CROSS-REFERENCE TO RELATED APPLICATIONS 
     This application is a divisional application that claims the priority of U.S. patent application Ser. No. 12/419,805 filed on Apr. 7, 2009 which in turn claims the priority of DE 10 2008 017 688.5 filed Apr. 8, 2008. The applications are incorporated by reference herein. 
    
    
     FIELD OF THE INVENTION 
     The invention relates to an apparatus for a variable setting of control times of gas exchange valves of an internal combustion engine. Furthermore, the invention relates to methods for producing a side cover with a sealing cover and at least one mating element which is produced separately from the sealing cover, for the apparatus for the variable setting of the control times of gas exchange valves. 
     BACKGROUND OF THE INVENTION 
     Apparatuses for the variable setting of the control times of gas exchange valves are used in modern internal combustion engines, in order for it to be possible to configure the phase relation between the crankshaft and the camshaft in a variable manner in a defined angular range, between a maximum early position and a maximum late position. For this purpose, the apparatus is integrated into a drive train, via which torque is transmitted from the crankshaft to the camshaft. This drive train can be realized, for example, as a belt, chain or gearwheel drive. 
     An apparatus of this type is known, for example, from EP 0 806 550 B1. The apparatus comprises an output element which is rotatably arranged with respect to a drive element, the drive element being drive-connected to the crankshaft and the output element being connected to the camshaft in a rotationally fixed manner. The apparatus is delimited in the axial direction in each case by one side cover. Here, a plurality of screws engage through the one side cover and the drive element. A region of greater thickness is provided per screw on the other side cover, in which region a thread is formed, into which the screw is screwed. The output element, the drive element and the two side covers delimit a plurality of pressure spaces, each of the pressure spaces being divided by means of a vane into two pressure chambers which act against one another. The vanes are displaced within the pressure spaces by feeding pressure medium to or discharging pressure medium from the pressure chambers, as a result of which targeted rotation of the output element with respect to the drive element and therefore of the camshaft with respect to the crankshaft is brought about. 
     A disadvantage of this embodiment is the complicated structure of the side cover which carries the threads. Regions of greater thickness have to be provided on the side cover, in order to impart the necessary strength to the screw connection. As a result, the weight of the apparatus is increased. Furthermore, the side cover has to be configured as an expensive sintered component. 
     SUMMARY OF THE INVENTION 
     The invention is based on the object of providing an apparatus for the variable setting of the control times of gas exchange valves of an internal combustion engine, functionally reliable fastening of the side cover to the apparatus being realized in a manner with optimized weight and costs. 
     According to the invention, the object is solved by the fact that the mating element is configured separately with respect to the sealing cover and is connected to the latter in a non-positive, positive or material-to-material manner. In this embodiment, the side cover is configured in multiple pieces, the mating elements being produced separately from the actual side cover and only subsequently being mounted on the latter. The side cover serves mainly for sealing the pressure chambers in the axial direction. As a result of the separate production of the sealing or side covers and the mating elements, the structure of the sealing cover can be reduced to its actual task, for example, it can be configured as a simple, thin-walled component. This can be carried out inexpensively, for example by being punched from a metal sheet of suitable thickness or by deep drawing processes. Here, both steel sheets and sheets made from lightweight metal, for example from aluminum, magnesium or the like, may be suitable. The fastening elements can be screws, for example. In this case, the mating elements are configured as thread carriers, for example threaded nuts, the thread section of the screws being screwed to the thread section of the nuts. As an alternative, the fastening elements can be configured as bolts, for example. In this case, the mating elements can be configured as annular bodies. The bolts engage in each case into one of the annular bodies and are welded to the latter. In these embodiments, the side covers can be composed of lightweight material, for example plastic, aluminum or the like. In this embodiment, only the fastening elements and mating elements have to be composed of weldable material, for example steel. The weight of the apparatus can therefore be reduced considerably. A further possibility comprises realizing a clip connection by the fastening element and the mating element. 
     In one embodiment, in which the sealing cover is composed of a lightweight metal material, there may be provision for the mating element to be composed of the same material as the fastening elements which engage into it. This prevents the connection from being released during operation on account of different coefficients of thermal expansion, the weight of the apparatus being reduced at the same time by the use of lightweight material. At the same time, corrosion problems can be avoided as a result, since the fastening is effected between components of the same material. Furthermore, the fastening elements and the mating elements can be produced from a suitable, strong material, with the result that the connection, for example the threads of a screw connection, have/has the necessary stability, while the side covers are produced from lightweight material. 
     In one development of the invention, the mating element has an axial projection, the free end of which engages into the corresponding opening, the external diameter of the projection being adapted at least in one region to the internal diameter of the opening and being smaller than the external diameter of the remaining mating element. In this case, the projection serves as a centering collar which fixes and secures the position of the mating element in the opening during mounting. There can be provision here for the mating element to have an axial stop which bears against an axial side face of the sealing cover when the mating element is mounted. A defined insertion depth of the mating element is fixed by the axial stop. The axial stop can be configured, for example, as an annular face. The annular face can be provided, for example, with anti-rotation safeguard elements which extend in the axial direction starting from the annular face. During the mounting, the anti-rotation safeguard elements are pressed into the axial side face of the side cover, as a result of which the mating elements are secured at least against rotation about its axis with regard to the opening. 
     Furthermore, the non-positive, positive or material-to-material connection can be produced between a circumferential face of the opening and the projection. 
     There can be provision here for the mating element to be fixed on the sealing cover by means of a press fit between the projection and the circumferential face of the opening. As an alternative, the projection can be provided with positively locking elements which engage into the circumferential face of the opening. Additional centering of the mating element and securing of the mating element against rotation and against loss during mounting are achieved by the production of a press fit or by pressing regions of the projection into the wall of the opening. 
     In a further implementation, there is provision for the side cover to be produced separately from the output element and the drive element. 
     According to the invention, the object is achieved by a method for producing a side cover with a sealing cover and at least one mating element which is produced separately from the sealing cover, for an apparatus for the variable setting of the control times of gas exchange valves of an internal combustion engine, having the following method steps:
         production of the sealing cover which comprises a metallic material,   formation of at least one opening on the sealing cover,   production of the mating element,   positioning of the mating element on the opening, and   production of the material-to-material connection between the sealing cover and the mating element.       

     In an alternative embodiment, the object is achieved according to the invention by a method for producing a side cover with a sealing cover and at least one mating element which is produced separately from the sealing cover and has a projection, for an apparatus for the variable setting of the control times of gas exchange valves of an internal combustion engine, having the following method steps:
         production of the sealing cover which comprises a metallic material,   formation of at least one opening on the sealing cover,   production of the mating element, the outer contour of the projection of the mating element being of oversized configuration with respect to the opening of the sealing cover,   pressing of the projection into the opening.       

     In an alternative embodiment, the object is achieved according to the invention by a method for producing a side cover with a sealing cover and at least one mating element which is produced separately from the sealing cover and has a projection, for an apparatus for the variable setting of the control times of gas exchange valves of an internal combustion engine, having the following method steps:
         production of the sealing cover which comprises a metallic material,   formation of at least one opening on the sealing cover,   production of the mating element, the outer contour of the projection of the mating element being adapted to the opening of the sealing cover,   positioning of the projection in the opening,   pressing of positively locking elements of the mating element into the sealing cover.       

     Here, the positively locking elements can be formed on the projection and can be pressed into the wall of the opening by radial widening of the projection. In one alternative embodiment, the mating element has anti-rotation safeguard elements which extend in the axial direction. Said anti-rotation safeguard elements are pressed into the side face of the sealing cover by application of an axial force. This advantageously takes place in a region of the sealing cover which surrounds the opening. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       Further features of the invention result from the following description and from the drawings, in which one exemplary embodiment of the invention is shown in simplified form. In the drawings: 
         FIG. 1  shows an internal combustion engine, but only in a very schematic manner; 
         FIG. 2  shows a cross section through one embodiment according to the invention of an apparatus for changing the control times of gas exchange valves of an internal combustion engine; 
         FIG. 3  shows a longitudinal section through the apparatus from  FIG. 2   a  along the line IIB-IIB, 
         FIG. 4  shows a longitudinal section through a side cover; 
         FIG. 5  shows a perspective illustration of a side cover; 
         FIG. 6  shows a perspective illustration of a mating element; 
         FIG. 7  shows the detail Z from  FIG. 4  before mounting of the mating element; 
         FIG. 8  shows the detail Z from  FIG. 4  during mounting of the mating element; and 
         FIG. 9  shows the detail Z from  FIG. 4  of a further embodiment of a sealing cover according to the invention. 
     
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
       FIG. 1  outlines an internal combustion engine  1 , a piston  3  which is seated on a crankshaft  2  being indicated in a cylinder  4 . In the embodiment shown, the crankshaft  2  is connected to an inlet camshaft  6  and outlet camshaft  7  via in each case one flexible drive  5 , it being possible for a first and a second apparatus  10  to ensure a relative rotation between the crankshaft  2  and the camshafts  6 ,  7 . Cams  8  of the camshafts  6 ,  7  actuate one or more inlet gas exchange valves  9   a  and one or more outlet gas exchange valves  9   b . There can likewise be provision for only one of the camshafts  6 ,  7  to be equipped with an apparatus  10 , or for only one camshaft  6 ,  7  to be provided which is furnished with an apparatus  10 . 
       FIGS. 2 and 3  show a first embodiment of an apparatus  10  according to the invention in cross section and in longitudinal section, respectively. 
     The apparatus  10  has a drive element  22  and an output element  23 . The drive element  22  has a housing  22   a  and two side covers  24 ,  25  which are arranged on the axial side faces of the housing  22   a . The output element  23  is configured in the form of an impeller wheel and has a hub element  26  which is of substantially cylindrical configuration and from the outer cylindrical circumferential face of which five vanes  27  extend to the outside in the radial direction in the embodiment shown. 
     Starting from an outer circumferential wall  29  of the housing  22   a , a plurality of side walls  30  extend radially to the inside. In the embodiment shown, the side walls  30  are configured in one piece with the circumferential wall  29 . The drive element  22  is mounted on the output element  23  by means of circumferential walls of the side walls  30  which lie radially to the inside, such that said drive element  22  can be rotated relative to said output element  23 . 
     A pulley  21  is arranged on an outer circumferential face of the circumferential wall  29 , via which pulley  21  torque can be transmitted from the crankshaft  2  to the drive element  22  by means of a belt drive (not shown). In the mounted state, the output element  23  is connected to a camshaft (not shown) by means of a central screw (not shown). To this end, the central screw reaches through a central hole of the output element  23  and is screwed to the camshaft. 
     In each case one of the side covers  24 ,  25  is arranged on one of the axial side faces of the housing  22   a  and is fixed on said housing  22   a  in a rotationally fixed manner. For this purpose, an axial opening  31  is provided in each side wall  30 . Furthermore, in each case five openings  33  which are arranged in such a way that they are aligned with the axial openings  31  are provided in the side covers  24 ,  25 . On that side of the first side cover  24  which faces away from the drive element  22 , each opening  33  is assigned a mating element  34 , a thread carrier in this exemplary embodiment, the thread section  37  of said mating element  34  being aligned with the respective opening  33 . In each case one fastening element  32  (a screw in the embodiment shown) reaches through an opening  33  of the second side cover  25 , an axial opening  31  and an opening  33  of the first side cover  24 . Here, a thread section of the screw  32  engages into the thread section  37  of the thread carrier  34 . 
       FIGS. 4 ,  5  show the first side cover  24  before mounting to the apparatus  10 . The side cover  24  comprises a thin-walled sealing cover  35 , in which five openings  33  are provided. During mounting of the first side cover  24 , each of the openings  33  is assigned in each case a thread carrier  34 .  FIG. 6  shows a thread carrier  34  by way of example. Said thread carrier  34  has a stepped profile with a projection  36  in cross section. Furthermore, a thread section  37  is provided within a hole of the thread carrier  34 . The external diameter of the projection  36  is adapted to the internal diameter of the openings  33  at least in a part region and therefore serves as centering collar, in order to position the thread carrier  34  at the respective opening  33 . The projection  36  is adjoined by an annular region which serves as axial stop  38 , the latter bearing against the sealing cover  35  in the mounted state of the thread carrier  34 . The axial stop  38  is provided with a plurality of anti-rotation safeguard elements  39  which extend in the axial direction starting from the annular face. 
       FIGS. 7 ,  8  show the mounting of the thread carrier  34  on the sealing cover  35 . First, the projection  36  is inserted into the opening  33 . Here, an axially directed force is exerted on the thread carrier  34 , which force is sufficient to press the anti-rotation safeguard elements  39  into the axial side face of the sealing cover  35 . Subsequently, a conical mandrel  40  engages into the hole of the thread carrier  34 , as a result of which the front edge region of the projection  36  is widened in the radial direction. Here, one or more positively locking elements  47  is/are displaced into the circumferential face of the opening  33 , as a result of which an additional positive connection is produced between the sealing cover  35  and the thread carrier  34 . The positively locking elements  47  can be, for example, an annular radial collar or radial tongues on the projection  36 . 
     In this embodiment, the thread carrier  34  is secured against rotations relative to the first side cover  24  by means of a positive connection via the antirotation safeguard elements  39  and a further positive connection of the front region of the projection  36 . At the same time, the second positive connection acts in the axial direction, with the result that the thread carrier  34  is held in the opening  33 . 
     Embodiments without anti-rotation safeguard elements  39  are likewise conceivable, with the result that the connection is produced only between the widened front region of the projection  36  and the circumferential face of the opening  33 . 
     A further alternative embodiment is shown in  FIG. 9 . In this embodiment, the external diameter of the projection  36  is configured to be slightly greater than the internal diameter of the opening  33 . The projection  36  is pressed into the opening  33  with the production of a press fit connection. Here, anti-rotation safeguard elements  39  can be provided (lower part of the figure) or they can be omitted (upper part of the Figure). To this end, the sealing cover  35  and the mating elements  34  are produced separately. The openings  33  are formed on the sealing cover  35 , the outer contour of the projection  36  of the mating element  34  being of oversized configuration with respect to the opening  33  of the sealing cover  35 . Subsequently, the projection  36  is pressed into the openings  33  with the production of a press joint. 
     In addition to one of the preceding embodiments or as an alternative to it, a material-to-material connection  48  can be provided between the mating element  34  and the sealing cover  35 . The material-to-material connection  48  can be formed, for example, between the projection  36  and the circumferential face of the opening  33  or the mating element  34  and an axial side face of the first side cover  24 . In the latter case, the projection  36  can also be omitted. 
     In this case, the sealing cover  35  and the mating elements  34  are produced separately. The openings  33  are formed on the sealing cover  35 , the outer contour of the projection  36  (if present) being adapted to the circumferential face of the opening  33  of the sealing cover  35 . Subsequently, the mating element  34  is positioned on the opening  33 . If there is a projection  36 , it is positioned in the opening  33 . Subsequently, the material-to-material connection  48  is produced between the sealing cover  35  and the mating element  34 . Here, the material-to-material connection  48  can be, for example, a welded connection, a soldered connection, an adhesively bonded connection or a similar connection. 
     A pressure space  41  is formed within the apparatus  10  between in each case two side walls  30  which are adjacent in the circumferential direction. Each of the pressure spaces  41  is delimited in the circumferential direction by substantially radially extending bounding walls  42  of adjacent side walls  30 , which bounding walls  42  lie opposite one another, in the axial direction by the side covers  24 ,  25 , radially to the inside by the hub element  26  and radially to the outside by the circumferential wall  29 . A vane  27  projects into each of the pressure spaces  41 , the vanes  27  being configured in such a way that they bear both against the side covers  24 ,  25  and against the circumferential wall  29 . Each vane  27  therefore divides the respective pressure space  41  into two pressure chambers  45 ,  46  which act against one another. 
     The output element  23  can be rotated in a defined angular range with respect to the drive element  22 . The angular range is delimited in one rotational direction of the output element  23  by the fact that the vanes  27  come to bear against in each case one corresponding bounding wall  42  (early stop  43 ) of the pressure spaces  41 . In an analogous manner, the angular range is delimited in the other rotational direction by the fact that the vanes  27  come to bear against the other bounding walls  42  of the pressure spaces  41 , which bounding walls  42  act as late stop  44 . 
     The phase position of the drive element  22  with respect to the output element  23  (and therefore the phase position of the camshaft with respect to the crankshaft) can be varied by pressure loading of one group of pressure chambers  45 ,  46  and pressure relief of the other group. The phase position can be kept constant by pressure loading of both groups of pressure chambers  45 ,  46 . 
     LIST OF DESIGNATIONS 
     
         
           1  Internal combustion engine 
           2  Crankshaft 
           3  Piston 
           4  Cylinder 
           5  Flexible drive 
           6  Inlet camshaft 
           7  Outlet camshaft 
           8  Cam 
           9   a  Inlet gas exchange valve 
           9   b  Outlet gas exchange valve 
           10  Apparatus 
           21  Pulley 
           22  Drive element 
           22   a  Housing 
           23  Output element 
           24  Side cover 
           25  Side cover 
           26  Hub element 
           27  Vane 
           28  - 
           29  Circumferential wall 
           30  Side wall 
           31  Axial opening 
           32  Fastening element/screw 
           33  Opening 
           34  Mating element/thread carrier 
           35  Sealing cover 
           36  Projection 
           37  Thread section 
           38  Axial stop 
           39  Anti-rotation safeguard element 
           40  Mandrel 
           41  Pressure space 
           42  Bounding wall 
           43  Early stop 
           44  Late stop 
           45  First pressure chamber 
           46  Second pressure chamber 
           47  Positively locking element 
           48  Material-to-material connection
An apparatus for variable setting of control times of gas exchange valves of an internal combustion engine which has a drive element, an output element and a side cover. The drive element is brought into drive connection with a crankshaft, the output element is brought into drive connection with a camshaft, and the output element is arranged such that it can be pivoted with respect to the drive element. The side cover, which has a sealing cover with an opening and a mating element, axially delimits the output element and/or the drive element, and is connected in a rotationally fixed manner to the drive or output element by means of a fastening element. The fastening element reaches at least partially through the opening and interacts with the fastening element producing a rotationally fixed connection between the side cover and output element or drive element.