Abstract:
A camshaft of an internal combustion engine may include at least one function device connected therewith via a shaft-hub connection. The function device may include at least two different function elements each operable for different function

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
       [0001]    This application claims priority to German Patent Application DE 10 2012 223 811.5 filed Dec. 19, 2012, which is hereby incorporated by reference in its entirety. 
       TECHNICAL FIELD 
       [0002]    The present invention relates to a camshaft of an internal combustion engine having at least one function device connected therewith via a shaft-hub connection according to the preamble of claim  1 . The invention additionally relates to a function device for such a camshaft and to an internal combustion engine having at least one such camshaft. 
       BACKGROUND 
       [0003]    Generic camshafts are thoroughly known, just as connecting function elements to such camshafts, for example via a thermal joining fit. However, function devices such as for example gear wheels, drive wheels, cams, pump actuating devices, such as for example pump cams for a high-pressure pump or an Oldham coupling for the rotary connection of vacuum or oil pumps are connected to the camshaft by way of pressed-in or thermally joined plugs up to now. For each function to be fulfilled, a separate function element, such as for example gear wheels or cams are required here, which for this purpose still have to be joined in a different way if need be. When joining camshafts in a cover module, an additional aggravating fact is that the space is limited, so that it is even more complex to keep a plurality of function elements to join a plug from the outside. 
       SUMMARY 
       [0004]    The present invention therefore deals with the problem of stating an improved embodiment for a camshaft of the generic type, which is characterized in particular by a simplified production. 
         [0005]    According to the invention, this problem is solved through the subjects of the independent claims. Advantageous embodiments are subject of the dependent claims. 
         [0006]    The present invention is based on the general idea of equipping a function device on a camshaft with at least two different function elements, which can each fulfil different functions. The function elements combined in the function device in this case are connected to the camshaft via a shaft-hub connection, for example via a thermal joining fit or a longitudinal press fit. The principle idea thus consists in combining or integrating as many function elements as possible—however, at least two—in a common function device and merely having to join this common assembly, i.e. the function device, to the camshaft or a camshaft tube. This offers substantial advantages, for example in the region of the weight, since a function device which is put together of a plurality of function elements is significantly lighter in construction weight than function elements that are each separately assembled. The function device according to the invention additionally makes possible a higher torque transmission than can be realised with a plug having a smaller internal diameter. At the same time, the assembly is substantially simplified since all function elements no longer have to be separately, i.e. individually, joined to the camshaft, but merely the function device, in which the individual function elements are already aligned correctly to one another with respect to an angle of rotation. This is a major advantage in particular if a camshaft is assembled within a cylinder head cover, since according to common knowledge only very little working space is available there. A further advantage can be seen in an optimised weight distribution, for example through masses which are opposed to a drive belt pulley, so that the function device can be utilised for offsetting unbalances at the same time. 
         [0007]    Practically, at least one function element is a gear wheel, in particular a coupling gear wheel, a cam, a pump actuating device, for example in the manner of a cam, an encoder wheel, a belt pulley, a coupling, in particular an Oldham coupling, or a chain wheel. Even this non-conclusive listing gives an idea as to how flexible the respective function device can be configured through the joining of individual function elements. 
         [0008]    According to a further advantageous embodiment and solution according to the invention, the function device is formed in one piece, in particular as a one-piece sintered component. In this case, the individual function elements of the function device are thus connected to one another as one piece, so that the function device can be completely formed in one piece. This makes possible in particular a rational production of the function device, since an aligned joining together of the individual function elements into the function device can be omitted. Alternatively to this, it can obviously also be provided that the individual function elements of the function device are connected to one another in a fixed manner, in particular welded, soldered, screwed or glued together. The separate formation of the individual function elements in turn offers the major advantage that the function device is extremely flexibly assemblable with respect to the individual function elements. The individual function elements in this case can be connected into the continuous function device via a friction welding connection or by means of laser welding. In order to be able to facilitate joining the individual function elements into the common function device in an angularly correct manner, positioning aids can be additionally provided on the individual function elements, which allow fixing of the individual function elements on one another exclusively in a predefined angular position. Such positioning aids can for example be formed as a single flat, for example as a clear grind, or as a multiple flat, in particular as a dual flat or triple flat. In this case, a function element thus has such a single or multiple flat as well as an associated complementary recess arranged on the opposite face end, as a result of which an angularly aligned axial inserting into one another of the individual function elements into the common function device is very easily possible. Obviously, the positioning aids can be alternatively formed also as a pin or associated opening, which allows a joining together of two function elements in merely one single or a plurality of predefined angular positions. These positioning aids can obviously be additionally utilised also for further adjusting and positioning operations after the assembly of the camshaft, for example when installing the camshaft in the cylinder head. 
         [0009]    If one of the function elements is designed as an Oldham coupling, a pump can for example be coupled to the cylinder head to the outside via this. Such an Oldham coupling makes possible a coupling, in which the torque is transmitted between two parallel shafts. Usually it consists of three discs, wherein the outer two are fastened on the respective shafts or on the pump and on the function element and the middle one is mounted with respect to the two other discs in two slot and key connections which are positioned orthogonally to one another. Such an Oldham coupling makes possible in particular compensating for minor parallel offsets between the camshaft and an axis of the pump, as a result of which at least minor production inaccuracies can be offset without problems, so that the entire construction altogether allows greater production tolerances. 
         [0010]    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. 
         [0011]    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. 
         [0012]    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 of functionally same components. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0013]    Here it shows, in each case schematically 
           [0014]      FIG. 1  a sectional representation through a camshaft with a function device according to the invention in an internal combustion engine, 
           [0015]      FIG. 2  a partially sectioned view of an internal combustion engine according to the invention in the region of two camshafts with the function device according to the invention, 
           [0016]      FIG. 3  a representation as in  FIG. 2 , however with bearing bridges, 
           [0017]      FIG. 4  different views of an a sectional representation through an embodiment of a function device according to the invention, 
           [0018]      FIG. 5-7  function devices in each case with different function elements. 
       
    
    
     DETAILED DESCRIPTION 
       [0019]    According to the  FIGS. 1-3 , a camshaft  1  of an internal combustion engine  2  according to the invention comprises at least one function device  3  that is connected to the camshaft  1  via a shaft-hub connection, in particular via a press fit connection, which is put together of at least two different function elements  4 . The individual function elements  4  in this case fulfil different functions and are merely combined in the common function device  3  to simplify the assembly. At least one function element  4  in this case can for example be formed as a gear wheel  5 , in particular as a coupling gear wheel, as a cam, as a pump actuating device, as an encoder wheel  6 , as a belt pulley, as a coupling  7 , in particular as an Oldham coupling, or as a chain wheel  5 ′. The function device  3  represented according to  FIG. 1  thus has three function elements  4 , namely the coupling  7 , the chain wheel  5 ′ or gear wheel  5  as well as the encoder wheel  6 . By combining a plurality of function elements  4  in a common function device  3  the production of the camshaft  1  is clearly simplified, since all function elements  4  no longer have to be separately joined to the camshaft  1  but merely a common function device  3 , as a result of which the joining process can be significantly rationalised. The function device  3  with a plurality of function elements  4  is additionally lighter in weight than the respective separate function elements  4 , as a result of which a weight saving can be achieved, which in turn has a positive effect on the fuel consumption. 
         [0020]    Compared with a plug, the function device  3  according to the invention additionally makes possible a higher torque transmission, since via the transverse press fit, for example produced by means of thermal joining, or a longitudinal press fit, a larger force-transmitting contact area can be created. The combined arrangement of a plurality of function elements  4  in a common function device  3  additionally offers major advantages in particular in the assembly of the function device  3  in a cover or a cylinder head  8 , since extremely confined space conditions are usually encountered there. 
         [0021]    According to  FIG. 2 , a view is shown from the top of the cylinder head  8  of the internal combustion engine  2  with two camshafts  1 , wherein on the lower camshaft  1  the function device  3  according to the invention is arranged. The latter, in turn, combines three function elements  4 , namely the coupling  7 , a gear wheel  5 , in the manner of a coupling gear wheel for coupling to the second camshaft  1 , as well as the encoder wheel  6 . Mounting the camshafts  1  on the cylinder head  8  in this case is effected by means of a bearing frame  9 , which is connected to the cylinder head  8 , i.e. an engine block, via screws  10 . By way of the coupling  7 , which in particular can be formed in the manner of an Oldham coupling, a pump  11  for example can be coupled to the camshaft  1  in a rotation-transmitting manner. The Oldham coupling in this case makes possible an at least minor parallelism of the axes of the camshafts  1  and the axis of the pump, as a result of which the production precision need not be as high as without such an Oldham coupling. 
         [0022]    Considering  FIG. 1  it is evident that the function device  3  is formed in one piece, in particular as a one-piece sintered component, so that a separate and prior assembly of the individual function elements  4  into the common function device  3  can be omitted. Obviously, the individual function elements  4  of the function device  3  can also be alternatively produced separately and subsequently connected to one another into the common function device  3  in a fixed manner, in particular welded, soldered, screwed or glued together. In the representations according to  FIG. 4  a function device  3  is shown for example, which integrates two function elements  4 , namely the gear wheel  5  and the coupling  7  in one piece. On the face end of the function device  3  facing away from the coupling  7 , a further function element  4 , for example an encoder wheel  6 , could now be additionally attached or welded on. 
         [0023]    In order to facilitate an assembly of a multi-part function device  3 , positioning aids  12  can be provided on the individual function elements  4 , which allow fixing of the individual function elements  4  to one another exclusively in a predefined angular position. According to the lowermost representation in  FIG. 4  and the  FIG. 6 , the positioning aid  12  in this case is formed as a two-flat, wherein for example the encoder wheel  6  has a recess that is complementary thereto, in order to make thus possible an angularly orientated fixing. In general, the positioning aid  12  in this case can also be formed as a single flat or as a multiple flat, in particular also as a triple flat. Generally, all other non-round shapes are obviously also conceivable for the accurate angular fixing of the individual function elements  4  on one another. 
         [0024]    With the function device  3  according to the invention, a plurality of functions in the form of different function elements  4  can thus be combined and in the manner of a common function device  3 , fixed on the camshaft  1  in a single operation. Because of this, not only the assembly operation can be significantly rationalised, but a cost-effective production achieved at the same time. By combining individual function elements  4  into the common function device  3 , the major advantage is additionally obtained that compared with a plug, higher torques can be transmitted and in particular an assembly of the function device  3  is possible even with comparatively little working space. Above all, this offers the possibility of keeping the function device  3  according to the invention with the individual function elements  4  in a cover and subsequently slide the camshaft tube through the function elements  4  and the individual bearing points for example of the bearing frame  9 . Through the integration of a plurality of function elements  4  in a common function device  3 , merely the fixing of a function device  3  is required in this case, which is clearly simpler than the previously required fixing of the individual function elements  4 . With the function device  3  according to the invention, a weight saving can be additionally achieved, since the individual function elements  4  can be formed in a weight-reduced manner. An unbalance offset in particular for example with respect to a belt pulley  13  (see  FIGS. 2 and 3 ) can also be achieved through a special arrangement of the individual function elements  4 .