Abstract:
An oil filter  1  for an internal combustion engine includes a filter body  3  and a plastic filter housing  2.  Integrally formed within the filter housing, a safety wall  7  is radially fitted around the feed channel  4  and the return channel  5  creating a collecting space  6  that surrounds both channels. If seal leaks occur when the device is connected to a flange, e.g. of an engine block, the leaked oil will accumulate in the collecting space.

Description:
FIELD OF THE INVENTION 
     This invention relates to an oil filter for an internal combustion engine. 
     DESCRIPTION OF THE PRIOR ART 
     A filter of this type is disclosed in EP 0 492 627. The collecting space is closed so that liquid penetrating into it cannot flow off to the outside. 
     The publication WO 97/16234 discloses a liquid filter for cleaning oil or fuel, which is flanged onto an engine block of an internal combustion engine. Arranged in the filter housing, which consists of plastic, is a cylindrical filter body whose unfiltered side is acted upon by contaminated liquid which is supplied via a feed channel. The outflow space of the filter body is connected to a return channel via which the cleaned liquid can be taken away out of the filter housing. The feed channel surrounds the return channel annularly, the outer wall of the feed channel being formed by the outer wall of the filter housing. The end-side connections of the feed and return channels are inserted via seals into receptacles on the engine block. 
     The liquid to be cleaned is guided through the feed channel to the filter body under positive pressure. There is the risk here of leakages occurring in the region of the connection of the filter housing to the engine block, for example as a consequence of material fatigue of the seals, so that unfiltered liquid passes to the outside and can cause contamination or flows inwardly into the return channel and mixes with the liquid which has already been cleaned. In order to reduce this risk, the seals have to be made from very high quality and expensive materials. In addition, even small leakages cause a sharp drop in pressure which means that the minimum pressure required for the filtration cannot be applied and the filtration cannot be carried out. 
     Because of the large external radius of the feed channel, a large amount of sealing material is needed in order to seal the feed channel, and because of this, in addition to the increased costs, the risk of there being a leakage place also increases and frequent maintenance intervals are required. 
     SUMMARY OF THE INVENTION 
     The invention is based on the problem of designing an operationally reliable and low-maintenance, plastic liquid filter of the generic type at low cost, even in the case in which , because of material and/or manufacturing errors, liquid under a high pressure unintentionally penetrates into the collecting space in a greater volume than this space is able to absorb without an increase in pressure. In addition, the filter according to the generic type is to be designed in a form which makes it possible for additional functional parts, such as, in particular, a cooler for the liquid to be filtered, and also pressure sensors to be integrated in a structurally efficient manner. 
     This problem is already solved in principle according to this invention. 
     The feed channel and the return channel are situated in a collecting space having a safety wall which is part of the filter housing and surrounds the feed channel and the return channel radially. If the liquid filter is connected to a connecting flange, for example an engine block of an internal combustion engine, the safety in the event of leaky seals is increased because both the inflowing unfiltered liquid and also the outflowing clean liquid are sealed off twice from the environment: within the feed and the return channels and, in addition, within the collecting space whose wall can be connected in a liquid-tight manner to the connecting flange at low cost. In addition, liquid penetrating into the collecting space can flow off through the outlet provided there, as a result of which an undesirably high pressure in the collecting space is reliably avoided. The pressure in the collecting space is restricted to the pressure at its outflow opening. 
     The collecting space can be configured to atmospheric pressure. The positive pressure in the flow of liquid which is supplied and taken away is completely absorbed by the feed and return channels, respectively. The collecting space remains unaffected by this, and acts as a safety reservoir in the event of leakages occurring. This means that the seal between the safety wall and the connecting flange is not required to be of more exacting quality, that is to say, a simple O-ring seal can be used, for example. 
     The plastic filter housing can be manufactured by injection moulding in a cast with sufficient dimensional accuracy that finishing is no longer required. In addition, a considerable advantage in terms of weight is obtained. The channels which are formed in the filter housing can be designed such that they have relatively thick walls in order to be able to absorb the pressures prevailing in the liquid; at the same time, the safety wall can be designed such that it has thin walls, since there is no positive pressure in the collecting space. 
     The connections of the feed channel and of the return channel are advantageously provided with a radial seal in order to obtain, a pressure- and liquid-tight seal between the filter housing and the connecting flange. Retaining forces acting in the axial direction are essentially transmitted via the safety wall of the collecting space, which is free of excess pressure, and in particular via fastening domes which are of reinforced design and in which metal bushings are expediently accommodated, so that the channels are relieved of high axial forces and undesired creeping behaviour of the plastic in the region of the channels is avoided. 
     The radial seals are preferably of spherical design in order to be able to compensate for axial tolerances. 
     Because of the connection of the collecting space to a discharge channel, liquid which has emerged into the collecting space, for example from the feed channel or the return channel via leaky radial seals, is conducted away out of the collecting space via the said discharge channel, and, in particular, into the oil sump of the internal combustion engine. As already set out further above, this prevents the collecting space from filling up with liquid and a positive pressure from building up in the collecting space. The discharge channel runs in the connecting flange and is connected to the collecting space via a recess in the connecting flange. 
     Furthermore, a pressure relief valve can be provided in the collecting space, which pressure relief valve is acted upon by the pressure on the clean side of the filter and when a limiting pressure is exceeded, opens towards the collecting space and thereby causes the pressure to be relieved. The liquid which has emerged into the collecting space is conducted away again out of the collecting space via the discharge channel. 
     The end sides of the channels respectively each end at a different axial distance, as does a housing receptacle into which the pressure relief valve can be inserted. Assembly is hereby facilitated by the filter housing being placed onto the connecting flange with an approximately uniform, axial assembly force, and first of all the component protruding the furthest, and then the components protruding to a lesser extent, are successively inserted into corresponding receptacles in the connecting flange. This also prevents the filter housing from tilting during assembly. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     Further advantages and expedient embodiments can be gathered from the description of the figures, in which: 
     FIG. 1 shows a side view of a liquid filter, 
     FIG. 2 shows a view along the sectional line II—II from FIG. 1, 
     FIG. 3 shows a view along the sectional line III—III from FIG. 1, and 
     FIG. 4 shows a view along the sectional line IV—IV from FIG.  1 . 
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     According to FIG. 1, the liquid filter  1 , which is expediently inserted in an internal combustion engine in order to filter oil or fuel, is placed with the filter housing  2 , which consists of plastic, onto a connecting flange  18 , in particular an engine block of an internal combustion engine. The liquid to be cleaned is first of all supplied at positive pressure via the connecting flange  18 , through an unfiltered liquid conduit  25 , and via a feed channel in the filter housing  2  to an oil cooler  24 , which is arranged above the filter  1 , and is then conducted through a filter body  3  which is located in a lateral, radially outwardly directed cylindrical section  26  of the filter housing  2 . After the cleaning, the clean liquid flows back via a return channel in the filter housing  2  into a clean conduit  17  in the connecting flange  18 . 
     The cylindrical section  26  having the filter body  3  is closed by a removable cover  27 . The filter housing  2 , the connecting flange  18  and the oil cooler  24  are held together via screws  29  which are guided in fastening domes  20  which are of integral design with the filter housing; in order to increase the stability, metal bushings may be injected into the fastening domes  20 . Connections  28  for feeding and taking away heat exchanger medium are arranged on the oil cooler  24 . The oil cooler  24  contributes to stabilizing and reinforcing the filter  1 . 
     The supply of the uncleaned liquid into the filter housing  2  can be seen from FIG.  2 . The uncleaned liquid flows via the radially inwardly guided unfiltered liquid conduit  25  in the connecting flange  18  as far as a recess in the connecting flange  18 , into which recess is inserted the vertically running feed channel  4  in the filter housing  2 . Arranged in the region of the connection  8  of the feed channel  4  is a radial seal  10  which is used to provide a liquid-tight seal between the feed channel  4  and the recess in the connecting flange  18 . The radial seal  10  is preferably of spherical design in order to compensate for axial tolerances. 
     A non-return valve  19  is arranged in the feed channel  4  in order to prevent the liquid to be cleaned from flowing back into the unfiltered liquid conduit  25 . 
     The unfiltered liquid flows further upwards in the arrow direction into the oil cooler  24  in which the liquid is moderated in temperature, i.e. is cooled or heated depending on the application. A radial seal  34  is arranged in the region of the connection of the oil filter  24  to the feed channel  4 . 
     The feed channel  4  lies in an annular collecting space  6  having a safety wall  7  which is part of the filter housing  2  and radially encloses the feed channel  4 . The collecting space  6  is of unpressurized design and is connected to a recess  30  in the connecting flange  18 , which recess opens into discharge channels  23  which run radially and lead to the oil sump of the internal combustion engine. The discharge channels  23  can run in parallel and can have differing diameters. 
     The end side  12  of the safety wall  7  engages in a circular cutout on the upper side of the connecting flange  18 , an O-ring seal  13  being arranged between the wall of the cutout and the safety wall in the region of the end side  12  of the safety wall  7 , in order to seal the collecting space  6  in a liquid-tight manner from the environment. 
     In the event of a leakage of the feed channel  4 , which is enclosed in the collecting space  6 , or of the radial seal  10  of the feed channel  4 , emerging liquid flows into the unpressurized collecting space  6  and is taken away downwards via the recess  30  and the discharge channel  23 . Liquid is thereby prevented from being able to pass into the environment. 
     The conducting of the liquid away from the filter housing  2  can be seen from FIG.  3 . After the liquid is cooled in the oil cooler  24 , the liquid is supplied to the filter body in the cylindrical section  26  of the filter housing  2 . After filtration, the cleaned liquid flows out of the radially inwardly situated outflow space  33  of the filter body into the return channel  5  which is formed in the filter housing  2  and extends in the vertical direction. The return channel  5  has, in the region of its connection  9 , a radial seal  11  which protrudes into a recess  31  in the connecting flange  18  and connects the return channel  5  to the connecting flange  18  in a pressure- and liquid-tight manner. The recess  31  opens into a horizontally running clean conduit  17  via which the cleaned liquid is guided radially out of the connecting flange  18  and, for example when oil is used as the liquid, can be used in order to lubricate bearings. 
     Protruding radially into the return channel  5  is a connecting piece  22  via which the pressure in the return channel  5  can be supplied to a pressure sensor  21  and to a turbocharger connection. 
     The connecting piece  22  is inserted into a connecting stub  35  and sealed in this connecting stub via a radial seal  36 . The fixing of the connecting piece  22  to the connecting stub  35  can be obtained by a bayonet fastening. This merely requires bayonet-fastening means which can be brought into engagement with one another to be provided on the connecting piece  22  and on the connecting stub  35 . The bayonet fastening can, in particular, be designed in such a manner that bit can be closed by latching of the bayonet-fastening means, without the latter having to be rotated towards one another. In the interior of the filter housing  2 , the connecting piece  22  serves for fixing the return channel  5 . The return channel  5  and the connecting piece  22  are connected by an axial slot  37  being provided at one end of the annular wall of the return channel  5 , into which slot a shaped piece emerging from the connecting piece  22  can be inserted in the manner of a snap fastening. 
     The above-described types of connection between the connecting piece  22  and the connecting stub  35 , on the one hand, and between the return channel  5  and the connecting piece  22 , on the other hand, mean that in the subject matter according to the invention, only sliding connections which can be produced in a simple manner in terms of manufacturing are present. The pressure sensor  2  can also be advantageously connected to the connecting piece  22  by a sliding connection having a radial seal and a bayonet fastening. Other functional parts can also be connected in a fluid-conducting manner to the filter housing in the same manner. 
     Arranged parallel to the return channel  5  is a pressure relief valve  15  which sits in a housing receptacle  16 , which is formed integrally together with the filter housing  2 . In the closed state, the pressure relief valve  15  closes a recess  32  in the connecting flange  18 , which recess communicates with the collecting space  6  and connects the collecting space  6  to the clean conduit  17 , so that when the pressure relief valve  15  is closed, the connection between the clean conduit  17  and the collecting space  6  is interrupted. Above a limiting pressure in the clean conduit  17  the pressure relief valve  15  opens by the valve body of the pressure relief valve  15 , which body is spring-stressed into the closed position, yielding and releasing the connection between the recess  32  and the collecting space  6 , so that liquid can flow from the clean conduit  17  into the collecting space  6 , and a positive pressure in the clean conduit  17  is reduced. The liquid which has escaped into the collecting space  6  can flow off via the recess  30  in the connecting flange  18 , which recess is illustrated in FIG.  2  and communicates with the collecting space  6 . 
     The return channel  5 , the housing receptacle  16  and the feed channel  4 , which is illustrated in FIG. 2, run parallel to one another. The end sides of the channels  4 ,  5 , of the housing receptacle  16  and expediently of the safety wall  7  advantageously end at a different distance axially. 
     It can be seen from the illustration according to FIG. 4 that the feed channel  4  having the non-return valve  19 , the return channel  5 , the pressure relief valve  15  in the housing receptacle  16  (FIG. 3) and the recess  30  in the connecting flange are all situated radially within the cylindrical safety wall  7  which bounds the collecting space  6 . In the event of a positive pressure in the clean conduit.  17 , which is illustrated in FIG. 3, the liquid flows via the pressure relief valve  15  into the collecting space  6  and flows off again via the recess  30 . 
     The safety wall  7  is situated within a housing outer wall  14 . The fastening domes  20  mark corner points in the outer wall  14 ; a total of four fastening domes  20  together forming a rectangle are provided.