Air filter and use of filter element in air filter

Abstract

The invention relates to an air filter (10), comprising: two filter elements (20, 26), each of which is designed as a flat filter element and has a filter medium body (48) with an inflow surface (22, 28) and an outflow surface (24, 30); -a filter housing (12) in which the two filter elements (20, 26) are arranged; the invention relates to an air filter comprising two filter elements (20, 26), and a flow guide device (32) for selectively guiding a flow of air to be filtered sequentially through the two filter elements (20, 26) or at least partially around a second one of the filter elements (26), the outflow surface (24) of a first one of the filter elements (20) and the inflow surface (28) of the second one of the filter elements (26) being spaced apart from each other, the flow guide device (32) being configured to selectively guide the flow of air to be filtered sequentially through the two filter elements (20, 26) or at least partially around the second one of the filter elements (26). The filter medium body (48) of at least one of the filter elements (20, 26) has an inherently varying height, and wherein the filter medium body (48) of the at least one filter element (20, 26) has a smaller height in the region of a larger width of the bypass channel (36).

Description

Technical Field

[0001] The present invention relates to an air filter, which comprises

[0002] - two filter elements, each of which is implemented as a flat filter element and comprises a filter medium body having an inflow surface and an outflow surface,

[0003] - a filter housing in which the two filter elements are arranged,

[0004] - and a flow guiding device for selectively guiding the air flow to be filtered to sequentially pass through the two filter elements or at least partially pass through a second filter element of the two filter elements,

[0005] wherein an outflow surface of a first filter element among the filter elements and an inflow surface of a second filter element among the filter elements are spaced apart from each other to form a widened bypass channel. Background Art

[0006] Such an air filter is disclosed in US2020 / 0376934 A1.

[0007] For highly separated cabin air filters, two filter elements are usually used. A first filter element among the filter elements may be a pre-filter element for separating larger particles and / or harmful gases. A second filter element among the filter elements may be a fine filter element for separating finer particles, for example, a HEPA filter element. In principle, the fluid can flow through the filter elements in succession.

[0008] However, when the particle concentration in the air to be filtered is low, it is not necessarily required to use a fine filter element. In order to reduce the pressure loss when flowing through the air filter, reduce the energy consumption of the blower of the air filter, and reduce the noise formation, therefore, in some cases of air filters, the fine filter element can be bypassed. For this purpose, after the air has flowed through the pre-filter element, the air is removed between the two filter elements. For this purpose, a bypass channel large enough in size is required between the filter elements. To form this bypass channel, the filter elements must be spaced apart from each other accordingly. This increases the installation space requirement of the air filter.

[0009] In the air filter known from the above US2020 / 0376934 A1, two cuboid filter elements are provided, which are positioned obliquely relative to each other such that a widened bypass channel is formed therebetween. By means of a bypass baffle, the bypass channel can be selectively opened or closed in order to achieve a bypass flow around the second filter element or to force the flow through the second filter element.

[0010] DE 10 2008 058 356 A1 discloses a filter element which comprises a folded bellows having adjacent upper folding ridges and adjacent lower folding ridges, wherein the lower folding ridges are positioned in a base plane, and wherein the upper folding ridges project away from the base plane at a folding height. The filter element is characterized by at least two different folding heights of the upper folding ridges. In this way, while ensuring high filtration efficiency and an optimized guidance of the fluid to be filtered, the filter element can be inserted into a filter housing deviating from a cuboid shape.

[0011] DE 10 2019 206 911 A1 describes an air filter element for an air filter device or an interior air filter for a motor vehicle. The air filter element comprises a plate-shaped filter body made of a filter material and a frame surrounding the same. The filter material is folded such that the filter body comprises a plurality of adjacent folds which are connected to one another by folding edges and follow one another in the filter length direction and extend in the filter transverse direction. The frame comprises two length end walls extending parallel to the filter transverse direction and two lateral strips extending parallel to the filter length direction. Inside the filter body, at least one short fold group is formed by at least two folds which follow one another in the filter length direction and are shorter than adjacent folds in the filter height direction. At the respective short fold group, at least one cutout is formed in the frame. In the region of the respective cutout, a bending tab is formed at the frame, which bending tab bends away from the frame towards the folds of the respective short fold group. The bending tab rests on at least some of the folds in the short fold group and is fixed there by material fusion.

[0012] The object of the present invention is to achieve a compact construction and a minimum flow resistance, especially in the case of bypassing the fine filter element, for an air filter having a pre-filter element and a fine filter element which selectively flows through or bypasses. Summary of the Invention

[0013] This object is solved by an air filter according to claim 1 and a use according to claim 12. Preferred embodiments or variants are disclosed in the respective dependent claims and the description.

[0014] According to the present invention, an air filter is provided. The air filter can in particular serve as a cabin air filter for a motor vehicle.

[0015] The air filter comprises two filter elements. The filter elements are each embodied as flat filter elements and comprise a filter medium body having an inflow surface and an outflow surface. In operation, the air to be filtered flows through the respective filter medium, from its inflow surface to its outflow surface.

[0016] The air filter further includes a filter housing, and two filter elements are arranged in the filter housing.

[0017] In addition, the air filter includes a flow guiding device for selectively guiding the air flow to be filtered to sequentially pass through the two filter elements or at least partially pass through the second filter element among the filter elements. Thus, in the first operating state, the flow guiding device enables a forced sequential flow through the first filter element and the second filter element in succession. In this context, the air flow is first guided through the first filter element and then through the second filter element. For the description of the present invention, the first filter element through which the air first flows is also referred to as the first filter element; the second filter element through which the air then flows is also referred to as the second filter element. In the second operating state, the flow guiding device permits bypassing (in the flow direction) of the second filter element. The air flow can be guided completely or partially (especially up to at least 50%) through the second filter element.

[0018] The first filter element can be an adsorption filter element, especially containing activated carbon.

[0019] The second filter element can be a HEPA filter element, preferably of H13 filter class or better according to EN 1822-1:2009.

[0020] The outflow surface of the first filter element among the filter elements and the inflow surface of the second filter element among the filter elements are spaced apart from each other, thereby forming a widened bypass channel. In principle, the bypass channel is widened transversely to the flat extension direction of at least one of the filter elements. In the second operating state, the bypass channel enables the air filtered by the first filter element to be diverted before it flows through the second filter element. Since the bypass channel is widened in the direction of the bypass flow through the bypass channel (or in other words, towards the outlet of the air filter), it contributes to the discharge of the air that has been filtered by the first filter element; and reduces the flow resistance of the air filter.

[0021] According to the present invention, the filter medium body of one of the filter elements includes an inherently varying height, wherein in the region of the larger width of the bypass channel, the filter medium body includes a reduced height. In other words, the inflow surface and the outflow surface of the filter medium body are spaced apart from each other differently along the bypass channel. Thus, the filter elements can be arranged closely adjacent to each other without restricting the bypass channel. In this way, the installation space requirement for accommodating the two filter elements remains small. The height or thickness of the filter medium body can be measured along the main passing direction of the air through the filter medium body. Usually, the height or thickness is measured perpendicular to the inflow surface or the outflow surface of the filter medium body. The width of the bypass channel especially describes its extension transversely to the main flow direction of the bypass flow through the bypass channel in the second operating state.

[0022] The filter medium body can be implemented by a filter mat, foam, honeycomb body, or porous material.

[0023] Preferably, the filter medium body is formed with folds having different heights. Particularly preferably, both filter medium bodies are formed with folds. One or more filter medium bodies can be made of folded filter paper. In the region of the larger width of the bypass channel, lower folds are provided. In other words, the folding edges of the folds of one filter element facing the other filter element are spaced apart differently from the folding edges facing away from the other filter element. As the folds become lower (the distance between the folding edges is smaller), the bypass channel thus gradually widens.

[0024] Preferably, the inflow surface of the first filter element and the outflow surface of the second filter element extend parallel to each other. In this way, a particularly compact configuration of the air filter can be obtained.

[0025] The height of the filter medium body preferably decreases continuously in the widening direction or the flow direction of the bypass channel. This is advantageous for the flow through the bypass channel.

[0026] As an alternative, the height of the filter medium body can decrease in a stepwise manner in the widening direction or the flow direction of the bypass channel. This can simplify the manufacture of the filter element.

[0027] It is also preferred that both filter elements include filter medium bodies having an inherently varying height. In this context, both filter medium bodies each have a reduced height in the region of the larger width of the bypass channel. In this context, the two filter elements can be arranged particularly close to each other while still allowing flow through the bypass channel with minimal resistance.

[0028] The minimum height of the folds of one or both filter medium bodies, in particular one filter element or both filter elements, can reach at least 5 mm, preferably at least 8 mm, and / or at most 20 mm, preferably at most 15 mm.

[0029] The maximum height of the folds of one or both filter medium bodies, in particular one filter element or both filter elements, can reach at least 30 mm, preferably at least 40 mm, and / or at most 70 mm, preferably at most 60 mm.

[0030] The filter element having a varying height can include at least one frame element. The frame element serves to laterally seal the filter medium body. The frame element can be a lateral strip for sealing the folds. Alternatively or additionally, the frame element can include a plastic frame in which the filter medium body is indirectly or directly glued or injection molded.

[0031] The frame element protrudes beyond the filter medium body in the region of the lower height. In particular, the frame element or the lateral strip may protrude beyond the folding edge of the fold in the region of the lower fold. The frame element may have a substantially constant height. The frame element advantageously includes at least one section with a reduced protrusion, in particular a recess. In other words, the protrusion of the frame element is locally reduced. Preferably, the filter housing includes a protrusion adjacent to the section with the lower protrusion. The protrusion engages at least partially in the recess. The protrusion may protrude inwards from the lateral wall of the filter housing. Due to this protrusion, the filter element can only be installed in an orientation in which the position of the section with the reduced protrusion coincides with the position of the protrusion. In this way, it is ensured that the bypass channel is widened in the desired direction. Incorrect installation of the filter element is excluded. Additionally, an improperly installed filter element, for example one that does not meet certain technical requirements (such as a pre-determined separation efficiency), can be prevented by the protrusion.

[0032] When both filter elements have a varying height, the two filter elements may each respectively include at least one frame element that protrudes beyond the filter medium body in the region of the lower height, where the frame elements each include at least one section with a reduced protrusion, in particular a recess. Adjacent to the section with the reduced protrusion, the filter housing may respectively include a protrusion. Preferably, at the filter housing, a common protrusion is provided that abuts the two sections with the reduced protrusion, in particular engages at least partially in the two recesses. When only one common protrusion is provided, the manufacture of the filter housing can be simplified as required.

[0033] One of the filter elements, in particular a filter element with a varying height and / or a filter element with relatively better separation, may include a seal. The seal may seal the two housing parts of the filter housing relative to each other.

[0034] Preferably, the seal forms a first seal section and a second seal section, where the first seal section surrounds the filter medium body and the second seal section surrounds the flow-through opening. The first seal section is used to seal the filter medium body relative to the filter housing. In particular, the first seal section seals the inflow of the associated raw side relative to the outflow of the associated clean side. Additionally, the first seal section can be used to seal the housing parts of the filter housing. The second seal section with the opening is generally used to seal the housing parts of the filter housing. The opening is in principle free of filter material. The second seal section with the opening can also be referred to as a handle at the filter element. The second seal section with the opening is in principle (radially) located outside the cross-section of the filter medium body. The first seal section and the second seal section may include a common section of the seal.

[0035] The flow path of the air stream guided successively through two filter elements can extend through the opening in the second frame section. This can simplify the flow guidance and configuration of the filter housing.

[0036] Preferably, the fluid connection between the outlet side of the second filter element and the outlet of the filter housing is established only via the flow-through opening. In the case of sequential flow through the two filter elements, all the filtered air then flows through said opening.

[0037] The seal can be formed of polyurethane, in particular polyurethane foam. The seal can be integrally formed at the filter medium body. The hardness of the seal can reach at least 13 Shore A hardness and / or at most 25 Shore A hardness. In another embodiment, the seal can be injection molded onto the plastic frame of the filter element, where the seal can be made of a thermoplastic elastomer material in particular. The seal can in particular include one or more sealing lips, which facilitates particularly good sealing tightness with a relatively small sealing preload.

[0038] Preferably, the second sealing section of the seal can be stiffened by a stiffening member. In this way, it can be ensured that the second frame section will contact the provided sealing position at the filter housing. The seal can be integrally formed at the stiffening member. In particular, the stiffening member can be embedded in the seal. In another embodiment, the plastic frame can surround the flow-through opening surrounded by the second sealing section, where in particular the second sealing section is also injection molded onto the plastic frame.

[0039] Air guiding ribs can be provided at the second sealing section. In this way, the flow through the air filter can be optimized, particularly in the region of the flow-through opening.

[0040] Preferably, the air guiding ribs and the stiffening member are implemented as a single piece. This simplifies the manufacture of the filter element. Preferably, the diversion device is implemented with a baffle that closes the bypass channel in a first position and opens the bypass channel in a second position. By pivoting the baffle, the switching between the operating states can be done in a particularly easy way. In the second position, the baffle can completely or partially prevent the flow through the flow-through opening of the second sealing section of the seal. The baffle can include one or more sealing lips, in particular for contacting the sealing position of the filter housing. Generally, the sealing lip between the filter housing and the baffle is provided at the bypass channel, at the outlet side, where the sealing lip can be provided at the filter housing or at the baffle.

[0041] The gist of the present invention also includes the use of a filter element in the above-mentioned air filter according to the present invention, the filter element being formed as a flat filter element and comprising a filter medium body having an inflow surface and an outflow surface, wherein the filter medium body comprises a height that varies inherently. Thus, the filter element is used in an air filter having an additional filter element, the additional filter element being implemented as a flat filter element and comprising an additional filter medium body having an additional inflow surface and an additional outflow surface, wherein the air filter comprises a filter housing, the two filter elements being arranged in the filter housing in use, and wherein the air filter further comprises a flow guiding device for selectively guiding the air flow to be filtered sequentially through the two filter elements or at least partially through one of the filter elements, and wherein a widened bypass channel is formed between the filter elements, and wherein the filter element comprises a reduced height in the region of the larger width of the bypass channel. The filter element having a varying height can be the first filter element or the second filter element (in the flow direction). In use, according to the present invention, the tapered geometry of the filter element is utilized in order to form a fluid-favorable bypass channel with minimal installation space requirements between the filter element and the additional filter element.

[0042] The filter medium body can be implemented by a filter mat, foam, honeycomb body or porous material.

[0043] Preferably, the filter medium body is formed with folds having different heights. The filter medium body can be made of folded filter paper. In use, the filter element is arranged such that the lower folds are located in the region of the larger width of the bypass channel.

[0044] The height of the filter medium body preferably decreases continuously. This is advantageous for the flow through the bypass channel.

[0045] As an alternative, the height of the filter medium body can decrease in a stepwise manner. This can simplify the manufacture of the filter element.

[0046] The filter element can include at least one frame element. The lateral strip effects a lateral seal of the filter medium body. The frame element can be the lateral strip for sealing the folds. The frame element protrudes beyond the filter medium body in the region of a lower height. In particular, the frame element or the lateral strip can protrude beyond the fold edges of the folds in the region of the lower folds. The frame element can include a substantially constant height. The frame element advantageously includes at least one section, in particular a recess, with a minimum protrusion. In other words, the protrusion of the frame element is locally reduced. When the filter housing includes a protrusion, the frame element designed in this way can enforce a defined mounting position of the filter element. The mounting of the filter element in the filter housing is only possible if the protrusion is arranged adjacent to the section with the reduced protrusion, in particular at least partially engaging the recess.

[0047] The filter element can include a seal that forms a first sealing section and a second sealing section, where the first sealing section surrounds the filter medium body and the second sealing section forms a flow-through opening. The first sealing section serves to seal the filter medium relative to the filter housing. In particular, the first sealing section can seal the inflow of the associated raw side relative to the outflow of the associated clean side. Additionally, the first sealing section can be used to seal the housing part of the filter housing. The second sealing section with the opening is generally used to seal the housing part of the filter housing. The opening is in principle free of filter material. The second sealing section with the opening is in principle (radially) outside the cross-section of the filter medium body. The first sealing section and the second sealing section can include a common section of the seal.

[0048] The filter element including the seal generally serves as a second filter element in the flow direction.

[0049] The flow path of the air flow sequentially guided through two filter elements can extend through the opening in the second frame section.

[0050] Preferably, the fluid connection between the outflow side of the (second) filter element and the outlet of the filter housing can be established only through the flow-through opening. In the case of sequential flow through two filter elements, all of the filtered air flow then flows through the opening.

[0051] The seal can be formed of polyurethane, in particular polyurethane foam. The seal can be integrally formed at the filter medium body. The hardness of the seal can reach at least 13 Shore A hardness and / or at most 25 Shore A hardness.

[0052] Preferably, the second sealing section of the seal is stiffened by a reinforcing member. In this way, it can be ensured that the second sealing section contacts a predefined sealing position of the filter housing. The seal can be integrally formed at the reinforcing member. In particular, the reinforcing member can be embedded in the seal.

[0053] At the second sealing section, air guiding ribs can be provided. In this way, the flow through the air filter can be optimized, especially in the region of the opening.

[0054] Preferably, the air guiding ribs and the strengthening member are formed as a single piece. This simplifies the manufacture of the filter element. Description of the Drawings

[0055] The following specific embodiments according to the embodiments of the present invention, according to the claims and with the aid of the drawings showing the details of the present invention, other features and advantages of the present invention are obtained. In a variant of the present invention, the above features and the features yet to be explained can each be implemented individually or several in any random convenient combination. The features illustrated in the drawings make it possible to clearly see the details according to the present invention. In the drawings, there is shown:

[0056] Figure 1 is a schematic cross-sectional view of an air filter according to the present invention, which has two conical flat filter elements, and a widened bypass channel is formed between the filter elements;

[0057] Figure 2 is Figure 1 a schematic cross-sectional view of the second filter element of the air filter in the flow direction;

[0058] Figure 3 is in a similar manner to Figure 1 a schematic perspective view of a cuboid filter element and a first conical filter element acting as the second filter element in an air filter. Detailed Description

[0059] Figure 1 An air filter 10 is shown. The air filter 10 includes a filter housing 12, and the filter housing 12 has a housing bottom part 14 and a housing top part 16. The air to be filtered is guided into the filter housing 12 through an inlet 17. The filtered air can be introduced, for example, into the passenger compartment of a motor vehicle not shown in detail through an outlet 18 of the filter housing 12.

[0060] Two filter elements 20, 26 are arranged in the filter housing 12. The two filter elements 20, 26 are formed as flat filter elements. The first filter element 20 includes a first inflow surface 22 and a first outflow surface 24 in the flow direction. The second filter element 26 is arranged behind the first filter element 20 in the flow direction. The second filter element 26 includes a second inflow surface 28 and a second outflow surface 30. At present, the first inflow surface 22 of the first filter element 20 and the second outflow surface 30 of the second filter element 26 extend parallel to each other.

[0061] The first filter element 20 can be a so-called ambient filter element or pre-filter element and in particular comprises activated carbon for adsorbing harmful gases. The second filter element 26 can be a HEPA filter element for filtering fine particles.

[0062] The air filter 10 further comprises a flow-guiding device 32, here formed by a baffle 34 which can pivot about an axis 33 by means of a pivot drive not shown in detail. In Figure 1 the air filter 10 is in a first operating state in which the fluid flows successively (sequentially) through the two filter elements 20, 26. For this purpose, the baffle 34 closes a bypass channel 36 formed between the two filter elements 20, 26 in a first position. For this purpose, a sealing lip 37 formed at the baffle 34 can contact the mouth 38 of the bypass channel 36 formed by the filter housing 10 in a tightly sealing manner. In the first operating state, the filtered air flows through a flow-through opening 40 to the outlet 18 after passing through the second filter element 26, here the flow-through opening 40 being formed in the transition region between the housing top part 16 and the housing bottom part 14. In the first operating state, the flow path 41 of the air is indicated schematically by dashed arrows in Figure 1 the drawing.

[0063] In a second operating state, the flow-guiding device 32 opens the bypass channel 36. For this purpose, the baffle 34 pivots away from the mouth 38 in the pivoting direction 42 indicated by the arrow. In a second position not shown in more detail, the baffle 34 can close a clean air passage 46 by means of a further sealing lip 44, the clean air passage 46 being arranged between the second filter element 26 and the outlet 18 in the flow direction.

[0064] In the second operating state, the air which has been filtered by the first filter element 20 flows through the bypass channel 36 to the outlet 18. In Figure 1 the drawing, in the second operating state, the flow path 47 of the air is indicated schematically by dashed arrows. The bypass channel 36 widens towards its mouth 38. Besides eliminating the flow resistance of the second filter element 26, this also reduces the flow resistance in the air filter 10.

[0065] Each of the two filter elements 20, 26 comprises a filter medium body 48. In the illustrated embodiment, the filter medium bodies 48 are each formed by folded filter paper. This is shown in an exemplary manner for the second filter element 26 in Figure 2Within, the folded portions 50 of the filter medium body 48 are delimited by folded edges 52 or 54 at the inflow side and the outflow side, respectively. In this context, the height 56 (which can be measured perpendicular to the outflow side or the inflow side) or the thickness of the filter medium body 48 decreases along the bypass channel 36, which in the illustrated embodiment corresponds to the height of the folded portion 50. The maximum height 56a of the filter medium body 48 or its folded portion 50 can reach, for example, 48 mm. The minimum height 56b of the filter medium body 48 or its folded portion 50 can reach, for example, 11 mm.

[0066] Here, in the second operating state, the thickness of the filter elements 20, 26 continuously decreases in the flow direction of the bypass channel 36 (in Figure 1 the figure, from left to right). Correspondingly, the bypass channel 36 continuously widens towards the mouth 38. Thus, the air flowing into the bypass channel 36 across the entire surface of the first filter element 20 obtains an increasing cross-section towards the mouth 38, such that the pressure difference between the first inflow surface 22 required to flow through the bypass channel 36 and the outlet 18 is kept minimal. This reduces energy consumption and can increase the driving range of a motor vehicle having the air filter 10.

[0067] Here, the two filter elements 20, 26 include respective frame elements 58 in the form of lateral bands, which seal the folded portions 50 transversely to the folded edges 52, 54 and transversely to the respective inflow or outflow surfaces 22 - 28, cf. Figure 1 and Figure 2 In the embodiment, the frame element 58 can be part of a plastic frame in which the filter medium body 48 is fastened directly or indirectly. For example, the filter medium body 48 can be directly glued into the plastic frame, or the material of the plastic frame can be molded around the filter medium body 48. Alternatively, the filter medium body can include lateral bands by means of which the filter medium body 48 is indirectly connected, in particular glued, to the plastic frame. As the folded portion 50 becomes lower, the frame element 58 gradually protrudes beyond the inflow side folded edge 52 of the second filter element 26 or the outflow side folded edge of the first filter element 20. Except for the respective recesses 60, the frame element 58 always has the same height. The recesses 60 each form a section 62 with a reduced protrusion in the frame element 58.

[0068] At the side wall of the filter housing 12, a protrusion 64 is formed, cf. Figure 1 In the installed state of the filter elements 20, 26, the protrusion 64 engages the recesses 60 of the respective frame elements 58. Thus, the filter elements 20, 26 can only be inserted into the filter housing 12 when they are correctly oriented and when their frame elements 58 have a reduced protrusion at the correct position.

[0069] The second filter element 26 currently includes a seal 66, where the seal 66 is made of polyurethane foam. Here, the seal 66 forms two rectangular seal sections 68, 70, and the seal sections 68, 70 include a common seal segment 71. The first seal section 68 is arranged on the outside and extends circumferentially at the outflow surface 30 of the filter medium body 48 of the second filter element 26. The second seal section 70 protrudes away from the filter medium body 48 like a handle and does not contain filter material. The second seal section 70 surrounds the flow-through opening 40, and in the illustrated embodiment, the flow-through opening 40 is fluidly positioned in front of the clean air passage 46.

[0070] On the one hand, the seal 66 is used to seal the bottom part 14 and the top part 16 of the housing relative to each other. On the other hand, the first seal section 68 is used to seal the second filter element 26 relative to the filter housing 12, such that in the first operating state, all of the air must pass through the filter medium body 48 of the second filter element 26.

[0071] The second seal section 70 is reinforced by a reinforcing member 72. The air guiding rib 74 is formed as a single piece with the reinforcing member 72. In the first operating state, the air guiding rib 74 is used to guide the filtered air in the region of the flow-through opening 40 to the clean air passage 46. In the embodiment, the reinforcing member 72 can be formed as a single piece with a plastic frame including the frame element 58.

[0072] The sealing function of the first filter element 20 relative to the filter housing 12 can be achieved via its frame element 58, where the frame element 58 is the lateral bands and top bands of the first filter element not shown in detail. In addition to the two lateral bands, the second filter element 20 generally also includes two top bands not shown in detail. The lateral bands and top bands form a circumferentially extending frame for the respective filter medium body 48.

[0073] Figure 3 Another second filter element 76 is shown, which can be used to replace similar to Figure 1The second filter element 26 in the air filter as illustrated. The filter element 76 includes a cuboid filter medium body 78. According to the present invention, the cuboid filter element 76 will be used together with a tapered filter element. In this context, as illustrated herein, the second filter element 76 can be implemented as a cuboid, and the first filter element 20 has a varying height 56, in particular folds 50 with different heights; alternatively, the first filter element can be implemented as a cuboid, and the second filter element has a varying height, in particular folds with different heights (not illustrated herein). In both cases, a decrease in the height (thickness) of one filter element or the folds becoming lower results in the widening of the bypass channel 36 formed between the two filter elements. When using a cuboid filter element, it should be understood that the protrusion 64 at the filter housing 12 only interacts with the protruding lateral band (partially recessed) of the tapered filter element to ensure the correct installation position. Regarding the configuration of the seal 66 and the reinforcing member 72 and the air guiding ribs 74, Figure 3 The second filter element 76 corresponds to the above-mentioned second filter element 26, as compared with Figure 1 and Figure 2 .

[0074] In summary, the present invention relates to an air filter having two filter elements. In a first operating state, a fluid flows successively (sequentially) through the two filter elements. Between the filter elements, a bypass channel is provided for at least partially bypassing one of the filter elements in a second operating state. The bypass channel widens in the direction of the bypass flow generated in the second operating state. At least one of the filter elements includes a filter medium body, and the thickness of the filter medium body decreases along the bypass channel in the direction of the bypass flow. A filter medium body having a varying height or thickness can be obtained by folding filter paper. The corresponding installation position of the tapered filter element can be ensured because the frame element for sealing the filter medium body, in particular the lateral band, has a substantially constant height such that it protrudes partially beyond the filter medium body, in particular beyond the lower folds, while the lateral band is partially recessed. The protrusion of the filter housing can engage in this section with a reduced protrusion.

[0075] List of reference numerals

[0076] Air filter 10

[0077] Filter housing 12

[0078] Housing bottom part 14

[0079] Housing top part 16

[0080] Inlet 17

[0081] Outlet 18

[0082] The first filter element 20

[0083] The first inlet surface 22

[0084] The first outlet surface 24

[0085] The second filter element 26

[0086] The second inlet surface 28

[0087] The second outlet surface 30

[0088] The flow guiding device 32

[0089] The axis 33

[0090] The baffle 34

[0091] The bypass passage 36

[0092] The sealing lip 37

[0093] The orifice 38

[0094] The flow-through opening 40

[0095] The flow path in the case of sequential flow 41

[0096] The pivoting direction 42

[0097] The additional sealing lip 44

[0098] The clean air passage 46

[0099] The flow path in the case of bypass flow 47

[0100] The filter medium 48

[0101] The fold 50

[0102] The fold edges 52, 54

[0103] The height 56 of the fold 50

[0104] The maximum height 56a

[0105] The minimum height 56b

[0106] The lateral strip 58

[0107] The recess 60

[0108] The section 62 with reduced convexity

[0109] The protrusion 64

[0110] The seal 66

[0111] The first sealing section 68

[0112] Second sealing section 70

[0113] Common sealing section 71

[0114] Reinforcing member 72

[0115] Air guiding rib 74

[0116] Second filter element 76

[0117] Filter medium 78

Claims

1. An air filter (10), comprising - two filter elements (20, 26), each of the two filter elements (20, 26) being formed as a flat filter element and comprising a filter medium body (48) having an inflow surface (22, 28) and an outflow surface (24, 30), - a filter housing (12) in which the two filter elements (20, 26) are arranged, - and a flow guiding device (32) for selectively guiding the air flow to be filtered to sequentially pass through the two filter elements (20, 26) or at least partially through a second filter element (26) of the filter elements, Among them, the outflow surface (24) of the first filter element (20) of the filter elements and the inflow surface (28) of the second filter element (26) of the filter elements are spaced apart from each other, thereby forming an enlarged bypass channel (36), wherein the filter medium body (48) of at least one of the filter elements (20, 26) comprises an inherently varying height (56), and wherein the filter medium body (48) of the at least one filter element (20, 26) has a reduced height (56) in a region of a larger width of the bypass channel (36).

2. The air filter (10) according to claim 1, characterized in that, In at least one of the filter elements (29, 26), the filter medium body (48) is formed with folds (15) having different heights (56), wherein a lower fold (50) is provided in a region of a larger width of the bypass channel (36).

3. The air filter (10) according to any one of the preceding claims, characterized in that, The inflow surface (22) of the first filter element (20) and the outflow surface (30) of the second filter element (26) extend parallel to each other.

4. The air filter (10) according to any one of the preceding claims, characterized in that, The height (56) of the filter medium body (48) of the at least one filter element (20, 26) decreases continuously or stepwise.

5. The air filter (10) according to any one of the preceding claims, characterized in that, Both filter elements comprise a filter medium body (48) having an inherently varying height (56), and wherein the two filter medium bodies (48) each have a reduced height (56) in a region of a larger width of the bypass channel (36).

6. The air filter (10) according to any one of the preceding claims, characterized in that, The filter element (20, 26) having a varying height (56) comprises at least one frame element (58) that protrudes beyond the filter medium body (48) in a region of a lower height, wherein the frame element (58) comprises at least one section (62) having a reduced protrusion, in particular a recess (60), and wherein the filter housing (12) adjacent to the section (62) having a reduced protrusion comprises a protrusion (64) that at least partially engages in the recess (60).

7. The air filter (10) according to any one of the preceding claims, characterized in that, At least one of the filter elements (26) comprises a seal (66) that forms a first seal section (68) and a second seal section (70), wherein the first seal section (68) surrounds the filter medium body (48), and the second seal section (70) surrounds a flow-through opening (40).

8. The air filter (10) according to claim 7, characterized in that, The flow path of the air stream that is sequentially guided through the two filter elements (20, 26) extends through the flow-through opening (40).

9. The air filter (10) according to claim 7 or 8, characterized in that, The fluid connection between the outlet side (30) of the second filter element (26) and the outlet (18) of the filter housing (12) is established only through the flow-through opening (40).

10. The air filter (10) according to any one of claims 7 to 9, characterized in that, The seal (66) seals the two housing parts (14, 16) of the filter housing (12) relative to each other.

11. The air filter (10) according to any one of the preceding claims, characterized in that, The flow guiding device (32) is formed with a baffle (34) that closes the bypass channel (36) in a first position and opens the bypass channel (36) in a second position.

12. Use of a filter element (20, 26) in an air filter (10) according to any one of the preceding claims, said filter element (20, 26) being embodied as a flat filter element and comprising a filter medium body (48) having an inflow surface (22, 28) and an outflow surface (24, 30), wherein, The filter medium body (48) includes an inherently varying height (56).

13. Use of the filter element (20, 26) according to claim 12, characterized in that, The filter medium body (48) is formed with folds (50) having different heights (56).

14. Use of the filter element (20, 26) according to claim 12 or 13, characterized in that, The height (56) of the filter medium body (48) decreases continuously or stepwise.

15. Use of the filter element (20, 26) according to any one of claims 12 to 14, characterized in that, The filter element (20, 26) includes at least one frame element (58) that protrudes beyond the filter medium body (48) in the region of a lower height (50), wherein the frame element (58) includes at least one section (62) with a reduced protrusion, in particular a recess (60).

16. Use of the filter element (20, 26) according to any one of claims 12 to 15, characterized in that, The filter element (26) includes a seal (66) that forms a first sealing section (68) and a second sealing section (70), wherein the first sealing section (68) surrounds the filter medium body (48) and the second sealing section (70) surrounds the flow-through opening (40).

17. Use of the filter element (20, 26) according to claim 16, characterized in that, The flow path of the air stream that is sequentially guided through the two filter elements (20, 26) extends through the flow-through opening (40).

18. Use of the filter element (20, 26) according to claim 16 or 17, characterized in that, The fluid connection between the outlet side (30) of the filter element (26) and the outlet (18) of the filter housing (12) is established only through the flow-through opening (40).

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