Abstract:
An internal combustion engine may include a cylinder head having a plurality of intake channels which lead to combustion chambers. A fresh gas distributor may be included for feeding fresh gas to the intake channels. The fresh gas distributor may have a flap arrangement including a flap shaft, which bears at least one flap for controlling the intake channels. The flap shaft may be mounted such that the flap rotates about a flap rotation axis. The fresh gas distributor may have a housing flange securing the fresh gas distributor to the cylinder head. The flap arrangement may be arranged in a region of the housing flange in a distributor housing of the fresh gas distributor. The cylinder head may have a recess, into which the fresh gas distributor is inserted in a region of the flap arrangement.

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     This application claims priority to German Patent Application No. 10 2012 203 232.0 filed Mar. 1, 2012 and International Patent Application PCT/EP2013/053581 filed Feb. 22, 2013, the contents of which are hereby incorporated by reference in their entirety. 
     TECHNICAL FIELD 
     The present invention relates to an internal combustion engine, in particular for a motor vehicle, having the features of the preamble of claim  1 . The invention also relates to a fresh gas distributor for such an internal combustion engine. 
     BACKGROUND 
     EP 0 726 388 B1 discloses a fresh gas distributor for an internal combustion engine, the fresh gas distributor acting in the usual manner to feed fresh gas to intake channels that are provided in the cylinder head of the internal combustion engine and lead to combustion chambers of the internal combustion engine. The fresh gas distributor has a flap arrangement, which has a flap shaft on which at least one flap is arranged to control one of the above-mentioned intake channels. The flap shaft is mounted such that it can rotate about a flap shaft rotation axis. The fresh gas distributor also has a housing flange, with which the fresh gas distributor can be fastened to the cylinder head. The flap arrangement is then arranged in the region of the housing flange in a distributor housing of the fresh gas distributor. In the known fresh gas distributor, the flap arrangement ends substantially flush with the housing flange on a side facing the cylinder head, so that the fresh gas distributor can be fastened simply on a flat installation side facing the fresh gas distributor. 
     SUMMARY 
     The present invention is concerned with the problem of specifying an improved embodiment for such an internal combustion engine and for an associated fresh gas distributor, which in particular has a reduced installation height. 
     This problem is solved according to the invention by the subject matter of the independent claims. Advantageous embodiments form the subject matter of the dependent claims. 
     The invention is based on the general concept of attaching the flap arrangement to the distributor housing in such a manner that the flap arrangement projects outwardly, that is, on a side provided for installation on the cylinder head, beyond the housing flange. This measure means that installation space can accordingly be saved in the interior of the distributor housing, so that the distributor housing can be realised with a reduced installation height in this installation direction, without the desired flow conditions in the interior of the distributor housing being excessively impaired thereby. For the internal combustion engine according to the invention, this means that a recess is formed on the cylinder head, into which the fresh gas distributor can be inserted in the region of the flap arrangement. Some of the installation space needed for the fresh gas distributor is thus shifted into the cylinder head, namely into the said recess. The intake channels begin or open into this recess. 
     Moreover, it is notable that the flap arrangement is arranged inside the distributor housing. The distributor housing thus has the function of a conventional intermediate flange, which in a conventional design contains the flap arrangement, is attached on the outside of the distributor housing and is arranged between the distributor housing and the cylinder head when in the installed state. The design presented here thus makes it possible to dispense with a separate intermediate flange for accommodating the flap arrangement. 
     According to a particularly advantageous embodiment, it can now be provided for the fresh gas distributor for a separate drive shaft to be arranged on an inwardly facing side, that is, on a side of the flap shaft facing away from the cylinder head when in the installed state, which drive shaft is mounted such that it can rotate about a drive shaft rotation axis running parallel to the flap shaft rotation axis. This drive shaft can now be connected or is connected when in the installed state to a flap drive on one side, while it is drive-connected to the flap shaft by means of a set of teeth on the other side. To pivot the flaps, the flap drive thus effects a rotation of the drive shaft, which leads to a rotary movement of the flap shaft by means of the toothed connection between the drive shaft and the flap shaft and thus to a corresponding pivoting of the flaps connected in a rotationally fixed manner to the flap shaft. It is notable that, owing to the use of the drive shaft, which is arranged offset in relation to the flap shaft in the interior of the distributor housing, the flap shaft and thus essential components of the flap arrangement can project outwardly beyond the housing flange so far that direct driving of the flap shaft is not possible or only possible with difficulty owing to the proximity of the cylinder head. The drive shaft thus allows indirect driving of the flap shaft, as a result of which it is possible to position the flap shaft close to the cylinder head. The insertion of the projecting region of the flap arrangement into the recess in the cylinder head is thereby greatly simplified. 
     The toothed connection between the drive shaft and the flap shaft can expediently comprise input teeth arranged on the flap shaft and output teeth formed on the drive shaft, which are in engagement with each other and therefore mesh with each other. 
     The set of teeth between the drive shaft and the flap shaft is expediently designed as a radial set of teeth with axially running teeth, as a result of which axial relative movements between the drive shaft and the flap shaft are possible. This design makes it possible to realise larger tolerances or a deliberately larger radial play and/or axial play for the flap shaft in order to keep the flap shaft with its flaps attached fixedly thereon movable within predefined limits in relation to a support frame of the flap arrangement, on which the flap shaft is rotatably mounted. The risk of the flaps sticking on the flap frame, which can arise owing to dirt owing to fed back exhaust gases and/or blow-by gases, can thereby be reduced. The functional reliability of the flap arrangement can thus be improved. 
     According to another advantageous embodiment, the drive shaft can penetrate the distributor housing, the drive shaft then being expediently drive-connected to the flap shaft inside the distributor housing, while it is drive-connected or can be connected to the flap drive outside the distributor housing. Owing to this measure, a housing duct can be realised offset to the flap shaft in a region that has a sufficient distance from the cylinder head for this purpose. 
     The drive shaft can expediently be rotatably mounted on the distributor housing with a main bearing, said main bearing being configured in such a manner that it supports both radial and axial forces. The main bearing can in particular be a bearing bushing, which comprises a cylindrical jacket for realising a radial sliding bearing and a collar that projects radially from the jacket for realising an axial sliding bearing. The axial support takes place for forces directed outwardly, that is, away from the interior of the distributor housing. 
     In addition to the main bearing, at least one secondary bearing can be provided, which likewise acts to bear the drive shaft on the distributor housing at an axial distance from the main bearing. In contrast to the main bearing, the secondary bearing is designed in such a manner that it only absorbs radial forces. Accordingly, the secondary bearing allows axial relative movements between the drive shaft and the distributor housing. 
     A drive shaft seal can optionally be provided, which seals the drive shaft from the housing. The drive shaft seal encloses the drive shaft and is arranged in a spatially fixed manner in relation to the distributor housing. The drive shaft seal is expediently positioned in the distributor housing in such a manner that the drive shaft seal touches the drive shaft only radially, but not axially. The drive shaft seal is thus arranged in particular in an axially contact-free manner in relation to the drive shaft. 
     The output teeth of the drive shaft can be teeth that extend entirely over 360°. However, an embodiment is preferred in which the output teeth are formed by a gearwheel segment that extends over less than 360°. The gearwheel segment preferably extends in the circumferential direction over no more than 180° or no more than 120°. 
     For drive coupling to the respective flap drive, the drive shaft can be connected outside the distributor housing in a rotationally fixed manner to a drive lever, with the aid of which for example a crank drive can be realised. The actual flap drive can then be formed by an electric or pneumatic or hydraulic servomotor. The drive can likewise be a compressed medium bottle. 
     In another advantageous embodiment, the input teeth can be formed on a gearwheel that is connected in a rotationally fixed manner to the flap shaft. In contrast to this, the output teeth are expediently formed integrally on the drive shaft. The gearwheel of the flap shaft is preferably arranged in an axially movable manner on the flap shaft, so that axial movements are possible between the flap shaft and the gearwheel. The rotationally fixed coupling can for example be realised by means of a form-fitting connection between the flap shaft and the gearwheel, an outer contour of the flap shaft that differs from a circular contour is inserted into an inner contour of the gearwheel that is complementary thereto. 
     The input teeth can be configured running around 360° of the gearwheel. However, an embodiment is preferred in which the input teeth are formed as a gearwheel segment that runs around less than 360° of the gearwheel. The gearwheel segment preferably extends over no more than 180° or no more than 120°. 
     According to another advantageous embodiment, which can be realised additionally or alternatively to the above embodiments of the gearwheel, the gearwheel can be formed convexly on an end face facing away from the flap shaft. The convex end face of the gearwheel expediently interacts as an axial stop with a wall of the distributor housing that faces the end face. The convex shape of the end face produces a substantially point-shaped contact between the end face and the wall, which is flat at least in the region of the axial stop. The point-shaped contact means that frictional forces that can hinder a rotary movement of the flap shaft can be minimised. 
     According to another advantageous development, the gearwheel can be mounted on the above-mentioned support frame of the flap arrangement with the aid of a radial bearing. 
     Additionally or alternatively to the above features, the gearwheel is expediently arranged on an axial end of the flap shaft, as a result of which it is possible to arrange the drive shaft also on an axial end of the distributor housing in relation to the flap shaft rotation axis. 
     In another advantageous embodiment, a partition or protective wall that separates a gearing space from a gas distributor space can be arranged in the distributor housing. The toothed connection between the drive shaft and the flap shaft is arranged in the gearing space. The drive shaft expediently extends only inside the gearing space in the distributor housing. In contrast to this, the distribution of the fresh gas fed to the distributor housing via a central fresh gas inlet to the individual intake channels of the cylinder head takes place in the gas distributor space. Accordingly, the flaps of the flap arrangement are arranged in the gas distributor space. A substantially gas-tight separation of the gearing space from the gas distributor space can thus be realised with the aid of the partition, as a result of which the components arranged in the gearing space are protected from impurities in the fresh gas flow. The fresh gas flow can contain, in addition to fresh air, fed back exhaust gas and/or fed back blow-by gas, so that the fresh gas can have the usual impurities of fed back exhaust gas, e.g. soot particles, and where applicable the usual impurities of fed back blow-by gas, such as oil mist. Such impurities can lead to jamming of movable parts, which can impair their functioning. The partition thus results in an increased functional and operational reliability of the flap arrangement and thus of the fresh gas distributor. 
     Particularly advantageous configurations of the invention have a receptacle for the partition on the distributor housing. This receptacle can be form-fitting, force-fitting or materially cohesive. With a receptacle formed in a form-fitting manner, a sunk groove can be provided on the housing, into which the partition is inserted and/or adhesively bonded in the manner of a tongue and groove connection. In other configurations, the receptacle can also be configured as a projecting contour, which interacts with the partition such that a form-fitting connection is formed. In other configurations, a materially cohesive connection between the partition and the distributor housing can be formed by the application of an adhesive or a welded connection. This furthermore forms a seal that prevents dirt entering the gearing region. The gearing region is the region that is separated off by the partition in which the toothed connection of the drive is situated. 
     In further configurations with a sunk receptacle, the distributor housing can have a bead arranged in the region of the receptacle, which has a groove on the inner side of the distributor housing. 
     According to another advantageous embodiment, the flap arrangement as mentioned further above can have a support frame, on which the flap shaft is rotatably mounted and which has an outlet opening for each flap and is controlled with the respective flap. In the installed state, this outlet opening is then connected upstream of the respective intake channel, so that the cross section through which flow can pass of the controlled outlet opening defines the cross section through which flow can pass of the associated or assigned intake channel. The cross section through which flow can pass of the assigned intake channel can thus be controlled by rotating the respective flap. 
     In a specific embodiment, the cylinder head can have two intake channels for the respective combustion chamber. The support frame then expediently likewise has two outlet openings for the respective combustion chamber, it being expediently possible for only one of said openings per combustion chamber to be controlled with the aid of the respective flap. Accordingly, the support frame then has a controlled outlet opening and an uncontrolled outlet opening per combustion chamber. The respective flap is only assigned to the controlled outlet opening, to control the cross section thereof through which flow can pass depending on the rotation position of said flap. 
     If the cylinder head has a plurality of combustion chambers, they can expediently be arranged next to each other in a straight row. The intake channels are then expediently arranged next to each other in a straight row. The flap shaft extends parallel to this straight row of combustion chambers and intake channels. In the associated support frame, the outlet openings also extend next to each other in a straight line parallel to the flap shaft. If a controlled outlet opening and an uncontrolled outlet opening are provided per combustion chamber, controlled and uncontrolled outlet openings alternate in the longitudinal direction of the flap shaft. 
     According to an advantageous embodiment, the above-mentioned partition can then be formed integrally on the support frame, as a result of which the support frame has an additional function. At the same time, the partition can be integrated in the fresh gas distributor in this manner, without the installation outlay for the production of the fresh gas distributor increasing. 
     According to another advantageous embodiment, the housing flange can have an end face facing the cylinder head, on which the support frame axially bears with a lateral edge. This means that the edge of the support frame is arranged axially between the end face of the housing flange and a bottom of the recess in the cylinder head when in the installed state. In this manner, particularly stable positioning and retaining for the flap arrangement can be realised, since it is accommodated in a form-fitting manner and in particular axially clamped between the housing flange and the cylinder head by the fastening of the housing flange on the cylinder head. 
     According to another advantageous embodiment, the housing flange can enclose a receiving opening, which faces the cylinder head, of the distributor housing in the circumferential direction. The flap arrangement is inserted into this receiving opening. In other words, the distributor housing itself has only one opening, namely the receiving opening, through which the fresh gas can exit. The distribution to the individual outlet openings that are assigned to the intake channels takes place only by the installation of the flap arrangement that has the outlet openings, in particular on the support frame. According to an advantageous embodiment, the housing flange can have on an inner lateral edge a collar, which projects in the direction of the cylinder head, encloses the receiving opening and has the end face against which the edge of the support frame axially bears. A type of holder is thereby realised with the aid of the collar on the housing flange, which holder, together with the region of the flap arrangement that projects beyond the housing flange, engages in the recess of the cylinder head. The installation height of the fresh gas distributor in the installation direction thereof is also reduced thereby. At the same time, the fixing of the flap arrangement between the cylinder head and the housing flange is simplified thereby. 
     In another advantageous embodiment, the housing flange can be fastened to an enclosure of the cylinder head, which surrounds the recess in the circumferential direction. In other words, the housing flange itself does not substantially enter the recess but remains in the provided installation plane between the cylinder head and the fresh gas distributor. Only the above-mentioned collar of the housing flange can engage in the recess. Owing to this configuration, a comprehensive redesign does not have to be made at the cylinder head, since in particular the fastening points between the housing flange and the cylinder head in the region of the enclosure can be retained. The recess in the cylinder head only has to be provided inside the enclosure. 
     At least one distributor seal that runs around in a closed manner in the circumferential direction can expediently be provided, which is arranged axially between the housing flange and the enclosure. For better positioning of the axially effective distributor seal, it can optionally be provided for a circumferential receiving groove to be formed in the housing flange, into which the distributor seal axially engages. Additionally or alternatively, a circumferential receiving groove can be made in the enclosure of the cylinder head, into which the distributor seal axially engages. 
     A fresh gas distributor according to the invention, which can be used in an internal combustion engine of the above-described type for feeding fresh gas, thus has a flap arrangement of the above-described type and a housing flange of the above-described type. This fresh gas distributor is further characterised in that at least one region of the flap arrangement projects outwardly, that is, in the direction of the cylinder head, beyond the housing flange. 
     The flap arrangement is preferably enclosed by the housing flange laterally and/or at the edges. The housing flange in particular defines a receiving opening, into which the flap arrangement is inserted. The distributor housing thus has the function of a conventional intermediate flange, which in a conventional design contains the flap arrangement, is attached on the outside of the distributor housing and is arranged between the distributor housing and the cylinder head when in the installed state. 
     It can further be provided for the distributor housing to have a common inlet opening for fresh gas, a common receiving opening for the flap arrangement and a common gas distributor space for fresh gas therebetween, which is connected on the inlet side to the inlet opening and to which on the outlet side the flap arrangement inserted into the receiving opening adjoins. A single-part or integral design for the distributor housing is thereby simplified, which favours inexpensive production. 
     Furthermore, the internal combustion engine according to the invention, which has a cylinder head of the above-described type and which can be equipped with a fresh gas distributor of the above-described type, is characterised in that it has a recess on an installation side provided for the installation of the fresh gas distributor, inside which recess the intake channels are arranged with their intake openings and into which the region of the flap arrangement that projects beyond the housing flange of the fresh gas distributor can penetrate when the fresh gas distributor is fastened to the cylinder head. 
     Further important features and advantages of the invention can be found in the subclaims, the drawings and the associated description of the figures using the drawings. 
     It is self-evident that the above-mentioned features and those still to be explained below can be used not only in the combination given in each case but also in other combinations or alone without departing from the scope of the present invention. 
     Preferred exemplary embodiments of the invention are shown in the drawings and are explained in more detail in the description below, the same reference symbols referring to the same or similar or functionally equivalent components. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       In the figures, 
         FIG. 1  schematically shows a highly simplified longitudinal section of an internal combustion engine in the region of a fresh gas distributor, 
         FIG. 2  schematically shows an exploded, isometric diagram of the fresh gas distributor. 
         FIGS. 3 to 5  schematically show a detail of the fresh gas distributor in different alternative configurations. 
     
    
    
     DETAILED DESCRIPTION 
     According to  FIGS. 1 and 2 , an internal combustion engine  1 , which can be used in particular in a motor vehicle, preferably for driving the vehicle, comprises a cylinder head  2 , which can only be seen partially here and has a plurality of intake channels  3 , which can only be seen in the region of intake openings  52  here and each lead to a combustion chamber  53  of the cylinder head  2 , which cannot be seen here and is only represented with a reference symbol. An embodiment in which two such intake channels  3  per combustion chamber  53  are provided in the cylinder head  2  is expedient. For example, the cylinder head  2  in a four-cylinder engine has four combustion chambers  53 , each of which are assigned two intake channels  3 , so eight intake channels  3  are provided in total. 
     The internal combustion engine  1  moreover comprises a fresh gas distributor  4 , with the aid of which fresh gas can be fed to the intake channels  3 . The fresh gas distributor  4  comprises a distributor housing  5 , which has a common inlet opening  6  and a receiving opening  7  on a side facing the cylinder head  2 . The fresh gas distributor  4  moreover has a flap arrangement  8 , which has a flap shaft  9 . The flap shaft  9  has at least one flap  10  per combustion chamber  53 , which flap is connected in a rotationally fixed manner to the flap shaft  9 . In the example, the flap shaft  9  has exactly one flap  10  per combustion chamber  53 , so only every second intake channel  3  can be controlled with the aid of the flap arrangement  8 . The flap shaft  9  is mounted such that it can rotate about a flap shaft rotation axis  11 . To this end, the flap arrangement  8  expediently has a support frame  12 , on which the flap shaft  9  is rotatably mounted. Several bearing points  13  are expediently provided for bearing the flap shaft  9 . The bearing points  13  are each provided on both sides of one of the flaps  10 . Eight bearing points  13  are therefore provided in the example. In the example, seven of the eight bearing points  13  are realised in that in each case a first bearing half shell  14  is formed integrally on the support frame  12 , while in each case a second bearing half shell  15  is separate component in relation to the support frame  12 , which for example is attached and thus latched onto the support frame  12  by means of a clip connection. 
     The fresh gas distributor  4  moreover has a housing flange  16 , which is in this case formed integrally on the distributor housing  5  on a side facing the cylinder head  2 . The housing flange  16  is used to fasten the fresh gas distributor  4  to the cylinder head  2 . Accordingly, the housing flange  16  has a plurality of through-openings  17  for screw fastenings, which can be reinforced with metallic bushings. The housing flange  16  itself and the distributor housing  5  are expediently produced from plastic. The support frame  12  expediently likewise consists of plastic. 
     The flap arrangement  8  is then arranged in the region of the housing flange  16  in the distributor housing  5 . To this end, the flap arrangement  8  is inserted with its support frame  12  into the receiving opening  7  of the distributor housing  5 . The distributor housing  5  can be designed as a single-part plastic injection-moulded part. The distributor housing  5  thus has a common inlet opening  6  for the fresh gas, a common receiving opening  7  for accommodating the flap arrangement  8  and a common gas distributor space  66  for fresh gas fluidically therebetween, which is fluidically connected on the inlet side to the inlet opening  6  and to which on the outlet side the flap arrangement  8  inserted into the receiving opening  7  adjoins. 
     Outlet openings  18 ,  19  are formed on the support frame  12 , one outlet opening  18 ,  19  per intake channel  3 . Since there are twice as many outlet openings  18 ,  19  provided as there are flaps  10  present, only every second outlet opening  18 ,  19  is assigned a flap  10 . The outlet opening  18  that can be controlled with the aid of the respective flap  10  is referred to below as controlled outlet opening  18 , whereas the other outlet opening  19  that is assigned to the same combustion chamber  53  and is not assigned to a flap  10  is referred to below as uncontrolled outlet opening  19 . The outlet openings  18 ,  19  assigned to the intake channels  3  are thus not formed on the fresh gas distributor  4  until the flap arrangement  8  is inserted. 
     According to  FIG. 1 , the cylinder head  2  has a recess  20  on an installation side facing the fresh gas distributor  4 , which recess is enclosed by an enclosure  21  running in a closed manner in the circumferential direction. The fresh gas distributor  4  then has, according to  FIG. 1 , a region  22  that projects outwards, that is, in the direction of the cylinder head  2 , beyond the housing flange  16  and is indicated in  FIG. 1  by a curly bracket. This is essentially a region  22  of the flap arrangement  8  that projects beyond the housing flange  16  in the stated direction, which corresponds to the installation direction of the fresh gas distributor  4 . 
     The flaps  10  consist of plastic and are expediently injection-moulded onto the flap shaft  9 ; the flap shaft  9  according to  FIG. 1  can have a hole or slot  23  in the region of the respective flap  10 , so that the injection-moulded plastic of the flap  10  penetrates the flap shaft  9  in a form-fitting manner and in the process fills the said slot  23 . The flap shaft  9  is moreover provided with input teeth  24 , which are expediently formed on a gearwheel  25 , which is connected rotatably to the flap shaft  9 . The flap arrangement  8  moreover comprises a drive shaft  26 , which has output teeth  27  and is mounted on the distributor housing  5  on a side of the flap shaft  9  facing away from the cylinder head  2 . The drive shaft  26  is mounted such that it can rotate about a drive shaft rotation axis  28 , which extends parallel to the flap shaft rotation axis  11 . The two rotation axes  11 ,  28  can expediently lie in one plane, which runs perpendicularly to the plane of the installation side of the cylinder head  2  and/or in which the installation direction lies. 
     The drive shaft  26  is arranged on the distributor housing  5  in such a manner that its output teeth  27  mesh with the input teeth  24  of the gearwheel  25 . Furthermore, the drive shaft  26  is drive-connected to a flap drive  29 , which is only shown in a simplified manner in  FIG. 1 , a corresponding drive connection being indicated in  FIG. 1  by an arrow  30 . The drive shaft  26  expediently penetrates the distributor housing  5 . The drive shaft  26  is then drive-connected to the flap shaft  9  by means of the toothed connection  31  formed with the aid of the input teeth  24  and the output teeth  27  inside the distributor housing  5 . The drive shaft  26  is however drive-connected to the flap drive  29  outside the distributor housing  5 . For example, the drive shaft  26  can be connected to a drive lever  32  for this purpose, with the aid of which for example a crank drive can be realised. The drive shaft  26  is mounted rotatably on the distributor housing  5  with the aid of a main bearing  33 . The main bearing  33  is designed such that it supports both radial and axial forces in relation to the drive shaft rotation axis  28 . To this end, the main bearing  33  is for example formed as a bearing bushing, preferably in the form of a cylindrical bushing  34 , which represents a radial sliding bearing and which has a radially projecting annular collar  35 , which represents an axial sliding bearing on a side facing the interior of the distributor housing  5 . In the example, a secondary bearing  36  in the form of a cylindrical bushing is also provided to realise a radial sliding bearing, which is arranged at an axial distance from the main bearing  33  and only absorbs radial forces. Furthermore, a drive shaft seal  37  is provided, which can for example be designed as an X-ring. The drive shaft seal  37  is arranged axially between the main bearing  33  and the secondary bearing  36  in the example. The drive shaft seal  37  is arranged in a rotationally fixed manner on the distributor housing  5  and positioned in an axially contact-free manner in relation to the drive shaft  26 . The drive shaft seal  37  is thus only radially in contact with the drive shaft  26 . 
     According to the preferred embodiment shown here, the output teeth  27  of the drive shaft  26  are designed as a gearwheel segment, so that the output teeth  27  extend over less than 360°. Analogously to this, the input teeth  24  of the gearwheel  25  are expediently likewise designed as a gearwheel segment that extends over less than 360°. The gearwheel  25  is connected in a rotationally fixed manner to the flap shaft  9 . To this end, the flap shaft  9  can for example be flattened at one of its axial ends, so that a corresponding flattened portion  38  then can be introduced axially into a complementary opening  39  in the gearwheel  25  in order to realise a form fit in the rotation direction. A coupling between the gearwheel  25  and the flap shaft  9  in which the gearwheel  25  is arranged in an axially movable manner on the flap shaft  9  is preferred. In the example, the gearwheel  25  has a convex shape on an end face  40  facing away from the flap shaft  9 , which is in particular rotationally symmetrical in relation to the flap shaft rotation axis  11 . In the installed state, this convex end face  40  is opposite a flat wall  41  of the distributor housing  5 , with which it interacts as an axial stop. The convex end face  40  allows a point-shaped contact with the said wall  41 . The gearwheel  25  is rotatably mounted on the support frame  12  with the aid of a radial bearing  42 . To this end, the radial bearing  42  in the form of a bushing is inserted into a bearing opening  43 , which is formed in the support frame  12 . The bearing of the gearwheel  25  defines the eighth bearing point  13  for the flap shaft  9  on the support frame  12 . 
     A partition  44 , which substantially separates a gearing space  65  from a gas distributor space  66  in a sufficiently gas-tight manner, is also arranged in the distributor housing  5 . The input teeth  24  and the output teeth  27  are situated in the gearing space  65 . Essential sections of the drive shaft  66  and of the gearwheel  25  are thus arranged in the gearing space  65 . In contrast to this, the flaps  10  and the outlet openings  18 ,  19  are arranged in the gas distributor space  66 . The gas distributor space  66  thus essentially acts only for guiding and dividing flow to the individual outlet openings  18 ,  19 . The partition  44  is integrally formed on the support frame  12  in the example. 
     The housing flange  16  encloses in the circumferential direction the receiving opening  7  into which the flap arrangement  8  is inserted. According to  FIG. 1 , the housing flange  16  has on an inner lateral edge a collar  45 , which projects from the rest of the housing flange  16  in the direction of the cylinder head  2  and which likewise encloses the receiving opening  7  in a closed manner in the circumferential direction. The housing flange  16  then has on this collar  45  an end face  46  that faces the cylinder head  2  and against which a lateral edge  47  of the support frame  12  bears axially, that is, in the installation direction. In the installed state according to  FIG. 1 , the said lateral edge  47  is thus arranged axially between the end face  46  of the housing flange  16  and a bottom  48  of the recess  20  of the cylinder head  2 . In particular, the housing flange  16  with its collar  45  can clamp the support frame  12  with the bottom  48  of the recess  20 , that is, with the cylinder head  2 . The housing flange  16  is fastened with the aid of its through-openings  17  to the enclosure  21  of the cylinder head  2 , that is, outside the recess  20 . 
     The fresh gas distributor  4  moreover comprises a distributor seal  49 , which is arranged in the region of the housing flange  16  and in the region of the enclosure  21  and runs around in a closed manner in the circumferential direction. To position the distributor seal  49 , a corresponding receiving groove  50  can be made in the housing flange  16 . Additionally or alternatively, a corresponding receiving groove  51  can be made in the enclosure  21 . However, only one receiving groove  50 ,  51  is expediently provided, namely only in the housing flange  16 . 
       FIG. 3  shows a detail of the fresh air distributor  4 ′ in an alternative configuration. In this case the distributor housing  5  has an outwardly pointing bead  54  that runs around in the region of the partition  44 . A receiving groove  55 , into which the partition  44  engages and thus produces a seal, is arranged inside the distributor housing  5 . 
       FIG. 4  shows a further alternative of the same detail of the distributor housing  4 . According to this configuration, the distributor housing  5  has an inwardly projecting contour  56 , which is again received in a groove  57  in the partition  44  and thus forms a sealed connection. This connection can also be realised as a clip connection, which can be inserted transversely to the longitudinal direction of the groove  57 . The peg shape of the contour  56  shown can however be replaced by other geometric configurations that form a tongue and groove connection. Furthermore, the tongue (contour  56 ) does not have to be formed to run around the partition  44 , since a tongue  56  arranged in part-regions also effects a sufficient connection. 
     In  FIG. 5 , a bead  58  is formed on an inner side of the distributor housing  4 , which bead contains the groove  55  into which the partition  44  is inserted. In all the variants of  FIGS. 3 to 5 , the tongue and groove connection is indicated with  59 .