Abstract:
A filter element ( 12 ), particularly for the intake air of an internal combustion engine. The filter element ( 12 ) has a filter body ( 13 ) and a seal ( 15 ) disposed circumferentially around the filter body ( 13 ). The seal ( 15 ) is bonded to the filter body ( 13 ) with an adhesive ( 31 ) and includes a hard component ( 26 ) and a soft component ( 27 ). The hard component ( 26 ), which rests directly on a housing section, prevents the filter element ( 12 ) from moving relative to this housing section, and since the filter element cannot move relative to the housing section, damage to the filter element is avoided.

Description:
BACKGROUND OF THE INVENTION 
     The present invention relates to a filter element, particularly for the intake air of an internal combustion engine or a compressor, comprising a filter body and a seal circumferentially disposed around the filter body. The invention further relates to a filter system incorporating such a filter element. 
     Published international patent application no. WO 2004/020075 discloses a filter system for the intake air of an internal combustion engine in which a filter element is clamped between two parts of the housing. The filter element is a wound filter formed of a coiled filter medium and a profiled seal disposed along the circumference. The profiled seal is formed of an elastic band circumferentially bonded to the filter medium coil. To this end, the seal has a circumferential surface extending parallel to the outside circumference of the filter coil and is adhesively bonded to the coiled filter medium. To obtain a good bond between the seal and the filter coil, the seal has a seal base, which is wider than the sealing bead. The seal base extends axially along the circumferential surface of the filter coil on both sides across the seal, so that the seal base protrudes in upward and downward direction. Since the seal is formed of an elastic material, the filter element can oscillate or vibrate axially inside the parts of the housing, which oscillation damages the filter element. 
     SUMMARY OF THE INVENTION 
     Accordingly, it is an object of the present invention to provide an improved filter element and filter system for filtering intake air of an internal combustion engine. 
     Another object of the invention is to provide a filter element and filter system in which a seal can be easily and cost-effectively attached to a filter body. 
     A further object of the invention is to provide a filter element and filter system in which damage due to vibration or oscillations is prevented. 
     These and other objects have been achieved in accordance with the present invention by providing a filter element comprising a filter body and a seal circumferentially disposed around the filter body, wherein the seal comprises a hard component and a soft component and is bonded to the filter body by an adhesive. 
     In accordance with a further aspect of the invention, the objects are also achieved by providing a filter system 
     Advantageous refinements, preferred embodiments and optional features are described in further detail hereinafter. 
     The filter element according to the invention is used to clean a fluid stream, particularly the intake air for an internal combustion engine or a compressor. The filter element can of course also be used for other filtration functions. To this end, the filter element has a filter body formed of a filter medium. The filter medium, which is adapted to separate impurities from the fluid stream, can be a pleated, annularly closed filter paper, for example. Other embodiments of the filter body are also feasible, however, e.g., a filter paper wound into a filter coil with alternately closed channels or a filter block formed of a filter foam. 
     A circumferential seal with a hard component and a soft component is arranged around the filter body. The hard component is formed of a dimensionally stable material, such as plastic or metal, and is ring-shaped or annular. The soft component is formed of an elastic material, such as an elastomer, a thermoplastic elastomer (TPE) or a polyurethane resin (PUR) foam, which forms a reliable seal together with an adjoining part of the housing. The soft component is joined to the hard component so as to form a dimensionally stable seal extending around the filter body. This connection can be achieved, for example, by adhesively bonding, welding or clipping the components together. The hard component makes the seal stable enough to prevent oscillations that could damage the filter element in the installed state. 
     The seal is bonded to the filter body by an adhesive. The adhesive can form a bond over a large area between the hard or soft component and the filter body. In one advantageous embodiment, the adhesive forms an adhesive wedge between one or both components of the seal and the filter body. The seal is slipped over the filter body, so that a gap is formed between the filter body and the seal. A liquid adhesive is metered into this gap, which after curing joins the filter body to the seal in a sealing manner. Because the seal, together with the filter body, forms the seat for the adhesive, no expensive tundishes are required to bring the adhesive into a corresponding mold. The prefabricated seal is an easily manufactured low-cost component. The adhesive wedge firmly and reliably bonds the seal to the filter body, so that slippage or detachment of the seal from the filter body is reliably prevented. 
     In accordance with to one advantageous embodiment of the invention, two-component injection molding is used to manufacture the seal. In this process, the soft component is injection molded directly onto the hard component. Injection molding the soft component onto the hard component creates a permanent bond between the hard component and the soft component, at least in partial areas, enabling the seal to be joined to the filter body as a one-piece component. In addition, two-component injection molding is a simple and cost-effective method to manufacture the seal. 
     In another advantageous embodiment of the invention, the soft component of the seal has a sealing lip, which makes contact with the filter body along a linear circumferential contact zone. The sealing lip contacts the filter body, thereby producing a seal tight enough so that the adhesive remains in the gap formed between the seal and the filter body and does not run out during the manufacturing process. Because of the linear contact zone, the sealing lip contacts the filter body so as to form a seal around the circumference. Any unevennesses of the filter body can be compensated for as well because the sealing lip adapts to the filter body and follows these imperfections. 
     In yet another advantageous embodiment of the invention, the adhesive wedge is stiffer than the soft component. The soft component is formed of a soft material, which exhibits optimal sealing properties in the housing. The adhesive wedge, which is formed, for example, of a hot-melt adhesive, a casting resin, a polyurethane resin, silicone, or an epoxy resin, imparts high stability to the seal. Since the filter body cannot move axially relative to the seal, which is fixed within the housing, mechanical loading of the filter element within the filter housing is substantially reduced. 
     In one specific embodiment of the invention, the seal has a circumferential sealing bead. The sealing bead can, for example, have a rectangular, round or oval cross section, although it is of course possible to realize all desired geometries. The sealing bead is configured in such a way that it can be clamped between two halves of the housing to create a reliable seal between an unfiltered side and a filtered side. The adhesive flows into a gap between the sealing bead and the filter body. The adhesive wedge formed by the adhesive has corresponding radii or arcs to join the sealing bead to the filter body. The sealing bead can be formed either by the soft component alone or by both the soft and the hard component. The soft component has a sealing area that can be deformed by a housing section. The seal is created in this sealing area, so that no unfiltered volume flow can reach the filtered fluid side of the filter element. 
     In another embodiment of the invention, the soft component has a damping zone, which communicates with the hard component on the one hand and the housing geometry on the other. In this damping zone, the material of the soft component is compressed, so that oscillations of the housing are transmitted to the filter element in a damped manner. This reduces the oscillations transmitted to the filter element, thus reducing the vibrational loading of the filter element. 
     It is advantageous if the soft component is provided with a hollow space. The hollow space reduces the mass of material required to form the geometry and changes the pressure properties of the seal. Cycle times can be shortened and component weight reduced as a result of the reduced mass of material. The changed pressure properties of the seal make it possible to form a sealing area and a damping zone using the same material; the material being more easily deformable in the sealing area than in the damping zone. The hollow space is preferably produced by gas or water-assisted injection molding. These processes can be well controlled and enable mass production of seals with consistent sealing properties. 
     In yet another specific embodiment of the invention, the hard component has a structure with elevations and indentations on the side opposite the soft component. This structure interacts or mates with a negative structure in the housing, and as a result, the filter element can be mounted only in a single predetermined position within the housing. This prevents the filter element from being incorrectly inserted into the housing. Once mounted, the filter element also cannot move radially, so that damage due to rubbing against the housing is avoided. 
     The filter system according to the invention is specifically intended to clean the intake air of an internal combustion engine, but it can, of course, also be used to remove impurities from other fluid streams, especially gas streams. The filter system comprises at least one filter housing and one filter element having the features described above. The filter housing has an inlet, through which the air to be filtered can flow into the filter housing, and an outlet, through which the filtered air can flow out of the filter housing. The filter housing comprises at least two housing sections between which the filter element is disposed. The filter element is joined to at least one of the housing sections, forming a seal. This sealing connection is formed by a seal disposed on the filter element. The seal comprises a hard component and a soft component, such that the hard component communicates with one of the housing sections and the soft component contacts the other housing section. The housing section communicating with the hard component axially encloses the filter element at least in part. The contact between the hard component and the housing section prevents the filter element from moving relative to this housing section. As a result, the filter element does not rub against this housing section, and damage to the filter element is avoided. 
     According to a further refinement of the filter system according to the invention, the housing section communicating with the soft component has a circumferential projection that communicates with the soft component to form a seal. This projection is pressed into the soft component when the filter element is installed, such that the surface of the soft component adapts to the projection and thereby produces a seal. The projection can have any cross-section, e.g., triangular, sinusoidal or trapezoidal. Preferably, the projection has a cross section that tapers with increasing distance from the housing section. Thus, at first, the projection contacts the soft component with a very small area. As the projection penetrates deeper into the soft component, the cross-sectional area of the projection increases. The deformation of the soft component is greater in the area of the projection than in the areas adjacent the projection. This produces a reliable seal in the area of the projection, but the force required to form the seal is relatively small. 
     In one advantageous embodiment, the geometry of the housing section communicating with the hard component includes elevations and/or indentations. The hard component also has elevations and/or indentations, such that the elevations of the housing section engage the indentations in the hard component, and the elevations of the hard component engage the indentations in the housing section. The geometries correspond in such a way that they prevent insertion of a wrong filter element or incorrect insertion of a correct filter element. The inability of the filter element to assume its proper position within the housing prevents the housing from being closed, and in that way, the selection of an improper filter element or mis-positioning of a filter element can be detected. This prevents the filter system from being operated with the wrong or with an incorrectly installed filter element and avoids damage to the internal combustion engine. The housing can be closed only if an appropriate filter element is inserted in the specified orientation, so that improperly filtered air cannot damage the internal combustion engine. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The invention will be described in further detail hereinafter with reference to illustrative preferred embodiments shown in the accompanying drawing figures, in which: 
         FIG. 1  is a partially cut-away representation of a filter system according to the invention; 
         FIG. 2  is a sectional view of a detail of a filter system according to the invention; 
         FIG. 3  is an enlarged detail view according to  FIG. 2 ; 
         FIG. 4  is a detail view of an alternative filter embodiment; 
         FIG. 5  is a detail view of another alternative filter embodiment; 
         FIG. 6  is a detail view of yet another alternative embodiment: 
         FIG. 7  is a detail view of a still further alternative embodiment: 
         FIG. 8  is a plan view of the hard component of the filter seal, and 
         FIG. 9  is a detail view of a seal with a keyed connection. 
     
    
    
     DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS 
       FIG. 1  is a general view of a filter system which is partially cutaway in the lower portion of the figure. The filter system has a housing  10  with a lid  11  and an oval filter insert  12 . The lid  11  is configured in such a way that it closes the housing  10 , so that the housing  10  and the lid  11  form a filter enclosure. The filter insert  12  comprises a filter coil  13  with alternately closed channels  14  and a seal  15 . The seal  15  is disposed between the lid  11  and the housing  10 . The construction and arrangement of the seal  15  will be described in greater detail with reference to the subsequent figures. 
     The lid  11  has an inlet  16  through which the air to be filtered flows into the filter housing. The outlet  17  for the filtered air is arranged in the housing  10 . The filter insert  12  is arranged in the filter housing such that the inlet  16  is separated from and sealed relative to the outlet  17 . The filter insert  12  extends axially into the housing  10 . The housing  10 , which in this illustrative embodiment has a two-part construction, is provided with mounting brackets  18  with which the housing  10  can be fixed in its installation space. Because of its two-part construction, the housing  10  can be easily and cost-effectively manufactured using a plastic injection molding process. The two housing sections are joined together in a connection area  19 . The joint in this area is produced by welding or adhesive bonding. In the interior of the housing  10 , the filter insert  12  rests on a shoulder  20 , which is located in proximity of the connecting area  19 . The construction of the seal  15 , which will be described below, prevents the filter insert  12  from moving relative to the housing  10 . This prevents rubbing locations from forming on the filter insert  12 . 
     The air to be filtered flows through the inlet  16  into the filter enclosure formed by the lid  11  and the housing  10 . The unfiltered air enters the open channels  14  of the filter insert  12  in the direction indicated by arrow  21 . The air then passes as shown by arrow  22  into adjacent channels  14  which are open toward the outlet  17 , and as it passes through the filter medium between channels, the impurities are retained. The filtered air flows out of the channels  14  which are open toward the outlet  17  as indicated by arrow  23  and exits the filter housing through the outlet  17 . 
       FIG. 2  is a sectional view of a detail of the filter system according to  FIG. 1 . Components corresponding to those of  FIG. 1  are identified by the same reference numerals. Only the section of the two-part housing  10  enclosing the filter insert  12  is shown. The other section of the housing  10  in which the outlet  17  is disposed is not depicted. The filter coil  13 , which is formed by a filter medium having alternately closed channels  14 , is spirally wound around a blade  24 . The blade  24  is sealingly and permanently connected to the filter coil  13 . An extraction handle  25  is arranged on the side of the blade  24  facing the inlet  16 . This extraction handle  25  can be used to pull the filter insert  12  out of the housing  10  after removal of the lid  11 . 
     The seal  15  of the filter insert  12  comprises an annular hard component  26  and a soft component  27  connected to this hard component  26 . The soft component  27  has a sealing lip  29 , which linearly contacts the filter coil  13 . The sealing lip  29  encloses the circumference of the filter coil  13  in part, such that a gap  30  is formed between the sealing lip  29  and the filter coil  13 , into which a measured amount of an adhesive  31  is dispensed. The adhesive  31  bonds the soft component  27  to the filter coil  13 . The bonds between the soft component  27  and the hard component  26  and the adhesive  31  create a firm connection to the filter coil  13 , so that the filter coil  13  is prevented from moving axially relative to the seal  15  formed by the hard and the soft components  26  and  27 . The hard component  26  contacts the oval area of the housing  10  in the region of a seal seat  28 . Because both the hard component  26  and the seal seat  28  of the housing  10  are essentially inflexible, the filter element  12  cannot move relative to the housing  10 . 
       FIG. 3  shows an enlarged detail A of  FIG. 2 . Again, components corresponding to those of  FIG. 2  are identified by the same reference numerals. The hard component  26  has a support area  32 , which supports the sealing lip  29  of the soft component  27  in such a way that the soft component does not lift off the filter coil  13  when the adhesive  31  is injected. In addition, the seal  15  is stiffened to prevent any oscillations between the outside circumference of the seal  15  and the filter coil  13 . The hard component  26  furthermore has a circumferential annular support bead  33 , which rests against the seal seat  28  of the housing  10 . In addition, the seal seat  28  has a likewise annular circumferential bead  34 , against which the hard component  26  rests. Thus, the hard component  26  has two support locations on the housing  10 , which are linear or torus-shaped. 
     The soft component  27 , which is vulcanized onto the hard component  26 , has a U-shaped sealing area  35  in addition to the sealing lip  29 . The U-shape is open toward the outside circumference. One leg of the U-shape is firmly joined to the hard component  26 . The opposite leg  36  contacts the lid  11 , which has a circumferential projection  37  that presses into the leg  36  of the soft component  27  and thereby forms a seal between the filter insert  12  and the lid  11  of the filter housing. 
       FIG. 4  illustrates an alternative embodiment of the seal  15  shown in  FIG. 3 . Again, components corresponding to those of  FIG. 3  are identified by the same reference numerals. The difference compared to the seal  15  depicted in  FIG. 3  lies in the geometry of the soft component  27 . In this embodiment, the soft component  27  also has a U-shaped geometry, but the U-shape is open toward the hard component  26 . The radially inner leg  36   a  of the U-shape merges into the sealing lip  29 , forming a firm connection between the support area  32  and the sealing lip  29 . The radially outer leg  36   b  is thicker. When the lid  11  is placed on the housing  10 , the outer leg  36   b  is compressed. In this compressed area, a damping zone  38  is formed between the seal  15  and the lid  11 . As a result, the oscillations transmitted from the lid  11  to the filter insert  12  and the housing  10  are reduced. In this embodiment, the side of the U-shape connecting the legs  36   a ,  36   b  forms a sealing area  35 ′ between the soft component  27  and the lid  11 . 
       FIG. 5  illustrates another alternative embodiment of the seals  15  depicted in  FIGS. 3 and 4 . Once again, components corresponding to those shown in  FIGS. 3 and 4  are identified by the same reference numerals. The difference compared to the seal  15  shown in  FIG. 3  lies in the geometry of the soft component  27  and the lid  11 . The soft component  27  has another circumferential lip-shaped sealing member  39  in addition to the sealing lip  29 , which contacts the filter coil  13 . The sealing lip  29 , which is connected to the hard component  26  merges, directly into the sealing member  39 . In the assembled state, the sealing member  39  contacts the projection  37  on lid  11  to form a seal in sealing area  35 ″. In addition, the soft component  27  has a damping foot  40 , which is firmly connected to the hard component  26  by an annular rectangular cross section. Similarly to  FIG. 4 , a damping zone  38  is created between the damping foot  40  and a shoulder  41 , which is formed on the lid  11 , since the damping foot  40  is compressed when the lid  11  is installed in the closed position. 
       FIG. 6  illustrates yet another alternative embodiment of the seals  15  shown in  FIGS. 3 to 5 . Components corresponding to those of  FIG. 3  are again identified by the same reference numerals. The difference compared to the seal  15  shown in  FIG. 3  lies in the geometry of the soft and hard components  27  and  26 . In this embodiment, the hard component  26  is configured as a flat ring with a support area  32  formed onto it. The soft component  27  has a hollow space  42 , which is produced by gas-assisted injection molding. Through the hollow space  42 , the wall thickness of the soft component  27  is configured in such a way that a sealing area  35  is formed generally centrally of the hollow space  42  in conjunction with the projection  37 . In the radially outer area of the soft component  27 , a damping zone  38  is formed by the compression of the material of the soft component between the lid  11  and the hard component  26 . 
       FIG. 7  illustrates another alternative embodiment of the seals  15  depicted in  FIGS. 3 to 6 . Components corresponding to those shown in  FIGS. 3 to 6  are once again identified by the same reference numerals. The difference compared to the seal  15  shown in  FIG. 3  lies in the geometry of the soft component  27  and the hard component  26 . In addition, the lid  11  has a shoulder  41  like the one shown in  FIG. 5 . The hard component  26 , apart from the support area  32 , which is formed onto the annular area, also has an extension  43 , which projects toward the soft component  27 . The soft component  27 , apart from the extension  43  projecting into it, has a rectangular cross-section with a sealing lip  29  formed thereon. Since the material of the soft component  27  is very flexible, it can be easily compressed by the projection  37 , thereby forming the sealing area  35 . The material of the soft component  27 , which is disposed between the shoulder  41  of the lid  11  and the extension  43  of the hard component  26 , is compressed such that a damping zone  38  is created. Thus, in this embodiment, too, the sealing area  35  is functionally and geometrically separate from the damping zone area  38 . 
       FIG. 8  is a plan view of the hard component  26  illustrating the side communicating with the housing  10 . The round shape shown in this figure is divided into four different sectors representing different embodiments. Instead of a circular shape, the hard component  26  can also have an oval or elliptical shape. 
     In the upper left area, the hard component  26  is configured in such a way that the flat annular area has bores  44 . Pins (not shown) disposed on the communicating housing  10  can engage in these bores  44 . The engagement of the pins in the bores  44  secures the filter insert  12  in the housing  10 , illustrated in  FIGS. 1 and 2 , against radial movement. The size and number of the bores  44  can be selected arbitrarily. The distribution of the bores around the circumference can also be selected arbitrarily. If there is only a single bore  44  and a single pin, the filter insert  12  can be mounted only in a single position. If there are several bores  44  in the hard component  26  but only a single pin in the housing  10 , the number of the mounting positions of the filter insert  12  corresponds to the number of the bores  44 . If there are several bores  44  and several pins, they can be arranged at regular intervals, so that several mounting positions are possible. The intervals between the bores and the pins can also be selected so that only certain installation variants are possible. 
     Instead of bores  44 , it is possible to provide rectangular elevations  45  alternating with indentations  46  on an annular surface  50 , as shown in the upper right portion of  FIG. 8 . The elevations  45  protrude axially above the annular surface  50  and the indentations  46  form a step down. Like the configuration of the bores  44 , the number and arrangement of the elevations  45  and the indentations  46  can be selected arbitrarily. 
     In the lower right portion of  FIG. 8 , the elevations  45  and indentations  46  are triangular and are distributed uniformly around the circumference of the hard component  26 . 
     In the lower left portion of  FIG. 8 , the elevations  45  are disposed along the outer periphery and the indentations  46  along the inner periphery, such that the elevations  45  are equidistant from each other, and the indentations  46  are equidistant from each other. 
       FIG. 9  illustrates a detail of a seal  15  with a keyed connection. The embodiment of the soft component  27  corresponds to that shown in  FIG. 6 . The cover  11  is not shown. The seal seat  28  of the housing  10  has a mating geometry which corresponds negatively to the elevations  45  and the indentations  46  of the hard component  26 . Thus, parts of the seal seat  28  project into the indentations  46  of the hard component  26 . Elevations  45  of the hard component  26  project into recesses in the seal seat  28 . This creates a keyed connection between the housing  10  and the filter insert  12  and prevents incorrect mounting of the filter insert  12 . 
     The foregoing description and examples have been set forth merely to illustrate the invention and are not intended to be limiting. Since modifications of the described embodiments incorporating the spirit and substance of the invention may occur to persons skilled in the art, the invention should be construed broadly to include all variations within the scope of the appended claims and equivalents thereof.