Air filter system

Abstract

Air filter system (100) for the intake air of an internal combustion engine, comprising - a housing (108) with a longitudinal axis (L), - a lid (110) that closes the housing (108) at one end (120), - an inlet (102) arranged on the housing (108) for supplying a medium to be filtered and an outlet (104) arranged on the housing (108) for discharging the filtered medium, - a replaceable filter element (10) which is arranged in the housing (108) and comprises a filter body (12), a first open end disk (16) arranged on one end face (15) and a second end disk (18) arranged on the opposite end face (17), - a housing-fixed support tube (14) which is arranged concentrically inside the filter element (10) around the longitudinal axis (L), wherein the filter system comprises a replaceable secondary element (28) with an open end (54) and a closed end (55) which is arranged inside the support tube (14) and is mounted with its open end in a housing seat (58), wherein the filter element (10) is mounted with its second end disk (18) resting on the support tube (14) and on the closed end (55) of the secondary element (28) against an inner cover contour (114) in a rotationally secure manner.

Description

Technical area

[0001] The invention relates to an air filter system, in particular for use as an air filter of an internal combustion engine, and to the use of a filter element in such a filter system. State of the art

[0002] WO 2009 / 047196 A1 discloses a filter system for internal combustion engines with a filter element. This filter system is used in particular for filtering the intake air of an internal combustion engine and consists of a housing and a cover for accommodating the filter element. The design of the filter element seals, with two annular bead-shaped arrangements and a sealing groove located between them, ensures both a sealing effect and axial support of the filter element within a housing. Especially when using plastic for sealing elements subject to vibration, a design is required that operates reliably even under extreme temperature fluctuations.

[0003] WO 2009 / 047196 A1 further describes a secondary element positioned inside a filter element of the filter system. The secondary element's task is to keep the filter system's outlet closed when the filter element is replaced, preventing dirt from entering this area while the filter element is being cleaned or replaced. During operation of the filter system, the cleaned air flows through the secondary element, which has a fleece lining on a supporting structure. The secondary element is attached to the outlet nozzle of the outlet via a screw thread and is simultaneously sealed in this area via an O-ring.

[0004] Other air filter systems with main and secondary elements are described, for example, in US 2010 / 0 146 917 A1 and US 2004 / 0 134 171 A1.

[0005] Air filter filter elements are generally designed to be replaced after a certain period of operation. Depending on the amount of dust generated, the service life of an air filter can range from a few days (construction machinery) to several months. The secondary element, located on the clean air side, usually remains in the filter system. However, if the secondary element is also heavily contaminated, it must also be replaced, as otherwise the air flow will be reduced excessively. The reliable and process-safe sealing of the filter element and secondary element in a housing is particularly important to protect the intake tract of a downstream internal combustion engine from penetrating dirt. Disclosure of the invention

[0006] An object of the invention is therefore to provide a filter system in which a reliable seal between the area of ​​the unfiltered and the area of ​​the filtered medium is possible, which seal can be maintained both during operation and, in particular, can be reliably restored after an assembly-friendly replacement of the filter element and / or secondary element.

[0007] The above-mentioned object is achieved in a filter system in which a filter element with a second end plate is mounted on a support tube and is mounted in a rotationally secure manner against an inner cover contour.

[0008] Advantageous embodiments and advantages of the invention emerge from the further claims, the description and the drawing.

[0009] A filter system is proposed which comprises a housing with a longitudinal axis, a cover which closes the housing at one end face, an inlet arranged on the housing for supplying a medium to be filtered and an outlet arranged on the housing for discharging the filtered medium, a replaceable filter element which is arranged in the housing and comprises a filter body, a first open end plate arranged on one end face and a second end plate arranged on the opposite end face, as well as a support tube which is fixed to the housing and which is arranged concentrically around the longitudinal axis in the interior of the filter element and serves in particular for radial support of the filter element.

[0010] The filter element is preferably mounted with the second end plate resting on the support tube against an inner cover contour in a rotationally secure manner and is thus firmly pressed between the support tube and the cover.

[0011] By mounting the second end plate of the filter element in a fixed position, the filter element itself is more resistant and clearly protected from environmental influences such as water ingress, high humidity, and the resulting softening / deformation of the filter paper in the filter body during operation. Furthermore, this creates a reliable seal between the unfiltered and filtered media areas, which can be maintained both during operation and reliably restored, especially after an easy-to-install replacement of the filter element and / or secondary element.

[0012] The filter body can, for example, consist of a zigzag-folded (pleated) filter bellows and be designed in a closed, ring-shaped manner. The folding can be produced, for example, by knife folding, for longer filter bodies, or rotary folding. The filter bellows can be made, for example, of paper or cellulose, or of a mixed fiber of plastic and cellulose. The filter bellows can also be designed with a smooth surface, rolled, and / or with a surface designed in various embossed shapes for stiffening and / or creating cavities for dust deposition. The filter bellows can have a coating and / or impregnation to repel moisture. Alternatively, it can also be coated with nanofibers. The filter body can also be structurally stiffened with a thread winding, at least one circumferential hot-melt adhesive bead, or a grid.Thread winding refers to a thread impregnated with hot-melt adhesive that is wound around the periphery of the filter body formed by the outer pleat edges. As the hot-melt adhesive cures, the thread stiffens and bonds to the pleat tips. The filter element is typically designed as a main filter element, with a secondary filter element arranged on its clean side and / or within its interior.

[0013] The filter system comprises a replaceable secondary element with an open end and a closed end, which is arranged inside the support tube and attached with the open end in a housing seat. The filter element is mounted with the second end plate on the support tube and rests on the closed end of the secondary element in a rotationally secure manner against an inner cover contour. The secondary element can be pressed into the housing seat or pressed into the housing seat via the second end plate by applying force. The fact that a strong axial force component acts on the secondary element when the cover is closed ensures that it is always in its end position as soon as the housing is closed by the cover. This ensures that the seal is reliably engaged.During production, it is also not necessary to check whether the secondary element has been mounted in its final position, as this is done by the cover at the very latest. When the cover is closed, a pressure force is transferred to the secondary element via the second end plate of the filter element. This ensures a secure final position of the secondary element when the cover is installed. Furthermore, in addition to the support tube, the filter element is clamped axially against the cover and thus against the housing via the second end plate, thus providing a fixed bearing on the front side, the cover-side end of the filter element.

[0014] Conveniently, the support tube can have recesses at its end facing the second end plate, with which the second end plate is or can be toothed. In addition, the interlocking of the support tube in the material of the end plate makes the filter element less sensitive to vibration effects.

[0015] It is also advantageous if the housing cover has rib-shaped protrusions with which the second end plate of the filter element is interlocked or interlockable. The additional anti-twist effect of the interlocking with the rib-shaped protrusions in the cover further enhances the vibration stiffness of the filter element's mounting in the housing.

[0016] In an advantageous embodiment, the second end plate has an outer, central support surface, which preferably runs perpendicular to the central axis or longitudinal axis of the filter element. A parallel, inner support surface is further preferably formed by the inner side of the second end plate.

[0017] In a favorable embodiment, the second end plate can have support studs for axial and / or radial force transmission between the cover and the second end plate. In this way, the force exerted on the end plate by closing the cover can be transmitted through the end plate and into the support tube, resulting in a secure mounting of the filter element.

[0018] Advantageously, the second end plate can also have support studs for axial and / or radial force transmission between the cover and the secondary element. This allows the force exerted on the end plate by closing the cover to be transmitted through it and into the secondary element, which in turn can be pressed firmly into its housing seat. This enables a secure support of the secondary element and, at the same time, a good seal between the unfiltered and filtered areas of the filter system.

[0019] Advantageously, the second end plate, like the first, can be made of polyurethane foam or an elastomer. Of course, it is also possible to manufacture the end plate from multiple plastic components to ensure optimal deformability over a wide temperature range, as may occur during practical use. Thermoplastics are also possible. Both end plates can be welded or glued to the filter body to ensure a stable connection.

[0020] The inner cover contour can, for example, be designed in one area as an annular groove into which support knobs engage in such a way that radial support on the radial walls of the groove is also possible.

[0021] Preferably, a central support knob is provided on the second end plate in the region of the longitudinal axis of the filter element and / or a plurality of eccentric support knobs arranged annularly or circularly around the longitudinal axis and regularly or irregularly spaced. The support knobs are preferably designed in one piece and / or made of the same material as the second end plate. The central support knob can preferably form the outer, central support surface. The radial position, i.e., the distance from the center point of the second end plate of the eccentric support knobs, is preferably selected such that the eccentric support knobs are arranged in direct axial continuation of a support tube of a corresponding housing.Therefore, the diameter of the circle on which the eccentric support studs are arranged, preferably with their centers, preferably corresponds to the diameter of the support tube, preferably to the mean value between the inner and outer diameters of the support tube. In other words, the eccentric support studs are arranged, for example, on a circle with the diameter of the support tube and / or the eccentric support studs are arranged radially in the region of the cross-section of the support tube. The force flow preferably occurs purely axially from the support tube via the second end plate and its eccentric support studs to the inner cover contour of the cover.

[0022] The inner cover contour preferably has a flat surface in the middle of the cover on which the central support knob can be supported. The second end plate is preferably designed to be elastic, at least in the area enclosed in a ring by the filter body, such that the middle area with the central support knob can be elastically pressed outwards by the secondary element until it rests against the cover. During assembly of the cover, the eccentric support knobs are then moved slightly towards the open end plate relative to the central support knob. When the housing cover is then removed to change the filter element, the second end plate is slightly pre-tensioned and makes it easier to remove the filter element from its friction-based sealing seat on the open end plate, since when the cover is removed, tension is exerted on the outer areas of the second end plate and thus on the filter body.

[0023] In a further preferred embodiment, rib-shaped, preferably radially extending, more preferably slightly extending into the interior of the filter housing, elevations are provided in the inner cover contour, preferably in the annular groove, with which the elastic material of the second end plate can interlock or claw, thus securing the filter element against possible twisting due to vibrations during operation. The elevations preferably press into the eccentric support nubs of the second end plate, thus achieving a positive fit in the direction of rotation around the longitudinal axis.

[0024] According to an advantageous development, recesses are also conceivable, additionally or alternatively, at the end of the support tube facing the second end plate, which also enable interlocking or claw engagement of the support tube with the second end plate, thus ensuring that the filter element is secured against rotation during vibrations. The second end plate, for example, connects positively to the end of the support tube facing the second end plate. For example, an elastic second end plate can penetrate into the recesses by deformation and / or compression during assembly, thus achieving a positive connection in the direction of rotation about the longitudinal axis.

[0025] For this purpose, a further embodiment is advantageous in which the second end plate is made of a material which is, for example, cast and soft compared to the housing material and support tube material (both usually injection-molded thermoplastics, in particular with a glass fiber content, or metal), expediently polyurethane foam or a similarly elastic material, preferably with a hardness in the range of approximately 10-30 Shore A.

[0026] In one embodiment, the distance between the inner surface of the second end plate and the axial outer surfaces of the support knobs is preferably selected or designed to be equal to or more preferably somewhat larger than the distance between the inner surface of the cover in the region of the longitudinal axis, ie in its center, and the axial end of the secondary element or between the inner surface of the cover in the region of the inner cover contour and the support tube.

[0027] Particularly preferably, at least one of the aforementioned distances on the second end plate is designed with an oversize of 1-5 mm, preferably relative to the distances defined by the cover on the one hand and the support tube and secondary element on the other. This ensures reliable fixed mounting of the filter element.

[0028] Advantageously, the first end plate can have a radial seal against the housing. This has the advantage that, in addition to providing a good seal and thus a reliable filtering effect, the radial seal and the axial tension of the support studs in the cover can provide radial guidance of the filter element within the housing, thus creating a very stable mount for the filter element within the housing.

[0029] For convenience, the secondary element, which is connected to the housing, can remain in the housing while the filter element is being replaced. This ensures that the additional air duct connected to the filter housing outlet is protected from contamination during the replacement process.

[0030] Advantageously, a cyclone separator can be provided near the inlet of the filter system, and a dirt outlet can be provided on the housing or cover. This cyclone separator consists of a guide geometry that causes the medium to be filtered to rotate. This rotation concentrates the dirt near the housing wall and removes it at a suitable location via a dirt outlet. By pre-separating most of the dirt from the air to be filtered, the service life of the actual filter element can be significantly extended.

[0031] The filter system can be used as an air filter, particularly as an air filter for an internal combustion engine. The safe operation of internal combustion engines also depends on reliable and cost-effective filtration of the intake air for combustion. The filter element described represents a cost-effective option for this.

[0032] The use of the filter system as a particulate filter, especially as a particulate filter in an internal combustion engine, is also advantageous. Here, too, the secure installation and cost-effective replaceability of the described filter element are crucial.

[0033] According to a further aspect, the invention relates to a filter element for installation in a filter system having one or more features as described above and below, wherein the filter element can be replaceably arranged in the housing of the filter system. The use of such a filter element in a described filter system provides a reliable seal between the area of ​​the unfiltered medium and the area of ​​the filtered medium, which can be maintained both during operation and, in particular, reliably restored after an easy-to-install replacement of the filter element. Short description of the drawings

[0034] 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.

[0035] Examples include: Fig. 1 a perspective view of a filter system according to an embodiment of the invention with tangential inlet, centric outlet and bottom-side dirt outlet; Fig. 2 a perspective view of a filter system according to an embodiment of the invention with the cover of the housing removed; Fig. 3 a perspective view of a filter system according to Fig. 2, but with the filter element removed so that a support tube is visible; Fig. 4 a longitudinal section through a filter system according to an embodiment of the invention; Fig. 5 an interior view of a cover of a housing according to an embodiment of the invention; Fig. 6 is a perspective view of a secondary element according to an embodiment of the invention; Fig. 7 a section through the cover-side part of a filter system according to an embodiment of the invention; Fig. 8 a section through the outlet-side part of a filter system according to an embodiment of the invention. Embodiments of the invention

[0036] 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.

[0037] Fig. 1 shows a perspective view of a filter system 100 according to an embodiment of the invention with a tangential inlet 102, a central outlet 104, and a bottom-side dirt outlet 106. A round filter design is shown, comprising a housing 108 closed at an end face 120 with a cover 110. In the air filter system, dust-laden air flows through the inlet 102, which is arranged tangentially to the housing wall and the internally installed air filter element, and also tangentially into the inlet chamber on the raw side, which surrounds the air filter element in a ring, so that the air inside the housing 108 is set into a rotational movement.Direct penetration of the air entering through inlet 102 into the folds of the air filter element present in the inlet area is prevented by an upstream protection device on the filter element, which is formed, for example, by a film formed as part of the filter element that surrounds the filter element in the upstream area in a ring. Alternatively, the upstream protection device can also be formed by a wall that surrounds the filter element in the instream area in a ring and extends from the axial housing wall on the outlet side into the filter housing interior. The filter element and upstream protection device are not shown in the drawing. Due to the cyclone effect caused by the rotational movement of the air, centrifugal forces act on the dust particles in the flowing air, so that some of them are deposited on the housing wall and can flow out of the filter system 100 via the dirt outlet 106. This places less strain on the filter element.The cleaned air can be discharged from the housing 108 via the central outlet 104.

[0038] Fig. Figure 2 shows a perspective view of a filter system 100 according to an embodiment of the invention with the cover of the housing 108 removed. Inside the housing 108, an assembled filter element 10 with a filter body 12, which is closed by a second end plate 18, can be seen. On the side of the second end plate 18 facing the open end of the housing 108, the end face 120, support nubs 20 for supporting the end plate 18 on a cover (not shown) can be seen.

[0039] In Fig. 3 is further a perspective view of a filter system 100 according to Fig. 2 with the filter element removed. At the open end of the housing 108, the end face 120, a support tube 14 fixed to the housing can be seen, which (with the filter element installed) is arranged inside the filter element and supports it radially inward and protects it against collapse. When the system is at rest, however, the support tube is spaced apart from the non-flowing filter body. This means that assembly of the filter element is not unnecessarily complicated by additional friction and the risk of damage to the filter medium when installing the filter element 10 is reduced. A secondary element 28 is provided inside the support tube 14 concentric to the longitudinal axis of the filter system 100. The closed end 55 of the secondary element 28 can be seen, which is designed as a handle 56 for easy removal of the inserted secondary element 28 from the housing 108 or the support tube 14.

[0040] In Fig. Figure 4 shows a longitudinal section through a filter system 100 according to an embodiment of the invention with a tangential inlet 102, a central outlet 104, and a bottom-side dirt outlet 106. The housing 108 of the filter system 100 is closed at the end face 120 with a cover 110. A filter element 10, which comprises a filter body 12 concentric about the longitudinal axis L, is closed at two opposite end faces 15, 17 by a first open and a second end plate 16, 18, which can be made, for example, of polyurethane foam or an elastomer. The filter body 12 can, for example, consist of a zigzag-folded (pleated) filter bellows and have a closed, ring-shaped design. The folding can be produced, for example, by knife folding, for longer filter bodies 12, or rotary folding.The filter bellows can be made of paper, cellulose, or a mixed fiber of plastic and cellulose, for example, and can be designed with a smooth surface, rolled, and / or embossed in various shapes for stiffening and / or creating cavities for dust deposition. The filter bellows can have a coating and / or impregnation to repel moisture. Alternatively, it can also be coated with nanofibers. The filter body 12 can also be structurally stiffened with a thread winding.

[0041] The second end plate 18 has support studs 20 which are arranged to extend axially outwards and, when installed in the receiving housing 108, are axially supported on the housing 108, more precisely the cover 110 of the housing 108, preferably in the region of an inner cover contour 114 of the cover 110. The inner cover contour 114 is designed, for example, in one region as an annular groove into which the support studs engage, so that radial support on the radial walls of the groove is also possible. Preferably, a central support stud 202 in the region of the longitudinal axis L of the filter element 10 and a plurality of eccentric support studs 20 arranged annularly or circularly around the longitudinal axis L and regularly or irregularly spaced are provided on the second end plate 18. The support studs are preferably designed in one piece and / or from the same material as the second end plate 18. The radial position, ieThe distance from the center point of the second end plate of the eccentric support studs 20 is preferably selected such that the eccentric support studs are arranged in direct axial continuation of the support tube 14. Therefore, the diameter of the circle on which the eccentric support studs 20 are arranged, preferably with their centers, preferably corresponds to the diameter of the support tube 14, preferably to the mean value between the inner and outer diameters of the support tube 14. In other words, the eccentric support studs 20 are arranged on a circle with the diameter of the support tube 14 and / or the eccentric support studs 20 are arranged radially in the region of the cross section of the support tube 14. The inner cover contour 114 preferably has a flat surface in the center of the cover 110, on which the central support stud 202 can be supported.The second end plate 18 is preferably designed to be elastic, at least in the area enclosed in a ring by the filter body 12, such that the central area with the central support knob can be elastically pressed outwards by the secondary element 28 until it rests against the cover. During assembly of the cover 110, the eccentric support knobs 20 are then slightly displaced relative to the central support knob 202 in the direction of the open end plate 16. When the housing cover 18 is then removed to replace the filter element, the second end plate 18 is slightly prestressed and facilitates the removal of the filter element 10 from its frictional sealing seat on the open end plate 16. In the interior 50 of the filter element 10, the support tube 14, which is fixed to the housing, is arranged concentrically around the longitudinal axis L and is firmly connected to the housing 108 at the outlet-side end of the support tube 14, for example by snapping, gluing, or welding.The surface of the second end plate 18 facing the support tube 14 rests on the open end of the support tube 14 facing the end plate 18. When the inner cover contour 114 of the cover 110 presses against the end plate 18 when the cover 110 is closed, this force is transmitted through the end plate 18 via the support studs 20 to the end plate 18, since the end plate can be supported on the support tube 14. The force flow preferably occurs purely axially from the support tube 14 via the second end plate 18 and its eccentric support studs 20 to the inner cover contour 114 of the cover 110. In this way, the filter element 10 is clamped axially against the cover 110 and thus against the housing 108 via the second end plate 18 and is thus fixedly mounted on the end face 17, the cover-side end of the filter element 10, in particular without loading the filter body 12 with axial forces.

[0042] Furthermore, rib-shaped, preferably radially extending, more preferably slightly extending into the interior of the filter housing, elevations 112 are provided in the inner cover contour 114, preferably in the annular groove, with which the elastic material of the second end plate 18 can interlock or claw, so that the filter element 10 is thereby secured against possible twisting due to vibrations during operation. The elevations press into the eccentric support knobs 20 of the second end plate, so that a positive connection in the direction of rotation about the longitudinal axis L is achieved. Furthermore, recesses 22 are also conceivable at the end of the support tube 14 facing the end plate 18, which recesses enable further interlocking or clawing of the support tube 14 with the end plate 18, in order to thus ensure further protection of the filter element 10 against twisting due to vibrations.The second end plate is pressed into the recesses 22 so that a positive connection in the direction of rotation about the longitudinal axis L is achieved. In order to enable the above-described function, it is preferable to use a second end plate made of, for example, a cast material which is softer than the housing material and support tube material (both are usually injection-molded thermoplastics, in particular with a glass fiber content, or metal), expediently polyurethane foam or a similarly elastic material, preferably with a hardness in the range of approximately 10-30 Shore A. The distance between the inner surface of the second end plate 18 and the axial outer surfaces of the support knobs 20, 202 is preferably selected or designed to be the same or preferably somewhat larger than the distance between the inner surface of the cover 110 in the region of the longitudinal axis, i.e. in its center, and the axial end of the secondary element 28 orbetween the inner surface of the cover 110 in the region of the inner cover contour 114 and the support tube 14. Particularly preferably, at least one of the mentioned distances on the second end plate is designed with an excess of 1-5 mm, preferably relative to the distances defined by the cover 110 on the one hand and the support tube 14 and the secondary element 28 on the other. In this way, a reliable fixed mounting of the filter element 10 can be ensured. In the case that, as is preferred, the second end plate is made of a cast polyurethane foam or a similarly elastic material, the thickness of the second end plate and thus also the above-mentioned distances defined by the second end plate can be easily adjusted by the amount of polyurethane metered into the casting shell.The casting shell is open on one side and accommodates the filter body before the polyurethane is metered in. The casting shell clearly defines the axially outward-facing shape of the second end plate 18, and the inner surface is formed by the polyurethane foaming freely in the casting shell and subsequently curing. The degree of possible elastic compression is determined from the . Fig. 7 and Fig. 8 in all areas where the drawings show slightly exaggerated material collisions for better visibility, which in reality manifest themselves in elastic deformations, here essentially of the material of the end plates.

[0043] On the opposite end face 15 of the filter element 10, a radial seal 26 is attached to the first end plate 16, with the aid of which the filter element 10 seals the unfiltered air space against the filtered air space.

[0044] Dust-laden air can flow in through inlet 102 in the direction of arrow 40, which in this case is shown as a tangential inlet and enables cyclone operation due to the rotational movement of the air caused by a cyclone separator 36. Dust particles can be partially pre-separated by the rotational movement and deposited on the inner housing wall and emptied from the filter system 100 downwards through the dirt outlet 106 when the filter housing 108 is installed in a horizontal position by gravity. During operation, after partial separation of the dust particles, the air flows through the filter body 12 in the direction of arrows 42, 44 into the interior 50 of the filter element. Depending on the filter medium, dust particles above a certain size remain trapped in the filter medium. Depending on the dust input, the filter element 10 must therefore be replaced after a certain service life. The filtered air flows out via outlet 104 in the direction of arrow 46.

[0045] A secondary element 28 is mounted inside the interior 50 of the filter element 10. It essentially consists of a supporting structure, the body 52, with a relatively permeable filter medium, for example, a fleece. When the filter element 10 is replaced, it remains in the housing 108 to protect the further air duct, for example, of an internal combustion engine, from penetrating dust particles and other objects. The secondary element 28 is inserted with its open end 54 into a housing seat 58 on the outlet-side part of the housing 108.The second end plate 18 of the filter element 10 rests on the closed end 55 of the secondary element 28 in the region of its center and / or longitudinal axis as well as the central support knob 202. As a result, when the housing cover 110 is closed, a force can be transmitted via the central support knob 202 of the end plate 18 into the closed end of the secondary element 28, which is designed, for example, as a handle 56 with which it can be removed from the housing seat 58 and thus from the housing 108, and the secondary element 28 is thus firmly pressed into its housing seat 58. In this way, the filter element 10 is clamped axially against the cover 110 and thus against the housing 108, in addition to the support tube 14, via the second end plate 18, and is thus fixedly mounted on the end face 17, the cover-side end of the filter element 10.It is also conceivable to design the length of the support tube 14 and the secondary element such that the second end plate 18 rests exclusively on the secondary element 28 or the support tube 14. However, a design such that the second end plate 18 can be placed both on the secondary element 18 and on the support tube 14 is preferred, since individual applications of an air filter according to the invention without a secondary element 28 are also conceivable. A solution in which the second end plate 18 rests exclusively on the secondary element 28 would be conceivable for applications in which rotation of the filter element 10 is uncritical during operation or is hindered by other means.

[0046] The filter element 10 can be used as an air filter, particularly as an air filter for an internal combustion engine. However, in principle, it could also be used as a particle filter of a similar design.

[0047] Fig. Figure 5 shows an interior view of a cover 110 of a housing of a filter system with rib-shaped elevations 112 in the inner cover contour 114 according to an embodiment of the invention. By interlocking the support studs of a second end plate of a filter element, the filter element can be protected against twisting during operation, even in the event of possible vibration excitation.

[0048] In Fig. Figure 6 shows a perspective view of a secondary element 28 according to an embodiment of the invention. The cylindrical body 52 of the secondary element 28, which is open at the outlet end 54 to discharge the filtered medium, is closed at the other end 55 and has a handle 56 for removal from the housing of the filter system. The second end plate of the filter element can be supported on this closed end 55, in particular on the handle 56, and thus transmit the force into the secondary element to press it into the housing seat and thus also seal the unfiltered space from the filtered space inside the secondary element 28.

[0049] Fig. 7 shows a section through the cover-side part of a filter system 100 according to an embodiment of the invention. It shows part of the filter element 10, consisting of the filter body 12 and the second end plate 18, as well as, inside the filter element 10, the support tube 14 mounted on the housing side and the secondary element 28, which is also mounted in a housing seat. After the filter element 10 has been mounted in the housing 108 and the cover 110 has been closed at the end face 120, the cover presses on the second end plate 18 via the support knobs 20. On the other side, the end plate 18 presses on the end of the support tube 14 facing the end plate 18, as well as on the closed end 55 of the secondary element 28 with the handle 56. The drawing shows a penetration of the end plate 18 with the cover 110, the support tube 14, and the secondary element 28.Since the material of the end plate 18 is preferably polyurethane foam or a similarly elastic material, the end plate 18 is actually compressed between the cover 110, the support tube 14, and the secondary element 28, thus transferring the force from the cover 110 to the support tube 14 and the secondary element 28. In this way, the filter element 10 is firmly clamped by the end plate 18 and thus securely mounted. Furthermore, the end plate 18 also presses the secondary element 28 firmly into its housing seat.

[0050] In Fig. Figure 8 shows a section through the outlet-side part 104 of a filter system according to an embodiment of the invention. It can be seen, firstly, that a radial seal 26 is attached to the first end plate 16 on the opposite end face 15 of the filter element 10, with the aid of which radial seal 26 the filter element 10 seals the unfiltered air space from the filtered air space. Secondly, the section clearly shows how the support tube 14 is firmly connected to the housing 108 at the outlet-side end via a snap-in connection 60. The secondary element 28, on the other hand, is inserted into a housing seat 58 and is therefore expediently pressed into the housing seat 58 via the closed end and the second end plate of the filter element. Fig.Figure 8 also shows a flexible film designed as an airflow shield. This is depicted as a thickened line at the end of the reference arrow 10. The film is applied around the outer circumference of the filter body 12 over the outer surface of the filter body 12 and is joined along a seam, for example, using an ultrasonic weld seam, to form a continuous, annular semi-finished product and embedded in the second end plate.

Claims

[1] Air filter system (100) for the intake air of an internal combustion engine, comprising - a housing (108) with a longitudinal axis (L), - a cover (110) which closes the housing (108) at one end face (120), - an inlet (102) arranged on the housing (108) for supplying a medium to be filtered and an outlet (104) arranged on the housing (108) for discharging the filtered medium, - a replaceable filter element (10) which is arranged in the housing (108) and comprises a filter body (12), a first open end plate (16) arranged on one end face (15) and a second end plate (18) arranged on the opposite end face (17), - a housing-fixed support tube (14) which is arranged concentrically around the longitudinal axis (L) in the interior of the filter element (10), wherein the filter system comprises a replaceable secondary element (28) with an open end (54) and a closed end (55), which is arranged in the interior of the support tube (14) and is mounted with the open end in a housing seat (58), wherein the filter element (10) is mounted with the second end plate (18) on the support tube (14) and on the closed end (55) of the secondary element (28) in a rotationally secure manner against an inner cover contour (114). [2] Air filter system according to claim 1, wherein the secondary element (14) is pressed into the housing seat (58). [3] Air filter system according to claim 1 or 2, wherein the support tube (14) has recesses (22) at its end facing the second end plate (18) with which the second end plate (18) is toothed. [4] Air filter system according to one of the preceding claims, wherein the cover (110) of the housing (108) has rib-shaped elevations (112) with which the second end plate (18) of the filter element (10) is toothed. [5] Air filter system according to one of the preceding claims, wherein the second end plate (18) has support knobs (20, 202) for axial and / or radial force transmission between the cover (110) and the second end plate (18). [6] Air filter system according to one of the preceding claims, wherein the second end plate (18) has at least one central support knob (202) for axial force transmission between the cover (110) and the secondary element (28) and / or a plurality of eccentric support knobs (20) for axial force transmission between the cover (110) and the support tube (14). [7] Air filter system according to one of the preceding claims, wherein the second end plate (18) consists of a polyurethane foam or an elastomer. [8] Air filter system according to one of the preceding claims, wherein the first end plate (16) of the filter element has a radial seal (26) relative to the housing (108). [9] Air filter system according to one of the preceding claims, wherein the secondary element (28), connected to the housing (108), remains in the housing (108) when the filter element (10) is changed. [10] Air filter system according to one of the preceding claims, wherein a cyclone separator (36) is provided in the region of the inlet (102) and a dirt outlet (106) is provided on the housing (108) or on the cover (110). [11] Use of an air filter element (10) in an air filter system (100) according to one of claims 1 to 10, wherein the filter element (10) can be exchangeably arranged in the housing (108) of the air filter system (100) and comprises a filter body (12), a first open end plate (16) arranged on one end face (15) and a second closed end plate (18) arranged on the opposite end face (17), wherein the filter element (10) has on the second end plate (18) on the inside of the second end plate (18) facing in the direction of the open end plate (16) a contact surface for contact with a housing-side support tube (14) and a secondary element (28) and on the outside of the second end plate (18) a support structure for rotationally secure support on an inner cover contour (114).

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