Filter element of a filter, multi-layer filter medium of a filter and filter

Abstract

Filter element (10) of a filter for filtering fluid in the form of urea solution, in particular of an internal combustion engine, in particular of a motor vehicle, with a multi-layer filter medium (12; 112; 212; 312; 412; 512), through which the fluid can flow for filtration and which has at least one filtration layer (32; 132) and at least one support layer (34; 134), wherein at least one filtration layer (132) has a nonwoven fabric, characterized in that at least one further filtration layer (32) is at least partially meltblown, that the at least one support layer (134) is designed as a grid, so that it can support the filter medium (12; 112; 212; 312; 412; 512) against pressures, the pressure gradients transversely or obliquely to the flow direction (26) of the fluid through the filter medium (12; 112; 212; 312; 412; 512) and that all layers of the filter medium are hydrophilic and made of polyamide.

Description

Technical area

[0001] The invention relates to a filter element of a filter for filtering fluid, in the form of urea solution, in particular of an internal combustion engine, in particular of a motor vehicle, with a multi-layer filter medium through which the fluid can flow for filtration and which has at least one filtration layer and at least one support layer.

[0002] Furthermore, the invention relates to a multi-layer filter medium of a filter for filtering fluid, in the form of urea solution, in particular of an internal combustion engine, in particular of a motor vehicle, which can be flowed through by the fluid for filtration and which has at least one filtration layer and at least one support layer.

[0003] Furthermore, the invention relates to a filter for filtering fluid, in the form of urea solution, in particular of an internal combustion engine, in particular of a motor vehicle, with a multi-layer filter medium through which the fluid can flow for filtration and which has at least one filtration layer and at least one support layer. State of the art

[0004] DE 10 2011 003 585 A1 discloses a urea filter material for a urea filter with three layers: a base layer, a cover layer, and an intermediate filter layer. All layers are made of polypropylene, in particular a polypropylene fleece. The base layer consists of a more stable polypropylene fleece, which primarily provides support for the filter layer. The filter layer, on the other hand, consists of a more voluminous polypropylene fleece to guarantee the desired filtering effect through a suitable pore size. The cover layer, in turn, is intended to ensure that the soft filter layer is not destroyed by mechanical friction. It is therefore made of a comparatively thin and smooth polypropylene fleece.

[0005] From the published patent application DE 29 48 925 A1, a tubular filter element with folded filter media sections arranged in groups is known, wherein the filter medium is arranged between two perforated arches for stabilization and wherein support wedges made of solid material support the outer side surfaces of the end folds and secure them against displacement.

[0006] A tubular filter element with several paper filter layers and a rigid support element outside the outermost and / or inside the innermost filter layer is described in the document US 4 033 881 A.

[0007] WO 2010 / 106 087 A1 describes a filter element for filtration of fuel with a pre-filter layer and a fine filter layer, wherein a support layer is attached to the raw side of the pre-filter layer and to the clean side of the fine filter layer to absorb longitudinal and transverse forces.

[0008] From DE 10 2010 011 512 A1 a filter medium with a non-woven filter layer made of synthetic individual fibers and an increasing particle separation efficiency in the direction of flow is known.

[0009] DE 198 54 565 A1 discloses a multi-layer filter medium with a main filter layer made of meltblown fleece, a paper layer for support without a filtration function and a pre-filter layer, which can also have a protective and supporting function.

[0010] From WO 2004 / 082 804 A1 a fuel filter with a particle filter and an upstream coalescer element is known.

[0011] The invention is based on the object of designing a filter element, a multi-layer filter medium and a filter of the type mentioned at the outset, in which / with which the service life and / or robustness is improved. Disclosure of the invention

[0012] This object is achieved according to one aspect of the invention by a filter element according to claim 1. In the filter element according to the invention, the at least one support layer is designed as a grid so that it can support the filter medium against pressures that have pressure gradients transversely or obliquely to the flow direction of the fluid through the filter medium.

[0013] Advantageously, the pressures can be directed substantially in the direction of flow of the fluid through the filter medium.

[0014] Advantageously, the support layer also serves to increase the inherent rigidity of the filter medium, thereby improving its processability. For example, it prevents the filter medium from buckling when pressed into a molten end plate.

[0015] The filter medium is composed of several layers. The layers can each have different properties with regard to their filtering properties, in particular pore size and / or pore density, and / or their mechanical properties, in particular pressure stability and / or dimensional stability and / or inherent rigidity. In this way, the layers can each be optimized with regard to their function. For filter layers with correspondingly small pore sizes, it is thus possible to dispense with the need for them to also be mechanically stable. At least two layers of the filter medium can advantageously be connected to one another. In particular, they can be connected to one another over a large area.

[0016] According to the invention, the at least one support layer is designed such that it can also compensate for pressure loads that are limited in area and almost point-like. It can thus also protect the other layers of the filter medium against singular pressure loads. Such pressure loads have a pressure gradient transverse or oblique to a flow direction of the fluid through the filter medium. Thus, the at least one support layer can better protect the entire filter medium from mechanical stress. The at least one support layer can thus also support the filter medium against pressure differences between the upstream and downstream sides that are uniform along the surface area of the layers of the filter medium, in particular transverse or oblique to the flow direction.

[0017] Advantageously, the at least one support layer can be resistant to frost and / or ice pressure. Frost and ice pressure can exert compressive loads on the filter medium, which exhibit a pressure gradient along the surface area of the filter medium. Thus, the at least one support layer can reliably and permanently stabilize the filter medium even when the fluid, in particular the urea solution, is cooled below its freezing point.

[0018] In addition, the at least one support layer can provide protection against ice impact. Particularly when using the filter element at low temperatures, especially below the freezing point of the fluid, ice particles may form in the fluid. The ice particles can exert almost point-like stress on the filter medium. Pressures from ice particles can cause correspondingly large pressure gradients.

[0019] Advantageously, the inherent rigidity of the filter medium can be achieved, or at least improved, by the at least one support layer. In this way, the filter medium can be more easily shaped and held in a corresponding manner. In particular, the filter medium can be folded, in particular pleated, more easily. After folding, the filter medium can better retain its shape thanks to the at least one support layer. Due to the improved inherent rigidity, the filter medium can be more easily connected to at least one corresponding frame element, in particular an end body, in particular an end plate, of the filter element. In particular, the filter medium can be welded, glued, or connected in another way, in particular mechanically, to the at least one frame element by means of the at least one support layer. It is also conceivable to injection-mold the frame element onto the filter medium.

[0020] The at least one support layer can additionally have flow-influencing, in particular flow-guiding, properties at least in sections. In this way, depending on the arrangement of the at least one support layer in the filter medium, the inflow of the fluid into the filter medium and / or the outflow of the fluid from the filter medium can be improved. Thus, the at least one support layer can also improve fluid drainage. Furthermore, a pressure difference between the upstream and downstream sides of the filter medium can be reduced.

[0021] To achieve the special support function against pressures with corresponding pressure gradients, the at least one support layer can have special properties. These special properties can be characterized, in particular, by a special structure and / or a special manufacturing method and / or a special material composition and / or special material properties.

[0022] In an advantageous embodiment, at least one support layer can comprise a fabric. Due to the special properties of the fabric, the special support function of the at least one support layer against pressures with corresponding pressure gradients can be improved. In particular, a fabric can absorb, transmit, and / or compensate for tensile loads and compressive loads transversely or obliquely to the flow direction of the fluid through the filter medium. A yarn diameter of a support layer with / made of fabric (fabric support layer) can advantageously be between approximately 100 µm and approximately 500 µm, preferably between approximately 300 µm and approximately 450 µm. A thickness of a fabric support layer can advantageously be between approximately 300 µm and approximately 900 µm, preferably between approximately 500 µm and approximately 800 µm. A basis weight of a fabric support layer can advantageously be between approximately 100 g / m 2 and about 300 g / m 2 , preferably between about 200 g / m 2and about 280 g / m 2 , amount to.

[0023] The thickness of a layer of the filter medium within the meaning of the invention is its extension approximately in the direction of the mean flow direction of the fluid through the filter medium.

[0024] According to the invention, the at least one support layer is a grid. Due to the special properties of the grid, the special support function of the at least one support layer against pressures with corresponding pressure gradients can be improved. In particular, a grid can absorb, transmit, and compensate for tensile loads and compressive loads transversely or obliquely to the flow direction of the fluid through the filter medium. The at least one support layer with / consisting of the grid (grid support layer) can advantageously have a thickness between approximately 500 µm and approximately 1300 µm, preferably between approximately 700 µm and approximately 1100 µm. The basis weight of the at least one grid support layer can be approximately between 50 g / m 2 and about 250 g / m 2, preferably between about 150 g / m 2 and about 230 g / m 2 , amount to.

[0025] In a further advantageous embodiment, at least one support layer can additionally comprise a spunbonded fabric. Spunbonded fabric can also be referred to as spunbond. Due to the special properties of the spunbonded fabric, the special support function of the at least one support layer against pressures with corresponding pressure gradients can be improved. In particular, spunbonded fabric can absorb, transmit, and compensate for tensile loads and compressive loads transversely or obliquely to the flow direction of the fluid through the filter medium. The thickness of a support layer with / made of spunbonded fabric (spunbonded support layer) can advantageously be between 300 µm and 1000 µm. The basis weight of a spunbonded support layer can advantageously be between 70 g / m 2 and about 250 g / m 2 , preferably between about 100 g / m 2 and about 170 g / m 2A spunbonded nonwoven support layer can advantageously have an air permeability of about 250 l / m 2 s to about 3000 l / m 2 s, preferably between about 500 l / m 2 s and about 1500 l / m 2 s. Fiber diameters of the fibers of a spunbonded nonwoven support layer can advantageously be between about 1 µm and about 50 µm.

[0026] In addition, the special support function against pressures with corresponding pressure gradients can be achieved by special arrangement of the at least one support layer in the multi-layer filter medium relative to the other layers and / or relative to the upstream side and / or the downstream side of the filter medium.

[0027] The specific properties of the at least one support layer can advantageously also be predetermined depending on the specific arrangement of the at least one support layer in the filter medium, or vice versa. The specific properties and the specific arrangement of the at least one support layer can be combined accordingly to achieve optimal filtration properties and / or an optimal service life of the filter element.

[0028] In a further advantageous embodiment, at least one filtration layer can be arranged behind at least one support layer with respect to the flow of the fluid through the filter medium. In this way, the at least one support layer can protect the at least one filtration layer from large particles, in particular ice impact. The at least one support layer can also act as a pre-filtration layer for the actual filtration layer. By filtering out large particles with the at least one support layer, the loading of the at least one filtration layer can be delayed. This can increase the service life of the filter medium and thus of the filter element.

[0029] In a further advantageous embodiment, at least one support layer can be arranged on an upstream side of the filter medium. In this way, the at least one support layer can protect all other layers of the filter medium from larger particles, in particular from ice impact. Furthermore, loading of the downstream, finer filtration layers can be delayed. The at least one support layer can advantageously have flow-influencing properties, which can improve the inflow of the fluid into the filter medium.

[0030] In a further advantageous embodiment, at least one filtration layer can be arranged upstream of the at least one support layer with respect to the flow of the fluid through the filter medium. In this way, the at least one filtration layer can be better supported on the at least one support layer. In particular, pressures of the fluid acting on the at least one filtration layer, in particular with a pressure gradient oblique or transverse to the flow direction, can be distributed more evenly across the at least one support layer.

[0031] In a further advantageous embodiment, at least one support layer can be arranged on a downstream side of the filter medium. In this way, the other layers of the filter medium, which are arranged upstream of the at least one support layer in the direction of fluid flow, can be better supported against the at least one support layer. The stability of the filter element during filter operation can thus be further improved. If the at least one support layer additionally has flow-influencing properties, it can improve the outflow of the fluid from the filter medium. Drainage is improved in particular by the fact that the filtration layer is kept at a distance by the support layers, thus ensuring the flow through.

[0032] Alternatively or additionally, at least one support layer can advantageously be located as an intermediate layer between two other, even different, layers of the filter medium. In this way, layers located on the upstream side can be supported against the at least one support layer. Furthermore, the at least one support layer can serve as a prefilter for layers located downstream in the flow direction.

[0033] According to the invention, all layers of the filter medium are hydrophilic. This results in good wettability of the filter medium with the fluid when filtering a urea solution.

[0034] The at least one filtration layer can advantageously have pore openings that are smaller than the smallest particles that can occur in the fluid, i.e., the urea solution. In this way, the particles can be reliably filtered out.

[0035] Preferably, the filtration layer has a gradient structure, i.e. the packing density increases in the flow direction.

[0036] At least one filtration layer comprises a nonwoven fabric. For example, a nonwoven fabric made of staple fibers can be used. The at least one filtration layer with / made of nonwoven fabric (nonwoven filtration layer) can have a thickness between about 400 µm and about 1500 µm. A basis weight of the at least one nonwoven filtration layer can advantageously be between about 150 g / m 2 and about 500 g / m 2 The at least one nonwoven filtration layer can advantageously have an air permeability of between about 80 l / m 2 s and about 250 l / m 2 s. A fiber diameter of the at least one nonwoven filtration layer can advantageously be between about 4 µm and about 200 µm.

[0037] Furthermore, at least one filtration layer is at least partially meltblown. Meltblown media within the meaning of the invention are referred to as "meltblown." The at least one meltblown filtration layer can advantageously have a thickness between about 200 µm and about 1000 µm. The at least one meltblown filtration layer can advantageously have a basis weight between about 50 g / m 2 and about 150 g / m 2 The at least one meltblown filtration layer can advantageously have an air permeability of between about 80 l / m 2 s and about 170 l / m 2 s. Advantageously, a fiber diameter of the at least one meltblown filtration layer can be between about 0.1 µm and about 15 µm.

[0038] The terms meltblown and spunbond are defined, for example, in “Nonwovens: Raw materials, production, application, properties, testing, 2nd edition, 2012, Weinheim”, ISBN: 978-3-527-31519-2.

[0039] In a further advantageous embodiment, the filter medium can have at least one barrier layer. The at least one barrier layer can prevent fibers, in particular nonwoven fibers, from being washed out of the filter medium from the layers preceding it in the direction of fluid flow. In this way, the component cleanliness of the filter element can be increased. Advantageously, the at least one barrier layer can be arranged downstream of the at least one filtration layer in the direction of fluid flow.

[0040] The at least one barrier layer can advantageously be located on the downstream side of the filter medium. In this way, the at least one barrier layer can capture the particles or fibers flowing through or flushed out by all previous layers of the filter medium in the flow direction. The cleanliness of the outflowing fluid can thereby be further improved.

[0041] In a further advantageous embodiment, the at least one barrier layer can comprise a spunbonded fabric. The at least one barrier layer can advantageously be a spunbonded fabric. The at least one barrier layer with / made of spunbonded fabric (spunbond barrier layer) can advantageously have a thickness between approximately 100 µm and approximately 300 µm. Advantageously, the at least one spunbond barrier layer can have a basis weight between approximately 15 g / m 2 and about 80 g / m 2 The air permeability of the at least one spunbond barrier layer can advantageously be between about 250 l / m 2 s and about 3000 l / m 2 s. At least one spunbond barrier layer can advantageously have a fiber diameter between 1 µm and 50 µm.

[0042] In a further advantageous embodiment, the filter medium can have at least one ultra-fine filter layer. The at least one ultra-fine filter layer can advantageously have a smaller pore size than the at least one filtration layer. The at least one ultra-fine filter layer can advantageously be arranged downstream of the at least one filtration layer in the flow direction of the fluid. In this way, the smallest particles that can pass through the at least one filtration layer can be filtered out of the fluid with the at least one ultra-fine filter layer. Larger particles can be filtered out first with the at least one filtration layer. These particles therefore do not reach the at least one ultra-fine filter layer. The loading of the at least one ultra-fine filter layer can thus be delayed. The multi-stage filtration can improve the separation efficiency.Furthermore, the requirements for the individual layers, in particular for the at least one filtration layer, can be reduced. This simplifies the manufacturing process for the individual layers, in particular the at least one filtration layer. Furthermore, the multi-stage filtration can increase the service life of the filter element.

[0043] The at least one ultrafine filter layer can advantageously be arranged on the downstream side of the filter medium. In this way, the at least one ultrafine filter layer can also filter out smaller particles that can pass through the preceding layers in terms of flow.

[0044] Alternatively or additionally, at least one ultrafine filter layer can advantageously be arranged upstream of at least one support layer in the direction of fluid flow. In this way, the at least one ultrafine filter layer can be supported on the at least one support layer.

[0045] In a further advantageous embodiment, the at least one ultra-fine filter layer can be at least partially meltblown. In particular, the at least one ultra-fine filter layer can be a meltblown ultra-fine filter layer. The at least one meltblown ultra-fine filter layer can advantageously have a thickness of between about 100 µm and about 500 µm. It can advantageously have a basis weight of between about 15 g / m 2 and about 100 g / m 2 The air permeability of the at least one meltblown fine filter layer can advantageously be between about 40 l / m 2 s and about 100 l / m 2 s. The at least one meltblown ultrafine filter layer can advantageously have fiber diameters between about 0.1 µm and about 15 µm.

[0046] In the field of internal combustion engines, especially diesel engines, urea solutions are used in exhaust gas treatment systems to reduce emissions, especially nitrogen emissions. The urea solution is purified using special urea filters. This removes any particles present in the urea solution. When the filter element is used in a urea filter, the at least one filtration layer serves to filter the urea solution.

[0047] The urea solution can be a urea water solution (HWL) and / or another type of urea solution, in particular with guanidine (iminourea), guanidine salts or guanidine esters.

[0048] Extensive studies have shown that the service life of the filter media, the filter elements and the filters, especially for urea solution, depends on the materials from which the filter media are made.

[0049] Advantageously, the multi-layer filter medium according to the invention is fully synthetic. Fully synthetic filter media are more resistant to urea solution and other particularly aggressive fluids than cellulose, in particular. Fully synthetic filter media can also be used to create long-life components.

[0050] According to the invention, all layers of the filter medium are made of the same material. This simplifies connections between the layers and / or the layers to at least one frame element, in particular an end body, of the filter element.

[0051] According to the invention, all layers of the filter medium are made of polyamide (PA). Polyamide has a higher resistance to urea solution or other particularly aggressive fluids than cellulose or polybutylene terephthalate (PBT). This allows for increased service life and durability of the filter element.

[0052] In a further advantageous embodiment, the filter element can be a hollow filter element. In the hollow filter element, the multi-layer filter medium can surround a cavity of the filter element in a closed manner at least in one circumferential direction. The flow through the hollow filter element can advantageously be from radially inside to radially outside with respect to an element axis. The inflow side of the filter medium is then located radially inside and the outflow side radially outside. Alternatively, the hollow filter element can also be flowed through from radially outside to radially inside. The inflow side of the filter medium is then located radially outside and the outflow side radially inside.

[0053] Advantageously, the hollow filter element can be a round filter element, an oval round filter element, a conical round filter element, a conical-oval round filter element, or another type of round filter element. The hollow filter element can also have a square cross-section.

[0054] The circumferentially closed filter medium of the hollow filter element can be connected to an end body, in particular an end plate, on at least one of its end faces. Advantageously, an end body can be arranged on each of the two end faces.

[0055] Advantageously, at least one end body of the hollow filter element can be made of a material that is also contained in the filter medium, in particular the material of which the filter medium is made. In this way, the filter medium and the at least one end body can be connected to one another more easily. In particular, the filter medium can be connected to the at least one end body by means of a welding process, in particular an infrared welding process, or an injection molding process.

[0056] The filter medium can also be connected to the at least one end body in another way than by welding. The filter medium can, in particular, be glued to the at least one end body or glued into it. Advantageously, an adhesive used for this purpose can be resistant to urea solution or urea-water solution.

[0057] The at least one end body can advantageously be made of a polymer or copolymer. The at least one end body can additionally contain a glass fiber content. In this way, the stability of the at least one end body can be further improved. Additionally or alternatively, at least one other type of filler, in particular talc, can also be included. The proportion of the filler can advantageously be less than 45%.

[0058] Advantageously, the polyamide filter medium can be connected to at least one end body with / made of polyamide, in particular polyamide 6 with up to 30%, in particular with about 30% glass fiber content (PA 6 GF30), by means of a welded joint.

[0059] The hollow filter element can also have at least one support body, in particular a central tube and / or struts and / or stiffening ribs. In this way, the hollow filter element can be additionally stabilized. In this way, different material pairings can also be realized between the at least one end body and the filter medium. This also makes it possible to join materials whose direct connection has a lower stability than, in particular, a welded connection between polyamide and polyamide, polypropylene and polypropylene, or polyamide and polypropylene. The at least one support body can advantageously be designed and / or arranged such that the hollow filter element is stiffened in the direction of its element axis, i.e. in the longitudinal direction.

[0060] The filter medium of the hollow filter element can advantageously be connected to its corresponding edges for circumferential closure, in particular by means of a bellows end seam. The bellows end seam can be realized by a welding process, in particular an ultrasonic welding process, and / or an adhesive bond. Alternatively, the edges of the filter medium can also be connected to one another in a form-fitting and / or force-fitting manner, in particular with a bellows seam clamp.

[0061] Instead of a hollow filter element, the filter element can be designed as a flat filter element. In a flat filter element, the edges of the filter medium are not connected to each other.

[0062] The filter medium can advantageously be pleated in a zigzag pattern. With a pleated filter medium, the active area for filtration can be increased relative to the required installation volume. The pleats can be sharp-edged or bent with a gentle bend radius. In the latter case, the zigzag fold is wave-like. The filter medium can advantageously be folded rotaryly, in particular using rotating rollers, or by means of a knife pleat.

[0063] The initial filtration efficiency of the filter element for particles larger than or equal to 10 µm(c) can be greater than 80%. The initial filtration efficiency for particles larger than or equal to 15 µm(c) can be greater than 92%. For particles larger than or equal to 20 µm(c), the initial filtration efficiency can be greater than 97%. The initial filtration efficiency for particles larger than or equal to 30 µm(c) can be 100%. The initial filtration efficiency of the filter element can be defined, in particular, according to ISO 19438.

[0064] The technical problem is further solved by a multi-layer filter medium according to claim 11.

[0065] The advantages and features shown above in connection with the filter element according to the invention and its advantageous embodiments apply accordingly to the multi-layer filter medium according to the invention and its advantageous embodiments and vice versa.

[0066] Furthermore, the technical problem is solved by a filter according to the invention according to claim 12.

[0067] The advantages and features shown above in connection with the filter element according to the invention and the multi-layer filter medium according to the invention and their respective advantageous embodiments apply accordingly to the filter according to the invention and vice versa. Short description of the drawings

[0068] Further advantages, features, and details of the invention will become apparent from the following description, in which exemplary embodiments of the invention are explained in more detail with reference to the drawings. Those skilled in the art will expediently consider the features disclosed in the drawings, the description, and the claims in combination individually and combine them to form useful further combinations. The figures show schematically: Fig. 1 is an isometric view of a filter element of a urea filter for urea solution of an internal combustion engine of a motor vehicle, with a two-layer filter medium according to a first embodiment; Fig. 2 a cross-section of the filter element from the Fig. 1; Fig. 3 a section of the two-layer filter medium from the Fig. 1 and Fig. 2 in a first embodiment not according to the invention; Fig. 4 a section of a three-layer filter medium according to a second embodiment not according to the invention, which in the filter element from the Fig. 1 and Fig. 2 can be used; Fig. 5 a section of a three-layer filter medium according to a third embodiment of the invention, which in the filter element from the Fig. 1 and Fig. 2 can be used; Fig. 6 a section of a three-layer filter medium according to a fourth embodiment not according to the invention, which in the filter element from the Fig. 1 and Fig. 2 can be used; Fig. 7 a section of a three-layer filter medium according to a fifth embodiment not according to the invention, which in the filter element from the Fig. 1 and Fig. 2 can be used; Fig. 8 shows a section of a three-layer filter medium according to a sixth embodiment of the invention, which in the filter element from the Fig. 1 and Fig. 2 can be used.

[0069] In the figures, identical components are provided with the same reference symbols. Embodiment(s) of the invention

[0070] In the Fig. 1 shows a filter element 10 of a filter (not shown otherwise) for urea solution of an internal combustion engine of a motor vehicle. Fig. 2 shows a cross-section of the filter element 10.

[0071] The filter element 10 is arranged in a filter housing (not shown). The filter housing has at least one inlet for the urea solution to be filtered and one outlet for the filtered urea solution. The filter is arranged in or on a tank for the urea solution.

[0072] The filter element 10 is designed as a so-called round filter element. The filter element 10 comprises a multi-layer filter medium 12 according to a first embodiment. The filter medium 12 forms a filter bellows 16. A section of the filter medium 12 is shown in the Fig. 3. The filter medium 12 is folded in a zigzag pattern. The folding of the filter medium 12 is carried out rotationally using rotating rollers. The filter medium 12 is folded along the folded edges, as shown in the Fig. 2, gently curved. The filter medium 12 is circumferentially closed with respect to an element axis 14. Corresponding edges of the filter medium 12 are tightly connected to one another by means of an ultrasonic welding process to circumferentially close the filter bellows 16. The filter element 10, in particular the filter bellows 16, has a round cross-section.

[0073] The filter bellows 16 is provided on its front sides with a connection end plate 18, in which Fig. 1 at the bottom and a terminal end plate 20 at the top, each tightly connected. The terminal end plate 18 has a connecting piece 22 with a passage opening 24 for the urea solution. In the illustrated embodiment, the passage opening 24 serves as the inlet for the urea solution.

[0074] The urea solution, indicated by an arrow 23, passes through the passage opening 24 into an element interior 25 of the filter bellows 16. From the element interior 25, the urea solution flows through the filter medium 12 from radially inside to radially outside, indicated by arrows 26, and is filtered there. The filtered urea solution enters an outlet space between the radially outer circumferential side of the filter bellows 16 and a radially inner circumferential side of a housing wall of the filter housing.

[0075] An inflow side 28 of the filter medium 12 faces a radially inner circumferential side of the filter bellows 16 facing the element interior 25. The inflow side 28 of the filter medium 12 can also be referred to as the "dirty side" or "dirty side." An outflow side 30 of the filter medium 12 faces a radially outer circumferential side of the filter bellows 16 facing away from the element interior 25.

[0076] The end faces of the filter bellows 16 are each tightly connected to the end plates 20 and 22. The tight connections are achieved using an infrared welding process. The end plates 20 and 22 are made of a similar, preferably the same, material as the filter medium 12. They are preferably made of polyamide (PA), polypropylene (PP), or a copolymer, for example, polypropylene / polyethylene (PP / PE).

[0077] To increase strength, the end plates 20 and 22 can additionally contain a glass fiber content and / or another filler, such as talc. The glass fiber content can be up to 45%. The filter medium 12 comprises polyamide. The end plates 20 and 22 can, for example, be made of PA 6 GF30 with a glass fiber content of 30%.

[0078] The filter element 10 has an overall initial filtration efficiency of more than 80% for particles larger than or equal to 10 µm(c). For particles larger than or equal to 15 µm(c), the initial filtration efficiency is greater than 92%. For particles larger than or equal to 20 µm(c), the initial filtration efficiency is greater than 97%. For particles larger than or equal to 30 µm(c), the initial filtration efficiency is 100%. The definition of the initial filtration efficiency is preferably according to ISO 19438.

[0079] The filter medium 12 is two-layered. It has a filtration layer 32 upstream of the flow 26. The filtration layer 32 is manufactured using a meltblown process. It is therefore referred to below as the meltblown filtration layer 32. The meltblown filtration layer 32 serves to filter out any particles contained in the urea solution. It forms the inflow side 28.

[0080] A thickness of the meltblown filtration layer 32, in which Fig. 3, indicated by a double arrow 36, is between approximately 200 µm and approximately 1000 µm. The basis weight of the meltblown filtration layer 32 is between 50 g / m 2 and 150 g / m 2 . The meltblown filtration layer 32 has an air permeability between approximately 80 l / m 2 s and about 170 l / m 2 s. The meltblown filtration layer 32 has fiber diameters between 0.1 µm and 15 µm. The meltblown filtration layer 32 is made of polyamide.

[0081] In the direction of flow 26, behind the filtration layer 32, the filter medium 12 has a support layer 34. In this embodiment, the support layer 34 is made of a spunbond fabric, which is explained in more detail below. It is therefore referred to below as the spunbond support layer 34. The spunbond support layer 34 is bonded to the filtration layer 32 over a large area.

[0082] The spunbonded support layer 34 forms the downstream side 30 of the filter medium 12. During operation of the filter element 10, the spunbonded support layer 34 fulfills a supporting function for the filtration layer 32. The filtration layer 32 can be supported against the spunbonded support layer 34. The spunbonded support layer 34 also supports the filter medium 12 against pressures that exhibit pressure gradients transverse or oblique to the direction of the flow 26 of the urea solution through the filter medium 12. The pressures are generally directed in the direction of the flow 26. Pressures with such pressure gradients are, for example, pressures limited to a specific area. They can be caused, for example, by ice impact. Ice impact can occur, for example, at temperatures below the freezing point of the urea solution. Furthermore, the spunbond support layer 34 contributes to the overall stability of the filter medium 12 and the filter element 10.For example, the spunbond support layer 34 compensates for pressure increases due to impaired flowability of the urea solution. The spunbond support layer 34 also increases the stiffness of the filter medium 12. It improves the strength of the filter medium 12. The spunbond support layer 34 contributes to maintaining the pleats of the filter medium 12. Furthermore, the spunbond support layer 34 increases the inherent stiffness of the filter medium 12. This simplifies the connection process with the end plates 20 and 22.

[0083] A thickness of the spunbonded support layer 34 is in the Fig. 3 by a double arrow 38. The thickness 38 of the spunbonded nonwoven support layer 34 is between 300 µm and 1000 µm. The basis weight of the spunbonded nonwoven support layer 34 is between 100 g / m 2 and 170 g / m 2 . The spunbonded support layer 34 has an air permeability of between 500 l / m 2 s and 1500 l / m 2s. The spunbonded nonwoven support layer 34 has fiber diameters between 1 µm and 50 µm. The spunbonded nonwoven support layer 34 is made of the same material as the meltblown filtration layer 32.

[0084] In the Fig. 4 shows a filter medium 112 according to a second embodiment not according to the invention, which can be used in the filter element 10. In contrast to the first embodiment from the Fig. 3, in the second embodiment, a support layer 134 is realized as a grid. The support layer 134 is referred to below as the grid support layer 134. The grid support layer 134 has a thickness 38 between 700 µm and approximately 1100 µm. The basis weight of the grid support layer 134 is between approximately 150 g / m 2 and about 230 g / m 2 . The grid support layer 134 is made of polyamide. Otherwise, the grid support layer 134 fulfills analogous functions to the spunbonded support layer 34 in the non-inventive embodiment from the Fig. 3.

[0085] Furthermore, in contrast to the first embodiment from the Fig. 3, instead of the meltblown filtration layer 32, a filtration layer 132 made of a nonwoven is provided. The filtration layer 132 made of nonwoven is referred to below as nonwoven filtration layer 132. The thickness 36 of the nonwoven filtration layer 132 is between 400 µm and 1500 µm. The basis weight of the nonwoven filtration layer 132 is between 150 g / m 2 and 500 g / m 2 . The nonwoven filtration layer 132 has an air permeability of between 80 l / m 2 s and 250 l / m 2 s. A fiber diameter of the nonwoven filtration layer 132 is between 4 µm and about 200 µm. The nonwoven filtration layer 132 is made of the same material as the grid support layer 134 of the filter medium 112. Otherwise, the nonwoven filtration layer 132 fulfills analogous functions to the meltblown filtration layer 32 in the first embodiment from the Fig. 3.

[0086] A barrier layer 40 is additionally provided between the nonwoven filtration layer 132 and the grid support layer 134. The barrier layer 40 is arranged downstream of the nonwoven filtration layer 132. The barrier layer 40 filters out any leached nonwoven fibers from the nonwoven filtration layer 132.

[0087] The barrier layer 40 is made of a spunbonded fabric. The thickness of the barrier layer 40 is Fig. 4 with a double arrow 42. The thickness 42 of the barrier layer 40 is between 100 µm and 300 µm. The barrier layer 40 has a mass per unit area between 15 g / m 2 and 80 g / m 2 The air permeability of the barrier layer 40 is between 250 l / m 2 s and 3000 l / m 2 s. The fiber diameter of the barrier layer 40 is between 1 µm and 50 µm. The barrier layer 40 is made of the same material as the mesh support layer 134 and the nonwoven filtration layer 132 of the filter medium 112.

[0088] In the Fig. 5 shows a filter medium 212 according to a third embodiment of the invention, which can be used in the filter element 10. In contrast to the second embodiment from the Fig. 4, a fine filter layer 44 is provided instead of the barrier layer 40.

[0089] The ultrafine filter layer 44 is manufactured using a meltblown process. The ultrafine filter layer 44 can be referred to as a meltblown layer. The pore size of the ultrafine filter layer 44 is smaller than the pore size of the nonwoven filtration layer 132. The ultrafine filter layer 44 acts as a fine filter, which can filter out smaller particles than the nonwoven filtration layer 132. The ultrafine filter layer 44 has a thickness 46 between 100 µm and 500 µm. The ultrafine filter layer 44 has a basis weight between 15 g / m 2 and 100 g / m 2 The air permeability of the fine filter layer 44 is between 40 l / m 2 s and 100 l / m 2s. The fiber diameter of the ultrafine filter layer 44 is between 0.1 µm and 15 µm. The ultrafine filter layer 44 is made of the same material as the mesh support layer 134 and the nonwoven filtration layer 132 of the filter medium 212. It is made of polyamide.

[0090] In the Fig. 6 to 8 show a fourth, a fifth and a sixth embodiment of a filter medium 312, 412 and 512, which are used in the filter element 10 of the Fig. 1 and Fig. 2 can be used, wherein the flow direction of the urea solution through the filter element 10 is reversed. In this case, the urea solution flows from radially outside to radially inside instead of from radially inside to radially outside.

[0091] In the fourth embodiment not according to the invention according to Fig. 6, the spunbonded nonwoven support layer 34 is located on the upstream side 28 of the filter medium 312. The spunbonded nonwoven support layer 34 has the features described above in connection with the first embodiment according to the Fig. 3 listed properties. In the event that the urea solution cools below freezing point and ice particles may form, the spunbond support layer 34 on the upstream side 28 of the filter medium 312 serves as protection against ice impact.

[0092] The barrier layer 40 is located on the downstream side 30 of the filter medium 312. The barrier layer 40 has the features described above in connection with the second embodiment according to the Fig. 4 listed properties and analogous functions.

[0093] The meltblown filtration layer 32 is arranged between the barrier layer 40 and the spunbonded support layer 34. The meltblown filtration layer 32 has the properties described above in connection with the first embodiment according to the Fig. 3 listed properties and analogous functions.

[0094] The spunbonded support layer 34, the barrier layer 40, and the meltblown filtration layer 32 of the filter medium 312 are made of the same material: polyamide.

[0095] In the Fig. 7, the grid support layer 134 is arranged on the inflow side 28 of the filter medium 412. The grid support layer 134 has the features described above in connection with the second embodiment according to the Fig. 4 listed properties and analogous functions.

[0096] The nonwoven filtration layer 132 is located between the grid support layer 134 and the barrier layer 40. The nonwoven filtration layer 132 has the properties described above in connection with the second embodiment according to the Fig. 4 listed properties and analogous functions.

[0097] The barrier layer 40 is located on the downstream side 30 of the filter medium 412. The barrier layer 40 has the features described above in connection with the second embodiment according to the Fig. 4 listed properties and analogous functions.

[0098] The mesh support layer 134, the barrier layer 40, and the nonwoven filtration layer 132 of the filter medium 412 are made of the same material. They are polyamide.

[0099] In the Fig. The sixth embodiment of a filter medium 512 according to the invention shown in Figure 8 is, in contrast to the fifth embodiment from the Fig. 7, the ultrafine filter layer 44 is arranged on the downstream side 30 of the filter medium 512 instead of the barrier layer 40. The ultrafine filter layer 44 has the features described above in connection with the third embodiment according to the Fig. 5 listed properties and analogous functions.

[0100] The mesh support layer 134, the ultrafine filter layer 44, and the nonwoven filtration layer 132 of the filter medium 412 are made of the same material: polyamide.

Claims

[1] Filter element (10) of a filter for filtering fluid in the form of urea solution, in particular of an internal combustion engine, in particular of a motor vehicle, with a multi-layer filter medium (12; 112; 212; 312; 412; 512), through which the fluid can flow for filtration and has at least one filtration layer (32; 132) and at least one support layer (34; 134), wherein at least one filtration layer (132) has a fleece, characterized by that at least one further filtration layer (32) is at least partially melt-blown, that the at least one support layer (134) is designed as a grid so that it can support the filter medium (12; 112; 212; 312; 412; 512) against pressures which have pressure gradients transversely or obliquely to the flow direction (26) of the fluid through the filter medium (12; 112; 212; 312; 412; 512), and that all layers of the filter medium are hydrophilic and made of polyamide. [2] Filter element according to claim 1 characterized bythat at least one filtration layer (32; 132) is arranged behind at least one support layer (34; 134) with respect to the flow (26) of the fluid through the filter medium (312; 412; 512). [3] Filter element according to claim 1 or 2, characterized by that at least one support layer (34; 134) is arranged on an inflow side (28) of the filter medium (312; 412; 512). [4] Filter element according to one of the preceding claims, characterized by that at least one filtration layer (32; 132) is arranged in front of the at least one support layer (34; 134) with respect to the flow (26) of the fluid through the filter medium (12; 112; 212). [5] Filter element according to one of the preceding claims, characterized by that at least one support layer (34; 134) is arranged on a downstream side (30) of the filter medium (12; 112; 212). [6] Filter element according to one of the preceding claims, characterized by that the filter medium (112; 312; 412) has at least one barrier layer (40). [7] Filter element according to claim 6, characterized by that the at least one barrier layer (40) comprises a spunbonded fabric. [8] Filter element according to one of the preceding claims, characterized by that the filter medium (212; 512) has at least one fine filter layer (44). [9] Filter element according to claim 8, characterized by that the at least one fine filter layer (44) is at least partially meltblown. [10] Filter element according to one of the preceding claims, characterized by that the filter element (10) is a hollow filter element. [11] Multi-layer filter medium (12; 112; 212; 312; 412; 512) for a filter element according to one of the preceding claims for filtering fluid in the form of urea solution, which can be flowed through by the fluid for filtration and which has at least one filtration layer (32; 132) and at least one support layer (34; 134), wherein at least one filtration layer (132) has a nonwoven fabric, characterized bythat at least one further filtration layer is at least partially melt-blown, that the at least one support layer (34; 134) is designed and / or arranged as a grid so that it can support the filter medium (12; 112; 212; 312; 412; 512) against pressures which have pressure gradients transversely or obliquely to the flow direction (26) of the fluid through the filter medium (12; 112; 212; 312; 412; 512), and that all layers of the filter medium are hydrophilic and made of polyamide. [12] Filter for filtering fluid in the form of urea solution, in particular of an internal combustion engine, in particular of a motor vehicle, with a filter element according to one of claims 1 to 10.

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