Abstract:
An exhaust gas turbocharger may include a compressor housing and a turbine housing. The turbine housing may be connected to the compressor housing via a plurality of spacer pins composed of a heat-insulating material. The plurality of spacer pins may respectively include a head and at least one axial pin.

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
       [0001]    This application claims priority to German Patent Application No. 10 2014 206 162.8, filed Apr. 1, 2014, the contents of which are hereby incorporated by reference in their entirety. 
       TECHNICAL FIELD 
       [0002]    The present invention relates to an exhaust gas turbocharger with a compressor housing and a turbine housing. 
       BACKGROUND 
       [0003]    From DE 10 2008 048 126 A1 a generic exhaust gas turbocharger with a compressor housing and a turbine housing is known, wherein the bearings of a rotor are seated in the turbine housing and in the compressor housing, since these are directly attached to one another, without the bearing housing that is usually arranged between turbine housing and compressor housing. The turbine housing in this case is connected to the turbine housing via a spacer ring, wherein the spacer ring is to serve as bearing ring for a variable turbine geometry at the same time. Radially outside the spacer ring, the turbine housing is also directly connected to the compressor housing, as a result of which heat transfer can occur here. 
         [0004]    From DE 200 09 004 U1 a further exhaust gas turbocharger with a gas turbine connected to the exhaust side of an internal combustion engine is known, wherein a turbine housing and a compressor housing are directly connected to one another to form a housing. Heat insulation between these two housings is not provided. 
         [0005]    With usual exhaust gas turbochargers, a bearing housing for mounting a rotor is located between the turbine housing and the compressor housing, which is why direct heat transfer between the turbine housing to the compressor housing and accompanied by this, heat expansion problems usually do not occur. With exhaust gas turbochargers, the rotors of which however are mounted in the turbine housing and in the compressor housing and with which no bearing housing is provided between these two housings, an undesirable heat transfer can occur which under certain conditions can result in an impairment of the function of the exhaust gas turbocharger. 
       SUMMARY 
       [0006]    The present invention therefore deals with the problem of stating an improved or at least an alternative embodiment for an exhaust gas turbocharger of the generic type, which in particular does not have the disadvantages known from the prior art. 
         [0007]    According to the invention, this problem is solved through the subject of the independent claims. Advantageous embodiments are subject of the dependent claims. 
         [0008]    The present invention is based on the general idea from connecting, in the case of an exhaust gas turbocharger without bearing housing, a turbine housing to a compressor housing via at least three heat-insulating spacer pins. The at least three spacer pins in this case have a comparatively low heat conductivity coefficient, as a result of which heat transfer between the comparatively hot turbine housing and the compressor housing can be greatly reduced. This is of elementary significance in particular for such exhaust gas turbochargers in which the turbine housing is arranged on the compressor housing without intermediate connection of a bearing housing. 
         [0009]    Practically, the spacer pins are formed from ceramic, in particular from zirconium oxide. Such spacer pins formed from ceramic cannot only be produced in a cost-effective manner but also have a very low heat transfer rate, i.e. a low heat conductivity coefficient, as a result of which in particular the heat transfer between the turbine housing and the compressor housing can be at least greatly reduced. In particular zirconium oxide has a high resistance to chemical, thermal and mechanical influences, just like obviously further ceramics as well, as a result of which the use in the above described manner is particularly advantageous. 
         [0010]    Practically, recesses for receiving the spacer pins are provided in the turbine housing and/or in the compressor housing. By way of such recesses it is possible to not only assign the spacer pins a heat-insulating function but also a centring function at the same time, which significantly simplifies the assembly of the exhaust gas turbocharger. The recesses in this case can be optionally formed in the manner of elongated holes in order to be able for example to compensate for heat expansion of the turbine housing, or alternatively as fitted bores, as a result of which reliable fixing for example is made possible. In this case, the spacer pins usually have a rotation-symmetrical shape. Alternatively, an angular shape is obviously also conceivable, wherein in this case the recesses have to be formed accordingly. Through the elongated hole-like design of the recesses, which advantageously run in radial direction, simple compensation for possible temperature expansions of the turbine housing is possible. 
         [0011]    In an advantageous further development of the solution according to the invention, the turbine housing is screwed to the compressor housing. Such a screw connection makes possible both a comparatively simple and secure assembly as well as a comparatively simple disassembly of the two housing parts, which is of major advantage in particular in the case of maintenance operations. 
         [0012]    Further important features and advantages of the invention are obtained from the subclaims, from the drawings and from the associated figure description with the help of the drawings. 
         [0013]    It is to be understood that the features mentioned above and still to be explained in the following cannot only be used in the respective combination stated but also in other combinations or by themselves without leaving the scope of the present invention. 
         [0014]    Preferred exemplary embodiments of the invention are shown in the drawings and are explained in more detail in the following description, wherein same reference numbers relate to same or similar or functionally same components. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0015]    It shows, in each case schematically 
           [0016]      FIG. 1  a sectional representation through an exhaust gas turbocharger according to the invention, 
           [0017]      FIG. 2  a partially sectioned view through the exhaust gas turbocharger, 
           [0018]      FIG. 3  different embodiments of a spacer pin, 
           [0019]      FIG. 4  a view of a turbine housing, 
           [0020]      FIG. 5  a view of a compressor housing with elongated hole-like recesses, 
           [0021]      FIG. 6  a representation as in  FIG. 5 , however with other recesses, 
           [0022]      FIG. 7  a possible embodiment of the exhaust gas turbocharger according to the invention with a spacer pin according to  FIG. 3   b.    
       
    
    
     DETAILED DESCRIPTION 
       [0023]    According to  FIGS. 1 ,  2  and  7 , an exhaust gas turbocharger  1  according to the invention comprises a compressor housing  2  and a turbine housing  3 . The compressor housing  2  in this case is screwed to the turbine housing  3  via screws  4 . According to the invention, the turbine housing  3  is now connected to the compressor housing  2  via at least three heat-insulating spacer pins  5 . Obviously, four or more spacer pins  5  can also be provided here. According to the invention, these are formed of a heat-insulating material, for example from ceramic, in particular from zirconium oxide, as a result of which a heat transfer between the comparatively hot turbine housing  3  and the compressor housing  2  is to be at least minimised. For in the shown embodiment of the exhaust gas turbocharger  1  according to the invention, a bearing housing which is usually arranged between the compressor housing  2  and the turbine housing  3  is omitted, so that the two housing parts  2 ,  3  are directly connected to one another. In order to be able to at least reduce an undesirably high heat transfer between the turbine housing  3  and the compressor housing  2 , the at least three heat-insulating spacer pins  5  are provided. 
         [0024]    Looking at the spacer pins  5  according to the  FIGS. 3   a  and  3   b , it is evident that these have a rotation-symmetrical shape, wherein it is obviously also conceivable that these have an angular shape. The spacer pin  5  shown according to  FIG. 3   a  has two axial pins  6 ,  6 ′, whereas the spacer pin  5  shown according to  FIG. 3  merely has one such axial pin  6 . With the axial pin  6  the spacer pin  5  is able to engage in an associated recess  7  on the turbine housing  3 . The recesses  7  (see  FIG. 4 ) in this case are likewise formed rotation-symmetrically, in particular even as a fitted bore, as a result of which the spacer pin  5  can be received therein fixed in position. 
         [0025]    In the same way, the recesses  7 ′ on the compressor housing  2  can also be formed, wherein it is also conceivable alternatively that these are formed elongated hole-like, as is shown according to the  FIGS. 5 and 6 . If the spacer pin  5  is formed as shown in  FIG. 3   a , it is able to engage both in the recesses  7  of the turbine housing  3  and also in the associated recesses  7 ′ of the compressor housing  2  and because of this assume a centring function between the two housings  2 ,  3 . Because of the elongated hole-like design of the recesses  7 ′ a heat expansion of the turbine housing  3  during the operation of the exhaust gas turbocharger  1  can also be easily compensated for. 
         [0026]    In the embodiment of the spacer pin  5  shown according to  FIG. 3   b  it is possible to let said spacer pin  5  engage in recesses  7 ′ of the compressor housing  2 , as is shown according to the  FIGS. 6 and 7 , wherein purely theoretically it is also conceivable that a spacer pin  5  designed in this manner does not assume any centring function so that this has to be assumed by other elements. Here, the recesses  7 ′ according to  FIG. 6  are embodied as radial slots, in which the spacer pin  5  with its head  9  at least partially engages. By way of its axial pin  6 , the spacer pin  5  engages in the recess  7  on the turbine housing  3 , as a result of which in turn an arrangement of the turbine housing  3  and compressor housing  2  compensating for temperature differences is made possible. 
         [0027]    With the spacer pins  5  formed according to the invention it is possible to at least reduce an undesirable heat transfer between the turbine housing  3  and the compressor housing  2 , in particular in the case of exhaust gas turbochargers  1 , in which the turbine housing  3  and the compressor housing  2  are connected to one another without the intermediate connection of a bearing housing. A rotor  8  in this case is mounted in the turbine housing  3  and in the compressor housing  2 .