Abstract:
A filter element for a fluid, including: an elongated grid-type supporting element; a filter medium supported on the supporting element; wherein the support element and filter medium is configured such that the fluid flows through the filter medium in a direction radially to a longitudinal axis of the filter element; wherein the supporting element is a grid plate and/or the filter medium is embedded in the material of the supporting element at least in some sections.

Description:
TECHNICAL FIELD 
       [0001]    The invention relates to a filter element for filtering a fluid and a filter element arrangement having such a filter element. 
       BACKGROUND OF THE INVENTION 
       [0002]    In practice, filter elements are used to separate impurities that are present in a fluid from that fluid. The filter elements usually have an elongated grid-type supporting element. A filter medium through which fluid can flow in a direction radially to the longitudinal axis of the filter element is supported on the supporting element. 
         [0003]    Such filter elements are used in filtering (diesel) fuels or urea solutions, for example, which are used for reducing nitrogen oxides in the exhaust gas from internal combustion engines in motor vehicles. In practice, however, the installation space available for the filter element, in particular in a motor vehicle, is often extremely limited and has a complex geometry, not least of all because of other components. Installation of the aforementioned filter elements is therefore frequently difficult. 
       SUMMARY OF THE INVENTION 
       [0004]    The object of the invention is therefore to provide a filter element, which may have a more compact design on the whole, with an unchanged filtration capacity and can be adapted even to complex installation spaces, so that the filter element has improved flexibility in use on the whole. 
         [0005]    The object according to the invention is thus achieved by a filter element for a fluid, having an elongated grid-shaped supporting element and having a filter medium, which is supported on the supporting element, such that a fluid flows through the filter medium it in a direction radially to the longitudinal axis of the filter element, such that the supporting element is designed as a grid plate and/or the filter element is embedded in the material of the supporting element in some sections. 
         [0006]    The filter element according to the invention may be implemented with the supporting element designed as a grid plate and/or when the filter medium is embedded in the material of the supporting element in some sections, and may thus be designed to be more compact on the whole but with no change in filtration power, even with a smaller cross section than is the case with the known filter elements, with a grid-shaped supporting element embodied as a supporting pipe, for example. Consequently, the filter element itself can be used in constricted installation conditions that would have been unsuitable for installation of a filter element in the past. In addition, the filter element can be manufactured inexpensively with a low expenditure of material and labor. The supporting element ensures reliable support of the filter medium, so that it does not collapse under the compressive load of the fluid flowing during operation. 
         [0007]    The supporting element may be designed in the form of a supporting cage. In this case, the supporting element is more preferably designed to be closed on all sides radially in relation to the longitudinal axis of the filter element. 
         [0008]    The grid plate of the filter element according to the invention may have a basic planar shape or a basic curved shape, i.e., in the form of a segment of a circle or a corrugated basic shape, for example. The filter element can therefore be better adapted again to an installation space of a complex design. The filter medium is preferably arranged in a manner corresponding to that of the grid plate in at least some sections. 
         [0009]    According to one embodiment of the invention, the filter medium may be embedded in the material of the supporting element in some sections. The supporting element may be integrally molded on the filter medium in particular. This offers advantages in terms of the manufacturing technology. With this embodiment, the supporting element and the filter medium together form an inseparable unit and can be mounted jointly in the respective installation position. 
         [0010]    According to an alternative embodiment of the invention, the filter medium is arranged in a ring shape around the supporting element, in particular in a ring shape around the supporting element in the form of a grid plate. In this case, the filter medium may be in pleated form in particular as filter bellows. Therefore, a particularly large effective filter surface area may be made available for the fluid to be filtered. 
         [0011]    According to the invention, the supporting element may be provided with an end plate on one or both ends. A further improvement in the mechanical stability of the filter element can be achieved by means of these end plates. In addition, the mounting of the filter element can therefore be simplified further, and sealing of a crude side that is to be separated from the clean side of the filter element is possible. The end disk and/or end disks may be provided in particular with a sealing element, by means of which a sealing contact with a filter housing or the like is made possible. 
         [0012]    The aforementioned end disk or end disks may advantageously be shaped according to technical manufacturing aspects of the supporting element. 
         [0013]    The supporting element may be made of plastic for cost reasons. The supporting element is especially preferably designed as an injection molded part. The supporting element can therefore be embodied easily and inexpensively in practically any freely selectable shape. The supporting element in this case is preferably made of a thermoplastic polymer. 
         [0014]    The at least one end disk of the filter element may have a continuous opening for the fluid. In this case, the grid plate is arranged at a distance axially from the continuous opening in order to ensure free flow of fluid through the continuous opening. 
         [0015]    At low ambient temperatures, an unwanted increase in viscosity may occur, or in the case of diesel fuels, there may be flocculation of paraffins. It is known that, if the temperature drops below the freezing point of the respective fluid to be filtered, freezing of the fluid may occur. The invention therefore also includes a filter element arrangement with a filter element of the type described previously and a heating element. In the case of a filter medium through which the fluid flows radially from the outside to the inside, the heating apparatus is preferably arranged on the outside of the filter element and preferably extends completely around it. 
         [0016]    According to the invention, the heating device additionally preferably includes an electric heating foil with a resistance heating element laminated between two plastic films, wherein the heating foil has electric terminal contacts by means of which the heating foil can be connected to an electric power supply. The heating device may have a first and a second flat heat conducting element between which the heating foil is arranged. The two heat conducting elements are embedded in an outer plastic layer together with the electric heating foil, wherein the electric terminal contacts of the heating foil lead out of the plastic layer. 
         [0017]    The heating device preferably has one or more through-openings for the fluid to be heated. This heating device is characterized by the use of a flexibly deformable heating foil such as that freely available in prefabricated form on the market, also low heating costs and a highly flexible design. The surface heating element can therefore be implemented on the whole with a planar, curved, ring-shaped, banana-shaped or even corrugated design and thus adapted easily to the shape of the filter element. In addition, the use of the standardized heating foils allows a narrow tolerance in the heating power of the heating device. This offers a reliable heating effect as well as safety advantages. 
         [0018]    Due to the fact that the heating foil is arranged between the two flat heat conducting elements and is cast together with them in the plastic layer, this yields a dimensionally stable sandwich design of the heating device on the whole. The two heat conducting elements ensure a uniform release of heat over the surface of the heating device. Due to the plastic layer as well as the two heat conducting elements, the heating foil can be reliably protected from any excess mechanical stress, for example due to a freezing pressure of the fluid such as that which is imminent when the heating device is not in operation. In the same way, penetration of fluid can be suppressed by the plastic layer, i.e., the plastic sheathing of the heating device even at high operating pressures in the area of the electric contacts of the heating foil. The current-carrying resistance heating elements are therefore optimally protected from chemical or physical influences of the fluid to be heated. 
         [0019]    The plastic layer may be made of a thermoplastic material, which is advantageous from the standpoint of the manufacturing technology. 
         [0020]    According to a particularly preferred refinement of the invention, the heating device has one or more through-openings for the fluid to be heated. Such a through-opening permits a continuous flow through the heating device in a direction of flow running obliquely to the surface of the surface heating element. The surface heating element therefore has an even broader spectrum of use and can be used in a filter element for filtering the fluid, for example. It should be noted that, due to the size and shape of the through-opening(s), a turbulent flow of fluid can be created and/or facilitated; this is advantageous for the most efficient possible transfer of heat from the heating device to the fluid. 
         [0021]    According to the invention, the electric contacts of the heating foil can each be connected to an electric plug connector, which is partially embedded in the plastic layer. A mechanically stable connection for a coupling part of an electric terminal cable can therefore be implemented. 
         [0022]    A joining means for the aforementioned coupling part of the electric terminal cable is especially preferably integrally molded on the plastic layer. The joining means may be designed in particular as a screw thread for screw connection of a union nut. As an alternative to this, the joining means may be embodied in the form of one or more catch means for catch engagement of the coupling part. Meanwhile, the joining means is an integral component of the plastic layer and can be created together with it in an inexpensive manner by means of an injection molding method. 
         [0023]    For a further improvement in the sealing of the surface heating element in the area of its electric contacts, it has been found to be advantageous if the surface heating element has a sealing element, by means of which the coupling part can be sealed. In the simplest case structurally, the sealing element may be embodied as an O-ring having rubber elastic deformability. The heating device in this case advantageously has an integrally molded shoulder on the plastic layer, for example, a ring groove on which the sealing element can be supported, forming a seal. 
         [0024]    The two heat conducting elements are preferably made of the same material. For the purpose of good thermal conductivity, these two elements may be made of metal or a metal alloy in particular. The heat conducting elements are especially preferably embodied as metal plates. 
         [0025]    According to a particularly preferred refinement of the invention, the plastic layer is provided with fastening means by which the heating device can be fastened onto the filter element, onto the filter housing or inside a fluid tank. The fastening means are advantageously integrally molded on the plastic layer from the standpoint of manufacturing technology and are therefore designed as an integral component of the heating device. In the simplest case the fastening means may be embodied at least partially as snap tongues. The heating device can therefore be fastened in its installed position without the use of tools, for example, on the filter element and/or on the filter housing or also in the fluid tank of a motor vehicle. 
         [0026]    The invention is explained in greater detail below on the basis of exemplary embodiments shown in the drawings. The feature shown here may be implemented individually either alone or in multiples in any combination in variants of the invention. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0027]    In the drawings: 
           [0028]      FIG. 1  shows a filter element for a fluid having a fluid medium through which the fluid can flow in a direction radially to the longitudinal axis of the filter element and which is supported on a curved grid plate on the inside; 
           [0029]      FIG. 2  shows a filter element arrangement having the filter element from  FIG. 1  and a heating device pushed onto the filter element, arranged on the filter element with a catch lock; 
           [0030]      FIG. 3  shows a longitudinal section through the filter element according to  FIG. 1 ; 
           [0031]      FIG. 4  shows another filter element having a supporting body in the form of a supporting cage, in which the filter medium is held embedded in the material of the supporting body in some sections; 
           [0032]      FIG. 5  shows a filter element arrangement with the filter element according to  FIG. 4  and a heating device attached to it for heating the fluid; 
           [0033]      FIGS. 6, 7  show another filter element arrangement, wherein a filter medium is arranged, so that it is held embedded in the material of the supporting body in a manner corresponding to that of the filter element shown in  FIG. 4  and having a heating device that is closed in the form of a circle, wherein the filter element is designed as shown in  FIG. 11  and is inserted into the heating device by means of a tongue-and-groove principle; 
           [0034]      FIG. 8  shows an alternative embodiment of  FIG. 1 ; 
           [0035]      FIGS. 9-11  show alternative embodiments and forms of representation of a filter element. 
       
    
    
     DESCRIPTION OF THE INVENTION 
       [0036]      FIG. 1  shows a filter element  10  for filtering a fluid containing impurities. In the present case, for example, the filter element has an essentially kidney-shaped or banana-shaped basic design with a longitudinal axis  12 . The filter element  10  may also have a different basic design, if this is required by the geometry of the respective installation space of the filter element  10 . The filter element  10  has at least one filter medium  14 . The filter medium  14  is shown as transparent in  FIG. 1  for reasons of illustration.  FIG. 8  shows an alternative view of the filter element  10 . The filter medium  14  is supported on the inside on a supporting element  16 , which is embodied as a grid plate and is arranged in a ring shape around the supporting element  16 . 
         [0037]    The supporting element  16  has a curved width, which is due to the desired basic shape of the filter element  10 . Longitudinal and transverse webs of the supporting element  16  are labeled as  18  and  20 , respectively. The longitudinal and transverse webs define the first through-openings  22  for the fluid  24  (represented here in the form of an arrow). 
         [0038]    At one end, a first end disk  26  is arranged on the supporting element  16 , and a second end disk  28  is also arranged at the other end. The supporting element  16  and the two end disks  26 ,  28  are formed together in one piece in this case. The two end disks  26 ,  28  may be integrally molded on the supporting element  16 . As an alternative, supporting element  16  in the form of a grid plate may be arranged loosely between the end disks  26 ,  28 . The filter medium  14  is arranged between the two end disks  26 ,  28  and is covered by them with a protective effect in the axial direction. During operation of the filter element  10 , the fluid  24  to be cleaned flowing through the filter medium  14  from the outside to the inside in a direction radially to the longitudinal axis  12  of the filter element  10 . 
         [0039]    In the present case, the filter medium  14  is embodied as filter bellows and extends around the full circumference of the supporting element  16 . The filter medium  14  is in contact with the inside of the supporting element  16 , which thus counteracts collapse of the filter medium  14  under the pressure of the fluid  24  during operation of the filter element  10 . For reasons of stability and/or sealing, the filter medium  14  is arranged so that it is embedded in the front end of the material of the two end disks  26 ,  28 . The first end disk  26  has a fluid outlet  30 , which is designed as a through-opening, which is fluidically connected to an outlet connection  32  of the filter element  10 . The outlet connection  32  may be provided with a sealing element  34 , for example, an O-ring, as shown in  FIG. 1 , to be able to insert the outlet connection  32  of the filter element into an outlet pipe on the installation end, so as to form a seal. The supporting element  16  or, more precisely, the lower transverse web  20  of the supporting element  16  shown in  FIG. 1 , has an indentation  35  in the region of the outlet  30 , so that the supporting element  16  is arranged at an axial distance from the fluid outlet  30 . Unhindered outflow of the fluid  24  out of the interior of the filter element  10  and through the fluid outlet  30  is therefore made possible. 
         [0040]    The length and/or structural height of the filter element  10  is labeled as  36 , the width is labeled as  38  and the thickness as  40 . 
         [0041]    Due to the insertion of a supporting element  16 , the filter element  10  may be supplied with a small thickness  40  and with a shape which is coordinated with and/or aimed at the geometry of a predetermined installation space and in particular deviates from a circular shape. 
         [0042]      FIG. 2  shows a filter element arrangement  8  with the filter element  10  from  FIG. 1  and a heating device  42  for the fluid  24 , mounted on the filter element  10  (see  FIG. 1 ). The heating device  42  is designed in the form of a sleeve or cuff and has a basic shape corresponding to the basic shape of the filter element  10 . The heating device  42  may be designed in particular in the form of a closed ring relative to the longitudinal axis  12  of the filter element  10 , as is the case with the heating device  42  shown in  FIG. 2 . The heating device  42  extends around the outside of the filter element  10 , so that the heating device is arranged upstream fluidically from the filter element  10 . The fluid  24  (see  FIG. 1 ) can therefore be heated and/or warmed up even before the flow of filter medium  14  reaches the filter element  10  (see  FIG. 1 ). 
         [0043]    According to  FIG. 2 , the heating device  42  has a plurality of second flow-through openings  44  (at the side) for the fluid around the circumference. These through-openings  44  may each be designed in the form of a slot. The through-openings  44  may be aligned in a row  46  one after the other in the axial direction, and a plurality of such rows  46  may be arranged in groups over the circumference of the heating device  42 . 
         [0044]    The heating device  42  is characterized by a multilayer structure. The surface of the heating device  42  is formed by a fluid-tight plastic layer  48  on the whole. The plastic layer  48  consists of a thermoplastic polymer. Two elongated curved heat conducting elements  50  are embedded in the plastic layer  48 , in particular completely embedded as shown in greater detail in  FIG. 3 . A heating foil  52 , which is flexible in the dismantled state, is arranged between the two heat conducting elements  50 . In other words, the heating foil  52  as well as the two heat conducting elements  50  are arranged in the plastic layer  48 , where they are completely embedded. The heating foil  52  is essentially covered at the side by the two heat conducting elements  50 . The two heat conducting elements  50  are each made of metal and serve to reinforce the heating foil  52 . In addition, the heat conducting elements  50  ensure a uniform and effective transfer of heat from the heating foil  52  to the fluid  24  flowing toward the heating device  42  (see  FIG. 1 ). 
         [0045]    First and second fastening means  54 ,  56  are used to fasten the heating device  42  onto the filter element  10 . The first fastening means  54  are each designed in the form of snap tongues. These snap tongues protrude away from the lower edge  58  of the heating device  42  in the direction of the longitudinal axis  12  of the filter element  10  and are thus locked with the first end disk  26  of the filter element  10 . The second fastening means  56  protrude inward away from the upper edge  60  of the heating device  42  and are designed as tongue-shaped profile protrusions of the plastic layer  48 . The filter element  10  with its second end disk  28  is in contact with the second fastening means  56  in the form of tongues on the heating device  42 . The second fastening means  56  serve as an axial stop for the heating device  42  when the heating device  42  is pushed onto the filter element  10 . The filter element  10  is arranged so that it is held in a fixed position axially inside of the heating device  42 . The filter element  10  and the heating device  42  may be replaced as needed independently of one another. 
         [0046]    The filter element  10  may be installed individually or jointly with the heating device  42  in the tank of a motor vehicle, in particular a tank for supplying a urea solution. 
         [0047]    The heating device  42  also has a connection region designated as  62  for a heating cable (not shown) by means of which the heating foil  52  can be connected to an electric power source (not shown). Two electric terminal contacts  64  of the heating foil  52  are held at each end in an electric plug connector  66 . The two electric plug connectors  66  are embedded in the outer plastic layer  48  of the heating device in some sections and are therefore held in the plastic layer  48  with a seal and in a fixed position relative to one another. Unwanted penetration and advance of the fluid toward the heating foil  52  can therefore be reliably suppressed. 
         [0048]    The connecting region  62  has a joining means  68  integrally molded on the plastic layer  48  and/or formed by the plastic layer for a coupling part of the electric connecting cable. The joining means  68  may be designed as a screw thread, as shown in  FIG. 2 , for a screw connection of a union nut (not shown). For additional sealing of the coupling part with respect to the connecting region  62 , an elastically deformable sealing element  70  embodied as an O-ring is used. 
         [0049]      FIG. 3  shows the wall structure of the heating device  42  in a detailed drawing of one section. The heating from  52  has a centrally arranged resistance heating element  72 , which is laminated between two plastic films  74 . The resistance heating element  72  may have electrically conductive metal wires or plastic fibers and/or plastic nanotubes, for example. The heating foil  52  is in turn in contact with the heat conducting elements  50 . The plastic layer  48  completely surrounds the heating foil  22  and the heat conducting elements  50 . 
         [0050]    Because of the multiply encapsulated arrangement of the resistance heating element  72 , the heating device  42  may be used for heating aggressive fluids such as a urea solution, for example, as well as for high-pressure applications without causing any risk of damage to the resistance heating element  72  and/or to the heat conducting elements  50  by the fluid  24 . The heating foil  52  is designed for operation on a DC voltage source. The heating foil  52  may also be designed for an AC voltage operation. 
         [0051]      FIG. 4  shows another filter element  10 , which differs from the filter element  10  shown in  FIG. 1  essentially in that the supporting element  16  is designed in the form of a cage and is integrally molded on the filter medium  14 . The filter element  10  is therefore arranged so that it is retained in the material of the supporting element  16  in some sections. The filter medium  14  is designed so that it is closed in the form of a ring together with the supporting element  16  relative to the longitudinal axis  12  of the filter element  10  and is reinforced in its ring-shaped arrangement by the longitudinal webs  18  and the upper and lower transverse webs  20  of the supporting element  16 . The length of the filter element  10 , i.e., its extent in the direction of the longitudinal axis  12  is designated as  36 . 
         [0052]      FIG. 5  shows a filter element arrangement  8 , which has the filter element  10  from  FIG. 4  with a heating device  42  fastened onto it. The filter element  10  has the supporting element  16 . The heating device  42  has a design similar to that of the heating device  42  shown in  FIG. 3 . The through-openings  22  of the individual rows  46  of the heating device  42  may overlap one another in the axial direction. In addition, the fastening means  54 ,  56  are all designed as catch elements. 
         [0053]      FIGS. 6 and 7  show another exemplary embodiment of a filter element arrangement  8  with a filter element  10  and a heating device  42 . The filter element  10  has a circular shape. The filter element  10  is designed in two parts and has two filter element half-shells  76 , only one filter element half-shell  76  of which is shown here in order to simplify the figure. The two half-shells  76  of the filter element  10  may be profiled, so that they are complementary to one another on their facing edge regions  78 , so these develop into one another essentially without a step on the inside circumference and on the outside circumference. The filter medium  14  of the filter element  10  is fastened onto the supporting element  16 , which is curved in the form of an arc of a circle in a manner corresponding to that of the filter element  10  shown in  FIG. 4 . The two filter element half-shells  76  each have a fluid outlet  30  on their first end disk  26  according to  FIG. 7 . 
         [0054]    The plastic layer  48  of the heating device  42  has second fastening means  56 , which are designed as an annular groove and forms an axial stop for the filter element  10 . The filter element  10  may be inserted axially into the heating device  42  until the filter element  10  comes to a stop with its second upper end disk  28  against the upper second fastening means  56  of the heating device  42 , as shown in  FIGS. 6 and 7 . The lower first fastening means  54  in  FIGS. 6 and 7  are each designed as snap tongues and are locked onto the first end disk  26  of the filter element  10 . 
         [0055]    The through-openings  22  of the heating device  42  are arranged so they run axially in the direction of the longitudinal axis of the filter element  10 . The through-openings  22  in the exemplary embodiments presented above may also be designed to be round, oval or polygonal. 
         [0056]      FIG. 8  shows an alternative view of the filter element  10  according to  FIG. 1 . 
         [0057]      FIGS. 9-11  show alternative embodiments and/or alternative diagrams of filter elements  10 , as explained above with reference to  FIGS. 6 and 7 . The filter elements  10  are shown as partial sectional views for the sake of better illustration. 
         [0058]    In summary, the invention relates to a filter element for a fluid, having an elongated grid-type supporting element and a filter medium, which is supported on the supporting element, such that the fluid can flow through the filter medium in a direction radially to the longitudinal axis of the filter element. The supporting element according to the invention is preferably designed as a grid plate or as a supporting screen. The invention also relates to a filter element arrangement having such a filter element and a heating device by means of which the fluid can be heated.