Abstract:
A rotor arrangement for an electric prime mover ( 6 ) of a motor vehicle has a rotor shaft ( 34 ), on which at least two laminate stacks ( 36, 38, 40, 42, 44, 46 ) are arranged. At least one laminate stack ( 36 ) is configured to enable a changed moment of inertia of this laminate stack ( 36 ) with respect to another laminate stack ( 38 ).

Description:
CROSS REFERENCE TO RELATED APPLICATION 
       [0001]    This application claims priority under 35 USC 119 to German Patent Appl. No. 10 2013 102 408.4 filed on Mar. 11, 2013, the entire disclosure of which is incorporated herein by reference. 
       BACKGROUND 
       [0002]    1. Field of the Invention 
         [0003]    The invention relates to a rotor arrangement for an electric prime mover for a motor vehicle. The rotor arrangement has a rotor shaft, on which at least two laminate stacks consisting of a number of individual laminations are arranged. The invention also relates to an electric prime mover for a motor vehicle and to an electric drive system. 
         [0004]    2. Description of the Related Art 
         [0005]    Rotor arrangements have been used in motor vehicles and in recent times, electric prime movers have been used for driving drive wheels of a drive axle of a hybrid or electric vehicle. For example, these electric prime movers may have a rotor arrangement with at least two laminate stacks that transfer oscillations in the natural frequency range of the laminate stacks to coupled machine elements, such as transmissions. This transfer can have a disadvantageous effect on noise emissions of the machine elements and the expected life. 
         [0006]    The object of the invention therefore consists in providing a rotor arrangement or an electric prime mover which avoids the above-described disadvantage in a simple and inexpensive manner. 
       SUMMARY OF THE INVENTION 
       [0007]    The invention relates to a rotor arrangement that has at least one laminate stack with means for enabling a changed moment of inertia of this laminate stack with respect to another laminate stack. Thus, it is possible to provide scattering of the moments of inertia of the individual laminate stacks, which means that the moments of inertia of all of the laminate stacks can no longer be added given a certain self-resonant frequency and can therefore result in the mentioned oscillations. 
         [0008]    The means for enabling a changed moment of inertia of the laminate stack with respect to another laminate stack may comprise geometric form elements, such as bores or cutouts. The means also may comprise material elements such as lightweight construction materials, introduction of heavy metals, etc. 
         [0009]    The invention also relates to an electric prime mover for a motor vehicle comprising a housing with a stator arrangement and such a rotor arrangement. 
         [0010]    The invention also relates to an electric drive system comprising such an electric prime mover. The electric prime mover can be drive-coupled to a drive axle of a motor vehicle. In this case, it is particularly advantageous if a transmission is provided. The transmission and the electric prime mover are arranged in a multi-part drive system housing, and the drive system housing is mounted on the drive axle via at least two bearings. This arrangement provides an extremely compact and high-performance embodiment for an electric drive system. 
         [0011]    The invention is described in more detail below with reference to the drawings. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0012]      FIG. 1  shows a schematic view of a drive train of a motor vehicle. 
           [0013]      FIG. 2  is a perspective view of a rotor arrangement of the invention. 
           [0014]      FIG. 3  is a detail view of a laminate stack. 
           [0015]      FIG. 4  shows a schematic cross-sectional view of an embodiment of an electric drive system. 
       
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
       [0016]      FIG. 1  shows an example of a hybrid drive train  2  for a motor vehicle. The hybrid drive train  2  is a parallel hybrid drive. More particularly, the drive train  2  has an internal combustion engine  4 , an electric prime mover  6  that can also be operated as a generator, a high-voltage source  8 , a disconnect clutch  10  and a double clutch transmission  12  that transfers torque onto the rear wheels  16  via a differential  14 . The electric prime mover  6  in this embodiment is a permanent magnet synchronous motor, with a stator arrangement and a rotor arrangement  32  (see  FIG. 2 ) provided in the housing of said synchronous motor in a known manner. A control device  18  also is provided. The internal combustion engine  4  has a motor shaft  20  connected in torsionally rigid fashion to a first clutch element  22  of the disconnect clutch  10 . A second clutch element  24  of the disconnect clutch  10  is connected in torsionally rigid fashion to the transmission input shaft  26  via a rotor shaft  34  illustrated in  FIG. 2 . The transmission input shaft  26  acts on the double clutch transmission  12 , which, in a known manner, has a first transmission clutch  28  and a second transmission clutch  30 . 
         [0017]      FIG. 2  is a perspective illustration of a rotor arrangement  32  of the electric prime mover  6 . As already mentioned, the rotor arrangement  32  has the rotor shaft  34 , on which six laminate stacks  36 ,  38 ,  40 ,  42 ,  44 ,  46  are arranged in a known manner. The laminate stacks  36 ,  38 ,  40 ,  42 ,  44 ,  46  are secured by corresponding support discs  48 . In conventional rotor arrangements, the laminate stacks  36 ,  38 ,  40 ,  42 ,  44 ,  46  are designed uniformly in terms of their moment of inertia. Thus, the oscillations due to self-resonant frequencies of the individual laminate stacks  36 ,  38 ,  40 ,  42 ,  44 ,  46  can be added, as a result of which these oscillations can be introduced into the adjoining machine elements, such as the disconnect clutch  10  and the double clutch transmission  12 . To prevent this problem, provision is made according to the invention for only the laminate stacks  36  and  46 ;  38  and  44  and  40  and  42  to have identical moments of inertia, or in other words for these three pairs have different moments of inertia. Hence, there is no longer simultaneous oscillation in the self-resonant frequency range. 
         [0018]    By way of example the laminate stack  36  in  FIG. 3  has different moments of inertia be providing geometric form elements, in this case bores  50  that reduce the moment of inertia of the laminate stack  36 . However, it is also possible for this change in the moment of inertia to be ensured via lightweight construction material or the introduction of heavy metals. 
         [0019]      FIG. 4  is a schematic cross-sectional view of an electric drive system  52 . The electric drive system has one multi-part drive system housing  54  in which the electric prime mover  6  is arranged. The electric prime mover  6  is drive-coupled to a drive axle  58 , in this case is a front axial, via a three-shaft transmission  56 . The multi-part drive system housing  44  is mounted on the drive axle via three bearings  60 ,  62 ,  64 . This arrangement provides an extremely compact, high-performance electric drive system.