Abstract:
An electric machine for a current generating unit configured to extend the range of an electric vehicle. The electric machine includes a cylindrical housing part produced by casting, which is configured to accommodate a stator and a rotor. The cylindrical housing part contains at least one cooling channel arrangement through which a coolant flows.

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
       [0001]    The present application is a National Stage Application of PCT International Application No. PCT/EP2011/070335 (filed on Nov. 17, 2011), under 35 U.S.C. §371, which claims priority to Austrian Patent Application No. A 1911/2010 (filed on Nov. 18, 2010), which are each hereby incorporated by reference in their respective entireties. 
     
    
     TECHNICAL FIELD 
       [0002]    The invention relates to an electric machine, especially for a current generating unit for extending the range of an electric vehicle, comprising a cylindrical housing part, especially produced by casting, for accommodating a stator and a rotor, said housing part containing at least one cooling channel arrangement through which a coolant flows in a meandering manner. 
       BACKGROUND 
       [0003]    DE 100 22 146 A1 describes a stator with cooling tubes for an electric machine with rotating internal rotor, which stator comprises at least electric core stack and several cooling tubes arranged by means of encapsulation, with the cooling tubes being embedded in a casting body which is formed by casting of heat-conducting material and which rests on the core stack and/or is comprised by the same. 
         [0004]    A cast moulded part of an electric motor is known from EP 0 899 852 A1. A stator frame of an electric motor is arranged as a cast moulded part with at least one axially extending internal rib of the housing which extends outside of the direct connection of the two face sides of the stator housing and/or is meandering or sinusoidal in the axial direction. 
         [0005]    An electric motor with a cooling spiral is further known from DE 101 31 119 A1, which is arranged as a meandering planiform structure and consists of material that conducts heat very well and of deflections made of plastic. 
         [0006]    In the case of housing parts that are produced especially by means of aluminium die-casting methods, a meandering configuration of the cooling channels which is advantageous for optimal heat dissipation can hardly be realised or only with difficulty with increased effort in the die-casting. 
       SUMMARY 
       [0007]    It is the object of the invention to avoid these disadvantages and to achieve optimal cooling in an electric machine in the simplest possible way. 
         [0008]    This is achieved in accordance with the invention in such a way that the cooling channel arrangement comprises a plurality of essentially parallel cooling chambers which extend substantially in the axial direction of the electric machine, which are preferably cast simultaneously and which are provided with an open configuration on at least one first front side of the housing part, with each cooling chamber being defined by walls preferably extending substantially in the axial direction, and that a deflecting device which is spaced from the walls is introduced into at least one cooling chamber from the first front side. 
         [0009]    The deflecting device is preferably formed by a plug and/or a guide element. The deflecting devices formed by the plug and/or guide ribs can be inserted in the axial direction into the cooling chambers in order to enable a meandering deflection of the coolant. 
         [0010]    It is especially advantageous if the deflecting device is detachably arranged in the cooling chamber, with preferably the walls being spaced in the axial direction from the front side. 
         [0011]    In order to achieve a sufficient cooling effect, deflecting devices can be arranged in at least two adjacent cooling chambers. 
         [0012]    It can further be provided within the scope of the invention that the deflecting device is inserted into a receiving opening of the housing part which is arranged in the region of the front side, wherein preferably the housing part can be covered on the front side by a cover part, and wherein the deflecting device can be arranged in the cover part. The deflecting devices can be detachably fixed in the cover part or can be simultaneously cast therewith. 
         [0013]    Simple production is enabled when the cooling chambers are flow-connected to a cooling chamber arranged in an annular fashion in the region of the first front side between an initial area and an end area, with at least one deflecting device crossing the cooling chamber in an especially preferred way in the axial direction. The annular space can be arranged in the housing part or in the cover part. 
         [0014]    The cooling effect or flow through the individual cooling chambers can be adjusted to the respective requirements by varying the cross sections and/or the axial extension of the deflecting devices. Furthermore, reduced heat dissipation can be achieved if a deflecting device is not arranged in each cooling chamber but only in thermally critical regions of the cooling channel arrangement. 
         [0015]    An especially good cooling effect can be achieved when the deflecting device forms a separation edge in the region of an end facing the cooling chamber, with preferably a flow cross section defined between the separation edge and a wall base of the cooling chamber being larger than a flow cross-section in the annularly arranged cooling chamber. This leads to stalls in the flow and turbulent flow, which supports the transport of heat. 
     
    
     
       DRAWINGS 
         [0016]    The invention will be explained below in closer detail by reference to the drawings, which schematically illustrate as follows: 
           [0017]      FIG. 1  illustrates an electric generating unit with an electric machine in accordance with the invention. 
           [0018]      FIG. 2  illustrates a cylindrical housing part in a sectional view along the line II-II. 
           [0019]      FIG. 3  illustrates the cylindrical housing part in a front view. 
           [0020]      FIG. 4  and  FIG. 5  illustrate a cooling channel arrangement on the electric side in a respective oblique view. 
           [0021]      FIG. 6  illustrates the cylindrical housing part in an oblique view. 
           [0022]      FIG. 7  illustrates the cylindrical housing part in a further oblique view. 
       
    
    
     DESCRIPTION 
       [0023]      FIG. 1  illustrates a current generating unit  40  (range extender), especially for extending the range of an electric vehicle, with a rotary-piston engine  1  and an electric machine  14  which is excited by permanent magnets for example being arranged in a housing  2 . The housing  2  comprises a chamber  3  in which a rotary piston is revolvingly arranged along a trochoidal running surface  5  of the housing  2 . The chamber  3  is formed by the trochoidal running surface  5  and by lateral running surfaces  6 ,  7 . The housing  2  comprises a central housing part  2   a  forming the trochoidal running surface  5 , lateral housing parts  2   b  and  2   c  and, in the embodiment, the lateral plates  8 ,  9  which define the central housing part  2   a.    
         [0024]    An eccentric shaft  10  which is arranged in an inner housing space  15  in each of the housing parts  2   b ,  2   c  and which is driven by the rotary piston  4  is rotatably held via bearings  11 ,  12  which are arranged as rolling bearings for example. The rotor  13  of the electric machine  14  which is arranged in the same housing  2  is arranged coaxially to the eccentric shaft  10 . 
         [0025]    The lateral first housing part  2   b  which accommodates the bearing  11  comprises a bell-shaped cylindrical jacket area  2   b , which opens a substantially cylindrical interior space  15   a  in which the rotor  13  and the stator  14   a  of the electric machine are arranged. The cylindrical interior space  15   a  is closed off by a cover part  2   d  adjacent to the housing part  2   b.    
         [0026]    The electric machine  14  and the rotary-piston engine  1  have a common cooling system  50 , with the flow successively passing through the cooling channel arrangements  51 ,  52 ,  53 ,  54  which are provided in the housing parts  2   d ,  2   b ,  2   a  and  2   c . As a result, the electric machine  14  and then the rotary-piston engine  1  will be cooled successively. A cooling chamber  51   b  of the cooling channel arrangement  51  on the electric side, which cooling chamber is arranged in an annular way between an initial area  55  and an end area  56 , can be formed partly by the cover part  2   d  and partly by the cylindrical housing part  2   b.    
         [0027]    A number of cooling chambers  51   a  which extend in the direction of the axis  10   a  of the eccentric shaft  10  are arranged in the housing part  2   b  in the region of the electric machine  14 , which cooling chambers are flow-connected to the annular cooling chamber  51   b  in the region of the front side  33  of the housing part  2   b.    
         [0028]      FIGS. 2 to 5  schematically illustrate a cooling channel arrangement  51  of the housing part  2   b  on the electric side, with the coolant entrance into the cooling chamber arrangement occurring in the initial area  55  and the coolant outlet in the end region  56  for example. The coolant can also be supplied and/or discharged at other locations of the coolant arrangement  51 , e.g. in the region of a cooling chamber  51  such as in the region of the piston-side front side  36  of the housing part  2   b . With the exception of optional inflow, outflow or transfer openings in other housing regions, the cooling chambers  51  a are substantially closed in the region of the piston-side front side  34  (e.g. by casting or by a cover part), so that forced deflection will occur at the end of each cooling chamber  51   a.    
         [0029]    In  FIG. 2 , the end area  56  is twisted into the plane of intersection and downwardly for illustrating the meandering flow of the coolant which is indicated by the arrows. 
         [0030]    In order to enable a meandering coolant flow which is optimal for the cooling of the electric machine  14  in the cylindrical jacket area  2   b ′ of the housing part  2   b  which encloses the stator  14   a  and the rotor  13 , deflection devices  57  are axially inserted into the cooling chambers  51   a , which deflection devices  57  can be formed for example by plugs  57   a , guide ribs or the like. The deflecting devices  57  are inserted for example in co-cast axial receivers  37  in the annular cooling chamber  51   b . It is also possible as an alternative to this to arrange the deflecting devices  57  in the cover part  2   d  in a releasable or non-releasable manner (e.g., by co-casting). 
         [0031]    The coolant which flows in the circumferential direction into the annular cooling chamber  51   c  will be deflected by the defecting devices  57  in the direction of axis  10   a  into the cooling chambers  51  a and returned along the walls  51   a ′ back to the cooling chamber  51 , where it is deflected again by the next deflecting device  57  into the next cooling chamber. As a result of this loop-like movement of the coolant, the cooling area of the housing part  2   b  which is relevant for the electric machine  14  will be cooled evenly, wherein fine tuning of the heat dissipation can occur by changing the cross-section and/or the length of the deflecting devices  57 . The deflecting devices  57  can consist of plastic or the like for example. 
         [0032]      FIG. 5  illustrates the streamlines of the coolant flow in the loop-like annular chamber  51   c . The deflecting devices  57  are only very few, i.e. they are inserted into the cooling chambers  51   a  to an extent that corresponds approximately to the axial extension of the annular chamber  51   b . The deflecting device  57  forms a separation edge  57   a , with a flow cross-section defined between the separation edge  57   a  and the wall base  51   a ″ of the cooling chamber  51   a  being larger than a flow cross-section in the annularly arranged cooling chamber  51   b . The illustration illustrates that this leads to stalls in the flow and swirling phenomena in the cooling chambers  51   a , by means of which the transport can be improved in these areas. 
         [0033]    The deflecting devices  57  which can be moved into the annular cooling chambers  51  allow a meandering coolant flow in the housing part  2   b  which encloses the electric machine  14  by means of simple production and therefore the best possible heat dissipation.