Abstract:
At least one of a variable turbine geometry and a variable compressor geometry for an exhaust gas turbocharger may include a housing including a first housing wall and a blade bearing ring having at least one guide blade rotatably mounted thereon. A control lever may be included for adjusting the at least one guide blade between a closing position and an opening position. An actuating shaft may be connected to the control lever in a rotationally fixed manner along a rotation axis. The actuating shaft may be rotatably mounted on the housing via a passage opening disposed in the first housing wall. The actuating shaft may directly support itself on the first housing wall in the passage opening.

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
       [0001]    This application claims priority to German Patent Application No. 10 2014 218 342.1, filed Sep. 12, 2014, the contents of which are hereby incorporated by reference in its entirety. 
       TECHNICAL FIELD 
       [0002]    The invention relates to a variable turbine and/or compressor for an exhaust gas turbocharger and an exhaust gas turbocharger having such a variable turbine and/or compressor geometry. 
       BACKGROUND 
       [0003]    For regulating the turbine or compressor output in an exhaust gas turbocharger, fluid-flow machines with a so-called variable turbine respectively compressor geometry are employed, which allow a variation of the inflow of a fluid such as for example exhaust gas or fresh air to the impeller of the fluid flow machine by means of adjustable guide blades. Such adjustability allows optimal adaptation of the fluid flow onto the impeller as a function of the fluid quantity entering at the moment. Adjusting the guide blades into an opening position with maximum flow cross section for the instance of a large quantity of exhaust gas or fresh air ensures that the gas molecules do not impinge on the impeller with too high a velocity. However, when the fluid quantity entering the fluid-flow machine decreases, for example because the internal combustion engine connected upstream of the turbocharger happens to be operated with low rotational speed at that time, adjusting the guide blades into a closing position with minimal flow cross section results in the gas molecules being accelerated. As a result, fewer gas molecules impinge on the impeller, however with increased velocity to that the impeller of the fluid-flow machine is accelerated. 
         [0004]    For adjusting the guide blades between their opening and closing position, actuating devices, typically in the manner of actuating levers, are often used, which are directly or indirectly coupled—for example via a so-called adjusting ring—to the rotatable guide blades. For moving the actuating device designed as actuating lever it is opportune to connect the same to an actuator lever via a so-called actuating shaft in a rotationally fixed manner. By means of the actuator lever, which in turn can be drive-connected to an electric actuator, the actuating lever can thus be moved between the opening and the closing position. With conventional variable turbine and/or compressor geometries, the actuating shaft is usually at least partly in a bearing bushing provided on the guide blade support ring or on the housing and is rotatably mounted in the same. A variable turbine geometry constructed in this manner is known for example from EP 0 226 444 B1. 
       SUMMARY 
       [0005]    It is now an object of the present invention to create an improved embodiment for a variable turbine and/or compressor geometry which compared with conventional variable turbine and/or compressor geometries is characterized by reduced production costs. 
         [0006]    Accordingly, the basic idea of the invention is to not rotatably mount the actuating shaft for adjusting the guide blades with the help of a component—typically a bearing bushing or similar—attached to the housing in a fixed manner on the housing, but to entirely do without such an additional component. In other words, the control lever according to the invention is directly mounted on the housing. To this end, a suitably dimensioned passage opening is provided on the housing in which the actuating shaft can be rotationally adjustably received relative to the housing. This results in the desired direct supporting of the actuating shaft on the housing. 
         [0007]    Since with the variable turbine respectively compressor geometry according to the invention a conventional bearing bushing or a similar component that is designed separately to the housing is omitted, elaborate assembly of the bearing bushing in the housing is also omitted, for example by means of pressing in. This results in substantially reduced production costs in the manufacture of the variable turbine respectively compressor geometry. 
         [0008]    A variable turbine and/or compressor geometry for an exhaust gas turbocharger according to the invention has a suitably dimensioned housing delimiting a housing interior. The variable turbine and/or compressor geometry comprises a blade bearing ring, on which a plurality of guide blades is rotatably mounted. For adjusting the guide blades between a closing position and an opening position, a control lever is provided. Connected to this control lever in a rotationally fixed manner is an actuating shaft, which is rotatably mounted on the housing and for the rotatable mounting is at least partly received in a passage opening, which in turn is formed in a first housing wall of the housing. According to the invention, the actuating shaft supports itself within the passage opening directly on the first housing wall. 
         [0009]    In a preferred embodiment, a protective coating can be provided on a wall section of the first housing wall delimiting the passage opening. Such protective coating improves the resistance of the housing to wear manifestations, which due to friction because of the rotation of the actuating shaft relative to the housing can occur in a more or less pronounced form. 
         [0010]    Particularly practically, the protective coating can contain carbon and nitrogen. For producing such a protective coating a thermochemical method known as “nitrocarburizing” to the person skilled in the art is recommended. With this method, the surface of the housing is enriched with nitrogen and carbon. This results in an abrasion-resistant nitrided layer, which in turn comprises a connecting layer and a diffusion layer. 
         [0011]    In another preferred embodiment, the housing has a second housing wall located opposite the first housing wall, which together with the first housing wall partly delimits the housing interior. In the second housing wall, a recess is provided, which with respect to a top view from the outside onto the first housing wall is aligned with the passage opening provided in the first housing wall. Thus, the actuating shaft cannot only support itself within the passage opening on the first housing wall but with an axial end section received in the recess, additionally also on said second housing wall. In any case, the actuating shaft supports itself directly on the respective housing wall. 
         [0012]    In order to increase the lifespan of the variable turbine and/or compressor geometry it proves to be advantageous to provide the already explained protective coating on the side of the housing facing the housing interior also in the region of the recess formed in the second housing wall. It is clear that the protective coating also in this case—just as the protective coating in the region of the passage opening—can contain carbon and nitrogen. In this way it can be ensured that a wear-resistance protective coating is present on all bearing points of the actuating shaft on the housing. This leads to reduced wear in the actuating shaft and in those sections of the housing, on which the actuating shaft mechanically comes into contact with the housing. 
         [0013]    For the stable fixing of the actuating shaft along an axial direction defined by the centre longitudinal axis of the actuating shaft it is proposed to design and dimension the recess provided in the second housing wall in such a manner that it acts as axial stop for the actuating shaft for a movement along its centre longitudinal axis to the second housing wall of the housing. 
         [0014]    In an advantageous further development, the control lever can be fastened to the actuating shaft in a rotationally fixed manner by means of a clamping connection, by means of a screw connection or by means of a press connection. 
         [0015]    In order to prevent axial movement of the actuating shaft within the housing—mostly caused through axial play of the actuating shaft in the housing due to tolerances—it is proposed in another preferred embodiment of the invention to arrange a spring-elastic element in the interior. For preloading the control lever towards the first housing wall, the same can support itself on the second housing wall on the one hand and on the control lever on the other hand. 
         [0016]    In an advantageous further development of this embodiment, the spring-elastic element can be or comprise a coil spring, which is arranged coaxially to the centre longitudinal axis of the actuating shaft and wraps the actuating shaft spirally radially on the outside. In this way the spring-elastic element can be attached to the actuating shaft in a space-saving manner. Alternatively to such a coil spring, the use of a suitably designed spiral spring, a wave spring or a disc spring is also conceivable. 
         [0017]    In another preferred embodiment, a bearing disc acting as sealing element can be provided between control lever and second housing wall, which seals the housing interior in the region of the passage opening against the outer surroundings of the housing. 
         [0018]    In a further preferred embodiment, the recess provided in the second housing wall can also be a passage opening, which fluidically connects the housing interior to the outer surroundings of the housing and in a first axial section facing the housing interior has a first opening diameter. This first axial section, moving away from the housing interior, merges into a second axial section with a second opening diameter that is smaller than the first opening diameter. The actuating shaft with this version is received in the first axial section. In the second axial section, a preload element can be received which—analogous to the spring-elastic element in the housing interior, for preloading the actuating shaft against the first housing wall at one end and on a face end of the actuating shaft assigned to the second housing wall. At the other end, the preload element can support itself on a housing wall of a compressor/turbine housing, which on a side of the second housing wall facing away from the housing interior can abut the same. In this way, a preload of the actuating shaft towards the first housing wall can also be achieved. In contrast with the spring-elastic element introduced above, the preload element is not arranged within the housing in the housing interior but outside the housing. Consequently the preload element is particularly easily accessible to a worker. 
         [0019]    As particularly practical in terms of design proves to be an advantageous further development of the embodiment explained above, with which the preload element is designed stamp-like. A preload element with such a geometrical configuration comprises a stamp shaft, which is arranged in the second axial section of the passage opening. This stamp shaft, moving away from the actuating shaft, merges into a stamp section which is received in a recess that is complementary to the stamp section. This recess is provided on the side of the second housing wall facing away from the housing interior. 
         [0020]    The invention furthermore relates to an exhaust gas turbocharger with a turbine and/or compressor geometry introduced above. 
         [0021]    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. 
         [0022]    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. 
         [0023]    Preferred exemplary embodiments of the invention are shown in the drawings and are explained in more detail in the following description, wherein same reference characters relate to same or similar or functionally same components. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0024]    It shows, in each case schematically, 
           [0025]      FIG. 1  an example of a variable turbine and/or compressor geometry according to the invention in a longitudinal section, 
           [0026]      FIG. 2  a first variant of the example of  FIG. 1 , 
           [0027]      FIG. 3  a second variant of the example of  FIG. 1 , 
           [0028]      FIG. 4  a detail representation of the control lever of the  FIGS. 1 to 3 , which is fastened to the actuating shaft by means of a screw connection, 
           [0029]      FIG. 5  a further detail representation of the control lever of the  FIGS. 1 to 3 , which is fastened to the actuating shaft by means of a clamping connection. 
       
    
    
     DETAILED DESCRIPTION 
       [0030]      FIG. 1  shows in a longitudinal section an example of a variable turbine and/or compressor geometry  1  according to the invention. The same comprises a housing  2  delimiting a housing interior  3 , which housing  2  comprises a first housing wall  7   a  and a second housing wall  7   b  located opposite the first housing  7   a.  The variable turbine and/or compressor geometry  1  also comprises a blade bearing ring, on which a plurality of guide blades is rotatably mounted (not shown). For adjusting the guide blades between their opening and closing position, the variable turbine and/or compressor geometry comprises an actuating device in the form of an actuating lever  37 , which is coupled to the rotatable guide blades for their adjustment between the opening and closing position via an adjusting ring (not shown) that is mounted on the housing. For moving the actuating lever  37 , the same is connected to an actuating shaft  5  in a rotationally fixed manner. The variable turbine and/or compressor geometry  1  furthermore comprises a control lever  4  that is connected to the actuating shaft  5  in a rotationally fixed manner, which in turn can be drive-connected to an electric actuator (not shown). The actuating shaft  5  has a centre longitudinal axis M, through the position of which an axial direction A of the actuating shaft  5  is determined. For rotationally fixing the control lever  4  on the actuating shaft  5 , a suitably dimensioned break-through  16  can be provided in the control lever  4 , which is engaged through by the actuating shaft  5 . 
         [0031]    Corresponding to  FIG. 4 , the control lever  4  can be fixed on the actuating shaft  5  in rotationally fixed manner by means of a screw connection  12 . Such a screw connection  12  can comprise a threaded bore  13  provided in the actuating shaft  5 , which is aligned with a passage opening  15  provided in the control lever  4 . For fixing the control lever  4  on the actuating shaft  5 , a threaded screw  14  is used. 
         [0032]      FIG. 5  shows a variant that is alternative to the scenario of  FIG. 4  for the rotationally fixed fastening of the control lever  4  on the actuating shaft  5  with the help of a clamping connection. In this case, the control lever  4  can be equipped with two pincer-like end sections  17   a,    17   b,  which in each case partly form a break-through  16  for receiving the actuating shaft  5  and between which a gap-like intermediate space  18  is additionally formed. In the end section  17   a,  a threaded bore  19   a  is provided, in the end section  17   b  a conventional bore aligned with the threaded bore  19   a,  which is aligned with the threaded bore  19   a.  By screwing a threaded screw  20  through the bore  19   b  into the threaded bore  19   a,  the two end sections  17   a,    17   b  are pressed against one another and in this way pressed against the actuating shaft  5  so that the desired clamping effect is achieved. With the variant of  FIG. 5  for both the actuating shaft  5  and also for the break-through  16 , a non-rotation symmetrical geometry such as for example the geometry of a polygon in the form of a hexagon—exemplarily shown for example in FIG.  5 —is recommended in the cross section perpendicularly to the centre longitudinal axis M. Alternatively or additionally to the screw respectively clamping connections shown in the  FIGS. 4 and 5 , fastening the actuating shaft  5  on the control lever  4  by means of pressing is also conceivable, in particular in connection with the non-rotation-symmetrical geometry of actuating shaft  5  and break-through  16  mentioned above. In this case, the screws  14  and  20  can be omitted. 
         [0033]    With conventional variable turbine and/or compressor geometries, the actuating shaft  5  is usually at least partially received in a bearing bushing attached to the blade bearing ring or on the housing  2  and rotatably mounted in the same. As illustrated in  FIG. 1 , the actuating shaft  5  with the variable turbine and/or compressor geometry  1  according to the invention by contrast is rotatably mounted directly on the housing  2 . To this end, the actuating shaft  5  is at least partly received in a passage opening  6 , which is formed in the first housing wall  7   a  of the housing  2 . As is further evident from  FIG. 1 , the actuating shaft  5  supports itself within the passage opening  6  directly—i.e. without using a bearing bushing or a similar component that is connected to the housing  2  in a fixed manner—on the first housing wall  7   a.  In the second housing wall  7   b  on the inside a recess  10  is provided, which is aligned with the passage opening  6  provided in the first housing wall  7   a.  The actuating shaft  5  is received in the recess  10  with an axial end section  11  and rotatably mounted in the same. This means that the actuating shaft  5  supports itself not only within the passage opening  6  on the first housing wall  7   a,  but within the recess  10  also on the second housing wall  7   b.  In both cases, the actuating shaft  5  supports itself directly on the two housing walls  7   a,    7   b.  Preferably, an inner diameter d i  of the passage opening  6  and of the recess  10  in each case corresponds to a shaft diameter d v  of the actuating shaft  5 . 
         [0034]    On a wall section  9  of the first housing wall  7   a  delimiting the passage opening  6  and—alternatively or additionally to this—in the region of the second housing wall  7   b  delimiting the recess  10 , a protective coating  8  can be provided which improves the resistance of the housing  2  to abrasion and wear. The protective coating  8  can be applied onto the wall section  9  and optionally also onto further regions of the housing  2  by means of “nitrocarburising” and contain carbon and nitrogen. The recess  10 , in particular its recess depth t, is dimensioned and designed in the example scenario in such a manner that it acts as axial stop for the actuating shaft  5  for a movement along the centre longitudinal axis M towards the second housing wall  7   b  of the housing  2 . 
         [0035]    The  FIG. 2  shows a variant of the example of  FIG. 1 . In order to prevent axial movement of the actuating shaft  5  within the housing  2 , brought about for example through axial play of the actuating shaft  5  in the housing  2  due to tolerances, a spring-elastic element  21  is arranged in the housing interior  3 , which preloads the control lever  4  and thus also the actuating shaft  5  that is fixed on the control lever  4  in a rotationally fixed manner towards the first housing wall  7   a.  To this end, the spring-elastic element  21  supports itself on the one end on the second housing wall  7   b  and on the other end on the control lever  4 . As is schematically shown in  FIG. 2 , the spring-elastic element  21  can be or comprise a coil spring  22 , which is arranged coaxially to the centre longitudinal axis M of the actuating shaft and radially wraps the actuating shaft  5  on the outside. In variants of the example, a suitable spiral spring, wave spring or disc spring can also be used instead of a coil spring. 
         [0036]    With a further version of the example of  FIG. 1  shown in  FIG. 3 , the recess  10  provided in the second housing wall  7   b  is also designed in the form of a passage opening  23 . Such a passage opening  23  has a first opening diameter d 1  in a first axial section  24   a  facing the housing interior  3 , which corresponds to the inner diameter d i  of the recess  10  in the example of the  FIGS. 1 and 2 . The first axial section  24   a  of the passage opening  23  moving away from the housing interior  3  merges into a second axial section  24   b  with a second opening diameter d 2 , that is smaller than the first opening d 1 . The actuating shaft  5  is received in the first axial section  24   a.  In the second axial section, a preload element  25  is arranged, which for preloading the actuating shaft  5  against the first housing wall  7   a  supports itself on the one end on a face end  26  of the actuating shaft  5  facing the second housing wall  7   b.  On the other end, the preload element  25  can support itself on a housing wall  27  of a compressor/turbine housing  29 . The compressor/turbine housing  29  abuts the second housing wall  7   b  on a side  28  of the same facing away from the housing interior  3 . In this way, a preload of the actuating shaft  5  towards the first housing wall  7   a  can be achieved. In addition to this, the preload element  25  following disassembly of the housing  2  from the compressor/turbine housing  29  is particularly easily accessible to a worker. 
         [0037]    The preload element  25 , as shown in  FIG. 3 , can be designed stamp-like and comprise a stamp shaft  30 , which is arranged in the second axial section  24   b  of the passage opening  23 . This stamp shaft  30  moving away from the actuating shaft  5  merges into a stamp section  31  which is received in a recess  32  that is complementary to the stamp section  31  and formed on the side  28  of the second housing wall  7   b  facing away from the housing interior and protrudes over the second housing wall  7   b  for as long as the compressor/turbine housing  29  is not mounted on the second housing wall  7   b.    
         [0038]    For sealing the housing interior  3  against the outer surroundings  33  of the housing  2 , a bearing disc  34  acting as sealing element can be provided between control lever  4  and first housing wall  7   a  in the examples of the  FIGS. 1 to 3 , which seals an interior space between the actuating shaft  5  and the wall section of the first housing wall  7   a  of the housing  2  forming the passage opening  6 . 
         [0039]    The recess  10 , as shown in  FIG. 3 , is also designed as passage opening  23  so that a receiving groove can be provided in the wall section of the second housing wall  7   b  delimiting the passage opening  23 , in which partly a sealing element  35 , for example in the manner of a sealing ring, is received. The sealing element  35  serves for sealing the housing interior  3  against the outer surroundings  33  in the region of the passage opening  33 .