Flat filter element with at least two filter medium bodies, filter system and use of a flat filter element

Abstract

The invention relates to a flat-filter filter element (10) for filtering fluid, in particular for filtering air, for a filter system (100), in particular for an air-filter system of a fuel cell system, comprising an array of at least two planar filter-material bodies (12, 32) which are mutually adjacent in an axial direction (80) and through which the fluid can flow successively in the axial direction (80). At least portions of at least the outermost downstream filter-material body (32, 12) and of at least the outermost upstream filter-material body (12, 32) are arranged, viewed in the axial direction (80), radially inside a peripheral frame element (50). The outermost downstream filter-material body (32) is connected to the frame element (50) via a downstream peripheral molded element (40), and the outermost upstream filter-material body (12) is connected to the frame element via an upstream peripheral molded element (20). The invention also relates to a filter system (100) and to a use of a flat-filter filter element (10).

Description

[0001] Flat filter element with at least two filter medium bodies, filter system and use of a flat filter element

[0002] Technical area

[0003] The invention relates to a flat filter element for filtering a fluid, in particular for filtering air, for a filter system, in particular for an air filter system of a fuel cell system, as well as a filter system for filtering a fluid, in particular for filtering air, in particular of a fuel cell system, with such a flat filter element and a use of a flat filter element in a filter system.

[0004] State of the art

[0005] Fuel cell systems often require a particulate filter and an adsorption filter to filter both particulates and harmful gases from the intake air. The filter elements are often designed as flat filters, for example, but other filter element shapes are also available.

[0006] DE 102009 016 739 A1 discloses a housing for filtering the supply air of a fuel cell, comprising a lower housing part and an upper housing part, which together define a chamber. The chamber is divided by at least one filter element into a raw air chamber and a clean air chamber. Both the lower housing part and the upper housing part are each assigned an air outlet nozzle for directing supply air into or out of the chamber. The filter element is at least partially embedded in a sealing compound.

[0007] EP 3 520 878 B1 discloses a filter element for filtering indoor air, comprising at least three filter layers. The filter layers are arranged in a frame, and the frame is composed of extruded profile strips. The first filter layer serves as a pre-filter, the second filter layer as a fine filter, and the third filter layer as an adsorption filter. A region is provided for each filter layer in the frame. Furthermore, each profile strip has a protruding shoulder between the second and third filter layers, which serves to separate the second filter layer from the third filter layer in the region of the frame.

[0008] US 2015273985 A1 discloses an interior air filter element that can be installed as a replaceable filter element for an interior air filter for a driver's cab of agricultural and work machines, in particular with spraying or atomizing devices for crop protection or fertilizers, in a vehicle-mounted filter housing. The interior air filter element comprises a pre-filter layer, an adsorption filter layer, a fine filter layer, in particular for separating aerosols, and a filter element frame. The geometry of the filter element frame defines a flow direction along which the intake air flows through the aforementioned filter layers. The filter element frame has two regions. In the first region of the filter element frame, a first effective cross-sectional area is provided with respect to the flow of the intake air through the filter layers. In the second region, a corresponding second effective cross-sectional area is provided.The first and second areas are separated by a circumferential seal. The circumferential seal serves to separate the dirty side of the cabin air filter element from the clean side when the cabin air filter element is installed in the filter housing of the cabin air filter. The first area is located upstream of the seal, while the second area is located downstream of the seal. The second effective cross-sectional area is only a fraction of the first effective cross-sectional area. The filter layers are attached to the filter element frame by adhesive.

[0009] US 2021276401 A1 discloses a vehicle interior filter system comprising a filter module and a further filter module arranged downstream of the filter module. Each filter module comprises one or more filter elements. The filter elements of the filter module are folded with a first pleat spacing and comprise a gas filter element. The filter elements of the further filter module are folded with a second pleat spacing and comprise a particle filter element. The second pleat spacing is smaller than the first pleat spacing. The filter elements of a filter module are each arranged in a frame. The frame is sealed with a seal against a module housing in which the filter module is arranged. When installed in a filter housing, the module housing is sealed against the filter housing with a front-end seal.

[0010] Disclosure of the invention

[0011] An object of the invention is to provide a service-friendly and cost-effective flat filter element with at least two filter medium bodies for filtering a fluid, in particular for filtering air, for a filter system, in particular for an air filter system of a fuel cell system.

[0012] A further object is to provide a filter system for filtering a fluid, in particular for filtering air, in particular of a fuel cell system, with such a service-friendly and cost-effective filter element.

[0013] Another task is to specify a use of a flat filter element in a filter system.

[0014] The above-mentioned object is achieved according to one aspect of the invention by a flat filter element for filtering a fluid, in particular for filtering air, for a filter system, in particular for an air filter system of a fuel cell system, having an arrangement of at least two flat filter medium bodies arranged adjacent to one another in an axial direction, which are arranged so that the fluid can flow through them one after the other in the axial direction, wherein at least the outermost downstream filter medium body and at least the outermost upstream filter medium body are arranged at least partially in the axial direction radially within a circumferential frame element, wherein the outermost downstream filter medium body is connected to a downstream circumferential cast element and the outermost upstream filter medium body is connected to the frame element by a circumferential upstream cast element,wherein the upstream casting element is connected to an upstream end of the frame element and the downstream casting element is connected to a downstream end of the frame element.,

[0015] The further object is achieved by a filter system for filtering a fluid, in particular for filtering air, in particular of a fuel cell system, with a filter housing with a fluid inlet and a fluid outlet, and with at least one flat filter element which is arranged between the fluid inlet and the fluid outlet, wherein a sealing surface of a first housing part of the filter housing rests against the cast element of the flat filter element and wherein a housing wall of a second housing part of the filter housing is pressed against the cast element in a sealing manner on an opposite side of the sealing surface.

[0016] The further object is achieved by using a flat filter element in a filter system for filtering a fluid, in particular for filtering air, in particular for an air filter system of a fuel cell system.

[0017] Advantageous embodiments and advantages of the invention emerge from the further claims, the description and the drawing.

[0018] According to one aspect of the invention, a flat filter element for filtering a fluid, in particular for filtering air, for a filter system, in particular for an air filter system of a fuel cell system, is proposed, comprising an arrangement of at least two flat filter medium bodies arranged adjacent to one another in an axial direction, which are arranged so that the fluid can flow through them one after the other in the axial direction. At least the outermost downstream filter medium body and at least the outermost upstream filter medium body are arranged, at least in some regions, radially within a circumferential frame element in the axial direction. The outermost downstream filter medium body is connected to the frame element by a downstream circumferential cast element, and the outermost upstream filter medium body is connected to the frame element by a circumferential upstream cast element.The upstream casting member is connected to an upstream end of the frame member and the downstream casting member is connected to a downstream end of the frame member.

[0019] The proposed filter element can be advantageously used for the intake air of fuel cells. Adsorption of pollutants and particle filtration can advantageously each be carried out in different filter medium bodies. The two filter medium bodies, in turn, can be inserted into the frame element, e.g., a plastic frame element, from opposite sides during manufacture of the filter element. This makes it easy to create a firm connection between the respective filter medium body and the frame element. Sealing to the housing parts of the filter housing is achieved via a seal that is firmly attached to the separate frame element. The sealing element is expediently formed via the downstream cast element, which simultaneously represents the firm connection between the downstream filter medium body and the frame element.

[0020] The frame element can advantageously be manufactured by means of a conventional plastic injection molding process in which liquefied plastic material is injected under pressure into a tool mold and cured.

[0021] The upstream filter medium body is closer to the upstream side of the filter element than the downstream filter medium body, which is located closer to the downstream side of the filter element.

[0022] The cast element can be manufactured using a plastic casting or plastic foaming process, for example, from the casting material polyurethane (PUR), in a suitable mold. The casting material can be rigid or flexible foam.

[0023] The seal can be designed so that a counterforce of the housing components ensures the seal. The seal can then be pressed between the frame element and the housing components.

[0024] The filter element thus has a frame element that supports the two filter media bodies with a cast element. The two filter media bodies are firmly connected to the frame element via two separate cast elements.

[0025] In the proposed flat filter element, both filter medium bodies for the two filtration stages are arranged one behind the other in the flow direction in the form of flat filter medium bodies.

[0026] The two filter media bodies can be designed as a folded bellows, a wound body, a loose bed (primarily for adsorbing harmful gases), a coated honeycomb body (primarily for adsorbing harmful gases), or a combination thereof. The height of the filter media bodies in the axial direction can vary. The flow through the filter element is such that the filter media body designed as a particle filter is always flowed through first. The filter element can advantageously be sealed to the filter housing in the axial direction.

[0027] In fuel cell systems, for example, particles and harmful gases can be advantageously filtered out of the intake air.

[0028] This allows for better utilization of the available installation space, resulting in advantages in terms of adsorption capacity, dust capacity, separation efficiency, and pressure drop of the filter element.

[0029] According to a favorable embodiment of the filter element, the outermost downstream filter medium body can be connected to the frame element at one of its outer edges, in particular its downstream outer edge, by means of the downstream circumferential cast element. This allows a firm connection to the frame element, which can also be designed as a sealing element for sealing in the filter housing.

[0030] According to a favorable embodiment of the filter element, the downstream axial end of the frame element, in particular its end face, can be at least partially enclosed by the downstream cast element. Alternatively or additionally, the upstream axial end of the frame element, in particular its end face, can be at least partially enclosed by the upstream cast element. This allows a firm connection of the cast elements to the frame element to be achieved, which can also be designed as a sealing element for sealing in the filter housing.

[0031] According to a favorable design of the filter element, the frame element can have an outwardly folded collar at its downstream end. In particular, the collar can be embedded in the downstream cast element. This results in a firm interlock between the cast element and the frame element. Even filter media bodies with a higher weight and greater dimensions thus receive sufficient stability for installation in the filter housing.

[0032] According to a favorable embodiment of the filter element, the frame element can have a circumferential edge at its upstream end. In particular, the circumferential edge can have a groove directed axially away from the downstream cast element. The upstream filter medium body can be reliably connected to the frame element via the upstream cast element via the groove for receiving the casting material.

[0033] According to a favorable embodiment of the filter element, the groove can be designed as an integrated casting shell for the upstream cast element. In particular, the groove can protrude into the interior of the frame element. This allows the casting process during production of the upstream cast element to be carried out very efficiently. Tooling costs for an additional casting shell can be saved. The cast element does not take up any space on the outer side of the frame element, allowing the filter element to be advantageously inserted into the filter housing.

[0034] According to a favorable design of the filter element, the upstream filter medium body can protrude largely from the frame element in the axial direction and be embedded with its downstream outer edge into the upstream cast element. This allows the frame element to be kept relatively short in the axial direction, as it essentially only needs to have the height of the downstream filter medium body. This allows for savings in plastic material for the frame element.

[0035] According to a favorable design of the filter element, the upstream filter medium body can extend substantially axially into the frame element and be embedded with its upstream outer edge into the upstream cast element. In this embodiment, the upstream filter medium body is laterally covered and protected by the frame element. The filter element thus represents a compact unit that is advantageous to handle.

[0036] According to a favorable design of the filter element, the frame element can have interruptions for interlocking on its circumference in the area of ​​the upstream and / or downstream cast element. The interruptions for interlocking with the casting material of the cast element allow a reliable and permanent connection to be established between the cast elements and the frame element.

[0037] According to a favorable embodiment of the filter element, at least one stiffening element can be arranged flatly between the outermost upstream and the outermost downstream filter medium bodies. In particular, an extended stiffening grid and / or one or more glue beads can be arranged between the outermost upstream and the outermost downstream filter medium bodies. The stiffening element can contribute to stiffening the entire filter element, especially in the case of very large, flat filter elements. Furthermore, the upstream filter medium body can be supported against the flow pressure of the fluid to be filtered.

[0038] According to a favorable embodiment of the filter element, the at least one stiffening element can be designed as a stiffening grid that is supported on the frame element. In particular, the stiffening grid can be connected to the frame element. In particular, the stiffening grid can be formed integrally with the frame element. In this way, the stiffening element can advantageously contribute to the stability of the entire filter element, especially in the case of large-area filter elements.

[0039] According to a favorable embodiment of the filter element, at least one of the filter medium bodies can have a side band running around its outer circumference, which is at least partially embedded in the associated cast element. The side band seals the filter medium body at the side walls, which is particularly advantageous for filter medium bodies in the form of folded filter bellows or as fills. By integrating it into the cast element, the filter medium body can be reliably sealed along the flow path. The side band can be formed, for example, from a nonwoven material, in particular a filter fleece, filter fabric, or filter scrim. The nonwoven material of the side band can, in particular, have lower air permeability than a filter medium of the filter medium body and / or have higher flexural rigidity than a filter medium of the filter medium body.

[0040] According to a favorable embodiment of the filter element, the outermost downstream filter medium body can have an additional filter layer on its downstream side, wherein the additional filter layer can be at least partially embedded in the downstream cast element. This can, in particular, prevent the discharge of adsorption particles from the downstream filter medium body by the fluid flow. Preferred embodiments for the additional filter layer are filter media based on cellulose and / or synthetic fibers, in particular nonwoven materials, and / or filter membranes.

[0041] Advantageously, the filter medium bodies can be designed as a folded filter bellows, and / or as a wound body and / or as a bed, and / or as a coated honeycomb body.

[0042] According to a favorable embodiment of the filter element, the outermost upstream filter medium body can be designed as a particle filter. Alternatively or additionally, the outermost downstream filter medium body can be designed as an adsorption filter. The particle filter can be made of cellulose, for example. The adsorption filter can advantageously be designed as an activated carbon filter and / or an ion exchanger.

[0043] According to a favorable embodiment of the filter element, the downstream cast element can be designed as a sealing element for sealing, in particular in the axial direction, between a raw side and a clean side when the filter element is installed as intended in a filter housing of the filter system. In particular, the cast element can be arranged radially outside the at least two filter medium bodies and can be designed to seal between a first housing part and a second housing part of the filter housing of the filter system. In this way, the cast element can fulfill multiple functions and can be designed both for connecting the downstream filter medium body and for sealing the filter element to the filter housing.By arranging it outside the two filter medium bodies, the cast element can be effectively pressed between the two housing parts, thus ensuring both the seal between the raw side and the clean side of the filter system and the seal against the environment.

[0044] According to a favorable embodiment of the filter element, at least one of the two filter medium bodies can be designed as a folded filter bellows, wherein the end edges of the folds of at least one of the two filter medium bodies are sealed with an end edge bond. The end edge bond can be at least partially embedded in the downstream and / or upstream cast element. This ensures secure lateral sealing of the filter medium body via the end edge bond and connection to the cast element.

[0045] According to a further aspect of the invention, a filter system for filtering a fluid, in particular for filtering air, in particular of a fuel cell system, is proposed, comprising a filter housing with a fluid inlet and a fluid outlet, and with at least one flat filter element arranged between the fluid inlet and the fluid outlet. A sealing surface of a first housing part of the filter housing bears against the cast element of the flat filter element, and a housing wall of a second housing part of the filter housing is pressed sealingly against the cast element on an opposite side of the sealing surface. The proposed filter system with a flat filter element can advantageously be used for the intake air of fuel cells. Adsorption and particle filtration can advantageously take place in different filter medium bodies.The two filter media bodies of the filter element are inserted into the frame element, for example, a plastic frame element, from opposite sides. This creates a secure connection to the frame element. The seal to the housing parts of the filter housing is achieved via a gasket that is firmly attached to the separate frame element. The sealing element is expediently formed by the downstream cast element, which also represents the secure connection between the downstream filter media body and the frame element.

[0046] The seal can be designed so that a counterforce of the housing components ensures the seal. The seal can then be pressed between the frame element and the housing components.

[0047] In the proposed filter system with a flat filter element, both filter medium bodies for the two filtration stages are arranged one behind the other in the flow direction in the form of flat filter medium bodies.

[0048] The two filter media bodies can be designed as a folded bellows, a wound body, a loose bed (primarily for adsorbing harmful gases), a coated honeycomb body (primarily for adsorbing harmful gases), or a combination thereof. The height of the filter media bodies in the axial direction can vary. The flow through the filter element is such that the filter media body designed as a particle filter is always flowed through first. The filter element can advantageously be sealed to the filter housing in the axial direction.

[0049] This allows for better utilization of the available installation space, resulting in advantages in terms of adsorption capacity, dust capacity, separation efficiency, and pressure drop of the filter system.

[0050] According to a favorable embodiment of the filter system, the frame element can have a collar extending in a lateral direction, which is embedded in the cast element. The collar can be pressed together with the cast element between the sealing surface and the end of the housing wall. The cast element can be designed so that a counterforce of the housing parts ensures the seal. The seal can then be pressed between the frame element and the housing parts. By embedding the collar of the frame element, the cast element has increased rigidity, and the filter element is securely fixed in the filter housing.

[0051] According to a further aspect of the invention, the use of a flat filter element in a filter system for filtering a fluid, in particular for filtering air, is proposed, in particular for an air filter system of a fuel cell system. The filter element can advantageously be designed as a particle filter and / or an adsorption filter, in particular as an activated carbon filter and / or as an ion exchanger. In this way, for example, in fuel cell systems, particles as well as harmful gases can be advantageously filtered from the intake air.

[0052] Short description of the drawings

[0053] Further advantages will become apparent from the following description of the drawings. The drawings illustrate exemplary embodiments of the invention. The drawings, the description, and the claims contain numerous features in combination. Those skilled in the art will also expediently consider the features individually and combine them into useful further combinations.

[0054] Examples include:

[0055] Fig. 1 is an isometric view of a filter system for filtering a fluid, in particular for

[0056] Filtering air, in particular a fuel cell system, according to an embodiment of the invention;

[0057] Fig. 2 is an isometric exploded view of the filter system according to Figure 1;

[0058] Fig. 3 a sectional view of the filter system according to Figure 1 with the filter element and marked

[0059] Excerpt IV;

[0060] Fig. 4 shows the enlarged section IV according to Figure 3 with the filter element;

[0061] Fig. 5 is an enlarged section of a sectional view of a filter system according to a further embodiment of the invention;

[0062] Fig. 6 shows a longitudinal section of a filter element according to a further embodiment of the

[0063] Invention with a marked section VII; and

[0064] Fig. 7 shows the enlarged section VII from the longitudinal section of the filter element according to Figure 6.

[0065] Embodiments of the invention

[0066] In the figures, identical or similar components are numbered with the same reference numerals. The figures show only examples and are not to be understood as limiting.

[0067] The directional terminology used below, including terms such as "left," "right," "top," "bottom," "before," "behind," "after," and the like, is intended solely to enhance understanding of the figures and is in no way intended to limit the scope of the invention. The components and elements depicted, as well as their design and use, may vary according to the considerations of a person skilled in the art and may be adapted to specific applications.

[0068] Figure 1 shows an isometric view of a filter system 100 for filtering a fluid, in particular for filtering air, in particular of a fuel cell system, according to an embodiment of the invention. Figure 2 shows an isometric exploded view of the filter system 100.

[0069] The filter system 100 comprises a filter housing 110 with a fluid inlet 102 and a fluid outlet 104, and with at least one flat filter element 10 arranged between the fluid inlet 102 and the fluid outlet 104. The fluid inlet 102 is arranged in a second housing part 114, and the fluid outlet 104 is arranged in a first housing part 112.

[0070] The filter element 10 has a circumferential frame element 50 (Figure 2) with a circumferential cast element 40 designed as an axial sealing element. When the filter element 10 is properly arranged in the second housing part 114 and the filter housing 110 is closed by the first housing part 112, the cast element 40 seals the interior of the filter housing 110 from the environment. At the same time, the cast element 40 seals a raw side 60 inside the filter housing 110 from a clean side 62 (Figure 3).

[0071] The outflow side 44 of the filter element 10 is directed in the direction of the fluid outlet 104 to the first housing part 112.

[0072] When the filter element 10 is inserted, screw tabs 58 of the frame element 50 of the filter element 10 are arranged between screw domes 124 and screw tabs 120 on the housing side and are screwed together by means of screws 122 (Figure 4).

[0073] Figure 3 shows a sectional view of the filter system 100 with the filter element 10 and marked section IV. Figure 4 shows the enlarged section IV with the filter element 10.

[0074] The flat filter element 10 comprises an arrangement of two flat filter medium bodies 12, 32 arranged one behind the other, adjacent to one another in an axial direction 80. The two filter medium bodies 12, 32 are arranged so that the fluid can flow through them one after the other in the axial direction 80. The flow direction 90 is marked with an arrow in Figure 3. The fluid enters the filter element 10 from the inflow side 29 and exits the filter element 10 at the outflow side 44.

[0075] The upstream filter medium body 12 is designed as a particle filter, while the downstream filter medium body 32 is designed as an adsorption filter.

[0076] The filter medium bodies 12, 32 can be designed, for example, as a folded filter bellows, and / or as a wound body, and / or as a loose bed, and / or as a coated honeycomb body. The particle filter can be made of cellulose, for example, and the adsorption filter can be an activated carbon filter and / or an ion exchanger, for example. In the embodiment shown in Figures 3 and 4, both filter medium bodies 12, 32 are designed as folded filter bellows.

[0077] The downstream filter medium body 32 and the outermost upstream filter medium body 12 are arranged at least partially radially within the circumferential frame element 50 in the axial direction 80. The downstream filter medium body 32 is connected to the frame element 50 by a downstream circumferential cast element 40, and the upstream filter medium body 12 is connected to the frame element 50 by a circumferential upstream cast element 20.

[0078] The upstream casting element 20 is connected to an upstream end of the frame element 50 and the downstream casting element 40 is connected to a downstream end of the frame element 50.

[0079] In this case, the upstream and / or downstream axial end of the frame element 50, in particular its end face, as can be seen in Figure 4, can be at least partially enclosed by the upstream or downstream cast element 20, 40.

[0080] The downstream filter medium body 32 is connected to the frame element 50 at one of its outer edges 38, 39, here at its downstream outer edge 38, by means of the downstream circumferential cast element 40.

[0081] As can be seen particularly in Figure 4, the frame element 50 has, at its downstream end, a collar 51 which is folded outward in the lateral direction 82 and is embedded in the downstream cast element 40. When the filter element 10 is inserted into the filter housing 110 as intended, the collar 51 is pressed with the cast element 40 between the sealing surface 126 and the end 128 of the housing wall 118.

[0082] The frame element 50 also has a circumferential edge 24 at its upstream end, which has a groove 25 directed in the axial direction 80 away from the downstream cast element 40. The groove 25 projects into the interior of the frame element 50. The groove 25 is designed as an integrated casting shell for the upstream cast element 20.

[0083] If, for example, polyurethane (PUR) is used as the casting material for the cast element 20, polyamide (PA) can advantageously be used as the plastic material for the frame element 50 in order to ensure a good connection of the cast element 20 to the groove 25.

[0084] As can be seen in Figure 4, the cast element 20 fills the groove 25. A portion of the outermost folds 22 of the upstream filter medium body 12 is thereby connected to the cast element 20.

[0085] The upstream filter medium body 12 protrudes largely from the frame element 50 in the axial direction 80 and is embedded with its downstream outer edge 18 in the upstream cast element 20.

[0086] The downstream cast element 40 is designed as an axial sealing element for sealing between the raw side 60 and the clean side 62. The cast element 40 is arranged radially outside the filter medium bodies 12, 32 and simultaneously seals between the first housing part 112 and the second housing part 114. A sealing surface 126 of the first housing part 112 bears against the cast element 40, and the housing wall 118 of the second housing part 114 is pressed sealingly against the cast element 40 on the opposite side of the sealing surface 126.

[0087] Advantageously, the frame element 50 can have interruptions (not shown) on its circumference in the region of the upstream and / or downstream casting element 20, 40 for interlocking with the casting material.

[0088] A stiffening element 30 is arranged flatly between the outermost upstream and the outermost downstream filter medium bodies 12, 32. In the illustrated embodiment, the stiffening element 30 is designed as an extended stiffening grid. Alternatively or additionally, the filter medium bodies 12, 32 can also be stiffened by one or more glue beads.

[0089] The stiffening element 30 can advantageously be supported on the frame element 50. Optionally, the stiffening element 30 can also be connected to the frame element 50, in particular formed integrally with the frame element 50.

[0090] As can be further seen in Figure 4, one filter medium body 32 has a side band 48 running around its outer circumference 46 for laterally sealing the filter medium body 32, which is at least partially embedded in the associated cast element 40.

[0091] The side band 48 can be formed, for example, from a nonwoven material, in particular a filter fleece, filter fabric, or filter scrim. The nonwoven material of the side band 48 can, in particular, have a lower air permeability than a filter medium of the filter medium body 32 and / or a higher flexural rigidity than a filter medium of the filter medium body 32.

[0092] On its downstream side 44, the downstream filter medium body 32 has an additional filter layer 56. The additional filter layer 56 is at least partially embedded in the downstream cast element 40. Preferred embodiments for the additional filter layer 56 are filter media based on cellulose and / or synthetic fibers, in particular nonwoven materials, and / or filter membranes.

[0093] The sectional view in Figure 4 also shows how the screw tab 58 of the frame element 50 is arranged between the screw dome 124 of the housing wall 118 of the second housing part 114 and the housing-side screw tab 120 of the housing wall 116 of the first housing part 112 and is screwed together by means of the screw 122. As a result, the filter element 10 is firmly fixed in the filter housing 110, and the two housing parts 112, 114 of the filter housing 110 are firmly closed and sealed by the downstream cast element 40. Figure 5 shows an enlarged section of a sectional view of a filter system 100 according to a further embodiment of the invention.

[0094] In this exemplary embodiment, the end edges 23 of folds 22 of the upstream filter medium body 12 are sealed with a front edge bond 28. The individual folds 22 are not visible in this illustration because they run perpendicular to the image plane. The front edge bond 28 on the outer edge 18 of the filter medium body 12 is at least partially embedded in the upstream cast element 20.

[0095] The downstream filter medium body 32 is designed as in the embodiment shown in Figures 3 and 4.

[0096] Figure 6 shows a longitudinal section of a filter element 10 according to a further embodiment of the invention with the marked section VII. Details are shown in the enlarged section VII in Figure 7.

[0097] The illustrated embodiment differs essentially in the connection of the upstream filter medium body 12 from the embodiments in Figures 3 to 5. The wall 52 of the frame element 50 is extended, so that the upstream filter medium body 12 projects largely into the frame element 50 in the axial direction 80. The upstream cast element 20 is arranged at the axial end 54 of the wall 52. The filter medium body 12 is embedded with its upstream outer edge 19 in the upstream cast element 20.

[0098] In this embodiment, too, an optional stiffening element 30 can be arranged between the two filter medium bodies 12, 32, as shown.

[0099] Reference symbol

[0100] 10 filter element

[0101] 12 filter medium bodies

[0102] 18 Outer edge

[0103] 19 Outer edge

[0104] 20 upstream cast element

[0105] 22 folds

[0106] 23 Front edge

[0107] 24 Rand

[0108] 25 grooves

[0109] 28 End edge gluing

[0110] 29 Inflow side

[0111] 30 stiffening grids

[0112] 32 filter medium bodies

[0113] 38 outer edge

[0114] 39 outer edge

[0115] 40 downstream cast element

[0116] 44 Downstream side

[0117] 46 outer circumference

[0118] 48 sideband

[0119] 50 frame element

[0120] 51 collar

[0121] 52 wall

[0122] 54 axial end

[0123] 56 filter layer

[0124] 58 screw connection tab

[0125] 60 raw pages

[0126] 62 Clean side

[0127] 80 axial direction

[0128] 82 lateral direction

[0129] 90 Flow direction

[0130] 100 filter system

[0131] 102 Fluid inlet

[0132] 104 Fluid outlet

[0133] 1 10 filter housing

[0134] 1 12 first housing part

[0135] 114 second housing part

[0136] 1 16 Housing wall

[0137] 1 18 Housing wall 120 Screw connection tab

[0138] 122 screw

[0139] 124 screw dome

[0140] 126 Sealing surface 128 End

Claims

Claims 1 . Flat filter element (10) for filtering a fluid, in particular for filtering air, for a filter system (100), in particular for an air filter system of a fuel cell system, having an arrangement of at least two flat filter medium bodies (12, 32) arranged adjacent to one another in an axial direction (80), which are arranged so that the fluid can flow through them one after the other in the axial direction (80), wherein at least the outermost downstream of the filter medium bodies (32, 12) and at least the outermost upstream of the filter medium bodies (12, 32) are arranged at least partially in the axial direction (80) radially within a circumferential frame element (50), wherein the outermost downstream filter medium body (32) is provided with a downstream circumferential cast element (40) and the outermost upstream filter medium body (12) is provided with a circumferential upstream cast element (20) with is connected to the frame element (50),wherein the upstream cast element (20) is connected to an upstream end of the frame element (50) and the downstream cast element (40) is connected to a downstream end of the frame element (50).

2. Filter element according to claim 1, wherein the outermost downstream filter medium body (32) is connected to the frame element (50) at one of its outer edges (38, 39), in particular its downstream outer edge (38), by means of the downstream circumferential cast element (40).

3. Filter element according to claim 1 or 2, wherein the downstream axial end of the frame element (50), in particular its end face, is at least partially enclosed by the downstream cast element (40) and / or wherein the upstream axial end of the frame element (50), in particular its end face, is at least partially enclosed by the upstream cast element (20).

4. Filter element according to one of the preceding claims, wherein the frame element (50) has an outwardly folded collar (51) at its downstream end, in particular wherein the collar (51) is embedded in the downstream cast element (40).

5. Filter element according to one of the preceding claims, wherein the frame element (50) has a circumferential edge (24) at its upstream end, in particular wherein the circumferential edge (24) has a groove (25) directed in the axial direction (80) away from the downstream cast element (40).

6. Filter element according to claim 5, wherein the groove (25) is designed as an integrated casting shell for the upstream casting element (20), in particular wherein the groove (25) projects into the interior of the frame element (50).

7. Filter element according to one of the preceding claims, wherein the upstream filter medium body (12) projects largely out of the frame element (50) in the axial direction (80) and is embedded with its downstream outer edge (18) in the upstream cast element (20).

8. Filter element according to one of claims 1 to 5, wherein the upstream filter medium body (12) projects largely into the frame element (50) in the axial direction (80) and is embedded with its upstream outer edge (19) in the upstream cast element (20).

9. Filter element according to one of the preceding claims, wherein the frame element (50) has interruptions for toothing on its circumference in the region of the upstream and / or downstream cast element (20, 40).

10. Filter element according to one of the preceding claims, wherein at least one stiffening element (30) is arranged flatly between the outermost upstream and the outermost downstream filter medium body (12, 32), in particular an extended stiffening grid and / or one or more glue beads are arranged.

11. Filter element according to claim 10, wherein the at least one stiffening element (30) is designed as a stiffening grid which is supported on the frame element (50), in particular wherein the stiffening grid is connected to the frame element (50), in particular is formed in one piece with the frame element (50).

12. Filter element according to one of the preceding claims, wherein at least one of the filter medium bodies (32) has a side band (48) running around its outer circumference (46) and being at least partially embedded in the associated cast element (40).

13. Filter element according to one of the preceding claims, wherein the outermost downstream filter medium body (32) has an additional filter layer (56) on its downstream side (44), wherein the additional filter layer (56) is at least partially embedded in the downstream cast element (40).

14. Filter element according to one of the preceding claims, wherein the outermost upstream filter medium body (12) is designed as a particle filter, and / or wherein the outermost downstream filter medium body (32) is designed as an adsorption filter.

15. Filter element according to one of the preceding claims, wherein the downstream cast element (40) is designed as a sealing element for sealing between a raw side (60) and a clean side (62) when the filter element (10) is installed as intended in a filter housing (110) of the filter system (100), in particular wherein the cast element (40) is arranged radially outside the at least two filter medium bodies (12, 32) and is designed for sealing between a first housing part (112) and a second housing part (114) of the filter housing (110) of the filter system (100).

16. Filter element according to one of the preceding claims, wherein at least one of the two filter medium bodies (12, 32) is designed as a folded filter bellows, wherein end edges (23) of folds (22) of at least one of the two filter medium bodies (12, 32) are sealed with an end edge bond (28), wherein the end edge bond (28) is at least partially embedded in the downstream and / or upstream cast element (40, 20).

17. Filter system (100) for filtering a fluid, in particular for filtering air, in particular a fuel cell system, with a filter housing (110) with a fluid inlet (102) and a fluid outlet (104), and with at least one flat filter filter element (10) according to one of the preceding claims, which is arranged between the fluid inlet (102) and the fluid outlet (104), wherein a sealing surface (126) of a first housing part (112) of the filter housing (110) bears against the cast element (40) of the flat filter filter element (10) and wherein a housing wall (118) of a second housing part (114) of the filter housing (110) is pressed against the cast element (40) in a sealing manner on an opposite side of the sealing surface (126).

18. Filter system according to claim 17, wherein the frame element (50) has a collar (51) extending in a lateral direction (82) which is embedded in the cast element (40), wherein the collar (51) is pressed with the cast element (40) between the sealing surface (126) and the end (128) of the housing wall (118).

19. Use of a flat filter element (10) according to one of claims 1 to 16 in a filter system (100) according to claim 17 or 18, for filtering a fluid, in particular for filtering air, in particular for an air filter system of a fuel cell system.