Abstract:
A filter device is disclosed, comprising an air filter for a fresh air system of a motor vehicle. The filter device further comprises a filter housing which contains a receiving space. An annular filter element is inserted into the receiving space. The device also comprises a cover for closing the receiving space. The cover is detachably fastened to the filter housing by means of a bayonet catch, so that the cover can be inserted axially into a cover receptacle formed on the filter housing and, when inserted, can be rotated between an unlocking position and a locking position.

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
       [0001]    This application claims priority to German Patent Application No. 10 2010 009 249.5 filed on Feb. 25, 2010 and to PCT Application No PCT/EP2011/051721 filed on Feb. 7, 2011, the contents of which are incorporated by reference in their entirety. 
     
    
     TECHNICAL FIELD 
       [0002]    The present invention relates to a filter device, particularly an air filter for a ventilation system of a motor vehicle or an internal combustion engine, with the features of the preamble of claim  1 . 
       BACKGROUND 
       [0003]    A filter device of this type is known from DE 600 04 456 T2. It comprises a filter housing which contains an accommodation space and also an annular filter element which is inserted axially into the accommodation space. Further, a lid for closing the accommodation space is present. For the known filter device, the lid is releasably fastened to the filter housing by means of a threaded closure. To this end, the lid has an external thread which can be screwed into an internal thread formed on the filter housing. To fasten and to loosen the lid, this must be rotated accordingly. For the known filter device, a securing device operating in the manner of a latch is additionally provided, which secures the screwed-in lid against rotation in the opening direction. 
         [0004]    The problem with a configuration of this type is the fact that relatively strict production tolerances must be complied with so that the rotational movement of the lid when reaching the closed position ends precisely where the securing device can latch and effect the desired rotational securing. When the lid is opened and closed multiple times, a changed rotational position of the lid in its closed position may arise owing to wear phenomena and dirt, so rotational securing with the aid of the securing device is made more difficult. 
       SUMMARY 
       [0005]    The present invention is concerned with the problem of specifying an improved or at least different embodiment for a filter device of the type mentioned at the beginning, which in particular has a high degree of functional reliability. 
         [0006]    This problem is solved according to the invention by the subject matter of the independent claim. Advantageous embodiments of the invention form the subject matter of the dependent claims. 
         [0007]    The invention is based on the general idea of releasably fastening the lid to the filter housing by means of a bayonet closure. A bayonet closure of this type is easy to handle and highly reliable. Furthermore, with the aid of a bayonet closure, an unlocking position and a locking position with defined relative positions between lid and filter housing, which are largely independent of wear and contaminations, can be specified. 
         [0008]    An embodiment in which a securing device secures the lid rotated into the locking position against being rotated back into the unlocking position is therefore particularly advantageous. As the bayonet closure allows a defined relative position between lid and filter housing in the locking position, a particularly high reliability results for the securing device effective in the locking position. 
         [0009]    In accordance with an advantageous development, the securing device may have a latching hook which is resilient in the radial direction and which, during the rotation of the lid from the unlocking position into the locking position, moves in the circumferential direction relatively to an obstacle, runs over the obstacle to reach the locking position and engages behind the obstacle in a form-fitting manner when the locking position is reached. Particularly effective rotational securing, which is activated automatically when rotating into the locking position and effectively prevents rotating back out of the locking position, is realised by means of this proposal. 
         [0010]    An embodiment, in which a rotational limit limits the rotation of the lid in the locking direction to the locking position and/or in the unlocking direction to the unlocking position, is particularly advantageous. By providing the lid or the filter housing with a rotational limit provided in addition to the bayonet closure, the bayonet closure can be realised particularly easily in terms of design, namely without an integrated rotational limit. As a result, a functional separation between the closure function and the rotational limiting function is achieved in such a manner that the bayonet closure only fulfils the closure function, whilst the rotational limit only fulfils the rotational limiting function. As a result, the automatic production of the bayonet closure in particular can be simplified. 
         [0011]    According to a further configuration, it can then be provided for the above-mentioned rotational limit to be integrated into the above-mentioned securing device. As a result, the securing device receives additional functionality. At the same time, the integration of the rotational limit and the securing device makes the filter device simpler to produce. 
         [0012]    To form the rotational limit, it can expediently be provided for the obstacle of the securing device to be allowed to engage radially into a recess delimited in the circumferential direction, which is displaced in the circumferential direction when the lid is rotated relatively to the obstacle. 
         [0013]    Of particular significance is an embodiment in which an emergency fixing device is provided, which can be activated if the securing device has failed or is defective or missing, in order to secure the lid in the locking position. As a result, a redundant fixing is provided for the rotational securing of the lid in the locking position, which fixing can then be activated if the (main) securing device is deactivated. 
         [0014]    For example, the emergency fixing device may have a bracket formed on the housing and a tab formed on the lid and radially protruding therefrom, which tab is axially flush with the bracket in the locking position. The emergency fixing device can be activated in that a securing element, e.g. a pin or a screw passes axially through the tab and axially penetrates the bracket. To this end, the tab may be provided with a corresponding passage opening. In this case, it is possible to introduce a passage opening of this type only in the context of the activation of the emergency fixing device. 
         [0015]    According to a particular embodiment, the lid may have a connector which projects through a central disc opening, which is constructed in an axial end disc of the filter element, into the interior of the filter element. A fluid line can be connected to the lid or to the connector thereof, which fluid line is fluid-connected in this manner to the interior of the filter element or communicates with the same. As a result, the lid may be provided with an additional function, as it has a connecting piece of the filter housing, e.g. an inlet or an outlet for the fluid, e.g. a gas or a liquid, to be cleaned with the aid of the filter element. 
         [0016]    Further important features and advantages of the invention result from the sub-claims, from the drawings and from the associated description of the figures on the basis of the drawings. 
         [0017]    It is to be understood that the above-mentioned features and the features which are still to be explained below, can be used not only in the respectively specified combination, but also in other combinations or alone, without departing from the scope of the present invention. 
         [0018]    Preferred exemplary embodiments of the invention are illustrated in the drawings and are explained in more detail in the description below, identical reference numbers referring to identical or similar or functionally identical components. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0019]    In the figures, 
           [0020]      FIG. 1  schematically shows a simplified longitudinal section through a filter device, 
           [0021]      FIG. 2  schematically shows an enlarged sectional view of the filter device in the region of a lid, 
           [0022]      FIG. 3  schematically shows an isometric view of the filter device in the region of the lid, 
       
    
    
     DETAILED DESCRIPTION 
       [0023]      FIG. 4  schematically shows an isometric view as in  FIG. 3 , but in another direction of observation in the region of a securing device. 
         [0024]    According to  FIGS. 1 to 4 , a filter device  1  comprises a filter housing  2 , a filter element  3  and a lid  4 . The filter device  1  is used for filtering a fluid. Preferably, it is provided for filtering a gas. In particular, it is an air filter or an air filter device for a ventilation system for supplying a vehicle interior and/or for supplying an internal combustion engine with fresh air. 
         [0025]    The filter housing  2  contains an accommodation space  5 , into which the filter element  3  is inserted. The housing  2  has an inlet  6  covered here by the filter element  3 , which inlet is indicated in  FIG. 1  by means of an arrow illustrated with a dashed line. Further, the housing  2  has at least one outlet. In the example, two outlets  7  and  8 , namely a primary outlet  7  and a secondary outlet  8  are provided. In the case of the particularly advantageous embodiment shown here, the primary outlet  7  is integrally formed on the lid  4 , whilst the secondary outlet  8  is integrally formed on the actual filter housing  2 . The primary outlet  7  leads e.g. to the internal combustion engine, whilst the secondary outlet  8  leads e.g. to an exhaust system of the internal combustion engine, for example in order to supply a catalytic converter or a particle filter with air. 
         [0026]    The filter element  3  is of annular structure, as a result of which it has a longitudinal central axis  9  which defines the axial direction of the filter element  3  and thus also of the housing  2 . The filter element  3  is axially inserted into the accommodation space  5  and separates a raw side  10  from a clean side  11  in the accommodation space  5 . In the example, flow passes through the filter element  3  radially from outside to inside in accordance with an arrow  12 . Accordingly, the filter element  3  envelops the raw side  10 , whilst an annular filter body  13  of the filter element  3  envelops the clean side  11 . The clean side  11  is thereby formed in an interior  14  of the filter element  3 , which is annularly enveloped by the filter body  13 . The filter body  13  consists of a suitable filter material. In particular it may be folded or pleated. 
         [0027]    The lid  4  closes the accommodation space  5 , to which end it is arranged on a lid receptacle  15  which is formed on the filter housing  2 . The lid receptacle  15  encloses or borders a housing opening  16  through which the filter element  3  can be inserted into the accommodation space  5  or removed therefrom if the lid  4  is removed from the housing  2 . 
         [0028]    The lid  4  is releasably fastened to the filter housing  2  with the aid of a bayonet closure  17 . In accordance with the conventional functioning of a bayonet closure  17  of this type, the lid  4  can be axially inserted into the lid receptacle  15  and can be rotated in the inserted state between an unlocking position and a locking position. The rotation of the lid  4  takes place about the longitudinal central axis  9  of the filter element  3 , in the case of the rotationally symmetrical construction shown here. For the axial insertion of the lid  4  into the lid receptacle  15 , the lid  4  is in this case already orientated towards the unlocking position with regards to its rotational position. 
         [0029]    According to  FIG. 2 , the bayonet closure  17  has a plurality of projections  18  which radially protrude on the lid  4  and are arranged in a distributed manner in the circumferential direction. The circumferential direction here relates to the axial direction defined by means of the longitudinal central axis  9 . In a manner complementary to that, the bayonet closure  17  has a plurality of holding segments  19  which radially protrude on the lid receptacle  15 . In the sectional illustration of  FIG. 2 , only one projection  18  and one holding segment  19  can be seen in each case. Expediently, the bayonet closure  17  has three or more such pairs of projections  18  and holding segments  19 . 
         [0030]    When inserting the lid  4  into the lid receptacle  15 , the projections  18  are moved axially past the associated holding segments  19 . If the lid  4  is then rotated from the unlocking position into the locking position, the projections  18  move under the holding segments  19  in such a manner that the respective projection  18  engages axially behind the associated holding segment  19 . It is clear that corresponding circumferential segments are present on the lid receptacle  15 , which are arranged in the circumferential direction between adjacent holding segments  19  and which make it possible for the projections  18  to be moved axially past the holding segments  19 . 
         [0031]    In the example shown here, the lid  4  sits on a lid edge  20  which protrudes radially outwards and, if the lid  4  is inserted into the lid receptacle  15 , sits on a collar  21  at the end, that is to say axially. The collar  21  is axially spaced from the filter housing  2  and forms an edging or border of the lid receptacle  15 . The above-mentioned projections  18  of the bayonet closure  17  are formed on the lid  4  axially spaced from the lid edge  20 . Furthermore, in the example, the holding segments  19  of the bayonet closure  17  are formed at the end face of the collar  21 . 
         [0032]    According to  FIGS. 3 and 4 , the filter device  1  according to the preferred embodiment shown here is equipped with a securing device  22 . With the aid of this securing device  22 , the lid  4  is secured against rotating back into the unlocking position if it is rotated into the locking position. 
         [0033]    In the exemplary embodiment shown here, the securing device  22  has a latching hook  23  which is resilient in the radial direction. The radial direction here relates to the axial direction defined by the longitudinal central axis  9 . If the lid  4  is rotated from the unlocking position into the locking position, the latching hook  23  is displaced relatively to an obstacle  24  which likewise represents a constituent of the securing device  22 . To reach the locking position, the latching hook  23  runs over the obstacle  24  in the circumferential direction. When the locking position is reached, the latching hook  23  engages behind the obstacle  24  in a form-fitting manner in the circumferential direction. In the preferred example shown, the latching hook  23  is arranged on the lid  4 , whilst the obstacle  24  is arranged on the filter housing  2  or on the lid receptacle  15 . A reversed arrangement is also fundamentally possible. The variant shown here, in which the latching hook  23  is integrally formed on the lid  4 , is preferred. It is also expedient to form the obstacle  24  integrally on the filter housing  2 . 
         [0034]    In order to facilitate the radial deflection of the latching hook  23  when running over the obstacle  24 , the obstacle  24  may have a ramped side  25  in accordance with  FIG. 4 . When rotating the lid  4  from the unlocking position into the locking position, the latching hook  23  strikes the ramped side  25  with its radially inwardly pointing end section  26 . If the lid  4  is rotated further, the end section  26  is then pushed radially outwardly along the ramped side  25 . In the process, the latching hook  23  may yield resiliently. As soon as the end section  26  has completely run over the ramped edge  25  or the obstacle  24  in the circumferential direction, the resilience of the latching hook  23  effects a springing back of the latching hook  23  and of the end section  26  radially inwards, as a result of which the latching hook  23  engages behind the obstacle  24  in the circumferential direction by means of its end section  26 . Should the lid  24  then be rotated back in the direction of the unlocking position, the end section  26  strikes an abutment side  27  of the obstacle  24 . This abutment side  27  is radially orientated and thus effects no radial displacement of the latching hook  23 . 
         [0035]    According to the preferred embodiment shown here, the filter device  1  is additionally equipped with a rotational limit  28 . This rotational limit  28  limits the rotation of the lid  4  in the locking direction to the locking position or in the unlocking direction to the unlocking position. In the example, the rotational limit  28  comprises a locking side  29  which can be seen in  FIG. 4  and an unlocking side  30  which can be seen in  FIG. 3 . These two sides  29 ,  30  are formed in the example by means of the ends in the circumferential direction of a recess  31  incorporated into the lid  4  at the edge. 
         [0036]    The two sides  29 ,  30  in this case interact with the obstacle  24  which is positioned on the filter housing  2  in such a manner that it engages radially into the said recess  31 . In the unlocking position, the obstacle  24  comes to bear on the unlocking side  30 . In the locking position, the obstacle  24  comes to bear on the locking side  29 . The rotational limit  28  presented here therefore limits the rotation of the lid  4  both in the locking direction to the locking position and in the unlocking direction to the unlocking position. 
         [0037]    Expediently, in the embodiment shown here, the rotational limit  28  is integrated into the securing device  22 . This may e.g. take place in that the obstacle  24  on the one hand interacts with the latching hook  23  and on the other hand interacts with the sides  29 ,  30  of the rotational limit  28 . In other words, to form the rotational limit  28 , the obstacle  24  of the securing device  22  engages radially into the recess  31  which is delimited on the one hand in the circumferential direction by means of the unlocking side  30  and on the other hand by means of the locking side  29 . If the lid  4  is rotated, the recess  31  is displaced relatively to the obstacle  24  which is immovable with respect to the housing  2 . 
         [0038]    According to  FIG. 3 , the filter device  1  shown here is additionally equipped with an emergency fixing device  32 . If the securing device  22  has failed or is defective or missing, this emergency fixing device  32  can be activated in order to secure the lid  4  in the locking position. The securing device  22  can for example be deactivated in that the latching hook  23  and/or the obstacle  24  is/are damaged or broken off. 
         [0039]    The emergency fixing device  32  here has a bracket  33  formed on the housing  2  and a tab  34  formed on the lid  4 . The tab  34  axially protrudes from the lid  4  and is axially flush with the bracket  33  in the locking position. This emergency fixing device  32  can for example be activated in that a securing element  35 , here only indicated in a rudimentary manner, passes axially through the tab  34  and axially penetrates the bracket  33 . The securing element  35  may be a pin. Likewise, the securing element  35  may be a screw. A corresponding opening for introducing the securing element  35  into the tab  34  or into the bracket  33  can be introduced, depending on requirements, for activating the emergency fixing device  32 . Likewise, it is fundamentally possible to provide the said opening right from the beginning at least at the tab  34 . 
         [0040]    According to the  FIGS. 1 to 3 , the lid  4  expediently has a connector  36  which envelops the primary outlet  7 . A corresponding fluid line can be connected to this connector  36 . The filter element  3  has one end disc  37  or  38  in each case at its axial ends. The respective end disc  37 ,  38  is connected to the filter body  13  in a sealed manner. The end disc  37  facing the lid  4  contains a central disc opening  39 , through which the connector  36  projects into the interior  14  of the filter element  3 . In this case, the connector  36  is expediently pushed into the end disc  37  in such a manner that in the process satisfactory sealing is produced at the same time. 
         [0041]    Further, it can be provided for the filter element  3  to be releasably fixed to the lid  4  in such a manner that the filter element  3  is pulled out of the accommodation space  5  when the lid  4  is removed. This fixing of the filter element  3  to the lid  4  can for example be realised in that the connector  36  produces a force-fitting connection between lid  4  and filter element  3  when pushed into the disc opening  39 . In addition or alternatively, a clip connection may be provided, which connects the lid  4  to the filter element  3 . 
         [0042]    In the example shown, the end disc  38  facing the secondary outlet  8  also has a central disc opening  40  which however has a smaller cross section than the disc opening  39  assigned to the primary outlet  7 . A connector  41  is formed on the housing  2  in the accommodation space  5 , which penetrates the disc opening  40  of the associated end disc  38  in a sealed manner as soon as the filter element  3  is correctly inserted into the accommodation space  5 . The said connector  41  is provided with a beveled end face  42  in order to make it easier to feed into or find the central disc opening  40 . 
         [0043]    According to the  FIGS. 3 and 4 , the lid  4  is ribbed on its outer side facing away from the accommodation space  5 . The individual ribs are designated  43  in this case. The ribs  43  extend from the connector  36  in the manner of a star, that is to say radially. As a result, the lid  4  has increased stability.