening elements without the arrangement of rotor pressure rings between the end faces of the rotor laminated core and the fastening elements,   wherein a fan is positioned on the tie rods on the first axial end face of the rotor laminated core and   wherein the fastening elements are arranged on the first axial end face of the rotor laminated core between the end face and the fan.       

     Advantageous embodiments of the rotor according to the invention are the subject matter of the dependent claims. 
     The rotor laminated core usually consists of a plurality of rotor sheets. In a preferred embodiment of the present invention the rotor sheets in each case have a yoke on their side facing away from the axis of rotation and in each case have a sheet hub on their side facing toward the axis of rotation. In this case the yokes and the sheet hubs of the rotor sheets are connected to one another via respective sheet spokes. 
     The embodiment of the fan can be determined as required. Preferably the fan has an annular disk running orthogonally to the axis of rotation and fan blades protruding from the annular disk. 
     The annular disk can have an outer ring on its side facing away from the axis of rotation and a disk hub on its side facing toward the axis of rotation. In this case the fan blades are arranged on the outer ring and the outer ring and the disk hub are connected to one another via disk spokes. This embodiment is particularly expedient if the rotor sheets have the aforementioned sheet hubs and sheet spokes. 
     The fact that the disk hub is positioned on the tie rods means that it is possible for the disk hub to be connected to the rotor shaft in a manner which is not rotationally fixed. The disk hub in this case merely serves to help position and center the fan during assembly. 
     It is preferably provided that the fan blades are embodied as sheet parts and are mounted onto the annular disk. This produces a design of the fan which is particularly simple in terms of construction. 
     Preferably the fan blades are mounted onto the annular disk from the radial interior to the radial exterior. This produces a simplified mounting of the fan blades on the annular disk. 
     Preferably the fan blades are welded to the annular disk. 
     In a particularly preferred embodiment the fan blades have axially inner sections which are arranged between the annular disk and the first axial end face. In this case the axially inner sections in particular can rest against the first axial end face. This causes the rotor laminated core to be stabilized even further. 
     It is possible for at least one balancing weight to be positioned on at least one of the tie rods on the first axial end face. In this case the fan can be arranged between the first axial end face and the balancing weight in particular. 
     In a further preferred embodiment the tie rods are potted in the recesses by means of a potting compound. 
     With regard to the electric machine, the object is achieved in that for an electric machine of the type cited in the introduction the rotor is embodied as explained above. 
     The electric machine can in principle be used for any purpose. Preferably it is used as a traction motor of a vehicle. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWING 
       The above-described characteristics, features and advantages of this invention, as well as the manner in which these are achieved, will become more clearly and easily intelligible in connection with the following description of the exemplary embodiments, which are explained in more detail in conjunction with the schematic drawings, in which: 
         FIG. 1  shows a longitudinal section of an electric machine, 
         FIG. 2  shows a cross-section of a rotor sheet, 
         FIG. 3  shows a detail of  FIG. 2 , 
         FIG. 4  shows a fan of the electric machine of  FIG. 1  perpendicular to an axis of rotation and 
         FIG. 5  shows a vehicle having an electric machine. 
     
    
    
     DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS 
     In accordance with  FIG. 1 , an electric machine has a stator  1  and a rotor  2 . The rotor  2  has a rotor shaft  3  and a rotor laminated core  4 . The rotor shaft  3  is mounted in bearings  5  so that the rotor shaft  3  and with it the entire rotor  2  can be rotated about an axis of rotation  6  of the electric machine. 
     Insofar as reference is made hereinbelow to “axial”, “radial” and “tangential”, these always relate to the axis of rotation  6 . The term “axial” means a direction parallel to the axis of rotation  6 . The term “radial” means a direction orthogonal to the axis of rotation  6  toward the axis of rotation  6  or away from it. The term “tangential” means a direction orthogonal to the axis of rotation  6  and orthogonal to the radial direction, that is to say at a constant radial spacing from the axis of rotation  6  in a circular manner about the axis of rotation  6 . 
     The rotor  2 , in accordance with the illustration of  FIG. 1 , is generally arranged radially inside the stator  1 . The electric machine is thus embodied as an internal rotor. However, the rotor  2  can alternatively be arranged radially outside the stator  2  in individual cases. In this case the electric machine is embodied as an external rotor. 
     The stator  1  of the electric machine is of minor importance within the context of the present invention. Therefore, only the rotor  2  is explained below in more detail. 
     According to  FIG. 1 , the rotor laminated core  4  extends from a first axial end face  7  of the rotor laminated core  4  to a second axial end face  8  of the rotor laminated core  4  when viewed in an axial direction. The rotor laminated core  4  consists of a plurality of rotor sheets  9 , which are stacked on top of one another in an axial direction. 
     According to  FIGS. 1, 2 and 3 , the rotor laminated core  4  has recesses  10 . The recesses  10 , according to  FIG. 2 , are arranged so as to be distributed around the axis of rotation  6 . The recesses  10  extend in an axial direction end-to-end through the rotor laminated core  4 , that is to say from the first axial end face  7  to the second axial end face  8 . A tie rod  11  is introduced into each of the recesses  10 . The tie rods  11  have a longer length than the rotor laminated core  4 . The tie rods  11  thus project axially beyond the end faces  7 ,  8  of the rotor laminated core  4 . 
     Positioned at both axial end faces  7 ,  8  of the tie rods  11  are fastening elements  12 , for example nuts  12 . By means of the fastening elements  12 , the rotor sheets  9  of the rotor laminated core  4  are pressed against one another. 
     According to  FIG. 3 , the recesses  10  have a larger cross-section than the tie rods  11 —even if only slightly. In order to avoid oscillation of the tie rods  11  during operation of the electric machine with certainty, the tie rods  11  are preferably potted in the recesses  10  by means of a potting compound  13 . Suitable potting compounds are known per se to the person skilled in the art. They are for example used in the prior art for potting permanent magnets of a permanently excited electric machine. 
     According to  FIG. 1  a fan  18  is positioned on the tie rod  11  on the first axial end face  7  of the rotor laminated core  4 . According to the illustration of  FIG. 1 , the fan  18  can in particular be positioned on the fastening element  12  located on the first axial end face  7 . In this case the fastening elements  12  are thus arranged between the first end face  7  and the fan  18 . The fan  18  in particular can be fastened to the tie rods  11  by means of further fastening elements  19 , for example by means of nuts  19 . 
       FIG. 2  shows not only the underlying principle of the present invention, but simultaneously also a preferred embodiment of the rotor sheets  9 . In particular according to  FIG. 2  the rotor sheets  9  in each case have a yoke  14  on their side facing away from the axis of rotation  6  and in each case have a sheet hub  15  on their side facing toward the axis of rotation  6 . The yokes  14  and the sheet hubs  15  of the rotor sheets  9  are connected to one another via respective sheet spokes  16 . The use of the affix “sheet” when denoting the sheet hubs  15  and the sheet spokes  16  serves to verbally distinguish said elements from other hubs and spokes. No further meaning is assigned to the affix “sheet” in this context. 
     The fan  18  can be embodied as required. Preferably the fan according to  FIGS. 1 and 4  has an annular disk  20  and fan blades  21 . The annular disk  20  runs orthogonally to the axis of rotation  6 . The fan blades  21  protrude from the annular disk  20 . In particular, they can protrude from the annular disk  20  in an orthogonal manner. 
     It is possible that the annular disk  20  is identical to an outer ring  22 . The outer ring  22  is essentially arranged with the same radial spacing as the yokes  14  of the rotor sheets  9 . the fan blades  21  are arranged on the outer ring  22 . According to  FIG. 5 , however, the annular disk  20  has a disk hub  23  in addition to the outer ring  22 . The outer ring  22  is in this case arranged on the side of the annular disk  20  facing away from the axis of rotation  6 , the disk hub  23  on the side of the annular disk  20  facing toward the axis of rotation  6 . The outer ring  22  and the disk hub  23  are connected to one another via disk spokes  24 . The use of the affix “disk” when denoting the disk hubs  23  and the disk spokes  24  serves to verbally distinguish said elements from other hubs and spokes. No further meaning is assigned to the affix “disk” in this context. 
     Should the annular disk  20  comprise the outer ring  22 , the disk hub  23  and the disk spokes  24 , the contour of the annular disk  20  preferably corresponds to that of a rotor sheet  9 . 
     The disk hub  23  can be connected to the rotor shaft  3  in a rotationally-fixed manner. Preferably, however, the annular disk  20  is dimensioned such that the disk hub  23  is connected to the rotor shaft  3  in a manner which is not rotationally fixed. The disk hub  23  thus merely serves to help position and center the fan  18  during assembly. 
     In a particularly preferred embodiment the fan blades  21  are embodied as simple sheet parts. The annular disk  20  can also be embodied as a simple sheet part. The fan blades  21  can be mounted to the annular disk  20  for example. 
     Preferably the fan blades  21  are mounted onto the annular disk  20  from the radial interior to the radial exterior. 
     The fan blades  21  can be connected to the annular disk  20  in any desired manner. Preferably the fan blades  21  are welded to the annular disk  20 . 
     The fan blades  21 , according to  FIG. 1 , have axially inner sections  25 . The axially inner sections  25  of the fan blades  21  are, according to  FIG. 1 , arranged between the annular disk  20  and the first axial end face  7 . Preferably the axial structural height of the axially inner section  25  is dimensioned such that the axially inner sections  25  rest against the first axial end face  7  under compressive stress. The spacing of the annular disk  20  or of the outer ring  22 , as the case may be, from the first axial end face  7  thus has a slight waviness when viewed in the circumferential direction about the axis of rotation  6 , wherein the minima lies in the region of the tie rods  11  and the maxima lies in the region of the fan blades  21 . 
       FIG. 1  likewise shows not only the underlying principle of the present invention, but simultaneously also a preferred embodiment of the electric machine. According to  FIG. 1 , to eliminate an imbalance (at least) one balancing weight  17  can be positioned on at least one of the tie rods  11 . Generally, according to the illustration of  FIG. 1  two balancing weights  17  are positioned, wherein each one of the balancing weights  17  is positioned on the corresponding tie rod  11  on the first and the second axial end face  7 ,  8 . With regard to the balancing weight  17  positioned on the second axial end face  8 , the fastening thereof is effected by means of a further fastening element  17 ′ (for example a nut  17 ′). For the balancing weight  17  positioned on the corresponding tie rod  11  on the first axial end face  7 , the fan  18  is preferably arranged between the first axial end face  7  and the balancing weight  17 . 
     The electric machine according to the invention can in principle be used for any purpose. Preferably, the electric machine according to  FIG. 5  is used as a traction motor  26  of a vehicle  27 . The vehicle  27  can for example be embodied as a rail vehicle or as a road transport vehicle. 
     The present invention has many advantages. This allows, for example, the rotor pressure rings of the prior art to be dispensed with. This results in advantages regarding both cost and weight. The electric machine can also be constructed so as to be more compact than in the prior art. The spoke-based construction means that it is possible for the yoke  14  to be cooled in a highly efficient manner. There is also less material required for manufacturing the electric machine. In cases where the fan  18  is present, on the one hand the fan blades  21  additionally support the rotor laminated core  4  and on the other hand an additional oscillation damping of the fan blades  21  is effected. The connection of the fan  18  to the tie rods  11  means that the connection is only subjected to very low torsional stresses as a result. 
     Although the invention has been illustrated and described in greater detail with reference to the preferred exemplary embodiment, the invention is not limited by the examples disclosed and the person skilled in the art will be able to derive other variations on this basis without moving beyond the scope of protection of the invention.